Abstract
Stable carbon and oxygen isotopes in soil carbonates provide an additional technique for investigating Quaternary ecogeomorphic changes in arid and semiarid regions. This study presents δ 13C and δ 18O values in surface and buried soils in a Basin and Range region of southern New Mexico and west Texas. Three landform categories were investigated for their isotopic content: (1) middle piedmont slopes; (2) a lower piedmont slope and adjacent playa depressions; and (3) an intermontane basin floor. Soils of the middle piedmont slopes had greatest δ 13C variability, ranging from −0.6‰ in buried soils to −11.1‰ (PDB) in surface soils. Soils of the basin floor had greatest variability in δ 18O values, ranging from −0.6‰ to −7.6‰ (PDB). Fossil pollen patterns roughly paralleled δ 13C shifts, with Cheno-Am pollen exhibiting greatest changes. Both isotope and pollen data across stratigraphic discontinuities suggest that a conversion from C 4 grasses to C 3 desert shrubs accompanied Holocene erosion.
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