Geology of Kerabari - Rajarani Area with Special Emphasis on Geological Structures and Strain Analysis of the Main Central Thrust, the Lesser Himalayan Sequence, and Higher Himalayan Crystalline, Eastern Nepal

Abstract

The geological study was carried out in the Kerabari - Rajarani area that covers south-eastern part of Dhankuta district and northern part of Morang district of eastern Nepal. The study was mainly focused on the lithostratigraphy, structural analysis, and strain analysis of the Main Central Thrust (MCT) and its hanging and foot walls by integrating field study and laboratory investigation. Geologically, the study area can be divided into the Sub-Himalaya, the Lesser Himalayan Sequence, and the Higher Himalayan Crystalline, respectively. The Lesser Himalayan Sequence is divided into the Bhedetar Group and the Dada Bajar Group, separated by the Chimra Thrust. The Bhedetar Group consists of the Chiuribas Formation, while the Dada Bajar Group comprises of the Ukhudanda Formation, the Mulghat Formation, the Okhre Formation, and the Patigau Formation, respectively. The key geological structures include the Main Central Thrust, the Chimra Thrust, the Main Boundary Thrust, and the Main Frontal Thrust, from north to south, respectively. The microstructural analysis of the quartz grains from the Lesser Himalayan Sequence and the Higher Himalayan Crystalline on either side of the MCT provide evidence of multiple phases of deformation. Likewise, the strain analysis of quartz grains from the MCT characterizes the MCT as the stretching fault thrust.