Petrography and paleoenvironment of Upper Cretaceous Anacacho Formation in southwest Texas
The diagenetic sequence of the Anacacho Formation began with early diagenetic events such as micritization, authigenic growth of glauconite in foraminiferal tests, and authigenic growth of framboidal pyrite nodules. Postdepositional diagenesis included the development of microspar, syntaxial overgrowths of spar, recrystallization of allochems, and calcite spar fill. Further burial caused severe compaction, evidenced by fracturing and pressure solution features. The sediments of the Anacacho Formation were then uplifted and subjected to ground water circulation in the fresh water phreatic zone. This resulted in dissolution of spar and microspar followed by precipitation of dog tooth sparry cement. Following the transgression of Upper Cretaceous and lower Tertiary marine shales, the unconformable surface of the Anacacho was sealed and ultimately trapped migrating hydrocarbons. As the hydrocarbons penetrated secondary fresh water porosity, dog tooth spar crystals were dislodged and incorporated into the hydrocarbon matrix by mechanical and/or chemical mechanisms. The hydrocarbons were devolitalized to asphalt following exposure of the Anacacho and, possibly, by thermal activity from local mafic intrusions. The biosparrudites in the Whites Mine area represent biostromal bank buildups on bathymetric highs that produced abundant skeletal debris. This debris migrated to the southwest, primarily as prograding sand waves, and resulted in deposition of biosparite in the Anacacho Mountains.
- Research Organization:
- Arco Exploration Co., Lafayette, LA
- OSTI ID:
- 6001193
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Vol. 67:3; ISSN AAPGB
- Country of Publication:
- United States
- Language:
- English
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