Abstract This paper is based on the field investigations conducted in the West Garo Hills of northeastern India. The work presents a brief report on the Neolithic manufacturing sites of the West Garo Hills. It addresses the various issues of lithic sequence, typological classifications, lithic technology, settlement pattern and site distribution pattern of the known sites and newly discovered sites in the West Garo Hills. Large clusters of Neolithic manufacturing sites have been located on the hilltops and hillslopes close to present-day rivers, streams, natural springs, water channels and modern Garo community habitats. Dolerite raw materials were mostly preferred for fashioning the artefacts, and manufacturing units are found close to the dyke basalt rock sources. Findings of habitation deposits or pottery are very sparse; however, evidence of plant and animal domestication, burial, bone tools, and metal use pose new hypotheses on their use owing to poor preservation. The Palaeolithic evidence and the region's transition to early farming cultures remain vague.

Abstract: The Cambrian Nongpoh granitoids, intrusive into the Precambrian gneissic complex and metasediments of the Shillong Group, represent a major phase of granitic magmatism in the Shillong Plateau. The Nongpoh granitoids comprise diorite, granodiorite, porphyritic and grey granites. Porphyritic granite is the dominant lithology exposed in the Nongpoh granitoids, and contains three types of enclaves, viz. xenoliths of gneissic rocks, dark grey porphyry and biotite-rich microgranular enclaves. The mafic magmatic enclaves (MMEs) of various dimensions and shapes, including rounded, ellipsoidal, rectangular, angular to subangular, and stretched bodies, were produced by evolving nature and contrasting kinematics of interacting felsic and mafic magmas. The biotite-rich enclaves are due to the injection of syn-magmatic mafic dykes in felsic magma. The various textural assemblages and sub-linear variations between silica and major oxides, chemical mixing and element diffusion suggest that multistage magma hybridization was the key process during the evolution of the Nongpoh granitoids. The 501 Ma age obtained by chemical (U–Th–Pb) dating of monazite in MME ascertained the age of the magma hybridization event in the Nongpoh granitoids, which is equivalent to the igneous activity at 500 Ma during the amalgamation of Eastern Gondwana.