The Neoproterozoic was an era of great environmental and biological change, but a paucity of direct and precise age constraints on strata from this time has prevented the complete integration of these records. We present four high-precision U-Pb ages for Neoproterozoic rocks in northwestern Canada that constrain large perturbations in the carbon cycle, a major diversification and depletion in the microfossil record, and the onset of the Sturtian glaciation. A volcanic tuff interbedded with Sturtian glacial deposits, dated at 716.5 million years ago, is synchronous with the age of the Franklin large igneous province and paleomagnetic poles that pin Laurentia to an equatorial position. Ice was therefore grounded below sea level at very low paleolatitudes, which implies that the Sturtian glaciation was global in extent.

The northern Stevenson Ridge map area is underlain by Paleozoic to Paleogene rocks that locally host Au and Cu-Au mineralization. The northern side of the Dawson Range is characterized by Paleozoic rocks typical of the Yukon-Tanana terrane, including the pre-Devonian Snowcap assemblage, Mississippian Simpson Range suite and Finlayson assemblage, and the Permian Klondike schist and Sulphur Creek plutonic suite of the Klondike assemblage. The Mississippian stratigraphy is intruded by the Triassic Pyroxene Mountain suite and the Early Jurassic Aishihik suite. Late Devonian metamorphosed volcanic, plutonic and sedimentary rocks of the White River assemblage and the Late Triassic Snag Creek gabbro suite occur southwest of the Dawson Range. These rocks are structurally overlain by a thrust sheet of the Early Permian ophiolitic Harzburgite Peak complex. The White River assemblage and the Yukon-Tanana terrane are juxtaposed along the post-Triassic Moose Creek fault, which is partly demarcated by lozenges of peridotite, indicating that it is a fundamental crustal fault. Other major post-Triassic faults imbricate the Yukon-Tanana terrane tectonostratigraphy, and determine the map pattern. These faults likely acted as conduits for Mesozoic fluids and magmatism and have been reactivated throughout the Cordilleran orogenesis. Late Cretaceous and younger faults throughout the area have only modest offsets.

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The late Paleozoic volcanic rocks of the northern Canadian Cordillera lying between Ancestral North America to the east and the accreted terranes of the Omineca belt to the west record early arc and rift magmatism along the paleo-Pacific margin of the North American craton. The Mississippian to Permian volcano-sedimentary Klinkit Group extends discontinuously over 250 km in northern British Columbia and southern Yukon. The two stratotype areas are as follows: (1) in the Englishman Range, southern Yukon, the English Creek Limestone is conformably overlain by the volcano-sedimentary Mount McCleary Formation (Lower Clastic Member, Alkali-Basalt Member and Volcaniclastic Member), and (2) in the Stikine Ranges, northern British Columbia, the Screw Creek Limestone is conformably overlain by the volcano-sedimentary Butsih Formation (Volcaniclastic Member and Upper Clastic Member). The calc-alkali nature of the basaltic volcaniclastic members of the Klinkit Group indicates a volcanic-arc setting ((La/Yb)N = 2.77–4.73), with little involvement of the crust in their genesis (εNd = +6.7 to +7.4). Alkali basalts in the Mount McCleary Formation ((La/Yb)N = 12.5–17.8) suggest periodic intra-arc rifting events. Broadly coeval and compositionally similar volcano-sedimentary assemblages occur in the basement of the Mesozoic Quesnel arc, north-central British Columbia, and in the pericratonic Yukon–Tanana composite terrane, central Yukon, suggesting that they all represent pieces of a single long-lived, late Paleozoic arc system that was dismembered prior to its accretion onto Ancestral North America. Therefore, Yukon–Tanana terrane is possibly the equivalent to the basement of Quesnel terrane, and the northern Quesnel terrane has a pericratonic affinity.