We have used 36Cl to date climatically sensitive saline-lake sediments from hydrologically closed basins in southeastern California, primarily sediments from Searles and Panamint basins. During wet periods of the past 2.0 m.y., lakes that formed in the closed basins fluctuated in size in direct response to the balance between runoff and evaporation. We have compiled a chronology for the KM-3 core from Searles Lake, based on ages determined by 36Cl for the evaporites, together with those determined by 14C and U-Th series for younger sediments, and by magnetostratigraphy for older sediments. This chronology, along with other criteria, such as correlations between Searles and Panamint basins, the chloride budget, and sedimentology, is used to reconstruct the history of lake fluctuations in the paleo-Owens River system. We infer that Searles Lake desiccated at most twice since 600 ka: during the interval around 290 ka, and from 10 ka to the present. The lake history curve shows that the Holocene Epoch is anomalously arid. Major overflows from Searles to Panamint occurred during the intervals between 1.3 Ma and 1.0 Ma, 750 ka and 600 ka, 500 ka and 400 ka, and 150 ka and 120 ka.

Comparing the lake-fluctuation chronology to the δ18O record of marine foraminifera, we infer that the strongest similarity is in the periodicities of the cycles-40 to 50 kyr before the Matuyama/Brunhes magnetic reversal (730 ka) and 100 kyr thereafter. We find, however, that at Searles Lake this fluctuation in the lake chronology is modulated by longer-term cycles of aridity and humidity. Thus, although the mid-latitude Quaternary climate record reflects the mid- to high-latitude ice-volume fluctuations that dominate the marine 18O record, it also contains evidence for climatic forcing of a different type.

First Page Preview

First page PDF preview
You do not currently have access to this article.