Impact of Paleosalinity, Paleoredox, Paleoproductivity/Preservation on the Organic Matter Enrichment in Black Shales from Triassic Turbidites of Semanggol Basin, Peninsular Malaysia

Abstract

Turbidite-associated black shale of the Semanggol Formation is extensively distributed in the northwestern part of the Western Belt, Peninsular Malaysia. The black shale occurs as a dark grey to black and thick to medium-bedded deposit. It represents the distal part of submarine fan system (outer-fan) overlying interbedded sandstone to shale facies of the mid-fan and conglomeratic pebbly sandstone facies of the inner-fan. Field observations and its widespread occurrence have resulted in the black shale being considered as a potential analog for a source rock in offshore Peninsular Malaysia. The present study includes detailed mineralogical (XRD, SEM, and EDX analysis), inorganic geochemical (major oxides, trace elements TEs, and rare earth elements REEs), and Rock-Eval pyrolysis analyses of the black shale samples, collected from the Gunung Semanggol, Bukit Merah, and Nami areas in northwestern Peninsular Malaysia. The primary focus of this study is to investigate the provenance, paleoredox conditions, paleoclimate, sedimentary rate, paleoproductivity, and upwelling system that would be helpful to understanding the role of these parameters in the enrichment of organic matter (OM) in the black shale. The Rock-Eval analysis shows that the black shale of the Semanggol Formation comprises type-III kerogens, which suggests organic input from a terrestrial source. The black shale also contains mature to postmature organic matter. Based on the mineralogical analysis, the mineral composition of the black shale comprises illite and kaolinite, with abundant traces of quartz and feldspar as well as few traces of titanium and zircon. Inorganic geochemical data designate black shale deposition in a passive margin setting that has experienced moderate to strong weathering, semi-arid to hot arid climate, and moderate sedimentation rate. Ratios of Ni/Co, U/Th, and V/(V+Ni) along with slightly negative to positive Ce* anomalies and UEF-MoEF cross-plot unanimously indicate anoxic/dysoxic water conditions that are suitable for organic matter preservation. Geochemical proxies related to modern upwelling settings (i.e., Cd/Mo, Co vs. Mn) show that the deep marine black shale was strongly influenced by persistent upwelling, a first-order controlling factor for organic matter enrichment in the distal part (outer fan of the submarine fan system) of the Semanggol Basin. However, productivity-controlled upwelling and a high sedimentary rate, as well as high-productivity in oxygen-depleted settings without strong anoxic conditions, has played an essential role in the accumulation of organic matter.

Determining of an oceanic anoxic event and paleoenvironmental conditions of the Gulneri Formation Kirkuk Oilfield, Northern Iraq

“…According to Table 6 and Figures 6 and 7, the vertical distribution of carbon isotope in the Gulneri Formation values is uneven, as it will be seen that the values are identical in the Gulneri Formation while abrupt shift existed in the lower part of the overlying Kometan Formation. Low oxygen conditions (anoxic/dysoxic) in combination with upwelling-controlled paleoproductivity (organic carbon fluxes) which is generally high as mentioned previously using P/Ti, P/Al, and Barium have major and favorable controls over organic matter preservation and enrichment (Al-Sagri, 2015; Sajid et al, 2020). The data of the present study are consistent with the paleontological evidence of anoxic deficiency recorded by Abdo (2013) along with the presence of shale bed and pyrite as well as the absence of benthic foraminifera and the widespread (Heterohelicid) and calcispheres, which indicates anoxic events (Kuhnt et al, 1986).…”

“…The ratio (Sr / Ba) can be used to evaluate the changes in the degree of salinity of the water column and the corresponding climatic conditions and is important for estimating the degree of ancient salinity of limestone rocks(Zheng and Liu, 1999). If the ratio is greater than 1, it represents the saline water environment and the range between 0.6 and 1 points to the brackish water environment, but if it is less than (0.6) it represents the fresh water environment(Zhen et al, 2020;Sajid et al, 2020). The values of the studied samples have ranged from 1.215 to 2.590 with an average of 2.033 (Table…”

Mineralogy and Geochemistry of the Paleocene–Eocene Palana Formation in Western Rajasthan, India: Insights for Sedimentary Paleoenvironmental Conditions and Volcanic Activity

“…In addition, upwelling processes affect the periodic influx of large masses of nutrients into the photic zone, and bioproductivity is closely related to nutrient supply in the sea [74,75].…”

“…In this case, upwelling zones show low abundances of both Co and Mn elements, while the contents of Co and Mn are relatively high in restricted basins [77]. This may be attributed to an insufficient fluvial input supply in regions affected by upwelling systems [77], where the Co and Mn enrichment in marine sediments is controlled by detrital input and authigenic enrichment [80] In addition, upwelling processes affect the periodic influx of large masses of nutrients into the photic zone, and bioproductivity is closely related to nutrient supply in the sea [74,75].…”

Sediment Mineralogy and Geochemistry and Their Implications for the Accumulation of Organic Matter in Gashydrate Bearing Zone of Shenhu, South China Sea

“…In most hydrate-bearing areas, the Total Organic Carbon (TOC) content in sediments exceeds 1 wt% [35][36][37]. It is typically challenging for natural gas hydrates to form in environments where the TOC content in sediments is less than 0.5 wt% [38].…”