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Permian and Eotriassic bivalves of the Middle Rockies. Bulletin of the AMNH ; v. 125, article 1

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dc.contributor.author Ciriacks, Kenneth Wilmer, 1938- en_US
dc.date.accessioned 2005-10-06T15:04:06Z
dc.date.available 2005-10-06T15:04:06Z
dc.date.issued 1963 en_US
dc.identifier.uri http://hdl.handle.net/2246/1222
dc.description 100 p., 16 p. of plates : ill. ; 27 cm. en_US
dc.description Thesis (Ph. D.)--Columbia University. en_US
dc.description Includes bibliographical references (p. 98-100). en_US
dc.description.abstract "The Permian-Triassic succession in the Middle Rockies of North America records one of the major gaps in the history of fossil invertebrates. Bivalve mollusks are the only invertebrates that are major components of both the Permian and the Eotriassic faunas. Seventy taxa, including two new genera and seven new species, are described from Permian rocks of the Park City group. Twenty-one taxa, including one new species, are described from Lower Triassic rocks. A proper interpretation of the magnitude of the local faunal break depends on the accurate dating of both the Permian and the Triassic sequences. Rocks of Park City age are subdivided into two age groups on the basis of bivalve correlations. Age group I, consisting of the basal members of the Park City and Phosphoria formations, is correlated with rocks of Upper Leonardian-Lower Wordian age in the West Texas standard Permian marine section. Age group II, including the remaining nine members of the Park City, Phosphoria, and Shedhorn formations, is correlated with rocks of Upper Wordian-Capitanian age in West Texas. This suggests an upper age limit of Kazanian (Capitanian) for the Park City group and indicates that the youngest Permian marine strata (Tartarian, Ochoan) are not locally represented. The Eotriassic Dinwoody formation is of early Scythian age. The nature of the Permian-Triassic contact indicates that at least locally, weathering and erosion took place and suggests a withdrawal of Permian seas and a period of emergence prior to transgression of the early Eotriassic sea. Generic and specific diversification in the Permian bivalves suggests that major evolutionary changes occurred in normal marine, shallow-water, carbonate facies. Latest Permian and earliest Triassic marine deposits are very restricted over the world and are notable for a general lack of calcareous facies. It seems that a major regression of the seas closed the Permian, which was followed by an early Triassic transgression in all of the known sequences. Perhaps the ecological changes recorded by these events were responsible for the revolutionary paleontological changes at this time rather than a very long time hiatus. Although bivalves are abundant in both the Permian and the Eotriassic faunas, only two species, out of 91 noted in the two local sequences, are closely comparable. Lower Eotriassic rocks contain an impoverished, intermediate fauna, which does not closely resemble younger Triassic faunas. The latter do not become established until the return of normal marine, clastic-free, carbonate facies in later Eotriassic time"--P. 5. en_US
dc.format.extent 48328773 bytes
dc.format.mimetype application/pdf
dc.language eng en_US
dc.language.iso en_US
dc.publisher New York : [American Museum of Natural History] en_US
dc.relation.ispartofseries Bulletin of the American Museum of Natural History ; v. 125, article 1 en_US
dc.subject.lcc QH1 .A4 vol.125, art.1, 1963 en_US
dc.subject.lcsh Bivalvia, Fossil -- Rocky Mountains. en_US
dc.subject.lcsh Mollusks, Fossil -- Rocky Mountains. en_US
dc.subject.lcsh Paleontology -- Permian -- Rocky Mountains. en_US
dc.subject.lcsh Paleontology -- Triassic -- Rocky Mountains. en_US
dc.subject.lcsh Paleontology -- Rocky Mountains. en_US
dc.title Permian and Eotriassic bivalves of the Middle Rockies. Bulletin of the AMNH ; v. 125, article 1 en_US
dc.type text en_US


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  • Bulletin of the American Museum of Natural History
    The Bulletin, published continuously since 1881, consists of longer monographic volumes in the field of natural sciences relating to zoology, paleontology, and geology. Current numbers are published at irregular intervals. The Bulletin was originally a place to publish short papers, while longer works appeared in the Memoirs. However, in the 1920s, the Memoirs ceased and the Bulletin series began publishing longer papers. A new series, the Novitates , published short papers describing new forms.

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