A high resolution multiproxy study (magnetic susceptibility, X-ray diffraction, XRF scanner, gray-colour values, Total Organic Carbon, Total Inorganic Carbon, Total Carbon and Total Biogenic Silica) of the sedimentary infill of Lago Chungará (northern Chilean Altiplano) was undertaken to unravel the environmental forcings controlling its evolution using a number of different multivariate statistical techniques. Redundancy analyses enabled us to identify the main provenance of the studied proxies whereas stratigraphically unconstrained cluster analyses allowed us to distinguish the "outsiders" as result of anomalous XRF scanner acquisitions. Principal Component Analysis (PCA) was employed to identify and isolate the main underlying environmental gradients that characterize the sedimentary infill of Lago Chungará. The first eigenvector of the PCA could be interpreted as an indicator of changes in the input of volcaniclastic material, whereas the second one would indicate changes in water availability. The chronological model of this sedimentary sequence was constructed using 17 AMS 14C and 1 238U/230Th dates in order to characterize the volcaniclastic input and the changes in water availability in the last 12,300 cal years BP. Comparison of the reconstructed volcaniclastic input of Lago Chungará with the dust particle record from the Nevado Sajama ice core suggested that the Parinacota volcano eruptions were the main source of dust during the mid and Late Holocene rather than the dry out lakes as has previously been pointed out. The comparison of the water availability reconstruction of Lago Chungará with three of the most detailed paleoenvironmental records of the region (Paco Cocha, Lake Titicaca and Salar Uyuni) showed an heterogeneous (and sometimes contradictory) temporal and spatial pattern distribution of moisture. Although the four reconstructions showed a good correlation, each lacustrine ecosystem responded differently to the moisture oscillations that affected this region. The variations in the paleoenvironmental records could be attributed to the dating uncertainities, lake size, lake morphology, catchment size and lacustrine ecosystem responses to the abrupt arid events.
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Acknowledgements We are indebted to D. Schnurremberger, M. Shapley and A. Myrbo of the Limnological Research Center staff for their field assistance during the coring campaign. Larry Edwards (University of Minnesota) and Rogert O. Gibert (University of Barcelona) are thanked for the 238U/230Th TIMS dates. This research work was funded by the projects BTE2001-3225, BTE2001-5257-E and GCL2004-00683 from the Spanish Science and Technology Ministry. We are indebted to Tomasz Golsar (Poznan Radiocarbon Laboratory) for helping with the calculation of the present-day reservoir effect of Lago Chungará and to George von Knorring and an anonymous referee for improving the final version of the paper.
Copyright 2008 Elsevier B.V., All rights reserved.
- Chilean Altiplano
- Lago Chungará
- Principal Component Analysis
- Redundancy Analysis
- Statistical analyses
- Stratigraphically unconstrained cluster analysis
- Water availability reconstruction