Pradeep K. Goswami

Geomorphic evidences of active faulting in the northwestern Ganga Plain, India: implications for the impact of basement structures

Active faults of the densely forest covered northwestern part of the Ganga Plain have been identified and mapped on the basis of geomorphic signatures as observed in the Digital Terrain Models, remote sensing data and field. The structural limit between the Ganga Plain and Himalaya in the north is defined by the Himalayan Frontal thrust (HFT), which is a direct consequence of the compression resulting from collision of Indian and Eurasian plates and present day principal displacement zone between them. This HFT is offset by dip-slip, oblique-slip and strike-slip faults, extending transversely through the Ganga Basin. Analysis of these faults in conjunction with the available geological and subsurface geophysical data reveals that the development of some of these transverse faults is localized along basement highs of the basin. These faults tear asunder the Himalayan thrust sheets and may have developed during the collision either because of a rheological contrast between the basement highs and adjacent sedimentary fill, or a lateral change in cover thickness across the basement highs, or due to the reactivation of pre-existing basement faults. The continuous pressing and prodding by these basement highs have caused bending of the strata, leading to conspicuous bending of the mountain belt. One of the tear faults has formed as a result of the along-strike propagation of an oblique ramp of the Main Boundary thrust (MBT), along which the Lesser Himalayan succession is thrust over the Siwalik. In addition to these tear faults, some transverse faults of limited lateral extent, cutting through the mountain belt and basin, may have formed during the last event of deformation along the HFT zone.

Geomorphic evolution of the Piedmont Zone of the Ganga Plain, India: a study based on remote sensing, GIS and field investigation

The geomorphic evolution of the Piedmont Zone of the Ganga Plain is not well understood, since the identification of various morpho-tectonic features in the field is very difficult because of the thick forest cover, extensive anthropogenic modifications in the landscape and easily reworkable gravels. Interpretation of satellite imagery, Digital Terrain Models (DTMs) and field data has helped in identification and mapping of various morpho-tectonic features in a hitherto unstudied part of the Piedmont Zone and the adjoining areas in north-western Ganga Plain, India. The Piedmont Zone has formed as a result of laterally coalescing alluvial fans of variable dimensions and talus deposits, and is traversed by active faults and thrusts. The variable subsidence rates along the basin margin (i.e. the Himalayan Frontal Thrust) and climatic events have controlled the accommodation space and basinward progradation of alluvial fans. The landscape of the Piedmont Zone is presently being continuously modified by the ongoing tectonic movements and seasonal climatic variations.

Tectonic evolution of Duns in Kumaun Sub-Himalaya, India: a remote sensing and GIS-based study

The tectonic evolution of the Sub‐Himalayan longitudinal intermontane valleys, called ‘Duns’, in the Kumaun region of India is not yet understood as the thick forest cover and extensive anthropogenic modifications of the landscape have made it difficult to identify the various tectonic and geomorphic features. In this paper we present a conceptual model of the tectonic evolution of Kota and Pawalgarh Duns of the region, based on interpretation of digitally processed IRS P6 LISS III imagery and analyses of Digital Terrain Models (DTMs) in a Geographic Information System (GIS), together with field investigations. The Duns were formed as the fault‐bend folded hills came up in front of the southern piedmont zone of the frontal Himalaya along the Himalayan Frontal Thrust (HFT) and the Pawalgarh Fault. The landscape of the Duns is further modified as a result of movement along subsequently developed transverse faults.

Channel morphology, hydrology and geomorphic positioning of a Middle Miocene river system of the Siwalik foreland basin, India

Systematic lithofacies, palaeocurrent, palaeomorphological and palaeohydrological analyses have provided detailed information about a hitherto unstudied river system of the Siwalik foreland basin of the Himalaya. Three distinct lithofacies associations, each representing a specific depositional setting, have been identified and named as ‘Facies Association A’, ‘Facies Association B’ and ‘Facies Association C’. The ‘Facies Association A’ comprises pebbly sandstone, cross-bedded sandstone, ripple-laminated sandy siltstone and bioturbated mudstone lithofacies and represents deposits of a braided channel. The ‘Facies Association B’ comprises cross-bedded sandstone, bioturbated mudstone, fine sandstone–mudstone alternation and lensoid to prismatic sandstone lithofacies and represents deposits of a channel, natural levee, crevasse-splay and flood plain of a meandering stream. The ‘Facies Association C’ comprises mottled siltstone–mudstone heterolith and fine sandstone lithofacies and represents deposits of the upland interfluve region. The braided stream had a maximum depth of 4.15 m, maximum width of 305 m and maximum discharge of 7045 cumec, whereas the meandering stream had a sinuosity of 1.26, maximum depth of 3.71 m, maximum width of 180 m and maximum discharge of 4070 cumec. The area had a regional radial outward flow pattern, but dominantly towards the SSW. However, the braided river had a bimodal flow pattern due to an active basement-high-induced bend along its course. A comparison of the sediment characters and morphological and hydrological parameters of these streams with those of the modern rivers of the Ganga (Gangetic) basin has enabled us to infer that this river system was located in the medial-distal megafan-interfan setting of the basin.

Climatic and tectonic controls on the sedimentary processes of an alluvial fan of the western Ganga Plain, India

Detailed facies analysis and morphotectonic investigations of the Malin River9s alluvial fan in the western Ganga Plain, India, reveal that the morphology of the fan is largely tectonically controlled whereas the sedimentary processes are mainly climatically controlled. The sedimentation occurred in two distinct evolutionary cycles which are separated by a time gap. The older cycle deposited thick gravelly units up to the distal-fan area, whereas the sediment fill of the younger cycle is gavel-dominated in the proximal-fan area, gravel–sand dominated in the middle-fan area and sand–mud dominated in the distal-fan area. The gravels of the older cycle were emplaced by intense sediment gravity flows during periods of strengthened monsoon and steeper regional gradient. During the younger cycle, the proximal to distal parts of the fan were dominated by different sedimentary processes. This was a time of relatively weaker monsoon and gentler regional slopes, when gravels could travel only up to the middle-fan area. The gravels in the proximal-fan area have mainly been deposited by sediment gravity flows and channel processes; in the middle-fan area channel processes, sheetfloods and sediment gravity flows have been the main sedimentary processes; and in the distal-fan area fluvial processes of channel migration and overbank deposition have been the main sedimentary processes.