HR: 1340h
AN: T13C-1375    [Abstracts]
TI: Turbiditic Sequences in Sediment Cores from the Continental Margin of Southern Chile as a Potential Record of Seismic Activity
AU: * Reichel, T
EM: Thomas.Reichel@bgr.de
AF: Bundesanstalt fuer Geowissenschaften und Rohstoffe (BGR), Stilleweg 2, Hannover, 30655 Germany
AB: The tectonically active continental margin of Chile offers an excellent opportunity to study the relationship between local seismic activity and mass movements in the marine sedimentary record. The historical earthquake record of the past 500 years shows that even very strong events of magnitude $>$ 7 (Richter scale) have been fairly common. Seismic events lead to remobilisation of sediments triggering downslope turbidites. Several deeply incised canyons channel most of the sediment into the trench, where the sediment sequence documents a regional record of events. Some intra-slope basins also bear a high potential for the preservation of a turbidite record of local significance. Sediment cores taken from different settings along the continental margin were analyzed for their succession of turbiditic layers. Age-dating - presently in progress - will be based on $\delta$$^{18}$O-; AMS$^{14}$C-, $^{210}$Pb-analyses in all cores. First results are: During the Pleistocene sedimentation rates were high and turbidite layers more frequent due to strong erosion in the hinterland associated with glacial activity and a colder and more humid climate. Even sediment cores in elevated and distant positions of the trench contain turbiditic-layers, although age-datings show that these layers are older than 10ka. An intra-slope basin near the foot of the slope gives a record of the Holocene turbiditic-sequences which contains 6 to 12 strong events. Further detailed age determination of the sequences - presently in progress - and comparison with the historical earthquake record promise an extension of the seismic record into the past beyond the last 500 years.
DE: 9355 Pacific Ocean
DE: 8105 Continental margins and sedimentary basins
DE: 8123 Dynamics, seismotectonics
DE: 3022 Marine sediments--processes and transport
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting