THE CASE FOR AN ACADIAN DESTRUCTIVE MARGIN

Reassessment of the geology of northern Massachusetts, coastal Maine, and southwestern New Brunswick indicates the presence of an Andean-type destructive margin at the western edge of Composite Avalon. The Stratigraphy from St. John, New Brunswick to Waterville, Maine, although broken by a series of thrust slices and younger high-angle faults, forms a consistent series of sections that are not confined to a single stratigraphic belt. The western edge of these thrust slices is at the eastern limit of the Waterville Formation and to the northeast along the east side of the Miramichi and Tetagouche Groups. Silurian and Lochkovian volcanic rocks and associated sedimentary rocks are the remnants of the volcanic arc. These have attributes of an Andean-type destructive margin and are similar to those preserved in the Huarmey basin in the Peruvian sector of the Andean arc. Granite, granodiorite, gabbro, and syenite are associated with the volcanic sections and roughly agree in position with Wyllie's analysis of the origin of these rocks in an Andean-type subduction complex.