OS23D-03
Vertical Methane Migration on the Hikurangi Margin off the Mahia Peninsula, New Zealand
Tuesday, 15 December 2015: 14:10
3009 (Moscone West)
Richard B Coffin1, Paula S Rose1, Brandon Yoza2, Thomas Jordan Boyd3, Gareth James Crutchley4, Joshu J Mountjoy5 and Ingo Andreas Pecher6, (1)Texas A & M University Corpus Christi, Department of Physical and Environmental Sciences, Corpus Christi, TX, United States, (2)University of Hawaii, Hawaii Natural Energy Institute, Honolulu, HI, United States, (3)US Naval Research Laboratory, Washington, DC, United States, (4)GNS Science-Institute of Geological and Nuclear Sciences Ltd, Lower Hutt, New Zealand, (5)NIWA National Institute of Water and Atmospheric Research, Wellington, New Zealand, (6)University of Auckland, Auckland, New Zealand
Abstract:
This study focuses on gas source and vertical migration patterns in sediments on the Hikurangi Margin, east of the North Island, New Zealand off the Mahia Peninsula, collected aboard the RV Tangaroa (TAN1508) during June 2015. Seismic and Topas data collected on board were used to organize a coring plan for this expedition. Selection of piston core locations was based on spatial variation in vertical gas migration across seismic patterns indicating BSR migration toward the sediment surface. Higher molecular weight gases were not observed at this location suggesting a biogenic gas source. Across this transect, methane concentrations varied by more than an order of magnitude at stations within a few hundred meters. The highest methane concentrations were 5051.7 ppm in Core 004 at and 2413.4 ppm in Core 036. Concentrations at other sites ranged from 23.8 to 125.9 ppm. Methane concentrations showed a strong correlation with seismic and Topas data that suggested high vertical migration and large shallow gas pockets. While these data focused on locations across a BSR, higher methane concentrations, ranging from 1529 to 7862 ppm were observed in three cores from a nearby site where a BSR was not observed. This presentation will compare spatial variation in the vertical gas migration and stable isotopic composition of sediment organic and inorganic carbon, methane and porewater dissolved inorganic carbon among the core locations to better understand vertical methane migration and shallow sediment methane cycling.
