PETROGRAPHY, GEOCHEMISTRY AND GENESIS OF THE
UPPER EOCENE CARBONATE TERRACES (II AND III),
QASR EL-SAGHA FORMATION, EL-FAIYUM, EGYPT.
ESMAT A. ABOU EL-AN WAR
Geological and Geophysical Sciences Department National Research Center, Cairo , Egypt |
The Upper Eocene rocks of Qasr El-Sagha Formation are subdivided into two members: Abu Lifa Member at top (terrace III) and Temple Member at the base (terrace II). Tectonically, when the Red Sea Hills were uplifted, the Faiyum area was dominated by fluviatile and deltaic conditions during the deposition of the Qasr El-Sagha Formation.
Petrographically, the carbonate rocks of the Qasr El-Sagha Formation were deposited in shallow inner shelf environments. They consist of five facies types: a) sandy dolomitic bioclastic wackestone, shallow inner ramp. b) sandy lirne-mudstone/ dolostone-back shoal, restricted lagoon. c) sandy dolomitic bioclastic wackestone-mudstone back shoal, open lagoon. d) dolomitic bioclastic wackestone /packstone,off shoal, open lagoon.e)sandy dolomitic bioclastic grainstone/
/ packestone, shoal environment. Diagenetically, the carbonate rocks of the Qasr El-Sagha Formation were subjected to three paragenetic stages.
Mineralogically, the dolomites of the Qasr El-Sagha Formation are non-stoichiometricallv formed in a mixed marine-meteoric zone. XRD revealed that the studied samples consist mainly of dolomite as well as calcite, quartz, halite and clay minerals.
Geochemicallv. the sediments of the Qasr El-Sagha Formation are impoverished in Sr and Na content but enriched in Fe2O3 . This may be attributed to the diagenetic processes which took place under less saline environment than sea water and progressive dolomitization in a mixed marine/ meteoric environment.
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