Paleoecology of a ciénega at the Mockingbird Gap Site, Chupadera Draw, New Mexico

The Mockingbird Gap Clovis site is a surface archaeological site located along Chupadera Draw in central New Mexico. Coring of the draw during archaeological investigation of the Clovis assemblage on the adjacent uplands revealed evidence for a regionally rare continuous, stratified depositional record beginning immediately before the Younger Dryas chronozone (YDC). Thirty sediment samples from the draw adjacent to the archaeological site were analyzed for microinvertebrates (ostracodes and mollusks) and gyrogonites (calcareous algae) to reconstruct its environmental history. Wet-dry cycles marked the presence/absence of microfossils. Based upon microfossils, this investigation highlights environmental change marked by the evolution from wetter/cooler to warmer/drier conditions at the Mockingbird Gap site and its response to climate change and groundwater fluctuations during and after the YDC. Four biofacies are recognized: the pre-Ciénega setting is sterile. Holarctic species near the base of core 08-1 indicate cooling conditions prior to 13,000 cal yr BP during the early Ciénega phase. Warmer, more saline conditions characterize the late-Ciénega biofacies between 11,000 and 10,000 cal yr BP. Presence of gypsum during formation of the post-Ciénega phase and the most salinity tolerant species after 10,000 cal yr BP is consistent with the aridification typifying the early Holocene.