Coeval ä¹³ C shifts recorded in buried soils at both piedmont slope and basin floor sites in the northern Chihuahuan Desert indicate a major shift from C₄ grasses to C₃ desert-scrub between 7 and 9 ka. The age assignments are based on stratigraphic correlations to charcoal dates and carbon-14 dates of carbonate. This shift is synchronous with a period of cooling in the North Atlantic that may have triggered a period of drought in the southwestern United States. Coinciding with this vegetation change, geomorphic evidence in Rio Grande, piedmont, and basin floor eolian environments indicates a major period of erosion. Subsequent gradual enrichment of pedogenic carbonate ä¹³ C values in younger deposits suggests that C₄ grasses rebounded in the late Holocene (approximately 4 ka), which is consistent with other evidence of increased moisture regionally. A period of less severe aridity at approximately 2.2 ka is indicated by erosion and subsequent deposition along the alluvial fans and within the basin, and correlates with depleted pedogenic carbonate ä¹³ C values suggesting a decrease in C₄ grasses. Isotope and packrat midden records should be used together to infer past environmental conditions at different elevations.