Holocene landscape dynamics in the Ghaggar-Hakra palaeochannel region at the northern edge of the Thar Desert, northwest India

Abstract

Precession-forced change in insolation has driven de-intensification of the Asian Monsoon systems during the Holocene. Set against this backdrop of a weakening monsoon, Indus Civilisation populations occupied a number of urban settlements on the Ghaggar-Hakra plains during the mid-Holocene from 4.5 ka until they were abandoned by around 3.9 ka. Regional climatic variability has long been cited as a potential factor in the transformation of Indus society, however there remain substantial gaps in the chronological framework for regional climatic and environmental change at the northern margin of the Thar Desert. This makes establishing a link between climate, environment and society challenging. This paper presents 24 optically stimulated luminescence ages from a mixture of 11 fluvial and aeolian sedimentological sites on the Ghaggar-Hakra floodplain/interfluve, an area which was apparently densely populated during the Indus urban phase and subsequently. These ages identify fluvial deposition which mostly pre-dates 5 ka, although fluvial deposits are detected in the Ghaggar palaeochannel at 3.8 ka and 3.0 ka, post-dating the decline of urbanism. Aeolian accumulation phases occur around 9 ka, 6.5 ka, 2.8 ka and 1.7 ka. There is no clear link to a 4.2 ka abrupt climate event, nor is there a simple switch between dominant fluvial deposition and aeolian accumulation, and instead the OSL ages reported present a view of a highly dynamic geomorphic system during the Holocene. The decline of Indus urbanism was not spatially or temporally instantaneous, and this paper suggests that the same can be said for the geomorphic response of the northern Thar to regional climate change

Neoglacial climate anomalies and the Harappan metamorphosis

“…6c; Dixit et al, 2014). The flood regime controlled by this variable and declining summer monsoon became more erratic and/or spatially restricted Durcan et al, 2017) making inundation agriculture less dependable. Whether fast or over generations, the bulk of Harappan settlements relocated toward the Himalayan foothills on the plains of the upper G-H interfluve (see Supplement; Possehl, 2002;Kenoyer, 1998;Wright, 2010;Madella and Fuller, 2006;.…”

Did the Harappan settlement of Dholavira (India) collapse during the onset of Meghalayan stage drought?

“…f), has also been cited as the cause of the abrupt collapse of the Egyptian Old Kingdom at the same time (Thompson et al ., ; Bronk Ramsey et al ., ; Walker et al ., , ). Nearer Dholavira, sedimentological evidence from the Thar Desert suggests westward expansion of the desert dune field during the Late Holocene (after ~4000 years BP ) overlying the older fluvial sediments that were deposited during the Holocene climate optimum (Clift et al ., ; Alizai et al ., ; Giosan et al ., ; East et al ., ; Durcan et al ., ).…”

Large-Scale, Multi-Temporal Remote Sensing of Palaeo-River Networks: A Case Study from Northwest India and its Implications for the Indus Civilisation

“…1900 years Before Christ). Although, dune formation in the Thar desert is a long process spanning at least 200 ka BP [56], some recent dating of dunes from the northernmost edge of the Thar desert, have suggested that dune deposits pre-date 4.9 ka BP, though some are around 1500 years old ( [27] (p. 4), [58][59][60]). Therefore, it seems logical to expect a long period of dune formation and interaction with rivers before the latter were finally erased.…”