Checklist for the use of potassium concentrations in siliciclastic sediments as paleoenvironmental archives
Résumé
Weathering indices quantify the release of mobile elements from source units of soils and sediments. They have been employed in geosciences for more than three decades, but their performance in sedimentary archives can still be improved by deciphering other forcing factors than climatic. From the most common alkali and alkaline earth metals included in the weathering indices, K seems to be most suitable for deciphering paleoclimate records of temperate to subtropical non-arid climates, assuming the interpretation respects the complex of controlling factors on sediment geochemistry. As a case study, normalised K concentrations in siliciclastic sediments of the Most Basin (Miocene period, central Europe) are revisited here and variations compared with modern fluvially transported solids. Existing knowledge on manifold controls of K concentrations in sediments is summarised and used to propose list of possible controlling factors, in particular Al/Si and Zr/Rb as grain-size proxies, Ti/Al as provenance proxy relevant for K concentration in parent rocks, and K/Rb as a measure for possible effects of metasomatism. The K/Al or K/Ti element ratios may be efficient in chemostratigraphic correlations in siliciclastic basins and efficient proxies for chemical weathering in the source area. The proposals in this work should stimulate future studies to overcome the underrepresentation of continental sediments in paleoclimate reconstructions.
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