الفهرس 
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Abstract
Six rudist-bearing outcrops from north Sinai, north Eastern Desert and north Western Desert form the backbone of this study. The exposed sections that measured at Gabal Raghawi, Gabal Maaza and Gabal Yelleg of north Sinai are divided into three formations that include Risan Aneiza Formation (Late Barremian-Middle Albian), Halal Formation (Middle Albian-Cenomanian) and Wata Formation (Turonian). While the Cretaceous successions are represented by Galala Formation (Middle Cenomanian-Early Turonian), Buttum Formation (Middle Turonian) and Wata Formation (Late Turonian) at Wadi El-Dakhl and Saint Paul sections in north Eastern Desert. This study is also concerned with the rudist-bearing limestone beds in the Rudist-bearing limestone-marl Member and the Actaeonella-bearing limestone-marl Member of the Turonian Abu Roash Formation at Abu Roash area in north Western Desert.
Orbitolinid foraminifera, calcareous algae, ammonites, rudists and non-rudist bivalves have been used to detect the age and correlation of the rock units as well as the stage boundaries. Many rudist levels associated with different fossil groups are identified from the studied sections. Nine rudist levels (GR I-IX) are recorded in the Late Barremian through Early Cenomanian succession at Gabal Raghawi of north Sinai. Rudist level GR 1 with Horiopleura sp. and Toucasia carinata, associated with Palorbitolina lenticularis is the oldest rudist level and suggests a Late Barremian-Early Aptian age. The second rudist level GR II contains Eoradiolites plicatus associated with Lithocodium aggregatum, Bacinella irregularis and Orbitolina (Mesorbitolina) parva. Six rudist levels (GR III-VIII) are well-developed during the Middle-Late Albian, and most of them are dominated with caprinids and radiolitids. The topmost part of Gabal Raghawi succession is characterized by dolomitic limestone yielding the Early Cenomanian rudist level GR IX that contains Eoradiolites liratus. At Gabal Yelleg of north Sinai, ten rudist levels (GY I-X) are recorded from the Albian-Turonian succession. Two rudist levels (GY I-II) are found in Albian, five levels (GY III-VII) in the Cenomanian and three levels (GY VIII-X) in the Turonian deposits. Three rudist levels GM I, GM II and GM III with reworked Eoradiolites liratus have been noted in the Cenomanian Halal Formation at Gabal Maaza of north Sinai. In north Eastern Desert, one rudist level can be traced at Wadi El-Dakhl (rudist level WD I) and Saint Paul (rudist level SP I) yielding Eoradiolites liratus. At Abu Roash section in north Western Desert, the Turonian succession contains three rudist levels. Levels Ab I and Ab II are recorded within the Rudist-bearing limestone-marl Member. Level Ab I consists of Durania gaensis, Praeradiolites ponsianus, Bournonia fourtaui, whereas, one rudist species Bournonia roashensis is found in the second rudist level Ab II. The last rudist level Ab III constitutes the upper part of Actaeonella-bearing limestone Member and contains Durania arnaudi.
Fourteen rudist species belong to Radiolitidae, two species belong to Requieniidae, two species belong to Caprinidae, one species belongs to Caprotinidae, one species belongs to Polyconitidae, two species belong to Monopleuridae and two species belong to Ichthyosarcolitidae are identified and systematically described from the studied sections. They belong to Archaeoradiolites, Eoradiolites, Praeradiolites, Radiolites, Distefanella, Bournonia, Biradiolites, Durania, Toucasia, Neocaprina, Sellaea, Horiopleura, Agriopleura, Mathesia and Ichthyosarcolites.
A detailed facies analysis has been carried out to construct a high resolution sequence stratigraphic framework. The platform deposits are subdivided into many microfacies and submicrofacies types that define facies belts ranging from intertidal siliciclastics to deep open marine facies. Wackestone and packstone with miliolids and cyanobacterium were deposited in restricted lagoon environments, while the open marine biota are widespread in open lagoons. The high energy subtidal shoals are dominated by oolitic or bioclastic grainstones and packstones. The rudist facies are deposited in shallow subtidal rudist biostromes in the form of bafflestone, floatstone and rudstone facies. The rudist biostromes grade seaward to the foreslope and deep marine facies (mudstone, wackestone and shale with ammonites, orbitolinids and planktic foraminifers).
Based on sequence stratigraphic analysis, fourteen large-scale depositional sequences can be recognized in the Late Barremian-Turonian succession of north Sinai. In places, particularly at Gabal Raghawi, the large-scale sequences can be subdivided into high resolution small- and medium-scale sequences. Four large-scale depositional sequences represent the late Middle Cenomanian-Late Turonian succession at Wadi El-Dakhl and Saint Paul sections of north Eastern Desert. The Turonian succession at Abu Roash area is divided into three depositional sequences bounded by three sequence boundaries. Based on sequence investigation, the evolution from siliciclastic- to rudist-dominated platforms coincides with the southward transgression of the sea during the Middle Albian to cover a new positive area (Gabal Yelleg). The rudists flourished the platform mostly during the highstand systems tracts and rarely through the transgressive system tracts.
A stable isotope study was conducted in an attempt to resolve some stratigraphic problems. The δ 13C composite curve can be subdivided into 34 characteristic segments in northern Sinai sections. C1 to C22 Carbon segments come from the Late Barremian-Early Cenomanian interval at Gabal Raghawi, entire Cenomanian C22-C30 segments are obtained from the Halal Formation at Gabal Yelleg and Gabal Maaza sections, while the Turonian segments (C30-C34) are derived from the Wata Formation at Gabal Yelleg section. The δ 13C record from the studied sections is consistent with previous documentation of the Tethyan realm. Five oceanic anoxic events are recorded at the Carbon-isotope excursion in the studied sections including OAE1a (Early Aptian), OAE1b (Late Aptian-Early Albian), OAEs1c-d (Late Albian) and OAE2 at the Cenomanian-Turonian boundary.
Keywords:
Cretaceous, Rudists, Associated Fauna, Lithostratigraphy, Sequence Stratigraphy, Chemostratigraphy, North Sinai, North Eastern Desert, North Western Desert, Egypt.