Articles | Volume 5, issue 1
Earth Surf. Dynam., 5, 199–209, 2017
Earth Surf. Dynam., 5, 199–209, 2017

Research article 28 Mar 2017

Research article | 28 Mar 2017

A new CT scan methodology to characterize a small aggregation gravel clast contained in a soft sediment matrix

Laurent Fouinat1, Pierre Sabatier1, Jérôme Poulenard1, Jean-Louis Reyss2, Xavier Montet3, and Fabien Arnaud1 Laurent Fouinat et al.
  • 1EDYTEM, Université Savoie Mont Blanc, CNRS 73376 Le Bourget du Lac CEDEX, France
  • 2LSCE, Université de Versailles Saint-Quentin CEA-CNRS, Avenue de la Terrasse, 91198 Gif-sur-Yvette CEDEX, France
  • 3University of Geneva Department of Radiology and Medical Informatics Genève, Rue Gabrielle-Perret-Gentil 4, C1211, Geneva, Switzerland

Abstract. Over the past decades, X-ray computed tomography (CT) has been increasingly applied in the geosciences community. CT scanning is a rapid, non-destructive method allowing the assessment of relative density of clasts in natural archives samples. This study focuses on the use of this method to explore instantaneous deposits as major contributors to sedimentation of high-elevation lakes in the Alps, such as the Lake Lauvitel system (western French Alps). This lake is located within a very steep valley prone to episodic flooding and features gullies ending in the lake. This variety of erosion processes leads to deposition of sedimentary layers with distinct clastic properties. We identified 18 turbidites and 15 layers of poorly sorted fine sediment associated with the presence of gravels since AD 1880. These deposits are respectively interpreted as being induced by flood and wet avalanche. This constitutes a valuable record from a region where few historical records exist. This CT scan approach is suitable for instantaneous deposit identification to reconstruct past evolution and may be applicable to a wider variety of sedimentary archives alongside existing approaches.

Short summary
This study focuses on the creation of a novel CT scan methodology at the crossroads between medical imagery and earth sciences. Using specific density signatures, pebbles and/or organic matter characterizing wet avalanche deposits can be quantified in lake sediments. Starting from AD 1880, we were able to identify eight periods of higher avalanche activity from sediment cores. The use of CT scans, alongside existing approaches, opens up new possibilities in a wide variety of geoscience studies.