John M. Armentrout2
(1) Mobil Oil Qatar, Inc, Dallas, TX
(2) Mobil Oil, Carrollton, TX
Abstract: 3D seismic facies of a Pleistocene turbidite system, western Green Canyon, Gulf of Mexico
Interpretation of a 3D seismic data volume from western Green Canyon defines a Pleistocene turbidite system with a seismic facies association similar to that mapped on the Amazon fan. The western Green Canyon depositional system differs in being restricted by local ‘mini-basin’ geometry. The most distal facies is parallel-bedded to long low-angle clinoforms. This facies rests on the P. annula (Large) maximum flooding surface and is often restricted to filling topographic lows within the minibasin, or filling the entire minibasin. At the base of this seismic facies a 'notched' pattern suggests small, incised channels. The low-angle clinoforms grade laterally toward the margins from high amplitude to low amplitude facies. This facies package is sometimes capped by very small-scale channels, through which the clinoform sediments were transported. Overlying the parallel-bedded facies is a package of more steeply angled clinoforms, interpreted as more proximal fan progrades. This facies is locally capped by a leveed channel system, incised channel system or a major incised valley.
Slump deposits are frequently found at any point throughout the facies succession and may be mistaken as either high-angled clinoforms or as a hummocky-mounded facies. Local channel margin collapse is common as well as syndepositional normal faulting in some of the slump deposits.
High amplitude facies are most often observed in the parallel-bedded, channel/levee and channel facies. Limited well calibration and rock-physics modeling suggest that amplitude contrast is present between normally pressured wet sands and shales. With burial to greater depth and pressure, the amplitude contrast reduces to near zero, making interpretations from amplitude patterns less reliable.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana