Paleoecologic Implications of Late Paleozoic Faunal Assemblages in Western United States: ABSTRACT

Abstract

Stratigraphic and paleontologic studies of interfingering marine and non-marine Late Paleozoic rocks in a End_Page 548------------------------------ small area near McCoy, Colorado, and in a large region in east-central Nevada indicate that at least eight major marine and paralic faunal assemblages occur in rocks of Pennsylvanian and Permian age. The eight recognized major faunal groups are: textulariid, fusulinid, coral, productid-Composita, chonetid, Heteralosia, Nuculana, and Euphemites faunas. The textulariid, fusulinid, coral, productid-Composita, and chonetid faunas required a salinity close to 35^pmil. The textulariid fauna probably lived at a depth of 50-70 m. and perhaps deeper; fusulinid fauna, 20-50 m.; and coral fauna, 10-30 m. The productid-Composita and chonetid faunas both may have lived at a depth of 4-10 m., but they had different energy requirements. The Heteralosia, Nuculana, and Euphemites faunas occupied very hallow-water environments with salinities different from 35^pmil. Overlap of faunas appears to have been a more common occurrence in the Colorado area than in Nevada because a greater inclination of the sea floor in Colorado allowed maximum development of different faunas to take place in areas close enough together to permit considerable faunal mixing. Geographic distribution of contemporaneous faunas indicates that inclination of the Colorado sea floor generally was about 10 m./km., whereas the inclination of the Nevada sea floor generally was about 1 m./km. End_of_Article - Last_Page 549------------