Palaeomagnetism of the Skinner Cove Formation of Western Newfoundland and the birth of the Iapetus Ocean

• Main Author: McCausland, Philip John Albert
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 1998
• Subjects: Skinner Cove; Newfoundland
• Online Access: https://research.library.mun.ca/6554/; https://research.library.mun.ca/6554/1/PhilipJohnAlbertMcCausland.pdf; https://research.library.mun.ca/6554/3/PhilipJohnAlbertMcCausland.pdf

The 550 Ma Skinner Cove Formation is a structural unit within the Humber Arm Allochthon of western Newfoundland, occurring as an alkali volcanic suite affected only by zeolite facies metamorphism. At 10 sites from its flows and dykes a magnetite-borne, stable characteristic 'A' remanence direction (tilt-corrected mean D=144°, I=31.5°; α₉₅=10.8°, k=21.1) is recognized and shown to be a primary thermal remanence by an intraformational conglomerate test. The palaeolatitude calculated for the Skinner Cove Formation from its ten 'A' site virtual geomagnetic poles is 18.6°S ±9°. -- An original relation between the Skinner Cove Formation and the Iapetan margin of Laurentia is suggested by several lines of evidence: As a structural slice it occupies a lower, less transported position in the Humber Arm Allochthon, implying an original adjacency to underlying slices of Laurentian margin sediments. The Skinner Cove volcanics have a within plate trace element geochemistry with enriched light rare earth elements (LREE), shared with other alkali volcanics of the northeastern Appalachians Humber Zone. Also, the ~550 Ma Skinner Cove volcanics are of similar age to alkali magmatic activity of Laurentia's Iapetan margin, marked by the ~554 Ma Tibbit Hill metavolcanics of Quebec and the ~555 Ma Lady Slipper Pluton of west Newfoundland. Hence, the 18.6°S palaeolatitude of the Skinner Cove Formation constrains Laurentia to an equatorial position at ~550 Ma. -- Comparison with other palaeomagnetically determined high southerly palaeolatitudes for ~570 Ma implies a large rapid northward drift of ~34 cm/yr for Laurentia during the latest Neoproterozoic. The start of Laurentia's rapid northward movement at ~570 Ma may mark the beginning of Iapetus sea-floor spreading, consistent with Laurentian geological data if thermally-delayed subsidence of the Laurentian margin is assumed. Further well-constrained palaeomagnetic results of ~580 ~550 Ma age from Laurentia and especially its suspected conjugate margins Amazonia and Rio de la Plata ...