Development of engineering geology in western United States

Geologic concepts and scientific-technical guidance for the planning-design and construction of engineered works was recognized in Europe by the 1800s and by the early 1900s in North America. This early geologic knowledge and experience provided the rudimentary principles that guided practitioners of the 19th century in serving the emerging projects in western United States. Case studies review the scientific-technical lessons learned and the legacy of geologic principles established in the planning and construction of major civil, mining, and military engineered works in the western states. These contributions to GeoScience knowledge and engineering geology practice include:

• •Tunnels and aqueducts across active fault zones, beneath young volcanic features, groundwater-charged faults, and land subsidence mitigation.
• •Controversial foundation design, Folsom and Auburn dams, Golden Gate Bridge.
• •Protective underground construction chambers, safety dependent geologic setting.
• •Geologic mapping as database management leasing, maintenance railroad trackway.
• •Causeway Great Salt Lake, geo-risks calculated, mitigated ‘as-constructed’.
• •Nuclear powerplants seismic design.
• •Urban Land-Use, on-going processes, acceptable geo-risks.
• •Dwelling Insurance, insuree's responsibilities.
• •Selecting technique/method to mitigate risk, preferably based on extensive database, evaluation of characteristics and historical origin adverse features/conditions that constitute a geo-risk.

     

Measurements and interpretations of36Cl in groundwater,Milk River aquifer,Alberta, Canada

The³⁶Cl/Cl ratios of 12 groundwater samples from the Milk River aquifer were determined by accelerator mass spectrometry. Using known Cl concentrations,³⁶Cl concentrations were deduced. Approximately linear relations were observed between the logarithm of the³⁶Cl concentration, the Cl concentration, and the distance from the recharge area along two flow paths. The results are discussed in two approaches:

• (1)in an interpretation of the linear relation between logarithm of the³⁶Cl concentration and Cl concentration excluding and includingin situ production of³⁶Cl;
• (2)in a diffusion model. The increase of the Cl concentration with the distance from the recharge area is considered to be due to diffusion of Cl from the underlying confining Colorado shale to the aquifer.

Flow velocities ranging between 0.04 and 0.14 m/a, and ages of the groundwater between 0.6 and 2 Ma are obtained at a distance of 80 km from the recharge area.     

Coprecipitation of alkali metal ions with calcium carbonate

The coprecipitation of alkali metal ions (Li⁺, Na⁺, K⁺ and Rb⁺) with calcium carbonate has been studied experimentally and the following results have been obtained:

• 1.(1) Alkali metal ions are more easily coprecipitated with aragonite than with calcite.
• 2.(2) The relationship between the amounts of alkali metal ions coprecipitated with aragonite and their ionic radii shows a parabolic curve with a peak located at Na⁺ which has approximately the same ionic radius as Ca²⁺.
• 3.(3) However, the amounts of alkali metal ions coprecipitated with calcite decrease with increasing ionic radius of alkali metals.
• 4.(4) Our results support the hypothesis that
  • 4.1.(a) alkali metals are in interstitial positions in the crystal structure of calcite and do not substitute for Ca²⁺ in the lattice, but
  • 4.2.(b) in aragonite, alkali metals substitute for Ca²⁺ in the crystal structure.
• 5.(5) Magnesium ions in the parent solution increase the amounts of alkali metal ions (Li⁺, Na⁺, K⁺ and Rb⁺) coprecipitated with calcite but decrease those with aragonite.
• 6.(6) Sodium-bearing aragonite decreases the incorporation of other alkali metal ions (Li⁺, K⁺ and Rb⁺) into the aragonite.

     

Buckling loads of fully embedded vertical piles

Determination of critical buckling loads of columns in a medium which offers resistance to lateral deflections depend on:

• (a) Length of the pile, L.
• (b) Flexural stiffness of the pile, EI.
• (c) Stiffness of the soil, K, and
• (d) Boundary conditions of the pile, both at the top and the tip.

In this paper, solutions for buckling loads have been obtained in closed form by energy methods for fully embedded vertical piles for boundary conditions, pinned top-pinned tip, fixed top-fixed tip, and a linear variation of soil stiffness. The effects of pile length, soil stiffness, and boundary conditions on buckling loads and mode of buckling have been studied for pile lengths up to 24 m with EI of 477 tm², K₀ [A] from 0 to 2000 t/m² and N_h [B] from 0 to 2000 t/m³.     

A quantitative fluorescence technique for evaluating thermal maturity: Instrumentation and examples

Fluorescence microscopy is useful not only for identifying most of the oil-prone organic matter (macerals) in sedimentary rocks and coals but also for assessing their thermal maturities (ranks). This report introduces a violet-light excitation system which induces more than one order of magnitude stronger fluorescence intensity that the commonly used UV-light excitation system. The red/green quotient from violet-light excited fluorescence, Q_v, of sporinite can be easily measured using this system. Several examples using coal and cuttings samples are presented to demonstrate the use of this technique for evaluating the thermal maturities of coals and sedimentary rocks.From the results of our studies we conclude that:

• 1.(1) Violet-light excited fluorescence from sporinites can be routinely measured to assess thermal maturity.
• 2.(2) Spectral (Quantitative) fluorescence technique is useful for evaluating thermal maturity when samples are poorly polished or deficient in vitrinite.
• 3.(3) Visual (Strew-mounted) kerogen slides can not be used for fluorescence measurements unless a non-fluorescent mounting medium is used.

     

Structural evolution of the Téfidet trough (East Aïr,Niger) in relation with the West African Cretaceous and Paleogene rifting and compression episodes

Located in northern Niger, the NW–SE Téfidet trough is the western branch of the Ténéré rift megasystem.Here we present a tectono-sedimentary analysis of the Téfidet trough, based on the combined use of satellite imagery, field observations and measures, and available literature. We use these data to analyse the sedimentary facies and the tectonic deformations (faults, folds, basins) in the Téfidet trough, and derive their relative chronology. Doing so, we characterize synrift and postrift deformations and their interactions with sedimentation.Altogether our analyses suggest that the Téfidet trough was affected from the Cretaceous to the Paleogene by three major tectonic periods.

• •The first period was a rifting stage with extension and transtension during the Albian–Aptian times. The mean extension was ∼N60° and dominantly produced NW–SE-trending normal faults, a few strike-slip faults locally associated with small folds with sigmoidal axis and small reverse faults, and progressive unconformities.
• •the second period was also a rifting time, which prevailed during the Upper Cretaceous. The regime was marked by transtensional to extensional tectonics, under a ∼N130° shortening and a ∼N60° trending stretching. The end of this period saw the closure of the Téfidet trough.
• •the third period was a postrift stage. It was characterized by a ∼N70° extensional to transtensional regime during the Oligocene–Pliocene. It mainly produced post-sedimentary extensional faults and fractures and alkaline volcanism. We eventually discuss these deformation phases in relation with the Cretaceous Gondwana breakup and its related rifting events in West and North Africa, and with the subsequent Africa–Europe collision.

     

In situ recovery,an alternative to conventional methods of mining: Exploration,resource estimation,environmental issues,project evaluation and economics

This paper discusses the history and application of in situ recovery (ISR) to a wide variety of metals. The increasing application of ISR may provide an important method to address a key issue for the mining industry, namely the cost of production.ISR transfers a significant proportion of hydrometallurgical processing to mineralised bodies in the subsurface to directly obtain solutions of metals of interest. As a result, there is little surface disturbance and no tailings or waste rock are generated at ISR mines. However, for ISR to be successful, deposits need to be permeable (either naturally or artificially induced), and the metals of interest readily amenable to dissolution by leaching solutions in a reasonable period of time, with an acceptable consumption of leaching reagents.The paper discusses the following aspects of ISR:

• •History. ISR for uranium was introduced in 1959 in the USA, and subsequently applied in many countries over last 50 years, particularly in the USSR. The share of uranium mined by ISR reached 51% of world production in 2014, and the capacity of ISR mining of uranium is now comparable with that from conventional uranium mines.
• •Commodities. A review of the use of ISR for mining other commodities, namely copper, gold, nickel, scandium, rhenium, rare earth elements, yttrium, selenium, molybdenum, and vanadium. ISR for copper was introduced in the 1970s and there were several successful natural tests and mines. Scandium, rhenium, rare earth elements, yttrium, selenium, molybdenum, and vanadium were mined in pilot tests as by-products of uranium extraction. ISR of gold, copper, nickel, rare earth elements and scandium has been successfully developed over recent years. The paper discusses other commodities that have potential to be mined using ISR.
• •Applicability of ISR is addressed by a discussion of the features of mineralisation that need to be considered during different stages of ISR projects. Permeability,¹ hydrogeological conditions and selective leachability are the most critical parameters for ISR, and must be defined in the evaluation and exploration stages. Morphology and depth of mineralisation, thicknesses and grades, distribution of mineralisation, presence of aquicludes, and environmental conditions are also important factors for ISR projects.
• •Environmental issues. ISR allows the extraction of mineralisation with minimal disturbance to existing natural conditions. In contrast to underground and open pit mining, there are smaller volumes of mining and hydrometallurgical effluents that require management. Clearly contamination of groundwater by ISR reagents is the critical aspect requiring management during an ISR operation. Control of leaching in ISR operations and various ways of cleaning aquifers are discussed in the paper.
• •Economics. ISR operations deliver a range of benefits including lower CapEx costs for mine development, processing plant and infrastructure. ISR enables production to start at low capital cost and then a modular increase in production, as well as very flexible production capacity. The costs of ISR for different commodities (copper, gold, nickel, scandium, rhenium, rare earth elements, yttrium, selenium, molybdenum, vanadium) are discussed, with economic parameters for uranium production from ISR and conventional provided for comparison. The CapEx, OpEx and common cut-off grades for ISR for different commodities are discussed.
• •Exploration, resource estimation and the development of ISR projects require a number of different approaches compared to conventional mining projects. These criteria and the necessary methodology for resource estimation for ISR projects are described in the article.

     

Chemical modelling of kerogens

Models of kerogens belonging to the three classical Types have been represented at the following evolution stages:

• •-beginning of diagenesis (sensu-stricto),
• •-beginning of catagenesis,
• •-end of catagenesis.

Chemical models are drawn, using analytical data obtained on natural samples: elemental analysis, electron microscopy, ¹³C NMR, thermogravimetry, functional analysis and pyrolysis.In order both to get a statistical representation and make comparisons easier, the same molecular weight of about 25,000 has been chosen for the different models of kerogens at the beginning of the diagenesis stage.     

Ore mineralization related to geological evolution of the Karkonosze–Izera Massif (the Sudetes,Poland) — Towards a model

The Karkonosze–Izera Massif is a large tectonic unit located in the northern periphery of the Bohemian Massif. It includes the Variscan Karkonosze Granite (about 328–304 Ma) surrounded by the following four older units:

• -Izera–Kowary (the Early Paleozoic continental crust of the Saxothuringian Basin),
• -Ještĕd (the Middle Devonian to Lower Viséan sedimentary succession deposited on the NE passive margin of the Saxothuringian Terrane), out of the present study area,
• -Southern Karkonosze (metamorphosed sediments and volcanics filling the Saxothuringian Basin), out of the present study area,
• -Leszczyniec (Early Ordovician, obducted fragment of Saxothuringian Basin sea floor).

The authors present a genetic model of ore mineralization in the Karkonosze–Izera Massif, in which ore deposits and ore minerals occurrences are related to the successive episodes of the geological history of the Karkonosze–Izera Massif:

• -formation of the Saxothuringian Basin and its passive continental margin (about 500–490 Ma)
• -Variscan thermal events:
  • -regional metamorphism (360–340 Ma)
  • -Karkonosze Granite intrusion (328–304 Ma)
• -Late Cretaceous and Neogene-to-Recent hypergenic processes.

The oldest ore deposits and ore minerals occurrences of the Karkonosze–Izera Massif are represented by pyrite and magnetite deposits hosted in the Leszczyniec Unit as well as by magnetite deposit and, presumably, by a small part of tin mineralization hosted in the Izera–Kowary Unit. All these deposits and occurrences were subjected to the pre-Variscan regional metamorphism.Most of the Karkonosze–Izera Massif ore deposits and occurrences are related to the Karkonosze Granite intrusion. This group includes a spatially diversified assemblage of small ore deposits and ore mineral occurrences of: Fe, Cu, Sn, As, U, Co, Au, Ag, Pb, Ni, Bi, Zn, Sb, Se, S, Th, REE, Mo, W and Hg located within the granite and in granite-related pegmatites, in the close contact aureole of the granite and within the metamorphic envelope, at various distances from the granite. Assuming world standards, all these deposits are now uneconomic. Various age determinations indicated that ore formation connected with the Karkonosze Granite might have taken place mostly between about 326 and 270 Ma.The last ore-forming episode in the Karkonosze–Izera Massif is related to hypergenic processes, particularly important in the northern part of the massif, in the Izera–Kowary Unit where some uranium deposits and occurrences resulted from the infiltration of ore solutions that originated from the weathering of pre-existing accumulations of uranium minerals. A separate problem is the presence of oxidation zones of ore deposits and occurrences, both the fossil and the recent.A full list of ore minerals identified in described deposits and occurrences of the Karkonosze–Izera Massif together with relevant, key references is presented in the form of an appendix.     

Seismic patterns in Northern China and the characteristics of the epicentral distribution of the medium strong earthquakes before the large events

In this paper, the seismic pattern in Northern China from 30 ° to 42 ° N latitude and 104 ° to 125 ° E longitude, and the characteristics of the epicentral distribution before large events are presented. The results suggest that:

• 1.(1) the earthquakes in the region are mainly located in the orthogonal curvilinear network formed by the seismic belts;
• 2.(2) the larger earthquakes (M ⩾6) occurred mainly in the nodal regions of this grid:
• 3.(3) the strike of the fracture planes of the earthquakes coincided with the directions of the seismic belts;
• 4.(4) the pattern of medium strong earthquakes (M ⩾ 4.7) prior to thirteen large earthquakes (M⩾ 7) are analysed to be of three types:
  • 4.1.(a) mainly arranged along the two intersecting belts,
  • 4.2.(b) randomly distributed,
  • 4.3.(3) forming seismic gaps.

A theoretical basis and rules for drawing the orthogonal grid is presented, and an idea for the prediction of the sites of future earthquakes in Northern China is suggested.     

The Thakkhola–Mustang graben in Nepal and the late Cenozoic extension in the Higher Himalayas

The Thakkhola–Mustang graben is located at the northern side of the Dhaulagiri and Annapurna ranges in North Central Nepal. The structural pattern is mainly characterised by the N020–040° Thakkhola Fault system responsible for the development of the half-graben. A detailed study of the substrate and the sedimentary fill in several outcrops indicates polyphased faulting:-pre-sedimentation faulting (Miocene), with a mainly NNW–SSE to N–S compressional stress expressed in the substratum by N020–040° and N180–N010° sinistral and N130–140° dextral conjugate strike-slip faults;-syn-sedimentation faulting (Pliocene–Pleistocene), characterised by a W–E to WNW–ESE extensional stress and tectonic subsidence of the half-graben during the Tetang period (Pliocene probably), followed by a doming of the Tetang deposits and a short period of erosion (cf. Pliocene planation surface and unconformity between the Tetang and Thakkhola Formations); the Thakkhola period (Pleistocene) is characterized by a W–E to WNW–ESE extensional stress and a major subsidence of the half graben;-post-sedimentation recurrent extensional faulting and N–S and NE–SW normal faults in the late Quaternary terrace formations.Geodynamic interpretation of the faulting is discussed in relation to the following:

• 1.the geographic situation of the Thakkhola–Mustang half-graben in the southern part of Tibet and its setting in the Tethyan series above the South Tibetan Detachment System (STDS);
• 2.the geodynamic conditions of the convergence between India and Eurasia and the dextral east–west shearing between the High Himalayas and south Tibet;
• 3.the possible relations between the sinistral Thakkhola and the dextral Karakorum strike-slip faults in a N–S compressional stress regime during the Miocene.

     

Sedimentmikrobioiogie und ihre geologischen Aspekte

The influence of bacteria on recent sediments was first discussed in 1885, whenFischer andGazert were discussing the cycle of substances in the sea as well as in sediments. The influence of bacteria on the cycling of C, N, S, P in recent sediments and the open sea was soon accepted by marine geologists. Nevertheless, only very few experiments have, so far, shown more than qualitative and quantitative data collection in various restricted areas. This is due to the extensive and complicated chain of reactions on the surface of sediments and in the sediment itself. Biologists are asking for the amount of organic and inorganic matter which is reworked and released to the sea. Geologists usually emphasize the amount of substances which are sedimentated. For biologists the sediment is only part of their dominant ecosystem (the sea). While, for geologists the “sea” is only furnishing and influencing their first range system sediment. How much then, are bacteria involved in the slow process of conversion from a recent sediment to sedimentary rocks? Bacteria influence more or less strongly and to a more or less advanced degree of diagenesis:

1. The organic matter in sediments and the final form in which it is found.
2. The anions CO₃ ^2?, NO₃ ^?, OH-, SO₄ ^2?, PO₄ ^3? as well as their intermediate stages and the resulting minerals.
3. The cations H⁺, NH₄ ⁺, Ca²⁺, Fe²⁺, Fe³⁺, and a series of metals which are dissolved or precipitated by microbial activities as for example Fe, Mn, Cu, Ag, V, Co, Mo, Ni, U, Se, Zn.
4. The equilibrium of silicium. At least diatoms and radiolarians are precipitating silica, while other reactions which have been proved are not yet shown to influence marine sediments.
5. p_H-values and oxidation-reduction potentials of the sediment.
6. The composition of interstitial waters.
7. The surface activity of minerals, since bacteria are growing especially on particle surfaces.
8. The energy content and temperature of sediments.
9. The texture of fine grained sediments.
10. The fossilization of microfauna, macrofauna and trace fossils.

Sedimentology and mineralogy may also influence the bacterial activities and the composition of the microflora within sediments. Methods and problems of sediment microbiology are demonstrated by some investigations in the German Bay (North Sea) in connection with the first German Underwater Station (UWL). Ecological work proves to be difficult in various directions. The main cause of difficulties in microbiological work on sediments are the great variety of different factors influencing the environment (microbial, chemical, physical, mineralogical), the difficulty of taking representative samples, and the small amount of data which has been collected so far.     

Chondrules in the Murray CM2 meteorite and compositional differences between CM-CO and ordinary chondrite chondrules

Bulk compositions were determined by broad-beam electron microprobe analysis for thirteen of the least aqueously altered chondrules in Murray (CM2). These and literature data reveal compositional differences between CM-CO and ordinary chondrite (OC) chondrules:

• 1.(a) CO chondrules are richer in refractory lithophiles and poorer in Cr, Mn and volatile lithophiles than OC chondrules; much lower refractory lithophile abundances in CM chondrules resulted from aqueous alteration,
• 2.(b) in CM-CO chondrites, abundances of refractory lithophiles are higher in nonporphyritic than porphyritic chondrules, whereas in H-L-LL3 chondrites the converse is true,
• 3.(c) Cr ranges are greater and Cr and Mn correlate more strongly in chondrules in CM-CO than in H-L-LL3 chondrites.

We find evidence for two important lithophile precursor components of CM-CO chondrite chondrules:

• 1.(1) pyroxene- and refractory-rich, FeO-poor;
• 2.(2) olivine-rich, refractory and FeO-poor.

The occurrence of a few FeO-rich chondrules attests to a third component similar to matrix: olivine- and FeO-rich, refractories not characterized. The first two components differ from those inferred for OC chondrules, consistent with formation at different locations. The pyroxene- and refractory-rich, FeO-poor lithophile precursor component probably formed by an incomplete evaporation of presolar silicates that brought these materials into the enstatite stability field.     

Multivariate mixing and mass balance (M3) calculations,a new tool for decoding hydrogeochemical information

To support and help hydrochemical evaluation a multivariate mathematical tool named M3 (Multivariate Mixing and Mass balance calculations) has been created within the Äspö Hard Rock Laboratory Research Programme. The computer code can be used to trace the origin of the groundwater and calculate the mixing portions and mass balances from ambiguous groundwater data. Groundwater composition data used traditionally to describe the reactions taking place in the bedrock can now be used to trace the effect from present and past groundwater flow with increased accuracy. The M3 model consists of the following 3 steps:

• •Multivariate analysis, called Principal Component Analysis (PCA) is used to summarise the information from the data set. The summarised information shown in the PCA plots is used for finding relationships, patterns, extreme waters and for further M3 modelling.
• •From the PCA plot mixing calculations are used to calculate the effect of the groundwater mixing on the obtained groundwater composition. This so-called ideal mixing model is used to calculate the mixing proportions given in %, for all the groundwater samples.
• •The final step in M3 calculations is the mass balance calculations. Deviations from the ideal mixing model are used to trace the sources and sinks of elements, given in mg/l, which can be due to mass balance reactions.

The tested margin of error of the model is ±10% for the Äspö site data, but depends on the data to be modelled. A mixing portion of less than 10% is regarded as under the detection limit of the model and such calculations are therefore uncertain. This method can be used to trace the origin and calculate the mixing portions and effects from the reactions on the observed groundwater composition with a higher resolution and convenience compared to many standard methods.     

Compositions and textures of relic forsterite in carbonaceous and unequilibrated ordinary chondrites

Several percent of the olivine in the C2, C3 and unequilibrated ordinary chondrites (UOC) can be distinguished by blue cathodoluminescence (CL) and an unusual composition for forsterite. This olivine has the following textural features:

• 1.(1) forms cores in single olivine grains;
• 2.(2) shows subhedral to euhedral boundaries against rim olivine;
• 3.(3) rarely contains inclusions;
• 4.(4) has embayments containing olivine like that of the rim;
• 5.(5) occurs within chondrules especially in UOC meteorites.

The blue olivine is always Fe-poor (0.25 < FeO < 1.0%) and shows the following average and maximum values (%): Al₂O₃ (0.25, 0.5), TiO₂ (0.05, 0.09), CaO (0.5, 0.8), Cr₂O₃ (0.15, 0.5), and MnO (0.02, 0.15); vanadium is present. Within a single olivine and within all blue olivines Al, Ca and Ti are strongly positively correlated as are Mn, Fe, and Cr in olivine surrounding the blue. The blue cores are not zoned but each element shows a marked change at the boundary of the blue with Al showing the most rapid change. These are interpreted as diffusion profiles between rim and core olivine.Textures suggest initial free growth probably from a gas and later addition of olivine by liquid crystallization to form single crystals or chondrules. The unusual olivine composition indicates high temperature growth from a refractory-rich reservoir with Al entering olivine in tetrahedral coordination. Vapor growth is suggested as the process allowing the high minor element levels. The occurrence of blue olivine in all primitive meteorites indicates that it is relic material which was widespread prior to chondrule and hence meteorite formation. Similarities in composition exist between this relic olivine and olivine of cosmic dust and Deep Sea Particles pointing to this olivine being a common component in all primitive extraterrestrial material.     

Mineralogy and petrology of alkaline granophyric xenoliths from the Thorsmörk ignimbrite,southern Iceland

The Thorsmörk ignimbrite, southern Iceland, contains a suite of granophyre xenoliths displaying magmatic or high-temperature sub-solidus mineral assemblages. These granophyres are consanguineous with the erupting comenditic magma. Four types of mineral assemblages are distinguished:

• 1.(A) oligoclase, edenitic hornblende, salitic pyroxene, magnesian biotite, magnetite and sphene;
• 2.(B) oligoclase, manganoan to sodic ferro-augite, fayalite, richterite, ilmenite and magnetite;
• 3.(C) anorthoclase, ferrohedenbergite to aegirine hedenbergite, ilmenite, magnetite and (riebeckite);
• 4.(D) cryptoperthite, aegirine hedenbergite to (aegirine), aenigmatite, arfvedsonite, ilmenite and magnetite.

Geothermometry shows that the xenoliths have crystallized between 900°C and 500°C at moderate oxygen fugacities, just above the FMQ buffer. It is further demonstrated that a hot vapour phase heavily charged with sodium and halogens, played a major role in the late sub-solidus crystallization of the different types.     

Nature of particulate organic matter in the River Indus,Pakistan

Suspended sediments from the Indus River collected during 1981 through 1983 were analyzed for POC and its constituent fractions including amino acids, amino sugars and sugars. Percentage of POC decreased with increasing suspended matter concentrations, which suggested dilution of organic matter by mineral matter.The concentrations of amino acids, amino sugars and sugars varied, respectively, between 180 and 2000 μg/l, 5 and 125 μg/l, and 60 and 1100 μg/l. Their contributions to POC varied between 2 and 60% for amino acids and amino sugars, and between 2 and 15% for sugars. They were high during low sediment discharge (February to June), and low during high sediment discharge (August and September). Suspended sediments associated with high sediment discharge periods were characterized by low ratios of:

• 1.(i) aspartic acid:β-alanine
• 2.(ii) glutamic acid:γ-aminobutyric acid
• 3.(iii) amino acids:amino sugars
• 4.(iv) hexoses:pentoses. These and the relative distribution pattern of the monosaccharides such as galactose, arabinose, mannose and xylose indicated that, not only dilution, but also differences in the sources and processes affect the POC transport in the Indus River. These result in transport of biodegraded organic matter during high sediment discharge periods: this appears to be common to other major rivers of the region, with depositional centers in deep sea areas. These rivers, with their high sediment loads, could contribute up to 8 to 11% of the global annual organic carbon burial in marine sediments.

     

Aridification — Climate change in South-Eastern Europe

Climatic change in SE Europe can be characterized by the term aridification, which means increasing semi-aridity, manifested in an increase of mean annual temperature and at the same time in a decrease in the yearly precipitation.The paper deals with research results obtained within the framework of the MEDALUS II project (funded by the Commission of the European Communities). The project had the following objectives:

• 1.(i) Assessment of the impact of global change on the climate of the investigated area, including possible future climates.
• 2.(ii) Physical processes of aridification, including studies of groundwater level change, soil moisture profile dynamics, soil development, vegetation change and soil erosion.
• 3.(iii) Land use change, involving research on present land use and suggestions for the future.

Various methods were applied with respect to the different research objectives.

• 1.(i) Statistical analysis of climatic oscillations and computer runs of climatic scenarios,
• 2.(ii) Analysis of ground water data, mapping and analysis of soils and vegetation, assessment of present and future soil, and
• 3.(iii) Land capability assessment through ranking environmental conditions according to the demands of the most widely grown arable crops in Hungary.

According to our results i) the average annual warming during the last 110 years was +0.0105 °C, and precipitation decreased by 0.917 mm/year; ii) a decline of −2 to −4 m in the annual mean groundwater level can be detected in the most sensitive areas, with gradual lowering of the water table in alkali ponds; complete desiccation of some of them severs the direct contact between groundwater and salt-affected soils, the solonchak soil dynamics cease, helophile and hygrophile plant associations disappear, and consequent changes in the soil erosion regime are likely to lead to disastrous erosion in the future; iii) the climatic changes induce a transformation in land use from arable crops to plantations, starting with orchards.     

The crustal structure of the axis of the Great Valley,California, from seismic refraction measurements

In 1982 the U.S. Geological Survey collected six seismic refraction profiles in the Great Valley of California: three axial profiles with a maximum shot-to-receiver offset of 160 km, and three shorter profiles perpendicular to the valley axis. This paper presents the results of two-dimensional raytracing and synthetic seismogram modeling of the central axial profile. The crust of the central Great Valley is laterally heterogeneous along its axis, but generally consists of a sedimentary section overlying distinct upper, middle, and lower crustal units. The sedimentary rocks are 3–5 km thick along the profile, with velocities increasing with depth from 1.6 to 4.0 km/s. The basement (upper crust) consists of four units:

• 1.(1) a 1.0–1.5 km thick layer of velocity 5.4–5.8 km/s,
• 2.(2) a 3–4 km thick layer of velocity 6.0–6.3 km/s,
• 3.(3) a 1.5–3.0 km thick layer of velocity 6.5–6.6 km/s, and
• 4.(4) a laterally discontinuous, 1.5 km thick layer of velocity 6.8–7.0 km/s. The mid-crust lies at 11–14 km depth, is 5–8 km thick, and has a velocity of 6.6–6.7 km/s. On the northwest side of our profile the mid-crust is a low-velocity zone beneath the 6.8–7.0 km/s lid. The lower crust lies at 16–19 km depth, is 7–13 km thick, and has a velocity of 6.9–7.2 km/s. Crustal thickness increases from 26 to 29 km from NW to SE in the model.

Although an unequivocal determination of crustal composition is not possible from P-wave velocities alone, our model has several geological and tectonic implications. We interpret the upper 7 km of basement on the northwest side of the profile as an ophiolitic fragment, since its thickness and velocity structure are consistent with that of oceanic crust. This fragment, which is not present 10–15 km to the west of the refraction profile, is probably at least partially responsible for the Great Valley gravity and magnetic anomalies, whose peaks lie about 10 km east of our profile. The middle and lower crust are probably gabbroic and the product of magmatic or tectonic underplating, or both. The crustal structure of the Great Valley is dissimilar to that of the adjacent Diablo Range, suggesting the existence of a fault or suture zone throughout the crust between these provinces.     

Major and trace element compositions (including REE) of mineral,thermal, mine and surface waters in SW Germany and implications for water–rock interaction

The near-surface water cycle in a geologically complex area comprises very different sources including meteoric, metamorphic and magmatic ones. Fluids from these sources can react with sedimentary, magmatic and/or metamorphic rocks at various depths. The current study reports a large number of major, minor and trace element analyses of meteoric, mineral, thermal and mine waters from a geologically well-known and variable area of about 200 × 150 km in SW Germany. The geology of this area comprises a Variscan granitic and gneissic basement overlain in parts by Triassic and Jurassic shales, sandstones and limestones. In both the basement and the sedimentary rocks, hydrothermal mineralization occurs (including Pb, Cu, As, Zn, U, Co and many others) which were mined in former times. Mineral waters, thermal waters and meteoric waters flowing through abandoned mines (mine waters) are distributed throughout the area, although the mine waters concentrate in and around the Schwarzwald.The present analyses show, that the major element composition of a particular water is determined by the type of surrounding rock (e.g., crystalline or sedimentary rocks) and the depth from which the water originates. For waters from crystalline rocks it is the origin of the water that determines whether the sample is Na–Cl dominant (deeper origin) or Ca–HCO₃ dominant (shallow origin). In contrast, compositions of waters from sedimentary rocks are determined by the availability of easily soluble minerals like calcite (Ca–HCO₃ dominant), halite (Na–Cl dominant) or gypsum (Ca–SO₄ dominant). Major element data alone cannot, therefore, be used to trace the origin of a water. However, the combination of major element composition with trace element data can provide further information with respect to flow paths and fluid–rock interaction processes. Accordingly, trace element analyses showed, that:

• −Ce anomalies can be used as an indicator for the origin of a water. Whereas surface waters have negative or strongly negative Ce anomalies, waters originating from greater depths show no or only weak negative Ce anomalies.
• −Eu anomalies can be used to differentiate between host rocks. Waters from gneisses display positive Eu anomalies, whereas waters from granites have negative ones. Waters from sedimentary rocks do not display any Eu anomalies.
• −Rb and Cs can also be indicators for the rock with which the fluid interacted: Rb and Cs correlate positively in most waters with Rb/Cs ratios of ∼2, which suggests that these waters are in equilibrium with the clay minerals in the rocks. Rb/Cs ratios >5 indicate reaction of a water with existing clay minerals, whereas Rb/Cs ratios <2 are probably related to host rock alteration and clay mineral formation.

The chemical compositions of carbonate precipitates from thermal waters indicate that rare earth elements (REEs), Rb and Cs concentrations in the minerals are controlled by the incorporation of clay particles that adsorb these elements.