The Precambrian-Cambrian boundary: Magnetostratigraphy and Carbon Isotopes resolve correlation problems between Siberia, Morocco, and South China

Abstract

Late Proterozoic and Early Cambrian age platform carbonates from the Siberian platform now have the most complete records of paleontological, magnetostratigraphic, and δ^(13)C variations preserved anywhere on Earth. New carbon isotopic data from Siberia extends the known pattern up through the first half of Early Cambrian time (the Late Tommotian up through the middle of the Atdabanian stage). These data reveal a fourth δ^(13)C cycle in the Siberian Precambrian/Cambrian boundary isotope curve, and in conjunction with the magnetostratigraphy provide two nonbiological techniques for testing proposed correlations. Similar patterns are present in both the carbon isotope and magnetic reversal stratigraphies in the upper Lie de Vin formation of Morocco, confirming recent biostratigraphic work. A unique match is also present in the comparison between Siberia and an important locality near Kunming in south China, and implies that at least half of the record of Atdabanian time is missing there. Hence, the Chinese section is not suitable as an international stratotype for the Precambrian/Cambrian boundary.

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