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SUCCESSion or STRATA, 185

wide stratum of the sandstone formation, followed by a formation of marine limestone and shales and slate. It is by observations

thus made near, -or upon the surface, and carefully compared by means of the fossils which are found imbeded in them, that geologists classify the various groups in the order we shall presently name, and, as each stratum is characterized by its peculiar fossils, and is never found taking the precedence of another which may be anywhere found before it, they are justly supposed to be the productions of different epochs. Thus, at one period of the earth’s history, peculiar limestones, sandstones, marls, and clays, were deposited over the whole globe, upon those portions covered by water; in which the zoophytes, fishes, drifted wood, plants, reptiles &c., characteristic of that epoch were imbedded. At another and previous period, were deposited the shales, the millstone grit, and the immense beds of coal, imbedding peculiar and distinct remains of animals and vegetables characteristic of that epoch. At a still earlier period we find other distinct sedimentary rocks, and under the whole, although sometimes appearing on the surface, by being upheaved and uncovered, are found the crystaline masses of granite, porphyry, and sienite. Above all these well marked sedimentary, or water deposits, lies a vast accumulation of what is termed drift, being water worn, transported materials, consisting of the ruins of older rocks, and forming our light covering soil, sometimes scarcely overlaying, and at others " of many feet in thickness, principally sand, clay, and gravel, and large masses of water worn or rounded stones, called boulders. The more recent deposit of this sort is called Alluvium, and in it are imbedded the remains of man and his works, and such is the character of the fluviatile or river deposits now going on, and to which we shall again allude. The older deposit is termed Diluvium, and is found to contain no traces of man or his works, but in it are imbeded the remains of huge animals and reptiles now extinct, and also with them the bones of many existing species of animals, and the fossil remains of many known species of plants are found. In the following chapter we shall endeavor to give a clear view of the succession of the various strata and a short description of each, which shall be intelligible to any one who may feel enough interested to read it, and in concluding this chapter we must be allowed to say, that if the present part of our work does not interest the reader, the book may as well be closed; we can learn him nothing, for there is no sympathy between us.

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£RRONG LG GICAL ARRANGEMENT OF STRATA. 187

C H A P T E R II.
Chronological Arrangement of Strata.

“What once had been the solid earth, I saw
To be a strait; and from the waves new lands
Arose. Far off from the resounding sea,
The shells were strown about.” Ovid.

ALTHOUGH geologists are perfectly agreed as to the order of succession of the various strata, yet they have different methods of expressing the same fact. In other words, the names which are used to designate the different formations vary somewhat, but in the great leading features all are agreed. Thus, it matters little, whether, after having divided all rocks into two great classes, fossiliferous, and non-fossiliferous or metamorphic, we subdivide the former with Dr. Buckland, into alluvium, diluvium, tertiary, and the secondary or transition series; or with Dr. Mantell, into modern and ancient alluvium, tertiary strata, and secondary formations; both include the same classes of rocks; or whether we name a certain order of rocks the saliferous strata, or the upper and lower red sandstone; both mean the same thing. The classification which we have adopted is principally that of Dr. Mantell, who gives the following as the chronological arrangement of the strata, commencing with the uppermost or newest deposits.

I. FOSSILIFEROUS STRATA.

1. ModeRN AND ANCIENT ALLuvium.—Comprising the modern and superficial deposits of waterworn and transported materials, sometimes called drift, and consisting of gravel, boulders, sand, clay, &c. The modern deposits are characterized by the remains of man, and contemporaneous animals and plants. The ancient, sometimes called Diluvium, by an immense proportion of large mammalia and carnivora of species and genera, both recent and extinct.

2. THE TERTARY SystEM.—An extensive series comprising many isolated groups of marine, and lacustrine, or lake formed deposits, characterized by the remains of animals and vegetables, the greater portion of which are extinct, Volcanoes of great extent were in activity during this epoch. Mr. Lyell subdivides this series into the pliocene, or more recent; the miocene, less recent; and the eocene, dawn of recent; according to the percentage of recent shells contained in each.

Secondary Formations.

3. THE CHALK or CRETAcEous SYSTEM.–A marine formation, being the bed of an ancient sea, comprising limestones, sandstones, marls, and clays, and abounding in the remains of zoophytes, molusca, cephalapoda, fishes &c., drifted wood, and marine plants, with crocodiles, turtles and other, now extinct reptiles, also birds.

The chalk formation embraces several beds or distinct strata, thus, we have the upper chalk with flints, and the lower without; the chalk marl, the firestone, the galt or stiff blue, or black clay, abounding in shells, the shanklin or green sand.

4. THE WEALDEN.—From the German wald, a wood, the whole tract so called in England having been once a dense forest. This formation is the only known secondary fluviatile, or river formed deposit. It is a fresh water formation, evidently the deposit of some enormous ancient rivers, its fossil remains being the spoils of river and land, it is characterized by the remains of enormous and peculiar reptiles, namely the iguanodon, hylaeosarus, megalosaurus, plesiosaurus, crocodile, turtle, &c.; of terrestrial plants, fresh water shell-fish, and birds. The group called the Wealden is composed of beds of stiff blue clay, with beds of shelly limestone, called Sussex marble, beds of sands and sandstones as found at Hastings in England, and the clays, sandstones, and shelly limestones, as found in the Isle of Purbeck. called Purbeck marble.

succEssion of STRATA. 189

5. THE Oolite.—This is a marine formation of vast extent and thickness, its name means egg stone, because, it is formed of small egg like grains. It consists of limestones and clays, which abound in marine shells, corals, fishes; reptiles, both terrestrial and marine; land plants of peculiar species, and the remains of two or more genera of marsupial animals, are likewise found in it.

6. THE LIAs.—This name is supposed to be a provincial corruption of the word layers, as it consists of shale, or indurated slaty clay, which splits into layers, alternating with clays and limestones, containing marine shells, cephalapoda, crinoidea and fishes. It is chiefly remarkable however, for its remains of enormous reptiles particularly the plesiosaurus and the ichthyosaurus. The Lias group consists of the upper lias shale, mixed with the lower oolite, containing saurian remains, belemnites and ammonites; the lias marls; calcareous, sandy, and ferruginous; the lower lias clay and shales intercalated with sands and septaria, and lastly a series of laminated limestones, with partings of clay, which change into vast beds of red marl and sandstone forming,

7. THE SALIFERous, or NEw RED SANDSTONE SYSTEM.—A marine formation comprising variegated marls and sandstones, and conglomerates, frequently of a red color. The name new is given to distinguish it from a formation of the same mineralogical character but much older. This series of deposits is remarkable for the traces or footsteps of marsupial animals. and birds, and contains fossil remains of marine and terrestrial plants, fishes and reptiles. This series forms the grand depository of rock-salt and lime, hence called the saliferous, salt bearing. Its variegated color is owing to oxide of iron. The series consists of the upper new red sandstone, containing gypsum and rock salt, with variegated red and white sandstones, conglomerates or detritus of older rocks cemented together, and the lower new red sandstone, consisting of magnesian limestones called dolomite, and marls and conglomerates colored with oxide. of iron. This series rests upon,

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