HR: 1340h
AN: V13B-1343    [Abstracts]
TI: High-Resolution Seismic Identification of the Caldera System and Dynamics of the Haakon Mosby Mud Volcano, Barents Sea Slope.
AU: * Perez-Garcia, C
EM: carolina.garcia@ig.uit.no
AF: Department of Geology. University of Tromsoe, Dramsveien 201, Tromsoe, 9037, Norway
AU: Feseker, T
EM: tfeseker@ifm-geomar.de
AF: IFM-GEOMAR. Leibniz-Institute of Marine Sciences at Kiel University, Gebäude Ostufer - Wischhofstr. 1-3, Kiel, 24148, Germany
AU: Feseker, T
EM: tfeseker@ifm-geomar.de
AF: Ifremer Centre de Brest, Z.I. Pointe du Diable B.P. 70 Plouzané, Brest, 29280, France
AU: Feseker, T
EM: tfeseker@ifm-geomar.de
AF: Alfred Wegener Institute for Polar and Marine Research, Postfach 12 01 61, Bremerhaven, 27515, Germany
AU: Mienert, J
EM: juergen.mienert@ig.uit.no
AF: Department of Geology. University of Tromsoe, Dramsveien 201, Tromsoe, 9037, Norway
AU: Berndt, C
EM: cbe@noc.soton.ac.uk
AF: National Oceanography Centre, Southampton, University of Southampton Waterfront Campus European Way, Southampton, SO14 3ZH, United Kingdom
AB: The Haakon Mosby Mud Volcano (HMMV) is an active 1 km wide cold seep structure located at 1250 m deep in the Bear Island Slide, southwestern Barents Sea. The HMMV is one of the few examples of mud volcanoes in non-compressional tectonic settings. Previous studies defined the deeper structure of the HMMV as an approximately 3 km deep seismic disturbance in Plio-Pleistocene deposits. Two-dimensional 3.5 kHz Sediment Echosounder Profiler data combined with Chirp seismic data collected during two cruises in 2005 and 2006 show the HMMV as an inverted-conical-shaped structure composed by five seismic units (U5-U1 from older to younger) and characterized by pull-down of reflections towards its geometrical centre as well as by a vertically oriented central area of poor seismic image quality. The lack of coherent reflectivity or "blanking" is likely due to the presence of gas in the section. Several studies have interpreted this lack of reflectivity as a "caldera" for mud volcanoes which constitutes the main pathway for fluid and gas in such structures. Isopach maps of the identified seismic units show that U5-U2 distribution is regional, but the youngest unit U1 is confined to the surroundings of the HMMV. The seismic signature of U5-U3 is mainly parallel or absent while unit U1 follows a hummocky trend, interpreted as mud flow deposits. Although the seismic unit U2 is mainly parallel, hummocky reflections as those in U1 have been identified westward of the geometrical centre of the volcano. Detailed analysis of the blanking effect over the seismic units reveals spatially overlapping calderas indicating different ages. Both size and position change, being circular and centrically located in U5-U3 units and oval and northeasterly displaced in both U2 and U1. The shallow structure of the HMMV can be described as a caldera complex in which five overlapping calderas have been identified. They record the migration dynamics of the HMMV over the time. Three years of in-situ sediment temperature measurements support the overlapping caldera as the main active centre of the HMMV. As no evidence of tectonic control has been observed, the deposition of mud flows seems to be controlled by the gravity gradient. The migration suggests a progressive restriction of the flux in the volcano which will affect the habitat distribution of the benthic communities in the HMMV.
DE: 3004 Gas and hydrate systems
DE: 3045 Seafloor morphology, geology, and geophysics
DE: 3075 Submarine tectonics and volcanism
DE: 7294 Seismic instruments and networks (0935, 3025)
DE: 8426 Mud volcanism
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting