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Fraser R.A.,University of Oxford | Bogaard A.,University of Oxford | Schafer M.,University of Basel | Arbogast R.,French National Center for Scientific Research | Heaton T.H.E.,NERC Isotope Geosciences Laboratory
World Archaeology | Year: 2013

In this paper we reconstruct the palaeodietary setting of LBK Vaihingen an der Enz, south-west Germany (later sixth millennium cal. bc) using δ13C and δ15N values of human and faunal bone collagen and of charred plant remains from cereal crops (e.g. emmer and einkorn wheat) and pulses (lentil and pea). Our examination of this Neolithic dietary ‘food web’ incorporates crop δ15N values within a linear-mixing model to examine the estimated proportions of animal and plant protein in the human diet. We interpret the stable isotope dietary model outcomes together with accompanying archaeobotanical and zooarchaeological evidence to shed light on the role of crops in land use strategies and human diet, and conclude that (manured) crops probably formed the dominant protein source. © 2013, Taylor & Francis.

Wilson G.P.,University of Portsmouth | Lamb A.L.,NERC Isotope Geosciences Laboratory
Journal of Quaternary Science | Year: 2012

In order to understand natural sea-level variability, and to enhance future predictions, accurate and precise estimates of Holocene tidal levels are required. Although the application of diatom-based transfer functions can yield such data, these work best when underpinned by local training sets. Urbanized estuaries offer little prospect of obtaining local training sets and, instead, the reliability of regional transfer functions has to be assessed. The performance of a published regional (UK) diatom-based tidal-level transfer function applied to fossil assemblages from two contrasting core sites in the Mersey Estuary, UK, is assessed using modern analogue techniques and sediment isotope data. We find that, although estimated tidal levels coincide with changes in organic matter source, the frequent lack of modern analogues mean that palaeotide estimates are without basis. This is likely a consequence of the site-specific nature of diatom assemblages in higher intertidal and supratidal areas in particular, where local factors are expected to exert a greater control on their ecology. This situation may be partly resolved by constructing and applying much larger regional training sets from multiple higher intertidal and supratidal sites (where intact). Otherwise the application of alternative techniques, such as regional foraminiferal tidal-level transfer functions, may be more appropriate. © 2011 John Wiley & Sons, Ltd.

Abram N.J.,British Antarctic Survey | Abram N.J.,Australian National University | Mulvaney R.,British Antarctic Survey | Arrowsmith C.,NERC Isotope Geosciences Laboratory
Journal of Geophysical Research: Atmospheres | Year: 2011

The accumulation, isotopic and chemical signals of an ice core from James Ross Island, Antarctica, are investigated for the interval from 1967 to 2008. Over this interval, comparison with station, satellite and reanalysis data allows for a detailed assessment of the environmental information preserved in the ice. Accumulation at James Ross Island is enhanced during years when the circumpolar westerlies are weak, allowing more precipitation events to reach the northeastern Antarctic Peninsula. The stable water isotope composition of the ice core has an interannual temperature dependence consistent with the spatial isotope-temperature gradient across Antarctica, and preserves information about both summer and winter temperature variability in the region. Sea salts in the ice core are derived from open water sources in the marginal sea ice zone to the north of James Ross Island and transported to the site by strengthened northerly and westerly winds in the winter. A strong covariance with temperature means that the sea salt record may be able to be utilized, in conjunction with the isotope signal, as an indicator of winter temperature. Marine biogenic compounds in the ice core are derived from summer productivity within the sea ice zone to the south of James Ross Island. This source region may have become significant only in recent decades, when the collapse of nearby ice shelves established new sites of open water with high summer productivity. These findings provide a foundation for interpreting the environmental signals in the James Ross Island ice core, which extends though the whole Holocene and represents the oldest ice core that has been recovered from the Antarctic Peninsula region. Copyright © 2011 by the American Geophysical Union.

Neill I.,CardiffUniversity | Kerr A.C.,CardiffUniversity | Hastie A.R.,University of Edinburgh | Pindell J.L.,CardiffUniversity | And 2 more authors.
Journal of Petrology | Year: 2013

An elemental and radiogenic isotope study of Cretaceous island arc rocks onTobago, West Indies, reveals the magmatic processes taking place at the eastern edge of the Pacific-derived Caribbean Plate during development of the Greater Antilles Arc. The ̃110-103Ma Volcano-Plutonic Suite comprises the ultramafic-intermediate Tobago Pluton and genetically related Tobago Volcanic Group. The volcanic rocks (breccias, tuffs, and mafic-intermediate lavas) have undergone shallow-level fractional crystallization involving plagioclase, clinopyroxene, olivine, and Fe-Ti oxides, but also preserve trace element evidence for 'cryptic' amphibole fractionation. The suite is inferred to have formed from a spinel lherzolite mantle wedge source fluxed largely by slab- and recycled volcanogenic sediment- derived fluids. A tonalitic mega-dyke intruding the pluton resembles high-silica adakites, and geochemical constraints indicate a likely origin by partial melting of the arc crust. A mafic dyke swarm (̃103-91Ma) is partly coeval with the volcanic rocks, but some, perhaps the youngest dykes, are derived from isotopically distinct arc mantle sources compared with the volcanic rocks. Rare Nbenriched and high-Nb dykes may relate to melting of a high field strength element-enriched source. Current Caribbean tectonic models involve the continuation of east-dipping Farallon Plate subduction beneath the proto-Caribbean seaway either until an Early Cretaceous initiation of proto-Caribbean subduction, or collision of the Caribbean Oceanic Plateau with the Greater Antilles Arc at ̃90-80Ma. Both models may be compatible with the tectono-magmatic history ofTobago, whereinTobago is thought to have detached from the fore-arc of the Caribbean arc system during Eocene intraarc extension, the growth of the Grenada Basin, and inception of the Lesser Antilles Arc. Tobago- or La Deésirade-like Mesozoic arc crust underlies much of the present-day Lesser Antilles Arc and not, as has recently been proposed, portions of the plume-derived Caribbean Oceanic Plateau ©The Author 2013.

Curtis C.J.,University College London | Evans C.D.,Environment Center Wales | Goodale C.L.,Cornell University | Heaton T.H.E.,NERC Isotope Geosciences Laboratory
Ecosystems | Year: 2011

Various studies over the last 15 years have attempted to describe the processes of N retention, saturation and NO3 - leaching in semi-natural ecosystems based on stable isotope studies. Forest ecologists and terrestrial biogeochemists have used 15N labelled NO3 - and NH4 + tracers to determine the fate of atmospheric deposition inputs of N to terrestrial ecosystems, with NO3 - leaching to surface waters being a key output flux. Separate studies by aquatic ecologists have used similar isotope tracer methods to determine the fate and impacts of inorganic N species, leached from terrestrial ecosystems, on aquatic ecosystems, usually without reference to comparable terrestrial studies. A third group of isotopic studies has employed natural abundances of 15N and 18O in precipitation and surface water NO3 - to determine the relative contributions of atmospheric and microbial sources. These three sets of results often appear to conflict with one another. Here we attempt to synthesize and reconcile the results of these differing approaches to identifying both the source and the fate of inorganic N in natural or semi-natural ecosystems, and identify future research priorities. We conclude that the results of different studies conform to a consistent conceptual model comprising: (1) rapid microbial turnover of atmospherically deposited NO3 - at multiple biologically active locations within both terrestrial and aquatic ecosystems; (2) maximum retention and accumulation of N in carbon-rich ecosystems and (3) maximum leaching of NO3 -, most of which has been microbially cycled, from carbon-poor ecosystems exposed to elevated atmospheric N inputs. © 2011 Springer Science+Business Media, LLC.

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