Paleodrainage reconstruction using Pb isotopes in K-feldspar sand grains: Examples from the NW European Triassic (original) (raw)

Abstract

The Pb isotopic composition of detrital K-feldspar is a powerful means of constraining sandstone provenance. It has been shown that K-feldspar retains the Pb signature of its source despite erosion, transport and diagenesis. The continental crust exhibits broad (100s km) variations in Pb isotopes and thus potential sourcelands can be characterised on a scale appropriate to that of major drainage systems. Electron microprobe analysis and imaging (BSE and CL) of detrital grains means that heterogeneities (e.g. inclusions, alteration) can be avoided during in-situ LA-MC-ICPMS analysis. Furthermore, as K-feldspar is a common and likely first cycle component of sandstones, the technique provides a means of tracking grains directly back to their source. In this way, the method can constrain palaeodrainage pathways and lengthscales, with consequent application to palaeogeographic reconstuctions.

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