Upper Albian (Cretaceous) rocks of western Trans-Pecos Texas crop out in an east-west trend along the northeastern margin of the ancient Chihuahua trough and adjacent Diablo platform. These rocks represent an alternating terrigenous-carbonate sequence within an overall transgressive phase.

Twelve lithofacies and six biofacies were recognized from thin section point-count analysis and empirical outcrop data. Environmental parameters derived from lithofacies and biofacies, the interrelationships of facies, and comparison with several carbonate depositional models provide the basis for the establishment of depositional environments represented by upper Albian strata.

A time-stratigraphic framework consisting of ammonite interval zones was used to trace the movement of environments through time and space. Distribution of these environments indicates initial transgression came from the south and proceeded northeastward across Trans-Pecos Texas. Upper Albian deposition was concluded with the onset of a major regressive phase marking the beginning of the Cenomanian Stage.

End_of_Article - Last_Page 562------------