PETROGRAPHY OF LUMSHIWAL SANDSTONE, THANDIANI SECTION, HAZARA BASIN, PAKISTAN: IMPLICATIONS FOR PROVENANCE, DIAGENESIS AND ENVIRONMENT OF DEPOSITION

Abstract

Detailed petrographic studies have been carried out of the Lower Cretaceous Lumshiwal Formation from Thandiani section, Hazara Basin. Petrography of sandstone gives valuable details about its formation, miniature texture, diagenetic highlights, provenance of sediments and their development. The sandstone from Lumshiwal Formation is fundamentally "quartz arenite" having white color. It is exceptionally hard and compact because of the richness and close interlocking of quartz grains. In addition to quartz, the sandstone from Lumshiwal Formation contains feldspars, rock fragments, glauconite, monazite, tourmaline, zircon, muscovite, chert and rarely apatite. The sandstone of the Lumshiwal Formation exhibits mineralogical maturity. It seems to be sub-mature in terms of textural maturity. This is indicated by its moderate degree of sorting. It has mineralogically mature character due to very high modal proportion of quartz as compared to feldspar. The sandstone from Lumshiwal Formation is very much solidified, hard and compact. Different types of cement for example silica, glauconitic cement and ferruginous cement is present in the sandstone unit from Lumshiwal Formation. Shallow marine environment is exhibited by the sandstone unit of the Lumshiwal Formation due to high abundance of quartz and presence of glauconite mineral.