HR: 0800h
AN: U11A-0801    [Abstracts]
TI: Comparative Study of the Sediment Record of Coastal Lagoons, Sri Lanka: Implications for Paleotsunamis
AU: * Jackson, K L
EM: kjackson@rsmas.miami.edu
AF: RSMAS - University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149
AU: Amelung, F
U11A-0801 AF: RSMAS - University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149
AU: Andres, M S
U11A-0801 AF: RSMAS - University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149
AU: Eberli, G
U11A-0801 AF: RSMAS - University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149
AU: Jayasena, C
U11A-0801 AF: University of Peradeniya, Dept. of Geology, Peradeniya, 0094 Sri Lanka
AU: Kehelpannala, K W
U11A-0801 AF: Institute of Fundamental Studies, Hantana Road, Kandy, 0094 Sri Lanka
AU: Peterson, L
U11A-0801 AF: RSMAS - University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149
AU: Rankey, E
U11A-0801 AF: RSMAS - University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149
AB: In light of the catastrophic Indian Ocean tsunami of December 26, 2004, information on the recurrence probability of such events is an important, yet unanswered, question. With a convergence rate of 6 cm per year, the subduction zone that initiated this event is capable of generating earthquakes of similar magnitude, and possibly tsunamis, every 350 years. Sri Lankan historical records suggest that at least one catastrophic tsunami occurred approximately 1600 years ago. To explore the frequency of tsunamis in Sri Lanka, we utilize the unique opportunity to compare tsunami-related coastal lagoon sedimentation from the 2004 event with older lagoon sediments. This comparison, calibrated with historical records, offers potential for deciphering the paleotsunami record in Sri Lanka. Southeastern Sri Lanka has abundant coastal lagoons, many of which were flooded by the 2004 tsunami. Sediment cores (1 to 3 m) collected from Karagan, Lunama, and Rekawa lagoons provide important information including tsunami sediment source, background sedimentation type and rates, and preservation potential. Typical background sediments are mud-dominated, organic-rich, siliciclastic deposits with a variety of molluscs. These mud-dominated layers are interbedded with sand-rich layers that commonly have sharp bases, fine upward, vary in thickness from 1 to 15 cm, and include grain sizes ranging from fine granule to fine sand. These distinct layers are potentially related to either paleotsunamis or storms. Determining the origin of these interbedded sand and mud layers will be a key to unlocking the tsunami record in Sri Lanka. Detailed examination of the 2004 tsunami deposits provides a model for how previous tsunamis are preserved in the sedimentary record of coastal lagoons. Sedimentological analyses, in conjunction with radiocarbon dating and mollusc identification, will provide chronology and environmental constraints on the sand events recorded in this mud-dominated environment. Deciphering the record of tsunamis in Sri Lanka provides a better understanding of the regional geologic history, how tsunamis historically have affected the area, and possible future tsunami risks.
DE: 4239 Limnology (0458, 1845, 4942)
DE: 4564 Tsunamis and storm surges
DE: 4863 Sedimentation (1861)
DE: 9340 Indian Ocean
SC: Union [U]
MN: Fall Meeting 2005