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ABSTRACT. The calcareous nannofossils from the Middle Miocene (Badenian) formations from Pâglişa (Cluj district) are typical for the Lower and Middle Badenian, respectivelly Moravian and Wielician (or Langhian). The detailed study of the calcareous nannofossils from the Pâglişa section revealed the presence of the nannoplankton assemblages belonging to the NN5 and NN6 zones. They have been remarked 40 species of calcareous nannofossils. There are mentioned especially the most representative species and their biostratigraphical significance.

Palaeomagnetic and rock magnetic data collected from the Upper Ordovician Red River, Silurian Interlake and Devonian Winnipegosis, Souris River and Birdbear carbonates in one well from southwestern Manitoba (Canada) reveal a complex magnetization history for the north-eastern Williston Basin. Rock magnetic analysis (thermal demagnetization, anhysteretic remanent magnetization (ARM)/saturation isothermal remanent magnetization (SIRM), S-ratios, partial ARM (pARM), SIRM crossover curves and points and coercivity) show three magnetic carriers for different magnetizations seen in this well. An Early–Mid-Jurassic remagnetization observed in the lower Red River and Souris River formations is carried by single-domain to pseudo-single-domain (SD–PSD) magnetite and was probably produced by basement fluids circulating along fractures and faults created by the Hartney impact/volcanic structure and/or tectonic movements along the Superior Boundary Zone. In the Winnipegosis Formation a possible primary depositional or early depositional magnetization (Devonian age) is carried by PSD pyrrhotite. In the Birdbear Formation two different magnetizations of uncertain age are present: one carried in hematite in the upper strata, possibly originating from the younger Amaranth Formation, and magnetite dominates in the lower strata. The upper Red River and Interlake formations contain both magnetite and pyrrhotite; however, the weaker palaeomagnetic data reveal little in terms of a magnetization age.

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Paleomagnetic and geochemical data obtained from six wells in southwestern Manitoba indicate that the Lower Amaranth redbeds were deposited earlier than Jurassic or Triassic, the most commonly cited depositional ages for this formation in the Williston Basin. The magnetization is carried primarily by detrital specular and pigmentary hematite and occasionally magnetite. Inclination-only analysis of paleomagnetic data (83 specimens from 60 plugs) indicates two possible depositional magnetization ages: Devonian-Pennsylvanian (D, found in very few samples) or Carboniferous to Permian, as suggested by the inclination and the polarity of the most predominant magnetization (B). An isolated magnetization (C) could be a mid-Jurassic to Neogene localized fluid flow remagnetization event. The oxygen and carbon isotope values of dolomite (-6.45% to 0.30% Vienna PeeDee Belemnite (VPDB) d 18 O, -1.57% to 5.44% VPDB d 13 C; n = 18) indicate that dolomitization could have occurred anytime between Carboniferous and Jurassic. However, the distribution of these values is a function of the three types of dolomite present in the Lower Amaranth strata: detrital, cement, and matrix replacive and reflects both the primary values and diagenetic overprints. Detrital and cement dolomite show depleted values in both oxygen and carbon isotopes, most likely inherited from the original values of the detrital dolomite, with superimposed effects of recrystallization. The matrix replacive dolomite has no detrital content, and its oxygen isotope values are similar to the expected values for primary or early diagenetic dolomite from Carboniferous to Jurassic times. Mixtures of detrital and replacive matrix dolomite give intermediate oxygen and carbon isotope values.Résumé : Les données paléomagnétiques et géochimiques obtenues de six puits dans le sud-ouest du Manitoba indiquent que les lits rouges de la partie inférieure de la Formation d'Amaranth ont été déposés avant le Jurassique ou le Trias, les âges le plus fréquemment cités pour la déposition de cette formation du bassin Williston. La magnétisation se trouve principalement dans l'hématite détritique spéculaire et pigmentaire et occasionnellement dans la magnétite. Une analyse de l'inclinaison magnétique seulement des données paléomagnétiques (83 échantillons, 60 carottes) indique deux âges possibles de magnétisation de déposition : Dévonien -Pennsylvanien (D, trouvé dans très peu d'échantillons) ou Carbonifère à Permien, tel que suggéré par l'inclinaison et la polarité de la magnétisation la plus prédominante (B). Une magnétisation isolée (C) pourrait être due à un événement de remagnétisation par un écoulement fluide localisé (Jurassique moyen à Néogène). Les valeurs des isotopes de l'oxygène et du carbone de la dolomie (-6,45 % à 0,30 % VPDB d 18 O, -1,57 % à 5,44 % VPDB d 13 C; n = 18) indiquent que la dolomitisation aurait pu se produire n'importe quand entre le Carbonifère et le Jurassique. Toutefois, la distribution de ces valeurs est fonction des trois types de dolomite présents dans ...