Palynology of uppermost Proterozoic and lowermost Cambrian formations, central Mackenzie Mountains, northwestern Canada

Abstract

The acritarch assemblages of strata from the base of the Upper Proterozoic Sheepbed Formation to the base of the Lower Cambrian (Atdabanian) Sekwi Formation are described. The sections sampled are in southwestern (internal) structural units where erosion beneath the "sub-Cambrian"(?) unconformity is least evident. Problems of lithostratigraphic correlation of post-Sheepbed, pre-Backbone Ranges formations remain. Acritarchs indicate the age of the Sheepbed Formation and the Blue-flower Formation above it is latest Proterozoic (Vendian), whereas that of the Vampire Formation is Early Cambrian (Atdabanian). The Backbone Ranges Formation has not yielded datable acritarchs, but it is for the most part Cambrian in age, based on other fossil evidence. Comparisons are made with the Russian Platform and southern Canadian Rocky Mountains successions. The total number of acritarch genera increases markedly across the Precambrian–Cambrian transition.

Biochronology of the autochthonous Lower Cambrian in the Laisvall–Storuman area, Swedish Caledonides

“…2). The co-occurrence of Comasphaeridium molliculum, C. mackenzianum, Skiagia ornata, and S. orbiculare in the sample SW-98-12 restricts the possible age to two zones: Skiagia-Fimbriaglomerella and Heliosphaeridium-Skiagia, whereas S. ciliosa in the sample SW-98-13 higher in the succession is known to appear in the Heliosphaeridium-Skiagia Zone and extend into the basal Middle Cambrian (Baudet, Aitken & Vanguestaine, 1989;Moczydłowska, 1991;Vidal & Peel, 1993;Figs 4b, 5c). Taken as a whole, the acritarch assemblage is consistent with the Heliosphaeridium-Skiagia Zone, corresponding to the Holmia kjerulfi Zone.…”

“…The stratigraphic ranges of Comasphaeridium molliculum, C. brachyspinosum, C. mackenzianum and Globosphaeridium cerinum are short and span the Skiagia-Fimbriaglomerella and Heliosphaeridium-Skiagia zones (Baudet, Aitken & Vanguestaine, 1989;Moczydłowska, 1991;Vidal & Peel, 1993;Figs 3, 5). Several other species such as Skiagia ornata, S. orbiculare, S. compressa, Pterospermella vitalis and Archaeodiscina umbonulata have the same first appearance datum but extend into the lowermost Middle Cambrian (Volkova et al 1983;Moczydłowska, 1998;Fig.…”

“…PMU-SW-98-1/2.F/48/2. (c) Comasphaeridium mackenzianum Baudet, Aitken & Vanguestaine, 1989. PMU-SW-98-12/2.F/30/2.…”

Microfossils from the Neoproterozoic Gangolihat Formation, Kumaun Lesser Himalaya: Their stratigraphic and evolutionary significance

“…C. minuta is observed only in the Jhiroli section and is an important part of the assemblage. Specimens of C. minuta are reported from Neoproterozic-Cambrian boundary by Knoll and Swett (1987), Volkova (1969) and Baudet et al (1989), but show a narrow size range. Small acanthomorphic acritarch M. pallidum is present in the Jhiroli and Utrora sections.…”

“…Small acanthomorphic acritarch M. pallidum is present in the Jhiroli and Utrora sections. M. pallidum was reported from the upper most Proterozoic and lower most Cambrian Formation of Central Mac- kenzie Mountain, Northwestern Canada (Baudet et al, 1989). T. vidalii was described from Upper Riphean (Neoproterozoic I) Hunnberg Formation and Draken Conglomerate Formation, Svalbard (Knoll et al, 1991;Knoll, 1984), Upper Riphean (Neoproterozoic I) in Russia (Jankauskas, 1989;Vidal et al, 1993) and Vendian (Neoproterozoic III) Chichkan Formation of Malokaroy Group of Central Asia (Sergeev, 1989).…”