Stable carbon isotopes, C3-C4 vegetation, and 12,800 years of climate change in central New Mexico, USA

A thick sequence of fine-textured alluvium in central New Mexico has provided an opportunity to reconstruct vegetation type and climate at the western edge of the Great Plains grassland. The analysis of thirty-eight AMS radiocarbon ages, delta C-13 values, and modem weather data has produced a 12,800 cal yr record of changing C-3-C-4 vegetation, temperature, and precipitation. The record begins with the Younger Dryas that was characterized by C-3 plants and was about 2.4 degrees C cooler with over 100 mm rainfall than today. After 11,000 cal yrs BP, the climate became less cool and less wet, reaching present-day conditions by 9000 yrs. The middle Holocene was C-4, warm, and dry although the delta C-13 record is incomplete for this interval. From 3300 to 1400 cal yrs BP, the climate was cool and wet with C-3 plants, averaging 0.5 therefore C cooler and 22 mm greater rainfall than today, matching other records in the region for a wetter climate. After 1400 cal yrs BP, the local climate became warm and dry, shifting to C-4 vegetation. The severe second century drought, first observed in tree-rings in southern Colorado, is supported by the delta C-13 data and occurred during the interval AD. 40 to A.D. 180. Hiatuses in the local alluvial and delta C-13 record extend from 9000 to 6000 cal yrs BP and from 1000 cal yrs BP to present. (C) 2012 Elsevier B.V. All rights reserved.