TECHNICAL ARTICLES

DETAILED BATHYMETRIC MAPPING AND SIDE SCAN SURVEYS IN THE INVESTIGATION OF COLD FLUID VENT SITES AND ASSOCIATED GAS HYDRATE OCCURRENCES
Examples using mobile swath bathymetry and deep tow side scan
Jens Greinert PhD (Post Doctoral Fellow)
Wilhelm Weinrebe PhD (Head of the GEOMAR Data-Processing Centre)
GEOMAR Research Centre for Marine Gesciences, Kiel, Germany
Peter Gimpel PhD (Director Survey Systems)
Jörg Brockhoff (Product Support Manager)
L3 Communications ELAC-Nautik GmbH, Kiel, Germany

Abstract
Investigations of meter-scaled fluid expulsion sites, as active cold vents or surface-near gas hydrate occurrences typically are called, require a detailed bathymetric knowledge in order to pre-classify potential areas of fluid expulsion for direct seafloor observations as well as TV-guided sediment sampling and lander deployments. Coupled with side scan sonar investigations more detailed information about the distribution of cold vent sites and their typical methane-derived carbonate cementation of the sediment can be determined. Gas hydrates which have formed close to the seafloor, are related to fluid vent sites, where extensive methane expulsion occurs. This occurrence as well as the distribution of carbonates can be investigated by side scan sonar and sub-bottom profiler surveys ‘calibrated’ with direct seafloor observations. This enables estimates of the regional quantity of surface-near gas hydrate, vent-induced carbonates and active cold vent sites.
GEOMAR has been investigating cold vents in the North and South American Pacific Coast, the Sea of Okhotsk and the Baltic Sea to study the geological, geotechnical and biological cycles since 1987. During the joint German-Russian project, KOMEX, in the Sea of Okhotsk, GEOMAR used a prototype swath bathymetry system which was towed at the water surface. Equipped with a 50kHz BOTTOMCHART MKII, this system enabled detailed bathymetric mapping independent of the vessel used. In the Derugin Basin of the Sea of Okhotsk, where up to 10m high barite build-ups cover the seafloor, bathymetric data sets the background for sediment and dredge sampling.

Download article as PDF:

Journal-106-Article3.pdf (337,15kB)
(RightClick > Save Target As to Download)
 

You will need Adobe Acrobat Reader version 3 or newer.
If you don't have a copy of that program you can obtain
one for free at the Adobe website