Sedimentation and stratigraphic preservation in wave -dominated tidal flats: Southwestern coast of Korea

This study of the modern sediments and Holocene deposits that accumulated on the open-coast tidal flats along the southwestern coast of Korea has revealed that: (1) sedimentation is controlled by the seasonal variation in the intensity of onshore-directed winds and waves, resulting in an environmental oscillation that takes place between tide-dominated mud deposition in summer and wave-dominated sand deposition in winter; (2) due to the low preservation potential of the muddy summer tidal deposits, the preserved deposits consist mainly of amalgamated winter storm beds that resemble those generally associated with shorefaces; (3) on the wave-dominated intertidal flats the wavelength of HCS becomes smaller in a landward direction because of a decrease of wave size; (4) the HCS wavelength is controlled by the bottom orbital diameter (d0) according to the relationship lambda ≈ 0.75 d0 which suggests that the bedform responsible for HCS is a type of orbital ripple; (5) the size of the waves on wave-dominated tidal flats is depth limited so that the length of the HCS ( 2 m long); (6) tidal modulated changes in wave size during storms (because of tidal changes in water depth) produce composite storm beds that should be distinct from the classic storm beds that characterize wave-dominated shorefaces and shelves with small tides; (7) bimodal levels of bioturbation should characterize the deposits formed on open-coast tidal flats, compared with the opportunistic bioturbation in shorefaces and shelves; and (8) unlike the tide-dominated coasts to the north and south, the southwestern-western coast of Korea is wave dominated and has developed a retrogradational, coarsening-upward succession as a result of barrier-island retreat during the later stages of the Holocene transgression, with tidally formed back-barrier deposits erosively overlain by wave-dominated deposits of the modern tidal flats.;The results of this research provide a missing link between the tide-dominated and wave-dominated end members of coastal settings and raise the question of how many ancient "shorefaces" are, in fact, open-coast tidal flats.*.;*This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Microsoft Office.