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Anoxia as the cause of the mid-Early Cambrian (Botomian) extinction event

Andrey Yu. Zhuravlev and Rachel A. Wood
Anoxia as the cause of the mid-Early Cambrian (Botomian) extinction event
Geology (Boulder) (April 1996) 24 (4): 311-314


New and revised Early Cambrian biostratigraphic data allow a quantitative analysis of changes in biotic diversity and extinction rate. The mid-Early Cambrian extinction can now be resolved into two distinct events: the well-known early Toyonian Hawke Bay regression event, and a newly observed but more severe disruption during the early Botomian, here named the Sinsk event. During the Sinsk event, the shallow-water benthos of the so-called Tommotian fauna, together with archaeocyaths and some trilobites, underwent a rapid decline. The Sinsk event is characterized by the significant accumulation of nonbioturbated laminated black shales in tropical shallow waters. Lamination is due to the fine alternation of clay- and organic-rich laminae with calcite-rich laminae containing abundant monospecific acritarchs. These shales are enriched by pyrite and elements typical of anoxic conditions and support a benthic biota of dysaerobic character. Our observations suggest that the extinction during the early Botomian was caused by extensive encroachment of anoxic waters onto epicontinental seas, associated with eutrophication and resultant phytoplankton blooms.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 24
Serial Issue: 4
Title: Anoxia as the cause of the mid-Early Cambrian (Botomian) extinction event
Affiliation: Russian Academy of Sciences, Palaeontological Institute, Moscow, Russian Federation
Pages: 311-314
Published: 199604
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 24
Accession Number: 1996-036441
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Cambridge Earth Sci. Publ. No. 4581; with GSA Data Repository Item 9616. IGCP Project No. 366
Illustration Description: illus. incl. sect.
N52°30'00" - N75°00'00", E82°00'00" - E139°00'00"
Secondary Affiliation: University of Cambridge, Department of Earth Sciences, Cambridge, GBR, United Kingdom
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 199612
Program Name: IGCPInternational Geological Correlation Programme
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