Abstract

This paper presents transatlantic correlations of geophysical anomalies plotted on an improved, Mesozoic, pre-drift reconstruction of the American and European plates. By its very nature, potential field data may be satisfied by a wide range of source properties which in turn can have a complex relation to the geology. However, several of the geophysical anomalies observed over Newfoundland and the British Isles appear to be characteristic of underlying tectono-stratigraphic zones. By correlating these anomalies with geological sources and by tracing the anomalies offshore, one can develop crude maps of the bedrock geology on the adjacent continental shelves. The improved plate reconstruction allows us to suggest five fairly reliable and five less reliable geophysical and geological correlations between Newfoundland, British Isles, France and the Iberian Peninsula. The five more reliable correlations are: 1) a magnetic “low” over the Ordovician-Silurian sedimentary sequences of the eastern Exploits and Botwood zones with a magnetic “low” over the Ordovician-Silurian sedimentary sequences in the northern part of tectono-stratigraphic zone 4 in Ireland; 2) a gravity “low” over the Acadian infrastructure of the Gander zone with a gravity “low” over the Caledonian infrastructure of the Leinster massif generally in tectono-stratigraphic zone E; 3) arcuate bands of magnetic “highs” over horsts with Precambrian volcanic rocks of the Avalon zone on, and east of, Newfoundland with magnetic “highs” in the Southwest Approaches that are probably caused by horsts of Precambrian igneous and metamorphic rocks similiar to those in British Isles zones H, I, J; 4) a prominent magnetic “high” with an unknown source on the eastern Grand Banks with a similar magnetic “high” in the Southwest Approaches that may be related to a Caledonian (?) subduction zone (suture); and 5) gravity “lows” over Caledonian and Hercynian granitoid rocks in France and over the associated South Armorican shear zone correlate with granitoid rocks in northwestern Iberian Peninsula.

The less reliable correlations involve: 1) possible trends of the Hercynian Front on the North American plate; 2) correlation of magnetic and gravity “highs” over the Notre Dame zone with magnetic and gravity “highs” over zone C in Ireland and Scotland; 3) possible extensions of the Great Glen fault on the North American plate; 4) possible European continuation of the gravity gradient along the western boundary of the Appalachian/Acadian orogen; and 5) possible positions of the Grenville Front east of Atlantic Canada.