ABSTRACT: Evenements holocenes mis en évidence dans une coupe de la terrasse Mitis à l'embouchure del la rivière Fouquette, sur la rive sud du moyen estuaire du Saint-Laurent [Evidence of Holocene events in a section into the Mitis terrace at the outlet of the Rivière Fourquette, south shore of the middle Saint Lawrence estuary].

CGRG Bibliography of Canadian Geomorphology
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Abstract

Near the outlet of the Rivière Fourquett, a vertical section into the 6-m terrace (Mitis terrace) exposes three lithostratigraphic units. The basal unit (between 3 and 6 m) is a rhythmite deposit composed of light grey, plastic and calcareous clay layers which are interbedded with sand laminae about 1 mm in thickness. This facies is characteristic of a tidal deposit in a relatively shallow environment (10-15 m), which is locally a wide depression between two Appalachian rock ridges. Ligneous organic debris occurring at various depts released 14C ages ranging from 8.7 to 10.6 ka BP corresponding to the last episode of the Goldthwait Sea on the south shore of the St. Lawrence estuary. Two metres in thickness, unit 2 is made of silt and fine sand laminae deposited in a subtidal or a lower intertidal environment. This unit has not been dated yet. At the surface, the 100-cm thick sand unit (unit 3) was probably deposited during the Mitis stage which is date at 2 ka BP. The Rivière Fourquette section shows that the nature of the 6-m Mitis terrace is occasionally complex; this terrace ca be formed of deposits older than the Mitis event. Data from this section indicate that the relative sea level at 9.5 ka BP was approximately 15 m higher than presently.

Bibliography of Canadian Geomorphology