HR: 0800h
AN: V51B-0567    [Abstracts]
TI: Contrasting Styles Between the Structure and the Magmatism of the West and South Hatton/Rockall Margins (North Atlantic Igneous Province)
AU: * Gernigon, L
EM: lg@cp.dias.ie
AF: Marine & Petroleum Geology Research Group Department of Geology, University College Dublin, Department of Geology, University College Dublin Belfield, Dublin 4, Ireland., Dublin, Dublin 4 Ireland
AU: Ravaut, C
EM: cr@cp.dias.ie
AF: Dublin Institute for Advanced Studies (DIAS), 5, Merrion Square, Dublin, Dublin 2 Ireland
AU: Shannon, P M
EM: P.Shannon@ucd.ie
AF: Marine & Petroleum Geology Research Group Department of Geology, University College Dublin, Department of Geology, University College Dublin Belfield, Dublin 4, Ireland., Dublin, Dublin 4 Ireland
AU: Chabert, A
EM: ac@cp.dias.ie
AF: Marine & Petroleum Geology Research Group Department of Geology, University College Dublin, Department of Geology, University College Dublin Belfield, Dublin 4, Ireland., Dublin, Dublin 4 Ireland
AU: O'Reilly, B M
EM: br@cp.dias.ie
AF: Dublin Institute for Advanced Studies (DIAS), 5, Merrion Square, Dublin, Dublin 2 Ireland
AU: Readman, P W
EM: pr@cp.dias.ie
AF: Dublin Institute for Advanced Studies (DIAS), 5, Merrion Square, Dublin, Dublin 2 Ireland
AB: The North Atlantic rifted margins area is usually characterised by a combination of regional uplift, crustal extension and magmatism leading to the formation of seaward dipping reflectors (SDRs). The temporal and spatial relationships of these volcano-tectonic processes are interpreted as the response to a deep mantle anomaly. Integration of new seismic, potential field and well calibration data allows us to clarify the structure and stratigraphy of both the West Hatton margin (WHM) and the south Rockall/Hatton margin (SHRM). The WHM represents a Late Paleocene-Early Eocene volcanic margin as suggested by the typical volcano-stratigraphic sequence (Inner SDRs, Outer High, Outer SDRs, oceanic crust) observed near the beakup axis. The Inner SDR wedges are typically underlain by thin and intruded sediments and continental crust. Oceanward, the deep structures of the Outer High and outer SDRs features are underlain by a massive, uniform thick high-velocity lower crustal body interpreted as breakup underplating that probably controlled the SDR emplacement by a mid-crustal updoming. To the south, the SHRM is a complex rifted zone linking the WHM with the Celtic and Iberian non-volcanic margins. The SHM was also influenced by an earlier Cretaceous phase of break-up and, compared to the WHM, the nature of the continent-ocean transition is different. Close to the C34 magnetic anomaly, the continent-ocean transition is defined by a sharp contrast between a smooth oceanic basement and block-faulted structure that exhibit both syn- and post-breakup features. Close to the oceanic crust, the complex may represent a combination of serpentinized peridotites and/or intruded continental basement. No SDRS are imaged, but evidence of magmatism is identified. Thin lava flows and transgressive sill complexes, magmatic plugs and seamounts intruding the Cretaceous oceanic crust are observed near the SRHM. Close to the Charlie-Gibbs Fracture Zone, the West Thulean Ridge defining the southern end of the volcanic province is also imaged. It probably represents a thick Paleocene oceanic volcanic plateau, uplifted and block faulted during Cenozoic time. The age of the magmatism along the SRHM is controversial. Evidence of Palaeogene magmatism can be observed but Early Cretaceous igneous activity is also indicated. The best example is the Barra Volcanic Ridge, which is reinterpreted here as a structural horst cut by Early Cretaceous extrusives and intrusives and subsequently by Tertiary dykes. Detailed stratigraphic analysis documents the contrasting subsidence/uplift patterns that differentiate the sedimentary architecture of the WHM and the SRHM. This project is funded by the Geological Survey of Ireland and the Irish Petroleum Infrastructure Programme.
DE: 8450 Planetary volcanism (5480)
DE: 9335 Europe
DE: 9604 Cenozoic
DE: 8109 Continental tectonics--extensional (0905)
DE: 0935 Seismic methods (3025)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting