An Upper Ordovician chitinozoan biozonation in British Avalonia (England and Wales)

An Upper Ordovician chitinozoan biozonation for British Avalonia is established. The new scheme is based on chitinozoan faunas from the historical Caradoc- and Ashgill-type sections in the Anglo-Welsh area; these data are supplemented with information from other key British sections that have accurate graptolite control. As a result, the chitinozoan biozonation for British Avalonia is tied to both the British chronostratigraphical framework and the graptolite biostratigraphy. It consists of 13 chitinozoan bio(sub)zones and for the first time provides a formal chitinozoan biozonal scheme for the Upper Ordovician of Britain, which can be tied with the well-established biozonation in Baltoscandia. This predominantly Baltoscandic signature of the new British chitinozoan biozonation is consistent with Avalonia's northwards migrating palaeogeographical position during the Ordovician.     

A new high-resolution planktic foraminiferal zonation and subzonation for the lower Danian

A new planktic foraminiferal zonation has been established for the lower Danian, based on some of most expanded and continuous pelagic sections known to date (from Spain, Tunisia and Mexico). This biozonation is considered valid for low and middle latitudes. The maximum stratigraphical distribution of the index-species approximately coincides in all the studied sections. The index-species are abundant and easily recognizable. We propose the following biozones and subzones: Guembelitria cretacea Zone and the Hedbergella holmdelensis and Parvularugoglobigerina longiapertura subzones; the Parvularugoglobigerina eugubina Zone, which is subdivided into the Parvularugoglobigerina sabina and Eoglobigerina simplicissima subzones and the Parasubbotina pseudobulloides Zone with the Eoglobigerina trivialis and Subbotina triloculinoides subzones. A biomagnetostratigraphic correlation and calibration of the stratigraphical ranges of these species suggest that the biohorizons used to define the new biozonation are very isochronous, at least in the geographical areas analysed.     

Chitinozoan bio- and lithostratigraphical study of the Ashgill Fosses and Génicot Formations (Condroz Inlier, Belgium)

Ashgill chitinozoans from the Fosses and the Génicot Formations were studied in seven sections in the western part of the Condroz Inlier, Belgium. Twenty-three previously published samples as well as thirty-five new samples were analysed. The combination of the results led to the definition of six local biozones and a local biozonation for the Ashgill of the region west of Fosses and eventually to the dating of both formations studied. Generally, the local biozonation allowed correlation of the sections. In combination with the detailed study of the lithostratigraphy, a hypothesis is proposed concerning the depositional history of both formations. Two conglomeratic levels in the Génicot Formation might be the sedimentological response to the sea level drop associated with the Hirnantian glaciation event. Two new species are defined: Spinachitina fossensis and Conochitina eustachensis.     

Stratigraphie, paléoécologie et foraminifères du paléogène des Alpes Maritimes et des Alpes de Haute-Provence (Sud-Est de la France)

Paleogene sedimentation in the Alpes Maritimes and Alpes de Haute Provence regions is composed of one complete sedimentary sequence. This sequence begins with the continental Formation from Microcodium and continues with the Cerithium layers, the Calcaires Nummulitiques and the Marnes Bleues, which are overlaid by the turbidites of the Grès d’Annot Formation. Sedimentation starts in the Nummulites perforatus zone close to the base of ‘the Truncorotaloides rohri zone (P 14) and ends in the Cassigerinella chipolensis-Pseudohastigerina micra zone (P 18) and the NP21 zone in the upper part of the Grès d’Annot. More biomarkers were used in order to define a more detailed local biozonation (biozones AMP 1 to AMP 7). Four local zones were also defined by the last occurrence of Nummulites millecaput and N. perforatus-N. ptukhiani and then by the first appearance of N. retiatus (AMGF 1-4). The evolution of benthic foraminiferal assemblages shows an increase in bathymetry from the internal platform in the Cerithium layers to the calcareous platform with large foraminifers, then to the external platform and the deep offshore environment of the Marnes Bleues and Grès d’Annot. Low faunal diversity in the Grès d’Annot together with the predominance of agglutinated species indicates a poorly oxygenated, organic rich and turbidite environment. Seven steps (SD 1 to SD 7) in the Eocene marine transgression are shown from East to West by detailed local biozonation and sequence analysis. Grès d’Annot sedimentation is also diachronous, beginning within the Truncorotaloides rohri zone (P 14, AMP 1) in the East and ending within the Pararotalia opima opima zone (P 20, middle Rupelian) in the West (Barrême). Small foraminifer Paleogene fauna from the Alpes Maritimes and Alpes de Haute Provence was studied from 400 samples. It is composed of 378 species. Two new taxa are proposed: Fissurina niceana n. sp. and Globocassidulina alpina n. sp. The species from the Escarène and Gorbio neighborhood described by M. von Hantken (1884) were re-examined.     

Cricetodontini from the Calatayud–Daroca Basin (Spain): A taxonomical description and update of their stratigraphical distributions

The most updated stratigraphical distributions of the Cricetodontini from the Calatayud–Daroca Basin are presented. Cricetodon sansaniensis (local biozone F, MN6, middle Aragonian) and Cricetodon jotae (local biozone G1, G2 and G3, MN6-MN7/8, Middle–Upper Aragonian) from the middle Miocene are described and discussed. Generally, the genera of Cricetodontini were used to define large time intervals, whereas the species were neglected in the local biostratigraphical studies. The results presented herein show that, for the Calatayud–Daroca Basin, most of the stratigraphical distributions of the species of Cricetodontini are strongly linked with the local biozonation. That reveals that they could be used as good biostratigraphical indicators. Moreover, the unusually long local biozone G3 could be redefined and subdivided based on the distributions of the four species of Cricetodontini present in it. However, it is recommended to complete the study of the whole rodent fauna before proposing a new biozonation.     

Synthèse biostratigraphique du plio-pléistocène de Guadix-Baza (Province de Granada,Sud-Est de l'Espagne)

In the Guadix-Baza basin, a continental sequence 0214 ranging from the Upper Miocene (Upper Turolian) to the Middle Pleistocene (Cromerian) has been established. An essay of biozonation by means of the Rodent succession is proposed, based on the following biozones: Trilophomys castroi, Mimomys occitanus, Mimomys cappetai, Mimomys cf. reidi, Mimomys ostramosensis, Allophaiomys pliocaenicus, Mimomys savini and Arvicola cantiana.     

Foraminiferal biozonation,biostratigraphy and trans-basinal correlation of the Oligo-Miocene Qom Formation,Iran (northeastern margin of the Tethyan Seaway)

During the Rupelian–Burdigalian (early Oligocene–early Miocene), the Qom Formation was deposited along the northeastern margin of the Tethyan Seaway in the Sanandaj–Sirjan, Urumieh–Dokhtar, and Central Iran basins. The biostratigraphic data from a total of 1152 thin sections from 10 outcrop sections along over 1000 km of the Tethyan Seaway margin are presented. A larger benthic foraminiferal (LBF) biozonation, consisting of five biozones, is proposed for dating the Rupelian–Burdigalian Qom Formation. It is correlated with global planktonic zones, LBF zones, southeastern Asian “Letter Stages”, shallow benthic foraminiferal zones (SB-zones) of southern European basins, and newly revised zones of the Asmari Formation in southwestern Iran. This biozonation subdivides the Rupelian stage into “early Rupelian” and “late Rupelian”, based on the first appearances of lepidocyclinids in the latter one. The early Rupelian strata are characterized by the presence of Nummulites without lepidocyclinids which are reported merely from southwestern and southern Kashan, where the thickest Rupelian deposits of the Qom Formation are recorded. The basal layers of the Qom Formation in southeasternmost outcrops (northwestern Jazmurian Lake) are late Rupelian in age based on the co-occurrence of lepidocyclinids and Nummulites spp. By comparison of the well-documented transgression of the Tethyan Seaway over the Iranian plate (from southeast to northwest) and the limitation of all reported early Rupelian strata of the Qom Formation to southwestern and southern Kashan, the following scenarios can be supposed: 1) the oldest deposits could be deposited in southeastern Iran, but they have not been reported, yet; 2) during early Rupelian, there was a transgression from the Zagros Basin to southwestern and southern Kashan areas, then the transgression progressed both northwestward and southeastward.     

Cambrian trilobite fauna of the Haydenaspis parvatya level (Series 2, Stage 4): Its stratigraphic position with respect to the Oryctocephalus indicus Biozone (Miaolingian Series,Wuliuan Stage) in the Spiti Himalaya,India

Refinement of the Cambrian biozonation in the Parahio valley, Spiti region (Himalaya) leads to the demarcation of the stratigraphic distance between the Haydenaspis parvatya level (Series 2, Stage 4) and the Oryctocephalus indicus Biozone (base of the Miaolingian Series, Wuliuan Stage), which has been a subject of debate. The present work suggests that these two trilobite beds in the Kaltarbo section are separated by 183.4 m of strata. Whether either taxon ranges beyond the beds they are found in this section or others in the Parahio Valley is yet unknown.     

Biostratigraphy and sedimentary evolution of Late Miocene and Pliocene continental deposits of the Granada Basin (southern Spain)

The Late Miocene and Pliocene continental sediments in the Granada Basin (southern Spain) have yielded large amounts of fossil small mammals in 37 localities from 11 sections. The aim of this paper is to integrate faunistic, stratigraphic, and sedimentary criteria to unravel the geological history of the continental infilling of the basin. The palaeontological study has led to a detailed biozonation on the basis of rodents, which helps to correlate in detail the different sedimentary units found in the basin, and to follow the changes of the different sedimentary systems and their palaeogeographical evolution through time. Combination of the proposed biostratigraphy and the reinterpretation of the magnetostratigraphic analyses of the Barranco del Purcal section allows us to assign an absolute age slightly older than 5.23 Ma to the Turolian–Ruscinian boundary (MN13‐MN14).     

Revision of the foraminiferal biozonation scheme in Upper Cretaceous carbonates of the Dezful Embayment,Zagros, Iran: Integrated palaeontological,sedimentological and geochemical investigation

Cretaceous carbonate successions of the Bangestan Group, such as the Sarvak and Ilam formations, are among the most prolific hydrocarbon reserves of the Middle East. However, relatively little is known about their detailed palaeontology and biostratigraphy. Moreover, due to lithological similarity of these carbonate formations recognition of their boundaries in subsurface studies is problematic. To investigate these units, biostratigraphic analyses were carried out on nearly 1100 m of cores, including core plug samples and thin sections prepared from five giant and supergiant oilfields in the northern and southern Dezful Embayment, SW Iran. Accordingly, 59 species of foraminifera (assigned to 43 genera) as well as 11 species of non-foraminifera (10 genera) were recognized. As a result, three biozones were identified, which in stratigraphic order are: Nezzazata-Alveolinids Assemblage Zone; Moncharmontia apenninica-Nezzazatinella-Dicyclina Assemblage Zone; and Rotalia skourensis-algae Assemblage Zone. These are compared with the Wynd's (1965) biozonation scheme, previously introduced in the Zagros area, and a revised scheme is presented. Accordingly, a Cenomanian–Turonian age and a Coniacian–Campanian age are envisaged for the Upper Sarvak and Ilam formations, respectively. In our new biostratigraphic scheme, the Sarvak–Ilam formations boundary is considered to be located above the Moncharmontia apenninica-Nezzazatinella-Dicyclina Assemblage Zone (equivalent of Valvulammina-Dicyclina Assemblage Zone of Wynd, 1965), that is Turonian in age. This zone is bounded by two palaeoexposure surfaces, which correspond approximately to the C–T boundary transitional interval and a post-Turonian, which can be possibly assigned to the Coniacian. Significant sedimentological features of these disconformities include bauxitic–lateritic horizons, karstified profiles and solution-collapsed breccias. Geochemical signatures of these meteorically altered surfaces are also considered to calibrate biofacies and biozones. Finally, we compared our new biozonation scheme with other studies in neighboring areas of SW Iran and the Middle East.     

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.     

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.     

The late Neogene rodent succession of the Guadix–Baza Basin (south‐eastern Spain) and its magnetostratigraphic correlation

In this paper a magnetostratigraphically calibrated biozonation of the Miocene–Pliocene continental record of the Guadix–Baza Basin (south‐eastern Spain) is presented. This biozonation is based on a rodent succession which ranges from the latest Miocene (c. 6 Ma) to the latest Pliocene (c. 2.6 Ma). A total of nine biozones have been defined for the late Miocene and Pliocene, all of them based on the range or concurrent‐range of rodent species: Apodemus gudrunae – Apocricetus alberti Zone, Apocricetus barrierei Zone, Paraethomys aff. abaigari Zone, Trilophomys Zone, Mimomys davakosi Zone, Dolomys adroveri Zone, Mimomys hassiacus Zone, Mimomys polonicus Zone and Kislangia ischus Zone. A magnetobiostratigraphical correlation has been established between these biozones and the standard ATNTS scale, on the basis of the palaeomagnetic analysis carried out on the sections of Negratín, Botardo‐1 and Gorafe. The correlation has been completed with previous palaeomagnetic analysis in the sections of Galera and Zújar. The magnetobiostratigraphical correlation here established indicates a late Messinian age for the Apodemus gudrunae – Apocricetus alberti Zone, a Zanclean age for the Apocricetus barrierei, Paraethomys aff. abaigari, Trilophomys and Mimomys davakosi zones and a Piazencian age for the Mimomys hassiacus, Mimomys polonicus and Kislangia ischus zones. The Dolomys adroveri Zone is mostly Zanclean in age, but its uppermost part belongs to the Piazencian. Therefore, unit MN13 is correlated with the late Messinian, MN14 is correlated with the early Zanclean, most of MN15 is correlated with the late Zanclean, while the uppermost part of MN15 and MN16 are correlated with the Piazencian.     

Corrélation de la biozonation des Charophytes avec celle des Foraminifères (Orbitolinidés dans le Valanginien inférieur du Bassin du Maestrat (Castellò, Espagne)

A correlation between the biozonations of orbitolinidsand charophytes is established in the Lower Valanginian from the Polacos Formation (Maestrat basin, Castelló, east of Spain). This correlation is based on the presence of the charophyte association: Perimneste micrandra-Perimneste ancora (rare), Globator trochiliscoides (primitive), Embergerella stellata, Flabellochara harrisii and Porocharaceae in the levels underlaying and overlaying the banks with the orbitolinid Valdanchella miliani. This charophyte assemblage is similar to the flora of the “Olba zone” from Grambast (1974), which was hypothetically attributed to the Hauterivian.According to our correlation, the olba flora was atleast already existing in the Lower Valanginian. Provisionally, the biostratigraphic boundary between the Berriasian and the Valanginian can be characterized in the continental domain of Tethys by the disappearance of Globator nurrensis and the first appearance of Embergerella stellata. Uncertainty still exists in the chronostratigraphy of the charophyte biozonation during the Middle Valanginian to Upper Hauterivan time interval.     

The Ramblian-Aragonian boundary and its significance for the European Neogene continental chronology. Contributions from the Ebro Basin record (NE Spain)

In this paper we report on the results of a paleontological and paleomagnetic sampling carried out in the Miocene of the central Ebro Basin. It includes the sections of Albalatillo, Lanaja, La Almolda and San Caprasio in the Sierra de Alcubierre, which delivered six new micromammal levels ranging from the MN3 to MN5 mammal units. The magnetobiostratigraphic study of the Sierra de Alcubierre enables one to shed light on the chronology of the Early to Middle Miocene European mammal biozonation (e.g., the Ramblian-Aragonian boundary). As a result, the first occurrence of the “Miocene Cricetids” and, therefore, the lower boundary of MN4 – zone B, is set back to the lower part of chron C5Cr, thus reducing significantly the supposed discrepancy of the First Occurrence of Democricetodon in the Swiss Molasse and the Aragonian type-section. Another significant result is the persistence of Vasseuromys in the Ebro Basin up to the Middle Miocene (MN5).     

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.     

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.     

Integrated conodont and radiolarian biostratigraphy of the upper Norian in Baoshan Block,Southwestern China

Two significant stratigraphical microfossils, conodonts and radiolarians, are usually used for the Upper Triassic chronostratigraphy. The Baoshan Block was located in eastern Tethys during the Late Triassic where the biostratigraphical data of Upper Triassic are still poorly known. We collected new samples from the Hongyan section (HY) for biostratigraphical study. This 24-m-thick section in Dabaozi Village, Baoshan City, is mainly composed of thin-layered limestones, sandstone and siltstone. The conodont fauna is referred to Sevatian 1 (late Norian), in which the species Mockina englandi, Mockina carinata and Mockina mosheri morphotype B are first recognized in the Baoshan Block, and thus eastern Tethys. The Norian radiolarian associations are first reported in the Baoshan Block, which correlate with the biozonation of North America and also that proposed for Central Japan. The radiolarian assemblages found in the analysed samples in HY section can be referred to the Sevatian Betraccium deweveri Zone. The Baoshan Block is a key area for conodont and radiolarian-based correlations between the Tethys, Japan and North American domains.     

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.     

Benthic foraminiferal bioevents in lower to upper Toarcian strata of Southern Beaujolais (SE France)

This paper documents changes in benthic foraminiferal assemblages compared with high resolution ammonite biozonation along the lower Toarcian to upper Toarcian marine succession of Southern Beaujolais in southeastern France. Eight ammonite and three benthic foraminiferal zones including five subzones are distinguished based on the occurrence of twelve foraminiferal events. Each benthic foraminiferal subzone is characterized by its taxonomic and morphogroup composition, which represents the paleoecological response of these taxa and morphotypes of benthic foraminifera in the Early Jurassic and early Middle Jurassic. Major changes in abundance and diversity occur at the end of the Toarcian Oceanic Anoxic Event (T-OAE) and near the Early-Middle Jurassic transition. The low-abundance foraminiferal assemblages recorded in the Serpentinus ammonite Zone are interpreted as reflecting adverse environmental conditions after the T-OAE. The later recovery and development of the foraminiferal assemblages is documented in the Bifrons up to the Aalensis zones and is attributed to improved bottom water oxygenation. Common occurrences of agglutinated foraminifera represented mostly by Trochammina pulchra Ziegler in the Dispensum Zone point to an influx of cooler water masses during the late Toarcian. The morphogroup analysis carried out on the foraminifera and their paleoecological interpretations shed light on the changes in the stratigraphic record at the end of the T-OAE up to the Toarcian/Aalenian boundary.