Vertical Grain Size Trends in Suspended Sediment Deposits and Applications to the Identification and Interpretation of Tsunami Deposits
Abstract
Tsunami deposit research and inverse tsunami sedimentation modeling have progressed greatly in the years since the 2004 Indian Ocean Tsunami, but many basic questions regarding tsunami sediment transport, deposition and identification still remain. The conceptual model of tsunami sedimentation often presented in the literature is that of suspended load falling out of suspension as the flow approaches the limit of inundation. This type of deposition creates a fining upward grain size trend that is often observed in modern tsunami deposits and has been postulated to be a key criterion for distinguishing non-historic tsunami deposits from other high-energy deposits. However, not all tsunami deposits exhibit normal grading, and there are many other situations in nature where normal grading occurs. In this study we utilize suspended sediment transport formulations found in the Jaffe and Gelfenbaum (Sedimentary Geology 2007; 200, 347- 361) inverse tsunami sedimentation model and idealized source material distributions to examine suspended sediment deposition at a level of detail that is not permitted in nature. We investigate the role of flow hydrodynamics and source material distributions in the vertical grain size trends of the resulting deposit. Comparing modeled grain size distributions to those of modern and non-historic tsunami deposits, we are able to better understand the formation of tsunami deposits and develop criteria to discriminate between tsunami and other normally graded deposits. This aids in the identification of non-historic tsunami deposits, and reveals details of the event's source material and flow characteristics that otherwise would not be apparent.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFMOS53A1289B
- Keywords:
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- 4200 OCEANOGRAPHY: GENERAL;
- 4255 Numerical modeling (0545;
- 0560);
- 4534 Hydrodynamic modeling;
- 4558 Sediment transport (1862);
- 4564 Tsunamis and storm surges