An Atlas of Mass‐Transport Deposits in Lakes

Sammartini, Maddalena; Moernaut, Jasper; Anselmetti, Flavio S.; Hilbe, Michael; Lindhorst, Katja; Praet, Nore; Strasser, Michael

doi:10.1002/9781119500513.ch13

Cited by 25 publications

(18 citation statements)

References 124 publications

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“…Black arrows mark onlapping of U2b onto surface highs of Unit 3 (U3) transparent seismic facies, a chaotic to patchy facies with some scattered diffraction hyperbolae can be recognized (Subunit 2c, Fig. 3), representing a partly blocky mass-movement unit (e.g., Sammartini et al 2020). The base of the more than 6 m thick mass-movement deposit is not imaged, probably due to high sand and gas content in the Central Basin.…”

Section: Seismic Reflection Data and Seismic-to-core Correlationmentioning

confidence: 99%

A tsunamigenic delta collapse and its associated tsunami deposits in and around Lake Sils, Switzerland

et al. 2021

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Large lacustrine mass movements and delta collapses are increasingly being considered as potential tsunamigenic sources and therefore hazardous for the population and infrastructure along lakeshores. Although historical reports document tsunami events in several lakes in Switzerland, and although the propagation of lake tsunamis has been studied by numerical wave modeling, only little is known about on- and offshore lacustrine tsunami deposits. In Lake Sils, Switzerland, a large prehistoric mass-movement deposit originating from the Isola Delta with a minimum estimated volume of 6.5 × 106 m3 and a basinal thickness of > 6 m in the seismic record has been identified by previous studies and radiocarbon dated to around 700 Common Era. Here, we combine (i) comprehensive sedimentological investigation of sediment cores recovered from the on- and offshore settings, (ii) mineralogical fingerprinting of the inflows from key catchments to characterize sediment provenance, and (iii) numerical tsunami modeling, to test the hypothesis of a tsunamigenic delta collapse in Lake Sils. We observe a clastic event deposit consisting of coarse-grained, fining-upward sand overlying an organic-rich peat deposit in the shallow water. This layer thins and fines landward on the coastal plain. Toward the deeper water (20–40 m), the deposit transforms into a thicker and more heterogeneous sediment package with multiple sequences of fining-upward sand and a well-pronounced clay cap at the top. Radiocarbon dating of the peat underlying the event deposit yields a maximum age of 225–419 calibrated Common Era. The tsunami models, which indicate wave heights reaching up to 5 m, simulate areas of inundation that coincide with the location of event deposits. Based on our results, we propose that the historically undocumented Isola Delta collapse generated a basin-wide tsunami that inundated the lakeshore, transporting large amounts of unconsolidated sediment along the lakeshore toward the coastal plain and into the deeper lake basin.

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Section: Seismic Reflection Data and Seismic-to-core Correlationmentioning

confidence: 99%

A tsunamigenic delta collapse and its associated tsunami deposits in and around Lake Sils, Switzerland

et al. 2021

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“…These outlier varves in the proximal basin include easily discernible slump deposits and thick turbidites (>35 cm; megaturbidites), apart from thinner turbidites (<20 cm). This study uses the term ‘megaturbidite’, as commonly used in lacustrine settings (Schnellmann et al., 2002; Fanetti et al ., 2008; Van Daele et al ., 2015; Praet et al ., 2017; Leithold et al ., 2019; Sammartini et al ., 2020), to define a turbidite with a thickness that exceeds the vertical seismic resolution (10 to 20 cm) and is characterized by a transparent seismic facies and ponded geometry. Four of these megaturbidites (MTs) are present in location 1: MT1, MT2, MT3 and MT4 (Fig.…”

Section: Results and Interpretationmentioning

confidence: 99%

Unravelling a 2300 year long sedimentary record of megathrust and intraslab earthquakes in proglacial Skilak Lake, south‐central Alaska

et al. 2022

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Seismic hazards in subduction settings typically arise from megathrust, intraslab and crustal earthquake sources. Despite the frequent occurrence of intraslab earthquakes in subduction zones and their potential threat to communities, their long‐term recurrence behaviour is barely studied. Sedimentary sequences in lakes may register ground shaking from different seismic sources. This study investigates two long sediment cores (13 m and 16 m) from Skilak Lake, a proglacial lake in south‐central Alaska, to evaluate whether different seismic sources leave a distinct imprint. The sedimentary record shows a continuously varved sediment sequence, occasionally interrupted by turbidites, slump deposits and tephra beds. Turbidites and slump deposits were objectively identified using a statistical outlier analysis on varve thickness. The earthquake origin of these deposits was ascertained by resemblance with deposits induced by instrumentally recorded earthquakes (for example, 1964 ce Mw 9.2 megathrust and 1954 ce Mw 6.4 intraslab earthquakes) and correlation with multiple coeval landslide deposits on sub‐bottom profiles. The Skilak Lake record chronicles 19 earthquakes with moderate to very high confidence level in the past 1350 years. The sedimentary evidence of instrumentally‐recorded intraslab and megathrust earthquakes within the past 70 years demonstrates that not only megathrust earthquakes, but also past intraslab events are recorded. Although reported seismic intensities at Skilak Lake are comparable for the 1964 ce megathrust and the 1954 ce intraslab earthquakes, the long duration and low frequency content of seismic ground motion during megathrust earthquakes facilitate the triggering of multiple, voluminous landslides and the generation of megaturbidites. In contrast, the shorter duration and higher frequency source spectrum of intraslab earthquakes may only induce surficial slope remobilization and the generation of thinner turbidites. This study demonstrates that the sedimentary record of Skilak Lake has the potential to decipher multiple seismic sources, which opens possibilities for a comprehensive seismic hazard analysis for south‐central Alaska.

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“…Intensified ground shaking and rapid emplacement of mass movement deposits at the end of the Younger Dryas might have been facilitated by rapid climatic changes in several places around the globe (Lowag et al ., 2012; Forsberg et al ., 2016; Brooks, 2018; Sammartini et al ., 2019). At a large scale, climatic processes leading to warmer and wetter conditions can make subaqueous slopes unstable and preconditioned for failure.…”

Section: Discussionmentioning

confidence: 99%

Did the Younger Dryas to Holocene climate transition favour high seismicity rates in the north‐western Alps?

et al. 2022

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An Atlas of Mass‐Transport Deposits in Lakes

Cited by 25 publications

References 124 publications

A tsunamigenic delta collapse and its associated tsunami deposits in and around Lake Sils, Switzerland

A tsunamigenic delta collapse and its associated tsunami deposits in and around Lake Sils, Switzerland

Unravelling a 2300 year long sedimentary record of megathrust and intraslab earthquakes in proglacial Skilak Lake, south‐central Alaska

Did the Younger Dryas to Holocene climate transition favour high seismicity rates in the north‐western Alps?

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