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The earliest Cambrian record of animals and ocean geochemical change

Adam C. Maloof, Susannah M. Porter, John L. Moore, Frank O. Dudas, Samuel A. Bowring, John A. Higgins, David A. Fike and Michael P. Eddy
The earliest Cambrian record of animals and ocean geochemical change
Geological Society of America Bulletin (November 2010) 122 (11-12): 1731-1774


The Cambrian diversification of animals was long thought to have begun with an explosive phase at the start of the Tommotian Age. Recent stratigraphic discoveries, however, suggest that many taxa appeared in the older Nemakit-Daldynian Age, and that the diversification was more gradual. We map lowest Cambrian (Nemakit-Daldynian through Tommotian) records of delta (super 13) C (sub CaCO) (sub 3) variability from Siberia, Mongolia, and China onto a Moroccan U/Pb-delta (super 13) C (sub CaCO) (sub 3) age model constrained by five U/Pb ages from interbedded volcanic ashes. The delta (super 13) C (sub CaCO) (sub 3) correlations ignore fossil tie points, so we assume synchroneity in delta (super 13) C trends rather than synchroneity in first appearances of animal taxa. We present new delta (super 13) C (sub org) , (super 87) Sr/ (super 86) Sr, uranium, and vanadium data from the same carbonate samples that define the Moroccan delta (super 13) C (sub CaCO) (sub 3) curve. The result is a new absolute time line for first appearances of skeletal animals and for changes in the carbon, strontium, and redox chemistry of the ocean during the Nemakit-Daldynian and Tommotian ages at the beginning of the Cambrian. The time line suggests that the diversification of skeletal animals began early in the Nemakit-Daldynian, with much of the diversity appearing by the middle of the age. Fossil first appearances occurred in three pulses, with a small pulse in the earliest Nemakit-Daldynian (ca. 540-538 Ma), a larger pulse in the mid- to late Nemakit-Daldynian (ca. 534-530 Ma), and a moderate pulse in the Tommotian (ca. 524-522 Ma). These pulses are associated with rapid reorganizations of the carbon cycle, and are superimposed on long-term increases in sea level and the hydrothermal flux of Sr.

ISSN: 0016-7606
EISSN: 1943-2674
Serial Title: Geological Society of America Bulletin
Serial Volume: 122
Serial Issue: 11-12
Title: The earliest Cambrian record of animals and ocean geochemical change
Affiliation: Princeton University, Department of Geosciences, Princeton, NJ, United States
Pages: 1731-1774
Published: 201011
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 550
Accession Number: 2010-098059
Categories: StratigraphyInvertebrate paleontology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Includes appendix
Illustration Description: illus. incl. 1 table, geol. sketch map
N20°00'00" - N53°00'00", E74°00'00" - E135°00'00"
N42°00'00" - N52°00'00", E87°00'00" - E120°00'00"
N50°00'00" - N80°00'00", W170°00'00" - E60°00'00"
Secondary Affiliation: University of California, Santa Barbara, USA, United StatesMassachusetts Institute of Technology, USA, United StatesWashington University, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201051
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