Pedogenesis of some Pennsylvanian underclays: groundwater, topographic, and tectonic controls

Conference · Tue Jan 01 04:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6596841

Gardner, T W; Williams, E G

Clay mineral analyses of several underclays from the Breathitt Formation (eastern Kentucky) and the Allegheny Group (western Pennsylvania) demonstrate systematic lateral and vertical variations which include changes in the kaolinite-illite ratio, mica loss ratio, weathering ratio, apparent mica thickness, as well as type and distribution of chlorite and illite polymorphs. Clay mineral analyses of overlying, unweathered shales indicate that approximately 30% of the regional variation in underclay mineralogy is inherited from the parent material. The remaining variation is due to in situ pedogenesis. Petrographic analysis of 43 thin sections from a fluvial sandstone subjacent to one of the underclays demonstrate ground water control of pedogenesis. Two distinct alteration zones separated by a diffuse, subhorizontal boundary are present in the sandstone; an upper zone characterized by kaolinization of feldspars, dissolution of chlorite and detrital dolomite, and absence of siderite and a lower zone characterized by ferroan dolomite replacement of both detrital feldspar and detrital dolomite, and authigenic pore fillings of chlorite and siderite. These systematic changes in sandstone and underclay mineralogy are consistent with a pedogenic model in which the process of podzolization is controlled by position of the groundwater table and topography. In this model peat deposition occurs above the underclay after water table levels intersect the land surface as a result of compaction, subsidence, or marine transgression.

• Research Organization: Pennsylvania State Univ., University Park (USA)
• OSTI ID: 6596841
• Report Number(s): CONF-8510489-
• Conference Information: Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Journal Volume: 17
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580300* -- Mineralogy
Petrology
& Rock Mechanics-- (-1989)
CHEMISTRY
CLAYS
DIAGENESIS
DISSOLUTION
FEDERAL REGION III
FEDERAL REGION IV
FELDSPARS
GEOCHEMISTRY
GEOLOGIC FORMATIONS
GROUND WATER
HYDROGEN COMPOUNDS
KENTUCKY
MICA
MINERALOGY
MINERALS
NORTH AMERICA
ORIGIN
OXYGEN COMPOUNDS
PENNSYLVANIA
PETROGENESIS
PETROGRAPHY
SOILS
TECTONICS
TOPOGRAPHY
USA
VARIATIONS
WATER
WEATHERING