THE AVALON TERRANE OF NEWFOUNDLAND - GEOPHYSICAL CORRELATIONS FROM ONSHORE TO OFFSHORE AS EVIDENCE FOR PRECAMBRIAN TO TERTIARY STRUCTURAL EVOLUTION

The Avalon Terrane in eastern Canada has a complex geological and stru ctural history from the Precambrian to the present. On land the terran e is typified by faulted Precambrian elastic basins bounded by arcuate belts of mafic and felsic volcanics. These basins are overlain by spa tially limited exposures of Cambro-Ordovician sediments. There is stru ctural evidence of Paleozoic events after the Cambro-Ordovician, inclu ding the juxtaposition of the Avalon against the rest of Newfoundland in Devonian-Carboniferous times, but no significant deposition. Offsho re there are Siluro-Devonian basins, extensive areas of Carboniferous deposition and the Mesozoic petroliferous basins of the Grand Banks ea ch having characteristic trends. Traditional studies of the Avalon hav e focused on either the onshore portion or the Mesozoic basins. This p aper presents an attempt to understand the relationship between the tw o using published geophysical data. Gravity and magnetic data were use d to produce basic and derived maps to interpret the orientation of ge ophysical features of the terrane. Directional filtering techniques we re used to identify and highlight particular trend orientations, and d irectional arrow plots were used to identify the spatial distribution of trends. Various age events in the Avalon Terrane are correlated wit h specific geophysical trend directions. The dominant arcuate and nort herly directed patterns are considered to be Precambrian with some Her cynian reworking. East-west trends are probably related to the emplace ment of the Collector Anomaly in the Devonian-Carboniferous and to the continuation into the Avalon of South Armorican trends from Europe. T he NW-oriented features correlate with major transfer faults, of Juras sic-middle Cretaceous age, in the Mesozoic basins and can be followed to the land area providing evidence for similar aged events onshore. T here is also evidence for NNE Tertiary trends offshore. The Mesozoic f eatures are closely related to the Atlantic opening history. The NW-or iented features appear to cross the Dover-Hermitage Fault, suggesting that more of Newfoundland than the Avalon Terrane may have been affect ed by Mesozoic events.