About This Item

Share This Item

The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 68 (1984)

Issue: 4. (April)

First Page: 455

Last Page: 456

Title: Characteristics of Mississippi Fan Sediments, DSDP Leg 96: ABSTRACT

Author(s): A. H. Bouma, J. M. Coleman


Sedimentologic, paleontologic, geochemical, and geotechnical studies were conducted on cores drilled at eight sites on the Mississippi fan during the Deep Sea Drilling Project Leg 96. Together with seismic and well log data, these studies allow development of a number of depositional facies within an overall fan-lobe model. The central middle-fan channel of the youngest Mississippi fan-lobe was an effective conduit for the transport of coarse-grained material; only clays and minor amounts of silt spilled over the channel margins. The channel fill deposit is basically an upward-fining sequence, commencing with coarse-grained sands and gravels, overlain by sands, sandy-silty muds, and muds. The basal coarse-grained sediment interval is approximately 134 m (450 ft) thick. Th swale deposits, the overbank deposits adjacent to the meandering channel, and the marginal overbank deposits, are characterized by fine-grained turbidites and hemipelagics. Basically, both sites contain a minor upward-coarsening sequence.

Deposits on the lower fan, in the area where the channel shifts position frequently, show alternating sequences of channel fill, levee, and overbank

End_Page 455------------------------------

deposits. Sediments near the channel terminus have upward-coarsening sequences (i.e. channel-mouth depositional lobes) and contain 47 to 65% sand.

Most of the sparse microfauna in both sands and muds are benthic species characteristic of inner and middle neritic origin. Traces of biogenic methane and other hydrocarbons were found in the underlying lobes but not in the youngest lobe. All sediments are underconsolidated, resulting from the extremely high accumulation rates of 6-12 m/1,000 yr (20-40 ft/1,000 yr).

End_of_Article - Last_Page 456------------

Copyright 1997 American Association of Petroleum Geologists