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Quo vadis, Tommotian?

Published online by Cambridge University Press:  08 November 2019

Dmitriy V. Grazhdankin*
Affiliation:
Precambrian Palaeontology and Stratigraphy Laboratory, Trofimuk Institute of Petroleum Geology and Geophysics, Koptyuga 3, Novosibirsk 630090, Russia Earth Sciences Division, Novosibirsk State University, Pirogova 1, Novosibirsk 630090, Russia
Vasiliy V. Marusin
Affiliation:
Precambrian Palaeontology and Stratigraphy Laboratory, Trofimuk Institute of Petroleum Geology and Geophysics, Koptyuga 3, Novosibirsk 630090, Russia Earth Sciences Division, Novosibirsk State University, Pirogova 1, Novosibirsk 630090, Russia
Olga P. Izokh
Affiliation:
Earth Sciences Division, Novosibirsk State University, Pirogova 1, Novosibirsk 630090, Russia Isotope Analytical Geochemistry Laboratory, Sobolev Institute of Geology and Mineralogy, Koptyuga 3, Novosibirsk 630090, Russia
Galina A. Karlova
Affiliation:
Precambrian Palaeontology and Stratigraphy Laboratory, Trofimuk Institute of Petroleum Geology and Geophysics, Koptyuga 3, Novosibirsk 630090, Russia
Boris B. Kochnev
Affiliation:
Precambrian Palaeontology and Stratigraphy Laboratory, Trofimuk Institute of Petroleum Geology and Geophysics, Koptyuga 3, Novosibirsk 630090, Russia Earth Sciences Division, Novosibirsk State University, Pirogova 1, Novosibirsk 630090, Russia
Georgiy E. Markov
Affiliation:
Precambrian Palaeontology and Stratigraphy Laboratory, Trofimuk Institute of Petroleum Geology and Geophysics, Koptyuga 3, Novosibirsk 630090, Russia
Konstantin E. Nagovitsin
Affiliation:
Precambrian Palaeontology and Stratigraphy Laboratory, Trofimuk Institute of Petroleum Geology and Geophysics, Koptyuga 3, Novosibirsk 630090, Russia Earth Sciences Division, Novosibirsk State University, Pirogova 1, Novosibirsk 630090, Russia
Zhiger Sarsembaev
Affiliation:
Precambrian Palaeontology and Stratigraphy Laboratory, Trofimuk Institute of Petroleum Geology and Geophysics, Koptyuga 3, Novosibirsk 630090, Russia Earth Sciences Division, Novosibirsk State University, Pirogova 1, Novosibirsk 630090, Russia
Sara Peek
Affiliation:
Department of Geology, University of Maryland, College Park, MD 20742, USA Menlo Park Stable Isotope and Tritium Laboratories, United States Geological Survey, Menlo Park, CA 94025, USA
Huan Cui
Affiliation:
Department of Geology, University of Maryland, College Park, MD 20742, USA Research Group of Analytical, Environmental and Geo-Chemistry, Division of Earth System Science, Vrije Universiteit Brussel (VUB), Brussels 1050, Belgium ET-HOME (Evolution and Tracers of the Habitability of Mars and Earth) Astrobiology Research Consortium, Belgium
Alan J. Kaufman
Affiliation:
Department of Geology, University of Maryland, College Park, MD 20742, USA Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD 20742, USA
*

Abstract

The concept of the Tommotian Regional Stage of the Siberian Platform has been closely linked to the idea of the ‘Cambrian Explosion’ of animals and protists when the entire Earth system shifted rapidly into Phanerozoic mode. We conducted a multidisciplinary study of an informal ‘synstratotype’ of the lower Tommotian boundary in the upper Mattaia Formation, Kessyusa Group in the Olenek Uplift, NE of the Siberian Platform. The Mattaia Formation characterizes an upper shoreface to inner-shelf depositional setting and provides important faunal ties and correlation with carbonate-dominated and aliminosiliciclastic open-shelf areas. A section of the upper Mattaia Formation at Boroulakh, Olenek River is suggested here as a model for the Global Boundary Stratotype Section and Point for the base of the Cambrian Stage 2. This level contains the lowermost occurrence of the cosmopolitan fossil helcionelloid mollusc Aldanella attleborensis. Section global markers near the base of the stage include a positive excursion of δ13C values reaching +5.4‰, a U–Pb zircon date of 529.7 ± 0.3 Ma, massive appearance of diverse small skeletal fossils (including Watsonella crosbyi), a sudden increase in diversity and abundance of trace fossils, as well as a conspicuous increase in depth and intensity of bioturbation. Coincidently, it is this level that has always been regarded as the lower Tommotian boundary on the Olenek Uplift.

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Type
Original Article
Copyright
© Cambridge University Press 2019 

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