Conodont Faunas Research Articles

Middle Ordovician (early Dapingian) conodonts in the Central Andean Basin of NW Argentina

Carlorosi, J., Heredia, S. & Aceñolaza, G, 2013. Middle Ordovician (early Dapingian) conodonts in the Central Andean Basin of NW Argentina. Alcheringa 37, 1–13. ISSN 0311-5518. This paper describes and analyzes the significance of a conodont fauna from the Alto del Cóndor Formation, exposed in the Los Colorados region of the Argentine Eastern Cordillera. Identified taxa are Baltoniodus triangularis, Baltoniodus sp. cf. B. triangularis, Drepanodus sp., Drepanoistodus basiovalis, Drepanoistodus sp. B., Erraticodon patu, Gothodus costulatus, Oistodus sp., Trapezognathus diprion, T. quadrangulum, Triangulodus sp. and Triangulodus? sp. The presence of Baltoniodus triangularis indicates the base of the Dapingian stage (Middle Ordovician). In addition, we report the coexistence of T. diprion and T. quadrangulum. The conodont association suggests a faunal affinity with Baltica and South China, both belonging to the Shallow-Sea Realm of the Temperate-Cold Domain. Josefina Carlorosi [josefinacarlorosi77@gmail]com], INSUGEO—Universidad Nacional de Tucumán—CONICET, Miguel Lillo 205, (4000) Tucumán, Argentina; Guillermo F. Aceñolaza [acecha@webmail.unt.edu.ar], Universidad Nacional de Tucumán—CONICET, Miguel Lillo 205, (4000) Tucumán, Argentina; Susana Heredia [sheredia@unsj.edu.ar], CONICET–CIGEOBIO and Instituto de Investigaciones Mineras, Facultad de Ingeniería, Universidad Nacional de San Juan, Urquiza y Libertador, (5400) San Juan, Argentina. Received 22.8.2012; revised 18.10.2012; accepted 24.10.12.

Upper Famennian and Lower Tournaisian sections of the Moravian Karst (Moravo‐Silesian Zone, Czech Republic): a proposed key area for correlation of the conodont and foraminiferal zonations

Foraminiferal and conodont faunas at the Devonian–Carboniferous (D–C) boundary in the southern part of the Moravian Karst (Czech Republic) were studied in different facies of the basin slope. The joint presence of foraminifers and conodonts in calciturbidites along with a positive δ13C excursion of the Hangenberg anoxic event enabled the high‐resolution calibration of the late Famennian–early Tournaisian interval (Upper expansa–crenulata conodont zones). The conodont stratigraphic and biofacies succession reveals a strong correlation with other European areas. The Siphonodella sulcata morphotype (close to Group 1 sensu Kaiser and Corradini and “nov. gen. nov. sp. 1” sensu Tragelehn) enters prior to the Hangenberg Event, which resembles Upper and Uppermost Famennian conodont successions from Franconia, Bavaria and Morocco. The diversification of the early siphonodellids takes place after the Hangenberg Event and after the protognathodid radiation. In terms of foraminiferal biostratigraphy, the D–C boundary interval is characterized by the first appearance datum (FAD) of Tournayellina pseudobeata close below the D–C boundary followed by a sequence of Tournaisian bioevents, where apart from the last appearance datums (LADs) of quasiendothyrs, the FADs of the Neoseptaglomospiranella species and chernyshinellids play an important role in a similar manner as in Eastern Europe. The correlation of these bioevents elsewhere is often hindered by glacioeustatically‐driven unconformities and widespread occurrences of unfavourable facies for plurilocular foraminifers (Malevka beds and Bisphaera beds). Copyright © 2013 John Wiley & Sons, Ltd.

A New Middle Ordovician Conodont Fauna from the Thong Pha Phum Area of Western Thailand

Abstract. Little is known about Ordovician litho- and biostratigraphy in northern and western Thailand because outcrops are scarce in these mountainous areas. Biostratigraphic and biogeographic studies of conodonts are limited to the uppermost Floian to lower Darriwilian strata in western Thailand. This paper describes and discusses a new Middle Ordovician conodont fauna that includes nine species from the Thong Pha Phum area of western Thailand. This is the first report of Eoplacognathus suecicus, Pygodus lunnensis, Protopanderodus calceatus, Protopanderodus cooperi, and Protopanderodus graeai in Thailand and indicates that a cool-water fauna existed in western Thailand and in southern peninsular Thailand during the Middle to Late Ordovician. The Dapingian to early Darriwilian sea-level rise likely resulted in an immigration of this “cooler or deeper water” fauna to the Thong Pha Phum area.

Correlation of Early Devonian (Lochkovian-early Pragian) conodont faunas of the South Urals (Russia)

Correlation of Early Devonian (Lochkovian-early Pragian) conodont faunas of the South Urals (Russia)

Conodont biostratigraphy in the Early to Middle Ordovician strata of the Oslobreen Group in Ny Friesland, Svalbard

The remotely located Cambro-Ordovician strata in Ny Friesland, NE Spitsbergen, Svalbard, are referred to the Oslobreen Group, which is composed of the Tokammane, Kirtonryggen and Valhallfonna formations. Herein we record the conodont succession of the Kirtonryggen and Valhallfonna formations. Collections of well-preserved conodonts (CAI 1) have been recovered from the Lower to lower Middle Ordovician interval in the region. Eight regional conodont zones are established in this preliminary study of the Oslobreen Group exposed at Hinlopenstretet, NE Svalbard. In ascending order these zones are: Rossodus manitouensis, Macerodus dianae, Oneotodus costatus, Oepikodus communis, O. evae, O. intermedius, Periodon aff. flabellum-Periodon hankensis and Periodon macrodentatus. The yield is relatively poor for the Kirtonryggen Formation, but the oldest Ordovician conodont faunas span the Tremadocian Rossodus manitouesis through Macerodus dianae zones followed by the Floian Oepikodus communis Zone. The taxa are typical of the tropical North American Midcontinent faunal province that dominated the region until open marine associations invaded the shallow shelf (i.e. Evae transgression). The pandemic Oepikodus evae becomes frequent and is succeeded by O. intermedius in abundance in the lower Valhallfonna Formation (Olenidsletta Member). The upper strata are characterised by the Periodon-Paroistodus assemblage characteristic for outer shelf and slope environments around Laurentia. In total, this formation comprises the Floian and Dapingian stages and ends in the early Darriwilian Periodon macrodentatus Zone in this region. The Ny Friesland faunas show affinities to coeval assemblages from Northeast Greenland and West Newfoundland. (Less)

Biostratigraphic significance of Darriwilian conodonts from Sierra de La Trampa (Central Precordillera, San Juan, Argentina)

The Eoplacognathus pseudoplanus Zone is defined by a conodont fauna composed by E. pseudoplanus (Viira) and Dzikodus tablepointensis (Stouge) among others in the Central Precordillera, Sierra de La Trampra region. We revised the biostratigraphical distribution and control biofacies of the conodonts D. tablepointensis and E. pseudoplanus in the Middle Ordovician of the Precordillera. This study confirms that these species has a similar biostratigraphical distribution to those of equivalent age in south-central China, Baltica and Midcontinent region. We also corroborate that the presence of D. tablepointensis is accurately positioned in the E. pseudoplanus Zone. In this paper we discuss for the first time the morphological affinities of D. tablepointensis and E. pseudoplanus elements from the Precordillera with those same species from southcentral China and Baltica. On the other hand, we review the genus “Polonodus” galerus Albanesi and propose it as Kallidontus? galerus (Albanesi), extending the biostratigraphical record of the genus Kallidontus from the late Tremadocian to middle Darriwilian.

Olenekian (Early Triassic) fossil assemblage from eastern Julian Alps (Slovenia)

New palaeontological and sedimentological data from the Lower Triassic strata of the eastern Julian Alps in Slovenia are presented., They are unusual for the Early Triassic of the Alps in representing a relatively deeper, unrestricted marine (mid-ramp) setting. There are two basic microfacies types in the section investigated (types A and B), which are organized as couplets with coarse-grained tempestitic deposits (microfacies A), overlain by laminated or bioturbated lime mudstones and/or marls (microfacies B), frequently containing ammonoids. This pattern is interpreted as storm deposition with occasional winnowing of bottom sediments and the formation of coarse-grained skeletal deposits (lags), followed by the slow settling of suspended particles, when the storm waned, in addition to background deposition. Dominantly lime mud deposition and the presence of ammonoids indicate deposition on a more distal, deeper ramp with an unrestricted connection to the open sea. Intense reworking of bottom skeletal-rich sediment and accumulation of storm lags suggest deposition above the storm wave base, possibly in a wide low-energy mid-ramp environment. Faunas from such settings have been reported relatively rarely from the Early Triassic of the Alps. The macrofauna contains ammonoids, bivalves and gastropods, whereas the microfauna is represented by foraminifer tests and conodont elements; rare fish remains also occur. In the foraminifer assemblages, species of Ammodiscus, Hoyenella , Glomospirella dominated , corresponding to the widespread “Glomospira-Glomospirella” foraminifer community, with some miliolids and nodosariids. The conodont fauna is characterized by Triassospathodus hungaricus (Kozur et Mostler), indicating an early Spathian (Olenekian) age. The fossil assemblage highlights the wide distribution of Early Triassic taxa in the Tethys and facilitates its worldwide correlation. Its relatively low diversity by comparison with shallow marine settings is interpreted as an evolutionary proximal-distal trend in the wake of the end-Permian mass extinction. Re-diversification first occurred in nearshore settings and expanded into deeper/distal marine environments through geological time.

An Early Ordovician conodont fauna from the Santa Rosita Formation at its type area in the Santa Victoria Range, Cordillera Oriental, Northwestern Argentina

The Cambrian - Lower Ordovician stratigraphic units from the Cordillera Oriental were originally defined in the Santa Victoria Range, Salta Province, northwestern Argentina, however, the extensive outcrops of this region lack detailed biostratigraphic studies. We describe and analyse the first reported conodont fauna from the Santa Rosita Formation at its type area, which produced significant biostratigraphic information. Over 4,500 well-preserved conodont elements were recovered from outcrops of the Santa Rosita Formation at the southern margin of the Santa Victoria River, near the homonymous locality. Collected specimens exhibit a CAI 3 and correspond to the Paltodus deltifer deltifer Subzone of the P. deltifer Zone (middle Tremadocian, Tr2). A number of species are described for the genera Acanthodus, Acodus, Decoriconus, Drepanodus, Drepanoistodus, Filodontus, Granatodontus, Hammannodus, Iapetonudus, Kallidontus, Paltodus, Paroistodus, Teridontus, Tilcarodus, Utahconus, Variabiloconus, Gen. and sp. indet., the protoconodont Phakelodus and the paraconodont Coelocerodontus. Two new conodont species, Drepanoistodus andinus Voldman, Zeballo and Albanesi and Filodontus carolinae Voldman, Albanesi and Zeballo, are diagnosed herein. The studied assemblages include conodont species of wide intercontinental distribution as well as endemic forms from the Central Andean Basin, which characterize a faunal province with a particular signature from the Shallow Water Realm.

Conodont biostratigraphy, and δ13C and δ34S isotope chemostratigraphy, of the uppermost Ordovician and Lower Silurian at Osmundsberget, Dalarna, Sweden

The previously established graptolite and chitinozoan Hirnanian-Telychian biostratigraphy in the unique Osmundsberget North outcrop in the Siljan region, south-central Sweden, is integrated with new conodont biostratigraphy and δ13Corg, δ13Ccarb and δ34Spyr chemostratigraphy. At this locality, the middle Hirnantian (latest Ordovician) topmost part of the Boda Limestone is overlain by the latest Hirnantian Glisstjärn Formation, and the late Aeronian–early Telychian (Llandovery) Kallholn Formation rests unconformably on the Glisstjärn Formation. Previous conodont work showed that the Glisstjärn Formation belongs to the lower Ozarkodina hassi Zone. New samples from calcareous interbeds in the dominantly shaly Kallholn Formation, some of which contain hundreds of condont elements, yielded Distomodus staurognathoides, Aspelundia fluegeli and other taxa indicating the D. staurognathoides Zone. In the East Baltic succession, the coeval interval, which is in the uppermost Raikküla–lowermost Adavere stages just below the geographically widespread Osmundsberg K-bentonite, has yielded a conodont fauna similar to that of the lower Kallholn Formation. A regional review of the D. staurognathoides Zone shows that there are possible equivalents to our study interval also in Norway and the Welsh Borderland, but equivalent strata are missing in large parts of North America, or have not produced diagnostic conodonts. The δ13Corg values from the study section are relatively uniform (mostly ranging between − 29‰ and − 30‰), and the late Aeronian and Valgu positive excursions have not been recognized.

Famennian ostracods from the Istanbul zone (Gebze, Kocaeli, NW Turkey) and their paleogeographical relations

Abstract Famennian (Late Devonian) ostracods of the Thuringian Mega-Assemblage were recovered for the first time from three incomplete sections of the Ayineburnu Member of the Büyükada Formation in the Denizliköy area (Gebze, NW Turkey), which were sampled for conodonts. Conodont faunas define an interval extending from the Upper rhomboidea? or Lower marginifera Zone into the Middle expansa Zone of the standard Upper Devonian conodont zonation. The ostracod faunas found here consist of species mainly with thin-walls, long spines and often smooth surfaces such as Rectonaria, Tricornina, Orthonaria, Triplacera, Beckerhealdia, Timorhealdia, Bohemina, Paraberounella and Acratia. These taxa indicate faunal relationship with Thuringia and the Rhenish Massif in Germany, the Cantabrian Mountains and Pyrenees in Spain, Holy Cross Mountains in Poland, North Africa and China.

Post-Lau Event (late Ludfordian, Silurian) recovery of conodont faunas of Bohemia

Post-Lau Event (late Ludfordian, Silurian) recovery of conodont faunas of Bohemia

Early Triassic (Induan–Olenekian) conodont biostratigraphy, global anoxia, carbon isotope excursions and environmental perturbations: New data from Western Australian Gondwana

The Early Triassic Induan–Olenekian Stage boundary (Dienerian–Smithian sub-stage boundary) has been identified at a depth of 2719.25m in the petroleum exploration well Senecio-1 located in the northern Perth Basin, Western Australia. Conodont faunas represent three conodont zones in ascending order, the Neospathodus dieneri Zone, the Neospathodus waageni eowaageni Zone and the Neospathodus waageni waageni Zone. The Induan–Olenekian (Dienerian–Smithian) boundary is placed at the base of the Neospathodus waageni eowaageni Zone equivalent to the first appearance of Neospathodus ex. gr. waageni utilised elsewhere and adopted by the IUGS ICS Triassic Subcommission to define the base of the Olenekian. Bulk kerogen δ13C carbon isotopes define a positive peak of c. 4 per mille that essentially coincides with the Induan–Olenekian boundary as seen in proposed Global Stratotype Sections and Points (GSSPs) in South China and Spiti, India demonstrating the global utility of this level for correlation. An anoxic zone is recognised in the lower part of the Senecio-1 core and the upper limit of this zone is dated as late Induan (late Dienerian). Temporal and spatial mapping of marine anoxia and dysoxia globally demonstrates that pulses of dysoxia/anoxia affected shallow-marine zones at different times in different locations. Dysoxia/anoxia in the shallow-marine environment appeared in the latest Permian at the extinction level, later than in the deep-marine environment, and appears to be largely restricted to the Induan (Griesbachian and Dienerian) and early Olenekian (Smithian). Temporally and geographically restricted upwelling of an oxygen minimum zone into the ocean surface layer due to environmental perturbations including extreme global warming, increased terrestrial chemical weathering intensity and continental erosion, sea level rise, and changes in marine nutrient inventories and productivity rates, is interpreted as a likely cause of observed variation in shallow-marine dysoxia/anoxia in the Early Triassic.

New conodont species and biostratigraphy of the Santa Rosita Formation (upper Furongian–Tremadocian) in the Tilcara Range, Cordillera Oriental of Jujuy, Argentina

A new conodont collection from the Alfarcito area of the Tilcara Range, Cordillera Oriental of northwestern Argentina, has been studied. The Santa Rosita Formation exposed in this area consists of the Tilcara, Casa Colorada, Pico de Halcón, Alfarcito, Rupasca and Humacha members, which have a combined total thickness of ca. 1100 m. The sequence is composed of interbedded shales and sandstones, including calcarenites and coquinas, mostly appearing in the upper parts of the units. An abundant fauna of conodonts (ca. 11 000 elements), associated with graptolites and trilobites, was recorded. The biostratigraphic analysis allows for the identification of the Cordylodus intermedius and C. lindstromi sensu lato zones at the base of the Alfarcito Member. The C. angulatus Zone spans the upper part of the latter unit, and the Paltodus deltifer Zone (Paltodus deltifer pristinus and P. deltifer deltifer subzones) is identified in the Rupasca and Humacha members. The new species Acanthodus raqueli, A. humachensis, Utahconus tortibasis, U. scandodiformis, U. purmamarcensis, Variabiloconus crassus, Kallidontus gondwanicus and Acodus primitivus are recorded from the two latter biozones and they are described herein. The genera Acanthodus and Variabiloconus are emended, and a new genus Tilcarodus is created to include T. humahuacensis (Albanesi and Aceñolaza). Copyright © 2012 John Wiley & Sons, Ltd.

Subdivision of the Lochkovian Stage based on conodont faunas from the stratotype area (Prague Synform, Czech Republic)

Relatively rich conodont faunas from sections in the Prague Synform (Barrandian area, Czech Republic) include a number of indexes and other important guide conodonts that can be correlated with other regions, especially with Nevada and the Spanish Central Pyrenees. The collation and detailed correlation of conodont data from the Lochkovian in two parallel sections in the Požáry quarries, together with biostratigraphic control of additional data from several (incomplete) sections with changing facies development, is the basis for a new detailed regional biozonal scale for the Lochkovian in the Prague Synform. The new subdivision follows, with modification, the global threefold conodont subdivision of the Lochkovian. Data from the Prague Synform enable further detailed subdivision of the lower, middle and upper Lochkovian into small‐scale units. The conodont distribution shows a large proportional discrepancy between the late Lochkovian elsewhere; the conodont record in the latest Lochkovian in the Prague Synform area, which appears to be rather restricted and requires further discussion. Copyright © 2012 John Wiley & Sons, Ltd.

TAXONOMY AND BIOSTRATIGRAPHIC RECORD OF THE UPPER TRIASSIC CONODONTS OF THE PIZZO MONDELLO SECTION (WESTERN SICILY, ITALY), GSSP CANDIDATE FOR THE BASE OF THE NORIAN

New taxonomic and biostratigraphic investigations on the late Carnian to Rhaetian (Upper Triassic) platform conodonts from the Pizzo Mondello section (Western Sicily, Italy, Sicano basin) are here presented. Pizzo Mondello is one of the two GSSP candidates for the Carnian/Norian boundary; the section is a 430 m thick continuous succession of upper Carnian to upper Norian marine limestones (Scillato Formation), characterized by uniform facies and high sedimentation rates, and ca. 20 m of Rhaetian white calcilutites (Portella Gebbia limestone). Pizzo Mondello offers one of the most complete conodont records for this time interval in the Tethys. The conodont faunas are characterized by a large variety of species, belonging to the genera Carnepigondolella , Epigondolella , Metapolygnathus , Misikella , Mockina , Neocavitella , Norigondolella , Paragondolella, and Parvigondolella . The richness of the populations allowed a detailed revision and description of all the Upper Triassic species and morphotypes recovered. The revision of the problematic species Carnepigondolella nodosa and Metapolygnathus communisti B was thus possible, leading to the establishment of two new species: Carnepigondolella tuvalica n.sp. and Carnepigondolella gulloae n.sp. The latter species would be a good proxy for the Carnian/Norian boundary in the case that the FAD of Halobia austriaca (sample FNP135a) will be selected as the primary biomarker for the base of the Norian.

U–Pb zircon age, sedimentary facies, and sequence stratigraphy of the Devonian–Carboniferous boundary, Daposhang Section, Guizhou, China

The Devonian–Carboniferous (D/C) boundary marks a major extinction event and an important evolutionary turnover in Paleozoic biotas, but understanding D/C boundary events is hampered by a lack of accurate and consistent ages. As a result, although a global stratotype section and point (GSSP) for the D/C boundary was defined in the section La Serre trench E’ (Montagne Noire, France) and accepted and ratified by the IUGS, problems arose concerning both the lithology of the La Serre section and the identification of S. sulcata. Due to these problems, in the very recent years, the ICS decided to reconsider the GSSP. The Daposhang section in Muhua, Guizhou, China, is one of the most important reference sections for the D/C boundary: it is a conformable succession across the D/C boundary that contains conodont faunas characteristic of restricted subtidal facies. A biostratigraphically well constrained tuff near the D/C boundary in the Daposhang section provides an excellent opportunity to date this important event in Paleozoic history. Sensitive high-mass resolution ion microprobe (SHRIMP) U–Pb analyses were conducted on single zircons extracted from the tuff (between beds 0 and 1, which may be temporally equivalent to the Hangenberg black shale) as well as an analysis of sedimentary facies and sequence stratigraphy across the D/C boundary in the Daposhang section. Bed 0 is below the D/C boundary, in the Upper praesulcata conodont zone, and bed 1 is directly above the D/C boundary, in the sulcata conodont zone. Zircon analyses yielded 20 concordant dates that form a cluster with a 206Pb/238U concordia age of 359.6±1.9Ma. An abundance of bioclastic packstone and wackestone and a lack of obvious high-energy sedimentary structures or evidence of reworking in layers spanning the D/C boundary suggest conformable deposition in a quiet, restricted subtidal paleoenvironment. Fifty-nine fifth-order cycles combine to depict a shallowing-upward succession (beds 029-01; highstand systems tract of a third-order sequence representing the terminal Devonian). The highstand systems tract is overlain by a deepening-upward succession (beds 0-29; maximum flooding surface and transgressive systems tract of a third-order sequence representing predominantly the basal Carboniferous) that begins at the D/C boundary. Fischer plot analysis of high-frequency cycles at the D/C boundary confirms this well developed sea-level pattern, which, together with the tuff and black shale depositional events, has potential for global correlation. On the basis of this new single-zircon SHRIMP age and previously published work on the biostratigraphy and sequence stratigraphy of the D/C transition interval, the deposition of tuff took place at approximately 359.6Ma, and the age of the D/C boundary at Daposhang, Guizhou, China, is estimated at 359.58Ma.

The Parautochthonous Gondwanan origin of the Cuyania (greater Precordillera) terrane of Argentina : a re-evaluation of evidence used to support an allochthonous Laurentian origin

A substantial, diverse body of evidence has been interpreted as suggesting that the Cuyania terrane of northwestern Argentina, which includes the Argentine Precordillera, rifted from the Ouachita embayment of Laurentia in the Early Cambrian, drifted across the Iapetus ocean as a microcontinent, and docked with the proto-Andean margin of Gondwana in the Mid to Late Ordovician. This is the so-called Laurentian microcontinent model. However, several lines of evidence (basement age and affinity, stratigraphic, paleomagnetic and paleobiogeographical records) also point to a parautochthonous origin of this terrane. In this parautochthonous model, Cuyania migrated along a transform fault from a position on the southern margin of West Gondwana (present coordinates) in the Mid Ordovician to its modern position outboard of the Famatina magmatic belt in Devonian time. With regard to basement age and characteristics, recently acquired U-Pb geochronology of detrital zircons from Cambrian and Ordovician sandstones and of zircons from igneous clasts in an Ordovician conglomerate are difficult to explain with the Laurentian model and indicate, instead, a Gondwanan origin of the Cuyania terrane. Furthermore, potential basement rocks of Cuyania of Neoproterozoic to Early Cambrian age and Early Mesoproterozoic age are characteristic of Gondwana, rather than Laurentia. Pb isotopic ratios of Grenvillian-age basement rocks are not only similar to those of Grenvillian basement in Laurentia but also to those in other areas of West Gondwana. In terms of the stratigraphic record, the similarity of the Cambrian-Ordovician carbonate platform succession of Cuyania to that of Laurentia reflects similar paleolatitude and eustatic histories but not a direct connection. Moreover, the Middle-Upper Ordovician siliciclastic successions of Cuyania do not represent a peripheral foreland basin, but instead were deposited in strike-slip related basins in a transform fault zone. Middle Ordovician K-bentonites do not indicate that Cuyania was approaching the Famatina Magmatic arc from the west (modern coordinates), but instead that it was located to the southeast. In light of paleomagnetic data, the Cambrian paleolatitude of Cuyania is consistent not only with the location of the Ouachita embayment of Laurentia but also with the southern margin of West Gondwana. Finally, most of the paleobiogeographic criteria used to support the Laurentian model must be reconsidered. Brachiopod and conodont faunas in lower Middle Ordovician strata of the Precordillera have many more genera in common with Laurentia than those in Lower Ordovician strata. Cambrian trilobites faunas of Cuyania are of very limited abundance and diversity in comparison to correlative faunas of southeastern Laurentia; many species are endemic to Cuyania; olenellid trilobites considered to be restricted to Laurentia probably had the ability to disperse between paleoplates with similar environments. Mid Ordovician graptolites of the Precordillera on the one hand and of the Famatinian belt and Cordillera Oriental on the other belong to different oceanic provinces and likely did not live in close proximity.

Conodont dating of the Middle Ordovician breccia cap-rock limestone on Osmussaar Island, northwestern Estonia

Various mechanisms have hitherto been suggested to explain the formation of the Kundan (Middle Ordovician) Osmussaar Breccia in northwestern Estonia. Following the recent discovery of L-chondritic chromite in these peculiar, sand- penetrated strata, it seems plausible that the breccia is impact-related. Herein, the conodont faunas of three thin limestone intervals overlying the breccia at Osmussaar Island have been investigated, with the aim of establishing the age of the event in terms of the Baltoscandian conodont-based biostratigraphical scheme. Based on the presence of Microzarkodina ozarkodella, the limestone directly overlying the breccia is assigned to the M. ozarkodella Subzone of the Lenodus (Eoplacognathus?) pseudoplanus Zone. This is reinforced by means of a faunal shift between this sample interval and the subsequent one, which is directly comparable with a faunal shift in the Maekalda section, mainland Estonia. The middle, orthoceratite-yielding interval is assigned to the uppermost L. (E.?) pseudoplanus Zone (or, alternatively, the lowermost Eoplacognathus suecicus Zone), whereas the uppermost interval, an oolitic limestone, is referable to the E. foliaceus Subzone, corresponding to the lower part of the Lasnamagi Stage. These results support a connection between the Osmussaar event and the stratigraphic interval yielding abundant meteorites and/or high levels of L-type chromite in Sweden, as they both can be referred to the lower and/or middle part of the Kunda Stage. The minor difference in age between the first limestones deposited after the brecciation and the meteorite and L-chromite-yielding interval in Baltoscandia can be explained as caused by a period of non-deposition, seen as numerous hiatuses of various extent in the Kunda Stage in northwestern Estonia.

Implications of Kungurian (Early Permian) conodonts from Hatahoko, Japan, for correlation between the Tethyan and international timescales

The correlation between the fusulinid-based Tethyan and the conodont-based international timescales of the Permian System has become one of themost disputed issues among the Permian community during the past two decades. In this paper, we document a conodont fauna consisting of four species including Sweetognathus guizhouensis, Pseudohindeodus augustus, Hindeodus permicus and a new genus Meiognathus pustulus from the lower part of a large exotic limestone block at Hatahoko in the Nyukawa area, Gifu Prefecture, central Japan, which all suggest aKungurian age. The Kungurian age indicated by the conodonts is consistent with the age of the associated brachiopods, but conflicts with the Murgabian age indicated by the associated fusulinids including Cancellina nipponica, Neoschwagerina simplex, Neofusulinella praecursor etc. This co-occurrence of Kungurian conodonts and Murgabian fusulinids in central Japan suggests that previously unrecognized temporal distributions of some key fusulinid or conodont elements need to be clarified and that the intensively-disputed correlation problem between the Kungurian containing theMurgabian fusulinids at the Luodian section in Guizhou, South China with the strata containing the ammonoid Waagenoceras in Oman and Sicily was caused by artificial conodont taxonomic discrepancies. The Luodian section in South China could serve as a key reference section for the correlation of the Kungurian Stage (late Early Permian) between the Tethyan and international timescales.

Middle to Late Ordovician (Darriwilian-Sandbian) conodonts from the Dawangou section, Kalpin area of the Tarim Basin, northwestern China

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.