Northern Dobrogea Research Articles

Large durophagous fish from the Spathian (late Early Triassic) of Romania hints at earlier onset of the Triassic actinopterygian revolution

AbstractFossil evidence suggests that ray‐finned fishes (Actinopterygii) diversified greatly after the largest mass extinction event at the Permian–Triassic boundary. This radiation resulted in a diversity peak in the Middle Triassic, which is manifested in diverse feeding specializations, especially among small‐bodied Neopterygii. We present new material from an early Spathian (Early Triassic) outcrop in northern Dobrogea, southeast Romania. The material includes isolated jaw and palatal bones that evidently belong to a single individual, a durophagous actinopterygian, and isolated scales referred to the same taxon. A systematic evaluation of this material indicates affinities with †Polzbergiidae, and provides a first glimpse of internal aspects of the feeding apparatus of that group. A pair of ectopterygoids with crushing dentition show a well‐developed lateral process, a feature that was previously proposed to be a synapomorphy uniting Cladistia (bichirs) with the Triassic †Scanilepiformes. The recognition of this structure in various Triassic ray‐fins (summarized herein) indicates that it was probably widespread among stem neopterygians. The new material belongs to a large individual with a heterodont dentition, therefore representing the earliest large, specialized, durophagous neopterygian. It increases the group's morphological diversity in the Spathian, and hints at an earlier trophic diversification after the mass extinction. Based on new data, we analyse changes in body size of bony fishes through the Early and Middle Triassic. Current evidence suggests that body size distribution remained skewed towards larger sizes in the late Early Triassic, and that the diversification of small‐bodied stem neopterygians had not yet been in full swing.

Mid-to late Holocene vegetation and environmental change at local and regional scales based on a multi-proxy analysis of the upper Danube Delta, Romania

The Danube Delta is Europe's largest wetland system and of unique biogeographical character. Whilst its geomorphological evolution is relatively well-known its ecological history is poorly understood, including the history of human impact, as a result of the dynamic nature of deltaic systems, and the scarcity of reliably dated successions. In this paper, we report a multi-proxy record of palynology, sediment texture, geochemistry, and ostracods from the upper reaches of the Danube Delta. We use these data to reconstruct a mid-to-late Holocene history of vegetation and environmental changes at local and regional scales, which serve as a model for understanding baseline conditions in delta apex regions. From 7500 to 6200 ​cal ​yr BP, the study site was part of an inter-distributary channel-levee system connected to coastal lagoons and sensitive to sea-level fluctuations but transitioned to a partially-disconnected lacustrine environment after 5700 ​cal ​yr BP. These geomorphologically-driven landscape changes strongly influenced the pollen source area making it complex to interpret palynoassemblages. Prior to 5700 ​cal ​yr BP, palynoassemblages were predominantly river-transported, reflecting widespread hinterlands, and providing information for the regional reconstruction of the vegetation history in the northern Dobrogea region. These data reveal the early presence of Carpinus and Fagus in southeastern Romania, prior to their spread through the Carpathian Basin. After 5700 ​cal ​yr BP, initiated by a slowdown in the relative rate of rise of the Black Sea, peat accumulation commenced within the shallow lake depocentre and airborne pollen became the dominant source. These pollen data record an expansion of herbaceous taxa and highly diverse marsh and aquatic taxa. Tree cover became dominated by Quercus, with low percentages of Carpinus, Betula, Ulmus, and Tilia. The earliest pollen evidence indicative of human impact commences c. 6500 ​cal ​yr BP) and, after 3200 ​cal ​yr BP, the decline in Quercus and a synchronous rise in archaeological artifacts, points to an opening of the landscape by forest clearance and an enlargement of arable areas. In particular, clearance and agriculture during the development of the Hallstattian Babadag culture (c. 3200-2800 ​yr BP) reflects an increase in population and settlement density during that late interval. Our paper comprises the first mid-to-late Holocene palynological record for the Danube Delta and highlights how human activity has profoundly altered the dryland region, creating landscapes comparable to today from around 3200 years BP, while the local deltaic landscape retained its character over the last six millennia.

Fedir Vovk as Founder of Ukrainian-Romanian Scientific Relations

Fedir Vovk (1847–1918), a native of Poltava region and a professor at the Sorbonne University and the University of Petrograd, an illustrious Ukrainian anthropologist and archaeologist, made a significant contribution to the development of national and world scientific thinking. In particular, he is known as the discoverer of Mizin culture, editor of the works of Taras Shevchenko, an active promoter of Ukrainian culture in Europe. Based on the study of a significant ethnographic material collected from different countries, including Romania, Hungary, Russia, F. Vovk published in 1892 a unique work, “The Ritual and Traditions of Marriage in Ukraine”, and in 1916 – two works: “Anthropological Features of the Ukrainian People” and “Ethnographic Features of the Ukrainian People”. Through his works, he rejected the theories of several Russian imperial historians about the fact that Ukraine is only “a south of Russia”. Of particular importance for the scientific activity of F. Vovk was his stay in Romania during 1878–1882. The scientist studied, in particular, the Ukrainian settlements in Northern Dobrogea. As the eloquent scientific results of these studies were, for example, the works “The Trans-Danubian «Sicea» in local memories and stories” (1883) and “Ukrainian Fishing in Dobrogea” (1899). F. Vovk also collaborated with the well-known writer, translator, publicist and public activist Zamfir Arbore-Rally (1848–1933) and rightly entered the scientific annals as one of the founders of the Ukrainian-Romanian scientific and cultural relations of the late (political) stage of the national-cultural renaissance and development of state-building processes in Central and Eastern Europe.

New insight into the organogenus Ioanella Granier & Berthou, 2002, with description of Ioanella dobrogiaca organosp. nov. from Triassic limestones of the Dobrogea (Romania)

ABSTRACT Triassic deposits are widespread in the Măcin Unit of Northern Dobrogea (SE Romania). At the Enisala Fortress hill, near the village of Enisala, they are predominantly represented by grey bioclastic limestones of Wetterstein-type facies of the latest Ladinian to Carnian age. Samples collected from the lower part of this unit, i.e. from strata cropping out on the right side of the road from Sarichioi to Enisala, yield an association of calcareous algae, among which one is described in this paper as a new representative of the organogenus Ioanella. Ioanella dobrogiaca organospecies nov. differs from the type-species of the genus, Ioanella lusitanica, by its morphological and dimensional characteristics. Its features allow us to refine the diagnosis of the organogenus Ioanella. Additionally, comparisons with other dasycladalean organogenera demonstrate that Ioanella is a discrete genus.

Quality and Health Risk Assessment Associated with Water Consumption—A Case Study on Karstic Springs

In rural areas without centralized water supply systems, inhabitants often use groundwater of unknown quality as drinking water, without understanding the possible negative consequences on their health. Karstic spring waters from Dobrogea region in Romania were assessed for their potential to be used as drinking water source, according to their quality and seasonal variation. The physico-chemical parameters of waters were compared with the guideline values for drinking water established by the World Health Organization and the Directive 98/83/EC. The nitrate and Cr concentrations exceeded the guideline value in the springs from Southern Dobrogea, but met the quality criteria in those from Northern Dobrogea, thus, to be used as drinking water, the karstic springs located in Southern Dobrogea require treatment for nitrates removal. Heavy metals pollution indices showed low to medium cumulative heavy metal pollution in all springs, while the human health risk assessment by oral exposure indicated possible noncarcinogenic risks of nitrates, both for adults and children in springs from South Dobrogea. A rigorous monitoring of the water quality before human consumption is recommended for all four studied water sources.

Lichens Bite the Dust - A Bioweathering Scenario in the Atacama Desert.

SummaryBioweathering mediated by microorganisms plays a significant role in biogeochemical cycles on global scales over geological timescales. Single processes induced by specific taxa have been described but could rarely be demonstrated for complex communities that dominate whole landscapes. The recently discovered grit crust of the coastal Atacama Desert, which is a transitional community between a cryptogamic ground cover and a rock-bound lithic assemblage, offers the unique chance to elucidate various bioweathering processes that occur simultaneously. Here, we present a bioweathering scenario of this biocenosis including processes such as penetration of the lithomatrix, microbial responses to wet-dry cycles, alkalinolysis, enzyme activity, and mineral re-localization. Frequently occurring fog, for example, led to a volume increase of microorganisms and the lithomatrix. This, together with pH shifts and dust accumulation, consequently results in biophysical breakdown and the formation of a terrestrial protopedon, an initial stage of pedogenesis fueled by the grit crust.

GEODYNAMIC FEATURES OF DOBROGEA FORMATION

The formation of Dobrogea as a modern geographical unit dates back to the late Neogene. The complex tectonic structure indicates multiphase changes in this key area that are buried under sediment or reflected in outcrops. Separate outcrops to Mesozoic sedimentary rocks and Precambrian-Paleozoic crystalline basement have been identified, while the main part of the region is characterized by Paleogene-Neogene outcrops. According to the peculiarities of the tectonic structure of Dobrogea, it is divided into the Southern, Central and Northern parts, which are separated by faults of the north-western extension and the Pre-Dobrogea depression. The main part of Dobrogea is located in Romania, within Ukraine there is the Prut ledge of the Northern Dobrogea and the Pre-Dobrogea depression, and part of the Southern Dobrogea goes within the borders of Bulgaria - the southern slope of the Dobrogea massif.The geodynamics of the joint zone determined the stages of formation, which were accompanied by platform transformations and tectonic-magmatic processes, as well as the formation of sedimentary complexes with coal, coal seams and oil and gas reservoirs. Based on the factor of destruction of Cretaceous and, possibly, Jurassic and Triassic deposits and their transformation into younger, Paleocene and Maikop deposits, it can be said that large accumulations of gas on structures in Paleogene traps are unlikely.Modern gas migration is characteristic of both the sedimentary strata of the Pre- Dobrogea Depression, ie the northern part of the study region, and the south-eastern part of Southern Dobrogea in carbonate deposits.

Halmyris: Geoarchaeology of a fluvial harbour on the Danube Delta (Dobrogea, Romania)

In Northern Dobrogea, north of the Dunavăţ promontory, the Roman fortress of Halmyris was founded in the late 1st century AD on a Getic settlement dating to the middle of the 1st millennium BC, probably associated with a Greek emporium of the Classical and Hellenistic periods. At the time of the foundation of Halmyris, the Danube delta had already prograded several kilometres to the east leading to the progressive retreat of the sea and the formation of a deltaic plain characterised by numerous lakes and river channels. Here, we present the results of a multiproxy study combining sedimentology and palaeoecology to (1) understand the evolution of fluvial landscapes around Halmyris since ca. 8000 years BP and (2) identify the fluvial palaeoenvironments close to the city in Getic/Greek and Roman times, in order to locate and characterise the waterfront and the harbour. Our overriding objective was to improve understanding of human–environment relations in river delta settings. We demonstrate that Halmyris, protected by the Danubian floods due to its location on a palaeo-cliff top, had direct access to the river. A secondary channel of the Saint George, flowing north of the site, has been elucidated between the 7th century BC and the 7th century AD and could have been used as a natural harbour.

Autumn Passage of Soaring Birds over Dobrogea (Romania): A Migration Corridor in Southeast Europe

The Dobrogea region in southeastern Romania, which is part of the Eurasian-East African Flyway, is listed as one of the important migration corridors for soaring birds on the western coast of the Black Sea. However, our knowledge regarding migration intensity, phenology and geographical patterns of soaring birds over the area is poor. To determine the migration intensity and phenology of soaring birds, we recorded the autumn migration in the Măcin Mountains (northern Dobrogea) from mid-August to the end of October between 2002–2007. To describe the geographical patterns of migration at a regional scale, we recorded migration intensity in the second half of September in 2010 and 2011, simultaneously from 15 and 13 counting points, respectively, covering the entire region of Dobrogea. In the Măcin Mountains we recorded a mean number (±SD) of 11,297 ± 2333.5 (CV = 20.7%) migrating raptors per year, and of 21,367 ± 10,949.3 (51.2%) and 455.6 ± 43.6 (9.6%) migrating White Storks Ciconia ciconia and Black Storks Ciconia nigra, respectively. Migration phenology parameters varied across raptor and non-raptor species. Migration occurred over a broad front, covering all of Dobrogea. However, migration intensity was more pronounced in the western, central and eastern parts of the region, and was less intensive in the northern central areas. Overall, we recorded 30 migrating raptor species and three non-raptor species. The most abundant raptors were Common Buzzard Buteo buteo, European Honey Buzzard Pernis apivorus, Lesser Spotted Eagle Clanga pomarina, Eurasian Sparrowhawk Accipiter nisus and Western Marsh Harrier Circus aeruginosus. The three non-raptor species were White Stork, Black Stork and Great White Pelican Pelecanus onocrotalus. Our study provides the first general overview of the autumn passage of soaring birds over Dobrogea, highlighting the importance of this area as part of a global migration network.

Improving knowledge of the subgenus Agrodiaetus (Lepidoptera: Lycaenidae: Polyommatus) in Eastern Europe: Overview of the Romanian fauna

The butterfly subgenus Agrodiaetus of the genus Polyommatus (Lepidoptera: Lycaenidae) is distributed in the western and central Palaearctic and represents a taxonomically challenging group due to its rapid diversification coupled, in many cases, with very limited availability of morphological diagnostic characters. In this study we provide a detailed overview of this subgenus in the Romanian fauna, a country where scattered, poorly documented records suggest the presence of three species: Polyommatus (Agrodiaetus) damon, P. (A.) admetus and P. (A.) ripartii. By analyzing material from museum collections and published records, and combining them with new faunistic findings and DNA data, we show that only P. admetus is currently undoubtedly present in the Romanian fauna (northern Dobrogea), where it reaches its north-eastern range limit in the Balkans. Historical records and DNA data suggest that the occurrence of P. admetus in northern Dobrogea is not likely to reflect a recent range expansion caused by climate or other environmental changes. Several historical records of this species that suggest its much wider distribution in Romania represent confusion with P. damon and Phengaris alcon. Polyommatus damon, reported mainly from western Romania, lacks records after 1938, while P. ripartii is only known from a single male labelled as originating from the Danube Delta, and requiring confirmation. There is a great need for directed studies to clarify the status of P. damon and P. ripartii, which are scarce and declining north of the Balkans and may represent taxa of conservation concern.

Les industries lithiques énéolithiques de la Dobroudja du Nord

The archaeological mission « Delta du Danube » is studying for more than six years the coevolution human-environment in the Danube Delta at the end of the Neolithic. This article offers a synthesis of the main results obtained from the analysis of the Gumelnița lithic industry in the Northern Dobrogea. The authors have taken into consideration both older collections as well as new ones discovered during the excavations deployed in the mentioned archaeological mission, most of all the tell settlement Taraschina (Maliuc commune). This variety of information allowed a good characterization of the Gumelnița lithic series discovered in the north of Dobrogea. The most important characteristic is represented by the import of raw material from the prebalkanic platform situated in the north-east of Bulgaria. These imports were oriented towards blade type products that were later transformed into a variety of finished objects. The typology is dominated by the end-scraper. A complete technological image will allow integrating the lithic information in the reflections regarding the socio-economic and environmental changes inside Gumelnița societies.

Thermal weathering of granite spheroidal boulders in a dry‐temperate climate, Northern Dobrogea, Romania

AbstractWeathering microforms associated with exfoliation were investigated on 40 granitic spheroidal boulders identified on Pricopan Ridge (Măcin Mountains) in order to establish a spatial distribution pattern. Continuous thermal monitoring allowed the frequency and intensity distribution assessment of short‐term temperature changes triggered by summer storms, of intense day–night amplitudes and frost cycles across a uniform rounded boulder. Rock strength estimated by Schmidt hammer tests differentiates a significantly weaker resistance on the southern face of the boulders (rebound values of 27 to 33) in comparison with the northern face (43–50). The lowest resistance of the north–south cross‐boulder profile corresponds to the southern gentle slopes (0°–45°) thus defining the most susceptible area to exfoliation and other weathering processes. It is argued that this low‐resistant sector fits well with the maximum frequency and intensity of thermal processes recorded on the low and mid slopes (0°–45°) of the boulders south side, with small differences from one process to another, whilst the sector of 20° to 30° south corresponds to the peak activity of all. In accordance, the overlay map of exfoliated surfaces places the high frequency area on a spherical cap developed similarly (between 5° north and 45° south). The smallest exfoliated surfaces normally appear around 30° south and are inferred to extend in time both to the boulder top and downslope. The correlations between the frequency/intensity maps of thermal processes and the frequency map of exfoliated surfaces point to a complementary action in the exfoliated surfaces development of the short‐term temperature changes and diurnal cooling and heating due to the directional insolation effect, as similarly inferred in the development of meridional cracks. Copyright © 2016 John Wiley & Sons, Ltd.

Climatic water balance dynamics over the last five decades in Romania’s most arid region, Dobrogea

The analysis of a territory’s climatic water balance dynamics against the background of climate change is a key component for increasing water resource management efficiency. The present study aims to analyse climatic water balance (CWB) dynamics in Romania’s most arid region, Dobrogea, located in the southeast. The study covers the 1961–2009 period, and is based on annual and seasonal CWB values (mm), provided by nine weather stations located throughout the region. The study, based on statistical and GIS techniques, is divided into two main stages, both carried out at annual and seasonal scales–trend analysis using the Mann-Kendall test, the Sen’s slope method, and CWB value distribution type analysis. In order to identify the probabilistic types of distributions, four mathematical models were identified–Pearson, Gamma, Chi-Squared and Wakeby, statistically verified with the P-P Plot, Q-Q Plot and Probabillity Difference Graph (PDG) curve tests. Thus, in terms of trends, the results showed a deficit increase especially at the northern stations, mainly for annual values (with a peak in the northeast, where CWB rates reached –3.2 mm/yr). While general CWB declines occurred in winter, spring and summer, apparent decrease rates were found in the northern region (highest negative rates–summer, northwest, –1.4 mm/yr). Autumn is an exception, due to overall increase rates which peaked in the southwest (2.3 mm/yr). However, the entire trend analysis indicated a general lack of statistical significance. The distribution type histogram analysis showed that, annually and seasonally, deficit values are generally dominant (more noticeable in the northern region), except for the winter season, mainly characterized by surplus intervals. Thus, the results suggest a climatic water deficit increase over the last five decades especially in northern Dobrogea, which signals the need for a spatial prioritization targeting a more efficient water resource management, necessary first and foremost for increasing regional agricultural system productivity.

History and influence of the Danube delta lobes on the evolution of the ancient harbour of Orgame (Dobrogea, Romania)

On the coast of Northern Dobrogea, south of the Danube delta, the Greek settlement of Orgame was founded in the mid 7th c. BC, probably by Milesian colonists. The ancient city was located on the Cape Dolojman which today overlooks a large lagoon complex. We undertook a chronostratigraphic study to: (i) understand coastal changes around Cape Dolojman since ca. 5000 years BP in connection with the construction of the Danube delta lobes, and (ii) identify potential sediment impacts related to human occupation of the site. Three cores were extracted from the lagoon area. Sedimentological and biological analyses were undertaken to reconstruct the evolution of the coastal palaeoenvironments. The results show a closure of the marine bay around 3500 cal. BP and its transformation into a lagoon environment. The first major environmental change was due to the construction of the lobe St. George I and the formation of the barrier Lupilor. Around 2000 cal. BP, the formation of an intra-lagoonal lobe, the Dunavatz, led to the gradual transformation of the lagoon into a fluvial-dominated system. Paradoxically, lagoon waters today still wash the ancient Greek harbour environment, which has not been totally infilled by alluvial sediments. To understand this paradox, in a context of coastal progradation, we compared and contrasted the geomorphological data with the nearby city of Istros/Histria, which was already landlocked at this time. The location of these two Greek colonies relative to the coastal sediment cell and barriers partly explains their contrasting palaeoenvironmental evolution. Until 2650 cal. BP, the increase in charcoal and organic matter in sedimentary archives is interpreted as an anthropogenic signal for a more extensive use of the vegetation cover following the foundation of the city of Orgame (e.g. for domestic use and funeral rites).

MODERNIZATION OF THE STRATIGRAPHIC SCHEMES OF MESOZOIC DEPOSITS IN UKRAINE

New data of the Triassic, Jurassic and Cretaceous stratigraphy in Ukraine are shown. The 32 stratigraphic schemes are created and improved for all Mesozoic divisions of the Carpathian region (Folded Carpathians, Transcarpathian depression and Carpathian foredeep with adjacent part of the East European Platform), Dobrogea (Northern Dobrogea and Predobrogea trog), Crimea (plains and mountains of Crimea, Kerch Peninsula), Ukrainian Shield, Donetsk folded structure, Dnieper-Donetsk and near Black Sea depressions, the Black and Azov seas. Biozone and interregional correlations schemes of these deposits have been made for the first time (11 schemes). All schemes are constructed on the correlation of modern international stratigraphic scales and in accordance with the requirements Stratigraphic Code of Ukraine. It is updated structural and facies zonation in some schemes. The deposits stratigraphic belonging is comprehensively substantiated by different groups of macro and microfossils, many of which are used for the first time. Biozone scales have been made or have been improved for some parts of the section. The age, volume and distribution of stratigraphic units, lithological and paleontological characteristics, stratigraphic correlation are revised, the new stratones are allocated. Mesozoic schemes of the Azov Sea and Transcarpathian depression foundation, Upper Cretaceous schemes of the north-western shelf of Black Sea and the plains of Crimea are created for the first time.

The Catalogue of “Alexandru RoȘca” Spider Collection from the “Grigore Antipa” National Museum of Natural History (Bucharest). II. Mimetidae, Oxyopidae, Pholcidae, Pisauridae, Theridiidae

Abstract We verified 145 specimens of Mimetidae, Oxyopidae, Pholcidae, Pisauridae, Theridiidae spiders from the “Alexandru Roșca” collection deposited in the “Grigore Antipa” National Museum of Natural History, Bucharest. Re-identification of the specimens actually presented in the Bucharest museum yielded records of 2 spider species not previously recorded for Romania: Pholcus ponticus Thorell, 1875 (Sibiu County) and Pisaura novicia (L. Koch, 1878) (Dâmbovița County). Pisaura novicia is further recorded from northern Dobrogea (Romania) and for the first time from the physiographic zone of the Ukrainian Carpathians based on our own material.

First Serologic Evidence for the Circulation of Crimean-Congo Hemorrhagic Fever Virus in Romania

Serum samples from sheep in localities situated in the county of Tulcea, Northern Dobrogea, were tested with an IgG sandwich ELISA using a recombinant Crimean-Congo hemorrhagic fever virus (CCHFV) antigen. In all, 131 sera out of 471 tested (27.8%) had IgG antibodies specific to CCHFV. This is the first evidence for the circulation of CCHFV virus in Romania.

A modern pollen rain study from the Black Sea coast of Romania

This paper documents the modern pollen rain in southeast Romania and explores the potential factors influencing vegetation communities. The analysis should help in the interpretation of the region's fossil pollen records. Thirty surface soil samples were collected along a southeast–northwest transect in Dobrogea, in a low plateau region separating the Razelm and Sinoie Lakes, near the Danube Delta. Numerical analysis of the surface samples revealed four palynologically distinct assemblages: coastal steppe, delta-marshland, forest-steppe and forest. A mixture of low rainfall and strong maritime winds, with high inputs of salty spindrifts, explains the steppe-like vegetation of the low coastal areas. Increasing inland moisture along the slopes controls the progressive gradient from wooded to forested areas. Human impact is nowadays of secondary importance in northern Dobrogea, due to a fall in agriculture pressures since the breakup of socialism in Eastern Europe.

Stage boundaries of the Triassic in Northeast Asia

The International Union of Geological Science approved the stage boundaries suggested by the international working groups for the Tethyan Triassic. In this work we estimate the possibility of their establishment and correlation in the Boreal sections of Northeast Asia, based on the analyzed distribution of ammonoids and conodonts. As the conodonts of the Induan Stage have not been identified for sure in the region under study, the lower boundary of the Triassic System is defined here at the base of the Otoceras concavum Zone of the ammonoid scale. In addition to the ammonoids Hedenstroemia hedenstroemi (Keyserling), the first occurrence of the conodonts Pseudogondolella nepalensis (Kozur et Mostler) is suggested to be the biomarker of the Olenekian Stage base. The lower boundaries of the Anisian and Ladinian stages, defined respectively at the basal levels of the Paracrochordiceras-Japonites Beds in Northern Dobrogea and the Eoprotrachyceras curionii Zone in the Brescian Prealps are recognizable, though with some reservations, at the base of the Grambergia taimyrensis and Eonathorstites oleshkoi zones in Northeast Asia. According to the priority principle and similarity between the ammonoid faunas of the Daxatina cf. canadensis Subzone and Frankites regoledanus Zone, the lower boundary of the Carnian Stage is defined at the base of the Alpine Trachyceras aon Zone. In Northeast Asia, this boundary is established at the base of the “Protrachyceras” omkutchanicum Zone, as we take into account the fact that the Daxatina and Stolleyites ammonoid genera occur in sections of British Columbia below the stratigraphic level of the Trachyceras forms. The lower boundary of the Norian Stage is concurrent with the base of the Guembelites jandianus Zone in the Alps and equivalent Stikinoceras kerri Zone in North America and Striatosirenites kinasovi Zone in Northeast Asia. The conodont species Norigondolella navicula (Huckriede) that is most important for the Boreal-Tethyan correlation cannot be used as a biomarker of the Norian lower boundary because of its problematic diagnosis and rare occurrence in the Boreal sections. The Rhaetian Stage base is defined at the appearance level of the Misikella conodont genus in the Hallstatt region, Austria, that is simultaneously the disappearance level of the characteristic Norian bivalves (Monotis) and ammonoids (Metasibirites). In Northeast Asia, this boundary is established at the top of the Monotis ochotica Zone. The correlation between the biostratigraphic units of the Middle-Upper Triassic conodont scale established in Northeast Asia and standard ammonoid zonation is verified.

Triassic biochronology: State of the art and main problems

According to known resolution of the IUGS, the International Stratigraphic Commission entrusted its subcommissions with a task to prepare proposals for the official approval of boundaries between Phanerozoic stages. Specially organized working groups were later renamed as special teams for seeking the Global Stratotype Sections and Points (GSSP) for these boundaries. In 2001, the GSSP of lower boundary for the Induan Stage, the basal one in the Triassic System, was officially approved to be in the Meishan section of southern China. The selection appeared to be lame, because the Permian-Triassic boundary layers of the stratotype section are lacking ammonoids. As a result, this boundary is now based only on the first occurrence level (FO) of conodont species Hindeodus parvus. Soon, the proposal of Chinese paleontologists to consider the western Pingdingshan section in the Anhui Province as the GSSP for the lower boundary of the Olenekian Stage may win the official recognition. This boundary between the Olenekian and Anisian stages, which is placed at the FO of conodont species Neospathodus waageni is the least debatable. The Mt. Desli Caira section in northern Dobrogea (Romania) is most appropriate for its global stratotype. In contrast, the Anisian-Ladinian boundary appeared to be most disputable. The Subcommission on Triassic Stratigraphy should select one of three GSSP candidates proposed. The lower Carnian boundary traditionally drawn at the aon Zone base suffered some changes. It is proposed to place it at the FO of the ammonoid genus Daxatina with the GSSP in the Dolomites of Italy. The Norian and Rhaetian boundaries are under discussion.