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Ordovician chitinozoans are as yet inadequately documented from the western Yangtze Platform, South China. Here we present a systematic study on chitinozoans from a Middle–Upper Ordovician succession at Songliang of Qiaojia, northestern Yunnan, southwestern China. Altogether 34 species of 12 genera are identified from the upper Hungshihyen and the Huadan formations. The top of the Hungshihyen Formation yields typical Early and Middle Ordovician forms, for instance, Lagenochitina obeligis and Belonechitina chenjiawuensis, with the latter only known from the lower Darriwilian in South China, thus suggesting an early Darriwilian age for this interval. The chitinozoans recovered from the Huadan Formation include Lagenochitina prussica and Spinachitina fossensis, both are mainly confined in Katian and sometimes ranging into younger strata. This indicates an age younger than the middle to late Darriwilian previously determined for the Huadan Formation. However, conflicts exist in age assignment of the Huadan Formation based on chitinozoan and other evidence, and further work is required.

Lagenochitina esthonica is a globally distributed chitinozoan in Early to Middle Ordovician rocks. It is regarded as an index species for the early Floian in North America and has a stratigraphically constrained range in other regions. Lagenochitina esthonica is distinguished from other chitinozoans by a distinct flexure, a nearly rounded-square chamber, and a cylindrical neck with a flaring collar. However, since the first description of the species in the 1950s, it has included two varieties: a relatively short form with a test length ~400 μm, and a slender form usually longer than 600 μm. In order to revise the taxonomy of the L. esthonica group, we carried out a statistical morphometric study of a large collection of well-preserved specimens from the Baltic region where the taxon was first established. Additionally, the stratigraphic and geographic distribution of both forms was analyzed based on available occurrence data. The results show that the short form occurs in the upper Tremadocian to lower Dapingian, whereas the slender form is mostly reported from the lower and middle Darriwilian. Both forms are identified on Baltica; the short form has also been reported from Laurentia and South China, whereas the other is known also from Avalonia and Gondwana. The morphological distinction, together with differences in stratigraphic and spatial ranges, suggest that the two forms represent separate species: the original stout L. esthonica, based on the morphology of the holotype, and the slender L. megaesthonica n. sp., described herein. The updated taxonomy enhances the stratigraphic and biogeographic usefulness of lagenochitinids globally.UUID: http://zoobank.org/ec49166e-2a8d-4941-8723-f023853c5a7e.

We present a δ13Ccarb chemostratigraphy for the Late Ordovician Hirnantian Stage based on 208 whole-rock samples from six outcrops in the Oslo–Asker district, southern Norway. Our data include the Norwegian type section for the Hirnantian Stage and Ordovician–Silurian boundary at Hovedøya Island. The most complete record of the Hirnantian Isotope Carbon Excursion (HICE) is identified in a coastal exposure at Konglungø locality where the preserved part of the anomaly spans a c. 24 m thick, mixed carbonate–siliciclastic succession belonging to the upper Husbergøya, Langåra and Langøyene formations and where δ13Ccarb peak values reach c. +6 ‰. Almost the entire HICE occurs above beds containing the Hirnantia Fauna, suggesting a latest Hirnantian age for the peak of the excursion. The temporal development of the HICE in southern Norway is associated with substantial shallowing of depositional environments. Sedimentary facies and erosional unconformities suggest four inferably fourth-order glacio-eustatically controlled sea-level lowstands with successively increased exposure and erosion to the succession. The youngest erosional unconformity is related to the development of incised valleys and resulted in cut-out of at least the falling limb of the HICE throughout most of the Oslo–Asker district. The fill of the valleys contains the falling limb of the HICE, and the postglacial transgression therefore can be assigned to the latest part of the Hirnantian Age. We address the recent findings of the chitinozoan Belonechitina gamachiana in the study area and its relationship to the first occurrence of Hirnantia Fauna in the studied sections, challenging identification of the base of the Hirnantian Stage.

The wide, trans-oceanic geographical distribution of myodocope ostracods during the Silurian (especially during the Ludlow and Pridoli epochs), and their widespread preservation in rocks of that age, permits the establishment of a transcontinental biostratigraphy of comparable resolution to coeval graptolite/chitinozoan/conodont biozones. Seven myodocope biozones, extending from the Homerian Stage, upper Wenlock Series Cyrtograptus lundgreni graptolite biozone to the middle part of the Ludfordian Stage of the Ludlow Series, enable a time-resolution for each biozone of circa 1 million years. These biozones can provide high-resolution correlation across Europe into Arctic Russia and Central Asia. There is also the potential for a myodocope biostratigraphy applicable from the uppermost Silurian (Pridoli) to the Carboniferous.

The Hungshihyen Formation represents the Lower to Middle Ordovician near-shore siliciclastic deposits on the western margin of the Yangtze Platform, South China. However, its age is still debated, largely because of insufficient studies. Here we documented the Bursachitina maotaiensis–B. qianbeiensis chitinozoan assemblage from the lower part of the Hungshihyen Formation at Songliang, Qiaojia County, eastern Yunnan Province. This assemblage is remarkably similar to an assemblage that roughly correlates to the middle part of the Corymobograptus deflexus graptolite Biozone in northern Guizhou Province, indicating that the Hungshihyen Formation at Songliang is probably of late Floian age and may extend into the early Dapingian. Additionally, a revision on the chitinozoans previously documented from the strata assigned to the same formation in the Wuding area was made according to the latest classification. The revision allows the recognition of the Euconochitina symmetrica–Eremochitina brevis assemblage, and therefore suggests a late Tremadocian age for this interval based on regional and global chitinozoan biostratigraphic correlations. Considering also its lithologic succession, we argue that the chitinozoan-bearing strata in the Wuding area previously assigned to the Hungshihyen Formation correspond most likely to the uppermost part of the underlying Tangchi Formation or the lowermost part of the Hungshihyen Formation. The base of the Hungshihyen Formation appears therefore to be diachronous in eastern Yunnan Province.

Chitinozoans were recovered from the Naranco, Huergas and Gustalapiedra formations of northern Spain, which yielded a diverse assemblage including 29 taxa in 9 named genera. The deposits are of early Givetian age, a time when Iberia was isolated from large continents as part of the Armorican Terrane Assemblage. The formations studied here consist of a large clastic unit interrupting carbonate deposition, with large limestone formations positioned above and below the formations analyzed here. This clastic unit includes the Kacak Event, an important global extinction event associated with anoxia in the marine realm. In this paper, the relatively well-preserved chitinozoan assemblage is described and considered from a biogeographical and stratigraphical perspective. The chitinozoan community was deposited in a short space of time and includes various taxa not previously known from the Middle Devonian, though the assemblage as a whole is attributable to the period. Only moderate similarity is seen with assemblages reported from Laurussia and Gondwana, with a slight bias towards the latter. This report adds to our knowledge of chitinozoan paleobiogeography and to other recent studies of Middle Devonian palynology in northern Iberia.

Four core and fifteen cutting samples of well RH-2 from the Ordovician of the Llanos Basin, Colombia, were palynologically analyzed. They yielded mostly diverse and well-preserved marine palynomorph assemblages, dominated by acritarchs. Forty-six acritarch taxa and two chitinozoan species were identified. Palynological assemblages indicate an Early Ordovician, maximum Floian age, for the upper core samples and a late Tremadocian?- Floian? age for the lower cutting samples. Based on a thorough revision of the updated stratigraphic ranges of the taxa, and especially on the First Appearance Datums (FADs) of selected acritarch taxa such as Arbusculidium filamentosum, Arkonia, Barakella, Aureotesta clathrata simplex, Coryphidium bohemicum and Frankea, the age of the four upper core samples could be constrained to the middle to late Floian and the 15 cutting samples most probably to the late Tremadocian or early to middle Floian. The recognized chitinozoan taxa, Eremochitina brevis and Velatachitina veligera, support the interpreted ages. The presence of taxa such as Arbusculidium, Arkonia, Aureotesta clathrata simplex, Coryphidium, Dactylofusa velifera var. brevis, Frankea and Striatotheca confirm affinities with the Perigondwana Province. Eisenackidium orientalis which first appears outside the Early to Middle Ordovician basins of Argentina, could become a useful species for correlations among Eastern Gondwana Ordovician basins. The genus Frankea, considered as a biostratigraphic and paleogeographic component of the Perigondwana Province, is recorded for the first time in Eastern Gondwana, and its occurrence could represent one of the oldest worldwide records of the genus. The palynological results constitute a step towards the establishment of a biostratigraphic framework for the Ordovician of Colombia.

The Upper Ordovician glaciogenic deposits are thought to have an important quantity of hydrocarbon across North Africa. Insight is provided about the IV-3 reservoir unit in the In-Adaoui-Ohanet field in the Illizi basin of south-east Algeria. The aim is to: 1) describe the lithofacies; 2) interpret the depositional environment; 3) describe the petrographic characteristics; 4) investigate the petrophysical properties; and 5) perform a biostratigraphic analysis of the unit IV-3 reservoir (Upper Ordovician) in the In-Adaoui-Ohanet field based on the core description and samples collected from the well IA-115. Lithofacies described in the study area are MT1, MT2, MT3, MT6, and MT9. Subglacial tillite is the depositional environment associated with lithofacies MT3, MT6, and MT9. These lithofacies are thought to be deposited medial to a distal fan, whereas lithofacies MT1 and MT2 are thought to be deposited in high-energy flows. Acritarch and Chitinozoan species are the most common biozones described in the study reservoir and they are thought to be affiliated with an Upper Ashgilian stage. Petrographic analysis shows that the study reservoir unit is formed by fine to coarse-grained sandstone. Quartz is considered to be the principal framework mineral (mean, 56.30%). Cementing minerals observed in this reservoir unit are quartz and carbonate. From a compositional point of view, the unit IV-3 reservoir in the In-Adaoui-Ohanet field is predominantly formed by quartz arenites, which are considered to be mature. Additionally, the tectonic setting of these arenites is most likely associated with a passive margin origin. The emphasis throughout this study is on the role of factors such as permeability, carbonate cement, and quartz overgrowth on the reservoir quality of unit IV-3 in the In-Adaoui-Ohanet field. The quality of this reservoir unit is highly influenced by the quartz overgrowth and pores that are plugged by carbonate cement, which dramatically reduces the pore network. An enhanced porosity was observed only in the MT3lithofacies (up to 22.3%). Additionally, from an economic point of view, the study reservoir unit is classified as a tight gas-bearing reservoir.

As 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.

Chitinozoans are a group of biostratigraphically valuable microfossils which appeared in the Tremadocian and diversified during the rest of the Great Ordovician Biodiversification Event, to become extinct in the Devonian. The early diversification of chitinozoans on the Baltica palaeocontinent has remained poorly known due to preservation and collecting bias. In this study we document the distribution of chitinozoans through the upper Tremadocian to lower Darriwilian strata in the Jagala waterfall section from northern Estonia, in order to better understand the regional diversity patterns and biogeographic links. Fifty samples were studied from the 7.5 m succession of sandstones, marls and carbonates revealing 47 chitinozoan species and 11 genera. The lowermost productive samples, attributed to the late Tremadocian, represent the earliest rich chitinozoan fauna from Baltica. Combined with previous reports this shows a diversity peak in the Tremadocian with balanced total diversity reaching 17, possibly followed by a decline in the Floian and then a rather gradual increase through the Dapingian and early Darriwilian. The new diversity curve shows more than three times higher values for the Tremadocian and Dapingian than indicated in previous studies, and thus less abrupt radiation in the Darriwilian. The Jagala section provided also new data on the regional biozonal species Conochitina cucumis and Cyathochitina regnelli, which characterize the middle and upper Volkhov and lower Kunda regional stages, respectively. Several other biostratigraphically significant taxa typical of other regions were recovered from the Jagala section, including Conochitina decipiens and Desmochitina bulla. A new short-ranging species Laufeldochitina toilaensis sp. nov. is introduced, having potential to become an index species for middle Dapingian strata. The early Darriwilian assemblage from Jagala includes Rhabdochitina sp. A with up to 2.7 mm long vesicle, making it the largest chitinozoan ever reported.

The end-Ordovician mass extinction (EOME) is widely interpreted as consisting of two pulses associated with the onset and demise of the Gondwana glaciation, respectively, with the second pulse eradicating the distinctive, glacially related Hirnantian benthic biota (HBB). A global review of occurrence data of latest Ordovician benthic marine organisms reveals that virtually all warm-water benthic assemblages previously assigned to the HBB comprise two distinct and clearly postglacial faunas, both younger (middle and late Hirnantian, respectively) than the cool-water Hirnantia fauna (latest Katian to early Hirnantian). The newly recognised three Transitional Benthic Faunas (i.e., TBFs 1–3) can be closely tied to graptolite, conodont, and chitinozoan biozonations, the Hirnantian Isotope Carbon Excursion (HICE), and the glaciation, thereby providing an integrated, much higher-resolution timescale for understanding the tempo and nature of the EOME. At this finer resolution, we postulate a more profound impact of the first pulse of the EOME than hitherto envisaged, as evidenced by opportunistic expansion of the Hirnantia fauna globally and the complete absence of metazoan reefs in its immediate aftermath. We also argue, based on high-quality data from well-documented benthic groups in South China (i.e., brachiopods, tabulate and rugose corals, trilobites, and sponges), that the magnitude of the second pulse of the EOME caused by the deglaciation has been overestimated because the two postglacial faunas (i.e., TBFs 2–3) were part of a subsequent recovery phase of marine ecosystems rather than contributing to biodiversity decline. Thus, it is more plausible to reinterpret the EOME as a single-pulse, rapid event that was followed by a prolonged initial recovery intermittently impeded by climatic shocks through the Hirnantian, prior to the onset of a progressive reestablishment of marine ecosystems during the early Silurian (Rhuddanian and Aeronian) associated with an overall amelioration of climatic conditions.

The nature and relation of the graptolite lundgreni Event and the conodont Mulde Event in the mid-Homerian and the ensuing development of atmospheric-oceanic models for the whole Silurian has been a matter of debate for several decades. Chitinozoans represent a promising tool in the correlation of graptolite and conodont biozonation, however, their dynamics through the mid-Homerian must first be well constrained. Based on supposed changes in chitinozoan faunas described in earlier studies from the Prague Basin, a continuous section ranging through the lundgreni Event has been selected and the chitinozoan content was investigated taxonomically and statistically for a detailed faunal dynamic study. Although the moderate to bad preservation of chitinozoans hinders the taxonomic work, an exceptionally diverse chitinozoan population has been observed. The range-through assumption compiled with data from other areas showed only two widespread species to disappear near the lundgreni Event: Cingulochitina cingulata and Margachitina margaritana. The statistical evaluation of chitinozoans indicates only minor changes in chitinozoan dynamics across the section. The differences in development of generic and specific richness and dominance is interpreted as being related to chitinozoans with selective ecological dependence, interpreted as a result of changes in environmental conditions during the mid-Homerian period. This pattern is in concordance with the results of a relative change test of the chitinozoan population and is more similar to the pattern of conodont faunal dynamics, rather than graptolite faunal dynamics during the mid-Homerian.

An integrated palynological and geochemical approach has been initiated to date and to precise the geochemical events of the Pimenteiras Formation, in the Late Devonian from the Parnaiba Basin, Brazil. Based on good biostratigraphic markers and presence of index species among miospores, acritarchs and chitinozoa, the investigated sequences are referred to the Middle to early Late Frasnian. Among Miospores, Chelinospora concinna and Verrucosisporites Witt-eras are likely to be from the BPi Interval Zone defined in the Amazon Basin. Chitinozoans of the Early to early Late Frasnian Angochitina (Lagenochitina) avelinoi zone of the Parnaiba Basin are present, and acritarch assemblages arc also consistent with a Middle to early Late Frasnian age, by comparison to assemblages previously described in other Brazilian basins. Some important accompanying species of palynomorphs are illustrated. In the studied outcrops, black shale intervals are referred to top of the Radioactive Sale B and Radioactive Shale C according to Rodrigues (1995) definitions. Top of Radioactive Shale B shows good concentration of terrestrial organic matter, but low potential source of gas. By comparison Radioactive Shale C of the upper part of the Pimenteiras Formation, with important concentration of marine organic matter have low to high potential as source of gas and condensate. This study shows that a progressive flooding took place during the Devonian period in the Parnaiba Basin with maximum marine transgression in the Frasnian. These global events of interest for hydrocarbon exploration, are regarded as markers for Gondwanan regional chronostratigraphic correlations. (C) 2020 Published by Elsevier B.V.

Extended introduction to the materials and methods, Figures S1–S4, Tables S1 and S2, and supplemental movies (Movies S1–S3).

The Qaidam Paleoplate is a microcontinent that is currently part of central Asia. Its position during the Ordovician is uncertain, with paleogeographic reconstructions placing it either near South China or near North China. Ordovician microfossils such as chitinozoans have not previously been reported from the Qaidam Paleoplate. In this paper, a chitinozoan microfauna from the middle part of the Shihuigou Formation in the Dameigou section, South Qilian Mountains, Qinghai Province, northwest China is documented. The assemblage is dated as Darriwilian (Undulograptus austrodentatus and Archiclimacograptus confertus graptolite biozones) on the basis of associated graptolites. The chitinozoan fauna is well-preserved and includes several biostratigraphically and paleogeographically important chitinozoan species, such as Lagenochitina langei, L. pirum, Rhabdochitina magna, R. usitata, Conochitina turgida, C. subcylindrica, C. decipiens, Clavachitina poumoti, Belonechitina nevillensis, B. cf. uniformipunctata and B. chydaea. The assemblage contains a specimen in which the collarette of a specimen of Desmochitina sp. is attached to the aboral pole of a specimen of Lagenochitina sp., possibly indicating that a single organism could produce more than one chitinozoan morphospecies. The Conochitina turgida–C. subcylindrica Biozone is indicated by the recovered chitinozoan assemblage. Biostratigraphically important species from the Qaidam microfauna suggest faunal affinities with Laurentia (North America), eastern Gondwana (Australia) and the peri-Gondwana area (southeast China). The chitinozoan paleogeographic data indicate that the Qaidam region was at low latitude during the Middle Ordovician, and that the area was near South China. The paleogeographic information deduced from chitinozoans is consistent with that obtained from graptolites and paleomagnetic analysis in previous studies.

Chitinozoan, graptolite and organic-rich immature Upper Ordovician mudstone was artificially matured using closed hydrous pyrolysis. The pyrolysis was performed at isothermal temperatures of 310-350 °C at 10 °C increments for 72 h. This temperature range simulates the subsurface thermogenic hydrocarbon generation window based on previous laboratory simulations. The objectives of this study are to (a) qualitatively and quantitatively assess the degree of physicochemical transformation of dispersed organic matter (DOM) and zooclasts in BRF petroleum source rock after artificial maturation; and (b) determine the relationship between graptolite, chitinozoan, vitrinite-like particle and bitumen reflectance (Ro) with increasing pyrolysis temperature and the thermal maturity. Petrographic analysis shows that bituminite and amorphous kerogen were the first organic macerals to thermally decompose after the first pyrolysis temperature. This is followed by liptodetrinite, thin-walled alginite, acritarch, and telalginite as pyrolysis temperature increases. Concurrently, the fluorescence properties of the telalginite shifted from greenish yellow to reddish-orange after the last stage (350 °C) pyrolysis. In addition, significant amount of bright fluorescing labile hydrocarbons produced during pyrolysis were observed oozing from pore spaces and on the surface of the rock matrix. Pore-filling, orange to reddish-orange fluorescing solid bitumen were also found in pores spaces created by the thermal decomposition of DOM. The lack of morphological evidence for the thermal decomposition of chitinozoans and graptolites suggests that these zooclasts macerals may have limited or have no contribution to the overall hydrocarbon generation. Nonetheless, their respective reflectance (Ro) increased (0.64% to 1.34% and 0.55% to 1.38%) as the pyrolysis temperature was increased. These Ro values are significantly higher than the vitrinite-like particles (0.49% to 1.07%) and solid bitumen (0.30% to 1.09%). The measured RocK-Eval Tmax and solid bitumen vitrinite reflectance equivalent (VRo-eqv) are comparable to the average vitrinite-like particles. The relationship between rate of increase in chitinozoan and graptolite, and vitrinite-like particles Ro, expressed by the equations: Ro-vit-like = 0.77 Rchi and Ro-vit-like = 0.79 Rgrap, are comparable to those observed in geologically matured source rocks.

The lower part of the Cape Phillips Formation (Upper Ordovician, Canadian Arctic) is an ideal unit to test the correlation of graptolite and chitinozoan reflectance, and to compare zooclast reflectance with Rock-Eval pyrolysis Tmax. The Cape Phillips Formation is an organic-rich limestone and shale containing abundant zooclasts, bitumen, and amorphous organic matter, and has biomarker characteristics consistent with a carbonate depositional environment and organic matter derived from marine algae. Random graptolite reflectance on thirty-seven samples in the Rograp range of 0.58%–1.02% (Tmax range of 424–441 °C) were examined. The correlation between random reflectance of graptolite and chitinozoan reflectance was determined to have the following linear model: ( Ro grap ) = 0.11 + 0.814 × ( Ro chi ) whereas the linear correlation between Rock-Eval Tmax (converted to vitrinite reflectance equivalent VRoeqv) and Rograp and Rochi were determined to be: VRo eqv ( Tmax ) = 0.232 + 0.499 × ( Ro grap ) for random reflectance of graptolites. VRo eqv ( Tmax ) = 0.231 + 0.482 × ( Ro chi ) for chitinozoan. Graptolite and chitinozoan reflectance are generally greater than vitrinite reflectance equivalent, but the difference between the equations to convert graptolite and chitinozoan reflectance to VRoeqv(Tmax) are so small that the equations could be used interchangeably and may represent a general solution to the conversion of zooclasts reflectance to VRoeqv(Tmax) in Lower Paleozoic rocks. The correlation between zooclast reflectance and Rock-Eval Tmax improves in samples that have undergone solvent extraction, indicating that hydrocarbons affect Tmax. Sample that has asymmetrical S2 peak on Rock-Eval pyrolysis also has very high total extract yield with resins and asphaltenes as the dominant extracted fractions. Rock-Eval analysis of samples before and after solvent extraction demonstrates that some portion of the soluble hydrocarbon is pyrolysed in the temperature range that overlaps the S2 peak. In extracted samples S2 peaks become more symmetrical and the Tmax value shifts compared to the unextracted samples.

In many unconventional hydrocarbon systems, organic matter (OM) substantially contributes to total porosity of the rock that led to a positive correlation between total organic carbon (TOC) and porosity. While organic porosity is an important reservoir property of unconventional hydrocarbon systems, TOC of these rocks consists of different macerals or petrographic fractions. These TOC fractions can be geochemically divided and quantified by the revised, extended slow heating (ESH) Rock-Eval analysis. This study discusses the contribution of different fractions of OM on porosity variation in the mature to overmature Utica Shale in southern Quebec, using ESH Rock-Eval analysis, helium pycnometery, scanning electron microscopy (SEM), and X-ray diffraction (XRD) mineralogy. Selected samples from three wells at depths of ∼400, 700, and 2000 m, covering a range of thermal maturity from late peak oil window (VRoeqv. ∼1%) to dry gas zone (VRoeqv. ∼2.1%) were analyzed in this study. The predominant OM constituents are solid bitumen, chitinozoans, and minor graptolites with mean TOC of 1.1 ± 0.4 wt. %. The mean porosity for oil and gas window samples decreases with depth from 3.9 ± 0.9 to 2.6 ± 0.5%, respectively. The SEM images reveal that organic porosity is limited to pores developed in solid bitumen, while regardless of thermal maturity, chitinozoans have a non-porous structure throughout the oil to dry gas window. This observation suggests that the impact of thermal maturity on porosity is different for different OM fractions (i.e., macerals), leading to different contribution of OM fractions to total porosity. The latter conclusion is further supported by the improved correlation observed between the solid bitumen fraction and porosity compared to TOC-porosity correlation for oil window samples. Our entire data set suggests that OM (i.e., bitumen fraction), especially in the dry gas window, is not the major controlling factor on the total porosity in the Utica Shale, whereas, intergranular porosity has the dominant control on total porosity. This observation suggests that the hydrocarbon storage potential may largely reside in inorganic pores rather than organic pores in the analyzed intervals of the Utica Shale. The decrease in total porosity observed from shallower samples (i.e., oil window) to deeper samples (i.e., dry gas window) also suggests that intergranular porosity is the dominant porosity component, which decreases with burial.

Chitinozoans are a key group in Ordovician and Silurian biostratigraphy, and the Baltic region hosts some of the largest collections of these microfossils in the world. Here, we present an online database – ‘CHITDB’ – for documenting and analysing the distribution of chitinozoans in the Baltic region. The system is integrated with the Estonian geocollections database and includes a public query portal ( ), which allows browsing and searching for chitinozoan taxa, samples, sections, references and SEM images, downloading raw data by sections, and generating range charts, summary reports and CONOP9 input files. The chitinozoan database holds currently over 35000 occurrence records of 300 chitinozoan taxa from 6400 micro-palaeontological samples and 100 sections. Quantitative stratigraphical analysis of this data set enabled compilation of the highest resolution chitinozoan diversity curves through the Ordovician and Silurian to date, and assessment of the rates of evolutionary changes. The new model incorporates K-bentonite and carbon isotope data that help to constrain time relationships between bioevents and environmental changes. The highest chitinozoan diversity in the Baltic region is encountered in late Darriwilian to mid-Katian and in the Telychian, when the standing diversity reached 30–35 species. Overall, the latest Ordovician and Silurian faunas show more dynamic diversity patterns, with higher extinction and origination rates, than was typical for most of the Ordovician Period.

An Euconochitina symmetrica Zone was defined in the G-locality at Levis, Quebec, within an interval belonging to Zone A of Raymond that contains Paratetragraptus approximatus. The interval was consequently attributed to the Floian. E. symmetrica was also recognized in Northern Gondwana, and the species was considered an undisputed marker for the base of the Floian. During the past decades, several occurrences of E. symmetrica have been reported from Avalonia, southern China, and even from Northern Gondwana in Tremadocian strata casting doubt on the Floian age of the Zone. Revisions of the graptolites in the G locality and N section at Levis provides a frame on which the age of the E. symmetrica Zone can be precisely documented. At both localities the E. symmetrica chitinozoan assemblage is older than the base of the Paratetragraptus approximatus graptolite Zone. Therefore, the presence of E. symmetrica can no longer be correlated with the graptolite P. approximatus Zone as it was initially suggested. It rather characterizes the upper Tremadocian Sagenograptus murrayi Zone, its upper part could however reach the Floian. An older assemblage characterized by a Lagenochitina gigas n. sp. assemblage (previously designated Lagenochitina maxima) occurs in strata correlated with the Tremadocian Aorograptus victoriae graptolite Zone. Correlation of the biostratigraphic ranges of the chitinozoan and graptolite faunas in the lower part of the Levis Formation allowed for a better positioning of the Lower Ordovician Laurentian chitinozoan zones on the Ordovician time scale.

Acritarchs and chitinozoans were documented from Ordovician strata and miospores from Lower Permian beds in the Zardkuh area. Ninety-one palynomorph species, comprising acritarchs (63 species of 31 genera), chitinozoans (16 species of 12 genera), and miospores (12 species of 10 genera) were recognized that form 10 local assemblage zones, comprising Zones A–F = acritarchs, G–I = chitinozoans, and J = miospores. Zone A occurs in the uppermost Ilebeyk Formation, indicating Late Cambrian; Zones B–E are present in the Zardkuh Formation, suggesting Early Ordovician (Tremadocian–Floian)–Middle Ordovician (Dapingian) and Zone F occurs in the Seyahou Formation, presenting Late Ordovician (Hirnantian). Likewise, three Gondwanan chitinozoan Zones G–I were established in this succession. Zones G–H occur in the Upper Shale Member of the Zardkuh Formation, supporting an Early-Middle Ordovician (Floian–Dapingian), and Zone I is restricted to the Seyahou Formation, suggesting Late Ordovician (Hirnantian) age. Finally, Zone J occurs in the Faraghan Formation, confirming Early Permian. Based on palynomorph zones, two hiatuses are present within the Paleozoic sequences of the study area. The first hiatus occurs between the Zardkuh and Seyahou formations, encompassing the Middle Ordovician (Dapingian) and much of the Late Ordovician (Sandbian and Katian). The second hiatus appears between the Seyahou and Faraghan formations, spanning the Silurian, Devonian, Carboniferous, and earliest Permian (Asselian). The palynomorph taxa, including Arbusculidium, Striatotheca, Coryphidium, Vavrdovella, Eremochitina, Velatachitina, and miospore taxa, confirm that the study area belongs to peri-Gondwana paleoprovince. Four new species are Vavrdovella mawlawii sp.nov., Vogtlandia zardkuhensis sp.nov, Pseudocoryphidium zagrosensis gen et sp.nov, and Pterospermella saadii sp.nov.

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.

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.

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.

The author examined the high-latitude Hirnantian diamictites of the Ghelli Formation and the early Silurian olive-gray shales of the Niur Formation exposed in the northeastern Alborz Mountains, Iran. These 404 m thick glacial deposits can be divided into three progradational-retrogradational cycles, each potentially controlled by the regional advance and retreat of the Hirnantian ice sheet. The glaciated source area was west of the study area, in the Arabian Shield region, where numerous tunnel valleys have been reported. Time calibration was performed based on a high-quality biostratigraphic control, mainly derived from the chitinozoan biozones Tanuchitina fistulosa , Acanthochitina barbata , Armoricochitina nigerica , Ancyrochitina merga , Tanuchitina elongata , Spinachitina oulebsiri , and Spinachitina fragili s. The land-derived miospores present in most chitinozoan assemblages, often abundant, seem associated with global sea-level changes during the Late Ordovician glaciation. The Ghelli Formation's high abundance of terrestrial miospores and low abundance of marine palynomorphs suggests its deposition in a shallow marine environment. Additionally, rhythmic bedded tidalites of claystone and sandstone indicate the growth of early land plants producing cryptospores on adjacent flooded areas. Based on marine palynomorphs (chitinozoans and acritarchs), the northeastern Alborz Mountains glacial deposits were dated as Hirnantian; the Niur Formation was assigned to the earliest Llandovery (Rhuddanian). Glacial deposits and marine palynomorphs suggest the presence of Hirnantian ice caps in the Alborz Mountains, at the margin of the Arabian Plate, and indicate the peripheral extension of the Late Ordovician ice sheet. Several biostrome beds forming pelmatozoan-bryozoan mud-mounds, mainly comprising bryozoans, echinoderms, tentaculites, and subordinate trilobites, were found in the glacial deposits of the Ghelli Formation, suggesting carbonate deposition during the Hirnantian. These carbonate beds are not related to the Boda warming event, which happened over the Gondwana landmass in the Katian interval; the glacial deposits of the Alborz Mountain Ranges are thus not correlated to those of the Gondwana paleocontinent. Climatic amelioration is more likely than local reduction of clastic input to be responsible for the biostrome beds in the Glacial Member of the Ghelli Formation, namely a short-lived episode of global warming during the Hirnantian interval (the Milankovitch cycles). Four new chitinozoan species, namely Armoricochitina persianense n. sp., Tanuchitina alborzensis n. sp., Spinachitina iranense n. sp., and Hyalochitina jajarmensis n. sp., are described and illustrated. Biometric data are also provided for the Iranian S . oulebsiri and A . nigerica .

Well-preserved miospore assemblages are recorded from the Late Ordovician (Katian–Hirnantian) Ghelli Formation in the Pelmis Gorge, located in the Alborz Mountain Range, Northeastern Iran. The palynomorphs were extracted from siliciclastic deposits that are accurately dated using marine palynomorphs (acritarchs and chitinozoans). The spore assemblages consist of 14 genera and 28 species (26 cryptospores and 2 trilete spore species). Six new cryptospore species are described: Rimosotetras punctata n.sp., Rimosotetras granulata n.sp., Dyadospora asymmetrica n.sp., Dyadospora verrucata n.sp., Segestrespora iranense n.sp., and Imperfectotriletes persianense n.sp. The study furthers knowledge of the development of the vegetative cover during the Late Ordovician. Various and abundant cryptospores in the Late Ordovician (Katian–Hirnantian) Ghelli Formation are probably related to the augmentation of land-derived sediments either during the global sea-level fall linked to the Late Ordovician glaciation or adaptation of the primitive land plants in a wide range of climatic conditions. These miospore taxa were produced by the earliest primitive land plants, which probably grew close to the shoreline and were washed in from adjacent areas, producing a high volume of miospores. The associated marine palynomorphs consist of acritarchs (13 genera and 18 species), chitinozoans (9 genera and 10 species), prasinophycean algae, scolecodonts, and graptolite remains, which are not discussed in detail herein. The established chitinozoan biozones of this part of the Palaeozoic sequence are the Armoricochitina nigerica Biozone, the Ancyrochitina merga Biozone, the Tanuchitina elongata Biozone, and the Spinachitina oulebsiri Biozone, suggesting a Late Ordovician age (Katian–Hirnantian). These chitinozoan biozones are widely evidenced only in the peri-Gondwanan Domain, indicating that the study area was part of this palaeo-continent in the Late Ordovician.

Chitinozoans from the Miaopo Formation (topmost Middle to lower Upper Ordovician) at Jieling, northern Yichang, western Hubei, were systematically studied, and 43 species of 16 genera were identified, which substantially increases the chitinozoan diversity of this particular time interval of the South China palaeoplate. Several key chitinozoan species from North Gondwana (e.g., Lagenochitina ponceti Rauscher) and Baltica (e.g., Laufeldochitina stentor (Eisenack) and Cyathochitina sebyensis Grahn) are reported for the first time in China. The chitinozoans of this formation are of late Darriwilian–early Sandbian age, and they have mixed North Gondwana and Baltica palaeogeographic affinities. The recognition of L. stentor, Armoricochitina granulifera and C. sebyensis guarantees a better biostratigraphic correlation between South China and Baltica. Most of the formation, except for its topmost part, is assigned to the L. stentor Biozone, which can be further subdivided into two subzones: the Cyathochitina megacalix sp. nov. Subzone (lower) and the A. granulifera Subzone (upper). Three new species are formally described: C. megacalix sp. nov., Cyathochitina raricostata sp. nov. and Eisenackitina tenuis sp. nov.

The QSIM-801 well from Central Saudi Arabia contains beds transitional between the Sajir Member of the Saq Formation and the Hanadir Member of the Qasim Formation. Core samples from these beds yielded rich assemblages of well-preserved palynomorphs of low thermal maturity. They are dominated by marine forms (acritarchs, chitinozoans and scolecodonts) but also include relatively abundant and diverse terrestrial forms (cryptospores and dispersed phytodebris), especially in samples from the upper part of the Sajir Member. The cryptospore assemblage is taxonomically consistent with other Middle Ordovician assemblages previously reported from Saudi Arabia, and is concordant with the late Dapingian to early Darriwillian (Llanvirn) age of the Sajir-Hanadir transitional beds, as suggested by palynological evidence (i.e., presence of Siphonochitina formosa and Linochitina pissotensis chitinozoan zones in the basal Hanadir). It includes a variety of monads and permanent dyads and tetrads, which are often characterized by well-developed surface ornamentation such as microgranulation, as well as, in some instances, by thick walls displaying distinct layering.

Investigation of 37 samples from continuously cored intervals of the upper part of the Quwarah Member of the Qasim Formation yielded well-preserved and diverse chitinozoan assemblages. Two biozones previously defined from the North Gondwanan Domain were recognized in the examined cores: the Tanuchitina elongata and Ancyrochitina merga. One new genus, Alhajrichitina, and five new species, Alhajrichitina adamantea, Hyalochitina incomposita, Rhabdochitina curvata, Tanuchitina contracta and Tanuchitina densimura, are described. The vertical distribution of these new taxa form the basis of the Tanuchitina elongata Partial Range Subzone, Hyalochitina incomposita Total Range Subzone, Tanuchitina contracta Partial Range Subzone, and Tanuchitina densimura-Belonechitina aff. robusta Concurrent Range Subzone. Two other assemblages, T. ontariensis and Angochitina cf. curvata are also recognized from the merga Biozone. These new subzones and assemblages improve regional and local stratigraphic correlations, and the recognition of the degree of the Hirnantian glacial erosion at the top of the Quwarah Member. An evolutionary lineage is proposed for the species assigned to Alhajrichitina nov. gen., originating with the Sandbian Lagenochitina dalbyensis, through the Katian Alhajrichitina adamantea and culminating with Rhuddanian species, Alhajrichitina nuayyimensis. Three minor diversity and abundance increases are recognized within the merga–elongata biozone interval. These events could represent minor pulses of sea level rise within a progressive, overall sea level drawdown. For this upper part of the core, a general trend of decreasing diversity is recognized and may indicate an upward shallowing. This trend is compatible with diversity trends from all paleocontinents. It could be speculated that fluctuations in sea level were caused by ice advance and retreat during the initiation of Hirnantian continental glaciation south of the study area.

The Middle Member of the Zorritas Formation in the Antofagasta region of northern Chile, yielded terrestrial and marine palynomorph assemblages which span the Devonian/Carboniferous boundary. The assemblages show a clear predominance of terrestrial palynomorphs with 70 miospore species, 18 marine phytoplankton species, two non-marine algae and one chitinozoan species, all coming from 15 productive levels. Palynomorphs are poorly preserved and most of them are reworked. Three palynological associations are recognized based on miospores. These are assigned to the Tournaisian–Visean, Tournaisian and probable latest Famennian. Age assignments are discussed in the frame of the spore zonal schemes established for Euramerica and western Gondwana. The stratigraphical distribution of spores allows the identification of the probable position of the Devonian/Carboniferous boundary within the Zorritas Formation. This system boundary is proposed for the first time in Palaeozoic sedimentary rocks of northern Chile. The presence of Gondwanan typical miospore species indicates affinities with this palaeocontinent even though the Tournaisian and Tournaisian–Visean miospore associations support the cosmopolitanism already suggested for the early Carboniferous flora. The significant number of reworked palynomorphs together with the sedimentological analysis of the studied sections, suggest that these deposits were severely impacted by the climatic change and major sea level fluctuations. Similar conditions were recorded in coeval western Gondwana basins. Fil: Rubinstein, Claudia Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Petus, Elodie. Université de Liège; Bélgica Fil: Niemeyer, Hans. Universidad Católica del Norte; Chile

The Zlíchovian/Dalejan boundary interval (Emsian, Lower Devonian) of the Pekárek Mill section was studied employing biostratigraphy (dacryoconarid tentaculites, conodonts) and palynology (chitinozoans, prasinophytes, scolecodonts) and microfacies analysis in order to shed more light on the timing and characteristics of the Daleje Event. The results of our study stress the great importance of the base of the Nowakia elegans Zone for the substage level division of the Emsian. Onset of the Daleje transgression is linked with higher terrigenous input, and coinciding changes in the chitinozoan assemblages were recorded at this level. The transgression at the base of the N. elegans Zone preceded the main transgression taking place in the N. cancellata Zone; it can be correlated with the Upper Zlíchov Event. For the first time, Emsian chitinozoans and a jawed polychaete fauna are described in detail from the Prague Basin and can be correlated with other northern Gondwanan regions. The family-level composition of scolecodont assemblage confirms the dominance of paulinitids in the peri-Gondwanan realm. Fil: Tonarová, Petr. Czech Geological Survey; República Checa Fil: Vodráková, Stanislava. Czech Geological Survey; República Checa Fil: Ferrová, Lenka. Czech Geological Survey; República Checa Fil: de la Puente, Graciela Susana. Universidad Nacional del Comahue. Facultad de Ingeniería. Departamento de Geología y Petróleo; Argentina Fil: Hints, Olle. Institute Of Geology, Tallinn University Of Technology; Estonia Fil: Frýda, Jiří. Czech Geological Survey; República Checa Fil: Kubajko, Michal. Czech Geological Survey; República Checa

Well-preserved cryptospore and chitinozoan assemblages were recovered from the Tierekawati Formation (late Katian, Late Ordovician) of the Mannan-1 borehole, south Tarim basin (Tarim Block), China. The chitinozoan assemblage is low in abundance and diversity (two genera, five species), and its age is restricted to the late Katian (Late Ordovician). The cryptospore assemblage consists of the tetrads (three genera, five species) and dyads (three genera, four species), with a low abundance and diversity. It has similarities to the previous records from the coeval deposits around the world. Comparison of two coeval cryptospore assemblages from two boreholes more than 300 km apart within the Tarim Block shows the separate landmasses of the south and north Tarim Block were covered with much the same cryptophyte vegetation. The different elements in the vegetation might be caused by the local palaeogeography and palaeoenvironment.