sedimentary pyrite formation an update sedimentary pyrite formation during early diagenesis is a major process for controlling the oxygen level of the atmosphere and the sulfate concentration in seawater over geologic time the amount of pyrite that may form in a sediment is limited by the rates of supply of decomposable organic matter dissolved sulfate and reactive detrital iron minerals organic matter appears to be the major control on pyrite formation in normal non euxinic terrigenous marine sediments where dissolved sulfate and iron minerals are abundant by contrast pyrite formation in non marine freshwater sediments is severely limited by low concentrations of sulfate and this characteristic can be used to distinguish ancient organic rich fresh water shales from marine shales under marine euxinic conditions sufficient h2s is produced that the dominant control on pyrite formation is the availability of reactive iron minerals calculations based on a sulfur isotope model indicate that over phanerozoic time the worldwide average organic carbon to pyrite sulfur ratio of sedimentary rocks has varied considerably high cs ratios during permo carboniferous time can be explained by a shift of major organic deposition from the oceans to the land which resulted in the formation of vast coal swamps at that time low cs ratios compared to today during the early paleozoic can be explained in terms of a greater abundance of euxinic basins combined with deposition of a more reactive type of organic matter in the remaining oxygenated portions of the ocean the latter could have been due to lower oceanic oxygen levels and or a lack of transportation of refractory terrestrial organic matter to the marine environment due to the absence of vascular land plants at that time

instability conditions of loose sand in plane strain when a loose sand specimen is loaded under an undrained condition it may become unstable the instability conditions may be specified by an instability line determined using undrained tests however the instability behavior of sand has seldom been studied under plane strain conditions experimental data obtained under both triaxial and plane strain conditions are presented in this paper to define the instability conditions of loose sand under plane strain conditions using the state parameter a unified relationship can be established between the normalized slope of instability line and the state parameters for both axisymmetric and plane strain conditions using this relationship the instability conditions established under axisymmetric conditions can also be used for plane strain conditions

hydrogen index and carbon isotopes of lacustrine organic matter as lake level indicators abstract optical and geochemical techniques were applied to organic matter of late quaternary sediments from lakes victoria and rukwa east africa variations in total organic carbon toc and hydrogen content expressed as hydrogen index hi can be related to known changes in lake level and used to identify periods of very low water or subaerial exposure in basinal sequences toc and hi both decline as an exposure surface is approached mainly due to the selective removal of unstable components by bacterial respiration and inorganic oxidation inert organic material of very low hi is typically concentrated at the overlying transgression surface the carbon isotopic composition of the particulate organic matter tends to be less negative in sediments associated with exposure surfaces although weathering may be partially responsible isotopic variations are mainly due to changes in the relative importance of material from plants using c4 photosynthesis such as grasses and sedges growing around the shore and on the exposed lake muds and of material from planktonic algae and terrestrial c3 plants

late palaeogene quaternary geology of halmahera eastern indonesia initiation of a volcanic island arc the late palaeogene quaternary stratigraphy of halmahera is described and new formation names are proposed based on recent field investigations of the ne and central part of the island this stratigraphic information provides new insights into the neogene history of halmahera and the development of the present island arc the late palaeogene and younger rocks rest unconformably on an ophiolitic basement complex which formed part of a late cretaceous early tertiary fore arc after volcanic arc activity ceased in the eocene the former fore arc terrane was uplifted and deeply eroded in the late palaeogene some of the late palaeogene early miocene river valleys are currently being re excavated by the present rivers slow subsidence began in the mid late oligocene and by the end of the miocene all eastern halmahera was the site of shallow water carbonate deposition there is no evidence for arc volcanism in central halmahera at this time and the reported oligo miocene volcanism in nearby regions is interpreted as volcanism related to the sorong fault system the miocene shallow water region subsided rapidly in the early pliocene and the sedimentary basin formed was filled with marls succeeded by siliciclastic turbidites with increasing amounts of calc alkaline volcanic debris from a pliocene volcanic arc built on the western arms of halmahera probably on the eroded early tertiary arc this phase of rapid subsidence in the pliocene back arc region resulted from the initiation of subduction of the molucca sea lithosphere eastwards beneath halmahera differential subsidence on nw se and ne sw sets of faults in the region immediately behind the active arc led to the formation of deep sediment filled basins adjacent to the eastern arms a major deformation event in the pleistocene resulted in folding and local thrusting at the junction between eastern and western halmahera and volcanism ceased in the pliocene arc the third halmahera arc the quaternary arc currently active in the northern part of the islands began activity within the last 1 ma and is built upon the deformed and partly eroded pliocene arc the pleistocene deformation event and shift in position of the arc are interpreted as the result of the interaction of the eastward dipping molucca sea plate with adjacent plates either with a fragment of the australian continent in the sorong fault zone and or with the philippine sea plate beneath northern halmahera

late quaternary tropical lowland environments on halmahera indonesia abstract results of a case study of landform development and sedimentation in humid tropical lowland environments on halmahera island eastern indonesia are presented with the aim to better characterise tropical lowland environments in the context of late quaternary environmental change studies first the geologic morphologic and environmental settings of the two areas the interior kao river plain and the kao coastal zone n halmahera are presented subsequently data concerning late pleistocene and holocene landform development sedimentation and coastal processes are discussed pleistocene landform development involved volcaniclastic sedimentation base levelling of coastal lowlands prolonged weathering and crust formation coastal uplift and eustatic sea level change a conspicuous ferricrete crust in the subsoil of the coastal plain is tentatively dated with 14 c ams analysis and isotopes of organic matter encapsulated in the soil ferricrete have been determined due to interacting sea level change neotectonic uplift climatic hydrologic and vegetational change unequivocal evidence for anomalous late pleistocene or holocene environmental conditions is difficult to obtain during the mid late holocene a low energy fluvial systems and swamps existed in the interior kao river plain a dense open swamp swamp forest vegetation contributed to extremely high sedimentation rates in this depositional basin palynological analysis of the organic swamp deposits indicates little or no change in sedimentary environmental settings and swamp vegetations and indications for early human presence in the area in the coastal area accretion and delta progradation occurred after the early mid holocene formation of a marine erosion cliff tentative evidence for early human presence in the kao area is derived from charcoal particle frequencies in sediments and the existence of natural grasslands in the coastal zone as most of the geologic and environmental characteristics of the tropical lowlands in the kao area are common in eastern indonesia the study provides useful information for ongoing research in the region

alpine metamorphism of calcareous metasediments in the western hohe tauern tyrol mineral equilibria in cohs fluids during tertiary regional metamorphism in the western hohe tauern reaching maximum p t conditions around 6 kb 550 c in calcareous metasediments reaction of pyrite to pyrrhotite is suggested by regional distribution and textural relations in rocks without graphite pyrite is common at all metamorphic grades in graphite bearing rocks however the dominant fe sulfide is pyrite at lower grade and pyrrhotite at higher grade furthermore in graphite bearing high grade rocks pyrite is restricted to assemblages with mg rich silicates several factors control pyrite pyrrhotite relations increase of temperature is most effective by increase of pyrrhotite vs pyrite stability field shift of silicate sulfide reactions toward the stability field of pyrrhotite creation of sulfur free fluids from devolatilization reactions and increase in the proportions of sulfur bearing fluid species presence of graphite also favours progress of pyrite to pyrrhotite reaction as shown by different f s 2 stabilities and changes in the amount of minerals and fluid during metamorphic heating of graphite bearing and graphite free assemblages an opposite effect is shown by assemblages with low fe contents in fe mg silicates due to the enlarged stability field of such minerals with increasing mg and f content another inhibition of pyrite to pyrrhotite reaction is suggested to be due to relatively high sulfur contents of h2o rich infiltrating fluids

eastern alpine tectono metamorphic evolution constraints from two dimensional p t t modeling we use two dimensional 2 d p t t modeling to constrain the thermal and rheological aspects of different scenarios for the late mesozoic and cenozoic tectonic evolution of the eastern alps inferred from excellent data sets from the tauern window tw models invoking subduction of the south penninic sp oceanic lithosphere during thrusting and subsequent erosion of the austro alpine aa upper plate nappe stack are inconsistent with the observed thermal evolution within the aa and penninic units in these models predictions for the aa peak thermal conditions are lower than observed after exhumation and cooling to midcrustal levels and subduction of the continental middle penninic mp block the aa undergoes a phase of renewed heating to almost the previous peak temperatures simultaneously the penninic units experience a phase of heating upon subduction followed by cooling after onset of subduction of the north penninic np basin the model predictions are inconsistent with the observed nearly isothermal uplift path of the sp after subduction and cannot explain observed inverted metamorphic peak conditions in the deeper aa amphibolite facies down to the higher penninic unit greenschist facies a model with the beginning of subduction of the sp occurring after crustal thickening of the aa and subsequent return to normal crustal thicknesses is compatible with the p t t data in this model peak temperature conditions are higher in the aa followed by a phase of strong cooling in the aa upper plate with the onset of underthrusting this model also explains successfully nearly isothermal exhumation of the mp and inverted metamorphic peak conditions in the deeper aa material accreted to the hanging wall from the oceanic crust sp experiences a phase of cooling during ongoing subduction of oceanic lithosphere and begins to heat up to its thermal climax after the subduction of trailing continental lithosphere the subsequent pt path of the penninic units strongly depends on the timing and rates of underthrusting by the foreland observed pt paths in the mp within the tw require continuous subduction of the np and the trailing european foreland under the exhuming mp block documented rapid cooling in the final uplift phase of the penninic units in the tw requires exhumation rates up to approximately 4 mm yr predictions of slightly elevated present day geothermal gradients in the tw area are consistent with available heat flow data as a result of mesozoic rifting followed by late mesozoic crustal thickening of the aa paleorheological reconstructions are characterized by a contrast between relatively strong oceanic lithosphere and adjacent weak continental lithosphere predicted decoupling of weak continental and oceanic lithosphere during subsequent subduction of the penninic units can explain observed late cretaceous crustal extension in the aa units in terms of gravitational spreading ongoing subduction leads to an overall strength increase due to underthrusting of cool oceanic lithosphere whereas subduction of continental lithosphere causes a strength decrease in the upper levels of the lithosphere continuous crustal thickening and relaxation of the depressed isotherms reduce the strength of the lower lithospheric mantle beneath the central orogen further enhanced by rapid late stage uplift predictions for the present day rheological structure of the eastern alps support the existence of a strong upper crustal layer two wedge shaped strong upper mantle layers to the north and the south of the orogen and a weak upper mantle underlying the central orogen

unstable behaviour of sand and its implication for slope instability results of some constant shear drained csd tests conducted on both loose and dense sand are presented using the critical state line and a modified state parameter a new framework for analysing the instability of granular soil slopes is proposed the test data were examined and interpreted using the new framework instability lines for sand with different void ratios were established within this framework the conditions for the occurrence of instability in both contractive and dilative granular soil slopes under various shear stress levels were examined using the proposed framework key words deformation laboratory tests liquefaction sands shear strength slope stability

determination of inorganic sulphur speciation with polarographic techniques some preliminary results for recent hypersaline anoxic sediments abstract polarographic techniques have been used to determine reduced inorganic sulphur speciation in recent anoxic marine sediments from two hypersaline basins the tyro and the bannock basins in the eastern mediterranean the following phases were determined acid volatile sulphur avs pyritic sulphur and zerovalent sulphur the determination of avs and pyrite was based respectively on the acidification and cr ii reduction of these sulphur components to h2s h2s was collected in base and the sulphide concentration was measured by polarography standard na2s and pyrite gave recoveries of 99 6 3 9 and 97 12 respectively total zerovalent sulphur in a sediment sample was measured by the reaction of sulphite with thiosulphate thiosulphate was measured directly by polarography pyrite is the main phase of inorganic reduced sulphur in the sediments from the tyro and the bannock basins and it has about the same average level 125 moles per gramme dry weight in the cores recovered from the two areas however the distribution of pyrite in the top 100 cm of the two cores differs significantly in the bannock basin a sharp increase is observed with depth whereas in the tyro basin there is a small decrease with depth the total amount of reduced inorganic sulphur is less than the total amount of sulphur in the sediments this indicates that there must be additional sulphur bearing phases one of these phases may be gypsum and indeed gypsum crystals have been observed in the bannock basin in neither basin is there a significant correlation between reduced sulphur and organic carbon the pyrite that occurs in these basins may have been formed syngenetically at the interface of the anoxic brine and oxic seawater diagenetic pyrite may have been formed within the sediments of the basins avs and total zerovalent sulphur are still observed at depth we therefore suggest that this may be due to the incomplete transformation of avs and zerovalent sulphur into pyrite

depositional and diagenetic c s fe signatures in early paleozoic normal marine shales the degree of pyritisation dop of cambrian silurian normal marine shales is always less than 0 70 similar to that found previously for sediments of devonian to cretaceous ages this indicates that dop can be used as a paleoenvironmental indicator of deposition from normal marine i e oxygenated bottom waters throughout the phanerozoic record although the range in dop is similar significant variations in normal marine cs ratios can occur relatively low cs ratios 1 5 result from lower reactive iron contents which are also independent of organic carbon variations reactive iron contents and hence normal marine cs ratios are able to vary at a regional or basinal level

crystallization and deformation of amphiboles and cummingtonite forming reactions in the garbenschists of the western tauern window eastern alps northeast italy western austria abstract a detailed microscopic study of the amphiboles crystallized during the late alpine metamorphism in the hornblende garbenschists of the western tauern window reveals sevesal stages of crystallization cr1 cr3 and deformation d1 d3 during the first stage of crystallization cr1 poikiloblastic green hornblende of tschermakitic composition overgrew a matrix showing a strong s1 foliation a slight tendency towards increasing tschermak s and edenite exchange with glaucophane component decreasing towards the rim suggests amphibole growth during heating and decompression this prograde metamorphism leads to simultaneous formation of cummingtonite and hornblende in 3 out of 16 studied samples the cummingtonite forming reactions are discussed both hornblende and cummingtonite show microcracks forming s2 which is oblique to s1 s2 is missing in quartz and feldspar and also in some cases in the rims of the hornblende but is traceable through trails of fluid inclusions the last deformational event d3 is a tensional one producing s3 as large cracks in the amphiboles correlation of deformation and exchange components with published p t paths suggests growth of amphibole cores at amphibolite facies conditions hornblende and cummingtonite rims formed at decreasing pressures but still rising temperatures s2 microcracks are due to tectonic deformation d2 while the s3 extensional cracks were formed by ductile thinning d3 at rising temperatures as revealed by the mineral parageneses found in the cracks this paper presents the petrological framework for detailed geochronological investigations giving the time calibration of the p t path of the alpine metamorphism of the western tauern window

c s fe relationships and the isotopic composition of pyrite in the new albany shale of the illinois basin u s a the relationship between pyritic sulfur content spyr and organic carbon content corg of shales analyzed from the new albany group depends upon corg for samples of 6 wt no spty corg correlation is apparent the degree of fe pyritization dop shows similar relationships to corg these c s fe relationships suggest that pyrite formation was limited by the availability of metabolizable organic carbon in samples where corg 6 wt apparent sulfur isotope fractionations relative to contemporaneous seawater sulfate 34s for pyrite formation average 40 for non calcareous shales and 25 for calcareous shales 34s values become smaller with increasing corg spyt and dop for all corg poar 6 wt and some corg nch 6 wt shales these trends suggest that pyrite formation occurred in a closed system or that instantaneous bacterial fractionation for sulfate reduction decreased in magnitude with increasing organic carbon content the isotopic trends observed in the new albany group are not necessarily representative of other shales having a comparable range of organic carbon content e g cretaceous shales and mudstones from the western interior of north america gautier 1986 34s values in the remainder of the corg rich new albany group shales are relatively large 38 to 47 and independent of corg spyr and dop which suggests that pyrite in these shales formed mostly at or above the sediment water interface by precipitation from an isotopically uniform reservoir of dissolved h2s

melting and subsolidus reactions in the system k2o cao mgo al2o3 sio2 h2o experiments and petrologic application experiments with synthetic starting materials of muscovite phlogopite zoisite kyanite and quartz were performed in the pressure temperature range 10 25 kbar 640 780 c under water excess conditions the reaction muscovite zoisite quartz vapor liquid kyanite was bracketed at 10 5 kbar 689 700 c 15 5 kbar 709 731 c and 20 kbar 734 745 c the equivalent reaction in the mg bearing system muscovitess zoisite quartz vapor liquid kyanite phlogopitess lies at the same temperature around 10 kbar and approximately 10 c higher around 20 kbar compared with the mg free reaction at slightly higher temperatures formation of melt and tremolitess was reversibly observed from the assemblage phlogopitess zoisite kyanite quartz around 10 5 kbar 690 710 c 15 5 kbar 720 750 c and 20 5 kbar 745 760 c in the subsolidus region the reaction muscovitess talcss tremolitess phlogopitess zoisite quartz vapor were located in the range 700 c 16 7 19 0 kbar and 740 c 19 7 20 8 kbar from these data a wedge shaped stability field of phlogopitess zoisite quartz appears with a high p t termination around 21 kbar 755 c muscovite tremolite talc or kyanite comes in at higher pressures these phase relations are in qualitative accord with petrographic observations from high pressure metamorphic areas formation and crystallization of melts in rocks of a wide compositional range involving zoisite epidote has been ascribed to relatively high pressures and is consistent with experimentally determined stability fields in the simplified kcmash system

equatorial weathering landform development and the formation of white sands in north western kalimantan indonesia abstract the morphology and geochemistry of weathering profiles in miocene granodiorites from the coastal lowlands of nw kalimantan indonesia 1 n lat indicate long term weathering rates landform development and mechanisms for the formation of white sands found widely in valleys and depressions samples are analysed from convex hill piedmont glacis and valley slope profiles all profiles above the saturated zone are strongly gibbsitic but kaolinite minerals are dominant below the water table the profiles are interpreted as expressions of the perhumid equatorial climate rainfall 3000 mm y 1 acting within a dynamic regime of landscape lowering during the neogene the current profiles being largely quaternary 0 4 0 6 ka possible effects of quaternary tectonic and environmental changes are considered including those caused by a late pleistocene drier climate when there was greater water table fluctuation and surface erosion landform evolution is a form of dynamic etchplanation with a long term rate of landscape and weathering profile lowering of ca 50 mm ka 1 within this regime some of the white sands may be residual weathering products locally redistributed by colluvial or alluvial processes they originated in the podzolising environment of the weathering profile and later experienced post depositional diagenetic changes within the hydromorphic regime of the valley floor

petrologic constraints on imbrication metamorphism and uplift in the sw tauern window eastern alps the pressure temperature time deformation pttd history of two tectonic units in the southwest tauern window austria italy is evaluated from p t paths of metamorphism and uplift geochronologic data and observations on fabric development petrologic data indicate burial of the lower schieferhulle lsh to depths of 35 km and the adjacent upper schieferhulle ush to only 24 28 km the units are now separated by only 2 km of section metamorphism was postkinematic in the lsh and synkinematic in the ush correlation of p t path reversals calculated from zoned garnets in the two units however indicates that juxtaposition of the lsh and ush occurred prior to metamorphism temperature time and depth time diagrams for both units show increasing cooling rates and decreasing uplift rates as the rocks approached the surface both the petrologic data and the depth time profiles for the lsh and ush point to a history of differential uplift in the early stages of decompression textural features indicate that the lsh behaved as an essentially rigid body during uplift whereas the ush experienced extensive ductile shearing the pttd data for the lsh and ush are incorporated into a model for continental collision in the eastern alps initial tectonic uplift of the lsh was accompanied by ductile thinning of the ush and overlying austroalpine units final uplift and erosion affected all of the units en masse

biogeochemical cycling in an organic rich coastal marine basin 7 sulfur mass balance oxygen uptake and sulfide retention sulfur and oxygen fluxes were quantified in the seasonally varying anoxic marine sedimentary system of cape lookout bight n c u s a over the three year study period 1981 1983 the mean annual sulfate reduction rate was determined to be 18 2 1 6 moles m 2 y 1 this value added to the estimate of the detrital sulfur input of 1 2 4 4 gave a total sulfur input of 19 4 4 7 moles m 2 y 1 the sulfide flux to the sediment water interface measured in anaerobic benthic chambers was 4 6 0 5 moles m 2 y 1 and represented 37 of the annual oxygen uptake rate of 25 2 2 8 moles m 2 y 1 the sulfide burial rate determined to be 15 5 3 1 moles m 2 y 1 was within 5 of the value predicted by summing the fluxes at the sediment water interface the cs weight ratio of sediment below the depth of diagenetic reaction was determined to be 2 75 the sulfide retention rate in these rapidly accumulating sediments 10 cm yr was 77 19 comparison of this result with previous studies shows that rapid sediment accumulation and the lack of bioturbation control this unusually high degree of sulfide retention

palynology of late quaternary coastal sediments perak malaysia abstract twenty eight samples of peat clay and silty clay from a tin mine exposure near pantai remis perak malaysia were palynologically analyzed six pollen zones and eight subzones were delineated based on the dominant floral components accelerator mass spectrometry ams radiocarbon and thermoluminescence datings on selected samples indicate late pleistocene and older age the occurrence ofpodocarpus imbricatus pollen suggests that the deposit is no older than late pliocene the fluctuation of sea level during the late pleistocene is believed to be the main factor that influenced the development of vegetation at the pantai remis area the presence of mangrove peat at depths between 13 0 m and 14 0 m which overlies a freshwaterpandanus peat indicates the position of a former shoreline at pantai remis when the area was inundated sometime during the last interglacial marine incursion during this period of high sea level thepandanus swamp was probably being gradually replaced by mangrove vegetation the mangrove sequence is regarded as equivalent to the kempadang formation a slight drop in sea level sometime during the last glacial interstadial stage probably caused a small open alluvial swamp to be developed over the mangrove forest this freshwater deposit may be the equivalent of the simpang formation

stable isotopic and trace element evidence for restricted fluid migration in 2 gpa eclogites mineral stable isotopic and trace element studies in 2 gpa banded eclogites of the tauern window eastern alps record mm to cm scale heterogeneities that reflect compositional variations in the accompanying metamorphic fluids a close correlation between dolomite mode and dolomite 18o is consistent with equilibrium partitioning among coexisting minerals and fluids small variations in dolomite 13c values correspond with 18o variations but an overall decrease in dolomite 13c by c 1 o across a 12 cm sample is a relict feature that pre dates eclogite equilibration garnet omphacite and clinozoisite rims show little systematic mineral mineral partitioning behaviour for ti v cr y sr or zr major elements however are well equilibrated among these same minerals despite the apparent lack of mineral mineral trace element equilibration most of the trace elements vary systematically with water activity calculated in each layer trace element behaviour during the eclogite metamorphism thus appears to have been controlled largely by mineral fluid interactions along grain boundaries shallow structural levels in other subduction complexes c 10 45 km typically exhibit fracture controlled permeability and extensive metasomatism but there is no field or geochemical evidence for extensive fluid advection during high pressure metamorphism in the tauern eclogites because most dewatering and devolatilization during tectonic burial occurs prior to eclogite conditions the volumetric fluid rock ratio in eclogites should generally be low low fluid rock ratios coupled with the possible non wetting nature of the fluids permits the production and preservation of fine scale chemical heterogeneities in deeply subducted eclogites and associated fluids however the eventual breakdown at greater depth of volatile bearing dolomite phengite clinozoisite zoisite or amphibole could lead to renewed fracture controlled fluid release from the subducted rocks to regions appropriate for arc magma generation

palynology of eastern indonesian marine piston cores a late quaternary vegetational and climatic record for australasia abstract pollen analyses of late quaternary sediments from nine marine piston cores reveal a continuous vegetation and environmental record for eastern indonesia and northern australia on the island of halmahera a montane oak forest largely replaced the tropical lowland vegetation during the last glacial period while fern cover was strongly reduced during its maximum 18 000 yr b p climate was cooler and slightly drier than today around 10 000 yr b p mangrove vegetation expanded following the rising sea level in our western new guinea record at 14 000 yr b p climate grew warmer and slightly wetter until it stabilised around 10 000 yr b p at that time the mid to upper montane forests expanded to their full altitudinal range and fern cover increased while montane oak forest grassland and woodland areas had contracted in our marine pollen records during the last glacial the climate of northern australia was distinctly drier than today grassland vegetation with sedges increased considerably at 38 000 and 24 000 yr b p replacing eucalypt forest and culminating in a maximum grassland cover at the height of the last glaciation 18 000 yr b p the rapid sea level rise allowed the expansion of mangrove forests and salt bush marshes which had become established on the large tidal flats of the drowning sahul shelf around 12 000 yr b p one piston core g6 4 extends to 300 000 yr b p and shows that glacial periods are characterized by high pollen concentrations in marine sediments recording expanding grassland vegetation during interglacial woodland and fern cover increased while pollen concentrations in the sediments were low after 190 000 yr b p a more open vegetation suggests that conditions were in general much more arid than before repeated mangrove vegetation expansions suggest major rises in sea level at around 244 000 220 000 and 130 000 yr b p

porphyroblast inclusion trails the key to orogenesis detailed microstructural analysis of inclusion trails in hundreds of garnet porphyroblasts from rocks where spiral shaped inclusion trails are common indicates that spiral shaped trails did not form by rotation of the growing porphyroblasts relative to geographic coordinates they formed instead by progressive growth by porphyroblasts over several sets of near orthogonal foliations that successively overprint one another the orientations of these near orthogonal foliations are alternately near vertical and near horizontal in all porphyroblasts examined this provides very strong evidence for lack of porphyroblast rotation the deformation path recorded by these porphyroblasts indicates that the process of orogenesis involves a multiply repeated two stage cycle of 1 crustal shortening and thickening with the development of a near vertical foliation with a steep stretching lineation followed by 2 gravitational instability and collapse of this uplifted pile with the development of a near horizontal foliation gravitational spreading near coaxial vertical shortening and consequent thrusting on the orogen margins correlation of inclusion trail overprinting relationships and asymmetry in porphyroblasts with foliation overprinting relationships observed in the field allows determination of where the rocks studied lie and have moved within an orogen this information combined with information about chemical zoning in porphyroblasts provides details about the structural metamorphic p t t paths the rocks have followed the ductile deformation environment in which a porphyroblast can rotate relative to geographic coordinates during orogenesis is spatially restricted in continental crust to vertical ductile tear transcurrent faults across which there is no component of bulk shortening or transpression

instrumented laboratory flowslides flowslides have been induced in small instrumented coking coal stockpiles by slowly raising the water table these strongly resembled field cases showing sudden collapse rapid fluid like motion and very flat final slopes failure initiated under essentially static drained conditions and with a mobilized secant effective strength parameter d much less than the steady state value highspeed measurements showed that excess pore pressures were generated during rather than before movement and liquefaction was therefore a result of shear failure rather than the cause des glissements par liquefaction furent provogues dans de petites reserves de charbon cokeflant a instrumentation par elevations lentes de la nappe aquifere ils ressemblaient beaucoup a des cas sur chantier avec affaissement abrupt un mouvement rapide quasi fluide et des pentes finales tres plates la rupture commenca dans des conditions drainees essentiellement statiques et avec un parametre o de resistance effective secante mobilisee

evaluating late holocene radiocarbon based chronologies by matching palaeomagnetic secular variations to geomagnetic field models an example from lake kalimpaa sulawesi indonesia palaeomagnetic and palaeoenvironmental data from indonesia and particularly from the island of sulawesi are scarce and exact dating has turned out to be a challenge in many archives from this region here we outline difficulties in radiocarbon dating of the palaeoenvironmental record from lake kalimpaa sulawesi indonesia these difficulties demand the integration of additional parameters to obtain a reliable chronology for this record thus we compare the palaeo magnetic secular variation data from this record with the cals3k 4 spherical harmonic geomag netic model of the 0 3 ka field korte constable 2011 the resulting age depth model for the lake kalimpaa sequence provides a profound basis for further multi proxy investigations on this record for the first time high resolution palaeomagnetic secular variation data continuously span ning the past 1300 years are presented for this region which complement existing records with lower temporal resolution or records missing the top most sections

determination of shear strength of hawaiian residual soil subjected to rainfall induced landslides the determination of shear strength parameters for the stability analysis of rainfall induced landslides requires both a knowledge of the stress history and a laboratory simulation of the failure stress path of the soil involved such soils exist on steep slopes and have experienced a highly anisotropic stress action through which they have been consolidated a series of tests has been carried out on residual soil from a steeply sloping site in hawaii typical of locations subject to rainfall induced landslides two types of tests were carried out anisotropicconsolidation undrained acu tests which mimic field consolidation stress paths of the soil and constant shear stress drained csd tests which best simulate the failure stress path for rainfall induced landslides substantial differences of soil behaviour in csd tests and acu tests are recognized the csd strength parameters are considered most appropriate for analysing the rainfall induced landslides typical csd derived parameters are o y 32

interactions between serpentinite devolatilization metasomatism and strike slip strain localization during deep crustal shearing in the eastern alps the greiner shear zone in the tauern window eastern alps changes from a zone of distributed dominantly sinistral shear in supracrustal rocks to a series of narrow gully forming dextral splays where it enters basement gneisses within these splays granodiorite is transformed into quartz poor biotite and or chlorite schists reflecting hydration removal of si ca and na and concentration of fe mg and al stable isotope analyses show a prominent increase in d and a decrease in 18o from granodiorite into the shear zones these changes indicate significant channelized flow of an externally derived low 18o high d fluid through the shear zones the shear zone schists are chemically similar to blackwall zones developed around serpentinite bodies elsewhere in the greiner zone and the stable isotope data support alteration via serpentinite derived fluid monazite in schist from one shear zone yields spot dates of 29 20 ma indicating that the fluid influx and switch from sinistral to dextral shear occurred at or shortly after the thermal peak of the alpine orogeny c 30 ma we suggest that alpine metamorphism of serpentinites released large amounts of high d low 18o si undersaturated fe mg saturated fluids that became channelized along prior zones of weakness in the granodiorite infiltration of this fluid facilitated growth of chlorite and biotite which in turn localized later dextral strain in the narrow splays via cleavage parallel slip this dextral strain event can be linked to other structures that accommodated tectonic escape of major crustal blocks during dextral transpression in the eastern alps this study shows that serpentinite devolatilization can play an important role in modifying both the chemistry and rheology of surrounding rocks during orogenesis

oxygen isotopes sea level changes and the temperature history of a coral reef environment in new guinea over the last 105 years abstract coral reef terraces consisting of an upward succession of fringing and barrier reef types are preserved on land along the raising coast of huon peninsula new guinea seven coral reef units i vii from the coast landwards spaced at about 20 kyr interval provide a rather complete record of sea levels oxygen isotopes and temperature of teh surface tropical ocean over the duration of the high sea level events of the last glacial cycle the systematic sampling of the coral reefs was restricted to the massive tridacna gigas species the giant clam which are about 0 7 0 enriched in 18o relative to calcite equilibrium value and the presence of symbionts seems to have no effect on the 18o of their aragonitic skeleton sea levels rose rapidly to 5 6 5 m above present during the last interglacial which on stratigraphic grounds and 18o compositions can be separated into an early phase whose 18o is similar to modern reef viia dated at 138 kyr and a late phase that is 0 6 0 heavier reef viib dated at 118 kyr fringing reefs vi v iv iii and ii record short lived high sea levels stands at 107 85 60 45 to 40 and 31 kyr respectively that stopped short of the present sea level 12 19 28 32 to 42 m the general decline of the high sea level stands corresponds to an average 18o enrichment of 1 7 0 measured between the early interstadials of isotope stage 5 vi and v and the late interstadials of isotope stage 3 iv iiia iiib and ii the maximum 18o enrichment of 1 7 0 relative to present was registered during a regressive phase of reef iiia stratigraphic evidence indicates that sea level lows in the range of 37 to 55 m below present have occurred in between the high sea level stands but those are unlikely to represent the lowest sea levels of the last glacial cycle sea levels and 18o ddta pair offer important clues regarding the partitioning of ice volume and temperature in 18o records the results suggest that the ice volume effect accounts for the observed 18o changes during the early interstadial culminations but only for 29 46 during the late interstadial culminations sea water cooling beyond the threshold limit of coral reef growth 18 c did not occur during the last glacial cycle the temperature of the surface tropical ocean was similar to present during the early interstadials of isotope stage 5 and cooler by 3 c below present during the later interstadials of isotope stage 3

the carbon isotope composition of organic matter occluded in iron nodules abstract this study presents 13 c and 14 c results for soil organic carbon and carbon occluded by iron nodules from a quaternary soil profile developed on basalt in western victoria australia the results suggest that the 13 c value of organic matter in the iron nodules is directly inherited from the surrounding soil profile without isotopic fractionation and that therefore the 13 c value of organic matter occluded by the iron nodules can be related to the vegetation present during nodule formation however 14 c results suggest that iron nodules are not closed systems with respect to organic carbon and that even chemically resistant immobile particulate carbon of probable microbial origin has been added to the nodule carbon pool since formation nevertheless the turnover time for chemically resistant particulate carbon in the iron nodules is at least three times that for the same fraction in the surrounding soil making iron nodules useful repositories of palaeoenvironmental information particularly where they have been removed from the active surface soil layer by burial

preservation of elemental and isotopic source identification of sedimentary organic matter the amount and type of organic matter in the sediments of lakes and oceans contribute to their paleoenvironmental and paleoclimatological records only a small fraction of the initial aquatic organic matter survives destruction and alteration during sinking and sedimentation selective degradation modifies the character of the surviving small fraction of organic matter which becomes incorporated in bottom sediments organic matter alterations can continue to sub bottom depths of hundreds of meters corresponding to millions of years source and paleoenvironmental information nonetheless remains preserved in the molecular elemental and isotopic compositions of organic matter c n and 13c values of total organic matter in particular appear to retain paleoenvironmental information for multi myr time periods

anisotropic shear strength characteristics of a tailings sand the deposition process of tailings in a tailings dam may lead to the anisotropy of mechanical properties of tailings to investigate the anisotropic shear strength characteristics of a tailings sand samples deposited under gravity were sheared in a modified direct shear apparatus along different orientations of the shear planes relative to the bedding plane the experimental results reveal that the anisotropy has a substantial effect on the peak shear strength of the tailings sand leading to a variation in peak friction angle of 10 it is found that the effect of anisotropy on the peak shear strength of the tailings sand is mainly attributed to the effect of anisotropy on soil dilatancy on the other hand the effect of anisotropy on the residual friction angle of the tailing sand is relatively smaller likely due to the partial erasure of anisotropy at large shear deformation the degree of anisotropy is reduced by an increase in normal stress to achieve more accurate stability analysis of tailings dams it is suggested to take into account the shear strength anisotropy of tailings soils

time calibration of a pt path from the western tauern window eastern alps the problem of closure temperatures new hornblende k ar and 39ar 40ar and mica rb sr and k ar ages are used to place specific timemarks on a well constrained pressure temperature path for the late alpine metamorphism in the western tauern window after identification of excess 40ar the closure behavior of ar in hornblende is compared with that of sr and ar in phengite and biotite samples were collected in three locations whose maximum temperatures were 570 c zemmgrund 550 c pfitscher joch and 500 540 c landshuter hutte

aspects of sand behaviour by modified constant shear drained tests constant shear drained tests csd are probably the most suitable to simulate the strength and deformation behaviour of soils in slopes under water infiltration conditions or lateral stress relief this is significant because soil behaviour following a csd stress path could differ from that of traditional compression triaxial tests in this paper csd tests on sand following an alternative procedure are presented and discussed the modified csd tests were conducted by increasing the pore water pressure at a constant rate from one end of the specimen with water free to drain from the opposite end among the results from specimens consolidated at variable initial void ratios and principal stress ratios it was revealed that specimens showed a tendency to dilate even for loose sands failure was reached at low axial strains and a pre failure type of instability could be identified the modified procedure has the potential to provide new insights into the failure mechanisms of slopes under a water infiltration condition

sources and accumulation rates of organic carbon in an equatorial peat bog burundi east africa during the holocene carbon isotope constraints the relationship between organic carbon accumulation rates and 13c 12c ratios of total organic carbon toc was investigated in an highland peat bog core ru 3 from equatorial africa this core yielded a sequence spanning the last 14 kyr and was analysed with a 100 300 yr resolution for toc 13c values the holocene section shows contrasted toc accumulation regimes and toc 13c varying between 28 5 and 19 5 with a few very short isotopic excursions dated at ca 9 3 7 5 4 2 ka b p the organic carbon accumulation rates range from 2 to 20 mg c cm 2 yr 1 they increase when toc becomes more depleted in 13c notably between 12 and 9 8 ka b p 8 5 and 7 8 ka b p and after 1 6 ka b p periods of restricted carbon storage correspond to heavier toc accumulation at 9 3 and between 7 5 and 1 6 ka b p at the study site the variations can be related to variable c4 plant inputs and possibly to changes in the fractionation between co2 and the organic carbon in c3 vascular plants the ru 3 record indicates restricted carbon storage during the periods of increased contribution from c4 plants and or of decreased fractionation between co2 and organic carbon in c3 plants changes in toc 13c values in core ru 3 seem to match fluctuations of east equatorial african lakes high lake stands correspond to low 13c intervals and vice versa this points to indirect climatic forcing of 13c changes in intertropical peats

the analysis of rainfall induced slope failures at iva valley area of enugu state nigeria this paper analyses the dominant mechanisms of slope failures and identifies potential obstacles to landslide hazard reduction at the iva valley area enugu nigeria the landscape is replete with landslide scars and gullies of varied sizes and the slope deposits comprise unconsolidated friable sands inter bedded with thin units of montmorillonitic claystone forty three landslide events were identified in the study area with most being shallow short run out movements with slip surface depth 2 m the study found the landslides mainly occur in the beginning of rainy season characterized by short duration high intensity rainfall an integrated approach comprising field mapping laboratory tests and numerical analyses reveals that the barren nature of the slopes prior to the outset of rainy season high rainfall intensity erosion overgrazing soil characteristics and the site s unique lithologic sequence are the main causes of instability shearing tests under several conditions showed that the soils strongly strain soften until low steady state strength is achieved a computer code based on this strength reduction technique used input parameters obtained from the field and laboratory studies to simulate a landslide with similar structure travel distance and distribution area it is noted that urbanization has gradually increased the vulnerability of the society s poor to landslide hazards as they now erect unplanned residence tents and blocks on the slopes this work is part of a regional study aimed at finding ways of protecting the vulnerable by generating data that could be used to build future landslide susceptibility map

comparison of laser grain size analysis with pipette and sieve analysis a solution for the underestimation of the clay fraction classically the grain size of soil and sediment samples is determined by the sieve method for the coarse fractions and by the pipette method based on the stokes sedimentation rates for the fine fractions results from the two methods are compared with results from laser diffraction size analysis which is based on the forward scattering of monochromatic coherent light from a point of view of laboratory efficiency the laser sizing technique is far superior accuracy and reproducibility are shown by measurements on certified materials it appears that laser grain size measurements of certified materials correspond very well with the certificated measurements tests were also done on a set of randomly selected sediments of fluvial aeolian and lacustrine origin except for the 2 m clay fraction there is a coarsening of the mean diameter of one to two size classes 0 25 caused by the non sphericity of the particles the platy form of the clay particles induces considerable differences eight size classes between pipette and laser measurements the 2 m grain size defined by the pipette method corresponds with a grain size of 8 m defined by the laser particle sizer for the studied sediments using a higher grain size level for the clay fraction when laser analysis is applied enables workers in the geological and environmental field to compare classical pipette analysis with a laser sizing technique

a 135 000 year record of vegetational and climatic change from the bandung area west java indonesia sedimentological and palynological analyses of sediment cores from the intramontane bandung basin west java indonesia provide a first palaeoclimatic record for the indonesian region covering continuously the last 135 000 years our data on palaeosol development indicate anomalously dry conditions for the final part of the penultimate glacial period around 135 000 yr b p and very warm and humid interglacial conditions from 126 000 to 81 000 yr b p during the transition to the last glacial period around 81 000 yr b p freshwater swamp forest of the bandung plain was replaced by an open swamp vegetation dominated by grasses and sedges indicating a change to considerably drier conditions possibly related to reduced moisture uptake by the nw monsoon as a consequence of lower sea levels at the onset of glacial conditions a strong reduction in asplenium ferns from 81 000 to 74 000 yr b p suggests that drier conditions may also have occurred in the mountains of the bandung area while increased numbers indicate that from 74 000 to 47 000 yr b p it was slightly wetter again inferred depression of montane vegetation zones and reduced fern percentages suggests distinctly cooler and possibly drier climatic conditions prevailed in the bandung area from 47 000 to approximately 20 000 yr b p for the last glacial maximum 4 7 c lower temperatures are recorded

the effects of ferromagnesian components on the paragonite muscovite solvus a semiquantitative analysis based on chemical data for natural paragonite muscovite pairs chemical data for 139 natural paragonite muscovite pg ms pairs illustrate the effects of ferromagnesian components on the p t x topology of the pg ms solvus the pairs were selected on the basis of reasonably accurate knowledge of the p t conditions of formation evidence for close approach to equilibrium at peak metamorphic conditions exclusion of pairs in which paragonite contains more than 5 mol margarite and exclusion of pairs from polymetamorphic rocks that contain more than one set of cogenetic pg ms pairs graphical analysis reveals considerable scatter in the data nevertheless it is evident that the muscovite limb of the solvus shifts markedly toward end member muscovite with increasing pressure from approximately 7 kbar to 21 kbar this shift is attributed to a pressure induced increase of the ferromagnesian content of muscovite which increases the size of the xii alkali site to the effect that k is more readily accommodated than na the data also suggest that the paragonite limb of the solvus migrates slightly toward end member paragonite with increasing pressure broadening of the pg ms solvus with increasing pressure reflects increasingly nonideal na k mixing as the phengite content of muscovite increases due to the wide scatter of data for pg phengitic ms pairs it is concluded that at the present time pg ms solvus thermometry is only viable for quasibinary pg ms pairs

causative mechanisms of rainfall induced fill slope failures slope failures in fill slopes formed by loosely compacted completely decomposed granite in hong kong occur commonly during intense tropical rainstorms the stress path greatly influences the shear strength of the soil mass and is therefore crucial to the identification of slope failure mechanisms the soil mass in this case is largely unsaturated in situ hydrologic response to rainstorms indicates that soil suction is reduced by rainfall infiltration which often becomes the triggering factor in initiating slope instability the constant dead load tests on unsaturated loosely compacted completely decomposed granite appropriately simulate the field stress path of rainfall induced fill slope failure by reducing suction the tests indicate that matric suction contributes to the dilative or contractive behavior of the unsaturated soils the anisotropically consolidated undrained triaxial tests demonstrate the consistently contractive behavior of the specimens on this basis we delineate the in situ stress conditions leading to the initiation of rainfall induced fill slope failure and the stress paths of the transformation from local failures to flowage based on a systematic study of fill slope case records in hong kong implications of such mechanisms on fill slope stability are given

fluid heterogeneities and hornblende stability in interlayered graphitic and nongraphitic schists tauern window eastern alps the assemblage hornblende white mica occurs in graphite free schists at two localities in the southwest corner of the tauern window eastern alps in interbedded graphitic layers 1 mm to 1 m thick however hornblende is typically replaced by pseudomorphs of biotite plagioclase epidote chlorite staurolite in the presence of white mica garnets adjacent to these pseudomorphs have pronounced growth discontinuities near their rims in contrast to the continuously zoned garnets in nongraphitic layers these observations imply that reactions of the type hbl white mica gar bio plag epid chl staur h2o occurred in the graphitic samples but that hbl white mica remained stable in graphite free layers calculation of the equilibrium constants for solid phases in five dehydration equilibria at locality 1 indicates thata h2o in the nongraphitic layers was 6 to 11 times greater thana h2o in the graphitic layers similar calculations involving six dehydration equilibria at locality 2 show no difference ina h2o between layers at the conditions of final equilibration initial differences in fluid composition maintained between the graphitic and nongraphitic layers caused the hbl white mica reaction to occur at differentp t conditions in different horizons of the schists these data indicate that systematic differences in fluid composition were generated during metamorphism of the interlayered graphitic and non graphitic schists but were subsequently homogenized at locality 2 the heterogeneities could initially have been produced while the rocks were in thep t field of co2 h2o immiscibility development of a penetrative layer parallel shear foliation at this time would have prevented subsequent mixing of the fluids across layers after temperatures exceeded the consolute temperature in the co2 h2o system late stage homogenization of fluids at locality 2 is thought to reflect loss of the buffer capacity of the mineral assemblage in response to total consumption of hornblende

a regional gradient in the composition of metamorphic fluids in pelitic schist pecos baldy new mexico two metamorphic isograds cut across graphitic schist near pecos baldy new mexico the southern isograd marks the first coexistence of staurolite with biotite whereas the northern isograd marks the first coexistence of andalusite with biotite the isograds do not record changes in temperature or pressure instead they record a regional gradient in the composition of the metamorphic fluid phase ortega quartzite which contains primary hematite lies immediately north of the graphitic schist mineral compositions within the schist change gradually toward the quartzite reflecting gradients in mu text o text 2 and mu text h text 2 text o the chemical potential gradients locally as high as 72 cal m in mu text o text 2 and 9 cal m in mu text h text 2 text o controlled the positions of the two mapped isograds the staurolite biotite isograd records where x text h text 2 text o fell below 0 80 at f text o text 2 near 10 23 bars the andalusite biotite isograd records where x text h text 2 text o fell below 0 25 at f text o text 2 near 10 22 bars dehydration and oxidation were coupled by graphite fluid equilibrium the chemical potential gradients apparently formed during metamorphism as graphite in schist reacted with hematite in quartzite local oxidation of graphite formed co2 which triggered dehydration reactions along the schistquartzite contact this process created a c o h fluid which infiltrated into overlying rocks upward infiltration local fluid rock equilibration and additional infiltration proceeded until the composition of the infiltrating fluid evolved to that in equilibrium with the infiltrated rock this point occurs very close to the staurolite biotite isograd pelitic rocks structurally above this isograd show no petrographic evidence of infiltration even though calculations indicate that volumetric fluid rock ratios may have exceeded 15 and thin rare calc silicate beds show extensive k metasomatism and quartz veining

organic carbon sulphur and iron in recent semi euxinic sediments of kau bay indonesia kau bay island of halmahera eastern indonesia is a 470 m deep basin separated from the pacific ocean by a sill that is at present only 40 m below sea level during weichselian time the sea level dropped below the depth of the sill and freshwater sediments were deposited these sediments are rich in organic matter corg 2 6 wt with terrigenous isotope characteristics 13corg 28 to 30 and are also rich in sulphur s 4 wt this sulphur enrichment is interpreted to be a late diagenetic feature related to diffusion of dissolved sulphate and sulphide from the marine sediments into the freshwater sediments the sulphur in these sediments has a 34s value of 15 the overlying holocene sediments consist of marine muds deposited in alternating low oxygen and h2s bearing bottom waters the marine sediments are also rich in organic matter corg 2 6 wt but of mixed terrigenous and marine origin 13c 25 to 19 moreover the sulphur content of these holocene sediments is lower s 1 2 wt and isotopically lighter 34s 20 in addition to pyrite large amounts of acid volatile sulphur avs compounds accumulate in kau bay the reactive iron content of the sediment limits the amount of iron that is sulphidized while the supply of oxidants controls the limited conversion of avs to pyrite total and reactive iron contents are strongly correlated with the amount of terrigenous organic matter as a consequence of their common provenance and depositional histories the marine sediments in kau bay show no simple relation between organic carbon and sulphur

graphite ch4 h2o co2 equilibria at low grade metamorphic conditions equilibrium calculations and published phase equilibria are used to show that at temperatures below 400 c and pressures above 300 bar the fluids coexisting with graphite in the c o h system consist either of co2 h2o mixtures or ch4 h2o mixtures bulk fluid compositions consisting of ch4 h2o will unmix to methane rich fluid and h2o rich liquid at temperatures below about 325 c compositions on the co2 h2o join will unmix only at temperatures below about 275 c oxygen fugacity in the ch4 h2o graphite three phase region is fixed at constant p and t and approximately equal to that of the quartz magnetite fayalite assemblage in the co2 h2o graphite three phase region oxygen fugacity is about three orders of magnitude greater from the end stages of diagenesis to temperatures of 300 c and possibly 400 c in salt rich systems many metamorphic rocks may contain ch4 h2o fluids rather than co2 h2o mixtures thus metamorphic reactions involving carbonate minerals would involve ch4 graphite and h2o rather than co2 the immiscibility between ch4 and h2o could result in the common occurrence of methane natural gas in low grade metamorphic terrains

dissolution and pyritization of magnetite in anoxie marine sediments concentrations of magnetite were determined with depth in sediments of varying h2s content taken from long island sound foam nwc and sachem sites and from a site in the rapidly depositing subaqueous portion of the mississippi delta for the three long island sound sites dissolution of magnetite during burial is clearly demonstrated and for all four sites the rate of magnetite dissolution is proportional to the concentration of dissolved pore water sulfide by combining magnetite depth distributions with sedimentation rate data and measurements of dissolved sulfide we find that magnetite dissolution is well described by the following rate law dcmagdt 1 1 10 5c0 5bcmagamag where cmag is the concentration of magnetite grams per gram of sediment cs is the concentration of dissolved sulfide mm and amag is the specific surface area of magnetite in the sediment cm2 per gram of magnetite this equation means that for a typical range of magnetite surface areas and dissolved sulfide concentrations the half life of magnetite in anoxic marine sediments ranges from about 50 to 1000 years sem observations of magnetite grains from the different sediment sites reveal that magnetite dissolution may be accompanied by extensive replacement by pyrite this only occurs if magnetite is in contact with high concentrations of h2s 1 mm for relatively long periods of time several hundred years with low concentrations of h2s 1 mm magnetite dissolution occurs without identifiable pyrite replacement we suggest that this feature of magnetite diagenesis may prove to be a useful paleosulfide indicator

pore pressure response during failure in soils three experiments were performed on natural slopes to investigate variations of soil pore water pressure during induced slope failure two sites in the wasatch range utah and one site in the san dimas experimental forest of southern california were forced to fail by artificial subsurface irrigation the sites were instrumented with electronic piezometers and displacement meters to record induced pore pressures and movements of the slopes during failure piezometer records show a consistent trend of increasing pressure during the early stages of infiltration and abrupt decreases in pressure from 5 to 50 minutes before failure displacement meters failed to register the amount of movement due to location and ineffectual coupling of meter pins to soil observations during the experiments indicate that fractures and macropores controlled the flow of water through the slope and that both water flow paths and permeability within the slopes were not constant in space or time but changed continually during the course of the experiments

the laterite profile ferricrete and unconformity summary the laterite profile consists of ferricrete overlying saprolite examples from our field observations and from the literature demonstrate that in many if not all cases ferricrete consists of detrital material younger than the underlying weathering zone s from which it is separated by an unconformity heretofore a detrital origin for ferricretes although occasionally mentioned has not been sufficiently considered the laterite originally described by buchanan is saprolite and does not harden significantly on exposure to the air some definition of laterite would exclude this original type material because of relief inversion ferricrete is now often exposed in high situations such as plateau margins relief inversion may have occurred at many times and places and individual occurences of ferricrete are not necessarily parts of a former widespread erosion surface

glacial conditions in the northern molucca sea region indonesia abstract palynological planktonic foraminiferal and stable isotope data from a sediment core in the northern mollucca sea have been used to evaluate regional glacial climatic and hydrographic conditions the palynological record shows that in glacial time the climate was drier than today indicating a weakened influence of the northwesterly winds at that time the drier climatic conditions at glacial time were associated with a higher lapse rate which together with a lower sea level resulted in a large expansion of the lower montane oak forests on the nearby island of halmahera glacial mollucca sea surface water salinities were probably higher than today while glacial surface water temperatures might have been close to present day values the deep chlorophyll maximum dcm layer in the northern molucca sea at glacial time was more productive and cooler than today probably the result of the inflow of cooler and nutrient enriched subtropical lower water from the pacific the less asymmetrical high latitude ice coverage at glacial time and the particularly strong increase in the pole to equator thermal gradient on the northern hemisphere provides theoretical evidence that the intertropical convergence zone itcz shifted equatorwards and oscillated over a more narrow latitudinal range than today this inferred configuration of the itcz at glacial time however fails to explain the observed increased aridity in the study area at that time we propose therefore that the drier glacial climatic conditions are related to a possible disturbance in the el nino southern oscillation enso system

evolution and effect of the stress concentration and rock failure in the deep multi seam coal mining supports crushing accident occasionally occurs in the protected seam exploitation of deep multi seam coal mining structure and results in adverse effect to the production to prevent its recurrence in a newly developed working field a 3d numerical extraction model was built based on the geologic and mining conditions of jining coal mine to evolve the changes state and characteristics of the reconstructed vertical and lateral stress in rock interlayer after protective seam exploitation stress release and increase zones of this mining structure were separated mining induced localized stress concentration and the interlayer rock failure behavior were explored the action of concentrated stress on the hydraulic supports in protected seam was discussed upon the major stress redistribution using the infinitesimal strain method a mechanical model was created to further explore from the vertical and lateral directions the cause and mechanism of localized stress concentration and rock failure behavior in rock interlayer the field investigation was finally performed to verify the numerical and mechanical results and the essential control measures were proposed to prevent this accident key findings of this study bring some new insights into the deep multi seam coal extraction and help to promote a more reliable underground mining