Abstract

The Carboniferous Baird Formation and Early Permian McCloud Limestone, Eastern Klamath Mountains, California, record depositional relations of volcaniclastic and carbonate sediments within an island-arc setting. Pennsylvania parts of the Baird include interbedded mudstone, sandstone, and pebbly sandstone of volcaniclastic composition. These beds accumulated by gravity displacement as volcaniclastic submarine fans. A locally conformable transition from the Baird to the overlying Wolfcampian McCloud Limestone is marked by limestone conglomerate of debris-flow origin interbedded with volcaniclastic sediments and skeletal wackestone. This slope-related sequence is overlain by skeletal wackestone and interbedded skeletal packstones, and the section represents a distally steepened carbonate ramp that prograded over volcaniclastic slope deposits. In other areas, diachronous bodies of McCloud Limestone disconformably overlie Upper Mississippian volcanics and volcaniclastics of the Baird Formation. Laterally variable age relations of the McCloud and Baird indicate that platforms developed at different times on elevated arc surfaces, prograding locally over relic volcaniclastic slopes and accumulating thick carbonate sequences through platform subsidence.

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