Integrated organic petrographic and geochemical analyses were made on
organic-rich marine carbonate and mixed clastic-carbonate rocks of
Middle–Late Jurassic and Early Cretaceous age from the Shushan Basin, Egypt
to evaluate their hydrocarbon potential. Analyses allowed the identification of
depositional settings, paleoclimate, and three third order genetic stratigraphic
sequences (SQ) with deposits assigned to highstand (HST), lowstand (LST) and
transgressive systems tracts (TST). Deposition of the source rocks in the rifting
Shushan Basin resulted from the interaction between Neotethyan sea level
changes, tectonic, and climate. The good reducing conditions developed
during the Neotethyan Middle–Late Jurassic (Bajocian–Kimmeridgian) second
order sea level rises and the climatically induced carbonate sedimentation resulted
in the deposition of the organic-rich carbonates of the Khatatba Formation (SQ 1,
early–middle TST) in inner–middle shelf settings under anoxic–dysoxic
conditions. The Late Jurassic (late Kimmeridgian) uplifting resulted in the
deposition of the organic-lean mixed clastic–carbonate strata of the Masajid
Formation (SQ 1, latest TST) in the same shelfal and reducing conditions, which
experienced a notable dilution of organic matter. The late TST deposits of SQ 1 are
good to very good oil-producing source rocks, where they show average good to
very good generative potential of late mature (late oil-to early wet gas-window)
highly oil-prone organic matter. The Early Cretaceous (Valanginian–Albian)
uplifting associated with the rifting of the Shushan Basin overprinted the
Neotethyan late Valanginian–Hauterivian second order sea level rises, Aptian
second order highstand sea level, and Albian second order sea level rise. The
coeval climatic shift toward more humid conditions resulted in the clasticdominated
deposition of the organic-lean regressive units of SQ 2 (HST and
LST of Alam El Bueib, Alamein, and Dahab formations) and SQ 3 (HST and LST of the lower–upper Kharita Formation) in marginal marine settings under
anoxic–dysoxic to oxic conditions. The HST and LST deposits of the SQ 2 and
SQ 3 show poor to good organic richness of early–mid mature (early–peak oilwindow)
oil/gas-prone and gas/oil-prone organic matter, respectively and exhibit
average fair oil source rock potential with no gas generation.