Petrography and geochemical characterization of the Lower Cretaceous deposits of the Vandam zone (southern slope of the Greater Caucasus, Azerbaijan): implications for maturity, paleoclimate and paleoweathering

This study presents a detailed petrographic and geochemical analysis of Lower Cretaceous deposits of the southern slope of the Greater Caucasus (Vandam zone).By analysing the siliciclastic rocks of the Kepuch and Gyrkhbulag formations, this research aims to assess the compositional maturity of the sediments and to reconstruct the paleoenvironmental conditions, including paleoclimate paleoweathering processes.Petrographic analysis reveals that the sediments were poorly sorted and made of angular to subangular grains, implying deposition relatively close to the source area.The mineralogical maturity of the sediments was assessed through the Index of Compositional Variability (ICV), while weathering intensities were evaluated using the Chemical Index of Alteration (CIA), Chemical Index of weathering (CIW), and the Plagioclase Index of Alteration (PIA).Based on geochemical classification, the sediments were classified as litharenites and wackes.The Al2O3-(CaO*+Na2O)-K2O (A-CN-K) diagram, along with weathering indices, suggest low to moderate weathering in the source area, consisted with the arid-to-semi-arid climate of the studied area.On the other hand, the Index of Compositional Variability (ICV), ranging from 0.9 to 1.59, indicates low compositional and mineralogical maturity.In addition, the discriminant diagrams of Zr/Sc-Th/Sc and Al2O3-Zr-TiO2 suggest that the sediments were primarily first-cycle deposits derived from igneous rocks, with minimal evidence of obvious recycling and hydraulic sorting.