Reconstructing past climatic changes from lacustrine deposits II
Together with our partners in Argentina we plan to regionally extend our investigations and establish a transect from the moist area around Jujuy (ongoing project on Yala lakes) into the dry Puna Plateau which is characterized by internally drained basins with ephemeral playa lakes or salar sytems. Presently, there are only very few low-resolution studies in this region of the Central Andes, e.g. from the Salar de Atacama (Bobst et al. 2001; Lowenstein et al. 2003) and Laguna Pozuelos (McGlue et al. 2013). These studies suggest that, in contrast to the extreme dry present day conditions, climate has been wet during several periods of the last glaciation but also during the early and mid Holocene. Some of these wet periods coincide with maxima in January insolation at 15°S, but others do not. On the other hand, the recent extreme dry climate also coincides with an insolation maximum, indicating that the mechanisms causing wet periods are still not fully understood. We propose to study a sediment core from a playa lake to investigate for the first time such environment with high-resolution methods. Proposed sites are the Centenario and Ratones playa lakes, where also the 'Eramine' company is currently working. In case we get access of long cores from Eramine we will study glacial and interglacial wet periods. If this will not be possible, we will use the new drilling system from our partner at University of Jujuy to take up to 10 m long cores that will allow us to study Holocene wet periods in detail. This project could establish a link to a resources project.
Reconstructing past climatic changes from lacustrine deposits I
Paleoclimate analyses of lacustrine sediments has provided essential insights into decadal to millennial-scale climate variability and its driving mechanisms. Lake basins are ideal sediment traps that continuously record environmental and climatic evolution. New analytical approaches now even allow for deciphering the timing and dynamics of abrupt climate changes and extreme hydrometeorological events causing short-term catchment runoff at seasonal resolution. The project aims at investigating sediment records of presently saline lakes in the Altiplano-Puna plateau. The Puna region is promising for reconstructing past variations in moisture availability at regional scales because of the very strong gradient in precipitation over short distances. This project, will apply identical analytical procedures to two lake sites in locations with significant differences in present-day precipitation. The main scientific goals and questions to be addressed include (1) testing previous ideas of wetter conditions during times of insolation maxima in January driven by variations in the Earth’s orbital parameters; (2) investigating both wetter and drier millennialscale intervals with respect to centennial and decadal-scale oscillations in moisture availability; (3) testing if the Younger Dryas cold period is reflected by wet or dry conditions in NW Argentina; and (4) testing the hypothesis that changes in climatic boundary conditions can cause changing frequencies of extreme meteorological events. To achieve these goals, we will first conduct a thorough site survey of several lake basins for coring in the Salta region. Main criteria for site selection are differences in precipitation regimes, basin morphology and type of sediment infill. Coring two lake basins is planed to be conducted in fall 2016 using the GFZ Niederreither system. Sediment analyses include sedimentological and micro-facies analyses on thin sections, high resolution (200 micron) micro-XRF scanning, organic and inorganic carbon determination, AMS-C14 dating, mineralogical analyses, and stable oxygen and carbon isotope analysis on carbonates.