Visual data exploration for hydrological analysis

Hydrological research projects for integrated water resources management such as the IWAS initiative often accumulate large amounts of heterogeneous data from different sources. Given the number of partners taking part in such projects, surveying and accessing the available data sets, as well as searching for a defined subset, becomes increasingly difficult. We propose an integrated approach for a system combining visual data management and numerical simulation which allows to survey and select data sets based on keywords such as a region of interest or given indicators. An adequate 3D visualisation of such subsets helps to convey information and significantly supports the assessment of relations between different types of data. Furthermore, the interface between the visual data management system and finite element codes allows for the straightforward integration of information into the numerical simulation process and the subsequent visualisation of simulation results in a geographical context. We demonstrate typical workflows for integration and processing within the system based on data from the IWAS model region in Saudi Arabia and the TERENO Bode Observatory in the Harz Mountains in Germany. In addition, we present examples for data import and export based on established standard file formats.     

Impact of recharge variations on water quality as indicated by excess air in groundwater of the Kalahari, Botswana

Groundwater is an important and often exclusive water resource in arid and semi-arid regions. The aim of the present paper was to gain insight into the processes and conditions that control the deterioration of groundwater quality in the semi-arid Kalahari of Botswana. Measurements of ³He, ⁴He, ²⁰Ne, ²²Ne, and of ¹⁴C of dissolved inorganic carbon (DIC) were combined with existing isotopic and hydrochemical data to investigate groundwater from the Ntane Sandstone Aquifer, which is affected by high nitrate concentrations of non-anthropogenic origin. All groundwater samples revealed neon concentrations in excess to air-saturated water, which we attributed to the addition of excess air during recharge. Neon concentrations ranged from values close to air saturation for ¹⁴C DIC rich samples (up to 80.5%MC) up to values of 90% in excess to air-saturated water for lower ¹⁴C DIC contents (2.6-61.3%MC). A strong linear correlation of excess Ne with nitrate concentrations suggests an intimate connection between groundwater quality and the processes and conditions during groundwater recharge. Low groundwater recharge rates under present-day semi-arid conditions are associated with low amounts of excess Ne and elevated nitrate concentrations. In contrast to this, higher excess Ne values in groundwater of lower ¹⁴C DIC and nitrate contents indicate that the high quality groundwater end-member presumably is related to higher groundwater table fluctuations during wetter climatic conditions in the past. We attribute the decline in groundwater quality with respect to nitrate to a decreasing rate and temporal variability of groundwater recharge, and to concurrent changes in biogeochemical activities following a transition to a drier climate during the Holocene. Under such conditions, a much stronger decrease in groundwater recharge compared to the release of nitrate from soil organic matter may result in elevated nitrate concentrations in the vadose zone and groundwater. This implies a strong impact of climate change on the transport of solutes like nitrate through the vadose zone which needs to be considered in predictions of future groundwater quality.     

Geochemical evidence for melting of carbonated peridotite on Santa Maria Island, Azores

The islands of the Azores archipelago emerge from an oceanic plateau built on lithosphere increasing in age with distance from the Mid-Atlantic Ridge from 10 to 45 Ma. Here, we present the first comprehensive major and trace element and Sr–Nd–Pb isotope data from Santa Maria, the easternmost island of the archipelago, along with published data from the other Azores islands situated much closer to the Mid-Atlantic Ridge axis. We can show that the distinctively more variable and more enriched trace element ratios at Santa Maria combined with a relatively small range in Sr–Nd–Pb isotope ratios are the result of low degrees of partial melting of a common Azores mantle plume source underneath thicker lithosphere. This implies that melt extraction processes and melting dynamics may be able to better preserve the trace element mantle source variability underneath thicker lithosphere. These conclusions may apply widely for oceanic melts erupted on relatively thick lithosphere. In addition, lower Ti/Sm and K/La ratios and SiO₂ contents of Santa Maria lavas imply melting of a carbonated peridotite source. Mixing of variable portions of deep small-degree carbonated peridotite melts and shallow volatile-free garnet peridotite could explain the geochemical variability underneath Santa Maria in agreement with the volatile-rich nature of the Azores mantle source. However, Santa Maria is the Azores island where the CO₂-rich nature of the mantle source is more evident, reflecting a combination of a smaller extent of partial melting and the positioning at the edge of the tilted Azores mantle plume.     

Meteorites from the Sahara: Find locations,shock classification,degree of weathering and pairing

Abstract— The Sahara is an extraordinary area for recovering meteorites. Between 1989 and 1993, 471 meteorites were collected in Algeria and Libya. Studies of 465 samples have been done. In addition to the classifications of the meteorites that were published in various “Meteoritical Bulletins” in past years, we present here the results on the determination of the shock metamorphism and the degree of weathering. Also, we have tried to solve the pairing problem by considering the find locations, the degree of shock metamorphism, the degree of weathering, and the mineral compositions of olivine and pyroxene. A comprehensive table listing all samples contains references about previous work on these meteorites.     

26Mg excess in hibonites of the Rumuruti chondrite Hughes 030

Abstract— The Rumuruti chondrites (R chondrites) constitute a new, well-established, chondrite group different from carbonaceous, ordinary, and enstatite chondrites. Most samples of this group are gas-rich regolith breccias showing the typical light/dark structure and consist of abundant fragments of various parent body lithologies embedded in a fine-grained, olivine-rich matrix. Most R chondrites contain the typical components of primitive chondrites including chondrules, chondrule and mineral fragments, sulfides, and rare calcium-aluminum-rich inclusions (CAIs). In Hughes 030, an interesting CAI consisting of abundant hibonite and spinel was found. Mg isotopic analyses revealed excess ²⁶Mg in components of R chondrites for the first time. The hibonite grains with high Al/Mg values (∼1500 to 2600) show resolved ²⁶Mg excess. The slope of the correlation line yields an initial ²⁶Al/ ²⁷Al = (1.4 ± 0.3) × 10⁻⁶, which is ∼40 times lower than the initial value measured in CAIs from primitive meteorites. The inferred difference in ²⁶Al abundance implies a time difference of ∼4 million years for the closure of the Al-Mg system between CAIs from primitive chondrites and the Hughes 030 CAI. Based on mineralogy and the petrographic setting of the hibonite-rich CAI, it is suggested that 4 million years reflect the time interval between the formation of the CAI and the end of its secondary alteration. It is also suggested that most of this alteration may have occurred in the nebula (e.g. Zn- and Fe-incorporation in spinels). However, the CAI could not have survived in the nebula as a free floating object for a long period of time. Therefore, the possibility of storage in a precursor planetesimal for a few million years, resetting the magnesium-aluminum isotopic system, prior to impact brecciation, excavation, and accretion of the final R chondrite parent body cannot be ruled out.     

Oxygen- and magnesium-isotope compositions of calcium-aluminum-rich inclusions from Rumuruti (R) chondrites

We report oxygen- and magnesium-isotope compositions of Ca,Al-rich inclusions (CAIs) from several Rumuruti (R) chondrites measured in situ using a Cameca ims-1280 ion microprobe. On a three-isotope oxygen diagram, δ¹⁷O vs. δ¹⁸O, compositions of individual minerals in most R CAIs analyzed fall along a slope-1 line. Based on the variations of Δ¹⁷O values (Δ¹⁷O = δ¹⁷O − 0.52 × δ¹⁸O) within individual inclusions, the R CAIs are divided into (i) ¹⁶O-rich (Δ¹⁷O ∼ −23-26‰), (ii) uniformly ¹⁶O-depleted (Δ¹⁷O ∼ −2‰), and (iii) isotopically heterogeneous (Δ¹⁷O ranges from −25‰ to +5‰). One of the hibonite-rich CAIs, H030/L, has an intermediate Δ¹⁷O value of −12‰ and a highly fractionated composition (δ¹⁸O ∼ +47‰). We infer that like most CAIs in other chondrite groups, the R CAIs formed in an ¹⁶O-rich gaseous reservoir. The uniformly ¹⁶O-depleted and isotopically heterogeneous CAIs subsequently experienced oxygen-isotope exchange during remelting in an ¹⁶O-depleted nebular gas, possibly during R chondrite chondrule formation, and/or during fluid-assisted thermal metamorphism on the R chondrite parent asteroid.Three hibonite-bearing CAIs and one spinel-plagioclase-rich inclusion were analyzed for magnesium-isotope compositions. The CAI with the highly fractionated oxygen isotopes, H030/L, shows a resolvable excess of ²⁶Mg (²⁶Mg^∗) corresponding to an initial ²⁶Al/²⁷Al ratio of ∼7 × 10⁻⁷. Three other CAIs show no resolvable excess of ²⁶Mg (²⁶Mg^∗). The absence of ²⁶Mg^∗ in the spinel-plagioclase-rich CAI from a metamorphosed R chondrite NWA 753 (R3.9) could have resulted from metamorphic resetting. Two other hibonite-bearing CAIs occur in the R chondrites (NWA 1476 and NWA 2446), which appear to have experienced only minor degrees of thermal metamorphism. These inclusions could have formed from precursors with lower than canonical ²⁶Al/²⁷Al ratio.     

Primitive andesites from the Taupo Volcanic Zone formed by magma mixing

Andesites with Mg# >45 erupted at subduction zones form either by partial melting of metasomatized mantle or by mixing and assimilation processes during melt ascent. Primitive whole rock basaltic andesites from the Pukeonake vent in the Tongariro Volcanic Centre in New Zealand’s Taupo Volcanic Zone contain olivine, clino- and orthopyroxene, and plagioclase xeno- and antecrysts in a partly glassy matrix. Glass pools interstitial between minerals and glass inclusions in clinopyroxene, orthopyroxene and plagioclase as well as matrix glasses are rhyolitic to dacitic indicating that the melts were more evolved than their andesitic bulk host rock analyses indicate. Olivine xenocrysts have high Fo contents up to 94%, δ¹⁸O_(SMOW) of +5.1‰, and contain Cr-spinel inclusions, all of which imply an origin in equilibrium with primitive mantle-derived melts. Mineral zoning in olivine, clinopyroxene and plagioclase suggest that fractional crystallization occurred. Elevated O isotope ratios in clinopyroxene and glass indicate that the lavas assimilated sedimentary rocks during stagnation in the crust. Thus, the Pukeonake andesites formed by a combination of fractional crystallization, assimilation of crustal rocks, and mixing of dacite liquid with mantle-derived minerals in a complex crustal magma system. The disequilibrium textures and O isotope compositions of the minerals indicate mixing processes on timescales of less than a year prior to eruption. Similar processes may occur in other subduction zones and require careful study of the lavas to determine the origin of andesite magmas in arc volcanoes situated on continental crust.     

Characterisation of contemporary local climate change in the mountains of southwest Bulgaria

The Pirin Mountains in southwest Bulgaria spatially mark a transition between the Mediterranean and temperate climate zones. Therefore they are also particularly relevant for research on high mountain climate and the effect of landscape transformation. Historical climate records gathered in the area have been researched, checked and statistically examined. The mountainous climate has been characterised and trends in the evolution of temperature and precipitation since 1931 have been outlined. There are objective evidences for an increasing annual mean temperature, longer vegetative periods and local droughts in spring and autumn. Significant changes also appear in climatic threshold values such as the number of frost change days. This last parameter is very important for the sustainability of mountainous ecosystems.     

Recommendation for the discrimination of human-related and natural seismicity

Various techniques are utilized by the seismological community, extractive industries, energy and geoengineering companies to identify earthquake nucleation processes in close proximity to engineering operation points. These operations may comprise fluid extraction or injections, artificial water reservoir impoundments, open pit and deep mining, deep geothermal power generations or carbon sequestration. In this letter to the editor, we outline several lines of investigation that we suggest to follow to address the discrimination problem between natural seismicity and seismic events induced or triggered by geoengineering activities. These suggestions have been developed by a group of experts during several meetings and workshops, and we feel that their publication as a summary report is helpful for the geoscientific community. Specific investigation procedures and discrimination approaches, on which our recommendations are based, are also published in this Special Issue (SI) of Journal of Seismology.     

Direct Sensor Orientation for Large Scale Mapping—Potential, Problems, Solutions

Georeferencing is one of the most important tasks in photogrammetry. Traditionally it has been achieved indirectly using the well-known method of aerial triangulation. With the availability of integrated GPS and inertial measurement units (IMU), this situation changed. Direct determination of exterior orientation is now possible. Today, direct and integrated sensor orientation is used for a wide range of sensors including lidar and SAR, as well as for digital line scanner systems and aerial cameras. This paper investigates the performance of direct and integrated sensor orientation for large scale mapping using the data-set of the 'Integrated Sensor Orientation' test of the European Organisation for Experimental Photogrammetric Research (OEEPE—now known as EuroSDR). The concept, potential, problems and solutions of direct and integrated sensor orientation are discussed.