mid and late holocene fluvial dynamics in the tropical guapi macacu catchment southeast brazil the role of climate change and human impact abstract deeply incised middle to late holocene fluvial sediments of several streams in the tropical guapi macacu river catchment in the state of rio de janeiro were investigated with stratigraphical sedimentological and geochronological methods these investigations revealed multiple changes of the fluvial dynamics during the holocene triggered by a millennial climate change and the post colonial increase of land use reduced fluvial dynamics and geomorphic stability prevailed in this region during the relatively dry mid holocene from 6 6 until 4 7 cal ka bp this phase of stability was followed by a period of geomorphic activity as indicated by increased fluvial dynamics from this date this overall environmental change corresponds well with the onset of quasi modern humid climate conditions in southeastern brazil during the mid to late holocene transition a new period of activity has taken place since 0 29 cal ka bp in relation with the start of european colonization and increased land use pressure large areas of atlantic forests were converted into agricultural and pasture land causing strong soil erosion and destabilized slopes the results of these investigations improve the existing holocene landscape evolution model and highlight that under the given specific climatic and environmental conditions even a closed forest cover does not necessarily result in geomorphic stability

scouring of gold from the lower crust quartz carbonate lodes have produced a major part of the world9s gold the source for the lodes which were emplaced along shear zones in the upper crust has been enigmatic the bamble belt of south norway is depleted in gold by more than an order of magnitude relative to its crustal abundance other elements present in gold deposits have also been lost gold dissolved and was removed in oxidized sulfur rich fluids rising through this broad ductile shear zone during high grade metamorphism deformation synchronous with metamorphism created the permeability that permitted a pervasive flow of fluids

present day south american climate abstract this paper documents the main features of the climate and climate variability over south america on the basis of instrumental observations gathered during the 20th century it should provide a modern reference framework for paleoclimate research in south america targeting high resolution proxies over the past few centuries several datasets suitable for present day climate research are first described highlighting their advantages as well as their limitations we then provide a basic physical understanding of the mean annual cycle of the precipitation and atmospheric circulation over the continent and the adjacent oceans in particular the diversity of precipitation temperature and wind patterns is interpreted in terms of the long meridional extent of the continent and the disruption of the large scale circulation caused by the andes cordillera the contrasting oceanic boundary conditions and the landmass distribution similarly the intensity and timing of the interannual and interdecadal climatic fluctuations exhibit considerable geographical dependence as some regions are more influenced by large scale phenomena rooted in the tropical oceans while others are more influenced by high latitude phenomena the impact of these large scale phenomena over south america is documented by a regression analysis between selected atmospheric indices and the precipitation and temperature fields we have included a discussion on the seasonality and long term stability of such impacts and complemented our general description by an updated review of the literature on climate variability over specific regions

weathering limited rainfall triggered shallow mass movements in undisturbed steepland tropical rainforest rainfall triggered landslides in undisturbed tropical rainforests may have been underestimated as contributors to slope development and denudation in the past theoretically ideal conditions for such geomorphic processes i e steep slopes and frequent high magnitude and intensity rainfall events occur in a number of tropical regions particularly within southeast asia therefore a high frequency of occurrence of shallow slope failures was expected in the undisturbed steeplands of southeast brunei stability conditions of the steep planar slopes were examined using a deterministic modelling approach in order to examine the possibility that most slopes could not fail in response to rainfall because they did not possess a sufficiently thick mantle of residual soil a simple hillslope hydrology model based on a soil moisture balance approach was used to simulate hillslope responses to measured and simulated rainfall events the stability of saturated slopes could then be analysed using the infinite slope model the input shear strength parameters for which were obtained from direct shear tests and then calibrated by back analysis of a failure which occurred in late 1991 the findings suggest that any slope of 40 and steeper should fail several times every year in response to storm events but that in reality most of the slopes have failed previously and have not yet regained a critical depth of residual soil some approximate values for rates of weathering and slope development suggest that any given slope will not fail at intervals of less than 10 000 years therefore the occurrence of shallow failures will be infrequent but nevertheless significant in terms of regional denudation and ecological diversity

mineral chemical and isotopic studies of namaqualand granulites south africa a grenville analogue the northwestern part of south africa and southern south west africa namibia is amongst the most extensive granulite terranes in africa this work reports the results of electron microprobe studies of minerals from two pyroxene cordieriteorthopyroxene gedrite sapphirine and garnet and or cordierite parageneses from namaqualand in the n w cape province of south africa determined pt conditions of prograde metamorphism based on thermodynamic calculations are 800 900 c and ca 6 7 kb and it is argued that rocks of unusual composition notably cordierite orthopyroxene rocks are restites after the extraction of granitic liquid from former argillites this interpretation is consistent with previously published data on similar rocks and with mccarthy s 1976 suggestion of extensive partial melting in the quartzofeldspathic rocks in the area

petrochemistry of the okiep copper district basic intrusive bodies northwestern cape province south africa copper mineralization is associated with noritic and pyroxenitic rocks in the granulite facies metamorphic terrane in the okiep district of namaqualand in the northwestern cape province of south africa these bodies have been interpreted to be postmetamorphic and the mineralization has been inferred to be magmatic however the sulfide mineralogy of many of the orebodies is dominated by bornitc whereas immiscible magmatic sulfide ores contain pyrrhotite and chalcopyrite hence the okiep ores cannot be primary magmatic sulfides geochemical evidence is presented to demonstrate that the ores have undergone an extensive oxidative event in which pyrrhotite and chalcopyrite were converted to magnetite and bornite up to 90 percent of the sulfur has been lost in the case of some samples from the carolusberg mine the high fe 2 o 3 tio 2 and cu s ratios the low s se ratio of whole rock samples and their variation in different orebodies provide quantitative evidence for this process it is possible to recalculate the original sulfide from these data and a cu content of approximately 10 percent is indicated however these ores only contain on the order of hundreds of parts per million of ni and so the cu ni ratio is extremely high compared to that of most sulfide ores derived from a differentiated basic magma the textural and mineralogieal evidence for this oxidation is best seen in samples from the carolusberg mine in many of the other mines a later low temperature hydrothermal alteration has obliterated the evidence for these reactions

holocene landscape evolution along the andean piedmont bolivian chaco abstract as part of the gran chaco the andean piedmont in eastern bolivia is characterized by a highly seasonal climate and large rainfall variability it receives sediments from small drainage basins in the subandean ranges therefore it should constitute a suitable sedimentary and geomorphic archive for the detection of past environmental changes this study reconstructs holocene landscape evolution along the andean piedmont in the bolivian chaco by combining large scale geomorphological analysis and the investigation of sedimentary sequences fluvial aggradation and channel avulsions are the dominant processes of piedmont construction and were particularly pronounced during the mid holocene this is interpreted to reflect a generally active landscape characterized by reduced forest cover as result of increased aridity widespread soil formation and landscape stability in all investigated catchments start after 4 cal ka bp indicating the onset of wetter conditions and successively denser forest cover in the bolivian chaco renewed sedimentation during the last millennium could imply a shift to more arid environmental conditions probably in relation to larger scale climatic phenomena such as the little ice age lia particularly during the last centuries the fluvial system of the study area has undergone the most profound changes of the entire holocene with sedimentation of very coarse sediments and subsequent incision this reflects important changes both in discharge and sediment supply and might be the result of either shorter term climate changes or increasing human impact

rapid subtropical north atlantic salinity oscillations across dansgaard oeschger cycles geochemical and sedimentological evidence suggest that the rapid climate warming oscillations of the last ice age the dansgaard oeschger cycles were coupled to fluctuations in north atlantic meridional overturning circulation through its regulation of poleward heat flux the balance between cold meltwater from the north and warm salty subtropical gyre waters from the south influenced the strength and location of north atlantic overturning circulation during this period of highly variable climate here we investigate how rapid reorganizations of the ocean atmosphere system across these cycles are linked to salinity changes in the subtropical north atlantic gyre we combine mg ca palaeothermometry and oxygen isotope ratio measurements on planktonic foraminifera across four dansgaard oeschger cycles spanning 45 9 59 2 kyr ago to generate a seawater salinity proxy record from a subtropical gyre deep sea sediment core we show that north atlantic gyre surface salinities oscillated rapidly between saltier stadial conditions and fresher interstadials covarying with inferred shifts in the tropical atlantic hydrologic cycle and north atlantic overturning circulation these salinity oscillations suggest a reduction in precipitation into the north atlantic and or reduced export of deep salty thermohaline waters during stadials we hypothesize that increased stadial salinities preconditioned the north atlantic ocean for a rapid return to deep overturning circulation and high latitude warming by contributing to increased north atlantic surface water density on interstadial transitions

high resolution fluvial record of late holocene geomorphic change in northern tunisia climatic or human impact abstract in northern tunisia the late holocene alluvial record of medjerda floodplain sediments indicates geomorphic changes due to fluctuations of past climate superimposed by the effects of human activity geomorphic activity occurred several times interrupting stable conditions enhanced fluvial dynamics occurred around 4 7 3 0 1 7 1 0 and 0 7 ka cal bp a peak of activity took place about 0 4 ka cal bp some periods of fluvial activity show event like phenomena in particular when an anthropogenic impact intensifies climatic aridification this has been the case around 1 7 1 0 0 7 and 0 4 ka cal bp with severe floods in the medjerda valley during antiquity as well as around 1 3 0 8 and 0 5 ka cal bp immature alluvial soils have developed the first one being the most distinct late holocene medjerda alluvial history shows that fluvial dynamics in northern tunisia were predominantly climate driven anthropogenic impact only intensified or weakened these processes

u pb zircon calendar for namaquan grenville crustal events in the granulite facies terrane of the o okiep copper district of south africa s xvi geokongres geological society of south africa stellenbosch pp 160 163 van zyl d 1978 a petrological approach towards the ore bearing potentialities of the okiep basic intrusives in namaqualand in verwoed w j ed mineralization in metamorphic terranes geological society of south africa special publication 4 323 329 vellet v 1958 the geology of the copper district namaqualand cape province south africa unpublished report of the o okiep copper company 110 pp waters d j 1989 metamorphic evidence for the heating and cooling path of namaqualand granulites in daly j s cliff r a yardley b w d eds evolution of metamorphic belts geological society london special publication 43 357 363 williams i s claesson s 1987 isotopic evidence for the precambrian provenance and caledonian metamorphism of high grade paragneisses from the seve nappes scandinavian caledonides ii ion microprobe zircon u th pb contributions to mineralogy and petrology 97 205 217 clifford et al crustal events in o okiep district

drought impacts on the fresh water potential of a karst aquifer in crete greece malia s coastal aquifer supplies water for domestic and irrigation purposes most of northern part of heraklion prefecture central crete the extensive exploitation of groundwater since the late 1960s has resulted in a continual decline in groundwater level and significant degradation in groundwater quality due to salinity intrusion in the coastal aquifer moreover the aquifer will likely to experience impacts of climate driven recharge changes in the coming years with adverse consequences for water supply in the region a regional groundwater flow model was developed to simulate the existing hydrogeological system and to evaluate the effects of combined impacts of groundwater exploitation and climate variability in future the investigation results suggest that the equivalent porous medium epm approach appears reasonable for the karst aquifers on a regional scale as it is capable to simulate the groundwater flow and the spreading of chloride concentration with sufficient accuracy however locally the transport of saline water may depend primarily on the karst conduit network rather than matrix permeability therefore the point information must be evaluated and not taken as undisputed furthermore the study provides a valuable guidance on predicting the seawater intrusion in aquifers under similar hydrogeological conditions and offers a considerable issue in management of the groundwater quality deterioration

mid and late holocene fluvial chronology of tunisia abstract regarding fluvial response to recent climate change it is important to identify and understand previous changes of fluvial dynamics related to past climatic shifts in this paper periods of increased flood activity in central tunisian river systems are presented changes in holocene flood dynamics are reconstructed through a comprehensive analysis of 195 radiocarbon dates from alluvial archives holocene floodplain deposits in central tunisia normally consists of cohesive overbank fines which exhibit excellent preservation conditions against lateral erosion and therefore permit chronostratigraphic records of the entire holocene at most based on published radiocarbon dates two 14 c cumulative probability density plots are created for central tunisia the former represents activity dates indicating phases of increased fluvial dynamics the latter documents stability dates showing periods of soil formation and enhanced landscape stability within the floodplain and the catchment due to geomorphological considerations activity dates and stability dates should be mutually exclusive there is a good match for the mid holocene with increased periods of flooding from 6 2 to 6 0 4 8 to 4 5 4 1 to 3 7 and 3 3 to 3 0 ka these flood periods coincide with low soil formation signals on the other hand periods of increased alluvial soil formation from 6 8 to 6 6 5 9 to 4 8 4 5 to 4 1 3 7 to 3 3 3 0 to 2 8 and 1 8 to 1 6 ka coincide with periods of low flood plain aggradation the data reveal a coupling with north atlantic cooling short term periods of enhanced fluvial dynamics in central tunisia match well with north atlantic cooling the findings indicate a strong climatic link from 4 7 ka until today compared to the holocene floodplain dynamics in tunisian drylands the temperate mid latitudes show mid holocene switches in fluvial dynamics with opposite signs especially after 5 ka north atlantic driven flooding in the temperate central european river systems contrast sharply to flood dynamics in arid to semiarid mediterranean tunisia while under temperate climate conditions floodplain sedimentation decreases it increases under more arid conditions this may indicate that fluvial archives of dissimilar climatic zones reveal different threshold values and sedimentation patterns and therefore different responses to climatic shifts

eemian and post eemian fluvial dynamics in the lesser caucasus abstract mountain regions such as the lesser caucasus are a focus of ongoing environmental changes to understand their future evolution information about their former geomorphic and environmental dynamics is required the former fluvial dynamics derived from fluvial sediment archives can offer such insights however the fluvial dynamics of the lesser caucasus since the eemian interglacial have not been systematically investigated so far thus we have studied late pleistocene and holocene sediments of several rivers originating from the central lesser caucasus the studied rivers show a mostly coherent record of fluvial dynamics minor aggradation occurred during early marine isotope stage mis 5 incision during late mis 5 or early mis 4 intensive silty aggradation at least during late mis 3 incision during early mis 2 coarse grained aggradation probably during some millenia until ca 19 ka and aggradation ca 14 13 ka following incision around the pleistocene holocene transition aggradation resumed around 6 0 3 4 2 0 and 0 5 0 15 cal ka bp generally periods of aggradation incision and stability could be linked with regional climatic or anthropogenic influences on regional landscape stability and water availability the fluvial dynamics of the central lesser caucasus mostly differed even between neighbouring regions and only in cases of significant hemispheric climatic fluctuations as around 20 ka during the pleistocene holocene transition or the little ice age were similar over regional fluvial patterns observed this demonstrates the individual character of river systems especially in mountain regions such as the southern caucasus with strong geoecological gradients thus to understand the former landscape dynamics of mountain landscapes investigations of fluvial sediment archives on a regional to sub regional scale are necessary

comment on linked variations in sediment accumulation rates and sea level in guanabara bay brazil over the last 6000 years by alberto g figueiredo jr mauro b de toledo renato c cordeiro jose m o godoy fabiano t da silva sergio c vasconcelos ricardo a dos santos palaeo 415 2014 83 90

a critical review of mid to late holocene sea level fluctuations on the eastern brazilian coastline abstract the eastern coast of brazil is 7000 km long and has been the subject of systematic paleo sea level investigations for more than 35 years more than 1000 samples have been radiocarbon dated and paleo sea level trends have been determined for 14 coastal sectors these trends have in common a mid holocene sea level maximum pmt above present sea level and a subsequent fall to the present time the time and elevation of the pmt the time when relative sea level rose above present mean sea level and the nature of late holocene sea level fall can however differ significantly discrepancies are observed not only between neighboring coastal sectors but also between different studies in a same coastal sector this paper discusses all the key radiocarbon dated samples used to establish regional trends in relative sea level on the eastern coast of brazil it is concluded that although many of the key sea level indicators are imprecise in time and space there is widespread evidence 30 of the data set for a progressive decline possibly with uneven rates of relative sea level since the end of the pmt

strong hemispheric coupling of glacial climate through freshwater discharge and ocean circulation the climate of the last glacial period was extremely variable characterized by abrupt warming events in the northern hemisphere accompanied by slower temperature changes in antarctica and variations of global sea level it is generally accepted that this millennial scale climate variability was caused by abrupt changes in the ocean thermohaline circulation here we use a coupled ocean atmosphere sea ice model to show that freshwater discharge into the north atlantic ocean in addition to a reduction of the thermohaline circulation has a direct effect on southern ocean temperature the related anomalous oceanic southward heat transport arises from a zonal density gradient in the subtropical north atlantic caused by a fast wave adjustment process we present an extended and quantitative bipolar seesaw concept that explains the timing and amplitude of greenland and antarctic temperature changes the slow changes in antarctic temperature and its similarity to sea level as well as a possible time lag of sea level with respect to antarctic temperature during marine isotope stage 3

variability of the south atlantic convergence zone simulated by an atmospheric general circulation model interannual and decadal variability of the south atlantic convergence zone sacz during austral summer season january february march jfm is investigated an attempt is made to separate the forced variability from the internal variability this is accomplished by applying a signal to noise optimization procedure to an ensemble of multidecadal integrations of the latest version of the ncar community climate model ccm3 forced with observed sst the result yields two dominant forced atmospheric responses a local response to atlantic sst anomalies with interannual decadal timescales and a remote response to pacific sst anomalies at interannual timescales the former is localized within the south atlantic ocean with almost no signal over land consisting of a dipolelike structure in precipitation close to the coast of south america accompanied by a clockwise anomalous circulation of surface winds the latter manifests itself mainly in the upper level circulation consisting of a northeastward shift of the sacz with associated rainfall anomalies during warm enso events

rare earth element geochemistry of an anorthosite diorite suite namaqua mobile belt south africa abstract a swarm of small dyke like plutons ranging in composition from anorthosite through diorite and norite to hypersthenite and glimmerite occurs in the western part of the namaqua mobile belt south africa known as the koperberg suite these rocks host important magmatic sulphide deposits zircon ages of approximately 1100 ma suggest that the suite was emplaced after the peak of the regional high grade metamorphism dated at 1200 ma a postulated comagmatic origin for the various rock types is confirmed by the ree distributions of anorthosite leucodiorite diorite hypersthenite and glimmerite the koperberg suite resembles the well known massif anorthosite complexes typified by the adirondack suite in most properties except for the dispersed mode of occurrence it is now shown that the similarity also holds for the ree spectra thus the predominant anorthosite and leucodiorite of the koperberg suite are comparable to similar rocks of the adirondacks and the burwash area ontario albeit more enriched in lree more mafic rock types such as norite mica diorite and glimmerite are substantially enriched in lree compared to mafic differentiates of massif anorthosites apatite is abundant in the mafic rocks and stores large proportions of the lanthanides the occurrence of apatite and mica rich assemblages indicates source magmas enriched in k ree and p a few intrusives exhibit excessively enriched ree patterns which are attributed to late hydrothermal alteration or metasomatism the ree data for syenite and two pyroxene assemblages from the copper district argue against a genetic relationship to the koperberg suite in spite of close spatial association

geochemical constraints of the petrogenesis of the o okiep koperberg suite and granitic plutons in namaqualand south africa a crustal source in namaquan grenville times the namaquan grenville orogeny late mesoproterozoic in the o okiep district is characterized by two tectono magmatic episodes the o okiepian episode 1210 1180 ma with the intrusion of batholitic granites and the klondikean episode 1040 1020 ma which includes the intrusion of the copper bearing koperberg suite and the rietberg granite this study focuses on the geochemistry major and trace elements sr and nd isotopes of intrusive rocks of the o okiep terrane to provide better constraints on their source rock characteristics and on their petrogenesis the o okiepian granites belong to the k rich granite kindred with shoshonitic affinities the concordia granite results from dehydration melting of a pelitic source the rietberg granite shows geochemical similarities with post collisional magmatic series the anorthosites and related rocks of the koperberg suite are cumulates their ree distribution is controlled by their apatite content a new rock type jotunite has been identified in the koperberg suite it is analogous to the rogaland chilled jotunite a characteristic which gives strong evidence that the koperberg rocks belong to the massif type anorthosite suite inversion modelling of plagioclase ree compositions from anorthosite permits the reconstruction of melt compositions and places constraints on the melting process and on the characteristics of the source rocks the occurrence of jotunite in the koperberg suite is strong additional evidence for a crustal source because jotunite is produced by remelting of gabbronorite under dry conditions the various intrusions in the koperberg suite show distinct isotopic signatures which resulted from isotopic heterogeneities of the crustal source and from minor contamination with the country rocks the characteristic negative end 1030 ma values 5t o 11 can be explained by remelting at 1030 ma of a 1900 ma old oceanic crust protolith with an enriched morb ree distribution the large range in sr initial ratios 0 709 0 748 may reflect hydrothermal alteration of the oceanic crust a process which may also explain the cu enrichment the koperberg intrusions were produced by forceful injection of cumulate crystal mush which were differentiated in deeper magma chambers or in conduits

geochemical and isotopic characteristics of different types of anorthosite in the namaqua mobile belt south africa abstract anorthosite genesis in the proterozoic namaqua mobile belt of south africa encompasses a range of intrusive histories including massif type as in the occurrences of plat sjambok and possibly koperberg suite and layered type as at oranjekom different compositional ranges at all levels of analytical resolution mineralogical geochemical and isotopical are revealed there is a spectrum from orthopyroxene dominance and extremely high lree koperberg suite to clinopyroxene horn blende dominance with normal ree patterns oranjekom plat sjambok and low iron oranjekom isotopic data for the various complexes rb sr sm nd indicate differences in magma evolution the oranjekom complex represents a depleted mantle origin with low to moderate contamination sr 6 to 9 nd 7 to 9 while the plat sjambok complex reflects a depleted mantle origin with a noticeable contribution from a crustal component sr 40 to 150 nd 5 to 1 in contrast the koperberg suite sr 300 nd 9 if derived from the mantle would require mixing between a highly enriched mantle source and an extremely enriched crustal contaminant high sr 700 to 800 nd 2 resulting in an unusual isotopic trend with a positive slope the waterkop pluton that has in the past been regarded as related to the plat sjambok complex represents a quite different syenitic magma from a slightly enriched mantle source with very little contamination and is not a cogenetic with the latter collectively the analytical data support original magma generation from different mantle sources followed by various intrusive histories ranging from rapid transit between source and emplacement in the upper crust oranjekom to prolonged travel and differentiation involving considerable crustal contamination koperberg suite the fact that the different intrusive types occur in different suspect terranes of the mobile belt may reflect originally contrasting tectonic settings during a late proterozoic continental collision that played a role during the assembly of rodinia

millennial scale precipitation changes in southern brazil over the past 90 000 years 1 a u th dated 90 000 year long speleothem oxygen isotope record from southern brazil anti correlates remarkably with the cave calcite records from eastern china but positively correlates with the speleothem record from northeastern brazil suggesting an interhemispheric anti phasing of rainfall on both millennial and orbital timescales likely related to displacement in the mean position of the intertropical convergence zone and associated asymmetry in hadley circulation the phase relationships among these records are consistent with the hypothesis that abrupt climate events during the last glacial period are triggered by oceanic circulation changes in the high latitudes and enhanced by tropical feedbacks

mineralization u pb geochronology and stable isotope geochemistry of the lower main zone of the lorraine deposit north central british columbia a replacement style alkalic cu au porphyry the lower main zone of the lorraine alkalic porphyry cu au district bc canada is hosted in an intrusive complex that comprises pre and late mineral biotite pyroxenites monzonites and syenites some of the biotite pyroxenites have interstitial sulfides which appear similar to net textured sulfides in magmatic ore deposits however the pyroxenites have undergone several stages of hydrothermal alteration main stage mineralization produced sulfide zonation patterns consisting of a bornite chalcocite or bornite chalcopyrite core grading outward to domains of chalcopyrite chalcopyrite pyrite and a peripheral domain of pyrite with minor chalcopyrite syenite in the inner bornite chalcopyrite zone typically contains abundant turbid k feldspar 70 whereas syenite marginal to the bornite chalcopyrite core contains less k feldspar 50 70 indicating an increase in k metasomatism of syenites toward the core of the deposit main stage mineralization predominantly occurs as fine grained disseminated sulfides in syenite biotite pyroxenite and fine grained k feldspar biotite rock textural analyses have shown that 1 primary magmatic diopside in contact with sulfides has corroded and actinolite altered margins suggesting alteration of primary minerals 2 scalloped relicts of biotite and diopside occur as inclusions in sulfides implying that sulfides have replaced primary minerals and 3 the deposit scale sulfide zonation patterns overprinted numerous rock types including the biotite pyroxenites that contain interstitial sulfides these results provide evidence for replacement style mineralization at lorraine where primary magmatic biotite and diopside were totally or partially replaced by sulfide minerals during main stage alteration u pb zircon dates from pre and late mineral syenite dikes show that the timing of main stage mineralization occurred between 178 8 and 176 0 ma lorraine is hosted within the quesnel island arc terrane and mineralization and magmatism at lorraine postdate accretion of the quesnel terrane to ancestral north america by approximately 7 to 10 m y the lorraine deposit represents the youngest known alkalic cu au porphyry deposit within the quesnel terrane and appears to coincide with the last gasp of alkalic magmatism within the quesnel terrane during the mesozoic

osl dating of sediments from a mountainous river in southeastern brazil late cenozoic tectonic and climatic implications abstract the upper das velhas river basin is located in the central portion of the quadrilatero ferrifero in southeastern edge of sao francisco craton southeastern brazil its drainage network has a strong lithostructural influence and mountainous river segments crossing different tectonic blocks the neotectonic activity in this cratonic edge is associated with epirogenetic brazilian shield uplift and with local and regional differential movements of crustal blocks due to wnw migration of south american plate this process cause an intraplate transfer of tectonic efforts forcing the reactivation of old faults nw se and ne sw and the generation of recent ones e w using optically stimulated luminescence osl dating and fluvial deposit data this paper focuses on the late cenozoic evolution of this mountainous river basin relating it to tectonic and climatic forcing even with few records of ancient alluvial deposits as a result of intense dissection three levels of river terraces were identified in some sites along the valley a higher terrace level t3 a cut in bedrock terrace of 48 ka an intermediate terrace level t2 of 7 5 ka and a lower terrace level t1 of 1 ka the t2 is found along the valley as a cut in bedrock terrace or as a fill terrace and is found t1 as a cut in bedrock terrace or as a nested fill terrace or even overlapping t2 sediments the diverse relation between these terraces may be related to unequal fluvial downcutting we identified three main downcutting periods i before t3 ii from t3 to t2 related to late pleistocene regional tectonics and iii from t2 to t1 which was a response to tectonics and climate change in the early holocene these stages of more intense downcutting should be a response to uplift pulses in the most active blocks cut in bedrock terraces show a greater unevenness in relation to lower levels while in the most stable blocks t1 is found as a nested fill terrace or overlapping t2

the south atlantic convergence zone intensity form persistence and relationships with intraseasonal to interannual activity and extreme rainfall abstract the characteristics of intensity geographical location and persistence of the south atlantic convergence zone sacz during the austral summer are investigated intensity and spatial features of the sacz are identified by performing a factor analysis of structural properties of outgoing longwave radiation olr data the first two leading factors explain 65 of the total variance of structural properties and characterize the sacz according to intensity and location oceanic versus continental an index is constructed based on the magnitude of the factor scores to identify intense weak and oceanic continental sacz the intense sacz category is associated with negative olr anomalies over a large area of tropical south america extending from the western amazon to the atlantic ocean the weak sacz category is observed with positive olr anomalies over tropical south america and negative olr anomalies over southeastern south america oceanic and continental aspects of the sacz are related to a

interpreting drivers of change in fluvial archives of the western mediterranean a critical view abstract fluvial archives in particular late glacial to holocene floodplain records may provide valuable information regarding past environmental conditions and stages of landscape evolution in view of the high significance of floodplain dynamics for the development of entire landscapes the number of studies that have been performed on floodplain sediments remains comparatively low especially regarding the western mediterranean region however one of the reasons could be seen in the high complexity and diversity of processes and factors that control and influence fluvial activity that often hampers a straightforward interpretation of floodplain dynamics therefore a basic demand on fluvial archive research is to address the complexity of the factors that control the characteristics of fluvial sequences in order to provide a robust basis for their interpretation as a starting point for discussion this paper aims to give an overview of fluvial dynamic patterns in the western mediterranean for the last 15 ka in order to examine their relevance for palaeoenvironmental reconstructions the basis for this is provided by previous investigations on four different river systems in spain and northern africa the results of which are herein synthesized in order to propose a regional late pleistocene and holocene fluvial history for the western mediterranean realm basic results are related to alluvial floodplain deposits and visible features within them such as alluvial soils incision marks and aggradation phenomena since fluvial systems are open systems we discuss our findings against the background of different influencing factors that could modify fluvial architecture and may restrict palaeoenvironmental reconstructions a more comprehensive interpretation focuses on signals that are common to each of the studied river systems in this respect we critically discuss the customary nature of cumulative probability functions for the identification of regional flooding episodes and point out the benefits of a stratigraphy supported approach for characterizing regional floodplain dynamics finally three alluvial soil formation periods were found in all settings a first phase after 15 ka ending with the younger dryas event a second one from 7 to 5 ka with a break between 6 5 and 5 5 ka and a third phase between 3 and 2 ka these soil formation periods were interrupted and framed by fluvial dynamic phases accompanied by channel aggradation floodplain deposition floodplain erosion and or river incision in particular after 5 ka around 1 6 and at 1 ka and during the little ice age lia floodplain aggradation affected river systems in iberia and northern africa as well a cautious assessment of these results and extensive comparisons with secondary archive information prompts us to relate the aggradation periods with climate forcing by means of a supra regional aridification that effected large areas of the western mediterranean in contrast the three mentioned soil formation periods can be linked with landscape stability most probably triggered by favorable climate conditions in the western mediterranean apart from these large scale patterns we discuss the reliability of information emerging from floodplain records against the background of individualistic river behavior and self organization regarding future work we want to emphasize the great potential of yet rarely applied system oriented approaches that also attach importance to sub catchment dynamics as a link between catchment slopes and the main river floodplain

interactions between sea surface temperature over the south atlantic ocean and the south atlantic convergence zone 1 interactions between the sea surface temperature sst over the south atlantic ocean 40 s equador and the south atlantic convergence zone sacz were studied through numerical experiments with an atmospheric general circulation model agcm and an ocean general circulation model ogcm the agcm experiments showed that warm sst anomalies over the south atlantic tend to intensify the sacz and shift it northward while cool sst anomalies over the south atlantic tend to weaken the sacz the ogcm experiments on the other hand showed that the intensification of the sacz contributes to cool the underlying ocean through the reduction of incident shortwave solar radiation causing the appearance of cold sst anomalies or the weakening of pre existing warm sst anomalies the most important finding in this work was the predominance of the cloud shortwave sst negative thermodynamic feedback between the atmosphere and the ocean over the southwest tropical atlantic this is one order of magnitude larger than the dynamic feedback associated with ekman pumping the latter was verified only during strong sacz events the results suggest that negative sst anomalies often observed underlying the sacz represent an ocean response to atmospheric forcing

what do yellowish brown soils and stone layers tell us about late quaternary landscape evolution and soil development in the humid tropics a field study in the serra dos orgaos southeast brazil abstract the occurrence spatial distribution and properties of yellowish brown soils and stone layers allow deriving conclusions about landscape evolution and soil development in the humid tropics in this study standard soil profiles and saprolite and subsoil samples along an altitudinal gradient from the high mountain ranges 1500 m a s l to the lowlands 8 m a s l in the serra dos orgaos mountain range in the brazilian state of rio de janeiro are analyzed field mapping techniques and laboratory methods are used to analyze the samples and reconstruct late quaternary landscape and soil development processes it is suggested that the formation of stone layers is polygenetic with dissolution processes geogenic bioturbation pedogenic and slope processes including coverage of terrace gravels geomorphic as possible mechanisms yellowing of the upper soil horizons is assumed to be the result of bio chemical processes xanthization chelation which took and take place in periods of wet climate conditions and closed forest cover in the late quaternary it can be distinguished between pre colonial and modern yellowish brown colluvial deposits with or without stone layer s it is suggested that the deposition of pre colonial colluvial soils primarily took place in dryer periods and forest retreat during the late pleistocene and holocene however it is proposed that the model of cyclic changes between geomorphic activity with colluviation on the one hand and stability and pedogenesis on the other hand need to be further differentiated due to small scale temporal and spatial climatic changes and sensitive vegetation responses to these fluctuations moreover it is suggested that due to the very steep relief and intense rainfall in the central mountain ranges of the serra dos orgaos accelerated displacement of soil material by landslides and mudslides took also place under closed forest cover in the late holocene modern colluvial deposits have originated from deforestation and land use intensification processes within the last 300 years they cover wide parts of the lower slopes foothills and depressions and indicate massive erosion and deposition processes since the european colonization

sensitivity of the thermohaline circulation to tropical and high latitude freshwater forcing during the last glacial interglacial cycle recent studies indicate that the tropical freshwater budget of the atlantic is modulated by changes in el nine southern oscillation enso if anomalies of the atlantic freshwater balance persist on the order of decades these might have a large influence on the north atlantic thermohaline circulation thc here we present a sensitivity study in which we use a model scenario for enso behavior during the last 120 kyr to force a simplified model of the thc with corresponding freshwater exchange between the tropical atlantic and pacific if the steady state strength of the north atlantic thc is similar to the present day its response to the forcing is of the order of 1 3 sv 1 sv 10 6 m 3 s 1 no mode changes of the thc are simulated for reasonable values of the coupling constant between freshwater exchange and enso if on the other hand the steady state overturning is significantly weaker a collapse of the thc occurs due to forcing from the tropics the modeled thc variation due to tropical freshwater perturbations are compared to those resulting from middle and high latitude freshwater forcing due to long term growth and decay of northern hemisphere ice sheets it is found that both forcings are of similar amplitude except during the deglaciation when high latitude forcing dominates a possible out of phase relationship between deep water formation in the north pacific and north atlantic is also explored

petrographical characteristics of the koperberg suite south africa an analogy to massif type anorthosites a swarm of anorthositic dioritic intrusives collectively termed the koperberg suite is scattered over an area of about 3000 km2 in the northwestern cape province namaqualand south africa the intrusive suite is renowned for its associated magmatic copper sulphide deposits transgressive field relationships and the preservation of primary igneous features suggest emplacement of the suite after the main metamorphic event which has been dated at c 1200 ma the distribution of the intrusions seems to have been controlled by vertical shearing which is manifested by antiformal disruptions steep structures in the country rocks post intrusion movement along some of these structures is deemed responsible for metamorphic textures in some mafic bodies igneous breccias associated with some intrusions present evidence of explosive tectonics at the time of emplacement the rock types which compose the mafic suite include andesine anorthosite leucodiorite hypersthene and mica diorite hypersthenite and glimmerite the occurrence of composite intrusions with two or more mafic varieties and the modal gradation between the rock types suggest consanguinity the anorthosite appears to be the oldest member of the series followed by increasingly more mafic varieties such as leucodiorite hypersthene diorite norite and hypersthenite owing to the presence of virtually monomineralic rock types various differentiation trends are recognized series that are dominated by hypersthene brown mica iron titanium oxides and amphibole can thus be delineated microprobe analyses of the major silicates indicate plagioclase compositions of andesine en58 68 for hypersthene and brown mica compositions on the biotite phlogopite boundary the predominance of anorthosite and leucodiorite in the suite suggest an affinity with the massif type anorthosite kindred this relation is supported by other criteria such as the preponderance of hypersthene the age of emplacement the sequence of intrusion en an ratios of plagioclase and hypersthene and the association of syenitic rocks as well as iron titanium oxide and apatite rich assemblages it is provisionally proposed that the okiep district represents the lower levels of an anorthosite complex of the massif type

variability in the mean latitude of the atlantic intertropical convergence zone as recorded by riverine input of sediments to the cariaco basin venezuela abstract changes in the strength and position of the intertropical convergence zone itcz are an important component of climate variability in the tropical atlantic the cariaco basin located on the northern margin of venezuela is sensitive to tropical atlantic climate change and its sediments provide a record of past itcz behavior today the cariaco basin experiences two distinct seasons that reflect the annual migration of the atlantic itcz between january and march when the itcz lies south of the equator northeasterly trade winds sit directly over cariaco basin and strong coastal upwelling and dry conditions dominate beginning in june july as the itcz moves north local rainfall reaches a maximum and the upwelling diminishes or disappears here we summarize new and previously published data on the river derived terrigenous fraction of cariaco basin sediments as well as comparisons to other paleoclimate records which together suggest a coherent climatologic response in the tropical atlantic triggered by a pattern of itcz migration that mimics the seasonal cycle during periods of cooler north atlantic ssts on time scales ranging from the little ice age to the younger dryas to the cold stadials of the last glacial decreased detrital delivery to cariaco basin from local rivers suggests a southward shift in the mean latitudinal position of the itcz during warm interstadials and periods of holocene and deglacial warmth northward shifts in itcz position and its belt of convective rainfall are inferred from increased detrital delivery to the basin whether the rapid shifts in itcz position and precipitation recorded by cariaco basin sediments and other regional records reflect a response to forcing originating in the high latitude atlantic or to forcing potentially sourced in the tropics is a key question yet to be fully answered

holocene river activity analysing 14c dated fluvial and colluvial sediments from germany records of fluvial dynamics in response to long term changes of climate and land use impacts are rare therefore cumulative probability functions cpfs of 401 14c ages originating from german rivers and hillslopes were compiled to reconstruct phases of increased geomorphic activity and stability during the holocene an improved analytical method is suggested to normalise cpfs and eliminated the effects of wiggles of the calibration curve and the young age bias nine periods of activity are identified peaking at 7050 6250 5525 3690 2250 1350 820 325 bc and since 875 ad and are compared with climatic palaeohydrological and human impact proxy data until 2250 bc events of geomorphic activity are mainly coupled to wetter and or cooler climatic phases due to growing population and intensive agricultural activities during the bronze age the increased geomorphologic activity between 1300 and 820 bc cannot unequivocally be related to climate since 875 ad the growing population density is considered as the major external forcing differential geomorphic activity of hillslopes and floodplains suggest that the hillslope channel coupling during the holocene is mainly controlled by human impact with a strong increased coupling after 1500 bc

paleocean circulation during the last deglaciation a bipolar seesaw hughen et al 1998 have documented that during the first 200 years of younger dryas time the 14c content of atmospheric co2 increased by 50 and that during the remainder of this 1200 year duration cold event it steadily declined the initial increase in 14c c was likely the result of a reduction in the atlantic s conveyor circulation however were the subsequent radiocarbon decline due to the rejuvenation of this potent heat pump then it is difficult to understand why the climate conditions in the northern atlantic basin remained cold throughout the younger dryas modeling exercises by stocker and wright 1996 mikolajewicz 1998 and schiller et al 1998 show that if the conveyor is terminated the transfer of radiocarbon into the deep sea shifts to the southern ocean thereby stabilizing the atmospheric 14c c ratio paleoclimatic evidence from the antarctic continent suggests that this model based scenario might have been played out in the real world while the younger dryas cooling has been documented in many places around the world including new zealand denton and hendy 1994 sowers and bender 1995 using their 18o in o2 based correlation between the ice core 18o in ice records for antarctica and greenland have demonstrated that in antarctica the younger dryas was a time of maximum warming the point of this paper is that the steep rise in 18o rise in antarctic ice which commenced close to the onset of the younger dryas might have been caused by heat released to the atmosphere in response to an increase in deep sea ventilation in the southern ocean

cold season synoptic scale waves over subtropical south america the most active winter synoptic scale wave patterns over south america are identified using an extended empirical orthogonal function eeof technique and are physically diagnosed using composite methods results show that the leading modes of short timescale variability propagate along two main paths over the subtropical jet latitudes 308s and over the subpolar jet latitudes 608s this research focuses on the subtropical mode and its evolution over south america the observed structure of the systems associated with the subtropical mode resembles that of midlatitude baroclinic waves both cyclonic and anticyclonic perturbations display significant modifications in their threedimensional structure as they evolve over extratropical and subtropical south america while the upper level perturbations are mostly unaffected when moving eastward the lower level perturbations advance following the shape of the andes mountains and exhibit an abrupt equatorward migration at the lee side of the mountains as a result of such detachment smaller eddy heat fluxes are observed in the vicinity of the orography and consequently a weaker eddy baroclinic growth is observed once the upper level system is on the lee side the perturbations acquire a more typical baroclinic wave structure and low level intensification of the system occurs the latter is largest around 1000 km east of the orography where enhanced moisture transports from tropical latitudes along the eastern portion of the low level cyclone favor precipitation occurrence over southeastern south america those precipitation processes seem to provide a diabatic source of energy that further contributes to the strengthening of the low level cyclone in addition an intensification of the cyclone once over the ocean was found in 60 of the situations considered which is consistent with previous research suggesting an additional source of moisture and heat flux due to the warm waters of the brazil current

paleolimnological record of the pampean plains argentina as a natural archive of south american hydroclimatic variability since the lgm to the current warm period abstract laguna mar chiquita lmc 30 54 s 62 51 w is a highly variable and shallow saline lake located in the pampean plains of argentina the paleolimnological record of lmc contains information on the environmental variability that occurred in a large area of southern south america since the last glacial maximum lgm until the present as inferred from the diatom assemblages sedimentary features and geochemical proxies prolonged intervals of high and lowstands have caused variations in water salinity trophic state and sedimentary processes this is the first paleolimnological reconstruction covering the hydroclimatic variability that occurred over the last 25 000 cal yr bp in the argentinean pampean region results are in accordance with well known global climatic phases the late pleistocene record is characterized by a scenario dominated by lowstands hypersaline and oligotrophic lake conditions radiocarbon ages 25 000 19 000 cal yr bp indicate that the onset of the record is coeval with the lgm later a progressive lake water level increase was registered at 17 000 cal yr bp which can be assigned to the heinrich stadial 1 a shift toward comparatively drier conditions identified in the record between 14 700 and 13 000 cal yr bp can be chronologically related to the antarctic cold reversal the transition from the late pleistocene to the holocene 13 500 10 500 cal yr bp is recorded by highstand phases while the early holocene record is characterized by high to intermediate water levels the hydrological reconstruction corresponding to the mid holocene is characterized by alternating phases of high lowstands the onset of the late holocene record is marked by the development of dry conditions and thus lowstand phases while around 1300 cal yr bp a distinct water lake level increase is recognized this humid phase ascribed to the medieval climatic anomaly is followed by the record of lowstands between 500 and 1000 cal yr bp being coeval with the little ice age the uppermost part of the record of lmc encompasses the current warm period showing a marked shift towards high lake water level conditions the hydrological variability registered in the paleolimnological record highlights the importance of laguna mar chiquita as an outstanding paleoclimate sensor of hydroclimatic variations for a large area of south eastern south america

the effect of trapped liquid crystallization on cumulus mineral compositions in layered intrusions a series of calculations have been carried out to evaluate the effect on cumulus mineral compositions of solidification of trapped intercumulus liquid in orthocumulates the calculation assumes local equilibrium between phases and that the system remains chemically closed during crystallization of the trapped liquid the latter assumption is held to be valid on a scale of tens to hundreds of centimeters it is not necessary to know the composition of the trapped liquid as the calculation only requires an estimate of feo content and trapping temperature the change in composition of a mineral from that of the initially precipitated cumulus crystals to the final composition after complete solidification is termed the trapped liquid shift its magnitude depends on the modal proportions of cumulus phases and the initial porosity and is only weakly dependent on initial phase compositions trapped liquid shifts are significant when compared with mineral composition changes occurring during fractional crystallization crystallization of 30 trapped liquid gives rise to shifts of up to 10 mol percent in mg number of olivine or pyroxene the size of the shift becomes greater when the initial cumulus assemblage has a lower total feo mgo content and vice versa as a result of the relationship between trapped liquid shift and cumulus mode mineral composition variations and trends may be generated in sequences of cumulates which originally had constant compositions of cumulus minerals for example in a cyclic unit grading from a pyroxenitic base to an anorthositic top crystallization of a uniform proportion of trapped liquid will result in an apparent iron enrichment trend from bottom to top of the cycle as has been observed in the upper critical zone of the bushveld complex

avulsion the relative roles of autogenic and allogenic processes abstract avulsion the abandonment of all or part of a channel belt in favor of a new course is controlled by both autogenic intrabasinal and allogenic extrabasinal processes however their relative roles are not known well the rhine meuse delta is without doubt the best studied delta regarding holocene avulsion processes based on studies of this delta an overview is given of 1 allogenic and autogenic processes influencing different aspects of avulsion 2 the relative importance of these processes in time and space and 3 observations that can be used to differentiate autogenic and allogenic causes of avulsion the following avulsion parameters are quantified and their allogenic and or autogenic nature are discussed period of activity of channel belts period between beginning and end of overbank sedimentation by the river channel interavulsion period time period between successive avulsions of a channel belt avulsion frequency number of avulsions per time interval in a given area and avulsion location in the rhine meuse delta the period of activity of the holocene channel belts varies considerably but shows no significant trend over time whereas extrabasinal factors climate base level and tectonics changed this suggests that this parameter is mainly autogenic controlled the average interavulsion period increased from 8000 cal yr bp to 2800 cal yr bp and decreased since then significant fluctuations occurred on a shorter time scale a maximum variability in the interavulsion period occurred between 3200 and 1800 cal yr bp this was a time when large channel belts gradually came into existence during this period the avulsion frequency also reached a maximum the long term increasing trend in interavulsion period is related to the decreasing rate of sea level rise the decreasing interavulsion period since 2800 cal yr bp can be explained by increased discharge and sedimentation resulting in an increase in the number of avulsions seven avulsion sequences as predicted by the mackey and bridge mackey s d bridge j s 1995 three dimensional model of alluvial stratigraphy theory and application journal of sedimentary research b65 1 pp 7 31 model may be recorded in the holocene dataset of the rhine meuse suggesting a periodicity of 500 600 yr each avulsion sequence coincides with a peak in the avulsion frequency the periodicity of 500 yr in the avulsion frequency is proposed to be autogenic however there is also a long term trend in the avulsion frequency that can be related to sea level rise and after 3000 14c yr bp to climate change and human influence avulsion locations are not randomly distributed over the delta and are related to the allogenic factors relative sea level rise local tectonics and changes in discharge and sediment load

a new greenland ice core chronology for the last glacial termination 1 we present a new common stratigraphic timescale for the north greenland ice core project ngrip and grip ice cores the timescale covers the period 7 9 14 8 kyr before present and includes the bolling allerod younger dryas and early holocene periods we use a combination of new and previously published data the most prominent being new high resolution continuous flow analysis cfa impurity records from the ngrip ice core several investigators have identified and counted annual layers using a multiparameter approach and the maximum counting error is estimated to be up to 2 in the holocene part and about 3 for the older parts these counting error estimates reflect the number of annual layers that were hard to interpret but not a possible bias in the set of rules used for annual layer identification as the grip and ngrip ice cores are not optimal for annual layer counting in the middle and late holocene the timescale is tied to a prominent volcanic event inside the 8 2 kyr cold event recently dated in the dye 3 ice core to 8236 years before a d 2000 b2k with a maximum counting error of 47 years the new timescale dates the younger dryas preboreal transition to 11 703 b2k which is 100 150 years older than according to the present grip and ngrip timescales the age of the transition matches the gisp2 timescale within a few years but viewed over the entire 7 9 14 8 kyr section there are significant differences between the new timescale and the gisp2 timescale the transition from the glacial into the bolling interstadial is dated to 14 692 b2k the presented timescale is a part of a new greenland ice core chronology common to the dye 3 grip and ngrip ice cores named the greenland ice core chronology 2005 gicc05 the annual layer thicknesses are observed to be log normally distributed with good approximation and compared to the early holocene the mean accumulation rates in the younger dryas and bolling periods are found to be 47 2 and 88 2 respectively

the copper bearing basic rocks of namaqualand south africa copper mineralisation is associated with rocks of basic intermediate composition which occur as a widespread swarm of relatively small irregularly shaped bodies within the gneissic terrain of the okiep district these basic rocks comprise the so called koperberg noritoid suite of namaqualand and constitute one of the three major copper producers in south africa while a metasomatic origin was briefly favoured for the noritoids most researchers have emphasized the cross cutting nature of the noritoids relative to their host rocks and prefer an origin involving magmatic injection high noritoid 87sr 86sr initial ratio values indicated to some workers that mobilisation of suitable crustal materials was more attractive than intrusion of mantle derived melts to account for the origin of the noritoid suite the present study has shown that the structure texture and mineralogy of the noritoids do not lend themselves to interpretation of the noritoids as pristine intrusive rocks and indicate that the noritoids have undergone high grade metamorphism after emplacement the geochemistry of the noritoid suite reveals a pronounced alkaline affinity and mineralogical control of the chemistry characterises the rocks as cumulates the dimensions of the noritoids appear unfavourable for development of cumulate rocks and it is considered possible that the present configuration of the noritoids results from dismemberment of larger intrusive bodies as a result of shear deformation during high grade metamorphism it has not been possible to identify a magma parent to the noritoid suite but we believe the parent to have been an alkaline mantle derived magma which suffered contamination by granitic anatects in the lower crust recognition of the metamorphic history of the namaqualand noritoids renders a comparison between them and the caraiba noritoids of interest

radiocarbon dating and the old wood problem the case of the hohokam chronology abstract many archaeological chronologies including that of the hohokam in southern arizona are based on a series of radiocarbon dates on wood this paper argues that because of variability in rates of wood decay processes in the environment and in systemic context such archaeological chronologies are potentially biased towards excessive antiquity by an old wood problem and must be reassessed following the theoretical insights of dean 1978 this paper sets forth principles and procedures for relating radiocarbon dates to cultural events emphasis is placed on identifying and taking into account the formation processes of 1 the dated specimens and 2 the deposits that yielded them this methodological framework is applied to hohokam radiocarbon dates and a chronology much shorter than the original gladwin haury formulation is supported

simulation of springs discharge from a karstic aquifer crete greece using limited data five major groups of springs and more than ten pumping wells comprise the main discharge outlets of agyia karstic aquifer w crete greece the mean annual discharge of the springs is 76 106 m3 while 12 106 m3 of water are pumped annually from myloniana and agyia s well fields for public water supply and irrigation the area is almost composed of entirely karstified carbonate rocks limestones with dolomites and karstic drainage contributes to infiltration and replenishment of the aquifer the present work studies the groundwater flow system in the region to investigate the impact of intensive exploitation of the aquifer especially during dry periods low water table conditions due to the lack of sufficient hydrogeologic data a part of the aquifer extending upwards of agyia springs was chosen for building the conceptual and numerical model the groundwater flow was simulated by establishing a reproduction of the measured water heads in the field and the springs discharge the appropriate set of boundary conditions and the repetition of the model s verification in different dry periods resulted in a sufficiently reliable model this can be used as a tool to assess different water resource management options during dry periods when the demand for water is high

stable isotopic evidence for crustal contamination and desulfidation of the cupriferous koperberg suite namaqualand south africa abstract the middle proterozoic koperberg suite occurs as a swarm of differentiated mafic dikes in a granulite facies terrane in the northwestern cape province of south africa rock types include pyroxenite norite anorthosite diorite and glimmerite and host an important repository of copper ore this paper reports petrographic and stable isotope data that places new constraints on the magmatic and metamorphic evolution of the koperberg suite and associated copper mineralization oxygen isotope ratios of the basic bodies are significantly enriched in 18 o 18 o plag 6 2 to 9 6 18 o opx 6 2 to 7 4 and 18 o rock 5 9 to 8 3 relative to mantle derived basic rocks this enrichment appears to be the result of crustal contamination granite gneiss country rocks exhibit 18 o values in the range from 7 8 8 7 the systematics of oxygen isotope data for coexisting minerals suggest that in addition to crustal contamination further modification took place due to low temperature post peak metamorphic exchange involving circulating fluids that had undergone isotopic exchange with the surrounding gneisses these fluids are probably related to the upper greenschist grade metamorphism associated with the regional pan african orogeny 500 550 ma this is indicated by the lack of temperature concordancy based on 18 o values of several mineral pairs involving orthopyroxene plagioclase biotite and magnetite sulfur isotope ratios from diorite and norite hosted sulfides are light relative to mantle values and co genetic mineral pairs show a lack of temperature concordancy the ranges in 34 s values for the sulfides are 34 s cpy 1 5 to 3 8 0 34 ss bo 1 9 to 4 1 0 and 34 s po 1 9 to 2 5 0 bulk ore samples show a systematic decrease in 34 s values with increasing cu s ratios this is seen as being diagnostic for an oxidation process and the degassing of a so 2 rich vapour phase petrographic observations and mineral chemistry data support this conclusion and indicate that the devolatilization event was caused by granulite facies metamorphism followed by a later lower temperature alteration event in our genetic model we envisage a mantle origin for the koperberg suite the original magma was modified through assimilation and fractional crystallization processes later modification occurred at the level of emplacement through differentiation and metamorphism crustal contamination can explain the origin of the enriched o isotope values the high levels of incompatible trace elements as well as the high initial 87 sr 86 sr ratios in the basic bodies

a minimum thermodynamic model for the bipolar seesaw 1 the simplest possible model is proposed to explain a large fraction of the millennial climate variability measured in the isotopic composition of antarctic ice cores the model results from the classic bipolar seesaw by coupling it to a heat reservoir in this thermal bipolar seesaw the heat reservoir convolves northern time signals with a characteristic timescale applying the model to the data of grip and byrd we demonstrate that maximum correlation can be obtained using a timescale of about 1000 1500 years higher correlations are obtained by first filtering out the long term variability which is due to astronomical and greenhouse gas forcing and not part of the thermal bipolar seesaw the model resolves the apparent confusion whether northern and southern climate records are in or out of phase synchronous or time lagged

organisation of the soil mantle in tropical southeastern brazil serra do mar in relation to landslides processes abstract the serra do mar complex in southeastern brazil is subject to frequent landslides especially on the atlantic coast the three dimensional organisation of the soil was studied in a 56 ha representative catchment upslope in situ soil material has developed from the parent rock and downslope the soil has resulted from landslide processes the soil mantle upslope is mainly characterised by slowly permeable kaolinitic horizons within a thick gibbsitic weathering horizon the field and microscopic relationships between the two suggest that the kaolinitic horizon has evolved at the expense of the gibbsitic material resilication of gibbsite to form kaolinite is postulated in this environment the kaolinitic horizons are overlain by a microaggregated horizon the difference in porosity and water movement between these two horizons was estimated by density measurements mercury porosimetry image processing and calculation of water retention and shrinkage curves the results indicate that water is retained briefly within the microaggregated horizon during intensive rainfall because of the inclination of the kaolinitic horizon any excess water within it flows laterally downslope and accumulates in the lowest part of the slope this leads to landslipping the main process of landform development in the region

related changes in biodiversity insolation and climate in the atlantic rainforest since the last interglacial abstract the long term colonia record is located in the atlantic rainforest domain in brazil 23 52 s 46 42 20 w 900 m a s l the 780 cm long core co3 provides a coverage of a complete interglacial glacial cycle for the first time in a neotropical rainforest information on the behavior of tropical climates compared to global changes in temperatures indicates specific climate responses in terms of precipitation at these latitudes winter extratropical circulation was very active during the last interglacial and most of the glacial floristic composition of the rainforest changed several times in each phase of expansion twice during the interglacial and three times during glacial episodes araucaria was well developed in the area of sao paulo until the beginning of the first dry phase of the glacial at ca 50 000 yr b p changes in insolation controlled the expansion of the rainforest and the tropical hydrological cycle as evidenced by a strong precession signal however precession had no impact on regional climatic features the two interglacials mis 5e and holocene showed completely different patterns attesting to the continuous evolution of the forest the biodiversity index shannon wiener index remained high during both the interglacial and glacial attesting to the permanence of small patches of rainforest refugia during drier phases the lowest shannon wiener indexes were recorded between 23 000 and 12 000 yr b p and 40 000 and 30 000 yr b p and characterize two marked phases of stress for the rainforest

self organized criticality in river basins challenging sedimentary records of environmental change for many years researchers have linked increases in sediment and bedload from drainage basins to external factors such as increased rainfall however natural systems have always shown a high degree of scatter or nonlinearity in this response which has made prediction of sediment yields difficult we identify and describe a mechanism for self organized criticality in the bedload sediment output from a simple drainage basin evolution model this implies that identical floods will give considerably different sediment yields which effectively renders the system unpredictable therefore existing empirical methods for estimating sediment yields may need to be radically reevaluated furthermore sedimentary records used to infer past climate or environmental conditions could simply reflect the internal system dynamics instead of external drivers

late quaternary vegetation climate and fire history from the tropical mountain region of morro de itapeva se brazil late quaternary paleoenvironments have been interpreted from a 35 000 yr b p pollen and charcoal record from morro de itapeva 22 47 s 45 32 w 1850 m a s l in the se brazilian highlands changes in taxa composition and elevational shifts in high elevation grassland campos de altitude araucaria forest cloud forest and atlantic rain forest all of which can be found in the study area today indicate climatic changes in the past expanded high elevation grasslands absence of araucaria forest cloud forest and atlantic rain forest during the recorded last glacial period ca 35 000 17 000 yr b p suggest a climate markedly cooler and drier than today development of a sphagnum peat bog rare presence of araucaria forest taxa and existence of a narrow cloud forest and rain forest belt at lower elevations during the late glacial period 17 000 ca 10 000 yr b p indicate a change to a cool and somewhat moister climates during the early holocene cloud forest developed close to the study site reflecting a warm and moist climate on the east facing slopes but a drier climate on the highland plateau evidenced by the rare presence of araucaria and podocarpus only during the late holocene moisture increases in the highlands suggested by the higher frequency of araucaria and podocarpus fires were more frequent during the last glacial than during the holocene

denudation history of the bocaina plateau serra do mar southeastern brazil relationships to gondwana breakup and passive margin development abstract the bocaina plateau which is situated on the eastern flank of the continental rift of southeastern brazil is the highest part of the serra do mar topographic relief in this area is suggested to be closely related to its complex tectono magmatic evolution since the breakup of western gondwana and opening of the south atlantic ocean apatite fission track ages and track length distributions from 27 basement outcrops were determined to assess these hypotheses and reconstruct the denudation history of the bocaina plateau the ages range between 303 32 and 46 5 ma and are significantly younger than the stratigraphic ages mean track lengths vary from 13 44 1 51 to 11 1 1 48 m with standard deviations between 1 16 and 1 83 m contrasting ages within a single plateau and similar ages at different altitudes indicate a complex regional tectonothermal evolution the thermal histories inferred from these data imply three periods of accelerated cooling related to the early cretaceous continental breakup early cretaceous alkaline magmatism and the paleogene evolution of the continental rift of southeastern brazil the oldest fission track ages 200 ma were obtained in the serra do mar region suggesting that these areas were a long lived source of sediments for the parana bauru and santos basins

genesis of the precambrian copper rich caraiba hypersthenite norite complex brazil caraiba the largest brazilian copper deposit under exploitation consists mostly of disseminated and remobilised bornite and chalcopyrite hosted in early proterozoic norite and hypersthenite the mafic igneous complex comprises multiple intrusions of dykes veins and breccias of norites and hypersthenites with minor proportions of amphibolised gabbronorite and peridotite xenoliths transported by the magma from deeper levels in the lithosphere the country rocks are high grade gneisses granulites and metasediments compositions of plagioclase an60 40 and orthopyroxene en70 60 fall in a narrow range similar to the koperberg suite from the okiep copper district south africa and to that in many massif type anorthosites whole rock major and trace element geochemistry indicate a parental magma enriched in fe lree p k and cu negative nb anomalies on multi element plots and fractionated ree patterns along with sulphide sulphur isotopes in the range 34s 1 495 to 0 643 suggest a primary mantle lithosphere source although a lower crustal source for the gabbronorite and peridotite xenoliths cannot be excluded geochronological and field evidence indicate that both norite and hypersthenite are likely to have been emplaced during a major sinistral transcurrent partly transpressional shearing event associated with the waning stage of evolution of the early proterozoic salvador curaca orogen

land sea correlation in southeastern brazil during the last 7 4 cal ka bp vegetational climatic and oceanographic inferences abstract the vegetation history and climate in southeastern brazil as well as the oceanic dynamics of the tropical atlantic ocean offshore were reconstructed for the last 7 4 cal ka bp this reconstruction was based on pollen fern spores and dinoflagellate cysts identified in a marine core cf10 04b it was possible to verify the presence of an ombrophilous forest from 7 4 cal ka bp near the base of the pi zone low concentrations of pollen and fern spores are recorded along with low frequencies of forest taxa and fern spores and an increase in pollen types of open vegetation suggesting less humid climatic conditions than currently observed in the coastal regions of southeastern brazil the assemblages of dinoflagellate cysts suggest a neritic zone with warm upper column temperature high salinity and oligotrophic environment evidenced by the presence of o centrocarpum spiniferites spp and l machaerophorum an increase in tropical waters tw and the approximation of the brazilian current bc in the middle shelf of southeastern brazil in the mid holocene probably influenced the low accumulation of cysts pollen grains fern spores and their associations it is still possible to verify that at approximately 4 6 cal ka bp an increase in the rainfall in the southeastern brazilian region was probably the fundamental factor for the expansion of vegetation mainly based on the considerable increases in hygrophytic and aquatic plants the marked increase in the accumulation of dinoflagellate cysts with the dominance of autotroph taxa mainly o centrocarpum followed by spiniferites spp evidences the warmer waters of the bc and more intense surface upwelling of the south atlantic central water sacw

sulfide oxidation as a process for the formation of copper rich magmatic sulfides typical magmatic sulfides are dominated by pyrrhotite and pentlandite with minor chalcopyrite and the bulk atomic cu fe ratio of these sulfides is typically less than unity however there are rar

reply to comment on linked variations in sediment accumulation rates and sea level in guanabara bay brazil over the last 6000 years by alberto g figueiredo jr mauro b de toledo renato c cordeiro jose m o godoy fabiano t da silva sergio c vasconcelos ricardo a dos santos palaeo 415 2014 83 90 by andre kirchner and udo nehren in 2015

the o okiep copper district namaqualand south africa a review of the geology with emphasis on the petrogenesis of the cupriferous koperberg suite the o okiep copper district is the oldest formal mining area in south africa between 1852 and 2002 the 2 500 km2 area yielded two million tons of copper from 32 mines ranging in ore tonnages from 140 000 to 37 million tons this paper summarizes the calendar of events from the formation of the first primitive crust 1 700 2 000 ma ago to early cambrian times 500 ma ago with particular emphasis on the namaquan grenville orogeny notably the o okiepian episode 1 180 1 210 ma ago of alpine type folding regional granite plutonism and granulite facies metamorphism and the klondikean episode 1 020 1 040 ma ago of open and tight folding and the intrusion of the rietberg granite and the koperberg suite almost all of the copper in the o okiep district occurs in the koperberg suite of which there are 1 700 small bodies that constitute 0 7 of the outcrop area the suite comprises jotunite anorthosite biotite diorite and hypersthenic rocks ranging from leuconorite to hypersthenite and it is one of only two world examples of economic copper mineralization in rocks of the anorthosite charnockite kindred the second example is caraiba brazil high isr and low end for a 1 030 ma intrusion age and high 2 of 10 1 for koperberg rock types indicate a crustal progenitor for the suite and the presence of jotunite suggests a subducted crustal source at ca 40 50 km depth the magmatic sulphide paragenesis in the koperberg suite is chalcopyrite pyrrhotite narrap type ore that in a number of ore bodies has been inverted under upper amphibolite facies conditions to bornite ti free magnetite carolusberg type ore meteoric fluids resulted in supergene cu enrichment in koperberg bodies to 500 m below the pre nama peneplane and lower greenschist facies metamorphism 500 570 ma ago is reflected by inter alia hoits type ore bearing second generation bornite chalcopyrite covellite chalcocite

a crustal progenitor for the intrusive anorthosite charnockite kindred of the cupriferous koperberg suite o okiep district namaqualand south africa new isotope data for the country rocks and the intrusives

sensitivity of the atlantic intertropical convergence zone to last glacial maximum boundary conditions 1 recent paleoproxy records suggest that the mean latitude of the atlantic intertropical convergence zone itcz varied synchronously with north atlantic climate over a range of timescales throughout the holocene and last glacial maximum we show that the present day meridional mode of atmosphere ocean variability in the tropical atlantic is a potentially useful model for understanding these paleoclimate changes the tropical atlantic in a coupled atmospheric general circulation and slab ocean model responds to last glacial maximum conditions with a southward displacement of the itcz this response arises primarily through the land ice sheet that forces increased north atlantic trades analogous to the forcing on the present day meridional mode changes to sea ice coverage and to ocean heat transport associated with a weakened atlantic thermohaline circulation also cause a meridional mode response though through different mechanisms our results highlight the potential for tropical atlantic paleoclimate to be driven from the high latitude influences in particular land ice on glacial interglacial timescales

late quaternary fluvial dynamics of the jarama river in central spain the jarama river and its catchment provide a valuable natural archive to study and reconstruct past environmental conditions in central spain this region is highly prone to changes in the hydrological cycle under predicted climate warming in particular with respect to aridity periods rainfall variability and the occurrence of extreme flood events this paper presents 15 exposures covering a time span of the last 44 ka which were documented in the field and of which seven exposures were soil chemical analyzed regarding soil texture organic matter as well as carbonate and iron content ages are based on radiocarbon dating on 32 samples latest holocene sediments were found within the channel belt where permanent remobilization of sediments takes place due to the migration of the meandering river course in more distal floodplain positions sediment sequences show a complex fluvial architecture referring to periods of varying character and intensity of alluviation as well as periods of geomorphic stability indicated by soil formation furthermore sedimentation patterns vary along different river sections aggradations of coarse gravels took place between 40 and 18 ka cal bp over the entire valley floor alluviation of fine material was documented between 17 and 16 at 7 5 between 5 1 and 3 3 at 2 8 between 2 1 and 1 5 at 1 0 and around 0 4 ka cal bp until recent times astonishingly in late holocene times between 4 2 and 3 1 ka cal bp aggradations of coarse gravels even in distal floodplain areas overlap with sedimentation of fine material in adjacent river sections pointing to a complex constellation of parameters involved periods of soil formation were detected around 43 at 31 between 16 and 12 6 after 7 5 until 5 1 between 2 8 and 2 1 and at times after 1 5 ka cal bp phases of geomorphic stagnation were found at 38 ka cal bp and for a duration of 200 years at 3 0 ka cal bp and refer to absent geomorphic or pedogenic processes all these patterns are an expression of the interaction between climatic variations tectonic impulses and human influences a comparison with other terrestrial archives enabled us to reconstruct late pleistocene and holocene palaeoenvironmental conditions on a regional scale and furthermore to link specific stages of floodplain development to prevalent influencing variables thus with emphasis on the fluvial system response a model of a cause and effect relationship is presented that concentrates on rapid climate changes long lasting climatic deteriorations and the role of human interventions

summertime precipitation variability over south america role of the large scale circulation abstract the observed large scale circulation mechanisms associated with summertime precipitation variability over south america are investigated particular attention is paid to the altiplano where a close relationship has been observed between rainfall and the position and intensity of the bolivian high empirical orthogonal function eof correlation and composite analyses suggest that on intraseasonal timescales typically 5 20 days rainy periods on the altiplano are associated with at least three types of circulation anomalies involving either extratropical cyclones cold core lows or the westward enhancement of the south atlantic high in each instance the primary support for high rainfall rates is a moist poleward flow at low levels along the eastern flank of the central andes in association with the south atlantic convergence zone sacz the warm low level flow along the sacz also inflates the overlying atmospheric column resulting in an intensification and southward shift of the bolivi

fluvial sediments of the algeti river in southeastern georgia an archive of late quaternary landscape activity and stability in the transcaucasian region abstract in order to obtain information about landscape activity and stability during the late quaternary in the transcaucasian region fluvial sediments of the lower algeti river in se georgia were studied by means of geomorphologic sedimentologic and geochronologic methods these investigations show that sediments aggraded by the late pleistocene braided algeti river were strongly incised around the pleistocene holocene transition and subsequently a small scale pattern of diachronous fluvial terraces deposited by the now meandering river developed in the new valley during the holocene prior to ca 3 cal ka bp active phases of river channel aggradation and overbank sedimentation about 6 cal ka bp and 3 4 3 2 cal ka bp can be linked with climate driven vegetation changes i e stronger fluvial dynamics with sedimentation occurred during more arid and colder periods whereas the caucasian holocene climate optimum between 6 and 3 4 cal ka bp was characterized by stable geomorphologic conditions after 3 cal ka bp strongly increased human impact documented by former pollen studies is reflected by the fluvial dynamics as well i e an activity phase of strong overbank sedimentation 2 7 2 1 cal ka bp occurred during a period when forests in the lesser caucasus were burnt down two subsequent activity phases with fluvial sedimentation can be linked with historic events that probably both influenced vegetation distribution of the region i e a period of flourishing of georgia during the middle age and a time of large scale destruction of the country due to a persian invasion at the end of the 18th century ad respectively thus whereas no influence of tectonic events or fluctuations of the caspian sea level on the fluvial dynamics could be detected se georgia shows its fragile character with respect to climate and human driven vegetation changes similar to other semi arid landscapes of the mediterranean region

mid to late holocene climate change an overview the last 6000 years are of particular interest to the understanding of the earth system because the boundary conditions of the climate system did not change dramatically in comparison to larger glacial interglacial changes and because abundant detailed regional palaeoclimatic proxy records cover this period we use selected proxy based reconstructions of different climate variables together with state of the art time series of natural forcings orbital variations solar activity variations large tropical volcanic eruptions land cover and greenhouse gases underpinned by results from general circulation models gcms and earth system models of intermediate complexity emics to establish a comprehensive explanatory framework for climate changes from the mid holocene mh to pre industrial time the redistribution of solar energy due to orbital forcing on a millennial timescale was the cause of a progressive southward shift of the northern hemisphere nh summer position of the intertropical convergence zone itcz this was accompanied by a pronounced weakening of the monsoon systems in africa and asia and increasing dryness and desertification on both continents the associated summertime cooling of the nh combined with changing temperature gradients in the world oceans likely led to an increasing amplitude of the el nin o southern oscillation enso and possibly increasingly negative north atlantic oscillation nao indices up to the beginning of the last millennium on decadal to multi century timescales a worldwide coincidence between solar irradiance minima tropical volcanic eruptions and decadal to multi century scale cooling events was not found however reconstructions show that widespread decadal to multi century scale cooling events accompanied by advances of mountain glaciers occurred in the nh e g in scandinavia and the european alps this occurred namely during the little ice age lia between ad w1350 and 1850 when the lower summer insolation in the nh due to orbital forcing coincided with solar activity minima and several strong tropical volcanic eruptions the role of orbital forcing in the nh cooling the southward itcz shift and the desertifi cation of the sahara are supported by numerous model simulations other simulations have suggested that the fingerprint of solar activity variations should be strongest in the tropics but there is also evidence that changes in the ocean heat transport took place during the lia at high northern latitudes with possible additional implications for climates of the southern hemisphere sh

southward migration of the intertropical convergence zone through the holocene titanium and iron concentration data from the anoxic cariaco basin off the venezuelan coast can be used to infer variations in the hydrological cycle over northern south america during the past 14 000 years with subdecadal resolution following a dry younger dryas a period of increased precipitation and riverine discharge occurred during the holocene thermal maximum since approximately 5400 years ago a trend toward drier conditions is evident from the data with high amplitude fluctuations and precipitation minima during the time interval 3800 to 2800 years ago and during the little ice age these regional changes in precipitation are best explained by shifts in the mean latitude of the atlantic intertropical convergence zone itcz potentially driven by pacific based climate variability the cariaco basin record exhibits strong correlations with climate records from distant regions including the high latitude northern hemisphere providing evidence for global teleconnections among regional climates

evidence for general instability of past climate from a 250 kyr ice core record recent results1 2 from two ice cores drilled in central greenland have revealed large abrupt climate changes of at least regional extent during the late stages of the last glaciation suggesting that climate in the north atlantic region is able to reorganize itself rapidly perhaps even within a few decades here we present a detailed stable isotope record for the full length of the greenland ice core project summit ice core extending over the past 250 kyr according to a calculated timescale we find that climate instability was not confined to the last glaciation but appears also to have been marked during the last interglacial as explored more fully in a companion paper3 and during the previous saale holstein glacial cycle this is in contrast with the extreme stability of the holocene suggesting that recent climate stability may be the exception rather than the rule the last interglacial seems to have lasted longer than is implied by the deep sea specmap record4 in agreement with other land based observations5 6 we suggest that climate instability in the early part of the last interglacial may have delayed the melting of the saalean ice sheets in america and eurasia perhaps accounting for this discrepancy

environmental changes at the eastern namib desert margin before and after the last glacial maximum new evidence from fluvial deposits in the upper hoanib river catchment northwestern namibia in the upper hoanib river catchment area northwestern namibia fine grained silty deposits are widespread accumulated as river end deposits they form excellent geomorphological archives of a highly sensitive desert margin area different sedimentary complexes are separated sedimentologically and by luminescence dating the deposits give evidence of climate oscillations at the eastern margin of the namib desert during the past 50 000 years in northwestern namibia the dry conditions of the desert margin area with less than 200 300 mm mean annual precipitation prevailed at 60 40 ka and at 34 24 ka when sediment complex i accumulated during the last glacial maximum lgm fluvial activity and sedimentation were most likely interrupted due to arid conditions between 12 ka and the mid holocene higher rainfall and runoff led to the aggradation of sediment complex ii the climate was more humid than before the lgm but drier than at present after 3 ka runoff increased and the hoanib river re eroded the older deposits forming deep channels a prominent more sandy and gravely 4 m terrace in the upper and middle course of the hoanib river dates to the little ice age lia it is likely that this terrace is genetically linked with the amspoort silt formation in the lower hoanib valley d 2005 elsevier b v all rights reserved

three dimensional simulation of seawater intrusion in coastal aquifers a case study in the goksu deltaic plain summary unplanned exploitation of groundwater from coastal aquifers may cause salt water intrusion in coastal aquifers coastal areas are generally overpopulated with fertile agricultural lands and diversified irrigated farming activities the objective of this study was to develop a model to control prevent seawater intrusion into the coastal aquifer with a case study of the silifke goksu deltaic plain a computer program for the simulation of three dimensional variable density groundwater flow seawat is used to model the seawater intrusion mechanism of the goksu deltaic plain along the mediterranean coast of turkey the calibration analysis of the developed seawater intrusion model is performed using field measured data in the water year of 2008 including static groundwater head electrical conductivity total dissolved solid tds and chloride concentration values collected from 23 observation wells and the existing data which were compiled and reviewed the main objectives for applying the seawater intrusion model to the goksu deltaic plain were 1 to determine the hydraulic and hydrogeologic parameters of the aquifer 2 to estimate the spatial variation of the salt concentration in the aquifer and 3 to investigate the impact of the increase and decrease in groundwater extractions the simulation results show that the goksu deltaic plain aquifer is especially sensitive to the increase in groundwater extraction

hydrological modeling in the karst area rižana spring catchment slovenia karst aquifers are known for their heterogeneity and irregular complex flow patterns which make them more difficult to model and demand specific modeling approaches this paper presents one such approach which is based on a conceptual model the model was applied in a karst area of the catchment of ri ana spring 200 km it is based on the mike she code and incorporates the main hydrological processes and geological features of the karst aquifer diffuse and concentrated infiltration allogenic recharge quick and slow groundwater flow shifting groundwater divides and groundwater outflow from the catchment area modeling of evapotranspiration and flow in the upper part of the unsaturated zone is more detailed for the modeling of groundwater flow in the karst aquifer a conceptual model was applied which uses drainage function for the simulation of groundwater flow through large conduits karst channels and large fissures the model was calibrated and validated against the observed ri ana spring discharge which represents a measured response of the aquifer the results of validation show that the model is able to adequately simulate temporal evolution of the spring discharge measured by nash sutcliffe coefficient 0 82 as well as overall water balance

salinization processes in an alluvial coastal lowland plain and effect of sea water level rise in coastal areas groundwater and aquifer systems are easily prone to pollution and contamination moreover sea level rises also threaten the viability of many coastal zones and small islands in the shiroishi lowland plain southwestern kyushu island of japan some environmental problems such as land subsidence and salinity intrusion due to over pumping of groundwater have long been recognized as water problems and become causes for public concern in this study an integrated surface and groundwater model was established and applied to the shiroishi site to simulate groundwater flow hydraulics and predict the salinity intrusion process in the alluvial lowland plain the simulated results show that groundwater levels in the aquifer greatly vary in response to varying climatic and pumping conditions it is also found that sea water intrusion would be expected along the coast if the current rates of groundwater exploitation continue furthermore sea water intrusion with a relative rise in sea water level due to aquifer compression and global climatic change was also considered as a result sea water intrusion appears to extend much farther in land from the coast compared to a reference case the study also suggests a possible alternative to mitigate the inverse effects by pumping groundwater

fluid heterogeneity during granulite facies metamorphism in the adirondacks stable isotope evidence the preservation of premetamorphic whole rock oxygen isotope ratios in adirondack metasediments shows that neither these rocks nor adjacent anorthosites and gneisses have been penetrated by large amounts of externally derived hot co2 h2o fluids during granulite facies metamorphism this conclusion is supported by calculations of the effect of fluid volatilization and exchange and is also independently supported by petrologic and phase equilibria considerations the data suggest that these rocks were not an open system during metamorphism that fluid rock ratios were in many instances between 0 0 and 0 1 that externally derived fluids as well as fluids derived by metamorphic volatilization rose along localized channels and were not pervasive and thus that no single generalization can be applied to metamorphic fluid conditions in the adirondacks

variability of southern hemisphere cyclone and anticyclone behavior further analysis abstract this paper presents some additional results on the use of an automatic scheme for tracking surface cyclones and anticyclones the southern hemisphere sh total amount of synoptic tracks every 12 h was analyzed for the 1973 96 period using sea level pressure from the national centers for environmental prediction national center for atmospheric research ncep ncar reanalysis composites for seven el nino en and la nina ln years were constructed in order to analyze the association between the hemispheric cyclone and anticyclone propagation and the phase of the el nino southern oscillation enso phenomenon a climatological view of cyclone and anticyclone tracks and orphan centers superposed on the same map is presented and analyzed a large area with overlapped cyclone and anticyclone tracks is seen between 30 and 60 s which is approximately the climatological position of the sh transient activity to the north of 30 s the subtropical south atlantic high is embedded in a region with just

oxygen isotope geochemistry of the scourian complex northwest scotland the scourian complex of northwest scotland underwent granulite facies metamorphism at 2 7 ga granulite facies orthogneisses have whole rock 18o values similar to those of igneous rocks of comparable compositions ultrabasic gneisses 5 5 5 9 basic gneisses 6 4 6 8 tonalitic gneisses 9 5 9 7 and steep 18o gradients of up to 3 in 10cm are recorded at two lithological contacts these data suggest that large volumes of pervasive metamorphic fluids have not infiltrated the rocks but do not preclude localized fluid rock interaction scourian paragneisses have lower 18o values 8 5 9 9 than typical metasediments and may have undergone fluid hosted isotopic exchange with the surrounding orthogneisses felsic sheets within tonalitic and basic gneisses have similar 18o values to their hosts these data combined with petrological and geochemical information suggest that the sheets were formed by local anatexis during granulite facies metamorphism fluid infiltration during the 2 5 ga amphibolite facies inverian retrogression caused homogenization of 18o values of the scourian gneisses unaltered tholeiitic scourie dykes have low 18o values of 2 0 it is unlikely that heated surface derived fluids infiltrated the scourian complex and these dykes were probably emplaced as low 18o magmas

late glacial and holocene sedimentation and fluctuations of river water level in the caqueta river area colombian amazonia the sequence of late glacial and holocene alluvial sedimentation in the middle caqueta river basin of colombian amazonia is described based on the study of the sediments and palynology of several river bank sections and on 30 radiocarbon dates an early late glacial sedimentation cycle is recognised followed by a minor late late glacial erosion phase the holocene valley fill consists of grey clays often present in the lower part of the sections deposited in open water and silty clays often with faint yellow mottling deposited under a regime of seasonal flooding the base of the holocene sections is formed by sands where exposed in two places the transition of sand to open water grey clay was dated around 10 000 yr bp and there is a suggestion that open water may have been more common at the beginning of the holocene than later when sedimentation by seasonal flooding became important in many places much of the earlier holocene sediments may have been removed by erosion and replaced by younger sediments by a process of lateral aggradation a considerable part of the present valley fill is younger than ca 3500 yr however in several places older holocene sediments are found apparently only little affected by later erosion lying below younger varzea silty clays during the holocene more organic sediments were formed in periods with reduced river discharge related to drier climates in the andes and possibly in amazonia these dry periods deduced from data in the caqueta river area correspond well with dry phases in other parts of northwestern south america e g between approximately 2700 1900 yr bp and approximately 3200 3800 yr bp rates of average net sedimentation calculated from dated sections that apparently lack major hiatuses caused by erosion were high in the lower holocene low during the middle holocene and increase again in the upper holocene levee deposits became coarser and the high river level of the caqueta increased during the late holocene these phenomena may be explained by the increasing influence of man on the vegetation cover in the andean headwater areas and possibly also in the amazonian catchment area of the caqueta river