Morphogenesis of hypogenic caves

Early-stage hypogene karstification in a mountain hydrologic system: A coupled thermohydrochemical model incorporating buoyant convection

“…breakthrough and the transition to turbulence is not expected under hypogene conditions, which is consistent with observations [Klimchouk, 2009]. There are two main reasons for this behavior : (i) the retrograde solubility of calcite, which maintains dissolution aggressiveness in upward flow across a geothermal gradient, and (ii) the overall flux through the system is limited by the low permeability of the rock matrix on the mountainsides, which inhibits the positive feedback the generates dissolution fingers.…”

“…Although the pattern of buoyant convection rolls is very organized and symmetric in the simulations with initially homogeneous aperture field, the behavior in the cases with initially heterogeneous aperture fields is much more complex, with a greater propensity for smaller localized convection rolls as the degree of heterogeneity increases. Our simulation results thus confirm Klimchouk's [2009] interpretation that several features in hypogene karst systems derive from buoyant convection. The localized rather than diffuse output of warm waters in the discharge zone in our simulation results is consistent with numerous observations of thermal karst springs.…”

“…However, we did not consider some other geologic and hydrogeologic features representative of other reported hypogene karst systems, such as mixed lithologies [e.g., Hobba et al, 1979, Ford and Williams, 2007, Klimchouk, 2009 and cross-formational flow systems [Klimchouk, 2009], which produce transverse speleogenesis in the sense of Klimchouk [2003]. To some extent, this was influenced by the computationally intensive nature of the simulations, which restricted the scope of our study.…”

“…Ford [2006] and Klimchouk [2009] suggest that the above alternative definitions are unified by noting that the most important common hydrogeological feature shared by hypogene karst systems is that they are formed in confined settings by flow of water into a soluble formation from below. The processes, mechanisms, and timescales associated with the origin and development of hypogene karst systems are of significant hydrogeological and speleological interest [Palmer, 1991;Ford and Williams, 2007;Klimchouk, 2009], and also relevant in the context of renewable geothermal energy development and subsurface carbon sequestration in deep karst systems [Dreybrodt and Gabrovsek, 2003;Klimchouk, 2007;Goldscheider et al, 2010]. One subset of hypogene karst systems is formed in settings where meteoric waters circulate to great depths and rise up along high-permeability vertical or subvertical fracture/ fault zones [Ford and Williams, 2007;Perry et al, 1979;Hobba et al, 1979;Severini and Huntley, 1983;Palmer, 1991;Goldscheider et al, 2010;Davidson et al, 2011].…”

“…For simplicity, and in the interest of maintaining a tractable scope for the paper, we did not consider multiple geologic units in the system above the basement rock. We acknowledge that many of the spring systems described by Hobba et al [1979] and hypogene cave systems described by Klimchouk [2009] involve cross-formational flow paths that cut across multiple geologic units. Our modeling approach can be extended readily to simulate karstification in limestone units that only comprise a part of the overall stratigraphy.…”