Stratotype Area Research Articles

Some lithogeochemical and isotope-geochemical features of clay rocks and hiatuses in the Riphean stratotype

Research subject. Clay rocks of the Lower, Middle, and Upper Riphean (respectively, the Burzyan, Yurmatau, and Karatau groups) of the Western slope of the Southern Urals. Changes in their characteristic values of a number of ratios of oxides and some trace elements that are indicators of rock composition in provenances are considered, taking into account the breaks of different duration present in the Riphean stratotype. Methods. Calculation of t he average values of TiO2/Al2O3, Th/Sc, La/Co and (La/Yb)N, typical for shales, fine-grained clay siltstones, and mudstones of the main lithostratigraphic units of the Riphean stratotype (formation and, in some cases, subformation) and analysis of their changes taking into account the hiatuses known in the Riphean stratotype (Pre-Mashak/Pre-Zigalga, Pre- Zilmerdak, Pre-Minyar, Pred-Uk). Results. It was established that throughout the entire Riphean, regardless of breaks in sedimentation, presumably associated with certain transformations in the areas of erosion and sedimentation, a number of lithogeochemical characteristics of fine-grained clastic rocks of the Burzyan, Yurmatau, and Karatau groups (such as TiO2/Al2O3, Th/Sc, La/Co, and, to a significant extent, (La/Yb)N) practically did not experience significant changes. Conclusions. The data obtained give reason to think that there were no fundamental changes in the composition of the sources of fine-grained aluminosiliciclastics for the Riphean sedimentary sequences for more than 1 Ga, and contradict the rather active scenario of tectonic processes at the end of the Early Precambrian and the entire Late Precambrian. Conversely, the data on the values of tNd(DM) and eNd(t) in 37 samples of clay rocks of the Riphean stratotype nevertheless reflect a change in the composition of the rocks of the feeding provinces and, one way or another, fit into the outline of subglobal events established by conventional geological methods in the stratotype area of the Riphean. In accordance with them, in the Ai and Mashak times, an increase in the proportion of juvenile material took place in the areas of erosion. Apparently, the Pre-Zilmerdak hiatus also led to the appearance of a significant proportion of basic igneous rocks among the rocks of the provenances.

Palynostratigraphy of the Oligocene and Neogene-Quaternary deposits of the Ishim and Irtysh Interfluve (by example of boreholes 3 and 6)

A biostratigraphic subdivision based on palynological data of Oligocene and Neogene-Quaternary deposits recovered by wells 3 and 6 in the south of Western Siberia on the border of the Tyumen and Omsk regions is presented. Eight spore and pollen assemblages are identified and compared with zonal assemblages of the West Siberia regional scale. Layers with dinocysts are identified in the Turtas Formation. To include them in the stratigraphic scheme of the new generation, it is proposed to consider the territory between the villages of Katai and Listvyagi as a stratotype area of this biostraton.

Outlines of the Siberian Platform sequence stratigraphy in the Lower and lower Middle Cambrian (Lena-Aidan area)

The development of Cambrian reefal complexes on the inherited pre-Cambrian uplifts determined a subdivision of the Siberian Platform basin into three facies belts: western saliferous basin, eastern open shelf, and transitional reefal belt. Facies shifts which affected all belts emphasised the sequence and parasequence boundaries. The study of the stratotype area of the Russian Lower Cambrian stages (middle courses of the Aidan and Lena rivers) allowed us to distinguish four (third-order?) sequences spanning the Tommotian-lower Mayan interval. The sequence boundaries, except for the base of the Nemakit-Daldynian Stage, are restricted to intrazonal levels rather than to the boundaries between stages and even between zones. Such a relationship between biostratigraphic and sequential boundaries excludes significant chronostratigraphic hiatuses in the Siberian Early Cambrian time scale. This fact together with high fossil content, and good magnetostratigraphic, chemostratigraphic (C and Sr isotopes), and radiometric data show that stable cratons located at low latitudes keep a better record of events serving the chronostratigraphic basis. A special attention should be paid to the fact of the absence of a pronounced correlation between biostratigraphic and sequential events.

Distribution of Microfossils in the Vendian Deposits of the Orsha Depression of the East European Platform, Belarus

—The complete sections of the Lower and Upper Vendian of the East European Platform were opened in the boreholes of Belarus. This allows us to consider this region as a stratotype area. In order to update the paleontological characteristics of the Vendian, organic-walled microfossils from the Bogushevsk-1, Bogushevsk-2 (Liozno), and Lepel-1 reference boreholes drilled in the north of the Orsha Depression were studied. The transitive assemblage I with Leiosphaeridia minutissima–Leiosphaeridia tenuissima was recognized in the Lower Vendian Liozno Formation of the Volyn Series and the Upper Vendian Kotlin Formation. The Redkino microfossil assemblages were identified at three stratigraphic levels in the Nizy, Selyava, and Chernitsa formations: assemblage II with Morania zinkovi, assemblage III with Morania zinkovi–Tynnia precambrica, and assemblage IV with Morania zinkovi–Tynnia precambrica–Striatella coriacea, respectively. The Kotlin assemblage V with Vendotaenia antiqua–Primoflagella speciosa was distinguished in the upper part of the Kotlin Formation (Bogushevsk-1 borehole). On the basis of the taxonomic composition, assemblages III and IV are correlated with the first Redkino biota of the Starorusskaya Formation; assemblage V is correlated with the third Kotlin biota of the Vasileostrovskaya Formation of the northwestern part of Russia. Our data show a high biostratigraphic potential of organic-walled microfossils, which should be used to substantiate regional stratigraphic units of the Upper Vendian in the updated stratigraphic scheme of the East European Platform.

LITHOLOGICAL AND FACIAL FEATURES, COMPOSITION, AND SEDIMENTATION CONDITIONS OF TERRIGENOUS-CARBONATE ROCKS OF THE MOTY GROUP (SHAMAN CLIFF, IRKUTSK REGION)

We have studied terrigenous-carbonate rocks in the area near the Sayan mountains in the Irkutsk Region (Russia), specifically at the Shaman Cliff, being the stratotype area of rocks that belong to the Moty group. The cliff’s lower part is composed of sandstones, which fragments gradually decrease in size upward the cross-section. The middle and upper parts are composed of sandy dolomites and dolomites, respectively. In terms of material characteristics, the terrigenous rocks correspond to arkoses. According to the genetic typification, the arkoses are composed of destructed primary igneous rocks. The terrigenous-carbonate rocks contain a carbonate component that gradually increases in the upper part of the cross-section. In the Shaman Cliff cross-section, we distinguish 32 lithological units and eight lithologicalgenetic types of deposits. Paleogeodynamic conditions are reconstructed for the formation of the sedimentation basin. Our study of the Shaman formation reveals specific features of the lithological facies, which suggest that these rocks accumulated in a coastal environment affected by tides. In the study area, clastic materials were mainly removed from an orogen that formed due to the Vendian accretion-collision events in the southern folded frame of the Siberian platform. Dolomites composing the upper part of the cliff are attributed to the Irkutsk formation of the Moty group. Their lithological features give evidence of shallow-marine conditions of their formation, without any supply of clastic material, which contributed to mass dispersal of the Cambrian biota described in [Marusin et al., 2021]. It is our first initiative to draw a boundary between the Shaman and Irkutsk formations of the Moty Group along the base of the carbonate eluvial breccia unit that marks the stratigraphic break. In the cross-section, this boundary represents the border between the Upper Vendian and Lower Cambrian.Our conclusions are generally consistent with the ideas of most researchers about the Late Vendian evolution of the southern margin of the Siberian platform. The results of our study can be used in further investigation of this area and provide a basis for correlating the studied strata with the same-age reference cross-sections of other regions in Siberia.

Campanian–Paleocene Jaworzynka Formation in its type area (Magura Nappe, Outer Carpathians)

The Campanian–Paleocene Jaworzynka Formation, a part of the Magura Nappe succession in the Polish Outer Carpathians, is described in terms of its detailed litho- and biostratigraphy. The formation stretches along the marginal part of the Siary Unit, from the Jaworzynka stratotype area in the Silesian Beskid Mts up to the Mszana Dolna area in the Beskid Wyspowy Mts. Its equivalent in the Moravskoslezské Beskydy Mts of the Czech Republic is the Soláň Formation. In the stratotype area, the formation displays complex structure. We distinguish four lithological units, i.e., Biotite Sandstone and Shale (I), Shale (II), Mutne Sandstone Member (III) and Thin-bedded Turbidite (IV) and provide the first detailed biostratigraphy of particular units. The first unit forms the most prominent part of the formation. It was deposited in the Middle Campanian–earliest Maastrichtian within the upper part of Caudammina gigantea Zone up to the lower part of the Rzehakina inclusa Zone. The second unit occurs only locally and its age is limited to the Maastrichtian, to the Rzehakina inclusa Zone. The third unit is composed of thick-bedded sandstones that in some parts may form more than the half of the total thickness of the formation. It is Late Maastrichtian–Danian in age and is placed in the upper part of the Rzehakina inclusa Zone and the lower part of the Rzehakina fissistomata Zone. It is usually covered by a thin package of thin-bedded turbiditic sandstone and shales of Danian–Thanetian age with foraminifera of the Rzehakina fissistomata Zone.

Spathian to Aegean (upper Lower Triassic to lower Middle Triassic) carbon isotope stratigraphy constrained by the conodont biostratigraphy of carbonates on top of a mid‐oceanic seamount formed in the Panthalassic Ocean

AbstractThe Taho Formation in western Shikoku Island, Japan, consists of Triassic carbonates that formed on a seamount in the Panthalassic Ocean. In order to investigate the stratigraphy and paleoceanography of this carbonate succession, we analyzed the biostratigraphy and chemostratigraphy of a 17.6 m‐thick section of the upper Taho Formation at the stratotype area in Tahokamigumi, Seiyo City. This section comprises bioclastic limestone containing Triassic bivalves, ammonoids, and conodonts. We recognized six conodont zones (in ascending order): the Novispathodus pingdingshanensis, Novispathodus brevissimus, Triassospathodus symmetricus, Triassospathodus homeri, Chiosella timorensis, and Magnigondolella cf. alexanderi zones. Thus, the studied carbonate succession is latest Smithian to Aegean in age. A δ13C profile of this section shows elevated values during the lowest Spathian followed by a gradual negative excursion, a subsequent positive excursion near the Spathian–Aegean boundary, and relatively constant values during the Aegean. The characteristic series of negative and positive excursions correlates with other δ13C records for this period, including the peak of the upper Smithian–lowest Spathian positive excursion (P3), lower to middle Spathian negative excursion (N4), and middle Spathian–lowest Aegean positive excursion (P4). This represents a new high‐resolution Spathian–Aegean δ13C record of the Panthalassic Ocean, for which ages are constrained by conodont biostratigraphy. The Taho δ13C profile exhibits a consistent positive offset of ~2 ‰ as compared with those from other regions (i.e., mostly in the Tethyan Ocean). This can be explained by preferential removal of 12C from seawater during photosynthesis and calcification by marine organisms over the platform, and/or the relatively high δ13C values of dissolved inorganic carbon in the Panthalassic Ocean due to less influence of 12C‐enriched terrestrial waters and high marine organic production/burial as compared with the more restricted Tethyan Ocean.

БИОСТРАТИГРАФИЯ И ЛИТОЛОГИЧЕСКИЕ ОСОБЕННОСТИ НИЖНЕКАМЕННОУГОЛЬНОЙ УРМУГТЭЙУЛЬСКОЙ СВИТЫ (ОРХОНСКИЙ ПРОГИБ, СЕВЕРНАЯ МОНГОЛИЯ)

The results of a biostratigraphic and lithological studies of the terrigenous Carboniferous Urmugteyul Formation in the stratotype area (left bank of the Sharyn-Gol River, Orkhon Trough) are presented in this research paper. Four members are distinguished in the composition of the formation; the first three members are assigned to the Lower Urmugteyul Subformation, the fourth is to the Upper Urmugteyul Subformation. The first palynological studies made it possible to limit the accumulation time of the Lower Urmugteyul Subformation to Late Tournaisian, and the Upper Urmugteyul Subformation to Late Visean. The nature of the structure and lithological features of the section, considered as part of two terrigenous facies associations, as well as the paleontological characteristics and analysis of palynofacies, indicate that the accumulation of the Lower Urmugteyul Subformation occurred in the alluvial-delta plain settings, and the Upper Urmugteyul Subformation is in the shallow shelf basin.

Oxygen and carbon stable isotope records of the Lochkovian-Pragian boundary interval from the Prague Basin (Lower Devonian, Czech Republic)

Climate changes close to the Lochkovian-Pragian Event are still widely discussed. Carbonate δ18O and δ13C and conodont apatite δ18O from medial to distal carbonate ramp sediments were analysed to provide further stable isotope data from the stratotype area in the Prague Basin. The uppermost Silurian to lower Emsian δ18O trends are put into an updated conodont biostratigraphy framework. Carbonate δ18O and δ13C are discussed in the context of facies-dependent diagenesis. The δ13C pattern measured from different sections enables the correlation of intervals with development of different facies inside the Prague Basin. Positive δ13C shifts are often coupled with trends of decreasing computed gamma-ray (CGR) values interpreted as regressions, whereas negative δ13C shifts commonly coincide with opposite trends in CGR. The Lochkovian-Pragian boundary interval coincided with an increase in carbonate δ13C and an increase in the δ18O of conodont apatite and carbonate, which we interpret as consequence of climate cooling. Generally, the Lochkovian was warmer than the Pragian and earliest Emsian.

The C, O, and Sr Isotope Chemostratigraphy of the Vendian (Ediacaran)–Cambrian Transition, Olekma River, Western Slope of the Aldan Shield

The Upper Neoproterozoic–Lower Cambrian section in the Olekma River basin is divided (from bottom to top) into the Dikimdia, Seralakh, Porokhtakh, and Pestrotsvetnaya formations, which are mainly composed of dolostones with a subordinate amount of sandstone, silty shales, gypsum, anhydrite, and native sulfur. The isotope data available allow one to substantially correct the stratigraphic units of the Olekma section, which is probably the most completed section on the Siberian Platform, including the transitional strata from the Vendian (Ediacaran) to the Cambrian. The Dikimdia Formation dolostones have typical Late Ediacaran values of 87Sr/86Sr = 0.70837–0.70843 and abnormally high δ13С values (up to 5.1‰), which gives reason to correlate this formation with the Ust’-Yudoma Formation (the stratotype area), the Dengying Formation in South China (548–550 Ma), the Uluntuy Formation of the Baikal Group, and the terminal Ediacaran sections in some other areas. The 87Sr/86Sr ratio decreases upward and reaches a minimum (0.70803–0.70818) near the Porokhtakh–Pestrotsvetnaya boundary. The lowermost part of the Porokhtakh Formation contains a negative carbon isotope excursion (δ13С = –4.4‰) marking the base of the Nemakit-Daldynian Stage, whereas ~8 m below the base of the Pestrotsvetnaya Formation the positive “pre-Tommotian” excursion (δ13С = 4.1‰) is located. There is a sharp decrease in Fe and Mn contents from ~3800 and ~300 ppm to ~2000 and ~130 ppm, respectively, in dolostones at the Ediacaran–Cambrian transition boundary which corresponds to the Seralakh–Porokhtakh boundary. High δ18О values (26.0 ± 1.2‰) do not provide reasons to associate the carbon isotope excursions, the 87Sr/86Sr trend, and variations of Fe and Mn contents with diagenetic alterations.

The Kasterlee Formation and its relation with the Diest and Mol Formations in the Belgian Campine

Stratigraphic analysis of cored and geophysically logged boreholes in the Kasterlee-Geel-Retie-Mol-Dessel area of the Belgian Campine has established the presence of two lithostratigraphic units between the classical Diest and Mol Formations, geometrically related to the type Kasterlee Sand occurring west of the Kasterlee village and the study area. A lower ‘clayey Kasterlee’ unit, equivalent to the lithology occurring at the top of the Beerzel and Heist-op-den-Berg hills, systematically occurs to the east of the Kasterlee village. An overlying unit has a pale colour making it lithostratigraphically comparable to Mol Sand although its fine grain size, traces of glauconite and geometrical position have traditionally led stratigraphers to consider it as a lateral variety of the type Kasterlee Sand; it has been named the ‘lower Mol’ or ‘Kasterlee-sensu-Gulinck’ unit in this study. In the present analysis, the greenish glauconitic Kasterlee Sand in its hilly stratotype area evolves eastwards into the lower ‘clayey Kasterlee’ unit and possibly also into an overlying ‘lower Mol’ or ‘Kasterlee-sensu-Gulinck’ unit, although it is equally possible that the latter unit has an erosive contact and therefore is stratigraphically slightly younger than the type Kasterlee Sand west of the Kasterlee village. A lateral extension of this detailed stratigraphic succession into the faulted zone of east Limburg is proposed.

The composition and formation conditions of the Upper Lochkovian Valgan Formation (Lower Devonian Ilych River, Northern Urals)

Research subject. A section of the Upper Lochkovian (Lower Devonian) Valgan Formation located in the stratotypic area on the Ilych River, Northern Urals, was investigated. Materials and methods . A study of the composition and structure of rock samples gathered from the section under consideration during fieldwork in 2015 was conducted. Results. The studied section with an exposed thickness of 51 m is characterized by the thin and uneven alterations of calcareous con-glogravelites, coarse-grained and fine-grained organic sandsones, bioclatic-pelitomorphic limestones and argillo-calcareous shales. These rocks demonstrate a gradational and convolute lamination. An individual interval of the studied section contains calcareous conglobreccias layers. The Valgan Formation is characterized by a cyclic structure, with the thickness of individual cyclites ranging from 5.0 to 25 cm. The character of their structure testifies to sedimentation in slope settings. An analysis of clastic material revealed two sources of the basin area formation: near ablation (represented by the fragments of background bioclastic-pelitomorphic limestones) and remote ablation (represented by biohermal rock clasts). It is proposed to consider the Valgan Formation as the Valgan gradation, which extends the Upper Lochkovian sulfate-carbonate Subformation to the east. Conclusions. Therefore, the Valgan gradation should be treated as an intermediate link between shallow-marine Upper Lochkovian biohermal structures and bathyal clayey and siliceous shales.

The Devonian–Carboniferous boundary in the stratotype area (SE Montagne Noire, France)

Sections with continuous sedimentation across the Devonian–Carboniferous (D-C) boundary in the Montagne Noire allow to build a virtual transect from shoreline to deep basin. Nearshore facies characterise the D-C boundary stratotype and neighbouring sections at La Serre in the Cabrieres klippen domain, and offshore facies are present at the Col de Tribes and Puech de la Suque sections in the Mont Peyroux nappe domain. Both domains exhibit equivalents of the Hangenberg Black Shale (HBS). At La Serre, an initial regressive trend is indicated by the presence of oculated trilobites in the topmost pre-HBS Wocklumeria Limestones. Above the HBS level, regressive depositional conditions characterise oolitic deposits that comprise lithic erosional flows with an admixture of transported shallow-water biotas. Maximum regression is recognised with the deposition of coarse breccias and local features of emergence prior to the first appearance of Protognathodus kockeli. The oolites are superseded by the transgression of outer shelf deposits. In the nappe domain, the HBS is intercalated in outer ramp nodular limestones, and it exhibits detrital elements pointing to its regressive nature. The regressive trend culminates than reverses when post-HBS carbonate sedimentation resumes. Protognathodus kockeli appears in the post-HBS carbonates. Associated oculated trilobites indicate shallower bathymetric conditions then those of the pre-HBS Wocklumeria Limestones. Thereafter, replacement of sighted trilobites by blind ones and the protognathodid biofacies by facies dominated by siphonodellids indicate a deepening trend. The near- and offshore sites of the D-C transition permit correlation of short-term bathymetric fluctuations with faunal turnovers and entries of biostratigraphic markers.

Флора артинского яруса (нижняя пермь) стратотипического региона (Средний Урал)

The paper deals with the characteristics of the floristic assemblage, which is typical of stratotype area of the Artinskian stage (Lower Permian), i.e. Arti District of Sverdlovsk region. Taxonomical composition of the Artinskian flora includes equisetophytes Paracalamites decoratus (Eichwald) Zalessky, Paracalamites spp., Calamites gigas Brongniart, ferns Pecopteris ex gr. leptophylla Bunbury, peltasperms Permocallipteris sp., Gracilopteris sp. (sp. nov.); ginkgophytes s.l. Psygmophyllum expansum (Brongniart) Schimper, conifers Tylodendron sp., Walchia sp., vojnovskyans Rufloria cf. duvanica Vladimirovich, Lepeophyllum sabanakovae Vladimirovich, Vojnovskya sp., and numerous and diverse isolated seeds. One of the seed morphotype is described in the present paper as a new species Ovalocarpus butmanii Naugolnykh et Linkevich. According to the author’s viewpoint, this species belonged to primitive ginkgophytes and could be produced by the plant with the leaves Psygmophyllum Schimper and seed-bearing organs Cheirocladus Naugolnykh. Round perforations most probably left by trunks of phytophagous insects of Palaeodictyoptera were found on the seeds Ovalocarpus butmanii.

High-resolution biostratigraphy and chemostratigraphy of the Cenomanian stratotype area (Le Mans, France)

The definition of the Cenomanian stage was based on the description of several type sections scattered in the vicinity of Le Mans (Sarthe, France). Despite limited exposures nowadays, the area remains a reference for the palaeontology of the Cenomanian due to its outstanding richness in marine macrofossils, especially molluscs, bryozoans, brachiopods and echinoderms. The publication in 2015 of the volume dedicated to the Cenomanian stratotype yielded the opportunity to restudy the last accessible outcrops. This paper provides a high-resolution stratigraphic scheme and palaeoenvironmental reconstruction for the middle and late Cenomanian interval in its type area. La Garenne Quarry is a window on the middle Cenomanian, where Praeglobotruncana rillella nov. sp. has been identified. The δ13Ccarb and δ18Ocarb record of a Cenomanian–Turonian succession close to Le Mans is correlated with the type section of Pueblo (Colorado). Isotopic and biotic events highlight the presence of several hiatuses in the sedimentary record of Le Mans especially around the Cenomanian–Turonian boundary with a dramatic truncation of the plateau of high δ13Ccarb values. Coiling reversal events among the surface dwellers Muricohedbergella delrioensis, indicate sea surface temperature changes with transient coolings, including the Plenus cold event, and warm conditions at the Cenomanian–Turonian boundary. Sandy to chalky facies have yielded empty, well-preserved shells of foraminifera allowing the description of Dicarinella falsohelvetica nov. sp. Oxygen isotopic analyses performed on right- and left-coiled M. delrioensis reveal a systematic offset during cold events which lead to discuss about the potential occurrence of cryptic species in the Mesozoic.

The lower and middle Turonian (upper cretaceous) stratigraphy of the Yenisei Western Siberia (left side) region by foraminifers and inoceramids

The article presents the results of the litho-biostratigraphic study of the lower part of the Upper Cretaceous sea deposits on the territory of the Bolshaja Kheta structural terrace on the left side of the Yenisei river in its lower reaches (the tops of the Dolgan suite, Dorozhkovo suite and the bottoms of the Nason suite; Turonian stage). Eleven lithological members surely extended on the Bolshaja Kheta structural terrace are selected. Each member has received the paleontological characteristic. The layers with fauna (inoceramids and foraminifers) are identified and compared with the zonal subdivisions of the Turonian in Western Siberia. It is established that the upper part of the Dolgan suite belongs to the Lower Turonian substages, the Mytiloides labiatus zone. Dorozhkovo suite in the studied area close to its stratotype area corresponds to the Lower and Middle Turonian.

An evaluation of biostratigraphic markers across multiple geological sections in the search for the GSSP of the base of the Serpukhovian Stage (Mississippian)

This paper aims to evaluate potential biostratigraphic markers for the Viséan–Serpukhovian boundary in sections of Europe and Asia, to help identify the base of the global Serpukhovian Stage, which is a high priority task for Carboniferous biostratigraphy. Sections in the Serpukhovian stratotype area in the Moscow Basin contain a gap at the base of the Tarusian Regional Substage (basal in the classical Serpukhovian), so the traditional boundary defined in these sections cannot be precisely correlated with other successions worldwide. The IUGS Task Group to establish a GSSP close to the traditional Viséan–Serpukhovian boundary focused on the search for a new boundary marker, primarily on the first appearance datum (FAD) of the conodont Lochriea ziegleri in the lineage Lochriea nodosa to Lochriea ziegleri, considering it to be a suitable biostratigraphic event. The FOD (first occurrence datum) of L. ziegleri has been recognized in many successions worldwide, although only in a few sections the supposed evolutionary lineage of L. ziegleri was inferred. There are serious impediments to the FAD of L. ziegleri being universally accepted as the boundary marker. This paper presents a review of the FOD levels of L. ziegleri documented so far from multiple sections along with other correlatable markers (foraminifers and ammonoids) that can serve as additional points of reference in sections where a conodont record is poor or absent. The reviewed sections are Naqing Section (South China), Verkhnyaya Kardailovka and Kugarchi sections (South Urals, Russia), Mariinsky Log and Ladeinaya Mountain Sections (western slope of the Middle Urals, Russia), Novogurovsky Section (Moscow Basin, Russia), Vegas de Sotres Section (Cantabrian Mountains, Spain), Lugasnaghta Section (County Leitrim, Ireland), Wenne River Bank Section (Germany), and Milivojevića Kamenjar Section (Družetić, NW Serbia). We also included a compilation of data from sections of North England and southern Scotland. In this paper, we will mainly focus on newly described sections, while the discussion of most previously described sections was summarized by Nikolaeva et al. (2001, 2002, 2005, 2009b) and other publications, so they are only briefly mentioned in this review. It should be added that there is no such a thing as a perfect GSSP section, as each section has certain disadvantages, either lithological, paleontological, or both, so it is important to hear and discuss all the different opinions to develop the optimum strategy for future research. In addition, we analyze published records from several sites in North England and southern Scotland. We discuss the first appearances of the ammonoid genera Cravenoceras, Edmooroceras, Lyrogoniatites, Dombarites, and Platygoniatites, the foraminifers Neoarchaediscus postrugosus, Hemidiscopsis muradymica, H. hemisphaerica, species of Janischewskina and Monotaxinoides, Eostaffella pseudostruvei group, Eostaffellina decurta, and Endothyranopsis plana. We publish here for the first time the useful accounts of foraminifers and conodonts from the Mariinsky Log Section and Ladeinaya Mountain Section (Middle Urals, Russia), and re-figure several important type specimens from Europe and the Urals.

First report on Guanshan Biota (Cambrian Stage 4) at the stratotype area of Wulongqing Formation in Malong County, Eastern Yunnan, China

Exceptionally preserved fossils, such as those from Cambrian Burgess Shale-type fossil-Lagerstätten are critical because of their unique contributions to knowledge of the phylogenetic radiation and palaeoecological expansion of metazoans during the Cambrian explosion. Critically, these deposits provide information that is usually unobtainable from shelly and skeletonized fossils alone. The Guanshan Biota (Cambrian Series 2, Stage 4) in the Yunnan Province of South China, has produced abundant and diverse, exquisitely preserved fossils that often retain soft tissues and organs. To date, most fossils from the Guanshan Biota have been collected from localities such as Gaoloufang and Gangtoucun, which have become inaccessible due to new urban expansions and constructions of residential buildings. Here we present the first report of soft bodied fossils from a new section at Kanfuqing, close to the Wulongqing village in Malong County, approximately 3 km east of the Wulongqing Formation stratotype section. Fossils retain soft morphology, and include brachiopods with delicate marginal setae, priapulids with well-preserved sclerites and vetulicolians with entire sections of body. In addition, this fauna includes rare occurrences of trilobites preserved with soft tissues replicated as pyrite pseudomorphs after weathering. This discovery represents an important palaeogeographical extension of soft-bodied fossils of the Guanshan fauna to the east of the Xiaojiang Fault (related to Tsinning tectonic movements ca. 700 Ma). The fauna from the new Kanfuqing section is similar to that reported from the Wulongqing Formation west of the Xiaojiang Fault, and thus has significant implications for early Cambrian palaeogeography, faunal successions and palaeoenvironments of eastern Yunnan.

A brachiopod shell show during the middle Cenomanian in the stratotype area (France) – exceptional residual colour pattern

The Mid. Cenomanian terebratulid brachiopod Sellithyris cenomanensis Gaspard, 1982 displays preserved residual colour patterns as pale radial bandings. A parallel is made with the common Triassic Coenothyris vulgaris (Schlotheim, 1820) and some extant species. The colour pattern is unequal comparing the dorsal and ventral valves of one specimen, and in the representatives of a sampled population. This ornamentation, not easily detected, is highlighted using ultraviolet (UV) light. Considerations concerning the pigments involved, their function and at least their alteration over time are tentatively analysed.

Ichnological record of palaeoenvironment from the Cretaceous-Paleogene boundary interval at El Kef, Tunisia: The first study of old and new sections at the stratotype area

Trace fossil analysis of the Cretaceous-Paleogene (K/Pg) boundary interval at El Kef (Tunisia) has provided new information on the response of the macrobenthic tracemaker community to the K/Pg boundary event. Ichnological data from the Global Stratotype Section and Point (GSSP) for the Cretaceous-Paleogene (K/Pg) boundary were completed with those from a new, well-exposed section nearby. The trace fossil assemblage consists of dominant Trichichnus, frequent Chondrites, and rare Thalassinoides and Zoophycos in the uppermost Maastrichtian, and only Trichichnus in the lowest Danian, the diversity being comparatively lower than in other K/Pg boundary sections worldwide. Bioturbational structures are observed continuously across the K/Pg boundary interval, without primary lamination; this discards anoxic conditions. However, the upward-decreasing diversity in the sections may be related to a transition from a moderately dysoxic or slightly dysoxic macrobenthic habitat in the sediment during the latest Maastrichtian to a strong or very strong dysoxia during early Danian. Comparison with micropaleontological data reveals a minor influence of the K/Pg boundary event on the macrobenthic tracemaker community, while the change in oxygenation of pore waters at the El Kef sections can be attributed to local or regional phenomenon, marked by increasing clay content in the Danian sediments.