NEW INSIGHTS INTO THE STRATIGRAPHY, MINERALOGY, AND DETRITAL ZIRCON PROVENANCE OF EDIACARAN TO CAMBRIAN RIFT TO PASSIVE MARGIN DEPOSITS, HUMBER MARGIN, WESTERN NEWFOUNDLAND

Ediacaran to lower Cambrian siliciclastic units in the Humber zone of western Newfoundland record the syn- to post-rift evolution of the northeast Laurentian margin during the protracted breakup of Rodinia. We combine field stratigraphic, detrital zircon U-Pb, and SEM-MLA micro-analytical imaging studies to test published rift models for northeastern Laurentia and investigate the maximum depositional ages, quantitative mineralogy, provenance, and regional correlation of syn-rift and post-rift units in western Newfoundland. Syn-rift, lithic feldspathic turbidite strata of the Blow Me Down Brook Formation (Curling Group, Humber Arm allochthon) are post-late Ediacaran and yield 579 – 2915 Ma detrital zircon grains with age peaks of 1069 Ma, 1308 Ma, 1467 Ma and 2723 Ma. Petrographic and MLA results (area %) show that syn-rift strata contain 50-53% quartz, 22-27% feldspar, up to 23% clay minerals, and igneous and metamorphic lithic fragments and trace chromite and garnet grains mostly derived from Proterozoic (Grenville) basement rocks in western Newfoundland. Archean detrital zircon and other polycyclic grains suggest original provenance from Archean cratons of the Canadian Shield. Clean quartz arenite strata of the Hawke Bay Formation (Labrador Group, Humber margin) were deposited along an early Cambrian passive margin and yield 559 – 3738 Ma detrital zircon grains with age peaks of 1009 Ma, 1042 Ma, 1319 Ma, 1848 Ma, and 2716 Ma. Hawke Bay Formation strata average 88% quartz, 5% feldspar, and 6% porosity, and the absence of garnet and chromite grains shows breakdown of Proterozoic basement sediment in shallow-water environments. Ongoing research will constrain the regional correlation of Ediacaran-Cambrian units and test the timing and basin-filling predictions of Laurentian rift models, but the available data indicate that deep- and shallow-water strata both exhibit similar detrital zircon evidence for mafic to felsic magmatic events in the Laurentian hinterland.