A SUBDUCTED OCEANIC SPREADING RIDGE MODEL FOR MID-PALEOZOIC EASTERN NEW ENGLAND AND SOUTHERN MARITIME CANADA
In the model, dextral fault systems include the Norumbega fault system between southwestern New Brunswick and southern Maine and New Hampshire, and the Kennebecasis, Belle Isle and Caledonia faults in southeastern New Brunswick. The potential role of the Chedabucto fault system in Nova Scotia will be discussed. A latest Silurian transition from arc- to within-plate- magmatism in the Coastal Volcanic Belt in eastern Maine may suggest the onset of ridge subduction. Examples of increased latest Silurian to Devonian within-plate magmatism include the Cranberry Island volcanic series and coastal Maine magmatic province in Maine, and the South Mountain Batholith in Nova Scotia. Widespread Devonian to earliest Carboniferous granitic to intermediate plutons, beyond the Coastal Volcanic Belt towards southern Maine and central New Hampshire, may outline the shape of a subsurface slab window. The fact that mid-Paleozoic magmatism is not nearly as widespread south of New England or north of Nova Scotia may imply that ridge-transform subduction did not occur in Newfoundland or in the southern Appalachians. The model presented here may thus provide a partial explanation for significant differences that have previously been recognized between the northern and southern Appalachians.