ABSTRACT: Apercu du Quaternaire a l'embouchure du Saguenay, Quebec (An outline of the Quaternary of the Saguenay and its entry)

CGRG Bibliography of Canadian Geomorphology
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Abstract

The outlet of the Saguenay fiord, near the head of the Laurentian Channel, is characterised by a sequence oforiginal morpho-sedimentary units including a raised (120-125 m) delta at Tadoussac, a thick fluvio-marine valley fill in Riviere du Moulin a Baude, a 60-m high marine terrace at Pointe aux Vaches, a complex terrace at Pointe aux Alouettes, wide silty-clayey (rhythmites) terraces at Pointe Hubert and Pointe au Bouleau, a large tidal flat at Pointe aux Alouettes, and three submerged half-moon shaped ridges. According to C-14 dates and aminochronology on shell fragments from a relict sand deposit at Pointe aux Alouettes, 35 ka or older, the areawas ice-free during a Wisconsinan interstadial. This marine event was followed by a period of sand and gravel deposition, a period of marginal ice shelf deposition, and by one or several glacial episodes. During Late Wisconsinan, partial deglaciation and marine submergence occurred before 11.1 ka. Diamicts interstratified with marine clay and a till deposit occurring to the S of the fjord outlet, the outwash raised delta at Tadoussac builtbetween II and 10.6 ka are correlated with the St. Narcisse event. Subsequently, the Goldthwait Sea at least by 10.4 ka submerged the ice-free topographic depressions of the Laurentidian Shield to a relative level 140-150 m. Then the Laurentide Ice Sheet retreated to the NW progressively thinning on the highlands while an ice tongue remained in the fjord. This isostatic recovery has been rapid, the 20-m level being emerged by 8 ka. Around 6 ka, the relative sea-level was approximately that of today. It rose subsequently, building the 6-m Mitis terrace dated between 1.2 and 1.6 ka.

Bibliography of Canadian Geomorphology