EarthRef.org Reference Database (ERR)
Development and Maintenance by the EarthRef.org Database Team

Detailed Reference Information
Johnson et al. 1991
Johnson, R.J.E., van der Pluijm, B.A. and Van der Voo, R. (1991). Paleomagnetism of the Moreton’s Harbour Group, northeastern Newfoundland Appalachians: Evidence for an Early Ordovician Island arc near the Laurentian margin of Iapetus. Journal of Geophysical Research 96: doi: 10.1029/91JB00870. issn: 0148-0227.

Paleomagnetic results have been obtained from mafic volcanic units in the upper part of the Moreton's Harbour group, which is part of an accreted island arc terrane that is preserved in the Notre Dame Bay subzone of the Central Mobile Belt to the Newfoundland Appalachians. Detailed thermal and alternating field demagnetization reveals a stable characteristic component of magnetization, carried by magnetite, at a large number of sites in pillow basalts and coeval basaltic dikes. The intrusives contain both polarities, and a primary age for the characteristic magnetization is indicated by a positive contact test for one of the dikes, and by a positive structural test involving a correction for block rotations (strike-correction). The overall mean direction for the characteristic component after tectonic (tilt and strike) correction (flows and intrusives: D=171¿, I=+22¿, k=22.6, α95=6.5¿, pole 29 ¿N, 135 ¿E; flows: D=166¿, I=+22¿, k=33.2, α95=6.5¿) corresponds to an Early Ordovician paleolatitude for the arc of 11¿S, which is indistinguishable from the expected paleolatitude of the North American margin. This implies that the arc formed at or near the margin of the craton. In contrast, the Avalon block, which formed the other margin of Iapetus, was widely separated from the arc and the craton at this time. The Early Ordovician paleolatitude of the arc terrane supports a tectonic model in which coeval ophiolitic sequences inboard of the arc were formed in a narrow ocean basin between the arc and the craton. Subsequent convergence between the arc and Laurentia in Middle Ordovician time resulted in closure of this narrow ocean basin and obduction of the back-arc basin oceanic crust onto the ancient margin of the craton, thus giving rise to the Taconic orogenic pulse in the Newfoundland Appalachians. ¿ American Geophysical Union 1991

DATABASE QUICK LINKS

MagIC Database

BACKGROUND DATA FILES

Abstract

MagIC SmartBook v1

Keywords
Geomagnetism and Paleomagnetism, Rock and mineral magnetism, Tectonophysics, Hydrothermal systems, Marine Geology and Geophysics, Midocean ridge processes, Geomagnetism and Paleomagnetism, Spatial variations attributed to seafloor spreading
Journal
Journal of Geophysical Research
http://www.agu.org/journals/jb/
Publisher
American Geophysical Union
2000 Florida Avenue N.W.
Washington, D.C. 20009-1277
USA
1-202-462-6900
1-202-328-0566
service@agu.org
Click to clear formClick to return to previous pageClick to submit