Analyses Of Ostracods Research Articles

Paleolimnological Investigations in Coastal Sarıkum Lagoon, Sinop, Turkey

Lagoons are dynamic systems, making ecosystem management difficult. Paleolimnological approach is the only way to track past long term environmental changes and background conditions that are essential to build environmental management plans. Here, we investigated a sediment record from Sarıkum Lagoon, on the Black Sea coastal plain in North Anatolia, through a multiproxy paleolimnological approach to reveal long term environmental change and background conditions in the lake. For which, dry weight, organic and carbonate carbon, chlorophyll a (including its main diagenetic products), magnetic susceptibility and ostracod analysis were undertaken. The core was dated via radionuclide technique. At around 30 cm of the sediment record, there are abrupt transitions in all proxies, indicating a massive sediment input, a transition from transitional water to lacustrine environment, and lake’s biota also changed. Biological proxies preserved in the sediments suggest that the latest zone, after this event, is represented by lacustrine and hydrologically more isolated conditions from the Black Sea. Whatever the reason of that event (e.g. earthquake, flood), Sarıkum Lagoon has had lacustrine conditions during the last ~ 2 and half centuries following that abrupt event. This long term environmental change information should be considered while making future ecosystem management and conservation plans for the lake. (e.g. keep the lake connected with the Black Sea).

PALAEOECOLOGICAL SITUATION IN PRE-DELTA AREA OF THE NORTH CASPIAN SEA DURING THE HOLOCENE

Palaeoecoligical reconstructions of predelta area of the North Caspian Sea were based on the multidisciplinary study of the core from the Rybachya borehole containing the Holocene deposits. Geochemical, grain size, mollusk fauna, diatom and ostracod analyses were performed, and the radiocarbon dating was carried out. The structure of deposits reflects palaeogeographic events of different scales including the inception of a palaeoincision in the Lower Khvalynian deposits, accompanied by erosion of the Upper Khvalynian deposits; its development during the Mangyshlak regression and gradual filling during the multistage Holocene Neocaspian transgression. The Holocene age of the deposits filling the palaeodepression is confirmed by radiocarbon dates - 8070 ± 110 and 7020 ± 140 cal. BP. The paleontological data indicate the interchange of tranquil and dynamic water regimes and the quasicyclical change in the conditions of the water basin, from brackish to freshwater and to marine during the stage of sedimentation, corresponding to the presentday conditions on the North Caspian shelf.

Quaternary environmental evolution of the Argentinean Pampa Deprimida based on mollusc and ostracod analysis

Quaternary environmental evolution of the Argentinean Pampa Deprimida based on mollusc and ostracod analysis

Benthic ostracods (Crustacea) from the Vitória-Trindade Chain, South Atlantic Ocean, with the description of five new species.

This work is the second part of the analysis of ostracods from the Vitória-Trindade Chain ̶ consisting of four seamounts and Trindade Island-which resulted in the recording of 28 species belonging to 14 genera and eight families. Five new species of Cytherellidae, Bairdiidae, Bythocytheridae, and Xestoleberididae are described in this paper, as follows: Keijcyoidea oceanica sp. nov., Bairdoppilata vitoriensis sp. nov., Vandenboldina kyryia sp. nov., Xestoleberis acuminata sp. nov. and Xestoleberis caperata sp. nov.

Upper Devonian environments and ostracods biofacies of the Kuznetsk Basin

The volcanogenic-carbonate-terrigenous Upper Devonian complex of deposits of the margin of the Kuznetsk Basin has been studied. The results of the studying of sedimentological processes, the composition of sedimentary rocks, the specifics of the petrographic composition of impurity pyroclastic material, make it possible to reconstruct the sedimentation conditions here in the Late Devonian. The predominance as an impurity and sometimes as the main component in sedimentary rocks of andesitic fine pyroclastics with a lower value of acidic and basic volcanic components has been established. From the Late Givetian — Early Frasnian to Famenmian, an uneven increase in the content of acid pyroclastics occurs in the rocks. The studied sections relate to the vast shelf and continental slope of the Siberian paleocontinent. The western direction of the paleoslope is determined. The studied sediments belong to the slope and basin type, they are represented by fine-grained tephroid and volcanomictic sandstones, fine-detrite limestones, olistostromes and slope landslide breccias, turbidites and rarer turbidite canalites, peculiar “conglomerate limestones” (paleoseismites). The composition of pyroclastics and volcanoclastics in sedimentary rocks indicates the manifestation of andesitic volcanism synchronously with sedimentation and the existence of paleogeodynamic conditions corresponding to the active continental margin possibly of the Andean type in the Late Devonian in the studied area. Based on the data obtained as a result of quantitative calculation of the generic composition of the ostracod associations from the studied sections of the Middle (upper part) and Upper Devonian within three structural-facies subdistricts of the margin of the Kuznetsk Basin, the analysis of ostracods was carried out. The features of the biofacial distribution of ostracods allowed us to identify 10 associations and establish their matching with certain parts of the basin from the Late Givetian to the Late Famennian time. The influence of volcanism on the composition of ostracod associations is traced, the appearance of pyroclastics in rocks reduces the taxonomic diversity of ostracod associations and quantitative composition. Variations in the taxonomic composition of ostracod associations correlate well with trends in T-R cycles, the genus is Bairdia is dominant during transgression.

Ostracoda and Paleoenvironment of Holocene-Raised Beach Sediment in Skarvsnes, East Antarctica

Four sediment samples were collected from an outcrop of the Holocene-raised beach in Skarvsnes (Lützow-Holm Bay, East Antarctica) at an elevation of 0–10 m through a geomorphological survey conducted during the 46th Japanese Antarctic Research Expedition (JARE 46). These samples were used for grain size, CNS (carbon, nitrogen, and sulfur) elemental, and ostracod analyses. The 14C dating of an annelid tube collected from the same outcrop was also conducted using an accelerator mass spectrometry. The resultant age was estimated at approximately 5,800 cal. year BP. A total of 16 ostracod species belonging to 10 genera were identified for the first time from all study samples near Lake Suribachi-Ike, Lützow–Holm Bay, East Antarctica. The phytal species were found to be the most dominant, suggesting rich seagrass and/or seaweeds at that time. Autecological methods and modern analog technique of ostracod assemblages were used to estimate the paleoenvironment. The result from the modern analog technique suggested that the paleo-water depth of approximately 30 m at that time is the most probable estimation, implying the glacial-isostatic uplift of approximately 30–40 m (5.1–6.8 mm/year) until sample date.

A Holocene Sedimentary Record and the Impact of Sea-Level Rise in the Karst Lake Velo Blato and the Wetlands on Pag Island (Croatia)

Lakes in coastal lowland areas represent a critically vulnerable environment as a transitional space between freshwater and seawater environments. The paleoenvironmental reconstruction and anthropogenic impact are assessed through the lake sediment cores from Velo, Malo, and Kolanjsko Blato using multi-proxy analyses (sedimentological, mineralogical, geochemical, 137Cs and ostracod analyses, and AMS 14C radiocarbon dating). The freshwater lake Velo Blato was formed at 8100 cal yr BP due to rising groundwater levels as a consequence of sea-level rise. The brackish conditions in Lake Velo Blato started at 7100 cal yr BP, giving the index point for the sea-level curve of 7-m lower than present. Lead concentrations showed slightly increased values in the last 1800 cal yr BP, while the spike in Malo Blato lake sediments probably derived from bird hunting with lead bullets. Kolanjsko Blato sediment core archives the sediment record of the last 2050 years, which represents a shallow brackish coastal wetland under marine influence. Enrichment factors showed the accumulation of Cu, Hg, P, Pb, S, and Zn in the sediments from Kolanjsko Blato in the last 650 cal yr BP, which coincides with the high organic carbon content, and in sediments from Malo Blato after the lake’s formation (from the depth of 20 cm upwards). Anthropogenic Cu introduced into the Kolanjsko Blato sediments is the highest in the surface sample. Surficial sediments from Velo Blato are characterized by the high organic carbon, S, P, and N content, indicating high productivity and eutrophication which led to occasional anoxic conditions on the lake bottom in the last 200 years.

Sediments of Lake Malye Chany as a Late Holocene paleoecological archive in the south of West Siberia (Russia)

Abstract. The paper presents the first results of multiproxy study of the sediment core from Lake Malye Chany. This lake is a part of the biggest drainless lake in Russian Lake Chany. The Kargat and Chulym Rivers flow into Malye Chany. The lake locates in the forest-steppe near the southern border of taiga zone which makes it a promising object for reconstructions of the vegetation shifts and other ecological changes of the past periods. The sediment core was investigated by sedimentological, pollen, chironomid, diatom, ostracod analyses. Based on pollen and chironomid data were maid quantitative reconstructins of climate, vegetation cover and biodiversity. According to radiocarbon dates the upper 200 cm of the core covers the last ca. 3900 years. It was established that reconstructed time boundaries of climate, vegetation and ecological changes coincide according to various reconstruction approaches. At the beginning of its existence, Lake Malye Chany was a shallow saline lake with warm water; only after 2.4 thousand years BP the water level rose and the lake became fresh and the water colder. Then the water level and salinity changed, and only 1 thousand years BP the lake became deep again. The last 200 years recorded a slight warming of the water. Landscapes developed from very dry steppe to modern forest-steppe, about 2 thousand years ago there was a short-term cooling and spread of taiga elements. Last 200-300 years, there has been a steppification.

Paleoecological reconstruction of Lake Sargul in Holocene based on ostracod analysis

Abstract. The ostracod record from Lake Sargul infers details of two-stage development of the lake ecosystem during the Holocene.

Sedimentology of a Late Quaternary lacustrine record from the south‐eastern Carpathian Basin

ABSTRACTThe Upper Pleistocene geoarchives in the south‐eastern Carpathian Basin are represented predominantly by loess–palaeosol records. In 2015, a 10 m sediment core composed of clay‐rich lacustrine sediments was recovered by vibracoring a dry lake basin located between the Vršac Mountains (Serbia) and the Banat Sands in the south‐eastern Carpathian Basin; a location relevant for placing regional archaeological results in a palaeoenvironmental context. Here, we present results from geoelectrical prospection and a lithostratigraphic interpretation of this sequence supported by a detailed granulometric study supplemented by ostracod analysis. An age model based on luminescence dating is discussed against sedimentological proxy data and its implication for palaeoenvironmental change. The cores show a stratigraphy of lighter ochre‐coloured and darker greyish sediment, related to the deposition of clay and silt trapped in an aquatic environment. Geophysical measurements show ~20 m thick lacustrine sediments. The grain‐size distributions including the variability in fine clay are indicative of a lacustrine environment. Fine particles were brought into the depositional environments by aquatic input and settled from suspension; also, direct dust input is constrained by grain‐size results. Riverine input and aeolian dust input interplayed at the locality.

Late Quaternary Landscape Dynamics at the La Spezia Gulf (NW Italy): A Multi-Proxy Approach Reveals Environmental Variability within a Rocky Embayment

The Gulf of La Spezia (GLS) in Northwest Italy is a rocky embayment with low fluvial influence facing the Mediterranean Sea. Past landscape dynamics were investigated through a multi-proxy, facies-based analysis down to a core depth of 30 m. The integration of quantitative ostracod, foraminifera, and pollen analyses, supported by radiocarbon ages, proved to be a powerful tool to unravel the late Quaternary palaeoenvironmental evolution and its forcing factors. The complex interplay between relative sea-level (RSL), climatic changes, and geomorphological features of the embayment drove four main evolution phases. A barrier–lagoon system developed in response to the rising RSL of the Late Pleistocene (likely the Last Interglacial). The establishment of glacial conditions then promoted the development of an alluvial environment, with generalised erosion of the underlying succession and subsequent accumulation of fluvial strata. The Holocene transgression (dated ca. 9000 cal year BP) caused GLS inundation and the formation of a low-confined lagoon basin, which rapidly turned into a coastal bay from ca. 8000 cal year BP onwards. This latter environmental change occurred in response to the last Holocene stage of global sea-level acceleration, which submerged a morphological relief currently forming a drowned barrier-island complex in the embayment.

Diversity analyses of nonmarine ostracods (Crustacea, Ostracoda) in streams and lakes in Turkey

In order to compare species compositions of ostracods, 25 streams and 15 lakes were sampled in the spring, summer, and autumn seasons of 2018. A total of 26 ostracod species were found in lakes (18 spp.) and streams (12 spp.). The Shannon index (H’) and evenness values of streams were higher than in lakes in all seasons. The highest H’ values for all combined (lakes + streams) and lake data were reported in the autumn season, and in spring the highest values were in streams. According to the β-diversity (β) index values, the variability of ostracod species composition in lakes was higher than in streams, and its value was highest in spring (0.40) and lowest in summer (0.34) among all seasons for combined data. Pairwise comparison of spring and autumn displayed higher β-diversity values than other comparisons, while its value was 0.41 between lakes and streams. According to canonical correspondence analysis results, elevation had a significant (P = 0.006) effect on distribution of species. All results suggested the importance of seasonality for evaluating the biodiversity of a region rather than the number of sampling sites, and the autumn season seems to be richer than other seasons in terms of species diversity.

Holocene marginal marine ostracod successions from the Kızılırmak River delta; Implications for depositional environments and sea-level changes at the Southern Black Sea coast

Holocene delta formations are unique records of regional sea-climate interactions. The Kızılırmak Delta is the biggest and richest wetland ecosystem in the Black Sea region of Turkey. The Black Sea was uniquely affected by rising sea levels due to its disconnection from the world oceans during the last glacial period. To understand the palaeoenvironmental impact on the delta plain we analysed a 14.5-m-long sediment core using palaeoecological ostracod analyses accompanied by a palaeo-salinity reconstruction based on sieve pore analysis on the ostracod Cyprideis torosa. This study depicts the interplay of terrestrial and marine settings forming mesohaline, shallow lagoons and deltaic lakes since ca. 7.9 ka cal BP. Lagoons with α-mesohaline to polyhaline salinities and β-mesohaline to oligohaline lake environments were identified. Reconstructed palaeo-sea level estimations depict a remarkable environmental variability. The lagoon habitats at 7.9 to 7.0 and 5.3 to 4 ka cal BP were dominated by Cyprideis torosa. Marine influence led to ostracod associations with Loxoconcha spp. and Tyrrhenocythere amnicola especially between 7.9 and 7.0 ka cal BP. Riverine influence in the same period, but especially at about 7.7 ka cal BP, caused dominating Amnicythere spp. Cyprideis torosa and Candona neglecta that characterise short phases of a mesohaline deltaic lake environment at about 7.7 and 7.0 ka cal BP as well as after 4 ka cal BP. With a subsequent salinity decrease, C. neglecta and (later on) Pseudocandona marchica became dominant with an interruption by another short-term lagoonal phase that might be associated with a ‘megadrought’ between 3.7 and 3.0 ka cal BP.

Comparative analyses of non-marine ostracods (Crustacea) among water basins in Turkey

Total of 26, 22 and 32 sites in Konya, Antalya and West Mediterranean basins in Turkey, respectively, were sampled twice during 2017 to compare the non-marine ostracod diversity. A total of 1787 individuals belonging to 31 species were recorded from all basins. Of which, nine species are common among basins when Fabaeformiscandona fragilis is new for Turkey. High species diversity was found at middle elevational intervals. The highest and lowest Shannon diversity index values were recorded for both Konya (H = 2.19) and Antalya (H = 1.90) basins, respectively. The highest beta diversities values are encountered between closed the Konya and other open basins. Species and environmental variables composition among basins and elevational intervals showed significant differences (p < 0.05, ANOSIM). Of species, cosmopolitans (e.g., Candona neglecta, Ilyocypris bradyi, Psychrodromus olivaceus) provide an important contribution to the differences in diversities among basins and elevational intervals. According to Canonical Correspondence Analysis, elevation appeared to be the common influential variables in all basins. Results suggest that alpha diversity is under the control of local and regional factors when beta diversity is primarily affected by regional factor. Although cosmopolitan species are positive indicators, they seem to make a significant contribution to alpha and beta diversities of ostracods.

Ostracod Analysis of Callovian and Lower Oxfordian Deposits of the Mikhailovtsement Section (Ryazan Region): Methods and Results

Various methods of ostracod analysis with reference to paleobathymetric and paleotemperature reconstruction are considered in detail, using Callovian–Lower Oxfordian ostracod assemblages from the Mikhailovtsement reference section (Ryazan Region) as an example. Based on generalization of the data obtained by different methods, seven transgressive–regressive events are reconstructed, five of which had a pan-European scale and were accompanied by the intensified boreal effect. For the Upper Callovian of the East European Platform, ostracod index species of paleotemperatures, paleoeutrophication, and paleodepths on the upper subtidal depths are recognized for the first time.

Late Quaternary environments in the Gobi Desert of Mongolia: Vegetation, hydrological, and palaeoclimate evolution

Considerable efforts have been devoted to decipher the late Quaternary moisture and thermal evolution of arid central Asia. However, disparate interpretations still exist concerning different proxies. The spatial and temporal heterogeneities have inhibited a holistic understanding of general patterns and underlying mechanisms. To address these issues, two parallel cores (ONW I, 6.00 m; ONW II, 13.35 m) were retrieved in the Gobi Desert of Mongolia from lake Orog Nuur. Multidisciplinary investigations including geomorphological mapping, radiocarbon dating, sedimentological, palynological and ostracod analyses enabled us to gain a comprehensive dataset for vegetation development and hydrological variability over the last ~45 kyr. Higher lake levels during the Marine Isotope Stage (MIS) 3 and early MIS 2 (~35–~24 kyr) were probably caused by increased precipitation. The sharp transition of Termination I (~11 kyr) is indicated by sedimentological, palynological, and ostracod data. During the late Pleistocene, the lower area of the Orog Nuur catchment was dominated by Artemisia steppe and gradually altered to Chenopodiaceae desert steppe in the Holocene. The early Holocene is also characterized by a relatively humid environment. The humid pulses during the MIS 3 and the early Holocene were also recorded in other archives and are possibly the trait of a larger scale phenomenon in arid central Asia. Four major harsh climatic periods were documented in the core at ~43 kyr, ~36 kyr, during the global Last Glacial Maximum, and the Younger Dryas as playa phases. Reduced westerlies' moisture transport and a retreated East Asian Summer Monsoon influence probably caused those dry phases in the Gobi Desert of Mongolia.

Late quaternary lake level changes of Taro Co and neighbouring lakes, southwestern Tibetan Plateau, based on OSL dating and ostracod analysis

Abstract The Late Quaternary lake history of Taro Co and three neighbouring lakes was investigated to reconstruct local hydrological conditions and the regional moisture availability. Ostracod-based water depth and habitat reconstructions combined with OSL and radiocarbon dating are performed to better understand the Taro Co lake system evolution during the Late Quaternary. A high-stand is observed at 36.1 ka before present which represents the highest lake level since then related to a wet stage and resulting in a merging of Taro Co and its neighbouring lakes Zabuye and Lagkor Co this time. The lake level then decreased and reached its minimum around 30 ka. After c. 20 ka, the lake rose above the present day level. A minor low-stand, with colder and drier conditions, is documented at 12.5 cal. ka BP. Taro Co Zabuye and Lagkor Co formed one large lake with a corresponding high-stand during the early Holocene (11.2–9.7 cal. ka BP). After this Holocene lake level maximum, all three lakes shrank, probably related to drier conditions, and Lagkor Co became separated from the Taro Co-Zabuye system at c.7 ka. Subsequently, the lake levels decreased further about 30 m and Taro Co began to separate from Zabuye Lake at around 3.5 ka. The accelerating lake-level decrease of Taro Co was interrupted by a short-term lake level rise after 2 ka BP, probably related to minor variations of the monsoonal components. A last minor high-stand occurred at about 0.8 ka before today and subsequently the lake level of Taro Co registers a slight increase in recent years.

Ostracods of the non-marine Lower Cretaceous Dabeigou Formation at Yushuxia (Luanping basin, North China): Implications for the early Jehol Biota age

The Dabeigou Formation in the Luanping basin in northern China is well known for its continuous non-marine Lower Cretaceous deposits and the preservation of the early Jehol Biota, including abundant ostracods. However, the age of the Dabeigou Formation is still disputed. Here, we present a detailed lithostratigraphic analysis and ostracod biostratigraphy of the newly exposed Yushuxia section of the Luanping basin. At this locality, the Dabeigou Formation can be subdivided into 46 layers, which is mainly composed of grey to dark grey fine clastics of semi-deep lake face. Ostracod analysis on samples from the Dabeigou Formation revealed 14 species of nine genera. Biostratigraphically, the ostracods of the Dabeigou Formation belong to the Luanpingella-Torinina-Eoparacypris Zone. Most of the species range from the latest Jurassic to the earliest Cretaceous. However, some species show a closer relation with ostracods from the upper Lower Cretaceous Dadianzi Formation (upper Hauterivian to Barremian), the Yixian Formation (lower Aptian) of North China, and the Purbeck–Wealden Group (uppermost Tithonian to lowermost Aptian) of Britain. Combined with the biostratigraphy of other fossils and the U-Pb age, it is suggested that the ostracod fauna of the Dabeigou Formation and the origin of early Jehol Biota might be of Early Cretaceous age entirely.

Diversity and paleoenvironmental significance of Middle Triassic ostracods (Crustacea) from northern Thailand: Pha Kan Formation (Anisian, Lampang Group)

The Pha Kan Formation that crops out at the Phra That Muang Kham section, south of Lampang city, was measured and sampled for ostracod analysis. We here report the occurrence of 29 species distributed among 14 genera. Four new species are described: Triassocypris phakanella Forel nov. sp., Leviella lampangensis Forel nov. sp., Bektasia yawella Forel nov. sp. and Hungarella poli Chitnarin nov. sp. The present data represent the first detailed report of Middle Triassic (Anisian) ostracods from the Sukhothai terrane and the first insight into diversity dynamics following the end-Permian extinction in this area. The ostracod assemblages of the Phra That Muang Kham section are discussed and document an important shift from siliciclastic to carbonate conditions, from a protected to an open marine environment, followed by a slight regressive trend up-section associated with repeated salinity fluctuations. This fauna illustrates the post-crisis recovery during the Middle Triassic and some hypothesis are issued on the distribution pathways of several taxa.

Sedimentary evolution of the Yangtze River mouth (East China Sea) over the past 19,000 years, with emphasis on the Holocene variations in coastal currents

Water mass variations in the early Yangtze estuary during the postglacial transgression have not been thoroughly studied. This research gap has hampered the understanding of riverine sediment ‘source to sink’ processes in this region. This study presents the results of integrated analyses of grain size, pollen-spore-dinocyst assemblages, benthic foraminifera and ostracods from a borehole, H5, located at the northern Yangtze mouth, to investigate the complete sedimentary history and associated variations in coastal currents since 19ka. At the core site, a fluvial floodplain developed from ca. 19–11.3ka, whereas an estuary to shelf to subaqueous delta prevailed during most of the Holocene. Based on changes in the dominant microfauna species, which mainly consist of Chinese coastal water species, two main current patterns were distinguished: one dominated by the Yellow Sea coastal current (YSCC) before ca. 7.9ka and one dominated by the Yangtze dilute water (YDW). Marked increases in open-sea saline species, including Bolivina robusta, and stratified water dinocyst species Spiniferites ramous and Spiniferites spp. were interpreted as the encroachment of the Taiwan warm current (TWWC) and the intensification of the YDW, respectively. The YDW and TWWC penetrated the area dominated by the YSCC before 7.9ka, which was likely related to intensity variations in the Kuroshio Current (KC) and Asian summer monsoon (ASM). Under maximal ASM and KC conditions, upwelling resulted from the intensified intrusion of the TWWC, as indicated by the blooming of Bolivina robusta from 7.9–6.3ka. After ca. 6ka, the YDW clearly weakened due to the decline of the ASM, yet the Yangtze plume prevailed due to the rapid seaward migration of the Yangtze mouth. Considering the dominance of the YSCC in the early Holocene, Yellow River-derived sediment likely represented a large proportion of the material delivered to the early Yangtze estuary.