The Student's Elements of Geology
by
Sir Charles Lyell
Part 5 out of 14
endure the climate of Europe. In the fossil specimens the same glands or
protuberances are preserved (see Figure 134) as those which are seen in the
axils of the primary veins of the leaves in the recent Til. (Contributions a la
Flore fossile Italienne. Gaudin and Strozzi. Plate 11 Figure 3. Gaudin page 22.)
Another plant also indicating a warmer climate is the Liquidambar europaeum,
Brong. (see Figure 135), a species nearly allied to L. styracifluum, L., which
flourishes in most places in the Southern States of North America, on the
borders of the Gulf of Mexico.
CHAPTER XIV.
MIOCENE PERIOD.-- UPPER MIOCENE.
Upper Miocene Strata of France.-- faluns of Touraine.
Tropical Climate implied by Testacea.
Proportion of recent Species of Shells.
faluns more ancient than the Suffolk Crag.
Upper Miocene of Bordeaux and the South of France.
Upper Miocene of Oeningen, in Switzerland.
Plants of the Upper Fresh-water Molasse.
Fossil Fruit and Flowers as well as Leaves.
Insects of the Upper Molasse.
Middle or Marine Molasse of Switzerland.
Upper Miocene Beds of the Bolderberg, in Belgium.
Vienna Basin.
Upper Miocene of Italy and Greece.
Upper Miocene of India; Siwalik Hills.
Older Pliocene and Miocene of the United States.
UPPER MIOCENE STRATA OF FRANCE.-- FALUNS OF TOURAINE.
The strata which we meet with next in the descending order are those called by
many geologists "Middle Tertiary," for which in 1833 I proposed the name of
Miocene, selecting the "faluns" of the valley of the Loire, in France, as my
example or type. I shall now call these falunian deposits Upper Miocene, to
distinguish them from others to which the name of Lower Miocene will be given.
No British strata have a distinct claim to be regarded as Upper Miocene, and as
the Lower Miocene are also but feebly represented in the British Isles, we must
refer to foreign examples in illustration of this important period in the
earth's history. The term "faluns" is given provincially by French
agriculturists to shelly sand and marl spread over the land in Touraine, just as
similar shelly deposits were formerly much used in Suffolk to fertilise the
soil, before the coprolitic or phosphatic nodules came into use. Isolated masses
of such faluns occur from near the mouth of the Loire, in the neighbourhood of
Nantes, to as far inland as a district south of Tours. They are also found at
Pontlevoy, on the Cher, about seventy miles above the junction of that river
with the Loire, and thirty miles south-east of Tours. Deposits of the same age
also appear under new mineral conditions near the towns of Dinan and Rennes, in
Brittany. I have visited all the localities above enumerated, and found the beds
on the Loire to consist principally of sand and marl, in which are shells and
corals, some entire, some rolled, and others in minute fragments. In certain
districts, as at Doue, in the Department of Maine and Loire, ten miles south-
west of Saumur, they form a soft building-stone, chiefly composed of an
aggregate of broken shells, bryozoa, corals, and echinoderms, united by a
calcareous cement; the whole mass being very like the Coralline Crag near
Aldborough, and Sudbourn in Suffolk. The scattered patches of faluns are of
slight thickness, rarely exceeding fifty feet; and between the district called
Sologne and the sea they repose on a great variety of older rocks; being seen to
rest successively upon gneiss, clay-slate, various secondary formations,
including the chalk; and, lastly, upon the upper fresh-water limestone of the
Parisian tertiary series, which, as before mentioned (Chapter 9), stretches
continuously from the basin of the Seine to that of the Loire.
(FIGURE 136. Dinotherium giganteum, Kaup.)
At some points, as at Louans, south of Tours, the shells are stained of a
ferruginous colour, not unlike that of the Red Crag of Suffolk. The species are,
for the most part, marine, but a few of them belong to land and fluviatile
genera. Among the former, Helix turonensis (Figure 38, Chapter 3) is the most
abundant. Remains of terrestrial quadrupeds are here and there intermixed,
belonging to the genera Dinotherium (Figure 136), Mastodon, Rhinoceros,
Hippopotamus, Chaeropotamus, Dichobune, Deer, and others, and these are
accompanied by cetacea, such as the Lamantin, Morse, Sea-calf, and Dolphin, all
of extinct species.
The fossil testacea of the faluns of the Loire imply, according to the late
Edward Forbes, that the beds were formed partly on the shore itself at the level
of low water, and partly at very moderate depths, not exceeding ten fathoms
below that level. The molluscan fauna is, on the whole, much more littoral than
that of the Pliocene Red and Coralline Crag of Suffolk, and implies a shallower
sea. It is, moreover, contrasted with the Suffolk Crag by the indications it
affords of an extra-European climate. Thus it contains seven species of Cypraea,
some larger than any existing cowry of the Mediterranean, several species of
Oliva, Ancillaria, Mitra, Terebra, Pyrula, Fasciolaria, and Conus. Of the cones
there are no less than eight species, some very large, whereas the only European
cone now living is of diminutive size. The genus Nerita, and many others, are
also represented by individuals of a type now characteristic of equatorial seas,
and wholly unlike any Mediterranean forms. These proofs of a more elevated
temperature seem to imply the higher antiquity of the faluns as compared with
the Suffolk Crag, and are in perfect accordance with the fact of the smaller
proportion of testacea of recent species found in the faluns.
Out of 290 species of shells, collected by myself in 1840 at Pontlevoy, Louans,
Bossee, and other villages twenty miles south of Tours, and at Savigne, about
fifteen miles north-west of that place, seventy-two only could be identified
with recent species, which is in the proportion of twenty-five per cent. A large
number of the 290 species are common to all the localities, those peculiar to
each not being more numerous than we might expect to find in different bays of
the same sea.
The total number of species of testaceous mollusca from the faluns in my
possession is 302, of which forty-five only, or fourteen per cent, were found by
Mr. Wood to be common to the Suffolk Crag. The number of corals, including
bryozoa and zoantharia, obtained by me at Doue and other localities before
adverted to, amounts to forty-three, as determined by Mr. Lonsdale, of which
seven (one of them a zoantharian) agree specifically with those of the Suffolk
Crag. Some of the genera occurring fossil in Touraine, as the corals Astrea and
Dendrophyllia, and the bryozoan Lunulites, have not been found in European seas
north of the Mediterranean; nevertheless, the zoantharia of the faluns do not
seem to indicate, on the whole, so warm a climate as would be inferred from the
shells.
It was stated that, on comparing about 300 species of Touraine shells with about
450 from the Suffolk Crag, forty-five only were found to be common to both,
which is in the proportion of only fifteen per cent. The same small amount of
agreement is found in the corals also. I formerly endeavoured to reconcile this
marked difference in species with the supposed co-existence of the two faunas,
by imagining them to have severally belonged to distinct zoological provinces or
two seas, the one opening to the north and the other to the south, with a
barrier of land between them, like the Isthmus of Suez, now separating the Red
Sea and the Mediterranean. But I now abandon that idea for several reasons;
among others, because I succeeded in 1841 in tracing the Crag fauna southward in
Normandy to within seventy miles of the Falunian type, near Dinan, yet found
that both assemblages of fossils retained their distinctive characters, showing
no signs of any blending of species or transition of climate.
The principal grounds, however, for referring the English Crag to the older
Pliocene and the French faluns to the Upper Miocene epochs, consist in the
predominance of fossil shells in the British strata identifiable with species
not only still living, but which are now inhabitants of neighbouring seas, while
the accompanying extinct species are of genera such as characterise Europe. In
the faluns, on the contrary, the recent species are in a decided minority; and
most of them are now inhabitants of the Mediterranean, the coast of Africa, and
the Indian Ocean; in a word, less northern in character, and pointing to the
prevalence of a warmer climate. They indicate a state of things receding farther
from the present condition of Central Europe in physical geography and climate,
and doubtless, therefore, receding farther from our era in time.
(FIGURE 137. Voluta Lamberti, Sowerby. Variety characteristic of Faluns of
Touraine. Miocene.)
Among the conspicuous fossils common to the faluns of the Loire and the Suffolk
Crag is a variety of the Voluta Lamberti, a shell already alluded to (Figure
123). The specimens of this shell which I have myself collected in Touraine, or
have seen in museums, are thicker and heavier than British individuals of the
same species, and shorter in proportion to their width, and have the folds on
the columella less oblique, as represented in Figure 137.
UPPER MIOCENE OF BORDEAUX AND THE SOUTH OF FRANCE.
A great extent of country between the Pyrenees and the Gironde is overspread by
tertiary deposits of various ages, and chiefly of Miocene date. Some of these,
near Bordeaux, coincide in age with the faluns of Touraine, already mentioned,
but many of the species of shells are peculiar to the south. The succession of
beds in the basin of the Gironde implies several oscillations of level by which
the same wide area was alternately converted into sea and land and into
brackish-water lagoons, and finally into fresh-water ponds and lakes.
Among the fresh-water strata of this age near the base of the Pyrenees are
marls, limestones and sands, in which the eminent comparative anatomist, M.
Lartet, has obtained a great number of fossil mammalia common to the faluns of
the Loire and the Upper Miocene beds of Switzerland, such as Dinotherium
giganteum and Mastodon angustidens; also the bones of quadrumana, or of the ape
and monkey tribe, which were discovered in 1837, the first of that order of
quadrupeds detected in Europe. They were found near Auch, in the Department of
Gers, in latitude 43 degrees 39' N. About forty miles west of Toulouse. They
were referred by MM. Lartet and Blainville to a genus closely allied to the
Gibbon, to which they gave the name of Pliopithecus. Subsequently, in 1856, M.
Lartet described another species of the same family of long-armed apes
(Hylobates), which he obtained from strata of the same age at Saint-Gaudens, in
the Haute Garonne. The fossil remains of this animal consisted of a portion of a
lower jaw with teeth and the shaft of a humerus. It is supposed to have been a
tree-climbing frugivorous ape, equalling man in stature. As the trunks of oaks
are common in the lignite beds in which it lay, it has received the generic name
of Dryopithecus. The angle formed by the ascending ramus of the jaw and the
alveolar border is less open, and therefore more like the human subject, than in
the Chimpanzee, and what is still more remarkable, the fossil, a young but adult
individual, had all its milk teeth replaced by the second set, while its last
true molar (or wisdom-tooth) was still undeveloped, or only existed as a germ in
the jaw-bone. In the mode, therefore, of the succession of its teeth (which, as
in all the old-World apes, exactly agree in number with those in man) it
differed from the Gorilla and Chimpanzee, and corresponded with the human
species.
UPPER MIOCENE BEDS OF OENINGEN, IN SWITZERLAND.
The faluns of the Loire first served, as already stated, as the type of the
Miocene formations in Europe. They yielded a plentiful harvest of marine fossil
shells and corals, but were entirely barren of plants and insects. In
Switzerland, on the other hand, deposits of the same age have been discovered,
remarkable for their botanical and entomological treasures. We are indebted to
Professor Heer, of Zurich, for the description, restoration, and classification
of several hundred species and varieties of these fossil plants, the whole of
which he has illustrated by excellent figures in his "Flora Tertiaria
Helvetiae." This great work, and those of Adolphe Brongniart, Unger, Goppert and
others, show that this class of fossils is beginning to play the same important
part in the classification of the tertiary strata containing lignite or brown
coal as an older flora has long played in enabling us to understand the ancient
coal or carboniferous formation. No small skepticism has always prevailed among
botanists as to whether the leaves alone and the wood of plants could ever
afford sufficient data for determining even genera and families in the vegetable
kingdom. In truth, before such remains could be rendered available a new science
had to be created. It was necessary to study the outlines, nervation, and
microscopic structure of the leaves, with a degree of care which had never been
called for in the classification of living plants, where the flower and fruit
afforded characters so much more definite and satisfactory. As geologists, we
can not be too grateful to those who, instead of despairing when so difficult a
task was presented to them, or being discouraged when men of the highest
scientific attainments treated the fossil leaves as worthless, entered with full
faith and enthusiasm into this new and unexplored field. That they should
frequently have fallen into errors was unavoidable, but it is remarkable,
especially if we inquire into the history of Professor Heer's researches, how
often early conjectures as to the genus and family founded on the leaves alone
were afterwards confirmed when fuller information was obtained. As examples to
be found on comparing Heer's earlier and later works, I may instance the
chestnut, elm, maple, cinnamon, magnolia, buckbean or Menyanthes, vine,
buckthorn (Rhamnus), Andromeda and Myrica, and among the conifers Sequoia and
Taxodium. In all these cases the plants were first recognised by their leaves,
and the accuracy of the determination was afterwards confirmed when the fruit,
and in some instances both fruit and flower, were found attached to the same
stem as the leaves.
But let us suppose that no fruit, seed, or flower had ever been met with in a
fossil state, we should still have been indebted to the persevering labours of
botanical palaeontologists for one of the grandest scientific discoveries for
which the present century is remarkable-- namely, the proofs now established of
the prevalence of a mild climate and a rich arborescent flora in the arctic
regions in that Miocene epoch on the history of which we are now entering. It
may be useful if I endeavour to give the reader in a few words some idea of the
nature of the evidence of these important conclusions, to show how far they may
be safely based on fossil leaves alone. When we begin by studying the fossils of
the Newer Pliocene deposits, such as those of the Upper Val d'Arno, before
alluded to, we perceive that the fossil foliage agrees almost entirely with the
trees and shrubs of a modern European forest. In the plants of the Older
Pliocene strata of the same region we observe a larger proportion of species and
genera which, although they may agree with well-known Asiatic or other foreign
types, are at present wanting in Italy. If we then examine the Miocene
formations of the same country, exotic forms become more abundant, especially
the palms, whether they belong to the European or American fan-palms, Chamaerops
and Sabal, or to the more tropical family of the date-palms or Phoenicites,
which last are conspicuous in the Lower Miocene beds of Central Europe. Although
we have not found the fruit or flower of these palms in a fossil state, the
leaves are so characteristic that no one doubts the family to which they belong,
or hesitates to accept them as indications of a warm and sub-tropical climate.
When the Miocene formations are traced to the northward of the 50th degree of
latitude, the fossil palms fail us, but the greater proportion of the leaves,
whether identical with those of existing European trees or of forms now unknown
in Europe, which had accompanied the Miocene palms, still continue to
characterise rocks of the same age, until we meet with them not only in Iceland,
but in Greenland, in latitude 70 degrees N., and in Spitzbergen, latitude 78
degrees 56', or within about 11 degrees of the pole, and under circumstances
which clearly show them to have been indigenous in those regions, and not to
have been drifted from the south (see Chapter 15). Not only, therefore, has the
botanist afforded the geologist much palaeontological assistance in identifying
distinct tertiary formations in distant places by his power of accurately
discriminating the forms, veining, and microscopic structure of leaves or wood,
but, independently of that exact knowledge derivable from the organs of
fructification, we are indebted to him for one of the most novel, unexpected
results of modern scientific inquiry.
The Miocene formations of Switzerland have been called MOLASSE, a term derived
from the French MOL, and applied to a SOFT, incoherent, greenish sandstone,
occupying the country between the Alps and the Jura. This molasse comprises
three divisions, of which the middle one is marine, and being closely related by
its shells to the faluns of Touraine, may be classed as Upper Miocene. The two
others are fresh-water, the upper of which may be also grouped with the faluns,
while the lower must be referred to the Lower Miocene, as defined in the next
chapter.
UPPER FRESH-WATER MOLASSE.
This formation is best seen at Oeningen, in the valley of the Rhine, between
Constance and Schaffhausen, a locality celebrated for having produced in the
year 1700 the supposed human skeleton called by Scheuchzer "homo diluvii
testis," a fossil afterwards demonstrated by Cuvier to be a reptile, or aquatic
salamander, of larger dimensions than even its great living representative, the
salamander of Japan.
The Oeningen strata consist of a series of marls and limestones, many of them
thinly laminated, and which appear to have slowly accumulated in a lake probably
fed by springs holding carbonate of lime in solution. The elliptical area over
which this fresh-water formation has been traced extends, according to Sir
Roderick Murchison, for a distance of ten miles east and west from Berlingen, on
the right bank of the river to Wangen, and to Oeningen, near Stein, on the left
bank. The organic remains have been chiefly derived from two quarries, the lower
of which is about 550 feet above the level of the Lake of Constance, while the
upper quarry is 150 feet higher. In this last, a section thirty feet deep
displays a great succession of beds, most of them splitting into slabs and some
into very thin laminae. Twenty-one beds are enumerated by Professor Heer, the
uppermost a bluish-grey marl seven feet thick, with organic remains, resting on
a limestone with fossil plants, including leaves of poplar, cinnamon, and pond-
weed (Potamogeton), together with some insects; while in the bed No. 4, below,
is a bituminous rock, in which the Mastodon tapiroides, a characteristic Upper
Miocene quadruped, has been met with. The 5th bed, two or three inches thick,
contains fossil fish, e.g., Leuciscus (roach), and the larvae of dragon-flies,
with plants such as the elm (Ulmus), and the aquatic Chara. Below this are other
plant-beds; and then, in No. 9, the stone in which the great salamander (Andrias
Scheuchzeri) and some fish were found. Below this other strata occur with fish,
tortoises, the great salamander before alluded to, fresh-water mussels, and
plants. In No. 16 the fossil fox of Oeningen, galecynus Oeningensis, Owen, was
obtained by Sir R. Murchison. To this succeed other beds with mammalia
(Lagomys), reptiles, (Emys), fish, and plants, such as walnut, maple, and
poplar. In the 19th bed are numerous fish, insects, and plants, below which are
marls of a blue indigo colour.
In the lower quarry eleven beds are mentioned, in which, as in the upper, both
land and fresh-water plants and many insects occur. In the 6th, reckoning from
the top, many plants have been obtained, such as Liquidambar, Daphnogene,
Podogonium, and Ulmus, together with tortoises, besides the bones and teeth of a
ruminant quadruped, named by H. von Meyer Palaeomeryx eminens. No. 9 is called
the insect-bed, a layer only a few inches thick, which, when exposed to the
frost, splits into leaves as thin as paper. In these thin laminae plants such as
Liquidambar, Daphnogene, and Glyptostrobus, occur, with innumerable insects in a
wonderful state of preservation, usually found singly. Below this is an indigo-
blue marl, like that at the bottom of the higher quarry, resting on yellow marl
ascertained to be at least thirty feet thick.
(FIGURE 138. Cinnamomum polymorphum, Ad. Brong. Upper and Lower Miocene.
a. Leaf.
b. Flower, natural size; Heer Plate 93 Figure 28.
c. Ripe fruit of Cinnamomum polymorphum, from Oeningen; Heer, Plate 94 Figure
14.
d. Fruit of recent Cinnamomum camphorum of Japan; Heer, Plate 152 Figure 18.)
All the above fossil-bearing strata were evidently formed with extreme slowness.
Although the fossiliferous beds are, in the aggregate, no more than a few yards
in thickness, and have only been examined in the small area comprised in the two
quarries just alluded to, they give us an insight into the state of animal and
vegetable life in part of the Upper Miocene period, such as no other region in
the world has elsewhere supplied. In the year 1859, Professor Heer had already
determined no less than 475 species of plants and more than 800 insects from
these Oeningen beds. He supposes that a river entering a lake floated into it
some of the leaves and land insects, together with the carcasses of quadrupeds,
among others a great Mastodon. Occasionally, during tempests, twigs and even
boughs of trees with their leaves were torn off and carried for some distance so
as to reach the lake. Springs, containing carbonate of lime, seem at some points
to have supplied calcareous matter in solution, giving origin locally to a kind
of travertin, in which organic bodies sinking to the bottom became hermetically
sealed up. The laminae, says Heer, which immediately succeed each other were not
all formed at the same season, for it can be shown that, when some of them
originated, certain plants were in flower, whereas, when the next of these
layers was produced, the same plants had ripened their fruit. This inference is
confirmed by independent proofs derived from insects. The principal insect-bed
is rarely two inches thick, and is composed, says Heer, of about 250 leaf-like
laminae, some of which were deposited in the spring, when the Cinnamomum
polymorphum (Figure 138) was in flower, others in summer, when winged ants were
numerous, and when the poplar and willow had matured their seed; others, again,
in autumn, when the same Cinnamomum polymorphum (Figure 138) was in fruit, as
well as the liquidambar, oak, clematis, and many other plants. The ancient lake
seems to have had a belt of poplars and willows round its borders, countless
leaves of which were imbedded in mud, and together with them, at some points, a
species of reed, Arundo, which was very common.
One of the most characteristic shrubs is a papilionaceous and leguminous plant
of an extinct genus, called by Heer Podogonium, of which two species are known.
Entire twigs have been found with flowers, and always without leaves, as the
flowers evidently came out, as in the poplar and willow tribe, before any leaves
made their appearance. Other specimens have been obtained with ripe fruits
accompanied by leaves, which resemble those of the tamarind, to which it was
evidently allied, being of the family Caesalpineae, now proper to warmer
regions.
(FIGURE 139. Acer trilobatum, normal form; Heer, Flora Tert. Helv. Plate 114
Figure 2. Size 1/2 diam. (Part only of the long stalk of the original fossil
specimen is here given ). Upper Miocene, Oeningen; also found in Lower Miocene
of Switzerland.)
(FIGURE 140. Acer trilobatum.
a. Abnormal variety of leaf; Heer, Plate 110 Figure 16.
b. Flower and bracts, normal form; Heer, Plate 111 Figure 21.
c. Half a seed-vessel; Heer, Plate 111 Figure 5.)
(FIGURE 141. Platanus aceroides, Gopp.; Heer, Plate 88 Figures 5-8. Size 2/3
diam. Upper Miocene, Oeningen.
a. Leaf.
b. The core of a bundle of pericarps.
c. Single fruit or pericarp, natural size.)
The Upper Miocene flora of Oeningen is peculiarly important, in consequence of
the number of genera of which not merely the leaves, but, as in the case of the
Podogonium just mentioned, the fruit also and even the flower are known. Thus
there are nineteen species of maple, ten of which have already been found with
fruit. Although in no one region of the globe do so many maples now flourish, we
need not suspect Professor Heer of having made too many species in this genus
when we consider the manner in which he has dealt with one of them, Acer
trilobatum, Figures 139 and 140. Of this plant the number of marked varieties
figured and named is very great, and no less than three of them had been
considered as distinct species by other botanists, while six of the others might
have laid claim, with nearly equal propriety, to a like distinction. The common
form, called Acer trilobatum, Figure 139, may be taken as a normal
representative of the Oeningen fossil, and Figure 140, as one of the most
divergent varieties, having almost four lobes in the leaf instead of three.
(FIGURE 142. Smilax sagittifera; Heer, Plate 30 Figure 7. Size 1/2 diameter.
a. Leaf.
b. Flower magnified, one of the six petals wanting at d. Upper Miocene,
Oeningen.
c. Smilax obtusifolia; Heer, Plate 30 Figure 9; natural size. Upper Miocene,
Oeningen.)
(FIGURE 143. Fruit of the fossil and recent species of Hakea, a genus of
Proteaceae.
a. Leaf of fossil species, Hakea salicina. Upper Miocene, Oeningen; Heer Plate
97 Figure 29. 1/3 diameter.
b. Impression of woody fruit of same, showing thick stalk. 2/3 diameter.
c. Seed of same, natural size.
d. Fruit of living Australian species, Hakea saligna, R. Brown. 1/2 diameter.
e. Seed of same, natural size.)
Among the conspicuous genera which abounded in the Miocene period in Europe is
the plane-tree, Platanus, the fossil species being considered by Heer to come
nearer to the American P. occidentalis than to P. orientalis of Greece and Asia
Minor. In some of the fossil specimens the male flowers are preserved. Among
other points of resemblance with the living plane-trees, as we see them in the
parks and squares of London, fossil fragments of the trunk are met with, having
pieces of their bark peeling off.
The vine of Oeningen, Vitis teutonica, Ad. Brong, is of a North American type.
Both the leaves and seeds have been found at Oeningen, and bunches of compressed
grapes of the same species have been met with in the brown coal of Wetteravia in
Germany. No less than eight species of smilax, a monocotyledonous genus, occur
at Oeningen and in other Upper Miocene localities, the flowers of some of them,
as well as the leaves, being preserved; as in the case of the very common
fossil, S. sagittifera, Figure 142, a.
Leaves of plants supposed to belong to the order Proteaceae have been obtained
partly from Oeningen and partly from the lacustrine formation of the same age at
Locle in the Jura. They have been referred to the genera Banksia, Grevillea,
Hakea, and Persoonia. Of Hakea there is the impression of a supposed seed-
vessel, with its characteristic thick stalk and seeds, but as the fruit is
without structure, and has not yet been found attached to the same stem as the
leaf, the proof is incomplete.
To whatever family the foliage hitherto regarded as proteaceous by many able
palaeontologists may eventually be shown to belong, we must be careful not to
question their affinity to that order of plants on those geographical
considerations which have influenced some botanists. The nearest living
Proteaceae now feel the in Abyssinia in latitude 20 degrees N., but the greatest
number are confined to the Cape and Australia. The ancestors, however, of the
Oeningen fossils ought not to be looked for in such distant regions, but from
that European land which in Lower Miocene times bore trees with similar foliage,
and these had doubtless an Eocene source, for cones admitted by all botanists to
be proteaceous have been met with in one division of that older Tertiary group
(see Figure 206 Chapter 16). The source of these last, again, must not be sought
in the antipodes, for in the white chalk of Aix-la-Chapelle leaves like those of
Grevillea and other proteaceous genera have been found in abundance, and, as we
shall see in Chapter 17, in a most perfect state of preservation. All geologists
agree that the distribution of the Cretaceous land and sea had scarcely any
connection with the present geography of the globe.
(FIGURE 144. Glyptostrobus Europaeus.
Branch with ripe fruit; Heer, Plate 20 Figure 1. Upper Miocene, Oeningen.)
In the same beds with the supposed Proteaceae there occurs at Locle a fan-palm
of the American type Sabal (for genus see Figure 151), a genus which ranges
throughout the low country near the sea from the Carolinas to Florida and
Louisiana. Among the Coniferae of Upper Miocene age is found a deciduous cypress
nearly allied to the Taxodium distichum of North America, and a Glyptostrobus
(Figure 144), very like the Japanese G. heterophyllus, now common in our
shrubberies.
Before the appearance of Heer's work on the Miocene Flora of Switzerland, Unger
and Goppert had already pointed out the large proportion of living North
American genera which distinguished the vegetation of the Miocene period in
Central Europe. Next in number, says Heer, to these American forms at Oeningen
the European genera preponderate, the Asiatic ranking in the third, the African
in the fourth, and the Australian in the fifth degree. The American forms are
more numerous than in the Italian Pliocene flora, and the whole vegetation
indicates a warmer climate than the Pliocene, though not so high a temperature
as that of the older or Lower Miocene period.
The conclusions drawn from the insects are for the most part in perfect harmony
with those derived from the plants, but they have a somewhat less tropical and
less American aspect, the South European types being more numerous. On the
whole, the insect fauna is richer than that now inhabiting any part of Europe.
No less than 844 species are reckoned by Heer from the Oeningen beds alone, the
number of specimens which he has examined being 5080. The entire list of Swiss
species from the Upper and Lower Miocene together amount to 1322. Almost all the
living families of Coleoptera are represented, but, as we might have anticipated
from the preponderance of arborescent and ligneous plants, the wood-eating
beetles play the most conspicuous part, the Buprestidae and other long-horned
beetles being particularly abundant.
(FIGURE 145. Harpactor maculipes, Heer. Upper Miocene, Oeningen.)
The patterns and some remains of the colours both of Coleoptera and Hemiptera
are preserved at Oeningen, as, for example in Harpactor (Figure 145), in which
the antennae, one of the eyes, and the legs and wings are retained. The
characters, indeed, of many of the insects are so well defined as to incline us
to believe that if this class of the invertebrata were not so rare and local,
they might be more useful than even the plants and shells in settling
chronological points in geology.
MIDDLE OR MARINE MOLASSE (UPPER MIOCENE) OF SWITZERLAND.
It was before stated that the Miocene formation of Switzerland consisted of,
first, the upper fresh-water molasse, comprising the lacustrine marls of
Oeningen; secondly, the marine molasse, corresponding in age to the faluns of
Touraine; and thirdly, the lower fresh-water molasse. Some of the beds of the
marine or middle series reach a height of 2470 feet above the sea. A large
number of the shells are common to the faluns of Touraine, the Vienna basin, and
other Upper Miocene localities. The terrestrial plants play a subordinate part
in the fossiliferous beds, yet more than ninety of them are enumerated by Heer
as belonging to this falunian division, and of these more than half are common
to subjacent Lower Miocene beds, while a proportion of about forty-five in one
hundred are common to the overlying Oeningen flora. Twenty-six of the ninety-two
species are peculiar.
UPPER MIOCENE OF THE BOLDERBERG, IN BELGIUM.
(FIGURE 146. Oliva Dufresnii, Bast. Bolderberg, Belgium; natural size.
a. Front view.
b. Back view.)
In a small hill or ridge called the Bolderberg, which I visited in 1851,
situated near Hasselt, about forty miles E.N.E. of Brussels, strata of sand and
gravel occur, to which M. Dumont first called attention as appearing to
constitute a northern representative of the faluns of Touraine. On the whole,
they are very distinct in their fossils from the two upper divisions of the
Antwerp Crag before mentioned (Chapter 13), and contain shells of the genera
Oliva, Conus, Ancillaria, Pleurotoma, and Cancellaria in abundance. The most
common shell is an Olive (Figure 146), called by Nyst Oliva Dufresnii; and
constituting, as M. Bosquet observes, a smaller and shorter variety of the
Bordeaux species.
So far as the shells of the Bolderberg are known, the proportion of recent
species agrees with that in the faluns of Touraine, and the climate must have
been warmer than that of the Coralline Crag of England.
UPPER MIOCENE BEDS OF THE VIENNA BASIN.
In South Germany the general resemblance of the shells of the Vienna tertiary
basin with those of the faluns of Touraine has long been acknowledged. In the
late Dr. Hornes's excellent work on the fossil mollusca of that formation, we
see accurate figures of many shells, clearly of the same species as those found
in the falunian sands of Touraine.
According to Professor Suess, the most ancient and purely marine of the Miocene
strata in this basin consist of sands, conglomerates, limestones, and clays, and
they are inclined inward, or from the borders of the trough towards the centre,
their outcropping edges rising much higher than the newer beds, whether Miocene
or Pliocene, which overlie them, and which occupy a smaller area at an inferior
elevation above the sea. M. Hornes has described no less than 500 species of
gasteropods, of which he identifies one-fifth with living species of the
Mediterranean, Indian, or African seas, but the proportion of existing species
among the lamellibranchiate bivalves exceeds this average. Among many univalves
agreeing with those of Africa on the eastern side of the Atlantic are Cypraea
sanguinolenta, Buccinum lyratum, and Oliva flammulata. In the lowest marine beds
of the Vienna basin the remains of several mammalia have been found, and among
them a species of Dinotherium, a Mastodon of the Trilophodon family, a
Rhinoceros (allied to R. megarhinus, Christol), also an animal of the hog tribe,
Listriodon, von Meyer, and a carnivorous animal of the canine family. The Helix
turonensis (Figure 38 Chapter 3), the most common land shell of the French
faluns, accompanies the above land animals. In a higher member of the Vienna
Miocene series are found Dinotherium giganteum (Figure 136 Chapter 14), Mastodon
longirostris, Rhinoceros Schleiermacheri, Acerotherium incisivum, and
Hippotherium gracile, all of them equally characteristic of an Upper Miocene
deposit occurring at Eppelsheim, in Hesse Darmstadt; a locality also remarkable
as having furnished in latitude 49 degrees 50 north the bone of a large ape of
the Gibbon kind, the most northerly example yet discovered of a quadrumanous
animal.
(FIGURE 147. Amphistegina Hauerina, d'Orbigny. Upper Miocene strata, Vienna.)
M. Alcide d'Orbigny has shown that the foraminifera of the Vienna basin differ
alike from the Eocene and Pliocene species, and agree with those of the faluns,
so far as the latter are known. Among the Vienna foraminifera, the genus
Amphistegina (Figure 147) is very characteristic, and is supposed by d'Archiac
to take the same place among the Rhizopods of the Upper Miocene era which the
Nummulites occupy in the Eocene period.
The flora of the Vienna basin exhibits some species which have a general range
through the whole Miocene period, such as Cinnamomum polymorphum (Figure 138
Chapter 14), and C. Scheuchzeri, also Planera Richardi, Mich., Liquidambar
europaeum (Figure 135 Chapter 13) Juglans bilinica, Cassia ambigua, and C.
lignitum. Among the plants common to the Upper Miocene beds of Oeningen, in
Switzerland, are Platanus aceroides (Figure 141 Chapter 14), Myrica
vindobonensis, and others.
UPPER MIOCENE STRATA OF ITALY.
We are indebted to Signor Michelotti for a valuable work on the Miocene shells
of Northern Italy. Those found in the hill called the Superga, near Turin, have
long been known to correspond in age with the faluns of Touraine, and they
contain so many species common to the Upper Miocene strata of Bordeaux as to
lead to the conclusion that there was a free communication between the northern
part of the Mediterranean and the Bay of Biscay in the Upper Miocene period.
UPPER MIOCENE FORMATIONS OF GREECE.
At Pikerme, near Athens, MM. Wagner and Roth have described a deposit in which
they found the remains of the genera Mastodon, Dinotherium, Hipparion, two
species of Giraffe, Antelope, and others, some living and some extinct. With
them were also associated fossil bones of the Semnopithecus, showing that here,
as in the south of France, the quadrumana were characteristic of this period.
The whole fauna attests the former extension of a vast expanse of grassy plains
where we have now the broken and mountainous country of Greece; plains, which
were probably united with Asia Minor, spreading over the area where the deep
Aegean Sea and its numerous islands are now situated. We are indebted to M.
Gaudry, who visited Pikerme, for a treatise on these fossil bones, showing how
many data they contribute to the theory of a transition from the mammalia of the
Upper Miocene through the Pliocene and Post-pliocene forms to those of living
genera and species.
UPPER MIOCENE OF INDIA. SIWALIK HILLS.
The Siwalik Hills lie at the southern foot of the Himalayan chain, rising to the
height of 2000 and 3000 feet. Between the Jumna and the Ganges they consist of
inclined strata of sandstone, shingle, clay, and marl. We are indebted to the
indefatigable researches of Dr. Falconer and Sir Proby Cautley, continued for
fifteen years, for the discovery in these marls and sandstones of a great
variety of fossil mammalia and reptiles, together with many fresh-water shells.
Out of fifteen species of shells of the genera Paludina, Melania, Ampullaria,
and Unio, all are extinct or unknown species with the exception of four, which
are still inhabitants of Indian rivers. Such a proportion of living to extinct
mollusca agrees well with the usual character of an Upper Miocene or Falunian
fauna, as observed in Touraine, or in the basin of Vienna and elsewhere.
The genera of mammalia point in the same direction. One of them, of the genus
Chalicotherium (or Anisodon of Lartet), is a pachyderm intermediate between the
Rhinoceros and Anoplothere, and characteristic of the Upper Miocene strata of
Eppelsheim, and of the south of France. With it occurs also an extinct form of
Hippopotamus, called Hexaprotodon, and a species of Hippotherium and pig, also
two species of Mastodon, two of elephant, and three other elephantine
proboscidians; none of them agreeing with any fossil forms of Europe, and being
intermediate between the genera Elephas and Mastodon, constituting the sub-genus
Stegodon of Falconer. With these are associated a monkey, allied to the
Semnopithecus entellus, now living in the Himalaya, and many ruminants. Among
these last, besides the giraffe, camel, antelope, stag, and others, we find a
remarkable new type, the Sivatherium, like a gigantic four-horned deer. There
are also new forms of carnivora, both feline and canine, the Machairodus among
the former, also hyaenas, and a subursine form called the Hyaenarctos, and a
genus allied to the otter (Enhydriodon), of formidable size.
The giraffe, camel, and a large ostrich may be cited as proofs that there were
formerly extensive plains where now a steep chain of hills, with deep ravines,
runs for many hundred miles east and west. Among the accompanying reptiles are
several crocodiles, some of huge dimensions, and one not distinguishable, says
Dr. Falconer, from a species now living in the Ganges (C. Gangeticus); and there
is still another saurian which the same anatomist has identified with a species
now inhabiting India. There was also an extinct species of tortoise of gigantic
proportions (Colossochelys Atlas), the curved shell of which was twelve feet
three inches long and eight feet in diameter, the entire length of the animal
being estimated at eighteen feet, and its probable height seven feet.
Numerous fossils of the Siwalik type have also been found in Perim Island, in
the Gulf of Cambay, and among these a species of Dinotherium, a genus so
characteristic of the Upper Miocene period in Europe.
OLDER PLIOCENE AND MIOCENE FORMATIONS IN THE UNITED STATES.
Between the Alleghany Mountains, formed of older rocks, and the Atlantic, there
intervenes, in the United States, a low region occupied principally by beds of
marl, clay, and sand, consisting of the cretaceous and tertiary formations, and
chiefly of the latter. The general elevation of this plain bordering the
Atlantic does not exceed 100 feet, although it is sometimes several hundred feet
high. Its width in the middle and southern states is very commonly from 100 to
150 miles. It consists, in the South, as in Georgia, Alabama, and South
Carolina, almost exclusively of Eocene deposits; but in North Carolina,
Maryland, Virginia, Delaware, more modern strata predominate, of the age of the
English Crag and faluns of Touraine. (Proceedings of the Geological Society
volume 4 part 3 1845 page 547.)
(FIGURE 148. Fulgur canaliculatus. Maryland.)
(FIGURE 149. Fusus quadricostatus, Say. Maryland.)
In the Virginian sands, we find in great abundance a species of Astarte (A.
undulata, Conrad), which resembles closely, and may possibly be a variety of,
one of the commonest fossils of the Suffolk Crag (A. Omalii); the other shells
also, of the genera Natica, Fissurella, Artemis, Lucina, Chama, Pectunculus, and
Pecten, are analagous to shells both of the English Crag and French faluns,
although the species are almost all distinct. Out of 147 of these American
fossils I could only find thirteen species common to Europe, and these occur
partly in the Suffolk Crag, and partly in the faluns of Touraine; but it is an
important characteristic of the American group, that it not only contains many
peculiar extinct forms, such as Fusus quadricostatus, Say (see Figure 149), and
Venus tridacnoides, abundant in these same formations, but also some shells
which, like Fulgur carica of Say and F. canaliculatus (see Figure 148),
Calyptraea costata, Venus mercenaria, Lam., Modiola glandula, Totten, and Pecten
magellanicus, Lam., are recent species, yet of forms now confined to the western
side of the Atlantic-- a fact implying that some traces of the beginning of the
present geographical distribution of mollusca date back to a period as remote as
that of the Miocene strata.
Of ten species of corals which I procured on the banks of the James River, one
agrees generically with a coral now living on the coast of the United States.
Mr. Lonsdale regarded these corals as indicating a temperature exceeding that of
the Mediterranean, and the shells would lead to similar conclusions. Those
occurring on the James River are in the 37th degree of N. latitude, while the
French faluns are in the 47th; yet the forms of the American fossils would
scarcely imply so warm a climate as must have prevailed in France when the
Miocene strata of Touraine originated.
(FIGURE 150. Astrangia lineata, Lonsdale. Syn. Anthophyllum lineatum.
Williamsburg, Virginia.)
Among the remains of fish in these post-eocene strata of the United States are
several large teeth of the shark family, not distinguishable specifically from
fossils of the faluns of Touraine.
CHAPTER XV.
LOWER MIOCENE (OLIGOCENE OF BEYRICH).
Lower Miocene Strata of France.
Line between Miocene and Eocene.
Lacustrine Strata of Auvergne.
Fossil mammalia of the Limagne d'Auvergne.
Lower Molasse of Switzerland.
Dense Conglomerates and Proofs of Subsidence.
Flora of the Lower Molasse.
American Character of the Flora.
Theory of a Miocene Atlantis.
Lower Miocene of Belgium.
Rupelian Clay of Hermsdorf near Berlin.
Mayence Basin.
Lower Miocene of Croatia.
Oligocene Strata of Beyrich.
Lower Miocene of Italy.
Lower Miocene of England.
Hempstead Beds.
Bovey Tracey Lignites in Devonshire.
Isle of Mull Leaf-Beds.
Arctic Miocene Flora.
Disco Island.
Lower Miocene of United States.
Fossils of Nebraska.
LINE BETWEEN MIOCENE AND EOCENE FORMATIONS.
The marine faluns of the valley of the Loire have been already described as
resting in some places on a fresh-water tertiary limestone, fragments of which
have been broken off and rolled on the shores and in the bed of the Miocene sea.
Such pebbles are frequent at Pontlevoy on the Cher, with hollows drilled in them
in which the perforating marine shells of the Falunian period still remain. Such
a mode of superposition implies an interval of time between the origin of the
fresh-water limestone and its submergence beneath the waters of the Upper
Miocene sea. The limestone in question forms a part of the formation called the
Calcaire de la Beauce, which constitutes a large table-land between the basins
of the Loire and the Seine. It is associated with marls and other deposits, such
as may have been formed in marshes and shallow lakes in the newest part of a
great delta. Beds of flint, continuous or in nodules, accumulated in these
lakes, and aquatic plants called Charae, left their stems and seed-vessels
imbedded both in the marl and flint, together with fresh-water and land shells.
Some of the siliceous rocks of this formation are used extensively for mill-
stones. The flat summits or platforms of the hills round Paris, and large areas
in the forest of Fontainebleau, as well as the Plateau de la Beauce, already
alluded to, are chiefly composed of these fresh-water strata. Next to these in
the descending order are marine sands and sandstone, commonly called the Gres de
Fontainebleau, from which a considerable number of shells, very distinct from
those of the faluns, have been obtained at Etampes, south of Paris, and at
Montmartre and other hills in Paris itself, or in its suburbs. At the bottom of
these sands a green clay occurs, containing a small oyster, Ostrea cyathula,
Lam., which, although of slight thickness, is spread over a wide area. This clay
rests immediately on the Paris gypsum, or that series of beds of gypsum and
gypseous marl from which Cuvier first obtained several species of Palaeotherium
and other extinct mammalia. (Bulletin 1856 Journal volume 12 page 768.)
At this junction of the clay and the gypsum the majority of French geologists
have always drawn the line between the Middle and Lower Tertiary, or between the
Miocene and Eocene formations, regarding the Fontainebleau sands and the Ostrea
cyathula clay as the base of the Miocene, and the gypsum, with its mammalia, as
the top of the Eocene group. I formerly dissented from this division, but I now
find that I must admit it to be the only one which will agree with the
distribution of the Miocene mammalia, while even the mollusca of the
Fontainebleau sands, which were formerly supposed to present at preponderance of
affinities to an Eocene fauna, have since been shown to agree more closely with
the fossils of certain deposits always regarded as Middle Tertiary at Mayence
and in Belgium. In fact, we are now arriving at that stage of progress when the
line, wherever it be drawn between Miocene and Eocene, will be an arbitrary one,
or one of mere convenience, as I shall have an opportunity of showing when the
Upper Eocene formations in the Isle of Wight are described in the sixteenth
chapter.
LOWER MIOCENE OF CENTRAL FRANCE.
Lacustrine strata, belonging, for the most part, to the same Miocene system as
the Calcaire de la Beauce, are again met with farther south in Auvergne, Cantal,
and Velay. They appear to be the monuments of ancient lakes, which, like some of
those now existing in Switzerland, once occupied the depressions in a
mountainous region, and have been each fed by one or more rivers and torrents.
The country where they occur is almost entirely composed of granite and
different varieties of granitic schist, with here and there a few patches of
Secondary strata, much dislocated, and which have suffered great denudation.
There are also some vast piles of volcanic matter, the greater part of which is
newer than the fresh-water strata, and is sometimes seen to rest upon them,
while a small part has evidently been of contemporaneous origin. Of these
igneous rocks I shall treat more particularly in the sequel.
The study of these regions possesses a peculiar interest very distinct in kind
from that derivable from the investigation either of the Parisian or English
Tertiary areas. For we are presented in Auvergne with the evidence of a series
of events of astonishing magnitude and grandeur, by which the original form and
features of the country have been greatly changed, yet never so far obliterated
but that they may still, in part at least, be restored in imagination. Great
lakes have disappeared-- lofty mountains have been formed, by the reiterated
emission of lava, preceded and followed by showers of sand and scoriae-- deep
valleys have been subsequently furrowed out through masses of lacustrine and
volcanic origin-- at a still later date, new cones have been thrown up in these
valleys-- new lakes have been formed by the damming up of rivers-- and more than
one assemblage of quadrupeds, birds, and plants, Eocene, Miocene, and Pliocene,
have followed in succession; yet the region has preserved from first to last its
geographical identity; and we can still recall to our thoughts its external
condition and physical structure before these wonderful vicissitudes began, or
while a part only of the whole had been completed. There was first a period when
the spacious lakes, of which we still may trace the boundaries, lay at the foot
of mountains of moderate elevation, unbroken by the bold peaks and precipices of
Mont Dor, and unadorned by the picturesque outline of the Puy de Dome, or of the
volcanic cones and craters now covering the granitic platform. During this
earlier scene of repose deltas were slowly formed; beds of marl and sand,
several hundred feet thick, deposited; siliceous and calcareous rocks
precipitated from the waters of mineral springs; shells and insects imbedded,
together with the remains of the crocodile and tortoise, the eggs and bones of
water-birds, and the skeletons of quadrupeds, most of them of genera and species
characteristic of the Miocene period. To this tranquil condition of the surface
succeeded the era of volcanic eruptions, when the lakes were drained, and when
the fertility of the mountainous district was probably enhanced by the igneous
matter ejected from below, and poured down upon the more sterile granite. During
these eruptions, which appear to have taken place towards the close of the
Miocene epoch, and which continued during the Pliocene, various assemblages of
quadrupeds successively inhabited the district, among which are found the genera
mastodon, rhinoceros, elephant, tapir, hippopotamus, together with the ox,
various kinds of deer, the bear, hyaena, and many beasts of prey which ranged
the forest or pastured on the plain, and were occasionally overtaken by a fall
of burning cinders, or buried in flows of mud, such as accompany volcanic
eruptions. Lastly, these quadrupeds became extinct, and gave place in their turn
to the species now existing. There are no signs, during the whole time required
for this series of events, of the sea having intervened, nor of any denudation
which may not have been accomplished by currents in the different lakes, or by
rivers and floods accompanying repeated earthquakes, or subterranean movements,
during which the levels of the district have in some places been materially
modified, and perhaps the whole upraised relatively to the surrounding parts of
France.
AUVERGNE.
The most northern of the fresh-water groups is situated in the valley-plain of
the Allier, which lies within the department of the Puy de Dome, being the tract
which went formerly by the name of the Limagne d'Auvergne. The average breadth
of this tract is about twenty miles; and it is for the most part composed of
nearly horizontal strata of sand, sandstone, calcareous marl, clay, and
limestone, none of which observe a fixed and invariable order of superposition.
The ancient borders of the lake wherein the fresh-water strata were accumulated
may generally be traced with precision, the granite and other ancient rocks
rising up boldly from the level country. The actual junction, however, of the
lacustrine beds and the granite is rarely seen, as a small valley usually
intervenes between them. The fresh-water strata may sometimes be seen to retain
their horizontality within a very slight distance of the border-rocks, while in
some places they are inclined, and in few instances vertical. The principal
divisions into which the lacustrine series may be separated are the following:--
first, Sandstone, grit, and conglomerate, including red marl and red sandstone;
secondly, Green and white foliated marls; thirdly, Limestone, or travertin,
often oolitic in structure; fourthly, Gypseous marls.
The relations of these different groups can not be learnt by the study of any
one section; and the geologist who sets out with the expectation of finding a
fixed order of succession may perhaps complain that the different parts of the
basin give contradictory results. The arenaceous division, the marls, and the
limestone may all be seen in some places to alternate with each other; yet it
can by no means be affirmed that there is no order of arrangement. The sands,
sandstone, and conglomerate constitute in general a littoral group; the foliated
white and green marl, a contemporaneous central deposit more than 700 feet
thick, and thinly foliated, a character which often arises from the innumerable
thin shells or carapace valves shed by the small crustacean called Cypris in the
ancient lakes of Auvergne; and lastly the limestone is for the most part
subordinate to the newer portions of both the above formations.
It seems that, when the ancient lake of the Limagne first began to be filled
with sediment, no volcanic action had yet produced lava and scoriae on any part
of the surface of Auvergne. No pebbles, therefore, of lava were transported into
the lake-- no fragments of volcanic rocks imbedded in the conglomerate. But at a
later period, when a considerable thickness of sandstone and marl had
accumulated, eruptions broke out, and lava and tuff were deposited, at some
spots, alternately with the lacustrine strata. It is not improbable that cold
and thermal springs, holding different mineral ingredients in solution, became
more numerous during the successive convulsions attending this development of
volcanic agency, and thus deposits of carbonate and sulphate of lime, silex, and
other minerals were produced. Hence these minerals predominate in the uppermost
strata. The subterranean movements may then have continued until they altered
the relative levels of the country, and caused the waters of the lakes to be
drained off, and the further accumulation of regular fresh-water strata to
cease.
LOWER MIOCENE MAMMALIA OF THE LIMAGNE.
It is scarcely possible to determine the age of the oldest part of the fresh-
water series of the Limagne, large masses both of the sandy and marly strata
being devoid of fossils. Some of the lowest beds may be of Upper Eocene date,
although, according to M. Pomel, only one bone of a Palaeotherium has been
discovered in Auvergne. But in Velay, in strata containing some species of
fossil mammalia common to the Limagne, no less than four species of Palaeothere
have been found by M. Aymard, and one of these is generally supposed to be
identical with Palaeotherium magnum, an undoubted Upper Eocene fossil, of the
Paris gypsum, the other three being peculiar.
Not a few of the other mammalia of the Limagne belong undoubtedly to genera and
species elsewhere proper to the Lower Miocene. Thus, for example, the
Cainotherium of Bravard, a genus not far removed from the Anoplotherium, is
represented by several species, one of which, as I learn from Mr. Waterhouse,
agrees with Microtherium Renggeri of the Mayence basin. In like manner, the
Amphitragulus elegans of Pomel, an Auvergne fossil, is identified by Waterhouse
with Dorcatherium nanum of Kaup, a Rhenish species from Weissenau, near Mayence.
A small species, also, of rodent, of the genus Titanomys of H. von Meyer, is
common to the Lower Miocene of Mayence and the Limagne d'Auvergne, and there are
many other points of agreement which the discordance of nomenclature tends to
conceal. A remarkable carnivorous genus, the Hyaenodon of Laizer, is represented
by more than one species. The same genus has also been found in the Upper Eocene
marls of Hordwell Cliff, Hampshire, just below the level of the Bembridge
Limestone, and therefore a formation older than the Gypsum of Paris. Several
species of opossum (Didelphis) are met with in the same strata of the Limagne.
The total number of mammalia enumerated by M. Pomel as appertaining to the Lower
Miocene fauna of the Limagne and Velay falls little short of a hundred, and with
them are associated some large crocodiles and tortoises, and some Ophidian and
Batrachian reptiles.
LOWER MOLASSE OF SWITZERLAND.
The two upper divisions of the Swiss Molasse-- the one fresh-water, the other
marine-- have already been described in the preceding chapter. I shall now
proceed to treat of the third division, which is of Lower Miocene age. Nearly
the whole of this Lower Molasse is fresh-water, yet some of the inferior beds
contain a mixture of marine and fluviatile shells, the Cerithium margaritaceum,
a well-known Lower Miocene fossil, being one of the marine species.
Notwithstanding, therefore, that some of these Lower Miocene strata consist of
old shingle-beds several thousand feet in thickness, as in the Rigi, near
Lucerne, and in the Speer, near Wesen, mountains 5000 and 7000 feet above the
sea, the deposition of the whole series must have begun at or below the sea-
level.
The conglomerates, as might be expected, are often very unequal in thickness, in
closely adjoining districts, since in a littoral formation accumulations of
pebbles would swell out in certain places where rivers entered the sea, and
would thin out to comparatively small dimensions where no streams or only small
ones came down to the coast. For ages, in spite of a gradual depression of the
land and adjacent sea-bottom, the rivers continued to cover the sinking area
with their deltas; until finally, the subsidence being in excess, the sea of the
Middle Molasse gained upon the land, and marine beds were thrown down over the
dense mass of fresh-water and brackish-water deposit, called the Lower Molasse,
which had previously accumulated.
FLORA OF THE LOWER MOLASSE.
In part of the Swiss Molasse, which belongs exclusively to the Lower Miocene
period, the number of plants has been estimated at more than 500 species,
somewhat exceeding those which were before enumerated as occurring in the two
upper divisions. The Swiss Lower Miocene may best be studied on the northern
borders of the Lake of Geneva, between Lausanne and Vevay, where the contiguous
villages of Monod and Rivaz are situated. The strata there, which I have myself
examined, consist of alternations of conglomerate, sandstone, and finely
laminated marls with fossil plants. A small stream falls in a succession of
cascades over the harder beds of pudding-stone, which resist, while the
sandstone and plant-bearing shales and marls give way. From the latter no less
than 193 species of plants have been obtained by the exertions of MM. Heer and
Gaudin, and they are considered to afford a true type of the vegetation of the
Lower Miocene formations of Switzerland-- a vegetation departing farther in its
character from that now flourishing in Europe than any of the higher members of
the series before alluded to, and yet displaying so much affinity to the flora
of Oeningen as to make it natural for the botanist to refer the whole to one and
the same Miocene period. There are, indeed, no less than 81 species of these
Older Miocene plants which pass up into the flora of Oeningen.
This fact is important as bearing on the propriety of classing the Lower Molasse
of Switzerland as belonging to the Miocene rather than to the latter part of the
Eocene period. There are, indeed, so many types among the fossils, both specific
and generic, which have a wide range through the whole of the Molasse, that a
unity of character is thereby stamped on the whole flora, in spite of the
contrast between the plants of the uppermost and lowest formations, or between
Oeningen and Monod. The proofs of a warmer climate, and the excess of
arborescent over herbaceous plants, and of evergreen trees over deciduous
species, are characters common to the whole flora, but which are intensified as
we descend to the inferior deposits.
(FIGURE 151. Sabal major, Unger sp. Vevay. Lower Miocene; Heer, Plate 41.)
Nearly all the plants at Monod are contained in three layers of marl separated
by two of soft sandstone. The thickness of the marls is ten feet, and vegetable
matter predominates so much in some layers as to form an imperfect lignite. One
bed is filled with large leaves of a species of fig (Ficus populina), and of a
hornbeam (Carpinus grandis), the strength of the wind having probably been great
when they were blown into the lake; whereas another contiguous layer contains
almost exclusively smaller leaves, indicating, apparently, a diminished strength
in the wind. Some of the upper beds at Monod abound in leaves of Proteaceae,
Cyperaceae, and ferns, while in some of the lower ones Sequoia, Cinnamomum, and
Sparganium are common. In one bed of sandstone the trunk of a large palm-tree
was found unaccompanied by other fossils, and near Vevay, in the same series of
Lower Miocene strata, the leaves of a palm of the genus Sabal (Figure 151), a
genus now proper to America, were obtained.
Among other genera of the same class is a Flabellaria occurring near Lausanne,
and a magnificent Phoenicites allied to the date palm. When these plants
flourished the climate must have been much hotter than now. The Alps were no
doubt much lower, and the palms now found fossil in strata elevated 2000 feet
above the sea grew nearly at the sea-level, as is demonstrated by the brackish-
water character of some of the beds into which they were carried by winds or
rivers from the adjoining coast.
(FIGURE 152. Banksia.
a. Fruit of fossil Banksia.
b. Leaf of Banksia Deekiana.)
In the same plant-bearing deposits of the Lower Molasse in Switzerland leaves
have been found which have been ascribed to the order Proteaceae already spoken
of as well represented in the Oeningen beds (see Chapter 14). The Proteas and
other plants of this family now flourish at the Cape of Good Hope; while the
Banksias, and a set of genera distinct from those of Africa, grow most
luxuriantly in the southern and temperate parts of Australia. They were probably
inhabitants, says Heer, of dry hilly ground, and the stiff leathery character of
their leaves must have been favourable to their preservation, allowing them to
float on a river for great distances without being injured, and then to sink,
when water-logged, to the bottom. It has been objected that the fruit of the
Proteaceae is of so tough and enduring a texture that it ought to have been more
commonly met with; but in the first place we must not forget the numerous cones
found in the Eocene strata of Sheppey, which all admit to be proteaceous and to
belong to at least two species (see Chapter 14). Secondly, besides the fruit of
Hakea before mentioned (Chapter 14), Heer found associated with fossil leaves,
having the exact form and nervation of Banksia, fruit precisely such as may have
come from a cone of that plant, and lately he has received another similar fruit
from the Lower Miocene strata of Lucerne. They may have fallen out of a decayed
cone in the same way as often happens to the seeds of the spruce fir, Pinus
abies, found scattered over the ground in our woods. It is a known fact that
among the living Proteaceae the cones are very firmly attached to the branches,
so that the seeds drop out without the cone itself falling to the ground, and
this may perhaps be the reason why, in some instances in which fossil seeds have
been found, no traces of the cone have been observed.
(FIGURE 153. Sequoia Langsdorfii. Ad. Brong., 1/3 natural size. Rivaz, near
Lausanne; Heer, Plate 21 Figure 4. Upper and Lower Miocene and Lower Pliocene,
Val d'Arno.
a. Branch with leaves.
b. Young cone.)
Among the Coniferae the Sequoia here figured is common at Rivaz, and is one of
the most universal plants in the Lowest Miocene of Switzerland, while it also
characterises the Miocene Brown Coals of Germany and certain beds of the Val
d'Arno, which I have called Older Pliocene, Chapter 13.
(FIGURE 154. Lastraea stiriaca, Unger; Heer's Flora, Plate 143 Figure 8. Natural
size. Lower and Upper Miocene, Switzerland.
a. Specimen from Monod, showing the position of the sori on the middle of the
tertiary nerves.
b. More common appearance, where the sori remain and the nerves are
obliterated.)
Among the ferns met with in profusion at Monod is the Lastraea stiriaca, Unger,
which has a wide range in the Miocene period from strata of the age of Oeningen
to the lowest part of the Swiss Molasse. In some specimens, as shown in Figure
154, the fructification is distinctly seen.
(FIGURE 155. Cinnamomum Rossmassleri, Heer. Daphnogene cinnamomifolia, Unger.
Upper and Lower Miocene, Switzerland and Germany.)
Among the laurels several species of Cinnamomum are very conspicuous. Besides
the C. polymorphum, before figured, Chapter 14, another species also ranges from
the Lower to the Upper Molasse of Switzerland, and is very characteristic of
different deposits of Brown Coal in Germany. It has been called Cinnamomum
Rossmassleri by Heer (see Figure 155). The leaves are easily recognised as
having two side veins, which run up uninterruptedly to their point.
AMERICAN CHARACTER OF THE FLORA.
If we consider not merely the number of species but those plants which
constitute the mass of the Lower Miocene vegetation, we find the European part
of the fossil flora very much less prominent than in the Oeningen beds, while
the foreground is occupied by American forms, by evergreen oaks, maples,
poplars, planes, Liquidambar, Robinia, Sequoia, Taxodium, and ternate-leaved
pines. There is also a much greater fusion of the characters now belonging to
distinct botanical provinces than in the Upper Miocene flora, and we shall find
this fusion still more strikingly exemplified as we go back to the antecedent
Eocene and Cretaceous periods.
Professor Heer has advocated the doctrine, first advanced by Unger to explain
the large number of American genera in the Miocene flora of Europe, that the
present basin of the Atlantic was occupied by land over which the Miocene flora
could pass freely. But other able botanists have shown that it is far more
probable that the American plants came from the east and not from the west, and
instead of reaching Europe by the shortest route over an imaginary Atlantis,
migrated in an opposite direction, crossing the whole of Asia.
ARCTIC MIOCENE FLORA.
But when we indulge in speculations as to the geographical origin of the Miocene
plants of Central Europe, we must take into account the discoveries recently
made of a rich terrestrial flora having flourished in the Arctic Regions in the
Miocene period from which many species may have migrated from a common centre so
as to reach the present continents of Europe, Asia, and America. Professor Heer
has examined the various collections of fossil plants that have been obtained in
North Greenland (latitude 70 degrees), Iceland, Spitzbergen, and other parts of
the Arctic regions, and has determined that they are of Miocene age and indicate
a temperate climate. (Heer "Miocene baltische Flora" and "Fossil-flora von
Alaska" 1869.) Including the collections recently brought from Greenland by Mr.
Whymper, the Arctic Miocene flora now comprises 194 species, and that of
Greenland 137 species, of which 46, or exactly one-third, are identical with
plants found in the Miocene beds of Central Europe. Considerably more than half
the number are trees, which is the more remarkable since, at the present day,
trees do not exist in any part of Greenland even 10 degrees farther south.
More than thirty species of Coniferae have been found, including several
Sequoias (allied to the gigantic Wellingtonia of California), with species of
Thujopsis and Salisburia now peculiar to Japan. There are also beeches, oaks,
planes, poplars, maples, walnuts, limes, and even a magnolia, two cones of which
have recently been obtained, proving that this splendid evergreen not only lived
but ripened its fruit within the Arctic circle. Many of the limes, planes, and
oaks were large-leaved species, and both flowers and fruit, besides immense
quantities of leaves, are in many cases preserved. Among the shrubs were many
evergreens, as Andromeda, and two extinct genera, Daphnogene and M'Clintockia,
with fine leathery leaves, together with hazel, blackthorn, holly, logwood, and
hawthorn. A species of Zamia (Zamites) grew in the swamps, with Potamogeton,
Sparganium, and Menyanthes, while ivy and vines twined around the forest trees
and broad-leaved ferns grew beneath their shade. Even in Spitzbergen, as far
north as latitude 78 degrees 56', no less than ninety-five species of fossil
plants have been obtained, including Taxodium of two species, hazel, poplar,
alder, beech, plane-tree, and lime. Such a vigorous growth of trees within 12
degrees of the pole, where now a dwarf willow and a few herbaceous plants form
the only vegetation, and where the ground is covered with almost perpetual snow
and ice, is truly remarkable.
The identity of so many of the fossils with Miocene species of Central Europe
and Italy not only proves that the climate of Greenland was much warmer than it
is now, but also renders it probable that a much more uniform climate prevailed
over the entire northern hemisphere. This is also indicated by the whole
character of the Upper Miocene flora of Central Europe, which does not
necessitate a mean temperature very much greater than exists at present, if we
suppose such absence of winter cold as is proper to insular climates. Professor
Heer believes that the mean temperature of North Greenland must have been at
least 30 degrees higher than at present, while an addition of 10 degrees to the
mean temperature of Central Europe would probably be as much as was required.
The chief locality where this wonderful flora is preserved is at Atanekerdluk in
North Greenland (latitude 70 degrees), on a hill at an elevation of about 1200
feet above the sea. There is here a considerable succession of sedimentary
strata pierced by volcanic rocks. Fossil plants occur in all the beds, and the
erect trunks as thick as a man's body which are sometimes found, together with
the abundance of specimens of flowers and fruit in good preservation,
sufficiently prove that the plants grew where they are now found. At Disco
island and other localities on the same part of the coast, good coal is
abundant, interstratified with beds of sandstone, in some of which fossil plants
have also been found, similar to those at Atanekerdluk.
LOWER MIOCENE, BELGIUM.
(FIGURE 156. Leda (Nucula) Deshayesiana, Nyst.)
(FIGURE 157. Vanessa pluto; natural size. Lower Miocene, Radaboj, Croatia.)
The Upper Miocene Bolderberg beds, mentioned in Chapter 14, rest on a Lower
Miocene formation called the Rupelian of Dumont. This formation is best seen at
the villages of Rupelmonde and Boom, ten miles south of Antwerp, on the banks of
the Scheldt and near the junction with it of a small stream called the Rupel. A
stiff clay abounding in fossils is extensively worked at the above localities
for making tiles. It attains a thickness of about 100 feet, and though very
different in age, much resembles in mineral character the "London clay,"
containing, like it, septaria or concretions of argillaceous limestone traversed
by cracks in the interior, which are filled with calc-spar. The shells,
referable to about forty species, have been described by MM. Nyst and De
Koninck. Among them Leda (or Nucula) Deshayesiana (see Figure 156) is by far the
most abundant; a fossil unknown as yet in the English tertiary strata, but when
young much resembling Leda amygdaloides of the London Clay proper (see Figure
213 Chapter 16). Among other characteristic shells are Pecten Hoeninghausii, and
a species of Cassidaria, and several of the genus Pleurotoma. Not a few of these
testacea agree with English Eocene species, such as Actaeon simulatus, Sowb,
Cancellaria evulsa, Brander, Corbula pisum (Figure 157), and Nautilus (Aturia)
ziczac. They are accompanied by many teeth of sharks, as Lamna contortidens,
Ag., Oxyrhinaxiphodon, Ag., Carcharodon angustidens (see Figure 196 Chapter 16),
Ag., and other fish, some of them common to the Middle Eocene strata.
KLEYN SPAWEN BEDS.
The succession of the Lower Miocene strata of Belgium can be best studied in the
environs of Kleyn Spawen, a village situated about seven miles west of
Maestricht, in the old province of Limburg in Belgium. In that region, about 200
species of testacea, marine and fresh-water, have been obtained, with many
foraminifera and remains of fish. In none of the Belgian Lower Miocene strata
could I find any nummulites; and M. d'Archiac had previously observed that these
foraminifera characterise his "Lower Tertiary Series," as contrasted with the
Middle, and they therefore serve as a good test of age between Eocene and
Miocene, at least in Belgium and the North of France. (D'Archiac Monograph pages
79, 100.) Between the Bolderberg beds and the Rupelian clay there is a great gap
in Belgium, which seems, according to M. Beyrich, to be filled up in the North
of Germany by what he calls the Sternberg beds, and which, had Dumont found them
in Belgium, he might probably have termed Upper Rupelian.
LOWER MIOCENE OF GERMANY.
RUPELIAN CLAY OF HERMSDORF, NEAR BERLIN.
Professor Beyrich has described a mass of clay, used for making tiles, within
seven miles of the gates of Berlin, near the village of Hermsdorf, rising up
from beneath the sands with which that country is chiefly overspread. This clay
is more than forty feet thick, of a dark bluish-grey colour, and, like that of
Rupelmonde, contains septaria. Among other shells, the Leda Deshayesiana, before
mentioned (Figure 156), abounds, together with many species of Pleurotoma,
Voluta, etc., a certain proportion of the fossils being identical in species
with those of Rupelmonde.
MAYENCE BASIN.
An elaborate description has been published by Dr. F. Sandberger of the Mayence
tertiary area, which occupies a tract from five to twelve miles in breadth,
extending for a great distance along the left bank of the Rhine from Mayence to
the neighbourhood of Manheim, and which is also found to the east, north, and
south-west of Frankfort. M. De Koninck, of Liege, first pointed out to me that
the purely marine portion of the deposit contained many species of shells common
to the Kleyn Spawen beds, and to the clay of Rupelmonde, near Antwerp. Among
these he mentioned Cassidaria depressa, Tritonium argutum, Brander (T.
flandricum, De Koninck), Tornatella simulata, Aporrhais Sowbyi, Leda
Deshayesiana (Figure 156), Corbula pisum, (Figure 158) and others.
LOWER MIOCENE BEDS OF CROATIA.
The Brown Coal of Radaboj, near Angram in Croatia, not far from the borders of
Styria, is covered, says Von Buch, by beds containing the marine shells of the
Vienna basin, or, in other words, by Upper Miocene or Falunian strata. They
appear to correspond in age to the Mayence basin, or to the Rupelian strata of
Belgium. They have yielded more than 200 species of fossil plants, described by
the late Professor Unger. These plants are well preserved in a hard marlstone,
and contain several palms; among them the Sabal, Figure 151, and another genus
allied to the date-palm Phoenicites spectabilis. The only abundant plant among
the Radaboj fossils which is characteristic of the Upper Miocene period is the
Populus mutabilis, whereas no less than fifty of the Radaboj species are common
to the more ancient flora of the Lower Molasse of Switzerland.
The insect fauna is very rich, and, like the plants, indicates a more tropical
climate than do the fossils of Oeningen presently to be mentioned. There are ten
species of Termites, or white ants, some of gigantic size, and large dragon-
flies with speckled wings, like those of the Southern States in North America;
there are also grasshoppers of considerable size, and even the Lepidoptera are
not unrepresented. In one instance, the pattern of a butterfly's wing has
escaped obliteration in the marl-stone of Radaboj; and when we reflect on the
remoteness of the time from which it has been faithfully transmitted to us, this
fact may inspire the reader with some confidence as to the reliable nature of
the characters which other insects of a more durable texture, such as the
beetles, may afford for specific determination. The Vanessa above figured
retains, says Heer, some of its colours, and corresponds with Vanessa Hadena of
India.
Professor Beyrich has made known to us the existence of a long succession of
marine strata in North Germany, which lead by an almost gradual transition from
beds of Upper Miocene age to others of the age of the base of the Lower Miocene.
Although some of the German lignites called Brown Coal belong to the upper parts
of this series, the most important of them are of Lower Miocene date, as, for
example, those of the Siebengebirge, near Bonn, which are associated with
volcanic rocks.
Professor Beyrich confines the term "Miocene" to those strata which agree in age
with the faluns of Touraine, and he has proposed the term "Oligocene" for those
older formations called Lower Miocene in this work.
LOWER MIOCENE OF ITALY.
In the hills of which the Superga forms a part there is a great series of
Tertiary strata which pass downward into the Lower Miocene. Even in the Superga
itself there are some fossil plants which, according to Heer, have never been
found in Switzerland so high as the marine Molasse, such as Banksia longifolia,
and Carpinus grandis. In several parts of the Ligurian Apennines, as at Dego and
Carcare, the Lower Miocene appears, containing some nummulites, and at Cadibona,
north of Savona, fresh-water strata of the same age occur, with dense beds of
lignite inclosing remains of the Anthracotherium magnum and Anthracotherium
minimum, besides other mammalia enumerated by Gastaldi. In these beds a great
number of the Lower Miocene plants of Switzerland have been discovered.
LOWER MIOCENE OF ENGLAND-- HEMPSTEAD BEDS.
We have already stated that the Upper Miocene formation is nowhere represented
in the British Isles; but strata referable to the Lower Miocene period are found
both in England, Scotland, and Ireland. In the Hampshire basin these occupy a
very small superficial area, having been discovered by the late Edward Forbes at
Hempstead near Yarmouth, in the northern part of the Isle of Wight, where they
are 170 feet thick, and rich in characteristic marine shells. They overlie the
uppermost of an extensive series of Eocene deposits of marine, brackish, and
fresh-water formations, which rest on the Chalk and terminate upward in strata
corresponding in age to the Paris gypsum, and containing the same extinct genera
of quadrupeds, Palaeotherium, Anoplotherium, and others which Cuvier first
described. The following is the succession of these Lower Miocene strata, most
of them exposed in a cliff east of Yarmouth:
(FIGURE 158. Corbula pisum. Hempstead Beds, Isle of Wight.)
(FIGURE 159. Cyrena semistriata. Hempstead Beds.)
1. The uppermost or Corbula beds, consisting of marine sands and clays, contain
Voluta Rathieri, a characteristic Lower Miocene shell; Corbula pisum (Figure
158), a species common to the Upper Eocene clay of Barton; Cyrena semistriata
(Figure 159), several Cerithia, and other shells peculiar to this series.
(FIGURE 160. Cerithium plicatum, Lam., Hempstead.)
(FIGURE 161. Cerithium elegans. Hempstead.)
(FIGURE 162. Rissoa Chastelii, Nyst, sp. Hempstead, Isle of Wight.)
(FIGURE 163. Paludina lenta. Hempstead Bed.)
2. Next below are fresh-water and estuary marls and carbonaceous clays in the
brackish-water portion of which are found abundantly Cerithium plicatum, Lam.
(Figure 160), Cerithium elegans (Figure 161), and Cerithium tricinctum; also
Rissoa Chastelii (Figure 162), a very common Kleyn Spawen shell, and which
occurs in each of the four subdivisions of the Hempstead series down to its
base, where it passes into the Bembridge beds. In the fresh-water portion of the
same beds Paludina lenta (Figure 163) occurs; a shell identified by some
conchologists with a species now living, Paludina unicolor; also several species
of Lymneus, Planorbis, and Unio.
3. The next series, or middle fresh-water and estuary marls, are distinguished
by the presence of Melania fasciata, Paludina lenta, and clays with Cypris; the
lowest bed contains Cyrena semistriata (Figure 159), mingled with Cerithia and a
panopaea.
4. The lower fresh-water and estuary marls contain Melania costata, Sowerby,
Melanopsis, etc. The bottom bed is carbonaceous, and called the "Black band," in
which Rissoa Chastelii (Figure 162), before alluded to, is common. This bed
contains a mixture of Hempstead shells with those of the underlying Upper Eocene
or Bembridge series. The mammalia, among which is Hyopotamus bovinus, differ, so
far as they are known, from those of the Bembridge beds. Among the plants,
Professor Heer has recognised four species common to the lignite of Bovey
Tracey, a Lower Miocene formation presently to be described: namely, Sequoia
Couttsiae, Heer; Andromeda reticulata, Ettings.; Nelumbium (Nymphoea) doris,
Heer; and Carpolithes Websteri, Brong. (Pengelly, preface to The Lignite
Formation of Bovey Tracey page 17. London 1863.) The seed-vessels of Chara
medicaginula, Brong, and Chara helicteres are characteristic of the Hempstead
beds generally.
The Hyopotamus belongs to the hog tribe, or the same family as the
Anthracotherium, of which seven species, varying in size from the hippopotamus
to the wild boar, have been found in Italy and other part of Europe associated
with the lignites of the Lower Miocene period.
LIGNITES AND CLAYS OF BOVEY TRACEY, DEVONSHIRE.
Surrounded by the granite and other rocks of the Dartmoor hills in Devonshire,
is a formation of clay, sand, and lignite, long known to geologists as the Bovey
Coal formation, respecting the age of which, until the year 1861, opinions were
very unsettled. This deposit is situated at Bovey Tracey, a village distant
eleven miles from Exeter in a south-west, and about as far from Torquay in a
north-west direction. The strata extend over a plain nine miles long, and they
consist of the materials of decomposed and worn-down granite and vegetable
matter, and have evidently filled up an ancient hollow or lake-like expansion of
the valleys of the Bovey and Teign.
The lignite is of bad quality for economical purposes, as there is a great
admixture in it of iron pyrites, and it emits a sulphurous odour, but it has
been successfully applied to the baking of pottery, for which some of the fine
clays are well adapted. Mr. Pengelly has confirmed Sir H. De la Beche's opinion
that much of the upper portion of this old lacustrine formation has been removed
by denudation. (Philosophical Transactions 1863. Paper by W. Pengelly F.R.S. and
Dr. Oswald Heer.)
At the surface is a dense covering of clay and gravel with angular stones
probably of the Post-pliocene period, for in the clay are three species of
willow and the dwarf birch, Betula nana, indicating a climate colder than that
of Devonshire at the present day.
Below this are Lower Miocene strata about 300 feet in thickness, in the upper
part of which are twenty-six beds of lignite, clay, and sand, and at their base
a ferruginous quartzose sand, varying in thickness from two to twenty-seven
feet. Below this sand are forty-five beds of alternating lignite and clay. No
shells or bones of mammalia, and no insect, with the exception of one fragment
of a beetle (Buprestis); in a word, no organic remains, except plants, have as
yet been found. These plants occur in fourteen of the beds-- namely, in two of
the clays, and the rest in the lignites. One of the beds is a perfect mat of the
debris of a coniferous tree, called by Heer Sequoia Couttsiae, intermixed with
leaves of ferns. The same Sequoia (before mentioned as a Hempstead fossil) is
spread through all parts of the formation, its cones, and seeds, and branches of
every age being preserved. It is a species supplying a link between Sequoia
Langsdorfii (see Figure 153) and Sequoia Sternbergi, the widely spread fossil
representatives of the two living trees Sequoia sempervirens and Sequoia
gigantea (or Wellingtonia), both now confined to California. Another bed is full
of the large rhizomes of ferns, while two others are rich in dicotyledonous
leaves. In all, Professor Heer enumerates forty-nine species of plants, twenty
of which are common to the Miocene beds of the Continent, a majority of them
being characteristic of the Lower Miocene. The new species, also of Bovey, are
allied to plants of the older Miocene deposits of Switzerland, Germany, and
other Continental countries. The grape-stones of two species of vine occur in
the clays, and leaves of the fig and seeds of a water-lily. The oak and laurel
have supplied many leaves. Of the triple-nerved laurels several are referred to
Cinnamomum. There are leaves also of a palm of which the genus is not
determined. Leaves also of proteaceous forms, like some of the Continental
fossils before mentioned, occur, and ferns like the well-known Lastraea stiriaca
(Figure 154), displaying at Bovey, as in Switzerland, its fructification.
The croziers of some of the young ferns are very perfect, and were at first
mistaken by collectors for shells of the genus Planorbis. On the whole, the
vegetation of Bovey implies the existence of a sub-tropical climate in
Devonshire, in the Lower Miocene period.
SCOTLAND: ISLE OF MULL.
In the sea-cliffs forming the headland of Ardtun, on the west coast of Mull, in
the Hebrides, several bands of tertiary strata containing leaves of
dicotyledonous plants were discovered in 1851 by the Duke of Argyll. (Quarterly
Geological Journal 1851 page 19.) From his description it appears that there are
three leaf-beds, varying in thickness from 1 1/2 to 5 1/2 feet, which are
interstratified with volcanic tuff and trap, the whole mass being about 130 feet
in thickness. A sheet of basalt 40 feet thick covers the whole; and another
columnar bed of the same rock, ten feet thick, is exposed at the bottom of the
cliff. One of the leaf-beds consists of a compressed mass of leaves
unaccompanied by any stems, as if they had been blown into a marsh where a
species of Equisetum grew, of which the remains are plentifully imbedded in
clay.
It is supposed by the Duke of Argyll that this formation was accumulated in a
shallow lake or marsh in the neighbourhood of a volcano, which emitted showers
of ashes and streams of lava. The tufaceous envelope of the fossils may have
fallen into the lake from the air as volcanic dust, or have been washed down
into it as mud from the adjoining land. Even without the aid of organic remains
we might have decided that the deposit was newer than the chalk, for chalk-
flints containing cretaceous fossils were detected by the duke in the principal
mass of volcanic ashes or tuff. (Quarterly Geological Journal 1851 page 90.)
The late Edward Forbes observed that some of the plants of this formation
resembled those of Croatia, described by Unger, and his opinion has been
confirmed by Professor Heer, who found that the conifer most prevalent was the
Sequoia Langsdorfii (Figure 153), also Corylus grossedentata, a Lower Miocene
species of Switzerland and of Menat in Auvergne. There is likewise a plane-tree,
the leaves of which seem to agree with those of Platanus aceroides (Figure 141
Chapter 14), and a fern which is as yet peculiar to Mull, Filicites hebridica,
Forbes.
These interesting discoveries in Mull led geologists to suspect that the basalt
of Antrim, in Ireland, and of the celebrated Giant's Causeway, might be of the
same age. The volcanic rocks that overlie the chalk, and some of the strata
associated with and interstratified between masses of basalt, contain leaves of
dicotyledonous plants, somewhat imperfect, but resembling the beech, oak, and
plane, and also some coniferae of the genera pine and Sequoia. The general
dearth of strata in the British Isles, intermediate in age between the formation
of the Eocene and Pliocene periods, may arise, says Professor Forbes, from the
extent of dry land which prevailed in that vast interval of time. If land
predominated, the only monuments we are likely ever to find of Miocene date are
those of lacustrine and volcanic origin, such as the Bovey Coal in Devonshire,
the Ardtun beds in Mull, or the lignites and associated basalts in Antrim.
LOWER MIOCENE, UNITED STATES: NEBRASKA.
In the territory of Nebraska, on the Upper Missouri, near the Platte River,
latitude 42 degrees N., a tertiary formation occurs, consisting of white
limestone, marls, and siliceous clay, described by Dr. D. Dale Owen (David Dale
Owen Geological Survey of Wisconsin etc. Philadelphia 1852.), in which many
bones of extinct quadrupeds, and of chelonians of land or fresh-water forms, are
met with. Among these, Dr. Leidy describes a gigantic quadruped, called by him
Titanotherium, nearly allied to the Palaeotherium, but larger than any of the
species found in the Paris gypsum. With these are several species of the genus
Oreodon, Leidy, uniting the characters of pachyderms and ruminants also;
Eucrotaphus, another new genus of the same mixed character; two species of
rhinoceros of the sub-genus Acerotherium, a Lower Miocene form of Europe before
mentioned; two species of Archaeotherium, a pachyderm allied to Chaeropotamus
and Hyracotherium; also Paebrotherium, an extinct ruminant allied to
Dorcatherium, Kaup; also Agriochoerus, of Leidy, a ruminant allied to
Merycopotamus of Falconer and Cautley; and, lastly, a large carnivorous animal
of the genus Machairodus, the most ancient example of which in Europe occurs in
the Lower Miocene strata of Auvergne, but of which some species are found in
Pliocene deposits. The turtles are referred to the genus Testudo, but have some
affinity to Emys. On the whole, the Nebraska formation is probably newer than
the Paris gypsum, and referable to the Lower Miocene period, as above defined.
CHAPTER XVI.
EOCENE FORMATIONS.
Eocene Areas of North of Europe.
Table of English and French Eocene Strata.
Upper Eocene of England.
Bembridge Beds.
Osborne or St. Helen's Beds.
Headon Series.
Fossils of the Barton Sands and Clays.
Middle Eocene of England.
Shells, Nummulites, Fish and Reptiles of the Bracklesham Beds and Bagshot Sands.
Plants of Alum Bay and Bournemouth.
Lower Eocene of England.
London Clay Fossils.
Woolwich and Reading Beds formerly called "Plastic Clay."
Fluviatile Beds underlying Deep-sea Strata.
Thanet Sands.
Upper Eocene Strata of France.
Gypseous Series of Montmartre and Extinct Quadrupeds.
Fossil Footprints in Paris Gypsum.
Imperfection of the Record.
Calcaire Silicieux.
Gres de Beauchamp.
Calcaire Grossier.
Miliolite Limestone.
Soissonnais Sands.
Lower Eocene of France.
Nummulitic Formations of Europe, Africa, and Asia.
Eocene Strata in the United States.
Gigantic Cetacean.
EOCENE AREAS OF THE NORTH OF EUROPE.
(FIGURE 164. Map of the principal Eocene areas of North-western Europe, showing:
Shaded dotted: Hypogene rocks and strata older than the Devonian.
Shaded horizontal lines: Eocene formations.
NB.-- the space left blank is occupied by fossiliferous formations from the
Devonian to the chalk inclusive.)
The strata next in order in the descending series are those which I term Eocene.
In the map in Figure 164, the position of several Eocene areas in the north of
Europe is pointed out. When this map was constructed I classed as the newer part
of the Eocene those Tertiary strata which have been described in the last
chapter as Lower Miocene, and to which M. Beyrich has given the name of
Oligocene. None of these occur in the London Basin, and they occupy in that of
Hampshire, as we have seen in Chapter 15, too insignificant a superficial area
to be noticed in a map on this scale. They fill a larger space in the Paris
Basin between the Seine and the Loire, and constitute also part of the northern
limits of the area of the Netherlands which are shaded in the map.
TABLE 16.1. TABLE OF ENGLISH AND FRENCH EOCENE STRATA.
COLUMN 1: NAME OF STRATA.
COLUMN 2: ENGLISH SUBDIVISIONS.
COLUMN 3: FRENCH EQUIVALENTS.
UPPER EOCENE.
A.1: Bembridge series, Isle of Wight: Gypseous series of Montmartre.
A.2: Osborne or St. Helen's series, Isle of Wight: Calcaire siliceux, or
Travertin Inferieur.
A.3: Headon series, Isle of Wight: Calcaire siliceux, or Travertin Inferieur.
A.4: Barton series. Sands and clays of Barton Cliff, Hants: Gres de Beauchamp,
or Sables Moyens.
MIDDLE EOCENE.
B.1: Bracklesham series: Calcaire Grossier.
B.2: Alum Bay and Bournemouth beds: Wanting in France?
B.2: Wanting in England?: Soissonnais Sands, or Lits Coquilliers.
LOWER EOCENE.
C.1: London Clay: Argile de Londres, Cassel, near Dunkirk.
C.2: Woolwich and Reading series: Argile plastique and lignite.
C.3: Thanet sands: Sables de Bracheux.
It is in the northern part of the Isle of Wight that we have the uppermost beds
of the true Eocene best exhibited-- namely, those which correspond in their
fossils with the celebrated gypsum of the Paris basin before alluded to in
Chapter 15 (see Table 16.1). That gypsum has been selected by almost all
Continental geologists as affording the best line of demarkation between the
Middle and Lower Tertiary, or, in other words, between the Lower Miocene and
Eocene formations.
In reference to Table 16.1 I may observe, that the correlation of the French and
English subdivisions here laid down is often a matter of great doubt and
difficulty, notwithstanding their geographical proximity. This arises from
various circumstances, partly from the former prevalence of marine conditions in
one basin simultaneously with fluviatile or lacustrine in the other, and
sometimes from the existence of land in one area causing a break or absence of
all records during a period when deposits may have been in progress in the other
basin. As bearing on this subject, it may be stated that we have unquestionable
evidence of oscillations of level shown by the superposition of salt or
brackish-water strata to fluviatile beds; and those of deep-sea origin to strata
formed in shallow water. Even if the upward and downward movements were uniform
in amount and direction, which is very improbable, their effect in producing the
conversion of sea into land or land into sea would be different, according to
the previous shape and varying elevation of the land and bottom of the sea.
Lastly, denudation, marine and subaerial, has frequently caused the absence of
deposits in one basin of corresponding age to those in the other, and this
destructive agency has been more than ordinarily effective on account of the
loose and unconsolidated nature of the sands and clays.
UPPER EOCENE OF ENGLAND.
BEMBRIDGE SERIES, A.1.
These beds are about 120 feet thick, and, as stated in Chapter 15, lie
immediately under the Hempstead beds, near Yarmouth, in the Isle of Wight, being
conformable with those Lower Miocene strata. They consist of marls, clays, and
limestones of fresh-water, brackish, and marine origin. Some of the most
abundant shells, as Cyrena semistriata var., and Paludina lenta, Figure 163
Chapter 15, are common to this and to the overlying Hempstead series; but the
majority of the species are distinct. The following are the subdivisions
described by the late Professor Forbes:
(FIGURE 165. Melania turritissima, Forbes. Bembridge.)
a. Upper marls, distinguished by the abundance of Melania turritissima, Forbes
(Figure 165).
(FIGURE 166. Fragment of carapace of Trionyx. Bembridge Beds, Isle of Wight.)
b. Lower marls, characterised by Cerithium mutabile, Cyrena pulchra, etc., and
by the remains of Trionyx (see Figure 166).
c. Green marls, often abounding in a peculiar species of oyster, and accompanied
by Cerithium, Mytilus, Arca, nucula, etc.)
(FIGURE 167. Bulimus ellipticus, Sowerby. Bembridge Limestone. 1/2 natural
size.)
(FIGURE 168. Helix occlusa, Edwards. Bembridge Limestone, Isle of Wight.)
(FIGURE 169. Paludina orbicularis. Bembridge.)
(FIGURE 170. Planorbis discus, Edwards. Bembridge. 1/2 diameter.)
(FIGURE 171. Lymnea longiscata, Brand. Natural size.)
(FIGURE 172. Chara tuberculata, seed-vessel. Bembridge Limestone, Isle of
Wight.)
d. Bembridge limestones, compact cream-coloured limestones alternating with
shales and marls, in all of which land-shells are common, especially at Sconce,
near Yarmouth, as described by Mr. F. Edwards. The Bulimus ellipticus, Figure
167, and Helix occlusa, Figure 168, are among its best known land-shells.
Paludina orbicularis, Figure 169, is also of frequent occurrence. One of the
bands is filled with a little globular Paludina. Among the fresh-water
pulmonifera, Lymnea longiscata (Figure 171) and Planorbis discus (Figure 170)
are the most generally distributed: the latter represents or takes the place of
the Planorbis euomphalus (see Figure 175) of the more ancient Headon series.
Chara tuberculata (Figure 172) is the characteristic Bembridge gyrogonite or
seed-vessel.
(FIGURE 173. Anoplotherium commune. Binstead, Isle of Wight.
Lower molar tooth, natural size.)
(FIGURE 174. Palaeotherium magnum, Cuvier.)
(FIGURE 175. Planorbis euomphalus, Sowerby. Headon Hill. 1/2 diameter.)
From this formation on the shores of Whitecliff Bay, Dr. Mantell obtained a fine
specimen of a fan palm, Flabellaria Lamanonis, Brong., a plant first obtained
from beds of corresponding age in the suburbs of Paris. The well-known building-
stone of Binstead, near Ryde, a limestone with numerous hollows caused by
Cyrenae which have disappeared and left the moulds of their shells, belongs to
this subdivision of the Bembridge series. In the same Binstead stone Mr. Pratt
and the Reverend Darwin Fox first discovered the remains of mammalia
characteristic of the gypseous series of Paris, as Palaeotherium magnum (Figure
174), Palaeotherium medium, Palaeotherium minus, Palaeotherium minimum,
Palaeotherium curtum, Palaeotherium crassum; also Anoplotherium commune (Figure
173), Anoplotherium secundarium, Dichobune cervinum, and Chaeropotamus Cuvieri.
The Palaeothere above alluded to resembled the living tapir in the form of the
head, and in having a short proboscis, but its molar teeth were more like those
of the rhinoceros. Palaeotherium magnum was of the size of a horse, three or
four feet high. The woodcut, Figure 174, is one of the restorations which Cuvier
attempted of the outline of the living animal, derived from the study of the
entire skeleton. As the vertical range of particular species of quadrupeds, so
far as our knowledge extends, is far more limited than that of the testacea, the
occurrence of so many species at Binstead, agreeing with fossils of the Paris
gypsum, strengthens the evidence derived from shells and plants of the
synchronism of the two formations.
OSBORNE OR ST. HELEN'S SERIES, A.2.
This group is of fresh and brackish-water origin, and very variable in mineral
character and thickness. Near Ryde, it supplies a freestone much used for
building, and called by Professor Forbes the Nettlestone grit. In one part
ripple-marked flagstones occur, and rocks with fucoidal markings. The Osborne
beds are distinguished by peculiar species of Paludina, Melania, and Melanopsis,
as also of Cypris and the seeds of Chara.
HEADON SERIES A.3.
These beds are seen both in Whitecliff Bay, Headon Hill, and Alum Bay, or at the
east and west extremities of the Isle of Wight. The upper and lower portions are
fresh-water, and the middle of mixed origin, sometimes brackish and marine.
Everywhere Planorbis euomphalus, Figure 175, characterises the fresh-water
deposits, just as the allied form, Planorbis discus, Figure 170, does the
Bembridge limestone. The brackish-water beds contain Potamomya plana, Cerithium
mutabile, and Potamides cinctus (Figure 37 Chapter 3), and the marine beds Venus
(or Cytherea) incrassata, a species common to the Limburg beds and Gres de
Fontainebleau, or the Lower Miocene series. The prevalence of salt-water remains
is most conspicuous in some of the central parts of the formation.
(FIGURE 176. Helix labyrinthica, Say. Headon Hill, Isle of Wight; and Hordwell
Cliff, Hants-- also recent.)
(FIGURE 177. Neritina concava, Sowerby. Headon series.)
(FIGURE 178. Lymnea caudata, Edw. Headon series.)
(FIGURE 179. Cerithium concavum, Sowerby. Headon series.)
Among the shells which are widely distributed through the Headon series are
Neritina concava (Figure 177), Lymnea caudata (Figure 178), and Cerithium
concavum (Figure 179). Helix labyrinthica, Say (Figure 176), a land-shell now
inhabiting the United States, was discovered in this series by Mr. Searles Wood
in Hordwell Cliff. It is also met with in Headon Hill, in the same beds. At
Sconce, in the Isle of Wight, it occurs in the Bembridge series, and affords a
rare example of an Eocene fossil of a species still living, though, as usual in
such cases, having no local connection with the actual geographical range of the
species. The lower and middle portion of the Headon series is also met with in
Hordwell Cliff (or Hordle, as it is often spelt), near Lymington, Hants. Among
the shells which abound in this cliff are Paludina lenta and various species of
Lymnea, Planorbis, Melania, Cyclas, Unio, Potamomya, Dreissena, etc.
Among the chelonians we find a species of Emys, and no less than six species of
Trionyx; among the saurians an alligator and a crocodile; among the ophidians
two species of land-snakes (Paleryx, Owen); and among the fish Sir P. Egerton
and Mr. Wood have found the jaws, teeth, and hard shining scales of the genus
Lepidosteus, or bony pike of the American rivers. This same genus of fresh-water
ganoids has also been met with in the Hempstead beds in the Isle of Wight. The
bones of several birds have been obtained from Hordwell, and the remains of
quadrupeds of the genera Palaeotherium (Palaeotherium minus), Anoplotherium,
Anthracotherium, Dichodon, Dichobune, Spalacodon, and Hyaenodon. The latter
offers, I believe, the oldest known example of a true carnivorous animal in the
series of British fossils, although I attach very little theoretical importance
to the fact, because herbivorous species are those most easily met with in a
fossil state in all save cavern deposits. In another point of view, however,
this fauna deserves notice. Its geological position is considerably lower than
that of the Bembridge or Montmartre beds, from which it differs almost as much
in species as it does from the still more ancient fauna of the Lower Eocene beds
to be mentioned in the sequel. It therefore teaches us what a grand succession
of distinct assemblages of mammalia flourished on the earth during the Eocene
period.
Many of the marine shells of the brackish-water beds of the above series, both
in the Isle of Wight and Hordwell Cliff, are common to the underlying Barton
Clay: and, on the other hand, there are some fresh-water shells, such as Cyrena
obovata, which are common to the Bembridge beds, notwithstanding the
intervention of the St. Helen's series. The white and green marls of the Headon
series, and some of the accompanying limestones, often resemble the Eocene
strata of France in mineral character and colour in so striking a manner as to
suggest the idea that the sediment was derived from the same region or produced
contemporaneously under very similar geographical circumstances.
(FIGURE 180. Solenastraea cellulosa, Duncan. Brockenhurst.)
At Brockenhurst, near Lyndhurst, in the New Forest, marine strata have recently
been found containing fifty-nine shells, of which many have been described by
Mr. Edwards. These beds rest on the Lower Headon, and are considered as the
equivalent of the middle part of the Headon series, many of the shells being
common to the brackish-water or Middle Headon beds of Colwell and Whitecliff
Bays, such as Cancellaria muricata, Sowerby, Fusus labiatus, Sowerby, etc. In
these beds at Brockenhurst, corals, ably described by Dr. Duncan, have recently
been found in abundance and perfection; see Figure 180, Solenastraea cellulosa.
Baron von Konen has pointed out that no less than forty-six out of the fifty-
nine Brockenhurst shells, or a proportion of 78 per cent, agree with species
occurring in Dumont's Lower Tongrian formation in Belgium. (Quarterly Geological
Journal volume 20 page 97 1864.) This being the case, we might fairly expect
that if we had a marine equivalent of the Bembridge series or of the
contemporaneous Paris gypsum, we should find it to contain a still greater
number of shells common to the Tongrian beds of Belgium, but the exact
correlation of these fresh-water groups of France, Belgium, and Britain has not
yet been fully made out. It is possible that the Tongrian of Dumont may be newer
than the Bembridge series, and therefore referable to the Lower Miocene. If ever
the whole series should be complete, we must be prepared to find the marine
equivalent of the Bembridge beds, or the uppermost Eocene, passing by
imperceptible shades into the inferior beds of the overlying Miocene strata.
Among the fossils found in the Middle Headon are Cytherea incrassata and
Cerithium plicatum (Figure 160 Chapter 15). These shells, especially the latter,
are very characteristic of the Lower Miocene, and their occurrence in the Headon
series has been cited as an objection to the line proposed to be drawn between
Miocene and Eocene. But if we were to attach importance to such occasional
passages, we should soon find that no lines of division could be drawn anywhere,
for in the present state of our knowledge of the Tertiary series there will
always be species common to beds above and below our boundary-lines.
BARTON SERIES (SANDS AND CLAYS), A.4 TABLE 16.1.)
(FIGURE 181. Chama squamosa, Eichw. Barton.)
Both in the Isle of Wight, and in Hordwell Cliff, Hants, the Headon beds, above-
mentioned, rest on white sands usually devoid of fossils, and used in the Isle
of Wight for making glass. In one of these sands Dr. Wright found Chama
squamosa, a Barton Clay shell, in great plenty, and certain impressions of
marine shells have been found in sands supposed to be of the same age in
Whitecliff Bay. These sands have been called Upper Bagshot in the maps of our
Government Survey, but this identification of a fossiliferous series in the Isle
of Wight with an unfossiliferous formation in the London Basin can scarcely be
depended upon. The Barton Clay, which immediately underlies these sands, is seen
vertical in Alum Bay, Isle of Wight, and nearly horizontal in the cliffs of the
mainland near Lymington. This clay, together with the Bracklesham beds,
presently to be described, has been termed Middle Bagshot by the Survey. In
Barton Cliff, where it attains a thickness of about 300 feet, it is rich in
marine fossils.
It was formerly confounded with the London Clay, an older Eocene deposit of very
similar mineral character, to be mentioned below, which contains many shells in
common, but not more than one-fourth of the whole. In other words, there are
known at present 247 species in the London Clay and 321 in that of Barton, and
only 70 common to the two formations. Fifty-six of these have been found in the
intermediate Bracklesham beds, and the reappearance of the other 14 may imply a
return of similar conditions, whether of temperature or depth or of a muddy
argillaceous bottom, common to the two periods of the London and Barton Clays.
According to M. Hebert, the most characteristic Barton Clay fossils correspond
to those of the Gres de Beauchamp, or Sables Moyens, of the Paris Basin, but it
also contains many common to the older Calcaire Grossier.
SHELLS OF THE BARTON CLAY.
(FIGURE 182. Mitra scabra, Sowerby.)
(FIGURE 183. Voluta ambigua, Sol.)
(FIGURE 184. Typhis pungens, Brand.)
(FIGURE 185. Voluta athleta, Sol. Barton and Bracklesham.)
(FIGURE 186. Terebellum fusiforme, Lam. Barton and Bracklesham.)
(FIGURE 187. Terebellum sopita, Brand.)
(FIGURE 188. Cardita sulcata, Brand. Barton.)
(FIGURE 189. Crassatella sulcata, Sowerby. Bracklesham and Barton.)
(FIGURE 190. Nummulites variolaria, Lam. Var. of Nummulites radiata, Sowerby.
Middle Eocene, Bracklesham Bay.
a. Natural size.
b. Magnified.)
Certain foraminifera called Nummulites begin, when we study the Tertiary
formations in a descending order, to make their first appearance in these beds.
A small species called Nummulites variolaria, Figure 190, is found both on the
Hampshire coast and in beds of the same age in Whitecliff Bay, in the Isle of
Wight. Several marine shells, such as Corbula pisum (Figure 158), are common to
the Barton beds and the Hempstead or Lower Miocene series, and a still greater
number, as before stated, are common to the Headon series.
MIDDLE EOCENE, ENGLAND.
BRACKLESHAM BEDS AND BAGSHOT SANDS (B.1, TABLE 16.1).
(FIGURE 191. Cardita (Venericardia) planicosta, Lam.)
(FIGURE 192. Nummulites (Nummularia) laevigata. Bracklesham. Dixon's Fossils of
Sussex, Plate 8.
a. Section of nummulite.
b. Group, with an individual showing the exterior of the shell.)
Beneath the Barton Clay we find in the north of the Isle of Wight, both in Alum
and Whitecliff Bays, a great series of various coloured sands and clays for the
most part unfossiliferous, and probably of estuarine origin. As some of these
beds contain Cardita planicosta (Figure 191) they have been identified with the
marine beds much richer in fossils seen in the coast section in Bracklesham Bay
near Chichester in Sussex, where the strata consist chiefly of green clayey
sands with some lignite. Among the Bracklesham fossils besides the Cardita, the
huge Cerithium giganteum is seen, so conspicuous in the Calcaire Grossier of
Paris, where it is sometimes two feet in length. The Nummulites laevigata (see
Figure 192), so characteristic of the lower beds of the Calcaire Grossier in
France, where it sometimes forms stony layers, as near Compiegne, is very common
in these beds, together with Nummulites scabra and Nummulites variolaria. Out of
193 species of testacea procured from the Bagshot and Bracklesham beds in
England, 126 occur in the Calcaire Grossier in France. It was clearly,
therefore, coeval with that part of the Parisian series more nearly than with
any other.
(FIGURE 193. Palaeophis typhoeus, Owen; an Eocene sea-serpent. Bracklesham.
a, b. Vertebra, with long neural spine preserved.
c. Two vertebrae articulated together.)
(FIGURE 194. Defensive spine of Ostracion. Bracklesham.)
(FIGURE 195. Dental plates of Myliobates Edwardsi. Bracklesham Bay.
Dixon's Fossils of Sussex, Plate 8.)
According to tables compiled from the best authorities by Mr. Etheridge, the
number of mollusca now known from the Bracklesham beds in Great Britain is 393,
of which no less than 240 are peculiar to this subdivision of the British Eocene
series, while 70 are common to the Older London Clay, and 140 to the Newer
Barton Clay. The volutes and cowries of this formation, as well as the lunulites
and corals, favour the idea of a warm climate having prevailed, which is borne
out by the discovery of a serpent, Palaeophis typhoeus (see Figure 193),
exceeding, according to Professor Owen, twenty feet in length, and allied in its
osteology to the Boa, Python, Coluber, and Hydrus. The compressed form and
diminutive size of certain caudal vertebrae indicate so much analogy with Hydrus
as to induce Professor Owen to pronounce this extinct ophidian to have been
marine. (Palaeontological Society Monograph Reptiles part 2 page 61.) Among the
companions of the sea-snake of Bracklesham was an extinct crocodile (Gavialis
Dixoni, Owen), and numerous fish, such as now frequent the seas of warm
latitudes, as the Ostracion of the family Balistidae, of which a dorsal spine is
figured (see Figure 194), and gigantic rays of the genus Myliobates (see Figure
195).
(FIGURE 196. Carcharodon angustidens, Agassiz.)
(FIGURE 197. Otodus obliquus, Agassiz.)
(FIGURE 198. Lamna elegans, Agassiz.)
(FIGURE 199. Galeocerdo latidens, Agassiz.)
The teeth of sharks also, of the genera Carcharodon, Otodus, Lamna, Galeocerdo,
and others, are abundant. (See Figures 196, 197, 198, 199.)
MARINE SHELLS OF BRACKLESHAM BEDS.
ALUM BAY AND BOURNEMOUTH BEDS. (LOWER BAGSHOT OF ENGLISH SURVEY), B.2, TABLE
16.1.)
(FIGURE 200. Pleurotoma attenuata, Sowerby.)
(FIGURE 201. Voluta Selseiensis, Edwards.)
(FIGURE 202. Turritella multisulcata, Lam.)
(FIGURE 203. Lucina serrata, Sowerby. Magnified.)
(FIGURE 204. Conus deperditus, Brug.)
To that great series of sands and clays which intervene between the equivalents
of the Bracklesham Beds and the London Clay or Lower Eocene, our Government
Survey has given the name of the Lower Bagshot sands, for they are supposed to
agree in age with the inferior unfossiliferous sands of the country round
Bagshot in the London Basin. This part of the series is finely exposed in the
vertical beds of Alum bay, in the Isle of Wight, and east and west of
Bournemouth, on the south coast of Hampshire. In some of the close and white
compact clays of this locality, there are not only dicotyledonous leaves, but
numerous fronds of ferns allied to Gleichenia which are well preserved with
their fruit.
None of the beds are of great horizontal extent, and there is much cross-
stratification in the sands, and in some places black carbonaceous seams and
lignite. In the midst of these leaf-beds in Studland Bay, Purbeck shells of the
genus Unio attest the fresh-water origin of the white clay.
No less than forty species of plants are mentioned by MM. de la Harpe and Gaudin
from this formation in Hampshire, among which the Proteaceae (Dryandra, etc.)
and the fig tribe are abundant, as well as the cinnamon and several other
laurineae, with some papilionaceous plants. On the whole, they remind the
botanist of the types of subtropical India and Australia. (Heer Climat et
Vegetation du Pays Tertiaire page 172.)
Heer has mentioned several species which are common to this Alum Bay flora and
that of Monte Bolca, near Verona, so celebrated for its fossil fish, and where
the strata contain nummulites and other Middle Eocene fossils. He has
particularly alluded to Aralia primigenia (of which genus a fruit has since been
found by Mr. Mitchell at Bournemouth), Daphnogene Veronensis, and Ficus
granadilla, as among the species common to and characteristic of the Isle of
Wight and Italian Eocene beds; and he observes that in the flora of this period
these forms of a temperate climate which constitute a marked feature in the
European Miocene formations, such as the willow, poplar, birch, alder, elm,
hornbeam, oak, fir, and pine, are wanting. The American types are also absent,
or much more feebly represented than in the Miocene period, although fine
specimens of the fan-palm (Sabal) have been found in these Eocene clays at
Studland. The number of exotic forms which are common to the Eocene and Miocene
strata of Europe, like those to be alluded to in the sequel which are common to
the Eocene and Cretaceous fauna, demonstrate the remoteness of the times in
which the geographical distribution of living plants originated. A great
majority of the Eocene genera have disappeared from our temperate climates, but
not the whole of them; and they must all have exerted some influence on the
assemblages of species which succeeded them. Many of these last occurring in the
Upper Miocene are indeed so closely allied to the flora now surviving as to make
it questionable, even in the opinion of naturalists opposed to the doctrine of
transmutation, whether they are not genealogically related the one to the other.
LOWER EOCENE FORMATIONS, ENGLAND.
LONDON CLAY (C.1, TABLE 16.1).
This formation underlies the preceding, and sometimes attains a thickness of 500
feet. It consists of tenacious brown and bluish-grey clay, with layers of
concretions called septaria, which abound chiefly in the brown clay, and are
obtained in sufficient numbers from sea-cliffs near Harwich, and from shoals off
the coast of Essex and the Isle of Sheppey, to be used for making Roman cement.
The total number of British fossil mollusca known at present (January, 1870) in
this formation are 254, of which 166 are peculiar, or not found in other Eocene
beds in this country. The principal localities of fossils in the London clay are
Highgate Hill, near London, the Island of Sheppey at the mouth of the Thames,
and Bognor on the Sussex coast. Out of 133 fossil shells, Mr. Prestwich found
only 20 to be common to the Calcaire Grossier (from which 600 species have been
obtained), while 33 are common to the "Lits Coquilliers" (see below), in which
200 species are known in France.
In the Island of Sheppey near the mouth of the Thames, the thickness of the
London Clay is estimated by Mr. Prestwich to be more than 500 feet, and it is in
the uppermost 50 feet that a great number of fossil fruits were obtained, being
chiefly found on the beach when the sea has washed away the clay of the rapidly
wasting cliffs.
(FIGURE 205. Nipadites ellipticus, Bowerbank. Fossil fruit of palm, from
Sheppey.)
Mr. Bowerbank, in a valuable publication on these fossil fruits and seeds, has
described no less than thirteen fruits of palms of the recent type Nipa, now
only found in the Molucca and Philippine Islands, and in Bengal (see Figure
205). In the delta of the Ganges, Dr. Hooker observed the large nuts of Nipa
fruticans floating in such numbers in the various arms of that great river, as
to obstruct the paddle-wheels of steamboats. These plants are allied to the
cocoanut tribe on the one side, and on the other to the Pandanus, or screw-pine.
There are also met with three species of Anona, or custard-apple; and
cucurbitaceous fruits (of the gourd and melon family), and fruits of various
species of Acacia.
Besides fir-cones or fruit of true Coniferae there are cones of Proteaceae in
abundance, and the celebrated botanist the late Robert Brown pointed out the
affinity of these to the New Holland types Petrophila and Isopogon. Of the first
there are about fifty, and of the second thirty described species now living in
Australia.
(FIGURE 206. Eocene Proteaceous Fruit.
Petrophiloides Richardsoni. London Clay, Sheppey. Natural size.
a. Cone.
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