Calcite Dissolution under Turbulent Flow Conditions: A Remaining Conundrum
A significant body of experimental and theoretical work has examined the dissolution rates of calcite, and other carbonate minerals, under varying chemical and hydrodynamic conditions (see Morse & Arvidson (2002) for a comprehensive review). The relationships derived from this work have been applied extensively to the development of mechanistic models of speleogenesis (e.g. Dreybrodt 1996; Dreybrodt et al. 2005; Birk et al. 2005; Rehrl et al. 2008; Kaufmann 2009; Szymczak & Ladd 2011). However, the primary focus of these models has been on the early stages of cave formation, with less attention toward the later stages of cave evolution and turbulent flow conditions. Recent efforts have begun to develop mechanistic models for processes governing later stages of cave evolution, considering factors such as turbulent flow structures (Hammer et al. 2011) and open channels (Perne 2012). However, such studies remain limited, in part due to significant quantitative uncertainties in a variety of processes that become important beyond the incipient speleogenesis stage (Covington et al. 2013). While speleogenetic models have not typically been run much beyond the transition from laminar to turbulent flow conditions, experimental and theoretical studies of carbonate dissolution have constrained dissolution rates and rate-controlling mechanisms under turbulent flow (e.g. Rickard & Sjöberg 1983; Dreybrodt & Buhmann 1991; Liu & Dreybrodt 1997). However, a direct application of these results and comparison to field observations leads to an apparent conundrum. According to the theory, solutional forms such as scallops and flutes should not exist in limestone; however, they clearly do exist at a wide variety of sites and scales. This conundrum suggests that there may be problems with the theory, problems with our understanding of scallop formation, or both.
M.D. Covington. "Calcite dissolution under turbulent flow conditions: a remaining conundrum," Acta Carsologica, v.43, 2014, p. 195. doi:10.3986/ac.v43i1.628