Date of Award
Master of Science (MS)
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, William H., "Long-Distance Turbidite Correlations in the Horseshoe Abyssal Plain" (1976). Geology Theses and Dissertations. 39.