Organic‐walled microfossils from the Ediacaran–Cambrian boundary stratotype section, Chapel Island and Random formations, Burin Peninsula, Newfoundland, Canada: Global correlation and significance for the evolution of early complex ecosystems

Abstract

Although a variety of trace and body fossils have been described from the Cambrian strata in the stratotype section (global stratotype section and point) of the Precambrian–Cambrian boundary in the Burin Peninsula, Newfoundland, a detailed analysis of its organic‐walled microfossils has been missing. The basal Cambrian Treptichnus pedum Ichnozone of the Chapel Island Formation is dominated by leiosphaerids and filamentous sheaths. The appearance of Granomarginata approximates the base of the overlying Rusophycus avalonensis Ichnozone. Common process‐bearing acritarchs, represented by small Asteridium and Comasphaeridium, first appear in the middle of the overlying Random Formation, and a more diverse acritarch assemblage at its top. The Random Formation also yields small carbonaceous metazoan fossils, the first report of this type of fossil in this formation. The initial low diversity of phytoplankton in the basal Cambrian strata, a holdover from Ediacaran extinctions, indicated that they have limited potential for precise global correlation of the global stratotype section and point. The pattern of increasing diversity of acritarchs through the lower Fortunian strata lagged behind and was potentially a response to the Cambrian radiation of metazoans, as most clearly represented by ichnofossils. The timing of phytoplankton radiation reflects a dynamic lag driven by metazoan‐induced changes in early Cambrian food webs.

Early Cambrian small carbonaceous fossils (SCFs) from an impact crater in western Finland

“…In Urbanek & Rozanov ; Jankauskas & Lendzion ; Palacios et al . ). Other shared elements include the abundance of carbonaceous protoconodonts ( P. compressa ; see fig.…”

“…), records of Terreneuvian (Fortunian + Stage 2) SCFs are currently limited to a handful of reports of metazoan‐derived structures captured in conventional acritarch investigations (Nagovitsin ; Palacios et al . , ). Initial reports from other Cambrian palaeocontinents have produced Terreneuvian SCFs comparable to that found at Vimpeli; samples from Avalonia (the Burin Peninsula, Newfoundland; Palacios et al .…”

“…Several Terreneuvian deposits with similar acritarch compositions have also yielded spine‐shaped ‘ Ceratophyton vernicosum ’, some of which are protoconodont elements assignable to Protohertzina compressa (Palacios et al . , ; Högström et al . ).…”

“…The SCF assemblage from Vimpeli is equivalent to that of the regional ‘Lontovan’ stage, placing it in the upper part of the global Fortunian stage (Meidla ; Palacios et al . ; Slater et al . ).…”

“…The acritarch Granomarginata prima for instance appears to be entirely constrained to Terreneuvian strata and has been reported from Terreneuvian sediments of the Chapel Island Formation, Newfoundland (Palacios et al . ), Terreneuvian deposits of the Ratcliffe Brook Formation, New Brunswick (Palacios et al . ), Fortunian strata from Arctic Norway (Högström et al .…”