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Sedimentology and Sequence Stratigraphy of the Middle to Late Miocene, Al-Jabal Al-Khdar Uplift and Soluq Trough, Cyrenaican NE Libya

Khaled S. Amrouni1, Michael C. Pope1, and Ahmed S. El-Hawat2
1Department of Geology and Geophysics, Texas A&M University, College Station, TX 77843; [email protected], [email protected]
2Department of Earth Sciences, Garyounis University, Benghazi, Libya; [email protected]

A sequence stratigraphic, chemostratigraphic and diagenetic study of the Middle to Late Miocene rocks in the Cyrenaica, northeast Libya, between 31°-33° N Latitude and 19°30'-21° E Longitude.The sequence stratigraphic study involves determining detailed regional facies relationships from field and lab observations. The field work includedmeasuring 25 stratigraphic sectionsbed-by-bed, 14Spectral gamma-ray profiles constructed using a hand-held gamma-ray scintillometer at 0.5 m intervals, and annotating panoramic digital photomosaics. The lab work includes petrographic and diagenetic studies of501 hand samples, thin sections and stable isotope (δ 18O and δ 13C) analyses.

The Ar-Rajmah Group carbonate rocks record threeparasequencesets separated by a sharp disconformity surface and maximum flooding zone respectively. The lower parasequence set is the Middle Miocene Benghazi Formation (40 m maximum thickness), the Middle and upper parasequencesets are the Late Miocene Wadi Al-Qattarah Formation (30 m and 31m maximum thicknesses respectively). The lower parasequence set is composed mainly of coral reefs, porites,red algae (rhodoliths), and open marine skeletal packstone containing large bivalves, gastropods, oysters, and echinoids. The Middleparasequence set has reworked red algae fragments at its base, shallowing upward into bioclastic grainstone, then cross-bedded oolitic grainstone. Microbialites (stromatolites, thrombolites, and laminites), and evaporites associated with pelletal mudstones, pelletal packstones, and siliciclastic fine to very fine quartz sandstone and green shale mark the upper part of this parasequence set. The siliciclastics appear only in the southern part of the field area. The upper sequence is dominated by continuous bodies of oolitic grainstone and microbialites associated with some bioclastic carbonates, red algae, and pellets.

AAPG Search and Discovery Article #90182©2013 AAPG/SEG Student Expo, Houston, Texas, September 16-17, 2013