Hydrocarbon potential of the Meso-Cenozoic Turkana Depression, northern Kenya. II. Source rocks: quality, maturation, depositional environments and structural control

Talbot, Michael R.; Morley, C.K.; Tiercelin, Jean-Jacques; Hérissé, Alain Le; Potdevin, Jean-Luc; Gall, Bernard Le

doi:10.1016/j.marpetgeo.2003.11.008

Cited by 29 publications

(18 citation statements)

References 18 publications

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“…The presence of Late Early Miocene freshwater rays (Myliobatiformes) in the Turkana region (21) also attests to the existence of a well-developed fluvial system at that time (22). These OligoMiocene paleoenvironmental conditions are compatible with an overall humid climate with precipitation of >1,000 mm/a (millimeters per year), deep freshwater lakes in the rift basins (18), and a vegetative cover with affinities to the Guinea-Congolia/Zambezia phytogeographic zone and ancient lowland forest (23,24) also present on the Ethiopian Plateau during that interval (25). Similarly, the phylogenetic analysis of Annonaceae suggests the existence of a trans-African forest and a warmer, moister climate before 16.8 Ma (26) during the Miocene climatic optimum (27).…”

Section: Resultsmentioning

confidence: 96%

“…The fluvial sandstones and conglomerates associated with the Turkana ziphiid are within the Oligo-Miocene Lokichar halfgraben (3,17), which hosts 7-km-thick sedimentary strata related to a fluvial and freshwater lacustrine depositional environment (18). This basin is superimposed on an area of widespread Cretaceous extension associated with the Anza Graben, a northwest to southeastoriented rift basin, which is also filled with Paleocene to Miocene fluviolacustrine strata that transition upward into marine units toward the Kenya-Somalia coast in the Lamu Embayment (Fig.…”

Section: Resultsmentioning

confidence: 99%

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A 17-My-old whale constrains onset of uplift and climate change in east Africa

Wichura

Jacobs

Lin

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Timing and magnitude of surface uplift are key to understanding the impact of crustal deformation and topographic growth on atmospheric circulation, environmental conditions, and surface processes. Uplift of the East African Plateau is linked to mantle processes, but paleoaltimetry data are too scarce to constrain plateau evolution and subsequent vertical motions associated with rifting. Here, we assess the paleotopographic implications of a beaked whale fossil (Ziphiidae) from the Turkana region of Kenya found 740 km inland from the present-day coastline of the Indian Ocean at an elevation of 620 m. The specimen is ∼17 My old and represents the oldest derived beaked whale known, consistent with molecular estimates of the emergence of modern straptoothed whales (Mesoplodon). The whale traveled from the Indian Ocean inland along an eastward-directed drainage system controlled by the Cretaceous Anza Graben and was stranded slightly above sea level. Surface uplift from near sea level coincides with paleoclimatic change from a humid environment to highly variable and much drier conditions, which altered biotic communities and drove evolution in east Africa, including that of primates.east Africa | Ziphiidae | uplift | drainage | paleoenvironment

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Section: Resultsmentioning

confidence: 96%

Section: Resultsmentioning

confidence: 99%

A 17-My-old whale constrains onset of uplift and climate change in east Africa

Wichura

Jacobs

Lin

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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“…Even with the expected reduction of porosity with depth of burial due to diagenetic alteration of the sandstones, residual porosity can be expected to remain of reasonable reservoir quality between 12% and 14% (Morley, 1999). Source rocks and oil have been confirmed in the Lokichar Basin, in the Loperot-1 well where total organic carbon (TOC) values are reported to be as high as 17%, with an average of 4.5% (Morley et al, 1999e;Talbot et al, 2004), and in the recently drilled Ngamia-1 well. On the outcrop level, the dark grey mudstones identified within the LS (lower and upper parts) were not subjected to geochemical analysis to determine their organic matter richness and hence their source rock potential.…”

Section: Discussionmentioning

confidence: 98%

“…2 and 3). The hydrocarbon potential in these basins (Morley, 1999) was confirmed by the Loperot-1 exploration well that encountered high TOC potential source rocks and significant oil shows (Wescott et al, 1999;Talbot et al, 2004). A second exploration well, named Ngamia-1, operated by African Oil Corp. and Tullow Oil in the Lokichar Basin closeby the Loperot-1 well, encountered in March and May 2012 several good quality oil-bearing reservoir zones at depths between 1041 and 1515 m. These facts, together with the proximity of these basins to the southern Sudanese oil-producing fields, and the similarity in the structural trends of the two regions (Schull, 1988) (Fig.…”

Section: Introductionmentioning

confidence: 88%

Stratigraphy, sedimentology and diagenetic evolution of the Lapur Sandstone in northern Kenya: Implications for oil exploration of the Meso-Cenozoic Turkana depression

Tiercelin

Potdevin

Thuo

et al. 2012

Journal of African Earth Sciences

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“…vegetation cover) (e.g. Talbot, 1988;Sladen, 1997;Talbot et al, 2004). The organic matter composition and TOC contents of lacustrine mudstones (including oil shales) may vary considerably due to variable contributions from algal, bacterial and higher land plant material, which, together with the preservation potential, can cause a wide range in HI (e.g.…”

Section: Organic Facies Oil Shalesmentioning

confidence: 99%

Petroleum Potential, Thermal Maturity and the Oil Window of Oil Shales and Coals in Cenozoic Rift Basins, Central and Northern Thailand

Petersen

Foopatthanakamol

Ratanasthien

2006

Journal of Petroleum Geology

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Oil shales and coals occur in Cenozoic rift basins in central and northern Thailand. Thermally immature outcrops of these rocks may constitute analogues for source rocks which have generated oil in several of these rift basins. A total of 56 oil shale and coal samples were collected from eight different basins and analysed in detail in this study. The samples were analysed for their content of total organic carbon (TOC) and elemental composition. Source rock quality was determined by Rock‐Eval pyrolysis. Reflected light microscopy was used to analyse the organic matter (maceral) composition of the rocks, and the thermal maturity was determined by vitrinite reflectance (VR) measurements. In addition to the 56 samples, VR measurements were carried out in three wells from two oil‐producing basins and VR gradients were constructed. Rock‐Eval screening data from one of the wells is also presented. The oil shales were deposited in freshwater (to brackish) lakes with a high preservation potential (TOC contents up to 44.18 wt%). They contain abundant lamalginite and principally algal‐derived fluorescing amorphous organic matter followed by liptodetrinite and telalginite (Botryococcus‐type). Huminite may be present in subordinate amounts. The coals are completely dominated by huminite and were formed in freshwater mires. VR values from 0.38 to 0.47%Ro show that the exposed coals are thermally immature. VR values from the associated oil shales are suppressed by 0.11 to 0.28%Ro. The oil shales have H/C ratios >1.43, and Hydrogen Index (HI) values are generally >400 mg HC/g TOC and may reach 704 mg HC/ gTOC. In general, the coals have H/C ratios between about 0.80 and 0.90, and the HI values vary considerably from approximately 50 to 300 mg HC/gTOC. The HImax of the coals, which represent the true source rock potential, range from ∼160 to 310 mg HC/g TOC indicating a potential for oil/gas and oil generation. The steep VR curves from the oil‐producing basins reflect high geothermal gradients of ∼62°C/km and ∼92°C/km. The depth to the top oil window for the oil shales at a VR of ∼0.70%Ro is determined to be between ∼1100 m and 1800 m depending on the geothermal gradient. The kerogen composition of the oil shales and the high geothermal gradients result in narrow oil windows, possibly spanning only ∼300 to 400 m in the warmest basins. The effective oil window of the coals is estimated to start from ∼0.82 to 0.98%Ro and burial depths of ∼1300 to 1400 m (∼92°C/km) and ∼2100 to 2300 m (∼62°C/km) are necessary for efficient oil expulsion to occur.

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Hydrocarbon potential of the Meso-Cenozoic Turkana Depression, northern Kenya. II. Source rocks: quality, maturation, depositional environments and structural control

Cited by 29 publications

References 18 publications

A 17-My-old whale constrains onset of uplift and climate change in east Africa

A 17-My-old whale constrains onset of uplift and climate change in east Africa

Stratigraphy, sedimentology and diagenetic evolution of the Lapur Sandstone in northern Kenya: Implications for oil exploration of the Meso-Cenozoic Turkana depression

Petroleum Potential, Thermal Maturity and the Oil Window of Oil Shales and Coals in Cenozoic Rift Basins, Central and Northern Thailand

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