extending the vostok ice core record of palaeoclimate to the penultimate glacial period the ice core record of local temperature dust accumulation and air composition at vostok station antarctica now extends back to the penultimate glacial period 140 200 kyr ago and the end of the preceding interglacial this yields a new glaciological timescale for the whole record which is consistent with ocean records temperatures at vostok appear to have been more uniformly cold in the penultimate glacial period than in the most recent one concentrations of co2 and ch4 correlate well with temperature throughout the record

assessing the impact of mid holocene insolation on the atmosphere ocean system a sequence of numerical simulations was performed in order to assess the role of early to mid holocene orbital forcing on the coupled atmosphere ocean system results from both an atmosphere only general circulation model gcm forced by specified sea surface temperatures and a coupled atmosphere ocean gcm consistently suggest a stronger south asian monsoon and a strengthened pacific walker circulation the latter feature interacts dynamically with the equatorial ocean in the coupled model to produce enhanced pacific upwelling a more pronounced cold tongue and an even stronger monsoon results suggest that the climate of the equatorial pacific was more similar to the la nina phase of the modern southern oscillation rather than the el niiio phase

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

dating methods and geomorphic evidence of palaeoenvironmental changes at the eastern margin of the south peruvian coastal desert 14 30 s before and during the little ice age abstract the atacama desert is known to be one of the driest places on earth however in the study area between ica and nasca south peru 75 76 w 14 15 s palaeoclimate proxies show several semi arid phases during the holocene a more humid period during the early holocene favoured an open grass land which allowed the accumulation of desert loess eitel b hecht s machtle b schukraft g kadereit a wagner g kromer b unkel i reindel m 2005 geoarchaeological evidence from desert loess in the nazca palpa region southern peru palaeoenvironmental changes and their impact on pre columbian cultures archaeometry 47 137 158 the paracas and nasca cultures existing in that region between the 9th century bc and 7th century ad had propitious conditions to evolve and to settle close to the rivers fed by the monsoonal precipitation in the cordillera occidental culminating aridity after 600 ad might have caused the collapse of the nasca civilization the onset of semi arid climate towards the end of the late intermediate period 14th century ad allowed a reoccupation of the area here we present 14c and osl data from sediments of river terraces a debris flow and loess snails scutalus sp indicating appreciable geomorphic activity between 1390 and 1714 cal ad this phase is isochronous to the little ice age period on the northern hemisphere and to an increase in the ice accumulation on the quelccaya glacier in the peruvian altiplano thompson l g mosley thompson e bolzan j f koci b r 1985 a 1500 year record of tropical precipitation in ice cores from the quelccaya ice cap peru science 229 971 973

fragile landscapes fragile civilizations how climate determined societies in the pre columbian south peruvian andes abstract this paper presents alternating periods of geo ecological fragility and stability in a highly sensitive environmental setting the desert margin area of southern peru 14 5 s there we have to state that fragility was dominantly triggered by climatic changes which induced several oscillations of the desert margin during the mid holocene the study area received the holocene maximum of precipitation soil formation occurred and the desert retreated as loess paleosoil formation documents in contrast the titicaca region further south east experienced extreme drought at that time this regional antagonism between humid and dry conditions was a result of meridional shifts in moisture transport across the andes and occurred also during pre columbian times considering a coincidence between environmental and cultural changes we state that success and decline of civilizations were dominated by hydrological oscillations triggering fertility as well as a critical loss of natural resources fragile periods i e periods of geomorphological activity occurred contemporaneous with cultural transitions in response to spatial changing resources cultural foci were shifted so the success of pre columbian civilizations was closely coupled to areas of geo ecological favorability which were directly controlled by distinct regional impacts of large scale circulation mechanisms including el nino southern oscillation enso this spatial view on non uniform environmental and cultural changes has not been thoroughly considered before therefore for the first time this paper offers geomorphological evidence for diachronous andean agri cultural development which was geographically determined

el nino variability off peru during the last 20 000 years here we present a high resolution marine sediment record from the el nino region off the coast of peru spanning the last 20 000 years sea surface temperature photosynthetic pigments and a lithic proxy for el nino flood events on the continent are used as paleo el nino southern oscillation proxy data the onset of stronger el nino activity in peru started around 17 000 calibrated years before the present which is later than modeling experiments show but contemporaneous with the heinrich event 1 maximum el nino activity occurred during the early and late holocene especially during the second and third millennium b p the recurrence period of very strong el nino events is 60 80 years el nino events were weak before and during the beginning of the younger dryas during the middle of the holocene and during medieval times the strength of el nino flood events during the last millennium has positive and negative relationships to global and northern hemisphere temperature reconstructions

eight glacial cycles from an antarctic ice core the antarctic vostok ice core provided compelling evidence of the nature of climate and of climate feedbacks over the past 420 000 years marine records suggest that the amplitude of climate variability was smaller before that time but such records are often poorly resolved moreover it is not possible to infer the abundance of greenhouse gases in the atmosphere from marine records here we report the recovery of a deep ice core from dome c antarctica that provides a climate record for the past 740 000 years for the four most recent glacial cycles the data agree well with the record from vostok the earlier period between 740 000 and 430 000 years ago was characterized by less pronounced warmth in interglacial periods in antarctica but a higher proportion of each cycle was spent in the warm mode the transition from glacial to interglacial conditions about 430 000 years ago termination v resembles the transition into the present interglacial period in terms of the magnitude of change in temperatures and greenhouse gases but there are significant differences in the patterns of change the interglacial stage following termination v was exceptionally long 28 000 years compared to for example the 12 000 years recorded so far in the present interglacial period given the similarities between this earlier warm period and today our results may imply that without human intervention a climate similar to the present one would extend well into the future

deglacial environmental changes on isla de los estados 54 4 s southeastern tierra del fuego the island of isla de los estados is situated at 54 5 degrees s 64 degrees w east of argentinian tierra del fuego and is located in a sensitive geographic position in relation to the zonal circulation between antarctica and south america its terrestrial records of the last deglaciation recording atmospheric conditions but within an oceanic setting can help to clarify changes of regional circulation patterns both atmospheric and marine here we present geochemical analyses from 16 10 ka cal bp of a peat core from lago galvarne bog at the northern coast of the island and a lake sediment core from laguna cascada 3 kin further south the data comprise tc tn loss on ignition analyses and continuous xrf scanning on both cores as well as age depth modeling based on ams c 14 dating deglaciation and onset of peat formation in the coastal areas began before 16 ka cal bp followed by a rapid glacial retreat and the start of lacustrine sedimentation further inland data suggest initially windy conditions with permafrost succeeded by gradually warmer and wetter conditions until ca 14 5 ka cal bp the warming trend slows down until ca 13 5 ka cal bp followed by arid conditions culminating around 12 8 ka cal bp our data suggest fairly warm conditions and the establishment of denser peat and forest vegetation ca 10 6 ka cal bp contemporaneous with the onset of the antarctic thermal optimum this indicates large scale shifts in the placement of zonal flow and the westerlies at the beginning of the holocene c 2008 elsevier ltd all rights reserved

modulation of the bipolar seesaw in the southeast pacific during termination 1 the termination of the last ice age termination 1 t1 is crucial for our understanding of global climate change and for the validation of climate models there are still a number of open questions regarding for example the exact timing and the mechanisms involved in the initiation of deglaciation and the subsequent interhemispheric pattern of the warming our study is based on a well dated and high resolution alkenone based sea surface temperature sst record from the se pacific off southern chile ocean drilling project site 1233 showing that deglacial warming at the northern margin of the antarctic circumpolar current system acc began shortly after 19 000 years bp 19 kyr bp the timing is largely consistent with antarctic ice core records but the initial warming in the se pacific is more abrupt suggesting a direct and immediate response to the slowdown of the atlantic thermohaline circulation through the bipolar seesaw mechanism this response requires a rapid transfer of the atlantic signal to the se pacific without involving the thermal inertia of the southern ocean that may contribute to the substantially more gradual deglacial temperature rise seen in antarctic ice cores a very plausible mechanism for this rapid transfer is a seesawinduced change of the coupled ocean atmosphere system of the acc and the southern westerly wind belt in addition modelling results suggest that insolation changes and the deglacial co2 rise induced a substantial sst increase at our site location but with a gradual warming structure the similarity of the two step rise in our proxy ssts and co2 over t1 strongly demands for a forcing mechanism influencing both temperature and co2 as ssts at our coring site are particularly sensitive to latitudinal shifts of the acc southern westerly wind belt system we conclude that such latitudinal shifts may substantially affect the upwelling of deepwater masses in the southern ocean and thus the release of co2 to the atmosphere as suggested by the conceptual model of toggweiler j r rusell j l carson s r 2006 midlatitude westerlies atmospheric co2 and climate change during ice ages

a late quaternary paleoenvironmental record in sand dunes of the northern atacama desert chile this paper reports a previously unidentified paleoenvironmental record found in sand dunes of the atacama desert chile long term aeolian deflation by prevailing onshore winds has resulted in the deposition of sand on the irregular surface of a miocene aged anhydrite outcrop two deposits 25 km apart along the prevailing wind trajectory were hand excavated then analyzed for vertical and temporal changes in physical and chemical composition radiocarbon ages of organic matter embedded within the deposits show that rapid accumulation of sediment began at the last glacial maximum and slowed considerably after the pacific ocean attained its present post glacial level over this time period grain sizes are seen to increase while accumulation rates simultaneously decrease suggesting greater wind speeds and or a change or decrease in sediment supply changes in 34 s values of sulfate in the sediment beginning 10 ka indicate an increase in marine sources similarly 2 h values from palmitic acid show a steady increase at 10 ka likely resulting from aridification of the region during the holocene due to the extreme aridity in the region these sand dunes retain a well preserved chemical record that reflects changes in elevation and coastal proximity after the last glacial maximum

meltwater pulse 1a from antarctica as a trigger of the bolling allerod warm interval meltwater pulse 1a mwp 1a was a prominent feature of the last deglaciation which led to a sea level rise of 20 meters in less than 500 years concurrent with mwp 1a was the onset of the bolling allerod interstadial event 14 600 years before the present which marked the termination of the last glacial period previous studies have been unable to reconcile a warm northern hemisphere with mwp 1a originating from the laurentide or fennoscandian ice sheets with the use of a climate model of intermediate complexity we demonstrate that with mwp 1a originating from the antarctic ice sheet consistent with recent sea level fingerprinting inferences the strength of north atlantic deep water nadw formation increases thereby warming the north atlantic region and providing an explanation for the onset of the bolling allerod warm interval the established mode of active nadw formation is then able to respond to subsequent freshwater forcing from the laurentide and fennoscandian ice sheets setting the stage for the younger dryas cold period the melting of continental ice sheets during the last deglaciation provided a freshwater source to the ocean that affected global sea level and the strength of the thermohaline circulation an exceptionally large melting event inferred from far field relative sea level records occurred

molluscs as evidence for a late pleistocene and early holocene humid period in the southern coastal desert of peru 14 5 s the southern peruvian coastal desert around palpa southern peru 14 5 s is currently characterized by hyper arid conditions however the presence of two species of molluscs scutalus pupoides and desert loess deposits indicates the past development of semi desert and grassland ecosystems caused by a displacement of the eastern desert margin due to hydrological changes radiocarbon dating shows that the transition to a semi arid climate in the southern peruvian coastal desert took place during the greenland interstadial 1 13 5 cal ka bp at the beginning of the holocene the mollusc fauna vanished due to increasing humidity and the development of grasslands dust particles were fixed by the grasses as indicated by abundant poaceae phytoliths and desert loess was formed the humid period we observe here is out of phase with the palaeoenvironmental records from the titicaca region which indicates dry conditions at that time this paper offers a new idea for this contradiction an orbitally driven meridional shift of the bolivian high might have altered the moisture supply across the andes

magmatic history and parental melt composition of olivine phyric shergottite lar 06319 importance of magmatic degassing and olivine antecrysts in martian magmatism several olivine phyric shergottites contain enough olivine that they could conceivably represent the products of closed system crystallization of primary melts derived from partial melting of the martian mantle larkman nunatak lar 06319 has been suggested to represent a close approach to a martian primary liquid composition based on approximate equilibrium between its olivine and groundmass to better understand the olivine melt relationship and the evolution of this meteorite we report the results of new petrographic and chemical analyses we find that olivine megacryst cores are generally not in equilibrium with the groundmass but rather have been homogenized by diffusion to mg 72 we have identified two unique grain types an olivine glomerocryst and an olivine grain preserving a primary magmatic boundary that constrains the time scale of eruption to be on the order of hours we also report the presence of trace oxide phases and phosphate compositions that suggest that the melt contained approximately 1 1 h2o and lost volatiles during cooling also associated with an increase in oxygen fugacity upon degassing we additionally report in situ rare earth element measurements of the various mineral phases in lar 06319 based on these reported trace element abundances we estimate the oxygen fugacity in the lar 06319 parent melt early in its crystallization sequence i e at the time of crystallization of the low ca and high ca pyroxenes the rare earth element composition of the parent melt and those of melts in equilibrium with later formed phases we suggest that lar 06319 represents the product of closed system crystallization within a shallow magma chamber with additional olivine accumulated from a cumulate pile we infer that the olivine megacrysts are antecrysts derived from a single magma chamber but not directly related to the host magma and suggest that mixing of antecrysts within magma chambers may be a common process in martian magmatic systems

a younger dryas icecap in the equatorial andes abstract morphologic and stratigraphic evidence shows that a late glacial ice cap existed on part of the eastern cordillera of ecuador lat 0 20 s on ground with a mean elevation of 4200 m where none exists now an outlet glacier from an ca 800 km 2 ice cap terminated at 3850 m altitude in the papallacta valley on the eastern side of the plateau radiocarbon dates show that moraines formed by this advance were ice free by 13 200 14 c yr b p tephras and the age of organic deposits at the plateau edge indicate ice free conditions before 11 800 14 c yr b p this interval was followed by the expansion of an ca 140 km 2 ice cap that discharged glaciers into adjacent valleys where terminal moraines were built at 3950 m altitude ams and conventional radiocarbon dates from macrofossils peat and gyttja above and below till of the readvance indicate that the ice cap formed between ca 11 000 and 10 000 14 c yr b p and was thus coeval with the european younger dryas event the ice cap developed in response to a surface temperature cooling of at least 3 c in the tropical andes a finding that is consistent with a coupled equatorial high latitude north atlantic climate system operating at the late glacial holocene transition these results are further evidence that younger dryas cooling may have been a global event

lake level chronology on the southern bolivian altiplano 18 23 s during late glacial time and the early holocene stratigraphic analyses of outcrops shorelines and diatoms from the southern bolivian altiplano uyuni coipasa basin reveal two major lacustrine phases during the late glacial period and the early holocene based on a chronology established by radiocarbon and u th control a comparison of14c and230th 234u ages shows that during times of high lake level radiocarbon ages are valid however during low water periods 14c ages must be corrected for a reservoir effect the lacustrine tauca phase started a little before 16 00014c yr b p and the lake level reached its maximum between 13 000 and 12 00014c yr b p a dry event ticana occurred after ca 12 000 and before 950014c yr b p a moderate lacustrine oscillation coipasa event occurred between ca 9500 and 850014c yr b p using a reservoir corrected conventional14c chronology comparisons between the lake level chronology in the uyuni coipasa basin and data from other southern tropical areas of south america suggest that the lacustrine evolution may reflect large scale climatic changes

melanges intrusive and extrusive sediments and hydraulic arcs water carrying sediment may intrude with or without associated extrusion wherever the fluid pressure exceeds the intrusion strength of the surrounding materials it has recently been suggested that thrust sheets moving toward continental interiors act as giant squeegees driving fluids through their substrates ahead of them active ice sheets and sedimentary prisms can also squeeze fluids through rocks such fluids potentially inject hydraulic melanges along their plumbing systems but these are difficult to distinguish from other melanges and from broken formations or olistostromes because of surficial slumping or extrusion miniature examples of melanges pumped through a marine slope by the tidal grounding of an ice sheet of permian carboniferous dwyka age in south africa are used to illustrate that there are even more categories of melange than previously suspected instead of being clarified by recent work the problem of deducing the origin of individual melanges becomes more difficult this is because melanges are formed by the mixing of thick hydrous slurries in any confined conditions and are not diagnostic of subduction nonetheless the results of hydraulic activity within a subglacial marine slope suggest that the sedimentary volcanoes developed on many accretionary prisms overlie relatively cold hydraulic arcs oceanward of the hot magmatic arcs behind subduction zones

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

antarctic timing of surface water changes off chile and patagonian ice sheet response marine sediments from the chilean continental margin are used to infer millennial scale changes in southeast pacific surface ocean water properties and patagonian ice sheet extent since the last glacial period our data show a clear antarctic timing of sea surface temperature changes which appear systematically linked to meridional displacements in sea ice westerly winds and the circumpolar current system proxy data for ice sheet changes show a similar pattern as oceanographic variations offshore but reveal a variable glacier response time of up to 1000 years which may explain some of the current discrepancies among terrestrial records in southern south america

experimental petrology crystallization history and parental magma characteristics of olivine phyric shergottite nwa 1068 implications for the petrogenesis of enriched olivine phyric shergottites abstract northwest africa nwa 1068 is one of the few olivine phyric shergottites e g nwa 1068 larkman nunatak lar 06319 and roberts massif rbt 04262 that is not depleted in light rare earth elements lree its ree pattern is similar to that of the basaltic shergottite shergotty suggesting a possible connection between the olivine phyric and the basaltic shergottites to test this possible link we have investigated the high pressure near liquidus phase equilibria for the nwa 1068 meteorite bulk composition our results show that the nwa 1068 bulk composition does not represent an unmodified mantle derived melt the olivine and pyroxene in our near liquidus experiments are more magnesian than in the rock itself which suggests that nwa 1068 contains cumulate minerals extra olivine we have then used these experimental results combined with the pyroxene compositions in nwa 1068 to constrain the possible high pressure crystallization history of the parental magma these results suggest that nwa 1068 had a complex polybaric history finally we have calculated a model parental magma composition for the nwa 1068 meteorite the calculated parental magma is an evolved basaltic composition which is too ferroan to be a primitive melt directly derived from the mantle we suggest that it ponded and crystallized at approximately the base of the crust this provided an opportunity for the magma to become contaminated by an enriched crustal component prior to crystallization the results and modeling from these experiments are applicable not only to the nwa 1068 meteorite but also to lar 06319 and possibly any other enriched olivine phyric shergottite

geochemical composition and provenance of aeolian sands in the ordos deserts northern china abstract identifying the provenance of aeolian sediments in deserts is of great importance for understanding the earth surface processes in this context we conducted detailed fieldwork in the ordos deserts maowusu and kubuqi in the middle portion of the desert belt in northern china and measured the major trace and rare earth elements ree of aeolian sands and their potential source rocks and sediments our results show that aeolian sands in the eastern northeastern and western southwestern maowusu mu us sandy land exhibit different degrees of mineralogical maturity and eu eu values thus we interpret that these aeolian sands have different provenances though in the same sandy land our data suggest that the local lacustrine sediments and sandstones are the main sources of aeolian sands in the eastern province of the maowusu sandy land while aeolian sands in the western maowusu sandy land and the kubuqi desert have the same external sources the comparison of geochemical compositions of sediments in the ordos deserts with their potential sources in adjacent regions indicates that there is no genetic linkage between the helan mountains the yinshan mountains and the ordos deserts although they are not far apart the qilian orogenic belt in the northeastern margin of the tibetan plateau is however the most likely original provenance for the western maowusu mu us sandy land and the kubuqi hobq desert but with fluvial sediments in the ningxia inner mongolian section of the yellow river as the immediate source in one side our results demonstrate that dune fields that are close to each other can have significantly different source sediments on the other hand our work suggests that some dune fields and landforms that are far apart from one another e g the badain jaran desert in western inner mongolia the ordos deserts and the fluvial sediments in ningxia inner mongolian section of the yellow river can share the same ultimate sources

moisture transport across central america as a positive feedback on abrupt climatic changes reconstruction of sea surface salinities in the eastern equatorial pacific ocean over the past 90 000 years detected strong millennial scale fluctuations that are associated with the migration of the tropical atlantic intertropical convergence zone thus millennial scale fluctuations of moisture transport constitute an important feedback mechanism for abrupt climate changes modulating the north atlantic freshwater budget and hence north atlantic ocean circulation moisture transport from the atlantic to the pacific ocean across central america leads to relatively high salinities in the north atlantic ocean1 and contributes to the formation of north atlantic deep water2 this deep water formation varied strongly between dansgaard oeschger interstadials and heinrich events millennial scale abrupt warm and cold events respectively during the last glacial period3 increases in the moisture transport across central america have been proposed to coincide with northerly shifts of the intertropical convergence zone and with dansgaard oeschger interstadials with opposite changes for heinrich events4 here we reconstruct sea surface salinities in the eastern equatorial pacific ocean over the past 90 000 years by comparing palaeotemperature estimates from alkenones and mg ca ratios with foraminiferal oxygen isotope ratios that vary with both temperature and salinity we detect millennial scale fluctuations of sea surface salinities in the eastern equatorial pacific ocean of up to two to four practical salinity units high salinities are associated with the southward migration of the tropical atlantic intertropical convergence zone coinciding with heinrich events and with greenland stadials5 the amplitudes of these salinity variations are significantly larger on the pacific side of the panama isthmus as inferred from a comparison of our data with a palaeoclimate record from the caribbean basin6 we conclude that millennial scale fluctuations of moisture transport constitute an important feedback mechanism for abrupt climate changes modulating the north atlantic freshwater budget and hence north atlantic deep water formation

relative timing of deglacial climate events in antarctica and greenland the last deglaciation was marked by large hemispheric millennial scale climate variations the bolling allerod and younger dryas periods in the north and the antarctic cold reversal in the south a chronology from the high accumulation law dome east antarctic ice core constrains the relative timing of these two events and provides strong evidence that the cooling at the start of the antarctic cold reversal did not follow the abrupt warming during the northern bolling transition around 14 500 years ago this result suggests that southern changes are not a direct response to abrupt changes in north atlantic thermohaline circulation as is assumed in the conventional picture of a hemispheric temperature seesaw

episodic eolian deposition in the past ca 50 000years in the alto ilo dune field southern peru abstract the alto ilo dune field in the coastal desert of southern peru is located at the edge of the atacama desert and is one of the driest landscapes on earth a stratigraphic sequence of eolian sands paleosols and debris flow deposits are identified in this dune field spanning the past 55 ka we infer that eolian deposition is preceded by an increase in sediment supply from local alluvial fans that are upwind of the alto ilo dune field and thus reflects periods of relative hydrologic excess eolian sediment supply may increase also with the concomitant fall in sea level providing an additional foreland source area for eolian particles the presence of paleosols indicate millennial scale periods of locally wetter conditions possibly associated with spread of lomas vegetation fed from coastal fog sources debris flows reflect significant rainfall events possibly associated with enso variability the chronology is provided by optically stimulated luminescence using multiple aliquot regeneration protocols which reveal four major eolian depositional episodes at ca 55 to 45 ka 38 to 27 ka 22 to 16 ka and 12 ka eolian deposition in the late pleistocene dominates the record and is generally coincident with metrics of hydrologic excess from the peruvian andes and the altiplano which appears to translate into enhanced sediment availability on the coast a significant period of soil development between 18 and 13 ka is consistent with timing of central andean pluvial event and indicates widespread wet conditions the holocene record of eolian deposition is sparse reflecting limited alluvial fan sources and decreasing particle availability upwind with the rise in postglacial sea level

partitioning behavior of chlorine and fluorine in the system apatite silicate melt fluid the partitioning behavior of cl among apatite mafic silicate melt and aqueous fluid and of f between apatite and melt have been determined in experiments conducted at 1066 to 1150 c and 199 205 mpa the value of dclapatite melt wt fraction of cl in apatite cl in melt 0 8 for silicate melt containing less than 3 8 wt cl at higher melt cl contents small increases in melt cl concentration are accompanied by large increases in apatite cl concentration forcing dclapatite melt to increase as well melt containing less than 3 8 cl coexists with water rich vapor that containing more cl coexists with saline fluid the salinity of which increases rapidly with small increases in melt cl content analogous to the dependency of apatite composition on melt cl content this behavior is due to the fact that the solubility of cl in silicate melt depends strongly on the composition of the melt particularly its mg ca fe and si contents once the melt becomes saturated in cl additional cl must be accommodated by coexisting fluid apatite or other phases rather than the melt itself because cl solubility depends on composition the cl concentration at which dclapatite melt and dclfluid melt begin to increase also depends on composition the experiments reveal that dfapatite melt 3 4 in contrast to cl the concentration of f in silicate melt is only weakly dependent on composition mainly on melt ca contents so dfapatite melt is constant for a wide range of composition the experimental data demonstrate that the fluids present in the waning stages of the solidification of the stillwater and bushveld complexes were highly saline the cl rich apatite in these bodies crystallized from interstitial melt with high cl f oh ratio the latter was generated by the combined processes of fractional crystallization and dehydration by its reaction with the relatively large mass of initially anhydrous pyroxene through which it percolated

synchronisation of palaeoenvironmental events in the north atlantic region during the last termination a revised protocol recommended by the intimate group abstract the north atlantic intimate group of the inqua palaeoclimate commission has previously recommended an event stratigraphy approach for the synchronisation of records of the last termination using the greenland grip isotopic record as the regional stratotype and intcal98 for the calibration of radiocarbon dates lowe j j hoek w intimate group 2001 inter regional correlation of palaeoclimatic records for the last glacial interglacial transition a protocol for improved precision recommended by the intimate project group quaternary science reviews 20 1175 1187 here we present a revised protocol for time stratigraphic correlation in the north atlantic region over a more extended time period 30 8 ka this employs the new ngrip isotopic record and associated greenland ice core chronology 2005 gicc05 as the regional stratotype intcal04 for the calibration of radiocarbon dates bayesian based statistical procedures for the construction of age models and tephrochronology to validate correlations between regional site records

absence of cooling in new zealand and the adjacent ocean during the younger dryas chronozone as the climate warmed at the end of the last glacial period a rapid reversal in temperature the younger dryas yd event briefly returned much of the north atlantic region to near full glacial conditions the event was associated with climate reversals in many other areas of the northern hemisphere and also with warming over and near antarctica however the expression of the yd in the mid to low latitudes of the southern hemisphere and the southwest pacific region in particular is much more controversial here we show that the waiho loop advance of the franz josef glacier in new zealand was not a yd event as previously thought and that the adjacent ocean warmed throughout the yd

an event stratigraphy for the last termination in the north atlantic region based on the greenland ice core record a proposal by the intimate group it is suggested that the grip greenland ice core should constitute the stratotype for the last termination based on the oxygen isotope signal in that core a new event stratigraphy spanning the time interval from ca 22 0 to 11 5 k grip yr bp ca 19 0 10 0 k 14 c yr bp is proposed for the north atlantic region this covers the period from the last glacial maximum through termination 1 of the deep ocean record to the pleistocene holocene boundary and encompasses the last glacial late glacial of the traditional northwest european stratigraphy the isotopic record for this period is divided into two stadial episodes greenland stadials 1 gs 1 and 2 gs 2 and two interstadial events greenland interstadials 1 gi 1 and 2 gi 2 in addition gi 1 and gs 2 are further subdivided into shorter episodes the event stratigraphy is equally applicable to ice core marine and terrestrial records and is considered to be a more appropriate classificatory scheme than the terrestrially based radiocarbon dated chronostratigraphy that has been used hitherto 1998 john wiley sons ltd

radiocarbon dating of minute gastropods and new constraints on the timing of late quaternary spring discharge deposits in southern arizona usa abstract gastropod shells are commonly preserved in quaternary sediments but are often avoided for radiocarbon dating because some taxa incorporate 14 c deficient carbon during shell formation recently brennan and quade 1997 quat res 47 329 336 found that some minute taxa vallonia pupilla and succineidae appear to yield reliable 14 c ages for late pleistocene samples a more rigorous evaluation of the 14 c inventory of minute gastropods is presented here which involved measuring the 14 c activity of specimens collected live in two geologic settings that maximize the potential for ingestion of old carbon 1 alluvium dominated by paleozoic carbonate rocks and 2 adjacent to extant springs with highly 14 c deficient water present at the surface we found that several minute taxa including vallonia incorporate significant and variable amounts of old carbon 2 to 30 during shell formation the 14 c activities of the land snails pupilla blandi and euconulus fulvus however are indistinguishable from the 14 c activity of live plants the 14 c activity of the semi aquatic gastropod catinella sp family succineidae deviates from modern values in the presence of 14 c deficient water by an amount equivalent to 10 of the local carbon reservoir effect these results imply that at least some minute gastropods can provide reliable 14 c ages even when 14 c deficient carbon is readily available to demonstrate an application of our findings we 14 c dated shells from p muscorum e fulvus and succinea sp family succineidae recovered from the coro marl a late pleistocene spring fed marsh deposit exposed at the murray springs paleoindian site in the san pedro valley of southern arizona usa radiocarbon ages obtained from the minute gastropods show that the unit was deposited between 25 000 and 13 000 14 c years ago the marl is situated 15 m above the modern water table at murray springs and is similarly positioned in discontinuous outcrops along a 150 km stretch of the san pedro valley thus the 14 c ages of minute gastropods presented here may be used to infer the timing of high water table levels throughout the valley

late quaternary palaeolakes rivers and wetlands on the bolivian altiplano and their palaeoclimatic implications drill cores of sediments from the rio desaguadero valley bolivia provide new information about the climate of tropical south america over the past 50 000 years the modern rio desaguadero is fed by lake titicaca overflow and by local tributaries in the wetter northern altiplano and discharges into lake poopo in the more arid central altiplano during the late quaternary the rio desaguadero valley was the site of several generations of palaeolakes and wetlands that formed during periods of increased precipitation and local runoff augmented by increased overflow from lake titicaca sediments recovered by drilling in eight localities along the 390 km long valley of the rio desaguadero yield a regional history of lacustrine sedimentation and effective precipitation lacustrine strata in the drill cores record 12 distinct wet periods in the past 50 000 years four of these wet periods resulted in the formation of major palaeolakes in the rio desaguadero valley during the last glacial maximum from before 20 000 to 16 000 cal yr bp during the late glacial from about 14 000 to 12 000 cal yr bp in the early holocene from about 10 000 to 7900 cal yr bp and in the late holocene from 4500 cal yr bp to present the period that appears to have been most arid was between 7900 and 4500 cal yr bp the altiplano wet periods were generally synchronous with north atlantic cold events respectively the last glacial maximum the younger dryas the 8200 cal yr bp event and the neoglacial implying a relationship between past precipitation variability in tropical south america and north atlantic sea surface temperature copyright 2005 john wiley sons ltd

understanding crystal populations and their significance through the magma plumbing system crystals are rarely composed of a single crystal population that have grown solely from the batch of magma in which they are resident on emplacement either by eruption or shallow intrusion close investigation of the majority of crystal populations reveal that they comprise up to four main components phenocrysts crystals co genetic with their magmatic host xenocrysts crystals wholly or in part foreign to the magmatic host and magma system antecrysts crystals which are recycled one or several times before inclusion in the host magma but have an origin within the magmatic system and microlites which represent small co genetic crystals which nucleate and grow rapidly on decompression and eruption textural analysis techniques are employed to quantify key aspects of the crystal population including crystal shape crystal size distributions spatial distribution patterns and textural modification using dihedral angles santorini provides a case study of an active volcanic system where a combined textural analysis study has been developed highlighting how the crystal population is being continuously modified by a series of replenishment and mixing events developing textural and microgeochemical techniques provides the next stage in the interrogation of crystal populations linking textures to isotopic heterogeneities and providing fingerprints of where crystals are sourced and re cycled

deposition models for chronological records abstract long term sedimentary sequences provide a wealth of useful information for research into the palaeo environment especially in relation to past climate change shorter records provide similar information in many archaeological contexts however if such records are to be used to provide precise timing of events and more critically the relative timing between different records methods are needed to provide accurate and precise age depth models for these sequences given the imprecision of individual calibrated radiocarbon determinations it is necessary to use the information we have about the deposition process to refine our chronologies and also to provide interpolation between dated levels in any sequence even with layer counted chronologies the uncertainties are sometimes hard to quantify this paper outlines a range of bayesian models for deposition which have been implemented in the computer programme oxcal these models can be used to combine information from the sediments themselves with radiocarbon or other direct dating information such models have the potential to integrate information between different records and provide a coherent chronology on which to base environmental or archaeological research