Kelly L. Jackson
Comparative Sedimentology and Geochemistry of Recent and Ancient
Tsunami Deposits in Karagan Lagoon, Sri Lanka
Committee Chairman: Dr. Eugene Rankey
Committee Members: Drs. Gregor Eberli, Falk Amelung, &
Ralph Mead
Sub-Committee Members: Drs. Peter Swart, Larry Peterson
I am currently working towards completing my
Master’s degree on the comparative sedimentology
of recent and ancient tsunami deposits in Sri Lanka.
In addition to tsunami sedimentology, my other
research interests include carbonate sedimentology,
basin analysis, sequence stratigraphy, carbonate
geochemistry, and chemical oceanography.
Project Summary:
Tsunamis have the potential to affect a wide variety of coastal systems. While tsunamis are
termed ‘waves of destruction,’ are they always important in shaping sedimentary systems and the
stratigraphic record? Sediment cores from Sri Lanka provide the unique opportunity to compare
2004 Indian Ocean tsunami-related coastal lagoon sedimentation with older lagoon sediments to
test this question. Preliminary results illustrate that the 2004 tsunami transported material into
lagoons, but the overall geomorphic and hydrologic conditions remained unchanged.
Information on the recurrence of tsunamis is important to understanding how tsunamis influence
coastal systems therefore this project addresses the question of the repeat frequency of these
destructive events. Sediment cores collected from Karagan Lagoon on Sri Lanka's southeastern
coastline feature mud-dominated background sedimentation, interrupted by sand layers with
sharp erosive bases. At least 7 sand layers are preserved within the upper 4 meters of sediment
and are interpreted to represent paleotsunami deposits.
This project focuses on studying the deposits of the most recent (2004) tsunami, developing
recognition criteria for tsunami deposits, applying these criteria to identify paleotsunami deposits
in Sri Lankan lagoons, and dating of these paleotsunami deposits to test 2 hypotheses:
1. Sri Lankan coastal lagoons preserve tsunami deposits. Interpreted paleotsunami deposits
(coarse quartz sand) are differentiated from mud-rich background lagoon sedimentation by
sedimentological and geochemical characteristics.
2. Karagan Lagoon contains a record of tsunamis with an average recurrence frequency of
every 300 years that is consistent with earthquake models.
To test these hypotheses, a multidisciplinary comparative sedimentological and geochemical
approach is being used to differentiate between interpreted paleotsunami deposits (sand layers)
and the mud-rich background sedimentation. Analyses include detailed sedimentological
descriptions, grain size and thin section analysis, gamma ray density, electrical resistivity,
magnetic susceptibility, XRD, XRF, 13C, 18O, and total organic carbon and nitrogen. AMS
radiocarbon dating is used to construct the chronology of the sediments in the cores.