lithologic and glacially conditioned controls on regional debris flow sediment dynamics debris flow is an efficient process of sediment transfer from slope base to piedmont depositional fans in mountain drainage basins to advance understanding of debris flow sediment dynamics at the regional scale we analyze a historical 1998 2009 database of debris flows from 77 basins of alto adige province northeastern italy by combining information on event volumetric deposition high resolution digital topography and quaternary sediment mapping we are able to link debris flow sediment flux to morphometry lithologic variability and sediment availability we show that basin wide specific sediment yield ssy scales as an inverse power function of basin area this function is strongly controlled by the way rock type and abundance of quaternary deposits affect the rate of downstream sediment recruitment when sediment flux associated with each debris flow event is subsumed across discrete spatial increments of the entire region a complex sedimentary signature in the area ssy space is apparent that is ssy increases downstream up to areas as large as 1 km2 and starts to decline beyond this scale regardless of sediment availability we propose that this area ssy relation is characteristic of debris flow dominated settings

deepening of inner gorges through subglacial meltwater an example from the unesco entlebuch area switzerland this paper explores the mechanisms by which inner gorges in the alps were formed it focuses on the ca 1 5 km long 80 m deep and a few hundred meter wide lammschlucht located in the northern foothills of the central alps we reconstructed the glacial cover using lateral moraines and hanging talus cones that record the elevation of the ice surface at the deglaciation stage of the lgm last glacial maximum we used the reconstructed ice thickness patterns to calculate the erosional potential of the subglacial meltwater the applied model is based on the principle of energy conservation and yields the pattern of downstream changes of the dynamic pressure which is considered a measure for erosion potential the model results suggest a maximum of the dynamic pressure at the end of the inner gorge we interpret therefore that the subglacial meltwater scoured the reach toward the end of the lammschlucht because of the enhanced dynamic pressure which was ultimately controlled by the ice overburden post glacial fluvial erosion then resulted in a readjustment through a regressive shift of the erosional front along the inner gorge farther upstream the current location of this front lies almost in the middle of the lammschlucht inner gorge where a step pool channel changes into a straight plane bed channel flowing on a deeply scoured bedrock

heterogeneity of the lower silurian longmaxi marine shale in the southeast sichuan basin of china this study characterizes the vertical heterogeneity of the lower silurian longmaxi marine shale in the southeast sichuan basin based on core description thin sections observation geological chemistry data interrogation and qemscan image analysis lithofacies associations mineralogy graptolite species occurrence rock fabrics as well as toc total organic carbon and gas content change noticeably and regularly in the lower silurian longmaxi marine shale within sequence stratigraphic framework lithofacies associations mainly include in situ graptolite rich and siliceous shale in the transgressive systems tract tst micro offsite graptolite rich shale and shale interbedded with siltstone laminaes in the early highstand systems tract ehst and micro offsite graptolite rich and carbonate rich shale in the late highstand systems tract lhst the tst has a greater abundance of diplogratus than ehst and lhst and has a lesser level of monograptus which is conversely higher in the ehst and lhst the tst shale is silica rich while the lhst shale is generally clay rich the ehst shale is more balanced in its silica and clay content than the tst and lhst are the sedimentary structure and fabric of shale shows that shale is homogenous in the tst with laminaes well developed in the ehst but decreasing in the lhst toc and gas content are highest in the tst and decrease upward the tst with high toc high gas content high brittle minerals silica rich and anoxic suboxic to dysoxic sedimentary environment is the most potential shale gas target interval in the study area our research also shows that the toc mainly controls shale gas accumulation and that the redox conditions mainly control the preservation of organic matter the silica also plays a significant role in shale gas content due to its contribution to hydraulic fracturing finally the study proposes a depositional and heterogeneity model for the lower silurian longmaxi marine shale in the study area

preservation of inner gorges through repeated alpine glaciations the origins of alpine valleys are controversial topographic data from the swiss alps suggest that the valleys have been incised progressively during consecutive glacial interglacial cycles

rate of fluvial incision in the central alps constrained through joint inversion of detrital 10be and thermochronometric data abstract we integrate constraints from published detrital thermochronometry and detrital 10 be concentrations in a single catchment to infer how erosion is shaping alpine topography we apply this analysis to the codera watershed in the bergell intrusion central european alps where rivers have incised into a glacial valley because thermochronometric ages of bedrock samples increase with elevation a distribution of detrital ages in river sediment provides a tracer for the source elevations of sediment within the catchment while detrital 10 be concentrations provide constraints on rates of erosion we find that modern erosion rates within the fluvial portion of the landscape are too low to permit the inferred 500 m of incision during the most recent interglacial based on the spatial pattern of modern erosion rates we predict that if the incised fluvial valley was formed during interglacial periods only it has formed over the last approximately 400 000 years

multiple origins of the paleogene natural gases and effects of secondary alteration in liaohe basin northeast china insights from the molecular and stable isotopic compositions abstract the molecular and isotopic c and h compositions of paleogene shahejie formation e 2 3 s and dongying formation e 3 d natural gases from 11 new gas samples as well as the data of 71 gases published from previous studies in the liaohe basin were analyzed and the results were considered in combination with geochemical and distribution characteristics of the source rocks the genetic type gas source correlation and secondary alteration of the natural gases were studied in detail and the source rock maturities of the gases were estimated the following conclusions were reached 1 with the exception of dry gases in the major part of the third member of the shahejie fm e 2 s 3 reservoirs the gases in other reservoirs are mainly wet 2 variable carbon and hydrogen isotopes of the alkane gases are observed in different reservoirs of the basin with 13 c 1 values ranging from 60 7 to 34 2 13 c 2 from 47 3 to 22 3 2 h ch 4 from 261 to 188 and 2 h c 2 h 6 from 269 to 148 3 the natural gases of the basin are of multiple origins and mixing of thermogenic and microbial is observed the mixing ratio in the first member of the shahejie fm e 3 s 1 is the highest among all the reservoirs 4 gases of different reservoirs suffered varying extents of biodegradation which caused partial reversal of the carbon isotope series of methane and its homologues 13 c 1 13 c 2 13 c 3 13 c 4 the reversal of the gases in the shallow reservoirs e 3 s 1 and e 3 d is greater while those in the deep reservoir e 2 s 3 is less 5 humic natural gases of the ed were mainly generated by source rocks at early maturity while the sapropelic ones of the ed and wd were generated during the mature and high mature stages 6 both the source rocks of e 2 s 3 and e 2 s 4 strata could contribute to the gas reservoirs of e 2 s 3 and e 2 s 1 in the west depression sapropelic gases in east depression were generated by e 2 s 3 source rocks while the other gases reservoired in the e 2 s 3 e 3 s 1 and e 3 d strata are probably sourced from the source rock strata of e 2 s 3 and e 3 s 1 2

geochemistry of the extremely high thermal maturity longmaxi shale gas southern sichuan basin abstract the marine shale of the silurian longmaxi formation in southern sichuan basin china is characterized by its huge thickness 100 600 m high toc values 0 35 18 4 favorable types of organic matter i and ii1 high ro values 1 8 4 2 abundant brittle minerals average 56 3 and strong gas generation intensity particularly its bottom section which has toc 2 and thickness of 20 70 m has recently been a main target for shale gas exploration and development geochemical parameters of 13 gas samples from longmaxi shale from 10 wells were analyzed in this study wetness of the gas molar fraction of ethane through pentanes in total gaseous hydrocarbon is only 0 24 0 70 making the longmaxi shale gas among the driest in the world carbon isotopic compositions of the alkane gases from longmaxi shale are characterized by 13c1 13c2 13c3 with the most positive 13c1 values in the world a positive relationship was observed between its 13c1 and 13c2 values reflecting the extremely high thermal maturity of the source rock 2hch4 values range from 140 to 151 and the 2hc2h6 values range from 130 to 173 the hydrogen isotopic compositions were mainly characterized by 2hch4

long term fluvial incision rates and postglacial river relaxation time in the french western alps from 10be dating of alluvial terraces with assessment of inheritance soil development and wind ablation effects studying river long profile development as a response to tectonic and climatic controls requires reliable age dating of paleo profile remnants preserved as river terraces cosmic ray exposure cre dating often represents the only method available to date river terraces but the interpretation of cosmogenic nuclide concentrations is complicated by pre depositional inheritance and post depositional disturbance of the terrace deposits through pedogenesis and surface inflation or deflation here we use cosmogenic 10be measurements to date alluvial terraces in the french western alps in order to estimate river incision rates and to infer river response to climatic fluctuations and tectonic forcing we assess inheritance by constructing 10be concentration vs pebble depth profiles and use a monte carlo technique to estimate terrace ages we find that inheritance is negligible on all terraces enabling us to date terraces as young as 5 ky terraces that predate the last glaciation experienced intense pedogenesis and wind ablation which led to significant scatter in the 10be concentrations of surface samples we assess these effects using a model of 10be ingrowth and show that the oldest cre ages of surface clasts are close to the probable terrace age we study two catchments which have undergone varying degrees of glacial disruption the buech river experienced variations in runoff and sediment flux during the last glaciation as well as occasional ice dammings of its outlet its upper terraces record incision rates averaged over 190 ky of 0 8 mm yr consistent with denudation rates estimated in the surrounding areas and suggesting long term stability of river incision rates climatic forcing is well documented for the drac river which was repeatedly dammed by glaciers during cold periods its postglacial incision history was triggered by an 800 m drop in base level following ice dam disappearance long profile development by knickpoint propagation explains the time lag of 2 5 ky between this base level drop and terrace abandonment upstream as well as subsequent peak incision rates of 6 cm yr followed by a gradual decrease in incision rates the present knickpoint location 55 km upstream from the glacial damming site enables us to calculate a fluvial response time of 15 20 ky controlled by knickpoint propagation rates of several meters per year within the drac river

ultra rapid landscape response and sediment yield following glacier retreat icy bay southern alaska abstract glacial retreat and opening of taan fjord an arm of icy bay alaska in the last two decades drove a base level fall of 400 m at the outlets of four tributary valleys in the region of the current tyndall glacier terminus response in the tributary valleys to this base level fall includes evacuation of stored sediment incision of slot gorges into bedrock and landsliding on valley walls fluvial transfer of eroded bedrock glacial deposits and stored nonglacial fluvial deposits after 1983 resulted in progradation of fan deltas toward the fjord centerline at the outlet of each of the four catchments in the largest nonglacial tributary valley 0 08 km 3 8 of the 0 59 km 3 of 500 m thick stored fluvial and colluvial deposits has been transferred to the adjacent fjord a percentage of the fjord sedimentation in the last two decades thus includes material eroded from bedrock and stored in the landscape during the previous glacial expansions distal deltaic deposits extend across the fjord floor and likely interfinger with distal proglacial deltaic deposits sourced from the tyndall glacier a paraglacial landscape response such as the one exhibited in upper taan fjord where sediment delivery to fjords from tributary sources in synchrony with sediment produced by primary bedrock erosion by glaciers helps to explain the order of magnitude discrepancy between sediment yields from alaskan tidewater glaciers on 10 0 to 10 2 year timescales and sediment yields and exhumation rates on 10 4 to 10 6 year timescales

origin of paleogene natural gases and discussion of abnormal carbon isotopic composition of heavy alkanes in the liaohe basin ne china abstract chemical components stable isotopic compositions and light hydrocarbons are investigated to determine the origin and isotopic anomalies of natural gases in the paleogene of the liaohe basin of northeastern china natural gas in paleogene is dominated by alkanes dry gas predominantly occurs in the shallow layers of the paleogene having burial depth less than 1900 m specifically in the dongying formation e3d and the first member of the shahejie formation e3s1 wet gas mostly occurs in the deep layer primarily in the third member of the shahejie formation e2s3 the relative content of methyl cyclohexane in the western depression wd of the liaohe basin is less than that in the eastern depression ed while the relative contents of alkanes in the c5 7 light hydrocarbons of the wd are higher than those of the ed natural gases are of multiple origins including microbial gas gas generated by microbial action on immature source rock coal derived gas gas generated by humic source rock and oil associated gas gas generated by sapropelic source rock in the wd oil associated gas is dominant while in the ed coal derived gas dominates the abnormally heavy carbon isotopic composition of paleogene heavy alkanes is primarily caused by bacteria oxidation rather than by being mixed with deep source gas natural gases from the e3d and e3s1 suffer the most severe bacterial oxidation the intensity of which gradually declines with the increasing depth the low average heptane and isoheptane values indicate that natural gases are mostly generated in the early mature stage of the source rock natural gases in e2s3 of the wd are mainly derived from e2s4 and e2s3 source rocks while those of e3d and e3s1 are predominantly generated by e2s3 source rock gases in the ed come principally from e2s3 source rock

rock type control on erosion induced uplift eastern swiss alps abstract there is growing evidence that quaternary rock uplift in parts of the european alps is a consequence of climate and erosion driven isostatic rebound contemporary rates of rock uplift u in the swiss alps show two distinctive dome like peak regions that attain 1 6 mm yr 1 we focus on the alpenrhein catchment and its surroundings where one of these peak regions spatially coincides with widely exposed cretaceous bundner schist and lower tertiary flysch field assessments and analyses of hillslope gradient distributions quantitatively demonstrate the low rock mass strength and high erodibility of these rocks this is reflected in mean postglacial catchment erosion rates d 4 mm yr 1 as opposed to 0 7 mm yr 1 in more resistant crystalline rocks though largely inferred from landslide and debris flow prone tributary catchments 2 the localised erosion rates in bundner schist and flysch are among the highest documented for the alps and corroborated by historic suspended sediment yields and thus export from the region we further find that the steepness of bedrock rivers the density of large landslides and d correlate with the highest values of u our observations highlight the possibility that erosion of mechanically weak bundner schist and flysch enhanced by large landslides may have contributed to regional crustal unloading and concomitant rock uplift irrespective of whether this is betraying a coupling between long term uplift and erosion modulated by rock type our findings indicate that long term 10 3 to 10 4 yr geomorphic signals contained in bedrock river steepness spatial density of large landslides and postglacial erosion rates strikingly correlate with regional gradients of historic 10 1 yr rock uplift rates

river incision and migration deduced from 36cl cosmic ray exposure durations the clue de la cerise gorge in southern french alps abstract we estimate recent 20 ka incision and lateral migration rate on a spectacular n s striking gorge cross cutting n dipping limestones in a fold and thrust belt of the external southern french alps upstream of the gorge the river makes a right angle turn and follows the limestone surface parallel to the bedding direction ew eighteen samples were gathered along two vertical river polished profiles and three others on the denuded north dipping surface layer in order to determine river incision and lateral migration timing and rates surface age exposures of polished river cliff and bedding surface have been obtained from 36cl cosmogenic nuclide dating and allow us to constrain the rate of vertical incision and of surface denudation of the jurassic limestone layer fifteen 36cl exposure ages have been obtained and range from 21 ka to 3 ka samples clearly define two age height linear trends which slopes correspond to incision rates of 1 and 0 3 mm yr respectively the transition from low to high incision rate occurs at about 12 ka i e during the younger dryas glacial phase data also indicate that the vertical incision of the n s branch of the gorge is coeval with the lateral northward river migration of its e w branch associated with the denudation of the limestones surface extrapolating incision rates deduced from 36cl exposure ages through time suggests that the incision of the clue and denudation of the jurassic limestones started about 500 600 ka ago

paleozoic aged microbial methane in an ordovician shale and carbonate aquiclude of the michigan basin southwestern ontario abstract interest in the origin and migrational history of methane in low permeability shales reaches beyond that of resource potential to include the evaluation of such formations as geological barriers for the purposes of isolating surface environments from the impacts of deep exploitation and the deep disposal of waste here we present detailed isotope and geochemical profiles of porewaters and methane from an ordovician shale and carbonate aquiclude on the eastern flank of the michigan basin where a deep geological repository for low and intermediate level nuclear waste is proposed the solute concentrations and stable isotopes of water 18 o and d indicate that this aquiclude hosts saline brine 39 tds originating as evaporated seawater methane concentrations are 13 c and d signatures that are consistent with archaeal methanogenesis and are accompanied by a well defined positive excursion in 13 c of co 2 below the aquiclude porewaters contain lower concentrations of methane with a thermocatalytic signature consistent with regional methane elsewhere in the michigan basin no evidence for archaea was identified by microcosm experiments or through pcr rrna analysis suggesting that the microbial methane present in these sediments is not the result of recent microbial activity based on these results and considering that archaeal activity has not been observed in such hypersaline brines with low water activities

formation of inner gorges abstract under certain conditions a distinctive type of landform the inner gorge evolves in drainage basins undergoing persistent base level lowering inner gorges are typical of basins in north coastal california u s a and one such basin was selected for detailed study based on analysis of along channel distribution of rock types streamside land sliding and stored sediment as well as computation of stream power the following set of conditions appears to accompany the formation of an inner gorge 1 inner gorge parent materials are relatively competent homogenous rock types 2 in inner gorge reaches there is an absence of any base level control that would prevent downcutting 3 continued downcutting occurs due to continued base level fall and this fall is most likely induced by tectonic uplift 4 mass slope failures that form steep straight slopes debris slides are the main denudational hillslope process in the inner gorge 5 sufficient stream power is available to transport landslide derived material out of the inner gorge reach such that alluvial sediment does accumulate in the reach over time and 6 the initial condition of the landscape is a low relief erosionally mature land surface into which the inner gorge is cut this initial condition implies that inner gorges develop in tectonically rejuvenated landscapes the processes of denudation on inner gorge slopes acting over a time scale of 105 years result in a style of landform evolution that approximates parallel slope retreat this type of slope retreat maintains the distinct inner gorge morphology during sustained downcutting though the analysis is confined to one basin in northern california so as to provide a detailed framework to understand inner gorge landform inner gorges appear to be commonplace in areas of moderate to high uplift where lithologic and tectonic conditions are appropriate for their formation a global search for this landform yet to be undertaken is needed to confirm whether it indeed occurs where the above conditions are met

distribution and inferred age of exfoliation joints in the aar granite of the central swiss alps and relationship to quaternary landscape evolution abstract exfoliation joints are well known natural fractures limited to near the ground surface relatively few details however are known about their distribution and age in the swiss alps exfoliation joints follow the landscape surface at the time of their formation the age of the associated landscape feature then provides a maximum age of exfoliation joints while landscape forms can change through time exfoliation joints preserve elements of former landscape morphologies by their undisturbed orientations the grimsel region of the central alps is well suited for analyzing the impact of erosional episodes and accompanying stress changes on exfoliation joint formation in granitic rocks mapping above and below ground revealed that exfoliation joints are widespread and occur between valley bottoms and mountain crests within glacial inner and hanging u shaped trough valleys glacial cirques and steep mountain crests and predominantly fluvial landforms gently inclined linear slopes above the inner trough valleys narrow inner valley gorges and steep v shaped side gullies based primarily on their geometric properties at the ground surface three exfoliation joint types were distinguished in our study area 1 closely spaced

surface exposure dating of the flims landslide graubunden switzerland abstract sixteen boulder and bedrock surfaces related to the flims landslide volume 8 12 km3 were dated with 36cl and 10be exposure ages range from 4900 250 yr to 15 440 1480 yr including corrections made due to snow cover and karst erosion ages of 11 410 590 yr and 13 340 1090 yr were obtained on bedrock surfaces outside of the landslide zone these are minima for deglaciation of segnes valley and provide constraints on possible amounts of inherited nuclides based on seven boulder ages which range from 8200 260 to 9520 990 yr a mean of 8900 700 years is calculated for the flims landslide we exclude three outliers one significantly older and two significantly younger than the others and the ages from the cassons bedrock site from the mean calculation the latter is excluded as shielding due to snow and vegetation cover is difficult to constrain there the oldest boulder on the landslide yielded an age 15440 1480 yr more than 5000 years older than any other boulder age suggesting that it included the surface of the pre slide bedrock the exposure ages are consistent with a single failure event the erratics and patches of till lying on the landslide debris must have been carried piggy back on top of the landslide rather than having been deposited by the late pleistocene vorderrhein glacier the flims rockslide is about the same age as the kofels 9800 yr and kandertal 9600 yr rockslides all three occurred during the marked transition to warmer wetter conditions during the early holocene

genetic and temporal relations between formation waters and biogenic methane upper devonian antrim shale michigan basin usa abstract controversy remains regarding how well geochemical criteria can distinguish microbial from thermogenic methane natural gas in most conventional deposits has migrated from a source rock to a reservoir rarely remaining associated with the original or cogenetic formation waters we investigated an unusual gas reservoir the late devonian antrim shale in which large volumes of variably saline water are coproduced with gas the antrim shale is organic rich of relatively low thermal maturity extensively fractured and is both source and reservoir for methane that is generated dominantly by microbial activity this hydrogeologic setting permits integration of chemical and isotopic compositions of coproduced water and gas providing a unique opportunity to characterize methane generating mechanisms the well developed fracture network provides a conduit for gas and water mass transport within the antrim shale and allows invasion of meteoric water from overlying aquifers in the glacial drift steep regional concentration gradients in chemical and isotopic data are observed for formation waters and gases dilute waters grade into dense brines 300 000 ppm over lateral distances of less than 30 km radiogenic 14c and 3h and stable isotope 18o and d analyses of shallow antrim shale formation waters and glacial drift groundwaters indicate recharge times from modern to 20 000 yr bp carbon isotope compositions of methane from antrim shale wells are typical of the established range for thermogenic or mixed gas 13c 47 to 56 however the unusually high 13c values of co2 coproduced with methane 22 and dissolved inorganic carbon dic in formation waters 28 require bacterial mediation the d values of methane and coproduced formation water provide the strongest evidence of bacterial methanogenesis methane ethane propane ratios and 13c values for ethane indicate 1 the presence of a thermogenic gas component that increases basinward and 2 progressive bacterial oxidation of ethane as the antrim shale subcrop is approached multiple episodes of pleistocene glaciation over northern michigan appear critical to the development of these gas deposits loading of thick ice sheets may have provided hydraulic head that enhanced dilation of preexisting fractures and influx of meteoric water the physical erosion cycle of repeated glacial advances and retreats exhumed the antrim shale around the northern margin of the michigan basin subjecting it to near surface physiochemical and biochemical processes the chemical and hydrologic relations demonstrated in the antrim shale reservoir suggest a dynamic connection between pleistocene glacial history of the midcontinent region and development of recoverable microbially generated natural gas reserves

thermogenic and secondary biogenic gases san juan basin colorado and new mexico implications for coalbed gas producibility the san juan basin is the most prolific coalbed gas basin in the world with 1992 production exceeding 440 gcf footnote 12 4 billion m3 resources of approximately 50 tcf 1 4 trillion m3 and proved reserves of over 6 tcf 170 billion m3 coalbed gas wells with the highest production initial potential greater than 10 mcf day or 0 28 million m3 day occur in the overpressured north central part of the basin hydrologic analysis indicates that overpressure in the fruitland formation is artesian in origin and represents repressuring that developed during the middle pliocene highly permeable laterally continuous coal beds override abandoned shoreline pictured cliffs sandstones and extend to the elevated recharge area in he northern basin to form a dynamic regionally interconnected aquifer system coal rank and basin hydrodynamics control the composition of fruitland coalbed gases which varies significantly across the basin chemically dry gases in the north central part of the basin coincide with meteoric recharge and regional overpressure the consistency of methane dgr13c values across the basin the presence of isotopically heavy carbon dioxide in coalbed gases and bicarbonate in formation waters and biodegraded n alkane distributions of some coal extracts indicate that coalbed gases in the north central basin are a mixture of thermogenic 25 50 secondary biogenic 15 30 and migrated thermogenic 12 60 gases migrated conventionally and hydrodynamically trapped gases in situ generated secondary biogenic gases and solution gases result in gas content that plot on or above the coal sorption isotherm bacteria transported basinward in groundwater flowing from the elevated northern basin margins metabolized wet gas components n alkanes and organic compounds in the coal and generated secondary biogenic methane and carbon dioxide subsequent to coalification uplift erosion and cooling these gases may be limited to basin margins where shallow depths and structural deformation result in higher permeability or may extend more than 35 mi 56 km basinward from the recharge zone the presence of appreciable secondary biogenic gas indicates an active dynamic flow system with overall permeability sufficient for high productivity basin hydrogeology reservoir heterogeneity location of permeability barriers no flow boundaries and the timing of biogenic gas generation and trap devel pment are critical for exploration and development of unconventional gas resources in organic rich rocks

recent vertical movements from precise levelling in the vicinity of the city of basel switzerland the southern end of the upper rhine graben is one of the zones in switzerland where recent crustal movements can be expected because of ongoing seismotectonic processes as witnessed by seismicity clusters occurring in this region therefore in 1973 a control network with levelling profiles across the eastern rhine graben fault was installed and measured in the vicinity of the city of basel in order to measure relative vertical movements and investigate their relationship with seismic events as a contribution to eucor urgent the profiles were observed a third time in the years 2002 and 2003 and connected to the swiss national levelling network the results of these local measurements are discussed in terms of accuracy and significance furthermore they are combined and interpreted together with the extensive data set of recent vertical movements in switzerland jura mountains central plateau and the alps in order to be able to prove height changes with precise levelling their values should amount to at least 3 4 mm 1 the present investigations however have not shown any significant vertical movements over the past 30 years

river gorge eradication by downstream sweep erosion narrow river gorges are often short lived features images of a bedrock gorge in taiwan which was carved after 1999 reveal rapid widening where the upstream floodplain meets the gorge an erosional front that propagates downstream as the gorge is erased

differential transport of co2 and ch4 in coalbed aquifers implications for coalbed gas distribution and composition coalbed gas content and composition are critical for the successful exploration and production of coalbed methane we investigated the differential transport of a preadsorbed co2 ch4 gas mixture along a coalbed aquifer by groundwater flow or across a coal bed by upward diffusion through pore water consistent analytical approximations and numerical solutions were obtained for typical cases the results suggest that differential transport of ch4 and co2 in a water saturated coal seam is mainly controlled by their adsorption equilibrium in coals and solubilities in water although co2 is about 20 times more soluble than ch4 in water at temperatures lower than 50c the transport of co2 from a coal seam is only several times more efficient than that of ch4 because of the stronger adsorption of co2 than ch4 in coals preferential transport of co2 over ch4 by groundwater advection can substantially accumulate more gas rich in co2 at downstream or near discharge zones if gas trapping structures exist and it may cause low total gas content of ch4 near recharge zones which may explain the co2 and ch4 distribution in the san juan and powder river basins and the undersaturation of gas in many other coals the separation and redistribution of coalbed gas by transport processes may also be complicated by late stage biogenic gas generation with infiltration of meteoric water with nutrients and gas producing microbes into the coal beds as suggested for some basins overall hydrogeologic systems strongly influence the distribution of coalbed gas content and composition in coal seams

constraints on the miocene landscape evolution of the eastern alps from the kalkspitze region niedere tauern austria abstract in order to unravel aspects of the miocene landscape evolution of the eastern european alps we present geomorphic and isotopic data from the western niedere tauern region austria the region is critical for such interpretations because it is one of the few regions along the topographic axis of the eastern alps where the highest peaks up to 2500 m a s l are dominated by limestone as such the region contains a record of miocene landscape forming events that survived the pleistocene glaciations not preserved elsewhere in the central eastern alps this record includes karst caves karstified planation surfaces and crystalline fluvial pebbles augenstein formation preserved on planation surfaces and in karst caves caves in the region occur in three distinct levels that correlate with well known cave levels in the northern calcareous alps although they are somewhat higher in the niedere tauern in part these cave elevations also correlate with three planation surfaces and knickpoints of major streams draining the region testifying their pre glacial origin we report details of a karst cave durchgangshohle from the highest cave level located at 2340 m a s l in this cave allochthonous fluvial gravels are present overgrown by speleothems one speleothem yielded an early middle pleistocene u pb age 682 17 ka we regard this as a minimum age for the erosion of the fluvial cave deposits during marine isotope stages 17 or 16 carbon and oxygen isotope data of these speleothems imply a climate that is consistent with this interpretation cosmogenic 21 ne data of fluvial quartz clasts collected from the surface on plateaus of the northern calcareous alps suggest minimum exposure durations of 115 and 262 ka they probably reflect successive exposure since removal of the sediment cover of the oligocene augenstein formation during the pleistocene while our geochronological data fail to record aspects of the earlier miocene uplift history they are consistent with the overall geomorphic history inferred from the geomorphic markers this suggests that the niedere tauern share a common uplift history with the northern calcareous aps and implies a moderate south north topographic gradient that has been maintained since the miocene

thermal history of sedimentary basins maturation indices and kinetics of oil and gas generation temperature is the most sensitive parameter in hydrocarbon generation thus reconstruction of temperature history is essential when evaluating petroleum prospects no measurable parameter can be directly converted to paleotemperature maturation indices such as vitrinite reflectance tmax from rock eval pyrolysis spore coloration thermal alteration index tai or concentration of biological markers offer an indirect approach all these indices are a function of the thermal history through rather complex kinetics frequently influenced by the type of organic matter their significance and validity are reviewed besides the problems of identification e g vitrinite and interlaboratory calibration it is important to simultaneously interpret kerogen type and maturation and to avoid difficult conversions from one index to another geodynamic models where structural and thermal histories are connected are another approach to temper ture reconstruction which could be calibrated against the present distribution of temperature and the present value of maturation indices kinetics of kerogen decomposition controls the amount and composition of hydrocarbons generated an empirical time temperature index tti originally introduced by lopatin does not allow such a quantitative evaluation due to several limitations no provision for different types of kerogen and different rates of reactions poor calibration on vitrinite reflectance it is of limited interest unless one has no access to a desk top computer kinetic models based on a specific calibration made on actual source rock samples can simulate the evolution of all types of organic matter and can provide a quantitative evaluation of oil and gas generated examples from the jurassic source rocks of the paris basin monterey formation of california green river shales of utah paleozoic source eds of the algerian sahara and miocene rocks of the mahakam delta indonesia illustrate various aspects of the discussion geological geochemical models are the most efficient way to integrate geological seismic and geochemical data and they should greatly help to reduce the risk in exploration

a study of hydrogeology and its effect on coalbed methane enrichment in the southern junggar basin china this paper analyzes regional hydrogeological conditions and divides the study area into three hydrogeological types and seven hydrogeological units to investigate hydrogeology and its effect on coalbed methane cbm enrichment in the southern junggar basin china from this work it is found that the groundwater flow paths in the study area are the joint effects of south to north and west to east flows this study also shows that microbial gases are widely developed although the depth limit of microbial gas occurrence is still unclear in the study area microbial co2 reduction is the leading formation path in the study area except for the houxia region where fermentation is the formation mechanism the abnormally high co2 in stagnant zones i e water flow is slow and stagnant is mainly associated with methanogenesis whereas relatively low co2 microbial or thermogenic is present where water flow is active the average cbm content within the xishanyao formation changes within various hydrogeological units moreover the average cbm content within the badaowan formation of the same hydrogeological unit e g fukang suggests that the hydrogeological and cbm enrichment conditions are different within various structural types overall the hydrogeological conditions exert control on the gas content in the study area that is the gas content is high in stagnant zones finally influenced by supplemental microbial gases changes in the cbm oxidation zone are relatively complex in the study area the depth of which has no obvious correlation with hydrogeological conditions and changes significantly from west to east

geochemical characteristics of gases from the largest tight sand gas field sulige and shale gas field fuling in china abstract this study performed a detailed geochemical analyses of the components stable carbon isotopes of alkane gas and co2 stable hydrogen isotopes of alkane gas and helium isotopes of reproducing gas from the largest tight gas field sulige and shale gas fuling field in china the comparative study shows that tight gas from the sulige gas field in the ordos basin is of coal derived origin which is characterized by a positive carbon and hydrogen isotopic distribution pattern 13c1 13c2 13c3 13c4 2h1 2h2 2h3 i e the carbon and hydrogen isotopes increase with increasing carbon numbers carbon dioxide from this field are of biogenic origin and the helium is crust derived shale gas from the fuling shale gas field belongs to oil derived gas which has complete carbon and hydrogen isotopic reversal of secondary alteration origin 13c1

epigenetic gorges in fluvial landscapes epigenetic gorges form when channels that have been laterally displaced during episodes of river blockage or aggradation incise down into bedrock spurs or side walls of the former valley rather than excavating unconsolidated fills and reinhabiting the buried paleovalley valley filling events that promote epigenetic gorges can be localized such as a landslide dam or an alluvial debris flow fan deposit at a tributary junction or widespread such as fluvial aggradation in response to climate change or fluctuating base level the formation of epigenetic gorges depends upon the competition between the resistance to transport strength and roughness of valley filling sediments and a river s ability to sculpt and incise bedrock the former affects the location and lateral mobility of a channel incising into valley filling deposits the latter determines rates of bedrock incision should the path of the incising channel intersect with bedrock that is not the paleovalley bottom epigenetic gorge incision by definition post dates the incision that originally cut the valley strath terraces and sculpted bedrock walls that form in relation to epigenetic gorges should not be used to directly infer river incision induced by tectonic activity or climate variability rather they are indicative of the variability of short term bedrock river incision and autogenic dynamics of actively incising fluvial landscapes the rate of bedrock incision associated with an epigenetic gorge can be very high 1 cm yr typically orders of magnitude higher than both short and long term landscape denudation rates in the context of bedrock river incision and landscape evolution epigenetic gorges force rivers to incise more bedrock slowing long term incision and delaying the adjustment of rivers to regional tectonic and climatic forcing copyright 2008 john wiley sons ltd

microbial production and modification of gases in sedimentary basins a geochemical case study from a devonian shale gas play michigan basin an expanded data set for gases produced from the antrim shale a devonian black shale in the michigan basin united states has allowed for a detailed examination of the related chemical and isotopic compositional changes in the solid gas liquid systems that discriminate between microbial and thermogenic gas origin in the antrim shale economic microbial gas deposits are located near the basin margins where the shale has a relatively low thermal maturity and fresh water infiltrates the permeable fracture network the most compelling evidence for microbial generation is the correlation between deuterium in methane and coproduced water along the basin margins there is also a systematic enrichment in 13c of ethane and propane with decreasing concentrations that suggests microbial oxidation of these thermogenic gas components microbial oxidation accounts not only for the shift in 13c values for ethane but also in part for the geographic trend in gas composition as ethane and higher chain hydrocarbons are preferentially removed this oxidation is likely an anaerobic process involving a syntrophic relationship between methanogens and sulfate reducing bacteria the results of this study are integrated into a predictive model for microbial gas exploration based on key geochemical indicators that are present in both gas and coproduced water one unequivocal signature of microbial methanogenesis is the extremely positive carbon isotope values for both the dissolved inorganic carbon in the water and the coproduced co2 gas in contrast the 13c value of methane is of limited use in these reservoirs as the values typically fall between the commonly accepted fields for thermogenic and microbial gas in addition the confounding isotopic and compositional overprint of microbial oxidation increasing the values to typically thermogenic values may obscure the distinction between methanogenic and thermogenic gas

aridity induced miocene canyon incision in the central andes the relationship between the rise of the andean mountain chain and the onset of aridity on its western margin is poorly understood canyon incision on both the eastern and western flanks of the chain is interpreted generally as a direct response to increased rock uplift but may equally have been the result of climate change here we record some of the oldest canyon incision on the western andean margin by tracking the downward migration of the local water table using u th he hematite geochronology on vertical drill core transects our data constrain the incision history of the quebrada de parca canyon in northern chile from ca 16 ma to the present day the erosional and topographic response of the quebrada de parca river suggests that incision was induced by a switch to a more arid climate in the middle miocene which reduced regional precipitation and river discharge geomorphic analysis of the modern river suggests that the central andes have gained only 700 m of elevation since incision began and had therefore reached at least 50 of their current elevation by middle miocene time we thus conclude that the onset of aridity at ca 16 ma occurred subsequent to the main andean uplift

fate of injected co2 in the wilcox group louisiana gulf coast basin chemical and isotopic tracers of microbial brine rock co2 interactions the 2800 sandstone of the olla oil field is an oil and gas producing reservoir in a coal bearing interval of the paleocene eocene wilcox group in north central louisiana usa in the 1980s this producing unit was flooded with co2 in an enhanced oil recovery eor project leaving 30 of the injected co2 in the 2800 sandstone post injection this study utilizes isotopic and geochemical tracers from co produced natural gas oil and brine to determine the fate of the injected co2 including the possibility of enhanced microbial conversion of co2 to ch4 via methanogenesis stable carbon isotopes of co2 ch4 and dic together with mol co2 show that 4 out of 17 wells sampled in the 2800 sandstone are still producing injected co2 the dominant fate of the injected co2 appears to be dissolution in formation fluids and gas phase trapping there is some isotopic and geochemical evidence for enhanced microbial methanogenesis in 2 samples however the co2 spread unevenly throughout the reservoir and thus cannot explain the elevated indicators for methanogenesis observed across the entire field vertical migration out of the target 2800 sandstone reservoir is also apparent in 3 samples located stratigraphically above the target sand reservoirs comparable to the 2800 sandstone located along a 90 km transect were also sampled to investigate regional trends in gas composition brine chemistry and microbial activity microbial methane likely sourced from biodegradation of organic substrates within the formation was found in all oil fields sampled while indicators of methanogenesis e g high alkalinity 13c co2 and 13c dic values and oxidation of propane were greatest in the olla field likely due to its more ideal environmental conditions i e suitable range of ph temperature salinity sulfate and iron concentrations

alluvial cover dynamics in response to floods of various magnitudes the effect of the release of glaciogenic material in a swiss alpine catchment abstract fluvial incision into formerly glaciated landscapes is commonly affected by the release of glaciogenic sediments from the hillslopes via landsliding hillslope failure and debris flow activity these deposits typically comprise abundant block size clasts here we determine the ability of the fluvial processes to evacuate glacially derived sediments in an alpine hanging valley blanketed by 100 m thick glacial till we assess along stream profiles of basal shear stress during annual decadal and centennial floods by means of the hydrological model hec ras we use bed surface grain size data to i evaluate the shields stress profiles for these floods ii determine at which timescale the bed undergoes significant changes and to iii predict transport capacity patterns for each flood in addition we present digital photogrammetry based estimates of bed elevation changes over two selected time intervals that experienced low and high magnitude floods respectively the results indicate that floods with return periods of 10 years are capable of mobilizing the coarse fraction of the bed material thereby substantially altering the channel geometry the predicted near critical shields stress values for these floods in the area where the glacial deposits are thickest suggest a strong hillslope channel coupling which may have resulted in the formation of the knickzone observed in this sector however decadal to centennial floods are required to transport the material over long distances and scour the bed in the upper part of the inner gorge in addition the observed downstream trend from bed scouring to deposition in the inner gorge for these floods and the opposite trend for low magnitude floods suggest that these patterns are not directly controlled by downstream variations of transport capacity we propose that the supply of sediment through hillslope failure and bank collapse significantly contributes to the sediment flux for high magnitude floods we conclude that the morphology and the timescale of sediment transport in this glacially conditioned landscape have been substantially controlled by the hillslope derived supply of coarse grained material

properties and shale oil potential of saline lacustrine shales in the qianjiang depression jianghan basin china abstract the geochemical and petrographic characteristics of saline lacustrine shales from the qianjiang formation jianghan basin were investigated by organic geochemical analysis x ray diffraction xrd scanning electron microscopy sem and low pressure nitrogen adsorption analysis the results indicate that the saline lacustrine shales of eq3 member with high oil content are characterized by type i and type ii oil prone kerogen variable toc contents 1 0 10 0 wt and an early maturity stage ro ranges between 0 41 and 0 76 the mineral compositions of eq3 saline shale show strong heterogeneity brittle intervals with high contents of quartz and carbonate are frequently alternated with ductile intervals with high glauberite and clay contents this combination might be beneficial for oil accumulation but may cause significant challenges for the hydraulic stimulation strategy and long term production of shale oil the interparticle pores and intraparticle pores dominate the pore system of eq3 shale and organic matter hosted pores are absent widely distributed fractures especially tectonic fractures might play a key role in hydrocarbon migration and accumulation the pore network is contributed to by both large size inorganic pores and abundant micro factures leading to a relatively high porosity 2 8 30 6 and permeability 0 045 6 27 md within the saline shale reservoir which could enhance the flow ability and storage capacity of oil the oil content s1 100 toc mg hc g toc and s1 mg hc g rock and brittleness data demonstrate that the eq33x section has both great potential for being a producible oil resource and hydraulic fracturing considering the hydrocarbon generation efficiency and properties of oil the mature shale of eq3 in the subsidence center of the qianjiang depression would be the most favorable zone for shale oil exploitation

substrate sediment and slope controls on bedrock channel geometry in postglacial streams the geometry of channels controls the erosion rate of rivers and the evolution of topography following environmental change we examine how sediment slope and substrate interact to constrain the development of channels following deglaciation and test whether theoretical relationships derived from streams reacting to tectonic uplift apply in these settings using an extensive data set of channel geometry measurements from postglacial streams in the scottish highlands we find that a power law width drainage area scaling model accounts for 81 of the spatial variation in channel width substrate influences channel form at the reach scale with bedrock channels found to be narrower and deeper than alluvial channels bedrock channel width does not covary with slope which may be due to downstream variations in sediment flux bedrock channel width to depth ratios increase with discharge or area and sediment flux consistent with increasing bed cover promoting lateral widening we find steep wide and shallow bedrock channels immediately below lakes which we interpret as the result of limited erosion due to a lack of sediment tools where sediment supply is sufficient to exceed transport capacity alluvial channels develop wider shallower geometries constrained primarily by flow hydraulics our results indicate that simple scaling models of channel width with drainage area are applicable at regional scale but locally channel width varies with substrate and in the case of bedrock channels with sediment flux

buried preglacial fluvial gorges and valleys preserved through quaternary glaciations beneath the eastern laurentide ice sheet the geomorphology geometry and sedimentary infill of buried gorges and v shaped valleys observed at the base of major river valleys in the formerly glaciated southeastern canadian shield region have been revealed from excavation and drilling data acquired during the construction of hydro electric dams and seismic data collected on lakes and offshore compilation of these previously published and unpublished data provided an exceptional opportunity to examine the morphology and spatial distribution of buried bedrock gorges and the mechanical processes responsible for their erosion in some valleys detailed observations of deep gorges have been allowed by their exhumation over large areas archive photographs show deep and large potholes natural pillars furrows flutes and scallops on the well polished bedrock walls of the gorges they also reveal that gorges and valleys have a sharp ending v shape and very narrow base and are superimposed by a u shaped valley forming a buried valley within valley topography the narrow and deep cross profile of these gorges their well polished slopes and the type of bedforms observed within them are typical features of fluvial bedrock channels drilling operations at many sites have also provided data on bedrock topography of these gorges within valleys and on the nature of their sedimentary infill the different lines of evidence presented in this paper indicate that gorges and v shaped valleys of the region were not eroded by the laurentide ice sheet during quaternary glaciations but are relics of a preserved preglacial fluvial system eroded during a lower base level this paleofluvial system is interpreted to be linked to fluvially cut channels observed on the seafloor of the estuary and gulf of st lawrence

seasonal scale abrasion and quarrying patterns from a two dimensional ice flow model coupled to distributed and channelized subglacial drainage abstract field data and numerical modeling show that glaciations have the potential either to enhance relief or to dampen topography we aim to model the effect of the subglacial hydraulic system on spatiotemporal patterns of glacial erosion by abrasion and quarrying on time scales commensurate with drainage system fluctuations e g seasonal to annual we use a numerical model that incorporates a dual morphology subglacial drainage system coupled to a higher order ice flow model and process specific erosion laws the subglacial drainage system allows for a dynamic transition between two morphologies the distributed system characterized by an increase in basal water pressure with discharge and the channelized system which exhibits a decrease in equilibrium water pressure with increasing discharge we apply the model to a simple synthetic glacier geometry drive it with prescribed meltwater input variations and compute sliding and erosion rates over a seasonal cycle when both distributed and channelized systems are included abrasion and sliding maxima migrate 20 up glacier compared to simulations with distributed drainage only power law sliding generally yields to a broader response of abrasion to water pressure changes along the flowline compared to coulomb friction sliding multi day variations in meltwater input elicit a stronger abrasion response than either diurnal or seasonal variations alone for the same total input volume an increase in water input volume leads to increased abrasion we find that ice thickness commensurate with ice sheet outlet glaciers can hinder the up glacier migration of abrasion quarrying patterns computed with a recently published law differ markedly from calculated abrasion patterns with effective pressure being a stronger determinant than sliding speeds of quarrying rates these variations in calculated patterns of instantaneous erosion as a function of hydrology sliding and erosion model formulation as well as model forcing may lead to significant differences in predicted topographic profiles on long time scales

chronology of the last glacial cycle in the european alps chronological data for glacier advances in the european alps between the last interglacial eemian and the holocene are summarised 115 to 11 ka during this time glaciers were most extensive extending tens of kilometres out onto the forelands between 30 and 18 ka that is synchronous with the global ice volume maximum of marine isotope stage mis 2 evidence for ice expanding to just past the mountain front for an earlier major glacier advance comes from swiss sites where advances have been luminescence dated to mis 5d 100 ka and mis 4 70 ka up to now no such evidence has been found in the eastern alps by 18 ka more than 80 of the late wurmian ice volume had gone subsequently glaciers readvanced reaching into the upper reaches of the main valleys during the lateglacial gschnitz stadial which likely occurred around 17 ka with final moraine stabilisation no later than 15 4 ka the link of the egesen stadial with the younger dryas climate deterioration is supported by exposure ages from four sites as well as minimum limiting radiocarbon dates from bogs within former glacier tongue areas key questions on the spatial and temporal variability of ice extents throughout the last glacial cycle have yet to be answered copyright 2008 john wiley sons ltd

abrupt glacial valley incision at 0 8 ma dated from cave deposits in switzerland glacial erosion dramatically alters mountain landscapes but the pace at which glaciers carve a previously fluvial landscape remains poorly defined because long term valley incision rates are difficult to measure here we reconstruct the lowering history of the aare valley switzerland over the past 4 m y by dating cave sediments with cosmogenic 26al and 10be incision accelerated from 120 m m y to 1200 m m y at 0 8 1 0 ma at least 1 m y after the onset of local glaciation rapid incision may have been triggered by lowering of the equilibrium line altitude at the mid pleistocene climate transition

pleistocene recharge to midcontinent basins effects on salinity structure and microbial gas generation the hydrogeochemistry of saline meteoric water interface zones in sedimentary basins is important in constraining the fluid migration history chemical evolution of basinal brines and physical stability of saline formation waters during episodes of freshwater recharge this is especially germane for interior cratonic basins such as the michigan and illinois basins although there are large differences in formation water salinity and hydrostratigraphy in these basins both are relatively quiescent tectonically and have experienced repeated cycles of glaciation during the pleistocene exploration for unconventional microbial gas deposits which began in the upper devonian age antrim shale at the northern margin of the michigan basin has recently extended into the age equivalent new albany shale of the neighboring illinois basin providing access to heretofore unavailable fluid samples these reveal an extensive regional recharge system that has profoundly changed the salinity structure and induced significant biogeochemical modification of formation water elemental and isotope geochemistry new formation water and gas samples were obtained from devonian mississippian strata in the illinois basin these included exploration wells in the new albany shale an organic rich black shale of upper devonian age and formation waters from over and underlying regional aquifer systems siluro devonian and mississippian age the hydrostratigraphic relations of major aquifers and aquitards along the eastern margin of the illinois basin critically influenced fluid migration into the new albany shale the new albany shale formation water chemistry indicates significant invasion of meteoric water with d values as low as 46 05 into the shale the carbon stable isotope system 13c values as high as 29 4 coupled with 18o d and alkalinity of formation waters alkalinity 24 08 meq kg identifies the presence of microbial gas associated with meteoric recharge regional geochemical patterns identify the underlying siluro devonian carbonate aquifer system as the major conduit for freshwater recharge into the fractured new albany shale reservoirs recharge from overlying mississippian carbonates is only significant in the southernmost portion of the basin margin where carbonates directly overlie the new albany shale recharge of dilute waters cl 1000 mm into the siluro devonian section has suppressed formation water salinity to depths as great as 1 km across the entire eastern illinois basin margin taken together with salinity and stable isotope patterns in age equivalent michigan basin formation waters they suggest a regional impact of recharge of 18o and d depleted fluids related to pleistocene glaciation devonian black shales at both basin margins have been affected by recharge and produced significant volumes of microbial methane this recharge is also manifested in different salinity gradients in the two basins because of their large differences in original formation water salinity given the relatively quiet tectonic history and subdued current topography in the midcontinent region it is likely that repeated cycles of glacial meltwater invasion across this region have induced a strong disequilibrium pattern in fluid salinity and produced a unique class of unconventional shale hosted gas deposits

inner gorges incision history a proxy for deglaciation insights from cosmic ray exposure dating 10be and 36cl of river polished surfaces tinee river sw alps france editor a yin keywords river gorges incision cre 10 be and 36 cl dating river polished surfaces 10 be and 36 cl cosmic ray exposure cre dating performed on river polished surfaces of river gorges in a mountain to sea river system in the french sw alps highlights transient erosional events involving incision rates 10 mm a 1 these events took place during the last two major deglaciation phases following 1 the last glacial maximum lgm at 16 14 ka 2 the younger dryas at 8 11 ka and during the warm and humid holocene climatic optimum at 4 5 ka these periods of high incision rates 3 30 mm a 1 alternated with periods of low incision rates 1 mm a 1 which probably correspond to a long term equilibrium between incision and relative uplift the alpine river staircase shape profiles evidence local and transient responses that are ascribed to cumulate disequilibrium after the long time spanned glaciations after each glaciation rivers rush down to get closer to their equilibrium profile incision is amplified both by the sediment discharge due to the erosion of moraines and by landslides triggered by the glacier retreat

cause of shale gas geochemical anomalies and mechanisms for gas enrichment and depletion in high maturity shales abstract this article reviews the abnormal characteristics of shale gases natural gases produced from organic rich shales and discusses the cause of the anomalies and mechanisms for gas enrichment and depletion in high maturity organic rich shales the reported shale gas geochemical anomalies include rollover of iso alkane normal alkane ratios rollover of ethane and propane isotopic compositions abnormally light ethane and propane 13 c values as well as isotope reversals among methane ethane and propane these anomalies reflect the complex histories of gas generation and associated isotopic fractionation as well as in situ mixing and accumulation of gases generated from different precursors at different thermal maturities a model was proposed to explain the observed geochemical anomalies gas generation from kerogen cracking at relatively low thermal maturity accounted for the increase of iso alkane normal alkane ratios and ethane and propane 13 c values normal trend simultaneous cracking of kerogen retained oil and wet gas and associated isotopic fractionation at higher maturity caused decreasing iso alkane normal alkane ratios lighter ethane and propane 13 c and corresponding conversion of carbon isotopic distribution patterns from normal through partial reversal to complete reversal relatively low oil expulsion efficiency at peak oil generation low expulsion efficiency at peak gas generation and little gas loss during post generation evolution are necessary for organic rich shales to display the observed geochemical anomalies high organic matter richness high thermal maturity high degrees of kerogen gas and oil gas conversions and late stage the stage of peak gas generation and post generation evolution closed system accounted for gas enrichment in shales loss of free gases during post generation evolution may result in gas depletion or even undersaturation total gas content lower than the gas sorption capacity in high maturity organic rich shales

the glacially overdeepened trough of the salzach valley austria bedrock geometry and sedimentary fill of a major alpine subglacial basin abstract overdeepened valleys are unambiguous features of glacially sculpted landscapes they result from erosion at the bed of the glacier and their size and shape is determined by ice dynamics and the characteristics of the underlying bedrock major overdeepened valleys representing vertical bedrock erosion of several hundreds of meters are characteristic features of many trunk valleys in the formerly glaciated parts of the alpine mountain belt the thick sedimentary fill usually hinders attempts to unravel bedrock geometry formation history and fill characteristics based on reflection seismic data and core logs from multiple deep drillings we construct a detailed bedrock model of the lower salzach valley trough one of the largest overdeepened valleys in the european alps the analysed overdeepened structure characterized by a strongly undulating topography two reaches of enhanced erosion can be identified and are suggested to be related to variations in bedrock erodibility and a triple glacier confluence the sedimentary fill shows clear characteristics of rapid infilling and subaqueous fan delta deposits indicate a strong influence of tributary streams associated surface lowering of the valley floor had a major impact on tributary stream incision but also on the available ice accumulation area at subsequent glaciations the extent to which fills of earlier glaciations have been preserved from erosion during the last glacial maximum remains ambiguous and demands further exploration to our knowledge the presented bedrock model is one of the best defined of any major overdeepened trunk valley

active deformation in the eastern swiss alps post glacial faults seismicity and surface uplift abstract post glacial tectonic faults in the eastern swiss alps occur as single lineaments clusters of faults or extensive fault zones consisting of several individual faults aligned along the same trend the orientation of the faults reflects the underlying lithology and the pre existing structures joints pervasive foliations within these lithologies most post glacially formed faults in the area around chur which undergoes active surface uplift of 1 6 mm year trend e w and cut across alpine and glacial features such as active screes and moraines additionally there are nnw and ene striking faults reactivating pervasive alpine foliations and shear zones based on a comparison with the nodal planes of recent earthquakes e w striking faults are interpreted as active faults because of very short rupture lengths and mismatches of fault location with earthquake distribution magnitude and abundance the faults are considered to be secondary faults due to earthquake shaking cumulative deformation in post or interseismic periods or creep and not primary earthquake related faults the maximum of recent surface uplift rates coincides with the youngest cooling of the rocks according to apatite fission track data and is therefore a long lived feature that extends well into pre glacial times isostatic rebound owing to overthickened crust or to melting of glacial overburden cannot explain the observed surface uplift pattern rather the faults earthquakes and surface uplift patterns suggest that the alps are deforming under active compression and that the aar massif basement uplift is still active in response to ongoing collision

signatures of late pleistocene fluvial incision in an alpine landscape uncertainty regarding the relative efficacy of fluvial and glacial erosion has hindered attempts to quantitatively analyse the pleistocene evolution of alpine landscapes here we show that the morphology of major tributaries of the rhone river switzerland is consistent with that predicted for a landscape shaped primarily by multiple phases of fluvial incision following a period of intense glacial erosion after the mid pleistocene transition 0 7 ma this is despite major ice sheets reoccupying the region during cold intervals since the mid pleistocene we use high resolution lidar data to identify a series of convex reaches within the long profiles of 18 tributary channels we propose these reaches represent knickpoints which developed as regional uplift raised tributary bedrock channels above the local fluvial baselevel during glacial intervals and migrated upstream as the fluvial system was re established during interglacial periods using a combination of integral long profile analysis and stream power modelling we find that the locations of 80 of knickpoints in our study region are consistent with that predicted for a fluvial origin while the mean residual error over 100 km of modelled channels is just 26 3 m breaks in cross valley profiles project toward the elevation of former end of interglacial channel elevations supporting our model results calculated long term uplift rates are within 15 of present day measurements while modelled rates of bedrock incision range from 1 mm yr for low gradient reaches between knickpoints to 6 10 mm yr close to retreating knickpoints typical of observed rates in alpine settings together our results reveal approximately 800 m of regional uplift river incision and hillslope erosion in the lower half of each tributary catchment since 0 7 ma

topographic fingerprints of bedrock landslides bedrock landslides in mountainous regions may be triggered by either storms or earthquakes the dominant mechanism in a region affects both landscape evolution and landslide hazard we describe a simple observational test to distinguish between storm and earthquake triggers based on a probabilistic measure of hillslope morphology in areas that are dominated by storm triggered landslides steep topographic slopes are concentrated on the lowermost parts of the hillslopes storm triggers act primarily on the hillslope toes and landslides preferentially remove material from those locations giving rise to inner gorges areas where most landslides are earthquake triggered have more uniform spatial distributions of steep topographic slopes because coseismic shaking causes failures at both ridge crests and hillslope toes earthquake triggered landslides lead to planar hillslopes and rare or absent inner gorges

pleistocene holocene climate change re establishment of fluvial drainage network and increase in relief in the swiss alps abstract data are presented about modern sediment discharge of the swiss rivers and related to the size of catchments the information reveals that the central alps have experienced denudation rates of 0 15 mm yr 1 in the foreland and 0 5 mm yr 1 in the alpine core mapping however indicates that modern erosion only affects 30 50 of the alpine surface and that fluvial and associated hillslope processes have focused erosion in 50 200 m deep valleys these valleys are incised into the glacial surface if this limited spatial extent of erosion is considered then effective erosion rates are significantly higher than average denudation rates these effective rates equal or locally exceed modern rates of rock uplift this implies that the modification of erosional processes related to the pleistocene holocene climate change has resulted in an increase in the relief at a local scale at a drainage basin scale however the relief appears not to change at present

inner gorge slot canyon system produced by repeated stream incision eastern alps significance for development of bedrock canyons abstract many inner bedrock gorges of the alps show abrupt downstream changes in gorge width as well as channel type and gradient as a result of epigenetic incision of slot canyons many slot canyons also are associated with older gorge reaches filled with quaternary deposits the age of slot canyons and inner bedrock gorges however commonly is difficult to constrain for the inner bedrock gorge system of the steinberger ache catchment eastern alps active slot canyons as well as older abandoned gorge reaches filled with upper wurmian proglacial deposits record three phases of gorge development and slot canyon incision a 234u 230th age of cement of 29 7 1 8 ka in fluvial conglomerates onlapping the flank of an inner gorge fits with late wurmian valley bottom aggradation shortly before pleniglacial conditions in addition the age indicates that at least the corresponding canyon reach must be older during advance of ice streams in the buildup of the last glacial maximum lgm the catchment was blocked and a proglacial lake formed bedrock gorges submerged in that lake were filled with fluviolacustrine deposits during the lgm the entire catchment was overridden by ice during post glacial reincision streams largely found again their preexisting inner bedrock canyons in some areas however the former stream course was missed and a slot canyon formed the distribution of pleistocene deposits the patterns of canyon incision and the mentioned u th cementation age however together record a further discrete phase of base level rise and stream incision well before the lgm the present course of steinberger ache and its tributaries is a patchwork of 1 slot canyons incised during post glacial incision 2 vestiges of slot canyons cut upon an earlier middle to late wurmian cycle of base level rise and fall 3 reactivated reaches up to 200 m in width of inner bedrock gorge that are watershed at present and more than at least 30 ka in age and 4 abandoned sediment filled reaches of bedrock canyons that also must be older than 30 ka and that are exposed alongside the active streams multi cyclic bedrock canyon systems composed of reaches of markedly different ages may be common in mountain ranges subject to glaciations and or mass wasting

the relief of the swiss alps and adjacent areas and its relation to lithology and structure topographic analysis from a 250 m dem abstract in this paper we discuss the large scale geomorphological characteristics of the swiss alps based on numerical analysis of a digital elevation model and compare these to an erodibility map constructed from a geotechnical map of switzerland and regional geomorphological studies comparing the erodibility map with the large scale morphometry shows an intimate relationship between mountain scale erodibility and topography on average higher mean elevations and steeper mean slopes correlate with regions where rocks of low erodibility prevail areas with high peaks as well as the main water divides are controlled by the presence of bedrock with low to very low detachability the drainage network of the swiss alps shows a close relationship to the lithological differences as well major longitudinal valleys follow easily erodible units in the eastern and western part of the swiss alps the highest values of local relief are located to the south of the main water divide whereas in the central part local relief is higher to the north of the main water divide the large scale geomorphic characteristics regarded in the framework of the geological history of uplift and denudation suggest that low and very low erodibilities lead to the development of areas of high elevations which are likely to persist over periods of 10 15 ma as the analysis of the lepontine area shows 20 ma after cessation of exhumation such high elevations are likely to be worn down and to manifest themselves as high relief only

geomorphology an ephemeral gorge the topography of the earth s surface can be read as an archive of past climatic and tectonic upheavals field data reveal how a bedrock gorge may be erased within a human lifetime taking with it the evidence of a major earthquake

mechanisms of shale gas storage implications for shale gas exploration in china this article reviews the mechanisms of shale gas storage and discusses the major risks or uncertainties for shale gas exploration in china at a given temperature and pressure the gas sorption capacities of organic rich shales are primarily controlled by the organic matter richness but may be significantly influenced by the type and maturity of the organic matter mineral composition especially clay content moisture content pore volume and structure resulting in different ratios of gas sorption capacity gsc to total organic carbon content for different shales in laboratory experiments the gsc of organic rich shales increases with increasing pressure and decreases with increasing temperature under geologic conditions assuming hydrostatic pressure gradient and constant thermal gradient the gsc increases initially with depth due to the predominating effect of pressure passes through a maximum and then decreases because of the influence of increasing temperature at greater depth this pattern of variation is quite similar to that observed for coals and is of great significance for understanding the changes in gsc of organic rich shales over geologic time as a function of burial history at an elevated temperature and pressure and with the presence of moisture the gas sorption capacities of organic rich shales are quite low as a result adsorption alone cannot protect sufficient gas for high maturity organic rich shales to be commercial gas reservoirs two models are proposed to predict the variation of gsc and total gas content over geologic time as a function of burial history high contents of free gas in organic rich shales can be preserved in relatively closed systems loss of free gas during postgeneration uplift and erosion may result in undersaturation the total gas contents lower than the sorption capacity and is the major risk for gas exploration in marine organic rich shales in china

bedrock landsliding river incision and transience of geomorphic hillslope channel coupling evidence from inner gorges in the swiss alps 1 the formation of inner gorges cut into bedrock has been explained as relief rejuvenation by fluvial incision in response to rapid base level drop repeated glaciations frequent pore pressure driven landsliding focused at hillslope toes or catastrophic outburst flows from natural dam failures prominent inner gorges occur in soft mesozoic bundner schist and lower tertiary flysch units of the formerly glaciated alpenrhein catchment eastern swiss alps their channel and hillslope morphologies differ from basins characterized by strong glacial or landslide imprints while formally resembling the theoretically predicted transient response of detachment limited bedrock rivers to rapid base level fall by headward knickpoint migration assuming a postglacial onset of fluvial bedrock incision into a last glacial maximum surface in response to base level drop induced by downwasting of trunk valley glaciers requires downcutting rates e 20 mm yr 1 and requires hillslopes to adjust by frequent landsliding toward development of a threshold state we test this scenario using data on surface uplift geomorphometry geomorphic hillslope coupling and probabilistic slope stability models we find that adjustment of inner gorge walls through landsliding is mainly strength limited and structurally controlled and threshold conditions are restricted to the lower 25 of local hillslope relief mass movement processes on upper hillslopes remain largely decoupled from channel incision despite inferred postglacial specific sediment yields of 104 m3 km 2 yr 1 from the studied basins conversely several constraints imposed by fluvial bedrock detachment postglacial sediment yields and bedrock landsliding argue for a pre holocene origin for at least some of the inner gorges in the area this implies partial protection of fluvial gorge topography by subglacial sediment fill during the last wurm extensive glaciation and implies that glaciers were insufficient to fully eradicate fluvially sculpted bedrock topography this leads us to conclude that lithology and major climate oscillations should be considered as further alternative controls on inner gorge formation

extensive microbial modification of formation water geochemistry case study from a midcontinent sedimentary basin united states the upper devonian antrim shale in the michigan basin is an economically significant source of microbially produced methane along the basin margins where meteoric recharge has been focused oxygen and hydrogen stable isotope compositions of antrim formation waters show that fresh waters recharged from pleistocene glaciation and modern precipitation suppressed basinal brine salinity to great depths and enhanced methanogenesis this paper presents results of integrated elemental and isotope analyses of antrim shale formation waters from the margins and center of the michigan basin focusing on solute sources and geochemical modifications associated with regionally extensive microbial methanogenesis cl br na systematics reveal that salinity is controlled not only by mixing between variable amounts of basinal brine and meteoric water but also by halite dissolution where fluids recharged through underlying devonian carbonate aquifers with localized evaporite deposits divalent cations carbonate system parameters and carbon isotope compositions of dissolved inorganic carbon have been systematically and profoundly altered by microbial methanogenesis large decreases in formation water ca mg and ca sr ratios accompany increasing carbonate alkalinity values in areas with high rates of microbial gas production thermodynamic and reaction path modeling show that these changes are consistent with calcite precipitation during progressive microbial methanogenesis similar variations in fluid chemistry are evident in databases from other sedimentary basins containing black shales and coal beds associated with microbial gas microbial methanogenesis may play an important role in the geochemical evolution of divalent cation relationships in crustal fluids and should be considered in models of formation water origin and evolution

rapid formation of a modern bedrock canyon by a single flood event deep river canyons are thought to form slowly over geological time see for example ref 1 cut by moderate flows that reoccur every few years in contrast some of the most spectacular canyons on earth and mars were probably carved rapidly during ancient megaflood events quantification of the flood discharge duration and erosion mechanics that operated during such events is hampered because we lack modern analogues canyon lake gorge texas was carved in 2002 during a single catastrophic flood the event offers a rare opportunity to analyse canyon formation and test palaeo hydraulic reconstruction techniques under known topographic and hydraulic conditions here we use digital topographic models and visible near infrared aerial images from before and after the flood discharge measured during the event field measurements and sediment transport modelling to show that the flood moved metre sized boulders excavated 7 m of limestone and transformed a soil mantled valley into a bedrock canyon in just 3 days we find that canyon morphology is strongly dependent on rock type plucking of limestone blocks produced waterfalls inner channels and bedrock strath terraces whereas abrasion of cemented alluvium sculpted walls plunge pools and streamlined islands canyon formation was so rapid that erosion might have been limited by the ability of the flow to transport sediment we suggest that our results might improve hydraulic reconstructions of similar megafloods on earth and mars

spatial patterns of erosion in a bedrock gorge understanding the physical processes driving bedrock channel formation is essential for interpreting and predicting the evolution of mountain landscapes here we analyze bedrock erosion patterns measured at unprecedented spatial resolution mm over 2 years in a natural bedrock gorge these spatial patterns show that local bedrock erosion rates depend on position in the channel cross section height above the streambed and orientation relative to the main streamflow and sediment path these observations are consistent with the expected spatial distribution of impacting particles the tools effect and shielding by sediment on the bed the cover effect vertical incision by bedrock abrasion averaged 1 5 mm a lateral abrasion averaged 0 4 mm a and downstream directed abrasion of flow obstacles averaged 2 6 mm a however a single plucking event locally exceeded these rates by orders of magnitude 100 mm a and accounted for one third of the eroded volume in the studied gorge section over the 2 year study period hence if plucking is spatially more frequent than we observed in this study period it may contribute substantially to long term erosion rates even in the relatively massive bedrock at our study site our observations demonstrate the importance of bedrock channel morphology and the spatial distribution of moving and static sediment in determining local erosion rates

metagenetic methane generation in gas shales i screening protocols using immature samples abstract the gas generative potential of organic matter is one key parameter for the calculation of total gas in place gip when evaluating thermogenic shale gas plays having first demonstrated that late gas forming structures are present in coals of anthracite rank 2 r0 we go on to examine other rocks at the immature stage of maturity and report on how to recognise which might generate significant amounts of late dry gas at geologic temperatures well in excess of 200 c in the zone of metagenesis r0 2 0 i e subsequent to primary and secondary gas generation by thermal cracking of kerogen or retained oil such a distinction could clearly be of major value when assessing risks and pinning down sweet spots a large selection 51 samples of source rocks i e shales and coals stemming from different depositional environments and containing various types of organic matter which contribute to the formation of petroleum in putative gas shales were investigated using open and closed system pyrolysis methods for the characterisation of kerogen type molecular structure and late gas generative behaviour a novel rapid closed system pyrolysis method which consists of heating crushed whole rock samples in mssv tubes from 200 c to 2 different end temperatures 560 c 700 c at 2 c min provides the basis for a newly proposed approach to discriminate between source rocks with low high or intermediate late gas potential it is noteworthy that late gas potential goes largely unnoticed when only open system pyrolysis screening methods are used high late gas potentials seem to be mainly associated with heterogeneous admixtures or structures in terrestrially influenced in some cases marine type iii and type ii iii coals and shales aromatic and or phenolic signatures are therefore indicative of the possible presence of elevated late gas potential at high maturities high temperature methane was calculated to potentially contribute an additional 10 40 mg g toc which would equal up to 30 of the total initial primary petroleum potential in many cases low late gas potentials are associated with homogeneous paraffinic organic matter of aquatic lacustrine and marine origin source rocks exhibiting intermediate late gas potentials might generate up to 20 mg g toc late dry gas and seem to be associated with heterogeneous marine source rocks containing algal or bacterial derived precursor structures of high aromaticity or with aquatic organic matter containing only minor amounts of aromatic phenolic higher land plant material

deep biogenic methane and drilling associated gas artifacts influence on gas based characterization of petroleum fluids classical interpretation of drilling mud gas molecular and isotopic data in petroleum systems can be impacted by both natural and engineering processes which can introduce allochthonous and or isotopically unrepresentative gas species this study investigates 1 widespread primary biogenic methane c1 and its impact on mud gas based petroleum system interpretation and on the properties of the petroleum fluids in the subsurface 2 differentiation of migration mixing versus diffusion leakage in petroleum systems and 3 bias introduced by gases generated at the drill bit including alkenes and isotopically changed gaseous alkanes our goal was to provide solutions to flag impacted intervals by the above processes minimize resulting interpretative bias and extract additional information about the fluid using advanced mud gas logging amgl tools and workflows an amgl interpretative methodology was developed using a combination of logs of c1 to pentane c5 concentrations and 13c c1 this approach allows identification of subsurface intervals containing nearly pure background primary biogenic c1 and can quantify its concentration per rock volume consequently thermogenic end member fluid types can be differentiated from mixtures with the biogenic c1 and assess its impact on the gas oil ratio of the mixture additionally two different processes can be responsible for mixing trends apparent on classical interpretation charts e g modified schoell diagram the presented analysis of amgl allows the deciphering of migration mixing versus diffusion leakage mixing trends using studied wells as examples another bias of mud gas based interpretation originates from artificial gases generated by drill bit metamorphism dbm evidence that dbm produced artificial alkanes in addition to alkenes via cracking of oil based drilling mud included strong correlation of concentrations among alkenes furthermore the concentration of alkenes strongly correlated with the magnitude of shift in 13c of c1 and ethane c2 between mud gas and solution gas from bottomhole fluids sampled at equivalent depths the artificial alkanes contributed by the drilling process can strongly bias and interfere with petroleum systems early interpretation based on mud gas molecular and isotopic ratios the bias depends on relative contributions of petroleum reservoir liberated mud gases and dbm gases which in this study reached half of the total c1 and c2 in the analyzed mud gas conversely alkene concentrations can be used as mud gas quality check parameters and early indicators of excess heat generated at the drill bit

identification of microbial and thermogenic gas components from upper devonian black shale cores illinois and michigan basins differentiation of microbial versus thermogenic methane in coalbed and black shale accumulations can affect strategies for exploration and may influence the total gas content in a given area early identification of these processes from crushed core materials even before formation fluids and produced gas samples are available could permit a more efficient and cost effective exploration total gas contents and compositional and isotopic data from new albany shale core materials are presented which delineate regional occurrence of microbial thermogenic and mixed gas generation in the illinois basin these trends are consistent with those identified from detailed prior studies of produced gas and water chemistry from the same locations the most useful markers for microbial gas in crushed core gases are elevated co2 contents characterized by high values 5 core gas analyses from wells in which microbial gas is identified commonly have significantly more total gas absorbed than do core samples from wells producing gases solely of thermogenic origin these observations are independent of variations in sample depth and organic carbon content in a given core thus this integrated case study of core and produced gases in the illinois basin illustrates that the areas containing microbial gas in addition to early thermogenic gas may be more productive than pure thermogenic zones for these early to immature unconventional gas deposits

10be derived assessment of accelerated erosion in a glacially conditioned inner gorge entlebuch central alps of switzerland inner gorges often result from the propagation of erosional waves related to glacial interglacial climate shifts however only few studies have quantified the modern erosional response to this glacial conditioning here we report in situ 10be data from the 64 km2 entlen catchment swiss alps this basin hosts a 7 km long central inner gorge with two tributaries that are 100 m deeply incised into thick glacial till and bedrock the 10be concentrations measured at the downstream end of the gorge yield a catchment wide erosion rate of 0 42 0 04 mm yr 1 while erosion rates are consistently lower upstream of the inner gorge ranging from 0 14 0 01 mm yr 1 to 0 23 0 02 mm yr 1 however 10be based sediment budget calculations yield rates of similar to 1 3 mm yr 1 for the inner gorge of the trunk stream likewise in the two incised tributary reaches erosion rates are similar to 2 0 mm yr 1 and similar to 1 9 mm yr 1 moreover at the erosional front of the gorge we measured bedrock incision rates ranging from similar to 2 5 mm yr 1 to similar to 3 8 mm yr 1 these rates however are too low to infer a post glacial age 1520 ka for the gorge initiation this would require erosion rates that are between 2 and 6 times higher than present day estimates however the downcutting into unconsolidated glacial till favored high erosion rates through knickzone propagation immediately after the retreat of the lgm glaciers and subsequent hillslope relaxation led to a progressive decrease in erosion rates this hypothesis of a two to sixfold decrease in erosion rates does not conflict with the 10be based erosion rate budgets because the modern erosional time scale recorded by 10be cover the past 23 ka only these results point to the acceleration of holocene erosion in response to the glacial overprint of the landscape

microbial generation of economic accumulations of methane within a shallow organic rich shale although methane of bacterial origin is ubiquitous in marine and freshwater sediments economic accumulations of bacterial gases occur mainly at depths of several kilometres in tertiary basins that had high sedimentation rates1 2 here we present an integration of geochemical and isotopic data from gas and water extracted from the upper devonian antrim shale along the northern margin of the michigan basin which demonstrates that significant volumes of bacterial gas have been generated in organic rich shales at depths of less than 600 metres the antrim shale is mainly a self sourced reservoir in contrast to conventional gas deposits that have migrated from a source to a reservoir and has become one of the most actively exploited gas reservoirs3 in the united states the gas forming processes operating at shallow depths in the antrim shale are not unique4 and an understanding of these processes should lead to the identification and development of other economic non conventional gas deposits around the world

paleowaters in silurian devonian carbonate aquifers geochemical evolution of groundwater in the great lakes region since the late pleistocene abstract changes in the climatic conditions during the late quaternary and holocene greatly impacted the hydrology and geochemical evolution of groundwaters in the great lakes region increased hydraulic gradients from melting of kilometer thick pleistocene ice sheets reorganized regional scale groundwater flow in paleozoic aquifers in underlying intracratonic basins here we present new elemental and isotopic analyses of 134 groundwaters from silurian devonian carbonate and overlying glacial drift aquifers along the margins of the illinois and michigan basins to evaluate the paleohydrology age distribution and geochemical evolution of confined aquifer systems this study significantly extends the spatial coverage of previously published groundwaters in carbonate and drift aquifers across the midcontinent region and extends into deeper portions of the illinois and michigan basins focused on the freshwater saline water mixing zones in addition the hydrogeochemical data from silurian devonian aquifers were integrated with deeper basinal fluids and brines in upper devonian black shales and underlying cambrian ordovician aquifers to reveal a regionally extensive recharge system of pleistocene age waters in glaciated sedimentary basins elemental and isotope geochemistry of confined groundwaters in silurian devonian carbonate and glacial drift aquifers show that they have been extensively altered by incongruent dissolution of carbonate minerals dissolution of halite and anhydrite cation exchange microbial processes and mixing with basinal brines carbon isotope values of dissolved inorganic carbon dic range from 10 to 2 87sr 86sr ratios range from 0 7080 to 0 7090 and 34 s so 4 values range from 10 to 30 a few waters have elevated 13cdic values 15 from microbial methanogenesis in adjacent organic rich upper devonian shales radiocarbon ages and 18o and d values of confined groundwaters indicate they originated as subglacial recharge beneath the laurentide ice sheet 14 50 ka bp 15 to 13 18o these paleowaters are isolated from shallow flow systems in overlying glacial drift aquifers by lake bed clays and or shales the presence of isotopically depleted waters in paleozoic aquifers at relatively shallow depths illustrates the importance of continental glaciation on regional scale groundwater flow modern groundwater flow in the great lakes region is primarily restricted to shallow unconfined glacial drift aquifers recharge waters in silurian devonian and unconfined drift aquifers have 18o values within the range of holocene precipitation 11 to 8 and 7 to 4 5 for northern michigan and northern indiana ohio respectively carbon and sr isotope systematics indicate shallow groundwaters evolved through congruent dissolution of carbonate minerals under open and closed system conditions 13cdic 14 7 to 11 1 and 87sr 86sr 0 7080 0 7103 the distinct elemental and isotope geochemistry of pleistocene versus holocene age waters further confirms that surficial flow systems are out of contact with the deeper basinal scale flow systems these results provide improved understanding of the effects of past climate change on groundwater flow and geochemical processes which are important for determining the sustainability of present day water resources and stability of saline fluids in sedimentary basins

fractured shale gas systems the first commercial united states natural gas production 1821 came from an organic rich devonian shale in the appalachian basin understanding the geological and geochemical nature of organic shale formations and improving their gas producibility have subsequently been the challenge of millions of dollars worth of research since the 1970s shale gas systems essentially are continuous type biogenic predominant thermogenic or combined biogenic thermogenic gas accumulations characterized by widespread gas saturation subtle trapping mechanisms seals of variable lithology and relatively short hydrocarbon migration distances shale gas may be stored as free gas in natural fractures and intergranular porosity as gas sorbed onto kerogen and clay particle surfaces or as gas dissolved in kerogen and bitumen five united states shale formations that presently produce gas commercially exhibit an unexpectedly wide variation in the values of five key parameters thermal maturity expressed as vitrinite reflectance sorbed gas fraction reservoir thickness total organic carbon content and volume of gas in place the degree of natural fracture development in an otherwise low matrix permeability shale reservoir is a controlling factor in gas producibility to date unstimulated commercial production has been achievable in only a small proportion of shale wells those that intercept natural fracture networks in most other cases a successful shale gas well requires hydraulic stimulation together the devonian antrim shale of the michigan basin and devonian ohio shale of the appalachian basin accounted for about 84 of the total 380 bcf of shale gas produced in 1999 however annual gas production is steadily increasing from three other major organic shale formations that subsequently have been explored and developed the devonian new albany shale in the illinois basin the mississippian barnett shale in the fort worth basin and the cretaceous lewis shale in the san juan basin in the basins for which estimates have been made shale gas resources are substantial with in place volumes of 497 783 tcf the estimated technically recoverable resource exclusive of the lewis shale ranges from 31 to 76 tcf in both cases the ohio shale accounts for the largest share

messinian climate change and erosional destruction of the central european alps at the end of the miocene the european alps ceased outward expansion and tectonic uplift and exhumation shifted into the orogen interior this shift is consistent with a change from orogenic construction to orogenic destruction reflecting an increase in the ratio of erosional flux to accretionary flux the coincidence of this change with an increase in sediment yield from the alps suggests a climate driven increase in erosional flux the timing of deformation and sediment release from the southern alps indicates that the tectonic change occurred synchronous with the last phase of the messinian salinity crisis we attribute the increase in erosional flux to a climatic shift to wetter conditions throughout europe likely augmented by the base level fall that occurred during the mediterranean dessication this climate change is represented in the stratigraphic record by the lago mare deposits of the mediterranean salinity crisis

variable late neogene exhumation of the central european alps low temperature thermochronology from the aar massif switzerland and the lepontine dome italy 1 several recent studies proposed an important increase in exhumation rate in the western european alps since circa 5 4 ma in order to assess potential spatial differences in exhumation histories we present new apatite fission track aft and apatite u th he ahe ages from the central aar massif guttannen area switzerland and the western lepontine dome formazza area italy internal u th zoning in apatites explains alpha ejection corrected ahe ages that are older than the corresponding aft ages in this study a qualitative interpretation of aft and ahe age elevation relationships suggests a two phase 9 7 and 5 3 ma exhumation scenario affecting the central alps with a stronger expression of the pliocene signal in the formazza area however a quantitative evaluation of exhumation scenarios using the 3 d heat equation solver pecube highlights the existence of several other likely scenarios casting doubt on the validity of a qualitative interpretation of the age elevation relationships in formazza scenarios suggested by quantitative modeling include continuous denudation at a rate of 750 m ma and a one step exhumation rate change from 300 to 1000 m ma at 5 ma in guttannen they include continuous denudation at a rate of 400 m ma with valley deepening and two periods of higher exhumation rate increasing from 300 to 700 m ma repeatedly at 9 7 and at 5 3 ma contingent upon further flexural isostatic modeling the magnitude of exhumation recorded in the axial region of the alps since circa 5 ma does not appear sufficient to solely explain the denudation recorded in the north alpine foreland basin

geomorphology deceptively old alpine gorges the timing and origins of alpine gorge formation are controversial a high resolution analysis of the inner gorges of the swiss alps suggests that these landforms were carved over successive interglacial periods and survived the intervening glaciations

experimental study on the gas generation processes of lacustrine and marine shales in north china source implications for shale gas abstract using a high pressure semi closed thermal simulation system two organic rich lacustrine and marine immature shales from north china were investigated to probe the dynamic processes and potential for the gas generation throughout the oil gas window the results identified at least two processes during gas generation as revealed by changes of the gas dry coefficient c1 c1 5 and carbon isotopic composition of methane 13cmethane the first process is associated with kerogen thermal degradation and occurs during the main phase of oil generation showing an increasing trend of the dry coefficient and 13cmethane the second process begins during the late phase of oil generation accompanied by increasing yields of wet gas components and 13c depleted methane due to the lack of aliphatic carbon in kerogen in the highly to over mature stage as demonstrated by ftir analyses the second process is mainly related to the cracking of kerogen generated bitumen which is retained in the shale the hydrogen content a key parameter for petroleum generation is then used to quantitatively evaluate the gas generation potential from kerogen thermal degradation and retained bitumen cracking mass balance calculations show that kerogen generated bitumen that is retained in lacustrine and marine shales is estimated to contribute 30 of the total gas yields at the stage of 1 5 2 0 ro this result is consistent with the theoretical calculations from xia et al 2013 and has important implications for the shale gas sources and further the shale gas resource assessments before exploration in shale gas petroleum systems

variability of rock mechanical properties in the sequence stratigraphic context of the upper devonian new albany shale illinois basin abstract rock mechanical properties of tight shale reservoirs are important parameters in the exploration and development of unconventional shale oil and gas understanding the stratigraphic variability of rock mechanical properties in black shale successions is important for identifying promising intervals for hydraulic stimulation high resolution hardness tests 6 cm spacing with an equotip bambino 2 hardness tester were conducted on a new albany shale core to study the stratigraphic variability of rock mechanical properties combined with high resolution geochemical analyses 8 cm spacing acquired with a portable x ray fluorescence spectrometer it is possible to relate hardness variability to shale composition the results of our study suggest an average quartz content of about 28 for the entire succession approximately half of that amount 13 is interpreted to be of biogenic origin biogenic quartz mainly derived from dissolution of radiolaria occurs as authigenic quartz precipitated in tasmanites cysts and as microcrystalline quartz precipitated in the shale matrix petrographic observations indicate that the hardness of the new albany shale is critically controlled by biogenic quartz content not by total quartz content as suggested in multiple prior studies biogenic quartz forms an interconnected stiff framework which increases the hardness of shales in contrast dispersed hard grains e g detrital quartz feldspar and dolomite do not contribute to brittle behavior when examined under a scanning electron microscope hard shales are rich in biogenic quartz and contrast visibly with soft shales that are characterized by high contents of clay minerals negative correlation between hardness and al2o3 content as well as differential compaction of clay minerals around hard grains indicate that clay minerals are an important ductile component in the new albany shale although the general softness of kerogen suggests that there should be an influence of organic matter on hardness this effect is counteracted by biogenic quartz cementation which has a comparable stratigraphic distribution pattern we propose a new mineral composition based brittleness index on the basis of biogenic quartz content to characterize the brittleness of tight shale reservoirs within a sequence stratigraphic context the hardness of the new albany shale increases in transgressive systems tracts reaches a maximum at maximum flooding surfaces and decreases in highstand systems tracts with the exception of the blocher member maximum flooding surface intervals have the highest potential to develop brittle fractures and should be potential targets for hydraulic stimulation

dating bedrock gorge incision in the french western alps ecrins pelvoux massif using cosmogenic 10be terra nova 22 18 25 2010 abstract we report in situ produced 10be data from the gorge du diable french western alps to date and quantify bedrock gorge incision into a glacial hanging valley we sampled gorge sidewalls and the active channel bed to derive both long term and present day incision rates 10be ages of sidewall profiles reveal rapid incision through the late holocene ca 5 ka at rates ranging from 6 5 to 13 mm yr 1 present day incision rates are significantly lower and vary from 0 5 to 3 mm yr 1 within the gorge our data imply either delayed initiation of gorge incision after final ice retreat from internal alpine valleys at ca 12 ka or post glacial surface reburial of the gorge our results suggest that fluvial incision rates 1 cm yr 1 into crystalline bedrock may be encountered in transient landscape features induced by glacial interglacial transitions

methanogenic microbial community of the eastern paris basin potential for energy production from organic rich shales abstract shallow thermally immature organic rich shales represent considerable resources in the paris basin france we investigated the presence of methanogenic consortia i e syntrophic bacteria and methanogens in the lower toarcian paper shales formation to link geochemical and lithological properties of the rocks to the spatial distribution of microbial communities the presence of methanogenic microbial populations demonstrated via their growth in enrichment cultures occurs throughout most of the rock layers and may be explained by the transport of organics and microorganisms within the formation the enriched consortia were able to utilize the organic matter of the rock as sole carbon source in microcosm indicating a strong potential of these microbial communities for methanogenesis in situ

volumetrically significant recharge of pleistocene glacial meltwaters into epicratonic basins constraints imposed by solute mass balances melting of kilometer thick continental ice sheets during pleistocene glaciation profoundly altered regional scale groundwater flow in the low lying stable interior of the north american craton in this paper we show that large volumes of glacial meltwater penetrated to great depths in underlying sedimentary basins through regionally extensive silurian devonian carbonate aquifers disrupting relatively stagnant saline fluids and creating a strong disequilibrium pattern in fluid salinity these dilute isotopically light meteoric waters migrated into overlying fractured organic rich upper devonian shales and significantly enhanced microbial methanogenesis generating a unique class of natural gas deposits along the shallow basin margins new data on formation water chemistry of upper devonian antrim shale gas wells along the northern and western margins of the michigan basin were integrated with previously published shale data and brines in subjacent silurian devonian carbonates this comprehensive database provides important constraints on fluid and solute transport and makes a compelling case for the reorganization of drinking water resources and salinity structures along the shallow basin margins by pleistocene glaciation na ca cl br relations and mass balance calculations were used to determine the relative volume of meteoric waters and sources of salinity in antrim shale fluids the majority of shale formation waters contain greater than 50 meteoric water with most containing over 80 meteoric water up to 300 m beneath the shale subcrop despite the presence of a strong salinity gradient meteoric water recharge dissolved variable amounts of halite from evaporite bearing silurian devonian carbonates along the flow path into the shale and displaced highly saline nacacl remnant marine brines the majority of antrim shale fluids owe greater than 60 of their salinity to halite dissolution while less than 40 of cl is from mixing with brines in silurian devonian strata oxygen and hydrogen isotope chemistry and carbon 14 age dating indicate these nacl brines were likely generated since the late pleistocene our conceptual model of fluid flow along the michigan basin margins and its role in generation of microbial gas were extrapolated to the larger glaciated midcontinent region where the silurian devonian carbonate subcrop is continuous along the illinois michigan and appalachian basin margins and is overlain by upper devonian black shales major differences in the hydrostratigraphy and fluid salinity of the epicratonic basins controlled the extent of meteoric water invasion and generation of microbial methane increased hydraulic gradients from melting of the continental ice sheets greatly enhanced recharge of dilute waters into deep silurian devonian aquifers and overlying fractured shales reversing regional scale groundwater flow and altering the major ion composition these fluid migration events occurred over relatively short time scales thousands of years compared to well documented basinal scale fluid migration events driven by tectonics and sediment compaction over millions of years understanding the hydrogeochemistry of the saline meteoric water mixing zones and the sources of salinity in sedimentary basins are both important for constraining fluid and solute transport chemical evolution of basinal fluids and physical stability of brines during meteoric water invasion