--> Abstract: Sequence Stratigraphy And Associated Seismic Facies Distribution In The Yellow Sea: A Modern Analog For Deposition In Muddy Foreland Basin Environments, by C. C. Moss and L. R. Bartek; #90928 (1999).

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MOSS, C. C., and L. R. BARTEK
University of Alabama, Department of Geology, Tuscaloosa, Alabama 35487-0338

Abstract: Sequence Stratigraphy and Associated Seismic Facies Distribution in the Yellow Sea: A Modern Analog for Deposition in Muddy Foreland Basin Environments

The Yellow Sea is an excellent modern analog of a foreland basintype of depositional system due to specific depositional boundary conditions including it's epicontinental setting, very high sediment supply, large tidal range, high frequency of major storms, and rapidly avulsing river systems. A grid of approximately 5024 km of high resolution (<1 m) seismic data was acquired from the Yellow Sea in order to develop a stochastic model of facies distribution associated with these depositional conditions

Seismic facies were objectively identified on the basis of reflection orientation, frequency, amplitude, and lateral continuity. Variation of seismic facies is related to variation in lithofacies composition which are inturn a product of variation in modes of depositional processes and are indicators of deposition in particular systems tracts. Moderate to high frequency, parallel horizontal reflections are assumed to indicate highstand deposition. Chaotic and inclined reflections as well as reflections with curved morphologies, with moderate frequency, and low to moderate amplitude are indicative of lowstand deposits. The chaotic and inclined reflections as well as reflections with curved morphologies are products of lateral accretion and channel fill associated with an avulsing braided fluvial system. Single, high amplitude reflections which truncate all underlying reflections and are generally horizontal to slightly inclined are interpreted as transgressive surfaces and the base of transgressive systems tracts. Qualitative assessment of the horizontal and vertical distribution of seismic facies suggests that lowstand braided fluvial deposits are widespread in the northern and western areas of the basin, and increasingly dominant towards the south. These are separated by thin transgressive systems; highstand deposits are also widespread, particularly in the northern and western parts of the basin, but are highly dissected by overlying lowstand deposits (increasing in frequency and extent to the south).

The University of Alabama Seismic Stratigraphy Group is currently developing stochastic models of sedimentation patterns in the Gulf of Mexico (off the Alabama coast) and the East China Sea, and these models will be compared with findings from the Yellow Sea. Early results indicate that the Gulf of Mexico has widespread highstand deposits dissected by relatively narrow incised valleys filled with lowstand deposits. The East China Sea appears to be more similar to the southern Yellow Sea, where lowstand deposits are laterally extensive and also dissect the underlying highstand deposits.

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