{"id":{"repo_id":"plymouth","oai_identifier":"oai:pearl.plymouth.ac.uk:gees-theses-1914"},"canonical_url":"https://search.dev.ndltd.org/etd/plymouth/oai:pearl.plymouth.ac.uk:gees-theses-1914","repository":{"repo_id":"plymouth","name":"University of Plymouth","base_url":"https://pearl.plymouth.ac.uk/do/oai"},"display":{"title":"Partitioning of fluid flow along faults and fractures in the Bristol Channel Basin: implications for low carbon geoscience projects in SW England","abstract":"The Bristol Channel Basin (BCB) is a Mesozoic continental rift basin and an important
analogue for offshore reservoirs. Previous studies have used relative cross-cutting
relationships and correlations with adjacent sedimentary basins to constrain its
development. For the first time, in-situ U-Pb carbonate geochronology has dated
calcite slickenfibres within normal, thrust, and strike-slip faults in the East
Quantoxhead and Kilve region of Somerset.
Protracted N-S extension (ca. 150–120 Ma) formed normal faults, while subsequent NS shortening (ca. 50–20 Ma) involved (i) cross-cutting strike-slip faults, (ii) minor E-Wstriking thrust faults, and (iii) reactivation of pre-existing normal faults. During
Cenozoic contraction, σ2 and σ3 were periodically interchangeable due to local stress
variations and fluid pressure changes.
Geochemical analyses indicate evolving fluid sources, with more saline waters during
extension transitioning to more freshwater during contraction. Larger normal faults
facilitated the upward migration of saline fluids from the Mercia Mudstone Group
(MMG), altering pore fluid composition and raising formation water temperatures in
the Blue Lias Group. These fluids also influenced fault mechanics, particularly along the
East Quantoxhead Fault (EQHF).
Microstructural analysis of vein generations highlights fault weakening through
progressive deformation. Celestine (SrSO₄), sourced from the MMG, localised strain
and promoted reactivation during contraction, as evidenced by reverse-sense S-C
Introduction
viii | P a g e
fabrics. In contrast, smaller faults lack celestine and exhibit simpler fluid histories,
although crystal-plastic textures (e.g., GBM, SGR) are observed.
Understanding fluid-driven changes in fault core composition and strength is critical
for evaluating fluid flow partitioning along fractures. Constraining fault population
evolution within the BCB sheds light on regional stress dynamics and can inform
studies of nearby basins. These insights have practical applications for managing fluid
flow in modern reservoirs, such as Enhanced Geothermal Systems (EGS).","abstract_html":"The Bristol Channel Basin (BCB) is a Mesozoic continental rift basin and an important<br/>analogue for offshore reservoirs. Previous studies have used relative cross-cutting<br/>relationships and correlations with adjacent sedimentary basins to constrain its<br/>development. For the first time, in-situ U-Pb carbonate geochronology has dated<br/>calcite slickenfibres within normal, thrust, and strike-slip faults in the East<br/>Quantoxhead and Kilve region of Somerset.<br/>Protracted N-S extension (ca. 150–120 Ma) formed normal faults, while subsequent NS shortening (ca. 50–20 Ma) involved (i) cross-cutting strike-slip faults, (ii) minor E-Wstriking thrust faults, and (iii) reactivation of pre-existing normal faults. During<br/>Cenozoic contraction, σ2 and σ3 were periodically interchangeable due to local stress<br/>variations and fluid pressure changes.<br/>Geochemical analyses indicate evolving fluid sources, with more saline waters during<br/>extension transitioning to more freshwater during contraction. Larger normal faults<br/>facilitated the upward migration of saline fluids from the Mercia Mudstone Group<br/>(MMG), altering pore fluid composition and raising formation water temperatures in<br/>the Blue Lias Group. These fluids also influenced fault mechanics, particularly along the<br/>East Quantoxhead Fault (EQHF).<br/>Microstructural analysis of vein generations highlights fault weakening through<br/>progressive deformation. Celestine (SrSO₄), sourced from the MMG, localised strain<br/>and promoted reactivation during contraction, as evidenced by reverse-sense S-C<br/>Introduction<br/>viii | P a g e<br/>fabrics. In contrast, smaller faults lack celestine and exhibit simpler fluid histories,<br/>although crystal-plastic textures (e.g., GBM, SGR) are observed.<br/>Understanding fluid-driven changes in fault core composition and strength is critical<br/>for evaluating fluid flow partitioning along fractures. Constraining fault population<br/>evolution within the BCB sheds light on regional stress dynamics and can inform<br/>studies of nearby basins. These insights have practical applications for managing fluid<br/>flow in modern reservoirs, such as Enhanced Geothermal Systems (EGS).","abstract_has_math":false,"creators":["Connolly, Joseph"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":["Mark Anderson, Gregory Price, David Peacock, Catherine Mottram"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2025,"date_issued":"2025-01-01T08:00:00Z","date_published":"2025-01-01T08:00:00Z","updated_at":"2026-07-24T03:47:57Z","subjects":[],"languages":["eng"],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://pearl.plymouth.ac.uk/gees-theses/472","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Mark Anderson, Gregory Price, David Peacock, Catherine Mottram"]},{"key":"dc:creator","label":"Author","values":["Connolly, Joseph"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.available","label":"Dc Date Available","values":["2025-07-09T07:00:00Z"]},{"key":"dc:date.issued","label":"Date","values":["2025-01-01T08:00:00Z"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://pearl.plymouth.ac.uk/gees-theses/472"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["The Bristol Channel Basin (BCB) is a Mesozoic continental rift basin and an important
analogue for offshore reservoirs. Previous studies have used relative cross-cutting
relationships and correlations with adjacent sedimentary basins to constrain its
development. For the first time, in-situ U-Pb carbonate geochronology has dated
calcite slickenfibres within normal, thrust, and strike-slip faults in the East
Quantoxhead and Kilve region of Somerset.
Protracted N-S extension (ca. 150–120 Ma) formed normal faults, while subsequent NS shortening (ca. 50–20 Ma) involved (i) cross-cutting strike-slip faults, (ii) minor E-Wstriking thrust faults, and (iii) reactivation of pre-existing normal faults. During
Cenozoic contraction, σ2 and σ3 were periodically interchangeable due to local stress
variations and fluid pressure changes.
Geochemical analyses indicate evolving fluid sources, with more saline waters during
extension transitioning to more freshwater during contraction. Larger normal faults
facilitated the upward migration of saline fluids from the Mercia Mudstone Group
(MMG), altering pore fluid composition and raising formation water temperatures in
the Blue Lias Group. These fluids also influenced fault mechanics, particularly along the
East Quantoxhead Fault (EQHF).
Microstructural analysis of vein generations highlights fault weakening through
progressive deformation. Celestine (SrSO₄), sourced from the MMG, localised strain
and promoted reactivation during contraction, as evidenced by reverse-sense S-C
Introduction
viii | P a g e
fabrics. In contrast, smaller faults lack celestine and exhibit simpler fluid histories,
although crystal-plastic textures (e.g., GBM, SGR) are observed.
Understanding fluid-driven changes in fault core composition and strength is critical
for evaluating fluid flow partitioning along fractures. Constraining fault population
evolution within the BCB sheds light on regional stress dynamics and can inform
studies of nearby basins. These insights have practical applications for managing fluid
flow in modern reservoirs, such as Enhanced Geothermal Systems (EGS)."]},{"key":"dc:title","label":"Title","values":["Partitioning of fluid flow along faults and fractures in the Bristol Channel Basin: implications for low carbon geoscience projects in SW England"]}]}],"canonical_facts":{"dc:contributor":["Mark Anderson, Gregory Price, David Peacock, Catherine Mottram"],"dc:creator":["Connolly, Joseph"],"dc:date.available":["2025-07-09T07:00:00Z"],"dc:date.issued":["2025-01-01T08:00:00Z"],"dc:description.abstract":["The Bristol Channel Basin (BCB) is a Mesozoic continental rift basin and an important
analogue for offshore reservoirs. Previous studies have used relative cross-cutting
relationships and correlations with adjacent sedimentary basins to constrain its
development. For the first time, in-situ U-Pb carbonate geochronology has dated
calcite slickenfibres within normal, thrust, and strike-slip faults in the East
Quantoxhead and Kilve region of Somerset.
Protracted N-S extension (ca. 150–120 Ma) formed normal faults, while subsequent NS shortening (ca. 50–20 Ma) involved (i) cross-cutting strike-slip faults, (ii) minor E-Wstriking thrust faults, and (iii) reactivation of pre-existing normal faults. During
Cenozoic contraction, σ2 and σ3 were periodically interchangeable due to local stress
variations and fluid pressure changes.
Geochemical analyses indicate evolving fluid sources, with more saline waters during
extension transitioning to more freshwater during contraction. Larger normal faults
facilitated the upward migration of saline fluids from the Mercia Mudstone Group
(MMG), altering pore fluid composition and raising formation water temperatures in
the Blue Lias Group. These fluids also influenced fault mechanics, particularly along the
East Quantoxhead Fault (EQHF).
Microstructural analysis of vein generations highlights fault weakening through
progressive deformation. Celestine (SrSO₄), sourced from the MMG, localised strain
and promoted reactivation during contraction, as evidenced by reverse-sense S-C
Introduction
viii | P a g e
fabrics. In contrast, smaller faults lack celestine and exhibit simpler fluid histories,
although crystal-plastic textures (e.g., GBM, SGR) are observed.
Understanding fluid-driven changes in fault core composition and strength is critical
for evaluating fluid flow partitioning along fractures. Constraining fault population
evolution within the BCB sheds light on regional stress dynamics and can inform
studies of nearby basins. These insights have practical applications for managing fluid
flow in modern reservoirs, such as Enhanced Geothermal Systems (EGS)."],"dc:identifier":["https://pearl.plymouth.ac.uk/gees-theses/472"],"dc:language":["eng"],"dc:title":["Partitioning of fluid flow along faults and fractures in the Bristol Channel Basin: implications for low carbon geoscience projects in SW England"],"dc:type":["Thesis"]},"updated_at":"2026-07-24T03:47:57Z"}