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This contribution reviews the newly revised biostratigraphy of Middle–Upper Ordovician marine shelf successions from the Junee–Narromine Volcanic Belt in central New South Wales, based on conodont studies from four areas covering the northern, central and southern sectors of the Belt. Seven conodont biozones ranging from the middle Darriwilian (Histiodella holodentata-Eoplacognathus pseudoplanus Biozone) to the lower Katian (Taoqupognathus blandus Biozone) are recognized in the Billabong Creek Formation exposed in the Gunningbland area. This includes the first known biostratigraphic succession in Australia that extends continuously from the middle Darriwilian to the basal Sandbian. These new data are crucial for a better understanding of the geological evolution of this region in central New South Wales, and for the enhanced correlation of Ordovician rocks throughout the Macquarie Volcanic Province, which hosts substantial porphyry Cu–Au mineral deposits. [ABSTRACT FROM AUTHOR]

Ordovician conodonts representing 28 genera and 28 named and three unnamed species were identified from 740 chert and siliceous siltstone spot samples (>3 000 thin sections) from deep-water turbiditic sequences of the Lachlan Orogen in central and southern New South Wales, Australia. Based on these faunas, a new conodont biozonal scheme has been established to divide the Ordovician turbiditic successions of the Lachlan Orogen into 12 superbiozones and biozones. They are (in ascending order) the Paracordylodus gracilis Superbiozone (including the Prioniodus oepiki Biozone), Periodon flabellum Superbiozone (including the Oepikodus evae Biozone in the lower part), Periodon hankensis Biozone, Periodon aculeatus Superbiozone (including the Histiodella labiosa, Histiodella holodentata, Histiodella kristinae, Pygodus serra and Pygodus anserinus biozones) and the Periodon grandis Biozone. The Pygodus anserinus Biozone is divided further into the lower and upper subbiozones. This new conodont biozonation scheme spanning the upper Tremadocian to middle Katian interval permits precise age-dating and correlation of deep-water siliciclastic rocks that characterize the Ordovician Deep-Sea Realm regionally and internationally. [ABSTRACT FROM AUTHOR]

Oxygen isotopic ratios of conodont apatite can be a robust proxy for sea surface temperatures and provide important constraints on global climate. The oxygen isotopic composition of seawater is a function of local, regional, and global processes. To determine the relative importance of regional and local influences (and therefore make global inferences), it is necessary to document high resolution δ18O records from a variety of paleogeographic and environmental settings. Available conodont δ18Ophos records for the Ordovician, however, are biased towards North American samples, often come from multiple discontinuous sections, and tend to focus only on specific intervals (e.g., the Katian Stage). To extend the paleogeographic range and test the generality of Ordovician δ18Ophos trends, we measured δ18Ophos values from species-specific conodont assemblages from New South Wales, Australia. Our results from this region show that Early Ordovician δ18Ophos averages are ∼2‰ lower than those in the Late Ordovician and are consistently ∼2.5‰ lower relative to values reported from North America and central Australia. This offset suggests that regional environmental conditions influenced the δ18Ophos record from New South Wales. Despite evidence suggesting a departure from open ocean conditions, our results still show increasing δ18Ophos values through the Early Ordovician in agreement with documented trends from other regions. This similarity suggests that the δ18Ophos increase (documented on separate continental blocks and different environmental settings) reflects global cooling rather than a change in the oxygen isotopic composition of the Ordovician oceans and strengthens the argument that biodiversification and climate change in the first half of the Ordovician were related. [ABSTRACT FROM AUTHOR]

Late Ordovician conodont fauna from allochthonous limestones in the Wairuna Formation of the Broken River Province, north Queensland, contains 23 species typical of the deeper water Protopanderodus biofacies. Many of these species also occur in allochthonous limestones in the Malongulli Formation and correlative units of the Macquarie Volcanic Province in central New South Wales, and are also recognized in North and South China, which supports assignment of the Wairuna Formation conodont fauna to the Taoqupognathus tumidus-Protopanderodus insculptus Biozone of middle Katian age. Associated linguliformean brachiopods include species of Acrosaccus, Atansoria, Biernatia, Conotreta, Elliptoglossa, Hisingerella, Nushbiella, Paterula and Scaphelasma, which are identical to those known from the Malongulli Formation. Subtle paleoecological differences between faunas of the Malongulli Formation limestones (interpreted as forming in a deeper water peri-platform and upper slope environment) and those of the Wairuna Formation limestones imply that the latter were likely originally deposited on the shelf edge and subsequently reworked downslope. This study provides compelling paleontological evidence of strong affinity between Late Ordovician limestones of the Macquarie Volcanic Province and the Broken River Province, suggesting these regions (today separated by 1600 km) were linked by a volcanic island chain characterized by identical geochemical signatures in volcanic rocks associated with the limestones. [ABSTRACT FROM AUTHOR]

The argument that temperature change and biological change during the Ordovician are correlated and, perhaps, causally related has been advanced by measurements of δ18Ophos values on conodont apatite, a phase more resistant to diagenetic alteration than carbonates. However, the available conodont δ18Ophos records are discontinuous and are biased towards North American samples. To test the generality of global patterns and to expand the geographical range of studied regions, we document δ18Ophos values from conodont apatite as well as δ13C and δ18Ocalcite values from bulk carbonate from New South Wales, Australia. New results span most of the Ordovician and include the first Late Ordovician phosphate δ18Ophos values from the Australian continent. The data from New South Wales show an ~1. 5‰VSMOW increase in δ18Ophos values during the Early and Middle Ordovician. This pattern matches previously documented trends from Laurentia and central Australia, but values in New South Wales are consistently ~2. 5‰VSMOW lower than those from other regions. We attribute these low δ18Ophos values to local paleoceanographic effects on the seawater δ18O value. [ABSTRACT FROM AUTHOR]

Review of the traditional separation of global Ordovician conodont distribution into the North American Midcontinent Province (NAMP) and North Atlantic Province (NAP) reveals a confusing variety of concepts and definitions that hinder biogeographic analysis. Use of this twofold scheme and its subsequent variants should be­discontinued in favour of the more detailed divisions proposed here. Major biogeographical entities of the Shallow-Sea and Open-Sea Realms, separated by the shelf-slope break, are both further subdivisible into Tropical, Temperate and Cold Domains. In the Cold domains, faunal differences between the two Realms and their subdivisions are not easily discernible, since biofacies zones and different habitats were highly condensed. Faunal differences are amplified in the tropical regions, where the North American Midcontinent Province and North Atlantic Province were originally defined. Recognition of endemic taxa is essential for finer classification within domains of the Shallow-Sea Realm (SSR). Our preliminary analysis of Early Ordovician conodont distribution identifies the Laurentian Province (in the Tropical Domain), Australian­(Tropical Domain), North China (Tropical Domain), South China (Temperate Domain), Argentine Precordillera (Temperate Domain) and Balto-Scandian Province (in the Cold Domain). The Open-Sea Realm (OSR) is dominated by cosmopolitan and widespread taxa, and formal subdivision at provincial level is yet to be achieved. The North Atlantic Province encompasses both the Open-Sea Realm and the Temperate and Cold Domains of the Shallow-Sea Realm. The North American Midcontinent Province sensu stricto is more or less equivalent to the Laurentian Province, representing shallow-water regions fringing Laurentia; in a broader sense the North American Midcontinent Province includes all provinces of the Tropical Domain within the Shallow-Sea Realm. [ABSTRACT FROM AUTHOR]

Presents a study which described species of Early Ordovician conodonts. Geological setting and previous investigations; Conodont ecology and biogeography; Biostratigraphy and regional correlation; Materials and methods; Results.

9172 Conodonts have been recovered from the uppermost Hunghuayuan Formation and the Zitai Formation at two sections in Shitai County, southern Anhui Province, South China, which was situated close to the margin of the Lower Yangtze Platform during the Early to Middle Ordovician. Systematic and multivariate statistical studies on these conodonts permit recognition of seven conodont biofacies: Tropodus biofacies, Diaphorodus biofacies, Oepikodus biofacies, Baltoniodus biofacies, Paroistodus biofacies, Periodon biofacies and Protopanderodus biofacies. Each biofacies is restricted to a particular lithofacies and stratal position and shows a consistent order and/or position within the succession. Turnover of these conodont biofacies is related to sea-level changes. The transgressive–regressive patterns demonstrated by the conodont biofacies compare closely to published sea level curves for South China, and highlight the utility of conodont biofacies as a means of confirming sedimentological evidence of relative sea-level change. [ABSTRACT FROM AUTHOR]

The septimembrate conodonts Acodus triangularis (Ding in Wang, 1993) and Prioniodus honghuayuanensis n.sp., are described and illustrated from Guizhou, South China where both species are widely distributed in Lower Ordovician strata. The adenticulate A. triangularis, which ranges through the middle and upper parts of the Honghuayuan Formation, is morphologically more primitive than the denticulate P. honghuayuanensis, which is present from the uppermost Honghuayuan Formation into the lower part of the succeeding Dawan Formation. Prioniodus honghuayuanensis, elements of which were previously ascribed to Oepikodus communis (Ethington & Clark, 1964), appears to be closely related to a species of Prioniodus from the basal Whiterockian of Utah, North America. [ABSTRACT FROM AUTHOR]

Describes species of Ordovician rhipidognathid conodonts found in Australia and Iran. Morphology of the species; Evidence of biogeographic affinities of Australia and South China; Exclusive occurrence of Bergstroemognathus to late Early Ordovician strata.

Forty-four conodont species are documented from the Dawangou section in the Tarim Basin, which spans the Darriwilian to Sandbian interval and is the global auxiliary stratotype for the base of the Upper Ordovician. Five conodont zones are recognized in this section, including the Yangtzeplacognathus crassus, Histiodella holodentata and H. kristinae zones in the upper part of the Dawangou Formation, the Pygodus anserinus Zone from the upper part of the Saergan Formation to the lower part of the Kanling Formation, and the Baltoniodus alobatus Zone in the upper part of the Kanling Formation. Presence of the P. serra Zone is based on occurrences of this species on shale bedding planes in the lower and middle Saergan Formation, but could not be confirmed in acid-leached samples studied from this interval. The Middle/Upper Ordovician boundary occurs within graptolitic black shale of the upper Saergan Formation. Although the boundary interval was intensively sampled, conodonts were very rare, probably due to stagnant or stratified basinal environments. This documentation of the conodont faunas and biostratigraphy of the Dawangou section is considered preliminary and more detailed conodont studies are required, but the remoteness of the site hinders the further extensive sample collection needed for this purpose. [ABSTRACT FROM AUTHOR]