HR: 16:30h
AN: S24A-03 INVITED    [Abstracts]
TI: A paleotsunami record from marshlands in West Aceh Province, Indonesia
AU: * Monecke, K
EM: kmonecke@kent.edu
AF: Kent State University, Department of Geology, Kent, OH 44242, United States
AU: * Monecke, K
EM: kmonecke@kent.edu
AF: Vassar College, Department of Earth Sciences and Geography, Poughkeepsie, NY 12604, United States
AU: Finger, W
EM: willi.finger@bluewin.com
AF: Swiss agency for development and cooperation (SDC), Lavaterstr. 66, Zurich, 8002, Switzerland
AU: Kongko, W
EM: liawid@yahoo.com
AF: Badan Pengkajan Dan Penerapan Teknologi (BPPT), Jl. Grafika, Jogjakarta, 55281, Indonesia
AU: McAdoo, B
EM: brmcadoo@vassar.edu
AF: Vassar College, Department of Earth Sciences and Geography, Poughkeepsie, NY 12604, United States
AU: Moore, A L
EM: moorean@earlham.edu
AF: Kent State University, Department of Geology, Kent, OH 44242, United States
AU: Sudrajat, S U
EM: sandmudhunter@yahoo.com
AF: Catholic Relief Services (CRS), Jl. Nasional, Meulaboh, NAD 33333, Indonesia
AB: Constraining the frequency and magnitude of large events in the Indian Ocean region is critical to assess and mitigate tsunami risk along this densely populated coastline in the future. As historical records of large tsunamis in the area are sparse, the geological record provides the best evidence of recurrence rates and size of ancient tsunamis. Based on sediment data from coastal marshland deposits we present a paleotsunami record for West Aceh Province, Indonesia, an area immediately adjacent to the seismic source that was severely affected by the December 2004 tsunami. The recent tsunami deposited a distinct, typically 10-20 cm thick sand sheet up to 2 km inland within a prograding beach ridge plain. Sediment cores from swales in between beach ridges revealed three older sand layers, up to 10 cm thick, and intercalated within organic-rich marshland deposits. At least two of the older sand layers can be followed for several hundred meters along shore normal transects. Coring sites of different transects can be laterally correlated by following pronounced older beach ridges running parallel to the shoreline. The three individual sand layers occur at different distances to the shoreline, with the youngest sand layer at ~500 m distance from the present coast and the oldest one between 1500 m to 2000 m inland within older beach ridge complexes. The spatial distributions as well as grain size trends suggest landward directed flows over a prograding beach ridge plain, which can be best explained by ancient tsunamis. Radiocarbon dating of these deposits indicate three events occurring around 1000 AD, between 1350AD-1550AD, and after 1800AD, with the latter potentially correlating with a historically reported event in 1907AD.
DE: 4217 Coastal processes
DE: 7221 Paleoseismology (8036)
DE: 9340 Indian Ocean
SC: Seismology [S]
MN: 2007 Fall Meeting