Geochemical Aspects of the Santonian Chalk of Ramsgate, England, and the Origin of the Chert and Clay Minerals

D. A. Spears
Department of Geology, University of Sheffield, Sheffield S1 3JD

Summary: The mineralogy and major-element geochemistry of thirty-seven samples from a borehole in the Upper Cretaceous Chalk (Santonian) of Kent has been determined. The mean carbonate content is 97% and the carbonate is a low-Mg calcite (0.42 mol % MgCO3). Most of the silica is deduced to be biogenic chert. The total clay content probably varies through the sequence due to changes in the rate of carbonate sedimentation. The clay composition remains relatively constant with smectite more abundant than illite. The smectite and K-feldspar could be formed from volcanic debris whereas illite and quartz are thought to be detrital.

Mineralogical Magazine; March 1979 v. 43; no. 325; p. 159-164; DOI: 10.1180/minmag.1979.043.325.17
© 1979, The Mineralogical Society
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