Acritarch biostratigraphy of the Lower Cambrian and the Precambrian-Cambrian boundary in southeastern Poland

Abstract

Acritarchs in the sedimentologically continuous, shallow-marine, Upper Vendian - Lower Cambrian subsurface sequence of the Lublin Slope, East European Platform (EEP), Poland are abundant and well-preserved. Forty-five form-species were recovered, and their taxonomic status is revised. Three new form-genera are erected. Asteridium n.gen. and Heliosphaeridium n. gen. include species with solid and hollow processes, respectively, previously referred to Micrhystridium Deflandre. Globosphaeridium n.gen. includes acritarchs with solid processes formerly attributed to Baltisphaeridium Eisenack. The genus Skiagia is emended. Microfossil preservation yields information on the thermal history of the Lublin basin. The acritarch succession in the Lublin Slope forms the basis for a new Lower Cambrian zonation, in ascending order the Asteridium tornaturn - Comasphaeridium velvetum, Skiagia ornata - Fimbriaglomerella membranacea, Heliosphaeridium dissimilare - Skiagia ciliosa, and Volkovia dentifera - Liepaina plana Assemblage-zones. A significant radiation at the upper part of the Włodawa Formation and within the Mazowsze Formation involves taxa of the Asteridiumtornatum - Comasphaeridium velvetum assemblage taken to mark the Pre cambrian-Cambrian boundary. The Kaplonosy IG-1 drillcore is proposed as reference section for the boundary. The Upper Vendian - Lower Cambrian biostratigraphy in Poland is revised. The Sabellidites-Vendotaenia Interval-zone is proposed, the range of the Platysolenites antiquissimus Zone is revised, and the Holmia kjerulfi Assemblage-zone is recognized. The Protolenus zone remains as an informal zone. Parts of the investigated sequence are correlated with the Schmidtiellus mickwitzi Zone elsewhere. The early Cambrian Mobergella Zone and the Klimontovian Stage are rejected. The Precambrian-Cambrian boundary is discussed in light of acritarch evidence from sequences in the East European, Baltoscandian, Siberian, South China and Avalon Platforms. The acritarch zone contemporaneous with the earliest trilobite zone in the Baltoscandian Platform and the EEP embraces part of the Tommotian and Meishucunian strata in Siberia and China. Units underlying the Tommotian in Siberia may be Cambrian. Lower Cambrian rocks of the EEP, the Baltoscandian Platform, and the Scandinavian Caledonides, are correlated on the basis of acritarchs.