ABSTRACT: A detailed study of a debris flow system on the Scotian Rise.

CGRG Bibliography of Canadian Geomorphology
Search Results

Author :

Date :

Title :

Publication :

Issue :

Page(s) :

Abstract

A channelised debris flow system located on the Central Scotian Rise (40 degrees 30'-42 degrees N, 61 degrees -63 degrees W)was studied using long range sidescan. seismic and core data, in order to better understand flow processes within marine debris fows and their significance to the architecture of the continental margin. Most data is available from a near surface debris flow, the Albatross Debris Flow, which occurred at around 14ka. The Albatross Debris Flow was the result of a 230km (super 3) failure of sediment on the slope. The distribution of the flow on the channel levees shows that the failure developed into a single large surge with a frontal height of 75m. Using flow theory developed for subareal debris flows and knowing flow thickness and density, the Albatross Debris Flow can be reasonably modelled only if the velocity was relatively low (0.5-2ms (super -1) ). The entire low became less viscous downslope, indicating basal mixing, and suggesting that the flow may have eventually transformed en masse into a turbidity current. The low velocity and high clay content of the flow prevented development of a turbidity current by surface removal. Seismic reflection profiles show that the channel system developed in the Pleistocene, probably by focusing of sediment gravity flows into specific corridors by salt diapirs of the Sedimentary Ridge Province. The profiles show a cyclic pattern channelised debris flows overlain by stratified acoustic facies which can be tentatively correlated with external forcing of the Pleistocene glaciations. Three of these older debris flows have been exposed by surface erosion on the lower rise. This erosion was the result of auto-accelerating turbidity currents which dominate the channels between debris events.

Bibliography of Canadian Geomorphology