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The Bannock Thrust Zone Southeastern Idaho

Description: Abstract: The Bannock overthrust in southeastern Idaho and northcentral Utah was originally described by Richards and Mansfield (1912) as a single large thrust fault that formed at the close of the Laramide orogeny and was folded by renewed compression near the end of Pliocene time. Later Mansfield expanded and revised his interpretation of the Bannock overthrust so that at least the northern part of the overthrust was thought to be a thrust zone in which the individual faults originated in a folded sole thrust. Detailed mapping in areas critical to Richards and Mansfield's interpretations has shown that the faults thought by them to be parts of one large thrust are separate faults, and that, although some of the thrust surfaces are curved, they were not folded in Pliocene time but probably were folded during a late stage of the thrusting. Extensions of the Bannock thrust to the north, south, east, and west based upon extrapolation of a single large folded thrust surface are not warranted. The Bannock overthrust is reinterpreted as a westward-dipping imbricate thrust zone possibly several tens of miles wide extending at least from southwestern Montana to north-central Utah. It is recommended that the name "Bannock overthrust" no longer be used, and that this zone of imbricate thrusts in the southeast corner of Idaho be called the Bannock thrust zone. The thrusts range in age from Late Jurassic to post- Early Cretaceous and are progressively younger from west to east; strong regional compressive forces do not appear to have been active in the area as late as Pliocene time. The upper plates of the thrusts moved to the northeast in response to an unknown force. Steep eastward-trending tear faults formed during thrusting probably in response to differential movement among the eastward-moving thrust plates. In Tertiary and Quaternary time ...
Date: 1963
Creator: Armstrong, Frank C. & Cressman, Earle Rupert
Partner: UNT Libraries Government Documents Department

Yampa Canyon in the Uinta Mountains Colorado

Description: From purpose of the report: A detailed office study of modern topographic and geologic maps and aerial photographs of Yampa Canyon and its environs in the Uinta Mountains.
Date: 1962
Creator: Sears, Julian D.
Partner: UNT Libraries Government Documents Department

Stratigraphy of Outcropping Permian Rocks in Parts of Northeastern Arizona and Adjacent Areas

Description: From introduction: In the spring and early summer of 1950 the writers undertook an investigation of the outcropping Permian rocks in northeastern Arizona, northwestern New Mexico, and parts of southern Utah. This work had as its specific objective the establishing of correlations of Permian rocks in the Zuni uplift, Defiance uplift, and Monument Valley upwarp. The determination of these relations, it is believed, will be of aid in the current activities of the Geological Survey in the Navajo Reservation which have as objectives the investigation of the mineral fuels and water resources of the area.
Date: 1961
Creator: Read, C. B. & Wanek, Alexander A.
Partner: UNT Libraries Government Documents Department

Foraminifera From the Northern Olympic Peninsula, Washington

Description: From introduction: This report deals with the stratigraphic and ecologic significance of Foraminifera contained in a Tertiary sequence that crops out in the northern part of the Olympic Peninsula, Wash. (pl. 1). The work was done as a part of a program of geologic investigations for oil and gas possibilities conducted by the U.S. Geological Survey.
Date: 1964
Creator: Rau, Weldon W.
Partner: UNT Libraries Government Documents Department