1984 Chapters (Layout Features)

Late Paleozoic motions of the Meguma Terrane, Nova Scotia: New paleomagnetic evidence

Spariosu, Dann J.; Kent, Dennis V.; Keppie, J. Duncan

Three rock units from southern Nova Scotia were sampled for a paleomagnetic study of the relationship of the Meguma terrane to the Atlantic-bordering continents during the Paleozoic. These include the Siluro-Ordovician White Rock Formation volcanics, sandstones of the Lower Devonian Torbrook Formation and red beds of the Lower Carboniferous Cheverie Formation. Progressive thermal and alternating field demagnetization of the White Rock basalts and rhyolites reveal a single component magnetization with a mean direction of D = 149.1°, I = 24.3°, α₉₅ = 10°, for N = 13 sites. Rotation of the site mean directions about the axis of the Torbrook Syncline suggest a post-folding (post Middle Devonian) age for this magnetization, which corresponds to a pole at 21.9° N Lat., 147.7° E Long. after correction for post-Triassic regional tilting. The magnetization of the Torbrook Formation (D = 15.8°, I = 29.6°, a 95 = 11.7°) is clearly a secondary magnetization whose pole (55.5° N Lat., 90.7° E. Long.) lies near Triassic poles from both North America and southern Nova Scotia. The age of the Cheverie Formation magnetization (D = 146°, I = 25°, α₉₅ = 6°, tilt corrected) appears to pre-date folding in the area (pre-Westphalian) and the corresponding pole (24° N Lat., 152° E Long.) lies near to the White Rock pole, suggesting a similar age of magnetization. The White Rock and Cheverie poles, which are constrained to have Early Carboniferous ages, are 30° or more away from the North American APW path over the same age range, a discrepancy which can be explained by a 15 - 19° northward motion of Meguma with respect to the North American craton along with a 20 - 25° counter - clockwise rotation. There is no paleolatitude discrepancy between these results and paleomagnetic results from the adjacent Avalon Zone although a similar rotational discrepancy is evident. These inferred motions of the Meguma terrane most likely took place during the Carboniferous, prior to the formation of Pangea.