| Summary: | GEOLOQY OP THJ3 HILL COUNTRY 7. its central parts were sunk deep below the ocean level. A sea, then extended northward from the Gulf of Mexico towards or perhaps quite to the Arctic Ocean. This sas during the last half of the Cretaceous Ago. The eastern borders of this sea appear to have extended to the eastern parts of Iowa and ftlincesota but no extensive formations of Cretaceous age are found there. At the west the waters extended farther than the main range of the Rocky Mountains, which as yet were not, upraised. It is easy to learn that the Cretaceous sea existed before these mountains were born, because geologists identify Strati), of that age tliat have been upheaved upon their flanks. How many hundreds of thousands of years the old inland sea existed, we do not know, but after undergoing some changes it was finally extinguished, chiefly owing to two causes, filling with sediment, and by the elevation again of the part of the continent covered by it. A laige volume might be written concerning what the geologists have ascertained relative to this sea, the strata formed of its consolidated or unconsolidated sediments, its gradual extinguishment, and the marine reptilia which swarmed in its waters and warred with its kind, and whose huge fossil remains are dug from the soft rocks of the Plains and Rocky Mountain foothills—pictorial restorations of which occur in some books, while their fossilized skeletons are: supposed to enrich museums and universities. The ancient sea not only included the Gulf of Mexico, but covered parts of Mexico, the states of Texas, Lousiana, Miss-, issippi, Alabama, Oklahoma, Kansas, Nebraska, South Dakota, North Dakota, more or less of the states adjoining these, with some northward extension into the Canadian provinces. It is not probable that the sea was extremely deep, yet in the longitude of the eastern part of North Dakota its bottom was as much as 3,000 feet lower than the present land surface, and likely much more. The variety of the Cretaceous rocks found in the region covered by the sea indicate widely variant depths in different portions of it during any particular epoch, and;; Scanned with a Zeutschel Zeta book scanner at 300 dpi. Edited in Multi-page TIFF Editor.
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