Evolution of landscape in a piedmont section of Eastern Himalayan foothills along India-Bhutan border: A tectono-geomorphic perspective  

作　　者：Chandreyee CHAKRABARTI GOSWAMI Prasun JANA John C WEBER 

机构地区：[1]Department of Geology,University of Calcutta,35,Ballygunge Circular Road,Kolkata 700029,India [2]Geological Survey of India,Northern Region,Sector E,Lucknow 226024,India [3]Department of Geology,Grand Valley State University,1 Campus Drive,Allendale,MI 49401 USA

出　　处：《Journal of Mountain Science》2019年第12期2828-2843,共16页山地科学学报（英文）

基　　金：the Fast Track Project for Young scientists granted to Chandreyee Chakraborty Goswami by the Department of Science and Technology, Government of India (Grant No. SR/FTP/ES-47/2013)

摘　　要：The present study area involves part of a deformed coalesced fan located along the Himalayan Frontal Thrust(HFT)on the east of river Tista near the India-Bhutan border.The area is marked by two spectacular E-W trending south-sloping scarps namely the Matiali(ca.60 m)and Chalsa(ca.90 m)Scarps and a north-sloping E-W trending Thaljhora(ca.80 m)Scarp.Our work comprises of a comparative study of geomorphology and geologic history in the adjacent interfluves of Jaldhaka-Gathia and Neora-Murti rivers to understand the tectonic history of the area.We mapped the Jaldhaka-Gathia river interfluve at a 1:25,000 scale and report a hitherto unidentified northerly sloping small scarp of ca.5 m height named the Nagrakata Scarp.This scarp was identified using satellite images,DEMs,and total station survey.We interpret that the two northsloping,E-W trending scarps(Thaljhora and Nagrakata Scarps)are manifestations of steep limbs of anticlines over blind south-dipping back thrusts.Together they form a wrinkle-ridge pair behind the north-dipping HFT,which is manifested by south-sloping Chalsa Scarp.We propose a plausible geomorphic model interpreting that deformation along the small fan in the Jaldhaka-Gathia interfluves is younger compared to fan deposition and deformation in the adjacent Mal-Murti interfluve.The most recent geomorphology of the Jaldhaka-Gathia interfluve is controlled by tectonism associated with the thrust below the Nagrakata Scarp where the youngest deformation episode is recorded to at around^6 ka and is likely related to motion on a splay off of the thrust beneath the Thaljhora Scarp.The present study area involves part of a deformed coalesced fan located along the Himalayan Frontal Thrust(HFT) on the east of river Tista near the India-Bhutan border. The area is marked by two spectacular E-W trending south-sloping scarps namely the Matiali(ca. 60 m) and Chalsa(ca. 90 m)Scarps and a north-sloping E-W trending Thaljhora(ca. 80 m) Scarp. Our work comprises of a comparative study of geomorphology and geologic history in the adjacent interfluves of Jaldhaka-Gathia and Neora-Murti rivers to understand the tectonic history of the area. We mapped the Jaldhaka-Gathia river interfluve at a 1:25,000 scale and report a hitherto unidentified northerly sloping small scarp of ca. 5 m height named the Nagrakata Scarp. This scarp was identified using satellite images, DEMs, and total station survey. We interpret that the two northsloping, E-W trending scarps(Thaljhora and Nagrakata Scarps) are manifestations of steep limbs of anticlines over blind south-dipping back thrusts.Together they form a wrinkle-ridge pair behind the north-dipping HFT, which is manifested by south-sloping Chalsa Scarp. We propose a plausible geomorphic model interpreting that deformation along the small fan in the Jaldhaka-Gathia interfluves is younger compared to fan deposition and deformation in the adjacent Mal-Murti interfluve. The most recent geomorphology of the Jaldhaka-Gathia interfluve is controlled by tectonism associated with the thrust below the Nagrakata Scarp where the youngest deformation episode is recorded to at around ～6 ka and is likely related to motion on a splay off of the thrust beneath the Thaljhora Scarp.

关 键 词：Eastern Himalayas Thaljhora Scarp Nagrakata Scarp Drainage Back-thrust Wrinkle-ridge 

分 类 号：P54[天文地球—构造地质学]