GROOVES AND ELONGATED PERCUSSION MARKS ON THE INTERTIDAL ROCK PLATFORM AT CAP-SANTE, UPPER ST-LAWRENCE ESTUARY

Erosion linear features observed at the surface of a limestone layer i nterstratified in the shaly platform at Cap-Sante, are reported for th e first time. Two categories of features are described. First, grooves up to 15 m long and 2-3 cm deep, and second elongated shallow cavitie s most being 60 to 80 cm long, 8 to 12 cm wide and 2-3 cm deep. Striat ions and scratchings also occurred at the same locality. Orientation o f grooves range from 75 degrees to 115 degrees with a main system at 9 0 degrees, while elongated cavities have a direction of 75 degrees to 85 degrees, which is similar to one system of joints in shales. Featur es are roughly parallel to the local shoreline and the direction of mo vement is downstream. It is suggested that the erosional features repo rted in this paper were made by shore ice under structural control.