multiproxy comparison of oceanographic temperature during heinrich events in the eastern subtropical atlantic abstract abrupt climate change episodes associated with catastrophic calvings of the laurentide and european ice sheets during the last glacial heinrich events he had far reaching effects in the atlantic we have measured minor and trace element concentrations in planktonic foraminiferal calcite in a core from the iberian margin md95 2040 and a core from the gulf of cadiz md99 2339 during he 1 4 and 5 to explore the use of the mg temperature proxy for constraining regional temperature changes during these unique periods of ice rafting high sedimentation rates throughout the length of both cores allow a detailed reconstruction of temperature during abrupt events mg ca derived temperatures reveal 5 13 c amplitude of cooling during he1 the largest and most well defined event in this region the northern site most likely experienced the higher end of this amplitude range cooling implied by the mg ca data is within the range of assemblage derived sea surface temperature sst changes from the same cores showing 10 c perturbations for each he but the mg ca data imply smaller changes during he4 and he5 cooling estimated from unsaturated alkenone ratios 3 c represent the smallest changes the prominence of he1 in this region is consistent with the changes over the wider north atlantic that show colder temperatures during he1 vs he4 we use cd ca to reconstruct nutrient concentrations and find very low values 0 02 0 04 mol mol at both locations during he these low values are consistent with core top planktonic cd ca from each region suggesting that the cooling during he was unlikely to be caused by more intense upwelling than in the modern temperature comparisons of other proxies alkenone u 37 k and assemblage data from the same core suggest that mg ca paleothermometry is sensitive to the relative size of each he this sensitivity is capable of highlighting other variables that influence the impact of heinrich events on sst including the background climate state

simulation of dynamics of the double diffusive system a numerical simulation model for the dynamics of a doublediffusive system is presented the model is an extension of an existing lake and reservoir model in addition to adapting the parameterizations of the original model to suit a thermohaline system the model accounts for the transport of salt and heat by double diffusive instability the role of the sidewalls both by virtue of their slope and by the differential heating that may occur there are explicitly included in the treatment of the double diffusive fluxes the use of the model as an aid in site selection for salt gradient solar ponds is described as an example of its application

an effect of dissolved nutrient concentrations on alkenone based temperature estimates the ratio of 37 carbon diunsaturated to diunsaturated and triunsaturated alkenones uk 37 produced by some haptophytes is widely used as a proxy for past sea surface temperatures however our isothermal culturing experiments with emiliania huxleyi clone ccmp372 show uk 37 values to also vary with nutrient availability and cell division rate these results provide a reasonable explanation for large isothermal variation in uk 37 values of single coccolithophorid strains grown in culture they also suggest that alkenone based estimates of past sea surface temperatures may have been influenced by dissolved nutrient concentrations as well as by temperature

mixed layer simulation of buoy observations taken during hurricane eloise a one dimensional mixed layer model is used to simulate observations made by a noaa buoy in the gulf of mexico during hurricane eloise the model predicted sst mixed layer depth and inertial current agree favorably with the observations in addition model experiments demonstrate the importance of the veering of the wind vector during the passage of the eye to the amplitude of the inertial current generated by the wind and the extent of vertical mixing

validation of fracture data recognition in rock masses by automated plane detection in 3d point clouds abstract this paper presents 1 an automated method to extract planes and their spatial orientation directly from 3d point clouds followed by 2 extensive validation tests accompanied by thorough statistical analysis and 3 a fracture intensity calculation on automatically segmented planes for the plane extraction a region growing segmentation algorithm controlled by several input parameters is applied to a point cloud of a granite outcrop within its complex surface shape more than 1000 compass measurements were conducted for validation in addition digitally handpicked planes in the software virtual reality geological studio vrgs were used for single plane comparison in a second test site we performed fracture intensity calculation in petrel based on results of the segmentation algorithm on mechanical layers of a clastic sedimentary succession the comparison of automated segmentation results and compass measurements of three different plane sets shows a deviation of 0 70 2 00 while the mean single plane divergence amounts to 4 97 hence this study presents a fast precise and highly adaptable automated plane detection method which is reproducible transparent objective and provides increased accuracy in outcrops with rough and complex surfaces moreover output formats of spatial orientation and location of planes are designed for simple handling in other workflows and software

a new methodological approach to assess the stability of discontinuous rocky cliffs using in situ surveys supported by uav based techniques and 3 d finite element model a case study abstract this paper aims to present a new methodological approach for the stability assessment of coastal cliffs constituted of discontinuous rock masses the method entails in situ specific geostructural and geomechanical surveys three dimensional uav based photogrammetric structural models laboratory geotechnical tests and two and three dimensional finite element analysis fem the application of the method to a case study is then presented and discussed it regards a 600 m long sea rocky cliff located at sant andrea melendugno south of apulia se italy and faced to the southern adriatic sea here the cliff is made up of an about 15 m thick sequence of laminate calcisiltites alternate with bioturbated calcarenites belonging to the uggiano la chiesa fm middle upper pliocene the structural discontinuities detected with photogrammetry techniques were compared and validated with those derived from conventional in situ survey methods later on the paper discusses assumptions and results of two and three dimensional finite element models developed to investigate the potential failure mechanisms of the sea cliff accounting for pre existing weak planes or discontinuities with unfavourable orientation the failure mechanisms obtained by both fem analysis agree well with those typically observed in the study area

origin and consequences of cyclic ice rafting in the northeast atlantic ocean during the past 130 000 years deep sea sediment cores recovered from the northeast atlantic ocean were examined in order to elucidate the influence of the earth s orbital parameters on major ice rafting analyses of coarse grained ice rafted debris and planktonic foraminifers revealed a strong reaction to the precession signal since 130 000 yr b p dropstone layers have been deposited each half period of a precessional cycle 11 000 1000 yr ice rafting occurs during times of winter minimum summer maximum insolation and summer minimum winter maximum insolation in the first case high summer insolation forces meltwater discharge from the ice sheets into the polar seas which subsequently enhances formation of sea ice during the winter in the second case growth of continental ice enhances iceberg production which also leads to a salinity reduction of surface seawater both situations result in a southward penetration of polar water thus the marine record of dropstones documents ice rafting not only during weichselian stades but also during cold events within interstades the regularity of ice rafting yields a useful framework to calibrate and elucidate climatic changes not only in the region of the north atlantic ocean but also in remote areas such as the pacific ocean and the antarctic

evidence from the northeastern atlantic basin for variability in the rate of the meridional overturning circulation through the last deglaciation a first study from the subtropical western atlantic using 231pa 230th ratios as a kinematic proxy for deep water circulation provided compelling evidence for a strong link between climate and the rate of meridional overturning circulation moc over the last deglaciation however these results warrant confirmation from additional locations and water depths because the interpretation of the sedimentary 231pa 230th ratio in terms of circulation vigor can be biased by variations in particle flux and composition we have measured 231pa 230th in a core from the iberian margin in the northeastern atlantic basin and have compared these new results to the data from the western atlantic basin we find that the reduction in the circulation during h1 and yd and the subsequent increases first recognized in the sediment deposited on bermuda rise are also evident in the eastern basin in a totally different sedimentary regime confirming that sedimentary 231pa 230th ratios record basin wide changes in deep water circulation however some differences between the eastern and western records are also recognized providing preliminary evidence to differentiate between renewal rates in the two north atlantic basins and between shallower and deeper overturning our results suggest the possible existence of two sources of glacial north atlantic intermediate deep water gnaiw one in the south labrador sea and another west of rockall plateau both sources contributed to the meridional overturning but the two had different sensitivity to meltwater from the laurentide and the fennoscandian ice sheets during the deglaciation these results indicate that additional information on the geometry and strength of the ventilation of the deep atlantic can be obtained by contrasting the evolution of sediment 231pa 230th in different sections of the atlantic ocean

atmospheric forcing intensifies the effects of regional ocean warming on reef scale temperature anomalies during a coral bleaching event 1 we investigate how local atmospheric conditions and hydrodynamic forcing contributed to local variations in water temperature within a fringing coral reef lagoon system during the peak of a marine heat wave in 2010 2011 that caused mass coral bleaching across western australia a three dimensional circulation model regional ocean modeling system roms with a built in air sea heat flux exchange module coupled ocean atmosphere experiment coare was coupled with a spectral wave model simulating waves nearshore swan to resolve the surface heat exchange and wave driven reef circulation in coral bay ningaloo reef using realistic oceanic and atmospheric forcing the model predictions were in good agreement with measured time series of water temperature at various locations in the coral reef system during the bleaching event through a series of sensitivity analyses we found that the difference in temperature between the reef and surrounding offshore waters dt was predominantly a function of both the daily mean net heat flux qnet and residence time whereas diurnal variations in reef water temperature were dependent on the diurnal fluctuation in the net heat flux we found that reef temperatures were substantially higher than offshore in the inner lagoon under normal weather conditions and over the entire reef domain under more extreme weather conditions 0 7 c 1 5 c although these temperature elevations were still less than that caused by the regional ocean warming 2 c 3 c the arrival of peak seasonal temperatures in the summer of 2010 2011 when net atmospheric heat fluxes were positive and abnormally high caused substantially higher thermal stresses than would have otherwise occurred if offshore temperatures had reached their normal seasonal maxima in autumn when net atmospheric heat fluxes were negative or cooling therefore the degree heating weeks calculated based on offshore temperature substantially underestimated the thermal stresses experienced by the reef in the period leading up to the observed bleaching

archaeal tetraether lipids record subsurface water temperature in the south china sea abstract the south china sea scs is the largest tropical marginal sea in the western pacific ocean while the u 37 k proxy is known to reflect the sea surface temperature sst of the 0 30 m mixed layer in the scs little is known about the applicability of the tex86 proxy here we present results from paired analyses of tex 86 h a modified version of tex86 and u 37 k from core top sediment samples from the scs tex 86 h based sst calculated from the global regression exhibited slightly higher values avg 28 7 c range 27 1 30 3 c than values from the world ocean atlas 1994 avg 27 4 c range 26 1 28 6 c and u 37 k based temperature values avg 27 3 c range 26 1 29 0 c moreover the linear relationship between tex 86 h and sst was poor r2 0 44 correlation analysis of tex 86 h with annual temperature and seasonal temperature at various depths revealed that tex 86 h correlated better with annual sea temperature at 30 125 m r 0 89 than with temperature in the 0 30 m mixed layer r 0 69 this suggests that tex 86 h reflects a deeper and cooler subsurface temperature rather than surface or mixed layer temperature in the scs as a result the global regression which results in higher sst values could not be applied to predict subsurface temperature in the scs and a local calibration of tex 86 h vs 30 125 m subsurface temperature was tentatively established furthermore the difference between u 37 k and tex 86 h derived temperature talkenone gdgt correlated moderately r 0 62 with the depth of the thermocline of the 18 c isotherm in the scs suggesting that the difference may provide a proxy for upper ocean vertical thermal gradient in this marginal sea

iceberg discharges into the north atlantic on millennial time scales during the last glaciation high resolution studies of north atlantic deep sea cores demonstrate that prominent increases in iceberg calving recurred at intervals of 2000 to 3000 years much more frequently than the 7000 to 10 000 year pacing of massive ice discharges associated with heinrich events the calving cycles correlate with warm cold oscillations called dansgaard oeschger events in greenland ice cores each cycle records synchronous discharges of ice from different sources and the cycles are decoupled from sea surface temperatures these findings point to a mechanism operating within the atmosphere that caused rapid oscillations in air temperatures above greenland and in calving from more than one ice sheet

a novel proxy for terrestrial organic matter in sediments based on branched and isoprenoid tetraether lipids we propose a novel tracer for terrestrial organic carbon in sediments based on the analysis of tetraether lipids using high performance liquid chromatography mass spectrometry hplc ms analysis of terrestrial soil and peats shows that branched tetraether lipids are predominant in terrestrial environments in contrast to crenarchaeol the characteristic membrane lipid of non thermophilic crenarchaeota which is especially abundant in the marine and lacustrine environment based on these findings an index was developed the so called branched and isoprenoid tetraether bit index based on the relative abundance of terrestrially derived tetraether lipids versus crenarchaeol this bit index was applied to surface sediments from the angola basin where it was shown to trace the outflow of the congo river furthermore analyses of particulate organic matter from the north sea showed relatively higher bit indices in water column particulate organic matter near large river inputs a survey of globally distributed marine and lacustrine surface sediments shows that the bit index in these environments correlates with the relative fluvial input of terrestrial organic material making this index generally applicable the new proxy allows the rapid assessment of the fluvial input of terrestrial organic material in immature sediments up to 100 ma old

position of the polar front along the western iberian margin during key cold episodes of the last 45 ka 1 this paper documents the migration of the polar front pf over the iberian margin during some of the cold climatic extremes of the last 45 ka it is based on a compilation of robust and coherent paleohydrological proxies obtained from eleven cores distributed between 36 and 42 n planktonic 18o globigerina bulloides ice rafted detritus concentrations and the relative abundance of the polar foraminifera neogloboquadrina pachyderma sinistral were used to track the pf position these three data sets compared from core to core show a consistent evolution of the sea surface paleohydrology along the iberian margin over the last 45 ka we focused on five time slices representative of cold periods under distinct paleoenvironmental forcings the 8 2 ka event and the younger dryas two recent cold events occurring within high values of summer insolation heinrich events 1 and 4 reflecting major episodes of massive iceberg discharges into the north atlantic and the last glacial maximum typifying the highest ice volume accumulated in the northern hemisphere for each event we generated schematic maps mirroring past sea surface hydrological conditions the maps revealed that the polar front presence along the iberian margin was restricted to heinrich events the sea surface conditions during the last glacial maximum were close to those at present day except for the northern sites which briefly experienced subarctic conditions

four climate cycles of recurring deep and surface water destabilizations on the iberian margin centennial climate variability over the last ice age exhibits clear bipolar behavior high resolution analyses of marine sediment cores from the iberian margin trace a number of associated changes simultaneously proxies of sea surface temperature and water mass distribution as well as relative biomarker content demonstrate that this typical north south coupling was pervasive for the cold phases of climate during the past 420 000 years cold episodes after relatively warm and largely ice free periods occurred when the predominance of deep water formation changed from northern to southern sources these results reinforce the connection between rapid climate changes at mediterranean latitudes and century to millennial variability in northern and southern polar regions

a precise search for drastic temperature shifts of the past 40 000 years in southeastern europe 1 climatic models simulate abrupt oscillations that are associated in the north atlantic with dansgaard oeschger and heinrich events however the geographic extension of temperature anomalies is largely uncontrolled due to the scarcity of quantitative records of sufficient time resolution on the european continent here we propose based on a recently developed temperature proxy tex86 a reconstruction of millennial scale temperature variations in a black sea sediment archive for the last 40 000 years prior to any paleoclimatological interpretations the effects of potential bias such as seasonality and depth of maximum export production on temperature reconstructions are considered for the black sea based on previous work a tentative method for temperature corrections taking into account varying terrigenous inputs is further proposed reconstructed temperatures for black sea core md042790 were remarkably stable during the last glacial however significant shifts toward lower temperatures of 2 c occurred during heinrich events 2 and 3 the deglaciation displayed a temperature increase of 10 c consistent with neighboring european reconstructions a younger dryas cooling of approximately 5 6 c was clearly expressed in the reconstruction in notable contrast to observations from nearby archives heinrich events imprinted our glacial temperature record consistent with a strong reorganization of oceanic circulation and a large spreading of the temperature anomaly from the north atlantic toward the southeast furthermore in contrast to high latitude records our black sea record lacks the signatures of dansgaard oeschger interstadials suggesting a decreasing temperature gradient away from the north atlantic

millennial scale sea surface temperature changes in the eastern mediterranean nile river delta region over the last 27 000 years 1 in this study we utilize two organic geochemical proxies the u37k index and tex86 to examine past sea surface temperatures sst from a site located near the nile river delta in the eastern mediterranean em sea the u37k and tex86 records generally are in agreement and indicate sst ranges of 14 c 26 c and 14 c 28 c respectively during the last 27 cal ka during the holocene tex86 based sst estimates are usually higher than u37k based sst estimates which is likely due to seasonal differences between the timing of the haptophyte and crenarchaeota blooms in the em and is related to the onset of the modern flow regime of the nile river both records show that sst varied on centennial to millennial timescales in response to global climate events i e cooling during the last glacial maximum lgm heinrich event 1 h1 and the younger dryas yd and warming during the bolling allerod and in the early holocene during deposition of sapropel s1 the h1 cooling was particularly severe and is marked by a drop in sst of 4 5 c in comparison to pre h1 sst with temperatures 1 c cooler than during the lgm in contrast to high latitude and western mediterranean records which indicate both an abrupt onset and termination of the yd event the transition from the yd to the holocene was much more gradual in the em

distribution of intact and core gdgts in marine sediments abstract we conducted a survey of archaeal gdgt glycerol dibiphytanyl glycerol tetraether distributions in marine sediments deposited in a range of depositional settings the focus was comparison of two pools presumed to have distinct geobiological significance i e intact polar gdgts ip gdgts and core gdgts c gdgts the former pool has been suggested to be related to living communities of benthic archaea in marine sediments while the latter is commonly interpreted to consist of molecular fossils from past planktonic archaeal communities that inhabited the surface ocean understanding the link between these two pools is important for assessment of the validity of current molecular proxies for sedimentary archaeal biomass and past sea surface temperatures the relative distributions of gdgts in the two pools in a core at a ch4 rich site in the black sea provide evidence for in situ production of glycosidic ip gdgts and their subsequent degradation to corresponding c gdgts on timescales that are short in geological terms in addition we monitored the relationship between the ip gdgt and c gdgt pools in a sample set from various ocean basins with subseafloor depth from a few cm to 320 m and 0 to 4 myr in age notable differences between the two pools can be summarized as follows the gdgt with acyclic biphytanes gdgt 0 and its analogues with two and three cyclopentane moieties gdgt 2 and 3 are generally more abundant in the pool of ip gdgts while crenarchaeol tends to be more abundant in the c gdgt pool consequently the ring index is generally higher for the c gdgts while tex86 a molecular proxy ratio not considering the two major gdgts tends to be higher in the ip gdgt pool these differences in the proportion of individual gdgts in the two pools are probably due to in situ production of ip gdgts with distributions differing from those of c gdgts despite these differences we observed significant correlation of these two ratios between the two pools specifically in both pools tex86 is high in sediments from warm oceanic regimes and low in cold regimes we discuss these relationships and suggest that recycling of core gdgts by benthic archaea is an important mechanism linking both molecular pools

preparation of accurate geological and structural maps cross sections or block diagrams from colour slides using multi model photogrammetry abstract the multi model photogrammetric method is a new technique that allows field geologists to make accurate three dimensional models of their choice using standard colour slides taken with ordinary field cameras the method greatly expands the geological potential of photogrammetry beyond conventional methods based on vertical aerial photographs or satellite data a computerized stereoscopic instrument in which the commercial software is replaced by multi model software is used for interpretation the multi model technique links a series of stereoscopic images of the same target viewed at different scales or from different angles to form one composite three dimensional model and permits instantaneous image shifts to be performed during interpretation the method can be applied to numerous geological situations where accuracy is required but where access or overview is difficult or impossible a significant proportion of geological and structural analysis can thus be moved from the field to the laboratory examples of geological and structural applications include studies of tertiary basalts in west greenland and precambrian gneisses in south india the scale of these studies varies from 1 200 000 to 1 25

classification and dynamic simulation of the vertical density structure of lakes1 field data from two lakes of widely differing geometry and size are analyzed in terms of four nondimensional numbers which allow the principal mixing processes in each lake to be identified the numbers are based on basin geometry density stratification wind stress and rates of inflow and outflow the procedure highlights the differences in the dynamics of the two lakes and allows assessment of the validity of the assumption of one dimensionality the result is that both lakes were dominated by one dimensional but different processes the dynamics of the epilimnion of the smaller lake were dominated by stirring from surface wind and cooling whereas shear at the pycnocline was also significant in the larger lake in neither case did the effects of the earth s rotation inflow or outflow generate significant horizontal gradients a one dimensional numerical model dyresm was used to simulate the vertical temperature and salinity structures of both lakes over lengthy periods with good results the model is based on the parameterization of the important physical processes in a framework of horizontal layers of variable thickness and was applied in both lakes without alteration the interpretative power of the model is demonstrated by examination of the formation and erosion of a thermal inversion in the larger lake

lidar uav or compass clinometer accuracy coverage and the effects on structural models abstract light detection and ranging lidar and structure from motion sfm provide large amounts of digital data from which virtual outcrops can be created the accuracy of these surface reconstructions is critical for quantitative structural analysis assessment of lidar and sfm methodologies suggest that sfm results are comparable to high data density lidar on individual surfaces the effect of chosen acquisition technique on the full outcrop and the efficacy on its virtual form for quantitative structural analysis and prediction beyond single bedding surfaces however is less certain here we compare the accuracy of digital virtual outcrop analysis with traditional field data for structural measurements and along strike prediction of fold geometry from stackpole syncline in this case the sfm virtual outcrop derived from uav imagery yields better along strike predictions and a more reliable geological model in spite of lower accuracy surface reconstructions than lidar this outcome is attributed to greater coverage by uav and reliable reconstruction of a greater number of bedding planes than terrestrial lidar which suffers from the effects of occlusion irrespective of the chosen acquisition technique we find that workflows must incorporate careful survey planning data processing and quality checking of derived data if virtual outcrops are to be used for robust structural analysis and along strike prediction

coherent millennial scale patterns in u37k and tex86h temperature records during the penultimate interglacial to glacial cycle in the western mediterranean 1 the tex86h temperature proxy is a relatively new proxy based on crenarchaeotal lipids and has rarely been applied together with other temperature proxies in this study we applied the tex86h on a sediment core from the alboran sea western mediterranean core odp 977a covering the penultimate climate cycle that is from 244 to 130 ka and compared this with previously published sea surface temperatures derived from the u37k of alkenones of haptophyta and mg ca records of planktonic foraminifera the tex86h temperature record shows remarkably similar stadial interstadial patterns and abrupt temperature changes to those observed with the u37k palaeothermometer absolute tex86h temperature estimates are generally higher than those of u37k though this difference 3 c in 81 of the data points is mainly within the temperature calibration error for both proxies suggesting that crenarchaeota and haptophyta experienced similar temperature variations during occasional events 5 of the analyzed time span however the tex86h exhibits considerably higher absolute temperature estimates than the u37k comparison with mg ca records of planktonic foraminifera as well as other mediterranean tex86 and u37k records suggests that part of this divergence may be attributed to seasonal differences that is with tex86h reflecting mainly the warm summer season while u37k would show annual mean biases in the global calibration of both proxies or specific biases in the mediterranean are an alternative though less likely explanation despite differences between absolute tex86h and u37k temperatures the correlation between the two proxies r2 0 59 95 significance provides support for the occurrence of abrupt temperature variations in the western mediterranean during the penultimate interglacial to glacial cycle

a model of the vertical mixing in lake erie in summer a vertical one dimensional model is proposed to describe the vertical mixing in the central portion of the central basin of lake erie in summer the model explicitly describes the various mechanisms which operate in the well mixed upper and bottom layers the model predictions are in good agreement with the observed thermal structure over the entire water column during a month long simulation period the central basin of lake erie has been the subject of intensive investigation in recent years due in large part to concern over the depletion of dissolved oxygen in the hypolimnion during the stratified summer period burns and ross 1972 burns 1976 the central basin encompasses an area about 80 km wide and 200 km long but with a mean depth of only 18 m and a maximum depth of 26 m during summer the lake is strongly stratified and is characterized by an upper mixed layer uml a strong temperature gradient region and a near isothermal bottom mixed layer bml see

variations in gdgt distributions through the water column in the south east atlantic ocean abstract the tetraether index of 86 carbon atoms tex 86 temperature proxy is widely used in reconstructions of past sea surface temperature most current calibrations are based on surface sediment distributions of the glycerol dialkyl glycerol tetraether lipids gdgts that comprise tex 86 and assume that these gdgts are exported from the upper mixed layer however gdgt export from deeper waters could impact sedimentary gdgt distributions and therefore tex 86 paleothermometry here we examine gdgt distributions in suspended particulate matter spm and underlying sediments collected from the southeast atlantic ocean our results reveal different gdgt distributions specifically the ratio between gdgts bearing 2 vs 3 cyclopentyl moieties 2 3 ratios between surface subsurface 50 200 m and deep water 200 m spm which suggests the occurrence of in situ deep production that is not apparent when considering tex 86 the gdgt distributions in sediments match those of subsurface waters rather than surface waters suggesting that they have not been preferentially derived from the upper mixed layer this is consistent with gdgt abundances being highest in shallow subsurface spm 100 to 200 m it remains unclear what governs the different 2 3 ratios throughout the water column but it is likely related to a combination of temperature and thaumarchaeotal community structure

comparison of alkenone estimates with other paleotemperature proxies 1 to a certain degree all sea surface temperature sst proxies suffer from uncertainty due to signal preservation problems and to perturbations by other environmental variables however a multiproxy reconstruction is justified because most biases should in principle cancel out as they are specific to the biological groups and or to the analyzed chemical species such a multiproxy strategy has proven crucial for calibrating these proxies and is also useful in assessing downcore profiles until now there have been only a dozen deep sea cores where it is possible to compare directly alkenone based ssts with other paleotemperature records from this still limited data set the broad picture is of general agreement for the amplitude of changes at low and middle latitudes the few observed discrepancies suggest that alkenone based temperatures are more comparable to those based on mg ca ratios than those obtained through statistical analysis of the foraminiferal distribution more systematic differences are noted at higher latitudes where alkenones indicate warmer temperatures during the glacial period than transfer functions based on foraminifera or diatoms several reasons have been invoked to resolve the mismatch but more ground truthing work is needed before deciding which temperature changes are the most accurate

generation and unstable evolution of a density driven eastern poleward current the iberian poleward current 1 the generation and evolution of a density driven eastern poleward current is investigated using a high resolution primitive equation numerical model the simulations focus on the iberian poleward current ipc as a case study the flow is generated by a meridional upper ocean density gradient balanced by an eastward surface intensified flow that adjusts at the coastal margin the resulting current system has a baroclinic character with poleward flow at the surface layer and equatorward flow underneath a few weeks after initialization the sheared along slope flow generates several vorticity structures downstream of the main topographic features in the lee of the topography persistent anticyclones are observed and deep cyclogenesis is induced in relation to the meandering of the upper layer jet these structures evolve preferentially as cyclone anticyclone eddy pairs and after interaction some dipoles are ejected offslope within a period of a few months the initial meridional gradient evolves into a complex system of fronts eddies and slope flows the dynamics of flow topography interaction is analyzed a comparison with satellite imagery of the ipc is conducted and similarity in scales and patterns is noted

significance of brittle deformation in the footwall of the alpine fault new zealand smithy creek fault zone abstract the smithy creek fault represents a rare exposure of a brittle fault zone within australian plate rocks that constitute the footwall of the alpine fault zone in westland new zealand outcrop mapping and paleostress analysis of the smithy creek fault were conducted to characterize deformation and mineralization in the footwall of the nearby alpine fault and the timing of these processes relative to the modern tectonic regime while unfavorably oriented the dextral oblique smithy creek thrust has kinematics compatible with slip in the current stress regime and offsets a basement unconformity beneath holocene glaciofluvial sediments a greater than 100 m wide damage zone and more than 8 m wide extensively fractured fault core are consistent with total displacement on the kilometer scale based on our observations we propose that an asymmetric damage zone containing quartz carbonate chlorite epidote veins is focused in the footwall damage zone asymmetry likely resulted from the fact that the hanging wall was mostly deformed at greater depth than the footwall rather than resulting from material contrasts across the fault plane kinematic inversions on mineralized fractures within the damage zone suggest veins formed in the current stress regime from fluids comparable to those now circulating in the footwall the smithy creek fault zone is therefore a rare exhumed example of the modern footwall hydrothermal system and of a structure actively accommodating footwall deformation near the alpine fault zone two significantly less mature subvertical faults having narrow 20 cm or less damage zones and similar orientations to nearby strike slip segments of the alpine fault crosscut the mineralized zone at smithy creek we envisage that hydrothermal mineralization strengthened the fault core causing it to widen as later slip was partitioned into the now weaker surrounding damage zone with progressive alteration formation of favorably oriented faults became preferable to reactivation of the existing structure

geomagnetic moment variation and paleomagnetic excursions since 400 kyr bp a stacked record from sedimentary sequences of the portuguese margin abstract a paleomagnetic study was performed in clayey carbonate sedimentary sequences deposited during the last 400 kyr on the portuguese margin northeast atlantic ocean declination and inclination of the stable remanent magnetization present recurrent deviations from the mean geomagnetic field direction the normalized intensity documents a series of relative paleointensity rpi lows recognized in other reference records three directional anomalies occurring during rpi lows chronologically correspond to the laschamp excursion 42 kyr bp the blake event 115 122 kyr bp and the icelandic basin excursion 190 kyr bp a fourth directional anomaly recorded at 290 kyr bp during another rpi low defines the portuguese margin excursion four non excursional rpi lows are recorded at the ages of the jamaica pringle falls mamaku calabrian ridge 1 and levantine excursions the rpi record is characterized by a periodicity of 100 kyr paleointensity lows often coinciding with the end of interglacial stages this record sets the basis of the construction of an authigenic 10be 9be record from the same sedimentary sequences carcaillet et al this issue

constraining ecological and biological bias in planktonic foraminiferal mg ca and δ18occ a multispecies approach to proxy calibration testing 1 parallel stable isotope 18occ and mg ca measurements performed in three planktonic foraminifer species provide multiple perspectives on past temperature change and thus allow published calibrations for these geochemical proxies to be tested against each other the comparison of simultaneous temperature records as recorded by both the 18occ and mg ca signature of each species reveals very clearly the nonpassive character of foraminifera as proxy carriers and allows the systematic temperature response of 18occ and mg ca in different foraminifer species to be explored on the basis of their mg ca signatures neogloboquadrina pachyderma right globigerina bulloides and globigerinoides ruber white are each found to exhibit a specific and narrow range of temperature variability however the interspecies offsets in optimum temperature habitat that are suggested in this way are not expressed by similarly scaled 18occ offsets hence it is demonstrated that the temperature modes variations that are recorded by each species cannot be calibrated to mg ca and 18occ variations via a single pair of calibrations for all three species species specific 18occ and or mg ca temperature calibrations are required on the basis of the average 18occ and mg ca offsets observed between the three species it appears that many of the temperature calibrations that are currently proposed for both of these proxies are inconsistent the data presented here cannot provide species specific mg ca and 18occ temperature calibrations however they do provide a simple method for testing our calibrations in application and clearly indicate that further calibration work using paired mg ca and 18occ is required before the full potential of these proxies may be realized

biogeochemical controls on glycerol dialkyl glycerol tetraether lipid distributions in sediments characterized by diffusive methane flux the tex86 tetraether index of tetraethers consisting of 86 carbon atoms is a proxy for sea surface temperature sst based on the distribution of isoprenoidal glycerol dialkyl glycerol tetraether gdgt membrane lipids synthesized by marine pelagic thaumarchaeota one of the caveats of this proxy is the production of additional gdgts by sedimentary euryarchaeota involved in anaerobic oxidation of methane aom that occurs at deep sea methane seeps but is also widespread in many continental shelf settings here gdgt distributions are investigated through the sulfate methane transition zone smtz in aarhus bay denmark to examine the extent the tex86 proxy is compromised in such a continental shelf setting where aom is characterized by a diffusive rather than rapid advective methane flux both free extractable and non extractable lipid fractions were analyzed as it was expected that pelagic derived and sediment derived gdgts could become incorporated into the molecular and sedimentary matrix to a different extent the results show a large change of tex86 values mainly due to the relative high amounts of gdgt 2 produced by aom related archaea both in the free and non extractable lipid fractions this additional gdgt input renders calculation of ssts based on tex86 inappropriate at the smtz the aom related gdgt signature however did not persist into deeper sediments perhaps reflecting rapid remineralization of the gdgts at the smtz although the process of aom at aarhus bay might not be representative for all continental margin settings it illustrates that aom in a variety of settings not just cold seeps can influence sedimentary gdgt distributions

phase relationships between millennial scale events 64 000 24 000 years ago a core recovered on the iberian margin off southern portugal can be correlated with greenland ice cores using oxygen isotope variability in planktonic foraminifera which closely matches the ice core records of temperature over greenland our age model identifies the base of every interstadial between 64 000 and 24 000 years ago and uses the greenland ice core project grip timescale the oxygen isotope signal in benthic foraminifera on this grip based timescale is quite different from the planktonic record and resembles the temperature record over antarctica when this is synchronized with greenland using the record of methane in the atmospheric air in the polar ice cores we interpret the benthic record as indicating significant fluctuations in ice volume during millennial events and we suggest that antarctic temperature changed as a function of ice volume

entrainment by bottom currents in lake erie previous studies of the central basin of lake erie have indicated on the basis of lakewide budgets of heat and dissolved oxygen that the thickness of the hypolimnion and the interaction of the hypolimnion with the overlying fluicl are important factors governing the dissolved oxygen concentration in the near bottom water data collcctcd during an intensive field program in 1979 contain an example of an event during which both the thickness and temperature of the hypolimnion incrcasc due to an erosion of the thermocline from below this thickening of the hypolimnion requires two conditions first the thermocline region or mctalimnion must be thick enough so that the effects of the energetic surface mixing processes are confined to the upper portion of the thermocline and second the currents in the thin hypolimnion must be strong enough to entrain overlying metalimnion water down into the hypolimnion an analysis of the current meter data suggests the source of turbulent energy driving the mixing is shearing stresses at the bottom during the entrainment event the contribution to bottom dissolved oxygen supply is about 10 of the daily demand the depletion of oxygen in the hypolimnion of the central basin of lake erie during summer has been a subject of concern in recent years e g charlton 1980 the thickness of the hypolimnion and the interaction of the hypolimnion with the overlying fluid are thought to be important factors governing the dissolved oxygen concentration from lakewide budgets of heat and dissolved oxygen burns and ross 1972 and burns 1976 concluded that thermocline water is at times entrained down into the hypolimnion and that this mechanism constitutes an episodic resupply of dissolved oxygen to the lower layer these conclusions while convincing provide neither a detailed picture of such a mixing event nor an understanding of the forcing which drives it in 1979 an intensive field program was undertaken in the central basin one purpose of which was to examine the downward entrainment process our approach here is to

miocene to pliocene development of surface and subsurface temperatures in the benguela current system 1 the initiation of the benguela upwelling has been dated to the late miocene but estimates of its sea surface temperature evolution are not available this study presents data from ocean drilling program odp site 1085 recovered from the southern cape basin samples of the middle miocene to pliocene were analyzed for alkenone based u37k sstuk and glycerol dialkyl glycerol tetraether gdgt based tex86 temptex water temperature proxies in concordance with global cooling during the miocene sstuk and temptex exhibit a decline of about 8 c and 16 c respectively the temperature trends suggest an inflow of cold antarctic waters triggered by antarctic ice sheet expansion and intensification of southern hemisphere southeasterly winds a temperature offset between both proxies developed with the onset of upwelling which can be explained by differences in habitat alkenone producing phytoplankton live in the euphotic zone and record sea surface temperatures while gdgt producing thaumarchaeota are displaced to colder subsurface waters in upwelling influenced areas and record subsurface water temperatures we suggest that variations in subsurface water temperatures were driven by advection of cold antarctic waters and thermocline adjustments that were due to changes in north atlantic deep water formation a decline in surface temperatures an increased offset between temperature proxies and an increase in primary productivity suggest the establishment of the benguela upwelling at 10 ma during the messinian salinity crisis between 7 and 5 ma surface and subsurface temperature estimates became similar likely because of a strong reduction in atlantic overturning circulation while high total organic carbon contents suggest a biogenic bloom in the pliocene the offset between the temperature estimates and the cooling trend was reestablished

establishing relationships between structural data from close range terrestrial digital photogrammetry and measurement while drilling data abstract geologists mine planners geotechnical and mining engineers always strive for maximum information to get a better insight of the rock mass before interacting with it over the recent decades close range terrestrial digital photogrammetry crtdp has been increasingly used for data acquisition and to support the conventional methods for rock mass characterization it provides a safe time saving and contact free way to gather enough data to minimize user dependent biases however it requires an expensive camera fieldwork and some software to extract the information from images in addition it can over estimate the rock fracturing sometimes due to weathering of the rock face or poor blasting practices measurement while drilling mwd data include the responses of different drilling parameters to the variations in the rock mass mwd data are produced in large quantity as they come from every hole drilled these data correspond to the inside variations of rock rather than the surface ones counted in photogrammetry in this paper structural data are obtained from different bench faces of an open pit mine using a commercial software package shapemetrix3d by 3gsm these data are compared to the mwd data of the boreholes that were blasted to produce these bench faces to establish certain relationships between drilling parameters and rock mass structures half casts of the boreholes with mwd data were visible on the bench faces of the pre split wall that allowed a better correlation the results show abrupt changes in mwd parameters for open joints or cavities with some infilling material and overall increases or decreases in parameters for closely spaced bedding planes fractures or foliations the results are promising and suggest the method can be used to characterize the rock mass modify the charging of explosives in blasting operations and facilitate the geological modeling of the rock mass

rapid mapping and analysing rock mass discontinuities with 3d terrestrial laser scanning in the underground excavation abstract whilst laser scanning techniques have been shown to facilitate rapid identification and analysis of rock mass characteristics relatively little research has been conducted for 3d laser scanning in underground spaces in the present study a semi automatic laser scanning method has been presented for non contact discontinuity identification and rock mass characterisation in a western australian underground gold mine the accuracy of the 3d laser scanning technique was compared with traditional window mapping with a strong correlation being noted the average dip dip direction discrepancy between the two methods was found to be 1 5 16 and attributed to the ability of 3d laser scanning to collect significant quantities of data when compared to traditional methods potential sources of error together with the influence of the scale effect were discussed with an optimum scanning resolution of 7 5 mm at 5 m being noted to provide a combination of significantly reduced collection and processing time and high levels of accuracy overall the present study demonstrated the potential of 3d laser scanning techniques to replace traditional methods with increased efficiency and accuracy in underground mines

precision of the current methods to measure the alkenone proxy u 37 k and absolute alkenone abundance in sediments results of an interlaboratory comparison study measurements of the u 37 k index and the absolute abundance of alkenones in marine sediments are increasingly used in paleoceanographic research as proxies of past sea surface temperature and haptophyte mainly coccolith bearing species primary productivity respectively an important aspect of these studies is to be able to compare reliably data obtained by different laboratories from a wide variety of locations hence the intercomparability of data produced by the research community is essential here we report results from an anonymous interlaboratory comparison study involving 24 of the leading laboratories that carry out alkenone measurements worldwide the majority of laboratories produce data that are intercomparable within the considered confidence limits for the measurement of alkenone concentrations however there are systematic biases between laboratories which might be related to the techniques employed to quantify the components the maximum difference between any two laboratories for any two single measurements of u 37 k in sediments is estimated with a probability of 95 to be c in addition the overall within laboratory precision for the u 37 k temperature estimates is estimated to be c 95 probability similarly from the analyses of alkenone concentrations the interlaboratory reproducibility is estimated at 32 and the repeatability is estimated at 24 the former is compared to a theoretical estimate of reproducibility and found to be excessively high hence there is certainly scope and a demonstrable need to improve reproducibility and repeatability of u 37 k and especially alkenone quantification data across the community of scientists involved in alkenone research

sea surface temperature reconstructions over the last 70 kyr off portugal biomarker data and regional modeling this study aims at providing robust temperature reconstructions for a key oceanographic setting in the north atlantic and at understanding the nature of the temperature signal recorded by the two biomarkers u 37 k and tex86 considering season and depth of production to do so high resolution signals of u 37 k and tex86 are determined for the last 70kyr for core md95 2042 located off portugal signals of u 37 k and tex86 present a tight correlation demonstrating a dominant temperature effect u 37 k signals correspond well to the annual mean sea surface temperature sst whereas tex86h derived temperatures are 5 6 degrees c higher which is unrealistically warm for this area unsuitable tex86 global linear calibrations on the iberian margin may suggest a possible occurrence of archaeal communities with specific temperature response to assess the impact of different season or depth of production of the biomarkers on the recorded temperature in the sediment modeled temperature proxies tproxies are introduced in a regional oceanic modeling system and tested for different seasons annual summer winter and depths surface and 0 200m of production for three climate modes present day pd last glacial maximum lgm and heinrich stadials hs similar temperature amplitudes between climate modes are found at md95 2042 core site for observations for both biomarkers and for modeled annual surface production tproxy 5 5 7 degrees c for t pd lgm and 3 4 degrees c for t lgm hs therefore we propose a new tex86h regional calibration to reconstruct present and past annual mean ssts on the iberian margin

impact of freshwater release in the north atlantic under different climate conditions in an oagcm abstract the response of climate to freshwater input in the north atlantic na has raised a lot of concern about the issue of climate stability since the discovery of abrupt coolings during the last glacial period such coolings have usually been related to a weakening of the atlantic meridional overturning circulation amoc probably associated with massive iceberg surges or meltwater pulses additionally the recent increase in greenhouse gases in the atmosphere has also raised the possibility of a melting of the greenland ice sheet which may impact the future amoc and thereby the climate in this study the extent to which the mean climate influences the freshwater release linked to ice sheet melting in the na and the associated climatic response is explored for this purpose the simulations of several climatic states last interglacial last glacial maximum mid holocene preindustrial and future 2 co2 are considered and the climatic response to a freshwater input computed interactively acc

high sea surface temperatures in tropical warm pools during the pliocene sea surface temperatures in the tropical oceans were thought to have remained stable during a period of warmth about five million years ago reconstructions of the sea surface temperature from the caribbean and pacific suggest that tropical temperatures have in fact changed in concert with global mean temperatures over the past five million years

physiological impacts on alkenone paleothermometry we conducted isothermal 15 c batch culture experiments with the coccolithophorid emiliania huxleyi strain nepcc 55a to evaluate the extent to which nutrient and light stress contribute to variability in the alkenone unsaturation index u37k alkenone content and composition were constant throughout exponential growth in both experiments when nutrients nitrate and orthophosphate were replete stationary phase nutrient starved cells continued to produce alkenones amassing concentrations alk 3 times higher than those dividing exponentially 1 5 2 pg cell 1 and the u37k of excess alkenone dropped by 0 11 units in contrast 5 days of continuous darkness resulted in a 75 decrease in cellular alk and a significant u37k increase 0 11 units given an established 0 034 unit c response for exponentially growing cells of this strain the observed range of u37k variability at 15 c corresponds to an uncertainty of 3 2 c in predicted growth temperature this level of variability matches that of the global u37k annual mean sea surface temperature calibration for surface marine sediments begging the question what is the physiological condition of alkenone producing cells exported to marine sediments comparison of our laboratory results for a strain of e huxleyi isolated from the subarctic pacific ocean with depth profiles for alkenones in surface waters from two contrasting sites in the northeast pacific ocean suggests that the answer to this question depends on the ocean regime considered a possibility with significant bearing on how stratigraphic u37k records in marine sediments are to be interpreted paleoceanographically

numerical characterization for rock mass integrating gsi hoek brown system and synthetic rock mass method abstract rock mass characterization is a key issue to derive mechanical properties of jointed rock mass in this research the strength modulus and post peak behaviour of rock masses with varied joint orientations and confining stresses are characterized by integrating an empirical geological strength index gsi hoek brown system and a synthetic rock mass srm numerical method the srm model is a 3d distinct element model supporting explicit simulation of discontinuous joints and crack propagation in the rock mass the rock mass structure as denoted by a discrete fracture network is correlated to the gsi system through a quantitative factor of rock block size the strength and modulus are then derived from the gsi hoek brown system and used as references for a series of synthetic rock mass models a comparative study shows that when the predominant joints are steeply inclined in the rock mass subjected to axial loading the empirical gsi hoek brown system provides reliable mechanical properties when the joints are less favorable to shear sliding the gsi hoek brown system underestimates the rock mass strength cracking characteristics are also investigated in selected srm models where few cracks are simulated when inclined joints are inserted in the rock mass and low confining stresses are applied this research finally shows the method to construct continuum rock mass models using the numerical parameters of the srm models the numerical results suggest that the global failure zone is thin when the post peak is elasto brittle and the failure zone is much wider when the post peak is elasto plastic the involvement of the additional failed zones is responsible for the post peak ductility the paper is meant to explore new methods to derive high quality geo data for jointed rock mass

an experimental field study to test the stability of lipids used for the tex86 and uk 37 palaeothermometers abstract we report a one year field experiment to study sedimentary degradation of isoprenoid glycerol dialkyl glycerol tetraethers gdgts and long chain alkenones lipids used for the tex86 and u 37 k sea surface temperature sst proxies respectively homogenised surface sediments from the namibian upwelling region were set out on moorings in oxic oder bay and arkona bay baltic sea and sub oxic to anoxic gottland basin baltic sea waters and in oxic atlantic waters off cape blanc for one year to assess the influence of oxygen exposure on gdgts and alkenones no selective degradation effect on both tex86 and u 37 k proxies was evident under anoxic and sub oxic conditions under oxic conditions gdgt concentrations and the tex86 did not significantly change as well however selective degradation of alkenones occurred at all oxic sites resulting in a small but significant increase of the u 37 k index by up to 0 06 units corresponding to a temperature increase of up to 1 8 c our results demonstrate that selective alkenone degradation is a relatively fast process and complement earlier evidence for selective degradation of alkenones in the laboratory water column and sediments in contrast our results suggest that the tex86 is relatively resistant to selective oxic degradation at least on relatively short years time scales

atlantic core top calibration of the u37k index as a sea surface palaeotemperature indicator abstract a field calibration of the uk index with sea surface temperature is discussed through analysis of an extensive suite of surface sediments n 109 from the northeastern atlantic 2 s 75 n values of u 37 k are compared with sea surface temperatures for overlying waters measured at different depths and seasons to obtain a correlation suitable for palaeotemperature reconstructions the best fit is obtained using surface 0 m temperatures corresponding to caloric winter and autumn months however the annual average spring and summer surface temperature equations also have high correlation coefficients and are also appropriate for climatic studies the results further validate the general applicability of the u 37 k as a climatic proxy because the calibration equations are valid over a wide range of surface water temperatures 0 28 c for different algal populations and are representative of the average contribution of alkenones to sediments as found in sediment cores

evidence for differential degradation of alkenones under contrasting bottom water oxygen conditions implication for paleotemperature reconstruction abstract the successful reconstruction of sea surface temperatures using alkenone paleothermometry u37k has relied on the premise that there is no significant differential degradation of alkenones with different states of unsaturation during diagenetic processes to test this assumption we conducted a comparative study of contemporary sediments in oxic and anoxic bottom waters from the santa monica basin offshore california long chain alkenones were quantified and sea surface temperature were calculated using the calibrated u37k t relationship of prahl et al 1988 our results show that temperature record from the oxic sediments is higher by as much as 4 c compared to those from time equivalent anoxic sediments as a result of differential degradation of long chain unsaturated alkenones and bioturbation mixing in the oxic sediments the differential degradation of c37 3 vs c37 2 alone could account for up to 2 5 c difference between these two records this finding has significant implication in the interpretation of paleo sea surface temperature data using alkenone paleothermometry

paleoceanographic reconstructions from planktonic foraminifera off the iberian margin temperature salinity and heinrich events a quantitative analysis of planktonic foraminifera in a core from the iberian margin allows a reconstruction of the evolution of oceanographic parameters during the last glacial cycle with a resolution of 1000 years a principal component analysis performed on 19 species allows the identification of 11 intervals characterized by increased abundances of the subpolar species the youngest six of these intervals are correlated with the last 6 heinrich events hes the five cold events older than stage 4 are dated at 81 90 110 129 and 140 ka respectively paleotemperatures reconstructed using the modern analog technique indicate 4 c decreases during all even numbered isotopic stages and stage 3 during the hes temperature decreases reach 10 c and seawater 18o anomalies reach 1 temperature and salinity reconstructions indicate that the environment of the iberian margin has been under the combined influence of global factors such as the migration of the polar front and iceberg discharge and of regional factors such as the precipitation evaporation regime on both oceanic and continental area

feasibility of bubble plume destratification of central lake erie abstractthe central basin of lake erie has chronic hypoxia that is exacerbated by strong seasonal temperature stratification near the lake bed a computational study was conducted to determine the feasibility of mechanically mixing the water column by using a bubble plume system to reduce stratification thus facilitating vertical transport of oxygen the most efficient design delivered an air flow rate of 0 4 0 5 m3 s 1 through 40 50 non interacting plumes which only mix the watercolumn during the late summer hypoxic events the optimal efficiency was computed using a new metric which neglects changes in stratification resulting from meteorologically induced mixing relative to those from artificial mixing

distribution of intact and core tetraether lipids in water column profiles of suspended particulate matter off cape blanc nw africa in the reconstruction of sea surface temperature sst from sedimentary archives secondary sources lateral transport and selective preservation are considered to be mainly negligible in terms of influencing the primary signal this is also true for the archaeal glycerol dialkyl glycerol tetraethers gdgts that form the basis for the tex86 sst proxy our samples represent four years variability on a transect off cape blanc nw africa we studied the subsurface production vertical and lateral transport of intact polar lipids and core gdgts in the water column at high vertical resolution on the basis of suspended particulate matter spm samples from the photic zone the subsurface oxygen minimum zone omz nepheloid layers nl and the water column between these furthermore we compared the water column spm gdgt composition with that in underlying surface sediments this is the first study that reports tex86 values from the precursor intact polar lipids ipls associated with specific head groups ipl specific tex86 we show a clear deviation from the sea surface gdgt composition in the omz between 300 and 600 m since neither lateral transport nor selective degradation provides a satisfactory explanation for the observed tex derived temperature profiles with a bias towards higher temperatures for both core and ipl specific tex86 values we suggest that subsurface in situ production of archaea with a distinct relationship between lipid biosynthesis and temperature is the responsible mechanism however in the nw african upwelling system the gdgt contribution of the omz to the surface sediments does not seem to affect the sedimentary tex86 as it shows no bias and still reflects the signal of the surface waters between 0 and 60 m

an automated purification method for archaeal and bacterial tetraethers in soils and sediments isoprenoid and branched glycerol dialkyl glycerol tetraethers gdgts are archaeal and bacterial polar lipids increasingly used as environmental biomarkers and are studied in a wide range of settings lacustrine and oceanic sediments water column particulate organic matter soils peats sedimentary rocks and extracts from archaeal and bacterial cultures in paleoclimatology for example typical work on a sediment core of several tens of m consists of several hundreds to more than a thousand hplc ms high performance liquid chromatography mass spectrometry analyses the measurements therefore require purification steps from total lipid extracts we propose an automated procedure for obtaining the gdgt core lipid fraction we first evaluate both the yield and efficiency of the separation using different cartridges we then compare the results from automated and classical manual procedures for a soil and a marine sediment as well as for a sedimentary paleosequence

applying photogrammetry and semi automated joint mapping for rock mass characterization abstract rock engineering in blocky rock masses demands a sound knowledge about the joint network since it consists of planes of weakness than can lead to block instabilities however collecting data about the joint network is time consuming seldom very detailed and depends strongly on the experience of the mapping geologist additionally the characterization is reduced to the identification of the most relevant joint structures with their characteristic orientation and spacing other parameters like the in situ block shape and the block size distribution or the main orientation of the blocks are seldom collected or determined if at all with the emergence and increasing application of digital surface mapping techniques in rock mass characterization like shapemetrix3d or the discontinuity set extractor the time needed on site could be reduced and the degree of detail in the mapping of discontinuities is improved significantly the work presented in this study displays a continuous work flow from the data collection in the field to the determination of the block size and shape distribution generated by the intersection of joint sets for the process a marble quarry in styria austria was digitized using photogrammetry the joint sets are semi automatically identified with the discontinuity set extractor whose results are transferred into the software shapemetrix3d where the joint set spacing along with its standard deviations are determined these parameters are used to generate statistical representation of representative rock mass units using 3dec itasca consulting group inc and determine the block sizes block shapes and main orientation of the blocks in a row of simulations

a study of the alkenone tex86 and planktonic foraminifera in the benguela upwelling system implications for past sea surface temperature estimates suspended particulate matter from seawater and core top sediments were collected during 2003 meteor cruise m57 1 in january february from the continental margin off western south africa for analysis of alkenones glycerol dibiphytanyl glycerol tetraether gdgt lipids and planktonic foraminifera alkenone analysis of suspended particulates in seawater and core top sediments indicates that u37k temperatures were representative of annual mean sea surface temperature in contrast gdgt analysis suggests that tex86 temperatures are cold biased due to upward transports of gdgts produced below the mixed layer the analysis of plankton tow samples revealed that the 18o of globorotalia inflata in core top sediments could be biased toward lower temperatures due to subsurface calcification accordingly our study shows that each paleotemperature proxy may record different temperature signals in the benguela upwelling system emphasizing the general need to constrain potential biases in each proxy for better interpreting paleoclimate records

past circulation along the western iberian margin a time slice vision from the last glacial to the holocene abstract fifteen iberian margin sediment cores distributed between 43 12 n and 35 53 n have been used to reconstruct spatial and temporal sub surface circulation along the iberian margin since the last glacial period time slice maps of planktonic foraminiferal derived summer sea surface temperature sst and export productivity pexp were established for specific time intervals within the last 35 ky the holocene recent and last 8 ky younger dryas yd heinrich stadials hs 1 2a 2b 3 and the last glacial maximum lgm the sst during the holocene shows the same latitudinal gradient along the western iberian margin as present day with cold but productive areas that reflect the influence of coastal upwelling centers the lgm appears as a slightly less warm but more productive period relative to the holocene and present day conditions suggesting that sea level minima forced a westward displacement of the coastal upwelling centers possibly accompanied by a strengthening of northward winds during the yd a longitudinal thermal front is depicted at 10 w with cold polar waters offshore and warmer subtropical waters inshore suggesting that the subtropical paleo iberian poleward current more likely flowed at a more inshore location masking the local sst signal and amplitude of variation a substantial cooling and drop in productivity is observed during all hs in particular hs1 and hs3 reflecting the penetration of icebergs derived meltwater these most extreme southward extensions of very cold waters define a strong sst gradient that marks a possible paleo azores front higher production south of this front was likely fed by frontal nutrient advection

calibration of mg ca thermometry in planktonic foraminifera from a sediment trap time series 1 paired mg ca and 18o measurements on planktonic foraminiferal species g ruber white g ruber pink g sacculifer g conglobatus g aequilateralis o universa n dutertrei p obliquiloculata g inflata g truncatulinoides g hirsuta and g crassaformis from a 6 year sediment trap time series in the sargasso sea were used to define the sensitivity of foraminiferal mg ca to calcification temperature habitat depths and calcification temperatures were estimated from comparison of 18o of foraminifera with equilibrium calcite based on historical temperature and salinity data when considered together mg ca mmol mol of all species except two show a significant r 0 93 relationship with temperature t c of the form mg ca 0 38 0 02 exp 0 090 0 003 t equivalent to a 9 0 0 3 change in mg ca for a 1 c change in temperature small differences exist in calibrations between species and between different size fractions of the same species o universa and g aequilateralis have higher mg ca than other species and in general data can be best described with the same temperature sensitivity for all species and pre exponential constants in the sequence o universa g aequilateralis g bulloides g ruber g sacculifer other species this approach gives an accuracy of 1 2 c in the estimation of calcification temperature the 9 sensitivity to temperature is similar to published studies from culture and core top calibrations but differences exist from some literature values of pre exponential constants different cleaning methodologies and artefacts of core top dissolution are probably implicated and perhaps environmental factors yet understood planktonic foraminiferal mg ca temperature estimates can be used for reconstructing surface temperatures and mixed and thermocline temperatures using g ruber pink g ruber white g sacculifer n dutertrei p obliquiloculata etc the existence of a single mg thermometry equation is valuable for extinct species although use of species specific equations will where statistically significant provide more accurate evaluation of mg ca paleotemperature

terrestrial laser scanning in geology data acquisition processing and accuracy considerations terrestrial laser scanning or lidar is a recent innovation in spatial information data acquisition which allows geological outcrops to be digitally captured with unprecedented resolution and accuracy with point precisions and spacing of the order of a few centimetres an enhanced quantitative element can now be added to geological fieldwork and analysis opening up new lines of investigation at a variety of scales in all areas of field based geology integration with metric imagery allows 3d photorealistic models to be created for interpretation visualization and education however gaining meaningful results from lidar scans requires more than simply acquiring raw point data surveys require planning and typically a large amount of post processing time the contribution of this paper is to provide a more detailed insight into the technology data collection and utilization techniques than is currently available the paper focuses on the workflow for using lidar data from the choice of field area and survey planning to acquiring and processing data and finally extracting geologically useful data because manufacturer specifications for point precision are often optimistic when applied to real world outcrops the error sources associated with lidar data and the implications of them propagating through the processing chain are also discussed

a study of the tex86 paleothermometer in the water column and sediments of the santa barbara basin california 1 particulate organic matter collected during a 2 year period as part of an ongoing sediment trap study and a high resolution sediment record from 1850 to 1987 a d from the santa barbara basin were analyzed for tex86 a temperature proxy based on marine crenarchaeotal membrane lipids highest fluxes of crenarchaeotal lipids in the water column were found in may june 1996 and from october 1996 to january 1997 and in general showed a good correlation with mass fluxes tex86 reconstructed temperatures from the sediment trap series ranged from 8 to 11 c and were usually substantially lower than sea surface temperatures sst indicating that unlike in previous studies the tex86 corresponds to subsurface temperatures likely between 100 and 150 m tex86 temperature variations observed in trap samples were not coupled to changes in sst or deep water temperatures and only to some degree with crenarchaeotal lipid fluxes this suggests that a complex combination of different depth origins and seasonal growth periods of crenarchaeota contributed to the variations in tex86 signal during the annual cycle tex86 temperatures in the two sediment cores studied 8 13 c were also substantially lower than those of instrumental sst records 14 17 5 c confirming that tex86 records a subsurface temperature signal in the santa barbara basin this result highlights the importance of performing calibration studies using sediment traps and core tops before applying the tex86 temperature proxy in a given study area

paleoceanographic changes in the eastern equatorial pacific over the last 10 myr to examine the late neogene evolution of tropical pacific oceanography we determined multiple geochemical proxy records for temperature u 37 k and tex86h indices and primary productivity algal biomarkers and diol indices in sediments recovered at odp site 1241 in the east equatorial pacific eep spanning a record of the last 10 myr the tex86h temperatures are lower than those recorded by u 37 k indices exhibiting large fluctuations and suggesting strong warming during the mid pliocene warm period mpwp 4 5 3 2 ma and significantly colder temperature during the late miocene cooling period 7 5 ma and after the middle pliocene warm period mpwp such variations could reflect changes in the eep thermocline temperatures but we suggest that they instead reflect changes in the depth of export production of glycerol dialkyl glycerol tetraether lipids in response to changes in the upper ocean structure a combination of temperature records inferred to represent different and likely varying depths in the water column as well as algal biomarker records for export production and ecosystem structure suggest that both productivity and inference upwelling were reduced in the eep during warmer periods such as the mpwp and prior to 7 ma in contrast stronger upwelling conditions and associated increased productivity likely prevailed from 7 to 5 ma and for the past 3 myr both corresponding to globally cool intervals a further increase in eep productivity occurred at ca 1 8 ma coincident with the development of the e w pacific sst gradient these results confirm previous work that protracted el nino like conditions prevailed during warmer intervals of the pliocene before ultimately descending into the current climate state

comparison and implication of tex86 and u37k temperature records over the last 356kyr of odp site 1147 from the northern south china sea abstract proxy records from the south china sea scs have played an important role in understanding late quaternary scs environmental changes and the east asian monsoon eam variations but few long sea surface temperature sst records have been generated from the scs the recently established tex86 index provides an opportunity to generate long sst records especially for tropical oceans but the applicability and climatic interpretation of the tex86 index for the scs need further study we report and compare orbital scale resolution ca 5 3 kyr tex86 and u37k temperature records of the past 356 kyr for odp site 1147 from the northern scs both records display clear and similar glacial interglacial patterns the u37k sst fluctuated between 22 3 c and 28 3 c with a glacial interglacial difference of 4 5 c while the tex86 temperature fluctuated between 20 3 c and 25 4 c with a slightly smaller glacial interglacial difference of ca 4 c the tex86 temperature has been consistently lower than the u37k temperature over the past 356 kyr consistent with previous studies suggesting that the u37k index is a proxy for sst but the tex86 index is a proxy for subsurface temperature thus it is proposed that the temperature difference t between the u37k and tex86 records reflects mixed layer depth mld changes in the northern scs which fluctuated between 0 3 and 4 0 c with high values mostly during interglacials and lower values mostly during glacial stages mld changes in the northern scs are interpreted to be driven by eam changes with stronger winter monsoon resulting in a deeper mld and a smaller t thus the combination of u37k and tex86 records and their t can be used to reconstruct east asian winter monsoon variations as well as their influences on the hydrographic structure of the scs

alkenones and alkenes in surface waters and sediments of the southern ocean implications for paleotemperature estimation in polar regions abstract the concentration of c37 c39 long chain alkenones and alkenes were determined in surface water and surface sediment samples from the subpolar waters of the southern ocean distributions of these compounds were similar in both sample sets indicating little differential degradation between or within compound classes the relative amounts of the tri to tetra unsaturated c37 alkenones increased with increasing temperature for temperatures below 6 c similar to the di and tri unsaturated c37 alkenones the c37 di tri and tetra unsaturated methyl alkenones are used in paleotemperature calculations via the u37k and the u37k ratios in these datasets the relative abundances of the c37 2 and the c37 3 alkenones as a proportion of the total c37 alkenones were opposite and strongly related to temperature the latter with more scatter but the abundance of the c37 4 alkenone showed no relationship with temperature the original definition of u37k includes the abundance of 37 4 in both the numerator and denominator and thus it is perhaps not surprising that there is considerable scatter in the values obtained for u37k at low temperatures of the two we suggest that u37k is the better parameter for use in paleotemperature estimations even in cold locations u37k values in the sediments fall on virtually the same regression line obtained for the water column samples of sikes and volkman 1993 indicating that their calibration is suitable for use in southern ocean sediments the comparison of water column data with sedimentary temperature estimates suggests that the alkenone distributions are dominated by contributions from the summer when the biomass of emiliania huxleyi and presumably flux to the sediment is expected to be high

iberian margin sea surface temperature during mis 15 to 9 580 300 ka glacial suborbital variability versus interglacial stability 1 past sea surface water conditions of the western iberian margin were reconstructed based on biomarker analyses of a marine deep sea core md03 2699 from the estremadura spur north off lisbon providing new insights into orbital and suborbital scale climate variability between marine isotope stage mis 15 to mis 9 580 to 300 ka we use biomarker based proxy records such as the alkenone unsaturated index to estimate sea surface temperature sst the total alkenone concentration to reconstruct phytoplankton productivity and terrestrial biomarkers to evaluate the continental input the results extend the existing biomarker record namely the sst for the iberian margin back to the sixth climatic cycle 580 ka a general trend of stable interglacials contrasts with glacial periods and glacial inceptions which are marked by high frequency variability thus several short lived climatic coolings were identified by large sst decreases the occurrence of ice rafted detritus and high percentages of the tetraunsaturated alkenone c37 4 some of these events were extremely cold and similar in their general trends to the well known heinrich events of the last glaciation we identified eight heinrich type events between 580 and 300 ka the general deglaciation pattern detected between mis 15 and mis 9 is similar in their general trends to that characterizing the more recent climatic cycles i e marked by two coolings separated by a short warming episode which may reflect the southward northward and southward migration of the polar front

alkenone temperature anomalies in the brazil malvinas confluence area caused by lateral advection of suspended particulate material alkenone temperatures derived from suspended particulate organic material which was collected in austral summer 2001 from surface waters 5 m south of the brazil malvinas confluence deviate from measured temperatures by 4 to 7 c when uk 37 ratios are converted to temperature using the muller et al 1998 calibration and up to 3 c when using the calibration of conte et al 2006 in contrast alkenone temperatures determined from particulate material sampled north of the confluence reveal close correspondence to in situ temperatures or show slightly higher values we suggest that the southern samples are biased by suspended organic detritus originating from the cold subpolar waters of the northward flowing malvinas current whereas the northern samples carry an uk 37 signal of tropical subtropical origin transported southward with the brazil current on the basis of surface ocean transport pathways and velocities simulated with the large scale geostrophic lsg ocean general circulation model we identify areas of the world ocean where alkenone temperatures are potentially biased to higher or lower values due to long particle residence times and lateral advection by surface currents

aging of marine organic matter during cross shelf lateral transport in the benguela upwelling system revealed by compound specific radiocarbon dating organic matter accumulation and burial on the namibian shelf and upper slope are spatially heterogeneous and strongly controlled by lateral transport in subsurface nepheloid layers much of the material deposited in depo centers on the slope ultimately derives from the shelf supply of organic matter from the shelf involves selective transport of organic matter we studied these selective transport processes by analyzing the radiocarbon content of co occurring sediment fractions here we present radiocarbon data for total organic carbon as well as three tracers of surface ocean productivity phytoplankton derived alkenones membrane lipids of pelagic crenarchaeota crenarchaeol and calcareous microfossils of planktic foraminifera in core top and near surface sediment samples the samples were collected on the namibian margin along a shelf slope transect 85 to 1040 m at 24 s and from the upper slope depo center at 25 5 s in core top sediments alkenone ages gradually increased from modern to 3490 radiocarbon years with distance from shore and with water depth crenarchaeol while younger than alkenones also increased in age with distance offshore it was concluded that the observed ages were a consequence of cross shelf transport and associated aging of organic matter radiocarbon ages of preserved lipid biomarkers in sediments thus at least partially depend on the relative amount of laterally supplied pre aged material present in a sample highlighting the importance of nepheloid transport for the sedimentation of organic matter over the namibian margin

thermal simulation of a lake with winter ice cover1 a one dimensional thermodynamic model of a two component ice and snow cover is added to an existing one dimensional lake mixing model emphasis is placed on the thermodynamic coupling between the ice and mixing models absent in previous models the two dimensional effects of partial ice cover are incorporated into this one dimensional framework by using a minimum ice thickness the model is applied to lake laberge yukon territory and to babine lake british columbia for periods covering the formation and demise of full ice cover the results of the model are compared to snow and ice measurements in the first case and to water column data during the spring period in the second the comparisons are good implying that the ice and snow model is performing satisfactorily and emphasizing the importance of the coupling between the ice and the underlying water the successful simulation of the observed mixed layer under the ice driven by convective stirring caused by short wave heating below the temperature of maximum density is an example of the ability of the model to provide physical insight into processes occurring in lakes

mediterranean outflow strengthening during northern hemisphere coolings a salt source for the glacial atlantic abstract high resolution grain size and magnetic susceptibility records from the eastern gulf of cadiz site md99 2339 1170 m water depth reveal contourites formed by the mediterranean outflow mow during the last 47 kyr bp oscillations in the mow s intensity occurred in phase with greenland temperature variations with a stronger outflow during northern hemisphere coolings such as dansgaard oeschger stadials heinrich events and the younger dryas benthic 13c data implies the western mediterranean deep water as one of the main sources feeding the outflow current while differential changes in the properties of the mediterranean source and entrained north atlantic central water largely control the mow s strength detailed studies for heinrich events 1 4 and 5 show that the flow strength peaked only when subtropical surface waters prevailed in the eastern gulf of cadiz while incursions of icebergs and subpolar surface water were not favorable for the mow s intensification as the mow was strong when the atlantic s thermohaline circulation thc was weakened the heat and salt injected by the mow into the intermediate north atlantic waters might have preconditioned the thc to switch from the stadial to the interstadial mode

structural geometry of raplee ridge monocline and thrust fault imaged using inverse boundary element modeling and alsm data abstract we model the raplee ridge monocline in southwest utah where airborne laser swath mapping alsm topographic data define the geometry of exposed marker layers within this fold the spatial extent of five surfaces were mapped using the alsm data elevations were extracted from the topography and points on these surfaces were used to infer the underlying fault geometry and remote strain conditions first we compare elevations extracted from the alsm data to the publicly available national elevation dataset 10 m dem digital elevation model ned 10 and 30 m dem ned 30 while the spatial resolution of the ned datasets was too coarse to locate the surfaces accurately the elevations extracted at points spaced 50 m apart from each mapped surface yield similar values to the alsm data next we used a boundary element model bem to infer the geometry of the underlying fault and the remote strain tensor that is most consistent with the deformation recorded by strata exposed within the fold using a bayesian sampling method we assess the uncertainties within and covariation between the fault geometric parameters and remote strain tensor inferred using the model we apply these methods to the raplee ridge monocline and find that the resolution and precision of the alsm data are unnecessary for inferring the fault geometry and remote strain tensor using our approach however the alsm data were necessary for the mapping of the spatial distribution of surface outcrops our models considered two scenarios one in which fault geometry and remote strains were inferred using a single deformed stratum and another in which all mapped strata were used in the inversion modeled elevations match those observed to within a root mean squared error of 16 18 m and show little bias with position along the fold both single and multilayer inversions image a fault that is broadly constrained to be 4 5 14 km in down dip height 13 30 km in along strike width with a tip line 2 0 9 5 km below the surface at the time of deformation poisson s ratio was not well resolved by the inversion the idealized elastic model is oversimplified when considering the complicated layered nature of this fold however it provides a good fit to the observations thus comparable surface displacements may be produced with a variety of rheological models so independent constraints on factors such as the fault geometry may be required to ascertain the appropriate rheology of the fold

temperature dependent variation in the distribution of tetraether membrane lipids of marine crenarchaeota implications for tex86 paleothermometry 1 recently a new geochemical temperature proxy the tex86 was introduced this proxy is based on the number of cyclopentane moieties in the glycerol dialkyl glycerol tetraethers gdgts of the membrane lipids of marine crenarchaeota which changes as a response to temperature however until now only sediment data have been used to establish this proxy and experimental work is missing we performed mesocosm studies with marine crenarchaeota incubated at temperatures ranging from 5 to 35 c and salinities of 27 and 35 to test the validity of the tex86 proxy growth of marine crenarchaeota in these mesocosms was evident from the substantial increase in the concentration of marine crenarchaeotal membrane lipids with amounts up to 3400 ng l with increasing temperature an increase in the number of cyclopentane moieties in the crenarchaeotal membrane lipids was observed different salinities did not show any effect on the gdgt distribution the tex86 showed a significant linear correlation to incubation temperature tex86 0 015 t 0 10 r2 0 79 this equation has a similar slope to the correlation obtained from core tops but differs in the intersection tex86 0 015 t 0 28 r2 0 92 this difference is mainly determined by the smaller amount of the regioisomer of crenarchaeol in the incubation series compared to core top samples these incubation experiments indicates that water temperature is indeed the major controlling factor for the membrane distribution of marine crenarchaeota and confirms that the tex86 proxy depends on a physiological response to regulate membrane fluidity

evidence for massive discharges of icebergs into the north atlantic ocean during the last glacial period sediments in the north atlantic ocean contain a series of layers that are rich in ice rafted debris and unusually poor in foraminifera1 here we present evidence that the most recent six of these heinrich layers deposited between 14 000 and 70 000 years ago record marked decreases in sea surface temperature and salinity decreases in the flux of planktonic foraminifera to the sediments and short lived massive discharges of icebergs originating in eastern canada the path of the icebergs clearly marked by the presence of ice rafted detrital carbonate can be traced for more than 3 000 km a remarkable distance attesting to extreme cooling of surface waters and enormous amounts of drifting ice the cause of these extreme events is puzzling they may reflect repeated rapid advances of the laurentide ice sheet perhaps associated with reductions in air temperatures yet temperature records from greenland ice cores appear to exhibit only a weak corresponding signal moreover the 5 10 000 yr intervals between the events are inconsistent with milankovitch orbital periodicities raising the question of what the ultimate cause of the postulated cooling may have been

spatial and temporal offsets between proxy records in a sediment drift chronologies for late quaternary marine sediment records are usually based on radiocarbon ages of planktonic foraminifera signals carried by other sedimentary components measured in parallel can provide complementary paleoclimate information a key premise is that microfossils and other indicators within a given sediment horizon are of equal age we show here that haptophyte derived alkenones isolated from bermuda rise drift sediments are up to 7000 years older than coexisting planktonic foraminifera this temporal offset which is apparently due to lateral transport of alkenones on fine grained particles from the nova scotian margin markedly influences molecular estimates of sea surface temperatures more broadly the observation raises questions about both the temporal and the geographic fidelity of paleoenvironmental records encoded by readily transported components of sediments

surveying and modeling of rock discontinuities by terrestrial laser scanning and photogrammetry semi automatic approaches for linear outcrop inspection abstract rock face diagnosis is a monitoring operation that is used to optimize rock risk treatment works in terms of ensuring that safety requirements are met at the lowest cost diagnoses require measuring the location and orientation of rock discontinuities at the surface of the rock mass these measurements are then entered into a structural model that extrapolates the data collected at the surface to the inner part of the rock mass currently most surveys are empirical and are carried out manually using a compass clinometer in addition they tend to examine only the most highly fractured area of a rock face even though safety considerations demand an exhaustive study of the whole face these deficiencies can be overcome by using dense 3d measurement techniques such as terrestrial laser scanning and optical imaging to obtain a more complete 3d model and structural statement hence we have developed a semi automatic process that allows 3d models to be combined with the results of field surveys in order to provide more precise analyses of rock faces for example by classifying rock discontinuities into subsets according to their orientation further research is being carried out in order to combine 3d data and 2d digital images as a support for structural survey trials carried out in a limestone quarry in the french alps allowed us to compare data sets obtained using manual surveying methods the well known laser scanning method and the lower cost photogrammetric survey method

hydrological impact of heinrich events in the subtropical northeast atlantic reconstructing the impact of heinrich events outside the main belt of ice rafting is crucial to understanding the underlying causes of these abrupt climatic events a high resolution study of a marine sediment core from the iberian margin demonstrates that this midlatitude area was strongly affected both by cooling and advection of low salinity arctic water masses during the last three heinrich events these paleoclimatic time series reveal the internal complexity of each of the last three heinrich events and illustrate the value of parallel studies of the organic and inorganic fractions of the sediments

automatic identification and characterization of discontinuities in rock masses from 3d point clouds abstract the routine application of remote surveying techniques which can quickly acquire 3d digital data with high resolution in particular digital photogrammetry light detection and ranging lidar and unmanned aerial vehicle uav for rock mass characterization has rapidly grown over the past decade in this paper a new method for automatic identification and interpretation of rock mass discontinuities clustering of discontinuity sets and characterization of discontinuity orientation persistence and spacing using 3d point clouds is presented the proposed method is based on a four stage procedure consisting of 1 normal vector calculation using the iterative reweighted plane fitting irpf method 2 discontinuity sets clustering by fast search and find of density peaks cfsfdp algorithm and fisher s k value iterative calculation to eliminate noise points 3 discontinuity segmentation using density ratio based method and discontinuity plane fitting using the random sample consensus ransac algorithm 4 persistence and spacing calculation using the theory of analytic geometry the method is applied to two case studies i e rock slopes and compared with the results from previous studies and from manual survey it is concluded that the proposed method is reliable and yields a great accuracy for automatic identification of discontinuities in rock masses

a radiocarbon based assessment of the preservation characteristics of crenarchaeol and alkenones from continental margin sediments crenarchaeotal glycerol dibiphytanyl glycerol tetraether gdgt lipids and alkenones are two types of biomarkers derived from planktonic marine microorganisms which are used for reconstruction of sea surface temperature we determined the radiocarbon contents of the archaeal gdgt crenarchaeol and of alkenones isolated from continental margin sediments systematic differences were found between the two biomarkers with higher radiocarbon content in crenarchaeol than in the phytoplankton derived alkenones these differences can be explained by variable contributions of pre aged laterally advected material to the core sites crenarchaeol appears to be more efficiently degraded during transport in oxygen replete environments than alkenones whether this reflects the influence of chemical structure or mode of protection e g particle association is not known

alteration of alkenone unsaturation ratio with depth in the black sea potential roles of stereomutation and aerobic biodegradation suspended particulate matter and sediment samples collected from the black sea were investigated in order to i obtain additional information about the haptophytes present in this zone and ii try to determine the cause biological or chemical of the strong loss of the more unsaturated alkenones with depth previously observed and reflected in u37k after nabh4 reduction and silylation we detected mec38 4 and etc38 4 alkenones the presence of these two tetraunsaturated alkenones suggests that the source s of alkenones in the black sea could be one or more unknown strain s of emiliania huxleyi adapted to the low salinity the detection of an etc36 2 alkenone exhibiting the same unusual 15 20 double bond positions as the etc36 2 ethyl alkenone previously detected in holocene unit ii black sea sediments shows that the unidentified source of this alkenone is still present today in the black sea water column as previously observed the mec37 2 concentration declines slowly with depth while mec37 3 and mec37 4 decrease dramatically resulting in a strong increase in u37k and u37k values the detection of stereomutated alkenones and epoxyalkenones in some samples suggests that the strong increase in u37k with depth in the oxic zone could be due to a combination of selective aerobic bacterial degradation and stereomutation but with biodegradation apparently predominating however the presence of two populations of haptophytes exhibiting distinct responses toward growth temperature could also play a role in this strong increase in u37k

effects of long term oxic degradation on the u37k tex86 and bit organic proxies abstract one of the primary prerequisites for the application of organic proxies is that they should not be substantially affected by diagenesis however studies have shown that oxic degradation of biomarker lipids can affect their relative distribution we tested the diagenetic stability of the u 37 k and tex86 palaeothermometers upon long term oxygen exposure for this purpose we studied the distributions of alkenones and glycerol dialkyl glycerol tetraethers gdgts in different sections of turbidites at the madeira abyssal plain map that experienced different degrees of oxygen exposure sediments were deposited anoxically on the shelf and then transported by turbidity currents to the map which has oxic bottom water this resulted in partial degradation of the turbidite organic matter as a result of long term exposure to oxic bottom water concentrations of gdgts and alkenones were reduced by one to two orders of magnitude in the oxidized parts of the turbidites compared to the unoxidized parts indicating substantial degradation high resolution analysis of the pleistocene f turbidite showed that the u 37 k index of long chain alkenones increased only slightly 0 01 corresponding to u 37 k while for other pliocene miocene turbidites it either remained unchanged or decreased substantially up to 0 06 corresponding to 6 c previous observations showed that the bit index a proxy for the contribution of soil organic matter to total organic carbon was always substantially higher in the oxidized part in all the turbidites as a result of preferential degradation of marine derived gdgts this relative increase in soil derived gdgts affects tex86 as the isoprenoid gdgt distribution on the continent can be quite different from that in the marine environment our results indicate that the organic proxies are affected by long term oxic degradation to different extents this should be taken into account when applying these proxies in palaeoceanographic studies of sediments which have been exposed to prolonged oxic degradation

retreat velocity of the north atlantic polar front during the last deglaciation determined by 14 c accelerator mass spectrometry the glacial oscillations which dominate the quaternary global climate are closely related to changes in incoming solar radiation but the details of palaeoclimatic spectra suggest that other parameters usually referred to as feedback have significantly increased the climatic response to extraterrestrial forcing1 the last deglaciation appears to be one of the more characteristic examples of nonlinearity because its abruptness strongly contrasts with the smooth shape of the associated solar radiation maximum dated at 11 000 yr bp in addition the presence of the younger dryas cold event concomitant with the solar radiation maximum could be interpreted as a transitory phenomenon caused by the rapid meltwater influx linked to the first phase of the ice sheet s disintegration2 3 here using accelerator mass spectrometry we date precisely the movements of the polar front during the whole period of glacial retreat 15 000 8 000 yr bp our results show that the polar front has moved between 35 n and 55 n in 1 000 yr for the earliest retreat 12 500 12 000 bp and moved almost instantaneously that is 400 yr during the two abrupt climatic changes associated with the younger dry as cold event

3 d digital outcrop model for analysis of brittle deformation and lithological mapping lorette cave belgium abstract acquiring and building digital outcrop models dom becomes an essential approach in geosciences this study highlights the strong potential of structure from motion sfm photogrammetry for full 3d mapping of inaccessible outcrops combining pictures captured from field and from unmanned aerial vehicle embedded digital cameras we present a workflow for i acquiring and reconstructing a dom of a geometrically complex natural cave site using digital photogrammetry in a lowlight environment ii georeferencing the 3d model in underground environments iii identifying and characterizing the geometry of inaccessible geological structures and their tectonic kinematics e g faults joints sedimentary bedding planes slickenlines for structural geology purposes we illustrate our method by modelling a challenging case study the main chamber of the lorette cave rochefort cave laboratory belgium first we produced a high resolution highly realistic model made of 395 million points cloud this allowed to draw a detailed lithostratigraphic log of the exposed sedimentary pile alternating decimetric carbonate mudstones with minor centimetric clay rich layers secondly we extract the orientation of brittle structures from the cave dom which consist of joints calcite filled veins fault planes with observable slickenlines and their kinematic indicators calcitic veins consist of tension gashes structures two subsets of tension gashes are distinguished based on their orientation wnw striking with low vs subhorizontal dips and morphology planar vs en echelon sigmoidal veins two faults subsets are identified i a first one comprises south dipping fault planes with mean strike dip of n069 s42 and consist of bedding surface slip ii a second one which corresponds to neoformed north dipping faults mean strike dip n279 n60 we recognize and characterize tectonic markers on fault planes directly from the high resolution dom slickenlines and asymmetrical microscarps pointing to a reverse shearing movement for all investigated faults based on their geometrical relations and fault slip data paleostress reconstruction points to a nw se to nnw sse subhorizontal compressive regime this one is interpreted as the record of early phases of variscan tectonics during the fold to fault progression this research paper also highlights future possibilities for rapid semi automatic interpretation of such 3d dataset for structural geology purposes as well as advances in technology and perspectives in terms of risk assessments and mitigation

comparison of organic uk 37 texh86 ldi and faunal proxies foraminiferal assemblages for reconstruction of late quaternary sea surface temperature variability from offshore southeastern australia several proxies have been developed to reconstruct past sea surface temperature sst but different proxies may reflect temperatures of different seasons and each proxy is characterized by certain uncertainties therefore a multiproxy approach is preferred to precisely reconstruct sst here we reconstruct sst of the ocean offshore southeastern australia murray canyons area for the last 135 ka using three independent organic proxies texh86 based on glycerol dialkyl glycerol tetraethers gdgts uk 37 based on alkenones and ldi based on long chain diols in addition to foraminiferal faunal assemblages the organic proxy records show similar trends with the highest temperature 21 c for uk 37 and texh86 and 25 c for ldi during the last interglacial and lowest temperature 8 c for texh86 10 c for uk 37 and 12 c for ldi during the last glacial maximum however the differences in absolute sst estimates obtained by the organic proxies varied over time with differences of up to 9 c between ldi and texh86 the seasonal sst reconstructions based on the modern analogue of foraminiferal assemblages also show similar trends as the organic proxies with highest temperatures during the last interglacial 23 c for the warmest month sst 20 c for mean annual and 18 c for the coolest month and lowest temperature during the last glacial maximum 14 c for the warmest month 11 c for mean annual and 9 c for the coolest month down core comparison between the reconstructed ssts of the organic and inorganic proxies shows that ldi inferred temperatures compare well with the temperature of the warmest month texh86 with the temperature of the coolest month and uk 37 with mean annual temperature an increase in texh86 sst estimates relative to those of other proxies during deglaciations and interglacials suggests that either winter temperatures rapidly warmed possibly due to an invigoration of the leeuwin current over the core site or there was a change in the growth season of the thaumarchaeota the source organism of gdgts our study shows the benefits of a multiproxy approach in the interpretation of sst proxies leading to a more robust knowledge of past ocean temperature changes

sr ca u ca and δ18o records in recent massive corals from bermuda relationships with sea surface temperature abstract high resolution records of sr ca u ca ratios and 18o have been obtained in two recent colonies of massive corals diploria labyrinthiformis from bermuda the three geochemical proxies display regular seasonal variations and are well correlated with each other however some important discrepancies are observed between the two colonies the average seasonal variations of the three geochemical proxies are lower by almost 50 in one of the profiles where the seasonal oscillation also displays a strong asymmetry with narrower summer maxima different calculations are discussed for calibrating sr ca and 18o with sea surface temperatures sst we show that the method using only temperature minima and maxima is slightly more accurate and is also more reliable our results from bermuda corals confirm that the temperature dependency of sr ca u ca and 18o is species dependent as previously shown by others and that vital effects are clearly involved in the geochemical incorporation of trace elements in the coral skeleton finally a simple model involving seasonal variation of the growth rate and a kinetic fractionation related to growth rate is presented to explain the differences between the two bermuda colonies it is shown that these factors may prevent corals from recording the complete temperature seasonality and could be the cause for the discrepancies observed between profiles resulting in significant biases of the sst reconstructions