Graptoloid evolutionary rates track ordovician-Silurian global climate change

Journal article
(Original article)


Publication Details

Author(s): Cooper RA, Munnecke A, Sadler PM, Crampton JS
Journal: Geological Magazine
Publication year: 2014
Volume: 151
Journal issue: 2
Pages range: 349-364
ISSN: 0016-7568
Language: English


Abstract


Graptoloid evolutionary dynamics show a marked contrast from the Ordovician to the Silurian. Subdued extinction and origination rates during the Ordovician give way, during the late Katian, to rates that were highly volatile and of higher mean value through the Silurian, reflecting the significantly shorter lifespan of Silurian species. These patterns are revealed in high-resolution rate curves derived from the CONOP (constrained optimization) scaled and calibrated global composite sequence of 2094 graptoloid species. The end-Ordovician mass depletion was driven primarily by an elevated extinction rate which lasted for c. 1.2 Ma with two main spikes during the Hirnantian. The early Silurian recovery, although initiated by a peak in origination rate, was maintained by a complex interplay of origination and extinction rates, with both rates rising and falling sharply. The global δC curve echoes the graptoloid evolutionary rates pattern; the prominent and well-known positive isotope excursions during the Late Ordovician and Silurian lie on or close to times of sharp decline in graptoloid species richness, commonly associated with extinction rate spikes. The graptoloid and isotope data point to a relatively steady marine environment in the Ordovician with mainly background extinction rates, changing during the Katian to a more volatile climatic regime that prevailed through the Silurian, with several sharp extinction episodes triggered by environmental crises. The correlation of graptoloid species diversity with isotopic ratios was positive in the Ordovician and negative in the Silurian, suggesting different causal linkages. Throughout the history of the graptoloid clade all major depletions in species richness except for one were caused by elevated extinction rate rather than decreased origination rate. © Cambridge University Press 2013.


FAU Authors / FAU Editors

Munnecke, Axel Prof. Dr.
Professur für Paläontologie (Schwerpunkt Faziesanalyse)


External institutions
University of California, Riverside (UCR)


How to cite

APA:
Cooper, R.A., Munnecke, A., Sadler, P.M., & Crampton, J.S. (2014). Graptoloid evolutionary rates track ordovician-Silurian global climate change. Geological Magazine, 151(2), 349-364. https://dx.doi.org/10.1017/S0016756813000198

MLA:
Cooper, Roger A., et al. "Graptoloid evolutionary rates track ordovician-Silurian global climate change." Geological Magazine 151.2 (2014): 349-364.

BibTeX: 

Last updated on 2018-14-12 at 09:08