Early diagenesis of the lower Vectis Formation,Wealden Group Lower Cretaceous,Barremian), Sandown,Isle of Wight |
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| Authors: | JM Huggett AS Gale C Hazell |
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| Institution: | 1. Petroclays Ltd., The Oast, Sandy Cross, Heathfield, E Sussex, TN21 8QP, UK;2. School of Earth & Environmental Sciences, University of Portsmouth, Burnaby Rd., Portsmouth, Hampshire, PO1 3QL, UK;3. Northumbria University, Sutherland Building, Newcastle-upon-Tyne, NE1 8ST, UK |
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| Abstract: | The Vectis Formation was deposited in a restricted lagoonal environment that periodically dried up, as indicated by the presence of desiccation surfaces. The fauna indicates that salinities fluctuated significantly during deposition, from fresh to brackish-marine. Pre-burial berthierine-rich clay replaced faecal pellets in the sediment, infilling desiccation cracks, during re-flooding of the lagoon. Concretions formed by early pyrite and apatite cementation during initial burial in lake sediment, with organic debris of fish and wood, acting as nuclei and a trigger for cementation. With subsequent partial or complete exhumation oxidation of the pyrite occurred, prior to cementation by Mn siderite. All further concretion cementation occurred within the oxic to sub-oxic diagenetic zones. Textural relationships indicate that commonly occurring baryte formedafter pyrite oxidation and represents the last diagenetic mineral phase. |
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| Keywords: | Vectis Lepidotes Apatite nodule Lagoon Barite Berthierine |
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