Physical and chemical evidence of the 1850 Ma Sudbury impact event in the Baraga Group, Michigan

Palaeoproterozoic supercontinents and global evolution: correlations from core to atmosphere

“…The largest, Vredefort in South Africa, is dated at 2.02 Ga; the second-largest, Sudbury, has an age of 1.85 Ga (both impacts reviewed by Grieve & Therriault 2000). No ejecta blanket has been discovered from Vredefort, but three regions of ejecta localities within 500-800 km from Sudbury are now reported (Addison et al 2005;Pufahl et al 2007). An impact spherule-bearing locality on the Nain or North Atlantic craton (Chadwick et al 2001) has age constraints of 1.88 -1.85 Ga (Garde et al 2002), barely within range of the Sudbury event.…”

“…gas structures trapped beneath a microbial mat. The second, consisting of discoidal and furrowed impressions in sandstone of the Stirling Ranges in Western Australia (Cruse & Harris 1994;Rasmussen et al 2002a) has recently been dated to the interval 1960 -1800 Ma (Rasmussen et al 2004). An extensive discussion on these putative trace fossils retains the original interpretation of their being produced by 'motile, mucus-producing, probably multicellular organisms', which on the basis of size alone were probably eukaryotic .…”

The Impact Crater Bandwagon (Some problems with the terrestrial impact cratering record)

“…However, only few workers have so far attempted to enlarge the distal impact record through dedicated search for impact tracers. In this context, a positive development has been the identification of the ejecta from the Sudbury impact structure in distal sedimentary sections in western Ontario and Minnesota (Addison et al 2005), and in Michigan (Kring et al 2006;Pufahl et al 2007). The ejecta of the Vredefort event that have been searched for in the Waterberg Group strata of northern South Africa are, however, still elusive (Reimold 2007).…”

Impactites: Their Characteristics and Spatial Distribution

“…In the Sudbury ejecta, accretionary lapilli occur only in the more proximal sites. This suggests that there was a turbulent ejecta cloud, which was conducive to the formation of accretionary lapilli that extended out to approximately 650 km, but not to approximately 900 km from the Sudbury impact structure (Pufahl et al, 2007;Cannon et al, 2010).…”

“…There are cases of ejecta preserved in the sedimentary record and, in some cases, they can be traced back to their source crater. For example, shocked quartz, altered splash-form melt spherules and accretionary-like lapilli occur in the stratigraphic column in the western Lake Superior region and have been linked to the Sudbury impact event approximately 400-900 km to the east (Addison et al, 2005;Pufahl et al, 2007;Cannon et al, 2010). Such links between shocked materials in the stratigraphic column and a particular impact structure are generally on the basis of 'equivalence' in age and, in some cases, in lithologies and specific minerals in the ejecta and the target area (e.g.…”