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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 69 (1985)

Issue: 2. (February)

First Page: 305

Last Page: 305

Title: Micropaleontology, Textural and Isotopic Characteristics of Turbidites on Continental Slope and Rise off Newfoundland: ABSTRACT

Author(s): Charles T. Schafer, David B. Scott

Article Type: Meeting abstract


Graded turbidite deposits observed in x-radiographs of gravity and piston cores collected from the lower slope and rise (2,300-3,210 m) occur below a well-documented 9,300 y.B.P. ash zone. The largest turbidite observed on the upper rise is 35-cm thick. C14 dates of foraminifera tests from intervals above and below this deposit average about 13,000 y.B.P. suggesting deposition during late glacial time. The base of this deposit is marked by a textural change to comparatively coarse sediments. It is also marked by an anomalous concentration of foraminiferal species (up to 50%) belonging to the miliolid family, that constitutes 2-4% of modern assemblages. A pronounced increase in the percentage of Valvulinaria artica in the turbidite suggests a middle-slope source The thinner gravity flows (10-15 cm thick) that occur in the deeper sections of the upper-rise cores have extrapolated C14 ages of less than 22,000 y.B.P. Their foraminiferal assemblages suggest outer-shelf to upper-slope sediment sources.

A comparatively thick (150 cm), graded turbidite sequence of unknown source occurs on the lower slope, just above ash zone 2 (approximate age is 64,000 y.B.P.). The related turbidity-current event apparently took place during the latter part of isotope stage 4. Texturally, this sequence is similar to the 35-cm thick upper-rise turbidite, but it lacks the anomalous concentrations of foraminiferal species in its basal interval. Oxygen isotope values (sinistral N. pachyderma) are relatively homogeneous throughout the sequence at a value of + 3.75 ppt compared to + 2.75 ppt for the upper Holocene section of the core.

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