trace metal geochemistry of remote rivers in the canadian arctic archipelago abstract trace metals are essential micronutrients for phytoplankton as well as useful tracers of biogeochemical processes in aquatic systems the largest arctic rivers are known to play an important role in the cycling of trace metals in the arctic ocean however these systems account for little more than half of arctic freshwater discharge leaving a major gap in our understanding of the trace metal geochemistry from smaller river systems this is especially problematic for rivers draining the arctic coastal margins as these continuous permafrost systems are anticipated to be particularly sensitive to climate change this study presents the first observations of dissolved and particulate trace metal concentrations and lead isotopes in 14 rivers in the canadian arctic archipelago caa dissolved concentrations of aluminum iron manganese nickel copper zinc cadmium and lead display clear spatial variability in their distributions small rivers located in the central islands of the caa have remarkably low concentrations of these trace metals while the rivers draining the southern continental landmass have higher values this geographic variability in dissolved metal concentrations reflects both differences in bedrock geology and the south north environmental gradients in the archipelago we extrapolate these findings to estimate the dissolved trace metal concentrations for other rivers draining the caa based on their geographic location elemental ratios measured in the suspended particulate matter in several rivers indicates a significant enrichment of nickel copper zinc and lead over the crustal composition in particular lead isotope composition shows an extremely large range varying from the highly radiogenic tree river 206pb 207pb 1 5121 in the south to the relatively unradiogenic glacier river 206pb 207pb 1 0153 in the central caa lack of correlation between the pb isotopic composition and pb enrichment suggests pb is derived from within the watershed this work presents the first observations of dissolved and particulate trace metal concentrations in small coastal draining rivers from the caa an important first step in developing a baseline against which to evaluate future change in the high arctic

anisotropy of magnetic susceptibility ams records synsedimentary deformation kinematics at pico del aguila anticline pyrenees spain

magnetic susceptibility of the rock matrix related to magnetic fabric studies non ferromagnetic minerals constitute what is called the rock matrix whose susceptibility k1 is directly accessible using only high magnetic fields measurements on minerals and a wide range of rock types show that k1 is mainly due to paramagnetism and hardly exceeds 10 3 si with an anisotropy degree p less than 1 35 different methods to estimate the role of the matrix component in low field susceptibility k and its anisotropy include petrological and chemical analysis evolution of p vs k low temperature studies and comparison of k with remanent magnetizations

the biogeochemistry of aluminum in the pacific ocean abstract vertical distributions and horizontal surface transects of dissolved and particulate al at several locations in the pacific ocean are presented here concentrations of dissolved al in the pacific range from 0 3 to 5 nmol kg in the surface waters from 0 1 to 1 nmol kg in mid depths and from 0 5 to 2 nmol kg in the deep waters from these data and published data from other regions it is evident that al has a unique oceanic chemistry relative to that of other metals external sources and rapid particle scavenging throughout the water column are the major controls on dissolved al distributions in the oceans vertical profiles generally exhibit a surface maximum a mid depth minimum and increasing concentrations toward the sediment water interface this suggests two sources of dissolved al one to the surface waters and one to the deep waters concentrations of dissolved al in surface waters are lowest within the eutrophic low salinity california current 0 3 1 nmol kg and increase westwardly into the subtropical gyre of the north pacific 5 nmol kg values in the south pacific gyre are fivefold lower these horizontal trends indicate that the primary source of dissolved al to the surface waters of the central pacific is from eolian input dissolved al supplied by rivers to the eastern north pacific appears to be rapidly scavenged in estuaries and or the highly productive coastal region the source of dissolved al to the deep waters is not known but could be due to a flux out of the sediments or a remineralization process suspended particulate al concentrations increase with depth at all stations and decrease with distance from the ocean boundary surface values range from 1 5 nmol kg near shore to 0 3 nmol kg in the central gyres of the pacific deep water concentrations range from 22 nmol kg near shore to 4 nmol kg in the north pacific central gyre and decrease to 1 3 nmol kg in the south pacific central gyre observed distributions indicate that suspended particulate al varies with the intensity of bottom sediment resuspension and the horizontal mixing of the resulting nepheloid layer out from ocean boundary regions particle residence times estimated are consistent with other reported values

clinker deposits powder river basin wyoming and montana a new source of high fidelity paleomagnetic data for the quaternary clinker rock baked and fused by in situ burning of underlying coal posesses a thermoremanent and or thermochemical magnetization that resides in magnetite hematite and goethite data from individual sites imply that clinker may provide a high resolution recording of the geomagnetic field e g within site virtual geomagnetic pole angular standard deviations are usually less than 10 but this is dependent on its thermal history and the time over which magnetic phases formed data from 17 sites in the powder river basin 13 normal polarity 4 reverse yield a mean of decl 348 incl 62 95 5 k 42 and a corresponding pole position of 81 lat 158 long with a virtual geomagnetic pole angular standard deviation of 17 3 the mechanism of clinker formation the wide geographic distribution and the range of available fission track ages suggest that clinker may contain a nearly complete geomagnetic field record for much of the quaternary

the anisotropy of magnetic susceptibility in biotite muscovite and chlorite single crystals the anisotropy of magnetic susceptibility ams of single crystals of biotite muscovite and chlorite has been measured in order to provide accurate values of the magnetic anisotropy properties for these common rock forming minerals the low field ams and the high field paramagnetic susceptibility are defined for the high field values it is necessary to combine the paramagnetic deviatoric tensor obtained from the high field torque magnetometer with the paramagnetic bulk susceptibility measured from magnetization curves of the crystals this leads to the full paramagnetic susceptibility ellipsoid due to the anisotropic distribution of iron cations in the silicate lattice the ellipsoid of paramagnetic susceptibility which was obtained for the three phyllosilicates is highly oblate in shape and the minimum susceptibility direction is subparallel to the crystallographic c axes the anisotropy of the susceptibility within the basal plane of the biotite has been evaluated and found to be isotropic within the accuracy of the instrumental measurements the degree of anisotropy of biotite and chlorite is compatible with previously reported values while for muscovite is smaller than previously published values the shape of the chlorite ams ellipsoid for all the samples is near perfect oblate in contrast with a wide distribution of oblate and prolate values reported in earlier studies reliable values are important for deriving models of the magnetic anisotropy where it reflects mineral fabrics and deformation of rocks d 2003 elsevier science b v all rights reserved

quantification of magnetic coercivity components by the analysis of acquisition curves of isothermal remanent magnetisation abstract a new method of analysing isothermal remanent magnetisation irm acquisition curves based on cumulative log gaussian analysis robertson and france phys earth planet inter 82 1994 223 234 is proposed it is based on the curve fitting of the irm acquisition curve versus the logarithm of the applied field with i the acquisition curve on a linear scale ii the acquisition curve expressed as a gradient and iii the acquisition curve on a probability scale even when a sample is not saturated its magnetic properties can be defined although with less certainty the number of magnetic components required for an optimal fit to a measured irm acquisition curve is evaluated statistically the method discriminates on the basis of different mineral coercivity therefore additional rock magnetic tests are still required to separate minerals with similar coercivities

an annual study of inorganic and organic nitrogen and phosphorus and silicic acid in the southeastern beaufort sea 1 water column samples from the mackenzie shelf the beaufort sea and the amundsen gulf were obtained during 2003 2004 to investigate nutrient dynamics in an arctic ecosystem influenced by a large river and flaw lead polynya nutrient inventories in the upper water column showed a significant seasonal drawdown of nitrate no3 and silicic acid si oh 4 1 1 75 mol mol and subsequent accumulation of nitrite no2 and ammonium nh4 dissolved organic nitrogen and phosphorus concentrations don and dop were elevated in surface waters during the time of peak phytoplankton growth bloom and postbloom phases and covaried in a 17 1 molar ratio vertical profiles showed the typical middepth maxima in no3 po43 and si oh 4 at salinity 32 33 1 the concentration of dop 0 76 0 27 mol p l 1 was also 2 times higher in this layer compared to the surface average and inversely correlated with the water mass tracer n n no3 16 po43 2 9 0 87 suggesting that pacific derived waters were a source of the enrichment below the mixed layer don was generally constant with depth although averaged profiles like those of urea suggested the presence of subsurface maxima at 50 m and between 250 and 300 m regeneration ratios varied with depth and were approximately 9 0 mol o2 mol no3 and 122 5 mol o2 mol po43 in shallow pacific derived waters halocline layer and 17 4 and 193 5 in deep atlantic waters atlantic layer respectively deep waters of the amundsen gulf contained an excess of 1 7 mol no3 l 1 0 12 mol po43 l 1 and 6 2 mol si oh 4 l 1 and a deficit in o2 relative to waters of similar density in the beaufort sea in proportions consistent with the remineralization ratios derived from oxygen nutrient regressions enhanced export of particulate matter from the overlying polynya and subsequent remineralization at depth are hypothesized to create this nutrient enrichment

spontaneous combustion of the upper paleocene cerrejon formation coal and generation of clinker in la guajira peninsula caribbean region of colombia abstract clinker referred here as red and brick looking burnt rocks found interbedded in the upper paleocene cerrejon formation is the result of spontaneous and natural combustion of coal seams in the recent geologic past these rocks have been mapped measured and characterized in the cerrejon coal mine at la guajira peninsula colombia these burnt rocks usually outcrop in irregular patterns as almost tabular bodies up to 100 m thick thinning and pinching out below ground surface to depths up to 448 m mapping revealed that clinker is usually found near deformed zones either faults or tight folds timing of spontaneous combustion seems to predate folding and faulting but seems to postdate the development of the cerrejon thrust fault and alluvial fan proceeding from the perija range clinker covers an area of around 2 9 10 6 m 2 with a volume of approximately 1 4 10 8 m 3 the calculation of the amount of heat released through coal burning indicates that complete combustion of 6 4 mt of 26 4 10 6 j kg coal would yield 17 10 13 j

surface freshening of the canada basin 2003 2007 river runoff versus sea ice meltwater 1 the extent of summer arctic sea ice has reduced dramatically in recent years and simultaneously we have observed surface freshening over the canada basin in 2006 and 2007 in order to identify the source of this fresh water either meteoric or sea ice meltwater salinity 18o and alkalinity were analyzed results show that sea ice meltwater increased in the surface water over the central part of the basin in 2006 and 2007 corresponding to the melting of an additional 2 7 m 1 3 m a 1 of sea ice anomalously fresh surface water observed in the southern part in 2007 however was mostly attributed to mackenzie river water extending into the basin interior a source that was mainly absent in the early 2000s comparison with previous data shows that the meltwater component of surface water in the southern part of the canada basin has progressively increased at a mean rate of 0 27 m a 1 since 1987 this can be explained by a reduction of winter sea ice formation rate by 0 45 m or more during the past two decades the runoff component showed larger variability in the southern basin but no obvious temporal trend in the central basin the river runoff component showed an increasing trend of 0 7 m a 1

field impressed anisotropies of magnetic susceptibility and remanence in minerals the application of alternating af or direct df magnetic fields to samples containing dispersed particles of magnetite titanomagnetite or maghemite has been found to alter significantly the measured low field susceptibility anisotropy even though the particle orientation is unchanged the acquisition of isothermal remanent magnetization irm is also strongly dependent on the previous af treatment given to the samples a method of quantifying the changes brought about by application of the fields is described the samples studied were intrinsically isotropic or only weakly anisotropic and the computed impressed susceptibility or irm ellipsoids produced by the applied fields were ellipsoids of revolution with the unique axis aligned with the applied field axis the size and shape of the field impressed ellipsoids were strongly dependent upon particle size these effects might thus form the basis of a rapid nondestructive means of estimating particle size in rocks the results also have important implications for magnetic fabric analysis and the static af demagnetization of rocks in particular to ensure that the intrinsic magnetic fabric is measured without any field impressed component of anisotropy samples should not be subjected to static af demagnetization prior to the determination of either low field susceptibility anisotropy or irm anisotropy samples should also not carry a significant remanence such as an irm acquired in a field greater than about 5 mt prior to low field susceptibility anisotropy analysis

sea ice sediment entrainment and rafting in the arctic abstract large areas of first year sea ice containing disseminated loads of silt and clay sized materials are common off the northern coast of alaska sand and coaser material is also found in this ice in the form of distinct masses of sediment laden ice sediment is entrained into the sea ice cover during fall storms when frazil or small discs of ice in suspension is actively forming in the supercooled water column at this time sea ice is unconsolidated and very mobile making long range ice rafting possible sediment rich ice may be advected off the shelf and upon melting deposit material in the deep arctic basin the amount of sediment incorporated into the ice cover varies considerably from year to year depending on the location and severity of storms accompanying freezeup in 1978 the seasonal ice cover in an area off northern alaska carried 16 times as much sediment as the total annual suspended sediment input from adjacent coastal rivers sea ice sediment transport is important in the overall sediment budget in northern polar regions particularly the transport of fine grained material but entrainment mechanisms are poorly understood

sediment transport by sea ice in the chukchi and beaufort seas increasing importance due to changing ice conditions abstract sediment laden sea ice is widespread over the shallow wide siberian arctic shelves with off shelf export from the laptev and east siberian seas contributing substantially to the arctic ocean s sediment budget by contrast the north american shelves owing to their narrow width and greater water depths have not been deemed as important for basin wide sediment transport by sea ice observations over the chukchi and beaufort shelves in 2001 02 revealed the widespread occurrence of sediment laden ice over an area of more than 100 000 km2 between 68 and 74 n and 155 and 170 w ice stratigraphic studies indicate that sediment inclusions were associated with entrainment of frazil ice into deformed multiple layers of rafted nilas indicative of a flaw lead environment adjacent to the landfast ice of the chukchi and beaufort seas this is corroborated by buoy trajectories and satellite imagery indicating entrainment in a coastal polynya in the eastern chukchi sea in february of 2002 as well as formation of sediment laden ice along the beaufort sea coast as far eastward as the mackenzie shelf moored upward looking sonar on the mackenzie shelf provides further insight into the ice growth and deformation regime governing sediment entrainment analysis of radarsat synthetic aperture sar imagery in conjunction with bathymetric data help constrain the water depth of sediment resuspension and subsequent ice entrainment 20 m for the chukchi sea sediment loads averaged at 128 t km 2 with sediment occurring in layers of roughly 0 5 m thickness mostly in the lower ice layers the total amount of sediment transported by sea ice mostly out of the narrow zone between the landfast ice edge and waters too deep for resuspension and entrainment is at minimum 4 106 t in the sampling area and is estimated at 5 8 106 t over the entire chukchi and beaufort shelves in 2001 02 representing a significant term in the sediment budget of the western arctic ocean recent changes in the chukchi and beaufort sea ice regimes reduced summer minimum ice extent ice thinning reduction in multi year ice extent altered drift paths and mid winter landfast ice break out events have likely resulted in an increase of sediment laden ice in the area apart from contributing substantially to along and across shelf particulate flow an increase in the amount of dirty ice significantly impacts sub ice algal production and may enhance the dispersal of pollutants

characterization of the magnetic fabric of rocks abstract an inextensive system of magnetic susceptibility anisotropy factors is suggested which is sufficient in the majority of practical applications for characterizing the magnetic fabric of rocks the system involves three newly devised factors the corrected anisotropy degree the shape factor and the difference shape factor the first of these characterizes the quantity of anisotropy somewhat better than the commonly used anisotropy degree the shape factor characterizes the quality of anisotropy i e the shape of the susceptibility ellipsoid in a convenient way its definition is based on a certain analogy between the anisotropy ellipsoid and the strain ellipsoid the difference shape factor can replace the shape factor when only the differences between the principal susceptibilities are given while the mean susceptibility is unknown

sources of sediment found in sea ice from the western arctic ocean new insights into processes of entrainment and drift patterns 1 the geochemical fingerprint of entrained fe oxide mineral grains in arctic ocean sea ice is used to determine precise sources of this sediment this approach substantiates the importance of the laptev sea as a source of sea ice and even the presence of russian ice in the beaufort sea off alaska fe oxide grains from the laptev sea were found in floes in the beaufort sea chukchi borderland and central arctic ocean demonstrating the importance of sea ice in distributing itself throughout the arctic ocean and the potential of transporting sediment from russian rivers to north american shelves banks island shelf is the most important source of sediment sampled from ice floes in the beaufort sea northern chukchi sea and chukchi borderland area although most of the entrained sediment fits the criteria for suspension freezing in shallow water the presence of winter polynyas with offshore winds and not the size of shallow areas appears to be the critical factor for sea ice entrainment seven of the 18 ice floes sampled contained fe oxide grains from more than one source area the two most common sources that are found in the same ice floes are banks island and the laptev sea multiple sources in ice floes suggest that either mingling of fragmented ice floes occurs or that a source area containing grains from both these sources has yet to be located the addition of fine sand sized windblown sediment is not thought to be significant

a description of water types on the mackenzie shelf of the beaufort sea during winter for a number of years during the 1980s observations of the physical and chemical properties of seawater in the southeastern beaufort sea have been acquired in late winter the most complete data set from 1987 has been used in a comparison of winter and summer macdonald et al 1989 water properties in the area most obvious is an increase in the salinity of surface waters in winter the magnitude of this increase varies dramatically from year to year part of the increase is a consequence of brine rejection during the growth of sea ice and part is associated with an intrusion over the shelf of a water mass of high nutrient and low oxygen concentrations which is a feature of the entire western arctic ocean principal component analysis was used to allow all five chemical tracers to be combined and viewed simultaneously the properties of the upper 120 m are found to lie to a close approximation on a plane this leads us to a simple interpretation based on a three component mixing model involving river runoff water from the nutrient maximum and an offshore near surface component it is shown that the best fit plane occupied by arctic surface waters in the beaufort sea closely matches that defined by the influences of river inflow of the freeze melt cycle and of photosynthesis and respiration however the effects of freezing melting and of river inflow cannot be clearly distinguished using the chosen suite of tracers it has been determined that if the waters of the upper 250 m are to be represented in the same manner a fourth end member is required

geologic history of natural coal bed fires powder river basin usa abstract coal bed fires ignited by natural processes have baked and fused overlying sediments to form clinker a hard red or varicolored rock through much of the northern great plains of the united states usa the gently dipping coal beds in the region burn when regional downwasting brings them above the local water table the resulting clinker forms a rim along the exposed edge of the coal bed in an ongoing process through geologic time the resistant clinker is left capping buttes and ridges after the softer unbaked strata erode away clinker outcrops cover more than 4100 km2 in the powder river basin prb which lies in wyoming wy and montana mt the clinker in place records tens of billions of tons of coal that have burned releasing gases into the atmosphere the amount of clinker that has eroded away was at least an order of magnitude greater than the clinker that remains in place fission track and uranium thorium helium ages of detrital zircon crystals in clinker and paleomagnetic ages of clinker show that coal beds have burned naturally during at least the past 4 million years ma the oldest in place clinker that has been dated collected from a high isolated clinker capped ridge has a fission track age of 2 8 0 6 ma evidence of erosion and downcutting is also preserved by clinker clasts in gravel terraces one clinker boulder in a terrace 360 m above the yellowstone river has a fission track age of 4 0 0 7 ma coal bed fires are caused by lightning wildfires spontaneous combustion or human activity on coal outcrops and in mines miners government agencies and ranchers have extinguished thousands of coal bed fires but natural ignition continues where fresh coal has access to air at any given time hundreds of fires mostly small are burning in the powder river basin the total amount of coal burned by natural fires in the last 2 ma is one to two orders of magnitude greater than the total amount of coal removed by mining in the past century however current annual rates of coal mining are three to four orders of magnitude greater than estimated prehistoric annual rates of coal consumption by natural fires

physical and geochemical properties across the atlantic pacific water mass front in the southern canadian basin temperature salinity nutrients oxygen and halocarbon data collected in the arctic ocean reveal a frontal structure previously unrecognized in the hydrography of the canadian basin samples were collected on a 1300 km section extending from the beaufort sea in the canada basin to the east siberian sea in the makarov basin these data collected in 1993 aboard the ccgs henry larsen reveal a lateral boundary between water masses of atlantic and pacific origin the term water mass assembly is introduced to describe the basic arrangement or vertical stacking of water masses found in the arctic ocean recognizing that water mass components within each assembly may differ from basin to basin using historical data two primary water mass assemblies are defined each consisting of three layers an upper layer an atlantic layer and a deep layer these two assemblies are marked by important differences one assembly here defined as the western arctic wa assembly is characterized by an upper layer of relatively fresh high nutrient water of pacific origin below this by an atlantic layer with a core temperature generally below 0 5 c and finally by a deep layer of higher salinities and colder temperatures about 0 5 c than found in the overlying atlantic layer the second assembly here defined as eastern arctic ea assembly is characterized by the absence of pacific water in the upper layer below this by an atlantic layer core as warm as 2 to 3 c and by a colder about 0 9 c deep layer because the presence or absence of pacific origin water is a key characteristic distinguishing the two assemblies we will refer to the water mass boundary between the two assemblies as the atlantic pacific front earlier research indicated that water masses in the arctic ocean were separated by a front above the lomonosov ridge into the canadian and eurasian basins although all larsen 93 stations from the canada basin a1 d1 display classic wa assembly characteristics the makarov basin station e1 shows ea assembly characteristics in the upper and atlantic layers and a wa assembly deep layer this suggests a relocation in the position of the atlantic pacific boundary away from the lomonosov ridge further larsen 93 data show the transition region between the atlantic and deep layers is fresher in the makarov basin than corresponding water in either the canada or eurasian basins implying a source of cold low salinity water perhaps from the laptev and east siberian shelves the front separating these two assemblies lies above the mendeleyev ridge and is marked by large lateral gradients in all measured properties in particular the penetration of anthropogenic halocarbons is 2 to 3 times deeper in the makarov basin than in the canada basin implying enhanced rates of ventilation this suggests that direct exchange between the canadian and eurasian basins has occurred recently near the perimeter and that physical and chemical properties including contaminants may have been transported by boundary currents more quickly from one basin to the other

partial anhysteretic remanence and its anisotropy applications and grainsize dependence the distribution of remanence coercivities in a rock sample can be obtained by differentiating alternating field af demagnetization curves of anhysteretic remanent magnetization arm however significant errors can be introduced by grain interactions and by the noise inherent in differentiation we have found that 1 this error can be significantly reduced by measuring partial arm s parm s and 2 parm patterns show a strong empirical correlation with grain size parm s are imparted by exposing a sample to a small direct magnetic field in the presence of a large decreasing af the direct field is switched on over a specified range of af s thus magnetizing a fraction of the magnetite grains in the corresponding coercivity range we have further found in both synthetic and natural sediments that measurement of the anisotropy of parm enables us to detect the preferred orientations of distinct subpopulations of magnetite particles related to the size and shape of the grains

susceptibility to spontaneous combustion of indian coals and lignites an organic petrographic autopsy abstract a critical analysis of various genetic and physical factors associated with certain early and late permian and oligocene coal seams and early eocene lignite seams of india revealed that the high secondary porosity and small particle size irrespective of petrographic and rank properties in sub humid climate favour spontaneous combustion large particle size high rates of gas emission and highly wet or dry seams in combination with each other tend to inhibit spontaneous heating in sub humid per humid and semi arid conditions the susceptibility to auto ignition of a coal or lignite seam is not uniform throughout its lateral extent and a high inherent porosity at any given rank stage and a high content of susceptible or oxidizable constituents are not sufficient to cause auto ignition however coal seams having high contents of exceedingly porous inertinite macerals become prone to spontaneous combustion in sub humid climate even without secondary porosity a scheme for indexing spontaneous combustion susceptibility based on the present study has been proposed which is particularly suited to the indian context

magnetic mineralogy of some granites from the french massif central origin of their low field susceptibility abstract with a view to a better understanding of the origin of the low field susceptibility in the variscan granitoids of the french massif central for which extensive structural mapping using the anisotropy of magnetic susceptibility ams technique is currently applied a detailed study of magnetic carriers has been undertaken origin of the susceptibility has been studied using high field and low temperature measurements in a cryogenic magnetometer together with standard rock magnetic techniques additional determinations of the opaque phases have been performed with the metallographic microscope x ray microdiffraction and electron microprobe techniques in almost all the granite types the magnetic susceptibility is essentially carried by the paramagnetic biotite crystals minor amounts of ubiquitous oxides ilmenite rutile titano haematite do not contribute significantly to the susceptibility this is also the case for rare occurrences of magnetite in some granitoids mainly the cordierite bearing anatexites sulphides are found to give a large contribution magnetic mineralogy identifies a mixture of ferromagnetic pyrrhotite and antiferromagnetic fe9s10 hexagonal pyrrhotite hpo the latter species is identified as forming the larger unaltered pyrrhotite grains the ferromagnetic pyrrhotite is identified to be mainly smythite fe9s11 a species formed by supergenic alteration of monoclinic pyrrhotite located along the basal cleavage planes the microfractures and the grain boundaries of the hpo this study which constitutes the first report of the magnetic properties of smythite in rocks indicates that magnetic carriers derived from low temperature alteration have to be taken into account for purposes of structural studies using ams

anchor ice seabed freezing and sediment dynamics in shallow arctic seas diving investigations confirm previous circumstantial evidence of seafloor freezing and anchor ice accretion during freeze up storms in the alaskan beaufort sea these related bottom types were found to be continuous from shore to 2 m depth and spotty to 4 5 m depth spotty anchor ice occurred as pillow shaped crystal aggregates on buried slabs of frozen sand surrounded by unfrozen sand considerations of required conditions for ice bonding and anchor ice growth allows regional extrapolation and suggests the possibility of anchor ice growth out to 20 m depth the estimated maximum depth of supercooling during fall storms anchor ice and seabed freezing apparently do not develop during a calm freeze up because of the abrupt growth of anchor ice during a freezing storm and its release soon after formation of a surface ice cover this ice type has not been documented before the concretelike nature of frozen bottom where present should prohibit sediment transport by any conceivable wave or current regime during the freezing storm but elsewhere particularly where the bonded crust is broken by grounded ice anchor ice lifts coarse material off the bottom and incorporates it into the ice canopy thereby leading to significant ice rafting of shallow shelf sediment and likely sediment loss to the deep sea

the distribution of aluminium in the greenland sea and its relationship to ventilation processes during two cruises to the greenland sea in 1988 and 1989 a total of 690 on board aluminium al determinations were performed on samples collected from profiles located along four transects in the greenland sea as part of the greenland sea project al concentrations range from extremely low values 0 4 nm in the polar waters of the east greenland current draining the arctic ocean to 17 9 nm in the newly formed norwegian sea deep water nsdw at the periphery of the greenland gyre the al content in the component water masses serves to constrain the make up of these water masses from the various mixing products of the region the enrichment of al in the nsdw both at its site of formation within the greenland sea up to 17 9 nm and in the lofoten basin of the norwegian sea up to 40 3 nm leads to the conclusion that there must be an additional external source of al to these water masses the apparent inability of water column or sedimentary diagenetic processes to provide this enrichment and the observation of enriched al values associated with a high salinity shelf brine leads us to the conclusion that these brines may be responsible for the observed enrichments the high concentration of al in the greenland sea deep water compared with the water masses that produce it suggests that al may be acting as an inverse tracer of the processes that ventilate this basin by convective overturn i e the al concentration which increases with time as a result of continuous brine or other external inputs is reduced during convective events it is also argued that this flushing of elevated al water during convective events may have a similar counterpart in the iceland sea and that this mechanism could go some way toward solving the al deficit that exists between the enriched north atlantic deep water and its depleted precursor water masses observed in the intermediate waters of the greenland and iceland seas

rock magnetic properties of trm carrying baked and molten rocks straddling burnt coal seams the subsurface spontaneous combustion of coal seams in xinjiang nw china during pleistocene to recent times produced large areas of thermally altered sedimentary rocks with large magnetic moments the natural remanent magnetization nrm and thermoremanent magnetization trm intensities and low field susceptibilities of such combustion metamorphic rocks range from 0 1 to 10 a m and 100 10 4 to 1000 10 4 si respectively which is two to three orders of magnitude higher than values typical of their sedimentary protoliths the dominant magnetic carriers in the burnt rocks appear to include relatively pure forms of magnetite maghemite and hematite as well as more complex spinel phases these magnetic phases mainly occur as fine pseudo single domain psd particles conspicuous is the presence of pure metallic iron fe in some samples this highly magnetic phase is inferred to appear as more or less elongated super paramagnetic and single domain sd inclusions in host silicate phases which prevent them from oxidizing the sd fe particles can carry a highly stable remanence having remanent coercivities ranging 70 140 mt the arm and irm stability of all burnt rock samples to alternating fields is shown to be relatively high median destructive fields b 1 2 a and b 1 2 i respectively range of 25 46 and 20 30 mt for dominant spinel bearing samples 34 36 and 47 53 mt for maghemite hematite bearing samples and 48 89 and 64 84 mt for metallic iron bearing samples consequently burnt rocks are high quality geomagnetic field recorders their very nature makes them useful for paleointensity determinations although age determination is a limiting factor furthermore remanence intensities and susceptibilities of these magnetically enhanced rocks are sufficient to produce observable magnetic anomalies this property illustrates the potential to delineate the areal extent and depth of extinct coal fires with magnetic exploration such information is necessary to refine estimates of hazardous co 2 emission and furthers our understanding of natural coal fires 2001 elsevier science b v all rights reserved

dissolved aluminium in the mediterranean abstract three vertical profiles of dissolved al and nutrients are reported from the eastern basin of the mediterranean profiles of al concentrations resemble those of the nutrient elements except that a proportionally higher residual concentration remains in the surface layer concentrations of al in the surface water inflow from the north atlantic which contains between 10 and 20 nm around gibraltar are elevated to 55 59 and 75 nm at the stations occupied calculations indicate that these concentrations are probably produced by dissolution al from aeolian dust and advective mixing of al rich deep waters into the surface layer balanced by a biologically associated removal process the al removed from the surface layer redissolves in the deep water to raise al concentrations to about 160 nm samples were also recovered from anoxic deep brines in the tyro and bannock basins in the brines al concentrations fall to about 15 nm while si concentrations approach 270 nm

modern dirty sea ice characteristics and sources the role of anchor ice extensive dirty ice patches with up to 7 kg m 2 sediment concentrations in layers of up to 10 cm thickness were encountered in 2005 and 2007 in numerous areas across the central arctic the fe grai

distribution of aluminium in waters of the north east atlantic 25 n to 35 n abstract dissolved al concentrations from the ne atlantic between 25 n and 35 n off the coast of nw africa range from 16 nm to 32 nm in a well mixed surface layer extending to 150 m depth increasing towards the maximum of the saharan dust plume mediterranean outflow water is detected as a high al anomaly corresponding to the salinity signal of the mediterranean water other than in surface and mediterranean waters al concentrations are invariant with depth but increase from 6 nm to 11 nm towards the continental margin the magnitude of the dissolved al signal in the surface layer is compatible with dissolution of al from the highest of present estimates of dust input to this area comparison with data from other areas indicates that al cannot be cycled through the oceans in parallel to silica as has been previously suggested

the esmolfe matanca granite penalva do castelo central portugal a keystone to understand the ascent and emplacement of magmas under low tectonic stress abstract the esmolfe matanca ilmenite type granite is analyzed using petrography microstructures anisotropy of magnetic susceptibility and microfracturing the granite occurs in two separated bodies outcropping in distinct villages esmolfe and matanca which are located in the termination of the juzbado penalva do castelo jpcsz and durico beirao dbsz shear zones the petrography shows a progressive textural overprint from magmatic through high medium and low t solid state deformation microstructures the presence of dominantly magmatic microstructures and the absence of deformation patterns at macroscopic scale may indicate an emplacement under low tectonic stress the directional magnetic data indicates a magma ascending and emplacement conditioned by the jpcsz and dbsz the magma passive intruded upwards along the confluence zone between the jpcsz and dbsz and it spread laterally forming an asymmetric laccolithic body the dbsz worked as physical barrier in esmolfe avoiding the spreading of the magma to the north leading to the rotation of the magnetic lineations and foliations drawing onion type trajectories in matanca the magnetic lineations and foliations are dominantly nw se oriented in the western side and ene wsw oriented in the eastern side parallel to the jpcsz regional trend the fluid inclusions planes demonstrated three distinct brittle deformational events linked to the rotation of 1

environmental characterization of burnt coal gangue banks at yangquan shanxi province china the environmental characteristics of coal gangue dumps in yangquan shanxi province china were investigated the amounts of coal gangue are very high in this coal region given the large coal production as a result widespread spontaneous coal gangue combustion gives rise to serious environmental problems coal gangue including bulk gangue and specific lithologies such as coal kaolinite rich material sandstone carbonate minerals and sulfide mineralizations fired coal gangue and condensate products from gas vents were fully characterized with respect to mineralogy chemistry and leaching potential the mineral paragenesis of the fired coal gangue cristobalite mullite hematite trydimite cordierite showed that the combustion temperature could reach 1200 c this was also corroborated by laboratory calcination tests during this combustion some elements such as c cl f s n as cd hg pb sn ge and se are emitted into the atmosphere however condensation processes accounted for the partial trapping of gaseous emissions of as s n hg and se thus condensate mineralizations of elemental sulfur and ammonium salts enriched in se as and other trace elements are frequent in the gas vents the leaching potential of trace elements in the fresh coal gangue was relatively low but the leaching of weathered coal gangue and the gas vents condensates could give rise to environmental problems as these materials produce acidic leachates and yield relatively high leachable levels of a number of elements

the distribution of dissolved and total dissolvable aluminum in the beaufort sea and canada basin region of the arctic ocean 1 vertical profiles of the concentrations of dissolved al d al and total dissolvable al t al are reported from a transect extending from the continental shelf of the beaufort sea into the canada basin in the arctic ocean sampling was performed in late summer and early autumn 2007 a year of historically extensive sea ice melt vertical profiles of d al displayed surface maxima 1 3 nmol kg 1 subsurface minima 300 m depth suggest that al is likely lost through particle scavenging in the interior of the canada basin concentrations of t al show that particulate al 0 2 m is the dominant form of al in the water column except at greater depths at the most offshore stations lateral transport of d al and t al off the shelf likely results from the offshore progression of cyclonic eddies spawned inshore oscillating upwelling and downwelling favorable winds and brine rejection during sea ice formation that can drive currents sufficiently energetic to resuspend shelf sediments

dust deposition to the surface waters of the western and central north pacific inferred from surface water dissolved aluminum concentrations 1 dissolved al was determined on similar to 3500 surface water samples collected in the nw pacific during the 2002 intergovernmental oceanographic commission ioc contaminant baseline survey in addition dissolved al was determined on samples collected at 9 vertical stations occupied along the cruise track surface water al distributions when converted to annual mineral dust deposition measures and brown 1996 imply extremely low depositions mean values 0 3 g m 2 yr 1 to surface waters of the subarctic gyre despite the atmospheric transport of large amounts of mineral dust across this region from the desert regions of china the calculated deposition values are also much lower than the 1 10 g m 2 yr 1 predicted for this region by the gesamp model duce et al 1991 the lowest mineral dust depositions correspond to the high nutrient low chlorophyll hnlc region of the nw pacific which implies that the biogeochemical status of this region is the result of low atmospheric micronutrient input similar to other hnlc regions in the subtropical gyre the al derived dust deposition mean values 0 1 0 6 g m 2 yr 1 agrees well with the 1 g m 2 yr 1 predictions of the gesamp model enriched concentrations of dissolved al in the coastal waters near kauai from fluvial sources indicate the potential role of remote high islands in adding reactive trace elements to the nearby surface waters in the vertical profiles elevated dissolved al concentrations 4 8 nm were found to correspond to the potential density of the western pacific subtropical mode waters which form in the recirculation zone of the kuroshio

the canada basin 1989 1995 upstream events and far field effects of the barents sea 1 the effects of upstream events on southern canada basin waters were examined using physical and geochemical data collected at one location between 1989 and 1995 these events included atlantic layer warming relocation of the atlantic pacific water mass boundary and increased ventilation of boundary current waters early signals of change in the canada basin first appeared in 1993 along the continental margin and by 1995 were evident in the basin interior and farther downstream differences in physical and geochemical properties nutrients oxygen 129i and cfcs were observed between 150 and 1600 m of the water column by 1995 the boundary between pacific and atlantic origin water was shallower and atlantic origin water occupied more of the canada basin water column atlantic origin lower halocline water was colder and more ventilated fram strait branch water was colder fresher and more ventilated and barents sea branch water was warmer fresher more ventilated and occupied a larger volume of the water column than in previous years water mass analysis showed that the composition of atlantic origin water in the canada basin in 1995 included 20 more water from the barents sea two related events upstream appear to be the source of this change an atmospheric regime shift in 1989 that increased cyclonic circulation a transition unprecedented within the latter half of the 20th century in magnitude geographic reach and apparent oceanographic impacts and a large volume of dense water flowed from the barents sea to the arctic ocean between 1988 and 1989 these two phenomena illustrate the close relationship between atmospheric and oceanic events whose combined influence was evident 6 years later and 5100 km downstream in the canada basin at depths 1000 m

oceanographic distributions of zinc cadmium copper and aluminium in waters of the central arctic vertical profiles are presented of dissolved cadmium zinc copper and aluminium at the lorex 79 site in the central arctic ocean cd zn and cu show unusually high surface concentrations of 0 3 3 and 5 nmoll 1 respectively these levels are related to contributions from surface run off and from the underlying nutrient rich bering sea winter water al has lower surface concentrations than observed elsewhere and shows no correlation with the nutrients the importance of aeolian supply is questioned and the results point to a major role for inorganic removal of al at least in the arctic ocean

magnetic anisotropy of some phyllosilicates magnetic susceptibility anisotropy of susceptibility and hysteresis of single microcrystals of chlorite biotite phlogopite muscovite zinnwaldite and fuchsite were measured in low and high magnetic fields with an alternating gradient force magnetometer micromag their properties are sufficient to account for the low field susceptibility ams of most micaceous rocks nearly all samples show some ferromagnetic contribution at low fields due to inclusions of pseudosingle domain and multidomain magnetite the paramagnetic contribution isolated at high fields usually exceeds the ferromagnetic contribution the paramagnetic susceptibility is intrinsic to the silicate lattice and agrees with values predicted from chemical composition within the limits of error the minimum susceptibility is nearly parallel to c another axis is parallel to b and the third susceptibility usually the maximum is close to a the paramagnetic susceptibility has a disk shaped magnitude ellipsoid with strong anisotropy p 2 the ferromagnetic contributions at low fields have more variably shaped ellipsoids with greater eccentricity p 5 the silicate lattice does not constrain their orientation our technique cannot determine the principal axes of the ferromagnetic component however its principal values usually correspond with the paramagnetic principal susceptibilities in order of magnitude thus the combined paramagnetic ferromagnetic anisotropy recognised in routine studies of ams should faithfully represent the petrofabric of most micaceous rocks nevertheless nearly 10 of our samples have incompatible anisotropy ellipsoids for the silicate host and magnetite inclusions these yield a net inverse ams that does not correctly represent the orientation of the silicate lattice therefore some caution is necessary in petrofabric ams studies of micaceous rocks

looking back at the centralia coal fire a synopsis of its present status abstract centralia is in the anthracite region of eastern pennsylvania the town is part of the western middle field a large synclinorium in columbia and schuylkill counties residents of centralia set fire to a garbage dump in 1962 and in the process ignited the buck mountain coal bed fractured and moderately dipping strata at the site permitted air to circulate into the subsurface thereby promoting combustion and making it difficult to extinguish the centralia fire as the fire advanced during the 1960s 1970s and early 1980s it did so along four fronts however the fire appears to be advancing on only two fronts today the pennsylvania department of environmental protection is currently monitoring the fire fire associated with the first or cemetery front is advancing approximately 20 m year although attempts were made to fight the fire they were unsuccessful for logistical and monetary reasons most residents of centralia relocated with the assistance of funds approved by the u s congress and disbursed by the state of pennsylvania the inexperience of community leaders in working with state bureaucracy contributed to the difficulties of fighting the fire

quantification of illite content in sedimentary rocks using magnetic susceptibility a rapid complement or alternative to x ray diffraction abstract the paramagnetic clay mineral illite can have important controls on fluid permeability and microporosity in sedimentary rocks increases in illite content of a few percent can reduce permeability by several orders of magnitude traditional x ray diffraction xrd techniques for quantifying illite content can be very time consuming requiring significant sample preparation and generally examine only a relatively small sample volume in contrast a technique based on magnetic susceptibility described here is very rapid cheap sensitive nondestructive and requires no extra preparation of the sample it is representative of a much larger sample volume and in the present paper utilizes standard 1 inch diameter cylindrical core plugs but it can be applied to other sample shapes and volumes the magnetic susceptibility derived estimates of illite content from core plugs correspond well with xrd results from small powdered samples of the same material in terms of both absolute values and overall trends with depth however neither the magnetic method nor xrd should be regarded as definitive each technique has merits and limitations and these help to explain some observed differences in the illite determinations by each method xrd may underestimate the illite content particularly in muddy rocks whereas the magnetic method theoretically provides an upper limit for the illite content the magnetic method is also capable of simultaneously estimating the quartz content in the present samples changes in the concentration and distribution of illite during core cleaning or core flooding experiments can also be potentially quantified by the magnetic technique the development of portable field sensors potentially allows the magnetic method to provide high resolution illite profiles on slabbed cores outcrops and unconsolidated samples without the need to cut core plugs the method could also be applied to whole core measurements and to downhole magnetic susceptibility data the processing of the magnetic susceptibility signal can also be extended to quantify other minerals in simple systems

magnetic fabrics in the western central pyrenees an overview abstract in the western central pyrenees numerous investigations during the past years have yielded an exceptional high density of localities more than 700 sites where the ams and rock magnetic properties have been determined this unique ams dataset helps in understanding the orogenic evolution of the pyrenees and its foreland basins processes related to ams development in different structural units permit to identify i an early recording of strain related to the transtensional or transpressional stages during the early triassic and early cretaceous ii a moderate shortening related to the fold and thrust belt and foreland basin evolution during the cretaceous tertiary orogenic stage and iii a relatively strong deformation that produced cleavage related to the emplacement of basement thrusts in the axial zone during the middle late eocene the main achievement of this contribution is the integration in cross section and map view of magnetic fabrics orientation and parameters in the western central pyrenees which allow constraining the processes affecting magnetic fabrics at the orogen scale ams results indicate i a dominant bedding controlled foliation very sensitive to subtle layer parallel shortening lps processes especially in the foreland basins ii magnetic lineations parallel to fold axes or strike of thrusts outside the cleavage front that can be deflected by vertical axis rotations in particular areas and iii an overall decrease of the definition of ams fabrics magnetic lineation or the anisotropy of the ellipsoid associated with incipient cleavage and intersection lineation fabrics in the internal zones of the orogen therefore ams is a sensitive indicator to delineate the strain patterns at the orogen scale in particular in those areas undergoing a modest degree of deformation

differentiating fluvial components of upper canada basin waters on the basis of measurements of dissolved barium combined with other physical and chemical tracers 1 the utility of dissolved barium ba as a quasi conservative tracer of arctic water masses has been demonstrated previously here we report distributions of salinity temperature and ba in the upper 200 m of the canada basin and adjacent areas observed during cruises conducted in 2003 2004 as part of the joint western arctic climate study and beaufort gyre exploration project a salinity oxygen isotope mass balance is used to calculate the relative contributions from sea ice melt meteoric and saline end members and ba measurements are incorporated to resolve the meteoric fraction into separate contributions from north american and eurasian sources of runoff large fractions of eurasian runoff as high as 15 5 were observed in the surface layer throughout the canada basin but significant amounts of north american runoff in the surface layer were only observed at the southernmost station occupied in the canada basin in 2004 nearest to the mouth of the mackenzie river smaller contributions from both eurasian and north american runoff were evident in the summer and winter pacific derived water masses that comprise the underlying upper halocline layer in the canada basin significant amounts of eurasian and north american runoff were observed throughout the water column at a station occupied in amundsen gulf in 2004 this suggests the export of runoff from both sources through the passages of the canadian arctic archipelago

reliability of magnetic fabric of weakly deformed mudrocks as a palaeostress indicator in compressive settings abstract in this work we compare the results of anisotropy of magnetic susceptibility ams with palaeostress analysis at local scale the ams data refer to 14 sites from weakly deformed mudrocks lower and middle miocene lacustrine sediments from two areas of the internal part of the ebro foreland basin the bardenas reales and monegros areas nine sites display a magnetic fabric related to a subtle tectonic overprint showing a roughly e w magnetic lineation whereas the rest of sites most of them located at the monegros area show a sedimentary fabric without a well defined magnetic lineation palaeostress data result from fault populations and joint sets exposed in the limestone beds interbedded with the mudrocks at the nearest possible outcrop from the ams site the origin of the magnetic lineation is related to a n s compression coeval with the earliest diagenesis of the studied sediments prior to consolidation the comparison between magnetic fabric and palaeostress data demonstrates the coaxiality between the ams and palaeostress ellipsoids both at local and regional scales thereby validating the reliability of ams as palaeostress indicator in compressive settings

gravimetric and magnetic fabric study of the sintra igneous complex laccolith plug emplacement in the western iberian passive margin the geometry and emplacement of the 96 km2 late cretaceous sintra igneous complex sic ca 80 ma into the west iberian passive margin is presented based on structural data gravimetric modeling and magnetic fabrics a granite laccolith 76 km2 1 km thick according to gravimetric modeling surrounds a suite of gabbro diorite syenite plugs 20 km2 4 km deep and is encircled by cone sheets and radial dykes anisotropy of magnetic susceptibility was interpreted from 54 sites showing fabrics of para and ferro magnetic origin most fabrics can be interpreted to have a magmatic origin according to the scarcity of solid state deformation in most part of the massif magnetic foliations are shallowly dipping in the granite laccolith and contain a sub horizontal ene wsw lineation the gabbro syenite body displays concentric magnetic foliations having variable dips and steeply plunging lineations the sic can be interpreted to be intruded along an nnw sse 200 km long fault perpendicular to the magnetic lineation within the laccolith and was preceded by the intrusion of basic sills and plugs the sic intruded the mesozoic series of the lusitanian basin during the post rift passive margin stage and its geometry was only slightly modified during the paleogene inversion that resulted in thrusting of the northern border of the intrusion over the country rocks

dissolved aluminium in the southern ocean dissolved aluminium al occurs in a wide range of concentrations in the world oceans the concentrations of al in the southern ocean are among the lowest ever observed an all titanium ctd sampling system makes it possible to study complete deep ocean sections of al and other trace elements with the same high vertical resolution of 24 depths as normal for traditional ctd rosette sampling overall 470 new data points of al are reported for 22 full depth stations and 24 surface sampling positions along one transect this transect consisted of 18 stations on the zero meridian proper from 51 degrees 57 s until 69 degrees 24 s and 4 stations somewhat to the northeast towards cape town from 42 degrees 20 s 09 degrees e to 50 degrees 17 s 01 degrees 27 e the actual concentrations of al in the southern ocean were lower than previously reported the concentration of al in the upper 25 m was relatively elevated with an average concentration of 0 71 nm n 22 s d 0 43 nm most likely due to atmospheric input by a suggested combination of direct atmospheric wet and dry input and indirect atmospheric input via melting sea ice below the surface waters there was a distinct al minimum with an average concentration of 0 33 nm n 22 s d 0 13 nm at an average depth of 120 m in the deep southern most weddell basin the concentration of al increased with depth to similar to 0 8 nm at 4000 m and a higher concentration of similar to 1 5 nm in the similar to 4500 5200 m deep weddell sea bottom water over the bouvet triple junction region where three deep ocean ridges meet the concentration of al increased to similar to 1 4 nm at about 2000 m depth over the ridge crest in the deep basin north of the bouvet region the concentration of al increased to higher deep values of 4 6 nm due to influence of north atlantic deep water in general the intermediate and deep distribution of al results from the mixing of water masses with different origins the formation of deep water and additional input from sedimentary sources at sea floor elevations no significant correlation between al and silicate si was observed this is in contrast to some other ocean regions in the southern ocean the supply of al is extremely low and any signal from al uptake and dissolution with biogenic silica is undetectable against the high dissolved si and low dissolved al concentrations here the al si relation in the deep ocean is uncoupled this is due to the scavenging and subsequent loss of the water column of al whereas the concentration of si increases in the deep ocean due to its input from deep dissolution of biogenic diatom frustules settling from the surface layer c 2011 elsevier ltd all rights reserved

disentangling magnetic subfabrics and their link to deformation processes in cleaved sedimentary rocks from the internal sierras west central pyrenees spain abstract here we present a detailed study of the magnetic fabrics and subfabrics of remagnetized upper cretaceous limolites that crop out in the internal sierras west central pyrenees affected by a penetrative pressure solution cleavage the bulk magnetic fabrics of these rocks rt ams show variable orientations that do not conform to what is typically reported for cleaved sedimentary rocks in contrast the paramagnetic subfabrics lt ams show remarkably constant directional properties so that their k max and k min axes cluster parallel to the intersection lineation and to the poles to bedding respectively these lt ams subfabrics indicate a preferred orientation of phyllosillicates that is consistent with a syn sedimentary late cretaceous period of nne oriented layer parallel shortening noticeably these phyllosillicate subfabrics are not further altered by the subsequent formation of cleavage in the late eocene early oligocene the ferrimagnetic subfabrics aarm also show remarkably constant orientation so that their k max axes are strikingly parallel to the shortening direction in the area we interpret this preferred orientation of ferrimagnetic grains as being caused by subhorizontal shear associated to cleavage formation which is consistent with the age and mechanisms authigenic growth and rotation of pre existing magnetite grains proposed for the pervasive remagnetization that affects the studied rocks

circulation of summer pacific halocline water in the arctic ocean 1 we present an analysis of arctic ocean hydrographic and sea ice observations from the 1990s with a focus on the circulation of water that originates in the north pacific ocean previous studies have shown the presence of two varieties of relatively warm summer halocline water in the vicinity of the chukchi sea i e the relatively fresh alaskan coastal water acw and the relatively saltier summer bering sea water sbsw here we extend these studies by tracing the circulation of these waters downstream into the arctic ocean we find that acw is generally most evident in the southern beaufort gyre while sbsw is strongest in the northern portion of the beaufort gyre and along the transpolar drift stream we find that this separation is most extreme during the early mid 1990s when the arctic oscillation was at historically high index values this leads us to speculate that the outflow to the north atlantic ocean through the canadian archipelago and fram strait may be similarly separated as arctic oscillation index values fell during the later 1990s acw and sbsw began to overlap in their regions of influence these changes are evident in the area north of ellesmere island where the influence of sbsw is highly correlated with a 3 year lag with the arctic oscillation index we also note the presence of winter bering sea water wbsw which underlies the summer varieties all together this brings the number of distinct pacific water types in our arctic ocean inventory to three acw sbsw and wbsw

time dependent irm a new technique for magnetic granulometry the intensities of isothermal remanent magnetizations irm acquired in 0 01 s and 10 s can differ by more than an order of magnitude depending on field strength and sample composition for 15 samples containing magnetite titanomagnetite maghemite hematite or pyrrhotite of distinct grain sizes ranging from superparamagnetic sp over stable single domain ssd to multidomain md behavior the irm acquisition has been meas ured for the two time constants in addition the viscous decay following irm acquisition within 2000 s has been determined in low fields 10 mt the irm 10s irm 0 01s ratios range from 1 03 for md grains up to 20 for sp ssd grains for fields larger than the coercivity of remanence the irm ratio approaches unity for all samples viscous decay after irm acquisition is for samples containing sp grains much larger than for ssd and md grains as well hence a viscous decay parameter sd irmto irmt log t to normalized by the saturation remanence can serve as an alternative to the frequency dependence of susceptibility the commonly used proxy for sp grains in feet it may be more sensitive because remanences cannot be masked by para or diamagnetic contributions and irms can well be measured on weakly magnetic sediments

combustion metamorphism of bituminous sediments and the formation of melts of granitic and sedimentary composition during combustion metamorphism i e the heating of sediments rich in organic matter by spontaneous subsurface combustion temperatures obtained are frequently high enough to cause partial or total melting of the original rocks these melts are of particular geochemical interest because at lower temperatures their composition closely simulates that of granitic and at higher temperatures that of common sedimentary rocks at the california localities studied here the parent rocks are mainly bituminous mudstones with smaller amounts of diatomites and phosphorites and lesser dolomites limestones shales and cherts it is estimated that rock melting started below 1000 c the first partial melts correspond to a melt fraction of about 5 have a constant composition which is controlled by the eutectic of the dominant mudstones and are undistinguishable in major and trace element composition from common s type granites compared with the original rocks these melts are enriched in sio2 al2o3 k2o na2o as well as in ta hf zr th and ree and are depleted in all other elements studied the only difference between these low temperature melts and granitic ones is their oxygen isotope composition which is that of the sedimentary parent rocks these melts intruded the country rocks as sills and dikes and cooled to glassy rocks simulating obsidians as temperatures rose the melts changed composition and left the magmatic field at the highest temperatures in excess of 1650 c their composition equals that of the original sediments from which they are derived except for volatile components such as h2o and co2 these melts formed intrusive bodies mainly stocks up to several kilometers across on cooling these melts formed fine grained but holocrystalline rocks the dominant minerals of which are cristobalite and tridymite calcic plagioclase cordierite wollastonite gehlenite andradite and apatite where the parent rocks included phosphorites two immiscible melts formed an emulsion in which droplets of apatitic composition are surrounded by a silicate melt almost devoid of p2o5

rock magnetism of late neogene and pleistocene deep sea sediments relationship to sediment source diagenetic processes and sediment lithology we use bivariate scatter plots to illustrate variations in selected rock magnetic properties low field susceptibility anhysteretic and isothermal remanence of late neogene and pleistocene deep sea sediments from 16 sites in the arctic ocean north atlantic equatorial atlantic and north pacific ocean and the arabian sea our intention is to examine the ability of the rock magnetic properties to differentiate the sediments according to factors such as lithology geographical area and the dominant mode of terrigenous sedimentation which at these sites is via ice rafting via bottom currents or via eolian processes overall correlations between sediment magnetic properties and gross lithology is poor and factors such as the source and transport path of terrigenous sediment and detrital magnetic minerals together with the action of reductive diagenetic processes are the major controls on the magnetic properties on the bivariate scatter plots sites with major ice rafted contributions tend to have high sedimentary ferrimagnetic mineral concentrations relatively coarse ferrimagnetic grain sizes and scattered sample point distributions in contrast sites where we infer significant bottom current supply of terrigenous material have tightly grouped sample point distributions carbonate sediments in which the terrigenous component is supplied by eolian processes tend to have a broad range of magnetic mineral concentration caused by glacial interglacial fluctuations in carbonate accumulation and eolian activity sediments containing significant volcanogenic material have high concentrations of relatively coarse grained ferrimagnetic material reductive diagenesis is a significant determinant of sediment magnetic properties in high productivity areas and has the effect of preferentially removing the fine grained ferrimagnetic fraction causing a coarsening of the ferrimagnetic grain size distribution and a rise in the antiferromagnetic ferrimagnetic ratio

eddy maintenance and attrition in a vertically sheared current under arctic ice abstract steady drift of an ice cover produces a vertically sheared current in the upper ocean of the arctic under the ice cover mesoscale shallow brine and freshening sources generate submerged anticyclones and cyclones respectively a submerged eddy extending deep into the water column experiences differential advections by the vertically sheared current interaction between subsurface eddies and the sheared current is examined using a three dimensional numerical model in a coordinate system moving with the ice the initial salinity field is in geostrophic balance with the sheared current and a pulse of brine or freshening forcing produces an anticyclone or a cyclone in a coordinate system moving with the ice eddies are in a vertically sheared backward ambient current to an observer looking into the direction of the backward ambient current eddies move with the current and deflect to the right left for counterclockwise clockwise rotating eddies in both hemispheres the lower half of the eddy

silicate versus trace mineral susceptibility in metamorphic rocks rates of change of magnetic susceptibility during leaching can characterize the presence of certain common types of magnetic minerals in metamorphic rocks in this study the results of leaching are confirmed by mineral separation optical microscopy scanning electron microscopy sem and microchemical analysis under sem leaching curves provide a simple rapid way of determining the relative roles of oxides sulfides and silicates in carrying the susceptibility in metamorphic rocks

kugmallit valley as a conduit for cross shelf exchange on the mackenzie shelf in the beaufort sea 1 kugmallit valley spans the midsection of a transect across the mackenzie shelf of the beaufort sea its greatest relief is 20 m and its width is 20 km using a yearlong record of ice drift ocean current temperature and salinity acquired near the center of the valley we describe a pattern of flow that is correlated with wind stress and ice motion and discuss its similarity to flow within larger submarine canyons that cut through the shelf break as in such canyons there is enhanced cross shelf transport within kugmallit valley during upwelling favorable surface stress the data also document the down valley flow of dense water from a flaw lead

quantitative considerations of dissolved barium as a tracer in the arctic ocean 1 dissolved barium ba was measured along transects across fram and denmark straits as part of the 1998 ark xiv 2 polarstern expedition results are combined with other available tracer observations to analyze water mass composition at fram strait a combination of pacific water and eurasian river runoff dominated 80 and 10 of the total mass respectively the upper east greenland current egc while the remainder of the section was dominated by north atlantic water a much smaller contribution of pacific water to the egc 50 at fram strait in 1987 suggests that this component can be quite variable in time north american river water was not detectable at fram strait in 1998 presumably the eurasian river water we observed at fram strait transited eastward along shelf within the arctic mixed with pacific water in the vicinity of the east siberian sea and was borne by the transpolar drift across the arctic ocean in the absence of significant net ice formation along the way such a pathway can be expected to produce more pronounced freshening of the egc than when eurasian river water mixes more directly off shelf into salty atlantic waters and pacific water is diverted largely through the canadian archipelago existing measurements at the main arctic gateways were used to construct a ba budget for the arctic ocean under conditions of simultaneous mass heat and salt conservation this preliminary budget is statistically consistent with the steady state hypothesis on the arctic basin scale ba appears to be conservative

barium as a tracer of arctic halocline and river waters dissolved barium ba concentrations are reported for water samples collected during six oceanographic cruises to the arctic in 1993 and during the 1994 arctic ocean section upper arctic 75 nmol ba 1 1 observed in the surface mixed layer of the arctic interior i e beyond the 200 m isobath occurred in the canada basin as a result of the biological removal of ba from surface waters of the chukchi sea and the tendency of the bering inflow to enter the arctic interior at depths below the relatively fresher mixed layer we hypothesize that the mackenzie river is the dominant source of the high ba observed in the surface waters of the canada basin features characterized by local salinity minima and ba maxima in surface waters down to depths of 30 50 m were observed over the arlis plateau and mendeleyev ridge in both 1993 and 1994 and over the makarov basin and lomonosov ridge in 1994 the physical and chemical properties of these waters suggest that they have been significantly influenced by fluvial discharge it could not be determined from available data whether these features arose from offshore transport of eurasian river discharge from the russian arctic seas meanders of the mackenzie river influenced beaufort gyre or a branch of bering inflow that crossed the chukchi shelf and entrained river water from north american and or eurasian sources in both 1993 and 1994 ba concentrations in the upper halocline layer as defined by a core salinity of 33 1 ranged between 42 and 77 nmol ba 1 1 with highest values observed in the canada basin the ba maximum and the related nutrient maxima and oxygen minimum that characterize the upper halocline in the canada basin suggest sources in the chukchi and beaufort seas and that the mechanism by which these waters are formed is linked with the influx of water through the bering strait the ba distributions for 1993 and 1994 delineate the lateral extent of upper halocline waters with canada basin character and show them to be chemically distinct from upper halocline waters in the eurasian basin the front separating these water types ran roughly along the mendeleyev and alpha ridges consistent with reports that the boundary between atlantic and pacific water mass assemblies in the arctic has recently been displaced from its historical position over the lomonosov ridge lateral gradients in both ba and the no parameter were observed within the lower halocline layer defined by an no minimum and core salinity of 34 2 34 4 along the 1994 arctic ocean section indicating that lower halocline waters receive additional inputs as they transit to the canadian basin from their region of formation in the eurasian sector of the arctic

analysis of the ferromagnetic contribution to the susceptibility by low field and high field methods in sedimentary rocks of the southern pyrenees and northern ebro foreland basin spain magnetic susceptibility in rocks is the sum of the contributions of different magnetic particles paramagnetic diamagnetic and ferromagnetic s l these contributions can be measured at variable temperatures or at variable fields hysteresis loops both are time consuming techniques that cannot be routinely used in magnetic fabrics analysis in this study we propose a simplified method to determine the ferro and paramagnetic contributions to the susceptibility based on the discrete measurement of susceptibility at two different fields near 0 and 2 5 t the results obtained in samples from the southern pyrenees and ebro basin indicate that the ferromagnetic contribution vary considerably within homogeneous susceptibility values and within the expected range of paramagnetic values standard bulk susceptibilities higher than 200 10 6 si contribute significantly to the ferromagnetic fraction 50 on average

composition and mode of occurrence of mineral matter in some colombian coals abstract the minerals in a range of colombian coal samples selected to represent the principal coal mining regions have been investigated using low temperature ashing and quantitative x ray diffraction techniques and the results compared to information from chemical analysis and mossbauer spectroscopy studies kaolinite illite interstratified illite smectite and quartz are the dominant mineral matter components in almost all of the coal samples with small but significant proportions of pyrite up to around 15 of the mineral matter being present in around half of the samples studied other minerals present in particular samples include chlorite muscovite paragonite ankerite dolomite calcite and siderite along with phosphate minerals apatite and goyazite jarosite and coquimbite are also noted in some of the pyrite bearing coals probably representing oxidation products of the pyrite developed with exposure or storage bassanite is present in the low temperature ash of some coals and in one sample occurs along with significant concentrations of hexahydrite alunogen tschermigite and paraluminite all of which were probably derived from interaction of inorganic elements in the organic matter with organic sulphur during maceral oxidation quantitative analysis of the minerals in the low temperature ash of the coal samples using rietveld based x ray diffraction techniques provides results that are consistent at least for the most abundant elements with the chemical composition of the coal ash as determined by standard analysis procedures the evaluation of mineral rich concentrates by mossbauer spectroscopy also provides results consistent with the xrd data especially as regards pyrite and some of the sulphate components optical microscopy indicates that much of the pyrite and in some cases also the carbonates occurs as anhedral crystals finely disseminated in the maceral components as aggregates of crystals including pyrite framboids as fine grained crystals replacing liptinite and as fracture fillings some sub angular to rounded quartz grains are also present possibly of detrital origin but most other minerals including the clay minerals occur mainly as aggregates of intimately admixed mineral and maceral constituents

biogeochemical evolution of cryoconite holes on canada glacier taylor valley antarctica 1 the cryoconite holes of the mcmurdo dry valleys are simple closed biogeochemical systems involving water ice mineral and organic debris which serve as ecosystems for consortia of microorganisms this study is the first to document the seasonal and annual chemical evolution of solutes in cryoconite holes samples of glacier ice frozen cryoconite holes and those containing water were collected during the austral summer of 2005 2006 the isolation age was calculated from the excess cl in the holes and varied from 0 to 5 years a consistent with the last hot summer when the cryoconite holes were open to the atmosphere the holes progressively deepen with isolation age variations in dic doc k and so42 suggest that dissolution of primary minerals in the cryoconite debris cyclical precipitation and dissolution of secondary carbonates net photosynthesis over summer and net respiration during the autumnal freeze are the principal reactions which perturb the seasonal and annual solute concentrations in the holes doc is generated in the holes at a rate of 7 5 g c cm 2 a 1 and non sea salt k accumulates in frozen holes at a rate of 0 073 eq cm 2 a 1 we infer that c cycling is complex even in these otherwise simple systems

a high resolution record of the matuyama brunhes transition from the mediterranean region the valle di manche section calabria southern italy abstract high resolution palaeomagnetic and rock magnetic investigations on the valle di manche section crotone basin calabria southern italy provide a detailed record of the matuyama brunhes m b reversal that to our best knowledge is the only available record of the last geomagnetic reversal for the mediterranean on land marine stratigraphy the m b transition can be pinpointed precisely as it develops within a 3 cm thick interval located just above a prominent tephra layer the pitagora ash where the sedimentation rates are about 27 cm kyr demagnetization analyses indicate a stable palaeomagnetic behaviour throughout the section for both normal and reversed polarity directions with demagnetization vectors aligned toward the origin of zijderveld diagrams after the removal of a small viscous low coercivity remanence component in the lower part of the studied interval some samples acquired a spurious gyromagnetic remanent magnetization grm during af demagnetization in high fields rock magnetic analyses confirm that magnetite is the main magnetic carrier for all measured specimens which also have an abundant paramagnetic fraction only the lower part of the record well below the m b boundary is characterized by a downward increasing presence of iron sulphides greigite according to our chronology which is based on a robust cross validated age model the final reverse to normal directional change of the m b transition occurred at ca 786 9 5 ka error includes uncertainty in orbital tuning and was very rapid of the order of 100 years or less

the role of dust deposition in determining surface water distributions of al and fe in the south west atlantic abstract underway dissolved al and fe determinations were made on surface water samples collected between 34 s and 8 n in the southern and tropical atlantic ocean using a towed surface water sampler the general distribution of dissolved al which ranged from 8 nm in the sub tropical gyre to 61 nm under the intertropical convergence zone itcz north of the equator corresponds clearly with atmospheric dust deposition patterns a striking correlation between al and surface water salinities between 28 s and 8 n further indicates that wet deposition is the predominant mechanism of delivery of this atmospheric source iron concentrations in contrast were more uniform varying between 0 6 and 0 8 nm south of the equator highest fe values up to 1 4 nm also were found associated with the maximum dust inputs at the itcz indicating an atmospheric source for this element whose input appears to be limited by the solubility of fe in sea water the lowest fe values 0 4 nm also were observed in the equatorial region and are assumed to result from the biological removal of fe from nutrient rich water masses originating in the nearby equatorial and coastal upwelling regions the high frequency data acquisition of the towed sampler revealed significant variations up to 50 in both al and fe concentrations over short distances most notably along the interface between the south equatorial and canary currents the high variability of a biologically important trace element such as fe in these dynamic regions is indicative of the interplay between chemical and biological patchiness in surface waters

dissolved iron in the arctic shelf seas and surface waters of the central arctic ocean impact of arctic river water and ice melt key points dfe in the arctic shelves and surface is linked to freshwater and alkalinity fluvial input main contributor to high dfe low alkalinity in central arctic remineralisation and biological depletion determine dfe in the arctic shelf seas abstract concentrations of dissolved 10 nm in the bottom waters of the laptev sea shelf may be attributed to either sediment resuspension sinking of brine or regeneration of dfe in the lower layers a significant correlation r2 0 60 between salinity and dfe is observed using 18o salinity nutrients and total alkalinity data the main source for the high 2 nm dfe concentrations in the amundsen and makarov basins is identified as eurasian river water transported with the transpolar drift tpd on the north american side of the tpd the dfe concentrations are low 4 above the shelf and low 4 off the shelf

seasonal variability of water mass distribution in the southeastern beaufort sea determined by total alkalinity and δ18o 1 we examined the seasonal variability of water mass distributions in the southeastern beaufort sea from data collected between september 2003 and august 2004 salinity total alkalinity ta and isotopic composition 18o of seawater were used together as tracers of freshwater input i e meteoric water and sea ice meltwater we used an optimum multiparameter analysis to identify the different water masses including the mackenzie river sea ice melt sim winter polar mixed layer pml upper halocline water uhw with core salinity of 33 1 psu pacific origin and atlantic water computed values of co2 fugacity in seawater fco2 sw show that the surface mixed layer sml remains mostly undersaturated 328 55 atm n 552 with respect to the average atmospheric co2 concentration 380 5 atm over the study period the influence of the mackenzie river fco2 sw 500 atm was relatively small in the southeastern beaufort sea and significant fractions were only observed on the inner mackenzie shelf the contribution of sea ice melt fco2 sw 600 atm was usually located between 120 and 180 m depth but could contribute to the sml during wind driven upwelling events in summer and autumn and during brine driven eddies in winter

identification of multicomponent anisotropies in rocks using various field and temperature values in a cryogenic magnetometer abstract a new technique involving magnetization measurements on a rotating sample in a cryogenic magnetometer with variable field from 0 to 4 t and variable temperature is presented it can be used to separate and identify multi component anisotropy in rocks the results obtained for anisotropy due to magnetite haematite pyrrhotite or phyllosilicates are interpreted according to different magnetization models

calibration and application of marine sedimentary physical properties using a multi sensor core logger abstract we examined geophysical data from a multi sensor core logger mscl a logging device providing continuous measurements of gamma ray attenuation p wave travel time and magnetic susceptibility on marine sediment cores in the first part we focused on the gamma ray system and compared two different calibration methods from the gamma ray attenuation we calculated densities and porosities by incorporating mass weighted attenuation coefficients the application of an iteration method reduces the error of the density and porosity estimates compared to grape data in addition we derived equations to calculate water content and dry bulk density from gamma ray attenuation measurements comparison with physical properties determined on discrete samples revealed a very good correlation of both data sets r 0 99 this correlation is valid for sediments from substantially different geological settings e g turbidites hemipelagic muds and opal rich sediments in the second part we applied our data to marine geological questions for sediments from the antarctic polar frontal zone there is indication that the content of biogenic opal can be assessed using a correlation of density and p wave velocity for sediments from the bengal fan the relationship between the mscl acoustic impedance the product of density and p wave velocity and the grain size distribution in discrete samples can be used to predict clay and sand silt ratios for sediment cores from the shelf and upper continental slope

trace element emissions from spontaneous combustion of gob piles in coal mines shanxi china the emissions of potentially hazardous trace elements from spontaneous combustion of gob piles from coal mining in shanxi province china have been studied more than ninety samples of solid waste from gob piles in shanxi were collected and the contents of twenty potentially hazardous trace elements be f v cr mn co ni cu zn as se mo cd sn sb hg tl pb th and u in these samples were determined trace element contents in solid waste samples showed wide ranges as compared with the upper continental crust the solid waste samples are significantly enriched in se 20x and tl 12x and are moderately enriched in f as mo sn sb hg th and u 2 5x the solid waste samples are depleted in v cr mn co ni cu and zn the solid waste samples are enriched in f v mn cr co ni cu zn sb th and u as compared with the shanxi coals most trace elements are higher in the clinker than in the unburnt solid waste except f sn and hg trace element abundances are related to the ash content and composition of the samples the content of f is negatively correlated with the ash content while pb is positively correlated with the ash the concentrations of as mn zn and cd are highly positively correlated with fe2o3 in the solid waste the as content increases with increasing sulfur content in the solid waste the trace element emissions are calculated for mass balance the emission factors of trace elements during the spontaneous combustion of the gobs are determined and the trace element concentrations in the flue gas from the spontaneous combustion of solid waste are calculated more than a half of f se hg and pb are released to the atmosphere during spontaneous combustion some trace element concentrations in flue gas are higher than the national emission standards thus gob piles from coal mining pose a serious environmental problem

age characteristics of a shelf break eddy in the western arctic and implications for shelf basin exchange 1 radioisotope evaluation of a cold core anticyclonic eddy surveyed in september 2004 on the chukchi sea continental slope was used to determine its age since formation over the shelf environment because the eddy can be shown to have been generated near the shelf break initial conditions for several age dependent tracers could be relatively well constrained a combination of 228ra 226ra excess 224ra and 228th 228ra suggested an age on the order of months this age is consistent with the presence of elevated concentrations of nutrients organic carbon suspended particles and shelf derived neritic zooplankton within the eddy compared to ambient offshore water in the canada basin but comparable to values measured in the chukchi shelf and shelf break environment hence this feature at the edge of the deep basin was poised to deliver biogeochemically significant shelf material to the central arctic ocean

mineralogy and geochemistry of boehmite rich coals new insights from the haerwusu surface mine jungar coalfield inner mongolia china abstract boehmite rich coal of pennsylvanian age was discovered earlier at the heidaigou surface mine jungar coalfield inner mongolia china this paper reports new results on 29 bench samples of the no 6 coal from a drill core from the adjacent haerwusu surface mine and provides new insights into the origin of the minerals and elements present the results show that the proportion of inertinite in the no 6 coal is higher than in other late paleozoic coals in northern china based on mineral proportions boehmite to kaolinite ratio and major element concentrations in the coal benches of the drill core the no 6 coal may be divided into five sections i to v major minerals in sections i and v are kaolinite sections ii and iv are mainly kaolinite with a trace of boehmite and section iii is high in boehmite the boehmite is derived from bauxite in the weathered surface benxi formation in the sediment source region the no 6 coal is rich in al2o3 8 89 tio2 0 47 li 116 g g f 286 g g ga 18 g g se 6 1 g g sr 350 g g zr 268 g g rees 172 g g pb 30 g g and th 17 g g the elements are classified into five associations by cluster analysis i e groups a b c d and e group a ash sio2 al2o3 na2o li and group b ree sc in y k2o rb zr hf cs u p2o5 sr ba ge are strongly correlated with ash yield and mainly have an inorganic affinity the elements that are negatively or less strongly correlated with ash yield with exceptions of fe2o3 be v and ni are grouped in the remaining three associations group c se pb hg th tio2 bi nb ta cd sn group d co mo tl be ni sb mgo re ga w zn v cr f cu and group e s as cao mno fe2o3 aluminum is mainly distributed in boehmite followed by kaolinite the high correlation coefficients of the li ash li al2o3 and li sio2 pairs indicate that li is related to the aluminosilicates in the coal the boehmite rich coal is high in gallium and f which occur in boehmite and the organic matter selenium and pb are mainly in epigenetic clausthalite fillings in fractures the abundant rare earth elements in the coal benches were supplied from two sources the bauxite on the weathered surface of the benxi formation and from adjacent partings by groundwater leaching during diagenesis the light rare earth elements lrees are more easily leached from the partings and incorporated into the organic matter than the heavy rees leading to a higher ratio of lrees to hrees in the coal benches than in the overlying partings