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

Journal Article · Sat Aug 01 00:00:00 EDT 1992 · Geology; (United States)

DOI:https://doi.org/10.1130/0091-7613(1992)020<0693:UPTSBA>2.3.CO;2· OSTI ID:6991710

Nelson, C H; Lee, H L ^[1]; Twichell, D C; Schwab, W C ^[2]; Kenyon, N H ^[3]

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1. Geological Survey, Menlo Park, CA (United States)
2. Geological Survey, Woods Hole, MA (United States)
3. Inst. of Oceanographic Sciences, Wormley, Surrey (United Kingdom)

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 is 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 predominance of chaotic silt in cores or outcrops from outer-fan lobes thus may predict similar settings for ancient fans.

• OSTI ID: 6991710
• Journal Information: Geology; (United States), Vol. 20:8; ISSN 0091-7613
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
ALLUVIAL DEPOSITS
GEOLOGIC SURVEYS
STRATIGRAPHY
CONTINENTAL SLOPE
DEPOSITION
DRILL CORES
GEOLOGIC MODELS
GULF OF MEXICO
MISSISSIPPI RIVER
PLEISTOCENE EPOCH
SAND
SONAR
ATLANTIC OCEAN
CARIBBEAN SEA
CENOZOIC ERA
CONTINENTAL MARGIN
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGY
MEASURING INSTRUMENTS
QUATERNARY PERIOD
RANGE FINDERS
RIVERS
SEAS
STREAMS
SURFACE WATERS
SURVEYS
580000* - Geosciences