The Ordovician–Silurian boundary, northern Canadian Cordillera: graptolite and conodont correlation

Lenz, A. C.; McCracken, A D

doi:10.1139/e82-111

Cited by 32 publications

(18 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The Ashgill graptolite biostratigraphy of the Peel River, Yukon, was reported by Lenz & McCracken (1982, and Chen & Lenz (1984 Mu, Chen & Lenz, 1984, Lenz & McCracken, 1988 and Arachniograptus laqueus. It roughly corresponds to the Dicellograptus complexus Zone as suggested by Chen & Lenz (1984) and Lenz & McCracken (1988 The P. pacificus and P. acuminatus zones in the Yukon are juxtaposed across a cryptic unconformity at which the N. extraordinarius and N. persculptus zones are missing.…”

Section: I Yukon Canadamentioning

confidence: 83%

Late Ordovician to earliest Silurian graptolite and brachiopod biozonation from the Yangtze region, South China, with a global correlation

et al. 2000

View full text Add to dashboard Cite

Late Ordovician to earliest Silurian is an important geological period marked by large geological and biological events. However, the strata and fossils of this interval are not complete in many parts of the world. Based on studies of 43 sites in South China, in particular the continuous sections on the Yangtze platform, we recognize a complete succession including seven graptolite zones and two shelly faunas. In ascending order, the graptolite zones are the Dicellograptus complanatus, Dicellograptus complexus, Paraorthograptus pacificus (including Lower Subzone, Tangyagraptus typicus Subzone and Diceratograptus mirus Subzone), Normalograptus extraordinarius–Normalograptus ojsuensis, Normalograptus persculptus, Akidograptus ascensus and Parakidograptus acuminatus zones. The shelly faunas are the Foliomena–Nankinolithus and Hirnantia faunas, which may be correlated with D. complanatus Zone and N. extraordinarius–N. ojsuensis to part of N. persculptus zones respectively. The biozonation through this interval from the Yangtze region can be correlated with that of other parts of the world such as Dob's Linn in Scotland, Spain and Portugal, Thuringia–Saxonia–Bavaria, Bohemia, Poland, Kazakhstan, Kolyma, Malaya Peninsula, Yukon, Canadian Arctic Islands, Nevada, Argentina, Niger and Victoria, Australia. The Hirnantian Substage, which has been proposed by us recently, includes the N. extraordinarius–N. ojsuensis Zone, Hirnantia fauna and N. persculptus Zone. The base of the Hirnantian Substage is marked by the First Appearance Data (FADs) of N. extraordinarius and N. ojsuensis, which have been determined to be synchronous on a global scale.

show abstract

Section: I Yukon Canadamentioning

confidence: 83%

Late Ordovician to earliest Silurian graptolite and brachiopod biozonation from the Yangtze region, South China, with a global correlation

et al. 2000

View full text Add to dashboard Cite

show abstract

“…Lungmachi Formation (Demirastrites triangulatus Subzone) in China (Chen and Lin, 1978). Road River Formation (Atavograptus atavus-L. acinaces Zones) in the Yukon Territory, Canada (Lenz and McCracken, 1982).…”

Section: Figures 36c Ementioning

confidence: 99%

Stratigraphy, structure, and graptolites of an Ordovician and Silurian sequence in the Terra Cotta Mountains, Alaska Range, Alaska

Churkin¹,

Carter²

1996

Professional Paper

View full text Add to dashboard Cite

New Zealand, Great Britain, Idaho, and Texas. Of the 95 species described and illustrated, 2 are new species, Pleurograptus collatus and Monograptus digitatus, 2 are new subspecies, M. digitatus digitatus and M. digitatus subdigitatus, and 3 are unnamed new species. Genus Didymograptus McCoy, 1851, sensu lato Didymograptus cf. D. cognatus Harris and Thomas Occurrence.-Collections 69ACn574 and 69ACn575; Climacograptus tubuliferus Zone.

show abstract

“…The Vinini Creek site (Nevada; hereafter VC) records deposition in a bathyal continental slope to ocean floor setting, slightly south of the paleoequator (15,31). The Blackstone River site (Ogilvie Mountains, Yukon, Canada; hereafter BR) was a shallower site located ∼3,000 km away, on the continental shelf, north of the paleoequator (32,33). Additionally, paleoenvironmental proxy data are available at these sites (21,22,30,34) that permit independent characterization of paleooceanographic changes.…”

mentioning

confidence: 99%

Graptolite community responses to global climate change and the Late Ordovician mass extinction

Sheets

Mitchell

Melchin

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Mass extinctions disrupt ecological communities. Although climate changes produce stress in ecological communities, few paleobiological studies have systematically addressed the impact of global climate changes on the fine details of community structure with a view to understanding how changes in community structure presage, or even cause, biodiversity decline during mass extinctions. Based on a novel Bayesian approach to biotope assessment, we present a study of changes in species abundance distribution patterns of macroplanktonic graptolite faunas (∼447-444 Ma) leading into the Late Ordovician mass extinction. Communities at two contrasting sites exhibit significant decreases in complexity and evenness as a consequence of the preferential decline in abundance of dysaerobic zone specialist species. The observed changes in community complexity and evenness commenced well before the dramatic population depletions that mark the tipping point of the extinction event. Initially, community changes tracked changes in the oceanic water masses, but these relations broke down during the onset of mass extinction. Environmental isotope and biomarker data suggest that sea surface temperature and nutrient cycling in the paleotropical oceans changed sharply during the latest Katian time, with consequent changes in the extent of the oxygen minimum zone and phytoplankton community composition. Although many impacted species persisted in ephemeral populations, increased extinction risk selectively depleted the diversity of paleotropical graptolite species during the latest Katian and early Hirnantian. The effects of long-term climate change on habitats can thus degrade populations in ways that cascade through communities, with effects that culminate in mass extinction.abundance | climate change | extinction | macroevolution | selection M ass extinctions affect communities over a range of hierar-

show abstract

The Ordovician–Silurian boundary, northern Canadian Cordillera: graptolite and conodont correlation

Cited by 32 publications

References 17 publications

Late Ordovician to earliest Silurian graptolite and brachiopod biozonation from the Yangtze region, South China, with a global correlation

Late Ordovician to earliest Silurian graptolite and brachiopod biozonation from the Yangtze region, South China, with a global correlation

Stratigraphy, structure, and graptolites of an Ordovician and Silurian sequence in the Terra Cotta Mountains, Alaska Range, Alaska

Graptolite community responses to global climate change and the Late Ordovician mass extinction

Contact Info

Product

Resources

About