PALEOMAGNETIC INVESTIGATIONS OF NORTHERN APPALACHIAN TERRANE HISTORY DURING THE MIDDLE TO LATE PALEOZOIC

Paleomagnetic studies of 10 formations from the northern Appalachians of Maine, New Brunswick, and Nova Scotia, ranging in age from Early Cambrian to Early Carboniferous, were undertaken in order to delineate the motions of various geologic terranes during the middle Paleozoic. Results yield information relating to the independent motions of three different terranes during the Devonian and Carboniferous. A clockwise rotation of portions of northern Maine and southeastern Quebec relative to Laurentia (paleo North America) is proposed to have taken place during the Middle Devonian, inferred from comparisons of results from the Lower Devonian Traveler Felsite and the Middle Devonian Mapleton Sandstone, northern Maine, with available paleomagnetic data.;Studies of Silurian, Devonian, and Carboniferous rocks from the Meguma terrane of Nova Scotia are interpreted to imply a counter-clockwise rotation of the terrane relative to Laurentia and the adjacent Acadia terrane, constrained to occur after the Early Carboniferous, and thought to have taken place before the Permo-Carboniferous assembly of Pangea. This terrane also appears to have been located in a southerly position relative to Laurentia. The earlier history of the Meguma terrane cannot yet be addressed because of the remagnetization of the older rocks.;Evidence for the sinistral motion of Acadia since the Late Devonian is reviewed in the context of the study of the Mapleton Formation and other recently obtained results. While the paleomagnetic results indicate that the Connecticut Valley--Gaspe Synclinorium may be included in the Acadia terrane, the absence of suitable loci for such transcurrent motion between these regions and the Laurentian craton represents conflicting evidence. It is concluded that the apparent displacement so far inboard may be an artifact of (1) imprecision in the data from northern Maine and Quebec, or of (2) remagnetization during the late Paleozoic of rocks from the craton.;A fold test on the Cambrian Ratcliffe Brook Formation of New Brunswick implies a Carboniferous or later magnetization. It is concluded that this result is not useful for analyses of terrane motions for earlier times.;Rock units from western New Brunswick were studied in order to delineate the boundary between regions with Laurentian affinity and those that may have been involved in the proposed transcurrent motion of the Acadia composite terrane. Problems in constraining magnetization ages, along with multicomponent magnetization, prohibit precise location of the boundary, although results from southwestern New Brunswick are consistent with displacement of this region in the Carboniferous.