Paleobotany
Introduction to Arctic Paleobotany and Paleozoic Floras
EA-Plant Sciences
(John Walton)
INTRODUCTION TO ARCTIC PALEOBOTANY
AND PALEOZOIC FLORAS
CONTENTS
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Page
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Introduction
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1
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Paleozoic Floras
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5
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Downtonian
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6
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Lower and Middle Devonian
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6
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Upper Devonian
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9
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Lower Carboniferous
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10
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Upper Carboniferous
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10
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Permocarboniferous
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11
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EA-PS.
Walton: Introduction to Arctic Palsobotany and Paleozoic Floras
PHOTOGRAPHIC ILLUSTRATIONS
With the manuscript of this article, the author submitted 3 photo–
graphs for possible use as Illustrations. Because of the high cost
of reproducing them as halftones in the printed volume, only a small
proportion of the photographs submitted by contributors to
Encyclopedia
Arctica
can be used, at most one or two with each paper; in some cases
none. The number and selection must be determined later bythe
publisher and editors of
Encyclopedia Arctica
. Meantime all photographs
are being held at The Stefansson Library.
EA-Plant Sciences
(John Walton)
INTRODUCION TO ARCTIC PALEOBOTANY
AND PALEOZOIC FLORAS
Introduction
One of the most interesting geological and botanical problems is
presented to us by the fossils found by travelers and explorers in the
Arctic. Collections of fossil plants from places far inside the Arctic
Circle have been made from 1854 onward, but although they have given us
valuable information about the geographical distribution of extinct floras,
they have not, until recently, added greatly to what is known of the
nature and structure of extinct plants. This is no doubt because these
regions were little accessible and the difficulties of transport of heavy
materials from them were great — at least as compared with the relatively
easy transport problems in temperate and inhabited countries. As a result,
collections made in the Far North were relativ
^
e
^
ly few in number and contained
fewer specimens. The great interest, however, of even the early collections
lies in the fact that they constitute the remains of plants which were very
different from those found alive in the same regions today. They would
seem to prove that the climate during the time they were buried and fossil–
ized was much warmer and more favorable for vigorous growth than the climate
which prevails in the same spots today.
EA-PS. Walton: Paleobotany
[:
]
^
:
^
Introduction and Paleozoic
The suggestion, however, has been made that they represent plant
fragments which were carried by rivers or ocean currents from the south
and deposited in the North there they are now found, just as the driftwood
picked up on the seashore may have been derived from distant forests
i
in other lands and climates. This explanation might account for the position
of some of these plant fossils but is inadequate for the majority of the
plant deposits; for in many instances there is clear proof that the plants
which are found as fossils in the Arctic are in or near their original
positions of growth, and were not drifted fragments. The presence of
fossil roots in the sedimentary rocks below the remains of branches,
leaves, and fruits, as well as below the coal seems which are found in
Spitsbergen, Greenland, and elsewhere in the Arctic gives adequate proof
that the depots of coal and fossil plants represent the remains of vege–
tation which grew where they are now found as fossils in the consolidated
sediments.
There is no reliable evidence which would indicate that fossil plants
and coal seems are less frequent in the continental deposits which range
from the Devonian to the Tertiary in the Arctic than in similar deposits in
more southern latitudes. In Spitsbergen itself, coal seams are found in
Devonian, Carboniferous, Jurassic, and Tertiary Strata, north of latitude
76° N.
These fossil plants differ markedly from the plants which live today
in these areas. One may state that, in general, they appear to be the
remains of plants of greater stature, with larger leaves and stems, than
the present-day inhabitants; and this suggests the existence of at least
a temperate climate when conditions for growth were more favorable than today.
EA-PS. WAlton: Paleobotany: Introduction and Paleozoic
It is, however, necessary to sound a note of caution. The fossil plants
of the Paleozoic and early Mesozoic eras, although showing varying degrees
of relationship to living types, are so distantly related to them that
it would be unwise to assume that their tolerance of climatic conditions
was the same as those of their living descendants.
That the arctic regions are not exceptional in affording evidence of
striking climatic changes in their history is shown by the fossils found
in deposits formed during or soon after the Quaternary ice age in Europe.
In these deposits, typical arctic species of plants are found. In India,
South Africa, and elsewhere in the Southern Hemisphere
[:
]
in the Permocarboni–
ferous period, there is indisputable evidence of extensive glaciations closely
associated with a flora in which
Glossopteris
is the dominant plant fossil.
In the Northern Hemisphere, in America and Europe, where there is no evidence
of glaciation in the Carboniferous and Permian,
Glossopteris
is not found
in the flora.
It is important to bear in mind, however, that these arctic fossil
floras do not differ appreciably from their contemporaries in other parts
of the world. For example, the Devonian and Carboniferous floras of
Spitsbergen and Arctic North America and Greenland contain some fossil
plant species identical with or closely similar to those found in Europe,
the United States, Canada, and North Africa, and indeed differ only
slightly from some of the Carboniferous floras of the Southern Hemisphere,
including Australia. The same applies generally to the floras of other
geological periods.
No evidence has been found from fossil plants in the Arctic which
suggests that in any geological period before the Quaternary any climate
EA-PS. Walton: Paleobotany: Introduction and Paleozoic
climate as cold as that of the present Arctic existed. In fact, the
evidence suggests that the present cold conditions in the parts of the
continents inside the Arctic Circle are probably very exceptional.
It is when we turn to the late Mesozoic and Tertiary periods that
evidence for warm climates in the arctic is still more convincing, for
in these periods many of the fossil plants belong to the same angiospermic
orders and gera and those alive today in temperate and even tropical climates.
The remarkable difference between the present flora and climate of the
Arctic and the floras and presumably the climates of pre-Quaternary periods
has given rise to much controversy. There are four theories which may be
considered. C. E. P. Brooks in
The Evolution of Climate
(London, 1922) has
suggested on meteorological grounds that if the area and depth of the
Arctic Sea were increased, and its interchange of water with more southern
oceans also increased, the mean temperature of the Arctic would be raised.
The effect of ocean currents or distribution of land masses is illustrated
at the present day by the flora of northern Canada in the Hudson Bay region
at latitude 60° N., where the soil is permanently frozen at a depth of two
or three feet from the surface and bears a flora closely similar in compo–
sition to that of theomore sheltered valleys in Spitsbergen, around latitude
78° N.
Although Sir Albert Seward remarked that we cannot assume that plants
are unalterable over long periods of time in their power of adjustment to
circumstances he found it difficult to believe that these considerations
would be sufficient to account for the luxuriance of the Rhaetic flora
in East Greenland. There would still be a long winter period of darkness
with presumably very low temperatures, and we do not whether species
EA-PS. Walton: Paleobotany: Introduction and Paleozoic
are capable of adapting themselves to photoperiodic conditions as diverse
as those which would exist between Greenland and tropical regions.
The third theory, which is opposed by the majority of geologists,
is Wegener’s mypothesis of continental drift which supposes that the
continental masses have been moving about the surface of the globe and
that some land masses at present near the poles may have been at, or much
nearer to, the equator in the past. If such changes had taken place, the
existence of the remains of tropical vegetation in strata now situated
within the Arctic Circle would be explained.
The fourth suggestion is that the axis of rotation of the earth has
changed. It is known of course, that minor cyclical changes in the position
of the poles occur, but any change large enough to account for the phenomenon
of the arctic fossil floras is said
[:
]
by physicists and astronomers to be
highly improbable.
Paleozoic Floras
Our first information about arctic fossil plants was obtained from
collections made by the expeditions sent out around the middle of the
nineteenth century to discover a northwest passage from the Atlantic to
the Pacific, or to search for a large expedition that had been lost in
that quest. In 1854, Captain Inglefield brought back fossil wood from
Atanikerdluk in Greenland, and M’Clintock collected samples of coal fossil
wood and the core of a fossil conifer from Mercy Bay in Banks Island. A
few years later, between 1858 and 1864, Nordenskiöld and Blomstrand made
collections in Spitsbergen, Novaya Zemlya, and Arctic Sibe
f
^
r
^
ia. Some of
the paleobotanical results obtained by investigations of these early
EA-PS. Walton: Paleobotany: Introduction and Paleozoic
collections appear in Oswald Heer’s
Flora Fossilis Arctica
(1868). For
further information the reader is advised to consult Sir Albert Seward’s
work,
Plant Life through the Ages
(Cambridge, 1931), in which the distri–
bution over the world of floras of all ages is comprehensively treated.
As a result of the relative accessibility of Spitsbergen, Bear Island,
and Greenland from Europe, most of our information about arctic fossil
floras from high latitudes comes from these parts of the Arctic. Spitsbergen
provides us with the farthest-north examples of several geological formations
in which fossil plants have been found.
Downtonian.
The earliest known terrestrial flora in the Arctic is
that of the Downtonian, and Professor O. A. Høeg (
Norgas Svalbard - og
Ishavs - Undersøkelser
. Skrift 83, 1942) has given a full account of it and
the Devonian in Spitsbergen. The Downtonian flora from the neighborhood
of Raudfjorden is a fragmentary one. One good example of the little spherical
alga
Pachytheca
and fragments of the large and little-known thalloid plant
Prototaxites
(
Nematophyton
) were found. There were also examples of forking
vascularized axes of the simple pteridophytes (
Zosterophyllum, Taenocrada
(?)
spitsbergensis
, and
Hostimella
sp.). Floras with similar genera and species
occur in the upper Silurian of Europe and Australia. There is no doubt that
the attribution to the Downtonian by Høeg is correct.
Lower and Middle Devonian
. The principal localities in which fossil plants
have been found in the Lower and Middle Devonian in Spitsbergen are around
Wijdefjorden and Wood Bay in the northwest, and Dickson Bay and Klaas Billen
Bay in the central part of West Spitsbergen. A quite considerable flora is
represented in the collection from these areas and, as Høeg has pointed out,
“there is not the slightest trace of any influence of a depauperating
EA-PS. Walton: Paleobotany: Introduction and Paleozoic
Arctic climate corresponding to modern conditions.”
The Psilophytales are one of the principal constituents of the flora.
These relatively simply constructed pteridophytes are characteristic of
the Silurian and Lower and Middle Devonian in all parts of the world.
The plant body in the Psilophytales consists of slender branching stems,
which are either smooth or have small projections ranging from short,
stiff prickles to small, leaflike appendages. The sporangia are usually
terminal on the main branches or on short laterals. The plants were leaf–
less and rootless; the lower parts of the stems, at least in some instances,
were rhizomes provided with absorptive hairs and functioning as roots.
The earliest known land plants are found in the Silurian, and it is
significant that in the Silurian and Lower and Middle Devonian and we find an
important proportion of plants in the flora exhibiting this simple or
primitive type of morphology, which recalls that of the algae in which
there is no clear differentiation of the shoot into leaves and stem. This
[:
]
relatively primitive type of construction undoubtedly suggests that,
during these geological periods, the transition from marine or freshwater
thalloid plants of algal affinities to the type of plant which
d
^
c
^
ould
exist on land was still in operation.
The psilophytales as a group are difficult to define and probably
consist of a plexus of phyla at a similar stage of evolution. Probably
considerably more than half of the genera found in these Silurian and
earlier Devonian floras are to be included provisionally in the Psilophytales.
In the Lower and Middle Devonian of Spitsbergen, we find examples of
the following genera and species of Psilophytales:
Psilophyton spinulosum
,
P. arcticum
, and other
Psilophyton
spp.,
Bucheria longa
,
Hostimella strictissima
,
and other
Hostimella
spp.
EA-PS. Walton: Paleobotany: Introduction and Paleozoic
There are also representatives in the upper part of the Middle Devonian
of lycopod-like plants which are probably the forerunners of the later Upper
Devonian and Carboniferous arborescent lycopods.
Bergeria mimsrensis
(Fig. 1)
bears a considerable resemblance to the large extinct lycopods of the later
Paleozoic.
The
This Spitsbergen
Bergeria
moreover bears a close and
detailed resemblance to
Leptophloeum,
a type of lycopod stem which has
been found in the Devonian of Maine, U.S.A., and Australia.
Protolepidendropsis pulchra
, as its generic name suggests, bears some
resemblance to the lepidodendroid plants of the Upper Devonian and Carboni–
ferous. Of the other forms worthy of note,
Enigmophyton
exhibits flabellate
leaves with open dichotomous venation bearing some resemblance to an irregu–
larly divided leaf of the living maidenhair tree,
Ginkgo bilboa
, but of
approximately twice the superficial area.
Enigmophyton
and
Platyphyllum
,
which occur in Spitsbergen, are plants of similar character and in having
an extended foliar lamina contrast strongly with the Psilophytales and
other constituents of the flora.
One of the most interesting of the Spitsbergen plants is a pteridophyte
called
Svalbardia polymorpha
. The plant, so far is is known, had slender
smooth axes up to 46 centimeters long. These branched at an acute angle
into numerous slender forking laterals; the branching was not dichotomous.
There was a clear tendency for the ultimate branchlets to be arranged in
one plane and to be slightly webbed, forming rather ill-defined foliar
pinnules, the branching systems thus bearing a considerable resemblance to
a fern frond. On the fertile parts, the small groups of branches bore
elongated oval sporangia which evidently dehisced by a longitundinal split.
Svalbardia
thus bears some features of resemblance to the better-known Upper
EA-PS. Walton: Paleobotany: Introduction and Paleozoic
Devonian genus
Archaeopteris,
and indeed its branching system might be
described as similar to fronds of
Archaeopteris
but with a more irregular
and less formal arrangement of the sterile and fertile parts.
Upper Devonian
. Collections were made in Ellesmere Island in Arctic
Canada by the Second Norwegian Arctic Expedition in the
Fram
, (L898-1902),
and the fossil plants were investigated by Nathorst.
The flora, omitting specimens of uncertain nature, consisted of
Archaeopteris archetypus
and
A. fissilis
. These are species of a genus
of fairly large plants which bore large bipinnate fronds, the foliar
pinnules being either cuneiform or divided into filiform divisions. Sporangia
were borne in large numbers on fertile pinnae on which the photosynthetic
lamina was not developed. Some at least of the species of
Archaeopteris
are known to have been
[:
]
heterosporous. The sporangium was elongated and
had no obvious annulus.
The species found on Ellesmere Island seem to be identical with some
found by Schmelhausen in the Upper Devonian of the Donets Basin, U.S.S.R.
Nathorst’s accounts, in 1902, of the Upper Devonian flora of Bear
Island contain descriptions of some genera and species of previously
unknown Pteridophyta.
Cephalotheca mirabilis
had finely divided foliage
leaflete borne on large fronds. The sporangia were grouped in large pendulous
bunches which hung on short pedicels at the base of the lateral pinnae.
Pseudobornia ursine
(Fig. 2), assigned to a group of Articulatae named
Pseudoborniaceae, had whorls of leaves with fimbriate margins borne on
ridged stems.
The Upper Devonian age of the flora is suggested by the relative
abundance of
Archaeopteris fimbriata
,
A. intermedia
, and
A. roemeriana
EA-PS. Walton: Paleobotany: Introduction and Paleozoic
(Fig. 2-a). The last species closely resembles
A. hibernica
from the
Upper Devonian of Ireland. The other genera and species indicate some
significant affinities with floras of the lower Carboniferous, as for
example
Sphenopteridium
sp. and
Sphenophyllum subtennerrimum
. There are
also representatives of the arborescent Lycopodiales,
Bothrodendron
kiltorkense
,
B. wi
k
^
g
^
kianum
, and other species of
Bothrodendron, Lepidodendron,
and
Stigmaria ficoides
.
Lower Carboniferous
. Strata of this age containing abundant evidence
of plant life occur in northern Greenland, Spitsbergen, and Alaska.
Nathorst, in 1911, described a few fossils from northeast Greenland. These
include fragments of fernlike fronds resembling those of the Pteridosperm
Telangium bifidum
,
Rhodea tenus
(Fig. 3-a), a
Sphenophyllum
,
Asterocalamites
scrobiculatus
, an extinct “horsetail” (Equisetales) of very wide geographical
distribution in the lower Carboniferous, and numerous examples of lycopods
of the
Lepidodendron
type. The species found in northeast Greenland are
consistent with a lower Carboniferous (Mississippian) age for the strata
in which they were found.
This flora is of special interest as it is the most northerly Paleozoic
flora so far recorded, being found between 80° and 81° N. latitude.
In 1894 and later in 1914 Nathorst described fossil plants from West
Spitsbergen. He records twenty-six genera including over fifty species,
a number of which are common and characteristic of the lower Carboniferous
in continental Europe. Among these may be mentioned several fernlike genera
and species, probably most of them are pteridosperms (a group of gymnospermous
plants which probably persisted from the Upper Devonian until well into
Jurassic times). The most characteristic features of this group were the
EA-PS. Walton: Paleobotany: Introduction and Paleozoic
large fernlike fronds on which seeds were borne in many of the genera.
The group has sometimes been referred to as the seed ferns. Among those
described by Nathorst are
Adiantites
^
sp.
^
apd
Cardiopteridium spetsbergense
(Fig. 3-b), which are characteristic constituents of the calciferous
sandstone series of the lower Carboniferous of central Scotland. The
extinct horsetails are presented by
Asterocalmites scrobiculatus
.
The arborescent lycopods are well represented, and from the discovery’
of tree stumps in positions of growth in the strata, and the existence of
considerable coal seams, it is evident that extensive and flourishing
forests existed there is lower Carboniferous times. Nathorst identifies
examples of
Lepidodendron, Lepidophloios
,
Sigillaria
, and
Porodendron
among the remains of these forest trees. Quite a large number of seeds and
polliniferous fructifications occur, including one names
Thysanotesta
which has a hairy plume attached to the seed body and which Nathorst
suggested was evidence of a wind-dispersal mechanism.
From Bear Island, Nathorst described a mainly Upper Devonian flora,
but there are a few species in it which are found in the lower Carboniferous.
It would, however, be unjustifiable on the bases of these elements to
conclude that a lower Carboniferous flora is represented in Bear Island.
Professor T. G. Halle has recently investigated collections from the
northern Scoresby Sound area of East Greenland, including some admittedly
fragmentary remains of Carboniferous plants which can be matched most
clearly with plants found in the Carboniferous limestone group in the upper
part of the lower Carboniferous is Scotland as well as with elements of
the Namurian flora in western Europe.
Upper Carboniferous.
Nordenskiöld in 1875 discovered fossil plants
EA-PS.
^
Walton:
^
Paleobotany: Introduction and Paleozoic
in Novaya Zemlya, in arctic Russia, in shales lying above and conformable
with limestone containing
Productus
and
Spirifer
— indicating that the
plant-bearing beds were of upper Carboniferous or possibly Permian age.
The plant remains are long stra-shaped leaves of
Cordaites
, an extinct
genus of gymnospermous trees. Recently Halle has identified the character–
istic upper Carboniferous genera
Alethopteris
and
Neuropteris
, which are
known to be the fronds of pteridosperms, in collections made in the
Scoresby Sound area of East Greenland. They indicate the presence of a
Westphalian horizon of the Upper Carboniferous.
Permocarboniferous.
Professor R. Florin has identified the pteridos–
perm genus
Callipteris
and a conifer
Lebachia
, fossils which indicate an
age not earlier than the upper Carboniferous Stephanian, and possibly the
Permian, in the northern Scoresby Sound area.
John Walton
Mesozoic Paleobotany
(EA-Plant Sciences. Thomas M. Harris)
MESOZOIC PALEOBOTANY
CONTENTS
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Page
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Triassic
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2
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Rhaetic and Basl Liassic
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2
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Lower Jurassic (Liassic)
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5
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Middle Jurassic (Lower Oölite)
|
6
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Upper Jurassic
|
6
|
|
Lower Cretaceous (Wealden)
|
7
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Middle Cretaceous
|
10
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Upper Cretaceous
|
10
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Upper Cretaceous Flora of Alaska and Greenland
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13
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General Conclusions: Past Climates
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16
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Comparison of Floras in Same Period
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18
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Bibliography
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22
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EA-Plant Sciences. Harris: Mesozoic Paleobotany
LIST OF FIGURES
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Page
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Fig. 1.
|
Mesozoic floras of the Arctic and Subarctic
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2-a
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Fig. 2.
|
Some Mesozoic ginkgoalean foliage of arctic regions
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15-a
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EA-Plant Sciences
(Thomas M. Harris)
MESOZOIC PALEOBOTANY
The arctic regions are as rich in Mesozoic plants as other parts of the
earth but they figure disproportionately large in the history of paleobotany.
During the nineteenth century certain Swedes were among the pioneers in sci–
entific arctic exploration and a young man, A. G. Nathorst, was appointed to
a new research post in paleobotany at Stockholm, largely to deal with arctic
fossil plants. Nathorst and those who followed him by no means confined them–
selves to the Arctic, or indeed to the Mesozoic; but Nathorst’s work on
Mesozoic plants certainly led the world and inspired workers in many other
countries.
As time passes, these old investigations, though often models of work
in their day, have become out of date and their significance gradually changes
from what they actually proved to the suggestions which they afford of future
possibilities for research. It is, of course, a common characteristic of work
on material from remote places that it consists of exhaustive investigations
of material collected at long intervals, and much of it is in need of revision.
In this article future needs are pointed out.
The subject matter is here arranged chronologically under the Triassic,
the Jurassic, and the Cretaceous. Recent geochronology assigns a length of
some fifteen million years to the Triassic, barely ten million years to the
Jurassic, and as long as forty million years to the Cretaceous; but our know–
ledge of the floras is not in this proportion, for the Jurassic are best known
EA-PS. Harris: Mesozoic Paleobotany
(especially if we include transitional beds at the two ends of that period),
next comes the Cretaceous, and the Triassic is the least known. This is
equally true of north temperate regions generally and of the Arctic.
^
(see Fig. 1)
^
^
1.
^
Triassic
The arctic Trias has few plants until its very end. Marine Triassic
is well known, as is continental Trias of the barren, desert sandstone
type — but not the deltaic type of rock in which plants occur. The sole
exception is in East Greenland where, in the early Trias of Hold with Hope
(just below the
Myalina kochi
zone), there is a shale with small plant frag–
ments including a
Selaginella
cone,
Selaginellites Polaris
(31), yielding
surprisingly well-preserved spores. Clearly this region should be searched
again for richer deposits; any progress in knowledge of the Trias would be
welcome. Our lack of knowledge of the Middle Trias, is surprising,
[:
]
although
the period is represented by two accessible and excellently preserved floras
in Austria and in Virginia.
According to Newton and Teall (
[:
]
^
4
^
3), ill-preserved Triassic plants occur
in Franz Josef Land; and Nathorst (37) recorded a few supposedly Triassic
plants from the island of Kotelnyi (New Siberia), but the specimens could
equally well have been Lower Jurassic. Now Lower Triassic plants have been
recorded from the Arctic, and there is thus no problem to decide whether a
flora belongs to the Mesozoic or Paleozoic.
^
2.
^
Rhaetic and Basal Liassic
The last stage of the Triassic is called the Rhaetic. It is included
in the Trias because its chief ammonites are of Triassic rather than Liassic
affinities, but from the paleobotanical angle it would be natural to include
Fig. 1. Mesozoic floras of the Arctic and Subarctic.
(the numbers refer to the sections in the next): 1, Triassic; 2, Liasso-Rhaetic;
3, ? Liassic; [4, Middle Jurassic wanting]; 5, Upper Jurassic; 6, Lower Cretaceous;
[7, Middle Cretaceous wanting]; 8, Upper Cretaceous.
EA-PS. Harris; Mesozoic Floras
it in the Jurassic. The Rhaetic marks the beginning of submergence of the
Triassic land by the Liassic sea, and its flora passes continuously into the
Liassic. This submergence was rather widespread, and a good many Rhaetic
floras are known or at least attributed to this period. The flora of
Scoresby Sound, East Greenland, is one of the largest of its period. It
was first discovered by Scoresby; Hartz (18) wrote a pioneering paper; and
it has been redescribed by Harris (17) and then more fully by Harris in a
series of papers (10-14, 16). A northward extension of this flora was more
recently described by the same author.
This flora occurs in a river delta which continued to receive deposits
on its surface through the Rhaetic into lower Liassic (
Angulatus
zone) time
and perhaps rather longer. It is followed by a Liassic marine fauna of
Jamesoni
zone which sets an upper limit to the age of the plant-bearing rocks.
The plant-bearing series are favorable for study, being geologically very
simple. Plants occur locally at all levels in the plant-bearing series in
what seem to be old river channels. There are many thin coal seams and old
land surfaces with vertical roots.
Although each plant bed has a flora with some features of its own, there
is a simple underlying scheme. Every bed of the lower 60 meters of the series
has a selection from a certain list of species, the “
Lepidopteris
flora,” and
each bed of the top 30 meters has selection from a second list, the “
Thaumatop
–
teris
flora.” These two floras have a few species which range through both,
but most are rigidly restricted except through about 5 meters of rock where
mixture occurs. Thus two plant zones can be clearly made out, and both are
widely recognizable, for example, in Europe (and even, it has been claimed, in
Japan). The older
Lepidopteris
zone is correlated with the European Rhaetic
EA-PS. Harris: Mesozoic Paleobotany
flora, the younger with the European basal Liassic flora. The flora of the
two zones comprises some 200 named species (although this number includes
separately named leaves, seeds, and other parts of the same plant, as well
as many unnamed types of charcoal and
[:
]
microspores); it is therefore among
the largest Mesozoic floras, and nearly everything was well enough preserved
for its microscopic structure to be investigated.
The name part of the flora is made up of cryptogams and seed plants.
The cryptogams include 1 filamentous alga, 4 thalloid hepatics, 6 Equisetales
(usually the commonest fossils), 15 lycopods, almost all being isolated mega–
spores, and 22 Filicales (often abundant). The families represented in this
last order are Osmandaceae, Dipteridaceae, Matoniaceae, Marattiaceae, and
Gleicheniaceae.
The seed plants includ 21 presumed cycads, 7 presumed pteridosperms, 8
Caytoniales, 31 Bennettitales (often abundant), 20 Ginkgoales (often abundant),
35 conifers, 1 possible dicotyledonous plant, and 25 unclassified reproductive
organs, mostly no doubt belonging to the members of the above groups. Several
of these seed plants are of great interest because leaves and reproductive
organs are associated and there is, moreover, structural evidence for associ–
ating them. This applies, for instance, to the cycads
Nilssonia
and
Beania
,
and to the pteridosper-like plants
Lepidopteris
and
Ptilxozamites
and their
reproductive organs.
The flora was investigated rather differently from other Mesozoic floras,
in that the larger microfossils were described — particularly leaf cuticles,
isolated megaspores, and isolated seeds. Many of these are widespread and
abundant although not found as ordinary fossils, and this was taken to indi–
cate the existence of an inland flora of different composition from that of
EA-PS. Harris: Mesozoic Paleobotany
the Deltaic marshes, and represented only by small water-borne fragments.
If these microfossils are excluded, the flora becomes astonishingly sim–
ilar to that of the corresponding one of south Sweden (Scania) where both
zones are present; nearly all the species are in common, and in the main the
same species are abundant. It is indeed so similar that it is not possible
to state with assurance the existence of any general difference. It may,
however, be true that Ginkgoales, especially
Czekanovskia
, are rather more
abundant in Greenland, and that
Thinnfeldin
, which is rare in Sweden, is even
rarer in Greenland. This genus is abundant in the floras of the same age in
southwest Germany.
The flora at present known represents one whole season’s collecting and
some material collected previously on brief visits. There are indications
that further collecting in Scoresby Sound is not likely to
[:
]
^
y
^
ield many new
species (since most of them were met rep
[:
]
eatedly) but it should certainly
yield much botanical interest. The northward extension of this flora,
previously mentioned, seems a little different from the representation in
Scoresby Sound and should repay both floristic and stratigraphic study.
^
3.
^
Lower Jurassic (Liassic)
Unfortunately we have no large standard middle or upper Liassic flora;
indeed the plants of the whole period are imperfectly known. The only near–
arctic flora claimed to be of this approximate age is from the Upper Matanuska
Valley, Alaska (28). It has only ten species, but all were identified, mostly
with Liassic ones from Bornholm. None of these identifications is supported
by microscopic evidence, but still a tentative determination of the age as
Liassic is reasonable, even though an age as old as Rhaetic or as young as
Lower Colite would not be excluded by the plants concerned.
EA-PS. Harris: Mesozoic Paleobotany
The interest of this flora lies in the research possibilities it suggest.
Much of the rock is volcanic ash; this suggest petrifactions. There are associ–
ated marine faunas; this suggests a possibility of accurate stratigraphy. If
the preservation is good (cuticles are not mentioned), here is a possibility
of advance in botanical knowledge of a little-known period.
^
4.
^
Middle Jurassic (Lower Cölite
).
Plants of this period are very poorly represented in the Arctic. A few
plants of this age (
Sagenopteris
and some others) occur in Alaska but little
is yet published about them (
See
Martin and Katz (32), Knowlton (28)). The
marine Jurassic of East Greenland is, however, fairly rich is undescribed
petrified wood.
^
5.
^
Upper Jurassic
One of the larger floras of Spitsbergen (Cape Boheman) has been regarded
as Upper (or even as old as Middle) Jurassic, but the majority if not all of
these floras are now generally included in the lowest Cretaceous, There is
thus no known and satisfactory arctic Upper Jurassic flora, and indeed this
is a period of which our knowledge is rather scant. It may be mentioned that
moderate-sized Upper Jurassic floras occur in northeast Scotland (49; 54),
though this is outside the limits of the regions here included.
A great deal of petrified wood is known from the arctic regions — much
of it originally preserved in marine Jurassic rocks and then removed by glacia–
tion and thus of rather insecure age, but other material accurately dated.
Collections of such wood have been described by Gothan from King Charles Land
and other parts of Spitsbergen (8; 9), its age being largely Upper Jurassic
or lowest Cretaceous. A few others were described by Walton (56) from Spits–
bergen.
EA-PS. Harris: Mesozoic Paleobotany
Mesozoic petrified woods have been rather neglected in recent years,
and
[:
]
^
G
^
othan’s accounts remain among the most complete
[:
]
yet written. In them,
several new types were recognized and others identified with known types.
There has never been any proof that petrified woods are not excellent and
well characterized types, as well as of evolutionary interest, and a return
should certa
[:
]
ly be made to the study of this material.
A small flora from a Spitsbergen boulder in undetermined age may be
mentioned here. It was described by Selling (45; 46) and includes some
lycopodinian megaspores and some excellently preserved gymnospermous roots.
^
6.
^
Lower Cretaceous (Wealden
)
This period, which in parts of Europe passes gradually down into the
Upper Jurassic (Purbeckian), was for a time include by some in the Jurassic,
but most of the considerable confusion which has existed about the correla–
tion of these floras is due to real doubt about their age and not merely to
the name of the period to which the Wealden is assigned. One such flora is
found in northern Siberia at the mouth of the Lena River, another on
[:
]
Andö
in the Lofoten Islands, Norway, and there is also a series of floras from Spits–
bergen and from Franz Josef Land which it is convenient to take all together.
The Lena River flora (22), which could equally well be Upper Jurassic,
shows some quite handsome specimens of Podozamites, Nilssonia, and other well–
known Mesozoic gymnospermous leaf types. Several ginkgoalean leaves occur. The
collection gives one the impression that further field work would yield valu–
able results.
The flora of Cape Boheman, Spitsbergen, has been regarded as the oldest.
It was described by Heer (19), and correlated with Middle Jurassic. Heer
EA-PS. Harris: Mesozoic Paleobotany
determined some 32 species, about half of which would seem nowadays to be
justifiably identified. The commonest fossils are ferns, members of the
Ginkgoales, and (possibly) coniferous leaves placed in the genus
Podozamites
,
which might, however, equally wall belong to the Ginkgoales. Cycad-like
leaves are remarkably rare or perhaps absent, the only ones mentioned being
determined on very weak evidence, and there are some curious cones which
would no doubt have botanical interest if studied.
Nathorst (42) pointed out that Herr’s identification of certain fossils
with Middle Jurassic ones was unreliable, and later (38) he stated that they
are younger than a marine Oxfordian
Aucella
horizon. Their age could there–
fore be Upper Jurassic or perhaps Lower Cretaceous. So far as the author
knows. The preservation of this flora is not good enough to permit microscopic
study.
There is another flora at Advent Bay, Spitsbergen, described by Nathorst
(42), which seems younger than the Cape Boheman flora and which certainly
seems to be of Wealden age. It includes several Ginkgoales and some conifers,
in particular
Elatides curvifolis
, whose identity is confirmed by Florin (6).
This is a characteristic species of the Wealden of Franz Josef Land. This flora
includes some interesting cones, and, as cuticles are preserved, there is again
scope for work of botanical interest.
The Walden floras of Franz Josef Land are of special importance because
much of the material is petrified. It is indeed one of the only two known
petrified floras of Mesozoic age; elsewhere, only a few genera such as
Cycadeoidea
are petrified. It has thus a special importance and has been the subject of
exhaustive investigation. Solus-Laubach (53) gave a useful account, and later
Florin (5; 6) dealt with the Ginkgoales which make up the bulk of the flora.
EA-PS. Harris: Mesozoic Paleobotany
Apart from these, there are only the conifer
Elatides curvifolia
and a few
fragments belonging to other groups.
Among the Ginkgoales there is a remarkable preponderance of species with
strap-shaped leaves borne on dwarf shoots. Such leaves were formerly called
Pheonicopsis
, but Florin distributes them on cuticle characters (particularly
stomatal distribution) into several new genera. The leaf vascular bundles of
these fossils show remarkably close agreement with those of the leaf of
Ginkgo
biloba
; differences exist, however, in the characters of the bundle-sheath
and of the secratory cavities.
As this flora is based on collections from five localities, there is some
reason to suppose that, although it remains far from exhaustively collected,
our knowledge of it is representative. No flora in the world of any age shows
such a preponderance of Ginkgoales, either reckoned as the fraction of the
total number of species in the flora or on relative abundance of specimens.
One may feel reasonably sure that this fact has some paleogeographical sig–
nificance, as, in floras of the same age in Europe, Ginkgoales are few but
conifers predominate.
A small flora from Cape Staratsch in Ice Fjord, Spitsbergen, was described
by Heer (22, and some notes in 1873). It includes a few fern fragments, a good
many conifer shoots and cones, and some Ginkgoales. There are no Bennettitales,
but there is one specimen referred (unjustifiably) to the monocotyledons. The
correlation of this flora is quite vague; Heer thought it younger than the
Wealden flora of Greenland, but this would seem unlikely. The plants are con–
sistent with a Lower Cretaceous age. Nathorst (42) referred to it as “Upper
Jurassic,” but by that he apparently meant “Wealden,” which is now placed at
the bottom of the Cretaceous.
EA-PS. Harris: Mesozoic Paleobotany
A small flora of uppermost Jurassic or Lower Cretaceous age has been
described from Andő in the Lofoten Islands, Norway, by Johansson (26). The
material was very limited and the plants unpromising little pieces of leaves;
but they were investigated microscopically and yielded three species of
Sci
–
adopitys
— more, indeed, than in any other flora. It is not, however, safe
to assume that the abundance of this remarkable genus of conifers is unique,
for such fossils in other floras have been either neglected or given a name
like
Pityphyllum
, which has been used so widely as to have no botanical mean–
ing.
^
7.
^
Middle Cretaceous
No arctic flora can be d
^
e
^
finitely ascribed to this period. This may well
be because of lack of standard floras in Europe, for some of the Spitsbergen
floras might belong to it — for example, that described by Heer (22) from
Cape Staratsch. Heer originally placed his Atane flora of Greenland some–
where in the middle Cretaceous, but Seward (48) has expressed doubt about the
correlation and revards it as much younger.
^
8.
^
Upper Cretaceous
This is the period during which the Mesozoic type of flora gave place
to the modern type, the change being largely the disappearance of the Ben–
nettitales and some other Mesozoic gymnosperms and their replacement by a
large number of kinds of dicotyledonous leaves. Other gymnosperms declined
only gradually.
The change has been re
^
g
^
arded as sudden, and so it certainly is in rela–
tion to the relative stability from Upper Trias to middle Cretaceous; but
its suddenness may be partly illusory. It was, however, slow enough to be
EA-PS. Harris: Mesozoic Paleobotany
scarcely perceptible during the long period, perhaps several million years,
when a great thickness of rock was deposited in Alaska and in West Greenland.
Heer considered that there were four main stages in the plant-bearing
series. The oldest is the Kome or Kuk series which he supposed was Lower
Cretaceous; then came the Atane series in the middle or Upper Cretaceous,
then the Patoot series of the uppermost Cretaceous, and finally a great Ter–
tiary flora which he placed in the Miocene. Each series is represented by
several isolated localities and there is no proof that the rocks ascribed
to one series form a geological unit.
Later writers have pushed these together. The Kome series is ascribed
to the middle part of the Upper Cretaceous, the next two to a younger stage
of the Upper Cretaceous (but their validity as recognizable stages is doubt–
ful), and finally the flora regarded by Heer as Miocene is moved into the
older part of the Eocene.
The geology was revised by White and Schuchert (57), but since then
efforts at correlation have been based almost entirely on the plants; and this
largely depends on the proportion of characteristically Mesozoic gymnosperms
to the characteristically more recent dicotyledons. Such
[:
]
correlation may
prove very reliable if the chan
[:
]
^
ge
^
in flora was everywhere simultaneous; but
if, as some have suggested, the Tertiary type of flora arose in the Arctic
and migrated south very slowly, it would be misleading. The author under–
stands that work at present in progress (in 1950) on the geology of the West
Greenland Cretaceous and Eocene (which have several marine horizons) is likely
to result in considerable clarification. If so, the geologists concerned will
deserve much gratitude.
Taking this flora, then, as a whole, we can certainly say that it
EA-PS. Harris: Mesozoic Paleobotany
comprises several stages (though our knowledge is not good enough to define
them) and includes a large number of species, many of which are represented
by fine large leaves with associated reproductive organs. Preservation is
very uneven in different localities; many provide only burnt-out casts (the
fossils most prized by the early investigators and still considered valu–
able by many modern paleobotanists), but others give excellent cuticles
and spores, and sometimes the fossils are so little altered that they can
be swelled with potash and then give good sections. Though much is known,
the possibilities for future work are very great.
Since Heer’s time, the flora has been investigated by several others.
Seward (48; 50) and Seward and Conway (51; 52) contributed a general re–
vision of Heer’s work, and special aspects are described by Arnold (1),
Miner (33; 34), Nathorst (37; 39; 40), and Tutin (55). Little further
reference will be made to Heer’s part in this work because Seward’s revision
of it was com
^
p
^
rehensive. It may be remarked, however, that even if Heer may
have been hasty in his description, his works are a monument to his industry
and boldness. His labors must be considered largely responsible for sev–
eral later researches on the arctic floras.
Among the most interesting cryptogams are a series of
[:
]
Gleichenia
–
like ferns (
Gleichniopsis
), some of which have numerous small sporangia and
thus approach the Polypodiaceae, though most of them are not yet securely
classified on sound characters. Equisetales occur but are not common;
evidently they had by that time become an unimportant element of the marshes.
Among the interesting gymnosperms, there are several undoubted Ben–
nettitales (including species of
Pseudocycas
,
Nilssonipotaris
, and
Ptilophyllum
)
EA-PS. Harris: Mesozoic Paleobotany
from all of which cuticles have been prepared showing bennettitalean stomata.
No true cycads occur — apart
[:
]
from a leaf assigned to
Pseudoctanis
, but
which has not been confirmed by microscopic study. Ginkgoales of several
genera are common and there is a wealth of conifers. Heer identified sev–
eral species of
Sequoia
, which are very abundant, and also of
Sciadopitya
,
a genus now confined to Japan.
Angiosperms are very numerous, especially in the later stages, though
these are often recognized as Tertiary. They are represented by very large
leaves of anything but arctic aspect. Genera determined include
Platanus
,
Aralia
,
Magnolia
,
Laurus
, and
Cinnamomum
, though Seward is characteristically
cautious in his identification. These matters are referred to when this flora
is compared with the Alaskan flora.
Upper Cretaceous Flora of Alaska and Greenland
Hollick (24) brings together what is known of this flora and adds greatly
to it. He considers there are in reality two floras — one from the Yukon
River which is correlated with the Dakota sandstone flora and “early” Upper
Cretaceous, the other from the Alaska Peninsula which is correlated with the
Montana flora and “late” Upper Cretaceous. Both floras occur in a thick series
of sediments, and there is hope that further collecting in marine beds may
lead to their division into further stages and more precise correlation.
Both floras are large; together they include over 200 named species and
they both include a similar, rather small proportion of “Mesozoic” gymnosperms.
The bulk of the species are dicotyledonous trees, represented by leaves, and
most of these are peculiar, being confined to one locality or even one speci–
men. This is a clear indication that progress is needed on the botanical side.
EA
[:
]
PS. Harris: Mesozoic Paleobotany
Nevertheless the dicotyledons in the two floras seem to have a similarity in
aspect; an important difference is the abundance of the
Platanus
-like leaf
Credneria in the Y
[:
]
^
u
^
kon River flora and its absence in the other. It appears
also that different gymnosperms occur in the two floras.
For the following description the two floras will be taken together and
at the same time compared with the West Greenland flora, which is only
slightly farther north.
Cryptogams
. In both the Alaskan and Greenland floras, the Equisetales
are rare or else unknown. Evidently this group had then lost its place as
the dominant one of swamp vegetation, presumably to reeds and swamp-inhabiting
trees.
Ferns occur in both regions but in strikingly different numbers. In
Alaska they are very rare, and, although several species are distinguished,
they are based on a few small pieces. In Greenland, ferns are among the most
abundant fossils and so most of the species are based on fine specimens. This
difference seems to suggest that the Greenland flora lived under a somewhat
different climate, perhaps one with more humid summers. It may be pointed out
that the specific determination of several of the Alaskan fern fragments and
their reference to such genera as the Mesozoic
Stachypteris
or the modern
Pteris
,
Asplenium
,
Phegopteris
, or
Dryopteris
, do not represent the discovery
of important facts about sori on which these genera are based, as the iden–
tifications were made from leaves without reference to reproductive organs.
Such determinations raise grave doubts about the validity of the determinations
in other groups, especially among the angiosperms. Most paleobotanists would
have preferred to call these fragments
Sphenopteris
sp.
A
,
Pecopteris
sp.
B
,
and so on.
EA-PS. Harris: Mesozoic Paleobotany
Gymnosperms
. Three species of
Sagenopteris
are distinguished, each from
a single imperfect leaflet. This must be one of the last records of the Cay–
toniales; closer study is most desirable.
Several species of
Nilssonia
(Cycadales) occur, some of them being
remarkably abundant and widespread. In view of their absence in West Greenland
this is rather surprising.
The Bennettitales on the other hand are rare and indeed doubtfully repre–
sented in Alaska, though common in Greenland. This is a “
Cycadites sp
.” Com–
parable with a Greenland
Pseudocycas
and a leaf placed in
Pterophyllum
which
might, in the absence of knowledge of its cuticle, belong to that genus or to
Fseudoctenis.
The Ginkgoales are well represented in both floras, and several of the
species look rather similar
^
(see Fig. 2)
^
. Their names are all different, but the specific
names of Ginkgoales are quite arbitrary in the absence of information about
cuticles. The abundance of this group in arctic floras in general is remarkable.
Conifers are important in both floras, and forms resembling in appearance
Saquoia sempervirens
are frequent. A different array of generic names are used
by Seward, Hollick and other paleobotanists, but this merely emphasizes the
need of further knowledge. A strange feature of the Alaskan flora is the genus
Podozamites
(absent from Greenland); further knowledge of the Alaskan material
of this presumably heterogeneous Mesozoic conifer group would be of value.
Angiosperms
. In both floras there are numerous species of dicotyledons,
represented by large and abundant leaves. Apart from
Platanus
, however, their
naming and treatment are almost entirely different. Seward, as is well known,
tended to unite a range of specimens into a few species, but Hollick distin–
guishes a great many, and this partly accounts for the much longer species list
Fig. 2. Some Mesozoic ginkgoalean foliage of arctic regions (original
specimens are 2-6 inches long): A,
Czekanowskia; B,
Sphenobaiera; C,
Baiera;
D,
Ginkgoitea^s^ obovata; E, leaf bundle of
Czekanowskia; F, leaf bundle of one
of the
Phoenicopsis’ group (
Stephenophyllum); G, leaf of
Ginkgoites taeniata;
H, leaf of Ginkgo digitata.
EA-PS. Harris: Mesozoic Paleobotany
in the Alaskan flora. Inspection of the figures suggests that there is indeed more
variety in the Alaska flora and that rather more species should exist there.
General Conclusions: Past Climates
Everyone who has collected fossil plants in the Arctic must have been
struck by the difference between the sparse flora growing there today and the
abundance of the fossils. Of course the subject is only part of the study of
the past climates of the world, but nowhere, save perhaps in true desert, can
the contrast be more marked.
The smaller Mesozoic arctic fossil floras give little basis for judgment
on climate, but the larger ones, and particularly the largest — the Liasso–
Rhaetic of East Greenland, the Lower Cretaceous of Spitsbergen, and the Upper
Cretaceous of West Greenland and Alaska — all indicate the existence of condi–
tions where large plants could flourish: that is to say, a climate with a
growing season favorable enough for trees to grow, many of them with large
leaves. One other significant fact is that all the fossil woods of the Meso–
zoic, and they range widely, show annual growth rings indicating the existence
of growing and resting seasons. This indeed is true of Mesozoic fossil woods
generally. Here, in the author’s opinion, the simple indications end, and
the more cautious scientists may reasonably conclude that this is all we know
of arctic Mesozoic climates.
It is possible to go further if we accept the rich of error through wrong
assumptions. The Mesozoic flora, in the main, is so unlike that of today
that we are precluded from using identifications as evidence of past climate.
If a late Tertiary northern flora has nearly all its species in common with
present floras two thousand miles to the south, we have a fact so impressive
EA-PS. Harris: Mesozoic Paleobotany
that nearly everyone accepts it as climatic evidence. The evidence is
rather less impressive, but of the same kind, when an early Tertiary flora
(e.g., the London clay flora) is shown to have to bulk of its genera in com–
mon with the Malayan flora.
In the Mesozoic, where one can only identify a modern genus here and
there, the evidence is so slight that, except at the end of the period, few
regard it as evidence at all. Thus we cannot use the fact that some of the
Mesozoic ferns are today tropical, still less that there were a good many
Mesozoic cycads (in the strict sense) and cycads are today more or less t
y
^
ro
^
pical.
(The bulk of the plants called fossil cycads are the unrelated and extinct
Bennettitales.
[:
]
) Exactly the same evidence, but with a different selection of
Mesozoic plants (
Cinkgo
,
Taxus
), would suggest a temperate climate. We are
thus forced to rely on other evidence not involving identification with living
forms. This is largely obtained in two ways: by morphological and anatomical
studies, and by comparison of one flora with others in the same period.
Evidence from Morphology and Anatomy
. Large tree
[:
]
leaves suggest a
favorable climate, thin cuticles a humid growing season. This of course
assumes that plant tissues of the Mesozoic were about as susceptible to damage
as those of today. It has already been said that fairly large tree leaves
occur in these floras. On the other hand, there is no sign of leaves of gi–
gantic size such as occur in a good many tropical trees, unless we include
the various cycadalean and bennettitalean leaves which are sometimes very large.
These large leaves may, however, equally well belong to herbaceous plants.
The cuticles do not provide any indication of temperature, but only of
the humidity of the growing season. All we can say is that in the Rhaeto-Liassic
flora of East Greenland most of the abundant species, especially of conifers,
EA-PS. Harris: Mesozoic Paleobotany
are thinly cutinized or have cuticles of only medium thickness. Thick cuticles
occur on some species but these are rare ones. The Ginkgoales, however, as
[:
]
a
family have rather thick cuticles in this as in other floras. Thickly cuti–
nized Ginkgoales are prominent in the Spitsbergen Lower Cretaceous floras.
In the Greenland Cretaceous flora and in the Alaskan flora, medium-sized
tree leaves occur which are comparable with those met in temperate forests
today, but which, it must be admitted, are very abundant in the tropics also,
though these fossil floras include an additional element of very large oval
leaves which are rather foreign to temperate floras. Neither flora would seem
to give much more than a suggestion of at least a temperate climate, but
nothing to show whether it was cool or warm temperate, or even to exclude a
tropical climate. We must bear in mind our ignorance of the aspect of a true
[:
]
tropical flora in Upper Cretaceous times.
Noting whatever is known about the cuticles of the Alaskan flora. Some–
thing is known about those of the Greenland Cretaceous one; the bulk of the
species seem to have thin or medium cuticles.
Comparison of Floras in the Same Period
It is a striking fact that many Mesozoic determinations stand close in–
vestigation by new types of evidence and are strongly confirmed by it. Many
Mesozoic species are thus real and recognizable, though usually only with cer–
tainty by microscopic investigation. Unfortunately the number of floras in
which a large proportion of the species have been microscopically examined
is few for any period; there happen to be several in Liasso-Rhaetic times, but
later on there is at most one for each main period, so we are not yet helped.
Without microscopic study, Mesozoic plant determination has such a large
EA-PS. Harris: Mesozoic Paleobotany
element of doubt that the universal distribution of Mesozoic, and particu–
larly Jurassic, plants is still a controversial subject.
Of the Rhaeto-Liassic period we have large floras in East Greenland,
southern Sweden, and southwestern Germany that have been suitably investi–
gated; this to some extent is illuminating other floras not yet so studied.
Already some studies have been made of cuticles in Rhaeto-Liassic plants of
China and Japan.
From this we can say that in East Greenland at latitude 70° N. and in
Sweden at latitude 57° N. there were almost identical floras — identical
Rhaetic floras being succeeded by identical lower Liassic floras. In south–
west Germany the same succession occurred, and the floras all had much in
common, but the German one was not so similar to the Greenland and Swedish
ones as they were to one another; for example the genus
Thinnfeldia
is very
abundant in Germany but rare or almost absent in the other floras. If floras
indicate climate, the climates of East Greenland and southern Sweden should
have been identical, but that of southwestern Germany rather different. If
we are to go further we must descend to weaker evidence from floras not yet
investigated in detail. The sweden-Greenland type of Rhaeto-Liassic flora
seems to have occurred in Poland and perhaps in China; at least, elements
agreeing perfectly occur in both those countries and in Japan at latitude 35° N.
Much more doubtfully, we can trace a chain of floras from Germany (lat. 50° N.)
through Persia (lat. 35° N.) to Tonkin at latitude 20° N.
These chains of floras are roughly parallel and have a remarkable obliquity
in relation to present latitude. If such distribution could be substantiated,
[:
]
it would indicate something very extraordinary — say a major shift of the
earth’s axis or of the earth’s crust (continental drift). Unfortunately it
EA-PS. Harris: Mesozoic Paleobotany
is
not
yet substantiated. In the first place, none of the determinations
in the Persian, Tonkin, and several other floras have so far been confirmed
by cuticles; and, much more serious, this obliquely running belt of Rhaeto–
Liassic floras includes nearly all the known Rhaeto-Liassic floras of the
Northern Hemisphere, which fact alone forces the species to have an oblique
distribution, though not of course making a northern and a southern flora
stay distinct.
In this sweeping away any constructive suggestion from this instance,
the author would nevertheless emphasize that he considers the method sound;
it is the evidence that is feeble. He beli
^
e
^
ves that the establishment of
floral belts in past times gives by far the best hope of working out past
plant geography and past climate.
So much for the evidence; it is clearly still inadequate although it
does indicate a very different world. This being the case, theory cannot be
expected to wait, and has not done so. The ideas expressed range between two
extreme views. According to one view, climates have been nearly stable, but
plants have changed — or, to speak crudely, luxuriant plants were once tough
enough to endure arctic rigor, but many of them, becoming increasingly tender,
were progressively exterminated in the northern part of their range, surviving
today perhaps only in Indo-Malaya.
By the other view plants — as, for example, palms — were always phy–
siologically much as they are now, and consequently, if they occur as fossils,
must indicate a climate without any severe cold, and indeed with considerable
warmth over much of the year.
The first view implies that p
^
a
^
leobotanical evidence is not of a nature
to help
[:
]
elucidate the problem of part climate and finds favor with few
EA-PS. Harris: Mesozoic Paleobotany
paleobotanists. The second leads straight to the conclusion that the Mesozoic
climate was mild over the Arctic generally, and invites at once the question —
by that cause could this be so? There are a good many quite different answers,
each of which can apparently be demonstrated to fail or be unlikely to be true
in the light of what appears to be fact.
Among advocates of particular theories may be mentioned Berry (3) (who
also gives a valuable summary of evidence); and the famous work of Kőppen and
Wegener (30). A general account (not particularly of the Arctic) favoring
no special theory is given by Scott (44), and there are older accounts of
some historical interest by Nathorst (35) and Seward (47).
EA-PS. Harris: Mesozoic Paleobotany
BIBLIOGRAPHY
1. Arnold, C.A. “Microfossils from Greenland Coal,” Mich. Acad. Sci., vol.15,
p.51, 1931.
2. Backlund, H. “On Fossil Plants from Solitude (Enhomhed) Island,” Geologiska
Főreningen, Stockh.
Főrh
. vol.38, pt.4, 1916.
3. Berry, E.W. “The past climate of the North Polar region,”
Smithson. Misc
.
Coll
. vol.82, no.6, 1930.
4. Drygalski, E. “Grőnland,”
Expedition der Gesellschaft fűr Erdkunde zu
^
Expedition der Gesellschaft fűr Erdkunde zu
^
Berlin
^
Berlin
^
, 1897.
5. Florin, R. “Die Forsilen Ginkgophyten von Franz-Joseph-Land nebst erőr–
terungun űber vermeintleieke Cordaitales mesozoiscken Alters. I,”
Palaeontographica
vol.81, B, p.71, 1936.
6. ----. “----. II,”
Ibid
., vol.82, B, p.1, 1936.
7. ----. “On the Geological history of the Sciadopitinere,”
Svensk. Bot
.
Tidskr
. vol.16, p.260, 1922.
8. Gothan, W. “Die Fossile Hőlzer von Konig Karls Land,” Svensk Vetenskap–
sakad.
Handl
. vol.42, no.10, 1907.
9. ----. “Die Fossile Holzreste von Spitzbergen,” Svensk Vetenskapsakad.
Handl
. vol.45, no.8, 1910.
10. Harris, T.M. “The fossil flora of Scoresby Sound, East Greenland. 1,”
Medd. Grønland
, vol.85, no.2, 1931.
11. ----. “----. 2,”
Ibid
. vol.85, no.3, 1932.
12. ----. “----. 3,”
Ibid
. vol.85, no.3, 1932.
13. ----. “----. 4,”
Ibid
. vol.112, no.1, 1935.
14. ----. “----. 5,”
Ibid
. vol.112, no.2, 1937.
15. ----. “Liassic and Rhaetic plants collected in 1936-38 from East
Greenland,”
Ibid
. vol.114, no.9, 1946.
16. ----. “A new member of the Caytoniales,”
New Phyto
. Vol.32, p.97,
1933.
17. ----. “The Rhaetic flora of Scoresby Sound, East Greenland,”
Medd
.
Grønland
, vol.68, p.43, 1926.
EA-PS. Harris: Mesozoic Paleobotany
18. Hartz, N. “Planteforsteinger fra Cap Sewart i Ostgronland, med. en
historisk Oversigt,”
Ibid
. vol.19, p.217, 1896.
19. Heer, O. “Beiträge zur fossilen Flora Spitzbergens,”
Flora Foss. Arct
.
vol.4, 1876.
20. ----. “ Flora Fossilis Groenlandica,”
Ibid
. vol.6, 1882.
21. ----. “Flora Fossilis Groenlandica 2,”
Ibid
. vol.7, 1883.
22. ----. “Die Keide Flora der Arctischen Zone.” Svenska Vetenskapsakad.
Handl
. vol.12, no.6,
[:
]
1874.
23. ----. “Nachtrage zur fossilen Flora Gronlands,”
Flora Foss. Arct
.
vol.6, 1880.
24.
[:
]
^
Hollick
^
, A. “The Upper Cretaceous floras of Alaska,” U.S.Geol.Surv.
Prof. Pap
. no.159, 1930.
25. Horn, G. “Beiträge zur Kenntris der Kohle von Svalbard,” Norsk Polar–
institutt,
Skr
. no.17, 1928.
26. Johnsson, N. “Neue Mesozoische Pflanzenaus Andö in Norwegen,”
Svensk
.
Bot. Tidskr
. vol.14, p.249, 1920.
27. Knowlton, F.H. “The Jurassic Flora of Cape Lisburne, Alaska,” U.S.Geol.
Surv.
Prof. Pap
. no.85, 1914.
28. ----. “A lower Jurassic flora from the upper Matanuska Valley, Alaska,”
U.S.Nat. Mus.
Proc
. vol.51, no.2158, 1916.
29. Koch, L. “Stratigraphy of Greenland,”
Medd. Grønland
, vol.
[:
]
73, 1929.
30. Köppen, W., and Wegener, A.
Die Klimate der geologischen Vorzeit
. Berlin,
1924.
31. Lundblad, B. “A selaginelloid strobilus from East Greenland (Triassic),”
Dansk. Geol. Foren.
Medd
, vol.11, pt.3, 1948.
32. Martin, G.C. and Katz, F.J. “A Geologic reconnaissance of the Iliamna region
of Alaska,” U.S.Geol.Surv.
Bull
. 485, 1912.
33. Miner, E.L. “Megaspores ascribed to selaginellites, from the Upper Cre–
[:
]
taceous coals of Western Greenland,” Wash.Acad. Sci.
J
. vol.22,
no.18, 19, 1932.
34. ----. “A new Gleichencopsis from the Upper Cretaceous of western
Greenland,”
Amer. J. Bot
. vol.21, no.5, 1934.
EA-PS. Harris: Mesozoic Paleobotany
35. Nathorst, A.G. “Fossil floras of the arctic regions as evidence of
geological climates,”
Geol. Mag
. Lond. 5, vol.8, p.217, 1911.
36. ----. “Fossil Plants from Franz Josef Land.” The Norwegian Polar
Expedition 1893-96.
Scientific Results
. III. London and
Christiania, 1899.
37. ----, “Palaeobot. Mitteilungen. Pseudocyca, ein neue Cycadophyten
gattung aus den Cenomanen Kreideablagerungen Grőnlands,” Svenska
Vetenskapsakad.
Handl
. vol.42, no.5, 1907.
38. ----. “Die Pflanzenfuhrenden Horizonte innerhalb der Grenzschichten
des Jura und eter Kreide Spitzbergens,” Geologiska Főrsningen,
Stockh.
Főrh
. vol.35, pt.4, 1913.
39. ----. “Ueber die Reste eines Brotfruetbaums, Artocarpus Dicksoni ns.p.,
Aus. Den Cenomanon Kreideablagerungen Grønland,” Svenska
Vetenskapsakad.
Handl
. vol.24, no.1, 1890.
40. ----. “Ueber Nathorstia,”
Ibid
. vol.43, no.6, 1908.
41. ----. “Ueber Trias- und Jurapflanzen von der Insel Kotelny,” Akad.
Nauk. Classe Phys. -Mat.
Mem. Zapiski
, ser.8, vol.31, no.2, 1906.
42. ----. “Zur Mesozoischen Flora Spitzbergens,” Svenska Vetenskapsakad.
Handl
. vol.30, no.1, 1897.
43. Newton, E.T. and Teall, J.J.H. “Notes on a collection of rocks and fossils
from Franz Joseph’s Land, made by the Jackson Harmsworth Ex–
pedition during 1894-1896,” Geol. Soc. Lond.
Quart. J
. vol.54,
1897.
44. Scott, W.B. Geological Climates. Smithsonian Inst.
Report
1927, pp.271-87,
1928.
45. Selling, O.H. “A Megaspore from the Mesozoic of Hope Island, Svalbard,”
Botaniska Notiser
, 1945, pt. 1, p.44, 1945.
46. ----. “On Cupressoid Root Remains of Mesozoic Age from the Arctic,”
Arkiv. f
őr Bot
. vol.31A, no.13, 1944.
47. Seward, A.C. “Arctic vegetation past and present,” Roy. Hort. Soc.
J
.
Lond. vol.50, pt. 1, 1925.
48.
[:
]
----. “The Cretaceous plant-bearing rocks of western Greenland,”
Roy. Soc. Lond.
Philos. Trans
. vol.215, p.57, 1926.
49. ----. “The Jurassic Flora of Sutherland,” Roy. Soc. Edinb.
Trans
. vol.
[:
]
47, IV, 1911.
EA-PS. Harris: Mesozoic Paleobotany
50. Seward, A.C. “Notes sur la Flore Cr
e
^
é
^
tacique du Groenland. Etude critique.”
G
e
^
é
^
ol. Soc. Belgique,
Livr. Jub
., p.229, 1925.
51. ----., and Conway, V. “Additional Cretaceous plants from western
Greenland,” Svenska Vetenskapsakad.
Handl
. ser.3, vol.15, no.3,
1935.
52. ----, and ----. “Fossil plants from Kingitok and Kagdlunguak,
West Greenland,”
Medd. Grønland
, vol.93, no.5, 1935.
53. Solms-Laubach, Graf Zu. “Die structurbeitenden Pflanzengesteine von Franz
Josefs Land,” Svenska Vetenskapsakad.
Handl
. vol.37, no.7, 1904.
54. Stopes, M.C. “The flora of the Inferior Oolite of Brora (Sutherland),”
Geol. Soc. Lond.
Quart. J
. vol.63, 1907.
55. Tutin, T.G. “A Cretaceous Gleicheniaceous fern from western Greenland,”
Ann. Bot
. vol.46, p.503, 1932.
56. Walton, J. “On some fossil woods of Mesozoic and Tertiary age from
the arctic zone,”
Ibid
. vol.41, 1927.
57. White, D. and Schuchert, C. “Cretaceous series of the western coast of
Greenland,” Geol. Soc. Amer.
Bull
. vol.9, 1897.
Thomas W. Harris
Arctic Forests of the Cenozoic
EA-Plant Sciences
(Ralph W. Chaney)
ARCTIC FORESTS OF THE CENOZOIC
CONTENTS
|
|
Page
|
|
Introduction
|
1
|
|
Metasequoia
|
3
|
|
Tertiary Forest Zones
|
5
|
|
Cool Temperate Floras
|
6
|
|
Temperate Floras
|
9
|
|
Floras Transitional to Warm Temperate
|
13
|
|
Summary of the Tertiary Forest Record
|
15
|
|
Pleistocene Vegetation
|
20
|
|
Conclusion
|
21
|
|
Bibliography
|
22
|
EA-PS. Chaney: Arctic Forests of the Cenozoic
PHOTOGRAPHIC ILLUSTRATIONS
With the manuscript of this article, the author submitted 4
photographs for possible use as illustrations. Because of the high
cost of reproducing them as halftones, they will not be used. All
photographs are being held at the Stefansson Library.
EA-Plant Sciences
(Ralph W. Ch
e
^
a
^
ney)
ARCTIC FORESTS OF THE CENOZOIC
Introduction
The widespread occurrence of anglosperms and conifers in Cenozoic
rocks provides an increasingly sound basis for our identification of the
plants which lived during the past seventy million years, and for the
reconstruction of the habitats which they occupied. These plant fossils
closely resemble many of the trees now living, as shown by the abundant
impressions of their leaves, and by accompanying remains of seeds, pollen,
and stems. The modern aspect of Cenozoic vegetation is further illus–
trated by the intimate association in the rocks of many genera which are
still found living together. Whereas the plants of the Paleozoic era, and
those of most of the Mesozoic, are largely of types no longer in existence,
the dawn of modern life at the beginning of the Cenozoic era has provided
familiar kinds of trees whose relationships may be readily established.
So we may turn to living forests, made up of genera which have survived
down to our day, to find answers to many questions regarding the environments
of the past. The answers to such questions are particularly significant in
a study of arctic vegetation, for these forests of past ages ranged into
latitudes beyond the northern limits of present-day trees.
Arctic exploration during the past hundred or more years has resulted
EA-PS. Chaney: Arctic Forests of the Cenozoic
in the discovery of many localities where Cenozoic plants are well preserved.
Most of the collections brought back by early explorers were of necessity
meager, and the Europeans who studied them, Goeppert and Heer, did not
always have a sound basis for the conclusions they reached. In later years
additional material has become available, especially in Greenland and Alaska;
we are now in a better position to determine what kinds of trees made up
these forests, and to describe the climatic and other environmental factors
which made possible their existence at high northern latitudes.
All of the Cenozoic floras which have so far been found in the Arctic
are referred to the early stages of the Tertiary period. Future discoveries
may provide evidence of still younger floras there, but for reasons which
will be discussed below we have little basis for supposing that the more
northerly localities have had a climate suitable for tree growth during
the past twenty-five million years, or from the Miocene down to the present.
Opinions differ as to the relative age of the Tertiary floras from several
areas, but we shall here assume that all of them are of approximately the
same age, and that they lived during the Paleocene and Eocene epochs. The
principal regions of occurrence are northern Siberia, the New Siberian
Islands, Alaska, northern Canada including the Arctic Archipelago, western
Greenland, Iceland, and Spitsbergen. A survey of the plants represented in
these localities indicates that there are well-marked differences in composi–
tion from north to south which are strongly indicative of climatic zones.
On the other hand, an abundant genus,
Metasequoia
, has been recorded from
Tertiary floras through a wide range of arctic latitudes. Earlier misidenti–
fications of this conifer have been in large measure responsible for several
misconceptions regarding the character of Tertiary forests in the Far North,
EA-PS. Chaney: Arctic Forests of the Cenozoic
and the climate under which they lived. It therefore seems desirable at
this point to consider the present status of Metasequoia, the dominant
conifer of the Tertiary period not only at high but at many middle latitudes
in the Northern Hemisphere.
METASEQUOIA
Only a few years ago Miki made the announcement that certain conifer
fossils previously referred to
Sequoia
and
Taxodium
from the Tertiary of
Japan were properly referable to a distinct genus, to which he gave the name
Metasequoia
(1941); the principal distinguishing characters indicated were
the decussate arrangement of the leaves and cone-scales, and the attachment
of the cones on naked stalks. Three years later living trees with similar
foliage and cones were found by Tsang Wang in Szechuan, China; an announce–
ment of this discovery was made by Hu in a paper in which he assigned a
fossil from Manchuria, originally described as
Sequoia
, to
Metasequoie
(1946).
A full description of these trees and of their occurrence in central China
soon appeared in a paper by Hu and Cheng (1948). By this time, through the
interest and support of Merrill, seeds had been widely distributed in North
America and Europe, and many of them had been successfully germinated.
Early in 1948, Chaney and Silverman visited the valleys in Szechuan and
Hupeh where
Metasequoia
had survived; here it was apparent that most of the
trees living in association with it were members of genera with which it had
been found in rocks of Cretaceous and Tertiary age (Chaney, 1948: 510).
More detailed studies of the ecology of living
Metasequoia
, subsequently
made by Chu and Cooper (1950), confirm this discovery. A detailed survey
of all the fossil material described under the name of
Sequoia
and
Taxodium
EA-PS. Chaney: Arctic Forests of the Cenozoic
in North America, and reference to illustrations of specimens of these
genera found elsewhere in the Northern Hemisphere, has been made by Chaney,
who concludes that most of the conifer remains from temperate North America
and Asia, and from all the arctic localities, are properly referable to
Metasequoia
(1950). Only in western Europe (
S.
langsdorfii
) and at scattered
localities in the United States (
S.
affinis
) is
Sequoia
a dominant conifer,
and in the United States
Taxodium
(
T.
dubium
) exceeded
Metasequoia
in abundance
only during the
[:
]
Miocene (Chaney, 1949; 127).
This revision comes to be more than a matter of nomenclature when it is
realized that the redwood of China (
M.
glyptostroboides
) has a deciduous habit,
unlike its close relative, the coast redwood (
S.
sempervirens
). A further
significant habit difference may be seen with another close relative, the
swamp cypress (
T.
distichum
), for
Metasequois
seems able to survive in regions
with severe and prolonged winters. (This statement is based upon the successful
planting of
Metasequoia
seedlings in many areas beyond the northern limits of
Taxodium
, and as far north as southeastern Alaska.) Here is a tree which has
shown itself to be hardy at high latitude on the basis of preliminary plantings,
and which also grows well under milder climatic conditions as far south as
Mexico and Florida. A correspondingly wide range of habitats has been pointed
out for the Tertiary representative of
Metasequoia
,
M. occidentalis
, which is
found associated in fossil floras with trees whose modern habitats range from
warm temperate to cool temperate (Chaney, 1949a). The conclusion that
Metasequoia
was dominant at high latitudes during Cenozoic time, and in the
Cretaceous as well, provides a tree admirably suited by its deciduous habit for
living in a region of long, though perhaps not extremely cold, winters. Assumption
of mold climate such as that now required by the coast redwood is no longer
EA-PS. Chaney: Arctic Forests of the Cenozoic
necessary for high northern latitudes during later geologic time; no
Sequoia
of the distichous type is known to have lived beyond southern
Alberta and Montana during the past. (
Sequoia
(
Sequoiadendron
) with spirally
disposed leaves like those of the living
S.
gigantea
ranged farther north in
the past, but like its modern relative may be supposed to have been suited
to wider extremes of temperature.) Not even
Taxodium
, which like
Metasequoia
has a deciduous habit,
[:
]
is known to occur in the fossil record at the most
northerly localities. From Grinnell Land south to the northern United States,
Metasequoia
was the dominant conifer of the Cenozoic forest, as judged by the
abundance of its foliage and cones in the fossil record.
TERTIARY FOREST ZONES
The vegetation which lived at high northern latitudes during the early
epochs of the Cenozoic era is commonly referred to as the Arcto-Tertiary Flora.
From this name it should not be concluded that all of the genera represented
had their origin during the Tertiary period, for many of them appeared during
the preceding Cretaceous period; nor are we justified in the inference of an
exclusively arctic origin for this major floral unit, for some of its members
appear also to have lived at lower latitudes during the early days of the
Cenozoic. However the use of the designation “Arctic Tertiary” is highly
appropriate with reference to this early Cenozoic vegetation of the North,
in view of its widespread distribution there, and of its southward migration
during later Tertiary epochs; large segments of the Arcto-Tertiary Flora still
survive in many parts of the Northern Hemisphere, especially in middle latitudes.
The outstanding feature of the Arcto-Tertiary Flora, both past and modern,
is its mixture of broad-leafed deciduous trees with conifers, both deciduous
EA-PS. Chaney: Arctic Forests of the Cenozoic
and evergreen. But an alysis of the early Cenozoic vegetation from various
localities in the Arctic indicates that it varied as widely from place to
place, and especially at different latitudes, as do the forests of today.
We shall therefore consider the record of these ancient forests with reference
to the climatic types which are represented. The location of the fossil
localities is shown on the accompanying map (Figure 1). Table I gives
lists of the principal general from the several localities; these include only
the better known and reliably identified woody plants.
Cool Temperate Floras
Floral units of this type are found in the interior of Siberia and
Canada, and on the most northerly of the islands of the Arctic Sea with the
exception of Spitsbergen. For reasons considered below, the Tertiary flora
of Spitsbergen is of a typically temperate type, with a much larger assemblage
of genera than is found at corresponding latitudes elsewhere. The following
localities contain representatives of the cool temperate forest, including
such typically northern families as the Pinaceae, Salicaceae, and Betulaceae,
and three genera now restricted to northeastern and central Asia,
Ginkgo
,
Metasequoia
, and
Cercidiphyllum
.
Interior of Siberia
. A small collection studied by Heer (1878) from
Tsohirimyi on the Lena River (lat. 65° 30′ N.), includes a fern (
Asplenium
),
leaves of
Ginkgo
, numerous foliage
^
shoots
^
of
Metasequoia
(by him referred to three
species of
Taxodium
),
[:
]
foliage shots of a more scaly type which may be
assignable to
Sequoiadendron
(by him referred to
Sequoia
) and fragmentary
leaves of angiosperms, two of which seem to represent
Cercidiphyllum crenatum
(his
Populus arctica
? and
Paliurus colombi
). Fragmentary angiosperm leaves
EA-PS. Chaney: Arctic Forests of the Cenozoic
from Tas-takh Lake are mentioned by Kryshtofovich (1929) as referable to
poplar and walnut, and it seems probable that the former would now be
recognized as
Cercidiphyllum
. Still farther north on the Taimyr River
(1868), Heer recognized only foliage resembling pine (pinites).
New Siberian Islands
. Similar plants have been described by
Schmalhausen
(1890) from latitude 76° N. A fern (
Aspidium
),
Metasequoia
represented by
foliage and cones, another conifer considered to represent Pinus, and
Cercidiphyllum crenatum
(
Populus richardsoni
) are all that can be surely
recognized from the material figured, with fruits named
Nyssidium geminatum
possibly representing
Cercidiphyllum
. Coniferous wood, some of which resembles
that of
Metasequoia
, is also figured.
Mackenzie Valley
. In his first volume of
Flora Fossilis Arctica
(1868),
Heer included a brief discussion of the occurrence of material collected by
Richardson in the Mackenzie Basin at 65° N. latitude, near the mouth of Great
Bear River. Several species are based on material so fragmentary as to give
no adequate basis for their generic identification; I recognize
Metasequoia
,
Populus
,
Salix
,
Betula
, and
Cercidiphyllum
, all of which are members of other
cool temperate floras. In a second paper (1880), to which were added specimens
collected by the Hudson’s Bay Company, Heer listed several additional genera;
but the specimens of
Juglans
,
Platanue
,
Magnolia
,
Tilia
, and
Viburnum
which
he figured can scarcely be considered convincing evidence of their occurrence.
The genera cited above appear to represent all that can be recognized with
any certainty.
Banks Island
. Cones referable to spruce (
Picea
) were assigned by Heer
(1868) to
Pinus
(
Abies
)
macclurii
, and wood specimens studied by Cramer, to
the form genus
Cupressinoxylon
, and to birch (
Betula macclintockia
). The
latitude of this occurrence is 740 N.
EA-PS. Chaney: Arctic Forests of the Cenozoic
Bathurst Island
. Fragmentary needles referred by Heer (1868) to pine
(
P. bathursti
) represent the only plant remains known from this locality
(latitude 76°N.). They appear to resemble spruce rather than pine, but
are not well enough preserved to establish the presence of either genus.
Southern Ellesmere Island
. The foliage of
Metasequois
figured by
Nathorst (he called it Sequoia) from this locality (latitude 77° 20′ N.)
is extremely well preserved; wood referable to
Metasequoia
is also recorded
(1915). It seems rather unlikely that the foliage shoots referred to
Glyptostrobus
are correctly identified in view of its present restriction
to southeastern China. However, they resemble
Glyptostrobus
, and the Tertiary
occurrence of this genus elsewhere at high northern latitudes suggests the
possibility of its wider temperature tolerance in the past. Fragments of
dictoyledonous leaves resemble those of
Cercidiphyllum
.
Grinnell Land
. This northernmost Tertiary flora, at latitude 82° N., is
also the largest
^
^
in the group here considered to represent a cool temperate type
of vegetation. Heer’s list of species (1878) contains many apparent misidenti–
fications, as pointed out by Berry (1922: 9). Our revision, based upon an
examination of the figures in
Flora Fossilis Arctica
, includes only the genera
whose presence seems clearly established:
Equisetum
,
Picea
(or
Abies
),
Pinus
,
Metasequoia
, indeterminate grasses and/or sedges,
Betula
,
Cercidiphyllum
.
To these may probably be added to water lilly,
Nymphaea
, which is represented
by characteristic roots;
Salix
and
Populus
,
which is represented by charac
–
teristic
listed by Heer, are wholly in place in this assemblage, and it is
possible
[:
]
that some of his specimens may represent these genera (see pl.8,
figs. 8, 6).
EA-PS. Chaney: Arctic Forests of the Cenozoic
Temperate Floras
These floras, for the most part of more southerly occurrence than the
preceding, are made up of plants which are typically temperate in their
modern distribution. Among the common families are the Pinadeae, Taxodiaceae,
Salicaceae, Betulaceae, Juglandaceae, Fagaceae, Ulmaceae, Platanceae,
Aceraoeae, and Cercidiphyllaceae. Grasses and sedges are well represented
in several units. All of the genera known to occur farther north have
been recorded here, together with many others which are widespread in
Tertiary floras of later age and at lower latitudes. This unit constitutes
the typical Arcto-Tertiary Flora which has survived in modified form in
so many areas of the Northern Hemisphere. Like those of the cool temperate
type, these floras contain a mixture of deciduous angiosperms and conifers,
as well as some evergreen conifers.
Iceland
. This small
[:
]
flora, as described by Heer (1868), is typically
temperate. It is significant to note that
Metasequoia
is not recorded, nor
is it known from the adjacent Tertiary floras of western Europe. It is
impossible to determine from Heer’s figures what conifer is represented by
his
Sequoia sternbergi
; it is surely not a member of the Taxodiaceae, but
may be
Abies
,
Picea
, or both; some of the seeds figueed as
Pinus
seem
clearly referable to
Abies
; other seeds appear to represent
Pinus
. In
addition to sedges and aquatic plants, there are recorded willow (
Salix
),
walnut (
Juglans
), several members of the Betulaceae and Fagaceae, and such
common genera as sycamore (
Platanus
) and maple (
Acer
). It is probable that
this list will be greatly supplemented when more recently made collections
have been studied.
Spitsbergen
. The occurrence of plant fossils at this northerly locality
EA-PS. Chaney: Arctic Forests of the Cenozoic
(lat. 77° 30′ to 78° 5′ N.), in Eocene strata associated with coal, has
long been known; Heer presented the results of his preliminary study in
Volume I of
Flora Fossilis Arctica
(1868), and in ensuing years added other
species to the list (1871, 1876). The flora is smaller than those from
Alaska and Greenland, but includes most of the temperate genera which
characterize these floras to the south. Among the common families are the
Taxodiaceae, Salicaceae, Betulaceae, Fagaceae and Cercidiphyllaceae.
Glyptostrobus
and
Magnolia
suggest a fairly mild temperature. Grasses
and sedges are unusually abundant. Plate 1 shows a specimen from the
collections of the United States National Museum; on this slab of carbona–
ceous shale, collected by Schuchert and White on Advent Bay, are many
foliage shoots of
Metasequoia
, together with leaves of walnut and birch.
Northeastern Siberia
. In his paper on the Tertiary Flora of the Korf
Gulf, Kamchatka (1934), Kryshtofovich gives a summary of current knowledge
of the vegetation of this general region. Goeppert (1867) first described
a small flora including
Metasequoia
(
Taxodium
),
Carpinus
,
Alnus
, and
Juglans
.
Nathorst published a list based on collections from Kamchatka by Dubovsky
in his paper on the fossil floras of Japan (1888), with the following genera:
Equisetum. Metasequoia
(
Sequoia
),
Salix
,
Populus
,
Alnut
,
Acer
,
Cercidiphyllum
(
Populus
),
Fraxinus
, and
Cornus
. Palibin’s list from the Commander Islands
(1905) includes a species of
Sequoia
which is now known to represent
Taxodium
in part and may also be assignable to
Metasequoia
; he also
reports the occurrence of
Glyptostrobus
,
Thuites
, two grasses, and leaves
referred to
Cinnamomum
which Kryshtofovich considers to have a doubtful
status. The flora of the Anadyr River, as listed by Kryshtofovich and
assigned to the Paleocene (in an undated paper) includes the following
EA-PS. Chaney: Arctic Forests of the Cenozoic
trees and shrubs:
Metasequois
(under the names
Taxodium
and
Sequoia
),
Glyptostrobus
,
Alnus
,
Acer
,
Cercidiphyllum
(
Populus
,
Vitis
, and
Nyssa
.
All are common members of other high latitude Tertiary floras, but without
referenced to his material it is impossible to confirm these determinations.
The Korf Gulf flora itself is the largest and most adequately illustrated
from this area, though several of Kryshtofovich’s figures are not convincing.
He indicates his opinion that it is of Oligocene age, but there appears to
be little basis for separating it from other Eocene floras of adjacent regions
and latitudes. In addition to
Equisetum
and a fern, he lists a total of 24
forms, all of which fall in the temperate families above mentioned. It is
difficult to tell from the illustrations whether all of his genera are
actually represented; a leaf doubtfully referred to
Quercus
seems not to
be assignable to that genus, and some question may be raised regarding the
leaves referred to
Carya
and
Celtis
; but the majority of Kryshtofovich’s
generic identifications seem to be sound.
Alaska
. The Tertiary floras of Alaska received their first comprehensive
treatment in Heer’s second volume of
Flora Fossilis Arctica
(1871). Extended
study by Knowlton and Hollick has provided material for a more recent publica–
tion in which Hollick considered their age to be Eocene (1936). He recognized
350 forms, including an alga, 13 ferns, and 2 species of
Equisetum
; among
the gymnosperms he describes 3 cycads, 2 species of
Ginkgo
, and 26 conifers;
angiosperms make up the remainder of the flora, with 14 monocotyledons and
288 dicotyledons, and with an additional 10 species assigned to form genera.
Many of Hollick’s genera do not seem to be properly identified, and he
seems to have recognized too many species in certain genera; however, there
is a sufficient number of well-characterized forms to provide an adequate idea
EA-PS. Chaney: Arctic Forests of the Cenozoic
of the forests which lived in Alaska during the Eocene. Since the plants
recorded from several regions and latitudes show significant differences,
I shall consider them in four groups, starting at the north.
The Bering Sea Region
. Collections on St. Lawrence Island and the
adjacent mainland have been made in recent years under my direction.
Material brought down from St. Lawrence Island (lat. 63° 30′ N.) by Collins
and Jones includes
Metasequoia
,
Alnus
or
Betula
,
Platanus
, and probably
Cercidiphyllum
(Chaney, 1934). A larger collection made by Mason has never
been described. The occurrence here
^
^
of
Platanus
is of interest, since it is
a typically temperate genus at the present time. On the opposite mainland,
at Coal Creek in the Norton Sound area, Mason collected
Taxodium
,
Platanus
,
and leaves which probably represent
Diospyros
.
The Yukon Basin
. In central Alaska fossil plants have been collected in
the valley of the Yukon from latitude 65° nearly to 66° North, and southward
in the drainage of the Tanana River to about latitude 63° N., as ma
n
y be
seen on the charts and map in Hollick’s
Professional Paper
. The common
families are Pinaceae, Taxodiaceae, Salicaceae, Juglandaceae, Betulaceae,
Fagaceae, Cercidiphyllaceae, Platanaceas, and Aceraceae. All the genera
have living species in temperate regions, with
Diospyros
the only genus
whose modern range is largely in the tropics.
Central Alaska
. (
Alaska Peninsula and Cook Inlet Region
). The florules
collected from latitude 56° N. in the Alaska Peninsula northeastward to the
Matanuska Valley, at nearly latitude 62° N., have essentially the same compo–
sition. They appear to represent an assemblage intermediate between that
of the Yukon Basin and southeastern Alaska, with many genera in common on
both sides; and with oaks more numerous than elsewhere. Although dominantly
EA-PS. Chaney: Arctic Forests of the Cenozoic
temperate in aspect, this intermediate flora includes several plants
which now range into southern regions, such as swamp cypress (
Taxodium
),
water pine (
Glyptostrobus
), palm (
Flabellaria
), magnolia (
Magnolia
), sweet
gum (
Liquidambar
), laurels (
Lindera
and
Persea
), and persimmon (
Diospyros
).
Floras Transitional to Warm Temperate
It would be going too far to state that either the flora from Kupreanof
Island in southeastern Alaska, or that from Disko Island in western Green–
land, are typically warm temperate in aspect. But the presence in the former
of cycads, a palm, representatives of the Lauraceae, and
Dillenia
is strongly
indicative of an ecotonal belt between the typically temperate floras in
central Alaska and the warm temperate to subtropical floras of the northern
United States; the Greenland flora, lying several degrees farther north, shows
less indication of mild temperatures, but with its palms and laurels it like–
wise bears an ecotonal relationship. Most of the trees at both localities
were typically temperate.
Southeastern Alaska
. The most productive localities in this region are
on Hamilton Bay at the north end of Kupreanof Island, in latitude 57° N. A
majority of the specimens are of temperate types, in such families as the
Pinaceae, Taxodiaceae, Salicaceae, Juglandaceae, Betulaceae, and Fagaceae;
but in addition to the warm temperate forms above mentioned, such genera as
Taxodium
,
Glyptostrobus
,
Zelkova
,
Magnolia
,
Diospyros
, and
Liquidambar
are
suggestive of moderate winter temperatures. The most abundant conifer,
Metasequoia
, is found today in a similar ecotone between the subtropical
lowland and the temperate upland forests of central China. Plate 2 shows
a slab of shale bearing a leaf of
Dioon
together with foliage shoots of
Metasequoia
. Plate 3 shows the association of this conifer with the more
EA-PS. Chaney: Arctic Forests of the Cenozoic
temperate
Alnus
and
Juglans
.
Western Greenland
. No arctic flora has aroused such wide interest, or
has so greatly stimulated scientific and popular imagination, as the
collections from Disko Island, on the west coast of Greenland. Again it was
Oswald Heer who first made known the details of this vegetation (1868, 1871,
1874, 1880); in his final volume of
Flora Fossilis Arctica
(1883) he listed
a Tertiary flora containing 282 forms; 8 of these represent fungi, and one
a moss; 19 are ferns; there is a doubtful species of lycopod, a
Psilotum
-like
plant, and an
Equisetum
; 27 gymnosperms are members of the Coniferales, and
Ginkgo
is also recorded; the remaining 223 forms represent angiosperms, with
21 monocotyledons, 182 dicotyledons, and 20 assigned to form genera. (As in
the case of Hollick’s Alaska list, Heer’s Greenland flora shows many generic
misidentifications and is characterized by over-speciation.)
Whether or not all of this material comes from Tertiary horizons, or
whether it may in part come from the older Cretaceous as has been suggested,
is a question which can not be considered here. The occurrence of most of
the typical species of this Greenland flora in other arctic floras recognized
as Eocene seems to indicate that most of the fossils of this assemblage occur
in rocks of Tertiary age. We need not consider here the unsound basis for
Heer’s reference of this and other northern floras to the Miocene; nor will
it be profitable to attempt any general revision of Heer’s determinations,
involving as they did the recognition of many species on the basis of evidence
no longer held adequate. For our purposes it will be sufficient to indicate
that the same temperate families found elsewhere in the Arctic are abundantly
represented, and that there is also a group whose modern
[:
]
equivalents range
into lower latitudes; this includes
Zelkova
,
Persea
,
Diospyros
,
Liquidambar
,
EA-PS. Chaney: Arctic Forests of the Cenozoic
Magnolia
, the palm,
Flabellaria
, and the three widespread genera of the
Taxodiaceae
,
Metasequoia
,
Taxodium
, and
Glyptostrobus
.
Summary of the Tertiary Forest Record
The geographic distribution of the well-established and abundant genera
recognized in the older Tertiary deposits of the Arctic is shown in Table I.
Complete analysis of this table cannot here be attempted, but it is readily
apparent that the floras may be divided into a relatively small northern
group and a major southern one. Whereas the genera of the northern group
are recorded also from the southernmost floras, the genera of the southern
group do not range far to the north. The Arcto-Tertiary Flora of the Eocene
is here shown to represent a homogeneous forest, limited to a few genera on
its northern borders, and on the south setting up an ecotonal relationship
with the warm temperate floras of lower latitudes. Fossil wood found at many
arctic localities shows well-marked growth rings characteristic of the seasonal
climate of temperate regions.
Complete reliance may not be placed upon conclusions derived from a
generic analysis, for some genera such as
Pinus
,
Populus
, and
Diospyros
now
cover a wide range of latitudes and environments; other genera such as
Ginkgo
,
Metasequoia
, and
Glyptostrobus
are so limited in their modern distribution
as to leave some doubt as to their earlier climatic requirements. However
there seems to be little question that forest zoning of the Arcto-Tertiary
Flora was well developed at the beginning of the Cenozoic era, and that this
zoning was closely related to climatic factors controlled by latitude, with
local modification resulting from ocean currents.
Comparison with the latitudinal occurrence of similar zones of vegetation
in the Northern Hemisphere today (Zon and Sparhawk, 1923: map opposite p. 14;
EA-PS. Chaney: Arctic Forests of the Cenozoic
|
Table I. Geographic Distribution of Tertiary Floras.
|
|
|
1
|
2
|
3
|
4
|
5
|
6
|
7
|
8
|
9
|
10
|
11
|
12
|
13
|
14
|
|
Ginkgo
|
x
|
|
|
|
|
|
|
|
|
x
|
x
|
|
x
|
x
|
|
Pinus
|
x
|
x
|
|
|
|
x
|
|
x
|
|
x
|
|
x
|
|
x
|
|
Picea
|
|
|
|
x
|
|
x
|
|
x
|
|
|
x
|
|
|
x
|
|
Metasequoia
|
x
|
x
|
x
|
|
x
|
x
|
|
x
|
x
|
x
|
|
|
x
|
x
|
|
Populus
|
|
|
x
|
|
|
|
|
x
|
|
x
|
x
|
x
|
x
|
x
|
|
Salix
|
|
|
x
|
|
|
|
x
|
x
|
|
x
|
x
|
x
|
|
x
|
|
Betula
|
|
|
x
|
x
|
|
x
|
x
|
x
|
|
|
x
|
x
|
|
x
|
|
Cercidiphyllum
|
x
|
x
|
x
|
|
x
|
x
|
|
x
|
x
|
x
|
x
|
x
|
x
|
x
|
|
Taxodium
|
|
|
|
|
|
|
|
|
x
|
|
x
|
x
|
x
|
x
|
|
Glyptostrobus
|
|
|
|
|
|
|
|
x
|
|
|
x
|
x
|
x
|
x
|
|
Juglans
|
|
|
|
|
|
|
x
|
x
|
|
x
|
x
|
x
|
x
|
x
|
|
Carya
|
|
|
|
|
|
|
|
x
|
|
x
|
x
|
|
|
|
|
Corylus
|
|
|
|
|
|
|
x
|
x
|
|
|
x
|
x
|
x
|
x
|
|
Carpinus
|
|
|
|
|
|
|
x
|
x
|
|
|
x
|
x
|
x
|
x
|
|
Alnus
|
|
|
|
|
|
|
x
|
x
|
x
|
x
|
x
|
x
|
x
|
x
|
|
Castanea
|
|
|
|
|
|
|
|
|
|
|
x
|
|
x
|
x
|
|
Fagus
|
|
|
|
|
|
x
|
|
|
|
|
x
|
x
|
x
|
x
|
|
Quercus
|
|
|
|
|
|
|
x
|
x
|
|
x
|
x
|
x
|
x
|
x
|
|
Ulmus
|
|
|
|
|
|
|
|
|
|
|
x
|
|
x
|
x
|
|
Zelkova
|
|
|
|
|
|
|
x
|
|
|
|
x
|
|
x
|
x
|
|
Platanus
|
|
|
|
|
|
|
x
|
|
x
|
x
|
|
x
|
|
x
|
|
Acer
|
|
|
|
|
|
|
x
|
x
|
|
x
|
x
|
x
|
|
x
|
|
Diospyros
|
|
|
|
|
|
|
|
|
|
x
|
x
|
|
|
x
|
|
Liquidambar
|
|
|
|
|
|
|
|
|
|
|
x
|
|
|
x
|
|
Cornus
|
|
|
|
|
|
|
|
x
|
|
|
x
|
x
|
|
x
|
|
Fraxinus
|
|
|
|
|
|
|
|
x
|
|
x
|
x
|
|
|
x
|
|
Tilia
|
|
|
|
|
|
|
|
|
|
|
|
x
|
x
|
|
|
Viburnum
|
|
|
|
|
|
|
|
|
|
x
|
x
|
x
|
|
x
|
|
Ceratozamia
|
|
|
|
|
|
|
|
|
|
|
|
|
x
|
|
|
Dioon
|
|
|
|
|
|
|
|
|
|
|
|
|
x
|
|
|
Flabellaria
|
|
|
|
|
|
|
|
|
|
|
x
|
|
x
|
x
|
|
Magnolia
|
|
|
|
|
|
|
|
|
|
|
x
|
x
|
x
|
x
|
|
Lindera
|
|
|
|
|
|
|
|
|
|
|
x
|
|
|
|
|
Persea
|
|
|
|
|
|
|
|
|
|
|
x
|
|
x
|
x
|
|
Sassafras
|
|
|
|
|
|
|
|
|
|
|
|
|
x
|
x
|
|
Malapoenna
|
|
|
|
|
|
|
|
|
|
|
|
|
x
|
|
|
Dillenia
|
|
|
|
|
|
|
|
|
|
|
|
|
x
|
|
|
1 |
Siberia, interior
|
8 |
Siberia, northeastern
|
|
2 |
New Siberia Islands
|
9 |
Alaska, Bering Sea
|
|
3 |
Mackenzie Valley
|
10 |
Alaska, Yukon Basin
|
|
4 |
Banks Island
|
11 |
Alaska, central
|
|
5 |
South Ellesmere Island
|
12 |
Spitsbergen
|
|
6 |
Grinnell Land
|
13 |
Alaska, southeastern
|
|
7 |
Iceland
|
14 |
Greenland
|
EA-PS. Chaney: Arctic Forests of the Cen
^
o
^
zoic
Munns, 1938; Kudlenok, in Balzak, Vasyutin and Feigin: 60) indicates
their more northerly position during the Eocene epoch. The northern limit
of the modern coniferous forest is approximately 70° N. in North America
and Eurasia, with a northward extension to about 74° on the Taimyr Peninsula;
the northernmost known occurrence of the cool temperate floras of the Eocene
(
Pinus
,
Picea
,
Metasequoia
, together with
Ginkgo
,
Populus
,
Salix
,
Betula
,
Cercidiphyllum
) is in Grinnell Land, at latitude 82° N. Tundra is now the
prevailing type of vegetation at this and all the other cool temperate Eocene
localities. It may be noted that
Salix
and
Betula
occur as shrubs in Spits–
bergen, at nearly latitude 80° N.;
Pinus
extends to 66° in Alaska, and
Picea
to 67°;
Ginkgo
is reported to have lived under cultivation in Iceland;
Metasequoia
, as elsewhere stated, has been planted in southeastern Alaska
and has survived an exceptionally cold winter;
Cercidiphyllum
ranges north
into Hokkaido, and there is no reason to believe it might not grow under
cultivation much farther north. This group of genera, while relatively
hardy today, does not extend as far north as its known Eocene limits, though
the discrepancies are less marked than in the case of the typically temperate
forest
[:
]
.
Considering the present northern limits of some of the more typical
temperate genera in North America,
Platanus
extends to 45° N.,
Juglans
and
Carpinus
to 47°,
Quercus
to 50°, and Acer to 55°. The mixed deciduous forest,
which includes most of the temperate unit of the Eocene, finds its northern
limit at about 50° in North America and Asia, extending north to
[:
]
60° in
Europe; its northernmost Eocene limits were from 60° to 65° in Alaska, Iceland,
and Kamchatka, and reached nearly to latitude 80° N. in Spitsbergen.
The group of southern genera, recorded from the Eocene of southeastern
EA-PS. Chaney: Arctic Forests of the Cenozoic
Alaska and western Greenland, includes four genera which have typically
temperate species in North America,
Sassafras
and
Lindera
which range
north to 45°,
Magnolia
which reaches 43°, and
Persea
which extends as
far north as 39°; all of these genera have their principal occurrence
much farther south. The northernmost limit of palm (
Sabal
) today is at
about latitude 35° N.
Dioon
and
Ceratozamia
are restricted to southern
Mexico, at about latitude 20°, while
Dillenia
and
Malapoenna
occur still
farther south. We may conclude that discrepancies between the Eocene and
modern distribution of the several forest types are greatest in the case of
the warm temperate genera, and least in the case of the genera making up
the cool temperate unit. Similar space relations for the Arcto-Tertiary
Flora in northeastern Asia have been noted from the Eocene to the present.
(Chaney and Hu, 1940: 126-134).
When we survey the older Tertiary vegetation at middle latitude in
Eurasia and North America, it becomes apparent that other zones occupied
by warm temperate and subtropical forests lay to the
[:
]
south, in
middle latitudes which are today occupied by temperate forests. Durham has
shown (1950) that tropical marine faunas lived as far north as Washington
during Eocene time, and has concluded from the study of faunal distribution
that “during the Cenozoic the continents and poles must have been in approxi–
mately the same positions as at present.” This conclusion is fully confirmed
by the distribution of Eocene vegetation, as outlined in an earlier paper by
the writer (1940: 481-486). Reference to the map of distribution (Figure 1)
will show that the cool temperate floras of the Eocene have a more southerly
position in the continental interiors (Siberia, Mackenzie Basin) than in the
Arctic Archipelago where the moderating influence of ocean currents from the
EA-PS. Chaney: Arctic Forests of the Cenozoic
south brought milder winter temperatures. The bending northward of
temperate forest distribution (temperate isoflor) may best be seen in the
case of Spitsbergen, which must during the Eocene, as now, have held a
[:
]
position north of the major seaway between Greenland and Norway.
A smaller seaway through Davis Strait appears to have been responsible for
the northward extension of the warm phase of the temperate flora to Disko
Island on the west coast of Greenland; the Eocene equivalent of the Japan
Current was responsible for the occurrence of cycads, laurels, and
Dillenia
in southeastern Alaska. Distribution of early Cenozoic forests strongly
supports the conclusion that continents and ocean basins have held essentially
their present position during at least this latest era of geologic time.
A question has often arisen in connection with the northern distribution
of trees during the Eocene: Would trees have been able to maintain themselves
at high latitudes during the long period of winter darkness? With the
recently acquired knowledge that our northernmost conifer was not an evergreen
Sequoia
but a deciduous
Metasequoia
, and with our realization that its
associates were largely deciduous plants which today range far to the north,
rather than the
[:
]
fanciful figs of earlier opinion, we may answer this
question in the affirmative. The amount of sunshine received by plants now
living within the Arctic Circle is wholly adequate for their growth and
reproduction. And if, as many climatologists have argued, the polar icecaps
of today are a recent development, we are not forced to include the handicap
of deeply frozen ground beneath our Eocene forests. Some sort of meridional
continental drift, always maintaining the relative positions of the northern
continents and their intervening seaways, might have carried the rocks con–
taining the fossil record of temperate forests northward from middle to high
EA-PS. Chaney: Arctic Forests of the Cenozoic
latitudes; but judging from the position of Eocene floras around it, the
North Pole seems to have maintained a constant position during the past
seventy million years. Rather than endorsing so complicated and unsupported
a theory as continental drift, and having in mind the record of the Arcto–
Tertiary Flora at successively lower latitudes — both in western North
America and eastern Asia — in rocks of younger age, I find more acceptable
the alternative of forest migration southward under the compulsion of
climatic change.
PLEISTOCENE VEGETATION
The records of high latitude forests during the epoch immediately
preceding our day are scattered and incomplete. I shall consider here the
only adequate material from North America, which has been studied by Chaney
and Mason (1936). The collection was made in the frozen alluvial deposits
near Fairbanks, Alaska, at latitude approximately 65° N.; these deposits
also contain abundant remains of Pleistocene mammals which are elsewhere
discussed by Colbert.
Twenty-seven plants have been recognized, all of which appear to be
closely related to, or identical with, species now living. There are five
species of fungi, a puffball (
Bovista
) and four-bracket fungi (
Fomes
,
Ganoderma
) which are parasitic on woody plants. Eight species of trees and
shrubs, represented by leaves, fruits, and wood, fall in the following genera:
Picea
,
Populus
,
Salix
,
Betula
; no differences can be noted between the
fossil specimens and living species of spruce, aspen, willow, and birch now
in boreal Alaska. There are fourteen species of herbs which make up the
largest element of the Fairbanks flora, as is also the case in the modern
EA-PS. Chaney: Arctic Forests of the Cenozoic
vegetation of today. These species are largely represented by seeds,
which from their mode of occurrence are interpreted to represent food
caches of rodents. Among the most abundant herbs are the cotton-sedge
(
Eriophorum
) and the common sedge (
Carex
), both of which are so character–
istic of living vegetation at high latitudes. Other herbs are a sandwort
(
Arenaria
); the moss-campion (
Silene
); a buttercup (
Ranunculus
); a
member of the mustard family,
Draba
; a cinquefoil (
Potentilla
); a member
of the primrose family,
(
Androsace
; A phlox similar to the circumpolar
species
P. sibirica
; and a dandelion,
Taraxacum ceratophorum
, which is
also circumpolar in its modern distribution.
Conclusion
No significant difference can be noted between the Pleistocene
vegetation of the Fairbanks area and the modern flora or this and other
regions at high northern latitudes. And while we may regret the gap in
the record from Eocene to Pleistocene — a gap found not only in Alaska
but elsewhere in the Arctic — it is fortunate to have this evidence of a
past so immediate that it almost merges into the present. Of the genera
known in Eocene floras of the North, only
Picea
,
Populus
,
Salix
, and
Betula
survived into the Pleistocene, and their present-day habit is more nearly
as shrubs than trees. During the tens of millions of years following the
Eocene, the Arcto-Tertiary Flora has been gradually shifted southward from
high latitudes, leaving behind only its hardiest members. In the modern
forests of northeastern Asia, eastern North America, and to a lesser extent
in western Europe, we may see the early Cenozoic vegetation of the Arctic,
and measure the changes which have come about during the era in which we
live.
Distribution of Tertiary Floras in the Arctic
EA-PS. Chaney: Arctic Forests of the Cenozoic
BIBLIOGRAPHY
1. Balzak, S.S., Vasyutin, V.F., and Feigin, G. 1949.
Economic geography
of the U.S.S.R.
Macmillan Co.
2. Berry, Edward. 1922. “A possible explanation of Upper Eocene climates.”
Proc. Am.Phil.Soc
. 61: 1-14.
3. Chaney, Ralph W. 1930. “A Sequois forest of Tertiary age on St.
Lawrence Island.”
Science
72; 653-654.
4. ----. 1940. “Tertiary forests and continental history.”
Bull
.
Geol.Soc.Am
. 51: 469-488.
5. ----. 1948. “The bearing of the living Metasequois on problems of
Tertiary paleobotany.”
Nat.Acad.Sci
. 34 (11): 503-515.
6. ----. 1949. “The Miocene occurrence of Sequois and related conifers
in the John Day Basin.”
Nat.Acad.Sci
. 35 (3): 125-129.
7. ----. 1949a. “Early Tertiary ecotones in western North America.”
Nat.Acad.Sci.
35 (7): 356-359.
8. ----. 1951. “A Revision of Fossil Sequois and Taxodium in western
North America based on the recent discovery of Metasequoia.”
Trans.Amer.Phil.Soc
. ns 40, Pt. 3:
9. Chaney, Ralph W. and Mason, H.L. 1936. “A Pleistocene flora from
Fairbanks, Alaska.”
Amer.Mus.Novitates
887: 1-17.
10. Chu, Kwei-ling and Cooper, William S. 1950. “An ecological reconnaissance
in the native home of Metasequois glyptostroboides.”
Ecology
31:
260-278.
11. Durham, J. Wyatt. 1950. “Cenozoic marine climates of the Pacific Coast.”
U.S.Geol.Soc.Am.Bull.
61: 1243-1264.
12. Goeppert, R. 1867. “Ueber die Tertiarflora der Polarländer.”
Jahresbericht d. Sches.Gesellechaft
44: 50.
13. Heer, Oswald. 1868.
Flora Fossilis Arctica
, 1. Pt.1. Taimyr: 41.
14. ----. 1868a.
Flora Fossilis Arctica
, 1. Pt.2. Miocene Flora von
Nordgronland: 86-130.
15. ----. 1868b.
Flora Fossilis Arctica
, 1. Pt. 2. Bathurst-Insel:
133-134.
16. ----. 1868c.
Flora Fossilis Arctica
, 1. Pt. 2. Miocene Pflanzen
des Bankslandes: 134-135.
EA-PS. Chaney: Arctic Forests of the Cenozoic
17. ----. 1868d.
Flora Fossilis Arctica
, 1. Pt. 2. Miocene Flanzen
vom Mackenzie: 135-139.
18. ----. 1868e.
Flora Fossilis Arctica
, 1. Pt. 2. Miocene Flora
von Island: 139-155.
19. ----. 1868f.
Flora Fossilis Arctica
, 1. Pt. 2. Miocene Flora
von Spitzbergen: 155-161.
20. ----. 1871.
Flora Fossilis Arctica
, 2. Pt. 2. Flora fossilis
Alaskana: 1-41.
21. ----. 1871a.
Flora Fossilis Arctica
, 2. Pt. 3. Der Miocene
Flora und Fauna Spitzbergens: 1 - 98.
22. ----. 1871b.
Flora Fossilis Arctica
, 2. Pt. 4. Contributions to
the fossil flora of North-Greenland: 445-488.
23. ----. 1874.
Flora Fossilis Arctica
, 3. Pt. 3. Nachträge zur
miocenen Flora Grőnlands: 1-29.
24. ----. 1876.
Flora Fossilis Arctica
, 4. Pt. 1. Beiträge zur
Fossilen Flora Spitzbergens: 1-93.
25. ----. 1878.
Flora Fossilis Arctica
, 5. Pt. 1. Die miocene Flora
des Grinnell-Landes: 1-38.
26. ----. 1878a.
Flora Fossilis Arctica
, 5. Pt. 2. Tertiare Pflanzen
vom Tschirimyi-Felsen an der Lena. Tschirimyi: 30-36.
27. ----. 1880.
Flora Fossilis Arctica
, 6. Pt. 2. Nachträge zur
fossilen Flora Grőnlands: 1-17.
28. ----. 1880a. Flora Fossilis Arctica, 6. Pt. 3. Miocenen Flora
von Nord-Canada: 1-17.
29. ----. 1883.
Flora Fossilis Arctica
, 7. Pt. 2. Die tertiäre
Flora von Grőnland: 47-142.
30. Hollick, Arthur. 1936. “The Tertiary floras of Alaska.”
U.S.Geol.Surv.Prof.Paper
182: 1-175.
31. Hu, Hsen-Hsu. 1946. “Notes on a Paleocene species of Metasequoia
in China.”
Bull.Geol.Soc. of China
26: 105-107.
32. Hu, Hsen-Hsu and Chaney, Ralph W. 1940. A Miocene flora from Shan
g
tung
Province, China. Carnegie Inst. Wash. 507.
33. Hu, Hsen-Hsu and Cheng, Wan-Chun. 1948. “On the new Family
Metasequoiaceae and on Metasequois glyptostroboides. a living
species of the Genus Metasequois found in Szechuan and Hupeh.”
Bull.Fan Mem.Inst. of Biol
. 1 (2): 153-161.
EA-PS. Chaney: Arctic
[:
]
Forests of the Cenozoic
34. Kryshtofovich, A.N. 1929. “Evolution of the Tertiary flora in Asia.”
New Phytologist
28 (4): 303-312.
35. ----. 1934. “The Tertiary flora of the Korf Gulf, Kamchatka.”
Trans.Far East Geol. and Prospecting Trust
62: 1-28.
36. ----. Undated. “New Contributions to the Tertiary and Cretaceous
Floras of the Aral-Caspian Province and its Correlation to
the floras of Northern Asia.” Ser.4, 2: 244.
37. Miki, S. 1941. “On the change of flora in Eastern Asia since
Tertiary Period (I). The clay or lignite beds flora in Japan
with special reference to the
Pinus trifolia
beds in Central
Hondo.”
Jap.Jour.Bot
. 11: 237-303.
38. Munns, E.N. 1938.
The distribution of important forest trees of the
United States
. U.S.Dept.Agric. 287.
39. Nathorst, A.G. 1888. “Zur fossilen Flora Japans.
Palaeontologische
Abhandlungen von Dames und Kayser
” 4, Heft 3: 52.
40. ----. 1915. “Tertiare Pflanzenreste aus Ellesmere-Land.”
Report of
the Second Norwegian Arctic Expedition in the “Fram” 1898-1902
.
35: 1-16.
41. Palibin, E.B. 1905. “Plant remains from the Commander Islands.”
Western Imp.Russ. Mineralogical Soc
. Ser.2, Pt.42: 28.
42. Schmalhausen, J. 1890. “Beschreibung der tertiaren Pflanzen von
New-Siberien.”
Mem.Acad.Imp.Sci.St. Petersburg
37: 10-22.
43. Schmidt, F.B. 1900. “New material from the shores of Okotsk Sea.”
Western Imp.Russ.Mineralogical Soc.
Ser.2, Pt.28: 50-51.
44. Zon, Raphael and Sparhawk, William. 1923.
Forest Resources of the
World
. McGraw-Hill Book Co.
Ralph W. Chaney
Pleistocene and Recent Paleobotany (Excluding Greenland)
EA-Plant Sciences
(G. Erdtman)
PLEISTOCENE AND RECENT PALEOBOTANY
(EXCLUDING GREENLAND)
CONTENTS
|
|
Page
|
|
Fossil-Bearing Deposits
|
2
|
|
Interpretation of Fossils
|
4
|
|
Dating of Fossiliferous Deposits
|
6
|
|
History of Climate and Vegetation
|
6
|
|
Future Work and Prospects
|
8
|
|
Bibliography
|
10
|
EA-Plant Sciences
(G. Erdtman)
PLEISTOCENE AND RECENT PALEOBOTANY
(
EXCLUDING GREENLAND
)
The present provides the key to the past, the truth of this cannot
be denied. Nevertheless, paleobotanists have as a rule not paid much
attention to fossil plant remains and potential fossils in Pleistocene
and Recent deposits. Stumps and stems of ferns and conifers — hundreds
of millions of years old — have been treated with respect, whereas
fossils buried in Quaternary strata for only five to fifty thousand years
have frequently been neglected. Paleobotanically speaking, the latter
have not yet come of age. However, to make the record complete, that is,
to trace the history of plants from the present day to remote ages,
botanists should first study the living plants, then actuopaleontology
(i.e., the transformation of living substance into fossils), and finally
paleontology itself, beginning with the most recent fossils proper. Until
this had been accomplished, more or less wide gaps will remain between our
knowledge of Pleistocene and Recent fossils, gathered by plant geographers,
Quaternary geologists, and others, and that of older fossils supplied by
paleobotanists.
Speaking of gaps, it should also be pointed out that our paleobotanical
EA-PS. Erdtman: Pleistocene and Recent Paleobotany
knowledge is derived so far chiefly from the study of megafossils (i.e.,
more or less large fossils: tree trunks, leaves, fruits, seeds, etc.)
Proper attention should, however, also be paid to the study of microfossils,
such as pollen grains and spores. Recognition of the importance of “paleo–
lapynology” (palynology: pollen and spore science; from the Greek verb
palyno,
to spread) as an auxiliary paleobotanical science is gradually
increasing. The ideal development of paleobotany would be to secure, as
far as possible, a continuous record of plant microfossils as well as
megafossils back through the ages.
The arctic region is still in many respects, including Pleistocene and
Recent paleobotany, a
terra incognita
. This article can, therefore, present
only a few facts and suggestions about a vast area where extreme conditions
tend to make investigations difficult, and where any results may be obtained
are particularly interesting.
Fossil-Bearing Deposits
The Pleistocene and Recent fossils (or subfossils) of the Arctic are
preserved in various ways: in ice, frozen soil, peats, or sediments of
different types. These media are not always stable: for example, peat and
sediment may be broken up and destroyed; and if the ice melts, imprisoned
“cryofossils” are released.
Investigations in Switzerland (64; 65) have shown that glacier ice
contains pollen grains and spores in amounts sufficient for analyses. This
opens a new approach to the study of glacial movements and the rate of firn
and ice formation. Investigations of this kind have, however, not yet been
made in the Arctic.
In temperate regions, peat deposits usually form the chief source of
EA-PS. Erdtman: Pleistocene and Recent Paleobotany
Pleistocene and Recent fossils. By investigating these natural archives — their
stratification, and included stumps, seeds, and microfossils — detailed pictures
may be obtained not only of vegetational history but also of climatic changes.
In the relatively mild and wet northwestern parts of Europe, peat accumulations
attain locally a thickness of 30 feet and span a period of 1
^
0,0
^
00 or more years.
The climate of the Arctic does not favor peat formation, and true peat of
considerable thickness is rarely found in
[:
]
^
arctic
^
regions. It is reported from
Alaska, however, that peat on the tundra reaches a thickness of 2 to 150 feet,
and may even attain 300 feet. This depth has, according to Russell (56), been
assigned by several observers to the peat of the subarctic tundra where it is
exposed on a sea cliff in Eschscholtz Bay, at the head of Kotzebue Sound. This
interesting locality has received more attention than any similar portion of the
shore of Alaska, owing to the fact that the ice is well exposed and the surface
layer of human is rich in mammalian remains. The peat is still forming,
[:
]
although the material lying below is frozen at a depth of only 8 to 14 inches.
In the unforested lands of northern and northwestern Canada, moss peat (
Sphagnum
bog) is said to be little developed (63). Concerning peats and boggy strata in
the Canadian Eastern Arctic, right up to northern Baffin Island, see Polunin
(52) and papers quoted therein. On Richards Island, in the Canadian Western
Arctic, 60 or 70 miles north of the present limit of trees, well preserved roots
and stumps of a former spruce forest are found
in situ
, now covered with a peat
deposit many feet thick.
Potamogeton epiphydrus var. nuttallii
, discovered in the
peat deposits of Pingorssera juk, is not now anywhere found in the Northwest
Territories (53a).
Conditions in Greenland are described by Iversen in Pleistocene and Recent
Paleobotany of Greenland. It will only be added here that peat has been found by
Backlund (8) in the northeastern part of that huge island, and that this was one
of the nor
h
^
t
^
hernmost finds or true peat so far made.
EA-PS. Erdtman: Pleistocene and Recent Paleobotany
According to Nathorst (44), peaty deposits are not rare in Spitsberge.
A deposit of
Amblystegium
peat, six feet deep, occurs in the Dape Thordsen
Peninsula, and Craig (16) mentions peat thicknesses of up to two or three
feet at several localities.
In the tundra peat in the Kanin Peninsula, whose maximum thickness is
18 feet according to Jacobi (27), finds of tree trunks up to 20 feet in
length have been made (55). Part of Kolguev Island is covered by tundra
peat (62), and quagmires exist on the South Island of Novaya Zemla (cf.
Holm, 24) where Lid (40) even speaks of a
Sphagnum
even speaks of a
Sphagnum
big. Here, as in Spitsbergen,
Sphagnum squarrosum
is the commonest species.
This species also occurs in a “dead” bog near Krestovaia Bay on the North
Island, in which peat formation has ceased and the peat itself is a sign
of conditions more favorable than those of the present day (37). The
scanty pollen flora of
[:
]
Carex-Hypnum
peats (3 to 4 feet deep)
on the west coast of the South Island has been studied by Kudrjaschos (37).
The finds of stray pollen of lime (
Tilia
) are particularly remarkable.
Further information on peat in Arctic Russia and Siber
f
^
i
^
a is given by
Alabyshev, Anufriev, Bronsov, Dokturovski, Igoshin, N. and S. Katz,
Lavrova, and others.
Interpretation of Fossils
Some fossils are autochthonous, i.e., remnants of plants living on
or near the spot; others are allochthonous, i.e., carried by different agencies,
usually wind or water, from more or less distant places. Allochthonous
specimens may also include redeposited fossils from older, broken-down
strata. Much confusion may arise if the allochthonous and autochthonous
components of a fossil record cannot be readily differentiated.
EA-PS. Erdtman: Pleistocene and Recent Paleobotany
Foremost among allochthonous megafossils are logs and other woody
debris carried by the great rivers to the Arctic Sea, distributed by
oceanic currents, thrown ashore, and finally embedded in sandy, clayey,
or peaty deposits. They also include seeds of the famous sea bean
(
Entad
[:
]
gigas
), a product of the West Indies that is occasionally found
floating ashore in Ireland, Norway, and even Spitsbergen. Long-distance
transportation of insects is reported by Elton (19); in the summer of 1924
vast swarms of hover flies (
Syrphus ribesii
) and spruce aphids (
Dilachnus
[:
]
piceae
) were blown from northern Europe to the icecap of North
East Land, Spitsbergen — a distance of over 800 miles. They were living
when they arrived, but perished later in a blizzard. Transportations in
reverse direction occur occasionally; animals and plant remains may thus
be carried by icebergs or other means from Spitsbergen to the northern
coasts of Europe.
Potential microfossils (such as pollen grains and spores) and small
particles of apt kind are not to be spread in greater quantities and over
longer distances than larger bodies. Ash from an eruption in Iceland
reached Finland (Helskngki) after 51 hours (57), and at the time this
article was being written (in Stockho
[:
]
^
l
^
m, October 1950), the sun occasionally
assumed a bluish shade from fine dust suspended at high altitudes in the
air. Volcanic eruptions in eastern Asia and forest fires in western
Canada are believed to have been responsible for this dust.
Pollen grains and spores were trapped by Charles Lindbergh during
flights over the inland ice of Greenland (cf. Meier, 43), and similar
experiments have been made in Arctic Canada and the Polar Basin by Nicholas
Polunin and worked out with the assistance of his colleagues (53).
EA-PS. Erdtman: Pleistocene and Recent Paleobotany
Some years ago the pollen grains in the atmosphere over the Atlantic
Ocean were investigated during a journey from Gőteburg to New York (20).
Pollen grains and spores were trapped all the way, even in midocean, and
200 miles off Newfoundland considerable quantities of alder pollen grains
were caught, having been carried there from Newfoundland by strong north–
easterly winds. The peat in Greenland contains small amounts of allochthonous
coniferous pollen grains from the continent of North America.
Dating of Fossiliferous Deposits
G. De Geer’s geochronological method, based on the study of sediments
with annual banding, has been instrumental in calculating the exact duration
of late Quaternary times (cf. De Geer 17). The same method will probably
prove useful in some outskirts of the Arctic, e.g., in Alaska (cf. Russell,
56). If absolute geochronology cannot be applied, the relative age of a
fossiliferous deposit can be ascertained by other methods. Among these is
the study of the deposits’ relation to the strand lines, which are widely
spread in different parts of the Arctic. Pioneer work in this difficult
field has been done by Tanner (61). Archaeological finds in or near the
deposits may also be instrumental in dating (14; 68).
History of Climate and Vegetation
In the arctic region practically no investigation of these aspects
have been made bymodern methods except by Iversen (see Pleistocene and
Recent: Greenland). Here, therefore, only a brief summary of some results
of research during the last hundred years (1850-1950) will be given.
Unfortunately, valuable information has often been published in more or
less local journals and periodicals, difficult of access to the general
EA-PS. Erdtman: Pleistocene and Recent Paleobotany
reader, and much of it is in Russian without summaries in other languages.
Climatic changes and their influence on the vegetation have been
dealt with by Andersson, Backlund, Heer, Nathorst, Neustadt and Tulina,
Obruchev, Subkov, Sukachev, Tyrrell, and others. Permanently frozen soils
and their relation to local vegetation have been described by von Baer,
Johnston, Malchenko, Kayser, Krueger, Nikiforoff, and others. According
to the findings of these authors, it can be safely concluded that the
arctic region during Quaternary times witnessed one or several interglacial
periods with milder c
e
^
l
^
imatic conditions than the present ones. It has,
furthermore, been established that during postglacial times the climate
was for a period warmer than now: thus the mean temperature during the
season of growth in Spitsbergen was probably 2.5 - 3°C. higher than at
present (3).
Remains of the seaweed
Pelvetia canaliculata
occur in the
Mytillus
layers at Advent Bay, Spitsbergen (23); the layers are probably inter–
glacial. A small leaf-fragment of, apparently,
Dryas integrifolia
has
been found in the same beds. Neither
Pelvetia canaliculata
nor
Dryas
integrifolia
occurs on Spitsbergen today. Similarly interglacial are the
remains of
Alnus fruticosa
and
Betula alba
(occurring together with remains
of mammoth, rhinoceros, horse, and saiga antelope) in the New Siberian
Islands. In the Taimyr Peninsula fossil wood, especially of
Larix
, is
frequent up to
^
latitude
^
74° 30' N. (7). The modern tree line lies in most places
near to parallel. The wood, which consists partly of large logs, rests
on permanently frozen soil and is locally overlain by ground ice. It may
be of interglacial age.
In Quaternary beds in the Seward Peninsula, Alaska, in regions now
EA-PS. Erdtman: Pleistocene and Recent Paleobotany
treeless, large trunks of trees have been found together with remains
of mammoth, horse, and other mammals (15; 41; 54).
The presence of
Salix herbacea
hybrids in Novaya Zemlya is one of
the many botanical indications of milder climatic conditions in post–
glacial times; pure
Salix herbacea
does not now grow in this sector of
the Arc
g
^
t
^
ic north of Vaigach Island (37). Still stronger arguments in
favor of an earlier postglacial climatic optimum have been provided by
zoologists (28; 35; 47). Forest fires and human influence have contributed
to widening the area of the arctic tundra, but cannot alone, as argued by
Wigge (67), be responsible for the shrinking and withdrawal of the northern–
most forests.
Future Work and Prospects
Paleontological researches in the critical zone of tension between
tundra and forest are likely to yield results of outstanding interest.
Studies like those of Aario and others in northern Finland may serve as
examples. The composition of the arctic tundra vegetation should be
compared with its “pollen and seed pictures,” i.e., the way in which the
actual vegetation is reflected by the seeds and pollen grains in living
(still growing) strata of fossiliferous deposits should be studied. Near
Bőteborg, about 8,000 pollen grains per year settle on one square millimeter
of the sea bottom, about 45 feet below the ordinary shore line. How many
grains are actually settling in the arctic waters or muskegs, and of
what kind are they? The composition of the present-day “pollen rains”
can to some extent be determined by pollen analyses of powdered lichens.
The lichens often contain large amounts of pollen grains and provide
EA-PS. Erdtman: Pleistocene and Recent Paleobotany
“mean values” for a score of years. Similar investigations, if made in
Canada and Siberia, would provide keys for unlocking some of the problems
connected with the history of climate and vegetation in the Arctic.
Research in the tension zones and farther north, in the true tundra,
would also contribute to the interpretation of some fossil records of
arctic or quasi-arctic conditions in areas of former glaciation. How does
a vegetation invading the soil laid bare by a withdrawing ice sheet compare
with present-day arctic vegetation? And to what extent can be composition
of this vegetation be explained on a purely ecological nonclimatic basis?
At the time of the disappearance of the last remnants of “dead” ice
in northern Scandinavia, the climate was probably more favorable than that
of the present day. The flora invading the virgin soils comprised sun-loving
“pioneers and vagabonds” (
Hippophaë
,
Artemisia
and other Compositae, etc.),
a colorful vanguard, later shaded to death and exterminated by forests of
birch, pine, alder, and some admixture of hazel, oak, lime, elm, and ash.
There are somd points in common between the pioneer flora and that
occurring in some places in or near the Arctic, e.g., in Kanin Peninsula.
Here
Matricaria
and
Sonchus
grow in profusion — note also the finding by
Jonas (30) of 90-100% composite pollen grains in “subarctic” strata
in German.
Helianthemum oelandicum
, a late-glacial member of the flora
of Sweden and Denmark, is also said to occur in Kanin (51).
The investi
v
^
g
^
ations of the Pleistocene and Recent deposits in the
Arctic should proceed step by step, beginning in the southern tension
zones. In this way they would be linked upwith those in the subarctic
forest areas and a strong, critical contact would be upheld with various
well-established data – geochronological, phytogeographical, climatological,
and archeological.
EA-PS. Erdtman: Paleobotany: Pleistocene and Recent
BIBLIOGRAPHY
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G. Erdtman
Pleistocene and Recent Paleobotany of Greenland
EA-PS. Iversen: Paleobotany of Greenland
LIST OF FIGURES
Fig. 1. Kingak (1620 m.) in the Godthaab Fjord area. During the glacial
ages, this mountain projected as a nunatak above the inland ice, and has,
therefore, been modelled by local glaciers (alpine type). Refuge area for
hardy arctic plants during glacial time. *
Fig. 2. Transport of one of the pontoons to a lake in the Tungmeralik valley.
Powerful planar erosion caused by the friction of the inland ice has resulted
in the dome-shaped mountains. In the foreground a birch-lichen mat is seen. *
Fig. 3. Scrub of alder (dark bushes) and willows on the bank of a small river.
Majaragssuit, interior of Godthaab Fjord. *
Fig. 4. Luxuriant mat of grasses and herbs adjacent to the ruins of a small
Norse farmstead. Tufts of
Poa glauca
and inflorescences of
Campanula rotundifolia
are conspicuous.
Archangelica officinalis
is seen to the left. In the background
is
Betula nana
scrub. *
Fig. 5. Composite pollen diagram from a lake 100 meters above recent sea-level.
The lowermost analyses are from samples deposited in brackish water, as indicated
by their diatom flora. Each analysis gives the relative frequency of the various
species. The basis of calculation is the total of all pollen (excepting that of
water plants. Before calculation, the pollen number of
Betula and Alnus
are
reduced to 1/4, that of
Juniperus
to 1/2, while the number is doubled in the case
of Ericaceae. The figures on the extreme left indicate the place in the diagram
where 3 different lakes were isolated from the fjord; the height above recent
sea-level of these lakes is 100 meters, 59 meters, and 8 meters, respectively.
As to the zones (I-V)), see the text.
^
— Page 14
^
Fig. 6. Pollen diagram from a lake adjacent to the Norse farmstead at Kapisilik;
of. fig. 5. The diagram comprises only the zones III-V. Zone V is subdivided in
a, b, c; b corresponds to the period of Norse colonization, i.e. from 1000 to
about 1400 A.D. The great thickness of the deposit from this period is due to
strong inflow of sand and charcoal. The frequency of microscopie charcoal
fragments on the slides is indicated on the extreme right
^
!
^
before the arrival
of the Vikings, charcoal is found only exceptionally. Macrobiotus, i.e. eggs of
Tartigrades, indicates the occurrence of moss carpets (
Aulacomnium
spp.,
Sphagnum
spp.), c.f. fig. 7.
^
— Page 14
^
Fig. 7. Profile from a small bog adjacent to a Norse farmstead at Ujaragssuit.
1 moss-peat; 2 sandy mud; 3 pure sand; 4 sandy gravel; 5 layer of charcoal,
washed down when the Icelandic Vikings arrived and burnt off the scrub. Wood
chips were found in the same layer. Beneath this level charcoal was absent;
above, scattered pieces of charcoal was found until 6, the uppermost charcoal
pieces; 7 pupae of
Agrotis oculta
. In the stratum of charcoal (5), pollen
grains of grasses and herbs suddenly become dominant. In the layer of pupae (7),
the pollen grains of herbs again become less frequent, while those of willow
increase sharply. Simulatenously the bog becomes covered with mosses, either
owing to the termination of colonization, or because of a climatic change to
dryer conditions.
^
— Page 14
^
EA-PS. Iversen: Paleobotany of Greenland
List of figures
Fig. 8. Sketch map drawn on the basis of information in Finn Salomonsen’s
work (The Birds of Greenland 1950). Some geese fly directly from Scotland to
South Greenland and vice versa (occasionally a direct connection between
Scotland-Ireland and North America may occur, exceptionally the migrants may
be diverted from their customary course).
^
— Page 15
^
Fig. 9.
Sisyrhinchium montanum
on a south-facing slope adjacent to the ruins
of a Norse farmstead near Kapisilik. Nearest locality outside Greenland is more
than 1000 km. to the
[:
]
-SW in Labrador. Presumably it was accidentally introduced
from the St. Lawrence Bay region during the Norse expeditions from Greenland to
America. It has been found at three ancient Nose farmsteads in the interior
of Bodthaab Fjord. Further, one locality is known from the little explored
Sdr. Strőmfjord regions, where so far no ruins of Norse farmsteads have been
found. The possibility that
Sisyrinchium
has immigrated with birds during the
post-glacial warm period cannot be excluded.
^
*
^
1
EA-Plant Sciences
(Johs. Iversen)
PLEISTOCENE AND RECENT PALEOBOTANY OF GREENLAND
The favorable climate in Greenland during the Tertiary period terminated
with a sharp decline in temperature. Snow and ice accumulated and the inland
ice came into existence. The luxuriant and rich Tertiary flora was followed
by the hardy and relatively depauperate arctic plants.
The deterioration of the climate culminated during the glacial ages; we
must assume that they brought about great advances of the ice even in Greenland.
We know, however, nothing about the varying extent of the inland ice during
the Pleistocene period, as the last advance seems to have reached farthest
of all.
Each glacial period, no doubt, decimated the flora of Greenland. Between
these periods of bitter cold, i.e., in the “interglacial” periods, the improve–
ment in climatic conditions gave rise to a recrudescense of the flora. The
isolated position of Greenland — wide waters divide southern Greenland from
the North American and European continents — is, however, a serious obstacle
to the immigration of plants. Hence, the question of the origin of the flora
of Greenland arises: did the flora, or any part of it, survive the glaciations
on ice-free refuges in Greenland, or must we assume that it was totally destroyed
in each successive glaciation?
The problem was first presented by the well-known Danish botanist Eugen
Warming, who in 1889 asserted that a considerable portion of the Greenland
EA-PS. Iversen: Paleobotany of Greenland
flora might have survived at any rate the last glaciation on ice-free moun–
tain peaks, the so-called “nunataks” (cf. fig. 1). Warming’s assertion
became the starting point of a lively scientific debate among botanists,
and opinions varied (and still vary) greatly — cf. a review of the initial
part of the discussion in Ostenfeld’s paper, also the recent contributions
by Gelting (1932, 1941), Bőcher (1938, 1948), and Dahl (1949).
The discussion has hitherto been based exclusively on the theoretical
evaluation of the present distribution of the plants in question; in this
contribution, however, the problem will be dealt with on the basis of some
recent pollen analytical material.
No interglacial deposits are known from Greenland. The inland ice
seems to have scoured them off totally during the last glacial age. On the
other hand small bits of concretions, often with fossilized marine fishes,
can be found high in the mountains, whither one can be sure that they have
been transported by glaciers; they must, therefore, be of interglacial age.
Fortunately, these concretions have been found to contain pollen grains that
are well preserved and present in ample number.
A pollen analysis from a small concretion found at the head of Godthaab
Fjord gives information as to the vegetation in this region during inter–
glacial time. In broad features we find the same subarctic vegetation type
which characterizes the postglacial warm period (cf. later). Scrub of birch,
alder, willow, and juniper were frequent; also various grasses, herbs, ferns,
and Ericaceae. On the beach grew chenopods and
Plantago maritima
. There is,
however, one striking difference: The presence of
Picea
, which is well repre–
sented in the pollen analysis. No conifers, except juniper, are known to have
lived in Greenland since the last ice age. The same applies to
Filipendula
,
EA-PS. Iversen: Paleobotany of Greenland
a herb demonstrated in the pollen analysis. These facts are an indication
that in Greenland, as in Europe, the interglacial flora was richer than
the postglacial one.
The development of the vegetation in postglacial time has been studied
by pollen analysis of the deposits in lakes and bogs of the interior of
Godthaab Fjord. The main investigation was carried out in Tungmeralik
(lat. 64°15′ to 64°25′ N, long. 51°50′ W.), one of the largest and most
sheltered valleys in southern Greenland, which contains a series of lakes
at varying altitudes. Numerous ruins of farmsteads from
[:
]
the ancient
Viking colonization are found in the valley. The material was
[:
]
gathered
during 1937 in a number of these lakes by borings from pontoons (fig. 2),
In addition, some bogs of other parts of the inland region of the Godthaab
Fjord district were investigated.
The vegetation in the territory studied is relatively luxuriant, though
somewhat impeded by drought. Following the water-courses and in other favor–
able and sheltered places we find willow scrub (fig. 3) interspersed with
Alnus crispa
. Predominant, however, is
Betula nana
, forming heaths or low
scrub, associated with Ericaceae or low willows and, on southerly slopes,
also with Juniperus.
Ledum groenlandicum
forms a luxuriant low scrub on
westerly slopes, while
Ledum decumbens
is generally found in exposed and
less favorable places.
Vaccinium uliginosum
and
Empetrum hermaphroditum
are very common, especially in the montane zone, where they form large heaths.
Vast areas are covered with lichen health, with scattered dwarf-shrubs or
grasses (cf. fig. 2). Luxuriant mats of grasses and herbs are found at the
old farmsteads. Even now, some 600 years after the settlements were aban–
doned, the vegetation still shows the results of the fertilization of those
days (cf. fig. 4).
EA-PS. Iversen: Paleobotany of Greenland
Long-distance transport of pollen, which in most arctic regions is an
extremely grave source of error in pollen analysis, is in Greenland of little
importance. This is, of course, because of its isolated position. All pollen
grains of conifers, except juniper, must have come across the sea; but this
long-distance conifer pollen (principally
Picea
pollen) amounts to approxi–
mately 1% only of the total pollen count, which is an extraordinarily low
figure. The pollen diagrams, therefore, give a clear and reliable picture
of the development of the vegetation in the inland region of Godthaab Fjord.
The diagrams may be divided into 5 well-defined zones, as will be seen
in figure 5. The first (lowest) period is characterized by the absence of
scrub as neither birch, nor willow, nor alder, nor juniper is present. Scat–
tered finds of pollen grains of birch and alder are no more than can easily
be explained, e.g., by long-distance transport from America. Pollen of willow
is also extremely sparse, and consists principally of
Salix herbacea
pollen,
which can be distinguished morphologically. On the other hand, there is a
fairly rich flora of herbaceous plants and dwarf shrubs; of special interest
is the presence of a series of thermophilic herbs, e.g.,
Atriplex
, the northern
limit of which is now in Godthaab Fjord. This shows that the climate was al–
ready then rather favorable, the temperature being almost at the same level
as today.
The second period (
II
) begins with the immigration of
Salix glauca
.
Shortly afterwards
Alnus crispa
arrives; but, contrary to the willow, alder
does not occur with any considerable frequency for a long time. Presumably
the summer temperature was not high enough for its full development.
The third period (
III
) is extremely sharply marked by the immigration
and dynamic expansion of
Betula nana
. It is obvious that the ecological
EA-PS. Iversen: Paleobotany of Greenland
conditions must long have been favorable to
B. nana
; it can have been lacking
only for historical reasons. Therefore it attains immediately its full fre–
quency; almost half of the total pollen is now of this species. Simultaneously
with birch, uniper immigrates, and also
[:
]
immediately attains maximal frequency.
The fourth
[:
]
period (
IV
) is the warm period in Greenland, at any rate as
far as can be told from the vegetation aspect. The alder, which hitherto has
been sparse, now becomes extremely frequent. Contemporary with the increase
of the alder,
Myriophyllum alterniflorum
begins to bloom luxuriantly in the
lakes.
Finally, the fifth period (
V
) is marked by the dete
^
r
^
ioration of the climate.
The alder scrub recedes while the
Empetrum-Vaccinium
heath advances (cf. also
fig. 6).
As mentioned earlier, the succession in the advent of the dominant plants
is mutually consistent in all the lakes; and by means of diagrams it is pos–
sible to correlate the vegetational development with the change of sea level.
The bottom layer in all the lakes investigated consists of
marine
clay of vary–
ing thickness. A proportion of the valley has thus been fjord, and the lakes
have become isolated gradually as the threshold was raised above sea-level by
the postglacial upheaval of the land.
The diagram already shown (fig. 5) is from a lake the water level of which
is now 100 meters above sea level. There was only a very thin layer of marine
clay at the bottom, covered by 3 1/2 meters of lacustrine mud. We must assume
that the lake became isolated from the fjord a short while after the ice had
receded from the valley.
Another diagram is from a large lake at an altitude of 50 meters above
recent sea-level. This lake became isolated from the fjord in the middle of
period II. The diagram, fig.6, is from a small lake at an atltitude of 8
EA-PS. Iversen: Paleobotany of Greenland
meters above recent sea level; it comprises only the later periods, zone III-V.
The diagram shows clearly that this lake became isolated shortly before the
commencement of period IV. We may assume that during the warm period the sea
level fell considerably below the recent shore-line.
It is more difficult to synchronize the vegetational development in
Greenland with that of other regions. The long-distance transport of conifer
pollen from North America, however, affords us the means of connecting pollen
diagrams from southwest Greenland with diagrams from the adjacent regions of
the American Continent. As has been mentioned, this conffer pollen amounts
to about 1% of the total, and no doubt it principally originates from the
forests of Labrador and Newfoundland. The vegetational development of this
region is dealt with in a paper by Wenner (). According to this author,
after the melting of the ice sheet, a period with subarctic scrub, of birch
and alder, intervened prior to the advent of the coniferous forest. In the
pollen diagrams from Greenland, the conifer pollen is lacking in period I
and most of period II, in which we have only long-distance transport of birch
and alder; but it is constant in the following periods. The arrival of
Betula
nana roughly coincides in time with the immigration of the coniferous forest
in Labrador. According to Wenner, this event may tentatively be dated about
the time of transition from Boreal to Atlantic periods.
If this holds good, zone III corresponds more or less to the Atlantic
period in the well-known Blytt-Sernander system, and, accordingly, the warm
period in Greenland, zone IV, synchronizes with the sub-Boreal period only.
This feature is a remarkable deviation from the conception arrived at for
example in Europe, where the warm period comprises not only the sub-Boreal
but also the Boreal and Atlantic periods.
EA-PS. Iversen: Paleobotany of Greenland
The usual grouping of the climatic development in postglacial time com–
prises the following periods: the Boreal, the Atlantic, the sub-Boreal, and
last, the sub-Atlantic periods. The three first together correspond to the
“postglacial warm period.” Between the Boreal period and the cold late–
glacial period we have a transition zone (the “pre-Boreal” period).
The decline in summer temperature, which is so clearly indicated in our
pollen diagrams by the final great fall of the alder curve, corresponds
roughly to the well known sub-Atlantic deterioration in climate in Europe
and elsewhere. This agrees with the fact, that the Viking colonization in
Greenland, which is clearly indicated in the pollen diagrams, occurred a good
while later than the decline of the alder.
The diagram fig. 6 is from a lake in the immediate vicinity of a Norse
farmstead. The interim of colonization is marked in the sediment by micro–
scopic particles of charcoal, and in the pollen flora by a sharp decline in
the curves of alder and willow, while grass and herb curves ascent. In small
bogs situated directly on the “tun”, i.e. paddock adjacent to the homestead,
this phenomenon is much more pronounced. This fact, together with the simul–
taneous occurrence of a distinct charcoal layer in the bogs (cf. fig. 7),
seem to prove that the Vikings on arrival burnt off the scrub and luxuriant
heaths; this in turn gave rise to mats of grasses and herbs (cf.
Iversen
1934).
When the colonization ceased about a century later, the scrub regenerated.
In the
immediate vicinity of the Norse ruins, however, the fertilized soil produces a very
luxuriant grass growth. The scrub was not able to return completely
The end of the Norse colonization in the Godthaab Fjord region seems to
have followed a rather dramatic course. In the bogs adjacent to the farm–
steads (cf. fig. 7), there is an almost continuous layer of insect pupae at
the exact horizon where various circumstances indicate that the settlements
was abandoned. The pupae belong to a species of moth (
Agrotis oculta
), the
EA-PS. Iversen: Paleobotany of Greenland
larvae of which may occur in such enormous masses that they totally destroy the
vegetation. In the summer of 1932 the attack in the interior of the Godthaab
region was exceptionally serious. For moles on end, not a single green plant
was to be seen in the Tungmeralik valley; everything was eaten off, and still
millions of famished larvae crawled about all over the ground. A serious of
similar disastrous attacks could have put an end to the large northern settle–
ment (Vestri bygd) of the Norse colonization, which latter depended entirely
on the local animal husbandry. In the southern settlement (Eystri bygd), as
we know, the colonization continued for a longer period, and other factors must
have occasioned the tragic extinction of the last Norse colony in Greenland.
Among these the isolation from Europe, attacks of Eskimos, a merging of the
Europeans with Eskimos, and a climatic development, unfavorable to a pastoral
economy, have been suggested and discussed (cf. Nansen 1911 and 1925, Nørlund
1924, Stefansson 1942).
We return to the problem of the origin of the flora of Greenland. Possibly
the most striking fact emerging from the pollen analytical investigation is the
late arrival of dwarf birch and juniper. That the interim between the withdrawal
of the ice from the valley and the appearance of dwarf birch covers thousands
of years is indicated by two facts. One of these is the thickness of the sedi–
ment deposited during that interim: in the uppermost lake it amounts to 1 meter
of pure plankton mud, apart from the marine clay. The other fact is that in the
same interim the coastline subsided from more than 100 meters above recent sea
level to about 40 meters, i.e. more than 60 meters in all. Before that interim
the inland ice withdrew from its maximal extension at the mouth of Godthaab
Fjord almost to its recent line.
One has to draw from this the conclusion that neither dwarf birch, nor
juniper, nor, I think
Salix glauca
, survived in the nunataks of the Godthaab
region, as in this case they would have followed the receding ice-border and
EA-PS. Iversen: Paleobotany of Greenland
gradually, as the soil ripened, would have increased in frequency. It pos–
sible that, for example,
Salix glauca
survived in the southern nunatak region
region around Cape Farewell; but the fact that these plants did not, apparently,
survive
[:
]
^
on
^
the numerous nunataks and other ice-free refuges in the outer region
of the Godthaab Fjord district, shows that at any rate with these species we
are quite near the limit of what has conceivably survived the glacial period
in Greenland. Pollen analysis does not support the hypothesis that the southern,
thermophilic element of the Greenland flora may have survived. Nor was this
really to be expected, when the great decline in temperature, throughout the
world during the glacial time, is borne in mind.
Of special interest in the assessment of the survival problem in Green–
land is the flora indicated in the earliest layer, which was deposited in the
lakes shortly after the withdrawal of the ice from the valley. Table I gives
a list of the plant species from this layer. Half of the species are very
hardy; they ascent to great altitudes in the mountains and most of them have
also been found in the northernmost high-arctic region of Greenland. The
majority of these species do not seem to be better adapted to long-distance
dispersal than are the dwarf birch and the willow. So their early occurrence
strongly suggest that in the Godthaab region they have survived the glaciations
on the nunataks.
Particularly interesting is the finding of some pollen grains of
Ledum
,
which is badly adapted to long-distance dispersal., and so one must assume
that it survived in the Godthaab region. I have found that in the inner part
of this region,
Ledum decumbens
ascends a little higher in the mountains than
Salix glauca
. Thus the highest altitude at which I have found it was 1035
meters above sea level, as compared to 1014 meters for
Salix glauca
and 850
EA-PS. Iversen: Paleobotany of Greenland
meters for
Betula nana
— both of which later, as mention
^
e
^
d before, failed to
survive. If this argument holds good, we get a lowering of the vegetatio
^
n
^
al
zones during the last glaciation of an order of about 1000 meters. This amount
is somewhat lower than that arrived at in central and southern Europe.
^
(Firbas, 1947).
^
The flora of the well-known “
Jensen Nunataks
” gives one an idea of the
plant life to be expected on the lower nunataks and semi-nunataks during
the glacial period. The nunataks mentioned emerge at a point 60 kilometers
from the edge of the inland ice, rising from an altitude at 1250 meters to a
height of 1500 meters above sea level, and this great height may be regarded
as compensating for the deterioration of temperature during the glacial period.
From “
Jensen Nunataks
” there is a catalogue of the flora embracing 26 species,
all distinctly arctic,
Cassiope hypnoides
being the only more or less wo
^
o
^
dy
plant. Eight of these species are represented in the pollen flora of the
oldest deposits (cf. Table 1).
Apartment from the 16 hardy species mentioned in Table 1, which are sup–
posed to be survivers, our list from the bottom layer contains a similar
number of relatively thermophilic species, which must have immigrated to
Greenland soon after the improvement of the climate. These species thus give
information as to which means of dispersal were particularly effective in
colonizing Greenland.
The long-distance transport of seeds carried by
air currents
seems rather
ineffective, as none of the early immigrants have seeds adapted to wind
[:
]
^
dis-
^
persal. On the other hand there are 4 southern pteridophytes, the micro–
scopic spores of which, of course, may easily be carried to Greenland by air
currents.
Transport by
currents of the ocean
, possibly on drifting ice, is certainly
EA-PS. Iversen: Paleobotany of Greenland
rather effective. Yet, the course of the arctic currents suggests that only
Icelandic and
not
American plants may be carried to Greenland by this means.
Two species from the earliest deposits have presumably arrived in this way.
A little higher in zone I,
Archangelica officinalis
(
Angelica archangelica
)
immigrates. This species is not found in America, but the fruits may have
been carried from Iceland on ice-floes which drifted out into the polar cur–
rent and subsequently lodged on the south or west coast of Greenland. The
great buoyancy of the fruits would then facilitate their being carried up onto
the beach when the ice melted.
The majority of the immigrants — all water marsh plants — have, how–
ever, arrived epizoically, being transported by birds. Of special interest
is the immigration of
Lomatogonium rotatum
. This annual prefers wet,
[:
]
clayey soil and it produces a profusion of small seeds, which easily adhere,
together with particles of clay, to the feet of geese and wading birds.
Kerner, (1898, p.621) has shown the effectiveness of this
kind of dispersal of small annuals on wet clayey soil.
From
Canada
^
Lomatogonium
^
it has been carried to southern Greenland, and thence on the Iceland
where the migration has so far come to an end.
So the significance of epizoic long-distance transport of birds is obvious.
Lately this has been doubted with reference to the fact that birds generally
clean themselves carefully before they set off on a long flight. It is, how–
ever, also known that birds which are not quite “fit,” neglect their toilette.
At any rate birds cannot get rid of what sticks to their feet immediately
before or at the moment they take to their wings. The rapid immigration of
species of
Potamogeton
to Greenland strongly suggests that other than small
seeds may be transported in this manner.
Thus a knowledge of the migration routes of the birds is of importance
when dealing with our problem. It is fortunate that the routes of the most
EA-PS. Iversen: Paleobotany of Greenland
important migratory birds of Greenland have been determined in the last few
years by Dr. Finn Salomonsen (). The map (fig. 8) is based on information
in Salomonsen’s work, and shows the most important migratory routes of the
geese. The bulk of the geese winter in the British Isles. Iceland is a
resting-place on the trip. Every spring, tens of thousands of geese leave
Iceland. Some fly to the Cape Farewell region, and thence to the North fol–
lowing the West coast. A large proportion rest at Angmagssalik on the east
coast of Greenland and subsequently cross the inland ice. Other species
fly to the Scoresby Sound region. Finally, the American stock of the Brent
Goose makes a non-stop flight from Ungava Bay in Labrador to Western Green–
land. This route is of special interest, as it starts so far south. It is
inconceivable that these immense numbers of geese would not occasionally
carry seeds with them to Greenland. I suppose that
Betula nana
has arrived
in Greenland from Iceland (or Scotland) by this means, particularly as one
of the geese, the White-fronted Goose, li,es to feed on scrub and heath.
Other birds from Greenland follow similar routes, but it might be worth
noting, that, so far as is known, there are no migratory routes between the
Scandinavian peninsula and Greenland.
The step-by-step immigration of southern plants following the route
North of Baffin Bay was only possible in Greenland during the warm period,
the period IV and one can scarcely at present point out any species whose
distribution makes this route of immigration seem probable.
A final group of immigrants was brought to Greenland by man. Ostenfeld
(1926) estimated that about 50 plant species were brought to Greenland from
Iceland by the Norsemen. The number, as emphasized by Porsild (1932) is
probably too high. We can, of course, be quite certain only in the case of
EA-PS. Iversen: Paleobotany of Greenland
e.g.
Capsella
,
Stellaria media
, and
Polygonum aviculare
sl. that have been
found in deposits from Norse culture; but it is evident that plants occurring
in natural habitats may also have been brought over in a similar manner. We
must also assume that the Norsemen brought some plant species from America,
where they went among other reasons to get timber.
Perhaps
Sisyrinchium montanum
was brought to Greenland in this way.
Indeed it may be the only thermophilic plant in Greenland of western origin,
the immigration of which is not easily explained by natural means of dis–
persal, e.g. during the warm period.
It must be remembered that plants which now have a peculiar, widely
scattered distribution, may in early times have had a much wider distribution;
thus the immigration difficulty may be regarded as negligible, so long as
means of crossing Davis Strait were present. Cases of postglacial restrict–
tions to scattered areas have been disclosed in recent pollen analytical in–
vestigation
[:
]
in Northern Europe.
Greenland is a vast region, and an isolated investigation of the Pleisto–
cene and recent paleobotany as of course a limited application outside the
area of investigation. Northern and East Greenland, up to the present, remain
totally unexplored in this conection.
^
Fig. 5.
^
^Fig. 6^^Fig. 7.^^8^ Migration routes of geese (according to Finn Salomonsen 1950).
O r
a^e^sting places —1 goose species. ≣ 4 goose species
EA-PS. Iversen: Paleobotany of Greenland
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[:
]
Nansen, F.
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