Mineralogical and chemical characteristics of Bajocian-Bathonian shales, G. Al-Maghara, North Sinai, Egypt: Climatic and environmental significance.

Ghandour, Ibrahim M.; Masuda, Harue; Maejima, Wataru

doi:10.2343/geochemj.37.87

Cited by 31 publications

(3 citation statements)

References 41 publications

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“…Periods with less carbonate flux and deposition were coupled to increased terrigenous input (high oxygen indices together with higher quartz and clay contents, here kaolinite). In general, kaolinite is associated with very low energy depositional environments (Chamley 1989;Hallam et al 1991), but can also be formed diagenetically (Ghandour et al 2003). Kaolinite is the predominant clay mineral in the Shiranish Formation and is at its lowest concentration in unit B (Fig.…”

Section: Mineralogy Of the Shiranish Formation And Early Diagenesismentioning

confidence: 99%

Sedimentology, geochemistry and hydrocarbon potential of the Late Cretaceous Shiranish Formation in the Euphrates Graben (Syria)

Ismail

Schulz

Wilkes

et al. 2010

PGC

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The Shiranish Formation consists of mudstones and wackestones in the central Euphrates Graben which are rich in organic carbon. Here the Shiranish Formation is more than 700 m thick with a minor increase in organic maturity with depth. The Shiranish Formation sediments are characterized by a continuously increasing hydrogen index to the top whereas the oxygen index is markedly lower in the Upper Shiranish Formation (USF). The Lower Shiranish Formation (LSF) is characterized by lower hydrogen indices and higher oxygen indices relative to the USF. These organic geochemical characteristics enable a rough subdivision into a lower and an upper part of the Shiranish Formation. Furthermore, mineralogical results enable a subdivision of the USF into two parts (USF-1, lower part; USF-2, upper part) each with individual mineralogical signatures due to a modified depositional environment and differing diagenetic history. The LSF resembles mineralogically the USF-2. Ankerite, together with higher pyrite contents in the LSF and USF-2, reflect similar diagenetic pathways which were controlled by higher clay contents. During early diagenesis, a traceable conversion of metabolizable organic matter led to mineral assemblages due to significant methanogenesis. Intervals in the USF with total organic carbon (TOC) contents up to around 4% and hydrogen indexes up to 500 mg HC/g TOC indicate the presence of very good potential source rock intervals for oil generation. Additionally, intervals of the LSF also contain gas-prone organic material. Bulk kinetic investigations show a broad activation energy of the LSF and a narrow activation energy pattern for the USF for hydrocarbon generation. Furthermore, the predicted petroleum formation temperatures are 1368C for the USF and 1448C for the LSF, respectively. This corresponds to c. 630 m difference in burial depth for petroleum formation. These differences in activation energies and corresponding depth to reach oil window maturity are controlled by facies, and less by maturity.

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Section: Mineralogy Of the Shiranish Formation And Early Diagenesismentioning

confidence: 99%

Sedimentology, geochemistry and hydrocarbon potential of the Late Cretaceous Shiranish Formation in the Euphrates Graben (Syria)

Ismail

Schulz

Wilkes

et al. 2010

PGC

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“…The presence of chlorite in the sandstones indicates a cold or possibly arid climate, as they are destroyed in warm and humid climates (Einsele, 1992). Illites are formed by mechanical weathering in high relief areas with cold and /or dry climate (Ghandour et al, 2003). Illite and chlorite are most abundant in ancient sediments than modern sediments (Grim, 1951).…”

Section: Implications On Palaeoclimatementioning

confidence: 99%

Unveiling the Presence of Limestone, Chert and Fossil Leaves in Disang Group Exposed in the North- easternmost Part of Assam-Arakan Basin, India: An Integrated Study on Lithology, Petrography, and Clay Mineralogy

Kachari,

Taye,

Chutia

2023

Preprint

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Disang Group of the north-easternmost part of Assam-Arakan Basin is predominantly made up of shales with sandstone and siltstone. The current study attempts to investigate its provenance, tectonic setting, paleoclimate, and diagenetic history using integrated approach of field investigation, petrography, and clay mineralogy. It has revealed for the first time that the Disang Group of the present study area also comprises fossil leaves, limestone, and chert in addition to the already reported shales, sandstone, and siltstone. Petrographic analysis of sandstones has shown that they are fine to medium-grained, poorly to moderately sorted, with sub-angular to sub-rounded grains, and are classified as quartz arenite, quartz wacke, arkosic wacke, and lithic greywacke. The studied rocks were derived mostly from plutonic as well as metamorphic source rocks in a variable climatic condition from arid to tropical humid, and the source areas were of low to moderate relief. Tectonic discrimination diagrams have suggested craton interior and recycled orogen provenance. The occurrence of clay minerals like chlorite, illite, and smectite-montmorillonite has implied weathering in a cold, arid climate. The diagenetic processes involved were of early to late stages. The presence of chert beds indicates deep marine and that of carbonates indicate shallow marine environment, whereas the fossil leaves are indicative of their deposition in a much shallower part of the basin. Thus, there must have been a change in environment from deep marine to shallow marine during the deposition of the Disang Group under study.

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“…Kaolinite is formed under tropical to subtropical humid climatic conditions (Hallam, Grose, & Ruffell, 1991). Furthermore, kaolinite is also formed by a diagenetic process due to the circulation of acidic solutions (Ghandour, Harue, & Wataru, 2003). The presence of illite and kaolinite suggests chemical weathering of feldspar and mica.…”

Section: Source Area Weathering and Paleoclimatementioning

confidence: 99%

Provenance, tectonic setting, and source area weathering of Middle Jurassic siliciclastic rocks of Chari Formation, Jumara Dome, Kachchh Basin, Western India: Sedimentological, mineralogical, and geochemical constraints

et al. 2019

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Kachchh Basin is well known for its Jurassic sediments and hydrocarbon prospects, but geochemically, these sediments remained less explored. Here, we present petrography, mineralogy, and geochemistry of the Middle Jurassic sandstone and shale of the Chari Formation exposed at Jumara Dome, Kachchh Basin, to understand their provenance, tectonic setting, source area weathering, and paleoclimate. Petrographic analysis shows that the sandstone consists of abundant quartz, feldspar (K-feldspar and plagioclase), mica (muscovite and biotite), and lithic fragments. The X-ray diffraction analysis of both sandstone and shale reveals the presence of abundant quartz, and lesser amount of kaolinite, illite, and chlorite. The presence of these clay minerals was also attested by scanning electron microscope analysis. Based on framework composition and geochemistry, the sandstone is classified as arkose to subarkose and shale as graywackes. Detrital modes and geochemical data suggest the derivation of these clastic rocks from a felsic source, partially influenced by sediment recycling and deposited in a passive margin setting in a rifted basin. Values of weathering indices including chemical index of alteration, plagioclase index of alteration, chemical index of weathering, and index of compositional variability indicate that the rocks of Jumara Dome are mature and the source area has undergone a moderate to high degree of chemical weathering under warm and humid climatic conditions. The petrography, bulk mineralogy, scanning electron microscope analysis, and geochemical composition in conjunction with paleocurrent data affirm the supply of detritus for Jumara Dome from the Aravalli Craton situated to the east and northeast and Nagar Parkar Massif situated to the north and northwest of the basin. This study endorses the formation of Transgondwanan seaway route during the Late Oxfordian, which caused a marine transgression onto the land.

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Mineralogical and chemical characteristics of Bajocian-Bathonian shales, G. Al-Maghara, North Sinai, Egypt: Climatic and environmental significance.

Cited by 31 publications

References 41 publications

Sedimentology, geochemistry and hydrocarbon potential of the Late Cretaceous Shiranish Formation in the Euphrates Graben (Syria)

Sedimentology, geochemistry and hydrocarbon potential of the Late Cretaceous Shiranish Formation in the Euphrates Graben (Syria)

Unveiling the Presence of Limestone, Chert and Fossil Leaves in Disang Group Exposed in the North- easternmost Part of Assam-Arakan Basin, India: An Integrated Study on Lithology, Petrography, and Clay Mineralogy

Provenance, tectonic setting, and source area weathering of Middle Jurassic siliciclastic rocks of Chari Formation, Jumara Dome, Kachchh Basin, Western India: Sedimentological, mineralogical, and geochemical constraints

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