CGRG Bibliography of Canadian Geomorphology
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Author : Dionne, J-C.
Date : 1998
Title : Sedimentary structures made by shore ice in muddy tidal-flat deposits, St. Lawrence estuary, Quebec.
Publication : Sedimentary Geology
Issue : 116(3-4):
Page(s) : 261-274
Abstract
Well-preserved sedimentary structures formed by shore ice are exposed in emergent muddy tidal-flat deposits along the shoreline of the St. Lawrence estuary. The sedimentary features are exposed in high-marsh micro-cliffs 1 to 2 m high. Features from two localities where they are the most abundant (Sainte-Anne-de-Beaupre, north-shore, and Montmagny, south shore) are reported here. Two categories are distinguished: first, bowl-shaped circular and elongated structures 30 to 100 cm across, which are former scoured depressions subsequently filled by stratified mud, fine sand and organic debris; and second, deformations (folds) a few decimeters to a few meters in size produced by ice-block pressure. Pebble- to boulder-size dropstones are associated with these structures. Most features were observed in mud-flat and low-marsh units (facies) vertically exposed at these localities. The age of these tidalite deposits ranges from about 200 to 600 years. These ice-made structures and deformations, well-preserved in a sequence of Recent emerged tidal sediments, suggest that similar features may be preserved in older rock formations. Consequently, they can be considered as a promising tool for interpreting the former climatic conditions in which tidalites and other shallow marine and lacustrine formations may have been deposited.
Bibliography of Canadian Geomorphology