HR: 1340h
AN: GP23A-0025    [Abstracts]
TI: Fossil Overlapping Spreading Centre in the Central Pacific at the Trace of the Pacific-Cocos-Nazca Triple Point
AU: * Meschede, M
EM: meschede@uni-greifswald.de
AF: University of Greifswald, Institute of Geography and Geology, Friedrich-Ludwig-Jahn-Str. 17a, Greifswald, D-17487 Germany
AU: Barckhausen, U
EM: Udo.Barckhausen@bgr.de
AF: Federal Institute for Geosciences and Natural Resources, Stilleweg 2, Hannover, D-30655 Germany
AU: Weinrebe, W
EM: wweinrebe@ifm-geomar.de
AF: Leibniz-Institut fuer Meereswissenschaften IFM-GEOMAR, Wischhofstr. 1-3, Kiel, D-24148 Germany
AU: Engels, M
EM: m.engels@bgr.de
AF: Federal Institute for Geosciences and Natural Resources, Stilleweg 2, Hannover, D-30655 Germany
AB: The Central Pacific region between 125° W/5° N and 110° W/10° S which contains the "plate tectonic mirror image" to the region of the Cocos plate currently being subducted beneath Central America has been the target of an investigation using multibeam bathymetry, magnetics and gravity. One of the main points of interest was the formation of the triple junction of Pacific, Cocos and Nacza plates in the Late Oligocene/Early Miocene (around 24 Myrs). This event indicates the breakup of the Farallon plate on the eastern side of the East-Pacific-Rise into Cocos and Nazca plates. At this time the first Cocos-Nazca spreading centre (CNS-1) a precursor of the currently active spreading centre (CNS-3) between Cocos and Nazca plates was initiated. The breakup process is a result of changing spreading directions caused by global changes in plate movement directions. This is documented in the area of investigation in the Central Pacific in changes in the strike direction of magnetic lineations from north to south and morphological structures of the seafloor. Irregularities in the magnetic lineation pattern in a small area in the centre of the investigation area and curved morphological structures on the oceanic seafloor are interpreted in terms of remnants of a fossil overlapping spreading centre. The overlapping spreading centre was formed as a consequence of shiftings in the spreading axis which subsequently are straightened out by processes like the one described.
DE: 3614 Mid-oceanic ridge processes (1032, 8416)
DE: 8038 Regional crustal structure
DE: 8150 Plate boundary: general (3040)
DE: 9355 Pacific Ocean
DE: 9605 Neogene
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005