HR: 0800h
AN: T31A-0282    [Abstracts]
TI: Turbidite sequences in marine sediments off southern Chile ? records of Quaternary climate - tectonics interactions
AU: Echtler, H P
EM: helle@gfz-potsdam.de
AF: GFZ Potsdam, Telegrafenberg, Potsdam, 14473, Germany
AU: * Blumberg, S
EM: sblumb@gfz-potsdam.de
AF: GFZ Potsdam, Telegrafenberg, Potsdam, 14473, Germany
AU: Lamy, F
EM: flamy@awi-bremerhaven.de
AF: AWI Bremerhaven, Am Handelshafen 12, Bremerhaven, 27570, Germany
AU: Arz, H
EM: harz@gfz-potsdam.de
AF: GFZ Potsdam, Telegrafenberg, Potsdam, 14473, Germany
AU: Wiedicke, M
EM: Michael.Wiedicke-Hombach@bgr.de
AF: BGR Hannover, Stilleweg 2, Hannover, 30655, Germany
AU: Haug, G H
EM: gerald.haug@erdw.ethz.ch
AF: ETH Zuerich, Universitaetsstra?e 6, Zuerich, 8092, Switzerland
AU: Oncken, O
EM: oncken@gfz-potsdam.de
AF: GFZ Potsdam, Telegrafenberg, Potsdam, 14473, Germany
AB: The active continental margin of South America is characterized by frequent, devastating and large-magnitude subduction earthquakes. In this environment the assessment of the history of major past earthquakes is hampered by the short historical and instrumental records. Here, we focus on marine turbidite records from offshore southern Chile that reflect the regional paleoseismic history of the forearc region since late Pleistocene time. The investigated records were retrieved from cores obtained from the Ocean Drilling Program (ODP), site 1232, and SONNE 50SL. The coring locations are at ~ 40ç and ~ 38çS lat, within the Peru-Chile trench, and are characterized by frequent interbedded strata of turbiditic and hemipelagic origin. Importantly, dated sections of the obtained cores indicate a recurrence time between 100 and 200 years for individual turbidite events. On the basis of the sedimentological characteristics and the nature of the active margin of southern Chile, we infer that the turbidites are seismogenic in origin, and represent paleo-earthquakes. However, the long-term changes in turbidite recurrence intervals also appear to be strongly influenced by climate and associated sea-level changes. For example, during the rising sea-level in the Holocene (ACHTUNG: es gab keine h?heren Meeresspiegel, sondern der Meeresspiegel ist seit 14 ka angestiegen) and Marine Isotope Stage (MIS) 5, recurrence of turbiditic layers is substantially higher, primarily reflecting a climate-induced reduction of sediment availability and enhanced slope stability (Dieser Satz ist inhaltlich nicht ganz klar). In addition, changes in the segmentation of tectonic uplift in the forearc and related drainage captures likely influenced the availability of sediment entering the marine realm, possibly determining the postglacial decrease in turbidite frequency. On the other hand, glacial turbidite recurrence times (including MIS 2, MIS 3, cold substages of MIS 5, and MIS 6), are within the same order of magnitude as earthquake recurrence intervals, derived from historical data and other terrestrial paleoseismic archives of the region. Only during these cold stages sediment availability and slope instability were pronounced enough to provide conditions conducive to a full record of the sequence of large earthquakes. Our data thus suggest that earthquake recurrence intervals on the order of 100 to 200 years are characteristic for southern Chile and were sustained during the last 140 kyrs.
DE: 1620 Climate dynamics (0429, 3309)
DE: 3002 Continental shelf and slope processes (4219)
DE: 3060 Subduction zone processes (1031, 3613, 8170, 8413)
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 8177 Tectonics and climatic interactions
SC: Tectonophysics [T]
MN: 2007 Fall Meeting