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Rock magnetic evidence for inclination shallowing in the early Carboniferous Deer Lake Group red beds of western Newfoundland

2010; Oxford University Press; Volume: 181; Issue: 1 Linguagem: Inglês

10.1111/j.1365-246x.2010.04537.x

1365-246X

Dario Bilardello, Kenneth P. Kodama,

Geological formations and processes

A paleomagnetic and rock magnetic study of the Carboniferous Deer Lake Group red beds of Newfoundland was performed to detect and correct for inclination shallowing. Results indicate a primary remanence carried by magnetite, with a mean direction of D= 179.7°, I= 33.7°, α95= 7.2° which corresponds to a paleopole position of 22.2°N, 122.3°E, A95= 7.6°. Correcting the inclination using anisotropy of anhysteretic remanence and the measured individual particle anisotropy gives a corrected direction of D= 178.8°, I= 50.9°, α95= 6.3° corresponding to a paleopole position at 8.4°N, 122.7°E, A95= 7.2°. This correction is larger than that of other red beds from the Maritime Provinces of Canada, but is consistent with paleoenvironmental reconstructions, placing North America in a more arid climate zone. Our inclination-corrected results have important implications for this portion of North America's apparent polar wander path and suggest a correction is needed for other red bed-derived APWPs. We have determined the range of flattening factors f, defined as the proportionality constant between the tangents of the measured (Im) and field (Io) inclinations, tan(Im) =ftan(I0), from this study and previous inclination correction studies to estimate inclination corrections. Using the range of haematite f factors observed in this study to correct the Neogene red bed inclinations from the Vallès-Penedès Basin (NE Spain) yields inclinations consistent with the known geomagnetic field inclination in the Neogene, thus indicating that the range of f factors reported here may be used to estimate the magnitude of inclination shallowing in red beds.