assessment of the impact of climate and anthropogenic factors on holocene mediterranean vegetation in europe on the basis of palaeohydrological records abstract correlations between lake level and river activity records from the western mediterranean and palaeohydrological records from northern africa and central europe suggest a distinction in the western mediterranean region between an early holocene period characterised by cooler and moister conditions than at present favourable to temperate deciduous trees and after 5000 yr bp a later holocene period with a warmer and drier climate the second phase was favourable to the extension of evergreen sclerophyllous trees possibly reinforced by human activities these two successive holocene periods reflect orbitally induced changes in summer insolation furthermore superimposed on this general climatic trend century scale climatic oscillations punctuated the whole holocene period decreases in river activity in the western mediterranean region occurred at ca 11 500 10 500 9000 7000 4000 3000 2000 and 800 cal yr bp these decreases coincided with lake level lowering in jura eastern france and glacier retreat in the northern alps and could be associated with a temporary expansion of sclerophyllous trees this general pattern could have resulted from an alternatingly southward northward displacement of the atlantic westerly jet

the interaction of tube waves with borehole fractures part ii analytical models we solve numerically the equations of elastodynamics that govern the propagation of waves in a fluid filled borehole intersected by one or more fluid filled fractures thus extending earlier work on formations presumed to be rigid the model is axis symmetric and it allows for arbitrary radial and vertical variations in the elastic properties of the formation we have developed a novel gridding scheme that takes advantage of the assumed thinness of the fracture compared to any relevant wavelength this technique obviates the necessity for a mesh within the fracture itself and thereby saves computational time and memory we illustrate our technique by means of examples with single and double fractures with or without washouts as well as examples with variable width fractures we compute the frequency dependent reflection and transmission coefficients of tube waves by fractures from the time waveforms generated by the present method major conclusions of this work are 1 reflections of tube waves by fr

classification of dolomite rock textures abstract dolomite rock textures can be classified according to crystal size distribution and crystal boundary shape the classification scheme presented here is largely descriptive but carries genetic implications because size distribution is controlled by both nucleation and growth kinetics and crystal boundary shape is controlled by growth kinetics size distributions are classified as unimodal or polymodal crystal boundary shapes are classified as planar or nonplanar if the evidence permits a complete classification includes a description of recognizable allochems matrix and void filling allochems and preexisting cements may be unreplaced partially replaced replaced mimically or replaced nonmimically allochems may be dissolved leaving molds matrix can be unreplace partially replaced or replaced by a unimodal or polymodal size dolomite unimodal size distributions generally indicated a single nucleation event on a unimodal substrate polymodal sizes can be formed by multiple nucleation events on a unimodal or polymodal substrate or differential nucleation on an originally polymodal substrate planar crystal boundaries develop when crystals undergo faceted growth and nonplanar boundaries develop when crystals undergo nonfaceted growth nonplanar boundaries are characteristic of growth at elevated temperature 50 c and or high supersaturation both planar and nonplanar dolomite can form as a cement replacement of caco3 or neomorphism of a precursor dolomite

low frequency fluid waves in fractures and pipes low frequency analytical solutions have been obtained for phase velocities of symmetrical fluid waves within both an infinite fracture and a pipe filled with a viscous fluid three different fluid wave regimes can exist in such objects depending on the various combinations of parameters such as fluid density fluid viscosity walls shear modulus channel thickness and frequency equations for velocities of all these regimes have explicit forms and are verified by comparisons with the exact solutions the dominant role of fractures in rock permeability at field scales and the strong amplitude and frequency effects of stoneley guided waves suggest the importance of including these wave effects into poroelastic theories

slow waves in fractures filled with viscous fluid stoneley guided waves in a fluid filled fracture generally have larger amplitudes than other waves and therefore their properties need to be incorporated in more realistic models in this study a fracture is modeled as an infinite layer of viscous fluid bounded by two elastic half spaces with identical parameters for small fracture thickness i obtain a simple dispersion equation for wave propagation velocity this velocity is much smaller than the velocity of a fluid wave in a biot type solution in which fracture walls are assumed to be rigid at seismic prospecting frequencies and realistic fracture thicknesses the stoneley guided wave has wavelengths on the order of several meters and an attenuation q factor exceeding 10 which indicates the possibility of resonance excitation in fluid bearing rocks the velocity and attenuation of stoneley guided waves are distinctly different at low frequencies for water and oil the predominant role of fractures in fluid flow at field scales is supported by permeability data showing an increase of several orders of magnitude when compared to values obtained at laboratory scales these data suggest that stoneley guided waves should be taken into account in theories describing seismic wave propagation in fluid saturated rocks

cirques have growth spurts during deglacial and interglacial periods evidence from 10be and 26al nuclide inventories in the central and eastern pyrenees cirques are emblematic landforms of alpine landscapes the statistical distribution of cirque floor elevations is used to infer glacial equilibrium line altitude and the age of their frontal moraines for reconstructing glacial chronologies very few studies however have sought to measure cirque floor and supraglacial ridgetop bedrock downwearing rates in order to confront these denudation estimates with theoretical models of quaternary mountain landscape evolution here we use 10 be nuclide samples n 36 from moraines bedrock steps and supraglacial ridgetops among a population of cirques in the east central pyrenees in order to quantify denudation in the landscape and detect whether the mountain topography bears any relevance to the glacial buzzsaw hypothesis minimum exposure ages meas obtained for a succession of moraines spanning the oldest dryas to the holocene produced a deglaciation chronology for three different pyrenean ranges maladeta bassies and carlit based on a series of corrections calibrations and chronostratigraphic tuning procedures meas on ice polished bedrock exposures were further used to model denudation depths at nested timescales during the wurm the younger dryas and the holocene results show that subglacial cirque floor denudation was lower during glacial periods wurm 10 mm ka than during deglacial and interglacial periods tens to hundreds of mm ka the relative inefficiency of glacial denudation in the cirque zone during the wurm would have resulted from i cold based and or ii low gradient glaciers situated in the upper reaches of the icefield and or from iii glacier load starvation because of arrested clast supply from supraglacial rockslopes situated in the permafrost zone denudation peaked during the younger dryas and holocene glacial advances a time when cirque glaciers became steeper warmer based and when frost cracking weakened supraglacial ridgetops thus enhancing sub glacial erosion by providing debris to the sliding glacier base cirques therefore grow faster during more temperate periods of cirque glaciation than under full glacial conditions another key finding was the very low rates of ridgetop lowering averaged over the wurm and holocene 10 25 mm ka a comparison of the denudation rates obtained from the cirque zone with regional estimates of crustal uplift indicates that the alpine topography is not in a steady state the low intensity of glacial denudation failed to bring the topography to a buzzsaw equilibrium state

evidence for late glacial and holocene environmental changes from subfossil assemblages in sediments of lake neuchâtel switzerland abstract ostracod and diatom assemblages mollusc remains plus pollen and sediment stratigraphy from three cores taken at sites 40 80 and 135 m deep in lake neuch tel switzerland show distinct changes since deglaciation shifts are interpreted in terms both of climatic change and major changes in the catchment input caused by the aar river entering or bypassing lake neuch tel three palaeoenvironmental phases are recognized 1 the late glacial with the inflow of the river before 10 000 yr b p 2 the early to mid holocene with temporary bypassing of the river between 10 000 and 4850 yr b p and 3 the mid to late holocene without river input after approx 4850 yr b p during periods with river input rhythmites were deposited ostracods indicate a well oxygenated hypolimnion suggesting deep ventilation enhanced by the river inflow the diatom assemblage indicates eutrophic to mesotrophic conditions and is dominated by generally well preserved periphytic species the high number of unidentifiable pollen suggests oxidation during transport in the river during periods without river input a massive calcareous silt with abundant authigenic calcite was deposited diatoms indicate a change to mesotrophic and oligotrophic conditions and decreased sedimentation rates and higher alkalinity enhanced the dissolution of diatoms terrestrial and littoral molluscs as well as periphytic diatoms indicate erosion of the shore when the lake level rose or fell with onset or offset of the river inflow before 12 600 yr b p the patchy vegetation cover led to intensive soil erosion and high sedimentation rates the lake was still frozen during the winter months after approx 12 600 yr b p the sediment changed from clastic rhythmites to thinly bedded non glacial rhythmites the vegetation cover became denser the abundance of ostracods increased and molluscs started to colonize the profundal zone of the lake the younger dryas approx 10 700 10 000 yr b p displays maximum abundance of ostracods indicating deep ventilation the transition to the holocene is characterized by a change in the ostracod assemblage and the river bypassed the lake between approximately 10 000 and 8900 yr b p when the river reentered the lake after approximately 8900 yr b p a new ostracod species appeared after two short periods of river bypassing between approximately 7200 and 6950 yr b p diatoms indicate a higher trophic level about 6000 5000 yr b p associated with higher erosion rates and increased nutrient input due to neolithic agricultural activities after approximately 4850 yr b p the river bypassed the lake again and the trophic level decreased in contrast to the early to mid holocene periods of decreased oxygen supply the mid to late holocene is characterized by deep ventilation this is attributed to the northward retreat of the polarfront and enhanced westerlies consequent to decreased insolation after 6000 yr b p the change of the river flow pattern correlates with glacier oscillations and may suggest a climatic control the final cessation of the inflow is attributed to diversion of the river consequent to isostatic uplift and late neolithic clearance activity

hydraulic fracture diagnostics from krauklis wave resonance and tube wave reflections abstractfluid filled fractures support guided waves known as krauklis waves the resonance of krauklis waves within fractures occurs at specific frequencies these frequencies and the associated attenuation of the resonant modes can be used to constrain the fracture geometry we use numerical simulations of wave propagation along fluid filled fractures to quantify fracture resonance the simulations involve solution of an approximation to the compressible navier stokes equation for the viscous fluid in the fracture coupled to the elastic wave equation in the surrounding solid variable fracture aperture narrow viscous boundary layers near the fracture walls and additional attenuation from seismic radiation are accounted for in the simulations we then determine how tube waves within a wellbore can be used to excite krauklis waves within fractures that are hydraulically connected to the wellbore the simulations provide the frequency dependent hydraulic impedance of the fracture which can then be used

holocene fire regime changes from multiple site sedimentary charcoal analyses in the lourdes basin pyrenees france one lake and three peat bogs from the lourdes glacial basin france were used for macrocharcoal analyses and fire frequency reconstruction over the entire holocene 11700 years the chronology was based upon thirty three 14c ams dates comparison of the distribution of both charcoal accumulation rate char and fire return intervals showed that charcoal accumulation significantly differs between the lake and the peat bogs but that frequency calculation overcomes the disparity between these site types a composite frequency was built from the four individual records to assess regional versus local variability and fire regime controls by comparisons with regional fire activity holocene climatic oscillations and vegetation history the millennial variability can be depicted as follows relatively high frequency between 8000 and 5000 cal a bp up to 5 fires 500 yrs relatively low frequency between 5000 and 3000 cal a bp down to 0 fires 500 yrs and an increase between 3000 and 500 cal a bp up to 4 fires 500 yrs from 8000 to 5000 cal a bp fire frequency displays strong synchrony between sites and appears to be mostly driven by increased summer temperature characterizing the holocene thermal maximum htm on the contrary during the last 3000 years fire frequency was heterogeneous between sites and most probably human driven however higher frequency at the millennial scale during the mid holocene strongly suggests that the perception of human driven fire regime depends on the strength of natural controls

acoustic modes of propagation in the borehole and their relationship to rock properties acoustic waveform measurements in boreholes have important applications in fracture hydrology and radioactive waste disposal but ambiguities in existing interpretation techniques remain a problem we have addressed the problem by using residue theory to predict the relative excitation of various modes contained in experimental waveforms a plane geometry model involving a layer of fluid between two elastic half spaces is shown to provide velocity dispersion curves for propagating modes that are very similar to those for the fluid filled borehole we use the plane geometry model to illustrate the effects of the confined borehole fluid on surface and body waves traveling along the borehole in the elastic solid we also computed excitation functions for some of the lowest order symmetric modes calculated the time domain response of the trapped modes following the shear head waves and compared them to waveforms recorded in boreholes through several homogeneous formations the insight into the mode composit

syneresis cracks subaqueous shrinkage in argillaceous sediments caused by earthquake induced dewatering abstract syneresis cracks often confused with subaerial desiccation phenomena are traditionally ascribed to subaqueous shrinkage whereby salinity changes caused deflocculation of clay this and other previously proposed mechanisms fail to account for their occurrence in low energy typically non evaporitic facies stratigraphically sporadic distribution intrastratal formation under shallow burial depths variation in morphology degree of contraction generation of sedimentary dikelets as crack fills and deformation of dikelets and enclosing layers instead it is suggested that ground motion from strong synsedimentary earthquakes caused argillaceous sediments to dewater interbedded sands and silts to be almost simultaneously liquefied and injected into the resulting fissures and then these dikelets to be distorted comparative rarity of syneresis cracks in phanerozoic versus precambrian marine strata is considered to be primarily an evolutionary consequence of theological changes caused by increased organic binding of clay flocs in the water column greater input of organic matter into the sediment and the diversification of sediment dwelling bacteria and meiofauna in phanerozoic deposits

deglaciation in the central pyrenees during the pleistocene holocene transition timing and geomorphological significance abstract in this study we document deglaciation in a sector of the southern central pyrenees the panticosa massif and the upper gallego and ossau valleys using cosmic ray exposure cre dating methods which were applied to samples from high altitude polished rock steps and rock glacier boulders the obtained cre dates show a coherent spatial distribution and confirm results previously obtained in this study area thus demonstrating the reliability and robustness of the method the results of analyses based on two distinct isotopes 10 be and 36 cl are consistent although the error is higher for results based on the 36 cl isotope the study provides evidence for ice extent in the high gallego valley during the oldest dryas with glacial advance until the bottom of the valleys although the main glacier tongues remained disconnected from each other during this period the extent of glacier advance was directly related to the elevation of the associated summits the younger dryas glaciers were constrained to cirques or very short ice tongues and dating of the polished rock steps indicates that the ice masses were present until the first millennium of the holocene the brazato rock glacier developed at the beginning of the holocene and remained active until the holocene thermal optimum because of the protective effect of large masses of blocks and boulders

exposure age chronology of the last glaciation in the eastern pyrenees abstract we present a chronology of ice recession in the eastern pyrenees based on in situ produced 10be data obtained from the tet paleoglacier complex the sampling strategy is based on the relative chronology provided by a detailed geomorphological map of glacial landforms results indicate that the last maximum ice advance occurred late i e during marine isotope stage 2 compared to the chronology currently established for the rest of the pyrenees despite debatable evidence for a glacial readvance during the oldest dryas stade ice cap melt out was rapid residual cirque glaciers having disappeared by the allerod interstade this is consistent both with north atlantic excursions established by the greenland ice cores and paleoenvironmental data for the region the rapid response of the east pyrenean ice cap to temperature variations is primarily linked to its small size compared to larger pyrenean ice fields to the dry mediterranean climate and to topography related nonlinearities in which a small vertical rise in equilibrium line altitude generates a large change in ice mass possible sources of age uncertainty are discussed in the context of sampling design for single nuclide 10be dating of landform sequences in formerly glaciated landscapes

a compositional classification for grain assemblages in fine grained sediments and sedimentary rocks reply abstract a tripartite compositional classification is proposed for sediments and sedimentary rocks that have grain assemblages with greater than 50 percent of a weight or volume of particles smaller than 62 5 m 4 phi tarl terrigenous argillaceous contains a grain assemblage dominated by more than 75 percent of particles of extrabasinal derivation including grains derived from continental weathering and also volcanogenic debris carl calcareous argillaceous contains less than 75 percent of particles of extrabasinal derivation debris and among its intrabasinal grains contains a preponderance of biogenic carbonate particles including carbonate aggregates sarl siliceous argillaceous contains less than 75 percent of particles of extrabasinal derivation and contains a preponderance of biogenic siliceous particles over carbonate grains these three classes of fine grained particulate sediments and rocks effectively separate materials that have distinct depositional settings and systematic contrasts in organic matter content and minor grain types in the subsurface the grain assemblages that define these classes follow contrasting and predictable diagenetic pathways that have significant implications for the evolution of bulk rock properties and thus assigning a fine grained rock to one of these classes is an important first step for predicting its economic and engineering qualities for purposes of description these three class names can be joined to modifier terms denoting rock texture more precise compositional divisions specific grain types of notable importance and diagenetic features

fracture evaluation using reflected stoneley wave arrivals we use the low frequency reflected stoneley wave mode to locate permeable fractures intersecting a borehole and to estimate their effective apertures assuming a model in which the average aperture of the fracture is roughly constant theoretical work relates the magnitude of the stoneley wave reflectivity to an effective fracture width we treat both the case of a horizontal fracture and the case of a fracture crossing the borehole at an angle laboratory experiments verify the analytic solution for the case of a horizontal fracture full waveform array sonic data were also acquired in a wellbore with a long recording time 25 5 ms in order to capture the late stoneley wave arrivals the data processing involves computation of the stoneley wave reflectivity response using the measured direct and reflected stoneley wave arrivals a least squares fit to the arrival time of the reflected wave arrivals is used to estimate the locations of permeable fractures and the effective width of the fractures is esti

the three forks playa lake depositional model implications for characterization and development of an unconventional carbonate play the upper devonian three forks formation of the williston basin is an important reservoir interval in the bakken petroleum system with estimates suggesting greater than 3 7 billion bbl of recoverable oil detailed stratigraphic analyses are sparse but current studies propose shallow marine tidal flat or coastal sabkha environments for its deposition based on stratigraphic sedimentological and petrographic analyses of 28 cores we infer that the three forks formation was deposited in a continental setting with little to no marine influence the setting was subaerial to subaqueous environments comparable to those found in playa lake systems or continental sabkhas late devonian paleography and tectonics provided the isolation and slow subsidence of the williston basin that led to the accumulation of the three forks formation in a hot and arid climate occasional floods were responsible for the deposition of the terrigenous sediments debrite like deposits reworking bedforms scouring and erosional surfaces flood waters collected in ephemeral lakes and ponds evaporated resulting in the deposition of subaqueous dolomite anhydrite and even halite the ponds and lakes progressively evaporated and contracted until they eventually dried out the drying is characterized by dewatering structures subaerially exposed and transported sediments with ripples scour surfaces evaporite cemented surfaces evaporite removal breccias halite pseudomorphs and a variety of cracks vertical successions record an upward trend of increasing proportions of subaqueous facies indicating a transition from arid to relatively less arid climatic conditions during three forks deposition this depositional system resulted in the accumulation of a complex mosaic of lithologies composed of different proportions and textures of silt sized detrital dolomite and quartz clay and evaporites in patchy to bull s eye configurations this depositional model provides a coherent understanding of the existing depositional lithofacies and their petrophysical and geomechanical properties and provides the background for the prediction of their lateral distribution from wire line logs

properties of low frequency trapped mode in viscous fluid waveguides we derived the velocity and attenuation of a generalized stoneley wave being a symmetric trapped mode of a layer filled with a newtonian fluid and embedded into either a poroelastic or a purely elastic rock the dispersion relation corresponding to a linearized navier stokes equation in a fracture coupling to either biot or elasticity equations in the rock via proper boundary conditions was rigorously derived a cubic equation for wavenumber was found that provides a rather precise analytical approximation of the full dispersion relation in the frequency range of 10 3 hz to 103 hz and for layer width of less than 10 cm and fluid viscosity below 0 1 pa s 100 cp we compared our results to earlier results addressing viscous fluid in either porous rocks with a rigid matrix or in a purely elastic rock and our formulae are found to better match the numerical solution especially regarding attenuation the computed attenuation was used to demonstrate detectability of fracture tip reflections at wellbore for a range of fracture lengths and apertures pulse frequencies and fluid viscosity

recent behaviour of the debeli namet glacier durmitor montenegro a small cirque glacier is present in a north east facing cirque on the mountain of sljeme 2455 m a s l in the durmitor massif montenegro sediment ridges in front of this glacier are interpreted as moraines and can be attributed to recent glacier activity over the past 130 years lichenometry was applied to determine the relative ages of different moraines using aspicilia calcarea agg one set of moraines dates from about 1878 ad whilst another set of inner moraines dates from about 1904 ad the most recent moraines appear to have formed within the last 11 years in front of an active glacier margin copyright 2007 john wiley sons ltd

permafrost conditions in the mediterranean region since the last glaciation the relatively warm climate conditions prevailing today in the mediterranean region limit cold geomorphological processes only to the highest mountain environments however climate variability during the late pleistocene and holocene has led to significant spatio temporal variations of the glacial and periglacial domain in these mountains including permafrost conditions here we examine the distribution and evolution of permafrost in the mediterranean region considering five time periods last glaciation deglaciation holocene little ice age lia and present day the distribution of inactive permafrost derived features as well as sedimentary records indicates that the elevation limit of permafrost during the last glaciation was between 1000 m and even 2000 m lower than present permafrost was also widespread in non glaciated slopes above the snowline forming rock glaciers and block streams as well as meter sized stone circles in relatively flat summit areas as in most of the northern hemisphere the onset of deglaciation in the mediterranean region started around 19 20 ka the ice free terrain left by retreating glaciers was subject to paraglacial activity and intense periglacial processes under permafrost conditions many rock glaciers protalus lobes and block streams formed in these recently deglaciated environments though most of them became gradually inactive as temperatures kept rising especially those at lower altitudes following the younger dryas glacial advance the early holocene saw the last massive deglaciation in mediterranean mountains accompanied by a progressive shift of permafrost conditions to higher elevations it is unlikely that air temperatures recorded in mediterranean mountains during the holocene favoured the existence of widespread permafrost regimes with the only exception of the highest massifs exceeding 2500 3000 m lia colder climate promoted a minor glacial advance and the spatial expansion of permafrost with the development of new protalus lobes and rock glaciers in the highest massifs finally post lia warming has led to glacial retreat disappearance enhanced paraglacial activity shift of periglacial processes to higher elevations degradation of alpine permafrost along with geoecological changes

dolomite occurrence evolution and economically important associations abstract dolomite is not a simple mineral it can form as a primary precipitate a diagenetic replacement or as a hydrothermal metamorphic phase all that it requires is permeability a mechanism that facilitates fluid flow and a sufficient supply of magnesium dolomite can form in lakes on or beneath the shallow seafloor in zones of brine reflux and in early to late burial settings it may form from seawater from continental waters from the mixing of basinal brines the mixing of hypersaline brine with seawater or the mixing of seawater with meteoric water or via the cooling of basinal brines bacterial metabolism may aid the process of precipitation in settings where sulfate reducing species flourish and microbial action may control primary precipitation in some hypersaline anoxic lake settings dolomite is a metastable mineral early formed crystals can be replaced by later more stable phases with such replacements repeated a number of times during burial and metamorphism each new phase is formed by the partial or complete dissolution of an earlier dolomite this continual re equilibration during burial detracts from the ability of trace elements to indicate depositional conditions and resets the oxygen isotope signature of the dolomite at progressively higher temperatures because subsurface dolomite evolves via dissolution and reprecipitation a bed of dolomite can retain or create porosity and permeability to much greater burial depths and into higher temperature realms than a limestone counterpart dolomitization also creates new crystals with new rhomb growth following the dissolution of less stable precursors repetition of this process without complete pore cementation can generate intercrystalline porosity a number of times in the rock s burial history intercrystalline porosity is a highly interconnected style of porosity that gives dolomite reservoirs their good fluid storage capacity and efficient drainage the fact that many dolomite reservoirs formed via brine reflux means that they sit beneath an evaporite seal in both platform and basinwide evaporite settings the same association of evaporites sulfate source and entrained hydrocarbons means that burial conditions are also suitable for thermochemical sulfate reduction and the precipitation of base metals this tends to occur at higher temperatures 60 c 80 c and so the resulting dolomites tend to be ferroan and consist of saddle shaped crystals

holocene and little ice age glacial activity in the marbore cirque monte perdido massif central spanish pyrenees the marbore cirque which is located in the southern central pyrenees on the north face of the monte perdido peak 42 40 0 n 0 5 0 w 3355 m contains a wide variety of holocene glacial and perig

holocene fire and vegetation dynamics in the central pyrenees spain abstract fire vegetation relationships are critical to understand transient mountain ecosystems and their long term landscape dynamics which is essential for alpine forest conservation in this paper we aim to 1 reconstruct the holocene fire history at high altitudes of the southern central pyrenees 2 add evidence to the debate on fire origin naturally or anthropogenically produced 3 determine the importance of fire as a disturbance agent for sub alpine and alpine vegetation in comparison with the plant community internal dynamics applying conditional inference trees we present and compare microcharcoal and pollen data series from two lacustrine sedimentary sequences in the central pyrenees basa de la mora bsm within the treeline ecotone at the sub alpine belt 1914 m a s l and marbore lake above the treeline at the alpine belt 2612 m a s l we evidence that fire activity was not the most important factor in driving vegetation dynamics regionally our results suggest that spatially the fire signal might be site dependent while over time climate exerted a strong influence on fire activity during the early to mid holocene showing more fires during the holocene thermal maximum htm ca 7000 6000 cal yr bp whereas fire activity decreased with the cold neoglacial period at ca 3700 cal yr bp fire activity increased coinciding with a regional landscape opening suggesting that human activities may have strengthened the importance of fire fire activity remained low over the last two millennia but a remarkable holocene maximum for the last centuries in both sequences is observed likely related to increasing human pressure

late quaternary glacial phases in the iberian peninsula abstract the only glaciers existing today in the iberian peninsula are small features located in the pyrenees though their number and extension has undergone significant changes over the late quaternary the wide range of glacial landforms and deposits distributed across different iberian ranges suggests the occurrence of several past periods with larger glacial systems the objective of this research is to summarize the current knowledge on the spatial and temporal patterns of glacial activity in the iberian mountains during the late quaternary to this purpose the chronological framework was divided in six periods glaciations prior to the last glacial cycle middle pleistocene last glacial cycle late pleistocene termination 1 holocene little ice age lia and present day the data were geographically divided considering the mountain systems where glacial evidence exists pyrenees cantabrian range nw ranges central range iberian range and sierra nevada during quaternary cold stages ice accumulated in the head valleys of these mountain ranges and glaciers flowed down valleys in all cases glaciers remained confined within the mountain systems and did not reach the surrounding lowlands depending on the combination of temperatures and moisture conditions more or less ice was stored in some ranges there is evidence of middle pleistocene glaciations one potentially correlating with marine isotope stage mis 12 and another correlating with mis 6 with glaciation dated to ca 130 170 ka however most of the glacial records correspond to the last glacial cycle and subsequent termination the maximum glacial expansion of this last pleistocene glaciation stage occurred well before the global last glacial maximum lgm between 30 and 60 ka in the cantabrian mountains and pyrenees at ca 30 ka in sierra nevada and nw ranges and almost synchronously to the lgm in the central range and iberian range a massive glacial retreat occurred in all ranges at 19 20 ka but the long term deglaciation process was interrupted by cold intervals such as the oldest and younger dryas which favoured glacial expansion in the highest mountains temperature increase recorded during the holocene conditioned the melting of glaciers which only reappeared in the highest massifs during the coldest periods such as the lia however post lia warming led to glacier disappearance in the cantabrian mountains sierra nevada and most massifs of the pyrenees together with an accelerated shrinkage of the small glaciers still existing in this range at elevations near 3000 m

depositional environments and diagenesis in lake parakeelya a cambrian alkaline playa from the officer basin south australia laminated and desiccated siliceous dolostones dolomitic mudstones and dolomitic sandstones in the cambrian parakeelya alkali member of the observatory hill formation accumulated in an alkaline playa four facies are recognized from lake centre to lake edge lake saline mudflat dry mudflat and sandflat facies the facies occur in cycles cycles of tens of metres thickness record the gradual expansion and contraction of the playa superimposed smaller cycles of tens of centimetres thickness record minor oscillations in the position of the strandline in a shallow lake the dominance of saline mudflat dry mudflat and sandflat facies indicates that the lake was rimmed by broad flat areas with negligible relief the high 18o values of primary and penecontemporaneous diagenetic carbonates of 24 to 28 smow indicate strong evaporation of ground and surface waters within the lake system calcite pseudomorphs of the sodium carbonate minerals trona and shortite have 18o values between 19 and 22 5 and contain fluid inclusions with variable salinites and homogenization temperatures up to around 110 c this suggests that the euhedral alkaline evaporites were dissolved by heated waters calcite pseudomorphs then precipitated from a mixed solution formed by the interaction of these incoming fluids with the relatively saline interstitial brines the sodium bicarbonate solutions formed by dissolution of the evaporites would have been dispersed by the basinal brines so that despite the closed drainage further groundwater concentration did not take place

u s geological survey 2013 assessment of undiscovered resources in the bakken and three forks formations of the u s williston basin province abstract the upper devonian three forks and upper devonian to lower mississippian bakken formations comprise a major united states continuous oil resource current exploitation of oil is from horizontal drilling and hydraulic fracturing of the middle member of the bakken and upper three forks with ongoing exploration of the lower three forks and the upper lower and pronghorn members of the bakken formation in 2008 the u s geological survey usgs estimated a mean of 3 65 billion bbl of undiscovered technically recoverable oil resource within the bakken formation the usgs recently reassessed the bakken formation which included an assessment of the underlying three forks formation the pronghorn member of the bakken formation where present was included as part of the three forks assessment due to probable fluid communication between reservoirs for the bakken formation five continuous and one conventional assessment units aus were defined these aus are modified from the 2008 au boundaries to incorporate expanded geologic and production information the three forks formation was defined with one continuous and one conventional au within the continuous aus optimal regions of hydrocarbon recovery or sweet spots were delineated and estimated ultimate recoveries were calculated for each continuous au resulting undiscovered technically recoverable resource estimates were 3 65 billion bbl for the five bakken continuous oil aus and 3 73 billion bbl for the three forks continuous oil au generating a total mean resource estimate of 7 38 billion bbl the two conventional aus are hypothetical and represent a negligible component of the total estimated resource 8 million barrels of oil

late pleistocene and holocene glaciation in the pyrenees a critical review and new evidence from 10be exposure ages south central pyrenees a compilation and a critical assessment of the 14c data set available show that the chronology of glacial events in the pyrenees is not well constrained after reviewing the literature on glacial reconstruction we suggest a simplified subdivision of the pyrenean last glacial cycle record into last pleniglacial deglaciation and neoglacial to improve the numerical glacial chronology we provide 10be surface exposure ages for 5 glacial erosion surfaces 9 moraines and 2 erratics in the upper noguera ribagorcana valley south central pyrenees published corrected 14c data and new 10be exposure ages indicate that the major phase of moraine building recorded in this valley during the last pleniglacial probably occurred after 25 ka bp this age calls in question the generally accepted hypothesis of a very early deglaciation of the pyrenees ca 70 40 ka bp and strongly suggests that the pyrenees could have been in pleniglacial conditions during the last glacial maximum lgm however we do not exclude the possibility that the maximum glacier extent during the last glacial cycle had taken place much earlier than the lgm as indicated by some published u th ams 14c and osl data we suggest that pleniglacial conditions could have taken place during a longer 30 20 ka period than generally assumed and that the last pleniglacial could include several glacier fluctuations recorded irregularly in different valleys with a last major glacier readvance taking place around the lgm in addition the deglaciation is represented by a series of moraines deposited between ca 13 7 0 9 and 10 1 0 6 ka this moraine series indicates a highly variable climatic pattern that is partly correlated with greenland stadial 1 the younger dryas and suggests that the deglaciation could have continued into the early holocene

rock glacier dynamics in a marginal periglacial high mountain environment flow movement 1991 2000 and structure of the argualas rock glacier the pyrenees the argualas rock glacier is located on the southern side of the central pyrenees argualas massif vertical electric sounding debris surface analysis and a topographic survey were performed on this rock glacier between 1991 and 2000 high precision measurement records were obtained using a total station horizontal and vertical movements of the rock glacier were measured by means of sixteen steel rods horizontal and vertical angles and distances to each rod were measured from three stations on a bedrock ridge total and annual average displacements were derived from the emergence value and the horizontal displacement of each rod then the horizontal and vertical displacement rates in different sectors of the rock glacier were compared the inferred surface deformation was characterized by both extensional and compressive flows as well as thinning of the frozen body the displacement rates showed temporal variations related to atmospheric thermal changes pointing to a high sensibility of the rock glacier

ground motion in the near field of a fluid driven crack and its interpretation in the study of shallow volcanic tremor we present a study of the motion of the ground in the near field of a fluid driven tensile crack embedded in a layered half space the source that we consider is the jerky opening of a channel connecting two fluid filled cracks and the cause of this opening is the excess pressure of fluid in one of the cracks we make a complete representation of the three components of ground motion in the space time and frequency domains and analyze the effects of fluid compressibility source depth and medium structure on the ground response the calculations show the presence of a dominant frequency of motion which depends not only on the source geometry and bulk modulus of the fluid but also on medium characteristics receiver position and the component of motion being considered using this source model we view an episode of volcanic tremor as a continuous sequence produced by numerous jerky openings of channels occurring randomly in time along a chain of cracks our results are applied to the october 5 6 1963 east rift eruption of kilauea volcano hawaii and found to be compatible with available seismic data suggesting that magma is transported through an ensemble of cracks with the area of 1 1 km each pair of cracks constituting an individual dike segment which opens in discrete increments at a rate of 1 s we obtain the following parameters for each dike segment opening increase in cavity volume 40 m3 stress drop 0 004 bar seismic moment 1019 dyn cm and force applied by the fluid to open the dike 1014 dyn the total moment integrated over the entire duration of tremor for the eruption is 0 5 1024 dyn cm roughly equivalent to a single magnitude m 5 earthquake the seismic source parameters and other field observations offer constraints on the process of mass transport and are compatible with the excess pressure and viscosity of magma of about 40 bars and 102 p respectively

crack stiffness from crack wave velocities we estimate crack stiffness by analyzing crack wave velocities we measured crack waves which propagated along an artificial subsurface fracture in higashi hachimantai hot dry rock model field iwate prefecture japan the artificial subsurface fracture was created at a depth of about 370 m by hydraulic fracturing we controlled contact conditions of the fracture surfaces by hydraulic pressurization a time frequency representation technique the pseudo wigner distribution is applied to determine the travel time of the crack wave the crack wave shows dispersion low frequency components below 100 hz have lower velocities we compare velocity data obtained in the field crack wave measurement to those calculated in a simple fracture model in which dimensionless crack stiffness reflects a degree of contact of the asperity on the fracture surfaces slope of the dispersion estimated from the field data agrees with that of the theoretical curves we estimate the dimensionless crack stiffness is 0 001 to 0 005 from this comparison this dimensionless crack stiffness 0 001 means that crack stiffness on propagation path of the crack waves is 74 gpa m

mid holocene glacial activity in the pyrenees radiocarbon dating of sediments from a bog at c 2100 m in the cirque de troumouse provides the first reliable dating of holocene glacier fluctuations in the pyrenees the oldest organic material in the bog provides a maximum date 5190 90 bp for moraines immediately downvalley which are either lateglacial or more probably holocene in age bracketing dates on laminated glacioacustrine sediments in the bog indicate a neoglacial event between 4955 90 and 4654 60 bp which was probably contemporaneous with moraine ridges immediately upvalley more recent neoglacial events as yet undated are indicated by younger silt rich sediments in the bog and two younger moraine sets on the cirque floor at altitudes of c 2250 2350 m little ice age events were more restricted in extent and are recorded by younger moraines at c 2360 and at c 2650 m resting on and immediately below the cirque wall