Port Miou and Le Bestouan (Cassis, France) : The Largest French Submarine Karst Springs

This book documents the exploration and engineering history and potential of two submarine karst springs, Port Miou and Le Bestouan, from the 1970s until now. These springs are the outlets of a vast and deep karst aquifer of more than 1000 km2 near the city of Cassis, France. It presents the latest hypotheses for the hydrological and speleological models of this karstic network explaining the intrusion of saline waters within the system with further applications to other karstic springs in the Mediterranean. Foreword 6 Contents 8 1 Presentation of the Cassis Springs 11 1.1 Location 11 1.1.1 Le Bestouan 11 1.1.2 Port Miou 11 1.2 Description of the Caves 11 1.2.1 Le Bestouan (from Douchet 2012) 11 1.2.2 Port Miou 15 References 20 2 Natural Context 21 2.1 Topography and Landscape 21 2.2 Geology 21 2.2.1 Generalities 21 2.2.2 Geological History 21 2.2.3 Lithology 25 2.2.4 Tectonics and Geomorphology 26 2.2.5 Present Structure 27 2.3 Climate 27 2.4 Socioeconomic Context 27 References 28 3 Evolution of Explorations and Studies 29 3.1 Generalities 29 3.2 First Descriptions 29 3.3 First Speleological Explorations 30 3.4 The SRPM Project 30 3.4.1 History of the SRPM Research Work 30 3.4.2 First Phase of Acquisition and Exploration: 1968–1972 30 3.4.3 Implementation of the 1st Underwater Dam and 2nd Phase of Hydrometric Data Acquisition 1972–1975 31 3.4.4 Second Dam: Creation of a Spillway and Complete Closure of the Cave by a Dam 1975–1977 34 3.4.5 Load Tests and 3rd Acquisition Phase in 1977–1978 34 3.5 End of the Hydrogeological Studies 36 References 36 4 Resumption of Research in 2000 38 4.1 New Hydrogeological Studies 38 4.2 A Marine Origin for the Salt Contamination 38 4.3 A Huge Aquifer to Explain the Discharge of Cassis Springs 38 References 40 5 Advances During the XXth Century 41 5.1 Exploration of Port Miou 41 5.2 Local Bathymetry 41 5.3 Messinian Evaporites 41 5.4 Messinian Salinity Crisis 41 5.5 Consequences on the Mediterranean Rivers and Aquifers 42 5.6 Application to Karst Aquifers and Cave Systems 42 6 A Messinian Model for Port Miou 45 6.1 Gilli’s Model 45 6.2 Cavalera Thesis in 2004–2007 45 6.2.1 Objectives 45 6.2.2 Hydrodynamics and Physico-Chemistry of Littoral Submarine Sources 45 6.2.3 Research on the Watershed 47 6.2.4 Research on Geochemical Tracers of the Seawater Inflow 47 6.2.5 Titanium Concentrations 49 6.3 Tassy’s Thesis in 2009–2012 50 6.4 Different Models of Saline Contamination 52 6.4.1 Brackish Karst Springs 52 6.4.2 Contamination by the Cave Entrance 53 6.4.3 Aspiration by the Bestouan 53 6.4.4 Presence of a Gallery at −80 m 53 6.4.5 Deep Diffuse Contamination 53 6.4.6 Suction of Seawater by a Very Deep Paleodrain 54 6.5 A Definitive Proof in 2016 55 6.5.1 Xavier Meniscus Report 55 References 56 7 Evolution of Explorations from the 1990s 58 7.1 Port Miou (from Acquaviva 2012) 58 7.1.1 Second Campaign of Explorations 58 7.1.2 Third Campaign of Explorations 58 7.1.3 Last and Current Campaign of Explorations 58 7.1.4 The Use of Closed-Circuit Rebreathers 58 7.2 Le Bestouan 59 7.3 Synthesis of the Explorations 59 7.4 Other Caves 59 References 61 8 Survey of Deep Flooded Caves 62 8.1 Generalities 62 8.2 Port Miou 62 8.2.1 Geophysic Location 62 8.2.2 Traditional Survey 62 8.2.3 Automatic Surveying 62 8.3 Le Bestouan 64 References 65 9 Watershed Definition 66 9.1 Watershed Definition 66 9.2 Structure 66 9.3 Hydrological Balance 66 9.4 Dye Tests 66 References 68 10 Developments and Conclusions 69 10.1 Current Research and Future Developments 69 10.1.1 Research 69 10.1.2 Site Valuation Projects 69 10.1.3 Geopolitics of Water and Water Lobbies 69 10.2 General Conclusion 70 References 71 Appendix_1 72 Front Matter ....Pages i-ix Presentation of the Cassis Springs (Eric Gilli)....Pages 1-10 Natural Context (Eric Gilli)....Pages 11-18 Evolution of Explorations and Studies (Eric Gilli)....Pages 19-27 Resumption of Research in 2000 (Eric Gilli)....Pages 29-31 Advances During the XXth Century (Eric Gilli)....Pages 33-36 A Messinian Model for Port Miou (Eric Gilli)....Pages 37-49 Evolution of Explorations from the 1990s (Eric Gilli)....Pages 51-54 Survey of Deep Flooded Caves (Eric Gilli)....Pages 55-58 Watershed Definition (Eric Gilli)....Pages 59-61 Developments and Conclusions (Eric Gilli)....Pages 63-65 Back Matter ....Pages 67-67