Authors: Stelck, C R.; Trollope, F H.; Norris, A W.; Pemberton, S G.

Source: Canadian Journal of Earth Sciences, Volume 44, Number 11, November 2007 , pp. 1627-1651(25)

Publisher: NRC Research Press

Abstract:

Early Cretaceous paleogeography and biostratigraphy of western Canada are reviewed in light of a reassessment of foraminiferal and microfloral data from unpublished university theses on the early Albian Loon River shales of the lower Peace River area of northern Alberta (Norris 1951; Trollope 1951). The Loon River Formation, once considered to be an obsolete term, comprises numerous “zones” of foraminifera, radiolarian, and algal cysts, in ascending order Rectobolivina sp., lower Radiolarian zone, lower Leiosphaeridia zone, Haplophragmoides yukonensis, upper Radiolarian zone, upper Leiosphaeridia zone, Trochammina mcmurrayensis, Valvulineria loetterlei, Haplophragmoides topagorukensis, Marginulinopsis collinsi, and Haplophragmoides gigas minor. The upper part of the Loon River Formation, from the upper Radiolarian zone onwards, correlates with the McMurray, Wabiskaw, and Clearwater formations of the Fort McMurray area of northeastern Alberta. Molluscan data from various localities in western Canada indicates that the entire Loon River succession occurred within the early Albian. The presence of Inoceramus dowlingi and Cleoniceras sp. with the Marginulinopsis collinsi microfauna permits correlation of the type Clearwater Formation and type McMurray Formation with the Moosebar Formation of northeastern Bristish Columbia. An anomalous thick sequence of Leiosphaeridia (algal cysts) beds, bounded above and below by radiolarian-bearing strata, occurs in the mid part of the Loon River shales outcropping ~40 km along the lower Peace River. The Trochammina mcmurrayensis microfauna occurs 2-3 m below Inoceramus dowlingi and 30 m above Cleoniceras sp., and above the upper Leiosphaeridia zone. The radiolarian and Leiosphaeridia beds are considered to be the offshore neritic homotaxial equivalent of deltaic strata in the upper part of the McMurray Formation. The mid and lower Loon River shales are potential oil sources for the tar of the McMurray Formation, and this is supported by recent radiometric dating of the tar by Rhenium-Osmium isotopic analysis.

La paléogéographie et la biostratigraphie du Crétacé précoce de l'Ouest canadien sont révisés à la lumière d'une réévaluation des données concernant la microflore et les foraminifères contenus dans des thèses universitaires non publiées portant sur les schistes argileux de Loon River (étage Albien) du secteur inférieur de la rivière Peace dans le nord de l'Alberta (Norris 1951; Trollope 1951). La Formation de Loon River, jadis considérée un terme désuet comprend de nombreuses « zones » de foraminifères, de radiolaires et de kystes algaires, en ordre ascendant, Rectobolivina sp., zone inférieure à radiolaires, zone inférieure à Leiosphaeridia, Haplophragmoides yukonensis, zone supérieure à radiolaires, zone supérieure à Leiosphaeridia, Trochammina mcmurrayensis, Valvulineria loetterlei, Haplophragmoides topagorukensis, Marginulinopsis collinsi et Haplophragmoides gigas minor. La partie supérieure de la Formation de Loon River, à partir de la zone supérieure à radiolaires, est en corrélation avec les formations de McMurray, de Wabiskaw et de Clearwater du secteur de Fort McMurray du Nord-Ouest de l'Alberta. Des données sur les mollusques de diverses localités de l'Ouest canadien indiquent que l'entière succession de Loon River date de l'Albien précoce. La présence de Inoceramus dowlingi et de Cleoniceras sp. avec la microfaune Marginulinopsis collinsi permet de faire des corrélations entre le type des formations de Clearwater et de McMurray et la Formation de Moosebar du Nord-Est de la Colombie-Britannique. Une épaisse séquence anomale de lits de Leiosphaeridia (kystes algaires), limitée au-dessus et en dessous par des strates à radiolaires se retrouve dans la partie centrale des schistes argileux de Loon River qui affleurent sur une distance d'environ 40 km le long du cours inférieur de la rivière Peace. La microfaune Trochammina mcmurrayensis se retrouve à deux à trois mètres sous la zone à Inoceramus dowlingi et à 30 m au-dessus de Cleoniceras sp. et au-dessus de la zone supérieure à Leiosphaeridia.

Document Type: Research article

Publication date: 2007-11-01

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