Petrology and geochemistry of sandstone from Lower Cretaceous Kikhla Formation, NW Libya: Implications for provenance and depositional setting.

Petrologia e geoquímica de arenitos da Formação Kikhla (Cretáceo Inferior), Noroeste da Líbya: implicações para proveniência e ambiente deposicional

Abstract

This study aims to determine and investigate the provenance of the source rocks and the depositional setting of the Kikhla Formation, northwestern Libya. It is mainly composed of mature quartzitic sandstone alternating with conglomerate and clay. The study proved that the sandstone is yellow-white in color and commonly carries quartz granular and small fragments of silicified wood. The environmental deposition is under differing fluvial conditions and by a large braided river. Texturally, the Kikhla sandstone is poorly cemented, coarse to very coarse grained and strongly unimodal and is classified as litharenite and subarkose by the modal composition, which is supported by geochemical studies. According to petrography and geochemistry, the Kikhla sandstone was deposited in a passive continental margin basin, mainly from granitic sources. On the basis of major elements ratios, and petrographic interpretation, the source rocks are most likely recognized as Proterozoic granites that were exposed via rifting. The CIA values (73.28-93.97) indicate a high degree of chemical weathering, which could be attributed to the arid climate conditions in the source area and mainly controlled by the source-rock provenance, hydraulic sorting during transport and deposition, diagenesis and depositional environment. According to chemical investigations, sandstone exhibits significant concentrations of SiO2, Na2O> K2O, and Fe2O3, which is compatible with the modal data.