The Distribution of High Frequency Shallow Seismic Facies on Continental Margins with Varying Boundary Conditions: A Study of the East China Sea Continental Margin
The purpose of this study is to test the hypothesis that the distribution of near surfacesedimentary deposits of continental margins with varying boundary conditions are indynamic equilibrium with the present day hydrodynamic regime and sediment supply.Processes involved are the high influx of sediment supply, strong coastal currents,periodicity of major storm events and the waves and currents they create, tidal range andcurrents, and the waves and currents associated with regional storm events. Due to theextreme nature of the hydrodynamic processes and the abundant sediment supply, the EastChina Sea Continental Margin was chosen for this project. Seismic records were examined and categorized into facies based on continuity,frequency, amplitude, and the geometry of the reflectors. This resulted in the classificationof 28 facies. “Seismic cores” of the upper sediments were then “created” based on thesefacies. “Seismic cores” of the upper sediments were then “created” based on thesefacies. The core lengths were then “normalized” to eliminate the difference in corelengths. Q-Mode factor and Markov analyses were conducted to classify statisticallysignificant lateral facies provinces and non-random vertical facies sequences within theprovinces.These analyses reveal 8 distinctive provinces in the study area and each contains atleast one non-random vertical facies sequence. Comparison of near surface faciesdistribution with the distribution of sources of sediment supply and hydrodynamic forcingmechanisms indicate that large areas on the East China Sea Continental Margin are indynamic equilibrium with the depositional conditions. This study has confirmed thatcombined Q-Mode factor analysis and Markov Process analysis are useful tools toquantitatively characterize the distributions of horizontal and vertical facies on continentalmargins with varying boundary conditions. Finally, a conclusion that can be drawn fromthis study is that observation of areas where there is disequilibrium between sedimentdistribution and hydrodynamic regime on the East China Sea (ECS) continental marginwhere there is adequate sediment supply and hydrodynamic activity to attain equilibriumconditions between the two; suggests that the probability of observing near surfacesediments in dynamic equilibrium on continental margins with lower sediment supply and agreatly reduced hydrodynamic climate is quite low.