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Abstract

R. Swennen, F. Roure, and J. W. Granath, eds., Deformation, fluid flow, and reservoir appraisal in foreland fold and thrust belts: AAPG Hedberg Series, no. 1, p. 317-330.

Copyright © 2004 by The American Association of Petroleum Geologists.

DOI:10.1306/1025697H13123

Late Cretaceous Chemical Remagnetization of the Paleozoic Carbonates from the Undeformed Foreland of the Western Canadian Cordillera

Philippe Robion,1 Jean Luc Faure,2 Rudy Swennen3

1Deacutepartement des Sciences de la Terre, Universiteacute de Cergy-Pontois, France
2Division Geacuteologie-Geacuteochimie, Institut Franccedilais du Peacutetrole, Rueil Malmaison, France
3Laboratorium voor Sediment petrologie en milieu geochemie, Afdeling Fysico-chemische Geologie, Katholieke Universiteit Leuven, Heverlee, Belgium

ACKNOWLEDGMENTS

The present study has been founded by Subthrust Reservoir Appraisal II Consortium. We thank E. Deville (Institut Franccedilais du Peacutetrole) and B. Gomez (Institut
Franccedilais du Peacutetrole), as well as several colleagues at the Geological Survey of Canada, for assistance in the field and at the Alberta Energy and utilities Board. The latter Board is also thanked for permitting sampling of the cores. We also greatly thank C. Kissel and C. Laj (Laboratoire des Sciences du Climat et de l'Environemen, Gif sur Yvette) for providing us their laboratory device measurements and for their constant assistance during paleomagnetic measurements. Special thanks go to F. Roure (IFP) and K. Osadetz (Geological Survey of Canada), who initiated this work. Finally, we acknowledge R. Enkin (Geological Survey of Canada) and D. Elmore (University of Oklahoma) for their reviews and especially R. Enkin and M. Molinaro (University of Cergy-Pontoise) for improving the text.

ABSTRACT

Viscous remanent Previous HitmagnetizationNext Hit (VRM) recently acquired in the Earth's magnetic field provides a compass to recover in-situ orientation of unoriented core material. This method was used to date a late chemical remanent Previous HitmagnetizationTop (CRM) in Paleozoic carbonate rocks (Devonian to Mississippian) from the foreland of the western Canadian Cordillera. The paleomagnetic data showed three distinct components: (1) a low-temperature component, which is commonly removed at temperatures below 180degC and is assumed to be induced by drilling; (2) a medium-temperature component, which is commonly removed below 250–400degC, with a steep normal polarity direction; and (3) a high-temperature component, which is isolated above 250–400degC. In the foothills, high-temperature magnetizations always have steep reverse polarities, whereas in the Interior Plains, both normal and reverse polarities with more scattered inclinations are observed. The agreement between theoretical and laboratory blocking temperatures supports the interpretation that the medium-temperature component has recorded Earth's magnetic field over the normal polarity Brunhes epoch as a VRM. The same approach for the high-temperature component led to the interpretation that the high unblocking temperatures indicate a CRM event that affected the Paleozoic carbonates long after deposition. This component is equivalent to the A component observed by Enkin et al. (2000) in exposed strata. By correcting declination values using the medium-temperature component, the direction of the high-temperature component in the Interior Plains is D = 330.4deg, I = 74.3, k = 84, alpha95 = 3.4deg, N = 22 specimens, and in the foothills, it is D = 331.3deg, I = 82.4deg, k = 30, alpha95 = 8.1degN = 12 specimens, corresponding to pole position consistent with the Late Cretaceous section of the North American apparent polar wander path.

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