The Heterogeneity of Paleocavern Systems Developed Along Syndepositional Fault Zones

Koša, Eduard; Hunt, David; Fitchen, William M.; Bockel-Rebelle, Marie-Odile; Roberts, Gerald

doi:10.2110/pec.03.78.0291

Cited by 13 publications

(34 citation statements)

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“…Vein fills are the best described in the literature, because they often host economic minerals (Evans, 1993;Oliver & Bons, 2001). Collapse-breccia fills * Author for correspondence: nhw1@esc.cam.ac.uk are receiving increasing attention (Koša et al 2003;Woodcock, Omma & Dickson, 2006). Finer sediment fills are usually described from fissures open to the contemporary land surface, typically in karst terrains (Ford & Williams, 1989;Wall & Jenkyns, 2004).…”

Section: Introductionmentioning

confidence: 99%

Fissure fills along faults: Variscan examples from Gower, South Wales

2009

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-The extent to which persistent, rather than transient, fissures (wide planar voids) can exist along upper crustal faults is important in assessing fault permeability to mineral and hydrocarbonbearing fluids. Variscan (late Carboniferous) faults cutting Dinantian (Lower Carboniferous) limestones on the Gower peninsula, South Wales, host clear evidence for fissures up to several metres wide. Evidence includes dendritic hematite growth and elongate calcite growth into open voids, spar ball and cockade breccia formation, laminated sediment infill and void-collapse breccias. Detailed mapping reveals cross-cutting geometries and brecciation of earlier fissure fills, showing that fissures were formed during, rather than after, active faulting. Fissures therefore probably formed by geometric mismatch between displaced fault walls, rather than by solution widening along inactive faults.

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Section: Introductionmentioning

confidence: 99%

Fissure fills along faults: Variscan examples from Gower, South Wales

2009

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“…It cannot be excluded that small fluxes of CH4 from shales or hydrocarbon deposits underlying the limestone are entering caves through natural fractures, but our present isotope data cannot confirm this source for cave 24. The Antes and Utica shales, which contain hydrocarbon gases, are stratigraphically below cave 24 (Coleman et al, 2014), and geologic faults and joints, which are often aligned with caves, may serve as conduits for the flow of hydrocarbons (Powell, 1969;Koša et al, 2003). A confirmation of hydrocarbons entering from deep sources may be obtained through measurements of 'radiocarbon-dead' CO2, Rn, and ethane.…”

Section: Subsurface-surface Atmospheric Exchangementioning

confidence: 99%

Subterranean Karst Environments as a Global Sink for Atmospheric Methane

Webster¹,

Drobniak²,

Etiope³

et al. 2017

Preprint

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Abstract:The air in subterranean karst cavities is often depleted in methane (CH4) relative to the atmosphere. Karst is considered a potential sink for the atmospheric greenhouse gas CH4 because its subsurface drainage networks and solution-enlarged fractures facilitate atmospheric exchange. Karst landscapes cover about 14 % of earth's continental surface, but observations of CH4 concentrations in cave air are limited to localized studies in Gibraltar, Spain, Indiana (USA), Vietnam, Australia, and by incomplete isotopic data. To test if karst is systematically acting as a global CH4 sink, we measured the CH4 concentrations, δ 13 CCH 4 , and δ 2 HCH 4 values of cave air from 33 caves in the USA and three caves in New Zealand. We also measured CO2 concentrations, δ 13 CCO 2 , and radon (Rn) concentrations to support CH4 data interpretation by assessing cave air residence times and mixing processes. Among these caves, 35 exhibited subatmospheric CH4 concentrations in at least one location compared to their local atmospheric backgrounds. CH4 concentrations and δ 13 CCH 4 and δ 2 HCH 4 values suggest that microbial methanotrophy within caves is the primary CH4 consumption mechanism as the atmosphere exchanges with subsurface air. The pattern of δ 13 CCH 4 and δ 2 HCH 4 values along CH4 concentration gradients in cave air provides evidence for incomplete oxidation by methanotrophy. Only 5 locations from 3 caves showed elevated CH4 concentrations compared to the atmospheric background and could be ascribed to local CH4 sources from sewage and outgassing swamp water. Several associated δ 13 CCH 4 and δ 2 HCH 4 values point to carbonate reduction and acetate fermentation as biochemical pathways of limited methanogenesis in karst environments and suggest that these pathways occur in the environment over large spatial scales. Our data show that karst environments function as a global CH4 sink. Estimates of CH4 flux in karst landscapes are needed in order to include the subterranean CH4 sink in climate models.

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“…Longley (1999) proposed an alternative model of dissolution, speculating that water expelled from basinal sediments, over which the platform had prograded, may have used fractures within the platform as avenues to escape upwards and mix with near-surface waters to produce undersaturated fluids, thus promoting a mixing-zone type of dissolution. More recently, Hunt et al (2002), Koša. et al (2003) and Hunt (2005, 2006) established that most of the apparent "dikes" and "fissures" reported from Slaughter Canyon (Melim andScholle, 1989, 2002;Melim, 1991;Osleger, 1998;Longley, 1999) are, in fact, early karst-modified syndepositional faults (Fig.…”

Section: Type 1 Dikesmentioning

confidence: 99%

“…During Capitanian times, the platform was subject to syndepositional tilting, folding, faulting, and fracturing (Hunt et al, 2002;Koša et al, 2003;Koša and Hunt, 2005). Basinward expansion of platform strata (Fig.…”

Section: Syndepositional Deformationmentioning

confidence: 99%