Trace Fossils, Basin Migration, Sedimentation, and Bathymetry of Ouachita Geosyncline of Oklahoma: ABSTRACT

Abstract

Flysch-type Nereites trace-fossil associations, paleocurrent data, and relatively numerous, thick sandstone beds with fluted soles, graded tops, contorted and convolute lamination, and ripple-drift indicate a continuous deep-water (bathyal-abyssal) axis for the Ouachita geosyncline during the deposition of the Stanley Group, Jackfork Group, Johns Valley Shale, and Atoka Formation of Oklahoma. Eventual migration of the basin onto the shelf is suggested by the west, northwest, and north overlap of the Atoka Formation on the Johns Valley Shale, Springer Formation, Chickachoc Chert, and Wapanucka Limestone, and by a transitional, shoal- to deep-water facies developed over the Chickachoc Chert and Wapanucka Limestone in the Atoka Formation. The transitional facies consists of a thick shale which is thought, on the basis of modern analogues, to have been deposited on a slope. Thin sandstone beds are present in this shale and are more numerous upward in the section. The sandstone beds are characterized by a trace-fossil association similar to a trace-fossil association in the basin axis, and by tooled soles, contorted lamination, ripples, and little grading. Down-slope, the transitional facies grades into the axial facies in which thick-bedded, axial-type sandstone becomes dominant. North of the Ouachita Mountains in the Arkoma basin, the top of the Atoka Formation is preserved. Physical-sedimentary structures and molasse-type Cruziana trace-fossil associations indicate shoal and near-shoal conditions. Toward the base of the section, there is no evidence for intermediate or deep-water facies. The older transition and deep-water facies are concealed in the thick Atoka section of the Arkoma basin or are farther south, beneath the Choctaw thrust which borders the west, northwest, and north margins of the Ouachita Mountains. End_of_Article - Last_Page 711------------