Gas-charged sediments in shallow waters off Redi along the central west coast of India

Abstract

This study reports the occurrence of gas-charged sediments in the nearshore areas of the west coast of India. High resolution shallow seismic reflection profiles on the nearshore area along central west coast of India, at water depths of 11-18 m are characterized by anomalous seismic subbottom signatures in the form of acoustic turbidity which extends from the uderlying reflector and reach within 4-5 m of the seafloor. Fine grained sediments apparently contain appreciable quantities of interstitial gas bubbles which are responsible for the anomalous seismic signatures. This could be due to shallow hydrocarbon gases, mostly methane, which might hsve been derived due to the biogenic degradation of organic matter accumulated under palaeo-estuarine conditions. These gas-charged sediments pose a potintial hazard for the offshore engineering constructions. Hence, the detection of these sediments forms an essential part of any offshroe site investiation programmes.