Stable Oxygen Isotope Values Research Articles

Synchronized proxy‐based temperature reconstructions reveal mid‐ to late Holocene climate oscillations in High Arctic Svalbard

ABSTRACTExisting paleoclimate data are exceedingly sparse from southern Spitsbergen, a High Arctic region predicted to experience significant environmental changes because of amplified warming. We analyzed biotic and isotopic paleolimnological proxies to reconstruct past climate from a lacustrine sediment core, with a basal age of ∼5500 a BP, in southern Spitsbergen (77°N). We used fossil Chironomidae assemblages to quantitatively reconstruct past mean July air temperatures and stable oxygen isotope values (δ18O) of these fossils to estimate changes in mean annual air temperature. These proxy records are strikingly similar and show that the coldest anomaly since the mid‐Holocene occurred between 350 and 50 cal a BP, during the ‘Little Ice Age’, whereas the warmest period in the summer temperature record occurred between 5500–5000 and ∼2000 cal a BP. Our findings indicate that the natural long‐term air temperature dynamics in our study area are most likely connected to solar minima and positive feedback mechanisms from sea‐surface temperature maxima. The results also highlight that the recent temperature increase is unprecedented in its rate with a ∼2 °C increase in the summer temperatures during the past ∼50 years.

Stable isotope geochemistry of travertines from northern Urumieh-Dokhtar volcano-plutonic belt, Iran

In Iran, almost all major travertine deposits with NW–SE trend are exposed in Urumieh-Dokhtar volcano-plutonic belt. In this study, morphology of travertine, source of CO2, and classification of travertine were investigated using geochemistry of carbon dioxide, stable carbon and oxygen isotopic analysis, SEM images and thin sections. Morphology of travertine in the study area includes mound and cascade. Stable carbon and oxygen isotope values of the north Urumieh-Dokhtar volcano-plutonic belt travertines range between 1.46 and 11.71‰ (VPDB) and − 6.08 and − 10.21‰ (VPDB), respectively. The high δ13C values suggest a contribution of CO2 liberated by thermometamorphic decarbonation besides its magmatic origin. Consequently, these travertines are classified as belonging to the thermogene category. A probable reason for the observed high carbon isotope composition in these deposits may be CO2 consumption as suggested by the presence of bacteria and diatom activities, verified by SEM images. Pisoid, crystalline crust and pebbly lithofacies were observed. The stable isotope compositions were compared to travertines around the world. Similarities in lithofacies and morphology exist between northern Urumieh-Dokhtar volcano-plutonic belt and travertines of Turkey and Spain. The Iranian travertines are located in areas with volcanic activity. Obviously, the geothermal system remained active throughout the late Quaternary to present.

Evolutionary history biases inferences of ecology and environment from \u03b413C but not \u03b418O values

Closely related taxa are, on average, more similar in terms of their physiology, morphology and ecology than distantly related ones. How this biological similarity affects geochemical signals, and their interpretations, has yet to be tested in an explicitly evolutionary framework. Here we compile and analyze planktonic foraminiferal size-specific stable carbon and oxygen isotope values (δ13C and δ18O, respectively) spanning the last 107 million years. After controlling for dominant drivers of size-δ13C and size-δ18O trends, such as geological preservation, presence of algal photosymbionts, and global environmental changes, we identify that shared evolutionary history has shaped the evolution of species-specific vital effects in δ13C, but not in δ18O. Our results lay the groundwork for using a phylogenetic approach to correct species δ13C vital effects through time, thereby reducing systematic biases in interpretations of long-term δ13C records—a key measure of holistic organismal biology and of the global carbon cycle.

Episodic deposition of Illinois Valley Peoria silt in association with Lake Michigan Lobe fluctuations during the last glacial maximum

AbstractThe chronology and cause of millennial depositional oscillations within last glacial loess of the Central Lowlands of the United States are uncertain. Here, we present a new age model that indicates the Peoria Silt along the Illinois River Valley accumulated episodically from ~28,500 to 16,000 cal yr BP, as the Lake Michigan Lobe margin fluctuated within northeastern Illinois. The age model indicates accelerated loess deposition coincident with regional glacial advances during the local last glacial maximum. A weakly developed paleosol, the Jules Geosol, represents a period of significantly slower deposition, from 23,700 to 22,000 cal yr BP. A gastropod assemblage-based reconstruction of mean July temperature shows temperatures 6–10°C cooler than modern during Peoria Silt deposition. Stable oxygen and carbon isotope values (δ18O and δ13C) of gastropod carbonate do not vary significantly across the pedostratigraphic boundary of the Jules Geosol, suggesting slower loess accumulation was a result of reduced glacial sediment supply rather than direct climatic factors. However, a decrease in δ18O values occurred between 26,000 and 24,000 cal yr BP, synchronous with the Lake Michigan Lobe’s southernmost advance. This δ18O decrease suggests a coupling of regional summer hydroclimate and ice lobe position during the late glacial period.

TUNNEL CONSTRUCTION IMPACT ON GROUNDWATER CHARACTER OVER 25 YEARS OF OBSERVATION AT MATSUMOTO TUNNEL, MATSUMOTO CITY, JAPAN

Over 25 years, approximately 11 million m3 of water inflow in the Matsumoto tunnel at thenorth of Matsumoto city was drained. Water inflow in the tunnel during tunnel construction varied from 1 to8 m3 per minute decreasing to 1 to 0.6 m3 per minute between 1993 and 1995. At present, inflow maintains arate of 0.6 m3 per minute. Currently, it remains at 0.6 T.U. (Tritium Unit) and the age of water in flowing intothe tunnel has been estimated to be over 30 years old from initial 3H concentration for surface water whichvaried from 4 to 10 T.U. As oxygen stable isotope values and HCO3- concentration of water inflow in thetunnel were uniform for 25 years, the source of water inflow in the tunnel is not thought to have changed.Roughly 14 to 39 million m3 water was still stored in rocks above the tunnel in the plateau from 10 %porosity measured by rock sample. When only 3 million m3 groundwater, less than one tenth of porositycoincided with effective porosity (0.48 %) or specific yield (0.6 to 1.2 %) was drained, groundwater leveldecreased widely. Drained water after over 25 years of tunnel construction was derived from unsaturatedsmall pore water excluding main pores or cracks. Therefore, total pore volume was used for slowgroundwater migration (flow velocity is 3 to 7 m per year). Cracks or main pores connecting with manypores were important for fast groundwater migration (flow velocity is over 100 m per year).

Can δD and δ18O stable isotopes be used to detect long-range dispersal among carabid beetles?

We studied if hydrogen (δD) and oxygen (δ18O) stable isotope values in three common carabid species in intensively managed agricultural landscapes in southernmost Sweden indicate long-range dispersal. We matched “emerging” (emergence tents) and “colonizing” (pitfall traps) individuals of three carabid species (Trechus quadristriatus, Harpalus rufipes, Pterostichus melanarius) to account for spatial and seasonal variability. There was higher dispersion of δD values among H. rufipes individuals as compared to values of the other two species, which suggests that H. rufipes individuals had the most variable spatial natal origin. The δD values were significantly lower among colonizing compared to emerging individuals in the flight capable and carnivorous species T. quadristriatus. This result suggests long-range migration of T. quadristriatus individuals from remote locations with deuterium depleted (lower δD) meteoric water. Our study provides a first effort towards understanding the δD and δ18O dynamics in epigean carabids in northern European agroecosystems. Additional research on larger (preferably continental) spatial scales and experimental trials that attempt to disentangle major unaccounted sources of variation and decoupling of δD and δ18O among carabids and other invertebrate natural enemies is urgently needed to allow a more frequent use of δD and δ18O dynamics as indicators of long-range dispersal.

A low seasonality scenario in the Mediterranean Sea during the Calabrian (Early Pleistocene) inferred from fossil Arctica islandica shells

Understanding past seasonal temperature variability in the ocean is essential to evaluate the effects of future climate change on marine ecosystems. Here, we estimate seasonal water temperature amplitudes from stable oxygen isotope (δ18Oshell) values of fossil shells of Arctica islandica (assuming δ18Owater=+0.9±0.1‰ V-SMOW). Specimens were collected from three Pleistocene successions (Emilian and Sicilian substages of the Calabrian) in Central and Southern Italy (i.e., Rome, Lecce and Sicily). Biostratigraphic analyses from Rome Quarry deposits indicate an age between 1.6 and 1.2Ma, whereas Sicily and Lecce successions are slightly more recent (between 1.1 and 0.62Ma). Prior to carbonate geochemical analysis, we checked the shells for potential diagenetic alterations (e.g., from aragonite to calcite) using confocal Raman microscopy. δ18Oshell transects indicate an annual temperature amplitude of about 3°C during the Early Pleistocene. This is in sharp contrast to reconstructions based on faunal assemblages, according to which the simultaneous occurrence of boreal and warm-water species in the Calabrian Mediterranean Sea suggests a much higher seasonality (ca. 10°C). The low seasonality and the relatively cold water (9–10°C) indicate the outcrops represent colder climatic conditions compared to modern times, and suggest the occurrence of a maximum glacial phase.

Stable isotopes and trace elements in modern ostracod shells: implications for reconstructing past environments on the Tibetan Plateau, China

Stable isotopes and trace elements in ostracod shells have been used widely in paleolimnological investigations of past lake hydrochemistry and climate because they provide insights into past water balance and solute evolution of lakes. Regional differences in lake characteristics and species-specific element fractionation, however, do not permit generalization of results from other regions or ostracod species to the southern Tibetan Plateau, in part because most common taxa from the southern Tibetan Plateau are endemic to the area. This study evaluated relations between present-day environmental conditions and the geochemical composition of modern ostracod shells from the southern Tibetan Plateau, to assess the suitability of using shell chemistry to infer hydrological conditions. We studied nine lakes and their catchments, located along a west–east transect in the south-central part of the Tibetan Plateau. Stable oxygen and carbon isotope values and trace element concentrations in recent shells from the four most abundant ostracod species (Leucocytherella sinensis, ?Leucocythere dorsotuberosa, Limnocythere inopinata, Tonnacypris gyirongensis) were measured, together with hydrochemical properties of host waters at the time of sampling. Results revealed significant between-species differences in stable isotope fractionation and trace element incorporation into shell calcite. Stable oxygen and carbon isotope values of ostracod shells were correlated significantly with the stable isotope composition of the respective water body $$ \left( {\updelta^{18} {\text{O}}_{{{\text{H}}_{ 2} {\text{O}}}} \,{\text{and }}\updelta^{13} {\text{C}}_{{{\text{H}}_{ 2} {\text{O}}}} } \right) $$ , reflecting salinity and productivity, respectively. Offsets between δ18Oshell and δ13Cshell and inorganic calcite, the latter representing isotopic equilibrium, suggest shell formation of T. gyirongensis during spring melt. L. sinensis reproduces throughout the monsoon season until September and shows several consecutive generations, and L. inopinata molts to the adult stage after the monsoon season in August/September. The influence of pore water δ13C was displayed by L. inopinata, suggesting shell calcification within the sediment. Mg/Cashell is primarily influenced by water Mg/Ca ratios and salinity and confirms the use of this shell ratio as a proxy for precipitation-evaporation balance and lake level. In addition, Sr/Ca and Ba/Ca can be used to infer changes in salinity, at least in closed-basin lakes with calcite saturation. Observed effects of water Sr/Ca and salinity on Sr/Ca incorporation are biased by the presence of aragonite precipitation in the lakes, which removes bioavailable Sr from the host water, resulting in low Sr/Cashell values. Changes in carbonate mineralogy affect the bioavailability of trace elements, a process that should be considered in paleoclimate reconstructions. Oxygen isotopes and Mg/Cashell ratios were unaffected by water temperature. Positive correlations among Fe/Ca, Mn/Ca and U/Ca in ostracod shells, and their negative correlation with δ13C, which reflects organic matter decay, show the potential to infer changes in redox conditions that can be used to reconstruct past oxygen supply to bottom waters and thus past water-circulation changes within lakes. The intensity of microbial activity, associated with organic matter decomposition, can be inferred from U/Ca ratios in ostracod shells. These findings highlight the value of fossil ostracod records in lake deposits for inferring paleoenvironmental conditions on the southern Tibetan Plateau.

The West Water Formation (Hualapai Plateau, Arizona, USA) as a calcrete-paleosol sequence, and its implications for the Paleogene-Neogene evolution of the southwestern Colorado Plateau

Analyses of stratigraphic sequences within the paleocanyons of the Hualapai Plateau, Arizona, are important because these deposits offer the only evidence for the Paleogene-Neogene geological history of the Grand Canyon area. In this paper, we focus on the origins and paleoenvironmental significance of the West Water Formation, located within the Milkweed and West Water paleocanyons on the Hualapai Plateau. We propose that the supposed “limestone unit” of the West Water Formation at and near its type section is not a limestone; rather, it is a 21m-thick valley calcrete, overprinted by a ~1–2m-thick pedogenic calcrete, and subsequently dolomitized in its upper-to-middle sections, with a superimposed 4m-thick red paleosol. We also propose that this unit is not coeval in age or origin with the Long Point limestone on the Coconino Plateau, and that the presence of a complex calcrete-dolocrete-paleosol alters previous interpretations associated with this unit. Evidence for a calcrete-paleosol origin, beyond the West Water Formation's lack of fossils, includes: its predominantly micritic calcite-palygorskite composition; its textures characteristic of valley and pedogenic calcrete deposits (as exhibited by thin section, SEM, and TEM analyses); and its association with a relatively thick overlying red paleosol that also contains abundant palygorskite. Stable carbon and oxygen isotope values from carbonate cements are also within the range expected of a near-surface calcrete. Carbonate minerals within the calcrete-dolocrete were precipitated at or near the water table in a valley setting due to evaporation and/or CO2 degassing in a semi-arid to arid environment of deposition. High 87Sr/86Sr values within the calcrete were inherited from groundwater infiltrating through Music Mountain Formation arkosic sediments, which were derived from a Precambrian source terrane to the south and southwest. No absolute ages exist for the Music Mountain Formation and West Water Formation in the Milkweed and West Water paleocanyons; these sediments could range in age from the Late Cretaceous to the latest Eocene-earliest Oligocene, and may record the Eocene-Oligocene Transition in the Grand Canyon area.

A potential groundwater aquifer for palaeoclimate reconstruction: Turonian aquifer, Tadla basin, Morocco

We undertook an environmental isotope investigation of groundwater from the Turonian Aquifer of Tadla Basin in Morocco in order to confirm that this aquifer could be a potential site for palaeoclimate reconstruction. The collected groundwater samples were examined for stable oxygen, hydrogen and carbon isotope ratio, as well as noble gases (He, Ne, Ar, Kr, Xe), 14C and 3H concentration. The measured stable oxygen and hydrogen isotope values show that the Turonian aquifer has two recharge areas, one with a heavier isotopic signature from the unconfined aquifer in the northern region (the area of Boujad), while the other is characterised by lighter isotopic composition in the north-eastern to the south-western part of the basin (to the North from Kasba Tadla). The calculated noble-gas solubility temperatures of the confined part of the aquifer are 2 °C higher than the recent mean annual air temperature (19 °C). Radiocarbon ages obtained from running different versions of Ingerson-Pearson models indicated that the recharge of this water occurred during the Holocene. We conclude that the Turonian aquifer might be a potential place for Late-Pleistocene palaeoclimate reconstruction if the research area were extended in the direct of flow path towards the western part of the basin and towards the foothills of the Phosphates Plateau.

PALAEOCLIMATIC EVOLUTION IN LOUTRA ARIDEAS CAVE (ALMOPIA SPELEOPARK, MACEDONIA, N. GREECE) BY STABLE ISOTOPIC ANALYSIS OF FOSSIL BEAR BONES AND TEETH

Carbon and oxygen stable isotope values (δ13C, δ18O) were obtained from structural carbonate in the bioapatite of bear bones (Ursus ingressus) from Loutra Arideas cave, Almopia Speleopark, Macedonia, N. Greece. Samples of Late Pleistocene bear bones were studied for palaeoclimatic reconstruction of the area. The age range of the fossil layers is from 32ka BP to a maximum of 38ka BP. Generally, the palaeoclimatic proxy is correlated with literature data for climatic variations in the area during Late Pleistocene, whereas dietary behavior was investigated taking into account possible diagenetic processes that may have affected the carbonate matrix of the bones.

Shell sclerochronology and stable isotopes of the bivalve Anomalocardia flexuosa (Linnaeus, 1767) from southern Brazil: Implications for environmental and archaeological studies

This study presents the first stable isotopic and sclerochronological calibration of the bivalve Anomalocardia flexuosa (Linnaeus, 1767) in relation to environmental variables in a subtropical coastal area of southern Brazil. We investigate incremental shell growth patterns and δ18O and δ13C values of modern specimens collected alive from the Laguna Lagoonal System (LLS). Shells of Anomalocardia flexuosa are also one of the main biological components of pre-Columbian archaeological shell mounds and middens distributed along the Brazilian coastline. We therefore selected archaeological specimens from a local late Holocene shell mound (Cabeçuda) to compare their stable carbon and oxygen isotope values with those of modern specimens. Shell growth increments, δ18O and δ13C values respond to a complex of environmental conditions, involving, for example, the effects of temperature and salinity. The isotopic information extracted from archaeological specimens from Cabeçuda shell midden in the LLS indirectly indicates that environmental conditions during the late Holocene were different from present day. In particular, intra-shell δ18O and δ13C values of archaeological shells reveal a stronger marine influence at 3ka cal BP, which is in contrast to the seasonal freshwater/seawater balance that currently prevails at the LLS.

Paleodietary analysis of the sacrificial victims from the Feathered Serpent Pyramid, Teotihuacan

The consumption of different types and quantities of food frequently serves as a practice that expresses and reinforces social distinctions among individuals within complex societies. This study explores the dietary behavior of probable sacrificial victims interred within the offering complex underlying the Feathered Serpent Pyramid as a line of evidence concerning the identities and life experiences of individuals selected for inclusion within one of Teotihuacan’s public monuments. Stable carbon, nitrogen, and oxygen isotope values from rib samples of 12 individuals within the Feathered Serpent Pyramid complex were compared with those of 14 individuals interred in residential contexts within the city. Results provide new information concerning daily subsistence at Classic period Teotihuacan (ca. A.D. 200–600) and highlight the dietary distinctiveness of individuals interred within the Feathered Serpent Pyramid as compared to the general residential population of the site, particularly in terms of the carbon isotope composition of protein sources consumed by a number of the sacrificial victims. Oxygen isotope analysis suggests that most individuals from the Feathered Serpent Pyramid resided within the local Teotihuacan area during the years immediately prior to their deaths, indicating that the unique dietary pattern seen in stable carbon isotope values cannot be attributed to nonlocal residence prior to sacrifice. Rather, these dietary differences may suggest that the group of individuals selected for interment within the Feathered Serpent Pyramid offering complex maintained a distinctive social or economic identity as compared to the rest of the Teotihuacan population during their lives.

Geochemical transect through a travertine mount: A detailed record of CO 2 -enriched fluid leakage from Late Pleistocene to present-day – Little Grand Wash fault (Utah, USA)

Abstract Active and fossil endogenic travertine mounts scattered along the Little Grand Wash fault are studied as records of Quaternary CO 2 -enriched fluid leakage. This study focusses on a particular area where a fossil mount formed in a near-surface setting by successive circulation/sealing episodes from Late Pleistocene to Mid-Holocene and where a modern surface travertine is still being formed by a CO 2 -enriched fluid source. The fossil mount is composed of horizontal and vertical veins whereby the vertical veins recorded numerous cycles of circulation/sealing/dissolution events and were used as conduits for the CO 2 -enriched fluid circulation from the depth to the surface or along sub-horizontal fractures where successive precipitation events are recorded. The modern travertine is being built at the surface by successive eruption of Crystal Geyser, an anthropic geyser active since the 1930's. δ 13 C and δ 18 O signatures and U/Th datings, ranging from 11.5 ky till present-day allows calibrating in detail the CO 2 enriched fluid leakage along a single fault segment and in a post glacial context, as last glaciations in the study area took place 15 ky ago. The dataset shows a high decrease of the oxygen stable isotope values till about 6 ky, then the variations reflect a constant range until present-day. This tends to restrain the period of local increase of the meteoric water input in the aquifer that is sourcing the CO 2 -enriched water. The fossil travertine represents a 7 ky-long record of CO 2 leakage above a natural reservoir, from Late Pleistocene to Mid-Holocene. The flux of CO 2 leakage through time and the total escaping volume have been computed and appears to be low in comparison with an anthropogenic leak provoked, for instance, by a non-sealed well.

Continuity or conquest? A multi-isotope approach to investigating identity in the Early Iron Age of the Southern Levant.

Across the Mediterranean and Near East, the transition from the Late Bronze Age (ca. 1550-1200 BC) to the Early Iron Age (ca. 1200-900 BC) was accompanied by profound cultural change. While this transformation was initially attributed to invasion or conquest, more recent, nuanced interpretations of archaeological and biological data now emphasize the decline of palatial economies, a shift away from centralized political authority, and internal social restructuring amidst rapid climate change in lieu of "collapse." Correspondingly, the hypothesis that Early Iron Age populations in Palestine represent the same ethnic group whose culture nevertheless underwent considerable change by actively adapting to internal and external forces was tested using biogeochemical data from individuals interred within an Early Iron Age tomb at the site of Tell Dothan. Human dental enamel from molars (n = 43) recovered from Tomb I at Tell Dothan was analyzed for radiogenic strontium isotope ratios and stable oxygen and carbon (VPDB) isotope values. Strontium (mean = 0.70816 ± 0.00005, 1σ) isotope ratios, as well as oxygen (mean = -2.3 ± 0.7‰, 1σ) and carbon (mean = -11.9 ± 0.5‰, 1σ) isotope values, all display little variability. The absence of non-locals at Tell Dothan indicates that population replacement does not adequately explain the sociopolitical changes observed in the archaeological record. Further, homogeneity among isotope values is indicative of a community that was not highly mobile, suggesting that decentralization and a corresponding transition to a more mobile lifestyle may not accurately reflect the adaptive strategies of all human groups during this period as a mechanism to cope with social and environmental change.

TEST APPEARANCE OF THE PLANKTONIC FORAMINIFERPULLENIATINA OBLIQUILOCULATAAS AN INDICATOR OF CALCITE DISSOLUTION IN DEEP-SEA SEDIMENTS

Deep-sea calcareous sediments are subject to dissolution that can alter the appearance and geochemistry of planktonic foraminiferal tests and faunal assemblages. Assessment of the impact of dissolution is often based on assumptions [e.g., position of a sediment sample with respect to the seawater calcite-saturation horizon (CSH)] and elaborate techniques (e.g., scanning-electron microscopy). To assess dissolution effects on calcareous sediments, we weighed and photographed tests of Pulleniatina obliquiloculata from South China Sea (SCS) sediment-surface samples spanning deposition above the CSH down to the calcite-compensation depth. Controlled by the calcite-saturation state of bottom waters (Δ[CO 3 2− ] bw ), the observed decrease in test weights by ~0.3 μg per μmol kg −1 was accompanied by decreasing Mg/Ca ratios (~0.12 mmol mol −1 per μg) and increasing stable oxygen isotope values δ 18 O; ~−0.13‰ per μg). Concomitant changes in test appearance demonstrated the potential of P. obliquiloculata to indicate distinct preservation stages. We present an economical, fast and non-destructive guideline to evaluate sediment preservation based on P. obliquiloculata appearance under a light microscope. In addition to the initial P. obilquiloculata test preservation, characterized by a smooth and shiny surface of slightly brownish-pinkish color in samples deposited in bottom waters with a Δ[CO 3 2− ] bw >21 μmol kg −1 (no dissolution), three dissolution stages can be distinguished: 1) Gentle dissolution (Δ[CO 3 2− ] bw ~10–21 μmol kg −1 , little alteration of planktonic foraminiferal Mg/Ca and δ 18 O) indicated by slightly brownish-pinkish tests with smooth and shiny surfaces only slightly damaged by fissures on top of the pores along the test’s periphery; 2) Moderate dissolution (Δ[CO 3 2− ] bw ~0–10 μmol kg −1 , clear alteration of Mg/Ca and δ 18 O) with extensive disintegration and coexistence of both slightly brownish-pinkish tests and white tests with initially smooth surfaces already decayed to small prismatic units; 3) Severe dissolution (Δ[CO 3 2− ] bw −1 , significant alteration of planktonic foraminiferal Mg/Ca and δ 18 O) indicated by only white tests showing several calcite layers, holes and broken final chambers.

Exploring Accumulation Rates of Shell Deposits Through Seasonality Data

Shell middens are often analysed as the result of short- or long-term depositional activities. In order to confidently interpret such deposits, it is necessary to have accurate estimations of shell accumulation rates, most commonly produced by radiocarbon dates. This paper introduces the application of seasonality data as a temporal measurement of short-term shell deposition. This gives access to an additional estimate of shell accumulation rates, which work on a shorter timescale than can be analysed through radiocarbon dating. We focus on shell deposits on the Farasan Islands, Saudi Arabia, which comprise over 3000 shell midden sites dating to the mid-Holocene (6500–4500 calBP). One site (JW1727) was chosen to (1) explore the potential of seasonality data to reconstruct accumulation rates, (2) analyse the intensity of exploitation and (3) assess the visibility of short-term shellfish deposits. Stable oxygen isotope values (δ18O) were obtained from the marine gastropod Conomurex fasciatus (Born 1778), representing 72 % of the shell weight of JW1727, to reconstruct season of capture. Seasonality data was grouped by their spatial distribution, which allowed successive episodes of deposition within a stratigraphic sequence to be connected. This allowed us to make an estimation of exploited shell meat of ∼200 kg over a 7-month period (∼400 shells/day). We argue that excavation methods and low resolution stratigraphic data cause imprecision in the seasonality data and the low visibility of rapidly accumulated shell deposits. Also, an increase of analysed shells per layer is key to understanding the seasonal brickwork of more middens in the future.

Stable isotopes show resource partitioning among the early Late Miocene herbivore community at Rudabánya II: Paleoenvironmental implications for the hominoid, Rudapithecus hungaricus

Examining how species use and partition resources within an environment can lead to a better understanding of community assembly and diversity. The rich early Late Miocene (early Vallesian) deposits at Rudabánya II (R. II) in northern central Hungary preserve an abundance of forest dwelling taxa, including the hominoid Rudapithecus hungaricus. Here we use the carbon and oxygen stable isotope compositions of tooth enamel carbonate from 10 genera of medium to large-bodied mammals to evaluate resource use and partitioning among the herbivore community, and to reconstruct the paleoenvironment of Rudapithecus. The range of stable carbon and oxygen isotope values (δ13CE and δ18OE) displayed by the R. II fauna indicates a variable forest environment, which included both open and closed canopy habitats. The relatively low δ13CE and δ18OE values found in all sampled taxa are consistent with high levels of precipitation and humidity. Significant differences in stable isotope values were observed among the sampled fauna, supporting the interpretation of resource specialization and partitioning. Higher δ13CE values found in Aceratherium incisivum (Rhinocerotidae), Lucentia aff. pierensis (Cervidae), Hippotherium intrans (Equidae), Tetralophodon longirostris (Gomphotheriidae), Propotamochoerus palaeochoerus and Parachleuastochoerus kretzoii (Suidae) suggest foraging in more open canopy habitats, while lower δ13CE values found in Miotragocerus sp. (Bovidae), Dorcatherium naui (Tragulidae), and Micromeryx flourensianus (Moschidae) imply a preference for more densely canopied habitats. Several of the sampled taxa yielded relatively higher δ18OE and δ13CE values indicative of fruit consumption, including the small ruminants, cervid, and bovid. The analyzed isotope values reflect a moderate degree of dietary niche overlap between taxa. An abundance of plant resources likely allowed for the coexistence of this diverse community of predominantly browsing herbivores. Within the gradient of more open to closed canopy forest, it is likely that Rudapithecus occupied dense closed canopy habitats where access to fruit was relatively continuous. The progressive fragmentation and replacement of humid forests by more open and seasonal woodlands during the late Vallesian would have had a significant influence on the extinction of this fossil ape.

Stable isotope geochemistry of pedogenic carbonates in loess-derived soils of northeastern Iran: Paleoenvironmental implications and correlation across Eurasia

Despite the occurrence of pedogenic carbonates in loess/paleosol sequences of northern and northeastern Iran, there is no information about stable isotope geochemistry of pedogenic carbonates in these regions. This paper presents the first stable isotope data on pedogenic carbonates in loess derived soils of northeastern Iran, southern Eurasian loess belt. Carbon and oxygen stable isotope values of pedogenic carbonates in different landforms were measured using mass spectrometry. Based on climatic data, there is no possibility for soil leaching and pedogenic carbonate formation under the present arid conditions. Stable oxygen and carbon isotopic data suggest two separate periods of carbonate formation. These periods are characterized by either lower or higher temperatures during post glacial than today and paleoecological conditions dominated by C3 and C4 plants, respectively. Hemispheric correlation of loess deposits based on isotopic data of pedogenic carbonates shows a strong positive correlation for the post glacial carbonates nodules of northeastern Iran and European Russia. This suggests a similar mechanism of carbonate formation and also the impact of Westerlies in these regions. We present the first quantitative isotopic data for paleoenvironment of northeastern Iran. However, more quantitative investigations about the Holocene and the last interglacial paleoenvironments of northeastern Iran are needed.

Discrepancies between the stable isotope compositions of water, macrophyte carbonates and organics, and mollusc shells in the littoral zone of a charophyte-dominated lake (Lake Lednica, Poland)

The aim of this study was to better understand the relations between carbon and oxygen stable isotope values of ambient water, mollusc shells, macrophytes and their carbonate encrustations, commonly used in palaeolimnological studies. Water, molluscs and macrophytes were sampled from the littoral zone in Lake Lednica, NW Poland. The influence of carbon species assimilated during photosynthesis and the net intensity of photosynthesis resulting from the size of charophyte species and the density of their stands were postulated to be the most important factors causing the species-specific δ13C values of charophyte thalli and encrustations. It was suggested that photosynthetic activity of charophytes affected not only the δ13C values of charophyte encrustations but also mollusc shells by changing δ13C values of DIC within charophyte stands. In addition, incorporation of metabolic carbon into the shell was proposed as the main cause of both the 13C depletion of mollusc shells relative to δ13C values of DIC and the species-specific δ13C values of shells. Mollusc shells were precipitated at the isotope equilibrium or close to the equilibrium with δ18O values of lake water. Charophyte encrustations were found to be 18O depleted due to the kinetic isotope effects during intense photosynthesis and thus fast precipitation of the calcite.