Sequence stratigraphy of the Mississippi fan (Plio-Pleistocene), Gulf of Mexico

Abstract

The Mississippi Fan is a large, mud-dominated submarine fan over 4 km thick, deposited in the deep Gulf of Mexico during the late Pliocene and Pleistocene. Analysis of 19,000 km of multifold seismic data defined 17 seismic sequences, each characterized by channel, levee, and associated ovcrbank deposits, as well as mass transport deposits. At the base of nine sequences are a series of seismic facies consisting of mounded, hummocky, chaotic, and subparallel reflections, which constitute 10-20% of the sediments in each the sequences. These facies are externally mounded and occur in two general regions of the fan: ( 1 ) in the upper and middle fan they are elongate in shape and mimic the channel's distribution; (2) in the middle fan to lower fan they are characterized by a fan-shaped distribution, increasing in width downfan. These facies are interpreted to have formed as disorganized slides, debris flows, and turbidites (informally called "mass transport complexes").Overlying this basal interval, characteristic of all sequences, are Well-developed channel-levee systems that constitute 80-90% of the fan's sediments. Channels consist of high amplitude, subparallel reflections, whereas the flanking levee sediments appear as subparallel reflections that have high amplitudes at the base changing upward to low amplitude. The vertical change in amplitude may reflect a decrease in grain size and bed thicknesses. Overbank sediments are characterized by interbedded subparallel to hummocky and mounded reflections, suggesting both turbidites from the channel, as well as slides and debris flows derived both locally and from the slope updip.

Connections Between Fluvial To Shallow Marine Environments and Submarine Canyons: Implications For Sediment Transfer To Deep Water

“…Examination of Quaternary systems, however, shows that all major submarine fans are fed by submarine canyons (Normark and Carlson 2003). Published examples where canyons feed submarine fans, or fed them during the last glacial period, include the Amazon (Damuth and Kumar 1975), the Mississippi (Normark et al 1986;Weimer 1989), the Zaire (Babonneau et al 2002), the Bengal (Weber et al 1997), the Rhone (Droz and Bellaiche 1985), the Indus (Prins et al 2000), the Nile . The schematic depositional model shows the geography of a hypothetical continental margin.…”

Seismic expression of depositional elements associated with a strongly progradational shelf margin: northern Santos Basin, southeastern Brazil

“…The term clinoform set is an informal classification used here to define groups of clinoforms with similar geometric characteristics, limited above and below by localized truncation surfaces and their downdip equivalent surfaces (e.g., Sydow et al, 1992). The term mass-transport deposit (MTD) is used in this text as a reference to mud-rich chaotic deep-marine deposits related to slumps and debris flows (e.g., Weimer, 1989;Omosanya & Alves, 2013;Alves et al, 2014;Deckers, 2015).…”

Improved recovery from Gulf of Mexico reservoirs. Volume I (of 4): Task 1, conduct research on mud-rich submarine fans. Final report, February 14, 1995--October 13, 1996

“…The medium size of this fan is still too large to have sufficient data density as was observed during DSDP Leg 96 (e.g., Bouma et al, 1985aBouma et al, , 1986Stelting et al, 1985) and follow-up studies (e.g., Weimer, 1989Weimer, , 1991contributions in Weimer andLink, 1991 andWeimer et al, 1994). Following the approach used by Mutti and Ricci Lucchi (1 972) and Walker (1 978) a model of the Mississippi Fan was constructed that demonstrates the partial bypassing of sand to the lower fan resulting in a general increase of the sandshale ratio from middle to outer fan.…”

“…However, the above-mentioned observations and the few findings of a direct connection of a thin levee sandstone to the channel fill, suggest more lateral switching than frequent progradation. Bifurcation is not uncommon and occasionally can be very intensive (see also Weimer, 1989Weimer, , 1991 (Fig. 22).…”