Amino sugars in fungal cell walls (such as chitin) represent an important source of nitrogen (N) in many forest soil ecosystems. Despite the importance of this material in soil nitrogen cycling, comparatively little is known about abiotic and biotic controls on and the timescale of its turnover. Part of the...
We determined pore fluid rare earth element (REE) concentrations in near-surface sediments retrieved from the continental margin off Oregon and California (USA). These sites represent shelf-to-slope settings, which lie above, within, and below the oxygen minimum zone of the Northeast Pacific. The sediments are characterized by varying degrees of net...
Radiogenic isotopes of hafnium (Hf) and neodymium (Nd) are powerful tracers for water mass transport and trace metal cycling in the present and past oceans. However, due to the scarcity of available data the processes governing their distribution are not well understood. Here we present the first combined dissolved Hf...
The ongoing retreat of glaciers globally is one of the clearest manifestations of recent global warming associated with rising greenhouse gas concentrations. By comparison, the importance of greenhouse gases in driving glacier retreat during the most recent deglaciation, the last major interval of global warming, is unclear due to uncertainties...
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from 39oN to 46oN latitude,
western USA and France. GeochimicaetCosmochimicaActa 58, 249-255 (1994
There is a lack of consensus regarding the roles of sulfide saturation versus volatile degassing on the partitioning of Cu and Ag during differentiation and eruption of convergent margin magmas. Because of their oxidized character, volatile-rich magmas from the Eastern Manus Back-arc Basin (EMBB) only reach sulfide saturation following magnetite-driven...
The aromatic carbon structure is a defining property of chars and is often expressed with the help of two
concepts: (i) aromaticity and (ii) degree of aromatic condensation. The varying extent of these two features
is assumed to largely determine the relatively high persistence of charred material in the environment...
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transmission
electron microscopy study. GeochimicaetCosmochimicaActa 69, 3911–3918.
Francis, J.T
Time-series observations are critical to understand the structure, function, and dynamics of marine ecosystems. The Hawaii Ocean Time-series program has maintained near-monthly sampling at Station ALOHA (22°45′N, 158°00′W) in the oligotrophic North Pacific Subtropical Gyre (NPSG) since 1988 and has identified ecosystem variability over seasonal to interannual timescales. To further...
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the NPSG ecosystem [Church et al., 2013; Karl and Church, 2014]. The
scientific rationale and
The rhenium-osmium isotopic system has the potential to track the maturation of arc crust at lower crustal levels because the ¹⁸⁷Os/¹⁸⁸Os in magmas is sensitive to the age and composition of crust with which they interact. We here present Re and Os isotopic data for a suite of samples from...
Analytical challenges in obtaining high quality measurements of rare earth elements (REEs) from small pore fluid volumes have limited the application of REEs as deep fluid geochemical tracers. Using a recently developed analytical technique, we analyzed REEs from pore fluids collected from Sites U1325 and U1329, drilled on the northern...
Ocean circulation is an important component in Earth's climate system. Predicting future climate and circulation changes requires an improved understanding of the past relationship between climate and ocean currents. The neodymium isotope composition (εNd) of water masses is frequently used as a quasi-conservative tracer to reconstruct ocean circulation. The current...
The apparent dissociation constants of carbonic acid were
determined as functions of temperature and salinity in seawater
at atmospheric pressure.
There is fair agreement between my values of K'₁ and those
of Buch et al. (1932), Lyman (1956), and Hansson (1971). My values,
on the average, are 6.7% lower than...
Heavy biodegraded crude oils have larger numbers of coeluting compounds than non- biodegraded oils, and they are typically not resolved with conventional gas chromatography (GC). This unresolved complex mixture (UCM) has been investigated using comprehensive two- dimensional gas chromatography-time-of-flight mass spectrometry (GCxGC-ToFMS) within a set of biodegraded petroleums derived from...
The thermodynamic history of the Earth is preserved in the trace element record created through igneous processes. The ability to interpret that record depends on the accuracy and precision of numerical models that connect igneous processes with their geochemical consequences. This project answers three major questions concerning the relationship between...
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;
Beattie, 1993; Bindeman et al., 1998; Bindeman and Davis, 2000). However, there
has been no consensus
The global mid-ocean ridge system is the largest magmatic system encompassing over 75% of the Earth’s total volcanism. As magmas ascend through the vertically variable oceanic crust, melts begin to crystallize and diversify and subsequently erupt at the surface. The interpretation of these erupted products observed on the seafloor requires...
Changes in the field of publishing and in scholarly communication have been impacting the distribution of scientific knowledge for years. The economics of publishing continues to have an impact on subscribers’ ability to maintain access and therefore the readership of established publications may diminish or look for legitimate alternatives to...
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Decades of experimental work has illustrated the high degree to which the partitioning of most elements is dependent on phase composition, temperature and pressure. In order to quantitatively describe clinopyroxene partitioning it is required to derive expressions using theoretical constraints calibrated with experimental data.
The experimental database available for such...
The ability to reconstruct past ocean currents is essential for determining ocean circulation’s role in global heat transport and climate change. Our understanding of the relationship between circulation and climate in the past allows us to predict the impact of future climate-driven circulation changes. One proposed tracer of past ocean...
Lipid biomarkers in sediments are widely used to infer environmental conditions that have
occurred in the geological past, but these reconstructions require a careful consideration of the
biotic and abiotic processes that degrade and alter the lipid biomarker compositions before
and after deposition. In this paper, we use alkenones produced...
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et al., 1997; Volkman et al., 1998; Rontani and Volkman, 2005; 58
Bianchi and Canuel, 2011
Marine heat waves are forecasted to increase in frequency and intensity under future climate scenarios, but little is known about the impact of these events on the one of the most commonly used proxies of ocean temperature - foraminiferal assemblages. This research explores the planktic foraminifera community along the Newport...
Plant wax lipids and lignin phenols are the two most common classes of molecular markers that are used to trace vascular plant-derived OM in the marine environment. However, their ¹³C and ¹⁴C compositions have not been directly compared, which can be used to constrain the flux and attenuation of terrestrial...