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Geological Survey of India Exposures of Himalayan Frontal Thrust (HFT) found in Panchkula District, Haryana The Himalayan Frontal Thrust (HFT) also known as Himalayan Frontal Fault (HFF) is a regional, southern most and youngest major structural discontinuity, parallel to the Himalayan ranges that separates the outermost Siwalik sub-Himalayas from the IndoGangetic plains. HFT is believed to be a blind fault as it has few surface exposures and therefore usually shown as “trace of HFT” in geological maps defining the southern topographic break of Himalayan ranges. This fault has been active during the Quaternary period and caused several modifications in the younger geological, geomorphological and drainage features. Many of the recent moderate earthquakes in Himalayas have originated in the zone between the HFT and Main Central Thrust (MCT). While carrying out lithostratigraphic mapping of Siwalik rocks in Haryana (Item:STM/NR/PHH/2010/008) the team comprising Sh. Rajinder Kumar and Hemant Kumar, Senior Geologists led by Dr H.S Saini, Director found good exposures of HFT at two locations in ‘nalla’ sections in the Panchkula district of Haryana where Siwalik rocks are overriding the younger sediment layers. In the exposures, HFT is a northerly dipping, WNW-ESE trending fault which has brought Tatrot Foramtion of Upper Siwalik over the Late Quaternary gravels (Fig 1). The hanging wall consisting of friable coarse grained, grey micaceous sandstone, mudstones shows deformation in the form of folding, faulting and crushing in about 500m thick zone. The deformation is also visible in the loose gravel of footwall in which pebble layers show warping and dragging. North of the fault, minor faults are traceable for over a km length. These exposure sites may be potentially appropriate for GPS measurements for slip rate, strain built up etc. Northern Region 1 Geological Survey of India Fig 1. Himalayan Frontal Thrust (HFT) showing Tatrot Formation of Upper Siwalik over the Late Quaternary gravels. Northern Region 2