Paper No. 87-10
Presentation Time: 10:40 AM
LIFE THROUGH THE 'VARANGER ICE AGES': MICROFOSSIL RECORD OF LATE NEOPROTEROZOIC GLACIAL-INTERGLACIAL UNITS FROM ARCTIC NORWAY
AGIĆ, Heda1, HÖGSTRÖM, Anette E.S.2, JENSEN, Sören3, EBBESTAD, Jan Ove4, MEINHOLD, Guido5, TAYLOR, Wendy L.6, PALACIOS, Teodoro3 and HØYBERGET, Magne7, (1)Department of Earth Sciences, University of California, Santa Barbara, CA 93106, (2)Tromsø University Museum, UiT, the Arctic University of Norway, Tromsø, N-9036, Norway, (3)Área de Paleontología, Universidad de Extremadura, Avenida de Elvas s/n, Badajoz, 06006, Spain, (4)Museum of Evolution, Uppsala University, Norbyvägen 16, Uppsala, SE 752 36, Sweden, (5)School of Geography, Geology and the Environment, Keele University, Staffordshire, Keele, ST5 5BG, United Kingdom, (6)Department of Geological Sciences, University of Cape Town, 13 University Ave, Rondebosch, 7701, South Africa, (7)Rennesveien 14, Mandal, N-4513, Norway
The late Neoproterozoic strata in Finnmark (Arctic Norway) provide a good sedimentary record of Neoproterozoic glaciations on the Baltica paleocontinent. The lower Vestertana Group exposed on the Digermulen Peninsula contains two glaciogenic units, the Smalfjord and Mortensnes formations. Chemostratigraphic correlation dated the Smalfjord diamictite to the Marinoan glaciation (650-635 Ma), yet its age was also proposed to be older, per correlation to glacial units in central and southern Scandinavia. The diamictites are bracketing shales and siltstones of the interglacial Nyborg Formation. Stratigraphic, paleontological, and sedimentological data are presented from the interglacial-glacial succession, investigated by the Digermulen Early Life Research Group. Palynological analysis yielded well-preserved organic-walled microfossils (OWM) from the Nyborg Fm., and from fine-grained diamictite matrix in the Mortensnes Fm. via a modified extraction method.
The interglacial Nyborg Fm. hosts a moderate diversity assemblage of prokaryotic and eukaryotic OWM, as well as acanthomorphic acritarchs such as Ceratosphaeridium, ?Cavaspina, and a novel process-bearing form. Organically preserved, enigmatic multicellular eukaryotic fossils occur in the upper Nyborg Fm. The Mortensens glacial assemblage is less diverse and contains bacterial filaments, leiosphaerids, toroidal forms, and Micrhystridium-type minute acanthomorphs.
The presence of Doushantuo-Pertatataka type acritarchs in the Nyborg Fm., and small acanthomorphs in the Mortensnes diamictite corroborate an early Ediacaran age for the interglacial-glacial succession on Digermulen. In addition to the trace fossil and body-fossil record of Ediacara-biota in the overlying Stáhpogieddi Formation, the microfossil biostratigraphy suggests Marinoan and Gaskiers glaciation equivalent ages of the Varanger glaciations in Finnmark. Protistan diversity in the succession declined through and following the glaciation, until late Ediacaran.
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