Analyses Of Ostracods Research Articles

Elsterian‐Holsteinian deposits at Kås Hoved, northern Denmark: sediments, foraminifera, ostracods, and stable isotopes

The coastal cliff section at Kås Hoved in northern Denmark represents one of the largest exposures of marine interglacial deposits in Europe. High‐resolution analyses of sediments, foraminifera, ostracods, and stable isotopes (oxygen and carbon) in glacial‐interglacial marine sediments from this section, as well as from two adjacent boreholes, are the basis for an interpretation of marine environmental and climatic change through the Late Elsterian‐Holsteinian glacial‐interglacial cycle. The overlying glacial deposits show two ice advances during the Saalian and Weichselian glaciations. The assemblages in the initial glacier‐proximal part of the marine Late Elsterian succession reveal fluctuations in the inflow of sediment‐loaded meltwater to the area. This is followed by faunal indication of glacier‐distal, open marine conditions, coinciding with a gradual climatic change from arctic to subarctic environments. Continuous marine sedimentation during the glacial‐interglacial transition is presumably a result of a large‐scale isostatic subsidence caused by the preceding extended Elsterian glaciation. The similarity of the climatic signature of the interglacial Holsteinian and Holocene assemblages in this region indicates that the Atlantic Ocean circulation was similar during these two interglacials, whereas Eemian interglacial assemblages indicate a comparatively high water temperature associated with an enhanced North Atlantic Current. The foraminiferal zones are correlated with other Elsterian‐Holsteinian sites in Denmark, as well as those in the type area for the Holsteinian interglacial in northern Germany and the southern North Sea. Correlation of the NW European Holsteinian succession with the marine isotope stages MIS 7, 9 or 11 is still unresolved.

Ostracods of the genus Palaeocytheridea Mandelstam in the Middle and Upper Jurassic of Europe: 1. Development of ideas on the content of the genus and the results of its revision

The analysis of ostracods (Crustacea) of the genus Palaeocytheridea, widespread in the Boreal and Tethyan regions of Europe, allows establishing several correlated sequences in the Middle Jurassic of these regions, thus showing the stratigraphical significance of this genus. However M.I. Mandelstam misdescribed the hinge in carapace valves of the ostracod genus Palaeocytheridea in his characterization of the type species of P. bakirovi Mandelstam, 1947, and subsequently P.S. Lyubimova (1955) replaced the original type species by Eucythere denticulata Sharapova, 1937, thus confusing the understanding of the content of the genus Palaeocytheridea and triggering the assignment to it of more than 90 forms, belonging not only to different genera but also to different families. The revision reveals 11 valid Palaeocytheridea species, belonging to the two subgenera: Palaeocytheridea s. str. and Malzevia subgen. nov. One species, Palaeocytheridea kalandadzei sp. nov., is described as new. This paper, the first of the series of three papers dealing with ostracods of the genus Palaeocytheridea, considers the history of the development of ideas on the content of the genus, presents the results of its revision, and describes new taxa.

Stable isotope values (δ18O & δ13C) of multiple ostracode species in a large Neotropical lake as indicators of past changes in hydrology

Modern lake hydrodynamics, ostracode species autecology, stable isotopes (δ18O and δ13C) of multiple ostracode species, ostracode taphonomy and sediment geochemistry were studied to improve interpretation of the late Pleistocene–early Holocene (∼24–10 ka) stable isotope record of ostracodes in sediment core PI-6 from Lago Petén Itzá, northern Guatemala. Oxygen and carbon stable isotopes in modern and fossil species assemblages of Lago Petén Itzá were used as indicators of changes in the balance between evaporation and precipitation, past lake level and carbon source. Ostracode taphonomy was used to detect past periods of strong currents, high-energy environments, and possible partial or full mixing of the lake. The modern lake water isotopic composition displays clear seasonal differences that are independent of lake level fluctuations. Modern benthic species displayed lower δ18O and δ13C values than nektobenthic species, with differences of 3.0‰ and 5.3‰, respectively. Valves of nektobenthic species display higher values of δ13C because these ostracodes live in shallower environments among abundant algae and aquatic plants, where productivity is high. The benthic species Limnocythere opesta Brehm, 1939 displayed the smallest average offset from δ18O water (+0.3‰) and the largest offset from δ13CDIC values (−4.1‰) among studied ostracode species. Nektobenthic species Heterocypris punctata Keyser, 1975 displayed the smallest difference relative to the δ13CDIC values (−0.1‰).Late Pleistocene–early Holocene climate conditions and water levels in Lago Petén Itzá can be summarized as follows: 1) high lake levels and cold conditions (Last Glacial Maximum [LGM], ∼24–19 ka), 2) fluctuating lake levels and cold conditions (Heinrich Stadial 1 [HS1], ∼19–15 ka), 3) high lake levels and warm and wetter conditions (Bølling-Allerød [BA], ∼15–13 ka), 4) low lake levels and dry conditions (Younger Dryas [YD], ∼13–11.5 ka) and 5) high lake levels and warm and wetter conditions (early Holocene, ∼11.5–10.0 ka). Average lake level fluctuation in Lago Petén Itzá during the late Pleistocene–early Holocene was as much as ∼25 m. Ostracode analyses suggest that the LGM was characterized by relatively low δ18O (+4.7 to +6.0‰), and δ13C values (−7.1 to −6.4‰) in ostracode valves, high inferred water depths and high percentages of broken adult and juvenile valves (>66%), suggesting a high-energy environment, strong currents, partial to full mixing, downslope transport, colder water temperatures and wetter conditions. An increase in the relative abundance of the benthic species L. opesta and higher numbers of broken valves suggest heavy precipitation events during the LGM (∼23.7, 21.7, 20.8 and 20.1 ka). HS1 was predominantly dry, but we identified times when lake levels were slightly higher, at the onset of the deglacial and a brief period (∼17–16 ka) between HS1b and HS1a. All studied climate proxies indicate wetter and warmer conditions and lake system stability during the BA. Lake levels dropped during the YD and gradually increased during the Preboreal and early Holocene. We demonstrate that modern and fossil ostracode isotopic signatures, species assemblages and taphonomy can be used together with physical and geochemical variables in Lago Petén Itzá sediments to make high-resolution inferences about late Pleistocene–early Holocene environmental changes in the lowland Neotropics.

Plant landscape and environmental changes recorded in marginal marine environments: The ancient Roman harbour of Portus (Rome, Italy)

The interpretation of past environment changes in coastal marshes, river mouths and drainage channels connecting fresh to salt water bodies, is a difficult task since several factors must be considered such as the variable influence of climate, sea level changes, coastline variations and changes in the river discharge. It is even more difficult if this attempt is carried out in basins and channels of an ancient harbour, used for centuries, connected to the sea and to a river. This is the case of the ancient harbour of Rome, located in the Tiber delta area, which had a prominent role during the imperial age in the Mediterranean. A town named Portus arose in the vicinity and, although sacked many times by Barbarians, was still very important during medieval times. The Romans managed the harbour, the city and the surroundings and the impact on the environment must have been very strong.A multi-proxy approach was used to characterize and date environment and landscape changes in the ancient port of Rome area, from the 1st century to the 15th century AD. Plant macrofossil results have been integrated not only with pollen and microcharcoal, but also with the Tiber River bi-millennial record available in literature. This integration, used to improve the chronological framing of the cores, was carried out using ostracod analyses, micro-crustaceans commonly occurring in marginal marine environments and widely used for palaeoenvironmental reconstructions. In particular, the ability of some species to live within specific salinity ranges has been a precious tool to identify the hydrological setting of the depositional environment.The cores recovered allowed recognition of two different sedimentary sequences; the older shows the silting of the harbour during the first centuries, and the younger records the sedimentation that occurred between the 4th and the 15th century AD. This multi-proxy approach applied to the study of plant remains indicates that 1) the human impact was lower during the first centuries AD than during late-Antiquity and Middle Ages or that 2) clues of human presence were easier to detect in a closed marshy area than in an open harbour. The correlations between macroremains, pollen percentage and concentration, freshwater, brackish water and salt water ostracods and the frequencies of Tiber River floods during a 1500 year time span link some environmental changes and the silting of the harbour to the variations in hydrological regime of the Tiber River.

Spatio-temporal patterns of Holocene environmental change in southern Sicily

Few examples of natural forest remain near the Mediterranean coast. Therefore, it is difficult to study how coastal forests respond to climatic change or their resilience to human impact.We developed new sedimentary record of Holocene vegetation and fire history at Lago Preola, a coastal lake in southwestern Sicily (Italy). In order to verify the existence of forest at large scale on the coast, we compare pollen from Lago Preola, a medium-sized lake (33ha), to Gorgo Basso, a small lake (3ha) located nearby with the aim of separating local from extra-local vegetation dynamics through time using pollen percentages and influx. We then compare Lago Preola pollen to the record from Biviere di Gela, a large lagoon (120ha) situated 160km to the east in southern Sicily, to examine differences in vegetation dynamics between the two coastal areas during the Holocene. Lake-level reconstructions and ostracode analyses from Lago Preola provide vegetation-independent evidence of climate change, and help to disentangle human and climatic impacts on vegetation. Pollen data indicate Pistacia-dominated shrublands replaced open grasslands in the region surrounding Lago Preola by 9500calyrBP. This change coincided with rising lake levels and the development of an ostracode fauna typical of fresh waters. Evergreen forest dominated by Quercus ilex and Olea europaea started to expand by 7000calBP and consolidated at 6500calyrBP, when lake levels were near their Holocene high. Similarities between pollen from Lago Preola and Gorgo Basso demonstrate that forest was the dominant vegetation type in coastal Sicily during the middle Holocene at both regional and local scales, and even developed in the drier climatic setting around Biviere di Gela. Lake levels fell at Lago Preola after 7000calyrBP, with a strong decline accompanied by increasing salinity after 4500calyrBP. However, no transition in vegetation matched these inferred hydrological changes. Instead, forests persisted in the surrounding region until 2200calBP when human disturbance intensified. We propose that different climatic factors control lake levels and vegetation in coastal Mediterranean ecosystems. Whereas lake levels are most sensitive to the abundance of winter precipitation, coastal forests depend on spring precipitation and are limited by the length of summer drought. Moisture availability remained suitable for evergreen forests in coastal Sicily during the late Holocene, and humans, not a drier climate drove the regional forest decline.

Paleoenvironmental changes on the northeastern and southwestern Black Sea shelves during the Holocene

Four paleoceanographic events are distinguished during the Holocene based on changes in macro- and microfossil assemblages studied from three sediment cores (Ak 521, 522, 2571) from the outer northeast shelf and from core MAR02-45 situated on the southwest shelf of the Black Sea, west to the Bosphorus. The lithology and fossils were previously studied from cores Ak 521 and Ak 522 and MAR02-45. However, high resolution ostracod analyses from the AMS-14C dated core, Ak 2571, allowed for a revision of the taxonomy and paleoecological interpretation of this microfaunal group on the NE shelf. Downcore changes in the relative abundance of the polyhaline ostracods are found to be contemporaneous in all three cores from the NE shelf. As a result, centennial-millennial scale fluctuations of the bottom-water salinity are resolved in the area. A broader scale examination of paleoenvironmental changes between the NE and SW shelves is also made and the surface to bottom salinity gradient is discussed. An uncalibrated radiocarbon based chronology is used throughout this paper to facilitate comparison with the regional chronostratigraphy of marine transgression and regressions in the Black Sea. The calibrated ages corrected for the changes in reservoir age through the Holocene are also provided. The first paleoceanographic event is associated with the pulse of Mediterranean water previously established at about 9.8–9.3ka BP. This event is clearly observed in the SW region but not on the NE shelf due to a hiatus in the longest core, Ak 521. The second event is represented on both the NE and SW shelves as a replacement of brackish benthic fauna and surface phytoplankton with marine ones between 8.4 and 6.9ka BP, indicating a gradual increase in salinity. The third event is marked by opposing trends in surface and bottom-water salinity changes. On the NE shelf, bottom-water salinity rose to modern values by ∼ 6.5ka BP and then decreased within the interval ∼6.4–5.3ka BP as recorded by the ostracod assemblages. On the SW shelf, surface-water salinity reached modern values by 5.6 ka BP and remained constant until present day as inferred from the dinoflagellate cyst assemblages. The fourth event is marked by a recurring increase in bottom-water salinity to modern values indicated by the polyhaline ostracod assemblages at ∼ 5.3ka BP in the NE region, after which only minor salinity fluctuations are observed.

Lower Triassic ostracods (Crustacea) from the Meishan section, Permian–Triassic boundary GSSP (Zhejiang Province, South China)

The Permian–Triassic boundary Global Stratotype Section and Point (GSSP) is located at the Meishan section, Zhejiang Province, South China. The Yinkeng Formation and base of the Helongshan Formation, of Early Triassic Griesbachian age, have been sampled for ostracod analysis for the first time. Twenty-three species were recognized. A new species is described and figured: Bairdia cahuzaci sp. nov. The stratigraphical distributions of all 23 species are given and diversity variations are discussed.

Late Holocene palaeoenvironmental evolution of the Roman harbour of Portus, Italy

We used two sediment cores from the ancient harbour of Rome (Italy) for palaeoenvironmental reconstruction. The imperial harbour of Rome and its town, Portus, were constructed in the Tiber Delta area. Today, they are ~3 km from the coast, close to Leonardo da Vinci International Airport. The port was excavated during the reign of Emperor Claudius, inaugurated by Nero in 64 AD, and substantially enlarged under Emperor Trajan. This paper focuses on analyses of ostracods in sediment cores from the harbour and provides insights into the palaeoenvironmental evolution of the harbour water bodies. Pollen data complement this ostracod-based reconstruction, providing information about the vegetation around the port. One core (PTS13) was taken from the dock area (darsena) excavated at the time of Claudius. The second core (PTS5) was collected from the Trasverso Channel (Canale Trasverso), excavated after the port inauguration and later dredged during the fourth century AD because it had filled in with silt. Radiocarbon, archaeological and pollen data indicate the two cores overlap in time slightly, or perhaps not at all, the core from the dock site (PTS13) containing the older record. Ostracods recovered from the two sites represent very different aquatic environments, driven in one case by the Tiber River input and in the other by “marine” harbour waters. Parallel study of ostracods and pollen in the cores reveals the impact of harbour management activities, which are linked to ship hull maintenance, as well as erosion and siltation in this coastal setting.

The site of Coste San Giacomo (Early Pleistocene, central Italy): Palaeoenvironmental analysis and biochronological overview

Facies and ostracod analyses have been performed on a continental core drilled at Coste San Giacomo (Anagni, central Italy), where a middle Villafranchian faunal assemblage was first discovered in 1978. The core intercepted the palaeontological level and penetrated the underlying sedimentary succession, previously largely unknown, for a total sediment recovery of 40 m. In addition, new field surveys led to the discovery of Hippopotamus sp. remains at the faunal site, thus pre-dating the dispersal of this large ungulate into Europe to the middle Villafranchian. The new sedimentological and palaeoecological data allowed to define a palaeoenvironment mainly ascribable to an alluvial plain, characterized by a marsh evolving into a floodplain with overbank deposits and a sand-bed fluvial-channel. This scenario is supported by the reassessed Coste San Giacomo faunal assemblage, consistent with running and/or clear waters as well as prairies and grasslands, under mild climatic conditions.

Sediment penetration depths of epi- and infaunal ostracods from Lake Geneva (Switzerland)

Many (palaeo-)environmental parameters can be deduced from ecological and chemical analyses of ostracods. However, the specific ecology of each taxon has a great impact on its reaction to changing environmental conditions. As a consequence, each taxon records these changes differently. The mean penetration depth (MPD) and relative individual abundances have been documented along sediment depth profiles for the dominant sub-littoral to profundal species of ostracods in western Lake Geneva, Switzerland, and this data can be used to estimate their preferential habitat in terms of sediment depths. Isocypris beauchampi, Limnocytherina sanctipatricii, Cypria ophtalmica forma lacustris at 13-m water depths, Limnocythere inopinata, and a winter generation of Herpetocypris reptans have the shallowest habitat preferences at the study sites (MPDs of 0.45, 0.48, 0.49, 0.60, and 0.81 cm, respectively). These results suggest that these populations may be regarded as being preferentially epifaunal forms. Populations of Cytherissa lacustris (MPDs of 0.61, 0.73, and 0.82 cm at 13-, 33-, and 70-m water depths, respectively), Cypria ophtalmica forma lacustris at 70 m (MPD = 0.96 cm), Fabaeformiscandona caudata (MPD = 0.99 cm), and a summer generation of Herpetocypris reptans (MPD = 1.03 cm) were identified as being infaunal. Candona neglecta is the species that was found the deepest in the sediment of Lake Geneva, with MPDs of 0.65, 1.22, and 1.30 cm at 13-, 33-, and 70-m water depths, respectively. Information on the sediment texture and oxygen concentrations inferred from the analyses of sediment pore water suggest that the oxygen content of the sediment pore water is not the only dominant parameter controlling the differences in ostracod sediment penetration depths observed among the different sites, but that they might also be influenced by the sediment ‘softness,’ which itself depends on grain size, water content, and the abundance of organic matter in sediment.

Evidence for Badenian local sea level changes in the proximal area of the North Croatian Basin

Quantitative analysis of palynomorphs, foraminifera and ostracods enabled the recognition of biotic events and the reconstruction of environmental change in the Badenian sediments from the Vrhovčak section of Mt. Samoborsko gorje (NW Croatia). During the Middle Miocene the investigated area of Mt. Samoborska gora was located at the south-western margin of the North Croatian Basin, which represents the south-western edge of the Pannonian Basin System and the Central Paratethys Basin. This marginal position within the basin controlled the specific evolution of the depositional area during the Badenian. The occurrence of coal bearing horizons and freshwater flora and fauna in the middle part of the Vrhovčak section provide new data for the reconstruction of Badenian palaeoenvironments. A fall in sea level and the probable isolation of this area in the Badenian seems to be responsible for the appearance of a new fauna and flora.The marine sediments from the base of the Vrhovčak section may be correlated to cycle TB 2.4 of the main Badenian transgression, which affected the entire Central Paratethys area. This was followed by a regression and lowstand (Ser2), which, correlated to the middle part of the section, with freshwater sediments and coal bearing horizons. The upper part of the Vrhovčak section with marine sediments represents the Late Badenian cycle TB 2.5.

The plant landscape of the imperial harbour of Rome

The research concerns the Tiber delta area, about 3 km far from the present seacoast, where the remains of the ancient harbour of Rome are located. In 42 AD, Claudius started the construction of the harbour and Nero completed it in 64 AD. Then, the emperor Trajan went on to add a hexagonal basin to the former structure, which had gradually silted up. The imperial harbour was connected to the Tiber River and ultimately to the city of Rome through the Trajan channel. During the imperial period, most of the supplies imported from the Mediterranean provinces reached the city of Rome through Portus. This study applies detailed pollen, microcharcoal, and ostracod analyses together with radiocarbon dating to the sediments recovered from two cores drilled in the area of the Claudius harbour. The objective of the drillings was to identify morphological and environmental features of the Tiber delta dating back to the Roman period, and to characterize the landscape of the harbour. The chronological framing of the records is based on stratigraphical criteria, radiocarbon dates, historical data and on the typology of pottery fragments. Pollen, plant macroremains, and ostracod assemblages indicate that the two cores record different periods of time. The dock core shows the first phases of the harbour activities, recording first a marine and then a brackish environment. The plant landscape is typical of a coastal environment and appears rather preserved. The human presence is clear, but not of great impact. The channel core records mainly a brackish water environment and a strong human impact related to the presence of Portus, the port town. Anthropic indicators such as cultivated and synanthropic taxa as well as strong fire use/occurrence are evidence of a high human pressure increasing in the first centuries AD.

Using variations in the stable carbon isotope composition of macrophyte remains to quantify nutrient dynamics in lakes

The apparent isotope enrichment factor emacrophyte of submerged plants (emacrophyte–DIC = δ13Cmacrophyte − δ13CDIC) is indicative of dissolved inorganic carbon (DIC) supply in neutral to alkaline waters and is related to variations in aquatic productivity (Papadimitriou et al. in Limnol Oceanogr 50:1084–1095, 2005). This paper aims to evaluate the usage of emacrophyte inferred from isotopic analyses of submerged plant fossils in addition to analyses of lake carbonate as a palaeolimnological proxy for former HCO3 − concentrations. Stable carbon isotopic analysis of modern Potamogeton pectinatus leaves and its host water DIC from the Tibetan Plateau and Central Yakutia (Russia) yielded values between −23.3 and +0.4‰ and between +14.0 and +6.5‰, respectively. Values of ePotamogeton–DIC (range −15.4 to +1.1‰) from these lakes are significantly correlated with host water HCO3 − concentration (range 78–2,200 mg/l) (r = −0.86; P < 0.001), thus allowing for the development of a transfer function. Palaeo-ePotamogeton–ostracods values from Luanhaizi Lake on the NE Tibetan Plateau, as inferred from the stable carbon isotope measurement of fossil Potamogeton pectinatus seeds (range −24 to +2.8‰) and ostracods (range −7.8 to +7.5%) range between −14.8 and 1.6‰. Phases of assumed disequilibrium between δ13CDIC and δ13Costracods known to occur in charophyte swards (as indicated by the deposition of charophyte fossils) were excluded from the analysis of palaeo-e. The application of the ePotamogeton–DIC-HCO3 − transfer function yielded a median palaeo-HCO3 − -concentration of 290 mg/l. Variations in the dissolved organic carbon supply compare well with aquatic plant productivity changes and lake level variability as inferred from a multiproxy study of the same record including analyses of plant macrofossils, ostracods, carbonate and organic content.

Palaeoenvironmental reconstruction of the Sarmatian (Middle Miocene) Central Paratethys based on palaeontological and geochemical analyses of foraminifera, ostracods, gastropods and rodents

AbstractPalaeoenvironmental changes in the upper Middle Miocene Central Paratethys were reconstructed by using qualitative and quantitative palaeontological analyses of foraminifera and ostracods, coupled with trace elemental (Mg/Ca) and stable isotope (δ18O and δ13C) analyses of their carbonate skeletons and of gastropod shells. Mean annual air temperatures were estimated using the oxygen isotope composition of contemporaneous rodent teeth. The studied aquatic fossils come from two boreholes in the Zsámbék Basin (northern central Hungary), while the terrestrial ones are from localities in NE Hungary and E Romania. In the studied Sarmatian successions, three zones could be distinguished, based on palaeontological and geochemical results. At the Badenian/Sarmatian boundary, faunal diversity decreased markedly. In the lower zone a transgressive event culminated in a seawater incursion into the semi-open basin system of the Central Paratethys. Stable bottom-water temperature (~15 °C) and variable salinities (20–32 ‰) are estimated for the Early Sarmatian Sea. The faunal changes (notably a strong reduction in biodiversity) occurring at the boundary between the lower and the middle zone can be explained by a sea-level highstand with dysoxic conditions. A relative sea-level fall is documented at the end of this middle zone. After a short regressive event, a marine connection between the Paratethys and the Mediterranean was established at the beginning of the upper zone. This is indicated by an increased microfaunal diversity and the re-appearance of marine Badenian ostracods and foraminifera, which are completely absent from the older Sarmatian series. During the upper zone, the temperatures and salinities are estimated to have fluctuated from 15 °C to 21 °C and from 15 ‰ to 43 ‰, respectively.

A multi‐proxy palaeoecological and palaeoclimatic record within full glacial lacustrine deposits, western Tennessee, USA

AbstractThe Fulton Section, along the Mississippi River in western Tennessee, USA, is a 1 km continuous exposure (∼20 m vertically) of Quaternary fluvial and lacustrine deposits, inset within Eocene sediments and buried by thick loess. Fossiliferous slackwater lake sediments record maximum aggradation during the last two major glaciations, with deposition between ca. 190–140 ka and 24– 18 14C ka BP, based on amino acid and radiocarbon chronology, respectively. During the onset of full glacial conditions (ca. 24–22 14C ka BP), a relatively permanent shallow lake environment is indicated by ostracods, aquatic molluscs, and both pollen and macrofossils of aquatic plants. By 21.8 14C ka BP, increasing emergent plants, amphibious gastropods (Pomatiopsis) and heavier δ18O compositions suggest marsh‐like conditions in a periodically drying lake. The surrounding uplands consisted of Picea–Pinus woodlands mixed with cool‐temperate hardwoods (e.g. Quercus, Populus, Carya), grasses and herbs. More open conditions ensued ca. 20 14C ka BP, with loess and slopewash gradually infilling the former lake by 18 14C ka BP. Modern analogue analyses of ostracods and palaeontological evidence imply a full glacial climate similar to today's mixed‐boreal zone in central Minnesota, USA, about 9°C cooler in mean annual temperature than present‐day western Tennessee. Copyright © 2009 John Wiley &amp; Sons, Ltd.

Middle Pleistocene climate and hydrological environment at the Boxgrove hominin site (West Sussex, UK) from ostracod records

The sediments of the Slindon Formation at the junction of the Chalk South Downs and the West Sussex Coastal Plain, as revealed and studied at Boxgrove, contain evidence for early Middle Pleistocene environments in southern England around half a million years ago. The archaeological importance of the deposits is attested to by the recovery of stone and organic tools, butchered fauna and fossil hominin remains. We combine palaeoecological and geochemical analyses of ostracods from the coastal plain deposits to reconstruct the climate and environment at one period of the hominin occupation. The stratigraphy of our study area is indicative of a terrestrial environment surrounding a small lake or pond. Ostracod assemblages from the sediments indicate that the ponds were shallow but permanent, and fed by groundwater and springwater. However, the species alone cannot confirm that these ponds were completely fresh. Application of Mutual Climatic Range (MCR) techniques shows that summer temperatures were similar to present-day values and winter temperatures were probably colder, whereas mean annual air temperature was similar to present or perhaps slightly cooler. Trace-element and strontium-isotope analyses of ostracods from the sediments support the conclusion that the ponds were fed largely by fresh groundwater derived from the chalk, although there may have been a minor seawater input. The carbon-isotope ratios of the ostracod shells are consistent with a groundwater source, although they also indicate that the dissolved inorganic carbon most likely did not reach equilibrium with atmospheric carbon dioxide, suggesting that the ponds had short residence time. The combination of palaeotemperature estimates with oxygen-isotope values from ostracod shells allowed us to reconstruct the oxygen-isotope ratio of the Pond water, which was close to the value of early Middle Pleistocene precipitation at this site. Values were similar to present day, suggesting that there may have been a change in seasonality or precipitation source, since the mean air temperatures might have been lower.

The impact of fish farming and bank construction on Ostracoda in Uranouchi Bay on the Pacific coast of southwest Japan-Faunal changes between 1954 and 2002/2005

ABSTRACT Uranouchi Bay, an enclosed bay in the southern part of Shikoku Island, southwest Japan, has a complicated geography, being long and narrow with some small inlets. Since 1955, it has been influenced by organic pollution from fish farming. In the spring of 1954, many surface sediment samples were collected in the bay, and were then studied by Ishizaki (1968) to examine ostracode thanatocoenoses. Comparison with this earlier work allows us to investigate faunal changes over this approximately 50-year period. We collected surface sediment and seaweed samples in the bay for ostracode analysis in 2002 and 2005. A total of 124 species were obtained from 29 samples. Comparison between the results suggests that ostracodes have decreased in number in the inner part of the bay and increased greatly in the middle and outer parts of the bay. The number of species and the species diversity has also increased in the middle and outer parts of the bay. Mud dwellers have mostly disappeared from the inner bay and a...

Response of cultural lake eutrophication to hemp-retting in Quidenham Mere of England in post-medieval

To study the influence of human activity on natural lake, chironomid fauna change in the 700-560cm lake sediment in Quidenham Mere of England associated with chironomid inferred TP presented that the lake experienced a whole eutrophication process due to human hemp-retting in Post-Medieval based on the history record and pollen analysis, which was confirmed by mollusc and ostracod analysis. However, the response of chironomid and mollusc to retting was the strongest with ostracod a little behind. It proved that cultural eutrophication existed in history and could be recovered by itself despite of some long-term unachievable destroy. And it was most important for external nutrient to be cut off during lake restoration even in ancient times.

An experimental evaluation of cleaning methods for fossil ostracod Mg/Ca and Sr/Ca determination

To evaluate the effect of sample preparation on the trace element composition of ostracod shells, fossil shells subjected to various cleaning steps were analyzed by ICP-AES. The variations in ostracod Mg/Ca ratios reveal that fossil ostracod samples cleaned by ultrasonic methanol yield lower values than those by other methods, including increasingly rigorous reductive cleaning. In our sample sets, shell Mg/Ca decreases ∼ ∼1.5 mmol/mol during clay removal. Sample Sr/Ca results do not seem to vary significantly under the equivalent cleaning steps. For ostracod analysis, pre-treatment using multiple methanol ultrasonic cleaning is suggested to be used for gaining an appropriate result.

Paratethyan–Mediterranean connectivity in the Sea of Marmara region (NW Turkey) during the Messinian

The Sea of Marmara region is thought to have been a gateway between Paratethys and the Mediterranean since the Middle Miocene, and is therefore an important control on water mass exchange between the two realms. The Miocene successions in the northeastern Aegean and northwestern Marmara regions indicate that the first Mediterranean marine transgression to affect these areas occurred during the late Serravallian. In the northeastern Aegean region, frequent marine incursions occurred during the Tortonian and Messinian stages. The Messinian stage in this area is represented by a package of brackish- to fresh-water carbonates with some marine sandstone–siltstone interbeds (Alçıtepe Formation), which conformably overlies the Tortonian Kirazlı Formation. The Messinian sequence is overlain with an erosional contact by a shallow marine siliciclastic sequence (Göztepe Formation) of Zanclean age. With its brackish- to fresh-water carbonates and broadly constrained age, the Messinian sequence is interpreted as being coeval with the Upper Evaporite–Lago Mare sequence observed in western Mediterranean basins. In the western Marmara region, the Pontian (Messinian) Alçıtepe Formation consists of bioclastic and oolitic limestones with basal clastic rocks. It conformably overlies the fluvio-lacustrine siliciclastic sediments of the Middle to Upper Miocene Kirazlı Formation and is overlain by fluvio-lacustrine sediments of the Kimmerian (5.5–3.2 Ma) Truva and Tevfikiye formations with an erosional contact. The bioclastic limestones of the Alçıtepe Formation in the western Marmara region contain a molluscan and ostracod fauna that are endemic to Paratethys. These fauna indicate deposition in a shallow, brackish- to fresh-water environment. Faunal and paleomagnetic analyses of a section of the Alçıtepe Formation at Yenimahalle (Çanakkale) confirm that the formation is of Pontian age and represents chron C3r (6.04–5.24 Ma). The ostracod analysis indicates that during deposition of the Alçıtepe Formation, salinity increased from brackish in the lower part to more saline conditions in the upper part. Ostracod valves have low 87Sr / 86Sr values relative to coeval Late Miocene ocean water. This indicates that exchange between the Sea of Marmara region and the global ocean was restricted throughout this period. Fossil and Sr-isotope evidence suggests, however, that there was a Paratethyan–Marmara connection during the deposition of the lower part of the Alçıtepe Formation, with Paratethyan influence reaching the north Aegean. Connection via Marmara between Paratethys and the Mediterranean was not re-established until the late Aktchagylian (Late Pliocene). The re-connection was caused by both increased activity on the North Anatolian Fault and global sea level rise.