Search

RESUMELa regeneration de l'epinette noire (Picea mariana (Mill.) B.S.P.) au centre de Terre-Neuve faisant suite a une perturbation causee par le feu ou des operations forestieres peut etre affectee par la presence de l'arbuste ericaceen Kalmia angustifolia L. La presente etude a ete realisee afin de tester les donnees de teledetection acquises en 1994 par le capteur multispectral CASI (Compact Airborne Spectrographic Imager) pour la detection de differentes densites de couvert de Kalmia sur des sites perturbes dans le centre de Terre-Neuve. Une approche basee sur la classification discriminante a ete developpee pour differencier les peuplements de Kalmia, plus de trois classes de couvert de Kalmia (couvert faible, moyen et dense) et les autres grands types de couvert tels que l'epinette noire, l'aulne, les secteurs de coupe sans Kalmia et les zones humides. Des images de quatre secteurs differents ont ete utilisees, couvrant trois periodes de l'annee. Les resultats de la classification ont ete testes par ...

The regeneration of black spruce (Picea mariana (Mill.) B.S.P.) in central Newfoundland following disturbance by fire or logging can be impeded by the ericaceous shrub Kalmia augustifolia L. This study was initiated to use multi-spectral aerial (Compact Airborne Spectrographic Imager) and satellite (Landsat Thematic Mapper) remote sensing to detect the presence of kalmia on disturbed sites. Two separate classification schemes were designed to include kalmia and other major cover types such as black spruce, alder, non-kalmia cutovers and wetlands. Discrimination of training samples revealed that kalmia could be detected and mapped with an accuracy of 96 per cent using the aerial data. Over larger areas, kalmia was discriminated—in wetlands, cutovers and burns—with 85 per cent accuracy using the satellite sensor imagery.

A granite that yields a U–Pb zircon age of 602 ± 10 Ma is associated with mafic and silicic volcanic rocks and metamorphic equivalents near Deer Lake in western Newfoundland. The granitic rocks are named the Round Pond granite, and the combined granite–volcanic suite is assigned to the Hughes Lake complex. All of the rocks are contained in the Hughes Lake structural slice that occurs above other allochthonous rocks and the autochthonous Cambrian–Ordovician carbonate sequence of western Newfoundland.The Round Pond granite is cut by metadiabase dykes. Mafic volcanic rocks, interpreted as coeval with the dykes, occur along the southeast side of the granite. A thick sequence of arkosic metagreywackes and psammitic to pelitic schists of the Mount Musgrave Group occurs stratigraphically above the mafic volcanic rocks. Regional correlations imply that the Mount Musgrave Group is of late Precambrian – Early Cambrian age, thus setting an upper stratigraphic limit to the age of the Hughes Lake complex.Perthitic and granophyric textures and the chemistry of the Round Pond granite are typical of anorogenic high-level hypersolvus intrusions. Nearby pink silicic volcanic rocks are probably consanguineous with the granite and together with the mafic volcanics form a bimodal suite.Bimodal volcanic suites and related mafic dykes and granitic intrusions imply rift tectonic settings. Occurrences along the west flank of the Appalachian Orogen are equated with the initiation of an ancient continental margin and the opening of an Iapetus Ocean. The 602 ± 10 Ma age of the Round Pond granite dates the rifting in western Newfoundland. Older isotopic ages on similar rocks in the southern Appalachians of the United States suggest a diachronous Precambrian rifting and Iapetus opening that propagated northward, much like the Mesozoic opening of the North Atlantic Ocean.