The Diamantina Monazite: A New Low‐Th Reference Material for Microanalysis

Most monazite reference materials (RMs) for in situ U‐Pb geochronology are rich in Th; however, many hydrothermal ore deposits contain monazite that is low in trace element contents, including Th, U and Pb. Because of potential problems with matrix effects and the lack of appropriate matrix‐matched RMs, such variations can bias dating of hydrothermal deposits. In this paper, we describe a polycrystalline low‐U and low‐Th Diamantina monazite from the Espinhaço Range, SE Brazil. It has a U‐Pb ID‐TIMS weighted mean ²⁰⁷Pb^*/²³⁵U ratio of 0.62913 ± 0.00079, ²⁰⁶Pb^*/²³⁸U of 0.079861 ± 0.000088 and ²⁰⁷Pb^*/²⁰⁶Pb^* of 0.057130 ± 0.000031, yielding a weighted mean ²⁰⁶Pb^*/²³⁸U date of 495.26 ± 0.54 Ma (95% c.l.). In situ dates acquired with different methods (LA‐(Q, SF, MC)‐ICP‐MS and SIMS) are within uncertainty of the ID‐TIMS data. U‐Pb LA‐(Q, MC)‐ICP‐MS runs, using Diamantina as a primary RM, reproduced the ages of other established RMs within < 1% deviation. The LA‐MC‐ICP‐MS analyses yielded homogeneous Sm‐Nd isotopic compositions (¹⁴³Nd/¹⁴⁴Nd = 0.511427 ± 23, 2s; ¹⁴⁷Sm/¹⁴⁴Nd = 0.1177 ± 13, 2s) and εNd_(495 Ma) of ?18.7 ± 0.5 (2s). SIMS oxygen isotope determinations showed measurement reproducibility better than ± 0.3‰ (2s), confirming Diamantina's relative homogeneity at test portion masses below 1 ng.     

New insights into lake responses to rapid climate change: the Younger Dryas in Lake Gościąż, central Poland

The sediment profile from Lake Gościąż in central Poland comprises a continuous, seasonally resolved and exceptionally well-preserved archive of the Younger Dryas (YD) climate variation. This provides a unique opportunity for detailed investigation of lake system responses during periods of rapid climate cooling (YD onset) and warming (YD termination). The new varve record of Lake Gościąż presented here spans 1662 years from the late Allerød (AL) to the early Preboreal (PB). Microscopic varve counting provides an independent chronology with a YD duration of 1149+14/–22 years, which confirms previous results of 1140±40 years. We link stable oxygen isotopes and chironomid-based air temperature reconstructions with the response of various geochemical and varve microfacies proxies especially focusing on the onset and termination of the YD. Cooling at the YD onset lasted ~180 years, which is about a century longer than the terminal warming that was completed in ~70 years. During the AL/YD transition, environmental proxy data lagged the onset of cooling by ~90 years and revealed an increase of lake productivity and internal lake re-suspension as well as slightly higher detrital sediment input. In contrast, rapid warming and environmental changes during the YD/PB transition occurred simultaneously. However, initial changes such as declining diatom deposition and detrital input occurred already a few centuries before the rapid warming at the YD/PB transition. These environmental changes likely reflect a gradual increase in summer air temperatures already during the YD. Our data indicate complex and differing environmental responses to the major climate changes related to the YD, which involve different proxy sensitivities and threshold processes.     

Cryptotephras in the Lateglacial ICDP Dead Sea sediment record and their implications for chronology

Due to a lack of visible tephras in the Dead Sea record, this unique palaeoenvironmental archive is largely unconnected to the well-established Mediterranean tephrostratigraphy. Here we present first results of the ongoing search for cryptotephras in the International Continental Drilling Program (ICDP) sediment core from the deep Dead Sea basin. This study focusses on the Lateglacial (~15–11.4 cal. ka BP), when Lake Lisan – the precursor of the Dead Sea – shrank from its glacial highstand to the Holocene low levels. We developed a glass shard separation protocol and counting procedure that is adapted to the extreme salinity and sediment recycling of the Dead Sea. Cryptotephra is abundant in the Dead Sea record (up to ~100 shards cm^-3), but often glasses are physically and/or chemically altered. Six glass samples from five tephra horizons reveal a heterogeneous geochemical composition, with mainly rhyolitic and some trachytic glasses potentially sourced from Italian, Aegean and Anatolian volcanoes. Most shards likely originate from the eastern Anatolian volcanic province and can be correlated using major element analyses with tephra deposits from swarm eruptions of the Süphan Volcano ~13 ka BP and with ashes from Nemrut Volcano, presumably the Lake Van V-16 volcanic layer at ~13.8 ka BP. In addition to glasses that match the TM-10-1 from Lago Grande di Monticchio (15 820±790 cal. a BP) tentatively correlated with the St. Angelo Tuff of Ischia, we further identified a cryptotephra with glass analyses which are chemically identical with those of the PhT1 tephra in the Philippon peat record (13.9–10.5 ka BP), and also a compositional match for the glass analyses of the Santorini Cape Riva Tephra (Y-2 marine tephra, 22 024±642 cal. a BP). These first results demonstrate the great potential of cryptotephrochronology in the Dead Sea record for improving its chronology and connecting the Levantine region to the Mediterranean tephra framework.     

Modelling and assessment of earthquake ground response in areas characterised by a thick buried low-velocity layer

Natural Hazards - It is known that local geology can alter the ground motion characteristics at a particular site. Whereas some sites are characterised by outcropping low-velocity layers, others...     

Hydrogeochemical and Geophysical Evaluation of the Recharge Zone of Guarani Aquifer in Municipally of Candelária,Rio Grande do Sul,Brazil

Geotechnical and Geological Engineering - A large part of the Guarani Aquifer is located in the state of Rio Grande do Sul (Brazil) and additionally possesses a recharge area located in its central...     

Defining the acceptable level of risk for civil protection purposes: a behavioral perspective on the decision process

This work analyzes how acceptable risk levels are determined in political decisions and related policies in the field of civil protection, i.e., regarding disaster risks and their reduction at the national and supranational level. We examined why establishing the acceptable level of risk is a political decision, and why this decision is not an easy task. Some behavioral elements which can de facto impede such a decision were recognized. Among these, the anomalies inherent in intertemporal choices, availability heuristic and mental accounting play a primary role, because they interfere with preferences for selfish versus others’ interests and with the evaluation of individual versus community gains and losses. Due to these processes, the political decision-maker, unless she is a statesperson, will easily prefer not to decide. Political decision-making, however, could be induced by a change of mind in the voters’ community. This reorientation of the society’s values and interests can be stimulated taking advance from research on social norms, which underlines the role played by some people that drive innovation in a community, e.g., the trendsetters. The scientific, technical and professional communities have the knowledge needed, are aware of the work to be done on the disaster risk reduction and can establish a direct relationship with single trendsetters and statespersons to promote decision-making on disaster risk reduction. Within this relationship, they can build trust, give advice and participate in in-depth discussions. In this interaction and collaboration, behavioral sciences can provide a valuable support for a better reciprocal understanding.     

Probabilistic assessment of annual repair rates in pipelines and of direct economic losses in water and sewage networks: application to Manizales,Colombia

A methodology for the development of fully probabilistic seismic risk assessments on water and sewage networks is presented in this paper together with a case study for the system of Manizales, Colombia. These kinds of assessments require the development of probabilistic seismic hazard analysis, the consideration of local site effects, when relevant, the assembly of databases to identify and characterize the exposed elements and the development and assignment of vulnerability models for each type of component. For the case of Manizales, a high-resolution exposure database has been developed (element by element, segment by segment) based on the information and data provided by the owner and operator of the network, Aguas de Manizales. Losses due to earthquakes are obtained after convoluting the hazard and vulnerability inputs in a fully probabilistic manner, using the state-of-the-art methodologies incorporated in the CAPRA risk assessment module. Several risk metrics such as the loss exceedance curve, the loss exceedance probabilities for different time frames and the average annual loss are obtained for the system as a whole as well as disaggregated by component. In addition, repair rates for the pipelines were also calculated. The risk results obtained in this study have been useful for the company in designing and implementing expansion and maintenance plans that explicitly account for seismic risk mitigation issues, as well as to explore and negotiate financial protection alternatives by means of risk transfer and retention schemes, thus becoming a valuable input in the continuous development of good disaster risk management practices in this city.     

Evaluating the effects of protection on two benthic habitats at Tavolara-Punta Coda Cavallo MPA (North-East Sardinia, Italy)

In this paper, two benthic habitats have been investigated in a fully protected site and two control sites at the Tavolara-Punta Coda Cavallo marine protected area (MPA) (NE Sardinia). Overall, a protection effect on the benthic assemblages was highlighted in the shallow subtidal (5 m deep) rather than at intertidal algal turf habitat. Structure of assemblages at the shallow subtidal habitat is different in the fully protected site vs. controls, while this was not true for the intertidal habitat. At the subtidal, this finding is probably linked to indirect effects due to an increase of consumers in the protected site (e.g., sea urchins), while the lack of direct impacts in the intertidal at control sites is indicative of very similar assemblages. Cover of encrusting algae was significantly higher at the subtidal protected site suggesting a possible higher grazing pressure. Possible causes underlying the inconsistency of results obtained between habitats include the possibility that trophic cascade effects have a different influence at different heights on the shore. The need to estimate the interconnection among benthic habitats through trophic links is also highlighted to provide an estimate of the vulnerability to protection of various habitats.     

On the reliability of long‐period response spectral ordinates from digital accelerograms

Using records from co‐located broadband and digital strong motion (SM) instruments, it is first shown that the displacement waveforms obtained by double integration of the accelerogram need not be free of unrealistic baseline drift to yield reliable spectral ordinates up to at least 10 s. Secondly, to provide objective criteria for selecting reliable digital SM records for ground motion predictions at long periods, a set of synthetic accelerograms contaminated by random long‐period noise has been used, and the difference between the original accelerograms and the spurious ones in terms of response spectra has been quantified, by introducing a noise index that can be easily calculated based on the velocity waveform of the record. The results of this study suggest that high‐pass filtering the digital acceleration record from a cutoff period selected to suppress baseline drifts on the displacement waveform appears to be in most cases too conservative and unduly depletes reliable information on long‐period spectral ordinates. Copyright © 2007 John Wiley & Sons, Ltd.