SURFACE AND SUB-SURFACE FEATURES OF AN ACTIVE GAS SEEP IN MALVINAS BASIN (SW ATLANTIC OCEAN)

MARÍA EMILIA BRAVO; JUAN PABLO ORMAZABAL; FERMIN IGNACIO PALMA; FEDERICO DAMIÁN ESTEBAN; JOSÉ ISOLA; SEBASTIÁN PRINCIPI; CÉSAR ARTUNDUAGA; ALEJANDRO ALBERTO TASSONE; LISA ANN LEVIN

Atenas

Congreso; INTERNATIONAL ASSOCIATION OF GEOMORPHOLOGISTS - REGIONAL CONFERENCE ON GEOMORPHOLOGY - Geomorphology of Climatically and Τectonically Sensitive Areas; 2019

INTERNATIONAL ASSOCIATION OF GEOMORPHOLOGISTS

Methane gas seeps are widely distributed, however, only a small fraction of the seeps from the seabed have been discovered as indicated by the fact that new findings are reported every year. Gas seep studies in the deep sea of Argentina are scarce, and do not characterize geological and biological features. This work is part of a multidisciplinary study intended to establish the trophic contribution of methane seepages in the Malvinas Basin. To that end, we analyzed a superficial and sub-superficial analysis of 2D multi-channel seismic data provided by the Argentine Secretary of Energy and selected an area characterized by chimneys and pockmarks to target in an exhaustive survey onboard the Austral oceanographic vessel. This survey was carried out using multibeam (EM122) and single beam echo sounders (EK80) to obtain detailed bathymetric data, as well as a sub-bottom profiler to obtain ultra-high resolution seismic data from the shallow sediment column. The results identified a pockmark-like field. From these, a pockmark with active gas seepage (evidenced by gas plumes in the water column) was selected for seafloor sampling. This pockmark has an elliptical shape and is located at 450 m water depth. Its diameter is 400 m and its depth varies between 2 and 6 m with a slope of 3º. Acoustic turbidity in contact with the surface of the seabed of the pockmark indicates that the seeping gas is mainly methane. This gas would come from a deep source, since it was observed associated with a chimney having an enhanced reflector in the multi-channel 2D records. These results allow, with a high margin of certainity, the sampling of the benthic communities associated with gas seepage.