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Abstract We describe > 200 ribbon-like macroscopic fossils from terminal Ediacaran strata at Mount Dunfee, Nevada, USA ∼ 115 m below the local placement of the Ediacaran–Cambrian boundary. They are preserved as casts and molds, composed of Fe-oxides and Fe-rich aluminosilicates in an aluminosilicate clay matrix. Measurements of 50 of the specimens provide a fossil size range of 0.22–0.74 mm-wide and 0.1–75.0 mm-long. Some specimens evidence original flexibility and appear to be fragmented, consistent with soft body preservation. They are therefore interpreted as body fossils, rather than trace fossils. Given this interpretation, we suggest that the fossils’ size range and ribbon-like morphologies are consistent with them being members of the problematicum Vendotaenia, which have not been previously reported from Ediacaran strata within the southern Great Basin. The phylogenetic affinity of vendotaenids is unresolved, but they are commonly interpreted as a form of eukaryotic macroalgae. This report firmly establishes vendotaenids in Ediacaran strata on Laurentia, broadening their known paleogeographic range during the end-Ediacaran Period. Additionally, the morphology of the fossils described here supports the notion that, although vendotaenids are reported from many Ediacaran paleocontinents globally, there was low macroalgal diversity at the end of the Ediacaran Period. 

Proterozoic strata in central Yukon are exposed in the Coal Creek, Hart River and Wernecke inliers. The Paleoproterozoic and Neoproterozoic strata are well correlated across the inliers; however, correlation of the Mesoproterozoic units remains ambiguous. We present two stratigraphic logs of Mesoproterozoic units PP1 and PP2 (previously termed PR1 and PR2, respectively) in the Coal Creek inlier. PP1 is dominantly siltstone and sandstone, whereas PP2 is mostly dolostone. In one section where the contact is well exposed, PP2 gradationally overlies PP1, suggesting that these units, at least locally, are conformable. Based on similarities in the stratigraphy and contact relationships with underlying and overlying units, we suggest that PP1 and PP2 are correlative with the Pinguicula Group formally defined in the Hart River and Wernecke inliers. Resolving how PP1 and PP2 correlate with Proterozoic strata exposed in other inliers provides insight into basin development along northwest Laurentia during the Meso–Neoproterozoic. 

Abstract We present chemostratigraphy, biostratigraphy, and geochronology from a succession that spans the Ediacaran-Cambrian boundary in Sonora, Mexico. A sandy hematite-rich dolostone bed, which occurs 20 m above carbonates that record the nadir of the basal Cambrian carbon isotope excursion within the La Ciénega Formation, yielded a maximum depositional age of 539.40 ± 0.23 Ma using U-Pb chemical abrasion–isotope dilution–thermal ionization mass spectrometry on a population of sharply faceted volcanic zircon crystals. This bed, interpreted to contain reworked tuffaceous material, is above the last occurrences of late Ediacaran body fossils and below the first occurrence of the Cambrian trace fossil Treptichnus pedum, and so the age calibrates key markers of the Ediacaran-Cambrian boundary. The temporal coincidence of rift-related flood basalt volcanism in southern Laurentia (>250,000 km3 of basalt), a negative carbon isotope excursion, and biological turnover is consistent with a mechanistic link between the eruption of a large igneous province and end-Ediacaran extinction.