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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]

Fossils, comprising sponge spicules, brachiopods, trilobites and assorted echinoderm plates, from a fault-bounded sliver along the Yarrol Fault 30 km south-south-east from the town of Calliope in central eastern Queensland, are described and illustrated for the first time. Due to their poor preservation, none of the fossils are identifiable to species level, but the trilobites, Arthrorhachis sp. and two pliomerid pygidia, belong to taxa not known outside the Ordovician, and Illaenus sp. compares closest with Middle Ordovician members of the genus. The brachiopods - including orthoids (?Phaceloorthis among others), plectambonitoids (Sericoidea), the protorthide Skenidioides and a siphonotretide - resemble forms previously described from the Late Ordovician (Katian) of central New South Wales and indicate an open marine deep-water habitat (120-200 m depth). This assemblage is significant in representing the first Ordovician fauna (and the oldest fossils) documented from the New England Orogen in Queensland. The tectonic implications of this confirmed Ordovician sedimentary succession within the New England Orogen in central Queensland are yet to be fully appreciated, but it does complement similarly aged successions occurring along the Peel Fault in the southern New England Orogen. Together these tiny fault blocks suggest that the island arc or arcs which developed during the early Palaeozoic were incorporated into the New England Orogen during the middle Palaeozoic, both in its northern part as well as in the south. [ABSTRACT FROM AUTHOR]

Richly fossiliferous Hirnantian shelly strata of near‐shore facies in northern Guizhou, South China, known as the Kuanyinchiao Formation, superbly record glacioeustatic sea‐level fluctuations and benthic faunal turnover. Recent studies of the temporal and spatial distribution of these carbonates and shelly fossils permit a critical stratigraphic revision and establishment of a robust regional stratigraphic correlation. The formation is revised to include three informal subdivisions, that is, units A, B, and C, in ascending order. Unit B of the formation typically is dominated by peloidal or oolitic grainstones, and unit C is composed of skeletal wackestone and calcareous mudstone, both units sharing distinctive coral and brachiopod faunas. This contrasts sharply with unit A of the formation, consisting of mudstone, silty mudstone, or calcareous mudstone, that yields the cool‐water Hirnantia fauna and associated coral fauna. In view of the presence of carbonate ooids and peloids, rugose corals, and a distinctive brachiopod assemblage, all indicative of warm‐water conditions, unit B, as well as unit C yielding the same shelly fauna, is interpreted as representing postglacial sedimentation immediately following the major Hirnantian glaciation, thus marking a significant climatic shift. Similar warm‐water carbonate rocks have been recognized in a number of regions along the margin of the Qianzhong Oldland, including Bijie, Renhuai, Tongzi, and Fenggang of northern Guizhou. Such a vast distribution area of these rocks indicates that postglacial carbonates are more widespread on the Yangtze Platform of South China than previously thought, providing a rare window into rocks and fossils of the survival interval immediately following the extinction event associated with the Hirnantian glacial episodes. [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]

Abstract: Early to Middle Ordovician cherts and cherty siltstones associated with distal turbidite deposition in back-arc basins, are widespread in the Hermidale and Albury–Bega Terranes of the Lachlan Orogen in New South Wales. Study of more than 2500 bedding plane-parallel thin sections prepared to a thickness of 50μm from these cherts enables recognition of four conodont zones that range in age from the late Tremadocian to latest Darriwilian. Comparable cherts are present in two small remnants of oceanic derivation now exposed on the coast of New South Wales, in the Narooma Terrane (Furongian to Darriwilian), and in the New England Orogen at Port Macquarie in allochthonous blocks (Late Ordovician). Associated fauna include radiolaria, sponge spicules, lingulide and acrotretide brachiopods, fragmentary graptolites, and rare filaments attributed to cyanobacteria. Some of these organisms were pelagic, or may have been attached to floating material, and hence became entrapped in siliceous ooze on the sea floor when they settled under gravity. Others (e.g. the brachiopods) may have been attached to sponges growing on the sea floor. The presence of burrows and bioturbation demonstrates that the deep-sea environment in the Middle Ordovician was well-oxygenated, though this contrasts with Lower Ordovician environments where evidence for infauna is lacking. Predominant colouration of the cherts examined in thin section ranges from honey and yellow-brown (typical of semitransparent cherts) through cream-coloured translucent lithologies to opaque varieties. Dark brown cherty rocks that show evidence of burrowing or bioturbation tend to have a higher silt component. The Ordovician is also a time of extensive chert deposition elsewhere, including terranes in Kazakhstan (commencing in the Late Cambrian); these siliceous sediments display many of the features described from eastern Australia. [Copyright &y& Elsevier]

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]

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]

Ordovician conodont studies have revealed a depositional hiatus extending from the late Floian to early Darriwilian on the North China Platform. Recognition of this widespread gap entails revision of the original concept of the Huaiyuan Epeirogeny, with definition of two distinct regional tectonic events: Event 1, which initiated this hiatus, and a subsequent Event 2 that was responsible for terminating Early Palaeozoic sedimentation in the region from the late Katian. The timing of these two events partly coincides with widely recognized eustatic sea-level falls, and separates Ordovician sedimentation into two episodes that can be broadly correlated with eustatic sea-level rises. In combination with these sea-level changes, the Huaiyuan Epeirogeny played a decisive role in shaping and controlling Ordovician sedimentation and sequence stratigraphic architecture on the North China Platform. Lower Ordovician carbonates were deposited during an apparent regression (decreasing accommodation space), resulting from rapid sediment accumulation exceeding the overall rate of basement subsidence and eustatic sea-level rise. Sedimentation ceased in the middle to late Floian when basement uplift commenced in the south and extended northward to affect the entire platform. The diachronous top surface of the Lower Ordovician succession reflects extensive erosion that is most pronounced in the south and southwest parts of the platform where the disconformity surface cut down into Tremadocian (or even upper Cambrian) strata. Deposition of the younger sequence (Darriwilian to Katian) was the result of the interplay between rejuvenated basement subsidence and the late Middle Ordovician eustatic sea-level rise. Event 2, which was initially coupled with eustatic sea-level fall induced by the end-Ordovician glaciations, terminated Ordovician deposition in the region with the top of the Ordovician marked by an unconformity, representing a hiatus of some 122 Ma extending from latest Ordovician to latest Mississippian. [ABSTRACT FROM AUTHOR]

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]