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TitreNew insights into the age and nature of lower Paleozoic cores from the Labrador margin, offshore eastern Canada
AuteurBingham-Koslowski, N
Source20th International Sedimentological Congress ISC, abstracts volume; 2018 p. 1
Année2018
Séries alt.Ressources naturelles Canada, Contribution externe 20180114
ÉditeurInternational Sedimentological Congress
RéunionISC2018 - 20th International Sedimentological Congress; Québec, QC; CA; août 13-17, 2018
Documentlivre
Lang.anglais
Mediapapier; numérique
Formatspdf
ProvinceTerre-Neuve-et-Labrador; Région extracotière de l'est; Région extracotière du nord
SNRC14; 15
Lat/Long OENS -65.0000 -52.0000 61.0000 56.0000
Sujetsmarges continentales; plate-forme continentale; échantillons carrotés; descriptions de carottes; microscopie des lames minces; milieu sédimentaire; géologie du substratum rocheux; lithologie; roches sédimentaires; structures sédimentaires; fossiles; microfossiles; palynologie; Puit Gudrid H-55 ; Puit Freydis B-87 ; Puit Indian Harbour M-52 ; Puit Roberval K-92 ; sédimentologie; paléontologie; Phanérozoïque; Paléozoïque; Ordovicien
ProgrammeAtlas régionale de Baffin, GEM2 : La géocartographie de l'énergie et des minéraux
Diffusé2018 08 01
Résumé(disponible en anglais seulement)
The lower Paleozoic of the eastern Canadian Atlantic margin is poorly understood due to the scarcity of offshore samples and the occurrence of diagenetic alteration and tectonic deformation. These strata underlie the Mesozoic rift succession of the Hopedale Basin along the Labrador margin, offshore eastern Canada. Paleozoic-aged rocks were penetrated by seven industry wells (Freydis B-87, Gudrid H-55, Hopedale E-33, Indian Harbour M-52, Roberval K-92, South Hopedale L-39, and Tyrk P-100), with six corresponding conventional core samples available from four of the wells (Gudrid H-55, Indian Harbour M-52, and two cores from each Freydis B-87 and Roberval K-92). These six cores and their associated thin sections are described as part of a regional study aimed at understanding the lower Paleozoic depositional environments that existed along the western margin of the Iapetus Ocean. Five of the six cores are carbonates with one of the cores from Freydis B-87 and the core from Indian Harbour M-52 being composed of limestone, whereas the cores from Gudrid H-55 and Roberval K-92 are dolostones.
The uppermost core recovered from Freydis B-87 is siliciclastic and is dominated by mudrock with cross-bedded and laminated sandstone beds. The second core consists primarily of fossiliferous wackestone with fragments of undifferentiated shells, brachiopods, echinoids, bivalves, gastropods, trilobites, and bryozoans. Ostracods, sponge spicules, and calcimicrobes are also observed in thin section. The Indian Harbour M-52 core consists predominantly of limestone with dolomite occurring in localized patches and along stylolites. Fragments of shells, bivalves, echinoids, gastropods, trilobites, and brachiopods, along with radiolarians and sponge spicules are also present. The core from Gudrid H-55 and the two cores from Roberval K-92 are composed entirely of fabric-destructive diagenetic dolomite resulting in no identifiable fossil components. Ordovician scolecodonts, chitinozoa, and acritarchs were recovered using conventional cores and cuttings from six of the seven Paleozoic wells on the Labrador margin with varying degrees of preservation. No identifiable lower Paleozoic palynomorphs were found in Roberval K-92; however, given the lithological similarities with Gudrid H-55 and its proximity to the other Paleozoic wells, it is likely also Ordovician in age.
The diverse fossil assemblages observed in the lower core from Freydis B-87 and the core from Indian Harbour M-52 implies that these sediments were deposited under normal marine conditions, with low to moderate energy levels. The high abundance of fossils in the Freydis B-87 carbonate core and the presence of calcimicrobes suggests a somewhat shallow depositional environment, at, or near the base of the photic zone. The identification of radiolarians, and the overall lower fossil content noted in Indian Harbour M-52 reflects its deposition in a deeper-water, open marine environment. A transition from carbonate to siliciclastic sediments in Freydis B-87 signifies the termination of the carbonate factory later in the Ordovician and is likely correlative to a major, possibly eustatic, shift in depositional conditions.
Résumé(Résumé en langage clair et simple, non publié)
Six carottes conventionnelles du Paléozoïque inférieur et des lames minces connexes provenant de la marge du Labrador, dans la zone extracôtière de l'Est canadien, recueillies dans le cadre de l'étude régionale du Paléozoïque. Cinq des six carottes étaient composées de carbonates. De ces cinq carottes, deux étaient faites de calcaire et les trois autres étaient entièrement constituées de dolomite. Parmi les fossiles observés, on retrouvait des fragments de coquillages, des bivalves, des échinides, des gastropodes, des trilobites, des bryozoaires et des brachiopodes, ainsi que des radiolaires, des ostracodes, des spicules d'éponges et des calcimicrobes. Les interprétations préliminaires laissent croire que les sédiments retrouvés dans les carottes de calcaire ont été déposés dans des conditions maritimes normales dans des eaux peu profondes à profondes.
GEOSCAN ID308349