Ordovician chitinozoan biozonation of the Brabant Massif, Belgium

Chitinozoans from seven Ordovician units (Abbaye de Villers, Tribotte, Rigenée, Ittre, Bornival, and Brutia formations and a new unnamed unit, here provisionally called the Asquempont unit) belonging to the mainly concealed Brabant Massif, Belgium are described herein. Fifty-six samples were taken from rocks cropping out at the south-eastern rim of the massif in the Orneau, Dyle-Thyle and Senne-Sennette valleys. Microfossil preservation is moderate to poor, and the chitinozoans occur in low numbers. Taxonomically, the recovered chitinozoans are distributed into 29 taxa, some placed under open nomenclature. Together with earlier published graptolite and acritarch data, the analysis of the chitinozoan assemblages resulted in an improved chronostratigraphy of the investigated formations. We propose a local chitinozoan biozonation with 11 zones for the Brabant Massif. The oldest investigated units yielded chitinozoans typical for North Gondwana, and younger units (starting in the middle Caradoc), yielded some taxa also common in Baltica. As the Brabant Massif formed part of the microcontinent Avalonia, the chitinozoan assemblages recovered from the massif support the inferred drifting of Avalonia from high latitudes towards middle latitudes in the Ordovician as was suggested earlier.     

Chitinozoan zonation of the Late Ordovician and the Early Silurian of the island of Anticosti, Québec, Canada

A reappraisal of chitinozoan distribution across the Ordovician-Silurian boundary on the Island of Anticosti has led to the recognition of a new zone, the Ancyrochitina ellisbayensis biozone, in the uppermost part of the Ellis Bay Formation. This biozone lies between the well defined Upper Ordovician Spinachitina taugourdeaui biozone and the lowest Silurian (Rhuddanian) Plectochitina nodifera biozone of the Becscie Formation. The occurrence of such diagnostic species as P. nodifera, Belonechitina postrobusta, Conochitina electa and Ancyrochitina ramosaspina in the Lower Silurian of Anticosti points to a close similarity to faunas in Estonia and north Latvia and indicates an age ranging from the Parakidograptus acuminatus to the Coronograptus cyphus in terms of graptolite zones. The chitinozoan biozonation harmonizes with that based on conodonts and, to a lesser extent, with the known graptolite faunal succession. Five new species: Ancyrochitina ellisbayensis sp. nov., Clathrochitina postconcinna sp. nov., Conochitina gunriveris sp. nov., Clathrochitina perexilis sp. nov., Bursachitina basiconcava sp. nov. and three species in open nomenclature are described.     

Chitinozoan biostratigraphy of the Upper Ordovician Fågelsång GSSP, Scania, southern Sweden

In the Fågelsång section, the new Global Stratotype Section and Point (GSSP) for the base of the Upper Ordovician Series, 22 samples from the E14 (a, b and c) and E15 outcrops have been studied for chitinozoans. They yield rich and rather diverse species assemblages of this microfossil group. The approximately 16-m-thick sampled part of the section can be subdivided, from bottom to top, into two biozones and a subbiozone: the Laufeldochitina stentor zone, the Eisenackitina rhenana subzone and the Lagenochitina dalbyensis zone. The boundary between the lowest biozone and the subzone is situated 1.7 m below the marker “Fågelsång Phosphorite” bed, thus only slightly lower (0.3 m) than the base of the Nemagraptus gracilis graptolite biozone, which defines the base of the Upper Ordovician Series. The base of the L. dalbyensis zone is located just above the Fågelsång Phosphorite, remarkably low compared to the graptolite biostratigraphy. It is evident that the chitinozoan biozonation provides an additional tool to recognise the base of the Upper Ordovician in this section. Furthermore, a distinct faunal change is shown across the phosphorite bed, possibly indicating a hiatus.     

Upper Ordovician and Lower Silurian chitinozoans from central Nevada and Arctic Canada

Late Ordovician and Early Silurian chitinozoans from the uppermost Vinini Formation, and the Hanson Creek Formation in central Nevada and the lower Cape Phillips Formation, Cape Manning section, in Arctic Canada have been re-investigated and a new chitinozoan biozonation is proposed. The Upper Ordovician of central Nevada can easily be correlated to that of Arctic Canada through the common occurrence of the Ordochitina nevadensis biozone in both regions. No such correlation, however, is possible with the Late Ordovician of Anticosti Island in eastern Canada because of the absence of the index Upper Ordovician chitinozoan zonal species of central Nevada such as Belonechitina tenuispinata sp. nov, Ordochitina nevadensis sp. nov. and Nevadachitina vininica gen. nov., sp. nov. in the former area.One new genus, Nevadachitina, and nine new species, Eisenackitina ripae, Belonechitina martinica, Nevadachitina vininica, Nevadachitina praevininica, Ordochitina nevadensis, Belonechitina tenuispinata, Belonechitina parvispinata, Tanuchitina laurentiana, Angochitina hansonica are described and illustrated in this paper and four species are left in open nomenclature.     

Integrated Silurian Chitinozoan and Graptolite Biostratigraphy of the Banwy River Section, Wales

The succession of 38 upper Llandovery–lower Wenlock chitinozoan taxa from graptolitic horizons in the Banwy River section (Powys, Wales) is described. Five new species are named: Bursachitina nestorae Conochitina leviscapulae Conochitina mathrafalensis Belonechitina cavei Belonechitina meifodensis . A further ten taxa are described under open nomenclature. Seven chitinozoan biozones are recognized in the Banwy River section, three of which ( Cingulochitina bouniensis Conochitina acuminata Salopochitina bella ) are new. The base of each biozone is correlated with the graptolite biostratigraphical scheme as follows: Angochitina longicollis Biozone — upper spiralis Biozone; Conochitina acuminata Biozone — lowermost lapworthi Biozone; Margachitina banwyensis Biozone — upper lapworthi Biozone; Margachitina margaritana Biozone — lowermost insectus Biozone; Cingulochitina bouniensis Biozone — upper murchisoni Biozone; Salopochitina bella Biozone — upper firmus Biozone. The succession of chitinozoan biozones in the Banwy River section is compared with that in other sections which have graptolite biostratigraphical control. This has highlighted the following: (1) the correlation of the base of the dolioliformis Biozone with the graptolite biozonation is imprecise; (2) E. dolioliformis is recorded only from levels after the first A. longicollis in Sweden (although this may reflect previously unrecognized synonymies); (3) the longicollis Biozone may be diachronous, its base correlating with levels low in the Telychian in Sweden, Norway and Estonia and with the upper Telychian spiralis Biozone in Wales and the Prague Basin; (4) data herein and from the Prague Basin indicate that the base of the margaritana Biozone correlates with a level low in the insectus Biozone.     

The graptolite correlation of the North American Upper Ordovician Standard

The North American Upper Ordovician reference standard, the Cincinnatian Series, contains rich shelly microfossil faunas in its type area in the Cincinnati Region but graptolites are uncommon in most of its shallow-water calcareous sediments. Consequently, the graptolite correlation of this key sequence has remained uncertain, in part, even controversial. A review of both previously published recently discovered graptolite Occurrences in the type Cincinnatian, combined with data from the important graptolite successions in Oklahoma New York-Quebec, has not only clarified the graptolite correlation of the Cincinnatian but also added new data on the morphology taxonomy, the vertical horizontal distribution, of several taxa. The information now at hand indicates that the Edenian Stage correlates with the C. spiniferus Zone, the Maysvillian Stage with the C. pygmaeus lower middle P. manitoulinensis Zone, the Richmondian Stage with the upper P. manitoulinensis , the D. complanatus , possibly part of the C. inuiti Zone. Comparison between graptolite conodont biostratigraphic evidence reveals no apparent conflict. Correlations are proposed between Upper Ordovician North American stages, graptolite conodont zones, successions in Texas, Oklahoma, Sweden, European graptolite zones, British series.     

重庆城口大塘口下奥陶统红花园组和湄潭组下部的几丁虫

文中图示和描述了重庆城口大塘口奥陶系红花园组和湄潭组下部营盘段的几丁虫计 6属, 17种。其中包括 7个未定种和 3个新种 (Conochitinadatangkouensissp. nov., C. wengxigouensissp. nov., Rhabdochitinachenk ouensesp. nov. )。讨论了几丁虫的地理和地层分布特点及其与笔石生物带的关系,阐明了红花园组和湄潭组下部营盘段不同笔石带(A. filiformis, D. bifidus和A. suecicus笔石带)中几丁虫的组合特征,并与国外同期地层几丁虫组合进行了对比。     

EARLY LLANDOVERY CHITINOZOANS FROM JORDAN

Abstract:  Chitinozoans recovered from cores BG-14 and WS-6 in southern and eastern Jordan are described. Sample ages are well-constrained by graptolite data to the ascensus-acuminatus and vesiculosus graptolite biozones. Eighteen chitinozoan taxa are recognized, with Spinachitina  fragilis , Plectochitina  nodifera , Ancyrochitina  laevaensis and Belonechitina  postrobusta allowing correlation with both local and global chitinozoan and graptolite biozonations for the Rhuddanian. One new species of chitinozoan is erected, Belonechitina  pseudarabiensis sp. nov.     

The new chronostratigraphic classification of the Ordovician System and its relations to major regional series and stages and to δ13C chemostratigraphy

The extensive work carried out during more than a decade by the International Subcommission on Ordovician Stratigraphy has resulted in a new global classification of the Ordovician System into three series and seven stages. Formal Global Boundary Stratotype Section and Points (GSSPs) for all stages have been selected and these and the new stage names have been ratified by the International Commission on Stratigraphy. Based on a variety of biostratigraphic data, these new units are correlated with chronostratigraphic series and stages in the standard regional classifications used in the UK, North America, Baltoscandia, Australia, China, Siberia and the Mediterranean‐North Gondwana region. Furthermore, based mainly on graptolite and conodont zones, the Ordovician is subdivided into 20 stage slices (SS) that have potential for precise correlations in both carbonate and shale facies. The new chronostratigraphic scheme is also tied to a new composite δ¹³C curve through the entire Ordovician.     

WUFENGIAN (ASHGILLIAN) GRAPTOLITE FAUNAL DIFFERENTIATION AND ANOXIC ENVIRONMENT IN SOUTH CHINA

A well-developed Wufengian(Ashgillian)graptolite fauna occurs in the central and southChina areas which belong to the same plate,thesouth China Plate.The graptolite fauna of cen-tral China(Yangtze platform)was first studiedoy Mu(1945,1954,1974),who,together with his colleagues,is now carrying on a systematic palaeo-ntological study of the Wufengian graptolites fromall sections of the Yangtze platform.In the pasttwenty years,the writers have investigated andsampled many Upper Ordovician sections andlocalities in South China.On the basis of thesesections which have been mostly published,thewriters have summarized the Wufengian graptoliteassemblages,the biofacies,lithofacies and confacies belta,the black shale and the anoxie paleoenvironment. Hereillustrates are the Wufengian grapcolites from Xingan and Lingui Counties of Guangxi,Chongyi County of Jiangxi,and Jiangshan Country of Zhejiang.     

Biostratigraphy, biodiversity and palaeoenvironments of the chitinozoans and associated palynomorphs from the Upper Ordovician of the Central Anti-Atlas, Morocco

The range, abundance and diversity of Upper Ordovician chitinozoans and of various other organic-walled microfossils (i.e., acritarchs, leiospheres, scolecodonts) have been documented in the Bou-Ingarf section, Central Anti-Atlas, Morocco. The goal of this study is to provide a refined biostratigraphic scheme for the Lower Ktaoua, the Upper Tiouririne, the Upper Ktaoua and the Lower Second Bani formations in order to locate the initial effects of the Late Ordovician glaciation on the composition of assemblages of organic-walled microfossils. Five Late Ordovician chitinozoan biozones belonging to the North Gondwana zonation are identified. During the late Caradoc and early Ashgill, no significant changes in chitinozoan assemblages are recorded that could be attributed to any dramatic climatic and/or environmental events. The almost absence of phytoplanktonic elements (acritarchs and leiospheres) and of cryptospores in the fistulosa/barbata and in the nigerica biozones are interpreted as resulting of lower offshore environmental conditions. The reappearance of a variety of palynomorphs in the lower part of the elongata biozone does not indicate drastic climatic changes but more likely a shallowing trend of the marine environment and an increased primary production, possibly related to a cooling of the surface water masses subsequently to early effects of a general climatic cooling. The first obvious evidence of the Late Ordovician glaciation occurs in the lower part of the elongata biozone, at the base of the sandy member topping the Lower Second Bani Formation. This sandy deposit is interpreted as the result of a dramatic fall of the sea level due to the development of the Hirnantian ice cap on Gondwana. This short-lived glaciation ended when the northern Gondwanan ice cap melted during the upper part of the elongata and the oulebsiri biozones. A biological crisis affected both the chitinozoans and the acritarchs just after this glaciation, i.e., in the latest Hirnantian.     

New insights into the paleobiogeography of the Early Ordovician graptolite fauna of northwestern Argentina

A multivariate analysis was used to determine the faunistic relationships of the northwestern Argentinean graptolite faunas of Floian age to faunas from Baltica, Avalonia, Laurentia and SW China. A statistical analysis at the species level of the five geographic regions for the Lower Floian was performed with the classic Jaccard's index. The resulting affinity dendrogram shows stronger relationships between Early Floian graptolite faunas of northwestern Argentina and those from Baltica, with less obvious similarities to Great Britain (Avalonia) faunas and only weak affinities to North American (Laurentia) and Chinese (SW China) graptolite faunas. The statistical analysis confirms the paleobiogeographic relationships previously observed in other areas of the Cordillera Oriental, and supports the hypothesis that during the Early Ordovician, northwestern Argentina was located at middle to high latitudes, corresponding to the Atlantic Faunal Realm of cold water graptolite biofacies. The studied graptolite material from the Quinilicán and Agua Chica sections is preserved in shales and siltstones interbedded with fine to medium-grained sandstones corresponding to the lower part of the Acoite Formation. The biostratigraphic implications of the associated graptolites are briefly discussed, and Trichograptus dilaceratus (Herrmann), Acrograptus gracilis (Törnquist), Expansograptus latus (T.S. Hall) and Corymbograptus v-fractus tullbergi (Monsen) are described from the Argentine Cordillera Oriental for the first time.     

Restudy of some Ordovician–Silurian boundary graptolites from Anticosti Island, Canada, and their biostratigraphic significance

The Ellis Bay Formation on Anticosti Island has long been recognized for the biostratigraphic importance of its latest Ordovician conodont, palynomorph, and shelly fossil assemblages. However, a sparse record of graptolites has made it difficult to correlate these assemblages with the graptolite biozonation. Restudy of some previously described and examination of newly collected normalograptid specimens from the Ellis Bay and lower Becscie formations, however, shows that biostratigraphically important taxa are present and these species provide important constraints on the age of the strata. Normalograptus parvulus and N. minor have been identified in the upper half of the Ellis Bay Formation, suggesting that these strata are late Hirnantian in age ( N. persculptus Biozone). Normalograptus imperfectus and Normalograptus sp. aff. N. acceptus occur in the basal beds of the Becscie Formation, indicating that these strata are earliest Silurian. These graptolite data support the hypothesis that the positive carbon isotope excursion seen in the uppermost strata of the Ellis Bay Formation is isochronous with that seen in the Hirnantian strata at Dob's Linn, Scotland, and does not span much of the lower to mid-Hirnantian, as is the case in Arctic Canada and Nevada, USA.     Anticosti Island , Hirnantian, graptolites, Ordovician, Silurian.     

Discovery of Anticostia uniformis from the Xiazhen Formation at Zhuzhai,South China and its stratigraphic implication

The Xiazhen Formation is an Upper Ordovician lithostratigraphic unit in the Jiangshan-Changshan-Yushan (JCY) area, which contains series of Late Ordovician reef successions. The reef successions of the Xiazhen Formation at Zhuzhai are critical for evaluation of the Late Ordovician marine diversity and palaeoecology. However, their age has long been uncertain and generally is regarded as of upper Katian, based on the occurrences of shelly fossils and correlation with the stratigraphic equivalent Changwu Formation. The newly discovered graptolite species Anticostia uniformis, in the Xiazhen Formation, together with the combined evidence of brachiopods and sedimentology, indicates an age range for the graptolite locality from the Dicellograptus complanatus Biozone to the Diceratograptus mirus Subzone of late Katian, but the graptolites do not rule out the possibility that it is Hirnantian.     

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

Kiipli, T., Kallaste, T., Nestor, V. & Loydell, D.K. 2010: Integrated Telychian (Silurian) K-bentonite chemostratigraphy and biostratigraphy in Estonia and Latvia. Lethaia , Vol. 43, pp. 32–44.
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 north-west.     

Biostratigraphy,biodiversity and palaeogeography of late Silurian chitinozoans from A1-61 borehole (north–western Libya)

High resolution biostratigraphic investigation of well preserved and highly diversified chitinozoan assemblages from core samples collected in the upper part of the Alternances Gréso-argileuses Formation (late Silurian) in well A1-61 (Tripolitania, north–western Libya) is undertaken. The chitinozoan assemblages document the range of several Pridolian taxa selected as index species for the global Silurian chitinozoan biozonation. Distribution of important accompanying species is also discussed. The abundance and the diversity of these chitinozoans are quantified and collated with the local environmental trends as deduced from the lithology, sedimentary features and from the associated organic walled microfossils (i.e. scolecodonts, eurypterid fragments, acritarchs, spores, leiospheres, cuticles and plant debris). The palaeogeographic distribution of late Silurian chitinozoans is discussed with a particular attention paid to a very distinctive chitinozoan assemblage characterising the middle part of the Pridoli of the Ibarmaghian Domain in northern Gondwana regions. Systematic notes, including detailed biometric investigations and SEM illustrations, are provided for selected taxa of taxonomic interest and useful for regional or more long distance correlation.     

The Ordovician acritarch genus Coryphidium

The acritarch genus Coryphidium Vavrdová, 1972 is one of the most frequently recorded acritarch taxa in the Ordovician. The original diagnoses, stratigraphical ranges and geographical distribution of all Coryphidium species are critically evaluated in a review of published literature supplemented by studies of material from the British Isles, Belgium, the Czech Republic, Germany, Spain, Morocco, Algeria, Tunisia, Libya and China, including sections from type areas. The taxonomic concept of the genus is here rationalized: the genus Coryphidium is emended and the informal category of coryphid acritarchs is introduced to include all morphotypes with the characteristic vesicle shape of the two genera Coryphidium and Vavrdovella Loeblich and Tappan, 1976. Nine of the previously described species can be attributed to the genus, and two other species possibly belong to it. The attribution to Coryphidium of the species C. sichuanense Wang and Chen, 1987 is rejected here. Intraspecific variability is very important and the attribution of Coryphidium specimens at the specific level is sometimes difficult. The genus is found in all palaeoenvironments from nearshore to offshore settings and apparently does not occupy specific palaeoecological niches. Coryphidium is very useful biostratigraphically and palaeobiogeographically. The review indicates that the genus first appears in the uppermost Tremadocian Araneograptus murrayi graptolite Biozone and is common through the upper Lower Ordovician and the Middle Ordovician, while Upper Ordovician occurrences might be the result of reworking. Palaeogeographically, Coryphidium is an indicator of the peri-Gondwanan acritarch “palaeoprovince” during the Early/Middle Ordovician.     

Revision of the Zone 13 graptolite biostratigraphy in the Marathon, Texas, standard succession and its bearing on Upper Ordovician graptolite biogeography

One of the long-standing problems in North American graptolite biostratigraphy is the distinct differences in assemblages of post-Climacograptus bicornis age between the classical graptolite sequences in the New York - Quebec and Marathon, west Texas, regions. These have been attributed either to faunal provincialism or to the presence of a major hiatus between the Woods Hollow and Maravillas formations in Texas. New collections from the key Marathon Picnic Grounds section contain diagnostic Late Ordovician graptolites that confirm the existence of a major stratigraphic gap below the Maravillas Formation. The lower Maravillas Formation (Zone 13) has a Late Ordovician, low-diversity Pacific Province graptolite fauna that includes the biostratigraphically diagnostic species Climacograptus nevadensis, C. tubuliferus, Orthograptus fastigatus and Dicellograptus ornatus. Zone 13 graptolite assemblages from the Marathon region correlate with the C. tubuliferus to D. ornatus zones in the Trail Creek, Idaho, succession, the Ea4-Bo2 interval in Victoria, the O. fastigatus Zone in the Canadian Arctic Islands, the O. quadrimucronatus to D. ornatus zones of the Canadian Cordillera, and the D. complanatus to D. anceps zones in Scotland. The hiatus between the Woods Hollow and Maravillas formations spans an interval corresponding to at least the Eal Ea3 interval in Australia, the C. americanus to upper A. manitoulinensis zones in the New York - Quebec succession, and the D. clingani and P. linearis zones in Scotland. These results agree with the magnitude of the hiatus previously indicated by conodont biostratigraphy. Late Ordovician graptolite distribution patterns in North America can be explained by an extension of Cooper, Fortey & Lindholm's (1991; Lethaia 24) Lower Ordovician graptolite biofacies model into the Upper Ordovician, which incorporates both lateral water-mass specificity and depth stratification. Using this model, we recognize in Laurentia two separate biofacies among tropical-zone Late Ordovician Pacific Province graptolite faunas, a cosmopolitan Oceanic biofacies, and a cratonic Laurentian biofacies. The lower Maravillas Formation graptolite fauna is clearly part of the Oceanic biofacies, whereas the coeval Appalachian faunas represent the Laurentian biofacies. □Graptolites, Ordovician, biostratigraphy, Texas, biofacies, biogeography.     

Latest Ordovician graptolites from the Mandalay Region,Myanmar

The graptolite fauna of the Mandalay Region, Myanmar, is poorly known. In this paper, 13 species in the genera Avitograptus, Korenograptus, Metabolograptus, Neodiplograptus and Normalograptus are described from the uppermost Ordovician strata of the area. Two of these species, Korenograptus selectus X. Chen n. sp. and Neodiplograptus mandalayensis X. Chen n. sp., are new. On the basis of the graptolite faunas, a biostratigraphic scheme for the uppermost Ordovician (Hirnantian: Metabolograptus extraordinarius Biozone and Metabolograptus? persculptus Biozone?) strata in this area is erected.     

The earliest known strophomenoids (Brachiopoda) from early Middle Ordovician rocks Of South China

The upper Daguanshan Formation (middle Expansograptus hirundo graptolite biozone, Dapingian, early Middle Ordovician) of the Shuanghe area, Changning County, southern Sichuan Province, contains three new genera and species of strophomenoids: Ochyromena plana, Shuangheella elongata, and Primotimena globula, which are attributed to the Strophomenidae, Rafinesquinidae and Glyptomenidae respectively. These are the earliest known strophomenoids from the South China palaeoplate, and also the oldest rafinesquinid and glyptomenid brachiopods worldwide. Global review of the superfamily Strophomenoidea of Middle Ordovician age suggests that the first diversity peak at the species level occurred in late Darriwilian (Llanvirn) time, mainly as a result of the rapid diversification of the family Strophomenidae. The first appearance datum (FAD) of strophomenoids and their possible westward dispersal were from North China (latest Floian) and/or South China (early Dapingian), through the Chu‐Ili terrane of Kazakhstan, Iran, and Baltica (early Darriwilian), to Avalonia and Laurentia (late Darriwilian). This points to the existence of early diversification hotspots of the strophomenoid superfamily in the North and South China palaeoplates during the early Middle Ordovician in generally shallow water (corresponding to BA2) environments. The high degree of similarity in the external morphology and ventral interior of the three new genera indicates that the early diversification of strophomenoids began with differentiation of the cardinalia, especially in the configuration of the bilobed cardinal process, a key evolutionary novelty for the strophomenoids.