geochemical insights into provenance of the middle devonian hamilton group of the central appalachian basin u s a abstract in order to better understand the relationship of clastic influx and organic matter accumulation and preservation in the middle devonian acadian foreland basin we conducted a high resolution provenance analysis of a composite section of the hamilton group the hamilton group includes the organic rich marcellus shale one of the most lucrative unconventional shale gas plays in the world and the overlying mahantango formation geochemical analysis of 121 samples from two nearby wells in monongalia county west virginia reveals subtle changes in clay provenance throughout deposition of the marcellus shale and the mahantango formation major element and trace element geochemistry suggest derivation from a felsic igneous granodioritic upper continental crustal source with additional influx from a recycled quartzose sedimentary source all weathering indices indicate increasing chemical weathering intensities throughout deposition of the marcellus shale followed by consistently moderate chemical weathering associated with accumulation of the mahantango formation sm nd isotopic analysis of ten samples throughout the hamilton group yield end values ranging from 7 06 to 11 75 and nd depleted mantle model ages dm ranging from 1 63 to 1 85 ga with ages becoming younger upsection our results suggest that the extrabasinal detritus of the hamilton group originated from a mixed sediment source with clay influx from both rocks associated with the superior craton to the north and northwest dm 2 7 ga and grenville sourced sediments derived from the adjacent acadian fold thrust belt to the east dm 1 4 1 6 ga older sm nd model ages felsic composition and evidence of sediment recycling suggest little to no contribution from the acadian volcanic arc indicating that volcanic tuff of the tioga ash beds represent isolated episodes of volcanic input into the basin model ages end values and trace element geochemistry indicate increased sediment influx from the acadian fold thrust belt throughout deposition of the hamilton group with the highest sediment influx having occurred during mahantango formation deposition increased clay influx from sediment shed off from the acadian fold thrust belt associated with marginal marine regression increased delivery of clastic detritus diluting the flux of organic matter and likely disrupting basin water stratification that aided in preservation of organic matter in the lower marcellus shale the middle devonian acadian basin serves as an example of the influence of detrital influx on organic matter accumulation and preservation in mud dominated depositional systems

sm nd evidence for a major 1 5 ga crust forming event in the central grenville province the majority of gray gneisses from an 80 000 km 2 area in the central quebec grenville province define a sm nd isochron that yields an age of 1 53 0 07 ga major element trace element and initial nd isotopic data all point to a subduction related orogenic source for this terrane it is attributed to a major crustal extraction event that formed a mid proterozoic island arc the age of the terrane agrees with published data from the eastern and western grenville province in newfoundland and ontario respectively we suggest that 1 5 ga are fragments were accreted along much of the length of the laurentian foreland within 100 m y of their formation in an event marked by widespread granitoid plutonism

provenance of glacial marine conglomerates in the permian lagar formation of southern tibet evidence for affinity of the lhasa terrane with australia abstract paleogeographic reconstructions of the lhasa terrane of the southern tibetan plateau are uncertain in paleozoic and investigating the paleogeographic location of the terrane via the current geographical configuration is difficult however gravels contained within glacial sediments offer an opportunity to solve this problem the lagar formation in the central lhasa sub terrane contains glacial marine deposits that incorporate gravel clasts composed of granitoids sandstone quartzite limestone and rhyolite these diamictites were derived from continental glaciation and were deposited mainly near a grounding line or ice front in littoral neritic to neritic environments we present new zircon u pb isotopic and whole rock geochemical data for the tonalitic conglomerates of the lagar formation the results indicate that the tonalites crystallized during the paleoproterozoic 1 76 ga and show a geochemical affinity with i type granite the tonalites typically have negative eu anomalies eu 0 31 0 37 high concentrations of rare earth elements depletion in high field strength elements enrichment in th marked positive zircon ehf t values 6 46 14 68 end t values of 1 24 to 1 76 and tdm2 ages of 2 37 2 13 ga all of these data indicate that the tonalites were produced by the partial melting of modified mafic crust or underplate in a subduction related environment on the basis of a comprehensive analysis of all 1 8 1 7 ga magmatism in east gondwana we propose that the most likely provenance of the tonalitic conglomerates is southern arunta and mt isa in northern australia therefore the central lhasa sub terrane may have been located near australia during the paleozoic

the role of groundwater in the amazon water cycle 3 influence on terrestrial water storage computations and comparison with grace 1 we explore the mechanisms whereby groundwater influences terrestrial water storage tws in the amazon using grace observations and two contrasting versions of the leaf hydro flood hydrological model one with and the other without an interactive groundwater we find that first where the water table is shallow as in northwestern amazonia and floodplains elsewhere subsurface stores vadose zone and groundwater are nearly saturated year round hence river and flooding dominate tws variation where the water table is deep as in southeastern amazonia the large subsurface storage capacity holds the infiltrated water longer before releasing it to streams hence the subsurface storage dominates tws variation second over the whole amazon the subsurface water contribution far exceeds surface water contribution to total tws variations based on leaf hydro flood simulations 71 of tws change is from subsurface water 24 from flood water and 5 from water in river channels third the subsurface store includes two competing terms soil water in the vadose zone and groundwater below the water table as the water table rises the length of vadose zone is shortened and hence the change in groundwater store is accompanied by an opposite change in soil water store resulting in their opposite phase and contributions to total tws we conclude that the inclusion of a prognostic groundwater store and its interactions with the vadose zone rivers and floodplains in hydrological simulations enhances seasonal amplitudes and delays seasonal peaks of tws anomaly leading to an improved agreement with grace observations

a tale of shales the relative roles of production decomposition and dilution in the accumulation of organic rich strata middle upper devonian appalachian basin abstract a new consensus on the processes responsible for organic carbon burial in ancient epeiric seas has emerged more firmly grounded in the uniformitarian framework of modern oceanography and biogeochemistry this consensus recognizes the interdependent roles of sedimentation primary production and microbial metabolism in favor of earlier end member models e g production vs preservation in this study one of the classic stratigraphic sequences upon which the preservation end member was based is re interpreted in light of this new consensus the study employs an extensive new sedimentological biogeochemical database from cores drilled in western new york the database spans over 500 m and 15 my of devonian deposition in the appalachian basin and provides a framework for comparative study of organic matter burial the major conclusions are 1 few organic rich units were deposited under pervasive anoxic sulfidic water columns 2 establishment and breakdown of seasonal thermoclines on annual or longer timescales were the predominant mode of stratification and 3 under such conditions remineralization of bio limiting nutrients may have played a key role in organic matter burial by creating a eutrophication pump this pump may have augmented an already rising nutrient inventory such that productivity levels exceeded the threshold required for development of suboxic to anoxic conditions in sediments and episodically in bottom waters a final conclusion asserts that the master variable for organic matter accumulation was relative sea level change which exerted influence on clastic dilution preservation and production processes sea level rise events led to sediment starvation and organic carbon concentration in distal basin sediments as well as to decreased effectiveness of seasonal mixing and thus longer build up intervals for remineralized nutrients episodic mixing of nutrient enriched bottom waters led to enhanced production ultimately increased clastic sediment delivery and water column mixing during relative sea level fall diluted surface sediment organic content such that respiratory demand could be met by increased oxygen supply thus terminating deposition of strata enriched in organic carbon

black shale deposition and faunal overturn in the devonian appalachian basin clastic starvation seasonal water column mixing and efficient biolimiting nutrient recycling integrated geochemical data suggest that black shale deposition in the devonian geneseo formation of western new york was initiated by the coincidence of siliciclastic starvation and the intensification of seasonal water column stratification and mixing once established however black shale deposition was maintained through efficient recycling of biolimiting nutrients which enhanced primary productivity recycling efficiency was achieved through a positive feedback loop of oscillating benthic redox conditions that enhanced n and p regeneration from sediments sustained high primary productivity by returning nutrients to the photic zone during mixing and ensured a downward flux of organic matter that drove or enhanced the episodic development of benthic anoxia during stratification this feedback was ultimately disrupted by rising siliciclastic influx which diluted organic matter and restored benthic redox stability the abrupt overturn of diverse long standing appalachian basin marine communities may have been the result of trophic resource destabilization during geneseo deposition

rare earth element redistribution and its effects on the neodymium isotope system in the austin glen member of the normanskill formation new york usa abstract three groups of ree patterns are observed for the sandstones and shales of the middle ordovician austin glen member of the normanskill formation one sandstone sample is enriched in middle and light rare earth elements the majority of samples are light rare earth element lree enriched with negative eu anomalies and flat heavy rare earth elements hrees whereas a third group appears to have lost lrees and middle rare earth element mrees homogeneous neodymium isotopic compositions for all samples at about the time of deposition nd 470 ma 8 2 1 1 2sd indicate that the source of the austin glen member was well mixed and that the neodymium had a long term enriched history the differences in the shape and abundances of the ree patterns combined with the neodymium isotope characteristics of the samples lead us to the conclusion that samarium and neodymium were fractionated and that the neodymium isotopic system might have been disturbed at about the time of deposition 470 ma most samples appear to have been affected by this process the two most altered shales lost about half of their neodymium and their sm nd ratios are higher than the sm nd ratios of average shales these two shales give clearly erroneous mantle extraction ages but the average tdm of the provenance can still be deduced 1700 1800 ma from the least disturbed sandstones with normal upper crustal sm nd ratios accordingly this study demonstrates that the rees may be transported and neodymium isotopes may be reequilibrated under certain sedimentary conditions e g diagenesis however in spite of evidence for ree redistribution provenance information tdm original ree patterns may still be inferred

k bentonites volcanic ash preservation and implications for early to middle devonian volcanism in the acadian orogen eastern north america lower to middle devonian marine strata in the appalachian foreland basin feature up to 80 or more thin k bentonites that represent ancient volcanic ashes the time vs space distribution of k bentonites through the lochkovian to eifelian stages representing 30 m y shows a distinct pattern of clustered multiple beds several scattered beds and thick intervals with no k bentonites four clusters of 7 to 15 individual closely spaced layers occur in the middle lochkovian bald hill k bentonites kalkberg new scotland formations late pragian or early emsian sprout brook k bentonites esopus formation and early eifelian two clusters the tioga middle coarse zone and tioga a g k bentonites onondaga formation detailed examination of these devonian k bentonites shows that in many cases they do not represent a single eruption multilayered beds fossil layers within beds authigenic minerals e g glauconite and phosphate nodules subjacent hardgrounds and an irregular distribution of beds through space and time raise questions about the depositional history and preservation potential of volcanic ash in marine environments and the degree to which the beds represent a primary record of volcanism these and other lines of evidence indicate that postdepositional physical biological and geochemical processes e g sedimentation rate event and background physical processes burrowing have modified the primary record of these water laid ash fall events these factors may lead to preservation of primary ash deposits or to their resedimentation and or partial to complete mixing with background sediments the preservation potential and resulting distribution of the devonian k bentonites can be analyzed across a spectrum of preservational magnafacies in this paper i present a model of ash preservation the model incorporates environmentally related physical biological and chemical processes active in epicontinental seas and marine foreland basins conclusions based on the model indicate that the middle lochkovian early emsian and early eifelian were times of peak volcanic activity in eastern north america related to times of increased tectonism in the acadian orogen

self affine scaling and subsurface response to snowmelt in steep terrain abstract the use of local scaling transformations is proposed as a framework for modeling the geometry and dynamic response of subsurface flow from steep hillslopes the study site is the upper sheep creek watershed a first order sub basin in the reynolds creek experimental watershed southwest idaho the goal of the research is to gain insight into the evolution of snowmelt subsurface flow and runoff generation in this rugged volcanic terrain in this phase of the study rescaling geometrically proportional self affine surface and bedrock slope profiles provide an analytical framework for defining the shape volume and dynamic changes of saturated flow for this hillslope system rescaling self affine hillslope trajectories along a stream reach collapses the flow domain to a unit cube a dynamic model for hillslope runoff is proposed and implications for modeling topographic controls on the snowmelt process are suggested

stability and damping in a dynamical model of hillslope hydrology a stability analysis is performed on the two state variable integral balance model of hillslope hydrology developed by duffy 1996 the motivation for the research is to develop a physically based low dimensional representation of inflow outflow behavior within a hillslope stream setting stability criteria are developed for the model equilibria and are evaluated using the results of numerical solutions of richards equation for a convex concave hillslope geometry we show that for homogeneous hillslopes of three widely varying soil types the single moisture equilibrium is classified as a stable node for low precipitation rates and a stable spiral for wet conditions the spiral equilibrium indicates that the hillslope system is lightly damped and transient oscillations of the state variables are expected for high precipitation rates the timescale of these oscillations is of the order of several days to weeks for the model hillslopes examined furthermore we demonstrate that the model contains a hopf bifurcation from a stable static equilibrium to a stable limit cycle the amplitude phase and frequency of the limit cycle are determined analytically using second order averaging however this behavior is shown to be nonphysical for the particular homogeneous soils and hillslope geometry investigated implications of lightly damped behavior in the hillslope system include moisture oscillations in the field under wet conditions and difficulty in numerical solution of richards equation 1 background the effects of microscale nonlinearity of saturated unsaturated flow on macroscale observable hydrologic behav ior remain largely unknown the highly nonlinear partial dif ferential equation for variably saturated flow richards 1931 indicates the possibility of complex dynamical behavior at the hillslope scale however because energy inputs and especially precipitation are strong and noisy it is difficult to separate the response to such forcing from the dynamics that may be inher ent in the soil groundwater system within the framework of dynamical systems hillslope soil moisture and associated hy drologic fluxes can be thought of as a noisy forced dynamical system consistent with this conceptualization a two state vari able integral balance dynamical model for hillslope hydrology has recently been introduced by duffy 1996 the purpose of this paper is to characterize the dynamical behavior of this model using both analytical methods and the results of numer ical solutions of richards equation in particular we explore conditions for stable and unstable moisture equilibria the approach taken here differs from the local analysis of stability of flow in porous media which is associated with a highly fingered spatial distribution of moisture during infiltra

new u pb zircon ages and the duration and division of devonian time newly determined u pb zircon ages of volcanic ashes closely tied to biostratigraphic zones are used to revise the devonian time scale they are 1 417 6 1 0 ma for an ash within the conodont zone of icriodus woschmidti i w hesperius early lochkovian 2 408 3 1 9 ma for an ash of early emsian age correlated with the conodont zones of po dehiscens lower po inversus 3 391 4 1 8 ma for an ash within the po c costatus zone and probably within the upper half of the zone eifelian and 4 381 1 1 3 ma for an ash within the range of the frasnian conodont palmatolepis punctata pa punctata zone to upper pa hassi zone u pb zircon ages for two rhyolites bracketing a palyniferous bed of the pusillites lepidophyta spore zone are dated at 363 8 2 2 ma and 363 4 1 8 ma respectively suggesting an age of363 ma for a level within the late famennian pa g expansa zone these data together with other published zircon ages suggest that the base and top of the devonian lie close to 418 ma and 362 ma respectively thus lengthening the period by20 over current estimates we suggest that the duration of the middle devonian eifelian and givetian is rather brief perhaps no longer than 11 5 myr 394 ma 382 5 ma and that the emsian and famennian are the longest stages in the period with estimated durations of15 5 myr and 14 5 myr respectively 1998 elsevier science b v all rights reserved

storage dependent drainable porosity for complex hillslopes 1 in hydraulic groundwater theory the parameter drainable porosity f a storage coefficient that accounts for the effect of the unsaturated zone on water table dynamics is usually treated as a constant for shallow unconfined aquifers the value of this parameter however depends on the depth to the water table and the water retention characteristics of the soil in this study an analytical expression for f as a function of water table depth is derived under the assumption of quasi steady state hydraulic equilibrium in this way accounting in part for the effects of the unsaturated zone on groundwater dynamics the derived expression is implemented in the nonlinear hillslope storage boussinesq hsb model troch et al 2003 to simulate the drainage response of complex hillslopes the model s behavior is analyzed by comparison to 1 the hsb model with a constant value for f and 2 measurements of water tables and outflow hydrographs on a 6 0 2 5 0 5 m laboratory hillslope experiment the comparison is conducted for a pure drainage case on two different hillslope shapes linearly convergent and divergent and for three different slope inclinations 5 10 and 15 comparison 1 is run in an uncalibrated and a fully calibrated mode and it enables us to evaluate the effect of a dynamic state dependent value for f on model output comparison 2 allows us to test the hsb model on several hillslope configurations and to analyze whether the concept of a storage dependent f enhances the model performance the comparison of the hsb models to the measurements from the laboratory hillslopes shows that it is possible to capture the general features of the outflow hydrograph during a drainage experiment using either one of the hsb models overall the original constant f hsb model with one fitting parameter more than the revised hsb model shows a slightly better fit on the hydrographs when compared to the revised variable f hsb model however the peak outflow values the first few minutes after initiation of the experiments are better captured by the revised hsb model the revised hsb model s performance in simulating water table movements is much more accurate than that of the original hsb model the improved match of the revised hsb model to piezometric measurements is worth stressing because the ability to model water tables is a key attribute of the model making it possible to investigate phenomena such as saturation excess runoff also noteworthy is the good match between the revised hsb model and the outflow measurements without any calibration for the divergent slopes the changing values of the calibrated drainable porosity parameter for the original hsb model as different configurations are simulated slope angle plan shape initial conditions together with the ability of the revised hsb model to more accurately simulate water table dynamics clearly demonstrates the importance of regarding drainable porosity as a dynamic storage dependent parameter

quantitative mineralogy for facies definition in the marcellus shale appalachian basin usa using xrd xrf integration abstract determining the mineralogy of mature sedimentary rocks particularly mudrock often defaults to qualitative or semi quantitative methods due to difficulties in correctly quantifying multiple unknown mineral phases constraining mineral abundances is particularly difficult in shale due to preferred mounting orientation of common phyllosilicate phases commonly leading to overestimation of clay minerals and mica we introduce a quantitative approach to constraining mineralogy within mudrock by integrating x ray diffraction xrd and x ray fluorescence xrf data sets collected on splits of the same samples the technique involves partitioning xrf cation concentrations into xrd identified silicate carbonate and sulfide phases then estimating quartz by xrf sio2 balance this method is applied to an example dataset from the economically significant marcellus shale middle devonian appalachian basin usa conventional reference intensity ratio rir interpretation identified nine mineral phases quartz muscovite illite pyrite chlorite albite calcite dolomite and barite their abundances were then re estimated using more highly accurate xrf derived elemental concentrations with stoichiometry from the identified xrd reference phases xrf al2o3 was used to corroborate the calculated xrd xrf results for quality control errors in relevant xrf concentrations can be quantified though not the assumptions in how they are employed nonetheless the resulting xrd xrf mineralogic abundances by this procedure are thought to be more accurate than rir and to remove preferred orientation bias induced that causes overestimation of clay minerals and mica and underestimation of quartz and other phases cluster analysis of the xrd xrf results identified four mineralogical facies that provide insight into potential primary depositional controls on organic matter preservation within the marcellus shale this xrd xrf integration method provides a general framework for estimating mineralogy quantitatively in mudrocks although dataset specific adjustments to the method may be required for different mineralogical suites

prediction of some weathering trends of plutonic and volcanic rocks based on thermodynamic and kinetic considerations abstract the exposed crust consists mainly of plagioclase 35 quartz 20 k feldspar 11 volcanic glass 12 biotite 8 and muscovite 5 quartz is a resistate thus feldspars and glass represent approximately 75 percent of the labile minerals the weathering characteristics of these constituents are summarized in the context of thermodynamic mass balance and kinetic considerations experimentally determined release rate constants were used to predict the proportions of ca na and k released by feldspars of plutonic rocks granites to gabbros to weathering solutions the chemical weathering trends of the weathered residues calculated from the kinetic data conform closely to the initial trends observed in some recent weathering profiles demonstrating the accuracy of the predictions since the weathering of feldspars is controlled by processes that should not change through geological time the relative release rates of ca na and k from the feldspars of granitic rocks can be calculated for future and past episodes of continental weathering experimentally determined release rate constants are not available for a wide range of volcanic glass compositions but the limited data indicate that compositional trends are predictable in weathering profiles developed on volcanic rocks the kinetic data available for rhyolitic glasses accurately predict the initial weathering trends observed in a recent rhyolite weathering profile

tectonics of the acadian orogeny in new england and adjacent canada paleogeographic analysis of post taconian rocks in new england and adjacent parts of canada has revealed the existence of two volcanic arcs which shut off at the time of the acadian orogeny one was built on arc basement previously accreted to north america during the taconic orogeny the other on precambrian continental basement of avalonia in the intervening merrimack fredericton trough metamorphosed and poly deformed turbidites and black shales record deep water conditions in silurian following mckerrow and ziegler 1971 this tract is interpreted as the site of an ocean which closed in siluro devonian by simultaneous subduction beneath both continental margins in the molucca sea in indonesia a comparable arc arc collision is in an early stage of development moore et al 1982 suggested that an accretionary prism built against one arc is overthrusting its counterpart which developed on the other side of the ocean an identical geometry with an avalonian accretionary prism overriding the conve

whole rock pb and sm nd isotopic constraints on the growth of southeastern laurentia during grenvillian orogenesis the conventional view that the basement of the southern and central appalachians represents juvenile mesoproterozoic crust the final stage of growth of laurentia prior to grenville collision has recently been challenged new whole rock pb and sm nd isotopic data are presented from mesoproterozoic basement in the southern and central appalachians and the granite rhyolite province as well as one new u pb zircon age from the granite rhyolite province these data combined with existing data from mesoproterozoic terranes throughout southeastern laurentia further substantiate recent suggestions that the southern and central appalachian basement is exotic with respect to laurentia sm nd isotopic compositions of most rocks from the southern and central appalachian basement are consistent with progressive growth through reworking of the adjacent granite rhyolite province however pb isotopic data including new analyses from important regions not sampled in previous studies do not correspond with pb isotopic compositions of any adjacent crust the most distinct ages and isotopic compositions in the southern and central appalachian basement come from the roan mountain area eastern tennessee western north carolina the data set indicates u pb zircon ages up to 1 8 ga for igneous rocks inherited and detrital zircon ages 2 0 ga sm nd depleted mantle model t dm ages 2 0 ga and the most elevated 207 pb 204 pb observed in southeastern laurentia the combined u pb geochronologic and sm nd and pb isotopic data preclude derivation of southern and central appalachian basement from any nearby crustal material and demonstrate that grenville age crust in southeastern laurentia is exotic and probably was transferred during collision and assembly of rodinia these new data better define the boundary between the exotic southern and central appalachian basement and adjacent laurentian granite rhyolite province

the influence of sediment recycling and basement composition on evolution of mudrock chemistry in the southwestern united states this paper reports systematic changes in mudrock composition through time on a single con tinental cmstal block the changes reflect both sediment recycling processes and changes through time in the composition of crystalline material being added to the sedimentary system and are related to tectonic evolution as the block matures from a series of accreted arc terranes to a stable craton the major and trace element distributions reflect different aspects of the provenance of the mudrocks in this study major elements record sediment recycling processes as well as changing proportions of sedi mentary and first cycle source rocks with the exceptions of kzo which tends to increase and sioz and a o3 which show no trend most major oxides tend to decline in relative abundance in younger mud rocks patterns shown by the index of compositional variability fe03 kro naao cao mgo mno tiojialro and by k20 a1203 indicate that the major oxide trends are due to decreasing proportions of nonclay silicate minerals and a concomitant increase in the proportion of clay minerals probably due to decreasing input of first cycle detritus coupled with recycling of sedimentary material excursions from progressive trends marked by increases in mgo k20 and cao reflect episodes of large scale input of nonclay first cycle minerals from crystalline source rocks due to large scale basement uplift the chemistry of low solubility trace elements in contrast is not sensitive to recycling effects and reflects the composition of first cycle input incompatible elements are progressively enriched relative to compatible elements in younger mudrocks and values for chondrite normalised rare earth elements also increase in addition the eu anomaly becomes systematically more negative in younger samples these trends cmnot be explained by diagenetic or weathering processes and therefore indicate that the proportion of fnc tionated granitic first cycle detritus being added to the sedimentary system becomes greater with time these results confirm the importance of tectonic setting in controlling mudrock chemistry and also demonstrate that there is a dynamic relationship between the tectonic evolution of a continental block and the composition of its sedimentary mantle

saturation regions in catchments and their relations to soil and topographic properties abstract criteria are derived for the existence of saturated areas on draining hillslopes in natural catchments these are given in terms of soil transmissivity the hillslope gradient and its wetness state characterised by the baseflow discharge from the catchment analyses are made for idealised hillslopes with uniform soils to obtain expression for the width of the saturated zone the size of saturated zones on undulating hillslopes with gradiational soils is shown to depend strongly on topographic convergence or divergence the effects of soil transmissivity hillslope geometry and drainage flux density are lumped into a dimensionless parameter whose value determines the location of seepage boundaries on slopes of specified geometry scaling relations for seepage area in catchments of different size are shown to be generally nonlinear and depend primarily on local hillslope gradients relative predictions of seepage zone size are confirmed by observed hydrographs from three catchments with different physical characteristics

the ciw index a new chemical index of weathering abstract a new chemical index of weathering that can be applied to modern soils and precambrian paleosis is proposed ciw al2o3 the value of this index increases as the degree of weathering increases and the difference between ciw index values of the silicate parent rock and soil or sediment reflects the amount of weathering experienced by the weathered material

stratigraphic context geochemical and isotopic properties of magmatism in the siluro devonian inliers of northern maine implications for the acadian orogeny this paper reports detailed stratigraphic analysis whole rock geochemistry and nd isotopic ratios of basalts from the northern maine inliers these data place constraints on first order controversies about the tectonic conditions leading up to and during the early stages of the acadian orogeny in northern maine late silurian and early devonian stratigraphic sequences indicate a progressive change from shallow water and subaerial exposure ripogenus and the forks formations east branch group to a rapidly subsiding basin prior to the onset of acadian deformation subsidence was accompanied by mafic to intermediate volcanism of the west branch spider lake and fish pond volcanics and that continued with intrusion of the syn deformational greenville plutonic belt including the flagstaff lake igneous complex whose properties we report in this paper trace element geochemistry indicates that magmatism is transdiscriminant showing aspects of within plate volcanic arc and back arc affinities and nd isotopic ratios are moderately positive 2 3 to 3 8 indicating either an uncontaminated and moderately enriched mantle source or a depleted mantle source contaminated by continental crust four possible tectonic models of the acadian orogeny and the siluro devonian sedimentary volcanic sequences of northern maine are evaluated in the context of a subsiding basin associated with this magmatism developed on the amalgamated laurentian plate these include 1 slab detachment during southeast directed subduction of the laurentian continental margin 2 laramide style thrust basins above a shallow northwest dipping subduction zone 3 back arc extension followed by thin skinned shortening above a northwest dipping subduction zone and 4 moluccan style dual dipping subduction zones

role of coupled flow dynamics and real network structures on hortonian scaling of peak flows we investigate how channel flow dynamics on real river networks produces scaling in peak flows scaling relations have been defined by log log linearity between peak flow statistics and drainage areas for idealized mean self similar networks like peano and mandelbrot viscek unlike idealized basins drainage areas and link lengths in real basins vary statistically we use horton strahler order as scale parameter instead of drainage area and use the hortonian framework to analyze these network structures a river network oriented gis is used to extract the drainage network for the walnut gulch basin arizona in the united states it provides the link connectivity structure and the geometric variables for numerically solving coupled link based mass and momentum conservation equations the equations are solved for spatially uniform and instantaneous injection of runoff under three different scenarios of flow in the channels 1 constant velocity 2 constant friction and 3 spatially variable friction we find that hortonian scaling in peak flows does not hold for the constant friction scenario the scaling exponents of peak flows for the other two cases are larger than the scaling exponent of the peaks of the width functions this property of scaling exponents for a real network is opposite to previous findings for idealized mean self similar networks an empirical scaling analysis of peak flows on the walnut gulch basin is briefly explained to provide preliminary empirical support to our theoretical findings

anoxia vs productivity what controls the formation of organic carbon rich sediments and sedimentary rocks discussion the prevailing explanation for the origin of organic rich sediments and rocks invokes deposition under conditions of anoxia however recent research suggests that high primary production and not water column anoxia provides the first order control on the accumulation of organic rich facies in the modern oceans oxygen minima do not appear to have any direct effect on carbon accumulation in continental margin or marginal sea environments sediments accumulating in the modern black sea the type euxinic basin are not particularly enriched in organic matter despite the presence of an anoxic water column although a sapropel containing extremely high carbon concentrations was deposited during the holocene at a time when the basin was oxic results of a recently published co pled ocean atmosphere model indicate that during the cretaceous thermohaline and surface circulation in the oceans was similar to or more intense than modern conditions despite the overall equable climate such conditions confound the idea that circulation in the cretaceous atlantic for example was punctuated by oceanic anoxic events brought about by more sluggish circulation sporadic temporal and spatial increases in primary production reflecting changes in the behavior and or state of the ocean atmosphere system constitute a more tenable explanation for the occurrence of modern and quaternary carbon rich sediments and cretaceous black shales consequently the fundamental control on the accumulation of carbon rich facies in the oceans and marginal seas is not the presence or absence of anoxia

linking the acadian orogeny with organic rich black shale deposition evidence from the marcellus shale abstract the trace and rare earth elements ree analyses were conducted on samples collected from a 30 m core of the marcellus shale obtained from greene county southwestern pennsylvania our results suggest that organic matter enrichment trends in the marcellus shale can be directly linked with the acadian orogeny the acadian orogeny has been recognized as a main sediment source for the marcellus shale synthesis of tectonic history and recent ash bed geochronology reveals that deposition of the organic carbon rich or zone characterized by toc 4 located between 2393 m and 2406 5 m core depth in the studied marcellus shale core was coincident with tectonically active and magmatic quiescent period of the acadian orogeny ca 395 380 ma this time period also corresponds to the highest rate of mountain building in the acadian orogeny the light rare earth lree and selected trace elemental e g ta cs composition of the or zone sediments is similar to that of the bulk continental crust supporting the lack of magmatic activity in the source area i e acadian orogeny in contrast subsequent deposition of the organic carbon poor op sediments characterized by toc

the absolute age of the eifelian tioga ash bed pennsylvania the tioga ash bed bed b of the zeigler pit union county pennsylvania lies in the polygnathus costatus costatus zone of the eifelian stage of the middle devonian series the 27 5 cm thick bed contains igneous zircon and monazite crystals that have been dated by precise u pb techniques zircons are characterized by inherited pb that occurs as barely perceptible interior regions enriched in inclusions the zircons are discordant and do not reveal the igneous age of the bed in contrast high quality monazite crystals lack any evidence of inheritance or loss of pb and multiple analyses have overlapping 207 pb 235 u ages of 390 0 pm 0 5 ma the monazite analyses are concordant or very slightly reversely discordant the consistency of the monazite data provides a new precise estimate of age for the lower eifelian

organic rich marcellus shale lithofacies modeling and distribution pattern analysis in the appalachian basin the marcellus shale is considered to be the largest unconventional shale gas resource in the united states two critical factors for unconventional shale reservoirs are the response of a unit to hydraulic fracture stimulation and gas content the fracture attributes reflect the geomechanical properties of the rocks which are partly related to rock mineralogy the natural gas content of a shale reservoir rock is strongly linked to organic matter content measured by total organic carbon toc a mudstone lithofacies is a vertically and laterally continuous zone with similar mineral composition rock geomechanical properties and toc content core log and seismic data were used to build a three dimensional 3 d mudrock lithofacies model from core to wells and finally to regional scale an artificial neural network was used for lithofacies prediction eight petrophysical parameters derived from conventional logs were determined as critical inputs advanced logs such as pulsed neutron spectroscopy with log determined mineral composition and toc data were used to improve and confirm the quantitative relationship between conventional logs and lithofacies sequential indicator simulation performed well for 3 d modeling of marcellus shale lithofacies the interplay of dilution by terrigenous detritus organic matter productivity and organic matter preservation and decomposition affected the distribution of marcellus shale lithofacies distribution which may be attributed to water depth and the distance to shoreline the trend of normalized average gas production rate from horizontal wells supported our approach to modeling marcellus shale lithofacies the proposed 3 d modeling approach may be helpful for optimizing the design of horizontal well trajectories and hydraulic fracture stimulation strategies

organic matter accumulation of the lacustrine lunpola oil shale central tibetan plateau controlled by the paleoclimate provenance and drainage system abstract the cenozoic lacustrine lunpola oil shale located in the central tibetan plateau has received little research interest in its depositional history although it is estimated to be a huge resource reserve this study investigates the palaeoclimate provenance and regional drainage system of the ancient lakes using a combined analysis of element geochemistry and stratigraphy to elucidate the depositional history of the lunpola oil shale most of the samples in the lower part of the section have chemical index of alteration cia values between 65 and 75 reflecting a moderate weathered source while samples in the upper part the section have cia values between 60 and 65 which indicate relatively weak chemical weathering in the source area this stratigraphic grouping suggests a paleoclimate transition from a relatively warm or humid period to a cold or dry period the zr sc and th sc ratios of the samples reveal that sorting and recycling were minor during deposition of the oil shale the geochemical results al2o3 cao na2o k2o a cn k diagrams high contents of th plots of co th la sc and cr th sc th demonstrate that the sedimentary sources were felsic rocks plots of la th sc th sc zr 10 th co zr 10 and ti zr versus la sc illustrate that the source rocks were from continental arc and active continental margin the baingoin batholiths to the south of the lunpola basin consisting mainly of cretaceous granodiorite and adamellite are likely responsible for supplying materials to the lunpola oil shale similar special ree patterns further suggest the affiliation of the oil shale with the batholiths provenance analyses indicate a main river from the south moreover stratigraphic study confirms an upstream ancient baingoin lake between the source area and the ancient lunpola lake in this drainage system paleoclimate clearly restricted the development of rivers around the lakes although terrestrial organic matter higher plants dominated the drainage area the main river originating from the south could only bring a certain amount of them to the lakes moreover considering the filtration of the upstream ancient baingoin lake minor terrestrial organic matter could be carried and deposited in the ancient lunpola lake therefore lacustrine algae could proliferate as the main organic source and preserve in the stratified hypersaline lake to form the largest oil shale resource in tibet

far field effects of appalachian orogenesis a view from the craton the sedimentary cover of the north american craton preserved little evidence of the paleozoic tectonic events that shaped the appalachian orogen on its eastern side a notable exception is the nnw trending hudson bay central high which corresponds to a normal fault array extending for a minimum length of 500 km a working hypothesis is proposed in which stresses applied to the continental margin during the silurian earliest devonian salinian orogeny were transmitted over a distance of 1400 km in the continental interior where they induced the normal fault reactivation of older structural discontinuities the shutdown of tectonic activity along the hudson bay central high during the latest early devonian to earliest middle devonian is interpreted as resulting from a change in the direction of plate convergence during the acadian orogeny

misuse of the term bentonite for ash beds of devonian age in the appalachian basin ash beds of devonian age in the appalachian basin have been incorrectly called bentonites the emphasis placed on the volcanic origin of the beds rather than on their mineralogical and physical characteristics apparently led to the erroneous application of the term bentonite recent study indicates that the lack of smectite in the tioga belpre and center hill bentonite beds compared with the type bentonite warrants the deletion of the term bentonite and the substitution of the term ash it is recommended that the ash beds of devonian age be referred to as the tioga ash bed the belpre ash bed and the center hill ash bed

geochemical and multi isotopic 87sr 86sr 143nd 144nd 238u 235u perspectives of sediment sources depositional conditions and diagenesis of the marcellus shale appalachian basin usa abstract we investigate sediment sources depositional conditions and diagenetic processes affecting the middle devonian marcellus shale in the appalachian basin eastern usa a major target of natural gas exploration multiple proxies including trace metal contents rare earth elements ree the sm nd and rb sr isotope systems and u isotopes were applied to whole rock digestions and sequentially extracted fractions of the marcellus shale and adjacent units from two locations in the appalachian basin the narrow range of end values from 7 8 to 6 4 at 390 ma is consistent with derivation of the clastic sedimentary component of the marcellus shale from a well mixed source of fluvial and eolian material of the grenville orogenic belt and indicate minimal post depositional alteration of the sm nd system while silicate minerals host 80 of the ree in the shale data from sequentially extracted fractions reflect post depositional modifications at the mineralogical scale which is not observed in whole rock ree patterns limestone units thought to have formed under open ocean oxic conditions have 238u values and ree patterns consistent with modern seawater the 238u values in whole rock shale and authigenic phases are greater than those of modern seawater and the upper crust the 238u values of reduced phases the oxidizable fraction consisting of organics and sulfide minerals are 0 6 greater than that of modern seawater bulk shale and carbonate cement extracted from the shale have similar 238u values and are greater than 238u values of adjacent limestone units we suggest these trends are due to the accumulation of chemically and more likely biologically reduced u from anoxic to euxinic bottom water as well as the influence of diagenetic reactions between pore fluids and surrounding sediment and organic matter during diagenesis and catagenesis

modeling the carbon and sulfur isotope compositions of marine sediments climate evolution during the devonian abstract a model of global biogeochemical cycles coupled to an energy balance climatic model modified after the combine model godderis y joachimski m m 2004 global change in the late devonian modeling the frasnian famennian short term carbon isotope excursions palaeogeogr palaeoclimatol palaeoecol 202 309 329 is used to calculate the short term evolution of atmospheric p co 2 during the devonian the geochemical cycles for carbon alkalinity phosphorus sulfur and oxygen are included in this model with also 13 c and 34 s cycles high resolution records of 13 c of marine carbonates and 34 s of marine sulfates are used as forcing parameters of the geochemical cycles in an inverse modeling atmospheric p co 2 and p o 2 at the end of the silurian are calculated to have been 3000 ppmv and 0 165 bar 0 75 pal respectively a long term decrease in p co 2 is modeled for almost the entire devonian short term lowering of p co 2 to concentrations around 2000 ppmv is calculated for the silurian devonian transition and the pragian contents around 900 ppmv are modeled for the eifelian givetian givetian frasnian and frasnian famennian boundaries as a consequence of enhanced organic carbon burial during deposition of lochkovian eifelian and frasnian grey and black shales organic carbon burial is enhanced by the increase of phosphorus delivery to the ocean triggered by short term sea level falls the corresponding short term global climatic cooling at the silurian devonian boundary at the end of the pragian and the givetian frasnian as well as frasnian famennian boundaries reached 2 c at the equator the rapid colonization of continental surface by land plants during the middle and late devonian increasing chemical alteration of the continents and co 2 consumption by silicate weathering is assumed to have caused cooling of surface seawater as suggested by the 18 o values of biogenic apatites

the hillslope storage boussinesq model for non constant bedrock slope in this study the recently introduced hillslope storage boussinesq hsb model is cast in a generalized formulation enabling the model to handle non constant bedrock slopes i e bedrock profile curvature this generalization extends the analysis of hydrological behavior to hillslopes of arbitrary geometrical shape including hillslopes having curved profile shapes the generalized hsb model performance for a free drainage scenario is evaluated by comparison to a full three dimensional richards equation re based model the model results are presented in the form of dimensionless storage profiles and dimensionless outflow hydrographs in addition comparison of both models to a storage based kinematic wave kw model enables us to assess the relative importance of diffusion processes for different hillslope shapes and to analyze the influence of profile curvature on storage and flow patterns specifically the comparison setup consists of a set of nine gentle 5 bedrock slope and nine steep 30 bedrock slope hillslopes of varying plan shape and profile curvature interpretation of the results shows that for highly conductive soils the simulated storage profiles and outflow hydrographs of the generalized hsb model and re model match remarkably for 5 bedrock slope and for all plan and profile curvatures the match is slightly poorer on average for 30 bedrock slope in particular on divergently shaped hillslopes in the assessment of the influence of hydraulic diffusion we find good agreement in simulation results for the kw model compared to results from the generalized hsb model and the re model for steep divergent and uniform hillslopes due to a relatively low ratio between water table gradient and bedrock slope compared to convergent or gentle hillslopes overall we demonstrate that in addition to bedrock slope hillslope shape as represented by plan and profile curvature is an important control on subsurface flow response

thickness trends and sequence stratigraphy of the middle devonian marcellus formation appalachian basin implications for acadian foreland basin evolution analysis of more than 900 wireline logs indicates that the middle devonian marcellus formation encompasses two third order transgressive regressive t r sequences mss1 and mss2 in ascending order compositional elements of the marcellus formation crucial to the successful development of this emerging shale gas play including quartz clay carbonate pyrite and organic carbon vary predictably within the proposed sequence stratigraphic framework thickness trends of marcellus t r sequences and lithostratigraphic units reflect the interplay of acadian thrust load induced subsidence short term base level fluctuations and recurrent basement structures rapid thickening of both t r sequences especially mss2 toward the northeastern region of the basin preserves a record of greater accommodation space and proximity to clastic sources early in the acadian orogeny however local variations in t r sequence thickness in the western more distal area of the basin may reflect the reactivation of inherited eocambrian basement structures including the rome trough and northwest striking cross structural discontinuities induced by acadian plate convergence episodes of block displacement locally warped the basin into northeast southwest trending regions of starved sedimentation and or erosion adjacent to depocenters in which regressive systems tract deposits were ponded block movement appears to have initiated in late early devonian time resulting first in thinning and local erosion of the oriskany sandstone in northwest pennsylvania this study in addition to providing the basis for a predictive sequence stratigraphic model that can be used to further marcellus exploration tells of a foreland basin more tectonically complex than accounted for by simple flexural models

a two state integral balance model for soil moisture and groundwater dynamics in complex terrain a dynamical model is devised for a hydrologic system where unsaturated and saturated storage serve as the principal control on rainfall runoff and where complex topography drainage area and variable depth of moisture penetration describe the flow geometry the model is formed by direct integration of the local conservation equation with respect to the partial volumes occupied by unsaturated and saturated moisture storage respectively this yields an integral balance model in just two state variables the relationship of the dynamical model to field data in complex terrain is found through a joint probability density for terrain features this serves as a volume weighting function to construct conditional averages for the state variables and fluxes over a specified range of terrain features the scale of averaging could range from hillslopes to river basins two examples of the joint probability of terrain features altitude and aspect are demonstrated for valley ridge and appalachian plateau digital elevation models the strategy of a dynamical model formed by conditional averages of state variables with respect to terrain features is proposed as a way of simplifying the dynamics while preserving the natural spatial and temporal scales contributing to runoff response the parametric form of the storage flux or constitutive relationships for the proposed model is determined from numerical experiments in a simple hillslope flow geometry the results show that a competitive relation exists between unsaturated and saturated storage except for the lowest precipitation rates saturation overland flow is proposed to be a storage feedback relation solutions to the integral balance model are presented in terms of the phase portrait which represents all possible solution trajectories in state space the timing and magnitude of peaks in the runoff hydrograph from pulse type input events demonstrate quick flow from near stream saturated storage saturation overland flow including rejected rainfall storage feedback and late time infiltration from upslope subsurface flow

temporal changes in nd isotopic composition of sedimentary rocks in the sevier and taconic foreland basins increasing influence of juvenile sources initial 143 nd 144 nd ratios of clastic sedimentary rocks in the ordovician taconic and sevier foreland basins increase with decreasing stratigraphic age this shift in isotopic composition reflects an increased influx of juvenile sediment to both basins for the taconic basin geologic and isotopic data are consistent with the juvenile sediment being derivedfromupliftedgrenvillecrust upthrustaspartofthetaconicallochthons sediment derivedfromthebronsonhillarc oracombinationofboth forthesevierforelandbasin there are few geologic constraints on source regions but the similar shift in isotopic ratios with time suggests a similar increase in the influence of juvenile sources such as exotic terranes sevier basin sedimentary rocks have higher nd values than those within the taconic basin thus juvenile source areas were of greater importance to sevier basin sediments

the midcontinent rift system one of the most prominent features on gravity and aeromagnetic maps of the united states is a series of major generally linear anomalies that extend from central kansas to lake superior and then turn southward into central michigan figures 1 2 this system of anomalies clearly reflects major geological features and as such it must represent a very significant episode in the history of the north american continental lithosphere the geologic features associated with these anomalies particularly axial basins filled with basalt and immature clastic rocks along with evidence of crustal extension indicate that the episode was probably one of incipient rifting