Facies, architecture and dynamic of a Late-Ordovician proglacial fan (Murzuq Basin, SW Libya)
Facies, architecture and dynamic of a Late-Ordovician proglacial fan (Murzuq Basin, SW Libya).
Thèses de doctorat,
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During the Late Ordovician, a continental-scale ice sheet extended over the north Gondwana platform. The resulting glaciogenic sedimentary successions constitute the most important petroleum reservoirs of the Saharan fields. This study was carried out from field data and satellite imagery of the plateau du Tissaghert in southwest Libya. The studied sedimentary succession shows three depositional systems. These systems correspond to a first Southern ice-marginal setting upstream, comprising a glacial basin with the associated glaciotectonic complex and a connected network of incised channels, which are developed during glacial advance and infilled during glacial retreat. This ice marginal system is connected downstream, to a second Northern proglacial fluvio-deltaic system that corresponds to a delta-plain setting including fluvioglacial channels and that evolves downstream into river-mouth and low-angle prograding delta front environments. The overall deltaic architecture builds up from repeated glacial outbursts, mainly during glacial advance and ice-front stabilization. A third postglacial transgressive tidal and wave-dominated system superimposes these two previous systems and depicts ice-front retreat and the subsequent global deglaciation. The two first glacially related systems represent the late part of a lowstand system tract, and the third system represents a subsequent transgressive system tract. They all characterize the signature of a glacial sequence consequently defined by a cycle of glacial advance and retreat. These results also allowed the creation of a 3D analog reservoir model of the Ordovician-Silurian petroleum system.
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