CGRG Bibliography of Canadian Geomorphology
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Author : Dionne, J-C.; Poitras, S.
Date : 1996
Title : Geomorphological observations on the boulder-strean tidal flat at Petite Rivere, Charlevoix, Quebec
Publication : Géographie physique et Quaternaire
Issue : 50(2):
Page(s) : 221-232
Abstract
Geomorphological observations on the boulder-strewn tidal flat, at Petite-Rivière, Charlevoix, Québec. At Petite-Rivière (Charlevoix), the shore is characterized by a strand up to 1100 m wide and over 15 km long. This large horizontal surface with a small slope gradient (0.45%) has been cut into ancient Quaternary deposits including silty-clayey rhythmites dated circa 65 ka. The tidal flat surface is covered by thin sheets of mud, sand, gravel, small blocks and a large number of huge boulders. Of the 533 boulders measured, 48.4% were 3 to 4 m long (a-axis), 22.5%, 4 to 5 m, and 8.4% exceeding 5 m. The largest boulder (840 x 660 x 450 cm) weighed approximatively 467 metric tons. Boulders are all from the Precambrian shield in the vicinity of Petite-Rivière. Except for the largest, many huge blocks showed evidence of recent displacement by shore ice over distances not exceeding 5 m. The size of a large number of boulders is however, over the usual competence of shore ice in a macro-tidal environment with larger spring tides about 6 m. Although some of the large boulders may have been released by icebergs in the past, most are likely lags from eroded glacial deposits in the shore zone. Consequently, most huge boulders have not been scattered by shore ice throughout the tidal flat during the Holocene. The large tidal flat at Petite-Rivière is an erosion platform with a lag of coarser debris
Bibliography of Canadian Geomorphology