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Upper Pleistocene turbidite sand beds and chaotic silt beds in the channelized, distal, outer-fan lobes of the Mississippi fan

Geology

By:
, , , , and
https://doi.org/10.1130/0091-7613(1992)020<0693:UPTSBA>2.3.CO;2

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Abstract

Cores from a Mississippi outer-fan depositional lobe demonstrate that sublobes at the distal edge contain a complex local network of channelized-turbidite beds of graded sand and debris-flow beds of chaotic silt. Off-lobe basin plains lack siliciclastic coarse-grained beds. The basin-plain mud facies exhibit low acoustic backscatter on SeaMARC IA sidescan sonar images, whereas high acoustic backscatter characteristic of the lobe sand and silt facies. The depth of the first sand-silt layer correlates with relative backscatter intensity and stratigraphic age of the distal sublobes (i.e., shallowest sand = highest backscatter and youngest sublobe). The high proportion (>50%) of chaotic silt compared to graded sand in the distal, outer-fan sublobes may be related to the unstable, muddy, canyon-wall source areas of the extensive Mississippi delta-fed basin slope. A predominace of chaotic silt in cores or outcrops from outer-fan lobes thus may predict similar settings for ancient fans.

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Additional publication details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Upper Pleistocene turbidite sand beds and chaotic silt beds in the channelized, distal, outer-fan lobes of the Mississippi fan
Series title:
Geology
DOI:
10.1130/0091-7613(1992)020<0693:UPTSBA>2.3.CO;2
Volume:
20
Issue:
8
Year Published:
1992
Language:
English
Publisher:
Geological Society of America
Contributing office(s):
Woods Hole Coastal and Marine Science Center
Description:
4 p.
First page:
693
Last page:
696
Country:
United States
Other Geospatial:
Mississippi Fan