a minimum sample size required from schmidt hammer measurements the schmidt hammer is a useful tool applied by geomorphologists to measure rock strength in field conditions the essence of field application is to obtain a sufficiently large dataset of individual rebound values which yields a meaningful numerical value of mean strength although there is general agreement that a certain minimum sample size is required to proceed with the statistics the choice of size i e number of individual impacts was usually intuitive and arbitrary in this paper we show a simple statistical method based on the two sample student s t test to objectively estimate the minimum number of rebound measurements we present the results as 1 the mean and median solutions each providing a single estimate value and 2 the empirical probability distribution of such estimates based on many field samples schmidt hammer data for 14 lithologies 13 81 samples for each with each sample consisting of 40 individual readings have been evaluated assuming different significance levels the principal recommendations are 1 the recommended minimum sample size for weak and moderately strong rock is 25 2 a sample size of 15 is sufficient for sandstones and shales 3 strong and coarse rocks require 30 readings at a site 4 the minimum sample size may be reduced by one third if the context of research allows for higher significance level for test statistics interpretations based on less than 10 readings from a site should definitely be avoided copyright 2009 john wiley sons ltd

rock weathering rates as functions of time the scarcity of documented numerical relations between rock weathering and time has led to a common assumption that rates of weathering are linear this assumption has been strengthened by studies that have calculated long term average rates however little theoretical or empirical evidence exists to support linear rates for most chemical weathering processes with the exception of congruent dissolution processes the few previous studies of rock weathering rates that contain quantitative documentation of the relation between chemical weathering and time suggest that the rates of most weathering processes decrease with time recent studies of weathering rinds on basaltic and andesitic stones in glacial deposits in the western united states also clearly demonstrate that rock weathering processes slow with time some weathering processes appear to conform to exponential functions of time such as the square root time function for hydration of volcanic glass which conforms to the theoretical predictions of diffusion kinetics however weathering of mineralogically heterogeneous rocks involves complex physical and chemical processes that generally can be expressed only empirically commonly by way of logarithmic time functions incongruent dissolution and other weathering processes produce residues which are commonly used as measures of weathering these residues appear to slow movement of water to unaltered material and impede chemical transport away from it if weathering residues impede weathering processes then rates of weathering and rates of residue production are inversely proportional to some function of the residue thickness this results in simple mathematical analogs for weathering that imply nonlinear time functions the rate of weathering becomes constant only when an equilibrium thickness of the residue is reached because weathering residues are relatively stable chemically and because physical removal of residues below the ground surface is slight many weathering features require considerable time to reach constant rates of change for weathering rinds on volcanic stones in the western united states this time is at least 0 5 my

cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models a number of in situ cosmogenic radionuclides and stable nuclides have been measured in natural exposed rock surfaces with a view to study their in situ production and rock erosion rates 1 the in situ radionuclides can be used for a high resolution tomography of the erosional history of an exposed surface two stable nuclides 3he 21ne and five radionuclides 10be 26al 36cl 14c 39ar having half lives in the range of 300 1 5 106 yr half life are measurable in many rock types a prerequisite for the application of the in situ nuclides for the study of erosional histories of surfaces is a knowledge of their production rates under different irradiation conditions altitude latitude irradiation geometry and shielding relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons 2 absolute nuclide production rates cannot generally be predicted with any accuracy because of lack of data on excitation functions of nuclides unless some normalization is possible as was done in the case of several cosmic ray produced isotopes in the atmosphere 3 based on a recent natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for 11 000 yrs were sampled the absolute production rates of 10be and 26al in quartz have been accurately estimated for mountain altitudes in sierra nevada 4 the absolute production rates of 10be and 26al in quartz can therefore be estimated fairly accurately for any given latitude and altitude some measurements of 14c in rocks of low erosion rate 5 similarly allow an estimate of its production rate attempts made to measure the in situ production rates of 3he in rocks have not yet led to a convergent production rate in view of the importance of knowing the production rates of isotopes of he ne and ar i present here theoretical estimates of their production rates based on available cross section data i discuss the information that can be extracted from the study of the in situ nuclides in rocks useful parameters characterizing the exposure history of a rock surface are 1 the effective surface exposure age and 2 the time averaged erosion rate the implications of these parameters for single and multiple nuclide studies are discussed in terms of the erosion models considered

methane flux and origin in the othrys ophiolite hyperalkaline springs greece abstract the occurrence and origin of methane ch4 generated by serpentinization of ultramafic rocks is of current timely interest in planetary geology astrobiology and energy resource exploration as it may contribute in particular to decipher the source of methane on mars the origin of life and the potential of abiotic hydrocarbon synthesis methane of dominant abiotic origin in serpentinized peridotites on continents ophiolites or igneous intrusions has been documented so far with complete carbon and hydrogen isotope composition in six countries in the philippines turkey oman new zealand japan and italy we report the discovery of two new sites in greece at archani and ekkara located in the othrys ophiolite massif portable sensors based on fourier transform infrared spectrometry ftir and tunable diode laser absorption spectroscopy tdlas allowed to realize that out of 21 ophiolitic springs methane is released only by four hyperalkaline ph from 10 7 to 11 3 and calcium hydroxide ca oh type waters all other 17 springs with ph

initial indications of abiotic formation of hydrocarbons in the rainbow ultramafic hydrothermal system mid atlantic ridge in the presence of water olivine of ultramafic rock is oxidized during the process referred to as serpentinization water in contact with the olivine is reduced to molecular hydrogen h2 with the concomitant oxidation of fe ii the molecular hydrogen formed may be used as an energy source by lithotrophic bacteria but may at high temperature also be combined with co2 for the abiotic formation of organic compounds such as hydrocarbons and fatty acids through fischer tropsch type ftt synthesis our analyses of fluids from the peridotite hosted rainbow hydrothermal field on the mid atlantic ridge indicate de novo synthesis of linear saturated hydrocarbons the chain length of the hydrocarbons is between 16 and 29 carbon atoms the discovery of ftt reactions in ultramafic hydrothermal systems on earth provides an alternative pathway for the formation of early membranes and the origin of life

surface and sub surface schmidt hammer rebound value variation for a granite outcrop this study presents rock strength variations at granite outcrops and in subsurface vertical profiles in the jizerske hory mountains czech republic schmidt hammer rebound values in subsurface profiles change gradually from the bedrock surface downward an exponential relation has been observed between the r values and depth in rock outcrops to a depth of around 4 5 m the exponential nature of the curve indicates that rock hardness increases more rapidly with depth in the uppermost 1 m section of the rock profile a detailed study of rebound values obtained from both intact and polished rock exposures reveal effects of surface grinding on results of the schmidt hammer method the range of data collected increases after grinding allowing more precise discrimination of rock surfaces in respect of age and weathering the schmidt hammer method may be used effectively as a relative age dating tool for rock surfaces that originated during the late pleistocene it is concluded that this time limitation can be significantly mitigated by surface grinding before measurement copyright 2010 john wiley sons ltd

serpentinization and heat generation constraints from lost city and rainbow hydrothermal systems abstract the discovery of ultramafic hosted hydrothermal systems at rainbow 36 n mar and lost city a vent site approximately 15 km west of the mar at 30 n provides unique perspectives on chemical and heat generating processes associated with serpentinization at a range of chemical and physical conditions heat balance calculations together with constraints imposed by geochemical modeling indicate that significant changes in temperature are not likely to occur at either vent system as a result of the exothermic nature of olivine hydrolysis at rainbow the relatively high temperatures in subseafloor reaction zones in excess of 400 c which must be linked to magmatic processes inhibit olivine hydrolysis effectively precluding mineralization induced heating effects geochemical modeling of the lost city vent fluids indicates temperatures in excess of those measured 40 75 c the relatively high subseafloor temperatures 200 50 c requires conductive cooling of the fluids on ascent to the seafloor a scenario in keeping with the mineralization of chimney structures actually observed although the intermediate temperatures predicted for subseafloor reaction zones at lost city could be expected to enhance olivine to serpentine conversion dissolved cl k cl and na cl ratios of the lost city vent fluids are virtually unchanged from seawater values and indicate little hydration of olivine which is a necessary condition for exothermic heat generation by serpentinization apparently the fluid rock mass ratio is too high or fluid residence times too low for this to occur to any significant extent thus in spite of the off axis location of the lost city vents and apparent lack of a localized heat source mineralization reactions likely play an insignificant role in accounting for hydrothermal circulation it is more likely that tectonic processes associated with the slow spreading mar permit access of seawater to relatively deep and still hot lithospheric units and or near axis magmatic heat sources before venting additional chemical and physical temperature flow rate data for lost city and similar hydrothermal systems are needed to test key elements of the proposed model

sulfur mineralogy and geochemistry of serpentinites and gabbros of the atlantis massif iodp site u1309 abstract in situ uplifted portions of oceanic crust at the central dome of the atlantis massif mid atlantic ridge 30 n were drilled during expeditions 304 and 305 of the integrated ocean drilling program iodp and a 1 4 km section of predominantly gabbroic rocks with minor intercalated ultramafic rocks were recovered here we characterize variations in sulfur mineralogy and geochemistry of selected samples of serpentinized peridotites olivine rich troctolites and diverse gabbroic rocks recovered from hole 1309d these data are used to constrain alteration processes and redox conditions and are compared with the basement rocks of the southern wall of the atlantis massif which hosts the lost city hydrothermal field 5 km to the south the oceanic crust at the central dome is characterized by ni rich sulfides reflecting reducing conditions and limited seawater circulation during uplift and exhumation seawater interaction in gabbroic dominated domains was limited as indicated by homogeneous mantle like sulfur contents and isotope compositions of gabbroic rocks and olivine rich troctolites local variations from mantle compositions are related to magmatic variability or to interaction with seawater derived fluids channeled along fault zones the concomitant occurrence of mackinawite in olivine rich troctolites and an anhydrite vein in a gabbro provide temperature constraints of 150 200 c for late circulating fluids along local brittle faults below 700 m depth in contrast the ultramafic lithologies at the central dome represent domains with higher seawater fluxes and higher degrees of alteration and show distinct changes in sulfur geochemistry the serpentinites in the upper part of the hole are characterized by high total sulfide contents high 34ssulfide values and low 34ssulfate values which reflect a multistage history primarily controlled by seawater gabbro interaction and subsequent serpentinization the basement rocks at the central dome record lower oxygen fugacities and more limited fluid fluxes compared with the serpentinites and gabbros of the lost city hydrothermal system our studies are consistent with previous results and indicate that sulfur speciation and sulfur isotope compositions of altered oceanic mantle sequences commonly evolve over time heterogeneities in sulfur geochemistry reflect the fact that serpentinites are highly sensitive to local variations in fluid fluxes temperature oxygen and sulfur fugacities and microbial activity

asphaltene bearing mantle xenoliths from hyblean diatremes sicily abstract microscopic blebs of sulfur bearing organic matter om commonly occur between the secondary calcite grains and fibrous phyllosilicates in extensively serpentinized and carbonated mantle derived ultramafic xenoliths from hyblean nephelinite diatremes sicily italy rarely coarse bituminous patches give the rock a blackish color micro fourier transform infrared spectra ftir point to asphaltene like structures in the om due to partially condensed aromatic rings with aliphatic tails consisting of a few c atoms x ray photoelectron spectroscopy xps analysis indicates the occurrence of minor s o either sulphonyl or sulphoxide functional groups in the om solubility tests in toluene thermo gravimetric tga and differential thermal dta analyses confirm the presence of asphaltene structures it is proposed that asphaltenes derive from the in situ aromatization with decrease in h c ratio of previous light aliphatic hydrocarbons field evidence excludes that hydrocarbon from an external source percolated through the xenolith bearing tuff breccia the discriminating presence of hydrocarbon in a particular type of xenolith only and the lack of hydrocarbon in the host breccia matrix are also inconsistent with an interaction between the ascending eruptive system and a supposed deep seated oil reservoir assuming that the hyblean unexposed basement consists of mantle ultramafics and mafic intrusive rocks having hosted an early abyssal type hydrothermal system one can put forward the hypothesis that the hydrocarbon production was related to hydrothermal activity in a serpentinite system although a bacteriogenesis or thermogenesis cannot be ruled out the coexisting serpentine ni fe ores and hydrocarbon strongly suggest a fischer tropsch type ftt synthesis subsequent variations in the chemical and physical conditions of the system for example an increase in the water rock ratio gave rise to partial oxidation and late carbonation of the serpentinite hosted hydrocarbon admitting an authigenic origin for most of the modal calcite 30 50 by volume in these rocks one can conclude as a general rule that un carbonated serpentinites tectonically emplaced at shallow crustal levels are potential reservoir rocks as well putative source rocks for exploitable petroleum reserves

origin of methane and light hydrocarbons in natural fluid emissions a key study from greece abstract greece a country characterised by intense seismic and volcanic activity has a complex geodynamic and geological setting that favours the occurrence of many gas manifestations in this study we address the origin of ch 4 and light hydrocarbons in cold and thermal emissions discharging along the hellenic territory also we investigate their possible relationship with the main geochemical composition of the gases and the different geological settings of the sampling sites for this purpose we collected 101 new samples that were analysed for their chemical o 2 n 2 ch 4 co 2 he ne ar h 2 h 2 s and c 2 c 6 hydrocarbons and isotopic r r a 13 c co 2 13 c ch 4 and 2 h ch 4 composition results show that ch 4 presents a wide range of concentrations from 13 c ch 4 from 79 8 to 45 0 vs v pdb 2 h ch 4 from 311 to 301 vs v smow greece was subdivided in four geologic units external eh and internal ih hellenides hellenic hinterland hh and active volcanic arc va and a decreasing ch 4 concentration from eh to hh was recognized whereas ch 4 showed intermediate concentrations in va the ch 4 c 2 h 6 c 3 h 8 ratios from 1 5 to 93 200 coupled with ch 4 isotopic features suggest that the light alkanes derive from different primary sources and are affected by secondary processes an almost exclusive biotic mainly microbial origin of ch 4 can be attributed to eh gases cold gases at ih have mainly a thermogenic origin although some gases connected to continental serpentinization may have an abiogenic origin methane in gases bubbling in thermal waters of ih hh and va and fumarolic gases of the va seem to have an abiogenic origin although their chemical and isotopic characteristics may have been produced by secondary oxidation of thermogenic ch 4 a process that in some of the sampled gases causes extremely positive isotopic values 13 c ch 4 up to 45 0 vs v pdb and 2 h ch 4 up to 301 vs v smow

30 000 years of hydrothermal activity at the lost city vent field strontium carbon and oxygen isotope data and radiocarbon ages document at least 30 000 years of hydrothermal activity driven by serpentinization reactions at lost city serpentinization beneath this off axis field is estimated to occur at a minimum rate of 1 2 10 4 cubic kilometers per year the access of seawater to relatively cool fresh peridotite coupled with faulting volumetric expansion and mass wasting processes are crucial to sustain such systems the amount of heat produced by serpentinization of peridotite massifs typical of slow and ultraslow spreading environments has the potential to drive lost city type systems for hundreds of thousands possibly millions of years

timing and climatic drivers for glaciation across semi arid western himalayan tibetan orogen abstract mapping and forty seven new 10 be ages help define the timing of glaciation in the ladakh and pangong ranges in northwest india five new local glacial stages are defined for the ladakh range from oldest to youngest these include the ladakh 4 glacial stage at 81 20 ka the ladakh 3 glacial stage not dated the ladakh 2 glacial stage at 22 3 ka the ladakh 1 glacial stage not dated and the ladakh cirque glacial stage at 1 8 0 4 ka three local glacial stages are defined for the pangong range which include the pangong 2 glacial stage at 85 15 ka the pangong 1 glacial stage at 40 3 ka and the pangong cirque glacial stage at 0 4 0 3 ka the new 10 be ages are combined with 645 recalculated 10 be ages from previous studies to develop the first regional framework of glaciation across the dryland regions of the greater himalaya transhimalaya pamir and tian shan at the western end of the himalayan tibetan orogen nineteen regional glacial stages are recognized that are termed semi arid western himalayan tibetan stages swhts these include swhts 9 at 311 32 ka swhts 7 at 234 44 ka tentative swhts 6 at 146 18 ka swhts 5e at 121 11 ka swhts 5a at 80 5 ka swhts 5a at 72 8 ka swhts 4 at 61 5 ka swhts 3 at 46 4 ka swhts 2f at 30 3 ka swhts 2e at 20 2 ka swhts 2d at 16 9 0 7 ka swhts 2c at 14 9 0 8 ka swhts 2b at 13 9 0 5 ka swhts 2a at 12 2 0 8 ka swhts 1e at 8 8 0 3 ka tentative swhts 1d at 6 9 0 2 ka tentative swhts 1c at 3 8 0 6 ka swhts 1b at 1 7 0 2 ka and swhts 1a at 0 4 0 1 ka regional glacial stages older than 21 ka are broadly correlated with strong monsoons swhts that are 21 ka or younger have smaller uncertainties and broadly correlate with global ice volume given by marine oxygen isotope stages and northern hemisphere climatic events oldest dryas older dryas younger dryas roman humid period and little ice age

tracing the composition and origin of fluids at an ancient hydrocarbon seep hollard mound middle devonian morocco a nd ree and stable isotope study abstract for the first time nd isotope signatures combined with rare earth element ree concentrations were used in investigations of ancient seep carbonates the study was performed on the fossil hydrocarbon seep deposit of the middle devonian hollard mound eastern anti atlas morocco where nd isotopes ree concentrations and carbon and oxygen isotope ratios were measured to investigate the origin former migration pathways and composition of fluids relatively high end values compared to local eifelian seawater as well as consistently appearing positive eu anomalies in mree enriched shale normalized ree patterns of the seep carbonates provided evidence for interaction between the seeping fluids and the lower devonian basaltic volcaniclastics underlying the studied seep deposit strongly reducing conditions and increased temperature of methane formation could have constituted an additional factor in the eu enrichment of the investigated carbonate phases the presence of exclusively negative ce anomalies in these carbonates is in line with observations of other workers that seep limestones may not necessarily display positive ce anomalies indicative of precipitation under anoxic conditions the negative ce anomalies are attributed here to mixing between anoxic pore waters and oxic ce depleted seawater necessary to enable carbonate precipitation at seeps the methane rich fluids ascended most likely from below the volcaniclastic unit and inherited the enriched end signatures and positive eu anomalies due to fluid rock interactions during their seepage to the seafloor the carbon isotope data are most consistent with thermogenic origin of methane although contribution of abiotic and biogenic methane sources cannot be excluded our results indicate that neodymium isotope and rare earth element analyses constitute one of the most valuable tools for reconstructing former fluid migration patterns the study shows also that nd isotopes and eu anomalies can serve as sensitive tracers of fluid rock interactions at submarine springs

accuracy of cosmogenic ages for moraines analyses of all published cosmogenic exposure ages for moraine boulders show an average age range of 38 between the oldest and youngest boulders from each moraine this range conflicts with the common assumption that ages of surface boulders are the same as the age of the landform the wide spread in boulder ages is caused by erosion of the moraine surface and consequent exhumation of fresh boulders a diffusion model of surface degradation explains the age range and shows that a randomly sampled small set of boulders n 3 7 will always yield a lower age limit for the moraine the model indicates that for identical dating accuracy six to seven boulders are needed from old and tall moraines 40 000 100 000 yr 50 100 m initial height but only one to four boulders from small moraines 20 000 100 000 yr 10 20 m by following these guidelines the oldest obtained boulder age will be 90 of the moraine age 95 probability this result is only weakly sensitive to a broad range of soil erosion rates our analysis of published boulder ages indicates that 3 of all moraine boulders have prior exposure and 85 of these boulders predate the dated moraine

exposure age chronology of the last glaciation in the eastern pyrenees abstract we present a chronology of ice recession in the eastern pyrenees based on in situ produced 10be data obtained from the tet paleoglacier complex the sampling strategy is based on the relative chronology provided by a detailed geomorphological map of glacial landforms results indicate that the last maximum ice advance occurred late i e during marine isotope stage 2 compared to the chronology currently established for the rest of the pyrenees despite debatable evidence for a glacial readvance during the oldest dryas stade ice cap melt out was rapid residual cirque glaciers having disappeared by the allerod interstade this is consistent both with north atlantic excursions established by the greenland ice cores and paleoenvironmental data for the region the rapid response of the east pyrenean ice cap to temperature variations is primarily linked to its small size compared to larger pyrenean ice fields to the dry mediterranean climate and to topography related nonlinearities in which a small vertical rise in equilibrium line altitude generates a large change in ice mass possible sources of age uncertainty are discussed in the context of sampling design for single nuclide 10be dating of landform sequences in formerly glaciated landscapes

sulfur in peridotites and gabbros at lost city 30 n mar implications for hydrothermal alteration and microbial activity during serpentinization variations in sulfur mineralogy and chemistry of serpentinized peridotites and gabbros beneath the lost city hydrothermal field at the southern face of the atlantis massif mid atlantic ridge 30n were examined to better understand serpentinization and alteration processes and to study fluid fluxes redox conditions and the influence of microbial activity in this active peridotite hosted hydrothermal system the serpentinized peridotites are characterized by low total sulfur contents and high bulk d 34 s values close to seawater composition low concentrations of 34 s enriched sulfide phases and the predominance of sulfate with seawater like d 34 s values indicate oxidation loss of sulfide minerals and incorporation of seawater sulfate into the serpentinites the predominance of pyrite in both serpentinites and gabbros indicates relatively high fo2 conditions during progressive serpentinization and alteration which likely result from high fluid fluxes during hydrothermal circulation and evolution of the lost city system from temperatures of 250 to 150 c sulfate and sulfide minerals in samples from near the base of hydrothermal carbonate towers at lost city show d 34 s values that reflect the influence of microbial activity our study highlights the variations in sulfur chemistry of serpentinized peridotites in different marine environments and the influence of long lived moderate temperature peridotite hosted hydrothermal system and high seawater fluxes on the global sulfur cycle

serpentinization carbon and deep life the aqueous alteration of ultramafic rocks through serpentinization liberates mantle carbon and reducing power serpentinization occurs in numerous settings on present day earth including subduction zones mid ocean ridges and ophiolites and has extended far into earth s history potentially contributing to the origins and early evolution of life serpentinization can provide the energy and raw materials to support chemosynthetic microbial communities that may penetrate deep into earth s subsurface microorganisms may also influence the composition and quantity of carbon bearing compounds in the deep subsurface however conditions created by serpentinization challenge the known limits of microbial physiology in terms of extreme ph access to electron acceptors and availability of nutrients furthermore the downward transport of surface carbon and subsequent mixing with calcium rich fluids at high ph contributes to the precipitation and immobilization of carbonate minerals the following chapter will explore the physiological challenges presented by the serpentinite environment data from studies of serpentinite hosted microbial ecosystems and areas in need of further investigation physical and chemical consequences of serpentinization serpentinization is an alteration process of low silica ultramafic rocks characteristic of the lower oceanic crust and upper mantle these rocks are rich in the minerals olivine and pyroxene water rock reactions result in the oxidation of ferrous iron from olivine and pyroxene resulting in the precipitation of ferric iron in magnetite fe3o4 and other minerals and in the release of diatomic hydrogen h2 at low temperatures 150 c the reaction results in extremely high ph commonly above 10 the combination of h2 and co2 or co under highly reducing conditions leads to formation of methane and other hydrocarbons through fischer tropsch type ftt synthesis mccollom and seewald 2001 charlou et al 2002 proskurowski et al 2008 mccollom 2013 serpentinization also results in volume changes in the altered materials making serpentinites less dense than

multiple origins of methane in the earth methane occurrences in the earth s crust are predominantly of biogenic origin i e their ultimate source is biologically formed organic matter methane can also form through inorganic reactions and is consequently termed abiogenic biogenic methanes can either form through bacterial or thermogenic processes bacterial processes follow a co2 reduction and or fermentation pathway the fermentation processes are quantitatively more important in recent fresh sediments and swamps methane formed by co2 reduction however is most common in older sediments and commercial gasfields temperature organic substrate and age may be the major factors controlling the relative importance of the two pathways stable isotope concentrations in thermogenic methanes seem to be controlled by the extent of conversion of organic matter the timing of gas expulsion and trapping the different character of methane in individual sedimentary basins may be a result of the geologic history geothermal methanes are most likely derived from pyrolysis of organic matter abiogenic methane occurs in hydrothermal vents and ophiolite complexes inorganic reactions either surficial or deep seated are the likely source of such methanes a uniform mantle origin of methane is not supported by the observed isotope variations in naturally occurring methanes

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

palaeoenvironments of the late miocene pruedo basin implications for the uplift of the central pyrenees the nature structure and extent of a palaeo basin sedimentary infill exposed in the aran valley central pyrenees was studied by combining stratigraphical and biostratigraphical analyses and an audio magnetotelluric survey the basin developed on top of a pre existing peneplain and was formed by the north maladeta fault activity the fluvio palustrine sequence filling the basin was at least 100 m thick specimens of the taxon hippuris cf parvicarpa nikitin were identified for the first time in a european palaeoflora the palynological and carpological analyses allowed us to 1 constrain the age of the basin infill as vallesian 11 1 8 7 ma 2 characterize the vegetation of the belt surrounding the basin as a mainly temperate to warm temperate assemblage and 3 estimate the palaeoaltitude of the site at between 700 and 1000 m which leads to an altitude change of 900 1200 m for the north maladeta fault downthrown block and 1640 1640 m for the upthrown block these data allowed us to estimate the regional uplift of the area at between 0 08 and 0 19 mm a 1 the different exhumation values obtained by other researchers for sites located at both sides of the north maladeta fault are in agreement with its activity as a normal fault since the late miocene supplementary materials details of the data acquisition processing and modelling for the porera profile are available at www geolsoc org uk sup18551

carbon isotope composition of organic compounds produced by abiotic synthesis under hydrothermal conditions although it is widely believed that production of organic compounds by fischer tropsch synthesis and related processes occurs in many geologic environments unambiguous identification of compounds with an abiotic origin in natural samples has been hampered by a lack of means to discriminate between abiotic compounds and organic matter from biological sources while isotopic compositions might provide a means to discriminate between biologic and non biologic sources of organic matter there are few data presently available to constrain the isotopic composition of compounds produced by abiotic processes in geologic systems here we report results of laboratory experiments conducted to evaluate the isotopic composition of organic compounds synthesized abiotically under hydrothermal conditions we find the organic products are depleted in 13c to a degree typically ascribed to biological processes indicating that carbon isotopic composition may not be a particularly effective diagnostic means to differentiate between biologic and non biologic sources furthermore our results suggest that the isotopic compositions of reduced carbon compounds found in many ancient rocks that have heretofore been attributed to biological sources could be consistent with an abiotic origin in a hydrothermal setting

temperature variations at diffuse and focused flow hydrothermal vent sites along the northern east pacific rise in the decade following documented volcanic activity on the east pacific rise near 9 50 n we monitored hydrothermal vent fluid temperature variations in conjunction with approximately yearly vent fluid sampling to better understand the processes and physical conditions that govern the evolution of seafloor hydrothermal systems the temperature of both diffuse flow low temperature and focused flow high temperature vent fluids decreased significantly within several years of eruptions in 1991 and 1992 after mid 1994 focused flow vents generally exhibited periods of relatively stable slowly varying temperatures with occasional high and low temperature excursions lasting days to weeks one such positive temperature excursion was associated with a crustal cracking event another with both positive and negative excursions demonstrated a subsurface connection between adjacent focused flow and diffuse flow vents diffuse flow vents exhibit much greater temperature variability than adjacent higher temperature vents on timescales of a week or less temperatures at a given position within a diffuse flow field often varied by 5 10 c synchronous with near bottom currents dominated by tidal and inertial forcing on timescales of a week and longer diffuse flow temperatures varied slowly and incoherently among different vent fields at diffuse flow vent sites the conceptual model of a thermal boundary layer immediately above the seafloor explains many of the temporal and spatial temperature variations observed within a single vent field the thermal boundary layer is a lens of warm water injected from beneath the seafloor that is mixed and distended by lateral near bottom currents the volume of the boundary layer is delineated by the position of mature communities of sessile e g tubeworms and relatively slow moving organisms e g mussels vertical flow rates of hydrothermal fluids exiting the seafloor at diffuse vents are less than lateral flow rates of near bottom currents 5 10 cm s the presence of a subsurface shallow reservoir of warm hydrothermal fluids can explain differing temperature behaviors of adjacent diffuse flow and focused flow vents at 9 50 n different average temperatures and daily temperature ranges are explained by variable amounts of mixing of hydrothermal fluids with ambient seawater through subsurface conduits that have varying lateral permeability

too young or too old evaluating cosmogenic exposure dating based on an analysis of compiled boulder exposure ages cosmogenic exposure dating has greatly enhanced our ability to define glacial chronologies spanning several global cold periods and glacial boulder exposure ages are now routinely used to constrai

glacial to interglacial vegetation changes in the northern and southern pyrenees deglaciation vegetation cover and chronology abstract new palynological investigations have been carried out in the southern northern and mediterranean part of the pyrenean chain pollen percentage and concentration diagrams are compared for a period including the end of the glacial period the late glacial and postglacial periods from the new results and from comparisons with previous published data the steppe and semi desert vegetation of the end of the last glacial period are described as well as the plant communities of the period 15 13 ka a dry climate was responsible for the early glacial retreat before 30 ka deglaciation was continuous up to about 15 14 ka without any readvance around 20 18 ka different aspects of the late glacial vegetation are studied and the first stages of the postglacial are described the younger dryas event is found everywhere but particularly clearly in the mediterranean area the most important 14 c dates are discussed and a plateau of 14 c ages is clearly visible around 10 000 bp

a northern lead in the orbital band north south phasing of ice age events abstract re analysis of existing data sets shows that they are fully consistent with northern insolation control of ice age cycles and do not provide strong support for alternate models invoking tropical or southern controls the coldest time of the last 100 ka in central greenland was nearly synchronous with the minimum in summer insolation about 24 ka bp thousand years before 1950 approximately one third of the total termination i warming since then was achieved over the almost 10 ka before the abrupt warming into the bolling which some workers have interpreted as the start of the warming southern warming as recorded in the byrd station antarctica ice isotopic record lagged northern warming co2 rise was roughly synchronous with southern warming methane rise may have been delayed a little as was sea level rise and the change in the isotopic composition of atmospheric oxygen was delayed significantly the data for the extrema just before termination ii are consistent with occurrence of the same phasing as for termination i but with somewhat different progression of the two terminations once initiated perhaps because of differences in the forcing

gas geochemistry and co2 output estimation at the island of milos greece abstract twenty gas samples have been collected from the natural gas manifestations of milos island the majority of which is found underwater along its coast furthermore three anomalous degassing fumarolic areas kalamos paleochori and adamas have been recognized on land almost all the gases are co2 dominated with co2 ranging from 88 to 99 vol for the samples taken underwater while the on land manifestations show a wider range 15 98 due to air contamination methane reaches up to 1 0 vol h2 up to 3 2 vol and h2s up to 3 5 vol indicating a hydrothermal origin of the gases the isotope composition of he points out to mantle contributions up to 45 while the c isotope composition of co2 from 1 9 to 1 3 vs v pdb with most of the values around 0 5 suggests a prevailing limestone origin isotope composition of ch4 ranging from 18 4 to 5 0 vs v pdb for c and from 295 to 7 vs v smow for h points to a geothermal origin with sometimes evident secondary oxidation processes additionally co2 flux measurements showed high values in the three fumarolic areas up to 1100 1500 and 8000 g m2 d at kalamos paleochori and adamas respectively with the highest co2 flux values up to about 23 000 g m2 d being measured in the sea at kanavas with a floating chamber the south western part of the island was covered with a lower density prospection revealing only few anomalous co2 flux values up to 650 g m2 d the total output of the island 30 5 t d is typical of quiescent closed conduit volcanoes and comparable to the other volcanic geothermal systems of the south aegean active volcanic arc nisyros kos nea kameni methana and sousaki

organic synthesis during fluid mixing in hydrothermal systems hydrothermal circulation can lead to fluid mixing on any planet with liquid water and a source of heat aqueous fluids with differing compositions especially different oxidation states are likely to be far from thermodynamic equilibrium when they mix and provide a source of free energy that can drive organic synthesis from co 2 and h 2 and or supply a source of geochemical energy to chemolithoautotrophic organisms results are presented that quantify the potential for organic synthesis during unbuffered fluid mixing in present submarine hydrothermal svstems as well as hypothetical systems that may have existed on the early earth and mars dissolved hydrogen present in submarine hydrothermal fluids owing to the high temperature reduction of h 2 o as seawater reacts with oceanic crustal rocks provides the reduction potential and the thermodynamic drive for organic synthesis from co 2 or bicarbonate as hydrothermal fluids mix with seawater the potential for organic synthesis is a strong function of the h 2 content of the hydrothermal fluid which is in turn a function of the prevailing oxidation state controlled by the composition of the rock that hosts the hydrothermal system hydrothermal fluids with initial oxidation states at or below those set by the fayalite magnetite quartz mineral assemblage show the greatest potential for driving organic synthesis these calculations show that it is thermodynamically possible for 100 of the carbon in the mixed fluid to be reduced to a mixture of carboxylic acids alcohols and ketones in the range 250 50 c as cold seawater mixes with the hydrothermal fluid as the temperature drops larger organic molecules are favored which implies that fluid mixing could drive the geochemical equivalent of a metaholic system this enormous reduction potential probably drives a large portion of the primary productivity around present seafloor hydrothermal vents and would have been present in hydrothermal systems on the early earth or mars the single largest control on the potential for organic synthesis is the composition of the rock that hosts the hydrothermal system

field verification of 2 d and 3 d suspended sediment models a tidal channel in the eastern scheldt estuary in the netherlands was closed by pumping a sand water mixture into the closure gap during the closure fields measurements of flow velocities and sand concentrations are carried out based on the results of the field measurements computations with two and three dimensional sediment transport models are carried out the two dimensional computations show that the depth integrated transport rates can be reasonably predicted in case of diverging flow but less satisfactory results are obtained for converging flow the three dimensional computations show quite good agreement between measured and predicted flow velocities sediment concentrations and transport rates both for flood and ebb flow a sensitivity analysis with respect to the time dependent concentration term the shape of the velocity profiles the turbulent mixing coefficients and the bed material gradiation is carried out the results show no significant influence of these parameters the main reason for the difference between measured and predicted results is caused by the formula modelling the sediment pickup rate

abiotic methane flux from the chimaera seep and tekirova ophiolites turkey understanding gas exhalation from low temperature serpentinization and implications for mars abstract the emission of abiotic methane ch 4 into the atmosphere from low temperature serpentinization in ophiolitic rocks is documented to date only in four countries the philippines oman new zealand and turkey serpentinization produces large amounts of hydrogen h 2 which in theory may react with co 2 or co to form hydrocarbons fischer tropsch type synthesis ftt similar mechanisms have been invoked to explain the ch 4 detected on mars so that understanding flux and exhalation modality of ophiolitic gas on earth may contribute to decipher the potential degassing on mars this work reports the first direct measurements of gas ch 4 co 2 flux ever done on onshore ophiolites with present day serpentinization we investigated the tekirova ophiolites at cirali in turkey hosting the chimaera seep a system of gas vents issuing from fractures in a 5000 m 2 wide ophiolite outcrop at this site at least 150 190 t of ch 4 is annually released into the atmosphere the molecular and isotopic compositions of c 1 c 5 alkanes co 2 and n 2 combined with source rock maturity data and thermogenic gas formation modelling suggested a dominant abiotic component 80 90 mixed with thermogenic gas abiotic h 2 rich gas is likely formed at temperatures below 50 c suggested by the low deuterium hydrogen isotopic ratio of h 2 d h2 720 consistent with the low geothermal gradient of the area abiotic gas synthesis must be very fast and effective in continuously producing an amount of gas equivalent to the long lasting 2 millennia emission of 100 t ch 4 yr 1 otherwise pressurised gas accumulation must exist over the same ophiolitic formation 3 km away from chimaera we detected an invisible microseepage of abiotic ch 4 with fluxes from 0 07 to 1 g m 2 d 1 on mars similar fluxes could be able to sustain the ch 4 plume apparently recognised in the northern summer 2003 10 4 or 10 5 t yr 1 over the wide olivine bedrock and outcrops of hydrated silicates in the syrtis major and nili fossae just one seep like chimaera or more realistically a weak spatially sporadic microseepage would be sufficient to maintain the atmospheric ch 4 level on mars

fe ni co o s phase relations in peridotite seawater interactions serpentinization of abyssal peridotites is known to produce extremely reducing conditions as a result of dihydrogen h2 aq release upon oxidation of ferrous iron in primary phases to ferric iron in secondary minerals by h2o we have compiled and evaluated thermodynamic data for fe ni co o s phases and computed phase relations in fo2 g fs2 g and ah2 aq ah2s aq diagrams for temperatures between 150 and 4008c at 50 mpa we use the relations and compositions of fe ni co o s phases to trace changes in oxygen and sulfur fugacities during progressive serpentinization and steatitization of peridotites from the mid atlantic ridge in the 15820 0 n fracture zone area ocean drilling program leg 209 petrographic observations suggest a systematic change from awaruite magnetite pentlandite and heazlewoodite magnetite pentlandite assemblages forming in the early stages of serpentinization to millerite pyrite polydymite dominated assemblages in steatized rocks awaruite is observed in all brucite bearing partly serpentinized rocks apparently buffering of silica activities to low values by the presence of brucite facilitates the formation of large amounts of hydrogen which leads to the formation of awaruite associated with the prominent desulfurization of pentlandite sulfide is removed from the rock during the initial stage of serpentinization in contrast steatitization indicates increased silica activities and that highsulfur fugacity sulfides such as polydymite and pyrite vaesite solid solution form as the reducing capacity of the peridotite is exhausted and h2 activities drop under these conditions sulfides will not desulfurize but precipitate and the sulfur content of the rock increases the co evolution of fo2 g fs2 g in the system follows an isopotential of h2s aq indicating that h2s in vent fluids is buffered in contrast h2 in vent fluids is not buffered by fe ni co o s phases which merely monitor the evolution of h2 activities in the fluids in the course of progressive rock alteration the co occurrence of pentlandite awaruite magnetite indicates h2 aq activities in the interacting fluids near the stability limit of water the presence of a hydrogen gas phase would add to the catalyzing capacity of awaruite and would facilitate the abiotic formation of organic compounds

low temperature volatile production at the lost city hydrothermal field evidence from a hydrogen stable isotope geothermometer although commonly utilized in continental geothermal work the water hydrogen and methane hydrogen isotope geothermometers have been neglected in hydrothermal studies here we report d ch4 and d h2 values from high temperature black smoker type hydrothermal vents and low temperature carbonate hosted samples from the recently discovered lost city hydrothermal field methane deuterium content is uniform across the dataset at 120 12 hydrogen d values vary from 420 to 330 at high temperature vents to 700 to 600 at lost city the application of several geothermometer equations to a suite of hydrothermal vent volatile samples reveals that predicted temperatures are similar to measured vent temperatures at high temperature vents and 20 60 c higher than those measured at the lost city vents we conclude that the overestimation of temperature at lost city reflects 1 that methane and hydrogen are produced by serpentinization at n110 c and 2 that isotopic equilibrium at temperatures b70 c is mediated by microbial sulfate reduction the successful application of hydrogen isotope geothermometers to low temperature lost city hydrothermal samples encourages its employment with lowtemperature diffuse hydrothermal fluids 2005 elsevier b v all rights reserved

regional synthesis of mediterranean atmospheric circulation during the last glacial maximum atmospheric circulation leaves few direct traces in the geological record making reconstructions of this crucial element of the climate system inherently difficult we produced a regional mediterranean synthesis of paleo proxy data from the sea surface to alpine altitudes this provides a detailed observational context for change in the three dimensional structure of atmospheric circulation between the last glacial maximum lgm 23 000 to 19 000 years ago and the present the synthesis reveals evidence for frequent cold polar air incursions topographically channeled into the northwestern mediterranean anomalously steep vertical temperature gradients in the central mediterranean imply local convective precipitation we find the lgm patterns to be analogous though amplified to previously reconstructed phases of enhanced meridional winter circulation during the maunder minimum the little ice age

formation of h2 ch4 and n species during low temperature experimental alteration of ultramafic rocks abstract hydrogen methane and ammonium are important chemical species for chemolithotrophic microorganisms that sustain subsurface endolithic communities it is well known that production of h 2 through serpentinization of the primary fe ii containing minerals olivine and pyroxene in ultramafic rocks and reduction of co 2 to ch 4 are processes that occur at higher temperatures knowledge is however limited about these reactions under low temperature conditions and how they are affected by fe ii containing secondary minerals such as brucite and serpentine which are commonly found in these environments in this experimental study we explored the formation of h 2 ch 4 and nh 4 during low temperature 25 c reactions between deionised water and 1 unaltered 2 medium altered and 3 highly altered dunites over a period of 99 days hydrogen was detected in all three experiments and the concentration increased over time the o 2 concentration decreased over time but o 2 was still present at significant levels when h 2 started to form this suggests that the h 2 was formed locally at the surface of mineral grains rather than in the hypoxic solution the highly altered dunite gave the highest and the unaltered dunite the lowest h 2 concentrations and while the o 2 concentration decreased fast with the medium altered dunite significant amounts of o 2 still remained with the unaltered dunite at the end of the experiments both the medium and highly altered dunite gave o 2 concentrations close to or below the detection limit during the last part of the experiment factors that likely affected the h 2 production are fe content mineralogy dissolution rates and surface areas of the minerals as well as the presence of catalytic minerals such as chromite and magnetite methane was also detected and increased with time in all experiments the results indicate that ch 4 formation also occurred locally on the surface of minerals detection of both nh 4 and no 3 in the aqueous solutions indicates that previously absorbed n species were leached out during the experiment increasing nh 4 and decreasing no 3 concentrations over time suggest no 3 reduction likely catalysed by mineral surfaces the results imply that low temperature water rock reactions in moderately to highly altered ultramafic rocks provide reduced chemical species that can be utilized as electron donors in energy yielding metabolic processes by subsurface microorganisms such reactions could play an important role in sustaining subsurface microbial communities particularly in ophiolites and near seafloor parts of the ultramafic oceanic lithosphere at slow spreading mid ocean ridges and possibly also in other rocks and sediments the results suggest that brucite and possibly also serpentine may be more important sources of fe ii and thus h 2 formation than olivine in low temperature ultramafic systems formation of h 2 in reducing microenvironments on mineral surfaces surrounded by oxic conditions increases the extent of h 2 formation and the subsurface habitat for aerobic h 2 oxidizing microorganisms

extending the upper temperature limit for life the upper temperature limit for life is a key parameter for delimiting when and where life might have evolved on a hot early earth the depth to which life exists in the earth s subsurface and the potential for life in hot extraterrestrial environments a combination of geological and

the use of the schmidt hammer and equotip for rock hardness assessment in geomorphology and heritage science a comparative analysis rapid field based measurements of rock hardness are of use in investigating many geomorphological and heritage science problems several different methods are now available for taking such measurements but little work has been done to assess their comparability and strengths and weaknesses we review here the capabilities of two types of schmidt hammer classic n type and silver schmidt bl type alongside two types of equotip standard type d and piccolo for investigating rock hardness in relation to rock weathering on various types of sandstone and limestone as well as basalt and dolerite whilst the two schmidt hammers and the two equotips show comparable results when tested at 15 individual sites interesting differences are found between the equotip and schmidt hammer values which may reveal information about the nature of weathering on different surfaces operator variance is shown to be an issue in particular for the equotip devices which also exhibit higher variability in measurements and necessitate larger sample sizes carborundum pre treatment also has varying effects on the data collected depending on the nature of the surface studied the equotip devices are shown to be particularly useful on smaller blocks and in situations where edge effects may affect schmidt hammer readings we conclude that whilst each device contributes to geomorphological research they do not necessarily produce comparable information indeed using schmidt hammer and equotip in combination and looking at any differences in results may provide invaluable insights into the structure of the near surface zones and the nature of weathering processes copyright 2010 john wiley sons ltd

a stratigraphical basis for the last glacial maximum lgm abstract the last glacial maximum lgm is widely used to refer to the episode when global ice volume last reached its maximum and associated sea levels were at their lowest however the boundaries of the interval are ill defined and the term and acronym have no formal stratigraphical basis this is despite a previous proposal to define it as a chronozone in the marine records on the basis of oxygen isotopes and sea levels spanning the interval 23 19 or 24 18 ka and centred on 21 ka in terrestrial records the lgm is poorly represented since many sequences show a diachronous response to global climate changes during the last glacial cycle for example glaciers and ice sheets reached their maximum extents at widely differing times in different places in fact most terrestrial records display spatial variation in response to global climate fluctuations and changes recorded on land are often diachronous asynchronous or both leading to difficulties in global correlation however variations in the global hydrological system during glacial cycles are recorded by atmospheric dust flux and this provides a signal of terrestrial changes whilst regional dust accumulation is recorded in loess deposits global dust flux is best recorded in high resolution polar ice core records providing an opportunity to define the lgm on land and establish a clear stratigraphical basis for its definition on this basis one option is to define the global lgm as an event between the top end of greenland interstadial 3 and the base onset of greenland interstadial 2 spanning the interval 27 540 23 340 ka greenland stadial 3 this corresponds closely to the peak dust concentration in both the greenland and antarctic ice cores and to records of the global sea level minima this suggests that this definition includes not just the coldest and driest part of the last glacial cycle but also the peak in global ice volume the later part of the lgm event is marked by heinrich event 2 which reflects the onset of the collapse of the laurentide at c 24 ka together with other ice sheets in the north atlantic region a longer and later span for the lgm may be desirable although defining this in chronostratigraphical terms is problematic whichever formal definition is chosen this requires the contribution of the wider quaternary community

geochemistry and geobiology of a present day serpentinization site in california the cedars ultra basic ph 11 12 reducing 656 to 585 mv groundwater springs discharging from serpentinized peridotite of the cedars ca were investigated for their geochemistry and geobiology the spring waters investigated were of meteoric origin however geochemical modeling suggests that there were two sources of groundwater a shallow source with sufficient contact with the cedars peridotite body to be altered geochemically by serpentinization and a deeper groundwater source that not only flows through the peridotite body but was also in contact with the marine sediments of the franciscan subduction complex fsc below the peridotite body we propose that the groundwater discharging from lower elevations gps1 and cs1 reflect the geochemistry of the deeper groundwater in contact with fsc while groundwaters discharging from springs at higher elevations ns1 and bsc were a mixture of the shallow peridotite only groundwater and the deeper groundwater that has been in contact with the fsc cell densities of suspended microbes within these waters were extremely low in the ns1 and bsc spring fluids cell densities ranged from 10 2 to 10 3 cells ml while suspended cells at gps were lower than 10 cells ml however glass slides incubated in the bsc and gps1 springs for 2 3 weeks were colonized by cells with densities ranging from 10 6 to 10 7 cells cm 2 attached to their surfaces all of the springs were very low 1 m in several essential elements and electron acceptors e g nitrate ammonium sulfate and phosphate required for microbial growth which is not uncommon at sites of continental serpentinization gases rich in n 2 h 2 and ch 4 were exsolving from the springs the stable carbon isotope value 13 c ch4 68 0 6 and the ch 4 c 2 10 3 of methane and other gaseous hydrocarbons exsolving from ns1 were typical of microbially sourced methane whereas the isotope values and the ch 4 c 2 of bsc and cs1 springs were more enriched in 13 c and had ch 4 c 2 10 3 suggesting a mixture of microbial and non microbial methane the concentrations of aromatic compounds and ethane propane iso and n butane were well described by simple physical mixing between the aromatic and alkane poor shallow groundwater and the relatively aromatic and alkane rich groundwater that flows through both the peridotite and the fsc suggesting that these aromatic and alkane compounds originated in the deeper fsc groundwater and are not produced in the shallow peridotite only groundwater the aromatic compounds most probably originated from the diagenesis degradation of organic matter in the marine sediments below the peridotite body while the gaseous alkanes may have multiple sources including thermal degradation of the organic matter in the marine sediments below the peridotite body and possibly by abiogenic reactions occurring within the peridotite body this geochemical study demonstrates the complexity of the cedars and the possible sources of hydrocarbons at continental sites of serpentinization

reduction of co2 during serpentinization of olivine at 300 c and 500 bar co 2 reduction processes occurring during experimental serpentinization of olivine at 300 c and 500 bar confirm that ultramafic rocks can play an important role in the generation of abiogenic hydrocarbon gas data reveal that conversion of fe ii in olivine to fe iii in magnetite during serpentinization leads to production of h 2 and conversion of dissolved co 2 to reduced c species including methane ethane propane and an amorphous carbonaceous phase hydrocarbon gases generated in the process fit a schulz flory distribution consistent with catalysis by mineral reactants or products magnetite is inferred to be the catalyst for methanization during serpentinization because it has been previously shown to accelerate fischer tropsch synthesis of methane in industrial applications involving mixtures of h 2 and co 2 the carbonaceous phase was predominantly aliphatic but had a significant aromatic component although this phase should ultimately be converted to hydrocarbon gases and graphite if full thermodynamic equilibrium were established its formation in these experiments indicates that the pathway for reduction of co 2 during serpentinization processes is complex and involves a series of metastable intermediates

brucite chimney formation and carbonate alteration at the shinkai seep field a serpentinite hosted vent system in the southern mariana forearc brucite carbonate chimneys were discovered from the deepest known 5700 m depth serpentinite hosted ecosystem the shinkai seep field ssf in the southern mariana forearc textural observations and geochemical analysis reveal three types i iii of chimneys formed by the precipitation and dissolution of constitutive minerals type i chimneys are bright white to light yellow have a spiky crystalline and wrinkled surface with microbial mat and contain more brucite these formed as a result of rapid precipitation under high fluid discharge conditions type ii chimneys exhibit white to dull brown coloration tuberous textures like vascular bundles and are covered with grayish microbial mats and dense colonies of phyllochaetopterus this type of chimney is characterized by inner brucite rich and outer carbonate rich zones and is thought to have precipitated from lower fluid discharge conditions than type i chimneys type iii chimneys are ivory colored have surface depressions and lack living microbial mats or animals this type of chimney mainly consists of carbonate and is in a dissolution stage stable carbon isotope compositions of carbonates in the two types i and ii of active chimneys are extremely 13c enriched up to 24 1 which may reflect biological 12c consumption under extremely low dissolved inorganic carbon concentration in alkaline fluid type iii chimneys have 13c compositions indicating re equilibration with seawater our findings demonstrate for the first time that carbonate chimneys can be form below carbonate compensation depth and provide new insights about linked geologic hydrologic and biological processes of the global deep sea serpentinite hosted vent systems this article is protected by copyright all rights reserved

application of schmidt hammer relative age dating to late pleistocene moraines and rock glaciers in the western tatra mountains slovakia abstract in order to evaluate the potential of the schmidt hammer for relative age dating of late pleistocene moraines and rock glaciers rebound r values were collected at 38 sites in two formerly glaciated valleys in the western tatras in northern slovakia a large statistical population of measurements obtained from moraine and rock glacier surfaces was used to analyze the variability of mean r values in the same lithology and overall southern valley exposition four separate sets of glacial periglacial morphosystems are present at different positions in the western tatras starting from valley outlets to the highest cirques which represent successive phases of deglaciation r value means and 95 confidence intervals for selected last glacial maximum lgm and late glacial lg 1 lg 2 and lg 3 stages respectively 40 1 1 1 46 0 5 53 5 1 0 and 60 5 0 3 are significantly statistically different and values for each age category are comparable for the two analyzed valleys the results of weathering indexes used in conjunction with geomorphological relationships were taken together to reconstruct the pattern of deglaciation on southern tatra slopes it is stated that the schmidt hammer technique may be successfully used as a relative age dating tool for late pleistocene glacial and periglacial deposits and with this method it is possible to differentiate between late glacial moraines and rock glacier systems of different age

multiple origins of methane at the lost city hydrothermal field abstract the high concentrations of methane in the vent fluids of the lost city hydrothermal field represent the sum of abiotic and biological sources and sinks stable isotopes of carbon are of limited value in discriminating between the various sources of methane because the isotope effects associated with the multiple processes forming and consuming methane are each poorly constrained and the products of these processes are pooled furthermore reservoir effects complicate interpretation the near quantitative reduction of inorganic carbon to methane under highly reducing conditions limits the isotope effects associated with methanogenesis however the carbon isotope compositions of lipids derived from anaerobic methanotrophs suggest that more than one isotopically distinct pool of methane exists at lost city in this analysis we integrate multiple lines of evidence to constrain the relative contribution of various processes at lost city the processes that we consider here include i fischer tropsch type ftt abiotic synthesis of methane and other hydrocarbons ii the sabatier process for the abiotic synthesis of methane alone iii biological methane production by methanosarcinales and iv biological methane consumption by anaerobic and aerobic methanotrophs this analysis suggests that abiotic processes particularly the sabatier reaction are likely to be the dominant source of methane at lost city biological methane is present in the vent fluids but does not compose a high fraction of the total methane pool these observations imply that ultramafic systems could have supplied abundant reduced carbon to the early earth even without biological catalysis

origin of methane in serpentinite hosted hydrothermal systems the ch4 h2 h2o hydrogen isotope systematics of the hakuba happo hot spring abstract serpentinite hosted hydrothermal systems have attracted considerable attention as sites of abiotic organic synthesis and as habitats for the earliest microbial communities here we report a systematic isotopic study of a new serpentinite hosted system the hakuba happo hot spring in the shiroumadake area japan 36 42 n 137 48 e we collected water directly from the hot spring from two drilling wells more than 500 m deep all water samples were strongly alkaline ph 10 and rich in h2 201 664 mol l and ch4 124 201 mol l despite the relatively low temperatures 50 60 c thermodynamic calculations suggest that the h2 was likely derived from serpentinization reactions hydrogen isotope compositions for happo 1 happo 3 were found to be as follows d h 2 700 710 d ch 4 210 300 and d h 2 o 85 84 the carbon isotope compositions of methane from happo 1 and 3 were found to be c 13 34 5 and 33 9 respectively the ch4 h2 h2o hydrogen isotope systematics indicate that at least two different mechanisms were responsible for methane formation happo 1 has a similar hydrogen isotope compositions to other serpentinite hosted systems reported previously the elevated d ch 4 with respect to the equilibrium relationship suggests that the hydrogen of the happo 1 methane was not sourced from molecular hydrogen but was derived directly from water this implies that the methane may not have been produced via the fischer tropsch type ftt synthesis but possibly by the hydration of olivine conversely the depleted d ch 4 with respect to the equilibrium relationship in happo 3 suggests the incorporation of biological methane based on a comparison of the hydrogen isotope systematics of our results with those of other serpentinite hosted hydrothermal systems we suggest that abiotic ch4 production directly from h2o without mediation by h2 may be more common in serpentinite hosted systems hydration of olivine may play a more significant role in abiotic methane production than previously thought

origins of methane discharging from volcanic hydrothermal geothermal and cold emissions in italy abstract we have addressed the origins of methane in fumarolic thermal and cold emissions discharging from a diversity of geological settings spread all over the italian peninsula and at panarea and pantelleria islands fluid discharges from the main geothermal systems of the peri tyrrhenian area including mt amiata larderello latera and manziana show 13c ch4 and d ch4 values 28 v pdb and 160 v smow respectively and c1 c2 concentration ratios 1000 these patterns suggest that ch4 discharged from these systems is primarily generated by abiogenic reduction of co2 and or co methane seems to have at least partially a different origin than the higher hydrocarbons that might be entirely related to the thermal decomposition of organic matter or alternatively to methane polymerization fumaroles from the volcanic systems of solfatara vesuvio panarea and pantelleria have c1 c2 concentration ratios in a wide range from 17 to 4300 but 13c ch4 and d ch4 values 21 v pdb and 120 v smow respectively such isotopic values are very similar to those reported for ch4 discharging from ultramafic hydrothermal systems in agreement with recent evidence provided for solfatara and pantelleria we therefore infer that the ch4 in the volcanic fumaroles is mainly abiogenic too the 13c ch4 from 21 6 to 36 9 v pdb and d ch4 from 113 to 164 v smow values as well as the c1 c2 concentration ratios from 19 to 2240 in the co2 rich fluid discharges located between the geothermal volcanic systems and the apennine sedimentary chain tend to decrease eastwards as the temperatures of the fluid reservoirs progressively diminish suggesting that the ch4 production is mainly related to thermogenic processes according to this general trend the ch4 dominated fluids from mud volcanoes located eastwards of the co2 rich emissions are fed by an almost pure thermogenic source the easternmost fluid discharges from the po valley and the adriatic coast where organic matter evolves at relatively shallow depths in the presence of a low geothermal gradient record the lowest 13c ch4 and d ch4 values i e as low as 69 v pdb and

the effect of rock moisture on schmidt hammer rebound tests on rock samples from marion island and south africa in an assessment of the influence of internal rock moisture content on schmidt hammer readings rebound r values are found to decrease with increasing moisture content for samples of basalt sandstone and dolerite the maximum decrease in r values is found between oven dry values and saturated rock rebound values the magnitude of which varies from 2 to 10 points on the r scale a quartzite block has the greatest decline of 6 points at 60 per cent saturation for certain rock types under differing site to site field moisture conditions the moisture effect can be a significant factor in the interpretation of the relative state of weathering from rebound values copyright 2002 john wiley sons ltd

a stratigraphic framework for abrupt climatic changes during the last glacial period based on three synchronized greenland ice core records refining and extending the intimate event stratigraphy due to their outstanding resolution and well constrained chronologies greenland ice core records provide a master record of past climatic changes throughout the last interglacial glacial cycle in the north atlantic region as part of the intimate integration of ice core marine and terrestrial records project protocols have been proposed to ensure consistent and robust correlation between different records of past climate a key element of these protocols has been the formal definition and ordinal numbering of the sequence of greenland stadials gs and greenland interstadials gi within the most recent glacial period the gs and gi periods are the greenland expressions of the characteristic dansgaard oeschger events that represent cold and warm phases of the north atlantic region respectively we present here a more detailed and extended gs gi template for the whole of the last glacial period it is based on a synchronization of the ngrip grip and gisp2 ice core records that allows the parallel analysis of all three records on a common time scale the boundaries of the gs and gi periods are defined based on a combination of stable oxygen isotope ratios of the ice 18o reflecting mainly local temperature and calcium ion concentrations reflecting mainly atmospheric dust loading measured in the ice the data not only resolve the well known sequence of dansgaard oeschger events that were first defined and numbered in the ice core records more than two decades ago but also better resolve a number of short lived climatic oscillations some defined here for the first time using this revised scheme we propose a consistent approach for discriminating and naming all the significant abrupt climatic events of the last glacial period that are represented in the greenland ice records the final product constitutes an extended and better resolved greenland stratotype sequence against which other proxy records can be compared and correlated it also provides a more secure basis for investigating the dynamics and fundamental causes of these climatic perturbations

late pleistocene and holocene glaciation in the pyrenees a critical review and new evidence from 10be exposure ages south central pyrenees a compilation and a critical assessment of the 14c data set available show that the chronology of glacial events in the pyrenees is not well constrained after reviewing the literature on glacial reconstruction we suggest a simplified subdivision of the pyrenean last glacial cycle record into last pleniglacial deglaciation and neoglacial to improve the numerical glacial chronology we provide 10be surface exposure ages for 5 glacial erosion surfaces 9 moraines and 2 erratics in the upper noguera ribagorcana valley south central pyrenees published corrected 14c data and new 10be exposure ages indicate that the major phase of moraine building recorded in this valley during the last pleniglacial probably occurred after 25 ka bp this age calls in question the generally accepted hypothesis of a very early deglaciation of the pyrenees ca 70 40 ka bp and strongly suggests that the pyrenees could have been in pleniglacial conditions during the last glacial maximum lgm however we do not exclude the possibility that the maximum glacier extent during the last glacial cycle had taken place much earlier than the lgm as indicated by some published u th ams 14c and osl data we suggest that pleniglacial conditions could have taken place during a longer 30 20 ka period than generally assumed and that the last pleniglacial could include several glacier fluctuations recorded irregularly in different valleys with a last major glacier readvance taking place around the lgm in addition the deglaciation is represented by a series of moraines deposited between ca 13 7 0 9 and 10 1 0 6 ka this moraine series indicates a highly variable climatic pattern that is partly correlated with greenland stadial 1 the younger dryas and suggests that the deglaciation could have continued into the early holocene

rapid age assessment of glacial landforms in the pyrenees using schmidt hammer exposure dating shed schmidt hammer sh sampling of 54 10 be dated granite surfaces from the pyrenees reveals a clear relationship between exposure and weathering through time n 52 r 2 0 96 p 0 01 and permits the use of the sh as a numerical dating tool to test this10 be sh calibration curve 100 surfaces were sampled from five ice front positions in the tet catchment eastern pyrenees with results verified against independent 10 be and 14 c ages gaussian modelling differentiates holocene 9 4 0 6ka younger dryas 12 6 0 9ka oldest dryas 16 1 0 5ka last glacial maximum lgm 24 8 0 9ka and wurmian maximum ice extent stages mie 40 9 1 1ka these data confirm comparable glacier lengths during the lgm and mie 300m difference in contrast to evidence from the western pyrenees 15km reflecting the relative influence of atlantic and mediterranean climates moreover pyrenean glaciers advanced significantly during the lgm with a local maximum at 25ka driven by growth of the laurentide ice sheet southward advection of the polar front and a solar radiation minimum in the northern hemisphere this calibration curve is available online http shed earth to enable wider application of this method throughout the pyrenees

surface dating of dynamic landforms young boulders on aging moraines the dating of landforms is crucial to understanding the evolution history and stability of landscapes cosmogenic isotope analysis has recently been used to determine quantitative exposure ages for previously undatable landform surfaces a pioneering application of this technique to date moraines illustrated its considerable potential but suggested a chronology partially inconsistent with existing geological data consideration of the dynamic nature of landforms and of the ever present processes of erosion deposition and weathering leads to a resolution of this inconsistency and more generally offers guidance for realistic interpretation of exposure ages

methods for measuring rock surface weathering and erosion a critical review studies of rates processes and modes of rock surface and near surface deterioration and also hardening are central to rock weathering and building stone research conservation and management there is a need to measure and monitor weathering at the rock atmosphere interface to facilitate understanding of climatic environmental and lithological controls on the evolution and development of surface weathering features this paper reviews long established and recently developed field and laboratory methods used by geomorphologists to monitor and measure the impact of weathering and erosion on physical and mechanical properties of exposed rock surfaces and their immediate subsurface key advances are highlighted their application to multi scalar understanding and modelling of rock surface weathering in different contexts is discussed and potential future advances to provide new insights into rock weathering durability and materials conservation are identified in highlighting key advantages and disadvantages of a wide range of methods to the broader earth science community the paper aims to contribute to further innovative thinking across disciplines to develop new methods for measuring and monitoring rock weathering

clumped isotopologue constraints on the origin of methane at seafloor hot springs abstract hot spring fluids emanating from deep sea vents hosted in unsedimented ultramafic and mafic rock commonly contain high concentrations of methane multiple hypotheses have been proposed for the origin s of this methane ranging from synthesis via reduction of aqueous inorganic carbon co2 during active fluid circulation to leaching of methane rich fluid inclusions from plutonic rocks of the oceanic crust to further resolve the process es responsible for methane generation in these systems we determined the relative abundances of several methane isotopologues including 13ch3d a clumped isotopologue containing two rare isotope substitutions in hot spring source fluids sampled from four geochemically distinct hydrothermal vent fields rainbow von damm lost city and lucky strike apparent equilibrium temperatures retrieved from methane clumped isotopologue analyses average 310 42 53 c with no apparent relation to the wide range of fluid temperatures 96 370 c and chemical compositions ph h2 co2 ch4 represented combined with very similar bulk stable isotope ratios 13c 12c and d h of methane across the suite of hydrothermal fluids all available geochemical and isotopic data suggest a common mechanism of methane generation at depth that is disconnected from active fluid circulation attainment of equilibrium amongst methane isotopologues at temperatures of ca 270 360 c is compatible with the thermodynamically favorable reduction of co2 to ch4 at temperatures at or below ca 400 c under redox conditions characterizing intrusive rocks derived from sub ridge melts collectively the observations support a model where methane rich aqueous fluids known to be trapped in rocks of the oceanic lithosphere are liberated from host rocks during hydrothermal circulation and perhaps represent the major source of methane venting with thermal waters at unsedimented hydrothermal fields the results also provide further evidence that water rock reactions occurring at temperatures lower than 200 c do not contribute significantly to the quantities of methane venting at mid ocean ridge hot springs

low long term erosion rates in high energy mountain belts insights from thermo and biochronology in the eastern pyrenees abstract we relate the high elevation of flat topography in the eastern pyrenees to the resurrection of a mountain belt which prior to 12 ma was a low relief landscape or peneplain bevelling eroded stumps of the pyrenean compressional orogen new apatite fission track and u th he data together demonstrate the consistently young age

schmidt hammer exposure age dating shd of late quaternary fluvial terraces in new zealand schmidt hammer sh r values are reported for surface clasts from numerically dated holocene and pleistocene fluvial terraces in the south island of new zealand the r values are combined with previously obtained weathering rind radiocarbon terrestrial cosmogenic nuclide and luminescence terrace ages to derive sh r value chronofunctions for greywacke clasts from four distinct locations our results show that different weathering rates affect the form of the sh r value versus age curve however a fundamental dependency between the two remains constant over timescales ranging from 102 to 105 years power law scaling constants suggest changes in clast weathering rates are primarily affected by climatic precipitation and temperature and sedimentologic variables source terrane petrology age uncertainties of 22 of the surface age suggest that schmidt hammer exposure age dating shd is a reliable calibrated age dating technique for fluvial terraces copyright 2013 john wiley sons ltd

a serpentinite hosted ecosystem the lost city hydrothermal field the serpentinite hosted lost city hydrothermal field is a remarkable submarine ecosystem in which geological chemical and biological processes are intimately interlinked reactions between seawater and upper mantle peridotite produce methane and hydrogen rich fluids with temperatures ranging from 40 to 90 c at ph 9 to 11 and carbonate chimneys 30 to 60 meters tall a low diversity of microorganisms related to methane cycling archaea thrive in the warm porous interiors of the edifices macrofaunal communities show a degree of species diversity at least as high as that of black smoker vent sites along the mid atlantic ridge but they lack the high biomasses of chemosynthetic organisms that are typical of volcanically driven systems

palaeogeography and 10be exposure age chronology of middle and late pleistocene glacier systems in the northern pyrenees implications for reconstructing regional palaeoclimates abstract we present constraints on the chronology palaeogeography and palaeoclimatic implications for western europe of middle and late pleistocene glaciation in the ariege catchment north eastern pyrenees based on 37 cosmogenic 10 be exposure ages obtained from moraines and glacially scoured bedrock exposures we have dated six regional glacial stades the chronology emphasises several conclusions that are new to the region i in the pyrenees the global lgm occurred several thousands of years after the maximum ice extent of the wurmian glaciation ii almost full glacier extent occurred again during the global lgm but only in the eastern pyrenees iii valley glaciers such as in the ariege trunk valley attained lengths of 25 km during the oldest dryas stadial the cosmogenic exposure ages additionally provide the first direct evidence of 10 km scale fluctuations of ice front positions during the late pleistocene glacial cycle probably at the time of marine isotope stage 3 as well as rare insights into middle pleistocene ice margin positions compared with existing evidence of glacial palaeogeography in other catchments of the pyrenan range the data also reveal a sharp contrast in relative ice extent between the glacierized catchments of the eastern pyrenees ariege carol malniu tet where wurmian mie and lgm ice fronts reached similar positions and the rest of the range where ice fronts at the time of the mis 2 and global lgm palaeotemperature minima lagged far behind the wurmian mie terminal moraines we ascribe this non uniform behaviour among catchments to non uniform palaeoclimatic conditions along the strike of the pyrenees a range of palaeoenvironmental proxies reviewed in the literature highlight a sharp difference in sea surface temperatures between the warmer western mediterranean and the cooler bay of biscay the consequences of such an e w temperature gradient on weather patterns during the global lgm are compatible with a strengthening of mediterranean low pressure systems particularly the semi permanent balearic low generating greater precipitation over the eastern pyrenees compared to atlantic weather systems further west

timing and climatic drivers for glaciation across monsoon influenced regions of the himalayan tibetan orogen abstract mapping and thirty eight 10 be terrestrial cosmogenic nuclide tcn ages help define the timing of glaciation in the monsoon influenced greater himalaya in central garwhal india glacial landforms in central garwhal are present only within a few kilometers of the present glaciers and all date to less than 12 5 ka this suggests that the lateglacial and or holocene glacial advances were more extensive than their predecessors and hence destroyed or buried evidence for earlier glaciation or that other processes such as intensive fluvial erosion and or hillslope mass movements have destroyed evidence of earlier glaciation prominent laterofrontal moraines date to the lateglacial the early holocene and the neoglaciation moraines next to the active ice and boulders on contemporary glaciers date to 10 1 10 2 years before present this suggests only a minor glacial advance during the little ice age occurred in central garhwal these young ages indicate that inheritance of tcns in areas that were recently glaciated is very small and likely has little effect when considering tcn ages on moraines older than the global last glacial maximum the new 10 be ages are combined with 1081 recalculated 10 be ages from previous studies to develop a regional framework of glaciation across the monsoon influenced and adjacent regions of the himalayan tibetan orogen we separate what appears to be continuous glaciation into 27 regional glacial stages plus 2 tentative glacial stages that are termed monsoonal himalayan tibetan stages mohits the regional glacial stages cover a wide chronologic range that includes five regional glacial stages older than the last glacial cycle mohits 13 at 483 38 ka to mohits 5e at 122 15 ka thirteen regional glacial stages within the last glacial cycle mohits 5b at 91 15 ka to mohits 2a at 12 9 0 9 ka and eleven regional glacial stages during the holocene mohits 1k at 11 4 0 7 ka to mohits 1a at 0 4 0 1 ka there are strong correlations both with periods of strong monsoons and northern hemisphere events throughout the entire chronologic range with 16 stages linked to the monsoon 11 stages linked to the mid latitude westerlies and two unassigned because of large age uncertainties overall we see a complex pattern of glaciation influenced by two climatic systems throughout the mid late quaternary