Conodont Assemblages Research Articles

Biostratigraphy of the Upper Devonian Khoshyeilagh Formation in NE Iran based on conodonts and other faunas

The Khoshyeilagh Formation located in the northeast of Iran yielded seven conodont species and sub-species and 19 macro- and microfossil taxa that allow recognition of two conodont biozones and one biozone based on calcareous microfossils. The latest Frasnian age (the Upper rhenana to linguiformis zones) is attributed to the topmost strata with Icriodus alternatus. Its replacement with I. cornutus indicates the Famennian (Lower triangularis to Lower crepida zones) corresponding to the Umbellina Zone. The fossil assemblages identified in the Khoshyeilagh Formation represent a shallow marine environment with a tropical climate at the time of deposition. The fossil species from the Khoshyeilagh Formation and the sedimentary basins in Algeria, Libya, Morocco, Poland, and Russia reveal a close connection between the Iranian plateau and the northern parts of Gondwana in the Late Devonian. The biofacies and lithofacies analyses show a sea-level decline at the end of Frasnian, followed by a considerable sea-level drop, as in other regions of the world. After a short time, in the Famennian, the deepening occurred in some parts of the area and the open marine facies (bioclast spicule wackestone-packstone) were deposited. This study is the first attempt to determine the Frasnian-Famennian boundary based on conodont assemblages and other fossil species such as umbellulids, tentaculites, and ostracods. The distribution of these species is interpreted in sedimentological, stratigraphic, sequence stratigraphy, and the global eustatic context. Keywords: biofacies, conodont, Frasnian-Famennian boundary, Late Devonian, NE Iran.

First recovery of late Early Triassic (Spathian) pelagic assemblages (radiolarians and conodonts) from block in the Upper Karakaya Complex near Ankara City, central Turkey: Biostratigraphical remarks and correlation

The Upper Karakaya Complex, belonging to the Karakaya Complex, includes different blocks and tectonic slices within a Triassic sheared matrix. This wide-spread unit mainly exposed in northern Turkey also crops out to the southern part of Ankara city near Gökcehüyük village. Instead of a continuous sequence of Carboniferous to Permian age described in a previous study, five different blocks of various origins and ages are identified in this study. One of the pelagic blocks composing of cherty limestone includes radiolarian and conodont assemblages typical of Spathian age, representing the Triassospathodus homeri Conodont Zone. It corresponds also to the Hozmadia ozawai Radiolarian Zone although the zonal guide could not be obtained from the radiolarian assemblage. This is so far the first recovery of pelagic assemblages (radiolarians and conodonts) from the Karakaya Complex. This result clearly indicates that pelagic sedimentation took place in the Karakaya Complex during late Early Triassic time. Compared to previous studies, it can be stated that radiolarian cherts have been deposited in the Karakaya Complex in two different time span from Middle to Late Devonian and Late Permian (Changhsingian) to early Late Triassic (Carnian) time, respectively.

Late Triassic to Early Jurassic radiolarian, conodont and ammonite assemblages from the Tavuscayiri block, Mersin Mélange, southern Turkey: Time constraints for the T/J boundary and sedimentary evolution of the southern margin of the northern Neotethys

The Mersin Mélange (northwest of Mersin city) includes a variety of large sedimentary blocks/tectonic slices of Palaeozoic and Mesozoic origins. Of these, the latter represents facial and tectonostratigraphic counterparts of the Beysehir-Hoyran Nappes (remnants of the northern Neotethys). The Tavuscayiri Block, located at the center of the mélange and close to the Orbuklukeli hill, is one of such Mesozoic occurrences, with a continuous pelagic sequence from the Upper Triassic to Lower Jurassic. At the Orbuklukeli hill, a succession of middle Norian to Toarcian age has been precisely dated, which starts with conodont assemblages for the Norian and Rhaetian and includes radiolarians for the upper Rhaetian. An acidic tuff layer corresponds to the T-J boundary, which passes above to an increasingly dominating chert-bearing limestone series, marking a gradually deepening-upward of the sequence. The early Hettangian radiolarians are poorly represented, but diverse and well-preserved radiolarians have been retrieved from the middle Hettangian to the Pliensbachian. A total of eighty-five taxa, including fourteen new species, have been determined. In addition to these, one new genus (Praeudalia Tekin, n. gen.) has been described from the Rhaetian part of the section. The top of the section is represented by nodular limestones in Ammonitico rosso facies, including a diverse Toarcian ammonite fauna. All lithologies of the Orbuklukeli section along the Tavuscayiri Block can be correlated with the previously described lithologies of the Kayabasi Group/Formation in the Bozkir Unit, and Gülbahar/Gümüslü units in the Lycian Nappes.

Age correlations for the Acoite Formation (Lower Ordovician) at Aguas Blancas Creek in the Cordillera Oriental of Jujuy Province, Argentina

Here, we use conodont and graptolite assemblages to age correlate the ‘Sepulturas limestones’ facies of the Acoite Formation exposed at Aguas Blancas Creek, near Altos de Lipán in the Cordillera Oriental of Jujuy Province, Argentina. An association of autochthonous conodont species is identified consisting of Drepanodus arcuatus, Drepanoistodus pitjanti, Erraticodon patu, Gothodus andinus, Paroistodus parallelus and Zentagnathus argentinensis. Tubaria referable to the graptolite genera Acrograptus, Baltograptus and Tetragraptus are also present. This assemblage corresponds to the middle interval of the Gothodus andinus Zone, together with the upper Tetragraptus azkharensis Zone, or possibly the lower Baltograptus cf. B. deflexus Zone, which collectively indicate an early to middle Floian (Early Ordovician) age. Lithological and faunal characteristics of the studied succession imply deposition in a shallow marine environment. We also suggest that the Aguas Blancas section is stratigraphically younger than the other upper outcrops exposed around the town of La Ciénaga, where the ‘Sepulturas limestones’ were originally defined. G.L. Guillermo [guillermo.albanesi@unc.edu.ar], CICTERRA (CONICET-UNC), CIGEA, Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba, Av. Vélez Sarsfield 1611, X5016GCA, Córdoba, Argentina; E.K. Rueda [ruedaroballo@gmail.com ]; G. Ortega [gladyscortega@gmail.com ] Museo de Paleontología, CIGEA, Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba, Av. Vélez Sarsfield 300, X5000JJC, Córdoba, Argentina; C.R Monaldi [crmonaldi@gmail.com ], Los Teros 197, 4401 Vaqueros, Salta, Argentina.

Ordovician gastropods from pebbles in Cretaceous fluvial sandstones in south-east Disko, West Greenland

The gastropods Sinuopea sp. and Lecanospira cf. compacta (Salter 1859) of probable early Ordovician age are described from cherty limestone clasts within fluvial strata of the Cretaceous Atane Formation of south-east Disko, central West Greenland. The record of Sinuopea possibly suggests an earliest Ordovician (Tremadocian) age, slightly older than the Floian–Dapingian age suggested by the oldest known conodont assemblages described from West Greenland. The determinations provide supporting evidence for a former periodic cover of Ordovician strata in the Archaean terrane of south western Greenland, extending deep into the heart of the Laurentian landmass.

Age Constraints on the Portezuelo Del Tontal Formation (Middle–Upper Ordovician) of the Western Argentine Precordillera: First Insights from Conodont Biostratigraphy

The first conodont fauna recovered from the lower levels of the Portezuelo del Tontal Formation (PTF) in the Sierra del Tontal, San Juan Province, is analysed, providing a precise biostratigraphic control for the scarcely fossiliferous, thick Ordovician siliciclastic sequences of the Western Argentine Precordillera. In the studied Cerro Condores stratigraphic section, the PTF is characterized by sandstone beds, with few with minor calcareous reaction, deposited under medium energy, open-marine, siliciclastic shelf conditions. The recovered assemblage consists of 50 conodont elements, including Ansella jemtlandica (Lofgren), Costiconus costatus (Dzik), Drepanodus arcuatus Pander, Parapaltodus simplicissimus Stouge, Paroistodus originalis (Sergeeva), Periodon macrodentatus (Graves and Ellison), Protopanderodus graeai (Hamar), and Spinodus spinatus (Hadding) as most conspicuous species. After the biostratigraphic assessment of species of the Paroistodus horridus complex, the PTF conodont asemblage is referred to the Darriwilian (Middle Ordovician) Yangtzeplacognathus crassus Zone, a critical interval in the tectonostratigraphic history of the Precordillera. The collection also contains reworked conodont specimens whose biostratigraphic ranges coexist during the latest Floian (Early Ordovician) Oepikodus intermedius Zone. The conodont assemblage from the PTF allows for a precise correlation with the eastern and central domains of the Precordillera, as well as other regions of the world, improving the knowledge on the dynamics of the Ordovician Precodilleran basin and the palaeogeographic distribution of its faunas.

A pelagic Upper Devonian sequence in Sarıyer, İstanbul

The Palaeozoic sequence in the Istanbul region is made up of a continuous transgressive sedimentary series extending from Ordovician continental clastic rocks to Lower Carboniferous turbidites. The middle part of this sequence consists predominantly of carbonates ranging from shallow marine Upper Silurian limestones to latest Devonian to earliest Carboniferous deep marine limestones and shales. Here, we describe a new Upper Devonian deep marine limestone-siltstone section from the Sariyer region in the European part of Istanbul. The 37-m thick section located in the campus of the Istanbul Technical University consists at the base of dark micritic limestones interbedded with carbonate-rich siltstones, which pass up into siltstones with rare micritic limestone lenses and beds. Conodonts indicate a late Famennian latest Devonian age for the ITU campus section; 5 conodont biozones are documented; Pseudopolygnathus granulosus, Polygnathus styriacus, Palmatolepis gracilis manca, Palmatolepis gracilis expansa, and Bispathodus aculeatus aculeatus. The Late Devonian fauna from the ITU Campus section are dominated by the important marker species of Palmatolepis, Bispathodus and Polygnathus. There are also some Branmehla, Mehlina, and Icriodus elements within the succession. The conodont assemblages are representative of the palmatolepid-bispathodid biofacies, which indicate deposition on an outer shelf to slope environment.

Siliceous–volcanic associations of the Northern Balkhash ophiolite Zone (Central Kazakhstan): Biostratigraphy, sedimentation and tectonic evolution in the Middle-Late Ordovician

The Northern Balkhash Zone is the largest and the most complex ophiolite zone of the Junggar-Balkhash region in the west of the Central Asian Orogenic Belt. The zone encompasses serpentinite mélange, containing fragments of dunite-harzburgite, dunite-verlite-pyroxenite complexes, layered and isotropic gabbro, sheeted dikes and plagiogranites, along with stacks of tectonic slivers composed of siliceous, siliceous-basaltic, and siliceous-volcanic-tuffaceous units. Conodont finds suggest the middle-late Darriwilian age of the siliceous-basaltic Itmurundy Fm., while the siliceous-basalt Tiuretai, siliceous Kazyk, and the siliceous-tuffaceous Uzuntobek formations are close in age, extend from the top of Darriwilian to the base of Katian.The siliceous-clastic-tuffaceous sediments of the Obaly Fm. are the Sandbian and Katian in age and the volcanic-sedimentary Dzhamanshuruk Fm. is broadly Upper Ordovician.Dating of these units has also permitted recognition of the units with intricate thrust-and-fold structure. Species of the genera Periodon, Pygodus, and Scabbardella dominate in the conodont assemblages in cherts. An uneven distribution of the conodonts in sections is caused by variable siliceous sedimentation rate that depends on productivity of radiolarians.The petrochemistry of the volcanics in the Itmurundy Fm. suggests that they correspond to OIB and E-MORB, being formed within seamounts or oceanic plateaus, while the Tiuretai basalts are close to N-MORB, erupted within a spreading center. The felsic volcanics in the Dzhamanshuruk Fm. have demonstrated an island arc affinity. The proposed evolution model suggests that during the Middle-Late Ordovician tectonic settings changed successively from the spreading center to island arc within the Northern Balkhash Zone of the Junggar-Balkhash region.

Carnian–Norian (Late Triassic) climate change: Evidence from conodont oxygen isotope thermometry with implications for reef development and Wrangellian tectonics

The Carnian–Norian (C–N) transition (Late Triassic) has long been postulated as an interval of major climatic changes, though the nature of such changes and their ecological impact remains largely unexplored. We use oxygen isotopes measured on monogeneric conodont assemblages (δ18OPO4) from the Canadian Cordillera to trace seawater temperature evolution at the western margin of Pangea and in the allochthonous Wrangellia Terrane. Different conodont taxa show conspicuous offsets in δ18OPO4, suggesting that they had preferential habitat depths and genus-specific temperature corrections must be applied. Thus, δ18OPO4 from the Williston Lake sections indicates low mid-latitude sea surface temperatures (SSTs) ranging from ∼28 to 35°C, favouring a generally warm Late Triassic climate scenario. The parvus Subzone of C–N transition, which marks the peak faunal turnover, records major climatic perturbations: SSTs peaking at ∼34°C then decreasing to ∼29°C. This is followed by a quick temperature rebound and a second pulse of cooling from 33 to 27°C in the asymmetrica-Norigondolella Subzone, marking the coldest temperatures in the ∼20 Myr study interval. A secular warming trend towards the late Norian reinstated after the transient cooling in the earliest Norian, coinciding with reef expansions in the Late Triassic. The middle–late Norian (Alaunian 3–Sevatian 1) represents a hothouse climate comparable to the Paleocene–Eocene Thermal Maximum and its warmth supressed both diversity and origination rates of reef-building biota. Early Norian δ18OPO4 data from Frederick Island, Haida Gwaii (part of the Wrangellia Terrane) are more depleted in 18O compared to coeval samples from the Black Bear Ridge, indicating ∼3–5°C warmer temperatures than the Laurentian epicontinental sea. The temperature difference supports a more southern, probably sub-equatorial position for at least part of the Wrangellia Terrane during the earliest Norian.

Conodonts of the Krevyakinian and Khamovnikian Substages of the Kasimovian Stage in the Type Region (Moscow Basin)

The Kasimovian Stage is a stage in the Pennsylvanian Subsystem, originally recognized in Russia. Its type area, despite the stage name (which is after the town of Kasimov in the Ryazan Region), is in the vicinity of the Voskresensk Region in the lower reaches of the Moscow River for the Krevyakian and Khamovnikian regional substages and the former village of Dorogomilovo (Moscow Region) for the Dorogomilovian Regional Substage. The stratotypes of the subdivisions of the Krevyakinian and Khamovnikian regional substages were established in the Voskresensk Region and no longer exist. The conodont assemblages of the Krevyakian and Khamovnikian and the lower part of the Dorogomilovian were studied in the neostratotype of the Kasimovian Stage (Afanasievo Section) and the Perkhurovo Reference Borehole drilled near the town of Voskresensk.

Lithofacies and Biofacies Characteristics of Lower Carboniferous Carbonates in Central Taurides, Turkey

The studied successions in the Central Taurides were mainly deposited in a shallow marine environment during the Early Carboniferous time. Conodonts are one of the most important microfossil groups for the Lower Carboniferous biostratigraphy. The measured sections are not rich in conodonts but important species including those of the Lower Carboniferous boundary conodonts. The conodont elements recorded in this study include Gnathodus cuneiformis, Gnathodus girtyi girtyi, Gnathodus girtyi simplex, Kladognathus sp., Lochriea commutata and Vogelgnathus campbelli. Based on the recovered conodont assemblages, Visean - Serpukhovian boundary has been recognized by the first occurrence of Gnathodus girtyi simplex. Conodont faunal variations in Paleozoic to Triassic marine deposits are generally environmentally controlled. Within the context of paleoenvironmental interpretations, different microfacies types could be determined by microfacies criteria reflecting patterns of the depositional environments. The types of microfacies and their environmental interpretations can provide a framework for conodont paleoecology. The defined facies types in BSE section are mainly crinoidal bioclastic packstone, bioclastic grainstone, sandy oolitic grainstone, quartz-peloidal grainstone and quartz arenitic sandstone facies. Crinoidal bioclastic packstones and bioclastic grainstones are suitable facies for conodonts owing to environmental conditions. Bioclasts associated with the conodonts are mainly crinoids, fusulinids, algae, echinoids, brachiopods and ostracods. Conodont elements could not be recorded from sandy oolitic grainstone and quartz arenitic sandstone facies due to the deposition in high energy environments under unstable conditions.

Ordovician conodonts and the Tornquist Lineament

The Holy Cross Mts. in southern Poland are generally believed to be split by a tectonic dislocation into two separate parts, a NE one being a part of the Baltic Craton and a SW part belonging to the Małopolska Terrane of a complex geotectonic history connected with the Trans-European Suture Zone (Tornquist Lineament). Unexpectedly, conodont assemblages of earliest Middle Ordovician (early Darriwilian) age from Pobroszyn in the northeastern Łysogóry region and from Szumsko in the southwestern Kielce region show virtually identical species composition. One of the dominant species both in Pobroszyn and Szumsko, Trapezognathus pectinatus sp. n., characterized by denticulated M elements, occurs elsewhere only on the northern margin of Gondwana. Separation of the Małopolska microcontinent from Baltica continued after the disappearance of Trapezognathus and an apparently allopatric speciation process was initiated by a population of Baltoniodus. Also in this case, denticulation developed in the M elements of the apparatus but the process of speciation of B. norrlandicus denticulatus ssp. n. was truncated by re-appearance of the Baltic lineage of Baltoniodus. Later conodont faunas from the region are of Baltic affinities, but remain distinct in showing a relatively high contribution from exotic species of Sagittodontina, Phragmodus, and Complexodus. The periodic North American Midcontinent tropical influences observable in the Baltic region did not reach the Holy Cross Mts. The Ordovician conodont faunas from the Holy Cross Mts. can be fit into a transect extending from Baltica to Gondwana, with several intermediate terranes. This new evidence disproves the long-held concept that the Łysogóry and Kielce regions had separate early Palaeozoic fates and that the Małopolska Terrane was unified with Baltica already in the earliest Ordovician. The Trans-European Suture Zone truly marks the presence of a wide Tornquist Sea in the early Palaeozoic.

Sporadoceratid ammonoids from the Shotori Range (east-central Iran) – a case of putative gigantism caused by hydraulic sorting?

The Shotori Range of east-central Iran (east of Tabas) has yielded Famennian ammonoid assemblages dominated by the family Sporadoceratidae. Four genera Maeneceras Hyatt, 1884, Iranoceras Walliser, 1966, Sporadoceras Hyatt, 1884 and Erfoudites Korn, 1999 are represented. The conodont assemblage of one sample containing Iranoceras revealed an Upper marginifera Zone age. The ammonoid assemblages are characterised by comparatively large specimens; they reach conch diameters of 300 mm (including the body chamber) and the mean size is larger than 100 mm. The preservation of the material from the Shotori Range and size comparison with sporadoceratid assemblages from the Anti-Atlas of Morocco and the Rhenish Mountains of Germany suggest that hydraulic sorting has resulted in a bias towards large conchs, explaining the size distribution, rather than latitudinal differences. The new species Maeneceras tabasense is described; the genus Iranoceras is revised with a new description of the two species Iranoceras pachydiscus (Walliser, 1966) and Iranoceras pingue (Walliser, 1966).

The last phase of conodont evolution during the Late Triassic: Integrating biostratigraphic and phylogenetic approaches

For the Upper Triassic, conodonts are the primary tools utilized in biostratigraphic investigations. For an effective biostratigraphic zonation, the species should be constrained by clear phylogenetic relationships, in which the stratigraphic ranges and taxonomy are reliable. Unfortunately, a phylogenetic framework for the Late Triassic pectiniform conodonts is almost missing, except for particular intervals, such as the Carnian/Norian boundary. The purpose of this study is to examine the latest Norian and Rhaetian pectiniform conodonts in detail in an attempt to determine their phylogenetic relationships, by applying novel phylogenetic methodologies that incorporate both morphological and stratigraphic data. This work is based on the conodont assemblages from the Upper Triassic strata of the Lagonegro Basin (southern Apennines, southern Italy) and the Csővár area (north-central Hungary), complemented with data from the literature. The calibrated phylogenetic analysis of the latest Norian and Rhaetian conodonts supports a two-step evolutionary history: a first radiation (~211–210 Ma) of the Parvigondolella species and the first representative of the genus Misikella, followed by a second phase (~206.5–205 Ma) leading to the final radiation of the Misikella species. Furthermore, the systematic revision of uppermost Triassic conodonts is provided along with the description of Misikella kolarae n. sp.

Natural assemblages of the conodont Clarkina in lowermost Triassic deep-sea black claystone from northeastern Japan, with probable soft-tissue impressions

We report the first discovery of Lower Triassic Clarkina assemblages: four natural conodont assemblages from Lower Triassic pelagic black claystones of the North Kitakami Belt in northeastern Japan (Akkamori section). The fossils were obtained from the 2.5-m horizon level above the black claystone base, which is assigned to the end-Permian mass-extinction event. This horizon has been dated to the earliest Triassic (Griesbachian) by the occurrence of Hindeodus parvus, which is the index species for the base of the Triassic, in the same and subjacent horizons. These four fossil assemblages include a paired segminiplanate-formed P1 element, which was identified as the genus Clarkina, and have fully or partially preserved the original components of conodont elements. The most complete assemblage among them includes 15 distinctive elements, namely S0 and pairs of M, S1, S2, S3, S4, P1, and P2. It is noteworthy that these fossil assemblages preserve probable impressions of ‘eyes,’ which were replaced by aggregations of silicate, phosphate, and sulphide minerals. The occurrence of several sets of fossils that retain the original positioning of the conodonts' elemental apparatuses, as well as the original presence of soft tissue, may be attributed to the process by which the conodonts' bodies were transported to the deep seafloor, and by which the activity of agents of decomposition was inhibited in near-abiotic sediments under anoxic conditions in the pelagic deep sea during the earliest Triassic.

Conodonts from Late Devonian island arc settings (Baruunhuurai Terrane, western Mongolia)

Upper Devonian marine deposits of the Baruunhuurai Terrane in western Mongolia represent island arc settings, which yielded a diverse conodont assemblage of 30 taxa, including species of Ancyrognathus (as well as one new species), Icriodus, Mehlina, Polygnathus and Palmatolepis. Biodiversity analysis of Ancyrognathus, Pelekysgnathus, Mehlina and Icriodus shows that the Mongolian conodont assemblage consists of two endemic and few cosmopolitan taxa. Representatives of the otherwise globally distributed genus Pelekysgnathus are absent. An important factor influencing the regional distribution of conodont taxa seems to be the siliciclastic-dominated sedimentation of the Baruunhuurai Terrane during the early Famennian.

Middle ordovician conodonts from the Chingiz Ridge (Kazakhstan): taxonomy of the Naiman Formation assemblage and its biogeographic affinity

Conodonts from carbonate rocks of the Naiman Formation (Chingiz Ridge, East Kazakhstan) have been studied in detail for the first time. The mixed conodont complex is characterized by a high taxonomic diversity and includes species of the stratigraphic interval from the upper part of the Dapingian to the middle of the Darriwilian of the Middle Ordovician. The conodont assemblage includes oceanic/deep-sea species of wide geographic distribution, in particular, abundant Periodon macrodentatus and P. zgierzensis, which are typical for siliceous deposits of Kazakhstan. For the first time, the occurrence of species Scolopodus? mufushanensis, Drepanoistodus latus and Anodontus longus is noted in Kazakhstan. This indicates the existence of the biogeographic climatic zones typical for pelagic biota. The species Protopanderodus? nogamii indicates that the Kazakhstan conodont fauna belongs to the Australasian biogeographic province of the Eastern Gondwana. The conodont assemblage includes a number of regionally endemic taxa that characterize the Kazakhstan fauna as an independent biogeographic unit and confirm the relative remoteness of water basins of Kazakhstan from the eastern margin of Gondwana as well as from other paleocontinents in the Ordovician.

Conodont Assemblage from the Upper Part of the Lower Olenekian Abrek Bay Section, South Primorye

Conodont Assemblage from the Upper Part of the Lower Olenekian Abrek Bay Section, South Primorye

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.

Integrated Radiolaria, benthic foraminifera and conodont biochronology of the pelagic Permian blocks/tectonic slices and geochemistry of associated volcanic rocks from the Mersin Mélange, southern Turkey: Implications for the Permian evolution of the northern Neotethys

AbstractBlocks and tectonic slices within the Mersin Mélange (southern Turkey), which are of Northern Neotethyan origin (Izmir–Ankara–Erzincan Ocean (IAE)), were studied in detail by using radiolarian, conodont, and foraminiferal assemblages on six different stratigraphic sections with well‐preserved Permian succesions. The basal part of the Permian sequence, composed of alternating chert and mudstone with basic volcanics, is assigned to the late Asselian (Early Permian) based on radiolarians. The next basaltic interval in the sequence is dated as Kungurian. The highly alkaline basic volcanics in the sequence are extremely enriched, similar to kimberlitic/lamprophyric magmas generated at continental intraplate settings. Trace element systematics suggest that these lavas were generated in a continental margin involving a metasomatized subcontinental lithospheric mantle source (SCLM). The middle part of the Permian sequences, dated by benthic foraminifera and conodont assemblages, includes detrital limestones with chert interlayers and neptunian dykes of middle Wordian to earliest Wuchiapingian age. Higher in the sequence, detrital limestones are overlain by alternating chert and mudstone with intermittent microbrecciated beds of early Wuchiapingian to middle Changhsingian (Late Permian) age based on the radiolarians. A large negative shift at the base of the Lopingian at the upper part of section is correlated to negative shifts at the Guadalupian/Lopingian boundary associated with the end‐Guadalupian mass extinction event. All these findings indicate that a continental rift system associated with a possible mantle plume existed during the late Early to Late Permian period. This event was responsible for the rupturing of the northern Gondwanan margin related to the opening of the IAE Ocean. When the deep basinal features of the Early Permian volcano‐sedimentary sequence are considered, the proto IAE oceanic crust formed possibly before the end of the Permian. This, in turn, suggests that the opening of the IAE Ocean dates back to as early as the Permian.