Stream sediment geochemistry as a tool for enhancing geological understanding: An overview of new data from south west England

Antonio Ferreira,Charlie Kirkwood,Bob Lister,Paul Everett

doi:10.1016/j.gexplo.2016.01.010

Antonio Ferreira, Charlie Kirkwood + Show 2 more

Open Access

https://doi.org/10.1016/j.gexplo.2016.01.010

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Abstract

The requirements for quantitative data in geological surveillance are ever increasing; traditional geological maps and 3D models are evolving into quantitative conceptual models based on a broad range of analytical measurements of surface and subsurface properties. The British Geological Survey's Geochemical Baseline Survey of the Environment (G-BASE) project provides one such source of data: national coverage of stream sediment, stream water and soil geochemistry. While this geochemical data is of obvious benefit to our understanding of the present day surface environment, the rich geological diversity of south west England provides an ideal setting in which to showcase the potential of such data to enhance our understanding of the underlying bedrock.In this paper we use compositional data analysis to extract lithostratigraphic information from G-BASE stream sediment data. We find that variations in G-BASE stream sediment geochemistry correspond very closely to mapped variations in bedrock geology. Geochemical variations between the 16 lithostratigraphic domains into which we classify the region provide insight into the distinct geological histories of the lithologies within each domain, particularly in relation to depositional environments and sediment provenance.

Highlights

As the British Geological Survey's work moves into the 21st century the requirements for quantitative data are ever increasing
The domain-weighted compositional principal component analysis successfully reduces the dimensionality of the data to allow holistic visualisation of the geochemical of the geological domains of south west England
Closing the exponential transformation of the first three principal components and displaying them on a ternary plot allows the geochemical contrasts between domains to be seen, and the inclusion of rays to indicate the orientations of the original element axes in the principal component space provides a convenient visualisation of the loadings on each element (Fig. 3)

Summary

Introduction

As the British Geological Survey's work moves into the 21st century the requirements for quantitative data are ever increasing. The Geochemical Baseline Survey of the Environment (G-BASE) project provides one such line of data: national coverage of stream sediment, stream water and soil geochemistry. The most recent regional dataset to become available is that of south west England. This is a geologically diverse region consisting of a spectrum of geological formations which preserve various stages of the region's Paleozoic tectonic cycle from passive margin to collisional orogenesis and subsequent erosion (Shail and Leveridge, 2009). While surface geochemical data is of obvious benefit to our understanding of the present day surface environment, south west England, with its rich geological history, provides an ideal setting in which to assess the potential of such quantitative datasets to enhance our understanding of the underlying bedrock

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