Sequence stratigraphy of the Mississippi Fan (Late Miocene-Pleistocene), northern deep Gulf of Mexico

Abstract

The Mississippi Fan (Late Miocene-Pleistocene) is a large submarine fan deposited in the northern deep Gulf of Mexico (Fig. l6.1). An isopach map of the Mississippi Fan indicates a maximum thickness of greater than 4 km (Fig. 16.2). The fan is the deep-water part of a large Neogene depocentre filling the northern Gulf of Mexico. From analysis of 19000 km of multifold seismic data across the fan, Weimer (1989, 1990, 199D defined 17 seismic sequences, each characterized by a series of channel, levee and associated overbank deposits, along with other mass transport deposits (Figs 16.3 and 16.4). Key seismic facies and lateral relationships are illustrated by sequences 11 and 12 (Figs 16.4–16.10). At the base of 11 sequences are a series of seismic facies consisting of mounded, hummocky, chaotic and subparallel reflections, which constitute 10-20% of the sediments in the sequences (Fig. 16.10). These facies are externally-mounded in cross-section and occur in two general regions of the fan (Fig. 16.10). In the upper and middle fan they occur below channels and are elongated in shape, mimicking the channel’s distribution. In the middle to lower fan they have a fan-shaped distribution, increasing in width downfan. These facies are interpreted to have formed as disorganized slides, debris flows and turbidites, and are informally called ‘mass transport complexes’.