Chemostratigraphy and provenance of clays and other non-carbonate minerals in chalks of Campanian age (Upper Cretaceous) from Sussex, southern England

D. S. Wray,C. V. Jeans

doi:10.1180/claymin.2014.049.2.10

Abstract

AbstractGeochemical analysis of acid-insoluble residues derived from white chalks and marl seams of Campanian age from Sussex, UK, has been undertaken. All display a broadly similar <2 μm mineralogical composition consisting of smectite or smectite-rich illite-smectite with subordinate illite and minor amounts of talc. Plots of K2O/Al2O3 and TiO2/Al2O3 indicate that most marl seams have an acid-insoluble residue composition which is slightly different to that of the over- and underlying white chalk, implying that marl seams are primary sedimentary features not formed through white chalk dissolution. On the basis of a negative Eu anomaly and trace element geochemistry one marl seam, the Old Nore Marl, is considered to be volcanically derived and best classified as a bentonite; it is considered to correlate with the bentonite M1 of the north German succession.

Highlights

AB ST R ACT : Geochemical analysis of acid-insoluble residues derived from white chalks and marl seams of Campanian age from Sussex, UK, has been undertaken
The aim of this paper is to investigate the geochemistry of the non-carbonate fraction of marly and white chalks as found at Peacehaven Steps on the Sussex coast
Visual analysis of peak shape and height indicate that the relative abundance of illite and smectite remain broadly constant throughout the section with the exception of the Old Nore Marl where the illite peak is notably smaller

Summary

Introduction

AB ST R ACT : Geochemical analysis of acid-insoluble residues derived from white chalks and marl seams of Campanian age from Sussex, UK, has been undertaken. In the white chalk succession of the Anglo-Paris Basin and eastern England marl seams are most abundant in beds of Turonian and early Coniacian age and here they have been extensively studied (Pacey, 1984; Deconinck & Chamley, 1995; Wray & Wood, 1998; Wray, 1999). Previous work has demonstrated that TuronianÀearly Coniacian marl seams have either a detrital origin, or are bentonites derived from the alteration of distal volcanic ash (Wray, 1999). Whilst it is possible to correlate detrital marl seams within a region, it has not been possible to confidently correlate them between regions

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