Mid-to Late Holocene flood frequency in the northeastern Alps as recorded in varved sediments of Lake Mondsee@en

Annually laminated (varved) lake sediments with intercalated detrital layers resulting from sedimentary input by runoff events are ideal archives to establish precisely dated records of past extreme runoff events. In this study, the mid- to late Holocene varved sediments of Lake Mondsee (Upper Austria) were analysed by combining sedimentological, geophysical and geochemical methods. This approach allows to distinguish two types of detrital layers related to different types of extreme runoff events (floods and debris flows) and to detect changes in flood activity during the last 7100 years. In total, 271 flood and 47 debris flow layers, deposited during spring and summer, were identified, which cluster in 18 main flood episodes (FE 1-18) with durations of 30-50 years each. These main flood periods occurred during the Late Neolithic (7100-7050 vyr BP and 6470-4450 vyr BP), the late Bronze Age and the early Iron Age (3300-3250 and 2800-2750 vyr BP), the late Iron Age (2050-2000 vyr BP), throughout the Dark Ages Cold Period (1500-1200 vyr BP), and at the end of the Medieval Warm Period and the Little Ice Age (810-430 vyr BP). […]具年纹层（varved）的湖泊沉积物夹有由径流事件沉积输入形成的碎屑层，是构建过去极端径流事件精确年代记录的理想地质档案。本研究结合沉积学、地球物理与地球化学方法，对上奥地利州蒙德塞湖的中全新世至晚全新世纹层沉积物开展了系统分析。该研究方案可区分两类与不同极端径流事件类型（洪水与碎屑流）相关的碎屑沉积层，并能够揭示过去7100年间洪水活动的变化规律。本次研究共识别出271层洪水沉积与47层碎屑流沉积，均形成于春夏季，这些沉积聚集为18个主要洪水事件期（FE 1-18），每期持续时长为30至50年。上述主要洪水期分别出现于新石器时代晚期（7100~7050 vyr BP与6470~4450 vyr BP）、青铜时代晚期与铁器时代早期（3300~3250 vyr BP与2800~2750 vyr BP）、铁器时代晚期（2050~2000 vyr BP）、整个黑暗时代冷期（1500~1200 vyr BP），以及中世纪暖期末期与小冰期（810~430 vyr BP）。[…]