Study Of Ostracods Research Articles

Ostracoda and foraminifera biostratigraphy and palaeoenvironmental evolution of the Aptian Santana Group, post-rift of the Araripe Basin, Brazil

The Santana Group, consisting of the Barbalha, Crato, Ipubi and Romualdo formations, records the post-rift sequence of the Gondwana break-up in the Araripe Basin. The post-rift phase of the South Atlantic rifting is dated as the Alagoas Stage, which corresponds to the ostracod biozone 011. A detailed ostracod stratigraphical distribution along the Santana Group, allowed to standardise a common ostracod for the biozone name and a code, the Pattersoncypris micropapillosa Biozone (OST-011). Four different ostracod associations were recognized establishing the subzones: Pattersoncypris cucurves (OST-011.1), Pattersoncypris cucurves-Neuquenocypris berthoui (OST-011.2), Damonella grandiensis (OST-011.3) and Pattersoncypris crepata (OST-011.4). Planktic foraminifera were also recovered in different associations, leading to identify two international biostratigraphic intervals and calibrate the ostracod subzones, the Early Aptian Leupoldina cabri Zone includes the OST-011.1 and OST-011.2 subzones, and the upper Late Aptian Hedbergella infracretacea–Microhedbergella miniglobularis composite zone correlated to the OST-011.4 subzone. Between these zones there is an interval without foraminiferal biostratigraphy resolution, the OST-011.3 subzone which is assigned to the lower Late Aptian. The palaeoenvironmental evolution of the Santana Group was reconstituted from the integrated study of ostracods, planktic and benthic foraminifera. Through the Aptian, the Araripe Basin evolved from a transitional to a marine environment, recording estuarine, fluvial to bayhead deltas, a bay coastal watershed that reached better-marine conditions under extreme aridity and the full installation of an epeiric sea flooding the area.

Holocene ostracods (Crustacea) from a whale-fall excavation site from the Chao Phraya delta, Central Thailand

Late Holocene ostracods were recovered from marine sediments of the Chao Phraya delta at a whale-fall excavation site located fifteen kilometers on land in the Am Pang Subdistrict, Ban Paew District, Samut Sakhon Province, north of the Gulf of Thailand. Thirteen species belonging to seven genera are identified. The deposition environment of the succession is for the first time characterized. The ostracod assemblages suggest that the entire succession associated with the whale-fall deposited in a shallow marine environment such as estuary, bay, inner shelf, subtidal, under less than 20 meters water-depth, in brackish to normal salinity with high mud content and turbidity, on a muddy substrate. This analysis is an important step toward the first in-depth study of ostracods associated with modern and fossil shallow-water whale-falls.

Identification and environmental background of Chara remains in the Holocene sequence of Lake Peţea (NW Romania) and the possibilities of using the results in archaeobotany

The charophyte remains play an important role in the reconstruction of the hydrological characteristics (pH, water depth, stream flow, carbonate content, isotope geochemistry-water chemistry and temperature) of the former lake habitats. This is of particular importance in environmental historical studies, since the possibilities for obtaining aquatic food resources and the techniques and tools used are fundamentally influenced by these hydrological conditions. Our gyrogonite samples were recovered from the Holocene sequence of the thermalspring fed Lake Peţea NW Romania. The presence of the recovered Chara cf. hispida Linnaeus, 1753 gyrogonites marks the emergence of an oligotrophic shallow water lake system characterized by high dissolved Ca and Mg content and relatively poor plant cover in the Early Holocene. The results of previous malacological and ostracod studies also indicate the development of a shallow water lake with a muddy substrate and water temperatures above 18°C. As a warm-water lake, the local micro-environment was also home to many exploitable tree species. The charophyte remains that we recovered were from the Mesolithic level of the lake, so we were able to provide information on the hydrology of the lake for this period. Unfortunately, there have been no detailed archaeological investigations in the area to date revealing any potentially Mesolithic remains. Thus, no information is currently available on actual human occupation from the period in question.

Ostracods from upper Yacoraite Formation (Danian), Salta Basin, Western Argentina: Taxonomy and paleoenvironmental indicators of climatic signals in lacustrine deposits

This paper presents the first study of nonmarine ostracods recovered from the Danian of the upper Yacoraite Formation (Balbuena IV sequence) Salta Basin. Six species were identified: Ilyocypris triebeli, Ilyocypris argentiniensis, Neuquenocypris (Alleniella)? sp. 1; Neuquenocypris (Alleniella)? sp. 2; Penthesilenula sp. and four indeterminate species. The ostracod fauna shows fluctuations in abundance, diversity, and preservation associated with different phases of the paleolake evolution. This distribution, clearly delineated by the depositional facies, corroborates previous geochemical analyses and high-resolution sequence stratigraphy developed for the section. In general, the most abundant occurrences of ostracods coincide with high-frequency transgressive tracts of the lake system, which form long-term wettest interval of the upper Yacoraite Formation.

Environmental evolution of the Miocene palaeolake of Venta del Moro (Valencia, Spain): a study of foraminifers, thecamoebians (Arcellinida) and ostracods

ABSTRACT The Venta del Moro site (Valencia, Spain) is especially known for its rich content in Late Miocene fossil mammals but it also holds other fossil vertebrates, invertebrates and plants. A micropalaeontological study of a 70-cm long sedimentary section carried out in the lacustrine beds of the site has yielded 2 foraminifer, 7 thecamoebian and 19 ostracod taxa (two of these last probably new species). A constrained cluster analysis allowed the recognition of three consecutive zones based on their micropalaeontological content. The variation of the microfossil assemblages closely matches lithology and reflects environmental changes in a palaeolake that was subject to a gradual drying process. Anoxic bottom conditions at the base of the sequence (Zone 1) prevented the occurrence of aerobic benthic microorganisms. Later, the appearance of ostracods and thecamoebians (Zone 2) documents the increasing oxygenation of the lake and suggests a permanent freshwater to slightly brackish lake with low temperature and stream influence. The dominance of foraminifers and the changes in the thecamoebian and ostracod assemblages in the upper part of the sequence (Zone 3) reflect more stable and oxygenised conditions and probably increasing temperature and evaporation in oligohaline temporary waters, during the final drying phase of the lake.

Ostracods from the Pingyi Basin (eastern China) and their significance for the K/Pg boundary

Abstract The Pingyi Basin is a late Mesozoic to Cenozoic fault basin in East China, containing a good record of Cretaceous to Paleogene non-marine carbonate and gypsum deposits. Abundant microfossils including gastropods, ostracods, charophytes and palynomorphs have been reported from this basin. A taxonomic study of ostracods from the Gejiazhuang section in the Pingyi Basin reveals a total of 17 species assigned to 11 genera. A further ostracod biostratigraphic correlation suggests the K/Pg boundary lies within Member 1 of the Bianqiao Formation in the Gejiazhuang section, which is supported by charophyte biostratigraphy.

New records of ostracods and ammonites from the Aalenian (mainly Concavum Zone) of the Zollernalb (Swabian Alb, SW Germany)

The lithostratigraphy and ammonite/ostracod biostratigraphy and the accompanying fauna of several sections and outcrops around the Hohenzollern (Zollernalb, SW Germany), ranging from the topmost Opalinuston Formation (uppermost Lower Aalenian) to the basal Wedelsandstein Formation (lowermost Lower Bajocian) are described and analyzed. The study of ostracods from 41 samples from the Aalenian and Lower Bajocian of the Heiligenbach, Hausterberg and Roschbach sections has yielded approximately 4,100 specimens. Significant changes in the ostracod assemblage occur at the base of the Lower Aalenian “Comptum” Subzone, at the Bradfordensis/Gigantea subzonal boundary, at the Bradfordensis/Concavum zonal boundary and at the Aalenian/Bajocian boundary (Concavum/Discites zones). A minor change occurs above the Calceola-Bank within the Concavum Zone. The following new ostracod species are described: Cytheropterina crassicostatasp. nov., Eucytherura ebertisp. nov. and Eucytherura foveolatasp. nov. In addition, 15 presumably new species are briefly described; 10 ‘incertae sedis’ taxa are figured, but left in open nomenclature. The ammonite faunas of the Inopernabank and Konglomeratbank beds (Upper Aalenian, Bradfordensis Zone, Gigantea Subzone) as well as the ammonite faunas from the Calceolabank and Rostrote Kalkbank beds (Upper Aalenian, Concavum Zone, Concavum Subzone, cavatum biohorizon) are described and correlated with those of other areas.

Some theoretical aspects of the systematic study of fossil ostracods (Arthropoda, Crustacea, Ostracoda) in the context of species problems in palaeontology

Theoretical contributions into the systematics and taxonomy of fossil ostracods conducted according to unified methodological stands have resolved some key problems of paleontology. For example, this is a problem of species and its derivatives, namely the identification of species, the estimation of the taxonomic weight of morphological characters, the determination of diagnostic characters of different taxonomic ranks, and taxa diagnoses. The unification of the terminology and the formalization of morphological description of fossil shells made it possible to estimate the taxonomic weight of morphological elements. A scheme to identify the rank of taxonomic characters (pyramid principle) has been developed. A unified terminological dictionary has been prepared to describe the morphological elements of ostracod shells in detail.

On some modern Ostracoda (Crustacea) from the Tibetan Plateau in SW China, with descriptions of three new species.

Studies of Holocene ostracods of the Tibetan Plateau have mostly centred around valves and carapaces collected from lake sediments, some at or near the substrate surface and others from short cores. Reports from habitats other than lakes are scarce, and few living species found in this region have appendages described, hindering further taxonomic and phylogenetic work. For this study collections of living ostracods were made in mostly ponds, as well as two rivers and one lake. Six species, including three previously undescribed, were recovered: Tonnacypris estonica (Järvekülg, 1960), Arctocypris edita n. sp., Cypris pubera O.F. Müller, 1776, Potamocypris variegata (Brady Norman, 1889), Ilyocypris tibeta n. sp., and Fabaeformiscandona monticulus n. sp. Specimens of Tonnacypris estonica include males, previously unknown for this species, and suggesting it is a geographical parthenogen. A revision of the fifth limb morphology of the genus Arctocypris, and a subsequent amended diagnosis of the genus are given. Based on carapace and appendage features, Eucypris mareotica (Fischer, 1855) is transferred to this genus: Arctocypris mareotica (Fischer, 1855) com. nov. There are now ca. 100 ostracod species reported from modern or subsurface sediments on the Tibetan Plateau, but only 19 of those can be confirmed as alive when collected (i.e. had appendages intact). The families Limnocytheridae and Ilyocyprididae are both relatively diverse on the plateau compared with the Palaearctic zoogeographical region generally. About one third of ostracod species reported from the Tibetan Plateau are only known from there, suggesting a potentially very high rate of endemism.

Paleoenvironmental Study of Khurmala Formation by Ostracoda in Shaqlawa and Dohuk area, Northern Iraq

A detail paleoenvironmental study of ostracods fauna to investigated the paleoenvironment of Khurmala Formation for two section Northern Iraq; the first (Hjran section) lies near Shaqlawa city, and the second (Dohuk section) lies near Dohuk city. Based on ostracods study conclude that Khurmala Formation were deposited in shelf environment, about (30 – 200) meter in depth.

Pleistocene ostracods from central and southern Greece: The marine and brackish record

Ostracods are important palaeoenvironmental tools and for this reason the study of their palaeoecology and geographic distribution must be enhanced in the frame of a unified geographic approach. The PLOSTRAC’s project (Study of Pleistocene ostracods from central and southern Greece: Digital imaging of a palaeoenvironmental tool) main aim is to study the Pleistocene ostracods deriving from sedimentary successions from central and southern Greece and provide a bibliographic database of Pleistocene ostracod-bearing sequences in the study area accompanied by SEM pictures of the identified species. This output can be used as a reference point for future studies not only in Greece but also in the Eastern Mediterranean region as well. This work presents new data from brackish and marine Pleistocene sequences in Peloponnesus, the Ionian Islands (Zakynthos and Cephalonia) and Crete. A total number of 166 taxa were identified from the processed samples. The ostracods belong mainly to the families Trachyleberididae and Hemicytheridae. The studied sedimentary sequences cover the entire Pleistocene Age and range between purely brackish to deep marine assemblages. Moreover, according to both the palaeoenvironmental interpretation of the studied sections and the published literature, across Northern Peloponnesus during the Pleistocene mostly brackish to shallow marine conditions prevailed. Moving to the south and also to the Ionian Islands and Crete deep marine palaeoenvironments were observed.

New marine data and age accuracy of the Romualdo Formation, Araripe Basin, Brazil

A combined biostratigraphic and palaeoecological study of foraminifera, ostracodes and microfacies was carried out on the Aptian in the Sítio Sobradinho section of the Araripe Basin, northeast Brazil. The analysed section represents a deepening-upward sequence with mid-ramp shoal and outer ramp to basin facies associations on a mixed siliciclastic-carbonate marine ramp. The analysed rocks are dominated by Early Cretaceous planktic foraminifera (Hedbergella aptiana, H. praelippa, H. sigali, Blesfucuiana cf. cumulus, Microhedbergella miniglobularis, Gorbachikella cf. kugleri, Pseudoguembelitria blakenosensis, Globigerinelloides clavatus, Globigerinelloides aff. aptiensis, Gubkinella sp. and Loeblichella sp.). Ostracoda fauna is composed mainly of Pattersoncypris crepata and Pattersoncypris micropapillosa. The occurrence of P. crepata associated with the Aptian planktic foraminifera demonstrates the potential of this ostracode species to date this interval. The planktic foraminifera from the upper Aptian (Microhedbergella miniglobularis Zone) of the Araripe Basin show characteristical Tethyan affinities.

О МЕЖРЕГИОНАЛЬНОЙ КОРРЕЛЯЦИИ СРЕДНЕЮРСКИХ ОТЛОЖЕНИЙ СИБИРИ И ЕВРОПЕЙСКОЙ РОССИИ ПО ОСТРАКОДАМ

The results of the study of Bajocian and Bathonian ostracodes from North of Siberia and European Russia are presented. Camptocythere scrobiculataformis JO14 Zone is considered as interregional correlation level.

PALEOENVIRONMENTAL FEATURES AND OSTRACOD INVESTIGATION OF PALEOGENE-NEOGENE SEQUENCES IN BABAESKİ- LÜLEBURGAZ- MURATLI-ÇORLU REGION (SOUTHEASTERN THRACE, TURKEY)

Aim of the study is to evaluate the Paleogene-Neogene sequences of Babaeski- Lüleburgaz- Muratlı-Çorlu (Southeastern Thrace, Turkey) region using the micropaleontological analysis on two borehole samples collected by Mineral Research and Exploration (MTA), measured sections and point samples taken from the neighborhood of Silivri, Türkmenli-Çorlu, Babaeski-Lüleburgaz, Edirne –Babaeski regions and Tekirdağ-Hayrabolu road. There the lignite sandstone, siltstone (Early Oligocene aged Danişmen Formation) and silts (Late Miocene-Pliocene aged Ergene Formation) with well-preserved ostracod fauna obtained from the the upper levels of the sequence along with some micro-Mollusca at some levels. The study results showed that lacustrine and lagoonal ostracods including marine species were generally found in the claystone, siltstone and marl of the lower and upper levels of lignite cuts in borehole. The ostracod assemblages identified in the study were compared with other ostracod studies in the Thrace Basin and other parts of Turkey as well as in the Oligocene in Paris, the Akiten Basin, Belgium. In the Early Oligocene sediments, the presence of the Tethys effect was observed in the investigated area. In addition, the ostracod species defined in the Late Miocene-Pliocene are compared with other ostracod studies carried out in the Thrace Basin and other parts of Turkey as well as in the Western and Eastern Carpathians, Caspian Basin and Baltic Sea. According to obtained fauna, the Paratethys effect was determined more than in Tethys in Late Miocene-Pliocene in the studied region.

Aalenian — Lower Bajocian (Middle Jurassic) ostracods from the Geisingen clay pit (SW Germany)

This study of ostracods from 26 samples from the Aalenian and Lower Bajocian of Geisingen (Baden-Württemberg, southern Germany) has yielded five faunal assemblages. The assemblages from the Lower Aalenian are dominated by small-sized ostracod species and are in general less diverse than those assemblages recorded from the Middle and Upper Aalenian. First order microfaunal changes occur at the base of the Lower Aalenian “Comptum” Subzone, at the Bradfordensis/Gigantea Subzonal boundary and at the Bradfordensis/Concavum Zonal boundary. A second order microfaunal change is also noted at the Aalenian/Bajocian boundary (Concavum/Discites Zones). The following new species are described: Polycope circulosa, Cardobairdia tesakovae, Cytheropterina alacostata, Cytheropterina bicuneata, Infracytheropteron bisulcatum, Procytheropteron catena, Aphelocythere dilgeri, Praeschuleridea concentrica, Pleurocythere ohmerti, Progonocythere scutula, and Kinkelinella (K.) geisingensis. 13 presumably new species of Cytherurids, 1 “Monoceratina” sp. and 1 Kinkelinella sp. as well as 6 specimens ‘incertae sedis’are figured, but left in open nomenclature. The holotype and a paratype of Polycope pelta Fischer, 1961 are figured for the first time in SEM photographs.

Diversity of marine planktonic ostracods in South China Sea: a DNA taxonomy approach

Ostracods (Crustacea, Ostracoda) are small bivalved crustaceans, contributing over 200 described species to the marine zooplankton community. They are widely distributed and are relatively abundant components of the mesozooplankton, playing an important role in the transport of organic matter to deep layers. However, identification of ostracods based on micro-morphological characters is extremely difficult and time-consuming. Previous fragmentary taxonomic studies of ostracods in the South China Sea (SCA), were based solely on morphology. Here, by analysing the mitochondrial COI gene, we explore the taxa across the SCA using molecular tools for the first time. Our results show that sequence divergence among species varies within a large range, from 12.93% to 35.82%. Sixteen of the taxonomic units recovered by DNA taxonomy agree well with morphology, but Paraconchoecia oblonga, Conchoecia magna and Halocypris brevirostris split into two clades each, each of which contains cryptic species.

Microbiostratigraphy of the Berriasian–Valanginian boundary in eastern Crimea: foraminifers, ostracods, organic-walled dinoflagellate cysts

AbstractThorough study of foraminifers, ostracods and dinoflagellate remnants from the Zavodskaya Balka and Koklyuk sections helps to characterize the detailed biostratigraphic division of the Berriasian / Valanginian boundary sequence in the Feodosiya district of eastern Crimea. The foraminifer and dinocyst associations from the lower part of the sequence are clearly comparable with common Berriasian associations throughout all Mountain Crimea. On the other hand, foraminifer, ostracod and dinocyst associations from its upper part have been recorded only in eastern Crimea. The upper foraminifer level corresponds to the boreal ammonite zones from the Tauricum-Verrucosum (Upper Berriasian-Valanginian). Most of the ostracod species are endemic. The base of the uppermost dinocyst level correlates with the Lower Valanginian Paratollia zone from north-western Europe.

SEDIMENTOLOGICAL AND PALAEOENVIRONMENTAL CHARACTER OF LAKE KORONIA SEDIMENTS

The aim of the present study is to investigate the sedimentological characteristics of Lake Koronia down to a depth of 3.5m below lake bottom. Sampling operations took advandage of a season that the lake bottom was exposed to subaerial conditions. The sedimentological analysis proved that sediments consist of mud to sandy mud, with 2 phases of very fine sand fractions. The proportion of dry organic matter contained into sediment, appears to be generally small while the rates of moisture and volatiles are relatively high. Furthermore, this study examines the distribution of ostracod populations in the sediments of the lake in relation to depth, grain size and other environmental conditions of this water body. Four ostracod species were identified: Candona neglecta, Darwinula stevensoni, Heterocypris spp. and Limnocythere inopinata. The study of freshwater ostracods provides information for the palaeoecological/palaeoenvironmental conditions during the sedimentation.

Остракоди крайових частин Борисфенської затоки Східного Паратетису в середньому сарматі

This work continues the analysis of assemblages of ostracoda from the Middle Sarmatian deposits of the Borisphen Gulf of the Eastern Paratethys. Ivanova at al. (2007), Bondar (2015) present data on the history of the study of Sarmatian ostracods, on the factual data, methods of study, and lithological and palaeontological description of the composite Sarmatian sections of the marginal parts of the Borisphen Gulf. This publication presents a palaeoecological analysis of the ostracod assemblages, which contributes to the description of the shallow-marine environment which existed in the Middle Sarmatian basin. The material studied consists mainly of benthic ostracods, closely associated with the near-bottom environment of the basin. This makes them a reliable indicator of the palaeoecological environment. Any changes of the living environment is leaded to restructuring of the entire ostracod assemblage. The main environmental factors, influencing the systematic and quantitative composition, and the domination of one taxa over others, include water depth, salinity, hydrodynamic conditions in the basin, temperature conditions, substrate type, and organic carbonate and oxygen content of the water. The reconstruction of the palaeoenvironment is based primarily on the actualistic approach, where the environmental parameters of modem communities are extrapolated to the ancient fauna with certain assumptions. A total of 16 species of ostracod, belonging to 6 genera of 6 families, were identified in the Middle Sarmatian deposits. Investigation of these ostracod assemblages included taxonomic, quantitative, taphonomic and palaeoecological analyses. The palaeoecological analysis of ostracods from the deposits of the marginal parts Middle Sarmatian sea demonstrates that the assemblages developed in the more or less favorable environments of a warm shallow basin (deep up to 20 m, temperature about 20 oC). Limited diversity of the species, abundance of certain specimens, large and heavy shells of ostracods are typical of the shallowest parts of a basin with active hydrodynamic environments (Aurila). The highest taxonomic diversity of the ostracod associations was encountered in the fairly shallow and calm environments with low sorting of substrate and weak near-bottom hydrodynamics (Loxoconcha, Leptocythere). The salinity of the basin was unstable. So there are Cyprideis torosa, Cyprinotus luminosus in the assemblages.

Ecology of Devonian ostracods: application to the Frasnian/Famennian boundary bioevent in the type region (Dinant Synclinorium, Belgium)

Three mega-assemblages and six assemblages of ostracods numbered 0 to V are recognised in the Devonian. They are indicative of lagoonal environments, semi-restricted environments and marine environments above and below fair-weather wave-base or storm wave-base. The water energy, the oxygenation and the temperature of marine waters seem to be the most important factors controlling the distribution of ostracods in the Devonian. These ostracod assemblages and mega-assemblages are also recognised in the Silurian and the Carboniferous. The ecological study of ostracods in the southern border of the Dinant Synclinorium, the type region for the definition of the Frasnian and Famennian stages, proves that the Late Devonian mass extinction is related to a period of hypoxy of marine waters followed and probably linked to a regression close to their boundary. The hypoxy is marked by the occurrence of the Myodocopid Mega-Assemblage, and its acme corresponds to the splendens Zone/sigmoidale Zone boundary of the parachronology based on Entomozoid ostracods. The sea-level fall is attested by the occurrence of ostracods indicative of semi-restricted water conditions in several sections, and particularly at Sinsin where stacked valves due to very small waves related to the lap are observed. Thus, the study of ostracods shows that intrinsic factors linked to the global tectonic regime are the most important factors explaining the Late Devonian mass extinction. The Frasnian/Famennian historic boundary of Gosselet (Annales de la Societe geologique du Nord, 4, 303–320, 1877) corresponding to the recovery of the mega-fauna after the acme of this mass extinction marks in reality the return to true marine water conditions after the semi-restricted marine episode. The Matagne Fm, the Senzeille Fm and the position of the F/F boundary in the Synclinorium of Dinant are discussed.