On the geological position of the Eocene deposits of Maryland and Virginia
1894; Yale University; Volume: s3-47; Issue: 280 Linguagem: Inglês
10.2475/ajs.s3-47.280.301
ISSN1945-452X
Autores Tópico(s)Geochemistry and Geologic Mapping
ResumoIN the spring of 1830,* T. A. Oonrad made a visit to the western shore of Maryland for the purpose of collecting fossil remains and observing the geological features of the region.He discovered in the vicinity of Ft.Washington beds that he correlated with the London Olay of England since they contained among other extinct species Venerical'dia planicosta of Lamarck.A few years lateJ•t he called attention to the resemblance of UUc'ltZZ(l3a gigantea of this locality to a European species, and noted the similarity of Ost1'ea compressirost'l'a and the European Osireu bellnvacina.In the same work he described many new species from Olaiborne, Alabama, mentioned others from Vallce's Ferry.South Oarolina, and classified Maryland, Alabama, and South Oarolina deposits alike as " Middle Tertiary or London OhW and Oalcaire Gl'Ossier."The Rogers in 1839:1: difIet'entiated this series from the overlying Miocene and underlying Oretaceous in Virginia and correctly referred it to an Eocene horizon and described several of its characteristic species.Oonrad, in the Proceedings of the National Institution, 1841, § mentioned many Eocene localities in the Gulf and Atlantic slope States and pointed out the resemblance of the Upper Marlboro rocks of Mat'yland to those of Bangor, England, Ost1'ea bellovaai7la he affirmed was found at either locality.Up to this time, no stl'ess had been laid on the stratigraphic position of the \'arious Eocene outcrops in America; to know that they were Eocene was all sufficing.In 1855, however, Oonradll established three subdivisions in the Alabama and Mississippi deposits of this series, naming them in descending order, the Vicksburg, Jackson and Olaiborne groups.In 1865 he instituted another, the I_ignite Formation, ~r wherein he seemingly dedil'ed to include beds lying between the" Buhr-stone~" as described by Tnomey, and the Oretaceous.To this formation he refelTed the dark colot'ed friable clays of Piscataway Oreek and the basal bed of Tuomey's section on Bashia Creek, Olark 00., Alabama; but the" Marlboro rock" to nse
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