Diagenesis, porosity and permeability in the Corallian Beds (upper Oxfordian) from the Harwell Research Site, Oxfordshire, UK

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Authors:Milodowski, A. E.; Wilmot, R. D.
Author Affiliations:Primary:
Br. Geol. Surv., Keyworth, United Kingdom
Univ. London, Queen Mary Coll., Dep. Geol. Sci., United Kingdom
Volume Title:Patterns of mineral diagenesis on the NW European continental shelf and their relations to facies and hydrocarbon accumulation
Volume Authors:Morgan, D. J., editor; Rawson, P. F.
Source:Clay Minerals, 19(3), p.323-341; Joint meeting of the Clay Minerals Group of the Mineralogical Society and the Petroleum Exploration Society of Great Britain ; Patterns of mineral diagenesis on the NW European continental shelf and their relations to facies and hydrocarbon accumulation, Cambridge, United Kingdom, April 7-8, 1984, edited by D. J. Morgan and P. F. Rawson. Publisher: Mineralogical Society, London, United Kingdom. ISSN: 0009-8558
Publication Date:1984
Note:In English. 35 refs.; illus. incl. 2 tables, strat. col.
Summary:These Corallian beds are a highly variable sequence of sandstones, mudstones and limestones. The more permeable lithologies of the upper part of the sequence constitute an important local aquifer. Diagenetic and post-lithification processes have strongly influenced the porosity, permeability and mineralogy of the aquifer rocks. Calcite cementation reduced the porosity and permeability of the sandstones and limestones in the upper part of the aquifer. Cementation occurred in at least three stages, ranging from early diagenesis to post-compactional diagenesis. Late-stage dissolution of calcite took place along fractures and bedding discontinuities, restoring the porosity and permeability of these sediments and developing secondary porosity and permeability where original clastic carbonate was removed. Invasion of the Corallian pore-waters by waters charged with CO2 is suggested as the mechanism by which calcite was removed. At the base of the aquifer, early diagenetic dissolution of biogenic silica created a high secondary porosity. Silica was reprecipitated in the dissolution voids and matrix as opal-CT. Authigenic smectite and zeolites are also associated with opal-CT. These phases are believed to have precipitated from pore-waters rich in ions derived from the alteration of volcanogenic detritus associated with the Corallian sediments. [D.J.M.]
Subjects:Aquifers; Carbon dioxide; Carbonate rocks; Cementation; Clastic rocks; Compaction; Diagenesis; Early diagenesis; Effects; Fractures; Ions; Jurassic; Limestone; Matrix; Mesozoic; Mudstone; Oxfordian; Permeability; Physical properties; Pore water; Porosity; Precipitation; Sandstone; Secondary porosity; Sedimentary petrology; Sedimentary rocks; SEM data; Solution; Upper Jurassic; Upper Oxfordian; England; Europe; Great Britain; Oxfordshire England; United Kingdom; Western Europe; Corallian Beds; Harwell Research Site; Southern Oxfordshire
Abstract Numbers:85M/2022
Record ID:1985033735
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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