reevaluation of the oxygen isotopic composition of planktonic foraminifera experimental results and revised paleotemperature equations cultured planktonic foraminifera orbulina universa symbiotic and globigerina bulloides nonsymbiotic are used to reexamine temperature 18o relationships at 15 25 c relationships for both species can be described by linear equations equations for o universa grown under low light ll and high light hl share a slope of 4 80 0 21 c 1 with a hl ll offset of 0 33 due to symbiont photosynthetic activity the effect of co32 on o universa is 0 002 mol 1 kg 1 and is insensitive to temperature for g bulloides ontogenetic effects produce size related trends in temperature 18o whereby larger shells are enriched in 18o relative to smaller specimens the o universa temperature 18o relationships are more accurate than previously published equations for describing plankton tow data our equations do not explain planktonic core top data with the same precision but provide a good fit to benthic cibicidoides data below 10 c temperature 18o relationships for g bulloides provide good agreement with field data for this species from the northeast pacific

production of co2 in the capillary fringe of a deep phreatic aquifer co2 profiles obtained along a 30 m thick unsaturated zone under land irrigated with sewage effluents show two production regions a seasonal one in the root zone and another at steady state near the water table 29 m on an annual basis the co2 flux from the deep source toward the atmosphere 6 3 g c m 2 yr 1 is balanced by a similar influx of soluble organic carbon soc from sewage effluents the 13c values of soil co2 indicate that co2 is produced from plant material in the root zone and from biodegradation of total sedimentary organic carbon in the capillary fringe high co2 concentration in the capillary fringe up to 2 is likely to reflect a decrease in diffusivity relative to the unsaturated zone due to increase in both water content and tortuosity induced by the capillary fringe structure the long residence time of soc and co2 in the unsaturated zone 29 years at the study site suggests that the unsaturated zone of deep aquifers may have a significant storage capacity for carbon and may act as a temporary carbon sink

groundwater recharge history and hydrogeochemical evolution in the minqin basin north west china the minqin basin is a type area for examining stress on groundwater resources in the gobi desert and has been investigated here using a combination of isotopic noble gas and chemical indicators the basin is composed of clastic sediments of widely differing grain size and during the past half century over 10 000 boreholes have been drilled with a groundwater decline of around 1 m a 1 modern diffuse recharge is unlikely to exceed 3 mm a 1 as determined using unsaturated zone profiles and cl mass balance a small component of modern 50 a groundwater is identified in parts of the basin from 3h 3he data probably from irrigation returns a clear distinction is found between modern waters with median 18o values of 6 5 0 5 and most groundwaters in the basin with more depleted isotopic signatures radiocarbon values as pmc range from 0 6 to 85 modern but it is difficult to assign absolute ages to these although a value of 20 modern c probably represents the late pleistocene to holocene transition the 13c compositions remain near constant throughout the basin median value of 8 1 13c and indicate that carbonate reactions are unimportant and also that little reaction takes place there is a smooth decrease in 14c activity accompanied by a parallel increase in 4he accumulations from s n across the basin which define the occurrence of a regional flow system noble gas temperatures indicate recharge temperatures of about 5 6 c for late pleistocene samples which is some 2 3 c cooler than the modern mean annual air temperature and the recharge temperature obtained from several holocene samples groundwaters in the minqin basin have salinities generally below 1 g l and are aerobic containing low fe but elevated concentrations of u cr and se mean values of 27 5 5 8 and 5 3 g l 1 respectively nitrate is present at baseline concentrations of around 2 mg l 1 but there is little evidence of impact of high no3 from irrigation returns strontium isotope and major ion ratios suggest that silicate reactions predominate in the aquifer the results have important implications for groundwater management in the minqin and other water stressed basins in nw china a region so far destined for rapid development the large proportion of the water being used at present is in effect being mined and significant changes are urgently needed in water use strategy

trying to understand alpine sediments before 1950 abstract most alpine geologists before and after the 1893 1902 breakthrough of the nappe theory paid surprisingly little attention to sedimentological phenomena they were preoccupied with stratigraphic and especially tectonic problems the alpine concept of geosyncline differed in several ways from the original one in 1894 marcel bertrand suggested a fourfold division of complexes informal lithostratigraphic assemblages among the sediments of the alps and of older mountain chains for the alps his classification may be expanded to comprise i late variscan detritals ii pre rift platform sediments iii syn rift deposits iv post rift platform and basin sediments v starved deep sea formations on oceanic or thinned continental crust vi bundnerschiefer or schistes lustres vii flysch and viii molasse the last named is not discussed here on the european helvetic margin the processes giving rise to shallowing upward sequences of condensed glauconite beds shales and limestones complex iv were discussed for a long time the work of arnold heim is particularly instructive gustav steinmann was one of the first to recognize the deep sea origin of certain rocks especially radiolarian cherts the controversy on the bathymetry of the alpine seas during the oceanic and post oceanic stages complexes v vii went on until about 1950 since 1916 the seas and islands around eastern indonesia were proposed as analogues to the late mesozoic paleogeographic pattern of the alps two 18th century scientists deserve a special mention moritz anton kappeler m a cappellerius 1767 provided an actualistic interpretation of ripple marks on steep standing sandstones and johann jacob scheuchzer 1718 understood the importance of graded bedding which he attributed to the action of the deluge

dissolved gas paleotemperatures and 18o variations derived from groundwater near uitenhage south africa abstract under the near ideal hydrologic conditions provided by the uitenhage artesian aquifer reliable estimates of paleotemperatures were obtained by measurement of the dissolved n2 and ar in groundwater confidently dated in the range 28 000 yr b p to the present using 14c the mean annual air temperature in this area during the last glaciation is calculated to have been on average 5 1 2 c lower than during the holocene the change in the 18 o 16 o ratio of the groundwater corrected for changes in ocean water amounted to 0 4 per c

carbon isotopes to constrain the origin and circulation pattern of groundwater in the north western part of the bohemian cretaceous basin czech republic abstract the bohemian cretaceous basin represents a complex hydrogeological system composed of several aquifers with very favourable hydrogeological properties these aquifers have been exploited for many years the sustainability of such resources might be guaranteed by well organised water management which requires a detailed knowledge about the functioning of the hydrogeological system although many efforts have previously been made to evaluate groundwater residence time the many intricate geochemical processes complicate groundwater dating the current study clarifies the functioning of this complex hydrogeological basin using hydrogeochemical and isotopic investigations chemical data and a combination of 13 c and 14 c isotopes within the cenomanian and the turonian layers indicate groundwater interactions with deep seated co 2 rock matrix surface waters and fossil organic matter very depleted 13 c values average 13 c 13 4 suggest interactions with fossil organic matter whereas enriched values account for the interaction with deep co 2 gas ascending from the upper mantle via the numerous faults and fractures and also to a lesser extent from calcite dissolution geochemical processes that take place in the system cause a clear depletion in 14 c that greatly complicates groundwater residence time evaluation different dilution correction models have been applied considering the different c origins the stable isotope content mainly 18 o values indicates both the contribution of modern precipitation and the partial infiltration of palaeowaters during colder climatic conditions from the end of the pleistocene the apparent 14 c groundwater ages range from modern to 11 1 ka bp which suggests some post glacial infiltration from melting ice sheets finally all the acquired information was used to propose a conceptual model of c origin within the basin

palaeorecharge conditions of the deep aquifers of the northern aquitaine region france summary the study was carried out in the northern part of the aquitaine basin extending in southwest france the basin has been intensively exploited for various purposes for many years although the geological context is well known there are still some gaps in the knowledge about the hydrogeochemical regime groundwater average residence time and the palaeohydrological conditions prevailing during the recharge period which would help to secure sustainable exploitation of the resources environmental isotopes 18 o 2 h 3 h 13 c together with radiocarbon were used to evaluate hydrochemical evolution residence time and palaeorecharge conditions for jurassic cretaceous and eocene aquifers radiocarbon activity in the aquifers varies widely between 0 and 94 pmc after radiocarbon corrections the ages indicate both modern and old waters sometimes exceeding the limit for 14 c dating the fontes and garnier model is best adapted to the specificity of the carbonate system the content in stable isotopes of water is varying between 7 7 and 4 9 for 18 o and 52 3 to 29 6 for 2 h the wide ranges of stable isotopic values imply variable climatic conditions a group of isotopically depleted samples was detected indicating colder climatic conditions during the recharge radiocarbon ages calculation together with isotopic signature point out that the depletion in stable isotopic values fits the period between 20 and 15 ka b p and therefore indicate the last glacial maximum lgm according to the correction model the transition from pleistocene to holocene would occur between 15 and 12 ka b p palaeohydrological data from the northern aquitaine basin does not confirm a significant hiatus in the recharge history the recharge conditions in south europe seem to have occurred under discontinuous permafrost conditions as documented by many palaeoclimatological archives this is in favour of an uninterrupted recharge of the confined aquifers of northern aquitaine basin such information should be considered by modellers in their attempts to simulate the hydrogeological functioning of large confined aquifers on the very long time range

water level fluctuations of lake tanganyika in phase with oceanic changes during the last glaciation and deglaciation there has been considerable controversy about the magnitude of fluctuations of the levels of lake tanganyika the earth s second deepest lake 1 470 m following the discovery of submerged valleys extending down to 550 m below present lake levels1 these fluctuations register changes in the precipitation evaporation evapotranspiration ratio in a large equatorial tropical area of catchment south of the equator here we report new palaeohydrological data back to 40 kyr bp from carbon dating of the total organic matter in two diatomaceous cores the results constrain the vertical lake level fluctuations more than has hitherto been possible2 5 and show that the fluctuations from 26 kyr bp are correlated with changes in global sea level and ice volume surpris ingly fluctuations seem to be in phase with those of the african lakes north of the equator which are clearly linked to the milankovitch mechanisms

isotopic evidence for plio pleistocene environmental change at gona ethiopia abstract a 4 5 ma record of fluvial and lacustrine deposits is well exposed at gona in the afar depression of ethiopia we use isotopic values of pedogenic carbonate and fossil teeth to reconstruct plio pleistocene environmental change at gona an increase in 13c values of pedogenic carbonates since 4 5 ma points to a shift from woodlands to grassy woodlands in the early pliocene 10 4 to 3 9 vpdb to more open but still mixed environments in the late pleistocene 3 0 to 1 4 vpdb this pattern is also seen in isotopic records elsewhere in east africa however at 1 5 ma the higher proportion of c4 grasses at gona is largely a result of a local facies shift to more water limited environments the wide range of 13c values of pedogenic carbonate within single stratigraphic levels indicates a mosaic of vegetation for all time intervals at gona that depends on depositional environment elements of this mosaic are reflected in 13c values of both modern plants and soil organic matter and plio pleistocene soil carbonate indicating higher amounts of c4 grasses with greater distance from a river channel in both the modern and ancient awash river systems 18o values of pedogenic carbonates increase up section from 11 9 in the early pliocene to 6 4 vpdb in the late pleistocene the wide range of 18o values in paleovertisol carbonates from all stratigraphic levels probably reflects short term climate changes and periods of strong evaporation throughout the record based on the comparison between 18o values of plio pleistocene pedogenic carbonates and modern waters we estimate that there has been a 6 5 increase in mean annual 18o values of meteoric water since 4 5 ma 18o values of pedogenic carbonate from other east african records indicate a similar shift increasing aridity and fluctuations in the timing and source of rainfall are likely responsible for the changes in 18o values of east african pedogenic carbonates through the plio pleistocene

palaeoclimatic and deforestation effect on the coastal fresh groundwater resources of se ivory coast from isotopic and chemical evidence summary in the south east of the ivory coast two aquifer systems have been studied in the sedimentary deposits at the south and in the fractured bedrock at the north of the study area 5 6 n 2 40 4 40 w 1 the continental terminal ct and 2 the paleoproterozoic bedrock pb in the studied area the vegetation cover has undergone significant changes since 1955 in addition to climate change rainforests have gradually disappeared due to natural and anthropological deforestation the impact of deforestation on groundwater of the pb and on the ct has been studied by a geochemical approach stable isotopes 18 o 2 h and 13 c contents radiocarbon 14 c contents and chemical data major ions have been measured on a set of 25 groundwater samples the residence time of the groundwaters is estimated with the 14 c using two models i the model of well mixed reservoir wmr model and ii the piston flow model pf model the range of the pb groundwater residence time 15 200 8300 to 300 100 a bp for both models shows that the recharge has started at the beginning of the post glacial period whereas the ct aquifer recharge is much more recent from 300 a bp to today the pb groundwater provides information about paleoclimatic conditions that occurred over the studied area during the late pleistocene the low contents indicate cold and or more humid conditions of recharge during that period the low content of 13 c is consistent with a vegetation cover dominated by rainforest c 3 plants after the 20th century the progressive evolution of vegetation cover from forest to cultivated plants and grasses is shown by the enrichment of groundwater in 13 c c 3 plants to c 4 plants the relatively high mineralization level mean of 143 7 mg l 1 and high 18 o 2 h values of modern pb groundwater reflect of a recharge process that is slowed by a thick layer 16 3 72 5 m of weathered formations above the pb formations groundwaters of the ct aquifer are constantly supplied by the fast infiltration of rainfall towards the water table explaining their very low total dissolved solids tds of 20 1 mg l 1 their high 14 c activities and their non evaporated characteristics

delineation of groundwater provenance in a coastal aquifer using statistical and isotopic methods southeast tanzania rapid population growth and urbanization has placed a high demand on freshwater resources in southeast costal tanzania in this paper we identify the various sources of groundwater and the major factors affecting the groundwater quality by means of multivariate statistical analyses using chemical tracers and stable isotope signatures the results from hierarchical cluster analyses show that the groundwater in the study area may be classified into four groups a factor analysis indicates that groundwater composition is mainly affected by three processes accounting for 80 6 of the total data variance seawater intrusion dilution of groundwater by recharge and sewage infiltration the hydrochemical facies of shallow groundwater was mostly of the na ca cl type although other water types were also observed the deep groundwater samples were slightly to moderately mineralized and they were of the nahco3 type this water type is induced mainly by dissolution of carbonate minerals and modified by ion exchange reactions the signal from the stable isotope composition of the groundwater samples corresponded well with the major chemical characteristics in the shallow groundwater both high nitrate and high chloride concentrations were associated with localized stable isotope enrichments which offset the meteoric isotopic signature this is inferred to be due to the contamination by influx of sewage as well as intrusion by seawater the depleted stable isotope values which coincides with a chemical signature for the deep aquifer indicates that this deep groundwater is derived from infiltration in the recharge zone followed by slow lateral percolation this study shows that a conceptual hydrogeochemical interpretation of the results from multivariate statistical analysis using hca and fa on water chemistry including isotopic data provides a powerful tool for classifying the sources of groundwater and identifying the significant factors governing the groundwater quality the derived knowledge generated by this study constitutes a conceptual framework for investigating groundwater characteristics this is a prerequisite for developing a sound management plan which is a requirement for ensuring a sustainable exploitation of the deep aquifer water resource in the coastal area of tanzania

seasonality in equatorial climate over the past 25 k y revealed by oxygen isotope records from mount kilimanjaro multiproxy analysis of a well dated 25 ka lake sediment sequence from lake challa on the eastern flank of mount kilimanjaro east africa reveals the climatic controls that govern both the lake s paleohydrology and the climate proxy record contained in the mountain s receding ice cap the oxygen isotope record extracted from diatom silica 18odiatom in lake challa sediments captured dry conditions during the last glacial period and a wet late glacial transition to the holocene interrupted by younger dryas drought further it faithfully traced gradual weakening of the southeastern monsoon during the holocene overall 18odiatom matches the branched isoprenoid tetraether bit index of rainfall induced soil runoff except during 25 22 ka and the past 5 k y when insolation forcing due to orbital precession enhanced the northeastern monsoon this pattern arises because during these two periods a weakened southeastern monsoon reduced the amount of rainfall during the long rainy season and enhanced the opposing effect of evaporation intensity and or length of the austral winter dry season importantly our lake based reconstruction of moisture balance seasonality in equatorial east africa also helps us understand the oxygen isotope record contained in mount kilimanjaro ice negative correlation between ice core 18o and lake challa 18odiatom implies that moisture balance is not the primary climate control on the long term trend in ice core 18o

dolomite formation in the shallow seas of the alpine triassic the alpine triassic units of switzerland northern italy and western austria offer an extensive geological archive in which the enigmatic process of dolomite formation can be studied in a palaeoenvironmental context recent studies clearly demonstrate that large amounts of the alpine triassic dolomites are late diagenetic or hydrothermal nevertheless as part of multiple generations of diagenetic overprint some generations of fine crystalline ca rich dolomite appear strictly confined to their depositional facies and show signs of very early formation at surface temperatures in specific ancient depositional environments in this review three cases of alpine triassic dolomites are discussed where dolomite rocks may have formed during or soon after sedimentation the sedimentary facies indicate contrasting palaeoenvironmental conditions and hence document three different possible processes of dolomite formation i in the dolomite mountains northern italy dolomite beds of the partly isolated middle triassic anisian ladinian latemar platform are confined to the very top of shallowing upward lagoonal facies cycles ii dolomite beds of the san giorgio basin southern switzerland an intra platform basin that opened during the anisian ladinian transition are associated with organic carbon rich shales which were deposited in a deeper water environment under anoxic conditions iii in the entirely dolomitized platform facies of the dolomia principale hauptdolomit formation a very early generation of fine crystalline dolomite occurs in the shallowest part of evaporative peritidal cycles this platform extended over thousands of square kilometres along the tethys margin during the late triassic carnian and norian and large amounts of carbonate were deposited under hypersaline sabkha like conditions representing three distinct depositional environments these three different triassic systems show features in common with several dolomitization models developed from the study of modern dolomite forming environments for example the sabkha model the evaporative lagoon lake model the organogenic model and the microbial model although these actualistic models may be applicable to reconstruct the palaeoenvironmental conditions during dolomite formation dolomite forming processes during the triassic were apparently quite different from the modern world in terms of distribution and scale recent developments in stable isotope geochemistry and high resolution geochemical probing offer the possibility to make better reconstructions of triassic palaeoceanographic conditions and suggest a non actualistic approach to better understand dolomite formation during the triassic

high resolution record of northern hemisphere climate extending into the last interglacial period high resolution record of northern hemisphere climate extending into the last interglacial period

evolution of the aveiro cretaceous aquifer nw portugal during the late pleistocene and present day evidence from chemical and isotopic data

the original swiss flysch a reappraisal of the type deposits in the swiss prealps abstract the flysch sequences of the swiss prealps alpine front ranges are described and interpreted in the light of a decade of study by a group research project at fribourg the geographical and geological settings are illustrated the stratigraphy and sedimentology the sedimentary petrography and the geodynamic setting are discussed correlations within and outside the prealps as well as outstanding problems are treated the flysch units and sequences covered are the gurnigel flysch the medianes flysch helminthoid flysch fouyet manche and mocausa flysch hundsruck flysch niesen flysch and the ultrahelvetic flysch the data from clast framework grain and heavy mineral analysis from micropalaeontology from facies analysis palaeocurrent measurements and stratigraphy allow the interpretation of sedimentary environments source terranes and depositional models in all cases flysch deposits are deep marine detrital accumulations and source areas were undergoing active tectonics individual models are based on the deep sea fan concept but interpretations tend to show significant modifications with respect to simple fan characteristics these departures are to some extent due to available grain size to active structuring of basins or to minor controls such as eustatic variations or climatic influence the integration of sedimentological data with stratigraphy and regional structure furnishes palinspastic reconstructions in map view these provide insights on the palaeogeography of the western alps from mid cretaceous to oligocene and give a picture of the evolution of the western mediterranean tethys during the same period the relationship between flysch deposition and alpine mountain building is confirmed while constraints on basin evolution are established

paleoclimatic investigations using isotopic signatures of the late pleistocene holocene groundwater of the stratified aquifers in kuwait abstract the study attempts to determine paleo recharge sources for two major aquifer units of kuwait namely kuwait group aquifer kga and dammam formation dfm were collected and analyzed for major ions and isotopes the obtained results of 14c ages indicated that the groundwater samples ranged from 31 9 ky to 3 9 ky in dfm and 23 3 ky to 0 8 ky in kga the variations in 18o signatures with respect to age reflected that there were two major sources of rainwater such as enriched southern indian ocean monsoon and the depleted northwesterly mediterranean vapor source the samples found to show variations during the three marine isotopic stages mis 1 3 heinrich events bolling allerod and dryas time periods in both aquifers a shift in the intertropical convergence zone itcz was witnessed in the groundwater of both aquifers from 7 8 ky to 4 9 ky the variation in the holocene climate is mainly due to the influence of tropospheric easterly jet governed by the swing in itcz as a result of holocene volcanism the mean 18o values of dfm samples 3 81 reflect depletion than kga samples 2 31 and the d excess values were 0 95 and 2 05 respectively thus it could be inferred that the dfm was predominantly recharged during late pleistocene period and it was in a relatively cooler climate than recharge environment of kga the study infers that kga was recharged between 26on and 26 8on latitudes and that of the dfm was noted to be recharged south west of kuwait in two different patches between 25 8on and 26 2on and 26 7on 27 4on latitudes during late pleistocene the kga was concluded to be recharged between 25 5on and 27 5on latitudes south of kuwait during holocene

stable isotope composition of tropical high altitude fresh waters on mt kenya equatorial east africa abstract the stable isotope composition of equatorial high altitude precipitation and surface water bodies has been studied on mt kenya 0 10 s 37 20 e in east africa during july 1997 regarding the local hydrology glacier meltwater was identified as the main source of replenishment for the lakes while direct precipitation and runoff appear to have a negligible contribution during this period of the year two through flow lakes exhibit nearly no evaporative isotopic enrichment relative to the inflow isotopic composition while two longer residence time lakes display an oxygen and hydrogen isotopic build up of 4 0 7 0 and 18 0 34 0 respectively the data indicate that stream waters are composed of a mixture of high altitude glacier meltwater and rainfall the isotopic composition of an ice sample obtained directly from the margin of a glacier is enriched relative to the average composition of the glacier suggesting mixing with local rain samples of ground frost crystals have an isotopic composition similar to the rain or slightly enriched in addition the results show the lack of a significant altitude effect on the mountain this study demonstrates the importance of the characterization of local hydrological settings when interpreting lacustrine equatorial isotopic records of past climate and confirms that for east africa the total range in oxygen and hydrogen isotopic composition of meteoric waters is smaller than in high latitudes

a high resolution paleoclimate record spanning the past 25 000 years in southern east africa high resolution profiles of the mass accumulation rate of biogenic silica and other geochemical proxies in two piston cores from northern lake malawi provide a climate signal for this part of tropical africa spanning the past 25 000 years the biogenic silica mass accumulation rate was low during the relatively dry late pleistocene when the river flux of silica to the lake was suppressed millennial scale fluctuations due to upwelling intensity in the late pleistocene climate of the lake malawi basin appear to have been closely linked to the northern hemisphere climate until 11 thousand years ago relatively cold conditions in the northern hemisphere coincided with more frequent north winds over the malawi basin perhaps resulting from a more southward migration of the intertropical convergence zone

north atlantic circulation and reservoir age changes over the past 41 000 years 1 constraints on the timing of atlantic meridional overturning circulation amoc changes during the last deglaciation are fundamental to understanding the climate s rapid response to insolation forcing however uncertainty about high latitude north atlantic hlna radiocarbon reservoir ages has previously precluded robust age model development for this critical region hlna reservoir ages also serve as a proxy for amoc strength we present regionally averaged hlna reservoir ages for 0 to 41 thousand years before the present kyr bp based on over 500 radiocarbon dates from 33 north atlantic cores an early deglacial increase to 1000 14c yr reservoir ages between 18 5 and 16 5 kyr bp suggests reduced amoc before peak heinrich stadial 1 hs1 ice rafted debris ird a rapid decrease in reservoir ages coincident with the ird maximum at 16 kyr bp indicates strong stratification of the upper water column caused by massive freshwater release

carbon isotopes in pore water of the unsaturated zone and their relevance for initial 14c activity in groundwater in the coastal aquifer of israel abstract this paper presents a study of the isotopic composition of dissolved inorganic carbon dic stable and radioactive in pore water of the unsaturated zone usz above the coastal aquifer of israel the carbon content and its isotopic composition in the gas and solid phases of the usz are also presented in the soil gas large quantities of co 2 with quite modern 14 c activity were measured along the section 0 15 to 2 7 and 97 to 109 pmc respectively in the inorganic fraction of the sediments the 14 c activity between 2 5 and 13 m was 33 to 1 5 pmc in the organic fraction the 14 c activity between 7 and 9 m was 40 to 33 pmc in the pore water the high values of tritium and 14 c at depths of 15 18 m have been attributed to the thermonuclear contamination of the 1960s a significant decrease with depth in the dic of pore water from 23 to 4 mmol c l along with a decrease with depth in dissolved inorganic 14 c from 100 pmc near the surface to 72 pmc at depth of 20 m were observed the 13 c values in the dic are similar to the values in the inorganic sediment 10 a first order reaction was applied to estimate the yearly rates of dic loss by net precipitation 3 2 year and of 14 c activity dpm l loss from the dic by gross precipitation from the dic on the sediment 4 4 year from the gradient of dissolved inorganic 14 c the initial level at the bottom of the usz which is the groundwater table of the coastal aquifer of israel was estimated to be 0 54 of contemporaneous atmospheric value of 14 c when the rain fell on the ground this value can be used for improved dating of groundwater with 14 c in the coastal aquifer of israel

atmospheric circulation patterns during late pleistocene climate changes at lake malawi africa abstract the climate of tropical africa transitioned from an interval of pronounced orbitally paced megadroughts to more humid and stable conditions approximately 70 000 years ago scholz et al 2007 the regional atmospheric circulation patterns that accompanied these climatic changes however are unclear due to a paucity of continental paleoclimate records from tropical africa extending into the last interglacial we present a new 140 kyr record of the deuterium hydrogen isotopic ratio of terrestrial leaf waxes d wax from drill cores from lake malawi southeast africa that spans this important climatic transition d wax shifts from highly variable and relatively d depleted to more stable and d enriched around 56 ka contemporary with the onset of more humid conditions in the region moisture source and transport history dominate the d wax signal at lake malawi with local rainfall amount playing a secondary role for much of the paleorecord analysis of modern moisture sources for lake malawi suggests that d depletion of waxes during the megadroughts may have been caused by an enhanced contribution of the drier d depleted air mass currently located in central southern africa to the lake malawi catchment this d depleted air mass is associated with the descending limb of the hadley cell which implies significant changes in the hadley circulation during the megadroughts and related changes in the position of the intertropical convergence zone over africa these findings demonstrate the ability of d wax to serve as an atmospheric tracer when used in conjunction with additional proxy records for moisture balance and elucidate potential mechanisms for pronounced hydrological change in southeast africa during the late pleistocene

residence time of chalk groundwaters in the paris basin and the north german basin a geochemical approach the comparative geochemical and isotopic study of confined and unconfined chalk groundwaters of the paris basin and the n german basin proves a significant chemical evolution during groundwater flow from the recharge zones to the deep confined aquifer different time dependent geochemical parameters have been tested as dating tools cation ratios sr2 ca2 mg2 ca2 n no 3 noble gas contents as paleotemperature indicators ne ar kr xe radiogenic he 13c 14c 18o 2h 3h cation ratios and 13c show the importance of incongruent dissolution processes in the chalk aquifer water rock interactions were taken into account in a multi step dissolution model to determine radiocarbon groundwater ages the oldest waters in the confined part of the paris basin chalk with maximum 14c ages of 14 000 a b p contain pleistocene recharge components as can be shown by a stable isotope depletion and noble gas temperatures significantly lower than in recent groundwaters chalk waters at the lagerdorf site in northern germany show a distinct stratification with respect to residence times and hydrochemistry

evolution of groundwater systems at the european coastline an overview is given of the status and origin of fresh and saline groundwaters in the sedimentary aquifers at or near the present european coastline results are presented as six regional maps summarizing as far as possible the conditions likely to have existed at the end of the pleistocene after the impact of glaciation when groundwaters might be expected to have reached their maximum offshore evolution prior to the encroachment of sea water during the holocene marine transgression in the eastern baltic the groundwater evolution was different to other european regions in that freshwater heads were higher than the present day promoting recharge during much of the late pleistocene near the north sea coasts there is generally evidence of freshwater movement to depths of 100 150 m but the absence of deeper freshwater palaeowater storage may relate to the low hydraulic gradients in the north sea basin in the southeastern part of the north sea brackish palaeowater is found between tertiary marine sediments c 300 m below the island of rcmo l 0 km off the danish west coast freshwater of pleistocene and holocene ages is found in aquifers at the english channel coast in several areas to depths in excess of 300 m offshore flow in the late pleistocene took place towards the central palaeovalley and some of this groundwater may be preserved off the present coastline in the two atlantic coastal areas of france and portugal spain a contrast exists due to the proximity of the continental margin and different hydraulic gradients in portugal freshwaters are found at the coastline and probably offshore that contain evidence of recharge during the lowered sea levels in most of the southwestern atlantic coast of spain fresh recent groundwater discharges along and beyond the coastline while in the old estuary of the guadalquivir river saline holocene water still encroaches the sediments on the mediterranean coast of france and spain some salinity encroachment took place during sea level rise in most of the spanish aquifers fresh recent groundwater has substituted for palaeowater except for the low lying areas ebro delta inca sa pobla plain where brackish holocene water is still present

late pleistocene temperature history of southeast africa a tex86 temperature record from lake malawi we present a tex86 derived surface water temperature record for lake malawi that provides the first continuous continental record of temperature variability in the continental tropics spanning the past similar to 74 kyr with millennial scale resolution average temperature during marine isotope stage mis 5a was 26 5 degrees c with a range from 25 7 to 27 3 degrees c comparable to holocene temperatures mis 4 was a relatively cold period with temperatures generally decreasing from 25 5 degrees c at 68 ka to a minimum of 20 degrees cat similar to 60 ka 1 5 2 degrees c colder than the last glacial maximum lgm termination of mis 4 is characterized by a rapid increase of 3 4 degrees c in only similar to 0 5 kyr temperatures were relatively stable throughout mis 3 at the resolution of this study with an average of 23 8 degrees c and a range from 25 1 to 22 9 degrees c the lack of millennial scale temperature variability during mis 3 suggests that lake malawi s documented response to the bipolar seesaw brown et al 2007 is not reflected in its thermal history our temperature estimates for the lgm and holocene are consistent with a previously published tex86 record from lake malawi with a temperature of similar to 22 6 degrees c for the lgm similar to 25 26 degrees c in the mid holocene and similar to 25 28 for the late holocene in general the present extended tex86 record indicates that temperature variability in tropical east africa during late mis 5 and mis 4 was as great as that associated with the deglaciation and holocene a decrease in southern hemisphere insolation between 70 and 60 ka may have played an important role in forcing temperatures during mis 4 but after 60 ka other factors such as the extent of the polar ice sheets or atmospheric co2 may have forced temperature in tropical africa to a greater extent than local summer insolation

abrupt changes in indian summer monsoon strength during 33 800 to 5500 years b p speleothem proxy records from northeastern ne india reflect seasonal changes in indian summer monsoon strength as well as moisture source and transport paths we have analyzed a new speleothem record from mawmluh cave meghalaya india in order to better understand these processes the data show a strong wet phase 33 500 32 500 years b p followed by a weak dry phase from 26 000 to 23 500 years b p and a very weak phase from 17 000 to 15 000 years b p the record suggests abrupt increase in strength during the bolling allerod and early holocene periods and pronounced weakening during the heinrich and younger dryas cold events we infer that these changes in monsoon strength are driven by changes in temperature gradients which drive changes in winds and moisture transport into northeast india

hydrochemical and 14c constraints on groundwater recharge and interbasin flow in an arid watershed tule desert nevada summary geochemical data deduced from groundwater and vein calcite were used to quantify groundwater recharge and interbasin flow rates in the tule desert southeastern nevada 14 c age gradients below the water table suggest recharge rates of 1 2 mm yr which correspond to a sustainable yield of 5 10 4 km 3 yr to 1 10 3 km 3 yr uncertainties in the applied effective porosity value and increasing horizontal interbasin flow components at greater depths may bias these estimates low compared to those previously reported using the water budget method the deviation of the groundwater 18 o time series pattern for the pleistocene holocene transition from that of the devils hole vein calcite which is considered a proxy for local climate change allows interbasin flow rates of northerly derived groundwater to be estimated the constrained rates 75 0 120 m yr are slightly higher than those previously calculated using darcy s law but translate into hydraulic conductivity values strikingly similar to those obtained from pump tests data further indicate that production wells located closer to the western mountainous margin will be producing mainly from locally derived mountain system recharge whereas wells located closer to the eastern margin are more influenced by older regionally derived carbonate groundwater

groundwater residence time and paleorecharge conditions in the deep confined aquifers of the coastal watershed south east tanzania summary analysis of radiocarbon and stable isotopes of c h and o in groundwater samples from the coastal watershed of southeastern tanzania is used to decipher the age of groundwater and the climatic conditions at the time of recharge radiocarbon dating was corrected on the basis of stable carbon isotope ratios and hydrochemical data two main recharge periods are recognised 1 a recent recharge period with residence times dated to younger than 1 3 ka bp for the shallow aquifer and some deep groundwater aquifers and 2 a paleorecharge occurring during the late pleistocene to holocene transition between 6 and 13 ka bp for the lower confined aquifer the climatic excursions arid and humid phases identified in this study match well with those identified from studies of paleo climatic records in tanzania and east africa the oxygen 18 and radiocarbon results show that there is a potential mixing of groundwater of varying ages along flow paths in the coastal aquifer system this has also been shown by redox parameters in some of the deeper aquifer samples the data also revealed that there is relatively simple pattern of lateral groundwater flow in the deeper confined aquifer isotopic evidence from this study and related studies in paleolimnology improves our knowledge of the past climates the data suggests that the paleorecharge to the confined aquifer was from inland under wetter climatic conditions than present therefore paleorecharge from the adjacent mountain regions to coastal area like ifakara morogoro and udzungwa mountains could be important parts of recharge area of the kimbiji aquifer however the hinterland mountains of dar es salaam mainly pugu mkuranga ruvu and kisarawe could also play an important role in replenishing the kimbiji coastal aquifers in contrast recharge in the shallow unconfined aquifer is characterized by local rainfall and river water infiltration this study is the first of its kind assessing fingerprinting of paleoclimates in southeastern coastal tanzania using the isotopic composition of deep groundwater aquifers the freshwater resources in the neogene aquifer contain paleo groundwater aquifers that have been mixed with recently recharged flow systems hence the resources may be sustainable this study also provides information that may be useful for designing optimum strategies for a sustainable management of groundwater resources in the coastal aquifer and it testifies to the importance of groundwater as a paleoclimatic archive such information is also essential for consideration by modellers in their attempts to simulate the hydrogeological processes in confined aquifers over very long time spans

evidence of past climatic change in the namib desert abstract a preliminary survey of some areas of the central and northern namib desert was undertaken in order to identify geomorphic and sedimentary features that could potentially provide information on past climatic change in the region wherever possible samples were collected for radiocarbon dating the visits to the skeleton coast area were especially revealing practically every river valley in this tract shows a sequence of terraces and deposits that would warrant a detailed study in all about 120 new radiocarbon dates were obtained for the region these have supplied a wealth of individual results and collectively have enabled the construction of a tentative chronological sequence of the changes in climate for the past 40 000 yr three periods of increased aridity in the hinterland but with decreasing intensity are postulated during the last glacial maximum the early holocene and between a d 1200 and a d 1600 the inter pleniglacial up to 23 000 yr b p the late glacial and the period between about 4000 yr b p and 1200 yr b p on the other hand were more humid than today also with decreasing intensity other indicators of past climate were also identified but since they lie beyond the range of radiocarbon dating they cannot as yet be placed in a chronological context of significance is the fact that convincing evidence was obtained for climatic change within the last millennium and especially the rainfall is found to have been increasing since the 16th century

how to stir a revolution as a reluctant rebel rudolf trumpy in the alps rudolf trumpy 1921 2009 was one of the great alpine geologists of the twentieth century and an influential figure in the international geological community he played a dominant role in the change of opinion concerning the alpine evolution by showing that normal faulting dominated the early development of the alpine realm from the triassic to the early cretaceous this provided a convenient model for later plate tectonic interpretations of collisional mountain belts his further recognition of strike slip faulting during all stages of the alpine evolution presaged the realisation that the alps were not built by a simple open and shut mechanism trumpy was educated during an intellectual lull a time when simplistic models of the earth behaviour inherited from the middle of the nineteenth century became prevalent under the influence of a close minded positivist approach to geological problems this period which we term the dark intermezzo lasted from about 1925 to 1965 the grand syntheses of suess and argand which preceded this period were viewed from this narrow angle and consequently misunderstood it was thought that earth history was punctuated by global orogenic events of short duration taking place within and among continents and oceans whose relative positions had remained fixed since the origin of the planet these views summarised under the term fixism were developed when the ocean floors were almost totally unknown when data began coming in from the post world war ii oceanographic surveys the world geological community was slow to receive and digest them trumpy followed these developments closely realising that his work was important in placing the geology of the mountain belts within the emerging new theoretical framework he adopted the position of a critic and emphasised where detailed knowledge of the alps unquestionably the best known mountain belt in the world supported and where it contradicted the new ideas his voice was listened to carefully and subsequent developments have shown his critique to have been prescient it is regrettable that he did not publish some of the theoretical criticisms he communicated to his colleagues during scientific meetings and informal conversations his hesitance in becoming involved in theoretical arguments in geology may have stemmed partly from his scientific upbringing during the dark intermezzo and partly because he genuinely believed that he was better off sticking to what he thought he knew for sure he nevertheless stressed that it is important for geologists to dream it is often said about teachers that one should do what they say not what they do in trumpy s case it was the opposite both scientifically and as a human being he was a most admirable man

geochemistry and residence time estimation of groundwater from the upper aquifer of the chihuahua desert comarca lagunera northern mexico 178 groundwater and surface waters have been sampled from april to september 1994 in an endoreic basin located in the n of mexico comarca lagunera in this area groundwater has been exploited over the past century mainly for irrigation and cattle supply recent intensive pumping has caused the lowering of the water table at a rate of 1 m a 1 chemical analyses have been performed on all collected samples and 37 of them have been selected for isotopic measurements 18o 2h 13c and14c water stable isotope contents 18o 2h show an increasing evaporation of the groundwater towards the nazas river they also indicate that the recharge occurs from the nazas river and from the mountains surrounding the depression sierra madre occidental water presents a large spatial variability of the chemical facies so4ca so4clna hco3 ca and hco3 na which is in relation with i their interaction with the geological formations of the basin carbonates gypsum and various silicates and ii evaporation this evaporation occurs in the upper part of the unsaturated zone during infiltration especially for the groundwater sampled near the nazas river the14c activity varies between 110 4 1 1 and 4 0 0 2 pmc the13c contents of the total dissolved inorganic c tdic range between 11 0 and 3 6 the calculated13c contents of the co2 in equilibrium with the tdic varying between 18 4 0 to 10 9 indicate two origins of c in solution the carbonate matrix 13c 0 9 and the soil co2 13c from 27 7 to 21 7 for the cultivated areas mean residence times have been determined after correction of the initial activities for dead c from the rock matrix the mean residence times confirm a modern recharge of the groundwater from the nazas and indicate the presence of palaeowaters in the northern and southern parts of the basin up to 30 ka bp

a summer monsoon pump to keep the bay of bengal salty the bay of bengal receives a large influx of freshwater from precipitation and river discharge outflow of excess freshwater and inflow of saltier water is required to prevent the bay from freshening relatively fresh water flows out of the bay along its boundaries and inflow of saltier water occurs via the summer monsoon current smc which flows eastward from the arabian sea into the bay this saltier water however slides under the lighter surface water of the bay maintaining the salt balance of the bay therefore demands upward mixing of this saltier subsurface water here we show that an efficient mechanism for this mixing is provided by upward pumping of saltier water in several bursts during the summer monsoon along the meandering path of the smc advection by currents can then take this saltier water into the rest of the basin allowing the bay to stay salty despite a large net freshwater input

hydrogen and oxygen isotopic compositions of water vapor over the bay of bengal during monsoon 1 dv and 18ov of 70 water vapor samples collected at 6 and 25 m above sea level over the bay of bengal bob during july august 2012 are reported this helps characterize the isotopic signature of monsoon vapor no significant vertical variation is observed in dv 18ov or deuterium excess defined as d 8 18o dv and 18ov are significantly correlated r 0 92 at each height the deuterium excess values do not because the variation of dv and 18ov relative to their uncertainties is much larger than that of the latter the temporal variations of dv and 18ov correlate well with air temperature rather than sea surface temperature the control of normalized humidity on deuterium excess is less prominent while the distribution of water vapor isotopologues over the bob is primarily determined by the ocean surface conditions they are significantly altered by laterally advected vapor from rain en route during the monsoon

unravelling the evolution of an alpine to post glacially active fault in the swiss alps abstract the gemmi fault is a prominent nw se striking lineament that crosses the gemmi pass in the central swiss alps a multidisciplinary investigation of this structure that included geological mapping joint profiling cathodoluminescence and scanning electron microscopy stable isotope measurements luminescence and u th dating 3d ground penetrating radar gpr surveying and trenching reveals a history of fault movements from the miocene to the holocene the main fault zone comprises a 0 5 3 m thick calcite cataclasite formed during several cycles of veining and brittle deformation displaced cretaceous rock layers show an apparent dextral slip of 10 m along the fault a detailed study of a small sediment filled depression that crosses the fault provides evidence for a post glacial reactivation of the fault a trench excavated across the fault exposed a late glacial age loess layer and late holocene colluvial like slope wash deposits that showed evidence for fault displacement of a few centimeters indicating a recent strike slip reactivation of the fault focal mechanisms of recent instrumentally recorded earthquakes are consistent with our findings that show that the fault at the gemmi pass together with other parallel faults in this area may be reactivated in today s stress field taking together all the observations of its ancient and recent activity the gemmi fault can be viewed as a window through geological space and time

wisconsin roots of the modern revolution in structural geology conventional wisdom long held that all important intellectual diffusion was from europe westward to north america until the 1940s but two examples of a reverse flow of fundamental concepts of structural geology during the 1920s challenge that dogma those concepts were products of the renowned wisconsin school of precambrian geology and their transplantation also involved princeton university the first example of wisconsin export concerns the use of sedimentary structures for establishing the original top facing or way up direction within complexly deformed strata although this technique was recognized in nineteenth century ireland that insight was ignored and lost only after its reintroduction to great britain from wisconsin in the 1920s was its importance gradually recognized in europe the second example concerns the recognition that small scale deformational structures visible in isolated outcrops reflect larger regional structures which are commonly not directly observable this fundamental inference also had its roots in wisconsin where englishman gilbert wilson learned it in 1925 1926 and then taught it at the imperial college in london these two key concepts of small scale structural analysis coupled with the use of the stereonet and insights from experimental deformation of rocks became the basis for a revolution in structural geology during the 1950s to 1970s after the triumphs of four generations of wisconsin faculty members who were outstanding both as scientists and administrators the wisconsin school faltered until the waves of that revolution washed back upon american shores during the 1960s

a paleoclimatic perspective on the 21st century glacier loss on kilimanjaro tanzania assessing the significance of current glacier loss on kilimanjaro tanzania demands a well constrained temporal perspective that context is provided by direct measurements ancillary observations of the ice fields and the analyses of the ice cores collected from them ice retreat mechanisms observed there today are consistent with the preservation of the oldest ice 11 7 ka in the central deepest part of the northern ice field nif this ice core derived paleoclimate history published by thompson and others 2002 is further confirmed by more recent paleoclimate records from tropical east africa mounting evidence suggests that the anticipated loss of the entire nif will be unprecedented within the past 10 000 years new evidence bears directly on the mechanisms driving the current ice loss measurements made in 2000 on the nif document that air temperature at 0 5 and 1 5 m above the surface remained below 58c while a surface temperature of 0 08c was sustained for up to 8 hours d 1 under clear conditions consistent with observations of melting on all kilimanjaro summit ice fields the linear relationship between oxygen and hydrogen isotopic ratios for all six ice cores drilled in 2000 lies very close to the global meteoric waterline and does not support sublimation evaporation as a major driver of ice loss today or in the past on kilimanjaro

pre oceanic rifting in the alps abstract a review of mesozoic mainly earliest jurassic to mid jurassic rifting in the western and central alps normal faults with throws up to a few kilometers are moderately inclined and involve rotation of crustal blocks the amount of stretching and thinning of the crust by jurassic rifting is discussed the rifting 200 165 m y pre dates the opening of the alpine oceans by spreading and transform movements 165 110 m y

relating orogen width to shortening erosion and exhumation during alpine collision we investigate along strike width changes of the thickened accreted lower plate talp in the central and in the eastern alps we set the width of the talp in relation to the inferred amount of collisional shortening and exhumation along six orogen scale cross sections taking the present day along strike gradients in the amount of collisional shortening to represent the temporal evolution of the collisional wedge it may be concluded that the cross sectional area of the talp diminishes during ongoing shortening indicating that the erosional flux outpaced the accretionary flux higher amounts of collisional shortening systematically coincide with smaller widths of the talp and dramatic increases of the reconstructed eroded rock column higher amounts of shortening also coincide with larger amplitudes of orogen scale upright folds with higher exhumation and with higher exhumation rates hence erosion did play a major role in reducing by 30 km the vertical crustal thickness in order to accommodate and allow shortening by folding long term climate differences cannot explain alternating changes of width by a factor of almost 2 along straight segments of the orogen on length scales less than 200 km as observed from the western central alps to the easternmost eastern alps sedimentary or paleontological evidences supporting such paleo climatic differences are lacking suggesting that erosional processes did not directly control the width of the orogen

late pleistocene paleohydrography and diatom paleoecology of the central basin of lake malawi africa analysis of sedimentary diatom assemblages 10 to 144 ka form the basis for a detailed reconstruction of the paleohydrography and diatom paleoecology of lake malawi lake level fluctuations on the order of hundreds of meters were in ferred from dramatic changes in the fossil and sedimentary archives many of the fossil diatom assemblages we observed have no analog in modern lake malawi cyclotelloid diatom species are a major component of fossil assemblages prior to 35 ka but are not found in significant abundances in the modern diatom communities in lake malawi salinity and alkalin ity tolerant plankton has not been reported in the modern lake system but frequently dominant fossil diatom assemblages prior to 85 ka large stephanodiscoid species that often dominate the plankton today are rarely present in the fossil record prior to 31 ka similarly prior to 31 ka common central basin aulacoseiroid species are replaced by species found in the shallow well mixed southern basin surprisingly tychoplankton and periphyton were not common throughout prolonged lowstands but tended to increase in relative abundance during periods of inferred deeper lake environments a high resolution lake level reconstruction was generated by a principle component analysis of fossil diatom and wetsieved fossil and mineralogical residue records prior to 70 ka fossil assemblages suggest that the central basin was periodically a much shallower more saline and or alkaline well mixed environment the most significant reconstructed lowstands are 600 m below the modern lake level and span thousands of years these conditions contrast starkly with the deep dilute dysaerobic environments of the modern central basin after 70 ka our reconstruction indicates sustained deeper water environments were common marked by a few brief but significant lowstands high amplitude lake level fluctuations appear related to changes in insolation seismic reflection data and additional sediment cores recovered from the northern basin of lake malawi provide evidence that supports our reconstruction