Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (9) Citing Articles via Google Scholar Google Scholar Articles by Lees, D. C. Articles by Cocks, L. R. M. Search for Related Content GeoRef GeoRef Citation

Quantifying paleogeography using biogeography: a test case for the Ordovician and Silurian of Avalonia based on brachiopods and trilobites

¹ D. C. Lees, R. A. Fortey, and L. R. M. Cocks. Department of Palaeontology, The Natural History Museum, Cromwell Road, South Kensington, London SW7 5BD, United Kingdom. dcl{at}nhm.ac.uk

Despite substantial advances in plate tectonic modeling in the last three decades, the postulated position of terranes in the Paleozoic has seldom been validated by faunal data. Fewer studies still have attempted a quantitative approach to distance based on explicit data sets. As a test case, we examine the position of Avalonia in the Ordovician (Arenig, Llanvirn, early Caradoc, and Ashgill) to mid-Silurian (Wenlock) with respect to Laurentia, Baltica, and West Gondwana. Using synoptic lists of 623 trilobite genera and 622 brachiopod genera for these four plates, summarized as Venn diagrams, we have devised proportional indices of mean endemism (ME, normalized by individual plate faunas to eliminate area biogeographic effects) and complementarity (C) for objective paleobiogeographic comparisons. These can discriminate the relative position of Avalonia by assessing the optimal arrangement of inter-centroid distances (measured as great circles) between relevant pairs of continental masses. The proportional indices are used to estimate the "goodness-of-fit" of the faunal data to two widely used dynamic plate tectonic models for these time slices, those of Smith and Rush (1998) and Ross and Scotese (1997). Our faunal data are more consistent with the latter model, which we use to suggest relationships between faunal indices for the five time slices and new rescaled inter-centroid distances between all six plate pairs. We have examined linear and exponential models in relation to continental separation for these indices. For our generic data, the linear model fits distinctly better overall. The fits of indices generated by using independent trilobite and brachiopod lists are mostly similar to each other at each time slice and for a given plate, reflecting a common biogeographic signal; however, the indices vary across the time slices. Combining groups into the same matrix in a "total evidence" analysis performs better still as a measure of distance for mean endemism in the "Scotese" plate model. Four-plate mean endemism performs much better than complementarity as an indicator of pairwise distance for either plate model in the test case.

This article has been cited by other articles:

				J. B. Murphy Geological evolution of middle to late Paleozoic rocks in the Avalon terrane of northern mainland Nova Scotia, Canadian Appalachians: A record of tectonothermal activity along the northern margin of the Rheic Ocean in the Appalachian-Caledonide orogen Geological Society of America Special Papers, January 1, 2007; 423(0): 413 - 435. [Abstract] [Full Text] [PDF]

				T. Servais, A. Blieck, M. Caridroit, X. Chen, F. Paris, and M. F. Tortello The importance of plankton and nekton distributions in Ordovician palaeogeographical reconstructions Bulletin de la Societe Geologique de France, November 1, 2005; 176(6): 531 - 543. [Abstract] [Full Text] [PDF]

				J. G. Meert, J.G. Meert, and B.S. Lieberman A palaeomagnetic and palaeobiogeographical perspective on latest Neoproterozoic and early Cambrian tectonic events Journal of the Geological Society, May 1, 2004; 161(3): 477 - 487. [Abstract] [Full Text] [PDF]