Description
The stratigraphy, with emphasis on sedimentary current structures, is described for a portion of the Coalinga Quadrangle comprised of Upper Cretaceous rocks. The section contains a sequence of marine shale, sandstone, and conglomerates. The shale formations have a flysch-like character, with repetitious, thin interbeds of sandstone. Sandstone formations are medium-to coarse-grained and generally massive. Sedimentary structures, which occur mainly in sandstone interbeds of the shale formations, include sole markings, graded-bedding, ripple marks, cross-laminations, and convolute laminations. Worm burrows and slump structures are infrequent. The subaqueous slopes, as determined from gravity-controlled structures, dipped westward during Cenomanian time and southward during Turonian time. Two types of currents dominated during the deposition of the Panoche Group: episodal currents and contour currents. Episodal currents traveled down the subaqueous slope and transported land-derived sediments, and contour currents traveled parallel to the isobaths of the subaqueous slope, redistributed and reworked part of the sediments. During Cenomanian time approximate direction of episodal currents was to the west and contour currents to the north. During Turonian time episodal currents traveled to the south-southeast, presumably due to a shift in the subaqueous slope caused by tectonic activity, and contour currents traveled to the southwest. The provenance from which the sediments were derived was to the east or southeast during Cenomanian time, and between the southeast and northeast during Turonian time.
