Deformation of The Basement Gneissic  Complex of The Assam Meghalaya Craton  in and Around Sumer –Nayabunglow Area,  Meghalaya, India

Tapos Kumar Goswami

Volume : III, Issue : III, March - 2014

Deformation of The Basement Gneissic Complex of The Assam Meghalaya Craton in and Around Sumer –Nayabunglow Area, Meghalaya, India

Tapos Kumar Goswami

Abstract :

The Basement Gneissic and Migmatitic Complex of the Assam Meghalaya craton near Sumer and Nayanbunglow area of Meghalaya underwent four phases of deformation. The tight isoclinal F1 folds with S1 axial planar cleavage and L1 fold axis lineation represents the earliest phase of intense compression. The F1 folds exhibits Class 2 and Class 1c geometry and refolded to open asymmetrical F2 folds with S2 axial planar cleavage and L2 fold axis lineations. The F1 and F2 are coaxial and F2 axial planar cleavage of S2 dips to the north. The third phase of deformation is weak and F3 folds with large wavelength and low amplitudes have axial planar cleavage dips to the southwesterly direction. All the three phases of deformation exhibit ductile phases of deformation and fold shapes reflect the competency contrast in the folded layer and the embedding medium. The fourth phase of deformation is ittle and the contarctional and extensional joints with small scale shear zones are ubiquitous.