The initiation of the Mesoproterozoic Bylot basins (Nunavut, Arctic Canada) as recorded in the Nyeboe Formation, Fury and Hecla Group

Abstract

ABSTRACT Reconstructing Precambrian sedimentary environments over broad cratonic regions often relies on a combination of facies, structural, and provenance analyses. The Mesoproterozoic (ca. 1270–1090 Ma) Fury and Hecla Group, exposed on the Melville Peninsula and northern Baffin Island (Nunavut, Canada), is considered broadly correlative with strata of the Borden, Hunting–Aston, and Thule basins (together referred to as the Bylot basins). We present the results of updated mapping and the first high-resolution sedimentologic and stratigraphic analysis of the lowermost unit in the Fury and Hecla Group, the Nyeboe Formation. The Nyeboe Formation comprises five distinct facies associations: alluvial to fluvial, eolian-backshore, marine-intertidal, marine foreshore to shoreface, and marine-offshore. Thin mafic units are interbedded within the marine shoreface facies and are interpreted to represent volcanic flows. Lateral relationships between facies associations are complex, but generally, facies associations transition from a terrestrial environment at the base to a nearshore marine environment at the top, indicating a transgression. Considering both the along-strike and -dip thickness trends, the presence of mafic volcanic rock units, and possible syndepositional fault orientations crosscutting the deposits, we infer that the Fury and Hecla Group was deposited in a regime of crustal thinning in a half-graben setting. Our results from the Nyeboe Formation suggest a lithostratigraphic correlation to the Nauyat and Adams Sound formations of the Borden Basin. Therefore, this study establishes a geodynamic link between the opening of the Fury and Hecla Basin to the other Bylot basins and contributes to the understanding of a large late Mesoproterozoic intracontinental-basin system.