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TitreLinking regional tectonic events with the stratigraphic succession and subsidence history of Orphan Basin, offshore Newfoundland, Canada
AuteurDafoe, L T; Keen, C E; Dickie, K; Williams, G L
Source4th Atlantic Conjugate Margins Conference; 2014 p. 108-109
Année2014
Séries alt.Secteur des sciences de la Terre, Contribution externe 20140154
ÉditeurAtlantic Conjugate Margins
Réunion4th Atlantic Conjugate Margins Conference; St. John's; CA; août 20-22, 2014
Documentlivre
Lang.anglais
Mediapapier; en ligne; numérique
Formatspdf
ProvinceTerre-Neuve-et-Labrador; Région extracotière de l'est
SNRC1; 2
Lat/Long OENS -53.0000 -41.0000 52.0000 46.0000
Sujetsevolution du bassin; bassins; discordances; chronostratigraphie; décrochement horizontal; antécédents tectoniques; évolution tectonique; affaissement; sedimentation; palynostratigraphie; données sismiques; épaisseur de la croûte; Bassin d'Orphan ; géologie structurale; stratigraphie; Crétacé; Jurassique
Illustrationsstratigraphic correlations; location maps
ProgrammeAnalyse des bassins frontaliers, Les géosciences pour les nouvelles sources d'énergie
Résumé(disponible en anglais seulement)
Offshore Newfoundland, the Orphan Basin is a large rift basin bordering the Atlantic continental margin that formed during multiple rift phases. Extension in the Jurassic and Early Cretaceous resulted in faulting and thinning of the continental crust that ended in Aptian time. Subsequent extension, approximately perpendicular to the earlier rift phase, was focused east of Orphan Knoll and culminated in seafloor spreading in the Santonian (chron 33R). These regional tectonic events are recorded in the stratigraphic succession of Orphan Basin. We have integrated seismic and well data to develop a regional stratigraphic framework and identified basin-wide unconformities and syn-rift sedimentary packages. Combining the stratigraphy with analysis of the subsidence history allows us to make inferences on tectonic influence.

A top Jurassic unconformity is confined to the eastern portion of Orphan Basin where the earliest stages of rifting took place and thick Late Jurassic sediments accumulated. A more basin-wide, Aptian unconformity is present across the basin and is associated with greater degrees of erosion in the central part of the basin and atop basement highs. An overlying Santonian-aged unconformity also records similar erosion along basin margins and atop basement highs, although is less pronounced compared to the Aptian horizon. We propose that these major erosional unconformities in Orphan Basin are related to tectonic events that reflect the breakup of crust and/or lithospheric mantle at a regional scale outside of the basin. Associated isostatic rebound related to breakup events may explain the relative uplift and erosion at these times.
Following the end of rifting within Orphan Basin in the Aptian, there is an anomalous lack of thermal subsidence normally associated with post-rift deposition. Mid- to Upper Cretaceous deposits reflect shallow marine to shelfal (< 200 m) paleowater depths. The onset of subsidence does not begin until Late Campanian-Early Maastrichtian time when a significant transgression takes place across the basin. Major, basin-wide thermal subsidence is marked by development of the Base Tertiary horizon, a prominent seismic reflector recording development of bathyal water depths in the basin and a maximum flooding event. A mechanism is required to explain the delayed nature of post-rift subsidence in the basin and may include one of the following previously proposed models: 1) magmatic underplating; 2) a hot spot located in the vicinity of the rift; 3) removal of mantle lithosphere and replacement by hotter asthenosphere; or 4) flow of buoyant, depleted continental mantle below the rift basin. Based on an association to crustal/mantle breakup events and the nature of mechanisms explaining the subsidence history, it is clear that tectonic events played a major role in controlling the nature of the Mesozoic and earliest Cenozoic stratigraphy.
Résumé(Résumé en langage clair et simple, non publié)
Situé au large des côtes de Terre Neuve, le bassin Orphan est une vaste zone pionnière qui renferme d'importantes réserves de pétrole du Jurassique le long de sa lisière sud-est (bassin du Bonnet flamand). Lors de l'ouverture de l'Atlantique Nord, cette région a subi plusieurs phases d'extension qui ont produit un large bassin contenant, à faible profondeur, des sédiments marins du Jurassique et du Crétacé et, à grande profondeur, des sédiments du Cénozoïque. Dans cette étude, nous évaluons l'importance des horizons repères du bassin et leurs liens avec les épisodes tectoniques locaux et régionaux associés au rifting et à la formation ultérieure de la croûte océanique. De plus, nous expliquons le phénomène de la subsidence tardive du bassin, qui s'observe généralement après la fin du rifting à l'intérieur d'un bassin. Ce processus a des incidences sur la production de roche mère mature et sur l'exploration du secteur par l'industrie.
GEOSCAN ID295074