Kit Hardman
The nature and significance of rift-related, near-surface fissure fill networks in fractured carbonates below regional unconformities
Hardman, Kit; Holdsworth, Robert E; Dempsey, Edward; McCaffrey, Ken
Authors
Robert E Holdsworth
Dr Eddie Dempsey E.Dempsey@hull.ac.uk
Senior Lecturer in Structural Geology and Geohazards
Ken McCaffrey
Contributors
Dr Eddie Dempsey E.Dempsey@hull.ac.uk
Supervisor
Abstract
Hosted in carbonate and crystalline basement rocks below regional unconformities, fissure-fill networks are a widely recognized, but relatively little described near-surface phenomenon (< 1-2km). Faults and fractures in otherwise tight Devonian carbonate basement rocks of the Tor Bay region, Devon, are associated with the development of millimetre- to decametre-wide fissures containing red early Permian sedimentary material, vuggy calcite mineralisation and wall-rock collapse breccias. These features preserve evidence concerning 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 early Permian development of the Portland-Wight Basin. Once formed, they were subjected to episodic, likely 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 likely 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.
Citation
Hardman, K., Holdsworth, R. E., Dempsey, E., & McCaffrey, K. (2020). The nature and significance of rift-related, near-surface fissure fill networks in fractured carbonates below regional unconformities. Journal of the Geological Society, https://doi.org/10.1144/jgs2020-074
Journal Article Type | Article |
---|---|
Acceptance Date | Jun 15, 2020 |
Online Publication Date | Jun 18, 2020 |
Publication Date | Jul 22, 2020 |
Deposit Date | Jun 24, 2020 |
Publicly Available Date | Jun 25, 2020 |
Journal | Journal of the Geological Society |
Print ISSN | 0016-7649 |
Publisher | Geological Society |
Peer Reviewed | Peer Reviewed |
DOI | https://doi.org/10.1144/jgs2020-074 |
Keywords | Geology |
Public URL | https://hull-repository.worktribe.com/output/3525658 |
Publisher URL | https://pubs.geoscienceworld.org/jgs/article-lookup?doi=10.1144/jgs2020-074 |
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Copyright Statement
© 2020 The Author(s). This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 License (http://creativecommons.org/ licenses/by/4.0/). Published by The Geological Society of London. Publishing disclaimer: www.geolsoc.org.uk/pub_ethics
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Copyright Statement
© 2020 The Author(s). This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 License (http://creativecommons.org/licenses/by/4.0/). Published by The
Geological Society of London. Publishing disclaimer: www.geolsoc.org.uk/pub_ethics
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