Paleomagnetic Evidence for PostDevonian Displacement of the Avalon Platform Newfoundland

The possibility that the Avalon Platform, where the Avalonian lithotectonic belt is best developed, was involved in late Paleozoic displacement was tested by paleomagnetic study of red sandstones of the Upper Devonian Terrenceville Formation of eastern Newfoundland. Two magnetization directions were identified by thermal demagnetization analysis of 60 oriented samples from 10 sites: a high blocking temperature, thermally discrete A component of normal and reversed polarity, and an intermediate blocking temperature, thermally distributed B component of reversed polarity. The B component (D = 185.9 ø, I = -3.3 ø, a95 = 7.2 ø for N = 8 sites) is interpreted as a postfolding secondary magnetization and gives a paleomagnetic pole position (latitude = 43.6øN, longitude = 117.1øE) near Early to Late Permian paleopoles for North America. The A component (D = 181.6 ø, I = 28.0 ø, a95 = 10.1 ø for N = 9 sites) is interpreted as the characteristic magnetization possibly dating from near the time of deposition of the Terrenceville Formation. The corresponding paleomagnetic pole position (latitude = 27.4øN, longitude = 123.5øE) falls within a group of Late Devonian-early Carboniferous paleopoles obtained from the Acadia displaced terrain, encompassing the coastal areas of New England and the Canadian maritimes which form another part of the AvalonJan belt. These paleopoles are systematically offset by 15 ø to 20 ø in latitude from coeval pole positions obtained from cratonic North America. Thus the AvalonJan belt of the northern Appalachians, which is thought to represent a remnant of a Precambrian and early Paleozoic microcontinent on tectonostratigraphic considerations, appears to correspond to a late Paleozoic displaced terrain on the basis of paleomagnetic evidence.