chemical weathering indices applied to weathering profiles developed on heterogeneous felsic metamorphic parent rocks abstract chemical weathering indices are commonly used for characterizing weathering profiles by incorporating bulk major element oxide chemistry into a single metric for each sample generally on homogeneous parent rocks weathering indices change systematically with depth however the weathering of heterogeneous metamorphic rocks confounds the relationship between weathering index and depth in this paper we evaluate previously defined chemical weathering indices for their suitability in characterizing weathering profiles developed on felsic heterogeneous metasedimentary bedrock from coweeta hydrologic laboratory north carolina usa among the weathering indices evaluated here the weathering index of parker wip is the most appropriate for application to weathering profiles on heterogeneous and homogeneous parent rock because the wip includes only the highly mobile alkali and alkaline earth elements in its formulation it yields values that differ greatly from those of the parent rock in addition the wip allows for aluminum mobility unlike other weathering indices these characteristics combine to make the weathering index of parker the most applicable index for studying the weathering of heterogeneous metasedimentary rocks however the wip should be applied judiciously as alkali and alkaline earth metals may be readily depleted during weathering in addition to reflecting weathering the chemical index of alteration cia chemical index of weathering ciw plagioclase index of alteration pia and vogt s residual index v may be sensitive to subtle geochemical changes such as hydrothermal alteration along a fault and or alteration at the water table weathering indices that include iron in their calculations were not included in this study because they do not distinguish between ferric and ferrous iron the oxidation state and distribution of iron in a weathering profile is influenced by the proportion of oxidation states in the pre weathered metamorphic rock and interaction with groundwater during weathering

the influence of an asymmetry in the sequence rock coal rock on the propagation of rayleigh seam waves small offsets in hard coal seams can be detected with the aid of seam channel waves transmission and reflection of seam waves depend among other parameters upon the symmetry properties of the sequence rock coal rock two typical unsymmetrical sequences are found in european coal deposits i coal seams with roof and floor of differing acoustic impedance and ii coal seams interlayered with rock and soil two dimensional analog models with appropriate impedance contrasts are used to study the effect of the unsymmetrical layers upon the propagation of rayleigh seam waves data analysis is based upon amplitude measurements both parallel and perpendicular to the layers and dispersion curves the effect of unsymmetrical roof rock 1 and floor rock 2 was studied with models containing homogeneous coal seams leaky mode wave groups with phase velocities cr in the range between the sv wave velocities r1 2 of the two rock materials i e r1 cr r2 form a characteristic part of the rayleigh seam wave signal using knott s energy coefficient calculations it is shown that in that range energy leakage into the surrounding rock by refracted sv waves is restricted to only one of the two interfaces namely coal rock 2 at the other interface coal rock 1 all waves are totally reflected thus the high amplitudes of these leaky mode wave groups are explained by quasi normal mode features the influence of a dirt bed on wave propagation was studied in models where the roof and the floor have the same elastic properties the maximum thickness of the dirt bed did not exceed 20 of the total seam thickness the effect of the bed s location within the seam was also investigated for all recorded normal mode wave groups either the total seam or the coal layers could be regarded as wave guides this was shown by the fact that the phases could be associated with the phase velocity dispersion curves calculated for the symmetrical sequence rock coal rock these curves are relevant under the condition that the thickness of the coal layer assumed under the calculation coincides with the thickness of the effective wave guide of the respective wave groups wave groups guided in the total seam are not influenced by either the thickness or the position of the dirt bed on the other hand for wave groups guided in the coal layers the quotient of signal amplitudes in the coal layers is influenced by the position of the dirt bed

depositional systems composition and geochemistry of triassic rifted continental margin redbeds of the internal rif chain morocco the middle to upper triassic redbeds at the base of the ghomaride and internal dorsale calcaire nappes in the rifian sector of the maghrebian chain have been studied for their sedimentological petrographic mineralogical and chemical features redbeds lie unconformably on a variscan low grade metamorphic basement in a 300 m thick upward fining and thinning megasequence successions are composed of predominantly fluvial red sandstones with many intercalations of quartzose conglomerates in the lower part that pass upwards into fine grained micaceous siltstones and massive mudstones with some carbonate and evaporite beds this suite of sediments suggests that palaeoenvironments evolved from mostly arenaceous alluvial systems middle triassic to muddy flood and coastal plain deposits the successions are characterized by local carbonate and evaporite episodes in the late triassic the growth of carbonate platforms is related to the increasing subsidence norian rhaetian during the break up of pangea and the earliest stages of the western tethys opening carbonate platforms became widespread in the sinemurian sandstones are quartzose to quartzolithic in composition testifying a recycled orogenic provenance from low grade palaeozoic metasedimentary rocks palaeoweathering indices chemical index of alteration chemical index of weathering and plagioclase index of alteration suggest both a k enrichment during the burial history and a source area that experienced intense weathering and recycling processes these processes were favoured by seasonal climatic alternations characterized by hot episodically humid conditions with a prolonged dry season these climatic alternations produced illitization of silicate minerals iron oxidation and quartz rich red sediments in alluvial systems the estimated burial temperature for the continental redbeds is in the range of 100 to 160 c with lithostatic tectonic loading of ca 4 to 6 km these redbeds can be considered as regional petrofacies that mark the onset of the continental rift valley stage in the western pangea middle triassic before the opening of the western part of tethys in the middle jurassic the studied redbeds and the coeval redbeds of many alpine successions betic tellian and apenninic orogens show a quite similar history they identify a mesomediterranean continental block originating from the break up of pangea which then played an important role in the post triassic evolution of the western mediterranean region

chemistry of modern soils as a guide to interpreting precambrian paleosols precambrian paleosols are potentially one of our best sources of information about the composition of the atmosphere early in earth s history to be used this way however an alteration profile must be shown to be an in situ product of vadose processes data from modern soils show that the ratios of less mobile elements such as zr ti and al can be used as a preliminary screen to test for the in situ nature of a profile if the ti zr ratio departs from that of the host rock by more than 40 or the ti al ratio departs by more than 50 for moderate degrees of weathering then a significant allochthonous contribution to the profile is indicated this technique correctly separates in place from allochthonous horizons when applied to independent data from two modern profiles a review of published precambrian profiles identifies two often cited examples denison and pronto as suspect based on these criteria in the interpretation of paleoatmospheres it is also necessary to show that fe is controlled not b

modelling guided waves in cross hole surveys in uncracked and cracked rock1 the theoretical behaviour of guided waves in cross hole seismic surveys is examined with dispersion curves and synthetic seismograms the modelling suggests and field observations confirm that the dominant energy in many cross hole seismic surveys propagates as guided waves as well as body waves with the energy tied to an interface or combination of interfaces whenever there are interfaces with significant velocity contrasts continuous between the wells the dispersion and waveforms of such modal solutions carry detailed information about the internal structure particularly the stress aligned structure of fluid filled inclusions in the immediate neighbourhood of the waveguide since the information content can be controlled to some extent by the choice of frequency and source type and the level of source and receiver in the two wells such guided waves in cross hole surveys may be important for monitoring changes in nearly horizontal reservoirs during hydrocarbon production processes initially we investigate the basic properties of propagation in isotropic strata and then examine the behaviour of guided waves in the stress aligned fluid filled inclusions

geological and industrial implications of extensive dilatancy anisotropy extensive dilatancy anisotropy is the hypothesized distribution of stress aligned fluid filled microcracks pervading most rocks in the earth s crust the geometry of the cracks and the aligning stress field can be monitored by analysing the waveforms of shear waves propagating through the rockmass the ability to estimate some of the parameters of the crack and stress geometry by analysing shear wave particle displacements has widespread implications

high resolution clay mineral and major elemental characterization of a permian triassic terrestrial succession in southwestern china diagenetic and paleoclimatic paleoenvironmental significance abstract relatively high resolution clay mineralogical and chemical index of alteration cia analyses were conducted on the terrestrial lubei section in southwestern china to gain a better understanding of the paleoclimatic paleoenvironmental evolution on land during the permian triassic transition p tr transition clay mineral species include illite smectite mixed layers i s illite irregular chlorite expandable mixed layers c e chlorite kaolinite vermiculite hydroxyl interlayered mineral him and corrensite cia values are as high as approaching 100 in the permian and show a gradual and subtle decrease towards the lowermost triassic where a sudden decrease to persistently

lagrangian sediment motion in a crescentic nearshore bar under storm induced waves and currents a fluorescent tracer experiment in conjunction with morphological and sedimentological data demonstrates the lagrangian sediment flux induced by storm waves and currents in a permanently submerged outer crescentic nearshore bar system the steady state bar form height 2 6 m wavelength 390 m is maintained in the presence of landward sediment advection under asymmetric oscillatory flow during storm buildup and decay and seaward advection under rip cell flows at the peak of the storm the seaward displacement of the bar crest in the areas of the convex seaward crescent reflects transport associated with the rip current which though variable in its location through time is never located over the landward projecting horns the storm studied had a recurrence interval of approximately 1 month and reworked upwards of 16 of the bar sediments the sediment flux indentified is therefore associated with an event of frequent occurrence and is most likely the control on both bar form and dynamics of the b

provenance paleo weathering and redox signatures of estuarine sediments from ghana gulf of guinea abstract this paper discriminates the source of sediment supply provenance degree of chemical weathering and redox conditions of holocene sediments cored from the ankobra and pra estuaries of ghana in the gulf of guinea using their geochemical characteristics considerable stratigraphical variations were observed in major element compositions in the sediments from both the ankobra al2o3 5 3 14 2 sio2 75 9 88 2 cao 0 3 1 2 k2o 0 5 1 2 and the pra al2o3 7 8 16 9 sio2 72 8 86 5 cao 0 3 0 4 k2o 0 7 1 2 estuaries elemental compositions were similar in both estuaries depicting similarities in their source rock characteristics some of the major and trace elements correlated significantly r2 0 8 with al2o3 in the pra estuary confirming their possible hydraulic fractionation geochemical classification showed the sediments from both estuaries were predominantly composed of sub arkoses with only a few litharenites the chemical index of alteration cia chemical index of weathering ciw plagioclase index of alteration pia the index of compositional variability icv the sio2 al2o3 ratios and sio2 vs al2o3 k2o nao suggest high degrees of chemical weathering coinciding with warm climatic conditions in the source regions as well as sub matured to mature estuarine sediments deposited under semi arid to semi humid conditions the sediment geochemistry and discrimination diagrams denote similar continental signature derivatives of the sediments from both estuaries both sediments are likely derived from intermediate to felsic granitoid source rocks as well as from a quartzose sedimentary provenance formed in a passive continental margin the ni co and v cr ratios depict sediment deposition under oxic conditions through time in both estuaries

abrupt chemical weathering increase across the permian triassic boundary previous studies have suggested a variety of causes for the end permian extinction event including a bolide impact flood basalt volcanism methane clathrate dissociation or some combination of catastrophic processes one common feature of these hypotheses is the prediction of an enhanced earliest triassic greenhouse new high resolution geochemical results from graphite peak antarctica support an abrupt increase in chemical weathering in the earliest triassic among otherwise genetically similar paleosols of similar provenance relative to the latest permian paleosols the earliest triassic paleosol exhibits greater leaching greater accumulation of immobile rees and evidence of lower soil po2 with no evidence of an erosional unconformity between the paleosols which are separated by 15 cm stratigraphically these results support a rapid shift perhaps 10 000 years to an earliest triassic greenhouse and a role for methane release in the extinction event and its aftermath

do red beds indicate paleoclimatic conditions a permian case study abstract terrestrial red beds have long been interpreted as desert deposits by comparison with modern red deserts more recently red beds have been interpreted as evidence of seasonally dry conditions and a permo triassic pangean monsoon red beds of cala viola sardinia are identified as paleosols and used to reconstruct late permian paleoclimatic conditions reconstruction of paleoenvironmental conditions based on the paleosols of the cala viola indicates warm humid conditions with no evidence of dry conditions as in a desert or of extreme seasonality as in a monsoon instead it is suggested that the red color of the paleosols is a result of former good drainage and that red color in general does not indicate specific paleoclimatic conditions

earthquake prediction a new physical basis summary subcritical crack growth in the laboratory occurs slowly but progressively in solids subjected to low stresses at low strain rates the cracks tend to grow parallel to the maximum compressive stress so that when this stress is aligned over a large enough region the cracks will also be aligned and possess effective seismic anisotropy it is suggested that such subcritical crack growth produces extensive dilatancy anisotropy eda throughout earthquake preparation zones this process is a possible driving mechanism for earthquake precursors observed at substantial distances from impending focal zones and provides in the shear wave splitting which has been observed in several seismic regions a possible technique for monitoring the build up of stress before earthquakes

guided wave propagation between boreholes testing for the continuity of permeability barriers between wells in oil and gas fields is important for estimating reserves and planning production procedures in thinly layered sedimentary reservoirs conventional seismic techniques such as reflection profiles vsps and crosshole tomography may not be wholly successful in determining continuity in this paper we suggest that seismic guided waves propagating parallel to the layering may be important for testing continuity between wells

chemical weathering of crystalline rocks in contrasting climatic conditions using geochemical proxies an overview abstract weathering profiles of granitoid rocks from the sila massif southern italy have been studied to characterize weathering processes that affect this area chemical weathering indices of the sila massif weathered granitoids were compared to those of different areas of the world characterized by different climates malaysia puerto rico georgia china nigeria colorado switzerland and sweden to decipher their weathering characteristics the geochemical indices show values of cia chemical index of alteration ranging from 55 to 97 ciw chemical index of weathering ranging from 60 to 100 pia plagioclase index of alteration ranging from 55 to 100 wip weathering index of parker ranging from 7 to 64 and rr ruxton ratio ranging from 2 14 to 3 96 all these geochemical proxies closely resemble each other and show variations mainly related to the different climatic and tectonic settings malaysia and puerto rico granitoids showing high cia values respectively 97 and 95 on average underwent very intensive chemical weathering alteration georgia china and nigeria showing medium high cia values respectively 86 90 and 92 on average underwent moderate intensive chemical weathering alteration southern italy and colorado granitoids showing medium low cia values 68 on average underwent moderate weak chemical weathering alteration whereas switzerland and sweden granitoids showing low cia values respectively 58 and 55 on average underwent weak chemical weathering alteration those values are mainly related to the climatic conditions in term of temperature and precipitation of each area cia vs climate histograms display a shift towards higher cia values with increasing of warm humidity tropical conditions whereas granitoids weathered under conditions inferred to be cold arid polar climate show lower cia values

pedogenesis and geochemical alteration of the picture gorge subgroup columbia river basalt oregon reddened clay rich horizons between basalt flows have historically been identified as baked zones or as zones of lateral groundwater movement the reddening has been attributed to thermal or chemical alteration of the permeable portion of the basalt flow many of these red horizons are instead paleosols that record significant hiatuses in basalt flow emplacement paleosols were identified in the field on the basis of features such as horizonation ped morphology and root traces terrestrial gastropods fossil plants and peats also occur locally plots of weathering indices such as base loss are consistent with a pedogenic origin for these horizons ca na mg fe 21 and p have been extensively lost from the a and bt horizons of the paleosols consistent with modern weathering patterns k and rb have been added to the upper portions of the profiles and lost in the lower portions of the profiles relative to the parent material with rb added disproportionately historically this pattern of enrichment has been cited as evidence of k metasomatism the apparent metasomatism can be explained using a new model in which there was extensive felsic volcanism contemporaneous with pedogenesis and k and rb were likely added by windborne ash the apparent discordance between k and rb contents of the paleosols can be explained by the presence of land plants because k is an important electrolyte and rb does not serve any major biological role this model could account for apparent k metasomatism in other paleosols following the advent of land plants and may be applicable to older paleosols as well

provenance and tectonic setting of the proterozoic turbidites in hunan south china geochemical evidence the geochemical composition of the middle upper proterozoic turbidites in hunan south china is related to provenance and tectonic setting of the sedimentary basin the turbidites are characterized by moderate sio 2 contents al 2 o 3 sio 2 typically 0 1 0 3 and moderate k 2 o na 2 o ratios generally 0 1 0 3 but relatively high fe 2 o 3 mgo contents 5 10 wt and unusually low contents of cao typically 1 wt abundances of ferromagnesian trace elements and incompatible elements are moderate the ree patterns are uniform and similar to the upper continental crust and typical post archean shales with lree enrichment flat hree and significant negative eu anomalies in general the slates show higher contents of fe 2 o 3 mgo and ferromagnesian trace elements and lower ratios of la sc and th sc than the associated graywackes suggesting that more mafic materials were incorporated into the clay size fraction compared to the upper proterozoic banxi group the middle proterozoic lengjiaxi group has higher concentrations for most ferromagnesian trace elements and lower la sc ratios implying more mafic components in the provenance of the latter the relationship among alkali and alkaline earth elements the chemical index of alteration cia and the th u ratios indicate that the source area was affected by a moderate weathering history the main source was old continental crust the yangtze craton dominated by felsic rocks of magmatic origin with a variable admixture of mafic components from continental island arcs e g the fangjingshan dayong and the sibao yiyang island arc chains the flysch deposition took place in a back arc basin rather than a failed intracontinental rift as proposed by some workers we suggest that suturing between the yangtze and cathaysia blocks did not occur until late proterozoic time and that the final assembly of the supercontinent rodinia in south china was probably marked by the jingning orogeny at 0 8 ga

the applicability of the chemical index of alteration as a paleoclimatic indicator an example from the permian of the parana basin brazil abstract the chemical index of alteration cia was expressed as cia molar to become a more sensitive measure of the degree of chemical weathering the cia molar has the value of 1 for fresh feldspars and for unweathered non peraluminous igneous rocks but increases towards infinity as chemical weathering progresses the utility of this index as a humidity indicator for both modern and ancient muds was tested a database comprising 281 entries with chemical data for modern and ancient sediments deposited under arid semi arid semi humid and humid climate was assembled from the literature and used to calibrate the relationship between humidity and cia molar values for both modern and ancient sediments the histograms display a shift towards higher values with increasing geological indicators of humidity whereas sediments deposited under conditions inferred to be arid from other geological indicators show values tightly clustered around 1 the permian of the parana basin was then used as an example of the applicability of the cia molar for paleoclimatic studies major element analyses al2o3 k2o na2o cao were performed on 55 claystones and shales from three drill cores in a stratigraphic succession spanning the early to late permian the cia molar for these rocks accorded with expectations based on sedimentologic and paleontologic evidence discriminating well between arid and humid conditions in the basin independently determined from sedimentological and paleontological indicators the use of the cia molar as a paleo humidity indicator however can be limited by the presence of carbonate rich sediments the occurrence of post depositional k addition metasomatism metamorphism diagenetic illitization as well as by inheritance of clays from sedimentary rocks in the source area nevertheless with appropriate caution the cia molar is a useful tool for the assessment of the humidity conditions in the rock record

fracture detection using crosshole surveys and reverse vertical seismic profiles at the conoco borehole test facility oklahoma summary shear waves in combined crosshole surveys chss and reverse vertical seismic profiles rvsps at the conoco borehole test facility oklahoma are analysed to examine the relationship between shear wave propagation and natural fracture systems the surveys cover a range of azimuths and angles of incidence and give the possibility of studying fracture induced azimuthal anisotropy in some detail the data display several features characteristic of seismic anisotropy shear wave splitting displaying substantial time delays up to 7 ms for source geophone distances of less than 50 m suggest large fracture densities estimates of fast shear wave polarizations and time delays confirm the n75de 10d fracture strike deduced from other geological and hydrological observations analyses of chs data including modelling with synthetic seismograms suggest that at least the dominant fracture set is rotated by 20d from the vertical one of the most important results of this study is the positive identification of guided waves propagating between wells along interfaces with sufficient velocity constrast in chs profiles it appears that combinations of chss and rvsps offer unique possibilities in evaluating fracture parameters at shallow depths this could be important for the study of fluid flow at shallow depths in hydrological investigations

modelling channel waves with synthetic seismograms in an anisotropic in seam seismic survey1 in seam seismic surveys with channel waves have been widely used in the united kingdom and elsewhere to map coal seams and to detect anomalous features such as dirt bands seam thinning and thickening and particularly in seam faulting although the presence of cleat induced anisotropy has been recognized in the past almost all previous analyses have assumed homogeneous isotropic or transversely isotropic coal seams channel waves however exhibit properties which cannot be fully explained without introducing anisotropy into the coal seam in this paper the authors model the observed in seam seismic channel waves with synthetic seismograms to gain an understanding of the effects of cleat induced anisotropy on the behavior of channel waves the results show a reasonable good match with the observations in traveltime relative amplitudes dispersion characteristics and particle motions the authors demonstrate that anisotropy in the surrounding country rocks contributes significantly to the coupling of channel wave particle motion although its effect is not as strong as the anisotropy in the coal seam the authors conclude that the effects of cleat and stress induced anisotropy are observed and can be modelled with synthetic seismograms and that anisotropy must be taken into account for the detailed interpretation of channel waves

greenhouse crises of the past 300 million years proxies of past co 2 and climate over the past 300 m y now reveal multiple global climate change events in unprecedented detail evidence for past co 2 spikes comes from expanded and refined data on stomatal index of fossil ginkgo and related leaves new evidence for synchronous climatic change comes from paleosols in montana utah and neighboring states each co 2 spike was coeval with unusually clayey red and decalcified paleosols which can be traced throughout the colorado plateau spikes in atmospheric co 2 also were coeval with increases in paleosol alkali depletion as an indication of high temperature and spikes in paleosol base depletion and depth to calcic horizons as indications of high precipitation in the colorado plateau times of warmer climate were also more humid perhaps due to greater moisture potential of warmer air seasonality of climate did not increase during warm wet spikes the mesozoic greenhouse was not persistently hot with cool spells but warm with hot flashes these data furnish power laws predicting the sensitivity and magnitude of change in mean annual temperature mat and mean annual precipitation map due to rising co 2 in a mid latitude mid continental region the magnitude of the coming anthropogenic greenhouse pales in comparison with past greenhouse spikes at times of global mass extinctions

suggestions for a consistent terminology for seismic anisotropy seismic anisotropy is an unfamiliar concept to many geophysicists and the use of misleading and ambiguous terminology has made it more difficult to understand i suggest here a consistent terminology in which simple expressions have specific meanings similar to their colloquial meanings it is hoped that use of such language will help to make the increasing number of papers reporting seismic anisotropy more readily comprehensible to the non specialist this not a manual of anisotropy and it is not intended for theoreticians it is a list of terms which may make anisotropy a little easier to understand for those more familiar with wave propagation in isotropic solids

effects of the internal shear wave window comparison with anisotropy induced splitting in the absence of anisotropy the observed polarizations of shear waves should be those radiated from the source modified only by interaction with internal interfaces and free surface topography it has been suggested that shear wave polarizations may be systematically distorted by internal interfaces which could lead to difficulties in interpreting anisotropy induced shear wave splitting since the literature now reports many investigations of shear wave splitting possible complications caused by internal interfaces would be important and need to be assessed in this paper we investigate the polarization of shear waves in full wave synthetic seismograms incident from a point source at an isotropic to isotropic interface over a range of angles of incidence particle motion due to plane and curved wave fronts has different characteristics internal shear wave windows can be defined analogous to the shear wave window at the free surface within the innermost window the polarizations at subsurface geophones as in vertical seismic profiles are recorded with little distortion but outside this window the waveforms become increasingly distorted for larger angles of incidence this is similar to the behavior of shear waves with respect to the shear wave window at the free surface except that the behavior at internal interfaces is more complicated because of additional critical angles and additional windows we conclude that the interaction of shear waves with internal interfaces is only a serious difficulty when interpretating wide offset vertical seismic profiles wide angle reflections and cross hole data

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

characterisation and palaeoclimate of a loess like permafrost palaeosol sequence in ne siberia abstract we studied a 15 m high loess like permafrost palaeosol sequence the tumara palaeosol sequence tps which developed on a middle pleistocene fluvio glacial terrace of the tumara river various analytical methods were applied to characterise the tps similar to typical loess palaeosol sequences e g in china europe etc pedogenetic clay formation mineral weathering and smaller grain sizes are interpreted as representing warmer and more favourable climatic conditions interglacials or interstadials soil organic matter som however reveals an unfamiliar inverse pattern high organic carbon contents c org 1 characterise the dark grey glacial palaeosols whereas lower contents c org 0 5 are found in the brown interglacial stadial palaeosols this can be explained with permafrost and water logging having inhibited som mineralisation during cold periods d l ratios of aspartic acid and lysine proved to be useful proxies for both som aging and palaeotemperature with amino acid racemization being enhanced in interglacial stadial palaeosols on the basis of the geochemical and grain size results further palaeoclimatically relevant proxies describing the palaoewind strength u ratio the mineral weathering chemical index of alteration rb k and the changing mineral input signal ba ti zr ti al were applied to the tps in combination with numeric dating results radiocarbon and luminescence and in the context of other northern hemispheric records the simple warm cold stratigraphy as derived from the palaeoenvironment climate proxies suggests that the tps represents the last 240 000 years

patterns of late palaeozoic deglaciation in the parana basin brazil abstract the itarare subgroup middle carboniferous early permian of the parana basin of southeastern brazil contains the thickest most extensive and one of the longest records of late palaeozoic glaciation in all of the gondwana supercontinent glacially controlled deposition started as early as the middle carboniferous when lobate termini of ice streams from the windhoek ice sheet wis and rio grande do sul and asuncion ice caps moved into the parana basin lobes reached sea level and advanced grounded at least as far as 200 km into the basin stabilizing as tidal intertidal margins glaciation and glacial sedimentation occurred penecontemporaneously with the transgressive phase of the late palaeozoic tectonic cycle of the parana basin while gondwana was gradually moving away from the south pole evolution involved complex interaction of tectonic palaeogeographic and palaeoclimatic factors initial flooding of the basin by an epicontinental sea in the middle carboniferous may have provided moisture necessary for the growth of glaciers conversely episodes of sea level rise probably affected the stability of marine glaciers the palaeoclimatic setting for the wis and other ice masses at the margins of the parana basin was mostly temperate multiple ice advances are evidenced by subglacial tillites resting on striated and or glaciotectonized basement and deformed glacigenic sediments identified at different stratigraphic levels in the itarare subgroup glaciation reached its maximum expansion sometime between the late carboniferous and early permian gradually diminishing and vanishing in the late early permian the reconstructed palaeogeographic evolution favors a model of irregular melt back of ice masses particularly along the eastern margin of the parana basin in analogy with the deglacial pattern of the pleistocene laurentide ice sheet in north america retreat of marine glaciers was mostly associated with relatively simple accumulations or complex build ups of ice contact proglacial facies associations in glacial estuarine embayments fast retreat was mainly controlled by decoupling associated with sea level rise and intense calving in the terrestrial environment more fragmentary evidence shows that retreat may have involved several mechanisms including downwasting of stagnant inactive ice margins and destabilization by surging of glaciers moving over deformable sediments highstand sea level following ice wastage is often marked by widespread deposition of relatively thin marine beds at least four stratigraphically different basinwide marine horizons are recognized isostatic rebound of deglaciated margins of the parana basin is recorded by transition from deep marine beds to shallowing coarsening upward prograding sequences of littoral fluvio deltaic facies basinwards sourced from raised basin margins eventually upon emersion these constituted platforms for interglacial and postglacial peat development although glaciation lasted for a long time glacial sedimentation alternated with relatively long periods of intense and widespread subaerial and subaquatic submarine reworking of previously deposited glacigenic sediments and deposition of normal non glacial sediments that comprise the bulk of the itarare subgroup sequence thin coal beds which locally rest on fossil soils denote climatic amelioration during these interglacial phases

paleoclimate and weathering of the tokaj hungary loess paleosol sequence abstract the tokaj loess paleosol sequence northeast hungary is a well studied site in southeast europe where detailed paleoenvironmental reconstructions of the quaternary have been carried out in this study the geochemical composition of samples from the upper part of the sequence 45 21 ka was analyzed and a variety of commonly used weathering indices and element ratios were applied to estimate weathering intensity a common semi quantitative proxy of paleoclimatic conditions further similarities and differences between these weathering indices and their sensitivity to changes in paleoclimatic conditions were assessed results indicate that all of them accurately track changes in weathering intensity and are with minor exceptions very similar to each other based on different transfer functions for major and trace element concentrations xrf mass specific magnetic susceptibility and stable carbon isotopic 13c data mean annual paleotemperature and mean annual paleoprecipitation for the time intervals of paleosol formation 45 27 ka and dust deposition 27 21 ka were calculated results differ depending on the respective transfer function and method but agree with x 13c based or slightly overestimate xrf based previously published paleoclimate data of the region xrf and 13c based results converge to a mean annual temperature mat range of 8 5 10 c paleosol and 8 9 c loess and a mean annual precipitation map range of 700 900 mm a 1 paleosol and 550 700 mm a 1 loess based results are most consistent with literature data and yield mats of 8 4 c paleosol and 6 6 c loess and maps of 300 500 mm a 1 paleosol and 220 mm a 1 loess

a decade of shear wave splitting in the earth s crust what does it mean what use can we make of it and what should we do next it is 10 years since shear wave splitting throught to be diagnostic of some form of seismic anisotropy was first positively identified in the earth s crust from the beginning it was argued that the splitting was probably associated with the presence of stress aligned cracks inclusions in the crust and that this would provide the opportunity for monitoring the in situ geometry of cracks and stress in a variety of different circumstances and in a variety of different applications

provenance analysis and tectonic setting of the ordovician clastic deposits in the southern puna basin nw argentina provenance studies on early to middle ordovician clastic formations of the southern puna basin in north western argentina indicate that the sedimentary detritus is generally composed of reworked crustal material tremadocquartzrich turbidites tolar chico formation mean composition q t 89 f7 l4 are followed by volcaniclastic rocks and greywackes tolillar formation mean q t 33 f42 l25 these are in turn overlain by volcaniclastic deposits mean qt24 f30 l46 of the diablo formation late arenig early llanvirn that are intercalated by lava flows all units were deformed in the ocloyic orogeny during the middle and late ordovician sandstones of the tolar chico formation are characterized by th sc ratios 1 la sc ratios 10 whereas associated fine grained wackes show slightly lower values for both ratios lree light rare earth elements enrichment of the arenites is 50 chondrite eu eu values are between 0 72 and 0 92 and flat hree heavy rare earth elements patterns indicate a derivation from mostly felsic rocks of typical upper crustal composition the e n d t s e d values scatter around 11 to 9 the calculated nd t d m residence ages vary between 1 8 and 2 0 ga indicating contribution by a palaeoproterozoic crustal component the th sc and la sc ratios of the tolillar formation are lower than those of the tolar chico formation normalized ree rare earth elements patterns display a similar shape to paas post archaean average australian shale but with higher abundances of hrees eu eu values range between 0 44 and 1 17 where the higher values reflect the abundance of plagioclase and feldspar bearing volcanic lithoclasts average e n d t s e d values are less negative at 5 1 and nd t d m are lower at 1 6 ga this is consistent with characteristics of regional rocks of upper continental crust composition which most probably represent the sources of the studied detritus the rocks of the diablo formation have the lowest th sc and la sc ratios lower lree abundances than the average continental crust and are slightly enriched in hrees eu eu values are between 0 63 and 1 17 the nd isotopes e n d t s e d 3 to 1 t d m 1 2 ga indicate that one source component was less fractionated than both the underlying early ordovician and the overlying middle ordovician units synsedimentary vulcanites in the diablo formation show the same isotopic composition our data indicate that the sedimentary detritus is generally composed of reworked crustal material but that the diablo formation appears to contain 80 of a less fractionated component derived from a contemporaneous continental volcanic arc there are no data indicating an exotic detrital source or the accretion of an exotic block at this part of the gondwana margin during the ordovician

petrographic and diagenetic signatures of climatic change in peri and postglacial karoo sediments of sw tanzania abstract the basal idusi formation of the karoo succession in sw tanzania represents deposits of the final late palaeozoic deglaciation event it reflects the change from a cold to a temperate more humid climate the lower unit of the idusi formation lisimba member consists of periglacial deposits with glaciolacustrine diamictites sandstones dropstone bearing mudstones and varvites as well as fluvial and deltaic conglomerates and sandstones the upper unit lilangu member is dominated by organic rich siltstones and sandstones which were accumulated in an eutrophic postglacial lake the petrography of the idusi formation reveals an arkosic composition indicating provenance from cratonic basement rocks the lisimba member is characterized by low mineralogical maturity with a high proportion of garnet fine grained matrix particles in the lisimba member authigenic formation of chlorite corrensite and laumontite at a moderate stage of burial was due to alkaline pore fluid conditions with high ionic strength caused by restricted percolation in the matrix rich sediments and their low mineralogical maturity the postglacial sedimentary rocks are characterized by early diagenetic kaolinite siderite pyrite and barite this paragenesis formed under the influence of acidic meteoric derived pore water and the decay of organic matter such early diagenetic conditions are frequently met in humid continental environments

quantitative paleoenvironmental and paleoclimatic reconstruction using paleosols abstract paleosols fossil soils are preserved throughout the geologic record in depositional settings ranging from alluvial systems to between basalt flows until recently paleosols were studied using primarily qualitative methods in recent years paleopedology has shifted from a largely qualitative field based on comparisons with modern analogues to an increasingly quantitative endeavor some of this change has been a result of applying existing techniques to new materials but many of the innovations have been the result of applying new techniques to new materials including thermodynamic modeling of soil formation isotope geochemistry and applications of empirical relationships derived from modern soils a variety of semi quantitative and quantitative tools has been developed to examine past weathering and pedogenesis and to reconstruct both paleoenvironmental and paleoclimatic conditions at the time that the paleosols formed though it is often not possible to achieve the same temporal resolution as with marine records for paleoclimatic reconstructions proxies based on paleosols are potentially a much more direct means of making paleoclimatic reconstructions because soils form at the earth s surface in direct contact with the atmospheric and climatic conditions at the time of their formation paleoclimatic and environmental properties that may be reconstructed using the new proxies include provenance weathering intensity mean annual precipitation and temperature during pedogenesis nutrient fluxes into and out of the paleosols the atmospheric composition of important gases including co2 and o2 the moisture balance during pedogenesis the soil gas composition reconstructed vegetative covering and paleo altitude

variation of chemical index of alteration cia in the ediacaran doushantuo formation and its environmental implications abstract the ediacaran period 635 541 ma witnessed rapid turnovers of marine organisms that eventually led to the early cambrian radiation the ediacaran doushantuo formation ca 635 551 ma serves as one of the most important and intensively studied stratigraphic units for understanding the co evolution of life and environment during this critical time interval to better understand the early middle ediacaran climate change we reconstruct a temporal variation curve of chemical index of alteration cia from a drill core and an outcrop of the doushantuo formation in combination with previously published cia data from segments of time equivalent strata the results show three distinct decreases in cia values that correlate well with the positive carbon isotope 13c excursion at the low doushantuo formation ep1 and the negative 13c excursion at the middle en2 and upper en3 doushantuo formation the decline of cia in ep1 is consistent with occurrence of glendonites at the same stratigraphic interval that suggests a cooling event the low cia values in en2 and en3 also suggest relatively colder periods that are consistent with evidence from strontium isotope 87sr 86sr and oxygen isotope 18o data with existing bio and chemostratigraphic constraints the cooling event associated with en2 might be synchronous with the gaskiers glaciation the other two cold periods associated with ep1 and en3 however have not been documented from other successions globally which needs to be tested in future studies

palaeosols in early himalayan foreland basin sequences demonstrate latitudinal shift related long term climatic change the palaeogene sedimentary record in the himalayan foreland basin contains palaeosols that are interpreted as reflecting changes in climate through time with the passage of the indian plate from the equator to 30 n latitude to understand spatial and temporal variation in the occurrence of diagnostic palaeosol types 12 exposed stratigraphic sections were investigated and studied in detail using petrographic and geochemical techniques including scanning electron microscopy and x ray mineralogy oxisol bauxite is a karst bauxite that occurs in crudely bedded and laminated forms it contains gibbsite goethite and kaolinite and shows chemical index of alteration values close to 100 demonstrating intense weathering no gradual change in the concentrations of trace and rare earth elements is recorded however their behaviour suggests that the oxisol was produced by weathering of basalt under a warm and humid climate histosol coal found stratigraphically higher than oxisols contains woody structures dominated by vitrinite maceral the histosol is interpreted as having originated from an undisturbed peat developed in a swamp of high tree density under wet tropical climatic conditions up section calcrete profiles of stages 3 and 4 containing rhizoliths pellets filamentous calcite and microcodium have developed by pedogenic processes large negative stable carbon 8 5 to 11 2 and oxygen isotope values 8 5 to 12 6 suggest that the studied calcretes formed under the influence of meteoric water and soil organic matter in dry sub tropical climatic conditions the formation of oxisol in a warm and humid climate was possible in the equatorial region when part of the indian subcontinent was close to the equator the coal developed under a humid climate when the northern tip of the indian subcontinent reached the intertropical convergence zone while the pedogenic calcrete formed once the sub tropical climatic zone was reached hence it is suggested that these palaeosols formed in different climatic zones during northward drift of the indian plate and that the drift brought them to their present positions between 30 n and 35 n within the sub tropical climatic zone

analysis of late palaeozoic glacial to postglacial sedimentary successions in south africa by geochemical proxies response to climate evolution and sedimentary environment abstract records of incisive climate changes during the late palaeozoic era are best documented in sedimentary basins of south africa glacial upper carboniferous early permian dwyka group and equivalents and postglacial deposits early to middle permian ecca and beaufort groups are known from the main karoo basin in south africa from the kalahari basin namibia and botswana and other late palaeozoic basins of south gondwana glacial deposits comprise diamictites and tillites followed by postglacial shales with variable organic matter contents and intercalated carbonate horizons this study covers the final glaciation phase upper pennsylvanian asselian sakmarian and the transition into the postglacial stage of the middle to late permian for sedimentary successions from the karoo and eastern kalahari basin element geochemical proxies chemical index of alteration zr ti rb k v cr and organic carbon content supported by mineralogical data record pronounced variation in sedimentary conditions these took place in the course of glacier retreat at the dwyka ecca boundary where climate and weathering processes are known to have changed the proxy signals indicate an increase in sea level and salinity and a shift in redox conditions from oxygenated to temporary anoxic euxinic conditions due to the synchronicity of these events distant sampling localities in the karoo basin can be correlated despite facies differences between the eastern kalahari and karoo basin the geochemical proxies point to a comparable climatic evolution during the postglacial phase for the early permian proxy signals indicate warm humid conditions in the karoo and kalahari basin during the middle permian increased aridity hampered chemical weathering processes as indicated by decreasing cia values results show that i proxies reflect provenance synsedimentary redox regime and late diagenetic alteration ii by combination of different independent geochemical proxies primary conditions of sedimentation and climate can be deduced iii the geochemical proxies applied are independent of local environments and iv the data reveal supra regional or even hemispherical changes in climate and sedimentary conditions thus geochemical proxies can be used as reliable markers for basin wide correlations knowledge about synchronicity on basin scale contributes to an improved understanding of sw gondwana s interaction with and influence on global climatic evolution

geochemical characteristics and organic matter enrichment mechanism of black shale in the upper triassic xujiahe formation in the sichuan basin implications for paleoweathering provenance and tectonic setting abstract the first third and fifth members henceforth referred to as t 3 x 1 t 3 x 3 and t 3 x 5 respectively of the upper triassic coal bearing xujiahe formation black shale are among the most significant hydrocarbon source rocks in the sichuan basin here we present geochemical data for the upper triassic black shales from core from well ld 1 to determine their paleoenvironmental conditions paleoweathering provenance transitions and tectonic setting the v v ni vs u th v cr vs u th and ni co vs u th bivariate plots and the tfe toc ts total fe total organic carbon total sulphur ternary diagram indicate that the synsedimentary redox regime of almost all the shale samples was oxidizing ba al sr al and p ti data combined with quantitative biogenic ba data indicate that moderate high primary paleoproductivity levels prevailed during deposition the sr cu ratio and c value combined with the sedimentary features are indicative of warm humid climate conditions the ti al deposition rate proxy and decompacted sedimentation rate are positively correlated with the total organic carbon toc content according to our multiproxy approach black shale development in the xujiahe formation was mainly controlled by the primary productivity level foreland basin setting high tectonic subsidence and sedimentation rate and exhibited a limited correlation with water column redox conditions through the compilation and calculation of various weathering indices for the xujiahe black shale we suggest that caution must be taken when inferring paleoclimate characteristics based on the chemical index of alteration cia because of the influence of multiple nonweathering factors provenance sensitive elemental ratios th sc vs zr sc and co th vs la sc indicate that the clastic contribution to xujiahe black shales was of a predominantly felsic character the black shales exhibit a transition from t 3 x 1 to t 3 x 3 to t 3 x 5 whereby t 3 x 1 was primarily sourced from the proterozoic to early paleozoic strata of the qinling orogeny t 3 x 3 was primarily sourced from the neoproterozoic complex in the longmen shan and t 3 x 5 was primarily sourced from the songpan ganzi flysch strata which contributed recycled material because of folding and strong southeastward thrusting

global aridity during the early miocene a terrestrial paleoclimate record from the ebro basin spain abstract paleosols are an important tool in the paleoclimatic and paleoenvironmental interpretation of continental deposits and can provide a high resolution proxy for paleoclimate results from geochemical climofunctions applied to early miocene strata exposed in the ebro basin spain demonstrate that mean annual precipitation was the dominant control on paleosol type and indicate that the paleoclimate was considerably wetter during the early miocene by up to 1150 mm yr 1 in comparison to modern values placing it in a subhumid climatic regime rather than an arid semiarid regime as previously suggested by sedimentological and paleontological approaches by making comparisons with published data on paleoclimate during the early miocene this article stresses the importance of regional climatic changes in global paleoclimatic interpretation

dispersion calculations for sh and p sv waves in multilayered coal seams recent work by rader schott dresen and ruter has provided a means of calculating dispersion and amplitude distribution curves for sh channel waves in multilayered media an alternative calculation procedure is presented and the p sv wave type is also included numerical results are given for a coal seam containing a band of dirt of either higher or lower seismic velocities than the coal itself

major element geochemistry and paleoclimatology of the permo carboniferous glacigene dwyka formation and postglacial mudrocks in southern africa abstract a chemical index of alteration cia is used to quantify the degree of weathering of fine grained materials in the glacigenic permo carboniferous dwyka formation and succeeding stratigraphic units of southern africa diamictites in the dwyka formation have low cia values compatible with their glacigenic origin interbedded mudrocks show a wide scatter of values suggesting that at least some of them were deposited during periods when ice had retreated from the source areas samples from the prince albert shale which immediately overlies the dwyka formation show high cia values suggesting a rapid transition to a much more intensive weathering regime warmer climatic conditions samples from the succeeding whitehill shale have a low average value so that weathering was once more inhibited perhaps by a temporary return to a colder climate the highest stratigraphic units sampled the upper shales have an average cia value comparable to that of average shales and suggesting normal weathering conditions major element geochemical data can supplement sedimentological and paleontological information and provide a valuable contribution to the detailed paleoclimatic interpretation of such glacigenic successions

paleoclimatology and provenance of the glaciogenic gowganda formation paleoproterozoic ontario canada a chemostratigraphic approach the gowganda formation dated as about 2 3 ga is widely but not universally interpreted as glaciogenic and our chemostratigraphic study supports such an interpretation the bulk compositions of diamictite matrix materials and associated argillites are considered to have resulted from the mixture of two detrital components one is glacial flour similar in composition to the unweathered archean upper crust whereas the other is chemically weathered detritus resembling average proterozoic shale in composition the first component has a chemical index of alteration cia value of 50 reflecting the abundance of feldspar and dearth of aluminous clay minerals the second component has a cia value of 70 and was produced primarily in weathering profiles by chemical weathering typical of temperate climatic regimes diamictite matrix materials 92 samples have an average cia value of 57 the argillites have higher values the average is 62 97 samples the lower cia values of the diamictites reflect a higher proportion of glacial flour suggesting a stronger influence of frigid climatic conditions than that which prevailed during deposition of the argillites systematic trends in cia values are developed across diamictite argillite boundaries and within a thick argillite between two major diamictite units these values reflect climatic variations with maximum amelioration during deposition of the middle section of the argillite rare earth element data and th sc and ti al ratios from the diamictite matrix materials all suggest a provenance that included a large supracrustal component 45 together with lesser amounts of tonalite trondhjemite granite and granite the proportion of supracrustal materials such as volcanic rocks and shales may have been exaggerated by selective comminution during glacial transport the matrix materials of the gowganda diamictites are severely depleted in ca and proportionally enriched in na relative to the source the anorthitic component of plagioclase has been selectively replaced by an albitic component during diagenesis and metamorphism a chemostratigraphic approach provides high resolution data for reconstruction of paleoclimatic conditions and valuable information concerning provenance and metasomatic processes

geochemistry of fine grained clastic sedimentary rocks of the neoproterozoic ikorongo group ne tanzania implications for provenance and source rock weathering abstract the neoproterozoic ikorongo group which lies unconformably on the late archaean nyanzian supergroup of the tanzania craton is comprised of conglomerates quartzites shales siltstones red sandstones with rare flagstones and gritstones and is regionally subdivided into four litho stratigraphic units namely the makobo kinenge sumuji and masati formations we report geochemical data for the mudrocks i e shales and siltstones from the ikorongo basin in an attempt to constrain their provenance and source rock weathering these mudrocks are compositionally similar to paas and ps indicating derivation from mixed mafic felsic sources however the siltstones show depletion in the transition elements cr ni cu sc and v and attest to a more felsic protolith than those for paas and ps the chemical index of alteration cia 52 82 reveal a moderately weathered protolith for the mudrocks the consistent ree patterns with lree enriched and hree depleted patterns la yb cn 7 3 38 3 coupled with negative eu anomalies eu eu 0 71 on average which characteristics are similar to the average paas and ps illustrate cratonic sources that formed by intra crustal differentiation geochemical considerations and palaeocurrent indications suggest that the provenance of the ikorongo group include high mg basaltic andesites dacites rhyolites and granitoids from the neoarchaean musoma mara greenstone belt to the north of the ikorongo basin mass balance calculations suggest relative contributions of 47 42 and 11 from granitoids high magnesium basaltic andesites and dacites respectively to the detritus that formed the shales corresponding contributions to the siltstones detritus are 53 43 and 4

channel waves in cross borehole data layered geological formations with large seismic velocity contrasts can effectively create channel waves in cross borehole seismic data the existence of channel waves for such waveguides can be confirmed by ray tracing wave equation modeling and modal analysis channel wave arrivals are identified in cross borehole data recorded at conoco s newkirk test facility for these data where velocity contrasts are about 2 to 1 tomography based on first arrival traveltimes is limited due to problems with extreme ray bending and seismic shadow zones however it may be possible to extract geological information using channel wave information the seismometer differencing method appears to be a promising approach for detecting waveguide boundaries by use of cross borehole data

pervasive autocorrelation of the chemical index of alteration in sedimentary profiles and its palaeoenvironmental implications the chemical index of alteration has been used widely for reconstruction of the palaeoclimate however the mechanisms and environmental factors controlling the chemical index of alteration of sediments are not yet fully understood in this study autocorrelations of the chemical index of alteration in nine sedimentary profiles from both the land and the sea spanning different geological times are discussed the sediments of these profiles have different origins dust fluvial or ocean sediments and are from various climate situations and sedimentary environments autocorrelations of chemical index of alteration series are ubiquitously evident in all profiles it is suggested here that autocorrelations may be caused by post depositional changes such as persistent weathering and diagenesis as a result the chemical index of alteration may not reflect climatic conditions during the time of sediment deposition this study strongly recommends the confirmation of the reliability and veracity of the chemical index of alteration before it is adopted to evaluate the weathering degree of parent rocks and to reconstruct the past climate significant autocorrelations in loess profiles were specifically observed suggesting that the existing understanding of loess deposition in terms of climate conditions requires re examination and that previous reconstructions of rapid climate changes for example in centennial millennial scales should be treated with caution

pennsylvanian sea level cycles nutrient availability and brachiopod paleoecology abstract as with modern organisms the spatial and temporal distribution of fossil communities was controlled by both the physical setting in which the organisms lived and by the organisms physiology and interactions by studying the sedimentological and geochemical context of fossil communities it is possible to assess the relative importance of the physical setting and the organisms physiology comparison of pennsylvanian brachiopod associations with changing sedimentological context water depth facies and nutrient availability indicates that body size is a function of water depth and nutrient availability for most spire bearing athyridids and spiriferids brachiopods but rarely for productid brachiopods spire bearing brachiopods dominate the associations in high nutrient settings and productid brachiopods dominate the associations in low nutrient settings this difference suggests that physiological differences between brachiopod orders such as lophophore filtering efficiency play an important role in controlling their distribution

waves long waves and nearshore morphology abstract recent field measurements on beaches of different slopes have established that wave motion at periods substantially longer than the incident waves dominates the velocity field close to the shore analysis of a number of extensive data sets shows that much of this long wave motion is in the form of progessive edge waves though forced wave motion standing edge waves and free waves propagating away from the shore may also contribute to the energy theoretically the drift velocities in bottom boundary layers due to edge waves show spatial patterns of convergence and divergence which may move sediment to form either regular crescentic or cuspate features when only one edge wave mode dominates or a bewildering array of bars bumps and holes when several phase locked modes exist together convincing field demonstration of the link between nearshore topography and edge waves only exists for the special case of small scale beach cusps on steep beaches formed by edge waves at the subharmonic twice the period of the incident waves at longer periods the link is proving more difficult to establish due to the longer time scales of topographic changes the interaction between pre existing topography and the water motion and the observation of broad banded edge wave motion which is not readily linked to topography with a well defined scale these ideas are however central to the study of nearshore processes as most of the plausible alternate hypotheses do not seem to lead to quantitative predictions clearly further theoretical and observational work is essential

whole rock geochemistry of upper paleozoic loessite western pangaea implications for paleo atmospheric circulation abstract average bulk major and trace element chemical composition of upper paleozoic loessite lithified loess from several widely scattered sites in western equatorial pangaea western north america approximates upper continental crust ucc but is more similar to the bulk composition of precambrian basement coring uplifts of the ancestral rocky mountains however distinct compositional signatures occur among the various loessite deposits controlled primarily by differences in al 2 o 3 mgo na 2 o k 2 o and rb furthermore values of the chemical index of alteration cia of these loessites are low 55 63 skewed toward lower values closely matching values for north american loess and precambrian basement although diagenesis can account for some of the compositional differences e g local sio 2 or k 2 o enrichment it fails to explain the major differences among the sites rather these differences are best explained as a result of variations in regional basement that sourced the loess coupled with transport wind pathways which varied from zonal easterlies to monsoonal westerlies in this region of tropical pangaea from late carboniferous to early permian time the low cia values generally reflect first cycle derivation from regional basement uplifts of the arm and for younger deposits a variable contribution from the suture zone uplifts and volcanism of the appalachian ouachita marathon collisional belt the variations in bulk chemical composition of the loessite coupled with previously collected detrital zircon geochronology suggest that these low latitude loessites are not simply the result of deflation of mid latitude erg deposits or coastal alluvial plain sediments these data represent a first attempt at geochemical characterization of pre quaternary loess and demonstrate the utility of loess geochemistry as a proxy for paleoatmospheric circulation in earth s deep time past

equilibrium slopes and cross shore velocity asymmetries in a storm dominated barred nearshore system abstract the near bed 0 10 m elevation horizontal velocities were measured across a two barred lacustrine shoreface during a storm and reveal a spatially coherent but temporally variable pattern in the low order moments of the velocity field large cross shore velocity asymmetries indicated 1 1 spatially extensive and temporally persistent offshore mean flows up to 0 18 m s 1 across the landward slope of the linear outer bar reflecting an undertow driven by a wave induced setup 2 2 an onshore directed skewness opposing the mean flow of wind wave origin and persistent under propagating bores in the inner bar system long after this asymmetry had disappeared from the outer bar extensive sediment reactivation with near zero net sediment flux over the whole of the upper shoreface indicated a sediment prism in a steady state volumetrically over the storm cycle uniform depths of sediment reactivation with zero bed elevation change over the storm cycle revealed local slopes in a steady state in the outer linear bar however time integration of the near bed velocity field at this location indicated an offshore net flux of water while sedimentary structures indicated bedform migration and thus at least bedload almost uniformly onshore when ripples and megaripples were present the sediment transport giving rise to the local equilibrium cannot be explained therefore on the basis of the mean properties of the near bed velocity vector but requires knowledge of the time varying instantaneous sediment transport vector onshore migration of the inner bar correlated well with the large and persistent onshore skewness of the velocity distribution in the inner surf zone associated with translatory surf bores throughout the storm decay period low frequency oscillations were only significant close to the shoreline but may have influenced the development of a sinuous three dimensional inner bar form as it migrated onshore

environmental changes during the upper pleistocene holocene in mediterranean ne spain as recorded by the mineralogy and geochemistry of alluvial records abstract landscape evolution and environmental conditions from last glacial maximum lgm to late holocene times were reconstructed from the mineralogical and geochemical characteristics of the alluvial morphochronostratigraphy recorded in bardenas reales natural park ebro basin ne spain alluvial architecture includes a lgm holocene gravelly unit 22 9 ka bp a lower holocene silty muddy unit 9 7 ka bp and an upper holocene sandy unit 5 0 1 ka bp increases in illite smectite mixed layers kaolinite chlorite and modified chemical index of alteration cia as well as the decrease in illite fwhm e are indicators of minor increases in the chemical weathering of the alluvial sediments the results suggest that this area although under broad semiarid conditions underwent the following environmental evolution i an increasing trend in moisture availability in the lower holocene and ii a variable pattern in water disposal at the onset of the upper holocene followed by a decrease in humidity during the last millennium this reconstruction proves the usefulness of mineralogical and geochemical proxies as indicators of rapid environmental changes under mediterranean conditions

earth s oldest reported glaciation physical and chemical evidence from the archean mozaan group 2 9 ga of south africa the pongola supergroup is a thick succession of archean 2 9 ga supracrustal rocks in the eastern part of the kaapvaal craton of southern africa its upper part the mozaan group 5000 m thick includes diamictites with a highly varied suite of clasts some of which are striated and faceted clasts in associated stratified siltstones are interpreted as ice rafted debris a glacial origin is also supported by geochemical investigation of diamictite matrix materials and associated mudstones plots of sio2 al2o3 and tio2 al2o3 suggest that these rocks underwent little chemical weathering an interpretation confirmed by calculation of a chemical index of alteration with low values typical of other glacial deposits the analyzed rocks are rich in fe average fe2o3 t is 24 wt like rocks of many other glaciomarine successions the diamictites and associated mudstones of the mozaan group have low th sc ratios suggesting preferential incorporation of mafic materials into the diamictite matrix material

geochemistry of precambrian and paleozoic siliciclastic rocks from the iberian range ne spain implications for source area weathering sorting provenance and tectonic setting abstract the major and trace element chemical composition of precambrian and paleozoic shales and sandstones from the iberian range spain has been investigated to determine the provenance and tectonic setting of these rocks as well as to appraise the influence of the weathering hydraulic sorting and recycling processes upon source rock signature the samples studied belong to a prograde sequence from diagenesis to anchizonal grade and are mainly composed of quartz illite mica phases and or kaolinite with chlorite feldspars and carbonates as minor components the major element distribution chemical index of alteration cia indices reflects that recycling processes have been important in homogenizing the composition of shales and sandstones the higher cia indices observed in the silurian and devonian shales 80 and 85 respectively compared with those of precambrian to ordovician and the carboniferous age about 70 indicate that their source area underwent more intense chemical weathering processes possibly due to climatic and or tectonic variations alternatively the source area of the silurian and devonian shales may have been composed of recycled sedimentary materials mineral fractionation is mainly observed in coarser rocks through zircon apatite and xenotime accumulation although the shales are not free of these phases the zircon content of the fine grained rocks is not high enough to affect rare earth element ree contents but phosphate minerals apatite and xenotime at least partially control the ree distribution the influence of apatite and xenotime are slightly higher in the precambrian shales as the phosphate concentration produces a decrease in the la sm ratios chondrite normalized ree patterns and negative eu anomaly size of the studied rocks are similar to that of post archean australian shales paas indicating that they originally come from a differentiated silicic source the higher ree contents in the studied shales in relation to paas indicate that recycling processes in the iberian range sources were probably more intense than that of paas the slight differences among the ree patterns of the different groups of shales probably do not reflect changes in source area composition but instead suggest variations in mineral sorting chemical weathering and or sediment recycling the th sc co th cr th cr v v ni ratios support a primitive silicic source for these rocks with the higher th sc and lower co th in cambrian and ordovician shales indicating a higher proportion of felsic material in their primitive source area the compositional maturity of analyzed sandstones is typical of cratonic environments and their la sc th and zr contents reflect their passive continental margin setting

distinguishing climate in the soil record using chemical trends in a vertisol climosequence from the texas coast prairie and application to interpreting paleozoic paleosols in the appalachian basin u s a a suite of vertisols clay rich soils with high shrink swell potential were examined across a climosequence climatic transect in twelve soil pits from the coast prairie of texas in order to determine if mean annual precipitation map exerts a control on the chemistry of these soils and if the observed chemical trends are useful for interpreting paleoclimate records of paleovertisols in the geologic record the precipitation regime of the climosequence spans a range between 144 and 86 cm year with moisture regimes classified as udic udic ustic ustic and aridic ustic in a general northeast to southwest direction other soil forming factors such as soil age 35 40 ka parent material fluviodeltaic beaumont formation of late pleistocene age landscape low relief coastal plain and vegetation prairie or mixed woody shrubs are relatively constant across the climosequence climate sensitive chemical proxies of map identified include dithionite citrate extractable fe fedith acid oxalate extractable fe feoxal caco3 equivalent caco3equiv s and ammonium acetate extractable na k and mg naacet kacet and mgacet respectively which vary across the climosequence because of differences in effective depths of leaching and intensity of wetting and drying cycles these standard usda wet chemical climate proxies are related to bulk oxide or element chemistry of soils and paleosols measured using xrf which supports the use of geochemical climate proxies for interpreting the paleoclimate records of paleovertisols application of the chemical index of alteration minus potash cia k geochemical climofunction to late mississippian paleosols from the appalachian basin of the eastern u s demonstrates evidence for a shift from a lower to a higher map paleoclimate that is consistent with previous paleoclimate models and with observed morphological changes in the paleosols we advocate actualistic research using bulk chemistry of soils and paleosols as a means of obtaining soil information useful for interpreting paleosols in the geological record

the rare earth element geochemistry on surface sediments shallow cores and lithological units of lake acigol basin denizli turkey abstract the sediments in lake acigol located in sw anatolia turkey were formed under tectono sedimentary events ree geochemical investigations of the lake acigol sediments from surface and shallow core sediments at different depths 0 10 cm 10 20 cm and 20 30 cm are presented to clarify the characteristics of ree and the nature of source rocks in the lake sediments and to deduce their paleoenvironmental proxies the chondrite normalized ree patterns of these sediments are shown as light enrichment in lree and flat hree with a negative eu anomaly that is close to the continental collision basin ccb in its profile this is not comparable with paas and ucc inorganic detrital materials control the ree characteristics of the lake acigol sediments and these sediments were accumulated in oxic and dysoxic depositional conditions and or at passive margins derived from oceanic island arc rocks they were affected by low chemical weathering either at the original source or during transport before deposition under arid or subtropical humid climatic conditions in addition we used gis techniques such as inverse distance weighted idw and geographically weighted regression gwr to investigate the spatial interpolation and spatial correlation of the rees from the lake surface sediments in lake acigol and its surrounding lithological units gis techniques showed that the lithological units e g hayrettin formation north of lake acigol have high ree contents however eu eu values were higher in some lake surface sediments than in lithological units and that refers to a negative eu anomaly therefore lake acigol sediments are derived from the weathered products mainly from local highly basic bedrock around the lake from the archean crust the chronology of lake acigol sediment was conducted using the constant rate of supply crs model using the crs methods for the calculation of sedimentation rate we obtained a 0 012 g cm 2 year value which is an average value for the first 20 cm depth of this lake the core activity profiles of 210 pb and 137 cs were measured to estimate the age of the sediments we observed activities of 8 08 5 5 bq kg for 210 pb and 0 86 0 6 bq kg for 137 cs

patterns of late paleozoic glacial sedimentation on the southeast side of the parana basin brazil abstract during the late paleozoic glaciation glaciers moved from southern africa over a platform composed of crystalline and sedimentary rocks into the subsiding parana basin of southeastern brazil in each successive glacial advance the platform was eroded and is marked by crescentic gouges striae roches moutonnees grooves and glacially modified valleys the glacial sediments which are found on the platform in southeastern brazil and margins of the parana basin were deposited from grounded ice and are termed terrestrial these sediments which are best exposed in the northern part of the study area are composed of supraglacial deposits such as layers of diamictite flow tillite interbedded with sandstones and minor amounts of lodgement tillite the supraglacial deposits are frequently faulted and the sandstones show pull apart structures and abnormal dips these features and others suggest that ice retreat in the terrestrial environment was primarily by down wasting the glaciogenic sediments found within the subsiding parana basin are termed basinal even though it is not certain that they were all deposited in a subaquatic environment they are composed primarily of sandstones siltstones shales and mudstones interbedded with massive and laminated diamictites it is suggested that the massive diamictite was deposited from the base of the advancing glaciers by basal melting during ice retreat from water filled parts of the basin unstable masses of glaciogenic debris flowed down slope resulting in layered debris flows and in some instances chaotic debris flows which may have been triggered by subaquatic slupms and slides as the ice continued to retreat to the margin of the basin a complex of subaquatic outwash including deltaic sands was deposited minor varvites were deposited in shallow restricted embayments in the shoreline which were flooded with fresh glacial meltwaters deposits of retreat including the varvites interfinger with marine fossiliferous sediments which suggests that the water level in the basin was rising during deglaciation it is not known how may times glaciers advanced into the parana basin but recent studies show that there were at least nine glaciations in the northern part of this study area covering a time span of from 10 to 35 million years

geochemical methods to infer landscape response to quaternary climate change and land use in depositional archives a review abstract understanding and quantifying the processes and geochemical cycles associated with catchment erosion the development of soils and weathering horizons and terrestrial habitat change beyond the scales of modern observations remain challenging such research however has become increasingly important to help predict future landscape change in light of increasing land use and rapid global warming we herein review organic and inorganic geochemical tools applied to depositional archives to better understand various aspects of landscape evolution on geological time scales we highlight the potentials and limitations of inorganic geochemical analytical methods such as major element geochemistry metal and radiogenic isotopes and in situ cosmogenic nuclides as qualitative semi quantitative and quantitative proxies for the transformation of bedrock material via regolith and soils to sediments we also show how stable isotope geochemistry applied to lacustrine endogenic carbonates can be used to infer rock water interactions vegetation change and soil development in limestone rich catchments proxies focusing on the silicilastic element of sediment formation transport and deposition are ideally combined with organic geochemical proxies for vegetation change and soil organic matter evolution in a catchment to gain a comprehensive picture of the critical zone s evolution over time multi proxy and multidisciplinary research combining organic and inorganic geochemical techniques from several sedimentary archives in the same catchment have high potential to provide comprehensive information on quaternary landscape evolution and thus improve the robustness of associated forecasting models

global changes during carboniferous permian glaciation of gondwana linking polar and equatorial climate evolution by geochemical proxies the most prevalent phanerozoic glaciation occurred during the carboniferous permian on the southern hemisphere gondwana supercontinent sediments from the pennsylvanian dwyka group deposited in the karoo basin of south africa provide a complete record of glaciation and deglaciation phases the direct correlation of glaciation events in southern gondwana basins with the well studied climate evolution of equatorial regions was previously hampered by lack of precise radiometric dating as dating has now become available for the karoo basin the gondwana glaciation can be viewed in a global paleoclimatic framework with high temporal resolution element geochemical proxies cia chemical index of alteration zr ti rb k v cr record three confined shifts in climate and paleoenvironment of the karoo basin these shifts were induced by changes in sea level weathering rate provenance and redox conditions because of the low availability and diagenetic overprint of carbonates ocean and atmosphere pco 2 variations had to be reconstructed from 1 3 c o r g values of marine organic matter the 1 3 c o r g signatures are affected by variable proportions of marine versus terrestrially derived organic matter and its state of preservation organic geochemical investigations toc total organic carbon c n lipid biomarkers indicate the organic matter in the central karoo basin was primarily of algal origin in agreement with element proxies the varying 1 3 c o r g values mirror shifts in pco 2 rather than variations of organic matter type a covariation trend between carbon isotope signatures of equatorial carbonates and 1 3 c o r g values from the karoo basin argues against local forcing factors and instead implies a global climate control mechanism the 5 7 m y duration of a complete glacial cycle is not in tune with any known orbital frequency processes such as changes in equator pole temperature gradients or newly developing atmosphere ocean circulation pathways can be regarded as controlling factors

shrimp u pb zircon dating and palynology of bentonitic layers from the permian irati formation parana basin brazil abstract this paper presents the first shrimp zircon age data from bentonitic ash fall layers intercalated with the irati sedimentary rocks as well as palynofossils retrieved from the petrobras six mine parana state southern brazil the permian irati formation is one the most important oil source horizons within the parana basin and consists mainly of siltstones gray claystones as well as organic rich claystones intercalated with limestones zircon morphology based on cathodoluminescence images includes two different populations a dominant population of euhedral prismatic elongate to acicular grains which are most likely related to an ash fall volcanism and a population of rounded to large prismatic grains that were interpreted as detrital grains shrimp analysis performed on the euhedral and prismatic grains revealed an age of ca 278 4 2 2 ma 7 points with 95 confidence interpreted as the crystallization age of the volcanic eruption based on this new dating the irati formation should be placed on the lower permian cisuralian artinskian in age modifying substantially the traditional ages previously attributed to this unit the palynofossils from this level include key species of the lueckisporites virkkiae zone such as l virkkiae l densicorpus l stenotaeniatus weylandites lucifer alisporites splendens typical species of this zone also occur in african and other south american argentina permian strata allowing stratigraphical correlations the origin of the ash falls is not clearly defined it may be related either to calc alkaline arc magmatism associated to the sanrafaelica orogeny 275 and 250 ma or to bimodal volcanic events associated to an early intracontinental rift developed within southwestern gondwana at ca 278 my the dating of this unit is significative to calibrate biostratigraphic schemes along the parana basin as well as equivalent zones in gondwana areas mainly in its occidental portion

late oligocene early miocene paleosols of distal fluvial systems ebro basin spain abstract the study of paleosols can be a vital tool in the paleoenvironmental interpretation of continental deposits because their physical and chemical characteristics are a reflection of variations in aspects of soil formation changes in paleosol characteristics can be used to determine the architecture and nature of parent material paleosol maturity topography climate and soil forming organisms including vegetation cover on the ancient floodplain and can be utilized to recreate a palaeocatena furthermore paleosols can provide quantitative data on paleoclimate where other sources such as organic matter and pedogenic carbonate are absent late oligocene early miocene strata exposed in the ebro basin spain have been identified as proximal alluvial fan fluvial and lacustrine continental facies in parts of the distal fluvial system pedogenically altered channel and overbank deposits interfinger with ephemeral lacustrine facies three main paleosol types developed in these sediments and have been described and compared to modern soils entisol like early successional soils inceptisol like young soils and alfisol like open woodland soils paleoenvironmental reconstructions suggest a mosaic of ecotypes with areas of open woodland composed of shrubs herbs and small trees and other plants of low stature and with each ecotype being controlled primarily by fluctuating paleohydrological conditions from field observations and geochemical analysis the climate was found to be humid continental mean annual temperature mat 10 14 c 4 c mean annual precipitation map 450 830 mm yr 1 200 mm yr 1 these results indicate that climatic conditions were wetter than the present day ebro basin mat 14 c map 320 mm yr 1 and differ from previous interpretations of an arid to semi arid environment based on sedimentological criteria alone

bars bumps and holes models for the generation of complex beach topography in shallow water any two waves of the same frequency are shown to produce complex patterns of drift velocity above the sea bed if the longshore components hi h of the wave numbers of the two waves are different these steady flow patterns exhibit a longshore periodicity of wave number hi h irrespective of whether the waves propagate in the same direction say hi he positive or in opposite directions he negative the interaction of two edge wave modes is examined in detail the drift velocities are calculated and a simple sediment transport model is used to predict the beach topography that would be in equilibrium with these flow patterns as expected crescentic sand bars are produced by the special case of standing edge waves hi h intriguingly for all other cases a combination of complex transverse bars plus meandering or straight offshore bars result patterns that are surprisingly reminiscent of many published descriptions of complex rhythmic topography the extension of the model to three or more waves produces topography that appears to be very irregular although the pattern should repeat over sufficiently long distances along the beach even with only three waves these distances may be very large compared to the scale of the bars

calculation of dispersion curves and amplitude depth distributions of love channel waves in horizontally layered media we present dispersion curves and amplitude depth distributions of the fundamental and first higher mode of love seam waves for two characteristic seam models the first model consists of four layers representing a coal seam underlain by a root clay of variable thickness the second model consists of five layers representing coal seams containing a dirt band with variable position and thickness the simple three layer model is used for reference it is shown that at higher frequencies depending on the thickness of the root clay and the dirt band the coal layers alone act as a wave guide whereas at low frequencies all layers act together as a channel depending on the thickness and position of the dirt band and the root clay in the dispersion curves of the group velocity secondary minima grow in addition to the absolute minima furthermore the dispersion curves of the group velocity of the two modes can overlap in all these cases wave groups in addition to the airy phase of the fundamental mode propagating with minimum group velocity occur on the seismograms recorded in in seam seismic surveys thus impeding their interpretation hence we suggest the estimation of the dispersion characteristics of love seam waves in coal seams under investigation preceding actual field surveys all numerical calculations were performed using a fast and stable phase recursion algorithm

preliminary comparison of ancient bole beds and modern soils developed upon the deccan volcanic basalts around pune india potential for palaeoenvironmental reconstruction abstract relict weathering mantles are frequently preserved in the form of paleosols which generally document the long term evolution of earth surface processes bole beds occur as prominent horizons composed of fine grained clayey or earthy material having colors in shades of red to chocolate brown green purple or gray often marking the flow contacts of deccan basalts which date to approximately 65 ma bole beds preserved between two successive lava flows can be studied relative to soils developed into the same basalts during the holocene the bole beds have slightly lower ph but significantly lower electrical conductivity values and organic matter contents compared to modern soils they also have higher sio 2 and lower al 2 o 3 and h 2 o crystal lattice water content than modern soils results indicate that the bole beds may not have been subjected to intense weathering and long term pedogenesis but nonetheless formed under uniform rainfall with surface runoff exceeding evaporation weathering chemistry suggests different types of protolith for red and green boles the high stratigraphic frequency of bole beds throughout the deccan volcanics makes them an important source of information about the frequency and environment of inter eruption intervals