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

stable oxygen isotope and pollen records from eastern scotland and a consideration of late glacial and early holocene climate change for europe the presence of marl deposits belonging to the lateglacial period in a former lake basin at lundin tower in fife scotland has allowed palaeoenvironmental investigations by means of carbonate 13c and 18o and organic matter 13c in addition to palynology the variations that emerge reveal strong similarities between the pollen and isotope records and these are interpreted as reflecting climatic shifts the classic late glacial pattern of oldest dryas bolling older dryas allerod younger dryas may be evident and other climatic oscillations are shown to have occurred not only during the allerod but also in the preboreal the problem of the time discordance between isotopic change and pollen representation is addressed through explanations involving lags in plant colonization a comparison of the 18o records from 43 sites across europe reveals two different regional patterns which raises fundamental questions over the nature of late glacial palaeoclimates

geomorphology and age of the marocche di dro rock avalanches trentino italy abstract the marocche di dro deposits in the lower sarca valley are some of the most distinctive rock avalanche deposits of the alps we use geomorphology and cosmogenic 36 cl exposure dating of boulders to divide the marocche di dro deposits into two rock avalanche bodies the marocca principale to the north and the kas to the south the deposits were previously undated and had been mapped as up to five different events the largest event marocca principale which comprises an estimated 1000 10 6 m 3 of predominantly rotzo formation limestones occurred 5300 860 yr ago the release area is located mainly in the alcove between mt casale and mt granzoline but likely extends all the way to mt brento the kas event took place 1080 160 yr ago with detachment below mt brento the kas debris with an estimated volume of 300 10 6 m 3 buried the southern third of the marocca principale deposit kas presents a barren stark landscape dominated by house sized tovel member rotzo formation boulders bearing distinctive chert lenses both the extreme relief of the rock wall more than 1300 m and the tectonic setting predispose the range front to massive failure for the two events initially translational movement likely quickly evolved into complex failure and massive collapse run out across the valley of several kilometers and run up on the opposite slope of hundreds of meters followed a summary of all dated and large historical landslides in the alps underlines the periods of enhanced slope activity discussed in the literature 10 9 kyr 5 3 kyr and 2 1 kyr the latter especially for the southern alps no deposits of the first temporal cluster are found at marocche di dro the age of marocca principale at 5300 860 yr suggests occurrence during the second period failure may have been related to the shift to wetter colder climate at the transition from the middle to the late holocene nevertheless a seismic trigger cannot be ruled out for the kas rock avalanche at 1080 160 yr ago we implicate the middle adige valley 1046 ce earthquake as trigger its epicentral distance is much closer to the sarca valley in comparison to that of the verona earthquake 1117 ce

a 37 meter record of paleoclimatological events from stable isotope data on continental molluscs in valle di castiglione near rome italy abstract new stable isotope analyses on molluscan shells from a long core drilled in the crater lake of valle di castiglione near rome extended the investigated portion of the core to 37 m the succession of 18o values in the core interval 37 2 3 m ranges from 2 8 to 6 9 with only six samples below 0 pdb these results point to arid climatic phases coupled with the high measured 18o values of the biogenic carbonate in contrast depleted 18o samples correspond to wet climatic periods in agreement with a strong evaporative control on the lake water isotopic composition the 13c content of the shells shows sharp changes controlled by the dissolved inorganic carbon isotope budget isotopic data suggest that the whole body of water behaved as a closed system thus resembling lacustrine systems located in arid and semiarid regions where hydrological control dominates the geochemical parameters

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

understanding past climatic and hydrological variability in the mediterranean from lake prespa sediment isotope and geochemical record over the last glacial cycle here we present stable isotope and geochemical data from lake prespa macedonia albania border over the last glacial cycle marine isotope stages 5 1 and discuss past lake hydrology and climate tic oxygen and carbon isotopes as well as responses to climate of terrestrial and aquatic vegetation toc rock eval pyrolysis carbon isotopes pollen the lake prespa sediments broadly fall into 5 zones based on their sedimentology geochemistry palynology and the existing chronology the glacial sediments suggest low supply of carbon to the lake but high summer productivity intermittent siderite layers suggest that although the lake was likely to have mixed regularly leading to enhanced oxidation of organic matter there must have been within sediment reducing conditions and methanogenesis mis 5 and 1 sediments suggest much more productivity higher rates of organic material preservation possibly due to more limited mixing with longer periods of oxygen depleted bottom waters we also calculated lakewater 18o from siderite authigenic glacial and calcite endogenic holocene and show much lower lakewater 18o values in the glacial when compared to the holocene suggesting the lake was less evaporative in the glacial probably as a consequence of cooler summers and longer winter ice cover in the holocene the oxygen isotope data suggests general humidity with just 2 marked arid phases features observed in other eastern and central mediterranean lakes

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

climatic forcing of carbon oxygen isotopic covariance in temperate region marl lakes carbon and oxygen stable isotopic compositions of lacustrine carbonate from a southeastern michigan marl lake display linear covariance over a range of 4 0 peedee belemnite pdb in oxygen and 3 9 pdb in carbon mechanisms of delta 13 c delta 18 o coupling conventionally attributed to lake closure in arid region basins are inapplicable to hydrologically open lake systems thus an alternative explanation of isotopic covariance in temperate region dimictic marl lakes is required we propose that isotopic covariance is a direct record of change in regional climate in short residence time temperate region lake basins summer meteoric precipitation is enriched in 18o relative to winter values and summer organic productivity enriches epilimnic dissolved inorganic carbon in 13c thus climate change toward longer summers and or shorter winters could result in greater proportions of warm month meteoric precipitation longer durations of warm month productivity and net long term enrichment in carbonate 18o and 13c isotopic covariance observed in the michigan marl lake cores is interpreted to reflect postglacial warming from 10 to 3 ka followed by cooler mean annual temperature a shift toward greater proportions of seasonal summer precipitation a shortening of the winter season or some combination of these three factors

on timing the vsp first arrival the advent of signal energy on a vsp or check shot trace may be defined as the first break an accurate pick of this first break would be possible in the absence of noise however real data traces are inevitably corrupted by noise and this leads to difficulty in identifying a break because the signal to noise ratio is low in its neighbourhood under such conditions an obvious alternative is to pick troughs where the local signal to noise ratio is likely to be much higher although trough picking is an effective way to minimize the noise problem it is sensitive to signal properties such as absorption and multiple reflections which have no effect upon the accuracy of break picks thus trough picking is signal sensitive and break picking is noise sensitive clearly an ideal first arrival picking scheme would combine the noise tolerant features of trough picking with the signal tolerant features of break picking this ideal may be approached by exploiting known properties of the vsp trace using conventional signal processing techniques the result of such processing is to reduce the problem to that of picking a trough correctly centered about the true break time

source requirements for the golden mile kalgoorlie significance to the metamorphic replacement model for archean gold deposits the golden mile at kalgoorlie represents a giant archean hydrothermal gold system localized by ductile shear zones and hosted mainly by a differentiated tholeiitic sill chlorite carbonate and pyrite alteration zones cover the whole mineralized area 1 km 3 km and calculations suggest that for the golden mile production around 1200 t au the amounts of components added to these alteration zones are 340 mt co2 20 mt k and 5 mt s if one adopts a metamorphic replacement model for gold mineralization in which all ore components derive from devolatilization of greenstones at amphibolite facies or above these data suggest that a source area involving a 5 km thick greenstone slab of area 8 km 8 km could produce the necessary co2 k s h2o and au this is considered a reasonable volume of greenstone belt and under such a model the minimum spacing of large gold deposits would be approximately 20 km along strike neither special au enriched source rocks nor unreasonably large volumes of greenstone b

interpreting stable isotope records from freshwater snail shell carbonate a holocene case study from lake golhisar turkey the oxygen and carbon stable isotope ratios from fossil snail shells within a small intramontane lake in southwest turkey are used to highlight the potential and problems of using freshwater snail carbonate as a palaeoenvironmental proxy two species gyraulus piscinarum and valvata cristata yielded different isotope ratios at the same sampling intervals probably due to differences in water isotope composition between different microhabitats isotope ratios from a number of individual shells from the same sampling intervals representing 7 25 years show large ranges up to 8 for 18o for each species only by analysis of a significant number of species specific shells 5 from each sampling interval can a true understanding of environmental change be obtained averages of the data provide an insight into longer term climatic variation while the ranges provide an estimate of short term decadal environmental variability

the late antiquity environmental crisis in emilia region po river plain northern italy geoarchaeological evidence and paleoclimatic considerations abstract for about four decades in italy local scientific literature has occasionally dealt with fluvial avulsions suggesting they should be considered as genetically linked to a peculiar climatic worsening that occurred in the late 6th century ad the so called paul the deacon deluge research performed by the soprintendenza per i beni archeologici dell emilia romagna over the last few years has allowed better definition of the timing of a more articulated alluvial history mainly concerning the roman imperial age and late antiquity 1st 6th century ad the main stratigraphic details of fourteen selected archaeological excavation sites eleven recently surveyed and three reviewed from the literature performed in the cities of modena bologna and related surroundings have been summarized eleven 14 c dates ranging between the years 130 ad and 810 ad allowed us to chronologically delimit a first framework for the riverbed network behaviour during ancient times in the central part of the region the alluvial process appeared to be continuous throughout the time span examined the fan trench was the most sensitive reach of the river system it started to aggrade during the 4th century ad during the 5th century ad and probably after the end of the 6th century ad a number of avulsions occurred this indicates that the fluvial system was in a metastable equilibrium whose behavioural threshold was finally overcome hence the importance of the supposed year 589 ad crisis the deluge appears to be less than previously supposed the riverbed aggradation became evident immediately after the roman empire s economic and demographic crisis of the 3rd century ad and it was probably due to the loss of the land preservation systems in the mountain catchment areas the long duration of the aggradation phase suggests that more than one human settlement phase in the minor catchment areas and or a minor climatic worsening pulse probably occurred during the 5th century ad the starting of the aggradation also coincided with the end of the petit maclu 1 high level phase of the european lakes notwithstanding this the climate s role as a forcing co factor can still be hard to evaluate positively due to the lack of local proxy data

the latest lgm culmination of the garda glacier italian alps and the onset of glacial termination age of glacial collapse and vegetation chronosequence abstract in the deglacial sequence of the largest end moraine system of the italian alps we focused on the latest culmination of the last glacial maximum before a sudden downwasting of the piedmontane lobe occupying the modern lake basin we obtained a robust chronology for this culmination and for the subsequent deglacial history by cross radiocarbon dating of a proximal fluvioglacial plain and of a deglacial continuous lake sedimentation we used reworked dinocysts to locate sources of glacial abrasion and to mark the input of glacial meltwater until depletion the palynological record from postglacial lake sediments provided the first vegetation chronosequence directly reacting to the early lateglacial withdrawal so far documented in the alps glacier collapse occurred soon after 17 46 0 2 ka cal bp which is the manerba advance culmination basin deglaciation of several overdeepened foreland piedmont lakes on southern and northern sides of the alps appears to be synchronous at millennial scale and near synchronous with large scale glacial retreat at global scale the pioneering succession shows a first afforestation step at a median modeled age of 64 years after deglaciation while rapid tree growth lagged 7 centuries between 16 4 0 16 and 15 5 0 16 ka cal bp a regressive phase interrupted forest growth marking a lateglacial phase of continental dry climate predating gi 1 this event spanning the most advanced phases of north atlantic h1 is consistently radiocarbon framed at three deglacial lake records so far investigated on the italian side of the alps relationships with the gschnitz stadial from the alpine record of lateglacial advances are discussed

seismic versus sonic velocities a vertical seismic profiling study vertical seismic profiling vsp techniques provide a method to measure accurately the seismic velocity and lithologic structure near the borehole the analysis of a vsp survey can also provide insight into seismic wave propagation especially when related to sonic measurements but vsp and sonic log velocities or traveltimes are often found to disagree recent field evidence of these differences suggests that the vsp traveltimes are delayed with respect to the integrated sonic times especially in the deep section 3000 ft by about 2 0 ms 1000 ft on the average the vsp has numerous applications in exploration geophysics such as calibrating the sonic log it is thus important to understand why the two measurements differ differences in the geometries source frequencies and instrumental errors of the two surveys are reviewed more detailed analysis of seismic wave propagation in the vsp shows that short path multiples and velocity dispersion can have a significant delaying effect on the seismic tr

holocene stable isotope stratigraphy at lough gur county limerick western ireland after the pronounced fluictuation of 4 in 18o during the younger dryas and the 1 dip during the preboreal oscillation values for 18o decreased very steadily from 2 5 to 5 3 from 9300 to about 8000 14c yr bp uncal this early holocene decrease of almost 3 is interpreted as a result of a declinle of almost 6 c in the temperature of precipitation the previous high temperature of much of the lateglacial and the preboreal 12000 9300 yr bp uncal may reflect warm summers related to greater insolation and warm winters caused by the influence of the laurentide ice sheet on atmospheric circulation after 8000 yr bp a disconformity interrupts the sequence but after about 5000 yr bp the 18o and 13c are irregular because of a low lake level as shown by the occurrence of littoral shells and woody detritus in the littoral core and because of anthropogenic factors as inferred from pollen indicators of forest disturbance and farming found in both the littoral and offshore cores

isotopic and geochemical composition of marl lake waters and implications for radiocarbon dating of marl lake sediments radiocarbon dates on organic and calcareous fractions of sediment cores from marl lakes may yield anomalous ages due to the assumption of a constant hardwater correction factor along the sediment sequence a study of eight marl lakes in southern ontario that are actively precipitating calcium carbonate was conducted in order to assess those isotopic and aqueous geochemical parameters in modern lakes that may be utilized to estimate the history and extent of variations in the hardwater effect along such sediment sequences results show an increase in the 13c composition of lake dic dissolved inorganic carbon as approach to isotopic equilibrium with atmospheric co2 occurs differences in the extent to which this equilibrium is established also appear responsible for observed differences in the 14c activity of dic between lakes of as much as 20 pmc percent modern carbon these variations have been related to the relative residence times of water in each lake by examination of their corresponding seasona

mayum an orogenic gold deposit in tibet china abstract located in western tibet china the mayum orogenic gold deposit was discovered in 2002 with estimated resources of 80 tonnes gold the gold mineralization is hosted by neoproterozoic cambrian schists and is controlled by nearly parallel e w trending bedding concordant fracture zones the au orebodies are composed of auriferous quartz veins and altered rocks with the au grades ranging from 2 23 g t to 69 56 g t and containing the 34s values of 18 separates of sulfides from auriferous quartz veins show a large variation from 0 2 to 16 8 the lead isotope compositions of sulfides from the gold ore are characterized by highly radiogenic values and very wide ranges of ratios 18 324 to 20 819 for 206pb 204pb 15 679 to 15 856 for 207pb 204pb and 38 401 to 41 204 for 208pb 204pb these data indicate that lead and sulfur in the quartz veins have multiple sources and were derived from the different wall rocks as the fluid flowed through them fluid inclusions indicate that the ore fluid was co2 rich with salinities mainly between 1 and 6 wt nacl equiv and homogenization temperatures predominantly ranging from 260 to 280 c the 18o values for quartz from auriferous veins range from 13 7 to 16 3 and the calculated 18oh2o values in equilibrium with quartz vary from 5 54 to 9 48 it suggests that the ore fluid may be derived from deep metamorphic deep crustal gold transporting fluids although a contribution from magmatic source cannot be ruled out 40ar 39ar age dating on the sericite from the alteration associated with the auriferous quartz veins in the mayum gold deposit gives a plateau like age of 59 34 0 62 ma later than the onset of the indo asian collision it is believed the gold mineralization was related to the indo asian collision and was formed during the early stage of orogenesis

holocene palaeohydrological changes in the northern mediterranean borderlands as reflected by the lake level record of lake ledro northeastern italy a lake level record of lake ledro northern italy spans the entire holocenewith a chronology derived from51 radiocarbon dates it is based on a specific sedimentological approach that combines data fromfive sediment profiles sampled in distinct locations in the littoral zone on a millennial scale the lake level record shows two successive periods from 11 700 to 4500 cal yr bp and from 4500 cal yr bp to the present characterized by lower and higher average lake levels respectively in addition to key seasonal and inter hemispherical changes in insolation the major hydrological change around 4500 cal yr bp may be related to a non linear response of the climate system to orbitally driven gradual decrease in insolation the ledro record questions the notion of an accentuated summer rain regime in the northern mediterranean borderlands during the boreal insolation maximum moreover the ledro record highlights that the holocenewas punctuated by successive centennial scale highstands correlations with the preboreal oscillation and the 8 2 ka event and comparisonwith the atmospheric 14c residual record suggest that short lived lake level fluctuations developed at ledro in response to 1 final steps of the deglaciation in the north atlantic area and 2 variations in solar activity

a stable isotope study of the garda lake northern italy its hydrological balance summary discontinuous measurements of the isotopic composition of surface water samples of the garda lake carried out between 1998 and 2006 showed almost constant 18 o d and d excess values through time during 2006 and 2007 monthly vertical profiles of water samples were collected in the northernmost section of the lake not far from the main inflow sarca river to check whether there was any detectable influence from this inflowing river and whether there was a vertical isotopic stratification of the lake water the isotopic measurement of water samples from the vertical profiles yielded isotopic values which were almost equal to those obtained from surface waters showing no detectable effect of the inflowing river water and no isotopic vertical stratification the attempt to evaluate the evaporation rate of lake water by means of current models was totally unsuccessful despite the marked summer warming of the surface layer no isotopic fractionation related to evaporation processes could be detected this anomalous behaviour may be related to the large amount of spring and summer precipitation characteristic of this area the water balance of the lake calculated according to the amount of the inflowing water sarca river water plus rain water on the lake plus 20 of the precipitations on the whole catchment basin and to the amount of outflowing water mincio river showed a large imbalance the river outflow alone resulting on average during the last decade at least double the inflow to explain this imbalance of the lake a large recharge by concealed groundwater is suggested its isotopic composition should be quite close to the mean isotopic composition of precipitations over that area this would be in agreement with the almost constant isotopic composition of both surface and deep waters and with the lack of vertical isotopic stratification a few measurements of the tritium concentration carried out on lake water show values that are considerably higher than modern tritium values either in precipitation or in the sarca river water these results are in good agreement with the hypothesis of a recharge of the lake by deep aquifers

gold and silver metallogeny of the south china fold belt a consequence of multiple mineralizing events abstract the south china fold belt is part of the south china block that is interpreted to be the result of multiple tectonic and magmatic events that formed a collage of accreted proterozoic and phanerozoic terranes the jurassic to early cretaceous yanshanian period 180 90 ma a time of major tectono thermal events that affected much of eastern and southeastern china is of great metallogenic importance in the fold belt this period is linked to subduction of the pacific plate beneath the eurasian continent and is manifested by voluminous volcano plutonic activity of predominantly calc alkaline affinity the distribution of gold and silver deposits in the south china fold belt indicates the presence of two distinct metallogenic provinces a region of basement uplifts which are controlled by shear zones and form neoproterozoic inliers of metamorphosed iron rich rock types defines the first province in this province orogenic lodes and volcanic related epithermal deposits represent the more significant precious metal mineralization the second province is essentially confined to a belt of yanshanian felsic intermediate volcanic and subvolcanic rocks that extends along most of the southeastern china coast in an area known as the coastal volcanic belt deposits in the coastal volcanic belt are silver and or copper rich volcanic hosted and epithermal in character the precious metal metallogeny of the south china fold belt is interpreted to have developed in at least three stages one as a result of collision events during the caledonian orogeny ca 400 ma the second during the indosinian orogeny ca 200 ma and the third during or soon after the formation of the yanshanian magmatic belt yanshanian orogeny 180 90 ma the latter was responsible for a hydrothermal event that affected large sections of the belt and its proterozoic substrate this may have resulted in the redistribution and enrichment of precious metals from preexisting orogenic gold lodes in neoproterozoic basement rocks which are now exposed as windows in zones of tectonic uplift the yanshanian hydrothermal activity was particularly widespread in the coastal volcanic belt and resulted in the formation of both low and high sulfidation epithermal gold and silver and locally copper and other base metal mineralization it is suggested that the coastal volcanic belt has greater potential for world class epithermal and porphyry deposits than previously realised

first evidence for late pleistocene to holocene earthquake surface faulting in the eastern monferrato arc northern italy geology pedostratigraphy and structural study of the pecetto di valenza site abstract the w po plain northern italy is commonly regarded as a region characterized by a low seismicity hazard due to the lack of historical and instrumental record of strong earthquakes nevertheless recent studies performed in the monferrato hills provide evidence of active faulting and possible paleoseismicity occurred in middle pleistocene to holocene times therefore for verifying the seismic potential of this area we firstly revised the available geological and geophysical information we selected the area between valenza and alessandria eastern monferrato arc which show the best structural geomorphic and stratigraphic setting for documenting recent tectonic deformation and faulting therein we identified for the first time evidence for earthquake surface displacement in a late quaternary pedosedimentary sequence exposed at pecetto di valenza the outcropping section has been logged and investigated according to an approach integrating sedimentological and micropedological data with structural analyses and radiocarbon dating this allowed reconstructing the recent surface evolution and the paleoseismic history of the site from the bottom the pedosedimentary sequence consists of a miocene marly bedrock whose weathering started in marine isotopic stage mis 7 or 5 interglacials a colluvial deposit follows whose formation can be attributed to mis 5e the upper part of the sequence consists of two loess covers showing different degrees of weathering possibly occurred at ca 30 ka bp for the deepest loess and in the middle holocene ca 4 ka bp for the uppermost one the loess accretion is therefore older and likely associated to the mis 3 and mis 2 glacial phases each deposit records the deformation induced by earthquake surface reverse faulting and warping giving constraints to the sequence of events that characterized this site in fact the structural analyses and a 2d balanced retrodeformation of the section integrating pedostratigraphic constraints allowed identifying at least two different phases of deformation and more than five fault scarp forming events which caused a total net displacement of ca 4 8 m during the past ca 40 ka our approach highlighted the interaction between the tectonically induced surface deformation and the aeolian deposition allowing reconstructing the recent evolution of a small drainage basin the results of this paleoseismic analysis reinforce the conclusion of previous authors that the monferrato arc should be viewed as a seismic gap characterized by strong earthquakes mmax 6 5 with long recurrence interval in the order of several thousands years this evidence has relevant implications for seismic hazard assessment which must be checked with further trench investigations along the mapped quaternary thrust faults affecting the western part of the po plain

sediments from lago di mezzano central italy a record of lateglacial holocene climatic variations and anthropogenic impact microscopic geochemical and pollen analysis of sediment samples of a lateglacial holocene profile from lago di mezzano a maar lake in central italy reveals evidence of significant climatic and human induced environmental changes time control is provided by a combination of varve chronology and radiocarbon dating the well known lateglacial climatic variations a warmer interstadial and the younger dryas cold phase are clearly represented in all the parameters during the interval between 9200 and 5600 cal bp of the holocene climatic optimum annually laminated organic rich diatom gyttja was deposited two periods of diminished total organic carbon are identified within this interval the first one p1 ranges from 8200 to 7800 cal bp while the second p2 is centred around 6500 cal bp during p1 a predominance of diatoms stephanodiscus parvus and s minutulus over other algae represented by the total organic carbon content is observed the timing of this period coincides with the early to mid holocene climatic transition reported from ice cores and lake sediments stager and mayewski 1997 p2 is characterized by a decrease in all biogenic parameters including biogenic opal organic carbon as well as arboreal pollen from 5000 cal bp to date the sediment pattern changes coincide with the mid holocene climatic deterioration in addition to these natural variations human impact has been recorded and recognized from sedimentological features such as turbidites and charcoal as well as from reduced arboreal pollen content two middle bronze age 3700 cal bp and 3300 cal bp etruscan early roman 2500 cal bp longobardic ad 900 and modern settlements since ad 1700 have been distinguished on the basis of these data

palaeoclimate interpretation of stable isotope data from lake sediment archives the isotope composition of authigenic and biogenic carbonates and diatom silica are commonly used as palaeoclimate proxies from lake sediments this article reviews the controls on the isotope composition of lacustrine skeletal and non skeletal deposits and illustrates how stable isotope studies contribute to an understanding of changes in temperature precipitation patterns evaporation and the carbon cycle it highlights the differences in the palaeoclimate potential of a wide range of lakes ranging from open to closed lake basins a large number of the case histories but not all are drawn from studies of temperate lakes from europe large closed lake systems in the tropics and elsewhere lose water predominantly through evaporation and contain sediments with variable and generally high 18o values fluctuations in the isotope composition of authigenic or biogenic minerals are mainly a function of long term changes in the precipitation evaporation ratio in contrast small open lakes which have a degree of through flow typically contain sediments with 18o values that vary by no more than a few these variations are generally ascribed to variations in temperature or the isotope composition of precipitation p from which either an annual or seasonally specific signal can be gained these types of lakes are common in northern europe and at high altitudes the interpretation of isotope data from a lacustrine succession requires a knowledge of the local processes that might control and modify the signal their effects need to be quantified and a robust calibration using the modern lake system is necessary to establish the relationship between the measured signal the isotopic composition of the host waters and climate

plant wax d h ratios in the southern european alps record multiple aspects of climate variability we present a younger dryas holocene record of the hydrogen isotopic composition of sedimentary plant waxes d wax from the southern european alps lake ghirla n italy to investigate its sensitivity to climatic forcing variations in this mid latitude region 45 n a modern altitudinal transect of d values of river water and leaf waxes in the lake ghirla catchment is used to test present day climate sensitivity of d wax while we find that altitudinal effects on d wax are minor at our study site temperature precipitation amount and evapotranspiration all appear to influence d wax to varying extents in the lake sediment record d wax values vary between 134 and 180 over the past 13 kyr the long term holocene pattern of d wax parallels the trend of decreasing temperature and is thus likely forced by the decline of northern hemisphere summer insolation shorter term fluctuations in contrast may reflect both temperature and moisture source changes during the cool younger dryas and little ice age lia periods we observe unexpectedly high d wax values relative to those before and after we suggest that a change towards a more d enriched moisture source is required during these intervals in fact a shift from northern n atlantic to southern n atlantic western mediterranean sea sources would be consistent with a southward migration of the westerlies with climate cooling prominent d wax fluctuations in the early and middle holocene are negative and potentially associated with temperature declines in the late holocene 4 kyr bp excursions are partly positive as for the lia suggesting a stronger influence of moisture source changes on d wax variation in addition to isotopic fractionations of the hydrological cycle changes in vegetation composition in the length of the growing season and in snowfall amount provide additional potential sources of variability although we cannot yet quantitatively assess these in the paleo record we conclude that while our d wax record from the alps does contain climatic information it is a complicated record that would require additional constraints to be robustly interpreted this also has important implications for other water isotope based proxy records of precipitation and hydro climate from this region such as cave speleothems

formation of gold deposits a metamorphic devolatilization model a metamorphic devolatilization model can explain the enrichment segregation timing distribution and character of many goldfields such as those found in archean greenstone belts slate belts and other gold only provinces in this genetic model hydrated and carbonated greenschist facies rocks particularly metabasic rocks are devolatilized primarily across the greenschist amphibolite facies boundary in an orogenic setting devolatilization operates on the scale of individual mineral grains extracting not just h2o and co2 but also s and in turn au elevated gold in solution is achieved by complexing with reduced s and by h2co3 weak acid buffering near the optimal fluid ph for gold solubility the buffering is more important than being at the point of maximum gold solubility low salinity ensures low base metal concentrations in the auriferous metamorphic fluid migration of this fluid upwards is via shear zones and or into hydraulic fracture zones in rocks of low tensile strength the geometry of the shear zones dictates the kilometre scale fluid migration paths and the degree of fluid focusing into small enough volumes to form economic accumulations of gold deposition of gold from solution necessitates breakdown of the gold thiosulphide complex and is especially facilitated by fluid reduction in contact with reduced carbon bearing host rocks and or by sulphidation of wallrocks to generate iron bearing sulphide and precipitated gold as such black slate carbon seams banded iron formation tholeiitic basalt magnetite bearing diorite and differentiated tholeiitic dolerite sills are some of the important hosts to major goldfields gold deposition is accompanied by carbonation sulphidation and muscovite biotite alteration where the host rock is of suitable bulk composition the correlation of major gold deposits with rock type even when the gold is primarily in veins argues for rock dominated depositional systems not fluid dominated ones as a consequence a general role in gold deposition for fluid mixing temperature decrease and or fluid pressure decrease and boiling is unlikely although such effects may be involved locally several geological features that are recorded at gold only deposits today reflect subsequent modifications superimposed upon the products of this generic metamorphic devolatilization process overprinting by higher grade metamorphism and deformation and or palaeo weathering may provide many of the most obvious features of goldfields including their mineralogy geochemistry geometry small scale timing features geophysical response and even mesoscopic gold distribution

pollen and oxygen isotope analyses on late and post glacial sediments of the tourbiere de chirens dauphine france the sequence of vegetation phases in the late glacial was studied in a sediment section from the bog tourbiere de chirens by means of pollen analysis 18o16o ratios of samples of lacustrine marl obtained from the same profile reflect variations of 18o16o in precipitation and thus provide an additional independent paleoclimatic record the observed 18o16o variations agree well with the climatic history as deduced from pollen analysis the climatic transition from the oldest dryas to the bolling period sensu lato as well as the beginning and end of the younger dryas cold phase is marked by abrupt changes in the 18o16o ratio which were observed also in other regions of the alps these drastic climatic changes probably took place simultaneously over large areas of central europe and occurred within short time spans

a fluid inclusion study of the hetai goldfield in the qinzhou bay hangzhou bay metallogenic belt south china abstract the hetai goldfield is located in the southern section of the qinzhou bay hangzhou bay metallogenic belt qhmb south china gold mineralization is controlled by ne trending ductile shear zones gold grade is higher at the shear zone centers and decreases sharply away from the shear zones regardless of the host rock type fluid inclusions fis preserved in the auriferous quartz veins have been analyzed to constrain their genesis three types of gold mineralization related fis including moderate salinity aqueous a type low salinity h 2 o co 2 b type and co 2 dominated c type have been newly identified the measured homogenization temperatures t h range from 130 c to 310 c with two peaks of about 245 c and 170 c the calculated pressures of fis range from 50 mpa to 170 mpa immiscibility and co 2 effervescence of fluids may have played an important role in gold precipitation during the ascent of the ore forming fluids the hetai goldfield is a typical example of orogenic gold deposits originating from auriferous metamorphic fluids

late holocene climate variability on the eastern flank of the patagonian andes chile a δ18o record from mollusks in lago cisnes 47 s stable isotopes in mollusk shells have been widely used for hydrological balance reconstructions however their use is restricted to lakes that preserve the calcareous material of the shells lago

detection of gas bubble boundary movement high resolution seismic surveys were performed on an underground gas storage of gaz de france at gournay sur aronde oise in order to obtain information about gas bubble boundaries within the reservoir for that purpose a light seismic source soursile and spreads with small spacing between geophone groups 10 m and small geophone group extension 10 m or 20 m were used in december 1982 a line recorded on the top of the anticline structure of the gas reservoir provided an estimation of the lateral extension of the bubble based on an amplitude anomaly dim spot associated with reservoir seismic horizons in order to estimate the displacement of the gas bubble within the reservoir three lines were recorded on the southeastern part of the anticline at different time periods april 1981 and january 1982 with different volumes of gas in the reservoir it is assumed that a variation of gas volume introduces a seismic velocity variation and as a result a travel time variation for the seismic waves that pass through the reservoir a method based on the residual time shifts observed on reflectors below the reservoir from one survey to the other was developed and implemented this method permitted a detection of a movement gas bubble boundary between april 1981 and january 1982 which agrees with drill hole data water level measurements

triassic mineralization with cretaceous overprint in the dahu au mo deposit xiaoqinling gold province constraints from shrimp monazite u th pb geochronology abstract the xiaoqinling terrane in central china is the second largest gold producing area in china previous application of age constraints has yielded ages for the gold mineralization ranging from paleoproterozoic through triassic indosinian to jurassic and cretaceous yanshanian shrimp u th pb dating of hydrothermal monazite in a mo mineralized quartz vein from the dahu au mo deposit in the northern xiaoqinling terrane identifies two mineralization episodes hydrothermal monazite intergrown with molybdenite yields an initial precipitation age of 216 5 ma which is identical to but more precise than the molybdenite re os isochron age of 218 41 ma a younger generation of monazite is distinguished by data falling on a mixing array it is inferred that the younger monazite was formed at the expense of the older ones during the yanshanian probably during a single event that occurred at 125 ma combining these results with available geochronological data and geological evidence we conclude that molybdenum mineralization accompanied by monazite deposition took place in the indosinian followed by a yanshanian tectono hydrothermal event that resulted in large scale gold mineralization in the xiaoqinling terrane our observation demonstrates that monazite is sensitive to hydrothermal overprint and thus is useful for dating fluid infiltration event

isotopic geochemistry of the sawayaerdun orogenic type gold deposit tianshan northwest china implications for ore genesis and mineral exploration the sawayaerdun gold deposit is hosted by carbonaceous metasediments and is considered to be the largest muruntau type gold deposit in the chinese tianshan metallogenic belt gold mineralization at sawayaerdun occurs in quartz veins associated with three major hydrothermal events an early barren quartz vein stage middle stage mineralized quartz veins with pyrite and late carbonate quartz veins the isotopic compositions of quartz and sulfides from the sawayaerdun gold deposit show some variation but are generally comparable to those of other orogenic type gold deposits fluids trapped in early stage quartz have a 18o range of 13 6 to 15 4 d of 48 to 75 13c of 0 5 to 4 2 and 30si of 0 2 to 0 in contrast isotopic compositions of fluids trapped in middle stage quartz have 18o values of 6 7 to 14 7 d of 56 to 110 13c of 0 4 to 10 1 and 30si of 0 3 to 0 diagenetic and hydrothermal pyrite have similar sulfur 1 8 to 0 9 and pb isotopic values that are associated with host rock compositions the early stage 18o and 13c rich fluids are probably derived from metamorphic decarbonation of the sedimentary host rock at depth leading to the precipitation of early barren quartz veins in the middle stage a decrease in the regional pressure and temperature regime could have resulted in the incorporation of external fluids into the ore forming system these external fluids with isotopic signatures similar to that of the host rock and generally rich in 34s and radiogenic pb mixed with original ore forming fluids to generate extensive metal precipitation late stage fluids trapped by calcite veins show isotopic compositions similar to meteoric water indicating the cessation of hydrothermal fluid circulation at sawayaerdun occurred at this time the metallogenetic model illustrated by stable and pb isotopes is also consistent with fluid inclusion studies in sawayaerdun the development of mineralization at sawayaerdun is strongly linked to fluid mixing as witnessed by the isotopic signatures of fluids from identified ore bearing zones the isotopic compositions of other anomalous zones at sawayaerdun are similar to those of the mineralized zones suggesting a high potential for further exploration 2012 elsevier b v

climate change versus land management in the po plain northern italy during the bronze age new insights from the vp vg sequence of the terramara santa rosa di poviglio abstract the sedimentary infilling of the moat surrounding the villaggio piccolo of the terramara santa rosa di poviglio was analysed in order to obtain palaeoenvironmental inferences from sediments and pollen assemblage the high resolution stratigraphic sequence preserves evidence of the environmental changes that occurred in the po plain in northern italy during the late holocene our interdisciplinary approach permitted to study climatic and anthropic contributions to the environmental changes in this region the relationships between these changes and land use changes were investigated focussing on adaptive strategies of the terramare people during the middle and recent bronze ages 1550 1170 yr bc the terramare are archaeological remains of banked and moated villages located in the central alluvial plain of the po river the terramara of santa rosa consists of two adjoining settlements villaggio grande and villaggio piccolo the moat that separates the two parts of the site is c 23 m large and reaches a maximum depth of 4 m from the extant ground level the stratigraphic sequence vp vg exposed by archaeological excavation inside the moat was sampled for pedosedimentary thin section and pollen analyses chronology is based on archaeological evidence stratigraphic correlations and radiocarbon dating pedosedimentary features and biological records pollen of aquatics and algal remains demonstrate that shallow water probably subjected to seasonal water level oscillations has always been present in the moat in the lower units of the sequence the laminations indicate standing water while occurrence of reworked pollen testified the supply of sediments to the plain from catchment zones located in the apennine open vegetation was widespread economy was based on wood management fruit collection on the wild or from cultivated woody plants crop fields with a fairly diversified set of cereals especially increasing in variety during dryness or phases of water crisis probably grapevines were cultivated near the moat where the wet habitat was favourable to the growing of wild plants the extraordinary high resolution of this sequence makes visible the management of woods including coppicing at the middle bronze and early recent bronze ages the economy of santa rosa di poviglio should have been probably less based on animal breeding than it was in the other terramare villages already studied for pollen this research also confirms the chronological correspondence between an environment stressed by dry conditions and the collapse of the terramare civilization

detection of open fractures with vertical seismic profiling in vertical seismic profiling surveys tube waves are generated by compressional waves impinging on subsurface fractures or permeable zones the problem of generation of these waves by a nonnormal incident p wave for an inclined borehole intersecting a tilted parallel wall fracture is formulated theoretically the amplitude of tube waves depends on the permeability the length of the fracture and the frequency the relative effects of these parameters are studied individually the problem is also formulated for a thin oblate ellipsoidal penny shaped fracture the results for the two fracture models are compared and contrasted field data from tyngsboro massachusetts are shown for open fractures in granite from tube wave amplitudes normalized to p wave amplitudes calculated permeabilities are of the order of 100 mdarcy

q log determination on downgoing wavelets and tube wave analysis in vertical seismic profiles1 seismic attenuation introduces modifications in the wavelet shape in vertical seismic profiles these modifications can be quantified by measuring particular signal attributes such as rise time period and shape index use of signal attributes leads to estimations of a seismic attenuation log q log to obtain accurate signal attributes it is important to minimize noise influence and eliminate local interference between upgoing and downgoing waves at each probe location when tube waves are present it is necessary to eliminate them before performing separation of upgoing and downgoing events we used a trace by trace wiener filter to minimize the influence of tube waves the separation of upgoing and downgoing waves was then performed in the frequency domain using a trace pair filter we used three possible methods based on signal attribute measurements to obtain g log from the extracted downgoing wavefield the first one uses a minimum phasing filter and the arrival time of the first extremum the two other methods determine the q factor from simple relations between the amplitudes of the first extrema and the pseudo periods of the down going wavelet the relations determined between a signal attribute and traveltime over quality factor were then calibrated using field source signature and constant q models computed by ganley s method q logs thus obtained from real data are discussed and compared with geological information specifically at reservoir level analysis of the tube wave arrivals at the level of the reservoir showed a tube wave attenuation that could not be explained by simple transmission effects there was also a loss of signal coherence this could be interpreted as tube wave diffusion in the porous reservoir followed by dispersion if this interpretation can be verified tube wave analysis could lead to further characterization of porous permeable zones

handbook of environmental isotope geochemistry vol 1 the terrestrial environment a p fritz and j ch fontes editors elsevier amsterdam 1980 xii 532 pp u s 90 25 dfl 185 00

p t x conditions of hydrothermal fluids and precipitation mechanism of stibnite gold mineralization at the wiluna lode gold deposits western australia conventional and infrared microthermometric constraints the wiluna lode gold deposits are located in the archean wiluna greenstone belt in the northern sector of the norseman wiluna belt in the yilgarn craton of western australia they are hosted in subgreenschist facies meta basalts and controlled by the wiluna strike slip fault system and associated shear veins and breccias the 13 individual lode gold deposits have produced around 115 t au from 1901 to 1946 and 1986 to today historically they also produced 38 3 t as and 3 5 t sb gold formed in two stages stage 1 gold pyrite arsenopyrite is finely disseminated in the wallrock and breccia fragments whereas stage 2 gold stibnite is located in massive shear veins and breccia matrix as fracture fill and in banded colloform textured veins stibnite gold orebodies only occur in some of the deposits e g moonlight and northern part of the west lode and also display a restricted vertical extent being preserved only in the uppermost 200 m of stibnite bearing lodes petrographic conventional and infrared microthermometric and laser raman analysis on stibnite bearing quartz veins and breccias reveal that the antimony and gold rich hydrothermal fluid was of mixed h2o nacl co2 ch4 type microthermometric measurements reveal maximum homogenization temperatures of 340 c average 290 25 c and a wide range of salinities between 0 2 and 23 eq wt nacl aqueous carbonic fluid inclusions contain variable xco2 ch4 0 03 to 0 82 with the carbonic phase containing a maximum xch4 of 0 21 combined petrographic and microthermometric evidence suggests that the fluid inclusion properties reflect fluid immiscibility of a low salinity medium xco2 ch4 homogeneous parent fluid at about 290 c and pressures between 700 and 1 700 bar fluid immiscibility was triggered by cyclic pressure release during fault zone movement the decompression adiabatic cooling of the hydrothermal fluids shifted the ore fluid to lower temperatures significantly reduced the degree of stibnite undersaturation and caused stibnite to precipitate the deposition of stibnite reduced the ore fluid h2s concentration thereby destabilized gold bisulfide complexes in solution and caused gold precipitation locally this mechanism explains the intimate spatial association of stibnite and gold in quartz veins and breccias in the stibnite gold orebodies at wiluna

the tempo of holocene climatic change in the eastern mediterranean region new high resolution crater lake sediment data from central turkey this study presents results from a multi proxy analysis of cores taken in a crater lake sequence from eski acigol in central turkey which cover the period from pre c 16000 cal yr bp to the present the sediments comprise an upper unit of generally non laminated banded to massive silts and peats of mid to late holocene age overlying a laminated unit of late pleistocene to early mid holocene age the laminae comprising mainly aragonite amorphous silica diatom frustules and organic matter were formed in a relatively deep dilute meromictic lake pollen data indicate an abrupt replacement of artemisia chenopod steppe by grass oak terebinth parkland during the period of laminae deposition marking the start of the holocene a gradual increase in tree pollen during the early holocene came to an end c 6500 cal yr bp u series and adjusted c 14 timescale when mesic deciduous taxa declined at the same time as lake levels fell human impact on regional vegetation is inferred from a sharp decline in oak around 4500 4000 cal yr bp diatom isotopic and mineralogical data indicate that during the second half of the holocene the lake became relatively shallow and oscillated between fresh and brackish evaporated water conditions the contrast between wetter early and drier late holocene climatic conditions is matched by other eastern and central mediterranean proxy climate data while the eski acigol sequence resembles holocene hydroclimatic changes in the saharo arabian zone and was also apparently linked to orbital forcing it is unlikely to have had the same direct cause i e an expansion and subsequent retreat of monsoon rainfall

stable isotope composition of late glacial land snail shells from grotta del romito southern italy palaeoclimatic implications abstract stable isotope composition of living and fossil land snail shells was determined at grotta del romito southern italy with the aim to reconstruct environmental and climatic variation in the area during late upper palaeolithic the investigated succession comprised 15 different excavated layers spanning between ca 13 000 and 14 500 yr cal bp the oxygen isotope composition of snail shells indicates a marked decrease at the layer d8 suggesting a climatic deterioration consistent with the gi 1d climatic event older dryas this climate deterioration may have been related to a substantial decrease of mean annual temperature with associated changes in the regional atmospheric circulation however the environmental conditions at the time of shell s growth in the other intervals sampled suggest condition comparable to the present day the carbon isotope composition of fossil snail shells is in agreement with other records which indicate a general increase of the 13 c values of organic matter during pleniglacial to late glacial caused by substantially lower atmospheric co 2 concentration at that time

hydrothermal origin of late proterozoic bedded chert at gusui guangdong china petrological and geochemical evidence the late proterozoic bedded chert from gusui in guangdong province southern china is characterized by bedded laminated massive and pseudobrecciated structures the chert is depleted in tio2 al2o3 and most trace elements however it is enriched in ba as sb hg and se in al fe mn ternary diagrams it falls into the hydrothermal field factor analysis shows that many elements show up in the principal trace element factor suggesting their enrichment results from leaching of the country rock by hydrothermal solutions the chert has low ree concentrations and displays an ree pattern consistent with a hydrothermal origin it may have formed in a late proterozoic rift or extension zone developed within the yunkai continental margin back arc basin with a fault system linking it to an unknown heat source at depth

multistage sedimentary and metamorphic origin of pyrite and gold in the giant sukhoi log deposit lena gold province russia gold mineralization at sukhoi log in eastern siberia is hosted in a deformed neoproterozoic organic bearing and pyritic black shale and siltstone sequence that is folded into a tight overturned anticline the deposit contains about 30 million ounces of gold at an average grade of 2 0 g t au and is one of the largest known undeveloped gold resources the high grade gold zone forms a gently dipping tabular body in the core of the anticline the best gold grades occur in narrow bedding parallel pyrite quartz veinlets that have been folded during the main deformation event lower grade gold is associated with disseminated pyrite developed in and around the high grade core of the deposit detailed paragenetic studies of the mineralization and host rocks have defined six stages of pyrite development in the carbonaceous sediments the two earliest forms of pyrite termed py1 and py2 are commonly developed in stratiform layers of micron sized crystals framboids and fine euhedra which are interpreted as synsedimentary to early diagenetic in origin coarser grained bedding parallel aggregates of inclusion rich pyrite termed py3 contain inclusions of arsenopyrite native gold and gold tellurides and are interpreted to form during late diagenesis and earliest deformation coarse euhedral pyrite py4 overgrows the earlier pyrite py1 py2 and py3 and the slaty cleavage developed in the host rocks indicating a syndeformation timing late stage inclusion free pyrite py5 overgrows and replaces earlier sulfides and is considered to be syn to late deformation laser ablation inductively coupled plasma mass spectrometry la icpms analyses of the various pyrite types indicate that the synsedimentary py1 contains the highest levels of invisible gold varying from 0 4 to 12 1 ppm with a mean of 3 22 ppm au and 1 900 ppm as py1 is also enriched in a suite of trace elements mo sb ni co se te ag cu pb zn mn ba cr u v which are similar to those concentrated by organic processes in euxinic sedimentary environments later generations of pyrite from py2 to py5 including pyrite in bedding parallel pyrite quartz veinlets contain progressively lower contents of invisible gold and most other trace elements however this metamorphic and postmetamorphic pyrite contains microinclusions of free gold arsenopyrite pyrrhotite sphalerite and chalcopyrite the paragenetic textural and chemical relationships at sukhoi log suggest that gold was clearly initially introduced prior to cleavage development accompanying sedimentation of the organic rich shales and fixed during diagenesis within the structure of diagenetic arsenian pyrite subsequently accompanying deformation gold was liberated from recrystallized diagenetic pyrite to become concentrated as free gold and gold tellurides within metamorphic pyrite and folded bedding parallel pyrite quartz veinlets two key processes are considered vital to the formation of the sukhoi log deposit original synsedimentary and early diagenetic concentration of gold dissolved within arsenian pyrite in organic rich black shales and metamorphic processes that liberated gold from the early forms of arsenian pyrite to be concentrated as free gold and gold tellurides within late diagenetic and metamorphic pyrite and associated pyrite quartz veinlets in the core of an overturned anticline these ore forming processes are unlikely to be unique to sukhoi log other black shale and turbidite hosted deposits that occur in rifted continental margin environments which have undergone collision and basin inversion may form by similar processes

giant mesozoic gold provinces related to the destruction of the north china craton abstract lode gold deposits in precambrian cratons represent the world s major gold source and were mostly generated during formation and stabilization of the cratons however there is an extraordinary exception in the north china craton ncc where lode gold deposits formed after prolonged stabilization of the craton molybdenite re os and hydrothermal sericite and biotite 40 ar 39 ar dating of major gold deposits from the xiaoqinling district southern ncc bracket their emplacement in the range of 154 1 1 1 to 118 9 1 2 ma n 23 postdating formation of the craton by more than 1 7 billion years fluid inclusions extracted from gold bearing pyrite have elevated 3 he 4 he ratios 1 52 0 22 ra and mantle like ne isotopes 20 ne 22 ne 10 02 9 22 and 21 ne 22 ne 0 033 0 027 indicating presence of mantle derived fluids in the ore system measured 34 s of pyrite and d and 18 o of hydrothermal micas and fluid inclusion waters in auriferous quartz further confirm a magmatic mantle source for sulfur and ore fluids gold deposits of similar ages also widely occur in the eastern and northern margins of the ncc which together with those in the xiaoqinling district have a total reserve of 2500 t gold forming the only known giant late mesozoic gold province in the world s precambrian cratons these deposits formed coevally with extensive felsic to mafic magmatism development of intracontinental rift basins and exhumation of metamorphic core complexes across the eastern ncc events interpreted as indicating thinning and destruction of the lithosphere beneath the craton rising of asthenosphere coupled with destruction of the lithosphere has generated voluminous mafic and felsic magmas that provided sufficient fluids sulfur and by inference other ore components to form the giant gold provinces

la icp ms trace element analysis of pyrite from the chang an gold deposit sanjiang region china implication for ore forming process abstract the chang an gold deposit yunnan province is one of five large gold deposits in the ailaoshan gold belt that is the most important ore belt of the sanjiang tethyan metallogenic domain geochemical study of pyrite in the deposit was conducted using laser ablation inductively coupled plasma mass spectroscopy three types of hydrothermal pyrite were identified in the ores and wall rocks i e the coarse euhedral crystals in syenite py1 the coarse grains disseminated in altered sandstones or sandstone ores py2 and the fine grained euhedral pyrite in sandstone ores py3 their trace elements exhibit different concentrations associations and rim core zoning implying different geneses and crystallization processes the cores of py1 were formed by magmatic fluids and have the lowest concentrations of au as cu and zn the cores of py2 were formed by metamorphic fluids and have relatively high au ag ni pb and cu concentrations the py3 grains and the growth rims of py1 and py2 show consistently high contents of au as pb and co suggesting that all of them were rapidly deposited from a mixing fluid system that was probably composed of fluids of metamorphic and magmatic origins this interpretation is supported by the observation that the high grade ores generally contain lots of py2 and py3 hence we consider that the deposit was formed during india asia collision slightly postdate the 33 35 ma tectono magmatism

relationship between co2 dominated fluids hydrothermal alterations and gold mineralization in the red lake greenstone belt canada abstract the red lake greenstone belt is one of the foremost au mining camps in canada and hosts the world class campbell red lake au deposit belt scale hydrothermal alteration is characterized by proximal ferroan dolomite zones associated with au mineralization surrounded by distal calcite zones both being accompanied by potassic alterations sericite muscovite and biotite at the campbell red lake and cochenour deposits au mineralization in particular high grade ore is associated with silica and sulfides especially arsenopyrite that replace carbonate quartz veins and the host rocks the prevalence of carbonic fluid inclusions and rare occurrence of aqueous bearing inclusions in carbonate quartz au veins in the campbell red lake deposit and the consistency of homogenization temperatures of carbonic inclusions within individual fluid inclusion assemblages fia have been interpreted to indicate that h2o poor co2 dominated fluids were responsible for the carbonate veining and au mineralization further studies of fluid inclusions in carbonate quartz veins within and outside the deformation zone hosting the campbell red lake deposit the red lake mine trend including the cochenour au deposit the redcon au prospect and outcrops in the distal calcite zone also reveal the dominance of carbonic fluid inclusions in vein minerals these studies indicate that co2 dominated fluids were flowing through fractures during carbonate vein formation and au mineralization both within and outside major structures the carbonic fluid may have been initially undersaturated with water or it may have resulted from phase separation of an h2o co2 nacl fluid in the latter case phase separation modeling indicates that the initial fluid likely had x co 2 values larger than 0 8 calculations based on hydrothermal mineral assemblages indicate x co 2 values in the host rocks from 0 025 to 0 85 reflecting a change from co2 dominated fluids in the fractures veins to h2o dominated fluids in the host rocks away from the fractures the co2 dominated fluids were likely advected from granulite facies in the deeper crust whereas the h2o dominated fluids were derived from the ambient host rocks of amphibole to greenschist facies calculations based on co2 requirements and source constraints indicate that the mineralizing fluids were likely two orders of magnitude more enriched in au than the commonly assumed values of a few g l which may explain why the campbell red lake deposit has a very high grade of au average 21 g t for the whole deposit and 81 g t for the goldcorp high grade zone fluid inclusion data suggest that the carbonate veining and au mineralization likely took place at depths from 7 to 14 km the development of crustiform colloform structures in the carbonate quartz veins which was previously interpreted to indicate relatively shallow environments may alternatively have been related to extremely high fluid pressures and the co2 dominated nature of the fluids which could have enhanced the brittle properties of the rocks due to their high wetting angles

holocene hydro climatic variability in the mediterranean a synthetic multi proxy reconstruction here we identify and analyze proxy data interpreted to reflect hydro climatic variability over the last 10 000 years from the mediterranean region to 1 outline millennial and multi centennial sca

the late cretaceous donlin creek gold deposit southwestern alaska controls on epizonal ore formation the donlin creek gold deposit southwestern alaska has an indicated and inferred resource of approximately 25 million ounces moz au at a cutoff grade of 1 5 g t the ca 70 ma deposit is hosted in the late cretaceous kuskokwim flysch basin which developed in the back part of the arc region of an active continental margin on previously accreted oceanic terranes and continental fragments a hypabyssal mainly rhyolitic to rhyodacitic and commonly porphyritic 8 3 km dike complex part of a regional ca 77 to 58 ma magmatic arc formed a structurally competent host for the mineralization this deposit is subdivided into about one dozen distinct prospects most of which consist of dense quartz carbonate veinlet networks that fill north northeast striking extensional fractures in the northeast trending igneous rocks the sulfide mineral assemblage is dominated by arsenopyrite pyrite and typically younger stibnite gold is refractory within the arsenopyrite sericitization carbonatization and sulfidation were the main alteration processes fluid inclusion studies of the quartz that hosts the resource indicate dominantly aqueous ore fluids with also about 3 to 7 mol percent co2 ch4 and a few tenths to a few mole percent nacl kcl the gold bearing fluids were mainly homogeneously trapped at approximately 275 to 300 c and at depths of 1 to 2 km some of the younger stibnite may have been deposited by late stage aqueous fluids at lower temperature measured 18o values for the gold bearing quartz range between 11 and 25 per mil the estimated 18o fluid values range from 7 to12 per mil suggesting a mainly crustally derived fluid a broad range of measured d values for hydrothermal micas between 150 and 80 per mil is suggestive of a contribution from devolatilization of organic matter and or minor amounts of mixing with meteoric fluids gold associated hydrothermal sulfide minerals are characterized by 34s values mainly between 16 and 10 per mil with the sulfur derived from diagenetic pyrite and organic matter within the flysch basin a smaller group of 34s measurements which shows values as depleted as 27 per mil suggests a different local sulfur reservoir in the basin for the later hydrothermal episode dominated by stibnite initial nd of 8 7 to 3 1 and 87sr 86sr measurements of 0 706 to 0 709 for the ore hosting dikes also indicate a crustal reservoir for some of the late cretaceous magmatism overlapping lead isotope data for these intrusive rocks and for sulfide minerals suggest a crustal contribution for the lead in both copper and gold bearing stockwork veinlets in hornfels occur at dome a prospect located at the northern end of the donlin creek deposit these stockworks are cut by the younger auriferous gold veins that define the main donlin creek gold mineralization highly saline gas rich heterogeneously trapped fluids deposited the stockworks at temperatures approximately 100 c hotter than those of the main gold forming event at donlin creek the genetic relationship of the dome prospect to the main donlin creek gold resource is equivocal the epizonal donlin creek deposit shows affinities to the gold systems interpreted by various workers as orogenic or intrusion related it shows important differences from typical epithermal and carlin like deposits the ore forming fluids were derived by either broad scale metamorphic devolatilization above rising mantle melts or exsolution from a magma that was dominated by a significant flysch melt component

first arrival picking on common offset trace collections for automatic estimation of static corrections the increase in the number of geophone groups in production records during recent years and the requirement for accurate basic static corrections for high resolution records have made it necessary to develop sufficiently accurate automatic techniques for the determination of static corrections a fully automatic method is presented which makes use of the delay time method in order to compute static corrections at each shot position delay times weathering and subweathering velocities are determined from automatic picks of the first arrivals on common offset trace collections it is assumed that the weathering is a single layer and that the dip of the subweathering layer under the geophone groups is small the picking routine is fully automatic and successful in most cases provided the signal to noise ratio is sufficiently high the subsequent filtering of erroneous values for picked times is performed by means of statistical techniques using curves of picked times on common offset trace collections if the distance between receivers and shot points on the profile is sufficiently short one can expect only little change in the picked times of two contiguous traces the method is well adapted to end on spreads with a great number of traces where distances between geophone groups are short examples are presented showing the possibilities of the method for the determination of long wavelength as well as short wavelength components of static corrections

potential forcing mechanisms of holocene lake level changes at nam co tibetan plateau inferred from the stable isotopic composition of shells of the gastropod radix the timing of lake level fluctuations on the tibetan plateau and their relationship with climatic changes is still under debate and the main reason for this is the lack of suitable archives for reconstructing the paleohydrology and paleoclimatology of the lakes here we present the results of analyses of the shell geochemistry of radix sp from an exposed terrace of nam co lake on the south central tibetan plateau optically stimulated luminescence osl dating reveals that deep water lacustrine sediments formed between ca 4 4 and 2 2 ka suggesting a high and stable lake level significantly above the present the results of sr ca 13c and 18o analyses of the fossil shells of radix sp indicate that during the mid to late holocene lake level variations in nam co were mainly controlled by variations in the indian summer monsoon a trend of decreasing evaporation also played an important role comparison with other results suggests a consistent pattern of mid to late holocene lake level changes acro

rapid hydrological changes during the holocene revealed by stable isotope records of lacustrine carbonates from lake igelsjon southern sweden a holocene sediment sequence from lake igelsjon south central sweden was studied by stable oxygen and carbon isotope analyses of different carbonate components the deposit which covers the time span from ca 11 500 cal bp to the present was laid down in a small kettle hole lake the hydrological balance of which is presently dominated by groundwater flow isotopic records obtained on bulk carbonates originating mainly from summer produced calcitic algal encrustations exhibit several rapid shifts of more than 2parts per thousand likely reflecting pronounced hydrological variations corresponding isotopic data obtained on calcitic gastropod opercula from parts of the profile show subdued responses to major climatic shifts probably related to an extended calcification season the isotopic records were complemented by studies of modern isotope hydrology and our interpretations are based on a simplistic climate hydrology model in which variations in groundwater generation within the lake catchment produce changes in groundwater level and related adjustments of lake level and surface volume ratio of the basin during the ice free season assumed periods of decreased lake volume in a relatively dry climate low lake level are characterised by enrichment in o 18 and c 13 resulting from increased evaporation inflow ratio and atmospheric equilibration respectively in clear contrast to this situation intervals of more humid climatic conditions give rise to increased lake volume high lake level possibly surface over flow and relatively depleted isotopic ratios relatively humid conditions which may correlate to a wide spread cooling event recorded by various proxies across the north atlantic region are indicated by distinct isotopic shifts at ca 8300 and 8000 cal bp bracketing a period of o 18 depletion the period between ca 8000 and 4000 cal bp was characterised by relatively dry and stable climatic conditions whereas the subsequent part of the holocene experienced a more humid and variable climate following marked and coherent depletions in o 18 and c 13 at ca 4000 cal bp c 2002 elsevier science ltd all rights reserved less

lateglacial and holocene climate and environmental change in the northeastern mediterranean region diatom evidence from lake dojran republic of macedonia greece abstract the juncture between the west east and north south contrasting holocene climatic domains across the mediterranean is complex and poorly understood diatom analysis of lake dojran republic of macedonia greece provides a new insight into lake levels and trophic status during the lateglacial and holocene periods in the northeastern mediterranean following a very shallow or even desiccated state at the core base at ca 12 500 cal yr bp indicated by sedimentological and hydro acoustic data diatoms indicate lake infilling from a shallow state with abundant benthos to a plankton dominated relatively high lake level and eutrophic state thereafter diatom inferred shallowing between ca 12 400 12 000 cal yr bp and a very low lake level and eutrophic oligosaline state between ca 12 000 11 500 cal yr bp provide strong evidence for younger dryas aridity the earliest holocene ca 11 500 10 700 cal yr bp was characterised by a high lake level followed by a lake level reduction and increased trophic level between ca 10 700 8 500 cal yr bp the lake was relatively deep and exhibited peak holocene trophic level between ca 8 500 3 000 cal yr bp becoming shallow thereafter the diatom data provide more robust evidence and strengthen previous lake level interpretation based on sedimentological and geochemical data during the earliest mid and late holocene and also clarify previous uncertainty in interpretation of lateglacial and early holocene lake level change our results are also important in disentangling regional climate effects from local catchment dynamics during the holocene and to this end we exploit extant regional palynological evidence for vegetation change in the highlands and lowlands the importance of seasonality in driving holocene climate change is assessed by reference to the summer and winter latitudinal temperature gradient ltg model of davis and brewer 2009 we suggest that increased precipitation drove the high lake level during the earliest holocene the early holocene low lake level and relatively high trophic state may result climatically from high seasonality of precipitation and locally from limited nutrient rich catchment runoff we argue that the mid holocene relatively deep and eutrophic state was driven mainly by local vegetation succession and associated changes in catchment processes rather than showing a close relationship to climate change the late holocene shallow state may have been influenced by a temperature induced increase in evaporative concentration but was coupled with clear evidence for intensified human impact this study improves understanding of lateglacial and holocene climate change in the northeastern mediterranean suggests the important role of the ltg on moisture availability during the holocene and clarifies the influence of catchment processes on palaeohydrology

tectonics and distribution of gold deposits in china an overview gold exploration in china has expanded rapidly during the last two decades since a modern approach to economic development has become a national priority china currently produces 180 tonnes t of gold annually which is still significantly less than south africa usa and australia however china is now recognized as possessing significant gold resources in a wide range of mineral deposit types present estimates of gold resources in china exceed 4 500 t which comprise 60 in gold only deposits more than 25 in base metal rich skarn porphyry and vein deposits and more than 10 in placer accumulations the major gold provinces in china formed during the main episodes of phanerozoic tectonism such tectonism involved interaction of china s three major precambrian cratons north china tarim and yangtze or south china when combined with cathaysia block with the angara or siberian kazakhstan kyrgyzstan and indian cratons resulting collisions included deformation of accreted oceanic sequences between the cratonic blocks the most important ore forming orogenies were 1 the late paleozoic variscan 405 270 ma which led to amalgamation of the angara north china and yangtze cratons 2 the indosinian 270 208 ma which led to the collision of north china and south china cratons 3 the yanshanian 208 90 ma which was largely influenced by the subduction of the izanagi pacific plates beneath eastern china and 4 the himalayan 90 ma indentation of the indian continent into eurasia no important precambrian gold systems are recognized in china mainly because of reworking of exposed precambrian rocks by these younger orogenies but there are a few caledonian 600 405 ma gold bearing systems in northern xinjiang most of china s orogenic epithermal and carlin like gold deposits are in the reworked margins of major cratonic blocks and in metasedimentary rock dominated fold belts adjacent to these margins accordingly the major gold provinces are present along the northern southeastern and southern margins of the north china craton along the southwestern and northwestern margins of the yangtze craton in the tianshan and altayshan orogenic belts in northern xinjiang and throughout the southeastern china fold belt gold placer deposits derived from these primary deposits are concentrated in the northernmost part of northeastern china and along the northwestern margin of the yangtze craton the major provinces with significant gold in porphyry related copper systems and base metal skarns are present in the yangtze river area along the northeastern and southeastern margin of the yangtze craton in the fold belt in southwestern china and scattered through northern china three quarters of the chinese gold only deposits occur within the north china craton margins half are located in the uplifted precambrian metamorphic rocks and most of the remainder are hosted in the phanerozoic granitoids that intruded the reworked precambrian terranes the abundance of granite hosted gold contrasts the north china craton with other precambrian cratons such as those in western australia central canada and zimbabwe where gold is mainly hosted in the archean greenstone belts this difference may be explained by the multiple episodes of phanerozoic tectonism along the north china craton margins resulting from the collision of the angara north china and south china cratons and from subduction of the izanagi pacific oceanic plates underneath the eastern china continent

holocene climate variability although the dramatic climate disruptions of the last glacial period have received considerable attention relatively little has been directed toward climate variability in the holocene 11 500 cal yr b p to the present examination of similar to50 globally distributed paleoclimate records reveals as many as six periods of significant rapid climate change during the time periods 9000 8000 6000 5000 4200 3800 3500 2500 1200 1000 and 600 150 cal yr b p most of the climate change events in these globally distributed records are characterized by polar cooling tropical aridity and major atmospheric circulation changes although in the most recent interval 600 150 cal yr b p polar cooling was accompanied by increased moisture in some parts of the tropics several intervals coincide with major disruptions of civilization illustrating the human significance of holocene climate variability c 2004 university of washington all rights reserved

brittle origins for disseminated gold mineralization in mylonite gaocun gold deposit hetai goldfield guangdong proince south china gold mineralization in the hetai goldfield in south china is almost entirely confined to a series of steeply dipping ductile shear zones generated during hercynian indosinian orogenesis of sinian host rocks approximately half of the mineralization is in the form of disseminations in the mylonite and the remainder was clearly emplaced as a result of brittle deformation in einlets and as sulfide cement to brecciated mesoscopic quartz eins heaily influenced by the presence of disseminated mineralization all publications on hetai determine a major role for ductile deformation in the introduction of gold into the deposit the brittle deformation is typically regarded as redistributing within the host structures the gold initially introduced as a result of ductile deformation mechanisms howeer textures of the sulfides associated with the gold indicate an entirely postductile deformation timing as they display none of the features attributed to ductile deformation during the eident brittle deformation phase competence contrasts at the microscopic scale allowed fracturing to focus on the quartz sericite domain boundaries of the mylonite foliation thus permitting the introduction of auriferous fluid into the mylonite to create disseminated mineralization the control exerted by preexisting structures is further reflected in the restriction of disseminated mineralization to the quartz domains presumably because the sericite domains accommodated the deformation in a more distributed fashion seeral other lines of eidence support an origin of the hetai deposit in an upper crustal regime a similar style of disseminated mineralization to that seen in the mylonite surrounds microeinlet terminations in the brecciated quartz eins as well as oerprinting pseudotachylite which is associated with cataclasite there are also large olumes of unmineralized mylonite indicating no connection between the intensity of strain and gold grade we conclude that in structurally controlled deposits the textural category of disseminated gold mineralization can be generated either under entirely ductile or entirely brittle conditions and that microtextural eidence has to be carefully analyzed to determine the mode of formation of a deposit

q estimation from vertical seismic profile data and anomalous variations in the central north sea four different methods of estimating q from vertical seismic profile vsp data based on measurements of spectral ratios pulse amplitude pulse width and zeroth lag autocorrelation of the attenuated impulse are described the last procedure is referred to as the pulse power method practical problems concerning nonlinearity in the estimating procedures uncertainties in the gain setting of the recording equipment and the influence of structure are considered in detail vsp data recorded in a well in the central north sea were processed to obtain estimates of seismic attenuation these data revealed a zone of high attenuation from approximately 4 900 ft to 5600 ft with a value of 25 3 results of the spectral ratio analysis show that the data conform to a linear constant q model in addition since the pulse width measurement is dependent upon the dispersive model adopted it is shown that a nondispersive model cannot possibly provide a match to the real data no unambiguous evidence is presented that e

last glacial to holocene palaeoenvironmental evolution at lago di pergusa sicily southern italy as inferred by pollen microcharcoal and stable isotopes abstract sediments of last glacial and holocene age from two different locations in the basin of lago di pergusa have been palynologically and isotopically investigated new data have been integrated with those available from previous researches carried out by the authors this study indicates once more that lago di pergusa was and still is very sensitive to climate changes in particular during the last glacial it played an important role in preserving the biodiversity as thermophilous and mesophilous taxa never completely disappeared in particular zelkova pollen indicates that the distribution area of this tree still living as a relic plant in south eastern sicily was wider during the last glacial where its last spread is found around 20 000 years bp the 18 o record mirroring the arboreal concentration trend confirms the climate inferences based on vegetation features both the late glacial and the postglacial reforestation periods show slower vegetation dynamics and forest development than expected with trends mirroring the slow and sustained decline of 18 o record the younger dryas oscillation is not pronounced in any of the lacustrine palaeoenvironmental proxies its termination occurring around 11 100 cal years bp the opening of the woodland recorded by a slow trend ranging from the neolithic around 8000 cal years bp to the eneolithic few centuries before 4000 cal years bp seems to be a natural forest clearance and not due to human impact anomalies in pollen microcharcoals and positive correlations between 18 o and ap curves are found after a climate change occurring at 4500 years bp and interpreted as a signal of human impact the new 18 o data presented in this paper throws new light to propose this hypothesis confirming an early aridification trend detected from pollen and a relatively late human impact inferred from fire dynamics in this central and montane region of sicily

stable isotope composition of the holsteinian mis 11 freshwater snail valvata piscinalis o f muller 1774 from eastern poland and its palaeoenvironmental implications stable oxygen and carbon isotope investigations were conducted on shells of the freshwater gastropod valvata piscinalis from palaeolake deposits of holsteinian age marine isotope stage 11 from eastern poland the isotope record of this species was used for the first time as an archive of environmental conditions for selected lakes between the protocratic stage and the post optimum period of the interglacial the lowest 18o and 13c values of 8 1 and 12 1 respectively were recorded in the picea alnus zone at ortel krolewski palaeolake the sparse vegetation and low productivity of that time are reflected in the relatively low 13c values the first significant increase of temperature was recorded in the taxus zone i e an increase in 18o the higher temperature influenced the expansion of macrophytes which stimulated enhanced photosynthesis similar mean 18o values in the taxus and pinus larix zones imply no distinct temperature change v piscinalis populations from ossowka hrud and roskosz palaeolakes record variations in lake productivity during the climatic optimum of the interglacial carpinus abies zone the 18o values of that time are relatively high up to 4 5 and reveal no significant differences between the lakes decreases of the oxygen isotope values in the szymanowo lake reflect post optimum cooling

measurements of attenuation from vertical seismic profiles values of attenuation have been extracted from five detailed velocity surveys significant amounts of attenuation are observed in all five wells measured values of attenuation vary by a factor of 10 ranging from less than 0 1 to 0 9 db wavelength correlation of attenuation with lithology is good considering the resolution limits of the surveys one of the surveys was performed in west texas and the other four were carried out in the gulf coast area the total number of recording depths in each survey varied from 31 to 208 with downhole recordings taken every 10 or 20 ft over key stratigraphic zones in all five surveys a monitor geophone was placed near the well to check for source consistency our procedure for measuring attenuation involved constructing the spectral ratio between each downhole pulse and one particular reference pulse a value of cumulative attenuation ca was then extracted from each spectral ratio and plotted as a function of geophone depth this method allowed us to use many m

hydrologic variation in the northern great plains during the last two millennia abstract reconstructions of lake water salinity at decadal resolution for the last 2000 yr are compared among three lakes in north dakota to infer regional patterns of drought the intersite comparisons are used to distinguish local variation in climate or hydrology from regional patterns of change at one lake diatom inferred salinity and lake water mg ca inferred from ostracode shell chemistry are coherent both in terms of direction and magnitude of change indicating that each is a robust technique for reconstructing lake water chemistry the data show that the last 2000 yr have been characterized by frequent shifts between high and low salinity suggesting shifts between dry and moist periods long intervals of high salinity suggest periods of multiple decades when droughts were intense and frequent thus indicating times when drought was more persistent than in the 20th century both the medieval period and little ice age were hydrologically complex and there is no clear evidence to suggest that either interval was coherent or unusual in effective moisture relative to long term patterns differences among the three sites may be attributed to variation in local hydrology and these differences emphasize the need for multiple sites in deriving regional climate interpretations from paleoecological data

late quaternary vegetation and hydrological change at ljubljansko barje slovenia abstract this paper investigates changes in the vegetation and hydrology at ljubljansko barje slovenia using a multi proxy approach pollen diatoms geochemical and stable isotope analysis during the lateglacial ljubljansko barje was a deep oligotrophic lake surrounded by open woodland comprised predominantly of pinus and betula which in the early holocene when the lake became shallower and mesotrophic fragilaria pinnata 15 n 3 3 13 c 33 7 c n 7 9 was replaced by broadleaved tree taxa tilia ulmus quercus corylus and picea this was followed by the spread of fagus and after 9200 cal yr bp abies and planktonic and oligotrophic diatom taxa aulacoseira italica gomphonema angustum as well as an increased allochthonous influx silt sio 2 al 2 o 3 between ca 6750 and 6000 cal yr bp the diatom data suggest shallower and oligotrophic conditions whereas the stable isotope record increased 13 c and decreased 15 n indicates terrestrial input changes in forest composition increase of quercus alnus corylus and the spread of herb taxa were probably advanced by human impact on the environment the beginning of organic sedimentation dated to 6000 cal yr bp was followed by an increase of fagus and abies and by eutrophication and peat growth at 5200 cal yr bp

a compilation of western european terrestrial records 60 8 ka bp towards an understanding of latitudinal climatic gradients terrestrial records of past climatic conditions such as lake sediments and speleothems provide data of great importance for understanding environmental changes however unlike marine and ice core records terrestrial palaeodata are often not available in databases or in a format that is easily accessible to the non specialist as a consequence many excellent terrestrial records are unknown to the broader palaeoclimate community and are not included in compilations comparisons or modelling exercises here we present a compilation of western european terrestrial palaeo records covering entirely or partially the 60 8 ka intimate time period the compilation contains 56 natural archives including lake records speleothems ice cores and terrestrial proxies in marine records the compilation is limited to include records of high temporal resolution and or records that provide climate proxies or quantitative reconstructions of environmental parameters such as temperature or precipitation and that are of relevance and interest to a broader community we briefly review the different types of terrestrial archives their respective proxies their interpretation and their application for palaeoclimatic reconstructions we also discuss the importance of independent chronologies and the issue of record synchronization the aim of this exercise is to provide the wider palaeo community with a consistent compilation of high quality terrestrial records to facilitate model data comparisons and to identify key areas of interest for future investigations we use the compilation to investigate western european latitudinal climate gradients during the deglacial period and despite of poorly constrained chronologies for the older records we summarize the main results obtained from nw and sw european terrestrial records before the lgm

environmental changes over the past 25 000 years in the southern middle atlas morocco a new fossil record from the southern middle atlas spans continuously the last 25000 years and provides evidence of an increased amount of snow precipitation during the last glacial period and a warm early holocene with rather dry climate conditions this environmental reconstruction is based on a multi proxy approach that integrates pollen micro charcoals grain size and geochemical analysis during the last glacial period we observe a strong presence of aquatic plants species that today flower during late spring and summer these occurrences are related to an increased amount of snow precipitation on the surrounding mountains which fed the marsh during the summer season although the early holocene reveals a slight and steady expansion of mediterranean oaks the semi arid artemisia steppe remained dominant in the landscape until 6 8ka cal bp thus the early holocene seems to have been less humid than elsewhere in north africa the atlas cedars began to establish around 6ka cal bp this indicates that the amount of annual rainfall increased after the mid holocene the late holocene is marked by an increase of fire events which may be related to a strengthening of the dry season and or a higher seasonality copyright c 2016 john wiley sons ltd

evolution of ore forming fluids in the sawayaerdun gold deposit in the southwestern chinese tianshan metallogenic belt northwest china the sawayaerdun gold deposit was discovered in the early 1990s and is the largest orogenic gold deposit in the chinese tianshan gold mineralization occurs in quartz veins which are hosted in carbonaceous metasediments and controlled by faults and fractures three major hydrothermal events can be identified at sawayaerdun an early barren quartz vein stage middle stage quartz veins with pyrite and gold mineralization and late carbonate quartz veins fluid inclusion studies of quartz pyrite and carbonate formed during the major hydrothermal stagesshow distinct changes in fluid temperature composition and redox conditions occurred during fluid evolution three types of fluid inclusions have been identified at sawayaerdun h2o nacl l v h2o nacl co2 l v and co2 l v fluids trapped in early barren quartz have high temperatures 280 420 c low salinities 3 wt nacl equiv high cl and are co2 rich middle stage quartz contains fluids with lower temperatures 210 310 c and variable salinities 0 8 17 5 wt nacl equiv they are commonly s rich co2 containing and relatively reduced compared with early stage fluids in contrast hydrothermal pyrite hosted in middle stage quartz veins trapped fluids formed over a narrower temperature range 220 270 c more oxidized high co2 ch4 ratio and have higher ca k and mg than fluids in quartz late stage carbonate is dominated by fluids with low temperatures 200 c and low contents of cl s and k fluid immiscibility probably commenced at the onset of mineralization along with middle stage quartz formation resulting in the generation of coexisting fluid inclusions with distinguishable vapor liquid ratios and salinities the compositional difference between fluids trapped in pyrite and quartz indicate fluid mixing may have occurred during the mineralization stage the oxidized fluids probably a mixture of meteoric water and fluids generated during water host rock interaction emerged into the ore forming system to generate extensive metals precipitation the fluid immiscibility and fluid mixing are most likely caused by pressure decrease during late paleozoic uplift and erosion in the chinese southern tianshan area comparison of fluids between four major mineralization zones at sawayaerdun indicate that zone ii is similar to the most important zone iv and the order of similarity is probably zone ii xi i which could be applied to the future mineral exploration in this area

variation in sr uptake in the shell of the freshwater gastropod bithynia tentaculata from lake arreo northern spain and culture experiments abstract the sr uptake features in bithynia tentaculata aragonite shells from monthly collections in lake arreo northern spain over a two year period are compared with those from the same species grown in culture experiments with similar waters under controlled temperature the shell aragonite of b tentaculata from lake arreo formed in isotopic equilibrium with the lake water a comparison of the stable oxygen isotope values 18o from the shells and waters allowed the selection of suitable shells for sr uptake studies the sr ca molar ratio in b tentaculata shells sr cashell from the lake and from the culture experiments positively correlate with some chemical parameters like conductivity and solute composition some environmental factors such as ph and t have minor influence on sr incorporation into shells as reported from other aragonitic mollusks the sr cashell exhibits a good positive correlation with the sr ca of the water sr caw using linear regression however a polynomial function equation better fits the sr cashell and the sr caw r2 0 890 p 2 923e 11 above a value of 0 0025 for sr caw the ratios of sr cashell present small changes this pattern reveals a noticeable variation of the partitioning coefficient kdsr with sr caw the kdsr for b tentaculata shell aragonite obtained in this study is 0 290 0 078 n 25 and it is close to the mean values obtained for other non marine aragonitic mollusks kdsr values in b tentaculata are influenced by the variations in sr caw that mask the t effect this feature together with the influence of physiological processes on the trace element incorporation may explain the observed kdsr pattern

mollusca stable isotope record of a core from lake frassino northern italy hydrological and climatic changes during the last 14 ka a core retrieved from lake frassino northern italy provided evidence of palaeohydrological change in this area during the last 14 ka lithological malacological and in particular stable isotope composition of freshwater shells allowed the delineation of the main phases of lake evolution between the lateglacial and holocene lateglacial conditions were drier than the holocene although a wetter period was inferred before c 14 ka according to the oxygen isotope composition of freshwater shells the holocene showed a clear bipartition the first part which lasted from 9100 to 7000 yr bp was drier and was followed by a rapid increase in humidity at 7000 6800 yr bp between 6800 and 5000 yr bp there were wetter and more stable conditions as indicated by smaller 18 o oscillations of pisidium and valvata shells from c 5000 to 2600 yr bp the record is characterized by larger fluctuations which may indicate that short term and particularly pronounced alternation of wet and dry periods occurred

a 15 000 year stable isotope record from sediments of lake steisslingen southwest germany abstract stable isotope records for carbon and oxygen in bulk carbonates carbon in bulk organic matter and for total and chromium reducible sulfur in a lacustrine sediment core from lake steisslingen southwest germany show several distinct and abrupt shifts during the last 15 000 years variations in the isotopic composition of authigenic carbonates indicate two major phases in the lake history in the pre holocene the hydrological budget of the lake was apparently stable variations of 18 o values of authigenic carbonates were therefore dominantly controlled by temperature changes a decrease in the 18 o carb values of about 2 at the allerod younger dryas transition is interpreted as a drop in mean annual air temperatures of approximately 5 c an abrupt temperature increase of a similar magnitude is inferred at the younger dryas preboreal boundary throughout most of the holocene the isotopic composition of authigenic carbonates was influenced by marked changes in the hydrological budget of the lake a major positive excursion in the 13 c carb and 18 o carb values at the beginning of the atlantic and a smaller one in the preboreal were related to evaporation effects which indicate that dry climatic conditions must have prevailed at that time a simultaneous increase in 13 c values of bulk organic matter at the beginning of the atlantic suggests a high level of productivity in the lake as a consequence aqueous sulfate became limited as indicated by variations in the 34 s values of total and chromium reducible sedimentary sulfur therefore we conclude that the beginning of the atlantic was characterized not only by dry but also by warm climatic conditions which triggered a higher productivity in the lake in the subatlantic sediments large variations in carbon oxygen and sulfur isotope ratios were observed as a result of human activities causing considerable perturbations in the biogeochemical element cycling of lake steisslingen results obtained by the study of the continuous 15 ka record of lake steisslingen document clearly that isotopic proxy data from lacustrine sediments can provide useful information on environmental and climatic changes of local regional and in the case of the younger dryas event of even hemispherical significance

thermomechanical stress strain numerical modelling of deglaciation since the last glacial maximum in the adamello group rhaetian alps italy abstract deglaciated areas in the valleys of the italian alps have recently exhibited a high potential for geomorphologic hazards from diffuse deep seated gravitational deformations dsgsds caused by rock mass creep processes that can evolve into rock falls and rock avalanches a multidisciplinary approach that integrated geomorphologic surveys and stress strain numerical simulations was used to investigate the effects of the stress release that was induced by the last glacial maximum lgm in the adame valley italian alps no evidence of dsgsds has been found in this area however data are available to develop a well constrained evolutionary model of the valley deglaciation the extent and thickness of the southern extension of the adamello glacier the widest glacier in italy during its primary growth phases including those of the lgm three late glacial stages and the little ice age lia were reconstructed using glacial geological surveys and were reproduced using a finite difference stress strain sequential model spanning from the lgm to the present a thermomechanical numerical configuration was developed based on geomechanical field measurements that were collected from rock outcrops and data from laboratory tests specifically performed on intact rock samples the numerical simulations demonstrate that thermomechanical viscous behaviour cannot be neglected because the resulting strains on the slopes are significantly higher than those resulting from conventional elastoplastic behaviour the last major thermal effect in the rock masses reproduced using the model occurred from 11 5 ka until the lia the resulting displacement rates are as much as several tens of mm ka which are consistent with the absence of dsgsds in the adame valley as these rates are significantly lower than those previously obtained from dsgsds and other large landslides in the alps based on thermomechanical numerical solutions these rates should persist for the next 1000 years assuming that no variations in current climatic conditions occur

holocene seasonality changes in the central mediterranean region reconstructed from the pollen sequences of lake accesa italy and tenaghi philippon greece this study presents pollen based climate reconstructions of holocene temperature and precipitation seasonality for two high resolution pollen sequences from the central lake accesa central italy and eastern mediterranean tenaghi philippon greece regions the quantitative climate reconstruction uses multiple methods to provide an improved assessment of the uncertainties involved in palaeoclimate reconstructions the multimethod approach comprises partial least squares regression weighted average partial least squares regression the modern analogues technique and the non metric multidimensional scaling generalized additive model method we find two distinct climate intervals during the holocene the first is a moist period from 9500 to 7800 cal bp characterised by wet winters and dry summers resulting in a strongly seasonal hydrological contrast stronger than today that is interrupted by a short lived event around 8200 cal bp this event is characterised by wet winters and summers at accesa wh

in situ investigation of seismic body wave attenuation in heterogeneous media field experiments have been carried out to study the nature and magnitude of seismic wave attenuation for a variety of lithologies in each survey two three component sets of geophones with wall clamping mechanisms were lowered down boreholes and signals originating from surface compressional and shear wave sources were recorded the data collected were corrected for spherical divergence and analyzed to determine intrinsic attenuation for situations of anomalous wavefront expansion and in cases where multiple reflection losses may be significant corrections were supplied by a synthetic seismogram programme to improve the estimates of intrinsic attenuation values of attenuation were obtained for pure sandstone sandstone marl sequences and fissured unfissured chalk sequences these formations were all near surface and relatively porous significant differences in the relative values of compressional and shear wave attenuation in the various lithologies were noted in particular compressional absorption in the fissured zones of chalk was twice the absorption associated with the seismic velocities and the absorption of shear waves fluctuated much less a large contrast in p wave attenuation was also observed between pure bunter sandstone and the sandstone marl sequence absorption was over three times as small in the former a smaller contrast was noted for shear attenuation the results obtained suggest that for the relatively homogeneous formations such as pure sandstone and unfissured chalk shear absorption was dominant over bulk absorption in contrast bulk absorption was larger than shear absorption for other formations e g the fissured chalk sequences and a partially saturated chalk section attenuation was found to be approximately proportional to frequency in all experiments

ore geology and fluid inclusion geochemistry of the tiemurt pb zn cu deposit altay xinjiang china a case study of orogenic type pb zn systems abstract the tiemurt pb zn cu deposit is hosted in a devonian volcanic sedimentary basin of the altay orogenic belt and is thus interpreted to have formed by sea floor hydrothermal exhalation in previous studies our investigation discovered that the deposit is not stratiform or stratabound but structure controlled instead the hydrothermal ore forming process can be divided into the early middle and late stage represented by pyrite quartz polymetallic sulfide quartz and carbonate quartz veinlets respectively the early stage veins and contained minerals are structurally deformed and brecciated suggesting a compressional or transpressional tectonic regime the middle stage veinlets intrude and infill the fissures of the early stage assemblages and show no deformation suggesting a tensional shear setting the late stage veinlets mostly infill open space fissures that crosscut veins and replacements formed in the earlier stages four types of fluid inclusions fis including aqueous type w carbonic aqueous type c pure carbonic type pc and solid bearing type s are identified at the tiemurt deposit the early stage minerals contain the c and w type primary fis that are totally homogenized at temperatures of 330 390 c with low salinities of 0 8 11 9 wt nacl eqv whilst the late stage quartz or calcite contains only the w type fis with homogenization temperatures of 118 205 c and salinities of 1 4 3 4 wt nacl eqv this indicates that the ore fluid system evolved from co2 rich probably metamorphic to co2 poor meteoric fluids and that a significant co2 escape must have occurred all the four types of fis can be only observed in the middle stage minerals and even in a microscopic domain of a crystal representing an association trapped from a boiling fluid system these fis homogenize at temperatures ranging from 270 to 330 c with two salinity clusters of 1 9 14 5 and 37 4 42 4 wt nacl eqv respectively this implies that metal precipitation resulted from fluid boiling co2 escape and transient oversaturation the estimated trapping pressures of fis range from 130 to 380 mpa suggesting an alternating lithostatic hydrostatic fluid system controlled by a fault valve at the depth of 13 km therefore the tiemurt pb zn cu deposit is likely an example of orogenic pb zn cu systems formed in collision orogeny rather than a pre collision vms or sedex system developed in devonian and a new metallogenic model is proposed to interpret the formation of the tiemurt pb zn cu deposit

the iberian roman humid period 2600 1600 cal yr bp in the zonar lake varve record andalucia southern spain abstract the iberian roman humid period irhp 2600 1600 cal yr bp is the most humid phase of the last 4000 yr in southern spain as recorded in the sedimentary sequence of zonar lake 37 29 00 n 4 41 22 w 300 m a s l a varve chronology supported by several ams 14 c dates allows study of the lake evolution at annual scale in response to human impact and climate changes there are four climate phases within this period i gradual transition 2600 2500 yr ago 650 550 bc from a previous arid period ii the most humid interval during the iberian early roman epoch 2500 2140 yr ago 550 190 bc iii an arid interval during the roman empire epoch 2140 1800 yr ago 190 bc ad 150 and iv a humid period synchronous with the decline of the roman empire 1800 1600 yr ago ad 150 350 varve thickness and geochemical proxies show a multi decadal cyclicity similar to modern north atlantic oscillation nao 60 20 years and solar variability cycles 11 yr the timing and the structure of this humid period is similar to that described in eastern mediterranean and northern european sites and supports the same large scale climate control for northern latitudes and the mediterranean region

a high resolution late glacial to holocene record of environmental change in the mediterranean from lake ohrid macedonia albania lake ohrid macedonia albania is the oldest extant lake in europe and exhibits an outstanding degree of endemic biodiversity here we provide new high resolution stable isotope and geochemical data from a 10 m core co1262 through the late glacial to holocene and discuss past climate and lake hydrology tic 13ccalcite 18ocalcite as well as the terrestrial and aquatic vegetation response to climate toc toc n 13corganic rock eval pyrolysis the data identifies 3 main zones 1 the late glacial holocene transition represented by low tic and toc contents 2 the early to mid holocene characterised by high toc and increasing toc n and 3 the late holocene present which shows a marked decrease in tic and toc in general an overall trend of increasing 18ocalcite from 9 ka to present suggests progressive aridification through the holocene consistent with previous records from lake ohrid and the wider mediterranean region several proxies show commensurate excursions that imply the impact of short term climate oscillations such as the 8 2 ka event and the little ice age this is the best dated and highest resolution archive of past late glacial and holocene climate from lake ohrid and confirms the overriding influence of the north atlantic in the north eastern mediterranean the data presented set the context for the international continental scientific drilling program scientific collaboration on past speciation conditions in lake ohrid project cores recovered in spring summer 2013 potentially dating back into the lower pleistocene and will act as a recent calibration to reconstruct climate and hydrology over the entire lake history

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

the oxygen and carbon isotopic records in holocene freshwater mollusc shells from the faiyum paleolakes egypt their paloenvironmental and paleoclimatic implications abstract stable oxygen and carbon isotopes of freshwater mollusc shells from a sequence of dated palaeolake deposits in the faiyum depression egypt provide an outline record of lake development during the holocene it is argued that the carbonate o 18 record provides a proxy for climate change and that the isotope changes are driven by variations in monsoon precipitation in nile headwaters and in local evaporation processes shells from sediments dated to ca 10 000 to 7700 cal bp had low values for oxygen and carbon isotopes indicating higher precipitation in the local area and intensified monsoonal activity leading to higher nile flood discharge and flooding of the entire faiyum depression this was followed by a transitional period characterized by marked variability but with precipitation on average less than before from ca 6000 to 4300 cal bp precipitation was decreased until a dramatic reduction in nile flood discharge occurred late in the fifth millennium bp this reduction signalled the onset of arid conditions in the faiyum partly as a consequence of changes in nile headwaters that was concomitant with declining lake levels in east africa lake level decline in the faiyum was further aggravated after 2700 bp as the nile inflow further weaken and regulation increased

palaeoclimatological reconstruction using stable isotope data on continental molluscs from valle di castiglione roma italy thirty molluscan shells from twenty levels from the first 4 5 m of a long core drilled in the crater lake of valle di castiglione near rome have been analysed for their oxygen and carbon stable isotope compositions the investigated portion of the core covers the last 14 2 ka bp the large range in 18o 11 suggests that hydrological conditions exercise the main control on the isotopic composition of the biogenic carbonate in the valle di castiglione palaeolake samples younger than about 5 ka show a marked 18o depletion which we attribute to the onset of a temperate wet climate corresponding to the maximum of humidity isotopic results are in good agreement with pollen analyses and prove to be a sensitive tool for reconstructing quaternary climatic evolution from the continental lacustrine sediments of central italy

millennial to interannual climate variability in the mediterranean during the last glacial maximum climate change during the late pleistocene is dominated by periodicities on millennial time scales as documented by ice cores and sedimentary marine and terrestrial records of global distribution interannual to decadal variations have also been demonstrated in dust concentrations in greenland ice cores but there is lack of comparable detail in sedimentary records an 8 5 m long multiproxy record from lake albano central italy spanning the time interval between 15 0 and 28 0 cal kyr bp reveals a high temporal resolution window into climate change during the last glacial maximum lgm distinct warm cold cycles of millennial to centennial duration indicate a major response of the lake to climate induced environmental changes flickering interannual to interdecadal variations within these cycles are interpreted to reflect oscillations of the north atlantic nao implying shifts in temperature wind strength source of moisture and atmospheric circulation pattern