CHARMNZ, 2006 Gas Hydrates Survey on the Hikurangi Margin, New Zealand: First Results From Seismic and Related Data
Abstract
CHARMNZ CH4 Hydrates on the AccRetionary Margins of New Zealand; R/V Tangaroa voyage TAN0607) in 2006 was the first survey dedicated to studying gas hydrates on the Hikurangi Margin east of New Zealand. During the two-week long cruise, we collected a variety of datasets, including multibeam bathymetry, 3.5-kHz data, seismic profiles, heat flow, piston cores for pore water chemistry and paleoceanography, dredge samples to study carbonates and for age dating, sonar profiles to detect vents, and CTDs to study methane in the water column. Some of these data will be presented in other presentations in this session. We present seismic profiles from our two main study areas. The seismic data were acquired with a 45/105 cu-in GI gun and a 600- m long 48-channel streamer. We acquired nine parallel seismic lines spaced ~1.85 km apart across an anticline offshore of the Wairarapa. Beneath this anticline, a high-reflectivity zone appears to intrude into the regional gas hydrate stability field as marked by bottom simulating reflections. We interpret this zone as free gas in a strongly upward-warping gas hydrate stability field, possibly caused by advective heat flow associated with fluid migration. The zone gets shallower from North to South which may reflect a time progression. Across Rock Garden, our second study area off Hawke's Bay, we collected seven parallel and two cross lines, again at ~1.85-km spacing. Our goal was to collect further evidence for our hypothesis that Rock Garden is being eroded by freeze-thaw cycles of hydrates beneath the seafloor. In this area, we also retrieved a temperature sensor that recorded bottom water temperatures for 15 months.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AGUFMOS33B1693P
- Keywords:
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- 3004 Gas and hydrate systems;
- 3025 Marine seismics (0935;
- 7294);
- 3060 Subduction zone processes (1031;
- 3613;
- 8170;
- 8413)