Sedimentologic and stratigraphic characteristics of beach ridge and tidal channel deposits in mesotidal barrier systems
Thesis/Dissertation
·
OSTI ID:5374669
Lithologic sequences exposed to the landward and seaward sides of beach ridges on Kiawah Island, South Carolina reflect the translation of subenvironments observable in modern backshore and foreshore settings. The landward sequence is: marsh-washover-berm crest/incipient dunes-dunes. Beach ridges are reworked by migrating tidal creeks into active channel-fill deposits. Ebb dominance causes all point bars to be skewed toward, or to trail away from, the ebb side of a meander bend. Facies distributions are controlled by point bar geometry, which is set up both by ebb dominance and by time-velocity asymmetry. On tight meanders, point bars are relatively small with steep flanks, and are fully welded to the inner bank. Chutes are absent. Intermediate meanders produce complex multilobed bars, with flood-dominant chutes and interlobe ramps. The chute and inner bar may be exposed to no ebb discharge and are both composed of fine-grained sediments. Gentle meanders produce long narrow bars with relatively deep, flood-dominant chutes. Chute bars occur infrequently, but where present are ebb-oriented. Bar extremities are ornamented with sand wave and mega-ripple fields. Point bars on very gentle meanders or nearly straight reaches are narrow and fully welded to the inner bank, resembling the skew shoals of fluvial systems. Little or no current segregation is present. Tidal creek and fluvial floodplain lithosomes are distinguishable on the basis of the relative predominance of channel versus overbank deposits. In addition, these deposits can be identified on the basis of biogenic sedimentary structures, cross-bed orientation, and vertical sequences.
- Research Organization:
- South Carolina Univ., Columbia (USA)
- OSTI ID:
- 5374669
- Country of Publication:
- United States
- Language:
- English
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