The end-Ordovician was an enigmatic interval in the Phanerozoic, known for massive glaciation potentially at elevated CO2 levels, biogeochemical cycle disruptions recorded as large isotope anomalies and a devastating extinction event. Ice-sheet volumes claimed to be twice those of the Last Glacial Maximum paradoxically coincided with oceans as warm as today. Here we argue that some of these rem...

Four metasedimentary zircon populations from different tectonometamorphic units of the Central and the Northern Schwarzwald (Variscan belt, SWGermany) were investigated using SEM, cathodoluminescence and SHRIMP dating. Despite partially strong modifications of primary internal morphologies during Variscan metamorphism at amphibolite (750 C, 0.4– 0.6 GPa) and granulite-facies conditions (950–1,0...

One of the characteristic features of Ordovician tectonism in the east Lachlan Fold Belt is the occurrence of calcalkaline to shoshonitic basalts, which have been recognised as part of an intraoceanic arc environment (Glen et al. 1998), consistent with early tectonic interpretations (Oversby 1971; Scheibner 1973). Aside from typical traceelement abundances of intraoceanic arcs, critical evidenc...

Cladistic parsimony analysis of the trilobite family Homalonotidae Chapman 1980 produced a hypothesis of relatedness for the group. The family consists of three monophyletic subfamilies, one containing Trimerus Green 1832, Platycoryphe Foerste 1919, and Brongniartella Reed 1918; one containing Plaesiacomia Hawle and Corda 1847 and Colpocoryphe Novák in Perer 1918; and one containing Eohomalonot...

Glacial episodes have been linked to Ordovician-Silurian extinction events, but cooling itself may not be solely responsible for these extinctions. Teratological (malformed) assemblages of fossil plankton that correlate precisely with the extinction events can help identify alternate drivers of extinction. Here we show that metal poisoning may have caused these aberrant morphologies during a la...

Cladistic parsimony analysis of the subfamily Deiphoninae Raymond, 1913 was conducted to produce a hypothesis of relationship for the group. The genera Deiphon Barrande, 1850 and Onycopyge Woodward, 1880 are found to be monophyletic, while the genus Sphaerocoryphe Angelin, 1854, as it was previously defined, is paraphyletic. A modified Brooks Parsimony Analysis using the phylogenetic hypothesis...

In order to obtain a Lower Palaeozoic pole for the Armorican Massif and to test the origin of the Ibero-Armorican arc, the Ordovician dolerites of the Crozon peninsula have been palaeomagnetically studied. The samples show a multicomponent magnetization which has been revealed by AF and thermal demagnetization and thoroughly investigated with rock magnetic experiments, polished section examinat...