modification and preservation of environmental signals in speleothems speleothems are primarily studied in order to generate archives of climatic change and results have led to significant advances in identifying and dating major shifts in the climate system however the climatological meaning of many speleothem records cannot be interpreted unequivocally this is particularly so for more subtle shifts and shorter time periods but the use of multiple proxies and improving understanding of formation mechanisms offers a clear way forward

10be and 26al evidence for exceptionally low rates of australian bedrock erosion and the likely existence of pre pleistocene landscapes analysis of in situ produced 10be and 26al demonstrate that some australian inselbergs granitic domes are among the most stable geomorphic surfaces in the world eroding at rates as low as 0 6 m myr twenty isotopic analyses of ten samples suggest that the bare bedrock tops of these isolated granitic domes have been exposed to cosmic radiation for at least 0 5 myr and are eroding at a mean model rate less than 0 7 0 1 m myr n 6 isotopic analyses of samples collected from the top of mt wudinna little wudinna and yarwondutta rock are most consistent with continuous exposure during erosion on the other hand samples collected from the flanks of some domes and the tops of other domes have isotopic abundances suggestive of complex exposure histories including burial and reexposure these unique isotopic data provide the first quantitative information for evaluating longstanding but previously untested hypotheses regarding the antiquity and development of these enigmatic landforms and indicate that some eyre peninsula inselbergs are probably relict features of pre pleistocene landscapes

late paleozoic glacial episodes in gondwanaland reflected in transgressive regressive depositional sequences in euramerica the late paleozoic glaciation of gondwanaland comprised two short episodes in the famennian i and visean ii confined to brazil and adjacent northwest africa and a long episode that started in the namurian iiia of eastern australia and bolivia argentina expanded to cover much of gondwanaland in the stephanian asselian iiib and collapsed in the early sakmarian iiic dropstones in eastern australia indicate that small ice centers lingered to the kazanian across the belt of low latitudes north of gondwanaland short ranging fossils in widespread shallow marine and paralic deposits indicate synchronous deposition of transgressive regressive sequences in different parts of euramerica these sequences correlate with glacial events in gondwanaland at three levels a four major regressions in euramerica in the famennian 1 visean 2 namurian 3 stephanian 4 and the tastubian transgression that preceded the sterlitamakian regression 5 also recorded in gondwanaland correlate with glacial episodes i ii and iiia iiib and iiic b the time interval of cyclothemic deposition in euramerica brigantian or latest visean to sterlitamakian correlates with that of glacial episode iii and c the dominant period of the euramerican cyclothems as estimated from the middle and late pennsylvanian deposits of the mid continent of north america and of the thickest known gondwanaland glacigenic sediment the earliest permian lyons group of western australia is 0 4 ma equivalent in turn to the long orbital eccentricity period of the quaternary ice age and the dominant period of fluctuation of the late miocene antarctic ice cap the three levels of correlations confirm wanless and shepard9s 1936 hypothesis that the late paleozoic cyclothems are controlled largely by sea level fluctuations related to the gondwanaland glaciation

pollen and lignin records of late quaternary vegetation lake washington analyses of lignin oxidation products and pollen for an 11 meter core from lake washington provide independent but similar reconstructions of the late quaternary vegetation in the puget lowland an exception is in sediments of the late pleistocene where pollen percentages and influx values suggest conifer forest whereas lignin compositions suggest a treeless source region this dissimilarity appears to result from different major provenances eolian transport of pollen to the lake from adjacent or downstream drainage basins as opposed to fluvial transport of lignified plant debris only from the lake washington drainage basin

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

short migration of methane into a gas hydrate bearing sand layer at walker ridge gulf of mexico 1 the mechanisms governing distribution of natural gas hydrates in marine sediment systems are not well understood we focus on a hole in the gulf of mexico walker ridge block 313 hole h where a 2 5 m thick gas hydrate bearing sand occurs within a 152 m thick fine grained mud interval containing gas hydrate in fractures the gas hydrate bearing sand is surrounded by two distinct hydrate free zones 10 m thick above and 3 m thick below we hypothesize that microbial methane generated within the hydrate free zones diffused into the sand and formed gas hydrate we show that the amount of methane produced in the hydrate free zones is likely enough to explain the gas hydrate content of the sand layer additionally we show that there is enough time for dissolved methane to diffuse from the hydrate free zones into the sand we conclude that methane transport over significant distances via fluid flow is not required but that microbial methane could migrate short distances to form gas hydrate in the sand layer

linking basin scale and pore scale gas hydrate distribution patterns in diffusion dominated marine hydrate systems the goal of this study is to computationally determine the potential distribution patterns of diffusion driven methane hydrate accumulations in coarse grained marine sediments diffusion of dissolved methane in marine gas hydrate systems has been proposed as a potential transport mechanism through which large concentrations of hydrate can preferentially accumulate in coarse grained sediments over geologic time using one dimensional compositional reservoir simulations we examine hydrate distribution patterns at the scale of individual sand layers 1 20 m thick that are deposited between microbially active fine grained material buried through the gas hydrate stability zone ghsz we then extrapolate to two dimensional and basin scale three dimensional simulations where we model dipping sands and multilayered systems we find that properties of a sand layer including pore size distribution layer thickness dip and proximity to other layers in multilayered systems all exert control on diffusive methane fluxes toward and within a sand which in turn impact the distribution of hydrate throughout a sand unit in all of these simulations we incorporate data on physical properties and sand layer geometries from the terrebonne basin gas hydrate system in the gulf of mexico we demonstrate that diffusion can generate high hydrate saturations upward of 90 at the edges of thin sands at shallow depths within the ghsz but that it is ineffective at producing high hydrate saturations throughout thick greater than 10 m sands buried deep within the ghsz furthermore we find that hydrate in fine grained material can preserve high hydrate saturations in nearby thin sands with burial

origin and morphology of limestone caves limestone caves form along ground water paths of greatest discharge and solutional aggressiveness flow routes that acquire increasing discharge accelerate in growth while others languish with negligible growth as discharge increases a maximum rate of wall retreat is approached typically about 0 01 0 1 cm yr determined by chemical kinetics but nearly unaffected by further increase in discharge the time required to reach the maximum rate is nearly independent of kinetics and varies directly with flow distance and temperature and inversely with initial fracture width discharge gradient and pco2 most caves require 104 105 yr to reach traversable size their patterns depend on the mode of ground water recharge sinkhole recharge forms branching caves with tributaries that join downstream as higher order passages maze caves form where 1 steep gradients and great undersaturation allow many alternate paths to enlarge at similar rates or 2 discharge or renewal of undersaturation is uniform along many alternate routes flood water can form angular networks in fractured rock anastomotic mazes along low angle partings or sponge work where intergranular pores are dominant diffuse recharge also forms networks and spongework often aided by mixing of chemically different waters ramiform caves with sequential outward branches are formed mainly by rising thermal or h2s rich water dissolution rates in cooling water increase with discharge co2 content temperature and thermal gradient but only at thermal gradients of more than 0 01 c m can normal ground water co2 form caves without the aid of hypogenic acids or mixing artesian flow has no inherent tendency to form maze caves geologic structure and stratigraphy influence cave orientation and extent but alone they do not determine branch work versus maze character

gas origin and migration in the ulleung basin east sea results from the second ulleung basin gas hydrate drilling expedition ubgh2 abstract we have investigated the gas chemistry of marine sediments up to 250 m below seafloor m bsf recovered during the second ulleung basin gas hydrate drilling expedition ubgh2 to identify and compare the gas origin and its migration at seismically non chimney truncated chimney and chimney sites in this basin the molecular and isotopic data c1 c2 ratios 300 13 c ch 4 d ch 4 kim et al 2012 and thought to reflect two phase methane transport processes in chimney sites deep sourced methane migrates independently of the carbon dioxide which remains dissolved in the aqueous phase leading to the extremely low c values observed in the upper 30 m bsf upward methane diffusion at non chimney sites may also add a transport induced fractionation as evidenced in mixing diagrams but this process does not significantly affect the c values 13 c co 2 shows usually minimum values at the sulfate methane transition zone smtz at all sites however in chimney sites these values have a much more depleted signature indicating faster rates of methane consumption by anaerobic oxidation of methane aom supported by the higher methane flux moreover here the massive hydrate that forms in shallow sediments incorporates gases with a lower c1 c2 ratio higher c2 c1 than the surrounding sediment as documented in hydrate bound gas bg and void gas vg samples gas hydrate dissociation during the core recovery is released enriched ethane c2h6 trapped in gas cage which leads to have high c2h6 in vg samples

lignin geochemistry of a late quaternary sediment core from lake washington long term lignin stability and paleovegetation patterns were investigated using cuo oxidation products of sediments from an 11 m core of late quaternary sediment collected from the mid basin of lake washington washington state relatively constant yields of lignin derived phenols normalized to organic carbon from the entire core indicate minimal in situ lignin degradation over the last 13 000 years compositional patterns within the phenolic suite and increased corresponding yields from baseextracted sediments indicate that sedimentary lignins are present predominantly as well preserved plant tissue fragments abundance patterns of vanillyl syringyl and cinnamyl phenols record four distinct sequences within the core characterized by 1 a high concentrations of gymnosperm wood in a basal horizon of glacial flour 11 10 m 2 b an essentially pure mixture of nonwoody angiosperm tissues in late pleistocene sediments 10 8 m 3 c relatively high concentrations of angiosperm woods in the bottom half of a limnic peat sequence deposited approximately 10 000 7 000 years b p 8 4 m and 4 d a progressive enrichment in gymnosperm woods at the expense of angiosperm woods over the last 7 000 years in the upper limnic peat 4 0 m vascular plant tissues account for less than half the total sedimentary organic carbon throughout the core

lead 210 sediment geochronology in a changing coastal environment abstract sediment accumulation rate studies utilizing excess 210 pb and 137 cs were conducted as part of recent investigations of biogeochemical cycling at a single site in cape lookout bight a rapidly changing coastal basin on the outer banks of north carolina u s a cores three meters in length reveal a depositional history for the bight interior characterized by a gradual transition in texture from coarse grained to fine grained material over the period 1946 1979 this transition is controlled by progressive enclosure of the bight by an active northerly migrating recurved spit the textural gradation is periodically interrupted by layers of well sorted sand associated with major storm events lead 210 data indicate that the upper meter of the sediment has accumulated at a rate of 3 35 to 4 71 g cm 2 yr 1 or approximately 8 4 to 11 8 cm yr 1 at o 0 84 below 120 cm depth dilution of clay and silt by low activity sand necessitates correction of the 210 pb profile in order to establish a geochronology grain size 210 pb distribution measurements at three depths reveal that the specific activity dpm g 1 of clay is 3 2 times that of silt and 24 7 times that of sand corrections of bulk sediment excess 210 pb activities based on these measurements lead to dates for textural changes which are consistent with charted changes in basin morphology and major storm events sixteen 137 cs measurements between 33 241 cm depth reveal a peak activity at 105 115 cm and indicate a minimum sedimentation rate of approximately 2 7 g cm 2 yr 1

ecological gradients within a pennsylvanian mire forest pennsylvanian coals represent remains of the earliest peat forming rain forests but there is no current consensus on forest ecology localized studies of fossil forests suggest intermixture of taxa heterogeneity while in contrast coal ball and palynological analyses imply the existence of pronounced ecological gradients here we report the discovery of a spectacular fossil forest preserved over 1000 ha on top of the pennsylvanian desmoinesian herrin no 6 coal of illinois united states the forest was abruptly drowned when fault movement dropped a segment of coastal mire below sea level in the largest study of its kind to date forest composition is statistically analyzed within a well constrained paleogeographic context findings resolve apparent conflicts in models of pennsylvanian mire ecology by confirming the existence of forest heterogeneity at the local scale while additionally demonstrating the emergence of ecological gradients at landscape scale

biogeochemical cycling in an organic rich coastal marine basin 6 temporal and spatial variations in sulfate reduction rates rates of sulfate reduction were measured over a 3 year period in the anoxic nearshore sediments of cape lookout bight north carolina using both a tube incubation method and a 35s sulfate direct injection technique the methods yielded similar depth integrated rates over the upper 30 cm ranging from less than 10 mol so 4 m 2 y 1 in winter to greater than 50 mol so 4 m 2 y 1 in summer there were also seasonal changes in the arrhenius activation energies for the sulfate reduction rates indicating that the assumption that ea is constant with temperature is not always valid the time averaged annual turnover rate for all three years was 20 4 11 4 mol so 4 m 2 y 1 surface rates ranged seasonally from less than 0 01 to over 3 mm so 4 d 1 between winter and summer respectively a subsurface rate maximum was observed to develop during the summer months which accounted for 28 percent of the annual depth integrated sulfate reduction rate subsurface rate maxima are the result of changes in the chemistry substrate type and or concentration and the microbiology in the sediments the possibility of the subsurface maximum being an artifact of the 35s method is also discussed however the sulfate reduction rates compare well with previous measurements of the carbon sediment water plus burial fluxes and with a depth integrated co2 production rate modelled from a co2 concentration profile from the same site

pliocene pleistocene incision of the green river kentucky determined from radioactive decay of cosmogenic 26al and 10be in mammoth cave sediments cosmogenic 26al and 10be in sediments washed into mammoth cave kentucky record the history of 3 5 m y of water table position governed by incision and aggradation of the green river a tributary of the ohio river upper levels of the cave formed during a period of slow river incision and were later filled with sediment due to river aggradation at 2 3 2 4 ma a brief surge of river incision ca 2 ma was followed by river stability and cave passage formation at a lower level rapid incision through 15 m of bedrock ca 1 5 ma was prompted by repositioning of the ohio river to its present course along an ice sheet margin renewed incision ca 1 2 ma and aggradation at 0 7 0 8 ma correlate with major ice advances in the ohio river basin measurements of 26al and 10be also indicate that sandstone capped uplands have maintained slow erosion rates of 2 7 m m y for the past 3 5 m y despite accelerated pleistocene river incision rates of 30 m m y

searching for travertines calcretes and speleothems in deep time processes appearances predictions and the impact of plants common models for modern calcite precipitation in and around caves soils springs and streams involve co 2 supplied by thick high p co 2 biogenic soils which were probably thin or non existent before vascular plants indeed plant influenced chemical weathering might have caused accelerated terrestrial carbonate production from the devonian onwards however terrestrial carbonates have also been documented from the archaean proterozoic cambrian ordovician and silurian mechanisms which could have caused non marine carbonates to precipitate without organic rich soils are described and some geological events likely to have influenced non marine carbonate precipitation up to the origin of vascular plants are highlighted as organisms have evolved so have the petrographic characteristics of non marine carbonates some examples of this are also given here

spatial patterns of sediment accumulation on a holocene carbonate tidal flat northwest andros island bahamas abstract to characterize spatial patterns of sedimentation and analyze the morphology of part of the modern tidal flats of northwest andros island in the bahamas this study integrated remote sensing geographic information systems gis and carbonate sedimentology the fundamental data are a landsat tm image that has been classified to create a thematic map of eight subfacies interpreted to represent a distinct tidal flat subenvironment such as adjacent marine exposed levee beach ridge pond and algal marsh spatial statistics of the thematic map characterize the patterns of sediment accumulation quantitative analysis highlights several interesting results concerning subfacies character and distribution 1 of the eight mapped subfacies low algal marsh is most widespread representing 27 5 of the total area whereas exposed levee beach ridge is the least widespread accounting for 10 of the area 2 the patches of different subfacies have different shape complexities with low algal marsh high algal marsh and mangrove ponds being the least complex and exposed levee beach ridge being the most complex 3 markov chain analysis suggests that lateral transitions between different subfacies are highly ordered and 4 frequency distribution of subfacies patch area and lacunarity gap size distribution data exhibit power law relationships over several orders of magnitude consistent with fractal characteristics the fractal nature of patch size and gaps between facies illustrate that on this tidal flat neither the size nor the spatial distribution of subfacies has a characteristic scale this statistical behavior is consistent with the presence of self organization or emergence of pattern in the absence of a template or external forcing the statistical self organization on the tidal flat is the cumulative expression of local processes but it becomes apparent only through analysis of the whole system these results are inconsistent with models suggesting that tidal flats include a migrating complex of randomly distributed randomly sized subenvironments ancient successions that include random patterns may reflect the more pronounced influence of forces external to the sedimentary system instead of an absence of those forces

estimating erosion rates and exposure ages with 36cl produced by neutron activation the isotopic composition of water soluble cl extracted from mineral grains in granitic rocks appears to reflect the relative age of debris flow fan surfaces and the erosion rate of bedrock outcrops our data indicate that some granitic landforms are stable landscape elements eroding on the order of meters to tens of meters per million years samples collected from debris flow fan surfaces of three distinct relative ages show the expected increase of model age with time but the 36cl exposure ages for boulders on any particular surface vary by a factor of more than five the method we used for extracting cl was designed to isolate the 35cl n 36cl production pathway and to simplify the chemical preparation of samples such isolation from fluid inclusions allows direct interpretation of measured 36cl cl ratios but requires a model to predict the thermal neutron production and absorption profile below the rock surface using such a model we find good agreement between measured and predicted 36cl cl for eight samples collected below the ground surface as well as consistency between several groups of samples collected near one another using elemental abundance data for 129 granitic rocks we modeled 36cl cl supported by radiogenic neutrons and find that it varies from 4 to 125 10 15 mean 21 18 1 however from the surface to a depth of 10 m thermal neutrons resulting from muon interactions have the potential to generate more 36cl than do radiogenic neutrons the production of 36cl in the subsurface has important implications for surface exposure dating of young low altitude samples collected from moraines and debris flow or alluvial fans especially at ages where erosion of the boulder surface is significant or where the source area for boulders is at altitudes much higher than the landform to be dated

an experimental approach to the palynology of cave deposits surface sediment speleothems and bat guano from two adjacent topographically different cave sites in eastern spain have been studied palynologically to elucidate the potential of cave sediments for palaeoenvironmental reconstruction a cave opening with a large entrance and constant width presented far fewer problems of alteration in the pollen assemblages than a sac like cave opening with a constricted entrance pollen concentration is linked primarily to the amount of pollen input rather than to the result of post depositional alteration sampling should be undertaken away from parietal and rear areas and avoiding moisture zones lateral differences in the pollen spectra indicate that sampling should be on the basis of a multiple profile approach and selection of dry rather than wet sediments if these procedures are followed within cave sediments can realistically reflect not only local but also regional vegetation of the site copyright 2000 john wiley sons ltd

sources and distributions of sedimentary organic matter in the columbia river drainage basin washington and oregon1 nonwoody angiosperm tissues and gymnosperm woods are the major types of vascular plant debris in bottom sediments from 16 sites within the columbia river and its tributaries in tributary sediments relative abundances of these types of tissue vary regionally and are consistent with drainage basin vegetation within the extensively dammed main river vascular plant debris mixtures are more uniform indicating downstream mixing of sedimentary material from reservoir to reserwoir vascular plant tissues account for an average of a third of the total sedimentary organic matter at the 16 river sites the remaining organic material has an atomic c n of 10 l 5 and a stable carbon isotope composition similar to average land plants organic matter in sediments of the columbia river system is generally enriched in nonwoody angiosperm tissues and ligninpoor organic matter in comparison to columbia river derived organic matter in modern marine sediments from the southern washington continental shelf

role of sediment in speleogenesis sedimentation and paragenesis although the effects of sedimentation in caves have been recognised for many years its role in speleogenesis is frequently overlooked influxes of sediment into a cave system fundamentally alter the way cave passages develop either by alluviation in a vadose environment forcing lateral corrosion and the development of notches or by upwards dissolution in a phreatic environment through a process known as paragenesis sediment influxes affect the hydrological functioning of a karst aquifer by changing the way conduits behave and subsequently develop both in plan and long section here we give an overview of the mechanisms of cave sedimentation and describe how the process of alluviation and paragenesis affect speleogenesis a characteristic suite of meso and micro scale dissolutional features can be used to recognise paragenetic development which is reviewed here in a vadose environment these include alluvial notches whilst in a phreatic environment half tubes anastomoses and pendants bedrock fins and paragenetic dissolution ramps result using these to identify phases of sedimentation and paragenesis is crucial for reconstructing denudation chronologies from cave deposits we suggest that sedimentation and paragenesis are most likely to occur in certain geomorphological situations such as ice marginal and periglacial environments beneath thick residual soils and where rivers can transport fluvial sediment into a cave either via stream sinks or back flooding

biogeochemical cycling in an organic rich coastal marine basin 7 sulfur mass balance oxygen uptake and sulfide retention sulfur and oxygen fluxes were quantified in the seasonally varying anoxic marine sedimentary system of cape lookout bight n c u s a over the three year study period 1981 1983 the mean annual sulfate reduction rate was determined to be 18 2 1 6 moles m 2 y 1 this value added to the estimate of the detrital sulfur input of 1 2 4 4 gave a total sulfur input of 19 4 4 7 moles m 2 y 1 the sulfide flux to the sediment water interface measured in anaerobic benthic chambers was 4 6 0 5 moles m 2 y 1 and represented 37 of the annual oxygen uptake rate of 25 2 2 8 moles m 2 y 1 the sulfide burial rate determined to be 15 5 3 1 moles m 2 y 1 was within 5 of the value predicted by summing the fluxes at the sediment water interface the cs weight ratio of sediment below the depth of diagenetic reaction was determined to be 2 75 the sulfide retention rate in these rapidly accumulating sediments 10 cm yr was 77 19 comparison of this result with previous studies shows that rapid sediment accumulation and the lack of bioturbation control this unusually high degree of sulfide retention

the impact of lithification on the diversity size distribution and recovery dynamics of marine invertebrate assemblages lithified marine sediments are not equitably distributed through time raising the possibility that lithification masks biological signals when data from unlithified and lithified sediments are compared or combined using mollusk dominated assemblages from the early cenozoic of the gulf coastal plain we find that lithification conceals small taxa decreases taxonomic resolution and exacerbates the undersampling of rare taxa lithified assemblages appear less diverse and have less even abundance distributions than coeval unlithified samples these limitations cannot be overcome by standardization procedures nor are they likely to be circumvented by collecting larger samples the effects of this bias however can be mitigated by restricting analyses to a single lithification state or to specific size classes since lithification selectively obscures small taxa the magnitude of this bias will be most severe when organisms are particularly small such as in the aftermath of mass extinctions in the study area lithification artificially protracts the recovery period following the cretaceous paleogene mass extinction by 7 m y

late quaternary paleoecology and paleoenvironments of the central mississippi alluvial valley a radiocarbon dated sediment core from powers fort swale located in the western lowlands of southeastern missouri provides sedimentological and palynological evidence for dynamic changes in fluvial regime and vegetation in the central mississippi alluvial valley during the late pleistocene and holocene intervals during the late wisconsinan glacial maximum glacial meltwater carried by the mississippi river maintained active braided streams sand grains in full glacial and late glacial sediments of powers fort swale show evidence of reworking by eolian activity with late pleistocene formation of sand dunes continuing until 11 600 yr b p within the western lowlands the sedimentological sequence indicates a progressive stepwise loss of glacial meltwater and coarse sediment supply during the late glacial interval resulting in abandonment of braided stream terraces the initial partial diversion of mississippi river flow occurred in the late glacial interval possibly as early as 16 300 yr b p as the mississippi river shifted from the western lowlands through the bell city oran gap in crowleys ridge and into the eastern lowlands by 14 500 yr b p the complete diversion of meltwater through this gap coincided with a change in the powers fort sediment core from a spruce dominated to an oak dominated pollen assemblage at 11 500 yr b p sedimentological changes reflected a changeover to a meandering river regime the transition to pollen assemblages characteristic of holocene temperate swamp forest occurred at 9500 yr b p

sedimentary corg p ratios paleocean ventilation and phanerozoic atmospheric po2 the corg p ratios of organic rich facies tocn1 exhibit considerable variation through the phanerozoic from b10 1 in the permian phosphoria formation to n1000 1 in some devonian black shales relative to the composition of phytoplankton c p 106 1 which provide the bulk of organic c and p to organic rich marine sediments the range of phanerozoic sedimentary corg p ratios largely reflects the influence of benthic redox conditions on diagenetic pathways of c and p remobilization enhanced preservationoforganiccatlowerredoxpotentials combinedwithenhancedsedimentaryretentionofremineralizedorganicpathigher redox potentials results in a strong relationship between benthic redox conditions and sedimentary corg p ratios the strong secular coherence of the phanerozoic corg p record i e limited variation within narrow time slices suggests that these ratios are controlled primarily by factors influencing benthic redox conditions on a global scale such as atmospheric po2 inversion and scaling of the phanerozoic corg p record yields a new atmospheric po2 model that has strong similarities to existing models based on elemental and isotopic mass balances yet differs in some potentially significant respects in particular the new model suggests that atmospheric po2 wasmarkedlylowerduringtheearlytomiddlepaleozoicthanpreviouslyinferred duringmostofthedevonian atmospherico2levels mayhavebeensufficientlylow b13 astopreventthesustainedcombustionofplantmaterial thisfeatureofthemodelmayaccount for ananomalous gapinthefossilcharcoalrecordduringthedevonian theredox dependentburialofpintheoceanresults inpositive and negative feedback mechanisms that tend to stabilize atmospheric oxygen concentrations on geologic timescales temporal variations in the burial of p relative to c suggest that the strength of these feedback mechanisms varied over the phanerozoic 2007 elsevier b v all rights reserved

lignin phenols in sediments of lake baikal siberia application to paleoenvironmental studies abstract sediments from three cores obtained from distinct depositional environments in lake baikal siberia were analyzed for organic carbon total nitrogen and lignin phenol concentration and composition results were used to examine changes in paleoenvironmental conditions during climatic cycles of the late quaternary c n ratios and organic carbon accumulation rates were significantly higher in the holocene compared with the late pleistocene reflecting overall warmer temperatures and increased runoff during the holocene a holocene maximum in organic carbon was observed at about 6 ka and may represent the warmest wettest period of the holocene at one site academician ridge pronounced late pleistocene maxima in organic carbon and biogenic silica were observed at about 80 85 ka probably indicative of an interstadial period with enhanced aquatic productivity total sedimentary lignin phenol contents were generally lower in the late pleistocene compared to the holocene but with several peaks in concentration during the late pleistocene these late pleistocene peaks in total sedimentary lignin content dated at about 80 50 and 30 ka directly precede or occur during peaks in sedimentary biogenic silica contents these periods likely represent relatively warm interstadial times with increased precipitation producing the observed increase in terrestrial runoff and aquatic productivity lignin phenol ratios s v c v and p v were used to examine changes in terrestrial vegetation type resulting from changes in paleoenvironmental conditions during the late pleistocene a degree of caution must be used in the interpretation of these ratios with regard to vegetation sources and paleoenvironmental conditions because of potential compositional changes in lignin resulting from biodegradation nevertheless results show that long glacial periods were characterized by terrestrial vegetation composed of a mix of non woody angiosperm vegetation and minor gymnosperm forest shorter interstadial periods are defined by a change to dominant gymnosperm forest and were observed at about 80 75 63 50 and 30 ka ranging from about 2 6 kyr in duration these interstadial periods of the late pleistocene defined by lignin phenol ratios generally occur during longer periods of enhanced sedimentary biogenic silica content about 10 15 ka in duration providing corroborative evidence of these warm interstadial periods

north american glacial meltwater history for the past 2 3 m y oxygen isotope evidence from the gulf of mexico a high resolution 18 o record from the northeastern gulf of mexico ocean drilling program leg 100 hole 625b provides a history of surface waters for the past 5 35 m y negative 18 o anomalies between 0 3 and 3 0 in planktic foraminifera beginning at 2 30 ma can only have resulted from the discharge of isotopically light glacial meltwater from the mississippi river meltwater anomalies implicate either the periodic presence of north american mid latitude glacial ice since the late pliocene or a drainage system very different from that of the present

characterization of gas hydrate reservoirs by integration of core and log data in the ulleung basin east sea abstract examinations of core and well log data from the second ulleung basin gas hydrate drilling expedition ubgh2 drill sites suggest that sites ubgh2 2 2 and ubgh2 6 have relatively good gas hydrate reservoir quality in terms of individual and total cumulative thicknesses of gas hydrate bearing sand hybs beds in both of the sites core sediments are generally dominated by hemipelagic muds which are intercalated with turbidite sands the turbidite sands are usually thin to medium bedded and mainly consist of well sorted coarse silt to fine sand anomalies in infrared core temperatures and porewater chlorinity data and pressure core measurements indicate that gas hydrate occurrence zones ghoz are present about 68 155 mbsf at site ubgh2 2 2 and 110 155 mbsf at site ubgh2 6 in both the ghoz gas hydrates are preferentially associated with many of the turbidite sands as pore filling type hydrates the hybs identified in the cores from site ubgh2 6 are medium to thick bedded particularly in the lower part of the ghoz and well coincident with significant high excursions in all of the resistivity density and velocity logs gas hydrate saturations in the hybs range from 12 to 79 with an average of 52 based on pore water chlorinity in contrast the hybs from site ubgh2 2 2 are usually thin bedded and show poor correlations with both of the resistivity and velocity logs owing to volume averaging effects of the logging tools on the thin hybs beds gas hydrate saturations in the hybs range from 15 to 65 with an average of 37 based on pore water chlorinity in both of the sites large fluctuations in biogenic opal contents have significant effects on the sediment physical properties resulting in limited usage of gamma ray and density logs in discriminating sand reservoirs

lignin geochemistry of north american coastal and continental shelf sediments abstract the concentrations and composition of lignin in coastal and shelf sediments at five locations along the north american continent georges bank north atlantic shelf northwestern gulf of mexico southern california norton sound and nearshore beaufort sea have been characterized using alkaline cuo oxidation lignin concentrations are generally highest at close proximity to the mouth of major rivers indicating that deposition of river borne vascular plant debris is the principal source of lignin to the offshore sediments arctic sediments contain the highest concentrations presumably as a result of an abundant supply of terrestrial organic material and the prevalence of frigid temperatures and surface ice cover during much of the year concentrations are lowest in the georges bank north atlantic sediments where a dynamic physical environment persists over much of the year and the supply of terrestrial organic matter to the offshore in the form of major rivers is lacking stable carbon isotopic compositions show that sediments containing the highest lignin concentrations also contain isotopically lighter organic matter consistent with a terrestrial source input vanillyl syringyl and cinnamyl phenol distributions in these offshore sediments are consistent with primary contributions from gymnosperm predominant and angiosperm woods and secondary contributions from nonwoody tissues these estimates may be subject to some uncertainty due to diagenetic alteration of individual lignin phenols in contrast p hydroxyl phenol yields are not strongly correlated with those of the other lignin derived phenols suggesting generation from both lignin and non lignin sources elevated acid aldehyde ratios relative to undegraded plant tissues suggest that the lignin transported to these offshore sediments has undergone some biodegradative oxidation

macrostratigraphy of north america abstract the geological record is a three dimensional mosaic of gap bound rock bodies that at any given scale of temporal resolution were emplaced more or less continuously at any geographic location the irregular alternation of processes responsible for the formation and destruction of rock bodies results in the preservation of hiatus bound rock packages that have a distinct time of first occurrence base or oldest portion a time of last occurrence top or youngest portion and a suite of defining characters e g lithologies thickness fossils etc many important aspects of the geologic record can be quantified by compiling the stratigraphic ranges of such gap bound rock packages these include the quantity and spatial and temporal distribution of preserved rock rates of rock formation sequence stratigraphic architecture and area weighted rates of expansion and contraction erosional truncation of rock emplacement settings this approach to characterizing the rock record is scalable per

quaternary downcutting rate of the new river virginia measured from differential decay of cosmogenic 26al and 10be in cave deposited alluvium the concentrations of the cosmogenic radionuclides sup 26 al and sup 10 be in quartz can be used to date sediment burial here we use sup 26 al and sup 10 be in cave deposited river sediment to infer the time of sediment emplacement sediment burial dates from a vertical sequence of caves along the new river constrain its quaternary downcutting rate to 27 3 4 5 m m y and may provide evidence of regional tectonic tilt 32 refs 3 figs 1 tab

biogeochemical cycling in an organic rich coastal marine basin 8 a sulfur isotopic budget balanced by differential diffusion across the sediment water interface abstract the sulfur isotopic composition of the sulfur fluxes occurring in the anoxic marine sediments of cape lookout bight n c u s a was determined and the result of isotopic mass balance was obtained via the differential diffusion model seasonal pore water sulfate 34 s measurements yielded a calculated sulfate input of 0 6 sulfate transported into the sediments via diffusion appeared to be enriched in the lighter isotope because its concentration gradient was steeper due to the increase in the measured isotopic composition of sulfate with depth similarly the back diffusion of dissolved sulfide towards the sediment water interface appeared enriched in the heavier isotope the isotopic composition of this flux was calculated from measurements of the 34 s of dissolved sulfide and was determined to be 15 9 the isotopic composition of buried sulfide was determined to be 5 2 and the detrital sulfur input was estimated to be 6 2 an isotope mass balance equation based upon the fluxes at the sediment water interface successfully predicted the isotopic composition of the buried sulfur flux within 0 5 thus confirming that isotopes diffuse in response to their individual concentration gradients

karst related outliers of the cretaceous chaswood formation of maritime canada the lower cretaceous chaswood formation is a terrestrial deposit preserved as scattered outcrops across maritime canada here we describe newly recognized outliers of the chaswood formation near windsor nova scotia a cretaceous age is confirmed only in bailey quarry where sediments are provisionally assigned a valanginian hauterivian 140 130 ma age based on palynology making them among the oldest known deposits of the chaswood formation at three nearby sites putative cretaceous sediments are recognized based on similar geological context facies and petrography however their age cannot be confirmed because sediments either lack palynomorphs or contain equivocal assemblages although the chaswood formation has been previously documented mainly in small tectonically generated basins these new found deposits are fluvial sands and gravels and lacustrine or floodplain clays associated with a karstified gypsum surface developed on the carboniferous windsor group deposits are preserved in karst val

culture based investigations of key microbial functional groups in gas hydrate bearing sediments of the krishna godavari basin in offshore india abstract results of national gas hydrate program 02 nghp 02 expedition have confirmed the resource potential of sand hosted gas hydrate accumulations in the deep offshore of krishna godavari basin kg basin nghp 02 has identified two types of gas hydrate accumulations one is thick layer type units developed in sand rich facies at depths of a few 100 m below sea floor mbsf and the other fracture type unit of variable thickness at shallow depths fracture type and layer type gas hydrates were observed in areas b c and e in the kg basin as defined under nghp 02 the importance of each type of gas hydrate occurrence as discovered during nghp 02 has led to the need for microbial profiling different classes of microbes anaerobic fermentative microbes afm methanotrophs and sulphate reducing bacteria srb were studied to understand the microbial system for biogenic gas generation in sedimentary sequences encountered in eight core holes 4 in area b 3 in area c and 1 in area e as established during nghp 02 this study reveals the availability of highest concentration of methane generating microbes that are closely associated with high total organic carbon toc content in the identified gas hydrate bearing sedimentary units cored in each borehole the presence of microbial consortia for methane generation through both processes of reduction of co2 and fermentation of formate acetate has been confirmed stratigraphic correlation between drill sites have also been generated to better understand the spatial relationship of various microbial processes an observation from the study is that the entire late miocene age sediments has potential to generate biogenic gas in holes nghp 02 05b 17b 22b and 23b late to early pleistocene age sediments are showing methane generating activity in holes nghp 02 01c 08b and 09b while early pleistocene to late pliocene age sediments contains methane generating microbes in holes nghp 02 05b 17b 19b 22b and 23b the existence of methane generating biogenic microbial system in areas b c and e of kg basin has been confirmed

a model for the diffusive growth of hydrate saturation anomalies in layered sediments 1 sediment particles affect the phase behavior of gas hydrates both by increasing the surface energy where pore geometry forces hydrate crystals to attain high curvatures and through wetting interactions that cause aqueous films to coat particle surfaces these effects produce only slight changes to the gas solubility through most of the hydrate stability zone so the particle size has only a modest influence on the rate of hydrate accumulation when the sediments are homogeneous in hydrate reservoirs however discontinuous changes in sediment properties are common and such stratigraphic boundaries often coincide with hydrate anomalies these anomalies are a natural consequence of variations in subsurface sediment properties by accounting for sediment hydrate interactions i show how compositional diffusion supplies the growth of hydrate spikes in coarse grained sediments immediately adjacent to hydrate free regions hfrs in more fine grained sediments where the solubility is slightly elevated over timescales comparable with milankovitch cycles hydrate spikes are typically less than a meter in width and contain essentially all of the hydrate that would have otherwise occupied the much larger adjacent hfr if sediment heterogeneities were absent hydrate can form in the more fine grained sediments only once the spike achieves a sufficiently high saturation level often 90 of pore volume that the solubility is continuous across the stratigraphic boundary the wetting interactions that stabilize much of the residual liquid when hydrate forms an interconnected skeleton spanning many pore diameters can also partially unload sediment particle contacts and lead to the growth of segregated hydrate nodules and lenses

earliest laterites and possible evidence for terrestrial vegetation in the early proterozoic paleosols preserve information about the composition of the atmosphere and paleoclimatic conditions here we report the discovery of the first pisolitic laterites of precambrian age the laterites are immediately above the regional unconformity at the base of the early proterozoic gamagara formation in paleokarst depressions on the campbellrand dolomite transvaal supergroup south africa the paleosol profiles are very well preserved and show zoning relict soil textures and chemical composition virtually identical to those of modern laterites the pisolitic laterites provide not only evidence for a highly oxygenated atmosphere and possible hot and humid climatic conditions in early proterozoic time but also indicate the presence of terrestrial life on the kaapvaal craton 2 0 2 2 b y ago

a middle proterozoic palaeokarst unconformity and associated sedimentary rocks elu basin northwest canada a major palaeokarst erosion surface is developed within the middle proterozoic elu basin northwestern canada this palaeokarst is named the sub kanuyak unconformity and truncates the parry bay formation a sequence of shallow marine dolostones that were deposited within a north facing carbonate platform under a semi arid climate the sub kanuyak unconformity exhibits up to 90 m of local relief and also formed under semi arid conditions when parry bay dolostones were subaerially exposed during a relative sea level drop of about 180 m caves and various karren developed within the meteoric vadose and phreatic zones their geometry size and orientation were largely controlled by northwest and northeast trending antecedent joints bedding and lithology near surface caves later collapsed forming valleys and intervening towers or walls and plains minor terra rossa formed on top of highs karstification was most pronounced in southern parts of bathurst inlet but decreased northward probably reflecting varying lengths of exposure time along a north dipping slope the kanuyak formation is up to 65 m thick and partially covers the underlying palaeokarst it consists of six lithofacies i breccia formed during collapse of caves as reworked collapse breccia and regolith ii conglomerate representing gravel dominated braided fluvial deposits iii sandstone deposited as braided fluvial and storm dominated lacustrine deposits iv interbedded sandstone siltstone and mudstone of sheet flood origin v dolostones formed from dolocretes and quiet water lacustrine deposits and vi red beds representing intertidal marine mudflat deposits rivers flowed toward the northwest and northeast within karst valleys and caves lakes were also situated within valleys marine mudflat sediments completely cover the palaeokarst to the north a regional correlation of the sub kanuyak unconformity with the intra greenhorn lakes disconformity within the coppermine homocline suggests that similar styles of karstification occurred over an extensive region the elu basin palaeokarst however was developed more landward and was exposed for a longer period of time than the coppermine homocline palaeokarst

estimation of the global amount of submarine gas hydrates formed via microbial methane formation based on numerical reaction transport modeling and a novel parameterization of holocene sedimentation this study provides new estimates for the global offshore methane hydrate inventory formed due to microbial ch4 production under quaternary and holocene boundary conditions a multi 1d model for particular organic carbon poc degradation gas hydrate formation and dissolution is presented the novel reaction transport model contains an open three phase system of two solid compounds organic carbon gas hydrates three dissolved species methane sulfates inorganic carbon and one gaseous phase free methane the model computes time resolved concentration profiles for all compounds by accounting for chemical reactions as well as diffusive and advective transport processes the reaction module builds upon a new kinetic model of poc degradation which considers a down core decrease in reactivity of organic matter various chemical reactions such as organic carbon decay anaerobic oxidation of methane methanogenesis and sulfate reduction are resolved using appropriate kinetic rate laws and constants gas hydrates and free gas form if the concentration of dissolved methane exceeds the pressure temperature and salinity dependent solubility limits of hydrates and or free gas with a rate given by kinetic parameters global input grids have been compiled from a variety of oceanographic geological and geophysical data sets including a new parameterization of sedimentation rates in terms of water depth we find prominent gas hydrate provinces offshore central america where sediments are rich in organic carbon and in the arctic ocean where low bottom water temperatures stabilize methane hydrates the world s total gas hydrate inventory is estimated at 0 82 x 10sup13 m3 2 10 x 10sup15 m3 ch4 at stp conditions or equivalently 4 18 995 gt of methane carbon the first value refers to present day conditions estimated using the relatively low holocene sedimentation rates the second value corresponds to a scenario of higher quaternary sedimentation rates along continental margins our results clearly show that in situ poc degradation is at present not an efficient hydrate forming process significant hydrate deposits in marine settings are more likely to have formed at times of higher sedimentation during the quaternary or as a consequence of upward fluid transport at continental margins

mount elbert gas hydrate stratigraphic test well alaska north slope overview of scientific and technical program abstract the mount elbert gas hydrate stratigraphic test well was drilled within the alaska north slope ans milne point unit mpu from february 3 to 19 2007 the well was conducted as part of a cooperative research agreement cra project co sponsored since 2001 by bp exploration alaska inc bpxa and the u s department of energy doe in collaboration with the u s geological survey usgs to help determine whether ans gas hydrate can become a technically and commercially viable gas resource early in the effort regional reservoir characterization and reservoir simulation modeling studies indicated that up to 0 34 trillion cubic meters tcm 12 trillion cubic feet tcf gas may be technically recoverable from 0 92 tcm 33 tcf gas in place within the eileen gas hydrate accumulation near industry infrastructure within ans mpu prudhoe bay unit pbu and kuparuk river unit kru areas to further constrain these estimates and to enable the selection of a test site for further data acquisition the usgs reprocessed and interpreted mpu 3d seismic data provided by bpxa to delineate 14 prospects containing significant highly saturated gas hydrate bearing sand reservoirs the mount elbert site was selected to drill a stratigraphic test well to acquire a full suite of wireline log core and formation pressure test data drilling results and data interpretation confirmed pre drill predictions and thus increased confidence in both the prospect interpretation methods and in the wider ans gas hydrate resource estimates the interpreted data from the mount elbert well provide insight into and reduce uncertainty of key gas hydrate bearing reservoir properties enable further refinement and validation of the numerical simulation of the production potential of both mpu and broader ans gas hydrate resources and help determine viability of potential field sites for future extended term production testing drilling and data acquisition operations demonstrated that gas hydrate scientific research programs can be safely effectively and efficiently conducted within ans infrastructure the program success resulted in a technical team recommendation to project management to drill and complete a long term production test within the area of existing ans infrastructure if approved by stakeholders this long term test would build on prior arctic research efforts to better constrain the potential gas rates and volumes that could be produced from gas hydrate bearing sand reservoirs

palynological evidence for late miocene pliocene and early pleistocene climate changes in the middle u s atlantic coastal plain abstract palynomorph assemblages from eight geologic formations in the middle atlantic coastal plain ranging in age from latest miocene to early pleistocene have been interpreted in terms of terrestrial paleoclimates the data suggest that a warm temperate to subtropical climate warmer than at present prevailed at the close of the miocene and the beginning of the pliocene at that time there was little or no temperature gradient within the study area 36 30 to 39 n this warm period was followed by a warm temperate interval in virginia and north carolina with temperatures probably not very different from those of today although a slight warming trend probably occurred during the deposition of the colerain beach member of the chowan river formation a definite cool interval is indicated by the presence of spruce pollen in the bacons castle formation of virginia this interval is interpreted to have begun about 2 3 2 4 ma or possibly slightly later simultaneous with the cooling that has been recorded in deep sea cores of the north atlantic ocean and in the pre tiglian of western europe this was followed by a warmer than present period that may be correlated with the tiglian of the latest pliocene finally palynological data from the cape may formation of new jersey suggest that a warm temperate warmer than at present climate prevailed during the early pleistocene

stratigraphy and geochronology of pitfall accumulations in caves and fissures bermuda abstract deep fractures fissures and avens skylights in limestone cave roofs create natural traps for sediments and biota fissures fill quickly with surface sediment and organisms soon after opening debris cones are formed as materials fall wash or drift on air through openings in cave skylights such deposits in admiral s and grand canyon cave bermuda contain distinct beds and are composed of mixtures of sediment and charcoal together with fossils of land snails crabs birds reptiles and bats the pitfall accumulations were periodically sealed over by calcite flowstone a stratigraphic record of surface activity and fauna through both glacial and interglacial periods has been preserved the succession also provides an ideal setting in which to compare several geochronological methods calibrated 14 c ages on charcoal and shells provide dated horizons at 1600 12 800 and about 35 000 14 c yr bp thermal ionization mass spectrometric tims ages on several flowstone layers constrain the entire sequence in the admiral s cave sequence between 126 300 900 yr termination ii and historical times a continuous relative age record generated by amino acid epimerization aae geochronology d alloisoleucine l isoleucine or aile ile on the pulmonate land gastropod poecilozonites verifies the biostratigraphy reveals a minimal degree of mixing between stratigraphic units and establishes an independent temporal link between the subterranean and subaerial deposits of bermuda this convergence between stratigraphy and geochronology yields a precisely dated succession from the oceanic island of bermuda and thus presents a unique opportunity to assess the rates and processes of evolutionary and climate change during that interval

morphogenesis of hypogenic caves abstract hypogenic speleogenesis is the formation of solution enlarged permeability structures by waters ascending to a cave forming zone from below in leaky confined conditions where deeper groundwaters in regional or intermediate flow systems interact with shallower and more local groundwater flow systems this is in contrast to more familiar epigenic speleogenesis which is dominated by shallow groundwater systems receiving recharge from the overlying or immediately adjacent surface hypogenic caves are identified in various geological and tectonic settings formed by different dissolutional mechanisms operating in various lithologies despite these variations resultant caves demonstrate a remarkable similarity in patterns and meso morphology which strongly suggests that the hydrogeologic settings were broadly identical in their formation hypogenic caves commonly demonstrate a characteristic suite of cave morphologies resulting from rising flow across the cave forming zone with distinct buoyancy dissolution components in addition to hydrogeological criteria hydrostratigraphic position recharge discharge configuration and flow pattern viewed from the perspective of the evolution of a regional groundwater flow system morphogenetic analysis is the primary tool in identifying hypogenic caves cave patterns resulting from ascending transverse speleogenesis are strongly guided by the permeability structure in a cave formation they are also influenced by the discordance of permeability structure in the adjacent beds and by the overall hydrostratigraphic arrangement three dimensional mazes with multiple storeys or complex 3 d cave systems are most common although single isolated chambers passages or crude clusters of a few intersecting passages may occur where fracturing is scarce and laterally discontinuous large rising shafts and collapse sinkholes over large voids associated with deep hydrothermal systems are also known hypogenic caves include many of the largest by integrated length and by volume documented caves in the world more importantly hypogenic speleogenesis is much more widespread than it was previously presumed growing recognition of hypogenic speleogenesis and improved understanding of its peculiar characteristics has an immense importance to both karst science and applied fields as it promises to answer many questions about karst porosity especially as deep seated settings are concerned which remained poorly addressed within the traditional epigenetic karst paradigm

u series dating and taphonomy of quaternary vertebrates from brazilian caves abstract the geochronology and taphonomy of internationally important fossil bearing cave deposits were studied both in the semi arid northern bahia area and the subtropical southeastern lagoa santa area of brazil taphonomic analysis suggests that the processes responsible for bone accumulation in the brazilian caves vary between sites and taphonomic bias can therefore be significant in causing differences in faunal composition in the toca da boa vista caves the presence of single articulated skeletons and the entrance related distribution indicate that random penetration of animals is the main mechanism of fossil accumulation a process that biases the assemblage to smaller species and takes place over extended time periods in nearby toca dos ossos cave transport by runoff in the cave river is predominant and biases the fauna remains to larger more robust bones and species deposition probably also occurred only at times of enhanced runoff giving a more contemporaneous assemblage similar processes were responsible for emplacement of the copious fossil remains in the more humid lagoa santa area where terrigenous fossil deposits are found intercalated by massive speleothem calcite layers in this area runoff under a drier climate probably accounts for the sediment emplacement inside caves in both areas the mode of emplacement implies bias in the fossil record resulting in fossil assemblages that do not mirror surface faunas limiting palaeoenvironmental reconstruction mass spectrometric u series analysis of speleothem calcite overlaying fossil remains gives minimum ages for fossil deposition these ages confirm the previous view that many of the deposits derive from the late glacial but also show that much older material some 350 000 yr is also present the habitat requirements of critical fossil species such as bats and monkeys strongly suggest that they derive from much wetter periods when forest cover was present in the currently semi arid northern bahia area taphonomy exerts a major control on the diversity and mode of emplacement of cave fossil deposits in eastern brazil and thus detailed sedimentological and hydrological studies coupled with a sound geochronological approach are essential in quantifying the relative importance of each taphonomic processes before faunal and palaeoecological interpretations can be attempted

pennsylvanian coniferopsid forests in sabkha facies reveal the nature of seasonal tropical biome pennsylvanian fossil forests are known from hundreds of sites across tropical pangea but nearly all comprise remains of humid coal forests here we report a unique occurrence of seasonally dry vegetation preserved in growth position along 5 km of strike in the pennsylvanian early kasimovian missourian of new mexico united states analyses of stump anatomy diameter and spatial density coupled with observations of vascular traces and associated megaflora show that this was a deciduous mixed age coniferopsid woodland 100 trees per hectare with an open canopy the coniferopsids colonized coastal sabkha facies and show tree rings confirming growth under seasonally dry conditions such woodlands probably served as the source of coniferopsids that replaced coal forests farther east in central pangea during drier climate phases thus the newly discovered woodland helps unravel biome scale vegetation dynamics and allows calibration of climate models

terrestrial plant biopolymers in marine sediments the vascular land plant biopolymers lignin and cutin were surveyed in the surface sediments of coastal and open ocean waters by controlled alkaline cuo oxidation reaction two contrasting oceanic regimes were studied the northwest mediterranean nwm sea which receives significant particulate terrigenous debris through riverine discharge and the northeast atlantic nea ocean with poorly characterised terrestrial carbon inputs in the nwm products of lignin and cutin co occurred at all stations elevated levels ca 0 5 3 0 mg lignin phenols 100 mg organic carbon ca 0 01 0 09 mg cutin acids 100 mg organic carbon were observed for near shore deltaic and shelf sediments the influence of terrestrial land plant inputs extended across the shelf and through the slope to the abyssal plain providing molecular evidence for advective offshore transfer of terrestrial carbon mass balance estimates for the basin suggest riverine inputs account for the majority of surface sedimentary lignin cutin most of which 90 is deposited on the shelf products of cuo oxidation of lignin and cutin were also detected in nea surface sediments at levels comparable to those observed for the nwm continental slope and were detectable at low concentrations ca 0 5 gg 1 in the sediments of the abyssal plains 4 000 m depth while atmospheric deposition of lignin cutin derived material cannot be discounted in this open ocean system lateral advective transfer of enriched shelf sediments is inferred as a possible transport process a progressive enrichment in cutin derived material relative to lignin was observed offshore with evidence of an increase in the degree of oxidative alteration of lignin residues to account for these observations preferential offshore transport of finer and more degraded material is proposed nonspecific oxidation products dominated the gas chromatograms of nea sediments which appear to originate from marine sources of sedimentary organic carbon preliminary mass balance calculations applied to the global ocean margin suggest riverine sources of both particulate lignin and cutin are important and that most 95 deposition of recognisable land plant biopolymers occurs in shelf seas

covariation in macrostratigraphic and macroevolutionary patterns in the marine record of north america students of earth history have long recog nized the correlation between the quantity of preserved sedimentary rock and the diversity of life recorded as fossils but paleontologists have yet to determine whether this pattern refl ects a causal relationship or a unidirec tional sampling bias in fossil data imposed by preserved rock quantity distinguishing between these two alternatives has been com plicated by the fact that many of the basic patterns of paleontologic and lithologic co variation have yet to be quantifi ed rigorously here we present the fi rst analyses of the co variation between the macrostratigraphic and macroevolutionary histories of north america based on geographically and tem porally explicit co occurrences of rocks and fossils the analyses use independent quan titative summaries of the stratigraphic and fossil records by integrating the paleobiology database paleodb and macrostrat a mac rostratigraphy database for north america which allows a more direct comparison of the stratigraphic and biological histories of the continent than has heretofore been possible within the macrostrat database the rock re cord is divided into discrete packages of sedi ment that are bound by hiatuses resolvable at the stage level using per interval per pack age rates of sediment package initiation and truncation and genus fi rst and last appear ances herein regional origination and extinc tion we fia substantially stronger positive correlation between sediments and biology for extinction like parameters than we do for origination like parameters four of the largest coincident pulses of regional extinc tion and sediment truncation occur during the widely recognized end ordovician late permian end triassic and end cretaceous mass extinction intervals a further compari son of the global ranges of north american genera to north american macrostratigra phy indicates that the regional and global extinction of genera are more likely to oc cur in the same stage than are global and regional originations together these results suggest that our general understanding of biodiversity dynamics from the fossil record may not be strongly biased by the preserva tion of sediments and leaves open the pos sibility that certain large perturbations to the earth system are responsible for major changes of state in both the sedimentary and biological systems

biogeochemical cycling in an organic rich coastal marine basin 9 sources and accumulation rates of vascular plant derived organic material abstract the sources degradation and burial of vascular plant debris deposited over the past several decades in the lagoonal sediments of cape lookout bight north carolina are quantified using alkaline cupric oxide lignin oxidation product lop analysis non woody angiosperms accounting for 92 32 of the recognizable sedimentary vascular plant debris are calculated to contribute 23 17 of the total organic carbon buried over the past decade upper meter of sediment column when combined with a previously established sedimentary organic carbon budget for this site martens and klump 1984 martens et al 1987 in preparation a vascular plant derived carbon burial rate of 26 20 mole c m 2 yr 1 is calculated for this same time interval the refractory nature and invariant depth distributions of the lignin oxidation products lop when coupled with evidence for constant degradation rates of metabolizable materials indicate that sediment accumulation at this site has been a steady state process with respect to source and burial of organic carbon since its conversion from an inner continental shelf to a lagoonal environment during the late 1960 s thus systematic down core decreases in labile organic matter result from early diagenetic processes rather than input rate variations

capillary effects on hydrate stability in marine sediments 1 we study the three phase liquid gas hydrate stability of the methane hydrate system in marine sediments by considering the capillary effects on both hydrate and free gas phases the capillary pressure a measure of the pressure difference across a curved phase interface exerts a key control on the methane solubility in liquid hydrate l h and liquid gas l g systems by calculating the l h and l g solubilities as a function of water depth pressure and pore size interface curvature we show how the solubility requirements for forming both gas hydrate and free gas can be met in a three phase zone the top of the three phase zone shifts upward in sediments as the water depth increases and the mean pore size decreases the thickness of the three phase zone increases as the distribution of pore sizes widens the top of the three phase zone can overlie or underlie the bulk three phase equilibrium depth at blake ridge we predict that the three phase zone is 27 7 m thick and that the top of the three phase zone lies 13 m above the predicted bulk equilibrium depth this reconciles the observation of the bottom simulating reflector bsr at blake ridge that is shallower than the predicted bulk equilibrium depth in contrast at hydrate ridge where water depth is shallower we predict that the three phase zone is 20 4 m thick and that the top of the three phase zone lies 0 7 m below the predicted bulk equilibrium depth our model which predicts an upward shift in the top of free gas occurrence with increasing water depth pressure is compatible with worldwide observations that the bsr is systematically shifted upward relative to the bulk equilibrium depth as water depth pressure is increased

the effect of lithologic heterogeneity on diffusive methane migration in hydrate systems abstract short range diffusive gas migration has been proposed as a means of supplying methane to coarse grained hydrate bearing sediments in this scenario methane is generated microbially in fine grained sediments and moves diffusively into adjacent coarse grained sediments due to a dissolved methane concentration gradient caused by pore size contrasts previous work has shown that short range diffusion is sufficient to supply thin isolated sands 1 m thickness with enough methane to achieve high hydrate saturations 80 in systems with a high ratio of clay to sand several notable hydrate reservoirs such as those encountered at daini atsumi knoll in the nankai trough and walker ridge block 313 and green canyon block 955 in the gulf of mexico exhibit tens of meters of alternating sand silt and clay layers that are decimeters in thickness the coarse grained layers in these settings are typically filled with hydrate to saturations exceeding 80 while short range diffusion is capable of filling thin isolated sands with hydrate thicker sands within more heterogeneous systems require mechanisms other than or in addition to short range diffusion using 1 d numerical simulations we demonstrate that short range diffusive migration of microbial methane is insufficient for reaching consistently high hydrate saturations in such systems this work shows that a different mechanism for gas transport such as advective migration is necessary to achieve these observed hydrate saturations in layered systems

cyclic changes in pennsylvanian paleoclimate and effects on floristic dynamics in tropical pangaea abstract wetland floras narrowly define perceptions of pennsylvanian tropical ecosystems the so called coal age such wetlands reflect humid to perhumid climate leading to characterizations of pennsylvanian tropics as everwet swampy these views are biased by the high preservation potential of wetlands sedimentation patterns paleosols and fossil floras indicate the presence of vegetation tolerant of subhumid to dry subhumid perhaps semi arid climate in basins between peat formation times understanding the significance of this seasonally dry vegetation has suffered from conceptual and terminological confusion a clearer view has emerged as models for framing the data have improved basinal floras typical of seasonally dry conditions relatively low soil moisture regimes are well documented but mainly from isolated deposits some of the earliest dominated by primitive pteridosperms flozfern floras occur in clastic rocks between european early pennsylvanian coal beds later early pennsylvanian fern cordaitalean vegetation different from coal floras is preserved in marine goniatite bullions conifers are first suggested by late mississippian potoniesporites pollen about the same time in north america broadleaf foliage lesleya and megalopteris occur in basin margin settings on drought prone limestone substrates the best known xeromorphic floras found between coal beds appear in the middle through late pennsylvanian containing conifers cordaitaleans and pteridosperms the middle pennsylvanian appearances of this flora are mainly allochthonous though parautochthonous occurrences have been reported parautochthonous assemblages are mostly late pennsylvanian the conifer flora became dominant in western and central pangaean equatorial lowlands in earliest permian location of the humid perhumid wetland flora during periods of relative dryness though rarely discussed is as or more perplexing than the spatial location of seasonally dry floras through time wetland plants had few migratory options and possibly survived in small refugia within and outside of basins coupled oscillations in climate sea level and vegetation were driven most likely by glacial interglacial fluctuations perhaps controlled by orbital cyclicity

molecular biomarkers study of an ombrotrophic peatland impacted by an anthropogenic clay deposit abstract northern peatlands are estimated to store up to one third of all terrestrial carbon as peat and even though a large extent of boreal peatlands is in pristine condition extensive areas have been affected by natural or anthropogenic disturbance here we aimed to study the bulk organic matter elemental composition and molecular inventory of a peat disturbed by a clay deposit in the mesotelm layer from 35 to 45 cm due to mining activity near the peatland zone we therefore investigated loss on ignition elemental analysis lignin monomers and non cellulose carbohydrates as well as the lipid fraction in general no significant impact on peatland evolution was noted the only odd result being an increase in complex lipids containing acyl groups in the clay deposit zone although this did not influence the distributions of the fatty acids which had a bimodal distribution at c 16 and c 24 c 26 typical of a non impacted sphagnum dominated peatland phospholipid analysis showed an increase in the quantity of mid chain branched fatty acids suggesting high sulfate reducing activity in the underlying clay deposit other lipid lignin and carbohydrate biomarkers showed a normal peatland evolution plant deposition being apparent in the bottom layer designated by the catotelm and microbial activity and production being highest in the upper layer represented by the acrotelm and mesotelm

magnetostratigraphy of sediments in mammoth cave kentucky clastic sediment deposits found within the caves of mammoth cave national park have yielded a magnetostratigraphic pattern of magnetic polarity reversals which indicates that they were deposited over a range of at least 1 million and most likely 2 million years

3 d basin scale reconstruction of natural gas hydrate system of the green canyon gulf of mexico our study presents a basin scale 3d modeling solution quantifying and exploring gas hydrate accumulations in the marine environment around the green canyon gc955 area gulf of mexico it is the first modeling study that considers the full complexity of gas hydrate formation in a natural geological system overall it comprises a comprehensive basin re construction accounting for depositional and transient thermal history of the basin source rock maturation petroleum components generation expulsion and migration salt tectonics and associated multi stage fault development the resulting 3d gas hydrate distribution in the green canyon area is consistent with independent borehole observations an important mechanism identified in this study and leading to high gas hydrate saturation 80 vol at the base of the gas hydrate stability zone ghsz is the recycling of gas hydrate and free gas enhanced by high neogene sedimentation rates in the region our model predicts the rapid development of secondary intra salt mini basins situated on top of the allochthonous salt deposits which leads to significant sediment subsidence and an ensuing dislocation of the lower ghsz boundary consequently large amounts of gas hydrates located in the deepest parts of the basin dissociate and the released free methane gas migrates upwards to recharge the ghsz in total we have predicted the gas hydrate budget for the green canyon area that amounts to 3 256 mt of gas hydrate which is equivalent to 340 mt of carbon 7 x 1011 m3 of ch4 at stp conditions and consists mostly of biogenic hydrates

diagenetic changes of lignin compounds in a more than 0 6 million year old lacustrine sediment lake biwa japan a vertical profile of lignin in the upper 700 m layer of a 1400 m sediment core of lake biwa an oligotrophic freshwater lake in japan was determined using a cuo oxidative degradation method the results indicated that lignin is found throughout the core demonstrating lignin to be very stable for over 0 6 million years moreover the upper 250 m approximately 0 6 million years old segment of the sediment core was investigated to determine the apparent long term degradation rate of lignin a downward lignin concentration decrease is observed over the upper 250 m of the core which corresponds to a calculated half life of at least approximately 40 104 years assuming that lignin decrease is due to its in situ degradation diagenesis

late archaean foreland basin deposits belingwe greenstone belt zimbabwe abstract the c 2 65 ga old sedimentary cheshire formation of the belingwe greenstone belt bdb central zimbabwe has been studied in detail for the first time to shed some light on the much debated evolution of this classical belt the cheshire formation rests sharply on a mafic volcanic unit zeederbergs formation and comprises a basal eastward sloping carbonate ramp sequence built of shallowing upward metre scale sedimentary cycles the cycles strongly resemble proterozoic and phanerozoic carbonate cycles and might have formed by small scale eustatic sea level changes the top of the carbonate ramp is represented by a karst surface the carbonates are overlain by and grade laterally to the east into deeper water sub wave base siliciclastic facies conglomerate shale and minor sandstone were deposited by high to low density turbidity currents and were derived from the erosion of zeederbergs like volcanic rocks from the east shortly after deposition the cheshire formation and underlying volcanics were affected by a northwest directed thrusting event thrusting gave rise to the deformation of semi consolidated sediments and resulted in the juxtaposition of a thrust slice of zeederbergs basalts onto cheshire sediments the stratigraphy asymmetric facies and sediment thickness distribution palaeogeographic constraints and evidence for an early horizontal tectonic event suggest that the cheshire formation formed in a foreland type sedimentary basin

an overview of the geology of the transvaal supergroup dolomites south africa in the neoarchaean intracratonic basin of the kaapvaal craton between approximately 2640 ma and 2516 ma two successive stromatolitic carbonate platforms developed deposition started with the schmidtsdrif subgroup which is probably oldest in the southwestern part of the basin and which contains stromatolitic carbonates siliciclastic sediments and minor lava flows subsequently the nauga formation carbonates were deposited on peritidal flats located to the southwest and were drowned during a transgression of the transvaal supergroup epeiric sea around 2550 ma ago this transgression led to the development of a carbonate platform in the areas of the preserved transvaal and griqualand west basins which persisted for 30 50 ma during this time shales were deposited over the nauga formation carbonates in the southwestern portion of the epeiric sea a subsequent period of basin subsidence led to drowning of the stromatolitic platform and to sedimentation of chemical iron rich silica precipitates of the banded iron formations bif over the entire basin carbonate precipitation in the archaean was largely due to chemical and lesser biogenic processes with stromatolites and ocean water composition playing an important role the stromatolitic carbonates in the preserved griqualand west and transvaal basins are subdivided into several formations based on the depositional facies reflected by stromatolite morphology and on intraformational unconformities interbedded tuffs and available radiometric age data do not yet permit detailed correlation of units from the two basins thorough dolomitisation of most formations took place at different post depositional stages but mainly during early diagenesis partial silicification was the result of diagenetic and weathering processes karstification of the carbonate rocks was related to periods of exposure to subaerial conditions and to percolation of groundwater such periods occurred locally at the time of carbonate and bif deposition main karstification however probably took place during an erosional period between approximately 2430 ma and 2320 ma

the mid carboniferous eustatic event stratigraphic and paleontologic evidence from mid carboniferous namurian basin and shelf successions in widely scattered parts of the world indicates that a major eustatic event occurred about 330 ma the event began with a regression that is recorded in most shelf sequences the regression was followed by a brief transgression about 328 ma and the event ended with a transgression that flooded large shelf areas about 325 ma the mississippian pennsylvanian unconformity in north america is a well known product of this event but equally prominent and contemporaneous unconformity surfaces are also present in europe north africa and elsewhere the event is believed to have caused numerous extinctions and it resulted in marked fluctuations in faunal diversity 94 references 2 figures

geocarbsulf a combined model for phanerozoic atmospheric o2 and co2 abstract a model for the combined long term cycles of carbon and sulfur has been constructed which combines all the factors modifying weathering and degassing of the geocarb iii model berner r a kothavala z 2001 geocarb iii a revised model of atmospheric co2 over phanerozoic time am j sci 301 182 204 for co2 with rapid recycling and oxygen dependent carbon and sulfur isotope fractionation of an isotope mass balance model for o2 berner r a 2001 modeling atmospheric o2 over phanerozoic time geochim cosmochim acta 65 685 694 new isotopic data for both carbon and sulfur are used and new feedbacks are created by combining the models sensitivity analysis is done by determining 1 the effect on weathering rates of using rapid recycling rapid recycling treats carbon and sulfur weathering in terms of young rapidly weathering rocks and older more slowly weathering rocks 2 the effect on o2 of using different initial starting conditions 3 the effect on o2 of using different data for carbon isotope fractionation during photosynthesis and alternative values of oceanic 13c for the past 200 million years 4 the effect on sulfur isotope fractionation and on o2 of varying the size of o2 feedback during sedimentary pyrite formation 5 the effect on o2 of varying the dependence of organic matter and pyrite weathering on tectonic uplift plus erosion and the degree of exposure of coastal lands by sea level change 6 the effect on co2 of adding the variability of volcanic rock weathering over time berner r a 2006 inclusion of the weathering of volcanic rocks in the geocarbsulf model am j sci 306 in press results show a similar trend of atmospheric co2 over the phanerozoic to the results of geocarb iii but with some differences during the early paleozoic and for variable volcanic rock weathering lower co2 values during the mesozoic atmospheric oxygen shows a major broad late paleozoic peak with a maximum value of about 30 o2 in the permian a secondary less broad peak centered near the silurian devonian boundary variation between 15 and 20 o2 during the cambrian and ordovician a very sharp drop from 30 to 15 o2 at the permo triassic boundary and a more or less continuous rise in o2 from the late triassic to the present

burial driven methane recycling in marine gas hydrate systems abstract natural gas hydrate may be buried with sediments until it is no longer stable at a given pressure and temperature resulting in conversion of hydrate into free gas this gas may migrate upward and recycle back into the hydrate stability zone to form hydrate as of yet however no quantitative description of the methane recycling process has been developed using multiphase flow simulations to model burial driven gas hydrate recycling in this study we present a series of 1d multiphase transport simulations to investigate the methane recycling process in detail by invoking the effects of capillary phenomena on hydrate and gas formation in pores of varying size we find that a free gas phase can migrate a significant distance above the bulk base of hydrate stability since the top of the free gas occurrence is often identified as the base of the hydrate stability zone from seismic data our results demonstrate that not only could this assumption mischaracterize a hydrate system but that under recycling conditions the highest hydrate saturations can occur beneath the top of the free gas occurrence we show that the presence of pore size distributions requires a replacement zone through which hydrate saturations progressively decrease with depth and are replaced with free gas this replacement zone works to buffer against significant gas buildup that could lead to fracturing of overlying sediments this work provides a framework for simulating flow and transport of methane within the 3 phase stability zone from a mass conservation perspective

the age fauna and palaeoenvironment of the late triassic fissure deposits of tytherington south gloucestershire uk important vertebrate faunas occur in fissure deposits of late triassic jurassic age in sw britain although the faunas are well described their age and palaeoenvironment remain poorly understood one such fissure system was documented in detail during quarrying operations at tytherington and has yielded in situ palynomorphs that add much information concerning its age and palaeoenvironment significantly the tytherington fauna is of the sauropsid type that has generally been dated as norian or pre penarth group transgression and was also regarded as representing a distinct upland fauna the palynomorphs which include a significant marine component demonstrate that the tytherington triassic fissures are infilled with late triassic rhaetian sediments that match specific levels in the westbury formation in addition many of the tytherington solutional fissures probably formed during the rhaetian and are consistent with a fluctuating saline to freshwater environment there is no prima facie evidence of solutional formation and infilling of the reptile bearing deposits before the rhaetian trangression the fissure reptile fauna which includes the early dinosaur thecodontosaurus inhabited a small fire swept limestone island in the rhaetian sea the features of the herpetofauna are entirely consistent with this island model which has quaternary analogues

evidence of multiple late bashkirian to early moscovian pennsylvanian fire events preserved in contemporaneous cave fills abstract during a low sea level stand and wet climate phase at the end of the mississippian lower palaeozoic limestones at the northern edge of the illinois basin were karstified the caves and fissures that formed were infilled subsequently with clastic sediments of pennsylvanian age late bashkirian early moscovian atokan duckmantian bolsovian westphalian b c the earliest infills comprise organic rich almost coaly sediments while sands silts and fine clays were deposited subsequently the sediments are fossiliferous and contain abundant plant fragments most notably cordaitalean and conifer remains many of the plants and megaspores are uncompressed and have undergone minimal thermal alteration charcoal occurs throughout the sedimentary infills but is most abundant in the later deposits where conifer remains predominate these conifers are currently amongst the oldest known from north america the presence of cordaitalean remains in the earliest coaly infills is supported by the detection of specific fernane derivatives the lipid extract of the cave fill sequence contains polyaromatic hydrocarbons pahs such as pyrene chrysene benzo ghi perylene and coronene which distribution further attests to the importance of wildfire in preserving the plant remains

decomposing biases in paleoenvironmental proxy data from pollen and micromammalian remains in caves an actualistic approach abstract multiple forms of bias must be taken into account when interpreting paleoenvironmental proxy records in terrestrial quaternary sequences this fact complicates attempts to correlate records from different types of proxy data accumulated at the same site we applied an actualistic approach to assess the correspondence between two major types of proxy data pollen and micromammalian remains in their representation of background vegetation within a cave site in mount carmel israel data on both pollen and micromammalian remains were extracted from a relatively large sample of 27 owl pellets accumulated inside the cave these pellets were compared to other pollen sources from inside as well as outside the cave including owl nest sediment and samples from moss and lichen these data were analyzed through multivariate correspondence analysis to examine associations among different pollen sources as well as between the pollen and micromammalian remains within the pellets the pooled composition of the pellets revealed close association between pellets and moss samples from inside the cave moss and lichen samples from outside the cave on the other hand showed clear over representation of pinus pollen in spite of some associations that we detected among specific pollen types and micromammalian taxa in the pellets when considering frequency data there was good correspondence among the cave sources in representation of the mediterranean quercus maquis vegetation formation extending below the cave we attribute these results in part to the relatively large sample of pellets and high taxonomic diversity these findings are also explained by the interaction between two key factors including the orientation of the cave towards the nearby quercus maquis and accumulation of both windblown pollen and pellets within the cave from this nearby source we conclude that long term pellet accumulations inside caves can contribute to inter proxy correlation when dealing with pollen and micromammalian remains from pellet sources and provide important and reliable sources of paleoenvironmental data

improving the resolution of impedance inversion in karst systems by incorporating diffraction information a case study of tarim basin chinaimpedance inversion with diffraction