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Paleogeographic, paleoceanographic, and tectonic controls on early Late Ordovician graptolite diversity patterns

Daniel Goldman and Shuang-Ye Wu
Paleogeographic, paleoceanographic, and tectonic controls on early Late Ordovician graptolite diversity patterns (in The Ordovician Earth system, Stanley C. Finney (editor) and William B. N. Berry (editor))
Special Paper - Geological Society of America (2010) 466: 149-161

Abstract

The Katian Age (early Late Ordovician) was a time of significant decline in marine biodiversity, but whether this decline was a real phenomenon or an artifact of the relatively few studies devoted to this interval requires further research. We examined the pattern of graptolite faunal changes across the boundary between the Climacograptus bicornis and Diplacanthograptus caudatus graptolite zones in North America and on several other continents. A sharp decline in species diversity occurs in the Appalachian Basin. Scores for normalized diversity dropped from 20 in the C. bicornis Zone to 7 in the D. caudatus Zone. Only 11% of the species present in the C. bicornis Zone carry over into the D. caudatus Zone. A similar pattern occurs in central Oklahoma. Regions at higher paleolatitude, such as Wales and Baltoscandia, exhibit low graptolite diversity in lower Katian strata, and then diversity declines further in higher strata. In other regions at low paleolatitude, such as Australasia and Scotland, however, diversity is fairly constant across this interval (although the percentage of carryover taxa remains low). We conclude that seawater temperature change or disruption of the oceanic density structure, which might accompany temperature change, provides explanations for the similarity between Laurentian and higher paleolatitude diversity patterns. Flooding of the Laurentian craton through the Sebree Trough by cool, subpolar Iapetus seawater may have adversely affected graptolite diversity there. Regions at high paleolatitudes likely underwent cooling associated with Katian climate deterioration. Thus seawater cooling, albeit driven by different mechanisms, may have produced similar diversity patterns at different paleolatitudes.


ISSN: 0072-1077
EISSN: 2331-219X
Coden: GSAPAZ
Serial Title: Special Paper - Geological Society of America
Serial Volume: 466
Title: Paleogeographic, paleoceanographic, and tectonic controls on early Late Ordovician graptolite diversity patterns
Title: The Ordovician Earth system
Author(s): Goldman, DanielWu, Shuang-Ye
Author(s): Finney, Stanley C.editor
Author(s): Berry, William B. N.editor
Affiliation: University of Dayton, Department of Geology, Dayton, OH, United States
Affiliation: California State University at Long Beach, Department of Geological Sciences, Long Beach, CA, United States
Pages: 149-161
Published: 2010
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 92
Accession Number: 2010-064076
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. charts, sketch map
N54°30'00" - N71°00'00", E05°00'00" - E32°00'00"
N54°40'00" - N61°00'00", W08°30'00" - W00°45'00"
N51°30'00" - N53°30'00", W05°15'00" - W02°40'00"
Secondary Affiliation: University of California, Berkeley, USA, United States
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: 201035
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