الفهرس | Only 14 pages are availabe for public view |
Abstract The ConiacianMaastrichtian outcrops in westcentral Sinai are represented by mixed siliciclastics and carbonates (Matulla Formation) followed upwards by a white carbonate section (Sudr Chalk). The Matulla Formation is subdivided here into a lower ?clasticdominated? member, a middle ?carbonate dominated? member and an upper ?shale dominated? member. Also the Markha Chalk Member and Abu Zenima Chalk Member of the Sudr Chalk are described in detail. The present macrofaunal systematic investigation led to the recognition of 75 species of which, eleven species are described for the first time from Egypt. and one brachiopod was not recorded before from Sinai. The biostratigraphic framework suggested here is based on the vertical distribution of the identified macrofauna and the age ranges of the specifically identified forms. The characteristics of the recognised biostratigraphic units are summarised below from older to younger:I Poorly fossiliferous interval, II Metatissotia fourneli Zone, III Oscillopha dichotomaPycnodonte (Ph.) proboscideum Zone, IV Pycnodonte (Phygraea) vesicularis Zone, V Terebratulina gracilis Zone and VI Ventriculites poculum Zone. The nonclastic facies are mostly limestones, representing about 71% of the total thickness. Eighteen limestone microfacies types are recognized in the studied Senonian succession and represented by lime mudstone (fossiliferous micrite), wackestone (sandy glauconitic, foraminiferal, ostracod, miliolid, shelly, silty and pelagic biomicrites), packstone (sandy biomicrite), grainstone (sandy, oolitic and foraminiferal biopelsparite), floatstone (silicified shelly and coated grain biomicrudite), rudstone (sandy shelly and biointrasparudite) and boundstone (framestone). The dolostones are included in two microfacies; finemedium crystalline and fossiliferous dolostone. The clastic microfacies includes sandstones (silty, calcareous, and phosphatic quartz arenite, and ferruginous subarkose) and shales (calcareous silty and calcareous clayey shale). Four important events took place in westcentral Sinai during the ConiacianMaastrichtian time including an Early Coniacian lowstand, a Late ConiacianEarly Santonian transgressive phase, a Late Santonian deformation and the CampanianMaastrichtian major transgression. The rise and fall of sea level in westcentral Sinai during the CampanianMaastrichtian time are not always in agreement with the global eustatic curve due probably to the effect of local tectonic movements. |