NEMESYS 2011

NEMESYS: R/V Sonne SO214 March-April 2011.

In 2011 research cruise SO-214 aboard German Research vessel R/V Sonne was carried out to acquire additional geophysical, geological, geo-chemical and biological data for the project NEMESYS. GNS Science was one the major partners in this project together with GEOMAR, NIOZ and BGR (Bialas, 2011). First leg (seismic leg) started on 9th March 2011 in the port of Wellington. The second leg left the port of Wellington on 6th April 2011 dedicated to intensive geological, geo-chemical and biological investigations.

The main objective of the project is to extend understanding of active methane seeps along the Hikurangi Margin. The survey consisted of two legs. During the first leg high resolution-multi frequency acoustic surveys were conducted. The second leg was dedicated to collection of geological, geochemical and biological data. Seeps’ morphology and timing of seepage at specific vent sites have been investigated through integration of backscatter and high resolution seismic data (Golding et al., in preparation).

Two high resolution 3D seismic surveys were successfully conducted during the first leg at active methane seep sites on Opouawe Bank and Omakere Ridge off the Hikurangi margin (Bialas, 2011). A third survey at the Porangahau Ridge could not be completed due to bad weather conditions. Good quality 2D seismic lines are however available form this region.

Multi-beam bathymetry from the survey and study areas within the framework of the NEMESYS project (modified form SO214 cruise report Bialas, 2011).

Multi-beam bathymetry from the survey and study areas within the framework of the NEMESYS project (modified form SO214 cruise report Bialas, 2011).

Ocean Bottom Seismometers (OBS) were deployed simultaneous to each 3D seismic survey to obtain wide angle velocity information. Detail attribute mapping reveals the 3D structures underlying seeps as well as shallow gas accumulations sustaining seepage and possibly concentrated hydrate zones. The figure below provides a structural overview of fluid flow systems at Omakere Ridge. Proto-thrusts, extensional faults and shear faults (possible manifestations of simple shear deformation) appear related to different fluid migration systems (Plaza-Faverola et al., submitted paper).

Maps from the P-Cable SO214-survey at Omakere Ridge

Attribute maps from the P-Cable SO214-survey at Omakere Ridge, acquired aboard R/V SONNE in 2011. Five seep sites have been studied: Kea, Kaka, Kakapo, Moa and Bear’s Paw. EF=extensional faults, RS=Riedel Shears, HAZ=high amplitude zones, TPF=thrust propagation fold, PT=proto-thrusts, BSR=bottom simulating reflector. Dashed lines in maps d and e indicate projection of seep morphology. Figure modified from Plaza-Faverola et al., submitted paper.

Bialas, J., 2011. FS SONNE Fahrtbericht/Cruise Report SO214 NEMESYS: 09.03.-05.04. 2011, Wellington-Wellington, 06.-22.04. 2011 Wellington-Auckland.