Conodont Zones Research Articles

Pennsylvanian conodont zonation of the Tapajos Group (Amazonas Basin, Brazil)

Pennsylvanian conodont zonation of the Tapajos Group (Amazonas Basin, Brazil)

Late Mississippian-Middle Pennsylvanian conodont zonation of Ukraine

Late Mississippian-Middle Pennsylvanian conodont zonation of Ukraine

Palynological and microfacies analysis of the Famennian part of the Russkiy Brod Quarry section, Central Devonian Field, Russia

Palynological investigations of samples from the Upper Devonian of the Russkiy Brod Quarry section (Zadonsk Horizon, Central Devonian Field, Russia) revealed the presence of the CZ (Cyrtospora cristifera-Diaphanospora zadonica) miospore Zone, in particular its upper part, the Za (Convolutispora zadonica) Subzone. This discovery indicates one of the lowest part of the Famennian (crepida conodont Zone). Palynofacies and microfacies analysis confirmed that deposition occurred in a shallow, marginal-marine environment. The good state of preservation of the palynomorphs enabled the recognition of additional internal exine layers in the structure of Tergobulasporites immensus and Crumenasporites monosaccus megaspore species.

New unornamented siphonodellids (Conodonta) of the lower Tournaisian from the Rhenish Massif and Moravian Karst (Germany and Czech Republic)

Conodonts of lower Tournaisian successions in the Remscheid-Altena Anticline of the Rhenish Massif (Germany) and from the Moravian Karst of the Bohemian Massif (Czech Republic) have been re-studied based on previous high-resolution conodont stratigraphy. New lower Tournaisian siphonodellids without ornamentation on the oral platform side were recorded here in carbonate pe- lagic and turbiditic settings. Siphonodella belkai, which was previously unknown in western Europe, is the most abundant species among the unornamented siphonodellids. Two morphotypes of Si. belkaias well asSi. kalvodai sp. nov. are defined herein. The new faunas occur in the jii, sandbergi, andquadruplicata conodont zones. Siphonodella kalvodai sp. nov. has its FAD in the jii Zone, and Si. belkai first occurs in the basal jii Zone in both regions. The basal jii Zone can therefore be correlated with the basal belkai Zone established in neritic and pelagic settings of the East European Platform and Uralian Mountains. The new faunas enable a more precise correlation between lower Tournaisian biozones established previously in Central, South and Western Europe, North America, China, and East European and Uralian regions. Distributional restrictions of unornamented siphonodellids indicate a subordinate ecological significance but points out their palaeogeographic provincialism, tied to the northern Palaeotethys or palaeoequatorial realm.

An intercalibrated Triassic conodont succession and carbonate carbon isotope profile, Kamura, Japan

The Kamura section, located in the Chichibu Belt of Kyushu Island in southern Japan, contains a succession of uppermost Permian to Upper Triassic shallow-marine atoll sediments from the mid-Panthalassic Ocean. In the present study, carbonate microfacies, conodont biostratigraphy, and carbonate carbon isotopes were analyzed, making it possible to construct a detailed biochronological framework for the Triassic of the central Panthalassic region. A total of 14 conodont zones are recognized from the uppermost Changhsingian to the upper Norian. The Lower Triassic contains the Hindeodus parvus, Isarcicella isarcica, and H. postparvus zones (Griesbachian), the Neospathodus dieneri Zone (Dienerian), and the Novispathodus ex gr. waageni-Parachirognathus Zone (Smithian), while no evidence of the upper Lower Triassic Spathian substage was recovered at Kamura. The overlying Middle Triassic section consists of the Chiosella ex gr. timorensis-Cratognathus, ‘Paragondolella’ ex gr. alpina-Pg. ex gr. excelsa, Budurovignathus hungaricus, and B. mungoensis zones, followed in the Upper Triassic by the Quadralella tadpole-Gladigondolella malayensis, Q. lobata-Q. carpathica, Primatella cf. orchardi-Pr. permica, Epigondolella rigoi-‘Pg.’ hallstattensis, and E. ex gr. bidentata-Norigondolella steinbergensis zones. The exact stratigraphic intervals present at Kamura were refined through intercalibration of the conodont biozonation data with its δ13Ccarb profile, which shows a characteristic series of negative and positive excursions that correspond to well-established global reference profiles. The Permian–Triassic boundary is placed 0.20m above the Mitai-Kamura formation contact (a reference datum corresponding to the end-Permian extinction horizon, =0m) based on the first appearance of H. parvus, and the Olenekian–Anisian boundary is placed 17.60m above the reference datum based on the first appearance of Ch. ex gr. timorensis.Kamura carbonates were assigned to six fabric types and 17 microfacies. The microfacies succession records a deepening immediately following the end-Permian mass extinction, a strong shallowing during the mid to late Smithian, development of an unconformity spanning the entire Spathian, and minor sea-level fluctuations during the Middle and Late Triassic. The Spathian unconformity is attributed to a eustatic fall related to a sharp cooling event at or close to the Smithian–Spathian boundary that exposed the Kamura atoll. The subsequent resumption of shallow-marine sedimentation in the earliest Middle Triassic was probably due to continued thermal subsidence of the oceanic crustal basement beneath the atoll. The present work is the most complete analysis to date of the conodont biostratigraphic, carbon isotope chemostratigraphic, and eustatic records of the Triassic System in the central Panthalassic Ocean and should serve as a regional reference standard in the future.

Revised Wuchiapingian conodont taxonomy and succession of South China

AbstractSouth China has become the most important area to establish a global stratigraphic framework of the Wuchiapingian Stage because complete Wuchiapingian sequences include the GSSPs for the base and top of the stage. As the markers of the Wuchiapingian GSSP, conodonts are the most important fossil group to establish the Wuchiapingian biostratigraphic framework. However, few documents have investigated in detail the conodont biostratigraphic succession through the entire Wuchiapingian Stage. Furthermore, the conodont taxonomy of several WuchiapingianClarkinaspecies is still debated. Therefore, we here review all WuchiapingianClarkinaspecies from South China and figure ontogenetic growth series from juvenile to adult individuals for each valid and important species in order to revise both Wuchiapingian conodont taxonomy and the biostratigraphic succession. Based on the Penglaitan, Dukou, and Nanjiang sections, seven conodont zones (Clarkina postbitteri postbitteri,C.dukouensis,C.asymmetrica,C.leveni,C.guangyuanensis,C.transcaucasica, andC.orientalis) are recognized. The WuchiapingianClarkinaspecies lineage is also reviewed to confirm the conodont biostratigraphic framework. The Guadalupian-Lopingian boundary (GLB) interval represents a sequence boundary. The time framework of the pre-Lopingian extinction interval indicates that the beginning of the end-Guadalupian regression is in the upper part of theJinogondolella postserrataZone, and the beginning of the early Lopingian transgression is in the lower part of theClarkina dukouensisZone in South China.

Hirnantian (Ordovician) through Wenlock (Silurian) conodont biostratigraphy, bioevents, and integration with graptolite biozones, Cape Phillips Formation slope facies, Cornwallis Island, Canadian Arctic Islands

Cornwallis Island in the Canadian Arctic Archipelago provides one of the world’s best areas for establishing an integrated graptolite–conodont biozonation for the Late Ordovician – Silurian given the well-exposed interfingering relationship of the basinal shale and carbonate platform facies. Building on earlier graptolite work, 180 samples were collected from nine sections of the Cape Phillips Formation, of which 118 yielded approximately 7600 conodont elements representing 54 species in 25 genera, including one new genus and species, Mayrodus melchini; the conodonts are well preserved, with minimal thermal alteration (colour alteration index, CAI 1). Nine conodont zones are recognized and defined for this region, namely the Amorphognathus ordovicicus, Distomodus kentuckyensis, Aspelundia expansa, As. fluegeli, and Pterospathodus celloni Interval zones, Pt. a. amorphognathoides Taxon-range Zone, Pt. pennatus procerus and Kockelella ranuliformis Highest-occurrence zones, and K. ortus absidata Taxon-range Zone. An integration of graptolite and conodont zones is documented. Earlier paleontological and isotope geochemical studies have demonstrated the dynamic nature of the Silurian ocean–climate system and identified major faunal turnovers or events. Five of these are recognized in the Cornwallis fauna and related to oceanographic and climate changes, in part referring to recent oxygen isotope data from conodonts from the Cornwallis collections: Hirnantian extinction event, Sandvika Event (late Aeronian, Llandovery), Snipklint Primo Episode (early Telychian, Llandovery), Ireviken Event (late Telychian, Llandovery–Sheinwoodian, Wenlock), and Mulde Event (early Homerian, Wenlock).

Integrated record of Ludlow (Upper Silurian) oceanic geobioevents – Coordination of changes in conodont, and brachiopod faunas, and stable isotopes

The Ludlow Epoch (Silurian) was marked by several globally recognized but mechanistically poorly understood biotic events. The most pronounced of them was the Lau Event, which strongly decimated conodont, graptolite, and brachiopod faunas. Additionally, this event coincides with the largest positive stable carbon isotopic anomaly in the whole Phanerozoic, as well as the resurgence of the so-called “anachronistic” microbial facies that were frequently encountered during survival episodes of the major mass extinction events. In this contribution, based on the analysis of the outer shelf facies succession (Milaičiai-103 core), from the Lithuanian part of the Silurian Baltic Basin, as integrated quantitative record of conodont, brachiopod and δ13C changes across most of the Ludlow is presented. The succession was subdivided into four conodont zones that served as a stratigraphic framework for analyzing the δ13C and palaeoecological trends. The depth constrained cluster analysis revealed successions of three statistically distinct conodont and six statistically distinct brachiopod assemblages that replace each other near the change points in the stable carbon isotopic curve. The application of a newly developed mathematical technique based on the analysis of recurrence patterns of the fossil assemblages revealed that both conodonts and brachiopods are represented by highly time specific assemblages in the aftermath of the Lau event (O. snajdri Interval Zone). The anomalous interval is confined to the transgressive and highstand phases of the 3rd order post-Lau transgression. The discussed interval is coeval with the extensive development of stromatolitic communities in the nearshore environments around the world. The results allow for the first time to quantify the profound ecosystem-wide geobiological impact of the mid-Ludfordian event that lasted up to the latest Ludfordian.

Restoration of reef ecosystems following the Guadalupian–Lopingian boundary mass extinction: Evidence from the Laibin area, South China

The Guadalupian–Lopingian boundary (GLB), also Middle–Late Permian boundary, mass extinction severely destroyed metazoan reef ecosystems, although some studies argued that both biotic and environmental turnover across the GLB are not so obvious. When compared with prolifically developed reefs in the Capitanian, the Wuchiapingian reef examples appear depauperate and almost 89% of the carbonate production in these bioconstructions was lost. Here, we report a typical sponge reef from the Wuchiapingian stage in the Tieqiao section, central Guangxi Province, South China. The Tieqiao reef might represent the only example of a Wuchiapingian metazoan reef in the eastern Palaeo-Tethys region. It provides insight into ecosystem restoration following the GLB extinction. Major constructors of the Tieqiao reef are sponges (Peronidella, Parauvanella, Sollasia, Tabulozoa, and Amblysiphonella), algae (Anthracoporella, Archaeolithporella, Permocalculus, Gymnocodium) and Tubiphytes. This reef is well constrained as middle–late Wuchiapingian in age by the Clarkina orientalis conodont zone. Carbonate carbon isotope excursions experienced negative spikes near the GLB and multiple perturbations in the early–middle Wuchiapingian, and remained relatively stable during re-establishment of metazoan reefs in middle–late Wuchiapingian. Conodont oxygen isotopes showed that the sea surface temperature (SST) was extremely high, >30°C during late Capitanian time, punctuated by a short cooling event and global regression associated with the GLB extinction, and followed by high SST and rapid rise in sea level in the early Wuchiapingian. The reemergence of the Tieqiao reef coincided with the initial cooling in surface oceans and sea-level fall during the middle–late Wuchiapingian. Accordingly, reef ecosystems experienced a long-term depletion worldwide in early–middle Wuchiapingian time and then recovered ~2.5Myr after the GLB extinction based on estimate in integration of both conodont biostratigraphy and radiometric ages.

Uppermost Permian to Lower Triassic conodont successions from the Enshi area, western Hubei Province, South China

We present recent study results of the Lower Triassic conodont succession from the Ganxi and Jianshi areas of Enshi city, western Hubei Province, South China, which were situated on a carbonate ramp at the northeastern margin of the Upper Yangtze Platform. Therein, the uppermost Permian to Lower Triassic succession is well exposed and yielded abundant conodonts. A total of nine conodont zones are differentiated: (1) Clarkina yini Zone, (2) Clarkina meishanensis Zone, (3) Hindeodus changxingensis Zone, (4) Hindeodus parvus Zone, (5) Hindeodus postparvus Zone, (6) Clarkina planata Zone, (7) Neoclarkina aff. discreta Zone, (8) Neospathodus dieneri Zone, and (9) Novispathodus waageni Zone. The Ns. dieneri M1, Ns. dieneri M2, and Ns. dieneri M3 Subzones have also been distinguished within the Ns. dieneri Zone, and the Nv. waageni eowaageni and Nv. waageni waageni Subzones are recognizable within the Nv. waageni Zone in Jianshi. Most of the zones occur in succession, but the C. planata Zone is a local ecozone reflecting deeper water biofacies during H. postparvus Zone time. In the Jianshi section, the Permian–Triassic boundary is placed at Bed 136-2 based on the appearance of Hindeodus parvus immediately above the disappearance of Changhsingian taxa, while the Induan–Olenekian boundary (IOB) is drawn at Bed 225+40cm based on the first appearance of Nv. waageni eowaageni within the upper range of the Ns. dieneri Zone indices. The Enshi conodont zones overall correlate well with those recognized elsewhere in South China and worldwide.

Стратиграфическое значение девонских брахиопод Урала

The article considers the history of the formation of the regional stratigraphic scale of the Devonian system of the Urals, historically developed on the basis of the study of benthic fauna (mainly brachiopods). Currently, it is represented by the following Regiostages and horizons of stratotypic areas (bottom-up): Mansian (Sarainaya and Sauma Horizons), Vitimian (Vizhai and Toshemka Horizons), Yurtishchian (Karpinsk and Tal'tiya Horizons), Loz'vian (Langur and Vysotinka Horizons), Ryauzyakian (Pashiya, Kyn, Sargaevo, Domanik, Mendym and Askyn Horizons), Zilimian (Makarovo, Murzakaevo, Kushelga and Lytva Horizons). Stratotypes of the four lower superhorizons are located on the eastern slope of the Urals, and two upper ones on its western slope. Regiostages are common to both subregions. The comparison focuses on the regional scale of the Urals with the International stratigraphic scale shows that the borders Pragian/Emsian, Emsian/Eifelian, Givetian/Frasnian, Frasnian/Famennian not coincide with the boundaries of the Ural regional horizons. The lower boundaries of the Devonian stages in the Urals are carried out according to the GSSP at the base of the conodont zones Icriodus woschmidti postwoschmidti (Lochkovian Stage), Eognathodus sulcatus sulcatus (Pragian Stage), Polygnathus dehiscens (Emsian Stage), Polygnathus costatus partitus (Eifelian Stage), Polygnathus hemiansatus (Givetian Stage), inside the lower subzone conodont zone Mesotaxis falsiovalis, higher extinction of Skeletognathus norrisi and coincides with the appearance Ancyrodella rotundiloba (Fransnian Stage), the base conodont zone Palmatolepis triangularis (Famennian Stage). The article deals with the stratigraphic distribution of the key genera and species of the Devonian brachiopods by series, stages and horizons. The regional and interregional correlation possibilities of the studying the brachiopod fauna in the Urals are shown. The tables show the stratigraphic distribution of the key genera of brachiopods in the Devonian sediments of the western and eastern slopes of the Urals according to the authors' data with the use of data of I.A. Breivel`, M.G. Breivel`, V.P. Sapel`nikov, A.P. Tyazheva and A.N. Khodalevich monographs. It is concluded that the brachiopods, due to its multiplicity, diversity, relatively rapid evolution in time and widespread in offshore sediments are widely used in the construction of regional stratigraphic scales. The results of the study of the Devonian brachiopods of the Urals, taking into account the distribution of this group of fauna in other regions, make it possible to reliably correlate the sediments at the regional and interregional levels. Some lag in the rate of evolutionary development from conodonts does not reduce the stratigraphic significance of the Devonian brachiopods, allowing detailed subdivision and the global correlation of Devonian deposits.

New Data on the Age of the Yukiang (Yujiang) Formation at Liujing, Guangxi, South China

AbstractThe age of the Yukiang (Yujiang) Formation has been shrouded in controversy for more than 75 years. New investigation at the Liujing section, Hengxian County, Guangxi, has revealed a conodont sequence assignable to two Early Devonian conodont zonations: the Eognathodus kindlei?–Polygnathus pireneae Zone and the Polygnathus nothoperbonus Zone from oldest to youngest. The Gaoling and Mahuangling members of the Nahkaoling (Nagaoling) Formation and the overlying Xiayiling Member and lower part of the Shizhou Member of the Yukiang Formation are proven to belong to the Pragian Eognathodus kindlei?–Polygnathus pireneae Zone. The co‐occurrence of Polygnathus pireneae and Pol. sokolovi in the lower part of the Shizhou Member demonstrates that this interval can be approximately correlated with the uppermost part of the Polygnathus pireneae Zone. However, precise level identification of the Pragian–Emsian Boundary (PEB) in the Liujing section remains dfficult due to the scarcity of suitable limestone samples for conodont analysis from the middle and upper parts of the Shizhou Member. The Daliancun and Liujing members of the Yukiang Formation and the lower part of the overlying Moding Formation are assigned to the Polygnathus nothoperbonus Zone with the nominal species of this biozone ranging from the bottom of the Daliancun Member to the lower part of the Moding Formation.

An early Tournaisian (Mississippian) bryozoan fauna from the Moravian Karst (Rhenohercynian Zone, Czech Republic)

Bryozoans are described from the lower Tournaisian of the Moravo-Silesian Zone (part of the Rhenohercynian Zone) of the Czech Republic for the first time. The studied fauna displays poor diversity and small size; it is represented by encrusting unilaminar and delicate branching growth habits. One species, Eridopora moravica, is new, and three other species are left in open nomenclature: Nikiforovella sp., Saffordotaxis sp., and ?Streblotrypella sp. Bryozoans found within calciturbidites of the Siphonodella sulcata and Siphonodella quadruplicata conodont zones inhabited originally the littoral zone at the southern margin of Laurussia. They indicate links between the eastern and western parts of the northern Palaeotethyan Siberian and Panthalassan realms.

An Integrated Stratigraphy of the Frasnian-Famennian Boundary Interval (Late Devonian) in the Moravian Karst (Czech Republic) and Kellerwald (Germany)

Rapid and profound changes in Earth surface environments and biota across the Frasnian-Famennian (Fr-Fa) boundary are well known and related to one of the five most severe mass extinction events in Earth history. Here, we present sedimentological, biostratigraphical, petrophysical (gamma-ray spectrometry, magnetic susceptibility) and geochemical (X-ray fluorescence) data from environmentally distinct sections in the Moravian Karst (Czech Republic) and compare them with the Steinbruch Schmidt section in the Kellerwald (Rheinisches Schiefergebirge, Germany). Both areas were located at the southern margin of Laurussia. The studied sections span the interval from the Lower or Upper rhenana to the Palmatolepis minuta minuta or younger conodont zones and the foraminiferal Eonodosaria evlanensis Zone and Eonodosaria evlanensis-Quasiendothyra communis Interzone including high resolution biozonation of the Fr-Fa boundary interval. In the Moravian Karst pure limestone facies of an inclined carbonate ramp reflect the worldwide trend in the widespread occurrence of calcimicrobes during upper Frasnian and lower Famennian. Geochemical and petrophysical data show a decrease in grain size of the siliciclastic supply and carbonate productivity in the Kellwasser Event intervals probably due to a deepening and correlate with maximum flooding surfaces and highstand system tracts in the Steinbruch Schmidt. Certain differences in some geochemical proxies between the Moravian Karst and Steinbruch Schmidt are due to lower carbonate dilution of the latter. Significant Zr, TiO2, Mn or Fe2O3 enrichments may indicate the influence of volcanic sources in the studied Moravian Karst Fr-Fa sections.

Restudy of the Early Devonian rugose coral Xystriphylloides from South China

Early Devonian rugose coral Xystriphylloides in South China is restudied from the perspective of its taxonomic definition, biostratigraphy, paleoecology, and implication for the Yujiang Event. The diagnostic characters of the genus are clarified and its taxonomic position is also revised. In particular the septa of Xystriphylloides are shown to be fibrous rather than trabeculate. Xystriphylloides distinctus Yu n. sp. is described. Species of Xystriphylloides are widely distributed in South China and North Vietnam, so they are useful for regional biostratigraphic correlation and regional geological mapping. As an important biostrome builder, Xystriphylloides became extinct below the base of the nothoperbonus Conodont Zone, so it can be considered as one of the important pieces of evidence for recognizing the first episode of the Early Devonian Emsian Yujiang Event, which is also significant for studying paleoecology and event stratigraphy.

Conodont and ammonoid biostratigraphies around the Permian-Triassic boundary from the Jianzishan of South China

Conodonts and ammonoids have played significant roles in the Permian-Triassic timescale. In order to uncover the nature of the Permian-Triassic mass extinction and subsequent recovery, we studied conodont and ammonoid biostratigraphies around the Permian-Triassic boundary from Jianzishan of Hubei, South China. A total of four conodont zones and two ammonoid beds are recognized. In ascending order, the conodont zones are Late Changhsingian Clarkina changxingensis Zone, Clarkina yini Zone and Griesbachian Hindeodus parvus Zone, Hindeodus postparvus Zone; the ammonoid beds are Late Griesbachian Ophiceras beds and Early Dienerian Ussuridiscus varaha beds. At Jianzishan, Ophiceras beds are stratigraphically younger than Hindeodus parvus Zone, but it is likely to be the same level with Hindeodus postparvus Zone. The Lower Dienerian in Bed 8 in this section is characterized by ammonoid Ussuridiscus varaha beds, which is associated with many Late Griesbachian conodonts including Hindeodus postparvus, Hindeodus praeparvus, Hindeodus typicalis, Hindeodus pisai, Hindeodus latidentatus, Hindeodus parvus, Hindeodus anterodentatus and Isarcicella turgida, indicating these conodont species could pass through the Griesbachian-Dienerian boundary and occurred in the Early Dienerian oceans.

High-resolution C-isotope chemostratigraphy of the uppermost Cambrian stage (Stage 10) in South China: implications for defining the base of Stage 10 and palaeoenvironmental change

AbstractThe Wa'ergang section in South China has been proposed as a potential Global Stratotype Section and Point (GSSP) for the base of Stage 10, the uppermost stage of the Cambrian System. In this study, high-resolution C-isotopic compositions are reported and we identified three large negative δ13C excursions, namely N1, N2 and N3, at Wa'ergang. The N1 is located just above the First Appearance Datum (FAD) of Lotagnostus americanus, corresponding to the possible base of the Proconodontus posterocostatus conodont Zone. The N2 was identified within the Micragnostus chuishuensis trilobite Zone and the Proconodontus muelleri conodont Zone. The N3 is located in the lowermost part of the Leiagnostus cf. bexelli – Archaeuloma taoyuanense trilobite Zone or Eoconodontus conodont Zone. The N1 and N2 can be correlated with the negative δ13C excursions preceding the Top of Cambrian Carbon Isotope Excursion (TOCE) observed globally. The N3 can be correlated with the TOCE or the HEllnmaria–Red Tops Boundary (HERB) Event. The inter-basinal correlation of N1 and L. americanus strongly supports that the base of Stage 10 may be best defined by the FAD of L. americanus. We also used a box model to quantitatively explore the genesis of the negative δ13C excursions from South China. Our numerical simulations suggest that weathering of the organic-rich sediments on the platform, probably driven by intermittent sea level fall and/or the oxygenation of the Dissolved Organic Carbon (DOC) reservoir in seawater, may have contributed to the generation of the negative δ13C excursions observed in the Stage 10 at Wa'ergang in South China.

Small-sized brachiopods from the Upper Frasnian (Devonian) of central Hunan, China

Abundant small-sized brachiopods of the uppermost Frasnian (probably the Palmatolepis linguiformis Conodont Zone) are reported here for the first time from South China. These brachiopods range in size from less than 1mm to approximately 7mm and consist of, in the order of abundance, the spiriferides (Thomasaria? baii n. sp., Thomasaria? liangi n. sp., Xiangia liaoi n. gen. n. sp., and Spiriferida gen. et sp. indet.), the terebratulide Qidongia tani n. gen. n. sp., the athyridide Athyris supervittata Tien and Athyris? sp., the rhynchonellide Levipugnax? liui n. sp., the spiriferinide Cyrtinaella? houi n. sp., the pentameride Gypidula xui n. sp., and the orthide Aulacella? sp., associated with abundant atrypid juveniles (mostly Iowatrypa pseudobodini), Productella sp., and Hypothyridina sp. This fauna represents the last and significant brachiopod flourishing episode in the Frasnian before the Frasnian–Famennian Event in South China.

Middle Cambrian through lowermost Ordovician conodonts from Hunan, South China

AbstractSince 1986, samples with a total mass of more than 14,000 kg, mainly from three key sections in western Hunan, South China, have been processed for conodonts. Previous work mainly focused on biostratigraphy, but the taxonomy has been performed only on the faunas of the middle Cambrian. Described herein are conodonts of the upper Cambrian (Furongian Series) through lowermost Ordovician from Hunan, South China. Conodonts of the middle Cambrian are redescribed, based on material that has been recovered for more than three decades. The fauna consists of 82 species belonging to 36 genera. Newly established genera areLugnathusn. gen.,Miaognathusn. gen.,Millerodontusn. gen.,Tujiagnathusn. gen.,Wangcunellan. gen. andWangcunognathusn. gen. New species areCoelocerodontus hunanensisn. sp.,Furnishina wangcunensisn. sp.,Laiwugnathus hunanensisn. sp.,Laiwugnathus transitansn. sp.,Lugnathus hunanensisn. gen. n. sp.,Miaognathus multicostatusn. gen. n. sp.,Millerodontus intermediusn. gen. n. sp.,Prosagittodontus compressusn. sp.,Tujiagnathus gracilisn. gen. n. sp.,Wangcunella conicusn. gen. n. sp.,Wangcunognathus elegansn. gen. n. sp.,Westergaardodina dimorphan. sp.,Westergaardodina gigantean. sp., andWestergaardodina solan. sp. The taxonomy of some conodont genera is revised. In the light of histological investigation, genera are assigned to euconodonts, paraconodonts, or protoconodonts. The 13 conodont zones previously proposed in the middle Cambrian through lowermost Ordovician remain the same, but taxa within these conodont zones are documented more clearly because of the revised taxonomy proposed herein.

The Devonian Horn River Group and the basal Imperial Formation of the central Mackenzie Plain, N.W.T., Canada: multiproxy stratigraphic framework of a black shale basin

This study proposes six new lithostratigraphic units and redefines two others within the Horn River Group (HRG), a shale-dominated succession recently prospected for shale hydrocarbons. Its lower Hare Indian Formation rests on a drowning unconformity. In the SOB area (the area between Norman Wells and the Keele tectonic zone), this formation consists of the Bluefish black shale, Francis Creek grey shale, and Prohibition Creek black shale members. The latter two are lateral equivalents of the grey shale Bell Creek Member (updated definition) in the northern part of the study area. The overlying Canol Formation in the SOB area is divided into the Vermillion Creek and Dodo Canyon members. The Prohibition – Dodo Canyon package is ≥100 m thick and composed of brittle siliceous mudrocks with median SiO2 68%–79%, Al2O3 6%–9%, varying amount of calcite and dolomite, and type I–II kerogen with median TOC 4.5%. The thin Canol Formation blanketing Kee Scarp carbonate banks is identified as its Dodo Canyon Member. The latter is a “sweet bed” for fracking with median SiO2 75%–79%, TOC 5.1%, and trace-metal signatures indicating strongest anoxia in the section. The Mirror Lake Member in the base of the overlying Imperial Formation consists of soft illite-rich grey shales with minor siderite and dolomite. The overlying Loon Creek Member is composed of Canol-like black shale facies in its basal part and less organic-rich, lighter-colored shales and siltstones above. The Loon Creek Member is partly coeval with an overlying succession of sandstones and siltstones of the Canyon Member in its updated definition. Conodont data do not indicate significant time gaps between lithostratigraphic units. The majority of standard conodont zones from the uppermost Eifelian (ensensis Zone) up to the middle Frasnian (punctata Zone) are recognized. Assemblages of the hemiansatus and semialternans/latifossatus zones are missing probably owing to scarcity of conodont samples. The base of the HRG approximates the Eifelian–Givetian boundary, and the Hare Indian Formation is mostly Givetian. The Vermillion Creek Member spans the Givetian–Frasnian boundary. In places where thick Kee Scarp carbonates aggrade on thick sections of the Bell Creek Member, the Kee Scarp – Canol contact is found within the transitans Zone and the Middle Frasnian punctata Zone conodont assemblage is found in the basal part of the Dodo Canyon Member. The main part of the Dodo Canyon Member and basal beds of the Imperial Formation remain undated.