Uppermost Ordovician (upper Katian-Hirnantian) graptolites of north-central Nevada, U.S.A

0361335 - GLÚ 2012 RIV CZ eng J - Journal Article
Štorch, Petr - Mitchell, Ch. E. - Finney, S. C. - Melchin, M. J.
Uppermost Ordovician (upper Katian-Hirnantian) graptolites of north-central Nevada, U.S.A.
Bulletin of Geosciences. Roč. 86, č. 2 (2011), s. 301-386. ISSN 1214-1119. E-ISSN 1802-8225
R&D Projects: GA AV ČR IAA301110908
Institutional research plan: CEZ:AV0Z30130516
Keywords : Ordovician * graptolites * mass extinction * biostratigraphy
Subject RIV: DB - Geology ; Mineralogy
Impact factor: 1.099, year: 2011
http://arl-repository.lib.cas.cz/uloziste_av/GLU-S/cav_un_epca-0361335_01.pdf

Rich graptolite fauna described from Katian and Hirnantian of central Nevada suggests that graptolite diversity decreased abruptly at the beginning of Hirnantian glaciation. Faunal turnover reached a peak in the lower part of the extraordinarius Biozone. Ordovician clades were rapidly replaced by normalograptids, presumably evolved in, and invading from, less-temperate higher latitude settings where overall graptolite diversity was extremely low already in pre-glacial times and the old fauna entirely vanished with ongoing glaciation. In tropics, however, elements of the old fauna locally survived and emerged from hypothetical refugia in the upper part of the extraordinarius Zone and, second times, in the persculptus Biozone. The last phase of mass extinction of the long-dominant Ordovician clades took place during postglacial transgression, along with major radiation among normalogratids. Reasons for ultimate extinction of the former fauna may be biological rather than environmental.
Permanent Link: http://hdl.handle.net/11104/0198672