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Active faulting and deformation of quaternary landform Sub-Himalaya, India

Kothyari G. C., Pant P. D., Joshi M., Luirei K., Malik J. N.

Geochronometria

2010

Vol. 37

63-71

Landforms developed across terrain defining boundary the Main Boundary Thrust (MBT) have imprints of recent tectonic activity. Depositional landforms such as colluvial fan bear signatures of later phases of tectonic activity in the form of faulting of colluvial fan deposits and development of fault scarps. Tectonic geomorphology applied to the MBT zone suggests recent subsurface activity along the MBT and its splay thrusts. Present day tectonic activity of MBT is indicated by ground creeping, thrusting of Lower Siwalik rocks over recent colluvial fan deposit, aligning of series of lakes along splay faults and laterally along a fault, deflected streams, fault scarps and waterfalls. In the present paper we are addressing the tectonic situation in the foothill region of southeastern Kumaun Sub-Himalaya, India based on detailed field work carried out in the region which brought forward some outstanding morphotectonic evidence of neotectonic activities in the MBT zone.

Terraces of the Bystrzyca river valley, Middle Sudetes, and their deformation along the Sudetic Marginal Fault

Krzyszkowski D., Biernat J.

Geologia Sudetica

1998

Vol. 31, nr 2

241-258

There are three stages in the evolution of the Bystrzyca river valley, dated to the Pliocene, the Early to late Middle Pleistocene, and the late Middle Pleistocene to recent. The Pliocene landscape was flat to hilly, with a weakly developed margin of the mountains. The valleys were shallow and wide, most probably with sinuous rivers, and are today represented by the 100-120 m high terrace. The scarp of the Sudetic Marginal Fault and the mountain landscape with deeply incised valleys were not formed until the Early Pleistocene tectonic phase, during which the uplift was about 60-70 m. The late Middle to Late Pleistocene stage of the valley development may be subdivided into several sub-stages, during each of which, one of three morphogenetic factors, namely fluvial activity, glacial erosion and sedimentation and tectonic uplift, prevailed. Five fluvial terraces have been found, one formed before glaciation and the other four during the post-glacial times. The valley was glaciated only once, during the early Saalian (Odranian) stage. The total postglacial uplift was about 40-50 m and fluvial activity that time was influenced by varying uplift rates. At first, erosion prevailed due to strong glacio-isostatic uplift. Then, it diminished quickly and was replaced by more localised tectonic uplift, which decreased with time. As a result, fluvial activity in the mountains and in the foreland became different, as is highlighted by the increased thickness of fluvial deposits in the foremoutain zone, the rapid change of terrace height, formation of a distinct, 25-30 m high, fault scarp along the Sudetic Marginal Fault, and the increased erodibility along the fault lines.