The Dauki fault in northeast India: Through remote sensing

Dauki fault extends roughly E-W along the southern margin of Meghalaya plateau. Using remote sensingstract: techniques followed by critical field checks, the author traced Dauki fault from Dauki towards east upto Leike over a length of 170 km. This fault is a single fault dipping towards south (normal fault). In the footwall block close to the fault trace, the older rocks such as Disang shale (Eocene) and the massive thick-bedded sandstones (Barail Group of Eocene-Oligocene) are exposed. In the hanging wall block close to the fault trace, the alternating sandstone shale sequence ('ribbed sequence', a regional marker) belonging to the upper part of Palaeogene is exposed. In the eastern part of hanging wall block, the regional marker abuts against the folded sedimentaries of Surma basin of Neogene along a tectonic contact, which is also co-folded. The N-S trending axial surfaces of folds in Surma basin bend towards NE to ENE while approaching the trace of Dauki fault, indicating dextral strike slip movement along Dauki fault. This inference is further supported by the outcrop pattern of Haflong thrust in the footwall block with the concavity facing west. This thrust belonging to the 'Belt of Schuppen' abruptly terminates against the younger Dauki fault. In the western part of hanging wall block of Dauki fault, the same marker horizon abuts against the non-folded, undeformed, near horizontal sedimentaries of Sylhet trough of Neogene. It is proposed that the Sylhet sediments were deposited in a pull-apart basin in the releasing bend of Dauki fault during the dextral strike slip movement. Thus the net slip for Dauki fault involves a vertical component and a dextral strike slip component, (oblique-slip fault). Sonapur landslide zone is located very close to this fault and the recurring landslide indicates that this fault is still active. The densely populated areas, such as Dacca and Silchar, are located on the loose alluvial sediments not far away from the active Dauki fault.