Falling sea levels around 4,200 years ago led to Lothal’s decline: study

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Archana Das, a researcher from Assam and a few others did a study to find out if it was only the relatively dry period due to changing weather conditions that caused the decline of metropolises such as Dholavira and Lothal back then. Harappan.

He pointed out that a major sea level receding around 4,200 years ago, which dried up the famous Lothal shipyard, could be one of the reasons for the decline of the port city.

The article ‘Evidence for seawater withdrawal with the advent of The Megalayan Era (~4200 a BP) in a coastal settlement of Harappan’ by Archana Das of the Seismological Research Institute (ISR) and other researchers from the Seismological Research Institute and the Birbal Sahni Institute of Paleosciences has been 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 geologists. At the beginning of the period, we are witnessing major climatic changes that have impacted contemporary human habitation. The deurbanization of the Harappan civilization coincides with the phase from 4,200 to 3,800 years before present (BP). The age is known to have started with recurrent monsoon droughts,” said Archana Das from ISR.

“Our study also indicates that this was the period marked by rapid sea level decline on the southwestern coast of Gujarat. This could have had a negative impact on Lothal.

The study used sediment analysis from a trench at Lothal in the area of ​​the former shipyard. The researchers studied the contents of carbon and sulfur and their stable isotopes as well as shells of foraminifera (a marine microorganism) and grains of sand for radiocarbon and optical dating.

“The results indicated four distinct phases of the environment covering 5,030 years to 2,070 years before present (BP). It can be determined from the carbon and sulfur content of the sediments. The coastal marine environment was present in the early phase. The second phase shows abrupt environmental changes, including the receding of the sea,” said Rajesh Agnihotri of BSIP, adding that the third phase also indicated a dry condition, while the fourth is in the dry condition. current.

The first phase showed that the organisms thrived in marine environments. The last part shows brackish water organisms, indicating the presence of seawater and freshwater at the site. About 2,000 years ago, the place remained dry as seen today.

“Our study provides clear multi-proxy evidence for a relative sea level fall during the early phase of the Meghalayan age (~4150 to ~3625 years BP). This relative sea level fall would have could have dried up the ancient site of Lothal, the oldest Harappan shipyard.This geological change could then have had a negative impact on the ancient Harappan trading activities by preventing the movement of ships/boats in the vicinity.The Meghalayan era is known for having started with the monsoon drought forcing the Harappans to migrate southwest to access water resources.The relative fall in sea level between the aforementioned time window could therefore have played a disastrous role for commercial activities as well than for the coastal resources of the ancient civilization,” the document states.

Archana graduated in geology from Gauhati University before doing his master’s degree at Maharaja Sayajirao University in Baroda, Vadodara. She did her PhD from Krantiguru Shyamji Krishna Verma Kachchh University, a Gujarat State University on “River Response to Climate, Tectonics and Sea Level Changes during the Late Quaternary Period on the Continent south of Kachchh, in western India”.

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