Limnic Environment Research Articles

Total organic carbon variability of lower Jurassic successions in the Mandawa Basin, SE Tanzania

Over many decades, an understanding of total organic carbon (TOC) variability in various sedimentary basins has been constrained by the availability of suitable samples for geochemical analysis. Many attempts rely on selected sidewall core or cuttings samples, which do not provide a continuous lithological record of the succession. As a result, TOC variability as a response to facies evolution is often underestimated. An advancement in TOC evaluation from well logging techniques often has permitted a continuous analysis of source rock intervals, while eliminating issues associated with obtaining discrete physical samples. Geochemical and wireline geophysical logs investigation here aimed at constraining TOC variability and depositional conditions prevailing during the early Jurassic in the Tanzanian Mandawa Basin (Mbuo, Nondwa and Mihambia Formations), which to date are poorly documented. TOC was deduced from both well cuttings samples and wire log data. Depositional conditions were defined via the use of spectral Gamma-Ray (Th/U, U) logging and lithofacies data. Sediment composition and TOC from cuttings were compared to illustrate how organic matter distribution is influenced by changes in sediment type. Complex mineral composition of heterolithic facies dominated log-response, complicated log interpretation, and thus limited the effectiveness of well logging techniques to predict TOC. Cuttings data reveal three organic-rich intervals, i) at the transition of Upper Mbuo to basal Nondwa Formation with the highest TOC of 3.5 (wt%), ii) in the Nondwa Formation with a TOC of 2 (wt%), and iii) in the Mihambia Formation with a TOC of 2.8 (wt%). An inverse linear relationship between Th/U and TOC signifies relatively shallow deposition in a well-mixed water column under oxic conditions. Intervals with higher TOC imply organic matter preservation under suboxic conditions upon two marine incursions in the Mihambia and Nondwa Formations, whereas a limnic environment prevailed at the Upper Mbuo to Nondwa transition. Inverse trends in TOC versus clastic components, a positive linear relationship between TOC and carbonates, and higher amount of clastics (>57 wt%) in the Mbuo and Mihambia Formations suggest a dominantly clastic sedimentary system with relatively stable carbonate and organic matter input in proximity to the source area. We, therefore, argue that the organic rich intervals observed in the Upper Mbuo, Nondwa and Mihambia Formations were deposited during periods of higher organic productivity driven by a rise in eustatic sea level, and coincide with a decline in terrigenous input from the hinterland.

Anthropogenic litter in freshwater environments – Study on lake beaches evaluating marine guidelines and aerial imaging

Studies on macroplastic pollution in freshwater systems are rare compared to the marine environment. Nevertheless, freshwater systems are worthy to be equally investigated as they are pathways of plastic to the ocean and lakes may act as (temporary) sinks. The aim of this study was to identify sources for plastics and influences on its distribution in a limnic environment. Anthropogenic litter (>5 mm) was monitored semi-annually over a three-year period at four sandy bank border segments of Lake Tollense in Mecklenburg-Western Pomerania, Germany. The selected beaches represent different expositions and vary in their level of anthropogenic activity. Considering all six samplings, mean abundance of anthropogenic litter is 0.2 ± 0.1 items/m2 or 130.9 ± 91.0 items/100 m beach length. The averaged mass of anthropogenic litter is 0.5 ± 1.0 g/m2 or rather 218.7 ± 284.6 g/100 m. Plastic consistently is the predominate material (72%) and cigarette butts are the most found items. A higher pollution by anthropogenic litter is found at the end of tourist season unveiling the impact of anthropogenic activity on litter abundance. Additionally, litter transport via tributaries into the lake plays a role.Testing the detection of anthropogenic litter via aerial images taken by unmanned aerial vehicles resulted in good recovery rates when minimizing the flight height. Furthermore, the analysis of anthropogenic litter distribution displayed on the images showed litter accumulation areas at the border of sandy beach areas. The deployment of marine guidelines in a freshwater environment did work well, however, small changes in the protocol are suggested for future lake beach studies dealing with anthropogenic litter pollution.

Thermal maturity and depositional palaeoenvironments of the Cretaceous-Palaeocene source rock Taratu Formation, Great South Basin, New Zealand

Thermal maturity and palaeodepositional environment of the Taratu Formation has been studied by evaluating its geochemical properties and organic petrographical features. Geochemical properties of the Cretaceous-Palaeocene Taratu source rock that are identified through pyrolysis indicate that this formation has excellent organic matter quality, quantity and hydrocarbon generation potential. Only the Cretaceous-aged sequence from this formation is thermally mature, with Tmax values ranging from 429 °C to 459 °C, while Palaeocene samples are found to be thermally immature. Organic matter of the Taratu Formation comprises primarily of oil and gas prone kerogen type II-III and gas prone kerogen type III, which is reflected by high HI (165.0–327.5 mg HC/g TOC) and low OI (5.00–25.7 mg CO2/g TOC) values. Tissue Preservation Index (TPI) and Gelification Index (GI) indicates that the Taratu Formation was previously deposited in a limnic environment. Further assessment of the source rock's palaeodepositional environment through correlating cross-plots of various biomarker data and evaluation of organic petrography suggests that the formation was subjected to brackish water influx.

Petrographic studies to delineate suitable coal seams for coal liquefaction and their palaeo-environmental analysis: A case study from the Ib river and Mand-Raigarh coalfields of the Mahanadi valley coalfields, India

A systematic approach has been carried out to delineate the coal seam zones from the Ib river coalfield, Odisha and the Mand-Raigarh coalfield, Chhattisgarh for the conversion of coal to oil as well as to establish the peat-forming environment of the mire and determine the depositional facies analysis of the coal seams. Zone R-I of Raniganj formation and Belpahar, Parkhani and Lajkura of Barakar formation from the Ib river coalfield and Seam nos. VII, VI, III and I of the Barakar formation from the Mand-Raigarh coalfield are identified based on their high percentage of liptinite and reactive content as well as their suitable maturity (mostly sub-bituminous rank) as potential for coal-to-oil conversion. The palaeo-depositional environment for peat formation has been constructed using the tissue preservation index and gelification index following coal facies analysis which shows that the peat formation in the Ib river coalfield took place under limnic to limno-telmatic conditions with prolonged wetness in the mire, whereas in the Mand-Raigarh coalfield, peat evolved under a clastic to an open marsh limnic environment with intermittent wet and dry spells. The microlithotype composition indicates that both the coalfields evolved under lower to upper deltaic settings.

Petrographic, palynofacies and geochemical characteristics of organic matter in the Saouef Formation (NE Tunisia): Origin, paleoenvironment, and economic significance

Saouef lignite layers and carbonaceous shales are studied in order to reconstruct the origin and depositional environment of organic matter (OM), as well as to evaluate their economic potential. The study is based on organic compositions, bulk geochemical parameters, biomarker data, and carbon isotope composition of OM (δ13C). Lignite samples, collected next to the Saouef village, were macroscopically identified as stratified matrix coal or as humic coal. Rock Eval pyrolysis and the palynofacies analysis indicate the predominance of Type-III-IV kerogen (OM). The depositional environment fluctuated between terrestrial environments with a low water table to the limnic environment. The OM is derived from higher land plant remains (e.g. wood, root, bark) from a mixed vegetation including conifers and angiosperms, and emerged macrophytes. The dominance of huminite over liptinite and intertinite maceral groups, along with the phytoclasts, confirms the woody origin of the OM. A high bacterial activity is evidenced by the abundance of hopanoids in the extractable OM as well as by the amorphous OM content. The high measured TOC values exceeding 20wt% in some samples may give an economic value of the organic layers of Saouef Formation. However, a Tmax<435°C and Rr<0.5% induce the immaturity of the samples despite the presence of expelled bitumen in one sample.

Holocene vegetation and hydroclimatic dynamics in SE Lithuania – Implications from a multi-proxy study of the Čepkeliai bog

Due to the scarcity of reliable palaeoecological and climatic proxy records from the Eastern Baltic covering the Holocene, there has been increased interest for multi-proxy studies in the region to detect local to regional environmental changes. The Čepkeliai wetland complex, SE Lithuania, provides an uninterrupted Holocene sediment sequence, which is used here to reconstruct palaeoenvironmental history in the southern part of the Eastern Baltic. High-resolution lithological (LOI, magnetic susceptibility), palaeobotanical (pollen, plant macrofossil, tree rings), isotopic (14C) and geochemical data were employed to reconstruct the peculiarities of vegetation and hydroclimate dynamics, as well as to discuss results in a local to regional context. Temporal lags of environmental reactions to Holocene climatic warming were recorded both in lithostratigraphical and biostratigraphical data, thus confirming regional significance of this phenomenon. A deep meso- to eutrophic basin – influenced by high surface runoff and surrounded by early boreal forest – existed at the site until about 11,300 cal BP. Thereafter, immigration of thermophylous taxa such as Ulmus (since 10,700–10,800 cal BP), Corylus (since 10,400–10,300 cal BP), Tilia and Quercus (after 9500 cal BP) as well as changes in the limnic environment point to an amelioration of the environmental situation, i.e. to a predominance of a warm and dry climatic regime. Instability of palaeobotanical and lithological records suggests that environmental anomalies of the Early Holocene occurred at about 11,200–11,000 cal BP, 10,600–10,300 cal BP, and 8200-7800 cal BP. These anomalies are thus contemporaneous with the pronounced climatic shifts (i.e. dry and cool intervals) known at the continental scale. An expansion of Picea was facilitated by the 8200-7800 cal BP climatic shift whereas early establishment of Alnus glutinosa suggests an onset of a wet interval (10,200 cal BP) which was previously unknown in the area. The stepwise lowering of the water table noted at about 7300–7200 and 6600–6700 cal BP, with the termination of the lake-phase and change to telmatic environment after 6100 cal BP, proves the positive reaction of the site to the dry climatic reversals of the Middle Holocene. Following the decay of the broad-leaved thermophilous forest after 4500 cal BP, a cold climatic reversal favored the formation of a diverse mosaic-like vegetation which was then replaced by homogenous Pinus-Picea vegetation after 3400 cal BP. The climatic and site-specific factors have been playing a leading role in the development of the site whereas signals of human interference remain negligible.

Mineralogical and geochemical characterization of the Saray and Pınarhisar coals, Northwest Thrace Basin, Turkey

This study investigates the mineralogical and geochemical characteristics of coals from the Saray and Pınarhisar coalfields in the Northwest Thrace Basin, using optical microscopy, scanning electron microscopy, X-ray diffraction and inductively coupled plasma mass spectrometry. The Saray and Pınarhisar coals were deposited in a limnic environment. The sulfur content of the coals ranges from 0.3 to 15.3% and high sulfur contents may originate from both seawater and volcanism. Pyritic and organic sulfur are the dominant sulfur forms (1.2% and 2.7% on average, respectively). The mineral matter of the coals consists mainly of pyrite, barite, gypsum, muscovite and kaolinite, with minor amounts of quartz, butlerite, tamarugite and rozenite. The coals are enriched in trace elements, including V (61ppm on average), Co (5.85ppm on average), Ni (79ppm on average), As (39.2ppm on average), Th (3.6ppm on average) and U (6.7ppm on average). Based on Pearson correlation coefficients, Ti, V, Cr, Fe, Co, Ni, Cu, Se, Rb, Au, Hg, Pb and Th have mainly inorganic affinities (rash-elements>+0.5) in the Pınarhisar coals; Fe, As and Au also have inorganic affinities (rash-elements≥+0.5) in the Saray coals. The element contents and correlation coefficients indicate that the Strandja Massif, the Tethyan ophiolite belt and the oldest basement sediments were included in the sediment source region for both coalfields, while the Strandja Massif was the prevailing sediment source region for Pınarhisar coalfield.

Petrography and palynology of Late Oligocene and Middle Miocene coals in the Gelibolu peninsula, NW Turkey

In this study, coal samples from two different coal zones located close to each other were examined. They occur in the Late Oligocene Osmancık and Miocene Gazhanedere formations in the Gelibolu peninsula, in the SW part of the Thrace Basin (NW Turkey). This paper focuses on the organic-petrographic composition and depositional conditions of the two coal zones by using coal petrography, including maceral ratios, and palynology. The maceral composition of the Oligocene coal samples is similar to that of the Miocene coal samples. The coal samples from both locations are characterized by a high content of huminite group macerals, ranging from 46% to 78%. The prevailing maceral from this group is gelinite (31%-65%), which is indicative of a high degree of gelification of organic matter. Relatively low contents of liptinite (not exceeding 9%) and inertinite (not exceeding 8%) were also determined. The tissue preservation of organic matter was poor. The content of mineral matter is inferred from microscopic studies and is variable but generally high, varying from 6% to 46%, similar to that of other Turkish coals; it consists mostly of quartz, calcite, clay minerals, and pyrite. This input of mineral matter is probably related to periodic inundations of swamp. The mean reflectance values of samples ranged from 0.42% to 0.50% Ro, suggesting that the rank of coal is subbituminous according to ASTM classification. Low tissue preservation index (TPI) and high gelification index values suggest that both coal zones were deposited in a limnic environment. The presence of framboidal pyrite and low TPI reflect high pH values (pH 6-7) and reducing conditions during peat deposition. Two different palynological assemblages may be distinguished based on the percentages of palynomorphs. The first assemblage including the stratigraphical marker species Dicolpopollis kockelii (Calamus) suggests the Late Oligocene. The age of the second assemblage is probably the end of Middle Miocene.

A fault controlled, newly discovered Eskişehir Alpu coal basin in Turkey, its petrographical properties and depositional environment

Recent findings suggest that Turkey contains about 15 billion tons of coal within its borders. A small proportion of it (NW part) is bituminous, but the rest is sub-bituminous and lignite coal. About 80% of the coals are utilized in power generation. The newly found coal field, Alpu Basin, contains about 1.3 billion tons of coal. The coal basin is a fault controlled and deeply buried basin which is close to the industrial areas in Turkey.In the studied area, there are two coal horizons in the Middle Miocene aged m2 unit. The average mineable coal seam thickness is approximately 13–14m. In order to determine the coalification degree, petrographic composition and depositional environment of the coals, petrographic and XRD analyses were conducted on coal samples taken from three boreholes which were drilled by MTA in the Eskişehir–Alpu Basin. According to the ASTM classification, the rank of the coals is sub-bituminous. Alpu coals contain two prominent types of maceral assemblages: either containing high amounts of funginites, macrinites, ulminite and gelinites, or high amounts of liptinites associated with detrital huminites (attrinite and densinites). The first type exhibits rather more homogeneous features, but the second has a more complex, mixed appearance with detrital macerals, intensive lineation, laminations and considerably higher pyrite contents. The Alpu coals contain montmorillonite, heulandite, α-quartz, pyrite, gypsum, kaolinite, illite, illite–montmorillonite, orthoclase and clay minerals which indicate variation in the pH conditions. The tissue preservation index (TPI) and gelification index (GI) indicate a limnic environment. The sample points are located between open marsh and clastic marsh areas on the TPI–GI diagram. This case indicates that the water table was variable during the coal formation.

Vegetation pattern and sedimentation changes in the context of the Lateglacial climatic events: Case study of Staroje Lake (Eastern Belarus)

A lake sediment core collected from the Staroje Lake, southeastern Belarus, reveals significant changes of the terrestrial and limnic environmental during the Lateglacial and Early Holocene in the periglacial zone of the Late Weichselian Glaciation. The combination of lithological (loss-on-ignition), palaeobotanical (pollen, non-pollen palynomorphs, diatoms) and isotopic (δ18O, δ13C, 14C) proxy parameters was applied for the reconstruction of the vegetation pattern and sedimentation regime. The Lateglacial pre-Interstadial (GS-2) vegetation was dominated by mineral-soil pioneers with scattered occurrence of Pinus and Betula; an Interstadial (GI-1) dominated by Pinus forest with increasing representation of open-ground species since approximately 13,500 cal BP; and Lateglacial Stadial (GS-1) with recurring opening of the vegetation pattern with scattered tree patches including those of Picea. Presence of Pinus stomata confirms the local origin of this plant since the pre-Interstadial. Starting from the Holocene, birch, later accompanied by other deciduous species (Ulmus, Alnus, Quercus, Corylus), took over in the local vegetation structure.Isotopic records (δ18O, δ13C) obtained on bulk carbonates as well as diatom data exhibit several shifts reflecting variations both in terrestrial and limnic environment. Distinct negative excursion of δ18O curve recorded during the first half of the GI-1 event suggests intensive groundwater discharge accompanied by active transportation of detrital carbon in to the basin. Limited basin productivity is also indicated by lithological and diatom records. Since approximately 13,700 cal BP, sedimentation regime in the lake stabilised and productivity of the basin started to increase in positive correlation with LOI data. A considerable decrease in δ18O values punctuated by a rapid jump in the middle of the interval was recorded during the GS-1 Stadial and could be associated with the deterioration of the environmental regime and degradation of the soil layer, increasing erosion activity alongside the rising input of detrital carbonates into the basin. The water table was low, as indicated by diatom data. Recovery of the environmental regime preceded the GS-1/Holocene boundary, as is seen in lithostratigraphical and isotopic data. During the early Holocene, stable isotopes show several episodes with altered levels suggesting instability of the environmental regime, most probably related with the global climatic alterations.

Potential of pollen and non-pollen palynomorph records from Tso Moriri (Trans-Himalaya, NW India) for reconstructing Holocene limnology and human–environmental interactions

The high-altitude lake Tso Moriri (32°55′46″N, 78°19′24″E; 4522 m a.s.l.) is situated at the margin of the Indian Summer Monsoon and westerly influences in the Trans-Himalayan region of Ladakh. Human settlements are rare and domestic and wild animals are concentrated in the alpine meadows. A set of modern surface samples and fossil pollen from a deep-water core was evaluated with focus on indicator types revealing human impact, grazing activities and lake system development during the last ca. 12 cal ka BP. The non-pollen palynomorph (NPP) record, comprising remains of limnic algae and invertebrates as well as fungal spores and charred plant tissue fragments, were examined in order to attest palaeolimnic phases and human impact, respectively. Changes in the early and middle Holocene limnic environment are mainly influenced by regional climatic conditions and glacier-fed meltwater flow in the catchment area. The NPP record indicates low lake productivity with high influx of freshwater between ca. 11.5 and 4.5 cal ka BP which is in agreement with the regional monsoon dynamics and published climate reconstructions. Geomorphologic observations suggest that during this period of enhanced precipitation the lake had a regular outflow and contributed large amounts of water to the Sutlej River, the lower reaches of which were integral part of the Indus Civilisation area. The inferred minimum freshwater input and maximum lake productivity between ca. 4.5–1.8 cal ka BP coincides with the reconstruction of greatest aridity and glaciation in the Korzong Valley, resulting in significantly reduced or even ceased outflow. We suggest that lowered lake levels and river discharge at a larger regional scale may have caused irrigation problems and harvest losses in the Indus Valley and lowlands occupied by sedentary agricultural communities. This scenario, in turn, supports the hypothesis that Mature Harappan urbanism (ca. 4.5–3.9 cal ka BP) emerged in order to facilitate storage, protection, administration, and redistribution of crop yields, and secondly, the eventual decline of the Harappan Culture (ca. 3.5–3 cal ka BP) was promoted by prolonged aridity. There is no clear evidence for human impact around Tso Moriri prior to ca. 3.7 cal ka BP, with a more distinct record since ca. 2.7 cal ka BP. This suggests that the sedimentary record from Tso Moriri primarily archives the regional climate history.

Late Pleistocene to Mid-Holocene landscape reconstruction in the western part of the Thessaloniki Plain, Greece: evidence for environmental changes, and implications for human occupation

This study presents new data from four boreholes in order to investigate the palaeoenvironmental changes and landscape configuration from the Late Pleistocene to the Mid-Holocene in the western part of the Thessaloniki plain. Palaeoenvironmental and archaeological records from northern Greece document the occurrence of significant landscape changes during the Holocene. While traces of human occupation are scarce in the western Thessaloniki plain during the transition from the Late Pleistocene (Lateglacial) to the Holocene (Mesolithic period), the climatic and environmental changes involved significant and abrupt impacts on surface processes. Recently published results indicated that palaeoenvironmental transitions in the area influenced the human occupation from the early Holocene (8000/7800 cal. BP) to recent times. However, the Late Pleistocene landscape configuration has not been clearly established. A new sequence is used for analyses of grain size, loss-on-ignition, carbonate content and rock magnetic properties. In addition, a series of 6 new AMS dates from the area provide a precise chronostratigraphy. The synthesis of the environmental proxies reveals distinct palaeoenvironmental changes within a well-constructed chronostratigraphic framework of more than 10k years, which is the longest sedimentary sequence reported for central Macedonia. The Late Pleistocene subsurface occurs at ~9 m depth and clearly indicates the presence of a large alluvial fan deposited by the Aliakmon River during the Younger Dryas (12.7k-11.7kyr BP). The abrupt transition to Early Holocene sediments reveals that a significant influx of fresh water generated a limnic sedimentary environment under detrital and human stress, from pre- to post-reforestation period in the area. Anthropogenic influence is also significantly recorded mainly by the magnetic properties of the lacustrine sediments after 9000 cal. BP. From Neolithic times to the present day, the study area was periodically occupied by a freshwater lake while palaeo-soils are clearly identified by anthropogenic activities and are dated from the Early Neolithic period.

Human-induced hydrological changes in Lake Aoki and their influences in limnic environment

The hydrological regime of Lake Aoki, central Japan has been altered when electric power plants started draining water to and from the lake since AD 1954. The use of lake water drops its level during winter and early spring and exposes the littoral sediments on the surface. In order to examine how these changes have affected the lake environment, a 23 cm long sediment core from Lake Aoki was investigated for its lithology, sedimentation rate, and total organic carbon (TOC) flux. The sediment below 10 cm was olive black silty clay, and it abruptly changed to grayish olive clayey silt above, corresponding to the timing of the hydrological perturbations (1954). The sedimentation rates were 5 mg cm-2 yr-1 and 85 mg cm-2 yr-1 before and after 1954, respectively, and the TOC content was more than eightfold higher in the post-1954 sediments. The large increase in sedimentation rate was resulted from the combine effects of high sediment load in the artificially added water and immobilization of littoral sediments during lake level lowering in early spring, whereas the elevated TOC flux was attributed to higher biological productivity stimulated by the continuous supply of additional nutrients to the lake via interbasianl mixing of water.

HAZRO DADAŞ (DİYARBAKIR) KÖMÜRLERİNİN ORGANİK JEOKİMYASAL VE PETROGRAFİK ÖZELLİKLERİ

This study was carried out in Hazro-Dadas (Diyarbakir) region which owns the only coal basin in the area. Chemical, petrographic analysis and organic geochemical evaluations of the Permian aged coals were taken into consideration. Coal quality investigation along with proximate (moisture, volatile matter, fixed carbon, ash) and elemental analyses (C, H, O, S, N) were performed and revealed. The huminite reflectances of organically abundant matter and coal levels were found to be between 0.458 and 1.141 % . This parameter complies with fluorescence colors, calorific value (average orijinal 3165 – 3432 Kcal/kg) and average T max coalification ranks. This is thought to be resulted from thin overburden and its possible low lithostatic pressure. Rock Eval analysis results show that Type II/III and III kerogen, with average Thydrocarbon generation. The coals are characterized with their abundance of huminite maceral group and gelinite maceral, with small amount of liptinite and inertinite macerals. Mineral matters of the Hazro-Dadas coals are clay, quartz and calcite minerals. HazroDadas coals is thought to have deposited in limnic environment swamps

A comprehensive molecular phylogeny of dalytyphloplanida (platyhelminthes: rhabdocoela) reveals multiple escapes from the marine environment and origins of symbiotic relationships.

In this study we elaborate the phylogeny of Dalytyphloplanida based on complete 18S rDNA (156 sequences) and partial 28S rDNA (125 sequences), using a Maximum Likelihood and a Bayesian Inference approach, in order to investigate the origin of a limnic or limnoterrestrial and of a symbiotic lifestyle in this large group of rhabditophoran flatworms. The results of our phylogenetic analyses and ancestral state reconstructions indicate that dalytyphloplanids have their origin in the marine environment and that there was one highly successful invasion of the freshwater environment, leading to a large radiation of limnic and limnoterrestrial dalytyphloplanids. This monophyletic freshwater clade, Limnotyphloplanida, comprises the taxa Dalyelliidae, Temnocephalida, and most Typhloplanidae. Temnocephalida can be considered ectosymbiotic Dalyelliidae as they are embedded within this group. Secondary returns to brackish water and marine environments occurred relatively frequently in several dalyeliid and typhloplanid taxa. Our phylogenies also show that, apart from the Limnotyphloplanida, there have been only few independent invasions of the limnic environment, and apparently these were not followed by spectacular speciation events. The distinct phylogenetic positions of the symbiotic taxa also suggest multiple origins of commensal and parasitic life strategies within Dalytyphloplanida. The previously established higher-level dalytyphloplanid clades are confirmed in our topologies, but many of the traditional families are not monophyletic. Alternative hypothesis testing constraining the monophyly of these families in the topologies and using the approximately unbiased test, also statistically rejects their monophyly.

Pliocene Non-Marine Ostracods of a Coal Basin in Southeastern Region of Turkey

The association of ostracods in the coal mining habitats of the province of Afsin–Elbistan was realized in the present study. As a result of the investigation, 37 samples from the area were analyzed and 8 taxa from 5 genera belonging to the families Darwinulidae, Candonidae and Cyprididae were recorded. Identified ostracod taxa Candona parallela pannonica Zalanyi, Candona neglecta Sars, Candona decimai Freels, Pseudocandona marchica Hartwig, Cyclocypris nitida Sieber, Vestalenula cylindrica (Straub), Heterocypris salina (Brady) and Heterocypris sp. point to a shallow, richly vegetated, limnic environment in the Pliocene time. The above-mentioned fauna indicates a warm, maybe subtropical climate because of the presence of Vestalenula. A large number of valves of Candona parallela pannonica Zalanyi within the samples signified a low sedimentation rate and thanatocoenosis, according to the key for the use of ostracods as a palaeoenvironmental indicator.

Distributions and temperature dependence of branched glycerol dialkyl glycerol tetraethers in recent lacustrine sediments from China and Nepal

[1] Glycerol dialkyl glycerol tetraether (GDGT) membrane lipids in surface sediments from 24 lakes in China and Nepal were analyzed. The result shows that branched GDGT lipids occur widely in the studied lake sediments. The different distribution of branched GDGTs between the Chinese soils from Weijers et al. (2007b) and the Chinese lake sediments indicates that the branched GDGTs in the lacustrine sediment are the mixture of allochthonous and autochthonous branched GDGTs. Our result supports the suggestion that temperature is the principal factor affecting the distribution of GDGTs. Seasonality, sources, and precipitation increase the uncertainty of the correlation between the methylation index of branched tetraethers (MBT)/cyclization ratio of branched tetraethers (CBT) proxy and the temperature. The correlations of the MBT/CBT index with mean annual air temperature (T) for the global lakes are T = 6.803 − 7.062 × CBT + 37.090 × MBT (n = 139, p < 0.0001, R2 = 0.62, and RMSE = 5.24°C); for the global lakes with pH < 8.5, T = 3.949 − 5.593 × CBT + 38.213 × MBT (n = 100, p < 0.0001, R2 = 0.73, and RMSE = 4.27°C). The significant correlation suggests that the MBT/CBT proxy might be used as a potential paleotemperature proxy in the limnic environment. The MBT/CBT proxy provides an independent way to evaluate and verify the sensitivities of the different proxies for paleotemperature reconstruction from lacustrine sediments.

A limnic ostracod fauna from the surroundings of the Central Paratethys (Late Middle Miocene/Early Late Miocene; Styrian Basin; Austria)

Aquatic biota of the marine Middle Miocene Paratethys and the Late Miocene Pannonian Lake, a long-lived lake in Central and Eastern Europe, are well known. However, knowledge of the marginal freshwater environments is still rather poor. Recently, a thin-shelled ostracod fauna was discovered in Late Sarmatian to Early Pannonian sediments of a clay pit at the northern margin of the Styrian Basin (St. Stefan, N Graz). 11 taxa are described taxonomically of which some are left in open nomenclature due to insufficient preservation: Vestalenula cylindrica (Straub, 1952), Paracandona cf. euplectella (Robertson, 1889), Candona ( Camptocypria) gratkornensis n. sp., Candona (?) sp., cf. Candonopsis arida Sieber (1905), ? Cypria sp., Cyclocypris nitida Sieber (1905), cf. Bradleystrandesia reticulata (Zaddach, 1844), Stenocypris sp., ? Cypridopsis sp., “Striate ostracod sp.”. The ostracod associations point to a shallow, sometimes richly vegetated, limnic environment. Indications of a “warm”, maybe subtropical climate are suggested by the occurrences of Vestalenula, cf. Candonopsis, ? Cypridopsis and Stenocypris. The ostracod fauna indicates a freshwater environment, detached from the marine Sarmatian Sea and respectively from the brackish Pannonian Lake and provides hereby an insight into the palaeohabitats of the surrounding wetlands.

Iron isotope variations in Holocene sediments of the Gotland Deep, Baltic Sea

Holocene sediments from the Gotland Deep basin in the Baltic Sea were investigated for their Fe isotopic composition in order to assess the impact of changes in redox conditions and a transition from freshwater to brackish water on the isotope signature of iron. The sediments display variations in δ 56Fe (differences in the 56Fe/ 54Fe ratio relative to the IRMM-14 standard) from −0.27 ± 0.09‰ to +0.21 ± 0.08‰. Samples deposited in a mainly limnic environment with oxygenated bottom water have a mean δ 56Fe of +0.08 ± 0.13‰, which is identical to the mean Fe isotopic composition of igneous rocks and oxic marine sediments. In contrast, sediments that formed in brackish water under periodically euxinic conditions display significantly lighter Fe isotope signatures with a mean δ 56Fe of −0.14 ± 0.19‰. Negative correlations of the δ 56Fe values with the Fe/Al ratio and S content of the samples suggest that the isotopically light Fe in the periodically euxinic samples is associated with reactive Fe enrichments and sulfides. This is supported by analyses of pyrite separates from this unit that have a mean Fe isotopic composition of −1.06 ± 0.20‰ for δ 56Fe. The supply of additional Fe with a light Fe isotopic signature can be explained with the shelf to basin Fe shuttle model. According to the Fe shuttle model, oxides and benthic ferrous Fe that is derived from dissimilatory iron reduction from shelves is transported and accumulated in euxinic basins. The data furthermore suggest that the euxinic water has a negative dissolved δ 56Fe value of about −1.4‰ to −0.9‰. If negative Fe isotopic signatures are characteristic for euxinic sediment formation, widespread euxinia in the past might have shifted the Fe isotopic composition of dissolved Fe in the ocean towards more positive δ 56Fe values.

Paleogeography and Quaternary terrace sediments and complexes, intermontane basins of Prebaikalia (Southeastern Siberia, Russia)

Several large lake stages, interspersed by cycles with low water levels and exposed areas with erosion are recorded in Prebaikalia depressions from the Upper Eopleistocene. Neotectonic activities were responsible for water-level changes and ingression of lake waters into river valleys. At the end of the Eopleistocene, the lake-regime was transformed, and finally replaced by a river. Two blocks of different elevation, associated with sediment aggregates of the upper (VII–IV) and low (III–I) terraces can be distinguished in the terrace complex. The upper terraces were formed in a limnic environment, and the lower terraces formed in a prevailing river environment with subordinate lacustrine conditions.