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TitrePetrology and Mineralogy of Lower Cretaceous sedimentary rocks, Dauntless D-35 well, Scotian Shelf
AuteurPe-Piper, G; Piper, D J W
SourceCommission géologique du Canada, Dossier public 6280, 2009, 112 pages, (Accès ouvert)
ÉditeurRessources naturelles Canada
Documentdossier public
Mediaen ligne; numérique
ProvinceRégion extracotière de l'est
Lat/Long OENS-57.3500 -57.3333 44.7500 44.7333
Sujetsfaciès diagénétiques; diagenèse; Crétacé inférieur; pétrographie; puits; pétrologie du sediment; interprétations géochimiques; minéraux détritiques; géochimie des roches totales; carottes; lithologie; grès; Formation de Missisauga ; Formation de Logan Canyon ; minéralogie; sédimentologie; géochimie; géologie marine; Mésozoïque; Crétacé
Illustrationslocation maps; tables; stratigraphic columns; photographs; ternary diagrams; plots
Diffusé2009 12 07
Résumé(disponible en anglais seulement)
The sedimentary petrography of the Lower Cretaceous (2160 - 3600 m) in the Dauntless D-35 well has been studied from cuttings samples and one short conventional core. The 3.5 m long conventional core was logged sedimentologically and sampled for petrographic thin sections. 37 cuttings samples were studied in detail and a "heavy mineral" fraction was separated. Detrital minerals diagnostic of provenance were analysed by electron microprobe and their chemical composition compared with elsewhere in the Scotian basin and with bedrock in the hinterland. Diagenetic minerals were characterized by scanning electron microscopy of rock chips, backscattered electron images of thin sections, and electron microprobe analysis.
The conventional core from the upper Missisauga Formation consists of medium-coarse grained sandstone beds deposited as river-mouth turbidites. These beds are cut by liquefied sandstone sills. Sandstones in the conventional core are largely silica cemented, but in places silica overgrowths were inhibited by the presence of chlorite rims. Kaolinite was an earlier pore-filling cement. Halite is interpreted as a later diagenetic cement. Lithological characterization of the cuttings samples shows substantial down-hole contamination. The "heavy mineral" fraction is dominated by carbonate cemented chips and few diagnostic detrital minerals or lithic clasts were found. The cuttings samples contain sideritecemented mudstone and siderite or calcite - Fe-calcite cemented muddy sandstone, both probably formed during sea-floor diagenesis. As in the Sable sub-basin, siderite with high Ca and Mg is most abundant in the Logan Canyon Formation. Late carbonate cements are rare.
In both cuttings and conventional core, K-feldspar makes up 3 - 5 % of the framework grains. Almandine garnet is sourced principally from (meta)mafic igneous rocks. All analysed tourmaline and most analysed biotite is of metasedimentary provenance. Chromite and chrome spinel indicates an ophiolitic source and is distinctive in the presence of ferrian chromite and the absence of boninitic chromite. Identifiable lithic clasts are principally of granite and volcanic rocks, the latter perhaps from Cretaceous volcanic rocks in Orpheus graben. The detrital assemblage is similar to that in the Peskowesk A-99 well, but differs in important respects from wells in the Sable sub-basin, notably the abundance of K-feldspar and different assemblages of garnet and chromite.