University of Khartoum

Sedimentology and Sequence Stratigraphy of the Lower Cretaceous Abu Gabra Formation (Neem Oil Fields)

Sedimentology and Sequence Stratigraphy of the Lower Cretaceous Abu Gabra Formation (Neem Oil Fields)

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Title: Sedimentology and Sequence Stratigraphy of the Lower Cretaceous Abu Gabra Formation (Neem Oil Fields)
Author: Nogd, Rashida Sir El khatim Ali
Abstract: This study investigates the facies and palynofacies, depositional environments, source area, sequence stratigraphy, sandstone petrography, wireline logs and seismic sections interpretation. Laboratory analysis included petrography analysis such as heavy minerals analysis, clay minerals analysis as well as palynofacies analysis. From lithofacies analysis, Abu Gabra Formation could be divided into three units based on sand/mud ratio and logs response. Fluvial dominated unit, deltaic dominated unit, deep to shallow lacustrine dominated unit represents the upper, upper middle, and middle Abu Gabra Formation.Both heavy and clay minerals analysis reveal two assemblage zones within Abu Gabra Units are directly related to depositional system within which they occur, zones with considerable (KstanG)%, and high (ZTR)% and consist of kaolinite, smectite, illite/smectite and chlorite zones in upper Abu Gabra Unit, and zone reflects high percentage of (KstanG), and low percentage (ZTR) with considerable amount of kaolinite, smectite, illite/smectite and chlorite zones in middle Abu Gabra unit reflect environmental/tectonic change.The depositional environment and sequence stratigraphy analysis of Abu Gabra Formation revealed three types of system tracts; lowstand system tract (LST) at upper Abu Gabra unit of fluvial environment, consisting of stacked braided and meandering channels; transgressive system tract (TST) at middle Abu Gabra unit, consisting of deep to shallow lacustrine environment. Highstand system tract (HST), at upper Abu Gabra unit, consisting of the fluvio-deltaic environment. Palynofacies analysis shows quantities and abundance of palynodebris and palynomorph deposited under tropical-subtropical conditions. From statistical analysis, the pollen and spores reveal the high percentage of Pteridophyte and bryophyte (46.1)%, from mainly herbaceous vegetation close to small lakes and delta. Gymnosperm pollen ( 41.3)%, such as Araucaria cites pollen has a wide ecological range from rainforest to cool temperature humid conditions Ephedripites occur in arid-semi arid conditions, therefore may be regarded as indicative of arid to semi-arid conditions. The occurrence of freshwater algae, (Algal spores (2.8%), might be attributed to their capability to tolerate the fluctuation of salinity.
URI: http://khartoumspace.uofk.edu/123456789/26106


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