Petrocalcic paleosols, Hensel (Gillespie) Sand, Gillespie County, Texas
Conference
·
· Geological Society of America, Abstracts with Programs; (United States)
OSTI ID:5975805
- 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--
- Conference Information:
- Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 25:1
- Country of Publication:
- United States
- Language:
- English
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