Quaternary coastline evolution of Lake Ohrid (Macedonia/Albania)     

Nadine Hoffmann  Klaus Reicherter  Christoph Grützner  Jochen Hürtgen  Andreas Rudersdorf  Finn A. Viehberg  Martin Wessels 《Central European Journal of Geosciences》2012,4(1):94-110

Lake Ohrid (between FYR of Macedonia and Albania), situated in an active tectonic region of the Balkanides, is characterized by N ?? S trending active faults. To reconstruct the Holocene shoreline evolution we investigated the coastline using sediment cores and geophysical methods to image sedimentary and tectonic structures. We revealed areas of differing sedimentation regimes. The plains north and south of the lake are dominated by clastic input related to climate variations and uplift/erosion, whereas the steep western and eastern margins are controlled by recent tectonics. Furthermore, no evidence for a much higher lake-level during the Holocene was found in the plains north and south of the lake, except rare temporary floodings. This is supported by mappings of the limestone cliffs around Lake Ohrid, which yielded no evidence for abrasional platforms or notches as indicators for past highstands.  相似文献   

Using Lead Isotopes to Determine Pottery Provenance in Cyprus: Clay Source Signatures and Comparison with Late Bronze Age Cypriote Pottery     

Virginie Renson  Ariane Jacobs  Jan Coenaerts  Nadine Mattielli  Karin Nys  Philippe Claeys 《Geoarchaeology》2013,28(6):517-530

This paper presents the lead isotopic composition of potential clay sources for pottery production, collected in the four major geological zones of Cyprus (Troodos Ophiolite, Circum Troodos Sedimentary Succession, Mamonia Terrane, Kyrenia Terrane) and evaluates its usefulness in Cypriote pottery provenance studies. The clay isotopic signatures from the four zones are compared to each other and to the isotopic composition of various utilitarian pottery wares from three Late Bronze Age sites, respectively located in southern Cyprus (Alassa‐Pano Mandilaris), east Cyprus (Enkomi), and southeast Cyprus (Hala Sultan Tekke). It also explores the potential of this method to better discriminate between potential raw materials used for the production of Base‐ring ware, one of the most characteristic fine pottery of Late Bronze Age Cyprus, which was widely spread in the Eastern Mediterranean (Courtois, 1981; Vaughan, 1991, 1994). Results show that three main lead isotopic fields can be distinguished among the Cypriote clay sources and the comparison of Plain sherds with the clay sources allows discrimination between local products and imports. They also clearly indicate that all the Base‐ring sherds analyzed in this study were made of the clays from the Kathikas Formation that crops out in only limited parts of southwest Cyprus.  相似文献   

The U, Th and Pb elemental and isotope compositions of mantle clinopyroxenes and their grain boundary contamination derived from leaching and digestion experiments     

Nadine Wittig  D. Graham Pearson  Joel A. Baker 《Geochimica et cosmochimica acta》2009,73(2):469-1435

Minerals from peridotites are known to be affected by trace element contamination on their grain boundaries. In this contribution we investigate the extent and origin of exogenous contamination associated with mantle clinopyroxenes from various localities (Middle Atlas, Beni Bousera [Morocco], Pyrenean Massif, Massif Central [France]) and test the efficacy of different leaching methodologies used to remove this contamination. In doing so we present new U-Th-Pb (double-spike) isotope and trace elemental data of clinopyroxenes and their leachates from spinel-facies sub-continental lithospheric mantle (SCLM, n = 18).Sequential leaching and dissolution of one clinopyroxene separate shows that multiple and short leaching attacks with dilute HCl at moderate temperatures (e.g., 120 °C) interspersed with rigorous ultra-pure water washes do not induce elemental fractionation and are sufficient to remove grain-boundary contamination. Short attacks with very dilute mixtures of HF and HCl induced strong parent/daughter elemental fractionation and significant elemental loss prior to the clinopyroxene digestion with HF/HNO₃. Such leaching is not suitable for studies investigating parent/daughter elemental or isotope ratios of mantle clinopyroxenes. Fluoride co-precipitates that formed in the presence of moderately dilute HF, used during leaching and typical HF/HNO₃ digestions, are an important sink for all trace elements studied here and lock up at least 60% of the trace elements considered.A suite of clinopyroxene-leachate pairs from Moroccan peridotites confirm extreme grain-boundary contamination and show that up to 65% of U, 82% of Th and 91% of Pb, respectively, are of exogenous origin. Pb isotopes of all leachates considered and nearly all reconstructed unleached clinopyroxenes have highly positive Δ7/4 and ²⁰⁷Pb/²⁰⁴Pb-²⁰⁶Pb/²⁰⁴Pb systematics reminiscent of enriched mantle (particularly EM II), whereas the corresponding extensively leached clinopyroxenes have very different Pb isotope systematics (verified by replicate digestions). Furthermore, the leachates are often marked by remarkably high ²³²Th/²³⁸U (leachate ? bulk silicate Earth) in addition to ²³⁸U/²⁰⁴Pb and ²³²Th/²⁰⁴Pb that are seemingly consistent with depleted mantle (DM) and high ²³⁸U/²⁰⁴Pb (HIMU) mantle mixing. After leaching, clinopyroxenes may have highly elevated ²³⁸U/²⁰⁴Pb and ²³²Th/²⁰⁴Pb that are distinct from typical DM- and HIMU mantle, whereas corresponding leachates bear strong resemblance to anthropogenic Pb recovered from rainwater, snow and aerosols.In the light of the great potential of Pb isotope contamination associated with mantle clinopyroxene we have compiled literature data of mantle peridotites. These data seem to suggest that the SCLM is nearly devoid of HIMU signatures but ostensibly represents an important repository for enriched mantle signatures. However, the dominance of enriched mantle is not verified when ⁸⁷Sr/⁸⁶Sr and ²⁰⁸Pb/²⁰⁴Pb ratios for the same database are considered. We highlight that the scarcity of HIMU-like SCLM and the alleged dominance of EM in continental roots may be reconciled if the current Pb isotope database of SCLM contains samples that were insufficiently leached prior to digestion and thus are contaminated by anthropogenic Pb. We stress the importance of replicate digestions, adequate leaching and leachate analysis to verify the U-Th-Pb elemental and isotope systematics of any given mantle (-derived) sample.  相似文献   

Contamination risk and drinking water protection for a large-scale managed aquifer recharge site in a semi-arid karst region,Jordan     

Julian Xanke  Tanja Liesch  Nadine Goeppert  Jochen Klinger  Niklas Gassen  Nico Goldscheider 《Hydrogeology Journal》2017,25(6):1795-1809

Karst aquifers in semi-arid regions are particularly threatened by surface contamination, especially during winter seasons when extremely variable rainfall of high intensities prevails. An additional challenge is posed when managed recharge of storm water is applied, since karst aquifers display a high spatial variability of hydraulic properties. In these cases, adapted protection concepts are required to address the interaction of surface water and groundwater. In this study a combined protection approach for the surface catchment of the managed aquifer recharge site at the Wala reservoir in Jordan and the downstream Hidan wellfield, which are both subject to frequent bacteriological contamination, is developed. The variability of groundwater quality was evaluated by correlating contamination events to rainfall, and to recharge from the reservoir. Both trigger increased wadi flow downstream of the reservoir by surface runoff generation and groundwater seepage, respectively. A tracer test verified the major pathway of the surface flow into the underground by infiltrating from pools along Wadi Wala. An intrinsic karst vulnerability and risk map was adapted to the regional characteristics and developed to account for the catchment separation by the Wala Dam and the interaction of surface water and groundwater. Implementation of the proposed protection zones for the wellfield and the reservoir is highly recommended, since the results suggest an extreme contamination risk resulting from livestock farming, arable agriculture and human occupation along the wadi. The applied methods can be transferred to other managed aquifer recharge sites in similar karstic environments of semi-arid regions.  相似文献   

Preliminary stratigraphic and structural architecture of Bhutan: Implications for the along strike architecture of the Himalayan system   总被引：5，自引：0，他引：5  

Nadine McQuarrie  Delores Robinson  Sean Long  Tobgay Tobgay  Djordje Grujic  George Gehrels  Mihai Ducea 《Earth and Planetary Science Letters》2008,272(1-2):105-117

High-precision in-situ ion microprobe (SIMS) oxygen isotope analysis of zircons from two diorite intrusions associated with the late Caledonian Lochnagar pluton in Scotland has revealed large differences in the degree of heterogeneity in zircon δ¹⁸O between the diorites. Zircon crystals from the Cul nan Gad diorite (CnG) show a unimodal distribution of oxygen isotope values (δ¹⁸O = 6.0 ± 0.6‰ (2σ)) and no or only minor grain-scale variation. Those from the Allt Darrarie diorite (AD1) show a large range in δ¹⁸O and an apparent bimodal distribution with modes of 6.6 ± 0.4‰ and 7.3 ± 0.4‰. Variations of up to 1.2‰ occur between and within grains; both an increase and decrease in δ¹⁸O with zircon growth has been observed. The δ¹⁸O composition of growing zircon can only change if open-system processes affect the magma composition, i.e. if material of contrasting δ¹⁸O composition is added to the magma. The variability in AD1 is interpreted to represent a cryptic record of magma mixing. A ‘deep crustal hot zone’ is a likely site for generation of the dioritic magmas which developed by mixing of residual melts and crustal partial melts or by melting of mafic lower crustal rocks. The overall small number of zircons with mantle-like δ¹⁸O values (5.3 ± 0.6‰ (2σ)) in the Lochnagar diorites is largely the product of crustal differentiation rather than crustal growth.

The δ¹⁸O of quartz from the CnG and AD1 diorites shows only minor variation (CnG: 10.9 ± 0.5‰ (2σ), AD1: 11.7 ± 0.6‰ (2σ)) within single populations, with no evidence of mixing. Quartz–zircon isotopic disequilibrium is consistent with later crystallisation of quartz from late magmatic fluids, and in case of the AD1 diorite after the inferred magma mixing from a homogenised, higher δ¹⁸O melt.

High-precision SIMS oxygen isotope analysis of zircon provides a new approach to identifying and resolving previously undetected early-stage magma mixing and constraining the compositions and origins of the component magmas. A combination of zircon, quartz and whole-rock data has proven to be a powerful tool in reconstructing the petrogenetic evolution of diorite from early crystallisation to late alteration.  相似文献   

Integrating biophysical and socio-economic evaluations to improve the efficacy of adaptation assessments for agriculture     

Nicholas P. Webb  Christopher J. Stokes  Nadine A. Marshall 《Global Environmental Change》2013,23(5):1164-1177

This paper demonstrates how biophysical and socio-economic assessments of adaptation options can be integrated to test the effectiveness of options and anticipate social risks and potential barriers to adoption. We present the approach by combining a model analysis with a multiple-criteria evaluation of 12 adaptation options by graziers from the Australian rangelands. Our results show that strategies to manage stocking rates and pasture spelling are likely to be effective in improving climate resilience in the rangelands and are easy-to-implement, short-term solutions. Improving land condition is found to have the greatest potential long-term benefits, but was not considered by the graziers to be feasible or effective due to perceived difficulties of implementation. Areas of concordance identified in the assessments may be used to engage with stakeholders and build a foundation for incorporating climate change considerations into management and policy. The approach also highlights discordant views within the assessments that may result from differing management objectives, adaptive capacity and climate-risk perception. These factors are potential impediments to adaptation. The integrated assessment approach enables adaptation strategies and policy recommendations to be developed that have greater relevance to individual stakeholders, and supports capacity building to facilitate the most effective adaptation actions.  相似文献   

How much material do the radar-bright craters at the Mercurian poles contain?     

Faith Vilas  Paul S. Cobian  Nadine G. Barlow  Susan M. Lederer 《Planetary and Space Science》2005,53(14-15):1496-1500

The depth-to-diameter (d/D) ratios were determined for 12 craters located near the Mercurian north pole that were identified by Harmon et al. (2001, Icarus 149) as having strong depolarized radar echos. We find that the mean d/D value of these radar-bright craters is the mean d/D value of the general population of non-radar-bright craters in the surrounding north polar region. Previous studies, however, show no difference between d/D values of Mercurian polar and equatorial crater populations, suggesting that no terrain softening which could modify crater structure exists at the Mercurian poles (Barlow et al., 1999, 194, Icarus 141). Thus, the change in d/D is governed by a change in crater depth, probably due to deposition of material inside the crater. The volume of infilling material, including volatiles, in the radar-bright craters is significantly greater than predicted by proposed mechanisms for the emplacement of either water ice or sulfur.  相似文献   

The retention of ammonia and sulfur dioxide during riming of ice particles and dendritic snow flakes: laboratory experiments in the Mainz vertical wind tunnel     

Nadine v. Blohn  Karoline Diehl  Anke Nölscher  Alexander Jost  Subir K. Mitra  Stephan Borrmann 《Journal of Atmospheric Chemistry》2013,70(2):131-150

Laboratory experiments were carried out in the Mainz vertical wind tunnel to determine the retention of the trace gases ammonia and sulfur dioxide dissolved in supercooled cloud droplets during riming. The conditions during riming were similar to the ones in atmospheric mixed phase clouds: temperatures from ?18 °C to ?5 °C, liquid water contents between 1 and 1.5 g m^?3, liquid drop radii between 10 and 20 μm, liquid phase concentrations from 1 to 22 mg/l. As collectors, floating ice particles and snow flakes with diameters between 6 mm and 1.5 cm were used. After riming the retention coefficients, i.e. the fractions of the species which remained in the ice phase after freezing were determined. Retention coefficients lying between 0.1 and 1.0 were measured depending on the solubility and dissociation of the trace gas, liquid phase concentration, ambient air temperature, and shape of rimed collector. This can be explained from the chemists’ point of view by the effective Henry’s law constant of the species and physically with the rate of latent heat removal from the rimed collector during freezing. Parameterizations derived from the different experimental cases describe the retention coefficients as a function of temperature. In general, an average retention of ammonia of 92?±?21 % was determined independently of liquid phase concentration while mean values for sulfur dioxide were 53?±?10 % at low liquid phase concentrations and 29?±?7 % at high liquid phase concentrations.  相似文献   

Cambrian sedimentary dykes in the Proterozoic basement of the Västervik area (southeast Sweden): episodic formation inferred from macro- and microfabrics     

Nadine Friese  Axel Vollbrecht  Bernd Leiss  Olaf Jacke 《International Journal of Earth Sciences》2011,100(4):741-752

Fabrics of Cambrian sedimentary dykes formed in Proterozoic granites of the Västervik area (Southeast Sweden) evidence repeated opening/filling and mineralisation/cementation events under varying conditions. Diagnostic features include (1) wall-parallel boundaries between epiclastic fillings and (2) early formed dyke sediments that appear as lithoclasts in subsequently formed sedimentary fillings. The psammitic components mostly consist of well-rounded quartz grains related to a coastal environment and fragments from the granitic host rock. Platy calcitic fragments embedded in the epiclastic matrix originally formed as microveins within already-lithified dyke sediments and the adjacent host rock. Convex downward-pointing, internal sagging structures, together with the preferred orientation of compositional boundaries and long axes of grains/rock fragments parallel to the dyke walls, are interpreted as the result of suction-controlled flow of unconsolidated fillings during episodes of downward dyke growth. Pressure solution of quartz grains are evidence of extensional phases with dyke propagation that were interrupted by phases of horizontal compression normal to the dyke walls. The N–S and NE–SW striking sedimentary dykes formed by opening of a pre-existing joint set during NW–SE oriented rifting during the Cambrian.  相似文献   

Stakeholders’ expectations towards a proposed marine protected area: A multi-criteria analysis of MPA performance criteria     

Nadine Heck  Philip Dearden  Adrian McDonald 《Ocean & Coastal Management》2011,54(9):687-695

In order to enable effective management of marine protected areas (MPAs), desired MPA achievements need to be identified as early as possible for the development of relevant and clear management goals, objectives and conservation targets. As the definition of MPA success is a social construct, the involvement of multiple groups in this process including government agencies, stakeholders, and other interested parties is increasingly advocated. This study investigates diverse groups’ opinions on the performance of a proposed National Marine Conservation Area (NMCA) on the West coast of Canada prior to its establishment. In order to analyse and quantify the importance of MPA performance criteria among multiple stakeholder groups, the Analytical Hierarchy Process (AHP) is applied. Findings reveal that marine stakeholder groups have distinct preferences for future MPA performance. Most differences are obvious between user and non-user groups. The study also finds that respondents’ characteristics other than stakeholder groups affiliations influence expectations towards the proposed MPA including livelihood dependency on the marine environment, amount of time spent in the area, and engagement in fishing activities.  相似文献