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TitreThe impact of early Cretaceous deformation on deposition in the passive-margin Scotian Basin, offshore eastern Canada
AuteurPe-Piper, G; Piper, D J W
SourceTectonics of Sedimentary Basins: Recent Advances; par Busby, C (éd.); Azor, A (éd.); 2012 p. 270-287,
Séries alt.Secteur des sciences de la Terre, Contribution externe 200901217
ÉditeurJohn Wiley & Sons, Ltd
Mediapapier; en ligne; numérique
ProvinceRégion extracotière de l'est
Lat/Long OENS -67.5000 -56.5000 46.1000 41.5000
Sujetsmilieux tectoniques; cadre tectonique; interprétations tectoniques; plate-forme continentale; marges continentales; origine; faciès; faciès sédimentaires; tectonique; géochronologie; Mésozoïque; Crétacé
Illustrationslocation maps; stratigraphic sections; profiles; plots
Diffusé2012 01 30
Résumé(disponible en anglais seulement)
This study examines the impact of syn-sedimentary continental basement tectonics on sediment deposition on a passive margin. In the latest Jurassic and Early Cretaceous of the Scotian Basin, more than 45 million years after the onset of sea-floor spreading, sandy deltas prograded tens of kilometers across an outer shelf ramp that was subsiding rapidly as a result of salt tectonics. The rate of sand supply was 3 - 4 times higher than in the early history of the passive margin. Active tectonics and uplift in the source area was the principal cause of such enhanced sand supply, rather than changes in the discharge point of a large passive-margin river or climatic change. Direct evidence for the active tectonics is found on land, where small basins formed along reactivated Late Paleozoic faults, while horsts were uplifted and shed coarsegrained sediment. The sources of sand to the deltas were determined by a variety of techniques. Principal component analysis of bulk geochemical composition of sandstones and shales allows sediment from different drainage basins to be discriminated. Comparison of the geochronology of detrital muscovite,monazite and zircon,minerals with different resistance to mechanical and chemical weathering, allows discrimination of first-cycle and polycyclic sources. Muscovite and monazite show that about half the sand supply is from first-cycle sources in crystalline basement from throughout the Appalachians, including the inner Scotian Shelf. More than 80% of the zircon is from polycyclic sources, from both sedimentary and metamorphic rocks. Seismic profiles show the role of deformation of the inner shelf in supplying detrital muscovite to the basin. Sediment accumulation was strongly influenced by salt tectonics, which itself was driven by deltaic loading. The steep topography caused by the tectonic re-activation resulted in hyperpycnal supply of sediment to prodeltaic shelf turbidites, which are an essential component of the natural gas reservoirs of the basin. This study illustrates the necessity of multiple techniques to understand the complex consequences of basement reactivation and increased sediment supply
on a passive continental margin.