GEOLOGY | August 2014 | www.gsapubs.org 659 INTRODUCTION Neoproterozoic sedimentary deposits of west- ern North America record large fluctuations in global biogeochemical cycles (e.g., Narbonne et al., 1994; Karlstrom et al., 2000; Halver- son et al., 2005), the diversification of multiple eukaryotic clades (e.g., Porter and Knoll, 2000; Samuelsson and Butterfield, 2001; Cohen and Knoll, 2012), the fragmentation of Rodinia ac- companied by localized mafic volcanism (e.g., Jefferson and Parrish, 1989; Prave, 1999; Mac- donald et al., 2010), and multiple global glacia- tions (e.g., Aitken, 1991; Hoffman et al., 1998). Understanding the causal relationships among these events requires accurate stratigraphic cor- relation in the context of geochronologically constrained age models. However, the geograph- ically disparate Neoproterozoic sedimentary rec- ords along the length of western North America have yet to be clearly linked in time and space due a paucity of radiometric age constraints, non-unique chemostratigraphic ties, abundant synsedimentary tectonism and associated lat- eral facies change, and a lack of biostratigraphi- cally useful microfossils. Correlations have been proposed for pre-glacial Neoproterozoic strata in the southwestern United States (e.g., Dehler et al., 2001, 2010), but these schemes have not been extended to the rich sedimentary archives of northwest Canada, due primarily to a lack of age control. Here we document new vase-shaped microfossil (VSM) assemblages from Yukon, Canada, that are indistinguishable in taxonomic composition and age from those described from the Chuar Group of the Grand Canyon (Arizona, USA) and successions of similar age worldwide (Porter and Knoll, 2000; Porter et al., 2003). Given their abundance, diversity, preservation, and time-calibrated record, VSMs could rep- resent the first temporally well-resolved bio- stratigraphic assemblage zone for pre-Ediacaran strata, opening a new window for regional and global stratigraphic correlation that goes beyond previous broad morphoclass-based biostrati- graphic comparisons. STRATIGRAPHY The Coal Creek inlier in the Ogilvie Moun- tains (Yukon, Canada) hosts an ~3-km-thick se- quence of ca. 780–540 Ma Windermere Super- group strata (Fig. 1; Mustard and Roots, 1997). The Mount Harper Group consists of three informal units; in stratigraphically ascending order , these are (1) the Callison Lake dolostone, an ~400-m-thick mixed siliciclastic and carbon- ate deposit; (2) the Mount Harper conglomer- ate, an ~1100-m-thick rift-related clastic suc- cession; and (3) the Mount Harper volcanics, an ~1200-m-thick intermediate to mafic volcanic complex (Mustard and Roots, 1997; Macdon- ald et al., 2010). Age constraints on the Mount Harper Group are provided by U-Pb chemical abrasion–thermal ionization mass spectrometry (CA-TIMS) ages on zircon of 811.51 ± 0.25 Ma from a tuff in the underlying Fifteenmile Group, 740 Ma vase-shaped microfossils from Yukon, Canada: Implications for Neoproterozoic chronology and biostratigraphy Justin V. Strauss 1 , Alan D. Rooney 1 , Francis A. Macdonald 1 , Alan D. Brandon 2 , and Andrew H. Knoll 1 1 Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts 02138, USA 2 Department of Earth and Atmospheric Sciences, University of Houston, Houston, Texas, 77204, USA ABSTRACT Biostratigraphy underpins the Phanerozoic time scale, but its application to pre-Ediacaran strata has remained limited because Proterozoic taxa commonly have long or unknown strati- graphic ranges, poorly understood taphonomic constraints, and/or inadequate geochrono- logical context. Here we report the discovery of abundant vase-shaped microfossils from the Callison Lake dolostone of the Coal Creek inlier (Yukon, Canada) that highlight the potential for biostratigraphic correlation of Neoproterozoic successions using species-level assemblage zones of limited duration. The fossiliferous horizon, dated here by Re-Os geochronology at 739.9 ± 6.1 Ma, shares multiple species-level taxa with a well-characterized assemblage from the Chuar Group of the Grand Canyon (Arizona, USA), dated by U-Pb on zircon from an interbedded tuff at 742 ± 6 Ma. The overlapping age and species assemblages from these two deposits suggest biostratigraphic utility, at least within Neoproterozoic basins of Laurentia, and perhaps globally. The new Re-Os age also confirms the timing of the Islay δ 13 C carbonate anomaly in northwestern Canada, which predates the onset of the Sturtian glaciation by >15 m.y. Together these data provide global calibration of sedimentary, paleontological, and geochemical records on the eve of profound environmental and evolutionary change. GEOLOGY, August 2014; v. 42; no. 8; p. 659–662; Data Repository item 2014244 | doi:10.1130/G35736.1 | Published online 9 June 2014 © 2014 Geological Society of America. For permission to copy, contact Copyright Permissions, GSA, or editing@geosociety.org. Fifteenmile Group Mount Harper Gp. Gibben Fm. Chandindu Reefal Assemblage Craggy Dolostone Callison Lake dolostone Mount Harper conglomerate Mount Harper volcanics Rapitan Group Hay Creek Group Upper Group 716.47±0.2 Ma Coal Creek Inlier, Ogilvie Mountains, Yukon Conglomerate Sandstone Shale Dolostone Basalt/Rhyolite Evaporite Diamictite U-Pb Age Re-Os Age Cover VSM Nodular Chert Intraclasts Fine lamination Exposure surface Stromatolite/Microbial 811.51±0.1 Ma 717.43±0.1 Ma U.S.A. Greenland CANADA Yukon Territory Alaska 400 km Hyland Group Whitehorse Mackenzie Mountains SG Windermere Supergroup Windermere SG Mackenzie Mtns SG Pinguicula Group Wernecke SG Coal Creek Inlier 141°W 68°N M a c k e n z i e M o u n t a i n s 739.9±6.1 Ma 0 m 10 20 33.1 –25 –8 –4 0 4 –35 –30 δ 13 C carb (‰) δ 13 C org (‰) 500 m Mount Gibben Ogilvie Mtns Mount Gibben Section J1204 Figure 1. Simplified map locations and schematic lithostratigraphy of the Coal Creek inlier, Yukon, Canada. Vase-shaped microfossils (VSMs) described herein are from Callison Lake dolostone. Measured section J1204 highlights location of fossil and Re-Os age horizon, as well as bounding δ 13 C carb and δ 13 C org (blue data points) data from the Islay anomaly. Geologic map of Yukon is adapted from Wheeler and McFeely (1991). Abbreviations: SG—Supergroup; Gp.—Group; Fm.—Formation; Mtns—mountains.