Physical and sequence stratigraphy of the Late Cretaceous Chispa Summit Formation, Jeff Davis County, Texas.

摘要

The Late Cretaceous Chispa Summit Formation of west Texas has historically been of interest to the petroleum industry; with new technologies, this old, uneconomical play could prove significant, if not for energy resources, for educational purposes, but little work has been conducted on the formation. The Eagle Ford Formation of southern Texas is time equivalent to the Chispa Summit Formation and is a highly prolific hydrocarbon resource.;Located in western Jeff Davis County, Texas, the Chispa Summit Formation consists of marine shales interbedded with limestone beds and sporadically located siliciclastic beds, measuring a total of 610 m at the type locality. In the study area, 70 m of the formation was measured resulting in a division of the formation into five facies associations. Fifteen thin sections were analyzed from the interpreted facies associations and were grouped into three diagenetic facies and six petrographic facies.;A sequence stratigraphic framework is presented by analysis of field and petrographic data. This framework includes one full cycle in addition to the beginning of another sequence (low-high-low). Comparison of sequence stratigraphic work from laterally equivalent formations support the framework developed for the Chispa Summit Formation.;Field observations and interpretations lead to two sedimentation models presented in this work. Model A is a dual sourced model where sediment is sourced from both the east and west of the basin, and hypothesizes tectonic events to account for an influx of siliciclastics into the basin. Model B is a single source model where sediment is sourced only from the east; this model is based primarily on relative change in sea level.