Stable Isotope Geochemistry

Morphometry of selected calcareous nannofossils across the Cretaceous-Paleocene boundary at the Bidart (France) and Elles (Tunisia) sections. Comparison with carbon and oxygen stable isotope ratios

by Nicolas Thibault

Thibault, N., Minoletti, F., Gardin, S., Renard, M., "published in 'Bulletin de la Société Géologique de France', 2004, v. 175, p. 399-412"

A detailed biometric analysis of five species of calcareous nannofossils was carried out on samples from themore A detailed biometric analysis of five species of calcareous nannofossils was carried out on samples from the
uppermost Maastrichtian and lowermost Danian of Bidart (Basque Country, SW France) and Elles (central Tunisia).
This study reveals the existence of two morphotypes of A. cymbiformis and an abrupt reduction of the five species immediately below the K-T boundary, likely in relation with a stressful environment, which would have developed just before
the deposition of the iridium level, followed by a sudden size increase in the basal Danian reflecting the reworking
pattern of the Cretaceous species. In addition, the comparison of biometric and isotopic data seems to indicate that the
two morphotypes of A. cymbiformis have different ecologies, the large one being favoured in cool waters.

Upper Campanian - Maastrichtian nannofossil biostratigraphy and high-resolution carbon-isotope stratigraphy of the Danish Basin: towards a standard <delta>13C curve for the Boreal Realm

by Nicolas Thibault

Thibault, N. et al., in press in Cretaceous Research, doi:10.1016/j.cretres.2011.09.001

High-resolution carbon isotope stratigraphy of the upper Campanian – Maastrichtian is recorded in the Boreal Realm... more High-resolution carbon isotope stratigraphy of the upper Campanian – Maastrichtian is recorded in the Boreal Realm from a total of 1968 bulk chalk samples of the Stevns-1 core, eastern Denmark. Isotopic trends are calibrated by calcareous nannofossil bio-events and are correlated with a lower-resolution δ13C profile from Rørdal, northwestern Denmark. A quantitative approach is used to test the reliability of Upper Cretaceous nannofossil bio-events and provides accurate biohorizons for the correlation of δ13C profiles. The Campanian–Maastrichtian boundary (CMB) is identified through the correlation of dinoflagellate biostratigraphy and δ13C stratigraphy between Stevns-1 and the Global boundary Standard Stratotype-section and Point at Tercis les Bains (SW France), allowing the identification of new chemical and biostratigraphic markers that provide a precise placement of the stage boundary on a regional scale. The boundary interval corresponds to the third phase of a stepwise 0.8‰ negative δ13C excursion, lies in calcareous nannofossil subzone UC16dBP, and encompasses the last occurrence of nannofossil Tranolithus stemmerikii and first occurrence of nannofossil Prediscosphaera mgayae. Fifteen δ13C events are defined and correlated to sixteen reliable nannofossil biohorizons, thus providing a well-calibrated standard high-resolution δ13C curve for the Boreal Realm.

Astronomical calibration of upper Campanian-Maastrichtian carbon isotope events and calcareous plankton biostratigraphy in the Indian Ocean (ODP Hole 762C): implication for the age of the Campanian-Maastrichtian boundary

by Nicolas Thibault

Thibault, N., Husson, D., Harlou, R., Gardin, S., Galbrun, B., Huret, E., Minoletti, F., Palaeo3. in press. http://www.sciencedirect.com/science/article/pii/S0031018212001769?v=s5

An integrated framework of magnetostratigraphy, calcareous microfossil bio-events, cyclostratigraphy and δ13C... more An integrated framework of magnetostratigraphy, calcareous microfossil bio-events, cyclostratigraphy and δ13C stratigraphy is established for the upper Campanian-Maastrichtian of ODP Hole 762C (Exmouth Plateau, Northwestern Australian margin). Bulk-carbonate δ13C events and nannofossil bio-events have been recorded and plotted against magnetostratigraphy, and provided absolute ages using the results of the cyclostratigraphic study and the recent astronomical calibration of the Maastrichtian. Fifteen carbon-isotope events and 40 nannofossil bio-events are recognized and calibrated with cyclostratigraphy, as well as 14 previously published foraminifer events, thus constituting a solid basis for large-scale correlations. Results show that this site is characterized by a nearly continuous sedimentation from the upper Campanian to the K-Pg boundary, except for a 500 kyr gap in magnetochron C31n. Correlation of the age-calibrated δ13C profile of ODP Hole 762C to the δ13C profile of the Tercis les Bains section, Global Stratotype Section and Point of the Campanian-Maastrichtian boundary (CMB), allowed a precise recognition and dating of this stage boundary at 72.15 Ma. Correlation of this boundary with the Lägerdorf - Kronsmoor - Hemmoor section shows that the CMB as defined at the GSSP is ~800 kyr younger than the CMB as defined by Belemnite zonation in the Boreal realm. ODP Hole 762C is the first section to bear at the same time an excellent recovery of sediments throughout the upper Campanian-Maastrichtian, a precise and well-defined magnetostratigraphy, a high-resolution record of carbon isotope events and calcareous plankton biostratigraphy, and a cyclostratigraphic study tied to the La2010 astronomical solution. This section is thus proposed as an excellent reference for the upper Campanian-Maastrichtian in the Indian Ocean.

Storm pulses and varying sources of hydrologic carbon export from a mountainous watershed

by Christopher Shope

POSTER: Multiproxy record of environmental and climatic variations during the Eemian from the Northern France calcareous tufa of Caours: combining petrography, malacology and geochemistry.

by Julie Dabkowski

Co-authored with Nicole Limondin-Lozouet, Pierre Antoine, Julian Andrews, Christine Chaussé, Pierre Carbonel, Jean-Luc Locht and Alina Marca-Bell.
Presented at the INQUA Congress 2011 (Bern), in session 69 "Reconstructing environmental impacts of climate changes from MIS 5 to present, based on terrestrial and lacustrine archives".

The site of Caours exhibits a calcareous tufa deposit of >10 000 m2 and up to 3.5 m thick, overlying lower terrace... more The site of Caours exhibits a calcareous tufa deposit of >10 000 m2 and up to 3.5 m thick, overlying lower terrace fluvial deposits of a Somme River (Northern France) tributary. The whole calcareous tufa sequence is attributed to the Eemian Interglacial (MIS 5e) according to its location within the Somme River terraces system, palaeontological data, and U/Th TIMS dating (average of 124 ± 4 ky BP). Since 2005, archaeological excavations of a Middle Palaeolithic site at the base of the tufa formation have provided long stratigraphic profiles (up to 20m long), supporting multidisciplinary studies. Palaeoenvironmental data from a petrographic study and molluscs were compared to geochemical proxies recording temperature (δ18O) and humidity (δ13C and trace elements Mg and Sr).
In thin section the main Cyanobacteria taxa precipiting tufa were identified as the fossil genus Broutinella and Ponsinella. Broutinella built massive “cauliflower” tufas. This subaqueous facies is associated with aquatic molluscs and ostracods. Ponsinella produces the “mille-feuilles” facies with thin laminations testifying of diffuse flow periods. This facies is associated to malacofauna dominated by land snails.
The cauliflower facies is dominant in the lower part of the sequence, where more pluvial conditions are suggested by δ13C data. This wettest part is also the warmest according to δ18O, and corresponds to the expansion of woodland molluscs. Moreover, the maxima of temperature and humidity (from δ18O and δ13C) are correlated with the Climatic Optimum (highest number of forest species diversity and mollusc shells). In the upper part, the mille-feuilles facies becomes better developed as spring flow waned, based on the δ13C data. Dry conditions are also indicated by mollusc fauna which record a landscape of mainly open areas and some forest remnants.
Clear environmental modifications caused by climatic changes are thus reconstructed from the tufa at Caours especially around the Interglacial Optimum.

A groundwater isoscape (δD, δ 18O) for Mexico

by Keith Larson

Wassenaar, L. I., S. L. Van Wilgenburg, K. W. Larson, and K. A. Hobson. 2009. A groundwater isoscape (δD, δ18O) for Mexico. Journal of Geochemical Exploration 102:123–136. doi: 10.1016/j.gexplo.2009.01.001.

Numerous studies have shown that precipitation isocapes drive δD and δ18O patterns in surficial waters and in... more Numerous studies have shown that precipitation isocapes drive δD and δ18O patterns in surficial waters and in terrestrial food webs. While the GNIP (Global Network for Isotopes in Precipitation) dataset provided a key foundation for linking precipitation-terrestrial isoscapes globally, it has insufficient spatial coverage in many countries like Mexico. To overcome this limitation, we hypothesized that shallow phreatic groundwaters in Mexico could be used as an isotopic integrator of long-term seasonally weighted precipitation inputs to the landscape to aid in calibrating spatial H and O isotope datasets for terrestrial, biological and hydrological research. Groundwater was sampled from 234 sites in Mexico at ~50 km latitudinal spacing to obtain high spatial resolution and country-wide coverage for the construction of a groundwater isoscape. Our data revealed that shallow groundwater infiltration in Mexico appears largely unaffected by evaporation and reflects seasonally weighted precipitation inputs. These precipitation inputs are primarily biased to summertime when highest rainfall occurs, but a small degree of post-precipitation evaporation revealed a lower d-excess zone that corresponded to the interior semi-arid ecozone. We developed a predictive general linear model (GLM) for hydrogen and oxygen isotopic spatial patterns in Mexican groundwater and then compared the results to a validation subset of our field data, as well external data reported in the literature. The GLM used elevation, latitude, drainage basin (Atlantic vs. Pacific), and rainfall as the most relevant predictive variables. The GLM explained 81% of the overall isotopic variance observed in groundwater, 68% of the variance within our validation subset, and 77% of the variance in the external data set. Our predictive GLM is sufficiently accurate to allow for future ecological, hydrological and forensic isoscape applications in Mexico, and may be an approach that is applicable to other countries and regions where GNIP stations are lacking.

GEOCHEMICAL AND PETROGRAPHICAL ANALYSES FOR SELECTING QUATERNARY MARINE SHELLS FOR RADIOMETRIC DATING AND PALEOCLIMATE RECONSTRUCTIONS: EXAMPLES FROM PATAGONIA

by Ilaria Consoloni

Ilaria Consoloni, Giovanni Zanchetta, Marina L. Aguirre, Ilaria Baneschi, Monica Bini, Gabriella M. Boretto, Luigi Dallai, Massimo D’Orazio, Anthony E. Fallick, Massimo Guidi, John C. Hellstrom, Ilaria Isola, Enrique Fucks, Francesco Mazzarini, Marta Pappalardo & Adriano Ribolini. Il Quaternario 24, 208-210.

ABSTRACT: Consoloni I. et al., Geochemical and petrographical analyses for selecting Quaternary marine shells for more ABSTRACT: Consoloni I. et al., Geochemical and petrographical analyses for selecting Quaternary marine shells for
radiometric dating and paleoclimate reconstructions: examples from Patagonia. (IT ISSN 0394-3356, 2011)
The selection of suitable samples is a fundamental target in order to obtain reliable results in the field of radiometric
dating and paleoclimate. Marine molluscs are particularly interesting in this respect in what different radiometric
methods (e.g. U/Th, ESR) can be applied coupled with chemical analyses to reconstruct past environment. For this kind
of material is imperative that the samples have not undergone any alteration. We present, as example, the study of
marine molluscs from Quaternary beach ridges from the Atlantic Patagonian coast. Multiproxy analyses show that the
degree of weathering is quite variable but not enough for undermining the paleoclimatic values of the stable isotopes
content and of some trace element, but enough severe to make problematic the application of U/Th dating methods.
However, the careful petrographic observation and trace element analyses can support the selection of suitable
samples for U/Th dating.

Stable Isotope Biogeochemistry of Seabird Guano Fertilization: Results from Growth Chamber Studies with Maize (Zea mays)

by Paul Szpak

Szpak P., F. J. Longstaffe, J.-F. Millaire, C. D. White. 2012. Stable Isotope Biogeochemistry of Seabird Guano Fertilization: Results from Growth Chamber Studies with Maize (Zea mays). PLoS One 7: e33741.

Background
Stable isotope analysis is being utilized with increasing regularity to examine a wide range of issues... more Background
Stable isotope analysis is being utilized with increasing regularity to examine a wide range of issues (diet, habitat use, migration) in ecology, geology, archaeology, and related disciplines. A crucial component to these studies is a thorough understanding of the range and causes of baseline isotopic variation, which is relatively poorly understood for nitrogen (δ15N). Animal excrement is known to impact plant δ15N values, but the effects of seabird guano have not been systematically studied from an agricultural or horticultural standpoint.


Methodology/Principal Findings
This paper presents isotopic (δ13C and δ15N) and vital data for maize (Zea mays) fertilized with Peruvian seabird guano under controlled conditions. The level of 15N enrichment in fertilized plants is very large, with δ15N values ranging between 25.5 and 44.7‰ depending on the tissue and amount of fertilizer applied; comparatively, control plant δ15N values ranged between −0.3 and 5.7‰. Intraplant and temporal variability in δ15N values were large, particularly for the guano-fertilized plants, which can be attributed to changes in the availability of guano-derived N over time, and the reliance of stored vs. absorbed N. Plant δ13C values were not significantly impacted by guano fertilization. High concentrations of seabird guano inhibited maize germination and maize growth. Moreover, high levels of seabird guano greatly impacted the N metabolism of the plants, resulting in significantly higher tissue N content, particularly in the stalk.

Conclusions/Significance
The results presented in this study demonstrate the very large impact of seabird guano on maize δ15N values. The use of seabird guano as a fertilizer can thus be traced using stable isotope analysis in food chemistry applications (certification of organic inputs). Furthermore, the fertilization of maize with seabird guano creates an isotopic signature very similar to a high-trophic level marine resource, which must be considered when interpreting isotopic data from archaeological material.

Stable isotopes in mollusk shells as indicators of benthic respiration and freshwater penetration on the Texas-Louisiana shelf

by Josiah Strauss

Co-authored with Ethan Grossman and Steven DiMarco, pre-print to be published in the Bulletin of Marine Science

To investigate the potential for mollusks to serve as proxies for benthic respiration and hypoxia in the Gulf of... more To investigate the potential for mollusks to serve as proxies for benthic respiration and hypoxia in the Gulf of Mexico (GOM), five gastropod (Conus austini Rehder and Abbott, 1951 and Strombus alatus Gmelin, 1791) and five bivalve (Pteria colymbus Röding, 1798 and Spondylus calcifer Carpenter, 1857) shells, from six Texas-Louisiana shelf localities during three periods from 1964 to 2009, were analyzed for oxygen and carbon stable isotopes (δ18O and δ13C). These results were compared with isotopic measurements of nearby shelf waters, which reveal significant correlations between δ13C of dissolved inorganic carbon and dissolved oxygen. Low and correlative δ18O and δ13C values for coastal S. alatus indicate that the 7-m collection depth was mixed with low salinity surface waters. Low δ18O values in C. austini from 24 m trace a low salinity event related to Hurricane Camille in 1969. The carbon isotopic compositions of Louisiana shelf C. austini do not exhibit the seasonal declines observed in the modern Louisiana hypoxic zone, suggesting limited or no hypoxia off Terrebonne Bay from 1968 to 1971. Of note, the δ13C values of these Conus specimens and others reported in the literature are up to 1.5‰ higher than those of modern GOM Conus, indicating a rate of δ13CDIC reduction nearly twice that associated with intrusion of 13C-depleted anthropogenic CO2 during the last four decades. We hypothesize that the larger rate of δ13CDIC depletion in Texas-Louisiana shelf waters reflects increasing oxidation of organic carbon fertilized by the increased flux of river-derived nutrients to the shelf.

STUDYING ANCIENT CROP PROVENANCE: IMPLICATIONS FROM δ13C AND δ15N OF CHARRED BARLEY IN A MIDDLE BRONZE AGE SILO AT EBLA (NW SYRIA)

by Valentina Caracuta

Published in Rapid Communications in Mass Spectromentry 6, 327.
Co-authored with Girolamo Fiorentino, Grazia Casiello, Francesco Longobardi, Antonio Sacco,

The discovery of a storeroom full of barley and other cereals (L.9512) in the proto-historic site of Ebla has provided... more The discovery of a storeroom full of barley and other cereals (L.9512) in the proto-historic site of Ebla has provided a unique opportunity to study the early city-state’s centralized storage system from a different perspective. Epigraphic evidence available within the site reveals a complex system of taxation which included gathering grain tributes from satellite sites and redistributing semi-finished products such as flour. In this paper, we intend to explore the possibilities of a combined approach, based on estimated barley grain volumes and δ13C-δ15N analyses. This approach is used to distinguish between grain from different harvesting sites and to identify any grain cultivated using special agricultural practices (e.g. manuring or irrigation). The basic assumption for this kind of analysis is that the growth-site conditions, natural or anthropogenic, of harvested cereals are reflected in their grain size and δ13C-δ15N values. Since the remains found in the storeroom were charred, the first task was to evaluate the effect of carbonization on the δ13C-δ15N and the size of the grains. Thus, the effect of charring was tested on modern samples of Syrian barley landraces. Once ascertained that fresh grains reduced to charred remains retain their original biometric and isotopic traits, the ancient material was examined. 13 groups were identified, each characterized by a specific average volume and specific carbon and nitrogen values. The analysis revealed that what had first appeared to be a homogeneous concentration of grain was in fact an assemblage of barley harvested from different sites .

Ferromanganese nodules and micro-hardgrounds associated with the Cadiz Contourite Channel (NE Atlantic): palaeoenvironmental records of fluid venting and bottom currents

by F. Javier González Sanz

González, F. J., Somoza, L., León, R., Medialdea, T., Torres, T., Ortiz, J. E., Lunar, R., Martínez-Frías, J., Merinero, R. 2012. Ferromanganese nodules and micro-hardgrounds associated with the Cadiz Contourite Channel (NE Atlantic): palaeoenvironmental records of fluid venting and bottom currents. Chemical Geology (doi:10.1016/j.chemgeo.2012.03.030)

Ferromanganese nodule fields and hardgrounds have recently been discovered in the Cadiz Contourite Channel in the Gulf... more Ferromanganese nodule fields and hardgrounds have recently been discovered in the Cadiz Contourite Channel in the Gulf of Cadiz (850–1000 m). This channel is part of a large contourite depositional system generated by the Mediterranean Outflow Water. Ferromanganese deposits linked to contourites are interesting tools for palaeoenviromental studies and show an increasing economic interest as potential mineral resources for base and strategic metals. We present a complete characterisation of these deposits based on submarine photographs and geophysical, petrographic, mineralogical and geochemical data. The genesis and growth of ferromanganese deposits, strongly enriched in Fe vs. Mn (av. 39% vs. 6%) in this
contourite depositional system result from the combination of hydrogenetic and diagenetic processes. The interaction of the Mediterranean OutflowWater with the continental margin has led to the formation of Late Pleistocene–Holocene ferromanganese mineral deposits, in parallel to the evolution of the contourite depositional system triggered by climatic and tectonic events. The diagenetic growth was fuelled by the anaerobic oxidation of thermogenic hydrocarbons (δ13CPDB=−20 to −37‰) and organic matter within the channel floor sediments, promoting the formation of Fe–Mn carbonate nodules. High 87Sr/86Sr isotopic values (up to 0.70993±0.00025) observed in the inner parts of nodules are related to the influence of radiogenic fluids fuelled by deep-seated fluid venting across the fault systems in the diapirs below the Cadiz Contourite Channel. Erosive action of the Mediterranean Outflow Water undercurrent could have exhumed the Fe–Mn carbonate nodules, especially in the glacial periods, when the lower core of the undercurrent was more active in the study area. The growth rate determined by 230Thexcess/232Th was 113±11 mm/Ma, supporting the hypothesis that the growth of the nodules records palaeoenvironmental changes during the last 70 ka. Ca-rich layers in the nodules could point to the interaction between the Mediterranean OutflowWater and the North Atlantic DeepWater during the Heinrich events. Siderite–rhodochrosite nodules exposed to the oxidising sea-bottom waters were replaced by Fe–Mn oxyhydroxides. Slow hydrogenetic growth of goethite from the seawaters is observed in the outermost parts of the exhumed nodules and hardgrounds, which show imprints of the Mediterranean Outflow Water with low 87Sr/86Sr isotopic values (down to 0.70693±0.00081). We propose a new genetic and evolutionary model for ferromanganese oxide nodules derived from ferromanganese carbonate nodules formed on continental margins above the carbonate compensation depth and dominated by hydrocarbon seepage structures and strong erosive action of bottom currents. We also compare and discuss the generation of ferromanganese deposits in the Cadiz Contourite Channel with that in other locations and suggest that our model can be applied to ferromanganiferous deposits in other contouritic systems affected by fluid venting.

Pollutant lead reveals the pre-Hellenistic occupation and ancient growth of Alexandria, Egypt

by Christophe Morhange

100 Years of benthic foraminiferal history on the inner Texas shelf inferred from fauna and stable isotopes: Preliminary results from two cores

by Josiah Strauss

Co-authored with Ethan Grossman, Joseph Carlin, Timothy Dellapenna

Coastal regions, such as the Texas–Louisiana shelf, are subject to seasonal hypoxia that strongly depends on the... more Coastal regions, such as the Texas–Louisiana shelf, are subject to seasonal hypoxia that strongly depends on the magnitude of freshwater discharge from local and regional river systems. We have determined benthic foraminiferal fauna and isotopic compositions in two 210Pb dated box cores (BR4 and BR5) to examine the evidence for nearshore hypoxia and freshwater discharge on the Texas shelf during the last 100years. The 210Pb chronologies of both cores reveal sedimentation rates of 0.2 and 0.1 cm yr−1, translating to ∼60 and ∼90 yearrecords. The fauna of both cores were almost exclusively composed of Ammonia parkinsoniana and Elphidium excavatum, indicating euryhaline ambient waters. The Ammonia–Elphidium (A–E) index, a qualitative measure of low oxygen conditions, shows an increase from values between 20 and 50 to near 100 in both cores, suggesting low oxygen conditions between 1960 and the core top. Between 1950 and 1960 (9–10 cm), low A–E values in BR4 coincide with high δ18O and δ13C values greater than 0‰ and −1‰ respectively. This event corresponds to severe drought (the Texas Drought of Record) over the Brazos River drainage basin and considerably reduced river discharge from 1948 to 1957. High A–E values prior to this event imply low-oxygen conditions were prevalent prior to anthropogenic exacerbation of Louisiana shelf hypoxia and at least since the dredging of a new Brazos River delta in 1929. Elphidium excavatum δ13C values are very low (−4‰) and indicative of significant vital effect. The δ13C values of A. parkinsoniana average −3‰ and exhibit little variability, most likely reflecting pore waters influenced by aerobic and anaerobic respiration. The association of lowered Brazos River discharge with more oxygenated shelf bottom waters suggests Brazos River discharge and shelf hypoxia are linked, but the influence of Mississippi–Atchafalaya discharge can also contribute to shelf stratification.

Homogeneous magnesium isotopic composition of seawater: an excellent geostandard for Mg isotope analysis

by Josiah Strauss

Texas Coastal Hypoxia Linked to Brazos River Discharge as Revealed by Oxygen Isotopes

by Josiah Strauss

Geochemical assessment of the palaeoecology, ontogeny, morphotypic variability and palaeoceanographic utility of “Dentoglobigerina” venezuelana

by Joe Stewart

Joseph A. Stewart, Paul A. Wilson, Kirsty M. Edgar, Pallavi Anand, Rachael H. James

Marine Micropaleontology 84-85 (2012) 74–86

To better understand the links between the carbon cycle and changes in past climate over tectonic timescales we need... more To better understand the links between the carbon cycle and changes in past climate over tectonic timescales we need new geochemical proxy records of secular change in silicate weathering rates. A number of proxies are under development, but some of the most promising (e.g. palaeoseawater records of Li and Nd isotope change) can only be employed on such large samples of mono-specific foraminifera¬ that application to the deep sea sediment core archive becomes highly problematic. “Dentoglobigerina” venezuelana presents a potentially attractive target for circumventing this problem because it is a typically large (>355 μm diameter), abundant and cosmopolitan planktic foraminifer that ranges from the early Oligocene to early Pliocene. Yet considerable taxonomic and ecological uncertainties associated with this taxon must first be addressed. Here, we assess the taxonomy, palaeoecology, and ontogeny of “D.” venezuelana using stable isotope (oxygen and carbon) and Mg/Ca data measured in tests of late Oligocene to early Miocene age from Ocean Drilling Program (ODP) Site 925, on Ceara Rise, in the western equatorial Atlantic. To help constrain the depth habitat of “D.” venezuelana relative to other species we report the stable isotope composition of selected planktic foraminifera species within Globigerina, Globigerinoides, Paragloborotalia and Catapsydrax. We define three morphotypes of “D.” venezuelana based on the morphology of the final chamber and aperture architecture. We determine the trace element and stable isotope composition of each morphotype for different size fractions, to test the validity of pooling these morphotypes for the purposes of generating geochemical proxy datasets and to assess any ontogenetic variations in depth habitat. Our data indicate that “D.” venezuelana maintains a lower thermocline depth habitat at Ceara Rise between 24 and 21 Ma. Comparing our results to published data sets we conclude that this lower thermocline depth ecology for the Oligo-Miocene is part of an Eocene-to-Pliocene evolution of depth habitat from surface to sub-thermocline for “D.” venezuelana. Our size fraction data advocate the absence of photosymbionts in “D.” venezuelana and suggest that juveniles calcify higher in the water column, descending into slightly deeper water during the later stages of its life cycle. Our morphotype data show that δ18O and δ13C variation between morphotypes is no greater than within-morphotype variability. This finding will permit future pooling of morphotypes in the generation of the “sample hungry” palaeoceanographic records.
Keywords: Planktic foraminifera, Dentoglobigerina venezuelana, morphotype, palaeoecology, ontogeny, taxonomy

Smits, E. & J. van der Plicht, 2009, Mesolithic and Neolithic human remains in the Netherlands: physical anthropological and stable isotope investigations, Journal of Archaeology in the Low Countries 1.1, 55-85.

by Journal of Archaeology in the Low Countries

This article presents an overview of the interdisciplinary study of skeletal remains from Late Mesolithic and Middle... more This article presents an overview of the interdisciplinary study of skeletal remains from Late Mesolithic and Middle Neolithic sites in the Lower Rhine Basin. The combination of archaeological, physical anthropological and chemical analysis has led to a better understanding of the treatment of the dead, demographic parameters and diet of the populations during the transition from forager to farmer in this area. Burial ritual was variable during this whole period, with an above-ground treatment of corpses
alongside the burial of deceased. The physical anthropological study has revealed that the sites were inhabited by family groups. Stable isotope analyses have indicated that immigrants were sometimes present and that diet varied per population. Intersite variation in diet is explained by the exploitation of the
local habitat. Intrasite variability in diet can be influenced by cultural and social factors as attested by the burial traditions and the isotope study of provenance. It is posited here that the Neolithisation process was not as unambiguous as in some other parts of Europe, but diverse with small-scale variations at the site level

Palaeoclimate of the Late Jurassic of Portugal: comparison with the Western United States

by Timothy Myers

Myers, T.S., Tabor, N.J., Jacobs, L.L., and Mateus, O. (in press) Sedimentology

Investigation of the palaeoclimatic conditions associated with Upper Jurassic strata in Portugal and comparison with... more Investigation of the palaeoclimatic conditions associated with Upper Jurassic strata in Portugal and comparison with published palaeoclimate reconstructions of the Upper Jurassic Morrison Formation in western North America provide important insights into the conditions that allowed two of the richest terrestrial faunas of this period to flourish. Geochemical analyses and observations of palaeosol morphology in the informally named Upper Jurassic Lourinhã formation of western Portugal indicate warm and wet palaeoclimatic conditions with strongly seasonal precipitation patterns. Palaeosol profiles are dominated by carbonate accumulations and abundant shrink-swell (vertic) features that are both indicative of seasonal variation in moisture availability. The δ18OSMOW and δDSMOW values of phyllosilicates sampled from palaeosol profiles range from +22.4‰ to +22.7‰ and -53.0‰ to -37.3‰, respectively. These isotope values correspond to temperatures of formation between 32°C and 39°C ± 3°, with an average of 36°C, which suggest surface temperatures between 27°C and 34°C (average 31°C). On average, these surface temperature estimates are 1°C higher than the highest summer temperatures modelled for Late Jurassic Iberia using general circulation models. Elemental analysis of matrix material from palaeosol B-horizons provides proxy (chemical index of alteration minus potassium) estimates of mean annual precipitation ranging from 766 to 1394 mm/year, with an average of approximately 1100 mm/year. Palaeoclimatic conditions during deposition of the Lourinhã formation are broadly similar to those inferred for the Morrison Formation, except somewhat wetter. Seasonal variation in moisture availability does not seem to have negatively impacted the ability of these environments to support rich and relatively abundant faunas. The similar climate between these two Late Jurassic terrestrial ecosystems is probably one of the factors which explains the similarity of their vertebrate faunas.

Evaluating the use of clay mineralogy, Sr-Nd isotopes and zircon U-Pb ages in tracking dust provenance: An example from loess of the Carpathian Basin

by János Kovács

Újvári. G. et al., 2012. Chemical Geology 304–305, pp. 83-96

Multiple competing hypotheses have been proposed to explain the source of loess dust in the Carpathian Basin yet none... more Multiple competing hypotheses have been proposed to explain the source of loess dust in the Carpathian Basin yet none has been demonstrated. Here bulk and grain-size differentiated Nd and Sr isotopic and bulk and clay mineralogical compositions, together with detrital zircon ages and morphologies from loess along the Danube in the Carpathian Basin are used to demonstrate that no single method is capable of unequivocally isolating sources, yet combined, they allow for discriminating likely provenance. Zircon ages indicate multiple sources for Carpathian Basin loess, restricting the use of bulk or grain-size differentiation methods. Ambiguities are further highlighted by the fact that the Sr-Nd isotopic composition of Greenland dust is very similar to Carpathian loess. This match demonstrates that such methods are not always capable of unequivocally excluding unlikely potential source areas and implies that current hypotheses regarding the origin of Greenland dust require further evaluation. Sr isotopes are also limited by high dolomite contents of loess, while palygorskite is of questionable utility as a Saharan dust indicator due to its rapid weathering under typical Carpathian climates. In terms of specific Carpathian loess sources, alluvial fans of the Danube River likely contribute, but detrital zircon ages and morphologies suggest that a proportion directly originates from eroded uplands and local rocks throughout the basin, while detrital dolomite implies local, primary sources such as the Transdanubian Range. An upper limit of 5-10% is placed on the North African contribution to fine dust in loess of the mid-Carpathian Basin based on mineralogy and grain size. Overall, results suggest that the single grain (zircon) approach is likely the most diagnostic method to identify sources in loess studies, although to solve complex provenance issues, simultaneous consideration of the isotopic characteristics of more than one heavy (or light) mineral is required.

Le collagène de l'os : un protéine support de l'empreinte géochimique de notre passé

by Dorothée Drucker