HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Full Text (PDF) Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Huggett, J.M. Articles by Wray, D.S. Search for Related Content GeoRef GeoRef Citation

Diagenetic Clinoptilolite and Opal-CT from the Middle Eocene Wittering Formation, Isle of Wight, U.K.

¹ Department of Mineralogy, Natural History Museum, Cromwell Road, London, SW7 5BD, U.K.; JMHuggett{at}petroclays.demon.co.uk
² Department of Earth and Environmental Sciences, University of Greenwich, Pembroke, Chatham Maritime, Kent, ME4 4TB, U.K.; Department of Palaeontology, Natural History Museum, Cromwell Road, London, SW7 5BD, U.K.
³ Department of Earth and Environmental Sciences, University of Greenwich, Pembroke, Chatham Maritime, Kent, ME4 4TB, U.K.

Thinly interbedded estuarine sandstones and mudstones in the middle Eocene Wittering Formation (Bracklesham Group), Isle of Wight, contain authigenic clinoptilolite, opal-CT, and possibly authigenic smectite over a thickness of 8.5 m. The clinoptilolite and opal-CT cements have resulted in these beds being the only ones tightly cemented in the Wittering Formation, the rest being soft sands and muds. The unit contains abundant siliceous sponge spicules, many of which are preserved as voids and were the likely source of the opal-CT. The presence of an organic-rich, rooted paleosol (histosol) immediately overlying the unit is believed to have contributed significantly to the early diagenetic history of the estuarine sediments, in particular the formation of zeolite. Although the pH and dissolved silica of unmodified seawater are too low for zeolite formation, high concentrations of dissolved silica are believed to have resulted from dissolution of siliceous sponge spicules (opal-A) and formation of silica-organic acid complexes. Organic-acid dissolution of feldspars (absent from the zeolite-bearing interval) is the most probable source of alumina and cations for zeolite formation. REE data show that volcanic ash was never present and cannot therefore have been the source of the zeolite. This investigation therefore demonstrates a novel route by which the pore-fluid chemistry required for zeolite formation can be achieved.

This article has been cited by other articles:

				C.M. Reid, N.P. James, T.K. Kyser, N. Barrett, and A.J. Hirst Modern estuarine siliceous spiculites, Tasmania, Australia: A non-polar link to Phanerozoic spiculitic cherts Geology, February 1, 2008; 36(2): 107 - 110. [Abstract] [Full Text] [PDF]

				J. M. HUGGETT and R. W. OB. KNOX Clay mineralogy of the Tertiary onshore and offshore strata of the British Isles Clay Minerals, March 1, 2006; 41(1): 5 - 46. [Abstract] [Full Text] [PDF]