Elsevier

Marine Geology

Volume 370, 1 December 2015, Pages 125-135
Marine Geology

Changes in distal sedimentation regime of the Rhone delta system controlled by subaquatic channels (Lake Geneva, Switzerland/France)

https://doi.org/10.1016/j.margeo.2015.10.013Get rights and content

Highlights

  • 1500 years of sublacustrine channel history in Lake Geneva

  • Turbidite frequency as hint for position of the main active channel

  • Two shifts of main active channel within 1500 years

  • Extreme events as causes for channel shift

  • Turbidite “progradation” due to human impact on river course (Rhone River)

Abstract

Seismic reflection profiles combined with sediment cores reveal centennial changes in the proximal and distal sedimentation regime in the Rhone River delta system (Lake Geneva), which is dominated by sublacustrine channels. From detailed analyses of the thickness distribution of depositional units and the occurrence of turbidites, at least two shifts of the primarily active sublacustrine channels are inferred for the past 1500 years. The first northward shift is dated at 1480 ± 20 cal AD and was likely linked to a centennial flood in the Swiss Rhone Valley that occurred in 1469 AD and acted either as a direct cause or as a preconditioning factor favoring the shifting. A shift back southward in 1720 ± 90 cal AD may have been caused either by long-term human impact related to the first embankment constructions on the Rhone River or by a natural event such as the 1755 AD Brig earthquake or the centennial flood of 1640 AD. Another important change in the sedimentation regime occurs in 1775 ± 125 cal AD when the onset of Rhone turbidite deposition is recorded in the distal sediments. This relative “progradation” of the Rhone turbidites is certainly due to the disconnection of the Vieux Rhone branch before 1826 and the subsequent first Rhone River correction, starting in 1863 that led to the present single active Rhone subaquatic channel.

Introduction

Submarine channel or canyon systems on continental margins serve as pathways for turbidity currents and other gravity flows transporting sediments to depositional areas in the deep basins (Kolla 2007). In large clastic lakes, the subaqueous flow of incoming rivers may develop meandering channels or canyons on their submerged delta slopes and distal fan lobes that are similar to their marine counterparts (Mulder and Chapron 2011). The activity of subaquatic channels with regard to gravity flows is often controlled by the position of the river mouth, which can shift regularly similar to avulsion in the river systems (Reitz et al. 2010). The river mouth position in turn is influenced by external factors that control the course of the river bed, such as regional tilting, changes of the drainage systems due to earthquakes, sediment deposition and avulsion during major floods (Wells and Dorr 1987), as well as continuous sediment accumulation (Migeon et al. 2006). Human impact, such as river embankments, river channelizing and river deviations, can also drastically change the pathways and the regime of the sublacustrine turbidity currents and thus influence the entire sublacustrine delta system (Anselmetti, F.S., et al., 2007, Loizeau, J.-L. and Dominik, J., 2000, Syvitski, J.P.M., et al., 2009, Wirth, S.B., et al., 2011). Understanding the timing and causes of shifts in subaquatic delta-related channel systems is important because they control the depositional patterns in the more distal areas of these environments. In the specific framework of paleoflood reconstruction (Gilli, A., et al., 2003, Glur, L., et al., 2013, Mulder, T. and Chapron, E., 2011, Mulder, T., et al., 2001a, Mulder, T., et al., 2001b, Wirth, S.B., et al., 2013) and paleoseismic reconstruction (Goldfinger, C., et al., 2012, Nelson, C.H., et al., 2012), for instance, the influence of the river/delta/canyon system evolution on the spatial variability of event-related deposits in the basin needs to be constrained as a prerequisite to the interpretation of any clastic sedimentary record.

In this study, we present a synthesis of seismic reflection and sediment core data from the distal parts of the Rhone delta system in Lake Geneva with the aim to reconstruct the evolution of its sedimentation regime during the last 1500 years.

Section snippets

Regional and sedimentological setting

Lake Geneva is the largest perialpine lake in Western Europe with a surface area of 580 km2 and a volume of 89 km3 of freshwater. Its basin was formed by glacial erosion during the Pleistocene (Wildi and Pugin 1998). The two main rivers feeding Lake Geneva are the Rhone and the Dranse River (Fig. 1). Using geochemical and petrophysical analysis the Rhone and Dranse turbidites can be distinguished as the drainage areas present different outcropping rocks. Dranse turbidites are characterized by

Historical Rhone River corrections

The Rhone River upstream of Lake Geneva is presently heavily impacted by human activities and settlements, mainly due to dams and embankment constructions (Vischer 2003), but also by water intake for agricultural and industrial purposes. The various measures of the so-called “Rhone corrections” led to a widespread loss of natural swamp areas in the Rhone valley. The natural River course before the diverse corrections was characterized by the alternation between a meandering system and single

Methods

Several seismic reflection, sediment coring and multibeam campaigns were conducted with the boat “La Licorne” of the Institute Forel, University of Geneva.

Seismic reflection data from the main basin of Lake Geneva were acquired with a 3.5 kHz pinger source in April 2010 and with a Sodera Mini GI airgun, with a central frequency of 330 Hz, together with GPS navigation (positioning error of 3–5 m) in 2002 (Fig. 1). The pinger data, which have a theoretical vertical resolution of 0.1 m, were processed

Seismic reflection in Rhone delta system

Airgun seismic reflection data (Dupuy, D., 2006, Zingg, O., et al., 2003) from the Rhone delta system image the present channels of the Rhone delta and reveal two buried paleochannels, ‘CI’ and ‘CII’ (Figs. 2A and 2B). The paleochannels CI and CII are located near the present courses of channels C5 and C8, respectively (Fig. 2B). Because of low seismic penetration on the sublacustrine delta slope due to gas blanking, it is difficult to correlate seismic units in the deep basin with those

Discussion: what is controlling the Rhone fan sedimentation?

The presented seismic and lithological datasets reveal several changes in the spatial deposition pattern, sedimentation rate and turbidite frequency, which occurred in the distal Rhone delta basin during the last ca. 1500 years. General sedimentation rate trends may be linked to the climatic influence on Alpine denudation rates and sediment transport during the Little Ice Age (around 1280 to 1860 cal AD; Holzhauser, H., et al., 2005, Holzhauser, H. and Zumbühl, H.J., 1999, Stuiver, M. and Quay,

Conclusions

Based on reflection seismic and sediment core data, we observe several shifts in the frequency and spatial distribution of turbidites in Lake Geneva, and we interpret this as a shift of the main subaquatic Rhone channel system through which river-borne underflows are assumed to be routed to the deep basin. The shift to a system with the main active channels C3/C4 located in the northern part of the delta is dated at 1480 ± 20 cal AD and is likely related, directly or indirectly, to the centennial

Acknowledgments

This work was funded by the Swiss National Science Foundation (Research grants 200021-121666 and 200020-146889 and R'Equip-146889). Katrina Kremer is currently funded as Postdoc by the Swiss National Science Foundation (Research grant 133481). We thank Flavio Anselmetti, Fred Arlaud, Philippe Arpagaus, Yves Cauderay, Robert Hofmann, Reto Seifert, and Chadia Volery for their help during seismic reflection and coring campaigns in the ‘Grand Lac’. Thanks to Adrian Gilli for access to the

References (51)

  • S. Fritsche et al.

    Historical intensity VIII earthquakes along the Rhone valley (Valais, Switzerland): primary and secondary effects

    Swiss J. Geosci.

    (2012)
  • A. Gilli et al.

    A 600-year sedimentary record of flood events from two sub-alpine lakes (Schwendiseen, Northeastern Switzerland)

    Eclogae Geol. Helv.

    (2003)
  • F. Giovanoli

    Horizontal transport and sedimentation by interflows and turbidity currents in Lake Geneva

  • S. Girardclos et al.

    Searching the Rhone delta channel in Lake Geneva since François-Alphonse Forel

    Arch. Sci.

    (2012)
  • L. Glur et al.

    Frequent floods in the European Alps coincide with cooler periods of the past 2500 years

    Nat. Sci. Rep.

    (2013)
  • C. Goldfinger et al.

    Turbidite event history — methods and implications for Holocene paleoseismicity of the Cascadia subduction zone

    U.S. Geological Survey Professional Paper

    (2012)
  • H. Holzhauser et al.

    Glacier fluctuations in the western Swiss and French Alps in the 16th century

    Clim. Chang.

    (1999)
  • H. Holzhauser et al.

    Glacier and lake-level variations in west-Central Europe over the last 3500 years

    The Holocene

    (2005)
  • J.J.H.C. Houbolt et al.

    Recent sediments in the eastern part of the lake of Geneva (Lac Léman)

    Geol. Mijnb.

    (1968)
  • K. Kelts et al.

    The limnogeology — ETH coring system

    Swiss J. Hydrol.

    (1986)
  • K. Kremer et al.

    Origin of turbidites in deep Lake Geneva (France–Switzerland) in the last 1500 years

    J. Sediment. Res

    (2015)
  • K. Kremer et al.

    Reconstructing 4000 years of mass movement and tsunami history in a deep peri-Alpine lake (Lake Geneva, France–Switzerland)

    Sedimentology

    (2015)
  • K. Kremer et al.

    Giant Lake Geneva tsunami in AD 563

    Nat. Geosci.

    (2012)
  • A. Lambert et al.

    Records of riverborne turbidity currents and indications of slope failures in the Rhone delta of Lake Geneva

    Limnol. Oceanogr.

    (1988)
  • A. Leemann et al.

    Holocene glacial activity and climatic variations in the Swiss Alps: reconstructing a continuous record from proglacial lake sediments

    The Holocene

    (1994)
  • Cited by (20)

    • Geomorphological impact, hydraulics and watershed- lake connectivity during extreme floods in mountain areas: The 1959 Vega de Tera dam failure, NW Spain

      2021, Geomorphology
      Citation Excerpt :

      The flow was most likely funneled through the reactivation of the subaquatic canyon in the westernmost area of the lake. Reactivation of inactive canyons during extreme floods has also been documented in other canyon/levee complexes in large perialpine lakes (Kremer et al., 2015b; Corella et al., 2016a). The flood-related underwater current would explain the mixed sandy layer in core 4A (retrieved in the canyon thalweg).

    • Modern sedimentary processes at the heads of Martínez Channel and Steffen Fjord, Chilean Patagonia

      2020, Marine Geology
      Citation Excerpt :

      The southern submarine channel being located immediately in front of the southern branch of Baker River (Fig. 3) supports this recent avulsion hypothesis. Such channel avulsions most likely occur during extreme discharge events, which have the potential to induce vigorous turbidity events, resulting in a complete re-organization of the subaquatic bedforms and channels (e.g., Kremer et al., 2015). Since very dilute river plumes are known to be able to trigger turbidity currents (Hage et al., 2019), this mechanism could explain our observations.

    View all citing articles on Scopus
    1

    Present address: Geological Institute, ETH Zurich, Sonneggstrasse 5, 8092, Zurich, Switzerland.

    2

    Present address: Institute of Physical Chemistry Rocasolano (IQFR-CSIC), 28003 Madrid, Spain.

    View full text