3D geological modelling of a coastal area: case study of the Vaches Noires Cliffs, Normandy, France
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ORIGINAL PAPER
3D geological modelling of a coastal area: case study of the Vaches Noires Cliffs, Normandy, France ´ Imen Hassen1 · Cyrille Fauchard1 · Raphael Antoine1 · Thomas Roulland2 · Olivier Maquaire2 · Stephane Costa2 · 2 Olivier Dugue´ Received: 7 April 2020 / Accepted: 7 August 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract This study aims to realize a regional scale 3D geological model (3D-GM) of the Pays d’Auge Plateau (PAP), in Normandy, France, leading to the study of the Vaches Noires Cliffs (VNCs), a local coastal site. A 3D-GM is built using a 3D implicit method based on the integration of surface geology, cross sections, and elevation data. The geometry of the geological layers is characterized, leading to an estimation of the volume of each geological unit and of the water resource within the Cretaceous aquifer of the study site. A hydrogeological model of the VNCs is proposed and the role of clayey soils on the erosive process of the cliffs is considered. Lastly, potential applications of 3D-GM are discussed in the framework of further researches on coastal retreat in Normandy. Keywords 3D geological modelling · Aquifer · Coast · Erosion
Introduction Three-dimensional geological modelling (3D-GM) allows to spatially represent the geological characteristics of a given area. Basically, it consists in inferring the geological formation units in a volume, based on the knowledge of generally sparse data. It uses all available information as input (Wu et al. 2005; Kaufmann and Martin 2009; Mallet 2002; McInerney et al. 2005; Calcagno et al. 2008; Fern´andez et al. 2003), such as on-site contact points and structural observations done by geologists, geological maps (including faults and boundaries of geological formations), cross sections, surface topography, seismic survey, and geotechnical boreholes. The mathematical approach of 3DGM is mainly based on potential-field interpolation method: thanks to an estimator, so-called cokriging, it takes into account contact location (for instance the boundary between two geological formations), orientation data (Lajaunie et al.
Imen Hassen
[email protected] 1
Cerema, ENDSUM Research Team, 10, chemin de la Poudri`ere, CS90245, F-76121 Le Grand Quevilly, France
2
Universit´e de Caen Normandie, UMR 6554 LETG/GEOPHEN, 14000 Caen, France
1997; Calcagno et al. 2008) and leads to a 3D geological representation of the whole studied system. Numerous studies highlighted the usefulness of 3D-GM in various earth sciences areas. Basic inputs are generally geological maps and cross sections. All other available data, even sparse, may play a major role in the 3D geomodelling process. In geology, Guillen et al. (2008) modelled granitic intrusions along crustal fault, using aerial gravimetric and magnetic data. In that case, considering 3D geophysical observations requires specific inversion schemes, allowing to find the best model fitting all data. Kaufmann and Martin (2009) described the geology of a gas storage area with classical a
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