Seal bypass at the Giant Gjallar Vent (Norwegian Sea): indications for a new phase of fluid venting at a 56-Ma-old fluid migration system.

Dumke, Ines, Berndt, Christian , Crutchley, Gareth J., Krause, Stefan, Liebetrau, Volker, Gay, Aurélien and Couillard, Mélanie (2014) Seal bypass at the Giant Gjallar Vent (Norwegian Sea): indications for a new phase of fluid venting at a 56-Ma-old fluid migration system. Open Access Marine Geology, 351 . pp. 38-52. DOI 10.1016/j.margeo.2014.03.006.

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Supplementary data:

Abstract

Highlights:
• The Giant Gjallar Vent is still active in terms of fluid migration and faulting.
• The Base Pleistocene Unconformity acts as a seal to upward fluid migration.
• Seal bypass in at least one location leads to a new phase of fluid venting.
The Giant Gjallar Vent (GGV), located in the Vøring Basin off mid-Norway, is one of the largest (~ 5 × 3 km) vent systems in the North Atlantic. The vent represents a reactivated former hydrothermal system that formed at about 56 Ma. It is fed by two pipes of 440 m and 480 m diameter that extend from the Lower Eocene section up to the Base Pleistocene Unconformity (BPU). Previous studies based on 3D seismic data differ in their interpretations of the present activity of the GGV, describing the system as buried and as reactivated in the Upper Pliocene. We present a new interpretation of the GGV’s reactivation, using high-resolution 2D seismic and Parasound data. Despite the absence of geochemical and hydroacoustic indications for fluid escape into the water column, the GGV appears to be active because of various seismic anomalies which we interpret to indicate the presence of free gas in the subsurface. The anomalies are confined to the Kai Formation beneath the BPU and the overlying Naust Formation, which are interpreted to act as a seal to upward fluid migration. The seal is breached by focused fluid migration at one location where an up to 100 m wide chimney-like anomaly extends from the BPU up to the seafloor. We propose that further overpressure build-up in response to sediment loading and continued gas ascent beneath the BPU will eventually lead to large-scale seal bypass, starting a new phase of venting at the GGV.

Document Type: Article
Additional Information: WOS:000335633700004
Keywords: Giant Gjallar Vent, fluid pipe, seal bypass, overpressure build-up, Vøring Basin, Norwegian Sea
Research affiliation: OceanRep > The Future Ocean - Cluster of Excellence > FO-R05
OceanRep > The Future Ocean - Cluster of Excellence > FO-R02
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
OceanRep > The Future Ocean - Cluster of Excellence > FO-R09
OceanRep > The Future Ocean - Cluster of Excellence
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Kiel University
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/j.margeo.2014.03.006
ISSN: 0025-3227
Projects: SUGAR II, Future Ocean, COSY
Expeditions/Models/Experiments:
Date Deposited: 31 Mar 2014 11:29
Last Modified: 23 Jun 2017 07:55
URI: http://oceanrep.geomar.de/id/eprint/24085

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