p An integrated chemostratigraphic and sequence stratigraphic analysis of extended (>1000 ft) lower Permian Wolfcamp cores, Reagan County, southern Midland Basin

Two cores of more than 1000 ft (300 m) of lower Permian (Wolfcampian) strata from Midland Basin, Texas were described bed by bed to establish an integrated lithostratigraphic, chemo-stratigraphic, and sequence stratigraphic framework. Ten lithofa-cies, where mudstones were defined as being finer than coarse silt in size, include (1) dolostone, (2) floatstone, (3) graded skel-etal grainstone, (4) graded skeletal wackestone and packstone, (5) graded calcisiltstone, (6) siliceous siltstone, (7) carbonate mudstone, (8) mixed siliceous-carbonate mudstone, (9) siliceous mudstone, and (10) argillaceous mudstone. Using this framework, in conjunction with significant stratigraphic surfaces, four deposi-tional sequences were identified and correlated between the two cores. Each sequence transitions up section from carbonate-rich intervals interpreted as lowstand deposits upward into siliceous mudstone beds where the dominant source of silica is biogenic, interpreted as pelagic-transgressive to highstand deposits. This dif-fers from the traditional deep-water reciprocal sedimentation model where quartz-rich strata are interpreted as lowstand depos-its, and carbonate-rich strata are interpreted as transgressive to highstand deposits.