Increasing the accuracy of dating and time distribution through late Pleistocene lake sediments by pollen aerosol sequencing

Abstract

Age control in Owens Lake sediments is effectively limited at present to the analytical limit of 14C analyses (<35 ka) and the occurrence of the Bishop Ash (759 ka). A number of recently published attempts to interpolate between these two control points are based on unrealistic geologic models. Radiometric dates are available for the interval between these two age controls, but in the lacustrine sequence preserved in Searles Lake, located downflow in this same hydrologic drainage. However, airborne pollen (pollen aerosol) fallout from the Sierra Nevada provided a characteristic and continuous common detrital signal to both Owens Lake and Searles Lake throughout the late Pleistocene, thereby enabling the fossil pollen record to be used as a means for exporting absolute ages from Searles Lake to Owens Lake. Provisional ages for intermittent depths then were assigned by interpolating linearly between the newly imported control points in Owens Lake. These results, based on a total of more than 350 pollen assemblage analyses and 5 published U-Th dates from Searles Lake, appear to provide a geologically reasonable and accurate age model for Owens Lake sediments through the interval spanning 65-135 ka (which includes all of the Last Interglacial interval).