CORE STL14: RECORDING PALEOCLIMATES SINCE THE EARLY PLEISTOCENE IN SOUTHWESTERN NORTH AMERICA

Long, continuous records of terrestrial paleoclimate offer insights into past natural climate variability and give context for future climate change predictions. STL14, an 80m composite core from the hydrologically closed Stoneman Lake, Arizona, contains a continuous record of lacustrine sedimentation since the Early Pleistocene (~1.5 Ma). Full-core sedimentology was analyzed using smear slides and core face observations. Lithofacies appear to be strongly linked to geophysical measures of wet bulk density and bulk magnetic susceptibility (MS), and these data exhibit a sawtooth pattern characteristic of glacial-interglacial climate cycles. Glacial episodes are associated with deep lake facies defined by well-preserved bedding, increased biosilica, boreal pollen taxa (e.g. Picea), and lower density and MS. Interglacial periods are associated with shallow water facies characterized by banded-to-massive siliciclastics, some authigenic calcite, the algae Phacotus, and higher density and MS. Linking glacial terminations with deep-to-shallow facies transitions is supported by preliminary age modeling that incorporates AMS radiocarbon dates, tephrochronology, and magnetostratigraphy. Water depth at Stoneman Lake appears to be largely influenced by the size of the Laurentide Ice Sheet and its effect on moisture transport to the southwest. MIS 8, 14, and 18 glacials are weakly expressed by sedimentary facies, perhaps indicating milder glacial conditions. Fewer instances of deep lake facies prior to MIS 20 (~800 ka) suggests consistently weaker glacial conditions prior to the mid-Pleistocene Transition. Few paleoclimate records from the American Southwest extend beyond the last glacial cycle, making STL14 a valuable resource for studying natural climate and ecologic variability through most of the Quaternary.