Geochemical constraints on the origin of enigmatic cemented chalks, Norfolk, UK

Woolhouse, G, Andrews, JE, Marca-Bell, A and Dennis, PF ORCID: (2009) Geochemical constraints on the origin of enigmatic cemented chalks, Norfolk, UK. Geological Magazine, 146 (2). pp. 291-299. ISSN 1469-5081

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Very hard cemented chalk stacks and crusts found locally in the upper part of the Cretaceous Chalk of north Norfolk, UK, are related to solution features. The solution features, mainly pipes and caves, formed after deposition of the overlying Middle Pleistocene Wroxham Crag, probably by routing of sub-glacial, or glacial, melt-waters derived from late Pleistocene glaciers. New geochemical (particularly stable isotope) data shows that cementation of the chalks, although related spatially to the solution features, was not caused by glacier-derived waters. The carbon isotope composition of the chalk cements is typically around -9.5‰, indicative of biologically active soils. Moreover, the oxygen isotope compositions of the cements, around -5‰, are incompatible with water d18O values much below -9 to -10‰ (which probably precludes isotopically negative glacier-derived water), as resulting palaeo-temperatures are below zero. Taken together, the isotope data suggest chalk cementation occurred under interglacial conditions similar to the present. Dissolved calcium carbonate for cementation came from dissolution of reworked chalk in overlying MIS 12 glacial tills.

Item Type: Article
Faculty \ School: Faculty of Science > School of Environmental Sciences
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Depositing User: Rosie Cullington
Date Deposited: 23 Feb 2011 12:16
Last Modified: 24 Oct 2022 00:34
DOI: 10.1017/S0016756808005487

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