HYDEE I - TAN1808

R/V Tangaroa TAN-1808, 8th September - 5th October 2018

Gas Hydrate Systems of the Southern Hikurangi Margin, Aotearoa, New Zealand

Summary

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 accumulations 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.

Collaborators:

  • GNS Science
  • NIWA
  • University of Auckland
  • University of Otago

Scientific Objectives:

TAN1808 was focused primarily on the collection of geophysical datasets that help characterise the way in which gas hydrates are forming in the deforming wedge of the Hikurangi subduction margin. The voyage enabled the characterisation of methane seepage through the seafloor, submarine slope stability and marine biodiversity, which are all related to the underlying gas hydrate system. The voyage objectives were to:

  1. Collect 2D seismic reflection data to map out sub-surface gas hydrate accumulations.
  2. Characterise methane escape at the seafloor and into the water column using EM302 multibeam echo-sounder technology.
  3. Image small-scale fluid flow and sedimentary processes using TOPAS single-beam echo-sounder technology.
  4. Deploy seafloor sampling equipment to collect samples that are representative of seafloor lithologies and the sediments that host gas hydrates.
  5. Collect targeted sediment samples that can be used to characterise the microbiology at the seafloor above gas hydrate accumulations.

Survey Operations

  • Multibeam bathymetry
  • 3.5 kHz echosounder
  • Short-streamer multichannel seismic
  • Dredges, gravity coring and Van-Veen grabs for seafloor sampling
  • Water column acoustic (echosounder)

Cruise participants

Crutchley Gareth GNS Voyage Leader, seismic
Mountjoy Joshu NIWA Co-leader, seafloor sampling, seismic
Davy Bryan GNS Sub-bottom profiler
Hillman Jess GNS Multibeam bathymetry and water column acoustics
Stewart Lucy GNS Microbiology
Watson Sally NIWA Seismic
Woelz Susi NIWA Seismic
Kane Tim NIWA Multibeam bathymetry and water column acoustics
Gerring Peter NIWA Engineer/technician
Quinn Will NIWA Engineer/technician
Turco Francesco University of Otago Student watchstander
Fougere Dannielle University of Otago Student watchstander
Macnaughtan Michael University of Auckland Student watchstander
Djeffal Adnan University of Auckland Student watchstander

 

Download: TAN1808 cruise report : TAN1808-Voyage-Report-2018.pdf (14.11 MB)

Acknowledgments:

Cruise and cruise participants were funded by MBIE Endeavour Fund under contract C05X1708.