الفهرس 
chapter 1: IntroductionOnly 14 pages are availabe for public view
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Abstract
For the current study, thirty-one cutting rock samples from the Upper Cretaceous Abu Roash A Member in BED 2-3 well, drilled in the Abu Gharadig Basin in the North Western Desert, Egypt, have been investigated. Due to the lack of reliable age control for the Abu Roash A Member, a high resolution palynological processing has been carried out and led to the identification of a highly-diverse, rich and well-preserved palynomorphs assemblage compared to the previous palynological studies for the same succession that were lean. Around 218 species of reported palynomorphs, belonging to 123 genera was identified throughout the succession. The palynomorphs assemblage was dominated be marine dinocysts, mainly 157 species, and the MFTLs that were also abundant, whereas discrete abundances of pollen grains, spores, prasinophytes, acritarches, and fresh-water algae represented only a minor part. For the first time across the Egyptian platform in NE Africa, such rich assemblages led to construct three palynological assemblage zones to be recognized, based on the first downhole occurrence are;
I- Isabelidinium belfastense - Odontochitina operculata - Isabelidinium acuminatum Assemblage Zone (early Campanian).
II- Dinogymnium acuminatum - Odontochitina porifera Assemblage Zone (Santonian).
III- Cyclonephelium filoreticulatum - Spinidinium echinoideum Assemblage Zone (late Coniacian).
A total of 16 species of dinocysts belonging to 13 genera are documented and identified, for the first time, in the Cretaceous (late Coniacian–early Campanian) record of Egypt.
Various palynological parameters were used to reveal significant variations during deposition throughout the studied sequence. Therefore, two alternating palynofacies assemblages were recognised in the Abu Roash A Member, based on AOM, phytoclasts, M/T ratio, P:G ratio, MFTLs and freshwater algae. PFA-1 was deposited in a distal, middle neritic environment with a high primary productivity that maintained the preservation of high AOM content. PFA-2 was deposited in a slightly shallower, distal inner neritic environment compared with PFA-1. It was also observed that the bicavate Chatangiella and Isabelidinium groups have adapted and thrived in areas where shallower marine settings prevailed.
The redox conditions were interpreted based on four approaches, the TS and TOC relationship, which indicated deposition during predominantly oxic to intermittently dysoxic conditions. The TS-TOC-FeT relationship that was in agreement with the results of the TS-TOC relationship; however, two samples plotted above the pyrite line, reflecting deposition during OM-limited conditions and pyrite formation diagenetically in anoxic pore water. Trace element ratios, like the V/(V + Ni) ratio, suggested euxinic redox conditions, whereas the Ni/Co ratio showed that all samples were deposited under oxic conditions. The V/Cr ratio was the most reasonable and pointed to oxic and marginally dysoxic conditions. Therefore, the trace-elemental ratios indicated that cautions should be taken when applying multiple redox proxies.
Consequently, according to well-preserved dinoflagellates and their correlated ages indicated varied rates of sediment accumulation. The rate of sediment accumulation was highest during the late Coniacian compared to the Santonian that had the lowest rate.
Additionally, a negative relationship exists between TOC and CaCO3 content because of the carbonate dilution effect and destruction of OM and, thus, reduction of TOC content. Trace-elements used as proxies for assessing the role of detrital influx indicate a limited input of terrigenous material during deposition into the Abu Gharadig Basin. Based on carbonate-associated minerals, trace elements and ratios (e.g. Ba/Al, TOC/P and P/Al) as well as dinocyst P:G ratio, the paleoproductivity conditions were commonly moderate to high with a phytoplankton bloom within the water column.
Dinocyst assemblages and groups were used to interpret that prevailing enhanced water-mixing and warm-temperate conditions of a greenhouse phase were interrupted by intermittent more thermohaline density stratified conditions of probably warmer greenhouse (hothouse) climate intervals. The water column was enriched with phytoplankton and abundant productivity; however, the OM depletion was attributed to dilution- and destruction-controlled regimes due to the carbonate dilution effect and the low rate of sedimentation at the sediment-water interface.
A highly diverse assemblage of well-preserved palynomorphs, mainly dinocysts, indicated a comparable pattern to the global eustatic sea-level of Haq (2014). Higher values of dinocyst diversity, based on the Shannon Index, numbers of dinocyst species along with higher PMI versus lower FWA and sporomorphs content indicate deeper marine conditions and transgression phase of sea-level and vice versa. This led to the reconstruction of four complete transgressive-regressive third order sequences and two incomplete ones in the S Tethys during this period of the Late Cretaceous. Additionally, trace elements and their ratios introduced unexpected markedly positive correlations with the palynomorphs assemblages. Maximum peaks of Mn content and Ti/Al ratio were associated with a relative sea-level rise at most of the succession compared to minimum values together with Si/Al, Sr/Ca and Zr/Al that matched well with regressive phases of sea-level.
Vertical excursions of the δ13Ccarb profile confirmed and correlated with gonyaulacoid dinocyst vs. FWA-Spore to give further support of the application of δ13Ccarb as an indicator of relative sea-level rise/fall cycles. Positive excursions correlated with gonyaulacoid dinocyst maxima and FWA-Spore minima and indicated relative rise of sea-level. The δ18Ocarb excursions were also tested and proved to be reliable for reconstructing the relative sea-level, whereby positive excursions paralleled the transgressive phases and negative excursions matched the regressive phases. However, specific anomalies were reported, which likely related to periods of diagenetic alterations.
Climate reconstructions were conducted based on palynomorphs analysis, where increased values of the skolochorate and warm-temperate peridinioid dinocyst groups and dinocyst species diversity, indicated warm greenhouse climate during this period. These results are in a good agreement with the δ18Ocarb rends and their correlations regionally during this period, whereby negative excursions presumed warmer greenhouse conditions compared to positive ones. Besides, the relationship between trace element ratios of Sr/Ca and Mn/Ca also correlated well with the former proxies as well as the clay mineral associations and indicated a prevalent humid to semi-arid warm greenhouse climate.
A climate-based relationship with sea-level changes was discussed and correlated with results from the Tarfaya Basin, NW Africa. It showed that the prevalence of warm-temperate peridinioids versus other warm dinocyst indicators at low-latitudes either in the Tethys or the Atlantic matched well with the prevalent warm-greenhouse and high transgressive trend of the global eustatic sea-level during this period.
Oceanographic mechanisms indicated that the study section in the S Tethys was dominated by high paleoproductivity and nutrient supply during enhanced water mixing as indicated by marine dinocysts and trace elements, supported by coastal upwelling as illustrated in ocean-atmosphere global circulation climate models. However, OAE 3 was not reported in the S Tethys. Instead, the succession in this study is equivalent to CORBs as a result of complex oceanographic processes resulting from water evaporation, salinization, creation of overturning circulations and enhancement of upwelling setting versus a low rate of sedimentation and dilution-destruction of organic matter due to oxidation.