Geology Commons^™

Magnetic Anisotropy Of Barbados Prism Sediments, Bernard A. Housen

Geology Faculty Publications

Anisotropy of magnetic susceptibility (AMS) results from sediments spanning the basal décollement of the Barbados accretionary prism show a striking progression across this structure that strongly supports the hypothesis that it is strongly overpressured. In the accretionary prism above the décollement, the minimum AMS axes are subhorizontal and nearly east–west trending, whereas the maximum AMS axes are nearly north–south trending, and shallowly inclined. At the top of the décollement, the AMS minimum axes orientations abruptly change to nearly vertical; this orientation is maintained throughout the décollement and in the underthrust sediments below. The AMS orientations in the prism sediments above …

Hessian (Leonardian, Middle Lower Permian) Depositional Sequences And Their Fusulinid Zones, West Texas, Charles A. Ross, June R. P. Ross

Geology Faculty Publications

The lower Leonardian (Lower Permian) Hess Limestone in the eastern part of the Glass Mountains, West Texas, forms a high, well-exposed escarpment of repetitious, shallow-water, platform limestone facies for about 35 km. The strike of the outcrops cuts the strike of depositional facies at relatively low angle so that the actual width of the carbonate platform, from its marginal rim to shore facies, was probably less than 10 km (Figs. 1, 2). At the platform margin, the Hess Limestone passes abruptly into coarse, conglomeratic slope deposits that form the Skinner Ranch Formation. The pebbles, cobbles, boulders, (some the size of …

Nealian And Lenoxian (Wolfcampian, Lower Permian) Depositional Sequences, Fusulinid Facies And Biostratigraphy, Glass Mountains, Texas, Charles A. Ross, June R. P. Ross

Geology Faculty Publications

The Wolfcampian Series crops out along the base of the Glass Mountains escarpment (King, 1930, 1937) and, in the western part of the Marathon Basin, in folded and faulted beds exposed in the Dugout structural fold belt, the westernmost belt in the Marathon Orogen (Ross, 1963). The Wolfcampian is divided into two stages, a lower Nealian Stage and an upper Lenoxian Stage (Ross and Ross, 1987a, 1987b). Strata of these two stages are separated by a major tectonic event in the history of the Marathon orogeny and, as a result, by a major angular unconformity that separates the structurally deformed …

Structural Geology Of The Décollement At The Toe Of The Barbados Accretionary Prism, Alex Maltman, Pierre Labaume, Bernard A. Housen

Geology Faculty Publications

The base of the Barbados accretionary prism is defined by a décollement, which separates material accreting to the Caribbean Plate from underthrusting Atlantic Ocean sediment. A three-dimensional seismic survey has shown the structure to contain intervals of negative polarity, interpreted as representing pockets of overpressured fluid. Consequently, Ocean Drilling Program Leg 156 was designed specifically to investigate the hydrogeological and deformational behavior of the décollement.

Analysis of recovered cores shows the structure to comprise a zone of intensified but heterogeneous deformation, 31 m thick, but 39 m thick if suprajacent breccia and various physico-chemical anomalies are included. The top of …