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Title: The sedimentology of the Dibunophyllum Zone in South Wales
Author: Thorne, Alan Martyn
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1978
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This study has involved an investigation of the Dibunophyllum Zone (Upper Avonian) limestones of South Wales. The aims of this work have been to erect a system of lithostratigraphy and to analyse environments of deposition and diagenesis. To achieve these objectives, detailed field logging has been supplemented by petrographic work on thin sections and pools and, where necessary, certain geochemical examinations. This investigation has shown that sedimentation in South Wales during Dibunophyllum Zone times was controlled by the presence of a high energy shoreline in the vicinity of the North Crop and an area of quiet water, offshore sedimentation in Gower and the Vale of Glamorgan. The massif of St. George's Land which lay to the north of the ancient shoreline provided a source for the occasional influx of terrigencous detritus. The overall pattern of sedimentation in South Wales was modified by seven periods of marine regression and transgression which led to the migration of the shoreline and offshore fades belts. The pattern of cyclic sedimentation that resulted from this history of regression and transgression forms a basis for the system of stratigraphy used in this study. This investigation also provides evidence to support the views of earlier workers who had suggested the possibility of a tectonic control on sedimentation in the north-eastern portion of the study area. Diagenesis in the marine, meteoric and subsurface environments are shown to have considerably altered the original character of the Dibunophyllum Zone sediments. Pressure solution and dolomitisation, in particular, have modified the field appearance of many limestones and played a large role in the formation of the pseudobreccias that occur throughout much of the Dibunophyllum Zone.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available