Stable Oxygen Isotope Analyses Research Articles

Triple oxygen stable isotope analysis of nitrite measured using continuous flow isotope ratio mass spectrometry

Oxygen stable isotopes (i.e., 16O, 17O, 18O) of nitrite (NO2−) are useful for investigating chemical processes and sources contributing to this important environmental contaminant and nutrient. However, it remains difficult to quantify the oxygen isotope compositions of NO2− due to the lack of internationally recognized NO2− reference materials with a well-known Δ(17O) value. Here we have adopted a combination of methodologies to develop a technique for measuring Δ(17O) of NO2− by reducing nitrate (NO3−) materials with internationally recognized Δ(17O) values to NO2− using activated cadmium catalyzed by chloride in a basic solution while conserving Δ(17O). The NO3− reference materials reduced to NO2− and sample NO2− unknowns are converted to N2O using sodium azide/acetic acid reagent and decomposed to O2 by passing through a heated gold tube and introduced into a continuous flow isotope ratio mass spectrometer for analysis at m/z 32, 33, and 34 for Δ(17O) quantification.The adapted method involves the following main points:•NO3− reference materials with internationally recognized oxygen isotope composition are reduced to NO2− under high pH conditions that conserve Δ(17O) values.•The NO3− reference materials reduced to NO2− and sample NO2− with unknown Δ(17O) values are reduced to N2O using chemical methods involving sodium azide/acetic acid.•The product N2O is extracted, purified, decomposed to O2, and analyzed for its isotope composition using a continuous flow isotope ratio mass spectrometer for Δ(17O) quantification. The Δ(17O) of NO2− samples are calibrated with respect to the NO3− reference materials with known Δ(17O) values.

Occurrence and Genesis of Cold‐Seep Authigenic Carbonates from the South‐Eastern Mediterranean Sea

AbstractMethane‐derived authigenic seep carbonates occur globally along continental margins. These carbonates are important archives to identify seep dynamics, the source of the ascending methane‐enriched fluids together with their timing, and are an important carbon sequestration mechanism. Recently, seep carbonates were discovered in the Levant Basin in the south‐eastern Mediterranean Sea. To elucidate past seepage activity and dynamics across the basin, different seep carbonate morphologies (chimneys, crusts and pavements) retrieved from the Levant Basin were mapped based on remotely operating vehicle data and analysed using standard sediment petrographic techniques, X‐ray diffraction and stable carbon and oxygen isotope analyses. Carbonate chimneys consist of micrite (δ13CVPDB of −10‰ to +5‰) with dispersed baryte and dolomite crystals, fan‐shaped aragonite (δ13CVPDB of −52‰ to −30‰) and high‐magnesium calcite cements, with the latter often growing from low‐magnesium calcite spherules. Botryoidal low‐magnesium calcite cements are forming in small cavities. Carbonate crusts consist of micrite with low‐magnesium calcite breccias, high‐magnesium calcite nodules (δ13CVPDB of −35‰ to −20‰) and cements, and partially replaced fan‐shaped aragonite cements. Carbonate pavements consist of low‐magnesium calcite microsparite, micritic dolomite and high‐magnesium calcite. Fan‐shaped aragonite is locally present as pore‐lining cement. Iron oxides are often seen coating the low‐magnesium calcite, high‐magnesium calcite and dolomite cements. Chimneys and crusts, characterised by high amounts of high‐magnesium calcite and aragonite, are interpreted to have formed through advective methane fluxes. Pavements, with high quantities of dolomite, are explained as the product of diffusive methane flux. Sediment petrographic and geochemical analysis of the different carbonate morphologies and cement phases therein witness distinct modes of ascending fluid fluxes and their mixing with marine pore water and/or sea water during precipitation of the individual phases.

Responses of Tree Growth and Intrinsic Water Use Efficiency to Climate Factors and Human Activities in Upper Reaches of Tarim River in Alaer, Xinjiang, China

With global warming and increasing human activities, exploring the impact of the rising atmospheric carbon dioxide concentration and climate change on forest ecosystems is crucial. In this study, we focus on Euphrates poplar (Populus euphratica Oliv.) in the upper reaches of the Tarim River in the Alaer region of Xinjiang. We use dendrochronological methods, tree-ring width, and stable carbon isotope series to explain basal area increment (BAI) and intrinsic water use efficiency (iWUE) changes. We further explore the influence of past climate change and human activities on the radial growth and iWUE of P. euphratica through stable oxygen isotope analysis combined with historical literature records. The results showed that relative humidity had an essential effect on Δ13C and δ18O fractionation in P. euphratica tree rings, whereas the vapor pressure deficit (VPD) was considered the main factor influencing the inter-annual variability of the iWUE and BAI. Since 1850, long-term variations in iWUE have exhibited an upward trajectory correlated with rising atmospheric CO2 levels. Approximately 13% of this iWUE increase can be attributed to changes in carbon-concentration-induced water use efficiency (cciWUE). Although Δ13C and δ18O were generally uncorrelated between 1850 and 2018, around 1918, their relationship changed from being weakly correlated to being significantly negatively correlated, which may record changes related to the upstream Tarim River diversion. During the period from 1850 to 2018, both the BAI and iWUE showed an increasing trend for P. euphratica growth; however, the relationship between them was not stable: during 1850–1958, both variables were mainly influenced by climatic factors, while during 1959–2018, the most important influence was due to human activities, specifically agricultural development and irrigation diversions. An abrupt surge in the BAI was observed from 1959 to 1982, reaching its peak around 1982. Surprisingly, post-1983, the escalating iWUE did not correspond with a continuation of this upward trajectory in the BAI, highlighting a divergence from the previous trend where the enhanced iWUE no longer facilitated the growth of P. euphratica. Despite P. euphratica having adapted to the continuously rising Ca, improving its iWUE and growth capacity, this adaptive ability is unstable and may easily be affected by human activities. Overall, the increase in Ca has increased the iWUE of P. euphratica and promoted its growth at a low frequency, while human activities have promoted its development at a high frequency.

Neolithic herding practices in the Southern Caucasus: Animal management in the early 6th millennium BCE at Masis Blur in Armenia’s Ararat Valley

The Southern Caucasus is traditionally an important area of livestock production and a key region in the spread of herding from southwestern Asia to Eurasia’s western steppe. Neolithic settlements appeared across the Southern Caucasus in the early 6th millennium BCE. How these communities used the landscape and managed livestock in the context of mixed farming is not well understood. Stable carbon (δ13C) and nitrogen (δ15N) isotope analysis of bone collagen and stable carbon and oxygen (δ18O) isotope analysis of tooth enamel from faunal remains from Masis Blur, one of the earliest Neolithic sites in the Southern Caucasus, clarify how communities maintained herds in this topographically varied region. δ13C and δ15N values indicate hunting wild fauna in diverse environments. δ13C and δ18O values from sequentially sampled livestock teeth demonstrate markedly different strategies for managing cattle and caprines. Negative covariation in δ18O and δ13C values in most caprines suggest seasonal mobility to C3-dominated high elevation pastures in the summers, and/or winter foddering with water-stressed C3 or wild C4 plants. These seasonal strategies were in place in the earliest known phase of occupation at Masis Blur, indicating that Southern Caucasus Neolithic communities likely exploited a range of environments linking the lowland plains and mountainous zones.

Pre-treatment methods for stable oxygen and carbon isotope analyses of structural carbonates of bones in marine teleost fishes.

Although the proportion of structural carbonates in vertebrate bones is low, the values of isotopes, namely stable oxygen (δ18 O) and carbon (δ13 C), in structural carbonates provide environmental and physiological information, which can be beneficial for estimating the palaeontological and ecological parameters of vertebrates. However, a few studies have analysed the isotopes of structural carbonates in modern teleost fishes, and a well-developed protocol for sample preparation is lacking. We examined different pre-treatment methods of preparing bone samples of three marine teleost fishes (Japanese flounder, Pacific bluefin tuna and yellowtail) and investigated the effects of the cleaning methods on the stable isotope values of structural carbonates among vertebrae in the same individual. Isotope values were analysed using isotope ratio mass spectrometry. Physical cleaning was the most promising pre-treatment method and resulted in δ18 O values that were comparable to those of otoliths. Chemical treatments with NaOH and H2 O2 changed the percentage of structural carbonates in the bone and affected δ18 O and δ13 C values. High-temperature treatments, such as boiling and roasting, altered δ18 O values due to the exchange of oxygen with environmental water or vapour. Our results suggest that chemical cleaning methods used to prepare bone phosphate or collagen samples for isotope analyses are not suitable for structural carbonates. Physical cleaning is the appropriate pre-treatment method for analysing the isotopes of structural carbonates. Also, we emphasise that standardising the vertebral number is necessary to make δ13 C values comparable between specimens in the same species.

Partitioning evapotranspiration using 18O abundance to understand water use efficiency in maize produced using ridge-furrow mulching system

The ridge-furrow mulching system (RFMS) is an efficient farming strategy that has been used widely for improving crop productivity in dryland agriculture. However, the physical mechanism that allows RFMS and its optimal ridge/furrow ratio to drive the efficient utilization of water in fields are unclear. Thus, we conducted a field research for two years with spring maize based on a long-term field experiment in a semiarid region of Northwestern China to quantify evaporation and transpiration, and their relationship with maize growth, yield and water use efficiency (WUE) under RFMS. Three planting patterns of ridge/furrow ratio were tested: (1) RF40, RFMS with 60 cm wide ridges and 40 cm wide furrows; (2) RF60, RFMS with 60 cm wide ridges and 60 cm wide furrows; (3) FP, traditional flat planting (control). Stable oxygen isotope (18O) analysis was used to partition the evapotranspiration (ET) into evaporation (E) and transpiration (T). The results showed that RFMS significantly increased the soil water content (SWC) in the early and late growing season, but not in the middle period (60–120 days after sowing, DAS) when dry matter accumulated rapidly and the highest transpiration occurred. RFMS significantly decreased the nonproductive evaporation, thereby increased the physiologically significant maize transpiration by 25.0–35.7% during the whole growing season. Therefore, the transpiration fraction of ET (T/ET) was 73% and 70% under RF40 and RF60 during the whole growing season, which were significantly higher than FP. Compared to FP, the maize yield and WUE increased significantly by 55.1% and 52.2% under RF40 and by 49.5% and 47.6% under RF60. We found RFMS drives optimization of ET fractions by increased transpiration but decreased evaporation and then improved WUE of maize, higher ridge/furrow ratio (RF40) create uneven line space and higher mulching area in the field, thus drives optimization of ET components and increased yield and WUE the most. Clarification of this physical mechanism improves our understanding of the optimization of maize production under RFMS, thereby helping to optimize the ridge/furrow ratio in semiarid regions.

An integrative palaeoenvironmental and chronostratigraphic study of the Lower Miocene in the North Alpine Foreland Basin – Are global climate signals detectable?

Uncertainties in relation to chronostratigraphic correlations have limited our understanding of the possible impact of global-scale climate signals on the epicontinental sediments of the North Alpine Foreland Basin (NAFB). In an effort to resolve the problem, we have carried out a detailed palaeoenvironmental and chronostratigraphic study of an 18-m thick section of the marine, middle Burdigalian Neuhofen Formation (NH Fm) at Mitterdorf (SE Germany). Based on section logging, sampling of microfossils and nannoplankton, and analyses of stable oxygen and carbon isotopes, we demonstrate that significant environmental changes took place during the deposition of the NH Fm at Mitterdorf. In particular, the presence of nannoplankton zones NN3 and NN4 necessitated a re-interpretation of existing magnetostratigraphic data from Mitterdorf. To determine whether the observed environmental changes can be placed in a supra-regional and global context, a new chronostratigraphic framework was established for the study area using a multi-proxy approach based on 3-D modeling, litho-, bio-, and magnetostratigraphy, already available data, and statistical analyses of new and previously published microfossil data. The results reveal that the Mitterdorf section can be correlated with polarity chrons C5Dr.2r and C5Dr.1n and that its age is 17.78–17.65 (vs. 17.65–17.50 Ma or 17.95–17.85 Ma in earlier works). Furthermore, the results show that the deposition of the entire NH Fm took place during the interval from 18.1 to 17.6 Ma, and that the accompanying environmental changes did not occur isochronously across its range. Nevertheless, comparison of literature-based global datasets with our new data indicates that the 3rd order sea level highstand at 17.85 Ma had an impact on the environment of the NH Fm. Furthermore, transition from eutrophic, open marine to mesotrophic, shallow marine conditions at Mitterdorf coincides with minima in orbital eccentricity and global carbon isotope values at 17.67 Ma. Our results are summarized in palaeoenvironmental models of three time-points within the middle Burdigalian in the NAFB.

Assessing Pleistocene–Holocene climatic and environmental change in insular Near Oceania using stable isotope analysis of archaeological fauna

ABSTRACTIn comparison to temperate and arid regions, environmental responses to the Last Glacial Maximum and the Terminal Pleistocene and Holocene boundary remain poorly known for many parts of the tropics, making it challenging to unravel human–landscape interactions across this timeframe. This is particularly the case in insular Near Oceania, where sea‐level fluctuations and potential changes in forest cover may have had major impacts on hunter–gatherer populations. Here, we apply stable carbon and oxygen isotope analyses to small‐mammal teeth from four Pleistocene–Holocene (spanning from 29 000 years ago to the late Holocene) sequences in the Bismarck Archipelago to reconstruct changes in environments directly exploited by human populations in this part of the world. Our results show a subtle response of tropical habitats in Near Oceania to relatively arid conditions during the late‐glacial period, something that has also been observed at sites in South and Southeast Asia, followed by a Terminal Pleistocene–Holocene expansion of tropical forest cover. Nevertheless, site‐based variability in environmental responses across this period highlight the need for more multidisciplinary studies of human occupation sequences in a region that is becoming increasingly central to exploring human adaptations, environmental modifications and social network development over the past 20 000 years.

Characteristics and Formation Stages of Natural Fractures in the Fengcheng Formation of the Mahu Sag, China: Insights from Stable Carbon and Oxygen Isotope and Fluid Inclusion Analysis

The Fengcheng Formation of the Mahu Sag is an unconventional reservoir that is of paramount importance for exploration and development of hydrocarbon resource. However, current research on natural fractures in the Fengcheng Formation remains limited, posing challenges for exploration of hydrocarbon resource in the region. This study is based on core observations, thin section identification, geochemical testing and the evolution of regional tectonic movements to investigate the characteristics and periods of formation of natural fractures to address this gap. According to the characteristics of natural fractures in the drilling core samples and microsections, the natural fractures in the Fengcheng Formation can be grouped into structural fractures and atectonic fractures. Structural fractures can be further divided into three subtypes: high-angle interlayer shear fractures, along-layer shear fractures, and tensile fractures. Additionally, non-tectonic fractures in this studied area are primarily bedding fractures, hydraulic fractures, and hydrocarbon-generating overpressure fractures. Vertically, fracture development is more prominent at the bottom of Feng #2 Formation and at the top of Feng #3 Formation. Results also indicate that natural fractures primarily formed during three distinct tectonic movement periods. The initial stage of fracture evolution pertains to the Late Permian period (243–266 Ma), filled with fibrous calcite, and exhibiting a uniform temperature of 70–100 °C. The second stage of fracture evolution occurred during the Late Indosinian to Early Yanshanian period (181–208 Ma), mostly filled or semi-filled with calcite, with a uniform temperature of 110–130 °C. The third stage of fracture development happened during the late Yanshanian to early Himalaya period (50–87 Ma), predominantly filled with calcite, and presenting a uniform temperature of 130–150 °C. Among the various types of structural fractures, the density of high-angle interlayer shear fractures demonstrates a positive correlation with daily gas production, indicating their vital role in promoting hydrocarbon resource production and transportation. Furthermore, microfractures generated by hydrocarbon-generating overpressure fractures exhibit small pore sizes and strong connectivity. These microfractures can create an effective permeability system by connecting previously isolated micropores in shale reservoirs, thus establishing interconnected pore spaces in the shale formation.

Diet and mobility in Late Antique Sicily: Isotopic data from the catacombs of Santa Lucia, Siracusa (Italy)

The catacombs of Santa Lucia were built during the 3rd century CE in Siracusa, Sicily, Italy, as a burial site for members of the local Christian community until the early 8th century CE. This site is an important cemeterial context of the Late Roman and Byzantine periods. The tombs and artifacts found suggest that individuals of varying wealth were buried in the catacombs. Historical accounts also confirm the presence of a significant Christian community from Syria and the Levant in Siracusa during this period. The objective of this research is to investigate the life histories of the Late Antique community interred in the catacombs using stable isotope analysis. This technique aimed to clarify the dietary differences between individuals of different social status and geographical origins, in order to re-evaluate the data from historical documents. To achieve this, we conducted stable carbon, nitrogen, and oxygen isotope analyses on skeletal samples from 25 individuals recovered from the catacombs of Santa Lucia, using established methods. The results revealed significant dietary diversity among the individuals buried in the catacombs, with evidence of the consumption of both C3 and C4 plants, as well as fish from both freshwater and sea sources.The oxygen isotopes show a particularly broad range in both the small sample set of bones and the larger set of teeth, suggesting a significant degree of mobility for most of the individuals tested. The high variability found in the diet and the evidence of mobility for most of the individuals tested not only between early age and adulthood, but also throughout their lives. It raises new questions and calls for the consideration of the archaeological and historical implications of these novel discoveries.

Ecological traits of the franciscana dolphin (Pontoporia blainvillei) from the Late Pleistocene to the present days based on stable isotope analysis

AbstractLate Pleistocene fossils from southern Brazil provide a unique opportunity to study the diet and habitat use of the extant franciscana dolphin (Pontoporia blainvillei) prior to human influence. Here, we subject 19 fossil and 21 contemporary specimens to stable carbon and oxygen isotope analysis (after first ruling out diagenesis via Fourier transform infrared spectroscopy). The two groups differ in their isotopic composition (PERMANOVA, p < .01), with fossils yielding more disparate δ13C values and recent samples more disparate δ18O values. Their isotopic niches show an overlap of ~20%, with that of the fossils being slightly wider (SEAc = 2.25‰2 versus 1.84‰2). We attribute these differences to impoverished modern fish communities and temporal changes in freshwater influx.

Integrated approaches to understanding animal exploitation and dairying in the Central European Early Neolithic: a case study from Ludwinowo 7 (Kuyavia, Poland; c. 5250–5000 cal BC)

Recent genetic studies point towards 6th millennium BC central Europe as the core region for the emergence of the lactase persistence (LP) gene mutation -13,910*T, making it important to understand the intensity of milk production and consumption among Linearbandkeramik (or LBK) farming groups. However, it is not known if milking was part of the LBK Neolithic “package” from the start, or if it displayed a discontinuous pattern in time and space. Documenting the changing nature of prehistoric animal exploitation requires integrating multiple strands of evidence and here we detail multi-proxy research into animal management strategies and the intensification of dairying in Neolithic Europe, using the LBK site of Ludwinowo 7 in central Poland as a case study. Lipid biomarker and stable isotope compositions of food residues from vessels provide qualitative and quantitative assessments of the major animal products acquired and processed, while zooarchaeological analyses identify slaughter and butchery practices, revealing the nature of meat, milk and fat exploitation. Stable carbon and oxygen isotope analyses on cattle teeth are also undertaken to define seasonal herd management. This combined approach offers an integrated picture of animal exploitation and milk use at the central European LBK site of Ludwinowo.

Formation process of Pliocene cold seep carbonates from the southern Western Foothills, Southwestern Taiwan: A synthetical rare earth element and C–O–Sr–Nd isotope study

In this work, the Pliocene dolomitic carbonate concretions and pipes from Chiahsien of the Western Foothills, southwestern Taiwan were studied. We conducted a synthetical analysis of stable carbon and oxygen isotopes, rare earth element (REE) contents, and Sr and Nd isotopes, to trace the compositions and sources of pore fluids from which carbonates have precipitated and reconstruct the carbonate formation processes. The carbonates with low δ13C values (as low as −48.6‰) are promoted by the anaerobic oxidation of biogenic methane. The 87Sr/86Sr ratios of samples reflect the mixing of coeval bottom seawater and seep fluid enriched in 87Sr. The Nd isotopic signatures of studied carbonates indicate multiple Nd sources, including detrital components, Fe–Mn oxyhydroxides, organic matter, and seawater. The MREE-bulge patterns in samples are typical of anoxic conditions, which are supported by Ce anomalies. Our results demonstrate that the seepage intensity played a key role in the formation processes of concretions and pipes by controlling the depth of the sulfate-methane transition zone (SMTZ). The concretions characterized by the lowest δ13C values formed at a deeper depth in sediments under low methane flux, which suffered no/less influence of seawater. The representative pipe with obvious concentric lamination grew in a rim-to-core pattern. In the early stage, the variable flux of highly channelized seepage caused the fluctuation of carbon and oxygen isotopes. During the later stage, the modification of isotopic compositions in the core part were resulted from meteoric alteration. Our work provides insights into the formation process related to seepage evolution in ancient cold seeps on Taiwan Island.

Of forests and grasslands: human, primate, and ungulate palaeoecology in Late Pleistocene-Holocene Sri Lanka

The Wet Zone region of Sri Lanka has provided some of the earliest direct evidence of human utilization of rainforest resources anywhere in the world. Stable isotope analysis of human and animal remains, alongside detailed zooarchaeological analyses, have demonstrated reliance on rainforest resources as far back as 48,000 years ago. However, changes in human adaptations and the varying niches of exploited fauna, through major periods of climatic change such as during the Pleistocene-Holocene transition, remain relatively under-explored. Here, we present the results of stable carbon (δ13C) and oxygen (δ18O) isotope analyses of dental enamel from 311 animal and eight human teeth recovered from recent excavations at Fa-Hien Lena and Kitulgala Beli-lena from contexts spanning the Late Pleistocene and Holocene. Our data for human teeth from the Terminal Pleistocene and Holocene layers of Fa-Hien Lena and the Holocene layers of Kitulgala Beli-lena show little departure from rainforest resource reliance between the Pleistocene and Holocene. Meanwhile, the most dominant faunal taxa, including cercopithecid monkeys, show a similar stability in canopied forest habitation across the different species. However, δ13C data from ungulates found at Fa-Hien Lena indicate human populations did have access to forest edge and grassland habitats, suggesting either specific foraging trips or long-distance trade with other communities. In addition, our reporting of an Early Holocene presence of rhinoceros in the Wet Zone forest of Sri Lanka, the last fossil occurrence of this now regionally-extirpated taxon, highlights ongoing human interactions with large mammal communities on the island. We argue that our data demonstrate the benefits of detailed isotopic and zooarchaeological studies for detailed insights into the nature of tropical human adaptations through time.

Late Pleistocene to late Holocene palaeoecology and human foraging at Kuumbi Cave, Zanzibar Island

BackgroundClimate change played a major role in shaping regional human-environment interactions in Africa during the late Pleistocene-Holocene, but this topic has not been exhaustively studied, particularly in eastern Africa. While there is growing evidence that the coastal and island settings in this region played a critical role in human evolution, combined archaeological and palaeoenvironmental studies have tended to focus on the arid interior and show the dominance of grasslands with patches of closed and open woodlands during the last 20,000 years.MethodsHere, we present stable carbon and oxygen isotope analyses of zooarchaeological remains (n = 229) recovered from Kuumbi Cave, Zanzibar Island, spanning the last glacial period and the Holocene (20,000 to 500 cal. BP).ResultsOur data demonstrate that the vicinity of Kuumbi Cave was consistently covered by mosaic habitats, dominated by forests and small patches of open woodland and grassland. The inhabitants of Kuumbi Cave exploited these diverse tropical habitats even after the regional arrival of agriculture.DiscussionWe suggest that the stable coastal forest mosaic habitats acted as a refugium for foragers during glacial periods and that the Iron Age inhabitants of Kuumbi Cave were not food producers migrating from the interior, but rather Indigenous foragers interacting with food production.

Of missions and marshes: Stable isotope analysis of Mission-Era Guale oyster harvesting on St. Catherines Island, Georgia

This article presents the results of oxygen stable isotope analysis on eastern oyster (Crassostrea virginica) samples (n = 25) from a Mission-Era (ca. AD 1565–1680) site, Pueblo Santa Catalina de Guale, on St. Catherines Island, GA. Stable isotope analysis was used to assess the seasonality of oyster harvesting on St. Catherines Island during the Mission Era to better understand how Spanish colonization and the Catholic mission system may have impacted Guale foodways. Five eastern oyster left valves were sampled from each known neighborhood of Pueblo Santa Catalina de Guale. Existing data regarding the seasonality of pre-colonial mollusk collection on St. Catherines Island and elsewhere in the coastal Southeast are discussed in conversation with the results of this analysis. This work indicates that Guale residents of St. Catherines Island during the Mission Era were harvesting oysters most intensely during cooler months. This pattern is consistent with estimates of pre-colonial shellfishing seasonality across the region and may even represent a modest increase in the seasonal constriction of shellfishing when compared to data from the preceding period. Salinity estimates based on the isotope data also suggest Guale people during the Mission Era were collecting from a comparatively narrower range of estuarine habitats. We argue that these subtle shifts are a consequence of the reorganization of Guale labor associated with missionization.

Multiproxy approach to reconstruct fossil primate feeding behavior: Case study for macaque from the Plio-Pleistocene site Guefaït-4.2 (eastern Morocco)

The genus Macaca belongs to Cercopithecidae (Old World monkeys), Cercopithecinae, Papionini. The presence of Macaca in North Africa is well known from the Late Miocene to the Late Pleistocene. However, the diet of fossil Macaca has been poorly described in the literature. In this study, we investigated the feeding habits of Macaca cf. sylvanus (n = 4) from the Plio-Pleistocene site Guefaït-4.2 in eastern Morocco through multiproxy analysis combining analyses of stable carbon and oxygen isotopes from tooth enamel, buccal microtexture, and low-magnification occlusal dental microwear. For both microwear analyses, we compared the macaques with a new reference collection of extant members of Cercopithecoidea. Our occlusal microwear results show for the fossil macaque a pattern similar to the extant Cercocebus atys and Lophocebus albigena, African forest-dwelling species that are characterized by a durophagous diet based mainly on hard fruit and seed intake. Buccal microtexture results also suggest the consumption of some grasses and the exploitation of more open habitats, similar to that observed in Theropithecus gelada. The δ13C of M. cf. sylvanus indicates a C3 based-diet without the presence of C4 plants typical of the savanna grassland in eastern Africa during this period. The high δ18O values of M. cf. sylvanus, compared with the contemporary ungulates recovered from Guefaït-4.2, could be associated with the consumption of a different resource by the primate such as leaves or fresh fruits from the upper part of trees. The complementarity of these methods allows for a dietary reconstruction covering a large part of the individual’s life.

Living in the dry zone: Stable isotope insights into palaeodiet in ancient Myanmar

Southeast Asia is becoming a region of increasing interest in discussions of past migration, the origins of agriculture, and past impacts of human land-use change on environments. Myanmar, situated at a geographic and cultural crossroads between East, South and Mainland Southeast Asia, is potentially a critical region for exploring these themes. However, direct data relating to subsistence in the region has been lacking. Here, we apply stable carbon and oxygen isotope analysis to tooth enamel from humans and associated fauna to examine the subsistence economy of two communities from Myanmar, Oakaie and Nyaung’gan, spanning the transitional period from the late Neolithic to the early Bronze Age (ca. 1300-700BC). Situated within the broader regional and local environmental context, our data demonstrate the δ13C values of the individuals from the communities of Oakaie and Nyaung’gan are significantly higher, and the δ18O values are significantly lower, than individuals from the other sites in Southeast Asia, however, neither are significantly different to the Chinese sites and they overlap broadly with individuals from Mayutian in Southern Yunnan Province. These findings provide a unique insight into the subsistence economy of the ancient inhabitants of the Central Dry Zone of Myanmar.

The formation conditions of gigantic dolomite concretions including whale bones exposed in Unosaki coast, Oga peninsula, Japan

Carbonate concretions occur in sedimentary rocks of widely varying geological ages throughout the world. Recently, more than 100 gigantic carbonate concretions with diameters ranging from 1 to 9 m have been identified along the Unosaki coast of Oga Peninsula, Akita Prefecture, Japan. The formation process of such gigantic concretions, some of which along the Unosaki coast contain whale bones, remains uncertain. A mineral composition analysis reveals that the major mineral of the concretions is dolomite. Considering the location of dolomite precipitation, their composition implies that the concretions were formed in a reducing environment in which sulfate ions were removed. Stable carbon and oxygen isotopic analysis reveals that the CaCO3 of whale bone and concretions contains light δ13C and heavy δ18O, suggesting that whale organic matter contributed to the formation of the concretions. The gigantic carbonate concretions were presumably formed by the accumulation and burial of whale carcasses with high sedimentation rates, and subsequent reaction of carbon decomposed by benthic and microbial activity with seawater.

The role of the microencruster-microbial reef-building consortium in organic reefs evolution (Late Jurassic, northern Tethys shelf, southern Poland)

The carbonate sediments of the Polish part of Tethys shelf contain Crescentiella-microbial-cement facies. The facies is associated with Middle Oxfordian-Lower Kimmeridgian microbial-grain dominated reefs, microbial-sponge dual hybride reefs, and less frequently sponge/coral-microbial-abiotic triple hybride reefs. The Crescentiella (incertae sedis) and microbialites form numerous cluster bioconstructions with stromatactis-like cavities in which rapid lithification was supported by early marine cementation. However, the factors controlling the development of such bioconstructions and the role of Crescentiella in the development of reef frameworks remain enigmatic. The sediments from five localities were investigated using thin-sections analyses supported by cathodoluminescence observations, stable oxygen and carbon isotope analyses and dispersive X-ray spectrometry. The development of Crescentiella-microbial-cement facies took place in three intervals spanning the Transversarium, Upper Bifurcatus, and Planula zones and coinciding with the period of maximum development of the Late Jurassic reefs in Poland. The reefs contain microencruster Crescentiella which was an important rigid framework constructor among the microbialites while the skeletal metazoans were rare. The inferred palaeosetting of the facies ranges from the seaward steep-fronted outer margin to the upper slope broad reef complex/microplatform where the development of skeletal metazoans was limited and mainly formed stratiform microbialites binding coated grain-bioclastic dominated sediments. The occurrence of Crescentiella-microbial-cement boundstone facies is useful for palaeogeographic, palaeobathymetric, and palaeotectonic investigations.