HR: 1340h
AN: T13A-1124    [Abstracts]
TI: Extensional and Transtensional Tectonics of the Manihiki Plateau, Western Equatorial Pacific Ocean
AU: * Coffin, M F
EM: mcoffin@ori.u-tokyo.ac.jp
AF: Ocean Research Institute University of Tokyo, 1-15-1 Minamidai Nakano-ku, Tokyo, 164-8639, Japan
AU: Werner, R
EM: rwerner@ifm-geomar.de
AF: Tethys Geoconsulting GmbH, Building 12 Wischhofstr. 1-3, Kiel, 24148, Germany
AU: Hauff, F
EM: fhauff@ifm-geomar.de
AF: Research Division 4: Dynamics of the Ocean Floor IFM-GEOMAR Leibniz Institute for Marine Sciences, Gebäude Ostufer Wischhofstr. 1-3, Kiel, 24148, Germany
AU: Hoernle, K
EM: khoernle@ifm-geomar.de
AF: Research Division 4: Dynamics of the Ocean Floor IFM-GEOMAR Leibniz Institute for Marine Sciences, Gebäude Ostufer Wischhofstr. 1-3, Kiel, 24148, Germany
AU: Scientific Party, F
EM: khoernle@ifm-geomar.de
AF: Research Division 4: Dynamics of the Ocean Floor IFM-GEOMAR Leibniz Institute for Marine Sciences, Gebäude Ostufer Wischhofstr. 1-3, Kiel, 24148, Germany
AB: Standing several kilometers above surrounding seafloor, the submarine Manihiki Plateau, an oceanic large igneous province (LIP), encompasses ~800,000 km² of seafloor in the western equatorial Pacific Ocean. Of Early Cretaceous (~120 Ma) age, the plateau comprises three major structural highs. The High Plateau to the east contains several islands, including the eponymous Manihiki atoll. To the west, the Western Plateaus lie approximately one kilometer deeper; they are bifurcated by elongated, overall northeast-trending, bathymetric lows known as the Danger Islands troughs (DITs). North of the Western Plateaus is the small, nearly separate North Plateau that is separated from the High Plateau (and contiguous NE portion of the Western Plateaus) by the High-North Basin. In May-June 2007, we acquired extensive multibeam bathymetry and reflectivity over all three structural highs and their flanks during the 40-day F.S. Sonne cruise 193. On the basis of these new as well as pre-existing data, we propose a tectonic model for post-emplacement, probable Late Cretaceous deformation of the Manihiki Plateau involving both extensional and transtensional deformation. In our model, the High-North Basin probably formed by seafloor spreading; the northwestern margin of the contiguous NE portion of the Western Plateaus-High Plateau and the southeastern margin of the North Plateau are conjugate rifted margins, whose separation approximately equals the right-lateral offset between the southern flanks of Western Plateaus on either side of the DITs. The curvilinear southwest boundary of the High-North Basin consists of several pull-apart basins that abut the steep northeast flank of the Western plateaus; LIP and normal oceanic crust are juxtaposed along this boundary. The right-lateral relict plate boundary continues uninterrupted to the south of the deep ocean basin as the DITs, which in the study area comprise a series of major en echelon, right- lateral faults that step to the right, producing extensional relay zones and pull-apart basins between fault tips where displacement was transferred. Geochronology of igneous rock samples dredged from the flanks of the High-North Basin and the DITs during the Sonne expedition may yield information on the timing of deformation, which would in turn contribute to a better understanding of regional Cretaceous plate kinematics.
DE: 3038 Oceanic plateaus and microcontinents
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
DE: 3045 Seafloor morphology, geology, and geophysics
DE: 8137 Hotspots, large igneous provinces, and flood basalt volcanism
DE: 8157 Plate motions: past (3040)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting