Ten thousand years ago, Pampa was river with far more vigour than it is now and also followed a different course, a study has found.
The finding was based on the recent unearthing of peat and ancient forest remains from the river basin at Puthukkulangara lying on the border of Pathanamthitta and Alappuzha districts.
The study team was led by K.P.N. Kumaran, Scientist Emeritus at the Agharkar Research Institute (ARI), Pune.
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The team of scientists from ARI, and National Center for Earth Science Studies (NCESS), Thiruvananthapuram, conducted a survey in the Pampa river basin recently in association with an eco group, Pampa Parirakshana Samiti.
Peat and fossil wood
For the study, the team drilled into the earth in a private property at Puthukkulangara and unearthed a buried treasure of peat and fossil woods of dense and wet evergreen forest.
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According to Dr Kumaran and D. Padmalal, senior scientist attached to the NCESS, the samples collected from a depth of 25 to 30 feet in the river basin suggest that the river has been subjected to marked changes in its hydrodynamic regimes since the past 10,000 years owing to monsoon variability. Pampa has lost its original vigour and also changed its course in the coastal lowlands, before emptying into the Vembanad lake as seen in the satellite imageries, Dr Kumaran said.
Dr. Padmalal said the peat sequence and remains of huge logs of ancient rainforest found 25 to30 ft below the ground indicated that the Pampa basin had a dense forest cover that got buried after a massive flood occurred sometime in the early Holocene geological epoch.
Holocene is a period of geological time that covers approximately the last 11,700 years of the planet’s history.
Signatures of such massive palaeoflood and burial of ancient forests have been found in other river basins in Kerala and parts of Peninsular India, he said.
Freshwater swamp
It is also interesting to observe that the subsurface development adjacent to the fossil log horizon in Puthukulangara borehole occurred in a freshwater swamp surrounded by dense, tropical, wet, evergreen forest.
The peat and fossil logs are yet to be analysed for their exact identity and probable time span, says Dr Kumaran.
He said the buried fossil woods and sub-fossil logs in the wetlands of coastal plains and river banks form an important source of information on environmental changes of the geological and the recent past.
Dr. Kumaran said their investigations since 1998 in the coastal plains and adjacent hinterland of Kerala showed several areas where logs of such fossils were found under thin burden of Quaternary deposits. As ‘growth ring formation’ is primarily related to climatic conditions, a specimen of this wood can serve as a potential sample for assessing the pattern of climatic changes in the immediate past few thousand years, he said.