Chemostratigraphy, Mineralogy, and Depositional Environment of the Wolfcamp Series, Midland Basin, Reagan County, Texas

Karen McCreight¹, Robert Baumgardner², H. Scott Hamlin², and Harry Rowe¹
¹ University of Texas at Arlington, Arlington, Texas 76019
² Bureau of Economic Geology, Austin, Texas 78713-8924

Increased interest in petroleum exploration of late Paleozoic strata in the Midland Basin, Texas, has spurred fundamental research into the mineralogical and geochemical signatures preserved in the strata and their linkages to depositional environments and well log interpretation. We demonstrate using geochemical methods that much of the mineralogical shifts in the two cores represent a dilution of siliciclastics by calcium carbonate. We present chemostratigraphic results from two drill cores recovered from Reagan County, Texas, that we interpret in terms of changes in mineralogy, organic deposition, and basinal hydrography. Geochemical and sedimentological interpretations are integrated to develop a multi-proxy model of depositional history for the late Pennsylvanian Wolfcamp Series. Preliminary investigation of the trace-metal chemistry of carbonate phases may provide useful chemostratigraphic information. Specifically, cross-plots of calcium versus magnesium, iron, manganese, and strontium indicate the occurrence of secondary carbonates with variable non-calcium substitution (in addition to the pure carbonate shed off the platform - presumed to be calcite) that may represent signatures from changing depositional conditions in the deep basin or diagenetic history.

AAPG Search and Discovery Article #90158©2012 GCAGS and GC-SEPM 6nd Annual Convention, Austin, Texas, 21-24 October 2012