Quaternary Foraminifera From the Walls of Wilmington, South Wilmington, and North Heyes Canyons, U.S. East Coast: Implications For Continental Slope and Rise Evolution

Document Type

Article

Publication Date

2-1-1992

Department

Marine Science

School

Ocean Science and Engineering

Abstract

The age, origin, and geologic development of outcropping sedimentary units of the continental slope and rise of the Wilmington Canyon region are assessed from analysis of foraminifera. DSRV Alvin was used to core outcrops and subcrops of strata in the walls and floors of Wilmington, South Wilmington, and North Heyes Canyons. Planktonic and benthic foraminifera were identified and counted in 34 samples and analyzed using Q-mode cluster analysis. Planktonic foraminifera were used to determine age of outcropping strata and surficial watermass conditions at the time of deposition. Benthic foraminifera were used to determine water depth of the unit at the time of original deposition. Pleistocene sedimentary units exposed by canyon incision into the continental slope appear to be in place within the resolution possible for depth assignments based on benthic foraminifera. In contrast, on the upper continental rise, units exposed in the north wall and floor of South Wilmington Canyon clearly represent a sequence of displaced blocks, three of which originated from shallower depths. The base of the north wall sequence consists of strata derived from inner and middle neritic depths (<100 m) which is overlain by a unit either slumped from nearby or deposited in situ at lower bathyal to abyssal depths. The lower bathyal to abyssal unit is overlain by a unit derived from the middle to outer neritic which is overlain, in turn, by a unit displaced from upper to middle bathyal depths. The Pleistocene strata of the canyon floor and north wall of South Wilmington Canyon are capped by a thin dusting of Recent contourite deposits. South Wilmington Canyon was incised into the upper rise during the Pleistocene after emplacement of the last slumped block. The age, climatic, and paleodepth data derived from foraminiferal information suggest that mass movement on the slope and rise is related to Pleistocene sea level lowstands and that the present morphology of South Wilmington Canyon and perhaps some other canyons in this region is a result of relatively recent canyon incision, presumably by erosional processes of turbidity flow, during the latter part of the Pleistocene.

Publication Title

PALAIOS

Volume

7

Issue

1

First Page

34

Last Page

66

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