The lower Borgarfjorður region, western Iceland, has been central to the reconstructions of the dynamics and collapse of the Icelandic Ice Sheet during the deglaciation. Here, extensive stratigraphical sections and landforms provide a rare opportunity to study past glacier dynamics in this part of Iceland. Previous studies reveal that a large outlet glacier in Borgarfjorður advanced during the Late Weichselian resulting in large-scale deformation of glaciomarine sediments and the formation of a series of ice-marginal moraines. However, the events recorded by these sediments and landforms are poorly constrained in time. We present and discuss 22 new radiocarbon dates in the context of recent reconstructions of the regional glacier dynamics in order to constrain the timing of the glacier oscillations. The results show that a dynamic, marine-terminating glacier advanced out of Borgarfjorður sometime after c. 13.0 cal. ka BP, resulting in the formation of an extensive moraine complex. The timing indicates that the advance occurred during climate cooling and widespread glacier expansions within the Younger Dryas. Followed by the first initial advance, the glacier exhibited at least five re-advances punctuated by phases of retreat. Each re-advance terminated proximal (within 5 km) to the outermost moraine complex although the extent of periodic retreat and the exact timing of these oscillations are unknown. All these phases of re-advance occurred prior to the onset of the Holocene (around 11.7 cal. ka BP), during which marine fauna re-colonized the area and the Borgarfjorður glacier retreated from the moraines. During the Early Holocene (sometime after c. 11.3 cal. ka BP), the Borgarfjorður glacier re-advanced to a position within ~5 km of the YD ice limit. This is the first recorded Early Holocene large-scale glacier advance in western Iceland and suggests that glacier expansion in this region coincided with widespread advances elsewhere in Iceland. (Less)

中文翻译：

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完善冰岛西部 Borgarfjörður 地区 Younger Dryas 和早全新世冰川振荡的历史

冰岛西部下博尔加峡湾地区一直是冰川消融期间冰岛冰盖动态和崩塌重建的核心。在这里，广泛的地层剖面和地貌为研究冰岛这一地区过去的冰川动态提供了难得的机会。先前的研究表明，Borgarfjorður 的大型出口冰川在晚魏克塞尔期推进导致冰川沉积物大规模变形并形成一系列冰缘冰碛。然而，这些沉积物和地貌记录的事件在时间上的约束很差。我们在最近重建区域冰川动力学的背景下提出并讨论了 22 个新的放射性碳日期，以限制冰川振荡的时间。结果表明，动态、在 c. 之后的某个时间，海洋终止冰川从 Borgarfjorður 前进。13.0 卡路里 ka BP，导致形成广泛的冰碛复合物。时间表明，这一进展发生在新仙女木内气候变冷和冰川广泛扩张期间。在第一次初始推进之后，冰川表现出至少五次再推进，中间有退步阶段。尽管周期性撤退的程度和这些振荡的确切时间未知，但每次重新前进都在最外层冰碛复合体的近端（5公里内）终止。所有这些重新前进的阶段都发生在全新世开始之前（大约 11.7 cal. ka BP），在此期间海洋动物重新在该地区定居，Borgarfjorður 冰川从冰碛中退缩。在全新世早期（大约在 11.3 cal. ka BP 之后的某个时间），Borgarfjorður 冰川重新前进到距离 YD 冰界约 5 公里的位置。这是冰岛西部首次记录的全新世早期大规模冰川推进，表明该地区的冰川扩张与冰岛其他地方的广泛推进相吻合。（较少的）