modeling of calcite dissolution by oxic respiration in supralysoclinal deep sea sediments abstract pore water profiles of co2 ph ca2 and o2 in situ concentrations were measured at two stations on the upper continental slope off gabon the present study evaluates these measurements concerning their implications for the calcium carbonate system in deep sea sediments the model cotrem which was used to simulate the dynamics of this complex geochemical system revealed a strong dependence of calcite dissolution on oxic respiration at both sites all simulated calcite dissolution kinetics reached a dynamic equilibrium with almost equal calcite dissolution rates but different sub saturation states and ph values the latter are mainly dependent on boundary conditions and kinetic rate law parameters boundary conditions are of immense importance they define which ph deviations between measured data and the simulated equilibration instantaneous kinetics have still to be fitted by kinetic restrictions per rate law for the equilibration these ph deviations set up the range of possible values for rate constants in a given rate law to yield a well simulated ph a failure in the implementation of these boundary conditions may lead to non linearly flawed rate constants which fit only one usually the maximal ph deviation well the whole depth distribution of ph deviations has to be fitted very well by a kinetic rate law only this procedure secures that the used boundary conditions and rate laws constants are acceptable nevertheless several kinetic rate laws may be used for good ph fits featuring clear differences in parameter values for rate constants and reaction orders the connection between these rate laws with different parameters is examined and the dependence of the rate constant on the given form of the rate law is demonstrated this study achieves rate constants of 0 038 and 18 d for a dissolution rate law of 4 5th reaction order and sub saturation dependence from the term 1 these results are well within the range of rate constants obtained during former field studies for the same form of the dissolution rate law

pyritization induced by anaerobic oxidation of methane aom an example from the upper devonian shale succession western new york usa abstract the diagenetic history of the upper devonian rhinestreet shale of the western new york region of the appalachian basin appears to reflect the upward diffusion of methane through these deposits shortly after their accumulation the most obvious diagenetic signature of this process is numerous horizons of authigenic calcium carbonate concretions interpreted to reflect mineralization induced by the anaerobic oxidation of methane aom focused along the sulfate methane transition smt zone additionally a 2 m thick section of the lower rhinestreet preserves a diagenetic record consistent with aom in the form of two pyritiferous stratigraphic horizons the stratigraphically lowest horizon is a 2 cm thick layer containing abundant 34 s enriched 11 8 and 18 4 v cdt coarsely crystalline pyrite the thinness of this interval suggests that aom related diagenesis remained fixed at this stratigraphic position for a brief period of time before these deposits were buried below the smt or the smt shifted position within the sediment column a second paleo smt appears to have stabilized 60 to 80 cm above the 2 cm thick pyritiferous horizon meter scale carbonate concretions being the most obvious evidence of this episode of aom more than this though the apparently fe limited nature of the host black shale induced the downward diffusion of 34 s enriched hydrogen sulfide produced by aom resulting in the precipitation of 34 s enriched 23 1 to 27 3 v cdt pyrite below the smt the maximum depth of diffusion of the sulfidization front was limited by the amount of hydrogen sulfide produced within and near the smt as well as by the availability of reactive iron in underlying deposits the focusing of aom related diagenesis at the two stratigraphic positions was likely caused by non steady state sedimentation however it is impossible to decipher relative timing of formation of the two paleo smts

control of sulfate pore water profiles by sedimentary events and the significance of anaerobic oxidation of methane for the burial of sulfur in marine sediments abstract gravity driven mass flow deposits proven by sedimentary and digital echosounder data are indicative for prevailing dynamic sedimentary conditions along the continental margin of the western argentine basin in this study we present geochemical data from a total of 23 gravity cores pore water so 4 is generally depleted within a few meters below the sediment surface by anaerobic oxidation of methane aom the different shapes of so 4 profiles concave kink and s type can be consistently explained by sedimentary slides possibly in combination with changes in the ch 4 flux from below thus mostly representing transient pore water conditions since slides may keep their original sedimentary signature a combined analysis and numerical modeling of geochemical physical properties and hydro acoustic data could be applied in order to reconstruct the sedimentary history we present first order estimates of the dating of sedimentary events for an area where conventional stratigraphic methods failed to this day the results of the investigated sites suggest that present day conditions are the result of events that occurred decades to thousands of years ago and promote a persisting mass transport from the shelf into the deep sea depositing high amounts of reactive compounds the high abundance of reactive iron phases in this region maintains low hydrogen sulfide levels in the sediments by a nearly quantitative precipitation of all reduced sulfate by aom for the total region we estimate a so 4 or ch 4 flux of 6 6 10 10 moles per year into the zone of aom projected to the global continental slope and rise area this may sum up to about 2 6 10 12 moles per year provided that the sulfur is completely fixed in the sediments it is about twice the global value of the recent global sulfur burial in marine sediments of 1 2 10 12 moles per year as previously estimated thus aom obviously contributes very significantly to the regulation of global sulfur reservoirs which is hitherto not sufficiently recognized this finding may have implications for global geochemical models as sulfur burial is an important control factor in the development of atmospheric oxygen levels over time

computer simulation of deep sulfate reduction in sediments of the amazon fan pore water concentration profiles of sediments at a site on the amazon fan were investigated and simulated with the numerical model cotrem column transport and reaction model to reveal the biogeochemical processes involved the pore water profiles for gravity core geob 4417 7 showed a distinct sulfate methane transition zone in which deep sulfate reduction occurs only a small sulfide peak could be observed at the reaction zone due to high amounts of iron minerals the produced sulfide is instantaneously precipitated in form of iron sulfides we present a simulation which starts from a steady state system with respect to pore water profiles for methane and sulfate furthermore sulfide iron ph pe calcium and total inorganic carbon tic were included in the simulation the program calculated mineral equilibria to mackinawite iron sulfides more stable than mackinawite iron hydroxides and calcite via saturation indices si by a module incorporating the program phreeqc parkhurst 1995 the measured sulfide and iron profiles are obtained in the simulation output by using a constant si 0 for mackinawite and calcite while a depth dependent si distribution is applied for the phreeqc phases pyrite and fe oh 3 a representing a composition and the kinetics of different iron sulfides and iron hydroxides these si distributions control the results of sulfide and iron pore water profiles especially conserving the sulfide profile at the reaction zone during the simulation the results suggest that phases of iron hydroxides are dissolved mackinawite is precipitated within and other iron sulfides are precipitated below the reaction zone the chemical reactivity of iron hydroxides corresponds to the rate of sulfide production the system h2o co2 caco3 is generally successfully maintained during the simulation deviations to the measured ph profile suggest that further processes are active which are not included in the simulation yet

iron cycling and stable fe isotope fractionation in antarctic shelf sediments king george island iron fe fluxes from reducing sediments and subglacial environments are potential sources of bioavailable fe into the southern ocean stable fe isotopes 56fe are considered a proxy for fe sources and reaction pathways but respective data are scarce and fe cycling in complex natural environments is not understood sufficiently to constrain respective 56fe endmembers for different types of sediments environmental conditions and biogeochemical processes we present 56fe data from pore waters and sequentially extracted sedimentary fe phases of two contrasting sites in potter cove king george island antarctic peninsula a bay that is affected by fast glacier retreat sediments close to the glacier front contain more easily reducible fe oxides and pyrite and show a broader ferruginous zone compared to sediments close to the icefree coast where surficial oxic meltwater streams discharge into the bay pyrite in sediments close to the glacier front predominantly derives from eroded bedrock for the high amount of easily reducible fe oxides proximal to the glacier we suggest mainly subglacial sources where fe liberation from comminuted material beneath the glacier is coupled to biogeochemical weathering processes likely pyrite oxidation or dissimilatory iron reduction dir our strongest argument for a subglacial source of the highly reactive fe pool in sediments close to the glacier front is its predominantly negative 56fe signature that remains constant over the whole ferruginous zone this implies in situ dir does not significantly alter the stable fe isotope composition of the accumulated fe oxides the nonetheless overall light 56fe signature of easily reducible fe oxides suggests pre depositional microbial cycling as it occurs in potentially anoxic subglacial environments the strongest 56fe depletion in pore water and most reactive fe oxides was observed in sediments influenced by oxic meltwater discharge the respective site showed a condensed redox zonation and a pore water 56fe profile typical for in situ fe cycling we demonstrate that the potential of pore water 56fe as a proxy for benthic fe fluxes is not straight forward due to its large variability in marine shelf sediments at small spatial scales 2 4 at the site proximal to oxic meltwater discharge vs 0 9 at the site proximal to the marine glacier terminus both at 2 cm sediment depth the controlling factors are multifold and include the amount and reactivity of reducible fe oxides and organic matter the isotopic composition of the primary and secondary ferric substrates sedimentation rates and physical reworking bioturbation ice scraping the application of 56fe geochemistry may prove valuable in investigating biogeochemical weathering and fe cycling in subglacial environments this requires however similarly to the use of 56fe for the quantification of benthic fluxes that the spatial and temporal variability of the isotopic endmember is known and accounted for since geochemical data from subglacial environments are very limited further studies are needed in order to sufficiently assess fe cycling and fractionation at glacier beds and the composition of discharges from those areas

redox processes in the oderbruch polder groundwater flow system in germany abstract large scale redox processes were investigated in a river recharged aquifer in the oderbruch polder alongside the river oder in north eastern germany major hydraulic and hydrochemical processes were identified qualitatively as a result of intensive drainage activities in the past 250 a the groundwater level within the polder is situated below the river water level and a levee prevents flooding of the lowland as a consequence river water permanently infiltrates into the shallow confined aquifer a sequence of redox reactions driven by organic matter degradation can be observed during infiltration of oxic river water into the groundwater up to 3 km from the river reduction processes from o2 respiration to so2 4 reduction dominate the groundwater chemistry while reduction of fe and mn hydr oxides is the source of the high amounts of dissolved fe2 and mn2 carbonate dissolution precipitation reactions control the actual groundwater concentration of mn2 the first order rate constant for so2 4 reduction was found to be 0 0169 a 1 fe2 is released into the groundwater at a rate of 0 0033 mmol l 1 a 1 the groundwater chemistry is strongly linked to the hydraulic conditions near the river the groundwater is confined and recharged by bank filtration only in contrast in the central polder the groundwater is unconfined and percolation of rainwater through the dried loam is possible because of texture changes such as shrinkage fissures geogenic pyrite present within the alluvial loam is oxidised and large amounts of so2 4 are released into the groundwater

early diagenetic processes fluxes and reaction rates in sediments of the south atlantic abstract porewaters recovered from sediment cores gravity corers box corers and multicorers from various subrogions of the south atlantic amazon river mouth equatorial upwelling congo river mouth benguela coastal upwelling area and angola basin were investigated geochemically objectives included determination of eh ph oxygen nitrate sulfate alkalinity phosphate ammonium fluoride sulfide cal mg sr fe mn and si in order to quantify organic matter diagenesis and related mineral precipitation and dissolution processes porewater profiles from the eastern upwelling areas of the south atlantic suggest that sulfate reduction in the deeper parts of the sediment may be attributed mainly to methane oxidation whereas organic matter degradation by sulfate reduction is restricted to the near surface sediments further a prominent concentration gradient change of sulfate and related mineralization products occurred typically in the upwelling sediments at a depth of 4 to 8 m far below the zone of bioturbation or bioirrigation because other sedimentological reasons seem to fail as explanations an early diagenetic sulfide oxidation to sulfate within the anoxic environment is discussed porewater profiles from the sediments of the amazon fan area are mainly influenced by reactions with fe iii phases the remarkable linearity of the concentration gradients of sulfate supports the idea of distinct reaction layers in these sediments in contrast to the upwelling sediments the sulfate gradient develops from the sediment surface to a sulfate reduction zone at a depth of 5 3 m probably because a reoxidation of sulfide is prevented by the reaction with iron oxides and the formation of iron sulfide minerals a comparison of organic matter degradation rates from the different areas of the south atlantic show the expected relationship to primary productivity oxygen is the dominating oxidant whereas organic matter degradation by nitrate mn iv and probably also fe iii reduction is several orders of magnitude lower sulfate reduction is quantitatively of similar importance as oxygen respiration in the organic rich sediments but may also include methane oxidation reoxidation of ammonium and mn2 by oxygen or nitrate do not alter significantly the estimation of organic matter degradation in the oxic zone but may contribute to the nitrate reduction in suboxic layers

simultaneous formation of iron rich layers at different redox boundaries in sediments of the amazon deep sea fan high resolution examinations of the solid phase have been performed on a gravity core that shows the typical amazon fan stratigraphy of the last 20 000 years the sedimentary record is characterized by two pronounced enrichments of solid phase fe the first fe peak from 0 34 to 0 37 m sediment depth consists of an indurated fe oxyhydroxide crust located close to the pleistocene holocene boundary this peak represents a widespread nonsteady state diagenetic feature on the fan the second fe peak is a pronounced enrichment of authigenic fe sulfides located between 6 15 and 6 45 m in the sediment the formation of this maximum is attributed to sulfate reduction that is mainly driven by anaerobic methane oxidation based on so42 pore water profiles and calculations of the time of formation of the fe sulfide enrichment we conclude that both fe rich layers formed more or less simultaneously the condition that caused both fe enrichments is a period of nonsteady state diagenesis induced by a pronounced decrease in sedimentation and organic carbon accumulation rates between the pleistocene and the holocene during this depositional change the redox boundaries and reaction fronts were fixed at particular sediment levels for a prolonged time thus producing higher concentrations of the authigenic minerals than possible under steady state diagenetic conditions

anaerobic methane oxidation on the amazon shelf anaerobic methane oxidation on the amazon shelf is strongly controlled by dynamic physical sedimentation processes rapidly accumulating physically reworked deltaic sediments characteristic of much of the shelf typically support what appear to be low rates of steady state anaerobic methane oxidation at depths of 5 8 m below the sediment water interface methane oxidation in these cases is responsible for 10 m methane charged sediment directly to seawater in this nonsteady state situation methane is a major source of recently produced co2 and an important reductant for sulfate these observations suggest that authigenic sedimentary carbonates derived from anaerobic methane oxidation may sometimes reflect physically enhanced nonsteady state exposure of methane to sulfate in otherwise biogeochemically unreactive deposits the concentration profiles of ch4 so 4 and co2 in the eroded deposit were reproduced by a coupled reaction transport model this area of the shelf was reexposed to seawater approximately 5 10 years ago based on the model results and the assumption that the erosion of the deposit occurred as a single event that has now ceased the necessary second order rate constant for anaerobic methane oxidation was 0 1 mm 1 d 1

brittle to ductile transition due to large strains along the white rock thrust wind river mountains wyoming abstract the deformed foreland of the rocky mountain cordilleras is characterized by major reverse faults that bring precambrian basement rocks to the surface the white rock thrust in the wind river mountains of wyoming is one such fault that developed at fairly shallow levels in the crust detailed study of grain size variations and textures within the fault zone provide a framework for discussion of the mechanics of movement along the fault textural criteria are suggested for distinguishing between dominantly brittle and dominantly ductile deformation a transition from brittle fracturing to ductile deformation is seen with increasing strain and resultant decrease in grain size along the fault zone diffusional creep in the final stages of deformation leads to strain softening and may allow large strains to take place along narrow zones at low deviatoric stresses this may be one way of obtaining large displacements along major faults at shallow levels in the crust

paleo redox fronts and their formation in carbonate mound sediments from the rockall trough abstract piston cores from the summits of coral topped carbonate mounds at the south west rockall trough margin reveal that the sediments have undergone significant post depositional modifications affecting the original geochemical signature and mineralogical composition of the sediments this diagenetic imprint provides information about the geochemical processes within cold water coral mounds the most prominent result of diagenetic alteration of the primary sediment composition is the absence or poor preservation of aragonitic coral skeletons in certain depth intervals associated with lithification this study focuses on the enrichment of redox sensitive elements and the dissolution of primary magnetic ferric iron minerals in the depth interval below lithification levels by combining the magnetic susceptibility with the xrf signal of fe and ti specifically intervals with susceptibility variations related to the conversion of strongly magnetic into weakly magnetic iron species can be defined in all three studied cores a succession is recognised with a lithified interval with aragonite dissolution and low mg calcite precipitates that is underlain by an interval of magnetite dissolution and of iron and manganese enrichment for the most recent lithified interval it is demonstrated that initial lithification occurred before an erosional regime was in place most likely near the end of interglacial or at the start of glacial periods

are 34s enriched authigenic sulfide minerals a proxy for elevated methane flux and gas hydrates in the geologic record abstract the sulfate methane transition smt zone is a diagenetic transition within anoxic marine sediments created by the metabolic activity of a consortium of sulfate reducing bacteria and methane oxidizing archaea as interstitial dissolved sulfate is consumed by microbially mediated sulfate reduction of sedimentary organic matter som and anaerobic oxidation of methane aom large enrichments of 34 s occur in the interstitial sulfate pool these isotopic enrichments are transmitted to the dissolved sulfide pool hs and subsequently into sulfide minerals so fes fes 2 we investigate the sulfur isotopic composition of pore water sulfate and sulfide minerals at three sites underlain by gas hydrates at the blake ridge the isotopic composition of sulfate sulfur is most positive at the smt showing maximum values of 29 1 49 6 51 6 vcdt at each of the respective sites 34 s values of bulk sulfide minerals tend to be more enriched in 34 s at and below the smt ranging from 12 7 to 23 6 corresponding to enrichments of 26 7 62 4 relative to the mean value of 38 8 in the sulfate reduction zone both enhanced delivery of methane to the smt and non steady state sedimentation appear necessary to create large 34 s enrichments in sulfide minerals similar associations of aom and large 34 s enrichments 0 occur in other gas hydrate terranes cascadia margin but their exact origin is equivocal at present an analysis of 34 s data from freshwater and marine sedimentary environments reveals that 34 s enrichments within sulfide minerals occur under a range of conditions but are statistically associated with aom and systems not limited by dissolved interstitial iron in methane rich sediments methane delivery to the smt increases the role of aom in sulfate depletion that impacts the formation and isotopic composition of authigenic sulfide minerals we hypothesize that under certain diagenetic conditions large 34 s enrichments within sulfide minerals in the geologic record potentially identify 1 the former occurrence of aom 2 present day and fossil locations of the sulfate methane transition zone and 3 a diagenetic terrane today characteristic of deep water methane rich marine sediments conducive to gas hydrate formation thus 34 s enriched sulfide minerals preserved in modern and ancient continental margin sediments may allow for the identification of aom related processes that occur in methane rich sediments

deep sulfate reduction completely mediated by anaerobic methane oxidation in sediments of the upwelling area off namibia abstract porewater concentrations of sulfate methane and other relevant constituents were determined on four sediment cores from the high productivity upwelling area off namibia which were recovered from the continental slope at water depths of 1300 and 2000 m at all four stations a distinct sulfate methane transition zone was observed several meters below the seafloor in which both sulfate and methane are consumed nutrient porewater concentration profiles do not show gradient slope changes at the depths of the transition zones flux calculations carried out on the basis of the determined porewater profiles revealed that anaerobic methane oxidation accounts for 100 of deep sulfate reduction within the sulfate methane transition zone and consumes the total net diffusive sulfate flux a significant contribution of organic carbon oxidation to the reduction of sulfate at these depths could therefore be excluded we state that porewater profiles of sulfate with constant gradients above the transition zones are indicative for anaerobic methane oxidation controlling sulfate reduction

cretaceous black shales as active bioreactors a biogeochemical model for the deep biosphere encountered during odp leg 207 demerara rise abstract a transport reaction model was designed to identify the combination and importance of biogeochemical processes operating in four sites drilled during odp leg 207 demerara rise equatorial atlantic almost 100 ma after their deposition deeply buried cretaceous black shales still act as active bioreactors in great sediment depths and control the biogeochemical reaction network of the whole sediment column according to a model calibrated at the four drill sites through inverse modeling techniques methanogenesis could be identified as a key process that dominates not only organic matter degradation but also sulfate availability through the anaerobic oxidation of methane above the black shales a complete depletion of sulfate within the black shale sequences promotes the remobilization of biogenic barium that reprecipitates as authigenic barite at the top of the sulfate depletion zone temporal dynamics of degradation processes caused continuous shifts of the barite precipitation zone during burial thus inhibiting the formation of an authigenic barite front or causing the dissolution of earlier formed fronts major deviations of pore water sulfate profiles from a linear gradient coincide with depths of decelerated or accelerated transport caused by local porosity minima or maxima model determined reaction rates are by far lower than those found in shallower sediments due to the low metabolic activities that are characteristic for the deep biosphere but even after almost 100 ma changing organic matter quality still influences the degradation within the black shale sequences as it is indicated by model results

ramifications of four dimensional progressive deformation in contractional mountain belts abstract studies of progressive deformation aim to identify and establish temporal sequences of structural stages each characterized by a suite of structures which form under specific rock and environmental conditions because of the natural spatial variation in rock type and environmental parameters in an orogen several structural stages may operate concurrently in different parts of an orogenic wedge at any given instant in time rocks experiencing different stages of deformation are bounded by deformation fronts as intrinsic and extrinsic conditions of deformation vary through time spatial migration of deformation fronts causes rocks to record temporal overprinting of structural stages in convergent orogens deformation fronts as mapped in their finite state are typically forelandward dipping due to the regional orogenic wedge geometry and thermal structure depending on the competing deformation processes deformation rate changes on either side of the front may cause deformation fronts to change orientation relief and surface area with time differences in migration rates of different deformation fronts could cause rearrangement of the sequence of structural stages with depth and laterally across the same mountain belt

multiply deformed terrains problems of correlation abstract the best tools available for carrying out a structural analysis in a complex area are overprinting style and patterns of orientation unfortunately all have limitations which are reviewed briefly and discussed in areas of continuous unfaulted outcrop the deformational history can be established purely on the basis of overprinting but even in such areas there can be problems since not all overprinting relationships are unambiguous most fold interference patterns are reliable overprinting relationships based on foliations however are commonly unreliable and various examples are cited and discussed even in areas where the sequence of deformational events can be established their temporal significance is unclear since the methods applied only determine local relative timing and absolute relationships must vary in space and time across an orogen

repeated occurrences of methanogenic zones diagenetic dolomite formation and linked silicate alteration in southern bering sea sediments bowers ridge iodp exp 323 site u1341 abstract diagenetic precipitates such as dolomite and the chemistry of residual deeply buried porewater often represent the only traces of past biogeochemical activity in marine sediments a 600 m thick sedimentary section recently drilled at integrated ocean drilling program iodp site u1341 on bowers ridge southern bering sea provides insight into such a 4 3 ma old paleo diagenetic archive hard lithified calcite dolomite layers and laminae of disseminated carbonate were recovered in diatom rich sediments over a depth range of 400 m carbon isotope values of the diagenetic carbonates between 16 6 and 14 4 vpdb and strontium isotope ratios of dolomites close to past seawater values suggest carbonate precipitation induced by the production of dissolved inorganic carbon dic during elevated rates of organic carbon mineralization primarily via sulfate reduction at shallow sediment depth below the paleo seafloor diagenetic carbonates at 280 440 m below seafloor were likely also produced by the intermittent onset of sulfate reduction coupled to the anaerobic oxidation of methane aom at sulfate methane transition zones smtz these microbially mediated processes do not occur in the sediment at this site at present but were likely connected to the presence of a methanogenic zone at 2 58 2 51 ma a minimum in sulfate concentrations in modern porewaters and low sedimentary ba al ratios resulting from former sulfate depletion are reminiscent of the presence of this large methanogenic zone the minimum in sulfate concentrations is reflected in a minimum in magnesium concentrations less radiogenic strontium and isotopically light calcium in the porewater it is proposed that magnesium was removed from the porewater during carbonate precipitation and volcanic ash alteration which occurred in the former methanogenic zone and also released strontium with a less radiogenic isotope ratio and isotopically light calcium into the porewater the isotopic composition of porewater calcium was also influenced by ammonium calcium exchange on clay minerals and carbonate recrystallization our study elucidates the response of porewater element concentrations and isotopic profiles interlinked with the formation of diagenetic carbonates to changes in the deposition of organic carbon in sediments of deeper water sites 2000 m water depth over prolonged timescales it shows that variations in biogeochemical processes in response to changes in oceanographic conditions and a dynamic subseafloor biogeochemical zonation have to also be taken into account at these deep water sites for a global assessment of organic carbon burial fluxes and remineralization

environmental and criminal geoforensics an introduction many subdisciplines within the earth sciences make use of either geophysical instruments to investigate the subsurface environment or use analytical methods to determine the origin or provenance of geological materials these same instruments and analytical methods can be used either directly or adapted to suit the acquisition of data that pertain to a wide range of forensic science investigations such approaches as discussed below are generally not new but in recent years there has been a significant resurgence globally in the application of geological and geophysical methods to aid forensic investigations traditionally such methods were used in forensic investigations related to serious criminal cases such as terrorism murder abduction and serious sexual assaults and to a lesser extent in the investigation of cases of fraud and theft but with increasing concern into the environmental impact of human activity with the release of contaminants into the atmosphere hydrosphere and lithosphere and their potential uptake into the biosphere there has been an increased amount of environmental legislation in turn there has commonly been an increase in the costs associated with the legal discharge or disposal of wastes consequently it is unsurprising that the illegal discharge and disposal of wastes has also increased identifying the distribution impact and source of such waste materials can in part be addressed through the application of geological techniques in much the same way as used traditionally for example in the investigation of murder cases the diversification of the use of geological techniques into the investigation of environmental crime will potentially significantly increase the range of investigations in which geologists may be asked to assist but will also lead to a new array of research questions to be addressed hence the need for this special publication in this short introduction the aim is to place the current work into its broad historical context and summarize the key findings from the papers presented within this volume the papers within this special publication were presented at two separate conferences in 2010 the third international soil forensics conference held at long beach california usa and organized by the sfi group and a conference on environmental and criminal forensics organized by the forensic geoscience group of the geological society of london and held at burlington house london in december 2010

simulation of early diagenetic processes in continental slope sediments off southwest africa the computer model cotam tested abstract pore water of marine sediments recovered from two stations of the continental slope off southwest africa were investigated we present computer simulations of in situ and laboratory concentration profiles of oxygen as well as laboratory concentration profiles of nitrate calcium ph and alkalinity the simulations were carried out with help of a numerical model cotam to describe the transport and the reaction of dissolved species in sediments cotam is based on an operator splitting approach comprising the independent calculation of transport and chemical reaction the consumption rates of oxygen and nitrate were determined by optimal fits to the measured pore water profiles of these species it could be shown that measured concentrations of nitrate in pore water correspond to a decomposition of organic matter with c n ratios between 3 and 3 7 however artificially increased subsurface nitrate concentrations due to core recovery cannot be excluded but our results show much greater deviations from expected concentrations assuming redfield stoichiometry than previously reported from comparative studies i e martin and sayles 1996 oxygen consumption in situ was shown to be distinctively lower than measured in multicorer cores after recovery simulations with varying denitrification rates indicate reduced diffusive nitrate release into the bottom water by up to 50 compared to shipboard results effects of nitrification and denitrification on pore water ph carbonate alkalinity and calcium concentrations were simulated by recalculating concentrations of these species with regard to calcite equilibrium for these calculations we used the standard software phreeqe as a subroutine of cotam calcium and carbonate alkalinity increase due to solid phase calcite dissolution ph was calculated to be an order of magnitude lower within the zone of oxygen depletion than indicated by shipboard results this difference is mainly related to non equilibrium conditions during ph measurements