Chitinozoan Biostratigraphy Research Articles

Ordovician chitinozoans and review on basin stratigraphy, biostratigraphy and paleobiogeography of northern Argentina along the Proto-Andean margin

Ordovician strata exposed across the Cordillera Oriental and the Sierras Subandinas in northwestern Argentina were part of a large retroarc foreland basin developed along the Proto-Andean margin within the Central Andes in South America. A revised chitinozoan biostratigraphy along and across-strike for the Tremadocian, Floian, Dapingian, Katian and Hirnantian stages, calibrated with other fossil groups in the basin, allow pinpointing the most characteristic events that affected the basin fill testing global versus local controls in accommodation, and suggesting comparisons with other peri-Gondwanan records. According to the chitinozoan data, the glacially-related Ordovician deposits in northwestern Argentina are restricted to the Hirnantian, and unconformably overlie late Katian deposits. In the Caspalá area (Cordillera Oriental), an interval with synsedimentary deformation and reworked chitinozoans correlate with glacially-related deposits in other sites of the eastern part of the basin (Río Capillas and Mecoyita areas). A glacial waning stage is determined by a thin interval of organic‐rich black shales with sparse dropstones at the top of the Zapla Formation, containing Spinachitina oulebsiri associated with Desmochitina gr. minor, which together are typical latest Hirnantian components in other regions of Gondwana. Our study strengthens the foreland systems tract for the Ordovician Central Andean Basin with a volcanically fed interarc and foredeep depozone to the west (Puna region); a lower-accommodation forebulge depozone in the central area (mostly the Cordillera Oriental region); and a backbulge depozone (Sierras Subandinas and Sierras de Santa Bárbara) extending as far as the eastern Paraná Basin (reaching Paraguay and Brazil). Contemporaneous unconformities driven by global sea-level fluctuations were amplified or reduced due to deepening-narrowing or widening-shallowing, allowing contrasted accommodation, respectively associated to loading and relaxation. Ordovician chitinozoans from the Central Andean Basin indicate Northern, Western and peri-Gondwanan affinities, although locally some more cosmopolitan species described in Baltica, Avalonia and South China, are also recorded.

Latest Sandbian brachiopods and chitinozoan biostratigraphy in North Estonia

Latest Sandbian brachiopods and chitinozoan biostratigraphy in North Estonia

Chitinozoan biostratigraphy of the regional Arenig Series in Wales and correlation with the global Lower–Middle Ordovician series and stages

AbstractThe Arenig Fawr area of North Wales constitutes the type area for the British Lower to Middle Ordovician Arenig Series and is complemented by sections in the Carmarthen and Whitland areas of South Wales. We describe chitinozoan assemblages from both areas in order to aid correlation of the Arenig Series in its type region with the global Ordovician series and stages. Chitinozoans recorded from Arenig Fawr provide permissive rather than conclusive evidence but suggest that the Henllan Ash Member correlates with the upper Floian Stage Slice Fl3 or lower Dapingian Stage Slice Dp1. Better results were obtained from South Wales where six chitinozoan assemblages are distinguished, ranging in age from late Tremadocian to middle Darriwilian (early Llanvirn). Most species are known from South China, Gondwana and/or Baltica where there are controls on ranges. They show that much of the lower Arenig (Moridunian) succession in South Wales correlates with the upper Floian Stage (Fl3). Correlatives of the lower and middle Floian Stage (Fl1, Fl2), if present, must be represented by the Ogof Hên Formation and lowest Carmarthen Formation. Chitinozoan assemblages from the upper Arenig Series (Fennian Stage) are more readily correlated with Gondwanan biozones and indicate correlation of the Fennian Stage with the Dapingian and lower Darriwilian (Dw1) stages. The middle Arenig Whitlandian Stage is constrained in South Wales to an interval from the uppermost Floian Stage to the basal Dapingian Stage, resulting in an inferred increased rate of sediment accumulation.

Chitinozoan biostratigraphy across the Aeronian–Telychian boundary (Silurian, Llandovery) in the Middle Yangtze region of China

Based on the comprehensive study of two sections and one borehole in the Middle Yangtze area, fruitful chitinozoan specimens were obtained. An optimized scheme of the chitinozoan biozonation across the Aeronian–Telychian boundary is proposed. Five chitinozoan biozones are recognized, including the Conochitina emmastensis Biozone, Conochitina malleus Biozone, Ancyrochitina shiqianensis Sub-biozone, Eisenackchitina daozhenensis Biozone and the Angochitina longicollis Biozone. The differences between the here introduced scheme for the Yangtze region and that in other regions of the world are discussed. The E. daozhenensis Biozone is more suitable as the lowest chitinozoan biozone of the Telychian in the Yangtze region and replaces Plectochitina brevicollis Biozone. Besides, this study demonstrated that the uppermost Shamao Formation is diachronous in the Middle Yangtze region based on the investigation of the stratigraphic correlation on the Luoreping and Shamao formations by chitinozoans.

Chitinozoan biostratigraphy of the Rheidol Gorge Section, Central Wales, UK: a GSSP replacement candidate for the Rhuddanian–Aeronian boundary

AbstractAs part of an international effort to evaluate potential replacement sections for the current Aeronian GSSP, the stratigraphy of the Rheidol Gorge section (central Wales, UK) is being restudied. A total of 28 samples from the Rhuddanian–Aeronian boundary interval at Rheidol Gorge were studied for chitinozoans. This famous Welsh Basin section, its stratigraphy rooted in the work of O.T. Jones and M. Sudbury, comprises a series of laminated black shales with abundant graptolites, alternating with grey mudstone intervals, deposited in anoxic to dysoxic/oxic seafloor conditions, respectively. The exposed section of c. 20 m spans the middle part of the upper Rhuddanian Pernerograptus revolutus Biozone through the lower Aeronian Neodiplograptus magnus Biozone of the lower to mid‐Llandovery Series (Cwmere and Derwenlas formations). Our chitinozoan analysis yielded an assemblage of over 2300 specimens distributed approximately uniformly throughout the entire succession. A total of 16 different taxa are identified, of which 12 remain in open nomenclature, reflecting the poor to moderately intact preservation of the specimens. Based on the presence of key species such as Spinachitina maennili and Conochitina iklaensis, the Rheidol Gorge section is referred to the Spinachitina maennili Biozone. This observation is in perfect alignment with the typical signature of other Rhuddanian–Aeronian boundary successions in the Welsh Basin and in other parts of the world.

Integrated Lower–Middle Ordovician graptolite and chitinozoan biostratigraphy of the Jiangnan Slope Region, South China

An integrated Early–Middle Ordovician graptolite and chitinozoan biostratigraphical study was carried out to improve the correlations between the two fossil groups in two sections in the Jiangnan Slope Region (deeper outer-shelf mud–sand–carbonate belt), South China. Six graptolite biozones and two chitinozoan biozones (including an undefined interval) were recognized. The chitinozoan Lagenochitina praepirum appears to be a stratigraphically useful species, despite being geographically restricted to South China, appearing at a level coincident with the first appearance of the index graptolite Levisograptus austrodentatus. Thus, the base of the Lagenochitina praepirum Biozone can also be regarded as the base of the Darriwilian Stage. The chitinozoan abundance in both sections is exceptionally low, and the assemblages do not contain the biostratigraphically important Belonechitina species. The distributions of both chitinozoans and graptolites are eco-dependent but show different onshore–offshore diversity trends. Chitinozoans are more diverse nearer to shore whereas graptolites are more diverse offshore, preferring slope facies. This may be caused by the different ecological preferences of chitinozoans and graptolites.

Tremadocian (Early Ordovician) chitinozoan biostratigraphy of South China: An update

The lowest Ordovician (Tremadocian) chitinozoan biostratigraphy of the South China Palaeoplate has been reviewed and updated, based on new investigation from the Upper Yangtze area. The systematic paleontology of Lagenochitina pestovoensis Obut 1973 and Lagenochitina destombesi Elaouad-Debbaj 1988, has been revised. Previous identifications of L. destombesi from South China are considered questionable, and the L. destombesi Biozone, recognized from Baltica, northern Gondwana and peri-Gondwana, is therefore no longer used for the middle-upper part of the Tremadocian in South China. Two chitinozoan biozones are recognized, including the Lagenochitina pestovoensis Biozone (lower) and the Euconochitina symmetrica Biozone (upper) for the middle and upper part of the South Chinese Tremadocian. International correlation of the E. symmetrica Biozone indicates that the base of this biozone in South China is lower than the records in North America and northern Gondwana, and that the biozone is confined within the upper Tremadocian in South China.

Chitinozoan biostratigraphy and carbon isotope stratigraphy from the Upper Ordovician Skogerholmen Formation in the Oslo Region. A new perspective for the Hirnantian lower boundary in Baltica

The end-Ordovician has received wide attention because it hosts major global events including mass extinctions, glaciations, significant sea-level fluctuations, and large-scale perturbations of the Earth's carbon cycle. Knowing the order and timing of these events and their components is crucial for understanding these environmental changes. Here, we use stable carbon isotope stratigraphy in combination with chitinozoan biostratigraphy to correlate the Upper Ordovician Belonechitina gamachiana chitinozoan Biozone. Its position has long been a matter of debate; some argue that it is of late Katian age and others that it is of early Hirnantian age. The Skogerholmen Formation from the Oslo-Asker District in Norway has been correlated with the lower-middle Pirgu Baltic Stage, hitherto believed to correspond to the international upper Katian Stage. Our study, however, reveals the presence of B. gamachiana, diagnostic of the eponymous Biozone, in the descending trend of a modest carbon isotope excursion in the lower part of this formation. This is strikingly similar to data from coeval end-Ordovician sections in North America, where the prevailing evidence suggests an early Hirnantian age for the B. gamachiana chitinozoan Biozone. This new correlation suggests that the lower Hirnantian boundary may be positioned within the Pirgu Baltic Stage.

Chitinozoan biostratigraphy of the Silurian Wenlock–Ludlow boundary succession of the Long Mountain, Powys, Wales – ERRATUM

Figure 3 from the above article was erroneously published upside down. Please see below the correct version of the figure. The publishers apologise for this error.

Chitinozoan biostratigraphy of the Silurian Wenlock–Ludlow boundary succession of the Long Mountain, Powys, Wales

AbstractSystematic collecting through the upper Wenlock (upper Homerian) and lower Ludlow (Gorstian and lowermost Ludfordian) Silurian rock succession of the Long Mountain, Powys, Wales, identifies some 48 chitinozoan species that distinguish four biozones, two subzones and an interregnum. Consideration of the chitinozoan biozones together with those of the graptolites enables a local three-fold subdivision of the late Homerianlundgrenigraptolite Biozone, and the distinction of lower and upper intervals for the Gorstianincipiensgraptolite Biozone. The base of the Ludlow Series in the Long Mountain more or less equates to the base of theCingulochitinaacme chitinozoan Biozone, although no key chitinozoan first or last appearance datums are associated with the series boundary itself. The new graptolite–chitinozoan biozonation allows enhanced correlation between upper Wenlock and lower Ludlow sedimentary deposits of the Lower Palaeozoic Welsh depositional basin and those of the palaeo-shelf in the stratotype Wenlock and Ludlow areas of Shropshire. Chitinozoans seem affected by the phenomena that caused the late Wenlock ‘Mulde extinction’ in graptolites but, with the final disappearance of 9 species and re-appearance of 11 species following an interval of overall low diversity, they seem to have suffered less severely than their macro-zooplanktonic contemporaries.

Middle to Late Ordovician graptolite and chitinozoan biostratigraphy of the Kandava-25 drill core in western Latvia

This paper presents integrated graptolite and chitinozoan biostratigraphical data for the upper Middle and lower Upper Ordovician of the Kandava-25 drill core in Latvia, a core that overwhelmingly contains the most diverse graptoloid fauna in the East Baltic carbonate-dominated sections. Graptolites are abundant in two intervals in the Kandava-25 core. The older strata (Stirnas and Furudal formations) contain the graptolites Pseudamplexograptusdistichus, Proclimacograptusangustatus, Archiclimacograptuscaelatus, Archiclimacograptus sebyensis, Archiclimacograptusosloensis n. sp., Dicaulograptushystrix, Haddingograptuseurystoma, Haddingograptus luperus, Haddingograptus maennili n. sp., Hustedograptusteretiusculus, Hustedograptus vikarbyensis, Gymnograptuslinnarssoni, Dicellograptusvagus, Dicellograptus intortus, Dicellograptus gurleyi, Dicranograptusirregularis and Nemagraptussubtilis. These species indicate that the lower interval belongs to the P. distichus and D. vagus zones, zones that correlate with the more widely recognizable Didymograptusmurchisoni (upper part) and H.teretiusculus zones. Thus, the lower interval is late Dariwillian (Lasnamägi and Uhaku regional stages) in age. A second graptolite-rich interval begins in the middle of the Dreimani Formation and contains Nemagraptusgracilis, Hustedograptusuplandicus, Orthograptuswhitfieldi, Orthograptus calcaratusincisus, Oepikograptusbekkeri, Dicellograptussextans, Dicellograptus salopiensis, Normalograptusrotundatus and Archiclimacograptusbalticus n. sp. This fauna is Sandbian (Kukruse and Haljala regional stages) in age. Chitinozoans are abundant and well preserved throughout the Kandava-25 core. Six chitinozoan biozones and five subzones can be recognized in the upper Middle and lower Upper Ordovician strata of the core. The co-occurrence of biostratigraphically important graptolites and chitinozoans in the Kandava-25 core provides direct tie-points for Ordovician graptolite and chitinozoan biozonations. http://zoobank.org/urn:lsid:zoobank.org:pub:CC9E068C-E56C-4197-89B8-E30C067B69CB

Chitinozoan biostratigraphy in the Haljala Regional Stage, Upper Ordovician: a high-resolution approach from NE Estonia

The distribution of chitinozoans in the Haljala Stage (Upper Ordovician, Sandbian) from Kerguta-565, Piilsi-729 and Vasknarva-639 drill cores in NE Estonia was examined from 128 closely spaced samples. The studied chitinozoan fauna was diverse – altogether 14 chitinozoan genera and 39 species were recorded. Based on chitinozoan ranges in the studied sections, 13 species were identified as biostratigraphically most valuable. The high-resolution sampling used in this study has allowed us to refine the stratigraphic usefulness and extent of distribution of several chitinozoan key species as well as elaborate internal biostratigraphy of the Haljala Stage.

The Llandovery–Wenlock boundary interval in west-central continental Estonia: an example from the Suigu (S-3) core section

A gap corresponding to several conodont and chitinozoan zones occurs in the Llandovery-Wenlock boundary interval in some sections in the western coastal region of Estonia and on islands in the Muhu Strait. New data from the Suigu (S-3) core section demonstrate that the gap has geographically wider distribution in western continental Estonia. Detailed study of faunas from that section revealed that here the gap corresponds to at least four conodont zones (from below): the Lower and Upper Pseudooneotodus bicornis and Lower and Upper Pterospathodus pennatus procerus zones, but probably also the upper(most) Upper Pt. amorphognathoides amorphognathoides Subzone and the Lower Kockelella ranuliformis Zone (or part of it) are missing. In sense of chitinozoan biostratigraphy, the gap correlates with most of the Margachitina margaritana Zone. Only the uppermost part of this zone is represented in the section. However, although the gap in the Suigu (S-3) core section is distinct and well dated biostratigraphically, the δ 13 C curve demonstrates no evidence of it. Causes of this controversy are still waiting to be revealed. Our data indicate that changes in sedimentation in the Llandovery-Wenlock boundary interval occurred earlier in the distal graptolite-bearing and later in the proximal environments. Most probably, sedimentation in the Baltic Palaeobasin in the late Telychian and early Sheinwoodian was strongly affected by tectonic evolution of the Baltoscandian foreland basin.

The extent of the Middle Ordovician Dapingian Stage in peri-Gondwanan Europe and north Africa: stratigraphic record, biostratigraphic tools and regional chronostratigraphy

The boundaries and subdivisions of the global Dapingian stage cannot be adequately characterized in the extensive south-polar Gondwana continental shelves. Correlatable sediments, dated to some extent by palynomorphs, are generally highly condensed in shale facies ( < 10 m thick) or are entirely lacking, whereas in shallow-water sandstones they may locally reach more than 100 m thick. In the absence of valuable data derived from key macrofossils (graptolites and conodonts), the regional chitinozoan biostratigraphy has gone through numerous conceptual variations in the last 20 years, which has not helped a precise definition of the base of the Dapingian, provisionally included in the “upper” Arenigian regional stage of peri-Gondwana.

Chitinozoan biostratigraphy across the Katian (Late Ordovician) GICE event in the Borenshult-1 drillcore (Sweden)

The Late Ordovician is a period of major global environmental changes. Its understanding requires an integrated stratigraphical approach. Here, chitinozoan assemblages are described from the Borenshult-1 drillcore from Motala (Sweden) and related to stable carbon isotope event stratigraphy. Fifty-six rock samples, corresponding to a stratigraphic interval ranging from the upper Sandbian to Llandovery, were dissolved and analysed for chitinozoans. This stratigraphic interval covers the Sandbian to Llandovery and includes, in ascending order, the Freberga, Slandrom, Fjäcka, Jonstorp, Loka and Motala formations.This study resulted in identification of two biozones the Spinachitina cervicornis Biozone (lower part of the Freberga Formation), as well as its Angochitina multiplex Subzone, and the Fungochitina spinifera Biozone (upper part of the Freberga Formation). The spinifera Biozone is characterized by the presence of Lagenochitina baltica, whereas the cervicornis Biozone is defined by the presence of its index species.Despite a low recovery of chitinozoans from Borenshult-1, we suggest that the Guttenberg Isotopic Carbon Excursion (GICE), as observed in the Borenshult-1 drillcore, correlates with the S. cervicornis Biozone. This fits well with chitinozoan and carbon isotope data from the Fjäcka section in central Sweden (Dalarna, Siljan region) and from the Smedsby Gård drillcore (Östergötland). The A. multiplex Subzone which is recognised in the Borenshult-1 and nearby Smedsby Gård drillcores, predates the GICE at both localities.

Chitinozoan biostratigraphy of the Upper Ordovician D. clingani and P. linearis graptolite biozones on the Island of Bornholm, Denmark

The last decade saw a revival of the debate on the exact stratigraphical position of the Upper Ordovician P. linearis graptolite biozone. Chitinozoan biostratigraphy can be useful to help address this question. Here, we provide a high-resolution chitinozoan biostratigraphy through the Dicellograptus Shale Formation at Vasagård on the Island of Bornholm (Denmark), which recently also was subject to a thorough revision of its graptolite fauna, representing the Dicellograptus folicaceus, Dicranograptus clingani and Pleurograptus linearis biozones. We have identified close to 9000 individual chitinozoan vesicles from 26 samples through the upper c. 9m of the Dicellograptus Shale Formation. The Spinachitina cervicornis, Fungochitina spinifera and Tanuchitina bergstroemi chitinozoan biozones are identified, and their boundaries carefully calibrated against the revised graptolite biostratigraphy. A correlation with the chitinozoan biozonation in the British Cautley district, which has a predominantly Baltoscandian, mid-latitude signature and is well-correlated with the graptolite and shelly fauna biozones described from the historical type region, is established.

Chitinozoan biostratigraphy of the Přídolí Series of the East Baltic

Chitinozoan biostratigraphy of the Přídolí Series of the East Baltic

The Dawangou auxiliary GSSP (Xinjiang autonomous region, China) of the base of the Upper Ordovician Series: putting global chitinozoan biostratigraphy to the test

Abstract. The Dawangou section, an auxiliary Global Stratoype Section and Point (GSSP) for the base of the Upper Ordovician Series, was sampled for chitinozoans. The 32 samples taken from the black shales of the Saergan Formation, spanning the Pterograptus elegans, Didymograptus murchisoni and Nemagraptus gracilis graptolite biozones, yielded 6536 chitinozoan vesicles. In addition to a diverse endemic assemblage, species important for international correlation were recovered, which enables the subdivision of the Saergan Formation into two chitinozoan biozones, one subzone and one provisionally recognized biozone: the Baltoscandian Laufeldochitina striata Biozone and the Laurentian Lagenochitina sp. A (sensu Achab, 1984) (/Belonechitina hirsuta) Biozone, and the Belonechitina tuberculata Subzone are recognized based on the presence of the index species, while the Baltoscandian Laufeldochitina stentor Biozone is provisionally recognized on the presence of Laufeldochitina sp. A aff. striata sensu Grahn et al., 1996 which has a range confined to the latter biozone. One new chitinozoan species is described: Cyathochitina giraffa sp. nov. and two species were assigned to a different genus: Belonechitina tuberculata comb. nov. and Hercochitina seriespinosa comb. nov.

Chitinozoan biostratigraphy of a new Upper Ordovician stratigraphic framework for Anticosti Island, Canada

Thickness and facies variations in the Upper Ordovician succession of Anticosti Island have made correlations between the western and eastern ends of the island difficult. This chitinozoan study reveals that most strata of the Ellis Bay Formation at the eastern end of the island correlate with the Vaureal Formation at the western end. In the eastern end, chitinozoans typical of the Ellis Bay Formation occur only in the upper part of the Lousy Cove Member, whereas chitinozoans diagnostic of the mid-upper Vaureal occur in the rest of the formation. Moreover, the eastern Schmitt Creek and Mill Bay members of the Vaureal Formation are older than the uppermost Vaureal eponym members in the western end. New east-west correlations, supported by geochemical, sedimentological, and sequence stratigraphic data, are proposed. Comparison with coeval Upper Ordovician successions suggests a Hirnantian age for the gamachiana Zone that occurs in the lower members of the Ellis Bay Formation. It also indicates that the Hirnantian Isotopic Carbon Excursion (HICE) on Anticosti begins in the D. anceps Zone, just below the base of the Hirnantian Stage, reaches a first peak in the lower N. extraordinarius Zone, a second modest peak high in the N. extraordinarius Zone, and a third, more important one, in the lower part of the N. persculptus Zone. These results are in agreement with the biostratigraphic and chemostratigraphic data at the Global Boundary Stratotype Section and Points (GSSPs) for the base of the Hirnantian and Silurian in south-central China and at Dob9s Linn in Scotland.

Integrated Telychian (Silurian) K-bentonite chemostratigraphy and biostratigraphy in Estonia and Latvia

The distribution of altered volcanic ash layers (K-bentonites) and Telychian chitinozoans in four East Baltic drill core sections are compared. This information is integrated with graptolite and conodont biozonations to give a precise correlation chart using four different stratigraphical tools: K-bentonite-based chemostratigraphy; chitinozoan biostratigraphy; graptolite biostratigraphy; and, conodont biostratigraphy. Thickness variations in the K-bentonites suggest that the source of the volcanic ash was to the west and northwest.