Controls on the compositional framework and petrogenesis of Early Cretaceous first cycle quartzose sandstone, North Gondwana

Abstract

Recent advances in sedimentary research have shown that quartz sandstones are scarce in the global geologic record and prolonged sediment transport does not automatically produce mineralogically mature sediments. Published data are based mainly on Cambro-Ordovician arenites. This paper discusses the formational controls of early Cretaceous syn-rift quartzose from northern Gondwana based on integrated petrographic, mineralogic, and electrofacies proxies on the Upper Sarir Sandstone Formation, Sirte Basin, Libya. The study aimed to understand the compositional framework and construe the sedimentological processes that produced the quartz-rich sandstones. Acquired samples (n = 40) from three boreholes (N8-97, N7-97, and N4-97) were subjected to petrographic analysis, x-ray diffractometry, and variable pressure scanning electron microscopy with energy dispersive x-ray spectrometry. Qualitative and quantitative datasets indicate that the mean framework composition (Q97F0L3) of the sample is quartz-dominated and primarily detrital, although diagenetic imprints, mostly quartz cementation, quartz overgrowth, and other authigenic precipitates, are present. Evidenced by the predomination of monocrystalline quartz grains (99.10%) over the polycrystalline type (0.90%), the dominance of non-undulatory extinction (72.50%), and noticeable euhedral crystals, the compositional framework of the studied quartzose reflects a predominant plutonic provenance with some metamorphic inputs. The possibility of significant sediment reworking is ruled out based on short to moderate transport distance (~100 km) interpreted from the interplay of textural parameters, depositional model, and paleogeography. A humid paleoclimate alongside its associated rigorous chemical weathering is constrained as the dominant control in the formation of the Upper Sarir quartzose sandstone from a dominant craton interior provenance. These conditions probably produced other early Cretaceous arenitic sandstones in other reaches of North Gondwanaland.