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The petrology of the calcrete and Calciferous Sandstone Measures of Arran and adjacent areas

Khalil Mohammed, Mosaad Mohammed; (1990) The petrology of the calcrete and Calciferous Sandstone Measures of Arran and adjacent areas. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

The Calciferous Sandstone Measures, but more especially the associated calcretes of Arran and adjacent outcrops in the Firth of Clyde have been examined in detail using petrographic, stereoscopic, cathodoluminescence, X-ray diffraction, heavy mineral analysis, and induction coupled plasma optical emission spectroscopic techniques. The calcretes (palaeosols) within the Kinnesswood Formation and Laggantuin Cornstone Member formed on overbank clays in a climatic regime subject to strong seasonal moisture contrasts. They show stages 3 and 4 maturity (of Steel) and composed of in situ low Mg-calcite precipitated as glaebules and crystallaria within glaebules, vein networks and laminae. Pseudo-anticlines are common. Extensive argillobedoturbation is recognized. Throughout the Firth of Clyde outcrops five distinctive cement zones are recognized in the calcretes, zone 1 and 3 reflecting precipitation in freshwater phreatic lenses, zone 2 in more reducing freshwater environment and zone 4 in more stagnant freshwater environment. Zone 5 is the youngest cement, Fe2+ free and Mn2+poor, and of minor importance. Eh appears to have been more important than pH during the precipitation of the calcrete cements, this inference being based on the variations of Fe2+, Mn2+ and Mg2+ in the zoned crystals. The sandstones of the Kinnesswood Formation and the other Inverclyde and Strathclyde Group formations are predominantly sublitharenites and subarkoses. Their composition, in terms of light and heavy minerals, lithic fragments, clay minerals and percent brown CL quartz, suggests a common provenance formed mainly of sedimentary rocks and low-grade metamorphic rocks. A Dalradian supergroup provenance is unlikely but the Torridonian sandstone outcrops to the NW were probably a major source.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: The petrology of the calcrete and Calciferous Sandstone Measures of Arran and adjacent areas
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Earth sciences; Sandstones
URI: https://discovery.ucl.ac.uk/id/eprint/10112489
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