broadband records of earthquakes in deep gold mines and a comparison with results from safod california for one week during september 2007 we deployed a temporary network of field recorders and accelerometers at four sites within two deep seismically active mines the ground motion data recorded at 200 samples sec are well suited to de termining source and ground motion parameters for the mining induced earthquakes within and adjacent to our network four earthquakes with magnitudes close to 2 were recorded with high signal noise at all four sites analysis of seismic moments and peak velocities in conjunction with the results of laboratory stick slip friction experi ments were used to estimate source processes that are key to understanding source physics and to assessing underground seismic hazard the maximum displacements on the rupture surfaces can be estimated from the parameter rv where v is the peak ground velocity at a given recording site and r is the hypocentral distance for each earthquake the maximum slip and seismic moment can be combined with results from laboratory friction experiments to estimate the maximum slip rate within the rupture zone analysis of the four m 2 earthquakes recorded during our deployment and one of special interest recorded by the in mine seismic network in 2004 revealed maxi mum slips ranging from 4 to 27 mm and maximum slip rates from 1 1 to 6 3 m sec applying the same analyses to an m 2 1 earthquakewithin a cluster of repeating earth quakes near the san andreas fault observatory at depth site california yielded similar results for maximum slip and slip rate 14 mm and 4 0 m sec

derivation of δ18o from sediment core log data implications for millennial scale climate change in the labrador sea sediment core logs from six sediment cores in the labrador sea show millennial scale climate variability during the last glacial by recording all heinrich events and several major dansgaard oeschger cycles the same millennial scale climate change is documented for surface water 18o records of neogloboquadrina pachyderma left coiled hence the surface water 18o record can be derived from sediment core logging by means of multiple linear regression providing a paleoclimate proxy record at very high temporal resolution 70 years for the labrador sea sediment core logs contain important information about deepwater current velocities and also reflect the variable input of ice rafted debris from different sources as inferred from grain size analysis the relation of density and p wave velocity and magnetic susceptibility for the last glacial faster deepwater currents which correspond to highs in sediment physical properties occurred during iceberg discharge and lasted from several centuries to a few millennia those enhanced currents might have contributed to increased production of intermediate waters during times of reduced production of north atlantic deep water hudson strait might have acted as a major supplier of detrital carbonate only during lowered sea level greater ice extent during coldest atmospheric temperatures over greenland deepwater currents increased during iceberg discharge in the labrador sea then surface water freshened shortly thereafter while the abrupt atmospheric temperature rise happened after a larger time lag of 1 kyr the correlation implies a strong link and common forcing for atmosphere sea surface and deep water during the last glacial at millennial timescales but decoupling at orbital timescales

the influence of shelf crossing glaciation on continental slope sedimentation flemish pass eastern canadian continental margin abstract flemish pass is a small perched slope basin seaward of the grand banks on the eastern canadian continental margin glacial ice crossed the grand banks to reach the upper continental slope during some mid to late quaternary glaciations but terminated on the middle shelf 200 km distant at the last glacial maximum this study investigates the effect of ice extent on slope sedimentation processes sediment in flemish pass comprises muds of hemipelagic and proglacial plume origin minor thin bedded turbidite sands and thick bedded mass transport deposits mtds a regional stratigraphy based on 500 km of high resolution seismic profiles and 60 piston cores up to 11 m long was dated using 30 radiocarbon dates the presence of ash zone ii and oxygen isotope stratigraphy this provided stratigraphic control for till tongues in water depths

the quaternary lancaster sound trough mouth fan nw baffin bay the development of the lancaster sound trough mouth fan tmf and glacial history in arctic canada were studied using a high resolution seismic profile across the entire fan and two piston cores stacked tills separated by erosion surfaces on the shelf pass seaward through till deltas into thick transparent glacigenic debris flow gdf deposits on the slope separated by thin well stratified glaciomarine layers an age model was built by ties to the ocean drilling program site 645 the deepest gdf on the seismic profile was indicative of the onset of shelf crossing glaciation in the early pleistocene the transition of the growth of lancaster sound tmf from an aggradational sequence unit m to an aggradational progradational sequence unit f occurred at the middle pleistocene transition in glacial cyclicity in the most recent glacial cycle gdf sheets were deposited during heinrich events 4 and 2 according to the correlation of the main detrital carbonate beds in two piston cores the outmost till wedge reflects the maximum advance of the grounding glacier far seaward of previously proposed last glacial maximum ice extent copyright 2011 john wiley sons ltd

variations in the provenance of sediment from ice sheets surrounding baffin bay during mis 2 and 3 and export to the labrador shelf sea site hu2008029 0008 davis strait based on quantitative x ray diffraction mineralogical analysis of cores hu2008029 0006 0008 857 m water depth located south of the davis strait sill we seek answers to two questions i the temporal correlation of nw labrador shelf sea heinrich h and baffin bay detrital carbonate bbdc events and ii the provenance of the sediments a sediment unmixing model sedunmix is used to determine provenance variations although 12 radiocarbon dates were obtained there were many age reversals and we favour a depth age model for hu2008029 0008pc based on correlations to well dated neighbouring cores north and south of davis strait we find no correlation between h and bbdc events except for h 0 which appears to be a broadly synchronous event along the ne canadian margin and is correlative with an episode of major moraine building along this flank of the laurentide ice sheet unmixing of the sediment composition based on six potential glacial source regions indicates that the bulk of the sediment in 0008pc is derived from glacial erosion of west greenland but is punctuated by intervals when dolomite rich sediments derived from outcrops north of baffin bay dominate the composition estimated dates on these bbdc events are 13 25 and 30 38 cal ka bp copyright 2013 john wiley sons ltd

relationships between gas geochemistry and release rates and the geomechanical state of igneous rock massifs in contrast to sedimentary sequences the relationships between the stressed state of igneous rocks and the chemistry and physical properties of gases contained within them are not well known here we attempt to fill this gap by using as an example the apatite nepheline and rare metal ore deposits hosted within the khibiny and lovozero alkaline nepheline syenite complexes of the kola peninsula nw russia these massifs are characterized by unusually high for igneous rocks contents of multi component essentially hydrogen hydrocarbon gases and also by high hardness elasticity and unevenly distributed subhorizontal tectonic stresses relationships between the chemical and dynamic characteristics of the gases and the geomechanical properties of the host rocks have been examined using field observations and laboratory experiments patterns of gas release variations in time and space gas emissions from rock pillars during artificial loading variations of gas pressure in sealed shot holes and changes in liberation rates of gaseous components during experimental rock loading are suggested to result from changes in rock stress and deformation state gas compositions in sealed shot holes in stressed rocks change with time partly this is due to belated release of gases held in fluid inclusions and isolated voids and their subsequent mixing with gases held in interconnected fracture systems as the included gases are preferentially released as fluid inclusion arrays are opened during later stages of stress build up partly it may also be because released gases may react with new fracture surfaces to generate enhanced levels of reduced h2 gases

structural mineralogical and petrophysical effects on deep crustal rocks of fluid limited polymetamorphism western gneiss region norway the proterozoic banded granulite facies complex of bardsholmen western gneiss region norway t 815 845 c was locally transformed to eclogite t 455 510 c p 12 kbar and amphibolite facies rocks t 460 c during the caledonian continental collision the granulite complex consists of mafic two pyroxene granulite and leucocratic orthopyroxene garnet bearing layers alternating on a scale from 1 cm to 10 m the granulite facies rocks change to eclogite facies rocks over centimetre scale distances along well defined fluid infiltration fronts the mafic granulite was transformed to omphacite garnet rich eclogites and the leucocratic rocks were converted to quartz phengite rich assemblages with minor garnet and local omphacite melange like lithologies consisting of mafic lenses of eclogite surrounded by felsic material represent an advanced stage in the process of converting deep crust to eclogite facies during amphibolitization this melange like lithology evolves to a rock where amphibolite lenses and layers are surrounded by granitoid gneiss a lithology typical of the western gneiss region the bardsholmen locality illustrates the profound control exerted by fluids on the timing of metamorphism the structural make up and petrophysical properties such as density and rheology of crustal root zones fluid induced metamorphism will therefore exert control on the attributes of orogenic belts such as topography and moho depth and influence the dynamics of collision zones by controlling the time of orogenic collapse and the buoyancy of the subducted crust we suggest that orogens may develop differently depending on the fluid budget

u th ages obtained by mass spectrometry in corals from barbados sea level during the past 130 000 years the study of the sea level record during the last glacial cycle has primarily proceeded indirectly by means of oxygen isotope measurements on foraminifera from deep sea sediments1 2 the direct approach of dating sea level indicators stagnated during the past decade mainly because the samples required to complete our knowledge of the past glaciations are below the present day sea level3 7 using the 14c ages of acropora palmata samples collected by drilling offshore the island of barbados fairbanks8 presented the first detailed chronology for the last deglaciation this radiocarbon chronology is limited to the past 30 kyr because of the short half life of 14c 5 730 yr we must therefore rely on other dating methods to obtain information for the whole last glacial cycle during the past four years 230th 234u dating of corals by thermal ionization mass spectrometry has been shown to be significantly more precise and accurate than the classical counting method9 14 we have used this technique to measure u th ages in coral samples from the barbados collection and from subaerially exposed outcrops see also ref 15 here we present results bearing on the sea level record for the past 130 000 years we conclude that the last deglaciation started 3 000 years earlier than previously thought and confirm that there were two surges in melt water8 at about 11 kyr and 14 kyr bp before present

quaternary sedimentary processes and budgets in orphan basin southwestern labrador sea abstract the continental slope in orphan basin northeast of newfoundland is underlain by several seaward thinning debris flow wedges alternating with acoustically stratified regionally extensive mainly hemipelagic sediments 18o stratigraphy and volcanic ash layers in a 11 67 m core indicate that the uppermost debris flow wedge formed during the last of several sea level lowstands in isotopic stages 2 4 similarly seismic reflection correlation of dated levels at dsdp site 111 with the orphan basin succession suggests that two deeper debris flow wedges were deposited during oxygen isotopic stages 6 and 8 the oldest of the debris flow deposits in at least three of the wedges formed well into the corresponding glacial cycle after ice sheets had reached the edge of the continental shelf slower deposition by hemipelagic processes and ice rafting formed the acoustically stratified units including heinrich layers the youngest three debris flow wedges each have volumes of 1300 1650 km3 approximately two thirds of this material is attributed to glacial erosion of mesozoic and tertiary strata beneath the northeast newfoundland shelf the remainder is believed to have been derived by glacial erosion of older bedrock that now forms the island of newfoundland the observed sediment volumes and the inferred basal and upper ages of the debris flow wedges imply an average glacial denudation rate of about 0 13 mm yr for this older bedrock and an average of about 60 m of glacial bedrock erosion since oxygen isotope stage 22 this denudation rate is similar to estimates from the barents sea region off norway

clay mineral signature of the nw atlantic boundary undercurrent abstract surface sediments were sampled along 2 transects across the iceland and irminger basins and in the labrador sea clay mineral assemblages deduced from x ray analyses of the carbonate free

origin and spatial distribution of gas at seismogenic depths of the san andreas fault from drill mud gas analysis abstract data are presented on the molecular composition of drill mud gas from the lower sedimentary section 1800 3987 m of the safod san andreas fault observatory at depth main hole measured on line during drilling as well as c and h isotope data from off line mud gas samples hydrocarbons h 2 and co 2 are the most abundant non atmospheric gases in drill mud when drilling seismogenic zones gas influx into the well at depth is related to the lithology and permeability of the drilled strata larger formation gas influx was detected when drilling through organic rich shales and permeable sandstones the saf san andreas fault encountered between approximately 3100 m and 3450 m borehole depth is generally low in gas but is encompassed by two gas rich zones 2700 2900 m and below 3550 m at the fault margins with enhanced 222 rn activities and distinct gas compositions within the fault two interstratified gas rich lenses 3150 3200 m and 3310 3340 m consist of co 2 and hydrocarbons upper zone but almost exclusively of hydrocarbons lower zone the isotopic composition indicates an organic source of hydrocarbons and co 2 in the entire sedimentary section of the well hydrocarbons in sedimentary strata are partly of microbial origin down to 2500 m borehole depth the contribution of thermogenic gas increases between 2500 m and 3200 m below 3200 m hydrocarbons fully derive from thermal degradation of organic matter the lack of h 2 in the center of the fault and the high concentration of h 2 in the fractured zones at the fault margins are consistent with h 2 formation by interaction of water with fresh silica mineral surfaces generated by tectonic activities however this needs to be verified by laboratory experiments based on these studies it is concluded that the fault zone margins consist of strata with enhanced permeability separated by a low permeability fault center

late quaternary stratigraphy and sedimentology of orphan basin implications for meltwater dispersal in the southern labrador sea abstract orphan basin is a deep water basin on the continental margin off newfoundland which throughout the late quaternary received proglacial sediment from local ice that crossed the continental shelf sediment from more distant sources was transported southward in the labrador current as proglacial plumes and in icebergs five sedimentary facies related to glacial processes are distinguished in cores recovered from orphan basin hemipelagic sediment nepheloid layer deposits layered mud beds rich in ice rafted detritus ird sand and mud turbidites and glaciogenic debris flow deposits ird rich beds correspond to periods of intensified iceberg calving and layered mud turbidites and glaciogenic debris flow deposits with glacial meltwater discharge in the late wisconsinan eight periods of meltwater discharge and iceberg calving from the newfoundland ice sheet are interpreted from the sediment facies in orphan basin these discharges coincide with the terminations of the colder periods of the d o cycles recorded in greenland ice cores the oldest minor meltwater event 27 5 28 5 cal ka corresponds to the first late wisconsinan ice advance across the grand banks and ne newfoundland shelf the following three meltwater discharges 23 23 5 23 8 24 5 and 25 27 cal ka deposited sand turbidites and glaciogenic debris flow deposits seaward of trinity trough which was occupied by an ice stream at this time and mud turbidites in the southern part of the basin derived from a mid shelf ice margin on the grand banks four periods of meltwater discharge occurred during the deglaciation and are centered at 15 18 5 19 75 and 20 75 cal ka the youngest is correlated to heinrich event 1 in the literature the 18 5 and 20 75 cal ka events have been recorded in multiple glacial settings in the north atlantic and therefore are interpreted as large scale events of meltwater discharge and iceberg calving but in orphan basin the 19 75 cal ka event is also of similar scale

origin and consequences of cyclic ice rafting in the northeast atlantic ocean during the past 130 000 years deep sea sediment cores recovered from the northeast atlantic ocean were examined in order to elucidate the influence of the earth s orbital parameters on major ice rafting analyses of coarse grained ice rafted debris and planktonic foraminifers revealed a strong reaction to the precession signal since 130 000 yr b p dropstone layers have been deposited each half period of a precessional cycle 11 000 1000 yr ice rafting occurs during times of winter minimum summer maximum insolation and summer minimum winter maximum insolation in the first case high summer insolation forces meltwater discharge from the ice sheets into the polar seas which subsequently enhances formation of sea ice during the winter in the second case growth of continental ice enhances iceberg production which also leads to a salinity reduction of surface seawater both situations result in a southward penetration of polar water thus the marine record of dropstones documents ice rafting not only during weichselian stades but also during cold events within interstades the regularity of ice rafting yields a useful framework to calibrate and elucidate climatic changes not only in the region of the north atlantic ocean but also in remote areas such as the pacific ocean and the antarctic

petrology chemistry and texture of modern river sands amazon river system key idea following the spirit of p d krynine the sands of the world s largest tropical river system are studied to reveal much about the general origin of sand and sandstone thin section and chemical study of 95 sand samples from the amazon river system in brazil peru ecuador and colombia a river system with great contrasts in climate and rock types reveals that sands derived from the andes are lithic arenites whereas sands derived from precambrian terrains are much richer in quartz as are sands in rivers draining tertiary molasse sand becomes more mature downstream along the main stem of the amazon solimoes maranon so that a sample analyzed at the mouth does not accurately reflect headwater composition dilution by quartz rich tributaries and quartz rich tertiary outcrops possible differential elimination of rock fragments and even possible weathering on the modern flood plain of the amazon contribute to enhanced maturity downstream we speculate that although data on modern large subarti

ocean atmosphere responses to climatic change in the labrador sea pleistocene plankton and pollen records abstract pleistocene climate change is examined using proxy climatic records from oxygen isotope data calcareous and organic walled marine microfossils pollen and terrestrial spores deposited during the past 0 9 ma at odp site 646 in the labrador sea 500 km north of the present polar front paleotransfer functions applied to planktonic foraminiferal assemblages show relative increases in interglacial summer 3 7 and winter 3 5 temperatures and in winter salinity 0 5 2 for the past 0 4 ma but only two earlier intervals early stage 11 and stage 17 have changes of comparable magnitude coccolith and dinoflagellate cyst accumulation rates show that primary productivity is generally correlated with temperature and salinity changes at the start of interglacials these productivity peaks lag the ice volume changes by 2 4 ka dinocyst blooms seem to precede coccolith peaks reflecting the tolerance of opportunistic species for large variations in temperature and salinity peaks in pollen and spore abundance are strongly correlated with ice volume which controls the position and stability of the polar jet stream in addition to the northern extent of forest vegetation time series analysis was made of 7 oceanographic variables sst summer and winter surface salinity coccoliths dinocysts planktonic and benthic foraminifera and 5 other variables 18 pollen spores percent sand foraminiferal test fragmentation and reworked palynomorphs most variables showed significant power peaks at 100 ka and or at 41 ka however sea surface responses showed minor peaks at 26 and 16 ka and microfossil productivity also showed significant peaks at 68 ka the high latitude labrador sea records thus display large non linear regional responses to climate changes in addition to the effects of orbital insolation forcing at 41 and 23 ka

changes in the western boundary undercurrent outflow since the last glacial maximum from smectite illite ratios in deep labrador sea sediments high resolution mineralogical studies were performed on late glacial and deglacial sediments from two deep piston cores from the labrador sea located at the inlet sw greenland rise and outlet labrador rise of the western boundary undercurrent wbuc gyre at the two sites smectites transported from the eastern iceland and irminger basins by the wbuc are observed clay mineral changes are used as proxies for the paleointensity reconstruction of the wbuc on the greenland rise a clay mineral index smectite illite s i ratio is defined a s i ratio of 1 characterized the last glacial maximum it increased after 17 ka and reached a maximum value of 4 during the early holocene the mineralogical changes are gradual and do not show any reversal during the younger dryas this pattern which is confirmed by first order estimations of smectite and illite fluxes suggests gradually increasing sedimentary fluxes and wbuc intensity since the last glacial maximum a peak in the velocity of the wbuc at 9 ka as recorded by clay assemblages is consistent with other regional studies based on pollen foraminifera or grain size measurements a massive dilution of smectites by illite and chlorite s i 3 occurs at 8 5 ka it corresponds to a period of rapid sediment accumulation and reflects an intensified illite rich detrital supply by meltwaters from the southern greenland ice margin on the labrador rise the smectite content varies between 20 and 60 with no obvious trend through time the mineralogical composition is strongly influenced by ice rafted deposition and by the abundance of fast deposit units cf heinrich layers in the north atlantic which contain abundant detrital carbonates spilled over from the north west atlantic mid ocean channel in such layers smectites are present but are diluted by the addition of illites chlorites and kaolinites this provides evidence for a discrete and continuous wbuc supply of fine particles from the irminger and iceland basins as far as the southeastern part of the labrador basin early deglacial smectite rich layers up to 60 are also observed at this site they indicate an increase in the outflow of the wbuc at 13 5 ka bolling allerod as previously reported from grain size or foraminiferal assemblage studies

lake agassiz outburst age and routing by labrador current and the 8 2 cal ka cold event abstract catastrophic drainage of glacial lake agassiz impounded by the laurentide ice sheet lis into hudson bay and strait is widely thought to have caused the 8 2 cal ka cold event though the path of its drainage in the north atlantic is poorly known analysis and compilation of 10 sediment cores from 8 sites distributed on the eastern canadian continental shelf and upper slope south of hudson strait revealed distinct beds with elevated detrital carbonate dc concentrations known by their distinct composition to originate from erosion of carbonate bedrock and carbonate rich glacial sediments in the hudson bay hudson strait region at all but one site radiocarbon ages bracketing and within the thickest and most widespread of these beds are coeval with the age constraints for the agassiz floods in hudson strait and southeastern hudson bay the dc distribution and concentration of this bed are consistent with southward transport in the labrador current transfer function analysis of dinoflagellate assemblage data from cores on the central labrador shelf in hudson bay and on the northeast newfoundland shelf reveal that early holocene seasonal ice cover was 5 6 months longer than at present requiring the application of a 200 year reduction to the radiocarbon age constraints on the lake agassiz outburst floods the age of the floods is reduced to about 8 33 cal ka 7 5 14 c ka from the previous determination of 8 47 cal ka 7 7 14 c ka with a similar reduction in their error ranges to 8 04 8 49 cal ka from 8 16 8 74 cal ka based on present current routing the agassiz floodwaters and icebergs are inferred to have travelled south in the labrador current and to have possibly become incorporated into the north atlantic current and transported to the nordic seas there the freshwater additions would have lessened deepwater production with a concomitant reduction in northward heat transport in the upper limb of the atlantic meridional overturning circulation thereby contributing to the 8 2 cal ka cold event variation in the calcite and dolomite content of the agassiz dc bed two salinity reductions during agassiz bed deposition and low level shorelines of lakes agassiz and ojibway suggest that more than one outburst was delivered during the final agassiz drainage the 8 2 cal ka cold event registered in greenland was coeval with a second or later flood which possibly accompanied the final collapse of the lis in hudson bay

earthquake rupture at focal depth part i structure and rupture of the pretorius fault tautona mine south africa we analyze the structure of the archaean pretorius fault in tautona mine south africa as well as the rupture zone that recently reactivated it the analysis is part of the natural earthquake laboratory in south african mines nelsam project that utilizes the access to 3 6 km depth provided by the mining operations the pretorius fault is a 10 km long oblique strike slip fault with displacement of up to 200 m that crosscuts fine to very coarse grain quartzitic rocks in tautona mine we identify here three structural zones within the fault zone 1 an outer damage zone 100 m wide of brittle deformation manifested by multiple widely spaced fractures and faults with slip up to 3 m 2 an inner damage zone 25 30 m wide with high density of anastomosing conjugate sets of fault segments and fractures many of which carry cataclasite zones and 3 a dominant segment with a cataclasite zone up to 50 cm thick that accommodated most of the archaean slip of the pretorius fault and is regarded as the principal slip zone psz this fault zone structure indicates that during its archaean activity the pretorius fault entered the mature fault stage in which many slip events were localized along a single psz the mining operations continuously induce earthquakes including the 2004 m2 2 event that rejuvenated the pretorius fault in the nelsam project area our analysis of the m2 2 rupture zone shows that 1 slip occurred exclusively along four pre existing large quasi planer segments of the ancient fault zone 2 the slipping segments contain brittle cataclasite zones up to 0 5 m thick 3 these segments are not parallel to each other 4 gouge zones 1 5 mm thick composed of white rock flour formed almost exclusively along the cataclasite host rock contacts of the slipping segments 5 locally new fresh fractures branched from the slipping segments and propagated in mixed shear tensile mode 6 the maximum observed shear displacement is 25 mm in oblique normal slip the mechanical analysis of this rupture zone is presented in part ii heesakkers et al earthquake rupture at focal depth part ii mechanics of the 2004 m2 2 earthquake along the pretorius fault tautona mine south africa 2011 this volume

radiolytic h2 in continental crust nuclear power for deep subsurface microbial communities 1 h2 is probably the most important substrate for terrestrial subsurface lithoautotrophic microbial communities abiotic h2 generation is an essential component of subsurface ecosystems truly independent of surface photosynthesis here we report that h2 concentrations in fracture water collected from deep siliclastic and volcanic rock units in the witwatersrand basin south africa ranged up to two molar a value far greater than observed in shallow aquifers or marine sediments the high h2 concentrations are consistent with that predicted by radiolytic dissociation of h2o during radioactive decay of u th and k in the host rock and the observed he concentrations none of the other known h2 generating mechanisms can account for such high h2 abundance either because of the positive free energy imposed by the high h2 concentration or ph or because of the absence of required mineral phases the radiolytic h2 is consumed by methanogens and abiotic hydrocarbon synthesis our calculations indicate that radiolytic h2 production is a ubiquitous and virtually limitless source of energy for deep crustal chemolithoautotrophic ecosystems

the isotopic composition of radiogenic helium and its use to study groundwater movement in confined aquifers abstract the 3 he 4 he ratio for radiogenic he is shown to be primarily determined by the abundance of li and neutron absorbing elements in the host formations and is almost independent of the radioelement abundance the 3 he 4 he ratios have been computed for various li contents in rock matrices with average abundances of other elements the 3 he 4 he ratio is specific for each formation and may therefore be used to study crustal diffusion of he it is shown however that both the 3he and 4he contents of continental basements are likely to exceed those of the mantle so that diffusion of mantle he through continental crust is not likely to occur changes in the 3 he 4 he ratio for dissolved he have potential for studying groundwater movement and mixing processes atmospheric he which was dissolved at recharge is progressively diluted by radiogenic he with an isotopic ratio characteristic of the aquifer as the groundwater migrates down dip mixing proportions for formation he and atmospheric he in aquifers for which there is admixture of fracture borne water and interstitially stored water can also be estimated from isotopic measurements these processes are discussed in relation to two aquifers in eastern england

evidence for wisconsinan glaciations in the verrill canyon area scotian slope a composite thickness of about 25 m of sediment has been cored from the verrill canyon on the scotian slope it is interpreted that the majority of this sequence was deposited in a glaciomarine environment during oxygen isotopic stage 2 and the top of stage 3 these sediments as seen in high resolution seismic reflection profiles are well stratified become thicker upslope are laterally variable in thickness and pass upslope into possible outer shelf tills three wedge shaped units of incoherent reflections interfinger with the parallel reflections and terminate in water depths greater than 700 m these wedge shaped units are interpreted as slumped diamict and outwash deposits the age of the uppermost wedge shaped unit is 26 000 21 000 yr based on extrapolation of radiocarbon dates this unit documents a late wisconsinan glacier readvance on the outer scotian shelf the underlying wedge shaped unit estimated to be 70 000 yrs old extends further west along the continental slope and may represent a more extensive early wisconsinan ice advance a third wedge shaped unit inferred to have formed during isotopic stage 6 is possibly a remnant of the first glaciation in the study area

anomalous hydrogen emissions from the san andreas fault observed at the cienega winery central california we began continuous monitoring of h2 concentration in soil along the san andreas and calaveras faults in central california in december 1980 using small h2 o2 fuel cell sensors ten monitoring stations deployed to date have shown that anomalous h2 emissions take place occasionally in addition to diurnal changes among the ten sites the cienega winery site has produced data that are characterized by very small diurnal changes a stable baseline and remarkably distinct spike like h2 anomalies since its installation in july 1982 a major peak appeared on 1 10 november 1982 and another on 3 april 1983 and a medium peak on 1 november 1983 the occurrences of these peaks coincided with periods of very low seismicity within a radius of 50 km from the site in order to methodically assess how these peaks are related to earthquakes three h2 degassing models were examined a plausible correlational pattern was obtained by using a model that 1 adopts a hemicircular spreading pattern of h2 along an incipient fracture plane from the hypocenter of an earthquake 2 relies on the feo h2o reaction for h2 generation and 3 relates the accumulated amount of h2 to the mass of serpentinization of underlying ophiolitic rocks the mass was tentatively assumed to be proportional to the seismic energy of the earthquake

a 750 kyr detrital layer stratigraphy for the north atlantic iodp sites u1302 u1303 orphan knoll labrador sea abstract integrated ocean drilling program iodp sites u1302 u1303 drilled on the se flank of orphan knoll labrador sea preserve a record of detrital layers and other proxies of hydrographic change that extend the record of ice sheet ocean interactions through most of the brunhes chron the age model is built by tandem matching of relative paleointensity rpi and oxygen isotope data 18o from neogloboquadrina pachyderma sin to reference records indicating a mean brunhes sedimentation rate of 14 cm kyr sedimentation back to marine isotope stage mis 18 is characterized by detrital layers that are detected by higher than background gamma ray attenuation gra density peaks in x ray fluorescence xrf indicators for detrital carbonate ca sr and detrital silicate si sr and an ice rafted debris ird proxy wt 106 m the age model enables correlation of site u1302 03 to iodp site u1308 in the heart of the central atlantic ird belt where an age model and a similar set of detrital layer proxies have already been derived ages of heinrich h layers h1 h2 h4 h5 and h6 are within 2 kyr at the two sites h0 h3 and h5a are not observed at site u1308 and agree with previous work at orphan knoll within 3 kyr at site u1308 brunhes detrital layers are restricted to peak glacials and glacial terminations back to marine isotope stage mis 16 and have near synchronous analogs at site u1302 03 detrital layers at site u1302 03 are distributed throughout the record in both glacial and most interglacial stages we distinguish heinrich like layers associated with ird from detrital layers marked by multiple detrital layer proxies including ca sr but usually not associated with ird that may be attributed to lofted sediment derived from drainage and debris flow events funneled down the nearby northwest atlantic mid ocean channel namoc the prominent detrital layers at sites u1302 03 and u1308 can be correlated to millennial scale features in the chinese speleothem monsoon record over the last 400 kyr implying a link between monsoon precipitation and laurentide ice sheet lis instability the detrital layer stratigraphy at site u1302 03 provides a long record of lis dynamics against which other terrestrial and marine records can be compared

geogas transport in fractured hard rock correlations with mining seismicity at 3 54 km depth tautona gold mine south africa abstract an on site gas monitoring study has been conducted in the framework of an earthquake laboratory the international nelsam dafgas projects at the tautona gold mine south africa five boreholes up to 60 m long were drilled at 3 54 km depth into the highly fractured pretorius fault zone and instruments for chemical and seismic monitoring installed therein over the span of 4 years sensitive gas monitoring devices were continuously improved to enable the direct observation of geogas concentration variations in the dafgas borehole the major gas concentrations are constant and air like with about 78 n 2 21 o 2 1 ar the geogas components co 2 ch 4 he and h 2 show the most interesting trends and variations on the minute by minute basis and significantly correlate with seismic data while the 222 rn activity remains constant time series and cross correlation analysis allow the identification of different gas components geogas and tunnel air and the identification of two processes influencing the borehole gas composition 1 pumping induced tunnel air breakthrough through networks of initially water saturated fault fractures and 2 seismicity induced permeability enhancement of fault fractures to above 5 10 10 m 2 the current set up of the gas monitoring system is sensitive enough to quantify the resulting geogas transport during periods of intense blasting activities including recorded blasts with seismic moment 1 10 9 nm located within 1000 m of the cubby and it is suggested also during induced earthquakes a final goal of the project

oceanographic regimes in the northwest labrador sea since marine isotope stage 3 based on dinocyst and stable isotope proxy records abstract sea surface temperature sst salinity and density gradients in the upper water column of the northwest labrador sea have been reconstructed based on high resolution analysis of a core hu2008 029 004pc spanning the last 36 ka raised off hudson strait the modern analogue technique was applied to dinocyst assemblages and combined with stable isotope data from neogloboquadrina pachyderma left coiled npl for this purpose three oceanographic regimes were identified broadly corresponding to the glacial deglacial and postglacial intervals the site remained under the direct influence of the laurentide ice sheet lis margin until the postglacial and did not record the bolling allerod warming and weakly recorded the younger dryas event the glacial regime lasted until 12 2 cal ka bp it was characterized by generally low concentrations of dinocysts within an assemblage indicative of quasi perennial sea ice the deglacial regime ca 12 2 8 3 cal ka bp was marked by increased biogenic fluxes and more diversified dinocyst assemblages and possibly an enhanced subsurface inflow of north east atlantic deep water warm summer 11 c but low winter 0 c sea surface temperatures sea ice cover during about 3 months per year and low summer salinity 28 suggest strong stratification in the upper water layer in relation to meltwater supply from the lis following the final drainage of glacial lake agassiz through hudson strait which is dated here at 8 3 cal ka bp and the subsequent lis collapse increased summer salinity up to 35 was accompanied by a reduced seasonal gradient of sea surface temperature from winter 3 8 c to summer 8 6 c suggesting enhanced penetration of north atlantic water weakened stratification of the surface water layer then allowed for winter convection and labrador sea water formation which is consistent with increased npl 13c values in response to higher ventilation of the subsurface water layer

neon identifies two billion year old fluid component in kaapvaal craton abstract the deep gold mines of the witwatersrand basin south africa have gained recent attention not only because of investigations of the deep fracture water and associated ch4 and h2 rich gases found there but because of recent reports of deep microbial communities persisting to depths of almost 3 km an exotic outpost of the earth s deep biosphere while shallower fluids in the basin to approximately 1 km were found to contain abundant populations of methanogens and sulphate reducing bacteria the deepest oldest most saline fracture waters in the basin hosted hitherto unrecognised low biomass and low biodiversity chemoautotrophic ecosystems independent from the photosphere shallow and deep fluids also show distinct differences in gas and fluid geochemistry paleometeoric waters are dominated by hydrocarbon gases with compositional and isotopic characteristics consistent with production by methanogens utilising the co2 reduction pathway in contrast the deepest most saline fracture waters contain gases that are dominated by high concentrations of h2 gas and ch4 and higher hydrocarbon gases with isotopic signatures attributed to abiogenic processes of water rock reaction the high salinities up to hundreds of g l highly altered 18o and 2h signatures and both 36cl and measurements of co occurring nucleogenic noble gases for these fracture waters are consistent with extensive water rock interaction over geologically long time scales in these high rock water ratio environments while the ultimate origin of these fluids has been attributed alternately to saline waters that penetrated the crystalline basement formation water or hydrothermal fluids in some cases their 18o and 2h isotopic signatures have typically been so profoundly overprinted by the effects of long term water rock interaction that for the most saline end members little evidence of their primary composition remains the key objective of the present study is to further investigate the origin of these fluids by integrating for the first time detailed neon isotope analyses on the dissolved gases helium isotopic analysis confirmed that there is no significant mantle derived component associated with these fluids and gases neon isotope results show distinct differences in neon composition that correspond to the different fluid geochemical end members previously identified typical crustal neon signatures type a are identified in the paleometeoric waters populated with abundant methanogens in contrast the deep more saline fracture waters contain an enriched nucleogenic neon signature unlike any previously reported in crustal fluids these samples show the highest 21ne 22ne ratios 0 160 0 003 ever reported in groundwater fluid inclusions in these rocks yield even higher 21ne 22ne ratios between 0 219 and 0 515 consistent with an extrapolated 21ne 22ne value of 3 3 0 2 at 20ne 22ne 0 we show that this enriched nucleogenic neon end member represents a fluid component that was produced in the fluorine depleted archaean formations and trapped in fluid inclusions 2 ga ago the observation of enriched nucleogenic neon signatures in deep fracture water implies the release of this billion year old neon component from the fluid inclusions and its accumulation in exceptionally isolated fracture water systems the observed association of this archean neon signature with h2 hydrocarbon rich geogases of proposed abiogenic origin dissolved in the same deep groundwater suggests that the fracture systems have also allowed for the accumulation of various products of water rock reactions throughout geologic times one of these fracture systems contained the deepest characterised microbial ecosystems on earth chemolithotrophs eking out an existence at maintenance levels independent from sunlight consequently the enriched nucleogenic neon isotope signature may indicate regions in the archaean crust where investigations of the deep biosphere might be focused

late quaternary sedimentation in baffin bay baffin bay is a small ocean basin that connects the arctic and atlantic oceans the adjacent continental shelves have been extensively reworked during quaternary glaciation the shelf break generally lies between 200 and 500 m the continental slope passes directly into the abyssal plain of baffin bay basin without any major submarine canyon deep sea fan system being present except for a large smooth sediment apron in northern baffin bay on the basis of over 50 piston cores six quaternary sediment facies are distinguished from detrital mineralogy reflected in colour and sediment texture facies a b and c are predominantly ice rafted or are debris flow deposits each with a distinct mineralogy facies d is turbidites and bottom current sorted sands silts and muds facies e is hemipelagic sediment facies f consists of sediments ranging from slumps through debris flow deposits to fine grained turbidites with a distinctive provenance in northern baffin bay these sediment facies appear to be part

dansgaard oeschger events is there a signal off the hudson strait ice stream abstract it is generally accepted that the dramatic heinrich h events were principally sourced from the major hudson strait drainage basin of the laurentide ice sheet but it is not known whether the higher frequency dansgaard oeschger d o events have an imprint on sediments deposited during the inter h intervals in ice proximal slope sediments this paper examines this question by an analysis of data from cores on the se baffin slope because the proxies for heinrich events are so massive in scale we removed the major h events h 1 h 2 and h 4 from the records so as to better examine the structure of data in the intervening hemipelagic sediments the period of interest extends between 15 and 40 cal ka interstadial events 2 8 resolution varies with the proxy to between 210 and 700 yrs per sample in hu87033 009 from the lower slope a total of twelve variables for example 18o mass magnetic susceptibility calcite dolomite ratio number of ird 2 mm show a variety of multi millennial oscillations although not all of the same amplitude nor frequency several parameters show little correlation with the gisp2 18o record however a comparison of cie sediment color l from hu87033 009 and hu97048 007 from the upper slope with the gisp2 oxygen isotope record suggests that a substantial correlation exists between the records such changes might be associated with either detrital carbonate content or foraminiferal concentrations analysis suggests however that the first possibility is correct hence suggestive of a glaciological response of the hudson strait ice stream with d o events in the nw labrador sea the sediment records from around h 3 time 30 cal ka show excursions which might be correlative within this event but its amplitude is not unusual compared to events both before and after this reaffirms the argument that h 3 represents a different glaciological response a significant issue discussed in this paper is the inherent ambiguity of correlating records whose errors in the time domain approach that of a dominating periodicity in this case ca 1 5 kyr

free hydrogen hydrocarbon gases from the lovozero loparite deposit kola peninsula nw russia abstract the lovozero nepheline syenite massif in the north eastern fennoscandian shield well known to mineralogists and petrologists is also interesting with its high contents of hydrogen hydrocarbon gases in different forms of presence which is untypical of magmatic rocks the article systematizes and generalizes little known and unpublished data on the composition location character and scale intensity of the free gases fg emission within a major loparite deposit confined to the massif 4 and 2 are dominant in the fg composition the molecular weight distribution of hydrocarbon gas components corresponds to the classic anderson schulz flory distribution with a steep gradient carbon and hydrogen of the gases are characterized by rather heavy isotope compositions becoming lighter from the transition of methane to ethane the fg volume has been estimated as 0 2 1 6 m 3 of gas per 1 m 3 of undisturbed rock the gas recovery of walls in underground workings has been up to 0 2 ml min m 2 for 4 and 0 5 ml min m 2 for 2 in several years after their heading the discharge of some shot holes that characterizes the gas emission intensity 1 8 2 m deep and 40 mm in diameter is up to 300 ml min but its 1 2 orders lesser values dominate the discharge time in some sections varies from several days to 20 years the overpressure of gases towards the air mainly does not increase 100 hpa sometimes reaching 120 kpa it has been defined that fg distribute irregularly at the distance of centimeters to hundreds of meters and their composition and particularly emission intensity perform different temporal fluctuations the abiogenic origin of fg has been proposed with fg appearing as a mixture of gases in various proportions a gases remaining in microfissures at the massif s consolidation after the capture by fluid inclusions and those lost during degassing and b gases occurred in mechanic chemical reactions partial emission and concentration of occluded and diffusely scattered gases under the unstable stress strain mode of the rock mass combustible and explosive hydrogen hydrocarbon fg can accumulate in the air of underground workings and cause accidents disrupting the workflow the background for using characteristics of spatial temporal variations of the fg emission as precursors of dangerous geodynamic phenomena has been indicated

patterns of ice rafted detritus in the glacial north atlantic 40 55 n the observation by heinrich 1988 that during the last glacial period much of the input of ice rafted detritus to the north atlantic sediments may have occurred as a succession of catastrophic events rekindled interest on the history of the northern ice sheets over the last glacial period in this paper we present a rapid method to study the distribution of these events both in space and time using whole core low field magnetic susceptibility we report on approximately 20 cores covering the last 150 to 250 kyr well defined patterns of ice rafted detritus appear during periods of large continental ice sheet extent although these are not always associated within their maxima most of the events may be traced across the north atlantic ocean for the six most recent heinrich layers hl two distinct patterns exist hl1 hl2 hl4 hl5 are distributed along the northern boundary of the glacial polar front over most of the north atlantic between 40 and 50 n hl3 is more restricted to the central and eastern part of the northern atlantic the nd sr isotopic composition of the material constituting different heinrich events indicates the different provenance of the two patterns hl3 has a typical scandinavia arctic icelandic young crust signature and the others have a large component of northern quebec and northern west greenland old crust material these isotopic results obtained on core su 9008 from the north american basin are in agreement with the study by jantschik and huon 1992 who used k ar dating of silt and clay size fractions of an eastern basin core me 68 89 these data confirm the large spatial scale of these events and the enormous amount of ice rafted detritus they represent

glaciomarine sedimentation in disraeli fiord high arctic canada abstract disraeli fiord represents a glaciomarine environment unique to the north coast of ellesmere island featuring floating glacier tongues multi year landfast sea ice and a strongly stratified water body which results from enclosure of the fiord by ward hunt ice shelf it is a very low energy depositional environment even at sites proximal to glaciers sediment enters the fiord by interflow and is deposited through suspension settling ice rafting is precluded by the year round sea ice cover sedimentation rates in the inner fiord since about 7000 yrs b p are estimated to be 5 10 cm ka a reflection of the limited sediment influx from the cold based glaciers which contact the fiord changes in sediment structure through the holocene reflect changes in the rate and process of sediment input as well as changes in fiord circulation all of which relate to regional climate during deglaciation early holocene sedimentation rates were orders of magnitude greater than at present subglacial meltwater was the dominant source of inflow with sediment transported in turbid plumes as over or interflow and deposited through suspension settling this is supportive of other studies indicating that a pronounced climatic amelioration led to warm based glaciers at this time

continental eclogites and the wilson cycle the wilson cycle the repeated opening and closing of oceans commonly along roughly the same lines is here attributed to the presence of eclogite facies roots of partially collapsed orogens we present a finite element thermal model that suggests that such roots will weaken the orogenic lithosphere relative to that of the adjacent foreland for hundreds of millions of years and make it a preferred site for later rifting

unravelling abiogenic and biogenic sources of methane in the earth s deep subsurface at four underground sites in precambrian shield rocks in canada and south africa hydrocarbon and hydrogen gases exsolving from saline fracture waters are analyzed for compositional and isotopic signatures dominated by reduced gases such as ch4 h 2 and higher hydrocarbons ethane propane butane the most 13 c enriched methane end members at all four sites show a pattern of carbon and hydrogen isotopic values similar to abiogenic gases produced by water rock interaction that have been identified previously at one site on the precambrian shield in canada the abiogenic nature of these gases was not previously recognized due to mixing with a second methane component produced by microbial processes the microbial methane end member is identified based on carbon and hydrogen isotopic signatures and dna gene amplification pcr data that indicate the presence of methanogens a framework is presented to estimate the relative contribution of abiogenic versus microbial hydrocarbon gases at these sites this approach has important implications for evaluation of potential abiogenic hydrocarbon reservoirs in a wide range of geologic settings including the longstanding controversy concerning the possible contribution of abiogenic gases to economic petroleum hydrocarbon reservoirs the association of high concentrations of h2 with 13 c enriched ch4 end members and h2 depletion in the 13 c depleted methanogenic end members further suggests the possibility that abiogenic gases may support h2 autotrophy linked to methanogenesis in the deep subsurface d 2005 elsevier b v all rights reserved

moment tensors and other source parameters of mining induced earthquakes in tautona mine south africa abstract induced seismicity exhibits diverse source mechanisms that are often difficult to constrain for small events here we use data from the in mine seismic network the natural earthquake laboratory in south african mines network and a temporary program for the array seismic studies of the continental lithosphere deployment in tautona mine south africa to determine full moment tensors of 100 mining induced earthquakes in the magnitude range 2 7 m w f test to determine the need for including an isotropic component with an extra degree of freedom in the solution the results indicate 82 of the events have well constrained solutions and 45 of the well constrained events require an isotropic source term throughout the magnitude range both deviatoric and implosive mechanisms are observed with implosive ratios of volume change to shear deformation v of 1 03 to 0 15 two explosive events are observed at m w 0 5 and 0 2 with v 0 15 and 0 51 respectively for the largest events we determine maximum slip and apparent stress a and find values consistent with those of natural tectonic earthquakes with 0 1 a 9 2 mpa our results support previous speculation on the nature of isotropic components of mining induced earthquakes in which events of all sizes begin as shear failure that may intersect a void tunnel or stope and cause collapse whereas only small events result in explosive sources

crustal structure of the middle urals based on reprocessing of russian seismic reflection data summary reprocessed russian seismic reflection data combined with existing russian geological maps and seismic interpretations provide the basis for a revised tectonic interpretation of the upper crust in the middle urals the main uralian fault muf the principal suture of the urals separating the east european craton to the west from accreted terranes to the east is found to penetrate to depths of at least 18 km and perhaps much deeper with a uniform eastward dip of 35 after migration as the muf appears to truncate reflections in both the foreland and hinterland of the urals it is arguably one of the youngest structural features of the orogen basement rocks of the east european platform underthrust the suture and comprise the deep crust a minimum of 30 km east of the surface expression of the muf the tagil volcanic arc complex greater than 1000 km in length along strike comprises at least the upper 10 km of the crust east of the muf this terrane shallows eastwards where it appears to be truncated by the west dipping serov mauk fault based on correlation with surface geology the hinterland of the urals east of the muf is characterized by a previously unrecognized zone of discontinuous mid crustal reflectivity at depths of 14 16 km that is discordant with upper crustal reflections this mid crustal zone of reflectivity is interpreted to represent either a major subhorizontal structural detachment or a zone of magmatic intrusion

origin of hydrogen and carbon dioxide in fault gases and its relation to fault activity gases occluded in fracture zones of active faults are characterized by a high concentration of h 2 and or co 2 a predominant gas species h 2 or co 2 is related to the lithofacies which the fault cuts carbon dioxide concentration in sediments fluctuates with temperature this evidence and sigma 13 c of co 2 about 20 suggests that co 2 originates from organic materials carbon dioxide with sigma 13 c of 5 to 17 in brecciated gneiss containing marble may have been produced by interaction between organically derived co 2 and the marble or alternatively may have been magmatically derived hydrogen usually occurs in sheared silicate rocks and its concentration fluctuates a great deal the concentration of h 2 from active faults associated with historical earthquakes usually amounts to as high as several percent in maximum whereas the concentration of h 2 from quaternary faults not associated with historical earthquakes is at most 1

sediment dynamics during heinrich event h1 inferred from grain size abstract throughout the last glacial period massive volumes of icebergs were discharged periodically through hudson strait during so called heinrich h events these icebergs transported sediments that were subsequently deposited in distinct layers across the north atlantic as they melted the objective of this research was to measure and describe sedimentation associated with a meltwater plume discharged during the h1 ice rafting event at about 17 ka by examining sediment texture the h1 layer was sampled in 11 piston cores that cover about 4000 km of the slope between hudson strait and the gulf of maine disaggregated inorganic grain size digs distributions were determined using a coulter counter additionally the caco 3 content and the 63 m fraction were measured and digs distributions were sorted using entropy analysis entropy analysis proved to be a useful tool for distinguishing between sediment delivery mechanisms textural interpretation of sediment dynamics during the h1 event was broadly consistent with facies interpretations h1 layer sediments were mainly delivered by plume and ice rafting with some samples showing higher energy sorting in general plume deposition was dominant within 1000 km of hudson strait and distal sediments were mainly delivered by ice rafting entropy analysis of digs distributions provides a robust means of understanding fine fraction

abiogenic methanogenesis in crystalline rocks isotopically anomalous ch4 rich gas deposits are found in mining sites on both the canadian and fennoscandian shields with 13cch4 values from 22 4 to 48 5 and dch4 values from 133 to 372 these methane deposits cannot be accounted for by conventional processes of bacterial or thermogenic methanogenesis compositionally the gases are similar to other ch4 rich gas occurrences found in canadian and fennoscandian shield rocks sherwood lollar et al 1993 however the isotopically anomalous gases of this study are characterized by unexpectedly high concentrations of h2 gas ranging from several volume percent up to 30 vol the h2 gases are consistently depleted in the heavy isotope with dh2 values of 619 to 659 3h 4he ratios in the range of 0 4 10 8 to 4 4 sx 10 8 indicate that there is no resolvable component of mantle derived he in these deposits based on these results a mantle derived source for the c bearing gases is unlikely several lines of evidence support an alternative abiogenic origin for the gases from sudbury canada and juuka and pori finland the d depleted h2 gas and calculated d ch4 h2 equilibration temperatures of 110 170 c at all three sites are in good agreement with results obtained for abiogenically produced ch4 and h2 in ophiolite sequences in oman and the philippines serpentinization and the hydration of ultramafic rocks are the proposed mechanisms for ch4 and h2 production in these ophiolite sequences the widespread occurrence of serpentinized and altered ultramafic rocks at juuka and at a number of other sites in both canada and finland implies that similar mechanisms may be involved in gas production at at least three sites on the shields the origin of the gases at the remaining shield sites is discussed alternative hypothesis include 1 production of the rest of the shield gases by mixing between abiogenic endmembers and bacterially generated hydrocarbon gas such as identified elsewhere on the canadian and fennoscandian shields sherwood lollar et al 1993 and 2 production of a series of isotopically distinct abiogenic ch4 endmembers at each site due to variability in the isotopic composition of available carbon sources we cannot conclusively distinguish between the alternative scenarios based on existing data however the evidence for an abiogenic ch4 endmember at at least three sites emphasizes the need for substantial revision of current theories of methanogenesis abiogenic processes of ch4 production may be considerably more widespread than previously anticipated

gas geochemistry and seismotectonics a review abstract publications on soil and spring gases have been examined regarding their relationships with both tectonic and seismic activities the main sources behaviours and uses of species detected in soils and springs are displayed and their mode of sampling and analysing briefly described the main patterns of degassing in soils are described and we outline the wide range of geochemical signatures as the result of both permeability and mineralogical contrasts because thermomineral waters have been in contact with great volumes of crustal rocks at various depths spring gases might be more representative of the local environment than soil gases moreover gas signature comparisons show that spring gases are much more enriched with deep gases and slightly contaminated by atmospheric gases therefore they can be considered as better samples for identifying precursors of earthquakes environmental perturbations are examined and it is shown from divergent cases that pressure temperature soil moisture or earth tides may generate very high perturbations of the degassing process such effects demonstrate that no systematic correction law can be proposed and that removing external contributions from gas concentrations must be performed case by case this demonstrates therefore the need for the simultaneous measurement of external parameters during gas monitoring a qualitative examination of about 150 claimed precursors proposed in the literature has been reviewed as noted by previous authors anomalies appear at distances sometimes much greater than typical source dimensions and occur in the field of strain higher than 10 9 most of them being in the field of strain higher than 10 8 taking into account the very high heterogeneity of such a set of data we can suggest that amplitudes of gas anomalies are independent of both magnitudes and epicentral distances of related earthquakes suggesting local conditions to control amplitudes on the contrary precursory time and duration of anomalies seem to increase both with magnitudes and epicentral distances abundant evidence demonstrates the major role of crustal fluids in the earthquake cycle many works have outlined the fact that crustal instabilities can appear as the result of low stress strain perturbations during loading it has been suggested that motion of fluids may occur at various scales from microcrack fluid transfer up to changes of hydraulic levels of water tables the study of subsequent anomalies is expected to supply a tool for earthquake prediction following previous authors we outline the need for further methodological improvements including the setting up of multiparameter station networks and the simultaneous recording of the main external parameters atmospheric pressure water and air temperature soil moisture for signal processing

detrital carbonate rich sediments northwestern labrador sea implications for ice sheet dynamics and iceberg rafting heinrich events in the north atlantic much of the bed of the central and eastern sectors of the laurentide ice sheet was underlain by paleozoic carbonates we propose that pulses of detrital carbonate rich sediments in two cores from the northwestern labrador sea reflect episodes when an ice stream from the hudson strait extended to the shelf break and delivered sediment onto the slope and deep sea plain atomic mass spectroscopy 14 c dating of planktonic foraminifera in cores hu75 009 iv 55 2 4 km water depth and hu87 033 009 1 4 km water depth and 150 km north northwest indicates that the youngest event occurred between ca 14 and 15 ka and another occurred between 19 and 21 ka the two carbonate intervals in northwestern labrador sea cores are coeval with heinrich events 1 and 2 in the eastern north atlantic lat 45 50 n long 20 w where they are associated with an increase in lithic fragments and a drastic reduction in the numbers of foraminifera these changes have been linked with the massive production of icebergs associated with ice sheet surges our evidence indicates that heinrich events 1 and 2 are associated with the dynamics of the hudson strait ice stream and denote considerable glaciological instability

deep sea records from the southeast labrador sea ocean circulation changes and ice rafting events during the last 160 000 years 1 results from two deep sea cores from northeast of newfoundland at 1251 and 2527 m water depth respectively indicate that during the time period from 160 000 to 10 000 years bp ice rafting events in the labrador sea were accompanied by rapid variations in deep and surface water circulation twelve ice rafting events occurred each coinciding with high concentrations of detrital carbonate and oxygen isotopic depletion of both surface and bottom waters eleven of these can be correlated with the north atlantic heinrich events h1 h11 the remaining very conspicuous ice rafting event took place early in mis substage 5e at a time when the planktic faunal assemblage suggests marked warming of the sea surface in the shallower core benthic delta 13 c values rise from a minimum during the deglaciation to peak substage 5e values following the last ice rafting event indicating that the ventilation of intermediate depths was renewed after the deglaciation was complete and continued throughout substage 5e the benthic foraminifera suggest that this well ventilated water mass was comparable to the modern labrador sea water lsw the benthic faunas suggest that a relatively warm intermediate water mass entered the se labrador sea during heinrich events generally low benthic delta 13 c values indicate that this water mass was poorly ventilated and rich in inorganic nutrients isotope data and benthic faunal distributions indicate that north atlantic deep water nadw formed in the norwegian greenland sea reached the se labrador sea between the heinrich events

geological setting and age of the flemish cap granodiorite east of the grand banks of newfoundland flemish cap a large isolated submarine knoll 600 km east of newfoundland consists of a central core of hadrynian rocks and an onlapping sequence of undisturbed to disturbed mesozoic cenozoic sediments the central core of the cap sampled with an electric rock core drill comprises pink fine to medium grained granodiorite dacite and volcanic siltstone the granodiorite samples collected in six out of eight cores are remarkably similar lithologically despite a separation of up to 65 km and probably represent a single pluton the aphanitic dacite and laminated cherty volcanic siltstone have been metamorphosed to subgreenschist prehnite facies but show no evidence of contact metamorphism u pb analyses of coarse and fine zircon fractions from a granodiorite core yielded upper intercepts of 751 and 833 ma respectively although not precise these ages probably represent the age of intrusion sometime in the 750 830 ma range and are older than those reported for similar hadrynian granitic rocks of e

interaction between fluid flow fracturing and mineral growth during eclogitization an example from the sunnfjord area western gneiss region norway in sunnfjord western gneiss region of south norway a proterozoic layered gabbro complex displays various degrees of transformation to eclogite in the unreacted parts layering in the gabbro is defined by modal variations of plagioclase olivine pyroxenes and minor fe ti oxide and spinel coronitic and foliated eclogite formed from the gabbro by hydration reactions at t 510 620 c causing a volume decrease of c 13 in the coronitic eclogite the mafic magmatic phases are replaced by aggregates of omphacite barroisite tremolite talc and rutile whereas the plagioclase domains are pseudomorphed by omphacite barroisite clinozoisite kyanite paragonite and garnet the felsic and mafic domains are separated by a garnet rim up to 5 mm thick garnet was also formed along dilational veins connecting and radiating out of coronas including the same eclogite facies minerals in addition microfractures filled by amphibole and omphacite cut through the corona and vein garnet oriented perpendicular to the garnet layering the transformation of dry gabbro to eclogite with hydrous minerals requires supply of water the timing of metamorphic reactions is therefore dependent on the timing of fluid introduction the inclusion pattern of garnet in the holt tyssedalsvatnet metagabbro complex indicates that transformation started under eclogite facies conditions brittle deformation in form of fractures allowing infiltration of fluids and mobilisation of elements is shown to be the most important process initiating transformation brittle deformation is thereby active in deep crustal levels corresponding to eclogite facies conditions fracturing is interpreted as having been caused by a combination of high fluid pressure volume changes during mineral transformations and external stresses ductile deformation started after the initial metamorphic transformation garnet chemistry and zoning pattern are controlled by the chemistry of the growth place the fluid influx and element supply abrupt chemical variations across corona garnet may have been formed by an interaction between rapid growth and transport along microfractures between plagioclase and mafic domain the metamorphic transition proceeded rapidly the transformation of the deep crust to eclogite can be viewed as a dynamic process where the volume changes result in fracturing and these fractures funnelling fluid and element enhancing mineral reaction the densification causes further fracturing indicating that the process is self driven provided that fluid is available

global review of human induced earthquakes the human induced earthquake database hiquake is a comprehensive record of earthquake sequences postulated to be induced by anthropogenic activity it contains over 700 cases spanning the period 1868 2016 activities that have been proposed to induce earthquakes include the impoundment of water reservoirs erecting tall buildings coastal engineering quarrying extraction of groundwater coal minerals gas oil and geothermal fluids excavation of tunnels and adding material to the subsurface by allowing abandoned mines to flood and injecting fluid for waste disposal enhanced oil recovery hydrofracturing gas storage and carbon sequestration nuclear explosions induce earthquakes but evidence for chemical explosions doing so is weak because it is currently impossible to determine with 100 certainty which earthquakes are induced and which not hiquake includes all earthquake sequences proposed on scientific grounds to have been human induced regardless of credibility challenges to constructing hiquake include under reporting which is 30 of m 4 events 60 of m 3 events and 90 of m 2 events the amount of stress released in an induced earthquake is not necessarily the same as the anthropogenic stress added because pre existing tectonic stress may also be released thus earthquakes disproportionately large compared with the associated industrial activity may be induced knowledge of the magnitude of the largest earthquake that might be induced by a project mmax is important for hazard reduction observed mmax correlates positively with the scale of associated industrial projects fluid injection pressure and rate and the yield of nuclear devices it correlates negatively with calculated inducing stress change likely because the latter correlates inversely with project scale the largest earthquake reported to date to be induced by fluid injection is the 2016 m 5 8 pawnee oklahoma earthquake by water reservoir impoundment the 2008 m 8 wenchuan people s republic of china earthquake and by mass removal the 1976 m 7 3 gazli uzbekistan earthquake the minimum amount of anthropogenic stress needed to induce an earthquake is an unsound concept since earthquakes occur in the absence of industrial activity the minimum amount of stress observed to modulate earthquake activity is a few hundredths of a megapascal and possibly as little as a few thousandths equivalent to a few tens of centimeters of water table depth faults near to failure are pervasive in the continental crust and induced earthquakes may thus occur essentially anywhere in intraplate regions neither infrastructure nor populations may be prepared for earthquakes human induced earthquakes that cause nuisance are rare but in some cases may be a significant problem e g in the hydrocarbon producing areas of oklahoma usa as the size of projects and density of populations increase the potential nuisance of induced earthquakes is also increasing and effective management strategies are needed

ophiolitic source rocks for taconic age flysch trace element evidence flysch generated along the appalachian orogen during the ordovician taconic orogeny ranges in age from late arenig to early caradoc allochthonous flysch and from late llanvirn to ashgill autochthonous flysch sandstones in these units are dominantly lithic arenites with a heavy mineral suite containing common to abundant mg rich chromite north of the canada united states border the only reasonable sources for the chromite were the lower ultramafic units of obducted ophiolites trace element analyses cr ni v cu ti zr y of flysch sandstones indicate a striking increase in cr and ni concentrations from the united states appalachians to the canadian appalachians in the united states units cr is in the range of 10 to 50 ppm canadian flysch units average an order of magnitude more cr these results suggest that ophiolite obduction either did not occur or was of minor importance during the taconic orogeny in the united states appalachians the difference in ophiolite abundance between the canadian and united states appalachians suggests a fundamental difference in tectonic style along the orogen a feature that must be accommodated by plate tectonic models new models will probably need to consider both obliquity of subduction and geological complexity of the ordovician collision zone in order to explain the spatial distribution of obducted ophiolite sheets

microbial hydrocarbon gases in the witwatersrand basin south africa implications for the deep biosphere in this study compositions and 13c and 2h isotopic values of hydrocarbon gases from 5 mines in the witwatersrand basin south africa support the widespread occurrence of microbially produced methane in millions of years old fissure waters the presence of microbial methane is to a large extent controlled by the geologic formations in which the gases are found samples from the witwatersand supergroup have the largest microbial component based on 13c and 2h signatures and ch4 c2 values based on mixing between a microbial ch4 component and a more 13c enriched and 2h depleted c2 rich end member conservative estimates of the contribution of microbial ch4 to the gas samples range from 90 microbial ch4 at beatrix masimong and merriespruit to between 5 and 80 microbial ch4 at evander and 18 microbial ch4 at kloof the witwatersrand basin s history of thermal alteration of organic rich ancient sedimentary units suggests a thermogenic origin for this 13c enriched end member alternatively the potential for an abiogenic origin similar to hydrocarbon gases produced by water rock interaction at other precambrian shield mines is discussed microbial methane is predominantly found in paleo meteoric fissure waters with 18o and 2h values that fall on the meteoric waterline and have temperatures between 30 to 40 c in contrast fissure waters with a larger component of nonmicrobial hydrocarbon gases show a trend towards more enriched 18o and 2h values that fall well above the meteoric waterline and temperatures of 45 to 60 c the enrichment in 18o and 2h in these samples and their high salinity are similar to the isotopic and compositional characteristics of saline groundwaters and brines produced by water rock interaction at precambrian shield sites elsewhere the reported 100 ma ages of fissure waters from the witwatersrand and ventersdorp formations suggest that these microbial hydrocarbon gases are the product of in situ methanogenic communities in the deep subsurface of the witswaterand basin small subunit ribosomal rna genes were amplified using archaeal specific primer sets from dna extracts derived from several of these waters fissure waters with a high proportion of microbial methane also contained sequences resembling those of known methanogens

serpentinization and the origin of hydrogen gas in kansas hydrogen gas occurs in ten kansas wells near the mid continent rift system since 1982 two wells have yielded small amounts of gases containing an average of 29 37 mole h2 the remainder being chiefly n2 with only traces of hydrocarbons isotopic compositions for hydrogen dgrd 740 to 836 pmil imply near ambient about 10 c equilibration temperatures for the gases which are among the most deuterium depleted in nature and resemble the h2 rich gases described from ophiolites in oman isotopic values for the kansas n2 differ slightly from those of the atmosphere but not enough to rule out an atmospheric origin because they are low in ch4 and co2 expected byproducts of biogenic activity the gases are probably abiogenic in origin the existence of such gases near a major rift system containing mafic rocks and not far from known kimberlites is consistent with an origin from reactions involving fe 2 oxidation for example during serpentinization because the gases may be associated with kimberlites and deep seated rifting mantle outgassing is possible but such an origin would be difficult to reconcile with the low isotopic temperatures the h2 gases from kansas and elsewhere seem to be too low in pressure to have commercial value however neither the kansas gases nor those from other h2 occurrences have been adequately examined to assess their importance as potential resources

h2 generation by reaction between h2o and crushed rock an experimental study on h2 degassing from the active fault zone granite and quartz were crushed under moist conditions in the temperature range of 25 270 c in order to obtain the information on the mechanism operative for h2 degassing along active faults it was found that the amounts of h2 gas released by crushing granite and quartz increased with temperature up to around 200 c and then decreased suddenly the results indicate that h2 gas is generated by a chemical reaction between water and such radicals as si and si o formed on the fresh surfaces when the si o si bonds are destroyed by crushing and that the existence of a maximum for amount of h2 gas is due to the decrease of the lifetime of si o radical at the temperature higher than about 200 c the results lend credence to the possibility that h2 gas is generated in the temperature range of 25 270 c along the active fault through the reaction between groundwater and the fresh surfaces of underground rocks formed by the fault movements

earthquake rupture at focal depth part ii mechanics of the 2004 m2 2 earthquake along the pretorius fault tautona mine south africa we analyze here the rupture mechanics of the 2004 m2 2 earthquake based on our observations and measurements at focal depth part i this event ruptured the archean pretorius fault that has been inactive for at least 2 ga and was reactivated due to mining operations down to a depth of 3 6 km depth thus it was expected that the pretorius fault zone will fail similarly to an intact rock body independently of its ancient healed structure our analysis reveals a few puzzling features of the m2 2 rupture zone 1 the earthquake ruptured four non parallel cataclasite bearing segments of the ancient pretorius fault zone 2 slip occurred almost exclusively along the cataclasite host rock contacts of the slipping segments 3 the local in situ stress field is not favorable to slip along any of these four segments and 4 the archean cataclasite is pervasively sintered and cemented to become brittle and strong to resolve these observations we conducted rock mechanics experiments on the fault rocks and host rocks and found a strong mechanical contrast between the quartzitic cataclasite zones with elastic brittle rheology and the host quartzites with damage elastic plastic rheology the finite element modeling of a heterogeneous fault zone with the measured mechanical contrast indicates that the slip is likely to reactivate the ancient cataclasite bearing segments as observed due to the strong mechanical contrast between the cataclasite and the host quartzitic rock

dating very old pore waters in impermeable rocks by noble gas isotopes the sup 4 he sup 40 ar and sup 136 xe content dissolved in the pore water of sedimentary rock samples was measured on samples from borehole cores near the repository for nuclear waste in morsleben germany due to the very low permeabilities of the rock formations conventional groundwater sampling was almost impossible hence the authors developed a new sampling method for noble gases in the pore water of freshly drilled rock cores this method provides vertical noble gas profiles in high depth resolution even in impermeable rocks by application of the new technique quantitative age information of groundwater and pore water have been derived the authors find palaeowaters from the last glaciation depleted in delta d and delta sup 18 o with a sup 4 he age of about 55 kyr the high saline pore solutions below are at least 6 mio years old this has been concluded from the profiles of radiogenic sup 4 he and sup 40 ar close to diffusion in steady state and from xenon isotopes produced by spontaneous fission of sup 238 u in the rocks a sup 4 he flux of 2 center dot 10 sup minus 7 cc stp cm sup 2 yr is derived from the profile which is due to local sup 4 he production within the investigatedmore sediments less

extension of gutenberg richter distribution to mw 1 3 no lower limit in sight 1 with twelve years of seismic data from tautona gold mine south africa we show that mining induced earthquakes follow the gutenberg richter relation with no scale break down to the completeness level of the catalog at moment magnitude mw 1 3 events recorded during relatively quiet hours in 2006 indicate that catalog detection limitations not earthquake source physics controlled the previously reported minimum magnitude in this mine within the natural earthquake laboratory in south african mines nelsam experiment s dense seismic array earthquakes that exhibit shear failure at magnitudes as small as mw 3 9 are observed but we find no evidence that mw 3 9 represents the minimum magnitude in contrast to previous work our results imply small nucleation zones and that earthquake processes in the mine can readily be scaled to those in either laboratory experiments or natural faults

quantitative mineralogy of the yukon river system changes with reach and season and determining sediment provenance the mineralogy of yukon river basin sediment has been studied by quantitative x ray diffraction bed beach bar and suspended sediments were analyzed using the rockjock computer program the bed sediments were collected from the main stem and from selected tributaries during a single trip down river from whitehorse to the yukon river delta during the summer of 2001 beach and bar sediments were collected from the confluence region of the tanana and yukon rivers during the summer of 2003 suspended sediments were collected at three stations on the yukon river and from a single station on the tanana river at various times during the summers of 2001 through 2003 with the most complete set of samples collected during the summer of 2002 changes in mineralogy of yukon river bed sediments are related to sediment dilution or concentration effects from tributary sediment and to chemical weathering during transport carbonate minerals compose about 2 wt of the bed sediments near whitehorse but increase to 14 wt with the entry of the white river tributary above dawson thereafter the proportion of carbonate minerals decreases downstream to values of about 1 to 7 wt near the mouth of the yukon river quartz and feldspar contents of bed sediments vary greatly with the introduction of pelly river and white river sediments but thereafter either increase irregularly quartz from 20 to about 50 wt or remain relatively constant feldspar at about 35 wt with distance downstream clay mineral content increases irregularly downstream from about 15 to about 30 wt the chief clay mineral is chlorite followed by illite smectite there is little to no kaolinite the total organic carbon content of the bed sediments remains relatively constant with distance for the main stem generally 1 to 2 wt with one exception but fluctuates for the tributaries 1 to 6 wt the mineralogies of the suspended sediments and sediment flow data were used to calculate the amount of mineral dissolution during transport between eagle and pilot station a distance of over 2000 km we estimate that approximately 3 wt of the quartz 15 wt of the feldspar 1 wt of the alkali and 25 wt of the plagioclase and 26 wt of the carbonates 31 wt of the calcite and 15 wt of the dolomite carried by the river dissolve in this reach the mineralogies of the suspended sediments change with the season for example during the summer of 2002 the quartz content varied by 20 wt with a minimum in mid summer the calcite content varied by a similar amount and had a maximum corresponding to the quartz minimum these modes are related to the relative amount of sediment flowing from the white river system which is relatively poor in quartz but rich in carbonate minerals suspended total clay minerals varied by as much as 25 wt with maxima in mid july and suspended feldspar varied up to 10 wt suspended sediment data from the summers of 2001 and 2003 support the 2002 trends a calculation technique was developed to determine the proportion of various sediment sources in a mixed sediment by unmixing its quantitative mineralogy results from this method indicate that at least three sediment sources can be identified quantitatively with good accuracy with this technique sediment mineralogies can be used to calculate the relative flux of sediment from different tributaries thereby identifying sediment provenance

formation of an archaean continent about 30 of the earth is covered by continents but only about 10 small kernels of these continentsae known as archaean cratonsae are continental fragments formed before 2 5 gyr ago the kaapvaal craton of south africa which formed and stabilized between 3 7 and 2 7 gyr ago is one of the oldest reasonably sized examples of these continental fragments it consists of a mosaic of subdomains that have been welded together by processes similar to those of modern day plate tectonics the earliest subdomains may have owed their origin to the onset of efficient recycling from the earth s hydrosphere into the mantle

exposed cross sections through the continental crust implications for crustal structure petrology and evolution abstract the continental crust is exposed in cross section at numerous sites on the earth s surface these exposures which appear to have formed by obduction along great faults during continental collision may be recognized by exposures of deep crustal rocks exhibiting asymmetric patterns of metamorphic grade and age across the faults and by distinctive bouguer anomaly patterns reflecting dipping basement structure and an anomalously deep mantle from an examination of five complexes which meet these criteria it is concluded that the most prominent layering in the crust is not compositional but metamorphic the lower crust consists of granulite facies rocks of mafic to intermediate composition while the intermediate and shallow levels consist predominantly of amphibolite facies gneisses and greenschist facies supracrustal rocks respectively post metamorphic granitic intrusions are common at intermediate to shallow levels position of discontinuities in refraction velocity where present commonly correspond to changes in composition or metamorphic grade with depth the continental crust is characterized by lateral and vertical heterogeneities of varying scale which are the apparent cause of the complex seismic reflections recorded by cocorp field observations coupled with geochemical data indicate a complex evolution of the lower crust which can include anatexis multiple deformation polymetamorphism and reworking of older crustal material the complexity of the crust is thus the result of continuous evolution by recycling and metamorphism through time in a variety of tectonic environments

late quaternary detrital carbonate dc layers in baffin bay marine sediments 67 74 n correlation with heinrich events in the north atlantic abstract episodes of glaciation in the region north of baffin bay resulted in the erosion of paleozoic carbonate outcrops in nw greenland and the canadian high arctic these events are recognized in the marine sediments of baffin bay bb as a series of detrital carbonate rich dc layers bbdc layers thin southward within baffin bay thus the contribution of baffin bay ice rafted carbonate rich sediments to the north atlantic is probably slight especially compared with sediment output from hudson strait during heinrich events we reexamine cf aksu 1981 a series of nine piston cores from the axis of baffin bay and across the davis strait sill and provide a suite of 21 ams 14 c dates on foramininfera which bracket the ages of several dc layers the onset of the last dc event is dated in six cores and has an age of ca 12 4 ka in northern and central baffin bay a thick dc layer occurs at around 4 m in the cores and is dated 40 ka there were three to six dc intervening events the youngest bbdc event possibly a double event lags heinrich event 1 h 1 off hudson strait dated at 14 5 ka but it is coeval with the pronounced warming seen in gisp2 records from the greenland ice sheet during interstadial 1 we hypothesize that bbdc episodes are coeval with major interstadial 18 o peaks from gisp2 and other greenland ice core records and are caused by or associated with the advection of atlantic water into baffin bay cf hiscott et al 1989 and the subsequent rapid retreat of ice streams in the northern approaches to baffin bay

gas geochemistry applied to earthquake prediction an overview terrestrial gases in groundwater and soil air have been extensively studied in recent years in seismically active areas especially in ussr china japan and united states in search of premonitory changes that might be useful for earthquake prediction concentrations of radon helium hydrogen mercury carbon dioxide and several other volatiles have been found generally to be anomalously high along active faults suggesting that the faults may be paths of least resistance for the terrestrial gases generated or stored in the earth to escape to the atmosphere temporal gas concentration changes with durations of a few hours to many months have been observed before many large earthquakes at a relatively small number of favorably situated stations at epicentral distances of up to several hundreds of kilometers these sensitive stations are generally located along active faults especially at intersections or bends of faults or some other structurally weak zones possibly because of tectonic strain concentration at such places however gas concentrations especially those measured at or near the ground surface may also be significantly affected by meteorological hydrological and other nontectonic changes in the environment the nontectonically induced variations must be carefully eliminated or recognized in the search of true earthquake related anomalies

discriminating characteristics of tectonic and human induced seismicity we analyze statistical features of background and clustered subpopulations of earthquakes in different regions in an effort to distinguish between human induced and natural seismicity analysis of end member areas known to be dominated by human induced earthquakes the geyser geothermal field in northern california and tautona gold mine in south africa and regular tectonic activity the san jacinto fault zone in southern california and the coso region excluding the coso geothermal field in eastern central california reveals several distinguishing characteristics induced seismicity is shown to have 1 higher rate of background events both absolute and relative to the total rate 2 faster temporal offspring decay 3 higher rate of repeating events 4 larger proportion of small clusters and 5 larger spatial separation between parent and offspring compared to regular tectonic activity these differences also successfully discriminate seismicity within the coso and salton sea geothermal fields in california before and after the expansion of geothermal production during the 1980s online material figures of examined regions earthquake epicenters and joint distributions of the time and space components of the nearest neighbor distance

structural inheritance in mountain belts an alpine apennine perspective abstract the geological structure of continental lithosphere shows complex variety that is inherited into orogenic belts and influences the localization and amplification of contractional structures during mountain building in the alpine apennine sector together with other sectors of the tethyan orogenic system the pre orogenic crustal template can include arrays of extensional faults other faults can form adjacent to the evolving mountain belt and subsequently become incorporated as the thrust belts migrate into their forelands while in some areas these inherited features may simply reactivate under inversion more commonly faults show complex partial reactivation structures in volumes of distributed strain faults may serve to nucleate large scale buckle folds for example along basement cover interfaces these different patterns of basement reactivation may reflect spatially varying strength depth profiles in continental lithosphere that are themselves inherited from spatially distinct geological histories even when not themselves reactivating basement faults can control deformation in the overlying sedimentary cover by offsetting otherwise regionally extensive detachment horizons the 3d form of thrust systems can be strongly compartmentalized by pre existing cross faults such as the oblique lineaments of the apennines on a large scale the distribution of pre existing faults and other weaknesses may affect the propensity for orogenic contraction in basement and therefore directly control larger scale tectonic processes in the central mediterranean the evolution of slab roll back and the related growth of overlying extensional basins e g tyrrhenian sea may be strongly modulated by the distribution of rift related weak zones in the adjacent continental crust the subduction of continental crust will strongly depend on the inherited structure of this crust specifically the distribution of deep crust of basic composition this develops relatively higher densities associated with eclogite metamorphism which act in turn to reduce the buoyancy of thickened continental crust that otherwise serves to inhibit further shortening investigating all these aspects from the scale of bulk crustal compositions to the geometry timing and strength of earlier fault zones preserved in orogenic belts requires the integration of substantial multidisciplinary geological data sets the extent to which continental orogenic belts represent the amplification of inherited geological heterogeneities as opposed to self ordered phenomena modulated by the syntectonic environment remains unclear

influence of the atlantic subpolar gyre on the thermohaline circulation during the past decade record high salinities have been observed in the atlantic inflow to the nordic seas and the arctic ocean which feeds the north atlantic thermohaline circulation thc this may counteract the observed long term increase in freshwater supply to the area and tend to stabilize the north atlantic thc here we show that the salinity of the atlantic inflow is tightly linked to the dynamics of the north atlantic subpolar gyre circulation therefore when assessing the future of the north atlantic thc it is essential that the dynamics of the subpolar gyre and its influence on the salinity are taken into account

impact of blasting on groundwater composition in a fracture in canada s underground research laboratory groundwater composition in a discrete water bearing fracture in granitic rock at the underground research laboratory manitoba was monitored during a period of underground excavation of adjacent rock to determine the impact of conventional blasting techniques and rock fracturing on the concentration of dissolved constituents this work has relevance to the study of hydrogeochemical anomalies associated with seismic activity short lived anomalies such as decreases in dissolved anion cl f br so4 and gas he rn concentrations and concurrent increases in no3 and o2 concentrations were seen shortly after two blasts located opposite the groundwater sampling site a third blast downstream of the site resulted in variability in dissolved gases concentrations but showed no impact on dissolved anion concentrations the results are compared with various models used to account for hydrogeochemical fluctuations associated with earthquakes the data best fit a general form of the aquifer breaching fluid mixing model in which hydrochemical responses are caused by localized changes in hydraulic conductivity along the plane of a fracture which in turn cause changes in mixing ratio of groundwater at the monitoring site

heinrich event 0 dc 0 in sediment cores from the northwest labrador sea recording events in cumberland sound layers of ice rafted limestone debris rich sediment were deposited in the northwest labrador sea and the north atlantic during the last glacial period 10 80 ka these sediments were deposited by heinrich events h events which record catastrophic collapses of the laurentide ice sheet in the region of the hudson strait these intervals of detrital carbonate rich sediments are referred to as detrital carbonate layers dc in the northwest labrador sea accelerator mass spectrometry ams 14c dates provide a strong constraint on the timing for these events h 1 dc 1 and h 2 dc 2 dc 0 also known as h 0 correlative to the younger dryas cooling event is not as distinct a sediment unit in the northwest labrador sea as dc 1 and dc 2 an analysis of sediments from two cores hu75009 iv 055 and hu75009 iv 056 off the mouth of the hudson strait in the northwest labrador sea basin sheds new light on the missing dc 0 sediment unit timing for the dc 0 event in cores 055 and 056 is bracketed between 11

holocene variations in mineral and grain size composition along the east greenland glaciated margin ca 67 70 n local versus long distance sediment transport quantitative x ray diffraction qxrd analysis of the 2 mm sediment fraction from surface sea floor samples and marine sediment cores that span the last 10 12 cal ka bp are used to describe spatial and temporal variations in non clay mineral compositions for an area between kangerlussuaq trough and scoresby sund 67 70 n east greenland bedrock consists primarily of an early tertiary alkaline complex with high weight of pyroxene and plagioclase farther inland and to the north the bedrock is dominantly felsic with a high fraction of quartz and potassium feldspars principal component pc analysis of the non clay sediment compositions indicates the importance of quartz and pyroxene as compositional end members with an abrupt shift from quartz and k feldspar dominated sediments north of scoresby sund to sediments rich in pyroxene and plagioclase feldspars offshore from the early tertiary basaltic outcrop coarse 2 mm or 1 mm ice rafted sediments are largely absent from the trough sediments between 8 and 5 cal ka bp but then increase in the last 4 cal ka bp compositional unmixing of the sediments in grivel basin and kangerlussuaq trough indicate the dominance of local over long distance sediment sources with pulses of sediment from tidewater glaciers in kangerlussuaq and nansen fjords reaching the inner shelf during the neoglaciation the change in ird is more dramatic in the sediment grain size proxies than in the quartz wt forty to seventy percent of the variance in the quartz records from either side of denmark strait is explained by low frequency trends but the data from the grivel basin east greenland are distinctly different with an approximate 2500 yr periodicity

evidence for an additional heinrich event between h5 and h6 in the labrador sea 1 an additional heinrich ice rafting event is identified between heinrich events 5 and 6 in eight cores from the labrador sea and the northwest atlantic ocean it is characterized by sediment rich in detrital carbonate 40 caco3 with high concentration of floating dropstones high coarse fraction 150 m content and has a sharp contact with the underlying but grades into the overlying hemipelagic sediment it also shows lighter 18onpl values indicating freshening due to iceberg rafting and or meltwater discharge this event is correlated with dansgaard oeschger event 14 and interpreted as an additional heinrich event h5a the thickness of h5a in the labrador sea reaches up to 220 cm this additional heinrich event has also been reported in cores ps2644 and so82 5 from the northern north atlantic with the recognition of h5a the temporal spacing between heinrich events 1 to 6 becomes more uniform 7 ka

eclogite formation and dynamics of crustal roots under continental collision zones field observations on deep parts of the root zone of the caledonian orogen are combined with the geophysical data available for recent continental collision zones such as the alps to provide a model for dynamics of crustal root zones rocks descending into the root zone are locally infiltrated by fluids which cause eclogitization along shear zones and fluid pathways the eclogite facies rocks vary in density from 3 1 to 3 6 g cm 3 reflecting the compositional variation in their protoliths where the amount of highly ductile eclogitic material reaches about 40 the descending crustal segment loses its coherence and disintegrates into a breccia where blocks of granulite facies rocks float in a matrix of eclogite material a density stratified root zone develops where light unreacted or partly eclogitized material floats on an ocean dominated by eclogite facies rocks the top of which may correspond to the moho catastrophic decent of this eclogitic layer may 1 transport blocks of light material to depths of 90 km which upon further disintegration due to eclogitization are released and return by buoyancy forces to the crust 2 result in extension and uplift of the partly eclogitized lighter material

provenance of sediment in the labrador current a record of hinterland glaciation over the past 125 ka the labrador current flows southward along the continental margin off eastern canada and is the principal source of sediment to the outer continental margin areas where ice sheets did not cross the continental shelf we present multi proxy mineralogical and geochemical records based principally on x ray diffraction and x ray fluorescence for core 2011031 059 from northern flemish cap to determine changes in supply and hence to reconstruct provenance evolution during the last glacial cycle the calcite to dolomite ratios in heinrich layers ranged from 2 to 4 suggesting carbonate layers derived from hudson strait as early as marine isotope stage mis 5a d mineral abundance shows three time dependent predominant sediment sources other than in heinrich layers i baffin bay shelves and adjacent land in mis 5 and 1 with high ca sr kaolinite and feldspars and low clay minerals and calcite dolomite ratios ii labrador in mis 3 with low clays and grey color and iii north east newfoundland shelf in mis 2 and 4 with higher concentrations of clay minerals red sandstones and transition elements these results allow a reconstruction of principal ice streams supplying the north west atlantic over the last full glacial cycle

a high resolution sea surface temperature record from the tropical south china sea 16 500 3000 yr b p the timing and magnitude of sea surface temperature sst changes in the tropical southern south china sea scs during the last 16 500 years have been reconstructed on a high resolution c 14 dated sediment core using three different foraminiferal transfer functions simmax28 ram fp 12e and geochemical u 37 k sst estimates in agreement with climap reconstructions both the fp 12e and the u 37 k sst estimates show an average late glacial interglacial sst difference of 2 0 degreesc whereas the ram and simmax28 foraminiferal transfer functions show only a minor 0 6 degreesc or no consistent late glacial interglacial sst change respectively both the u 37 k and the fp 12e sst estimates as well as the planktonic foraminiferal delta o 18 values indicate an abrupt warming ca 1 degreesc in 200 yr at the end of the last glaciation synchronous within dating uncertainties with the bolling transition as recorded in the greenland ice sheet project 2 gisp2 ice core whereas the ram derived deglacial sst increase appears to lag during this event by ca 500 yr the similarity in abruptness and timing of the warming associated with the bolling transition in greenland and the southern scs suggest a true synchrony of the northern hemisphere warming at the end of the last glaciation in contrast to the foraminiferal transfer function estimates that do not indicate any consistent cooling associated with the younger dryas yd climate event in the tropical scs the u 37 k sst estimates show a cooling of ca 0 2 0 6 degreesc compared to the bolling allerod period these u 37 k sst estimates from the southern scs argue in favor of a northern hemisphere wide synchronous cooling during the yd period c 2001 university of washington

heinrich events massive late pleistocene detritus layers of the north atlantic and their global climate imprint 1 millennial climate oscillations of the glacial interval are interrupted by extreme events the so called heinrich events of the north atlantic their near global footprint is a testament to coherent interactions among earth s atmosphere oceans and cryosphere on millennial timescales heinrich detritus appears to have been derived from the region around hudson strait it was deposited over approximately 500 250 years several mechanisms have been proposed for the origin of the layers binge purge cycle of the laurentide ice sheet jokulhlaup activity from a hudson bay lake and an ice shelf buildup collapse fed by hudson strait to determine the origin of the heinrich events i recommend 1 further studies of the timing and duration of the events 2 further sedimentology study near the hudson strait and 3 greater spatial and temporal resolution studies of the layers as well as their precursory intervals studies of previous glacial intervals may also provide important constraints

a 1 ma record of sediment flux south of the grand banks used to infer the development of glaciation in southeastern canada abstract a 20 m long piston core from a basement ridge on the continental rise off southeastern canada provides a 0 9 ma record of distal continental margin sedimentation sediment sources are distinguished by sand and clay sized mineralogy and detrital palynomorphs they include detritus eroded from a northern canadian shield and lower paleozoic rocks transported southward through the labrador sea b the grand banks and c the gulf of st lawrence and newfoundland isotopic stratigraphy allows correlation of glacial and interglacial stages with changes in sources and flux rates via different transport processes nepheloid layer ice rafting and distal turbidity currents the glacial history of southeastern canada is interpreted from variation in the flux and type of detrital material and correlation with other data from the continental margin from stages 27 to 15 the grand banks formed a forested coastal plain limited local glaciation may have occurred in stages 18 and 16 tertiary regolith and cretaceous clays were stripped from land areas in stages 14 and 12 culminating in the excavation of the laurentian channel late in stage 12 extensive cold based ice sheets are inferred for glacial stages 10 8 and 6 with less severe glaciation in stages 4 and 2 extent of this local appalachian ice correlates poorly with global ice volumes

petrographic evidence from the eastern canadian margin of shelf crossing glaciations abstract it is difficult to evaluate when and where glaciers extended across the outer continental shelf off eastern canada the outer shelf and upper slope are commonly hard bottomed or have a great thickness of post glacial sediment in either case making direct sampling and dating of ice margin sediment impossible the timing and extent of glacier ice is important for understanding continental slope sedimentation and ice sheet dynamics we have therefore determined the lithologic components of the 1 4 mm granule fraction of over 100 well dated samples from 40 cores from the more distal parts of the deep water margin off nova scotia and newfoundland this fraction is demonstrably ice rafted in these cores and geographic variation in component results from input of icebergs at different calving margins the samples show that heinrich layers have a distinctive granule fraction that shows some areal variation as a result of dilution by sources other than hudson strait heinrich event 2 ca 21 ka is widespread as far southwest as the west scotian slope but by the last glacial maximum lgm numerous discrete sources of ice rafted granules are recognised implying that calving ice margins were present in several places off newfoundland and nova scotia including off banquereau a distinctive purplish lgm gravelly mud is recognised on the eastern newfoundland margin derived from a calving margin on the ne newfoundland shelf at the time of heinrich event 1 ca 14 ka there was a calving ice outlet somewhere on the grand banks and another in halibut channel retreat of ice from the gulf of st lawrence can be tracked by changing granule petrology from the lgm to 13 ka these data suggest that final ice retreat from many parts of the outer shelf was later than is shown in many recent ice margin reconstructions