Pan-Continental River System Draining Grenville Orogen Recorded by U-Pb and Sm-Nd Geochronology of Neoproterozoic Quartzarenites and Mudrocks, Northwestern Canada

Abstract

Regional lithostratigraphic correlation of early Neoproterozoic Sequence B on the northwest margin of Laurentia includes a 0.5-2 km-thick, laterally continuous, quartzarenite marker of mainly fluvial origin. Concordant U-Pb ages of 54 single detrital zircons from five regionally dispersed samples cluster in the Archean (2.8-2.6 Ga), Paleoproterozoic (2.0-1.9 Ga), and Mesoproterozoic (1.6-1.0 Ga). The vast majority (85%) of the zircons are of Mesoproterozoic age, with a high proportion clustering between 1.25-1.0 Ga, closely matching the age of synorogenic intrusions in the Grenville Province of North America. A $$100 3 \pm 4 Ma$$ zircon from the Pinguicula group in the eastern Ogilvie Mountains provides a maximum age for the quartzarenite marker. Sm-Nd isotopic data from intercalated mudrocks indicate a major contribution from sources with relatively juvenile model ages ($$T_{DM} = 1.54-1.74 Ga$$), consistent with the provenance indicated by the detrital zircons. The isotopic data support both regional lithostratigraphic correlations and the existence of a braided river system of pan-continental proportions that may have emanated from sources along the entire 5000 + km length of the Grenville orogenic front. Proximal parts of this river system may be preserved in a foreland basin setting in the subsurface of the midcontinental USA and perhaps in a thick molassic sequence in central-eastern Greenland.