Quaternary surface development in the frontal Mikir massif, NE India: A possible key to understand the tectonic controls and geotechnical significance

• Quaternary mapping in SE frontal part of the Mikir massif brought out three surfaces. • Naga Thrust and its subsidiary splay affect the deposition of these alluvial surfaces. • Soils of S2 surface provide best foundation strata. Quaternary geological mapping has been carried out in the south-eastern frontal part of the Mikir massif in northeastern India. Geomorphological and surface geological studies have led to the delineation of three Quaternary surfaces viz., S1, S2, and S3, in the order of decreasing antiquity. A preliminary assessment of the prevailing active tectonics has been achieved through seismotectonic study by analyzing seismic events for the period 1988–2013. Episodic reactivation of the Dhansiri Fault, Barpathar Fault and Kaliyani Shear Zone is evident by the presence of epicentral clusters along these faults. Field evidence of active tectonics, such as steep scarp faces, damming effects, and pressure ridges, also confirms the prevailing neotectonics in the area. The proposed tectonic model for the deposition of Quaternary surfaces shows that the Naga Thrust and its subsidiary splays (Barpathar Fault) control the present-day disposition of these surfaces. Geotechnical evaluation of soil samples shows that soils of S1 surface are having low shear strength, high liquid limit, and high compressibility index. Whereas samples from the S2 surface show low liquid limit, low compressibility index, high cohesiveness, and higher angle of internal friction. Hence, these S2 surfaces provide the best foundation strata for the construction of any civil engineering structures in the area.