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Geosciences

The reading of Earth history satisfies a fundamental human urge to know how the world around us came to be. Throughout its 4.6 billion year history the Earth has undergone enormous transformation and stable isotope analysis has been at the forefront of developing our knowledge of these transformative processes. By understanding the macro and micro cycling mechanisms of the light stable isotopes through the lithosphere by natural processes the Earth history is continually being understood in ever more detail.

Paleoclimate

One of the earliest applications of light stable isotope mass spectrometry was the reconstruction of ancient climate based on the oxygen isotopic composition (δ18O) of preserved ancient marine carbonate, and continues to be one of the widely utilised methods for interrogating Earth’s climate history. This paleothermometer is based on the fundamental principle that the fractionation of oxygen isotopes into calcite is temperature dependent. The isoprime precisION with Dual Inlet and MultiCarb enables very precise and reliable automated measurement of carbonates, ideal for generating high-resolution paleo temperature records.

Cosmology

The sulfur isotope analysis of extra-terrestrial sulphide minerals, e.g. from meteorites, has provided a variety of insights into the origins of the Earth and the solar system. The isotopic composition of meteoritic sulfur (Canyon Diabolo triolite) was also used as a the original reference point for the bulk earth from which to evaluate global scale fractionations in the sulfur cycle. Sulfur-bearing minerals are easily analysed with our range of elemental analyser (EA-IRMS) systems, which utilise advanced purge and trap (APT) technology for unbeatable separation and peak focussing of SO2, ensuring perfect resolution and unparalleled sensitivity for mineral sulfur analysis. 

Stratigraphy

Fluctuations in δ13C through geological time are brought about by changes in the balance of fluxes of the carbon cycle.  Because the residence time in the carbon cycle is brief (10 ka), changes in flux are recorded accurately and globally in the sedimentary record. As such, occasional spikes in the global δ13C are useful as stratigraphic markers for chemostratigraphy, especially during the Paleozoic. The iso FLOW uses our novel UltiTrap technology to enable precise, high throughput continuous flow analysis of bulk carbonates to identify these isotope excursions.

Geoscientific publications using our instruments

Our customers use our instruments to do some amazing research in the geosciences. To show you how they perform their research and how they use our IRMS instruments, we have collected a range of peer-reviewed publications which cite our products. You can find the citations below and then follow the links to the publishing journal should you wish to download the publication.

If you would like to investigate our available citations in more detail, or email the citation list to yourself or your colleagues then take a look at our full citation database.

248 results:

Magmatic Evolution of the Early Pliocene Etrüsk Stratovolcano, Eastern Anatolian Collision Zone, Turkey
Lithos (2016)
Vural Oyan, Mehmet Keskin, Vladimir A. Lebedev, Andrey V. Chugaev, Evgenii V. Sharkov

The Pliocene Etrüsk stratovolcano, located in the northeast of Lake Van (Eastern Anatolia; Turkey), is one of the important volcanic centres in the Eastern Anatolian collision zone. Mt. Etrüsk overlies a widespread volcanic plateau, consisting of basaltic and hawaiitic lavas formed by fissure eruptions between 4.9–4.5 Ma. These basic lavas contain a phenocryst phase consisting of olivine, plagioclase and clinopyroxene. Trace element ratio diagrams imply that these basic magmas were generated from a mantle that contained a clear subduction component that is related to the subducted sediments rather than fluids or altered oceanic crust. Results of the melting models on the basaltic plateau lavas indicate that there was a marked variation both in the mantle source mineralogy (i.e. the ratio of garnet peridotite to spinel peridotite in the source varies between 60/40 % and 40/60 %) and the degree of melting (i.e. F between 0.8–4 %). This can be explained by a model in which magmas were generated by partial melting of both metasomatised lithospheric and deeper asthenospheric mantle sources in an extensional setting in response to the partial delamination of the lithospheric mantle of Eastern Anatolia and then mixed with each other during Pliocene times. Central eruptions that formed the Etrüsk volcano lasted ~600 kyr between 4.3–3.7 Ma during Zanclean times. The estimated depth of the Etrüsk magma chamber is ~9–12 km. The volcano erupted lavas with a rather narrow compositional range from latite to rhyolite, which are either transitional or mildly alkaline in character. The Etrüsk lavas contain plagioclase, clino- and orthopyroxene, biotite, K-feldspar and rarely, minor amounts of olivine and amphibole in the phenocryst phase. A composite chemo-stratigraphic section of the volcano and petrological models indicate that the evolved lavas of the Etrüsk volcano differentiated from a parental magma composition, which is similar to that of the most primitive plateau basalt lavas underlying the volcano, via the AFC process, and experienced at least two major magma replenishment episodes at 4.1 Ma and 3.8 Ma during the magma chamber evolution.

Sulfur and oxygen isotopes of sulfate extracted from Early Cambrian phosphorite nodules: Implications for marine redox evolution in the Yangtze Platform
Journal of Earth Science (2016)
Wenlang Qiao, Xianguo Lang, Yongbo Peng, Kaiyuan Jiang, Wu Chen, Kangjun Huang, Bing Shen

Phosphorite nodule beds are discovered in the black shale of basal Niutitang Formation throughout the Yangtze Platform in South China, recording an important phosphorite-generation event. Platform-wide phosphorite precipitation requires special oceanographic and geochemical conditions, thus the origin of the Niutitang phosphorite nodules may provide valuable information about the ocean chemistry in the Early Cambrian. In this study, we measured sulfur and oxygen isotopic compositions of sulfate extracted from phosphorite nodules collected from the basal Niutitang Formation. Phosphorite associated sulfate (PAS) is a trace amount of sulfate that incorporates into crystal lattice during phosphorite precipitation, accordingly PAS records the geochemical signals during phosphorite nodule formation. Sulfur isotopic composition of PAS (δ34SPAS) ranges from -1.16‰ to +24.48‰ (mean=+8.19‰, n=11), and oxygen isotopic value (δ18OPAS) varies between -5.3‰ and +26.3‰ (mean=+7.0‰, n=8). Most phosphorite nodules have low δ34SPAS and low δ18OPAS values, suggesting PAS mainly derived from anaerobic oxidation of H2S within suboxic sediment porewater. We propose that phosphate was delivered to the Yangtze Platform by a series of upwelling events, and was scavenged from seawater with the precipitation of FeOOH. The absorbed phosphate was released into suboxic porewater by the reduction of FeOOH at the oxic-suboxic redox boundary in sediments, and phosphorite nodule precipitated by the reaction of phosphate with Ca2+ diffused from the overlying seawater. The platform-wide deposition of phosphorite nodules in the basal Niutitang Formation implies the bottom water might be suboxic or even oxic, at least sporadically, in Early Cambrian. We speculate that the intensified ocean circulation as evident with frequent occurrences of upwelling events might be the primary reason for the episodic oxidation of the Yangtze Platform in Early Cambrian.
Tags: oxygen , sulfur , geol , elem

The termination and aftermath of the Lomagundi-Jatuli carbon isotope excursions in the Paleoproterozoic Hutuo Group, North China
Journal of Earth Science (2016)
Zhenbing She, Fanyan Yang, Wei Liu, Luhua Xie, Yusheng Wan, Chao Li, Dominic Papineau

The Lomagundi-Jatuli Event (LJE) is one of the largest and earliest positive carbon isotope excursions preserving δ13Ccarb values between +5 and +16‰ in Paleoproterozoic carbonates worldwide. However, the duration, amplitude and patterns of these excursions remain poorly constrained. The 2.14–1.83 Ga Hutuo Group in the North China Craton is a >10 km thick volcano- sedimentary sequence, including >5 km thick well-preserved carbonates that were deposited in supra- tidal to sub-tidal environments. C-O isotopic and elemental analyses of 152 least altered samples of the carbonates revealed a three-stage δ13C evolution. It began with an exclusively positive δ13Ccarb (+1.3 to + 3.4‰) stage in the ~2.1 Ga carbonate in the Dashiling and Qingshicun Formations, followed by a transition from positive values to oscillating positive and negative values in ~3 000 m thick carbonates of the Wenshan, Hebiancun, Jianancun, and Daguandong Formations, and end with exclusively negative δ13Ccarb values preserved in > 500 m thick dolostones of the Huaiyincun and Beidaxing Formations. It appears that much of the LJE, particularly those extremely positive δ13Ccarb signals, was not recorded in the Hutuo carbonates. The exclusively positive δ13Ccarb values (+1.3 to + 3.4‰) preserved in the lower formations likely correspond to the end of the LJE, whereas the subsequent two stages reflect the aftermath of the LJE and the onset of Shunga-Francevillian event (SFE). The present data point to an increased influence of oxygen on the carbon cycle from the Doucun to the Dongye Subgroups and demonstrate that the termination of the LJE in the North China Craton is nearly simultaneous with those in Fennoscandia and South Africa.
Tags: carbon , oxygen , geol , gashead

Active layer hydrology in an Arctic tundra ecosystem: quantifying water sources and cycling using water stable isotopes
Hydrological Processes (2016)
Heather M. Throckmorton, Brent D. Newman, Jeffrey M. Heikoop, George B. Perkins, Xiahong Feng, David E. Graham, Daniel O'Malley, Velimir V. Vesselinov, Jessie Young, Stan D. Wullschleger, Cathy J. Wilson

Climate change and thawing permafrost in the arctic will significantly alter landscape hydro-geomorphology and the distribution of soil moisture, which will have cascading effects on climate feedbacks (CO2 and CH4), and plant and microbial communities. Fundamental processes critical to predicting active layer hydrology are not well understood. This study applied water stable isotope techniques (δ2H and δ18O) to infer sources and mixing of active layer waters in a polygonal tundra landscape in Barrow, Alaska (USA) in August and September of 2012. Results suggested that winter precipitation did not contribute substantially to surface waters or subsurface active layer pore waters measured in August and September. Summer rain was the main source of water to the active layer, with seasonal ice-melt contributing to deeper pore waters later in the season. Surface water evaporation was evident in August from a characteristic isotopic fractionation slope (δ2H versus δ18O). Freeze-out isotopic fractionation effects in frozen active layer samples and textural permafrost were indistinguishable from evaporation fractionation, emphasizing the importance of considering the most likely processes in water isotope studies, in systems where both evaporation and freeze-out occur in close proximity. The fractionation observed in frozen active layer ice was not observed in liquid active layer pore waters. Such a discrepancy between frozen and liquid active layer samples suggests mixing of melt water, likely due to slow melting of seasonal ice. This research provides insight into fundamental processes relating to sources and mixing of active layer waters, which should be considered in process-based fine and intermediate scale hydrologic models
Tags: hydrogen , oxygen , geol , clim , gashead

Roles of forest bioproductivity, transpiration and fire in a nine-year record of cave dripwater chemistry from southwest Australia
Geochimica et Cosmochimica Acta (2016)
P.C. Treble, I.J. Fairchild, A. Baker, K.T. Meredith, M.S. Andersen, S.U. Salmon, C. Bradley, P.M. Wynn, Stuart Hankin, A. Wood, E. McGuire

Forest biomass has the potential to significantly impact the chemistry and volume of diffuse recharge to cave dripwater via the processes of nutrient uptake, transpiration and forest fire. Yet to-date, this role has been under-appreciated in the interpretation of speleothem trace element records from forested catchments. In this study, the impact of vegetation is examined and quantified in a long-term monitoring program from Golgotha Cave, SW Australia. The contribution of salts from rain and dry-deposition of aerosols and dissolved elements from soil mineral and bedrock dissolution to dripwater chemistry are also examined. This study is an essential pre-requisite for the future interpretation of trace element data from SW Australian stalagmite records, whose record of past environmental change will include alterations in these biogeochemical fluxes. Solute concentrations in dripwater vary spatially, supporting the existence of distinct flow paths governed by varying amounts of transpiration as well as nutrient uptake by deeply-rooted biomass. Applying principal components analysis, we identify a common pattern of variation in dripwater Cl, Mg, K, Ca, Sr and Si, interpreted as reflecting increasing transpiration, due to forest growth. Mass-balance calculations show that increasing elemental sequestration into biomass has the largest impact on SO4, providing an explanation for the overall falling dripwater SO4 concentrations through time, in contrast to the transpiration-driven rising trend dominating other ions. The long-term rise in transpiration and nutrient uptake driven by increased forest bioproductivity and its impact on our dripwater chemistry is attributed to i. the post-fire recovery of the forest understorey after fire impacted the site in 2006 CE; ii. and/or increased water and nutrient demand as trees in the overlying forest mature. The impact of climate-driven changes on the water balance is also examined. Finally, the implications for interpreting SW Australian speleothem trace element records are discussed.

High-resolution trace element and stable/radiogenic isotope profiles of late Pleistocene to Holocene speleothems from Dim Cave, SW Turkey
Palaeogeography, Palaeoclimatology, Palaeoecology (2016)
Ezgi Ünal-İmer, James Shulmeister, Jian-Xin Zhao, I. Tonguç Uysal, Yue-Xing Feng

Multiple climate-sensitive trace element/Ca and stable isotope (O and C) profiles derived from Dim Cave speleothems (S-SW Turkey) provide evidence of climatic changes and define a series of palaeohydrological conditions for the period ~9–90kyr. Dim Cave speleothem Mg/Ca, Sr/Ca, U/Ca, Ba/Ca, and Y/Ca ratios demonstrate similar patterns over glacial–interglacial scales, in agreement with δ18O and δ13C records. Three episodes of more positive moisture balance (71–63kyr, 51–40kyr, and 18–10kyr) were observed based on Y/Ca (and to a lesser extent Zr/Ca), 87Sr/86Sr ratios, calcite micromorphology, and growth rates. Increasing concentrations of Y and Zr (and U) and elevated 87Sr/86Sr ratios are attributed to enhanced levels of terrestrial input during these periods. Correlations between δ13C, δ18O and Mg/Ca during 40–18kyr (corresponding with the lowest growth rate of ~0.8mm/kyr), 63–51, and 80–71kyr (relatively low growth rates), as well as co-varying and enhanced Mg/Ca, Sr/Ca, and to a lesser extent Ba/Ca, ratios point to the prior calcite precipitation, wall–rock interaction, and preferential dolomite dissolution over calcite in the host dolomitic limestone during these periods. This relationship suggests that water–rock interactions are maximised during episodes of slower drip rates of water through the karst under drier conditions. Chondrite-normalized rare earth element and yttrium (REY) patterns of the stalagmites reveal seawater signatures closely linked to the dolomitic limestone. Excluding the aragonite formation during ~80–75kyr, which is an autogenic effect, trace element/Ca ratios appear to respond to millennial scale global cooling periods such as Heinrich events.

Solar-, monsoon- and Kuroshio-influenced thermocline depth and sea surface salinity in the southern Okinawa Trough during the past 17,300 years
Geo-Marine Letters (2016)
Libo Wang, Jun Li, Jingtao Zhao, Helong Wei, Bangqi Hu, Yanguang Dou, Zhilei Sun, Liang Zou, Fenglong Bai

Factors influencing millennial-scale variability in the thermocline depth (vertical mixing) and sea surface salinity (SSS) of the southern Okinawa Trough (OT) during the past 17,300 years were investigated based on foraminifer oxygen isotope records of the surface dweller Globigerinoides ruber sensu stricto and the thermocline dweller Pulleniatina obliquiloculata in the AMS 14C dated OKT-3 core. The thermocline depth is influenced by surface thermal buoyancy (heat) flux, in turn controlled by the annual mean insolation at 30°N and the strength of the East Asian winter monsoon (EAWM). Strong insolation and weak EAWM tend to increase buoyancy gain (decrease buoyancy loss), corresponding to shallow thermocline depths, and vice versa. Regional SSS is influenced by the global ice volume, the Kuroshio Current (KC), and vertical mixing. A deep thermocline coincides with a high SSS because strong vertical mixing brings more, saltier subsurface KC water to the surface, and vice versa. Local SSS (excluding the global ice volume effect) became lower in the northern OT than in the southern OT after ~9.2 ka, implying that Changjiang diluted water had stronger influence in the northern sector. SSS show no major changes during the Bølling/Allerød and Younger Dryas events, probably because the KC disturbed the North Atlantic signals. This argues against earlier interpretations of sea surface temperature records of this core. Wavelet and spectral analyses of the Δδ18OP-G (δ18O of P. obliquiloculata minus G. ruber s.s.) and δ18Olocal records display 1,540-, 1,480-, 1,050-, 860-, 640-, and 630-year periods. These are consistent with published evidence of a pervasive periodicity of 1,500 years in global climate as well as EAWM and KC signatures, and a fundamental solar periodicity of 1,000 years and intermediary derived periodicity of 700 years.
Tags: oxygen , geol , ocea , mulitcarb

Assessment of coral δ44/40Ca as a paleoclimate proxy in the Great Barrier Reef of Australia
Chemical Geology (2016)
Xuefei Chen, Wenfeng Deng, Hongli Zhu, Zhaofeng Zhang, Gangjian Wei, Malcolm T. McCulloch

The Ca isotopic composition (δ44/40Ca) in a Porites spp. coral from the Great Barrier Reef was analyzed at monthly intervals for two consecutive years. It was found that variations in skeletal δ44/40Ca values over the 2-year period are slightly greater than the analytical precision of the measurements, although other coralline geochemical records (i.e., δ13C, δ18O, δ11B and Sr/Ca ratios) show remarkable variations. To evaluate the potential of δ44/40Ca as a paleoclimate proxy in corals, we compared δ44/40Ca with other well-established indicators, and found that δ44/40Ca values show little relationship to δ18O, Sr/Ca, Δδ18O, or δ11B values, thus suggesting that the influence of seawater temperature, seawater pH and river inputs on skeletal δ44/40Ca is limited or overwhelmed by other factors. However, skeletal δ44/40Ca values are significantly related to δ13C values (r=0.46, p<0.05; n=27), thus indicating that Ca isotopic fractionation in corals is subjected to vital effect. The strong influence of biogenic factors on δ44/40Ca in corals, limit the applicability of coral δ44/40Ca to paleoclimate reconstruction.
Tags: carbon , oxygen , geol , clim , mulitcarb

Phosphogenesis associated with the Shuram Excursion: Petrographic and geochemical observations from the Ediacaran Doushantuo Formation of South China
Sedimentary Geology (2016)
Huan Cui, Shuhai Xiao, Chuanming Zhou, Yongbo Peng, Alan J. Kaufman, Rebecca Plummer

The Ediacaran Period witnessed one of the largest phosphogenic events in Earth's history. Coincidently, some phosphorite deposits in South China are associated with the largest carbon isotope negative excursion in Earth history (i.e., Shuram Excursion), suggesting an intimate coupling of the biogeochemical carbon and phosphorous cycles. However, the geomicrobiological linkage between these anomalies remain poorly understood. In this study, we investigated the petrography and geochemistry of phosphorite samples collected from the uppermost Doushantuo Formation in South China. Carbon isotope compositions of authigenic calcite cements and nodules in the phosphorites samples are as low as −34‰ (V-PDB). Petrographic and geochemical investigations indicate that the 13C-depleted carbonates likely formed as the result of microbial sulfate reduction that released phosphorous from iron oxyhydroxide, concentrating phosphorous in pore waters, and thereby promoting phosphate mineralization. The timing of this event appears to coincide with enhanced sulfate delivery to seawater through continental weathering. The basin-scale distribution of Doushantuo phosphorites suggests a redox control associated with the availability of iron oxyhydroxide and the recycling of pore water phosphorous. Both inner and outer shelf regions were likely characterized by an oxic water column, and were the main loci for phosphogenesis; on the contrary, intra-shelf and slope regions, which are lean in phosphorite, were subjected to euxinic or ferruginous water column conditions. The intimate coupling between Ediacaran phosphogenesis and the Shuram Excursion suggests strong links among seawater redox conditions, carbon–sulfur–phosphorous cycling, and fossil phosphatization. Increased microbial sulfate reduction driven by enhanced sulfate reservoir in the Ediacaran ocean may played an essential role on these biogeochemical events.

Exploring Accumulation Rates of Shell Deposits Through Seasonality Data
Journal of Archaeological Method and Theory (2016)
Niklas Hausmann, Matthew Meredith-Williams

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
Tags: carbon , oxygen , geol , ocea , clim , mulitcarb