GEOSCAN, résultats de la recherche


TitreA lithogeochemical assessment of the Lower Cretaceous sediments of the Scotian Basin
AuteurPe-Piper, G; Triantafyllidis, S; Piper, D J W; Moulton, B; Hubley, R F
SourceCommission géologique du Canada, Dossier public 5644, 2007, 138 pages, (Accès ouvert)
ÉditeurRessources naturelles Canada
Documentdossier public
Mediapapier; en ligne; numérique
ProvinceRégion extracotière de l'est
Lat/Long OENS-64.0000 -58.0000 45.7500 42.0000
Sujetsplate-forme continentale; talus continental; sédiments de fond; carottes de sédiment marin; sédiments marins; canyons sous-marins; lithogéochimie; minéraux détritiques; levés géochimiques; analyses géochimiques; géochimie des sédiments marins; géochimie des roches totales; roches sédimentaires; grès; potassium; géochimie des terres rares; terres rares; Plate-Forme de Néo-écossaise; géochimie; géologie marine; sédimentologie; Phanérozoïque; Cénozoïque; Quaternaire; Tertiaire; Crétacé; Mésozoïque
Illustrationstables; sketch maps; plots; graphs; stratigraphic sections; ternary diagrams
ProgrammeLes géosciences à l'appui de la gestion des océans
ProgrammeLe Programme de recherche et de développement énergétiques (PRDE)
Diffusé2007 10 01; 2012 02 09
Résumé(disponible en anglais seulement)
Whole rock geochemical analyses have been made from conventional core samples of Lower Cretaceous sandstones and shales from the wells: Naskapi N-30, Alma K-85, Alma F-67, Glenelg N-49, Glenelg E-58, North Triumph B-52, Peskowesk A-99 and Dauntless D-35; and from picked cuttings samples from the wells: Sambro I-29, Dauntless D-35, Fox I-22, Crow F-52, and Argo F-38. Samples with abnormal abundances of P, Mg, Ca and Fe result from important amounts of carbonate or phosphate cernent; after removing these samples, 79 reliable analyses were obtained. Published geochemical discrimination diagrams for clastic sediments were evaluated. These diagrams aim to identify effects of source-area weathering, hydraulic sorting during transport, and the character of the source area rocks ( and hence by inference, their tectonic setting). The chemical effects of source area weathering are difficult to interpret because they may be mirrored by the effects ofburial diagenesis. However, there is petrographic evidence for rapid erosion and transport from the source area. Source area rocks were identified as predominantly of intermediate to felsic composition, characteristic of a continental island arc or passive margin. This is consistent with the petrographically identified source areas predominantly within the Appalachian orogen. Sorne discrimination diagrams suggest that the sources to the western Scotian basin were more mafic and those to the east more felsic, consistent with petrographic evidence for important K-feldspar supply to the east and predominant plagioclase supply to the west. Chemical discrimination diagrams did not provide unambiguous characterization of the predominant source rocks for different parts of the basin. Nevertheless, there are significant changes in elemental abundances in different parts of the basin that are interpreted to represent supply from different source rocks. In the east, Peskowesk (and generally also Fox and Dauntless) sandstones are lower in Ti and have a high K/Rb ratio. Sandstones from the Glenelg and North Triumph fields have distinctively high Hf and Th/U ratios and low La/Sm ratios compared with wells both to the east and west. Mudrocks show an increase from west to east in Nb and Y and a decrease in Sr and Hf. There are systematic variations in Th content ofmudrocks between the western (Naskapi and Alma), central (Glenelg and North Triumph) and eastern (Fox, Peskowesk and Dauntless) areas. Data are insufficient in most wells except Alma and Peskowesk to document stratigraphie variation in key elements. Systematic variation in the chemical composition of sediment in the Scotian Basin is consistent with published petrographic evidence for supply from several different rivers. Regional variation in some elements such as Ti and K may have important consequences for diagenesis. More samples will be needed to evaluate hypotheses proposed in this report.