Hostname: page-component-78c5997874-xbtfd Total loading time: 0 Render date: 2024-11-10T19:27:19.438Z Has data issue: false hasContentIssue false
  • English
  • Français

Graptoloid evolutionary rates track Ordovician–Silurian global climate change

Published online by Cambridge University Press:  07 June 2013

ROGER A. COOPER ,
PETER M. SADLER ,
AXEL MUNNECKE  and
JAMES S. CRAMPTON
ROGER A. COOPER*
Affiliation:
GNS Science, PO Box 30368 Lower Hutt, New Zealand
PETER M. SADLER
Affiliation:
Department of Earth sciences, University of California, Riverside, CA 92521, USA
AXEL MUNNECKE
Affiliation:
GeoZentrum Nordbayern, Fachgruppe Paläoumwelt, University Erlangen-Nuremberg, Loewenichstraβe 28, Erlangen D-91054, Germany
JAMES S. CRAMPTON
Affiliation:
GNS Science, PO Box 30368 Lower Hutt, New Zealand
*
†Author for correspondence: r.cooper@gns.cri.nz
Get access Rights & Permissions [Opens in a new window]

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 δ13C 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.

Keywords

climatic forcingdiversityextinctionplankton
Type
Original Articles
Information
Geological Magazine , Volume 151 , Issue 2 , March 2014 , pp. 349 - 364
Copyright
Copyright © Cambridge University Press 2013 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Ainsaar, L., Kaljo, D., Martma, T., Meidla, T., Männik, P., Nõlvak, J. & Tinn, O. 2010. Middle and Upper Ordovician carbon isotope chemostratigraphy in Baltoscandia: a correlation standard and clues to environmental history. Palaeogeography, Palaeoclimatology, Palaeoecology 294, 189–201.Google Scholar
Alroy, J. 2008. Dynamics of origination and extinction in the marine fossil record. Proceedings of the National Academy of Sciences, USA 105, 11536–42.Google Scholar
Alroy, J. 2010. Fair sampling of taxonomic richness and unbiased estimation of origination and extinction rates. In Quantitative Methods in Paleobiology, Paleontological Society Short Course, October 30th 2010 (eds Alroy, J. & Hunt, G.), pp. 55–80. Paleontology Society Papers.Google Scholar
Bambach, R. K., Knoll, A. H. & Wang, S. C. 2004. Origination, extinction, and mass depletions of marine diversity. Paleobiology 30 (4), 522–42.Google Scholar
Bapst, D. W., Melchin, M. J., Sheets, H. D. & Mitchell, C. E. 2012. Graptoloid diversity and disparity became decoupled during the Ordovician mass extinction. Proceedings of the National Academy of Sciences 109 (9), 3428–33.CrossRefGoogle ScholarPubMed
Bergström, S. M., Chen, X., Gutéirrez-Marco, J. C. & Dronov, A. 2009. The new chronostratigraphic classification of the Ordovician System and its relations to major regional series and stages and to δ13C chemostratigraphy. Lethaia 42, 97–107.Google Scholar
Bergström, S. M., Lehnert, O., Calner, M. & Joachimski, M. M. 2012. A new upper Middle Ordovician–Lower Silurian drillcore standard succession from Borenshult in Östergötland, southern Sweden: Significance of δ13C chemostratigraphy. GFF 134 (1), 39–63.Google Scholar
Bickert, T. 2006. Influence of geochemical processes on stable isotope distribution in marine sediments, In Marine Geochemistry (eds Schulz, H. D. & Zabel, M.), pp. 339–69, 2nd edition, Springer, Berlin.Google Scholar
Brenchley, P. J., Carden, G. A. F. & Marshall, J. D. 1995. Environmental changes associated with the ‘First Strike’ of the Late Ordovician mass extinction. Modern Geology 50, 69–82.Google Scholar
Buggisch, W., Keller, M. & Lehnert, O. 2003. Carbon isotope record of Late Cambrian to Early Ordovician carbonates of the Argentine Precordillera. Palaeogeography, Palaeoclimatology, Palaeoecology 195, 357–73.Google Scholar
Bulman, O. M. B. 1964. Lower Palaeozoic plankton [presidential address]. Quarterly Journal of the Geological Society of London 120, Part 4(480), 455–76.Google Scholar
Calner, M. 2008. Silurian global events: at the tipping point of climate change. In Mass Extinctions (ed Elewa, A. M. T.), pp. 21–58, Springer-Verlag, Heidelberg.Google Scholar
Came, R. E., Eiler, J. M., Veizer, J., Azmy, K., Brand, U. & Weidman, C. R. 2007. Coupling of surface temperatures and atmospheric CO2 concentrations during the Palaeozoic era. Nature 449, 198–201.CrossRefGoogle ScholarPubMed
Chen, X., Melchin, M. J., Sheets, H. D., Mitchell, C. E. & Fan, J.-X. 2005. Patterns and processes of latest Ordovician graptolite extinction and recovery based on the data from South China. Journal of Paleontology 79 (5), 842–61.Google Scholar
Chen, X., Rong, J. Y., Fan, J. X., Zhan, R. B., Mitchell, C. E., Harper, D. A. T., Melchin, M. J., Peng, P., Finney, S. C. & Wang, X. F. 2006. The global boundary stratotype section and point (GSSP) for the base of the Hirnantian Stage (the uppermost of the Ordovician System). Episodes 29, 183–96.Google Scholar
Cooper, R., Rigby, S., Loydell, D. K. & Bates, D. E. B. 2012. Palaeoecology of the Graptoloidea. Proceedings of the Yorkshire Geological Society 112, 23–41.Google Scholar
Cooper, R. A. & Sadler, P. M. 2012. The Ordovician Period. With a contribution by F. M. Gradstein & O. Hammer. In The Geologic Time Scale 2012 (eds Gradstein, F. M., Ogg, J. G., Schmitz, M. & Ogg, G.), pp. 489–524, Elsevier.Google Scholar
Cramer, B. D., Brett, C. E., Melchin, M.J., Männik, P., Kleffner, M., McLaughlan, P. I., Loydell, D., Munnecke, A., Jeppsson, L., Corradini, C., Brunton, F. R. & Saltzman, M. R. 2011. Revised correlation of Silurian provincial series of north America with global regional chronostratigraphic units and δ13Ccarb chemostratigraphy. Lethaia 44, 185–202.Google Scholar
Cramer, B. D., Condon, D. J., Söderlund, U., Marshall, C., Worton, G. J., Thomas, A. T., Calner, M., Ray, D. C., Perrier, V., Boomer, I., Patchett, P. J. & Jeppsson, L. 2012. U-Pb (zircon) age constraints on the timing and duration of Wenlock (Silurian) paleocommunity collapse and recovery during the ‘Big Crisis’. Geological Society of America Bulletin 124, 1841–57.Google Scholar
Cramer, B. D., Loydell, D. K., Samtleben, C., Munnecke, A., Kaljo, D., Männik, P., Martma, T., Jeppsson, L., Kleffner, M. A., Barrick, J. E., Johnson, C. A., Emsbo, P., Joachimski, M. M., Bickert, T. & Saltzman, M. R. 2010. Testing the limits of Paleozoic chronostratigraphic correlation via high-resolution (<500,000yrs) integrated conodont, graptolite, and carbon isotope (δ13Ccarb) biochemostratigraphy across the Llandovery-Wenlock boundary: is a unified Phanerozoic timescale achievable? Geological Society of America Bulletin 122, 1700–16.Google Scholar
Cramer, B. D. & Munnecke, A. 2008. Early Silurian positive δ13C excursions and their relationship to glaciations, sea-level changes and extinction events: discussion. Geological Journal 43, 517–19.Google Scholar
Cramer, B. D. & Saltzman, M. R. 2007. Early Silurian paired δ13Ccarb and δ13Corg analyses from the Midcontinent of North America: implications for paleoceanography and paleoclimate. Palaeogeography, Palaeoclimatology, Palaeooceanology 256, 195–203.Google Scholar
Delabroye, A. & Vecoli, M. 2010. The end-Ordovician glaciation and the Hirnantian Stage: a global review and questions about Late Ordovician event stratigraphy. Earth-Science Reviews 98, 269–82.Google Scholar
Díaz-MartÍnez, E. & Grahn, Y. 2007. Early Silurian glaciation along the western margin of Gondwana (Peru, Bolivia and northern Argentina): palaeogeographic and geodynamic setting. Palaeogeography, Palaeoclimatology, Palaeoecology 245, 62–81.CrossRefGoogle Scholar
Finnegan, S., Bergmann, K., Eiler, J. M., Jones, D. S., Fike, D. A., Eisenman, I., Hughes, N. C., Tripati, A. K. & Woodward, W. F. 2011. The magnitude and duration of Late Ordovician-Early Silurian glaciation. Science 331, 903–6.Google Scholar
Finney, S. C. & Berry, W. B. N. 1997. New perspectives on graptolite distributions and their use as indicators of platform margin dynamics. Geology 25 (10), 919–22.Google Scholar
Finney, S. C., Berry, W. B. N. & Cooper, J. D. 2007. The influence of denitrifying seawater on graptolite extinction and diversification during the Hirnantian (latest Ordovician) mass extinction event. Lethaia 40, 281–91.CrossRefGoogle Scholar
Finney, S. C., Berry, W. B. N., Cooper, J. D., Ripperdan, R. L., Sweet, W.C., Jacobson, S. R., Soufiane, A., Achab, A. & Noble, P. J. 1999. Late Ordovician mass extinction: a new perspective from stratigraphic sections in central Nevada. Geology 27, 215–18.Google Scholar
Foote, M. 1994. Temporal variation in extinction risk and temporal scaling of exctinction metrics. Paleobiology 20 (4), 424–44.Google Scholar
Foote, M. 2000. Origination and extinction components of taxonomic diversity: general problems. Paleobiology 26(suppl.), 74–102.Google Scholar
Foote, M. & Miller, A. I. 2007. Principles of Paleontology. W H Freeman & Co., New York, 354 pp.Google Scholar
Ghienne, J. F. 2003. Late Ordovician sedimentary environments, glacial cycles, and post-glacial transgression in the Taoudeni Basin, West Africa. Palaeogeography, Palaeoclimatology, Palaeoecology 189, 117–45.CrossRefGoogle Scholar
Giles, P. S. 2012. Low-latitude Ordovician to Triassic brachiopod habitat temperatures (BHTs) determined from δ18O(brachiopod calcite): a cold hard look at ice-house tropical oceans. Palaeogeography, Palaeoclimatology, Palaeoecology 317/813 25–431.Google Scholar
Goldman, D., Mitchell, W. I., Melchin, M. J., Fan, J.-X., Wu, S.-Y. & Sheets, H. D. 2011. Biogeography and mass extinction: extirpation and re-invasion of Normalograptus species (Graptolithina) in the Late Ordovician paleotropics. Proceedings of the Yorkshire Geological Society 58 (4), 227–46.Google Scholar
Gradstein, F. M, Ogg, J. G., Schmitz, M. D., Ogg, G. M. et al. 2012. The Geologic Time Scale 2012. Elsevier, 1176 pp.Google Scholar
Gutiérrez-Marco, J. C., Lenz, A. C., Robardet, M. & Picarra, J. M. 1996. Wenlock-Ludlow graptolite biostratigraphy and extinction: A reassessment from the southwestern Iberian Peninsula (Spain and Portugal). Canadian Journal of Earth Sciences 33 (5), 656–63.Google Scholar
Hayes, J. M., Strauss, H. & Kaufman, A. J. 1999. The abundance of 13C in marine organic matter and isotopic fractionation in the global biogeochemical cycle of carbon during the past 800 Ma. Chemical Geology 161, 103–25.CrossRefGoogle Scholar
Hayward, B. W., Ashwag, T. S., Kolodziej, A., Crundwell, M. P., Steph, S., Scott, G. H., Neil, H. L., Bostock, H. C., Carter, L. & Grenfell, H. R. 2012. Planktic foraminifera-based sea-surface temperature record in the Tasman Sea and history of the Subtropical Front around New Zealand, over the last one million years. Marine Micropaleontology 82–3, 13–27.Google Scholar
Hingaga, K. R., Arthur, M. A., Pilson, M. E. Q. & Whitaker, D. 1994. Carbon isotope fractionation by marine phytoplankton in culture: the effects of CO2 concentration, pH, temperature, and species. Global Biogeochemical Cycles 8, 91–102.Google Scholar
Jaeger, H. 1991. Neue Standard-Graptolithenzonenfolge nach der ‘Großen Krise’ an der Wenlock/Ludlow-Grenze (Silur). Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 182 (3), 303–54.Google Scholar
Jeppsson, L. 1997. The anatomy of the mid-early Silurian Ireviken Event and a scenario for P-S events. In Paleontological Events: Stratigraphic, Ecologic, and Evolutionary Implications (eds Brett, C. E. & Baird, G. C.), pp. 451–92, Columbia University Press, New York.Google Scholar
Jeppsson, L. & Aldridge, R. J. 2000. Ludlow (late Silurian) oceanic episodes and events. Journal of the Geological Society, London 157, 1137–48.Google Scholar
Jeppsson, L., Talent, J. A., Mawson, R., Simpson, A. J., Andrew, A. S., Calner, M., Whitford, D. J., Trotter, J. A., Sandström, O. & Calcon, H.-J. 2007. High-resolution Late Silurian correlations between Gotland, Sweden, and the Broken River region, NE Australia: lithologies, conodonts and isotopes. Palaeogeography, Palaeoclimatology, Palaeoecology 245, 115–37.Google Scholar
Kaljo, D., Boucot, A. J., Corfield, R.M., Le Herisse, A., Koren’, T.N., Kříž, J., Männik, P., Märss, T., Nestor, V., Shaver, R. H., Siveter, D. J. & Viira, V. 1995. Silurian bioevents. In Global Events and Event Stratigraphy in the Phanerozoic (ed Walliser, O. H.), pp. 173–224, Springer-Verlag, Berlin.Google Scholar
Kaljo, D., Grytsenko, V., Martma, T. & Motus, M. A. 2007. Three global carbon isotope shifts in the Silurian of Podolia (Ukraine): stratigraphical implications. Estonian Journal of Earth Sciences 56, 205–220.CrossRefGoogle Scholar
Kaljo, D., Hints, L., Männik, P. & Nõlvak, J. 2008. The succession of Hirnantian events based on data from Baltica: brachiopods, chitinozoans, conodonts, and carbon isotopes. Estonian Journal of Earth Sciences 57 (4), 197–218.Google Scholar
Kaljo, D. & Martma, T. 2011. Carbon isotope trend in the Mirny Creek area, NE Russia, its specific features and possible implications of the uppermost Ordovician stratigraphy. In Ordovician of the World (eds Gutiérrez-Marco, J. C., Rábano, I. & García-Bellido, D.), pp. 267–73, Cuadernos del Museo Geominero, 14, Instituto Geológico y Minero de España, Madrid.Google Scholar
Koren’, T. N. 1987. Graptolite dynamics in Silurian and Devonian time. In Third International Graptolite Conference ‘Palaeobiology and Geological Use of Graptolites’, Reitzels Forlag Hans, Copenhagen, Denmark.Google Scholar
Koren’, T. N. 1991. The lundgreni extinction event in central Asia and its bearing on graptolite biochronology within the Homerian. Proceedings of the Estonian Academy of Sciences, Geology 40 (2), 74–8.CrossRefGoogle Scholar
Koren’, T. & Bjerreskov, M. 1999. The generative phase and the first radiation event in the early Silurian monograptid history. Palaeogeography, Palaeoclimatology, Palaeoecology 154, 3–9.Google Scholar
Kozlowski, W. & Munnecke, A. 2010. Stable carbon isotope development and sea-level changes during the Late Ludlow (Silurian) of the Lysogóry region (Rzepin section, Holy Cross Mountains, Poland). Facies 56, 615–33.Google Scholar
Le Heron, D. P. 2007. Late Ordovician glacial record of the Anti-Atlas, Morocco. Sedimentary Geology 201, 93–110.Google Scholar
Lenz, A. C. 1993. Late Wenlock-Ludlow (Silurian) graptolite extinction, evolution, and biostratigraphy: perspectives from Arctic Canada. Canadian Journal of Earth Sciences 30 (3), 491–8.Google Scholar
Loydell, D. K. 1994. Early Telychian changes in graptoloid diversity and sea level. Geological Journal 29 (4), 355–68.Google Scholar
Loydell, D. 2007. Early Silurian positive δ13C excursions and their relationship to glaciations, sea-level changes and extinction events. Geological Journal 42 (5), 531–46.Google Scholar
Loydell, D. K., Männik, P. & Nestor, V. 2003. Integrated biostratigraphy of the lower Silurian of the Aizpute-41 core, Latvia. Geological Magazine 140, 205–29.Google Scholar
Maletz, J., Carlucci, J. & Mitchell, C. E. 2009. Graptoloid cladistics, taxonomy and phylogeny. Bulletin of Geosciences 84 (1), 7–19.Google Scholar
Manda, S., Štorch, P., Slavík, L., Frýda, J., Křiž, J. & Tásaryová, Z. 2012. The graptolite, conodont and sedimentary record through the late Ludlow Kozlowskii Event (Silurian) in the shale-dominated succession of Bohemia. Geological Magazine 149 (3), 507–31.Google Scholar
Melchin, M. J. 2008. Restudy of some Ordovician–Silurian boundary graptolites from Anticosti Island, Canada, and their biostratigraphic significance. Lethaia 41, 155–62.Google Scholar
Melchin, M. J. & Holmden, C. 2006. Carbon isotope chemostratigraphy in Arctic Canada: sea-level forcing of carbonate platform weathering and implications for Hirnantian global correlation. Palaeogeography, Palaeoclimatology, Palaeoecology 234 (2–4), 186–200.Google Scholar
Melchin, M. J., Koren’, T. N. & Štorch, P. 1998. Global diversity and survivorship patterns of Silurian Graptoloids. In Silurian Cycles: Linkages of Dynamic Stratigraphy with Atmospheric, Oceanic and Tectonic Changes (eds Landing, E. & Johnson, M. E.), pp. 165–82. New York State Museum Bulletin.Google Scholar
Melchin, M. J. & Mitchell, C. E. 1991. Late Ordovician extinction in the Graptoloidea. In Advances in Ordovician Geology (eds Barnes, C. R. & Williams, S. H.), pp. 143–56. Geological Survey of Canada, Ottawa.Google Scholar
Melchin, M. J., Mitchell, W. I., Nacyk-Cameron, A., Fan, J. X. & Loxton, J. 2011. Phylogeny and adaptive radiation of the Neograptina (graptoloida) during the Hirnantian mass extinction and Silurian recovery. Proceedings of the Yorkshire Geological Society 58 (4), 281–309.Google Scholar
Melchin, M. J., Sadler, P. M. & Cramer, B. D. 2012. The Silurian Period. With contributions by R. Cooper, O. Hammer and F. M. Gradstein. In The Geological Time Scale 2012 (eds Gradstein, F. M., Ogg, J. G., Schmitz, M., Ogg, G. et al.), pp. 525–59, Elsevier.Google Scholar
Mitchell, W. I., Goldman, D., Klosterman, S. L., Maletz, J., Sherwin, L. & Melchin, M. J. 2007. Phylogeny of the Diplograptoidea. Acta Palaeotologica Polonica 46 (Suppl.), 332–9.Google Scholar
Munnecke, A., Calner, M., Harper, D. A. T. & Servais, T. 2010. Ordovician and Silurian sea-water chemistry, sea level, and climate: a synopsis. Palaeogeography, Palaeoclimatology, Palaeoecology 296, 389–413.Google Scholar
Munnecke, A., Delabroye, A., Servais, T., Vandenbroucke, T. R. A. & Vecoli, M. 2012. Systematic occurrences of malformed (teratological) acritarchs in the run-up of Early Palaeozoic δ13C isotope excursions. Palaeogeography, Palaeoclimatology, Palaeoecology 367–8, 137–46.Google Scholar
Munnecke, A., Samtleben, C. & Bickert, T. 2003. The Ireviken Event in the lower Silurian of Gotland, Sweden: relation to similar Palaeozoic and Proterozoic events. Palaeogeography, Palaeoclimatology, Palaeoecology 195 (1–2), 99–124.Google Scholar
Munnecke, A., Zhang, Y., Liu, X. & Cheng, J. 2011. Stable carbon isotope stratigraphy in the Ordovician of South China. Palaeogeography, Palaeoclimatology, Palaeoecology 307, 17–43.Google Scholar
Peters, S.E., Kelly, D.C. & Fraass, A.J. 2013. Oceanographic controls on the diversity and extinction of planktonic foraminifera. Nature 493 (7432), 398–401.Google Scholar
Pucéat, E., Joachimski, M. M., Bouilloux, A., Monna, F., Bonin, A., Motreuil, S., Morinière, P. & Hénard, S. 2010. Revised phosphate–water fractionation equation reassessing paleotemperatures derived from biogenic apatite. Earth and Planetary Science Letters 298, 135–42.Google Scholar
R Development Core Team. 2011. R: A Language and Environment for Statistical Computing. R Foundation for Statistical Computing, Vienna, Austria.Google Scholar
Rasmussen, C. M. O. & Harper, D. A. T. 2011. Did the amalgamation of continents drive the end Ordovician mass extinctions? Palaeogeography, Palaeoclimatology, Palaeoecology 311 (2), 48–62.Google Scholar
Raup, D. M. 1985. Mathmematical models of cladogenesis. Paleobiology 11 (1), 42–52.Google Scholar
Rickards, R. B. 1975. Palaeoecology of the Graptolithina, an extinct class of the phylum Hemichordata. Biological Reviews of the Cambridge Philosophical Society 50, 397–436.Google Scholar
Rigby, S. 1991. Feeding strategies in graptoloids. Palaeontology 34 (4), 797–815.Google Scholar
Sadler, P. M. 2004. Quantitative biostratigraphy: achieving finer resolution in global correlation. Annual Review of Earth and Planetary Sciences 32, 187–213.Google Scholar
Sadler, P. M. & Cooper, R. A. 2011. Graptoloid evolutionary rates: sharp contrast between Ordovician and Silurian. In Ordovician of the World. 11th International Symposium on the Ordovician System (eds Gutiérrez-Marco, J.-C., Rabano, I. & Garcia-Bellido, D.), pp. 499–504, Insituto Geologico y Minero de Espana, Madrid.Google Scholar
Sadler, P. M., Cooper, R. A. & Melchin, M. J. 2009. High-resolution, early Paleozoic (Ordovician-Silurian) timescales. Geological Society of America Bulletin 121 (5/6), 887–906.Google Scholar
Sadler, P. M., Cooper, R. A. & Melchin, M. J. 2011. Sequencing the graptolite clade: building a global diversity curve from local range-charts, regional composites and global time-lines. Proceedings of the Yorkshire Geological Society 58 (4), 329–43.Google Scholar
Saltzman, M. R. 2005. Phosphorous, nitrogen, and the redox evolution of the Paleozoic oceans. Geology 33, 573–76.CrossRefGoogle Scholar
Saltzman, M. R. & Thomas, E. 2012. Carbon isotope stratigraphy. In The Geologic Time Scale 2012 (eds Gradstein, F. M., Ogg, J. G., Schmitz, M. D., Ogg, G. M. et al.), pp. 207–32. Elsevier.Google Scholar
Saltzman, M. R. & Young, S. A. 2005. Long-lived glaciation in the Late Ordovician? Isotopic and sequence-stratigraphic evidence from western Laurentia. Geology 33, 109–12.Google Scholar
Samtleben, C., Munnecke, A., Bickert, T. & Pätzold, J. 1996. The Silurian of Gotland (Sweden): facies interpretation based on stable isotopes in brachiopod shells. Geologische Rundschau 85, 278–92.Google Scholar
Samtleben, C., Munnecke, A. & Bickert, T. 2000. Development of facies and C/O-isotopes in transects through the Ludlow of Gotland: evidence for global and local influences on a shallow-marine environment. Facies 43, 1–38.Google Scholar
Sepkoski, J. J. 1995. The Ordovician radiations: diversification and extinction shown by global genus-level taxonomic data. In Ordovician Odyssey: Short Papers for the Seventh International Symposium on the Ordovician System (eds Cooper, J. D., Droser, M. L. & Finney, S. C.), pp. 393–6, Pacific Section Society for Sedimentary Geology (SEPM), Fullerton, California.Google Scholar
Servais, T., Lehnert, O., Li, J., Mullins, G. L., Munnecke, A., Nützel, A. & Vecoli, M. 2008. The Ordovician Biodiversification: revolution in the oceanic trophic chain. Lethaia 41 (2), 99–109.Google Scholar
Servais, T., Owen, A. W., Harper, D.A.T., Kröger, B. & Munnecke, A. 2010. The Great Ordovician Biodiversification Event (GOBE): the palaeoecological dimension. Palaeogeography, Palaeoclimatology, Palaeoecology 294, 99–119.Google Scholar
Sheehan, P. M. 2001. The Late Ordovician mass extinction. Annual Review of Earth and Planetary Sciences 29, 331–64.Google Scholar
Štorch, P. 1994. Graptolite biostratigraphy of the Lower Silurian (Llandovery and Wenlock) of Bohemia. Geological Journal 29 (2),137–65.Google Scholar
Štorch, P. 1995. Biotic crises and post-crisis recoveries recorded by Silurian planktonic graptolite faunas of the Barrandian area (Czech Republic). Geolines 3, 59–70.Google Scholar
Štorch, P., Mitchell, C. E., Finney, S. C. & Melchin, M. J. 2011. Uppermost Ordovician (upper Katian-Hirnantian) graptolites of north-central Nevada, USA. Bulletin of Geosciences 86 (2), 301–86.Google Scholar
Trotter, J. A., Williams, I. S., Barnes, C. R., Lecuyer, C. & Nicoll, R. S. 2008. Did cooling oceans trigger Ordovician biodiversification? Evidence from conodont thermometry. Science 321, 550–4.Google Scholar
Turner, B. R., Armstrong, H. A., Wilson, C. R. & Makhlouf, I. M. 2012. High frequency eustatic sea-level changes during the Middle to Early Ordovician of Southern Jordan: indirect evidence for a Darriwilian Ice Age in Gondwana. Sedimentary Geology 251–2, 34–48.Google Scholar
Underwood, C. J., Crowley, S. F., Marshall, J. D. & Brenchley, P. J. 1997. High-resolution carbon isotope stratigraphy of the basal Silurian Stratotype (Dob's Linn, Scotland) and its global correlation. Journal of the Geological Society 154, 709–18.Google Scholar
Urbanek, A. 1993. Biotic crises in the history of Upper Silurian graptoloids: a palaeobiological model. Historical Biology 7, 29–50.Google Scholar
Vandenbroucke, T. R. A., Armstrong, H. A., Williams, M., Sabbe, K., Zalasiewicz, J. A., Nolvak, J. & Verniers, J. 2010. Epipelagic chitinozoan biotopes map a steep latitudinal temperature gradient for earliest Late Ordovician seas: implications for a cooling Late ordovician climate. Palaeogeography, Palaeoclimatology, Palaeoecology 294, 202–19.Google Scholar
Vecoli, M., Riboulleau, A. & Versteegh, G. J. M. 2009. Palynology, organic geochemistry and carbon isotope analysis of a latest Ordovician through Silurian clastic succession from borehole Tt1, Ghadamis Basin, southern Tunisia, North Africa: palaeoenvironmental interpretation. Palaeogeography, Palaeoclimatology, Palaeoecology 273, 378–94.Google Scholar
Webby, B. D., Droser, M. L. & Paris, F. 2004. The Great Ordovician Biodiversification Event. Columbia University Press, 484 pp.Google Scholar
Zhang, T.-G., Trela, W., Jiang, S.-Y., Nielsen, J. K. & Shen, Y. 2011. Major oceanic redox condition change correlated with the rebound of marine animal diversity during the Late Ordovician. Geology 39 (7), 675–8.Google Scholar