The source of topography across the Cumberland Peninsula, Baffin Island, Arctic Canada: differential exhumation of a North Atlantic rift flank

Abstract

Elevated topography is evident across the continental margins of the Atlantic. The Cumberland Peninsula, Baffin Island, formed as the result of rifting along the Labrador–Baffin margins in the late Mesozoic and is dominated by low-relief high-elevation topography. Apatite fission-track (AFT) analysis of the landscape previously concluded that the area has experienced a differential protracted cooling regime since the Devonian; however, defined periods of cooling and the direct causes of exhumation were unresolved. This work combines the original AFT data with 98 apatite new (U–Th)/He (AHe) ages from 16 samples and applies the newly developed ‘broken crystals’ technique to provide a greater number of thermal constraints for thermal history modelling to better constrain the topographic evolution. The spatial distribution of AFT and AHe ages implies that exhumation has been significant toward the SE (Labrador) coastline, and results of thermal modelling outline three notable periods of cooling: in the pre-rift stage (460–200\u2005Ma), from synrift stage to present (120–0\u2005Ma) and within the post-rift stage (30–0\u2005Ma). Pre-rift cooling is interpreted as the result of exhumation of Laurentia and synrift cooling as the result of rift-flank uplift to the SE and differential erosion of landscape, whereas the final post-rift period is probably an artefact of the modelling process. These results suggest that the source of the Cumberland Peninsula s modern-day elevated topography is uplift during rifting in the Cretaceous and the isostatic compensation following continuous Mesozoic and Cenozoic differential erosion. This work highlights how interaction of rift tectonics and isostasy can be the principal source for modern elevated continental margins, and also provides insight into the pre-rift exhumational history of central Laurentia. Supplementary material: Thermal histories are available at: https://doi.org/10.6084/m9.figshare.c.4528409