Origin and Depositional Environments of Abu Shaybah Formation, Ghanimah Area, NW of Libya

تاريخ النشر


نوع المقالة

رسالة ماجستير

عنوان الرسالة

كلية الهندسة - جامغة طرابلس


سليم معمر قجوم



Abu-Shaybah Formation is located on the coastal of the Meditrranean sea South of Ghanimah North West of Libya, between Tripoli and Al Khumes, about 100 km East of Tripoli. It lies on the eastern end of Jabel Nafusa flank. Abu Shaybah Formation Ghanimah area of Late Triasic age, consists of sandstone. The sedimentary structure in the lower most part from studied outcrops reflect NW paleocurrent direction indicating that Jabel Nafusa uplift poorly effect the study area. The upper part of studied succession changing in pallaeocurrent dirction to NE due to Jabel Nafusa uplifting. The extreme changing of paleocurrent direction and paleoslope direction to East due to continuous increase in Jabel Nafusa uplift, direction of vertical joints in Wadi Qirrim presented from NW to SE dirction. The rocks of Abu Shaybah Formation analyzed using differnt kinds of technique, Polrized Microscpe, XRF, SEM techniques. The study of sedimentary texture (grain size, roundness, sorting, and sphiricity) and sedimentary structures showed that Abu Shaybah Formation outcrops deposited in response to two fining upword cycles, formed mainly in Braided Stream Rivers with some effects of meandering. The sequences of Abu Shaybah Formation outcrops that exposed in Wadi Qirrim have been identified on many types of sedimentary facies associated with given sedimentary stucture as, Planar cross bedding, Convolute bedding, Trouph cross bedding, Ripple bedding, Shrinkage cracks, Plant rootlets, Concretions, Unconformity, Channels, Massive bedding, Laminated bedding, and the results which located on the grain size of quartz also loacted on the grain size of heavy minerals like tormaline, zircon and reutile.