Burial History of Tipam Sandstone of Miocene Age, Upper Assam, India: Evidence from Petrography and Clay Mineralogy

Petrography, X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM) analyses were performed to investigate the mineralogical and diagenetic characteristics of the Tipam sandstone of the Upper Assam Basin, Northeast India. The studied sandstones are medium to fine-grained, sub-angular to sub-rounded with moderate sorting and belong to the sub-lithic arenite category. The sediments were mostly derived from granitic, metamorphic and recycled orogenic sources as well. The diagenetic features of the Tipam sandstone include compaction, cementation, authigenesis, replacement and dissolution. All these diagenetic features can be linked to progressive change in the diagenetic regimes, i.e., eogenesis, mesogenesis and telogenesis. Illite, kaolinite, chlorite, and montmorillonite are the dominant clay minerals present in these sandstones. The presence of all these clay minerals points to a diverse provenance, which is also supported by the petrographic study. The present petrographic and clay mineralogical study indicates the wide variability of porosity and permeability within the Tipam sandstone, highlighting the critical role of diagenesis in controlling reservoir quality and heterogeneity.