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

• 来源期刊: 山地科学学报（英文版）
• 年，卷（期）: 2019,（12）
• 页码范围: 2828-2843
• 页数: 16页
• 语种: 英文

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.5m height named the Nagrakata Scarp.This scarp was identified using satellite images,DEMs,and total station survey.We interpret that the two north-sloping,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 teetonism 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.