Acritarchs from the Duolbagáisá Formation (Cambrian Series 2, Miaolingian) on the Digermulen Peninsula, Finnmark, Arctic Norway: towards a high-resolution Cambrian chronostratigraphy

Abstract

New information on acritarchs from the Duolbagáisá Formation, Digermulen Peninsula, Arctic Norway, enable recognition of the three Cambrian Series 2 acritarch-based zones: the Skiagia ornata–Fimbriaglomerella membranacea, Heliosphaeridium dissimilare–Skiagia ciliosa and Volkovia dentifera–Liepaina plana Assemblage zones. Acritarchs of the Skiagia ornata–Fimbriaglomerella membranacea Zone (Cambrian Stage 3) appear near the base of the unit, close to an undetermined trilobite. In the Upper Member of the Duolbagáisá Formation, in levels with Kjerulfia n. sp. and Elliptocephala n. sp., appears an assemblage with abundant Skiagia ciliosa, indicative of the Heliosphaeridium dissimilare–Skiagia ciliosa Zone. A few metres higher appear Liepaina plana, Heliosphaeridium notatum and Retisphaeridium dichamerum, which indicate the Volkovia dentifera–Liepaina plana Zone (Cambrian Stage 4). The transition between the Duolbagáisá Formation and the overlying Kistedalen Formation is marked by the appearance of Comasphaeridium longispinosum, Multiplicisphaeridium llynense and Eliasum llaniscum, diagnostic of the Miaolingian Series. This coincides with the disappearance of Skiagia; occurrences of Skiagia in Miaolingian strata consist of reworked material related to the Hawke Bay regression at the Cambrian Stage 4–Wuliuan transition. The absence of Skiagia in higher levels of the Duolbagáisá Formation and Kistedalen Formation suggests that no unconformity formed during the Hawke Bay regression in this area. The chronostratigraphical significance of the Skiagia ornata–Fimbriaglomerella membranacea, Heliosphaeridium dissimilare–Skiagia ciliosa and Volkovia dentifera–Liepaina plana zones is critically analysed. Correlation of the Duolbagáisá Formation with peri-Gondwanan terrains of Avalonia and Iberia is established. The Digermulen Peninsula has great potential as a reference section for establishing a Cambrian chronostratigraphy based on acritarchs.

Acritarchs from the Duolbagáisá Formation (Cambrian Series 2, Miaolingian) on the Digermulen Peninsula, Finnmark, Arctic Norway: towards a high-resolution Cambrian chronostratigraphy

“…The Ediacaran–Cambrian transition is recognized within the Manndrapselva Member on the basis of ichnofossils (i.e. Treptichnus pedum ) and organic-walled microfossils (Högström et al 2013; Palacios et al 2017 b ; Jensen et al 2018). The lower part of the Breidvika Formation, the uppermost unit of the Vestertana Group, yields Platysolenites antiquissimus and Rusophycus sp., and acritarchs diagnostic of the Asteridium – Comasphaeridium Zone (Vidal, 1981; Högström et al 2013; Palacios et al 2017 b ).…”

“…Treptichnus pedum ) and organic-walled microfossils (Högström et al 2013; Palacios et al 2017 b ; Jensen et al 2018). The lower part of the Breidvika Formation, the uppermost unit of the Vestertana Group, yields Platysolenites antiquissimus and Rusophycus sp., and acritarchs diagnostic of the Asteridium – Comasphaeridium Zone (Vidal, 1981; Högström et al 2013; Palacios et al 2017 b ). Banks (1970) reported Platysolenites antiquissimus from the lower part of the formation, but McIlroy et al (2001) documented specimens only from the upper part.…”

“…and rare ellipsocephalids (Nikolaisen & Henningsmoen, 1990; Ebbestad et al 2017, 2018). The overlying Kistedalen Formation contains trilobites and acritarchs of Miaolingian–Furongian age (Nikolaisen & Henningsmoen, 1985, 1990; Welsch, 1986; Palacios et al 2015). The boundary between the Duolbagáisá and Kistedalen formations has been suggested to approximate the Cambrian Series 2–Miaolingian boundary (Nielsen & Schovsbo 2015; but see below).…”

“…The Digermulen Peninsula (Fig. 1) in Arctic Norway includes one of the most complete successions of Cryogenian–Lower Ordovician strata in the world with an important record of diverse organic-walled microfossils (Vidal, 1981; Welsch, 1986; Högström et al 2013; Palacios et al 2015, 2017 b ) well suited for establishing a high-resolution Cambrian chronostratigraphy. Acritarchs represent a polyphyletic group of form-taxa, most of which represent organic-walled cysts.…”

“…On the Digermulen Peninsula, as well as in sections on Newfoundland and in New Brunswick, Canada, the name-bearing taxa of the Asteridium – Comasphaeridium Zone are absent from basal Fortunian strata, which instead are characterized by acritarchs lacking processes ( Leiosphaeridia spp., Granomarginata squamacea and G . prima ) (Palacios et al 2011, 2017 b , 2018; Högström et al 2013). The first assemblages in well-exposed successions with a good record of organic-walled microfossils, including those diagnostic of the Asteridium – Comasphaeridium Zone, have been located in New Brunswick at levels dated to 531 Ma (Palacios et al 2011) and on Newfoundland at levels above the Watsonella crosbyi Zone (Palacios et al 2018).…”