Upper Devonian iridium anomalies, conodont zonation and the Frasnian-Famennian boundary in the Canning Basin, Western Australia

摘要: Abstract Two iridium anomalies have been identified near the Frasnian-Famennian boundary (Upper Devonian) in Canning Basin of Western Australia. Both are associated with cyanobacterium Frutexites and located marginal slope facies. The first was Virgin Hills Formation on west flank McWhae Ridge southeastern end Devonian outcrop belt. This anomaly, initially as being from Famennian Upper Palmatolepis triangularis Zone, is now known to be Early crepida basis presence Palmatolepsis bed. second found drill core Napier just south Range, older than Frasnian Montagne Noire Conodont Zone 12 or 13 Klapper (1989) = rhenana Ziegler Sandberg (1990). These two thus significantly below above not extinction event linguiformis Zone. In association beds containing abundant microstromatolites indicates that concentrations probably a process organic concentration. There no evidence either example directly an impact event.