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Successive first downhole sporomorph-events: Applied biostratigraphic tool for fault delineation within Baharyia Formation, Abu Sennan area, Abu Gharadig Basin, Egypt
Journal of African Earth Sciences ( IF 2.2 ) Pub Date : 2020-12-22 , DOI: 10.1016/j.jafrearsci.2020.104095
Somia G. Said , Sameh S. Tahoun , Tamer R. Galal , Nadia K. Effat

Two hundred and seventy four samples, covered the Bahariya sections encountered in 13 boreholes, drilled in three main fields of the General Petroleum Company concession, Abu Gharadig Basin, north Western Desert, were critically investigated for their palynomorphs content. A standard acid-based palynological processing technique is employed to extract the palynomorphs. Fair to moderate diversity and moderate to good preserved palynomorph assemblage has been recovered. This study yielded 107 species of spores, pollen grains and dinoflagellate cysts. Six remarkable successive first downhole appearance (FDA) sporomorph-events are defined and biostratigraphically utilized for dividing the Bahariya Formation and delineating the Bahariya/Kharita contact. The upper Bahriya unit includes the first Afropollis jardinus event dated latest early Cenomanian, while the middle Bahriya unit comprises the second Elatersporites klaszii event dated early Cenomanian. The lower Bahriya unit, dated early Cenomanian-late Albian, contains the third, fourth, and fifth Cretaceieporites densimurus, Trilobosporites laevigatus and Stellatopollis sp. events, respectively. The contact between Bahriya Formation and the upper part of the underlying Kharita Formation, dated early-middle Albian, is placed on Concavisimisporites punctatus event. The authors found the possibility of these six zones to be widely traced and provide potential bio-correlation tool for the Bahariya sections in Abu Gharadig Basin. According to the presence or absence of such six successive events and their average zonal thicknesses, the intra-formational disconformities and positions of the faults could be allocated with confidence. The remarkable thinning in the thickness of such zones could localize the position of disconformities caused by non deposition or erosion/faulting within the Bahariya sections. The aforementioned six events could be correlated and nicely matched with their equivalent six log-based cycles on the log responses. The authors encourage the Egyptian industrial geologists to follow the presented successive six sporomorph-events in the future palynological-steering exploration and production activities in the Bahariya rock unit and effectively utilize such events as intra- and inter-basinal dating tool and possible correlation control for the Bahariya sections across the northern basins of Egypt.



中文翻译:

连续的首次井下孢子岩事件:埃及阿布加拉迪格盆地阿布森南地区巴哈里利亚组巴哈里亚组断层轮廓的应用生物地层学工具

对在通用石油公司特许经营权的三个主要领域(西北沙漠阿布加拉迪格盆地)钻的274个样品进行了覆盖,覆盖了13个钻孔中的巴哈里亚断面,并对其地貌进行了严格的调查。采用标准的基于酸的孢粉加工技术来提取孢粉。已恢复到中等至中等的多样性以及中等至良好保存的古朴形态组合。这项研究产生了107种孢子,花粉粒和鞭毛藻囊肿。定义了六个显着的连续首次井下外观(FDA)孢子事件,并通过生物地层学来划分Bahariya组和描述Bahariya / Kharita接触。上巴里耶部队包括第一批非洲菊事件发生在西诺曼尼亚早期,而Bahriya中部则包括第二次Elatersporites klaszii事件。较低的Bahriya单元,日期为早Cenomanian晚期的Albian,包含第三,第四和第五Cretaceieporites densimurusTrilobosporites laevigatusStellatopollis sp 事件分别。Bahriya地层与下阿尔卡比亚早期中下部Kharita地层上部之间的接触被置于点状凹穴上事件。作者发现这六个区域的可能性被广泛追踪,并为阿布加拉迪格盆地的巴哈里耶剖面提供了潜在的生物相关工具。根据这六个连续事件的存在与否及其平均纬向厚度,可以可靠地分配断层内的不整合性和断层的位置。这些区域的厚度显着变薄,可以定位由Bahariya断面内的非沉积或侵蚀/断层引起的不整合的位置。前面提到的六个事件可以与它们在日志响应中等效的六个基于日志的周期相关联并很好地匹配。

更新日期:2020-12-23
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