The nature and origin of furrows in lake-bed sediments: Okanagan Lake, British Columbia, Canada

Abstract

Recent sonar surveys of Okanagan Lake, in the central interior of British Columbia, revealed the presence of linear, contour-parallel furrows at depths of 50–130 m. Underwater video imagery shows these furrows to be approximately 0.5–1 m wide by 0.5–1 m deep with variable lengths extending 1–100 m. Their cross-sectional topology varies from semi-rectangular features with steep-walled sides that expose weak laminations in the sediments to shallow U-shaped troughs that appear to be infilled by lacustrine mud. The most likely origin of the furrows is extension deformation (i.e., tension fracturing) caused by periodic failure along the steeply inclined marginal slopes of this deep, glaciated lake basin. A positive feedback mechanism leading to arrested downslope movement, based on the recent findings reported in Carey et al. (2019), is suggested to apply. Less likely alternative explanations are considered and dismissed. The furrows highlight the nature of long-term geomorphic processes in lacustrine environments that contribute to sediment transport and deposition on the lake bed but are not directly linked to the action of surface waves and currents.