Paleoenvironmental and tectonic evolution of the Salt Range Formation (Salt Range, Western Himalayas, Pakistan): Inference from geochemical characteristics

Abstract

The Salt Range Formation (SRF) of the western Himalaya in Pakistan provides key information about the late Neoproterozoic (terminal Ediacaran) period, offering clues for understanding the paleoclimate, origin, and tectonic evolution of the northwestern Indian margin, that has not been thoroughly studied. This study integrates field observations and geochemical analyses from six representative stratigraphic sections across the Salt Range, Pakistan. The sandstones of the SRF are compositionally immature, indicated by their SiO₂ and Al₂O₃ contents, ranging from 44.36 to 61.35 wt.% (average 53.75 wt.%) and 11.7–19.42 wt.% (average 14.46 wt.%), respectively. The Cr/Th ratios (range 3.09–25.52; average 7.02) suggests that the provenance is dominantly influenced by felsic to intermediate continental rocks, with a minor mafic component and limited sedimentary recycling. Weathering indices, including PIA (46.13–98.14 average 78.73) and CIA (45.61–75.89, average 60.24), indicate moderate chemical weathering under semiarid climatic conditions, consistent with evaporite deposition in arid to semiarid environments. The provenance data suggest that the source terrains were relatively proximal, indicating sedimentation in an active tectonic setting. Tectonic reconstructions point to deposition along an evolving active continental margin, which progressively transitioned toward continental collision. This finding sharply contrasts with the traditionally held view of a terminal-Ediacaran passive margin along the northwestern margin of the Indian Plate. Collectively, these finding provide significant new constraints on sediment dispersal, paleoclimate evolution, and tectonic reorganization in northern Gondwana during this pivotal interval in Earth's history.