Associate Editor for G3 (Geophysics, Geochemistry, Geosystems) - December 2011
Congratulations to Melanie Leng who has become an Associate Editor for G-cubed for 2 years (2012–14). She will be co-handling papers for the theme "Development of Isotopic Proxies for Paleoenvironmental Interpretation: A Carbon Perspective (DIPPI-C)".
Mineralogical Society Distinguished lecturer 2011-2012: Professor Randy Parrish
The programme aims to promote interest and discussions across the broad field of Mineral Sciences (including all aspects of petrology and geochemistry at the Earth's surface and at depth). The Mineralogical Society has appointed Prof Parrish as one of this season's distinguished lecturers, on the basis of being a good communicator and an expert in his field, to give lectures at universities and related institutions. The lectures will be intended to appeal to undergraduates and research students, as well as to more advanced scientists. The two lectures on offer are: "100 years of geochronology: Arthur Holmes and his legacy to U-Pb dating and Earth history" and "Addressing political agendas, depleted uranium, and nuclear proliferation with mass spectrometry and environmental science".
Jonathan joins NIGL on a one year isotope apprenticeship following completion of his doctoral thesis from Loughborough University (2006–2010) titled 'Holocene environmental change in coastal Denmark: interactions between land, sea and society.' The project involved using a range of palaeoenvironmental techniques (particularly diatoms, sedimentary pigments and isotopes from foraminiferal tests) for reconstruction of salinity, productivity and nutrient status over the last ~9,000 years in three shallow coastal systems in Denmark. At NIGL, Jonathan will be trained as an isotope geoscientist and will work in a technical role on a range of projects, preparing and running isotope samples.
Andrew Smye: new appointment - September 2011
Andrew joins NIGL as a PDRA after recently completing his doctoral thesis at the University of Cambridge where he studied the time and length scales of processes responsible for metamorphism in the Eastern Alps. During his time at NIGL, Andrew will be involved in a range of research projects including the development of an in-situ U-series technique.
NERC's Peer Review College - September 2011
Congratulations to Dr Tim Heaton and Dr Jane Evans who have been nominated to sit on the NERC Peer Review College from September 2011 to September 2014.
Dr Andrea Snelling: PDRA appointment - July 2011
Andrea Snelling continues at NIGL with PDRA positions working on NERC grants: "Bering Sea diatom isotope records during the onset of Northern Hemisphere Glaciation" with Nottingham University and "Seasonal climate, silicon cycling and diagenesis at Rostherne Mere, Cheshire: generation of δ18Odiatom and δ30Sidiatom signals, with implications for palaeoclimatology and biogeochemistry" with Loughborough University.
Wendy Austin-Giddings: new appointment - June 2011
Wendy has recently joined NIGL as a research assistant working on U-Pb carbonate analysis in the plasma ionisation mass spectrometry laboratory (PIMS). She is currently also finalising her PhD which assesses tsunami hazard from the collapse of ocean island volcanoes in the Canary Islands, through the investigation and development of techniques to identify reworked tsunami deposits.
Jane Evans appointed Special Associate Professor - June 2010
Congratulations to Jane Evans who has been appointed Special Associate Professor in the School of Humanities at the University of Nottingham. The appointment is on the basis of Jane being a distinguished practitioner in the field of isotopes in archaeological science and is aimed at strengthening links between BGS and the university.
Dr Nick Roberts: new appointment - June 2010
Nick Roberts has joined NIGL as a research support scientist, working primarily in the plasma ionisation mass spectrometry (PIMS) facility. Nick will be involved in improving current techniques in U-Th-Pb geochronology and Lu-Hf isotope analysis, and will also be involved in developing methodologies on the single-collector mass-spectrometer, including Uranium-series dating of carbonates. Nick has recently finished a PhD at the University of Leicester, of which a significant component involved LA-ICP-MS and TIMS analyses at NIGL.
Dr Adam Martin: new PDRA – October 2009
Adam Martin has recently joined NIGL as a Post-Doctoral researcher. The post is part of an international multi-disciplinary project, FAR-DEEP (Fennoscandia Arctic Russia - Drilling Early Earth Project). FAR-DEEP is an internationally supported (ICDP, NGU and various national research councils) project with one overarching goal: to develop a comprehensive, self-consistent model explaining the transformation of Earth from an anoxic to oxic planet and the subsequent transition to an aerobic Earth System. NIGL will be responsible for the integration of high-precision geochronology into the models developed from the FAR-DEEP research, and will work closely with other UK researchers from the Scottish Universities Environmental Research Centre and University of St-Andrews, using mainly high precision TIMS and LA-ICP-MS techniques. His research background is in the petrology and chemistry of the Antarctic lithosphere; U-Pb, Ar-Ar, and K-Ar chronology; and low-sulphidation epithermal gold deposits.
Dr Laura Bracciali: new PRDA - September 2009
Laura Bracciali has recently joined NIGL as a Post Doctoral Research Associate investigating the evolving composition of the Brahmaputra River sediments through Neogene time by means of a multi-technique provenance study, with the aim of testing competing hypotheses of drainage evolution and erosion-tectonic coupling. Her research background deals with aspects of igneous and sedimentary petrology, including field work, petrography, trace element/isotope geochemistry, as applied to understanding problems of orogenic evolution and palaeotectonic reconstructions.
Her appointment is associated with a three year NERC standard grant awarded to Randy Parrish.
NERC's Peer Review College - July 2009
Congratulations to Randy Parrish who has been nominated to sit on the NERC Peer Review College from July 2009 to July 2012.
Silicon Editorial Board appointment for Prof Melanie Leng – February 2009
Congratulations to Melanie Leng on her appointment to the Editorial Advisory Board of Silicon. The appointment is to run for two years. Silicon is an international, interdisciplinary journal solely devoted to the most important element of the 21st Century. Silicon’s coverage is unique in presenting all areas of silicon research and development across all disciplines. Silicon is a quarterly journal publishing the very latest cutting edge research in materials chemistry, materials physics, materials biology, materials engineering and environmental science.
Professor Sarah Metcalfe awarded Visiting Research Associate – November 2008
Sarah Metcalfe (School of Geography, Nottingham University) has been awarded a VRA at NIGL/BGS. Sarah will be spending her time at NIGL working with Melanie Leng on improved understanding of controls on isotopic composition of Mexican lake systems to develop their use to reconstruct changes in the Mexican monsoon. This will also be tied in with their mutual interest in comparing the tropical Americas with the near East and the balance between mid-latitude and tropical climate systems over time.
April 2012 - Congratulations to Holly Miller who recently passed her PhD entitled "The Origins of Nomadic Pastoralism in the Southern Levant: stable isotope, chipped stone and architectural analysis of archaeological evidence".
Herded sheep and goats were introduced to the steppic region of Eastern Jordan late in the seventh millennium cal BC. The evidence for initial pastoral activities in this arid area, some 500 years after domestic caprines are known to have been kept at large village sites in the neighbouring and more hospitable Mediterranean regions, suggests that these early herding groups began to develop a lifeway that pastoral nomads continue to live in some regions of the world today.
13C/12C and 15N/14N ratios from the bone collagen of animal remains from Mediterranean sites, where C4 plants were less common and water availability was greater, was compared to those of the steppic sites, where C4 vegetation was abundant and water scarce. The results of this study were used to pinpoint the foraging range of the herded animals, suggesting the regions in which they, and their accompanying herders, spent lengths of time. It was determined that differences in the isotopic ratios of animals from two sites in the arid region signify different herding strategies used to bring animals to the area. Animals from one site have indications of a diet that included Mediterranean vegetation, suggesting that their herders had more frequent contact with village groups. At the second site, animal diets, and thus movements, were restricted to the steppe, suggesting the development of a lifestyle based around frequent mobility within the arid regions, and allowing the rejection of a theory that stated early Neolithic Southern Levantine herding was village based.
In combination with chipped stone and architectural analysis, the results of the stable isotope study have allowed an investigation of the social and economic behaviours and practices of the communities that initially saw the potential of the Southern Levantine steppe as an area for pastoral activities.
Liverpool supervisors- Drs Jessica Pearson and Douglas Baird, NIGL- Dr Angela Lamb and Mrs Carolyn Chenery
December 2011 - Congratulations to Michael Wallace who successfully defended his PhD thesis: Crop watering practices in the Neolithic and Bronze Age: the stable carbon isotope approach
In the ancient past, agriculture was central to the daily routines of life and economic organisation. The major limiting factor on crop production in dry regions, such as Western Asia, is the availability of water. In these regions, rainfed crops are susceptible to drought-induced failure and, while farmers can water their crops artificially, this places demands on labour and water supplies. The effort and resources afforded to crops by farmers can indicate the scale of production, whereas the preferential treatment of certain crops over others offers insights into the cultural and economic role of different crops. Charred crop remains are ubiquitous at archaeological sites in dry regions, and this thesis assesses the utility of stable carbon isotope analysis as a means of inferring crop water status. Experiments were conducted to establish the relationship between 13C/12C ratios and water status in modern crops grown under known conditions. Laboratory tests were also undertaken to determine the extent to which the ratios may be altered post-mortem. In light of the findings from these experiments, isotope analysis was carried out on crop remains from nine Neolithic and Bronze Age sites, primarily located in Western Asia. The results showed that while the precision of the method is limited (by natural variations, unknown differences in growing conditions and plant physiology, and small post-mortem alterations), 13C/12C analysis can nevertheless provide a reliable indication of the water status of ancient crops.
On this basis it was possible to develop interpretations regarding agricultural arrangements at individual sites, and to identify regional trends in ancient crop production.
The thesis project was tied to a NERC Standard Grant, on which NIGL were co-investigators. Michael was supervised at Sheffield University by Glynnis Jones, and at NIGL by Tim Heaton and Chris Kendrick.
December 2011 - congratulations to Wendy Austin-Giddings on her PhD entitled "The Deposition and Reworking of Tsunami Sediments in Agaete, Gran Canaria"
Coarse-grained, polymict, deposits, draping hillslopes at high elevations on ocean island volcanoes, have been variously interpreted as sourced either from sea-level highstands or from tsunamis; their origin is thus controversial. A detailed facies analysis of coarse-grained, fossiliferous sediments located at Agaete, on the north-west coast of Gran Canaria, has been undertaken. Previously interpreted as the result of a sea-level highstand, these deposits have recently been re-interpreted as sourced from a tsunami; itself triggered by a volcano flank failure. The Agaete Fossiliferous Conglomerates occur at several locations in the Barranco de Agaete, up to 188m apsl. and 2 kilometres inland from the coast. They comprise seven facies, all of which are variably graded, matrix- and clast-supported, range from ~0.3 to 2 m thick, and contain a diverse assemblage of volcanic clasts, large beachrock boulders and a shallow marine fauna. All the facies have sharp, erosional bases. A facies at one site contains large palaeosol rip-up clasts up to 1.5 m across and at its base truncates plant roots. The upper facies of the conglomerates are all finer-grained, reverse-graded, clast-supported and better-sorted than the lower facies of the group. At one location the upper conglomerates comprise prograding beds that are interpreted as alluvial.
The lower facies of the conglomerates are interpreted as primary tsunami deposits, whereas the upper facies are interpreted as tsunami deposits that have been reworked. The alternative, marine highstand, interpretation of the coarse-grained deposits is discounted on the basis of (i) an absence of supporting geomorphological features such as a marine terrace and/or a wave cut platform; (ii) the composition of the sediments; (iii) diagenetic features; (iv) distance from the coast; and (v) elevation of the deposits. Gran Canaria is in its erosional post-shield stage of development and the north-western coastline has experienced 40-50 m of tectonic uplift over the past 1.75Ma. Thus uplift of highstand deposits cannot account for the occurrence of the Agaete sediments at elevations of up to 188 m apsl. The Güimar lateral collapse event on the neighbouring island of Tenerife, dated at around 0.8Ma BP, is presented as the most likely tsunami source.
Wendy was a BGS BUFI student and supervised by Prof Dave Tappin at BGS, Prof Bill McGuire at UCL, and Prof Randy Parrish at NIGL.
December 2011 - congratulations to Ronan Roche on his PhD entitled "A multi-proxy reconstruction of mid-Holocene environmental conditions at a nearshore Great Barrier Reef site: King Reef, Northern Queensland"
Major changes in sediment and nutrient inputs to Australia's Great Barrier Reef have been documented since European settlement of the region (~1840 A.D.) and the concurrent introduction of modern agricultural methods. This study focussed on King Reef, a mid-Holocene (~5800-4600 yr B.P.) age coral reef in the Wet Tropics region of Australia's Great Barrier Reef. Combined records of Sr/Ca and oxygen isotope ratios of coral skeleton were used to estimate sea- surface temperature and the oxygen isotopic value of the surrounding seawater (δ18Osw ) which is strongly correlated with sea-surface salinity. At 4665 yr B.P. sea-surface temperatures indicated by Sr/Ca ratios were ~1 to 1.4°C higher than modern values. δ18Osw values were slightly higher in winter (+0.1‰) and lower in summer (-0.1‰) resulting in an increased annual range. Overall mean seasonal mid-Holocene δ18Osw values were similar to modern values, however, a comparison of δ18Osw during drought periods suggests enrichment by 0.3 to 0.38‰.
This enrichment suggests that evaporation was enhanced due to higher sea-surface temperatures in the mid-Holocene, which would have resulted in a stronger Australian-Indonesian monsoon system. These results may indicate that riverine influence and associated sediment input at the study site was high during the mid-Holocene, and that nearshore reefs within Australia's Great Barrier Reef have previously experienced conditions of high sediment input during their phase of active accretion.
Ronan was supervised at NIGL by Tim Heaton and Melanie Leng.
November 2011 - Congratulations to Alistair Seddon who successfully defended his PhD entitled: Palaeoecology, Biogeography and Evolution of Benthic Littoral Diatoms from the Galápagos Islands
This thesis presents palaeoecological and biogeographic evidence to investigate whether the Galápagos Islands, famous for their biogeographical isolation in terrestrial organisms, are also isolated for diatoms. Are diatom assemblages principally controlled by environmental changes at the local and regional scale (abiotic processes), or does biogeographical isolation (reshuffling the nature of biotic processes) also play a role? Ten new species of diatom belonging to the genus Navicula sensu stricto were described from coastal lagoons in the Galápagos. Using a multi-proxy approach, these lagoons are dynamic, threshold environments which have exhibited non-linear responses to environmental change over the past 3,000 years. However, ecological turnover, rather than evolutionary processes such as rapid morphological speciation, were the main influences in the formation of Galápagos diatom biodiversity on Holocene timescales. Indeed, newly discovered Galápagos taxa to be restricted to the shorelines of cyanobacterial mats in assocation with a larger number of 'generalist' species. As yet, the true biogeographic extent of the novel taxa are unknown, but it is likely that they are simply 'niche specialists' with smaller global population sizes and, as a result, a limited global distribution.
July 2011 - Congratulations to Katy Wilson who successfully defended her PhD thesis entitled: Plio-Pleistocene Reconstruction of East African and Arabian Sea Palaeoclimate
Superimposed upon a long-term trend of aridification, the climate history of Africa was punctuated by episodes of extreme variability, characterised by the precessionally-forced appearance cycling of large lake systems within the East African Rift Valley. In order to investigate the nature of low-latitude climate variability during the Late Pliocene and Early Pleistocene, high-resolution analyses from one of the lake phases were combined with the reconstruction of long-term changes in the transport of wind-borne terrigenous dust to the Arabian Sea. Climate in both regions is strongly influenced by relative changes in the strength of the Indian Ocean monsoons, which determine rainfall distribution in equatorial East Africa and generate the low-level winds which transport dust offshore from the Arabian Peninsula. The Baringo-Bogoria basin in the East African Rift Valley contains a well-dated package of fluvio-lacustrine sediments and diatomite units documenting a major humid phase between 2.7 and 2.55 million years ago (Ma). Stable oxygen isotope measurements of diatom silica, combined with the XRF analysis of whole-sample geochemistry, reveal that the deep lake phase was characterised by wet-dry cycles lasting, on average, 1,400 years.
Over longer timescales, variations in the aeolian delivery of lithogenic matter to the Arabian Sea, reflected in the normalised flux of titanium, show that monsoonal circulation prior to 2.6 Ma was highly variable and primarily driven by orbitally-forced changes in tropical summer insolation, modulated by the 400,000 year cycle of orbital eccentricity. Millennial-scale fluctuations in the dust record also support the evidence of abrupt wet-dry cycles in East Africa. Such high-resolution cycles are rarely found in older records, thus giving a valuable insight to the nature of short-term fluctuations in Plio-Pleistocene climate.
Katy was supervised by Mark Maslin and Ans Mackay at UCL and Melanie Leng at NIGL
June 2011 - Congratulations to Gareth Preston who successfully defended his PhD these entitled: From Nomadic Herder-Hunters to Sedentary Farmers: the relationship between climate, environment and human societies in the United Arab Emirayes from the Neolithic to the Iron age
Owing to its archaeological and climatic history, the United Arab Emirates (UAE) acts as a natural laboratory in which to examine the relationship between climate, the environment and early human populations from the onset of the Neolithic to the termination of the Iron Age (~11 500 - 2300 cal. yr BP). Despite this, such studies have to date been hindered by the paucity of high-quality palaeoenvironmental data from the region. To help fill this gap in knowledge, this thesis reports the results of high-resolution, multi-proxy investigations (bulk physical, geochemical and isotopic) carried out on two palaeolake sediment sequences in the Emirate of Ra's al-Khaimah, UAE; Awafi (25° 42' 57" N; 57° 55' 57" E) and Wahalah (25° 38' 48Ė¯ N, 55° 47' 26Ė¯ E). The new data reveals that climate has varied greatly between ~8500 - 4200 cal. yr BP, with periods during which conditions were more pluvial than the present punctuated by phases of intense aridity. It is demonstrated that this variability had a considerable impact on the natural environment of the UAE, resulting in significant changes in landscape stability, water availability, and vegetation over both long and short-term timescales. Furthermore, it is suggested that abrupt increases in aridity recorded in the palaeolake sediments between ~8000 - 7800 cal. yr BP, from ~5900 cal. yr BP and at ~4200 cal. yr BP, reflect the response of the regional landscape to global climatic variations.
By placing the archaeological record of the UAE into this detailed framework of landscape evolution it is demonstrated that the region's early Holocene populations adapted with the prevailing climate by altering their subsistence strategies (e.g. from hunter-gatherer to animal husbandry and eventually sedentary agriculture) and settlement patterns (e.g. by moving between the interior, Arabian Gulf, and Gulf of Oman coasts), as well as utilising new technologies (e.g. irrigation). Indeed, this study provides compelling evidence for the potential of climatic-environmental change to influence the behaviour of early human societies. Understanding this relationship is made all the more imperative given the growing concerns over contemporary climate change.
Gareth was supervised by Adrian Parker and Martin Hodgson at Oxford Brookes and Melanie Leng at NIGL.
May 2011. Congratulations to Tom Broadbent who passed his PhD: Low latitude Pacific palaeoceanographic change across the Eocene/Oligocene boundary
Evidence from both terrestrial and marine environments indicates a cooling of Earth's climate across the Eocene/Oligocene boundary (EOB), with the likely development of continental scale glaciation. The most geographically widespread and persuasive line of evidence for the shift in Earth's climate comes from variation in stable isotopes measured from benthonic foraminiferal carbonate, with a geologically rapid and globally observed >1 ‰ increase in δ18O. Increasing foraminiferal δ18O reflects either a cooling in the deep ocean or an increase in the δ18O of seawater, which is related to removal of light oxygen isotopes through continental glaciation. However, despite the global recognition of an increase of >1.0 ‰ in benthonic foraminiferal δ18O and fundamental change in Earth's climate, the proportion of change, i.e. temperature decrease and/or ice volume development, is poorly constrained.
Deconvolution of the foraminiferal δ18O requires and independent proxy to isolate the temperature or ice-volume change, one such proxy is foraminiferal Mg/Ca ratios. Foraminiferal Mg/Ca ratios are a palaeotemperature proxy, however, their application has lead to the observation of bottom-water warming and thus suggesting bipolar glaciation; a scenario inconsistent with a warmer Earth and unsupported by sedimentary evidence. The warming observed in bottom-water Mg/Ca palaeotemperatures, however, was determined from a deep-ocean site that experienced significant deepening of the carbonate compensation depth (CCD) concomitant with Mg/Ca increase, leading to the hypothesis increasing carbonate ion saturation (Δ[CO32-]) caused enhanced foraminiferal uptake of Mg and thus the observed temperature increase. This study aimed to deconvolute the foraminiferal δ18O record using paired benthonic foraminiferal records from a site with minimal change in Δ[CO32-] amongst other proxies.
Tom was supervised at Bangor University by Leon Clarke and at NIGL by Melanie Leng and Ian Millar.
May 2011. Congratulation to Chris Brodie who successfully defended his PhD thesis: The effect of acid treatment methods on bulk organic materials, and a long-core geochemical palaeoenvironmental reconstruction from South China.
The first aim of this thesis was an investigation of the effect of acid treatment on C/N, δ13C and δ15N of organic materials. Three common acid pre-treatment methods were compared (capsule method; rinse method; fumigation method), using a range of acid reagents (HCl; H2SO3; H3PO4), on a range of terrestrial and aquatic, modern and geological sample materials. An inherent assumption of these acid treatment methods is that any offsets in C/N, δ13C and δ15N are linear and proportional, and that any bias is not greater than instrument accuracy and precision. The C/N, δ13C and δ15N values of OM are not just dependent upon environmental processes but also on acid treatment method, which adds significant non-linear biasing to the OM signal several orders of magnitude above instrument precision. This biasing is caused by the inefficient removal of IC from sample materials and the alteration of OM by the acid treatment process. Consequently, this can significantly alter the environmental interpretation of these proxies. The second aim of this thesis concerned a reconstruction of palaeoenvironmental change from Lake Tianyang, Leizhou Peninsula, south China (20°31'1.11" N, 110°18'43.02" E) using a suite of geochemical proxies (δ13C of bulk OM; XRF elemental ratios, magnetic susceptibility).
The lake sedimentary sequence is substantially older than previously reported, with the upper ~40 m representing ~30 ka BP. In addition, the δ13C (taken to be an aridity indicator where values are above known inaccuracy and imprecision) show a striking glacial - interglacial imprint. The sedimentological evidence suggest the lake has been continually silting up since Marine Isotope Stage 9. The Tianyang δ13C record and elemental ratios (MIS 9 - MIS 6 inclusive) show a strong glacial - interglacial imprint, though the elemental ratios lose this imprint during MIS 5 likely due to an increase in catchment erosion.
Chris was supervised at Durham University by James Casford, Jerry Lloyd and at NIGL by Melanie Leng, Tim Heaton with support from Chris Kendrick.
April 2011. Congratulations to Melanie Bugler who has successfully defended her PhD: An investigation into use of the freshwater gastropod Viviparus as a recorder of past climatic change
Through isotopic analysis of Viviparus lentus (V. lentus) a high resolution record of stepwise changes in δ18O and δ13C across the Eocene / Oligocene transition and Oi-1 glacial maximum has been produced for the continental Solent Group strata, Isle of Wight (UK). Comparison of this V. lentus δ18Ocarb. record with high resolution marine δ18Ocarb. records shows that similar isotopic shifts exist in the near coastal continental and marine realms. In order to calculate palaeotemperatures from this new continental record an investigation into the biology of modern Viviparus and its effect on the isotopic composition of its shell carbonate was undertaken. Experimental measurements of the 18O/16O isotope fractionation between the biogenic aragonite of Viviparus and its host freshwater were undertaken on samples derived from the Somerset Levels in order to generate a genus specific thermometry equation. The results from using this new Viviparus equation on fossil V. lentus shell fragments suggests that aquatic and terrestrial biota were being affected by climate change associated with the Late Eocene Event. This coincides with a decrease in mammal species richness in the Osborne Member, reaching its climax at the end of the Osborne / Seagrove Bay Members.
This event is followed by a brief warming in the Bembridge Limestone which was marked by a within-Europe mammal turnover involving dispersal from the south and an increase in species richness, concurrent with this is an increase in size of Harrisichara gyrogonites. An additional investigation into seasonal isotopic variability using whole well preserved V. lentus specimens has also revealed a shift from tropical /subtropical to temperate climatic zones occurring before the Eocene /Oligocene boundary and Oi-1 glacial maximum. Overall the evidence provided by these investigations would suggest that climatic change was already in progress prior to the build up of glacial ice on Antarctica.
Mel was supervised by Stephen Grimes at Plymouth and Melanie Leng at NIGL.
A full list of publications can be found in the NIGL Annual Reports. This section
highlights some of our high-impact papers as they go to press. A full list of NERC staff publications and outputs can be found in the NERC Open Research Archive (NORA)
Quaternary Science Reviews - May 2012
Boreal ecosystems are highly vulnerable to climate change, and severe ecological impacts in the near future are virtually certain to occur. We undertook a multiproxy study on an alpine lake at the modern tree-line in boreal, southern Siberia. Steppe and tundra biomes were extensive in eastern Sayan landscapes during the early Holocene. We conclude that lakes in continental, boreal regions undergo different models of lake ontogeny than oceanic boreal regions. Unlike other regions discussed, climate is a more important driver of ecosystem change than catchment changes. We also demonstrate that the start of the period coincident with the onset of the Little Ice Age resulted in important thresholds crossed in catchment vegetation and aquatic communities.
Mackay, A.W., Bezrukova, E.V., Leng, M.J., Meaney, M., Nunes, A., Piotrowska, N., Self, A., Shchetnikov, A., Shilland, E., Tarasov, P., Wang, L., White, D. 2012. Aquatic ecosystem responses to Holocene climate change and biome development in boreal, central Asia. Quaternary Science Reviews, 41, 119-131.
Science — 238U/235U Systematics in Terrestrial Uranium Bearing Minerals — 30th March 2012
Minerals, such as zircon, naturally capture uranium when they form, which in turn undergoes a chain of radioactive decays to other elements, ending with lead. Dating of zircon and other minerals underpins much if what we know about geological time. This new research has shown that, by more accurately measuring the relative amount of the uranium isotopes 238U and 235U, we now have a better understanding of how much time has passed since a mineral or rock has formed. We have measured, for the first time, 238U/235U in a suite of U-bearing minerals, including 45 zircon samples typical of those dated to quantify geological time in a wide range of rock types. A major impact of this work is an 'average zircon' 238U/235U to replace the 'consensus value' of 137.88, the accuracy of which could not be verified. Using this new value will decrease all previous zircon uranium-lead (U-Pb) age determinations, by up to 700,000 years for samples that are about 4.4 billion years old — the age of the Earth's oldest minerals.
The new 238U/235U ratio will allow geologists to place more accurate limits on the exact timing of a broad range of geological processes, from the initial formation of our planet, continents and economic mineral deposits, to past evolutionary events and climate changes. In addition to the implications for U-Pb zircon geochronology, this study provides insight into uranium isotopic fractionation processes at magmatic temperatures, the possible role of weathering to driving changes of 238U/235U in seawater, and comparison of the terrestrial 238U/235U database to extra-terrestrial meteorite samples.
The volume of Earth's continental crust depends on the rate of addition of continental crust from the mantle compared to the rate of continental loss back to the mantle, which at present is roughly balanced. Models for the growth rate of continental crust vary, with isotope data suggesting various episodes of increased growth rate throughout Earth's history; these episodes have been correlated with the supercontinent cycle, but may be a consequence of preferential preservation of continental crust during these cycles. The global balance between addition and loss of continental crust is controlled by: 1) the extent of internal orogens versus exterior orogens, with the latter favouring continental addition, and 2) the balance between exterior orogens in retreating mode versus those in advancing mode, with the latter favouring continental loss. A greater balance of continental addition versus loss should exist during supercontinent break-up, due to a high magmatic flux in retreating accretionary orogens, whereas the amalgamation of supercontinents should involve increased continental loss due to increased sediment subduction and tectonic erosion. Zircon U-Pb and Hf isotopes provide insight to models of crustal growth rate since they sample the continental crust at their time of formation. Using the distribution of data within εHf(t)-time space of a global zircon database, it is demonstrated that the data are in accord with the concept of increased continental loss during supercontinent amalgamation.
Periods featuring increased continental addition relative to continental loss, and hence increased continental crust growth rate, occur at ~ 1.7–1.2 Ga, ~ 0.85–0.75 Ga, and ~ 0.45–0.35 Ga, and follow the formation of the Columbia (Nuna), Rodinia and Gondwana supercontinents respectively. Distinct increases in continental loss compared to continental addition, i.e. decreased continental growth rate, occur at c. 1.0–0.9 Ga, and ~ 0.6–0.55 Ga, correlating with the periods of Rodinia and Gondwana amalgamation respectively. Formation of Pangea by introversion rather than extroversion, means that continental addition in exterior orogens was concurrent with continental loss in interior orogens; a similar process may have been responsible for formation of the Columbia supercontinent. Peaks in the compilation of U-Pb zircon ages correlate with the timing of supercontinent amalgamation, and are likely to be a consequence of preferential preservation of continental crust during this part of the supercontinent cycle.
Roberts, N. M. W., 2012. Increased loss of continental crust during supercontinent amalgamation. Gondwana Research 21, 994-1000.
Palaeogeography, Palaeoclimatology, Palaeoecology - February 2012
We aim to reconstruct the climatic and environmental conditions in the Valsequillo Basin during the deposition of the Valsequillo gravels between c. 40 000 and 8000 years ago, when large mega-fauna and potentially humans occupied the basin. Fossil freshwater (Fossaria sp. and Sphaeriidae (Family)) and terrestrial (Polygyra couloni, Holospira sp. and Cerionidae (Family)) snail shells from sections within the Barranca Caulapan were collected for oxygen and carbon stable isotope analysis. Oxygen and carbon isotopes in terrestrial and freshwater snail shells relate to local climatic parameters and environmental conditions prevailing during the lifetime of the snail. Whole shell isotope analysis showed that c. 35 000 years ago climate in the Valsequillo Basin was similar to the present day. Between c. 35 000 and 20 000 BP conditions became increasingly dry, after which conditions became wetter again, although this record is truncated. Intra-shell isotopic analyses show that the amount of precipitation varied seasonally during the late Pleistocene. If people did reach this part of the Americas in the late Pleistocene they would have experienced changing long-term and seasonal climatic conditions and would have had to adapt their life strategies accordingly.
Stevens, R.E., Metcalfe, S.E., Leng, M.J., Lamb, A.L., Sloane, H.J., Naranjo, E., Gonzalez, S. 2012. Reconstruction of late Pleistocene climate in the Valsequillo Basin (Central Mexico) through isotopic analysis of terrestrial and freshwater snails. Palaeogeography, Palaeoclimatology, Palaeoecology, 319-320, 16-27.
Rapid Communications in Mass Spectrometry - February 2012
Stable isotope analysis of cellulose is an increasingly important aspect of ecological and palaeoenvironmental research. Since these techniques are very costly, any methodological development which can provide simultaneous measurement of stable carbon and oxygen isotope ratios in cellulose deserves further exploration. A large number (3074) of tree-ring a-cellulose samples were used to compare the stable carbon isotope ratios (δ13C) produced by high-temperature (1400 °C) pyrolysis/gas chromatography (GC)/isotope ratio mass spectrometry (IRMS) with those produced by combustion GC/IRMS. Although the two data sets are very strongly correlated, the pyrolysis results display reduced variance and are strongly biased towards the mean. The low carbon isotope ratios of tree-ring cellulose during the last century, reflecting anthropogenic disturbance of atmospheric carbon dioxide, are thus overestimated. The likely explanation is that a proportion of the oxygen atoms are bonding with residual carbon in the reaction chamber to form carbon monoxide. The 'pyrolysis adjustment', proposed here, is based on combusting a stratified sub-sample of the pyrolysis results, across the full range of carbon isotope ratios, and using the paired results to define a regression equation that can be used to adjust all the pyrolysis measurements. In this study, subsamples of 30 combustion measurements produced adjusted chronologies statistically indistinguishable from those produced by combusting every sample.
This methodology allows simultaneous measurement of the stable isotopes of carbon and oxygen using high-temperature pyrolysis, reducing the amount of sample required and the analytical costs of measuring them separately.
Woodley, E.J., Loader, N.J., McCarroll, D., Young, G.H.F, Robertson, I, Heaton, T.H.E., Gagen, M.H. and Warham, J.O. 2012. High-temperature pyrolysis/gas chromatography/isotope ratio mass spectrometry: simultaneous measurement of the stable isotopes of oxygen and carbon in cellulose. Rapid Communications in Mass Spectrometry, 26, 109-114.
A shell of Gigantoproductus okensis shows twenty growth lines with marked changes of fabric, indicating periodical reduction of growth rates caused by environmental perturbations. The number of growth lines suggests a lifespan of 20 years in agreement with the survival rates of extant brachiopods, and with spiral deviation analysis. Geochemical analyses across the growth profile show a heterogeneous distribution of stable isotopes and trace elements. It is possible to distinguish primary from altered carbonate, and to interpret the isotopic data. The oxygen isotope signal in the unaltered parts is periodical and annual, with oscillation of 1.1 per mille. The higher values are at the growth lines (winter), and therefore most likely related to monsoon circulation during the Visean. The annual periodicity seems also present in the altered part of the shell, suggesting that diagenesis could have reset the primary values, but preserved their cyclicity.
Angiolini, L., Stephenson, M., Leng, M.J., Jadoul, F., Millward, D., Aldridge, A., Andrews, J., Chenery, S., Williams, G. 2012. Heterogeneity, cyclicity and diagenesis in a Mississippian brachiopod shell of palaeoequatorial Britain. Terra Nova, 24, 16-26.
This paper presents a significantly simplified method for in-situ U-Th-He dating removing the need to know any absolute concentrations. This is done by calculating the normalised U, Th, and He concentrations of a conventionally dated calibration standard from its measured Th/U ratio and known U-Th-He age, and scaling these concentrations to the raw U, Th, and He signals of the sample. The Th/U ratio of the standard can be determined from its measured 208Pb/206Pb ratio, removing the need to use NIST glass as a reference material. We introduce an LA-ICP-MS-based method to correct for variable ablation depths between the standard and the unknown, using the strength of the ablated 29Si signal. Finally, we propose a pseudo-depth profile method to assess the effects of compositional zoning on the accuracy of in-situ U-Th-He data.
The effectiveness of the proposed method has been demonstrated on three samples of gem-quality Sri Lanka zircon, which yield ages that are in agreement with previously published conventional U-Th-He measurements.
Vermeesch, P., Sherlock, S. C., Roberts, N. M. W., Carter, A., 2012. A simple method for in-situ U-Th-He dating. Geochimica et Cosmochimica Acta 79, 140-147.
Stable carbon isotope time-series (δ13C) from tree-rings are capable of providing valuable palaeoclimatic information, but analysis of individual tree-rings is time consuming and expensive. Pooling material from several tree-rings prior to isotopic analysis reduces costs, but does not allow the magnitude of uncertainty in the mean δ13C chronology to be calculated unless the pool is broken and each tree-ring measured individually at regular intervals. Here we use a comparison of pooled and mean individual (the arithmetic mean of isotopic data from tree series measured individually) δ13C records between AD 1650 and 2007, comprising cores from 21 Scots pine (Pinus sylvestris L.) trees growing in the western Highlands of Scotland. The aim is to determine whether the true error structure of the time series is better captured by using the overall mean error estimate for the entire time series or by linear interpolation between the equally spaced measurements.
We conclude that where autocorrelation exists within the error structure of a chronology, annual estimates of 95% confidence intervals, developed through linear interpolation at 5-year or 10-year intervals, are preferable to using the overall mean uncertainty. The method outlined increases the viability of pooled δ13C records for palaeoclimatic research by retaining error structure whilst reducing analytical time and costs. The method is applied here using tree-ring data, but could theoretically be applied to any well-replicated time-series.
Woodley, E. J., Loader, N. J., McCarroll, D., Young, G. H. F., Robertson, I., Heaton, T. H. E., Gagen, M. J., 2012. Estimating uncertainty in pooled stable isotope time-series from tree-rings. Chemical Geology 294-295, 243-248.
Levels of nitrate in Malta's groundwater are amongst the highest in Europe (median concentrations of 14 mg NO3-N L-1 in the main sea-level aquifer, and 37 mg NO3-N L-1 in the younger groundwaters of the perched aquifers). As part of a Rural Development Programme for Malta, the British Geological Survey was contracted to investigate the source/s of this nitrate, with specific emphasis on a combined 15N/14N and 18O/16O study. In addition to analysing a wide variety of groundwater samples, a special feature of the study was a determined effort to measure, rather than assume (as is common in many studies) the 15N/14N and 18O/16O compositions of the major potential sources of nitrate: fertilizers, septic and sewage wastes, animal manures, and soils. The data allowed the former two sources to be ruled out and, whilst some direct leaching of manure-derived nitrate could not be discounted, the data suggested that soil nitrification is the major source of nitrate in the groundwaters. Malta has a very long history of cultivation, during which time the soils may have developed high 15N/14N values reflecting greater mobility of nitrogen in soils with low C/N ratios.
The 15N/14N and 18O/16O values of nitrate in the groundwaters suggest that it is derived by microbial nitrification of organic N in these soils, with virtually no reduction in nitrate levels by denitrification.
Heaton, T.H.E., Stuart, M.E., Sapiano, M. and Micallef Sultana, M. 2012. An isotope study of the sources of nitrate in Malta's groundwater. Jounal of Hydrology, 414-415, 244-254.
Multiproxy analysis of a well-dated 25 ka lake sediment sequence from Lake Challa, on the eastern flank of Mount Kilimanjaro (East Africa), reveals the climatic controls that govern both the lake's paleohydrology and the climate-proxy record contained in the mountain's receding ice cap. The oxygen isotope record extracted from diatom silica (δ18Odiatom) in Lake Challa sediments captured dry conditions during the last glacial period and a wet late-glacial transition to the Holocene interrupted by Younger Dryas drought. Further, it faithfully traced gradual weakening of the southeastern monsoon during the Holocene. Overall, δ18Odiatom matches the branched isoprenoid tetraether (BIT) index of rainfall-induced soil runoff, except during 25–22 ka and the past 5 k.y. when insolation forcing due to orbital precession enhanced the northeastern monsoon.
This pattern arises because during these two periods, a weakened southeastern monsoon reduced the amount of rainfall during the long rainy season and enhanced the opposing effect of evaporation intensity and/or length of the austral winter dry season. Importantly, our lake-based reconstruction of moisture-balance seasonality in equatorial East Africa also helps us understand the oxygen isotope record contained in Mount Kilimanjaro ice. Negative correlation between ice core δ18O and Lake Challa δ18Odiatom implies that moisture balance is not the primary climate control on the long-term trend in ice core δ18O
Barker, P.A., Hurrell, E.R., Leng, M.J., Wolff, C., Cocqyut, C., Sloane, H.J., Verschuren, D. 2011. Seasonality in equatorial climate over the last 25 k.y. revealed by oxygen isotope records from Mount Kilimanjaro. Geology, 39, 1111-1114.
Glacioeustatic- and temperature-corrected planktonic foraminiferal oxygen isotope records from the Amazon Fan provide a means of monitoring past changes in the outflow of the Amazon River. This study focuses on the last deglaciation and reveals that during this period there were significant variations in the outflow, which implies large changes in moisture availability in the Amazon Basin. Aridity in the Amazon Basin seems to occur between 20.5 ka (calendar) to 17.0 ka and 13.6 ka to 11 ka. The second arid period correlates with the start of the Antarctic Cold Reversal and aridity continues throughout the Younger Dryas period. We find that the large-scale trends in Amazon River outflow are dissimilar to high-latitude variability in either hemisphere. Instead high-resolution variations correlate with the δ18O difference between Greenland and Antarctica ice core temperature records. This suggests a link between Hemispheric temperature gradients and moisture availability over the Amazon.
Based on our results and previously published work we present a new testable 'dynamic boundary-monsoon intensity hypothesis', which suggests that tropical moisture is not a simple belt that moves north or south. Rather, the northern and southern boundaries of the South American Summer Monsoon (SASM) are independently dynamic and driven by temperature gradients within their individual hemispheres. The intensity of rainfall within the SASM, however, is driven by precessionally modulated insolation and the resultant convection strength. Combining these two influences produces the dynamic heterogenic changes in the moisture availability observed over tropical South America since the Last Glacial Maximum.
Maslin, M.A., Ettwein, V.J., Wilson, K.E., Guilderson, T.P, Burns, S.J., Leng, M.J. 2011. Dynamic boundary-monsoon intensity hypothesis: evidence from the deglacial Amazon River discharge record. Quaternary Science Reviews, 30, 3823-3833.
The Intergovernmental Panel on Climate Change (IPCC) provides a conservative estimate on rates of sea-level rise of 3.8 mm/yr at the end of the 21st century, which may have a detrimental effect on ecologically important mangrove ecosystems. Understanding factors influencing the long-term resilience of these communities is critical but poorly understood. We investigate ecological resilience in a coastal mangrove community from the Galapagos Islands over the last 2700 years. Palaeoecological methods (AMS radiocarbon dating, stable carbon isotopes) were used to reconstruct sedimentation rates and ecological change at Diablas lagoon. Bulk geochemical analysis was also used to determine local environmental changes, and salinity was reconstructed using a diatom transfer function. Changes in relative sea level (RSL) were estimated using a glacio-isostatic adjustment model.
Non-linear behaviour was observed in the Diablas mangrove ecosystem as it responded to increased salinities following exposure to tidal inundations. A negative feedback was observed which enabled the mangrove canopy to accrete vertically, but disturbances may have opened up the canopy and contributed to an erosion of resilience over time. A combination of drier climatic conditions and a slight fall in RSL then resulted in a threshold response, from a mangrove community to a microbial mat.
Seddon, A.W.R., Froyd, C.A., Leng, M.J., Milne, G.A., Willis, K.J. 2011. Ecosystem Resilience and Threshold Response in the Galápagos Coastal Zone. PLOS ONE, 6 (7), DOI: 10.1371/journal.pone.0022376.
Carbon and oxygen isotope ratios in the shells of the freshwater Unio mollusc yield information on the isotopic composition of the water in which the shell was formed, which in turn relates to climatic conditions prevailing during the bivalves' life span. Here we analysed shells from one modern Unio, from a modern lake shore in Anatolia, and 4 subfossil Unio shells from Çatalhöyük (dated between 7200 BC and 5000 BC, Neolithic and Chalcolithic periods). Sequential carbon and oxygen isotope analysis along the surface of the shells provides information on seasonal or shorter-term variability of lake waters during the lifetime of the organisms. Stable isotope analysis along the growth of freshwater bivalves is one of the few methods for investigating seasonal water fluctuations in the past.
Bar-Yosef, D., Leng, M.J., Aldridge, D.C., Arrowsmith, C., Gümüs, B.A., Sloane, H.J. 2011. Modern and early-middle Holocene shells of the freshwater mollusc Unio, from Çatalhöyük in the Konya basin, Turkey: Preliminary palaeoclimatic implications from molluscan isotope data. Journal of Archaeological Science, 39, 76-83.
This paper compares the existing methods of oxygen-isotope analyses of opal-A and aims to characterize additional possible working standards to calibrate the oxygen isotope analysis of biogenic silica. For this purpose, an inter-laboratory comparison was organized. Six potential working standard materials were analysed repeatedly against NBS28 by eight participating laboratories using their specific analytical methods. The materials cover a wide range of oxygen isotope values (+23 to +43‰) and include diatoms (marine, lacustrine), phytoliths and synthetically-produced hydrous silica. To characterize the proposed standards, chemical analyses and imaging by SEM were also performed. Despite procedural differences at each laboratory, all methods are in reasonable agreement with a SD for oxygen isotope analysis values between 0.3 and and 0.9‰.
Based on the results, we propose four additional biogenic silica working standards for oxygen isotope analysis, available on request through the relevant laboratories.
Chapligin, B., Leng, M.J., Webb, E., Alexandre, A., Dodd, J.P., Ijiri, A., Lucke, A., Shemesh, A., Abelmann, A., Herzschuh, U., Longstaffe, F.J., Meyer, H., Moschen, R., Okazaki, Y., Rees, N.H., Sharp, Z.D., Sloane, H.J., Sonzogni, C., Swann, G.E.A., Sylvestre, F., Tyler, J.J., Yam, R. 2011. Inter-laboratory comparison of oxygen isotope compositions from biogenic silica. Geochimica et Cosmochimica Acta, 75, 7242-7256.
This paper explores the impact of animal manure application on the δ15N values of a broad range of crops (cereals and pulses): under a range of manuring levels/regimes, and at a series of locations extending from northwest Europe to the eastern Mediterranean. We included both agricultural field experiments and areas where 'traditional' farming is practised. Our aim is to ground-truth interpretation of δ15N values in archaeobotanical crop remains as evidence of past growing conditions and husbandry practices. The results confirm the potentially radical impact of manuring on δ15N values in cereals, depending on manuring level, but indicate only a slight effect on pulses, which can fix atmospheric nitrogen. The expected geographical trend towards greater δ15N with increasing climatic aridity is not apparent, probably because the growing conditions for crops are 'buffered' through crop management. Each of these observations has fundamental implications for archaeobotanical interpretation of δ15N values as evidence of land use practices and (together with analysis of bone collagen/tooth enamel in potential consumers) palaeodiet.
Fraser, R., Bogaard, A., Heaton, T., Charles, M., Jones, G., Christensen, B.T., Halstead, P., Merbach, I., Poulton, P.R., Sparkes, D. and Styring A., 2011. Manuring and stable nitrogen isotope ratios in cereals and pulses: towards a new archaeobotanical approach to the inference of land use and dietary practices. Journal of Archaeological Sciences, 38, 2790-2804.
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 surfacewater 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.
Curtis, C.J., Evans, C., Goodale, C.L. and Heaton, T.H.E., 2011. What have stable isotope studies revealed about the nature and mechanisms of N saturation and nitrate leaching from semi-natural catchments? Ecosystems, 14, 1021-1037.
Precise relative sea level (RSL) data is important for inferring regional ice sheet histories, as well as helping to validate numerical models of ice sheet evolution and glacial-isostatic adjustment. Here we develop a new RSL curve for the Fildes Peninsula, South Shetland Islands (SSIs), a sub-Antarctic archipelago peripheral to the northern Antarctic Peninsula ice sheet, by integrating sedimentary evidence from isolation basins with geomorphological evidence from raised beaches. This combined approach yields not only a Holocene RSL curve, but also the spatial pattern of how RSL change varied across the archipelago.
Watcham, E.P., Bentley, M.J., Hodgson, D.A., Roberts, S.J., Fretwell, P.T., Lloyd, J.M., Larter, R.D., Whitehouse, P.L., Leng, M.J., Monien, P. and Moreton, S.G. 2011. A new Holocene relative sea level curve for the South Shetland Islands, Antarctica. Quaternary Science Reviews, 30, 3152-3170.
There is a known bias in C/N, δ13C and δ15N values of organic matter (OM) due to pre-analysis acid treatment methods. We report here, for the first time, the results of a pre-analysis acid treatment method comparison of measured C/N, δ13C and δ15N values in bulk OM from a sedimentary sequence of samples to illustrate this bias. Here we show that acid treatment significantly reduces the accuracy (between method biases) and precision (within method bias) of δ13C and δ15N values of OM, suggesting a differential response of sample OM between methods and sample horizons, and in some cases inefficient removal of inorganic carbon. We show that different methods can significantly influence environmental interpretation in some of our sample horizons (i.e. interpretation of aquatic vs. terrestrial OM source; C3 vs. C4 vegetation).
Brodie, C.R., Casford, J.S.L., Lloyd, J.M., Leng, M.J., Heaton, T.H.E., Kendrick, C.P., Zong, Y.Q. (2011) Evidence For Bias In C/N, δ13C and δ15N Values Of Bulk Organic Matter, And On Environmental Interpretation, From A Lake Sedimentary Sequence By Pre-Analysis Acid Treatment Methods. Quaternary Science Reviews. 30, 3076 - 3087. doi: 10.1016/j.quascirev.2011.07.003
At NIGL we are closely collaborating with Nu Instruments to develop the Nu Attom HR ICP-MS as a functional, reliable and efficient tool for isotope ratio analysis. Laser ablation sampling coupled to measurement via ICP-MS is an increasingly used tool within Earth and environmental science, and can be used for determining quantitative trace element concentrations of materials, as well as for isotopic dating of minerals in particular within U-Pb geochronology. Within this application note, we report the use of the Nu Attom for determining U-Th-Pb isotopes in zircon and monazite crystals, and demonstrate the ability to combine these isotope ratio measurements with other trace element concentrations using the wide mass range available in rapid peak scanning mode.
Nick M W Roberts, Sabine Pawlig, Matthew Horstwood. 2011. Nu Attom HR ICP-MS: Laser Ablation U-Pb Geochronology, Nu Instruments Application Note AN11.
Magnetic and geochemical core data spanning the last 17,000 years are correlated with new seismic stratigraphy from Lake Tana, Ethiopia, to infer past lake-level change and hence effective precipitation. The data confirm that low lake-level coincides with Heinrich Event 1 (H1) in the North Atlantic, as previously shown from diatom and pollen evidence. The lake deepened at 15.3 cal kyr BP and abruptly returned to freshwater conditions, when the lake overflowed into the Blue Nile. Low runoff and lake levels and therefore rainfall are inferred between 13.0 and 12.5 cal kyr BP and may represent southerly suppression of the ITCZ and the associated monsoon front at the time of the Younger Dryas. Two drought episodes occurred at 8.4 and 7.5 cal kyr BP, and are also interpreted as a southward shift in the monsoon front. The first of these events appears to have preceded and been more significant than the 8.2 cal kyr BP.
Precipitation declined after 6.8 cal kyr BP, although we do not see an abrupt end to the African Humid Period. This period culminated in a dry episode at ~ 4.2 cal kyr BP, supporting the view that reduced Nile flow was a contributing factor to the demise of the Egyptian Old Kingdom.
Marshall, M.H., Lamb, H.F., Huws, D., Davies, S.J., Bates, R., Bloemendal, J., Boyle, J., Leng, M.J., Umer, M., Bryant, C. 2011. Late Pleistocene and Holocene drought events at Lake Tana, the source of the Blue Nile. Global and Planetary Change, 78, 147-161.
The Paleocene-Early Eocene carbonate successions of the Indus Basin in Pakistan formed on the north-western continental shelf margin of the Indian Plate in the eastern Tethys Ocean. Based on Larger Benthic Foraminifera eight Tethyan foraminiferal biozones spanning the Paleocene-Eocene boundary interval are identified. Stable isotope analysis through the P-E boundary interval identifies more positive δ13C values for the Late Paleocene and less positive values for the earliest Eocene. However, there is insufficient sampling resolution to identify the PETM δ13C maximum negative excursion itself. During Late Paleocene times LBF assemblages in the Indus Basin were taxonomically close to those of west Tethys, facilitating biostratigraphic correlation. However, this faunal continuity is lost at the P-E boundary and the earliest Eocene succession lacks typical west Tethys Nummulites, whilst Alveolina are rare: LBFs such as Miscellanea and Ranikothalia continue to dominate.
The apparent absence of Nummulites from the earliest Eocene of Pakistan and rarity of Alveolina -elsewhere used as the prime marker for the base of the Eocene, may imply a geographical barrier between East and West Tethys faunas, perhaps caused by India-Asia collision. Later, faunal links were re-established and many foraminifera with west Tethys affinities appeared in east Tethys.
Afzal, J., Williams, M., Leng, M.J., Aldridge, R.J., Stephenson, M.H. 2011. Evolution of Paleocene to Early Eocene larger benthic foraminifera assemblages of the Indus Basin, Pakistan. Lethaia, 44, 299-320.
The Tyrone Igneous Complex is one of the largest areas of ophiolitic and arc-related rocks exposed along the northern margin of Iapetus within the British and Irish Caledonides. New U-Pb zircon data and regional geochemistry suggest that the Tyrone Plutonic Group represents the uppermost portions of a c. 480 Ma suprasubduction-zone ophiolite accreted onto an outboard segment of Laurentia prior to 470.3 ± 1.9 Ma. The overlying Tyrone Volcanic Group formed as an island arc that collided with the Laurentian margin during the Grampian phase of the Caledonidan orogeny. Early magmatism is characterized by transitional to calc-alkaline, light REE (LREE)-enriched island-arc signatures, with an increasing component of continentally derived material up sequence. Tholeiitic rhyolites with flat to U-shaped REE profiles and LREE-depleted basalts, located stratigraphically below a c. 473 Ma rhyolite of the upper Tyrone Volcanic Group, suggest initiation of intra-arc rifting at c. 475 Ma.
Metamorphic cooling ages from the Tyrone Central Inlier imply arc-continent collision before 468 ± 1.4 Ma, with the emplacement of the Tyrone Volcanic Group onto the margin. A suite of 470.3 ± 1.9 Ma to 464.3 ± 1.5 Ma calc-alkaline intrusions are associated with the continued closure of Iapetus.
Cooper, M.R., Crowley, Q.G., Hollis, S.P., Noble, S.R., Roberts, S., Chew, D., Earls, G., Herrington, R. and R.J. Merriman. 2011.
Age constraints and geochemistry of the Ordovician Tyrone Igneous Complex, Northern Ireland: implications for the Grampian orogeny. Journal of the Geological Society,168, 837-850.
An isotope dilution thermal ionization mass spectrometry U-Pb zircon age of 411.5 ± 1.3 Ma obtained from an andesitic lava occurring within the Lower Devonian Rhynie Outlier (Aberdeenshire, NE Scotland) effectively dates the Rhynie Chert Konservat-LagerstƤtte. Biostratigraphical constraints on the Rhynie Chert-bearing succession indicate that this age lies within the interval early (but not earliest) Pragian-(?)earliest Emsian. Accordingly, the Pragian-Emsian boundary must post-date or closely approximate to 411.5 ± 1.3 Ma, while the Lochkovian-Pragian boundary must predate 411.5 ± 1.3 Ma. Integration of this new high-precision age with an improved temporal framework for late Caledonian intrusive activity in NE Scotland suggests that the Rhynie hot-spring system (the 'parental' hydrothermal system to the Rhynie cherts) was unrelated to any 'Newer Granite' intrusion.
Rhynie was instead powered by a basaltic andesite magma whose generation and ascent were directly linked to the transcurrent fault movements responsible for the formation of the Rhynie basin.
Parry, S.F., Noble, S.R., Crowley, Q.G. and Wellman, C.H., 2011. A high-precision U-Pb age constraint on the Rhynie Chert Konservat-Lagerstätte: time scale and other implications. Journal of the Geological Society, 168, 863-872.
Here we present combined radioisotopic dating (U-Pb zircon) and cyclostratigraphic analysis of the carbon isotope excursion at the Paleocene-Eocene (P-E) boundary in Spitsbergen to determine the numerical age of the boundary. Incorporating the total uncertainty from both radioisotopic and cyclostratigraphic data sets gives an age ranging from 55.728 to 55.964 Ma, within error of a recently proposed astronomical age of ∼55.93 Ma. Combined with the assumption that the Paleocene Epoch spans twenty-five 405 kyr cycles, our new age for the boundary suggests an age of ∼66 Ma for the Cretaceous-Paleogene boundary. Furthermore, our P-E boundary age is consistent with the hypothesis that the onset of the Paleocene-Eocene thermal maximum at the boundary occurred on the falling limb of a 405 kyr cycle, suggesting the event was initiated by a different mechanism to that which triggered the other early Eocene hyperthermals.
Charles, A. J., D. J. Condon, I. C. Harding, H. Pälike, J. E. A. Marshall, Y. Cui, L. Kump, and I. W. Croudace. 2011. Constraints on the numerical age of the Paleocene-Eocene boundary. Geochemistry. Geophysics, Geosystems., 12, Q0AA17, doi:10.1029/2010GC003426.
We present LA-MC-ICPMS and ID-TIMS U-Pb ages of metamorphic allanite from the Eclogite Zone, Tauern Window, which when coupled with rare earth element analysis and thermobarometric modelling, demonstrate that the European continental margin was subducted to between 8 and 13 kbar (30-45 km) by 34.2 ± 3.6 Ma. These data define: (i.) an upper limit on the timing of eclogite facies metamorphism at 26.2 ± 1.8 kbar (70-80 km) and 553 ± 12 °C, (ii.) plate velocity (1-6 cm·a-1) exhumation of the Eclogite Zone from mantle to mid-crustal depths, and (iii.) a maximum duration of 10 Ma (28-38 Ma) for juxtaposition of Alpine upper-plate and European basement units and subsequent conductive heating thought to have driven regional Barrovian (re)crystallisation at ca. 30 Ma.
Given that the Tauern Window is a classic locality for understanding rates of conductive thermal relaxation in tectonically thickened crust, this work raises questions of fundamental importance concerning the length scales of the mechanisms responsible for heat transfer within orogenic crust.
Andrew J. Smye, Mike J. Bickle, Tim J.B. Holland, Randall R. Parrish and Daniel J. Condon. 2011. Rapid formation and exhumation of the youngest Alpine eclogites: A thermal conundrum to Barrovian metamorphism. Earth and Planetary Science Letters, Volume 306, Issues 3-4, Pages 193-204, doi:10.1016/j.epsl.2011.03.037.
In this study, we have used in-situ U-Pb, Hf and O isotopic analyses of zircon grains to gain insights into both magmatic processes and duration of magmatism in igneous rocks from the Tuscan Magmatic Province (0.1-9 Ma), Italy. From zircon isotopic data we show that construction of the Monte Capanne pluton (Elba) may have occurred over a period of c. 0.5 Ma. A significant range of both 176Hf/177Hf (determined by LA-MC-ICPMS) and δ18O (determined by ion microprobe) in zircon (∼ 7 epsilon Hf units and ∼ 5‰, respectively) is present, which, together with zircon morphology and trace element data, emphasises the importance of mixing and replenishment involving magma batches with both metaluminous and peraluminous affinities. While mixing undoubtedly occurred between mafic (metaluminous) and felsic (peraluminous) magmas, the range of Hf and O isotopic data suggests a diversity within the peraluminous component.
The unradiogenic Hf composition (εHf(t) <- 4) and relatively heavy δ18O signature (> 6‰) of the inferred mantle-derived component strongly supports the idea that the mantle source involved in Tuscan magmatism was severely modified by subduction-related, crustal-derived metasomatic fluids.
D. Gagnevin, J.S. Daly, M.S.A. Horstwood and M.J. Whitehouse. 2011. In-situ zircon U-Pb, oxygen and hafnium isotopic evidence for magma mixing and mantle metasomatism in the Tuscan Magmatic Province, Italy. Earth and Planetary Science Letters, Volume 305, Issues 1-2, Pages 45-56, doi:10.1016/j.epsl.2011.02.039.
Three dated (U-Pb, zircon) ash beds from biostratigraphically constrained Avalonian successions of Shropshire and Pembrokeshire delimit the traditional “Lower”/”Middle” Cambrian boundary and resolve a problematic regional correlation. In Shropshire, a date of 514.50 ± 0.25 million years (Ma) from near the top of the Lower Comley Sandstone Formation provides a maximum age for the boundary between Cambrian Stages 3 and 4, while a date of 509.02 ± 0.20 Ma from the basal Quarry Ridge Grits, Upper Comley Sandstone Formation, provides a minimum age for the boundary between Cambrian Stages 4 and 5 (and thus Series 2 and 3). These dates directly constrain the age of the intervening Comley Limestones, which contain diverse small shelly fossils, and a key early occurrence of exceptional, three-dimensionally preserved arthropods.
In Pembrokeshire, an ash bed from the Caerfai Bay Shales Formation dates to 519.38 ± 0.28 Ma, equivalent to a horizon low in the Lower Comley Sandstone Formation of Shropshire, possibly around the level where trilobites make their first local appearance.
Harvey, T.H.P., Williams, M., Condon, D.J., Wilby, P.R., Siveter, D.J., Rushton, A.W.A., Leng, M.J., Gabbott, S.E. 2011. A refined chronology for the Cambrian succession of southern Britain. Journal of the Geological Society, London, 168, 705-716.
Rapid Communications in Mass Spectrometry - April 2011
This systematic study compares the effects of pre-analysis acid treatment methods on the measured δ15N values of terrestrial and aquatic, modern and ancient, environmental materials. We investigate the effect of acid treatment on the measured δ15N of sample organic matter in light of the increasing application of "dual-mode" isotope analysis, where δ13C and δ15N are measured simultaneously from the same pre-treated sample aliquot. We investigate 3 common methods;
untreated samples
acidification followed by sequential water rinse (rinse method)
acidification in silver capsules (capsule method)
We also investigate the influence of capsule type (silver and tin) on δ15N.
Brodie, C.R., Heaton, T.H.E., Leng, M.J., Kendrick, C.P., Casford, J.S.L., Lloyd, J.M. 2011. Evidence for bias in measured d15N values of terrestrial and aquatic organic materials due to pre-analysis acid treatment methods. Rapid Communications in Mass Spectrometry, 25, 1089-1099.
This study is the first systematic comparison of the effect of acid treatment methods on the reliability of organic carbon [C] and nitrogen [N], and carbon isotope (δ13C) values on a range of terrestrial and aquatic, modern and geological environmental materials. We investigated the 3 most common methods:
acidification followed by sequential deionised water rinses ("rinse method")
acidification in silver capsules ("capsule method")
acidification by exposure to an acid vapour ("fumigation method")
Brodie, C.R., Leng, M.J., Casford, J. S. L., Kendrick, C.P., Lloyd, J.M., Yongqiang, Z., and Bird, M.I. 2011. Evidence for bias in C and N concentrations and δ13C composition of terrestrial and aquatic organic materials due to pre-analysis acid preparation methods. Chemical Geology, 282, 67-83.
The last millennium is a key period for understanding environmental change in East Africa, as there is clear evidence of marked fluctuations in climate (effective moisture) that place modern concern with future climate change in a proper context, both in terms of environmental and societal impacts and responses. Here, we compare sediment records from two small, nearby, closed crater lakes in western Uganda (Lake Kasenda and Lake Wandakara), spanning the last 700 (Wandakara) and 1200 years (Kasenda) respectively.
Ryves, D.B., Mills, K., Bennike, O., Brodersen, K.P., Lamb, A.L., Leng, M.J., Russell, J.M. and Ssemmanda. I. 2011. Environmental change over the last millennium recorded in two contrasting crater lakes in western Uganda, eastern Africa (Lakes Kasenda and Wandakara). Quaternary Science Reviews, 30, 555-569.
This paper covers the sedimentology, benthic foraminifera, molluscs, and δ18O and δ13C of Ammonia tepida tests in two late Holocene sediment cores from Lake Qarun (Egypt). The cores, QARU2 (upper section, 8.2 m) and QARU4 (1.4 m), span approximately the past 500 years of sedimentation.
Abu-Zied, R., Flower, R., Keatings, K., Leng, M.J. 2011. Benthic foraminifera and their stable isotope composition in sediment cores from Lake Qarun, Egypt: changes in water salinity during the past ∼500 years. Journal of Paleolimnology, 45, 167-182.
Palaeogeography, Palaeoclimatology, Palaeoecology - January 2011
Biogeochemical cycles and sedimentary records in lakes are related to climate controls on hydrology and catchment processes. Changes in the isotopic composition of the diatom frustules (δ18Odiatom and δ13Cdiatom) in lacustrine sediments can be used to reconstruct palaeoclimatic and palaeoenvironmental changes. The Lago Chungará diatomaceous laminated record is made up of white and green multiannual rhythmites related to mixing events and deposition over several years. Analyses of both δ18Odiatom and δ13Cdiatom in these rhythmites are interpreted in terms of shifts in the precipitation/evaporation ratio and changes in the lake water dissolved carbon concentration, respectively.
ENSO and solar activity are the most likely main climate forcing mechanisms.
Hernández, A., Bao, R., Giralt, S., Barker, P.A., Leng, M.J., Sloane, H.J., Sáez, A. 2011. Biogeochemical processes controlling oxygen and carbon isotopes of diatom silica in Late Glacial to Holocene lacustrine ryythmites. Palaeogeography, Palaeoclimatology, Palaeoecology, 299, 413-425.
Journal of the Geological Society, London - January 2011
The Moine Thrust Zone in the Scottish Highlands developed during the Scandian Event of the Caledonian Orogeny, and now forms the boundary between the Caledonian orogenic belt and the undeformed foreland. The Scandian Event, and the formation of the Moine Thrust Zone, have previously been dated by a range of isotopic methods, and relatively imprecise ages on a suite of alkaline intrusions localized along the thrust zone have provided the best age constraints for deformation. Recent British Geological Survey mapping has improved our understanding of the structural relationships of some of these intrusions, and this work is combined with new U-Pb dates in this paper to provide significantly improved ages for the Moine Thrust Zone. Our work shows that a single early intrusion (the Glen Dessarry Pluton) was emplaced within the orogenic belt to the east of the Moine Thrust Zone at 447.9 ± 2.9 Ma.
A more significant pulse of magmatism centred in the Assynt area, which temporally overlapped movement in the thrust zone, occurred at 430.7 ±; 0.5 Ma. Movement in the thrust zone had largely ceased by the time of emplacement of the youngest intrusions, the late suite of the Loch Borralan Pluton, at 429.2 ± 0.5 Ma, and the Loch Loyal Syenite Complex.
Goodenough, K.M., Millar, I.L., Strachan, R.A., Krabbendam, M. & Evans, J.A. Timing of regional deformation and development of the Moine Thrust Zone in the Scottish Caledonides: constraints from the U-Pb geochronology of alkaline intrusionsJournal of the Geological Society, London, Vol. 168, 2011, pp. 99-114. doi: 10.1144/0016-76492010-020.
Proceedings of the Geologists Association - January 2011
Using material from the Aeronian (Silurian) interval from Wales and Scotland as examples, we show that the carbon isotope composition of graptolite periderm (δ13Cgrap.) provides a signal that is locally different but not consistently so from surrounding whole-rock samples (δ13Cwhole-rock). Graptolite periderm δ13C seems not influenced by astogenetic stage of development or gross rhabdosome type and differences between δ13Cgrap. from different metamorphic grades are minimal. Taken as a whole, the Aeronian interval examined shows little overall change, but large variations are seen on the small scale, possibly reflecting very local carbon cycling.
For carbon isotope stratigraphy in such rocks, therefore, large-scale bulk sampling will likely reduce inhomogeneities and give more reproducible results. Furthermore, in situations where terrestrial organic matter has been incorporated into the sediment, then graptolite carbon may more faithfully reflect bulk marine organic matter.
Andrea M. Snelling, Melanie J. Leng, Jan A. Zalasiewicz, Christopher C. Kendrick and Alex A. Page. 2011. Carbon isotope composition of graptolite periderm and whole-rock from the Aeronian (Silurian, Llandovery) in Wales and Scotland and its use in chemostratigraphy. Proceedings of the Geologists Association 122 (1) 82-91
July 2011 – Planet Earth News – Ethiopian lake reveals history of African droughts
The summer 2011 edition of Planet Earth reports on a new survey of Lake Tana in Ethiopia (the source of the Blue Nile), the study shows that drought may have contributed to the demise of the Egyptian Old Kingdom, around 4 200 years ago.
February 2012: NERC Standard grant: Silicon isotope records of recent environmental change and anthropogenic pollution from Lake Baikal, Siberia
NIGL have secured a NERC Standard Grant in collaboration with other scientists at Nottingham University and University College London to investigate the impact of recent environmental change and anthropogenic pollution on Lake Baikal, Siberia.
Lake Baikal is the world's oldest lake in south eastern Siberia that began to form over 20 million years ago. A key feature of Lake Baikal is the high degree of biodiversity with over 2,500 flora and fauna, the majority of which are endemic. Such high levels of endemicity have led to the lake being cited as the "most outstanding example of a freshwater ecosystem" and resulted in the site being designated a World Heritage Site in 1996. Industrial development and changes in catchment land-use since the 1950's, however, pose real and serious threats to the stability of the lake's ecosystem with pollution entering the lake from major conurbations, industrial centres, mining and agricultural practises.
This project will develop the application of silicon isotope measurements in Lake Baikal to provide information on changes in biogenic nutrient utilisation in association with forcings such as: global warming, increases in water temperatures, ice cover and ice thickness.
October 2011: AHRC grant "Dama International: fallow deer (Dama dama dama) and European society 4000 BC - AD 1600"
Congratulations to Dr Naomi Sykes (Nottingham University), Dr Jane Evans (NIGL) and Prof Alan Hoelzel (Durham):
Visit any stately home and you will find a herd of European fallow deer (Dama dama dama). These elegant animals are one of natural history's puzzles because, despite their name, they are not of European origin: they are native to Turkey from where people have gradually transported them around the globe. The distribution of fallow deer is thus a direct record of human population movements, trade and ideology with the potential to provide cultural evidence of the highest quality and relevance for a range of disciplines and audiences. There are many publications devoted to fallow deer but these largely recycle 'received wisdom'. In fact, astonishingly little is known about fallow deer; their history is obfuscated by ambiguous linguistic, textual, iconographic and archaeological evidence. To rectify this situation we carried out a pilot study, The Fallow Deer Project, whose results have challenged established theories about the species' history and provided new insights into Roman, Anglo-Saxon and Norman society. It also highlighted the scarcity of scientific work on fallow deer and demonstrated how a new dataset will enable us to explore some of the highest-profile issues in European archaeology: e.g. the nature and spread of the Neolithic in the eastern Mediterranean and the structure and worldview of societies in the Bronze Age Aegean, Iron Age Greece and Gaul, and the Roman, Byzantine, Islamic and Norman Empires.
To realise this potential, our transdisciplinary team will employ methods proven by our pilot study - e.g. the integration of archaeology, history, geography and anthropology with genetics, stable isotope analysis and osteological research - to answer the following questions:
Were fallow deer domesticated?
Under what circumstances were fallow deer established across Europe?
Did the collapse of the Roman Empire cause extirpation of fallow deer?
Did the Normans reintroduce fallow deer via Islamic influence?
5) How do human-Dama relationships reveal worldview?
May 2011: Congratulations to Matt Horstwood for his contribution to the most cited article 2005 to 2010 in Chemical Geology:
Thomas F.D. Mason, Dominik J. Weiss, John B. Chapman, Jamie J. Wilkinson, Svetlana G. Tessalina, Baruch Spiro, Matthew S.A. Horstwood, John Spratt, Barry J. Coles. Zn and Cu isotopic variability in the Alexandrinka volcanic-hosted massive sulphide (VHMS) ore deposit, Urals, Russia Original Research Article. Chemical Geology, Volume 221, Issues 3-4, 5 October 2005, Pages 170-187.
The oxygen isotope composition of phosphate: a potential tool in UK freshwater studies?
High concentrations of phosphate are a primary cause of 'eutrophication' in water: an over-enrichment in nutrients leading to excessive growth of algae, which can be very damaging to the aquatic environment. Many rivers in the UK, and other parts of the world suffer from this problem because phosphate-rich waters from sewage works or from farming activities are pumped or drain into the rivers. Dealing with this problem involves knowing where the phosphate comes from, and understanding what happens to it when it gets into the river.
The project is headed by Tim Heaton (NIGL), with Daren Gooddy and Dan Lapworth (BGS), and Roland Bol and Steve Granger (Rothamsted Research).
The phosphate ion contains oxygen atoms which can be of different isotope types: oxygen of atomic mass 18 and oxygen of atomic mass 16 (both are naturally-occurring, non-radioactive isotopes). Preliminary studies have shown that the proportions of these two isotopes differ depending on where the phosphate came from (e.g. sewage compared with agricultural fertilizer), and that changes in the proportion of the two isotopes indicate the way in which the phosphate is being used in the water. However, this preliminary work has been mainly done in saline waters in estuaries and coastal areas, and we want to see if it might work in fresh water environments in the UK.
The plan is therefore two-fold:
to analyse the proportions of oxygen-18 and oxygen-16 in phosphate from a small number of sewage and agricultural effluents, to see if they differ. If they do, we may be able to use such measurements to determine where phosphate pollution is coming from
to see if the proportions of oxygen-18 and oxygen-16 in phosphate coming from a point-source (e.g. the outfall of a sewage works) change as the phosphate is carried downstream. If they do, we may be able to use such measurements to determine the phosphorus demand or 'limitation' of the system — an important factor in controlling eutrophication.
August 2010: NERC Small grant
Bering Sea diatom isotope records during the onset of Northern Hemisphere Glaciation
The progressive advancement of ice-sheets across the Northern Hemisphere in the late Pliocene and the development of glacial-interglacial cycles which punctuate the Quaternary marks a significant threshold in the Earth's climate history. Of particular note are the transitions associated with the onset of major Northern Hemisphere Glaciation (NHG), c. 2.85-2.73 Ma, when large ice-sheets developed across Greenland, Eurasia and Northern America. This project aims to investigate the nature of these changes in the Bering Sea by measuring diatom δ13C, δ18O and δ30Si from 3.2-2.5 Ma at IODP Site U1341. Situated south of the sea-ice extent at the western flank of Bowers Ridge, the results will permit an assessment of linkages between the Pacific Ocean and Bering Sea with regards to meltwater influx and the biological pump.
Establishing an understanding of the latter is critical for determining the role of the oceans in regulating atmosphere CO2 concentrations over this time-frame.
This project is headed by George Swann (NIGL) and includes Andrea Snelling (NIGL) and Jenny Pike (Cardiff).
June 2010: Prof Randy Parrish receives Murchison Medal
Congratulations to Randy for being awarded the Murchison Medal by the Geological Society of London. The Murchison Medal is awarded to people who have made a significant contribution to science by means of a substantial body of research. Council looks at breadth as well as depth in pure and applied hard rock science.
The Svalbard exemplar of Neoproterozoic glaciation
Although life successfully moderates surface conditions on Earth, some events in Earth History have threatened the viability of most life forms. Arguably the most profound and long-lasting challenge in the last 2 billion years was glaciation on a near-global scale, with the best documented event being around 650 to 630 million years ago ("Marinoan" glaciation). The Snowball Earth hypothesis proposes that snow and ice became so widespread that the Earth become much more reflective of solar radiation and cooled to a mean temperature of around -50 degrees Celsius. Glaciation was eventually terminated by the build-up of carbon dioxide emitted from volcanoes, that was not used up by the weathering of rocks since rocks were buried beneath the extensive snow and ice cover. Almost all facets of the Snowball Earth hypothesis, and of alternative hypotheses, are open to challenge, there is general agreement that glaciation reached tropical latitudes at sea level.
New lines of evidence are needed to refresh the debates and constrain future modelling efforts.
This project is headed by Ian Fairchild (Birmingham) and includes Dan Condon (NIGL) as a Co-I.
April 2010: NERC AFI grant
Terrestrial Holocene climate variability on the Antarctic Peninsula
The Antarctic continent is an important part of the Earth system, both influencing and responding to global ocean and atmospheric circulation. A key question in understanding and attribution of Antarctic climate change is whether the recorded changes on the Peninsula are unusual compared with past natural climate variability. Moss banks are ideal deposits for reconstructing climate change over the land surface of the Antarctic Peninsula because of their location in relation to recorded temperature changes, their age, and their attributes as archives.
The moss banks have accumulated peat over the past 5-6000 years at locations throughout the western Antarctic Peninsula. They are formed of only one or two species, annual growth can be traced in the surface peats and preservation of moss remains is good. We will use multi-proxy indicators of past climate (stable isotopes, measures of decay, testate amoebae and moss morphology) to reconstruct climate variability from critical locations across the observed gradient in rate of temperature change between 69o and 61o S.
This project is headed by Dan Charman (Exeter) with Melanie Leng (NIGL) as a project partner.
February 2010: New funding - British Isotopes in Rainfall Project
This new project, in association with The Climatological Observers Link (COL) and other selected rainfall observation stations, aims to map the variability in oxygen and hydrogen isotopes in UK rainfall initially over a series of rainfall events in March 2010. The project is being run by Dr Matt Jones (Nottingham), Dr Jon Tyler (Oxford) and Prof Melanie Leng (NIGL).
Dating the "Taung Child" Australopithecus africanus type specimen through U-Pb measurements of associated calcite crystals
The "Taung Child" was found in 1924 at the Buxton limestone quarry, Northwestern Province, South Africa. The "Taung Child" was the first early hominid found in Africa and became the type specimen of Australopithecus africanus. Mining activities continued at the quarry and the geological context of the specimen was lost, hampering attempts to date the hominid and understand its ecological context. Because of this, current estimates for the age of the "Taung Child" range from 3 million to 1 million years old. Such chronological uncertainty greatly hampers our understanding of early hominid evolution in Africa. We propose to take samples of calcite crystals attached to the endocast of the "Taung Child" and other associated fossils for uranium-lead dating using state-of-the-art facilities at the NERC Isotope Geosciences Laboratory. Pilot evidence demonstrates the suitability of such calcite crystals for high-precision age determination, and permission to sample the calcites has been granted by the Hominid Access Committee.
The proposed radiometric dates for the "Taung Child" are likely to alter the current age-range for Australopithicus africanus, perhaps changing our understanding of ancestor-decendant relationships among early hominin species.
The methods undertaken in this study can be applied to other early hominin specimens from the "Cradle of Humankind" World Heritage Site, South Africa, thereby improving the chronology of human evolution in Africa, and the methods will be refined to maximize the scientific information obtained from the minimum use of valuable fossil material, thereby improving generic methods of analysis of rare and invaluable museum collections.
This project is headed by Prof Randy Parrish (NIGL), with Dr Philip Hopley, Birkbeck College London; Dr Colin Mentor, University of Johannesburg; and Dr Bernhard Zipfel, University of the Witwatersrand.
January 2010: NERC Small grant
Critically testing the role of δ30Si (diatom) as a novel productivity signal in temperate lakes.
Despite occupying only ~3% of the earth's land surface, lakes are productivity hotspots and play an important role in the biological fixing, mineralisation and burial (collectively cycling) of carbon, at both a landscape and global scale. Lakes are sensitive to environmental change, yet the ways that lake ecosystems respond (in terms of their overall structure, and processes such as lake productivity) are poorly understood. A NERC-funded project aims to characterise the seasonal dynamics of silicon and δ30Si and link these to diatom productivity in an eutrophic, freshwater lake (Rostherne Mere, Cheshire, UK) to test critically the use of δ30Sidiatom as a productivity proxy in freshwater systems. New analytical developments also make it possible to measure δ18O in diatom silica from the same samples, thus providing the opportunity to link δ30Si and diatom productivity to climatic and hydrological variability. We will monitor bulk sediment formation, planktonic diatom dynamics, climate, hydrology and lake function (stratification) over an 18-month period (including two spring seasons) at high resolution by means of automatic traps, automatic water sampler, on-lake weather station, and a thermistor chain.
The team of researchers include: Dr David Ryves (Loughborough University), Dr Jon Tyler (Oxford University) and Prof Melanie Leng (NIGL) and Dr Phillip Barker (Lancaster University).
2010 Schlumberger Medal of the Mineralogical Society
Congratulations to Professor Randy Parrish who has been awarded the 2010 Schlumberger Medal of the Mineralogical Society.
This annual award was founded in 1990 through the generous sponsorship of Schlumberger Cambridge Research and has the purpose: To recognize scientific excellence in mineralogy and its applications; mineralogy being broadly defined and reflecting the diverse and worldwide interests and membership of the Society with its various specialist groups. Evidence of such excellence should be in the form of published work by a currently active scientist. Professor Parrish will be presented with this award at the 44th Annual conference of the Volcanic and Magmatic Studies Group in Glasgow in January 2010.
Meetings arising from DIPPI-C (Development of Isotopic Proxies for Palaeoenvironmental Interpretation: A Carbon Perspective)
An inter-disciplinary working group specialising in the analysis and interpretation of carbon based proxies in the natural environment bring together palaeoclimatologists, geochemists, biochemists, plant physiologists, ecologists and soil scientists that utilise bulk carbon isotopes; compound specific carbon isotopes; and biomarker distributions to develop a timely and rigorous inter-disciplinary review of the science underpinning these molecular and isotopic proxies in the environment.
Meeting and workshops:
2011 Schedule
WORKING GROUP LAUNCH EVENT
DIPPI-C will be officially launched at AGU Fall Meeting 2011, San Francisco.
The DIPPI-C convenors are chairing "Modern insights into the palaeo-carbon cycle: A δ13C and biomarker perspective I-III" (sessions B13K, B14D and B21E) on Monday 5th December (PM) and Tuesday 6th December (AM).
In addition, the DIPPI-C working group launch event will be held on Wednesday 7th December (10 - 12 am) in the Marriott Hotel, San Francisco (room details to follow).
2012 Schedule
1st DIPPI-C workshop/meeting to be held at Durham University, UK on 8th - 10th May 2012
AOGS, Singapore on 13th - 17th August 2012: session proposal submitted
2013 Schedule
2nd DIPPI-C workshop/meeting to be held at The University of Hong Kong, Hong Kong SAR in Autumn 2013
Special Session - Isotopes and Biogenic Silica: understanding lake sediment archives
Palaeolimnology is built on proxies of environmental processes, all of which have different sensitivities and provide different perspectives into environmental changes. Biogenic silica from lake sediments has become an important host of information regarding catchment silica cycling and stable isotopes of various elements are now being used to reconstruct climate and biogeochemical cycles. The IBiS group is working towards understanding the silica cycle and exploiting the use of isotopes in various forms of biogenic silica to help with environmental reconstruction, especially though not exclusively, from lake sediments. Over the last few years the IBiS working group have aimed to advance techniques in isotope analysis, in addition the community initiated international calibration exercises for both O and Si isotopes. Most recently researchers have moved towards electron microscope imaging and whole-rock geochemistry to enable mass balance approaches to remove contamination effects from the δ18Odiatom record. With the resolution of many fundamental methodological issues, researchers are now exploiting biogenic silica for O, Si, C and N isotope records to provide environmental reconstructions over the very recent past (last few hundreds) of years to Quaternary time scales.
These records have enabled unique insights into climate dynamics from regions where other proxies are not available or insensitive, and the long term functioning of major biogeochemical cycles. We welcome contributions from all working on isotopes and biogenic silica from lake sediment archives and especially contemporary studies that enable calibration of the sediment record.
The summer 2011 edition of Planet Earth reports on a new survey of Lake Tana in Ethiopia (the source of the Blue Nile), the study shows that drought may have contributed to the demise of the Egyptian Old Kingdom, around 4 200 years ago.
