Hinterland environments of the Late Jurassic northern Weald Basin, England

Abstract

Reconstructing provenance in sandstones can be challenging, especially when the hinterland palaeogeology is unknown due to burial, diagenesis or weathering of the original outcrops. As sedimentary processes alter the distribution of minerals in the depositional environment, the use of multiple provenance methods reduces uncertainties, because, together, they can account for depositionally‐controlled textural and mineralogical re‐distribution in a basin. Here, we have applied petrography, X‐ray fluorescence geochemistry and sedimentology to understand the provenance of shallow marine Corallian sandstones with the aim of deducing the palaeogeology, palaeoenvironment and sediment distribution within the northern parts of the Upper Jurassic Weald Basin, onshore UK. The Corallian sandstones had a mixed mafic‐felsic (intermediate), metasedimentary recycled orogen source. The hinterland experienced significant physical and chemical weathering under humid conditions. Corallian sandstones were relatively more chemically mature up‐dip and more texturally mature down‐dip. Chemically unstable grains and heavy minerals were relatively concentrated down‐dip. Heterogeneous, sedimentologically‐controlled mineral distribution patterns highlight potential errors which may be made in deriving source‐area maturity. This study is significant as it illustrates the combined roles of provenance and deposition in controlling primary mineral distribution that then influenced the style of burial diagenesis. The work presented here emphasizes the importance of a multi‐proxy approach to improve provenance analysis.