itrf2008 plate motion model 1 the itrf2008 velocity field is demonstrated to be of higher quality and more precise than past itrf solutions we estimated an absolute tectonic plate motion model made up of 14 major plates using velocities of 206 sites of high geodetic quality far from plate boundaries deformation zones and glacial isostatic adjustment gia regions derived from and consistent with itrf2008 the precision of the estimated model is evaluated to be at the level of 0 3 mm a wrms no gia corrections were applied to site velocities prior to estimating plate rotation poles as our selected sites are outside the fennoscandia regions where the gia models we tested are performing reasonably well and far from gia areas where the models would degrade the fit antarctica and north america our selected velocity field has small origin rate bias components following the three axis x y z respectively 0 41 0 54 0 22 0 64 and 0 41 0 60 95 per cent confidence limits comparing our model to nnr nuvel 1a and the newly available nnr morvel56 we found better agreement with nnr morvel56 than with nnr nuvel 1a for all plates except for australia where we observe an average residual rotation rate of 4 mm a using our selection of sites we found large global x rotation rates between the two models 0 016 ma and between our model and nnr morvel56 of 0 023 ma equivalent to 2 5 mm a at the earth surface

reconstruction of wisconsinan age ice dynamics and compositions of southern ontario glacial diamictons glaciofluvial lacustrine and deltaic sediment abstract macrofabric analysis of till sections in south central ontario confirms that clast orientation yields information related to changing ice dynamics during the wisconsinan glaciation test stations in six sections yield unimodal to multimodal macrofabrics that indicate ice flow direction ranging from se nw vectors when ice was thin and flowing radially to variable ne sw nne ssw and n s vectors when ice thickened ice loci appear to range from the lake ontario basin and southern quebec thin ice labrador ungava thicker ice and hudson bay thickest ice the north south fabric may identify the intergrowth of keewatin labrador ice presumably the maximum ice thickness of the last glacial maximum lgm the preliminary data support the theory that topography directed ice movement during preliminary and closing stages of glaciation in southern ontario while thick ice generated flow vectors largely unaffected by underlying topography hence leading to clast azimuthal variations reflecting changing ice loci with glacier growth the fabrics analyzed suggest that inferring difference between ductile and brittle lodgement tills is possible as well as to identifying possible glacial tectonic action overburden loading that disturbs the least friction fit position of clasts in till the changing dynamics within till sheets are supported in part by variations in glacial crushing seen in sem imagery that depict a range of microtextures from full scale fractures under brittle conditions to those indicating less viscous transport under ductile regimes to some degree changes in flow direction are further supported by geochemical variations that relate to bedrock regolith up glacier controlling ca dilution and variable concentrations of rare earth elements rees

implications of quartz grain microtextures for onset eocene oligocene glaciation in prydz bay odp site 1166 antarctica abstract this paper presents the results of the scanning electron microscopic sem analysis of quartz grains from a selection of samples at site 1166 ocean drilling program leg 188 drilled site 1166 on the prydz bay continental shelf antarctica to document onset and fluctuations of east antarctic glaciation this site recovered upper pliocene holocene glacial sediments directly above cretaceous through lower oligocene sediments recording the transition from preglacial to early glacial conditions sem analysis of quartz grains at site 1166 was used to characterize the glacial and preglacial sediments by their diagnostic textures angular edges edge abrasion as well as arcuate to straight steps are the most frequent features in glacial deposits the highest frequency of grains with round edges is present in middle late eocene fluvio deltaic sands however angular outlines fractured plates with subparallel linear fractures and edge abrasion indicating glacier influence are also present preglacial carbonaceous mudstone and laminated gray claystone show distinctive high relief quartz grains and some chemical weathering on grain surfaces the results of the microtextural analysis of quartz grains are used to verify some critical periods of ice sheet evolution such as the transition from the east antarctic preglacial to glacial conditions on the continental shelf from middle late eocene to late eocene early oligocene time

spatiotemporal characterization of land subsidence and uplift in phoenix using insar time series and wavelet transforms the effects of land subsidence pose a significant hazard to the environment and infrastructure in the arid alluvial basins of phoenix arizona improving our understanding of the source and mechanisms of subsidence is important for planning and risk management here we employ multitemporal interferometric analysis of large synthetic aperture radar data sets acquired by ers and envisat satellites to investigate ground deformation the ers data sets from 1992 to 1996 and envisat 2003 2010 are used to generate line of sight los time series and velocities in both the ascending and descending tracks the general deformation pattern is consistent among data sets and is characterized by three zones of subsidence and a broad zone of uplift the multitrack envisat los time series of surface deformation are inverted to obtain spatiotemporal maps of the vertical and horizontal deformation fields we use observation wells to provide an in situ independent data set of hydraulic head levels then we analyze vertical interferometric synthetic aperture radar and hydraulic head level time series using continuous wavelet transform to separate periodic signal components and the long term trend the isolated signal components are used to estimate the elastic storage coefficient the inelastic skeletal storage coefficient and compaction time constants together these parameters describe the storage response of an aquifer system to changes in hydraulic head and surface elevation understanding aquifer parameters is useful for the ongoing management of groundwater resources

properties of the atlantic derived halocline waters over the laptev sea continental margin evidence from 2002 to 2009 1 a series of transects carried out in 2002 2009 across the laptev sea continental margin show consistent cross slope differences of the lower halocline water lhw over the slope the lhw core is on average warmer and saltier by 0 39 c and 0 26 practical salinity unit respectively relative to the off slope lhw underlying atlantic water aw thermohaline properties exhibit an opposite pattern it is colder and fresher over the slope and warmer and saltier off the slope although on slope and off slope lhws have different formation histories our results suggest that an important part of the heat and salt lost from the aw is gained by the overlying lhw over the continental slope area this implies the role of enhanced vertical mixing over the sloping topography which contributes to the difference between the on and off slope lhw properties the distribution of chemical tracers dissolved oxygen and nutrients provides further evidence supporting this interpretation and additionally suggests that the lhw may also be influenced by water from the outer shelf

using gis for modelling the impact of current climate trend on the recharge area of the s susanna spring central apennines italy though the s susanna spring system is one of the biggest water sources in the central apennines its hydrogeological dynamics have been scarcely investigated this study tried to clarify some of the factors controlling the recharge discharge processes of this spring by modelling the available climate series water balance equations and new isotopic and quantitative data using statistical and raster overlay functions embedded in a geographic information system gis oxygen and hydrogen isotopic data were recorded monthly over a 2 year period at the spring itself and in eight rain gauges in reatini mountains the effective infiltration rate was calculated using the kennessey coefficients and the turc equation finally the recharge area was identified with the help of an expert evaluation procedure local 18o and d versus altitude regression curves were used to validate the digital recharge model by comparing their expected values with the values actually measured recharge process was framed within the perspective of the ongoing local climate trends the current discharge rate of 4 1 m3 s 1 is significantly lower than the average value of 5 5 m3 s 1 measured up to the 1980s confirming the fall in the recharge discharge rate the hydrogeological system shows a delayed response due to an average groundwater residence time in the aquifer which is estimated to be about 15 20 years on the basis of the offset between calculated and observed isotope data at the main spring for this reason the system is presently not equilibrated and is gradually changing towards a final equilibrium discharge estimated in about 3 4 m3 s 1 copyright 2009 john wiley sons ltd

the hydrogeology of high mountain carbonate areas an example of some alpine systems in southern piedmont italy the hydrogeological characteristics of some springs supplied by high mountain carbonate rock aquifers located in the south of piedmont in italy are presented in this work the aquifers have different geological structural conditions including both deep and superficial karstification their catchment areas are located in a typical alpine context at a high altitude of about 2000 m these aquifers are ideal representations of the different hydrogeological situations that can be encountered in the high altitude carbonate aquifers of the mediterranean basin it is first shown how the high altitude zones present typical situations in particular related to the climate which control the infiltration processes to a great extent snowfall accumulates on the ground from november to april often reaching remarkable thicknesses the snow usually begins to melt in spring and continues to feed the aquifer for several months this type of recharge is characterized by continuous daily variations caused by the typical thermal excursions the hourly values are somewhat modest but snowmelt lasts for a long time beginning in the lower sectors and ending after various months in the higher areas abundant rainfall also occurs in the same period and this contributes further to the aquifer supply in the summer period there is very little rainfall but frequent storms in autumn abundant rainfall occurs and there are therefore short but relevant recharge events it has been shown how the trend of the yearly flow of the high mountain springs is influenced to a great extent by the snowmelt processes and autumn rainfall it has also been shown by means of the annual hydrographs of the flow and the electric conductivity of the spring water how the different examined aquifers are characterized by very different measured value trends according to the characteristics of the aquifer

the use of gps horizontals for loading studies with applications to northern california and southeast greenland received 23 august 2012 revised 15 january 2013 accepted 20 january 2013 published 25 april 2013 1 we describe how gps measurements of horizontal crustal motion can be used to augment vertical crustal motion measurements to improve and extend gps studies of surface loading we show that the ratio of the vertical displacement to the horizontal displacement combined with the direction of the horizontal motion can help determine whether nearby loading is concentrated in a small region for example in a single lake or glacier and where that region is we illustrate this method by applying it to two specific cases an analysis of gps data from northern california to monitor the level of lake shasta and the analysis of data from a single gps site in southeast greenland to determine mass variability of two large nearby outletglaciers helheim glacier and midgaard glacier the californiaexampleserves largely as a proof of concept where the results can be assessed by comparing with independent observations lake shasta tide gauge data in this case our greenland results show that both helheim and midgaard have experienced notable interannual variations in mass loss rate over the last decade helheim sm ass loss accelerated rapidly in mid 2003 decelerated in late 2005 and increased again in 2008 2009 before returning to about its pre 2003 rate in late 2010 midgaard s mass loss accelerated in mid 2004 and remained more or less constant before returning to its pre 2003 rate in late 2008

insar measurements of compaction and subsidence in the ganges brahmaputra delta bangladesh many of the world s largest river deltas are sinking due to sediment loading compaction and tectonics but also recently because of groundwater extraction hydrocarbon extraction and reduced aggradation little is known however about the full spatial variability of subsidence rates in complex delta systems this study reconstructs subsidence rates in the eastern portion of the ganges brahmaputra delta gbd bangladesh covering more than 10 000 km2 at a high spatial resolution of 100 m the map was produced using interferometric synthetic aperture radar insar covering the period 2007 to 2011 eighteen advanced land observing satellite phased array l band sar scenes were used to generate 30 interferograms calibrated with gps interferograms were stacked to yield average subsidence rates over the study period small baseline subset insar was then applied to validate the results against an additional gps record from dhaka bangladesh land subsidence of 0 to 10 mm yr is seen in dhaka with variability likely related to local variations in shallow subsurface sediment properties outside of the city rates vary from 0 to 18 mm yr with the lowest rates appearing primarily in pleistocene madhupur clay and the highest rates in holocene organic rich muds results demonstrate that subsidence in this delta is primarily controlled by local stratigraphy with rates varying by more than an order of magnitude depending on lithology the ability of l band insar to differentiate between stratigraphic units in this humid vegetated subtropical river delta demonstrates the power of interferometry as a tool for studying the subsurface in deltaic environments

comment on anomalous ocean load tide signal observed in lake level variations in tierra del fuego by a richter et al 1 where z is the deviation of the sea level from the equilibrium tide due to the dynamic forces hendershott 1972 for this small enclosed lake these dynamic forces are very small u2 is the tidal potential of degree two g the gravity value on the earth s surface and a a constant p is the self potential of the tidal water plus the potential field created by the earth s elastic deformation under the weight of the tide this potential at a particular point r can be computed by convolving the tides in the lake and all surrounding ocean tides h with a green s function g

late quaternary deglacial history of the merida andes venezuela radiocarbon dated sediment cores from seven lakes and two bogs spanning the cordillera de merida in the venezuelan andes were used to identify and date the regional history of late pleistocene and holocene glacial activity coring sites were selected at different elevations across a pronounced rain shadow from southeast wet to northwest dry sediment lithostratigraphy and magnetic susceptibility in conjunction with ams radiocarbon dates on macrofossils and char coal were used to constrain deglaciation the local expression of the last glacial maximum occurred between 22 750 and 19 960 cal yr bp on the wetter southeastern side of the cordillera de merida glaciers had significantly retreated by 15 700 cal yr bp followed by several minor glacial advances and retreats between 14 850 and 13 830 cal yr bp at least one major glacial readvance occurred between 13 830 and 10 000 cal yr bp in the wetter southeastern sector of the region the drier northwest side of the cordillera de merida records initial glacial retreat by 14 240 cal yr bp multiple sites on both sides of the merida andes record a further phase of extensive deglaciation approximately 10 000 cal yr bp however the north northwest facing mucubajo catchment remained partially glaciated until ca 6000 cal yr bp deglacial ages from the venezuelan andes are consistently younger than those reported from the southern hemisphere andes suggesting an inter hemispheric deglacial lag in the northern tropics of the order of two thousand years copyright 2005 john wiley sons ltd

lakes as paleoseismic records in a seismically active low relief area rieti basin central italy abstract small lakes in low relief areas are atypical candidates for studies on paleoseismicity but their sediments can contain seismically induced event layers seismites generated through strong ground shaking sediment transport hydrological reorganization and or changes in groundwater chemistry and flow lakes lungo and ripasottile are shallow lakes

using a spatially realistic load model to assess impacts of alaskan glacier ice loss on sea level 1 ice loss from glaciers results in highly nonuniform patterns of sea level change due to the effects of self attraction and loading to quantify these spatial effects it is necessary to obtain an ice load model that is both spatially realistic and regionally complete we demonstrate a technique to produce such a model for the alaskan glaciers by combining mass balance rates from a gravity recovery and climate experiment grace mascon solution with realistic glacier geometries this load model can be used to solve the sea level equation to determine gravitationally self consistent sea level and gravity rates the model predicts a significant drop in relative sea level in the near field of the glaciers with coastal rates of around 9 mm yr compared to a global average rise of 0 2 mm yr and significant differences to those predicted by a coarser model the magnitude and sensitivity of these near field rates imply that the near field tide gauge records could contain significant information about the spatial distribution of ice loss comparison of model gravity rates with an independently produced spherical harmonic grace solution verifies that our technique can successfully capture the mass changes estimated in the mascon solution within our higher resolution model finally we use our ice load model to examine the possibility of detecting the effects of ice loss in estimates of ocean bottom pressure obp from grace we use the model to simulate the effects of grace signal leakage and show that the obp signal from leakage has a similar pattern to but larger amplitude than the sea level fingerprint expected from ice loss

improved methods for observing earth s time variable mass distribution with grace using spherical cap mascons we discuss several classes of improvements to gravity solutions from the gravity recovery and climate experiment grace mission these include both improvements in background geophysical models and orbital parameterization leading to the unconstrained spherical harmonic solution jpl rl05 and an alternate jpl rl05m mass concentration mascon solution benefitting from those same improvements but derived in surface spherical cap mascons the mascon basis functions allow for convenient application of a priori information derived from near global geophysical models to prevent striping in the solutions the resulting mass flux solutions are shown to suffer less from leakage errors than harmonic solutions and do not necessitate empirical filters to remove north south stripes lowering the dependence on using scale factors the global mean scale factor decreases by 0 17 to gain accurate mass estimates ocean bottom pressure obp time series derived from the mascon solutions are shown to have greater correlation with in situ data than do spherical harmonic solutions increase in correlation coefficient of 0 08 globally particularly in low latitude regions with small signal power increase in correlation coefficient of 0 35 regionally in addition to reducing the error rms with respect to the in situ data reduction of 0 37 cm globally and as much as 1 cm regionally greenland and antarctica mass balance estimates derived from the mascon solutions agree within formal uncertainties with previously published results computing basin averages for hydrology applications shows general agreement between harmonic and mascon solutions for large basins however mascon solutions typically have greater resolution for smaller spatial regions in particular when studying secular signals

evidence for a younger dryas glacial advance in the andes of northwestern venezuela abstract deposits of push moraine outwash and glaciolacustrine sediments recovered from two areas in the northwestern venezuelan andes document the latest pleistocene advance of merida ice underlying peats provide maximum ages on till and outwash evidently emplaced during the younger dryas yd climatic event one example recovered from the humboldt massif where the farthest extent of yd ice buried peat in the surface of late glacial till provides a within glacier advance age of 12 4 ka cal bp the peat lies on moraine deposited during a stillstand event when the humboldt glacier retreated to the area of lago verde at 4000 m a s l approximately 0 5 km upvalley toward lago suero yd till buries peat deposited in glaciolacustrine sediments of presumed late glacial age farther north in the mucunuque mucubaji catchment of the eastern cordillera a push moraine of possible yd age buries older till of late glacial age 0 2 km upvalley outwash of yd age buries glaciolacustrine peat and organic rich alluvial sediment dated to 13 7 and 13 3 ka cal bp the latest merida advance documented here is approximately synchronous with the yd cold event of europe and the north atlantic region ca 11 6 12 7 ka cal bp the yd event in both areas of the northwestern venezuelan andes nearly reestablished earlier late glacial ice positions and termination appears to have been abrupt the valleys in both areas were evacuated of yd ice without emplacement of recessional moraines as during the main deglaciation at the humboldt site equilibrium line altitudes ela s for the late glacial were about 50 m lower than during the inferred yd in the mucunuque mucubaji catchment ela s for the late glacial 3900 m a s l are difficult to establish given the absence of lateral moraines

till as a glacial tectomict its internal architecture and the development of a typing method for till differentiation abstract till has been studied for over a century yet still a clear understanding of the mechanics of deposition and or emplacement of till eludes us tills in the past have been generally subdivided into sediments formed in various sub environments of the glacial system as such it has been generally agreed that tills can be separated in terms of these types based on various attributes such as clast fabric increasingly such separation into various sub types of till has become however highly debatable and tenuous based upon the use of micromorphology and a greater in depth appreciation of the internal architecture of till it has become apparent that previously established classifications of till are erroneous micromorphology reveals that deposition and or emplacement of tills is a complex tectonic process such that lodgement melt out and flow tills as previously defined do not appear to exist rather a new term better describes tills as glacial tectomicts by using micromorphology in establishing the presence of sets of microstructures a statistical method is introduced that permits differentiation of tills from other diamictons the implications for this new understanding of tills allied to statistical typing is considerable in terms of till formation glacial stratigraphy and understanding glacial environments in terms of stress histories porewater transmission subglacial deformation mechanics till rheological phase changes and the timeline of till formation

vertical gps ground motion rates in the euro mediterranean region new evidence of velocity gradients at different spatial scales along the nubia eurasia plate boundary we use 2 5 to 14 years long position time series from 800 continuous global positioning system gps stations to study vertical deformation rates in the euro mediterranean region we estimate and remove common mode errors in position time series using a principal component analysis obtaining a significant gain in the signal to noise ratio of the displacements data following the results of a maximum likelihood estimation analysis which gives a mean spectral index 0 7 we adopt a power law white noise stochastic model in estimating the final vertical rates and find 95 of the velocities within 2 mm yr with uncertainties from filtered time series 40 smaller than from the unfiltered ones we highlight the presence of statistically significant velocity gradients where the stations density is higher we find undulations of the vertical velocity field at different spatial scales both in tectonically active regions like eastern alps apennines and eastern mediterranean and in regions characterized by a low or negligible tectonic activity like central iberia and western alps a correlation between smooth vertical velocities and topographic features is apparent in many sectors of the study area glacial isostatic adjustment and weathering processes do not completely explain the measured rates and a combination of active tectonics and deep seated geodynamic processes must be invoked excluding areas where localized processes are likely or where subduction processes may be active mantle dynamics is the most likely process but regional mantle modeling is required for a better understanding

horizontal motion in elastic response to seasonal loading of rain water in the amazon basin and monsoon water in southeast asia observed by gps and inferred from grace 1 we find seasonal horizontal crustal motions observed by gps positioning in elastic response to heavy rainfall in the amazon basin and to monsoons in southeast asia to be consistent with those inferred from gravity recovery and climate experiment grace gravity observations of water mass loading solid earth moves toward the amazon during heavy spring rainfall and toward southeast asia during summer monsoons and back away from these areas 6 months later when the water load is minimum vertical oscillations observed by gps and inferred from grace are 2 to 3 times larger than horizontal oscillation near the margins of the areas of large mass loading some discrepancies between gps and grace are probably caused by local effects that influence gps measurements because the gps sites that show significant discrepancies also do not match nearby gps sites however when the load is short wavelength the limited spatial resolution of grace can cause systematic misfits

origin of the international terrestrial reference frame 1 with recent improvements in space geodesy the earth s center of mass cm and center of figure cf are no longer indistinguishable the current origin of the international terrestrial reference frame itrf is defined as the cm which shows measured seasonal variations of several millimeters to 1 cm with respect to true cm as scientists study earth s dynamic deformations on seasonal and shorter timescales and begin to compare observed geocenter motion with predictions from geophysical models the reference frame origin presents significant error due to missing the geocenter motion this paper discusses the nature of the origin of the itrf and explores the sensitivity of gps measurements to geocenter motion we find that since the values of nonlinear geocenter motion are not included in the positions of the itrf sites the behavior of the current itrf origin reflects cm on secular timescale but reflects cf on seasonal and short timescales the nature of the itrf origin depends on both the adopted kinematic model and unmodeled network motion the realized itrf origin should be defined by a new nomenclature to reflect its nature accurately by the new nomenclature the origin will maintain its current long term stability while improving its stability on seasonal timescales to the submillimeter level with the degree 1 deformation approach gps measurements are able to provide potentially valuable information on geocenter variations on seasonal and short timescales

active tectonics and earthquake potential of the myanmar region this paper describes geomorphologic evidence for the principal neotectonic features of myanmar and its immediate surroundings we combine this evidence with published structural geodetic and seismic data to present an overview of the active tectonic architecture of the region and its seismic potential three tectonic systems accommodate oblique collision of the indian plate with southeast asia and extrusion of asian territory around the eastern syntaxis of the himalayan mountain range subduction and collision associated with the sunda megathrust beneath and within the indoburman range and naga hills accommodate most of the shortening across the transpressional plate boundary the sagaing fault system is the predominant locus of dextral motion associated with the northward translation of india left lateral faults of the northern shan plateau northern laos thailand and southern china facilitate extrusion of rocks around the eastern syntaxis of the himalaya all of these systems have produced major earthquakes within recorded history and continue to present major seismic hazards in the region

numerical simulations of global scale high resolution hydrological crustal deformations 1 high resolution load induced crustal deformations calculated from numerical models are tested for their ability to predict hydrologically induced station height variability as they are known to be large enough to affect epoch wise parameters obtained from the analysis of global geodetic networks loading contributions due to terrestrial water storage as given by global hydrological models are calculated on a 0 5 global regular grid with daily temporal resolution apart from the dominant seasonal variations the hydrological loading signal discloses also rapid changes exceeding 1 mm in several regions that can be associated with major precipitation events and river floods locally strong loading signals with exceptionally high amplitudes in many cases even with nonseasonal nature occur along the major river channels only high resolution loading calculations considering also the water mass anomalies stored in the model river flow can resolve the correct amplitudes in the surrounded area up to 100 km distance the comparison of the modeled hydrological surface deformation with gps station time series shows that high resolution hydrological loading estimates based on global scale models are able to explain a considerable fraction up to 54 of the observed vertical station movements caused by continental water storage variations

characterization of pebble fabrics in modern terrestrial glacigenic sediments pebble fabric data are available from several facies of glacigenic sediments deposited by modern glaciers where sedimentary processes can be observed or inferred with relatively little ambiguity over 100 samples from contemporary environments illustrate fabrics characterizing melt out till deformed and undeformed lodgement till sediment flow deposits and ice slope colluvium lodgement till fabric variability is related to the two layer structure of these sediments a structureless friable upper layer with low shear strength and high consolidation coefficient overlying a very compact material of horizontal platy structure fabric strength assessed by eigenvalue analysis is weaker and pebble dip is more dispersed in the upper structureless horizon stronger fabrics in the lower platy horizon may be primary depositional fabrics which are destroyed by subglacial shearing to give weaker fabrics in the upper horizon alternatively upper horizon fabrics may be characteristic of all recently deposited lodgement tills with stronger fabrics developing at depth by dewatering and consolidation there is a general reduction in fabric strength and an increase in particle dip associated with the transition from melt out tills through undeformed and deformed lodgement tills to sediment flow deposits and ice slope colluvium there is however considerable overlap in the fabric strengths characteristic of sediment flow deposits and deformed lodgement tills fabric data from modern glacial sedimentary facies are used to assist in interpreting the mode of deposition of some quaternary glacial sediments relatively strong fabrics characteristic of melt out tills and undeformed lodgement tills are more likely to be diagnostic of genesis than weaker fabrics associated with deformed sediments

2700 years of mediterranean environmental change in central italy a synthesis of sedimentary and cultural records to interpret past impacts of climate on society abstract abrupt climate change in the past is thought to have disrupted societies by accelerating environmental degradation potentially leading to cultural collapse linking climate change directly to societal disruption is challenging because socioeconomic factors also play a large role with climate being secondary or sometimes inconsequential combining paleolimnologic historical and archaeological methods provides for a more secure basis for interpreting the past impacts of climate on society we present pollen non pollen palynomorph geochemical paleomagnetic and sedimentary data from a high resolution 2700 yr lake sediment core from central italy and compare these data with local historical documents and archeological surveys to reconstruct a record of environmental change in relation to socioeconomic history and climatic fluctuations here we document cases in which environmental change is strongly linked to changes in local land management practices in the absence of clear climatic change as well as examples when climate change appears to have been a strong catalyst that resulted in significant environmental change that impacted local communities during the imperial roman period despite a long period of stable mild climate and a large urban population in nearby rome our site shows only limited evidence for environmental degradation warm and mild climate during the medieval warm period on the other hand led to widespread deforestation and erosion the ability of the romans to utilize imported resources through an extensive trade network may have allowed for preservation of the environment near the roman capital whereas during medieval time the need to rely on local resources led to environmental degradation cool wet climate during the little ice age led to a breakdown in local land use practices widespread land abandonment and rapid reforestation our results present a high resolution regional case study that explores the effect of climate change on society for an under documented region of europe

paleopedology of middle wisconsin weichselian paleosols in the merida andes venezuela abstract buried spodosols podzols within a thick lithostratigraphic section in the northern venezuelan andes are interbedded with tills and a succession of multicyclic lacustrine clays silts and sands from the early and middle stades of the wisconsinan weichselian glaciation the peats dated by ams radiocarbon allow calculations of the time required for pedogenesis these spodosols were studied to determine compositional changes from initial to full soil development during lake low water stands peats of variable thickness developed along with soils belonging to the spodosol order on a relative time scale the initial stage of soil genesis produced peat with a weathered mineral zone bs initial spodic horizon of a few centimeters thickness with a longer time for soil genesis of a few centuries a thin spodosol developed with an e bs horizon sequence with still longer time spans of a few thousand years between 55 and 60 ka more mature spodosols with e bs cox cu profiles formed beneath very thick peat in conjunction with groundwater fluctuations the lowermost peat vii in the section varies from 15 to 26 5 cm in thickness the paleosols are sandy with little evidence of either clay transformations or silt accretion from airfall influx apparent from the particle size analysis xrd analysis of the clay fraction shows minor weathering of illite to vermiculite and chlorite in the bs horizons chemically extractable forms of fe and al show increases of both soluble and insoluble minerals from the e to the bs horizons in the buried spodosols a considerably different trend compared with the surface soils entisols geochemical trace element analysis shows a moderate degree of translocation of soluble chemical elements from the e to the bs horizons

a new global mode of earth deformation seasonal cycle detected we have detected a global mode of earth deformation that is predicted by theory precise positioning of global positioning system sites distributed worldwide reveals that during february to march the northern hemisphere compresses and the southern hemisphere expands such that sites near the north pole move downward by 3 0 millimeters and sites near the equator are pulled northward by 1 5 millimeters the opposite pattern of deformation occurs during august to september we identify this pattern as the degree one spherical harmonic response of an elastic earth to increased winter loading of soil moisture snow cover and atmosphere data inversion shows the load moment s trajectory as a great circle traversing the continents peaking at 6 9 1022 kilogram meters near the north pole in winter indicating interhemispheric mass exchange of 1 0 1016 0 2 1016 kilograms

tidal asymmetry and residual circulation over linear sandbanks and their implication on sediment transport a process oriented numerical study received 12 january 2007 revised 24 july 2007 accepted 17 september 2007 published 22 december 2007 1 a series of process oriented numerical simulations is carried out in order to evaluate the relative role of locally generated residual flow and overtides on net sediment transport over linear sandbanks the idealized bathymetry and forcing are similar to those present in the norfolk sandbanks north sea the importance of bottom drag parameterization and bank orientation with respect to the ambient flow is examined in terms of residual flow and overtide generation and subsequent sediment transport implications are discussed the results show that although the magnitudes of residual flow and overtides are sensitive to bottom roughness parameterization and bank orientation the magnitude of the generated residual flow is always larger than that of the locally generated overtides also net sediment transport is always dominated by the nonlinear interaction of the residual flow and the semidiurnal tidal currents although cross bank sediment transport can occur even in the absence of a cross shore residual flow on the other hand net sediment divergence convergence increases as the bottom drag decreases and as bank orientation increases the sediment erosion deposition is not symmetric about the crest of the bank suggesting that originally symmetric banks would have the tendency to become asymmetric

chattermark trails surface features on detrital quartz grains indicative of a tropical climate abstract with respect to weathering erosional processes and sediment transport quartz is one of the most stable minerals and makes up to 98 of the mineral volume of siliciclastic sands pettijohn et al 1987 although a major component in a wide variety of rocks quartz has almost no characteristic properties that allow determining parent rock types quartz does not contain characteristic cleavage planes and quartz grains react to impact or collision with other sediment particles by producing conchoidal fractures very similar to those observed for broken glass for sedimentologists physical geographers and soil scientists detrital quartz grains are poor in characteristic features except for a suite of surface features that may be indicative of various transport environments or even climate related alterations one of these surface features are chattermark trails chattermark trails are a series of linearly arranged rune like grooves on surfaces of minerals grains such as quartz and garnet lacking any type of cleavage these trails have been described from many unconsolidated sediments and are attributed mostly to glacial sediments laboratory experiments on polished quartz beads reveal that chattermark trails are not primary surface features but become visible after etching by dilute hydrofluoric acid comparison of the etched and non etched surface of the same quartz bead reveals that mechanically produced invisible cracks related to blunt collisions with other polished quartz beads became visible only after chemical etching chattermark trails on detrital quartz grains are the product of two processes the dynamic one is an invisible transport related blunt collision followed by a second stationary process which enables quartz dissolution to make the chattermarks visible in the broad field of laterite research it is well accepted that quartz dissolution in surface or near surface deposits is restricted to stationary chemical weathering in a wet tropical or at least subtropical climate drawing on this information chattermark trails are no longer considered a product of a specific sedimentary environment but reveal a distinct history of the quartz grain they are formed by blunt collisions in a sediment transport stage before experiencing some dissolution during a depositional stage in a tropical climate grains can be remobilized in an active sediment transport system collectively the results reveal that chattermark trails on quartz grains provide unique insights into the transport and climate history of sediments

modeling earth deformation from monsoonal flooding in bangladesh using hydrographic gps and gravity recovery and climate experiment grace data 1 the ganges brahmaputra and meghna rivers converge in bangladesh with an annual discharge second to the amazon most of the flow occurs during the summer monsoon causing widespread flooding the impounded water represents a large surface load whose effects can be observed in gravity recovery and climate experiment grace and gps data bangladesh is at the center of the second largest seasonal anomaly in the grace gravity field reflecting water storage in southeast asia eighteen continuous gps stations in bangladesh record seasonal vertical motions up to 6 cm that inversely correlate to river level we use 304 river gages to compute water height surfaces with a digital elevation model to separate surface water from groundwater porosity of 20 was used to estimate groundwater mass and calculate the water load results show 100 gt of water are stored in bangladesh 7 5 of annual discharge but can reach 150 gt during extreme events the calculated water mass agrees with monthly grace water mass equivalents from bangladesh within statistical limits we compute the deformation due to this water load on an elastic half space and we vary young s modulus to fit gps data from our two most continuous records the water loading can account for 50 of the variance in the gps data the best fitting young s modulus is 117 124 gpa for dhak and 133 135 gpa for sust although the upper bound is not well constrained these estimates lie between sediment 30 75 gpa and mantle 190 gpa values indicating that response to loading is sensitive to structure throughout the lithosphere and is not absorbed by the weak sediments

chemical and isotopic δ18o δ2h δ13c 222rn multi tracing for groundwater conceptual model of carbonate aquifer gran sasso infn underground laboratory central italy summary a hydrochemical and isotope study was conducted on the drainage waters of an underground laboratory located inside the gran sasso massif central italy the study was expected to improve the conceptual model of groundwater circulation at the base of an over 1000 thick unsaturated zone in the gran sasso partitioned karst aquifer this lithostratigraphically and tectonically complex aquifer is typical of africa europe thrust and fold collision belt in the mediterranean area in this case investigations on water rock interactions during recharge in complex aquifers overlaid by a thick unsaturated zone have been made thanks to the strategic location of the gran sasso underground laboratories located in the core of a huge carbonate aquifer knowledge of the local basic hydrogeological setting was the starting point for a detailed hydrogeochemical and isotopic study which was carried out at the aquifer scale and at the fine scale in the underground laboratories the water rock interaction processes were investigated both spatially and in temporal sequences analysing recharge waters and groundwater in the underground laboratories by multitracing techniques including major ions and 18o 2h and 13c stable isotopes use of 222rn provides information on transit time in the aquifer processes proved to be typical of carbonate rocks with clear influence of vertical movement of water on chemical physical parameters through the unsaturated zone conversely in the saturated zone these processes proved to be dominantly affected by local geological structural conditions a conceptual model with dual flow velocity is proposed directly related to the local geological structural setting 222rn decay enables to calculate an effective velocity of around 10 m day for the fracture network through the sequence of less permeable dolomites and underlying limestone lag time between recharge and chemical changes in the saturated zone testifies to an effective velocity of about 35 m day for fast flow through recent and active extensional faults

a soil chronosequence in late glacial and neoglacial moraines humboldt glacier northwestern venezuelan andes abstract late glacial and neoglacial little ice age deposits on the humboldt massif were analyzed for relative age dating parameters including geomorphic and weathering characteristics geochemical and soil properties the soil chronosequence formed in chemically uniform parent materials provides an important database to study soil evolution in a tropical alpine environment extractable and total fe and al concentrations examined to assess their use in relative age determination and as paleoenvironmental indicators provide an important measure of the accumulation and downward profile movement over time of organically bound al ferrihydrite and other crystalline forms hematite and goethite of extractable fe ferrihydrite is particularly useful in determining former perched water levels in soils with relation to paleoclimate the ratios of most fe extracts are time dependent the fe d fe t ratio within statistical limits shows a slow increase from lia little ice age to late glacial soils which closely correlates with other alpine soil studies in the middle latitudes and other tropical alpine locales values of al d dithionite and al o oxalate extractable generally do not correlate with time however al p pyrophosphate extractable measured against al t total provides insight on the downward translocation over time of organically bound al low leaching rates in this chronosequence are further supported by clay mineralogy trends and the geochemical data

global estimates of lunar iron and titanium contents from the chang e 1 iim data 1 until recently global high spatial resolution maps of feo and tio2 of the moon were only derived from clementine data in this study we show global maps of feo and tio2 using chang e 1 interference imaging spectrometer iim at a spatial resolution of 200 m pixel with a newly developed calibration presented here spectra obtained by iim compare well with telescopic spectra spectral parameters previously shown to be sensitive to iron and titanium derived from the calibrated iim data are highly correlated with the measured elemental concentration with r2 0 96 for feo and 0 95 for tio2 the maps were developed using this calibration histograms of basalt feo estimates have a negatively skewed distribution while tio2 distributions are unimodal they also revealed that the lunar highland crust is relatively uniform on the quadrant scale several hundred to thousand kilometers scale but inhomogenous on the global scale the area of highest elevation of the moon has very low feo and tio2 raising the question about south pole aitken spa whether its ejecta deposits covered the highest elevation and when it was formed although the average feo and tio2 abundances for basalts are highly correlated local areas of elevated iron can be associated with both high and low titanium

reconstruction of the early merida pre lgm glaciation with comparison to late glacial maximum till northwestern venezuelan andes abstract valley glaciers have been well studied in the northwestern venezuelan andes over the last 20 year period with most sourcing reconstructions limited to the last glacial maximum lgm and confined to the mapping of moraine positions and the detailed analysis of pedostratigraphic sequences reaching back into the middle wisconsinan weichselian glaciation using bedding macrofeatures fabric analysis magnetic azimuths with mirror images clast inclination and microtextural evidence determined with the fe sem field emission scanning electron microscopy and eds energy dispersive spectroscopy and micromorphology of the ped5 composite section of early to late merida age was analyzed to reconstruct the till succession and glacial dynamics the fabric is used to reconstruct the build up of valley ice in the lower mucunuque valley the icecap spreading over the upper catchments of neighbouring drainage basins toward the headwaters of the mucuchache valley over a time frame estimated to be

seasonal and long term vertical deformation in the nepal himalaya constrained by gps and grace measurements 1 we analyze continuous gps measurements in nepal southern side of the himalaya and compare gps results with grace observations in this area we find both gps and grace show significant seasonal variations further comparison indicates that the observed seasonal gps height variation and grace derived seasonal vertical displacement due to the changing hydrologic load exhibit very consistent results for both amplitude and phase for continuous gps stations whose observation time span are longer than 3 years the average wrms reduction is 45 when we subtract grace derived vertical displacements from gps observed time series the comparison for annual amplitudes between gps observed and grace derived seasonal displacements also shows consistent correlation the good seasonal correlation between gps and grace is due to the improved gps processing strategies and also because of the strong seasonal hydrological variations in nepal besides the seasonal signal grace also indicates a long term mass loss in the himalaya region assuming no gia effect this mass loss therefore will lead to crustal uplift since the earth behaves as an elastic body we model this effect and remove it from gps observed vertical rates with a 2d dislocation model most gps vertical rates especially in the central part of nepal can be interpreted by interseismic strain from the main himalayan thrust and several exceptions may indicate the complexity of vertical motion in this region and some potential local effects

reconstruction of the pre merida glaciation northwestern venezuelan andes abstract valley glaciers have been well studied in the northwestern venezuelan andes over the last 20 year period but most reconstructions have been limited to the last glacial maximum lgm analyses have been confined to the mapping of moraine positions and the detailed analysis of pedostratigraphic sequences reaching back through the middle to the early wisconsinan weichselian glaciation using bedding macrofeatures fabric analysis magnetic azimuths with mirror images clast inclination and microtextural evidence much has been learned about the lithology source of ice growth of an ice cap in the eastern cordillera and weathered state of surface paleosols analysis of two sections of pre merida age the only two such sections known in the sierra de santa domingo eastern cordillera provides new information on lithology source of the ice and weathered state of sediment of pre merida age the fabric in these sections is used to deduce the build up of valley ice in the lower el caballo valley from an ice cap similar to one that developed later in early merida time 90 ka to 65 ka the presence of weathered tills in both sections suggests two glaciations perhaps correlative with the illinoian and kansan glaciations of north america the weathered state of tills and outwash in both sections is assessed on the basis of geochemical inaa and mineral composition xrd and microtextural evidence determined by sem eds

glacigenic clast fabrics genetic fingerprint or wishful thinking the interpretation of glacigenic diamictons is a subjective process for which quantitative support is frequently sought from parameters such as clast shape and fabric it has been widely suggested that different glacigenic diamicton facies possess distinct clast fabric signatures this paper examines this concept using a data set of 111 clast fabrics and a synthesis of published results eigenvalues are calculated and compared for a variety sedimentary facies it is concluded that clast fabric alone is not able to discriminate between different glacigenic facies and it is argued that clast fabric offers little quantitative support in the interpretation of glacigenic sediments it is suggested therefore that although clast fabric may continue to have a role as an indicator of relative strain at specific sites its use in the discrimination of glacigenic facies is limited consequently we should be much more selective in undertaking such analyses in the future copyright 1999 john wiley sons ltd

isotopic composition of precipitation in italy a first overall map abstract composite monthly samples of atmospheric precipitation were collected over different periods of time ranging from one to seven years at 77 different locations throughout italy these samples were measured for their oxygen and hydrogen isotopic composition to obtain basic information for hydrological and meteorological studies in this area on the basis of the results obtained a first map of the isotopic composition of precipitations in italy has been drawn up the main features of this map are the following 1 no isotopic latitudinal gradient has been found along the tyrrhenian coast from sicily to the italian french border despite the considerable range of latitude 2 a minor latitudinal gradient is found in the southeasternmost section of the country apulia partially favored by the local morphology 3 a marked shadow effect of the apennines is apparent along the southern section of the po valley and along the central section of the adriatic coast 4 the contribution of water vapor from the northernmost section of the adriatic sea affects the eastern and central sections of the po plain 5 the shadow effect of the alps is considerably smaller than expected 6 the isotopic vertical gradients calculated in nine different areas and based on groups of two to five different stations vary but are essentially close to about 0 2 100 m 7 when mean monthly temperature values were available their relationship with the isotopic composition of precipitation was found to be on average very poor 8 the relationship between mean 18o and mean d calculated for the collection locations shows shifts of both the slope and the deuterium excess when compared to the global meteoric water line these shifts are different for northern central and southern italy 9 in a few cases anomalously low monthly values suggest the existence of pronounced amount effects

a comparison of annual vertical crustal displacements from gps and gravity recovery and climate experiment grace over europe 1 we compare approximately 3 years of gps height residuals with respect to the international terrestrial reference frame with predictions of vertical surface displacements derived from the gravity recovery and climate experiment grace gravity fields for stations in europe an annual signal fit to the residual monthly heights corrected for atmospheric pressure and barotropic ocean loading effects should primarily represent surface displacements due to long wavelength variations in water storage a comparison of the annual height signal from gps and grace over europe indicates that at most sites the annual signals do not agree in amplitude or phase we find that unlike the annual signal predicted from grace the annual signal in the gps heights is not coherent over the region displaying significant variability from site to site confidence in the grace data and the unlikely possibility of large amplitude small scale features in the load field not captured by the grace data leads us to conclude that some of the discrepancy between the gps and grace observations is due to technique errors in the gps data processing this is evidenced by the fact that the disagreement between gps and grace is largest at coastal sites where mismodeling of the semidiurnal ocean tidal loading signal can result in spurious annual signals