Gas hydrate systems of the southern Hikurangi Margin, Aotearoa, New Zealand

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SR_2018-40-pdf
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Crutchley, G.J.; Mountjoy, J.J.; Davy, B.W.; Hillman, J.I.T.; Watson, S.; Stewart, L.C.; Woelz, S.; Kane, T.; Gerring, P.; Quinn, W.; Turco, F.; Fougere, D.; MacNaughtan, M.; Djeffal, A. 2018 Gas hydrate systems of the southern Hikurangi Margin, Aotearoa, New Zealand. Lower Hutt, N.Z.: GNS Science. 83 p. GNS Science report 2018/40; doi: 10.21420/73WW-1W83

Abstract:

The TAN1808 voyage took place between the 8th of September and the 5th of October 2018, aboard RV Tangaroa. Geophysical data and seafloor samples were collected in several study areas off the Wairarapa coast and further to the south, off the coast of north-eastern South Island. Approximately 2750 line kilometres of multi-channel seismic data were acquired, providing detailed characterisation of gas hydrate ccumulations in the sub-seafloor. Multibeam bathymetry and water column data, as well as single-beam echo-sounder data, were acquired in tandem with seismic data. The hydro-acoustic datasets enabled detailed mapping of seafloor morphology and backscatter character, as well as shallow sub-seafloor imaging. A total of 93 active methane seeps were identified from multibeam water column data. 48 seafloor samples were collected using a range of sampling techniques (gravity coring, grab sampling and dredging). These samples give new insight into seafloor composition above gas hydrate accumulations as well as the reservoir sediments within which gas hydrates form. Three of the seafloor samples collected were targeted for microbiological analyses of the gas hydrate system. (auth)