�coulements de surface et souterrains UE 13 (2e ann�e) � Ph. Audra

							                Ch.1 – Introduction to
                 Karst development
                 and speleogenesis
                           Philippe AUDRA

   hydro
            h
          t ec
         pr o




Master
Gestion de projets
hydrotechnologiques & environnementaux
    Introduction: the initial conditions

   Progressive permeability / porous aquifers

   5 conditions:
    •   Soluble and fissured rock (limestone…)
    •   Water (solvent, transport)
    •   Acidity (CO2 from vegetation)
    •   Hydraulic head
    •   and time…


   Large karst development in:
    - Wet regions (rain + vegetation)
    - Mountains (topographic gradient) / plateau (long evolution)
             Karst development
             and speleogenesis

   1 – An organized aquifer
   2 – An evolutive dynamic
   3 – Vertical cave pattern
                            1. An organized aquifer
                                                          1.1. Karst inception


                                                                                  Initial fissured media

                                                                                  Hydraulic head
                                                                                     Organization
                                                                                     Flow concentration (main drain)
                                                                                     Piracies


                                                                                  => branchwork pattern

                                                                                  Breakthrough time ~ 10 ka

                                                                                  Large drains ~ 100 ka
Development of a karst aquifer

Dreybrodt W. & Siemers J. 2000
Cave evolution on two-dimensional networks of primary fractures in limestone
Speleogenesis. Evolution of karst aquifers, p. 201-211
                     1. An organized aquifer
                                           1.2. Vertical organization


                                                       Recharge (diffuse / concentrated)

                                                       Unsaturated (vadose) zone
                                                         Epikarst
                                                         Vadose zone


                                                       Saturated (phreatic) zone

                                                       Epiphreatic zone
Vertical organization of a karst aquifer                 Drain (transmissive)
                                                         Annex systems (capacitive)
                                                         Vadose + phreatic flow


                                                    => Highly heterogeneous
1. An organized aquifer
     1.2. Vertical organization




              The epikarst structure

              Mangin A. 1975
              Contribution à l’étude hydrodynamique des aquifères karstiques
              Annales de Spéléologie
1. An organized aquifer
   1.3. Perched vs. dammed karst


                      Perched karst
                          Spring above base level
       Base
                          No phreatic zone
       level              Low storage
                          Main drain along impervious
                           basement


                      Dammed karst
                          Spring at base level
                          Large phreatic zone
                          high storage
                          Main drain at the water table
           Base
           level
                            2. An evolutive dynamic
                                2.1. Information from recession curves




                                                                    Non linear: drains

                                                                    Linear: annex system




A karst spring recession curve

Mangin A. 1975
Contribution à l’étude hydrodynamique des aquifères karstiques
Annales de Spéléologie
                       2. An evolutive dynamic
                      2.2. Exchanges: drain  annex systems

                                            High water
                                             • Water higher in drain =>
                                               recharge annex systems


                                            Low water
                                             • Water higher in annex
                                               systems => recharge drain


                                         => Long linear recession




Exchanges: drain  annex systems.
Left: high water; right: low water

Collignon B. 1988
Spéléologie, approches scientifiques
                            2. An evolutive dynamic
                       2.3. Karst aquifers classification [after Mangin]


                                                                    Highly transmissive karst
                                                                     (Aliou type)
                                                                      Sharp flood peak
                                                                      Short recession
                                                                      Low storage
                                                                 => Highly organized,
                                                                   evoluted karst, large drains

                                                                    High storage karst
                                                                     (Torcal type)
                                                                      Delayed and gentle flood
                                                                      Very long recession
Classification of karst aquifers                                      Huge reserve
Mangin A. 1975                                                   => Complex karst
Contribution à l’étude hydrodynamique des aquifères karstiques
Annales de Spéléologie
3. Vertical cave pattern
3.1. Main types of vertical cave pattern

                        Juvenile karst
                        Contact caves
                        Water table cave
                        Looping Cave




                   Palmer A. N. & Audra Ph. 2004
                   Patterns of caves
                   Encyclopedia of cave and karst science, p. 573-575
                       3. Vertical cave pattern
                         3.1. Main types of vertical cave pattern

                                                           Juvenile karst
                                                            •   First karstification
                                                            •   Recent uplift
                                                            •   Sparse fracturing => steep WT
                                                            •   Vadose entrenchment of initial
                                                                phreatic tube


                                                        => Young, rapidly developing
                                                          karst (PNG), evaporites




Muruk system, Papua New-Guinea [Photo. J.-P. Sounier]
                          3. Vertical cave pattern
                            3.1. Main types of vertical cave pattern

                                                   Contact cave
                                                    • Perched karst
                                                    • Torrential flow =>
                                                      mechanical erosion
                                                    • Large galleries with boulders
                                                    • No significant phreatic
                                                      passages




Grotte de Méailles [Photo. J.-Y. Bigot]
                         3. Vertical cave pattern
                           3.1. Main types of vertical cave pattern

                                                   Water table cave
                                                    • Dammed karst
                                                    • Phreatic zone below base
                                                      level
                                                    • Regular discharge => WT
                                                      cave




Upstream series, Muruk [Photo. J.-P. Sounier]
                         3. Vertical cave pattern
                           3.1. Main types of vertical cave pattern

                                                                  Looping caves
                                                                     •   Top of loops = highest floodwater
                                                                         level (transition)
                                                                     •   Looping tubes = epiphreatic
                                                                     •   vadose + phreatic morphologies
                                                                     •   Soutirages = loops draining after
                                                                         flood




                                                    Häuselmann, Jeannin & Monbaron 2003
                                                    Role of epiphreatic flow and soutirages in conduit morphogenesis
                                                    Zeitschrift für Geomorphologie
Hölloch, Switzerland [Photo. U. Widmer, Ballmann]
3. Vertical cave pattern
 3.2. Influence of base level changes

                      Base level lowering
                       • Cave levels


                      Base level rising
                       • Flooded spring
                       • Flooded karst
                       • Cave levels “per
                         ascensum”
                         3. Vertical cave pattern
                  3.2. Influence of base level changes (lowering)

                                                            Cave levels
                                                              • Base level drop => phreatic
                                                                zone drop
                                                              • Stability of base level =>
                                                                new cave level
                                                              • Correlation with terraces
                                                              • Upper level abandoned
                                                              • Vadose extends downwards




                                                          Palmer A. N. 1987
                                                          Cave levels and their interpretation
                                                          The NSS Bulletin, n°. 49, p. 50-66.
Grotte de Saint-Benoît, France [Photo. J.-Y. Bigot]
                              3. Vertical cave pattern
                          3.2. Influence of base level changes (rising)

                                                            Flooded spring
                                                             • River aggradation
                                                             • Flooding of spring zone




River aggradation produces flooding of the spring area
[Jaillet & al. 2002]




  Echo Spring, Mammoth Cave (USA)
                           3. Vertical cave pattern
                       3.2. Influence of base level changes (rising)

                                                                               Flooded cave system
                                                                                  •   Major base level rise
                                                                                  •   Phreatic zone moves upward
                                                                                  •   Conduits flooding
                                                                                  •   Filling of adjacent passages
                                                                                  •   Main flow lines remain active
                                                                                  •   Vauclusian spring appear
                                                                                      from new ascending routes
                                                                                      or relict conduits reactivation




                                                        Bini 1994
                                                        Rapports entre la karstification périméditerranéenne et
                                                        la crise de salinité du Messinien…
                                                        Karstologia

                                                        Audra Ph., Mocochain L., Camus H., Gilli É., Clauzon G., Bigot J.-Y. 2004
                                                        The effect of the Messinian Deep Stage on karst development
                                                        around the French Mediterranean.
                                                        Geodinamica Acta, vol. 17, n° 6, p. 27-38
Fontaine de Vaucluse, -308 m (-254 m below sea level)
                            3. Vertical cave pattern
                        3.2. Influence of base level changes (rising)

                                                                                       Cave level “per
                                                                                        ascensum”
                                                                                            • Cave levels develop
                                                                                              according to the successive
                                                                                              stages of base level rise
                                                                                            • Deep flow lines remain active
                                                                                            • Level connected by chimney-
                                                                                              shafts



                                                       Chimney-shaft [Photo. J.-Y. Bigot]




                                                                                                 Mocochain & al. 2006
                                                                                                 Geodynamic evolution of the peri-
                                                                                                 Mediterranean karst during the
                                                                                                 Messinian and the Pliocene…
                                                                                                 Sedimentary Geology


Horizontal tube, Saint-Marcel Cave, France [Photo. J.-Y. Bigot]
                              Conclusion

   Heterogeneous
   Evolutive
    => complex!


   Conditions for speleogenesis
    • Passive parameters: Geological structure (perched /dammed)
    • Boundary conditions
           Recharge (un)regular
           Geomorphological evolution (base level changes)
    => Polygenic cave patterns