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Stable oxygen and carbon isotopes of carbonates in lake sediments as a paleoflood proxy
Geology ( IF 5.8 ) Pub Date : 2019-10-16 , DOI: 10.1130/g46593.1
Lucas Kämpf 1, 2 , Birgit Plessen 1 , Stefan Lauterbach 3 , Carla Nantke 4 , Hanno Meyer 5 , Bernhard Chapligin 5 , Achim Brauer 1, 6
Affiliation  

Lake sediments are increasingly explored as reliable paleoflood archives. In addition to established flood proxies including detrital layer thickness, chemical composition, and grain size, we explore stable oxygen and carbon isotope data as paleoflood proxies for lakes in catchments with carbonate bedrock geology. In a case study from Lake Mondsee (Austria), we integrate high-resolution sediment trapping at a proximal and a distal location and stable isotope analyses of varved lake sediments to investigate flood-triggered detrital sediment flux. First, we demonstrate a relation between runoff, detrital sediment flux, and isotope values in the sediment trap record covering the period 2011-2013 CE including 22 events with daily (hourly) peak runoff ranging from 10 (24) m3 s-1 to 79 (110) m3 s-1. The three-to ten-fold lower flood-triggered detrital sediment deposition in the distal trap is well reflected by attenuated peaks in the stable isotope values of trapped sediments. Next, we show that all nine flood-triggered detrital layers deposited in a sediment record from 1988 to 2013 have elevated isotope values compared with endogenic calcite. In addition, even two runoff events that did not cause the deposition of visible detrital layers are distinguished by higher isotope values. Empirical thresholds in the isotope data allow estimation of magnitudes of the majority of floods, although in some cases flood magnitudes are overestimated because local effects can result in too-high isotope values. Hence we present a proof of concept for stable isotopes as reliable tool for reconstructing flood frequency and, although with some limitations, even for flood magnitudes. (Less)

中文翻译:

湖泊沉积物中碳酸盐的稳定氧和碳同位素作为古洪水代理

作为可靠的古洪水档案,越来越多地探索湖泊沉积物。除了包括碎屑层厚度、化学成分和颗粒大小在内的已建立的洪水替代物之外,我们还探索了稳定的氧和碳同位素数据,作为具有碳酸盐基岩地质的集水区中湖泊的古洪水替代物。在来自 Mondsee 湖(奥地利)的案例研究中,我们将近端和远端位置的高分辨率沉积物捕集与湖泊沉积物的稳定同位素分析相结合,以研究洪水引发的碎屑沉积物通量。首先,我们展示了涵盖 2011-2013 CE 期间的沉积物捕集记录中径流、碎屑沉积物通量和同位素值之间的关系,包括 22 次事件,每日(每小时)峰值径流范围从 10 (24) m3 s-1 到 79 (110) 立方米 s-1。远端圈闭中三到十倍的低洪水触发碎屑沉积物沉积物很好地反映在被困沉积物稳定同位素值的衰减峰值。接下来,我们表明,与内生方解石相比,1988 年至 2013 年沉积物记录中沉积的所有九个洪水触发碎屑层的同位素值都升高。此外,即使没有导致可见碎屑层沉积的两个径流事件也以较高的同位素值来区分。同位素数据中的经验阈值允许估计大多数洪水的震级,尽管在某些情况下,洪水震级被高估了,因为局部效应会导致同位素值过高。因此,我们提出了稳定同位素的概念证明,作为重建洪水频率的可靠工具,尽管有一些局限性,即使是洪水规模。(较少的)
更新日期:2019-10-16
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