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ABSTRACT: Mud Volcanism at the Manihiki-Plateau

Helmut Beiersdorf

In February 1987 a complex of mud volcanoes was discovered on the northeastern edge of the Manihiki-Plateau during a cruise of

R/V MOANA WAVE. Forty out of about 100 cones coalesce to form an edifice about 25 km in diameter, 1900 m high, rising from a plateau depth of 3200 m.

SeaMARC II side-scan images suggest radial fluid sediment flow from the center of this feature. Recent foraminiferal ooze was cored from a satellite cone. One dredge haul from the summit of the edifice recovered burrowed limestone with embedded Middle Eocene foraminifera. It suggests that parts of the sedimentary basement cover of the Manihiki Plateau have been mobilized together with pore fluids and moved upward. The causes of the movement as well as its mechanism, however, remain unknown because of the lack of direct measurements. There is a likelihood that overpressured methane, generated from organic carbon-rich sediments, acts as driving force.

Therefore, BGR submitted a proposal to the Federal Ministry of Research and Technology (BMFT) to investigate the mud volcano complex and reference area with the most relevant outcropping sedimentary sequence of the northeastern Manihiki Plateau in detail. The preliminary results from these investigations carried out with R/V SONNE in spring of 1990 are presented.

AAPG Search and Discovery Article #90097©1990 Fifth Circum-Pacific Energy and Mineral Resources Conference, Honolulu, Hawaii, July 29-August 3, 1990