Depositional Environments, History, and Biostratigraphy of Upper Albian Rocks, Trans-Pecos Texas: ABSTRACT

Abstract

Upper Albian rocks in Brewster, Presidio, Jeff Davis, Reeves, and Pecos Counties, Texas, between the Adkinsites brazoensis and Pleisioturrilites brazoensis zones are divided into 10 lithofacies and associated depositional environments. These lithofacies represent deposition in environments ranging from nearshore high-energy carbonate and quartz sands, to offshore high-energy carbonate shoals and rudistid banks, to medium- to low-energy offshore shales and biomicrites, to deeper water low-energy micrites. All or parts of the Benevides, Loma Plata, Sue Peaks, Santa Elena, Boracho, Fort Terrett and Fort Lancaster Formations are included in this study. The wide variety of lithofacies present reflects variations in local source areas, depositional slope, source area and basin stability, and paleogeography. Distribution and thickness of lithofacies during the late Albian indicate that the Glass Mountains area and Diablo platform were structural highs separated by a shelf basin which occupied the position of the Paleozoic Hovey channel. The northern part of the area was a gently sloping shallow-water shelf; the southern part was the northern edge of the Chihuahua trough. The use of ammonite zones to trace lithofacies and depositional environments through space and time shows an initial transgressive followed by a lesser regressive sequence. The overall effect of late Albian deposition was transgressive. End_of_Article - Last_Page 759------------