CHAPTER IX.
Strata of the Tertiary Series.
The Tertiary Series introduces a system of new phenomena, presenting formations in which the remains of animal and vegetable life approach gradually nearer to species of our own epoch. The most striking feature of these formations consists in the repeated alternations of marine deposites, with those of fresh water (see Pl. 1, sect. 25, 26, 27, 28).
We are indebted to Cuvier and Brongniart, for the first detailed account of the nature and relations of a very important portion of the tertiary strata, in their inestimable history of the deposites above the chalk near Paris. For a short time, these were supposed to he peculiar to that neighbourhood; further observation has discovered them to be parts of a great series of general formations, extending largely over the whole world, and affording evidences of, at least, four distinct periods, in their order of succession indicated by changes in the nature of the organic remains that are imbedded in them.[1]
Throughout all these periods, there seems to have been a continually increasing provision for the diffusion of animal life, and we have certain evidence of the character and
- ↑ In Vol. II. of his Principles of Geology, Mr. Lyell has given an interesting map, showing the extent of the surface of Europe, which has been covered by water since the commencement of the deposition of the tertiary strata.
M. Boué, also, has published an instructive map, representing the manner in which central Europe was once divided into a series of separate basins, each maintaining, for a long time, the condition of a freshwater lake; those which were subject to occasional irruptions of the sea, would, for a while, admit of the deposition of marine remains; the subsequent exclusion of the sea, and return to the condition of a freshwater lake, would allow the same region to become the receptacle of the exuvæ of animals inhabiting fresh water.—Synoptische Darstellung der Erdrinde. Hanau, 1827. The same map on a larger scale, appears
