multi method dating comparison for mid pleistocene rangitawa tephra new zealand abstract the rangitawa tephra a widespread mid pleistocene marker in the new zealand region is dated by fission track thermoluminescence tl infrared stimulated luminescence irsl k ar and single crystal laser fusion sclf 40 ar 39 ar methods as well as by matching to the astronomical timescale via oxygen isotope stratigraphy in deep sea cores fifty one independent numerical age estimates for rangitawa tephra range from 173 to 456 ka however only 15 of these results are considered to be reliable five zircon fission track results four isothermal plateau fission track itpft age estimates on glass shards four sclf 40 ar 39 ar results and two astronomically calibrated age estimates from deep sea cores the weighted mean of the nine reliable fission track age determinations is 345 12 ka in excellent agreement with the weighted mean of 340 7 ka for the two reliable astronomically calibrated age estimates the weighted mean of the four reliable 40 ar 39 ar results 302 8 ka is significantly younger and further ar ar dating is recommended to investigate this difference since the tl and irsl dating methods are experimental for sediments beyond 200 ka we have excluded these from the group of reliable age results tl and irsl results on dunesand appear to be systematically younger than tl results on loess and loess results depend upon analytical procedures

improved schmidt hammer exposure ages for active and relict pronival ramparts in southern norway and their palaeoenvironmental implications abstract eight pronival protalus ramparts from alpine southern norway were dated using schmidt hammer exposure age dating shd based on local high precision linear calibration equations shd ages were 1355 1240 to 815 1000 years for three active ramparts and 8730 1050 to 14 635 1060 years for five relict ramparts different parts of the same rampart yielded ages that were in generally good agreement r value frequency distributions enabled the identification single age and mixed age boulder populations and the differentiation of active and relict rampart surfaces the relict ramparts are located outside younger dryas glacier limits and probably formed over a period of 6000 years between deglaciation following the last glacial maximum of the late weichselian 18 000 years ago and the end of the younger dryas 11 700 years ago at that time glacial debuttressing and permafrost degradation apparently enhanced the release of rock debris from rock faces to the ramparts the active ramparts which are located in areas deglaciated after the younger dryas are relatively uncommon in the study area due to diminished paraglacial effects and limited debris supply associated with seasonally frozen ground during the holocene thus the legacy of glaciers glacier permafrost interaction and the specific type of periglacial environment must all be considered when assessing the palaeoenvironmental and palaeoclimatic significance of pronival ramparts

schmidt hammer exposure age dating shd of snow avalanche impact ramparts in southern norway approaches results and implications for landform age dynamics and development schmidt hammer exposure age dating shd was applied to the problem of dating the diachronous surfaces of five distal river bank boulder ramparts deposited by snow avalanches plunging into the jostedola and sprongdola rivers in the jostedalsbreen region of southern norway approaches to local high precision linear age calibration which controlled in different ways for boulder roundness were developed the mean age shdmean and the maximum age shdmax of surface boulders were estimated for whole ramparts crests and distal fringes interpretation was further assisted by reference to r value distributions shdmean ages with 95 confidence intervals ranged from 520 270 years to 5375 965 years whereas shdmax ages expected to be exceeded by 5 of surface boulders ranged from 675 to 9065 years shd ages from the jostedola ramparts tended to be older than those associated with the sprongdola rampart crests were younger than the respective distal fringes and use of relatively rounded boulders yielded more consistent shd ages than angular boulders the shdmean ages indicate differences in recent levels of snow avalanche activity between ramparts and provide insights into rampart dynamics as boulders are deposited on rampart crests and in smaller numbers on the distal fringes shdmax ages provide minimum age estimates of rampart age i e the time elapsed since the ramparts began to form and suggest that at least some of the ramparts have been developing since the early holocene copyright 2015 john wiley sons ltd

global carbon cycle perturbation across the eocene oligocene climate transition the eocene oligocene transition eot 34 ma marks a tipping point in the long term cenozoic greenhouse to icehouse climate transition paleorecords reveal stepwise rapid cooling and ice growth across the eot tightly coupled to a transient benthic 13c excursion and a major and permanent deepening of the carbonate compensation depth ccd based on biogeochemical box modeling merico et al 2008 suggested that a combination of 1 glacioeustatic sea level fall induced shelf basin carbonate burial fractionation and 2 shelf carbonate weathering can account for the carbon cycle perturbation but this finding has been questioned alternative proposed mechanisms include increased ocean ventilation decreased carbonate burial increased organic carbon burial increased silicate weathering and increased ocean calcium concentration here we use an improved version of the biogeochemical box model of merico et al 2008 to reevaluate these competing hypotheses and an additional mechanism the expansion of carbon capacitors such as permafrost and peatlands we find that changes in calcium concentration silicate weathering and carbonate or organic carbon burial each yield a response that is fundamentally at odds with the form and or sign of the paleorecords shelf basin carbonate burial fractionation ccd change plus shelf carbonate weathering sequestration of 12c enriched carbon into carbon capacitors and possibly increased ocean ventilation 13c excursion offers the best fit to the paleorecords further work is needed to understand why the eot carbon cycle perturbation is so unique when the forcing mechanisms hypothesized to be responsible cooling and ice growth are not peculiar to this event

small aperture seismic array data processing using a representation of seismograms at zero crossing points abstract a new method for representing seismograms by using zero crossing points is described this method is based on decomposing a seismogram into a set of quasi harmonic components and subsequently on determining the precise zero crossing times of these components an analogous approach can be applied to determine extreme points that represent the zero crossings of the first time derivative of the quasi harmonics such zero crossing and or extreme point seismogram representation can be used successfully to reconstruct single station seismograms but the main application is to small aperture array data analysis to which standard methods cannot be applied the precise times of the zero crossing and or extreme points make it possible to determine precise time differences across the array used to retrieve the parameters of a plane wave propagating across the array namely its backazimuth and apparent phase velocity along the earth s surface the applicability of this method is demonstrated using two synthetic examples in the real data example from the p ibram haje array in central bohemia czech republic for the mw 6 4 crete earthquake of october 12 2013 this method is used to determine the phase velocity dispersion of both rayleigh and love waves the resulting phase velocities are compared with those obtained by employing the seismic plane wave rotation to translation relations in this approach the phase velocity is calculated by obtaining the amplitude ratios between the rotation and translation components seismic rotations are derived from the array data for which the small aperture is not only an advantage but also an applicability condition

soil development rates in the transantarctic mountains soil chronosequences were identified at three sites 78 85 s within the transantarctic mountains for determining rates of soil development in cold desert ecosystems more than 175 soils were sampled in xerous and ultraxerous environments on moraines containing sandstone and dolerite and ranging from late holocene ca 6 ka to pre late quaternary ca 250 ka in age based on five linear and nonlinear models highly significant correlations p 0 01 exist between drift age and the following surface boulder weathering features and soil properties percentage of boulders containing desert varnish spalling and pitting depths of staining visible salts ghosts pseudomorphs and coherence in soils electroconductivity in the zone of salt enrichment and total profile salts in the absence of leaching soluble salts readily accumulate in cold desert soils a morphogenetic sequence of soluble salts is presented that relates field observations with laboratory data soil color is highly correlated p 0 01 with dithionite extractable fe within a site the proportion of clasts 15 mm on the surface of the desert pavement increases with time due likely to deflation of fines by strong winds therefore the dominant processes in these cold desert soils are salinization rubification reddening due to oxidation of iron bearing minerals and desert pavement formation

calcium carbonate veins in ocean crust record a threefold increase of seawater mg ca in the past 30 million years chemical sr mg and isotopic 18o 87sr 86sr compositions of calcium carbonate veins ccv in the oceanic basement were determined to reconstruct changes in sr ca and mg ca of seawater in the cenozoic we examined ccv from 10 basement drill sites in the atlantic and pacific ranging in age between 165 and 2 3 ma six of these sites are from cold ridge flanks in basement 46 ma which provide direct information about seawater composition ccv of these young sites were dated using the sr isotopic evolution of seawater for the other sites temperature corrections were applied to correct for seawater basement exchange processes the combined data show that a period of constant low sr ca 4 46 6 22 mmol mol and mg ca 1 12 2 03 mol mol between 165 and 30 ma was followed by a steady increase in mg ca ratios by a factor of three to modern ocean composition mg ca sr ca relations suggest that variations in hydrothermal fluxes and riverine input are likely causes driving the seawater compositional changes however additional forcing may be involved in explaining the timing and magnitude of changes a plausible scenario is intensified carbonate production due to increased alkalinity input to the oceans from silicate weathering which in turn is a result of subduction zone recycling of co2 from pelagic carbonate formed after the cretaceous slow down in ocean crust production rate

spatial gradient analysis for linear seismic arrays i incorporate the spatial gradient of the wave field recorded from one dimensional arrays into a processing method that yields the horizontal wave slowness and the change of geometrical spreading with distance in general the model for seismic wave propagation is enough to be appropriate for body and surface waves propagating from nearby seismic sources but can be simplified into a plane wave model although computation of the spatial gradient requires that array elements be closer than 10 of the horizontal wavelength seismic array apertures in the usual sense may extend over many horizontal wavelengths and illuminate changes within the wave field array images of horizontal slowness and the relative geometrical spreading changes of seismic waves are derived using filter theory and used to interpret observed array wave fields errors in computing finite difference spatial gradients from array nodes are explicitly considered to avoid spatial aliasing in the estimates i apply the method to interpret waves in strong ground motion and small scale refraction data sets use of the wave spatial gradient accentuates spatial differences in the wave field that can be theoretically exploited in fine scale tomographic studies of structure and is complementary to frequency wavenumber or beam forming array processing techniques

wave gradiometry in two dimensions the spatial displacement gradient of a seismic wave is related to dis placement and velocity through two spatial coefficients for any one dimension one coefficient gives the relative change of wave geometrical spreading with distance and the other gives the horizontal slowness and its change with distance the essential feature of spatial gradient analysis is a time domain relation between three seismo grams that yields information on the amplitude and phase behavior of a seismic wave filter theory is used to find these coefficients for data from 2d areal arrays of seismometers termed gradiometers a finite difference star is used to compute the displacement gradient for irregularly shaped gradiometers and a relation for the frequency dependent error in the displacement gradient is obtained and applied to ensure accurate estimates this kind of array analysis is useful for gradiometers at any distance from a source and yields a variety of time domain and frequency domain views of wave amplitude changes and horizontal phase velocity estimates across the gradiometer for example time dependent horizontal slowness and wave azimuth plots are natural results of the analysis these time domain maps may be used in conjunction with time distance and horizontal slowness distance models to locate seismic sources or may be used directly to study earth structure these methods are demonstrated by using data from a small aperture 40 m seismic gradiometer

frequency and size of quaternary surface ruptures of the pitaycachi fault northeastern sonora mexico movements along the pitaycachi fault since the miocene juxtaposed different alluvial units and created 2 to 45 m high fault scarps downslope from a pedimented mountain front prior to 1887 in 1887 a major earthquake formed a 75 km long 1 2 to 4 m high scarp along the trace of prehistoric surface ruptures diverse evidence from many study sites indicates that about 200 000 yr elapsed between the prior youngest pleistocene event and the 1887 surface rupture cumulative displacements of pliocene to mid pleistocene alluvial fans and stream terraces decrease with decreasing age the trace of the prior rupture was largely buried by sheets of late pleistocene and holocene piedmont alluvium late pleistocene soils are offset about the same amount as the height of the 1887 scarp valleys that are as much as 40 m deep and 0 5 to 0 9 km wide have been eroded since the prior event they contain multiple late pleistocene and holocene stream terraces that were not faulted until 1887 pre 1887 alluvial fault scarps were degraded to 2 to 9 slopes before the 1887 event even in resistant materials such as clay rich soil horizons with unweathered rhyolite cobbles and calcrete scarp height maximum slope regressions and diffusion equation analyses for reconstructed pre 1887 scarp profiles indicate that the prior event occurred more than 100 000 yr ago acceleration of scarp degradation rates during the holocene and or relatively resistant materials exposed in the scarps would increase the age estimates to 200 000 yr or more very long recurrence intervals are the characteristic style of movement on the pitaycachi fault at one site six ages of diverse valley fills were inset into pedimented granodiorite upslope from the fault between the prior and 1887 events only 3 m of relief remained before the 1887 rupture increased the scarp height from 3 to 6 m some hillslopes have triangular talus facets of carbonatecemented colluvium that resulted from infrequent fault movements and intervening periods of erosion smooth hillsides of resistant volcanic rocks between the facets show that virtually all of the prior surface rupture event scarps had been removed by prolonged slope degradation

the evolution of pco2 ice volume and climate during the middle miocene abstract the middle miocene climatic optimum 17 15 ma mco is a period of global warmth and relatively high co2 and is thought to be associated with a significant retreat of the antarctic ice sheet ais we present here a new planktic foraminiferal 11b record from 16 6 to 11 8 ma from two deep ocean sites currently in equilibrium with the atmosphere with respect to co2 these new data demonstrate that the evolution of global climate during the middle miocene as reflected by changes in the cyrosphere was well correlated to variations in the concentration of atmospheric co2 what is more within our sampling resolution 1 sample per 300 kyr there is no evidence of hysteresis in the response of ice volume to co2 forcing during the middle miocene contrary to what is understood about the antarctic ice sheet from ice sheet modelling studies in agreement with previous data we show that absolute levels of co2 during the mco were relatively modest 350 400 ppm and levels either side of the mco are similar or lower than the pre industrial 200 260 ppm these new data imply the presence of either a very dynamic ais at relatively low co2 during the middle miocene or the advance and retreat of significant northern hemisphere ice recent drilling on the antarctic margin and shore based studies indicate significant retreat and advance beyond the modern limits of the ais did occur during the middle miocene but the complete loss of the ais was unlikely consequently it seems that ice volume and climate variations during the middle miocene probably involved a more dynamic ais than the modern but also some component of land based ice in the northern hemisphere

bulk sediment qp and qs in the mississippi embayment central united states we have estimated p wave ands wave anelastic attenuation coefficients for the thick unconsolidated sediments of the mississippi embayment central united states using the spectral distance decay of explosion p and rayleigh waves the sediment trapped p wave psed is observed to ranges of 80 km at 10 hz and 1 hz rayleigh waves are observed out to 130 km from a 5000 lb borehole explosion in the northern part of the embayment rayleigh waves of 4 hz are seen to distances of 3 km from a smaller 50 lb explosion analysis of the group velocity and amplitude distance decay of both waves yields an average qs of 100 and qp of 200 for embay ment sediments that are independent of frequency scatter in the q estimates comes from interference of multiple p wave reverberations and rayleigh wave modes the attenuation model is self consistent in that it is the same as obtained by the analysis of synthetic seismograms using the inferred q values inferred qp and qs values are more than three times higher than previous estimates and imply that unconsolidated sediments of the embayment do not significantly attenuate small strain earthquake ground motions these estimates represent a lower bound to q of the sediments since significant scattering is observed in the waveform data that contributes to the distance decay of wave amplitude higher q values also imply that the unconsolidated sedi ments of the embayment will form an efficient wave guide for surface waves radiated from shallow earthquakes or large earthquakes that rupture into the sediments pro ducing high amplitude long duration wave trains that should be considered in earth quake hazard assessments

the effects of measurement uncertainties in seismic wave gradiometry abstract in seismic wave gradiometry the spatial gradient and the time derivative of the measured wavefield are used to estimate the slowness vector and changes in the radiation pattern when using a seismic array to estimate the seismic spatial derivatives the array aperture cannot be greater than approximately 10 of the target wavelength to avoid spatial aliasing effects however there has been little research into the minimum practical array aperture in this article we investigate the effects of measurement uncertainties on the accuracy of gradiometrically estimated wave parameters as well as provide recommendations on design criteria for gradiometric arrays the design parameters are based on wavefield slowness frequency and measurement uncertainty

mg fractionation in crustose coralline algae geochemical biological and sedimentological implications of secular variation in the mg ca ratio of seawater the mg ca ratio of seawater has varied significantly throughout the phanerozoic eon primarily as a function of the rate of ocean crust production specimens of the crustose coralline alga neogoniolithon sp were grown in artificial seawaters encompassing the range of mg ca ratios shown to have existed throughout the phanerozoic significantly the coralline algae s skeletal mg ca ratio varied in lockstep with the mg ca ratio of the artificial seawater specimens grown in seawater treatments formulated with identical mg ca ratios but differing absolute concentrations of mg and ca exhibited no significant differences in skeletal mg ca ratios thereby emphasizing the importance of the ambient mg ca ratio and not the absolute concentration of mg in determining the mg ca ratio of coralline algal calcite specimens grown in seawater of the lowest molar mg ca ratio mmg ca 1 0 actually changed their skeletal mineralogy from high mg skeletal mmg ca 0 04 to low mg calcite skeletal mmg ca 0 04 suggesting that ancient calcitic red algae which exhibit morphologies and modes of calcification comparable to neogoniolithon sp would have produced low mg calcite from the middle cambrian to middle mississippian and during the middle to late cretaceous when oceanic mmg ca approached unity by influencing the original mg content of carbonate facies in which these algae have been ubiquitous this condition has significant implications for the geochemistry and diagenesis of algal limestones throughout most of the phanerozoic the crustose coralline algae s precipitation of high mg calcite from seawater that favors the abiotic precipitation of aragonite indicates that these algae dictate the precipitation of the calcitic polymorph of caco3 however the algae s nearly abiotic pattern of mg fractionation in their skeletal calcite suggests that their biomineralogical control is limited to polymorph specification and is generally ineffectual in the regulation of skeletal mg incorporation therefore the mg ca ratio of well preserved fossils of crustose coralline algae when corrected for the effect of seawater temperature may be an archive of oceanic mg ca throughout the phanerozoic magnesium fractionation algorithms that model algal skeletal mg ca as a function of seawater mg ca and temperature are presented herein the results of this study support the empirical fossil evidence that secular variation of oceanic mg ca has caused the mineralogy and skeletal chemistry of many calcifying marine organisms to change significantly over geologic time

benthic foraminiferal mg ca paleothermometry a revised core top calibration core top samples from different ocean basins have been analyzed to refine our current understanding of the sensitivity of benthic foraminiferal calcite magnesium calcium mg ca to bottom water temperatures bwt benthic foraminifera collected from hawaii little bahama bank sea of okhotsk gulf of california ne atlantic ceara rise sierra leone rise the ontong java plateau and the southern ocean covering a temperature range of 0 8 to 18 c were used to revise the cibicidoides mg ca temperature calibration the mg ca bwt relationship of three common cibicidoides species is described by an exponential equation mg ca 0 867 0 049 exp 0 109 0 007 bwt stated errors are 95 ci the temperature sensitivity is very similar to a previously published calibration however the revised calibration has a significantly different preexponential constant resulting in different predicted absolute temperatures we attribute this difference in the preexponential constant to an analytical issue of accuracy some genera notably uvigerina show apparently lower temperature sensitivity than others suggesting that the use of constant offsets to account for vital effects in mg ca may not be appropriate downcore mg ca reproducibility as determined on replicate foraminiferal samples is typically better than 0 1 mmol mol 1 2 s e thus considering the errors associated with the cibicidoides calibration and the downcore reproducibility bwt may be estimated to within 1 c application of the revised core top mg ca bwt data to cenozoic foraminiferal mg ca suggests that seawater mg ca was not more than 35 lower than today in the ice free ocean at 50 ma

rock varnish microlamination dating of late quaternary geomorphic features in the drylands of western usa abstract varnish microlamination vml dating is a correlative age determination technique that can be used to date and correlate various geomorphic features in deserts in this study we establish a generalized late quaternary i e 0 300 ka varnish layering sequence for the drylands of western usa and tentatively correlate it with the specmap oxygen isotope record we then use this climatically correlated varnish layering sequence as a correlative dating tool to determine surface exposure ages for late quaternary geomorphic features in the study region vml dating of alluvial fan deposits in death valley of eastern california indicates that during the mid to late pleistocene 5 15 ky long aggradation events occurred during either wet or dry climatic periods and that major climate shifts between glacial and interglacial conditions may be the pacemaker for alteration of major episodes of fan aggradation during the holocene interglacial time however 0 5 1 ky long brief episodes of fan deposition may be linked to short periods of relatively wet climate vml dating of alluvial desert pavements in death valley and the mojave desert reveals that pavements can be developed rapidly

the effects of secular calcium and magnesium concentration changes on the thermodynamics of seawater acid base chemistry implications for eocene and cretaceous ocean carbon chemistry and buffering reconstructed changes in seawater calcium and magnesium concentration ca2 mg2 predictably affect the ocean s acid base and carbon chemistry yet inaccurate formulations of chemical equilibrium constants are currently in use to account for these changes here we develop an efficient implementation of the miami ionic interactionmodel to predict all chemical equilibrium constants required for carbon chemistry calculations under variable ca2 and mg2 we investigate the impact of ca2 and mg2 on the relationships among the ocean s ph co2 dissolved inorganic carbon dic saturation state of caco3 and buffer capacity increasing ca2 and or mg2 enhances ion pairing which increases seawater buffering by increasing the concentration ratio of total to free uncomplexed carbonate ion an increase in ca2 however also causes a decline in carbonate ion to maintain a given thereby overwhelming the ion pairing effect and decreasing seawater buffering given the reconstructions of eocene ca2 and mg2 ca2 20mm mg2 30mm eocene seawater would have required essentially the same dic as today to simultaneously explain a similar to modern and the estimated eocene atmospheric co2 of 1000 ppm during the cretaceous at 4 times modern ca2 ocean buffering would have been at a minimum overall during times of high seawater ca2 caco3 saturation ph and atmospheric co2 were more susceptible to perturbations of the global carbon cycle for example given both eocene and cretaceous seawater ca2 and mg2 a doubling of atmospheric co2 would require less carbon addition to the ocean atmosphere system than under modern seawater composition moreover increasing seawater buffering since the cretaceous may have been a driver of evolution by raising energetic demands of biologically controlled calcification and co2 concentration mechanisms that aid photosynthesis

vertical seismic wave gradiometry application at the san andreas fault observatory at depth abstractwe have developed vertical seismic wave gradiometry vswg to estimate velocity impedance and attenuation structure in the vicinity of boreholes using borehole array waveforms of check shot explosions near the borehole head we have extended wave gradiometry wg theory from a purely local relation of the wavefield and wavefield spatial gradient to one that incorporated the ray ansatz over the length of the borehole for a traveling wave in a vertically inhomogeneous medium we checked the ray assumption against acoustic full wave synthetic seismograms and it was found to yield robust measures of the medium velocity anelastic attenuation and impedance structure trade off but in cases of high anelastic attenuation realistic bounds can be placed on the seismic impedance that effectively constrains the average attenuation we have applied these methods to data collected at the san andreas fault observatory at depth borehole in central california in 2005 and we found that the wg velocity estimat

scleractinian corals produce calcite and grow more slowly in artificial cretaceous seawater the mineralogies of most biotic and abiotic carbonates have alternated in synchroneity between the calcite hexagonal and aragonite orthorhombic polymorphs of caco3 throughout the phanerozoic eon these intervals of calcite and aragonite production or calcite seas and aragonite seas are thought to be caused primarily by secular variation in the molar magnesium calcium ratio of seawater mmg ca 2 5 aragonite 1 high mg calcite mmg ca 2 5 low mg calcite a ratio that has oscillated between 1 0 and 5 2 throughout the phanerozoic in laboratory experiments we show that three species of scleractinian corals which produce aragonite in modern seawater and which have flourished as important reef builders primarily during aragonite seas of the past began producing calcite in artificial seawater with an ambient mmg ca ratio below that of modern seawater 5 2 the corals produced progressively higher percentages of calcite and calcified at lower rates with further reduction of the ambient mmg ca ratio in artificial seawater of imputed late cretaceous composition mmg ca 5 1 0 which favors the precipitation of the calcite polymorph scleractinian corals produced skeletons containing 30 low mg calcite skeletal mmg ca 0 04 these results indicate that the skeletal mineral used by scleractinian corals is partially determined by seawater chemistry furthermore slow calcification rates resulting from the production of largely aragonitic skeletons in chemically unfavorable seawater mmg ca 2 probably contributed to the scleractinians diminished reef building role in the calcite seas of late cretaceous and early cenozoic time

investigating controls on boron isotope ratios in shallow marine carbonates abstract the boron isotope ph proxy has been widely used to reconstruct past ocean ph values in both planktic foraminifera and corals species specific calibrations are required in order to reconstruct absolute values of ph due to the prevalence of so called vital effects physiological modification of the primary environmental signals by the calcifying organisms shallow marine abiotic carbonate e g ooids and cements could conceivably avoid any such calibration requirement and therefore provide a potentially useful archive for reconstructions in deep pre cenozoic time however shallow marine abiotic carbonates could also be affected by local shifts in ph caused by microbial photosynthesis and respiration something that has up to now not been fully tested in this study we present boron isotope measurements from shallow modern marine carbonates from the bahama bank and belize to investigate the potential of using shallow water carbonates as ph archives and to explore the role of microbial processes in driving nominally abiogenic carbonate deposition for bahama bank samples our boron based ph estimates derived from a range of carbonate types i e ooids peloids hardground cements carbonate mud stromatolitic micrite and calcified filament micrite are higher than the estimated modern mean annual seawater ph values for this region furthermore the majority 73 of our marine carbonate based ph estimates fall out of the range of the estimated pre industrial seawater ph values for this region in shallow sediment cores we did not observe a correlation between measured pore water ph and boron derived ph estimates suggesting boron isotope variability is a depositional rather than early diagenetic signal for belize reef cements conversely the ph estimates are lower than likely in situ seawater ph at the time of cement formation this study indicates the potential for complications when using shallow marine non skeletal carbonates as marine ph archives in addition variability in 11b based ph estimates provides additional support for the idea that photosynthetic co2 uptake plays a significant role in driving carbonate precipitation in a wide range of shallow water carbonates

chronology of late wisconsinan glaciation in middle north america abstract we propose a chronology of late wisconsinan glacial fluctuations in middle north america from alberta to wisconsin based on radiocarbon dates derived solely from wood previous chronologies of the southwestern margin of the north american continental ice sheet have depended to a considerable degree on radiocarbon dates from fine grained organic sediment this material is commonly contaminated with older carbon resulting in chronologic confusion by using only dates from wood much of the confusion disappears however because of the scarcity of wood dates only four of the sixteen identified fluctuations are accurately dated an advance into iowa about 14 000 to 13 500 bp an advance into south dakota and iowa about 12 300 bp an advance into the lake michigan basin about 11 700 bp and an advance into the lake superior basin about 9900 bp in addition the beginning of late wisconsinan glaciation before 20 000 bp is fairly well documented none of the fluctuations in the western part of the region are accurately dated

relative age dating of transported regolith and application to study of landform evolution in the appalachians abstract surficial deposits in the appalachians generally are thin discontinuous and difficult to date in the absence of numerical dates particularly for older deposits relative age indices based on degree of weathering and soil development have been used to distinguish and correlate deposits of different ages a favorite locale of relative age studies has been stream terraces where chronosequences have been developed to shed light on the relationship between time and weathering soil development the lack of applicable numerical dating techniques has led some researchers to establish relative chronosequences in which height of stream or fan terraces above modern river level arl serves as a proxy for time approximate incision rates can then be used to estimate numerical ages of the deposits relative age correlations between the weathering indices on the terraces and comparable indices on dated deposits on the coastal plain and in nearby glaciated regions suggest that ages so estimated are the right order of magnitude relative age indices show correlations with height arl that are as high as those with time perhaps because more data sets are available for relative chronosequences than for true chronosequences analogous relative age sequences can be established for alluvial fans and even for hillslope colluvium many weathering indices have been employed but weathering rind thickness on mafic to intermediate clasts has proved to be a particularly consistent and useful parameter in addition to showing how weathering and soil development progress over time relative age dating has shed light on the manner in which landforms evolve along some rivers for example the areal extent of old highly weathered alluvium far exceeds that of younger alluvium suggesting that formerly floodplains and low terraces were much more extensive than at present in addition the manner in which weathering indices on some river terrace sequences vary with height arl suggests that incision rate has changed through time relative age mapping of alluvial fans produces a map pattern of older and younger fan surfaces that allows the sequence of fan development to be inferred in one case suggesting a scenario different from those previously described for fans mapping also shows that the relative abundance of young intermediate and old fan surfaces varies greatly from one area to another several studies have demonstrated clustering of relative age values into a small number of groups suggesting temporal grouping and thus episodic deposition on fans regression of weathering rind thickness against height above modern drainageways of remnant fan surfaces in two areas suggests that fans are being incised more rapidly in one area than in another relative age of hillslope colluvium also aids geomorphic interpretation young brown colluvium is much more common than old red colluvium near the glacier border where red colluvium rarely occurs at the surface but typically is covered by brown colluvium probably mobilized during the late pleistocene distant from the ice margin however red colluvium is extensively exposed on interfluves relatively stable hillslopes can also be distinguished from active ones in this manner for example colluvium on hillslope noses is somewhat more weathered than that on hollow floors and sideslopes

reconstructing past seawater mg ca and sr ca from mid ocean ridge flank calcium carbonate veins proxies for past seawater chemistry such as mg ca and sr ca ratios provide a record of the dynamic exchanges of elements between the solid earth the atmosphere and the hydrosphere and the evolving influence of life we estimated past oceanic mg ca and sr ca ratios from suites of 1 6 to 170 million year old calcium carbonate veins that had precipitated from seawater derived fluids in ocean ridge flank basalts our data indicate that before the neogene oceanic mg ca and sr ca ratios were lower than in the modern ocean decreased ocean spreading since the cretaceous and the resulting slow reduction in ocean crustal hydrothermal exchange throughout the early tertiary may explain the recent rise in these ratios

atmospheric pco2 since 60 ma from records of seawater ph calcium and primary carbonate mineralogy a 60 m y record of atmospheric p co2 has been refined from knowledge of 1 secular changes in the major ion composition of seawater particularly ca and mg and 2 oscillations in the mineralogy of primary oceanic carbonate sediments both factors have had a significant impact on the chemistry of the ocean carbonate buffer system calculated atmospheric p co2 oscillated between values of 100 300 ppm and to maxima of 1200 2500 ppm from 60 to 40 ma and varied between 100 and 300 ppm from 25 ma to the present the refined p co2 values are significantly lower than previous estimates made from seawater ph data where total dissolved inorganic carbon was assumed constant and more in line with modeling and stomatal index estimations of atmospheric p co2 for the tertiary

quaternary alkalinity fluctuations recorded in rock varnish microlaminations on western u s a volcanics abstract rock varnish contains an alternating micron scale layering of manganese rich and manganese poor microchemical laminations holocene varnishes have lower mn fe ratios when exposed to alkaline environments and higher mn fe ratios when exposed to less alkaline environments this is consistent with abiotic and biotic mechanisms of varnish formation as alkalinity inhibits the concentration of manganese in both models mn fe variations with depth in varnishes in the western u s are interpreted as fluctuations in alkalinity or local microenvironmental influences if enough varnishes are sampled from different rocks in a region local effects can be ruled out k ar dating of volcanics in the coso cima lunar crater and crater flat volcanic fields in the western basin and range provide numerical age control throughout the quaternary and allow the number of alkalinity fluctuations to be assessed for given periods of time alkalinity fluctuations in varnishes are likely tied to fluctuations in the abundance of alkaline aerosols which are in turn related to fluctuations in the cover of water over playas and the cover of vegetation over soils microchemical laminations in varnish therefore have the potential to serve as an indicator of environmental fluctuations for the entire quaternary

alluvial terrace systems in zhangjiajie of northwest hunan china implications for climatic change tectonic uplift and geomorphic evolution abstract this paper reports the latest details from two comprehensive investigations of alluvial terrace sequences in zhangjiajie northwest hunan province china seven alluvial terrace units along the maoxi river and four terrace sequences along the suoxi river record significant regional geomorphic history rates of regional quaternary uplift and climate change are reconstructed using topographic and stratigraphic evidence from terrace and adjacent cave deposits along with electron spin resonance esr and thermo luminescence tl dating controls between 928 ka and 689 ka the time averaged uplift rate or incision rate was 0 16 m ka the rate decreased to 0 05 m ka between 689 ka and 347 ka and then increased slightly to 0 11 0 14 m ka after 347 ka the inferred incision rate increased roughly from 0 21 0 32 m ka to 0 51 m ka from the late pleistocene to present the seven alluvial phases t7 t1 and their associated chronology are consistent with climatic variations at regional and or global scales suggesting that these terraces represent climate driven pauses imprinted atop the record of long term tectonically induced incision by rivers insights from these alluvial terrace staircases and cave features indicate that the spectacular sandstone peak forest landscape of the study area has emerged since the middle period of the middle pleistocene

chronology of a probable neotectonic pleistocene rock avalanche cordon del plata central andes mendoza argentina abstract placetas amarillas 1 rock avalanche located at 32 43 s 69 25 w was geomorphologically stratigraphically and chronologically studied this extraordinary event dammed a secondary gully causing the formation of a barrier lake indicated by relict lacustrine and diatomite deposits stratigraphically its deposit is overlain by alluvial fans where three tephra layers are intercalated dating using ar ar method of the middle ash level at 350 80 ka determined a middle pleistocene or older age for this event furthermore the younger age of placetas amarillas 2 is established by relative dating techniques such as soil development and rock varnish development the ages established in this research indicate that placetas amarillas 1 may be temporally correlated with the tigre dormido rock avalanche suggesting that the occurrence of these rock avalanches may be related to regional neotectonic activity nevertheless climatic conditions are not underestimated as the tigre dormido event occurred before formation of an outwash terrace related to a glaciation of early middle pleistocene age

modeled reconstructions of the oceanic carbonate system for different histories of atmospheric carbon dioxide during the last 20 ma a box model was used to estimate oceanic carbonate system parameters total dissolved inorganic carbon alkalinity co2 aq co3 2 hco3 and ph in the surface and deep ocean over the past 20 ma geological data were used to constrain boundary conditions including the carbonate compensation depth ccd and seawater temperature salinity and ionic composition in addition 14 000 13c measurements of planktic and benthic foraminifera were compiled sensitivity tests were performed to evaluate potential errors arising from uncertainties in model boundary conditions values of surface water ph were modeled assuming four different histories of atmospheric co2 and compared with proxy based estimates of ph the system is underconstrained and therefore multiple co2 histories can be invoked to explain the same ph trend depending on the assumptions made regarding ocean overturning and biological productivity despite this uncertainty we conclude that if co2 was strongly coupled to temperature and ice volume over the last 20 ma predicted values of surface ocean ph fit poorly with current proxy based ph reconstructions

stratigraphy and thermoluminescence dating of late glacial cover sand in denmark in western jutland deposits with a texture and structure similar to dutch cover sands have been found investigations have been carried out on the lithology and the lithostratigraphic sequences pollen analysis is used for biostratigraphic correlation and ages have been obtained by the radiocarbon method as well as by thermoluminescence techniques using both quartz and eldspar the five sites are presented separately and the data are integrated into a general stratigraphic outline of the late glacial cover sand sequence in jutland during the latest part of the upper pleniglacial and the earliest late glacial older cover sand type was deposited locally this sediment was also deposited during the later parts of the late glacial younger cover sand type was deposited primarily during the early dryas and late dryas but some sand of this type was also laid down during the allerod and the earliest holocene the palaeobotanical records are discontinuous but plant growth was probably present throughout the late glacial only during the altered did the deposition of sand decrease long enough to allow a relatively stable vegetational development the investigation shows that the sequence of events in jutland is similar to the dutch record

rates of hornblende etching in soils in glacial deposits of the northern rocky mountains wyoming montana u s a influence of climate and characteristics of the parent material abstract hornblende grains in the soil matrix of glacial deposits in the northern rocky mountains etch at rates that depend primarily upon the influences on soil moisture of the climate and the texture of the parent materials etching is a logarithmic function of age of the parent material and etching rates decline rapidly after a period of initial high rates over the first 10 15 ka after deposition in this study a comparison of etching rates was made among four chronosequences in the wind river range of western wyoming and the tobacco root range of southwestern montana which have differences in mean annual precipitation map and texture of the till parent materials using rates calculated for the first 12 ka after deposition etching is slowest 0 02 m ka 1 in coarse textured granitic parent materials where the map is 25 40 cm in contrast etching is faster by an order of magnitude 0 21 m ka 1 where the map is 110 150 cm and the parent material is finer textured because 15 sedimentary rock material has been mixed with the granitic component within individual chronosequences deposits at higher elevations have accelerated etching rates due to higher orographic precipitation or the influence of late lying snow

millennial scale varnish microlamination dating of late pleistocene geomorphic features in the drylands of western usa abstract varnish microlamination vml dating is a climate based correlative age determination technique used to correlate and date various geomorphic features in deserts in this study we establish a generalized late pleistocene 18 74 ka millennial scale microlamination sequence in fine grained fast accumulating rock varnish for the drylands of western usa radiometrically calibrate the sequence and correlate it with the 18 o record in the gisp2 greenland ice core we then use this climate correlated varnish microstratigraphy to estimate surface exposure ages for radiometrically dated late pleistocene geomorphic features in the study region the vml dating of debris flow deposits on the sehoo recessional shorelines of lake lahontan at the jessup embayment of central nevada yields a minimum limiting age of 14 95 15 95 ka in good agreement with a calibrated 14 c age of 15 22 0 12 ka for the timing of the lake recession the vml dating of a giant ejecta block on the rim of meteor crater in northern arizona yields a minimum limiting age of 49 15 ka closely matching a thermoluminescence tl age of 49 3 ka and slightly younger than a recently updated cosmogenic 36 cl age of 56 0 2 4 ka for the meteor impact event the vml dating of distal q2c fan surfaces on hanaupah canyon alluvial fan in death valley california yields a minimum limiting age of 73 55 ka in accord with cosmogenic 36 cl depth profile ages of 66 22 14 ka and 72 24 20 ka for the same fan deposits the close agreement between the vml age estimates and the independently derived radiometric ages for these geomorphic features attests to the validity and reliability of millennial scale vml dating to further assess its potential in desert geomorphological research we use the vml method to study alluvial fan responses to millennial scale climatic changes the vml dating of a small tributary fan in death valley reveals two episodes of fan aggradation one ceasing at 73 55 86 75 ka during the dry period of the last interglacial mis 5a and the other finishing at 66 15 ka during the wet period of the last glacial mis 4 the vml and 36 cl dating of the distal q2c fan surfaces on hanaupah canyon fan reveal two episodes of large scale fan aggradation ended at 72 24 20 ka and 73 55 ka during the wet period of mis 4 fanhead incision and associated within channel or fantoe aggradation are found to take place during the relatively dry period of the glacial to interglacial climatic transition 12 24 ka and the holocene interglacial dry period 0 12 ka these data indicate that on the millennial to sub milankovitch timescale 10 3 10 4 years fan aggradation is a discrete sedimentational process under various climatic conditions because fan aggradation is ultimately controlled by the intensity and frequency of precipitation events which in turn are modulated by major climatic oscillations such as heinrich events dansgaard oeschger do events and glacial interglacial shifts these major climatic changes could be the pacemaker of regionally contemporaneous large area fan segmentation

quaternary highstands in bear lake valley utah and idaho surficial deposits in bear lake valley utah and idaho demonstrate that bear lake and its surrounding wetlands expanded and contracted several times during the quaternary period deposits in 40 outcrops and the geomorphology of the valley were studied to reconstruct the water level history temporal control was provided by amino acid geochronology on 29 samples of aquatic mollusks calibrated by 14 c dating and tephrochronology samples of three molluscan genera were heated and analyzed to determine intergeneric differences in aspartic asp and glutamic glu acid racemization the covariance of asp and glu racemization in these genera was used to identify aberrant amino acid analyses the rate of glu racemization was calibrated by using a parabolic model that was used to estimate sample ages although the paucity of exposures uncertainty of the depositional setting and postdepositional uplift of deposits hamper an accurate reconstruction of water level in bear lake valley several conclusions can be drawn during the middle pleistocene lacustrine or wetland environments in northern bear lake valley may have extended up to 1830 masl meters above sea level 6000 ft twice between ca 1000 100 ka bear hollow phase during the late pleistocene the shoreline of bear lake transgressed at least three times 1 to 1817 masl 5960 ft at 47 39 cal calendar year corrected ka jensen spring phase 2 to 1814 masl 5950 ft at ca 16 15 cal ka raspberry square phase and 3 to 1814 masl at ca 9 cal ka willis ranch phase bear river currently bypasses bear lake but flowed into the lake during highstands and allowed the water level to rise to the valley threshold at nounan narrows water levels have lowered to 1806 masl 5923 ft since the middle pleistocene likely because of downcutting by bear river at nounan narrows because downcutting at nounan narrows controls the maximum attainable water level in bear lake valley effects of climate change on lake level are limited and bear lake may actually have been smaller than today when lake bonneville transgressed to its maximum shoreline during the last glacial maximum

history of carbonate ion concentration over the last 100 million years abstract instead of having been more or less constant as once assumed it is now apparent that the major ion chemistry of the oceans has varied substantially over time for instance independent lines of evidence suggest that calcium concentration ca2 has approximately halved and magnesium concentration mg2 approximately doubled over the last 100 million years on the other hand the calcite compensation depth and hence the caco3 saturation has varied little over the last 100 my as documented in deep sea sediments we combine these pieces of evidence to develop a proxy for seawater carbonate ion concentration co32 over this period of time from the calcite saturation state which is proportional to the product of ca2 times co32 but also affected by mg2 we can calculate seawater co32 our results show that co32 has nearly quadrupled since the cretaceous furthermore by combining our co32 proxy with other carbonate system proxies we provide calculations of the entire seawater carbonate system and atmospheric co2 based on this reconstructed atmospheric co2 is relatively low in the miocene but high in the eocene finally we make a strong case that seawater ph has increased over the last 100 my

analysis of regional events recorded at noress abstract events recorded by noress are analyzed to determine the velocities and times of coherent crustal phases to be used in accurate locations and determination of crustal structure the events straddle two azimuthal directions and range in distance from 50 to 300 km thus sampling two cross sections of the crust and upper mantle one in the caledonides to the northwest of noress and the other to the south along the eastern rim of the oslo graben f k analysis is used to search for coherent phases in the data all vertical channels are then stacked with the appropriate time delays calculated from the phase velocities and azimuths obtained for the coherent arrivals finally a composite seismogram is made for each event by piecing together time sections from the stacks where each time piece represents a coherent arrival all detectable coherent phases are enhanced in the composite seismograms and on closer inspection it is possible to improve some of the locations from the noress bulletin this causes a number of events to group together to the same location travel time curves are constructed from plane layered homogeneous models to match travel times and phase velocities in the composite seismograms

introduction to the special issue on rotational seismology and engineering applications rotational seismology is an emerging field for studying all aspects of ro tational ground motions induced by earthquakes explosions and ambient vibrations it is of interest to a wide range of geophysical disciplines including strong motion seismology broadband seismology earthquake engineering earthquake physics seis mic instrumentation seismic hazards seismotectonics and geodesy as well as to physicists using earth based observatories for detecting gravitational waves generated by astronomical sources predicted by einstein in 1916 in this introduction to the bssa special issue on rotational seismology and engineering applications we will include 1 some background information 2 a summary of the recent events that led to this special issue and 3 an overview of its 51 papers 27 articles 11 short notes 4 reviews 6 tutorials and 3 supplementary articles our comments on these 51 papers are very brief and give just a hint of what the papers are about papers in this special issue demonstrate that earthquake monitoring cannot be limited to measuring only the three components of translational motion we also need to simultaneously measure the three components of rotational motion and the many components of strains a golden opportunity to improve our understanding of earth quakes lies in the near field of large earthquakes within about 25 km of the earthquake ruptures where nonlinear rock and soil response influences ground motions in a com plicated way

aragonitic algae in calcite seas effect of seawater mg ca ratio on algal sediment production abstract secular variation in seawater mg ca would have subjected the aragonite producing codiacean algae to two intervals of low mg calcite seas mmg ca mmg ca 2 seas since their origin in the ordovician it is asserted that the aragonite high mg calcite affinity of modern and recent tropical seas mmg ca 2 has enabled the aragonitic codiaceae to act as major carbonate sediment producers in these seas to test this assertion specimens of the sediment producing codiacean alga udotea flabellum were grown in artificial seawaters formulated at mmg ca ratios 1 0 2 5 5 2 that have occurred in the oceans throughout the geologic history of the codiaceae while the u flabellum algae produced exclusively aragonite in both the artificial boundary seawater mmg ca 2 5 and the artificial aragonite high mg calcite seawater modern seawater mmg ca 5 2 the algae produced a portion 25 3 of their caco3 as low mg calcite 4 mol mgco3 in the artificial calcite seawater mmg ca 1 0 suggesting that their caco3 polymorph control can be partially overridden by ambient seawater chemistry primary productivity calcification and linear growth of the algae decreased with reductions in ambient mg ca despite increases in absolute ca concentration of the seawater reduced calcification in the lower mg ca seawaters is probably due to kinetic difficulties of producing aragonite from seawater that favors the nucleation of calcite the decreased linear growth and primary production are likely associated with reductions in the ambient co2 available for photosynthesis resulting from the reduced calcification these findings support the assertion that the dominant ecological and sedimentological roles of codiacean algae in recent tropical seas is facilitated by a seawater mg ca ratio that favors the nucleation of aragonite over calcite furthermore producing aragonite in seawater that favors the nucleation of low mg calcite mmg ca

array observations of microseismic noise and the nature of h v in the mississippi embayment abstract ambient ground motion data were collected using phased seismic arrays in fall 2002 and spring 2007 within the mississippi embayment and at a single station external to the embayment these data allowed us to determine the wave field composition of ambient noise for understanding wave propagation mechanisms giving rise to spectral peaks using nakamura s h v technique ambient ground motions in the frequency band of 0 1 0 33 hz 10 3 sec period were dominated by spatially localized rayleigh and love wave microseisms generated by high ocean waves along the north american seaboard in the time periods of analysis seismic waves important in forming the h v peak near 4 sec period are composed of relatively high phase velocity rayleigh and love waves that convert to propagating homogeneous shear waves in the thick unconsolidated sediments of the embayment the h v resonant period is controlled by both constructive and destructive interference of these shear waves a simple relationship for the h v peak is given using a propagator matrix formulation that predicts the resonance frequency of a layered medium for surface wave motion at the base of the system the amplitude of the observed h v peak however does not give an accurate estimate of shear wave amplification because it depends on the slowness of the incident wave the inconsistency in estimated average shear wave velocities using the h v method and differential travel times of local earthquake sp phases in the mississippi embayment may be explained by misidentification of sp wave conversion points from deeper interfaces

old crow tephra found at the palisades of the yukon alaska abstract a 20 cm thick volcanic ash layer at the palisades along the yukon river is geochemically correlated with the old crow tephra a buried organic and wood rich layer above the old crow tephra probably records the last interglaciation the recognition of the old crow tephra provides the first chronologic information on the age of the thick sequence of pleistocene sediments at the palisades an important ice age mammal site in central alaska and a key locakity for the reconstruction of the history of the yukon river and the last interglaciation in central alaska

soil and geomorphic evolution within the rolling red plains using pleistocene volcanic ash deposits abstract pleistocene volcanic ash deposits are found within alluvium from the arkansas river south to the brazos river this drainage area includes tributaries originating in the high plains the raton volcanic field and the rocky mountain front range within the states of colorado new mexico kansas texas and oklahoma thirteen ash deposits are dated from within the high plains of kansas and texas eastward into central oklahoma to understand the geomorphic history and improve soil and geologic mapping within the study area unsolidated tertiary and quaternary sediments deposited in a west to east direction overlie triassic permian and pennsylvanian bedrock volcanic ash deposits are predominantly early to middle pleistocene age volcanic ash deposits were dated by the fission track method on shards the ash deposits are contained within four land resource regions the southern and central high plains the high plains breaks the rolling red plains and the reddish prairies extensive middle pleistocene constructional stream terrace surfaces occur within the rolling red plains multiple stream terrace surfaces were recognized across the study area with the highest level being dated early pleistocene to pliocene and the lowest bordering the holocene floodplains topographic cross sections 100 km long at 1 24 000 scale transecting dated ash deposits and perpendicular to major river systems were used to distinguish terrace levels constructional terrace surfaces dated by ash deposits range from 21 to 100 m above and 1 to 16 km distance from present river channels soil orders formed in quaternary alluvium are entisols inceptisols mollisols alfisols and vertisols ustic and udic soil moisture regimes and a thermic 15 to 22 c mean annual temperature soil temperature regime dominate the study area the same soil series is often mapped on terrace surfaces spanning early to middle pleistocene age because current classification does not recognize differences in deeply weathered soils greater than 2 m and lacks recognition of loess soil great groups found on early and middle pleistocene surfaces were paleustolls and argiustolls

silicate weathering and carbon cycle controls on the oligocene miocene transition glaciation changes in both silicate weathering rates and organic carbon burial have been proposed as drivers of the transient mi 1 glaciation event at the oligocene miocene transition omt 23 ma however detailed geochemical proxy data are required to test these hypotheses here we present records of li ca mg ca cd ca u ca 18o 13c and shell weight in planktonic foraminifera from marine sediments spanning the omt in the equatorial atlantic ocean li ca values increase by 1 mol mol across this interval we interpret this to indicate a 20 increase in silicate weathering rates which would have lowered atmospheric co2 potentially forcing the antarctic glaciation circa 23 ma 13c of thermocline dwelling planktonic foraminifera track the global increase in seawater 13c across the omt and during the mi 1 event hence supporting a hypothesized global increase in organic carbon burial rates high 13c previously measured in epipelagic planktonic foraminifera and high cd ca ratios during mi 1 are interpreted to represent locally enhanced primary productivity stimulated by increased nutrients supply to surface waters the fingerprint of high export production and associated organic carbon burial at this site is found in reduced bottom water oxygenation inferred from high foraminiferal u ca and enhanced respiratory dissolution of carbonates characterised by reduced foraminiferal shell weight replication of our results elsewhere would strengthen the case that weathering induced co2 sequestration preconditioned climate for antarctic ice sheet growth across the omt and increased burial of organic carbon acted as a feedback that intensified cooling at this time

comparison of electronic and mechanical schmidt hammers in the context of exposure age dating are q and r values interconvertible application of schmidt hammer exposure age dating shd to landforms has substantially increased in recent years the original mechanical schmidt hammer records r rebound values although the newly introduced electronic schmidt hammer silverschmidt facilitates greatly improved data processing it measures surface hardness differently recording q velocity values that are not a priori interconvertible with r values this study is the first to compare the performance of both instruments in the context of field based exposure age dating with a particular focus on the interconvertibility of r values and q values the study was conducted on glacially polished pyroxene granulite gneiss jotunheimen southern norway results indicate that mean q values are consistently 8 10 units higher than mean r values over the range of values normally encountered in the application of shd to glacial and periglacial landforms a convenient conversion factor of 10 units may therefore be appropriate for all but the softest rock types close to the technical resolution of the instruments the electronic schmidt hammer should therefore be regarded as a useful complement and potential replacement for the mechanical schmidt hammer conversion of published r values data to q values requires however careful control and documentation of instrument calibration copyright 2014 john wiley sons ltd

a cenozoic record of the equatorial pacific carbonate compensation depth atmospheric carbon dioxide concentrations and climate are regulated on geological timescales by the balance between carbon input from volcanic and metamorphic outgassing and its removal by weathering feedbacks these feedbacks involve the erosion of silicate rocks and organic carbon bearing rocks the integrated effect of these processes is reflected in the calcium carbonate compensation depth which is the oceanic depth at which calcium carbonate is dissolved here we present a carbonate accumulation record that covers the past 53 million years from a depth transect in the equatorial pacific ocean the carbonate compensation depth tracks long term ocean cooling deepening from 3 0 3 5 kilometres during the early cenozoic approximately 55 million years ago to 4 6 kilometres at present consistent with an overall cenozoic increase in weathering we find large superimposed fluctuations in carbonate compensation depth during the middle and late eocene using earth system models we identify changes in weathering and the mode of organic carbon delivery as two key processes to explain these large scale eocene fluctuations of the carbonate compensation depth

retrodiction of secular variations in deep sea caco 3 burial during the cenozoic abstract deep sea sediments record changes in oceanic carbonate chemistry and caco 3 sedimentation rate through temporal variations in the total burial of caco 3 and the position of the carbonate snowline i e the ocean depth at which caco 3 free sediments are first recorded this paper links mathematically secular changes in snowline to those in the burial rate through a set of relatively simple equations when the available cenozoic deep sea burial records are employed to predict secular variations in snowline the process fails at some time in the past indicating that these records are not consistent with each other the burial records are more likely the source of this problem as they involve far more uncertainties than the snowline records as a consequence we introduce a method for estimating carbonate burial through the use of a canonical caco 3 depth profile which can respond dynamically to secular changes in carbonate sedimentation and the positions of both the snowline and the carbonate saturation horizon the resulting synthetic caco 3 burial record is consistent with snowline records and indicates that the burial rates offered by davies and worsley 1981 are generally too high with highly questionable maxima at 25 and 47 ma bp our estimates of burial are more consistent with the range advanced by mackenzie and morse 1992 nevertheless our results differ from the latter with respect to timing and magnitude of the variations our approach allows simultaneous calculation of the mean carbonate ion concentration of the deep sea we find that carbonate ion levels fell through the cenozoic and are similar to those calculated by tyrrell and zeebe 2004 using a different model secular variations in caco 3 burial are found to be primarily driven by changes in the ca 2 co 3 2 ion product within the bottom waters with an increase in the sedimentation rate of caco 3 of secondary importance over the cenozoic

dissociation of oceanic methane hydrate as a cause of the carbon isotope excursion at the end of the paleocene isotopic records across the latest paleocene thermal maximum lptm indicate that bottom water temperature increased by more than 4 c during a brief time interval 104 years of the latest paleocene 55 6 ma there also was a coeval 2 to 3 excursion in the 13c of the ocean atmosphere inorganic carbon reservoir given the large mass of this reservoir a rapid 13c shift of this magnitude is difficult to explain within the context of conventional hypotheses for changing the mean carbon isotope composition of the ocean and atmosphere however a direct consequence of warming bottom water temperature from 11 to 15 c over 104 years would be a significant change in sediment thermal gradients and dissociation of oceanic ch4 hydrate at locations with intermediate water depths in terms of the present day oceanic ch4 hydrate reservoir thermal dissociation of oceanic ch4 hydrate during the lptm could have released greater than 1 1 to 2 1 1018 g of carbon with a 13c of approximately 60 the release and subsequent oxidation of this amount of carbon is sufficient to explain a 2 to 3 excursion in 13c across the lptm fate of ch4 in oceanic hydrates must be considered in developing models of the climatic and paleoceanographic regimes that operated during the lptm

small aperture array translational and rotational seismograms from distant sources an example of the jan mayen mw 6 8 of 30 august 2012 earthquake abstract we present the seismic rotation rate due to the earthquake of mw 6 7 at the jan mayen island obtained from broad band seismograms at a distance of about 2740 km the order of magnitude of the rotation rate amplitude is only 10 9 rad s in this case it is studied with a focus on rotation to translation relations a joint analysis of the rotational and translational data allowed us to determine the true backazimuth and phase velocity of s and rayleigh waves for the surface waves we studied the frequency dependence of both the backazimuth and phase velocity wave dispersion the results are independently confirmed by a method based on time delays between translational records within a small aperture array both methods revealed an unusual velocity drop in the dispersion curve between the periods of 18 and 22 s this feature may be an indication of a low velocity zone in the lower crust

late quaternary deformation of marine terraces on the cascadia subduction zone near cape blanco oregon the cape blanco region of south coastal oregon sits on the upper plate of the cascadia subduction zone about 60 70 km east of the base of the continental slope though the region has no historic coseismic deformation late quaternary deposits and landforms show abundant evidence of uplift folding and faulting a set of five late quaternary marine terraces and one uplifted holocene beach berm are preserved in the cape blanco region stratigraphic and altitudinal surveys of these physiographic features combined with several numerical and correlation age determinations permit a reconstruction of tectonic deformation near cape blanco in approximately the last 200 000 years the most cogent aspects of the neotectonics in this part of the cascadia subduction zone are that an east west trending anticline deforms the lower three terraces 80 125 ka as well as accounting for uplift of the holocene storm berm latest movement on the anticline was no more than 2 000 years ago but the anticline also deforms sediments as old as middle miocene the anticline is consistent with a north south principal contraction axis at cape blanco in about the last 100 000 years an older terrace at cape blanco approximately 200 ka is offset by two reactivated faults whose movements prior to the eocene served to suture several terranes to the north american continent tectonic tilting in the older terrace is not consistent with a north south principle axis of contraction but the axis of tilt is parallel to north northwest striking structures developed in the quaternary fold belt offshore on the continental shelf the observed deformation indicates that regional stress in the vicinity of cape blanco in the late quaternary has been accommodated by a variable pattern of strain

a new boron isotope ph calibration for orbulina universa with implications for understanding and accounting for vital effects boron isotope ratios as measured in planktic foraminifera can be a useful tracer of past ocean ph and hence help to discern the concentration of co2 in the ancient atmosphere however different species of planktic foraminifera demonstrate different patterns of boron isotope variation with ambient seawater ph therefore when applying the proxy to questions in the geological past species specific calibrations are preferable beyond the evolutionary history of a calibrated species we must rely on our understanding of the causes of the observed vital effects in the modern ocean and the applicability of that understanding to extinct species here we present a new open ocean calibration of the planktic foraminifera orbulina universa measured via multi collector inductively coupled mass spectrometry mc icpms unlike other symbiont bearing foraminifera o universa record a 11b 11b and hence ph that is lower than its surrounding seawater but with a ph sensitivity roughly equal to that of aqueous borate ion we discuss the significance of this for application of the boron isotope proxy in deep time with recommendations for best practice and future research directions

echinoderm skeletal preservation calcite aragonite seas and the mg ca ratio of phanerozoic oceans abstract the alternation between abiotic calcite and aragonite precipitation in shallow seawater and the oscillation of seawater mg ca ratio throughout the phanerozoic are both popular hypotheses echinoderms with well preserved stereom provide new empirical evidence that supports both these hypotheses analyses are reported from 29 specimens cambrian to eocene age containing ossicles preserved either as mg calcite 3 3 to 8 mole mgco3 or as mixed calcite and dolomite 5 to 12 5 mole mgco3 echinoderms with high mole mgco3 occur in the early cambrian and late carboniferous to triassic low values come from the silurian and jurassic to cretaceous the average composition of echinoderms with preserved stereom does not fall below 3 5 mol mgco3 during the phanerozoic and reaches its highest mean value of 16 0 mol mgco3 today an empirical partition coefficient of 0 03182 for modern tropical echinoids is used to indicate the mg ca ratio of ancient seawater from the mg ca ratio of fossil stereom some assumptions are involved and a likely error is calculated from the mg2 variation of modern echinoids high mean seawater mg ca ratios are calculated for early cambrian 3 3 and the late carboniferous to triassic 2 3 but never reached today s value of 5 2 low mg ca ratios 1 1 are indicated from jurassic to cretaceous echinoderms the 29 echinoderm samples plot close to first order mg ca seawater oscillations derived from geochemical models and mg ca ratios determined from fluid inclusions but considerable discrepancies exist when shorter 106 myr time intervals are considered further data and improved understanding of mg partitioning is required before accurate secular variation in the mg ca of seawater can be determined from echinoderms however they are an underused resource in this context and provide an excellent seawater archive

regional wave propagation in southern california and nevada observations from a three component seismic array we present results from a study conducted to characterize regional wave propagation in southern california and nevada the data are from events whose paths sample the southern coast ranges the southern sierra nevada mountains and the southern basin and range these regional earthquake data were recorded by a small aperture three component seismic array located at the pinon flat observatory southern california the data are analyzed using a statistical array processing algorithm that provides estimates of the propagation direction frequency wavenumber and particle motion polarization characteristics of the coherent arrivals observed at the array perhaps the most striking feature shared by these data is the extent to which the p s and lg wave trains are composed of coherent forward scattered multipathed energy the nature of the p s and lg wave trains suggests that spatially anisotropic scattering plays an important role in regional wave propagation in southern california and nevada and that scattering sources are located not on elliptical shells whose foci are the source and the receiver but instead in a limited volume subparallel to the path of the direct arrivals the high amplitude coherent nature of numerous of the pg and lg coda waves suggests that strong scattering in the source zone plays an important role in shaping the pg and lg wave trains while the p s and lg wave trains for these regional events share some general characteristics they also exhibit fairly significant differences these differences illustrate the important role regional and source zone structure play in shaping the wave field and the need to account for both complex scattering and three dimensional propagation effects in regional waveform modeling the coda for these regional data do not begin to exhibit a character consistent with the random scattering model for coda generation until the arrival of the surface waves the fact that much of the surface wave coda cannot be effectively modeled as plane waves suggests that it is not the product of scattering from distant heterogeneities

what caused the long duration of the paleocene eocene thermal maximum 1 paleorecords show that the paleocene eocene thermal maximum petm 56 ma was associated with a large carbon cycle anomaly and global warming 5 k which persisted for at least 50 kyr conventional carbon cycle climate models that include a single initial carbon input pulse over 10 kyr fail to reproduce the long duration of the petm without invoking additional slow carbon release over more than 50 kyr hereafter referred to as bleeding however a potential carbon source for the bleeding as well as its release mechanism has hitherto remained elusive here i present first principle calculations of heat transfer in marine sediments which demonstrate that a bottom water temperature anomaly as generated during the petm takes tens of thousands of years to penetrate the top few hundred meters of deep sea sediments while the initial temperature rise has been suggested to cause dissociation of the majority of oceanic methane hydrate within 10 kyr my calculations reveal a long tail of hydrate dissociation causing smaller but continued carbon release substantially beyond 10 kyr in addition i suggest that temperature enhanced metabolic processes in marine sediments and the absence of methane hydrate deposition during the petm contributed to prolonged carbon input during the event enhanced fluxes of methane over this time scale would have sustained the carbon isotope excursion and amplified long term greenhouse warming by elevating atmospheric concentrations of steady state ch4 or in oxidized form co2

suggested terminology for quaternary dating methods abstract classification of quaternary dating methods should be based on the level of quantitative information and the degree of confidence contained in the age estimates produced by the dating methods we recommend the use of the terms numerical age calibrated age relative age and correlated age to describe these levels we also classify dating methods by type into sideral isotopic radiogenic chemical and biological geomorphic and correlation methods the use of absolute is inappropriate for most dating methods and should be replaced by numerical the use of date should be minimized in favor of age or age estimate we recommend use of the abbreviations ka and ma for most ages calender dates can be used where appropriate and yr b p can be used for radiocarbon ages

seawater transport during coral biomineralization cation transport during skeletal growth is a key process controlling metal calcium me ca paleoproxy behavior in coral to characterize this transport cultured corals were transferred into seawater enriched in the rare earth element tb 3 as well as stable isotopes of calcium strontium and barium subsequent nanosims ion images of each coral skeleton were used to follow uptake dynamics these images show a continuous region corresponding to new growth that is homogeneously enriched in each tracer isotope ratio profiles across the new growth boundary transition rapidly from natural abundance ratios to a ratio matching the enriched culture solution the location of this transition is the same for each element within analytical resolution the synchronous incorporation of all these cations including the dissimilar ion terbium which has no known biological function in coral suggests that 1 there is cation exchange between seawater and the calcifying fluid and 2 these elements are influenced by similar transport mechanisms consistent with direct and rapid seawater transport to the site of calcification measured using isotope ratio profiles seawater transport rates differ from place to place on the growing coral skeleton with calcifying fluid turnover times from 30 min to 5 7 h despite these differences all the elements measured in this study show the same transport dynamics at each location using an analytical geochemical model of biomineralization that includes direct seawater transport we constrain the role of active calcium pumping during calcification and we show that the balance between seawater transport and precipitation can explain observed me ca variability in deep sea coral

comparison and contrast of processes of soil formation in the san timoteo badlands with chronosequences in california the degree of soil development associated with geomorphic surfaces in the san timoteo badlands area stb california allows correlation of the surfaces soil development indices based on field descriptions and laboratory analysis provide a basis for comparison of these soils to each other and to dated soil chronosequences at cajon pass merced and anza california the soils in this study record a complex tectonic and climatic history include preserved surfaces intermediate in soil development to those at cajon pass and do not preserve a record of the major late pleistocene to early holocene aggradational event observed elsewhere in the region pedogenesis is similar to that of regional soils in southern california with time the profiles develop progressively thicker argillic horizons and they increase in redness clay and secondary iron oxide content and amount and thickness of clay films with increasing soil age the ratio of dithionite extractable fe to total fe increases while the ratios of fe2 to fe3 and of oxalate to dithionite extractable fe decrease these trends are more subdued in the stb than elsewhere in the region perhaps because the slightly higher temperature and lower precipitation of the stb may slow the rate of transformation of ferrihydrite to hematite we use weighted means of soil development indices and rubification index values to compare the soils of this study to those at cajon pass merced and anza wide range age estimates using the maximum limits of these values result in 27 500 305 000 yr for surface q1 43 000 570 000 yr for surface q2 and 300 000 700 000 yr for surfaces q3 and q4 weighing most heavily the nearest dated chronosequences anza and cajon pass yields best estimates of age this method constrains the time of formation of the q1 surface to between 27 500 and 67 000 yr and the q2 surface to 43 000 67 000 yr and does not change the age estimates of the older surfaces

dynamic deformations of shallow sediments in the valley of mexico part i three dimensional strains and rotations recorded on a seismic array abstract we study the spatial variation in earthquake ground motions or equivalently the dynamic displacement gradient field using a novel analysis procedure borrowed from geodesy seismic data recorded in the valley of mexico by a microarray of three three component surface accelerographs and two three component accelerographs at depths of 30 m and 102 m constrain our estimates of the dynamic displacement gradient field from which strains and rotations derive for four moderate earthquakes at distances of 250 to 300 km our study focuses on the effects of low velocity surface materials on the deformation at the surface the gradients corresponding to deformation across vertical planes dominate and vertical axis rotations are of similar magnitudes as strains the greatest peak surface gradient we observed was 206 strain for the 14 september 1995 m w 7 5 earthquake at a distance of 300 km however much larger gradients occur across horizontal planes u z where u is a horizontal displacement and z is depth at some depth between 0 and 30 m these values are about a factor 10 greater than the corresponding gradient components at the surface u z for the 14 september earthquake equaled or exceeded 665 strain at depth the dynamic deformations experienced in mexico city undoubtedly have occurred before and will occur again in other densely populated areas however in many other regions the sediment response will not remain linear and elastic resulting instead in liquefaction and ground failure

increased production of calcite and slower growth for the major sediment producing alga halimeda as the mg ca ratio of seawater is lowered to a calcite sea level abstract laboratory experiments were conducted to subject the calcareous alga halimeda a prolific producer of aragonite in the modern ocean to a variety of ambient mg ca ratios these experiments were based on three predictions 1 that halimeda would calcify at a lower rate when the ambient mg ca ratio was reduced from its high level in modern seawater 5 2 2 that this alga would grow more slowly under these conditions because its calcification yields as a byproduct co2 which is available for photosynthesis and 3 that the calcite content of halimeda s skeleton would increase as a percentage of total caco3 as predicted reduction of the mg ca ratio of ambient artificial seawater from its modern level to estimated early oligocene and early eocene levels 2 5 and 1 5 respectively resulted in progressively lower rates of calcification production of organic matter and linear growth for halimeda incrassata colonies the ambient mg ca ratio exerted a stronger influence over the rate of calcification than ca2 which in the geologic past has risen in seawater whenever the ambient mg ca ratio has declined thus although elevation of ca2 at such times would have promoted the calcification and growth of halimeda the concomitant decline of the mg ca ratio would have had a stronger negative effect in addition the percentage of skeletal material consisting of calcite rose from 8 in modern day seawater to 16 in artificial early oligocene seawater and 46 in artificial early eocene seawater magnesium was incorporated into this calcite as a function of the ambient mg ca ratio with a fractionation pattern differing only slightly from that of nonskeletal calcite halimeda exerts less biological control over its biomineralization than the related genera penicillus and udotea which in previous experiments produced only 22 25 of skeletal caco3 as calcite in seawater having a very low mg ca ratio 1 0 nonetheless it is likely that many taxa of green algae that produce little or no calcite today would have produced a substantial proportion of skeletal low mg caco3 as calcite in ancient seas such as those of the cretaceous whose mg ca ratios were close to unity

a comparative study of quaternary dating techniques applied to sedimentary deposits in southwest victoria australia abstract at five sites in western victoria a total of five quaternary dating techniques have been applied to shell beds varying in age from holocene to beyond the last interglacial to examine the age concordancy of the methods 89 analyses were conducted 16 by radiocarbon 26 by uranium series disequilibrium 26 by amino acid racemisation 5 by thermoluminescence and 16 by electron spin resonance the latter previously reported by goede 1989 uncertainties associated with diagenetic environments of samples precluded reliable numerical age assignments for beds older than holocene instead relative dating of shell beds was based on a reference site goose lagoon which was assigned to the last interglacial based on its morphostratigraphic setting and concordant results of three of the dating methods amino acid racemisation uranium series disequilibrium and electron spin resonance overall there was considerable agreement between methods although not all were applied to each site uranium series dating proved most problematical migration of radionuclides between groundwater and shells introduced large errors at one site and led to appreciable uncertainties at others

calibration of the b ca proxy in the planktic foraminifer orbulina universa to paleocene seawater conditions the b ca ratio of planktic foraminiferal calcite a proxy for the surface ocean carbonate system displays large negative excursions during the paleocene eocene thermal maximum petm 55 9 ma consistent with rapid ocean acidification at that time however the b ca excursion measured at the petm exceeds a magnitude that modern ph calibrations can explain numerous other controls on the proxy have been suggested including foraminiferal growth rate and the total concentration of dissolved inorganic carbon dic here we present new calibrations for b ca versus the combined effects of ph and dic in the symbiont bearing planktic foraminifer orbulina universa grown in culture solutions with simulated paleocene seawater elemental composition high ca low mg and low total boron concentration b t we also investigate the isolated effects of low seawater b t high ca reduced symbiont photosynthetic activity and average shell growth rate on o universa b ca in order to further understand the proxy systematics and to determine other possible influences on the petm records we find that average shell growth rate does not appear to determine b ca in high calcite saturation experiments in addition our paleocene calibration shows higher sensitivity than the modern calibration at low b oh 4 dic given a large dic pulse at the petm this amplification of the b ca response can more fully explain the petm b ca excursion however further calibrations with other foraminifer species are needed to determine the range of foraminifer species specific proxy sensitivities under these conditions for quantitative reconstruction of large carbon cycle perturbations

blind testing of rock varnish microstratigraphy as a chronometric indicator results on late quaternary lava flows in the mojave desert california rock varnish is a manganiferous dark coating ubiquitous in desert landscapes to test the validity of varnish microstratigraphy as a chronometric indicator varnish samples were collected from radiometrically dated and undated late quaternary lava flows in amboy cima and pisgah volcanic fields avf cvf pvf in the mojave desert of california western united states varnish microstratigraphies show a replicable layering sequence that appears to record regional climate changes that likely correspond in time to the younger dryas and heinrich events in the north atlantic region microstratigraphic patterns on these volcanic fields match patterns found in varnishes from other western us sites with available radiometric age constraints based on this regional chronology varnishes from the a flow h flow and a stone pavement surface in the cima volcanic field were estimated to be 16 5 24 74 85 and 74 85 ka respectively these ages are consistent with previously published cosmogenic 3 he ages of 18 20 72 74 and 80 85 ka for these geomorphic surfaces varnishes from the i flow at cima yielded a puzzling age estimate of 39 ka which is consistent with an older 3 he age of 37f6 ka reported for the i flow but inconsistent with a younger 3 he age of 31f7 ka and a cosmogenic 36 cl age of 27f1 3 ka for the same flow reinterpretation of the original varnish age data with knowledge of then available field mapping results of the i flow suggests that the i cone is polycyclic and different flow units were probably unintentionally sampled in the field the revised varnish ages of 30 and 39 ka for the i flow thus may be in good agreement with their corresponding 3 he and 36 cl ages in a blind test of the method varnishes from the phase 1 flow at pisgah an unnamed flow called here the ivflow at cima and the amboy flow were estimated to be 24 30 46 60 and 74 85 ka respectively these ages agree well with 36 cl ages of 22 5f1 3 46f2 and 79f5 ka reported for the same flows by phillips geomorphology 2002 these test results provide convincing evidence that varnish microstratigraphy once radiometrically calibrated can be used as a valid dating tool to estimate surface exposure ages of desert landforms in the western us drylands d 2002 elsevier science b v all rights reserved

convergent cenozoic co2 history reconstructions of atmospheric carbon dioxide concentrations over the past 65 million years are heading towards consensus it is time for systematic testing of the proxies against measurements and against each other

use of multiparameter relative age methods for age estimation and correlation of alluvial fan surfaces on a desert piedmont eastern mojave desert california numerical and calibrated age determinations of the late quaternary alluvial fan deposits of the soda mountains piedmont in the mojave desert provide an opportunity to study the utility of the multiparameter relative age ra method for distinguishing and mapping geomorphic surfaces on a desert piedmont most ra parameters could not discriminate between deposits of holocene age although pavements have formed over locally significant parts of surfaces as young as middle holocene several parameters including lithologic composition particle size soil development and varnish cover permit distinguishing between holocene surfaces and late pleistocene surfaces statistically significant differences in initial particle size and lithology of the deposits inferred to be the result of complex interaction among hillslope alluvial fan and eolian processes and climatic change create conditions unfavorable for use of most ra techniques in contrast soil profile development and varnish cover data are successful in discrimination among deposits of holocene and pleistocene age this is attributed to the development of pedogenic features and varnish that are strongly dependent on dust influx and to the relatively minor dependence of these features on differences in the depositional character of the fan

constraining the evolution of neogene ocean carbonate chemistry using the boron isotope ph proxy abstract over the course of the neogene the earth underwent profound climatic shifts from the sustained warmth of the middle miocene to the development of plio pleistocene glacial interglacial cycles major perturbations in the global carbon cycle have occurred alongside these shifts however the lack of long term carbonate system reconstructions currently limits our understanding of the link between changes in co2 carbon cycling and climate over this time interval here we reconstruct continuous surface ocean ph co2 and surface ocean aragonite saturation state using boron isotopes from the planktonic foraminifer trilobatus trilobus and we perform a sensitivity analysis of the key variables in our calculations e g 11 bsw ca sw ccd we show that the choice of 11 b sw influences both seawater ph and co2 while ca sw reconstructed dissolved inorganic carbon exerts a significant influence only on co2 over the last 22 myr the lowest ph levels occurred in the middle miocene climate optimum mmco 17 14 myr ago reaching 7 6 0 1 units in all our scenarios the extended warmth of the mmco corresponds to mean co2 and aragonite saturation state levels of 470 630 ppm and 2 7 3 5 respectively despite a general correspondence between our co2 record and climate all co2 scenarios show a peak at 9 ma not matched by corresponding changes in climate reconstructions this may suggest decoupling i e significant co2 change without a discernible climate response for a limited interval in the late miocene 11 6 8 5 ma although further refinement of our understanding of the temporal evolution of the boron isotopic composition of seawater is necessary to fully evaluate the nature of the relationship between co2 and climate nonetheless from our long term view it is clear that low latitude open ocean marine ecosystems are unlikely to have experienced sustained surface ph and saturation levels below 7 7 and 1 7 respectively during the past 14 million years 66 ci

soil geomorphic research a selective overview abstract much soil geomorphologic research involves tracking the development of soils with time otherwise known as soil chronosequences most of these have been undertaken on landforms underlain by quaternary depsits of varying ages in general there is a predictable variation in both soil horizon sequence and amounts of constituents such as clay fe and caco 3 with time the rate at which these constituents accumulate in the soil is a function of parent material bioclimate and atmospheric dust influx and because of the latter soils in aridic regions can form at rapid rates profile properties can be used to estimate the ages of deposits and faulting events but the error on the estimated age can be 50 or greater the position of salt accumulations in soil profiles is one of the best indications of climatic change and these can be modelled to compare with various climatic parameters present and past profile characteristics due to pedogenic thresholds however can mimic those due to climatic change so close dating is necessary to differentiate the effects of both soil geomorphic data are essential to understand the origin of ancient paleosols in the sedimentary rock records but a major problem still is one of recognition of these features as soils and to separate the effects of pedogenesis from those of diagenesis

factors affecting b ca ratios in synthetic aragonite abstract measurements of b ca ratios in marine carbonates have been suggested to record seawater carbonate chemistry however experimental calibration of such proxies based on inorganic partitioning remains limited here we conducted a series of synthetic aragonite precipitation experiments to evaluate the factors influencing the partitioning of b ca between aragonite and seawater our results indicate that the b ca ratio of synthetic aragonites depends primarily on the relative concentrations of borate and carbonate ions in the solution from which the aragonite precipitates not on bicarbonate concentration as has been previously suggested the influence of temperature was not significant over the range investigated 20 40 c however partitioning may be influenced by saturation state and or growth rate based on our experimental results we suggest that aragonite b ca ratios can be utilized as a proxy of co 3 2 boron isotopic composition 11 b is an established ph proxy thus b ca and 11 b together allow the full carbonate chemistry of the solution from which the aragonite precipitated to be calculated to the extent that aragonite precipitation by marine organisms is affected by seawater chemistry b ca may also prove useful in reconstructing seawater chemistry a simplified boron purification protocol based on amberlite resin and the organic buffer tris is also described

influence of solution chemistry on the boron content in inorganic calcite grown in artificial seawater abstract the ratio of boron to calcium b ca in marine biogenic carbonates has been proposed as a proxy for properties of seawater carbonate chemistry applying this proxy to planktic foraminifera residing in the surface seawater largely in equilibrium with the atmosphere may provide a valuable handle on past atmospheric co 2 concentrations however precise controls on b ca in planktic foraminifera remain enigmatic because it has been shown to depend on multiple physicochemical seawater properties to help establish a firm inorganic basis for interpreting the b ca records we examined the effect of a suite of chemical parameters ca 2 ph dic salinity and po 4 3 on b ca in inorganic calcite precipitated in artificial seawater these parameters were primarily varied individually while keeping all others constant but we also tested the influence of ph and dic at a constant calcite precipitation rate r by concurrent ca 2 adjustments in the simple ca 2 ph and dic experiments both r and b ca increased with these parameters in the ph ca 2 and dic ca 2 experiments at constant r on the other hand b ca was invariant at different ph and decreased with dic respectively these patterns agree with the behavior of solution b total dic ratio such that at a fixed b total it is independent of ph but decreases with dic based on these results r and b total dic ratio appear to be the primary controls on b ca in inorganic calcite suggesting that both b oh 4 and b oh 3 are possibly involved in b incorporation moreover b ca modestly increased with salinity and po 4 3 inorganic calcite precipitated at higher r and in the presence of oxyanions such as so 4 2 and po 4 3 in growth solutions often undergoes surface roughening due to formation of crystallographic defects vacancies and occasionally amorphous hydrous caco 3 these non lattice sites may provide additional space for b particularly b oh 3 consequently besides the macroscopic influence of r and bulk solution chemistry molecular scale processes associated with calcite nucleation can be an important consideration for b incorporation especially in complex ionic solutions lastly the covariance of b ca with dic and salinity observed here qualitatively agrees with those in planktic foraminifers it follows that their impact on foraminiferal b ca is partly inorganically driven which may explain why the effect is evident across different species

aminostratigraphic correlation and geochronology of two quaternary loess localities central mississippi valley abstract amino acid epimeric aile ile values from terrestrial molluscs are used to define and correlate three aminozones in loess sequences exposed across the central mississippi valley in arkansas and tennessee three superposed aminozones are defined at wittsburg quarry arkansas primarily using aile ile values from total hydrolysates of the gastropod genus hendersonia peoria loess aile ile 0 07 0 01 roxana silt 0 14 0 02 and a third loess 0 28 0 06 loess units at wittsburg quarry can be correlated on lithologic characteristics eastward across the mississippi valley to the old river section near memphis tennessee however only one loess unit is fossil bearing peoria loess aile ile 0 05 at that section radiocarbon analyses of charcoal from the upper roxana silt ca 26 000 to 29 000 yr old and mollusc shell carbonate from the basal roxana silt ca 39 000 yr old are used to calibrate amino acid epimeric data for the central mississippi valley these data applied to the apparent parabolic kinetic model of r m mitterer and n kriausakul 1989 quaternary science reviews 8 353 357 suggest an illinoian 120 000 yr age for the third loess in the central mississippi valley that is correlative with part of the loveland loess in illinois and iowa

improved moraine age interpretations through explicit matching of geomorphic process models to cosmogenic nuclide measurements from single landforms abstract the statistical distributions of cosmogenic nuclide measurements from moraine boulders contain previously unused information on moraine ages and they help determine whether moraine degradation or inheritance is more important on individual moraines here we present a method for extracting this information by fitting geomorphic process models to observed exposure ages from single moraines we also apply this method to 94 10 be apparent exposure ages from 11 moraines reported in four published studies our models represent 10 be accumulation in boulders that are exhumed over time by slope processes moraine degradation and the delivery of boulders with preexisting 10 be inventories to moraines inheritance for now we neglect boulder erosion and snow cover which are likely second order processes given a highly scattered data set we establish which model yields the better fit to the data and estimate the age of the moraine from the better model fit the process represented by the better fitting model is probably responsible for most of the scatter among the apparent ages our methods should help resolve controversies in exposure dating we reexamine the conclusions from two published studies based on our model fits

pleistocene glacial history of the southern ahklun mountains southwestern alaska soil development morphometric and radiocarbon constraints abstract four new ams 14 c ages glacial mapping and measurements of soil development loess thickness and moraine morphology constrain the age and extent of at least three quaternary advances by outlet lobes of an ice cap over the ahklun mountains of southwestern alaska the relative age data are from 107 sites correlated to 25 ice marginal positions in the kanektok goodnews togiak and kulukak river valleys and along the southeastern flank of the range radiocarbon ages provide minimum ages for six and a maximum age for one of the former ice margins soil and morphometric parameters subdivide the ice limits into three relative age groups one to three pre wisconsin advances probably middle pleistocene in age are represented by drift with relatively thick b horizons 60 5 cm with bt horizons thick loess caps 80 12 cm and broad moraines 135 134 m with gentle side slopes 7 5 an extensive early wisconsin sensu lato s l advance 39 9 ka and three associated stillstands or readvances are characterized by intermediate soil and morphometric parameters bw and weak bt horizons with thicknesses of 40 11 cm loess thicknesses of 69 46 cm crest widths of 38 13 m and slope angles of 14 4 the maximum late wisconsin advance 16 9 ka and two readvances or stillstands are associated with thin 20 5 cm weakly to moderately developed bw horizons thin loess caps 28 8 cm narrow crest widths 28 9 m and steep slope angles 18 3 the data confirm that early wisconsin glaciers in southeast beringia were much more extensive than late wisconsin glaciers which were apparently limited by availability of moisture

beyond methane towards a theory for the paleocene eocene thermal maximum abstract extreme global warmth and an abrupt negative carbon isotope excursion during the paleocene eocene thermal maximum petm have been attributed to a massive release of methane hydrate from sediments on the continental slope 1 however the magnitude of the warming 5 to 6 c 2 3 and rise in the depth of the ccd 2 km 4 indicate that the size of the carbon addition was larger than can be accounted for by the methane hydrate hypothesis additional carbon sources associated with methane hydrate release e g pore water venting and turbidite oxidation are also insufficient we find that the oxidation of at least 5000 gt c of organic carbon is the most likely explanation for the observed geochemical and climatic changes during the petm for which there are several potential mechanisms production of thermogenic ch4 and co2 during contact metamorphism associated with the intrusion of a large igneous province into organic rich sediments 5 is capable of supplying large amounts of carbon but is inconsistent with the lack of extensive carbon loss in metamorphosed sediments as well as the abrupt onset and termination of carbon release during the petm a global conflagration of paleocene peatlands 6 highlights a large terrestrial carbon source but massive carbon release by fire seems unlikely as it would require that all peatlands burn at once and then for only 10 to 30 ky in addition this hypothesis requires an order of magnitude increase in the amount of carbon stored in peat the isolation of a large epicontinental seaway by tectonic uplift associated with volcanism or continental collision followed by desiccation and bacterial respiration of the aerated organic matter is another potential mechanism for the rapid release of large amounts of co2 in addition to the oxidation of the underlying marine sediments the desiccation of a major epicontinental seaway would remove a large source of moisture for the continental interior resulting in the desiccation and bacterial oxidation of adjacent terrestrial wetlands

chronology of lake bonneville 30 000 to 10 000 yr b p abstract 368 radiocarbon ages between 30 and 10 cal ka for samples collected from outcrops and shorelines from the lake bonneville basin have been compiled for this paper samples include 1 organic materials from sources outside the lake such as wood charcoal plant fragments from emergent aquatics and dispersed wetland organics and 2 carbonate materials deposited in the lake such as mollusk shells tufa charophyte debris ooids and marl in general organic materials provide rather than precise ages for lacustrine events but their interpretation is less complicated than interpretation of results from carbonate samples the data set shows evidence of contamination of different carbonate samples with both younger carbon and older carbon for example a radiocarbon reservoir at certain places within the lake during the middle transgressive phase accounts for ages of mollusk shells that are older than basal wood ages at similar altitudes the large number of ages permits an accurate reconstruction of the lake chronology conflicts between ages can be detected and reliable ages can be meaningfully integrated in interpretations if fewer ages were available the chronology might look simpler but its accuracy would be unknown

holocene glacier fluctuations in the american cordillera abstract in many areas of the american rocky mountains colorado wyoming utah idaho montana cascade range washington oregon and the sierra nevada california radiocarbon ages suggest that ice receded to near present limits before 10 ka bp a pre altithermal readvance or stillstand left moraines ca 1 3 km beyond and ca 50 300 m below present glacier margins at one locality on glacier peak in washington these deposits are perhaps dated to the early holocene but in general these deposits are probably at least 10 ka old glacial advances during the altithermal ca 8 to 5 ka bp elsewhere are rare radiocarbon evidence for altithermal glacial advances in the colorado front range is questionable the earliest radiocarbon dated neoglacial advances occurred about 5 ka bp in the washington cascades moraines and related deposits believed to be of early neoglacial age i e 5 to 3 ka bp elsewhere are poorly dated for example moraines believed to date to the early neoglacial in colorado triple lakes and wyoming temple lake are actually late pleistocene age based on radiocarbon ages derived from lake sediments at the type localities although relative age data i e lichens rock weathering soils from many areas suggest a three fold neoglacial sequence little supporting radiocarbon evidence is available however tephrochronology distinguishes three neoglacial advances near mount rainier in washington in most mountain ranges of the western united states fresh unweathered sharp crested moraines usually adjacent to present ice margins or near headwalls in empty cirques date to the little ice age of the last several centuries however detailed photographic or other historical records of glacial fluctuations during the last century are rare and detailed mass balance studies rarer still whether or not pre little ice age glacial fluctuations in the american cordillera are synchronous must await better radiometric dating of local moraine sequences

model of seawater composition for the phanerozoic we present an inverse model of phanerozoic seawater com position calibrated against updated paleoseawater compositions from fluid inclusions in marine halites the model considers step wise alteration of seawater composition via 1 variable input of river water 2 variable rates of alteration of seawater through reactions at mid ocean ridges and 3 variable rates of alteration of seawater through reactions on ridge flanks and across the ocean floor in general the model achieves agreement with paleoseawater fluid inclusion data for na 1 c a 2 1 s o 4 2 2 and k 1 particularly when variable runoff is considered variable rates of basalt seawater interactions at both ridges and ridge flanks are required to understand the evolution of seawater particularly the observed near constant concentration of k 1 through time

evaluating the planktic foraminiferal b ca proxy for application to deep time paleoceanography abstract the cenozoic era has been characterized by large perturbations to the oceanic carbon cycle and global climatic changes but quantifying the magnitude and cause of these shifts is still subject to considerable uncertainty the boron calcium b ca ratio of fossil planktic foraminifera shells is a promising tool for reconstructing surface ocean carbonate chemistry during such events previous studies indicate that symbiont bearing planktic foraminiferal b ca depends on the b oh 4 dic ratio of seawater and potentially when combined with foraminiferal 11 b proxy reconstructions of b oh 4 an opportunity to reconstruct surface ocean dic in the geologic past there are however two barriers towards interpreting records from the pre pleistocene era 1 changes in seawater major ion chemistry in the past might have affected foraminiferal b ca and 2 modern foraminifera species show variable b ca calibration sensitivities that cannot be constrained in now extinct species here we address these challenges with new experiments in which we have cultured modern symbiont bearing foraminifera globigerinoides ruber pink and trilobatus sacculifer in seawater with simulated early cenozoic seawater chemistry high ca low mg and low b t we explore mechanisms that can account for the inter species trends that are observed in foraminiferal b ca and propose a framework that can be used to apply b ca calibrations to now extinct species for reconstructing climate perturbations under varying seawater chemistries

multiwavelet seismic wave gradiometry abstract a new technique to determine uncertainty estimates for wave parameters obtained by seismic wave gradiometry is established using the multiwavelet transform wave gradiometry uses spatial gradients as measured by a small scale seismic array to estimate the wave parameters of propagation azimuth slowness geometrical spreading and radiation pattern the advantage of wave gradiometry is that the wave parameters are estimated on a point by point basis for the entire seismogram previous work on wave gradiometery employed the continuous wavelet transform to decompose the wave field into narrow band realizations prior to gradiometric analysis so that the wave parameters are resolved as functions of both time and frequency to build on this approach i incorporated the multiwavelet transform the multiwavelet transform decomposes the wave field into a series of mutually orthogonal wavelet coefficients which can then be analyzed by wave gradiometry each result can then be treated as a sample from a statistical population the method is tested on synthetic data with and without noise a relatively low degree of uncorrelated noise can have a significant impact on the quality of the results finally multiwavelet gradiometry is applied to a single earthquake recorded by a small subset of usarray stations and shows that the method accurately and robustly determines the wave parameters

low magnesium calcite produced by coralline algae in seawater of late cretaceous composition abstract shifts in the mg ca ratio of seawater driven by changes in midocean ridge spreading rates have produced oscillations in the mineralogy of nonskeletal carbonate precipitates from seawater on time scales of 108 years since cambrian time skeletal mineralogies of anatomically simple organisms functioning as major reef builders or producers of shallow marine limestones have generally corresponded in mineral composition to nonskeletal precipitates here we report on experiments showing that the ambient mg ca ratio actually governs the skeletal mineralogy of some simple organisms in modern seas coralline algae produce skeletons of high mg calcite 4 mol mgco3 we grew three species of these algae in artificial seawaters having three different mg ca ratios all of the species incorporated amounts of mg into their skeletons in proportion to the ambient mg ca ratio mimicking the pattern for nonskeletal precipitation thus the algae calcified as if they were simply inducing precipitation from seawater through their consumption of co2 for photosynthesis presumably organic templates specify the calcite crystal structure of their skeletons in artificial seawater with the low mg ca ratio of late cretaceous seas the algae in our experiments produced low mg calcite 4 mol mgco3 the carbonate mineral formed by nonskeletal precipitation in those ancient seas our results suggest that many taxa that produce high mg calcite today produced low mg calcite in late cretaceous seas

secular oscillations in the carbonate mineralogy of reef building and sediment producing organisms driven by tectonically forced shifts in seawater chemistry the primary mineralogy of oolites and early marine carbonate cements led sandberg nature 305 1983 19 22 to divide the phanerozoic eon into three intervals of aragonite seas and two intervals of calcite seas hardie geology 24 1996 279 283 has shown that these oscillations together with synchronous oscillations in the mineralogy of marine potash evaporites can be explained by secular shifts in the mg ca ratio of seawater driven by changes in spreading rates along mid ocean ridges the hardie model also predicts that high mg calcite should precipitate along with aragonite as it does in today s aragonite sea we have uncovered oscillations in the carbonate mineralogy of hypercalcifying organisms ones that have produced massive skeletons large reefs or voluminous bodies of sediment that correspond to sandberg s aragonite seas and calcite seas and that are predicted by the hardie model particular groups of corals sponges and algae appear to have been dominant reef builders only when favored by an appropriate mg ca ratio in seawater in early and middle paleozoic calcite seas calcite i reefs were dominated by calcitic tabulate heliolitid and rugose corals and calcitic stromatoporoids in contrast during the period of late paleozoic early mesozoic aragonite seas aragonite ii aragonitic groups of sponges scleractinian corals and phylloid algae as well as high mg calcitic red algae were principal reef builders during late cretaceous time at the acme of calcite ii massive rudists displaced aragonitic hermatypic corals in today s aragonite sea aragonite iii scleractinian corals are again dominant reef builders along with high mg calcitic coralline algae major sediment producing algae exhibit temporal patterns similar to those of reef builders calcitic receptaculitids flourished during calcite i whereas aragonitic dasycladaceans did not become dominant rock formers until aragonite ii during calcite ii calcitic nannoplankton formed massive coccolith chalks in warm shallow seas of the late cretaceous after the mg ca ratio of seawater had reached a very low value and calcium concentration a very high value as the mg ca ratio of seawater rose and calcium concentration fell during the cenozoic era individual coccoliths on average became less massive and encrusted cells less thickly by pliocene time during aragonite iii the prominent genus discoaster secreted only narrow rayed coccoliths that covered less than 25 of the cell surface also during aragonite iii the aragonitic green alga halimeda emerged as the dominant skeletal sediment producer in reef tracts the influence of seawater chemistry on skeletal secretion appears to have been especially strong for morphologically simple taxa that exert relatively weak control over their own calcification such groups include algae sponges corals and bryozoans morphological simplicity also permits these groups to adopt vegetative or colonial modes of growth that confer success in competition for space on reefs this linkage in addition to the basic chemical demands of hypercalcification has given the mg ca ratio of seawater strong control over the success of individual reef building taxa more generally this ratio appears to have strongly influenced evolutionary changes in the skeletal mineralogy of sponges and cheilostome bryozoans throughout their history we conclude that throughout phanerozoic time a chain of causation has extended from mid ocean ridge processes via seawater chemistry to the mineralogical and biological composition of reef communities and bioclastic carbonate deposits

the schmidt hammer as a holocene calibrated age dating technique testing the form of the r value age relationship and defining the predicted age errors most recent developments of schmidt hammer exposure age dating shd as a calibrated age dating tool have been limited by the use of locations at two age control points this has necessitated 1 making assumptions about a linear r value age relationship and 2 basing predictions of age errors only on r value variance at the two age control points this paper analyses 9900 r values obtained from multiple age control points on a sequence of glacio isostatically raised shorelines with well constrained ages skuleskogen high coast world heritage site and environs gulf of bothnia northern sweden ranging from modern to 10 5 ka in age the sampling design involved 30 measurements on granite beach boulders from 30 sites at 11 age control points the r value age relationship is best described by a linear function ordinary least squares ols with an r 2 of 0 89 p 0 0001 predicted age errors are calculated using two approaches 1 ols regression which takes account of the uncertainties associated with the regression line and the age control points and 2 weighted total least squares wtls regression which in addition takes account of possible shoreline age errors and the heteroscedasticity of r value residuals with increasing age with both approaches 95 predicted age errors are relatively modest 355 455 years and 300 515 years respectively with larger r value variance and hence uncertainty for older surfaces and the possibility of further improvement from a more selective field sampling scheme that differentiates between age related and non age related rock surface variability our results also indicate that for certain lithologies and weathering environments it is possible to construct reliable calibrated age curves from relatively few age control points

holocene rock varnish microstratigraphy and its chronometric application in the drylands of western usa abstract analyses of hundreds of rock varnish samples from latest pleistocene and holocene geomorphic features in the drylands of western usa reveal a regionally replicable holocene microlamination sequence this sequence consists of 12 approximately evenly spaced weak dark layers intercalated with 13 orange yellow layers preliminary radiometric age calibration indicates that six dark layers in the upper portion of the sequence were deposited during the last 6000 yr diagnostic of the little ice age and late holocene wet events five dark layers in the lower portion of the sequence were deposited after the termination of the pleistocene but slightly before 7000 ybp indicative of the early holocene wet events and one dark layer in the middle portion of the sequence was deposited around 6500 ybp suggestive of the middle holocene wet phase our age calibration further indicates that the holocene wet events represented by the dark layers largely correlate in time with the millennial scale holocene cooling events in the north atlantic region this radiometrically calibrated and climatically correlated holocene microlamination sequence was then used as a unique correlative dating tool to determine surface exposure ages of geomorphic and geoarchaeological features in western usa deserts the varnish microlamination vml dating of debris flow fan deposits in death valley california yields minimum ages of 12 500 12 500 11 100 11 100 10 300 9400 and 2800 ybp for six debris flow fan building events suggesting that such events were more likely to have occurred during relatively wet periods of the holocene the vml dating of a prehistoric grinding stone from chili of northern new mexico yields a minimum age of 900 1100 ybp for the abandonment of this occupation site by the anasazi indians the vml dating of a prehistoric flaked stone a primary core from ocotillo southern california yields a minimum age of 12 500 ybp for the flaking of this stone artifact suggesting at least a paleo indian human occupation at ocotillo during the terminal pleistocene these results indicate that when properly applied the vml dating technique has the great potential to yield numerical age assignments for surface stone tools petroglyphs and geoglyphs of prehistoric age in the drylands of western usa

secular variations in the carbonate chemistry of the oceans over the cenozoic abstract oceanic carbonate chemistry during the cenozoic has affected the climatology ecology and marine geology of our planet yet we have limited means to know the evolution of that chemistry due to a lack of preserved and unaltered seawater samples and a continuing paucity of proxies modeling is often used to address this problem here we offer a simple data driven secular timescale inverse model for the mean cenozoic carbonate chemistry of the oceans inputs for the model include carbonate compensation depth ccd caco3 burial seawater temperature atmospheric co2 and carbonate ion records as well as a simple set of original but justified assumptions the model retrodicts the total dissolved inorganic carbon dic carbonate alkalinity calk and ph of the surface and deep waters of the ocean the retrodicted dic and calk records do not indicate any unusually elevated values in the early cenozoic as found in some past studies if the ccd record from lyle et al 2008 is employed the changes in dic and calk appear entirely related to changes in the alkalinity input to the pelagic oceans and atmospheric co2 however with the ccd from palike et al 2012 the increases in dic and calk during the last 15 ma reflect the effects of ocean cooling using either ccd record our model provides consistent retrodictions of the available ph record our results are not consistent with many past modeling assumptions such as constancy of alkalinity in surface waters or the ratio of shallow and deep carbonate ion concentrations finally we use our results to provide new estimates of atmospheric co2 based on boron isotopes and find significantly lower co2 values in the early cenozoic than previous values