Standard Conodont Zonation Research Articles

Kedzydshor Formation and conodonts of the Lower Frasnian on the Izyayu River (South of the Tchernyshev Uplift)

Research subject. Conodonts of the Lower Frasnian Kedzydshor Formation of the southern part of the Tchernyshev Uplift. Materials and methods. Materials obtained during a study of the section of the Kedzydshor Formation located on the Izyayu River were used. The biostratigraphic subdivision of the section was based on taxonomic definitions of conodonts and correlations with the Standard and Frasnian conodont zones. Results. In comparison with the stratotype of the Kedzydshor Formation, carbonate-argillaceous deposits cropping out on the Izyayu River are represented by fragments of the middle and upper parts of the Kedzydshor Formation in the stratigraphic range of the Lower falsiovalis Zone of the standard conodont zonation of the Lower Frasnian. The predominantly carbonate interval of the section is conventionally correlated with the FZ1 conodont zone, while the overlying terrigenous interval – with FZ2. The polygnatid and polygnatid-ancyrodellid conodont biofacies dominate in the section under study. Conclusions. New data on the distribution of cono donts across the Kedzydshor Formation in the Izyayu River section were obtained. The obtained data were compared with the local stratigraphic units of the Timan-North Urals Region. The Kedzydshor Formation is one of the most complete sequences of the Middle-Upper Devonian transition, thus representing the basis for searching and substantiating the position of the debatable lower boundary of the Frasnian Stage of the Upper Devonian.

Features of the sedimentation, stratigraphy and carbon isotope record of the upper Tournaisian of the Verkhnyaya Usa depression (Polar Urals)

Research subject. Upper Tournaisian clayey-siliceous-carbonate deposits of the Malaya Usa section (Polar Urals).Material and methods. The composition and structure of the deposits (50 samples, 51 thin sections) of the section were considered to determine the conditions of sedimentation; 13 samples were chemically disintegrated in 7–10% solution of acetic acid, and thin sections were studied for biostratigraphic analysis (conodonts, ostracods, and foraminifers); the carbon and oxygen isotopic composition of carbonate deposits (49 samples) were analyzed. A three-stage screening test of samples for isotopic-studies was carried out.Results. The Malaya Usa section comprises mainly micritic limestones with fossils silicified to various degree (wackstone to packstone). The features and composition of the sediments indicate sedimentation in low dynamic conditions below the wave base. Biostratigraphic analysis is based on the identification of foraminifers, as well as a few conodonts and ostracods. Foraminifers characterize the Eotextularia diversa–Dainella chomatica Zone, which is approximately comparable to the Upper typicus–anchoralis–latus conodont zonal interval and Entomoprimitia malinovkaensis‑Marginia tschigovae ostracode zones of the top of the Tournaisian. The isotope-geochemical data obtained from the section demonstrate a general lightening trend in the isotopic composition of δ13Ccarb up the section. This trend, along with the biostratigraphic data, mades it possible to compare the δ13Ccarb sequence of the Malaya Usa section with sequences from a number of geographically separated sections of the world (Belgium, South China, USA), which are considered as the Tournaisian isotope carbon event (TICE).Conclusions. The deposits of the studied section were probably formed under the conditions of a very gentle slope (ramp), where the material accumulated at the foot as a filling sequence in the southern part of the Korotaikha intrashelf paleodepression. Using the Malaya Usa section as an example, it is shown that not only the peak positive deviations of the TICE in the upper part of the isosticha Zone and in the lower part of the typicus Zone, but also the isotopic structure of the upper Tournaisian has a significant correlation potential. The use of the isotope-geochemical method as an auxiliary application to biostratigraphy made it possible to improve the age determination of the section from the interval of the Upper typicus–anchoralis–latus conodont zonal interval to the Upper typicus Zone of the standard conodont zonation.

Biostratigraphy of Devonian-Carboniferous boundary in Tuyeh-Darvar section, north of Iran

Devonian-Carboniferous boundary is not clear in the Eastern Alborz Mountains. In the current study Tuyeh-Darvar section with about 170 m, thickness is selected. In this investigation, the primary goal is revision of Devonian/Carboniferous Boundary (known as DCB) and the other goal is the redefinition of the DCB as a famous necessity (based on ICS program in 2008 for defining the boundary and to find a new GSSP). According to Conodont data from acid-leaching 53 carbonate samples(by acid acetic) that obtained from Late Devonian and Early Carboniferous deposits in this section, and based on standard conodont Zonation 6 Zone are recognized;1. Bi.ultimus/or Si.praesulcata Zone, 2. Pr.kockeli /or Si.sulcata Zone, 3. Si.duplicata to Si.sandbergi bio interval, 4. Si.crenulata Zone, 5.Gnathodus-P.inornatus Zone, and 6.Ps.multistriatus Zone. Considering to the Conodont Zones above mentioned, Conodont faunas and other evidences, in the Tuyeh-Darvare section the DCB, is located within cream to grey silt stone beds, which are lies between K6 limestone and K8 dark carbonate beds (about 7.10 m above the base of recent studied section).

Frasnian age (upper devonian) key section biostratigraphic characteristic of Voronezh anteclise middle part (well 16, Schigry, Nizhnekrasnoe village, Kursky region)

Conodonts, scolecodonts, and foraminifers were studied from Frasnian age deposits of Well 16 Schigry (Nizhnekrasnoe village, Voronezh anteclise). Six conodont complexes are identified: I in Timan regional stage, II and III in Sargaevo regional stage, and IV and VI in Semiluky regional stage. Correlation by local zonal units and Standard Conodont Zonation is performed. Shallow environment is confirmed for Timan regional stage, the deepest environment settings is confirmed for Semiluky regional stage. Five scolecodont complexes are identified: complexes 1 and 2 for Sargaevo regional stage, complexes 3 and 4 for Semiluky regional stage, and complex 5 for the upper part of Semiluky regional stage and Voronezh regional stage. Foraminifers are presented by two complexes: first for Sargaevo regional stage and the second for the Semiluky regional stage. The characteristic microfossils species are given in plates.

Biostratigraphic Characteristic of the Frasnian Age (Upper Devonian) Reference Section in the Central Voronezh Anteclise (Shchigry-16 Borehole, Nizhnekrasnoe Village, Kursk Oblast)

Conodonts, scolecodonts, and foraminifers from the Frasnian Age (Upper Devonian) (Shchigry-16 borehole, Nizhnekrasnoe village, Voronezh anteclise) were studied. Six conodont assemblages were identified: I for the Timan regional stage, II and III for the Sargaevo regional stage, and IV–VI for the Semiluky regional stage. These assemblages were correlated with local zonal subdivisions and the Standard Conodont Zonation. It was established that a shallow-water environment was characteristic of the Timan regional stage; the deepest environment was characteristic of the Semiluky regional stage. Five scolecodont assemblages were identified: 1 and 2 in the Sargaevo regional stage, 3 and 4 in the Semiluky regional stage, and 5 in the upper part of Semiluky and Voronezh regional stages. Two foraminiferal assemblages are distinguished for the Sargaevo and Semiluky regional stages. The characteristic microfossils species are given in plates.

Conodont zonation and the Devonian/Carboniferous (Famennian/Tournaisian) boundary in the Naltaş section, eastern Taurides, Turkey

Conodont faunas from the Devonian/Carboniferous Naltaş section (eastern Taurides, Turkey) are presented. The faunas include important marker species of the latest Devonian earliest Carboniferous interval, belonging to the genera Siphonodella, Bispathodus, Polygnathus, Pseudopolygnathus, Apatognathus and Branmehla. Four conodont zones, comparable to the standard conodont zonation, are established in the studied succession, from the oldest to the youngest: (1) Bispathodus ultimus, (2) Siphonodella praesulcata Zones (Upper Famennian), (3) Siphonodella sulcata and (4) Siphonodella bransoni Zones (Lower Tournaisian). The Devonian/Carboniferous boundary in the eastern Taurides is recognized by the first appearance of Siphonodella sulcata.

Famennian Fusulinina (Foraminifera) from the Holy Cross Mountains (central Poland)

Calcareous foraminifers representing 9 species and 5 genera were investigated in two Famennian sections located in the south‐western part of the Holy Cross Mountains (HCM), central Poland. They constitute redeposited material that, together with crinoids and calcareous algae, comprise the dominant component of limestone turbidite beds intercalated with deep‐marine marly sediments. The calcareous material was redeposited from an unknown carbonate platform located probably to the south of the HCM area. The first appearance data of foraminifers, mainly from the quasiendothyrid group, correlated to the Standard Conodont Zonation, indicate a diachronous appearance of the same species in different parts of Europe due to a migration delay from the foraminiferal evolutionary centre located in the south‐eastern shelves of Laurussia in the neighbouring areas. As a result, the Moravian foraminiferal zonation, where index taxa appeared in similar stratigraphic intervals, was chosen as the most applicable to the stratigraphy in the central Polish area. The Quasiendothyra communis–Eonodosaria evlanensis Interzone, the Quasiendothyra communis–Quasiendothyra regularis Zone and Quasiendothyra kobeitusana–Quasiendothyra konensis Zone were distinguished, respectively, in the HCM sections. Copyright © 2012 John Wiley & Sons, Ltd.

Devonian stratigraphy in Estonia: current state and problems

An updated version of the Devonian stratigraphical chart of Estonia with comments is presented. Estonian regional stratigraphical units are correlated with the standard conodont zonation and miospore zonation, used in the western part of the East European Platform. The fossil fish zonations, largely accepted in the Main Devonian Field, are discussed. Differences in the position of series and stage boundaries and age determination of regional units in the Baltic area, Belarus and NW Russia are dealt with. Two key markers for the correlation of the Middle Devonian of the Baltic area and Scotland, based mainly on placoderms, are described. Special attention is paid to occurrences of inarticulate brachiopods and finds of rare articulate brachiopods in siliciclastic rocks of the Baltic area, indicating their marine origin.

Geochemical and palynological study of the Upper Famennian Dasberg event horizon from the Holy Cross Mountains (central Poland)

AbstractIntegrated palynological, organic and inorganic geochemical and petrographical methods have been used for deciphering the depositional redox conditions and character of organic matter of the Famennian Dasberg event horizon from the deep-shelf Kowala succession of the Holy Cross Mountains. The ages of the investigated samples have been established, using miospore data, as VF (Diducites versabilis–Grandispora famenensis) and LV (Retispora lepidophyta–Apiculiretusispora verrucosa) miospore Zones of the Middle/Upper Famennian. In the standard conodont zonation, this corresponds to the uppermost postera to lowermost praesulcata Zones. The presence of green sulphur bacteria biomarkers and dominance of small-sized framboids together with the presence of large framboids and low values of the U/Th ratio may indicate that during sedimentation of the lower Dasberg shale, intermittent anoxia occurred in the water column, or the anoxic conditions prevailed in the upper part of the water column, while the bottom waters were oxygenated, at least briefly. Deposition of the upper Dasberg shale was characterized by both bottom water and water column anoxia. The lack of acritarcha taxa from these intervals could have been due to anoxia in the photic zone. Moreover, organic content is high in those samples. There is no geochemical evidence for anoxia during sedimentation of the deposits sandwiched between the lower and upper Dasberg shales, or in the deposits which underlie and overlie both Dasberg shale horizons. The two discrete anoxic events are interpreted to be the result of major transgressions and the blooming of primary producers. Above the Dasberg shales, small fragments of charcoal and raised concentrations of polycyclic aromatic hydrocarbons are detected. This supports the presence of wildfires during deposition of shales just above the boundary of VF/LV palynological zones. Temperatures calculated from the fusinite reflectance values suggest that the charcoal was formed in low-temperature ground and/or surface fires. The typical marine character of sedimentation combined with the high proportion of charcoals suggests that wildfires were large-scale, and that there was intensive transport of terrestrial material. The main causes of intensive wildfires were a significant rise of O2 in the atmosphere and important progress in the land plant diversity during Late Devonian times. Palynofacies studies suggest that the transgression corresponds to the part IIf of the Late Devonian sea-level curve.

The biostratigraphical distribution of earliest tetrapods (Late Devonian): a revised version with comments on biodiversification

Abstract The 13 presently known genera of Late Devonian tetrapods are situated in the recently completed miospore zonation of Western Gondwana and Euramerica, in relation to the standard conodont zonation. Some of them are still unprecisely dated. The stratigraphic sequences of East Greenland, North China and East Australia are briefly reviewed to discuss the age of the tetrapods collected there and to analyse consequences in relation to the Frasnian–Famennian and Devonian–Carboniferous boundaries. Two episodes of biodiversification seem to have occurred: the first in the Frasnian and the second in the late and latest Famennian. Due to the currently known fossil evidence, the consensus scenario advocates a late Middle Devonian to early Late Devonian origin of tetrapods on the Old Red Sandstone Continent (Euramerica) at a time of warm climate and recovering atmospheric oxygen level during the building of a pre-Pangaean configuration of landmasses.

Calibrating the Devonian Time Scale: A synthesis of U–Pb ID–TIMS ages and conodont stratigraphy

The recalibrated Devonian time scale represents an important improvement of Devonian chronology regarding two aspects. Firstly, a data set of 13 biostratigraphically well-bracketed U–Pb ID–TIMS zircon and monazite ages constitutes the framework of the scale. Secondly, approximately time-linear biostratigraphic scales have been used for the interpolation between the isotopic ages. The new construction thus represents a ‘biochronometric’ time scale, which allows the assignment of numeric ages not only to stage boundaries but also to each biozone boundary. The method of interpolation applied also enables the projection of the geochronological error onto the time scale. According to the newly calibrated scale, the Devonian lasted 57.4 ± 5.7 Ma from 418.1 ± 3.0 to 360.7 ± 2.7 Ma. This is, compared to previously published time scales, the longest time span ever calculated for this period. The age interpolations for the eight stage boundaries are: Famennian–Tournaisian (= Devonian–Carboniferous) 360.7 ± 2.7 Ma Frasnian–Famennian 376.1 ± 3.6 Ma Givetian–Frasnian 383.7 ± 3.1 Ma Eifelian–Givetian 388.1 ± 2.6 Ma Emsian–Eifelian 391.9 ± 3.4 Ma Pragian–Emsian 409.1 ± 3.8 Ma Lochkovian–Pragian 412.3 ± 3.5 Ma Pridolian–Lochkovian (= Silurian–Devonian) 418.1 ± 3.0 Ma The duration of the Middle Devonian is calibrated here as quite short with 8.2 Ma and the Emsian and the Famennian are the longest stages with interpolated durations of 17.2 and 15.4 Ma, respectively. Together, all Devonian stages contain 57 conodont zones (including subzones, according to the standard conodont zonation) giving a mean duration of about 1 Ma. In the highly resolved part of the time scale (mid-Eifelian to the Devonian–Carboniferous boundary), zonal resolution averages 0.6 Ma. In contrast, the lowest resolution is shown in the early Emsian to mid-Eifelian interval with zonal durations of up to 5.5 Ma ( serotinus Zone).

Devonian polygnathids from the Frasnian of the Rheinisches Schiefergebirge, Germany, and the Russian Platform

Ranges of polygnathids from Frasnian sections of the Rheinisches Schiefergebirge are studied in faunas from the Standard Conodont Zonation. Polygnathids from various coeval sections of different facies in many regions of the Russian Platform are compared, and possible correlations of epicontinental successions with the Standard Scale are discussed. Some trends in polygnathid evolution are described.

Miospores from the Frasnian–Famennian Boundary deposits in Eastern Europe (the Pripyat Depression, Belarus and the Timan–Pechora Province, Russia) and comparison with Western Europe (Northern France)

A zonal subdivision of the Frasnian–Famennian transitional deposits in the Pripyat Depression and Timan–Pechora Province, based on a detailed palynological study, has been completed. The data obtained on miospores and conodonts from the Timan–Pechora Province enable a correlation to be made with the Standard Conodont Zonation. The lateral extent of the palynozones in Eastern Europe and the correlation with Western Europe are discussed. The following previously published new combinations are validated: Auroraspora speciosa (Naumova) Obukhovskaya, comb. nov., Corbulispora viminea (Nekriata) Obukhovskaya and Nekriata, comb. nov., Cristatisporites imperpetuus (Sennova) Obukhovskaya, comb. nov., Cymbosporites acanthaceus (Kedo) Obukhovskaya, comb. nov., Grandispora subsuta (Nazarenko) Obukhovskaya, comb. nov., and Verrucosisporites evlanensis (Naumova) Obukhovskaya, comb. nov.

A new latest Telychian, Sheinwoodian and Early Homerian (Early Silurian) Standard Conodont Zonation

AbstractThe new standard conodont zonation includes, in succession from below: LowerPs. bicornisZone, UpperPs. bicornisZone, LowerP. procerusZone, UpperP. procerusZone, LowerK. ranuliformisZone, UpperK. ranuliformisZone,0. s. rhenanaZone, LowerK. walliseriZone, MiddleK. walliseriZone,K. patulaZone, uppermostK. walliserirange, postK. walliseriinterregnum,K. o. ortusZone and0. s. sagittaZone. Lower boundaries for each zone are defined or redefined. A less detailed biostratigraphic nomenclature at the superzone level is suggested for use where collections are inadequate: ThePterospathodusZonal group, the UpperPterospathodusZonal group, theP. amorphognathoidesZonal group, thePs. bicornisSuperzone, theP. procerusSuperzone, theK. ranuliformisSuperzone, theO. s. rhenanaSuperzone, theK. walliseriZonal group, the UpperK. walliseriSuperzone and theK. o. ortusSuperzone. These partly overlap and can be used according to the taxa present. The proposed zonation is applied to most known conodont sequences. The taxonomic concept of the taxa used is discussed; new taxa includeNudibelodina sensitiva, Ozarkodina paraconfluensandO. martinssoni.The species nameOzarkodina ortusis a senior synonym ofKockelella absidata.

Biostratigraphical correlationsof Early Devonian ichthyofaunas of the Old Red Continent

The Old Red Continent was a Devonian landmass which included North America; northern Europe and severalterranes. In Early Devonian times; vertebrate-bearing localities were situated all around this landmass. A major problem of biostratigraphical correlation occurs between the Lower Devonian vertebrate zonations and the standard conodont zonation. All boundaries stratotypes are very poor in vertebrate remains; or yielded vertebrate taxa which do not allow to discriminate the stages boundaries. However; preliminary data lead to biostratigraphical correlations between some other vertebrate-bearing formations and conodont zones; particularly in the Emsian.

Multielement reconstructions of Palmatolepis and Polygnathus (Upper Devonian, Famennian) from the Canning Basin, Australia, and Bactrian Mountain, Nevada

Upper Devonian (Famennian) sequences were sampled at two sections in the Canning Basin, Western Australia, and a section at Bactrian Mountain, Nevada, over an interval ranging from the Upper crepida Zone into the Lower marginifera Zone of the standard conodont zonation for the Famennian. Over 30,000 conodont elements have been identified among 43 species and subspecies within six genera. New complete and partial multielement reconstructions are illustrated for: Palmatolepis falcata, P. glabra prima, P. loba, P. minuta minuta, P. perlobata perlobata, P. perlobata maxima, P. quadrantinodosalobata, P. rhomboidea, P. schindewolfi, P. subgracilis, P. wolskae, Polygnathus cf. P. diversus, P. glaber glaber, P. nodocostatus nodocostatus, P. subnormalis, and P. cf. P. triphyllatus. The reconstructions are based on stratigraphic occurrence, detailed morphologic similarities, and a few exceptional low-diversity faunas. Additionally, Palmatolepis adamantea n. sp. is proposed based on the Pa element.A more precise understanding of the taxonomic boundaries of Palmatolepis is achieved through knowledge of the entire apparatus, rather than confined to the Pa elements. Reconstructions presented here provide a more comprehensive understanding of the range of morphologic variation that exists in Palmatolepis, and show that a single generalized elemental plan can be demonstrated for all members of the genus. The differences in the non-Pa elements can thus be used to refine taxonomy and increase understanding of phylogenetic relationships at the specific and subspecific level.

Devonian eustatic fluctuations in Euramerica

The Devonian System of Euramerica contains at least 14 transgressive-regressive (T-R) cycles of eustatic origin. These are separated into three groups (or depophases) and from Carboniferous cycles by three prominent regressions. Twelve post-Lochkovian T-R cycles are recognized, and they commonly appear to result from abrupt deepening events followed by prolonged upward shallowing. Deepening events in the western United States (especially Nevada), western Canada, New York, Belgium, and Germany have been dated in the standard conodont zonation and are demonstrably simultaneous in several or all five regions. This synchroneity indicates control by eustatic sea-level fluctuations rather than by local or regional epeirogeny. Facies shifts in shelf sedimentary successions are more reliable indicators of the timing of sea-level fluctuations than are strandline shifts in the cratonic interior, because the latter are more influenced by local epeirogeny. Strandline shifts are most useful in estimating the relative magnitude for sea-level fluctuations. Devonian facies progressions and the three prominent regressions are of a duration and an order of magnitude that could have been caused by episodes of growth and decay of Devonian oceanic ridge systems. The described T-R cycles could have formed in response to mid-plate thermal uplift and submarine volcanism. The latter process may have been a control on small-scale (1–5 m thick), upward-shallowing cycles within the major T-R cycles. Continental glaciation could have been a factor in sea-level fluctuations only in the Famennian and could not have been responsible for the Devonian facies progressions or the numerous T-R cycles. The Frasnian extinctions were apparently cumulative rather than due to a single calamity. Two rapid sea-level rises occurred just before, and one at, the Frasnian-Famennian boundary. It is probable that this series of deepening events reduced the size of shallow-shelf habitats, caused repeated anoxic conditions in basinal areas, and drowned the reef ecosystems that had sustained the immensely diverse Devonian benthos.