Abstract

Terraces in the lower Matane River Valley (eastern Quebec, Canada) were studied to describe the stratigraphic architecture of a glacially eroded valley fill. The Matane River Valley hosted a glacial tongue connected with a regional ice cap during the early opening of a calving bay in the modern St. Lawrence Estuary and was subsequently flooded by the Goldthwait Sea as the Laurentide Ice Sheet margin retreated. Stratigraphic, sedimentological, light detection and ranging (LIDAR), and geochemical analyses as well as radiocarbon measurements allowed the identification of four stratigraphic units deposited during and following deglaciation: glacial outwash (unit I), delta bottomsets (unit II), delta foresets (unit III), and fluvial deposits (unit IV). Stable isotope (13C) and C/N ratio values reveal the relative influence of the two end-members (algae and terrestrial plants) on organic matter sources between the stratigraphic units. Climate, major relative sea level fluctuations, and sediment yield are recognized as the main controls on depositional environments in glacially eroded valleys of the northern shore of the Gaspé Peninsula during the Holocene. This paper presents a model of the evolution of the Matane River Valley, which in many points is similar to existing conceptual fjord-valley fill models.

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