north atlantic current variability through marine isotope stage m2 circa 3 3 ma during the mid pliocene 1 the mid pliocene was an episode of prolonged global warmth and strong north atlantic thermohaline circulation interrupted briefly at circa 3 30 ma by a global cooling event corresponding to marine isotope stage mis m2 paleoceanographic changes in the eastern north atlantic have been reconstructed between circa 3 35 and 3 24 ma at deep sea drilling project site 610 and integrated ocean drilling program site 1308 mg ca ratios and 18o from globigerina bulloides are used to reconstruct the temperature and relative salinity of surface waters and dinoflagellate cyst assemblages are used to assess variability in the north atlantic current nac our sea surface temperature data indicate warm waters at both sites before and after mis m2 but a cooling of 2 3 c during mis m2 a dinoflagellate cyst assemblage overturn marked by a decline in operculodinium centrocarpum reflects a southward shift or slowdown of the nac between circa 3 330 and 3 283 ma reducing northward heat transport 23 35 ka before the global ice volume maximum of mis m2 this will have established conditions that ultimately allowed the greenland ice sheet to expand leading to the global cooling event at mis m2 comparison with an ice rafted debris record excludes fresh water input via icebergs in the northeast atlantic as a cause of nac decline the mechanism causing the temporary disruption of the nac may be related to a brief reopening of the panamanian gateway at about this time

dinoflagellate cyst assemblages as tracers of sea surface conditions in the northern north atlantic arctic and sub arctic seas the new n 677 data base and its application for quantitative palaeoceanographic reconstruction the distribution of dinoflagellate cyst dinocyst assemblages in surface sediment samples from 677 sites of the northern north atlantic arctic and sub arctic seas is discussed with emphasis on the relationships with sea surface parameters including sea ice cover salinity and temperature of the coldest and warmest months difficulties in developing a circum arctic data base include the morphological variation within taxa e g operculodinium centrocarpum islandinium cezare and polykrikos sp which probably relate to phenotypic adaptations to cold and or low salinity environments sparse hydrographical data together with large interannual variations of temperature and salinity in surface waters of arctic seas constitute additional limitations nevertheless the use of the best analogue technique with this new dinocyst data base including 677 samples permits quantitative reconstruction of sea surface conditions at the scale of the northern north atlantic and the arctic domain the error of prediction calculated from modern assemblages is 1 3 ca nd 1 8 c for the temperature of february and august respectively 1 8 for the salinity and 1 5 months yr 1 for the sea ice cover application to late quaternary sequences from the western and eastern subpolar north atlantic labrador sea and barents sea provide reconstructions compatible with those obtained using the previous dinocyst data base n 371 which mainly included modern data from the northern north atlantic copyright 2001 john wiley sons ltd journal of quaternary science

major types and time space distribution of mesozoic ore deposits in south china and their geodynamic settings the ore deposits of the mesozoic age in south china can be divided into three groups each with different metal associations and spatial distributions and each related to major magmatic events the first event occurred in the late triassic 230 210 ma the second in the mid late jurassic 170 150 ma and the third in the early mid cretaceous 120 80 ma the late triassic magmatic event and associated mineralization is characterized by peraluminous granite related w sn nb ta mineral deposits the triassic ore deposits are considerably disturbed or overprinted by the later jurassic and cretaceous tectono thermal episodes the mid late jurassic magmatic and mineralization events consist of 170 160 ma porphyry skarn cu and pb zn ag vein deposits associated with i type granites and 160 150 ma metaluminous granite related polymetallic w sn deposits the late jurassic metaluminous granite related w sn deposits occur in a ne trending cluster in the interior of south china such as in the nanling area in the early mid cretaceous from about 120 to 80 ma but peaking at 100 90 ma subvolcanic related fe deposits developed and i type calc alkaline granitic intrusions formed porphyry cu mo and porphyry epithermal cu au ag mineral systems whereas s type peraluminous and or metaluminous granitic intrusions formed polymetallic sn deposits these cretaceous mineral deposits cluster in distinct areas and are controlled by pull apart basins along the south china continental margin based on mineral assemblage age and space time distribution of these mineral systems integrated with regional geological data and field observations we suggest that the three magmatic mineralization episodes are the result of distinct geodynamic regimes the triassic peraluminous granites and associated w sn nb ta mineralization formed during post collisional processes involving the south china block the north china craton and the indo china block mostly along the dabie sulu and songma sutures jurassic events were initially related to the shallow oblique subduction of the izanagi plate beneath the eurasian continent at about 175 ma but i type granitoids with porphyry cu and vein type pb zn ag deposits only began to form as a result of the breakup of the subducted plate at 170 160 ma along the nne trending qinzhou hangzhou belt also referred to as qin hang or shi hang belt which is the neoproterozoic suture that amalgamates the yangtze craton and cathaysia block a large subduction slab window is assumed to have formed in the nanling and adjacent areas in the interior of south china triggering the uprise of asthenospheric mantle into the upper crust and leading to the emplacement of metaluminous granitic magma and associated polymetallic w sn mineralization a relatively tectonically quiet period followed between 150 and 135 ma in south china from 135 ma onward the angle of convergence of the izanagi plate changed from oblique to parallel to the coastline resulting in continental extensional tectonics and reactivation of regional scale ne trending faults such as the tan lu fault this widespread extension also promoted the development of ne trending pull apart basins and metamorphic core complexes accompanied by volcanism and the formation of epithermal cu au deposits granite related polymetallic sn w deposits and hydrothermal u deposits between 120 and 80 ma with a peak activity at 100 90 ma

relationships between dinoflagellate cyst assemblages in surface sediment and hydrographic conditions in the bering and chukchi seas palynological analyses were performed on 52 surface sediment samples from the eastern part of the bering sea and chukchi sea in order to document the regional distribution of dinoflagellate cyst assemblages and their relationship with sea surface conditions the assemblages present a relatively high species diversity 20 taxa are recovered routinely especially in the bering sea where they are dominated by operculodinium centrocarpum and the cyst of pentapharsodinium dalei accompanied mainly by spiniferites elongatus s l spiniferites ramosus impagidinium pallidum brigantedinium spp islandinium minutum selenopemphix quanta selenopemphix nephroides quinquecuspis concreta and the cyst of polykrikos kofoidii the percentages of the main taxa vary with latitude and principal component analysis shows that the distribution of assemblages is closely related to hydrographic conditions notably the seasonal duration of sea ice cover and the sea surface temperature in february the dinoflagellate cyst assemblages from the bering sea differ significantly from those of subarctic seas of the north atlantic with respect to their species composition and relationships with sea surface conditions in particular the occurrence of the cyst of polykrikos kofoidii and quinquecuspis concreta and the positive correlation between the percentages of operculodinium centrocarpum and the extent of sea ice constitute peculiar features in the bering sea assemblages copyright 2001 john wiley sons ltd journal of quaternary science

u pb geochronology of zircon and polygenetic titanite from the glastonbury complex connecticut usa an integrated sem empa tims and shrimp study abstract u pb ages for zircon and titanite from a granodioritic gneiss in the glastonbury complex connecticut have been determined using both isotope dilution thermal ionization mass spectrometry tims and the sensitive high resolution ion microprobe shrimp zircons occur in three morphologic populations 1 equant to stubby multifaceted colorless 2 prismatic dark brown with numerous cracks and 3 elongate prismatic light tan to colorless cathodoluminescence cl imaging of the three populations shows simple concentric oscillatory zoning the zircon tims age weighted average of 207pb 206pb ages from group 3 grains 450 5 1 6 ma mswd 1 11 and shrimp age composite of 206pb 238 u age data from all three groups 448 2 2 7 ma mswd 1 3 are interpreted to suggest a relatively simple crystallization history titanite from the granodioritic gneiss occurs as both brown and colorless varieties scanning electron microscope backscatter bse images of brown grains show multiple cross cutting oscillatory zones of variable brightness and dark overgrowths colorless grains are unzoned or contain subtle wispy or very faint oscillatory zoning electron microprobe analysis empa clearly distinguishes the two populations brown grains contain relatively high concentrations of fe2o3 ce2o3 up to 1 5 wt nb2o5 and zr cerium concentration is positively correlated with total ree y concentration which together can exceed 3 5 wt oscillatory zoning in brown titanite is correlated with variations in ree concentrations in contrast colorless titanite both as discrete grains and overgrowths on brown titanite contains lower concentrations of y ree fe2o3 and zr but somewhat higher al2o3 and nb2o5 uranium concentrations and th u discriminate between brown grains typically 200 400 ppm u all analyses but one have th u between about 0 8 and 2 and colorless grains 10 60 ppm u th u of 0 0 17 in contrast to the zircon u pb age results shrimp u pb data from titanite indicate multiple growth episodes in brown grains oscillatory zoned cores formed at 443 6 ma whereas white in bse cross cutting zones are 425 9 ma colorless grains and overgrowths on brown grains yield an age of 265 8 ma using the total pb method or 265 5 ma using the weighted average of the 206pb 238u ages however empa chemical data identify zoning that suggests that this colorless titanite may preserve three growth events oscillatory zoned portions of brown titanite grains are igneous in origin white cross cutting zones probably formed during a previously unrecognized event that caused partial dissolution of earlier titanite and reprecipitation of a slightly younger generation of brown titanite colorless titanite replaced and grew over the magmatic titanite during the permian alleghanian orogeny these isotopic data indicate that titanite like zircon can contain multiple age components coupling shrimp microanalysis with empa and sem results on dated zones as presented in this study is an efficient and effective technique to extract additional chronologic data to reveal the complexities of igneous crystallization and metamorphic growth

an assessment of a ka band radar interferometer mission accuracy over eurasian rivers the water elevation recovery satellite mission is dedicated to the determination of land surface water extent elevation and slope using a ka band radar interferometer karin as its primary instrument determining these parameters to the accuracy desired for hydrologic applications is challenging the scientific objectives of the mission have been set up to 10 cm for the height budget and 10 murad 1 cm 1 km for the slope budget in this paper we implement a virtual mission simulation and use it to examine the measurement performances for three case studies in europe a relatively small river such as the meuse in northern western europe the lena river in russia one of the major siberian rivers and lake leman in western europe we simulate karin data with the associated instrument and geophysical error sources and implement ground processing techniques to go from the original raw data to science data we examine the impact of external errors in detail and implement calibration techniques that rely on the use of ancillary topographic data such as the shuttle radar topography mission digital elevation model dem we find that the impact of external errors can be reduced to a few centimeters the random error budget can also be reduced below 10 cm by means of appropriate processing the scientific requirements of the mission are shown to be met for all cases

paleosalinity confidence limits and future applications error propagation is investigated through the only commonly applied technique for reconstruction of paleosalinity based on oxygen isotope residuals although this technique is known to be fairly inaccurate there remained a need for thorough assessment of confidence limits in a variety of global settings here it is found that a theoretical minimum error bar of between 0 3 and 0 7 applies to paleosalinity estimates and that real life practical limits are rarely better than 0 6 best results are expected in the latitudinal ranges 50 n and 70 s taking care to avoid the sea ice margin confidence intervals at low and mid latitudes including marginal seas are very wide at least 1 8 for the mediterranean and 2 2 for the equatorial atlantic it appears that oxygen isotope distributions are best used in their own right to investigate circulation and advective processes in coupled ocean atmosphere cryosphere models instead of calibrating them to paleosalinity to define restoring boundary conditions however isotope residual based paleosalinity maps from large numbers of regionally averaged studies in the above mentioned latitudinal bands may help in defining initial conditions and first order validation arguments for models

interannual and decadal cycles in river flows of southeastern south america abstract the time series of annual streamflow of four rivers in southeastern and south central south america the negro paraguay parana and uruguay rivers for the period 1911 93 are analyzed application of the multitaper method shows that the following features are significant at the 95 level 1 a nonlinear trend 2 a near decadal component and 3 interannual peaks with enso timescales the trend and near decadal components are most marked in the two more central rivers the paraguay and parana with enso timescale variability most pronounced in the negro and uruguay rivers in the southeast composites of sst are made for each of the statistically significant oscillatory components of river flow by reconstructing each component using singular spectrum analysis these composites confirm the influence of enso on the streamflow variability of the negro and uruguay rivers with el nino associated with enhanced streamflow on the decadal timescale high river runoff is associated with anomalously coo

water level fluctuations in the plata basin south america from topex poseidon satellite altimetry 1 time series of water level in major rivers of the plata basin are examined using altimetry data from the topex poseidon satellite over the period 1993 2001 ten sites are selected on the parana three on the paraguay one the uruguay and seven on wetlands it is confirmed that the seasonal cycle of river levels decreases in amplitude with increasing latitude of the site the normalized time series for sites along the same river differ mainly by a time lag corresponding to propagation speeds of about 0 1 ms 1 the interannual variability of the lower parana with a strong peak in early 1998 and minima in early 1996 and 2000 shows the remote effects of el nino southern oscillation enso the variability of the upper parana and paraguay shows similar enso impacts with smaller amplitudes after 1995 and the effects of regional features climate variability before that date e g the south american monsoon the results support the usefulness of satellite altimetry for a dense and continuous monitoring of river water levels

late holocene variability in pelagic fish scales and dinoflagellate cysts along the west coast of vancouver island ne pacific ocean fish stocks and dinoflagellates are essential components of the marine food chain sediment cores from a predominantly anoxic basin in effingham inlet vancouver island british columbia archive a late holocene 500 5300 years bp record of paleoproductivity in the north american coastal upwelling domain cud we present evidence that late holocene changes in the dinoflagellate cyst assemblages sedimentary record and fish stocks in the northeastern pacific ocean fluctuated at least partially in accordance with regional and global climate cycles principal components analysis pca and trend wavelet and spectral analyses were used to identify relationships cycles and trends in sediment grey scale values and the abundances of fish scales and dinoflagellate cysts on centennial to millennial time scales most observed cycles fluctuated in intensity over time particularly following transition of the regional climate to a higher rainfall phase that impacted coastal oceanic dynamics 3400f150 years ago correlation of the marine paleoproductivity records observed in effingham inlet with solar influenced climate proxy cycles observed in the north atlantic region indicates that solar forcing at different scales might have influenced the climate in the northeast pacific as well in particular an 1100 to 1400 year cycle in regional climate is well represented in the fish productivity proxy and sedimentological record it was also observed that colder water high productivity selenopemphix nephroides and anchovydominated banchovy regimeq ecosystems alternate with warmer water herring dominated bherring regimeq ecosystems at millennial time scales the fish scale record preserved in effingham inlet indicates that the ne pacific is now in transition from an danchovy t to a dherringt dominated regime d 2005 elsevier b v all rights reserved

status of alkenone paleothermometer calibration report from working group 3 1 the alkenone unsaturation index u37k has now proven its worth as a tool for paleothermometry u37k measured in most modern sediments throughout the world ocean can be translated using established calibrations into realistic seemingly reliable estimates of mean annual temperature at the sea surface sst however it remains mysterious why water temperature estimates based on this biotic index correspond to mean annual sst and whether such estimates apply back in geological time solving these mysteries is imperative and will require thoughtful concerted research effort by the biological chemical and geological oceanographic community this report summarizes what is now known about alkenones in particular their use in estimating the growth temperature of specific haptophyte algae that synthesize and export these compounds to the marine sediment record it highlights future field and laboratory research directions that should be taken to clarify and bolster utility of alkenones as a generally valued paleoceanographic tool

atlas of modern dinoflagellate cyst distributions in the black sea corridor from aegean to aral seas including marmara black azov and caspian seas abstract we present the first comprehensive taxonomic and environmental study of dinoflagellate cysts in 185 surface sediment samples from the black sea corridor bsc which is a series of marine basins extending from the aegean to the aral seas including marmara black azov and caspian seas for decades these low salinity semi enclosed or endorheic basins have experienced large scale changes because of intensive agriculture and industrialisation with consequent eutrophication and increased algal blooms the bsc atlas data provide a baseline for improved understanding of linkages between surface water conditions and dinoflagellate cyst dinocyst distribution diversity and morphological variations by cross reference to dinocyst occurrences in sediment cores with radiocarbon ages covering the past c 11 700 years the history of recent biodiversity changes can be evaluated the seabed cyst samples integrate seasonal and multi year data which are not usually captured by plankton samples and the cyst composition can point to presence of previously unrecorded motile dinoflagellate species in the bsc results show the presence of at least 71 dinocyst taxa of which 36 can be related to motile stages recorded in the plankton comparison with sediment core records shows that five new taxa appear to have entered or re entered the region over the past century statistical analysis of the atlas data reveals the presence of four ecological assemblages which are primarily correlated with seasonal and annual surface water salinity and temperature correlation with phosphate nitrate and silicate nutrients chlorophyll a and bottom water oxygen is less clear but may be important for some taxa biodiversity indices reveal strong west east biogeographical differences among the basins that reflect the different histories of mediterranean versus ponto caspian connections the atlas data provide a standardised taxonomy and regional database for interpreting downcore cyst variations in terms of quantitative oceanographic changes the atlas also provides a baseline for monitoring further changes in the bsc dinocysts that may accompany the accelerating development of the region

dinoflagellate cyst assemblages from effingham inlet vancouver island british columbia canada a palynological study of surface samples from effingham inlet southwestern vancouver island british columbia was carried out to assess environmental and oceanographic controls on the distribution of dinoflagellate cyst species generally dinoflagellate cyst assemblages from all samples are dominated by operculodinium centrocarpum sensu wall and dale 1966 spiniferites spp and round brown protoperidinioid cysts the differences among the assemblages are mainly in relative and absolute abundance of various taxa presence and absence of various protoperidinioid taxa species diversity shannon diversity index dinoflagellate cyst concentration in the samples and ratio of terrestrial to marine palynomorphs dinoflagellate cyst assemblages in the two sub basins of this inlet are quite distinct with the inner basin characterized by lower diversity and the outer basin being characterized by higher diversity due to the occurrence of several protoperidiniacean species primary productivity in this inlet is enhanced by periodic incursion of nutrient rich surface water from the pacific ocean which is related to coastal upwelling primary productivity is higher in the outer basin than the inner basin 7 2002 elsevier science b v all rights reserved

process length variation of the cyst of the dinoflagellate protoceratium reticulatum in the north pacific and baltic skagerrak region calibration as an annual density proxy and first evidence of pseudo cryptic speciation process length variation of cysts of the dinoflagellate protoceratium reticulatum claparede et lachmann butschli in surface sediments from the north pacific was investigated the average process

dinoflagellate cyst distribution in surface sediments along the south western mexican coast 14 76 n to 24 75 n abstract in this study we explore the relationship between the modern assemblages of organic walled dinoflagellate cysts and sea surface conditions temperature salinity primary productivity and water depth and distance to the coast statistical treatments were performed on 95 surface sediment samples from sites located along the south western mexican coast 14 76 n to 24 75 n redundancy analysis rda illustrates that the principal parameters correlated with the regional cyst distribution are the distance to the coast and the productivity in the upper water column which is closely related to upwelling intensity empirical observations coupled with rda provide insight into the spatial coverage of some cyst taxa produced by dinoflagellate species potentially responsible for harmful algal blooms along the coast they also allow the recognition of four zones of assemblages which are linked to the upwelling intensity and the productivity and characterize la paz bay the south western mexican margin from 15 95 n to 23 11 n the northern part of the gulf of tehuantepec and the southern part of the gulf of tehuantepec

alkenones and multiproxy strategies in paleoceanographic studies 1 we assess multiproxy strategies involving alkenone based and other paleoceanographic indicators in an effort to define uncertainties and to advance understanding of past oceanic and climatic changes looking to the future we recommend a parallel strategy of applying proxies to the geologic record while continuously seeking refinements in methods and understanding of mechanisms that control each proxy a multiproxy strategy increases confidence in results and provides oceanographic context for more effective interpretation of processes a combination of proxies allows derivation of additional properties such as upper ocean paleosalinity or paleo pco2 for a more complete view of the oceanographic and climate mechanisms involved in changing earth s environment

interannual and interdecadal variability of the south atlantic convergence zone interannual variations of the summertime january march atmospheric circulation over subtropical south america are examined during the period 1958 97 using the national centers for environmental prediction national center for atmospheric research reanalysis data it is found from an empirical orthogonal function analysis that an anomalous upper tropospheric large scale stationary eddy in the lee of the andes tends to accompany a dipole in anomalous vertical motion an anomalous cyclonic anticyclonic eddy accompanies an intensified diffuse south atlantic convergence zone sacz with anomalous descent ascent to the southwest the cold core equivalent barotropic vertical structure of the anomalous cyclonic eddy and the 200 hpa vorticity balance are both characteristic of a stationary rossby wave the tendency for the eddy to be advected downstream by the mean westerlies is compensated by meridional advection of planetary vorticity and stretching associated with vertical motion the anomalous cyclonic flow at low levels reinforces the thermally direct circulation associated with the sacz a weak funneling of submonthly rossby wave activity into this descent region is also identified the interannual time series of the eddy is significantly correlated with north south dipolar sea surface temperature sst anomalies over the southwest atlantic one standard deviation 200 hpa wind speed anomalies of up to 5 m s21 are accompanied by sst anomalies of up to 0 38c a near cyclic 15 yr component is identified which the authors corroborate from independent analyses of southwest atlantic ssts and river flows both are

partitioning of the cretaceous pan yangtze basin in the central south china block by exhumation of the xuefeng mountains during a transition from extensional to compressional tectonics abstract the formation of a series of intermountain basins is likely to indicate a geodynamic transition especially in the case of such basins within the central south china block cscb determining whether or not these numerous intermountain basins represent a division of the cretaceous pan yangtze basin by exhumation of xuefeng mountains is key to understanding the late mesozoic to early cenozoic tectonics of the south china block scb here we present apatite fission track aft data and time temperature modeling in order to reconstruct the evolution history of the pan yangtze basin fourteen rock samples were taken from a ne sw trending mountain basin system within the cscb including from west to east the wuling mountains wuling shan the south and north mayang basins the xuefeng mountains xuefeng shan and the hengyang basin cretaceous lacustrine sequences are well preserved in the south and north mayang and hengyang basins and sporadically crop out in the xuefeng mountains whereas paleogene piedmont proluvial lacustrine sequences are only found in the south mayang and hengyang basins aft results indicate that the wuling and xuefeng mountains underwent rapid denudation post 84 ma whereas the south and north mayang basins were more slowly uplifted from 67 and 84 ma respectively following a quiescent period from 32 to 19 ma both the mountains and basins have been rapidly denuded since 19 ma both the aft data and sedimentary facies changes suggest that the cretaceous deposits that cover the south north mayang and hengyang basins through to the xuefeng mountains define the cretaceous pan yangtze basin integrating our results with tectonic background for the scb we propose that rollback subduction of the paleo pacific plate produced the pan yangtze basin which was divided into the south north mayang and hengyang basins by the abrupt uplift and exhumation of the xuefeng mountains from 84 ma to present apart from a period of tectonic inactivity from 32 to 19 ma this late late cretaceous to paleogene denudation resulted from movement on the ziluo strike slip fault which formed due to intra continental compression most likely associated with the eurasia indian plate subduction and collision sinistral transpression along the ailao shan red river fault at 34 17 ma probably transformed this compression to the extrusion of the indochina block and produced the quiescent window period from 32 to 19 ma for the mountain basin system in the cscb therefore the initiation of exhumation of the xuefeng mountains at 84 ma indicates a switch in tectonic regime from cretaceous extension to late late cretaceous and cenozoic compression

marine dinocysts acritarchs and less well known npp tintinnids ostracod and foraminiferal linings copepod and worm remains

improving hydrological information acquisition from dem processing in floodplains extraction of hydrological information from digital elevation models dems is a required step when conducting any spatially distributed hydrological modelling in particular automated methods are proposed to extract the drainage structure from the dem however a realistic river network is not always derived from conventional dem processing methods indeed inaccuracy occurs in flat areas corresponding to floodplains in these areas additional sources of information are required to extract the correct drainage direction from the dem in this study it is demonstrated that traditional approaches of dem preprocessing such as the commonly known stream burning fail to provide correct maps of drainage directions and catchment areas when the extension of flat areas is large a new method is proposed to take advantage of available imagery data this method is based on a double dem burning process dem is first burned in the main rivers using the channel network and then in the floodplain using the spatial distribution of floodplains provided by classified satellite images in this sense the method has been referred to as the floodplain burning approach or simply fb approach spatial distribution of floodplains is derived from a multitemporal sar image classification a system of equations is used to vary the elevation offset required to be burnt in each cell representing the floodplain according to the minimal distance from the channel network which is calculated by a distance transformation the fb approach was applied to a sub basin located within the larger amazon river basin the region is characterized by large floodplain extensions basin delineation maps derived from the new method were compared with those obtained from the traditional stream burning method and highlighted more realistic results copyright 2008 john wiley sons ltd

meridional shifts in the marine itcz and the tropical hydrologic cycle over the last three glacial cycles 1 paleoproxy studies show a strong correlation between tropical climate and high latitude temperature variability recorded in the greenland ice cores over the last glacial cycle in particular abrupt cooling events in the greenland ice sheet project ii 18o ice record appear synchronous with a southward migration of the intertropical convergence zone itcz in the atlantic a weakening of the indian and east asian monsoon systems and a strengthening of the south american monsoon system because this high to low latitude climate teleconnection significantly alters the tropical hydrologic cycle around the globe it plays a critical role in regulating global climate on glacial interglacial time scales we compare 18oseawater reconstructions a salinity proxy generated from previously published mg ca and oxygen isotope data on globigerinoides ruber white var obtained from western caribbean core odp 999a and western equatorial pacific core 806b across the last three glacial cycles to show that systematic variations in surface salinity at these sites suggest the tropical hadley cell hydrologic system undergoes systematic reorganizations that differ dramatically between warm interglacial and cold glacial periods furthermore cross spectral and phase angle analyses of the ice volume corrected caribbean and western pacific 18osw records reveal a 100 kyr frequency in both records that is almost 180 out of phase and a 23 kyr frequency that is nearly in phase this results in the development of a very large 18osw gradient between the caribbean and the western equatorial pacific on glacial interglacial time scales that is best explained by a southward shift in both the atlantic and pacific itcz during north atlantic cold phases

an overview and brief description of common marine organic walled dinoflagellate cyst taxa occurring in surface sediments of the northern hemisphere abstract organic walled resting cysts of planktonic dinoflagellates occur commonly in modern marine sediment where they represent with rare exceptions the only geologically preservable part of the life cycle although many species do not produce fossilizable resting cysts upper quaternary sediments contain a diverse cyst record that is used frequently for paleoenvironmental reconstruction and stratigraphic analysis reconstructions of past sea surface conditions rely on an understanding of the distributions of dinoflagellate cysts in modern sediments linked to their respective environmental parameters underpinned by sound taxonomy and standardized nomenclature stratigraphic studies additionally require knowledge of morphological details to distinguish extant from similar extinct taxa here 51 dinoflagellate cyst species and two informal cyst morphotypes that are commonly encountered during routine palynological analysis of upper quaternary marine sediments from the northern hemisphere are briefly described taxonomically and illustrated in addition their lowest stratigraphic occurrences are provided

nd sr pb isotopic constraints on metal and fluid sources in w sb au mineralization at woxi and liaojiaping western hunan china this paper presents nd sr pb isotope data on scheelite inclusion fluids and residues of gangue quartz and sulfides from the w sb au ore deposits at woxi and liaojiaping ljp in the xuefeng uplift belt xub western hunan china sm and nd concentrations in scheelite from woxi are much lower than in scheelite from ljp and can be distinguished by their high 147sm 144nd ratios of 1 25 from the much lower ratios around 0 26 in scheelites from the ljp end values compared to values at 200 ma which is the average timing of granitoid emplacement during the indosinian yanshanian periods in the xub are around 10 for the ljp and compare well with the range of 5 to 11 defined by the granitoids whereas they are around 27 for scheelite from woxi this might indicate that rees in the mineralizing fluids at ljp originated from granitoids that are concentrated along the southern border of the xub whereas in the case of woxi the original fluids might have been masked by rees released during intense high temperature wall rock alteration of unexposed precambrian basement rocks at depth sr isotopes of scheelite from these two deposits show similar relations to host nearby rocks in that 87sr 86sr t 200 ma ratios of 0 721 for ljp scheelite agree with values ranging between 0 718 0 726 for granitoids whereas these ratios are much higher i e 0 745 for scheelite from woxi and correspond to the 87sr 86sr t 200 ma ratio range of 0 743 0 749 for precambrian host slates crushing experiments to release inclusion fluids from gangue quartz and sulfides deposited during later stages of ore deposition in both deposits failed to provide accurate and geologically meaningful two point fluid residue tie lines in rb sr isochron diagrams however sr released from fluid inclusions generally reveals lower initial 87sr 86sr ratios than the respective residues and shows affinities to 87sr 86sr t 200 ma values of indosinian yanshanian granitoids both at woxi and ljp pb stepwise leaching of scheelite and sulfides did not result in sufficient spreads in pb isotope diagrams and therefore no information regarding exact mineralization ages in the two deposits could be deduced overall ore pb isotopes reveal upper crustal signatures and are compatible with pb isotope signatures of the predominant precambrian slates in the woxi area steep trajectories through late stage quartz sulfide mineralization in pb isotope diagrams may hint at mixing scenarios involving pb from the host rocks and a component with lower 207pb 204pb and 208pb 204pb ratios relative to 206pb 204pb ratios which cannot be linked to any known reservoir in the xub mining district sr isotopes of four out of seven residual sulfide samples from woxi plot along a paleomixing line at an age of 199 8 ma supporting a mixing scenario for the fluids indicated by the pb isotopes and pointing to a possible genetic relationship with the emplacement of indosinian yanshanian granitoids the budgets of rees rb sr and pb in the original fluids were severely affected by contamination of these elements apparently during intense wall rock alteration but after sealing of the major pathways the mineralizing fluids tend to have better preserved their original signatures these attest a genetic relationship between the metallogeny in the xub w sb au province and the emplacement of indosinian yanshanian granitoids during mesozoic intracontinental tectonic uplift and thrusting

using altimetry waveform data and ancillary information from srtm landsat and modis to retrieve river characteristics in this paper spaceborne radar altimeters are shown to have the potential for monitoring the height of large rivers with accuracies of approximately 1 m however the need for a better height accuracy and the observations of smaller continental basins have led to studies on how to improve and extend the use of nadir altimeter data conventional retracking techniques over land are limited to the examination of altimeter waveforms on a case by case basis due to the arbitrary geometry which may be present at altimeter river crossings this approach may be limited to large rivers which approximate ocean crossings to overcome this limitation we introduce a waveform fitting method which uses the entire set of waveforms associated with a water crossing rather than individual waveforms by using ancillary data such as digital elevation model obtained from shuttle radar topography mission and gtopo30 and classification maps obtained from landsat and modis it is possible to recast the retracking problems as a maximum likelihood estimation problem theoretical power returns based on the a priori knowledge of the observed scenes are generated resulting in a parametric library of waveform histories which is then used to constrain the estimation for demonstration we concentrate on the river meuse in northern western europe and on the river lena in russia the meuse has important social impact since it has flooded in the past and better real time predictions of its changing stage may improve flood forecasting skill furthermore it presents a challenge to conventional nadir altimeter waveform retracking we will present both theoretical performance results and demonstrate the feasibility based on real altimeter data

mineralogy and titanite geochronology of the caojiaba w deposit xiangzhong metallogenic province southern china implications for a distal reduced skarn w formation the caojiaba tungsten deposit 19 03 mt 0 37 wt wo3 is hosted by skarn along the contact between clastic and carbonate rocks in the xiangzhong metallogenic province of southern china the deposit is characterized by an early prograde skarn containing low andraditic garnet ad0 7 21 9 and hedenbergitic pyroxene hd52 9 77 3 overprinted by a retrograde biotite chlorite assemblage and then by quartz scheelite veins similar to well studied reduced tungsten skarns worldwide scheelite has low moo3 0 01 0 16 wt and ore commonly contains up to 1 5 ppm au and up to 0 33 wt sb sensitive high resolution ion microprobe shrimp u pb analyses of hydrothermal titanite coexisting with scheelite in three skarn ore samples provide ages between 206 5 ma and 196 3 ma 2 our new ages demonstrate that the tungsten mineralization took place at caojiaba between 206 and 196 ma overlapping the 228 201 ma emplacement age of granitic rocks in the xiangzhong metallogenic province mineralogical and geochronological evidence collectively indicates that caojiaba is a distal reduced w skarn deposit the 226 196 ma granite related w mineralization recognized throughout the province has a possible link with the widespread sb au mineralization in the region

re os dating of molybdenite from darongxi tungsten deposit in western hunan and its geological implications the darongxi tungsten deposit is a medium sized scheelite deposit in the xuefeng uplift area of western hunan several molybdenite bearing quartz veins cutting the tungsten orebodies in this deposit were discovered for the first time in this study and the re osisotopic agesof molybdenites collected from this deposit were precisely determined it is shown that re os dating of eight molybdenite samples yielded187re 187os model ages ranging from 217 0 ma to 221 1 ma with an average of 219 0 1 2 ma which coincide well with the isochron age 223 3 3 9 ma all the age data reveal that molybdenite bearing quartz in the darongxi deposit was formed during the late triassic these re os ages are almost consistent with the emplacement time of the dashenshan granite 224 3 1 0 ma and hence the authors hold that the molybdenite bearing quartz veins were spatially and temporally related to the granite emplacementin the darongxi ore district considering that the tungsten ore bodies were formed in the time between the emplacement of granite and the formation of molybdenite bearing quartz veins the authors consider that the tungsten mineralization in the darongxi deposit took place at about223 ma the results obtained in this study demonstrate that there exist multi period tungsten mineralization in western hunan and a regional indosinian granitic mineralization throughout south china

titanite scale insights into multi stage magma mixing in early cretaceous of nw jiaodong terrane north china craton abstract the early cretaceous guojialing type granodiorites in northwestern jiaodong terrane carry significant records for strong mantle crust interaction during the destruction of north china craton ncc however the definite petrogenetic mechanism and detailed magmatic process remain an enigma titanite in igneous rocks can serve as an effective petrogenetic indicator here we present integrated geochronological and geochemical studies on titanites from guojialing type granodiorites and their dioritic enclaves to constrain their petrogenesis titanites from granodiorites g type and plagioclase rich dioritic enclaves e type i present an identical u pb age 130 ma and an indistinguishable wide range of zr and total rees contents and th u ratios however these two types of titanites exhibit distinct micro scale textures and geochemical compositions g type titanites are characterized by oscillatory zonings with two light bse zones lbz and two or three dark bse zones whereas e type i titanites are marked by core mantle rim zonings drastic increase of lrees zr hf and fe and decrease of nb ta al and f contents are observed in lbz of g type titanites whereas remarkable reduction of lrees zr and hf and elevation of f contents are observed from the cores to the mantles of e type i titanites based on zr in titanite thermometry g type titanites are interpreted to have experienced twice notable temperature increase while e type i titanites are inferred to have undergone a rapid cooling process furthermore we suggest that the drastic chemical changes in g type and e type i titanites are ascribed to early stage magma mixing between a colder felsic magma and a fe ree rich hotter dioritic magma compared to g type and e type i titanites titanites from plagioclase poor dioritic enclaves e type ii are characterized by their occurrence in interstitial space and present a relatively younger u pb age 128 ma and much narrower and lower range of zr total rees contents and th u ratios but reveal high f contents 0 35 0 76 wt and extreme high nb ta ratios up to 65 6 such titanites are perceived to record late stage mingling during which f rich and ree poor hybrid granodioritic magma squeezed into the incompletely consolidated dioritic enclaves with accompanying fluid rock interaction combining our results with previous isotopic studies a new genetic model for guojialing type granodiorites is envisaged which involves multi stage magma mixing between archean lower crust derived felsic magma and mafic lower crust derived dioritic magma triggered by mantle derived mafic magma underplating during the course of asthenospheric upwelling in early cretaceous such process further implicates the reactivation of jiaodong lower crust during the destruction of ncc

infrared microthermometric and noble gas isotope study of fluid inclusions in ore minerals at the woxi orogenic au sb w deposit western hunan south china abstract the woxi au sb w deposit hosted by the neoproterozoic low grade metamorphic clastic rocks is located in a brittle ductile shear zone within the xuefengshan range south china orebodies are predominantly banded quartz veins which are strictly controlled by bedding faults and display significant vertical extents up to 2 km without obvious vertical metal zoning fluid inclusions hosted in quartz scheelite and stibnite from quartz scheelite and quartz sulfide gold veins have been studied using conventional and infrared microscopy respectively four types of fluid inclusions were identified based on petrography including type i two phase liquid rich aqueous inclusions type ii two or three phase co 2 rich inclusions type iii two phase vapour rich aqueous inclusions and type iv single phase aqueous inclusions the fluid inclusions in ore minerals scheelite and stibnite and their coexisting quartz largely share similar characteristics in terms of their types homogenization temperatures and salinities this is consistent with the fact that these ore minerals are always intergrown with quartz microthermometric and laser raman data indicate a low to moderate temperature 140 240 c low salinity 2 rich n 2 bearing aqueous ore forming fluid such fluid is further identified as a deeply non magmatic crustal fluid rather than a mantle source fluid by the significantly low 3 he 4 he ratios 0 002 0 281 ra and a small amount of meteoric water or host rock buffered fluid could be involved w ore precipitation was probably associated with mixing between a deeply originated crustal fluid and host rock buffered fluid based on the fluid inclusion features in scheelite and quartz i however au and sb ore deposition probably resulted from boiling which was caused by the marked pressure drop geological features such as banded structure and crack sealing structure also indicate that fluid pressure fluctuation induced by fault valve mechanism occurred during ore precipitation these characteristics of the ore forming fluids in the woxi deposit are in good agreement with the definition of orogenic gold deposits and the woxi au sb w deposit is probably an atypical orogenic gold deposit for its unique ore forming element association

climate variability and vadose zone controls on damping of transient recharge abstract increasing demand on groundwater resources motivates understanding of the controls on recharge dynamics so model predictions under current and future climate may improve here we address questions about the nonlinear behavior of flux variability in the vadose zone that may explain previously reported teleconnections between global scale climate variability and fluctuations in groundwater levels we use hundreds of hydrus 1d simulations in a sensitivity analysis approach to evaluate the damping depth of transient recharge over a range of periodic boundary conditions and vadose zone geometries and hydraulic parameters that are representative of aquifer systems of the conterminous united states u s although the models were parameterized based on u s aquifers findings from this study are applicable elsewhere that have mean recharge rates between 3 65 and 730 mm yr 1 we find that mean infiltration flux period of time varying infiltration and hydraulic conductivity are statistically significant predictors of damping depth the resulting framework explains why some periodic infiltration fluxes associated with climate variability dampen with depth in the vadose zone resulting in steady state recharge while other periodic surface fluxes do not dampen with depth resulting in transient recharge we find that transient recharge in response to the climate variability patterns could be detected at the depths of water levels in most u s aquifers our findings indicate that the damping behavior of transient infiltration fluxes is linear across soil layers for a range of texture combinations the implications are that relatively simple homogeneous models of the vadose zone may provide reasonable estimates of the damping depth of climate varying transient recharge in some complex layered vadose zone profiles

surface sediment dinoflagellate cysts from the hudson bay system and their relation to freshwater and nutrient cycling abstract surface sediment samples from the hudson bay system were analysed in order to examine the role of key regulators of arctic marine productivity light and nutrients as affected by freshwater stratification and sea ice cover on the spatial distribution and production of dinoflagellate cysts total cyst fluxes vary from 0 2 10 6 to 30 6 10 6 cysts m 2 a 1 with the highest values observed in eastern hudson bay a total of 24 cyst taxa representing 11 genera of five orders were identified and distribution maps of the most common taxa have been produced this is the first record of echinidinium aculeatum echinidinium karaense cf echinidinium delicatum islandinium brevispinosum selenopemphix quanta cysts of protoperidinium americanum cysts of cf biecheleria sp and polarella glacialis in the hudson bay system dinoflagellate cyst assemblages show distinct spatial patterns revealing three compositional domains eastern hudson bay western central hudson bay and hudson strait the eastern domain is characterised by a dominance of autotrophic cysts of pentapharsodinium dalei whereas the western central domain is characterised by autotrophic operculodinium centrocarpum with some contribution by heterotrophic polykrikos sp var arctic morphotype and polykrikos spp sites from hudson strait are distinguished by an overwhelming prevalence of heterotrophic protoperidiniaceae cysts mainly islandinium minutum and have the highest values of sedimentary biogenic silica used as a proxy for diatom productivity sediment geochemical tracers are used as proxies for freshwater inputs lignin and its biomarkers and nitrate availability nitrogen isotopes and sea ice concentrations derived from passive microwave data as a proxy for light availability sea ice regulated length of the dark season has a negligible influence on the proportion and production of heterotrophic dark adapted versus autotrophic light dependent dinoflagellate cysts perhaps due to the location of our study area on the southern fringe of the arctic instead cyst populations in hudson bay are primarily regulated by vertical stratification and nitrate availability while in hudson strait the pivotal mechanism constitutes food availability

mid piacenzian variability of nordic seas surface circulation linked to terrestrial climatic change in norway during the mid piacenzian nordic seas sea surface temperatures ssts were higher than today while ssts provide crucial climatic information on their own they do not allow a reconstruction of potential underlying changes in water masses and currents a new dinoflagellate cyst record for ocean drilling program odp site 642 is presented to evaluate changes in northward heat transport via the norwegian atlantic current nwac between 3 320 and 3 137 ma the record is compared with vegetation and sst reconstructions from site 642 and ssts from odp site 907 iceland sea to identify links between ssts ocean currents and vegetation changes the dinocyst record shows strong atlantic water influence via the nwac corresponds to higher than present ssts and cool temperate vegetation during marine isotope stage mis transition m2 m1 and km5 reduced atlantic water inflow relative to the warm stages coincides with near modern ssts and boreal vegetation during mis m2 km6 and km4 km2 during most of the studied interval a strong sst gradient between sites 642 and 907 indicates the presence of a proto arctic front af an absent gradient during the first half of mis km6 due to reduced atlantic water influence at site 642 and warm presumably atlantic water reaching site 907 is indicative of a weakened nwac and egc we conclude that repeated changes in atlantic water influence directly affect terrestrial climate and that an active nwac is needed for an af to develop obliquity forcing may have played a role but the correlation is not consistent

u pb re os and 40ar 39ar geochronology of the nambija au skarn and pangui porphyry cu deposits ecuador implications for the jurassic metallogenic belt of the northern andes new u pb re os and 40ar 39ar dates are presented for magmatic and hydrothermal mineral phases in skarn and porphyry related ores from the nambija and pangui districts of the subandean zone southeastern ecuador nambija has been one of the main gold producing centers of ecuador since the 1980s due to exceptionally high grade ores average 15 g t but frequently up to 300 g t au pangui is a recently discovered porphyry cu mo district the geology of the subandean zone in southeastern ecuador is dominated by the i type subduction related jurassic zamora batholith which intrudes triassic volcanosedimentary rocks the zamora batholith is in turn cut by porphyritic stocks which are commonly associated with skarn formation and or porphyry style mineralization high precision u pb and re os ages for porphyritic stocks u pb zircon associated prograde skarn u pb hydrothermal titanite and retrograde stage skarn re os molybdenite from veins postdating gold deposition of the nambija district are all indistinguishable from each other within error 145 ma and indicate a late jurassic age for the gold mineralization previously gold mineralization at nambija was considered to be early tertiary based on k ar ages obtained on various hydrothermal minerals the new jurassic age for the nambija district is slightly younger than the 40ar 39ar and re os ages for magmatic hydrothermal minerals from the pangui district which range between 157 and 152 ma mineralization at nambija and pangui is associated with porphyritic stocks that represent the last known episodes of a long lived jurassic arc magmatism 190 to 145 ma a jurassic age for mineralization at nambija and pangui suggests that the northern andean jurassic metallogenic belt which starts in colombia at 3 n extends down to 5 s in ecuador it also adds a new mineralization style au skarn to the metal endowment of this belt

in situ la icpms trace elements and u pb analysis of titanite from the mesozoic ruanjiawan w cu mo skarn deposit daye district china abstract in this paper we present u pb ages and trace element compositions of titanite from the ruanjiawan w cu mo skarn deposit in the daye district eastern china to constrain the magmatic and hydrothermal history in this deposit and provide a better understanding of the u pb geochronology and trace element geochemistry of titanite that have been subjected to post crystallization hydrothermal alteration titanite from the mineralized skarn the ore related quartz diorite stock and a diabase dike intruding this stock were analyzed using laser ablation inductively coupled plasma mass spectrometry la icpms titanite grains from the quartz diorite and diabase dike typically coexist with hydrothermal minerals such as epidote sericite chlorite pyrite and calcite and display irregular or patchy zoning these grains have low lree hree and high th u and lu hf ratios coupled with negative eu and positive ce anomalies the textural and compositional data indicate that titanite from the quartz diorite has been overprinted by hydrothermal fluids after being crystallized from magmas titanite grains from the mineralized skarn are texturally equilibrated with retrograde skarn minerals including actinolite quartz calcite and epidote demonstrating that these grains were formed directly from hydrothermal fluids responsible for the mineralization compared to the varieties from the quartz diorite stock and diabase dike titanite grains from the mineralized skarn have much lower ree contents and lree hree th u and lu hf ratios they have a weighted mean 206 pb 238 u age of 142 2 ma mswd 0 7 2 in agreement with a zircon u pb age of 144 1 ma mswd 0 3 2 of the quartz diorite and thus interpreted as formation age of the ruanjiawan w cu mo deposit titanite grains from the ore related quartz diorite have a concordant u pb age of 132 2 ma mswd 0 5 2 which is 10 12 ma younger than the zircon u pb age of the same sample and thus interpreted as the time of a hydrothermal overprint after their crystallization this hydrothermal overprint was most likely related to the emplacement of the diabase dike that has a zircon u pb age of 133 1 ma and a titanite u pb age of 131 2 ma the geochronological results thus reveal two hydrothermal events in the ruanjiawan deposit an early one forming the wu cu mo ores related to the emplacement of the quartz diorite stock and a later one causing alteration of the quartz diorite and its titanite due to emplacement of diabase dike it is suggested that titanite is much more susceptible to hydrothermal alteration than zircon results from this study also highlight the utilization of trace element compositions in discriminating titanite of magmatic and hydrothermal origins facilitating a more reasonable interpretation of the titanite u pb ages

tectonics of the middle triassic intracontinental xuefengshan belt south china new insights from structural and chronological constraints on the basal decollement zone in orogenic belts a basal decollement zone often develops at depth to accommodate the shortening due to folding and thrusting of the sedimentary cover in the early mesozoic intracontinental xuefengshan belt of south china such a decollement zone is exposed in the core of anticlines formed by the emplacement of the late orogenic granitic plutons our detailed multi scale structural analysis documents a synmetamorphic ductile deformation in the basal decollement the neoproterozoic pelite and sandstone and the intruding early paleozoic granites were deformed and metamorphosed into mylonites and orthogneiss respectively the metamorphic foliation contains a nw se stretching lineation associated with top to the nw kinematic indicators the ductile shearing of these high strained rocks can be correlated with nw verging folds and thrusts recognized in the neoproterozoic to early triassic sedimentary cover monazite u th pbtot chemical dating and zircon sims u pb dating provide age constraints of the ductile shearing between 243 and 226 ma and late orogenic granite emplacement around 235 215 ma in agreement with recent geochronological data these new results show that the xuefengshan belt is an early mesozoic orogen dominated by the nw directed shearing and thrusting at the southeastern boundary of the xuefengshan belt the chenzhou linwu fault separates the early mesozoic domain to the nw from the early paleozoic domain to the se the tectonic architecture of this belt was possibly originated from the continental underthrusting to the se of the south china block in response to northwest directed subduction of the paleo pacific plate

granite related yangjiashan tungsten deposit southern china the yangjiashan scheelite bearing deposit 38 663 metric tons of wo3 with an average ore grade of 0 70 wo3 is hosted in quartz veins in a biotite monzogranite intrusion and surrounding slate in the xiangzhong metallogenic province of southern china the monzogranite has a zircon shrimp u pb age of 406 6 2 8 ma 2 n 20 mswd 1 4 cassiterite coexisting with scheelite yields a weighted mean 206pb 238u age of 409 8 5 9 ma 2 n 30 mswd 0 20 and molybdenite intergrown with scheelite yields a weighted mean re os age of 404 2 3 2 ma 2 n 3 mswd 0 10 these results suggest that the yangjiashan tungsten deposit is temporally related to the devonian intrusion the d and calculated 18oh2o values of quartz intergrown with scheelite range from 87 to 68 and 1 2 to 3 4 respectively sulfides have a narrow range of 34s values of 2 9 to 0 7 with an average value of 1 6 n 16 the integration of geological stable isotope and geochronological data combined with the quartz muscovite greisen style of ore supports a magmatic hydrothermal origin for the tungsten mineralization compared to the more common tungsten skarn quartz wolframite vein and porphyry tungsten deposits as well as orogenic gold deposits worldwide the yangjiashan tungsten deposit is an unusual example of a granite related gold poor scheelite bearing quartz vein type of deposit the calcium needed for the formation of scheelite is derived from the sericitization of calcic plagioclase in the monzogranite and ca bearing psammitic country rocks and the relatively high ph reduced and ca rich mineralizing fluid may be the main reasons for the formation of scheelite rather than wolframite at yangjiashan

climate variability in southern south america associated with el nino and la nina events a comprehensive view is given of the precipitation and circulation anomalies associated with the various stages of el nino en and la nina ln events all over southern south america ssa this view comprises the delineation of coherent regions with respect to precipitation anomalies the identification of the seasons of maximum anomalies the indication of their magnitude and the assessment of their consistency during those events in addition the spatial and temporal variability of these anomalies is detailed by calculating the expected precipitation percentiles and the consistency of wet and dry anomalies for each station and each three month running season during en and ln events composites of circulation anomalies and an assessment of their consistency are also presented and their connection with the precipitation anomalies is discussed southern brazil presents the strongest average signal in en events the general behavior toward opposite signals in the precipitation and circulation anomalies over ssa during almost the same periods of the en and ln events indicates a large degree of linearity in the response to these events the timing of the anomalies changes throughout ssa leading to the identification of eight different coherent regions in the en case and six in the ln case this regionalization is mostly caused by different processes leading to precipitation anomalies in ssa during those events all these regions show a significant response in some part of each event the magnitude and consistency of this response show a large spatial variability and some areas present very strong and consistent anomalies sometimes not disclosed when large coherent regions are analyzed in spite of the differences in timing some features of the precipitation anomalies are rather uniform throughout the region during en and ln events in en episode there is a tendency to lower than median precipitation in the year before the event which continues until march of the year of the event in a vast region east of the andes the strongest positive precipitation anomalies occur in spring of this year when the circulation anomalies concur to enhance rainfall over several regions during the summer of the mature stage the positive precipitation anomalies almost disappear and then reappear in some regions in late summer early autumn and in winter of the year following the starting year of the event this description holds partially for the ln event but with opposite signs although there is a larger spatial variability in the ln related anomalies in the following year and some shifts in timing as for precipitation the symmetry of the geopotential height anomaly fields with opposite signs between ln and en cases is also remarkable especially during the year 0

further evidence of changes in the hydrological regime of the river paraguay part of a wider phenomenon of climate change abstract analysis of flow measured at 20 sites rainfall measured at 36 sites and a 95 year record of water level at one site in the basin of the river paraguay area 1095 10 3 km 2 showed that the flow regime during the approximate period 1960 1970 differed substantially from the flow regime both before and after the long record of ladario water levels suggested that the changes between one period and the next were considerably abrupt and that the periods differed not only in terms of mean water levels but also in terms of the year to year correlational structure within the record despite the fragmentary nature of rainfall records from 36 sites an explanation for the increased flows since 1970 was found in the increases of rainfall as assessed in terms of the frequency of annual rainfalls more than the long term mean rainfall there was some degree of consistency in the change of rainfall pattern across the paraguay basin as a whole a detailed examination of daily rainfall characteristics at two gauges where records were fairly complete showed that during the 1960 1970 period when river flows were low dry spells were more persistent and on days when rain did fall the amounts of rain were generally smaller the results obtained were compared with results obtained by other researchers using flow records from the rivers paraguay parana negro and uruguay in the la plata basin and rainfall records from other parts of south america there is now strong evidence of changes in the runoff regime of the la plata basin during the last 40 years not all of which can be attributed to land use change as there is complementary evidence of change in rainfall regime the results were also compared with findings from the congo basin which appears to exhibit changes in flow regime that are a mirror image of those found for the paraguay at ladario

dinoflagellate cysts as indicators of water quality and productivity in british columbia estuarine environments abstract palynological analyses of 60 surface sediment samples from estuarine environments near vancouver island including the georgia strait gs the effingham eff and the seymour belize sb inlets were performed in order to document the distribution of dinoflagellate cyst assemblages and their relationship to hydrographic conditions productivity and nutrient concentrations we tested transfer functions using the analogue method and suggest that dinoflagellate cyst assemblages can be used to reconstruct primary productivity temperature and salinity the eff and sb inlets are characterized by a dominance of autotrophic taxa particularly operculodinium centrocarpum whereas the protoperidinioid and gymnodinial heterotrophic taxa such as quinquecuspis concreta and brigantedinium spp dominate the assemblages of the gs multivariate analysis shows that this distribution is closely linked to primary productivity sea surface temperature sst and spring silica concentration the abundance of autotrophic taxa in the eff and sb inlets is associated with high primary productivity and low summer sst indicating summer upwelling of coastal british columbia whereas the heterotrophic taxa that characterizes the gs assemblages are related to low productivity high summer sst and high silica concentration during spring multivariate analysis shows that the most important environmental parameters related to dinocyst distribution in the restricted embayment of the gs are distance to the shore distance to vancouver harbor spring sea surface salinity sss spring phosphate concentration and spring productivity the autotrophic taxa are generally more common in coastal and shallow waters but spiniferites ramosus and pentapharsodinium dalei show an opposite correlation to spring productivity and salinity p dalei is particularly abundant around vancouver harbor near highly urbanized shores and within the fraser river plume where salinity is low and spring productivity and continental runoff are high s ramosus shows its highest abundance on the western coast of gs protoperidinioid and gymnodinial cysts characterize distal zones within the central and southern gs that are associated with a mixture of brackish waters coming from the fraser river and deep upwelling waters entering the gs via juan de fuca strait the relationship between dinoflagellate cyst assemblages and primary productivity in these estuarine systems differs from that in oceanic and outer neritic zones where the abundance of heterotrophic taxa is commonly associated with upwelling and high productivity

precipitation anomalies in southern brazil associated with el nino and la nina events the impact of el nino and la nina events warm and cold phases of the southern oscillation on rainfall over southern brazil is investigated through the use of a large dataset of monthly precipitation from 250 stations this region is partly dominated by rough orography and presents different climatic regimes of rainfall as previous global studies on southern oscillation precipitation relationships used data from only two stations in southern brazil this region was not included in the area of consistent southern oscillation related precipitation in southeastern south america the present analysis is based on the method by ropelewski and halpert the sensitivity of which is assessed for this region the spatial structure of the rainfall anomalies associated with warm cold events is analyzed and subregions with coherent anomalies are determined their distribution indicates the influence of relief latitude and proximity to the ocean these areas are subjected to further analysis to determine the seasons of largest anomalies and assess their consistency during warm cold events the whole of southern brazil was found to have strong and consistent precipitation anomalies associated with those events their magnitude is even larger than in argentina and uruguay all of the subregions have consistent wet anomalies during the austral spring of the warm event year with a pronounced peak in november the southeastern part also shows a consistent tendency to higher than average rainfall during the austral winter of the following year there is also a consistent tendency to dryness in the year before a warm event during the spring of cold event years strong consistent dry anomalies prevail over the whole region also with maximum magnitude in november they are even stronger and more consistent than the wet anomalies in warm event years consistent anomalies do not occur over large areas in the years before and after cold events the wet anomalies during the austral spring of the warm event year weaken and even reverse during the following january the same tendency though not so clear is observable in the dry anomalies of cold events the seasons of largest anomalies disclosed by this study differ from those found by previous global studies for other regions in southeastern south america this study expands the area of consistent warm cold event related precipitation defined by previous studies in southeastern south america by including a region of larger anomalies and provides a spatial and temporal refinement to the warm cold event precipitation relationship

molecular isotopic and dinoflagellate evidence for late holocene freshening of the black sea abstract the black sea is the world s largest anoxic basin with oxygen free conditions below water depths of approximately 100 m resulting from strong density stratification the salinity of its surface water likely varied substantially over time due to variations in freshwater input from large rivers and in the saline bottom water of mediterranean origin coming across the shallow sill of the bosporus however long term reconstructions of surface water salinities are lacking the invasion of the coccolithophorid emiliania huxleyi in the black sea at approximately 2720 a responsible for a marked change in sediment composition lithology has been commonly attributed to salinity levels rising above 11 we analyzed the d values of long chain alkenones produced by haptophyte algae mainly e huxleyi in a core from the eastern basin of the black sea to reconstruct past variations in sea surface salinities and combined this with relative salinity changes generated from organic walled dinoflagellate cyst dinocyst distributions from the same core combined results indicate a substantial freshening of black sea surface waters in the last 3000 years suggesting that sea surface salinity was substantially higher than the present day salinity of approximately 18 at the time e huxleyi invaded the black sea

holocene temperature trends in the extratropical northern hemisphere based on inter model comparisons large uncertainties exist in holocene climate estimates especially for the early holocene when large scale reorganization occurred in the climate system to improve our understanding of these uncertainties we compare four holocene simulations performed with the loveclim ccsm3 hadcm3 and famous climate models the simulations are generally consistent for the large scale northern hemisphere extratropics while the multi simulation consistencies are heterogeneous on the sub continental scale consistently simulated temperature trends are found in greenland northern canada north eastern and north western europe and central west siberia these holocene temperatures show a pattern of an early holocene warming mid holocene warmth and gradual decrease towards the pre industrial in winter and the extent of early holocene warming varies spatially with 9 c warming in northern canada compared with 3 c warming in central west siberia in contrast mismatched temperatures are detected in alaska the warm early holocene winter in loveclim primarily results from strongly enhanced southerly winds induced by the ice sheets in eastern siberia the intense early holocene summer warmth anomaly in ccsm3 is caused by large negative albedo anomalies due to overestimated snow cover at 0 ka in the arctic cool winter conditons in famous can be attributed to extensive sea ice coverage probably due to simplified sea ice representations thus the holocene temperature trends in these regions remain inconclusive

paleoceanography of northeastern fram strait since the last glacial maximum palynological evidence of large amplitude changes abstract sea surface conditions in northeastern fram strait since the last glacial maximum lgm were reconstructed from cores msm5 5 712 2 and ps2863 1 2 based on palynological assemblages ecological preferences of dinocysts and application of the modern analog technique dinocyst in lgm sediments are sparse but their assemblages reflect mild summer conditions given the regional context and evidence from other tracers the dinocyst assemblages of the lgm could relate to regional fluxes of dinocysts during exceptional mild summers from 19 to 14 7 ka dinocyst data suggest very cold conditions with extensive sea ice cover while abundant reworked palynomorphs indicate intense glacial erosion an abrupt transition at 14 7 14 5 ka was marked by a peak in summer temperatures coinciding with a rapidly deposited sediment layer related to a regional meltwater plume event in western svalbard from 14 7 to 12 6 ka large seasonal temperature contrasts with mild summers and cold winters together with low salinity indicate continuous melting of the svalbard barents sea ice sheet fostered by warm climate at 12 6 ka the regional onset of the younger dryas was marked by cooling and increased salinity on a regional scale the 12 6 12 ka interval corresponds to an important transition involving enhanced circulation of arctic waters around svalbard and establishment of coastal fronts along its northern and western margins modern like oceanic conditions with relatively high salinity and low seasonal temperature contrast developed at about 7 6 ka since then a slight cooling is observed especially in winter this study offers a comprehensive picture of the deglacial phases in eastern fram strait with unique data on the sea surface salinity which controls surface water stratification and plays an important role in ocean circulation

the giant south china mesozoic low temperature metallogenic domain reviews and a new geodynamic model abstract the south china craton was formed by amalgamation of the yangtze and cathaysia blocks during the neoproterozoic during the mesozoic voluminous granitic plutons and associated w sn polymetallic deposits were formed in the cathaysia block the giant south china low temperature metallogenic domain ltmd includes an area of 500 000 km 2 in the yangtze block and is composed of the chuan dian qian pb zn youjiang au as sb hg and xiangzhong sb au metallogenic provinces the chuan dian qian pb zn province contains numerous mvt pb zn deposits whereas the other two provinces are characterized by carlin type au deposits and vein type sb hg and as deposits these epigenetic deposits which formed under low temperature conditions 100 250 c are typically hosted in sedimentary rocks and are locally controlled by faults and fractures the deposits formed dominantly at 200 230 ma and 130 160 ma corresponding to indosinian triassic and yanshanian jurassic to cretaceous orogenies respectively indosinian mineralization is recognized in all three provinces but yanshanian mineralization occurred only in the youjiang and xiangzhong provinces the indosinian orogeny which involved collision of the indochina block with the south china craton resulted in circulation of basinal brines that leached ore forming elements from adjacent sedimentary strata to form the chuan dian qian pb zn province deep seated granitic magmas generated during this orogeny caused extensive circulation of meteoric water that mobilized ore forming elements from the sedimentary strata to form the carlin type au deposits in the youjiang province and the sb au deposits in the xiangzhong province the indosinian orogeny was the key factor in establishing the metallogenic framework of the ltmd it produced widespread mineralization in the three metallogenic provinces each of which has unique features reflecting differences in the nature and composition of the basement rocks the yanshanian metallogeny was less important and overprinted the older ore deposits in the youjiang and xiangzhong provinces

calculation of river discharge and prediction of lake height from satellite radar altimetry example for the lake chad basin 1 the application of satellite radar altimetry to the determination of lake and river elevations has been used in numerous projects and is well validated here we show that with the aid of ground based information this technique can be extended to determine river discharge and predict downstream lake and marsh height the lake chad basin provides an ideal case study due to its well known hydrology and complex lake and marsh morphology and because prediction of lake and marsh height has been identified as potentially useful to people living in the region altimetric stage measurements from the topex poseidon satellite at the chari ouham confluence estimate river discharge about 500 km downstream at n djamena 10 days in advance r2 0 9562 via simple linear correlation methods the stage measurements successfully estimate the height of the permanent waters of the lake 600 km downstream 39 days in advance r2 0 9297 predicting the water height on the western marshes of the lake bed is poorer r2 0 7958 due to a change in response time of the local stage to the seasonal floods coincident with an observed increase in mean water level in the latter half of the 1990s before 1997 a 96 day phase lag results in the best fit r2 0 6463 after 1997 the best fit is obtained with a 66 day phase lag r2 0 8139 the excellent river discharge and lake height predictions show that altimetry is a useful tool where ground based data are difficult to obtain and where rapid water resource assessment is desirable

re os dating and sulfur isotope composition of molybdenite from tungsten deposits in western namaqualand south africa implications for ore genesis and the timing of metamorphism both stratiform stratabound and granite related models have been used to explain the genesis of w mo deposits in the okiep copper district in western namaqualand south africa apparently stratabound mineralization fe rich wolframite with accessory molybdenite occurs in foliation parallel quartz veins in high grade 750 c 5 6 kbar metapelites of the wolfram formation and less commonly in small bodies of silicified leucogranites and pegmatites six re os ages for molybdenites from four deposits nababeep tungsten far west kliphoog narrap tweedam range between 1000 4 and 1026 5 ma these molybdenites define a well constrained 187re 187os isochron with an age of 1019 6 ma which is interpreted as the age of w mo mineralization this age is significantly younger than proterozoic protolith ages for supracrustal rocks and the emplacement ages for the main intrusive suites but geologic evidence requires overlap with a period of high grade metamorphism we suggest that w mo mineralization is genetically linked to intra crustal magmatic processes at 1020 ma thereby precluding the 1060 ma concordia granite as the source for mineralizing fluids a narrow range of positive 34s compositions 3 6 to 4 5 for eight molybdenites from five w mo mines is consistent with a so2 rich fluid and a granite related genetic model post peak metamorphic deformation and metamorphism of w mo ores is most likely related to the retrograde stage of the namaquan orogeny which overlaps emplacement of late orogenic evolved granites and pegmatites and the formation of w mo deposits in western namaqualand therefore the effects of retrograde namaquan metamorphism extend at least to 1020 ma or alternatively these w mo veins were affected by a poorly constrained later event e g early pan african

statistically assessing the correlation between salinity and morphology in cysts produced by the dinoflagellate protoceratium reticulatum from surface sediments of the north atlantic ocean mediterranean marmara black sea region and baltic kattegat skagerrak estuarine system abstract recent studies have correlated dinoflagellate resting cyst morphology to salinity and density variations in the water column suggesting that morphology can be used for paleoceanographic reconstructions however the univariate statistics used by these studies are appropriate only where morphology is related to a single variable density is a function of salinity and temperature so more advanced statistical methods are needed to understand which parameters affect morphology in this study based on surface coretop sediments a set of environmental variables sea surface salinity temperature nitrate and phosphate was simultaneously correlated to morphological variations seen in resting cysts produced by the dinoflagellate protoceratium reticulatum operculodinium centrocarpum sensu wall and dale approximately 3200 measurements were obtained from the north atlantic ocean and used to generate a working model based on the akaike information criterion hierarchical partitioning was then applied to establish the independent and joint effects for each predictor variable results from these analyses showed that while salinity constitutes the dominant variable affecting process length in the cysts of p reticulatum in the north atlantic it is not the sole explanatory variable and that multicollinearity exists temperature and nutrients also showed a significant relationship to the morphology requiring multiple regression to construct a representative model the applicability of the north atlantic working model was finally evaluated by comparing the results to data from the mediterranean marmara and black seas and baltic kattegat skagerrak estuarine system this comparison showed regional differences in morphological environmental correlation while salinity constitutes the most important explanatory factor in both the north atlantic and baltic skagerrak system this is not so for the mediterranean black sea region where temperature is the dominant variable it is concluded that a predictive salinity model based on p reticulatum cyst morphology has at best a regional application

contribution palynostratigraphique dinokystes pollen et spores a la connaissance de la mer de champlain coupe de saint cesaire quebec high resolution continental pollen and spores and marine dinoflagellate cysts microfloral records were obtained from a section consisting of about 0 5 m of glaciolacustrine and 2 5 m of champlain sea deposits at the saint cesaire site the pollen and spore assemblages indicate the existence of a regional open vegetation of shrub tundra to forest tundra fluctuations in the percentages of picea and shrub and herb taxa are related to regional afforestation and paleogeographical evolution of the basin the champlain sea sediments contain an abundant dinocyst flora dominated by operculodinium centrocarpum brigantedinium spp and algidasphaeridium minutum which indicate cold arctic conditions in surface waters fluctuations in concentration 102 104 cm 3 and relative abundance of dinocyst species are attributed to changes in dinoflagellate productivity and paleoceanographic conditions notably paleosalinity morphological variations of operculodinium centrocarpum and algidasphaeridium minutum led to

in situ la icp ms u pb geochronology and trace element analysis of hydrothermal titanite from the giant zhuxi w cu skarn deposit south china the zhuxi w cu skarn deposit is the largest w deposit in the jiangnan porphyry skarn tungsten belt in south china and is also among the largest deposit of this type in the world titanite is a common mineral in the zhuxi deposit and occurs in three textural settings titanite i associated with retrograde altered exoskarn with weak mineralization titanite ii in retrograde altered endoskarn with disseminated cu ore and titanite iii from altered granite with disseminated w ore here we present la icp ms u pb data on the three types of titanite which show 207pb corrected weighted mean 206pb 238u ages of 148 1 7 4 ma n 25 mswd 0 22 148 9 1 5 ma n 28 mswd 0 37 and 149 9 1 3 ma n 31 mswd 0 28 respectively these ages are consistent with the previously reported ages of the ore related granite the coeval nature of the w and cu ores suggests that the w and cu ores formed synchronously and are associated with the granitoids the ce and eu anomalies in the three types of titanite record redox fluctuation during the mineralization process and suggest variable contamination of the magmatic hydrothermal system by reduced carbonate wall rock that contains abundant carbonaceous matter our study demonstrates that hydrothermal titanite commonly occurring in reduced type w skarn deposits has potential for isotopic dating and in constraining the redox conditions for the mineralization process

holocene temperature evolution in the northern hemisphere high latitudes model data comparisons abstract heterogeneous holocene climate evolutions in the northern hemisphere high latitudes are primarily determined by orbital scale insolation variations and melting ice sheets previous inter model comparisons have revealed that multi simulation consistencies vary spatially we therefore compared multiple model results with proxy based reconstructions in fennoscandia greenland north canada alaska and siberia our model data comparisons reveal that data and models generally agree in fennoscandia greenland and canada with the early holocene warming and subsequent gradual decrease to 0 ka bp hereinafter referred as ka in fennoscandia simulations and pollen data suggest a 2 c warming by 8 ka but this is less expressed in chironomid data in canada a strong early holocene warming is suggested by both the simulations and pollen results in greenland the magnitude of early holocene warming ranges from 6 c in simulations to 8 c in 18 o based temperatures simulated and reconstructed temperatures are mismatched in alaska pollen data suggest strong early holocene warming while the simulations indicate constant holocene cooling and chironomid data show a stable trend meanwhile a high frequency of alaskan peatland initiation before 9 ka can reflect a either high temperature high soil moisture or large seasonality in high latitude siberia although simulations and proxy data depict high holocene temperatures these signals are noisy owing to a large spread in the simulations and between pollen and chironomid results on the whole the holocene climate evolutions in most regions fennoscandia greenland and canada are well established and understood but important questions regarding the holocene temperature trend and mechanisms remain for alaska and siberia

laser ablation icp ms titanite u th pb dating of hydrothermal ore deposits a case study of the tonglushan cu fe au skarn deposit se hubei province china abstract titanite from the tonglushan cu fe au skarn deposit daye district eastern china has been successfully dated by laser ablation inductively coupled plasma mass spectrometry la icp ms hydrothermal titanite from both skarn ores and calcite veins cutting the ore bodies are characterized by having much lower ree and th u and lu hf ratios compared to their magmatic equivalents from the ore related yangxin quartz diorite intrusion and a late stage albitite dike titanite from the yangxin quartz diorite and an albitite dike which intrudes both the quartz diorite intrusion and ore bodies yield weighted mean 206pb 238u ages of 136 0 1 5 ma and 120 6 2 3 ma 2 respectively in agreement within analytical uncertainty to their 208pb 232th ages in situ analysis of epidote enclosed hydrothermal titanite in thin sections of a skarn ore sample yields a mean 206pb 238u age of 135 9 1 3 ma and 208pb 232th age of 138 2 4 5 ma whereas titanite in calcite from a calcite dominated vein cross cutting the skarn ore body has consistent 206pb 238u and 208pb 232th ages of ca 121 ma the data thus reveal two independent hydrothermal events the earlier event was responsible for the known cu fe au skarn mineralization at tonglushan and throughout the daye district and was caused by coeval magmatism that has resulted in the emplacement of the yangxin quartz diorite the later event previously unrecognized was associated with a second magmatic pulse as represented by the albitite dikes and provides potential for discovering new mineral deposits at tonglushan and possibly over the daye district this study represents the first direct dating of skarn deposits using titanite u th pb geochronometer and signifies the utilization of titanite for precise dating of hydrothermal ore formation

geologic evidence for a mantle superplume event at 1 9 ga 1 both preserved and restored areal distributions of proterozoic marine intracratonic passive margin and platform sediments show a prominent peak at 1 9 ga indicating that shallow marine sediments were widespread on the continents and that sea level was high at this time the chemical index of alteration in shales deposited at this time was high suggesting warm climates possibly due to enhanced co2 levels in the atmosphere high sea level and warms climate may also explain an abundance of black shale banded iron formations and shallow marine phosphate deposits and an increase in the number of occurrences and diversity of stromatolites in general and microdigitate stromatolites at 1 9 ga all of these observations are consistent with a 1 9 ga superplume event the occurrence of only a minor positive carbon isotope shift in marine carbonates at 1 9 ga indicates that the relative rates of burial of organic and oxidized carbon remained about the same as at present slightly low 87sr 86sr isotopic ratios in seawater at 1 9 ga reflect increased mantle input of sr from the proposed superplume event whereas higher ratios at 1 85 1 75 ga may reflect increased input of continental sr from a growing supercontinent the first massive sulfate evaporites in the geologic record at 1 8 1 6 ga follow the possible 1 9 ga superplume event this may reflect an increase in both oxidation state and carbonate deposition in the oceans as plume related volcanism wanes

distribution of common modern dinoflagellate cyst taxa in surface sediments of the northern hemisphere in relation to environmental parameters the new n 1968 database abstract we present a new version of the standardized northern hemisphere modern dinoflagellate cyst dinocyst database which includes abundances of 71 taxa at 1968 sites across the northern hemisphere cross referenced with 17 environmental parameters extracted mostly from the 2013 world ocean atlas several taxa with tropical to warm temperate affinities were added to the previous database version dinocyst concentrations in the surface sediments reach 106 cysts g 1 with maximum values along the continental margins and minimum values offshore in distal open ocean settings assemblages are characterized by the co occurrence of phototrophic n 41 and heterotrophic taxa n 30 with maximum proportions of heterotrophic taxa in high productivity regions notably at the sea ice edge and in upwelling regions the main pattern of assemblage distributions includes north south and nearshore offshore gradients with maximum diversity of species along the continental margins and towards the south in warm temperate and tropical areas canonical correspondence analyses performed on heterotrophic and phototrophic taxa independently yield consistent results hence suggesting similar but not identical ecological affinities for both taxonomic groups for both groups sea surface temperature and sea ice are the most determining parameters but the phototrophic taxa seem more sensitive to onshore offshore gradients marked by salinity changes productivity related parameters also determine dinocyst distribution especially primary productivity in the fall and winter with a stronger relationship for the combined dataset of phototrophic and heterotrophic taxa

phanerozoic tectonothermal events of the xuefengshan belt central south china implications from upb age and luhf determinations of granites the xuefengshan belt characterized by large scale fold and thrust structures and widespread granites is a key area to decipher the tectonic evolution of the south china block in this belt two magmatic episodes are recorded by early paleozoic and early mesozoic granites in this paper we carried out precise sims zircon usingle bondpb dating and in situ lusingle bondhf isotopes measurements on these granitic plutons our study indicates that the early paleozoic and the early mesozoic granites are late orogenic products of the early paleozoic orogen and the middle triassic xuefengshan orogen respectively in the xuefengshan belt the early paleozoic event is poorly registered since this area corresponds to the outer zone of the early paleozoic orogen the silurian early devonian granites are late orogenic plutons emplaced after the main tectonic and metamorphic stage in the wuyi baiyun yunkai belt coeval with a widespread subsequent extensional event in eastern and southern south china on the other hand triassic granites are formed in an intracontinental environment with weakly to strongly peraluminous signatures zircon usingle bondpb ages presented here associated with a summary of newly acquired data in the same region suggest that the emplacement of anatectic granites occurred around 225 215 ma not in a rather wide range of ca 245 200 ma in situ zircon ehf t values indicate a crust derived source without a mantle derived input for the two generations of granites combining our data with recent studies we infer that the central area of the south china block has experienced two tectonothermal events the early paleozoic magmatism developed as a result of the collapse of the early paleozoic orogen while these early mesozoic granites can be the late orogenic products of the intracontinental xuefengshan orogen most likely manifesting the far field effect by the

hydraulic visibility using satellite altimetry to parameterize a hydraulic model of an ungauged reach of a braided river what hydraulic information can be gained from remotely sensed observations of a river s surface in this study we analyze the relationship between river bed undulations and water surfaces for an ungauged reach of the xingu river a first order tributary of the amazon river this braided reach is crosscut more than 10 times by a envisat environmental satellite track that extends over 100 km rating curves based on a modeled discharge series and altimetric measurements are used including the zero flow depth z0 parameter which describes river s bathymetry river widths are determined from jers japanese earth ressources satellite images hydrodynamic laws predict that irregularities in the geometry of a river bed produce spatial and temporal variations in the water level as well as in its slope observation of these changes is a goal of the surface water and ocean topography satellite mission which has a final objective of determining river discharge first the concept of hydraulic visibility is introduced and the seasonality of water surface slope is highlighted along with different flow regimes and reach behaviors then we propose a new single thread effective hydraulic approach for modeling braided rivers flows based on the observation scales of current satellite altimetry the effective hydraulic model is able to reproduce water surface elevations derived by satellite altimetry and it shows that hydrodynamical signatures are more visible in areas where the river bed morphology varies significantly and for reaches with strong downstream control the results of this study suggest that longitudinal variations of the slope might be an interesting criteria for the analysis of river segmentation into elementary reaches for the surface water ocean topography mission that will provide continuous measurements of the water surface elevations the slopes and the reach widths

high resolution dinoflagellate cyst record of environmental change in effingham inlet british columbia canada over the last millennium abstract we present a high resolution sedimentary record of dinoflagellate cysts spanning the last 900 years recovered from effingham inlet a glacial fjord on the west coast of vancouver island canada the combination of seasonal coastal upwelling supporting high levels of marine primary productivity in surface waters together with restricted bottom water circulation in the silled fjord fosters the preservation of laminated sediments in the inner basin of effingham inlet geochemical data are used to assess the sedimentary facies of the core which is composed primarily of laminated units 50 2 occasionally interrupted by seismites 39 5 and homogenous units 10 2 the chronology of the 2 m long core is based on varve counting and fifteen 14c dates and is anchored by a seismite previously dated at ad 1946 the dinoflagellate cyst assemblages are diverse total of 47 taxa abundant average concentrations of 102 900 cyst g 1 of dry sediment and characterized by a proportionally equal contribution of autotrophic and heterotrophic cyst taxa in most samples overall cyst assemblages are characterized by operculodinium centrocarpum 36 2 accompanied by brigantedinium spp 18 0 and dubridinium spp 6 6 multivariate analyses are used to extract the dominant patterns of variability in autotrophic and heterotrophic dinoflagellate cyst assemblages separately and help in identifying the temperature and primary productivity gradients encoded in the cyst sedimentary record in this particular estuary specific intervals identified in the dinoflagellate cyst record are interpreted to represent the local expression of the medieval climate anomaly from the base of the record ad 1090 to 1230 the little ice age ad 1230 to late 19th century and warming in the second half of the 20th century the timing of these intervals are consistent with the regional paleoclimate and help constrain past climatic and oceanographic variability on the west coast of vancouver island the origin of homogenous units in the sedimentary record of effingham inlet and paleoseismicity in the region are also discussed

multiple mesozoic mineralization events in south china an introduction to the thematic issue mesozoic mineral deposits in south china include world class deposits of w sn and sb and those that provide the major sources of ta cu hg as tl pb zn au and ag for the entire country these deposits can be classified into polymetallic hydrothermal systems closely related to felsic intrusive rocks sn w mo granites cu porphyries polymetallic and fe skarns and polymetallic vein deposits and low temperature hydrothermal systems with no direct connection to igneous activities mvt deposits epithermal au and sb deposits recent studies have shown that they formed in the triassic indosinian jurassic cretaceous early yanshanian and cretaceous late yanshanian stages indosinian deposits include major mvt pb zn ag deposits and granite related w sn deposits early yanshanian deposits are low temperature sb au and high temperature w sn and cu porphyry types many late yanshanian deposits are low temperature au as sb hg and u deposits and also include high temperature w sn polymetallic deposits the formation of these deposits is linked with a specific tectonothermal evolution and igneous activities this special issue brings together some of the latest information in eight papers that deal with the origins and tectonic environments of mineral deposits formed in these stages we anticipate that this issue will stimulate more interests in these ore deposits in south china

genetic types mineralization styles and geodynamic settings of mesozoic tungsten deposits in south china abstract south china hosts the most abundant and largest tungsten w deposits in the world being a famous w metallogenic region located at the eastern part of the south china block which was formed by amalgamation of the yangtze and cathaysia blocks during the neoproterozoic these w deposits were mainly formed during the mesozoic the w mineralization is dominanted by greisen quartz vein skarn and porphyry types all of which are genetically related to the evolution of highly fractionated granitoids four episodes of w mineralization are recognized 1 late triassic 230 210 ma in the central and western parts of south china 2 middle jurassic ca 170 ma to early cretaceous ca 140 ma in the interior of south china with the mineralization being concentrated in southern jiangxi province between 165 and 150 ma 3 early cretaceous 136 120 ma with deposits across south china and 4 late cretaceous 100 80 ma mainly in the southwestern parts of south china these four periods of mineralization are closely related to the closure of paleo tethys and subduction of the paleo pacific plate in the late triassic these two events caused local extensional environments facilitating emplacement of the peraluminous granitoids and formation of the w deposits in the middle jurassic break off of the subducting oceanic plate resulted in emplacement of highly fractionated granites in the nanling region later anticlockwise rotation of the paleo pacific plate created widespread s type granitoids and associated middle jurassic to early cretaceous w mineralization in the interior of south china since 136 ma rollback of the subducting pacific plate resulted in weak w mineralization across south china finally a change of direction in the retreating plate from se to ese resulted in intensive mineralization of the southwestern part of south china

orogenic gold common or evolving fluid and metal sources through time abstract orogenic gold deposits of all ages from paleoarchean to tertiary show consistency in chemical composition they are the products of aqueous carbonic fluids with typically 5 20 mol co 2 although unmixing during extreme pressure fluctuation can lead to entrapment of much more co 2 rich fluid inclusions in some cases ore fluids are typically characterized by significant concentrations of ch 4 and or n 2 common estimates of 0 01 0 36 mol h 2 s a near neutral ph of 5 5 and salinities of 3 7 wt nacl equiv with na k ca mg this fluid composition consistency favors an ore fluid produced from a single source area and rules out mixing of fluids from multiple sources as significant in orogenic gold formation nevertheless there are broad ranges in more robust fluid inclusion trapping temperatures and pressures between deposits that support a model where this specific fluid may deposit ore over a broad window of upper to middle crustal depths much of the reported isotopic and noble gas data is inconsistent between deposits leading to the common equivocal interpretations from studies that have attempted to define fluid and metal source areas for various orogenic gold provinces fluid stable isotope values are commonly characterized by the following ranges 1 18 o for precambrian ores of 6 to 11 and for phanerozoic ores of 7 to 13 2 d and 34 s values that are extremely variable 3 13 c values that range from 11 to 2 and 4 15 n of 10 to 24 for the neoarchean 6 5 to 12 for the paleoproterozoic and 1 5 to 10 for the phanerozoic secular variations in large scale earth processes appear to best explain some of the broad ranges in the o s and n data fluid rock interaction particularly in ore trap areas may cause important local shifts in the o s and c ratios the extreme variations in d mainly reflect measurements of hydrogen isotopes by bulk extraction of waters from numerous fluid inclusion generations many which are not related to ore formation radiogenic isotopes such as those of pb sr nd sm and os measured on hydrothermal minerals are even more difficult to interpret for defining metal source particularly as the low salinity ore fluids transport limited amounts of these elements and significant amounts of these may be locally added to the minerals during alteration reactions at the sites of gold deposition noble gas and halogen data are equally equivocal fluid exsolution from granitoids emplaced into the upper and middle crust metamorphism of the crust or fluids entering trans crustal fault zones from below the crust all remain as permissive scenarios associated with orogenic gold formation as the abundant geochemical data are equivocal however geological and geochronological data weigh heavily against a magmatic hydrothermal model in the upper to middle crust there is no universal temporal association between orogenic gold and magmatism and where there is an overlap in age there is no specific type of magmatism consistently associated with gold formation nor element zonation around any specific pluton a crustal metamorphic model for fluid and metal sources is very consistent with geological geochronological and geochemical data although metamorphism on a regional scale that releases these components into major fault zones can be associated with many processes along active continental margins these can include crustal thickening and radiogenic heating slab rollback and heating during crustal extension or subduction of a spreading ridge heating the base of an accretionary prism in rare examples where phanerozoic orogenic gold deposits are hosted in precambrian high grade metamorphic terranes fluids and metals must however enter a transcrustal fault system from a sub crustal source this could either be a devolatilized subducted relatively flat perhaps stalled slab and its overlying sediment or the corner of the fertilized mantle wedge that releases a fluid during a thermal event

in situ la icp ms u pb geochronology and trace elements analysis of polygenetic titanite from the giant beiya gold polymetallic deposit in yunnan province southwest china abstract the beiya gold polymetallic deposit located in the middle of the jinshajiang ailaoshan alkaline porphyry metallogenic belt is one of the largest gold deposits in china the mineralization mainly occurs in skarn along the intrusive contacts between the alkaline porphyries and middle triassic limestone in this paper we present u pb age as well as major and trace element geochemistry of titanite from the beiya deposit and distinguish the titanite into a magmatic and a hydrothermal suite our study indicates that the titanite from the ore related porphyry and from the mineralized skarn is texturally and geochemically very different the euhedral envelope shaped titanite from the ore related porphyry has lower feo f hfses nb ta and lu hf together with higher tio2 and th u than the subhedral titanite from the mineralized skarn the titanite from the porphyry also displays higher lree hree and more subtle negative eu anomaly than its mineralized skarn counterpart this suggests a magmatic and a hydrothermal origin for respectively the titanite from the ore related porphyry and from the mineralized skarn in situ magmatic titanite u pb dating has yielded an eocene age of 36 0 5 9 ma consistent with the porphyry zircon u pb age 36 07 0 43 ma obtained in previous studies hydrothermal titanite has yielded a weighted average 206pb 238u age of 33 1 1 0 ma mswd 2 0 which represents the age of the retrograde skarn alteration and the maximum age for the gold mineralization together with the previous molybdenite re os age we have further constrained the beiya gold polymetallic metallogeny to 33 1 34 1 ma the mineralization age is slightly younger than the porphyry emplacement indicating that the beiya metallogeny was likely to be a post magmatic hydrothermal product of the himalayan orogenic event the ree characteristics of hydrothermal titanite also reveal that the ore forming fluids may have been derived from a highly oxidized magma

late permian to early triassic changes in acritarch assemblages and morphology in the boreal arctic new data from the finnmark platform abstract the late permian extinction interval is in many marine locations characterized by the development of anoxic conditions the finnmark platform is one of few exceptions as sedimentological and palynofacies evidence indicate oxygenated conditions throughout the event changes in acritarch assemblages and morphology were studied in order to better understand the link between acritarchs and environmental conditions the main taxa are of micrhystridium baltisphaeridium and leiospheres while veryhachium and the prasinophytes cymatiosphaera and tasmanites were present in low abundances increased concentrations of acritarchs particularly micrhystridium show that the environmental changes at the start of the extinction event may have resulted in enhanced marine productivity a shift from micrhystridium baltisphaeridium dominance before and during the extinction event to leiosphere dominance after the extinction event indicates a shift towards a more inshore environment the new data are compared with published late permian acritarch records from east greenland china and pakistan a striking difference between the east greenland and finnmark platform which are both expanded upper permian lower triassic sections is that the acritarch record from greenland shows a strong decrease in process length of the acritarch micrhystridium together with a change in the acritarch assemblage this change in morphology was interpreted to represent a decrease in salinity at the site resulting from increased run off the differences between the east greenland and the finnmark records are likely due to their palaeogeographical settings as the east greenland section was located in a narrow and elongated basin which was likely more sensitive to evaporation and run off changes than the finnmark platform

reconstructing salinity changes and environmental influence on dinoflagellate cysts in the central baltic sea since the late 19th century abstract we present a record of dinoflagellate cyst assemblage composition abundance and morphology from the central baltic sea spanning the late 19th to the early 21st centuries environmental time series were analyzed in relation to changes in community structure and diversity as inferred from the sediment record and average summer sea surface salinity sss was reconstructed based on the average process length of protoceratium reticulatum resting cysts the reconstructed summer sss was compared to instrumental data for a critical evaluation of this approach the most abundant species in this record were p reticulatum and biecheleria baltica and on average ten taxa were identified per sample the cyst record of b baltica indicated that although this species has been present in the gotland basin at least since the 1880s its concentrations have increased significantly since the 1980s possibly linked to eutrophication variations in assemblage composition and p reticulatum cyst morphology reflected patterns of major instrumentally recorded hydrographic and environmental changes in the baltic sea during the past century the variability in microfossil relative abundances was best explained by the average spring sss as well as by the average no3 concentrations during spring and by the combined effects of average summer sss and nao variability reconstructed summer sss and instrumental sss showed notable differences depending on the year and function applied for reconstruction although roughly reflecting the same patterns the reconstructed values are offset when compared to instrumental measurements we put forward suggestions for improvement of the process length method and recommend using the reconstructed values as an indication of relative changes in past summer sea surface salinity preferably as part of a multiproxy approach