PLIOCENE PERIOD.
This last period of the Tertiary epoch was marked, in some parts of Europe, by great movements of the terrestrial crust, always due to the same cause—namely, the continual and gradual cooling of the globe. This leads us to recall what we have repeatedly stated, that this cooling, during which the outer zone of the fluid mass passed to the solid state, produced irregularities and inequalities in the external surface, sometimes accompanied by fractures through which the semi-fluid or pasty matter poured itself; leading afterwards to the upheaval of mountain ranges through these gaping chasms. Thus, during the Pliocene period, many mountains and mountain-chains were formed in Europe by basaltic and volcanic eruptions. These upheavals were preceded by sudden and irregular movements of the elastic mass of the crust—by earthquakes, in short—phenomena which have been already sufficiently explained.
In order to understand the nature of the vegetation of the period, as compared with that with which we are familiar, let us listen to M. Lecoq: “Arrived, finally,” says that author, “at the last period which preceded our own epoch—the epoch in which the temperate zones were still embellished by tropical forms of vegetation, which were, however, slowly declining, driven out as it were by a cooling climate and by the invasion of more vigorous species—great terrestrial commotions took place: mountains are covered with eternal snow; continents now take their present forms; but many great lakes, now dried up, still existed; great rivers flowed majestically through smiling countries, whose surface man had not yet come to modify.
“Two hundred and twelve species compose this rich flora, in which the Ferns of the earlier ages of the world are scarcely indicated, where the Palms seem to have quite disappeared, and we see forms much more like those which are constantly under our observation. The Culmites arundinaceus (Unger) abounds near the water, where also grows the Cyperites tertiarius (Unger), where floats Dotamogeton geniculatus (Braun), and where we see submerged Isoctites Brunnii (Unger). Great Conifers still form the forests. This fine family has, as we have seen, passed through every epoch, and still presents us with its elegant forms and persistent evergreen foliage; Taxodites, Thuyoxylum, Abietites, Pinites, Eleoxylon, and Taxites being still the forms most abundant in these old natural forests.
“The predominating character of this period is the abundance of the group of the Amentaceæ; whilst the Conifers are thirty-two in number, of the other we reckon fifty-two species, among which are many European genera, such as Alnus; Quercus, the oak; Salix, the willow; Fagus, the beech; Betula, the birch, &c.
“The following families constitute the arborescent flora of the period besides those already mentioned:—Balsaminaceæ, Lauraceæ, Thymelæaceæ, Santalaceæ, Cornaceæ, Myrtaceæ, Calycanthaceæ, Pomaceæ, Rosaceæ, Amygdaleæ, Leguminosæ, Anacardiaceæ, Juglandaceæ, Rhamnaceæ, Celastrinaceæ, Sapindaceæ, Meliaceæ, Aceraceæ, Tiliaceæ, Magnoliaceæ, Capparidaceæ, Sapoteaceæ, Styracaceæ, Oleaceæ, Juncaceæ, Ericaceæ.
“In all these families great numbers of European genera are found, often even more abundant in species than now. Thus, as Brongniart observes, in this flora we reckon fourteen species of Maple; three species of Oak; and these species proceed from two or three very circumscribed localities, which would not probably, at the present time, represent in a radius of several leagues more than three or four species of these genera.”
An important difference distinguishes the Pliocene flora, as compared with those of preceding epochs, it is the absence of the family of Palms in the European flora, as noted by Lecoq, which forms such an essential botanical feature in the Miocene period. We mention this, because, in spite of the general analogy which exists between the vegetation of the Pliocene period and that of temperate regions in the present day, it does not appear that there is a single species of the former period absolutely identical with any one now growing in Europe. Thus, the European vegetation, even at the most recent geological epoch, differs specifically from the vegetation of our age, although a general resemblance is observable between the two.
Fig. 174.—Skeleton of the Mastodon of Turin.
The terrestrial animals of the Pliocene period present us with a great number of creatures alike remarkable from their proportions and from their structure. The Mammals and the batrachian Reptiles are alike deserving of our attention in this epoch. Among the former the Mastodon, which makes its first appearance in the Miocene formations, continues to be found, but becomes extinct apparently before we reach the upper beds. Others present themselves of genera totally unknown till now, some of them, such as the Hippopotamus, the Camel, the Horse, the Ox, and the Deer, surviving to the present day. The fossil horse, of all animals, is perhaps that which presents the greatest resemblance to existing individuals; but it was small, not exceeding the ass in size.
The Mastodon, which we have considered in our description of the preceding period, still existed in Pliocene times; in [Fig. 174] the species living in this latter age is represented—it is called the Mastodon of Turin. As we see, it has only two projecting tusks or defences in the upper jaw, instead of four, like the American species, which is described in [page 343]. Other species belonging to this period are not uncommon; the portion of an upper jaw-bone with a tooth which was found in the Norwich Crag at Postwick, near Norwich, Dr. Falconer has shown to be a Pliocene species, first observed in Auvergne, and named by Messrs. Croizet and Jobert, its discoverers, Mastodon Arvernensis.
The Hippopotamus, Tapir, and Camel, which appear during the Pliocene period, present no peculiar characteristics to arrest our attention.
The Apes begin to abound in species; the Stags were already numerous.
Fig. 175.—Head of Rhinoceros tichorhinus, partly restored under the direction of Eugene Deslongchamps.
The Rhinoceros, which made its appearance in the Miocene period, appears in greater numbers in the Pliocene deposits. The species peculiar to the Tertiary epoch is R. tichorhinus, which is descriptive of the bony partition which separated its two nostrils, an anatomical arrangement which is not found in our existing species. Two horns surmount the nose of this animal, as represented in [Fig. 175]. Two living species, namely, the Rhinoceros of Africa and Sumatra, have two horns, but they are much smaller than those of R. tichorhinus. The existing Indian Rhinoceros has only one horn.
The body of R. tichorhinus was covered with very thick hair, and its skin was without the rough and callous scales which we remark on the skin of the living African species.
Contemporaneously with this gigantic species there existed a dwarf species about the size of our Hog; and along with it several intermediate species, whose bones are found in sufficient numbers to enable us to reconstruct the skeleton. The curvature of the nasal bone of the fossil Rhinoceros and its gigantic horn have given rise to many tales and popular legends. The famous bird, the Roc, which played so great a part in the fabulous myths of the people of Asia, originated in the discovery in the bosom of the earth of the cranium and horns of a fossil Rhinoceros. The famous dragons of western tradition have a similar origin.
In the city of Klagenfurth, in Carinthia, is a fountain on which is sculptured the head of a monstrous dragon with six feet, and a head surmounted by a stout horn. According to the popular tradition still prevalent at Klagenfurth, this dragon lived in a cave, whence it issued from time to time to frighten and ravage the country. A bold cavalier kills the dragon, paying with his life for this proof of his courage. It is the same legend which is current in every country, from that of the valiant St. George and the Dragon and of St. Martha, who nearly about the same age conquered the fabulous Tarasque of the city of Languedoc, which bears the name of Tarascon.
But at Klagenfurth the popular legend has happily found a mouth-piece—the head of the pretended dragon, killed by the valorous knight, is preserved in the Hôtel de Ville, and this head has furnished the sculptor for his fountain with a model for the head of his statue. Herr Unger, of Vienna, recognised at a glance the cranium of the fossil Rhinoceros; its discovery in some cave had probably originated the fable of the knight and the dragon. And all legends are capable of some such explanation when we can trace them back to their sources, and reason upon the circumstances on which they are founded.
The traveller Pallas gives a very interesting account of a Rhinoceros tichorhinus which he saw, with his own eyes, taken out of the ice in which its skin, hair, and flesh had been preserved. It was in December, 1771, that the body of the Rhinoceros was observed buried in the frozen sand upon the banks of the Viloui, a river which discharges itself into the Lena below Yakutsk, in Siberia, in 64° north latitude. “I ought to speak,” the learned naturalist says, “of an interesting discovery which I owe to the Chevalier de Bril. Some Yakouts hunting this winter near the Viloui found the body of a large unknown animal. The Sieur Ivan Argounof, inspector of the Zimovic, had sent on to Irkutsk the head and a fore and hind foot of the animal, all very well preserved.” The Sieur Argounof, in his report, states that the animal was half buried in the sand; it measured as it lay three ells and three-quarters Russian in length, and he estimated its height at three and a half; the animal, still retaining its flesh, was covered with skin which resembled tanned leather; but it was so decomposed that he could only remove the fore and hind foot and the head, which he sent to Irkutsk, where Pallas saw them. “They appeared to me at first glance,” he says, “to belong to a Rhinoceros; the head especially was quite recognisable, since it was covered with its leathery skin, and the skin had preserved all its external characters, and many short hairs. The eyelids had even escaped total decay, and in the cranium here and there, under the skin, I perceived some matter which was evidently the remains of putrefied flesh. I also remarked in the feet the remains of the tendons and cartilages where the skin had been removed. The head was without its horn, and the feet without hoofs. The place of the horn, and the raised skin which had surrounded it, and the division which existed in both the hind and fore feet, were evident proofs of its being a Rhinoceros. In a dissertation addressed to the Academy of St. Petersburg, I have given a full account of this singular discovery. I give there reasons which prove that a Rhinoceros had penetrated nearly to the Lena, in the most northern regions, and which have led to the discovery of the remains of other strange animals in Siberia. I shall confine myself here to a description of the country where these curious remains were found, and to the cause of their long preservation.
“The country watered by the Viloui is mountainous; all the stratification of these mountains is horizontal. The beds consist of selenitic and calcareous schists and beds of clay, mixed with numerous beds of pyrites. On the banks of the Viloui we meet with coal much broken; probably coal-beds exist higher up near to the river. The brook Kemtendoï skirts a mountain entirely formed of selenite or crystallised sulphate of lime and of rock-salt, and this mountain of alabaster is more than 300 versts (about 200 miles), in ascending the Viloui, from the place where the Rhinoceros was found. Opposite to the place we see, near the river, a low hill, about a hundred feet high, which, though sandy, contains some beds of millstone. The body of the Rhinoceros had been buried in coarse gravelly sand near this hill, and the nature of the soil, which is always frozen, had preserved it. The soil near the Viloui never thaws to a great depth, for, although the rays of the sun soften the soil to the depth of two yards in the more elevated sandy places, in the valleys, where the soil is half sand and half clay, it remains frozen at the end of summer half an ell below the surface. Without this intense cold the skin of the animal and many parts of it would long since have perished. The animal could only have been transported from some southern country to the frozen north at the epoch of the Deluge, for the most ancient chronicles speak of no changes of the globe more recent, to which we could attribute the deposit of these remains and of the bones of elephants which are found dispersed all over Siberia.”[92]
In this extract the author refers to a memoir previously published by himself, in the “Commentarii” of the Academy of St. Petersburg. This memoir, written in Latin, and entitled “Upon some Animals of Siberia,” has never been translated. After some general considerations, the author thus relates the circumstances attending the discovery of the fossil Rhinoceros, with some official documents affirming their correctness, and the manner in which the facts were brought under his notice by the Governor of Irkutsk, General Bril: “The skin and tendons of the head and feet still preserved considerable flexibility, imbued as it were with humidity from the earth; but the flesh exhaled a fetid ammoniacal odour, resembling that of a latrine. Compelled to cross the Baïkal Lake before the ice broke up, I could neither draw up a sufficiently careful description nor make sketches of the parts of the animal; but I made them place the remains, without leaving Irkutsk, upon a furnace, with orders that after my departure they should be dried by slow degrees and with the greatest care, continuing the process for some time, because the viscous matter which incessantly oozed out could only be dissipated by great heat. It happened, unfortunately, that during the operation the posterior part of the upper thigh and the foot were burnt in the overheated furnace, and they were thrown away; the head and the extremity of the hind foot only remained intact and undamaged by the process of drying. The odour of the softer parts, which still contained viscous matter in their interior, was changed by the desiccation into one resembling that of flesh decomposed in the sun.
“The Rhinoceros to which the members belonged was neither large for its species nor advanced in age, as the bones of the head attest, yet it was evidently an adult from the comparison made of the size of the cranium as compared with that of others of the same species more aged, which were afterwards found in a fossil state in divers parts of Siberia. The entire length of the head from the upper part of the nape of the neck to the extremity of the denuded bone of the jaw was thirty inches; the horns were not with the head, but we could still see evident vestiges of two horns, the nasal and frontal. The front, unequal and a little protuberant between the orbits, and of a rhomboidal egg-shape, is deficient in the skin, and only covered by a light horny membrane, bristling with straight hairs as hard as horn.
“The skin which covers the greater part of the head is in the dried state, a tenacious, fibrous substance, like curried leather, of a brownish-black on the outside and white in the inside; when burnt, it had the odour of common leather; the mouth, in the place where the lips should have been soft and fleshy, was putrid and much lacerated; the extremities of the maxillary bone were bare. Upon the left side, which had probably been longest exposed to the air, the skin was here and there decomposed and rubbed on the surface; nevertheless, the greater part of the mouth was so well preserved on the right side that the pores, or little holes from which doubtless the hairs had fallen, were still visible all over that side, and even in front. In the right side of the jaw there were still in certain places numerous hairs grouped in tufts, for the most part rubbed down to the roots, and here and there of two or three lines still retaining their full length. They stand erect, are stiff, and of an ashy colour, but with one or two black, and a little stiffer than the others, in each bunch.
“What was most astonishing, however, was the fact that the skin which covered the orbits of the eyes, and formed the eyelids, was so well preserved and so healthy that the openings of the eyelids could be seen, though deformed and scarcely penetrable to the finger; the skin which surrounded the orbits, though desiccated, formed circular furrows. The cavities of the eyes were filled with matter, either argillaceous or animal, such as still occupied a part of the cavity of the cranium. Under the skin the fibres and tendons still remained, and above all the remains of the temporal muscles; finally, in the throat hung some great bundles of muscular fibres. The denuded bones were young and less solid than in other fossil crania of the same species. The bone which gave support to the nasal horn was not yet attached to the vomer; it was unprovided with articulations like the processes of the young bones. The extremities of the jaws preserved no vestige either of teeth or sockets, but they were covered here and there with the remains of the integument. The first molar was distant about four inches from the extreme edge of the jaw.
“The foot which remains to me, and which, if I am not mistaken, belongs to the left hind limb, has not only preserved its skin quite intact and furnished with hairs, or their roots, as well as the tendons and ligaments of the heel in all their strength, but also the skin itself quite whole as far as the bend in the knee. The place of the muscles was filled with black mud. The extremity of the foot is cloven into three angles, the bony parts of which, with the periosteum, still remain here and there; the horny hoofs had been detached. The hairs adhering in many places to the skin were from one to three lines in length, tolerably stiff and ash-coloured. What remains of it proves that the foot was covered with bunches of hair, which hung down.
“We have never, so far as I know, observed so much hair on any rhinoceros which has been brought to Europe in our times, as appears to have been presented by the head and feet we have described. I leave you then to decide if our rhinoceros of the Lena was born or not in the temperate climate of Central Asia. In fact, the rhinoceros, as I gather from the relations of travellers, belongs to the forests of Northern India; and it is likely enough that these animals differ in a more hairy skin from those which live in the burning zones of Africa, just in the same way that other animals of a hotter climate are less warmly covered than those of the same genera in temperate countries.”[93]
Of all fossil ruminants one of the largest and most singular is the Sivatherium, whose remains have been found in the valley of Murkunda, in the Sewalik branch of the Sub-Himalayan Mountains. Its name is taken from that of Siva, the Indian deity worshipped in that part of India.
The Sivatherium giganteum had a body as bulky as that of an ox, and bore a sort of resemblance to the living Elk. It combined in itself the characteristics of different kinds of Herbivores, at the same time that it was marked by individual peculiarities. The massive head possessed four deciduous, hollow horns, like the Prongbuck; two front ones conical, smooth, and rapidly rising to a point, and two hinder ones of larger size, and branched, projected forward above the eyes.[94] Thus it differed from the deer, whose solid horns annually drop off, and from the antelope tribe, sheep and oxen, whose hollow horns are persistent, and resembled only one living ruminant, the prongbuck, in having had hollow horns subject to shedding. [Fig. 176] is a representation of the Sivatherium restored, in so far, at least, as it is possible to do so in the case of an animal of which only the cranium and a few other bones have been discovered.
Fig. 176.—Sivatherium restored.
As if to rival these gigantic Mammals, great numbers of Reptiles seem to have lived in the Pliocene period, although they are no longer of the same importance as in the Secondary epoch. Only one of these, however, need occupy our attention, it is the Salamander. The living Salamanders are amphibious Batrachians, with smooth skins, and rarely attaining the length of twenty inches. The Salamander of the Tertiary epoch had the dimensions of a Crocodile; and its discovery opens a pregnant page in the history of geology. The skeleton of this Reptile was long considered to be that of a human victim of the deluge, and was spoken of as “homo diluvii testis.” It required all the efforts of Camper and Cuvier to eradicate this error from the minds of the learned, and probably in the minds of the vulgar it survived them both.
Upon the left bank of the Rhine, not far from Constance, a little above Stein, and near the village of Œningen, in Switzerland, there are some fine quarries of schistose limestone. In consequence of their varied products these quarries have often been described by naturalists; they are of Tertiary age, and were visited, among others, by Horace de Saussure, by whom they are described in the third volume of his “Voyage dans les Alpes.”
In 1725, a large block of stone was found, incrusted in which a skeleton was discovered, remarkably well preserved; and Scheuchzer, a Swiss naturalist of some celebrity, who added to his scientific pursuits the study of theology, was called upon to give his opinion as to the nature of this relic of ancient times. He thought he recognised in the skeleton that of a man. In 1726 he published a description of these fossil remains in the “Philosophical Transactions” of London; and in 1731 he made it the subject of a special dissertation, entitled “Homo diluvii testis”—Man, a witness of the Deluge. This dissertation was accompanied by an engraving of the skeleton. Scheuchzer returned to the subject in another of his works, “Physica Sacra,” saying: “It is certain that this schist contains the half, or nearly so, of the skeleton of a man; that the substance even of the bones, and, what is more, of the flesh and of parts still softer than the flesh, are there incorporated in the stone; in a word, it is one of the rarest relics which we have of that accursed race which was buried under the waters. The figure shows us the contour of the frontal bone, the orbits with the openings which give passage to the great nerves of the fifth pair. We see there the remains of the brain, of the sphenoidal bone, of the roots of the nose, a notable fragment of the maxillary bone, and some vestiges of the liver.”
And our pious author exclaims, this time taking the lyrical form—
“Betrübtes Beingerüst von einem altem Sünder
Erweiche, Stein, das Herz der neuen Bosheitskinder!”
“O deplorable skeleton of an accursed ancient,
Mayst thou soften the hearts of the late children of wickedness!”
The reader has before him the fossil of the Œningen schist ([Fig. 177]). It is obviously impossible to see in this skeleton what the enthusiastic savant wished to perceive. And we can form an idea from this instance, of the errors to which a preconceived idea, blindly followed, may sometimes lead. How a naturalist of such eminence as Scheuchzer could have perceived in this enormous head, and in these upper members, the least resemblance to the osseous parts of a man is incomprehensible!
Fig. 177.—Andrias Scheuchzeri.
The Pre-Adamite “witness of the deluge” made a great noise in Germany, and no one there dared to dispute the opinion of the Swiss naturalist, under his double authority of theologian and savant. This, probably, is the reason why Gesner in his “Traité des Pétrifactions,” published in 1758, describes with admiration the fossil of Œningen, which he attributes, with Scheuchzer, to the antediluvian man.
Pierre Camper alone dared to oppose this opinion, which was then universally professed throughout Germany. He went to Œningen in 1787 to examine the celebrated fossil animal; he had no difficulty in detecting the error into which Scheuchzer had fallen. He recognised at once that it was a Reptile; but he deceived himself, nevertheless, as to the family to which it belonged; he took it for a Saurian. “A petrified lizard,” Camper wrote; “could it possibly pass for a man?” It was left to Cuvier to place in its true family the fossil of Œningen; in a memoir on the subject he demonstrated that this skeleton belonged to one of the amphibious batrachians called Salamanders. “Take,” he says in his memoir, “a skeleton of a Salamander and place it alongside the fossil, without allowing yourself to be misled by the difference of size, just as you could easily do in comparing a drawing of the salamander of the natural size with one of the fossil reduced to a sixteenth part of its dimensions, and everything will be explained in the clearest manner.”
“I am even persuaded,” adds the great naturalist, in a subsequent edition of this memoir, “that, if we could re-arrange the fossil and look closer into the details, we should find still more numerous proofs in the articular faces of the vertebræ, in those of the jaws, in the vestiges of very small teeth, and even in the labyrinth of the ear.” And he invited the proprietors or depositaries of the precious fossil to proceed to such an examination. Cuvier had the gratification of making, personally, the investigation he suggested. Finding himself at Haarlem, he asked permission of the Director of the Museum to examine the stone which contained the supposed fossil man. The operation was carried on in the presence of the director and another naturalist. A drawing of the skeleton of a Salamander was placed near the fossil by Cuvier, who had the satisfaction of recognising, as the stone was chipped away under the chisel, each of the bones, announced by the drawing, as they made their appearance. In the natural sciences there are few instances of such triumphant results—few demonstrations so satisfactory as this, of the certitude of the methods of observation and induction on which palæontology is based.
During the Pliocene period Birds of very numerous species, and which still exist, gave animation to the vast solitudes which man had not yet occupied. Vultures and Eagles, among the rapacious birds; and among other genera of birds, gulls, swallows, pies, parroquets, pheasants, jungle-fowl, ducks, &c.
In the marine Pliocene fauna we see, for the first time, aquatic Mammals or Cetaceans—the Dolphin and Balæna belonging to the period. Very little, however, is known of the fossil species belonging to the two genera. Some bones of Dolphins, found in different parts of France, apprise us, however, that the ancient species differed from those of our days. The same remark may be made respecting the Narwhal. This Cetacean, so remarkable for its long tusk, or tooth, in the form of a horn, has at all times been an object of curiosity.
The Whales, whose remains are found in the Pliocene rocks, differ little from those now living. But the observations geologists have been able to make upon these gigantic remains of the ancient world are too few to allow of any very precise conclusion. It is certain, however, that the fossil differs from the existing Whale in certain characters drawn from the bones of the cranium. The discovery of an enormous fragment of a fossil Whale, made at Paris in 1779, in the cellar of a wine-merchant in the Rue Dauphine, created a great sensation. Science pronounced, without much hesitation, on the true origin of these remains; but the public had some difficulty in comprehending the existence of a whale in the Rue Dauphine. It was in digging some holes in his cellars that the wine-merchant made this interesting discovery. His workmen found, under the pick, an enormous piece of bone buried in a yellow clay. Its complete extraction caused him a great deal of labour, and presented many difficulties. Little interested in making further discoveries, our wine-merchant contented himself with raising, with the help of a chisel, a portion of the monstrous bone. The piece thus detached weighed 227 pounds. It was exhibited in the wine-shop, where large numbers of the curious went to see it. Lamanon, a naturalist of that day, who examined it, conjectured that the bone belonged to the head of a whale. As to the bone itself, it was purchased for the Teyler Museum, at Haarlem, where it still remains.
There exists in the Museum of Natural History in Paris only a copy of the bone of the whale of the Rue Dauphine, which received the name of Balænodon Lamanoni. The examination of this figure by Cuvier led him to recognise it as a bone belonging to one of the antediluvian Balænæ, which differed not only from the living species, but from all others known up to this time.
Since the days of Lamanon, other bones of Balæna have been discovered in the soil in different countries, but the study of these fossils has always left something to be desired. In 1806 a fossil Balæna was disinterred at Monte-Pulgnasco by M. Cortesi. Another skeleton, seventy-two feet long, was found on the banks of the river Forth, near Alloa, in Scotland. In 1816 many bones of this animal were discovered in a little valley formed by a brook running into the Chiavana, one of the affluents of the Po.
Cuvier has established, among the cetacean fossils, a particular genus, which he designates under the name of Ziphius. The animals to which he gave the name, however, are not identical either with the Whales (Balænæ), the Cachelots or Sperm Whales, or with the Hyperoodons. They hold, in the order of Cetaceans, the place that the Palæotherium and Anoplotherium occupy among the Pachyderms, or that which the Megatherium and Megalonyx occupy in the order of the Edentates. The Ziphius still lives in the Mediterranean.
Fig. 178.—Pecten Jacobæus.
(Living species.)
The genera of Mollusca, which distinguish this period from all others, are very numerous. They include the Cardium, Panopæa, Pecten ([Fig. 178]), Fusus, Murex, Cypræa, Voluta, Chenopus, Buccinum, Nassa, and many others.
The Pliocene series prevails over Norfolk, Suffolk, and Essex, where it is popularly known as the Crag. In Essex it rests directly on the London Clay. Near Norwich it rests on the Chalk.
The Pliocene rocks are divided into lower and upper. The Older Pliocene comprises the White or Coralline Crag, including the Red Crag of Suffolk, containing marine shells, of which sixty per cent. are of extinct species. The Newer Pliocene is represented by the Fluvio-marine or Norwich Crag, which last, according to the Rev. Osmond Fisher, is overlaid by Chillesford clay, a very variable and more arctic deposit, often passing suddenly into sands without a trace of clay.
The Norfolk Forest Bed rests upon the Chillesford clay, when that is not denuded.
A ferruginous bed, rich in mammalian remains, and known as the Elephant bed, overlies the Forest Bed, of which it is considered by the Rev. John Gunn to be an upper division.
The Crag, divided into three portions, is a local deposit of limited extent. It consists of variable beds of sand, gravel, and marl; sometimes it is a shelly ferruginous grit, as the Red Crag; at others a soft calcareous rock made up of shells and bryozoa, as the Coralline Crag.
The Coralline Crag, of very limited extent in this country, ranges over about twenty miles between the rivers Stour and Alde, with a breadth of three or four. It consists of two divisions—an upper one, formed chiefly of the remains of Bryozoa, and a lower one of light-coloured sands, with a profusion of shells. The upper division is about thirty-six feet thick at Sudbourne in Suffolk, where it consists of a series of beds almost entirely composed of comminuted shells and remains of Bryozoa, forming a soft building-stone. The lower division is about forty-seven feet thick at Sutton; making the total thickness of the Coralline Crag about eighty-three feet.
Many of the Coralline Crag Mollusca belong to living species; they are supposed to indicate an equable climate free from intense cold—an inference rendered more probable by the prevalence of northern forms of shells, such as Glycimeris, Cyprina, and Astarte. The late Professor Edward Forbes, to whom science is indebted for so many philosophical deductions, points out some remarkable inferences drawn from the fauna of the Pliocene seas.[95] It appears that in the glacial period, which we shall shortly have under consideration, many shells, previously established in the temperate zone, retreated southwards, to avoid an uncongenial climate. The Professor gives a list of fifty which inhabited the British seas while the Coralline and Red Crag were forming, but which are all wanting in the glacial deposits;[96] from which he infers that they migrated at the approach of the glacial period, and returned again northwards, when the temperate climate was restored.[97]
In the Upper or Mammaliferous (or Norwich) Crag, of which there is a good exposure in a pit near the asylum at Thorpe, bones of Mammalia are found with existing species of shells. The greater number of the Mammalian remains have been supposed, until lately, to be extraneous fossils; but they are now considered by Mr. Prestwich as truly contemporaneous. The peculiar mixture of southern forms of life with others of a more northern type lead to the inference that, at this early period, a lowering of temperature began gradually to set in from the period of the Coralline Crag to that of the Forest Bed, which marks the commencement of the Glacial Period.
The distinction between the Mammaliferous Crag of Norwich and the Red Crag of Suffolk is purely palæontological, no case of superposition having yet been discovered, and they are now generally considered as contemporaneous. Two Proboscidians abundant during the Crag period were the Mastodon Arvernensis and the Elephas meridionalis. In the Red Crag the Mastodon is stated by the Rev. John Gunn to be more abundant than the Elephant, while in the Norwich beds their proportions are nearly equal.
At or near the base of the Red Crag there is a remarkable accumulation, varying in thickness from a few inches to two feet, of bones, teeth, and phosphatic nodules (called coprolites), which are worked for making superphosphate of lime for agricultural manure.
The foreign equivalents of the older Pliocene are found in the sub-Apennine strata. These rocks are sufficiently remarkable in the county of Suffolk, where they consist of a series of marine beds of quartzose sand, coloured red by ferruginous matter.
At the foot of the Apennine chain, which forms the backbone, as it were, of Italy, throwing out many spurs, the formations on either side, and on both sides of the Adriatic, are Tertiary strata; they form in many cases, low hills lying between the Apennines of Secondary formation and the sea, the strata generally being a light-brown or bluish marl covered with yellow calcareous sand and gravel, with some fossil shells, which, according to Brocchi, are found all over Italy. But this wide range includes some older Tertiary formations, as in the strata of the Superga near Turin, which are Miocene.
The Antwerp Crag, which is of the same age with the Red and Coralline Crag of Suffolk, forms great accumulations upon divers points of Europe: at Antwerp in Belgium, at Carentan and Perpignan, and, we believe, in the basin of the Rhône, in France. The thickest deposits of this rock consist of clay and sand, alternating with marl and arenaceous limestone. These constitute the sub-Apennine hills, alluded to above as extending on both slopes of the Apennines. This deposit occupies the Upper Val d’Arno, above Florence. Its presence is recognised over a great part of Australia. Finally, the seven hills of Rome are composed, in part, of marine Tertiary rocks belonging to the Pliocene period.
XXV.—Ideal Landscape of the Pliocene Period.
In [Plate XXV.] an ideal landscape of the Pliocene period is given under European latitudes. In the background of the picture, a mountain, recently thrown up, reminds us that the period was one of frequent convulsions, in which the land was disturbed and upheaved, and mountains and mountain-ranges made their appearance. The vegetation is nearly identical with the present. We see assembled in the foreground the more important animals of the period—the fossil species, as well as those which have survived to the present time.
At the close of the Pliocene period, and in consequence of the deposits left by the seas of the Tertiary epoch, the continent of Europe was nearly what it is now; few permanent changes have occurred since to disturb its general outline. Although the point does not admit of actual proof, there is strong presumptive evidence that in this period, or in that immediately subsequent to it, the entire European area, with some trifling exceptions, including the Alps and Apennines, emerged from the deep. In Sicily, Newer Pliocene rocks, covering nearly half the surface of the island, have been raised from 2,000 to 3,000 feet above the level of the sea. Fossil shells have been observed at the height of 8,000 feet in the Pyrenees; and, as if to fix the date of upheaval, there are great masses of granite which have penetrated the Lias and the Chalk. Fossil shells of the period are also found at a height of 10,000 feet in the Alps, at 13,000 feet in the Andes, and at 18,000 feet in the Himalayas.
In the mountainous regions of the Alps it is always difficult to determine the age of beds, in consequence of the disturbed state of the strata; for instance, the lofty chain of the Swiss Jura consists of many parallel ridges, with intervening longitudinal valleys; the ridges formed of contorted fossiliferous strata, which are extensive in proportion to the number and thickness of the formations which have been exposed on upheaval. The proofs which these regions offer of comparatively recent elevation are numerous. In the central Alps, Cretaceous, Oolitic, Liassic, and Eocene strata are found at the loftiest summits, passing insensibly into metamorphic rocks of granular limestone, and into talcose and mica-schists. In the eastern parts of the chain the older fossiliferous rocks are recognised in similar positions, presenting signs of intense Plutonic action. Oolitic and Cretaceous strata have been raised 12,000 feet, Eocene 10,000, and Miocene 4,000 and 5,000 feet above the level of the sea. Equally striking proofs of recent elevation exist in the Apennines; the celebrated Carrara marble, once supposed—from its crystalline texture and the absence of fossils, and from its resting—1. on talcose schists, 2. on quartz and gneiss—to be very ancient, now turns out to be an altered limestone of the Oolitic series, and the underlying crystalline rocks to be metamorphosed Secondary sandstones and shales. Had all these rocks undergone complete metamorphism, another page in the earth’s history would have been obscured. As it is, the proofs of what we state are found in the gradual approach of the rocks to their unaltered condition as the distance from the intrusive rock increases. This intrusive rock, however, does not always reach the surface, but it exists below at no great depth, and is observed piercing through the talcose gneiss, and passing up into Secondary strata.
At the close of this epoch, therefore, there is every probability that Europe and Asia had pretty nearly attained their present general configuration.
[81] Lyell’s “Elements of Geology,” p. 187.
[82] This limestone belongs to the Bembridge beds, and forms part of the Fluvio-marine series. See “Survey Memoir on the Geology of the Isle of Wight,” by H. W. Bristow.
[83] Similar beds of Miliolite limestone are found in the Middle Bagshot beds on the coast of Sussex, off Selsey—the only instance in England of the occurrence of such calcareous deposits of Middle Eocene age.—H. W. B.
[84] “Elements of Geology,” p. 292.
[85] “Memoir of the Geological Survey of Great Britain. The Geology of Middlesex, &c.;” by W. Whitaker, p. 9.
[86] Prestwich. Quart. Jour. Geol. Soc., vol. x., p. 448.
[87] Detailed sections of the whole of the Tertiary strata of the Isle of Wight have been constructed by Mr. H. W. Bristow from actual measurement of the beds in their regular order of succession, as displayed at Hempstead, Whitecliff Bay, Colwell and Tolland’s Bays, Headon Hill, and Alum Bay. These sections, published by the Geological Survey of Great Britain, show the thickness, mineral character, and organic remains found in each stratum, and are accompanied by a pamphlet in explanation.
[88] “Elements of Geology,” p. 300.
[89] Ibid., p. 305.
[90] Quarterly Journal of Geol. Soc., vol. vii., p. 89.
[91] See Bristow’s “Glossary of Mineralogy,” p. 11.
[92] “Pallas’s Voyage,” vol. iv., pp. 130-134.
[93] “Commentarii Academiæ Petersburgicæ,” p. 3.
[94] Dr. James Murie, Geological Magazine, vol. viii., p. 438.
[95] Edward Forbes in “Memoirs of the Geological Survey of Great Britain,” vol. i., p. 336.
[96] For full information on these deposits the reader is referred to the “Memoirs on the Structure of the Crag-beds of Norfolk and Suffolk,” by J. Prestwich, F.R.S., in the Quart. Jour. Geol. Soc., vol. xxvii., pp. 115, 325, and 452 (1871). Also to the many Papers by the Messrs. Searles Wood published in the Quar. Jour. Geol. Soc., the Ann. Nat. Hist., the Phil. Mag., &c.
[97] Lyell’s “Elements of Geology,” p. 203.