Current-controlled Sedimentary Features into Lake Saint-Jean (Québec, Canada): a Record of Wind-driven Processes?

Wednesday, 17 December 2014
Alexis Nutz1, Mathieu Schuster1, Jean-François Ghienne1, Claude Roquin1, Murray B. Hay2, Fabien Retif3, Raphaël Certain4, Nicolas Robin4, Olivier Raynal4, Pierre A. Cousineau5 and Frederic Antony Bouchette3, (1)UMR 7516 CNRS-Université de Strasbourg, Institut de Physique du Globe de Strasbourg, Strasbourg, France, (2)Université du Québec à Chicoutimi, Département des sciences humaines, Chicoutimi, Canada, (3)Université Montpellier II et CNRS, GEOSCIENCES-M, Montpellier, France, (4)Université de Perpignan Via Domitia, CEFREM, Perpignan, France, (5)Université du Québec à Chicoutimi, Centre d’étude sur les Ressources minérales (CERM), Chicoutimi, Canada
Lake Saint-Jean is the third largest natural lake in Québec (Canada), however very few studies have focused on the basin-scale limnogeology of this lake. An initial very high-resolution seismic survey of Lake Saint-Jean was conducted in 2011, providing more than 300 km of seismic sections throughout the lake. These seismic profiles permitted the identification of numerous depositional units at a basin-scale (Nutz et al., Boreas 2014).

In this contribution, we focus on prominent large-scale, high-energy sedimentary features that are rather atypical in lakes: a sand-prone sedimentary shelf, sediment drifts and extensive erosional surfaces. All of these features may be attributed to wind-driven hydrodynamics affecting the central portion of the lake, at depths well below the wave base. Coupling the seismic profiles with a series of sediment cores and recent dating results, we now can propose a detailed characterization of these sedimentary features including age and context of emplacement, as well as the dominant depositional processes at work. Indeed, a numerical simulation of wind-induced bottom-current distribution based on realistic wind regimes was also applied in order to validate our previous wind-forcing interpretation.

This research provides a more thorough understanding of depositional processes at the origin of fine-grained sediment accumulations in lakes. The prevalence of wind-driven processes in some lacustrine depositional systems is also addressed through the presentation of a conceptual depositional model well-suited for high-energy, wind-driven water-bodies. This model is of interest to all geoscientists dealing with present-day lake systems (e.g., reservoir lake management) as well as researchers working with paleo-lacustrine records and strata (e.g., bottom lake anoxia, hiatial surfaces, hydrocarbon exploration).