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Early P alaeozoic evolution of L ibya: perspectives from J abal E ghei with implications for hydrocarbon exploration in Al K ufrah B asin
Author(s) -
Heron D. P. Le,
Meinhold G.,
Elgadry M.,
Abutarruma Y.,
Boote D.
Publication year - 2015
Publication title -
basin research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.522
H-Index - 83
eISSN - 1365-2117
pISSN - 0950-091X
DOI - 10.1111/bre.12057
Subject(s) - geology , sedimentary depositional environment , outcrop , geochemistry , geomorphology , structural basin
This paper presents new stratigraphic and sedimentological data of the O rdovician, S ilurian, and M esozoic succession exposed on the western flank of A l K ufrah B asin. Field data (logged sections, photographs, palaeocurrent analyses) are presented from the J abal E ghei region. This region lies ca . 200 km E of the closest stratigraphic tie point at M ourizidie on the eastern flank of the M urzuq B asin. The succession starts with the H awaz F ormation ( M iddle O rdovician) comprising >100 m of cross‐bedded and bioturbated sandstones that are interpreted as deposits of tidal currents in an open shelf setting. The contact between the H awaz and M amuniyat formations is an erosional unconformity, incised during advance of L ate O rdovician ice sheets towards the NE . The M amuniyat F ormation comprises >150 m of massive and graded sandstones tentatively assigned to the H irnantian, and contains an intraformational, soft‐sediment striated surface that is interpreted to record re‐advance of ice sheets over J abal E ghei. The outcrop section suggests the sandstone would form an excellent reservoir in the subsurface. The M amuniyat F ormation is overlain by the T anezzuft F ormation (uppermost O rdovician–lowermost S ilurian). This includes sandy limestone/calcareous sandstone, a P lanolites horizon, and then 50 m of interbedded shale, silt and fine‐grained, graded and hummocky cross‐stratified sandstone recording deposition from both shallow marine turbidity currents and storm flows. A striated pavement in the lower part of this sequence is overlain by calcareous lonestone‐bearing intervals (interpreted as ice‐rafted debris). These features testify to late phases of glacial advance probably post‐dating the regional H irnantian glacial maximum. The basal S ilurian ‘hot shale’ facies is not developed in this area, probably because late glacial advance suppressed the preservation of organic matter. The upper part of the T anezzuft F ormation is truncated by an unconformity above which palaeosol‐bearing fluvial deposits (undifferentiated M esozoic) occur.