ABSTRACT: Morphosedimentologie d'une plate-forme intertidale rocheuse en zone tempérée froide, île d'Anticosti, Québec. [Morphosedimentology of an intertidal rock platform in a cold temperature zone,Anticosti Isalnd, Quebec. ]

CGRG Bibliography of Canadian Geomorphology
Search Results

Author :

Date :

Title :

Publication :

Issue :

Page(s) :

Abstract

Intertidal rock-platform is the dominant coastal landform of southwest Anticosti Island and is the main control of coastal dynamics. Transverse bars are the most remarkable sediment bodies being formed at the surface of this limestone rock-platform. The bars extend on the landward side of small bedrock knolls that were produced by differential erosion of the shore platform, and so we propose the name of 'platform edge transverse bar'. Bar sediments consist almost exclusively of limestone cobbles that are derived from the surrounding platform. Pebble roundness and grain-size trends indicate that sediments are coarser and very angular at the proximal end of the bars, near the outer limit of the platform; clasts become progressively better rounded and finer-grained as they are transported shoreward by waves and longshore currents. Whether at high or low tide, wave attenuation takes place mainly at the outer limit of the platform; this provides an explanation for the apparently low rate of shoreline erosion and it also suggests that only severe storms are likely to displace the coarse intertidal sediments and to modify the main coastal landforms. However, the presence of sediments on the platform indicates that some erosion is taking place, mainly by frost action. The rocky coastal platform with its low erosion rate is thus a highly stable landform, and, as a result, coastal evolution seems to be slow in the 50 years period of an air photo analysis.

Bibliography of Canadian Geomorphology