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Abstract: Miocene Example of a Meandering Submarine Channel-levee System From 3-D Seismic Reflection Data, Gulf of Mexico Basin

Michael T. Roberts, Behtaz Compani

Submarine fan models and outcrop studies have emphasized sand-rich systems which correspond to Type I and II fans of Mutti (1985). Type III fans ("slope fans" in the sequence stratigraphy literature) are shale-rich systems characterized by up- and out-building levees flanking relatively narrow, sinuous channels, and include overbank deposits such as splays. They are known chiefly from sonar and seismic reflection studies of Pleistocene to Recent deposits. The defining characteristics of these channel-levee systems are difficult to recognize at the scale of many outcrops. We illustrate a Miocene example of a meandering channel-levee complex and associated splays using flattened time slices and sections from a 3-D survey. This system was deposited in deep water about 75 mil s south of its coeval shelf edge. Wells penetrated thinly interbedded sand-shale levee deposits over 150 ft thick with good reservoir characteristics. 3-D seismic data show two adjacent channel-levee systems with several splays. Unlike "slope fans", these deposits appear to sit on a sequence boundary. Levees are up to 400 ft thick and 2 miles wide. Splays are up to a mile or more across and 100 ft thick. Channels are about 500 ft across and highly sinuous with a meander belt width of up to 2 miles. These systems are not readily interpretable on 2-D seismic data where they exhibit low relief and discontinuous amplitudes. Type III fans can contain good quality sand and laminated sand-shale reservoirs in channel, levee and splay settings, as illustrated by outcrops of analog Mesozoic and Pa eozoic rocks.

AAPG Search and Discovery Article #90951©1996 AAPG International Conference and Exhibition, Caracas, Venezuela