Behavior of isotopic systematics during deformation and metamorphism: a Hf,Nd and Sr isotopic study of mylonitized granite

A combined compositional and Hf, Nd and Sr isotopic study was performed on a suite of samples of progressively deformed granite from a mylonite zone in the Harquahala Mountains, western Arizona, to evaluate the effects of deformation and metamorphism on the isotopic systematics of typical continental crustal rocks. The 1.4 Ga Harquahala Granite was deformed during Mesozoic thrusting along the Harquahala thrust. Granite in the resulting 60 m wide shear zone ranges from protomylonite to ultramylonite. In most of these mylonites, the protolith is not megascopically recognizable, and can be discerned only by the progressive transition to undeformed granite. Isotopic analyses of Hf, Nd and Sr from the shear zone document the immobility of the Hf and Nd isotopic systems relative to that of the Sr isotopic system during deformation. The Rb–Sr isotopic data show considerable scatter on an isochron plot, exhibiting both gains and losses of Rb and Sr from the whole-rock systems. In contrast, the Sm–Nd and Lu–Hf isotopic systematics are mostly well behaved on isochron diagrams, plotting mostly in tight clusters or along 1.4 Ga isochrons. These results show that while the Sr isotopic system in crustal rocks is quite susceptible to later tectonic disturbance, both Hf and Nd isotopic systems can provide reliable model age information in continental crustal terranes even when the rocks have been subjected to low to medium grades of deformation and metamorphism.     

Global change revealed by palaeolimnological records from remote lakes: a review

Over recent decades, palaeolimnological records from remote sites have provided convincing evidence for the onset and development of several facets of global environmental change. Remote lakes, defined here as those occurring in high latitude or high altitude regions, have the advantage of not being overprinted by local anthropogenic processes. As such, many of these sites record broad-scale environmental changes, frequently driven by regime shifts in the Earth system. Here, we review a selection of studies from North America and Europe and discuss their broader implications. The history of investigation has evolved synchronously with the scope and awareness of environmental problems. An initial focus on acid deposition switched to metal and other types of pollutants, then climate change and eventually to atmospheric deposition-fertilising effects. However, none of these topics is independent of the other, and all of them affect ecosystem function and biodiversity in profound ways. Currently, remote lake palaeolimnology is developing unique datasets for each region investigated that benchmark current trends with respect to past, purely natural variability in lake systems. Fostering conceptual and methodological bridges with other environmental disciplines will upturn contribution of remote lake palaeolimnology in solving existing and emerging questions in global change science and planetary stewardship.     

Impact of Air Pollution on Genetic Material of Shallot (Allium cepa L. var. ascalonicum) Exposed at Differently Polluted Sites in Slovenia

Test shallot plants Allium cepa L. var. ascalonicum were exposed to field conditions at six research plots in the most polluted areas in Slovenia in the vegetation seasons in 1999 and 2000. The intention of this research was to evaluate the influence of air pollution on mitotic activity and frequency of chromosomal aberrations in meristematic tissues of root tips of bioindication plants. Significant differences in the mitotic index and in frequency of chromosomal aberrations at different sampling plots in pot experiments were found and the correlation between the ozone concentration and the mitotic index was determined. The results showed the presence of cytotoxic substances at chosen sampling sites, which caused the decrease of mitotic cell division and the presence of genotoxic substances, which resulted in the increase of frequency of chromosomal aberrations.     

Die kurzwellige Strahlung von Sonne und Himmel auf verschieden orientierte und geneigte Flächen

Zusammenfassung In Locarno-Monti am Alpensüdfu? wurde w?hrend zwei Jahren die kurzwellige Strahlung von Sonne + Himmel (Globalstrahlung) auf eine horizontale, je eine um 30° bzw. 60° nach Süden und je eine um 30° nach Osten bzw. Westen geneigte Auffangfl?che mit Solarimetern registriert. Die Tages- und Jahresg?nge der Globalstrahlung zeigen an wolkenlosen Tagen gro?e Unterschiede im Strahlungsgenu? der verschieden orientierten und verschieden geneigten Fl?chen. Im Mittel aller Tage sind diese Unterschiede zwar kleiner, jedoch wegen der gro?en relativen Sonnenscheindauer in Locarno-Monti immer noch sehr ausgepr?gt. Bei vollkommen bedecktem Himmel verschwinden die Unterschiede fast v?llig. Aufgrund der Beziehungen zwischen der Globalstrahlung und der relativen Sonnenscheindauer genügen Parallelmessungen von wenigen Jahren, um daraus klimatologische Mittelwerte der Globalstrahlung auf verschieden orientierte und geneigte Fl?chen berechnen zu k?nnen. Das Verh?ltnis der Strahlung auf geneigte H?nge zu der auf die horizontale Fl?che h?ngt von der Jahreszeit und der Bew?lkung ab. Diese Beziehung kann dazu dienen, bei Kenntnis der Globalstrahlung auf eine horizontale Fl?che jene auf eine geneigte Auffangfl?che zu bestimmen. Schlie?lich wird auf die Bedeutung dieser Untersuchungen für die praktische Meteorologie hingewiesen.

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Summary For a two years' period the total (short wave) radiation of sun and sky falling on a horizontal surface, on southern slopes of 30° and 60° inclination, resp., and on eastern and western slopes of 30° inclination has been recorded with solarimeters at Locarno-Monti (Switzerland). On cloudless days the diurnal and annual variations of the total radiation indicate rather big differences between the radiation falling on the surfaces of different inclination and orientation. Considering the radiation covering all days, these differences are smaller but still distinctly marked because of the high relative duration of sunshine at Locarno-Monti. On overcast days all surfaces receive almost the same amount of radiation. Climatological averages of the total radiation falling on surfaces of different orientation and inclination can be deduced using the relation between the total radiation and the duration of sunshine. The ratio between the radiation falling on inclined planes and the radiation falling on a horizontal surface depends on season and cloudiness. By means of these relations the radiation falling on inclined surfaces can be calculated using the radiation falling on the horizontal surface. Finally the importance of such investigations for applied meteorology is pointed out.

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Résumé Le rayonnement de courte longueur d'onde du soleil et du ciel (rayonnement global) a été enregistré pendant deux ans à Locarno-Monti, au pied sud des Alpes, au moyen de solarimètres présentant différentes orientations. Les surfaces réceptrices étaient respectivement horizontale, inclinées de 30° et 60° vers le sud, ainsi que de 30° vers l'est et l'ouest. Les variations journalières et saisonnières du rayonnement global mettent en évidence les grandes différences d'éclairement des surfaces réceptrices selon leur azimut et leur inclinaison, lors des journées ensoleillées surtout. Ces différences sont plus faibles lorsque l'on prend tous les jours en considération, mais restent cependant bien marquées par suite de la grande durée relative d'insolation à Locarno-Monti; elles disparaissent presque complètement par ciel entièrement couvert. En s'appuyant sur les relations entre le rayonnement global et la durée relative d'insolation, l'on peut calculer des moyennes climatologiques du rayonnement global tombant sur des surfaces d'orientation différente à l'aide de quelques années seulement d'enregistrements parallèles. Le quotient des rayonnements re?us par une pente inclinée et par une surface horizontale dépend de la saison et de la couverture nuageuse. Une fois cette relation connue, il est possible d'évaluer le rayonnement global re?u par une surface inclinée à partir des valeurs relatives à une surface horizontale. Enfin, l'on signale l'importance de ces recherches pour la météorologie appliquée.

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Riassunto A Locarno-Monti al piede meridionale delle Alpi durante due anni fu registrata con solarimetri la radiazione ad onde corte del sole + cielo (radiazione globale) su superfici orizzontale, inclinate di 30° e rispettivamete 60° e rivolte verso sud, nonchè su superfici orizzontale, inclinate di 30° e rivolte verso est, rispettivamente verso ovest. Gli andamenti giornaliero ed annuale della radiazione globale mostrano nei giorni senza nuvole grandi differenze nella quantità di radiazione ricevuta dalle superfici diversamente inclinate e orientate. Nella media di tutti i giorni tali differenze sono si più piccole, tuttavia sempre ancora ben pronunciate causa l'elevata durata relativa dell'insolazione. Con cielo completamente coperto le differenze scompaiono quasi completamente. In base alle relazioni tra la radiazione globale e la durata relativa dell'insolazione, sono sufficienti misure parallele di soli pochi anni per poter calcolare valori climatologici della radiazione globale su diverse superfici orientate e inclinate. Il rapporto tra la radiazione su pendii inclinati e quella su superfici orizzontale dipende dalla stagione e dalla nuvolosità. Questa relazione può servire, conoscendo la radiazione globale su una superficie orizzontale, a determinare quella su una superficie di ricezione inclinata. Da ultimo viene accennato all'importanza di queste ricerche per la meteorologia pratica.

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Early Weichselian interstadial (MIS 5c) summer temperatures were higher than today in northern Fennoscandia

Only fragmentary biostratigraphical interstadial data exist from northern European high latitudes. The palaeoenvironmental interpretations for the early part of the Last Glaciation in northern Fennoscandia are mainly based on palynological evidence that suggests open birch woodland and a sub-arctic climate. Plant macrofossils from the Sokli sediment sequence in Finnish Lapland provide different evidence of interstadial climate conditions. The assemblage includes several species that currently have considerably more southern distribution ranges. This indicates that ca 100,000 years ago summer temperatures were warmer than today. The mean minimum July temperature may have been as high as 16 °C and the effective temperature sum may have been 1000 in day-degree units (d.d.), the modern values being 13 °C and 650 d.d., respectively. The contemporary astronomical forcing mechanisms may have resulted in a weaker north–south temperature gradient and a longer growing period, creating more favourable climate conditions compared with today.     

Identification of groundwater exfiltration,interflow discharge,and hyporheic exchange flows by fibre optic distributed temperature sensing supported by electromagnetic induction geophysics

Water exchange across the sediment–water interface of streams impresses a characteristic thermal pattern at the interface. The use of fibre optic distributed temperature sensing at the sediment–water interface in a small sand‐bed stream identifies such temperature patterns. Groundwater and interflow can be differentiated based on the temporal evolution of temperature patterns. Additionally, sudden temperature changes at the sediment–water interface observed during the transit of floods enable spatial identification of local up and downwelling. Electromagnetic induction geophysics can detect subsurface texture structures that support groundwater–surface water exchange. Our results show that areas of permanent temperature anomalies observed with fibre optic distributed temperature sensing match areas of comparatively homogeneous electrical conductivity. This indicates groundwater discharge and enables differentiating groundwater discharge from interflow and local downwelling.     

Quantitative WD‐XRF calibration for small ceramic samples and their source material

A wavelength‐dispersive X‐ray fluorescence (WD‐XRF) calibration is developed for small powdered samples (300mg) with the purpose of analyzing ceramic artifacts that might be available only in limited quantity. This is compared to a conventional calibration using a larger sample mass (2g). The comparison of elemental intensities obtained in both calibrations shows that the decrease in analyzed sample mass results in a linear decrease in measured intensity for the analyzed elements. This indicates that the small‐ and large‐sample calibrations are comparable. Moreover, the elemental contents of four ceramic sherds and two potential clay sources fall well within the range of the certified reference materials that are the basis of the calibration curves. The advantage with the analytical method presented here is that it is rapid and requires only a small amount of sample that can easily be re‐used for further analyses. This method has great potential in ceramic provenance studies. © 2011 Wiley Periodicals, Inc.