Perspectives on the Great Ordovician Biodiversification Event - local to global patterns

• Published in: Paleobiology
• Main Author: Franeck, Franziska
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2020
• Subjects: Norway; Ny Friesland; Svalbard; Arctic
• Online Access: http://hdl.handle.net/10852/79941; http://urn.nb.no/URN:NBN:no-83041

Biodiversity on Earth has seen many increases and decreases throughout its history. Unrevealing these changes is crucial for understanding mechanisms and dissecting principles behind diversification and extinction events. One of the largest increases in biodiversity throughout the Earth’s history happened around 467 million years ago: the Great Ordovician Biodiversification Event (GOBE). This thesis provides new insights into the GOBE from global, regional, and local perspectives. Paper I quantifies global, Baltic, Laurentian, and onshore-offshore diversification dynamics. Results indicate that origination rates peaked at the Dapingian/ Darriwilian boundary. While both origination and extinction rates appear to be greater in Baltica than in Laurentia, there is no evidence that diversification dynamics were different when comparing onshore and offshore areas. Paper II examines if origination rates are greater for hard substrate taxa prior to the GOBE, as suggested, but not formally tested, by previous studies. Results provide evidence that this may be the case for attaching echinoderms and bryozoans. In paper III the focus is set on faunal shifts within two disparate Ordovician sections. One of them spans the GOBE, while the other one was deposited prior to the GOBE. Results show that shifts in faunal compositions happened across the GOBE section, in contrast to no faunal shifts in the pre-GOBE section. Paper IV zooms out and focuses on biodiversity accumulation over the entire Early Palaeozoic, and examines diversification dynamics and genus longevities. Results show that genera underwent greater turnover in the Cambrian compared to the Ordovician, and that genus longevities increased from c. 5 million years to c. 10 million years between these two periods. Paper V is a geological, and sequence stratigraphic description of an Early to Middle Ordovician section in Ny Friesland, Svalbard, Norway, and provides the basis for Paper III.