Climate and early karstification : what can be learned by models?

• Autorzy: Dreybrodt W. , Gabrovsek F.
• Języki publikacji: EN

Abstrakty

EN

First an overview is given on the present state of modelling of karst aquifers and karst conduits. Emphasis is placed to early karstiffication in rock massives with low fissure density as suggested for states 1 and 2 in Ford's four-state-model. In this case early karstification proceeds under the condition of a constant hydraulic head. The evolution of a single isolated karst conduit, as well as evolution of karst conduits in two-dimensional netwworks of fracturres are discussed. From these models the parameters determining early karstification can be identified. These are the initial aperture widths of the fractures, their lengths, the hydraulic head, and the viscosity o,f water, as well as the parameters of the non-linear dissolution kinetics of limestone, and the equilibrium concentration of calcium with respect to calcite. Early karstification under constant head conditions is characterized by a feedback-mechanism which couples flow rates through the conduits to the dissolutional widening of the fracture. After an initially slow increase in flow and in aperture width of the fracture a dramatical increase of flow rates and fracturre widening occurs at breakthrough. The breakthrough time, when this event happens can be quantified from the parameters defined above. This time can be considered as a measure of intensity of karstification. Large scale climatic parameters, especially temperature exert influence to breakthrough time. Under otherwise identical geological conditions breakthrough times in tropic and moderate climates are about 5 times shorter than in arctic/alpine climate. Micro-climatic conditions, however, are of similar importance. If the vegetation on a karstplateau exhibits regions with different CO2 partial pressure in the soil, waters from these differing regions may mix at fracture-confluences in the karst massive. Mixing corrosion causes renewed solutional power at these confluences. Therefore breakthrough times can be reduced significantly. We present details of this mechanism and its influence to breakthrough times. Already moderate differences in in differently vegetated areas are sufficient to reduce breakthrough times by a factor of four. Although macro- and micro-climatic variables exert a significant influence to karstification it is not possible to draw conclusions on climatic conditions from the structure of a karst aquifer in retrospective.

Słowa kluczowe

EN

climate; early karstification; karst; modelling

• Wydawca: Faculty of Geology of the University of Warsaw ; Komitet Nauk Geologicznych PAN
• Czasopismo: Acta Geologica Polonica
• Rocznik: 2002
• Tom: Vol. 52, nr 1
• Strony: 1--11
• Opis fizyczny: Bibliogr. 32 poz..

Twórcy

autor

Dreybrodt W.

• Karst Processes Research Group, Institute of Experimental Physics, University of Bremen, D-28334 Bremen, Germany

autor

Gabrovsek F.

• Karst Processes Research Group, Institute of Experimental Physics, University of Bremen, D-28334 Bremen, Germany
• Karst Research Institute, ZRC-SAZU, Postojna, Slowenia

Bibliografia

• 1. BÖGLI , A. 1980. Karst hydrology and physical speleology. Springer; Berlin.
• 2. CLEMENS, T., HÜCKINGHAUS , D., SAUTER, M., LIED, R. & TEUTSCH, G. 1997. Modelling the genesis of karst aquifer systems using a coupled reactive network model. In: Hard Rock Geosciences. IAHS Publication, pp. 1-241, Colorado, 3-10.
• 3. DREYBRODT W. 1988. Processes in karst systems - Physics, Chemistry and Geology. Springer Series in Physical Environments, 4. Springer; Berlin – New York.
• 4. DREYBRODT W. 1990. The role of dissolution kinetics in the development of karstification in limestone: A model simulation of karst evolution. Journal of Geology, 98, 639-655.
• 5. DREYBRODT W. 1996. Principles of early development of karst conduits under natural and man-made conditions revealed by mathematical analysis of numerical models. Water Resources Research, 32, 2923-2935.
• 6. DREYBRODT W. 2000. Equilibrium Chemistry of karst water in limestone Terranes. In: K LIMCHOUK , A., FORD, D.C., PALMER , A.N. & DREYBRODT , W. (Eds), Speleogenesis: Evolution of karst aquifers. National Speleological Society, USA.
• 7. DREYBRODT, W. & E ISENLOHR, L. 2000. Limestone dissolution rates in karst environments. In: KLIMCHOUK , A., FORD , D.C., PALMER , A.N. & D REYBRODT , W. (Eds), Speleogenesis: Evolution of karst aquifers. National Speleological Society, USA.
• 8. DREYBRODT, W. & GABROVSEK F. 2000a. Dynamics of the evolution of a single karst conduit. In: KLIMCHOUK, A., FORD, D.C., PALMER , A.N. & D REYBRODT , W. (Eds), Speleogenesis: Evolution of karst aquifers. National Speleological Society, USA.
• 9. DREYBRODT, W. & GABROVSEK F. 2000b. Influence of fracture roughness on karstification. conduit In: KLIMCHOUK , A., FORD , D.C., PALMER , A.N. & D REYBRODT , W. (Eds), Speleogenesis: Evolution of karst aquifers. National Speleological Society, USA.
• 10. DREYBRODT, W. & S IEMERS , J. 2000. Cave evolution on twodimensional networks of primary fractures in limestone. In: K LIMCHOUK , A., F ORD , D.C., PALMER , A.N. & D REYBRODT, W. (Eds), Speleogenesis: Evolution of karst aquifers. National Speleological Society, USA.
• 11. EISENLOHR L., M ETEVA, K., GABROVSEK , F. & DREYBRODT , W. 1999. The inhibiting action of intrinsic impurities in natural calcium carbonate minerals to their dissolution kinetics in aqueous H 2 O-CO 2 solutions. Geochimica Cosmochimica, Acta, 63, 989-1002.
• 12. FORD, D.C., 1971 Geological Structure and a new explanation of limestone cavern genesis. Cave Research Group of Great Britain, Transactions, 13, 81-94.
• 13. FORD, D.C., 1999. Perspectives in karst hydrogeology and cavern genesis. In: PALMER , A.N., PALMER , M. & SASOVSKY , I.D. (Eds), Karst modeling, Karst Waters Institute, Charles Town, West Virginia, USA, pp. 17-29.
• 14. FORD, D.C. & EWERS , R.O. 1978. The development of limestone caves in the dimensions of length and depth. Canadian Journal of Earth Sciences, 15, 1783-1798.
• 15. FORD, D.C. & WILLIAMS, P.W. 1989. Karst geomorphology and hydrology. Unwin Hyman; London.
• 16. GABROVSEK , F. 2000. Evolution of early karst aquifers. From simple principles to complex models. Založba ZRC, SAZU, 150 pp. Ljubljana.
• 17. GABROVSEK, F. & D REYBRODT, W. 2000. A model of early evolution of karst conduits affected by subterranean CO2 sources. Environmental Geology. 39, 531-543.
• 18. GABROVSEK, F. & D REYBRODT, W. 2000. The role of mixing corrosion in calcite aggressive H2O-CO2-CaCO 3 solutions in the early evolution of karst aquifers. Water Resources Research, 5, 1179-1188.
• 19. GROVES , C.G. & HOWARD, A.D. 1994. Early development of karst systems. 1. Preferential flow path enlargement under laminar flow. Water Resources Research, 30, 2837-2846.
• 20. HOWARD, A.D. & GROVES, C.G. 1995. Early development of karst systems 2. Turbulent flow. Water Resources Research, 31, 19-26.
• 21. KAUFMANN , G. & B RAUN , J. 1999. Karst aquifer evolution in fractured rocks. Water Resources Research, 35, 3223-3238.
• 22. KAUFMANN , G. & B RAUN , J. 2000. Karst aquifer evolution in fractured, porous rocks. Water Resources Research, 36, 1381-1392.
• 23. PALMER , A. N. 1984. Recent trends in karst geomorphology. Journal of Geological Education, 32, 247-253.
• 24. PALMER , A. N. 1991. The origin and morphology of limestone caves. Bulletin of the Geological Society of America, 103, 1-21.
• 25. PALMER , A. N. 2000. Digital modeling of individual solution conduits. In: K LIMCHOUK , A., F ORD , D.C., PALMER , A.N. & D REYBRODT, W. (Eds), Speleogenesis: Evolution of karst aquifers. National Speleological Society, USA.
• 26. RHOADES, R. & SINACORI , M.N. 1941. The pattern of groundwater flow and solution. Journal of Geology, 49, 785-794.
• 27. SIEMERS , J. & D REYBRODT, W. 1998. Early development of karst aquifers on percolation networks of fractures in limestone. Water Resources Research, 34, 409-419.
• 28. SMITH, D.I. & ATKINSON, T.C. 1976. Process, landforms and climate in limestone regions. In: DERBYSHIRE, E. (Ed.), Geomorphology and Climate. John Wiley and Sons; London
• 29. SVENSSON, U. & DREYBRODT, W. 1992. Dissolution kinetics of natural calcite minerals in CO2 -water systems approaching calcite equilibrium. Chemical Geology, 100, 129-145.
• 30. SWINNERTON , A.C. 1932. Origin of limestone caverns. Geological Society of America Bulletin, 34, 662-693.
• 31. WHITE, W.B. 1977. The role of solution kinetics in the development of karst aquifers. In: TOLSON, J.S. & DOYLE, F.L. (Ed.) UAH-Press; Huntsville, Alabama, USA.
• 32. WHITE, W.B. 1988. Geomorphology and hydrology of karst terrains. Oxford University Press; New York