Cretaceous

“ The imperfection and want of continuity of the records in Europe have made it necessary in dealing with the Cretaceous European Cretaceous. floras for us to give the first place to America. But it is now advisable to return to Europe, where Upper Cretaceous plants are not uncommon, and the position of the deposits in the Cretaceous series can often be fixed accurately by their close association with marine strata belonging to definite subdivisions. ”

“ The plant-remains of the Lower Cretaceous greatly resemble those of the Jurassic period, consisting mainly of Ferns, Cycads, and Conifers. The Upper Cretaceous rocks, however, both in Europe and in North America, have yielded an abundant flora which resembles the existing vegetation of the globe in consisting mainly of Angiospermous Exogens and of Monocotyledons. ”

“ Yet the struggle for continued dominion was hard and protracted; and toward its close some of the champions of the reign of reptiles were the greatest and most magnificent examples of the type; as if they had risen in their might to defy approaching ruin. Thus some of the most stupendous forms appear in the later Cretaceous, after the great subsidence had made progress and almost attained its consummation. Like the antediluvian giants, they were undismayed even when the land began to sink beneath their feet ”

“ Thus it is true that a great and apparently somewhat abrupt change takes place at the close of the Cretaceous, and terminates for ever the reptilian age. Even in regions like Western America, where physically the later Cretaceous shades gradually into the earlier Tertiary, so that there have been doubts as to the limits of these several periods, the same great change in animal life occurs. ”

“ Organic Remains.—The fossils of the cretaceous system are eminently marine: nearly all the plants which it contains (they are few) are of marine types; and the sponges, stellerida, mollusca, Crustacea, fishes, and reptiles, all appear to have been inhabitants of the ocean. Mammalia are not known in the cretaceous rocks. It appears that (excluding the Maestricht and Gosau beds) nearly the same large proportion of extinct genera, and the same differences of proportionate development of molluscous groups, is traced in the cretaceous as in the oolitic system ”

“ It will give a sufficient idea of the importance of the Cretaceous period in connection with these organisms to state that, in the rocks of the period, 268 genera of animals, hitherto unknown, and more than 5,000 species of special living beings have been found; the thickness of the rocks formed during the period being enormous. Where is the geologist who will venture to estimate the time occupied in creating and destroying the animated masses of which this formation is at once both the cemetery and the monument? ”

“ The flora of the Eocene period, although full of interest, does not convey the impression of newness that is afforded by the fauna of the period. The reason for this difference is this: the newer flora had been introduced and had developed to a considerable extent in the Cretaceous period, and there is no sharp break between the flora of the earlier and that of the later period ”

“ The next series of rocks in ascending order is the great and important series of the Cretaceous Rocks, so called from the general occurrence in the system of chalk (Lat. creta, Page 257 chalk) . As developed in Britain and Europe generally, the following leading subdivisions may be recognised in the Cretaceous series:—
I. Wealden.—The Wealden formation, though of considerable importance, is a local group, and is confined to the southeast of England, France, and some other parts of Europe. ”

“ As we work our way through the great series of the Tertiary formations, we find species of animals identical with those which live at the present day, diminishing in numbers, it is true, but still existing in a certain number in the oldest of the Tertiary rocks. And not only so, but when we examine the rocks of the Cretaceous epoch itself, we find the remains of some animals which the closest scrutiny cannot show to be in any respect different from those which live at the present time. ”

“ There is a striking difference between the Cretaceous faunas of the two areas, the fossils from the north being closely allied to those of Europe, while those of the south (Pondicherry and Trichinopoly) are very different and are much more nearly related to those from the Cretaceous of Natal. ”

“ The absence in strata of Tertiary age of the chambered Cephalopods, the Belemnites, the Hippurites, the Inocerami, and the diversified types of Reptiles which form such conspicuous features in the Cretaceous fauna, render the palæontological break between the Chalk and the Eocene one far too serious to be overlooked. ”

“ Still more unaccountable, upon any theory of development according to ordinary laws of reproduction, are those unique, isolated types limited to a single epoch, or sometimes even to a single period. There are some very remarkable instances of this in the Cretaceous deposits. To make my statement clearer, I will say a word of the sequence of these deposits and their division into periods.
These Cretaceous beds were at first divided only into three sets, called the Neocomian, or lower deposits, the Green-Sands, or middle deposits, and the Chalk, or upper deposits. ”

“ In all these localities, the Cretaceous remains, like those of the Jurassic epoch, have one organic character, distinct and unique. This fact is especially significant, because the contact of their respective deposits is in many localities so immediate and continuous that it affords an admirable test for the development-theory. If this is the true mode of origin of animals, those of the later Jurassic beds must be the progenitors of those of the earlier Cretaceous deposits. ”

“ And thus ends a long era of world evolution, extending from the early appearance of land life down to the more recent times of the immediate ancestors of the human species and its collateral branches. This, the Cretaceous age, covers fifty million years and brings to a close the premammalian era of land life, which extends over a period of one hundred million years and is known as the Mesozoic. ”

“ And now following on these came our Wealden strata, the beginning of the Cretaceous period. You see what ages and ages had gone before, and that when Wealden times came, far back as they are, the world's history was comparatively approaching modern times. We must remember that all these formations, of which we have given a rapid sketch, are of great thickness,—thousands of feet of rock,—and represent vast ages of time. See what we have got to from looking at the shells in the sea cliff! We have come to learn something of the world's old history. ”

“ An immense amount of literature has been printed on the subject of the Cretaceous formation and its inhabitants. Very recently there have been immense advances made in the restoration of species existing in Cretaceous times. This article, therefore, is in the nature of scientific news, and a separation of facts from a mass of errors. In looking over the works of others, one is impressed by the many mistakes made by specialists, owing to imperfect skeletons and collections. ”

“ The old world again perished, and the dawn of the Tertiary shows to us at once the dynasties of the Mammalian age, which was to culminate in the introduction of man. With the great Cretaceous subsidence the curtain falls upon the age of reptiles, and when it rises again, after the vast interval occupied in the deposition of the green-sand and chalk, the scene has entirely changed. There are new mountains and new plains, forests of different type, and animals such as no previous age had seen. ”

“ We can scarcely doubt that we should already have traced back the evidence of this class of fossils much farther had not our enquiries been arrested, first, by the vast gap between the tertiary and secondary formations, and then by the marine nature of the cretaceous rocks. ”

“ But the prevalence of the great reptiles up to the close of the Cretaceous would seem to render the co-existence of large mammals unlikely. It has further been supposed that geological changes in the southern211 and northern hemispheres may have alternated with each other, so that there may be in the former Cretaceous beds in which the remains of ancestors of the Eocene mammals may be found. But we do not as yet know of such deposits. ”

“ These two little plants, once probably very widely diffused over the northern hemisphere, have continued to exist through the millenniums separating the Cretaceous from the present time, and in which the greater part of our continent was again and again under the sea, in which great mountain chains have been rolled up and sculptured into their present forms, and in which giant forms, both of animal and plant life, have begun, culminated and passed away. Truly God hath chosen the weak things of the world to confound those that are strong. ”

“ In your country the development of the cretaceous series of rocks is enormous; the conditions under which the later cretaceous strata have been deposited are highly favourable to the preservation of organic remains; and the researches, full of labour and risk, which have been carried on by Professor Marsh in these cretaceous rocks of Western America, have rewarded him with the discovery of forms of birds of which we had hitherto no conception. ”

“ The Cretaceous is not only limited within a relatively narrow shore zone, but also, like the Palæozoic, it is broken down toward the west, not reappearing from beneath the Tertiary cover of the desert region or upon the granite-gneisses that form the foundation for all the known sedimentary strata of the immediate coast. ”

“ It has, indeed, been supposed by some that the remains of the early mammals occurring in the gravels are derived from older beds, and that their presence in association with flint implements no more proves the contemporaneity of the men who made those implements with the old Quaternary fauna, than their association with Chalk fossils proves that mankind were originally inhabitants of the bed of the Cretaceous ocean. ”

“ It is not till we arrive at the Cretaceous period that they begin to appear, sparingly at first, and only playing a conspicuous part, together with the palms and other endogens, in the Tertiary epoch. ”

“ We may be content, therefore, to suppose that at the close of the Cretaceous there was established somewhere a sort of Eden for the first placental mammals, in which they were introduced and could live unharmed by the decaying monsters of the reptilian age, until the time came when they could increase and multiply and replenish the earth. ”

“ A very similar distribution of land and water in the Cretaceous age gave a warm and equable climate in those portions of North America not submerged, and coincided with the appearance of the multitude of broad-leaved trees of modern types introduced in the early and middle Cretaceous, and which prepared the way for the mammalian life of the Eocene. ”

“ The earliest of these fossil angiosperms is not in a true sense a primitive form, and no records of such types have yet been discovered. Some of the early forms of the Lower Cretaceous are distinctly similar to modern genera, such as Ficus, Sassafras and Aralia; others bore leaves closely resembling our elm, maple, willow, oak, eucalyptus, &c. Before the close of the period many other representatives of living genera had appeared, beech, walnut, tamarisk, plane, laurel (Laurus) , cinnamon, ivy, ilex, viburnum, buckthorn, breadfruit, oleander and others ”

“ The relations with the underlying Jurassic rocks are not so clearly defined, partly because the earliest Cretaceous rocks are obscured by too great a thickness of younger strata, and partly because the lowest observable rocks of the system are not the oldest, but are higher members of the system that have overlapped on to much older rocks. ”

“ This marine extension made itself felt over the old central plateau of France, the N. of Great Britain, the Spanish peninsula, the Armorican peninsula, and also in the Bavarian Jura and Bohemia; it affected the northern part of Africa and East Africa; in N. America the sea spread over the entire length of the Rocky Mountain region; and in Brazil, eastern Asia and western Australia, Upper Cretaceous deposits are found resting directly upon much older rocks. ”

“ It is probable that during the Cretaceous time, in some land where we have not yet had a chance to study the rocks, these creatures grew to their varied forms, and that in the beginning of the Tertiary time, they spread into the regions where we find their bones.
Beginning with the Tertiary time, we find these lower kinsmen of man, through whom man came to be. The mammals were marked by much greater simplicity and likeness to each other than they now have. ”

“ There are hardly any mines or quarries in the beds of this age to bring these fossils to light. In the most of the other rocks there is more to tempt man to explore them for coal ores or building stones.
In passing from the Cretaceous to the Tertiary, we [pg 89] enter upon the threshold of our modern world. We leave behind all the great wonders of the old world, the gigantic reptiles, the forests of tree ferns, the seas full of ammonites and belemnites, and come among the no less wonderful but more familiar modern forms. ”

“ At the close of the Cretaceous age the animal life, both sea and land, was again revolutionized, but by causes which we cannot yet fully understand, as the physical conditions remain nearly the same, and the flora suffered little change. ”

“ Year after year have geologists advanced in the belief that the cretaceous period, about whose origin there have been so many uncertainties, must have owed its existence to long-continued accumulations of the remains of primæ val Foraminiferæ ”