Cenozoic deposits

p. 265-371, [9] folded leaves of plates : ill., maps ; 26 cm.Includes bibliographical references (p. 363-369) and indexes."The objectives of the present report are (1) to interpret in detail the geology of the Sheep Creek-Snake Creek beds of Sioux County, northwestern Nebraska, which have produced more than 30,000 vertebrate fossil specimens, and (2) to supply precise data for these fossils so that future research will conform to historical data and field observations. An erosional remnant of former high plains, which contains the historic Sheep Creek-Snake Creek beds, has preserved a record of geologic history from early through late Miocene time. A remnant of paleovalley that once contained the streams of the early Miocene Sheep Creek (late Hemingfordian) and the late Miocene Snake Creek formations can be seen in the northwest part of the area. The early Medial Miocene (early Barstovian) Olcott Formation (New), the former Lower Snake Creek beds of Matthew, 1924a, crops out in the classic Sinclair Draw and Olcott Hill area that was explored in the early 1900s. The revised and restricted Snake Creek Formation is divided into three new members: the Medial Miocene Murphy Member (early Clarendonian) on Olcott Hill and in East Pliohippus Draw, the Medial Miocene Laucomer Member (late Clarendonian) on Olcott Hill, and the late Miocene Johnson Member that carries early and late Hemphillian faunas. The present report also deals with the documentary data of early collectors whose numerous synonymous names for some of the 57 quarries has led to the dissipation of faunas"--P. 271