Ostracod Zones Research Articles

New contributions to the taxonomy of non-marine ostracods from the Neogene megawetlands, western Amazonas state, Brazil

The taxonomic review of the ostracods from Solimões Formation in the western Amazonas State, Brazil, allowed the identification of eight genera and twenty-two species of the genus Cyprideis Jones, 1857. Two species are new: Cyprideis goeldiensis sp. nov and Cyprideis javariensis sp. nov.; and Cyprideis sp. 1 remains in open nomenclature. For the first time, the species Cyprideis santaelenae Sousa and Ramos 2023, originally described to the Pebas Formation, in Peru, was recorded in the Solimões Formation. A new morphotype of the species Cyprideis matorae Gross et al. 2014 is here identified. The stratigraphical distribution of the Cyprideis species in the borehole 1AS-32-AM permitted the identification of four ostracod zones: Cyprideis caraionae Zone, Cyprideis minipunctata Zone, Cyprideis cyrtoma Zone and Cyprideis paralela Zone, presenting a time range from the middle Miocene (Serravallian) to the late Miocene (Tortonian). Based on the ostracod assemblage, an environment of a semiconfined lake, with mesohaline features and sporadic marine influence is attested to the western Amazonia during the Miocene. The species turnover of Cyprideis occurred during the Tortonian.

Devonian-Carboniferous boundary beds in the Kuz-Yama section (Northern Cis-Urals) - Conodonts, ostracods, and carbon isotope record

The Devonian-Carboniferous boundary interval is characterized by biotic crisis, global transgressive-regressive sequences and carbon cycle change, probably caused by climatic changes and volcanic activity. This interval attracts the attention of researchers worldwide in relation to selecting a new Devonian-Carboniferous boundary level. However the Northern Cis-Urals region remains poorly studied in this respect. This study focuses on the Kuz-Yama key section (Northern Cis-Urals) and contributes to our knowledge of the regional expression of the Devonian-Carboniferous boundary in northeastern Europe. The study of the Kuz-Yama section (Verkhnyaya Pechora Trough) involved an examination of the calciturbidites, hemipelagic shales and carbonates that constitute the poorly constrained uppermost Famennian to lower Tournaisian deep-water succession. The conodont and ostracod associations are poorly diversified. The presence of Polygnathus zikmundovae, in association with a positive δ13Ccarb excursion (up to 3.9 ‰), marks the base of the Late praesulcata conodont Zone (=base of the Protognathodus kockeli conodont Zone) in the lower part of the succession. The Devonian-Carboniferous boundary is indicated by the appearance of Siphonodella sulcata, that coincides with a positive shift in the decoupling of δ13Ccarb and δ13Ccon values, probably caused by a global decrease in CO2 associated with the regional crisis within pelagic ecosystems. The sulcata conodont Zone, bounded by the first occurrence of Siphonodella sulcata at the bottom and Siphonodella bransoni at the top of the section, contains Tournaisian ostracods. The ostracods compose mixed associations of the shallow-water Pseudoleperditia venulosa-Coryellina alba-Cribroconcha primaris ostracod Zone and the deep-water Armilla uralica ostracode Zone. The co-occurrence of shallow-water and deep-water conodont and ostracod taxa in the Tournaisian part of the section enhances the correlation of the shallow-water and deep-water conodont and ostracod zonations. The base of the shallow-water Siphonodella ludmilae conodont Zone roughly correlates with the base of the deep-water bransoni Zone. The base of Armilla uralica deep-water ostracod Zone in the Kuz-Yama section lies within the Pseudoleperditia venulosa-Coryellina alba-Cribroconcha primaris shallow-water ostracod Zone. The following sequence of events can be recognised in the Kuz-Yama section: first occurrence of Polygnathus zikmundovae Zhuravlev (approximately corresponding to the base of the Protognathodus kockeli Zone), positive shift in the inorganic δ13C (= Hangenberg carbon isotope excursion), latest Famennian regression, negative shift in the δ13C of conodont elements just below the base of the sulcata Zone, entry of the Tournaisian transgression, positive shift in decoupled inorganic and conodont δ13C near the base of sulcata Zone, positive shift in inorganic δ13C in the sulcata Zone, appearance of the Tournaisian ostracods, first occurrences of the conodonts Siphonodella bransoni Ji and S. ludmilae Zhuravlev & Plotitsyn (= base of the bransoni Zone). In general, this sequence corresponds to that identified around the Devonian-Carboniferous boundary in other regions.

Ostracod zonation of the Givetian-Frasnian boundary interval in the Timan-North Urals Region

Research subject.Ostracods and Givetian-Frasnian boundary deposits of the Timan-North Urals Region.Materials and methods.The work was based on the results of studying ostracods from the stratotype sections of the Southern Timan, which are considered referential for regional and global correlations. The analysis of the distribution intervals of the most significant taxa was based on the results of previous studies, both published and archival materials on the Timan-Urals Region. Ostracods were considered in association with conodonts, which is an important criterion for applying a reasonable biostratigraphic subdivision. The use of different-scale regional cyclicity of sedimentation and individual “marking” levels of manifestation of global events were shown.Results.The ostracod distribution in the Givetian-Frasnian boundary interval of the Timan-Northern Urals region was analyzed. The following most significant taxa were identified: Cavellina devoniana, Cavellina uchtensis, Cavellina batalinae, Cavellina chvorostanensis, Nodella faceta, Nodella ex gr. hamata. The correlation of established assemblages with ostracods from the Franco-Belgian basin was shown. The difference consists in the absence of a polyzygid assemblage with Polyzygia beckmanni beckmanni, which was established at the base of the Nismes Formation of Belgium near the historical boundary between the Givetian and Frasnian stages. The determined relationship of biostratigraphic data in combination with the transgressive-regressive sequence of sedimentation shows a more reasonable solution to the problem of the position of the lower boundary of the Frasnian stage of the Upper Devonian in the Timan-Northern Urals Region.Conclusions.An updated version of the scheme of zonal subdivision of the Givetian-Franian boundary interval in the Timan- Northern Urals region has been developed, taking into account the ostracod distribution of the Cavellinidae and Nodellidae families, as well as the discrepancies in the levels of the first appearance of index species and the boundaries of zones in the regional stratigraphic scheme. The correlation of ostracod zones relative to the conodont scale is shown.

Features of the sedimentation, stratigraphy and carbon isotope record of the upper Tournaisian of the Verkhnyaya Usa depression (Polar Urals)

Research subject. Upper Tournaisian clayey-siliceous-carbonate deposits of the Malaya Usa section (Polar Urals).Material and methods. The composition and structure of the deposits (50 samples, 51 thin sections) of the section were considered to determine the conditions of sedimentation; 13 samples were chemically disintegrated in 7–10% solution of acetic acid, and thin sections were studied for biostratigraphic analysis (conodonts, ostracods, and foraminifers); the carbon and oxygen isotopic composition of carbonate deposits (49 samples) were analyzed. A three-stage screening test of samples for isotopic-studies was carried out.Results. The Malaya Usa section comprises mainly micritic limestones with fossils silicified to various degree (wackstone to packstone). The features and composition of the sediments indicate sedimentation in low dynamic conditions below the wave base. Biostratigraphic analysis is based on the identification of foraminifers, as well as a few conodonts and ostracods. Foraminifers characterize the Eotextularia diversa–Dainella chomatica Zone, which is approximately comparable to the Upper typicus–anchoralis–latus conodont zonal interval and Entomoprimitia malinovkaensis‑Marginia tschigovae ostracode zones of the top of the Tournaisian. The isotope-geochemical data obtained from the section demonstrate a general lightening trend in the isotopic composition of δ13Ccarb up the section. This trend, along with the biostratigraphic data, mades it possible to compare the δ13Ccarb sequence of the Malaya Usa section with sequences from a number of geographically separated sections of the world (Belgium, South China, USA), which are considered as the Tournaisian isotope carbon event (TICE).Conclusions. The deposits of the studied section were probably formed under the conditions of a very gentle slope (ramp), where the material accumulated at the foot as a filling sequence in the southern part of the Korotaikha intrashelf paleodepression. Using the Malaya Usa section as an example, it is shown that not only the peak positive deviations of the TICE in the upper part of the isosticha Zone and in the lower part of the typicus Zone, but also the isotopic structure of the upper Tournaisian has a significant correlation potential. The use of the isotope-geochemical method as an auxiliary application to biostratigraphy made it possible to improve the age determination of the section from the interval of the Upper typicus–anchoralis–latus conodont zonal interval to the Upper typicus Zone of the standard conodont zonation.

A Late Pleistocene (MIS4-MIS2) palaeohydrological reconstruction from Lake Chalco, Basin of Mexico

We present a palaeohydrological reconstruction of Lake Chalco from 70 to 11.5 ka BP based on ostracod records consisting of three species: Limnocytherina axalapasco, Candona patzcuaro, and Cypridopsis vidua. Overall, the presence of these species helped investigate Lake Chalco water level fluctuations, and thus water salinity variations. Moreover, this work helped improve our knowledge of L. axalapasco and Candona alchichica, two endemic species of Central Mexico, the latter of which was replaced by C. patzcuaro after the cold and dry MIS4. Five ostracod zones reflect the main environmental changes that occurred during the Late Pleistocene. During 70–62 ka BP (Zone 5), shallow and very variable salinity conditions were inferred with a possible occupancy of submerged macrophytes. The Lake Chalco water level increased from 62 to 49 ka BP (Zone 4) and relatively less saline conditions were inferred. The warmer period from of 49–39 ka BP (Zone 3) was characterised by lower lake levels and a gradually increasing salinity. The evaporation rates continued to increase during 39–27 ka BP (Zone 2). However, a higher runoff input helped maintain a relatively high lake level. Later on, cold and dry conditions from 27 to 11.5 ka BP (Zone 1) inhibited the ostracod occupancy in Lake Chalco.

Late Pleistocene and Holocene palaeoecological reconstruction of Lake Texcoco (Basin of Mexico) based on its ostracod record

AbstractWe present a palaeohydrological reconstruction of Lake Texcoco over the last 32.7 cal ka based on ostracod records consisting of two species, Candona patzcuaro and Limnocytherina axalapasco. Overall, the presence of these species suggests that Lake Texcoco was highly saline and experienced occasional desiccation periods. Moreover, this work helps improve our knowledge of L. axalapasco, an endemic species of central Mexico; their eggs could remain dormant‐resting to survive long dry periods. Four ostracod zones reflect the main environmental changes that occurred during the Late Pleistocene and Holocene. From 32.7 to 30 cal ka bp (Zone 4), Lake Texcoco's water levels were stable and alkaline with saline conditions. Zone 3, representing the period from 30 to 18 cal ka bp, includes a period of enhanced precipitation (greatest abundance of C. patzcuaro) from 30 to 26 cal ka bp. From 26 to 18 cal ka bp, an abundance of L. axalapasco reflects shallower and more saline conditions. The Last Glacial Maximum was characterised by cold and humid conditions with enhanced runoff, especially at 25.3, 21.9, and 20.7 cal ka bp. Zone 2 (18–7 cal ka bp) represents the driest period on record. Finally, shallow and saline lake conditions have prevailed over the last 7 cal ka (Zone 1).

Zonation of Lithuanian Silurian graptolites and other faunal groups

The Baltic Silurian Basin, Lithuanian Depression and other structures are shown in the map, with marked by isopachs (contour lines of equal thickness) of the Silurian beds with graptolites and fauna of other groups. The Silurian facies vary greatly in the Depression – from clayey open-sea deep shelf to carbonaceous ones of shallow shelf, and low-energy lagoon facies. The history of investigations on East Baltic area graptolites begins from 1953–1958, when 15 graptolite zones were singled out, and proceeds to 35 zones defined now. Peculiarities in the graptolite scale from C. cyphus to N. lochkovensis inclusive are discussed. Transgressions and regressions of the Silurian marine basin, as well as shorter transgressions with wedges and graptolites of clayey facies shifted towards basin shores and regressions with partial extinction of graptolites are elucidated. During these investigations the graptolite scale has been detailed and added with new zones. Graptolite evolution in the zones has been analysed. Stages of graptolite evolution are analysed in relation to the following bioevents: Stačiūnai, Likėnai, Valgu, Ireviken, Mulde, Linde, Lau, Klev and Šilalė. Finally, two tables present graptolite zone correlation with conodont, vertebrate and ostracod zones revealing a highly detailed stratigraphy of the Lithuanian Silurian.

Остракоды пограничных отложений девона и карбона из опорного разреза на р. Ыджыд-Каменка (Печорская гряда)

This article presents new data on ostracodes and their stratigraphic distribution in the boundary deposits of the Devonian and Carboniferous (D3-C1) in the reference section Kamenka River (Pechora Uplift). The positions of the Kamenka River section and stratotypic sections of the southern Urals relative to the transgressive-regressive sequence are considered. The ostracode assemblage of the Ps. venulosa — Cor. alba — Cr. primaris zone, which occurs in the section on the Kamenka River and appears in sections of the southern Urals from the base of this zone, is represented by the following taxa: Pseudoleperditia venulosa (Kummerov), Coryellina alba Kotschetkova, Bairdia zaninae Posner, Blessites feluyensis Tschigova, Shishaella alekseevae Tschigova, Knoxiella complanata (Kummerov), Cavellina subeichwaldi Buschmina. The taxonomic characteristics of the upper part of the Pseudoleperditia venulosa — Coryellina alba — Cribroconcha primaris ostracode zone (Gumerovian Regional Substage (Horizon)) are supplemented Acratia subordinaria Buschmina, Healdianella ex gr. alba Lethiers, Phlyctiscapha ? pusilla Gurevitsсh, Pustulobairdia ex gr. confragosa (S. et Sm.), Acanthoscapha pechorica Sobolev, Acratina romboiformis Sobolev, and Rectobairdia eleganta Sobolev first appear at this level A gradual and insignificant change in the ostracode association is observed during the transition from the Gumerovian Horizon to the Malevkian Horizon, which precludes drawing the boundary between them. It is suggested that it would have been more appropriate to draw the boundary at the base of the global Hangenberg transgressive event near the base of the Ps. venulosa — Cor. alba — Cr. primaris ostracode zone (South Urals), which coincides with the initial phase of this transgression.

Eocene ostracods from southern Tibet: Implications for the disappearance of Neo-Tethys

The Yadong area was located in the residual Neo-Tethyan basin during the Paleogene. It contains a record of the youngest marine deposition in the Tethyan Himalayas. Therefore, biostratigraphic data from this area are essential to constrain the timing of elimination of the Tethyan Ocean and the India-Asia collision. Ostracods are one of the most diverse groups of living crustaceans, inhabiting marine, non-marine and even some semi-terrestrial habitats. They provide important evidence to reconstruct paleoenvironment and biogeography. This investigation examined ostracod faunas recovered from the Paleogene Zhepure Formation in the Gulupu section, Tüna, Yadong, southern Tibet. The formation can be further divided into a lower Limestone Member and an overlying Shale Member, which are conformable. Abundant, diverse well-preserved marine ostracods were recovered from the Shale Member. We report 29 species from 15 genera. The stratigraphic distribution of the Eocene ostracod assemblages found reveals three ostracod zones, and shows strong affinity to sections previously investigated throughout the Neo-Tethyan region. The Zhepure Formation also yields diverse planktonic and benthic foraminifers, charophytes, nannofossils, and pteropods and indicates that open marine conditions existed widely during the Eocene. Based on this study of little-known Eocene ostracods, we suggest that final closure of the Tethyan seaway occurred after early Late Eocene.

Integrated biozonation based on palynology and ostracods from the Neogene of Solimões Basin, Brazil

Biostratigraphic analysis integrating spores-pollen and ostracods from boreholes 1AS-8-AM and 1AS-7D-AM, at Atalaia do Norte, Amazonas state, Brazil, allowed to infer Early to Late Miocene for studied sequences. Five palynological zones previously proposed for the Solimões Formation were identified: Verrutricolporites (Early Miocene), Psiladiporites–Crototricolpites (late Early to early Middle Miocene), Crassoretitriletes (Middle Miocene), Grimsdalea (late Middle to Late Miocene), and Asteraceae (Late Miocene). At the same time, four ostracods (Cyprideis) zones were identified but with limits modified: C. sulcosigmoidalis (late Early to early Middle Miocene); C. caraionae (late Middle to early Late Miocene); C. minipunctata (late Middle to Late Miocene); and C. cyrtoma (early Late Miocene). Furthermore, a new ostracod zone, Cyprideis paralela interval zone (Late Miocene), is formally proposed. Two main bioevents of Cyprideis radiation, related to marine incursions, have been identified: one at late Middle Miocene/early Late Miocene (Grimsdalea zone) and another at Late Miocene (Asteraceae zone). This study attests the viability and importance of using multiple microfossil for more accurate dating and correlation between basins.

Holocene Ostracoda (Crustacea) from the shallow Lake Vrana (Dalmatia, Croatia) and their paleoenvironmental significance

Lake Vrana in Dalmatia is a coastal karstic brackish water environment characterized by a high species richness of ostracods that evolved into their current morphologies during the Holocene. The results of this study reveal five ostracod zones within an 11 m sediment core taken from the central part of the lake. This sedimentary sequence reveals significant changes in both depositional and environmental conditions at local and regional scales; the oldest freshwater deposits, interpreted as the Late Pleistocene/Holocene transition, mainly comprise the species Candona neglecta, Juxilyocypris cf. schwarzbachi, Hungarocypris madaraszi, Darwinula stevensoni, and Mixtacandona sp. Although the lake had not formed at this time, it is well known that the living environment of most ostracod species is connected to flooded plains, marshes, rivers, springs, and interstitial waters. In the deepest and oldest sediments within the core, from depths between 1101 cm and 945 cm, the presence of C. neglecta and J. cf. schwarzbachi are indicative of cold water, while the dominant taxa at depths between 945 cm and 874 cm are the brackish species Cyprideis torosa and C. angulata, possibly suggesting the influence of seawater because of the presence of a permeable karstic ridge that separates the lake from the ocean. In contrast, the dominant ostracod taxa at depths between 874 cm and 813 cm are species typical of freshwater environments subject to colder climatic conditions indicating a marshy, low-energy wetland. We know that the first permanent freshwater body formed at about 8130 cal yr BP (a depth of 813 cm), while large proportions of Pseudocandona marchica, Heterocypris salina, D. stevensoni, and Metacypris cordata are all indicative of warmer, shallow waters that are rich in vegetation and have variable water level. Similarly, from 5240 cal yr BP onwards, a marine influence within the core is evidenced by the presence of Cy. torosa, while present lake water conditions (i.e., alternating seasonal changes in salinity from freshwater to brackish) were established by 2750 cal yr BP. The ostracod assemblages in sediments from Lake Vrana in Dalmatia have significant potential for reconstructing the evolution of this lake as well as for understanding environmental changes and rising sea level.

Detailed biostratigraphic scales as based on the palaeobiogenetical approach (an example of the Upper Bajocian – Lower Bathonian ostracod scale of the Russian Platform)

Two new species of ostracods of the family Progonocytheridae Sylvester-Bradley Camptocythere (C.) lateres Tesakova et Shurupova, sp. nov. and C. (C.) angustius Tesakova et Shurupova, sp. nov. from the Michalskii and Besnosovi ammonite zones (Upper Bajocian – Lower Bathonian, Middle Jurassic) of the Sokur section (Saratov) are described. The changes in ontogenesis in the phylogeny of Camptocythere (C.) lateres Tesakova et Shurupova in the stratigraphical interval corresponding to the Palaeocytheridea kalandadzei ostracod Zone, and especially to the beds with C. (C.) lateres, have been studied. The levels of the change in the predominant type of sculpture (corresponding to evolutionary boundaries) are recognized in the sculpture development among the adult representatives of the species in its phylogeny. This palaeobiogenetic (heterochrony) approach allows subdivision of the beds with C. (C.) lateres into three stratigrapical intervals characterized by changes in the type of sculpture.

The distribution of Early Callovian foraminifers and ostracods in the Bartolomeevka section (Saratov region): Comparative analysis

The distribution of foraminifers in the Lower Callovian Khlebnovka Formation (Gowerianus and Elatmae ammonite Zones) of the Bartolomeevka section (Saratov region) was analyzed along with defining the Haplophragmoides infracalloviensis–Guttulina tatariensis zone that is correlated with ostracod zones and beds. The comparative analysis of the distribution of foraminifers and ostracods through the section with allowance for changes in their diversity and abundance in sediments of the Elatmae Zone revealed two transgressive–regressive cycles. The sediments of both cycles were deposited approximately at the same depths. The older and younger transgressions associated with the Arctic and Tethyan water masses, respectively. The foraminiferal assemblages demonstrate close relationshipships with bathymetry and water temperatures.

Ostracods of the genus Palaeocytheridea Mandelstam in the Middle and Upper Jurassic of Europe: 3. Stratigraphy and paleobiogeography

The analysis of distribution of endemic and cosmopolitan ostracods of the genus Palaeocytheridea shows that, in the Bajocian and Bathonian, the Tethyan and Boreal-Atlantic regions of Western and Eastern Europe developed in partial isolation, while beginning from the middle of the Lower Callovian, these parts of the European paleobasin were connected. For the Middle Jurassic of Western and Eastern Europe and, in particular, for Ukraine, the ostracod zones are recognized based on stratigraphic distribution of species of the genus Palaeocytheridea.

Biostratigraphy and lithostratigraphy of the Mid-Carboniferous boundary beds in the Muradymovo section (South Urals, Russia)

AbstractThe uninterrupted succession of the Mississippian–Pennsylvanian boundary beds in the Muradymovo section in the South Urals contains diverse fossils and has a high correlative potential. The Muradymovo section is located in the Zilair Megasynclinorium (ZM), which belongs to the West Uralian Subregion and displays carbonate-siliciclastic deep-water facies of the Bukharcha Formation, which is partly Serpukhovian (Kosogorian, Protvian and Yuldybaevian) and partly Bashkirian (Syuranian). In the southern ZM, the lower part of the formation contains argillaceous carbonates with beds of shale and siltstone, subordinate clastic limestones and limestone breccia, while the upper part is mostly limestone with cherty interbeds. In the north of the ZM, the formation mainly consists of limestone. The Muradymovo succession contains no identifiable gaps in the Mid-Carboniferous Boundary (MCB) portion and has a succession of foraminiferal, conodont, ammonoid and ostracod zones. The MCB in this section coincides with the base of the Bogdanovkian and is defined by the entry ofDeclinognathodus noduliferus.This level falls within the upper part of the foraminiferalMonotaxinoides transitoriusZone, is near the base of the ammonoidHomoceras–HudsonocerasGenozone and can be correlated worldwide.

Ordovician sediments in the southeastern Siberian Platform: lithostratigraphy and ostracod zoning

The results of studying Ordovician ostracods from the southeastern Siberian Platform are presented. Ordovician sections are described in brief from outcrop and core studies. Four of the ostracod zones distinguished in the Ordovician strata of the Siberian Platform have been found in the Volgian, Kirenskian–Kudrinoan, Chertovskayan, and Baksanian Horizons. Stratigraphic correlation takes into account the available data on the distribution of other groups (e.g., conodonts and cephalopods)..

Middle Oxfordian - Lower Kimmeridgian ostracod zones from the Mikhalenino section (Kostroma region) and their comparison with synchronous strata of the Eastern and Western Europe

Tesakova, e.M., DeMiDov, s.M., Guzhov, a.v., RoGov, M.a., kiselev, D.N. (2012): Middle Oxfordian - Lower Kimmeridgian ostracod zones from the Mikhalenino section (Kostroma region) and their comparison with synchronous strata of the Eastern and Western Europe. - N. Jb. Geol. Palaont. Abh., 266: 000-000; Stuttgart. Abstract: The study focuses on Oxfordian-Kimmeridgian ostracods from the Mikhalenino sec- tion (Kostroma region, Russia). In the Upper Oxfordian - Lower Kimmeridgian (Densiplicatum - Bauhini ammonite Zones) we distinguished ostracod zones: Sabacythere attalicata - Eucytherura costaeirregularis (Densiplicatum Zone), Eucyterura - Tethysia (Tenuiserratum to Bauhini Zone). In the lower Kimmeridgian, Kitchini ammonite Zone (Subkitchini Subzone), we identified ostracod zones Schuleridea triebeli, Neurocythere jakovlevae - Klentnicella rodewaldensis and Galliaecyth- eridea fragilis. A comparison has been made between the beds with the ostracod fauna from the Mikhalenino section and coeval strata from Western and Eastern Europe. In addition, a new species, Neurocythere jakovlevae kolpeNskaya in Tesakova et al., sp. nov., was described from the Lower Kimmeridgian, Kitchini Zone, Subkitchini Subzone.

Badenian Ostracoda from the Pokupsko area (Banovina, Croatia)

Badenian Ostracoda from the Pokupsko area (Banovina, Croatia)In this paper we present the results of the investigations on the Badenian (Middle Miocene) ostracods from the Pokupsko area. For the first time the presence of Badenian aged sediments in Croatia can be supported by the occurrence of ostracod biozonal markers. Four Badenian ostracod zones are established: Lower Badenian Biozone NO7Acanthocythereis hystrix-Bythocypris lucida, Middle Badenian Biozone NO8Eocytheropteron inflatum-Olimfalunia spinulosa, and the two Upper Badenian Biozones NO9Neomonoceratina laskarevi-Miocyprideis sarmatica elongataand NO10Carinocythereis carinata-Phlyctenophora farkasi.On the basis of the generally accepted paleoecology of selected genera, we identified the following ostracod faunas: shallow-water marine, shallow-water brackish-marine, shallow-water reef, and deep-water marine. The paleontological and trace element analyses suggest that the Pokupsko ostracod fauna lived in shallow (50 m deep), warm, and limpid waters, connected to a deeper sea and occasionally exposed to freshwater inflows.

Ostracode biostratigraphy and carbon and oxygen isotopic studies across the Paleocene/Eocene boundary in the subsurface of Jaisalmer Basin, Rajasthan, India

The ostracode fauna across the Paleocene/Eocene boundary has been studied at 5 m intervals between 690–810 m in the Ghotaru Fort Well (GTF Well-A), Jaisalmer Basin, Rajasthan. Ostracodes and foraminifera have been utilized to provide the biostratigraphic framework. Four ostracode zones designated as POS-I to POS-IV in the Late Paleocene and one zone EOS-I in the earliest Early Eocene age sediments have been recognized. Quantitative ostracode and qualitative foraminiferal data were used to interpret the paleoenvironment across the Paleocene/Eocene boundary. Occurrence of the benthic foraminiferaDiscocyclina seunesi andMiscellanea miscella at 735–740 m depth in this well suggests a latest Late Paleocene age. The frequency and diversity of ostracodes at this depth is low. The ostracodes recorded near the top of the Paleocene are:Anommatocytkere indica, Echinocythereis contexta, Phyrocythere alfuraihi andSchizocythere prolata. This ostracode assemblage along with benthic foraminifera suggests that sediments were deposited in an inner neritic environment. This is followed by an earliest Early Eocene age transgression marked by the extinction of preceding Late Paleocene ostracodes and advent of a new ostracode suite represented byAlocopocythere abstracta in the 725–730 m interval. In the 720–725 m interval, however, there is a turnover to an entirely new suite of ostracodes represented byParagrenocythere reticulospinosa, Phalcocythere sentosa, Hornibrookella avadheshi, H. jaisalmerensis, Alocopocythere abstracta, Gyrocytbere parvicarinata, Schizocythere appendiculata, Bairdoppilata kalakotensis, Uroleberis khoslai, Loxoconchella ? guhai, Cytherella jaisalmerensis andC. tawaica. This ostracode assemblage is indicative of Early Eocene age and deposition in an inner neritic environment. The Paleocene/Eocene boundary in well GTF-A is recognised on the basis of ostracodes and foraminifera at 735–740 m, which in turn coincides with an overall sea level fall attributed to global warming, and this is further corroborated by a negative carbon excursion (δ13C=−13.63) across the Paleocene/Eocene boundary.

Succession of late Pleistocene and Holocene ostracode assemblages in a transgressive environment: A study at a coastal locality of the southern Baltic Sea (Germany)

The present study documents the hydrological and coastal evolution of a southern Baltic Sea lagoon by analyzing ostracode associations. Six ostracode zones were distinguished from a 13.5 m long vibro-core in the Pudagla Lowland (NE Germany) using SPLITINF (binary divisive clustering) zonation. Sediments of a Pleistocene freshwater stage are overlain by deposits of a Preboreal brackish water environment, which are not related directly to the development of the Baltic Sea. Different boreal freshwater habitats developed in the study area until marine water protruded the Pudagla site in the course of the Littorina Transgression. A gradual succession in the species assemblage reflects the subsequent transgression. Freshwater species (i.e., Metacypris cordata, Fabaeformiscandona protzi, and Herpetocypris sp.) are substituted in pre-Littorina inland waters (ca. 7.2 14C ka BP) by halotolerant species (i.e., Candona angulata, Sarscypridopsis aculeata, and Plesiocypridopsis newtoni; ca. 6.5 14C ka BP) and finally, the ostracode fauna is dominated by Cyprideis torosa associated with Cytheromorpha fuscata and Loxoconcha elliptica when brackish–marine water conditions are established (ca. 6.4 14C ka BP).