Changes

Although in present world deltas, river-mouth tidal ridges form one of the major sand bodies associated with rivers prograding into basins displaying macro- or high-tidal ranges, literature on these river-mouth tidal ridges is sparse. Many past river deltas undoubtedly existed in similar environmental settings, and they must therefore form prominent sand bodies in many ancient-rock deltaic sequences. Major literature associated with these types of features includes that of Off,<ref name=Off_1963>Off, Theodore, 1963, [http://archives.datapages.com/data/bulletns/1961-64/data/pg/0047/0002/0300/0324.htm Rhythmic linear sand bodies caused by tidal currents]: AAPG Bulletin, v. 47, p. 324-341.</ref> Keller and Richards,<ref name=Kellerandrichards_1967>Keller, G. H., and A. F. Richards, 1967, Sediments of the Malacca Straits, southeast Asia: Jour. Sed. Petrology, v. 37, p. 102-127.</ref> Reineck and Singh,<ref name=Reineckandsingh_1967>Reineck, H. E., and I. B. Singh, 1967, Primary sedimentary structures in the Recent sediments of the Jade, North Sea: Marine Geol., v. 5, p. 227-235.</ref> Houbolt,<ref name=Houboult_1968>Houbolt, J. J. H. C., 1968, Recent sediments in the southern bight of the North Sea: Geol. en Mijnbouw, v. 47, p. 245-273.</ref> Klein,<ref name=Klein_1970>Klein, G. de V., 1970, Depositional and dispersal dynamics of intertidal sand bars: Jour. Sed. Petrology, v. 40, p. 1095-1127.</ref> Ludwick,<ref name=Ludwick_1970>Ludwick, J. C., 1970, Sand waves and tidal channels in the entrance to Chesapeake Bay: Old Dominion Univ., Inst. Oceanography, Tech. Rept. 1, 79 p.</ref> Meckel,<ref name=Meckel_1975>Meckel, L. D., 1975, Holocene sand bodies in the Colorado Delta, Salton Sea, Imperial County, California: in M. L. Broussard, ed., Deltas, models for exploration, 2nd ed: Houston Geol. Soc., p. 239-265.</ref> and Wright and Thom.<ref name=Wrightandthom_1975>Wright, L. D., and B. G. Thom, 1975, Sediment transport and deposition in a macrotidal river channel: Ord River, Western Australia: Estuarine Research, v. II: New York, Academic Press, p. 309-321.</ref>

Although in present world deltas, river-mouth tidal ridges form one of the major sand bodies associated with rivers prograding into basins displaying macro- or high-tidal ranges, literature on these river-mouth tidal ridges is sparse. Many past river deltas undoubtedly existed in similar environmental settings, and they must therefore form prominent sand bodies in many ancient-rock deltaic sequences. Major literature associated with these types of features includes that of Off,<ref name=Off_1963>Off, Theodore, 1963, [http://archives.datapages.com/data/bulletns/1961-64/data/pg/0047/0002/0300/0324.htm Rhythmic linear sand bodies caused by tidal currents]: AAPG Bulletin, v. 47, p. 324-341.</ref> Keller and Richards,<ref name=Kellerandrichards_1967>Keller, G. H., and A. F. Richards, 1967, Sediments of the Malacca Straits, southeast Asia: Jour. Sed. Petrology, v. 37, p. 102-127.</ref> Reineck and Singh,<ref name=Reineckandsingh_1967>Reineck, H. E., and I. B. Singh, 1967, Primary sedimentary structures in the Recent sediments of the Jade, North Sea: Marine Geol., v. 5, p. 227-235.</ref> Houbolt,<ref name=Houboult_1968>Houbolt, J. J. H. C., 1968, Recent sediments in the southern bight of the North Sea: Geol. en Mijnbouw, v. 47, p. 245-273.</ref> Klein,<ref name=Klein_1970>Klein, G. de V., 1970, Depositional and dispersal dynamics of intertidal sand bars: Jour. Sed. Petrology, v. 40, p. 1095-1127.</ref> Ludwick,<ref name=Ludwick_1970>Ludwick, J. C., 1970, Sand waves and tidal channels in the entrance to Chesapeake Bay: Old Dominion Univ., Inst. Oceanography, Tech. Rept. 1, 79 p.</ref> Meckel,<ref name=Meckel_1975>Meckel, L. D., 1975, Holocene sand bodies in the Colorado Delta, Salton Sea, Imperial County, California: in M. L. Broussard, ed., Deltas, models for exploration, 2nd ed: Houston Geol. Soc., p. 239-265.</ref> and Wright and Thom.<ref name=Wrightandthom_1975>Wright, L. D., and B. G. Thom, 1975, Sediment transport and deposition in a macrotidal river channel: Ord River, Western Australia: Estuarine Research, v. II: New York, Academic Press, p. 309-321.</ref>

River distributaries debouching into high-tidal regions commonly display a funnel-shaped configuration, with widths attaining several kilometers. Linear, elongate tidal ridges aligned parallel with each other in the direction of tidal flow are the most prominent channel and river mouth accumulation forms. They appear to be directly related to bidirectional sediment transport patterns, high-tidal amplitudes, and tidal-current symmetry. Tidal ridges described by Coleman<ref name=Coleman_1976 /> and Wright and Thom<ref name=Wrightandthom_1975 /> in the Ord River are typical of the study shoals found in river-dominated deltaic distributaries.

River distributaries debouching into high-tidal regions commonly display a funnel-shaped configuration, with widths attaining several kilometers. Linear, elongate tidal ridges aligned parallel with each other in the direction of tidal flow are the most prominent channel and river mouth accumulation forms. They appear to be directly related to bidirectional sediment transport patterns, high-tidal amplitudes, and tidal-current symmetry. Tidal ridges described by Coleman<ref name=Coleman_1976>Coleman, J. M., 1976, Deltas: Processes of deposition and models for exploration: Continuing Education Publ. Co., Champaign, IL (now available from Burgess Publishing Co., 7108 Ohms Lane, Minneapolis, MN 55435), 102 p.</ref> and Wright and Thom<ref name=Wrightandthom_1975 /> in the Ord River are typical of the study shoals found in river-dominated deltaic distributaries.

Those tidal ranges in the Ord River range in relief from 10 to 22 m and compositely account for over 5 x 10⁶ cu m of total sand accumulation. Tidal ridges average roughly 2 km in length and 300 m in width, with crests emergent or near the surface at low tide. A few are permanently emergent and vegetated by mangrove. In some deltas, tidal ridges attain extreme lengths of 10 to 15 km. Deltas displaying similar types of shoals have been described by Off<ref name=Off_1963 /> and Meckel.<ref name=Meckel_1975 /> Meckel<ref name=Meckel_1975 /> referred to tidal ridges at the mouth of the Colorado delta, Gulf of California, as tidal bars. Ridges at the mouth of the Colorado display relief of 7 to 10 m and a crest to crest spacing of several kilometers. In cross-sect on they vary from roughly symmetrical to distinctly asymmetrical, with steep sides commonly facing the downstream direction of tidal propagation.

Those tidal ranges in the Ord River range in relief from 10 to 22 m and compositely account for over 5 x 10⁶ cu m of total sand accumulation. Tidal ridges average roughly 2 km in length and 300 m in width, with crests emergent or near the surface at low tide. A few are permanently emergent and vegetated by mangrove. In some deltas, tidal ridges attain extreme lengths of 10 to 15 km. Deltas displaying similar types of shoals have been described by Off<ref name=Off_1963 /> and Meckel.<ref name=Meckel_1975 /> Meckel<ref name=Meckel_1975 /> referred to tidal ridges at the mouth of the Colorado delta, Gulf of California, as tidal bars. Ridges at the mouth of the Colorado display relief of 7 to 10 m and a crest to crest spacing of several kilometers. In cross-sect on they vary from roughly symmetrical to distinctly asymmetrical, with steep sides commonly facing the downstream direction of tidal propagation.