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Title: Microbial carbonates : concepts, controls and distribution on Neoproterozoic carbonate platforms, Congo Craton
Author: Le Ber, Erwan
ISNI:       0000 0004 8497 7731
Awarding Body: Royal Holloway, University of London
Current Institution: Royal Holloway, University of London
Date of Award: 2014
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Despite more than one hundred years of research, microbialites and more specifically stromatolites present several conundrums. Stromatolites are the main constituents of Neoproterozoic platforms, and are components of frontier petroleum systems. Assessing the factors influencing microbial sediment geometries and distribution is a crucial step toward the evaluation of their potential role in petroleum systems. This thesis presents a multi-area, multi-scale and multi-disciplinary study of microbially dominated carbonate platforms located in Democratic Republic of Congo, Zambia and Namibia. Literature reviews, field data and sample analyses are synthesised, both leading to discussions on current knowledge and understanding of each study area. At the inter-regional scale, it appears that the break-up of supercontinent Rodinia at the beginning of the Neoproterozoic was accompanied by the development of rift shoulders. Such a setting favoured the initiation of carbonate platforms along the edges of the Congo Craton. Aspects of three of these platforms are developed to a regional-scale by: 1) questioning platform orientation in the West Congolian Group of Democratic Republic of Congo; 2) illustrating the development of organic-rich shales deposited in the vicinity of stromatolites in the Roan Group of Zambia; and 3) presenting a substantial dataset, with new interpretations, for complex facies of the post-Sturtian Rasthof Formation of northern Namibia. Outcrop analysis in northern Namibia favours the detailed analysis of microbial fabrics. Stratigraphically, the Rasthof Formation represents a cap carbonate deposited in the aftermath of the Sturtian glaciation. Based on regional to microscopic-scale observations, the features encountered in the cap carbonate sequence are discussed. The facies locally exhibit evidence for elevated energy levels compatible with shallow water conditions, questioning the amplitude of the supposed post-glacial flooding. Fundamental mesoscopic to microscopic observations are presented to explain the variety of the microbial facies and geometries found in the Rasthof Formation.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available