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Origin of clay minerals in the Bonarelli Horizon (Umbrian Apennines, central Italy)

Published online by Cambridge University Press:  09 July 2018

M. F. Brigatti  and
L. Poppi
M. F. Brigatti
Affiliation:
Istituto di Mineralogia e Petrografia, Università di Modena, Via S. Eufemia, 19-41100 Modena
L. Poppi
Affiliation:
Dipartimento di Scienze Mineralogiche, Università di Bologna-Piazza di Porta S. Donato, 1-40126 Bologna, Italy
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Abstract

Chemical, thermal, X-ray and statistical analyses were carried out on the clay fraction of the Bonarelli Horizon (Umbrian region, Central Italy) in order to investigate its origin. The vertical lithological sequence (organic carbon, siliceous and clay layers of varying colour and thickness) seems to change regularly, allowing the horizon to be subdivided into five sub-horizons (A to E). Sub-horizon B is clearly distinguishable from the others on the basis of the clay fractions. The presence of organic material and authigenic sulphates, constant chemical composition within a single sub-horizon, and regular repetition of the layers, show that the Bonarelli Horizon is the result of an alternation of anoxic events in a continental margin facies. A substantial contribution of volcanoclastic material is suggested for sub-horizon B.

Type
Research Article
Information
Clay Minerals , Volume 26 , Issue 1 , March 1991 , pp. 127 - 139
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1991

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