Archana Das, a research scholar from Assam and a few others have come up with a study on whether it was only the relatively dry spell due to changing weather patterns that brought about the decline of metropolises such as Dholavira and Lothal in the Harappan period.
It highlighted that a major receding of sea level around 4,200 years ago that dried up the famed dockyard at Lothal could be one of the reasons for the decline of the port town.
The paper ‘Evidence for seawater retreat with the advent of Meghalayan era (~4200 a BP) in a coastal Harappan settlement’ by Archana Das from the Institute of Seismological Research (ISR) and other researchers from the Institute of Seismological Research and Birbal Sahni Institute of Palaeosciences is published online recently in the American Geophysical Union (AGU) journal Geochemistry, Geophysics, Geosystems.
“The last 4,200 years are identified as the Meghalayan Age by the geologists. At the start of the period, we see major climatic shifts that impacted contemporary human habitations. The deurbanization of the Harappan civilization coincides with the phase from 4,200 to 3,800 years before the present (BP). The age is known to have begun with recurring monsoonal droughts,” said Archana Das of ISR.
“Our study also indicates that it was the period marked by a rapid drop in sea levels in coastal southwestern Gujarat. It could have resulted in adverse impact to Lothal.”
The study employed analysis of sediments from a trench at Lothal in the ancient dockyard area. The researchers studied carbon and sulphur contents and their stable isotopes along with shells of foraminifera (a marine microorganism) and sand grains for radiocarbon and optical dating.
“The results indicated four distinct phases of the environment spanning 5,030 years to 2,070 years before present (BP). It can be ascertained from sediment carbon and sulfur content. The coastal marine environment was present in the early phase. The second phase shows abrupt environmental change including receding sea,” said Rajesh Agnihotri of BSIP, adding that the third phase also indicated dry condition, whereas the fourth one is of present-day condition.
The early phase showed the organisms thriving in marine environments. The later part shows brackish water organisms, indicating the presence of both seawater and freshwater at the site. From about 2,000 years ago, the place remained dry as it’s observed today.
“Our study clearly provides multi-proxy evidence for a relative sea-level fall during the initial phase of the Meghalayan age (~4150 to ~ 3625 years BP). This relative sea-level fall might have dried up the ancient Lothal site, the oldest Harappan dockyard. This geological change might have then adversely impacted ancient Harappan trade activities by impeding ship/ boat movements in the vicinity. The Meghalayan era is known to have begun with monsoonal dryness forcing Harappans to migrate towards the south-western direction to access water resources. The relative sea-level fall between the aforesaid time-window thus might have played a disastrous role for trade activities as well as coastal resources of the ancient civilization,” mentioned the paper.
Archana completed her graduation in Geology from Gauhati University before doing her Masters from the Maharaja Sayajirao University of Baroda, Vadodara. She did her PhD at Krantiguru Shyamji Krishna Verma Kachchh University, a state university in Gujarat on ‘Fluvial Response to Climate, Tectonics and Sea Level Changes during Late Quaternary period on the Southern Kachchh mainland, Western India’.