ABSTRACT: Seismic stratigraphy of the lower St. Lawrence River estuary (Quebec) Quaternary deposits and seismic signature of the underlying geological domains.

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Abstract

The lower St. Lawrence River estuary is a narrow Quaternary basin filled with several stacked sedimentary units. Recently, high-resolution seismic-reflection surveys conducted in the lower St. Lawrence River estuary permitted identification of eight seismic units overlying three lithotectonic domains with different seismic signatures. Units 1 and 2 have highly variable thickness and fill most of two major bedrock depressions that exist in the study area. Unit 3 is present over the entire lower St. Lawrence River estuary basin, partly infilling ponded basins found on the shoulders of the estuary. Units 4 and 5 have a more constant thickness, suggesting that they were deposited in a hemipelagic setting. Units 6, 7, and 8 result from local processes like the sedimentation of submarine fans, mass-wasting deposits, and contourite drifts occurring along the flanks of the Laurentian Channel. The thickness of the Quaternary succession shows a strong correlation with the bedrock topography, indicating that the lower St. Lawrence River estuary was an effective sediment trap.

Bibliography of Canadian Geomorphology