Tracking Crustal-scale Appalachian Orogenic Trends from Onshore to Offshore in Atlantic Canada, using Constrained 3-D Gravity Inversion

Abstract:

The surface geology of Atlantic Canada can be broadly divided and categorized according to the accreted terranes and colliding Laurentian and peri-Gondwanan realms that were amalgamated during the closing of the Iapetus Ocean during Appalachian Orogenesis during the early to mid-Paleozoic. The offshore extent of these zones has previously been interpolated across the late Paleozoic Maritimes Basin using mapped potential field data; meanwhile the trends have been less clearly defined seaward of the island of Newfoundland into the Atlantic Ocean. The Maritimes basin has been interpreted to have formed in a tectonic environment involving both dextral strike-slip and extension, but these movements are difficult to quantify with geologic data. Constrained 3-D gravity inversions have proven useful for tracking variations in crustal thickness along many of the rifted margins of the southern North Atlantic. Here, we present results from applying gravity inversion methods both within the Maritimes Basin and outboard of the island of Newfoundland, in order to track the crustal-scale Appalachian trends from onshore to offshore across the entire Atlantic Canada region. The results not only complete our regional view of the Appalachian orogenic trends beyond the mappable geology but also provide clues about possible sites where inheritance may have impacted later extensional tectonism during the opening of the modern North Atlantic Ocean.