ABSTRACT
Few studies on modern abyssal plain turbidites have attempted to
assess the lateral extent of individual units and few have
therefore been able to provide any information on the evolution of
turbidity deposits across long abyssal plain distances. In the
4755 m-deep Horseshoe Abyssal Plain, ten distinct lithologic units
(six of these Iberian Peninsula-derived turbidites) were
delineated in nine piston cores on the basis of stratigraphic
position, thickness (range of 20 cm to greater than 500 cm),
color, sediment type, sedimentary structures, x-ray mineralogy,
and the ubiquitous presence of units in all abyssal plain and
supplying canyon piston cores. In order to make this correlation
more rigorous, detailed grain size analyses, light and heavy
mineralogy of sands, HCl treatment, and volatile solids
determinations were performed on three of the six turbidite units,
which have volumes of 5.7, 8.0, and 12.1 km3. These analyses
further confirm correlation over the entire 15,000 km2 area of the
Horseshoe Abyssal Plain and certainly provide long-distance
correlations for six individual turbidites of over 300 km for each
flow. In addition, shallow subbottom reflectors and transparent
zones seen on 3.5 kHz-P.D.R. profiles can be tied into the in situ
stratigraphy of the piston cores.
The results of previous studies on modern abyssal plain
turbidites, ancient turbidite deposits, and experimental lab
studies are compared with results from the Horseshoe Abyssal Plain
deposits and it is concluded that minor physiographic disturbances
on the otherwise flat abyssal plain floor have resulted in marked
sedimentological variation. It was found that regular grain size
decrease and thickness decrease with increasing distance from the
supplying canyon were not observed for individual bedding units.
The ruling notions about lateral variations within turbidites are
questioned.
Hoyt, W.H., 1976. Long-Distance Turbidite Correlations in the
Horseshoe Abyssal Plain. Unpublished MSc. thesis, State University
of New York at Albany. 136pp., +x.
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