Sequence Stratigraphy of the Alaminos Fan (Upper Miocene-Pleistocene), Northwestern Deep Gulf of Mexico
Christopher H. Morton, Paul Weimer, 2000. "Sequence Stratigraphy of the Alaminos Fan (Upper Miocene-Pleistocene), Northwestern Deep Gulf of Mexico", Deep-Water Reservoirs of the World, Paul Weimer
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The Alaminos Fan (uppermost Miocene to lower Pleistocene) is a moderate sized, mud-dominated submarine fan in the northwestern deep Gulf of Mexico. Located in the southern portion of the Alaminos protraction area, the fan is bounded to the north by the salt tongues of the Sigsbee Escarpment; the fan overlies and extends southeast of the northern portion of the Perdido fold belt. Interpretation of 1500 km of 2D multifold seismic data has defined five depositional sequences, four of which consist of thin shallow distributary channel-fills, thicker aggradational levee/ overbank, and areas of mass transport complex (MTC) and/or localized slides. Distributary and channel-fill deposits are characterized by high amplitude and subparallel reflections having poor to good continuity. Levee/ overbank deposits are characterized by low-moderate amplitude, parallel to subparallel reflections with good continuity. MTC’s and/or slides are characterized by a series of hummocky to chaotic reflections with variable amplitude and poor continuity.
Channels in the two oldest sequences have come from the lower slope east of the modern Alaminos Submarine Canyon. Channels in the two youngest sequences came from the Alaminos Submarine Canyon, and extend across the "Baha" fold of the Perdido Foldbelt, to the unconfined setting to the southeast. All channels have a low to relatively high degree of sinuosity, from 0 to 5.5 km lateral migration, and widths of up to 1.5 km. MTC’s and/or localized slides exhibit varying degrees of geometry as well. Two sequences have elongated MTC's, mimicked by overlying channels, and one MTC that is areally widespread. Localized slides exhibit varying degrees of width and length but are not as areally extensive as the MTC’s.
Typical vertical succession of an Alaminos fan sequence begins with an erosional base, which is overlain by an MTC. This, in turn, is overlain by a relatively thin zone of distributary channels (high amplitude reflections) that is areally widespread (up to16 km wide). This zone evolves upward into one main aggradational channel that has low to high sinuosity, shows lateral migration, and bifurcates downfan. Lastly, a condensed section drapes the sequence, and may be eroded by an overlying fan sequence.
Sediment age is unknown, but is tentatively interpreted as being sourced from Texas deltas and the Mississippi Delta during the latest Miocene to early Pleistocene (about 6.6 to 1.9 Ma).