Structural control on karst water circulation and speleogenesis in a lithological contact zone: The Bossea cave system (Western Alps, Italy)

Abstract A water level rise of almost 3 m in the space of two years in the Sterkfontein Cave system since late-2009 necessitated the re-routing of the tourist path through the cave to successively higher elevations on three occasions. It also raised concern for a possible association with copious acidic and sulphate-rich mine water drainage from the West Rand Goldfield (a.k.a. Western Basin) starting in early-2010, and the related threat to the UNESCO-inscribed fossil site. Although these circumstances have had little impact on the tourist value of the site, a prognosis of the impact on cave water level and quality is indicated by virtue of its karst setting and palaeontological significance. Historical and recent potentiometric data, together with ancillary hydrogeological and hydrochemical information acquired in the course of a water resources monitoring programme for the broader Cradle of Humankind World Heritage Site, provides new insight into the hydrogeology of the cave system. An improved understanding of the hydrophysical and hydrochemical response of the cave water system sheds light on the location of this system within the water resources environment. It is proposed that the present-day maximum cave water level is constrained to an elevation of ~1440 m above mean sea level. The recent electrical conductivity of 78 mS/m for cave water is 32% greater than the 59 mS/m recorded in mid-2010 and earlier. Similarly, the recent sulphate concentration of 161 mg/L is 178% greater than the 58 mg/L recorded before 2010. Compared to coeval values for ambient karst groundwater represented by the normative Zwartkrans Spring water, the magnitude of the increases in the springwater are similar, viz. 48% (from 84 to 124 mS/m) in salinity and 166% (from 154 to 409 mg/L) in sulphate. Although a distinct mine water impact is evident in both instances, the values indicate a muted impact on the cave water chemistry compared to the springwater. These and other documented observations better inform the threat from various poorer quality water sources to the fossil site in particular, and to the broader karst water resource in general. This contextualises concern for the hydroenvironmental future of Sterkfontein Cave and other nearby fossil sites such as Swartkrans, Rising Star and Bolt’s Farm. The dynamic response of the water resources environment to a variety of hydrological and hydrogeological drivers reinforces the need for monitoring vigilance across a range of disciplines.

Download Full-text

Application of Hydrochemical and Isotopic Data to Determine The Origin and Circulation Conditions of Karst Groundwater in An Alpine and Gorge Region in The Qinghai–Xizang Plateau: A Case Study Of Genie Mountain

10.21203/rs.3.rs-648724/v1 ◽

2021 ◽

Author(s):

Jianfei Ma ◽

Xiangquan Li ◽

Feng Liu ◽

Changchang Fu ◽

Chunchao Zhang ◽

...

Keyword(s):

Water Cycle ◽

Karst Aquifer ◽

Atmospheric Precipitation ◽

Water Circulation ◽

Karst Water ◽

Karst Groundwater ◽

Isotopic Data ◽

Karst Springs ◽

Recharge Sources ◽

Xizang Plateau

Abstract Understanding of the recharge origin, runoff channels, and discharge characteristics of karst groundwater is very important for construction of underground projects and identification of water supply targets. Complex structural systems, lithological differences, and extreme heterogeneity of aquifers combine to create a complex karst aquifer structure in alpine and gorge areas; however, because of the topography, direct investigation of aquifer structure is difficult. In this study, field survey, hydrochemical, and isotopic data are analyzed to reveal the development of karst groundwater and to describe the karst water cycle in Genie Mountain, Qinghai–Xizang Plateau. The results show that atmospheric precipitation and melting ice and snow are the groundwater recharge sources, and groundwater circulation is shallow, with groundwater ages generally no more than 60 yr. The groundwater cycle can be divided into three levels: epikarst water circulation; mid to deep karst water circulation; and deep geothermal water circulation. The karst springs located in the outlet of the Huolong gully contain markedly higher levels of Na + and SO 4 2 − than other karst springs because of the leaching effect of groundwater on mirabilite. The presence of evaporites also indicates that the groundwater of Huolong gully is influenced by evaporation. The runoff of thermal springs undergoes deep circulation and is controlled by faults. This water mainly dissolves carbonate rock, with little influence of evaporation. This study shows that hydrochemical and isotopic methods can be used to discriminate different water types, and can be applied to study the characteristics of complex groundwater runoff in alpine and gorge areas.

Download Full-text

Karst porosity development in layered and fractured carbonates: field evidences of structural control on sulfuric acid speleogenesis (Majella Massif, Italy)

10.5194/egusphere-egu2020-3935 ◽

2020 ◽

Author(s):

Luca Pisani ◽

Marco Antonellini ◽

Ilenia Maria D'Angeli ◽

Jo De Waele

Keyword(s):

Stable Isotopes ◽

Sulfuric Acid ◽

Water Table ◽

Structural Control ◽

Functional Organization ◽

Structural Evolution ◽

Secondary Minerals ◽

Eastern Front ◽

Cave System ◽

Spatial Geometry

Sulfuric acid speleogenesis (SAS) has been widely recognized as one of the most aggressive processes involving carbonate dissolution and rapid formation of karst porosity under hypogenic conditions. Italian carbonate sequences, and especially those outcropping in the Central Apennines, host some of the best studied hypogenic SAS caves of Italy (such as Frasassi, Monte Cucco, Acquasanta Terme, just to mention the most famous).The Cavallone-Bove cave system (CBS) is one of the longest natural caves in Abruzzo region (over 1 km of length) and opens at ca 1470 m asl in the Taranta Gorge, Majella Massif. The sulfuric-acid origin of this inactive hypogenic system has been previously proven by D&#8217;Angeli et al. (2019) using field evidences, secondary minerals and stable isotopes analysis. 40Ar/39Ar dating of alunite deposits suggested the SAS process occurred about 1.52 &#177; 0.28 Ma.Both caves are characterized by a main sub-horizontal rounded or trapezoidal passage with only minor secondary branches and sub-vertical rift-conduits (feeders). Spatial geometry and arrangement of CBS conduits differs significantly from typical SAS water table caves, where complex anastomotic or maze network patterns are observed. Combining classical geological surveys, fracture stratigraphy and cave morphogenetical analysis we characterized the speleogenesis of the CBS. Field observations, remote sensing, detailed geological and geomorphological surveys were performed to characterize the structural evolution of the carbonate sequence hosting the caves, and to explain the relationship with the peculiar spatial and functional organization of CBS.Our work highlights that lithostratigraphy and fractures pattern guide the development of karst macro-porosity in a specific stratigraphic interval within the Santo Spirito Formation, consisting mainly of layered micritic limestones, confined at the top by a chert interlayers dominant member. Through-going faults and fracture-clusters zones are identified as the main permeability pathways for ascending and laterally spreading H2S fluids, influencing the spatial localization of conduits. These fluids reacted close to past water table in oxi-conditions, creating aggressive H2SO4. Sulphur stable isotopes signatures of secondary minerals suggest an origin for these H2S bearing fluids from deep-seated Triassic evaporites interacting with hydrocarbons, thus migrated upward through a network of interconnected fractures. Permeability pathways for this vertical ascending flow were provided by NW-SE persistent strike-slip fault zones segmenting the eastern front of the Majella anticline structure and NNE-SSW striking fracture-clusters localized in the hinge zone of the fold.

Download Full-text

Water mixing processes within a crystalline massif: Sudety mountains, SW Poland

Hydrology Research ◽

10.2166/nh.2009.025 ◽

2009 ◽

Vol 40 (1) ◽

pp. 53-64 ◽

Cited By ~ 2

Author(s):

Bartłomiej Rzonca ◽

Sebastian Buczyński

Keyword(s):

Carbonate Rocks ◽

Drainage Basin ◽

Water Circulation ◽

Crystalline Schist ◽

Primary System ◽

Mountainous Area ◽

Karst Water ◽

Mixing Processes ◽

Stream Discharge ◽

Sw Poland

We present the results of a water circulation study in a small drainage basin in a mountainous area of a complicated structure. Two types of waters were found in the basin; the sulphate waters were linked to gneiss and crystalline schist rocks, while the bicarbonate waters were linked to a marble interbed. The paper looks at a number of water circulation and mixing scenarios and discusses the origin of the bicarbonate waters. Measurements and calculations helped to identify two karst water circulation systems within the marble interbed that were probably not connected to each other. The primary system collects waters migrating via fissures from a non-carbonate section of the drainage basin above. Initially these waters are of the sulphate type: acidic and corrosive to the carbonate rocks. After passing into the marble interbed, they gradually assume a bicarbonate nature by becoming saturated with products of the chemical dissolution of carbonate rocks. This karst system is drained by springs. The other system begins in a sinkhole that intercepts a portion of the stream discharge (or all of it during extreme droughts) and ends with dispersed outflows directly into the channel lower down in the drainage basin.

Download Full-text

Isotope hydrological studies of the perennial ice deposit of Saarhalle, Mammuthöhle, Dachstein Mts, Austria

The Cryosphere ◽

10.5194/tc-5-291-2011 ◽

2011 ◽

Vol 5 (1) ◽

pp. 291-298 ◽

Cited By ~ 14

Author(s):

Z. Kern ◽

I. Fórizs ◽

R. Pavuza ◽

M. Molnár ◽

B. Nagy

Keyword(s):

Isotope Composition ◽

Ice Core ◽

Freezing Process ◽

Karst Water ◽

Stable Isotope Composition ◽

Cave System ◽

Ice Accumulation ◽

The 1960S ◽

Ice Water ◽

Perennial Ice

Abstract. A 5.28 m-long ice core was extracted from a major cave ice body in the Mammuthöhle cave system. The upper ~1.2 m of ice most likely originate from precipitation fallen before the 1960s (based on <8.5 TU). Characteristic fluctuations in electrical conductivity were observed in the cave ice profile, which seem to mirror the fluctuation of karst and surface water in the water supply of the ice accumulation. The stable isotope composition does not support the hypothesis that ice layers with low conductivity are formed by freezing out of water vapour. Isotope fractionation effects during the freezing process are indicated by the enrichment of heavy stable isotopes (2H, 18O) in the ice compared to the potential sources (local precipitation, karst water) and by the characteristically low d-excess values. In addition, the cave ice water line shows a slope coefficient of 8.13. A two-component open-system model (i.e. a depleted component mixed with the freezing water) can adequately explain the measured isotopic compositions of the Saarhalle cave ice.

Download Full-text

Litho-structural control, morphotectonics, and deep-seated gravitational deformations in the evolution of Alpine relief: A case study in the lower Susa Valley (Italian Western Alps)

Quaternary International ◽

10.1016/j.quaint.2006.10.015 ◽

2007 ◽

Vol 171-172 ◽

pp. 143-159 ◽

Cited By ~ 16

Author(s):

P. Cadoppi ◽

M. Giardino ◽

G. Perrone ◽

S. Tallone

Keyword(s):

Structural Control ◽

Western Alps

Download Full-text

Drip rate and tritium activity in the Niedźwiedzia Cave system (Poland) as a tool for tracking water circulation paths and time in karstic systems

Geochronometria ◽

10.1515/geochr-2015-0025 ◽

2015 ◽

Vol 42 (1) ◽

Cited By ~ 1

Author(s):

Michał Gąsiorowski ◽

Helena Hercman ◽

Agata Pruszczyńska ◽

Marcin Błaszczyk

Keyword(s):

Precipitation Intensity ◽

Transition Time ◽

Karst Water ◽

Karst System ◽

Tritium Activity ◽

Cave System ◽

The Mean ◽

Upper Level ◽

Rain Events ◽

Transition Times

Abstract The Niedźwiedzia Cave system is composed of 3 horizontal levels of passages and cham-bers. Changes in the drip rate of water from the upper level stalactites correlate well with changes in precipitation intensity. The transition time between the surface and the upper level of the cave was es-timated to 14 days. Drip sites in the middle and lower levels of the cave exhibited two types of re-charge: some did not correlate with precipitation intensity, whereas others correlated well with rain events. The transition times for the latter sites were estimated to be greater than 6 months. This esti-mate was confirmed by the calculation of the transition time based on tritium activity. The oldest wa-ter in the entire karst system was observed in a karst spring. The mean tritium age for this water dur-ing winter was estimated to be 3.9 ± 0.6 yr. More precise calculations of the tritium age of karst water require longer precipitation activity datasets.

Download Full-text