RETURN TO THE SEDIMENTARY RECORD OF ENVIRONMENTAL CHANGE IN THE AMERICAN DESERTS

Desert wetlands represent repositories of proxy data that reveal the complex record of climate and ecology resulting in the formation of the American Deserts. The >50 ka record from the Cuatrocienegas Basin, Coahuila MX suggest that the formation of the modern day Chihuahuan Desert may have resulted more from the loss of montane and eastern deciduous forest taxa during the late-glacial, rather than the migration of desert taxa from unidentified refugia elsewhere. Other desert wetlands reveal complex records of uneven preservation of pollen and macrofossils between wet and dry intervals. Research over the past decade has shown that paleobotanical analyses combined with isotopic and loss-on-ignition data can be used to determine sedimentary characteristics suggestive of changes in regional hydrology and state-changes of wetland surfaces to terrestrial grasslands. In proper settings, desert wetlands contain numerous proxy data of environmental change. In this context, drought intervals have been shown to result in poor preservation of most organic material and increased inorganic carbon content, whereas pluvial periods are identified by the ability to recognize paleobotanical fossil material and lower inorganic content.