The two Late Wisconsin Mississippi Fanlobes are depositional units, which were identified on the basis of reflection terminations (including erosional truncation, toplap, downlap, and onlap) and define seismic sequences. The sequence boundaries defined are Horizon "20" (40-55,000 years B. P.), and Horizon "30" (approximately 84,000 years B. P.), and are interpreted to represent condensed sections representing quiet periods or periods of low sediment accumulation rates associated with high stands of sea-level. Seismically, the sequence boundaries are observed as high amplitude, sometimes seen as a doublet reflector, continuous reflectors that can be correlated nearly throughout the entire fan. The two fanlobe sequences defined were: Sequence VII, which has as its base Horizon "30" and as its top Horizon "20", and reaches a maximum thickness of 350 meters; Sequence VIII, has Horizon "20" as its base and the modern fan surface (Horizon "0") as its top, with maximum thickness of 500 meters in the middle fan region. The mapping of sequence boundaries (Horizons "20" and "30"), in two and three dimensions, illustrate the similarity of these paleo-isobath surfaces with the modern bathymetric map (Horizon "0"), indicating the cyclic nature of fanlobe development in response to changing sea-level. Three-dimensional modeling of the fanlobe sequences (Sequence VII and Sequence VIII), dramatically illustrates the influence of pre-existing topography on fanlobe geometry. Distribution of facies on the modern fan surface as well as within the fanlobe sequences, convey that mass movement and channel/overbank processes are primary processes responsible for fanlobe construction and are the main components of individual fanlobe sequences. Reflection configuration patterns (both internal and external geometries) within the depositional sequences, or fanlobes, were determined in order to perform a reflection character analysis on each of the four subdivisions (upslope erosional canyon, upper fan, middle fan, and lower fan) of a fanlobe sequence.

West: -90.0000 East: -85.0000 North: 29.0000 South: 24.0000

Expedition: 96

Site: 96-615

Site: 96-617

Site: 96-620

Site: 96-621

Provider: SEDIS Publication Catalogue

Data set link: http://sedis.iodp.org/pub-catalogue/index.php?id=2012-088307 (c.f. for more detailed metadata)

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