Polygonal Cracks in Bhuban Sandstones of Surma Basin, North East India

A crack system found developed on the surface of sandstone belonging to Bhuban Formation of Surma Group near Vanchengpui village in Mizoram. These polygonal crack system with circular or disc shape cracks overlapping one another are the conspicuous characteristic feature representing their process of formation. The crack system is developed on the domal surface of the exposed bed-rock and are limited to the top thin layer. The thickness of crack bearing layer varies from 3 to 13 cm and the cracks maintain perpendicular relationship with the slope surfaces. Field investigations and analysis of the crack present in the area reveals that the crack system developed in the sandstone are due to weathering processes coupled with compressive stresses.