The geology of the Torquay district

Shannon, W.G.

doi:10.1016/s0016-7878(28)80020-4

Cited by 8 publications

(1 citation statement)

References 20 publications

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“…A little deformed and shallowly dipping (<10 o ) cover sequence of red, early Permian sandstones and breccias outcrops mainly within the central part of the Tor Bay coast (Fig. 2) (George et al 1927;Shannon 1928;Strange 2001). These rocks belong to the Torbay Breccia Formation, part of the Exeter Group (Ussher 1903;Henson 1971).…”

Section: Regional Context and Stratigraphymentioning

confidence: 99%

Nature and significance of rift-related, near-surface fissure-fill networks in fractured carbonates below regional unconformities

Hardman

Holdsworth

Dempsey

et al. 2020

JGS

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Fissure-fill networks are a widely recognized, but relatively little described, near-surface phenomenon (<1–2 km) hosted in carbonate and crystalline basement rocks below regional unconformities. Faults and fractures in otherwise tight Devonian carbonate basement rocks of the Tor Bay region, Devon, SW England are associated with the development of millimetre- to decametre-wide fissures containing red-coloured early Permian sedimentary material, vuggy calcite mineralization and wall rock collapse breccia. These features preserve evidence about the style and history of fault deformation and reactivation in near-surface settings and on fluid-related processes, such as elutriation and/or mineralization. Field observations, palaeostress analysis and fracture topology analyses show that the rift-related faults and fractures created a network of long-lived open cavities during the development of the Portland–Wight Basin in the early Permian. Once formed, they were subjected to episodic, probably seismically induced, fluid fluxing events and local karstification. The large, well-connected networks of naturally propped fractures were (and possibly still are) important fluid migration pathways within otherwise low-permeability host rocks. These structures are probably equivalent to those observed in many other rift-related, near-surface tectonic settings and suggest that the Tor Bay outcrops can be used as a global analogue for sub-unconformity open fissure systems hosted in low-permeability basement rocks.Supplementary material: Appendix A is available at https://doi.org/10.6084/m9.figshare.c.5023103

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Section: Regional Context and Stratigraphymentioning

confidence: 99%