Sedimentary processes of turbidite systems fed by delta in lacustrine rift basin: an example from Dongying depression, East China

Sedimentary processes of turbidite system in lacustrine rift basins with generally smaller scale and fault activities have not been understood well. Delta-fed turbidite systems in Eocene Dongying depression (DYD), Bohai Bay... [ view full abstract ]

Sedimentary processes of turbidite system in lacustrine rift basins with generally smaller scale and fault activities have not been understood well. Delta-fed turbidite systems in Eocene Dongying depression (DYD), Bohai Bay basin were studied using cores, well logs and 3D seismic data. Four basic sedimentary processes, i.e., debris flow, turbidity current, slide and slump, were interpreted by deep-water lithofacies analyses. Statistics of deep-water sedimentary processes from cored wells and planar mapping of sedimentary elements based on seismic attributes calibrated by core and well logging data demonstrate that turbidite systems fed by delta were dominated by debris flow and slump, rather than turbidity current.
Sand–rich supply from deltaic sediments and short–distance transportation restricted by scale of deep–water area and fault activities are two key controls to debrite-dominated turbidite system in rifted DYD. Sedimentary evolution of fluxoturbidite system are not complete from slide to turbidity current when transportation distance was not enough long. Consequently, most of sediments of fluxoturbidite system in DYD deposited by debris flow in gentle low–lying area, or/and slumps at the slope feet of delta front or at the hanging walls of growth faults. At the same stage, development of debrites is conflict with that of slumps. Therefore, there are more slumps or/and slides when growth faults have more activities.
Distribution and characteristics of depositional elements besides slumps and slides provided evidences for interpretation of Eocene deep-water sedimentary processes in DYD. Sedimentary architecture of turbidte system fed by Dongying delta is generally characterized by (i) ‘transportational channel’ with only scattered sandstones, (ii) being short of overbank deposits and (iii) tongue-like sands. Transportational channel without overbank deposition can be resulted from hydroplaning mechanism of subaqueous debris flow. Tongue-like sands developed at the end of channels due to frozen-style deposition of weakening debris flow with less scale volumes of sediments.
Lacustrine turbidite system fed by delta in DYD is dominated by debrites and slumps which control development of transportational channels and tongue-like sands. These findings deepen understanding of lacustrine deep-water deposition and have significant implications for assessment of lacustrine gravity flow sandstone fed by delta.