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

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

Atenas

Conferencia; Regional Conference on Geomorphology; 2019

International Association of Geomorphologists

Methane gas seeps are widely distributed, however, only a small fraction of the seeps fromthe seabed have been discovered as indicated by the fact that new findings are reportedevery year. Gas seep studies in the deep sea of Argentina are scarce, and do notcharacterize geological and biological features. This work is part of a multidisciplinary studyintended to establish the trophic contribution of methane seepages in the Malvinas Basin. Tothat end, we analyzed a superficial and sub-superficial analysis of 2D multi-channel seismicdata provided by the Argentine Secretary of Energy and selected an area characterized bychimneys and pockmarks to target in an exhaustive survey onboard the Australoceanographic vessel. This survey was carried out using multibeam (EM122) and singlebeam echo sounders (EK80) to obtain detailed bathymetric data, as well as a sub-bottomprofiler to obtain ultra-high resolution seismic data from the shallow sediment column. Theresults 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. Thispockmark has an elliptical shape and is located at 450 m water depth. Its diameter is 400 mand its depth varies between 2 and 6 m with a slope of 3º. Acoustic turbidity in contact withthe 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 chimneyhaving an enhanced reflector in the multi-channel 2D records. These results allow, with a highmargin of certainity, the sampling of the benthic communities associated with gas seepage.