Depositional architecture of tide-dominated and wave-dominated deltas
Speaker: Pan, Tsun-You
Abstract
A delta is a discrete shoreline protuberance formed at a point where a river enters the ocean or other large body of water, and it can be classified as (1) river-dominated, (2) wave-dominated, or (3) tide-dominated delta. Middle Devonian Kernave and Arukula formations in the Baltic Basin in Canada were interpreted as tide-dominated delta deposits. The tide-dominated deposits consist of three progradational to aggradational packages, which are 20-40 m thick. The lower upward-coarsening portion consists of prodelta to distal-tidal-bar and proximal-tidal-bar deposits. The upper upward-fining portion consists of tidal flat, supratidal muds, occasional tidal gully and distributary channel, and paleosol deposits. During the delta evolution, the depositional architecture and delta morphology changed from Stratigraphic Unit 1 through 3, including lateral changes between eastern and western parts of the basin. the upper Cretaceous Alderson member (Lea Park Formation) in western Canada is a 180-m-thick, gas-charged shale unit, which contained Diagnostic features include deformed, muddy mantle-bearing burrows, massive to micro-stratified shale laminae, shale-on-shale erosional contacts, and abundant trace fossils. Ichnologic and sedimentologic study reveals that the strata were interpreted as wave-dominated subaqueous delta instead of deeper marine deposits. The delta was in an alongshore-sediment-transport-influenced marine depositional system, which was sourced by rivers carrying a significant suspended-sediment load. The differences between these two deltas: (1)Paleosols indicated that there is more area exposed to subaerial environment in tide-dominated delta. (2) Coarse-grained channel deposits indicated the high energy of tidal currents. (3) Planar- and trough-cross stratifications in tidal bar strata indicated the influence of tides. (4) the influence of the longshore current is more important in the wave-dominated delta.
Reference
Hovikoski, J., Lemiski, R., Gingras, M., Pemberton, G., McEachern, J. A., 2008. Ichnology and sedimentology of a mud-dominated deltaic coast: Upper Cretaceous Alderson Member (Lea Peak Fm), western Canada. Journal of Sedimentary Research, 78, 803–824.
Tanavsuu-Milkeviciene, K., Plink-Bjorklund, P., 2009. Recognizing tide-dominated versus tide-influenced deltas: Middle Devonian strata of the Baltic basin. Journal of Sedimentary Research, 79, 887–905.