Luminescence chronology of alluvial fan in North Bengal, India: Implications to tectonics and climate

Abstract

Alluvial fans are important geomorphic archives because of its strategic location at mountain front which can provide clues to the past climate and tectonics. In general, they provide information about optimum climate condition suitable for fan formation. We provide a detailed luminescence chronology of alluvial fan in north West Bengal, India. The regional fan surface (T44) has been dissected by E-W trending Himalayan thrusts known as Matiali and Chalsa thrusts and have various terraces named as T3, T2and youngest one as T1. Luminescence ages suggest that the formation of the alluvial fan (regional surface) started before 171 ka and continued till 72 ka covering a time span of nearly 100 ky; suggesting of weaker monsoon at 72 ka. Matiali fault activated after 171 ky. Chalsa fault is suggested to be active during 48–41 ka. The last aggradational phase was around 6 ka which led to the formation of T1aterrace. The study suggests that climatic fluctuation during the period were shaping the morphology of the alluvial fan, along with tectonic activities on the two faults.

An embryonic fold and thrust belt south of the Himalayan morphological front: Examples from the Central Nepal and Darjeeling piedmonts

“…Landforms that originated in major humid climate periods of reasonable duration were related to widespread alluviation and planation, whereas fans linked to shorter climatic events have smaller lateral extents and are alluviated above the previous, more planar landforms, which are only locally preserved in the piedmont. Therefore, the inter-megafan piedmont surface is diachronic and has variable ages, ranging from 24 ka (Vassallo et al, 2015) to 4.8 ka (Thakur et al, 2007) in the western Himalayas, 90 ka (Gibling et al, 2005) to 4.8 ka in the central Himalayas (Srivastava et al, 2003;Parkash et al, 2000), to 60 ka to 3.5 ka in the eastern Himalayas [see section 4.2 and Appendix B: Supplementary data for a compilation of the results of Goswami et al (2019), Singh et al (2016), Starkel et al (2015), , Kumar et al (2010), and Guha et al (2007)].…”

“…11), the surfaces of which were abandoned at approximately 3.5-5, 37-40, and 58-60 ka, respectively. Another unit may have been abandoned at 23-28 ka (Singh et al, 2016, Guha et al, 2007.…”

“…Figure 11: Age distribution of the sediment dated in the Gorubathan Recess. Individual data (numbers on right axis and black dots) from Goswami et al (2019), Singh et al (2016), Starkel et al (2015), , Kumar et al (2010), andGuha et al (2007), are presented in Appendix B: Supplementary data. Most of the data are obtained by Optically Stimulated Luminescence techniques.…”

Spatiotemporal Migration of the River Ganga in Middle Ganga Plane: Application of Remote Sensing and GIS Technique

“…The process of channel migration becomes crucial to a populace living in or near the floodplain or to government organizations involved in planning or upholding the infrastructure within or nearby the floodplains. Fluvial architecture and channel pattern are sensitive indicators of river migration and can accommodate in response to changing sediment load, hydrology, and active tectonics (Goswami et al 1999;Schumm et al 2000;Pati et al 2008;Shukla et al 2012;Singh 2015;Singh et al 2016Singh et al , 2017Kanhaiya et al 2019). Lateral shifting of river banks implies an asymmetric position of the channel in the river valley.…”

Luminescence chronology of fluvial and marine records from subsurface core in Kaveri delta, Tamil Nadu: Implications to sea level fluctuations

“…Nevertheless, in a bedrock terrain like Kaveri's, sediment yield could be high during end of an arid phase followed by the initiation of humid phase, i.e. during the transition of aridhumid phases similar to alluvial fan deposition (Singh et al, 2016(Singh et al, , 2017. Hence, the deltaic deposition is expected to be high during the arid-humid transition and increase in sea level forcing the river to aggrade.…”