Conodont Stratigraphy Research Articles

Refined conodont stratigraphy at Martenberg (Rhenish Massif, Germany) as base for a formal middle/upper Frasnian substage boundary

The famous Martenberg section of the eastern Rhenish Massif, Germany, type-section of classical Frasnian goniatite and conodont zonations, has been restudied in order to document the microfacies development and to refine the conodont stratigraphy around the global semichatovae Event/Transgression, the proposed level to define a future upper Frasnian substage. More than 8.000 platform elements were identified and include new taxa. Palmatolepis jamieae is subdivided into the subspecies Pa. jamieae jamieae, Pa. jamieae savagei n. ssp., Pa. jamieae rosa n. ssp., and Pa. jamieae ssp. δ. Another new species, Pa. adorfensis n. sp., was previously partly identified as Pa. jamieae, while Pa. descendens n. sp. has previously been described in open nomenclature from Inner Mongolia. Morphotypes are defined in Icriodus symmetricus, Pa. ljaschenkoae, and Pa. proversa. A global literature survey shows that the eustatic semichatovae Event can be recognised in more than 20 regions of all continents with (sub)tropical Upper Devonian outcrops. At Martenberg, the transgression is preceded by a thin but distinctive interval with unconformities, microbial mats, sheet cracks, and currents that brought in the regionally youngest volcaniclastics. The new conodont data confirm that no typical Pa. jamieae (sensu the holotype) occur in the two beds originally supposed to represent the jamieae Zone in its reference section. We fully support the conclusion of Ovnatanova and Kononova (2020) that the jamieae Zone should be abandoned. Early Pa. jamieae subspecies and the related new taxa enter at Martenberg and in a few other regions in the globally easily recognisable Frasnian Zone 10 (= plana Zone). Frasnian Zone 11 (feisti Zone) is subdivided into subzones FZ 11a (= feisti Subzone) and FZ 11b (= nasuta Subzone). The base of the latter coincides with the semichatovae Transgression, the semichatovae Subzone of more shallow shelf settings, and is proposed to define in future the upper Frasnian substage base. On a global scale, the Martenberg section is currently the best bed-by-bed documented section for facies changes, conodont and goniatite biostratigraphy at the middle/upper Frasnian transition. Therefore, it is a prime candidate for a future GSSP selection. A global literature survey identified more than 20 other pelagic conodont successions that have the potential for precise correlation and a better understanding of the environmental changes associated with the semichatovae Event.

The Hushoot Shiveetiin gol section (Baruunhuurai Terrane, Mongolia): sedimentology and facies from a Late Devonian island arc setting

A Late Devonian to (?)Early Mississippian section at Hushoot Shiveetiin gol in the Baruunhuurai Terrane of the Central Asian Orogenic Belt (CAOB) exposes large parts of cyclic Famennian shallow-water siliciclastic shelf deposits composed of siltstones, sandstones, shales, volcaniclastics, and intercalated autochthonous carbonates. The youngest part of the section, possibly Early Mississippian, is represented by arkosic sandstones with large plant remains. The facies reflects a range from shallow-intertidal to outer ramp settings. In terms of conodont stratigraphy, the Hushoot Shiveetiin gol section ranges from the Palmatolepis minuta minuta Biozone to at least the Palmatolepis rugosa trachytera Biozone. Hiatuses of several conodont biozones occur due to the facies setting (erosion and reworked sediments which are recognized by reworked conodonts) rather than thrusting or folding. The environmental setting was characterized by coeval subaerial volcanism resulting in numerous pyroclastic deposits. The depositional environments and intense volcanic activity at the Hushoot Shiveetiin gol section limited the stratigraphic distribution, abundance, and diversity of many elements of the fauna such as brachiopods. Ostracods were very abundant and diverse through many parts of the section. Although limited in stratigraphic distribution, the crinoid fauna is the most diverse Palaeozoic fauna collected from Mongolia to date and supports the hypothesis that the CAOB was a biodiversity hotspot in the aftermath of the Frasnian–Famennian extinction event.

Conodont stratigraphy and conodont biofacies of the shallow-water Kuh-e-Bande-Abdol-Hossein section (SE Anarak, Central Iran)

The Middle to Upper Devonian Kuh-e-Bande-Abdol-Hossein section in eastern Central Iran is an overall shallow marine, nearshore to open marine facies setting that contains a highly variable conodont record generally characterised by an Icriodid-Polygnathid biofacies. The lithology and the palaeoenvironmental setting is similar to other localities in Central Iran and exhibits numerous hiatuses. A continuous biostratigraphic record could not be established, but the section preserves the Givetian/Frasnian boundary. Based on the conodont record, major gaps also occur in the Famennian which confirms earlier results reported from other sections of similar palaeoenvironments in Central Iran.

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.

Emsian (Lower Devonian) conodont stratigraphy and correlation of the Anti-Atlas (Southern Morocco)

Emsian (Lower Devonian) conodont stratigraphy and correlation of the Anti-Atlas (Southern Morocco)

Ambiguities in conchostracan biostratigraphy: A case study of the Permian–Triassic boundary

In recent years, conchostracan biostratigraphy has become a popular tool for the recognition of the Permian–Triassic boundary and for the chronostratigraphic subdivision of the Triassic in intracontinental settings, including also the bone-bearing Keuper strata of Poland. The ambiguous nature of the new bio-chronostratigraphic approach was characterized in a case study of the Permian–Triassic boundary interval. The most important problems were: (1) the lack of documentation of the index species, (2) the indirect correlation with the conodont stratigraphy in marine reference sections through the sporomorph spectra, (3) the lack of definition and documen- tation of supporting palynologic zones, and (4) difficulties in reliable taxonomic determination of Conchostraca. Testing and, if necessary, revision of the zonation by several independent research groups is suggested.

Recovery dynamics of foraminifers and algae following the Permian-Triassic extinction in Qingyan, South China

The Qingyan Biota is one of the most diverse biota among the global Middle Triassic fossil assemblages, yielding more than 300 species belonging to 17 fossil groups, and marking the radiation of benthic organisms after the Permian-Triassic mass extinction. This study aims to uncover the detailed foraminiferal and algal recovery dynamics through the Early to Middle Triassic at the Qingyan section in southern Guizhou, South China. Newly obtained microfossils from the Lower and Middle Triassic in Qingyan comprise 33 species and 24 genera of foraminifers, and 6 species (6 genera) of calcareous algae. Conodont stratigraphy shows that only two species, Hemigordiellina sp. and “Nodosaria” sp., are yielded in the Induan, and eight species in the Olenekian, namely Endotriadella radstadtensis, E. wirzi, Hemigordiellina spp., Meandrospira pusilla, “Nodosaria” elabugae, “N.” skyphica, “N.” sp., and “Tolypammina” sp. Anisian microfossils are rather abundant and diverse in Qingyan, including 31 foraminiferal and 6 algal species. These diverse microfossil assemblages plus conodont stratigraphic data provide a window into the biotic recovery in the aftermath of the Permian-Triassic extinction.

A palynological study from Sweden reveals stable terrestrial environments during Late Silurian extreme marine conditions

ABSTRACTA palynological study of the upper Silurian Öved–Ramsåsa Group in Skåne, Sweden yields a well preserved spore assemblage with low relative abundances of marine microfossils. In total, 26 spore taxa represented by 15 genera were identified. The spore assemblage is dominated by long-ranging cryptospore taxa, and the trilete spore Ambitisporites avitus-dilutus. However, key-species identified include Artemopyra radiata, Hispanaediscus lamontii, H. major, H. verrucatus, Scylaspora scripta and Synorisporites cf. libycus. Importantly, Scylaspora klintaensis was identified, allowing correlation with the Klinta 1 drillcore (Skåne). A Ludlow age is inferred for the exposed succession, which agrees well with previous conodont stratigraphy. The organic residue is dominated by phytodebris and spores, but with high relative abundances of acritarchs at two levels, possibly related to flooding surfaces.Based on the palynofacies analysis, a near-shore marine environment is proposed. The close proximity to land is inferred by the high proportions of spores, and the dispersed assemblage most likely represents the local flora growing on delta plains. The palynological signal also infers a stable terrestrial environment and vegetation, in contrast to unstable conditions in the marine environment characterised by ooid formation in an evaporitic environment. Comparisons with coeval spore assemblages from Gotland, Avalonia and Laurentia show relatively close similarities in taxonomic composition at the generic level.

Revised conodont stratigraphy of the Cellon section (Silurian, Carnic Alps)

The Cellon section, located in the Carnic Alps, is a reference section for the Silurian of the world. The conodont association of the section is revised according to the most recent taxonomy and the biostratigraphy updated in the basis of the recently published zonation schemes. Seventy taxa (species and sub-species) belonging to 23 genera have been identified, allowing the discrimination of 15 biozones from the upper Llandovery to the end of the Přídolí . However, some of the uppermost Llandovery and Wenlock biozones, corresponding to black shale intervals, have not been documented.

Guadalupian–Lopingian conodont and carbon isotope stratigraphies of a deep chert sequence in Japan

To improve international stratigraphic correlation of the Lower Guadalupian–Lower Lopingian (Permian), we examined the stratigraphies of conodonts and organic carbon isotopes from pelagic chert sequences in the Gujo-hachiman section, Gifu, southwest Japan. Age-diagnostic conodonts, such as Jinogondolella nankingensis and Jinogondolella shannoni were found in the study section. The conodont stratigraphy in the Gujo-hachiman section was correlated with those in South China and West Texas, USA, to date the study section. From these correlations, it was found that the study section was from the upper Roadian (Lower Guadalupian) through Wuchiapingian (Lower Lopingian). Kerogen δ13C values were relatively high, around −29.0‰ in the upper Roadian–Wordian (Middle Guadalupian), decreasing over time to −29.4‰. A negative–positive swing in δ13C values of around 1‰ magnitude was recognized in the middle Capitanian (Upper Guadalupian). A similar negative–positive swing was also found in the Guadalupian–Lopingian (G–L) transitional zone in the Gujo-hachiman section, and is comparable to the isotopic change around the G–L boundary in the Penglaitan section, South China. Subsequently, δ13C values decreased to values below −30.0‰ above the G–L transitional zone, i.e., at the lower Wuchiapingian. Overall, δ13C values decreased from the lower Capitanian to the lower Wuchiapingian by over 1.4‰. A gradual increase in the δ13C values followed this long-term negative trend. These δ13C trends in the Gujo-hachiman section are comparable with time-equivalent δ13C records in different sections, suggesting that they record first-order variations in atmospheric δ13C. The high δ13C values during the upper Roadian–Wordian interval could reflect high primary productivity in the surface water of the pelagic Panthalassa Ocean, and imply global cooling. In contrast, the negative δ13C shift during the Capitanian–Wuchiapingian interval implies global warming.

A long-lasting steady period of isotopically heavy carbon in the late Silurian ocean: evolution of the δ13 record and its significance for an integrated δ13, graptolite and conodont stratigraphy

A long-lasting steady period of isotopically heavy carbon in the late Silurian ocean: evolution of the δ13 record and its significance for an integrated δ13, graptolite and conodont stratigraphy

Middle Devonian olistostromes in the Rheno-Hercynian zone (Rheinisches Schiefergebirge) — An indication of back arc rifting on the southern shelf of Laurussia

The Rheinisches Schiefergebirge in the Rheno-Hercynian zone of the mid-European Variscides was geographically situated on Laurussia's southern shelf during the Devonian. In its eastern part (Lahn–Dill area), Givetian coarse clastic sediments, formerly misinterpreted as transgressional conglomerates, are recognised as olistostrome deposits intercalated in basinal sediments that document a phase of rifting on the southern shelf of Laurussia. The clastic components, redeposited as olistolithes and rounded boulders, are locally derived rocks of Emsian and Givetian age. The olistostromes show facies patterns comparable with other syn-rift deposits. The proximal facies is characterised by olistolithes and slideflow debrites, overlain by debrites and intercalated with turbidites. The distal facies is represented by intercalation of debrites and turbidites. Both grade upwards into basinal sedimentation. Based on conodont stratigraphy, the redeposition lasted from the Middle varcus Zone to the disparilis Zone. During the Middle varcus Zone footwall uplift raised the sedimentary column of the source area by about 500 m above, which brought it above sea level. Rifting of the Laurussian shelf as a result of hinterland transtension and extension caused by the oblique collision of Peri-Gondwana with Laurussia provides the most plausible explanation for the development of the olistostromes, olistolithes and slideflow debrites in the eastern Rheinisches Schiefergebirge.

Volcanism and reef development in the Devonian: A case study from the Lahn syncline, Rheinisches Schiefergebirge (Germany)

New data from the Rheinisches Schiefergebirge in Germany offer insights into a complex marine basinal facies setting on the southern shelf area of the Old Red Continent. This interdisciplinary approach has the aim of providing a reconstruction of depositional and palaeoecological conditions of volcanic island induced reef growth during the Middle Devonian time. Devonian volcanic activity culminated in a Givetian–Frasnian phase producing mainly alkali-basaltic to basanitic melts. Some volcanic buildups reached sea level and gave rise to the development of reefs during times of reduced volcanic activity. Reef communities in the Lahn syncline were dominated by corals and stromatoporoids. In terms of conodont stratigraphy they began to flourish during the Middle varcus-subzone in the Givetian and lasted until the Late falsiovalis-subzone in the Frasnian. A facies model is presented for the entire area that clarifies the association of volcanism and reef development.

Conodont stratigraphy and correlation of the Ordovician volcanogenic and volcanogenic sedimentary sequences in the South Urals

Conodont stratigraphy and correlation of the Ordovician volcanogenic and volcanogenic sedimentary sequences in the South Urals

Re–Os depositional ages and seawater Os estimates for the Frasnian–Famennian boundary: Implications for weathering rates, land plant evolution, and extinction mechanisms

Four TOC-rich shale intervals spanning the Frasnian–Famennian (F–F) boundary were recovered in a drillcore (West Valley NX-1) from western New York (USA) and radiometrically dated using Re–Os. Two of the black shale intervals (WVC785 from ∼ 2.9 m below, and WVC754 from ∼ 6.4 m above the F–F boundary, respectively) yielded statistically overlapping ages with uncertainties of < 1.1%. An interpolated age and associated graphically determined uncertainty of 372.4 ± 3.8 Ma provides new absolute age constraints on the F–F boundary. This date is ∼ 4.1 Ma younger than the latest proposed F–F boundary age of 376.1 Ma obtained by interpolation of U–Pb dates from volcanic zircon [Kaufmann, B., 2006. Calibrating the Devonian Time Scale: A synthesis of U–Pb ID-TIMS ages and conodont stratigraphy. Earth-Science Reviews 76, 175–190], and within uncertainty of the International Commission on Stratigraphy accepted date of 374.5 ± 2.6 Ma. A third date (from sample WVC802, ∼ 8.2 m beneath the F–F boundary) yielded an imprecise age of 357 ± 23 Ma, owing in part to a limited Re/Os range. The initial 187Os/ 188Os (0.45 to 0.47), reflecting contemporaneous seawater Os values, are low but similar to the value of 0.42 reported for the Exshaw Fm (Canada) at the Devonian–Mississippian boundary (ca. 361 Ma) [Selby D., Creaser R.A., 2005. Direct radiometric dating of the Devonian–Mississippian time-scale boundary using the Re–Os black shale geochronometer. Geology 33, 545–548]. This may suggest fairly constant and low global continental weathering rates during the Late Devonian, although in view of the short residence time of Os in seawater (∼ 1–4 × 10 4 yr), further measurements are needed to assess potential short-term variation in seawater Os ratios. Owing to low Os and Re abundances at the F–F boundary, our data are inconsistent with long-term volcanism and bolide impact as potential Late Devonian mass extinction mechanisms. In addition, the Frasnian–Famennian ocean appears to have been depleted with respect to Re, possibly indicating an exhaustion of the Re seawater reservoir owing to high burial rates of redox-sensitive elements under dysoxic/anoxic conditions leading up to the F–F boundary.

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).

Microfacies development, sea-level change, and conodont stratigraphy of Famennian mid- to deep platform deposits of the Beringhauser Tunnel section (Rheinisches Schiefergebirge, Germany)

High resolutional microfacies data from the Beringhauser Tunnel section in the northern part of the Rheinisches Schiefergebirge allow the reconstruction of a relative sea-level curve. Distinctive sedimentological signals in this cephalopod limestone section indicate the positions of sea-level lowstands that correlate well with pre-existing sea-level curves. Only slight differences in some lowstand positions have been observed by means of conodont biostratigraphy. The basal Famennian portion of the succession at the Beringhauser Tunnel section exposes microbial sedimentary structures reported from the Rheinisches Schiefergebirge for the first time that are indicative of initial mud-mound formation or mud-mound flanks. Further mud-mound growth with the development of a synsedimentary relief was stopped, probably due to drowning.

Carbonate platform evolution and conodont stratigraphy during the middle Silurian Mulde Event, Gotland, Sweden

Evidence from sedimentology and conodont biostratigraphy is used to reinterpret the mid-Homerian (Late Wenlock) succession on Gotland, Sweden. A new conodont zonation includes from below: the Ozarkodina bohemica longa Zone (including five subzones), the Kockelella ortus absidata Zone and the Ctenognathodus murchisoni Zone (two taxa are named, Ozarkodina bohemica longa and Pseudooneotodus linguicornis). These new zones are integrated with facies in order to correlate strata and infer the major depositional environments and the controls on deposition during the mid-Homerian Mulde Event. Reef-associated and skeletal carbonate deposition predominated before and after the event, i.e. during the uppermost O. s. sagitta Zone and, again, in the C. murchisoni Zone. These periods are characterized by the expansion of reefs and shoal facies across marls in the topmost Slite Group on eastern Gotland and in the lower parts of the Klinteberg Formation on western Gotland, respectively. The intervening O. b. longa and K. o. absidata zones are initially characterized by rapid facies changes, including siliciclastic deposition, and later stabilisation of a carbonate depositional system. The composition of sediments and depositional rates are closely related to the creation and destruction of accommodation space and reflects a classical case of depositional bias of the carbonate and siliciclastic depositional systems. Based on coastline migration, stratal boundaries, and the stratigraphic position of major reef belts, several facies associations can be fitted into a sequence stratigraphic model for platform evolution. A highstand systems tract (HST) situation prevailed prior to, and during the early part of the event; the upper Slite Group including the lower Fröjel Formation. This HST was characterized by prolific skeletal production and regional reef development except for during the latest stage when carbonate production declined at the onset of the Mulde Event. Platform growth was inhibited during a following regressive systems tract (RST) when regional siliciclastic deposition predominated; the Gannarve Member. The subsequent lowstand resulted in regional emersion and karstification, i.e. a complete termination of the platform. The post-extinction transgressive systems tract (TST) is exclusively composed of non-skeletal carbonates; the Bara Member of the Halla Formation. Re-occurrence of reefs and a prolific skeletal production marks platform recovery during a second HST; the remaining Halla and the lower Klinteberg formations. Integration of high-resolution biostratigraphy and sequence stratigraphy reveals that the major physical control on platform evolution was a 5th order eustatic sea-level change during an early part of the Mulde Event, and that the bulk of the strata accumulated when the platform aggraded and prograded during the highstand systems tracts. Thus, Silurian oceanic events and associated sea-level changes had profound impact on the neritic carbonate system. The Gotland-based middle and late Homerian sea-level curve shows two rapid regressions, both leading to truncation of highstand systems tracts. The first lowstand occurred at the very end of the C. lundgreni Chron, and the second at the end of the Co.? ludensis Chron. The intervening interval was characterized by stillstand or possibly slow transgression.

Lithofacies and stratigraphy of the Ordovician Guniutan Formation in its type area, China

The Lower to Middle Ordovician Guniutan (Kuniutan) Formation in the eastern Yangtze Gorges, China has been demonstrated to be similar to the ‘Orthoceratite Limestone’ in Baltoscandia with respect to facies, stratigraphic development and conodont biostratigraphy. Thus the ‘Orthoceratite Limestone’ appears to be a much more widely distributed and characteristically Ordovician facies than has hitherto been assumed. Five lithostratigraphic subdivisions of the Guniutan Formation are here defined in ascending order as the Nanya, Puxi, Wuguixi, Daping and Niangjiafang members. It is shown that these members, which represent considerable spans of time as indicated by their conodont stratigraphy, may be fairly thin but nevertheless regionally extensive. A new conodont zone, with Eoplacognathus crassus as the zonal fossil, is established to accommodate the precise dating of the Wuguixi and Puxi members. Microfacies data from the Guniutan Formation, available for the first time, show that its dominant component particles are sand-sized echinoderm and arthropod debris, as in the Baltoscandian ‘Orthoceratite Limestone’.

Conodont stratigraphy of the Lower Triassic in the Thakkhola region (eastern Himalaya, Nepal)

Conodont stratigraphy of the Lower Triassic in the Thakkhola region (eastern Himalaya, Nepal)