Internal architecture and mobility of tidal sand ridges in the East China Sea

Abstract

On the basis of bathymetric and seismic data and data from piston cores collected by the Chinese-French marine geology and geophysics investigation of 1996, we discuss the internal architecture and mobility of tidal sand ridges in the East China Sea (ECS). We characterized the sand ridges on the middle to outer shelf of the ECS as tide-dominated sand ridges with southwest dipping beds, indicating that the regional net sediment transport is toward the southwest. As the sand ridges gradually migrate toward the southwest, new sand ridges are continually replacing old ones, and several generations of sand ridges have developed in the study area. High-resolution seismic data, acoustic Doppler current profiler data, and two 14 C-dated piston cores, DGKS9614 and DGKS9612-from a sand ridge swale and crest respectively-show that these sand ridges, which are at water depths of 90-100 m, have been migrating for the last ca. 2-3 ky at least, though these ridges have previously been interpreted as moribund or relict. Sequence stratigraphic interpretation of seismic profiles and core data show that tidal ridges in the ECS evolved from muddier sand ridges formed during the last transgression to sandier shelf sand ridges in response to the shoreline retreat, which resulted in a decrease of riverine muddy sediments and recycling of sandy materials by tidal currents. Most active sand ridge formation occurred during the last transgression, but the present sand ridges on the middle to outer shelf are still being influenced by the modern hydrodynamics. Therefore, these sand ridges on the ECS shelf should be referred to as "quasi-active sand ridges" rather than as moribund or relict sand ridges.

Comparison of buried sand ridges and regressive sand ridges on the outer shelf of the East China Sea

“…Most researchers consider that the sand ridges on the ECS shelf were formed during the TST after the LGM, and that the only differences were the formation time. Many researchers believe that most sand ridges were stable with obvious regression features; however, some other researchers consider that the sand ridges were slightly active (Liu et al 2007). Sand waves are the most significant indicator for the activity of sand ridges; however, it is seldom that they have been reported found on the middle or outer ECS shelf, except at the Yangtze shoal (Ye et al 2004).…”

Analisis estratigrafico secuencial de las formaciones Anacleto y Allen (Cretacico Tardio) en el borde nororiental de Cuenca Neuquina, Argentina

“…En esta etapa el sedimento del lecho marino fue erosionado, transportado y redepositado bajo la acción de las corrientes de mareas. El apilamiento de los depósitos caracteriza al período de transgresión tardía en estos sistemas, debido al alto suministro de sedimentos y el adecuado espacio de acomodación (Liu et al, 2007).…”

Large‐scale sediment bodies and superimposed bedforms on the continental shelf close to the Strait of Gibraltar: interplay of complex oceanographic conditions and physiographic constraints

“…In most cases, sand banks and ridges have been reported in environments clearly dominated by a single hydrodynamic agent, either uni-directional storm-driven currents in North American shelves (Amos and King, 1984;Dyer and Huntley, 1999;Snedden and Dalrymple, 1999) or reciprocal tidal currents in the North Sea (Berné et al, 1994;Dyer and Huntley, 1999;Trentesaux et al, 1999) and in the Eastern China and Yellow Seas (Park et al, 2006;Liu et al, 2007;Shinn et al, 2007). These hydrodynamic agents dominate the net bedload transport and hence control the migration trends of large-scale sediment bodies.…”