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Stratigraphy and correlations between some Upper Ordovician conodont and graptolite zonal sequences (after Webby et al., 2004). The Amplexograptus manitoulinensis graptolite Zone and corresponding biozones are shaded gray. N. Am. = North American.
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Previously published age determinations for Ordovician formations in the Sofala–Mudgee– Gulgong–Dunedoo region have, with rare exceptions (a record of late Darriwilian conodonts, and identifications of Bolindian graptolites), supported deposition of these strata largely in the Gisbornian. Revision of a conodont fauna from the Sofala Volcanics has l...
Citations
... In fact, conodonts are now the fossil group of choice for biostratigraphic work in rocks dated from Late Cambrian age through the Triassic (Sweet and Donoghue, 2001). Fig. 12. Anatomical reconstruction of a living conodont (from Aldridge et al., 1995) Scolecodonts Scolecodonts, jaws of polychaete worms, are common and diverse microfossils in Ordovician sedimentary rocks (Hints, 2000;Eriksson and Bergman, 2003;Eriksson et al., 2005;Eriksson and Mitchell, 2006). Fossils are usually preserved as individual elements (much like conodont preservation) and are regarded as parts of complex jaw apparatuses ( Fig. 13; Eriksson and Mitchell, 2006). ...
... Fig. 12. Anatomical reconstruction of a living conodont (from Aldridge et al., 1995) Scolecodonts Scolecodonts, jaws of polychaete worms, are common and diverse microfossils in Ordovician sedimentary rocks (Hints, 2000;Eriksson and Bergman, 2003;Eriksson et al., 2005;Eriksson and Mitchell, 2006). Fossils are usually preserved as individual elements (much like conodont preservation) and are regarded as parts of complex jaw apparatuses ( Fig. 13; Eriksson and Mitchell, 2006). Scolecodont fossils are known from Cambrian age rocks but are most abundant in Ordovician, Silurian, and Devonian marine sediments (Hints, 2004). ...
S colecodonts are the mouth pieces of jaw-bearing polychaete annelid worms that occur in abundance as microfossils in the fossil record. Historical scolecodont collections (e.g., Hinde, 1879, 1880, 1882; Stauffer, 1933, 1939; Eller, 1934, 1936, 1940, 1942) are of crucial importance for the taxonomy of fossil polychaetes because they often include taxa with nomenclatural priority over more recently established ones. One significant problem, however, is that most publications dealing with these collections have rudimentary hand-drawings of the fossils that do not allow unambiguous identifications. In this study, all specimens assigned to Arabellites by Hinde (1879) have been re-examined and photographed. Over the years Arabellites has been used for a plethora of morphologically variable scolecodonts of uncertain taxonomic affinity, rendering its status questionable (e.g., Kielan-Jaworowska, 1962, 1966; Kozur, 1970; Jansonius and Craig, 1971; Szaniawski and Wrona, 1973; Eriksson and Bergman, 2003). However, first-hand studies of the type material have allowed new discussions of this genus. Moreover, Glycerites Hinde, 1879, is briefly discussed as it proved to be intimately linked to Arabellites .
The genus Arabellites was established by Hinde (1879) in his paper on Paleozoic, predominantly Ordovician and Silurian, scolecodonts from Canada and Scotland. In the description, Hinde (1879, p. 377) noted that “I propose to include in this genus jaws of widely different form, which have a general resemblance to those of the existing genus Arabella Grube.” The nomenclatural use of already existing generic names of extant polychaetes with the addition of the suffix - ites , for fossil ones, was not uncommon by Hinde and his contemporaries. It has, however, been criticized (e.g., Sylvester, 1959; Kielan-Jaworowska, 1966) because it causes confusion and implies phylogenetic relationships that do not necessarily exist. Moreover, the International …
Articulated polychaete jaw apparatuses and scolecodonts from the uppermost Llandovery-lower Wenlock Ireviken Event strata of Gotland, Sweden, are illustrated and discussed and one new species, Kalloprion kilmisteri, that disappears at datum 2 of the Ireviken Event is described.
Current paleogeographic reconstructions extend Late Ordovician Taconic-derived siliciclastics across the central Canadian craton prior to the terminal Ordovician glacioeustatic lowstand. Revision of the Late Ordovician Dawson Point Formation of the Timiskaming outlier greatly reduces the distribution of these siliciclastics, and documents a greater spread of shallow-water carbonate of Richmondian age. As revised, the Dawson Point Formation contains two informal members: a deep-water graptolitic shale that grades upward into shallow-water siliciclastic redbeds, and an upper member of shallow-water, muddy, crinoidal limestone with interbedded shale, likely representing low-energy shoals on a muddy shelf. Deep-water shale accumulation began in the upper manitoulinensis graptolite Zone following foundering of the regional foreland carbonate platform. Basin development documents a northward-younging (-1 million years) from southern Ontario foreland basins, in keeping with regional tectonic-driven transgression along eastern North America. The shale-to-carbonate succession of the Dawson Point Formation correlates with the Georgian Bay Formation on Manitoulin Island, wherein the upper carbon ate-domin ated divisions of both formations are equivalent to the siliciclastic Queenston Formation of southern Ontario. In absence of additional biostratigraphic information, the upper member of the Dawson Point Formation is likely Richmondian (or late Ashgillian) in age. The revised Late Ordovician history of the Timiskaming outlier may identify a once significant volume of shallow-water carbonate across the central Canadian craton, with related sequestration of carbon dioxide possibly aiding global cooling. Erosion of the carbonate, driven by developing glacioeustatic lowstand conditions, was likely contemporaneous with early Himantian peritidal deposition of the uppermost Queenston Formation in southern Ontario.
