Extensive shell beds were found in the valley of Rivière aux Anglais, near Baie-Comeau, along the North Shore of lower St. Lawrence River. Those particular accumulations, more or less well stratified and ranging from 2 to 15 m thick, represent the top parts of unconsolidated formations of the Goldthwait Sea between 10.4 and 9.6 ka BP. About 10 mounds have been discovered up to now. Their sizes vary, but reach 50 × 103 m2. Most overlie fine stratified sediments, such as fine sand, silt, and clay. They consist mainly of shell remains, which sometimes represent up to 90-95% of the volume. We can find various species of cirripeds (3), gastropods (7), brachiopods (1), echinoderms (1), and mostly pelecypods (11) including a large percentage of unbroken shells. Stratigraphic evidence suggests that these are natural formations (faluns) formed in a marine environment by sedimentation inside a seashore of ria type, where the sea currents and waves played a prominant role in the concentration of shell remains. The quantity of shells implies an environment of strong primary productivity, but also particular climatic conditions (frost) leading to a high number of deaths.

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