paleoenvironmental changes in the western mediterranean since the last glacial maximum high resolution multiproxy record from the algero balearic basin abstract the present study uses a multiproxy approach in order to further understand the evolution of climate responses in the western mediterranean as of the last glacial maximum sediments from odp site 975 in the algero balearic basin have been analysed at high resolution both geochemically and mineralogicallly the resulting data have been used as proxies to establish a sedimentary regime primary marine productivity the preservation of the proxies and oxygen conditions fluctuations in detrital element concentrations were mainly the consequence of wet arid oscillations productivity has been established using ba excess according to which marine productivity appears to have been greatest during cold events heinrich 1 and younger dryas the s1 time interval was not as marked by increases in productivity as was the eastern mediterranean in contrast the s1 interval was first characterized by a decreasing trend and then by a fall in productivity after the 8 2 ky bp dry cold event since then productivity has remained low here we report that there was an important redox event in this basin probably a consequence of the major oceanographic circulation change occurring in the western mediterranean at 7 7 ky bp this circulation change led to reventilation as well as to diagenetic remobilization of redox sensitive elements and organic matter oxidation comparisons between our paleoceanographic reconstruction for this basin and those regarding other mediterranean basins support the hypothesis that across the mediterranean there were different types of responses to climate forcing mechanism the algero balearic basin is likely to be a key area for further understanding of the relationships between the north atlantic and the eastern mediterranean basins

an 8000 year history of landscape climate and copper exploitation in the middle east the wadi faynan and the wadi dana national reserve in southern jordan abstract investigations of geomorphology geoarchaeology pollen palynofacies and charcoal indicate the comparative scales and significance of palaeoenvironmental changes throughout the holocene at the junction between the hyper arid hot wadi arabah desert and the front of the mediterranean belt mountains of edom in southern jordan through a series of climatic changes and episodes of intense mining and smelting of copper ores early holocene alluviation followed the impact of neolithic grazers but climate drove fluvial geomorphic change in the late holocene with a major arid episode corresponding chronologically with the little ice age causing widespread alluviation the harvesting of wood for charcoal may have been sufficiently intense and widespread to affect the capacity of intensively harvested tree species to respond to a period of greater precipitation deduced for the roman byzantine period a property that affects both taphonomic and biogeographical bases for the interpretation of palynological evidence from arid lands with substantial industrial histories studies of palynofacies have provided a record of human and climatic causes of soil erosion and the changing intensity of the use of fire over time the patterns of vegetational climatic change and geomorphic changes are set out for this area for the last 8000 years

stable isotope records of late quaternary climate and hydrology from mediterranean lakes the isomed synthesis lake isotope records can be used to assess the spatial coherency of late quaternary climate change across the circum mediterranean region we place modern and palaeo data within a simple conceptual lake response model to show that the isotope hydrology of most mediterranean lakes has been influenced strongly by water balance even in those systems that are chemically dilute i e freshwater 18o data on biogenic and endogenic carbonates from 24 lake basins are used to reconstruct multi millennial scale trends since the lgm while it is difficult to make direct comparisons between lake records in terms of single climatic parameters coherent regional isotopic trends can be identified during glacial times mediterranean lakes deposited carbonates isotopically heavier in 18o compared to the holocene partly due to source area effects isotopic enrichment was most marked during intervals corresponding to the h1 and younger dryas events confirming that late pleistocene cold stages in the north atlantic region were marked by aridity around much of the mediterranean almost all mediterranean lake records shifted to more depleted isotopic values during the last glacial interglacial transition lgit this shift is the reverse of the trend which characterised the same transition in lakes from northern and central europe and suggests that temperature changes were not an important direct driver of mediterranean lake isotopic records over glacial interglacial timescales in the early holocene many lakes in the eastern part of the region were more depleted isotopically than in recent millennia this corresponds with marine sapropel formation both chronologically and geographically and implies that increases in local rainfall contributed significantly to the creation of a freshwater lid and anoxia in the east mediterranean sea in contrast no such pattern is currently apparent from lake isotope records from the west mediterranean suggesting a possible nw se contrast in climate history during the holocene

holocene climatic changes in the western mediterranean from south east france to south east spain abstract holocene climatic changes along coastal regions from south east france to south east spain were studied using pollen ratios comparing modern pollen rain vegetation and climate along selected transects from the atlantic ocean to the mediterranean we obtained threshold values of two different ratios corresponding to the different climatic conditions along the transects these pollen ratios and threshold values were employed to characterize the holocene climatic changes from nine mediterranean coastal sites the results were compared with data from marine and continental pollen sequences distributed in the western mediterranean basin and with additional regional data independent of human activity lake level fluctuations alpine glacier advance and retreat chronology 14 c anomaly and cooling phases in eastern france and central europe the role of anthropogenic activities and climate on the changes in vegetation is discussed six major changes in vegetation cover were identified they correspond to aridification phases that occurred around 9500 9000 yr bp 10 900 9700 cal bp 7500 7000 yr bp 8400 7600 cal bp 4500 4000 yr bp 5300 4200 cal bp 3700 3300 yr bp 4300 3400 cal bp 2600 1900 yr bp 2850 1730 cal bp and 1300 1000 yr bp 1300 750 cal bp these arid episodes were regional responses to more global climatic changes and determined the changes in the vegetation cover humans undoubtedly enhanced the vegetation changes but none the less had to adapt to these new climatic conditions

multiproxy record for the last 4500 years from lake shkodra albania montenegro a multi proxy record is presented for approximately the last 4500 cal a bp from lake shkodra albania montenegro lithological analyses c n ratio and d 13 c of the organic and inorganic carbon component suggest that organic matter and bulk carbonate are predominantly authigenic the d 18 o record of bulk carbonate indicates the presence of two prominent wet periods one at ca 4300 cal a bp and one at ca 2500 2000 cal a bp the latter phase is also found in southern spain and central italy and represents a prominent event in the western and central mediterranean in the last 2000 years four relatively wet intervals occurred between ca 1800 and 1500 cal a bp 150 450 ad 1350 1250 600 700 ad 1100 800 850 1150 ad and at ca 90 cal a bp 1860 ad between ca 4100 and 2500 cal a bp d 18 o values are relatively high with three prominent peaks indicating drier conditions at ca 4100 4000 cal a bp ca 3500 and at ca 3300 cal a bp four additional drier events are identified at 1850 ca 100 ad 1400 ca 550 ad 1150 800 ad and ca 750 cal a bp 1200 ad the pollen record does not show changes in accordance with these episodes owing to the poor sensitivity of vegetation in this area which is dominated by an orographic rainfall effect and where changes in altitudinal vegetation belts do not affect the pollen rain in the lake catchment however since ca 900 cal a bp a significant decrease in the percentage arboreal pollen and in pollen concentrations suggest major deforestation produced by human activities copyright 2012 john wiley sons ltd

ice push disturbances in high boreal and subarctic lakeshore ecosystems since ad 1830 northern quebec canada ice scars on lakeshore trees were surveyed on the islands of two large lakes in northern quebec clearwater lake 1270 km2 and bienville lake 900 km2 respectively at the southern edge of the subarctic and at the northern limit of the boreal zones correspondence of ice scar chronologies with hydrological and climatological instrumental registers indicated that shore ice pushes are due to lake floods in the ad 1930s a shift in the flood regimes occurred in the high boreal ice push activity was much more frequent prior to 1930 than in the subarctic major regional ice pushes occurred in ad 1854 1903 1914 1936 1947 1954 1959 60 1970 and 1979 prior to 1930 local major events were concentrated south of the subarctic zone but the situation inverted after 1930 a northward shift in the average position of the arctic front is postulated as having been the driving force of local hydrologic regimes that allowed ice disturbances to occur especially a in controlling the amount of snowfall ice scars

environmental change in crete a 9000 year record of holocene vegetation history and the effect of the santorini eruption palynological investigations were carried out in the coastal lowland of northwestern crete in the area of lake kournas results comprise the longest continuous vegetation record 9000 radiocarbon years for crete from about 8500 to 7500 bp open deciduous oak forest occurred and appears to reflect the driest conditions of the holocene after 7500 bp tree pollen numbers increase some of these tree species are thought to be autochthonous but for at least six species this is doubted and the presence of their pollen is ascribed to long distance transport up to 6000 bp the local vegetation included deciduous and evergreen oaks pistacia phillyrea and a variety of herbs only after 7000 bp some species e g mercurialis annua cynocrambe and spores of pteridium might indicate the effects of neolithic habitation towards 6000 bp plane tree and styrax storax appear from about 6000 bp olive is present and human activity becomes more evident slowly pollen types indicative of the exploitation of present day mediterranean vegetation e g poterium and ericaceae appear and the presence of the alga gloeotrichia indicates a rise in phosphate a striking aspect of the sediment core nearest to the sea is a pumice layer originating from the theran santorini eruption from the manner of its deposition it is concluded that no tsunami met the cretan beach influence of the eruption from thera on the vegetation is hardly visible decrease of economically important cultivated plants e g olive already took place decades up to about a century before the volcanic eruption around the time of the eruption the values of some pollen types hardly changed others increased and another group decreased this pollen behaviour appears to be explained rather by socio economic changes such as withdrawing of the inhabitants to the interior for reasons other than volcanic effects it is concluded from the pollen cores that no major climatic changes affected northwestern crete during the holocene but the first two millennia of the holocene tended to be drier than the following period when there was an increase in moisture demanding trees it is difficult to assign changes in the cretan vegetation to climatic effects in a period when human impact was gathering strength

using ice scars as indicators of exposure to physical lakeshore disturbances corvette lake northern quebec canada the hypothesis tested in this study is that ice scars recorded by lakeshore tree stands can be used as an integrative proxy indicator of the overall hydrodynamic disturbance regimes affecting northern lakeshores a 2 km long shore segment was divided into 21 sections according to shore orientation and slope an ice scar chronology and a wave exposure index value were obtained for each shore section a significant relationship was found between ice scar chronology and wave exposure index which indicates that the mechanical action and physical force of ice activity mainly depend on the same environmental factors determining exposure to wave action i e fetch wind direction and velocity and shore slope the spatial and temporal variability of ice scar chronology features also corresponded to the distribution of geomorphological features associated with ice activity along the shoreline analysis of the hydrological signal associated with these ice scar chronology features indicated that an increase in ice push frequency observed in the 1930s can be associated to an increase in wave action related to more frequent spring floods maintaining high lake levels during the ice free period this study demonstrates that ice scars have strong potential as proxy indicators of shore exposure and provide a temporal frame to reconstruct the history of lakeshore disturbance regimes at a local scale together ice scars and wave exposure index provide essential information to interpret the evolution of lakeshore vegetation mosaics in time and space copyright 2012 john wiley sons ltd

reconstruction of holocene high altitude vegetation cover in the french southern alps evidence from soil charcoal the study presented here from the southern french alps demonstrates the reliability of soil charcoal analysis for the study of holocene past treeline positions the occurrence of charcoal in mineral soils along transects from 1950 m up to 2920 m demonstrates the role of fire in the establishment of the present vegetation patterns the abrupt decrease of charcoal concentration at about 240 0 2 600 m which varies across the study sites corresponds to the modern transition between subalpine forest and alpine tundra charcoal particles formedinsitu providehighspatial resolutiondataforthereconstructionofpastforestandtreelinechanges soil charcoal analysis indicated that 1 treeline was 300 m higher around 6800 cal bp than today and 2 the uppermost forest belt up to 2810 m was colonized by larch larix decidua mill and arolla pine pinus cem bra l thispineispresenttodaybutpatchilydistributed itisabsentfromthethreeareasstudied radiocarbon dates ranging from c 6800 cal bp to the modern period along with historical and archaeological data sug gest that the present pattern of the uppermost forest belt and the patchy distribution of arolla pine in the stud ied area are the results of anthropogenic fire mainly agropastoral activities the question of global warming consequences on treelines in this part of the french alps is discussed

reconstructed summer degree days in central alaska and northwestern canada since 1524 abstract three time series based on precisely dated annual tree ring widths have been used to reconstruct june plus july degree days for the central alaska and northwestern canada region the time series are the longest recently developed chronologies for the area and represent 57 core samples from 27 trees the degree day reconstruction extending back to a d 1524 exhibits much year to year variation and extended warming and cooling trends including a general warming trend from about 1840 to 1960 the reconstruction is in agreement with some subaretic glacial information and with data of percentage melting from arctic ice cores this and similar reconstructions can provide quantitative information to compare with general circulation and energy budget models for longer time periods than are available in recorded meteorological data

climate environment and society in southern italy during the last 2000 years a review of the environmental historical and archaeological evidence abstract this paper examines the interrelationship between the natural and human history of sicily over the last 2000 years it presents a close comparison of the data from the key multi proxy site of lago di pergusa located inland in the eastern part of sicily with the existing archaeological and textual evidence on the socio economic processes the article also includes a review of the available natural proxy archives from the central mediterranean on the basis of the isotope and pollen data from the lago di pergusa core prg2 we identified two humid periods ca 450 750 ad and ca 1400 1800 ad as well as a dry one ca 1100 1350 ad our evidence corresponds closely with other environmental palaeoclimate proxies from the mediterranean region in our synthesis of the environmental historical and archaeological evidence from southern italy we argue that during both periods of increased humidity that is during the late antique byzantine times and during the late medieval and early modern periods intense agricultural use of the sicilian landscape developed on an unprecedented scale this in turn contributed to the impressive demographic and economic expansion visible during these periods a sudden period of aridity followed the first of these eras of humidity related agricultural growth this climatic shift dated to around 750 ad corresponds to a decrease in synanthropic taxa and a recovery of arboreal vegetation we argue that in this case a climatic change contributed to socio economic decline moreover as this change occurred prior to the arab invasion of sicily in ad 827 the environmental processes may help to explain the collapse of byzantine society on sicily which in turn made the muslim conquest possible after this event there occurred a longer period of agricultural decline lasting until around 1000 ad after which we see the first signs of a slow recovery ongoing research in nearby archaeological sites will help defining if it was a local change or a regional potentially climate induced phenomenon although textual evidence records considerable population losses during the later middle ages as a result of the black death the effects of the plague are not obviously apparent in the pollen data except for some short term fluctuations

little ice age clearly recorded in northern greenland ice cores four ice cores drilled in the little investigated area of northern and northeastern greenland were evaluated for their isotopic 18o and chemical content from these rather uniform records a stable isotope temperature time series covering the last 500 years has been deduced which reveals distinct climate cooling during the 17th and the first half of the 19th century timing of the preindustrial temperature deviations agrees well with other northern hemisphere temperature reconstructions however their extent 1 c significantly exceeds both continental records as well as previous southern and central greenland ice core time series a 20 30 increase in the sea salt aerosol load during these periods supports accompanying circulation changes over the north atlantic comparison with records of potential natural climate driving forces points to an important role of the long term solar influence but to only episodically relevant cooling during years directly following major volcano eruptions

light rings in subarctic conifers as a dendrochronological tool abstract light rings are characterized by one or a very few latewood cell layers an indication of shortened growing seasons and are particularly frequent in black spruce picea mariana mill bsp at the treeline in quebec the construction of a light ring chronology spanning the period ad 1398 1982 showed that the highest frequency 25 of light rings among 160 trees and krummholz occurred in 1593 1620 1634 1784 1816 1817 1853 1969 and 1972 these diagnostic rings be a useful cross dating tool for dendroecologists working with living and dead krummholz with a low growth variability about two thirds of the 65 light ring years coincide with years or triads of major volcanic eruptions the climatic conditions low temperature occurring at the end of the growing season in part induced by the climatic effect of volcanism seem to initiate light rings

experiments in waterlogging and sedimentology of charcoal results and implications abstract fossil charcoal has a sporadic occurrence in sedimentary rocks since devonian time it is moderately common as a component of the organic material found in a wide variety of facies but there are also some notable concentrations which occur locally these occurrences have considerable palaeobotanical and palaeoecological value because the process of charring may result in excellent preservation of plant tissue if assemblages of charred material are to be used to interpret palaeoenvironments it is important to understand the behaviour of charcoal during transport from the site of the fire charcoal is an unusual sedimentary material because most fresh material floats but with prolonged immersion becomes waterlogged and sinks we carried out a series of waterlogging experiments on uncharred material and charcoal from a range of different plant types and tissues these show considerable variations in the rates of waterlogging of different charred and uncharred plant tissues and it is suggested that buoyancy contrasts are likely to result in separation during transport and deposition furthermore experiments in a flume tank have shown that the process of deposition of charcoal in sand is controlled by the rate of migration of bedforms which is in turn determined by depth flow velocity and sediment supply allochthonous assemblages of charred and uncharred plant debris will most probably be biased and not fully representative of the contemporaneous plants or vegetation the presence of charcoal concentrations may be used as an aid in interpreting palaeohydraulic conditions

holocene changes in seasonal precipitation highlighted by fire incidence in eastern canada postglacial fire history has been reconstructed for eastern canada from charcoal influx anomalies from 30 sites taken from a lacustrine charcoal database the reconstruction exhibits coherent patterns of fire occurrence in space and time the early holocene is characterised by high fire incidence there is a major change to much lower occurrence slightly after 8 ka bp a return to more fire appears after 3 ka bp this sequence does not fit with the hydro climatic reconstruction deduced from lake level reconstructions for northeastern north america which indicates a dry early and mid holocene and a wet late holocene fire occurrence however closely matches summer relative humidity inferred from 18o the differences between fire frequency and lake level history are due to changes in the seasonality of precipitation and drought frequency lake levels are essentially controlled by winter precipitation while summer precipitation controls fire occurrence the early holocene before 8 7 5 ka bp experienced dry summers due to higher solar radiation and dry adiabatic winds from the residual laurentide ice sheet the middle holocene was dominated by wet summers due to stability of the atlantic air mass over eastern canada after 2 5 ka bp summers became drier albeit not as fire conducive as during the early holocene late holocene summers conducive to fire are explained by more frequent incursions of dry cool pacific or cold arctic air masses over eastern canada

environment and landscape management during the middle neolithic in southern france evidence for agro sylvo pastoral systems in the middle rhone valley abstract rescue excavations in the middle rhone valley have provided opportunities to develop innovative strategies for the study of palaeoenvironments these strategies involve sampling and analysis of botanical remains recovered not only from archaeological sites but also in off site pedosedimentary sequences thought to be poor in botanical remains thus these remains phytoliths pedo charcoal give access to unexplored depositional contexts such as alluvial plains moreover off site data are useful because they minimise the hazard of cultural bias e g selection of species during wood gathering comparison of data collected in the alluvial plain with data obtained via anthracological analyses of karstic caves and rock shelters in the hinterland suggests a complex agro sylvo pastoral management of the landscape during the middle neolithic we propose a pattern that supposes considerable specialization in use of plains vs slopes in the landscape and a strong and continuous human pressure on the vegetation and soils between 4500 and 3500 cal bc nevertheless these constraints are not sufficient to explain the persistence of such a system for more than a millennium favourable climatic conditions are thought to have been a determining factor in the persistence of an ecologically meta stable relationship between human societies and their natural environment

effective stress history and the potential for seismicity associated with hydraulic fracturing of shale reservoirs the influence of effective stress history on reservoir stability and the response to hydraulic fracturing are simulated for two hypothetical shale reservoirs it is numerically demonstrated that the effective stress history influences the present day stability of faults and natural fractures any assumption of a homogeneous stress state is shown to be unrealistic in the majority of fractured shale reservoirs the simulations demonstrate that depending upon the effective stress history shear displacements can be induced by stress changes associated with stimulation without a change of fluid pressure in the destabilized fractures elastoplastic shale and other fractured reservoirs are shown to have a memory of past geomechanical states these numerical findings demonstrate the value of interpreting reservoir effective stress history when planning fluid injection a previous case history is summarized to illustrate the overwhelming dependence of stress history analyses on a wide spectrum of earth science disciplines it also illustrates the application of stress history analyses to activities other than hydraulic fracturing the current inexperience of effective stress history description means that new approaches must be identified to optimize the necessary multidisciplinary investigations supplementary material details of the simulations are available at www geolsoc org uk sup18743

charcoal recognition taphonomy and uses in palaeoenvironmental analysis abstract charcoal predominantly the product of wildfires is abundant in many sedimentary rocks deposited in a wide range of environments from terrestrial to marine it also occurs in some volcanic rocks this paper outlines aspects of charcoal formation both natural and experimental and briefly considers the taphonomic processes leading to a final assemblage this is done using examples from recent fires and through experimentation the ways in which charcoal assemblages are recognized in the field and extraction in the laboratory are also considered methods of charcoal identification are presented the range of charcoalified plant organs that can be found is discussed and a wide range of study methods outlined including light microscopy dark field light microscopy reflectance microscopy scanning electron microscopy and synchrotron radiation x ray tomographic microscopy emphasis in this paper is on the study of macro and meso charcoal above180 m finally there is a consideration of the broad use of charcoal from plant evolution studies fire history studies vegetation studies anatomical studies climate and atmospheric studies and the wider importance of charcoal for the earth and biological sciences charcoal is information rich but yet is an under utilized resource

ice flood history reconstructed with tree rings from the southern boreal forest limit western quebec historic ice flood frequency and lake levels were reconstructed for the southern limit of the boreal forest in western quebec by dendrochronological analyses of ice scarred white cedar thuja occidentalis l trees growing on the shore of lake duparquet results reveal a significant increase in major ice floods since the end of the little ice age and in particular since the beginning of this century this rise was also not related to oversampling of younger scarred trees in addition time between white cedar establishment and the first recorded scar has significantly decreased in the last 200 years and this applies for trees occupying similar topographic conditions white cedar s increased exposure in the 150 years to scarring strongly suggests that lake duparquet water levels at breakup are reaching higher elevations this is supported by an approximate 100 cm rise in maximum ice scar height since the end of the little ice age years leading to abundant ice scars are those with heavy winter and

a recent downward expansion of shoreline shrubs at lake bienville subarctic quebec abstract the regeneration patterns of alnus crispa air pursh in response to water level lowerings were studied along the shores of lake bienville 898 km 2 in subarctic quebec during a period of high waters in the 1970s pruning by drifting ice was important and contributed to sprouting and crown densification of well established shrub individuals low water levels prevailed between 1980 and 1985 when massive shrub colonization along the lakeshores occurred shrub establishment was favored on shorelines where geomorphic activity ice pushes and wave action was moderate or low well established shrubs have undergone moderate ice push damages since 1985 which limit the expansion of the population by seeds but favor the densification of the stem metapopulations interannual and decennial fluctuations in water levels of northern basins should be studied more closely to better understand hydroclimatic regimes and causes of periods of low hydraulicity especially in regions where the potential for hydroelectricity is high

tufas and travertines of the mediterranean region a testing ground for freshwater carbonate concepts and developments actively forming travertine and tufa sites are widespread in temperate and warm climates such as the mediterranean region but also develop in other climatic regimes from the arctic to equatorial latitudes the terms travertine and tufa are sometimes applied indiscriminately today however each has a specific definition most studied deposits are active or of quaternary especially holocene age there are fewer tertiary and even less late mesozoic examples on record in part this is because of a recognition problem as these deposits commonly preserve as fragmentary erosional remnants physico chemical precipitation of calcium carbonate is commonly considered to be the main mechanism contributing to tufa and travertine deposition rapid cooling of waters further aids the process in thermal travertine sites however biomediation of calcium carbonate associated with prokaryote microphyte biofilms is now recognized to be equally important in slow flowing and near static sites much of this precipitation occurs in close association with cyanobacterial heterotrophic bacterial and diatoms the mediterranean region figures significantly in the development of travertine and tufa research consequently this article employs key literature on mediterranean examples to illustrate developments and concepts in freshwater carbonate research modern work started in the 1950s and defined many previously unknown outcrops many such sites became the targets for early radiocarbon dating studies since the late 1970s a number of laboratory based and field based classification schemes have been proposed some schemes were based on associated macrovegetation types others were based on petrological characteristics or on geometry and sedimentary facies characteristics of late the sedimentological modelling has benefited greatly from the use of shallow geophysical techniques in order to better define the internal geometries of the deposits two distinct research strands were developed during the 1990s both aimed at a better understanding of environmental change the first considered biocomponents the research was multifaceted and ranged from exploring the role of micro organisms in cement and lime mud precipitation to biostratigraphic analysis of contained pollen and invertebrate remains these provided proxy environmental information which has helped to define past climate variability in the region the second research strand focussed on geochemical signatures as a proxy tool for defining environmental change this definition was made possible by new petrological studies which have greatly aided the recognition of primary depositional fabrics this improved knowledge has reduced the sampling dangers of diagenetic contamination inherent in earlier geochemical studies lithofacies modelling has also brought to light important early post depositional neomorphic changes which obscure primary fabrics and complex diagenetic histories have been revealed stable isotope signatures of carbon and oxygen have also been used to define palaeo water temperature fine tuning of depositional time frames has also been achieved from absolute dating techniques employing radiocarbon and uranium thorium

dendroecological evidence of lake level changes during the last three centuries in subarctic quebec abstract dendroecological analysis of black spruces picea mariana mill bsp near the shore of clearwater lake in the eastern canadian subarctic yielded information on water level over the past three centuries tree positions growth froms layering tree ring patterns and ice scars provide direct evidence of a major rise in lake level from the 17th century to the present trees on the lake shore were progressively submerged by the increasing water level which reached a maximum in this century higher levels began around the mid 18th century when shoreline spruce trees started to lean because extensive wave erosion caused landward shore displacement high mortality of leaning spruce and abundant ice scar formation occurred during this century the rise in water level in inferred to have been caused by snowier winters occurring parallel to climatic warming

response of fractured rock subject to fluid injection part ii characteristic behaviour abstract distinct element modelling has been used to investigate the mechanics of naturally fractured reservoirs subject to a constant rate of fluid injection constant stress boundary conditions were imposed with magnitudes typical of those pertaining at approximately 3 km depth in some sedimentary environments fluid leak off through fracture walls and fracture dilation during shear were modelled the progressive nature of the changes of stress and displacement occurring within the coupled fluid rock system were examined for four combinations of uniform fracture geometry and applied stress the effects of a uniform change of pore pressure on the directional nature of hydraulic conductivity in a fractured medium were characterised the influence of variation of injection rate pore fluid compressibility and leak off rate was examined effects associated with contrasts of shear stiffness between fractures and blocks and with inelastic deformation were interpreted

freshwater to marine like environments from holocene lakes in northern sahara continuous swamp and lacustrine sequences from the northern edge of the great western erg are dated at 9 300 3 000 yr bp diatoms ostracods molluscs and foraminifera show great changes in salinity ranging from freshwater to marine like environments the stable isotope composition of carbonates indicates that the evaporation of groundwater supplies is responsible for these fluctuations in salt contents until now evidence for the occurrence of a wet climatic phase of early and middle holocene age in the north north west sahara was based on a restricted number of 14c dates from scattered lacustrine deposits and paleosols1 8 the present study complements this knowledge and highlights the importance of local hydrological factors in interpreting palaeolimnological changes

late holocene paleoecohydrology and carbon accumulation estimates from two boreal peat bogs in eastern canada potential and limits of multi proxy archives abstract the stratigraphy of four peat sequences collected in two peat bogs located in the eastmain river watershed 52 n 76 w james bay lowlands quebec canada was investigated to reconstruct past hydroclimatic conditions of peat accumulation and associated carbon dynamics during the late holocene analyses of macrofossils testate amoebae peat humification c n ratio and bulk density were performed at high resolution along each peat core allowing the potential of each proxy indicator under varying nutrient status and hydroclimatic conditions to be evaluated some synchronous changes were recorded both within and between peatlands suggesting the influence of allogenic factors in the development of these peatlands other reconstructed changes have highlighted autogenic succession processes related to the local geomorphic and hydrologic context highest peat carbon accumulation rates lorca were correlated with either wet conditions or high woody debris percentages suggesting that residence time of the biomass in the acrotelm and the nature of plant material can both influence carbon accumulation rates in peat bogs this study provides the first high resolution paleoecohydrological reconstructions from the mid boreal ecoregion of eastern canada a region in which peatlands occupy 30 to 60 of the land surface

recent dynamics of subarctic dunes as determined by tree ring analysis of white spruce hudson bay quebec the radial growth patterns of white spruce were studied on a number of trees growing in subarctic dunes along the eastern coast of hudson bay to calculate the rates of accumulation erosion and migration of cold climate sand dunes the average rate of sand accumulation in sheltered dunes forest sites was 2 5 to 3 3 cm yr which is two to three times lower than in highly exposed dunes with a rate of sedimentation of 7 65 cm yr the average erosion rate was 1 4 1 7 cm yr about two times lower than the accumulation rate the migration rate of sheltered dunes was 18 to 30 cm yr three to five times lower than for an exposed dune which advanced at a speed of 74 cm yr this migration rate established for highly exposed dunes in the subarctic with tree ring methods is about 10 times lower than that established for a barchan in the sahara with other methods

numerical simulation of seismicity due to fluid injection in a brittle poroelastic medium summary it has recently been shown that rather small perturbations in eiective stress due to uid injection or withdrawal may trigger microseismic events such events typically in the magnitude range below magnitude 4 ml have similar characteristics to normal tectonic earthquakes with double couple focal mechanisms implying a dominant shear motion at the source in this paper we examine the nature of this mechanical uid rock interaction for the case of uid injection in a hydrocarbon reservoir our model is based on the combination of a model of seismicity in dry rocks and a model of pore uid pressure diiusion the former involves a nite diierence approximation of the equation of motion and the latter follows a lattice boltzmann approach they are coupled via the concept of eiective stress applied both to the mohr coulomb rupture criterion and to the volumetric elastic deformations which in turn perturb the pore pressure the simplifying assumptions are that the uid and solid phases have the same bulk moduli and that strain compatibility conditions are not included 2 d plane strain simulations of uid injections in an anisotropically pre stressed elastic brittle medium illustrate the capabilities of the model spontaneous inception and growth of shear fractures in both the near and far elds and explicit calculation of their seismic radiation which feeds back into pore pressure perturbations they also show that as expected the amount and rate of stress drop during the brittle rupture control the size and spatial density of the resulting fractures our model should prove to be relevant at least in two cases as a simulation tool in the investigation of correlations between injection and producer wells which are thought to be of geomechanical origin in certain oil elds and as a forward model in the inversion of focal mechanisms of pore pressure induced shear events

isolation and water level fluctuations of lake kachishayoot northern quebec canada this study combines different methods including grain size macrofossil and pollen analyses to reconstruct paleogeographical and paleoclimatological conditions for periods before during and after the isolation of a small lake lake kachishayoot in northern quebec after the retreat of the laurentide ice sheet around 8000 14c yr b p the area was submerged by the tyrrell sea the transition from marine to lacustrine environment occurred about 5400 yr b p two major periods of water level fluctuations were inferred from organic and mineral sediments a high water level that occurred after 3200 yr b p and a low water level that started before 2200 yr b p our chronological data for the first period are consistent with those from nearby lac des pluviers and from other lakes in east central canada and in the northeastern united states during the low water level period however there is no evidence for minor fluctuations whereas other lakes in northern quebec and east central canada underwent several brief lowerings long term changes in atmospheric circulation caused by changing global boundary conditions likely explained long term water level fluctuations of lake kachishayoot

copper production at baratti populonia southern tuscany in the early etruscan period 9th 8th centuries bc abstract populonia is commonly regarded as one of the most important iron working centres in europe in the 1st millennium bc however multiple layers of copper slags have been recently discovered at the bottom of the slag deposit occurring along the shoreline of the underlying baratti gulf copper slag layers have been radiocarbon dated to the 9th 8th centuries bc i e to an early metallurgical stage predating the later large scale iron production the overall features of copper slags indicate a single step smelting process of copper rich ores containing variable amounts of zn and pb chemical and textural features of copper slags indicate an optimised high efficiency metallurgical process

spring flood reconstruction from continuous and discrete tree ring series 1 this study proposes a method to reconstruct past spring flood discharge from continuous and discrete tree ring chronologies since both have their respective strengths and weaknesses in northern environments ring width or density series provide uninterrupted records that are indirectly linked to regional discharge through a concomitant effect of climate on tree growth and streamflow conversely discrete event chronologies constitute conspicuous records of past high water levels since they are constructed from trees that are directly damaged by the flood however the uncertainty of discrete series increases toward the past and their relationships with spring discharge are often nonlinear to take advantage of these two sources of information we introduce a new transfer model technique on the basis of generalized additive model gam theory the incorporation of discrete predictors and the evaluation of the robustness of the nonlinear relationships are assessed using a jackknife procedure we exemplify our approach in a reconstruction of may water supplies to the caniapiscau hydroelectric reservoir in northern quebec canada we used earlywood density measurements as continuous variables and ice scar dates around lake montausier in the james bay area as a discrete variable strong calibration 0 57 0 61 0 75 and validation 0 27 0 44 0 58 r2 statistics were obtained thus highlighting the usefulness of the model our reconstruction suggests that since 1965 spring floods have become more intense and variable in comparison with the last 150 years we argue that a similar procedure can be used in each case where discrete and continuous tree ring proxies are used together to reconstruct past spring floods

postglacial water level changes of a small lake in southern quebec canada sediment stratigraphy and palaeobotanical data from five cores were used to reconstruct the postglacial water level changes of a small lake in southern quebec the cores were taken along two transects from the centre of the lake to the margins lake level was relatively high before 11 000 cal bp when sedimen tation was characterized by the deposition of silty gyttja 13 000 cal bp and marl 13 000 11 000 cal bp from 11 000 to 7000 cal bp a sediment hiatus was indicated by the lack of two regional pollen zones between the marl and the overlying gyttja suggesting either nondeposition or erosion of the previously deposited sedi ments due to a low lake level the lake level was approximately 2 m lower than present on the basis of macrofossil assemblages a rise in the water level of about 1 m occurred around 7000 cal bp which was interrupted by a second lowering between 6100 and 4400 cal bp as indicated by a hiatus in the pollen stratigra phy during this low period the water level was at leas

14 c and th u dating of pleistocene and holocene stromatolites from east african paleolakes during recent humid episodes stromatolites were built along paleolake margins some 60 m above the modern water level of lakes natron and magadi southern gregory rift valley three generations of stromatolites are observed the more recent ones frequently covering pebbles and boulders eroded from the older ones the youngest one yielded 14c ages ranging from approximately 12 000 to 10 000 yr b p their 13c values 2 6 suggest isotopic equilibrium between the paleolake total inorganic dissolved carbon and the atmospheric co2 thereby lending credence to the reliability of the 14c an initial 230th232th ratio in the detrital component was determined by thu measurements on the 14c dated stromatolites using this value a 230th234u chronology for the older stromatolites was calculated ages of 240 000 and 135 000 10 000 yr were obtained for the first and second generations respectively a humid episode apparently characterized eastern africa during each glacial interglacial transition 18o and 13c measurements on stromatolites when compared to values on modern waters and carbonates provide paleohydrological information long residence time of the paleolake waters and less seasonally contrasted regimes are inferred

kinematically equivalent but geomechanically different simulations of fault evolution the role of loading configurations geomechanical simulations are used to demonstrate the importance of the way that models are loaded in this paper the development of permanent damage during faulting using frictional slip models of a reverse fault is investigated although the use of different loads and constraints can produce the same faulted geometry for the same rock type and at the same burial depth the models develop very different stress and strain states permanent strain magnitudes and distributions between models are quite dissimilar including the distributions of permanent dilation and compaction this work demonstrates that boundary loads and boundary constraints are significant factors in determining what stress and deformation states evolve in the simulation model the examples also illustrate that final deformed geometry alone is a very poor basis from which to predict either stress state or open fracture distribution bulk finite strain does not allow a prediction of local principal stress directions magnitudes or signs at least in the vicinity of fault damage zones

shaping mediterranean landscapes the cultural impact of anthropogenic fires in tyrrhenian southern tuscany during the iron and middle ages 800 450 bc ad 650 1300 charcoal analysis applied in sediment facies analysis of the pecora river palaeochannel tyrrhenian southern tuscany italy detected the occurrence of past fire events in two different fluvial l

holocene mountain forest changes in central mediterranean soil charcoal data from the sila massif calabria southern italy abstract soil charcoal analysis was performed on soil profiles excavated in the area of cecita lake on the sila massif calabria southern italy charcoals identification combined with a good number of radiocarbon dating and the pedological analysis of the soils allowed drawing a detailed history of the holocene vegetation changes in the area five periods characterised by high concentration of radiocarbon dates mirroring increased fire activity are documented at ca 10400 9000 bp 8200 7200 bp 5100 3700 bp 3300 2400 bp and 600 bp to the present furthermore a severe environmental change took place between the middle bronze age and the final bronze age iron age ca 3600 to 3000 bp when the mixed deciduous oak silver fir woodland which dominated the landscape until the early bronze age declined and was substituted by a calabrian pine forest or by an open landscape available climate pollen and historical archaeological data are taken into account to investigate the possible causes of the detected environmental change and of the periods of increased fire activity if climate seems to play a role in the fire regime during the first part of the holocene human action seems to be the triggering factor in the environmental change and the fire regime during the late holocene

assessment of soil erosion sensitivity and post timber harvesting erosion response in a mountain environment of central italy article i nfo this study aimed to assess the effects of forest management on the occurrence of accelerated soil erosion by water the study site is located in a mountainous area of the italian central apennines here forest harvesting is a widespread forestry activity and is mainly performed on the moderate to steep slopes of the highlands through modeling operations based on data on soil properties and direct monitoring of changes in the post forest harvestingsoilsurfacelevelatthehillslope scale we show thattheobserved site became pronetosoilero sion after human intervention indeed the measured mean soil erosion rate of 49 t ha 1 yr 1 for the harvested watershed is about 21 times higher than the rate measured in its neighboring undisturbed forested watershed 2 3 t ha 1 yr 1 the erosive response is greatly aggravated by exposing the just harvested forest with very limited herbaceous plant cover to the aggressive attack of the heaviest annual rainfall without adopting any conservation practices the erosivity of the storms during the first four months of field measurements was 1571 mj mm h 1 ha 1

plant landscape and environmental changes recorded in marginal marine environments the ancient roman harbour of portus rome italy abstract the interpretation of past environment changes in coastal marshes river mouths and drainage channels connecting fresh to salt water bodies is a difficult task since several factors must be considered such as the variable influence of climate sea level changes coastline variations and changes in the river discharge it is even more difficult if this attempt is carried out in basins and channels of an ancient harbour used for centuries connected to the sea and to a river this is the case of the ancient harbour of rome located in the tiber delta area which had a prominent role during the imperial age in the mediterranean a town named portus arose in the vicinity and although sacked many times by barbarians was still very important during medieval times the romans managed the harbour the city and the surroundings and the impact on the environment must have been very strong a multi proxy approach was used to characterize and date environment and landscape changes in the ancient port of rome area from the 1st century to the 15th century ad plant macrofossil results have been integrated not only with pollen and microcharcoal but also with the tiber river bi millennial record available in literature this integration used to improve the chronological framing of the cores was carried out using ostracod analyses micro crustaceans commonly occurring in marginal marine environments and widely used for palaeoenvironmental reconstructions in particular the ability of some species to live within specific salinity ranges has been a precious tool to identify the hydrological setting of the depositional environment the cores recovered allowed recognition of two different sedimentary sequences the older shows the silting of the harbour during the first centuries and the younger records the sedimentation that occurred between the 4th and the 15th century ad this multi proxy approach applied to the study of plant remains indicates that 1 the human impact was lower during the first centuries ad than during late antiquity and middle ages or that 2 clues of human presence were easier to detect in a closed marshy area than in an open harbour the correlations between macroremains pollen percentage and concentration freshwater brackish water and salt water ostracods and the frequencies of tiber river floods during a 1500 year time span link some environmental changes and the silting of the harbour to the variations in hydrological regime of the tiber river

impacts of holocene climatic variations on alluvial fan activity below snowpatches in subarctic quebec abstract in the lake guillaume delisle area of subarctic quebec storm generated alluvial fans have been active sporadically throughout the holocene in this study we propose that the persistence of late lying snowpatches in fan catchments during holocene cold episodes promoted alluvial fan activity by lowering the precipitation threshold required to trigger a torrential event this hypothesis was tested by characterizing the depositional processes responsible for alluvial fan formation below snowpatches and by reconstructing the holocene alluvial fan activity stratigraphic and sedimentary analyses conducted on seven alluvial fans revealed that they were deposited by torrential activity leading to waterlaid transient or hyperconcentrated deposition the chronology of the storm generated alluvial fans based on 22 radiocarbon dates indicates that torrential activity was enhanced during the cooler late holocene i e after ca 3500 cal yr bp snowier winters and cooler summers were beneficial to nival activity allowing the persistence of larger snowpatches throughout the summer and fall seasons rainfall induced thaw of such snowpatches during rainstorm events is inferred to have contributed to alluvial fan activity by increasing water availability three peaks of alluvial activity occurred during the late holocene 2950 2750 1900 1400 and 800 300 cal yr bp and are indicative of increased storminess resulting in higher fan activity increased fan activity during cooler episodes was concurrent with increased runoff activity in the immediate pronival area this stresses the importance of nivation below snowpatches and pinpoints the role of nivation in enhancing geomorphological activity during period of cooler and more humid climate in subarctic environments

hydro climatic analysis of mechanical breakups reconstructed from tree rings necopastic watershed northern quebec canada we used a 54 year 1950 2003 ice scar chronology constructed from damaged trees to investigate relationships between large scale hydro climatic conditions and mechanical breakup magnitude in the necopastic river watershed james bay northern quebec our objectives were 1 to identify hydrologic and climatic variables that explain variations in mechanical breakup magnitude at the watershed scale 2 to organize these variables in terms of importance and 3 to construct a predictive model for ice floods in the necopastic watershed we used parametric correlation analysis to measure the degree of linear association between variables and classification trees ct coupled with a cross validation approach to construct the predictive model and to organize variables according to their importance in the necopastic watershed the type and magnitude of breakups are determined by an interaction between forces that maintain the ice cover in place and forces that tend to dislodge it in contrast with lakes early and rapidly rising floods rather than abnormally high flood discharge create conditions that favour intense mechanical breakups moreover cold and snowy spring conditions during high positive arctic oscillation ao indices delay the thermal degradation of the ice cover and preserve its mechanical properties over longer time periods

the holocene climatic evolution of mediterranean italy a review of the continental geological data we present a synthesis of geological stratigraphic geomorphological and stable isotope data collected from continental archives to highlight the environmental and climatic differences between the first and second half of the holocene of central and southern italy the beginning of the holocene is marked by rapid environmental change in mediterranean italy between c 9500 cal bp and c 6000 5500 cal bp average temperatures were probably higher and environmental conditions were generally stable between c 9000 and 7000 cal bp meteoric precipitation was at its highest the end of the wetter period seems to occur later at c 6000 5000 cal bp since c 6000 5000 cal bp rapid climatic excursions are apparent in different palaeoclimate proxies with both variability in meteoric precipitation and temperature evident of particular relevance is the event occurring at c 4200 cal bp this event heralds a period of significant environmental change in the apennines and more generally in central italy

spatio temporal patterns of holocene environmental change in southern sicily abstract few examples of natural forest remain near the mediterranean coast therefore it is difficult to study how coastal forests respond to climatic change or their resilience to human impact we developed new sedimentary record of holocene vegetation and fire history at lago preola a coastal lake in southwestern sicily italy in order to verify the existence of forest at large scale on the coast we compare pollen from lago preola a medium sized lake 33 ha to gorgo basso a small lake 3 ha located nearby with the aim of separating local from extra local vegetation dynamics through time using pollen percentages and influx we then compare lago preola pollen to the record from biviere di gela a large lagoon 120 ha situated 160 km to the east in southern sicily to examine differences in vegetation dynamics between the two coastal areas during the holocene lake level reconstructions and ostracode analyses from lago preola provide vegetation independent evidence of climate change and help to disentangle human and climatic impacts on vegetation pollen data indicate pistacia dominated shrublands replaced open grasslands in the region surrounding lago preola by 9500 cal yr bp this change coincided with rising lake levels and the development of an ostracode fauna typical of fresh waters evergreen forest dominated by quercus ilex and olea europaea started to expand by 7000 cal bp and consolidated at 6500 cal yr bp when lake levels were near their holocene high similarities between pollen from lago preola and gorgo basso demonstrate that forest was the dominant vegetation type in coastal sicily during the middle holocene at both regional and local scales and even developed in the drier climatic setting around biviere di gela lake levels fell at lago preola after 7000 cal yr bp with a strong decline accompanied by increasing salinity after 4500 cal yr bp however no transition in vegetation matched these inferred hydrological changes instead forests persisted in the surrounding region until 2200 cal bp when human disturbance intensified we propose that different climatic factors control lake levels and vegetation in coastal mediterranean ecosystems whereas lake levels are most sensitive to the abundance of winter precipitation coastal forests depend on spring precipitation and are limited by the length of summer drought moisture availability remained suitable for evergreen forests in coastal sicily during the late holocene and humans not a drier climate drove the regional forest decline

tree ring dating of extreme lake levels at the subarctic boreal interface abstract the dates of extreme water levels of two large lakes in northern quebec have been recorded over the last century by ice scars on shoreline trees and sequences of reaction wood in shore trees tilted by wave erosion ice scar chronologies indicate high water levels in spring whereas tree tilting by waves is caused by summer high waters a major increase in both the amplitude and frequency of ice floods occurred in the 1930s no such change was indicated by the tree tilting chronologies but wave erosion occurred in exceptionally rainy years according to the modern record spring lake level rise is due to increased snowfalls since the 1930s however the absence of erosional marks in a large number of years since 1930 suggests a high frequency of low water level years resulting from dry conditions intercalary years with very large numbers of marked trees e g 1935 indicate that the interannual range of summer lake levels has increased since the 1930s increased lake flood frequency is postulated to be related to a slower expansion of arctic anticyclones favoring the passage of cyclonic air masses over the area and resulting in abundant snowfall in early winter conditions in summer are due to the rate of weakening of the anticyclones controlling the position of the arctic front in summer this position influences the path of the cyclonic air masses which control summer precipitation and consequently summer lake levels in the area

tree ring analysis of hydro climatic thresholds that trigger ice jams on the mistassini river quebec this study documents the spatiotemporal variations in the frequency and magnitude of ice jams in the mistassini river and applies that information to the identification of the hydro climatic threshold conditions associated with major events ice jams cause severe upheavals in water flow which result in flooding upstream of the ice jam front and therefore represent a significant geohazard to riparian populations to analyze the spatiotemporal variations in the magnitude frequency of ice jams the mistassini river was first divided into six different sites representing different geomorphological contexts a 50 year ice jam chronology was constructed from 85 damaged trees from all of the study sites this chronology was then coupled with hydro climatic variables to construct classification trees which helped identify the conditions and hydro climatic thresholds favourable to the triggering of ice jams in a predictive model the results indicate complex interactions between the characteristics of flow ice cover and river morphology that affect the frequency and magnitude of ice jam events on the mistassini river these factors affect the frequency and magnitude of ice jam events the triggering of extreme events seems particularly influenced by exceptional ice conditions and sites with high sinuosity and islands copyright 2015 john wiley sons ltd

charcoal taphonomy and significance in geology botany and archaeology abstract charcoal occurs in the natural environment as either a result of wildfire or volcanic processes in addition people may make charcoal either for domestic or industrial use charcoal may be used as a fuel for domestic heating and cooking through a range of industrial uses such as iron smelting more recently the charcoalification process has been used to make biochar that is relatively inert and promotes atmospheric co 2 reduction with such a wide range of uses research has been published in a broad range of journals and often whole areas of study are unfamiliar to other charcoal researchers here we review a range of charcoal studies and their inter relationships we present some of the results of a major international meeting on charcoal brussels september 2008 highlighting the potential of charcoal studies as part of palaeoenvironmental investigations both in a geological and archaeological context

particle motion and the theory of charcoal analysis source area transport deposition and sampling principles from particle motion physics were applied to recurring problems of the interpretation of stratigraphic charcoal data 1 fires within catchments of lakes often produce no record in fossil charcoal curves and 2 periods characterized by no local fire e g 20th century fire suppression often display as much charcoal as times when local fire was frequent quantitative theory on source area transport deposition and sampling of charcoal shows the relationship between particle sizes counted by alternative methods of charcoal analysis pollen slides for particles 5 80 m in diameter petrographic thin sections for particles 50 10 000 m diameter and charcoal diagrams the relationship between diameter and critical and deposition velocities results in fundamental aerodynamic differences between the sizes of particles quantified by the two methods charcoal recorded on pollen slides is of a size that is difficult to lift but once entrained it remains in suspension thin section charcoal is lifted at relatively low wind velocities but it is not suspended at normal surface wind speeds thermal buoyancy during fire lofts charcoal above the forest canopy depending on particle size and wind speed pollen slide charcoal sizes are underrepresented near the fire because they remain in suspension and are preferentially exported from the burn area thin section charcoal is convected to lower heights on average and is deposited nearby following fire thin section charcoal is redistributed locally by wind and thus may enter lakes because of cohesive forces and aerodynamics more pollen slide charcoal remains on the ground and less enters lakes source areas for pollen slide charcoal are subcontinental to global and diagrams of pollen slide charcoal are biased toward nonlocal charcoal they can be used to interpret importance of fire for broad spatial and temporal scales thin section charcoal represents the catchment fire regime simulation models that generate charcoal during fire mix sediments and then sample at specified intervals indicate that 1 in the absence of sediment mixing the pollen slide method should consistently resolve individual fires that occur with an expectation of 30 50 yr 2 unless samples are continuous neither method will produce useful estimates of fire frequency and 3 even a modest amount of sediment mixing will obscure the signal