paleoredox changes across the paleocene eocene thermal maximum walvis ridge odp sites 1262 1263 and 1266 evidence from mn and u enrichment factors an understanding of sediment redox conditions across the paleocene eocene thermal maximum petm 55 ma is essential for evaluating changes in processes that control deep sea oxygenation as well as identifying the mechanisms responsible for driving the benthic foraminifera extinction sites cored on the flanks of walvis ridge ocean drilling program leg 208 sites 1262 1266 and 1263 allow us to examine changes in bottom and pore water redox conditions across a 2 km depth transect of deep sea sediments of petm age recovered from the south atlantic here we present measurements of the concentrations of redox sensitive trace metals manganese mn and uranium u in bulk sediment as proxies for redox chemistry at the sediment water interface and below all three walvis ridge sites exhibit bulk mn enrichment factors ef ranging between 4 and 12 prior to the warming values at crustal averages mn ef 1 during the warming interval and a return to pre event values during the recovery period u enrichment factors across the petm remains at crustal averages u ef 1 at site 1262 deep and site 1266 intermediate depth u enrichment factors at site 1263 shallow peaked at 5 immediately prior to the petm and dropped to values near crustal averages during and after the event all sites were lower in dissolved oxygen content during the petm before and after the petm the deep and intermediate sites were oxygenated while the shallow site was suboxic our geochemical results indicate that oxygen concentrations did indeed drop during the petm but not sufficiently to cause massive extinction of benthic foraminifera

lake banyoles northeastern spain a last glacial to holocene multi proxy study with regard to environmental variability and human occupation analyses of a 67 m long sediment core from lake banyoles northeastern spain have revealed evidence for the palaeoclimate history of the northern iberian peninsula investigations have included hi

slow release of fossil carbon during the palaeocene eocene thermal maximum a brief period of warming 55 9 myr ago has been attributed to the release of massive amounts of carbon geochemical and model data suggest the peak rate of carbon emission during this interval was relatively slow and significantly lower than present day levels of carbon emissions to the atmosphere

an abyssal carbonate compensation depth overshoot in the aftermath of the palaeocene eocene thermal maximum the palaeocene eocene thermal maximum was associated with a massive release of carbon marine sediments suggest a temporary deepening of the calcite compensation depth indicating extensive silicate weatheringin the aftermath of the event the palaeocene eocene thermal maximum was associated with a massive release of carbon marine sediments suggest a temporary deepening of the calcite compensation depth indicating extensive silicate weatheringin the aftermath of the event during the palaeocene eocene thermal maximum petm about 56 million years ago thousands of petagrams of carbon were released into the atmosphere and ocean in just a few thousand years followed by gradual sequestration over approximately 200 000 years if silicate weathering is one of the key negative feedbacks that removed this carbon a period of seawater calcium carbonate saturation greater than pre event levels would be expected during the event s recovery phase in marine sediments this should be recorded as a temporary deepening of the depth below which no calcite is preserved the calcite compensation depth ccd previous and new sedimentary records from sites that were above the pre petm ccd show enhanced carbonate accumulation following the petm a new record from an abyssal site in the north atlantic that lay below the pre petm ccd shows a period of carbonate preservation beginning about 70 000 years after the onset of the petm providing the first direct evidence for an over deepening of the ccd this record confirms an overshoot in ocean carbonate saturation during the petm recovery simulations with two earth system models support scenarios for the petm that involve a large initial carbon release followed by prolonged low level emissions consistent with the timing of ccd deepening in our record our findings indicate that sequestration of these carbon emissions was most likely the result of both globally enhanced calcite burial above the ccd and at least in the north atlantic an over deepening of the ccd

development of a novel empirical framework for interpreting geological carbon isotope excursions with implications for the rate of carbon injection across the petm abstract as an episode of rapid global warming associated with the release of massive quantities of carbon to the atmosphere and oceans the paleocene eocene thermal maximum petm 56 ma is considered a potential analog for modern anthropogenic carbon emissions however the prevailing order of magnitude uncertainty in the rate of carbon release during the petm precludes any straightforward comparison between the paleo record and the modern similar barriers exist to the interpretation of many other carbon isotope excursions in the geological record here we use the earth system model cgenie to quantify the consequences of differing carbon emissions rates on the isotopic record of different carbon reservoirs we explore the consequences of a range of emissions scenarios from durations of carbon input of years to millennia and constant versus pulsed emissions rates and trace how the isotopic signal is imprinted on the different carbon reservoirs from this we identify a characteristic relationship between the difference in carbon isotope excursion sizes between atmospheric co2 and dissolved inorganic carbon dic and the duration of carbon emissions to the extent that available isotopic data spanning the petm constrain the size of the marine and atmospheric carbon isotopic excursions applying this empirical relationship suggests the duration of the component of carbon emissions that dominates the isotopic signal could be less than 3000 yr however utilizing the ratio of excursion size in the atmosphere to ocean as a metric to constrain duration of carbon emissions highlights the necessity to strengthen estimates for these two measurements across the petm our general interpretive framework could be equally applied in assessing rates of carbon emissions for other geological events

influence of vegetal cover on sediment particle size distribution in natural rainfall conditions in a semiarid environment abstract sediment samples were collected during four years from two plots one covered by natural vegetation and the other a replica of the same plot from which the vegetation was removed manually disturbed plot in order to evaluate the effects of vegetal cover on sediment particle size distribution particle size was measured using a coulter ls130 laser diffraction device the effective size distribution of the sediment was compared with equivalent measurements of the same samples after chemical and mechanical dispersion ultimate size distribution to investigate the detachment and transport mechanisms involved in sediment mobilisation the ratio between the ultimate particle size composition of the transported sediment and that of the parent soil provided a measure of the particle size selectivity of the transported sediment the median effective particle was coarser than the median ultimate particle for almost all the events recorded in both plots confirming that much of the sediment in the runoff includes a substantial proportion of aggregates moreover the texture of the sediment was finer than that of the matrix soil with a depletion of clay and sand in exchange for an enrichment in silt indicating the existence of transport selectivity in both plots the effect of vegetal cover on the size distribution of the sediment was particularly evident after high intensity rainfall events an i30 of 40 mm h 1 was found to be the threshold value for changes to be produced in the sediment texture of the disturbed plot with aggregates being broken down and 10 20 more sand particles being observed at this value than after events of lower intensity no differences were found in the natural plot after rainfall of varying intensities the vegetal cover in the natural plot reduced the energy available for erosion from the rainfall by 50 and the energy from the runoff by 75 hindering the break down of aggregates and the transport of dense particles moreover the presence of vegetation meant the raindrop was the predominant contributor to soil loss in contrast to the disturbed plot where both raindrop and runoff contributed to the erosion

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

late quaternary large scale rotational slides induced by river incision the arroyo de gor area guadix basin se spain the arroyo de gor is a highly incised stream up to 200 m that has eroded into the pliocene pleistocene infill of the guadix basin in the betic cordillera se spain this paper concentrates on a particular reach of this stream namely the cenascuras gorafe reach where abundant inactive rotational slides can be recognized on both hillslopes of the canyon shaped valley the rotational slides have surface areas of 5 15 ha and volumes of mobilized material of 5 15 hm3 these rotational slides can be recognized by their main scarps which are still well featured at both margins of the valley as well as by the counter hillslope rotation of the strata in their bodies the surfaces of rupture are concave their width being greater than their length i e the landslides are elongated in a direction perpendicular to the landsliding displacement and parallel to the stream at depth the surfaces of rupture developed on fine grained sediments mostly clays underlying the conglomerates and sands affected by the rotational slides the clays at the surface of rupture are smectite rich and show several features produced by the landsliding such as striations and sigmoidal shaped structures the cenascuras gorafe canyon has been developed by a combination of entrenchment fracturing and landsliding initial deep entrenchment of the stream is attributed to a base level lowering related to the capture of the former endorheic basin by the gualdalquivir river in the late pleistocene this river incision created a canyon with subvertical unstable walls which due to gravitational instability would give way to vertical open tension cracks some distance from the canyon edge the tension cracks would end at depths equal to the base of the canyon which also coincides with the contact between the conglomerates and the underlying clays the rotational slides are thought to have occurred during heavy rains by a combination of piping which would have lengthened the tension cracks and infiltration which would reduce the shear strength along the gently dipping contact between conglomerates and the underlying clays thus the blocks bounded by the tension cracks and the subhorizontal lithological contact would slide under their own weight on the subhorizontal surfaces of reduced shear strength several age constraints lead us to tentatively assign the landslides to the isotope stage 5 around 32 ka an interglacial period agreed to be wetter and slightly warmer than the present day semi arid climate

recovering the true size of an eocene hyperthermal from the marine sedimentary record 1 hyperthermals episodes of abrupt global warming associated with the massive injection of carbon into the oceans and atmosphere represent possible analogs for future climate change however uncertainties in their magnitude rate and duration arising as a result of mixing processes and changes in carbonate preservation as the sediment record is formed complicate their use in constraining climate sensitivity and the role of carbon cycle feedbacks here we use cgenie an earth system model of intermediate complexity to assess likely magnitude and rate of carbon input taking a small hyperthermal event from the early middle eocene c22nh3 49 2ma as a case study we develop an iterative method combined with a sediment model simulating the formation and mixing of deep sea sediments to converge on an estimate for the true magnitude of the carbon cycle perturbation in the atmosphere and ocean that drives the event in inverting the 0 95 benthic 13 cexcursion recorded atocean drilling program site 1258 we obtain an estimate of at least 1 45 for the atmospheric co2 13 c excursion that drove event c22nh3 we also assess controls on intersite variation of event shape in model sediments and find that sedimentation rate is the strongest determinant of modeled event size with higher sedimentation rate sites recording the atmospheric signal more accurately our revised estimate for the size of c22nh3 implies a total carbon input almost two thirds higher than would be deduced if the recorded 13 c excursion magnitude was taken at face value

high resolution records of the late paleocene thermal maximum and circum caribbean volcanism is there a causal link two recently drilled caribbean sites contain expanded sedimentary records of the late paleocene thermal maximum a dramatic global warming event that occurred at ca 55 ma the records document significant environmental changes including deep water oxygen deficiency and a mass extinction of deep sea fauna intertwined with evidence for a major episode of explosive volcanism we postulate that this volcanism initiated a reordering of ocean circulation that resulted in rapid global warming and dramatic changes in the earth s environment

high resolution deep sea carbon and oxygen isotope records of eocene thermal maximum 2 and h2 eocene thermal maximum 2 etm2 and h2 were two short lived global warming events that occurred 2 m y after the paleocene eocene thermal maximum petm ca 56 ma we have generated benthic foraminiferal stable carbon and oxygen isotope records of four sites along a depth transect on walvis ridge 3 5 1 5 km paleodepth southeast atlantic ocean and one site on maud rise weddell sea to constrain the pattern and magnitude of their carbon isotope excursions cies and deep sea warming at all sites etm2 is characterized by 3 c warming and a 1 4 cie the h2 event that occurred 100 k y later is associated with 2 c warming and a 0 8 cie the magnitudes of the 13 c and 18 o excursions of both events are signifi cantly smaller than those during the petm but their coherent relation indicates that the 13 c change of the exogenic carbon pool was similarly related to warming during these events despite the much more gradual and transitioned onset of etm2 and h2

shallow hypersaline lakes as paleoclimate archives a case study from the laguna salada malaga province southern spain abstract although numerous studies concerning the holocene climate of the southern iberian peninsula were accomplished within the last few decades the climate history of this region is still poorly understood various studies deal with a combination of proxies which are neither easy to compare nor is their connection easy to explain e g due to spatial patterns and time transgression within this study the suitability of the lacustrine sediments from the laguna salada andalucia region southern spain as a paleoclimate archive is investigated the lake sediments were evaluated using a multi proxy approach including sedimentological mineralogical geochemical and biological analyses the sediments reflect the evolution of the lake from pre medieval times onwards and characeae as well as ostracod analyses give an indication of paleosalinity moreover does the geochemical composition provide profound information concerning changes of elemental and mineralogical composition nevertheless a robust high resolution chronology could not be achieved owed to the scarcity of material available for radiocarbon dating and contamination problems furthermore poor preservation of pollen restricted the reconstruction of vegetation history which could have complemented important information concerning climatic changes and human activity

large landslides induced by fluvial incision in the cenozoic duero basin spain abstract the pleistocene opening of the endorheic duero river drainage basin northwestern spain and central portugal has led to river incision creation of steep valley sides and development of large 0 1 km2 and episodically active rotational and roto translational landslides along river reaches where a weak geological lithology has been exposed by river erosion these landslides occur in the central part of the duero basin despite low precipitation weak contemporary seismicity and low regional relief these landslides occurred as a result of the downcutting of the duero river and its tributaries through a sequence of miocene basin fill sediments in the last few thousand years the incision reached a series of high plasticity low strength clay layers within the sedimentary sequence owing to this mechanism these landslides occurred in a specific area at a specific period of time all of the large landslides are located at the outside of meander bends suggesting that river lateral erosion facilitated slip failures recent anthropogenic activities to control river flows and to stabilize river banks have decreased the possibility of future landslides in this area

cyclostratigraphy and the problem of astrochronologic testing abstract when milankovitch cycles are preserved in the geologic record they provide a direct link between chronometer and climate change and thus a remarkable opportunity to constrain the evolution of the surficial earth system the identification of such cycles has allowed exploration of the geologic record with unprecedented temporal resolution and has spurred the development of a rich theoretical framework for climatic change accompanying these successes however has been a persistent skepticism how does one reliably test for astronomical forcing pacing in stratigraphic and paleoclimate data especially when time is poorly constrained from this perspective it would seem that the merits and promise of astrochronology a phanerozoic time scale measured in 20 000 to 400 000 year increments also serves as its achilles heel if the confirmation of such geologically short temporal rhythms defies rigorous hypothesis testing the implications are substantial since much of our understanding of paleoclimate change throughout the cenozoic and beyond is firmly rooted in astrochronologic interpretation in this study a conceptual framework for assessing earth system response to astronomical insolation changes and the propagation of that signal into the geologic record is used as a guide to understand the nature of the problem of astrochronologic testing this framework emphasizes three challenges contamination stratigraphic distortion and temporal calibration a statistical optimization method timeopt meyers 2015 is formulated as a solution to these three challenges providing an approach for astrochronologic testing that objectively evaluates time scale uncertainty while simultaneously identifying an optimal model for climate and depositional system response to astronomical forcing new extensions to the technique are presented allowing explicit reconstruction of distortions to the primary forcing that are known to be omnipresent in the stratigraphic record to illustrate the utility of this approach it is applied to five well studied stratigraphic series throughout the phanerozoic supporting their astronomical origin and yielding constraints on the evolution of the earth system and the astronomical solutions themselves future directions that build on this foundation are discussed including the utility of process based null models approaches for earth system transfer function reconstruction and mapping out ancient solar system behavior and earth moon history using the geologic archive of milankovitch cycles the timeopt approach recognizes astronomy geochronology paleoclimatology and depositional system reconstruction as a unified geoscientific inverse problem

carbonate saturation dynamics during the paleocene eocene thermal maximum bathyal constraints from odp sites 689 and 690 in the weddell sea south atlantic abstract spatiotemporal patterns of carbonate dissolution provide a critical constraint on carbon input during an ancient 55 5 ma global warming event known as the paleocene eocene thermal maximum petm yet the magnitude of lysocline shoaling in the southern ocean is poorly constrained due to limited spatial coverage in the circum antarctic region this shortcoming is partially addressed by comparing patterns of carbonate sedimentation at the site 690 petm reference section to those herein reconstructed for nearby site 689 biochemostratigraphic correlation of the two records reveals that the first 36 ka of the carbon isotope excursion cie signaling petm conditions is captured by the site 689 section while the remainder of the cie interval and nearly all of the cie recovery are missing due to a coring gap a relatively expanded stratigraphy and higher carbonate content at mid bathyal site 689 indicate that dissolution was less severe than at site 690 thus the bathymetric transect delimited by these two petm records indicates that the lysocline shoaled above site 689 1 100 m while the calcite compensation depth remained below site 690 1 900 m in the weddell sea region the ensuing recovery of carbonate sedimentation conforms to a bathymetric trend best explained by gradual lysocline deepening as negative feedback mechanisms neutralized ocean acidification further biochemostratigraphic evidence indicates the tail end of the cie recovery interval at both sites has been truncated by a hiatus most likely related to vigorous production and advection of intermediate waters

profile convexities in bedrock and alluvial streams abstract longitudinal profiles of bedrock streams in central kentucky and of coastal plain streams in southeast texas were analyzed to determine the extent to which they exhibit smoothly concave profiles and to relate profile convexities to environmental controls none of the kentucky streams have smoothly concave profiles because all observed knickpoints are associated with vertical joints if they are migrating it either occurs rapidly between vertical joints or migrating knickpoints become stalled at structural features these streams have been adjusting to downcutting of the kentucky river for at least 1 3 ma suggesting that the time required to produce a concave profile is long compared to the typical timescale of environmental change a graded concave longitudinal profile is not a reasonable prediction or benchmark condition for these streams the characteristic profile forms of the kentucky river gorge area are contingent on a particular combination of lithology structure hydrologic regime and geomorphic history and therefore do not represent any general type of equilibrium state few stream profiles in se texas conform to the ideal of the smoothly strongly concave profile major convexities are caused by inherited topography geologic controls recent and contemporary geomorphic processes and anthropic effects both the legacy of quaternary environmental change and ongoing changes make it unlikely that consistent boundary conditions will exist for long further the few exceptions within the study area i e strongly and smoothly concave longitudinal profiles suggest that ample time has occurred for strongly concave profiles to develop and that such profiles do not necessarily represent any mutual adjustments between slope transport capacity and sediment supply the simplest explanation of any tendency toward concavity is related to basic constraints on channel steepness associated with geomechanical stability and minimum slopes necessary to convey flow this constrained gradient concept cgc can explain the general tendency toward concavity in channels of sufficient size with minimal lithological constraints and with sufficient time for adjustment unlike grade or equilibrium based theories the cgc results in interpretations of convex or low concavity profiles or reaches in terms of local environmental constraints and geomorphic histories rather than as disequilibrium features

assessing ocean alkalinity for carbon sequestration over the coming century humanity may need to find reservoirs to store several trillions of tons of carbon dioxide co2 emitted from fossil fuel combustion which would otherwise cause dangerous climate change if it were left in the atmosphere carbon storage in the ocean as bicarbonate ions by increasing ocean alkalinity has received very little attention yet recent work suggests sufficient capacity to sequester copious quantities of co2 it may be possible to sequester hundreds of billions to trillions of tonnes of c without surpassing post industrial average carbonate saturation states in the surface ocean when globally distributed the impact of elevated alkalinity is potentially small and may help ameliorate the effects of ocean acidification however the local impact around addition sites may be more acute but is specific to the mineral and technology the alkalinity of the ocean increases naturally because of rock weathering in which 1 5 moles of carbon are removed from the atmosphere for every mole of magnesium or calcium dissolved from silicate minerals e g wollastonite olivine anorthite and 0 5 moles for carbonate minerals e g calcite dolomite these processes are responsible for naturally sequestering 0 5 billion of co2 tons per year alkalinity is reduced in the ocean through carbonate mineral precipitation which is almost exclusively formed from biological activity most of the previous work on the biological response to changes in carbonate chemistry have focused on acidifying conditions more research is required to understand carbonate precipitation at elevated alkalinity to constrain the longevity of carbon storage a range of technologies have been proposed to increase ocean alkalinity accelerated weathering of limestone enhanced weathering electrochemical promoted weathering ocean liming the cost of which may be comparable to alternative carbon sequestration proposals e g 20 100 tco2 1 there are still many unanswered technical environmental social and ethical questions but the scale of the carbon sequestration challenge warrants research to address these

abrupt deep sea warming palaeoceanographic changes and benthic extinctions at the end of the palaeocene a remarkable oxygen and carbon isotope excursion occurred in antarctic waters near the end of the palaeocene 57 33 myr ago indicating rapid global warming and oceanographic changes that caused one of the largest deep sea benthic extinctions of the past 90 million years in contrast the oceanic plankton were largely unaffected implying a decoupling of the deep and shallow ecosystems the data suggest that for a few thousand years ocean circulation underwent fundamental changes producing a transient state that although brief had long term effects on environmental and biotic evolution

spatiotemporal patterns of carbonate sedimentation in the south atlantic implications for carbon cycling during the paleocene eocene thermal maximum abstract rapid carbon input into the ocean atmosphere system caused a dramatic shoaling of the lysocline during the paleocene eocene thermal maximum petm a transient 170 kyr global warming event that occurred roughly 55 ma carbon cycle models invoking an accelerated carbonate silicate feedback mechanism to neutralize ocean acidification predict that the lysocline would subsequently deepen to depths below its original position as the marine carbonate system recovered from such a perturbation to test this hypothesis records of carbonate sedimentation and preservation for petm sections in the weddell sea odp site 690 and along the walvis ridge depth transect odp sites 1262 1263 and 1266 were assembled within the context of a unified chronostratigraphy the meridional gradient of undersaturation delimited by these records shows that dissolution was more severe in the subtropical south atlantic than in the weddell sea during the petm a spatiotemporal pattern inconsistent with the view that atlantic overturning circulation underwent a transient reversal deepening of the lysocline following its initial ascent is signaled by increases in caco3 and coarse fraction content at all sites carbonate preservation during the recovery period is appreciably better than that seen prior to carbon input with carbonate sedimentation becoming remarkably uniform over a broad spectrum of geographic and bathymetric settings these congruent patterns of carbonate sedimentation confirm that the lysocline was suppressed below the depth it occupied prior to carbon input and are consistent with the view that an accelerated carbonate silicate geochemical cycle played an important role in arresting petm conditions

a model of suboxic sedimentary diagenesis suitable for automatic tuning and gridded global domains and solid phase mno2 the model misses some of the very high sediment surface mno2 concentrations observed in for example the california borderlands we believe that these sites must receive a higher input of reactive mn than the crustal abundance of the clay rain the model was deployed on every 2 2 grid point below 1000 m of the global seafloor using gridded maps of organic carbon rain to the seafloor and overlying water chemistry the deep sea carbon burial efficiency is 7 with 95 of respiration by oxic metabolism the model was also run against a new depth oxygen hypsometry of the global ocean with sediment area as a function of overlying oxygen concentration and average depth related to carbon fluxes to include the effects of shallow water sediments this analysispredictsthat shallow waters 1000 m account for 88 ofrespiration and oxygen accounts for 66 of respiration overall denitrification is closely coupled to organic nitrogen fluxes to the sediment and the global rate is estimated to be 1 4 10 14 mol yr 1 a factor of 6 8 higher than the corresponding estimate from middelburg et al 1996 throwing the nitrogen cycle in the ocean into imbalance index terms 4863 oceanography biological and chemical sedimentation 4851 oceanography biological and chemical oxidation reduction reactions 4804 oceanography biological and chemical benthic processes benthos 4805 oceanography biological and chemical biogeochemical cycles 1615 keywords diagenesis

a blast of gas in the latest paleocene simulating first order effects of massive dissociation of oceanic methane hydrate carbonate and organic matter deposited during the latest paleocene thermal maximum is characterized by a remarkable 2 5 excursion in delta 13c that occurred over approximately 10 4 yr and returned to near initial values in an exponential pattern over approximately 2 x 10 5 yr it has been hypothesized that this excursion signifies transfer of 1 4 to 2 8 x 10 18 g of ch4 from oceanic hydrates to the combined ocean atmosphere inorganic carbon reservoir a scenario with 1 12 x 10 18 g of ch4 is numerically simulated here within the framework of the present day global carbon cycle to test the plausibility of the hypothesis we find that 1 the delta 13c of the deep ocean shallow ocean and atmosphere decreases by 2 3 over 10 4 yr and returns to initial values in an exponential pattern over approximately 2 x 10 5 yr 2 the depth of the lysocline shoals by up to 400 m over 10 4 yr and this rise is most pronounced in one ocean region and 3 global surface temperature increases by approximately 2 degrees c over 10 4 yr and returns to initial values over approximately 2 x 10 6 yr the first effect is quantitatively consistent with the geologic record the latter two effects are qualitatively consistent with observations thus significant ch4 release from oceanic hydrates is a plausible explanation for observed carbon cycle perturbations during the thermal maximum this conclusion is of broad interest because the flux of ch4 invoked during the maximum is of similar magnitude to that released to the atmosphere from present day anthropogenic ch4 sources

initial assessment of the carbon emission rate and climatic consequences during the end permian mass extinction numerous lines of geochemical and stable isotopic evidence indicate that the end permian mass extinction was accompanied by abrupt climate change induced by co2 addition catastrophic end permian siberian volcanism may have released a large amount of co2 into the atmosphere and pushed the earth s system beyond a critical threshold causing the mass extinction however the injection rate total amount and source of co2 are largely unknown we conducted a suite of simulations using the recently published carbon isotope records and u pb ages from meishan section in zhejiang province china an earth system model of intermediate complexity cgenie http www genie ac uk was used to extract the pattern of co2 release needed to replicate the observed carbon isotope excursion across the permian triassic boundary this analysis leads us to suggest that the source of co2 must have been significantly heavier than typical biogenic or thermogenic methane to explain the significant warming that occurred during and after the extinction event nevertheless as with the paleocene eocene thermal maximum end permian rates of co2 addition were likely small compared with modern fossil fuel burning but considerably more protracted such that the likely total co2 emitted significantly exceeded the modern fossil fuel reserves peak emission rates corresponded to the onset of the maximum extinction interval consistent with carbon cycle disruption including volcanogenic co2 induced warming and perhaps ocean acidification as a trigger for the end permian mass extinction

variations to calcareous nannofossil caco 3 content during the middle eocene c21r h6 hyperthermal event 47 4 ma in the gorrondatxe section bay of biscay western pyrenees abstract the carbonate content of calcareous nannofossils is dependent on seawater composition one of the factors that affect seawater chemistry and consequently the degree of calcification in coccolithophores is temperature as seen in present day warming oceans the depth at which carbonates are dissolved calcite compensation depth ccd can rise due to an increase in hco 3 and decrease in ph leading to a major dissolution on the seabed and burndown similar processes have also been deduced for eocene hyperthermal events such as the petm and etm2 this study reports changes in coccolith carbonate mass from a hemipelagic setting gorrondatxe at 1500 m paleodepth during the core of a minor eocene hyperthermal event namely the c21r h6 event 47 44 47 32 ma image analysis techniques were used to determine differences in the carbonate mass of selected calcareous nannofossil taxa revealing species specific patterns the caco 3 mass of chiasmolithus solitus decreased by 50 over the course of the c21r h6 event and many specimens also lost their crossed central bars an additional indication of mass loss reticulofenestra sp 3 5 m showed a similar trend but the percentage of mass lost was lower toweius pertusus interpreted as being reworked mirrored the behaviour of chiasmolithus solitus suggesting that the caco 3 mass loss may have occurred on the seabed rather than in the water column in general it can be concluded that the lysocline rose to 1500 m paleobathymetry in the bay of biscay during the c21r h6 event formation of corrosive bottom water in the north atlantic ocean is regarded as being responsible for the rise in the lysocline

dynamics of fossil fuel co2 neutralization by marine caco3 a detailed model of the ocean circulation and carbon cycle was coupled to a mechanistic model of caco3 diagenesis in deep sea sediments to simulate the millennium scale response of the oceans to future fossil fuel co2 emissions to the atmosphere and deep sea simulations of deep sea injection of co2 show that caco3 dissolution is sensitive to passage of high co2 waters through the atlantic ocean but caco3 dissolution has a negligible impact on atmospheric pco2 or the atmospheric stabilization co2 emission in the coming centuries the ultimate fate of the fossil fuel co2 will be to react with caco3 on the seafloor and on land an initial caco3 dissolution spike reverses the net sedimentation rate in the ocean until it is attenuated by an enhanced vertical gradient of alkalinity after about 1000 years the magnitude of the initial spike is sensitive to assumptions about the kinetics for caco3 dissolution but subsequent behavior appears to be less model dependent neutralization by seafloor caco3 occurs on a timescale of 5 6 kyr and is limited to at most 60 70 of the fossil fuel release even if the fossil fuel release is smaller than the seafloor erodible inventory of caco3 additional neutralization by terrestrial caco3 restores a balance between caco3 weathering and seafloor accumulation on a timescale of 8 5 kyr while the deficit of seafloor caco3 the lysocline is replenished with an e folding timescale of approximately 18 kyr the final equilibrium with caco3 leaves 7 8 of the fossil fuel co2 remaining in the atmosphere to be neutralized by the silicate rock cycle on a time frame of hundreds of thousands of years

influence of variable rates of neritic carbonate deposition on atmospheric carbon dioxide and pelagic sediments short term imbalances in the global cycle of shallow water calcium carbonate deposition and dissolution may be responsible for much of the observed pleistocene change in atmospheric carbon dioxide content however any proposed changes in the alkalinity balance of the ocean must be reconciled with the sedimentary record of deep sea carbonates the possible magnitude of the effect of shallow water carbonate deposition on the dissolution of pelagic carbonate can be tested using numerical simulations of the global carbon cycle boundary conditions can be defined by using extant shallow water carbonate accumulation data and pelagic carbonate deposition dissolution data on timescales of thousands of years carbonate deposition versus dissolution is rarely out of equilibrium by more than 1 5 x 10 13 mole yr 1 results indicate that the carbonate chemistry of the ocean is rarely at equilibrium on timescales less than 10 ka this disequilibrium is probably due to sea level induced changes in shallow water calcium carbonate deposition dissolution an interpretation that does not conflict with pelagic sedimentary data from the central pacific

an extraterrestrial 3he based timescale for the paleocene eocene thermal maximum petm from walvis ridge iodp site 1266 in the deep sea the paleocene eocene thermal maximum petm is often marked by clay rich condensed intervals caused by dissolution of carbonate sediments capped by a carbonate rich interval constraining the duration of both the dissolution and subsequent cap carbonate intervals is essential to computing marine carbon fluxes and thus testing hypotheses for the origin of this event to this end we provide new high resolution helium isotope records spanning the paleocene eocene boundary at odp site 1266 in the south atlantic the extraterrestrial 3he 3he et concentrations replicate trends observed at odp site 690 by farley and eltgroth 2003 by assuming a constant flux of 3he et we constrain relative changes in accumulation rates of sediment across the petm and construct a new age model for the event in this new chronology the zero carbonate layer represents 35 kyr some of which reflects clay produced by dissolution of paleocene pre petm sediments above this layer carbonate concentrations increase for 165 kyr and remain higher than in the latest paleocene until 234 48 34 kyr above the base of the clay the new chronology indicates that minimum 13 c values persisted for a maximum of 134 27 19 kyr and the inflection point previously chosen to designate the end of the cie recovery occurs at 217 44 31 kyr this allocation of time differs from that of the cycle based age model of rohl et al 2007 in that it assigns more time to the clay layer followed by a more gradual recovery of carbonate rich sedimentation the new model also suggests a longer sustained 13 c excursion followed by a more rapid recovery to pre petm 13 c values these differences have important implications for constraining the source s of carbon and mechanisms for its subsequent sequestration favoring models that include a sustained release of carbon after an initial pulse

towards the time dependent modeling of sediment core data on a global basis the procedure for the simulation of a time dependent sediment stratigraphy for 4 different sediment species with a global biogeochemical ocean general circulation model is presented in this feasibility study a sediment column for the last 131 kyr was accumulated through use of a variable ocean velocity field mixed from preindustrial and glacial ocean time slices in a kinematic approach the biogenic components of sediment are entirely a model product artificial sediment cores were recovered from the simulated stratigraphy the approach is the foundation for a systematic comparison of paleoclimate simulations with the sediment record through use of adjoint model codes the direct 4 dimensional data assimilation of paleoclimate observations will become possible in the long range

evaluation of paleocene eocene thermal maximum carbon isotope record completeness an illustration of the potential of dynamic time warping in aligning paleo proxy records

compactional behavior of fine grained sediments examples from deep sea drilling project cores laboratory experiments statistical analysis of field data and theoretical models are combined in the attempt to derive standard compaction curves for various deep sea sediments which are in compaction equilibrium with the overburden a revised and generalized version of athy s law together with laboratory experiments allows the classification of sediments in terms of the amount of porewater structurally bound to the particles surfaces especially suction pressure experiments are useful in quantifying the forces that bind water on the particle surfaces the sediments analyzed almost range from systems of suspended grains to nearly perfect colloidal systems the methods and equations required to derive the relevant parameters are given for both downhole porosity density measurements and laboratory experiments

the role of the global carbonate cycle in the regulation and evolution of the earth system we review one of the most ancient of all the global biogeochemical cycles and one which reflects the profound geochemical and biological changes that have occurred as the earth system has evolved through time that of calcium carbonate caco3 in particular we highlight a mid mesozoic revolution in the nature and location of carbonate deposition in the marine environment driven by the ecological success of calcareous plankton this drove the creation of a responsive deep sea sedimentary sink of caco3 the result is that biologically driven carbonate deposition provides a significant buffering of ocean chemistry and of atmospheric co2 in the modern system however the same calcifying organisms that under pin the deep sea carbonate sink are now threatened by the continued atmospheric release of fossil fuel co2 and increasing acidity of the surface ocean we are not yet in a position to predict what the impact on caco3 production will be or how the uptake of fossil fuel co2 by the ocean will be affected this uncertainty in the future trajectory of atmospheric co2 that comes from incomplete understanding of the marine carbonate cycle is cause for concern

warming the fuel for the fire evidence for the thermal dissociation of methane hydrate during the paleocene eocene thermal maximum dramatic warming and upheaval of the carbon system at the end of the paleocene epoch have been linked to massive dissociation of sedimentary methane hydrate however testing the paleocene eocene thermal maximum hydrate dissociation hypothesis has been hindered by the inability of available proxy records to resolve the initial sequence of events the cause of the paleocene eocene thermal maximum carbon isotope excursion remains speculative primarily due to uncertainties in the timing and duration of the paleocene eocene thermal maximum we present new high resolution stable isotope records based on analyses of single planktonic and benthic foraminiferal shells from ocean drilling program site 690 weddell sea southern ocean demonstrating that the initial carbon isotope excursion was geologically instantaneous and was preceded by a brief period of gradual surface water warming both of these findings support the thermal dissociation of methane hydrate as the cause of the paleocene eocene thermal maximum carbon isotope excursion furthermore the data reveal that the methane derived carbon was mixed from the surface ocean downward suggesting that a significant fraction of the initial dissociated hydrate methane reached the atmosphere prior to oxidation

an alternative model for caco3 over shooting during the petm biological carbonate compensation decreased caco3 content of deep sea sediments argues for rapid and massive acidification of the oceans during the paleocene eocene thermal maximum petm 56 ma bp in the course of the subsequent recovery from this acidification sediment caco3 content came to exceed pre petm levels known as over shooting past studies have largely attributed the latter to increased alkalinity input to the oceans via enhanced weathering but this ignores potentially important biological factors we successfully reproduce the caco3 records from walvis ridge in the atlantic ocean including over shooting using a biogeochemical box model replication of the caco3 records required 1 introduction of a maximum of 6500 gtc of co2 directly into deep ocean waters or 8000 gtc into the atmosphere 2 limited deep water exchange between the indo atlantic and pacific oceans 3 the disappearance of sediment bioturbation during a portion of the petm and 4 most central to this study a 50 reduction in net caco3 production during acidification in our simulations over shooting is an emergent property generated at constant alkalinity input no weathering feedback as a consequence of attenuated caco3 productivity this occurs because lower net caco3 production from surface waters allows alkalinity to build up in the deep oceans alkalinization thus promoting deep water super saturation restoration of caco3 productivity later in the petm particularly in the indo atlantic ocean leads to greater accumulation of caco3 ergo over shooting which returns the ocean to pre petm conditions over a time scale greater than 200 ka

effects of sea level sea ice extent and nutrient availability on primary production at the umnak plateau bering sea iodp site u1339 during marine isotope stage mis 5 abstract this study investigates how primary production responded to changes in nutrient availability sea level and sea ice coverage at the umnak plateau during marine isotope stage mis 5 and parts of mis 4 and mis 6 the umnak plateau during mis 4 and mis 6 had low primary production resulting from extensive sea ice coverage that enhanced stratification and limited nutrient replenishment this nutrient limitation was relieved during the deglaciation going into mis 5 when previously exposed continental shelves were flooded and the eastern aleutian island passes were opened by an increase in sea level resulting in an increase in productivity opening and closing of the eastern aleutian island passes during the rest of mis 5 reflected fluctuations in sea level and likely affected nutrient sources and productivity at the umnak plateau nutrients during sea level lowstands were likely sourced by the aleutian north slope current whereas most of the sea level high stands throughout mis 5 had nitrogen sourced by an increase in nitrogen fixation and the assimilation of remineralized nitrogen which led to highly depleted nitrogen isotope values never before seen for the northern pacific higher sea level and productivity near the beginning of mis 5 likely reflected mis 5e however a discrepancy between two diatom productivity proxies suggests that changing environmental conditions stimulated a change in the dominant diatom species this highlights the complexities associated with productivity in the bering sea and emphasizes the need to continue studying how productivity and ecosystems changed during previous warm periods

new chronology for the late paleocene thermal maximum and its environmental implications the late paleocene thermal maximum lptm is associated with a brief but intense interval of global warming and a massive perturbation of the global carbon cycle we have developed a new orbital chronology for ocean drilling program odp site 690 weddell sea southern ocean by using spectral analysis of high resolution geochemical records the lptm interval spans 11 precessional cycles yielding a duration of 210 to 220 k y the 13 c anomaly associated with the lptm has a magnitude of about 2 5 to 3 we show that about 2 of the excursion occurs within two steps that each were less than 1000 yr in duration the remainder developed through a series of steps over 52 k y the timing of these steps is consistent with a series of nearly catastrophic releases of methane from gas hydrates punctuated by intervals of relative equilibria between hydrate dissociation and carbon burial further we are able to correlate the records between odp sites 690 and 1051 western north atlantic on the scale of 21 k y cycles which demonstrates that the details of the 13 c excursion are recognizable between distant sites comparison of cycle records at sites 690 and 1051 suggests that sediment representing the interval 30 k y just prior to and at the onset of the lptm are missing in the latter location this unconformity probably resulted from slope failure accompanying methane hydrate dissociation within 10 k y of the start of the lptm

temporal variations of large wood abundance and mobility in the blanco river affected by the chaiten volcanic eruption southern chile abstract the aim of this study is to analyze the temporal variation in abundance and transport of in channel wood along a river affected by a volcanic eruption considering the mobility and retention rates in detail the 2008 eruption of chaiten volcano southern chile severely affected the blanco river basin causing changes in channel morphology and large wood lw dynamics along the fluvial corridor of the river a fourth order stream on the southern slope of the volcano temporal dynamics of lw were investigated from january 2015 until march 2016 in three 80 m long study reaches of the active channel in the lower course of the river every wood element 1 m in length and 0 1 m in diameter within the active channel of each reach was georeferenced measured tagged and characterized wood mobility rate defined as the number of tagged wood pieces repositioned or not found within each study reach to total tagged lw in the same reach and retention rate defined as the number of tagged lw pieces found within each study reach to total tagged wood pieces in the same reach were calculated considering two periods one in summer and one in autumn winter a regional flood frequency analysis estimated flood magnitude defining a recurrence interval of 1 year for summer floods and 10 25 years for autumn winter floods results highlighted how eight years after the eruption the types of lw are still influenced by the impacts of pyroclastic density currents on riparian vegetation the characteristics and abundance of monitored lw are typical of a river system with frequent wood transport the mobility rate ranges between 42 and 94 during the summer and autumn winter period respectively while the wood volume decreases during the summer and increases in autumn winter large wood mobility was also found to vary according to the predominant morphological settings with lower values in narrower channels compared to wider wetted areas in this context the greatest abundance of lw was detected after the higher floods corresponding to an input of lw up to 285 35 m3 ha 1 along the blanco river ordinary floods deliver lw mainly through fluvial transport and bank erosion during higher floods appears as an additional and important wood recruitment process the bank erosion processes with up to 5200 m2 of eroded area confirmed the widening tendency occurring in river systems following volcanic disturbances as there are dead riparian trees along the easily erodible banks it is reasonable to suppose that the blanco river will continue to widen for a long period recruiting and transporting downstream huge volumes of lw in this context these analyses appear of fundamental importance to better manage the river system also for decreasing hazards to the downstream village of chaiten

characteristics of the size distribution of recent and historical landslides in a populated hilly region despitetheavailabilityofstudiesonthefrequencydensityoflandslideareasinmountainousregions frequency areadistributions of historical landslide inventories in populated hilly regions are absent this study revealed that the frequency area distribution derived from a detailed landslide inventory of the flemish ardennes belgium is significantly different from distributions usually obtainedinmountainousareaswherelandslidesaretriggeredbylarge scalenaturalcausalfactorssuchasrainfall earthquakesorrapid snowmelt instead the landslide inventory consists of the superposition of two populations i e i small b1 2 10 2 km 2 shallow complexearthslides that areat most30yrold and ii large n1 2 10 2 km 2 deep seatedlandslides that areolder than100yr both subpopulations are best represented by a negative power law relation with exponents of 0 58 and 2 31 respectively this study focused on the negative power law relation obtained for recent small landslides and contributes to the understanding of frequency distributions of landslide areas by presenting a conceptual model explaining this negative power law relation for small landslides in populatedhilly regions according to the model hilly regions canberelatively stable under the present dayenvironmental conditions andlandslidesaremainlytriggeredbyhumanactivitiesthathaveonlyalocalimpactonslopestability therefore landslidescausedby anthropogenic triggers are limited in size and the number of landslides decreases with landslide area the frequency density of landslide areas for old landslides is similar to those obtained for historical inventories compiled in mountainous areas as apart from the negative power law relation with exponent 2 31 for large landslides a positive power law relation followed by a rollover is observed for smaller landslides however when analysing the old landslides together with the more recent ones the present day higher temporal frequency of small landslides compared to large landslides obscures the positive power law relation and rollover 2007 elsevier b v all rights reserved

sedimentary response to paleocene eocene thermal maximum carbon release a model data comparison possible sources of carbon that may have caused global warming at the paleocene eocene boundary are constrained using an intermediate complexity earth system model confi gured with early eocene paleogeography we fi that 6800 pg c 13 c of 22 is the smallest pulse modeled here to reasonably reproduce observations of the extent of seafl oor caco 3 dis solution this pulse could not have been solely the result of methane hydrate destabilization suggesting that additional sources of co 2 such as volcanic co 2 the oxidation of sedimentary organic carbon or thermogenic methane must also have contributed observed contrasts in dissolution intensity between atlantic and pacifi c sites are reproduced in the model by reduc ing bioturbation in the atlantic during the event simulating a potential consequence of the spread of low oxygen bottom waters

modeling the calcite lysocline a numerical model of calcite dissolution in contact with sediment pore water is used to predict the depth and shape of the calcite lysocline in the deep sea model results are compared with lysocline data from 13 regions in the atlantic pacific and indian oceans the model lysocline shape is sensitive to the calcite dissolution rate constant the calcite organic carbon and refractory material rain rates and the rates of oxic versus anoxic organic carbon degradation in the sediment the model is able to reproduce the observed lysocline within the constraints of the sediment trap and calcite accumulation data using a calcite dissolution rate constant of 30 100 d 1 a molar ratio of organic carbon to calcite rain rates of 0 5 1 0 and an initial caco3 fraction of 90 excluding organic carbon this rate constant is consistent with microelectrode results presented by archer et al 1989 the model predicts that 30 50 of the calcite rain to the sea floor at the saturation horizon dissolves in response to organic carbon respiration consistent with previous modeling studies the range in the best fit value of the organic inorganic carbon rain rates arises from model sensitivity to uncertainty in the rate of anoxic carbon degradation in the sediment and in the rain rate of refractory material rather than from scatter in the data lysocline data from the western equatorial atlantic are anomalous to the rest of the data this anomaly may be explained by high rates of refractory material sedimentation from the amazon river

investigation of a landslide in maskinonge quebec several first time landslides occurred in the maskinonge area quebec during the summer which is rather unusual they have been studied in detail including a site investigation the results show

reversed deep sea carbonate ion basin gradient during paleocene eocene thermal maximum 1 the paleocene eocene thermal maximum petm 55 ma ago was marked by widespread caco3 dissolution in deep sea sediments a process that has been attributed to massive release of carbon into the ocean atmosphere system the pattern of carbonate dissolution is key to reconstructing changes in deep sea carbonate chemistry and ultimately the rate magnitude and location of carbon input here we show that during the petm the deep sea undersaturation was not homogeneous among the different ocean basins application of a sediment model to a suite of data records from different sites and ocean basins shows that a globally uniform decrease in deep sea carbonate ion concentration co32 is inconsistent with the data rather we demonstrate that deep sea co32 increased from the atlantic through the southern ocean into the pacific our results show that the petm deep sea co32 basin gradient during dissolution was reversed relative to the modern

co2 driven ocean circulation changes as an amplifier of paleocene eocene thermal maximum hydrate destabilization changes in ocean circulation have been proposed as a trigger mechanism for the large coupled climate and carbon cycle perturbations at the paleocene eocene thermal maximum petm ca 55 ma an abrupt warming of oceanic intermediate waters could have initiated the thermal destabilization of sediment hosted methane gas hydrates and potentially triggered sediment slumps and slides in an ensemble of fully coupled atmosphere ocean general circulation model aogcm simulations of the late paleocene and early eocene we identify such a circulation driven enhanced intermediate water warming critically we find an approximate twofold amplification of atlantic intermediate water warming when co2 levels are doubled from 2x to 4x preindustrial co2 compared to when they are doubled from 1x to 2x this warming is largely focused on the equatorial and south atlantic and is driven by a significant reduction in deep water formation from the southern ocean this scenario is consistent with altered petm circulation patterns inferred from benthic carbon isotope data and the intensity of deep sea carbonate dissolution in the south atlantic the linkage between intermediate water warming and gas hydrate destabilization could provide an important feedback in the establishment of peak petm warmth

erosivity of intact clay influence of the natural structure erodibility drill hole tests have been conducted on three eastern canadian clays on intact structured specimens on specimens destructured by consolidation and on remolded and reconsolidated speci

an alternative age model for the paleocene eocene thermal maximum using extraterrestrial 3he a continuous age model for the brief climate excursion at the paleocene eocene boundary has been constructed by assuming a constant flux of extraterrestrial 3he 3he et to the seafloor 3he et measurements from odp site 690 provide quantitative evidence for the rapid onset few kyr and short duration 120 kyr of global warming and of the associated disturbance to the earth s surficial carbon budget at this time these observations support astronomically calibrated age models indicating extremely rapid release of isotopically light carbon possibly from seafloor methane hydrate as the proximal cause of the event however the 3he et technique indicates a previously unrecognized and extreme increase in sedimentation rate coincident with the return of climate proxies to pre event values the 3he et based age model thus suggests a far more rapid recovery from the climatic perturbation than previously proposed or predicted on the basis of the modern carbon cycle and so may indicate additional or accelerated mechanisms of carbon removal from the ocean atmosphere system during this period 3he et was also measured at odp site 1051 to test the validity of the site 690 chronology comparison of these data sets seems to require removal of several tens of kyr of sediment within the climatic excursion at site 1051 an observation consistent with sediment structures and previous age modeling efforts the site 1051 age model shows a 30 kyr period in which climate proxies return toward pre event values after which they remain invariant for 80 kyr if this rise represents the recovery interval identified at site 690 then the 3he et based age models of the two sites are in good agreement however alternative interpretations are possible and work on less disrupted sites is required to evaluate the reliability of the proposed new chronology of the climate excursion regardless of these details this work shows that the 3he et technique can provide useful independent evidence for the development and testing of astronomically calibrated age models

impact of dissolution on the sedimentary record of the paleocene eocene thermal maximum the input of massive amounts of carbon to the atmosphere and ocean at the paleocene eocene thermal maximum petm 55 53 ma resulted in pervasive carbonate dissolution at the seafloor at many sites this dissolution also penetrated into the underlying sediment column the magnitude of dissolution at and below the seafloor a process known as chemical erosion and its effect on the stratigraphy of the petm are notoriously difficult to constrain here we illuminate the impact of dissolution by analyzing the complete spectrum of sedimentological grain sizes across the petm at three deep sea sites characterized by a range of bottom water dissolution intensity we show that the grain size spectrum provides a measure of the sediment fraction lost during dissolution we compare these data with dissolution and other proxy records electron micrograph observations of samples and lithology the complete data set indicates that the two sites with slower carbonate accumulation and less active bioturbation are characterized by significant chemical erosion at the third site higher carbonate accumulation rates more active bioturbation and possibly winnowing have limited the impacts of dissolution however grain size data suggest that bioturbation and winnowing were not sufficiently intense to diminish the fidelity of isotopic and microfossil assemblage records

regulation of atmospheric co2 by deep sea sediments in an earth system model 1 we have extended the genie 1 earth system model to include a representation of sedimentary stratigraphy and the preservation of biogenic carbonates delivered to the ocean floor this has enabled us to take a novel approach in diagnosing modern marine carbon cycling assimilating observation of the calcium carbonate caco3 content of deep sea sediments with an ensemble kalman filter the resulting calibrated model predicts a mean surface sediment content 32 5 wt close to the observed value 34 8 wt and a global burial rate of caco3 in deep sea sediments of 0 121 pgc yr 1 in line with recent budget estimates of 0 10 0 14 pgc yr 1 we employ the genie 1 model in quantifying the multimillennial scale fate of fossil fuel co2 emitted to the atmosphere in the absence of any interaction between ocean and sediments an equilibrium partitioning of co2 is reached within 1000 years of emissions ceasing with 34 645 ppm remaining in the atmosphere out of a total fossil fuel burn of 4173 pgc an additional 12 of co2 emissions 223 ppm are sequestered as bicarbonate ions hco3 by reaction with deep sea carbonates seafloor caco3 neutralization on a timescale of 1 7 ka excess of carbonate weathering on land over deep sea burial results in a further net transformation of 14 of co2 emissions 261 ppm into hco3 terrestrial caco3 neutralization on a timescale of 8 3 ka we have also assessed the importance of a changing climate in modulating the stabilization of atmospheric co2 through ocean sediment interaction increased ocean stratification suppresses particulate organic carbon export which in turn enhances seafloor caco3 preservation the resulting reduction in the sequestration of fossil fuel co2 represents a new positive feedback on millennial scale climate change

a data driven model of the global calcite lysocline gridded maps of sediment calcium carbonate calcite concentration and overlying water saturation state archer 1996 are combined with maps of benthic oxygen fluxes and sediment accumulation rates from jahnke 1996 and cweink 1986 to drive a diagenetic model of calcium carbonate preservation in deep sea sediments the only model input for which we cannot draw a detailed map is the rain rate of calcite to the seafloor so i use the model to calculate the calcite rain rate required to simulate the observed distribution of calcite concentration on the seafloor the predictive power of the model can be checked by searching for input parameters to which the model is sensitive and comparing the model requirements with independent data the model is sensitive to the ratio of organic carbon to calcite rain rates the rain ratio and within the constraint of pelagic sediment trap rain ratio data is unable to reproduce the calcite field without respiratory dissolution the promotion of calcium carbonate dissolution by the oxic degradation of organic carbon however relative to variability in sediment trap data the required model rain ratio is insensitive to the extent of anoxic respiration the stoichiometric ratio of o c during respiration the bioturbation rate the dissolution rate constant the effect of borate chemistry and small offsets in the saturation state for caco3 the model is sensitive to the accumulation rate of non caco3 material and predicts an atlantic pacific difference in non caco3 rain rate which is consistent with observations the model predicts that the dissolution flux of caco3 from sediments is 25 40 1012 mol yr 1 roughly half of the total deep sea caco3 dissolution rate estimated from the water column alkalinity distribution broecker and peng 1987 archer and maier reimer 1994 wollast 1994 the model also predicts that only 20 30 of the flux of caco3 to the seafloor globally escapes dissolution

mid holocene vegetation history and neolithic land use in the lake banyoles area girona spain abstract this paper focuses on high resolution analysis of pollen and sedimentology and botanical macro remains analysis in a core from lake banyoles girona spain the core sequence comprises a high resolution mid holocene ca 8 9 3 35 cal ka bp vegetation succession and sedimentological geochemical and geomorphological proxies are related to both climatic and anthropogenic causes deforestation processes affected natural vegetation development in the early neolithic 7 25 5 55 cal ka bp and late neolithic 5 17 3 71 cal ka bp in the context of broadleaf deciduous forest resilience against cooling and drying oscillations changes in sedimentation dynamics and in lake water level caused the emergence of dry land on the lake margin where riparian forest was established from 5 55 cal ka bp onwards the data show that in the context of an increasing aridification process neolithic land use played an important role in vegetation history and environmental evolution

hydrogeological and geophysical properties of the very slow moving ripley landslide thompson river valley british columbia landslides along a 10 km reach of thompson river south of ashcroft british columbia have repeatedly damaged vital railway infrastructure while also placing public safety the environment natura

redox controlled carbon and phosphorus burial a mechanism for enhanced organic carbon sequestration during the petm abstract geological records reveal a major perturbation in carbon cycling during the paleocene eocene thermal maximum petm 56 ma marked by global warming of more than 5 c and a prominent negative carbon isotope excursion of at least 2 5 within the marine realm the entire event lasted about 200 000 yr and was associated with a massive release of light carbon into the ocean atmosphere system over several thousands of years here we focus on the terminal stage of the petm during which the ocean atmosphere system rapidly recovered from the carbon cycle perturbation we employ a carbon cycle box model to examine the feedbacks between surface ocean biological production carbon oxygen phosphorus and carbonate chemistry during massive co 2 release events such as the petm the model results indicate that the redox controlled carbon phosphorus feedback is capable of producing enhanced organic carbon sequestration during large carbon emission events the locale of carbon oxidation ocean vs atmosphere does not affect the amount of carbon sequestered however even though the model produces trends consistent with oxygen excess accumulation rates of organic carbon 1700 pg c during the recovery stage export production and 13 c data it fails to reproduce the magnitude of change of sediment carbonate content and the ccd over deepening during the recovery stage the ccd and sediment carbonate content overshoot during the recovery stage is muted by a predicted increase in caco 3 rain nonetheless there are indications that the caco 3 export remained relatively constant during the petm if this was indeed true then an initial pulse of 3 000 pg c followed by an additional slow leak of 2 500 pg c could have triggered an accelerated nutrient supply to the surface ocean instigating enhanced organic carbon export consequently increasing organic carbon sequestration resulting in an accelerated restoration of ocean atmosphere biogeochemistry during the termination phase of the petm

the evolution towards steady state erosion in a soil mantled drainage basin semi quantitative data from a transient landscape in the swiss alps abstract this paper presents semi quantitative data concerning the pattern of erosion under present day humid climatic conditions for a ca 10 km2 large soil mantled drainage basin located in the northern foothills of the central swiss alps the present day pattern of erosion was presumably initiated at ca 15 ka at the time when the last glacial period was terminated present day erosional processes are characterized by fluvial dissection and hillslope mass failure resulting in linear geomorphic features as fluvial dissection proceeds the rivers tend to adapt steady state longitudinal stream profiles in this case the stream profiles display power law relationships between channel gradient and upstream size of the drainage basin our study shows that establishment of steady state longitudinal stream profiles requires a balanced mass flux between processes on hillslopes and in channels this situation is interpreted for locations where the downslope flux of mass on hillslopes does not exceed the erosional potential and the transport capacity in channels consequently the development of steady state drainage systems appears to be controlled by erosional processes in channels as they dictate the elevation of the base level in contrast systems that are at transient states of longitudinal stream profile development very often display non balanced mass flux between processes in channels and on hillslopes specifically low mechanical strength of the bedrock e g glacial till marls results in a downslope flux of mass that exceeds the transport capacity and the erosional potential in the channel causing the elevation of the channel floor to increase in this case processes on hillslopes are not necessarily coupled with erosion in channels and appear to control the evolution of the drainage basin for a limited time interval besides interpretations of controls on surface erosion this paper also estimates post glacial sediment yield for the analyzed drainage basin these estimates are achieved by determination of the difference between the elevation of the glacial and the present day surface the data show that ca 30 of the analyzed drainage basin experiences present day surface erosion furthermore average post glacial sediment yield measures ca 4 6 m ka if the post glacial volume of sediment is related to the area that has experienced surface erosion or ca 1 4 m ka if it is related to the whole drainage basin interestingly the erosional efficiency appears to be significantly higher for systems that display steady state stream profiles than for transient rivers

sediment flux from a mountain belt derived by landslide mapping in humid uplands landsliding is the dominant mass wasting process in the western southern alps of new zealand landslides are scale invariant and have a power law magnitude frequency distribution independent studies from other regions suggest that this is a general property of landsliding this observation is of critical importance to the evaluation of the impact of events of different length scales over different time intervals on landscape evolution it is particularly useful when estimating regional geomorphic rates because it constrains the frequency and overall significance of extreme events which cannot otherwise be evaluated by integrating the complete response of the system we estimate the regional denudation rate due to landsliding to be 9 4 mm yr 1 sediment discharge from the western southern alps is dominated by landslide derived material

climate science cracking the palaeoclimate code the geological record contains evidence of how earth s climate responded to periodic changes in our planet s orbit and rotation an investigation reveals how this record can be leveraged to constrain estimates of past climate dynamics

a transient rise in tropical sea surface temperature during the paleocene eocene thermal maximum the paleocene eocene thermal maximum petm has been attributed to a rapid rise in greenhouse gas levels if so warming should have occurred at all latitudes although amplified toward the poles existing records reveal an increase in high latitude sea surface temperatures ssts 8 to 10 c and in bottom water temperatures 4 to 5 c to date however the character of the tropical sst response during this event remains unconstrained here we address this deficiency by using paired oxygen isotope and minor element magnesium calcium ratios of planktonic foraminifera from a tropical pacific core to estimate changes in sst using mixed layer foraminifera we found that the combined proxies imply a 4 to 5 c rise in pacific sst during the petm these results would necessitate a rise in atmospheric pco 2 to levels three to four times as high as those estimated for the late paleocene

interpreting transient carbonate compensation depth changes by marine sediment core modeling 1 with the advent of computationally fast intermediate complexity models of earth s climate and carbon cycle the marine record can be interpreted much more directly than before specifically the mechanistic simulation of deep sea sediment cores provides an important step in bridging the model data divide here i use this methodology to help interpret the excursion in carbonate compensation depth ccd during the paleoceneeocene thermal maximum that is recorded in cores recovered from walvis ridge in the south atlantic by explicitly simulating the expected geological record of a massive co2 release in an earth system model i show how reduction in the intensity of subsurface mixing of the sediment by benthic animals substantially magnifies the recorded shoaling of the ccd conversely to quantify correctly the carbon release consistent with the observed ccd changes one must account for any bioturbational changes a reduction in sediment mixing intensity also appears to be important to reproducing the sharpness of the contact between carbonate rich late paleocene sediments and the overlying early eocene clay layer at walvis ridge assuming a relatively rapid approximately 1 ka duration co2 release further helps to account for some of the paleoceanographic observations finally interbasin differences in bioturbational regime help resolve some of the observed disparity in carbonate preservation between walvis ridge and sites outside of the atlantic although changes in ocean ventilation and circulation are also likely to play a critical role in this

balancing the deglacial global carbon budget the hydrate factor abstract the discovery that methane from dissociation of gas hydrates could be an important factor in the global carbon cycle resolves the major discrepancy in estimates of the increase of terrestrial biomass from the last glacial period to the present carbon isotope budgeting using the marine carbon isotopic record results in an estimate centered around 500 gtc whereas palaeovegetation reconstruction with biosphere models gives averages around 1000 gtc the discrepancy may be resolved by considering release of isotopically light methane through destabilization of gas hydrates this provides a unique means of estimating the contribution of gas hydrates to the deglacial rise in atmospheric methane a release of 120 gtc methane makes a biospheric carbon transfer of 1000 gtc compatible with the marine carbon isotope data this however represents less than 30 of the enhanced atmospheric methane production between 18 and 8 ka observed in ice cores supporting the theory that glacial interglacial variations in atmospheric methane were driven primarily by changes in the extent of tropical and temperate wetlands and not by methane release from clathrates by balancing the deglacial carbon budget we demonstrate that global carbon models will have to incorporate glacial interglacial vegetation shifts of at least 1000 gtc which many currently find difficult

understanding the causes and consequences of past marine carbon cycling variability through models abstract on geological time scales the production and degree of recycling of biogenic carbon in the marine realm and ultimately its removal to sediments exerts a dominant control on atmospheric co 2 and hence variability in climate this is a highly complex system involving a myriad of inter connected biological chemical and physical processes for this reason alone linking observations often highly abstracted in the form of proxies to the primary processes involved and ultimately to explanatory hypotheses for specific geological events and transitions is challenging the past few decades have seen a progressive improvement in theoretical and process based understanding of the various components that make up the marine carbon cycle and hand in hand with this the development of numerical model representations of the complete system models have also been designed and or adapted with paleoclimate questions in mind and applied to quantitatively explore the role of the marine carbon cycle in both perturbations and long term geologic evolutionary trends in global climate and possible feedbacks between them however we must ask whether paleoclimate models incorporate sufficiently appropriate representations of the dynamics and sensitivities of the marine carbon cycle and indeed whether in the geological context we really know what these dynamics are here we provide a comprehensive overview of how marine carbon cycling and the biological carbon pump is treated in available paleoclimate models with the aim of critically evaluating their ability to help interpret past marine carbon cycle and climate dynamics to this end we first provide an overview of commonly used paleoclimate models and some of their associated paleo applications drawing from a wide range of global carbon cycle box models and earth system models of intermediate complexity emics secondly we review and evaluate the three dominant processes involved in the cycling of organic and inorganic carbon in the marine system and how they are represented in models namely biological productivity at the ocean surface remineralisation dissolution of particulate carbon within the water column and the benthic pelagic coupling at the seafloor we generate and employ illustrative examples using the model genie to show how different parameterisations of water column and sediment processes can lead to significantly different model projections our compilation reveals the prevalence of static parameterisations of marine carbon cycling among existing paleoclimate models which are commonly empirically derived from present day observations although such approaches tend to represent carbon transfer in the modern ocean well they are potentially compromised in their ability to reflect the true degree of freedom and strength of feedbacks with respect to past climate events particularly those characterised by environmental boundary conditions that differ fundamentally from today finally we discuss the importance of using models of different complexities and how questions of model uncertainty may start to be addressed

patterns and magnitude of deep sea carbonate dissolution during eocene thermal maximum 2 and h2 walvis ridge southeastern atlantic ocean 1 eocene thermal maximum 2 etm2 or h1 53 7 ma represents a short lived warming episode associated with the injection of a large mass of 13c depleted carbon into the ocean atmosphere system the mass of injected carbon the extent of deep sea dissolution and the amount of warming during etm2 appear to be approximately half of those documented for the paleocene eocene thermal maximum petm 55 5 ma but the pattern of lysocline migration during etm2 has not yet been documented sufficiently to decipher potential differences in carbon sources and sequestration mechanisms we present high resolution carbonate dissolution and bulk stable isotope records across etm2 and the successive h2 event 53 6 ma on a common age model for four sites along the walvis ridge depth transect 1500 to 3600 m paleowater depth to assess lysocline evolution the onset of etm2 is characterized by multiple depth dependent transitions of carbonate dissolution up to 96 of the total flux associated with rapid depletions in bulk carbonate carbon up to 1 1 5 and oxygen up to 0 7 1 5 isotope values h2 shows a 0 7 negative carbon isotope excursion with a coeval decrease in 18o of 0 5 and 80 of carbonate dissolution during etm2 the lysocline recovered within 30 ka we attribute this rapid recovery to terrestrial caco3 neutralization through enhanced chemical weathering of carbonates in soils and rocks according to theory carbonate dissolution was lower after recovery than prior to etm2 indicating carbonate ion oversaturation and a deeper position of the lysocline spectral analysis indicates that the changes in carbonate dissolution and 13c values were precession paced implying that weathering feedbacks and short term perturbations in the carbon cycle were important in determining early eocene background and hyperthermal ocean co32 conditions

erosion and channel change as factors of landslides and valley formation in champlain sea clays the chacoura river quebec canada the champlain sea clays of eastern canada are incised by numerous rivers their slopes have been modified by landslides on the chacoura river near trois rivieres quebec several large landslide scars more or less recent are visible the role of erosion channel incision lateral channel migration and erosion of slopes due to agricultural drainage as a trigger of these landslides is important the aim of this study is to understand how erosion and landslides are related to valley development from a detailed analysis of aerial photographs and dems a map of the phenomena has been drawn by identifying various elements such as landslides limits of the slope position of the channel and the area covered by forest it is shown that channel change and erosion are strongly linked to landslides by the fact that they change the bank morphology in an unstable way a slide in itself is a natural way for the slope to achieve stability but when it occurs in a stream it creates a disturbance to the stream flow enhancing local erosion which may change the river path and generate more erosion downstream or upstream resulting in more slides cross valley sections and a longitudinal profile show that landslides are a major factor of valley formation it appears that the upper part of the chacoura river valley is still unaffected by landslides and has v shaped sections the lower part has been subject to intense erosion and many landslide scars can be seen this shows that the valley morphology is transient and that future activity is more likely to occur in the upper part of the river therefore the identification of areas prone to erosion will help determine the possible location of future large landslides just like the ones that occurred in the lower part

glacial interglacial variability of atmospheric co2 due to changing continental silicate rock weathering a model study an 11 box model of the oceanic carbon cycle including sedimentary processes is used to explore the role chemical weathering of continental silicate rocks might play in driving atmospheric co2 levels on glacial interglacial timescales histories for the consumption of co2 by silicate rock weathering processes are derived from the marine ge si record taking the major uncertainties in the knowledge of the ge and si cycles into account several histories for the evolution of the riverine dissolved silica fluxes are calculated from this record the investigation of the systematics between riverine dissolved silica and bicarbonate fluxes under different weathering regimes leads us to the tentative conclusion that although there is no correlation between dissolved silica and total bicarbonate concentrations in the major rivers there may exist a negative correlation between weathering intensity and the ratio of dissolved silica to bicarbonate derived from silicate weathering alone with this correlation as a working hypothesis it is possible to interpret the dissolved silica fluxes in terms of equivalent co2 consumption rates the calculated histories indicate that glacial rates of co2 consumption by chemical silicate rock weathering could have been twice and possibly up to 3 5 times as high as they are today when used to force the carbon cycle model they are responsible for glacial interglacial pco2 variations in the atmosphere of typically 50 60 ppm and up to 95 110 ppm these variations are superimposed to a basic oscillation of 60 ppm generated by the model mainly in response to coral reef buildup and erosion processes the total pco2 signal has an amplitude of about 80 90 ppm and up to 125 135 ppm although these large amplitudes indicate that silicate weathering processes should be taken into account when studying glacial interglacial changes of co2 in the atmosphere it also raises new problems such as too high co2 levels during the period from 110 70 kyr b p requiring further study

relative efficiency of three representative matorral species in reducing water erosion at the microscale in a semi arid climate valencia spain abstract in the mediterranean region where rainfall is scarce but often of high intensity the matorral vegetation cover provides essential protection to the soil against the erosivity of rainfall and reduces considerably the water erosion rate three representative species of the mediterranean matorral displaying different morphologies rosmarinus officinalis l stipa tenacissima l anthyllis cytisoides l were selected for study at the microscale plant scale for their relative efficiency in reducing water erosion on slopes the mechanical protection of the soil against raindrop detachment and the improvement of the soil properties by the biological influence of an isolated plant were compared for the three species the quantification of interrill erosion and splash erosion rates under natural rainfall conditions was obtained using erosion microplots of individual plants and splash cups placed at different distances from the plant axis respectively soil samples were also taken in the microenvironment of the plants in order to evaluate possible differential influences of the three species on soil properties relevant to water erosion the results show that the three selected species reduced runoff and soil loss in different ways the screen effect arising from the very dense canopy of stipa tussocks represents an effective way to counteract rainfall erosivity and reducing splash erosion however in the case of rosmarinus in addition to the mechanical protection offered by its canopy and litter covers the latter which lies permanently at the soil surface under the plant canopy improves moreover the topsoil structure because of the important incorporation of organic matter below the canopy cover the role of litter cover in controlling erosion seems therefore to be predominant under rosmarinus as for anthyllis these deciduous shrubs provide little physical protection against the energetic impact of rain at the soil surface as compared to a bare surface nevertheless the three plant species have a positive influence on their microenvironment through the improvement of soil properties under their canopy thus in open matorral patchy vegetation fertile soil islands developed below the plant canopy these differ considerably from the bare soil inter plant areas that give rise to higher soil loss rates

power law correlations of landslide areas in central italy abstract we have studied the frequency area statistics of landslides in central italy we consider two data sets data set a contains 16 809 landslide areas in the umbria marche area of central italy they represent a reconnaissance inventory of very old old and recent modern landslides the noncumulative frequency area distribution of these landslides correlates well with a power law relation exponent 2 5 over the range 0 03 km 2 a l 2 data set b contains 4233 landslides that were triggered by a sudden change in temperature on 1 january 1997 resulting in extensive melting of snow cover an inventory of these snow melt triggered landslides was obtained from aerial photographs taken 3 months after the event these landslides also correlate well with a power law relation with exponent 2 5 over the range 0 001 km 2 a l 2 we show that the correlation of data set b is essentially identical to the correlation of 11 000 landslides triggered by the 17 january 1994 northridge california earthquake we attribute a rollover for small landslides in data set a to incompleteness of the record due to erosion and other processes and to limitations in the reconnaissance mapping technique used to complete the inventory on the other hand we conclude that rollovers for small landslides in data set b and the california earthquake data are real and are associated with the surface morphology we conclude that the power law distribution is valid over a wide range of landslide areas and discuss possible reasons we also discuss the contribution of the snow melt and earthquake triggered landslide events to the total landslide inventory

the source and fate of massive carbon input during the latest paleocene thermal maximum lithologic faunal seismic and isotopic evidence from the blake nose subtropical western north atlantic links a massive release of biogenic methane 55 5 million years ago to a warming of deep ocean and high latitude surface waters a large perturbation in the combined ocean atmosphere carbon cycle the largest of the past 90 million years a mass extinction event in benthic faunas and a radiation of mammalian orders the deposition of a mud clast interval and seismic evidence for slope disturbance are associated with intermediate water warming massive carbon input to the global exogenic carbon cycle pelagic carbonate dissolution a decrease in dissolved oxygen and a benthic foraminiferal extinction event these events provide evidence to confirm the gas hydrate dissociation hypothesis and identify the blake nose as a site of methane release

age offsets among different biogenic and lithogenic components of sediment cores revealed by numerical modeling for modeled sediment cores of the open ocean a method for predicting simultaneously the ages of four different solid sediment compounds with respect to their depositional year onto the sediment surface is presented the simulation of time dependent age distribution in the sediment mixed layer and the eventually accumulating sediment is a prerequisite of a proper data assimilation of marine sediment core data into predictive climate models through such a data assimilation marine paleoclimate data could then be efficiently used in order to optimally determine adjustable model parameters the age simulation is based on a passive tracer transport method taking into account varying vertical advection rates within the sediment top layers chemical pore water reactions and bioturbation it turns out that different weight fractions of the modeled sediment have different ages in one horizontal geometric depth in core level depending on the particle rain onto the sediment and the reactivity of the material within the sediment pore waters for simultaneous consideration of paleoclimatic tracers associated within one and the same weight fraction e g for calcium carbonate tracers such as foraminiferal 13c and calcium carbonate weight percentages this may not be critical however for simultaneous consideration of calcium carbonate and opal weight percentages the age difference in the observed weight fractions may have to be corrected the age offset between caco3 and opal depends critically on the sediment accumulation rate low accumulation sites are more strongly affected than high accumulation sites

coupling between landslides and eroding stream channels reconstructed from spruce tree rings examples from the carpathians and sudetes central europe the analysis of the positive feedback between landslides and erosion requires determination of the precise temporal and spatial relations between events of colluvium delivery and fluvial erosion in our study we use decennial datasets on the occurrence of landsliding and erosion achieved through dendrochronological methods four sites covering areas of landslide slopes and adjacent valley floors with stream channels were studied landsliding on slopes was dated from the tree ring eccentricity developed in stems tilted due to bedrock instability erosion in channels was dated using the wood anatomy of roots exposed by erosion of the soil cover analysis of the temporal relations between dated landsliding erosion and precipitation record has revealed that two types of repeating sequences can be observed 1 rainfall landsliding erosion 2 rainfall erosion landsliding these sequences are an indication of the occurrence of slope channel positive feedback in the sites studied in the first type landsliding triggered by rainfall delivers colluvia into the valley floor and causes its narrowing which in turn causes increased erosion in the second type erosion triggered by rainfall disturbs the slope equilibrium and causes landsliding landsliding and erosion once triggered by precipitation can occur alternately in years with average precipitation and reinforce one another bidirectional coupling between landsliding and channel erosion was shown notably through the effects of channel shifting and forced sinuosity and by increased erosion of the slopes opposite the active landslides observations also suggest that the repetition of sequences described over longer periods of time can lead to a general widening of the valley floor at the expense of slopes and to a gradual change of the valley cross profile from narrow v shaped into a wide flat bottomed thus landsliding erosion coupling positive feedback was recognized as an important factor shaping hillslope valley topography of the mid mountain areas studied copyright 2014 john wiley sons ltd

global deep sea burial rate of calcium carbonate during the last glacial maximum global databases concentrations rates in holocene and last glacial of calcium carbonate and mass accumulation maximum sediments were used to estimate the deep sea sedimentary calcium carbonate burial rate during these two time intervals sparse calcite mass accumulation rate data were extrapolated across regions of varying calcium carbonate concentration using a gridded map of calcium carbonate concentrations and the assumption that accumulation of noncarbonate material is uncorrelated with calcite concentration within some geographical region mean noncarbonate accumulation rates were estimated within each of nine regions determined by the distribution and nature of the accumulation rate data for core top sediments data coverage 67 of the high calcite the regions of reasonable encompass 75 sediments globally and within these regions we estimate an accumulation rate of 55 9 3 6x1011 mol yr 1 the same regions cover 48 of glacial high caco3 sediments the smaller fraction is due to a shift of calcite deposition to the poorly sampled south pacific and total 44 1 6 0x1011 mol yr 1 projecting to 100 coverage south and total 44 1 6 0x1011 both estimates yields accumulation estimates of 8 3x1012 mol yr 1 today and 9 2x1012 mol yr 1 during glacial time this is little better than a guess given the incomplete data coverage but it suggests that glacial deep sea calcite burial rate was probably not considerably faster than today in spite of a presumed decreasein shallow water burial during glacial time

the earliest evidence of hearths in southern europe the case of bolomor cave valencia spain abstract most researchers agree about the importance of the fire during the pleistocene the controlled use of fire could allow advances in the ways of life not only for its value as a constant source of light and heat but also because it contributed to the processing of food to warding off the carnivores and especially to human socialization as fire can be understood as a focus of concentration of activities and structuring of inhabited space apart from the many utilities that the hearths may have had during the pleistocene this research does not allow specification of the chronological and geographical context of the first controlled use of fire from this perspective the present study contributes to this discussion with the data from bolomor cave valencia spain this site contains a sedimentary deposit composed of seventeen stratigraphical levels ranging from mis 9 to mis 5e c 350 100 ky the stratigraphical series presents clear evidence of the controlled and reiterative use of fire the used analytic techniques have confirmed the presence of hearths at levels ii iv xi and xiii of the site this paper discusses the hearths from level xiii chronologically located in mis 7c with an amino acid racemization aar date of 228 53 ky these combustion structures are the most ancient known today not only at bolomor cave and in spain but also in southern europe from this perspective the aim of this study is to make known the hearths from level xiii of bolomor cave and to provide data that contribute to the general debate about the presence knowledge and use of fire in the european middle pleistocene

a palaeogene perspective on climate sensitivity and methane hydrate instability the palaeoceneeocene thermal maximum petm a rapid global warming event and carbon cycle perturbation of the early palaeogene provides a unique test of climate and carbon cycle models as well as

release of methane from a volcanic basin as a mechanism for initial eocene global warming a 200 000 yr interval of extreme global warming marked the start of the eocene epoch about 55 million years ago negative carbon and oxygen isotope excursions in marine and terrestrial sediments show that this event was linked to a massive and rapid approximately 10 000 yr input of isotopically depleted carbon it has been suggested previously that extensive melting of gas hydrates buried in marine sediments may represent the carbon source and has caused the global climate change large scale hydrate melting however requires a hitherto unknown triggering mechanism here we present evidence for the presence of thousands of hydrothermal vent complexes identified on seismic reflection profiles from the voring and more basins in the norwegian sea we propose that intrusion of voluminous mantle derived melts in carbon rich sedimentary strata in the northeast atlantic may have caused an explosive release of methane transported to the ocean or atmosphere through the vent complexes close to the palaeocene eocene boundary similar volcanic and metamorphic processes may explain climate events associated with other large igneous provinces such as the siberian traps approximately 250 million years ago and the karoo igneous province approximately 183 million years ago

a new element of trampling an experimental application on the level xii faunal record of bolomor cave valencia spain in level xii of bolomor cave valencia spain modifications have been observed on some of the bone fragments that make up the faunal record these alterations consist of small notches located on the oblique fracture angles of some bones the frequency at which these modifications appear in the assemblage has obliged to plan several experimental series to know the process that causes them to be more exact this study aims to verify whether these small chips are the result of trampling for this purpose two experimental series have been developed the first of which has the objective of differentiating between the variables related to the original state of the bone green semi dry and dry and the second is aimed at reproducing the modifications observed in the archaeological set taking into account the data obtained in the previous series following these experiments the appearance of small notches is observed on the oblique fracture angles of some bones in semi dry state these resulting chips are similar to those documented in bolomor cave level xii therefore it is deduced that trampling is the principle cause of these modifications in the bone record this fact has important archaeological implications as the spatial distribution of this modification can provide information about the intrasite movements of the human groups