silicification and dolomitization of anhydrite nodules in argillaceous terrestrial deposits an example of meteoric dominated diagenesis from the triassic of central spain cauliflower shaped nodules are widespread in a single red mudstone bed in the buntsandstein triassic facies of the iberian range they consist mostly of quartz dolomite and calcite but other minerals such as barite kaolinite and iron oxyhydroxides are also present the nodules are spherical ovoid or elongate in shape and range from 1 to 8 cm across the surface of the nodules is irregular and some show a pedogenic coating of microspar the sedimentological and petrographic data suggest that the initial anhydrite nodules formed through a progressive increase in the porewater concentration of ca2 and so4 2 in a vadose environment occasionally under the influence of pedogenic processes partial replacement of the anhydrite by megaquartz occurred under more dilute conditions in the same type of setting as indicated by the presence of organic filaments on the quartz crystal surfaces in type a nodules the dissolution of the innermost anhydrite was complete and different types of quartz cement filled the porosity fracturing and meteoric cementation by calcite and minor amounts of kaolinite were the latest processes affecting these nodules in type b nodules the dissolution of the anhydrite was incomplete inhibiting quartz cementation and enabling later dolomitization of the anhydrite dolomitization appears to have been driven by sulphate reduction as indicated by the presence of bacterial bodies within the dolomite crystals dedolomitization and precipitation of barite kaolinite and calcite spar cements occurred later under the influence of meteoric solutions the nodules may mark the former locations of the water table and provide evidence for an episode of highly evaporitic conditions throughout wide areas of the basin their occurrence reveals not only a complex diagenetic history but is also indicative of palaeogeographic and palaeoclimatic conditions

microbially induced cementation to control sand response to undrained shear current methods to improve the engineering properties of sands are diverse with respect to methodology treatment uniformity cost environmental impact site accessibility requirements etc all of these methods have benefits and drawbacks and there continues to be a need to explore new possibilities of soil improvement particularly as suitable land for development becomes more scarce this paper presents the results of a study in which natural microbial biological processes were used to engineer a cemented soil matrix within initially loose collapsible sand microbially induced calcite precipitation micp was achieved using the microorganism bacillus pasteurii an aerobic bacterium pervasive in natural soil deposits the microbes were introduced to the sand specimens in a liquid growth medium amended with urea and a dissolved calcium source subsequent cementation treatments were passed through the specimen to increase the cementation level of the sand particle matrix the results of both micp and

rapid growth and strain rates inferred from synkinematic garnets penokean orogeny minnesota recent reinterpretations of the early proterozoic penokean orogeny in minnesota invoke a plate tectonic model with characteristics similar to phanerozoic collisional belts deformation during collision produced large flattening strains 89 and the development of a tectonic foliation and progressive metamorphism up to amphibolite facies as indicated by the presence of synkinematic s1 garnets biotite garnet thermometry and plagioclase garnet biotite muscovite barometry give southward increasing temperatures and pressures and indicate burial to depths of 21 25 km similar to medial and internal zones of collisional orogens worldwide gibbs method modeling on zoned synkinematic garnets indicates virtually no change in pressure p or temperature t during garnet growth growth and rotation of garnets at a point in p t space in an actively evolving deformational and thermal regime are surprising and suggest rapid garnet growth rates and high rates of strain during orogeny this is consistent with previous studies that indicate more rapid rates of tectonometamorphic processes in the precambrian relative to younger orogenic belts

tectonic denudation of the darwin metamorphic core complex in the andes of tierra del fuego southernmost chile implications for cordilleran orogenesis cordillera darwin in the southernmost chilean andes is a tectonically denuded metamorphic core complex similar to those widely developed in the north american cordillera detailed comparison can be drawn with the shuswap metamorphic core complex in british columbia and washington analysis of the geotectonic history of the darwin complex reinforces the view that the presence of tectonically thickened continental crust is critical for development of most if not all known core complexes and also suggests that inversion of a marginal basin during a compressional regime is one way of initiating such a crustal welt the cordillera darwin complex is unique in the andes and antarctandes this indicates that although low angle normal faulting occurs at high levels in convergent plate settings such as the central andes and the himalayas extensional denudation of deep crustal levels in active andean type orogens may require special tectonic circumstances uplift of the darwin complex began at about 70 ma in a localized extensional setting within the developing transform zone between the south american and antarctic plates this strike slip setting is analogous to some metamorphic core complexes in north america and possibly to a recently identified core complex in new zealand it is likely to be a common one for core complexes in convergent orogens

proterozoic metamorphism and cooling in the southern lake superior region north america and its bearing on crustal evolution abstract metamorphism along the southern margin of the archean superior province has been historically attributed to the penokean orogeny a narrow corridor of amphibolite facies rocks north of the main suture does record 1 83 1 80 ga metamorphic monazite u th pb ages that mark the culmination of arc accretion however subsequent widespread amphibolite facies metamorphism and associated magmatism is recorded along the regions of greatest penokean crustal thickening the tectonically buried archean proterozoic continental margin in minnesota new monazite geochronology reveals a profound midcrustal metamorphic imprint caused by emplacement of the 1 775 ga east central minnesota batholith at moderate depths in northern wisconsin and upper peninsula michigan metamorphic monazite growth at 1 78 1 745 ga and far from geon 17 intrusions reflect a previously little recognized regional amphibolite facies metamorphic event associated with ca 1 76 ga yavapai interval accretion not solely penokean induced crustal collapse south of the penokean suture penokean terrane rocks were twice metamorphosed to upper greenschist facies first during yavapai accretion and again during geon 16 mazatzal accretion geon 16 overprinting also affected a small part of the continental margin in the northeast orogen the peavy metamorphic node south directed basement thrusts there likely accommodated substantial mazatzal foreland shortening suggesting thick skinned deformation mazatzal amphibolite facies metamorphism occurred throughout iowa and southernmost wisconsin south of the baraboo quartzite 40 ar 39 ar mineral cooling ages from eastern wisconsin reveal a limited metamorphic aureole associated with the intrusion of the 1 47 ga wolf river batholith in part reflecting its rapid emplacement at shallow crustal levels a local area of anomalously young 40 ar 39 ar mica ages away from known midcontinent rift exposures probably reflect shallow crustal level reheating during rifting not exhumation the pattern and degree of proterozoic metamorphism preserved across the northern interior of the north american midcontinent is highly variable and is a reflection of multiple accretionary and intrusive events between 1 87 and 1 47 ga collectively the geo and thermochronologic data reveal a progressive tectonic younging toward the south and overall waning of proterozoic metamorphism in this region these results demonstrate a changing tectonic environment from active margin to continental interior as laurentia grew southward and stabilized over a few hundred million years

geotechnical tests of sands following bioinduced calcite precipitation catalyzed by indigenous bacteria recentexperimentshaveshownthatexogenousbacteriacanbeintroducedintosoilforthepurposeofinducingcalciteprecipitation a series of tests are documented in this paper that demonstrate that natural indigenous bacteria can also be stimulated to induce calcite precip itation with measurable changes in geotechnical properties tests reported in this paper include a microcosm experiment with cone penetration testing and cyclic triaxial shear tests these experiments demonstrate that indigenous bacteria can induce significant quantities of calcite pre cipitation that calcite precipitation can result in measurable changes to geotechnical soil properties and that the cyclic resistance ratio can be increased substantially with moderate levels of calcite precipitation using indigenous bacteria to modify soil properties is a significant step in making biomodification of soils economically viable doi 10 1061 asce gt 1943 5606 0000781 2013 american society of civil engineers ce database subject headings biological processes soil liquefaction cement bacteria soil stabilization earthquake author keywords biological processes liquefaction cementation bacteria calcite stabilization earthquake soil improvement

biogeochemical processes and geotechnical applications progress opportunities and challenges consideration of soil as a living ecosystem offers the potential for innovative and sustainable solutions to geotechnical problems this is a new paradigm for many in geotechnical engineering realising the potential of this paradigm requires a multidisciplinary approach that embraces biology and geochemistry to develop techniques for beneficial ground modification this paper assesses the progress opportunities and challenges in this emerging field biomediated geochemical processes which consist of a geochemical reaction regulated by subsurface microbiology currently being explored include mineral precipitation gas generation biofilm formation and biopolymer generation for each of these processes subsurface microbial processes are employed to create an environment conducive to the desired geochemical reactions among the minerals organic matter pore fluids and gases that constitute soil geotechnical applications currently being explored include cementation of sands to enhance bearing capacity and liquefaction resistance sequestration of carbon soil erosion control groundwater flow control and remediation of soil and groundwater impacted by metals and radionuclides challenges in biomediated ground modification include upscaling processes from the laboratory to the field in situ monitoring of reactions reaction products and properties developing integrated biogeochemical and geotechnical models management of treatment by products establishing the durability and longevity reversibility of the process and education of engineers and researchers

development of pervious concrete pile ground improvement alternative and behavior under vertical loading permeable granular columns are used to increase the time rate of consolidation reduce liquefaction potential improve bearing capacity and reduce settlement however their behavior depends on the confinement provided by surrounding soil which limits their use in very soft clays and silts and organic and peat soils this research effort aims to develop a new ground improvement method using pervious concrete piles pervious concrete piles provide higher stiffness and strength that are independent of surrounding soil confinement while offering permeability comparable to granular columns this proposed ground improvement method can improve the performance of different structures supported on poor soils to achieve the goal of the research project four vertical load tests were performed on one granular column and three pervious concrete piles in this paper the material properties of pervious concrete the developed installation method and the vertical load response of pervious concrete and aggregate piles are presented and the variation of soil stresses and displacement during pile installation are briefly discussed the experimental test results show that the ultimate load capacity of the pervious concrete pile was 4 4 times greater than that of an identical granular column in addition the ultimate load capacity of a pervious concrete pile installed using the developed technique was 2 6 times greater than a precast pervious concrete pile the used installation method created nonuniform lateral soil displacement and increased vertical and horizontal soil stresses

evolution of lithospheric strength after thrusting modeling of an eroding thrust belt indicates that immediately after thrusting the lithosphere is about twice as strong as unthickened cratonic lithosphere but after 10 to 20 m y it becomes weaker than cratonic lithosphere reaching a minimum of 40 to 70 of cratonic strength 30 to 100 m y after thrusting this may explain why rifting of thrust belts commonly occurs several tens of million years after thrusting ceases relative weakening results from 1 elevation of the geotherm caused by burial of radioisotope enriched surface rocks and 2 replacement of strong mantle rocks by weak crustal rocks in the lithospheric column low denudation rates enhance weakening by allowing radioisotope enriched rocks to remain buried longer our modeling indicates that 1 magmatism after thrusting is favored by high concentrations of heat producing elements in the lower plate and by slow denudation rates and 2 factors that affect denudation rate such as climate and the development of external drainage can significantly influence evolution of a thrust belt

the goodman swell a lithospheric flexure caused by crustal loading along the midcontinent rift system rb sr biotite ages of archean and early to middle proterozoic crystalline rocks in northern wisconsin and adjacent upper peninsula of michigan describe a regionally systematic pattern related to differential uplift an age low occurs in northern wisconsin where values range from 1070 1172 ma for rocks with crystallization ages of 1760 to 1865 ma these values overlap with the main episode of mafic igneous activity 1090 to 1120 ma along the midcontinent rift system mrs we interpret these low biotite ages as registering closure due to cooling below the 300 c isotherm as a consequence of uplift and rapid erosion of an area that we are informally naming the goodman swell the position of the goodman swell is independent of the archean and early proterozoic regional geologic framework but closely linked with the curvilinear concave to the south mrs we interpret the swell to be a forebulge imposed on an elastic crust by loading of mafic igneous rocks along and within the axis of the mrs the southward concavity of load axes resulted in flexural interaction that localized the swell because of rapid uplift the swell may have been a source area for clastic sediments in the rift sequence

40ar 39ar ages for minerals from the amphibolite dynamothermal aureole mont albert gaspe quebec new 40ar 39ar ages are presented for two hornblendes and one biotite from the dynamothermal aureole that is situated at the base of the mont albeit ophiolite analysis by the incremental release technique reveals a small component of excess 40ar in one hornblende though both exhibit plateau type spectra the biotite was analyzed by the total fusion technique all apparent ages are concordant and average 456 3 ma dynamothermal aureoles form during the obduction process which juxtaposes ophiolites and amphibolite protoliths during a compressional tectonic event at a plate margin in this instance thrusting of the mont albert ophiolite over rocks of the shickshock group the concordance of biotite and hornblende ages indicates rapid postmetamorphic cooling and firmly dates obduction at 456 3 ma ago an age younger than any of the other northern appalachian ophiolites the high pressure metamorphism of the amphibolite is inconsistent with the present high structural level of the composite mont albert

petrology and geochemistry of diagenetically altered tuffaceous rocks from the middle triassic of central spain abstract petrographical and geochemical analysis of altered tuffaceous rocks of the middle triassic from the iberian range in central spain shows that pedogenic processes and subsequent diagenesis have strongly modified the original mineralogy and textures these rocks are related to a magmatic episode that occurred at the buntsandstein muschelkalk unconformity in this region during the evolution of the iberian trough the tuffaceous rocks accumulated in saline ponds in an open and terminal flood plain setting their alteration is typified by neoformation of k feldspar and illite precipitation of chert and carbonate cements and replacements were also important processes resulting in intercalated chert beds and nodules much of the silica appears to be derived from extensive devitrification and weathering of glassy volcanic ash x ray diffraction analysis microscopic observations and edx microanalysis reveal that the chert consists of various types of chalcedony tridymite micro and megaquartz illite k feldspar and small amounts of albite in some of the nodules dolomite ankerite is also common enclosing anhydrite and barite relicts which are partially silicified different levels of ammonium enrichment have been found in each petrofacies type tuffs and tuffaceous rocks contain from 27 to 326 ppm mean 139 of nh4 underlying arkosic sandstones with authigenic k feldspar contain nh4 ranging from 48 ppm to 191 ppm mean 124 the nh4 was probably derived from decay of organic matter in the evaporitic environment of deposition and its incorporation into feldspar and illite as they formed from unstable volcanic glass sanidine plagioclase and vitric volcanic fragments this transformation could have occurred via the intermediate phases of smectite and zeolites the tuffaceous rocks also have a high content of b ranging from 61 ppm to 170 ppm mean 101 however high levels of b are not positively correlated with high levels of nh4 in the samples both b and nh4 can be contained in either k feldspar or illite but it is not possible to know how much is present in each mineral without separating the minerals comparison of spidergrams of the tuffaceous rocks with those in the underlying arkosic sandstones indicates similar patterns with positive anomalies in la sm and y and negative in nb p ti and yb although the tuffaceous rocks are slightly richer in total ree these data suggest that the distribution of ree must also be controlled by weathering and diagenetic reactions and cannot be used for discrimination between volcanic and nonvolcanic sandstones

on the origin of early proterozoic gneiss domes and metamorphic nodes northern michigan biotite 40 r 39 r cooling ages from medium pressure 500 600 mpa rocks in the watersmeet district northern michigan suggest significant cooling uplift and concomitant deformation during gneiss dome formation at 1755 ma well after the close of the 1870 1830 ma penokean orogeny however an 1822 ma hornblende plateau date indicates that the isograds surrounding the dome are penokean in age we attribute gneiss dome formation and doming of penokean aged isograds to an episode of orogenic collapse superimposed on an earlier history of crustal shortening this contrasts with the compressional origin for gneiss domes preserved in the low pressure 200 300 mpa republic district the different origins may reflect the fact that collapse was localized along the overthickened region of the orogenic belt in contrast to the watersmeet area hornblende and biotite 40ar 39ar ages obtained from the republic area are 1720 1680 ma given the relatively shallow depth of this region it is unlikely that temperatures re

unusual sedimentary geodes filled by gold bearing hematite laths unusual mineralized and silicified carbonate rich geodes were found hosted in lower triassic red mudstones in central spain from their borders to their centres the geodes display a a millimetric carbonate crust b a quartz rim c massive dolomite d gold bearing iron rich infills hematite laths and goethite with up to 7000 ppm of gold and e calcite cements that sometimes seal the central hollow textural evidence indicates that the geodes were originally anhydrite which was subsequently replaced by quartz and dolomite the resultant porosity from this replacement or by later dissolution has been filled by epithermal gold bearing iron oxide hydroxides romanechite and calcite 13c values indicate the participation of meteoric waters in an environment which was characterized by both a sub desert climate and a temperate tropical climate oxygen signatures reflect very variable temperatures for all minerals with the exception of calcite which appears to have precipitated at 38 c iron oxide temperature values can reach up to 85 c epithermal stage the mineralogical assemblages of these unusual geodes denote early diagenetic replacement followed by the epithermal activity this mineralization is linked to the late hercynian calc alkaline volcanism of central spain the hiendelaencina mining district

an assessment of isotopic equilibrium in goethites from a bog iron deposit and a lateritic regolith abstract hydrogen and oxygen isotope ratios have been measured in goethites from a lateritic regolith in the eastern amazon basin of brazil and a young bog iron deposit in new jersey usa the presence of exchangeable hydrogen and admixed minerals required the use of material balance calculations to determine relevant d and 18o values for the brazilian goethite d is 121 and 18o of 1 2 adjusted for al content these values yield a calculated temperature of formation of 24 3 c which is in good agreement with the modern average annual temperature in that locale goethite from the new jersey bog has a d of 134 and 18o of 0 9 its calculated temperature of formation 23 3 c resembles summer temperatures in southeastern new jersey bacterially mediated rates of precipitation of ferric hydroxide appear to be higher in the bog during the summer months crerar et al 1979 thus the temperature calculated for the new jersey goethite could indicate that the conversion of ferric hydroxide to goethite also occurs predominantly in the summer 13c values of the fe co3 oh component in goethite 21 7 for brazil and 19 3 for new jersey reflect the 13c values of the associated organic carbon 28 4 for brazil and 26 3 for the new jersey values of pco2 in the regolith 0 063 bar and bog 0 039 bar were calculated from the measured abundances of the fe co3 oh component the values of 13c and pco2 obtained from the goethites suggest that the ambient co2 in these systems originated primarily from oxidized organic matter in the low ph high pco2 waters characteristic of bogs and laterites isotopic equilibrium may be closely approached during the formation of goethite from ferric hydroxide ferrihydrite even if the initial precipitation of the ferric hydroxide precursor is bacterially mediated therefore meaningful paleotemperatures might commonly be calculated from stable isotope ratios of nonexchangeable oxygen and hydrogen in geothites from such environments

postcollisional cooling of the penokean orogen in east central minnesota new 40ar 39ar thermochronologic data from the internal zone of the penokean orogen in east central minnesota indicate rapid cooling from mid crustal temperatures early proterozoic metamorphosed cover rocks yield concordant hornblende and biotite plateau ages of 1755 ma underlying archean basement gneiss yields concordant muscovite and biotite plateau ages of 1705 ma these are some of the oldest cooling ages recorded in rocks buried during the 1830 1860 ma penokean collisional orogeny cooling was coeval with regional rhyolitic volcanism and granite emplacement suggesting a period of tectonic activity in this region during mid to late 1700 ma based on similarities with phanerozoic extensional regimes we suggest preliminarily that these data might be explained by a previously unrecognized major extensional episode in the lake superior region

the obliquely convergent plate boundary in the south island of new zealand implications for ancient collision zones abstract the alpine fault of new zealand forms the western boundary of a zone of distributed deformation formed by the oblique convergence of continental crust belonging to the pacific and australian plates structural and geodetic data from the alpine fault show that a large proportion of the total plate displacement is accommodated by rapid oblique slip on the fault the remaining displacement is distributed over a 200 km wide zone to the east the collision may be modelled as a two sided deforming orogen with the partitioning of deformation being controlled by erosional differences between the narrow high strain inboard and broad low strain outboard sides in ancient collision zones little evidence may remain of the nature and amount of displacement on the inboard side partitioning of deformation among pre existing structures complicates interpretation of the outboard zone radiometric ages may post date collision by several tens of millions of years and indicate slow isostatic uplift and unroofing collision ages if preserved may be recognized by high uplift rates calculated from muscovite biotite pairs

thermal history of low metamorphic grade paleoproterozoic sedimentary rocks of the penokean orogen lake superior region evidence for a widespread 1786 ma overprint based on xenotime geochronology abstract paleoproterozoic strata in northern michigan wisconsin and minnesota were deposited between 2 3 and 1 75 ga within the rifted margin and subsequent foreland basin of the penokean orogen these strata show evidence for multiple regional metamorphic events previously attributed entirely to the penokean orogeny 1875 1835 ma metasandstones from the marquette range supergroup and the animikie mille lacs and north range groups were sampled at multiple localities across minnesota wisconsin and michigan for metamorphic xenotime suitable for in situ shrimp u pb geochronology all samples are from the northern penokean foreland basin where the metamorphic grade is greenschist to sub greenschist and the strata are virtually undeformed xenotime u pb ages in these samples have a bimodal population with means of 1786 4 ma n 32 and 1861 10 ma n 9 xenotime of both ages are contained in metasandstones from the basal chocolay group in michigan and wisconsin and the mille lacs group and north range groups in minnesota the older age records a regional low temperature thermal event that is slightly older than the overlying menominee group in michigan and the animikie group in minnesota and ontario this 1861 ma event coincides with regional uplift that led to the formation of the unconformity between the menominee group and the overlying baraga group in michigan hence xenotime growth must have occurred at shallow burial depths younger units from the menominee and baraga groups in michigan and the animikie group in minnesota record only the 1786 ma event a dominant 1800 1790 ma metamorphic monazite population that overprints penokean interval monazite has been documented within amphibolite to granulite facies rocks immediately north of the niagara fault zone within the vicinity of gneiss domes and granitic plutons in contrast the 1786 ma xenotime ages are from low grade virtually undeformed rocks 50 150 km from the high grade zones and thus do not appear to reflect a local thermal imprint rather the geographic extent of the 1786 ma xenotime growth event suggests that it reflects a basin wide subtle thermal pulse it is proposed that the xenotime ages record widespread subtle heating triggered by renewed subduction along the orogen due to yavapai interval convergence the 1800 1700 ma yavapai terrane forms an accretionary belt throughout the central and southwestern u s and truncates the southern part of the penokean orogen in central wisconsin and southeastern minnesota about 200 km south of the sample sites alternatively an 1800 1765 ma interval of gravitational collapse of overthickened crust of the penokean orogen immediately north of the niagara fault zone may have driven a northward flow of hydrothermal fluids which subtly but pervasively altered the northern parts of the penokean foreland and resulted in xenotime growth

oblique subduction footwall deformation and imbrication a model for the penokean orogeny in east central minnesota the penokean orogeny was a major early proterozoic 1875 1825 ma tectonic event in the great lakes region in east central minnesota it is marked by multiply deformed and highly metamorphosed supracrustal rocks of the early proterozoic denham and thomson formations structural features similar to those in the supracrustal rocks also exist in the basement archean 2700 ma mcgrath gneiss such features are here explained in a tectonic model consisting of southward directed oblique subduction along the great lakes tectonic zone intense deformation occurred in the footwall of the major thrust which marked the boundary between downgoing and overriding plates during a type continental subduction sedimentary rocks thomson formation deposited on the footwall during loading caused by thrusting eventually became incorporated into the deformation zone early formed structures related to footwall deformation are a dominantly well developed foliation in the gneiss and isoclinal recumbent folds with a bedding subparallel foliation in the denham and lower thomson formations progressive metamorphism during subduction reached the garnet zone of the amphibolite facies various deformation inversions show that this early phase of deformation involved extreme flattening with z vertical and large amounts of extension in both the north south and east west directions footwall deformation was followed by imbrication and accretion onto the hanging wall during uplift associated with continued compression and isostatic rebound later formed structures associated with imbrication and deformation within the hanging wall consist of folding of the foliation and development of shear zones in the mcgrath gneiss and open to close upright to overturned folds in the denham and thomson formations the peak metamorphic event represented by staurolite occurred after the later deformation at temperatures of about 470 530 c and a minimum pressure of 3 4 kbar minimum depth of 12 4 km increasing temperature associated with decreasing pressure uplift is explained by conductive relaxation caused by crustal thickening and erosion this tectonic model may have more widespread implications for explaining similar structural features found in many precambrian terranes worldwide

experimental optimization of microbial induced carbonate precipitation for soil improvement abstractimplementation of laboratory tested biomediated soil improvement techniques in the field depends on upscaling the primary processes and controlling their rates microbial induced carbonate precipitation micp holds the potential for increasing the shear stiffness and reducing the hydraulic conductivity by harnessing a natural microbiological process that precipitates calcium carbonate the study presented herein focuses on controlling micp treatment of one dimensional flow half meter scale column experiments treatment was optimized by varying procedural parameters in five pairs of experiments including flow rates flow direction and formulations of biological and chemical amendments monitoring of column experiments included spatial and temporal measurements of the physical chemical and biological properties essential to the performance of micp including shear wave velocity permeability calcium carbonate content aqueous calcium aqueous ammonium aqueous urea and bacterial density rela

tectono stratigraphic evolution of the early proterozoic wisconsin magmatic terranes of the penokean orogen the early proterozoic penokean orogen developed along the southern margin of the archean superior craton the orogen consists of a northern deformed continental margin prism overlying an archean basement and a southern assemblage of oceanic arcs the wisconsin magmatic terranes the south dipping niagara fault suture zone separates the south facing continental margin from the accreted arc terranes the suture zone contains a dismembered ophiolite the wisconsin magmatic terranes consist of two terranes that are distinguished on the basis of lithology and structure the northern pembine wausau terrane contains a major succession of tholeiitic and calc alkaline volcanic rocks deposited in the interval 1860 1889 ma and a more restricted succession of calc alkaline volcanic rocks deposited about 1835 1845 ma granitoid rocks ranging in age from about 1870 to 1760 ma intrude the volcanic rocks the older succession was generated as island arcs and or closed back arc basins above the south dipping subducti

evolution of buntsandstein fluvial sedimentation in the northwest iberian ranges central spain abstract the buntsandstein sediments in central spain permian and triassic are mainly continental redbeds that form the base of a sequence that passes up into siliciclastic and carbonate tidal sediments the muschelkalk facies buntsandstein sedimentation began with conglomeratic and sandy fluvial facies whose detailed sedimentological analysis is the main subject of this work massive sheets are the most important conglomerate facies they were formed by deposition as longitudinal bars channel fill conglomerates are the second most important facies lateral accretion deposits also occur in the conglomerates they evolved from longitudinal bars because of decreasing flow or because the bars had reached a certain height sandstones are composed of eleven different facies large linguoid or transverse bars were the main bedforms in this environment these bedforms may be related downstream to large oblique troughs developed when the tabular bedform grew to a certain size or when a tabular bedform reached another one that acted as an obstacle compound and composite compound bars consisting of large sets of trough cross bedding with scoured wavy bases are al o recognized in the sandstone facies two major cycles occur in the complete conglomerate sequence which correspond to different physiographic models the lower cycle was mainly formed by channels and bars that were smaller than those in the upper cycle the upper cycle is more extensive than the lower one and has characteristics that indicate a higher stability paleocurrents for both cycles have a north northeasterly trend the vertical evolution of these sediments is clearly related to the different fault systems that controlled their distribution the paleogeography of the sandstone facies together with paleocurrents perpendicular to the conglomerate paleoccurents indicate deposition from a separate dispersal system that extensively overlies the previous one this unit which can be followed extensively over most of the iberian ranges and even outside the iberian ranges represents the growth of a fluvial braidplain over a large area of iberia during the lower triassic

silicification of evaporites in permian guadalupian back reef carbonates of the delaware basin west texas and new mexico abstract outcrops of the seven rivers yates and tansill formations contain widespread evaporites replaced by quartz and calcite the original evaporites consisted of discrete horizons scattered nodules enterolithic layers and individual crystals or crystal fragments of gypsum and or anhydrite within a finely crystalline dolomite matrix based on field and petrographic observations silicification of evaporites proceeded from the exterior to the interior of the nodules the earliest replacement was by euhedral black megaquartz that contains abundant fluid inclusions water and hydrocarbons and solid inclusions mainly anhydrite and dolomite the siliceous replacements were followed by precipitation of equant blocky calcite spar which filled pores left by latestage dissolution of evaporites the fluid inclusions in the replacive megaquartz are primary and many contain both hydrocarbons and water daughter minerals of halite gypsum or possibly antarcticite cacl2 6h2o are also found within the aqueous inclusions homogenization temperature data for hydrocarbon and aqueous fluid inclusions average 67 7 c and 67 1 c respectively hydrocarbonbearing and aqueous inclusions are thus interpreted to have formed simultaneously from the same fluids eutectic melting and final melting temperatures for aqueous inclusions indicate that the fluids were concentrated brines consisting of cacl2 and nacl oxygen isotope values for the megaquartz replacements averaged 28 4 smow indica ing precipitation from evaporative waters with an isotopic composition of 2 9 smow evaporite silicification was coeval with or slightly postdated hydrocarbon migration the fluid inclusion data provide a record of the fluid temperatures and compositions that prevailed during silica precipitation these data coupled with regional stratigraphy and published geothermal gradients suggest a burial depth of approximately 1 3 km during silicification the source of the silica for evaporite replacement is problematic we postulate however that silica may have been derived from dissolution of siliciclastics in back reef units organic acids that form from breakdown of hydrocarbons increase the solubility of quartz by bonding with silicic acid as these products and associated brines moved into cooler oxidizing zones the organic acids broke down releasing silica into solution this organically mobilized silica eventually precipitated as megaquartz replacements of preexisting evaporites

enhancing the axial compression response of pervious concrete ground improvement piles using biogrouting abstractthis paper presents an innovative grouted ground improvement pile alternative biogrouted pervious concrete pile biogrouting is a potential ground improvement technique that utilizes soil bacteria to induce calcium carbonate caco3 precipitation to cement soil particles the most commonly investigated biogrouting method is microbial induced carbonate precipitation micp previous large scale applications of micp have encountered practical difficulties including bioclogging which results in a limited zone of cemented soil around injection points and heterogeneous distribution of caco3 the research presented in this paper focuses on evaluating the feasibility of micp biogrouting of a limited soil zone surrounding permeable piles to improve their responses when subjected to axial compression loading to investigate this two instrumented pervious concrete piles with diameters of 76 mm and lengths of 1 07 m with and without micp biogrouting were subjected to compression loading at the soil struc

late cretaceous quartz geodes after anhydrite from burgos spain quartz geodes cauliflower like appear in a specific level of the late cretaceous north of burgos due to their anhydrite relicts and spherulitic quartz length slow chalcedony they are considered as pseudomorphs of anhydrite nodules formed during early diagenesis at the same level compact chert nodules sporadically appear presenting a considerable amount of sponge spicules with fibrous texture length fast chalcedony the silicification of the anhydrite nodules took place before total compaction and cementation of the sediment the source of silica is principally biogenic sponge spicules there is no link between the depositional environment and the existence in itself of anhydrite nodules indirectly it is possible to see the effects of an arid climate which have not been recorded in the lithologic column here described modified journal abstract

the chocolay group lake superior region u s a sedimentologic evidence for deposition in basinal and platform settings on an early proterozoic craton the early proterozoic chocolay group in the lake superior region is a cratonal sequence consisting of a basal unit overlain successively by quartzite dolomite and slate formations two regional depositional environments are described 1 present day structural troughs marquette menominee and felch michigan show evidence of having sedimentary basin precursors and 2 other areas gogebic range michigan show evidence of sedimentation in platform settings the basal unit in the marquette and menominee troughs is as much as 160 m thick and was probably deposited by alluvial processes in the gogebic range the basal unit is less than 10 m thick and resembles lag deposits at the base of transgressive sequences the overlying quartzite contains cross beds that show two regional sedimentary vector paleocurrent distributions 1 unimodal low variance distributions with sedimentary vectors oriented subparallel to local structural trough axes marquette menominee and felch troughs and 2 polymodal distributions with sedimentary vectors showing greater dispersion about the mean gogebic range as indicated by many varieties of sedimentary structures silicified evaporites cryptalgal structures intraclast breccias and so on the carbonates and interstratified siliciclastics of the chocolay group were deposited in subtidal to supratidal conditions taylor noted in 1972 that certain members of the chocolay group carbonates thicken toward the center of the marquette trough with concomitant facies changes the uppermost pelite unit of the chocolay group was probably deposited below normal wave base it is concluded that the basins and platforms were formed on a craton undergoing rift type tectonism

middle proterozoic uplift events in the dunbar dome of northeastern wisconsin usa isotopic ages of granitic and metamorphic rocks exposed in the dunbar structural dome of northeastern wisconsin identify a protracted series of tectonic and hydrothermal events that culminated in major regional uplift during middle proterozoic keweenawan ca 1 100 ma continental rifting and volcanism the major rock forming events and the structural development of the dome occurred during the interval 1 862 4 ma to 1 836 6 ma whole rock rb sr ages are partly reset in response to a widely recognized but cryptic event in wisconsin and michigan at about 1 630 ma the scale and systematic character of the whole rock resetting strongly suggests the presence of a fluid phase derived in situ from water dissolved in the silicates or externally from a subthrust plate of low grade metamorphic rocks the regional nature of the 1 630 ma disturbance possibly indicates that it is related to a major tectonic event such as an active plate margin far to the south rb sr biotite ages for the dunbar dome this study the southern complex of the marquette district van schmus and woolsey 1975 and the felch trough area aldrich and others 1965 provide a remarkably coherent pattern that reflects multiple episodes of differential uplift younger events superimposed on a regional 1 630 ma imprint are recorded at 1 330 ma and 1 140 ma the 1 330 ma disturbance could reflect stabilization following intrusion of the wolf river batholith at 1 485 ma the 1 140 ma uplift event occurred during keweenawan rifting and volcanism as a result of stresses imposed on a mosaic of fault bounded blocks with possible subcrustal influence the remarkably small variance in the 1 140 ma biotite age peak argues for rapid uplift and cooling and hence rapid erosion detritus from the uplift probably was being shed into nearby tectonic basins most of which did not survive subsequent uplift and erosion

evidence for nappe development during the early proterozoic penokean orogeny minnesota two major phases of early proterozoic penokean folding are now recognized in the thomson formation of east central minnesota effects of the first deformation are found only in the southern two thirds of the exposed thomson formation the second deformation affected the entire region of outcrop several lines of evidence indicate that northward directed nappes developed during the early phase of folding this evidence includes lithologic differences between the areas of one and two deformations the pervasive nature of an s 1 foliation in the area of its occurrence facing directions of f 2 folds and the refraction pattern of the s 1 foliation in graded metagraywacke slate beds taken together the data show that an area of several hundred square kilometres is on the upper limb or limbs of a large northward directed recumbent fold or folds nappes of the early phase of penokean deformation

the role of mixing zone dolomitization in sandstone cementation evidence from the triassic buntsandstein the iberian range spain abstract petrographic and geochemical data suggest that dolomite cement in shallow marine sandstones of the triassic buntsandstein in the ateca horst of the iberian range spain has precipitated in the zone of mixing between phreatic meteoric and marine waters dolomite or rhombohedric crystals consisting of concentric bands of alternating syntaxial dolomite and calcite have filled isolated voids 350 12 mm in diameter subsequently limpid dolomite followed by sparry calcite precipitated in void center as the latest cements the carbonates have low 13 c pdb 9 5 to 6 0 and 18 o pdb 8 1 to 3 2 values and are enriched in radiogenic strontium 87 sr 86 sr 0 710112 to 0 720293 indicating a dominantly meteoric component in the porewaters the overall sequence of carbonate cementation suggests precipitation from porewaters that evolved in the mixing zone with successively increased meteoric influence and finally to fully meteoric probably due to a major sea level fall

tectonic systems tract and depositional architecture of the western border of the triassic iberian trough central spain abstract during the permian and triassic a sedimentary wedge developed overlying a listric normal fault on the western border of the iberian trough central spain an area was selected for study that provides optimal conditions for a detailed analysis to be made of relationships between geometric strata arrangements tectonic control and sedimentary responses the excellent quality of the outcrops allows the observed patterns of strata to be related to fault growth and developmental of the basin the recognition and mapping of local discontinuities throughout the study area were possible packages of similar strata with different angularity can be discerned between the two main discontinuities geometrical relationships can be established for depositional unit boundaries the architectural style and sediment dispersal patterns interpreted as the results of interactions between sedimentation and tectonics are integrated into a three dimensional tectono sedimentary facies model to explain the basin s infilling is interpreted to be tectonic the rift related three dimensionally linked depositional systems recognized might be defined as tectonic systems tract prosser s 1993 rift related linked depositional systems and their seismic expression in williams g d dobb a eds tectonics and seismic sequence stratigraphy geol soc london spec publ 71 35 66 five such tracts are recognized and related to specific phases of tectonic development

biocalcification of sand through ureolysis biological processes may provide great and previously unexplored opportunities for cost effective in situ improvement of the engineering properties of soil a laboratory study was conducted to evaluate the changes in geomechanical properties of sand attributable to the formation of calcium precipitates induced through ureolysis catalyzed by sporosarcina pasteurii s pasteurii specifically direct shear and california bearing ratio cbr tests were conducted on sand specimens subjected to treatment by growing resting and dead s pasteurii cells in completely stirred tank reactors and completely mixed biofilm reactors respectively scanning electron microscopy analyses were also conducted to evaluate microbially induced precipitation the results of the study show that the bacterial cells effectively improved the geomechanical properties of the sand growing cells improved the sand properties owing to microbially induced precipitation and related pore volume changes whereas dead and resting cells ge

bio grouting to enhance axial pull out response of pervious concrete ground improvement piles bio grouting is an environmentallly friendly sustainable and low cost ground improvement technique which mainly utilizes microbial induced carbonate precipitation previous large scale applications of micp have encountered practical difficulties including bio clogging which resulted in a limited zone of cemented soil around injection points the research presented in this paper focuses on evaluating the feasibility of cementing a limited soil zone surrounding permeable piles using micp bio grouting to improve the mechanical response of permeable piles under axial pull out loading two instrumented pervious concrete piles test units one with and one without micp bio grouting were subjected to pull out loading at the soil structure interaction facility at lehigh university the pervious concrete pile served as an injection point during the micp bio grouting the mechanical responses of the test units and surrounding soil were analyzed along with shear wave s wave velocities moisture and caco3 c

quartz geodes early diagenetic silicified anhydrite nodules related to dolomitization abstract quartz geodes interpreted to be silicified anhydrite nodules are common in the mississippian ramp creek formation and harrodsburg limestone sanders group of southern indiana the abundance of a stenohaline fauna in the sanders group and the absence of sedimentologic features indicative of supratidal or hypersaline conditions such as stromatolites desiccation crocks and birdseye vugs suggest a subtidal normal marine depositional environment geodes in the ramp creek and harrodsburg formations as well as other geode bearing strata are almost invariably associated with dolomite seepage reflux of magnesium rich brines produced during the deposition of the lower st louis limestone is a likely mechanism for dolomitization of the sanders group replacement of calcite an aragonite by dolomite in hypersaline pore water may have increased the activity of calcium so that supersaturation with respect to anhydrite or possibly gypsum was reached and nodules formed in the still unlithified sediments

biogrouting coarse materials using soil lift treatment strategy this paper investigates the feasibility of using a soil lift biogrouting treatment strategy to improve the mechanical properties of coarse sand with the view of applying it to stone columns sand piles and rammed earth columns type of applications a two phase percolation approach was adopted in this study that included percolating a bacterial suspension sporosarcina pasteurii in the first phase and a cementation solution in the second phase this process was repeated every two treatments the study reveals that an increase in the number of soil lifts negatively influenced the mechanical properties of the biocemented coarse sand however the minimum strength and stiffness achieved 2 8 mpa in this study was sufficient to mitigate slumping of a soil column that may occur during installation or excessive radial expansion furthermore it is shown that a single lift treatment can lead to a very high increase in strength and stiffness up to 8 9 mpa and 2 3 gpa respectively however calcite distribution

geochemistry and evolution of the early proterozoic post penokean rhyolites granites and related rocks of south central wisconsin u s a

evidence for east west crustal extension in the eastern alps implications for the unroofing history of the tauern window the contact between the western border of the tauern window and the overlying austroalpine nappes austria and italy is marked by a structural petrologic and geochronologic discontinuity that developed in the early stages of unroofing of the window within the window pressure temperature time paths j selverstone 1985 indicate that significant ductile thinning occurred shortly after the cessation of thrusting paleocene eocene sense of shear indicators rotated porphyroblasts asymmetric augen and pressure shadows s c fabrics associated with a west plunging stretching lineation indicate that this thinning occurred in response to top to the west low angle normal shear during metamorphism the same sense of normal shear is present in the mesozoic members of the austroalpine sequence west of the window in these rocks however west directed shear occurred at low temperatures 300 c after the thermal peak of metamorphism structural data and the regional geometry imply that the western end of the tauern window is a low angle normal fault brenner line that juxtaposed brittlely deformed rocks of the austroalpine nappes against more ductilely deformed rocks from the window biotite k ar and rb sr data suggest a miocene age for final movement on the brenner line these data indicate a prolonged history of east west extension in the eastern alps that affected all crustal levels early ductile thinning of lower crust followed by mid to upper crustal low angle normal faulting a model is presented that relates the young east west extension to displacement transfer from dextral movement on the periadriatic lineament in this model the brenner line and by analogy the simplon line can be thought of as detachment faults that tectonically unroofed the tauern window and lepontine thermal highs respectively

uplift patterns and orogenic evolution in the scottish dalradian rb sr and k ar mineral ages from the dalradian rocks of angus and perthshire indicate considerable diachronism of cooling following the caledonian regional metamorphism the oldest mineral ages 515 ma are similar to the independent estimates of peak metamorphic age and hence indicate very rapid cooling they occur in the highest grade samples of the angus region and are associated with localized uplift regional rapid uplift events at 460 440 ma and 410 390 ma may also be recognized and correlated with structural and igneous activity and metamorphic age dates within the scottish highlands thermal models show the importance of localized and discontinuous uplift in determining both the timing of metamorphism and the shape of the p t paths they suggest that the major diachronous metamorphism and granite production in the scottish highlands is depth controlled rather than representing major lateral diachronism of thickening or heat sources localized uplift may exercise considerable control on mineral facies variation within orogenic belts the local uplift in angus introduces hot high pressure tarfside nappe rocks into higher level tay nappe rocks thus the uniform block uplift models frequently used in the interpretation of metamorphic and structural phenomena in orogenic belts are an oversimplification of the real events

evolving fluvial architecture during a marine transgression upper buntsandstein triassic central spain abstract the sedimentation in central spain during the late anisian middle triassic limos y areniscas de rillo formation recorded the evolution from an alluvial environment into a coastal one with a diversity of environments this evolution was the result of one of the episodes of the tethys sea transgression over iberia during the first and second stages of this evolution mixed load low sinuosity channels evolved upwards into a distal braidplain with ephemeral run off and poorly defined channels during a third stage the characteristics of the sediments indicate the existence of both continental and marine waters in a transitional zone with seasonal hydrological fluctuations the fourth stage records the sedimentation in an upper intertidal to supratidal environment in a semiarid coastline with the presence of thin cryptalgal sheets and chicken wire textures the final evolution consists of an environment with a high percentage of fluvial channel deposits probably related to a meandering pattern this evolution has been correlated with the depositional sequences established for the ne of spain where the anisian transgressive event resulted in the formation of an inter to supratidal carbonate ramp so lowstand transgressive and highstand system tracts from depositional sequence 1 have been recognized in the centre of spain

detachment faulting and late paleozoic epithermal ag base metal mineralization in the spanish central system hydrothermal activity during late hercynian time resulted in epithermal silver base metal pb zn cu vein formation in the eastern part of the spanish central system during the hercynian orogeny the central iberian crust was thickened by compressional tectonics heated weakened and subsequently overthickened by massive late hercynian granitic intrusions subsequently the central iberian crustal welt underwent extensional collapse through lithosphere scale low angle detachment faulting the detachment systems evolved through tectonic denudation isostatic rebound and upward arching to define an extensional province much like the u s basin and range andesitic volcanism and hydrothermal activity occurred during extension inducing epithermal type hydrothermal convecting systems that leached transported and precipitated silver and base metals along fractures crosscutting the hiendelaencina metamorphic core complex

pb and nd isotope and trace element constraints on the origin of basic rocks in an early proterozoic igneous complex minnesota abstract a suite of early proterozoic basic to granitic rocks exposed near st cloud minnesota are cut by northeast trending basaltic dikes pb isotope data for all of these rocks overlap and plot about an 1800 ma pb pb correlation line the basic rocks which are light ree enriched have nd values between 0 4 and 4 8 petrogenetic considerations suggest that the basic rocks were derived from a light ree enriched source which had an fe mg ratio greater than that for pyrolite the enrichment in fe mg is probably a result of the addition of basic melts to the source the light ree enrichment may have a mantle origin by the addition of mantle derived light ree enriched basic melts or fluids or a sedimentary origin by the addition of light ree enriched fluids or melts derived from subducted sediments with an early proterozoic provenance in either case the nd isotopes suggest that the light ree enriched component existed since c 2300 ma the igneous complex may have formed at a convergent margin an anorthositic gabbro near mora has an nd of 5 indicating that it was derived from a mantle source with a history of light ree depletion this gabbro may have been part of an early proterozoic ocean crust

mechanical behavior of sands treated by microbially induced carbonate precipitation abstractthe mechanical behavior of sands treated using microbially induced carbonate precipitation micp has been investigated at the macroscale and the microscale triaxial and confined compression tests with embedded shear and compression wave s wave and p wave sensors were conducted on two micp treated sands ottawa 50 70 and 20 30 silica sands triaxial compression tests were conducted at three different confining pressures 25 50 and 100 kpa tests were also performed at calcium chloride cacl2 concentrations of 0 1 and 0 3 m resulting in specimens with average calcium carbonate caco3 content ranging from 1 5 to 2 5 for the 50 70 sand and from 1 to 1 6 for the 20 30 sand in contrast to previous research the results of triaxial tests presented in this paper show an increase of the soil strength even at 1 calcium carbonate content after the tests samples taken from the specimens were utilized to measure the caco3 content and to perform analysis using scanning electron microscopy sem

mathematical characterization of pile soil interface boundary for consolidation analysis of soil around permeable pipe pile permeable pipe pile is proposed to accelerate the dissipation of excess pore water pressure through drainage holes around the pile circumference into the pile s cavity this investigation generaliz

the hiendelaencina epithermal silver base metal district central spain tectonic and mineralizing processes the northeastern sector of the spanish central system hosts important stephanian permian silver base metal epithermal mineralizations defining the so called hiendelaencina district the overall geotectonic evolution of this region indicates a major late variscan extensional period involving the unroofing of dome shaped metamorphic core complexes which ultimately led to the radial brittle disruption of these bodies allowing the ascent of andesitic magmas and high level hydrothermal activity the deposits are hosted by high grade metaphorphic rocks belonging to these complexes mineralogical and fluid inclusion studies reveal that the mineralizations were formed during two to four hydrothermal stages these are the result of complex interactions between fluids of contrasted temperatures and salinities data on sulphur isotopes suggest that two sources of sulphur existed magmatic andesitic derived with 34s 6 and metasediment derived with initial 34s probably 25

mobility of gold and silver in lateritic weathering profiles some observations from western australia experimental evidence suggests that very acid chloride solutions generated in lateritic profiles by ferrolysis oxidation and hydrolysis of iron are responsible for the dissolution of gold and silver au is subsequently reprecipitated by reduction of the aucl 4 super ion with fe super 2 reduction of the agcl complex does not similarly occur because of the relative redox potentials of fe super 2 fe super 3 and ag agcl thus chemical refinement of gold occurs during lateritization the development of low ph and the redistribution of gold and silver in lateritic weathering profiles appear to be more common over granitic and gneissic basement and may be inhibited by the presence of carbonate in the weathering zone of basic rock sequences modified journal abstract