REEVES, E. and L. BARTEK
University of Alabama Geology Graduate School, Tuscaloosa, Alabama

Abstract: Dynamic Equilibrium of Process-Response Relationships and Facies Distribution on a Storm and Tidally Influenced Continental Shelf, Yellow Sea

A series of statistical analyses identifies the statistically significant relationships among data derived from cores and proximity to major depositional forcing mechanisms (axes of major oceanic currents, bathymetry (wave-base), amphidromic points (tidal velocities), etc.) and sources of sediment in the Yellow Sea (YS). These analyses were conducted in order to quantitatively determine the process-response relationship between sedimentary processes on a continental shelf with very high, fine-grained sediment supply, very strong tidal currents, and subject to significant impact by storm generated waves (an analog for some foreland basin depositonal systems). This depositional setting has the potential for a state of dynamic equilibrium between sediment transport/depositional processes; and the distribution of sedimentary facies. ANOVA, Q-mode factor analysis, and Binomial Markov process analysis identify groups of cores with compositions that are similar as well as the non-random vertical facies successions within cores. Regression analysis identifies controlling factors on sedimentary facies distribution.

The relationships between the distribution of facies and proximity to areas influenced by specific processes and sources of sediment indicate that facies distribution on most of the shelf is influenced by a combination of processes rather than being dominated by a single process. There are two significant sources of sediment for the YS: the modern Yellow River (MYR) and the ancient Yellow River delta (AYRD). The AYRD is the dominant source of sediment for tidal shoals in the extreme SW portion of the YS. Due to the shallow depth along the western portion of the YS, storms and the tides winnow and redistribute the muddy sediment from the area and leave a lag of sandy facies across the extreme southwestern portion of the YS. In the NW portion of the YS, along the path of the Yellow Sea Coastal Current, the area is characterized by rapid accumulation of muddy facies from the MYR. Strong tidal and thermochaline currents control facies distribution in the eastern portion of the YS. Large tidal ridges composed of lag deposits of coarse-grained sands derived from Pleistocene deposits cover the inner shelf of eastern YS. The central portion of the YS is the deepest portion of the basin, contains an amphidromic point and is an area where flow expands. Consequently tidal current and thermohaline current velocities are low and waves interact with the bottom less frequently so accumulation of finegrained sediment, derived from the MYR is rapid.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas