Geochemical сharacteristics of the Upper Cretaceous еerrigenous сomplex of the northeastern slope of the Lesser Caucasus (Lok-Karabakh Zone): paleoweathering, sedimentary recycling, and paleoclimatic conditions

This study is devoted to the geochemical characteristics of the Upper Cretaceous terrigenous complex of the northeastern slope of the Lesser Caucasus (Lok-Karabakh zone). The Upper Cretaceous deposits of the Lok-Karabakh zone of the Lesser Caucasus are characterized by wide development, forming an almost continuous strip along its northeastern foothills, covering the Shamkir and Murovdag anticlinoriums and significantly expanding in the arch zones of the Gazakh, Agjakend and Khojavend troughs. The aim of this research is to reconstruct the paleoclimatic conditions, assess the degree of weathering, and determine the level of re-sedimentation of sedimentary material, which allows for a more complete understanding of sedimentation and sediment transformation processes during the Late Cretaceous period. Samples were collected from four different outcrops (Tezekend, Agdam, Gadjikend, and Ashygly) in the studied area, and their analysis was carried out using the modern high-precision method of inductively coupled plasma mass spectrometry (ICP-MS), ensuring the high reliability of the obtained data. To evaluate chemical weathering, the following indices were applied: Chemical Index of Alteration (CIA), Chemical Index of Weathering (CIW), and Plagioclase Index of Alteration (PIA), which are widely used in geochemical research as reliable indicators of the transformation of primary silicate minerals into clay minerals. The Al2O3-CaO+Na2O-K2O (A-CN-K) diagram, together with the weathering indices, suggests moderate weathering in the source area, reflecting arid and semi-arid conditions in the studied region, which is further supported by the diagram of Al2O3+K2O+Na2O-SiO2 and Ga/Rb-K2O/Al2O3. The composition of the supplying province, according to the Roser and Korsch discrimination diagram, corresponds to magmatic rocks of basic and intermediate composition. The mineralogical maturity was assessed using the Index of Chemical Variability (ICV), the values of which (ICV > 1) confirm the low degree of maturity of the sedimentary material and the predominance of clay minerals from the smectite group. The analysis of the Zr/Sc - Th/Sc and Al2O3-Zr-TiO2 discrimination diagrams also indicates the predominance of first-cycle detrital material, suggesting the absence of recycling and hydraulic sorting of the sediments. The obtained data provide important grounds for further paleogeographic reconstructions and the evaluation of the evolution of the sedimentary basins of the Lesser Caucasus.