Abstract
Abundant and diverse microfossils from shales of the uppermost Ura Formation, central Siberia, document early to middle Ediacaran life along the southeastern margin of the Siberian Platform. The Ura Formation is well exposed in a series of sections in the Lena River basin but the best microfossil assemblages come from a locality along the Ura River. Here, the uppermost twenty meters of the formation contain diverse microfossils exceptionally well preserved as organic compressions. Fossils include nearly two dozen morphospecies of large acanthomorphic microfossils attributable to the Ediacaran Complex Acanthomorph Palynoflora (ECAP), a distinctive assemblage known elsewhere only from lower, but not lowermost, to middle Ediacaran rocks. Discovery of ECAP in strata previously considered Mesoproterozoic through Cryogenian confirms inferences from chemostratigraphy, dramatically changing stratigraphic interpretation of sedimentary successions and Proterozoic tectonics on the Siberian Platform. Systematic paleontology is reported for 36 taxa (five described informally) assigned to 23 genera of both eukaryotic and prokaryotic microfossils. One new genus and two new species are proposed: Ancorosphaeridium magnum n. gen. n. sp. and A. minor n. gen. n. sp.
Highlights
EARLY RESEARCH painted Ediacaran microfossils as a depauperate assemblage of cyanobacteria and simple leiospherids, with limited biostratigraphic potential (e.g., Volkova et al, 1979; Volkova, 1985)
Diverse Ediacaran microfossils are known from a number of localities along the margins of the East European Platform and the Siberian craton, affording an opportunity to investigate the stratigraphic and geographic ranges of key taxa within and between cratons
We contribute to this effort, describing in systematic detail a previously reported (Vorob’eva et al, 2008) assemblage of Ediacaran microfossils from the Ura Formation (Dalnyaya Taiga Group, Patom Supergroup) and placing it in the context of stratigraphic development on the Siberian craton
Summary
EDIACARAN MICROFOSSILS FROM THE URA FORMATION, BAIKALPATOM UPLIFT, SIBERIA: TAXONOMY AND BIOSTRATIGRAPHIC SIGNIFICANCE. ABSTRACT—Abundant and diverse microfossils from shales of the uppermost Ura Formation, central Siberia, document early to middle Ediacaran life along the southeastern margin of the Siberian Platform. The Ura Formation is well exposed in a series of sections in the Lena River basin, but the best microfossil assemblages come from a locality along the Ura River. The uppermost twenty meters of the formation contain diverse microfossils exceptionally well preserved as organic compressions. Fossils include nearly two dozen morphospecies of large acanthomorphic microfossils attributable to the Ediacaran Complex Acanthomorph Palynoflora (ECAP), a distinctive assemblage known elsewhere only from lower, but not lowermost, to middle Ediacaran rocks. Systematic paleontology is reported for 36 taxa (five described informally) assigned to 23 genera of both eukaryotic and prokaryotic microfossils. One new genus and two new species are proposed: Ancorosphaeridium magnum n. gen. n. sp. and A. minor n. gen. n. sp
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