Conodonts of the Table Head Formation (Middle Ordovician), western Newfoundland

On the Great Northern Peninsula, western Newfoundland, the transqressive Table Head Formation (Middle Ordovician) overlies the Lower Ordovician St. George Group. The Table Head strata are overlain by carbonate breccias and easterly derived flysch deposits. The Table Head sediments include limestones, mainly rubbly, with dolostones at the base (lower Table Head), overlain by limestones interbedded with shales (middle Table Head) and black graptolitiferous shales at the top (upper Table Head). The lower Table Head limestones represent the last platform carbonate deposit before the bank foundered probably due to the emplacement of Lower Ordovician allochthons in western Newfoundland. -- The formation has been studied in detail from eight localities in the area from Bellburns community in the south to St. John Island in the north. Additional information from localities on Port au Port Peninsula and Hare Bay is included. The Table Head sediments all along on the west coast of Newfoundland compare with those in the study area. The thickness of the different units varies considerably and reaches its maximum at Table Point. The detailed investigation of the rocks revealed that carbonate accumulation was interrupted by "catastrophic" downwarps of the shelf. These may be related to the emplacement of the allochthons. -- A total of approximately 17,000 conodonts was recorded within the study area. An additional 3,000 were recorded from elsewhere in western Newfoundland. The conodont fauna is described in multi-element taxonomy, and a supragenetic classification is applied. 35 genera and Panderodontidae, and the new recognized family Cornuodontidae n. fam.. -- Two phylo-zones and four biointerval-zones are defined. The phylo-zones are based on phylogenetically related and facies independent species of Histiodella. The species from the basal lower Table Head on Newfoundland belong to Midcontinent Fauna 4, and are correlative with strata from North America. The conodonts reinforce trilobite and cephalopod data that indicate a late Whiterockian (early Llanvirnian age for these strata. The North Atlantic Province conodonts from the middle Table Head have a number of species in common with the Eoplacognathus suecicus Zone of Scandinavia. The top of the middle Table Head at Table Point may be as young as the E. suecicus-P. sulcatus Subzone. -- The Table Head strata accumulated in lagoonal, shelf (inner-outer) and slope environments. The lateral distribution of conodonts can be directly related to these depositional environments, and a sequence of three biofacies and sub-biofacies is introduced. The lagoonal (Midcontinent Province) and slope (North Atlantic Province) biofacies are distinct, whereas the shelf biofacies is less distinct. The occurrence of occasional invaders from the open oceanic biofacies can be related to the oscillating transgression

Cambrian (Series 3 – Furongian) conodonts from the Alum Shale Formation at Slemmestad, Oslo Region, Norway

Nine samples from the Alum Shale of Slemmestad, Oslo Region, were processed for conodonts. The limestone-rich interval extending from the mid Cambrian Paradoxides paradoxissimus trilobite Zone to the Lower Ordovician Boeckaspis trilobite Zone yielded a sparse conodont fauna. The fauna is dominated by the protoconodont species Phakelodus elongatus (Zhang in An et al., 1983) and Phakelodus tenuis Müller, 1959, the paraconodont species Westergaardodina polymorpha Müller & Hinz, 1991, Westergaardodina ligula Müller & Hinz, 1991, Problematoconites perforatus Müller, 1959 and Trolmenia acies Müller & Hinz, 1991; the euconodont species Cordylodus proavus Müller, 1959 is present in the Acerocarina Superzone. The presence of the cosmopolitan Cordylodus proavus Müller, 1956 at Slemmestad provides an important tie for regional and international correlation.publishedVersio

Towards a revised Sandbian conodont biozonation of Baltica

One of the key objectives of the studies proposed by the Ordovician Subcommission is the improvement of regional stratigraphy for further advancements in global correlation. The results of this work can be found in numerous updates and reviews published in the recent Geological Society, London, Special Publications âA Global Synthesis of the Ordovician Systemâ. Several of these papers refer to the Baltic Ordovician conodont biozones. While different schemes share many common features, their correlation with stages and biozones differ in detail. Considering the recent developments in the studies of the Sandbian stratigraphy in the Baltoscandian region, it is possible to complement the current conodont biozonation. Pygodus anserinus, Amorphognathus tvaerensis and A. superbus conodont zones are recognized in the Sandbian Stage in Baltica. The lower boundary of the stage is located within the Pygodus anserinus Zone, and the main part of the stage corresponds to the Amorphognathus tvaerensis Zone. In Scandinavia, the upper boundary of the stage correlates with a level within the A. superbus Zone or lies in a conodont-poor interval in the eastern Baltic region. The lower boundary of the A. inaequalisSubzone is tentatively correlated with the base of the Sandbian in Scandinavia but is located in the uppermost Darriwilian in the eastern Baltic region. In both areas, the A. tvaerensis Zone is subdivided into the Baltoniodus variabilis, B. gerdae and B. alobatus conodont subzones. The A. inaequalis Subzone â in some cases indicated as a zone â has been included in the regional stratigraphic charts for more than a decade. However, so far, A. inaequalis (Rhodes) has been reliably identified and also illustrated only from Avalonia, i.e. outside the palaeocontinent Baltica. A recent restudy of collections from the Fjäcka main section and the Smedsby GÃ¥rd drillcore (both from Sweden), as well as from several Estonian sections, did not prove the occurrence of A. inaequalisin these areas. The A. tvaerensis Zone comprises almost the whole Sandbian, both in Scandinavia and the eastern Baltic areas. During this long age, the morphology of the P and M elements of A. tvaerensis (Bergström) gradually changed, and elements of distinct morphology appeared and were assigned to a new species, Amorphognathus viirae Paiste, Männik et Meidla, 2022, in the upper part of the range of the species. In succession, A. viirae appears in the upper part of the B. gerdae Subzone. Cur­rently, A. viirae has been identified in numerous Estonian sections, as well as in the Fjäcka main section and the Smedsby GÃ¥rd drillcore in Sweden. Based on published figures, it occurs evidently in the Mójcza Formation of the Holy Cross Mountains (Poland) and the Black Knob Ridge section in Oklahoma (USA), in the GSSP for the base of the Katian Stage. A. inaequalis has also been reported and an eponymous zone identified in two other sections located on the palaeocontinent Baltica, in the Bliudziai-150 drillcore (Lithuania) and the Kovel-1 drillcore (Ukraine). During the restudy of collections from these sections, no elements of A. inaequalis were found in either of them. The earliest recorded elements of the genus Amorphognathus have been assigned to A. tvaerensis, and the specimens from the upper range of this species reidentified as A. viirae. Analysis of the new material and revision of previous collections has revealed problems related to the Sandbian conodont biozonation of the palaeocontinent Baltica and demonstrated the need for its updating. The new proposed zonation excludes the A. inaequalis Subzone, as the occurrence of its nominal taxon on the palaeocontinent Baltica could not be proved. Additionally, a new unit, the A. viirae Zone, has been included in the zonation. It corresponds to the upper part of the former B. gerdae Subzone, which is now treated as a zone. Also, all subzones based on the succession of Baltoniodus species have been elevated to the rank of zones

The Xiaoyangqiao section, Dayangcha, North China: the new global Auxiliary Boundary Stratotype Section and Point (ASSP) for the base of the Ordovician System

In 2019 the Sub-Commission on the Ordovician System approved the Xiaoyangqiao section, North China as a new ASSP section for the base of the Ordovician System. The sedimentary succession of the section is exposed in a natural outcrop near the Dayangcha Village at a position of 42°3'24''N, 126°42'21''E. It has a well-preserved, abundant and diverse fossil record across the boundary with key markers (conodonts and graptolites), which provide improved intercontinental correlation of the Cambrian– Ordovician boundary. The appearance of the first planktonic graptolites is immediately below the base of the Cordylodus lindstromi Conodont Zone. Other fossils, including acritarchs, brachiopods and trilobites are also present in the Xiaoyangqiao ASSP section. Non-biotic secondary global markers near the base of the Ordovician System include a positive carbon isotopic excursion with the maximum peak (named HSS) below the boundary, a prominent unnamed negative peak immediately below the boundary and a prominent carbon isotope excursion with positive peaks above the boundary. The latter excursion is associated with the appearance of the planktonic graptolites in the Ordovician. The strength of the Xiaoyangqiao ASSP section is the correlation between the conodonts and graptolites, correspondence of sea-level lowstands, and the matches of geochemical parameters

Redox conditions across the Cambrian–Ordovician boundary: Elemental and isotopic signatures retained in the GSSP carbonates

The final publication is available at Elsevier via https://doi.org/10.1016/j.palaeo.2015.09.014 © 2015. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/Lime mudstone samples (rhythmites) were collected at high resolution from outcrops of the Cambrian–Ordovician GSSP boundary section at Green Point (western Newfoundland, Canada). The sequence (~45 mthick) consists of slope carbonates with alternating shale and siltstone interbeds, and it spans the boundary located between the Martin Point and Broom Point members of the Green Point Formation (Cow Head Group). Samples were extracted frommicritic rhythmites by microdrilling and subsequently screened using petrographic and geochemical criteria to evaluate their degree of preservation. Although the δ13Corg profile (−29.7 to−25.6‰ VPDB) shows insignificant variations, the TOC values (0.1 to 4.1%) exhibit a generally upward decreasing trend. A negative δ13Ccarb excursion, reflecting a sealevel rise, marks a geochemical anomaly that correlates with an increase in the N contents (0 to 2.9%) of organic matter and the δ15Norg values (−0.6 to +6.0‰), which suggests a change to more reducing oceanic conditions. The U contents vary from 0.1 to 3.0 ppm and the δ238U values (−0.97 to −0.18‰) generally decrease with the negative δ13Ccarb excursion. The U isotopic variations suggest a widespread increase in reducing conditions associated with sealevel rise during this interval. The investigated sedimentary rocks were slope carbonateswhere dysoxic conditions likely dominated throughout the entire section. Therefore, the changes in the TOC, N, δ15Norg, and δ238U profiles across the boundary are not as sharp as would be expected by a local change from oxic shallow-water to dysoxic/anoxic deep-water settings.Petroleum Exploration Enhancement Program (PEEP) NSERC Discovery Grant || (RGPIN-435930) Carlsberg Foundation || (2013_01_0664

The detailed Middle to early Late Ordovician faunal succession and δ13Ccarbon chemistry of the Kårehamn drill core, offshore eastern Öland, Sweden: implications for stratigraphy and correlation

The Middle to lower Upper Ordovician stratigraphy of the KÃ¥rehamn core, drilled ca 7 km offshore to the east of the KÃ¥rehamn village, northeastern Ãland, is presented. The investigated core is one of four drill cores obtained during the preparation of the KÃ¥rehamn offshore wind farm. It is ca 41 m long and has a diameter of 10 cm. The lithostratigraphy, faunal (conodonts and chitinozoans) succession and δ13Ccarbon isotope chemistry pattern are built upon this complete core. The drilling stopped at 64.5 m b.s.l. in the Swedish Orthoceratite limestone, within the upper Lenodus variabilis Conodont Zone. The horizon is largely equivalent to the strata that in Sweden were previously named âlimestone with Asaphus âranicepsââ, which is within the Orthoceratite limestone. It is characterized by and composed of mainly light-grey, highly fossiliferous and stylolitic limestone with little clay material. The next unit includes the Yangtzeplacognathus crassus and lower Lenodus pseudoplanus conodont zones. The upper Lenodus pseudoplanus (with Microzarkodina ozarkodella late form sensu Lindström), Eoplacognathus suecicus and E. foliaceus conodont zones are recorded from the overlying succession of the upper Orthoceratite limestone. This interval corresponds to the Segerstad, Skärlöv and Seby topoformations of Jaanusson, all of which are included in the upper part of the Swedish Orthoceratite limestone. The prominent δ13Ccarbon isotope MDICE peak recorded from the KÃ¥rehamn drill core is biostratigraphically precisely assigned to the upper part of the newly redefined Eoplacognathus suecicus Conodont Zone. The conformably overlying Folkeslunda Limestone is the top unit of the Orthoceratite limestone; it is composed of lime mudstone and grey bedded wackestone. Biostratigraphically, it is referred to the Eoplacognathus reclinatus Subzone of the Pygodus serra Conodont Zone corresponding to the lower part of the Laufeldochitina striata Chitinozoan Zone. The Furudal Limestone â on Ãland known as the Källa Limestone and Persnäs Limestone â overlies the Orthoceratite limestone and represents an important change of the depositional environment in the Baltic Basin. The Källa Limestone contains the Eoplacognathus robustus Conodont Subzone of the Pygodus serra Conodont Zone and the Laufeldochitina striata Chitinozoan Zone. Pygodus protoanserinus Zhang is the transitional taxon from P. serra to P. anserinus and is securely and precisely recorded for the first time in the region. The important conodont species Pygodus anserinus Lamont and Lindström is recorded from the Persnäs Limestone (= upper Furudal Formation) from which also theLaufeldochitina striata Chitinozoan Zone is documented. Pygodus anserinus extends into the overlying Dalby Formation, in which it is succeeded by the lower Amorphognathus tvaerensis Conodont Zone. The diagnostic chitinozoans Eisenackitina rhenana, Laufeldochitina stentor, Conochitina savalaensis, Belonechitina intonsa and Conochitina viruana are well documented from the same formation. The top of the core is within the Baltoniodus variabilis Conodont Subzone of theAmorphognathus tvaerensis Conodont Zone of the Bergström conodont zonation. The precise integrated biostratigraphy of the conodonts and chitinozoans along with the carbon isotope curve are results of this study, which largely agree with those of previous research of the Baltic Basin and thus provide data for precise correlation across the Baltic Basin. The fossil assemblages are clearly related to the east Baltic chronostratigraphic scheme and to the new chronostratigraphic scheme of Scandinavia, and the succession is referred to the established stages of the two systems

Ordovician (Floian-lower Darriwilian) conodont biofacies of the San Juan Formation in the Cerro Viejo of Huaco, Argentine Precordillera

The conodont biofacies from the San Juan Formation at the Cerro Viejo of Huaco, Central Precordillera of Argentina, are analyzed for the identification of faunal dynamics and sea-level changes. The Prioniodus elegans and Oepikodus evae zones, Floian in age (Lower Ordovician), are identified in the lower San Juan Formation at the inner part of the Huaco anticline. In the western flank of the anticline the succession of the carbonate stratigraphic unit extends from the Floian/Dapingian boundary (Lower-Middle Ordovician) up to the lower Darriwilian (Middle Ordovician) Lenodus variabilis Zone. For the interpretation of conodont biofacies through the Los Gatos creek section, 5044 conodonts from rock samples of the Floian to the lower Darriwilian are studied. Conodont abundance and generic diversity graphs, and cluster analysis, reveal the following biofacies. The Juanognathus-Bergstroemognathus, Protopanderodus-Reutterodus-Drepanodus, Protopanderodus-Oepikodus, Juanognathus-Semiacontiodus and Rossodus-Periodon-Protopanderodus biofacies are determined, which indicate various deposits stacking from inner to middle and outer carbonate ramp environments of the San Juan Formation. The associated analysis of biofacies and lithology allow for the recognition of two transgressive events in the San Juan Formation at the Los Gatos creek section, which could be related to transgressive systems tracts (TST) that occurred during the Lower and Middle Ordovician. The recovered conodonts have a CAI that varies from 2 to 2.5, indicating a burial paleotemperature between 60 and 155 °C. Furthermore, the variation of CAI in conodonts of the same sample, the presence of conodonts with corroded surface lamella, recrystallization and crystal overgrowths, and the presence of stylolites in limestone beds of the San Juan Formation indicate the circulation of hydrothermal fluids.Fil: Mango, Matías Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Albanesi, Guillermo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentin

Conodonts in Ordovician biostratigraphy

The long time interval after Pander's (1856) original conodont study can in terms of Ordovician conodont biostratigraphical research be subdivided into three periods, namely the Pioneer Period (1856-1955), the Transition Period (1955-1971) and the Modern Period (1971-Recent). During the pre-1920s, the few published conodont investigations were restricted to Europe and North America and were not concerned about the potential use of conodonts as guide fossils. Although primarily of taxonomic nature, the pioneer studies by Branson & Mehl, Stauffer and Furnish during the 1930s represent the beginning of the use of conodonts in Ordovician biostratigraphy. However, no formal zones were introduced until Lindstr\uf6m (1955) proposed four conodont zones in the Lower Ordovician of Sweden, which marks the end of the Pioneer Period. Because Lindstr\uf6m's zone classification was not followed by similar work outside Baltoscandia, the time interval up to the late 1960s can be regarded as a Transition Period. A milestone symposium volume, entitled 'Symposium on Conodont Biostratigraphy' and published in 1971, summarized much new information on Ordovician conodont biostratigraphy and is taken as the beginning of the Modern Period of Ordovician conodont biostratigraphy. In this volume, the Baltoscandic Ordovician was subdivided into named conodont zones, whereas the North American Ordovician succession was classified into a series of lettered or numbered faunas. Although most of the latter did not receive zone names until 1984, this classification has been used widely in North America. The Middle and Upper Ordovician Baltoscandic zone classification, which was largely based on evolutionary species changes in lineages and hence includes phylozones, has subsequently undergone only minor changes and has been used slightly modified also in some other regions, such as New Zealand, China and eastern North America. The great importance of conodonts in Ordovician biostratigraphy is shown by the fact that conodonts are used for the definition of two of the seven global stages, and seven of the 20 stage slices, now recognized within this system