Uranium-Series Dating of Sediments from Searles Lake: Differences Between Continental and Marine Climate Records

Abstract

One of the major unresolved questions in Pleistocene paleoclimatology has been whether continental climatic transitions are consistent with the glacial δ¹⁸O marine record. Searles Lake in California, now a dry salt pan, is underlain by sediment layers deposited in a succession of lakes whose levels and salinities have fluctuated in response to changes in climate over the last 3 x 10⁶ years. Uraniumseries dates on the salt beds range from 35 x 10³ to 231x 10³ years. This range of dates allows identification of lake-sediment horizons that are time correlatives of the boundaries of marine isotope stages from the recent 3/4 boundary back to the 8/9 boundary. The 5/6 boundary coincided with a deepening of the lake, but the analogous 1/2 boundary coincided with desiccation. The 3/4, 4/5, 6/7, 7/8, and 8/9 boundaries correspond in age to horizons that record little or no change in sedimentation or climate. These hydrologic results demonstrate that the continental paleoclimate record at this mid-latitude site does not mimic the marine record.