Geohydrological models and earthquake effects at Yucca Mountain, Nevada

 Yucca Mountain, the proposed site for the high-level nuclear waste repository, is located just south of where the present water table begins a sharp rise in elevation. This large hydraulic gradient is a regional feature that extends for over 100 km. Yucca Mountain and its vicinity are underlain by faulted and fractured tuffs with hydraulic conductivities controlled by flow through the fractures. Close to and parallel with the region of large hydraulic gradient, and surrounding the core of the Timber Mountain Caldera, there is a 10- to 20-km-wide zone containing few faults and thus, most likely, few open fractures. Consequently, this zone should have a relatively low hydraulic conductivity, and this inference is supported by the available conductivity measurements in wells near the large hydraulic gradient. Also, slug injection tests indicate significantly higher pressures for fracture opening in wells located near the large hydraulic gradient compared to the opening pressures in wells further to the south, hence implying that lower extensional stresses prevail to the north with consequently fewer open fractures there. Analytical and numerical modeling shows that such a boundary between media of high and low conductivity can produce the observed, large hydraulic gradient, with the high conductivity medium having a lower elevation than the water table. Further, as fractures can close due to tectonic activity, the conductivity of the Yucca Mountain tuffs can be reduced to a value near that for the hydraulic barrier due to strain release by a moderate earthquake. Under these conditions, simulations show that the elevation of the steady-state water table could rise between 150 and 250 m at the repository site. This elevation rise is due to the projected shift in the location of the large hydraulic gradient to the south in response to a moderate earthquake, near magnitude 6, along one of the major normal faults adjacent to Yucca Mountain. As the proposed repository would only be 200–400 m above the present water table, this predicted rise in the water table indicates a potential hazard involving water intrusion. Received: 7 June 1996 / Accepted: 19 November 1996     

A Comparison of Predation Rates by Non-indigenous and Indigenous Crabs (Juvenile Carcinus maenas, Juvenile Cancer irroratus, and Adult Dyspanopeus sayi) in Laboratory and Field Experiments

Mean daily consumption rates on Mytilus spp. were compared among juveniles of the non-indigenous Carcinus maenas, juveniles of the indigenous Cancer irroratus, and adults of the indigenous Dyspanopeus sayi between June and August 2005 to assess the relative impact of juvenile C. maenas in field (Benacadie Channel (45°54′ N, 60°53′ E), Bras d’Or Lakes, Nova Scotia, Canada) and laboratory experiments. This study examined: (1) whether consumption rates in a field setting vary among species; (2) the effect of laboratory and field settings on species-specific consumption rates, and whether rates vary between settings for each species; and (3) the effects of temperature and salinity on the consumption rates of these species. In field experiments, there was no significant difference in consumption among C. maenas, C. irroratus, and D. sayi (0.100?±?0.067, 0.450?±?0.189, and 0.800?±?0.423 mussels crab^?1 d^?1, respectively). However, both C. maenas and C. irroratus consumed two to four times more prey in the laboratory than in the field. D. sayi prey consumption was also greater (although not significant) in the laboratory than in the field. In the laboratory, consumption rate was greater for C. irroratus in salinities of 26 than 17 (2.75 and 1.69–1.81 mussels crab^?1 d^?1, respectively), and in 17°C than 13°C (1.10–1.21 and 0.56–0.64 mussels crab^?1 d^?1, respectively) for C. maenas. In all experiments, consumption rates of juvenile C. maenas were lower than or similar to those of the juvenile and adult indigenous species, suggesting that the potential predatory impact of juvenile C. maenas on Mytilus spp. may not be as significant as that of the adults of this non-indigenous species.     

Geochemical and radioactivity mapping in Poland

In 1990 the Polish Geological Institute initiated geochemical mapping of the country aimed at determining the actual conditions of chemistry in the Earth's surficial environments (soils, water sediments, and surficial waters as well) and sea-floor deposits in the Polish economic sector of the Baltic Sea. The geochemical mapping on different scales covered the entire area of the country and selected more important urban agglomerations and industrial districts. Approximately 15,100 samples of soils, 16,200 samples of fresh water sediments, 14,600 samples of surface waters and 467 samples of marine deposits were collected and analysed. A list of geochemical atlases published by the Polish Geological Institute is presented. Investigation of the distribution of radionuclides (natural and artificial) has been done since 1992. Concentrations of U, Th, K, post-Chernobyl Cs and γ dose rate were measured. Approximately 20,000 points covering the whole country were measured. More detailed mappings were executed in the areas polluted by Cs.     

Assess hydrological responses to a warming climate at the Lysina Critical Zone Observatory in Central Europe

Climate warming is having profound effects on the hydrological cycle by increasing atmospheric demand, changing water availability, and snow seasonality. Europe suffered three distinct heat waves in 2019, and 11 of the 12 hottest years ever recorded took place in the past two decades, which will potentially change seasonal streamflow patterns and long-term trends. Central Europe exhibited six dry years in a row since 2014. This study uses data from a well-documented headwater catchment in Central Europe (Lysina) to explore hydrological responses to a warming climate. We applied a lumped parameter hydrologic model Brook90 and a distributed model Penn State Integrated Hydrologic Model (PIHM) to simulate long-term hydrological change under future climate scenarios. Both models performed well on historic streamflow and in agreement with each other according to the catchment water budget. In addition, PIHM was able to simulate lateral groundwater redistribution within the catchment validated by the groundwater table dynamics. The long-term trends in runoff and low flow were captured by PIHM only. We applied different EURO-CORDEX models with two emission scenarios (Representative Concentration Pathways RCP 4.5, 8.5) and found significant impacts on runoff and evapotranspiration (ET) for the period of 2071–2100. Results from both models suggested reduced runoff and increased ET, while the monthly distribution of runoff was different. We used this catchment study to understand the importance of subsurface processes in projection of hydrologic response to a warming climate.     

Spatio-temporal variability of atmospheric rivers and associated atmospheric parameters in the Euro-Atlantic region

We study the spatio-temporal variability of Atmospheric Rivers (ARs) and associated integrated water vapor and atmospheric parameters over the Euro-Atlantic region using long-term reanalysis datasets. Winds, temperature, and specific humidity at different pressure levels during 1979–2018 are used to study the water vapor transport integrated between 1000 and 300 hPa (IVT300) in mapping ARs. The intensity of ARs in the North Atlantic has been increasing in recent times (2009–2018) with large decadal variability and poleward shift (~ 5° towards the North) in landfall during 1999–2018. Though different reanalysis datasets show similar spatial patterns of IVT300 in mapping ARs, bias in specific humidity and wind components led to IVT300 mean bias of 50 kg m⁻¹ s⁻¹ in different reanalysis products compared to ERA5. The magnitude of winds and specific humidity in the lower atmosphere (below 750 hPa) dominates the total column water vapor and intensity of ARs in the North Atlantic. Reanalysis datasets in the central North Atlantic show an IVT300 standard deviation of 200 kg m⁻¹ s⁻¹ which is around 33% of the ARs climatology (~ 600 kg m⁻¹ s⁻¹). Though ARs have a higher frequency of landfalling over Western Europe in winter half-year, the intensity of IVT300 in winter ARs is 3% lower than the annual mean. The lower frequency of ARs in the summer half-year shows 3% higher IVT300 than the annual mean. While ARs in the North Atlantic show a strong decadal change in frequency and path, the impact of the North Atlantic Oscillation (NAO) and Scandinavian blocking on the location of landfall of ARs are significant. Furthermore, there is a strong latitudinal dependence of the source of moisture flux in the open ocean, contributing to the formation and strengthening ARs.

     

Flood-type trend analysis for alpine catchments

ABSTRACT

In many places, magnitudes and frequencies of floods are expected to increase due to climate change. To understand these changes better, trend analyses of historical data are helpful. However, traditional trend analyses do not address issues related to shifts in the relative contributions of rainfall versus snowmelt floods, or in the frequency of a particular flood type. We present a novel approach for quantifying such trends in time series of floods using a fuzzy decision tree for event classification and applied it to maximal annual and seasonal floods in 27 alpine catchments for the period 1980–2014. Trends in flood types were studied with Sen’s slope and double mass curves. Our results reveal a decreasing number of rain-on-snow and an increasing number of short rainfall events in all catchments, with flash floods increasing in smaller catchments. Overall, the results demonstrate the value of incorporating a fuzzy flood-type classification into flood trend analyses.     

PGE fractionation in seafloor hydrothermal systems: examples from mafic- and ultramafic-hosted hydrothermal fields at the slow-spreading Mid-Atlantic Ridge

The distribution of platinum group elements (PGEs) in massive sulfides and hematite–magnetite±pyrite assemblages from the recently discovered basalt-hosted Turtle Pits hydrothermal field and in massive sulfides from the ultramafic-hosted Logatchev vent field both on the Mid-Atlantic Ridge was studied and compared to that from selected ancient volcanic-hosted massive sulfide (VHMS) deposits. Cu-rich samples from black smoker chimneys of both vent fields are enriched in Pd and Rh (Pd up to 227 ppb and Rh up to 149 ppb) when compared to hematite–magnetite-rich samples from Turtle Pits (Pd up to 10 ppb, Rh up to 1.9 ppb). A significant positive correlation was established between Cu and Rh in sulfide samples from Turtle Pits. PGE chondrite-normalized patterns (with a positive Rh anomaly and Pd and Au enrichment), Pd/Pt and Pd/Au ratios close to global MORB, and high values of Pd/Ir and Pt/Ir ratios indicate mafic source rock and seawater involvement in the hydrothermal system at Turtle Pits. Similarly shaped PGE chondrite-normalized patterns and high values of Pd/Pt and Pd/Ir ratios in Cu-rich sulfides at Logatchev likely reflect a similar mechanism of PGE enrichment but with involvement of ultramafic source rocks.     

Contrasting sources of Late Paleozoic rhyolite magma in the Polish Lowlands: evidence from U–Pb ages and Hf and O isotope composition in zircon

International Journal of Earth Sciences - The Polish Lowlands, located southwest of the Teisseyre–Tornquist Zone, within Trans-European Suture Zone, were affected by bimodal, but dominantly...     

Recruitment of Mytilus edulis L. in the Thames estuary,with evidence for differences in the time of maximal settling along the Connecticut shore

In the Thames Estuary at the eastern end of Long Island Sound, most mussels achieve maximal gonadal development during the summer and larval settlement occurs primarily during the fall. The timing of reproductive events is several months later than has been reported for other populations of mussels in Long Island Sound but corresponds to that of mussels inhabiting the south shore of Long Island. The data support the growing body of evidence which indicates that temperature is not a major factor determining the reproductive period of this bivalve.     

Papua New Guinea Highlands: palaeomagnetic constraints on terrane tectonics

Oblique convergence since the Early Cenozoic between the northward-moving Australian plate, westward-moving Pacific plate and almost stationary Eurasian plate has created a world-ranking tectonic zone in the eastern Indonesia–New Guinea–Southwest Pacific region (Tonga–Sulawesi megashear) that is notorious for its complex mix of tectonic styles and terrane juxtapositions. Unlike an ancient analog—the Mesozoic–Cenozoic Cordillera of North America—palaeomagnetic constraints on terrane motions in the zone are few. To improve the framework of quantitative control on such motions and therefore our understanding of the development of the zone, results of a palaeomagnetic study in the Highlands region of Papua New Guinea (PNG), in the southern part of the New Guinea Orogen, are reported. The study yields new insights into terrane tectonics along the Australian craton's active northern margin and confirms the complexity of block rotations to be expected at the local scale in tectonically intricate zones. The study is based on more than 500 samples (21 localities) collected from an interior and an exterior zone of New Guinea's central cordillera. The two zones are separated by the Tahin and Stolle–Lagaip–Kaugel Fault zones and collectively represent the para-autochthonous northern margin of the Australian craton. Samples from the interior zone, which in the study area comprises a cratonic spur of uncertain—probably displaced—origin, come from Triassic to Miocene sediments and subordinate volcanics of the Kubor Anticline, Jimi Terrane, and Yaveufa Syncline (16 localities) in the central and eastern Highlands. Samples from the exterior zone, which represent a basement-involved, Pliocene foreland fold-and-thrust belt, come from Middle Eocene to Middle Miocene carbonates and clastics (five localities) in the southern Highlands of the Papuan Fold Belt. Results permit us to constrain the tectonic evolution of the two zones palaeomagnetically. Using mainly thermal demagnetization techniques, three main magnetic components have been identified in the collection: (1) a recent field overprint of both normal and reverse polarity; (2) a pervasive overprint of mainly normal polarity that originated during extensive Middle to Late Miocene intrusive activity in the central cordillera; and (3) a primary component which has been identified in only 7 of the 21 localities (5 of 11 stratigraphic units represented in the collection). All components show patterns of rotation that are consistent within the zones, but differ between them. In the interior zone (central and eastern Highlands), large-scale counterclockwise rotations of between 30°+ and 100°+ have been established throughout the Kubor Anticline and Jimi Terrane, with some clockwise rotation present in the southern part of the Yaveufa Syncline. In contrast, in the Mendi area of the exterior zone (southern Highlands), clockwise rotations of between 30°+ and 50°+ can be recognized. These contrasting rotation patterns across the Tahin and Stolle–Lagaip–Kaugel Fault zones indicate decoupling of the two tectonic zones, probably along basement-involved faults. The clockwise rotations in the southern Highlands of the Papuan Fold Belt are to be expected from its structural grain, and are probably governed by regional basement faults and transverse lineaments. In contrast, the pattern of counterclockwise rotations in the Kubor Anticline–Jimi Terrane cratonic spur of the central and eastern Highlands was unexpected. The pattern is interpreted to result from non-rigid rotation of continental terranes as they were transported westward across the northeastern margin of the Australian craton. This margin became reorganised after the Middle Miocene, when the steadily northward-advancing Australian craton impinged into the westward-moving Pacific plate/buffer-plate system. Transpressional reorganisation under the influence of the sinistral Tonga–Sulawesi megashear became enhanced with Mio-Pliocene docking, and subsequent southward overthrusting, of the Finisterre Terrane onto the northeastern margin of the Australian craton.