Lower Cretaceous sediments of the north-western Indian Plate margin deposited in the Barmer, Cambay, Narmada, Kachchh and Jaisalmer basins of the West Indian Rift System (WIRS) and in the Lower and Middle Indus Basins (LMIB) are dominated by mineralogically mature quartz arenites. Such an extreme quartz-rich detrital mineralogy is surprising given that the local highs flanking the WIRS and LMIB comprise a variety of Precambrian basement terrains including the Malani Igneous Suite, Delhi Supergroup, Aravalli Belt and the Bundelkhand Craton with a varied igneous and metamorphic mineralogy. Most published studies assume that the overall provenance is the Aravalli Mountain Range although there is little palaeogeographical or mineralogical evidence to support this. Presented here are new mineralogical data for the fluvial Ghaggar-Hakra Formation of the Barmer Basin and a compilation of published detrital mineralogies of the sandstones across the WIRS and LMIB to better constrain their provenance.
For the Lower Cretaceous Ghaggar-Hakra Formation 99 thin sections from both outcrop and cores were point-counted for grain size, Trask sorting and detrital and authigenic mineral composition. All the samples are quartz-arenites or sub-lithic arenites with little or no detrital feldspar preserved in thin section, consistent with published data for the WIRS. Most detrital grains are well rounded monocrystalline quartz. Early diagenesis in these sandstones comprises dolomites and other altered carbonate cements which are interpreted to be pedogenic in origin and are commonly grain replacive. This together with the presence of common oversized pores suggests that the sandstones were more feldspathic at deposition, but have lost most detrital feldspar through grain dissolution processes. Recalculated detrital mineralogies indicates that the sandstones were originally quartz-arenites or sub-arkoses.
Such mineralogies remain more mature than would be expected from first-cycle sandstones derived from granitic and metamorphic basement, even allowing for in-situ early diagenesis and weathering in the Early Cretaceous Epoch. Our developing inference is that much of the Lower Cretaceous alluvium in the WIRS and LMIB originates from erosion of late-Cambrian and Lower Palaeozoic sandstones which were exposed across the north-western Indian Plate margin throughout the Cretaceous, with only minor contributions from the basement highs.
Beaumont, H., Burley, S., & Gould, T. (2020, December). Provenance and origin of Lower Cretaceous quartz arenites from the northern Indian Plate: Tropical weathering or a multi-cycled sediment source?. Presented at British Sedimentological Research Group AGM, Virtual