Slide-Block Geology, Coyanosa and Adjacent Areas, Pecos and Reeves Counties, Texas: ABSTRACT

Abstract

A large-scale submarine slide occurred in early Wolfcampian (Permian) time in the Coyanosa and adjacent areas of the southeastern Delaware basin of West Texas. The slide, which bisects the Coyanosa field, comprises all rocks above the Upper Devonian Woodford Shale, the surface of detachment. Maximum dimensions were 16 mi from east to west, 9 mi north to south, and 2,000 ft thick. Lateral displacement from east to west was about 7 mi. Wildcat and development drilling in the area has revealed many paradoxical structural and stratigraphic conditions in the Mississippian through Wolfcamp interval. These sequences include repeated sections, exotic blocks, displaced facies, and abrupt stratigraphic hiatuses. The sole of the allochthonous plate was a thick, competent Mississippian limestone. Thick Permo-Pennsylvanian conglomerates shed from the rising Central Basin platform on the eastern side of Coyanosa, coupled with steepening of the flexure on the western and southwestern flank of Coyanosa, triggered the slide. End_Page 340------------------------------ The slide was along the bedding plane in the eastern two thirds of the area. In the western third of the area the arcuate leading edge cut up section along the western and southwestern flank of Coyanosa and continued along the sea floor to just beyond Rojo Caballos. Rapid emplacement is implicit from the westerly thinning wedge of detritus which was churned up by the toe of the slide as it traversed the sea floor. Alternate interpretations to submarine sliding require almost inexplicable faulting and erosion to account for the observed phenomena. End_of_Article - Last_Page 341------------