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Granitic dike dated at 1136.30±60.58 Ma intrudes pelitic gneiss of the Indian Head Range basement complex in western Newfoundland. The granitic dike is associated with extensive regional granite plutonism, calibrating late-Shawinigan magmatism on the distal eastern margin of Laurentia.

The Humber Margin of Newfoundland preserves the most distal exposures of Proterozoic basement in northeastern Laurentia. Age uncertainty has permitted a range of hypotheses for its origin and links to subsequent tectonic events, including breakup of the supercontinent Rodinia and large orogen-parallel displacement during Appalachian orogenesis. To test these models and better define the basement and Paleozoic rifted margin of North America, a geochronological study of two basement inliers using tandem in situ and isotope dilution U-Pb zircon and titanite geochronology was used. New basement ages and a revised compilation of detrital zircon ages from overlying rift-related deposits contribute to a geochronologic reference datum for western Newfoundland’s crystalline basement, whose protolith has a restricted age range from 1500 to 950 Ma. New age constraints from the Humber Margin calibrate Mesoproterozoic sedimentary successions, an episode of late Shawinigan magmatism, protracted Grenvillian metamorphism, and Ediacaran rift-related magmatism. These age constraints overturn a model of large orogen-parallel displacement within the Humber Margin and can be used to re-evaluate the identity of adjacent terranes. See paper by Hodgin, Macdonald, Crowley, and Schmitz. p. 1045–1079.