The Bay of Mont-Saint-Michel northeastern littoral: an illustrative case of coastal sedimentary body evolution and stratigraphic organization in a transgressive/highstand context
Résumé
The aim of the present paper is primarily of pedagogic order. It presents the landscapes of the northeastern littoral of the Bay of Mont-Saint-Michel and explains how these landscapes can be understood in terms of stratigraphic organization and evolution. The northeastern coast of the Bay displays contrasted landscapes and morphodynamic processes along a restricted area. This coast consists in an elongated sandy barrier made of beaches and aeolian dunes, and back barrier tidal flats. A wide estuarine channel-and shoal system migrates in front of the beaches. Because of direct wave attack, the barrier experiences a severe retreat in the north whereas in the south, due to sufficient sediment supply, beaches and dunes tend to prograde. These contrasted processes give rise to different sedimentary bodies and surfaces, the nature, geometry, extension, and time-scale of which are described and discussed through examination of the landscapes. The present-day depositional system can be thus used to illustrate and test sequence stratigraphic concepts such as system tracts, ravinement surfaces and process time-scales.