Speleogenesis, geometry, and topology of caves: A quantitative study of 3D karst conduits

Abstract

International audienceKarst systems are hierarchically spatially organized three-dimensional (3D) networks of conduits behaving as drains for groundwater flow. Recently, geostatistical approaches proposed to generate karst networks from data and parameters stemming from analogous observed karst features. Other studies have qualitatively highlighted relationships between speleogenetic processes and cave patterns. However, few studies have been performed to quantitatively define these relationships. This paper reports a quantitative study of cave geometries and topologies that takes the underlying speleogenetic processes into account. In order to study the spatial organization of caves, a 3D numerical database was built from 26 caves, corresponding to 621 km of cumulative cave passages representative of the variety of karst network patterns. The database includes 3D speleological surveys for which the speleogenetic context is known, allowing the polygenic karst networks to be divided into 48 monogenic cave samples and classified into four cave patterns: vadose branchwork (VB), water-table cave (WTC), looping cave (LC), and angular maze (AM). Eight morphometric cave descriptors were calculated, four geometrical parameters (width-height ratio, tortuosity, curvature, and vertical index) and four topological ones (degree of node connectivity, α and γ graph indices, and ramification index) respectively. The results were validated by statistical analyses (Kruskal-Wallis test and PCA). The VB patterns are clearly distinct from AM ones and from a third group including WTC and LC. A quantitative database of cave morphology characteristics is provided, depending on their speleogenetic processes. These characteristics can be used to constrain and/or validate 3D geostatistical simulations. This study shows how important it is to relate the geometry and connectivity of cave networks to recharge and flow processes. Conversely, the approach developed here provides proxies to estimate the evolution of the vadose zone to epiphreatic and phreatic zones in limestones from the quantitative analysis of existing cave patterns

Coupling SKS and SWMM to Solve the Inverse Problem Based on Artificial Tracer Tests in Karstic Aquifers

“…The mean flow section along the tracer transport is about 9 m 2 , the mean flow velocity is 0.16 m/s and the mean length of the conduits between injection and recovery point was about 905 m. Dividing the length of the total conduits by the apparent distance between injection and recovery point gives and estimation of tortuosity. In karst systems, the tortuosity generally varies from 1.10 to 1.40 depending on the morphology of the conduit networks [70]. Considering an apparent distance of 850 m between injection and recovery sites [13], the mean tortuosity here is about 1.06, getting closer to the range of value for an angular maze conduit network morphology [70].…”

“…In karst systems, the tortuosity generally varies from 1.10 to 1.40 depending on the morphology of the conduit networks [70]. Considering an apparent distance of 850 m between injection and recovery sites [13], the mean tortuosity here is about 1.06, getting closer to the range of value for an angular maze conduit network morphology [70]. The variability of the mean flow section along the transport and the length of transport appears to be lower than for the mean flow velocity.…”

Heterogeneity‐Induced Mixing and Reaction Hot Spots Facilitate Karst Propagation in Coastal Aquifers

“…The topology of karst conduits has been strongly linked to their spatial location and the governing flow characteristics (e.g., Audra & Palmer, 2015; Gabrov et al, 2014; Palmer, 1992). For example, anastomosic caves, defined by their braided patterns, typically occur across bedding planes in the epiphreatic zone, whereas angular mazes tend to be associated with fractured media due to seepage from overlying insoluble rocks (Jouves et al, 2017). While near‐surface features such as flank margin caves (Mylroie et al, 1990) can be observed in many coastal carbonate environments along the salt‐freshwater mixing zone, limited accessibility has prevented large‐scale speleological surveys of karst conduits in coastal aquifer.…”

Karst and urban flood-induced solid discharges in Mediterranean coastal rivers: The case study of Las River (SE France)

“…Karst aquifers also have a peculiar hydrodynamic functioning due to large and permeable conduits, related to the speleogenetic history of the carbonate rocks (Jouves et al 2017). Groundwater flows through the karst network and converges to the springs that concentrate the water discharge in few outlets.…”