Chemical composition of loess from a local and worldwide view.

B. Schnetger: Institut für Mineralogie der Philipps Universität Marburg.

Abstract: Fifteen samples of primary Jungwürm-loesses from southern Lower Saxony and northern Hessia (FRG) were analyzed for major and trace elements and modal mineralogy (3 samples). The carbonate fraction was analyzed for Sr and stable isotopes (carbon and oxygen). Most of the elements are close to estimates of the composition of the upper continental crust (on a carbonate-free basis and Al-normalized). Usually in loesses those elements are concentrated, which are associated with mechanically and chemically weather-resistant minerals. The investigated loesses are specifically enriched in these elements when compared with an average loess from wordwide sampling. Their composition is strongly influenced by the source rock geochemistry. Three rock components could be identified in agreement with the surrounding geology:
1) a high content of heavy minerals derived from reworked sediments (Buntsandstein and clastic rocks of the Rhenohercynian Belt),
2) a basaltic component from basalts of the Hessian Depression and/or an ultramafic component which was recognized in the clastic rocks of the Rhenohercynian Belt and
3) carbonates from limestones of neary outcrops.
The carbonate fraction most probably consists of diagentically altered marine limestones derived from Mesozoic sediments of this area. Specific climatic conditions, prevailing during the ice age led to enhanced erosion and accumulation of dolomitic limestone.

This paper has been published in: Neues Jahrbuch Mineralogische Abhandlungen, Monatshefte: H, 1, 29-47 (1992)

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