Reply to “Discussion of Timing and tectonic setting of Ordovician volcanic rocks of the Miramichi terrane in eastern Maine and southwestern New Brunswick” by Cees van Staal and Leslie Fyffe

The migrating single arc model proposed for the Miramichi terrane in the northern Appalachian orogen (van Staal et al. 2016; Fyffe et al. 2023a) is a masterful combination of decades of field, geochemical, and geochronological research in a coherent tectonic explanation based on what was known at that time -almost entirely from New Brunswick because nearly all information from eastern Maine was from before the plate tectonic era.There are now abundant field, geochronological, and geochemical data from northern and eastern Maine, partly because of our work in the Miramichi terrane (e.g., Ludman and Berry 2003;Ludman 2024; and Ludman et al. 2021, 2025) but more significantly because 1:24 000-scale mapping by Wang (2025a, b) has revolutionized understanding of the Munsungun-Winterville terrane, not represented at all in New Brunswick, and the extensive Weeksboro-Lunksoos Lake terrane represented in New Brunswick by only the tiny Popelogan and even smaller Oxford Brook inliers.Ludman et al. (2021), Fyffe et al. (2023a) Ludman et al. (2024, 2025), the Discussion of van Staal and Fyffe (2025), and this response are conversations about whether new information from Maine supports the migrating single arc model or suggests the presence of more than one arc.As practitioners of the scientific method, we welcome the discussion of van Staal and Fyffe (2025) as a healthy test of our hypothesis. Purpose of Ludman et al. (2025)Prior to Ludman et al. (2025), there were fewer than a handful of dated Miramichi volcanic rocks in the southwestern part of the inlier: a single age for the entire Meductic Group in the Eel River-Benton area in New Brunswick and three of probably correlative rocks in the Greenfield area in Maine, but none from the intervening Danforth area at the Maine-New Brunswick border.Our goals for the 2025 paper were to close the data gap, facilitate correlation among the three volcanic suites, and use the new data to test the migrating single arc model in the area where that arc began.Most of these goals were accomplished: two of the three lower Meductic Group formations were dated; the first five ages from the Danforth area were obtained; five new ages from the Greenfield area were added, and the three volcanic suites were correlated convincingly.This response tests the migrating single arc model further, and results of that test are reported below.

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