Geochemical record of Late Quaternary paleoclimate from lacustrine sediments of paleo-lake San Felipe, western Sonora Desert, Mexico

摘要

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) kyr BP is possibly due to the position of westerly storm tracks at 31°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.