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Title: Relationships of Bexar shale, Hensel sandstone, and Hensel dolomite (basal upper Trinity, Comanchean Cretaceous) in south-central Texas

Abstract

The Bexar Shale has been considered the offshore equivalent of the Cow Creek Limestone, the overlying Hensel sandstone, or of the disconformity between them in outcropping sections. Cores and outcrops in Comal, Kendall, and northern Bexar Counties preserve calcitic and dolomitic caliche in the top of the Cow Creek Limestone. Above the caliche is 8-16 m(25-50 ft) of laminated or bioturbated, dolomitic siltstone and silty dolomite (Hensel dolomite). Dolomite is euhedral and silt-sized. The lower part contains collophane grains and oyster shells replaced partly by chalcedony. Carbonate grains within the upper part include angular and well-rounded mollusk and echinoid fragments; many are pyritic and coated by glauconite. Terrigenous grains in Hensel dolomite grade upward from silt to coarse subarkose sand from central Texas. In southern Bexar County, about 35 m (115 ft) of silt-, clay-, and calcite-mudstone referable to the Bexar Shale sharply overlie shallow marine Cow Creek Limestone, and grade abruptly upward into about 7 m (23 ft) of Hensel dolomite. Dolomite is overlain by calcarenite of the Glen Rose Formation containing subarkose sand grains. Similar distinctive sand grains occur in well cuttings of basal Glen Rose beds northeastward through Travis County. The Bexar represents a flood of clay-sizedmore » sediment from a distant source, spread across the San Marcos arch during a rapid transgression. Slightly younger sand, silt, and local clay of the Hensel sandstone were eroded from central Texas by a few flash floods during a major period of caliche formation in the area.« less

Authors:
Publication Date:
OSTI Identifier:
6609379
Report Number(s):
CONF-8405216-
Journal ID: CODEN: AAPGB
Resource Type:
Conference
Journal Name:
Am. Assoc. Pet. Geol., Bull.; (United States)
Additional Journal Information:
Journal Volume: 68:4; Conference: AAPG annual convention, San Antonio, TX, USA, 20 May 1984
Country of Publication:
United States
Language:
English
Subject:
02 PETROLEUM; 03 NATURAL GAS; DOLOMITE; SEDIMENTATION; SANDSTONES; SHALES; TEXAS; GEOLOGY; STRATIGRAPHY; ALKALINE EARTH METAL COMPOUNDS; CALCIUM CARBONATES; CALCIUM COMPOUNDS; CARBON COMPOUNDS; CARBONATE MINERALS; CARBONATES; FEDERAL REGION VI; MAGNESIUM CARBONATES; MAGNESIUM COMPOUNDS; MINERALS; NORTH AMERICA; OXYGEN COMPOUNDS; ROCKS; SEDIMENTARY ROCKS; USA; 020200* - Petroleum- Reserves, Geology, & Exploration; 030200 - Natural Gas- Reserves, Geology, & Exploration

Citation Formats

Amsbury, D L. Relationships of Bexar shale, Hensel sandstone, and Hensel dolomite (basal upper Trinity, Comanchean Cretaceous) in south-central Texas. United States: N. p., 1984. Web.
Amsbury, D L. Relationships of Bexar shale, Hensel sandstone, and Hensel dolomite (basal upper Trinity, Comanchean Cretaceous) in south-central Texas. United States.
Amsbury, D L. 1984. "Relationships of Bexar shale, Hensel sandstone, and Hensel dolomite (basal upper Trinity, Comanchean Cretaceous) in south-central Texas". United States.
@article{osti_6609379,
title = {Relationships of Bexar shale, Hensel sandstone, and Hensel dolomite (basal upper Trinity, Comanchean Cretaceous) in south-central Texas},
author = {Amsbury, D L},
abstractNote = {The Bexar Shale has been considered the offshore equivalent of the Cow Creek Limestone, the overlying Hensel sandstone, or of the disconformity between them in outcropping sections. Cores and outcrops in Comal, Kendall, and northern Bexar Counties preserve calcitic and dolomitic caliche in the top of the Cow Creek Limestone. Above the caliche is 8-16 m(25-50 ft) of laminated or bioturbated, dolomitic siltstone and silty dolomite (Hensel dolomite). Dolomite is euhedral and silt-sized. The lower part contains collophane grains and oyster shells replaced partly by chalcedony. Carbonate grains within the upper part include angular and well-rounded mollusk and echinoid fragments; many are pyritic and coated by glauconite. Terrigenous grains in Hensel dolomite grade upward from silt to coarse subarkose sand from central Texas. In southern Bexar County, about 35 m (115 ft) of silt-, clay-, and calcite-mudstone referable to the Bexar Shale sharply overlie shallow marine Cow Creek Limestone, and grade abruptly upward into about 7 m (23 ft) of Hensel dolomite. Dolomite is overlain by calcarenite of the Glen Rose Formation containing subarkose sand grains. Similar distinctive sand grains occur in well cuttings of basal Glen Rose beds northeastward through Travis County. The Bexar represents a flood of clay-sized sediment from a distant source, spread across the San Marcos arch during a rapid transgression. Slightly younger sand, silt, and local clay of the Hensel sandstone were eroded from central Texas by a few flash floods during a major period of caliche formation in the area.},
doi = {},
url = {https://www.osti.gov/biblio/6609379}, journal = {Am. Assoc. Pet. Geol., Bull.; (United States)},
number = ,
volume = 68:4,
place = {United States},
year = {Sun Apr 01 00:00:00 EST 1984},
month = {Sun Apr 01 00:00:00 EST 1984}
}

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