Evolution of the Murzuq Basin, southwest Libya, and surrounding region during the Devonian
During the Devonian the area currently delimited by the Murzuq Basin in SW Libya, was part of a slowly subsiding, extensive, low angle, platform cratonic margin, situated on northern Gondwana. Phases of tectonism occurred during the Gedinnian, Emsian, Frasnian and Fammenian which caused the localised uplift and erosion of regions within the basin and created areas of differential subsidence and sedimentation that persisted throughout the Devonian. During the Early Devonian continental deposition prevailed across much of northern Gondwana, with up-dip areas such as the Murzuq Basin, covered by large, coarse-grained, siliciclastic braided and meandering alluvial systems, feeding fluvially dominated deltas and tidally influenced shorelines to the NW. During the Mid to Late Devonian marginal to open marine conditions prevailed across much of northern Gondwana, including the Murzuq Basin, with subordinate continental deposition. The up-dip alluvial systems had braided and meandering channels, passing down-dip to the NW into fluvially dominated deltas flanked by tidally influenced fine-grained shoreface successions. During the Devonian relative sea level fluctuations led to the formation of regionally extensive sequence boundaries and flooding surfaces. The Lower Devonian succession in the Murzuq Basin contains 7 sequences that record a transgressive sequence set while the Middle to Upper Devonian succession contains a further 6 sequences formed during a general highstand. The relative sea level fluctuations that controlled the formation of these sequences were of 2d to 6'h order duration. Correlation of the Emsian, Givetian and Frasnian relative sea level fluctuations across North Africa and North America indicate their eustatic origin. Available data does not allow the driving mechanisms of the remaining sequences to be confidently interpreted. However, the continental to marine sequences deposited on this slowly subsiding cratonic margin were influenced by local, regional and eustatic processes.