Late Ordovician Faunas Research Articles

The Ordovician of the Middle East (Iran, Afghanistan, Pakistan)

Abstract Ordovician studies in Iran have shown significant progress since the beginning of the century. A number of individual faunas have been documented and a biostratigraphical framework based on conodonts, chitinozoans, acritarchs and trilobites developed. Correlation of Ordovician successions with the International Chronostratigraphic Chart has been significantly improved, and the position of the series and stage boundaries can be recognized with greater precision. While geographical proximity to temperate latitude Gondwana is apparent for most Iranian terranes, biogeographical links of Alborz and Kopet-Dagh with South China prevailed through the Early–Middle Ordovician. In Pakistan, Ordovician deposits have a restricted distribution in the Karakorum block (Chitral). Here they are represented by the Yarkhun and Vidiakot formations with Floian–Darriwilian acritarchs, chitinozoans and early Darriwilian conodonts. In Peshawar District of the North-West Frontier Province, an Early–Middle Ordovician age is likely for the Misri Banda Quartzite with Cruziana rugosa trace fossils. It is overlain conformably by carbonates of the Panjpir Formation, which has an inferred Middle Ordovician–Silurian age. Presently available information on the Ordovician of Afghanistan is mostly based on reconnaissance studies performed almost half a century ago, and a few monographed Early and Late Ordovician faunas.

Late Ordovician palaeogeography and the positions of the Kazakh terranes through analysis of their brachiopod faunas

AbstractDetailed biogeographical and biofacies analyses of the Late Ordovician brachiopod faunas with 160 genera, grouped into 94 faunas from individual lithotectonic units within the Kazakh Orogen strongly support an archipelago model for that time in that area. The Kazakh island arcs and microcontinents within several separate clusters were located in the tropics on both sides of the Equator. Key units, from which the Late Ordovician faunas are now well known, include the Boshchekul, Chingiz-Tarbagatai, and Chu-Ili terranes. The development of brachiopod biogeography within the nearly ten million year time span of the Late Ordovician from about 458 to 443 Ma (Sandbian, Katian, and Hirnantian), is supported by much new data, including our revised identifications from the Kazakh Orogen and elsewhere. The Kazakh archipelago was west of the Australasian segment of the Gondwana Supercontinent, and relatively near the Tarim, South China and North China continents, apart from the Atashu-Zhamshi Microcontinent, which probably occupied a relatively isolated position on the south-western margin of the archipelago. Distinct faunal signatures indicate that the Kazakh terranes were far away from Baltica and Siberia throughout the Ordovician. Although some earlier terranes had joined each other before the Middle Ordovician, the amalgamation of Kazakh terranes into the single continent of Kazakhstania by the end of the Ordovician is very unlikely. The Late Ordovician brachiopods from the other continents are also compared with the Kazakh faunas and global provincialisation statistically determined.

A new Lagerstätte from the Late Ordovician Big Hill Formation, Upper Peninsula, Michigan

A new exceptionally preserved marginal marine biota is reported from the Late Ordovician Big Hill Formation of Stonington Peninsula in Michigan's Upper Peninsula. The new Lagerstätte hosts a moderately diverse fauna of medusae, linguloid brachiopods, non-mineralized arthropods and orthocone nautiloids, alongside dasycladalean green algae. The biota is similar to those of Lagerstätten from the Late Ordovician of Canada, revealing an extensive distribution of a distinctive marginal marine palaeocommunity in Laurentia at this time. The Big Hill biota extends the geographical range of exceptionally preserved Late Ordovician faunas in Laurentia and indicates that further examples remain to be discovered.

Late Ordovician brachiopods from the Chingiz Terrane, Kazakhstan, and their palaeogeography

The Late Ordovician Akdombak Formation of the Chingiz-Tarbagatai Terrane, Kazakhstan, has yielded brachiopods from four successive horizons, three Katian and the upper one of Hirnantian age. Comparable faunas of an earlier Katian age are also described from the upper part of the Taldyboi Formation, also within the Chingiz-Tarbagatai Terrane, but there are no Hirnantian rocks there. The new subfamily Alpeisinae is erected within the Wangyuiidae (Plectorthoidea), and the following new genera are introduced: Holmerglossa (Linfguloidea), Wrightiops (Craniopsoidea), Buminomena (Strophomenoidea), Alpeis, Ashinaorthis and Enbektenorthis (all Orthoidea) and Rongatrypa (Atrypoidea), as well as 10 new species: Bokotorthis minuta, Craniops pristinus, Chonetoidea enbektenensis, Dalmanella kotyrzhalica, Diambonioidea koknaiensis, Enbektenorthis molesta, Kassinella kasbalensis, Kozlowskites botobaicus, Leangella (Leangella) bakanasensis Phragmorthis eximia and Strophomena (Tetraphalerella) namasensis. Eleven ecological associations are recognized, which inhabited a spectrum of depths ranging from Benthic Assemblage Zone (BA) 1 to BA 5 depth ranges. Comparison of the faunas with the neighbouring Kazakh terranes is chiefly with the Chu-Ili, North Tien Shan and Boshchekul terranes since, although others have Late Ordovician faunas, their brachiopods are unknown or unrevised. There is much in common between the brachiopods of the Kazakh terranes, but individual faunas contain different species, many of which are endemic to one terrane. The Chingiz-Tarbagatai brachiopods show some similarities to contemporaneous faunas from the equatorial sectors of Gondwana, including Australia, and some with North China and South China, but have very little in common with those from Baltica and Laurentia. Thus the Chingiz-Tarbagatai Terrane was probably part of an archipelago which lay in a subequatorial position to the north-west of the Australasian sector of Gondwana and the adjacent South China continent in the Late Ordovician.http:zoobank.org/urn:lsid:zoobank.org:pub: C502E307-C67D-4216-869D-17D199812088

Chapter 14 Palaeobiogeography of Ordovician echinoderms

Abstract The palaeobiogeographical distribution of the six major clades of Ordovician echinoderms (asterozoans, blastozoans, crinoids, echinozoans, edrioasteroids and stylophorans) is analysed based on a comprehensive and up-to-date database compiling 3701 occurrences (1938 species recorded from 331 localities) of both complete specimens and isolated ossicles. Although historically biased towards a limited number of regions (Europe, North America, Russia), the resulting dataset makes it possible to identify six main palaeobiogeographical provinces for Ordovician echinoderms: Laurentia, Baltica, West Gondwana, East Gondwana, Avalonia and Siberia. At a global scale, the high endemicity of echinoderms during the Early to Middle Ordovician coincides with the time of maximum dispersal of continental masses. Late Ordovician faunas tend to become more cosmopolitan, possibly as a consequence of changing palaeogeography and/or relatively higher sea-levels in the Sandbian–Katian interval. Regional biodiversity patterns of Ordovician echinoderms confirm that their major diversification during the Ordovician is not a single, universal evolutionary event, but rather results from the complex addition of contrasted local evolutionary trends.

Heliolitine tabulate corals from Late Ordovician and possibly early Silurian allochthonous limestones in the Broken River Province, Queensland, Australia

Dixon, O.A. & Jell, J.S., iFirst article. Heliolitine tabulate corals from Late Ordovician and possibly early Silurian allochthonous limestones in the Broken River Province, Queensland, Australia. Alcheringa, 1–30. ISSN 0311-5518. Coral faunas of Late Ordovician (Ashgill) and possibly early Silurian age are present in allochthonous limestone blocks incorporated in debris flow deposits in the Broken River Province of north Queensland. The limestones occur in the Carriers Well Formation and Crooked Creek Conglomerate, which now lie within structurally deformed fault slices, and are evidence of the existence of a former carbonate platform of this age situated to the west. The fauna from the Carriers Well Formation includes 15 taxa belonging to the heliolitine coral families Heliolitidae, Pseudoplasmoporidae, Plasmoporidae, Plasmoporellidae and Sibiriolitidae. New taxa present are Wairunalites greeni gen. et sp. nov. and Plasmoporella marginata sp. nov. The fauna includes other species belonging to Heliolites, Plasmoporella and Sibiriolites in common with Late Ordovician faunas of New South Wales, central Asia and northern China. A limestone block in the Crooked Creek Conglomerate contains a few non-diagnostic heliolitine corals, together with rugosan, favositine and halysitine corals similar to those in the blocks of the Carriers Well Formation, but it also contains several alveolitine tabulates suggesting a possible early Silurian age.

Late Ordovician trilobites from the Xiazhen Formation in Zhuzhai, Jiangxi Province, China

Trilobites from mudstone of the Upper Ordovician Xiazhen Formation of South China are described. The reef-associated, unique fauna comprises 25 species, 14 genera, and ten families. Five new species are named: Remopleurides xiazhenensis sp. nov., Hibbertia aodiensis sp. nov., Vietnamia yushanensis sp. nov., Ceraurinus zhuzhaiensis sp. nov., and Pliomerina tashanensis sp. nov. The paucity of trilobites in reef-associated carbonates is interpreted that the trilobites diversified after the reef system decimated. Compared to the Late Ordovician trilobite faunas in other areas of South China, the Xiazhen mudstone fauna is unique in that the phacopids including Vietnamia, Ceraurinus, and Pliomerina account for 75% of the specimens collected. The occurrence of the same trilobite assemblage at different sampling localities along the dip direction of the formation suggests that the outcrops may be overlapped due to structural movement. The Xiazhen trilobite fauna is unique among the Late Ordovician fauna in that i...

A Hirnantian (latest Ordovician) reefal bryozoan fauna from Anticosti Island, eastern Canada: taxonomy and chemostratigraphy

The Natiscotec outcrop on Anticosti Island, Canada (Ellis Bay Formation, Laframboise Member, Hirnantian, Late Ordovician), exposes a patch reef some 20–30 m in diameter, 2–3 m thick, with abundant rugose corals, as well as favositids and heliolitids. Reef capping and flanking sediments include typical Hirnantian brachiopods, such as Hirnantia , Hindella , and Eospirigerina . Within the reef peloidal microbialites encrusting bryozoan colonies are common. The bryozoan fauna includes three cystoporates, seven trepostomes, and three phylloporines. Two genera and two species are new: the cystoporate Natiscotecella tenuis n. gen. and n. sp. and the phylloporine Dilaminocladia natiscotecensis n. gen. and n. sp. Three more species are also new: the cystoporates Ceramopora clara n. sp. and Acanthoceramoporella spinigera n. sp. and the trepostome Revalotrypa honguedensis n. sp. Furthermore, we identify the three trepostomes Atactoporella aff. ortoni (Nicholson, 1874), Hallopora elegantula (Hall, 1852), and Monotrypella cf. aequalis Ulrich, 1882, and a phylloporine Parachasmatopora porkunensis Lavrentjeva, 1985. Four species are identified at generic level and in open nomenclature: the three trepostomes Lioclemella sp., Calloporella sp., and Trepostomata sp. and a phylloporine ? Ralfinella sp. The bryozoan fauna shows some affinities with the Late Ordovician fauna of Scandinavia. Stable carbon isotope investigations from brachiopod shells of the same outcrop yield values for δ13C of up to +6.7‰, which represent the highest values reported from the Anticosti succession so far. This indicates that the stratigraphic position of the outcrop is at or close to the peak of the globally recognized Hirnantian δ13C excursion.

Biostratigraphical and palaeoecological significance of graptolites, trilobites and conodonts in the Middle-Upper Ordovician Andersö Shale: an unusual ‘mixed facies’ deposit in Jämtland, central Sweden

ABSTRACTAlthough only about 20m thick, the Andersö Shale contains one of the most diverse, if not the most diverse, late Middle-early Late Ordovician faunas known in Baltoscandia. It includes more than 20 trilobite species, more than 20 species of other shelly fossils, about 10 graptolite species, and about 20 conodont species. Based on its lithology, its geographical position near the foreland basin margin, and the presence of trilobites of the raphiophorid association and conodonts of the Periodon-Pygodus biofacies, this formation is interpreted to represent an outer shelf-upper slope (ramp) deposit laid down in moderately deep water. The co-occurrence of some widespread and biostratigraphically diagnostic conodonts, graptolites and trilobites makes it possible directly to compare distribution patterns of these fossils, establish ties between graptolite and conodont zones, and correlate the formation with units elsewhere in Europe, North America and China. Stratigraphically and faunally, the Andersö Shale is of particular interest in straddling the Middle-Upper Ordovician Series boundary as this boundary is recognised in the new global classification of the Ordovician System.

Tectonic and paleogeographic significance of Late Ordovician conodonts in the Canadian Appalachians

Conodonts of Late Ordovician age are well represented in Laurentian parts of eastern Canada, but are rare in the Appalachian orogenic belt. They are known from the Anticosti Basin, the Matapedia Belt, and the Exploits Subzone of the Dunnage Zone. Two new discoveries are described: one from unnamed strata on Markey Brook, west-central New Brunswick, and one from the Goss Point Formation (Avalon Zone, southwestern New Brunswick). Faunas from the Anticosti Basin are of undoubted Midcontinent Faunal Region affinity. Those from the Matapedia Belt are highly mixed both paleoecologically and provincially, containing elements of shallow- and deep-water Midcontinent affinity and elements typical of the Atlantic Faunal Region. Faunas from the Exploits Subzone and Markey Brook are also mixed, suggesting endemic faunas of Atlantic affinity with local influx of Midcontinent faunas from Laurentia. The Goss Point Formation, previously believed to belong to the Mascarene Group (a Silurian cover sequence on the Avalon Zone), also yields mixed faunas. Provincial mixing of all faunas east of the Anticosti Basin suggests that Late Ordovician faunas around Iapetus Ocean may have been more homogeneous than earlier Ordovician faunas. Therefore, the Iapetus Ocean may have been smaller or current patterns may have changed to permit trans-Iapetan migration. A strong global pattern of provincialism for Late Ordovician conodonts is recognized and a new Australasian Province is proposed. Conodonts permit identification of a previously unrecognized Ordovician volcano-sedimentary succession that has economic and tectonic implications for the region.

The Ordovician‐Silurian boundary successions in östergötland and Västergötland, S. Sweden

Abstract A detailed lithostratigraphic and biostratigraphic study of the Ordovician‐Silurian boundary section at Råssnäsudden near Motala has resulted in the recognition of two new lithostratigraphic units, the Motala Formation and the Loka Formation. The former is a slightly more than 5 m thick unit of nodular limestone and calcareous mudstone of late Rhuddanian and early Aeronian age. Its typical lithofacies can be traced into lower Silurian successions in Västergötland and into the subsurface of Gotland. The latter unit, which is poorly represented at Rässnäsudden but well developed in Västergötland, consists of shallow‐water limestone, sandstone, siltstone, and mudstone and was formerly known as the Dalmanitina Beds or the Tommarp Formation. The shelly fossil fauna of the Loka Formation in Östergötland is in some respects more reminiscent of coeval faunas of the North American Midcontinent than ofthat of the Loka Formation in Västergötland. In terms of the graptolite succession, the Motala Formation corresponds to an interval from the acinaces Zone to the revolutus Zone and it belongs to the D. kentuckyensis Zone in the conodont zone sequence. Its conodont fauna, the first to be recorded from early‐middle Llandoverian strata in Sweden, is of cosmopolitan type and has little in common with Late Ordovician faunas. Bergström, S.M. & Bergström, J., 1996: The Ordovician‐Silurian boundary successions in Östergötland and Västergötland, S. Sweden. GFF, Vol. 118 (Pt. 1, March), pp. 25–42. Stockholm. ISSN 1103–5897.

Ordovician faunas, island arcs and ophiolites in the Scandinavian Caledonides

ABSTRACTOrdovician faunal data from the Scandinavian Caledonides is tested with new geochemical information from zircons to give U/Pb ages and source origins of volcanic arc and ophiolite sequences. Early Ordovician (Arenig‐Llanvirn), low latitude, Toquima‐Table Head faunas from the upper Upper Allochthon are associated with an island arc system formed adjacent to Laurentia. Contemporaneous mafic magmas were contaminated by crustal material during subduction and associated granites contain inherited zircons of Archaean age. The nearest source for such rocks is on the Laurentian rather than the Baltic side. Higher latitude Celtic province faunas from the upper Upper Allochthon are from one insular site accessible to forms from both Laurentia and Baltica.The late Ordovician low‐latitude Holorhynchus and subtropical Hirnantia faunas occur in overstep sequences above deeply eroded early Ordovician arc complexes. The transgression appears to be coeval with a second generation of spreading‐related complexes. Single detrital zircons from sediments show sources from Archaean, Proterozoic and early Ordovician terranes. This suggests that deposition was in a basin situated along the same continental margin (Laurentia) to which the early Ordovician ophiolite/arc sequences had already become accreted. The late Ordovician faunas link both Laurentia and Baltica at a time of narrowing of lapetus.The new geochemical data together with the faunal information is supported by recent palaeomagnetic studies.

Stratigraphy and regional setting of the Cliefden Caves limestone group (Late Ordovician), central‐western New South Wales

Abstract The 460 m‐thick Cliefden Caves Limestone Group is the oldest and best exposed, extensive body of limestone in N.S.W. Its Late Ordovician faunas and floras are comparatively well preserved and it has some excellent silicified horizons, especially in the upper part of the sequence. In the nominal type area at Cliefden Caves, the limestone has been subdivided into three formations—the Fossil Hill Limestone (lower), the Belubula Limestone (middle) and the Vandon Limestone (upper). Only the Belubula Limestone remains undifferentiated. The Fossil Hill Limestone has been further subdivided into six members (Gleesons, Kalimna, Wyoming, Taplow, Dunhill Bluff and Transmission Limestone Members, respectively), and the Vandon Limestone into two members (Trilobite Hill and Mount Lewin Limestone Members). Each of these subdivisions is defined herein, with a designated type section and a description of its content and distribution. In late Gisbornian to early‐middle Eastonian time, the Cliefden Caves Limestone ...

Montoya Group Stratigraphy (Ordovician) of Trans-Pecos Texas

Sections measured in the Franklin and Organ mountains show the Lower Ordovician El Paso formation to have been progressively truncated toward the north, and to be overlain disconformably by the Middle (?) and Upper Ordovician Montoya group. This group from the base up is divided into: the Cable Canyon sandstone (coarse, orthoquartzitic) replaced in the Baylor Mountains by a St. Peter sandstone equivalent; the Upham formation (dolomite or limestone) containing a Red River fauna, which is probably upper Trenton or possibly lower Cincinnatian in age; the Aleman formation (also dolomite or limestone with much chert, in bands or nodules) with a Maquoketa fauna, notably the coral Palaeophyllum thomi, which crops out in a marker bed for 140 miles; and the Cutter formation (non-cherty dolomite) with a late Ordovician fauna near its base.