Phanerozoic Record of Northern Ellesmere Island, Canadian High Arctic, Resolved Through 40Ar/39Ar and (U‐Th)/He Geochronology

Abstract

AbstractThe northern margin of Ellesmere Island, Canada, has experienced a complex geological history throughout the Phanerozoic, including multiple episodes of orogenesis and first‐order depositional cycles related to Circum‐Arctic evolution. Whereas previous studies have documented the structural and stratigraphic record of these events, supporting geochronological data are sparse. To constrain the age of these tectonic episodes, we apply 40Ar/39Ar geochronology and (U‐Th)/He low‐temperature thermochronology methods to polydeformed fault zones that bisect the Pearya terrane and Franklinian Basin of northern Ellesmere Island. Multiple single crystal 40Ar/39Ar dating of micas resulted in sample‐dependent date dispersion, with some samples exhibiting robust Paleozoic ages corresponding to the assembly and accretion of the Pearya terrane. Other samples yielded intra‐sample date dispersion that spanned the Late Paleozoic and Mesozoic, suggestive of a previously unreported post‐Ellesmerian and pre‐Eurekan history. Zircon and apatite (U‐Th)/He dates are largely Eocene in age, with dominant populations of c. 48 and c. 41 Ma, respectively. Inverse thermal history modeling of (U‐Th)/He data indicates episodic Mesozoic burial and unroofing coinciding with changes in the regional stress regime, and rapid cooling during nascent (>53 Ma) and initial (53–47 Ma) phases of Eurekan deformation. When integrated, our data provide temporal constraints on the timing of deformation, structural reactivation, and the Phanerozoic burial and erosive history of northern Ellesmere Island.