Graptolite Biozones Research Articles

Llandovery green/grey and black mudrock facies of the northern Holy Cross Mountains (Poland) and their relation to early Silurian sea-level changes and benthic oxygen level

The Llandovery mudrock facies in the northern Holy Cross Mountains reveal lithological variability allowing their interpretation in the context of post-Ordovician climate and sea-level changes in the Caledonian foredeep basin developed along the present SW margin of Baltica. They form a succession up to 50m thick made up of grey and greenish clayey mudstones interrupted by black shales. The sedimentary and geochemical data (total organic carbon, pyrite framboids and trace metals) clearly show that the black shales document periods of the significant sediment starvation and oxygen- deficient conditions. Their occurrence is confined to the persculptus–acuminatus, vesiculosus, cyphus, convolutus–sedgwickii, turriculatus–crispus, crenulata and spiralis graptolite biozones and they can be correlated with post-glacial transgressions. In contrast, the grey and greenish mudstones are interpreted as lithofacies reflecting permanent benthic oxygenation driven by deep-water ventilation during the Aeronian and Telychian regressions supported by sedimentary and geochemical studies, and diameters of pyrite framboids

Shale gas enrichment pattern and exploration significance of Well WuXi-2 in northeast Chongqing, NE Sichuan Basin

Abstract The shale gas enrichment pattern of Well Wuxi-2 in northeast Chongqing was studied, based on the data of the drilling, graptolite biostratigraphy, geochemistry, rock minerals, microscopic characteristics of reservoir beds and tectonic conditions, etc. The organic-rich shale of Upper Ordovician Wufeng Formation—Lower Silurian Lungmachi Formation is 89.8 m thick in Well WX-2. The graptolite biozonations are completely developed in this well, and the organic-rich shale intervals extend upward from the late Katian of the Ordovician to the early Telychian of the Lower Silurian. The deposition time of the organic-rich shale is far longer and the thickness is larger than those in other areas of the Sichuan Basin. The highest measured gas content exceeded 8 m 3 /t in Well WX-2, and the gas content is mainly controlled by TOC. The organic nano-pores are the main storage space, and the minerals contribute less to the storage space. The organic pores larger than 50 nm are well-developed and those less than 10 nm are the main reservoir space of adsorbed gas. The target intervals of Well WX-2 are located under the neutral surface of compressional Tianba anticline. Two vertical fracture (cleavage) development zones, which are beneficial for shale gas storage and complex fracture network formation during later fracturing, were formed in brittle layers of this organic-rich shale. Compressional faults existed in two limbs of the Tianba anticline, with non-permeable shale developing on both sides of fault planes and development of clay smear, which shows that the faults have good sealing properties, and are favorable for shale gas preservation. Thus the good match between the above various accumulation conditions forms the “tectonic sweet-spot” of shale gas in this study area.

Palynomorphs of the Fezouata Shale (Lower Ordovician, Morocco): Age and environmental constraints of the Fezouata Biota

The present study documents new palynological investigations of the Fezouata Shale from the Anti-Atlas (Morocco). Palynomorphs were extracted from samples collected from both outcrops and drill cuttings. Outcrop samples were taken near Zagora, and include some that were collected during excavation of stratigraphic horizons where exceptionally well-preserved fossils of the Fezouata Lagerstätte occur. Subsurface samples were taken from the AZ-1 (Adrar Zouggar Mountain) borehole, which was extracted some 300km to the southwest of Zagora. The palynological samples yielded acritarchs, chitinozoans, scolecodonts, conodonts and fragments of graptolites. The abundance and quality of preservation of palynomorphs varies greatly, but rich and diverse assemblages were recovered from several samples. The diversity and composition of the assemblages points to an open shelf environment. Generally mixed preservation states suggest resedimentation or differential transport histories. The acritarchs can be assigned to the diagnostic messaoudensis-trifidum acritarch assemblage, which is typical of the Tremadocian/Floian boundary interval of the Gondwanan margin in high southern palaeolatitudes. The acritarch taxa present in some of the lower parts of the Fezouata Shale including levels of exceptional preservation can be attributed to sub-assemblages 1–2 of the messaoudensis-trifidum assemblage and thus point to a late Tremadocian age of the Fezouata Lagerstätte, confirming biostratigraphic data provided by graptolites of the Araneograptus murrayi graptolite biozone. Chitinozoans from the Fezouata Shale are from the E. symmetrica and E. brevis biozones and include various species that are well-known from several localities on the Gondwanan margin and from other palaeocontinents (Baltica, Laurentia, and South China), demarcating broad links between those regions. The coincidence between index fossils of these three groups, hitherto not all found in the same level, suggests that the age assignments of chitinozoan biozones may be in need of revision.

Age of the KalanaLagerstätte, early Silurian, Estonia

The Kalana quarry in central Estonia is known for its exceptionally well-preserved non-calcified algal and other fossils. The interval with the fossil Konservat Lagerstatte in the Kalana section has previously been tentatively dated as early Aeronian. Recent findings of graptolites now enable more precise dating of these beds. The strata yielding the Lagerstatte are not older than the mid-Aeronian and correspond to the Pribylograptus leptotheca graptolite Biozone. In terms of conodont biostratigraphy they correlate with the middle of the Pranognathus tenuis conodont Biozone. It has also become evident that the uppermost Jogeva Beds of the Nurmekund Formation, and probably also the uppermost Ikla Member of the Saarde Formation, are younger than previously thought and correlate with the Pribylograptus leptotheca graptolite Biozone. Our data additionally indicate that the conodont genus Aulacognathus had appeared by the mid-Aeronian.

Hydrocarbon potential and palynological study of the Latest Ordovician – Earliest Silurian source rock (Sarchahan Formation) in the Zagros Mountains, southern Iran

Source rock studies are one of the key issues of petroleum exploration activities. In the supercontinent of Gondwana, ice ages related to the Upper Ordovician (Hirnantian) and rising sea levels caused by glacial melting at the end of the Ordovician and Early Silurian (Llandoverian) created excellent source rocks along the margin of Gondwana. Investigations conducted in the Arabian Peninsula have been indicated indicating that the lower Qalibah Formation (the so-called Qusaiba Member or Hot Shale) is a good source rock for the Paleozoic petroleum system in this area. Likewise, the Sarchahan Formation was recently introduced as a source rock in the Zagros Basin of Iran, which is probably equivalent to the Qalibah Formation in the Arabian Peninsula. In this study, samples were prepared from surface and subsurface Paleozoic rock units in Iran's Zagros Basin. The emphasis of the paper was on the Sarchahan Formation in Kuh-e Faraghan, ranging in age from the Late Ordovician (Hirnantian) to Lower Silurian (Llandoverian) to determine whether the high richness of organic matter in the Sarchahan Formation is related to the Late Ordovician or Lower Silurian. The basal part of the Sarchahan Formation belongs to the Late Ordovician (Hirnantian) because of the presence of the persculptus graptolite biozone, while the remainder belongs to the Lower Silurian. The Ordovician and early Llandoverian parts of the Sarchahan Formation contain type II and III kerogen with TOC ranging from 2.94 to 7.19, but the rest of the Sarchahan Formation (late Llandoverian) has TOC ranging from 0.1 to 0.58. Therefore, the Hot Shale in Iran falls within the Hirnantian and early Llandoverian (Rhuddanian), and not the latest Llandoverian (Aeronian and Telychian). Utilizing organic petrography, kerogen type was found II/III. The carbon stable isotope studies revealed that the source rock of hydrocarbons in Dalan and Kangan reservoirs has been the Sarchahan Formation. Based on analytical data, the kerogenous shales in the lower part of the Sarchahan Formation are at end of gas window, and the gamma ray amount is approximately 180 API. This research indicates the differences between the source rocks in the southern and northern Persian Gulf and suggesting, the Hot Shale should be considered in different views and used in modeling studies of sedimentary basins for future exploration targets.

Early Devonian graptolites from the Qinzhou–Yulin region, southeast Guangxi, China

Early Devonian graptolites are widely distributed within the 30°N and 30°S parallels of paleolatitude, with only a few known locations outside the 30° parallel. Only three early Devonian graptolite locations, i.e., west Yunnan, southeast Guangxi (in low paleolatitude), and south Xizang (Tibet) (in middle-high paleolatitude), have been reported in China. An Early Devonian graptolite fauna of moderate diversity, including three genera and 14 species, is described from the Qinzhou–Yulin region in southeast Guangxi, China, including Uncinatograptus jadae sp. nov. and Neomonograptus aequabilis latus subsp. nov. Based on these taxa, four biozones, the Uncinatograptus uniformis Biozone, the tentative Uncinatograptus praehercynicus Biozone, the tentative Neomonograptus falcarius Biozone, and the Uncinatograptus yukonensis Biozone, are erected in ascending order. The Lower Devonian graptolite biozonation in Guangxi agrees with the global standard. However, the graptolite biodiversity below the Uncinatograptus yukonensis Biozone in the Qinzhou–Yulin region is lower than those of the other parts of the world. In the present study, the tentatively recognized Neomonograptus falcarius Biozone has only the index species. In the study region, the species Uncinatograptus hercynicus (Perner) is absent. Thus, we tentatively employ the Uncinatograptus praehercynicus Biozone as a possible substitute for the Uncinatograptus hercynicus Biozone.

Graptolite-Trilobite Biostratigraphy in the Santa Victoria Area, Northwestern Argentina. A Key for Regional and Worldwide Correlation of the Lower Ordovician (Tremadocian—Floian)

Abstract. New graptolite-trilobite records provide relevant information for the biostratigraphic framework of the lower Paleozoic in western Gondwana. Aorograptus victoriae (T. S. Hall), together with Adelogratus cf. A. altus Williams and Stevens and Ancoragraptus bulmani (Spjeldnaes) are described for the first time in the Santa Victoria area. These species come from the upper beds of the Santa Rosita Formation, expanding the distribution of the A. victoriae Biozone. The complete succession of the Aorograptus victoriae, Araneograptus murrayi, Hunnegraptus copiosus, Tetragraptus phyllograptoides, T. akzharensis, Baltograptus cf. B. deflexus and Didymograptellus bifidus biozones is confirmed for the first time at a single locality in the Cordillera Oriental, indicating a late Tremadocian—late Floian age for the upper deposits of the Santa Rosita Formation and the Acoite Formation in the studied area. The co-occurrence of trilobites with the records of these graptolite biozones enables a better resolution o...

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

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

A bio-chemostratigraphical test of the synchroneity of biozones in the upper Silurian of Estonia and Latvia with some implications for practical stratigraphy

The paper discusses the reliability of different biozones in terms of their synchroneity when crossing facies boundaries within a sedimentary basin. Graptolite biozones are the most trusted ones, but also biozones based on conodonts, chitinozoans and less 'authoritative' groups like ostracodes and vertebrates are used. The integration of bio- and chemostratigraphy aids the understanding of the pattern and timing of fossil distribution. Despite different environments most of the analysed biozones are in general synchronous units and in the majority of cases their time signals do not contradict each other. The much discussed Ozarkodina crispa (and its two morphs) has a stratigraphical range in the East Baltic that is longer than commonly recognized elsewhere. Its first occurrences in Estonia have been reported from shallow-water facies below the Mid-Ludfordian Carbon Isotope Excursion. The geographical distribution of Oz. crispa is much wider in the upper Ludfordian open shelf rocks and a few occurrences are also known in the lowest Přidoli in the East Baltic. Analogous ecostratigraphical trends are characteristic of some other fossil species. The analysis demonstrates that, when properly studied, all of the fossil groups considered can provide useful biostratigraphical information. The subdivision of the Přidoli Series into two stages is discussed. Bio-chemostratigraphical data confirm the late Ludfordian age of the Kuressaare Formation and its correlatives. The bio- and chemostratigraphical testing of biozonal indices suggests some tentative correlations with other areas, in particular the type Ludlow area, and enables identification of the Silurian-Devonian boundary in the East Baltic.

Early Silurian chitinozoans from the Qusaiba type area, North Central Saudi Arabia

Sixty one core samples from three shallow core holes (Qusaiba-1, Baq'a-3 and Baq'a-4) penetrating the Qalibah Formation (Qusaiba Member) in the North Central Saudi Arabia were investigated. These core slabs corresponding to grey–greenish hemipelagic shale or silty-shale yield well-preserved and very abundant early Silurian chitinozoans. Most of the recorded chitinozoan assemblages are diverse and include several new species occurring with well-known species. An informal early Rhuddanian chitinozoan assemblage dominated by Cyathochitina caputoi is documented in the lowermost part of the Qusaiba Member. The six chitinozoan biozones defined above this basal assemblage range from Aeronian to Telychian. They are considered of regional value for northern Gondwana. From the lowest to the highest they are the Angochitina qusaibaensis (pro parte), Conochitina alargada, Angochitina hemeri, Angochitina macclurei, Tanuchitina obtusa and Euconochitina silurica biozones. The older regional biozones have been previously documented in Saudi Arabia whereas the two youngest ones, the eponymous index species of which were described from the subsurface of the Algerian Sahara, are documented for the first time in the Arabian Peninsula. Four subbiozones, of at least of regional application, are also defined in order to improve the precision of biostratigraphic correlation between Silurian lithostratigraphic units cropping out along the Arabian Shield and their counterparts in the subsurface of Central Saudi Arabia. Thanks to the closely spaced and to the regular sampling, the total range of several highly diagnostic forms as well as the interval of uncertainty between the successive chitinozoan biozones are better constrained. A hiatus with a duration of late Rhuddanian to early Aeronian separates the lowest informal chitinozoan assemblage from the qusaibaensis Biozone. A recent detailed study of the graptolites in the three cored holes provides independent chronostratigraphical control calibrating the previous chitinozoan-based age assignments. The qusaibaensis (pro parte), the alargada, and the hemeri chitinozoan biozones occur with the mid-Aeronian convolutus graptolite Biozone whereas the macclurei chitinozoan Biozone extends through the early Telychian guerichi and turriculatus graptolite biozones. The obtusa and the silurica chitinozoan biozones occur in an interval devoid of usable graptolites. They are referred to the mid–late Telychian as they do not contain typical Sheinwoodian species.Besides the abundant chitinozoans and acritarchs, sporadic occurrences of scolecodonts and of eurypterid cuticle fragments are also noted in the organic residues. The presence of eurypterids reflects a shallowing trend in the sedimentary record, which is consistent with the distribution of the graptolite remains (siculae and/or rhabdosomes). Indeed, graptolites are common throughout the Qusaiba Member, except in the youngest processed samples presaging the shallower environments prevalent in the Sharawra Member. The taphonomy of the chitinozoans (isolated vesicles, chain-like structures, clusters, coprolites) and their environmental context is briefly discussed.Fifteen new species are described and illustrated: Ancyrochitina alhajrii sp. nov., Ancyrochitina camilleae sp. nov., Armoricochitina crassicarinata sp. nov., Armoricochitina gengi sp. nov., Bursachitina baqaensis sp. nov., Conochitina viiuae sp. nov., Cutichitina minivelata sp. nov., Cyathochitina neolatipatagium sp. nov., Fungochitina merrelli sp. nov., Muscochitina olivieri sp. nov., Plectochitina alisawyiahensis sp. nov., Plectochitina alnaimi sp. nov., Plectochitina jaquelineae sp. nov., Plectochitina lucasi sp. nov., and Spinachitina geerti sp. nov.

New data of early Late Ordovician chitinozoans from the Miaopo Formation at Jieling, Yichang, central China

Chitinozoans from the uppermost Darriwilian–lower Sandbian Miaopo Formation at Jieling of western Hubei Province are reported, for the first time, including 30 species of 14 genera from 10 collections which are much more diverse and abundant than previously known. Two chitinozoan assemblages are recognized: the Laufeldochitina cf. striata Assemblage and the Eisenackitina cf. rhenana Assemblage. The L. cf. striata Assemblage is correlative to the upper Hustedograptus teretiusculus graptolite biozone. The base of the E. cf. rhenana Assemblage coincides with the base of the Nemagraptus gracilis graptolite biozone, indicating that E. cf. rhenana has the potential for recognizing the base of Upper Ordovician.

Integrated middle–upper Homerian (Silurian) stratigraphy of the Viduklė-61 well, Lithuania

Integrated lithostratigraphical, cyclostratigraphical, graptolite and conodont biostratigraphical and chemostratigraphical (δ13C) data are presented from the upper Jaagarahu, Gėluva and Dubysa regional stages, including the lundgreni Event (middle Homerian) in the Viduklė-61 well, Lithuania. The Viduklė-61 well is located in the west of Lithuania in the deep-water facies zone. Because of its completeness, this section is the “keystone” for middle–upper Homerian stratigraphy that allows us to combine different kinds of data into a coherent picture of large-scale biotic and environmental turnover. Three formations are distinguished: the upper part of the Riga Formation, with the Ančia Member in the uppermost part, the Siesartis Formation and the lower part of Dubysa Formation. The Grötlingbo bentonite is in the upper part of Ančia Member. In the Gėluva regional stage, two 4th-order and six 5th-order cycles have been distinguished. In the studied interval of the Viduklė-61 core, the following graptolite biozones were recognized: lundgreni (upper part), parvus, nassa, praedeubeli, deubeli, ludensis and nilssoni (lower part). Conodonts enabled recognition of the bohemica longa Biozone. A single find of Ctenognathodus murchisoni Pander in the nassa graptolite interzone indicates an earlier than previously thought origin of this species.

Evolution of the late Ludlow to early Lochkovian brachiopod, trilobite and bivalve communities of the Prague Basin and their link with the global carbon cycle

New data on the evolution of the Late Silurian to early Lochkovian brachiopod, trilobite and bivalve communities of the Prague Basin and their link with water depth oscillations, bioevents and the global carbon cycle (inferred from new δ13C data) are presented. The results of analyses revealed that some of the benthic communities had rather high potential for stratigraphic correlation, not only within the Prague Basin but also in various peri-Gondwanan basins. It is noteworthy that the stratigraphic ranges of the vast majority of benthic communities match well with both the graptolite biozonation and/or changes in global carbon cycle. Abrupt changes in the global carbon cycle are linked to distinct changes in the evolution of benthic communities and biofacies. Each phase of the mid-Ludfordian carbon isotope excursion may be characterized by a distinct benthic community. Analogous, but still less known changes in benthic communities are documented during the mid-Prˇídolí and Transgrediens events. Stratigraphic ranges of the vast majority of benthic communities of the Prague Basin correspond well with changes in carbon isotope composition of marine carbonates, suggesting that the evolution of marine communities was closely linked to changes in global carbon cycle.

Late Katian Paraorthograptus pacificus Graptolite Biozone from Xing'an, northern Guangxi, China

Based on the study of recently collected graptolites from the Huang'ai – Shengping – Tianlingkou section of Xing'an, northern Guangxi, China, the Paraorthograptus pacificus Biozone (upper Katian, Upper Ordovician) was first recognized in the upper part of the Tianlingkou Formation in this region. The P. pacificus fauna includes 13 species belonging to 6 genera: P. pacificus (Ruedemann), Dicellograptus ornatus Elles and Wood, Dicellograptus minor Toghill, Anticostia lata (Elles & Wood), Appendispinograptusvenustus (Hsü), Appendispinograptus supernus (Elles & Wood), Appendispinograptus leptothecalis (Mu & Ge), Rectograptus abbreviatus Elles & Wood, Rectograptus socialis (Lapworth), Rectograptus songtaoensis Li, Rectograptus cf. songtaoensis Li, Rectograptus sp. and Yinograptus disjunctus Yin & Mu. This assemblage can be easily correlated with the graptolite fauna of the same biozone in the Wufeng Formation in the Yangtze region. Compared with the P. pacificus fauna in the Yangtze region, the diversity of the present pacificus fauna is rather low. The Tianlingkou Formation in northern Guangxi is a clastic deposit with turbidites and represents rapid deposition. Thus, it is an unsuitable environment for graptolite preservation.

An Early–Middle Ordovician acritarch and prasinophyte assemblage from the Meitan Formation in Qijiang, Chongqing, South China

Acritarchs and prasinophytes representing 39 species in 26 genera are identified from the Early–Middle Ordovician Meitan Formation in the Guanyinqiao section, Qijiang, Chongqing in South China. This palynomorph assemblage is dominated by the genera Polygonium (35.2%), Striatotheca (15.2%), Stelliferidium (12.5%) and Leiosphaeridia (10.2%) showing similarities to assemblages from deflexus–suecicus graptolite biozone (Meitan Formation, upper Floian–lower Dapingian) in the Honghuayuan section and can be correlated to the contemporaneous global acritarch assemblages. The composition of the acritarch assemblage from the Meitan Formation of the Guanyinqiao section implies an inner-shelf depositional environment for the studied successions.

Gorstian palaeoposition and geotectonic setting of Suchomasty Volcanic Centre (Silurian, Prague Basin, Teplá-Barrandian Unit, Bohemian Massif)

A multidisciplinary palaeomagnetic, whole-rock geochemical and volcanological study was carried out in Gorstian deposits of the Suchomasty Volcanic Centre in the western segment of the Prague Basin (Teplá-Barrandian Unit, Bohemian Massif). Phreato-Strombolian eruptions of alkali basalts, transitional between enriched mid-ocean rift basalt and ocean-island basalt, associated with effusions of lava flows within the lower–middle Scanicus chimaera graptolite Biozone at the Vinařice locality, yield a mean palaeomagnetic direction that allows for computation of a palaeolatitude of 24.4°S. Present data support that the Prague Basin was a continental rift basin, situated on presumed Perunica microplate. The Perunica microplate drifted at southern subtropical palaeolatitudes of 24.4° in Gorstian time and experienced either 170° counter-clockwise or 190° clockwise rotation during the Variscan Orogeny.

Silurian bentonites in Lithuania: correlations based on sanidine phenocryst composition and graptolite biozonation – interpretation of volcanic source regions

Integrated correlation of bentonites (altered volcanic ashes) and graptolite biozonation is presented. Detailed study of two Lithuanian drill core sections extended previous knowledge of the occurrence and composition of bentonites to the south. Identification of graptolite species allowed bentonites to be assigned their proper stratigraphical position. Silurian bentonites in Lithuania are mostly characterized by wide and very wide XRD 20 1 reflections of the main component of sanidine phenocrysts. Only fourteen of the 69 samples studied contained sanidine with a sharp reflection, which gave the best correlation potential. In the Lithuanian sections one bentonite was found in the Rhuddanian, five bentonites were recognized in the Aeronian, 17 bentonites in the Telychian, 26 in the Sheinwoodian, 10 in the Homerian and six in the Ludlow. All bentonites found in Lithuania are characterized by the main component of sanidine. A large number of Lithuanian bentonites are not known in Latvia and Estonia, indicating that volcanic ashes reached the East Baltic area from two source regions - the Central European and Norwegian Caledonides.

Carbon isotope chemostratigraphy of the Llandovery in northern peri-Gondwana: new data from the Barrandian area, Czech Republic; pp. 220–226

The first complete δCorg record of the uppermost Hirnantian to lower Telychian strata of the Barrandian area (northern peri-Gondwana) is presented based on 168 new samples. The new data from the study area reveal that the evolution of the Llandoverian organic carbon isotope reservoir was similar to that on other palaeoplates, but it differs from the development of the coeval carbonate carbon isotope reservoir in the absence of two δC excursions (i.e. the early Aeronian positive excursion in the upper part of the Demirastrites triangulatus graptolite Biozone and a negative excursion occurring close to the boundary between the Cystograptus vesiculosus and Coronograptus cyphus graptolite biozones).

On the integration of Ordovician conodont and graptolite biostratigraphy: new examples from Gansu and Inner Mongolia in China

Wang, Z.H., Bergström, S.M., Zhen, Y.Y., Chen, X. & Zhang, Y.D., 2013. On the integration of Ordovician conodont and graptolite biostratigraphy: New examples from Gansu and Inner Mongolia in China. Alcheringa 37, 510–528. ISSN 0311-5518.Few Ordovician successions in the world contain both biostratigraphically highly diagnostic conodonts and graptolites permitting an integration between standard biozones based on these fossil groups. The Sandbian Guanzhuang section in the vicinity of Pingliang in the Gansu Province has an outstanding graptolite record through most of the Nemagraptus gracilis and Climacograptus bicornis graptolite biozones. Calcareous interbeds in the succession yield biostratigraphically important conodonts, including some species used for biozonations in Baltoscandia and the North American Midcontinent. Likewise, the middle–upper Darriwilian Dashimen section in the Wuhai region of Inner Mongolia hosts both diverse graptolites of the Pterograptus elegans, Didymograptus murchisoni and lowermost Nemagraptus gracilis biozones, and conodonts of Midcontinent and Baltoscandic types. The distribution patterns of these index fossil groups provide an unusual opportunity to closely correlate conodont and graptolite biozones in the middle to upper Darriwilian to Sandbian interval. For instance, the base of the C. bicornis Biozone is approximately coeval with the base of the Baltoscandic B. gerdae Subbiozone and a level near the middle of the North American P. aculeata Biozone.Zhi-hao Wang [zhwang@nigpas.ac.cn] Xu Chen [xu1936@gmail.com], and Yuan-dong Zhang [ydzhang@nigpas.ac.cn], Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China; Stig M. Bergström [stig@geology.ohio-state.edu], School of Earth Sciences, Division of Earth History, The Ohio State University, Columbus, OH 43210, USA; Yong Yi Zhen [yongyi.zhen@austmus.gov.au], Australian Museum, 6 College Street, Sydney NSW 2010, Australia.

Silurian graptolite biozones of Lithuania: present and perspectives

Graptolites are a group of extinct colonial invertebrate organisms, which belong to hemichordates. They are the most important organism group of Silurian biostratigraphy in Lithuania. A lot of new material appeared recently that made possible the potential for the improvement of the graptolite biozonation of Lithuanian Silurian. In Lithuania graptolites are distributed from Coronograptus cyphus (upper Ruddanian) to Neocolonograptus lochkovensis (lower Pridolian). The intervals of Rhuddanian–Aeronian, Telychian–Sheinwoodian, Gorstian–Ludfordian and Ludlow–Pridoly boundaries are still problematic in Lithuania and further studies are necessary.