Skip to main content Accessibility help

Graptoloid evolutionary rates track Ordovician–Silurian global climate change



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.


Corresponding author

Author for correspondence:


Hide All
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, 189201.
Alroy, J. 2008. Dynamics of origination and extinction in the marine fossil record. Proceedings of the National Academy of Sciences, USA 105, 11536–42.
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. 5580. Paleontology Society Papers.
Bambach, R. K., Knoll, A. H. & Wang, S. C. 2004. Origination, extinction, and mass depletions of marine diversity. Paleobiology 30 (4), 522–42.
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.
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, 97107.
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), 3963.
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.
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, 6982.
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.
Bulman, O. M. B. 1964. Lower Palaeozoic plankton [presidential address]. Quarterly Journal of the Geological Society of London 120, Part 4(480), 455–76.
Calner, M. 2008. Silurian global events: at the tipping point of climate change. In Mass Extinctions (ed Elewa, A. M. T.), pp. 2158, Springer-Verlag, Heidelberg.
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, 198201.
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.
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.
Cooper, R., Rigby, S., Loydell, D. K. & Bates, D. E. B. 2012. Palaeoecology of the Graptoloidea. Proceedings of the Yorkshire Geological Society 112, 2341.
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. 489524, Elsevier.
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, 185202.
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.
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.
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.
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, 195203.
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.
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, 6281.
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.
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.
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.
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.
Foote, M. 1994. Temporal variation in extinction risk and temporal scaling of exctinction metrics. Paleobiology 20 (4), 424–44.
Foote, M. 2000. Origination and extinction components of taxonomic diversity: general problems. Paleobiology 26(suppl.), 74102.
Foote, M. & Miller, A. I. 2007. Principles of Paleontology. W H Freeman & Co., New York, 354 pp.
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.
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 25431.
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.
Gradstein, F. M, Ogg, J. G., Schmitz, M. D., Ogg, G. M. et al. 2012. The Geologic Time Scale 2012. Elsevier, 1176 pp.
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.
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.
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, 1327.
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, 91102.
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.
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.
Jeppsson, L. & Aldridge, R. J. 2000. Ludlow (late Silurian) oceanic episodes and events. Journal of the Geological Society, London 157, 1137–48.
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.
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. 173224, Springer-Verlag, Berlin.
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, 205220.
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), 197218.
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.
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.
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.
Koren’, T. & Bjerreskov, M. 1999. The generative phase and the first radiation event in the early Silurian monograptid history. Palaeogeography, Palaeoclimatology, Palaeoecology 154, 39.
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.
Le Heron, D. P. 2007. Late Ordovician glacial record of the Anti-Atlas, Morocco. Sedimentary Geology 201, 93110.
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.
Loydell, D. K. 1994. Early Telychian changes in graptoloid diversity and sea level. Geological Journal 29 (4), 355–68.
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.
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.
Maletz, J., Carlucci, J. & Mitchell, C. E. 2009. Graptoloid cladistics, taxonomy and phylogeny. Bulletin of Geosciences 84 (1), 719.
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.
Melchin, M. J. 2008. Restudy of some Ordovician–Silurian boundary graptolites from Anticosti Island, Canada, and their biostratigraphic significance. Lethaia 41, 155–62.
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), 186200.
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.
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.
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), 281309.
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.
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.
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, 389413.
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.
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), 99124.
Munnecke, A., Zhang, Y., Liu, X. & Cheng, J. 2011. Stable carbon isotope stratigraphy in the Ordovician of South China. Palaeogeography, Palaeoclimatology, Palaeoecology 307, 1743.
Peters, S.E., Kelly, D.C. & Fraass, A.J. 2013. Oceanographic controls on the diversity and extinction of planktonic foraminifera. Nature 493 (7432), 398401.
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.
R Development Core Team. 2011. R: A Language and Environment for Statistical Computing. R Foundation for Statistical Computing, Vienna, Austria.
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), 4862.
Raup, D. M. 1985. Mathmematical models of cladogenesis. Paleobiology 11 (1), 4252.
Rickards, R. B. 1975. Palaeoecology of the Graptolithina, an extinct class of the phylum Hemichordata. Biological Reviews of the Cambridge Philosophical Society 50, 397436.
Rigby, S. 1991. Feeding strategies in graptoloids. Palaeontology 34 (4), 797815.
Sadler, P. M. 2004. Quantitative biostratigraphy: achieving finer resolution in global correlation. Annual Review of Earth and Planetary Sciences 32, 187213.
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. 499504, Insituto Geologico y Minero de Espana, Madrid.
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), 887906.
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.
Saltzman, M. R. 2005. Phosphorous, nitrogen, and the redox evolution of the Paleozoic oceans. Geology 33, 573–76.
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.
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.
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.
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, 138.
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.
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), 99109.
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, 99119.
Sheehan, P. M. 2001. The Late Ordovician mass extinction. Annual Review of Earth and Planetary Sciences 29, 331–64.
Štorch, P. 1994. Graptolite biostratigraphy of the Lower Silurian (Llandovery and Wenlock) of Bohemia. Geological Journal 29 (2),137–65.
Štorch, P. 1995. Biotic crises and post-crisis recoveries recorded by Silurian planktonic graptolite faunas of the Barrandian area (Czech Republic). Geolines 3, 5970.
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.
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.
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, 3448.
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.
Urbanek, A. 1993. Biotic crises in the history of Upper Silurian graptoloids: a palaeobiological model. Historical Biology 7, 2950.
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.
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.
Webby, B. D., Droser, M. L. & Paris, F. 2004. The Great Ordovician Biodiversification Event. Columbia University Press, 484 pp.
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.



Altmetric attention score

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed