Integrating carbon isotope excursions into automated stratigraphic correlation: an example from the Silurian of Baltica

 

Authors: Sadler PM

Published in: Bulletin of Geosciences, volume 87, issue 4; pages: 681 - 694; Received 31 July 2011; Accepted in revised form 10 January 2012; Online 16 May 2012

Keywords: biostratigraphy, chemostratigraphy, bentonite, graphic correlation, constrained optimization, Silurian, Baltica,

full text (PDF, 1.34 MB)

Export to RIS

 

Abstract

To correlate the burgeoning volume of biostratigraphic information available from the Silurian rocks of Baltica, it is advantageous to use numerical algorithms. Graphical correlation and related numerical methods routinely incorporate taxon range-ends and bentonites. Bentonites must be matched exactly. Local taxon ranges match or under-represent true ranges and may be stretched to fit hypotheses of correlation. Carbon isotope excursions are better handled as conservative uncertainty intervals – a new data class with properties and freedoms that are the opposite of taxon ranges. Uncertainty intervals match or over-represent truly correlative segments and inflexion points in the local series of isotopic ratios; they may be shrunk to fit correlations between sections. By these means, three fundamentally different kinds of stratigraphic information may be combined in a mutually supportive fashion without over-stating the precision of any of them. When incorporated as uncertainty intervals, Silurian isotopic excursions improve automated construction of inter-regional, ordinal time-lines of taxon first- and last-appearances at both the coarsest and finest resolution. The known succession of a few named excursions helps to stack relatively brief stratigraphic sections into their correct order in longer time-lines. The limits and details of individual excursions support some of the highest-resolution segments of optimized time-lines of individual taxon originations and extinctions. At intermediate scales, local taxon ranges are the unrivalled information source. For the best results, detailed taxon ranges, bentonite analyses and stable isotope time series need to be developed from the same rocks as often as possible.

References

ALROY, J. 2004. Appearance event ordination: a new biochronologic method. Paleobiology 20, 191–207.View article

BERGSTRÖM, S.M., TOPRAK, F.O., HUFF, W.D.&MUNDIL, R. 2008. Implications of a new, biostratigraphically well-controlled, radio-isotopic age for the lower Telychian stage of the Llandovery series (Lower Silurian, Sweden). Episodes 31, 309–314.View article

BRENCHLEY, P. J., CARDEN, G. A., HINTS, L., KALJO, D., MARSHALL, J. D., MARTMA, T., MEIDLA, T. & NOLVAK, J. 2003.High resolution stable isotope stratigraphy of Upper Ordovician sequences: constraints on the timing of bioevents and environmental changes associated with mass extinction and glaciation. Geological Society of America Bulletin 115(1), 89–104.View article

CRAMER, B.D., BRETT, C.E.,MELCHIN, M.J., MÄNNIK, P.,KLEFFNER, M.A., MCLAUGHLIN, P.I., LOYDELL, D.K., MUNNECKE, A., JEPPSSON, L., CORRADINI, C., BRUNTON, F.R. & SALTZMAN, M.R. 2011a. Revised correlation of Silurian Provincial Series of North America with global and regional chronostratigraphic units and ?13Ccarb chemostratigraphy. Lethaia 44, 1700–1716.View article

GRUBB, B.J. & FINNEY, S.C. 1995. Graphic correlation of Middle Ordovician graptolite-rich shales, southern Appalachians: successful application of a technique to inadequate stratigraphic sections, 151–158. In MANN, K.O. & LANE, H.R. (eds) Graphic Correlation. SEPM Special Publication 53.View article

KEMPLE, W.G., SADLER, P.M. & STRAUSS, D.J. 1995. Extending graphic correlation to many dimensions: stratigraphic correlation as constrained optimization, 65–82. In MANN, K.O. & LANE, H.R. (eds) Graphic Correlation. SEPM Special Publication 53.View article

KIIPLI, T. & KALLASTE, T. 2006. Wenlock and uppermost Llandovery bentonites as stratigraphic markers in Estonia, Latvia, and Sweden. GFF 28, 139–146.View article

KIIPLI, T., RADZEVIČIUS, S., KALLASTE, T., MOTUZA, V., JEPPSSON, L. & WICKSTRÖM, L.M. 2008. Wenlock bentonites in Lithuania and correlation with bentonites from sections in Estonia, Sweden, and Norway. GFF 30(4), 203–210.View article

MACLEOD, N. & SADLER, P.M. 1995. Estimating the line of correlation, 51–64. In MANN, K.O. & LANE, H.R. (eds) Graphic Correlation. SEPM Special Publication 53.View article

MALKOWSKI, K., RACKI, G., DRYGANT, D. & SZANIAWSKI, H. 2007. Carbon isotope stratigraphy across the Silurian-Devonian transition in Podolia, Ukraine: evidence for a global biogeochemical perturbation. Geological Magazine 146(5), 674–689.View article

MANN, K.O. & LANE, H.R. 1995. Graphic correlation: a powerful stratigraphic technique comes of age. SEPM Special Publication, 3–13. In MANN, K.O. & LANE, H.R. (eds) Graphic Correlation. SEPM Special Publication 53.View article

NESTOR, H., EINASTO, R., NESTOR, V., MÄRSS, T. & VIIRA, V. 2001. Description of the type section, cyclicity and correlation of the Riksu Formation (Wenlock, Estonia). Proceedings of the Estonian Academy of Sciences, Geology 50(3), 149–173.View article

NESTOR, H. & NESTOR, V. 2002. Upper Llandovery to middle Wenlock (Silurian) lithostratigraphy and chitinozoan biostratigraphy in southwestern Estonia and northernmost Latvia. Proceedings of the Estonian Academy of Sciences, Geology 51(2), 67–87.View article

NESTOR, H. & NESTOR, V. 2009. Upper Llandovery to Middle Wenlock (Silurian) lithostratigraphy and chitinozoan biostratigraphy in southwestern Estonia and northernmost Latvia. Proceedings of the Estonian Academy of Sciences, Geology 51(2), 67–87.View article

SADLER, P.M. 2010. Brute-force biochronology: sequencing paleobiologic first- and last-appearance events by trial and error, 271–289. In ALROY, J. & HUNT, G. (eds) Quantitative Methods in Paleobiology, Paleontological Society Papers 16.View article

SHAW, A.B. 1995. Early history of graphic correlation, 15–19. In MANN, K.O. & LANE, H.R. (eds) Graphic Correlation. SEPM Special Publication 53.View article

STOUGE, S. & RASMUSSEN, J.A. 1996. Upper Ordovician conodonts from Bornholm and possible migration routes in the Palaeotethys ocean. Bulletin of the Geological Society of Denmark 43(1), 54–67.View article

VIIRA, V. & EINASTO, R. 2003. Wenlock-Ludlow boundary beds and conodonts of Saaremaa Island, Estonia. Proceedings of the Estonian Academy of Sciences, Geology 52(4), 213–238.View article