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Title: Sedimentology of the lower Carboniferous in south-western Libya
Author: Petitpierre, Laurent
ISNI:       0000 0004 2721 6645
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2012
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Several hydrocarbon discoveries in the Marar Formation (Tournaisian and Viséan) were recently made in the Lower Carboniferous strata of the Ghadames and Murzuq Basins situated in SW Libya. Despite large exposures exhibiting thick sections, there is an absence of regional studies focusing on this stratigraphic interval and only rare case studies provide new sedimentary data. More generally, geological knowledge of Carboniferous in North Africa (Saharan Platform) is also understudied when compare to other regions of the world. Detail analyses of the sedimentary record on Saharan Platform may noticeably contribute to refine the current understanding of global geological episodes such as the Late Paleozoic Ice Age. The main aim of this study is to produce valuable field data for both industry and interpretations for assessing academic hypothesis. In order to develop accurate and detail correlations of sedimentary strata over long distances (over 350 km) a primary aims is to define a synchronous key marker horizon that is ideally detectable in both surface and subsurface datasets. A secondary aim is to characterise spatial variability and geometries of sedimentary bodies. Acquired during three fieldwork seasons in the area (along ca 385 km), over 4800 m of sedimentary logging, facies analyses and 800 outcrop gamma ray readings are compiled in this study. I therefore characterise the micro, meso, macro-scale geometries, regional distribution, gamma ray response and mineralogy of the Collenia stromatolites that mark the uppermost part of the Marar Formation. Mainly based on series of detailed sedimentary logging and photographic panoramas, two types of reservoirs facies are described: 1- several metres thick shorefaces sandstones that are continuous for several tens of kilometres; 2- several tens of metres thick incised valley in filled with fluvial sandstones of fewer lateral extend. A sea level curve, produced on basis of the detailed sequence stratigraphic framework of the area, reveals that eustasy almost solely explains relative changes of sea level during the Viséan. Considering the glacial record preserved on northern Gondwana during the same interval, we conclude that the onset of the Late Paleozoic Ice Age is older than uppermost Viséan and more gradual than previously thought.
Supervisor: Redfern, Jonathan Sponsor: North Africa Research Group
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: murzuq ; Carboniferous ; Saharan platform ; incised valleys ; visean ; marar formation ; collenia