Petrocalcic paleosols, Hensel (Gillespie) Sand, Gillespie County, Texas
- Raba-Kistner Consultants, Inc., San Antonio, TX (United States)
- Univ. of Texas, San Antonio, TX (United States). Geology Dept.
Paleocalcretes are common in all sediment types of the Hensel Sand in Gillespie County, Texas. Calcretes in mudstone are nodular, grading from rhizoconcretions to total replacement. In sandstone the paleosols tend to form undulating hardpans having cracked upper surfaces. Massive calcretes in basal conglomerates have greatly reduced the original permeability, restricting groundwater flow. Hensel Sand overlies upper Precambrian to Middle Pennsylvanian rocks; displacive crystallization of the calcitic globules and fibers was able to lift and displace 1m2 to 2m2 blocks of flaggy Upper Cambrian limestone in to spectacular teepee structures. Gillespie Sand is that portion of the basal Cretaceous Hensel Sand that stratigraphically overlies the middle Glen Rose Salenia/Corbula beds', and underlies upper Glen Rose or basal Fredericksburg rocks. It formed as non-marine valley fill during prolonged, episodic marine transgression. This study documents ubiquitous calcrete development in Central Texas during the lower part of the Middle Albian State; calcretes are now known from the Lower Aptian (Sycamore Sand) through the Middle Albian (Paluxy and upper Antlers Sands). A seasonal arid to semi-arid climate is indicated for at least 5 million years.
- OSTI ID:
- 5975805
- Report Number(s):
- CONF-9303212-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 25:1; Conference: 27. annual Geological Society of America (GSA) South-Central Section meeting, Fort Worth, TX (United States), 15-16 Mar 1993; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
Similar Records
Relationships of Bexar shale, Hensel sandstone, and Hensel dolomite (basal upper Trinity, Comanchean Cretaceous) in south-central Texas
Stored groundwater--A force to reckon with in the geomorphology of central and north Texas