ABSTRACT: Nouvelles donnees sur la transgression Laurentienne, cote sud moyen estuaire du Saint-Laurent, Quebec (Additional evidence for the Laurentide transgression on the south shore of the middle St. Lawrence estuary).

CGRG Bibliography of Canadian Geomorphology
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Abstract

A vertical section in the 10-12 m terrace at the mouth of Ruisseau Bellechasse, near Berthier-sur-Mer, on the south shore of the middle Holocene estuary, provides evidence for a 12-m maximum level for the middle Holocene Laurentian transgression. This level is two meters higher than suggested in the past. The 4-m thick intertidal unit deposited during the transgression overlies an erosion surface cut into stratified silt and clay deposit (rhythmites), poorly fossiliferous and dated circa 10 ka. Radiocarbon dates on wood and on aquatic and intertidal plant debris in situ released ages BP between 5.4 and 6 ka (n-8). This chronology is slightly older than at Montmagny - Cap-Saint-Ignace reference sites, located approximately 30 km downstream. The Anse de Bellechasse section does not present the full sequence of Holocene events observed at Montmagny. However, there are a few fluvial terraces related to the St. Lawrence water level; one was built up circa 1.4 ka, two other between 0.5 and 0.7 ka suggesting minor fluctuations of base level during the last two millennia,

Bibliography of Canadian Geomorphology