In South America the cretaceous strata have been discovered in Columbia, as at Bogota and elsewhere, containing Ammonites, Hamites, Inocerami, and other characteristic shells.[225-A]
In the South of India, also, at Pondicherry, Verdachellum, and Trinconopoly, Messrs. Kaye and Egerton have collected fossils belonging to the cretaceous system. Taken in connection with those from the United States they prove, says Prof. E. Forbes, that those powerful causes which stamped a peculiar character on the forms of marine animal life at this period, exerted their full intensity through the Indian, European, and American seas.[225-B] Here, as in North and South America, the cretaceous character can be recognized even where there is no specific identity in the fossils; and the same may be said of the organic type of those rocks in Europe and India which succeed next in the ascending and descending order, the Eocene and the Oolitic.
CHAPTER XVIII.
WEALDEN GROUP.
The Wealden divisible into Weald Clay, Hastings Sand, and Purbeck Beds — Intercalated between two marine formations — Weald clay and Cypris-bearing strata — Iguanodon — Hastings sands — Fossil fish — Strata formed in shallow water — Brackish water-beds — Upper, middle, and lower Purbeck — Alternations of brackish water, freshwater, and land — Dirt-bed, or ancient soil — Distinct species of fossils in each subdivision of the Wealden — Lapse of time implied — Plants and insects of Wealden — Geographical extent of Wealden — Its relation to the cretaceous and oolitic periods — Movements in the earth's crust to which it owed its origin and submergence.
Beneath the cretaceous rocks in the S.E. of England, a freshwater formation is found, called the Wealden (see Nos. 5. and 6. Map, [p. 242.]), which, although it occupies a small horizontal area in Europe, as compared to the chalk, is nevertheless of great geological interest, not only from its position, as being interpolated between two great marine formations (Nos. 7. and 9. Table, [p. 103.]), but also because the imbedded fossils indicate a grand succession of changes in organic life, effected during its accumulation. It is composed of three minor divisions, the Weald Clay, the Hastings, and the Purbeck Beds, of which the aggregate thickness in some districts may be 700 or 800 feet; but which would be much more considerable (perhaps 2000 feet), were we to add together the extreme thickness acquired by each of them in their fullest development.
The common name of Wealden was given to the whole, because it was first studied in parts of Kent, Surrey, and Sussex, called the Weald, (see Map, [p. 242.]), and we are indebted to Dr. Mantell for having shown in 1822, in his Geology of Sussex, that the whole group was of fluviatile origin. In proof of this he called attention to the entire absence of Ammonites, Belemnites, Terebratulæ, Echinites, Corals, and other marine fossils, so characteristic of the cretaceous rocks above, and of the Oolitic strata below, and to the presence of Paludinæ, Melaniæ, and various fluviatile shells, as well as the bones of terrestrial reptiles and the trunks and leaves of land plants.
Fig. 227.