Palaeomagnetism and magnetic anisotropy of Carboniferous red beds from the Maritime Provinces of Canada: evidence for shallow palaeomagnetic inclinations and implications for North American apparent polar wander

Abstract

SUMMARY A palaeomagnetic and magnetic anisotropy study was conducted on the lower-middle Carboniferous Maringouin and Shepody red bed formations of the Maritime Provinces of Canada to detect and correct inclination shallowing. Because of the shallow inclinations commonly observed in red beds and the strong dependence of North America's Palaeo-Mesozoic apparent polar wander (APW) on red beds, inclination shallowing may substantially affect large portions of North America's APW path. Hematite is the primary magnetic mineral carrier in these red beds, accompanied by secondary magnetite, maghemite, goethite and pigmentary hematite. Thermal and chemical demagnetization of the Shepody Fm. successfully isolated characteristic remanence directions of D= 177°, I= 20.4°, α95= 6.5°, N= 19 and D= 177.8°I= 17.7°, α95= 6.9°, N= 16, respectively. Thermal demagnetization of the Maringouin Fm. isolated a characteristic remanence direction of D= 178.7°, I= 24.9°, α95= 14.5°, N= 9. High field anisotropy of isothermal remanence followed by alternating field and thermal cleaning on leached samples was used to isolate the fabric of hematite. Individual particle anisotropy was measured directly from magnetic separates using a new technique. Hematite's magnetic fabric and particle anisotropy were used to apply an inclination correction. Our inclination corrections indicate up to 10° of inclination shallowing, corresponding to corrected palaeopole positions of 27.2°N, 118.3°E, A95= 6.2° and 27.4°N, 117.2°E, A95= 13.1° for the Shepody and Maringouin formations, respectively. This correction corresponds to a ∼ 6° increase in colatitude for Carboniferous North America, which translates into approximately a 650 km change in North America's palaeogeographic position. The proposed position of North America supports a Pangea B-type reconstruction.