The Precambrian Hazara Formation from Hazara Mountains, Northern Pakistan

Abstract

The late Neoproterozoic Hazara Formation along the Lora Maqsood Road near Haripur, Lesser Himalayas, North Pakistan, is studied for sedimentology, petrography, and major and trace element analysis to determine the paleoenvironment, provenance, paleoweathring intensity, and tectonic settings. The Hazara Formation is characterized by greywacke sandstone, siltstone, shale, argillite, claystone, limestone, and coarsening and finning upward turbidite lithofacies. Based on bedding style, grain size, and sedimentary structures, 11 types of lithofacies were identified within the sequence. The macroscopic studies indicate that the sequence has undergone through slight metamorphism although the texture is altered sedimentary features and bed geometries are well preserved. Compaction seems to affect the part of argillaceous sediments of an enormous thickness of the Hazara Formation to make slate-like appearance which may preferably be called argillites. The same effect is seen on sandstone to make it so hard to name it orthoquartzite. Petrographic analysis of limestone reveals that the limestone is micritic in nature; stylolites and pressure solution structures are also present in the limestone. The petrographic analysis of sandstone categorized it as feldspathic greywacke in the QFR diagram. The quartz content is higher in sandstone and may reach to 70% which indicates a weathered felsic source. The petrographic analysis suggests a continental block provenance with stable craton and an uplifted basement source. The Chemical Index of Alteration and the Chemical Index of Weathering values indicate moderate to high weathering conditions with a warm and moist climate in the source region. A sedimentary-tectonic model based on the geochemical data of sandstone indicates deposition along with active continental margin tectonic settings. The paleocurrent flow analysis indicates that the dominant source region of the sediments of the Hazara Formation was situated south to southeast, which may probably be the central Indian craton, Aravali orogeny, and Bundelkhand craton of southern India.