PALEOWIND EVIDENCE FROM LATE PLEISTOCENE LAKE BONNEVILLE, UTAH

Lake Bonneville has been studied intently for well over a century. Two principal motivations for much of this work have been to reconstruct its chronology and to determine what the history of its oscillations reveals about past changes in the regional climate. Most geomorphic, morphostratigraphic, and core stratigraphic research on Lake Bonneville that contributes to paleoclimate knowledge provides information relevant to variations in effective moisture, and occasionally these have been used to hypothesize changes in regional atmospheric circulation. Results of a few investigations are directly applicable to paleotemperature reconstruction. Lake Bonneville research focused specifically on understanding the paleowind regime has virtually not been attempted even though paleowind evidence could also reveal important information about circulation patterns. The work reported on here is an attempt to start to fill this gap by using the distribution and texture of eolian fine-grained sediment deposited on Lake Bonneville landforms of known age to derive information regarding paleowind patterns. Comparative statistical analyses of eolian sediment thickness and texture data collected from a study region occupying approximately 17% of the area of Lake Bonneville reveal that different wind directions dominated in approximately the 14.5 to 14.0 ka interval than shortly after about 14.0 ka. Results indicate that a wind regime with more northerly and easterly components during Provo shoreline time shifted to one with more westerly or southwesterly components after Provo shoreline time. This suggests a displacement of storm tracks over this period from locations south of the study area to more northerly positions. This work demonstrates that the nature and distribution of eolian fine-grained sediment in the Bonneville basin offers a viable means for reconstructing important aspects of the regional Bonneville basin paleoclimate.