GNGTS 2016 - Atti del 35° Convegno Nazionale

512 GNGTS 2016 S essione 3.1 affected by faults with a symmetric configuration (blue dashed lines). This suggests that these structures could be a direct response to fluid escape. Study area 3 – Ross Sea. Within the Victoria Land Basin new details have been focused on the BSR recognized by Geletti and Busetti (2011), along the seismic profiles ���������� IT90AR-63S and IT90AR-64S� ��� ��������� ������� ��� ��� �������� ��� ��������� ���������� �������� . The crossplot between the AVO gradient and intercept attributes confirms an anomalous trend respect to the surrounding sediments, probably produced by variations in fluid saturation; also the irregular trending of the interval velocity, characterized by velocity inversions within the sedimentary succession between the seabed and the BSR, could highlight a methane migration through the normal fault system that affect the Terror rift and Discovery graben. Conclusions. ���� ����� �������� ��� ������� �������� �� ��� �������� �� ��� ��� ������� This study presents the results deriving by the analysis of new and already described in literature BSRs, located in different sectors of the Antarctic offshore characterized by a different crustal domains: Dove Basin-Ona High (South Scotia Sea); South Shetland Trench; Victoria Land Basin (Ross Sea). Fossil-diagenetic BSRs have been observed in the deep basins at a water depth of 2500-4000 m, where the temperature and pressure conditions are not favorable for methane hydrates. On the South Shetland accretionary complex the recognized fault system seems to represent a preferred pathway for fluids migration. Fluids, probably originated also from the deep crust, can migrate toward the sea-bottom, as proved by the presence of a mud volcano. In the continental domain the fault systems drive the fluid migration as testified by seabed structures produced by methane gas seeps and expulsion. Gases could have a biogenic origins from the organic matter contained in the shallower sediments. This analysis is a contribution to the general understanding of formation of BSR in the Antarctic region by integration of seismic processing and interpretation, in particular within areas with no available borehole or calibration data. Acknowledgements. The Italian Programma Nazionale di Ricerche in Antartide (PNRA) provided financial support for this work (VALFLU project). The authors gratefully acknowledge Paradigm though the OGS Focus and Geodepth processing software, and Schlumberger through the University of Trieste Petrel academic grant for interpretation software. References Civile D., Lodolo E.,Vuan A.; 2012: Tectonics of the Scotia-Antarctica plate boundary constrained from seismic and seismological data. Tectonophysics, 550-553, 17-34 Geletti R. and Busetti M.; 2011: A double bottom simulating reflector in the western Ross Sea, Antarctica. Journal of Geophysical Research, 116, B04101, doi:10.1029/2010JB007864. Lodolo E., Camerlenghi A., Madrussani G., Tinivella U., and Rossi G.; 2000: Assessment of gas hydrate and free-gas distribution on the South Shetland margin (Antarctica) based on multichannel seismic reflection data. Geophys. J. Int., 148(1), 103–119, doi:10.1046/j.0956-540x. 2001.01576.x. Lonsdale, M. J.; 1990: The relationship between silica diagenesis, methane, and seismic reflections on the South Orkney microcontinent. Proc. Ocean Drill. Program Sci. Results, 113, 27–36, doi:10.2973/odp.proc.sr.113.177.1990. Mocnik A., Civile.D., Del Ben A., Geletti R.; 2015: Seismic analysis of a BSR in the Dove Basin (South Scotia Sea). Proceedings of 34°GNGTS, Trieste 17-19 November 2015, ISBN: 978-88-940442-7-0 Rebesco, M., R. D. Larter, P. F. Barker, A. Camerlenghi, L. E. Vanneste; 1997: The history of sedimentation on the continental rise west of the Antarctic Peninsula, in Geology and Seismic Stratigraphy of the Antarctic Margin, Part 2, Antarct. Res. Ser., vol. 71, edited by P. F. Barker and A. K. Cooper, pp. 29–49, AGU, Washington, D. C. Somoza L., Leon R., Medialdea T., Perez L.F., Gonzales F.J. Maldonado A.; 2014: Seafloor mounds, craters and depressions linked to seismic chimneys breaching fossilized diagenetic bottom simulating reflectors in the Central and Southern Scotia Sea, Antartica. Global and Planetary Change, DOI: 10.1016/j.gloplacha.2014.08.004. Volpi V., Camerlenghi A., Hillendbrand C.D., Rebesco M., Ivaldi R.; 2003: Effects of biogenic silica on sediment compaction and slope stability on the Pacific margin of the Antarctic Peninsula. Basin Research, 15, 339-363.