Tidally Modulated Storm Sedimentation on Open-Coast Tidal Flats, Southwestern Coast of Korea: Distinguishing Tidal-Flat from Shoreface Storm Deposits
Byongcheon Yang, Robert W. Dalrymple, Seungsoo Chun, Michael F. Johnson, Heejun Lee, 2008. "Tidally Modulated Storm Sedimentation on Open-Coast Tidal Flats, Southwestern Coast of Korea: Distinguishing Tidal-Flat from Shoreface Storm Deposits", Recent Advances in Models of Siliciclastic Shallow-Marine Stratigraphy, Gray J. Hampson, Ronald J. Steel, Peter M. Burgess, Robert W. Dalrymple
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Observations of physical processes on the open-coast tidal flats along the southwestern coast of Korea show that tidal modulation of wave energy, as a result of changing water depth, produces composite storm beds that should be distinct from the classic storm beds that characterize wave-dominated shorefaces and shelves with small tides.
Storms (typhoons) during the low-energy summer generate muddy storm beds that superficially resemble the upward-thinning tidal rhythmites that form between spring and neap tides. Sandy, winter storm beds contain both falling-tide deposits that consist of decreasing-energy facies successions and rising-tide deposits that consist of increasing-energy facies successions. Over most of the tidal flat, bioturbation levels are low, even in the summer mud deposits, because of episodic high-energy conditions and high rates of sedimentation. Bimodal levels of bioturbation (negligible in the thin intra-storm, low-tide mud drapes versus more intense in inter-storm, fair-weather deposits) should characterize deposits formed on open-coast tidal flats. The style of bioturbation on the lower flat is similar to that reported from upper shorefaces, whereas the inner flat contains a mixed Skolithos-Cruziana assemblage that is much less diverse than that found in shelf deposits. These observations show that a spectrum of storm-bed types is to be expected between wave-dominated (i.e., shoreface and shelf) and tide-dominated (i.e., tidal-flat) settings.