Locating the BACE of the Cambrian: Bayan Gol in southwestern Mongolia and global correlation of the Ediacaran-Cambrian boundary

The diversification of animals during the Cambrian Period is one of the most significant evolutionary events in Earth's history. However, the sequence of events leading to the origin of 'modern' ecosystems and the exact temporal relationship between Ediacaran and Cambrian faunas are u...

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Bibliographic Details
Published in:Earth-Science Reviews
Main Authors: Topper, Timothy, Betts, Marissa J., Dorjnamjaa, Dorj, Li, Guoxiang, Li, Luoyang, Altanshagai, Gundsambuu, Enkhbaatar, Batkhuyag, Skovsted, Christian B.
Format: Report
Language:English
Published: ELSEVIER 2022
Subjects:
Cambrian
Ediacaran
GSSP
ASSP
Protohertzina
Treptichnus
Chemostratigraphy
Chronostratigraphy
BACE
PALEONTOLOGICAL LATE EDIACARAN
CARBON-ISOTOPE STRATIGRAPHY
SKELETAL FOSSIL ASSEMBLAGES
EARLY MARINE DIAGENESIS
SMALL SHELLY FOSSILS
SOUTH CHINA
STRATOTYPE SECTION
CHRONOSTRATIGRAPHIC CORRELATION
INTEGRATED CHEMOSTRATIGRAPHY
DEPOSITIONAL-ENVIRONMENTS
Geology
Geosciences
Multidisciplinary
Newfoundland
Online Access:http://ir.nigpas.ac.cn/handle/332004/40849
https://doi.org/10.1016/j.earscirev.2022.104017
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Summary:The diversification of animals during the Cambrian Period is one of the most significant evolutionary events in Earth's history. However, the sequence of events leading to the origin of 'modern' ecosystems and the exact temporal relationship between Ediacaran and Cambrian faunas are uncertain, as identification of the Ediacaran-Cambrian boundary and global correlation through this interval remains problematic. Here we review the controversies surrounding global correlation of the base of the Cambrian and present new high-resolution biostratigraphic, lithostratigraphic and 813C chemostratigraphic data for terminal Ediacaran to basal Cambrian strata in the Zavkhan Basin of Mongolia. This predominantly carbonate sequence, through the Zuun-Arts and Bayangol formations in southwestern Mongolia, captures a distinct, negative delta C-13 excursion close to the top of the Zuun-Arts Formation recognized as the BAsal Cambrian carbon isotope Excursion (BACE). In this location, the nadir of the BACE closely coincides with first occurrence of the characteristic early Cambrian protoconodont Protohertzina anabarica. Despite recent suggestions that there is an evolutionary continuum of biomineralizing animals across the Ediacaran-Cambrian transition, we suggest that this continuum is restricted to tubular forms, and that skeletal taxa such as Protohertzina depict 'true' Cambrian representatives that are restricted entirely to the Cambrian. Employing the first appearance of the trace fossil Treptichnus pedum to define the base of the Cambrian suffers significant drawbacks, particularly in carbonate settings where it is not commonly preserved. As T. pedum is the only proxy available to correlate the Cambrian Global boundary Stratotype Section and Point (GSSP) defined at Fortune Head, Newfoundland, we suggest that the GSSP be redefined elsewhere, in a new stratigraphic section that contains secondary markers that permit global correlation. We propose the nadir of the BACE as the favored candidate to define the base of the Cambrian. ...

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