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

Abstract

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.

Petrography and geochemistry of the Middle Jurassic Fort Member Sandstone, Jaisalmer Formation, Western India: Implications for weathering, provenance, and tectonic setting

“…The geochemical signatures of clastic sediments are generally utilized to infer their source rocks (Absar, Raza, Roy, Naqvi, & Roy, 2009; Armstrong‐Altrin et al, 2013; Ghaznavi, Khan, Quasim, & Ahmad, 2018; Khan et al, 2020). Due to low solubility, Ti and Zr act as immobile elements during weathering, transportation, and diagenesis (Absar & Sreenivas, 2015; Ayers & Watson, 1993).…”

“…21.2) suggests a felsic source composition. Furthermore, owing to different concentration in felsic and mafic rocks, some immobile trace element ratios such as La/Sc, Th/Sc, Zr/Sc, Cr/Zr, Th/Cr, and La/Th are widely used as provenance tracers (Absar, 2021; Cullers, 2000; Cullers, Basu, & Suttner, 1988; Khan et al, 2020; Taylor & McLennan, 1985). The low Cr/Th (1.66–5.65, avg.…”

“…From the above discussions, it is evident that Jaisalmer Basin was opened as a rift basin and can be further verified from the composition of clastic rocks. It is well known that major and trace element compositions of clastic rocks, are useful indicators of tectonic setting of sedimentary basins (Bhatia, 1985; Khan et al, 2020; Roser & Korsch, 1986). Thus, the major element discriminant plots, including the Al 2 O 3 /SiO 2 versus Fe 2 O 3 + MgO (Figure S1A, Bhatia, 1983), SiO 2 versus K 2 O/Na 2 O (Figure S1B), and SiO 2 /Al 2 O 3 versus K 2 O/Na 2 O (Figure S1C) diagrams (Maynard, Valloni, & Yu, 1982; Roser & Korsch, 1986), were employed for the evaluation of tectonic settings, the tectonic discriminant diagrams show a passive margin setting for the FMS.…”

“…As a result, the geochemistry of these rocks helps in determining provenance in terms of the evolution of continental crust (Condie, 1993; McLennan, 2001), palaeoweathering conditions in the source region (Fedo, Nesbitt, & Young, 1995; Harnois, 1988; Nesbitt & Young, 1984) and tectonic setting of the basin (Bhatia & Crook, 1986; Roser & Korsch, 1986; Verma & Armstrong‐Altrin, 2013, 2016). Furthermore, the petrography of the sandstone, when combined with the geochemistry, reveals more on source rock characteristics as well as the tectonic setting (e.g., Bhatia & Crook, 1986; Khan, Quasim, Amir, & Ahmad, 2020; Roser & Korsch, 1986).…”

Geochemical characteristics and the significance of two major coal‐bearing strata claystones from the Datong Coalfield (North China)

“…Palaeosedimentary environmental conditions (e.g., palaeosalinity and redox condition) differently affect the geochemical characteristics of sediments (Hong et al, 2017; Khan, Quasim, Amir, & Ahmad, 2020). This study uses the distribution of trace elements and differences in their ratios to infer the sedimentary environmental conditions under which the two types of claystones (SK‐claystone and tonstein) were formed.…”