A model of coastal evolution in a transgressed thermokarst topography, Canadian Beaufort Sea

• Published in: Marine Geology
• Main Authors: Ruz, Marie-Hélène, Hill, Philip, Héquette, Arnaud
• Other Authors: Centre d'Etudes Nordiques (CEN), Université Laval Québec (ULaval)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 1992
• Subjects: [SDE]Environmental Sciences; Barrier Islands; Beaufort Sea; Thermokarst; Tundra
• Online Access: https://hal.science/hal-04314565; https://doi.org/10.1016/0025-3227(92)90133-3

The coast of the Southern Canadian Beaufort Sea consists of bluffs of ice-bearing Quaternary sediments, and of spits and barrier islands enclosing (more or less completely) lagoons and complex embayments formed by the breaching of thaw lakes. The study of the evolution of this coast developed in a thermokarst topography and of the shallow stratigraphy of the inner continental shelf has resulted in the development of a conceptual model of coastal evolution. Five stages have been defined in this model which form an idealized continuum of coastal evolution. According to the model, the formation of embayments, spits and barrier islands is primarily controlled by the pre-existing topography, relative sealevel rise and local sediment supply. Sealevel rise over a topography of thermokarst basins formed in ice-bearing sediments leads to the formation of embayments and rapidly eroding headlands from which spits develop. Geomorphic evidence suggests that barrier islands mainly form by spit breaching or by erosion of tundra islands. Breached-lake basins act as sediment sinks and may restrict the development of coastal accumulation features. Spits and barrier islands are rapidly retreating landward, the mean retreat rates being 2.2 m a−1 and 3.9 m a−1 respectively. On an annual time-scale, spits and barrier islands retreat in response to episodic storm-generated overwash events, but on a geologic time-scale, relative sealevel rise in the major forcing mechanism of landward migration. While retreating landward, these coastal accumulation features may be drowned and possibly partially preserved in breached lake basins. During the Holocene transgression, the shoreface has undergone erosional retreat, partly eroding the pre-existing topography but preserving the bottom of some breached thaw lakes and lagoons which are now overlain by a transgressive sand sheet on the inner shelf. Our observations provide the basis of a semi-quantitative model of shoreline changes for the barrier coast of the Canadian Beaufort Sea which relates ...