Comparison of stratigraphic situation and genesis of paleo soil bauxite-laterite basal horizon in Shemshak formation of Central Alborz, Sections (Glandrood - Lavij - Vaz)

This study analyzes the geographic distribution of the Shemshak Formation in the Central Alborz, comparing stratigraphic sequences, lithology, tectonic influences, and depositional environments across the Glendrow, Lovej, and Vaz sections. The goal is to understand the sedimentary sequences and geological processes of the Triassic-Jurassic period. Sampling was carried out at key sections, with locations recorded via GPS. Mineralogical and petrological analyses were performed on 100 thin sections and polished samples using transmitted light microscopy and petrographic reflection. additionally, ten samples from the bauxite-laterite zone and ten from the base of the Shemshak Formation’s laterite horizon were analyzed to identify climatological influences and tectonic events, using XRF and XRD at the Geological Organization of Iran, Binalud Mines. The presence of a bauxite-laterite horizon is crucial for reconstructing regional geology, with findings indicating that the Elika Formation underlies the Shemshak, deposited during the Early Cimmerian orogenic phase. The development of the Shemshak Formation occurred within a foreland basin transitioning into a back-arc basin, comprising diverse sedimentary rocks such as quartzite conglomerates, quartz arenites, sublitharenites, litharenites, mudstones, and claystones, often with coal interbeds. Palynological and paleosol data suggest a depositional environment from continental to coastal-deltaic. Tectonic and climatic influences, evidenced by discontinuities and east-west Glenrod faults, played a significant role in shaping the formation’s sedimentary environment.