干旱区生态环境知识资源中心

Stratigraphy, mineralogy, major and trace elements, organic carbon, carbonate, sulfate and AMS (14)C dates are used to infer Late Quaternary depositional environments and paleo-hydrological conditions in the paleo-lake San Felipe located in the western part of Sonora Desert. Sediment stratigraphy divides the depth profile into aeolian and pluvio-lacustrine regimes. Aeolian regime is constrained to >44.5 (14)C kyr BP. The pluvio-lacustrine regime consists of two stratigraphic units with characteristic geochemical proxies indicating changing chemical weathering, clastic input, salinity and provenance and provides a measure of varying climatic conditions between ca. 37 and 3 (14)C kyr BP. Lower catchment erosion and inflow into the basin, higher lake productivity, precipitation of Na-sulfate mineral and higher clastic input from the proximal aeolian deposits during ca. 37-14 (14)C kyr BP are comparable to the regional registers of dominant winter rainfall related to westerly storm tracks and colder conditions. In the last 12 (14)C kyr BP, higher sedimentation and inflow and lower productivity are comparable to dominant summer rainfall. Higher humidity and lake productivity during ca. 37-29 (14)C kyr BP is possibly due to the position of westerly storm tracks at 31 degrees N and the gradually reducing humidity till ca. 14 (14)C kyr BP is related to northerly migration of westerly storm tracks. Regional arid conditions during ca. 11 (14)C kyr BP and ca. 6 (14)C kyr BP are characterized by influx of coarser quartz and feldspars into the basin. (C) 2009 Elsevier Ltd. All rights reserved.