http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Soil characteristics and genesis of carbonates in the Rolling Plains of Texas
The Rolling Plains covers about 10 million hectares in the northwestern portion of Texas. Soils within the region have ustic soil moisture regimes and thermic temperature regimes. A total of 13 pedons were studied; nine were satellite pedons, and four from a hillslope site near Haskell, Texas representing stable and erosional landforms. Stable landscape positions have argillic horizons, completely to partially leached of carbonates, while less stable erosional sites have cambic horizons and carbonates to the surface. Detailed analyses herein are from Argiustolls, Paleustolls and Ustochrepts of the hillslope sequence. Objectives of this work were to differentiate pedogenic from lithogenic carbonate forms, their distribution, and probable source of carbonate minerals relative to the soils and underlying stratigraphic units. The red loam to clay loam soils are vertically stratified and overlie gray sandstone and red bed shales respectively. These three major stratigraphic units were identified by particle-size distribution, elemental assay and micromorphic analyses. Quartz overgrowths, identified by SEM, occurred throughout the upper two stratigraphic units, but authigenic kaolinite was observed only in the sandstone unit. These two features are considered to be early post-depositional diagenic products Macromorphic forms of pedogenic carbonates are filaments, threads, and concretions; corresponding micromorphic forms are calcans, neocalcans, crystallaria and nodules. These features are good field and micromorphic evidence of contemporaneous pedogenesis involving calcite dissolution and reprecipitation. Pedogenic carbonates are calcite and occur primarily in the solum while euhedral dolomite is a lithogenic post-depositional product occurring in sandstone Cr horizons. Pedogenic calcite was precipitated 10,000 to 20,000 years B.P. as confirmed by radiocarbon dating. Dolomite is too old to date by radiocarbon methods. Stable carbon isotopic ratios for calcite (-0.9 [ppt]), dolomite (-4.9[ppt]) and organic matter (-14 to -19[ppt]) suggest that pedogenic calcite formed under an environment that had minimal exchange with biogenically derived CO2, and that dolomite was not a precursor carbonate for pedogenic calcite...
Includes bibliographical references (leaves 172-188).