timing of millennial scale climate change at siple dome west antarctica during the last glacial period using atmospheric methane and the isotopic composition of o2 as correlation tools we place the dd record of ice from the siple dome west antarctica ice core on a precise common chronology with the gisp2 greenland ice core for the period from 9 to 57 ka the onset of major millennial warming events in siple dome preceded major abrupt warmings in greenland and the pattern of millennial change at siple dome was broadly similar though not identical to that previously observed for the byrd ice core also in west antarctica the addition of siple dome to the database of well dated antarctic paleoclimate records supports the case for a coherent regional pattern of millennial scale climate change in antarctica during much of the last ice age and glacial interglacial transition

orbital control on carbon cycle and oceanography in the mid cretaceous greenhouse we established a new high resolution carbonate carbon isotope record of the albian interval of the marne a fucoidi formation central apennines italy which was deposited on the southern margin of the western tethys ocean bulk carbonate sampled with 10 15 cm spacing was used for the construction of a continuous carbon isotope curve through the albian stage spectral analyses reveal prominent 400 kyr cyclicity in the 13c curve which correlates with milankovitch long eccentricity changes cycles occurring in our record resemble those observed in several cenozoic 13c records suggesting that a link between orbital forcing and carbon cycling existed also under mid cretaceous greenhouse conditions based on comparisons with cenozoic eccentricity carbon cycle links we hypothesize that 400 kyr cycles in the mid cretaceous were related to a fluctuating monsoonal regime coupled with an unstable oceanic structure which made the oceanic carbon reservoir sensitive to orbital variations in the tethys these oceanographic conditions lasted until the late albian and then were replaced by a more stable circulation mode less sensitive to orbital forcing

late cenozoic relief evolution under evolving climate a review abstract the present review paper is an attempt to summarize quantitative evidence of late cenozoic changes in topographic relief different meanings of the word relief as it is commonly used and detail the metrics used to quantify it we then specify methodological tools used to quantify relief change primarily low temperature thermochronometry and terrestrial cosmogenic nuclides and analyze published evidence for different regions our review first shows that relief changes and rates of changes are more important at mid than high or low latitudes and appear to be insensitive to mean precipitation rates it also show that relief change is positive relief increases in most of the reported cases 80 we subsequently define two functional relationships between relief and erosion depending on the chosen definition of relief and propose a conceptual model of landscape memory we conclude following others that erosion rates depend non linearly on relief evolution itself being a function of the spatial distribution and rates of erosion the relief increases documented in this review may be to erosion rate increases during the same timescales lastly we discuss the importance of glacial and periglacial processes on late cenozoic relief and erosion rate changes and stress the importance of frost shattering and glacial erosion at mid and high latitudes

correlation of basinal carbonate cycles to nearshore parasequences in the late cretaceous greenhorn seaway western interior u s a upper cretaceous limestone shale couplets developed within the late transgressive stage of the greenhorn cyclothem may be correlated from carbonate dominated basinal sequences in central kansas and colorado westward to clastic cycles in southern utah six such basinal couplets have been traced to corresponding upward coarsening progradational cycles developed on the western margin of the western interior basin in the central basin in colorado and kansas these sedimentary cycles are represented by limestone shale and marlstone shale couplets 0 5 1 0 m in thickness more calcareous parts of these couplets may be correlated westward into condensed fossiliferous concretion and shell beds in proximal offshore lithofacies of arizona and utah these concretion and shell beds are physically traceable farther landward westward into bioturbated fossil rich transgressive lag deposits that bound 10 to 20 m thick coarsening upward progradational strand plain deposits parasequences in southwestern utah thus the progra dational phase of parasequence deposition correlates with accumulation of clay rich sediment in the central basin and the transgressive phase is characterized by reduced terrigenous input and deposition of carbonate rich sediment we consider milankovitch style orbital forcing of climate and tectonically induced fluctuations in rates of foredeep basin subsidence as possible forcing mechanisms for these basinwide events based on the widespread distribution of the limestone shale couplets as well as on estimated sedimentation rates and geochronology it has been widely speculated that these carbonate cycles reflect milankovitch cycles with periodicities on the order of 20 k y to 100 k y if so then stratigraphic data suggest that orbital forcing of climate affected eustasy and or sediment input and biogenic production in the western interior basin alternatively thrusting events in the sevier orogenic belt may have produced episodic changes in the rates of foredeep basin subsidence and consequent changes in base level which could have controlled the deposition of the greenhorn parasequences and carbonate cycles in either case correlation of these units demonstrates a consistent basinwide sedimentary response to high frequency base level or sediment input changes in the western interior epicontinental basin

nd isotopic excursion across cretaceous ocean anoxic event 2 cenomanian turonian in the tropical north atlantic late cretaceous fish debris from demerara rise exhibits a dramatic positive excursion of 8 nd units during ocean anoxic event 2 oae2 that is superimposed on extremely low nd t values 14 to 16 5 observed throughout the rest of the studied interval the oae2 nd excursion is the largest yet documented in marine sediments and the majority of the shift is estimated to have occurred over nd values on demerara rise are explained as the nd isotopic signature of the south american craton whereas eruptions of the caribbean large igneous province or enhanced mixing of intermediate waters in the north atlantic could have caused the excursion

erosional power in the swiss alps characterization of slope failure in the illgraben landslides and rockfalls are key geomorphic processes in mountain basins their quantification and characterization are critical for understanding the processes of slope failure and their contributions to erosion and landscape evolution we used digital photogrammetry to produce a multi temporal record of erosion 1963 2005 of a rock slope at the head of the illgraben a very active catchment prone to debris flows in switzerland slope failures affect 70 of the study slope and erode the slope at an average rate of 0 39 0 03 m yr the analysis of individual slope failures yielded an inventory of 2500 failures ranging over 6 orders of magnitude in volume despite the small slope area and short study period the slope failures form a characteristic magnitude frequency distribution with a rollover and a power law tail between 200 m and 1 6 106 m with an exponent of 1 65 slope failure volume scales with area as a power law with an exponent of 1 1 both values are low for studies of bedrock landslides and rockfall and result from the highly fractured and weathered state of the quartzitic bedrock our data suggest that the magnitude frequency distribution is the result of two separate slope failure processes type 1 failures are frequent small slides and slumps within the weathered layer of highly fractured rock and loose sediment and make up the rollover type 2 failures are less frequent and larger rockslides and rockfalls within the internal bedded and fractured slope along pre determined potential failure surfaces and make up the power law tail rockslides and rockfalls of high magnitude and relatively low frequency make up 99 of the total failure volume and are thus responsible for the high erosion rate they are also significant in the context of landscape evolution as they occur on slopes above 45 and limit the relief of the slope copyright 2012 john wiley sons ltd

in situ cosmogenic radiocarbon production and 2 d ice flow line modeling for an antarctic blue ice area surface 14 c activity that differs by up to 25 from the activity calculated using an ablation only approximation which is used in all prior work and 3 that at high ablation margin sites solar modulation of the cosmic ray flux may change the strength of the dominant spallogenic production by up to 10 as part of this effort we model twodimensional ice flow along the central flow line of taylor glacier we present two methods for parameterizing vertical strain rates and assess which method is more reliable for taylor glacier finally we present a sensitivity study from which we conclude that uncertainties in published cosmogenic production rates are the largest source of potential error the results presented here can inform ongoing and future 14 c and ice flow studies at ice margin

pleistocene ice and paleo strain rates at taylor glacier antarctica ice exposed in ablation zones of ice sheets can be a valuable source of samples for paleoclimate studies and information about long term ice dynamics we report a 28 km long stable isotope sampling transect along a flowline on lower taylor glacier antarctica and show that ice from the last glacial period is exposed here over tens of kilometers gas isotope analyses on a small number of samples confirm our age hypothesis these chronostratigraphic data contain information about past ice dynamics and in particular should be sensitive to the longitudinal strain rate on the north flank of taylor dome averaged over millennia the imprint of climatic changes on ice dynamics may be discernible in these data

scale invariance in the spatial development of landslides in the umbria region italy understanding the spatial distribution of mass movements is a major issue in the management and forecasting of landslide risk in this context the present study examines the most widespread types of landslide in the umbria region central italy that is slides and flows in order to establish if it is possible to identify a well defined structure in their spatial pattern by using the landslide inventory map available for the area and by resorting to the principles of fractal theory the scaling properties of the landslide sample were investigated the application of the box counting algorithm to the maps of landslide triggering points and landslide areas allowed for the identification of a clear scale invariant structure two distinct types of fractal behaviour were recognized separated by a scale value of 1 km and characterized by capacity dimensions of 1 35 and 1 76 in the ranges of 25 m 1 km and 1 16 km respectively the comparison between the scaling exponents obtained from a map of points and one of areas and the elaboration of the cumulative frequency distributions of landslide areas supported the interpretation of this result the higher capacity dimension describes the spatial distribution of landslides in the umbria region while the lower contains additional information about their geometries suggesting that the latter also possess scaling properties based on the finding of two different types of behaviour of landslides in space the hypothesis is discussed that the contribution of each causal factor i e predisposing and triggering factors to the occurrence of landslide events and to their spatial development could be different in the two scale ranges identified depending on its spatial variability at local and regional scale according to this hypothesis factors with high local variability i e topographic attributes would mainly affect the assortment of landslide geometries while those with high regional variability e g rainfalls and lithology would mainly affect the pattern of the landslides

tertiary carbonate dissolution cycles on the sierra leone rise eastern equatorial atlantic ocean abstract most of the tertiary section on sierra leone rise off northwest africa consists of chalk marl and limestone that show cyclic alterations of clay rich and clay poor beds about 20 60 cm thick on the basis of biostratigraphic accumulation rates the cycles in oligocene and miocene chalk have periods which average about 44 000 years and those in eocene siliceous limestone have periods of 4000 27 000 years several sections were sampled in detail to further define the cycles in terms of content of caco 3 clay minerals and relative abundances of calcareous nannofossils extending information gained by analyses of pleistocene cores from the continental margin of northwest africa to the tertiary cycles on sierra leone rise both dilution by noncarbonate material and dissolution of caco 3 could have contributed to the observed relative variations in clay and caco 3 however dissolution of caco 3 as the main cause of the carbonate clay cycles on the sierra leone rise rather than dilution by clay is suggested by the large amount of change several thousand percent in terrigenous influx required to produce the observed variations in amount of clay and by the marked increase in abundance of dissolution resistant discoasters relative to more easily dissolved coccoliths in low carbonate parts of cycles the main cause of dissolution of caco 3 was shoaling of the carbonate compensation depth ccd during the early neogene and climatically induced fluctuations in the thickness of antarctic bottom water

isotopic variation in rhythmically bedded chalks paleotemperature variation in the upper cretaceous detailed sampling at 2 cm intervals of a rhythmically bedded chalk marl sequence in southeast england has revealed a cyclic variation in oxygen isotopic composition of the carbonate component these changes are most consistent with paleotemperature fluctuations of up to 4 5 c contrary to some recent models chalk horizons are interpreted to reflect periods of warmer temperature and higher primary productivity than those responsible for marl deposition the effects of different faunal content diagenesis and variations in the water chemistry can all be discounted

telling a different story the promote role of vegetation in the initiation of shallow landslides during rainfall on the chinese loess plateau abstract vegetation is widely used for controlling landslides around the world however rainfall induced shallow landslides occur frequently on vegetation covered slopes on the chinese loess plateau during the rainy season to probe this phenomenon we conducted on site investigations and measurements in the nanxiaohegou catchment on the loess plateau to explore the effects of soil properties and vegetation on shallow loess landslides most of the loess landslides on vegetation covered slopes were small scale with depths ranging from 0 3 m to 1 0 m corresponding to the topsoil being saturated due to rainfall majority of shallow landslides occurred on herbage covered area which made up 69 of total landslides there are significant differences in soil properties between the upper layer root soil composite and the lower layer loess of the sliding surface our study demonstrated that root plays a leading role in landslide erosion and that the most adverse effect of vegetation on landslides is mainly the increase in soil moisture content in the shallow soil through the root zone creating preferential infiltration flow paths there are remarkable differences in landslide erosion depths and landslide erosion intensities among different vegetation types the landslide erosion depth and landslide erosion intensity increased linearly with increasing main root depth indicating that the vegetation root depth determines the landslide erosion intensity during rainfall therefore the potential implications of vegetation especially the herbage to promote landslide occurrences during rainfall should be given more attention in the future

untangling the palaeocene climatic rhythm an astronomically calibrated early palaeocene magnetostratigraphy and biostratigraphy at zumaia basque basin northern spain abstract the magnetostratigraphy of a 54 m long section above the cretaceous tertiary boundary at the sea cliff section of zumaia in the basque basin northern spain has been established the section encompasses the entire danian and the lower part of the selandian stages as indicated by calcareous plankton biostratigraphy the studied interval consists of hemi pelagic limestone marl alternations in the form of couplets and bundles which range from centimetre decimetre to metre scale respectively and a few thin bedded calcareous turbidites the magnetostratigraphy based on samples from about 200 stratigraphic levels allows the identification of six reversal boundaries from chron c29r to c26r at a bed level the spatial or temporal evolution of periodicities from a lithologically coded series is studied with the continuous wavelet transform technique a preliminary age model based on the standard ck95 gpts indicates that the basic lithologic carbonate marl couplet corresponds to the 19 23 kyr precession cycle 21 31 cm cycle in the depth domain and that a bundle cycle usually groups of four to six basic couplets with global periodicity centred at 1 22 m corresponds to the 110 kyr eccentricity cycle we have tuned the bundle cycles to the va03 r7 eccentricity orbital solution astrophys j 592 2003 620 630 following an initial match of a node of the 2 4 ma eccentricity modulatory cycle in the target time series to particularly carbonate rich bundles from the upper part of the zumaia section that displays significant power of a 4 4 m period cycle corresponding to the 404 kyr eccentricity cycle consistency between lithologic patterns and characteristics in the eccentricity target is reasonably met although the 404 kyr eccentricity cycle is not persistent throughout the tuning however appears robust as it brings the age of the k t boundary at 65 8 ma it is argued that a sea level signal tectonically driven is superimposed on the climatic forcing at the milankovitch band masking the full expression of the low frequency astronomical periods we provide a cycle tuned duration for all intervening early palaeocene polarity chrons and estimate relative ages for bioevents the cycle tuned chronology indicates that the ck95 gpts overestimates the duration of chrons c28 and c27 by 20 and 26 respectively our data may prove useful to better constrain early palaeocene biostratigraphy of calcareous plankton and in the redefinition of the boundary between the danian and selandian stages

orbital cyclicities above and below the cretaceous paleogene boundary at zumaya n spain agost and relleu se spain abstract the rhythmicity of hemipelagic limestone marl successions covering the cretaceous paleogene k pg boundary is investigated and evidence of orbital control is presented three sections were surveyed and sampled in detail two are located near agost and relleu in the province of alicante and one near zumaya in the basque country the distance between agost and relleu is about 30 km between agost and zumaya about 600 km the carbonate content of 2779 samples was determined and used as a proxy to determine cyclicities lithologically all three successions are very similar although in the maastrichtian of the zumaya succession 63 7 m 339 light green siliciclastic turbidite layers varying in thickness between 0 1 and 12 cm intercalate with the calcisiltites conventional paleomagnetic and micropaleontologic datum planes are few and show the usual associated uncertainties power spectra based on the few reliable datum planes available are unstable more datum planes were created in an unconventional way i e by visual correlation of the local maxima and minima of the carbonate curves to those of the relevant part of the theoretical eccentricity curve the validity of the method is based on the assumption that the eccentricity periods are considered practically stable throughout geologic time the results support the hypothesis that the carbonate rhythmicity at agost relleu and zumaya are orbitally controlled most likely orbital forcing and random processes play a role in the frequency of occurrence and the thickness of turbidites in the maastrichtian of zumaya the age of the k pg boundary is estimated at 64 56 0 4 ma

radiometric 81kr dating identifies 120 000 year old ice at taylor glacier antarctica we present successful 81kr kr radiometric dating of ancient polar ice krypton was extracted from the air bubbles in four 350 kg polar ice samples from taylor glacier in the mcmurdo dry valleys antarctica and dated using atom trap trace analysis atta the 81kr radiometric ages agree with independent age estimates obtained from stratigraphic dating techniques with a mean absolute age offset of 6 2 5 ka our experimental methods and sampling strategy are validated by i 85kr and 39ar analyses that show the samples to be free of modern air contamination and ii air content measurements that show the ice did not experience gas loss we estimate the error in the 81kr ages due to past geomagnetic variability to be below 3 ka we show that ice from the previous interglacial period marine isotope stage 5e 130 115 ka before present can be found in abundance near the surface of taylor glacier our study paves the way for reliable radiometric dating of ancient ice in blue ice areas and margin sites where large samples are available greatly enhancing their scientific value as archives of old ice and meteorites at present atta 81kr analysis requires a 40 80 kg ice sample as sample requirements continue to decrease 81kr dating of ice cores is a future possibility

west greenland and global in situ 14c production rate calibrations the in situ cosmogenic nuclide 14 c is unique compared with other nuclides because of its short half life and when combined with longer lived isotopes e g 10 be in situ 14 c can be a powerful tool for deciphering recent and complex surface exposure histories like all in situ cosmogenic nuclides quantifying earth surface processes with in situ 14 c requires a well constrained in situ 14 c production rate we present a production rate calibration from an independently dated moraine in west greenland previously used as an in situ 10 be production rate calibration site the local in situ 14 c production rate is 22 8 1 4 atoms g 1 a 1 69 28un 50 76u w 350m asl and when scaled to sea level high latitude using time dependent lal stone scaling lm we calculate a spallation only in situ 14 c production rate of 12 0 0 9 atoms g 1 a 1 and a 14 c 10 be production rate ratio of 3 1 0 2 the west greenland in situ 14 c production rate is indistinguishable from the new zealand promontory point and scottish highlands in situ 14 c production rates when combined we calculate a global production rate of 12 1 0 5 atoms g 1 a 1 lm copyright 2014 john wiley sons ltd

earthquake induced chains of geologic hazards patterns mechanisms and impacts large earthquakes initiate chains of surface processes that last much longer than the brief moments of strong shaking most moderate and large magnitude earthquakes trigger landslides ranging from small failures in the soil cover to massive devastating rock avalanches some landslides dam rivers and impound lakes which can collapse days to centuries later and flood mountain valleys for hundreds of kilometers downstream landslide deposits on slopes can remobilize during heavy rainfall and evolve into debris flows cracks and fractures can form and widen on mountain crests and flanks promoting increased frequency of landslides that lasts for decades more gradual impacts involve the flushing of excess debris downstream by rivers which can generate bank erosion and floodplain accretion as well as channel avulsions that affect flooding frequency settlements ecosystems and infrastructure ultimately earthquake sequences and their geomorphic consequences alter mountain landscapes over both human and geologic time scales two recent events have attracted intense research into earthquake induced landslides and their consequences the magnitude m 7 6 chi chi taiwan earthquake of 1999 and the m 7 9 wenchuan china earthquake of 2008 using data and insights from these and several other earthquakes we analyze how such events initiate processes that change mountain landscapes highlight research gaps and suggest pathways toward a more complete understanding of the seismic effects on the earth s surface

topographical and geological variation of effective rainfall for debris flow occurrence from a large scale perspective abstract understanding the spatial heterogeneity of the debris flow rainfall threshold is meaningful for regional warning systems however regional topographical and geological impacts have not been well quantified using the hengduan mountains with distinct climatic topographical and geological settings as a typical study area this study focused on the geological and topographical variations of effective rainfall for debris flow occurrence from a large scale perspective results showed that the probability of debris flow occurrence was smallest in the cold arid zone and largest in the humid zone the mean dimensionless effective rainfall the ratio of effective rainfall to mean annual precipitation was about 5 2 for an initial warning and 7 7 for serious warnings the contributions to the differences are regional climate geomorphology and geology in sequence of importance the zone with more complex terrain thicker soil and higher sand content would be more beneficial to debris flow formation multiple regression analysis suggested that the geologically related aspects may have a slightly greater effect than topographical factors on effective rainfall in general this work could be in favor of other similar regional national and even global work for debris flow early warning

rainfall triggered mass movements on steep loess slopes and their entrainment and distribution abstract mass movements are predominant geomorphic processes on steep hillslopes however the mechanisms governing the erosion and entrainment of mass movements remain poorly understood in this study experiments on natural loess slopes were conducted to induce a series of mass movements under simulated rainfalls in the liudaogou catchment on the loess plateau of china a novel topography meter was used to observe random mass movements a total of 499 mass movements in 42 rainfall events and an average of 11 mass movements for each rainfall event were observed three mass movement types were detected landslides 67 mudflows 21 avalanches 12 the volume of landslides dramatically increased through the entrainment of a wet gully bed material and the volume of landslide mass was magnified by 29 on average through material entrainment based on the observed data the probability of mass movement occurrences decreased with the increasing mass movement volume in a power law relationship the critical rainfall amount for mass movement failure was approximately 25 6 mm at a rainfall intensity of 50 mm h 1 these results can serve as guides to mitigate geological hazards and assess erosion processes on steep loess slopes of the loess plateau

the age of the air in the firn and the ice at summit greenland in the framework of the eurocore drilling project 1989 at summit central greenland air samples were collected from a drill hole in the firn at several depth levels the samples have been analyzed for 85kr co2 ch4 cfc s f 11 and f 12 contents and for the isotopic composition of nitrogen and oxygen the measured data are compared with the results of a diffusion model co2 for example takes 12 years with a standard deviation of 7 5 years to diffuse from the surface to the firn ice transition under the present climatic conditions at summit the difference between the age of the ice and the mean age of the occluded air is approximately 210 years an enrichment of the heavier isotopes due to separation by gravity has been observed molecular diffusion alone suffices to explain the observed concentration trends in the firn column we can however not exclude the existence of a convective zone below the surface we have also measured the density and closed porosity along the firn core that has been retrieved when drilling the hole the porosity data reveal that the air is occluded into bubbles mainly between 65 and 80 m corresponding to densities of 790 and 830 kg m3 respectively

experimental study of shallow mass movements on gully slopes and associated sediment under rainfall on the chinese loess plateau abstract mass movements on gully slopes are the main contributors to gully bank expansion and are the major source of sediment delivered to rivers however they are often overlooked because they are either too small or too time consuming to measure in the field to resolve this challenge a novel topography meter was used to observe shallow mass movements on the gully slopes of the loess plateau under simulated rainfall the experiment showed that the cumulative shallow mass movement volume logarithmically increased with the rainfall amount the critical rainfall for shallow mass movement occurrence was about 28 mm at a rainfall intensity of 50 mm h 1 the results also show that soil water content was a key element controlling the occurrence of the shallow mass movements and the minimal soil water content for permitting shallow mass movements was about 23 1 25 6 for 10 20 cm deep soil shallow mass movement on gully slopes has a significant influence on sediment yield the sediment concentration and sediment transport rate during mass movement failure were on average 3 6 times and 4 0 times higher than that during pre failure events respectively our results have important implications for understanding the connectivity of sediment discharge and mass movements on gully slopes in hilly and gully watersheds

effects of climate tectonics and sea level changes on rhythmic bedding patterns in the niobrara formation upper cretaceous u s western interior regional correlation of interbedded pelagic hemipelagic limestones and calcareous shales of the fort hays limestone member of the niobrara formation confirms development of at least two levels of cyclicity occurrence of time parallel rhythmically deposited beds that can be correlated over distances exceeding 800 km lends strong support to the hypothesis that these cycles were induced by milankovitch type climatic forcing however visual observation and fourier analysis of variations in shale and limestone thickness demonstrate that the pattern of fort hays cyclicity lacks regional uniformity complications in the cyclic pattern may have resulted from the influence of orbital parameters having differing periodicities additionally departures from simple cyclical patterns resulted from sedimentary effects of the sevier orogeny and from erosional events associated with sea level changes documentation of thickness variations within the regionally persistent fort hays bedding sequence furnishes a basis for fine scale analysis of cretaceous crustal movements within the western interior seaway

machine learning and fractal theory models for landslide susceptibility mapping case study from the jinsha river basin abstract the quality of non landslide negative samples may result in unreasonable prediction results for machine learning ml models the aim of this study is to improve the performance of ml models by perfecting the quality of non landslide samples in landslide susceptibility modelling so as to produce more reliable susceptibility maps the middle and lower reaches of jinsha river basin mlrjb were chosen as the study area and the elevation slope aspect curvature lithology distance to faults slope of slope slope of aspect precipitation land use and ndvi were considered as predisposing factors for landslide susceptibility mapping firstly three non landslide samples are randomly selected from the low slope area landslide free area and very low susceptibility area based on fractal theory ft model generation and then three sample scenarios are constructed with 4445 landslide positive samples next the performance of cross application of three sample scenarios in the support vector machines svm and naive bayes nb models are compared and evaluated based on the statistical indicators such as accuracy recall precision receiver operating characteristic roc curve and area under the roc curve auc the evaluation results show that the non landslide negative samples generated on the basis of ft model are more reasonable and that the hybrid method supported by ft and ml models exhibits the highest prediction efficiency around 94 overall accuracy produced by scenario ft followed by scenario ss 87 and scenario rs 65 finally with the validation of landslide and unstable slopes data the landslide susceptibility map produced by the hybrid method composed of ft model and the svm model is the ultimate output product for landslide prevention

water mass circulation on demerara rise during the late cretaceous based on nd isotopes abstract circulation in the north atlantic during the late cretaceous has implications for poleward heat transport and nutrient distribution during an extreme greenhouse interval with episodes of ocean anoxia nd isotopes of fossil fish teeth and debris represent one of the few water mass tracers that can be used to reconstruct deep ocean circulation we present nd isotopic data interpreted as bottom water values for 290 samples from three ocean drilling program sites on demerara rise sites 1258 1260 and 1261 along with 102 analyses from four other north atlantic sites cape verde goban spur bermuda rise and blake nose that provide additional geographic and bathymetric control our results confirm the presence of a water mass with low end values 14 to 17 that are believed to be influenced by continental material during local water mass formation at low latitudes this demerara bottom water dbw is the primary water mass in the region from the cenomanian to coniacian and from the late campanian through early maastrichtian following a hiatus of 10 my a positive 8 end unit excursion occurs during ocean anoxic event 2 oae2 that cannot be explained by changes in weathering inputs diagenesis or magmatic sources of nd instead it appears to represent an influx of bottom waters sourced from the tethys or north atlantic this replacement of dbw during oae2 argues for decreased production of dbw or enhanced production of tethys north atlantic waters during peak greenhouse conditions from the late campanian through early maastrichtian dbw becomes the only water mass recorded at demerara rise and it appears to expand to abyssal depths at cape verde in the campanian this water mass is ultimately replaced by waters that appear to be sourced from the north atlantic starting in the late maastrichtian observed variations in circulation in the tropical north atlantic during the late cretaceous can account for extensive deposition of black shales in the region prior to the hiatus as well as local warming during a global cooling event in the maastrichtian

high precision 14c measurements demonstrate production of in situ cosmogenic 14ch4 and rapid loss of in situ cosmogenic 14co in shallow greenland firn abstract measurements of radiocarbon 14 c in carbon dioxide co 2 methane ch 4 and carbon monoxide co from glacial ice are potentially useful for absolute dating of ice cores studies of the past atmospheric ch 4 budget and for reconstructing the past cosmic ray flux and solar activity interpretation of 14 c signals in ice is complicated by the fact that the two major 14 c components trapped atmospheric and in situ cosmogenic are present in a combined form as well as by a very limited understanding of the in situ component this study measured 14 ch 4 and 14 co content in glacial firn with unprecedented precision to advance understanding of the in situ 14 c component 14 ch 4 and 14 co were melt extracted on site at summit greenland from three very large 1000 kg each replicate samples of firn that spanned a depth range of 3 6 5 6 m non cosmogenic 14 c contributions were carefully characterized through simulated extractions and a suite of supporting measurements in situ cosmogenic 14 co was quantified to better than 0 6 molecules g 1 ice improving on the precision of the best prior ice 14 co measurements by an order of magnitude the 14 co measurements indicate that most 99 of the in situ cosmogenic 14 c is rapidly lost from shallow summit firn to the atmosphere despite this rapid 14 c loss our measurements successfully quantified 14 ch 4 in the retained fraction of cosmogenic 14 c to 0 01 molecules g 1 ice or better and demonstrate for the first time that a significant amount of 14 ch 4 is produced by cosmic rays in natural ice this conclusion increases the confidence in the results of an earlier study that used measurements of 14 ch 4 in glacial ice to show that wetlands were the likely main driver of the large and rapid atmospheric ch 4 increase approximately 11 6 kyr ago

cold conditions in antarctica during the little ice age implications for abrupt climate change mechanisms abstract the little ice age lia is one of the most prominent climate shifts in the past 5000 yrs it has been suggested that the lia might be the most recent of the dansgaard oeschger events which are better known as abrupt large scale climate oscillations during the last glacial period if the case then according to broecker 2000a 2000b antarctica should have warmed during the lia when the northern hemisphere was cold here we present new data from the ross sea antarctica that indicates surface temperatures were 2 c colder during the lia with colder sea surface temperatures in the southern ocean and or increased sea ice extent stronger katabatic winds and decreased snow accumulation whilst we find there was large spatial and temporal variability overall antarctica was cooler and stormier during the lia although temperatures have warmed since the termination of the lia atmospheric circulation strength has remained at the same elevated level we conclude that the lia was either caused by alternative forcings or that the sea saw mechanism operates differently during warm periods

without power landslide inventories in the face of climate change projected scenarios of climate change involve general predictions about the likely changes to the magnitude and frequency of landslides particularly as a consequence of altered precipitation and temperature regimes whether such landslide response to contemporary or past climate change may be captured in differing scaling statistics of landslide size distributions and the erosion rates derived thereof remains debated we test this notion with simple monte carlo and bootstrap simulations of statistical models commonly used to characterize empirical landslide size distributions our results show that significant changes to total volumes contained in such inventories may be masked by statistically indistinguishable scaling parameters critically depending on among others the size of the largest of landslides recorded conversely comparable model parameter values may obscure significant i e more than twofold changes to landslide occurrence and thus inferred rates of hillslope denudation and sediment delivery to drainage networks a time series of some of earth s largest mass movements reveals clustering near and partly before the last glacial interglacial transition and a distinct step over from white noise to temporal clustering around this period however elucidating whether this is a distinct signal of first order climate change impact on slope stability or simply coincides with a transition from short term statistical noise to long term steady state conditions remains an important research challenge copyright 2011 john wiley sons ltd

bottom water anoxia inoceramid colonization and benthopelagic coupling during black shale deposition on demerara rise late cretaceous western tropical north atlantic 1 the bulk rock geochemistry and inoceramid isotopic composition from cenomanian to santonian finely laminated organic rich black shales recovered during ocean drilling program leg 207 on demerara rise western tropical north atlantic suggest persistent anoxic free h2s conditions within the sediments and short term variations within a narrow range of anoxic to episodically dysoxic bottom waters over a 15 ma time interval in addition to being organic rich the 50 90 m thick sections examined exhibit substantial bulk rock enrichments of si p ba cu mo ni and zn relative to world average shale these observations point to high organic burial fluxes likely driven by high primary production rates which led to the establishment of intensely sulfidic pore waters and possibly bottom waters as well as to the enrichments of cr mo u and v in the sediments at the same time the irregular presence of benthic inoceramids and foraminifera in this facies demonstrates that the benthic environment could not have been continuously anoxic the 13c and 15n values of the inoceramid shell organics provide no evidence of chemosymbiosis and are consistent with pelagic rain as being a significant food source demerara rise inoceramids also exhibit well defined regularly spaced growth lines that are tracked by 13c and 18o variations in shell carbonate that cannot be simply explained by diagenesis instead productivity variations in surface waters may have paced the growth of the shells during brief oxygenation events suitable for benthic inoceramid settlement these inferences imply tight benthopelagic coupling and more dynamic benthic conditions than generally portrayed during black shale deposition by invoking different temporal scales for geochemical and paleontological data this study resolves recent contradictory conclusions e g sulfidic sedimentary conditions versus dysoxic to suboxic benthic waters drawn from studies of either sediment geochemistry or fossil distributions alone on demerara rise this variability may be relevant for discussions of black shales in general

statistical approaches for the definition of landslide rainfall thresholds and their uncertainty using rain gauge and satellite data abstract models for forecasting rainfall induced landslides are mostly based on the identification of empirical rainfall thresholds obtained exploiting rain gauge data despite their increased availability satellite rainfall estimates are scarcely used for this purpose satellite data should be useful in ungauged and remote areas or should provide a significant spatial and temporal reference in gauged areas in this paper the analysis of the reliability of rainfall thresholds based on rainfall remote sensed and rain gauge data for the prediction of landslide occurrence is carried out to date the estimation of the uncertainty associated with the empirical rainfall thresholds is mostly based on a bootstrap resampling of the rainfall duration and the cumulated event rainfall pairs d e characterizing rainfall events responsible for past failures this estimation does not consider the measurement uncertainty associated with d and e in the paper we propose i a new automated procedure to reconstruct ed conditions responsible for the landslide triggering and their uncertainties and ii three new methods to identify rainfall threshold for the possible landslide occurrence exploiting rain gauge and satellite data in particular the proposed methods are based on least square ls quantile regression qr and nonlinear least square nls statistical approaches we applied the new procedure and methods to define empirical rainfall thresholds and their associated uncertainties in the umbria region central italy using both rain gauge measurements and satellite estimates we finally validated the thresholds and tested the effectiveness of the different threshold definition methods with independent landslide information the nls method among the others performed better in calculating thresholds in the full range of rainfall durations we found that the thresholds obtained from satellite data are lower than those obtained from rain gauge measurements this is in agreement with the literature where satellite rainfall data underestimate the ground rainfall registered by rain gauges

dynamics and mass balance of taylor glacier antarctica 1 geometry and surface velocities 1 taylor glacier antarctica exemplifies a little studied type of outlet glacier one that flows slowly through a region of rugged topography and dry climate this glacier in addition connects the east antarctic ice sheet with the mcmurdo dry valleys a region much studied for geomorphology paleoclimate and ecology here we report extensive new measurements of surface velocities ice thicknesses and surface elevations acquired with insar gps and gpr the latter two were used to construct elevation models of the glacier s surface and bed ice velocities in 2002 2004 closely matched those in 2000 and the mid 1970s indicating negligible interannual variations of flow comparing velocities with bed elevations shows that along much of the glacier flow concentrates in a narrow axis of relatively fast flowing ice that overlies a bedrock trough the flow of the glacier over major undulations in its bed can be regarded as a cascade it speeds up over bedrock highs and through valley narrows and slows down over deep basins and in wide spots this pattern is an expected consequence of mass conservation for a glacier near steady state neither theory nor data from this taylor glacier study support the alternative view recently proposed that an outlet glacier of this type trickles slowly over bedrock highs and flows fastest over deep basins

dynamics and mass balance of taylor glacier antarctica 2 force balance and longitudinal coupling 1 taylor glacier antarctica exemplifies an ice sheet outlet that flows through a region of rugged topography and dry climate in contrast to other well studied outlets taylor glacier moves very slowly despite a thickness of order 1 km and driving stresses averaging 1 5 bars here we analyze new measurements of glacier geometry and surface velocity to elucidate flow dynamics of taylor glacier force balance and basal temperatures are calculated at six locations along the glacier s length using an algorithm developed for this study the effects of stress gradient coupling on longitudinal flow variations are also examined we ask whether kamb and echelmeyer s 1986 linearized theory adequately describes the observed response of flow to large amplitude variations in driving stress the force balance calculations indicate that no basal motion is needed to explain the observed flow of taylor glacier inferred basal temperatures are within a few degrees of the melting point in regions of kilometer thick ice and well below the melting point elsewhere deformation of subfreezing ice largely controls the flow of taylor glacier basal drags are mostly in the range 0 9 to 1 2 bars and lateral drags are in the range 0 2 to 0 5 bar stress gradient coupling strongly reduces the variability of velocities along the glacier the velocity variations can be described as the convolution of a forcing function with a spatial filter as kamb and echelmeyer suggested but the form of the forcing function differs from the theoretical relation derived for small amplitude perturbations the power on driving stress is one not three

regional landslide susceptibility assessment using multi stage remote sensing data along the coastal range highway in northeastern taiwan abstract typhoons megi 2010 and saola 2012 brought torrential rainfall which triggered regional landslides and flooding hazards along provincial highway no 9 in northeastern taiwan to reduce property loss and saving lives this study combines multi hazard susceptibility assessment with environmental geology map a rock mass rating system rmr remote sensing analysis and micro topography interpretation to develop an integrated landslide hazard assessment approach and reflect the intrinsic state of slopeland from the past toward the future first the degree of hazard as indicated by historical landslides was used to determine many landslide regions in the past secondly geo mechanical classification of rock outcroppings was performed by in situ investigation along the vulnerable road sections finally a high resolution digital elevation model was extracted from airborne lidar and multi temporal remote sensing images which was analyzed to discover possible catastrophic landslide hotspot shortly the results of the analysis showed that 37 of the road sections in the study area were highly susceptible to landslide hazards the spatial distribution of the road sections revealed that those characterized by high susceptibility were located near the boundaries of fault zones and in areas of lithologic dissimilarity headward erosion of gullies and concave shaped topographic features had an adverse effect and was the dominant factor triggering landslides regional landslide reactivation on this coastal highway are almost related to the past landslide region based on hazard statistics the final results of field validation demonstrated that an accuracy of 91 could be achieved for forecasting geohazard followed by intense rainfall events and typhoons

origin of limestone marl alterations in the upper maastrichtian of zumaya spain abstract near the town of zumaya in northern spain upper maastrichtian strata consist of limestone marl rhythms with thin interbedded sandstones the marls and limestones are primarily pelagic and hemipelagic deposits while the sandstones are the product of turbidity currents stratigraphic variations in the volume of marl and limestone form three hierarchical or composite cycles the first order cycles consist of 20 30 m alternations between stratal sequences consisting of interbedded limestone and marl and sequences composed almost exclusively of marl within the interbedded limestone marl sequences second order cycles occur that consist of 5 10 m alternations between limestone or marl domination the third order cycles consist of the bed by bed alternation of limestone and marl these hree composite cycles are the product of shifts in the clay carbonate ratio on various rock and time stratigraphic scales in order to determine if the cyclicity was the result of changes in the supply of siliciclastic material or carbonate material detailed stratigraphic measurements were made of volume percent average bed thickness and stratigraphic frequency for each lithology product moment coefficients indicate that a negative correlation exists between percentage marl and sandstone frequency and a positive correlation exists between limestone percent and sandstone frequency assuming that turbidite deposition is not genetically related to limestone or marl deposition the correlation coefficients suggest that there were increased sedimentation rates during marl accumulation correlation coefficients also showed that increases in amount of marl in a section occur through bed thickening rather tha the increased number of marl beds in contrast limestone dominated intervals are achieved by reduction of marl bed thickness and increases in marl and limestone bed frequency this confirms the suggestion that marl dominated episodes were associated with increases in the sedimentation rate from this analysis we propose that changes in the influx of siliciclastic material and not changes in productivity or dissolution led to the production of limestone marl rhythms as well as the first and second order cycles seen in the zumaya section

record of cosmogenic in situ produced 14c in vostok and taylor dome ice samples implications for strong role of wind ventilation processes we present results of studies of in situ cosmogenic 14 c in several ice samples from the vostok and taylor dome cores spanning the time intervals of 20 and 11 k y b p respectively the results are in variance with our findings for the greenland ice sheet project 2 gisp 2 samples where near quantitative 14 c retention was observed the partitioning of 14 c in the co and co 2 phases is however quite similar in the gisp and two antarctic ice samples noting that most of the in situ 14 c is produced in the ice during its accumulation to thicknesses of up to 10 m we interpret the observed 14 c deficiencies in antarctic ice samples as due to grain metamorphism recrystallization and sublimation or evaporation caused by wind ventilation simplified models for wind ventilation exhibit an interesting feature of the firnification processes they differently affect the concentrations of in situ 14 c and of the cosmogenic nuclides 10 be and 36 cl scavenged from the atmosphere in the accumulating firn by studying the concentrations of in situ cosmogenic 14 c and the atmospheric cosmogenic nuclides in the same ice samples one can hope to obtain fairly realistic models of the chemical impacts of firnification processes specifically relationships between precipitation and accumulation and the main processes contributing to modifications in the nuclide concentrations

changes in north atlantic circulation at the end of the cretaceous greenhouse interval ocean circulation patterns during the late cretaceous greenhouse interval remain disputed marine sediment geochemistry suggests that the end of the greenhouse interval coincided with the onset or intensification of deep water formation in the north atlantic ocean

solar activity during the last 1000 yr inferred from radionuclide records identification of the causes of past climate change requires detailed knowledge of one of the most important natural factors solar forcing prior to the period of direct solar observations radionuclide abundances in natural archives provide the best known proxies for changes in solar activity here we present two independent reconstructions of changes in solar activity during the last 1000 yr which are inferred from be 10 and c 14 records we analyse the tree ring c 14 data shcal intca104 from 1000 to 1510 ad and annual data from 1511 to 1950 ad and four be 10 records from greenland ice cores camp century grip milcent and dye3 together with two be 10 records from antarctic ice cores dome concordia and south pole in general the be 10 and c 14 records exhibit good agreement that allows us to obtain reliable estimates of past solar magnetic modulation of the radionuclide production rates differences between be 10 records from antarctica and greenland indicate that climatic changes have influenced the deposition of be 10 during some periods of the last 1000 yr the radionuclide based reconstructions of past changes in solar activity do not always agree with the sunspot record which indicates that the coupling between those proxies is not as close as has been sometimes assumed the tree ring c 14 record and be 10 from antarctica indicate that recent solar activity is high but not exceptional with respect to the last 1000 yr c 2006 elsevier ltd all rights reserved less

dust composition changes from taylor glacier east antarctica during the last glacial interglacial transition a multi proxy approach abstract mineral dust is transported in the atmosphere and deposited in oceans ice sheets and the terrestrial biosphere temporal changes in locations of dust source areas and transport pathways have implications for global climate and biogeochemical cycles the chemical and physical characterization of the dust record preserved in ice cores is useful for identifying of dust source regions dust transport dominant wind direction and storm trajectories here we present a 50 000 year geochemical characterization of mineral dust entrapped in a horizontal ice core from the taylor glacier in east antarctica strontium sr and neodymium nd isotopes grain size distribution trace and rare earth element ree concentrations and inorganic ion cl and na concentrations were measured in 38 samples corresponding to a time interval from 46 kyr before present bp to present the sr and nd isotope compositions of insoluble dust in the taylor glacier ice shows distinct changes between the last glacial period lgp in this study ranging from 46 7 15 3 kyr bp the early holocene in this study ranging from 14 5 8 7 kyr bp and zero age samples the 87sr 86sr isotopic composition of dust in the taylor glacier ice ranged from 0 708 to 0 711 during the lgp while the variability during the early holocene is higher ranging from 0 707 to 0 714 the end composition ranges from 0 1 to 3 9 during the lgp and is more variable from 1 9 to 8 2 during the early holocene the increased isotopic variability during the early holocene suggests a shift in dust provenance coinciding with the major climate transition from the lgp to the holocene the isotopic composition and multiple physical and chemical constraints support previous work attributing southern south america ssa as the main dust source to east antarctica during the lgp and a combination of both local ross sea sector dust sources and ssa after the transition into the holocene this study provides the first high time resolution data showing variations in dust provenance to east antarctic ice during a major climate regime shift and we provide evidence of changes in the atmospheric transport pathways of dust following the last deglaciation

oxygen isotope composition of diagenetic calcite in organic rich rocks evidence for 18o depletion in marine anaerobic pore water upper cretaceous organic rich carbonates in israel contain benthonic foraminifera and varying amounts of early diagenetic infilling of sparry calcite the sparry calcite has oxygen isotope values down to 9 5 pdb that are significantly lower than those of the coexisting skeletal calcite averaging 2 pdb low 18o values are very common in carbonates that are associated with organic matter these occurrences are conventionally explained as being due to carbonate formation under conditions of low salinity and or elevated temperature on the basis of petrographic data and local geologic evidence however none of the conventional explanations can be applied in this case we advance an alternative model that relates the light oxygen compositions of the diagenetic calcite to depletion of 18o in pore water of normal salinity the proposed operating mechanism is a direct consequence of organic matter decomposition in the sulfate reducing zone being inherent to reducing marine environments this model can be applied to many organic rich rock associations

measurements of in situ 14c concentrations in greenland ice sheet project 2 ice covering a 17 kyr time span implications to ice flow dynamics we present results of measurements of 14c in co and co2 phases for selected greenland ice sheet project 2 firn and ice samples up to a depth of 1838 m 16 6 kyr b p the results show that 14c in ice consists of both in situ produced cosmogenic 14c which can be either in the form of co or co2 and trapped atmospheric 14co2 in agreement with our previous work on studies of 14c concentrations in antarctic firn and ice samples and some gisp2 samples we found that the cosmogenic in situ produced 14c from spallation of oxygen nuclei is greater than the trapped atmospheric 14c component also we can show the total 14c amounts in ice are consistent with an efficient retention of the in situ variety of 14c in older ice where we expect lower average temperatures at the time of formation the firn samples appear to have lost much of the 14c probably during storage the ice accumulation rates are estimated after due corrections for the co2 content of trapped air and secondary 14c production in ice during storage at altitude these values are in good accord with the recent model estimates of cutler et al 1995 except for two samples at depths 1518 5 m 9740 years b p and 1698 5 m 12 360 years b p in the first case the in situ 14c concentration is significantly higher than that predicted by either of the models by a factor of about 2 in the second case the estimate of cutler et al 1995 is a 50 lower accumulation rate but the 14c result is consistent with adjacent samples a possible reason for the first discrepancy may be the decreased atmospheric pressure at that time at the site as suggested by d raynaud et al unpublished manuscript 1995

exploiting historical rainfall and landslide data in a spatial database for the derivation of critical rainfall thresholds critical rainfall thresholds for landslides are powerful tools for preventing landslide hazard the thresholds are commonly estimated empirically starting from rainfall events that triggered landslides in the past the creation of the appropriate rainfall landslide database is one of the main efforts in this approach in fact an accurate agreement between the landslide and rainfall information in terms of location and timing is essential in order to correctly estimate the rainfall landslide relationships a further issue is taking into account the average moisture conditions prior the triggering event which reasonably may be crucial in determining the sufficient amount of precipitation in this context the aim of this paper is exploiting historical landslide and rainfall data in a spatial database for the derivation of critical rainfall thresholds for landslide occurrence in sicily southern italy the hourly rainfall events that caused landslides occurred in the twentieth century were specifically identified and reconstructed a procedure was proposed to automatically convert rain guages charts recorded on paper tape into digital format and then to provide the cumulative rainfall hyetograph in digital format this procedure is based on a segmentation followed by signal recognition techniques which allow to digitalize and to recognize the hyetograph automatically the role of rainfall prior to the landslide events was taken into account by including in the analysis the rainfall occurred 5 15 and 30 days before each landslide finally cumulated rainfall duration thresholds for different exceedance probability levels were determined the obtained thresholds resulted in agreement with the regional curves proposed by other authors for the same area antecedent rainfall turned out to be particularly important in triggering landslides

the power law relationship between landslide occurrence and rainfall level article i nfo article history zhejiang province is highly prone to the occurrence of landslides during the annual rainy season from may to september we studied the relationship between landslide frequency and rainfall level based on 1414 shallow landslides that have detailed records on the location the date of occurrence and the corresponding daily rainfall data from 1257 rain gauges during the 1990 2003 period in the region cumulative rainfall levels were examined for the periods from the failure day to the prior 10 days the results show that the cumulative frequency of the landslide occurrence correlates well with the landslide triggering rainfall and that their relationship can be described using two power law relations with different scaling exponents for two different ranges of the rainfall level the rainfall level corresponding to the intersection point of two fitted correlation lines can be defined as the upper bound for shallow landslide triggering cumulative rainfall threshold thcr a large number of shallow landslides may be induced when the amount of cumulative rainfall reaches the thcr value the 814 landslides that occurred from 2004 to 2007 in the region are used to examine the method which shows that about 80 of these landslides are induced when the cumulative 1 day rainfall is 200 mm we suggest that the power law relationship between rainfall level and landslide occurrence can be used to estimate the probability of various levels of landslide activity during a rainfall event as a guide for making decisions related to emergency preparedness

rainfall conditions typhoon frequency and contemporary landslide erosion in japan dealing with predicted increases in extreme weather conditions due to climate change requires robust knowledge about controls on rainfall triggered landslides we explore relationships between rainfall and landslide size throughout the japanese archipelago we test whether the total volume of landslides can be predicted directly from rainfall totals intensity and duration using a nationwide inventory of 4744 rainfall triggered landslides recorded from a d 2001 to 2011 we find that larger landslides were more abundant at the expense of smaller ones when total maximum and mean rainfall intensity exceeded 250 mm 35 mm h and 4 mm h respectively frequency distributions of these rainfall parameters are peaked and heavily skewed yet neither the most frequent nor the most extreme values of these rainfall metrics coincide consistently with the maximum landslide volumes a striking decrease of landslide volumes at both mean and maximum rainfall intensity as well as duration points to an exhaustion in hillslope geomorphic response regardless of sample size landslide type mobilized volume dominant lithology or reporting bias our results underscore substantial offsets between the peaks of rainfall metrics and maximum associated landslide volumes thus complicating straightforward estimates of geomorphic work from metrics of rainstorm magnitude or frequency only the rainfall total appears to be a suitable monotonic predictor of landslide volumes mobilized during typhoons and frontal storms

measurements of 14c in ancient ice from taylor glacier antarctica constrain in situ cosmogenic 14ch4 and 14co production rates abstract carbon 14 14c is incorporated into glacial ice by trapping of atmospheric gases as well as direct near surface in situ cosmogenic production 14c of trapped methane 14ch4 is a powerful tracer for past ch4 emissions from old carbon sources such as permafrost and marine ch4 clathrates 14c in trapped carbon dioxide 14co2 can be used for absolute dating of ice cores in situ produced cosmogenic 14c in carbon monoxide 14co can potentially be used to reconstruct the past cosmic ray flux and past solar activity unfortunately the trapped atmospheric and in situ cosmogenic components of 14c in glacial ice are difficult to disentangle and a thorough understanding of the in situ cosmogenic component is needed in order to extract useful information from ice core 14c we analyzed very large 1000 kg ice samples in the 2 26 19 53 m depth range from the ablation zone of taylor glacier antarctica to study in situ cosmogenic production of 14ch4 and 14co all sampled ice is 50 ka in age allowing for the assumption that most of the measured 14c originates from recent in situ cosmogenic production as ancient ice is brought to the surface via ablation our results place the first constraints on cosmogenic 14ch4 production rates and improve on prior estimates of 14co production rates in ice we find a constant 14ch4 14co production ratio 0 0076 0 0003 for samples deeper than 3 m which allows the use of 14co for correcting the 14ch4 signals for the in situ cosmogenic component our results also provide the first unambiguous confirmation of 14c production by fast muons in a natural setting ice or rock and suggest that the 14c production rates in ice commonly used in the literature may be too high

evidence for large century time scale changes in solar activity in the past 32 kyr based on in situ cosmogenic 14c in ice at summit greenland abstract we present results of estimates of cosmic ray flux in greenland at the summit 3200 m a s l 72 6 n 38 5 w during the past 32 kyr we derive these estimates based on concentrations of in situ cosmogenic 14 c produced in ice crystals based on the secular equilibrium concentration of in situ produced 14 c in quartz in terrestrial rocks we find that on century time scales the cosmic ray production rate of 14 c at the summit was close to its estimated long term average production rate except during 3 periods i during 8500 9500 yr b p and 27 000 32 000 yr b p when the production rate was higher by about a factor of 2 and ii during 12 000 16 000 yr b p when the production rate was lower by a factor of 1 5 the observed variation in cosmic ray flux at the polar site is best attributed to changes in solar activity resulting in variable modulation of terrestrial cosmic ray flux changes in the geomagnetic field in the past do not affect the cosmic ray flux at polar latitudes likewise climate changes do not affect the in situ 14 c record in ice during the first two epochs the solar activity must have been very low as during maunder minimum virtually no sunspots resulting in essentially no modulation of the cosmic ray flux by the solar plasma during the low cosmic ray flux epoch 12 000 16 000 yr b p the observed decrease in cosmic ray flux corresponds to high solar activity as seen in 1958 sun spot number 190 we discuss the proxy evidence from tree ring and sediment based records of atmospheric 14 c 12 c ratios during the three epochs these records have been used as a measure of changes in cosmic ray flux and solar activity in the past however since they are also appreciably affected by climatic changes a comparison of the two records is potentially valuable for delineating the nature of past changes in solar activity and large scale ocean circulation and air sea exchange

cretaceous rhythmic bedding sequences a plausible link between orbital variations and climate abstract simple oscillation cycles have been recognized in cretaceous pelagic sequences as a marked periodicity in carbonate and or organic carbon content the estimated periodicities of these cycles resemble milankovitch type variations in orbital elements however during warm geologic periods the nature of the link between orbital variations and the sedimentary record has been problematic climate model studies show that the intensity of continental margin precipitation in specific low latitude regions is a function of land sea thermal contrast which is sensitive to orbital variations cretaceous climate model simulations are characterized by regions of intense precipitation the locations of which are controlled by geographic configuration in particular in the model simulation the northern margin of the tethys ocean has all the climatic characteristics necessary to exhibit a sensitivity to orbital variations detailed studies of the biota sedimentology and geochemistry of the bedding rhythms in greenhorn cyclothem in the western interior seaway of north america are best interpreted in terms of variations in precipitation runoff and stable stratification of the seaway combined the geologic and model studies support a link between orbital periodicities variations of intense precipitation associated with specific paleogeographic situations and cretaceous bedding patterns this hypothesis has important implications for the sensitivity of the atmosphere hydrosphere lithosphere system to external forcing

sublimation and surface energy budget of taylor glacier antarctica taylor glacier an outlet of the east antarctic ice sheet flows through the transantarctic mountains and terminates in the dry valleys understanding how this glacier fluctuates is important for studies of glacial geology paleoclimate ice dynamics and ecology sublimation is the primary mass loss process for most of the glacier four years of specific balance measurements from the ablation zone show sublimation rates up to 40 cma 1 we used data from an array of weather stations as inputs to a model for latent heat flux and hence sublimation rate calculated and measured ablation rates agree to within uncertainties indicating that wind speed and vapour pressure gradient a function of temperature and humidity are the governing variables as expected from theory measurements and model results together allowed us to examine the spatial and temporal variations of sublimation on the glacier on average sublimation is about two times faster in summer than winter rapid sublimation occurs during storms and katabatic wind events but such periods contribute less to the annual total than do slow persistent losses spatially sublimation reaches a maximum midway along the glacier where descending surface air currents are focused by the topography of the aptly named tributary windy gully

rainfall intensity duration thresholds for the initiation of landslides in zhejiang province china abstract zhejiang province located in the southeast coastal region of china is highly prone to rainfall triggered landslides because of its geologic geomorphologic and climatic settings the rainfall landslide relationship is critically important for predicting rainfall induced landslides this study defines landslide triggering rainfall intensity duration thresholds for the entire zhejiang region and the 62 individual areas that comprise the region based on 1569 shallow landslides which occurred from 1990 to 2013 and their corresponding detail rainfall records from 2457 rain gauges in the region the results indicate that the rainfall thresholds vary spatially over the region for rainfall durations from 1 to 24 h the threshold tends to increase from the northwestern part of zhejiang to its southeastern coastal region and it is lower in the central and coastal hill basin regions than that in the western and southern mountainous regions variability of the threshold in space is mainly affected by the slope forming materials and terrain slope gradients different soil types have different thresholds and the thresholds for weathered rock slides are generally higher than those for soil slides for the soil weathered rock on slopes the slope gradient has no obvious influence on the thresholds when the slope angle is

an effective antecedent precipitation model derived from the power law relationship between landslide occurrence and rainfall level abstract antecedent rainfall is an important predisposing factor in triggering landslides because it reduces soil suction and increases the pore water pressure in soils the existing approaches to quantify the antecedent rainfall were derived from empirical methods used to develop rainfall runoff models in which the daily decays of rainfall within a given period preceding a given day are considered as independent processes in this study a methodology accounting for the effective antecedent rainfall that influences landslide occurrence is developed from a power law relationship between the frequency of landslide occurrence and the landslide triggering rainfall level in this model the decay rate of the daily rainfall is related to a scaling exponent defined by the power law relationship the decay process of daily rainfall within a given period preceding a given day is not independent but is interrelated and the impact of rainfall in the preceding k days on soil moisture is associated with the precipitation from the preceding k 1 days

late cretaceous to late eocene palaeogeographic evolution of southwest europe abstract a synthesis of personal research concerning the peri pyrenean region and previously published data is presented as a series of palaeogeographic reconstructions subsequent to the progressive regression at the end of the cretaceous the sea invaded three times parts of the earlier senonian marine domain on both sides of the eastern palaeo pyrenees pre cuisian climatic rewarming combined with cuisian continental epeirogenic deformations resulted in major biogeographic modifications during the cuisian local tectonics forced the sea from the northern pyrenean basin whereas in the southern pyrenean basin the sea retreated much later as a consequence of the pyrenean tectonic phase however the pyrenean tectogenesis seems to have affected a much larger region including the alps shoreline migrations are compared and related to the geodynamic behaviour of the meridional and septentrional european provinces in order to distinguish between tectonic and eustatic causes

high resolution intra and interbasinal correlation of the danian selandian transition early paleocene the bjala section bulgaria and the selandian gssp at zumaia spain abstract the danian selandian d s boundary has been identified for the first time in the black sea coast at bjala bulgaria based on a new integrated bio magneto and cyclostratigraphic study several correlation criteria as established for the basal selandian gssp from zumaia basque basin are evaluated noteworthy is the almost complete lack of calcareous nannoplankton species braarudosphaera bigelowi in the bulgarian sections a sharp decrease of which was indicated as suitable criteria for defining the d s boundary as it occurred both at zumaia and in the classical locations of the north sea basin conversely the second evolutionary radiation of the calcareous nannofossil genus fasciculithus together with the occurrence of fasciculithus tympaniformis that define the np4 np5 zonal boundary seem to be reliable criteria to approximate the d s boundary in detail however the best approach is to integrate biostratigraphic data within a magnetostratigraphic and or cyclostratigraphic framework refinements on the placement of chron c27n at zumaia and robust bed by bed correlation between several basque sections and bjala indicates that the d s boundary is located 30 precession cycles 630 ky above c27n in addition to the precession related marl limestone couplets and 100 ky eccentricity bundles recognized in the studied sections expression of the stable 405 ky long eccentricity allows direct tuning to the astronomical solutions a correlation of the land based sections with previously tuned data from odp site1262 from the southern atlantic is challenged our choice is consistent with original tuning at zumaia but shifts one 100 ky cycle older previous tuning from site 1262 along the interval above c27n under the preferred tuning scheme the d s boundary can be given an age of 61 641 0 040 ma on the la04 orbital solution

limestone marl alternations as environmental archives and the role of early diagenesis a critical review limestone marl alternations and other micritic calcareous rhythmites have long appealed to sedimentologists as they appeared to directly reflect high frequency environmental change in particular when orbital forcing gained popularity amongst sedimentologists and paleoclimatologists in 1980s such rhythmites seemed to offer an ideal tool for high resolution chronostratigraphy and environmental reconstruction however in spite of the fact that orbital forcing has become a routine interpretation of calcareous rhythmites and that the processes of formation of calcareous rhythmites are considered well understood research in the past 10 years again has questioned their primary origin and their direct interpretability detailed petrographic paleontological and geochemical data from numerous successions through geological time provided the basis for testing whether or not the regular alternation of limestone beds and marl or shale interlayers represents bimodally fluctuating environmental conditions in a direct way in particular these data supplemented by box model simulations imply that post depositional alteration diagenesis has the potential to not only seriously distort primary environmental signals but also to mimic primary signals this questions the use of micritic calcareous rhythmites for high resolution chronostratigraphy and for environmental interpretations where independent data of diagenetically inert parameters are not available diagenetic changes appear to have a yet widely underestimated influence on the appearance of limestone marl alternations and other calcareous rhythmites the aim of the present review is to summarize new approaches and give an overview of our research results in this field of the past decade this review also aims at pointing to still enigmatic aspects that need to be addressed before the interpretation of micritic calcareous rhythmites can be considered a reliable tool for high resolution chronostratigraphy and paleoenvironmental interpretation

an overview of the post messinian paleoenvironmental history of the western mediterranean a review of the pliocene pleistocene paleoenvironmental history of the western mediterranean is presented based on micropaleontological and geochemical studies of ocean drilling program odp leg 107 material and marine outcrops in southern italy the calcareous plankton biochronology proposed for the mediterranean by rio et al 1990 and 1991a provides the necessary age control for determining the timing of major climatic and oceanographic changes in the region the early pliocene period in the mediterranean was not a time of warm stable climate rather it was marked by relatively high amplitude climatic oscillations in marginal areas these climatic oscillations resulted in the rhythmic deposition of limestone marl couplets which have an average duration of approximately 19 000 years it is proposed that these sedimentary couplets are the result of precessionally induced changes in monsoon intensity which in turn cause variability in coastal divergence and upwelling the 18o and the calcareous plankton foraminifera and coccoliths records for tyrrhenian sea odp site 653 reveal a cooling of surface waters at 3 1 ma coincident with this cooling is an increase in the frequency of diatomite formation in southern italy bianco section the global cooling at 2 4 ma and the associated expansion of northern hemisphere glaciation resulted in a shift to more arid conditions in the mediterranean region this climate change may have altered the mediterranean water balance resulting in the establishment of antiestuarine water exchange with the atlantic at this time the 18o record for site 653 is also marked by a sharp cooling across the pliocene pleistocene boundary in the boundary stratotype section at vrica this cooling is manifested as an increase in the abundance of the planktonic foraminifer neogloboquadrina pachyderma

isotope signatures associated with early meteoric diagenesis the environments in which carbonate diagenesis proceeds have been documented in previous studies of holocene and late pleistocene sediments and limestones on barbados west indies variations in the carbon and oxygen isotopic composition of limestones produced during early freshwater diagenesis have been observed in this study to occur in specific patterns six potentially useful patterns emerge when one views stable isotope data within a stratigraphic framework 1 the subaerial exposure surface is characterized by strongly 12c enriched limestones 13c compositions of underlying limestones grow progressively heavier with increasing depth 2 the subaerial exposure surface may also be marked by slight 18o enrichment 3 an abrupt shift in 18o values may differentiate sediments above the exposure surface from those below 4 sediments altered in the marine meteoric mixing zone may be characterized by positive covariance between their 18o and 13c compositions 5 the vadose phreatic boundary may be marked by a sharp increase in 13c values in the seaward portions of a fresh groundwater system and 6 samples contemporaneously altered in a single fresh groundwater system within an areally restricted region should display a narrow range of 18o and a wide range of 13c compositions analysis of samples from five palaeozoic and mesozoic formations which contained petrographic evidence of early freshwater diagenesis showed that isotope patterns similar to those observed in barbados limestones have been preserved in rocks as old as mississippian these isotope patterns could prove to be useful for identifying diagenetically induced porosity trends in carbonate rocks they might be used to identify limestones diagenetically altered in meteoric environments to identify mixing zone cements and dolomites and to trace the regional and vertical distributions of early meteoric groundwater systems in ancient carbonate formations

factors controlling landslide frequency area distributions a power law relation for the frequency area distribution fad of medium and large landslides e g tens to millions of square meters has been observed by numerous authors but the fad of small landslides diverges from the power law distribution with a rollover point below which frequencies decrease for smaller landslides some studies conclude that this divergence is an artifact of unmapped small landslides due to lack of spatial or temporal resolution others posit that it is caused by the change in the underlying failure process an explanation for this dilemma is essential both to evaluate the factors controlling fads of landslides and power law scaling which is a crucial factor regarding both landscape evolution and landslide hazard assessment this study examines the fads of 45 earthquake induced landslide inventories from around the world in the context of the proposed explanations we show that each inventory probably involves some combination of the proposed explanations though not all explanations contribute to each case we propose an alternative explanation to understand the reason for the divergence from a power law we suggest that the geometry of a landslide at the time of mapping reflects not just one single movement but many including the propagation of numerous smaller landslides before and after the main failure because only the resulting combination of these landslides can be observed due to a lack of temporal resolution many smaller landslides are not taken into account in the inventory this reveals that the divergence from the power law is not necessarily attributed to the incompleteness of an inventory this conceptual model will need to be validated by ongoing observation and analysis also we show that because of the subjectivity of mapping procedures the total number of landslides and total landslide areas in inventories differ significantly and therefore the shapes of fads also differ considerably

a warning system for rainfall induced shallow failures abstract it is widely recognised that soil slips and debris flows are triggered by short intense storms owing its geologic geomorphologic and climatic settings the piedmont region nw italy is highly prone to the occurrence of this kind of landslides in the last two centuries in fact a total of 105 severe meteoric events which triggered shallow failures occurred and of these 18 events took place from 1990 to 2002 a fair number of rainfall thresholds have been proposed in the literature defined both on empirical or on physical bases empirical thresholds are defined collecting rainfall data for landslide meteoric events and for events without landslides while physical thresholds are based on numerical models that consider the relation between rainfall pore pressure and slope stability the main objective of this paper is the identification of the empirical triggering thresholds for the piedmont region four meteoric events were selected and analysed november 4 5 1994 july 7 8 1996 april 27 30 2000 october 13 16 2000 because they supply a wide range of variation for both rainfall parameters duration intensity cumulative rainfalls and the number of induced landslides in the intensity duration plot the critical limit is described by the equation i 19d 0 50 where i rainfall intensity expressed in mm h and d rainfall duration expressed in hours such a limit is traced to envelop 90 of the points on the graph in the ni d diagram the triggering thresholds are given by the equations ni 0 76d 0 33 and ni 4 62d 0 79 where ni normalised intensity with respect to the annual precipitation map expressed in mm h pma 100 in the article the different meaning of these thresholds is discussed finally the diagram ni ncr is proposed the triggering threshold is given by the expression ni 0 09ln ncr 0 54 where ncr is the normalised cumulative critical rainfall mm pma 100 the application of the triggering thresholds as a fundamental element in a warning system dedicated to the safeguarding of population in landslide prone areas is discussed in detail an operating procedure which is presently being verified and tested in the studied area is described

taking the pulse of the sun during the holocene by joint analysis of 14c and 10be we have studied solar variations during the holocene i e last similar to 11 700 yr by combining a new model of the earth s dipole moment with c 14 data from the intcal04 record and 10 be data from the grip ice core joint spectral analysis of the two nuclide records suggests that the periodic behavior of the sun was particularly pronounced between 6000 4500 yr bp and 3000 2000 yr bp with dominating periodicities of similar to 88 similar to 150 similar to 220 and similar to 400 years while this rhythmic behavior faded during other time intervals the fact that the two reconstructions based on radionuclides with distinct geochemical properties agree with respect to both the frequency and timing of the periodic behavior strongly suggests that they reflect the actual behavior of the sun subtle but systematic differences between the amplitude spectra may point to an interplay between the climate system and the similar to 220 and similar to 400 year solar cycles during intervals when these were particularly prominent citation knudsen m f p riisager b h jacobsen r muscheler i snowball and m s seidenkrantz 2009 taking the pulse of the sun during the holocene by joint analysis of 14 c and 10 be geophys res lett 36 l16701 doi 10 1029 2009gl039439 less

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

proximate environmental forcing in fine scale geochemical records of calcareous couplets upper cretaceous and palaeocene of the basque cantabrian basin eastern north atlantic abstract calcareous couplets are key elements in reconstructing the evolution of a sedimentary basin due to the influence of forcing mechanisms such as climate sea level and tectonism on their depositional patterns proposed forcing mechanisms however are often not mutually exclusive and even constraining the relative importance of different processes is problematic added to the question of discriminating forcing mechanisms a major challenge is to produce high sampling density so that observations lie within temporal resolutions equal to or finer than the timescales on which different forcing operates here we show fine scale 1 sample 2 cm caco3 18o and 13c records and sedimentological observations from three different sites isla de castro sopelana ma and sopelana da with calcareous couplets in the basque cantabrian basin eastern north atlantic to illustrate the potential of fine sampling strategies to help distinguish proximate environmental forcing partial redistribution of carbonate during burial diagenesis has been proposed for these sediments our caco3 18o and 13c data could thus be dismissed as diagenetic signals if only one sample was collected from each bed detailed observations of the fine scale geochemical records however challenge purely diagenetic explanations combined with sedimentology the caco3 18o and 13c values partially altered by diagenesis are interpreted to have resulted from alternating climates the proximate forcing through which alternating climates caused the geochemical patterns though was different in each section due to their specific palaeogeographic positions in the basin and the properties of the seawater masses the proximity of continental areas of high relief to the isla de castro section supported a high continental influence during its deposition the sopelana ma sediments are assigned to a transgressive system tract a condition that is interpreted to have promoted a high influence of oceanic processes in its depositional setting finally a relatively cool oxygen rich water mass with high oxidation potential influenced the geochemical and depositional patterns of sopelana da beyond the climatic and oceanographic dynamics inferred for a basin that linked the western tethys with boreal domains during major marine transgressions of the late cretaceous to palaeocene an implication of our work is that if similar fine scale geochemical records were applied to calcareous couplets spanning major events in earth s history e g ocean anoxic events alternative forcing scenarios leading to and out of these events could be discriminated

dynamics and mass balance of taylor glacier antarctica 3 state of mass balance 1 taylor glacier flows from the east antarctic ice sheet and terminates in the mcmurdo dry valleys where it has left a geomorphologic record of past incursions here we use new data on the flow thickness and surface balance of taylor glacier to calculate ice fluxes and assess the current state of mass balance overall the glacier is close to a state of zero net balance and has largely adjusted to reduced snowfall on the taylor dome source region in the mid holocene one region of the upper ablation zone appears to be losing mass evidence from ice surface morphology and stable isotope profiles suggests that this mass loss is a long term phenomenon hence probably a lingering response to the earlier drying of taylor dome our data give a general indication of the size of ablation or accumulation changes needed for ice to advance far into taylor valley as occurred 70 to 130 ka ago

sedimentary vs diagenetic control on rhythmic calcareous successions pliensbachian of asturias spain the diagenetic overprint in rhythmic hemipelagic successions can either enhance or change the original distribution of caco3 but it is difficult to evaluate its effect because in most field examples it is not possible to distinguish between sedimentary and diagenetic features the rhythmic succession of the pliensbachian of asturias spain shows alternation of bioclastic and laminated burrowed intervals the original content of carbonate brought by storms from shallow areas was larger in the bioclastic horizons however there is a widespread mismatch between facies alternations and the observed lithological rhythms the diagenetic redistribution of caco3 resulted in successive limestone marl clay couplets that do not match either in number or in the location of the boundaries the sedimentary cycles defined by facies alternations we conclude that interpreting the limestone marl rhythms as a direct response to primary changes is highly questionable unless there is unequivocal proof of a sedimentary origin of the alternation of the two lithologies

maastrichtian foraminiferal and paleoceanographic changes on milankovitch timescales milankovitch scale alternations in maastrichtian hemipelagic strata from ocean drilling program hole 1050c blake nose provide a natural experiment of paleoceanography and foraminiferal paleoecology in a tropical subtropical greenhouse ocean cycles are 30 50 cm thick and thought to reflect the 21 kyr precessional cycle high planktic 18o values are correlated with high planktic but low benthic 13c values indicating that cooler and or more saline surface waters were associated with higher productivity high productivity intervals are also characterized by high ca concentrations enrichment in feldspar and kaolinite and high relative abundance of heterohelix spp globigerinelloides spp and laeviheterohelix glabrans conversely low productivity intervals have low planktic 18o values high fe and ti concentrations enrichment in quartz illite and chlorite and relative increases in globotruncana spp and pseudoguembelina spp potential forcing mechanisms for observed covariation include cyclic variation in water column stratification variation in continental nutrient fluxes and changes in the intensity of upwelling

bedding rhythms and cyclic sequences as documented in organic carbon carbonate patterns upper cretaceous western interior u s abstract a three component sedimentation model is introduced for estimating the relative effects of major changes in sediment flux coupled organic carbon carbonate changes reflecting different dilution concentration styles are utilized to detect the changing flux between the carbonate siliciclastic and organic matter components the three component model is then applied to upper cretaceous rhythmically bedded units of the greenhorn and niobrara cycles of the western interior seaway the cycles are related to third order sea level changes the western interior seaway was sensitive to small scale climatic cycles only during periods of maximum flooding due to combined variations in carbonate productivity redox conditions and siliciclastic supply from continental sources rhythmic deposition is different for different parts within the periods of maximum flooding for each of the two investigated third order sea level cycles section intervals reflecting peak flooding show variations in carbonate productivity and variations in redox conditions slightly more regressive intervals show variations in calcareous productivity and siliciclastic dilution with stagnant dysaerobic bottom waters for most of the investigated bedding rhythms persistent dysaerobic bottom waters are largely uninfluenced by variations in pelagic carbonate productivity except for section intervals representing peak flooding this suggests the existence of a circulation pattern in which a mixed surface water zone was underlain by more stratified oxygen depleted water masses with slow circulation

instruments and methods a novel method for obtaining very large ancient air samples from ablating glacial ice for analyses of methane radiocarbon we present techniques for obtaining large 100 l stp samples of ancient air for analysis of 14 c of methane 14 ch4 and other trace constituents paleoatmospheric 14 ch4 measurements should constrain the fossil fraction of past methane budgets as well as provide a definitive test of methane clathrate involvement in large and rapid methane concentration ch4 increases that accompanied rapid warming events during the last deglaciation air dating to the younger dryas preboreal and oldest dryas bolling abrupt climatic transitions was obtained by melt extraction from old glacial ice outcropping at an ablation margin in west greenland the outcropping ice and occluded air were dated using a combination of d 15 no f n 2 d 18 oo f o 2 d 18 oice and ch4 measurements the ch4 blank of the melt extractions was 4 ppb measurements of d 18 o and d 15 n indicated no significant gas isotopic fractionation from handling measured ar n2 cfc 11 and cfc 12 in the samples indicated no significant contamination from ambient air ar n2 kr ar and xe ar ratios in the samples were used to quantify effects of gas dissolution during the melt extractions and correct the sample ch4 corrected ch4 is elevated over expected values by up to 132 ppb for most samples suggesting some in situ ch4 production in ice at this site

secular variation in late cretaceous carbon isotopes a new δ13c carbonate reference curve for the cenomanian campanian 99 6 70 6 ma carbon stable isotope variation through the cenomanian santonian stages is characterized using data for 1769 bulk pelagic carbonate samples collected from seven chalk successions in england the sections show consistent stratigraphic trends and 13c values that provide a basis for highresolution correlation positive and negative 13cexcursions and inflection points on the isotope profiles are used to define 72 isotope events key markers are provided by positive 13c excursions of up to 2 the albian cenomanianboundary event mid cenomanian event i thecenomanian turonian boundary event the bridgewick hitch wood and navigation events of late turonian age and the santonian campanian boundary event isotope events are isochronous within a framework provided by macrofossil datum levels and bentonite horizons an age calibrated composite 13c reference curve and an isotope event stratigraphy are constructed using data from the english chalk the isotope stratigraphy is applied to successions in germany france spain and italy correlation with pelagic sections at gubbio central italy demonstrates general agreement between biostratigraphic and chemostratigraphic criteria in the cenomanian turonian stages confirming established relationships between tethyan planktonic foraminiferal and boreal macrofossil biozonations correlation of the coniacian santonian stages is less clear cut magnetostratigraphic evidence for placing the base of chron 33r near the base of the upper santonian is in good agreement with the carbon isotope correlation but generates significant anomalies regarding the placement of the santonian and campanian stage boundaries with respect to tethyan planktonic foraminiferal and nannofossil zones isotope stratigraphy offers a more reliable criterion for detailed correlation of cenomanian santonian strata than biostratigraphy with the addition of campanian 13c data from one of the english sections a composite cenomanian campanian age calibrated reference curve is presented that can be utilized in future chemostratigraphic studies the cenomanian campanian carbon isotope curve is remarkably similar in shape to supposedly eustatic sea level curves increasing 13c values accompanying sea level rise associated with transgression and falling 13c values characterizing sea level fall and regression the correlation between carbon isotopes and sea level is explained by variations in epicontinental sea area affecting organic matter burial fluxes increasing shallow sea floor area and increased accommodation space accompanying sea level rise allowedmore efficient burial ofmarine organic matter with the preferential removal of 12c from the marine carbon reservoir during sea level fall reduced seafloor area marine erosion of previously deposited sediments and exposure of basin margins led to reduced organiccarbon burial fluxes and oxidation of previously deposited organic matter causing falling 13c values additionally drowning of carbonate platforms during periods of rapid sea level rise may have reduced the global inorganic relative to the organic carbon flux further enhancing 13c values while renewed platform growth during late transgressions and highstands prompted increased carbonate deposition variations in nutrient supply changing rates of oceanic turnover and the sequestration or liberation of methane from gas hydrates may also have played a role in controlling carbon isotope ratios

information on past solar activity and geomagnetism from 10 be in the camp century ice core a nearly continuous record of the concentration of 10be from ice core data is compared with the tree ring derived record for 14c over the same period and it is found that short term trends in these data sets provide a record of solar activity no definitive relationship between the long term trends and the geomagnetic dipole moment is found

precise interpolar phasing of abrupt climate change during the last ice age a new ice core from west antarctica shows that during the last ice age abrupt northern hemisphere climate variations were followed two centuries later by a response in antarctica suggesting an oceanic propagation of the climate signal to the southern hemisphere high latitudes