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 d¹³C and d¹⁸O 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 d¹³C variability, ranging from -0.6‰ in buried soils to -11.1‰ (PDB) in surface soils. Soils of the basin floor had greatest variability in d¹⁸O values, ranging from -0.6 ‰ to -7.6‰ (PDB). Fossil pollen patterns roughly paralled d¹³C shifts, with Cheno-Am pollen exhibiting greatest changes. Both isotope and pollen data across stratigraphic discontinuities suggest that a conversion from C₄ grasses to C₃ desert shrubs accomopanied Holocene erosion. © 1998 Elsevier Science B.V.