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TitleInversion of apatite fission track data, Port au Port Peninsula area, western Newfoundland: implications for hydrocarbon prospectivity and the extent of the regional Maritimes Basin
AuthorStockmal, G SORCID logo; Issler, D RORCID logo; Grist, A M; Slingsby, A; Waldron, J W F
SourceGAC-MAC-CSPG-CSSS Halifax 2005, building bridges - across science, through time, around the world: abstracts/AGC-AMC-SCGP-SCSS Halifax 2005, Jeter des ponts entre les disciplines scientifiques, les époques, et unifier le monde : recueil des résumés; GAC-MAC-CSPG-CSSS Joint Meeting, Abstracts vol. 30, 2005 p. 187-188
Alt SeriesEarth Sciences Sector, Contribution Series 2004333
MeetingHalifax 2005: GAC/MAC/CSPG/CSSS Joint Annual Meeting; Halifax, Nova Scotia; CA; May 2005
Mediapaper; on-line; digital
File formatpdf
ProvinceNewfoundland and Labrador
AreaPort au Port Peninsula
Lat/Long WENS -59.0000 -58.5000 48.7500 48.5000
Subjectsstructural geology; economic geology; fossil fuels; sedimentology; general geology; petroleum exploration; offshore wells; thermal maturation; Round Head Thrust (RHT); Garden Hill pool; Humber Arm Allochthon; Cambrian; Ordovician
ProgramNorthern Resources Development Program
AbstractPort au Port #1, drilled in 1994/95, was the first of six new wells drilled in the Port au Port Peninsula area of western Newfoundland in the
latest round of hydrocarbon exploration that began in the early 1990s. It penetrated the Cambro-Ordovician platform and underlying Grenville basement in the hanging wall of the SE-dipping Round Head Thrust (RHT), terminated in a large, folded slice of the platform succession in the footwall of this inverted basement-involved structure, and discovered the Garden Hill pool (51 API oil). Subsequent wells
confirmed the existence of a thin-skinned triangle zone involving the Humber Arm Allochthon, and the thick-skinned and inverted nature of
the RHT. Inversion of the RHT and development of the Garden Hill structure post-dates the Middle Devonian (Acadian) emplacement of
the allochthon into the triangle zone. Following post-orogenic erosion, the regional latest Devonian to Early Permian Maritimes basin was
deposited. On the Port au Port Peninsula the youngest Maritimes basin units are Visean (Early Carboniferous). To constrain the timing of structural trap development versus peak hydrocarbon maturation, we have reassessed the low-temperature thermochronology of the area using state-of-the-art apatite fission track (AFT) inverse time-temperature modelling. This technique yields an objective set of thermal histories that fit observed AFT ages and track length distributions. Other maturation indicators (e.g., conodont alteration index values, Tmax values) and the geological history provide additional critical modelling constraints. Results indicate that following post-depositional burial and post-orogenic erosion, all AFT samples were reheated into the AFT partial annealing window (~60-120 °C; ~oil window) in post-Visean times, due to burial beneath the Maritimes basin. The magnitude and timing of peak temperatures, however, are dependent in part upon structural position with respect to the RHT. At the deepest stratigraphic levels within the Cambro- Ordovician platform, in the immediate hanging wall of the RHT, peak temperature occurred prior to fault inversion (during Acadian orogenesis). At equivalent stratigraphic levels in the RHT footwall, and at shallower levels in both footwall and hanging wall, peak temperatures were not achieved until post-Visean burial beneath the Maritimes basin. Peak thermal maturity therefore post-dated the late Acadian development of large, thick-skinned structural traps, and these structures therefore have high potential prospectivity. Modelled AFT samples from elsewhere in western Newfoundland, Anticosti Island, and the Gulf of St. Lawrence all indicate that the Maritimes basin was substantially thicker and of greater extent than commonly believed, with concomitant implications for petroleum exploration.

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