direct determination of the timing of sea level change during termination ii an outcrop within the last interglacial terrace on barbados contains corals that grew during the penultimate deglaciation or termination ii we used combined 230th and231pa dating to determine that they grew 135 8 0 8 thousand years ago indicating that sea level was 18 3 meters below present sea level at the time this suggests that sea level had risen to within 20 of its peak last interglacial value by 136 thousand years ago in conflict with milankovitch theory predictions orbital forcing may have played a role in the deglaciation as may have isostatic adjustments due to large ice sheets other corals in the same outcrop grew during oxygen isotope 18o substage 6e indicating that sea level was 38 5 meters below present sea level about 168 0 thousand years ago when compared to the 18o signal in the benthic v19 30 v19 28 record at that time the coral data extend to the previous glacial cycle the conclusion that deep water temperatures were colder during glacial periods

evidence from u th dating against northern hemisphere forcing of the penultimate deglaciation milankovitch proposed that summer insolation at mid latitudes in the northern hemisphere directly causes the ice age climate cycles1 this would imply that times of ice sheet collapse should correspond to peaks in northern hemisphere june insolation but the penultimate deglaciation has proved controversial because june insolation peaks 127 kyr ago whereas several records of past climate suggest that change may have occurred up to 15 kyr earlier2 3 4 5 6 7 8 there is a clear signature of the penultimate deglaciation in marine oxygen isotope records but dating this event which is significantly before the 14c age range has not been possible here we date the penultimate deglaciation in a record from the bahamas using a new u th isochron technique after the necessary corrections for recoil mobility of 234u and 230th and a small age correction for sediment mixing the midpoint age for the penultimate deglaciation is determined to be 135 2 5 kyr ago this age is consistent with some coral based sea level estimates but it is difficult to reconcile with june northern hemisphere insolation as the trigger for the ice age cycles potential alternative driving mechanisms for the ice age cycles that are consistent with such an early date for the penultimate deglaciation are either the variability of the tropical ocean atmosphere system or changes in atmospheric co2 concentration controlled by a process in the southern hemisphere

time frequency seismic data de noising marine seismic data are always affected by noise an effective method to handle a broad range of noise problems is a time frequency de noising algorithm in this paper we explain details regarding the implementation of such a method special emphasis is given to the choice of threshold values where several different strategies are investigated in addition we present a number of processing results where time frequency de noising has been successfully applied to attenuate noise resulting from swell cavitation strumming and seismic interference our seismic interference noise removal approach applies time frequency de noising on slowness gathers p domain this processing trick represents a novel approach which efficiently handles certain types of seismic interference noise that otherwise are difficult to attenuate we show that time frequency de noising is an effective amplitude preserving and robust tool that gives superior results compared to many other conventional de noising algorithms for example frequency filtering p or fx prediction as a background some of the physical mechanisms responsible for the different types of noise are also explained such physical understanding is important because it can provide guidelines for future survey planning and for the actual processing

on the spatial properties of ambient noise in the tonga trench including effects of bathymetric shadowing in september 2012 the free falling deep diving instrument platform deep sound iii descended to the bottom of the tonga trench where it resided at a depth of 8515 m for almost 3 h recording ambient noise data on four hydrophones arranged in a vertical l shaped configuration the time series from each of the hydrophones yielded the power spectrum of the noise over the frequency band 3 hz to 30 khz the spatial coherence functions along with the corresponding cross correlation functions were recovered from all available hydrophone pairs in the vertical and the horizontal the vertical coherence and cross correlation data closely follow the predictions of a simple theory of sea surface noise in a semi infinite ocean suggesting that the seabed in the tonga trench is a very poor acoustic reflector which is consistent with the fact that the sediment at the bottom of the trench consists of very fine grained material having an acoustic impedance similar to that of seawater the horizontal coherence and cross correlation data are a little more complicated showing evidence of a bathymetric shadowing of the noise by the walls of the trench and b highly directional acoustic arrivals from the research vessel supporting the experiment

age budget and dynamics of an active salt extrusion in iran the hormuz salt of kuh e namak iran began rising through its phanerozoic cover in jurassic times and had surfaced by cretaceous times in miocene times the still active zagros folds began to develop and the salt is still extruding to feed a massive topographic dome and two surface flows of salt which have previously been called salt glaciers but are here called namakiers two crude but independent estimates for the rate of salt extrusion and loss are shown to balance the salt budget if the current salt dynamics are assumed to be in steady state first to replace the extrusive salt likely to be lost in solution in the annual rainfall the salt must rise at an average velocity of about 11 cm a second the foliation pattern shows that the extruding and partially dissolved salt column spreads under its own weight the maximum height of the salt dome is consistent with a viscous fluid with a viscosity of 2 6 x 1017 poises extruding from its orifice at a rate of almost 17 cm a k both estimates are consistent in indicating that salt can extrude onto the surface 42 85 times faster than the average long term rate at which salt diapirs rise to the surface the structure fabrics textures and deformation mechanisms of the impure halite all change along the path of the extrusive salt from the dome down the length of both namakiers such changes tend to occur when the flowing salt encounters changes in its boundary conditions and the recognition of buried namakiers is discussed in the light of such observations episodes of salt flow at a rate of 0 5 m per day have been measured along the margin of the n namakier after significant rain showers such brief episodes of rapid flow alternate with long periods when the namakier is dry and stationary the shape of the colour bands cropping out on the n namakier indicate that the flow over the surface of impure salt with a mylonitic texture obeys a power law with n 3 although the reported annual rainfall has the potential of dissolving both namakiers in about 2000 years a superimposed thin marine cover may protect static parts of them for as long as 30 000 to 300 000 years

evidence for an east west regional gravity trend in northern tunisia insight into the structural evolution of northern tunisian atlas abstract the atlas orogeny in northern algeria and tunisia led to the destruction of tethys oceanic lithosphere and cumulated in a collision of microplates rifted off the european margin with the north african continental margin the location of the boundary between african plate and kabylian microplate is expressed in northern algeria by a crustal wedge with double vergence of thrust sheets whereas in northern tunisia the geologic environment is more complex and the location of the plate boundary is ambiguous in this study we analyzed gravity data to constrain the crustal structure along the northern margin of tunisia the analysis includes a separation of regional and residual gravity anomalies and the application of gradient operators to locate density contrast boundaries the horizontal gradient magnitude and directional gradient highlight a prominent regional e w gravity gradient in the northern tunisian atlas interpreted as a deep fault active since at least the early mesozoic having a variable kinematic activity depending on the tectonic regime in the region the main e w gravity gradient separates two blocks having different gravitational and seismic responses the southern block has numerous gravity lineaments trending in different directions implying several density variations within the crust whereas the northern block shows a long wavelength negative gravity anomaly with a few lineaments taking into account the geologic context of the western mediterranean region we consider the e w prominent feature as the boundary between african plate and kabylian microplate in northern tunisia that rifted off europe this hypothesis fits most previous geological and geophysical studies and has an important impact on the petroleum and mineral resource prospection as these two blocks were separated by an ocean and they did not belong to the same margin

practical modifications to improve the sledgehammer seismic source we have examined frequency and amplitude changes in high resolution seismic reflection data associated with practical modifications to the sledgehammer method our seismic data acquired at three sites with different near surface geology demonstrate the effects of seating the plate prior to recording of centered versus noncentered impacts of subsurface plate emplacement of various plate surface covers and of aluminum versus steel impact plates impacts on well seated plates produced as much as 4 db higher seismic amplitude than data recorded using unseated plates and increased the ratio of high to low frequencies sledgehammer impacts on the edge of the plate decreased seismic amplitude by 6 to 12 db for frequencies above 100 hz compared to centered impacts placement of the impact plate 1 meter below the ground surface produced a 12 db amplitude increase for frequencies above 130 hz at one test site plates made of either steel alloy or aluminum produced equivalent seismic signals the site dependent nature of some of our results suggests that other investigators may benefit from conducting similar experiments prior to acquiring shallow seismic reflection data when using the sledgehammer source

high resolution record of climate stability in france during the last interglacial period the last interglacial period 127 110 kyr ago has been considered to be an analogue to the present interglacial period the holocene which may help us to understand present climate evolution but whereas holocene climate has been essentially stable in europe variability in climate during the last interglacial period has remained unresolved because climate reconstructions from ice cores1 2 continental records3 4 and marine sediment cores5 6 give conflicting results for this period7 here we present a high resolution multi proxy lacustrine record of climate change during the last interglacial period based on oxygen isotopes in diatom silica diatom assemblages and pollen climate transfer functions from the ribains maar in france contrary to a previous study8 our data do not show a cold event interrupting the warm interglacial climate instead we find an early temperature maximum with a transition to a colder climate about halfway through the sequence the end of the interglacial period is clearly marked by an abrupt change in all proxy records our study confirms that in southwestern europe the last interglacial period was a time of climatic stability and is therefore still likely to represent a useful analogue for the present climate

present day temperatures in northern scandinavia during the last glaciation scandinavia is generally considered to have been covered extensively with ice throughout marine isotope stages mis 4 2 between 75 and 10 ka here we present evidence for ice free warm conditions in the central area of the scandinavian glaciations during mis 3 our multiproxy data obtained from a lacustrine sequence in northern fin land reveal not only significant response in the northeastern sector of the scandinavian ice sheet to warming during the early part of mis 3 but also indicate rapid climate warming to present day temperatures in this ice free period new climate model simulations for interstadial conditions in mis 3 confirm the high mean july temperatures northeast of the scandinavian ice sheet in response to the high insolation values and the presence of the ice sheet during mis 3

persistent solar influence on north atlantic climate during the holocene surface winds and surface ocean hydrography in the subpolar north atlantic appear to have been influenced by variations in solar output through the entire holocene the evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon 14 and beryllium 10 and centennial to millennial time scale changes in proxies of drift ice measured in deep sea sediment cores a solar forcing mechanism therefore may underlie at least the holocene segment of the north atlantic9s 1500 year cycle the surface hydrographic changes may have affected production of north atlantic deep water potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally

termination ii interstadial stadial climate change recorded in two stalagmites from the north european alps abstract understanding the sequence of events that take place during glacial interglacial climate transitions is important for improving our knowledge of abrupt climate change here we present a new stacked high resolution precisely dated speleothem stable isotope record from the northern alps which provides an important record of temperature and moisture source changes between 134 and 111 ka for europe and the wider north atlantic realm the record encompasses the penultimate deglaciation termination ii tii which lies beyond the limit of radiocarbon dating thus providing an important new archive for a crucial period of rapid paleoclimate change warmer and wetter ice free conditions were achieved by 134 1 0 7 ka modelled ages as indicated by the presence of liquid water at the site temperatures warmed further at 133 7 0 5 ka and led into an interstadial synchronous with slightly elevated monsoon strength during the week monsoon interval the interstadial experienced an unstable climate with a trough in temperature associated with a slowdown in atlantic meridional overturning circulation amoc and a reduction in north atlantic deep water nadw formation the interstadial ended with a more extreme cold reversal lasting 500 years in which nadw formation remained active but the subpolar gyre weakened allowing cool polar waters to penetrate southwards the main warming associated with tii was very rapid taking place between 130 9 0 9 and 130 7 0 9 ka coeval with initial monsoon strengthening temperatures then plateaued before being interrupted by a 600 year cold event at 129 1 0 6 ka associated once again with penetration of polar waters southwards into the north atlantic and a slowdown in monsoon strengthening sub orbital climate oscillations were thus a feature of tii in the north atlantic realm which broadly resemble the bolling allerod younger dryas 8 2 ka event pattern of change observed in termination i despite monsoon records indicating strong differences between the last and penultimate deglaciation

depth dependence of wind driven broadband ambient noise in the philippine sea in 2009 as part of philsea09 the instrument platform known as deep sound was deployed in the philippine sea descending under gravity to a depth of 6000 m where it released a drop weight allowing buoyancy to return it to the surface on the descent and ascent at a speed of 0 6 m s deep sound continuously recorded broadband ambient noise on two vertically aligned hydrophones separated by 0 5 m for frequencies between 1 and 10 khz essentially all the noise was found to be downward traveling exhibiting a depth independent directional density function having the simple form cos where 90 is the polar angle measured from the zenith the spatial coherence and cross spectral density of the noise show no change in character in the vicinity of the critical depth consistent with a local wind driven surface source distribution the coherence function accurately matches that predicted by a simple model of deep water wind generated noise provided that the theoretical coherence is evaluated using the local sound speed a straightforward inversion procedure is introduced for recovering the sound speed profile from the cross correlation function of the noise returning sound speeds with a root mean square error relative to an independently measured profile of 8 2 m s

start of the last interglacial period at 135 ka evidence from a high alpine speleothem a detailed study of growth periods of a flowstone from spannagel cave in the zillertal alps austria at 2500 m above sea level a site highly sensitive to climate changes offers unprecedented new insights into pleistocene climate change in central europe flowstone sample spa 52 has a high u content to 116 ppm analyses of this sample reveal that episodes of calcite deposition started at 204 3 ka 135 1 2 ka and 122 ka suggesting that at these times the mean air temperature at this high alpine site was within 1 5 c of the present day condition the beginning of growth at 135 ka corresponds to the ending of the last glaciation and is concordant with a midpoint age for the penultimate deglaciation at 135 2 5 ka as deduced from the absolutely dated oxygen isotope curve in sediments from the bahamas as well as with recent coral evidence from barbados indicating a high sea level already by 135 8 0 8 ka this set of data supports evidence against northern hemisphere forcing of termination ii because the insolation maximum is at 127 ka

interglacial environments of coastal east antarctica comparison of mis 1 holocene and mis 5e last interglacial lake sediment records we reconstruct terrestrial and freshwater environments of the last two quaternary interglacials in coastal east antarctica by examining multi proxy evidence in a lake sediment core the record from progress lake in the larsemann hills consists of two discrete sediment units the lower unit contains the first known evidence of antarctic coastal environments during a previous interglacial likely to be mis5e biogeochemical biological and sedimentological climate proxies revealed a productive biological community and an active hydrological regime consistent with the warmer conditions detected in continental ice cores at this time the diatom assemblage was similar to that currently found in the sub and maritime antarctic biome and included some sub antarctic endemic taxa that have not previously been reported from east antarctica this suggests southward expansion of the sub antarctic diatom biome during mis5e mosses were also present in the lake or the catchment but are rare in the region today two discrete periods of enhanced productivity show that the mis5e environment was not stable mis5e ended abruptly with a rapid transition to glacial conditions the lake was covered by a layer of firnified snow and ice and phototrophic biological activity ceased for a period of c 90 000 years the upper unit was deposited in mis1 after 3470 3687 cal yr bp after phototrophic biological production resumed lower species diversity pigment production an antarctic continental diatom assemblage and an absence of moss layers suggest cooler conditions during mis1

halokinesis and structural evolution of the major features in eastern and southern tunisian atlas abstract the eastern and southern tunisian atlas is marked by the presence of three major faults the n s axis fault the nw se gafsa fault and the e w northern chott fault seismic lines crossing these structures show the existence of significant halokinetics that began in the early jurassic the aim of this paper is to study and better understand the triassic salt movements which are mainly linked to periods when the major basement faults were reactivated resulting in extension compression transtension or and transpression analysis of the seismic data allows us to conclude that the triassic salt migration started in the early jurassic and continued during the late jurassic and the early cretaceous although these periods are characterized by an extensional tectonic regime the synsedimentary halokinesis is accompanied by thickening and thinning of the overlying series salt remobilization was accentuated during the compressional deformation which occurred from the late tertiary to quaternary and resulted in local diapiric extrusions along the major structural features

tectonic evolution of the northern african margin in tunisia from paleostress data and sedimentary record abstract a reconstruction of the tectonic evolution of the northern african margin in tunisia since the late permian combining paleostress tectonic stratigraphic and sedimentary approaches allows the characterization of several major periods corresponding to consistent stress patterns the extension lasting from the late permian to the middle triassic is contemporaneous of the rifting related to the break up of pangea during liassic times regional extensional tectonics originated the dislocation of the initial continental platform in northern tunisia the evolution of the liassic ne sw rifting led during dogger times to the north african passive continental margin whereas in southern tunisia a n s extension associated with e w trending subsiding basins lasted from the jurassic until the early cretaceous after an upper aptian early albian transpressional event ne sw to ene wsw trending extensions prevailed during late cretaceous in relationship with the general tectonic evolution of the northeastern african plate the inversions started in the late maastrichtian paleocene in northern tunisia probably as a consequence of the africa eurasia convergence two major nw se trending compressions occurred in the late eocene and in the middle late miocene alternating with extensional periods in the eocene oligocene early middle miocene and pliocene the latter compressional event led to the complete inversion of the basins of the northwestern african plate originating the maghrebide chain such a study supported by a high density of paleostress data and including complementary structural and stratigraphic approaches provides a reliable way of determining the regional tectonic evolution

a field investigation of source parameters for the sledgehammer we examined amplitude and frequency changes in shallow seismic reflection data associated with simple source parameter modifications for the sledgehammer seismic data acquired at three sites with different near surface geology show the potential effects of varying the hammer mass the hammer velocity the plate mass and the plate area at these study sites seismic amplitudes depend on plate surface area and on hammer mass but not heavily on hammer velocity or plate mass furthermore although the total bandwidth of the recorded data was independent of source parameter changes the peak frequency at one site was increased approximately 40 hz by increasing the area of the plate the results indicate that the effects of modifying the source parameters for the sledgehammer are site dependent the experiments described are quick cheap and simple and can be duplicated by others at prospective sites to answer site specific questions

the depth dependence of rain noise in the philippine sea during the philippine sea experiment in may 2009 deep sound a free falling instrument platform descended to a depth of 5 1 km and then returned to the surface two vertically aligned hydrophones monitored the ambient noise continuously throughout the descent and ascent a heavy rainstorm passed over the area during the deployment the noise from which was recorded over a frequency band from 5 hz to 40 khz eight kilometers from the deployment site a rain gauge on board the r v kilo moana provided estimates of the rainfall rate the power spectral density of the rain noise shows two peaks around 5 and 30 khz elevated by as much as 20 db above the background level even at depths as great as 5 km periods of high noise intensity in the acoustic data correlate well with the rainfall rates recovered from the rain gauge the vertical coherence function of the rain noise has well defined zeros between 1 and 20 khz which are characteristic of a localized source on the sea surface a curve fitting procedure yields the vertical directional density function of the noise which is sharply peaked accurately tracking the storm as it passed over the sensor station

a paleoclimate record of the last 17 600 years in stalagmites from the b7 cave sauerland germany abstract petrographical and geochemical parameters of stalagmites from the b7 cave in iserlohn letmathe northern rhenish massif nw germany record late and postglacial climate changes temperature and or precipitation fabrics and microfacies of the stalagmite profiles lead to a differentiation of four hierarchies of rhythms clastic layers in the stalagmites are caused by flooding events and are time markers twenty four tims th u age dates provide a time calibration of stalagmite growth phases one stalagmite reveals an early growth period between 17 6 and 16 7 ka bp between 9 6 and 5 5 ka bp atlantic episode of the holocene the growth rate of the stalagmites was higher than before and after this time with dominant light porous microfacial laminae and high 18 o and 13 c values representing partly kinetic fractionation effects this part of the holocene is interpreted as a mainly warm episode with frequent interruptions of dripping within the past 4 ka the profiles with predominant dark compact facies reveal low isotopic values which may be interpreted as a temperature proxy record the stalagmite records resemble records from an irish stalagmite correlation with the 14 c record from european tree rings suggests that colder periods in the north atlantic were accompanied by drier winters in central europe

oxygen isotope record of sea level and climate variations in the sulu sea over the past 150 000 years the sulu sea is located in the warm pool of the western pacific ocean where mean annual temperatures are the highest of anywhere on earth because this large heat source supplies the atmosphere with a significant portion of its water vapour and latent heat understanding the climate history of the region is important for reconstructing global palaeoclimate and for predicting future climate change changes in the oxygen isotope composition of planktonic foraminifera from sulu sea sediments have previously been shown to reflect changes in the planetary ice volume at glacial interglacial and millenial timeseales and such records have been obtained for the late pleistocene epoch and the last deglaciation1 3 here i present results that extend the millenial time resolution record back to 150 000 years before present on timescales of around 10 000 years the sulu sea oxygen isotope record matches changes in sea level deduced from coral terraces on the huon peninsula4 this is particularly the case during isotope stage 3 an interglacial period 23 000 to 58 000 years ago where the sulu sea oxygen isotope record deviates from the specmap deep ocean oxygen isotope record5 thus these results support the idea4 6 that there were higher sea levels and less continental ice during stage 3 than the specmap record implies and that sea level during this interglacial was just 40 50 metres below present levels the subsequent rate of increase in continental ice volume during the return to full glacial conditions was correspondingly faster than previously thought

compressional and shear wave properties of marine sediments comparisons between theory and data according to a recently developed theory of wave propagation in marine sediments the dispersion relationships for the phase speed and attenuation of the compressional and the shear wave depend on only three macroscopic physical variables porosity grain size and depth in the sediment the dispersion relations also involve three real parameters assigned fixed values representing microscopic processes occurring at grain contacts the dispersion relationships are compared with extensive data sets taken from the literature covering the four wave properties as functions of all three physical variables with no adjustable parameters available the theory matches accurately the trends of all the data sets this agreement extends to the compressional and shear attenuations in that the theory accurately traces out the lower bound to the widely distributed measured attenuations the theory predicts the intrinsic attenuation arising from the irreversible conversion of wave energy into heat whereas the measurements return the effective attenuation which includes the intrinsic attenuation plus additional sources of loss such as scattering from shell fragments and other inhomogeneities in the medium provided one wave or physical property is known say the compressional speed or the porosity all the remaining sediment properties may be reliably estimated from the theory

timing and nature of the penultimate deglaciation in a high alpine stalagmite from switzerland abstract the timing and nature of the penultimate deglaciation also known as termination ii t ii is subject of controversial discussions due to the scarcity of precisely dated palaeoclimate records here we present a new precisely dated and highly resolved multi proxy stalagmite record covering t ii from the high alpine schafsloch cave in switzerland an area where climate is governed by the north atlantic the inception of stalagmite growth at 137 4 1 4 kyr before present bp indicates the presence of drip water and cave air temperatures of above 0 c and is related to a climate induced change in the thermal state from cold to warm based of the glacier above the cave the cessation of stalagmite growth between 133 1 0 7 and 131 9 0 6 kyr bp is most likely related to distinct drop in temperature associated with heinrich stadial 11 the resumption of stalagmite growth at 131 9 0 6 kyr bp is accompanied by an abrupt increase in temperature and precipitation as indicated by distinct shifts in the oxygen and carbon isotopic composition as well as in trace element concentrations the mid point of t ii is around 131 8 0 6 kyr bp in the schafsloch cave record is significantly earlier compared to the age of 129 1 0 1 kyr bp in the sanbao cave record from china the different ages between both records can be best explained by the competing effects of insolation and glacial boundary forcing on seasonality and snow cover extent in eurasia

underwater noise due to rain open ocean measurements measurements of underwater noise produced by rain over the open ocean were made at a site some 1 km off ucluelet on the west coast of vancouver island british columbia canada a hydrophone was placed near the bottom in 55 m of water in the path of the prevailing eastward moving pacific storm systems the spectral noise level dependence on rain rate between zero and 20 mm h was determined for various frequencies and sea states a straight line least squares fit to the sample values of spectral level plotted against the log of rain rate was found to best represent the relationship representative rain noise spectra for various rain rates and sea states were derived

field comparison of shallow seismic sources near chino california data from a shallow seismic source comparison test conducted in an area with a water table depth in excess of 30 m and near surface velocities less than 330 m s were acquired from 13 different sources at a single site near chino california the sources included sledgehammer explosives weight drop projectile impacts and various buffalo guns a possible reflecting event can be interpreted at about 70 ms at this particular test site the lowly sledgehammer is among the best sources to provide data to see the possible reflection our previous work and that of our colleagues suggests that any source could dominate the comparison categories addressed here given the appropriate set of site characteristics

gravity contributions to the understanding of salt tectonics from the jebel cheid area dome zone northern tunisia detailed gravity measurements integrated with geological data were computed to constrain the mechanisms that were active during the emplacement of the triassic evaporite bearing folds of jebel cheid from the salt dome zone in the atlassic region the gravity analysis consists in mapping the contrasting gravity responses complete bouguer anomaly residual anomaly and derivative maps the main results display a positive amplitude gravity anomaly as the response of triassic evaporite bodies and important ne sw trending features at the boundaries between the triassic outcrops and their enveloping strata in contrast with gravity calculations of a salt dome structure usually resulting in negative gravity anomaly models the jebel cheid clearly expresses a positive gravity anomaly furthermore this result is supported by synthetic gravity interpretation

the demise of the last interglacial recorded in isotopically dated speleothems from the alps abstract the transition from interglacial to glacial climate has attracted much attention in paleoclimatic research partly because orbital forcing dictates that such a return to a new ice age is inescapable albeit in the distant future only the detailed series of steps that leads to glacial inceptions remains poorly understood however and studies of past glacial inceptions are often compromised by incomplete records imprecise chronological control and or uncertainties associated with proxy transfer functions here we present results from u th dated speleothems from a cave in the austrian alps entrische kirche cave which grew continuously between ca 127 and 114 ka and intermittently also during subsequent stadials and interstadials the alpine setting of this cave is prone to periglacial and glacial processes as well as temperature and precipitation changes which are recorded in these cave deposits we use high resolution stable isotope data to constrain paleoenvironmental changes associated with the demise of the last interglacial unprecedented in detail for central europe peak interglacial conditions are characterized by high 18 o values and high growth rates from ca 127 to 124 ka a major drop in 18 o by 3 occurred at ca 118 ka which coincided with cold event c26 in the north atlantic this isotopic shift which occurred at or close to isotopic equilibrium cannot be explained by simple uniform cooling modelling suggests that enhanced seasonality dominated by significant changes in winter precipitation are required to reconcile the isotope data with the fact that calcite deposition continued across the mis 5e d transition i e no cave freezing this period of enhanced seasonality lasted for several millennia during which the catchment area of the cave remained geomorphologically stable and ice free eventually speleothem growth terminated at ca 114 ka which is in line with widespread ice rafting in the north atlantic cold event c24 and the onset of fully stadial conditions during mis 5d

estimation of the roll angle in a triplet towed array using oceanic surface generated ambient noise this paper proposes a roll angle estimation method for the triplet towed array using the oceanic ambient noise recorded in the mid frequency range of 1 to 10 khz here the dominance of oceanic surface generated noises such as wind driven and shipping noises is expected the ratio between the approximated phase parts of the noise coherence function regarding the triplet hydrophones is used for the roll estimation advantage of this technique is that explicit input regarding the oceanic environment is not required especially for an ocean with an azimuthally uniform noise field or dominant noise sources at the end fire direction of the horizontal array in other cases a roll angle bias occurs depending on the horizontal directionality this proposed technique is applied to ocean ambient noise measurements that were collected in the east sea of korea during august 2015 the roll angles of the triplet array are estimated from the measurements and compared with roll sensor measured data the estimated roll angles agree with the measured ones within the root mean square error of 10 and their difference tends to decrease with increasing wind speed

geometry and structural evolution of lorbeus diapir northwestern tunisia polyphase diapirism of the north african inverted passive margin detailed geologic mapping structural analysis field cross sections new dating based on planktonic foraminifera in addition to gravity signature of lorbeus diapir are used to characterize polyphase salt diapirism this study highlights the role of inherited faulting which controls and influences the piercement efficiency and the style and geometry of the diapir and also the localization of evaporite early ascent displaying diapiric growth during extension salt was extruded along the graben axis developed within extensional regional early cretaceous tectonic associated with the north african passive margin evolution geologic data highlight reactive diapirism during albian time most extreme extension period and passive diapirism during the late cretaceous post rift stage northeastern maghreb salt province gives evidences that contractional deformations are not associated with significant diapirism during shortening the initial major graben deforms as complex anticlines where diapirs are squeezed and pinched from their feeding

the structure of jebel el mourra tunisia a diapiric structure causing a positive gravity anomaly detailed gravity data integrated with geological data and mining well data are analysed to constrain the shape of the triassic evaporitic body at jebel el mourra northern tunisian atlas and the mechanism of its emplacement at the surface the gravity data analysis included the construction of a gravity anomaly maps and synthetic and forward 2 5d gravity models the complete bouguer and residual gravity anomaly maps indicate a positive amplitude gravity anomaly over the triassic evaporitic outcrops and prominent ne sw trending features associated with the boundary of the triassic rocks and surrounded layers a nw se trending gravity model that crosses the triassic evaporitic outcrop at jebel el mourra shows that the positive gravity anomaly can be explained by a deep rooted salt diapir conventional models of salt dome formation suggest that they produce negative gravity anomalies however this study shows that this model is not universal the studied area is an example of a diapir expressed by positive gravity anomaly and this result is supported by synthetic gravity models at different stages of salt piercing

gravity constraints on the structure of the northern margin of tunisia implications on the nature of the northern african plate boundary summary bouguer gravity data were analysed to determine the general crustal and upper mantle structure in northern tunisia residual gravity anomalies were determined by removing the gravitational effect of crustal thickness variations imaged by regional seismic experiments residual gravity anomalies contain short wavelength anomalies superimposed on a long wavelength component that decreases in amplitude northward towards the tunisian coastline an edge enhancement analysis e g enhanced analytic signals of the short wavelength anomalies suggests a previously unknown east west trending gravity anomaly south of 37 n with source depths of between 3 and 7 km modelling of residual and bouguer gravity anomalies indicate that there are two possible solutions for the residual gravity decrease in northern tunisia 1 thickening of cenozoic and mesozoic sediments north of a strike slip fault or 2 a crustal and uppermantle low density zone interpreted as being crustal material of the remnant subducted african plate the latter result is favoured based on seismic tomographic images of the mediterranean region which implies that subducting material exists under the african coast geological interpretations suggesting that the tell atlas may be a thrust wedge accreted by underplating of the african continental crust and seismic refraction models indicating a thinning of sediments in northern tunisia the east west trending gravity anomalies south of 37 n correspond to an important structural feature that may be related to either a structural boundary e g a transform fault or subduction beneath the african plate

major cooling intersecting peak eemian interglacial warmth in northern europe abstract the degree of climate instability on the continent during the warmer than present eemian interglacial around ca 123 kyr ago remains unsolved recently published high resolution proxy data from the north atlantic ocean suggest that the eemian was punctuated by abrupt events with reductions in north atlantic deep water formation accompanied by sea surface temperature cooling here we present multi proxy data at an unprecedented resolution that reveals a major cooling event intersecting peak eemian warmth on the north european continent two independent temperature reconstructions based on terrestrial plants and chironomids indicate a summer cooling of the order of 2 4 c the cooling event started abruptly had a step wise recovery and lasted 500 1000 yr our results demonstrate that the common view of relatively stable interglacial climate conditions on the continent should be revised and that perturbations in the north atlantic oceanic circulation under warmer than present interglacial conditions may also lead to abrupt and dramatic changes on the adjacent continent

evidence for triassic salt domes in the tunisian atlas from gravity and geological data abstract detailed gravity data were analyzed to constrain two controversial geological models of evaporitic structures within the triassic diapiric zone triassic massifs of jebel debadib and ben gasseur of the northern tunisian atlas based on surface observations two geological models have been used to explain the origin of the triassic evaporitic bodies 1 salt dome diapiric structure or 2 a salt glacier the gravity analysis included the construction of a complete bouguer gravity anomaly map horizontal gravity gradient hgg map and two and a half dimensional 2 5d forward models the complete bouguer gravity anomaly map shows a prominent negative anomaly over the triassic evaporite outcrops the hgg map showed the location of the lateral density changes along northeast structural trends caused by triassic cretaceous lithological differences the modeling of the complete bouguer gravity anomaly data favored the diapiric structure as the origin of the evaporitic bodies the final gravity model constructed over jebel debadib indicates that the triassic evaporitic bodies are thick and deeply rooted involving a dome diapiric structure and that the triassic material has pulled upward the younger sediment cover by halokinesis taking in account kinematic models and the regional tectonic events affecting the northern margin of africa the above diapirs formed during the reactive to active to passive stages of continental margin evolution with development of sinks otherwise this study shows that modeling of detailed gravity data adds useful constraints on the evolution of salt structures that may have an important impact on petroleum exploration models

the classic marine isotope substage 5e since its identi cation nearly fty years ago marine iso tope stage 5 mis 5 has been placed onto absolute time scaleson the basis of three independent approaches cesare emiliani who set up the isotope stages emiliani 1955 depended onuranium series dating of the sediments a method that today isregarded as not generally capable of yielding useful precisionor accuracy broecker and van donk 1970 pioneered the ap proach of correlating to radiometrically dated marine coral ter races thishasbeenmuchaidedinrecentyearsbyimprovementsin the precision and accuracy of these age determinations thathave owed from the development of thermal ionization massspectrometry tims for uranium series dating edwards

a late eemian aridity pulse in central europe during the last glacial inception how do ice ages begin it s an obvious question to ask as we enjoy the relative luxury of an interglacial but a hard one to answer a look at past transitions may give some clues as to how this period will one day come to an end a climate reconstruction based on sediments found beneath a lake in the eifel mountains in germany provides evidence of an extreme climate event lasting 468 years right at the end of the last interglacial dust storms aridity bushfires and the loss of trees associated with a warm climate coincided with a southward shift of the warm waters of the north atlantic drift in terms of insolation the rate of delivery of the sun s radiation to earth conditions then were similar to those we have now investigating the processes that led to the end of the last interglacial period is relevant for understanding how our ongoing interglacial will end which has been a matter of much debate see for example refs 1 2 a recent ice core from greenland demonstrates climate cooling from 122 000 years ago3 driven by orbitally controlled insolation with glacial inception at 118 000 years ago4 5 6 7 8 here we present an annually resolved layer counted record of varve thickness quartz grain size and pollen assemblages from a maar lake in the eifel germany which documents a late eemian aridity pulse lasting 468 years with dust storms aridity bushfire and a decline of thermophilous trees at the time of glacial inception we interpret the decrease in both precipitation and temperature as an indication of a close link of this extreme climate event to a sudden southward shift of the position of the north atlantic drift the ocean current that brings warm surface waters to the northern european region the late eemian aridity pulse occurred at a 65 n july insolation of 416 w m 2 close to today s value of 428 w m 2 ref 9 and may therefore be relevant for the interpretation of present day climate variability

crustal structure beneath the tell and atlas mountains algeria and tunisia through the analysis of gravity data abstract bouguer and isostatic residual gravity anomaly maps were analyzed for the general crustal structure under the tell and atlas mountains of algeria and tunisia two dimensional gravity models and profiles of topography free air and bouguer gravity anomalies were constructed to provide estimates of the crustal thickness and the degree of isostatic compensation the thickest crust 38 40 km was found beneath the saharian atlas in northern algeria whereas under the tunisian atlas it is approximately 34 36 km there is little evidence of crustal thickening due to the formation of the tell mountains large amplitude negative bouguer small amplitude positive free air gravity and small amplitude positive isostatic residual gravity anomalies suggest that saharian and tunisian atlas are partially isostatically compensated with regions of possible overcompensation in algeria the boundary between the saharian and tunisian atlas is characterized by negative isostatic residual anomalies suggesting overcompensation and a thick crustal root however the cause may be low density material in the upper crust the amplitude and width of bouguer gravity anomalies and two dimensional gravity models across the saharian and tunisian atlas indicate that there was a greater amount of crustal shortening in algeria than in tunisia

sub milankovitch climatic cycles in holocene stalagmites from sauerland germany calcitic stalagmites from caves in the sauerland germany prove the existence of sub milankovitch cycles in precipitation during the last 6000 yr the 18o record dated with th u is interpreted as an indicator of paleohumidity spectral analysis of 18o from 6000 a bp up to the recent top of a stalagmite from the atta cave yields statistically significant peaks at 1450 117 64 and 57 a additionally we find a good correlation of the stalagmite s 18o and 14c from european tree rings the 1450 a cycle in the stalagmite probably is analogous to the pervasive millennial scale climate cycle described by bond et al science 278 1997 1257 1266 294 2001 2130 2136 derived from the amount of ice rafted debris in deep sediments from the north atlantic our results suggest that the centennial to millennial shifts observed in the north atlantic are accompanied by synchronous shifts of the climate in northern and central europe which most probably can be attributed to solar irradiation variations

repeatability analysis of land time lapse seismic data co2crc otway pilot project case study time lapse seismics is the methodology of choice for remotely monitoring changes in oil gas reservoir depletion reservoir stimulation or co 2 sequestration due to good sensitivity and resolving power at depths up to several kilometres this method is now routinely applied offshore however the use of time lapse methodology onshore is relatively rare the main reason for this is the relatively high cost of commercial seismic acquisition on land a widespread belief of a relatively poor repeatability of land seismic data prevents rapid growth in the number of land time lapse surveys considering that co 2 sequestration on land is becoming a necessity there is a great need to evaluate the feasibility of time lapse seismics for monitoring therefore an understanding of the factors influencing repeatability of land seismics and evaluating limitations of the method is crucially important for its application in many co 2 sequestration projects we analyse several repeated 2d and 3d surveys acquired within the otway co2 sequestration pilot project operated by the cooperative research centre for greenhouse technologies co2crc in australia in order to determine the principal limitations of land time lapse seismic repeatability and investigate the influence of the main factors affecting it our findings are that the intrinsic signal to noise ratio s n signal to coherent and background noise levels and the normalized root meansquare nrms difference are controlled by the source strength and source type however the post stack s n ratio and corresponding nrms residuals are controlled mainly by the data fold for very high fold data the source strength and source type are less critical

stable climatic conditions in central germany during the last interglacial stable isotopic data from the high resolution limnic sequence in the opencast mine at grobern central germany confirm the relatively stable climate of the last interglacial deduced from pollen analyses after significant warming during the transition from the saalian to the eemian stable warm climatic conditions set in once the climatic optimum was reached in the course of biozones e4 to e5 from the middle of biozone e6b a gradual temperature decrease can be observed reaching a minimum at the start of biozone e7 the division of the early weichselian glacial in central germany into two stadials herning rederstall and two interstadials brorup odderade is also documented by the findings copyright 2000 john wiley sons ltd

subsidence history in basins of northern algeria abstract the tellian foreland in algeria represents a part of the southern tethyan margin during the mesozoic its tectonic evolution includes a rifting stage during the triassic and liassic times characterised by tilted blocks and early diapiric events during the liassic a post rift regime from middle jurassic up to the late cretaceous and basin inversion during the tertiary related to the african and european plates convergence the subsidence modelling supported by surface and subsurface data integration emphasises different subsidence phases 1 liassic subsidence phase under tethyan and atlantic control related to crustal thinning 2 late jurassic cretaceous and tertiary subsidence phases where the first one is linked to diapiric events and the second in eastern algeria to the effects of the rifting event developed more easterly in the gulf of gabes and sirte the last one is flexural and occurs in foreland basins during the tertiary taking into account the subsidence record of each structural domain a correlation between tectonic events and the subsidence phases can be established

spreading of salt structures in the gulf of mexico abstract past and present overhangs on diapirs ductile intrusions of salt are potential hydrocarbon traps and increasing numbers of larger overhangs are being recognised as seismic acquisition and processing improves salt overhangs develop by three process drag by ductile surroundings sinking around salt diapirs thinning of diapiric stems or the topic considered here gravity spreading gravity spreads salt where it is easier for salt to flow sideways than it is to float or sink the potential level to which individual salt diapirs rise depends on the pressure applied to their source by the overburden load and any lateral forces the potential level to which salt diapirs rise can be independent of both the top free surface and the level of neutral buoyancy of the salt even the most vigorous diapirs cannot rise indefinitely they gravitationally spread at barriers they cannot penetrate below at or above their level of neutral buoyancy it has been suggested that salt diapirs spread below their level of neutral buoyancy in weak layers beneath stiff barriers however no case of deep subsurface salt spreading appears to have been documented instead shales rise with salt along the us gulf coast some salt diapirs in the gulf of mexico may simulate ductile ice flows and spread both upwards and downwards to a subsurface level of neutral buoyancy in surroundings of similar strain rate however most diapirs in the gulf are driven above their level of neutral buoyancy so that they spread downwards back towards it these spread over denser or stifter layers in less dense and weaker barriers of air water or unconsolidated sediments this work focuses on the geological implications of the shapes of the tops of small scale secondary salt bodies that spread superficially in weaker and less dense barriers under the northern gulf of mexico analytical material and natural models are used to show that the shape of the top free surface of spreading salt contains information about both the properties of the materials involved and their kinematics many salt diapirs in the gulf spread downslope from viscous salt fountains in muds over sand salt flowing downslope towards a lower level of neutral buoyancy exhibits dynamic extrusion the temporary dynamic nature of salt sheets is emphasised by restating standard arguments for overburden strength in terms of low strain rates contrary to recent views that salt spreading occurs in weak horizons during fast sedimentation it is argued that most salt spreads superficially during periods of slow sedimentation small salt laccoliths advance downslope at long term rates between 1 and 5 mm a after burial spreading and gliding of their overburdens can detach such laccoliths from their source and smear them to salt sills that advance downslope at 8 mm a as development wells are likely to be complicated by such active salt flow we should begin now direct measurements of the rates at which salt spreads at superficial levels beneath the northern gulf of mexico

climate variability in northwest greece during the last interglacial isotopic and palynological data over the period 115 000 to 135 000 years ago from a lacustrine sequence in northwest greece show distinct oscillations during the intervals leading into and out of the full interglacial whereas in between changes were less pronounced but included a brief fluctuation after peak interglacial conditions temperatures decreased and precipitation increased in a series of steps these data suggest that eemian climate variability was similar to that of the holocene both in terms of amplitude and possibly of pacing

structural setting of northern tunisia insights from gravity data analysis jendouba case study detailed gravity data in conjunction with available surface geology are analyzed to infer the organization of the underlying structures in jendouba area gravity data analysis benefits from the gravity bouguer anomaly upward continuations residual distribution derivatives and euler deconvolved maps the main results display a positive amplitude gravity anomaly as the response of triassic evaporitic bodies and important ne trending features at the boundaries between the triassic outcrops and their enveloping strata integration of gravity geological and structural maps let to the identification of major structural directions and trends of the study area it confirms some structural elements gathered from outcrops it defines also new ones

alpine evidence for atmospheric circulation patterns in europe during the last glacial maximum the configuration of alpine accumulation areas during the last glacial maximum lgm has been reconstructed using glacial geological mapping the results indicate that the lgm ice surface consisted of at least three major ice domes all located south of the principal weather divide of the alps this implies that the buildup of the main alpine ice cover during oxygen isotope stage ois 2 was related to precipitation by dominant southerly atmospheric circulation in contrast to today s prevalent westerly airflow such a reorganization of the atmospheric circulation is consistent with a southward displacement of the oceanic polar front in the north atlantic and of the associated storm track to the south of the alps these results combined with additional paleoclimate records from western and southern europe allow an interpretation of the asynchronous evolution of the different european ice caps during the last glaciation 18o stages ois 4 and 3 were characterized by location of the polar front north of 46 n gulf of biscay this affected prevailing westerly circulation and thus ice buildup in western scandinavia the pyrenees vosges and northern alps at the lgm however the polar front lay at 44 n causing dominating southerly circulation and reduced precipitation in central and northern europe

diapirism in northern tunisia abstract the diapirs of northern tunisia composed mainly of evaporitic triassic material are the result of a complex evolution initiated by local basement movements of nne ssw faults which at the end of the early cretaceous this first uplift occurring during a period without any folding of the sedimentary series is purely halokinetic such diapiric activity remained in active progress throughout the cretaceous and early tertiary causing local disturbance in the related series and then during the alpine atlas orogeny the diapiric structures underwent deformation according to their position in the orogenic area

stable isotope compositions of speleothems from the last interglacial spatial patterns of climate fluctuations in europe abstract studies on the last interglacial lig can provide information on how our environment behaved in a period of slightly higher global temperatures at about 125 4 ka even if it is not the best analogue for the holocene the available lig climate proxy records are usually better preserved and can be studied at a higher resolution than those of the preceding interglacials allowing detailed comparisons this paper presents complex stable hydrogen carbon and oxygen isotope records obtained for carbonate 13 c and 18 o carb and fluid inclusion hosted water d and 18 o w of a stalagmite from the baradla cave system in central europe that covers most of the lig as proven by u th dates comparing its c and o isotope data with records reported for other speleothem cave hosted carbonate deposits from europe revealed the complex behavior of these climate proxies with a concerted relative increase in 18 o of carbonates from 128 to 120 ka and synchronized shifts in the opposite direction after 119 ka the hydrogen isotope analyses of inclusion hosted water extracted from the bar ii stalagmite also correspond to the regional climate proxy records with meaningful deviations from global temperature trends beside following the general paleotemperature pattern from the climate optimum high d values up to 64 around 120 ka to the subsequent cooling starting at about 119 ka low d values down to 90 at about 109 ka a period between 126 5 and 123 ka with low d values down to 81 is detected in the bar ii stalagmite although the isotope shifts are muted in the c o isotope data of carbonate due to competitive fractionation processes the 13 c data show a positive relationship with the d pattern indicating humidity and possibly temperature variations the periods with low d values fit well to temperature and humidity changes inferred from proxy records from western europe to the eastern mediterranean spatial distributions of these variables show that at about 125 2 ka the mediterranean region was characterized by warm humid conditions and enhanced seasonality with elevated winter precipitation the combined interpretation of stable isotope data revealed that the alpine and mediterranean regions behaved differently during greenland stadial 26 gs26 119 to 116 2 ka while the alpine records fluctuated in close agreement with the central greenland ice core 18 o data the bar ii stalagmite show a positive 18 o carb anomaly the baradla data indicate enhanced aridity and seasonality for a part of gs26 with the relative dominance of summer precipitation and mediterranean moisture contribution following the gs26 event the effect of long term global cooling becomes dominant in the baradla isotope records and leads to glacial inception at about 109 ka

the seismic signature of rain abstractrain has long been a problem for land seismic surveys in terms of its effect on the condition of the surface and near surface and also due to the seismic noise it creates when raindrops hit the ground i measured the seismic signature of rainfall using water dripped from height using a pipette and natural rain in winchester england over a three month period my results indicated that rain noise is concentrated at frequencies of greater than 80 hz with a detectable range of less than 1 m drops of water landing directly on a geophone result in events with amplitudes nearly 30 times larger than those landing next to the geophone items placed on the surface of the ground such as cables absorb the energy of the impact and reduce the level of the resulting seismic noise burying geophones results in attenuation of rain noise by between 7 7 and 8 6 db 0 1 m but given the effort required to bury geophones it is likely that data processing algorithms or the placement of vibration absorbent ma

timing and duration of the last interglacial evidence for a restricted interval of widespread coral reef growth abstract we report new mass spectrometric u series ages for eight last interglacial fossil reefs along the continental margin of western australia corals were selected in growth position from localities that are characterized by apparently low levels of diagenesis and relative tectonic stability so that the fossil reefs provide critical information on last interglacial sea levels without requiring corrections for tectonic movements in addition we have improved the constraint on the timing of onset of reef growth by recovering drill core coral from the base of the reefs uranium and thorium isotopes were measured with high levels of precision leading to improvements in age resolution and allowing samples which have undergone diagenetic exchange of uranium and thorium to be more easily identified and discarded these data supplement our previous results for rottnest island and leander point leading to more than seventy mass spectrometric u series ages from which constraints can be placed on the timing duration and character of the last interglacial sea level highstand reliable ages show that reef growth started contemporaneously at 128 1 ka along the entire western australian coastline while relative sea levels were at least 3 m above the present level because western australia is located far from the former penultimate glacial maximum ice sheets and are not significantly effected by glacial unloading these data constrain the timing of onset of the last interglacial period to 128 1 ka assuming reef growth started soon after sea level approached interglacial levels a unique regressive reef sequence at mangrove bay constrains the timing of termination of the last interglacial period to 116 1 ka the major episode of reef building however both globally and locally along the western australian coast is restricted to a very narrow interval occurring from 128 ka and 121 ka suggesting that global ocean surface temperatures were warm and or sea levels were stable enough to allow prolific reef growth only during the earlier part of the last interglacial

speleothems and paleoglaciers abstract ice and speleothems are widely regarded as mutually exclusive as the presence of liquid water is a fundamental prerequisite for speleothem deposition here we show that speleothems may form in caves overlain by a glacier as long as the temperature in the cave is above freezing and the conduits are not completely flooded by melt water carbonate dissolution is accomplished via sulfide oxidation and the resultant speleothems show high 13c values approaching and locally exceeding those of the parent host rock lack of soil derived biogenic c the 18o values reflect the isotopic composition of the melt water percolating into the karst fissure network and carry an atmospheric temperature signal which is distinctly lower than those of speleothems formed during periods when soil and vegetation were present above the cave these subglacial speleothems provide a means of identifying and dating the former presence of warm based paleoglaciers and allow us to place some constraints on paleotemperature changes

high resolution palynological record off the iberian margin direct land sea correlation for the last interglacial complex abstract we present high resolution pollen dinocyst and isotopic data for the last interglacial complex from marine core md952042 southwestern margin of the iberian peninsula 37 48 n 10 10 w 3148 m direct land sea correlation from this core indicates that during this period north atlantic sea surface temperatures were in phase with iberian climate our palynological analysis suggests a younger dryas like event at the marine isotope stage mis 6 5 transition the analysis also indicates that the eemian spans from the lightest isotopic values of mis 5e ca 126 ky bp to the heavier isotopic values towards the mis 5e 5d transition therefore the eemian is not entirely equivalent to mis 5e pollen analysis identifies four climatic phases of low amplitude during the eemian a mediterranean climate in southwestern europe is gradually replaced by oceanic conditions the middle of the eemian is characterized by an increase in precipitation on the land and ocean associated with a slight cooling this seems to be the result of a displacement of the polar front as far south as southern europe during this period after the eemian three relatively short climatic phases on land melisey i st germain ia and montaigu cold event occurred contemporaneously with three shifts of sea surface temperatures the montaigu event first identified in terrestrial pollen sequences is therefore also recorded in core md952042 on the basis of pollen dinocyst and planktonic isotopic data our results also show that the warm periods of mis 5 are not characterized by similar climatic conditions on land

submarine salt glacier of northern tunisia a case of triassic salt mobility in north african cretaceous passive margin stratigraphical sedimentological and structural data and a bouguer gravity map of medjez el bab meb in northern tunisia are used to illustrate a cretaceous example of salt extrusion on a passive continental margin located just south of the teboursouk thrust front a preferential decollement surface used by the continuous tertiary shortening in this area the meb structure is a simple n40 e box anticline removing the two tertiary foldings eocene and miocene leads to the exposure of the original feature of a simple submarine salt glacier the triassic salt rocks appear as an albian interstratified body between two cretaceous series with stratigraphic normal polarity suggesting a bedding parallel extrusion at the sediment water interface of the triassic salt in cretaceous times the formation of such salt extrusions are associated with extensional faulting probably both in the cover and basement the presence of a slope and basinwards salt flow this scenario is similar to the allochthonous salt described in other salt provinces characterizing passive margins

millennial scale climate variability during the last interglacial recorded in a speleothem from south western france abstract a stalagmite bdinf recovered from an archaeological cave bourgeois delaunay la chaise de vouthon in sw france provides a rare high resolution precisely dated continental palaeoclimate record covering the warmest part of the last interglacial 128 1 121 1 ka the growth interval spans the pluvial period recorded in soreq and peqiin cave speleothems during sapropel event s5 suggesting that the eastern mediterranean and western europe experienced relatively wet conditions simultaneously during this part of the last interglacial stable oxygen and carbon isotope ratios from bdinf show prominent millennial scale variations which are interpreted respectively in terms of changes in the amount of rainfall reaching the cave and soil biological activity the timing of the oxygen isotope changes agrees with similar excursions recorded in speleothems from corchia cave italy where close coupling between rainfall amount and regional sea surface temperatures has been demonstrated three warmer wetter periods are interspersed with four cooler drier periods the first warmer wetter period is the most prominent as is the case at corchia and coincides with the sst optimum off western europe this is followed by a prominent cooler drier excursion centred on 126 ka which can be linked to a period of increased loess deposition recorded in annually laminated lake sediments from eifel germany although there is already ample evidence for last interglacial climate instability we show for the first time that specific climatic events occurred more or less synchronously between southwestern europe central mediterranean italy and northern europe germany

on the shapes of natural sand grains 1 digitized outlines of sand grains from a dozen locations including deserts beaches and seabeds have been acquired using an optical microscope linked to a desktop computer fourier analysis of the outlines returns the normalized power spectrum of each sample averaged over several hundred grains regardless of the origin of the samples these power spectra all exhibit essentially the same inverse power law dependence on the harmonic number n varying as n 10 3 for 2 n 20 this universal spectrum provides the basis of a numerical technique for synthesizing the irregular outline of a sand grain the outline is represented as a random pulse train in which identically shaped microasperities with normally distributed amplitudes are randomly superimposed on the perimeter of a circle by identifying the spectrum of the microasperities with the observed inverse power law dependence derived from the optical images the synthetic outlines are constrained to show the same statistical properties as the outlines of the real grains the synthesized and real outlines are qualitatively similar in that visually it is difficult to distinguish between them the new numerical technique for synthesizing irregular outlines of sand grains has potential for investigating the random packing of realistically rough particles through computer simulation

timing and progression of the last interglacial derived from a high alpine stalagmite 1 u th dating and oxygen isotope analysis of a stalagmite from spannagel cave in the austrian alps provides information about the timing and progression of the last interglacial climate we determined two distinct growth intervals warm climate from 130 7 thousand years ka before the present to 130 0 ka and from 125 7 ka to 118 2 ka the latter containing two periods of ceased stalagmite growth colder climate at around 123 8 ka and 120 5 ka high resolution 18o analysis of stalagmite spa 50 reveals a clear regular cyclic pattern with periods of 197 109 and 21 years which are likely to be related to the suess gleissberg and hale cycles respectively indicating that eemian climate in the alps was forced by the sun

rapid sea level and climate change at the close of the last interglaciation mis 5e evidence from the bahama islands the geology of the last interglaciation sensu stricto marine isotope substage mis 5e in the bahamas records the nature of sea level and climate change after a period of quasi stability for most of the interglaciation during which reefs grew to 2 5 m sea level rose rapidly at the end of the period incising notches in older limestone after brief stillstands at 6 and perhaps 8 5 m sea level fell with apparent speed to the mis 5d lowstand and much cooler climatic conditions it was during this regression from the mis 5e highstand that the north atlantic suffered an oceanographic reorganization about 118 3 ka ago during this same interval massive dune building greatly enlarged the bahama islands giant waves reshaped exposed lowlands into chevron shaped beach ridges ran up on older coastal ridges and also broke off and threw megaboulders onto and over 20 m high cliffs the oolitic rocks recording these features yield concordant whole rock amino acid ratios across the archipelago whether or not the last interglaciation serves as an appropriate analog for our greenhouse world it nonetheless reveals the intricate details of climatic transitions between warm interglaciations and near glacial conditions

rapid fluctuations in sea level recorded at huon peninsula during the penultimate deglaciation about 140 000 years ago the breakup of large continental ice sheets initiated the last interglacial period sea level rose and peaked around 135 000 years ago about 14 meters below present levels a record of last interglacial sea levels between 116 000 years to 136 000 years ago is preserved at reef vii of the uplifted coral terraces of huon peninsula in papua new guinea however corals from a cave situated about 90 meters below the crest of reef vii are 130 000 2000 years old and appear to have grown in conditions that were 6 c cooler than those at present these observations imply a drop in sea level of 60 to 80 meters after 130 000 years sea level began rising again in response to the major insolation maximum at 126 000 to 128 000 years ago the early about 140 000 years ago start of the penultimate deglaciation well before the peak in insolation is consistent with the devils hole chronology

transferring radiometric dating of the last interglacial sea level high stand to marine and ice core records in order to derive a radiometric age marker for the end of the penultimate glacial interglacial transition we compiled published u series isotope measurements on corals from the period extending from stage 6 to the middle of the last interglacial and computed the corresponding open system ages using thompson et al model thompson w g spiegelman m w goldstein s l speed r c an open system model for u series age determinations of fossil corals earth planet sci lett 210 2003 365 381 we obtain a global mean age of 126 calendar kyr bp ka 1 7kyr 2 for the beginning of the last interglacial sea level high stand after showing that the phase relationships observed between changes in sea level north atlantic benthic and planktonic foraminifera oxygen isotopic records and atmospheric methane over the last deglaciation were likely also valid over the penultimate deglaciation we derive an age of 131 2ka 2kyr 2 for the abrupt increase in atmospheric ch4 and north atlantic surface temperature marking the end of the penultimate glacial interglacial transition this age is consistent with u th dates of the penultimate glacial interglacial transition recorded in speleothems from sites where speleothems isotopic records are synchronous with north atlantic temperature records over the last deglaciation finally we show that the phase obtained between the climatic response and northern hemisphere summer insolation is not constant from termination ii to termination i implying that northern hemisphere summer insolation alone cannot explain the timing of terminations

diatom responses to limnological and climatic changes at ribains maar french massif central during the eemian and early wurm abstract high resolution diatom analysis was carried out to assess the limnological and climatic changes that took place at ribains maar french massif central during the late pleistocene 131 105 ka bp with a focus on the eemian interglacial in particular numerical analyses were used to show that most of the variability in the fossil diatom assemblages was due to climate independently from the changes in the lake catchment vegetation as represented by pollen data diatom based quantitative reconstructions of the past limnological conditions as well as a comprehensive literature review on the auto ecological requirements for the principal diatom taxa were used to interpret the record an absolute time scale for the sequence was derived by matching the major pollen shifts with the radiometrically dated changes in oxygen isotopes observed in italian stalagmites this study shows that at ribains maar the transition from the riss saalian glacial to the eemian interglacial was marked by a gradual increase in the contribution of spring blooming diatom species indicating a longer growing season and milder winter spring conditions at that time a short cooling event interrupts this trend and may correspond to a stadial at the start of the eemian a peak in benthic taxa and the suppression of spring blooming flora probably reflects the effects of deglaciation on the catchment during the eemian interglacial itself three main phases were distinguished within the diatom record the first phase 8000 years in duration was dominated by stephanodiscus minutulus which suggests that intense mixing in the water column took place during spring the pollen record was simultaneously dominated by quercus and corylus that typify this phase as the climatic optimum of the eemian the second phase almost equal in duration to the first phase 7000 years is generally dominated by cyclotella taxa and suggests a less productive lake and much reduced period of spring mixing compared with the first phase in the pollen diagram this corresponds to an interval dominated by carpinus picea abies that indicates a cooler and wetter climate the third and last phase of the eemian 2000 year long saw the return to stephanodiscus dominated assemblages indicating a warming that may correspond to the dansgaard oeschger event 25 identified in the greenland ice core record in the early stage of the wurm glacial weichselian assemblages in the melisey i stadial 3000 year long were dominated by either aulacoseira subarctica or asterionella formosa which suggest colder spring conditions than during the late eemian but not as cold as the ones indicated by the pollen record stephanodiscus spp again dominate during the saint germain ia interstadial 5000 year long suggesting a return to the conditions that prevailed before the melisey stadial in agreement with the pollen record the record ends with the montaigu cold event which is characterised by a pinus peak in the pollen record and corresponds to a large abundance of a subarctica in the diatom sequence throughout the eemian the abundance of stephanodiscus spp which is thought to be driven by winter conditions show cyclic fluctuations that most likely match the cooling events identified in a pollen record from germany variation in insolation throughout the eemian may have been the driving factor behind the species succession observed in the diatom sequence while this study demonstrates that diatom analysis of lake sediment can provide very detailed information on long term climate change a review of the few other diatom investigations published on european eemian deposits shows that this technique has been so far seldom used to its full potential in this context in central and southern europe

structural evolution of djebel debadib anticline a clue to the regional tectonic style of the tunisian atlas djebel debadib is a northeast trending anticline in the tunisian atlas near el kef tunisia the core of the anticline consists of a deformed triassic gypsum matrix breccia containing clasts of supratidal dolomite terrigeneous clastic rocks and ophites metabasites locally low grade metasedimentary rocks occurring as clasts in the evaporite may represent fragments of basement rock plucked from salt subcrop during deep seated flowage the multiply deformed triassic rocks are juxtaposed against cretaceous or younger rocks and jurassic and neocomian strata are not present in outcrop these characteristics have been cited in many studies to suggest a history of diapirism to explain both the internal structure of the triassic rocks and the contact relations with the younger rocks a previously unreported unconformity developed on the triassic rocks and overlain by aptian albian strata indicates that an important period of piercement occurred during the early cretaceous for the djebel debadib diapir from the mid cretaceous to the late eocene the continental margin of northern tunisia was a regional basin in which a thick sequence of carbonate rocks was deposited beginning in late oligocene time sandy clastic sediments accumulated on the older carbonate rocks above a regional unconformity and during the middle miocene atlas orogeny numerous northeast southwest folds deformed the rocks of the tunisian trough including the diapiric triassic masses these folds commonly boxlike in geometry were extensively faulted during the late miocene and pliocene a four phase tectonic model is recognized for the tunisian atlas 1 early mesozoic rifting of the north african continental margin 2 diapiric emplacement of the late triassic liassic evaporites into overlying strata beginning in the early cretaceous 3 folding of the cover strata in response to regional compression culminating in the middle miocene atlas orogeny 4 the development of transvers grabens during late orogenic normal faulting latest miocene to recent a major regional decollement is not considered necessary to account for the shortening of the sedimentary cover during the middle miocene deformation rather the principal driving mechanism of regional crustal shortening was the reactivation of early mesozoic normal faults as reverse faults that displaced basement rocks this model implies that the small amount of shortening recorded in the tunisian atlas involved active shortening and structural thickening of basement and the concurrent deformation of the sedimentary cover

autochthonous versus allochthonous upper triassic evaporites in the sbiba graben central tunisia abstract two dimensional seismic data and well data from the sbiba graben in central tunisia north africa reveal its asymmetrical structural geometry affected by e w n s nw se and ne sw master strike slip faults these faults have been intruded by upper triassic evaporites which can be classified into the following three types 1 sealed evaporite anticlines and domes along folded structures 2 extrusional wrinkles of salt walls at the borders of the graben related to along strike displacement of the master fault zone and 3 evaporite outpouring at the center of the graben interpreted as the result of fault and diapir movement detailed seismic stratigraphic analysis highlights a complex interplay between fault growth and evaporite movement which strongly controlled the evolution of the graben during the mesozoic tectonic stresses induced multidirectional faulting along inherited faults the vertical rising of the upper triassic evaporites was initiated locally at the intersection of master faults during regional extensional and transtensional events in the sub evaporite basement the interaction of normal faulting and evaporite diapirism caused lateral outpouring of surface piercing evaporites this phenomenon is well expressed in upper cretaceous upper cenomanian to lower turonian strata the master faults which cut the diapir at the border and the crest have caused the extrusion of evaporites the downward gravity driven flow of these evaporites across the slope surface and subsequent accumulation and preservation in mesozoic sediments is related to the fault escarpment and the adjacent fault induced depression there is an apparent relation between tectonic inheritance and inversions of the graben where interconnected deep faults and diapirs have been reactivated during extensional and contractional tectonic episodes causing evolution of the structures with the associated sedimentary lapouts several autochthonous triassic evaporites and associated fault escarpments have induced salt canopy structures

rapid changes in ocean circulation and heat flux in the nordic seas during the last interglacial period the apparent similarity of climate variability in the north atlantic region in the last interglacial period1 5 and the present interglacial holocene has recently been challenged by the rapid oscillations in climate conditions indicated by some marine6 7 and terrestrial climate records8 10 for the last interglacial ocean circulation in the northern north atlantic seems to be intimately coupled to the processes of climate change on various time scales11 12 so that climate variability and the associated mechanisms of change should be well recorded by sediments from these high latitudes previous studies in this region5 13 have indeed indicated an apparently less stable last interglacial climate than at middle latitudes of the north atlantic ocean4 here we present detailed records from marine sediments in the nordic seas of oceanographic conditions during the last interglacial the records show three large sea surface temperature fluctuations a weakening of the east west sea surface temperature gradient with time and changes in deep water properties in contrast similar analyses of a core from the same region indicate that sea surface temperature during the holocene has been relatively stable our data along with those from the labrador sea7 indicate rapid changes in ocean circulation and oceanic heat fluxes at high northern latitudes during the last interglacial which may have been associated with marked temperature changes on adjacent continents

environmental variability between the penultimate deglaciation and the mid eemian insights from tana che urla central italy speleothem trace element record abstract a trace element record mg sr ba al si p y zn covering the ca 133 ka to ca 124 ka time interval was acquired from a flowstone core from tana che urla cave central italy it was compared with stable isotope data to investigate the environmental evolution in response to regional and extra regional climate changes in the period corresponding to the latter part of the penultimate deglaciation and the first part of the last interglacial eemian trace element geochemical changes on centennial and millennial time scales responded to changes in hydrological input variations in the supply and transport of catchment erosion products to the cave including those linked to intense rainfall events and to the state of the overlying soil and vegetation abrupt increases in precipitation and the progressive development of soil and vegetation occurred at ca 132 ka in response to the development of the global deglacial phase the major changes in trace element composition are coherent with the previous hydrological interpretation of speleothem oxygen stable isotope composition 18o as predominantly a rainfall amount proxy however reduced growth rate persisted until ca 130 ka suggesting still depressed temperatures an abrupt event of climatic deterioration with marked decrease in precipitation and soil degradation is apparent between ca 131 and 130 ka cool wet conditions between ca 132 and 131 ka and the subsequent dry period may represent the local hydrological response to an interval of north atlantic cooling and ice rafted debris ird deposition known as heinrich event 11 h11 after 129 6 ka there was a rapid recovery according to all of the studied speleothem properties indicating the onset of full interglacial conditions a minor amplitude event of reduced precipitation is recorded within the lig at ca 127 ka the record highlights the growing regional evidence for a complex penultimate deglacial climate involving major reorganization of oceanic and atmospheric patterns

geology and models of salt extrusion at qum kuh central iran profiles through the summit of a small nearly axisymmetric extrusion of oligocene and miocene salt and simple analogue models of it simulate the profiles of piles of ductile nappes extruded from convergent orogens the salt extrudes from a reactive diapir along a major strike slip fault at about 82 mm a 1 and rises 315 m above the central plateau of iran the salt has the distinctive smooth profile of a viscous fountain in which an asymmetric apron of allochthonous salt gravity spreads over its surroundings from a summit dome curtain folds developed in the source layer extrude from the diapir and are refolded by major recumbent folds with circumferential axes that simulate nappes minor flow folds with circumferential axes refold major folds in the top 10 50 m of surficial salt master joints 100 m long indicate brittle failure of dilated salt by regional stress fields tuned to the dimensions of qum kuh analytical and analogue models of viscous extrusions constrain the dynamic salt budget and a time of extrusion of at least 42 000 years new analogue models suggest that the number amplitude and spacing of major recumbent folds within the extruded salt and ductile nappe piles record the number amount and relative timing of fluctuations in the driving forces

3 d seismic survey in the amazonian rain forest the challenges of the sao mateus prospect exploration for hydrocarbons in the rain forest is one of the great challenges in 3 d seismic acquisition the amazon basin figure 1 poses unique obstacles with which petrobras due to its long history of exploration in the area is uniquely familiar

stable isotope microsampling of speleothems for palaeoenvironmental studies a comparison of microdrill micromill and laser ablation techniques three different techniques are currently in use to microsample speleothem and tufa specimens at moderate to high spatial resolution manual microdrilling using a dentist drill semi automated micromilling and laser ablation while a separate handling step is involved in the first two techniques transferring the sample powder to an on line carbonate preparation system linked to an isotope ratio mass spectrometer the laser is directly interfaced with the mass spectrometer via a gas preparation device in this study we compare stable c and o isotope results obtained by these three preparation techniques using continuous he flow mass spectrometry on the same speleothem samples the overall consistency of the results is satisfactorily high in particular between the micromill and the laser data although the precision of the laser data is slightly lower than analyses obtained by the other two methods in particular with respect to 18o the speed of acquisition renders laser ablation a useful reconnaissance technique for rapidly analyzing long sections of speleothems micromilling is the method of choice to obtain highly spatially resolved isotope data of high analytical precision while microdrilling is still an low cost alternative for sampling at comparably low resolution e g of fast growing stalagmites

role of preexisting faults in the geodynamic evolution of northern tunisia insights from gravity data from the medjerda valley abstract the middle medjerda valley belongs to the tellian zone of tunisia it behaves as a post orogenic basin where surface structural indices are almost completely absent it is noteworthy to recall that alpine and atlasic tectonic prints are well expressed on both sides of this basin this paper presents an integrated study comprising geology and gravity data subsurface geological modeling was based on gravity data interpretation including the complete bouguer anomaly upward continuation residual and derivatives 2 5d gravity modeling was essential for subsurface geometric features characterization in spite of its sub horizontal and smooth topography and the low density of the homogenous quaternary series covering the area well contrasted and variable gravity responses are observed reflecting the heterogeneities of the geological substratum the enhanced horizontal gravity gradient confirms structural systems that are already evidenced by surface geology it supports also the presence of new masked fault systems the main structural features inferred are i nw directed grabens located at mellegue and s ez zaouam depressions ii triassic diapirs associated to ne thrust faults of el merdja bousalem ben bechir and mjez el assa these structures are generally covered by the quaternary series the presence of both distensive and compressive structures within a compressive regime is explained by the solicitation of preexisting fault systems in the area during the nw directed shortening occurred at the upper miocene age the geodynamic evolution of northern tunisia was dominated by strike slip thrust movements through the reactivation of deep major inherited faults e g i the dextral ew oriented fault system of ghardimaou thibar and ii the sinister ns accident of dehmani bousalem ras rajel these accidents shaped the medjerda basin and contribute to its complex geological architecture

field comparison of shallow seismic sources choosing a seismic source for a shallow reflection survey can be the most pivotal decision for the engineering geophysicist the intent of this paper is to present data that will assist in selection of a shallow seismic source best meeting the goals within the constraints of specific projects particularly in areas where the water table is near the surface the data were collected and displayed as seismograms and amplitude spectra for 15 different shallow seismic sources in october 1985 at a single site in new jersey they show the different characteristics of each source considering the almost three orders of magnitude difference in total source energy between the largest and smallest source we chose a display format that presented the data as objectively as possible while still allowing direct source to source comparisons two strong reflections at about 100 and 130 ms probably mark the top and bottom of a clay unit 80 m below the surface at this site our previous work and that of our colleagues

high precision constraints on timing of alpine warm periods during the middle to late pleistocene using speleothem growth periods a long standing problem in the reconstruction of warm climate periods during the late quaternary is the difficulty of determining absolute ages for undisturbed terrestrial climate archives speleothems offer an important source of information about the timing and duration of middle and late pleistocene warm phases a flowstone from the high elevation spannagel cave zillertal alps austria provides a new absolutely dated climate record which includes the most prominent warm phases between 260 and 50 ka before present new data from the penultimate interglacial improve our knowledge about the timing and progression of warm periods in the alps corresponding to marine isotope stages 7 and 8 speleothem growth phases were identified from 261 to 249 from 236 to 229 and from 200 to 192 ka an early onset of the last interglacial is corroborated by a growth phase commencing at 136 7f2 8 ka and the youngest section of the flowstone provides further evidence for an alpine climate during time intervals corresponding to marine isotope stages 5a and 3 sufficiently warm to allow speleothems to grow the high resolution stable isotope profile taken along the growth axis of the flowstone provides information about the hydrological conditions during the growth phases d 2005 elsevier b v all rights reserved

physical modelling of overburden deformation around salt diapirs abstract salt diapirs produce highly complex deformation patterns in the surrounding overburden which are difficult to image seismically or model numerically to further the understanding of deformation around salt structures we have used physical models with brittle granular overburdens and simulated sedimentation accompanying diapiric rise rigid linear indentors produce a crestal horst above the indentor with two flanking graben large amounts of indentation produce predominantly reverse faults along the margins of the diapir and extensional faults over the crest in contrast hemispherical indentors produced inward dipping concentric reverse faults forefully intruded polymer diapirs produce a narrow crestal graben above the diapir crest downbuilt polymer diapirs produce extensional faults on the flanks of the diapirs which offset the diapir walls no clear secondary rim synclines were developed as polymer is withdrawn evenly from the whole of the polymer layer across the model strong and anisotropic layered overburden were simulated using cohesive clay and mica respectively detachments were formed along mica layers which suppressed faults with large throws cohesive layer deformation began with tensile fractures permitting rotation of fractured rafts around the sides of the diapir these progressively slip off the crest and create large gaps in the stratigraphy

radiometric isotopic and petrographic evidence of changing interglacials over the past 550 000 years from six stalagmites from the serra do courel in the cordillera cantabrica of northwestern spain abstract seventy u th ages from six stalagmites from the cordillera cantabrica in northwestern spain indicate deposition during interglacial but not glacial stages over the last 550 kyr stable isotope data and petrographic observations suggest that within each interglacial conditions typically progressed from drier to wetter consideration of the most precise u th ages suggests that stalagmite deposition occurred in times more predictable from european pollen records than from the global marine isotope record for example during the last interglacial ages suggest deposition in an interval better characterized as the eemian as opposed to mis 5e and during the st germain i or mis 5c interval the same holds for mis 7 where ages suggest deposition during mis 7a and mis 7c but not mis 7e these age ranges for interglacials consistently later than those suggested by the benthic marine record are compatible with warm conditions maintained by thermohaline circulation that simultaneously supplied the moisture for growing ice sheets of the subsequent glaciation trends both within and across these six stalagmites suggest that cooler temperatures were associated with wetter conditions both during interglacials and in conditions intermediate between interglacials and glacials in northern spain in contrast other researchers results from a stalagmite from the last glacial maximum and subsequent deglaciation suggest colder temperatures were associated with drier conditions the two trends combine to suggest wettest conditions in times intermediate between interglacials and glacials compatible with a model in which modern climatic belts from dry arctic to wet european to dry marginal saharan have moved over northern spain in the cycle from glacial to interglacial times extrapolation to a warmer future would suggest drier conditions in the northern iberian peninsula than those of today

gravity analysis of salt structures an example from the el kef ouargha region northern tunisia triassic outcrops in the atlassic zone of northern tunisia may be modelled in two ways salt bodies piercing through cretaceous terrains or triassic salt flows stratified within an albian series both models find support from gravity data and are debatable to evaluate the mass distribution changes with depth the bouguer anomaly of the el kef ouargha region was successively decomposed into regional and residual components to construct multiple pseudo depth slices and apparent density maps analyses of gravity lows clearly show a vertical continuity of less dense materials below the triassic salt outcrops these features can be explained by salt diapirism during mesozoic and cenozoic further gravity data tend to indicate less dense materials below aptian outcropping in jebel aite oued bou adila thus suggesting triassic materials occurring at depth in addition dense entities were recognized under mio pliocene and quaternary deposits which are thought to correspond to cretaceous paleoshoals currently collapsed by non outcropping faults our findings lend support to a diapir model intruding overburden rather than the salt glacier model stratified in the albian series proposed by some authors as the genetic structural model for triassic material bearing series in the north of tunisia

freshwater forcing of abrupt climate change during the last glaciation large millennial scale fluctuations of the southern margin of the north american laurentide ice sheet occurred during the last deglaciation when the margin was located between about 43 and 49 n fluctuations of the ice margin triggered episodic increases in the flux of freshwater to the north atlantic by rerouting continental runoff from the mississippi river drainage to the hudson or st lawrence rivers we found that periods of increased freshwater flow to the north atlantic occurred at the same time as reductions in the formation of north atlantic deep water thus providing a mechanism for observed climate variability that may be generally characteristic of times of intermediate global ice volume