Paper No. 9
Presentation Time: 4:05 PM
SYNTECTONIC STRATIGRAPHY IN A NARROW SEA, CRETACEOUS, TRANS PECOS, TEXAS
LANGFORD, Richard P., Geology, University of Texas at El Paso, 500 W. University Ave. Geological Sciences Bldg, El Paso, TX 79968, PAVLIS, Terry, Geological Sciences, University of Texas at El Paso, 500 W. University Ave, El Paso, TX 79968, PAGE, Seth J., Geological Sciences, University of Texas at El Paso, 500 W. University, El Paso, TX 79968 and BUDHATHOKI, Pawan, Geological Sciences, University of Texas at El Paso, El Paso, TX 79968, langford@utep.edu
Up to five kilometers of Aptian and Albian strata were deposited in a narrow sea extending from the Gulf of Mexico to southeast Arizona. The northeastern Margin of this trough is well exposed in several mountain ranges in West Texas, where thrusting has juxtaposed thick basin-fill sediments with thinner basin margin deposits. Neogene normal faults have exposed the basin fill oblique to the margin of the Cretaceous basin, allowing for correlation of strata over 10- to 20 -km sections extending obliquely into the basin. Initial stratigraphic correlation has allowed us to develop a preliminary sequence stratigraphy through approximately 1.3 km of Latest Aptian and Albian strata.
Features distinctive to the tectonically active narrow seas are, in the clastic sediments, rapid lateral changes in shale and conglomerate percentages as well as 2 km wide changes in clast lithologies reflecting points sources and little dispersion and mixing of sediments from different sources. Onlap of strata onto sequence boundaries on tilted fault blocks and filling of valleys and down faulted lows with shale indicate rapid subsidence and the importance of sea level changes in creating the basin margin stratigraphy. The sediments thicken basinward and are thickest in the highest thrust sheet containing the most distal strata. However, formations, members and sequences can be traced from one thrust sheet to the next, even though the shortening on the thrust must have been at least 10 km.
