Sedimentary Facies Recovered from Amazon Fan during ODP Leg
155: II. Synthesis of Depositional Processes from Core and Wire-Line Log
Data
W. R. Normark, J. E. Damuth, C. Pirmez, and R. D. Flood
Ocean Drilling Program Leg 155 drilled 34 holes at 17 sites on the Amazon
Deep-Sea Fan and recovered more than 4000 m of sediment from the various fan
sub-environments. Eight sites focused on the sedimentary facies and depositional
record of the most recently active channel-levee system from upper to lower fan.
Three of these sites recovered continuous sections up to 100 m thick of
aggrading sandy channel fills beneath the channel axis, as well
as sandy lobe
deposits from the lower fan. Seven sites penetrated as deep as 434 m and sampled
older buried channel-levee systems and thick, interbedded muddy mass-transport
units. Suites of wire- line logs, including FMS, run at eight sites reveal
log
motifs of various sedimentary facies and provide lithologies for intervals of
non-recovery.
The detailed descriptions of cored sequences and the analysis
of wire-line
logs permit classification of sedimentary facies within the fan and provide
insights into the distribution of these facies types throughout the different
morphological units and sub-environments of the fan, which have previously been
identified on the basis of seismic facies and morphological expression.
Distinctive sedimentary facies and structures are present within the levee (overbank),
channel (HAR units), base-of-levee (HARP units) and end-of-channel (lobe)
deposits of the channel-levee systems, as
well
as in the large, muddy mass
transport deposits, which are interbedded between channel-levee systems. In
addition, offset holes provide insights into larger-scale sedimentary structures
in levee, channel, lo e and mass-flow deposits.
AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California