late eocene to early miocene ice sheet dynamics and the global carbon cycle paired benthic foraminiferal trace metal and stable isotope records have been constructed from equatorial pacific ocean drilling program site 1218 the records include the two largest abrupt 1 myr increases in the cenozoic benthic oxygen isotope record oi 1 in the earliest oligocene 34 ma and mi 1 in the earliest miocene 23 ma the paired mg ca and oxygen isotope records are used to calculate seawater 18o w calculated w suggests that a large antarctic ice sheet formed during oi 1 and subsequently fluctuated throughout the oligocene on both short 0 5 myr and long 2 3 myr timescales between about 50 and 100 of its maximum earliest oligocene size the magnitudes of these fluctuations are consistent with estimates of sea level derived from sequence stratigraphy the transient expansion of the antarctic ice sheet at mi 1 is marked in the benthic 18o record by two positive excursions between 23 7 and 22 9 ma each with a duration of 200 300 kyr bottom water temperatures decreased by 2 c over the 150 kyr immediately prior to both rapid 18o excursions however the onset of each of these phases of ice growth is synchronous within the resolution of the records with the onset of a 2 c warming over 150 kyr we suggest that the warming during these glacial expansions reflect increased greenhouse forcing prompted by a sudden decrease in global chemical weathering rates as antarctic basement silicate rocks became blanketed by an ice sheet this represents a negative feedback process that might have operated during major abrupt growth phases of the antarctic ice sheet

new constraints on atmospheric co2 concentration for the phanerozoic earth s atmospheric co2 concentration ca for the phanerozoic eon is estimated from proxies and geochemical carbon cycle models most estimates come with large sometimes unbounded uncertainty here we calculate tightly constrained estimates of ca using a universal equation for leaf gas exchange with key variables obtained directly from the carbon isotope composition and stomatal anatomy of fossil leaves our new estimates validated against ice cores and direct measurements of ca are less than 1000 ppm for most of the phanerozoic from the devonian to the present coincident with the appearance and global proliferation of forests uncertainties obtained from monte carlo simulations are typically less than for ca estimates from other approaches these results provide critical new empirical support for the emerging view that large 2000 3000 ppm long term swings in ca do not characterize the post devonian and that earth s long term climate sensitivity to ca is greater than originally thought key points a novel co2 proxy calculates past atmospheric co2 with improved certainty co2 is unlikely to have exceeded 1000 ppm for extended periods post devonian earth s long term climate sensitivity to co2 is greater than originally thought

marked decline in atmospheric carbon dioxide concentrations during the paleogene the relation between the partial pressure of atmospheric carbon dioxide pco2 and paleogene climate is poorly resolved we used stable carbon isotopic values of di unsaturated alkenones extracted from deep sea cores to reconstruct pco2 from the middle eocene to the late oligocene approximately 45 to 25 million years ago our results demonstrate that pco2 ranged between 1000 to 1500 parts per million by volume in the middle to late eocene then decreased in several steps during the oligocene and reached modern levels by the latest oligocene the fall in pco2 likely allowed for a critical expansion of ice sheets on antarctica and promoted conditions that forced the onset of terrestrial c4 photosynthesis

geology and u pb geochronology of archean basement and proterozoic cover in the priest river complex northwestern united states and their implications for cordilleran structure and precambrian continent reconstructions precambrian basement rocks exposed within tectonic windows in the north american cordillera help to define the precambrian crustal structure of western north america and possible reconstructions of the late proterozoic supercontinent rodinia new geologic mapping and u pb dating in the infrastructure of the priest river metamorphic complex northern idaho documents the first archean basement 2651 20 ma north of the snake river plain in the north american cordillera the archean rocks are exposed in the core of an antiform and mantled by a metaquartzite that may represent the nonconformity between basement and the overlying hauser lake gneiss which is correlated with the prichard formation of the belt supergroup a structurally higher sheet of augen gneiss interleaved with the hauser lake gneiss yields a u pb zircon crystallization age somewhat greater than 1577 ma the slivers of augen gneiss were tectonically interleaved with the surrounding hauser lake gneiss near the base of the spokane dome mylo

thresholds for cenozoic bipolar glaciation the long standing view of earth s cenozoic glacial history calls for the first continental scale glaciation of antarctica in the earliest oligocene epoch 33 6 million years ago1 followed by the onset of northern hemispheric glacial cycles in the late pliocene epoch about 31 million years later2 the pivotal early oligocene event is characterized by a rapid shift of 1 5 parts per thousand in deep sea benthic oxygen isotope values3 oi 1 within a few hundred thousand years4 reflecting a combination of terrestrial ice growth and deep sea cooling the apparent absence of contemporaneous cooling in deep sea mg ca records4 5 6 however has been argued to reflect the growth of more ice than can be accommodated on antarctica this combined with new evidence of continental cooling7 and ice rafted debris8 9 in the northern hemisphere during this period raises the possibility that oi 1 represents a precursory bipolar glaciation here we test this hypothesis using an isotope capable global climate ice sheet model that accommodates both the long term decline of cenozoic atmospheric co2 levels10 11 and the effects of orbital forcing12 we show that the co2 threshold below which glaciation occurs in the northern hemisphere 280 p p m v is much lower than that for antarctica 750 p p m v therefore the growth of ice sheets in the northern hemisphere immediately following antarctic glaciation would have required rapid co2 drawdown within the oi 1 timeframe to levels lower than those estimated by geochemical proxies10 11 and carbon cycle models13 14 instead of bipolar glaciation we find that oi 1 is best explained by antarctic glaciation alone combined with deep sea cooling of up to 4 c and antarctic ice that is less isotopically depleted 30 to 35 than previously suggested15 16 proxy co2 estimates remain above our model s northern hemispheric glaciation threshold of 280 p p m v until 25 myr ago but have been near or below that level ever since10 11 this implies that episodic northern hemispheric ice sheets have been possible some 20 million years earlier than currently assumed although still much later than oi 1 and could explain some of the variability in miocene sea level records

global change across the oligocene miocene transition high resolution stable isotope records from iodp site u1334 equatorial pacific ocean the oligocene miocene transition omt 23 ma is interpreted as a transient global cooling event associated with a large scale antarctic ice sheet expansion here we present a 2 23 myr long high resolution 3 kyr benthic foraminiferal oxygen and carbon isotope 18o and 13c record from integrated ocean drilling program site u1334 eastern equatorial pacific ocean covering the interval from 21 91 to 24 14 ma to date five other high resolution benthic foraminiferal stable isotope stratigraphies across this time interval have been published showing a 1 increase in benthic foraminiferal 18o across the omt however these records are still few and spatially limited and no clear understanding exists of the global versus local imprints we show that trends and the amplitudes of change are similar at site u1334 as in other high resolution stable isotope records suggesting that these represent global deep water signals we create a benthic foraminiferal stable isotope stack across the omt by combining site u1334 with records from odp sites 926 929 1090 1264 and 1218 to best approximate the global signal we find that isotopic gradients between sites indicate interbasinal and intrabasinal variabilities in deep water masses and in particular note an offset between the equatorial atlantic and the equatorial pacific suggesting that a distinct temperature gradient was present during the omt between these deep water masses at low latitudes a convergence in the 18o values between infaunal and epifaunal species occurs between 22 8 and 23 2 ma associated with the maximum 18o excursion at the omt suggesting climatic changes associated with the omt had an effect on interspecies offsets of benthic foraminifera our data indicate a maximum glacioeustatic sea level change of 50 m across the omt

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

assessing short and long time displacements in the venice coastland by synthetic aperture radar interferometric point target analysis 1 the venice lagoon in italy is a unique environment vulnerable to loss in surface elevation relative to the mean sea level we present detailed synthetic aperture radar sar interferometric analyses on persistent point targets for the historical center of venice the tourist area of sottomarina and the zennare farmland close to the southern lagoon edge the selected areas are characterized by different degrees of development and our analyses show the remarkable capability of sar interferometric point target analysis ipta to map land displacement rates in densely urbanized zones and to detect movement information on isolated structures with a mm year accuracy a detailed analysis of the time series from 1992 to 2000 provided by ipta shows that the vertical component of the measured displacements are the superposition of a short timescale generally seasonal movement on the order of 1 cm that is likely related to the fluctuation of environmental variables temperature piezometric head in the aquifer system underlying the lagoon sea lagoon water level and a long term ground deformation associated with building construction the geomorphology of the area and the human development of natural resources if venice is confirmed to be generally stable significant long term subsidence on the order of 4 mm year is detected at the sottomarina coastland the highest displacement rates of up to 8 10 mm year are recorded in the farmland bounding the lagoon margin where the movements are found to be highly site specific

late quaternary environmental evolution of the como urban area northern italy a multidisciplinary tool for risk management and urban planning abstract the historical center of como northern italy is prone to lake flooding and subsidence due to the presence of unconsolidated silty sediments with poor mechanical properties the sedimentary basin beneath the town contains over 180 m thickness of late quaternary lacustrine palustrine and alluvial deposits the landscape evolution and the present day environmental setting of the como area have been reconstructed based on i more than 250 core logs and related geotechnical tests ii detailed stratigraphic sedimentological paleobotanical and geotechnical analysis of several key boreholes iii multi year hydrogeological monitoring iv estimation of subsidence rates and v integration of geomorphology archeological findings and historical documents based on our environmental analysis we derived an integrated geological and geomorphological model of the latest pleistocene to holocene local landscape evolution this model was used to help design an engineering facility to mitigate flood hazards in the como urban area in 2012 we carried out investigations during a re evaluation of the design parameters for the flood mitigation project at the como lake shore the new campaign included seven boreholes many in situ and laboratory tests and four 14c dates we found an organic silty unit historical in age with bad mechanical properties that was critical in the design of the flood mitigation project we also obtained index properties for static and dynamic conditions necessary for robust engineering planning the results were used to update the project and better define future executive phases although the importance of acquiring independent experimental data is often overlooked they can significantly improve the reliability of engineered systems as demonstrated by the como town case history

surface deformation from persistent scatterers sar interferometry and fusion with leveling data a case study over the choushui river alluvial fan taiwan abstract the choushui river alluvial fan craf one of the most important agricultural areas in taiwan suffers severe subsidence caused by groundwater withdrawal we use 20 envisat images from 2006 to 2008 to derive vertical deformation over craf by persistent scatterer interferometry psi which effectively reduces errors affecting conventional dinsar techniques the pixel density over craf is 107 6 pixels km 2 compared to 0 19 points km 2 of the leveling benchmarks psi yields vertical displacements matching the leveling result to 0 6 cm year rms and provides a higher spatial resolution of subsidence than the latter we also develop a data fusion method that considers the high precision low point density leveling result as a smoothed correction to the psi result the combined field is more representative of overall deformation characteristics than the psi only or leveling only field and it is better suited for the assessment of the impact of subsidence over craf

geochemistry of the gneissic basement complex near valemount british columbia further evidence for a varied origin rare earth elements and other trace elements have been determined by activation analysis and x ray fluorescence for representative samples from each of the four blocks of basement gneisses near val

understanding the hydrogeology of the venice lagoon subsurface with airborne electromagnetics abstract the occurrence of alternating dry wet conditions in transitional environments such as wetlands deltas and lagoons usually challenges the use of traditional direct and geophysical surveys for comprehensive hydrogeologic investigations moreover significant mixing between continental fresh groundwater and marine salty surface waters generally takes place in these flat coastal areas airborne electromagnetics aem is a promising tool in this respect as it provides in a fast and cost effective manner large scale distribution of bulk electrical conductivities that can be used profitably to develop hydrogeologic models the results of a skytem aem survey in the venice lagoon italy show the capability of this technique to significantly improve the knowledge of the hydrogeologic setting of the lagoon and nearby coastland subsurface irrespective of the different features characterizing the area the environment consists of salt marshes mud flats shallows tidal channels islands together with reclaimed farmlands crossed by natural watercourses and drainage channel networks in particular the aem shows i the presence of fresh water with resistivity larger than 20 m underneath the central part of the lagoon at depths from 10 to 25 m below m s l ii the interface between different relevant stratigraphic units e g the clayey layer bounding the holocene pleistocene sedimentation and iii the occurrence of areas with possible submarine fresh groundwater discharge moreover the source and inland extent of the saltwater contamination in the shallow coastal aquifers along the southern margin of the lagoon are clearly revealed aem data were complemented with very high resolution seismic vhrs acquisitions the integrated analysis of the two data sets allows distinguishing between lithostratigraphic heterogeneity and variability of the subsurface fluids

climate pco2 and terrestrial carbon cycle linkages during late palaeozoic glacial interglacial cycles the late palaeozoic was marked by a series of glacial interglacial cycles geochemical and fossil data suggest a role for terrestrial vegetation carbon cycle feedbacks in the climate response to orbital forcing

spatial and temporal deformation characteristics of marine alluvial deposits due to land reclamation implications from insar observation and geotechnical estimate ground deformation of reclaimed land is a key issue for reclamation design construction and sustainable development in coastal areas as this consolidation process of the underlying compressible marine sediment sequences over very long time periods could lead to damage of both ground constructions and underground facilities in this case study we have investigated the spatial and temporal characteristics of residual reclamation settlement of chek lap kok airport hong kong one of the largest land reclamation projects worldwide a total of 25 time series envisat asar datasets acquired between december 2003 and october 2008 were used to retrieve settlement rates and deformation history at high resolution and accuracy by means of advanced synthetic aperture radar interferometry insar the insar derived results show a fairly homogenous and stable pattern in the sectors of the airport site corresponding to the two original islands of chek lap kok and lam chau in contrast a relatively high spatial settlement variability ranging from moderate 3 7 mm yr to strong 10 mm yr settlement rates was discovered within the majority of the reclaimed portion of the airport a joint analysis of insar observations and geological materials indicates that the variability of the recorded residual settlement was highly correlated with the variations of thickness and pre consolidation state of alluvial deposits below the reclamation a quantitative comparison analysis also has been carried out between time series insar observations and theoretical estimates of residual settlement modelled by geotechnical investigations the results imply that a primary consolidation process in alluvial deposits below the reclamation might be delayed with respect to the predicted results and may still have been occurring in most reclaimed areas during the investigation period 2003 2008 the time to complete it could stretch to decades depending on hydraulic conductivity and natural drainage conditions copyright 2010 john wiley sons ltd

quantifying groundwater exploitation induced subsidence in the rafsanjan plain southeastern iran using insar time series and in situ measurements abstract decades of groundwater overexploitation for agriculture and industrial development have resulted in substantial land subsidence in the rafsanjan plain of southeastern iran this work presents the results of an insar time series analysis obtained by the exploitation of envisat alos and sentinel 1 s1 sar data archives between june 2004 and may 2016 to investigate land subsidence in the plain the insar analysis revealed an area of approximately 1000 km 2 within the study area showing subsidence of 5 cm year and locally exceeding 30 cm yr in the last decade this area of significant subsidence is limited in its spatial extent to the agricultural land and is partly influenced by quaternary faults the temporal and areal relationships of subsidence and groundwater level data suggest that a significant part of the observed subsidence in the rafsanjan region is caused by intense groundwater extraction that has led to widespread compaction within the upper parts of the up to 300 m thick unconsolidated sediments causing irreversible and inelastic deformation of the aquifer the average volume storage loss of the aquifer system due to overexploitation is estimated to have been approximately 300 million cubic metre mcm yr over the last decade

early jurassic late pliensbachian co2 concentrations based on stomatal analysis of fossil conifer leaves from eastern australia the stomatal index a measure of stomatal density of an extinct australian early jurassic araucariacean conifer species allocladus helgei jansson is used to reconstruct the atmospheric carbon dioxide concentration pco 2 in the early jurassic the fossil leaves are preserved in a single bed palynologically dated to late pliensbachian similar to 185 183 mya atmospheric pco 2 is estimated from the ratios between the stomatal index of a helgei and the stomatal indices of three modern analogs nearest living equivalent plants co2 concentration in the range of similar to 750 975 ppm was calibrated from the fossil material with a best estimated mean of similar to 900 ppm the new average pco 2 determined for the late pliensbachian is thus similar to although similar to 10 lower than previously inferred minimum concentrations of similar to 1000 based on data from the northern hemisphere but may help constrain pco 2 during this period our results are the first pco 2 estimates produced using jurassic leaves from the southern hemisphere and show that i paleo atmospheric pco 2 estimates are consistent at a global scale though more investigations of southern hemisphere material are required and ii the stomatal proxy method can now be used without the context of relative change in pco 2 when applying the correct methodology c 2014 the authors published by elsevier b v on behalf of international association for gondwana research less

tectonic denudation of the shuswap metamorphic terrane of southeastern british columbia large scale over thrusting and regional extension are both known to have been operative within the shuswap metamorphic terrane of the southern omineca belt the monashee core complex of the northern shuswap terrane is interpreted to be a crustal scale duplex that was developed during late mesozoic shortening and thickening of the crust uplift of the monashee complex caused by basement duplexing is estimated to have been in excess of 25 km late cretaceous overthrusting of high grade metamorphic and related plutonic rocks during later stages of uplift and basement duplexing led to weakening of the crust and to gravitationally driven extension of a regional crustal welt shuswap culmination denudation and spreading of this uplifted metamorphic terrane are attributed to displacements across listric normal shear zones and faults localized along the outward dipping flanks of the shuswap culmination total extension across the shuswap culmination at the northern end of the monashee complex is estimated to be no greater than 30 this model of denudation and gravity induced spreading is extrapolated southward into the valhalla and okanagan regions where extension may be far more significant

paleobotanical evidence for near present day levels of atmospheric co2 during part of the tertiary understanding the link between the greenhouse gas carbon dioxide co 2 and earth9s temperature underpins much of paleoclimatology and our predictions of future global warming here we use the inverse relationship between leaf stomatal indices and the partial pressure of co 2 in modern ginkgo biloba and metasequoia glyptostroboides to develop a co 2 reconstruction based on fossil ginkgo and metasequoia cuticles for the middle paleocene to early eocene and middle miocene our reconstruction indicates that co 2 remained between 300 and 450 parts per million by volume for these intervals with the exception of a single high estimate near the paleocene eocene boundary these results suggest that factors in addition to co 2 are required to explain these past intervals of global warmth

a small baseline approach for investigating deformations on full resolution differential sar interferograms this paper presents a differential synthetic aperture radar sar interferometry difsar approach for investigating deformation phenomena on full resolution difsar interferograms in particular our algorithm extends the capability of the small baseline subset sbas technique that relies on small baseline difsar interferograms only and is mainly focused on investigating large scale deformations with spatial resolutions of about 100 spl times 100 m the proposed technique is implemented by using two different sets of data generated at low multilook data and full single look data spatial resolution respectively the former is used to identify and estimate via the conventional sbas technique large spatial scale deformation patterns topographic errors in the available digital elevation model and possible atmospheric phase artifacts the latter allows us to detect on the full resolution residual phase components structures highly coherent over time buildings rocks lava structures etc as well as their height and displacements in particular the estimation of the temporal evolution of these local deformations is easily implemented by applying the singular value decomposition technique the proposed algorithm has been tested with data acquired by the european remote sensing satellites relative to the campania area italy and validated by using geodetic measurements

stomatal proxy record of co2 concentrations from the last termination suggests an important role for co2 at climate change transitions a new stomatal proxy based record of co2 concentrations co2 based on betula nana dwarf birch leaves from the hasseldala port sedimentary sequence in south eastern sweden is presented the record is of high chronological resolution and spans most of greenland interstadial 1 gi 1a to 1c allerod pollen zone greenland stadial 1 gs 1 younger dryas pollen zone and the very beginning of the holocene preboreal pollen zone the record clearly demonstrates that i co2 were significantly higher than usually reported for the last termination and ii the overall pattern of co2 evolution through the studied time period is fairly dynamic with significant abrupt fluctuations in co2 when the climate moved from interstadial to stadial state and vice versa a new loss on ignition chemical record used here as a proxy for temperature lends independent support to the hasseldala port co2 record the large amplitude fluctuations around the climate change transitions may indicate unstable climates and that tippingpoint situations were involved in last termination climate evolution the scenario presented here is in contrast to co2 records reconstructed from air bubbles trapped in ice which indicate lower concentrations and a gradual linear increase of co2 through time the prevalent explanation for the main climate forcer during the last termination being ocean circulation patterns needs to re examined and a larger role for atmospheric co2 considered

comment on recent subsidence of the venice lagoon from continuous gps and interferometric synthetic aperture radar by y bock s wdowinski a ferretti f novali and a fumagalli

model test of soil deformation response to draining recharging conditions based on dfos abstract intense groundwater exploitation and seasonal fluctuations of water level in phreatic aquifer cause land subsidence disasters to better understand the land subsidence mechanism caused by groundwater withdrawal a small scale sand clay interbedded model box was built to carry out consolidation and rebound tests during two drainage recharge cycles distributed fiber optical sensing dfos technologies were introduced for coupled monitoring of soil strain and water content to analyze response characteristics of each layer to water level changes the results indicate that soil layers were compressed during drainage and rebound during recharge with clay layer deformation more obvious than sand layer deformation deformation of the sand layer was synchronous with water content changes while that of the clay layer lagged behind water content changes due to its lower permeability coefficient the segmented compression clay layer curve shows that the water content rapidly decreased when it was lower than the liquid limit while the clay layer compression rate obviously accelerated during drainage when the water content was higher than that of the liquid limit during recharge the rebound rate significantly increased under the condition of repeated drainage and recharge the soil microstructure changed with decreasing porosity and permeability coefficient leading to a longer consolidation time with increasing cycling times the soil gradually tended toward elastic deformation the observations propose a novel technology dfos technology for monitoring land subsidence caused by seasonal water level fluctuations and dewatering projects the test results are of great significance to investigate land subsidence mechanisms and evaluate soil layer compression potential

paleoclimatic and paleoenvironmental records of the oligocene miocene transition central jylland denmark a multidisciplinary study of the oligocene miocene o m transition was carried in two boreholes harre 1 and horn 1 from the danish land area in order to improve the understanding of the paleodimatological and environmental changes across the mi 1 the earliest miocene cooling event dinoflagellate cyst dinocyst biostratigraphy supported by re evaluation of the foraminiferid biostratigraphy a new set of magnetic data and stable carbon isotope delta c 13 records were applied to improve the age model for the studied succession as well as the positioning of the o m boundary these data further enabled a correlation of the two investigated profiles with the well established stratigraphical framework for the danish area the bit index an organic proxy indicating the relative input of soil derived organic matter dinocyst assemblages and palynofacies have been applied for establishing the paleoenvironmental changes across the oligocene miocene o m boundary our data indicate a shallowing upward trend in the latest oligocene resulting in the establishment of a very restricted marine setting in the earliest miocene our study confirms that the o m boundary is located at a sequence boundary the local sequence boundary b sb b and corresponds to an increase in terrestrial organic matter input a mean air temperature record based on the mbt cbt proxy reveals an similar to 2 degrees c drop in temperature at the o m and the sequence boundary our findings confirm previous suggestions that this sequence boundary is a result of the glacio eustatic sea level fall related with the mi 1 cooling event the unconformity at the sequence boundary probably correlates with the coldest part of mi 1 and thus no deposits from this period have been preserved this suggests that the temperature drop might have been greater than 2 degrees c

recent subsidence of the venice lagoon from continuous gps and interferometric synthetic aperture radar 1 coastal regions are increasingly affected by larger storms and rising sea level predicted by global warming models aggravating the situation in the city of venice where tidal induced seasonal flooding coupled with natural and anthropogenic subsidence have been perennial problems in light of accelerated efforts to protect venice from the rise in sea level we assess land subsidence in the venice lagoon over the last decade through a combined analysis of gps position time series from 2001 55 to 2011 00 for four stations installed by the magistrato alle acque di venezia and thousands of observations of insar permanent scatterers using radarsat 1 images from 2003 3 to 2007 85 we determine that the northern lagoon subsides at a rate of 2 3 mm yr whereas the southern lagoon subsides at 3 4 mm yr the city of venice continues to subside at a rate of 1 2 mm yr in contrast to geodetic studies in the last decade of the 20th century suggesting that subsidence has been stabilized the gps results indicate a general eastward tilt in subsidence and that the natural subsidence rate related to the retreat of the adriatic plate subducting beneath the apennines is at least 0 4 0 6 mm yr our combined gps and insar analysis demonstrates high spatial resolution in the vertical direction with a precision of 0 1 0 2 mm yr with respect to a global reference frame continued efforts to secure the city of venice from flooding must also take into account the significant local and regional subsidence rates as well as the expected rise in sea level

enhanced paleoproductivity across the oligocene miocene boundary as evidenced by benthic foraminiferal accumulation rates abstract the oligocene to miocene boundary 23 ma marks one of the major cenozoic cooling steps a corresponding but slightly lagging 13 c maximum in benthic foraminifer calcite of globally distributed sediment cores has been attributed to increased organic matter burial either on land or in the oceans to test this idea we reconstruct the organic carbon flux to the sea floor at three atlantic ocean drilling program odp sites using benthic foraminiferal accumulation rates bfar and compare them with the stable isotope records our data show that the 18 o and 13 c maximum that characterizes the oligocene miocene boundary is accompanied by a pronounced maximum in bfar derived paleoproductivity at two of the sites at tropical atlantic site 926 the paleoproductivity increase at the oligocene miocene boundary is smaller than at the higher latitude sites but high resolution sampling of a 2 million year interval 22 24 ma reveals that on eccentricity time scales productivity and stable isotope records are significantly correlated the productivity records are in phase with the 18 o and 13 c records at the short term 125 ky component of eccentricity at the long term eccentricity period 400 ky productivity is in phase with 18 o but leads the 13 c record by an amount that is consistent with published phase lags between the 18 o and 13 c records these results imply that there was enhanced flux of organic matter to the ocean floor during the o m climate transition and support that marine primary productivity may have played a role in the carbon cycle and atmospheric co 2 draw down at this time

improving the ginkgo co2 barometer implications for the early cenozoic atmosphere abstract stomatal properties of fossil ginkgo have been used widely to infer the atmospheric concentration of co2 in the geological past paleo pco2 many of these estimates of paleo pco2 have relied on the inverse correlation between pco2 and stomatal index si the proportion of epidermal cells that are stomata observed in recent ginkgo biloba and therefore depend on the accuracy of this relationship the si p co2 relationship in g biloba has not been well documented however here we present new measurements of si for leaves of g biloba that grew under pco2 from 290 to 430 ppm we prepared and imaged all specimens using a consistent procedure and photo documented each count as in prior studies we found a significant inverse relationship between si and pco2 however the relationship is more linear has a shallower slope and a lower correlation coefficient than previously reported we examined leaves of g biloba grown under pco2 of 1500 ppm but found they had highly variable si and a large proportion of malformed stomata we also measured stomatal dimensions stomatal density and the carbon isotope composition of g biloba leaves in order to test a mechanistic model for inferring pco2 this model overestimated observed pco2 performing less well than the si method between 290 and 430 ppm we used our revised si pco2 response curve and new observations of selected fossils to estimate late cretaceous and cenozoic pco2 from fossil ginkgo adiantoides all but one of the new estimates is below 800 ppm and together they show little long term change in pco2 or relation to global temperature the low paleogene pco2 levels indicated by the ginkgo si proxy are not consistent with the high pco2 inferred by some climate and carbon cycle models we cannot currently resolve the discrepancy but greater agreement between proxy data and models may come from a better understanding of the stomatal response of g biloba to elevated pco2 better counts and measurements of fossil ginkgo or models that can simulate greenhouse climates at lower pco2

evolution of the early antarctic ice ages understanding the stability of the early antarctic ice cap in the geological past is of societal interest because present day atmospheric co2 concentrations have reached values comparable to those estimated for the oligocene and the early miocene epochs here we analyze a new high resolution deep sea oxygen isotope 18o record from the south atlantic ocean spanning an interval between 30 1 my and 17 1 my ago the record displays major oscillations in deep sea temperature and antarctic ice volume in response to the 110 ky eccentricity modulation of precession conservative minimum ice volume estimates show that waxing and waning of at least 85 to 110 of the volume of the present east antarctic ice sheet is required to explain many of the 110 ky cycles antarctic ice sheets were typically largest during repeated glacial cycles of the mid oligocene 28 0 my to 26 3 my ago and across the oligocene miocene transition 23 0 my ago however the high amplitude glacial interglacial cycles of the mid oligocene are highly symmetrical indicating a more direct response to eccentricity modulation of precession than their early miocene counterparts which are distinctly asymmetrical indicative of prolonged ice buildup and delayed but rapid glacial terminations we hypothesize that the long term transition to a warmer climate state with sawtooth shaped glacial cycles in the early miocene was brought about by subsidence and glacial erosion in west antarctica during the late oligocene and or a change in the variability of atmospheric co2 levels on astronomical time scales that is not yet captured in existing proxy reconstructions

climate response to orbital forcing across the oligocene miocene boundary spectral analyses of an uninterrupted 5 5 million year my long chronology of late oligocene early miocene climate and ocean carbon chemistry from two deep sea cores recovered in the western equatorial atlantic reveal variance concentrated at all milankovitch frequencies exceptional spectral power in climate is recorded at the 406 thousand year ky period eccentricity band over a 3 4 million year period 20 to 23 4 my ago ma as well as in the 125 and 95 ky bands over a 1 3 million year period 21 7 to 23 0 ma of suspected low greenhouse gas levels moreover a major transient glaciation at the epoch boundary approximately 23 ma mi 1 corresponds with a rare orbital congruence involving obliquity and eccentricity the anomaly which consists of low amplitude variance in obliquity a node and a minimum in eccentricity results in an extended period approximately 200 ky of low seasonality orbits favorable to ice sheet expansion on antarctica

the enigma of oligocene climate and global surface temperature evolution falling atmospheric co2 levels led to cooling through the eocene and the expansion of antarctic ice sheets close to their modern size near the beginning of the oligocene a period of poorly documented climate here we present a record of climate evolution across the entire oligocene 33 9 to 23 0 ma based on tex86 sea surface temperature sst estimates from southwestern atlantic deep sea drilling project site 516 paleolatitude 36 s and western equatorial atlantic ocean drilling project site 929 paleolatitude 0 combined with a compilation of existing sst records and climate modeling in this relatively low co2 oligocene world 300 to 700 ppm warm climates similar to those of the late eocene continued with only brief interruptions while the antarctic ice sheet waxed and waned ssts are spatially heterogenous but generally support late oligocene warming coincident with declining atmospheric co2 this oligocene warmth especially at high latitudes belies a simple relationship between climate and atmospheric co2 and or ocean gateways and is only partially explained by current climate models although the dominant climate drivers of this enigmatic oligocene world remain unclear our results help fill a gap in understanding past cenozoic climates and the way long term climate sensitivity responded to varying background climate states

tectonic interpretation of west verging folds in the selkirk allochthon of the southern canadian cordillera the selkirk allochthon a composite tectonic slice composed of north american paleocontinental margin deposits and more distal possibly marginal basin suspect terrane was displaced eastward toward the craton in the late jurassic and late cretaceous the carnes nappe a major west verging recumbent anticline within the selkirk allochthon is considered the southern continuation of scrip nappe which in the monashee mountains has an inverted limb length of 50 km the west verging nappe and associated structures are interpreted as having originated in the early to middle jurassic during accretion of western allochthonous terranes and prior to eastward displacement of the selkirk allochthon the reversal from westward vergence away from the north american craton to eastward vergence is considered as marking a fundamental change in the evolution of the orogenic belt and may reflect a transition from underthrusting of western allochthonous terranes on blind shear zones to east directed breakthrough thrusts

reply to comment by p teatini et al on recent subsidence of the venice lagoon from continuous gps and interferometric synthetic aperture radar 1 unlike most published scientific comments the comment submitted by p teatini l tosi and t strozzi on bock et al 2012 does not dispute the scientific merits of our study but rather reinforces its approach and main results regarding venice subsidence their main points appear to be that our study 1 did not cite the two last papers that they published tosi et al 2010 teatini et al 2012a 2 received considerable attention worldwide for a rather small level of subsidence 3 used a methodology that is not original 4 misrepresented some of their earlier work and 5 published uncertainties that were too optimistic

precambrian gneiss and late proterozoic sedimentation in north central british columbia u pb analyses of zircons from gneissic granite in the sifton and deserters ranges flanking the northern rocky mountain trench in north central british columbia indicate crystallization ages of 1 85 b y and 728 m y respectively augen gneiss in the sifton ranges appears to be basement rock associated with a sequence of amphibolite quartzite schist and carbonate thrust southerly over upper proterozoic strata of the ingenika group gneissic granite in the deserters range is nonconformably overlain by pebble conglomerate and pure quartzite in turn overlain by a thick sequence of amphibolite schist phyllite gritty clastic rocks carbonate quartzite and diamictite assigned to the upper proterozoic misinchinka group the deserters data establish a probable maximum age for rocks of the windermere supergroup in the northern rocky mountains the age and structural setting of these gneisses are similar to other gneisses of the omineca crystalline belt of the canadian cordillera

pacific ocean and cenozoic evolution of climate 1 the pacific ocean has played a major role in climate evolution throughout the cenozoic 65 0 ma it is a fundamental component of global heat transport and circulation the dominant locus of primary productivity and consequently the largest reservoir for carbon exchange between the oceans and the atmosphere a satisfactory understanding of the cenozoic evolutionary history of the pacific and its impact on global climate is currently data limited nevertheless the large dynamic range of cenozoic conditions sets the stage to greatly expand our understanding of global climate and biogeochemical cycles past earth experiments are particularly useful to understand interactions between climate and geosystems under different greenhouse gas loads we highlight in this review four important problems in which the pacific played a major role the effect of changing geographic boundary conditions on ocean circulation interactions between the carbon cycle and climate the pacific ocean s influence on north american climate and its water cycle and the gradual evolution of climate systems

evidence of the present relative land stability of venice italy from land sea and space observations 1 the city of venice is very vulnerable to loss in surface elevation as a result of subsidence and eustacy because of its small elevation above sea level the alarm of the scientific community related to this persistent problem is increasing because of the forecasts of sea level rise caused by global warming in order to evaluate the present relative subsidence of venice a study has been performed by combining high precision leveling satellite radar interferometry sri and tide gauge measurements the analysis of the most recent data points out with an unprecedented detail the present ground stability of the city

extended orbitally forced palaeoclimatic records from the equatorial atlantic ceara rise abstract we extend existing high resolution oligocene miocene proxy records from ocean drilling program odp leg 154 the extended record spans the time interval from 17 86 to 26 5 ma the data are age calibrated against a new astronomical solution that affords a re evaluation of the intricate interaction between orbital milankovitch forcing of the climate and ocean system and the fidelity with which this forcing is recorded in oxygen and carbon stable isotope measurements from benthic foraminifera and associated lithological proxy records of magnetic susceptibility colour reflectance and the measured sand fraction our records show a very strong continual imprint of the earth s obliquity cycle modulate in amplitude every 41 ka a very strong eccentricity signal in the carbon isotope records and a strong but probably local imprint of climatic precession on the coarse fraction and magnetic susceptibility records our data allowed us to evaluate how the interaction of long multi million year beats in the earth s eccentricity and obliquity are implicated in the waxing and waning of ice sheets presumably on antarctica our refined age model confirms the revised age of the oligocene miocene boundary previously established by analysis of the lithological data and allows a strong correlation with the geomagnetic time scale by comparison with data from odp site 1090 southern ocean

isotopic and geochemical characterization of salinization in the shallow aquifers of a reclaimed subsiding zone the southern venice lagoon coastland summary the coastal plain bordering the southern venice lagoon is a reclaimed lowland characterized by high subsidence rate and ground level and water table depth below sea level in this agricultural region where the surface hydrologic network is entirely artificially controlled by irrigation drainage canals salinization problems have long been encountered in soils and groundwaters here we use isotopic and geochemical tracers to improve our understanding of the origin of salinization and mineralization of the semi confined aquifer 0 40 m and the freshwater inputs to this hydrological system water samples have been collected at different seasons in the coastal adriatic sea lagoon rivers and irrigation canals as well as in the semi confined aquifer at depths between 12 and 35 m 14 boreholes and in the first confined aquifer three boreholes drilled between 40 and 80 m depth stable isotopes 18 o and d and conductivity profiles show that direct saline intrusion from the sea or the lagoon is observed only in a restricted coastal strip while brackish groundwaters are found over the entire topographic and piezometric depression in the centre of the study area fresh groundwaters are found only in the most western zone the sharp isotopic contrast between the western and central regions suggests disconnected hydrological circulations between these two parts of the shallow aquifer the border between these two regions also corresponds to the limits of the most strongly subsiding zone our results can be interpreted in terms of a four end member mixing scheme involving 1 marine water from the lagoon or the open sea 2 alpine and pre alpine regional recharge waters carried either by the main rivers adige bacchiglione and brenta irrigation waters or by the regional groundwater circulation 3 local precipitation and 4 evaporated waters infiltrated from the surface infiltration from the surface is also revealed by the stratification of the electrical conductivity profiles showing that the brackish groundwaters are overlain by a shallow layer of less saline water all over the central depression in the first confined aquifer the groundwaters have isotopic compositions similar to the deep groundwaters of the venetian confined aquifers 40 400 m depth the isotopic data and the br cl ratio show that the origin of the salinization of the phreatic aquifer can be ascribed to seawater intrusion alone with no indication of the involvement of deep brines identified at 450 m depth in the process the chemical composition of the saline and brackish groundwaters is characterized by an excess of sodium and a deficit of calcium compared to conservative mixing between fresh groundwaters and seawater this suggests that the phreatic aquifer is progressively freshening as a consequence of the beneficial influence of the extensive irrigation drainage network including raised canals acting as a hydraulic barrier along the coast this freshening tendency may have been lasting since the reclamation in the mid twentieth century and has probably been accelerated by the ban on groundwater abstraction since the 1970s

inflation rate of the colli albani volcanic complex retrieved by the permanent scatterers sar interferometry technique 1 we analyzed 99 ers sar images of the colli albani volcano using the permanent scatterers technique we retrieved the average surface displacement velocities for over 100 000 scatterers for the period 1993 2000 showing that present deformation is concentrated in the area of most recent volcanic activity with rates up to 2 6 mm yr in the satellite line of sight we inverted the observed deformation using several analytical solutions for volcanic sources in an elastic half space the best fit is obtained with two mogi sources aligned in a n s direction at 5 and 7 km depth beneath the western flank of the volcano

surface flow evolution throughout a glacier surge measured by satellite radar interferometry 1 the surface flow evolution over 6 years of a glacier surge in svalbard is revealed by satellite radar interferometry from ers 1 and ers 2 eleven surface velocity maps generated by combining multi temporal differential interferograms utilising 36 ascending and descending pass images give an unprecedented overview of the spatio temporal development of the surge the surge is characterised by gradual initiation and termination phases and flow restrictions appear to remain spatially consistent despite the relatively large changes in surface velocity results from this type of study are expected to help constrain physically based models of surge behaviour

rapid cenozoic glaciation of antarctica induced by declining atmospheric co2 the sudden widespread glaciation of antarctica and the associated shift towards colder temperatures at the eocene oligocene boundary 34 million years ago refs 1 4 is one of the most fundamental reorganizations of global climate known in the geologic record the glaciation of antarctica has hitherto been thought to result from the tectonic opening of southern ocean gateways which enabled the formation of the antarctic circumpolar current and the subsequent thermal isolation of the antarctic continent5 here we simulate the glacial inception and early growth of the east antarctic ice sheet using a general circulation model with coupled components for atmosphere ocean ice sheet and sediment and which incorporates palaeogeography greenhouse gas changing orbital parameters and varying ocean heat transport in our model declining cenozoic co2 first leads to the formation of small highly dynamic ice caps on high antarctic plateaux at a later time a co2 threshold is crossed initiating ice sheet height mass balance feedbacks that cause the ice caps to expand rapidly with large orbital variations eventually coalescing into a continental scale east antarctic ice sheet according to our simulation the opening of southern ocean gateways plays a secondary role in this transition relative to co2 concentration

qualitative and quantitative evaluation of the influence of anthropic pressure on subsidence in a sedimentary basin near rome this paper presents the results of analyses measuring variations in anthropic pressure and the influence of anthropic pressure on the variations in subsidence rates from 1954 to 2005 in the tivoli guidonia area located to the east of rome italy in the last 60 years this area underwent exceptional demographic growth as well as an increase in the quarrying and hydrothermal industries the calculation of the increase in anthropic pressure was based on two factors the expansion of built up areas and the increase in quarrying photogrammetric techniques permitted a multi temporal analysis of aerial photos taken in 1954 1985 1993 1998 and 2005 the aim of this analysis was to estimate the increase in both urban surface area and travertine quarrying non conventional techniques such as the reconstruction of photograms using photo retouching software allowed for the use of aerial photos from 1954 these photos were fundamental for establishing a medium term evaluation of anthropic activity in the area the results of the photogrammetric analysis were compared to the phases of acceleration and stabilization in subsidence phenomena deduced from a radar interferometry study published by the italian ministry of the environment this comparison showed a close relationship between the rise and temporary halt of anthropic development and the rise and fall of subsidence rates furthermore data on the distribution of private wells in the study area variations in the groundwater table level and the precipitation regime were analyzed but although helpful in defining the geological context and considerable transformations of the territory they were considered as qualitative data due to the lack of systematic measures or an unclear relationship to the variations in subsidence rate despite the difficulties involved in evaluating both the amount of anthropic pressure and the role of different human activities on environmental change it was possible to estimate the variations in anthropic pressure and their influence on potentially dangerous geological processes

rapid atmospheric co2 changes associated with the 8 200 years b p cooling event by applying the inverse relation between numbers of leaf stomata and atmospheric co2 concentration stomatal frequency analysis of fossil birch leaves from lake deposits in denmark reveals a century scale co2 change during the prominent holocene cooling event that occurred in the north atlantic region between 8 400 and 8 100 years b p in contrast to conventional co2 reconstructions based on ice cores from antarctica quantification of the stomatal frequency signal corroborates a distinctive temperature co2 correlation results indicate a global co2 decline of 25 ppm by volume over 300 years this reduction is in harmony with observed and modeled lowering of north atlantic sea surface temperatures associated with a short term weakening of thermohaline circulation

can venice be raised by pumping water underground a pilot project to help decide 1 recent field evidence suggests that injecting fluids below the ground surface can induce an anthropogenic land uplift of a few tens of centimeters over a time interval that may range from a few months to a few years at the same time new modeling studies using a lot of realistic hydrogeological and geomechanical information from the northern adriatic basin indicate that pumping seawater into a 600 800 m deep brackish aquifer below the venice lagoon might help raise the city uniformly by 25 30 cm over 10 years a this could provide venice with an important innovative defence from and a substantial mitigation to the so called acqua alta i e the increasingly frequent floods that plague the city to test the feasibility of an actual program of anthropogenic venice uplift a pilot project is designed with the aim of investigating the occurrence over a limited area selected on purpose within or in the margin of the lagoon where three boreholes down to 800 m are drilled and seawater properly treated for geochemical compatibility is pumped into the selected aquifer during 3 a using an improved reconstruction of the geology and lithostratigraphy from a new seismic survey to be carried out in the lagoon subsurface the pilot project plans the instrumentation of the injection wells and other boreholes for the continuous monitoring and accurate measurement of 1 pore water overpressure 2 expansion of the injected unit by the radioactive marker technique 3 compaction if any of the upper fresh water aquifer system with the aid of an extensometer and 4 vertical and horizontal motions of land surface via spirit leveling gps and interferometric synthetic aperture radar preliminary numerical simulations show that a constant saltwater injection rate of 12 103 m3 s 1 from each well might provide a maximum 7 cm uplift at the center of the selected site over a 3 a time namely a limited amount that is nevertheless accurately measurable and should not raise concerns for the stability of the buildings and the preservation of the infrastructures in the area a continuous control of the experiment is envisaged based on much refined hydrologic and geomechanical models properly updated and calibrated to the detailed lithostratigraphy resulting from the new seismic campaign the ad hoc field analyses and the current field observations of the event the completion of the pilot project is expected to require 4 a including an initial year needed for the necessary authorizations and the operative implementation of the injection program the planned cost is in the range of 5 meuro a the present paper addresses the major issues concerned with the design of the pilot project and discusses the results from the experiment simulations with a glance at their prospective application to an actual project of anthropogenic uplift of venice

middle eocene co2 and climate reconstructed from the sediment fill of a subarctic kimberlite maar eocene paleoclimate reconstructions are rarely accompanied by parallel estimates of co 2 from the same locality complicating assessment of the equilibrium climate response to elevated co 2 we reconstruct temperature precipitation and co 2 from latest middle eocene ca 38 ma terrestrial sediments in the posteruptive sediment fill of the giraffe kimberlite in subarctic canada mutual climatic range and oxygen isotope analyses of botanical fossils reveal a humid temperate forest ecosystem with mean annual temperatures mats more than 17 c warmer than present and mean annual precipitation 4 present metasequoia stomatal indices and gas exchange modeling produce median co 2 concentrations of 630 and 430 ppm respectively with a combined median estimate of 490 ppm reconstructed mats are more than 6 c warmer than those produced by eocene climate models forced at 560 ppm co 2 estimates of regional climate sensitivity expressed as mat per co 2 doubling above preindustrial levels converge on a value of 13 c underscoring the capacity for exceptional polar amplification of warming and hydrological intensification under modest co 2 concentrations once both fast and slow feedbacks become expressed

monitoring severe aquifer system compaction and land subsidence in taiwan using multiple sensors yunlin the southern choushui river alluvial fan during 1992 2007 excessive pumping of groundwater caused large scale aquifer system compaction and land subsidence in the choshui river alluvial fan especially in the area of yunlin county the subsidence impedes surface water runoff and endangers the operation of taiwan high speed rail leveling global positioning system gps multi level compaction monitoring well and differential interferometric synthetic aperture radar dinsar are used to study the extent of subsidence in yunlin and its mechanism these sensors complement each other in spatial and temporal resolutions a leveling network totaling 434 km in length was deployed to derive subsidence at every 1 5 km along the routes and the result is accurate to few mm and shows a basin like subsidence pattern centering at tuku township four multi level compaction monitoring wells co located with gps pillars detect compactions at different depths showing that the aquifer system compaction the cause of subsidence occurs mostly below depths 200 m where reduction of groundwater pumping is most needed the vertical displacements from gps and leveling agree to within 1 cm and are larger than the cumulative compaction detected by the compaction monitoring wells suggesting that compaction also occurs below 300 m the depth of the wells the vertical displacements derived using dinsar and 8 envisat sar images agree with the leveling result to 1 2 cm

age and geological setting of gold creek gneiss crystalline basement of the windermere supergroup cariboo mountains british columbia gold creek gneiss the most recently discovered body of crystalline basement in the canadian cordillera is a northwest trending granitic to dioritic orthogneiss straddling the eastern end of the canoe river valley near the southeastern end of the cariboo mountains u pb geochronometry of zircons from two samples of quartz diorite orthogneiss from two separate localities yielded similar nearly linear discordant arrays with upper intercepts of 2 08 ga the patterns of discordance in both samples preclude assigning a precise age although a date between 2 0 and 2 1 ga is geologically reasonable north of canoe river gold creek gneiss is inferred to be nonconformably overlain by quartzite and marble which in turn are inferred to be unconformably overlain by a conglomerate and diamictite bearing unit at the base of the lower kaza group of the windermere supergroup in contrast with other exposures of basement and cover in the area neither contact is marked by anomalously high strain or mylonitic rocks

astronomical calibration age for the oligocene miocene boundary the stratotype section for the base of the miocene is at a reversed below to normal above magnetic transition that is claimed to represent magnetic chron c6cn 2n o deep sea drilling project dsdp site 522 is the only location we are aware of that unambiguously records the three normal events of c6cn we have quantitatively determined the range of the short lived nannofossil sphenolithus delphix and the lower limit of s disbelemnos in dsdp holes 522 and 522a in order to calibrate their precise relationship to the magnetostratigraphy and to confirm the completeness of the record at this site astronomical tuning of ocean drilling program odp sites 926 928 and 929 shows that s disbelemnos appears at 22 67 ma and that the entire range of s delphix is from about 22 98 ma to 23 24 ma using these ages linear interpolation in dsdp site 522 suggests that the age of c6cn 2n o and of the oligocene miocene boundary is 22 92 0 04 ma our value conservatively expressed as 22 9 0 1 ma is 0 9 m y younger than the currently accepted age of the oligocene miocene boundary and of c6cn 2n o which was assigned an age of 23 8 ma based on an estimate of 23 8 1 ma for the oligocene miocene boundary the bulk sediment carbon isotope data from dsdp site 522 is correlated to the record from benthic foraminifera at odp site 929 to refine the calibration of magnetic reversals from c6cn 1n o to c7n 2n o at dsdp site 522 on the astronomical time scale

integrated analysis of sar interferometric and geological data for investigating long term reclamation settlement of chek lap kok airport hong kong abstract we investigated the long term reclamation settlement of chek lap kok airport hong kong one of the largest reclamation projects worldwide an advanced insar technique was applied to two independent asar data sets along ascending 25 scenes and descending 22 scenes orbits acquired between 2003 and 2008 and allowed us to generate deformation velocity maps and displacement time series for the investigated area intercomparison of deformation velocity results from the two asar data sets and their validation against leveling survey measurements were carried out in order to assess accuracy and reliability of the insar observations the intercomparison and validation results demonstrated the potential of elaborate insar processes on local scale areas to monitor and detect a long term residual settlement in such complex reclamation area the insar derived deformation velocity maps showed a fair stability in areas of the two original rocky islands of chek lap kok and lam chau and on most of the buildings at the site due to foundation on piles reaching the granite bedrock whereas a generally moderate 3 7 mm year to strong 10 mm year and spatially variable settlement trend was detected in the majority of reclamation areas of the airport the consistent relationship we found between the observed settlement pattern and the underlying geological conditions suggested that this recoded differential settlement was mainly related to the variations in thickness and soil properties of both the fill materials and the alluvial deposits below the reclamation a geological and geotechnical interpretation of the lithostratigraphy of the alluvial deposits beneath the reclamation implied that the relatively large settlement rate measured up to 2008 was resulted from a still active primary consolidation process

a new project to monitor land subsidence in the northern venice coastland italy the paper deals with the implementation of a levelling and global positioning system gps network to control land subsidence in the coastal area north of the venice lagoon about 480 km of levelling lines with 527 benchmarks 45 of which suited for differential gps measurements were established in 2004 a complete survey of the net was carried out in 2004 soon after its establishment the 2004 records have been compared with previous scattered data obtained by the use of levelling surveys dgps and sar interferometry the results show a trend in land settlement that increases from the lagoon margin to the north and jeopardize the venice coastland groundwater withdrawals for domestic agricultural and health spas uses peat oxidation of reclaimed marshlands for farming natural consolidation of the holocene deposits and tectonics of the pre quaternary basement are the causes of land subsidence in the study area since most of the area lies below the mean sea level and on account of the expected sea level rise due to global change a detailed monitoring of land displacements in the near future will be of paramount importance to plan necessary works for coastland protection

extremely elevated co2 concentrations at the triassic jurassic boundary abstract although progress has been made in recent years in reconstructing the environmental conditions at the triassic jurassic boundary tjb published records of atmospheric co 2 concentrations have been of low resolution and or based on multi taxon estimates this is addressed here by reconstructing co 2 concentrations across the tjb using stomatal frequencies of four phylogenetically and ecologically distinct plant groups from two depositionally geographically and taphonomically separate boundary sections in east greenland and northern ireland with stomatal proxy methods and regression analysis the resulting co 2 records then are compared with an additional existing tjb record from a geological section in sweden the final results indicate that pre tjb rhaetian the co 2 concentration was approximately 1000 ppm that it started to rise steeply pre boundary and had doubled to around 2000 2500 ppm at the tjb the co 2 concentration then remained elevated for some time post boundary before returning to pre tjb levels in the hettangian these results are in very good accordance with published c isotope fire and leaf dissection records and clearly indicate steeply rising and lingering co 2 concentration at the tjb

dynamic antarctic ice sheet during the early to mid miocene geological data indicate that there were major variations in antarctic ice sheet volume and extent during the early to mid miocene simulating such large scale changes is problematic because of a strong hysteresis effect which results in stability once the ice sheets have reached continental size a relatively narrow range of atmospheric co2 concentrations indicated by proxy records exacerbates this problem here we are able to simulate large scale variability of the early to mid miocene antarctic ice sheet because of three developments in our modeling approach i we use a climate ice sheet coupling method utilizing a high resolution atmospheric component to account for ice sheet climate feedbacks ii the ice sheet model includes recently proposed mechanisms for retreat into deep subglacial basins caused by ice cliff failure and ice shelf hydrofracture iii we account for changes in the oxygen isotopic composition of the ice sheet by using isotope enabled climate and ice sheet models we compare our modeling results with ice proximal records emerging from a sedimentological drill core from the ross sea andrill 2a that is presented in a companion article the variability in antarctic ice volume that we simulate is equivalent to a seawater oxygen isotope signal of 0 52 0 66 or a sea level equivalent change of 30 36 m for a range of atmospheric co2 between 280 and 500 ppm and a changing astronomical configuration this result represents a substantial advance in resolving the long standing model data conflict of miocene antarctic ice sheet and sea level variability

mapping surface deformation and thermal dilation of arch bridges by structure driven multi temporal dinsar analysis abstract arch bridges are important transportation infrastructures widely distributed in china but they are prone to structural defects due to aging without routine inspection and maintenance therefore structural health monitoring shm of these bridges is urgently needed by civil engineers to effectively reduce the risk of bridge damage or collapse on public safety an essential method for shm the modern differential synthetic aperture radar interferometry dinsar technique can detect subtle deformation of bridges at relatively low costs nevertheless identifying dense point like targets pts on such partially coherent arch bridges in sar image is more difficult than that for other man made objects owing to their complex structures and backscattering behaviors furthermore the complex mechanical properties of arch bridges due to the varying arch beam interactions make it hard to separate the surface deformation and thermal dilation accurately and the lack of specific structural knowledge that can help to understand the deformation evolution process limits the global structural risk assessment aiming at these problems we developed a structure driven multi temporal dinsar approach for arch bridge specific shm by introducing three structure driven steps i e backscattering geometrical interpretation linear thermal dilation estimation and validation and deformation feature points dfps based risk assessment into the traditional dinsar method the reliability of pts identification thermal dilation separation and structural risk assessment for arch bridges are significantly improved the effectiveness of our approach was fairly presented by two case studies of the rainbow and lupu bridges and the experimental results were verified by leveling benchmark validation cross sensor comparison as well as structural reliability assessment our results revealed that arch bridges exhibit a similar pattern of pts distribution that is dense around piers and sparse on the spans as well as a symmetrical progressive pattern of surface deformation with the subsidence increasing from piers and reaching a peak at the central spans in contrast magnitudes and mechanisms of thermal dilation are different and highly dependent on the materials and structural characteristics of specific bridges

unlocking the ice house oligocene miocene oxygen isotopes eustasy and margin erosion oxygen isotope records and glaciomarine sediments indicate at least an intermittent presence of large continental ice sheets on antarctica since the earliest oligocene circa 35 ma the growth and decay of ice sheets during the oligocene to modern ice house world caused glacioeustatic sea level changes the early eocene was an ice free greenhouse world but it is not clear if ice sheets existed during the middle to late eocene doubt house world benthic foraminiferal 18o records place limits on the history of glaciation suggesting the presence of ice sheets at least intermittently since the earliest oligocene the best indicator of ice growth is a coeval increase in global benthic and western equatorial planktonic 18o records although planktonic isotope records from the western equatorial regions are limited subtropical planktonic foraminifera may also record such ice volume changes it is difficult to apply these established principles to the cenozoic 18o record because of the lack of adequate data and problems in stratigraphic correlations that obscure isotope events we improved oligocene to miocene correlations of 18o records and erected eight oxygen isotope zones oi1 oi2 mi1 mi6 benthic foraminiferal 18o increases which are associated with the bases of zones oil circa 35 8 ma oi2 circa 32 5 ma and mil circa 23 5 ma can be linked with 18o increases in subtropical planktonic foraminifera and with intervals of glacial sedimentation on or near antarctica our new correlations of middle miocene benthic and western equatorial planktonic 18o records show remarkable agreement in timing and amplitude we interpret benthic planktonic covariance to reflect substantial ice volume increases near the bases of zones mi2 circa 16 1 ma mi3 circa 13 6 ma and possibly mi5 circa 11 3 ma possible glacioeustatic lowerings are associated with the 18o increases which culminated with the bases of zone mi4 circa 12 6 ma and mi6 circa 9 6 ma although low latitude planktonic 18o records are required to test this these inferred glacioeustatic lowerings can be linked to seismic and rock disconformities for example we link 12 oligocene early late miocene inferred glacioeustatic lowerings with 12 of the sequence boundaries inferred eustatic lowerings of haq et al 1987

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

groundwater monitoring at a building site of the tidal flood protection system mose in the lagoon of venice italy to protect venice against tidal flooding the mose system experimental electro mechanic module has been under construction since 2003 this safeguarding system is composed of four batteries of mobile barriers at the lagoon s inlets lido malamocco chioggia which will be lifted before the occurrence of exceptional high tides 1 10 m above the mean sea level isolating the venetian lagoon from the sea the end of the construction work is foreseen by 2016 in this paper the results of the groundwater monitoring at the building site of punta sabbioni at the lido inlet are described a large dewatered basin tura formerly occupied by the sea and close to the shoreline was used for the precasting of the mobile barriers and the impact of groundwater control was therefore monitored in the phreatic and shallow confined aquifers although a slurry wall barrier was excavated to isolate the tura a drawdown cone in the confined aquifer was observed extending to 1 km from the construction site in contrast the phreatic aquifer was only influenced by tides rainfall and evapotranspiration and the slurry wall of the tura had a positive effect of decreasing the groundwater salinity by limiting the seawater intrusion as confirmed by the electrical conductivity profiles measured inside the piezometers the monitoring activity was successful in assessing the impacts of the construction work on the aquifer system and in distinguishing them from the effects of natural driving forces

high frequency paleoclimate signals from foulden maar waipiata volcanic field southern new zealand an early miocene varved lacustrine diatomite deposit abstract a freshwater diatomite deposit near dunedin south island new zealand provides an exceptional archive of mid latitude seasonal climate variation during latest oligocene early early miocene time the diatomite accumulated in a small 1 5 km diameter maar floored lake that formed during basaltic volcanism except for exposures of basanite dated at 23 2 ma by 40 ar 39 ar and remnants of a paleogene sandstone and conglomerate cover the diatomite body is surrounded by otago schist geophysical profiles indicate that the total diatomaceous sediment thickness may exceed 100 m two depositional facies are described from 15 5 m of weakly consolidated fresh diatomite accessible in two pits a thinly laminated facies comprising 60 of the section consists of dark brown and white couplets of average thickness 0 5 mm both brown and white laminae are composed essentially of frustules of a single pennate diatom along with 1 2 of siliceous sponge spicules dark laminae also contain abundant 5 7 5 m diameter siliceous chrysophycean stomatocysts and organic matter decalcified complete skeletons of galaxias a southern hemisphere group of freshwater or diadromous fish are found throughout diverse well preserved leaves some with attached scale insects are dominated by lauraceae rare flowers are also present trace fossils preserved in the laminated comprise 1 1 5 mm wide pale diatomaceous strings of probable faecal origin and isolated 20 40 mm diameter sand lenses interpreted as faecal remains of swimming waterfowl the second diatomite facies group comprises dark brown speckled beds interpreted as sediment gravity flows up to 14 cm thick and interspersed throughout the study section they incorporate abundant laminated diatomite flecks and leaves and minor woody plant matter and terrigenous silt almost all are capped by 1 8 mm of white diatomite that is interpreted as post flow fall out of resuspended diatom frustules associated breccia and swirly beds up to 8 cm thick are composed of variably contorted clasts of laminated diatomite in a speckled matrix nodules spheroids and films of authigenic framboidal pyrite are commonly associated with plant and fish remains as in modern lakes white laminae likely formed from diatom blooms when light flux temperature or nutrients were optimal during spring early summer dark laminae accumulating during autumn winter months laterally continuous pinstripe lamination absence of bioturbation and excellent fish and plant preservation indicate that the profundal lake and floor were anoxic periodic variations in couplet thickness of 3 10 years compare with quaternary records of el nino southern oscillation variability and indicate that the early early miocene low altitude new zealand climate was seasonal and strongly ocean influenced as it is today

terrasar x reveals the impact of the mobile barrier works on venice coastland stability land subsidence and eustacy concurred to make the relative sea level in venice italy 23 cm higher over the last century in order to protect the city and its lagoon environment from increased flooding a series of mobile barriers are under construction at the three inlets of lido malamocco and chioggia connecting the adriatic sea to the inner water body since 2003 work has been proceeding with the reinforcement and extension of the existing jetties and the construction of breakwaters harbors and a small island within the lido inlet we detected significant local settlements of a few centimeters between march 2008 and january 2009 at the three inlets induced by the construction works through an interferometric analysis of 30 satellite radar images acquired by the new german terrasar x mission on a more regional scale we observe that the city of venice and the other major urban settlements on the lagoon littorals are not impacted by subsidence during this period the very high spatial resolution of 3 m and the short repeat time interval of 11 days of terrasar x enable the investigation of displacements with an unprecedented observed level of details opening new perspectives to geodynamic s research and civil engineering sectors for the monitoring of large infrastructures with potential vulnerability to terrain motion

rapid stepwise onset of antarctic glaciation and deeper calcite compensation in the pacific ocean the ocean depth at which the rate of calcium carbonate input from surface waters equals the rate of dissolution is termed the calcite compensation depth at present this depth is 4 500 m with some variation between and within ocean basins the calcite compensation depth is linked to ocean acidity which is in turn linked to atmospheric carbon dioxide concentrations and hence global climate1 geological records of changes in the calcite compensation depth show a prominent deepening of more than 1 km near the eocene oligocene boundary 34 million years ago 2 when significant permanent ice sheets first appeared on antarctica3 4 5 6 but the relationship between these two events is poorly understood here we present ocean sediment records of calcium carbonate content as well as carbon and oxygen isotopic compositions from the tropical pacific ocean that cover the eocene oligocene boundary we find that the deepening of the calcite compensation depth was more rapid than previously documented and occurred in two jumps of about 40 000 years each synchronous with the stepwise onset of antarctic ice sheet growth the glaciation was initiated after climatic preconditioning7 by an interval when the earth s orbit of the sun favoured cool summers the changes in oxygen isotope composition across the eocene oligocene boundary are too large to be explained by antarctic ice sheet growth alone and must therefore also indicate contemporaneous global cooling and or northern hemisphere glaciation

modelling the interseismic deformation of a thrust system seismogenic potential of the southern alps this article focuses on the montello thrust system in the eastern southern alps as a potential seismogenic source this system is of particular interest because of its lack of historical seismicity nevertheless the system is undergoing active deformation we developed a finite element model using visco elasto plastic rheology the free parameters of the model essentially the locking status of the three thrusts included in the study were constrained by matching the observed horizontal gps and vertical levelling data we show that the amount of interseismic fault locking and thus the seismic potential is not necessarily associated with the fastest slipping faults more specifically the locked bassano thrust has a greater seismic potential than the freely slipping montello thrust the findings suggest that faults with subtle evidence of quaternary activity should be carefully considered when creating seismic hazard maps

carbon sequestration activated by a volcanic co 2 pulse during ocean anoxic event 2 ninety four million years ago during ocean anoxic event 2 there was a marked increase in the burial of organic carbon in marine sediments measurements of stomata in fossil leaves show that the two main pulses of carbon burial were associated with a decline in atmospheric co2 levels of up to 26 the cretaceous ocean anoxic event 2 about 94 million years ago is thought to be linked to extensive volcanism which triggered a biogeochemical chain of events that eventually led to widespread marine anoxia and a remarkable increase in carbon burial in marine sediments1 2 3 it has been suggested that the event was accompanied by a substantial decrease in atmospheric co2 concentrations4 but the quantification of the drawdown remains controversial5 6 here we reconstruct atmospheric co2 concentrations throughout the ocean anoxic event from counts of the stomata in fossil leaves and use terrestrial carbon isotopes to link the reconstruction to marine records of the event7 8 we find that before the onset of ocean anoxia atmospheric co2 concentrations increased by 20 over background levels of 370 100 70 ppm this was part of a long term rise in atmospheric co2 levels presumably caused by volcanism which reached a peak of 500 400 180 ppm however two pulses of extensive carbon burial during the ocean anoxic event as indicated by positive carbon isotope excursions are associated with decreased atmospheric co2 concentrations we conclude that the sequestration of marine organic carbon led to a decrease in atmospheric co2 concentration of up to 26 during ocean anoxic event 2

global trends of pco2 across the cretaceous paleogene boundary supported by the first southern hemisphere stomatal proxy based pco2 reconstruction reliable reconstructions of atmospheric carbon dioxide concentrations pco2 are required at higher resolution than currently available to help resolve the relationship between mass extinctions and changes in palaeo pco2 levels such reconstructions are needed 1 at a high temporal resolution for constraining the pre and post extinction atmospheres and 2 at a sufficient spatial resolution to constrain potential inter hemispheric differences here we estimate pco2 based on fossil lauraceae leaf cuticle specimens derived from three localities with strata spanning the latest cretaceous to the mid paleocene including a new cretaceous paleogene boundary k pg locality in new zealand we use two independent methods of stomatal density based pco2 reconstructions a transfer function calibrated using herbarium material and the stomatal ratio method producing three calibration sets our results based on the mean values of each of the three calibration methods indicate pco2 ranging between ca 460 and 650 ppm during the latest cretaceous falling precipitously to average values between ca 360 and 430 ppm across the k pg boundary and further to ca 305 320 ppm in the mid paleocene a spike of extremely high pco2 at the k pg could not be confirmed but our results are nonetheless consistent with previously published pco2 records from the northern hemisphere and show that stomatal density worldwide was responding to significant changes in pco2 across the k pg

carbon cycle feedbacks during the oligocene miocene transient glaciation ice sheet models suggest that once formed the large high altitude east antarctic ice sheet was relatively self stabilizing due to its cold upper surface the ice sheet hysteresis problem results from an inability to reconcile this expectation with geological evidence for episodes of ice sheet retreat a classic example of this problem is manifested in benthic foraminiferal oxygen isotope records across the oligocene miocene boundary ca 23 ma which display a transient 1 excursion to higher values the inferred increase and subsequent decrease in ice volume has been linked to advance and retreat of the antarctic ice sheet across the continental shelf however oxygen isotope records alone do not provide unambiguous records of temperature and ice volume hindering assessment of the driving mechanism for these variations here we present new benthic foraminiferal mg ca li ca and u ca records across the oligocene miocene boundary from ocean drilling program sites 926 and 929 our records demonstrate that atlantic bottom water temperatures varied cyclically with the main cooling and warming steps followed by ice growth and decay respectively we suggest that enhanced organic carbon burial acted as a positive feedback as climate cooled several lines of evidence suggest that the deglaciation was associated with an input of carbon to the ocean atmosphere system culminating in a previously unidentified seafloor dissolution event we suggest that one of the initial sources of carbon was organic matter oxidation in ocean sediments this study demonstrates that carbon cycle feedbacks should be considered when evaluating the stability of ancient ice sheets

quantitative evidence that compaction of holocene sediments drives the present land subsidence of the po delta italy 1 deltas are highly dynamic coastal systems that over the last few decades have generally experienced a substantial area loss caused by trapping of river sediments in upland drainage basins as well as land subsidence due to natural and anthropogenic causes a major example is the po delta in the mediterranean in northeastern italy this area has experienced as much as 3 m of land subsidence from the 1930s to the 1970s primarily because of the extraction of gas bearing waters however present subsidence rates are largely unknown and the ground settlement is supposedly controlled by natural long term deep processes we have combined radar interferometric point target analysis ipta with previous geomorphological investigations on aerial satellite images and seismic surveys and geochronological data from core samples and geomechanical in situ tests to assess the current sinking of the delta and to understand the processes controlling the vertical movement the high density of the measurable point targets more than 15 000 allows characterization of the spatial variation in the vertical land motions vlm ranging from 1 to 15 mm yr we find that subsidence rates are significantly correlated with the age of highly compressible holocene deposits that compose the shallowest 30 40 m of the sedimentary sequence a typical log type consolidation equation applicable at the scale of the entire delta has been obtained we conclude that the consolidation of late holocene sediments is the major cause of the present land subsidence in the po river delta this finding has significant impact on the understanding of many other modern deltas that were formed in the lower holocene epoch

interaction between permafrost and infrastructure along the qinghai tibet railway detected via jointly analysis of c and l band small baseline sar interferometry abstract the qinghai tibet railway qtr is the highest and longest plateau linear structure in the world the embankment is prone to instability primarily due to the freezing and thawing of the permafrost overlying active layer the infrastructure construction changes environmental conditions and in turn has influenced permafrost evolutions in this study we have investigated the feasibility of extracting surface motions in permafrost regions by means of satellite sar interferometry the relationship between surface deformation permafrost active layer and other environmental conditions were further analyzed in total 19 l band alos palsar slc images acquired from 21 june 2007 to 30 december 2010 and 38 c band envisat asar slc images acquired from 18 november 2004 to 17 december 2009 were employed to cover the beiluhe experimental site qinghai china a hybrid persistent scatterer interferometry model based on interferometric point target analysis ipta and small baseline strategy was firstly developed for surface motion estimation minimizing the seasonal decorrelation effect then the results from c and l band data were analyzed and compared based on a statistical calibration model ground leveling data acquired from fenghuo mount tunnel front with a one month interval were used for insar derived results validation revealing good agreement in displacement rates as well as time series the qtr has been in operation since 2006 our study has observed distinct surface motions along the embankment primarily in the range of 20 to 20 mm yr implying the necessity of continued satellite based surveillance along the qtr

new magnetobiostratigraphic chronology and paleoceanographic changes across the oligocene miocene boundary at dsdp site 516 rio grande rise sw atlantic new magnetobiostratigraphic data for the late oligocene through early miocene at deep sea drilling project dsdp hole 516f provide a significantly revised age model which permits reevaluation of developments that led to the mi 1 glacial event at the oligocene miocene boundary our new high resolution paleomagnetic study which is supported by quantitative calcareous nannofossil and planktonic foraminiferal analyses significantly refines previous age models for oligocene miocene sediments from dsdp hole 516f with ages that are systematically younger than those previously determined in some parts of the oligocene the discrepancy with previous studies exceeds 450 kyr based on this new age model we infer a progressive increase in sedimentation rate and paleoproductivity between circa 23 9 ma and circa 22 9 ma with the highest rate coinciding with the mi 1 glacial event at the oligocene miocene boundary this productivity increase would have resulted in higher rates of carbon burial and in turn a drawdown of atmospheric co2 immediately afterward an abrupt decrease in sedimentation rate and paleoproductivity suggests that the mi 1 deglaciation was associated with decreased carbon input into the ocean elevated sedimentation rates are also documented at 24 5 ma coincident with the oi2d glacioeustatic event the presence of volcanic material within the sediments during these glacial events is interpreted to have resulted from redeposition of sediment scoured from nearby sites on the rio grande rise due to transient variations in bottom water flow patterns

geodetic tools for hydrogeological surveys 3d displacements above a fractured aquifer from gps time series deep porous reservoirs are subject to charge and discharge of fluids oil gas or water either naturally or induced by human exploitation this leads to a variation in pressure inside the reservoir and consequently to a deformation of the overlying material the knowledge of the ground surface displacements allows inferring the fluid migrations and the hydromechanical properties in the porous reservoir different kinds of geodetic tools are able to measure this ground deformation gps radar interferometry insar tiltmeters or leveling each of them has its own spatial and time characteristics and accuracies that conduct to different kind of applications after a review of the geodetic studies applied to hydrogeological processes we describe two examples of gps time series measurements above the granitic fractured aquifer of ploemeur located in french brittany these time series records the 3d displacements induced by the sum of different processes in this site the involved processes are mainly the ground deformation related to piezometric level variations in the aquifer that we are looking for and the ocean tide loading that can reach several centimeters in the study area we present the protocol of the gps data survey and the processing strategy applied to extract the effect of hydrogeological process with sufficient accuracy two different experiments were studied the long term deformation corresponding to seasonal hydrological cycle and the short term deformation associated to a pumping test for a same variation in piezometric levels the vertical ground displacements show larger amplitude for long term signal than for short one indicating a behavior depending on the duration of the hydrogeological load this difference of reactivity in time can be related to the heterogeneity of the studied aquifer finally this work shows that geodetic measurements provide important constraints for characterizing aquifer system response

abrupt plant physiological changes in southern new zealand at the termination of the mi 1 event reflect shifts in hydroclimate and pco2 abstract a rise in atmospheric co2 is believed to be necessary for the termination of large scale glaciations although the antarctic ice sheet is estimated to have melted from 125 to 50 its modern size there is thus far no evidence for an increase in atmospheric co2 associated with the mi 1 glacial termination in the earliest miocene here we present evidence from a high resolution terrestrial record of leaf physiological change in southern new zealand for an abrupt increase in atmospheric co2 coincident with the termination of the mi 1 glaciation and lasting approximately 20 kyr quantitative p co 2 estimates made using a leaf gas exchange model suggest that atmospheric co2 levels may have doubled during this period from 516 111 ppm to 1144 410 ppm and subsequently returned back to 425 53 ppm the 20 kyr interval with high p co 2 estimates is also associated with a period of increased moisture supply to southern new zealand inferred from carbon and hydrogen isotopes of terrestrial leaf waxes the results provide the first high resolution record of terrestrial environmental change at the oligocene miocene boundary document a 20 kyr interval of elevated p co 2 and increased local moisture availability and provide insight into ecosystem response to a major orbitally driven climatic transition

assessing pre and post deformation in the southern arava valley segment of the dead sea transform israel by differential interferometry abstract differential radar interferometry using archived ers data over the region of the dead sea transform allows to detect ground movement subsidence or uplift in playas within the southern arava valley segment of the dead sea rift these measurements are consistent with a mean displacement rate of about 0 4 cm month in the direction of the radar beam during the 8 month period preceding the nuweiba earthquake of 22 november 1995 in the 3 years following the earthquake the measured rate was smaller by a factor of 10 these movements are not related to salt diapirs or water pumping activities in the area the exact location along faults suggests a possible correlation with pre seismic and post seismic fault deformation a simple fault model consistent with the observed phenomena associates the observed subsidence uplift to right and left stepping en echelon fault patterns related to inter seismic tensional accumulation along the faults further observations are necessary on this site and similar fault areas to corroborate the correlation between seismic activity and the observed phenomena monitoring of these sites should continue with differential global positioning system gps measurements and radar interferometric analysis using envisat and radarsat as well as archived data including j ers

atmospheric co2 from the late oligocene to early miocene based on photosynthesis data and fossil leaf characteristics abstract the late oligocene represents a comparatively cool phase followed by a warming event the so called late oligocene warming that predates the mi 1 glacial event at the oligocene miocene transition there is evidence that these climate events were linked to level changes in atmospheric co2 in this study atmospheric co2 from the late oligocene to the early miocene is reconstructed by a terrestrial proxy stomatal parameters of angiosperm leaves fossil leaves of six plant species were considered laurophyllum pseudoprinceps l acutimontanum both lauraceae platanus neptuni platanaceae eotrigonobalanus furcinervis quercus rhenana and q praerhenana all fagaceae the plant material originates from various sites in germany late oligocene to the early miocene and austria early miocene a mechanistic theoretical approach based on stomatal data photosynthesis and gas exchange control was used since this approach also requires climate data as input parameters for calculating assimilation and transpiration rates palaeoclimate of these sites were also derived in detail considerable differences were found between results obtained by the two lauraceae taxa and all other taxa with the lauraceae indicating a high co2 level if lauraceae are included a co2 level of about 700 ppm for the late and latest oligocene is obtained and about 500 ppm for the early miocene all non lauraceae taxa belonging to different families indicate a consistently lower level of co2 of about 400 ppm for all considered sites and time slices a value of 400 ppm is also consistent with other proxy data that are available for that time period a steady level of 400 ppm would indicate a decoupling of co2 and cooling warming events from the late oligocene to the early miocene more data provided by different proxies are desirable to unravel the interactions between atmosphere and climate for the late oligocene and the early miocene

miocene climate evolution of northern europe a palynological investigation from denmark a palynological investigation has been conducted on lower upper miocene sediments from jylland denmark corresponding to the time interval of about 19 to 8 ma the sediments derived from the sdr vium drill core were deposited in marine to marginal marine environments as shown by the relatively high abundance of dinoflagellate cysts in all samples nevertheless rich and diverse pollen assemblages occur throughout the succession and the palynological analysis reveals that coastal areas of the study area were during the miocene dominated by taxodium swamp forests that also hosted terrestrial angiosperms such as nyssa betula alms and elements of the myricaceae further inland a mixed deciduous evergreen forest prevailed in areas with better drained soils or on elevated areas gymnospermous conifer forests prevailed including taxa such as pinus sequoia and sciadopitys overall the climate in the study area was warm temperate during major parts of the miocene with mean annual temperatures between 15 5 and 20 degrees c by employing the coexistence approach combined with the method of allocating taxa into standardized climatic groups four different climatic miocene events are detected within the studied succession correlated to the coeval climate record of northwestern europe the oldest event is a cooling during the earlier burdigalian at approximately 19 ma coinciding with the mbi 1 oxygen isotope excursion at ca 18 5 ma in mid burdigalian a warming phase is reconstructed characterized by the highest precipitation rates observed in the sedimentary succession a warming trend starting in the latest burdigalian corresponds to the globally recognized middle miocene climatic optimum mmco while a longer term late neogene cooling was initiated in the mid serravallian about 13 ma c 2011 elsevier b v all rights reserved less

shuswap terrane of british columbia a mesozoic core complex the shuswap terrane of the northwest cordillera owes its distinctive characteristics to deformation and high grade regional metamorphism that occurred primarily during the mesozoic within the terrane the monashee complex the overlying selkirk allochthon and the intervening monashee decollement record strain and metamorphism that occurred in middle to late jurassic time during and subsequent to the accretion of a western allochthonous terrane the selkirk allochthon moved eastward across the monashee complex after emplacement of the western allochthonous terrane but before late mesozoic to early cenozoic telescoping of the rocky mountain belt in this latter event the monashee complex and overlying allochthonous slices were transported eastward relative to the north american craton on a sole fault that developed during listric thrusting of the rocky mountain foreland synmetamorphic to late metamorphic elongation lineations and associated fabrics of the mylonitic rocks of the monashee decollement zone were generated by shear strain during the middle jurassic emplacement of the selkirk allochthon and are not related to any upper crustal extension that occurred in the tertiary uplift normal faulting brittle reactivation of the mylonitic decollement zone widespread resetting of k ar and rb sr mineral dates and arching of the terrane are events that culminated in the eocene

deep time evidence of a link between elevated co2 concentrations and perturbations in the hydrological cycle via drop in plant transpiration the physiological effects of high co 2 concentrations i e co 2 on plant stomatal responses may be of major importance in understanding the consequences of climate change by causing increases in runoff through suppression of plant transpiration radiative forcing by high co 2 has been the main consideration in models of global change to the exclusion of plant physiological forcing but this potentially underestimates the effects on the hydrological cycle and the consequences for ecosystems we tested the physiological responses of fossil plants from the triassic jurassic boundary transition tr j succession of east greenland this interval marks a major high co 2 driven environmental upheaval with faunal mass extinctions and significant floral turnover our results show that both stomatal size expressed in fossil material as sl the length of the stomatal complex opening and stomatal density sd the number of stomata per mm 2 decreased significantly during the tr j we estimate using a leaf gas exchange model that the decreases in sd and sl resulted in a 50 60 drop in stomatal and canopy transpiration at the tr j we also present new field evidence indicating simultaneous increases in runoff and erosion rates we propose that the consequences of stomatal responses to elevated co 2 may lead to locally increased runoff and erosion and may link terrestrial and marine biodiversity loss via the hydrological cycle

land subsidence in houston texas measured by radar interferometry and constrained by extensometers 1 we present results from a radar interferometry study over the houston galveston texas gulf coast region from the nearly 60 potential interferograms considered an atmospheric artifact assessment is performed and a tractable set of interferograms selected for detailed processing and error analysis the subsequent interferogram time series spanning 1996 1998 is constrained by coincident extensometer data with root mean square error less than 2 5 mm the interferogram time series confirms that historic subsidence in east houston has stopped consistent with current groundwater use patterns broad scale subsidence bowls are observed in west and northwest houston where maximum subsidence rates are in excess of 2 and 4 cm yr 1 respectively linear interferogram phase signatures associated with approximately 1 cm of differential subsidence across faults including the long point fault in northwest houston are observed near the seabrook extensometer a hereto unidentified subsidence bowl with a maximum subsidence rate in excess of 3 cm yr 1 is revealed this study demonstrates that when used in conjunction with a set of traditional geodetic measurements radar interferometry can measure the spatial and temporal evolution of urban land subsidence within even the most challenging of environments

mid cretaceous pco2 based on stomata of the extinct conifer pseudofrenelopsis cheirolepidiaceae stomatal characteristics of an extinct cretaceous conifer pseudofrenelopsis parceramosa fontaine watson are used to reconstruct atmospheric carbon dioxide p co 2 over a time previously inferred to exhibit major fluctuations in this greenhouse gas samples are from nonmarine to marine strata of the wealden and lower greensand groups of england and the potomac group of the eastern united states of hauterivian to albian age 136 100 ma atmospheric p co 2 is estimated from the ratios between stomatal indices of fossil cuticles and those from four modern analogs nearest living equivalent plants using this approach and two calibration methods to explore ranges results show relatively low and only slightly varying p co 2 over the hauterivian albian interval a low of 560 960 ppm in the early barremian and a high of 620 1200 ppm in the albian data from the barremian wealden group yield p co 2 values indistinguishable from a soil carbonate based estimate from the same beds the new p co 2 estimates are compatible with sedimentological and oxygen isotope evidence for relatively cool mid cretaceous climates

sar interferometry on a very long time scale a study of the interferometric characteristics of man made features anthropogenic features show up as highly coherent objects even in heavily decorrelated interferograms in order to assess whether the information from such features is still usable the stability of their phase and coherence is analyzed through a series of interferograms the results indicate that these features can remain interferometrically stable over several years

mapping regional land displacements in the venice coastland by an integrated monitoring system abstract an original integrated monitoring method is designed to infer an accurate and reliable figure of regional land displacements in coastal areas where the presence of internal waters wetlands farmlands urban and industrial centers usually reduces the efficiency of single ground based and satellite based measuring techniques five different methods i e spirit leveling differential global positioning system dgps continuous gps cgps interferometric synthetic aperture radar insar and interferometric point target analysis ipta are integrated into a subsidence integrated monitoring system sims to overcome the limits characterizing each technique the sims has been used over the past decade to provide a new image of the land displacements in the venice region the result exhibits a resolution never obtained before the central lagoon including the city of venice shows a general stability while the northern and southern lagoon extremities and their related catchment sectors sink with serious rates averaging 3 to 5 mm year the sinking rates increase up to 10 15 mm year in the coastland south of the lagoon relatively small uplifts less than 1 mm year are observed at the alpine foothills and in a wide area comprised between the euganean hills and the lagoon the observed land displacements have been associated to the geological features of the study region i e tectonics seismicity differential consolidation of the middle upper pleistocene and holocene deposits and to anthropogenic activities such as land reclamation and groundwater withdrawal

the southern omineca belt british columbia new perspectives from the lithoprobe geoscience program geological isotopic and geochronology studies carried out by university and government researchers concurrently with the lithoprobe program have greatly refined our understanding of the regional geology crustal structure and tectonics of the omineca belt sound correlations have been established between surface geology and seismic reflection data cretaceous eocene thrust faults that are imaged in the subsurface in the shuswap complex may be part of a break forward thrust system that feeds into the purcell anticlinorium and the foreland belt the monashee decollement is the western continuation of the sole thrust beneath the foreland belt and provides a means of linking shortening across the entire orogen the thermal peak of metamorphism in the central and southern shuswap complex is now known to have occurred in the late cretaceous paleogene in contrast with earlier held views north american basement rocks are now known to extend beneath the eastern half of the canadian cordillera geochronology

significant transient pco2 perturbation at the new zealand oligocene miocene transition recorded by fossil plant stomata abstract the reorganisation of earth s climate system from the oligocene to the miocene was influenced by complex interactions between tethyan tectonics orbital parameters oceanographic changes and carbon cycle feedbacks with climate modelling indicating that pco2 was an important factor oscillating episodes of climate change during the oligocene miocene transition omt have however been difficult to reconcile with existing pco2 records here we present a new pco2 record from the omt into the early miocene reconstructed using the stomatal proxy method with a database of fossil lauraceae leaves from new zealand the leaf database derives from three relatively well dated sites located in the south island of new zealand foulden maar mataura river and grey lake atmospheric pco2 values were obtained based on four separate calibrations with three nearest living equivalents using the stomatal ratio method as well as transfer functions our results based on the mean values of each of the four calibrations indicate pco2 ranging 582 732 ppm average 650 ppm at the omt falling precipitously to mean values of 430 538 ppm average 492 ppm for the earliest miocene and 454 542 ppm average 502 ppm in the early miocene the much higher values of pco2 at the omt indicate that pco played an important role in climate dynamics during this time potentially including the abrupt termination of glaciations

orbitally induced climate and geochemical variability across the oligocene miocene boundary to assess the influence of orbital scale variations on late oligocene to early miocene climate and ocean chemistry high resolution 5 kyr benthic foraminiferal carbon and oxygen isotope and percent coarse fraction time series were constructed for ocean drilling program site 929 on ceara rise in the western equatorial atlantic these time series exhibit pervasive low to high frequency variability across a 5 myr interval 20 5 25 4 ma the records also reveal several large scale secular variations including two positive 1 6 oxygen isotope excursions at 22 95 and 21 1 ma suggestive of large but brief glacial maxima mi 1 and mi 1a events of miller et al 1991 and a long term cyclical increase in the carbon isotopic composition of seawater shift of 1 52 that reaches a maximum coincident with peak 18o values at 22 95 ma lower resolution 25 kyr records constructed from benthic and planktonic foraminifera as well as bulk carbonate at a shallower site on ceara rise site 926 for the period 21 7 24 9 ma covary with site 929 18o values reflecting changes in antarctic ice volume likewise covariance among carbon isotopic records of bulk sediment benthic and planktonic foraminifera suggest that the low frequency cycles 400 kyr and long term increase in 13c values represent changes in the mean carbon composition of seawater co2 the time series presented here constitute the longest most continuous and highest resolution records of pre pliocene climate and oceanography to date the site 929 carbon and oxygen isotope power spectra show significant concentrations of variance at 400 100 and 41 kyr demonstrating that orbitally induced oscillations have been a normal characteristic of the global climate system since at least the oligocene including periods of equable climate and times with no apparent northern component water production

quantitative palaeoclimate estimates for early miocene southern new zealand evidence from foulden maar abstract a rich and diverse plant macrofossil assemblage from an earliest miocene diatomite deposit in southern new zealand provides a detailed record of mid latitude southern hemisphere terrestrial climate in an oceanic setting quantitative palaeoclimate estimates for temperature and precipitation variables were obtained using the climate leaf analysis multivariate program clamp and the bioclimatic analysis approach in addition the surface area of fossil podocarpus travisiae leaves preserved at the site was used as a proxy for mean annual temperature clamp and bioclimatic analysis both estimated mean annual temperatures at 18 5 19 5 c with a moderate seasonal temperature range between summer and winter of 10 c and leaf size in podocarpus suggested a mat of about 21 c precipitation rates were high at around 1700 2000 mm per year clamp analysis suggested a 600 mm difference between the dry and wet season whereas bioclimatic analysis indicated a 200 250 mm difference between summer and winter when compared to clamp analysis on modern vegetation on subtropical oceanic islands it would seem that clamp overestimates seasonal precipitation differences