GNGTS 2022 - Atti del 40° Convegno Nazionale

GNGTS 2022 Sessione 3.2 403 seismic profiles). Therefore we suggest the hypothesis that the mounds of the Roosevelt Subbasin formed as mud volcanoes instead of glacial moraines. The age of the Roosevelt Subbasinmounds is inferred by indirect correlation and comparison with the eastern Ross Sea seismic sequences, after Brancolini et al. (1995) and the recent work by Perez et al. (2021), that improved the chronostratigraphic framework (after the IODP Exp 374, McKay, De Santis, Kulhanek et al. , 2019; Perez et al., 2021).  The sea bed where the mounds grew is an erosional surface truncating with low angle a package of sub-horizontal reflectors, however it doesn’t show glacial valleys incisions or other peculiar features suggesting deep erosion from grounding ice streams. The base of the mounds is possibly a transgressive marine surface, a residual, coarse sedimentary lag, swept by bottom currents, similar to the present day sea bed in the outer continental shelf. This would justify the strong amplitude of the reflector lying at the base of the mounds. The occurrence of current typical moat-sediments drifts within the mounds and the aggradational geometry of the strata infilling the depressions among the mounds would indicate open marine sediment deposition during a period of relative high sea level, during and after the mound formation. The two hypothesis to explain the origin of the buried mounds in the Roosevelt Subbasin risen by Sorlien et al. (2017) and by our work, have implications for quite a diverse WAIS scenario, and confirming one of them with future shallow drilling would be very important for ice sheet volume and thermal rheology modelling reconstructions. The seismic profiles reprocessed for this work are used to locate drill sites and define targets of the IODP Pre-998 proposal (McKay, De Santis et al. , 2020). References Bohem G., Brancolini G., Fais S., Snidarcig A., Vesnaver A.; 1993. BGTA vol. XXXV, 137-138. Brancolini G., Busetti M., Marchetti A., De Santis L., Zanolla C., Cooper A.K., Cochrane G.R., Zayatz I., BelYaev V., Knyazev M., Vinnikovskaya O., Davey F.J., Hinz K.; 1995: Descriptive text for the seismic stratigraphic atlas of the Ross Sea, Antarctica . Geology and seismic stratigraphy of the Antarctic Margin, Antarctic Research Series, vol. 68, 271-286. Hovland, M.; 2008. Deep-water coral reefs: Unique biodiversity hot-spots . Springer Science & Business Media. Lawver L., Lee J., Kim Y., Davey F.; 2012. Geosphere , 8(3), 645-653. doi:10.1130/GES00766.1; Løseth, H., Gading, M., and Wensaas, L.; 2009: Hydrocarbon leakage interpreted on seismic data . Marine and Petroleum Geology, 26(7), 1304-1319. Geletti and Busetti 2011. J. Geophys. Res. Solid Earth, 116(B4) McKay, R. M., De Santis, L., and Kulhanek, D. K.; 2019: Ross Sea West Antarctic Ice Sheet History . Proceedings of the International Ocean Discovery Program, 374. Marschalek, J, Zurli, L, Talarico, F, Van de Flierdt, T, Vermeesch, P, Carter, A, Beny, F, Bout-Roumazeilles, V, Sangiorgi, F, Hemming, S, Perez, L, Colleoni, F, Prebble, J, Van Peer, T, Perotti, M, Shevenell, A, Browne, I, Kulhanek, D, Levy, R, Harwood, D, Sullivan, N, Meyers, S, Griffith, E, Hillenbrand, C-D, Gasson, E, Siegert, M, Keisling, B, Licht, K, Kuhn, G, Dodd, J, Boshuis, C, De Santis, L, McKay, R. A large West Antarctic Ice Sheet explains early Neogene sea-level amplitude . Nature 600, 450–455 (2021). https://doi.org/10.1038/s41586-021-04148-0 Pérez, L. F., Santis, L. D., McKay, R. M., Larter, R. D., Ash, J., Bart, P. J., Böhm G., Brancatelli G., Browne I . , Colleoni F., Dodd J.P., Geletti R., Harwood D.M., Kuhn G., Laberg J.S., Leckie R.M., Levy R.H., Marschalek J., Mateo Z., Naish T.R., Sangiorgi F., Shevenell A.E., Sorlien C.C, van de Flierdt T., International Ocean Discovery Program Expedition 374 Scientists; 2021: Early and middle Miocene ice sheet dynamics in the Ross Sea: Results from integrated core- log-seismic interpretation . Bulletin, 134(1-2), 348-370. doi: https://doi.org/10.1130/B35814.1 Sorlien C. C., Luyendyk B. P., Decesari R. C., Wilson D. S., Bartek L. R.; 2007: Oligocene development of the West Antarctic Ice Sheet recorded in eastern Ross Sea strata. The Geological Society of America, V.35, 5, 467-470.