Abstract Fjords can transition from marine embayments to lacustrine waterbodies under glacio-isostatic change following their deglaciation. However, little is known on how a transition from fjord to lake is influenced by glacial dynamics and how it influences sedimentation in and around the basin. Here, we analyse bathymetry imagery and subbottom imagery in Lake Mekinac in southern Quebec, and deglacial landforms from LiDAR imagery around the lake to document the evolution of a fjord basin into a lacustrine body during the transition from the Late Pleistocene to the Holocene. These analyses helped refine the glacial history of the area and show that the study area was probably under the up-ice reach of the St. Lawrence Ice Stream during full glacial conditions. The mapping of moraines in and around Lake Mekinac shows that deglaciation of the study area was marked by stabilization of the ice-margin during the Mars-Batiscan Event, which is traditionally correlated to the climate deterioration at the end of the Younger Dryas. The architecture of acoustic facies in the lake indicate a transition from glacial conditions (U1), to proglacial-paraglacial (U2) and to postglacial conditions (U3). The subbottom of Lake Mekinac also contains multiple mass movement deposits related to progradation of the Du-Milieu River delta and probably to late-Holocene earthquakes. The acoustic architecture of sediments within the lake indicates that the sedimentation regime was most dependant on the sediment input regime and that the transition from fjord to lake did not significantly influence sedimentation during deglaciation of the watershed. Further work on dating the mass movement deposits that characterise the sediment architecture should provide a better assessment of natural hazard associated with seismological events.

中文翻译：

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峡湾-梅基纳克湖和邻近地区（南加拿大盾）的冰川到冰川后环境变化的形态沉积记录

摘要 在冰川消融后的冰川均衡变化下，峡湾可以从海洋海湾过渡到湖泊水体。然而，关于从峡湾到湖泊的过渡如何受到冰川动力学的影响以及它如何影响盆地内部和周围的沉积，我们知之甚少。在这里，我们分析了魁北克南部梅基纳克湖的测深图像和海底图像，以及湖周围 LiDAR 图像的冰消地貌，以记录从晚更新世到全新世过渡期间峡湾盆地演变为湖体的过程。这些分析有助于完善该地区的冰川历史，并表明在完整的冰川条件下，该研究区很可能处于圣劳伦斯冰流的冰上游。Mekinac 湖内和周围的冰碛绘图显示，研究区冰川消融的特点是火星-巴蒂斯坎事件期间冰缘的稳定，这在传统上与新仙女木末期的气候恶化有关。湖中声相的结构表明从冰期条件 (U1) 到前冰期-副冰期 (U2) 和冰期条件 (U3) 的过渡。Mekinac 湖的底部还包含多个与 Du-Milieu 河三角洲的进积和可能与全新世晚期地震有关的质量运动沉积物。湖内沉积物的声学结构表明，沉积状态最依赖于沉积物输入状态，并且从峡湾到湖泊的过渡在流域冰川消融过程中没有显着影响沉积。对表征沉积物结构的质量运动沉积物进行年代测定的进一步工作应该可以更好地评估与地震事件相关的自然灾害。