GEOCHRONOLOGIC CONSTRAINTS ON NEOPROTEROZOIC RIFTING OF RODINIA: INSIGHTS FROM NORTHERN BRITISH COLUMBIA (Invited Presentation)

The Neoproterozoic breakup of the supercontinent Rodinia has been implicated as a causal factor for initiation of global glaciation, diversification of crown group eukaryotes, and a second rise of oxygen. However, Rodinian paleogeography and dynamics of continental separation around its centerpiece, Laurentia, remain poorly constrained. Here, geochronological, geochemical, and stratigraphic data from Gataga Mountain in northern British Columbia are integrated to better constrain the age of rift-related volcanism and test the causal connection to global glaciation. Three informal sequences were documented; a basal quartzite, the Gataga volcanics, and an overlying mixed carbonate-siliciclastic succession. The interfingering volcanics and beds of matrix-supported diamictite with exotic clasts are interpreted as reflecting sub-ice shelf sedimentation and volcanism. Magmatic ages in the upper Gataga volcanics span 696.2 ± 0.2 to 690.1 ± 0.2 Ma, and detrital zircon from the underlying non-glacial quartzite provide a maximum age constraint on the onset of glaciation <735.8 ± 0.6 Ma. Overlying the Gataga volcanics, a mixed carbonate-siliciclastic succession contains minor basalt flows that are geochemically distinct from the underlying volcanics. Together, the stratigraphy and geochemical signature of volcanic rocks at Gataga Mountain suggest two episodes of Neoproterozoic extension. These results are integrated with existing geologic and geochronologic data along western Laurentia to suggest that Gataga volcanism may be part of southward propagating extension along the margin.