Paleozoic Facies Model in Murzuq Basin in southwestern Libya Atlas and Interpretation

الملخص

Sedimentologic investigation of the Paleozoic sedimentary facies in the Gargaf High, the Ghat area, and in the Dor El Goussa areas, has been carried out to delineate type facies, facies model, the depositional environment, and cyclicity as well as to infer the paleoclimatic conditions under which the formations were deposited. These formations belong to the Gondwana cycle and are typically interpreted as being deposited in a cratonic basin truncated by the Hercynian unconformity. The succession starts with the Hassaouna Formation (Cambrian) comprising (300m) of coarse to conglomeratic, cross-bedded sandstones; a few intervals with trace fossils can be found in its upper portion, structurally deformed with dips 30-60, it can be assigned to a fluvial environment.The Achebyat Formation (Tremadocian) is represented by 65 m of coarse-grained, Tigillite-bioturbated sandstone; trace fossils, some authors prefer to include it in the Lower part of Haouaz Formation.The Hawaz Formation comprise a siliciclastic, shallow to transitional marginal marine succession. It is often dramatically truncated by Late Ordovician glaciation unconformities generating a major discontinuity Melez Chograne Formation (Caradocian) is formed by shale and diamictites with sandstone intercalations, coarsening-upward sequence, with sigmoidal lobes on top. The unit thickness may attain 60 m, but it is commonly absent due to its unconformable contact with Memouniat Formation. The Memoniat Formation (Ashgillian) represents the second glacial cycle in the basin, and its thickness reaches 150 m in Gargaf High and 0-80 m in outcrops around Ghat. It overlies unconformably with the Middle Ordovician and even directly with the Cambrian.