|Processes, morphodynamics, and facies of tide-dominated estuaries|Dalrymple, R.W.; Mackay, D.A.; Ichaso, A.A.; Choi, K.S. (2012). Processes, morphodynamics, and facies of tide-dominated estuaries, in: Davis Jr., R.A. et al. (Ed.) Principles of tidal sedimentology. pp. 79-107. hdl.handle.net/10.1007/978-94-007-0123-6_5
Facies; Morphology; Sediment transport; Sedimentology; Tidal currents; Tidal energy; Fresh water
|Authors|| || Top |
- Dalrymple, R.W.
- Mackay, D.A.
- Ichaso, A.A.
- Choi, K.S.
As defined in this chapter, an estuary forms during a shoreline transgression and then fills during a progradational phase that is transitional to a delta. The spatial distribution of processes, grain sizes and facies within tide-dominated estuaries is predictable in general terms. Tidal currents dominate sedimentation along the axis, with wave-dominated sedimentation occurring along the flanks of the estuary in its outer part. Tidal energy increases into the estuary but then decreases toward the tidal limit, with a gradual transition to river-dominated sedimentation at its head. The interaction of the tidal wave with the morphology of the estuary, and with river currents, causes the outer estuary to be flood-dominant, with a net landward movement of sand. By contrast, the inner estuary is ebb-dominant, creating a bedload convergence within the estuary. The axial sandy deposits are typically finest at this location. In transgressive-phase estuaries, the main channel shows a low—high—low pattern of sinuosity, with the tightest bends (sinuosity = 2.5) occurring at the bedload convergence. These bends experience neck cutoff in the transition to the progradational phase of estuary filling. The estuary-mouth region is characterized by cross-bedded sands deposited on elongate sand bars, although wave-generated structures can be important in some cases. Estuaries that are down-drift of major rivers have anomalously muddy outer estuarine deposits. Further landward, upper-flow-regime parallel lamination can be widespread. The margins of the inner estuary are flanked by muddy salt-marsh and tidal-flat deposits that can contain well-developed tidal rhythmites and evidence of seasonal variations in river discharge.