Geological perspective Part 1: Understanding the Meghalayan age

Manasi Saraf Joshi
Friday, 20 July 2018

After the scientists world over officially declared this age as the Meghalayan Age, Sakal Times in its two-part series tries to understand the geological and archaeological changes that took place

Pune: The Indian geoscientific community has expressed happiness over the global recognition from the Meghalayan caves which started a new chapter in the research of climate change. 

While talking to Sakal Times, SJ Sangode from Department of Geology, Savitribai Phule Pune University (SPPU) said, “The record in Meghalaya deserves international recognition and the current development will stir new studies opening discussions on climate change of the recent past affecting major civilisations and their linkages elsewhere including the Indian subcontinent or entire Asia.”

“The roughly 200 years duration of intense aridity at 4,200 years before present which marks the onset of Meghalayan age during Holocene needs to be studied for its extent and intensity over the Indian subcontinent,” Sangode said. 

“The newly-termed Meghalayan Age is an important part of the geological time scale for Indian researchers to work in detail on possible ocean-atmospheric connections, monsoon variability, agricultural productivity and the cultural shifts, and finding its teleconnections globally,” Sangode said.  

Sangode said that the caves in Meghalaya are the repositories for such studies preserving distinct anomalies in the speleothems and needs to be explored in detail for many years to come. The current announcement of the Meghalayan Age emphasises the intense aridification globally at 4,200 years ‘before present’ (BP) causing an occurrence of mega-droughts and fall of civilisations like mesopotamia and is considered as a major climate change event during cooling of several oceans.

“This boundary at 4,200 years before present corresponds to about 2,200 BC and hence, the historical records are to be re-examined for their significance with global climate change event,” Sangode added. 

Destructive droughts for over two centuries during this event disrupting major civilisations are well reported in Egypt, Greece, Syria, Palestine, Mesopotamia, the Indus Valley and the Yangtze River Valley.

With the new ratification, the middle phase of the Holocene will now be referred to as the Northgrippian, and runs from 8,300 years ago up to the start of the Meghalayan. The onset for this age was an abrupt cooling, attributed to vast volumes of freshwater from melting glaciers in Canada running into the North Atlantic and disrupting ocean currents. The oldest phase of the Holocene - the exit from the ice age - will be known as the Greenlandian according to the stratigraphic commissions.

When asked how the age is defined, Sangode said that the ages in geological time scale are defined by major biotic events; and the duration, therefore, ranges anywhere from few thousand to millions of years. “The biotic changes are recorded by the occurrence of fossils globally – their appearance, evolution, grouping and extinctions. The ages are further refined using isotope dating methods in the lab,” Sangode added.

Although, there is disquiet amongst researchers globally over the way the change has been introduced in the geological time scale without sufficient discussion on the matter.  “Many other stratigraphic boundaries took several rounds of arguments before agreement from the international community, and the present declaration is relatively quick,” Sangode added. 

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