Northeastern Section - 37th Annual Meeting (March 25-27, 2002)

The plate tectonic setting and structural/thermal evolution of the Silurian-Devonian “Acadian orogen” is complex and enigmatic, owing largely to the following factors: (1) polymetamorphism; (2) polydeformation; (3) lack of continuity in age and composition of rocks across strike; (4) lack of structural continuity in exposed crustal levels across strike; and (5) lack of absolute age control on both regional and pluton-driven thermal events. To gain insight into Acadian-age orogenesis, we have chosen an area where complexities owing to the above factors are minimized, and where we can combine field- and laboratory-based studies with 3-D coupled thermal and mechanical modeling to address fundamental questions about this orogen.

We have initiated a multidisciplinary study along a 120 km-long transect across a representative region of Acadian-age orogenesis in Maine. We plan to integrate structural and microstructural analysis, chemical and isotopic dating of metamorphic monazite, and modern petrologic and thermobarometric studies with 3-D coupled thermal and mechanical modeling. The ideal nature of this transect, and our approach of integrating data-gathering and interpretation with 3-D modeling, will provide new insights into the thermal and tectonic evolution of this portion of the orogen. These results can then be carried into central and western New England where thermal and deformational histories are considerably more complex.

Questions we plan to address include: (a) whether or not plutonism and metamorphism were broadly syntectonic; (b) what controlled orogen-scale deformation partitioning, and how did it relate to localized uplift and exhumation during transpression; (c) was there a positive feedback relation between strain concentration and exhumation; (d) what were the relative roles of conductive and advective heating and their temporal and spatial relations with deformation and deformation partitioning; and (e) what plate tectonic setting best fits the combined results of geologic analysis and geodynamic modeling?