the terrestrial alteration of saharan shergottites dar al gani 476 and 489 a case study of weathering in a hot desert environment abstract rare earth element ree and other selected trace and minor element concentrations were determined in various phases of dar al gani 476 and 489 two basaltic shergottites recently found in the libyan sahara whereas merrillite and feldspathic glass compositions do not seem to have been altered since the fall of these meteorites olivine and pyroxenes commonly show light ree enrichments sometimes accompanied by ce anomalies that are attributed to terrestrial alteration sr and ba enrichments are also observed the calcium carbonate that resides in most cracks is essentially devoid of ree but a fine grained amorphous silicate material that fills some veins and pockets has striking light ree enrichments and elevated p sr and ba it is argued that this material likely to be impact melt as well as the notoriously light ree poor olivine and pyroxenes were preferentially affected by a crustal light ree rich contaminant caution is urged when using whole rock or even mineral separate compositional and isotopic data for hot desert meteorites

26al 26mg systematics in d orbigny and sahara 99555 angrites implications for high resolution chronology using extinct chronometers abstract we report on an investigation of the 26al 26mg isotope systematics in the d orbigny and sahara 99555 angrites high precision mg isotope compositions and al mg ratios were measured in mineral separates and whole rock samples from d orbigny and sahara 99555 using multiple collector inductively coupled plasma mass spectrometry mc icpms plagioclase separates from both angrites have resolvable excesses in 26mg 26mg that correlate with their respective al mg ratios 26al 26mg systematics in the mineral separates and whole rocks define precise isochrons that correspond to 26al 27al ratios of 5 06 0 92 10 7 and 5 13 1 90 10 7 and initial 26mg values of 0 006 0 040 and 0 016 0 047 for d orbigny and sahara 99555 respectively the slopes and initial 26mg values are identical for these two meteorites within errors and the data for both angrites considered together define an isochron corresponding to a 26al 27al ratio of 5 10 0 55 10 7 and initial 26mg value of 0 012 0 019 relative to the efremovka e60 cai the 26al 27al values reported here for these angrites imply 26al 26mg ages of 4562 42 0 29 ma and 4562 43 0 53 ma for d orbigny and sahara 99555 respectively these 26al 26mg ages are concordant with model ages determined using other extinct radionuclide chronometers e g 53mn 53cr and 182hf 182w but are 2 myr younger than the absolute 207pb 206pb ages that have been reported recently for these angrites the reason for this discrepancy is not presently known but may imply disturbance of one or more of the isotope systems under consideration or a possible bias in the 207pb 206pb ages of the angrites resulting from natural or analytical causes

minor and trace element partitioning between pyroxene and melt in rapidly cooled chondrules we present minor and trace element ree sr y and zr data for pyroxenes and mesostases in four porphyritic chondrules from the semarkona ordinary chondrite apparent partition coefficients for clinoenstatite orthoenstatite pigeonite and augite are compared with experimental and petrologic data from the literature and the effects on apparent partition coefficients of the rapid cooling rates at which chondrules crystallized are evaluated for most elements the effects of cooling at rates of hundreds of degrees per hour cannot be distinguished from variations in equilibrium data resulting from differences in temperature or composition however for lree apparent partition coefficients are significantly higher than comparable equilibrium data and the ratio of hree lree partition coefficients is lower particularly for ca poor pyroxene we attribute this flattening of ree patterns to the effect of rapid cooling apparent partition coefficients of all ree and y in augite are higher than equilibrium data particularly in one chondrule with a high al 2o3 content we suggest that this may be attributed to an increase in the uptake of trivalent trace element cations in the pyroxene crystal structure as a result of charge balanced substitutions with al 31 cations

chromium vanadium and titanium valence systematics in solar system pyroxene as a recorder of oxygen fugacity planetary provenance and processes pyroxene is arguably the most powerful single phase geochemical and petrologic recorder of solar system processes from nebular condensation through planetary evolution over a wide range of temperatures pressures and f o 2 it is an important mineral phase in the crusts and mantles of evolved planets in undifferentiated and differentiated asteroids and in refractory inclusions the earliest solar system materials here we review the valence state partitioning behavior of cr cr 2 cr 3 ti ti 3 ti 4 and v v 2 v 3 v 4 v 5 among crystallographic sites in pyroxene over a range of f o 2 from approximately fayalite magnetite quartz fmq to 7 log units below iron wustite iw 7 and decipher how pyroxene can be used as a recorder of conditions of planetary and nebular environments and planetary parentage the most important crystallographic site in pyroxene with respect to its influence on mineral melt partitioning is m2 its ca content has a huge effect on partitioning behavior because the large ca cation expands the structure as a result distribution coefficients d s for cr and v increase with increasing ca content from orthopyroxene to pigeonite to augite in addition it is noted that v 3 is favored over v 4 in olivine and pyroxene in pyroxene in refractory inclusions ti 3 is favored over ti 4 and incorporation of ti is facilitated by the high availability of al for coupled substitution the most important results from analysis of pyroxene in martian meteorites e g que 94201 are the oxygen fugacity estimates of iw 0 2 and iw 0 9 derived from partitioning and valence data for cr and v respectively obtained from experiments using appropriate temperatures and melt compositions in angrites changes in v valence state may translate to changes in f o 2 from iw 0 7 during early pyroxene crystallization to iw 0 5 during later episodes of pyroxene crystallization in addition to f o 2 the partitioning behavior of cr v and ti between pyroxene and melt is also dependent upon availability of other cations especially al for charge balancing coupled substitutions

ce anomalies in the lew85300 eucrite evidence for ree mobilization during antarctic weathering abstract there is abundant evidence for widespread ree mobilization in antarctic eucrites resulting in ce and eu anomalies and lower whole rock ree abundances relative to typical eucrites using secondary ion mass spectrometry sims we investigated the microdistribution of ce anomalies in the antarctic polymict eucrite lew85300 ce anomalies positive and or negative are present in all three of the minerals plagioclase pyroxene and silica analysed the anomalies occur in grains from all four clasts as well as in mineral and lithic fragments from the surrounding matrix thus there appears to be no lithologic association silica which has been heavily shocked and altered exhibits a lree enriched pattern with negative ce and eu anomalies consistent with a derivation of the ree from ca phosphate dissolution trivalent ree are leached from the phosphates with preferential retention of tetravalent ce and redeposited on silica pyroxene is also widely affected by ree mobilization due to an extensive shock induced microcrack network along cleavage planes a tendency for the largest ce anomalies to occur at low lree concentrations suggests that pyroxene itself experienced ree leaching with concomitant ce retention ce anomalies are rare in plagioclase because this mineral lacks an extensive network along which ree can be mobilized the widespread ree mobilization and evidence for other forms of weathering requires that trace element data be used cautiously especially for antarctic eucrites

regional imprints of millennial variability during the mis 3 period around antarctica the climate of the last glacial marine isotopic stage 3 mis3 period is characterized by strong millennialscale variability with a succession of dansgaardeoeschger events first identified in greenland ice cores and associated with variations of the atlantic meridional overturning circulation amoc these abrupt events have a smooth and lagged counterpart in water stable isotopes from antarctic ice cores in this study we aim at depicting and understanding the circum antarctic expression of this millennial scale variability to illustrate the mechanisms potentially at work in the response of the southern high latitudes to an abrupt decrease of the amoc we first present results from experiments performed with the ipsl cm4 atmosphere ocean coupled model under glacial boundary conditions when the amoc is perturbed by imposing an additional freshwater flux in the north atlantic our model produces the classical bipolar seesaw mechanism generally invoked to explain the warming of the southern ocean antarctic region however this mechanism can be locally offset by faster atmospheric teleconnections originating from the tropics even though the precise location of this fast response is not coherent among different climate models our model results are confronted with a synthesis of antarctic records of ice core stable isotope and sea salt sodium including new data obtained on the taldice ice core the ipslcm4 produces a dipole like pattern around antarctica with warming in the atlantic indian sectors contrasting with an unexpected cooling in the east pacific sector the latter signal is not detected in our data synthesis both ice core data and simulations are consistent in depicting a more rapid response of the atlantic sector compared to the indian sector this feature can be explained by the gradual impact of ocean transport on which faster atmospheric teleconnections are superimposed detailed investigations of the sequence of events between different proxies are conducted in three ice cores earlier shifts in deuterium excess and significant changes in sea salt sodium fluxes in the most coastal sites taldice and edml compared to edc suggest reorganizations in local moisture sources possibly linked with sea ice cover this study demonstrates the added value of circum antarctic ice core records to characterize the patterns and mechanisms of glacial climate variability

millennial scale sea surface temperature and patagonian ice sheet changes off southernmost chile 53 s over the past 60 kyr 1 glacial millennial scale paleoceanographic changes in the southeast pacific and the adjacent southern ocean are poorly known due to the scarcity of well dated and high resolution sediment records here we present new surface water records from sediment core md07 3128 recovered at 53 s off the pacific entrance of the strait of magellan the alkenone derived sea surface temperature sst record reveals a very strong warming of ca 8 c over the last termination and substantial millennial scale variability in the glacial section largely consistent with our planktonic foraminifera oxygen isotope 18o record of neogloboquadrina pachyderma sin the timing and structure of the termination and some of the millennial scale sst fluctuations are very similar to those observed in the well dated sst record from odp site 1233 41 s and the temperature record from drowning maud land antarctic ice core supporting the hemispheric wide antarctic timing of sst changes however differences in our new sst record are also found including a long term warming trend over marine isotope stage mis 3 followed by a cooling toward the last glacial maximum lgm we suggest that these differences reflect regional cooling related to the proximal location of the southern patagonian ice sheet and related meltwater supply at least during the lgm consistent with the fact that no longer sst cooling trend is observed in odp site 1233 or any sst chilean record this proximal ice sheet location is documented by generally higher contents of ice rafted debris ird and tetra unsaturated alkenones and a slight trend toward lighter planktonic 18o during late mis 3 and mis 2

enso variability and teleconnections during glacial climates abstract understanding the origin of sub milankovitch and millennial scale abrupt climate change still poses a major challenge an important role of communicating the orbital scale forcing into abrupt climate change on millennial and centennial timescales has been hypothesized for the tropics in earlier studies based on the assumption of stationary teleconnections this paper presents a modelling study for the last glacial maximum and marine isotope stage 3 using the comprehensive climate model ccsm3 glacial boundary conditions and freshwater hosing at high latitudes of the north atlantic are imposed to mimic a heinrich stadial and dansgaard oeschger stadials and interstadials it is shown that glacial enso variability is strongly enhanced by a substantial slowdown of the atlantic meridional overturning circulation the simulations also suggest that glacial boundary conditions induce major modifications to enso teleconnections and that the blueprint of modern enso teleconnections should only be applied with caution to glacial climate periods

geoarchaeological evidence for dredging in tyre s ancient harbour levant abstract chrono stratigraphic data from tyre s ancient northern harbour delineate extensive dredging practices during the greco roman and byzantine periods radiocarbon dates from four cores consistently cluster between ca 500 b c and 1000 a d and indicate rapid rates of sedimentation in the basin namely 10 mm yr during the greco roman and byzantine periods compared to 0 5 1 mm yr for the period 6000 4000 b c absence of strata between 4000 b c and 500 b c is not consistent with a natural base level sediment sink and cannot be interpreted as a depositional hiatus in the high stand systems tract ancient dredging is further corroborated by persistent age depth inversions within the fine grained harbour facies these data support removal of middle bronze age to persian period sediment strata with deliberate overdeepening of the harbour bottom by greco roman and byzantine societies

worldwide initiation of holocene marine deltas by deceleration of sea level rise radiocarbon dated deltaic sequences of holocene age from different parts of the world began to accumulate within a restricted time range from about 8500 to 6500 years ago evaluation of major delta processes indicates that deceleration in sea level rise was the key factor in holocene delta formation within many deltas there is as much as a 2000 year age range between basal deposits in seaward and landward cores this age difference records the progressive landward migration of near mean sea level depositional environments during the lower to mid holocene establishment of a chronostratigraphic framework for holocene delta development provides a fundamental global baseline for distinguishing sea level change from vertical land motion by tectonism and isostasy and for evaluating rates of future marine incursion into low lying deltas

petrogenesis of angrites abstract the recent discovery of two new angrites sahara 99555 and d orbigny has revived interest in this small group of achondrites we measured trace element abundances in the individual minerals of these two angrites and compared them with the three antarctic angrites lew 86010 lew 87051 and asuka 881371 trace element variations in four of these meteorites lew 87051 asuka 881371 sahara 99555 and d orbigny indicate rapid crystallization under near closed system conditions consistent with their mineralogical and textural features all four appear to be closely related and crystallized from very similar magmas discrepancies between their bulk ree compositions and melts calculated to be in equilibrium with the major phases may be due in part to kinetic effects of rapid crystallization prior crystallization of olivine and or plagioclase may also account for the elevated parent melt composition of clinopyroxene in some of the angrites such as asuka 881371 lew 86010 also crystallized from a melt and represents a liquid composition but trace element trends in clinopyroxene and olivine differ from those of the other angrites this meteorite seems to have crystallized from a different source magma

late holocene coastline and landscape changes to the west of ephesus turkey abstract palaeogeographical research regarding coastline and landscape changes has been conducted in the kucuk menderes graben and the environs of the ancient city of ephesus in western turkey for a few decades based on geophysical data multi proxy and microfaunal analyses of sediment cores 14 c ams age estimates and diagnostic ceramics this study presents for the first time results of an area close to the present coastline where a byzantine church is located on top of a small hill the results reveal that this mica schist hill turned into an island during the 2nd 1st millennium bce it was reconnected to the mainland via a tombolo during the 5th century ce drill cores and geophysical measurements surrounding the hill show massive stone layers which were deposited intentionally during the 5th 6th century ce when the byzantine church was built geophysical images point to wall structures in the surroundings of the hill the area to the northeast hosts a small harbour site when the coastline continued to shift further to the west this site was still connected to the sea by the kucuk menderes river

alexander the great s tombolos at tyre and alexandria eastern mediterranean tyre and alexandria s coastlines are today characterised by wave dominated tombolos peculiar sand isthmuses that link former islands to the adjacent continent paradoxically despite a long history of inquiry into spit and barrier formation understanding of the dynamics and sedimentary history of tombolos over the holocene timescale is poor at tyre and alexandria we demonstrate that these rare coastal features are the heritage of a long history of natural morphodynamic forcing and human impacts in 332 bc following a protracted seven month siege of the city alexander the great s engineers cleverly exploited a shallow sublittoral sand bank to seize the island fortress tyre s causeway served as a prototype for alexandria s heptastadium built a few months later we report stratigraphic and geomorphological data from the two sand spits proposing a chronostratigraphic model of tombolo evolution

timing of millennial scale climate change at siple dome west antarctica during the last glacial period using atmospheric methane and the isotopic composition of o2 as correlation tools we place the dd record of ice from the siple dome west antarctica ice core on a precise common chronology with the gisp2 greenland ice core for the period from 9 to 57 ka the onset of major millennial warming events in siple dome preceded major abrupt warmings in greenland and the pattern of millennial change at siple dome was broadly similar though not identical to that previously observed for the byrd ice core also in west antarctica the addition of siple dome to the database of well dated antarctic paleoclimate records supports the case for a coherent regional pattern of millennial scale climate change in antarctica during much of the last ice age and glacial interglacial transition

fast advective recovery of the atlantic meridional overturning circulation after a heinrich event ice core reconstructions and ocean sediment analysis have revealed that the climate of the last glacial period was highly variable with rapid stadial interstadial transitions and glacial meltwater pulses heinrich events modulating the climate evolution in the northern and southern hemispheres heinrich events had the potential to weaken the atlantic meridional overturning circulation amoc substantially mechanisms that led to the resumption of the amoc after such events have not been fully disentangled yet here a coupled atmosphere ocean sea ice model of intermediate complexity is employed to identify important negative climate feedbacks that contribute to a fast recovery of the glacial amoc shortly after the amoc collapse thermal processes weaken the stratification in the northern north atlantic making it more vulnerable to perturbations eventually 300 400 years after the main collapse of the amoc the mean advection of salinity anomalies within the horizontal gyres generates an unstable stratification that will be homogenized through the resumption of convective activity eventually isopycnal slopes in the north atlantic are readjusted thereby reinitiating the large scale meridional overturning flow

origin and consequences of cyclic ice rafting in the northeast atlantic ocean during the past 130 000 years deep sea sediment cores recovered from the northeast atlantic ocean were examined in order to elucidate the influence of the earth s orbital parameters on major ice rafting analyses of coarse grained ice rafted debris and planktonic foraminifers revealed a strong reaction to the precession signal since 130 000 yr b p dropstone layers have been deposited each half period of a precessional cycle 11 000 1000 yr ice rafting occurs during times of winter minimum summer maximum insolation and summer minimum winter maximum insolation in the first case high summer insolation forces meltwater discharge from the ice sheets into the polar seas which subsequently enhances formation of sea ice during the winter in the second case growth of continental ice enhances iceberg production which also leads to a salinity reduction of surface seawater both situations result in a southward penetration of polar water thus the marine record of dropstones documents ice rafting not only during weichselian stades but also during cold events within interstades the regularity of ice rafting yields a useful framework to calibrate and elucidate climatic changes not only in the region of the north atlantic ocean but also in remote areas such as the pacific ocean and the antarctic

the sensitivity of the climate response to the magnitude and location of freshwater forcing last glacial maximum experiments abstract proxy records indicate that the locations and magnitudes of freshwater forcing to the atlantic ocean basin as iceberg discharges into the high latitude north atlantic laurentide meltwater input to the gulf of mexico or meltwater diversion to the north atlantic via the st lawrence river and other eastern outlets may have influenced the north atlantic thermohaline circulation and global climate we have performed last glacial maximum lgm simulations with the ncar community climate system model ccsm3 in which the magnitude of the freshwater forcing has been varied from 0 1 to 1 sv and inserted either into the subpolar north atlantic ocean or the gulf of mexico in these glacial freshening experiments the less dense freshwater provides a lid on the ocean water below suppressing ocean convection and interaction with the atmosphere above and reducing the atlantic meridional overturning circulation amoc this is the case whether the freshwater is added directly to the area of convection south of greenland or transported there by the subtropical and subpolar gyres when added to the gulf of mexico the amoc reduction is less for the smaller freshwater forcings but is not linear with the size of the freshwater perturbation the recovery of the amoc from a slow state is 200 years for the 0 1 sv experiment and 500 years for the 1 sv experiment for glacial climates with large northern hemisphere ice sheets and reduced greenhouse gases the cold subpolar north atlantic is primed to respond rapidly and dramatically to freshwater that is either directly dumped into this region or after being advected from the gulf of mexico greenland temperatures cool by 6 8 c in all the experiments with little sensitivity to the magnitude location or duration of the freshwater forcing but exhibiting large seasonality sea ice is important for explaining the responses the northern hemisphere high latitudes are slow to recover antarctica and the southern ocean show a bipolar response with warming and reduced sea ice this warming continues after the cessation of the freshwater forcing and shows a dependence on the duration of the freshwater forcing equatorward of the expanded sea ice the simulated temperature and salinity anomalies are sensitive to the amount of colder and fresher waters that are advected out of the subpolar north atlantic in the tropical atlantic the recovery of the intertropical convergence zone itcz from its more southerly position during the freshwater forcing is much more rapid than the recovery of the amoc and is more related to the recovery of low latitude surface temperatures than greenland temperature or sea ice these results have implications for using proxy records as indirect measures of the amoc

stratigraphy of late holocene deposits of the ancient harbour of marseilles southern france the late holocene stratigraphy of marseilles harbour is presented together with archaeological evi dence and radiocarbon data an anthropogenic oyster midden dated between c 4260 and 3400 14 c yr bp is followed by a period of siltation that ended the accretionary growth of an algal marl deposit this event was caused by early human settlement subsequently the coastline was subject to progradation it is argued here that the development of the e rst town of marseilles c 2600 years ago accelerated soil erosion and sediment deposition in the harbour area

the meteoritical bulletin no 85 2001 september meteoritical bulletin no 85 lists information for 1376 newly classified meteorites comprising 658 from antarctica 409 from africa 265 from asia 262 of which are from oman 31 from north america 7 from south america 3 from australia and 3 from europe information is provided for 11 falls dergaon dunbogan gujba independence itqiy moravka oued el hadjar sayama sologne valera and worden noteworthy non antarctic specimens include 5 martian meteorites dar al gani 876 northwest africa 480 and 817 and sayh al uhaymir 051 and 094 6 lunar meteorites dhofar 081 280 and 287 and northwest africa 479 482 and 773 an ungrouped enstatite rich meteorite itqiy a bencubbin like meteorite gujba 9 iron meteorites and a wide variety of other interesting stony meteorites including ch ck cm co cr cv r enstatite and unequilibrated ordinary chondrites primitive achondrites hed achondrites and ureilites

rare earth elements in angra dos reis and lewis cliff 86010 two meteorites with similar but distinct magma evolutions abstract rare earth element ree and selected trace element abundances were measured with an ion microprobe in individual grains of merrillite fassaite olivine kirschsteinite and plagioclase of lew 86010 the second known angrite and compared with measurements in merrillite and fassaite of angra dos reis ador the rare merrillite is highly enriched in ree the ree patterns show steep decreases from la 3 300 cl to tm 100 cl in lew 86010 and from la 1 500 cl to tm 130 cl in ador ree patterns in fassaite of both meteorites are similar although concentrations are higher in ador whereas ador pyroxenes show a high degree of equilibration the lew 86010 pyroxenes show much variation in composition the abundances of the ree zr al and ti correlate positively with fe fe mg and those of cr sc and v correlate negatively consistent with an igneous origin in a closed system pyroxene and plagioclase cores in lew 86010 formed in equilibrium with a melt whose composition is close to that of the meteorite bulk composition the ador melt had higher ree concentrations but a lower fe mg ratio than that of lew 86010 despite numerous common characteristics the two meteorites were produced in separate magmatic events involving similar but distinct processes and parent melts the unusual angrite composition is not due to purely nebular processes

generation of abnormal trace element abundances in antarctic eucrites by weathering processes abstract based on rees antarctic eucrites can be divided into two groups those showing normal trace element characteristics e g similar to juvinas and those showing abnormal trace element abundances many antarctic eucrite polymict eucrite and basaltic clast samples show the abnormal trace element abundances with ree patterns exhibiting positive ce anomalies sometimes negative ce anomalies positive eu anomalies and low abundances of the remainder of the rees with the lrees generally being at lower relative abundances than the hrees most samples of crystalline clasts from the polymict eucrites lew85300 lew85302 and lew85303 show the abnormal patterns while the glassy matrixes of these meteorites show normal patterns exterior samples generally show more abnormal patterns larger anomalies greater depletions than interior samples from the same meteorites comparison of all basaltic eucrite literature data combined with our data shows that positive and negative ce anomalies and positive eu anomalies are found in about 61 of antarctic eucrite analyses and are virtually unknown in non antarctic eucrite analyses further positive ce anomalies and positive eu anomalies are commonly associated with antarctic eucrites having low ree concentrations consideration of mineral melt partition coefficients shows that it is unlikely that ce anomalies are magmatic features from the hed parent body cerium anomalies on earth are generally restricted to the weathering zone where the relative ease of oxidizing ce to the 4 state allows for fractionation of ce from the 3 rees we believe the unusual ree patterns of abnormal antarctic eucrites arise from weathering effects generated in or on the antarctic ice our suggested scenario involves formation of melt water and its equilibration with the atmosphere which promotes dissolution of ree rich phosphates and oxidation of ce tetravalent ce can then be fractionated from the trivalent ree in solution the details of the weathering process are unclear and will require detailed chemical and sem investigations of eucrites for their elucidation we predict that rapidly chilled eucrites with glassy rather than crystalline mesostases will be more likely to survive the antarctic environment without alteration of their ree patterns occasional s se and k enrichments are likely due to weathering in the antarctic environment as well but these enrichments are not well correlated with ce anomalies

geochemical investigation of a sediment core from the trajan basin at portus the harbor of ancient rome a journal published by elsevier the attached copy is furnished to the author for internal non commercial research and education use including for instruction at the authors institution and sharing with colleagues other uses including reproduction and distribution or selling or licensing copies or posting to personal institutional or third party websites are prohibited in most cases authors are permitted to post their version of the article e g in word or tex form to their personal website or institutional repository authors requiring further information regarding elsevier s archiving and manuscript policies are encouraged to visit a b s t r a c t from the 1st century ad and for the duration of the roman empire the portus complex was the main harbor of rome its location on the tiber delta next to the tyrrhenian sea produced rapid environmental changes that together with historical vicissitudes largely determined the fate of the harbor we have assembled data on the mineralogy sedimentology geochemistry and ostracod populations of a sediment core drilled in the access channel of the hexagonal basin of trajan with the expectation that such a combined data set will shed new light on how the connections of the inland trajan basin with the tiber river the earlier claudius harbor on the nearby shoreline and the sea evolved through the centuries the data define four distinct periods which geochemistry characterizes by different conditions of salinity and oxygenation these in turn can be related to historical periods and events by means of 14

human influence and the changing geomorphology of mediterranean deltas and coasts over the last 6000 years from progradation to destruction phase the present geomorphology of the mediterranean s coasts is largely a product of an intricate long term relationship between nature and human societies a cradle of ancient civilisations the mediterranean has seen its shores occupied by humans since prehistory and is therefore a particularly pertinent unit of analysis the morphotectonic context and other forcing agents e g climate shaped out a highly diversified coastal morphology and generated a sediment supply regime potentially favourable to the formation of numerous open coast deltas and bay head deltas in infilled rias as sea level stabilised during the mid holocene this supply of riverine sediment has also been the key agent in mediating human occupation of the mediterranean s clastic coasts expressions of this relationship have been extensively archived in clastic coastal deposits including base level deltaic and estuarine sedimentary sinks which comprise records to explore the interactions between geosystems and the human environment the stratigraphic sequences in these coastal sedimentary archives comprise in many places a clearly identified anthropogenic signature notably in ancient harbours some of which underwent extremely rapid silting up due to massive sediment sourcing generated by new agricultural practices from the neolithic onwards increasing human influence especially over the last 3000 years has been in turn an important driver of changes in sediment supply strongly modulating deltaic development pulses of sediment supply from catchments rendered vulnerable by human perturbations during the roman period resulted in a new cycle of inception of many other deltas and in rapid delta growth e g the ebro the po the arno and the ombrone another progradation dynamic during the little ice age at a time of strong rural population growth river discharge increases technological developments and urbanisation further consolidated delta growth understanding the life cycle of these deltas since their initial formation is in turn key to unravelling the relative role of natural and anthropogenic forcing agents rapid climate changes are deemed to have contributed through both the stripping of landscapes rendered fragile by human activities and active fluvial sediment transport to the coast but disentangling climate change effects from human impacts in the mediterranean remains a challenge the patterns of subsequent deltaic growth and delta morphodynamics reflect adaptations to pulsed sediment supply river discharge variations the microtidal fetch limited context of the mediterranean and direct engineering interventions the progradation dynamic of the roman period and little ice age contrasts markedly with the situation of common coastal destabilisation over the last two centuries particularly well documented for the last 50 years this period has been characterised by reduced sediment flux to base level geosystems due to catchment reforestation retenion within reservoirs fluvial regulation and dredging resulting in the erosion of deltas and barrier lagoon and beach dune systems large stretches of shoreline and narrow coastal plains have been massively engineered for coastal defence and protection against erosion but also for the construction of marinas leisure harbours and artificial beaches resulting in the emergence of veritable artificial seafronts these interventions have collectively and progressively raised societies to a pervasive and overarching position in the geomorphic stability instability of the mediterranean s coasts a situation that will be exacerbated by pressures from sea level rise paving the way for rampant coastal erosion and delta destruction

mn cr dating of fe and ca rich olivine from quenched and plutonic angrite meteorites using secondary ion mass spectrometry this research was supported by grants dp034277 and dp0666751 from the australian research council to tri and ya and an australian national university phd research scholarship

pollutant lead reveals the pre hellenistic occupation and ancient growth of alexandria egypt 1 it is generally accepted that alexandria ad aegyptum was founded ex nihilo in 331 bc by alexander the great rapidly growing into one of antiquity s most opulent economic and intellectual centers however ancient texts by strabo 17 1 6 and pliny nh 5 11 62 suggest the existence of a pre hellenistic settlement named rhakotis this literary evidence has fuelled contentious scholarly debate for decades here we present new geochemical data from alexandria s ancient bay sediments elucidating unequivocal proof for pollutant lead pb input into the harbor during the egyptian old kingdom 2686 2181 bc a second contamination peak is detected during the iron age 1000 800 bc at the end of the prosperous ramesses reigns these findings evidence thriving pre hellenistic settlements in alexandria during the greek and roman periods we expound the largest pb pollution ever encountered in ancient city sediments with pb levels twice as high as those measured in contemporary industrialized estuaries

the harbour of elaia a palynological archive for human environmental interactions during the last 7500 years abstract elaia the harbour city for ancient pergamon western turkey was investigated using geoarchaeological methods the rise and fall of elaia were closely linked to the flourishing period of pergamon which ruled wide parts of today s western turkey in hellenistic times in the framework of this research the palynological analysis of a 9 m sediment core ela 70 retrieved from the enclosed harbour of the city was carried out to reconstruct the vegetation and environmental history of the wider gulf of elaia region an age depth model based on 11 calibrated radiocarbon ages starting from 7 5 ka bp provides the basis for the high resolution study of sediments from the hellenistic period as well as before and after the lower part of the pollen diagram is characterised by high percentages of deciduous oaks and pines suggesting the dominance of open forests close to the coring site the change from oak forests to a cultural landscape with olive pistachio walnut and grape started around 850 bc reaching a maximum ca 250 bc and continuing to ca ad 800 this period is characterised by increase of fire activity soil erosion intensity and pastoral farming such long lasting intensive land use likely led to the climax ecosystem turnover from open deciduous oak forests to pine stands while salt marshes developed around the coring site the discovery of the dinoflagellate cysts of peridinium ponticum a black sea endemic species in the harbour of elaia evidences maritime trade between the aegean sea and the black sea its first occurrence coincides with the time of the mithridatic wars 1st century bc in conclusion palynological data in addition to historical and archaeological records provide a deeper insight into human environmental interactions as derived from the geoarchaeological archive of the harbour of elaia

age and isotopic relationships among the angrites lewis cliff 86010 and angra dos reis results of a wide ranging isotopic investigation of the unique antarctican angrite lew 86010 lew are presented together with a reassessment of the type angrite angra dos reis ador the principal objectives of this study are to obtain precise radiometric ages initial sr isotopic compositions and to search for the erstwhile presence of the short lived nuclei 146sm and 26al via their daughter products the isotopic compositions of sm u ca and ti were also measured this allows a detailed appraisal to be made of the relations between and the geneology of these two angrites lew proves to be severely contaminated with modern terrestrial pb which is shown to result from terrestrial weathering nevertheless concordant pb pb model ages of pyroxene separates were obtained 2 4 55784 52 ga for lew and 4 55780 42 ga for ador uranium isotopic compositions are normal within error the inferred initial pb isotopic composition is within error of primordial pb as defined by canon diablo troilite because of the extreme upb ratios of both angrites this places an upper limit of 2 ma on the time between volatile element loss of the angrite parent body or its precursor planetesimals and the final crystallization of the angrites as differentiates initial 87sr86sr ratios were found to be indistinguishable in lew ador and the cumulate eucrite moore county the derived initial 87sr86sr for all three meteorites is 0 698970 15 2 a 147sm 143nd isochron for lew was obtained yielding an age of 4 553 34 ga with an initial 143nd144nd of 0 506682 49 2 146sm142nd isotope systematics were also measured anomalies on 142nd arising from extinct 146sm were clearly resolved resulting in an initial 146sm144sm of 0 0071 17 with nd142 2 57 0 62 at the time of isotopic closure both of these sm nd methods imply derivation of lew from a reservoir with chondritic smnd ratio they are also quite consistent with the previously reported systematics for ador overall the age and isotopic similarities between lew and ador are striking it suggests almost simultaneous production on the same asteroid even though recent experimental studies imply that the two are not comagmatic calcium and titanium do not exhibit enrichments in the n rich isotopes in contrast to cais making it unlikely that the angrite parent body is inherently rich in early condensates from the solar nebula no evidence was found for live 26al in lew when combined with the pb pb age and initial 87sr86sr data this firmly excludes 26al being an important heat source in the early solar system heat supplied for for example 1 the differentiation of the angrite and eucrite parent bodies and 2 metamorphism of the chondrite parent bodies must come from some other source the debate over live vs extinct 26al in the earliest solar system remains unresolved by this new data from lew however both the angrite and eucrite parent bodies have extremely low rbsr and high upb ratios compared to the solar nebula therefore the common initial 87sr86sr of 0 698970 can be firmly associated with the u pb angrite age above and the formation of both bodies this enables an absolute chronology of the early solar system to be established based upon 87sr86sr differences the oldest cais are a minimum of 11 4 ma older than the angrites i e 4 569 5 ga the age and isotopic constraints are discussed with respect to current collapse condensation and accretion timescales calculated for the solar nebula

demise of a harbor a geochemical chronicle from ephesus a b s t r a c t at the end of the first century bc ephesus became the roman capital of asia minor and the most important commercial religious and cultural center of the region in order to evaluate the status of anthropogenic fluxes in the port of ephesus a 12 m long sediment core drilled in the roman basin was investigated to shed light on the paleo environmental evolution of the harbor using grain size distri bution analysis 14 c ages major and trace element geochemistry and pb isotope compositions with the help of complementary sedimentological data and principal component analysis five distinct units were identified which together reflect the different stages of water history in the harbor among the major disruptive events affecting the port were earthquakes and military events both of which were partic ularly effective at destroying the water distribution system seasonal floods of the cayster river kucuk menderes were the major source of the silt that progres sively infilled the harbor silting in was further enhanced by the westward migration of the river mouth a single major disruptive event located at 550 cm core depth and heralding the development of anoxia in the harbor marks the end of the dynamic regime that otherwise controlled the harbor water throughout the roman empire period this remarkable event may correspond to a major disruption of the aqueduct system or to a brutal avulsion of the cayster river bed it clearly represents a major disturbance in the history of life at ephesus it is poorly dated but probably occurred during the reign of augustus or shortly after lead isotope and trace metal evidence suggest that in the four bottom units pollution was subdued with respect to other pb metal inputs presumably those from aqueducts and natural karstic springs near the top of the core which coincides with harbor abandonment and the more recent period anthropogenic pb contam ination is clearly visible in both pb abundances and isotopic compositions

impact histories of angrites eucrites and their parent bodies abstract eucrites which are probably from 4 vesta and angrites are the two largest groups of basaltic meteorites from the asteroid belt the parent body of the angrites is not known but it may have been comparable in size to vesta as it retained basalts and had a core dynamo both bodies were melted early by 26al and formed basalts a few myr after they accreted despite these similarities the impact histories of the angrites and eucrites are very different angrites are very largely unshocked and none are breccias whereas most eucrites are breccias and many are shocked we attribute the lack of shocked and unbrecciated angrites to an impact possibly at 4558 myr ago the radiometric age of the younger angrites that extracted the angrites from their original parent body into smaller bodies these bodies which may have had a diameter of approximately 10 km suffered much less impact damage than vesta during the late heavy bombardment because small bodies retain shocked rocks less efficiently than large ones and because large bodies suffer near catastrophic impacts that deposit vastly more impact energy per kg of target our proposed history for the angrites is comparable to that proposed by bogard and garrison 2003 for the unbrecciated eucrites with ar ar ages of 4 48 gyr and that for unbrecciated eucrites with anomalous oxygen isotopic compositions that did not come from vesta we infer that the original parent bodies of the angrites and the anomalous eucrites were lost from the belt when the giant planets migrated and the total mass of asteroids was severely depleted alternatively their parent bodies may have formed in the terrestrial planet region and fragments of these bodies were scattered out to the primordial main belt as a consequence of terrestrial planet formation

changes in the atmospheric ch4 gradient between greenland and antarctica during the last glacial and the transition to the holocene significant variations in the interpolar difference of atmospheric ch4 concentration over the holocene period were observed by chappellaz et al 1997 here we extend this study to the last glacial and the transition to the holocene we observe a gradient of 3 4 parts per billion by volume ppbv during the last glacial maximum it increases to 26 10 ppbv during the bolling allerod and remains at 26 9 ppbv during the younger dryas cold period on average we find an interpolar difference of 14 4 ppbv during the cold phases and of 37 10 ppbv during the warm periods of the last glacial with a three box model we derive from the measured gradients the contributions of methane from the tropics and the mid to high latitudes of the northern hemisphere the tropics have been the largest source in all glacial epochs the contribution by the northern latitudes have been very small during the last glacial maximum but surprisingly large during the earlier part of the glacial epoch the model result suggests completely unexpected that the higher atmospheric ch4 concentration during the warm dansgaard oeschger events are caused by a higher source strength of the northern latitudes and not of the tropics

late quaternary sea ice history in the indian sector of the southern ocean as recorded by diatom assemblages abstract a modern analog technique mat5201 31 has been applied to fossil diatom assemblages to provide down core estimates of february sea surface temperatures ssts and of sea ice duration over the past 220 000 years at 56 40 s 160 14 e at the core location sea ice progression lagged the sst drop by 1 ka at interglacial glacial transitions and sea ice retreat was almost synchronous to the sst increase at glacial interglacial terminations sea ice increased continuously during glacial periods to reach its maximum extent at the end of glacial times although ssts were almost constant during glacials this indicates that ssts are the major parameter determining the advance and retreat of sea ice at transitions but that the sea ice advance during glacial conditions may be related to positive feedbacks of the ice on albedo air temperature and meridional wind stress the strong correlation r 0 75 between sea ice duration at the core location and the vostok co2 record argues for a control of antarctic sea ice extent on atmospheric co2 concentration via the modification of the ocean to atmosphere gas balance

thermal histories of angrite meteorites trace element partitioning among silicate minerals in angra dos reis lewis cliff 86010 and experimental analogs we measured rare earth element ree abundances in selected silicate phases in the angrites angra dos reis ador and lewis cliff lew 86010 in order to further clarify the thermal history of ador we also carried out a preliminary experimental study designed to examine apparent ree partitioning between silicates fassaite olivine kirschsteinite and melt in synthetic analogs of angrites under disequilibrium conditions at liquidus temperatures silicates in ador are homogeneous with respect to major minor and trace elements which is consistent with the interpretation that ador underwent extensive subsolidus equilibration ree distributions in olivine and kirschsteinite in ador are similar to those in lew 86010 and are consistent with the formation of kirschsteinite by exsolution from olivine during cooling and or annealing there is no evidence for a disequilibrium trace element signature that could have been inherited from rapid cooling at liquidus temperatures this is supported by our petrographic observations of the occurrence of kirschsteinite within olivine aggregates in ador olivine kirschsteinite pairs in ador record closure temperatures around 600 650 c

human environment interaction in the hinterland of ephesos as deduced from an in depth study of lake belevi west anatolia abstract lacustrine sediments are important archives for high resolution palaeoenvironmental reconstructions of the holocene despite the density of ancient cities and settlements along the western coast of turkey the archives from coastal lakes in this area have until now not been recognized to their fullest potential and are therefore only poorly studied the exceptional geo bio archive of lake belevi is located close to the ancient city of ephesos in western turkey two sediment cores have been analysed using geochemical sedimentological microfaunal palynological and archaeoparasitological methods the in depth study of these holocene deposits is supported by a robust age depth model that used 33 radiocarbon dates and tephrochronology the results reveal the existence of a freshwater lake in the early holocene which turned brackish when the rising sea level connected it with the sea the delta evolution of the kucuk menderes led to the re establishment of a freshwater lake the natural vegetation was represented by open oak woodlands there are hints for first agricultural activities in the environs of belevi as early as 8000 cal yr bp intensive cultivation of olea is proven since 3000 cal yr bp starting during the 3rd millennium bp the human impact with enhanced deforestation activities and correlative high sedimentation rates is attested for sites such as belevi ephesos elaia pergamon and miletos for the first time tephra from the eruption of minoan santorini has been identified in the environs of ephesos this ash covered the vegetation by a thick layer wherefore low growing plants were strongly affected the comparison between the results from the quasi natural area of lake belevi and the area around the city of ephesos gives insights into the development and use of the landscapes the environmental changes as well as the duration and intensity of the human impact

petrogenesis and provenance of ungrouped achondrite northwest africa 7325 from petrology trace elements oxygen chromium and titanium isotopes and mid ir spectroscopy northwest africa nwa 7325 is an ungrouped achondrite that has recently been recognized as a sample of ancient differentiated crust from either mercury or a previously unknown asteroid in this work we augment data from previous investigations on petrography and mineral compositions mid ir spectroscopy and oxygen isotope compositions of nwa 7325 and add constraints from cr and ti isotope compositions on the provenance of its parent body in addition we identify and discuss notable similarities between nwa 7325 and clasts of a rare xenolithic lithology found in polymict ureilites nwa 7325 has a medium grained protogranular to poikilitic texture and consists of 10 15 vol mg rich olivine fo 98 25 30 vol diopside wo 45 mg 98 55 60 vol ca rich plagioclase an 90 and trace cr rich sulfide and fe ni metal we interpret this meteorite to be a cumulate that crystallized at 1200 c and very low oxygen fugacity similar to the most reduced ureilites from a refractory incompatible element depleted melt modeling of trace elements in plagioclase suggests that this melt formed by fractional melting or multi stage igneous evolution a subsequent event likely impact resulted in plagioclase being substantially remelted reacting with a small amount of pyroxene and recrystallizing with a distinctive texture the bulk oxygen isotope composition of nwa 7325 plots in the range of ureilites on the ccam line and also on a mass dependent fractionation line extended from acapulcoites the e54cr and e50ti values of nwa 7325 exhibit deficits relative to terrestrial composition as do ordinary chondrites and most achondrites its e54cr value is distinct from that of any analyzed ureilite but is not resolved from that of acapulcoites as represented by acapulco in terms of all these properties nwa 7325 is unlike any known achondrite however a rare population of clasts found in polymict ureilites the magnesian anorthitic lithology are strikingly similar to nwa 7325 in mineralogy and mineral compositions oxygen isotope compositions and internal textures in plagioclase these clasts are probably xenolithic in polymict ureilites and could be pieces of nwa 7325 like meteorites using constraints from chromium titanium and oxygen isotopes we discuss two possible models for the provenance of the nwa 7325 parent body 1 accretion in the inner solar system from a reservoir similar to that of acapulcoites in 17o e54cr and e50ti or 2 early 1 ma after cai formation accretion in the outer solar system beyond the snow line before 54cr and 50ti anomalies were introduced to this region of the solar system the mid ir emission spectrum of nwa 7325 obtained in this work matches its modal mineralogy and so can be compared with spectra of new meteorites or asteroids planets to help identify similar materials and or the parent body of nwa 7325

influence of the intertropical convergence zone on the east asian monsoon a palaeoclimate record spanning the past 16 000 years with nearly annual time resolution has been obtained from lake huguang maar in china the magnetic properties and titanium content of the lake sediments are thought to reflect changes in the east asian winter monsoon strength thus providing a complement to palaeoclimate archives that record the strength of the rain bearing summer monsoon the records point to an anti correlation between winter and summer monsoon strength best explained by migration of the intertropical convergence zone itcz a belt of low pressure air at the equator interestingly the decline of china s tang dynasty and the mayan civilization broadly coincide with drought periods recorded in lake huguang maar and cariaco basin sediments respectively did major shifts in the position of the itcz catalyse simultaneous events in civilizations on opposite sides of the pacific ocean the asian australian monsoon is an important component of the earth s climate system that influences the societal and economic activity of roughly half the world s population the past strength of the rain bearing east asian summer monsoon can be reconstructed with archives such as cave deposits1 2 3 but the winter monsoon has no such signature in the hydrological cycle and has thus proved difficult to reconstruct here we present high resolution records of the magnetic properties and the titanium content of the sediments of lake huguang maar in coastal southeast china over the past 16 000 years which we use as proxies for the strength of the winter monsoon winds we find evidence for stronger winter monsoon winds before the bolling allerod warming during the younger dryas episode and during the middle and late holocene when cave stalagmites suggest weaker summer monsoons1 2 3 we conclude that this anticorrelation is best explained by migrations in the intertropical convergence zone similar migrations of the intertropical convergence zone have been observed in central america for the period ad 700 to 900 refs 4 6 suggesting global climatic changes at that time from the coincidence in timing we suggest that these migrations in the tropical rain belt could have contributed to the declines of both the tang dynasty in china and the classic maya in central america

trace element distributions within ordinary chondrite chondrules implications for chondrule formation conditions and precursors the concentrations of thirty six lithophile elements in the major silicate phases of chondrules have been determined by ion microprobe two types of porphyritic chondrule olivines normal and incompatible rich have been identified the incompatible rich olivines which have forsterite contents that are greater than fo98 appear to have formed under highly reducing conditions the olivine and low ca pyroxene grains in porphyritic chondrules have relatively unfractionated l chondrite normalized ree abundances compared to expectations from equilibrium distribution coefficients this is consistent with porphyritic chondrules having formed at cooling rates of the order of 1000 c h or faster the alkali metal na k rb and cs to al ratios in chondrule glasses vary by two orders of magnitude the lower values possibly being the result of volatile loss from chondrules no correlation was found between alkali metal depletions in chondrule glasses and enrichments in the surrounding rims but any such correlation may have been destroyed by the diffusive redistribution of these elements in rims that is likely to occur even under mild metamorphic conditions the refractory lithophiles with the exception of mg are all highly incompatible in silicate melts and are as a result concentrated in the chondrule glasses the refractory lithophiles in the glass are in most cases unfractionated from one another suggesting that neither vapor phase nor crystal liquid fractionation played a major role in the formation of chondrules or their precursors based largely on the observation that the refractory lithophiles are concentrated in the chondrule glasses it is suggested that previously reported correlations between these elements in bulk chondrule analyses are due to chondrules themselves as opposed to refractory condensates having been their own immediate precursors a simple monte carlo simulation using the compositions of the major chondrule silicate phases reported here supports this hypothesis it is argued that the upper limit of about one observed in the atomic na al ratios of chondule glasses is not due to an albitic precursor but simply reflects that for na to be incorporated into the structure of the melt it must take part in the coupled substitution naalo2 sio2

human impact on holocene sediment dynamics in the eastern mediterranean the example of the roman harbour of ephesus during the past millennia many erosion and accumulation processes have been modified by anthropogenic impact this holds especially true for the environs of ancient settlements and their harbours along the mediterranean coasts our multi proxy investigations in the roman harbour and the harbour canal of ephesus western turkey reveals that humans have significantly triggered soil erosion during the last three millennia since the eighth century bc and especially since the hellenistic period a high sed imentation rate indicates fast alluviation and delta progradation of the kucuk menderes deforestation agriculture especially ploughing and grazing especially goats were the main reasons for erosion of the river catchment area one consequence was significant siltation of the hellenistic roman harbour basin this sediment trap archives the human impact which was strongly enhanced from hellenistic roman to byzantine times second first centuries bc to the sixth seventh centuries ad evidenced by high sedimentation rates raised values of heavy metal contaminations lead pb copper cu the occurrence of fruit tree pollen and of intestinal parasites from the middle to the end of the first millennium ad the influence of ephesus declined which resulted in a decrease of human impact studies of several ancient settlements around the mediterranean sea tell a comparable story they also confirm that during their most flourishing periods the human impact totally overprinted the climatic one to detect the latter geo bio archives of relatively pristine areas have to be investigated in detail

taken from the sea reclaimed by the sea the fate of the closed harbour of elaia the maritime satellite city of pergamum turkey abstract during hellenistic times when the pergamenian kingdom was prospering pergamum was operating an important harbour used by merchants and military at the city of elaia this paper focuses on the development utilisation and decay of the closed harbour of elaia which is discussed in the context of the landscape evolution of the environs of the ancient settlement based on geoarchaeological archaeological and literary evidence the construction of two harbour moles in order to provide shelter against wave action and enemies can be attributed to the early hellenistic period geoelectric measurements revealed the construction profile of the moles coring evidence indicated that together with mole construction a greater area of the formerly shallow marine and sublittoral terrain was consolidated most probably to create space for harbour installations the closed harbour basin was used intensely during hellenistic and roman times later continued siltation hindered further usage in combination with the decline of the city of elaia in late antiquity this was the reason why the harbour was abandoned scenarios for the time of the maximum transgression of the sea around 2500 bc the early hellenistic times around 300 bc and late antiquity ad 500 are presented

the holocene sea level story since 7500 bp lessons from the eastern mediterranean the black and the azov seas abstract this paper addresses the obvious controversy between the so far published sea level curves of the black sea and the mediterranean it starts with a discussion of the methods of reconstructing sea level curves the evaluation of sea level indicators and the application of the radiocarbon dating method at least since 7500 bp when the black sea and the mediterranean were connected both water bodies must have reacted synchronously on glacio eustatic changes it is documented that none of the mediterranean sea level curves shows the major wiggles postulated for the black sea which are supposed to reflect trans and regression cycles the very shallow bathymetric condition of the azov sea and the northern black sea should have led to considerable and traceable shoreline displacements there is neither archaeological nor historical evidence of mid and late holocene regressions of several meters the tectonic setting of the black and azov seas implicates that the tectonic signal often overrides the eustatic one therefore only local sea level curves can be established in this paper based on vibracores a locally valid sea level curve for the taman peninsula is demonstrated layers of paralic peat were used as sea level indicators and for 14 c dating the shape of this curve follows the one known from the mediterranean this study also revealed that the present peninsula of taman evolved out of a former archipelago

metamorphic angrite northwest africa 3164 5167 compared to magmatic angrites abstract northwest africa nwa 3164 and 5167 are two angrites with a granulitic texture unlike that of other angrites with a variable up to millimeter grain size besides mineralogical and chemical similarities to other angrites nwa 3164 and 5167 exhibit unique characteristics ca rich olivine dominates in nwa 3164 49 vol fo57 nwa 5167 40 vol fo59 fassaitic clinopyroxene is the second major phase in nwa 3164 29 vol in nwa 5167 36 vol with a significant tschermak component in addition two al rich phases are present plagioclase an99 and hercynitic spinel 6 and 7 vol respectively for nwa 3164 17 and 4 vol respectively for nwa 5167 heavily weathered iron sulfide and kamacite 9 wt in nwa 3164 4 wt in nwa 5167 are the remaining minor phases a unique feature among angrites all mineral phases are homogeneous like other angrites nwa 3164 and 5167 exhibit a superchondritic ca al ratio with negligible amounts of alkalis and very low silica content the presence of metal results from the incorporation of exogenous iron following impact subsequent annealing resulted in the observed granulitic texture major element composition indicates that both nwa 3164 and 5167 are derived from a picritic angrite precursor after incorporation of metal and annealing after correction for iron and fo90 olivine incorporation bulk rock ree abundances of both nwa 3164 and nwa 5167 appear lower than those of quenched angrites showing the lowest absolute abundances among angrites laser ablation inductively coupled plasma mass spectrometry la icp ms analyses of clinopyroxene olivine and anorthite indicate that difference of rare earth element ree abundances between nwa 3164 and nwa 5167 can be explained by adding traces of phosphate to nwa 3164 nwa 3164 5167 trace elements abundances are similar showing depletion in volatile elements and enrichment in refractory lithophile elements such as ca ti and al the most incompatible elements are depleted as well unlike other angrites this indicates that the source of these younger angrites was more depleted in incompatible elements when compared to the older magmatic angrites the low hf w is understood as the result of exogenous iron incorporation and therefore the hf w and w isotopic heterogeneity of the angrite parent body apb mantle is secondary comparison with other angrites suggests that iron incorporation may be necessary to explain their low hf w and w isotopic compositions

relationship between antarctic sea ice and southwest african climate during the late quaternary here we compare late quaternary southwest african climate records from the west coast of southern africa published winter rainfall and trade wind intensity records from a core off the coast of namibia to records of antarctic sea ice extent this comparison reveals coherent changes between antarctic sea ice extent and the southwest african winter rain region since 45 k y b p with enhanced winter rainfall and trade wind vigor during periods of increased sea ice presence we propose an oceanic and atmospheric coupling between antarctic sea ice and the winter rainfall zone of southwest africa that may lead to increased desertification in the region if global warming persists

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

a 70 kyr sea surface temperature record off southern chile ocean drilling program site 1233 1 we present the first high resolution alkenone derived sea surface temperature sst reconstruction in the southeast pacific ocean drilling program site 1233 covering the major part of the last glacial period and the holocene the record shows a clear millennial scale pattern that is very similar to climate fluctuations observed in antarctic ice cores suggesting that the southern hemisphere high latitude climate changes extended into the midlatitudes involving simultaneous changes in air temperatures over antarctica sea ice extent extension of the antarctic circumpolar current and westerly atmospheric circulation a comparison to other midlatitude surface ocean records suggests that this antarctic millennial scale pattern was probably a hemisphere wide phenomenon in addition we performed sst gradient reconstructions over the complete latitudinal range of the pacific eastern boundary current system for different time intervals during the last 70 kyr the main results suggest an equatorward displaced subtropical gyre circulation during marine isotope stages 2 and 4

geoarchaeology of sidon s ancient harbours phoenicia abstract geoarchaeological data from sidon s ancient harbour areas elucidate six evolutionary phases since the bronze age 1 at the time of sidon s foundation during the third millennium bc medium sand facies show the city s northern and southern pocket beaches to have served as proto harbours for middle to late bronze age societies 2 towards the end of the late bronze age and the early iron age expanding international trade prompted coastal populations into modifying these natural anchorages in sidon s northern harbour transition from shelly to fine grained sands is the earliest granulometric manifestation of human coastal modification the lee of zire island was also exploited as a deep water anchorage or outer harbour at this time 3 although localised sediments evoke developed port infrastructure during the phoenician and persian periods high resolution reconstruction of the northern harbour s iron age history is problematic given repeated dredging practices during the roman and byzantine periods 4 fine grained silts and sands in the northern harbour are coeval with advanced roman engineering works significantly deforming the coastal landscape bio and lithostratigraphical data attest a leaky lagoon type environment indicative of a well protected port 5 the technological apogee of sidon s northern harbour is recorded during the late roman and byzantine periods translated stratigraphically by a plastic clays unit and brackish lagoon fauna 6 a final semi abandonment phase comprising coarse sand facies concurs silting up and a 100 150 m progradation of the port coastline after the seventh century ad we advance three hypotheses to explain these stratigraphic data namely cultural tectonic and tsunamogenic finally our results are compared and contrasted with research undertaken in sidon s sister harbour tyre

distinct 238 u 235 u ratios and ree patterns in plutonic and volcanic angrites geochronologic implications and evidence for u isotope fractionation during magmatic processes angrites are differentiated meteorites that formed between 4 and 11 myr after solar systemformation when several short lived nuclides e g 26 al 26 mg 53 mn 53 cr 182 hf 182 w were still alive as such angrites are prime anchors to tie the relative chronology inferred from these short lived radionuclides to the absolute pb pb clock the discovery of variable u isotopic composition at the sub permil level calls for a revision of pb pb ages calculated using an assumed constant 238 u 235 u ratio i e pb pb ages published before 2009 2010 in this paper we report high precision u isotope measurement for six angrite samples nwa 4590 nwa 4801 nwa 6291 angra dos reis d orbigny and sahara 99555 using multi collector inductively coupled plasma mass spectrometry and the irmm 3636 u double spike the age corrections range from 0 17 to 1 20 myr depending on the samples after correction concordance between the revised pb pb and hf w and mn cr ages of plutonic and quenched angrites is good and the initial 53 mn 55 mn 0 ratio in the early solar system ess is recalculated as being 7 1 10 6 at the formation of the solar system the error bar incorporates uncertainty in the absolute age of calcium aluminum rich inclusions cais an uncertainty remains as to whether the al mg and pb pb systems agree in large part due to uncertainties in the pb pb age of cais a systematic difference is found in the u isotopic compositions of quenched and plutonic angrites of 0 17 a difference is also found between the rare earth element ree patterns of these two angrite subgroups the 238 u values are consistent with fractionationduring magmatic evolution of the angrite parent melt stable u isotope fractionation due to a change in the coordination environment of u during incorporation into pyroxene could be responsible for such a fractionation in this context pb pb ages derived from pyroxenes fraction should be corrected using the u isotope composition measured in the same pyroxene fraction

chemical alteration and ree mobilization in meteorites from hot and cold deserts the effects of terrestrial weathering on ree mobilization are evaluated for a variety of uncommon meteorites found in antarctica and in hot deserts the meteorites analyzed include 7 non cumulate eucrites 10 shergottites 3 nakhlites 2 lunar meteorites 4 angrites 10 acapulcoites 1 winonaite and 1 brachinite in situ concentration measurements of lanthanides and selected other minor and trace elements were made on individual grains by secondary ion mass spectrometry sims in antarctic meteorites oxidation converts ce 3 to ce 4 which is less soluble than the trivalent ree resulting in ce anomalies the mineral most affected is low ca pyroxene however not all grains of a given mineral are and distinct analyses of a single grain can even yield ree patterns with and without ce anomalies the effect is most pronounced for antarctic eucrites in which ce anomalies are observed not only in individual minerals but also in whole rock samples although ce anomalies are observed in meteorites from hot deserts as well the most characteristic signs of chemical alteration in this environment are a lree enrichment with a typical crustal signature as well as sr ba and u contaminations these can modify the whole rock ree patterns and disturb the isotope systematics used to date these objects the lree contamination is highly heterogeneous affecting some grains and not others of a given mineral mainly olivine and low ca pyroxene the two minerals with the lowest ree concentrations the major conduit for ree movement is through shock induced cracks and defects and the highest levels of contamination are found in altered material filling such veins and cracks meteorites that experienced low shock levels and those that are highly recrystallized are the least altered copyright 2003 elsevier ltd

holocene coastal change in the ancient harbor of yenikapi istanbul and its impact on cultural history an extensive rescue excavation has been conducted in the ancient harbor of istanbul yenikapi by the sea of marmara revealing a depositional sequence displaying clear evidence of transgression and coastal progradation during the holocene the basal layer of this sequence lies at 6 m below the present sea level and contains remains of a neolithic settlement known to have been present in the area indicating that the sea level at 8 9 cal ka bp was lower than 6 m below present sea level advanced to its maximum at 6 8 7 cal ka bp drowning lykos stream and forming an inlet at its mouth after 3 cal ka bp coastal progradation became evident subsequent construction of the byzantine harbor theodosius 4th century ad created a restricted small basin and accumulation of fine grained sediments the sedimentation rate was increased due to coastal progradation and anthropogenic factors during the deposition of coarse grained sediments at the upper parts of the sequence 7th 9th centuries ad the harbor was probably abandoned after the 11th century ad by filling up with lykos stream detritus and continued seaward migration of the coastline

holocene stratigraphy and geomorphological evolution of the aegean coastal plains of anatolia abstract three main stages can be distinguished in the sedimentary development and geomorphological formation of the present delta plains on the aegean coast of turkey the early holocene is characterized by post glacial transgression and dependent sedimentation the middle holocene was the period when sea level reached the present level and apart from small fluctuations stopped rising alluviation and deltaic progradation were prevalent during this transition period from marine to terrestrial environments as for the late holocene deltaic progradation slowed down and delta plains were covered by floodplain sediments these characteristics can be observed in the same sequence throughout the aegean coast of turkey

reassessing the origin and chronology of the unique achondrite asuka 881394 implications for distribution of 26al in the early solar system abstract the achondrite asuka 881394 has mineralogy broadly similar to that of eucrites but is isotopically chemically and texturally distinct from them previous u pb chronology shows that it is very old forming within the first 0 8 ma of the formation of calcium aluminum rich inclusions cais however the age difference between asuka 881394 and other very old solar system materials cais quenched angrites measured with the 26al 26mg and 53mn 53cr extinct radionuclide chronometers and 207pb 206pb chronometer is not the same this could be interpreted to reflect heterogeneity in the distribution of 26al and 53mn in the early solar system given the significant implications for the early solar system chronology if 26al and 53mn are indeed heterogeneously distributed in this study we further investigate the origin of asuka 881394 and the apparent age discordance between short lived and absolute chronometers by focusing on measurement of its e54cr composition renewed measurements of the absolute pb pb age and new high precision measurements of its 26al 26mg systematics new cr isotope data places additional constraints on the origin of asuka 881394 its e 54cr value of 0 37 0 10e is resolvable outside of uncertainty from hed meteorites 0 72 0 10e reinforcing evidence from oxygen isotopic analyses that suggest it originated from a distinct parent body unlikely to be 4 vesta new pb pb analyses combined with using a directly measured 238u 235u ratio for age calculation result in a recalculated pb pb age of 4564 95 0 53 ma 1 5 ma younger than the previously reported age with this age asuka 881394 remains one of the oldest known achondrites in our solar system new high precision 26al 26mg data produce an initial 26al 27al ratio of 1 48 0 12 10 6 within error of previous data this ratio corresponds to an al mg age of 4563 69 0 36 ma or 4564 83 0 21 ma relative to cais and the d orbigny angrite respectively thus depending on which age anchor is used the 26al 26mg age is either 1 26 ma or 0 12 ma younger than the new pb pb age the latter being unresolved within analytical uncertainty though a potential age discrepancy between 26al 26mg and pb pb could be a result of heterogeneous distribution of 26al we demonstrate with our new high precision mg isotope data in conjunction with petrographic evidence that the mg isotope system has been disturbed in asuka 881394 we suggest that the 26al 26mg system closed to diffusion after the u pb system either due to slow cooling on the parent body or low grade metamorphic re equilibration of mg thus we can satisfactorily explain the observed age discrepancy between 26al 26mg and u pb systems in asuka 881394 without invoking heterogeneous distribution of 26al 27al ratio in the early solar system comparison of the asuka 881394 data with that of other anomalous achondrites from distinct parent bodies suggests that these could also have evolved from a source region with a canonical 26al 27al ratio because these achondrites have significant differences in their e54cr 17o systematics which could be indicative of location within the early protoplanetary disk it is consistent with homogeneous distribution of 26al in the early solar system angrites remain an outlier either because they evolved from a source with a lower 26al 27al ratio or because their 26al 26mg or pb pb data are problematic in either case this suggests that basaltic angrites are questionable as the age anchor for the entire solar system as a whole and other very old well preserved achondrites should be considered for that role

olivinites in the angrite d orbigny vestiges of pristine reducing conditions during angrite formation abstract olivinites together with olivine megacrysts are the most magnesian phases found in angrites their chemical composition mg 90 is out of equilibrium with the groundmass and far away from that of possible precipitates from angrite parent melts therefore olivinites as well as olivine megacrysts were considered as xenoliths and xenocrysts we report here a detailed study of five olivinites from the angrite d orbigny our results indicate that d orbigny experienced metasomatic alteration processes which led to enrichments in feo and mno relative to the original composition changing the initial mg rich composition of the olivines to the one seen now as this process took place in equilibrium with a chondritic reservoir e g fe mn ratios spreading around primitive values the primitive mg rich olivine chemical composition was changed towards a more fayalitic one while preserving a chondritic signature this chondritic signature was preserved in the fe mn ratio of the olivinites olivine megacrysts augite grains in olivinites and groundmass olivine of d orbigny therefore the fayalite content of about 35 mol that characterizes the groundmass olivine of this rock as well as other angrites does not correspond to its original composition but may be the result of a late metasomatic process that affected these rocks if so olivinites and mg rich olivines might not be compositionally exotic phases but are an early constituent phase that retained the pristine more reducing conditions that have been preserved in some angrites where they form either a small part of the rock e g asuka 881371 and d orbigny or the majority of it nwa 8535

the u pb systematics of angrite sahara 99555 abstract angrite sahara 99555 hereafter sah precisely dated by baker et al baker j bizzarro m wittig n connelly j and haack h 2005 early planetesimal melting from an age of 4 5662 gyr for differentiated meteorites nature 436 1127 1131 has been proposed as a new reference point for the early solar system timescale and for calculation of the revised minimum age of our solar system the pb pb age of sah of 4566 18 0 14 ma reported by baker et al differs from the pb pb age of d orbigny another basaltic angrite of 4564 42 0 12 ma amelin y 2008 u pb ages of angrites geochim cosmochim acta 72 221 232 despite the fact that the relative 53mn 53cr and 182hf 182w ages of these meteorites are identical here i report u pb data for 21 whole rock and pyroxene fractions from sah analyzed using the same approach as d orbigny amelin 2008 these fractions contain between 1 3 and 8 9 pg of total common pb slightly more than analytical blank measured 206pb 204pb ratios are between 625 and 2817 for d orbigny blank corrected 206pb 204pb ratios are between 1173 and 6675 eight acid washed whole rock fractions yielded an isochron age of 4564 86 0 38 ma mswd 1 5 data for pyroxene fractions plot mostly above the whole rock isochron and do not form a linear array in 207pb 206pb vs 204pb 206pb isochron coordinates the 207pb 206pb model dates of the pyroxene fractions vary from 4563 8 0 3 to 4567 1 0 5 ma the difference between whole rock and pyroxene u pb systematics may be a result of re distribution of radiogenic pb at a mineral grain scale several million years after crystallization complexities of sm nd lu hf and possibly 26al 26mg mineral systematics of sah described previously may be related to the same process that caused the re distribution of radiogenic pb disturbance of isotopic chronometers renders sah an imperfect anchor for the early solar system timescale the problems with age determination revealed by the studies of sah call for greater attention in pb isotopic dating of angrites and other achondrites

a geochemical and sedimentological perspective of the life cycle of neapolis harbor naples southern italy since the discovery of the ancient harbor of naples in 2004 during construction work on an underground railway geoarchaeological studies undertaken on the archaeological excavation have revealed the main stratigraphic and paleo environmental levels of the harbor site near the piazza municipio however knowledge of the dynamics and paleoenvironmental changes in the water column of the harbor as well as the processes of transport and deposition of sediments that led to siltation and infilling of the harbor basin has been lacking due to the absence of high resolution data to fill these gaps we have undertaken a threedimensional study longitudinal transverse and vertical of the harbor deposits by carrying out geochemical and sedimentological analyses of four stratigraphic sections of the archaeological excavation the results show that after a phase of relative calm during the first half of the 1st c ad siltation of the harbor progressed exponentially up to the 5th c ad when dredging operations were carried out to obtain a water level sufficient for the development of maritime and harbor activities we attribute this acceleration of siltation to a combination of climatic anthropic and volcanic factors volcanic activity was responsible for a high energy tsunami type event during the eruption of vesuvius in 79 ad from the 5th c ad onwards the harbor basin of neapolis does not appear to have been functional as evidenced by its transformation into a lagoon following coastal progradation the last stage of infilling was the development of a flood dominated fan delta under the combined influences of climatic cooling in the early medieval cool period and agro pastoral activities in the catchment area of the harbor several generations of paleo channels containing flash flood deposits as well as sheet wash from sheet floods are indicative of high environmental instability in this period

phase equilibrium constraints on angrite petrogenesis parameterizations of liquidus boundaries and solid solution in the cmas fe system shi 1992 have been employed to depict the liquidus equilibria relevant to the petrogenesis of angrites angrites are basaltic achondrites characterized by highly aluminous augite fassaite intermediate mg fe olivine and late stage cafe olivine kirschsteinite two important features of the equilibria on the olivine liquidus surface relevant to angrite petrogenesis are 1 the presence of a thermal divide on the ol aug plag liq boundary curve which separates the compositions of source materials that produce low silica angritic melts that crystallize highly aluminous augite from those that produce higher silica melts with tholeiitic to eucritic crystallization patterns and 2 the change in the pseudo invariant point on the low silica side of the thermal divide from a plagioclase peritectic involving spinel ol aug plag sp liq at high to intermediate mg mg mg fe to two pseudo eutectics involving kirschsteinite ol aug plag kir liq and ol kir plag sp liq at low mg the fassaitic aluminous augite pyroxene composition in angra dos reis ador the presence of minor green spinel and the absence of primary kirschsteinite prinz et al 1977 indicate that crystallization of the ador parental liquid was governed by the intermediate mg set of equilibria such that following crystallization of ol aug plag the plagioclase reacted completely at the plagioclase peritectic with the interstitial liquid which subsequently crystallized beyond the plagioclase peritectic onto the ol aug sp liquidus boundary curve the ador bulk composition is consistent with trapping 10 of the parental liquid in a cumulate with cotectic proportions of fassaite and olivine lewis cliff lew 86010 crystallized from a liquid with mg similar to that of ador but on the ol plag cotectic closer to the thermal divide such that the first pyroxene to crystallize had much lower al content than that of ador in the late stages of crystallization the 86010 residual liquid and that of lew87051 encountered the low mg set of equilibria involving kirschsteinite these relationships require either a higher degree of melting for the 86010 parent magma or source region different than ador s these relationships are also consistent with compositionally dependent ree partition coefficients between fassaite and the ador liquid being as much as 1 5 2 times higher than those for the 86010 liquid at the onset of pyroxene crystallization the combination of a trapped liquid component higher partition coefficients and smaller degrees of melting help to explain the observation that ador an apparent cumulate has ree concentrations twice as high as those in 86010 mittlefehdlt and lindstrom 1990 an apparent chilled liquid the absence of a strong negative eu anomaly in the ador parent liquid however requires relatively high degrees of partial melting to eliminate plagioclase in the source region resorption of plagioclase at the peritectic eliminates the eu anomaly that develops during crystallization so ultimately different source regions are required progressive iron loss from devolatilized primitive chondrites allende murchison produces source regions capable of producing a wide range of melt compositions with angritic to eucritic crystallization behavior the compositions of carbonaceous and ordinary chondrite provide a similar range of potential source region compositions however primitive chondrite fe source regions that produce angrite like melts have mg that is too low whereas chondrite fe sources that have mg sufficiently high to yield the mg in angrite minerals have too much silica or orthopyroxene component to yield angrite like liquids no single group of meteorites fe simultaneously satisfies the constraints of mg and silica component however mixtures of fe depleted chondrite plus a low silica component similar to ca al rich inclusions cais can satisfy the constraints the absence in angrites of 48ca and 50ti anomalies typical of cais lugmair and galer 1992 suggests that the low silica component was not simply an enrichment of cais but was the result of direct accretion of high temperature condensate grossman 1972 into sizable thermally shielded planetesimals thus angrites cryptically record mixing of planetesimal sized heterogeneities in the early solar system

excess hafnium 176 in meteorites and the early earth zircon record 1 the long lived176lu to 176hf decay system is a powerful tool to understand ancient chemical fractionation events associated with planetary differentiation detrital hadean zircons 3 8 gyr from the jack hills metasedimentary belt of western australia record extremely enriched hf isotope signals suggesting early extraction of a continental crust 4 5 gyr but fail to identify a prevalent complementary depleted mantle reservoir suggesting that crust formation processes in the early earth were fundamentally distinct from today however this conclusion assumes that the hf isotope composition of bulk chondrite meteorites can be used to estimate the composition of earth prior to its differentiation into major silicate reservoirs namely the bulk silicate earth bse we report a176lu 176hf internal mineral isochron age of 4869 34 myr for the pristine sah99555 angrite meteorite this age is 300 myr older than the age of the solar system confirming the existence of an energetic process yielding excess 176hf in affected early formed solar system objects through the production of the 176lu isomer t1 2 3 9 hours thus chondrite meteorites contain excess 176hf and their present day composition cannot be used to infer the lu hf parameters of bse using a revised bse estimate based on the sah99555 isochron we show that earth s oldest zircons preserve a record of coexisting enriched and depleted hafnium reservoirs as early as 4 3 gyr in earth s history with little evidence for the existence of continental crust prior to 4 4 gyr this new view suggests continuous juvenile crustal growth and recycling throughout the hadean and archean eras perhaps analogous to modern plate tectonics

glacial interglacial changes in ocean surface conditions in the southern hemisphere the stable isotope signatures of oxygen and hydrogen in the water of preserved ice and snow are both widely used to infer local temperatures of past environments a derived quantity based on these two signatures the deuterium excess 1 provides additional palaeoclimatic information2 3 4 as this parameter depends on the meteorological and oceanic characteristics of the water s source regions in particular their temperature2 3 and relative humidity4 published studies mainly focus on records from the past 40 000 years here we present a deuterium excess history obtained from ice cores from vostok east antarctica spanning the full glacial interglacial cycle of the past 150 000 years the deuterium excess record shows a strong anticorrelation with the earth s orbital obliquity 41 000 year periodicity and values are markedly higher during the cold stage 5d following the last interglacial than during the other cold stages we interpret the relationship with obliquity as resulting from changes in the latitudinal insolation gradient affecting ocean surface conditions and thus the delivery of moisture to the polar region we argue that the high 5d values relative to other cold stages are driven by relatively less moisture delivered from high latitudes and more from low latitudes the deuterium excess in antarctic precipitation thus provides long term spatially integrated information on ocean surface conditions and ocean atmosphere circulations in the southern hemisphere

response in atmospheric circulation and sources of greenland precipitation to glacial boundary conditions the response in northern hemisphere atmospheric circulation and the resulting changes in moisture sources for greenland precipitation to glacial boundary conditions are studied in ncar s ccm3 atmospheric general circulation model fitted with a moisture tracking functionality we employ both the climap sst reconstruction and a modification thereto with reconstructions of glacial ice sheets and land masks the individual components of the boundary conditions are added first one at a time and finally together these steps show the atmospheric circulation to respond approximately linearly to the boundary condition changes and the full glacial change may thus be decomposed into contributions from sst and topography changes respectively we find that using the climap sst reconstruction leads to a shift from atlantic toward pacific source regions not found with the modified reconstruction having cooler tropics and less sea ice the occurrence of such a shift depends chiefly on the sst reconstruction and not on the existence of the large northern hemisphere glacial ice sheets the influence of these circulation changes on important factors for ice core interpretation such as precipitation seasonality condensation temperatures and source temperatures are assessed

the non igneous genesis of angrites support from trace element distribution between phases in d orbigny d orbigny is an exceptional angrite chemically it resembles other angrites such as asuka 881371 sahara 99555 lewis cliff lew 87051 and lew 86010 but its structure and texture are peculiar it has a compact and porous lithology abundant glasses augite bearing druses and chemical and mineralogical properties that are highly unusual for igneous rocks our previous studies led us to a new view on angrites they can possibly be considered as cais that grew to larger sizes than the ones we know from carbonaceous chondrites thus angrites may bear a record of rare and special conditions in some part of the early solar nebula here we report trace element contents of d orbigny phases trace element data were obtained from both the porous and the compact part of this meteorite we have confronted our results with the popular igneous genetic model according to this model if all phases of d orbigny crystallized from the same system as an igneous origin implies a record of this genesis should be expressed in the distribution of trace elements among early and late phases our results show that the trace element distribution of the two contemporaneous phases olivine and plagioclase which form the backbone of the rock seem to require liquids of different composition abundances of highly incompatible elements in all olivines including the megacrysts indicate disequilibrium with the bulk rock and suggest liquids very rich in these elements 10 000 x ci which is much richer than any fractional crystallization could possibly produce in addition trace element contents of late phases are incompatible with formation from the bulk systems residual melt these results add additional severe constraints to the many conflicts that existed previously between an igneous model for the origin of angrites and the mineralogical and chemical observations this new trace element content data reported here corroborate our previous results based on the shape structure mineralogy chemical and isotopic data of the whole meteorite as well as on a petrographic and chemical composition study of all types of glasses and give strength to a new genetic model that postulates that d orbigny and possibly all angrites could have formed in the solar nebula under changing redox conditions more akin to chondritic constituents e g cais than to planetary differentiated rock

harbor areas at ancient troy sedimentology and geomorphology complement homer s iliad for at least two thousand years scholars have debated the location of troy and the events and geographic features described in homer s iliad geologic evidence is used to present a series of maps of the trojan plain that show the geomorphic changes over the past six millennia the geologic evidence correlates very well with the relevant homeric geography

reconciliation of the excess 176 hf conundrum in meteorites recent disturbances of the lu hf and sm nd isotope systematics abstract the long lived 176 lu 176 hf and 147 sm 143 nd radioisotope systems are commonly used chronometers but when applied to meteorites they can reveal disturbances specifically lu hf isochrons commonly yield dates up to 300 myr older than the solar system and varying initial 176 hf 177 hf values we investigated this problem by attempting to construct mineral and whole rock isochrons for eucrites and angrites meteorites from different parent bodies exhibit similar disturbance features suggesting that a common process is responsible minerals scatter away from isochron regressions for both meteorite classes with low hf phases such as plagioclase and olivine typically being most displaced above or left of reference isochrons relatively hf rich pyroxene is less disturbed but still to the point of steepening lu hf errorchrons using our lu hf and sm nd data we tested various hf and lu redistribution scenarios and found that decoupling of lu hf from 176 hf 177 hf must postdate the accumulation of significant radiogenic 176 hf therefore early irradiation or diffusion cannot explain the excess 176 hf instead disturbed meteorite isochrons are more likely caused by terrestrial weathering contamination or common laboratory procedures the partial dissolution of phosphate minerals may predominantly remove rare earth elements including lu leaving relatively immobile and radiogenic hf behind robust lu hf and improved sm nd meteorite geochronology will require the development of chemical or physical methods for removing unsupported radiogenic hf and silicate hosted terrestrial contaminants without disturbing parent daughter ratios

petrology and geochemistry of d orbigny geochemistry of sahara 99555 and the origin of angrites petrology and geochemistry of d orbigny geochemistry of sahara 99555 and the origin of angrites

geochemistry and genesis of the angrites the angrites angra dos reis lew86010 and lew87051 are petrologically and compositionally similar achondrites all angrites have high feomno ratios of 80 94 and very low ci normalized na sm ratios of 0 001 0 003 high abundances of oxidized fe and low abundances of moderately volatile na most likely resulted from parent body processes such as magmatic outgassing rather than nebular processes all angrites have fractionated ca al ratios with angra dos reis exhibiting the most extreme ratio 3 1 ci this ca al fractionation may be due to small amounts of residual spinel in the source region after removal of the angrite melts or to crystallization of spinel from precursor melts for lew86010 and lew87051 the fractionated ca al ratios are not caused by the presence of significant cumulus material for angra dos reis cumulus material may be the cause of the high ca al ratio refractory element ca eu al sc la ce sm tb yb lu ti hf th and ta abundances of lew86010 and lew87051 show similar patterns while angra dos reis has both greater enrichments in these elements and more fractionated patterns compositional and petrologic constraints indicate that lew86010 and lew87051 are related via olivine control the refractory element abundances and mg of lew86010 can be approximated by removal of olivine from lew87051 suggesting that lew86010 may be a residual melt from a lew87051 like precursor alternatively lew87051 may have formed via olivine accumulation from a lew86010 like precursor the origin of the unusual refractory element pattern in angra dos reis remains obscure the differences between the lew86010 lew87051 duo and angra dos reis suggest that either the angrite parent body was heterogeneous or that angra dos reis was formed on a separate parent body based on feomno ratios and normative mineralogies the angrite parent body ies may be similar in bulk composition to one of the carbonaceous chondrite groups particularly ci cm co

magnetic classification of stony meteorites 3 achondrites a database of magnetic susceptibility measurements of stony achondrites acapulcoitelodranite clan winonaites ureilites angrites aubrites brachinites howardite eucrite diogenite hed clan and martian meteorites except lunar meteorites is presented and compared to our previous work on chondrites this database provides an exhaustive study of the amount of iron nickel magnetic phases essentially metal and more rarely pyrrhotite and titanomagnetite in these meteorites except for ureilites achondrites appear much more heterogeneous than chondrites in metal content both at the meteorite scale and at the parent body scale we propose a model to explain the lack of or inefficient metal segregation in a low gravity context the relationship between grain density and magnetic susceptibility is discussed saturation remanence appears quite weak in most metal bearing achondrites hed and aubrites compared to martian meteorites ureilites are a notable exception and can carry a strong remanence similar to most chondrites

a review of the delta po evolution italy related to climatic changes and human impacts abstract climate changes and sea level rise are important issues especially for deltas such as the po delta italy the evolution of the po delta shows a succession in space and a superposition in time of complex environmental natural processes during the last few centuries anthropogenic action has played a major role the formation of the po delta began about 2000 years ago and has undergone many phases of development between 1500 ad and 1600 ad the venetian technicians diverted the po river course with these interventions the renaissance delta was cut off from the hydraulic network and the modern delta began to form until the middle of the 20th century progradation of the delta was noticeable due to the abundant sediment supply in the following decades coastal erosion occurred this was caused by the reduction of the solid supply of the po due to dam and barrier construction and to river bed excavation these and other interventions e g reclamation methane extractions from superficial ground water table have deeply modified the physical and ecological characteristics of the po delta the morphological characteristics of the po delta make the largest italian wetland particularly unstable and very fragile when subjected to human pressure furthermore the delta evidences multiple threats that will probably be exacerbated in the following decades by the effects of expected climatic changes only the application of careful policies concerning coastal defence flood mitigation anthropogenic subsidence reduction and salt wedge intrusion control will allow reduction of the present or predicted negative effects this paper reviews how natural and human factors have controlled the po delta through time and discusses management strategies taking into account the importance of the human factor and the potential effects of climatic changes

expression of the bipolar see saw in antarctic climate records during the last deglaciation ice core records of climate from greenland and antarctica show asynchronous temperature variations on millennial timescales during the last glacial period 1 the warming during the transition from glacial to interglacial conditions was markedly different between the hemispheres a pattern attributed to the thermal bipolar see saw 2 however a record from the ross sea sector of east antarctica has been suggested to be synchronous with northern hemisphere climate change 3 here we present a temperature record from the talos dome ice core also located in the ross sea sector we compare our record with ice core analyses from greenland based on methane synchronization 4 and find clearly asynchronous temperature changes during the deglaciation we also find distinct differences in antarctic records pointing to differences in the climate evolution of the indo pacific and atlantic sectors of antarctica in the atlantic sector we find that the rate of warming slowed between 16 000 and 14 500 years ago parallel with the deceleration of the rise in atmospheric carbon dioxide concentrations and with a slight cooling over greenland in addition our chronology supports the hypothesis that the cooling of the antarctic cold reversal is synchronous with the bolling allerod warming in the northern hemisphere 14 700 years ago 5 the period from about 8 to 25kyr before present bp includes the climate transition from the last glacial to the holocene as documented from polar ice cores and other climate archives the pattern of climate changes throughout this transition is different between antarctica and the surrounding southern ocean and the northern hemisphere the steady antarctic deglacial warming reaches a first maximum antarctic isotopic maximum aim1 ref 1 followedbyaninterruptiontowardscoolerconditionsduring the antarctic cold reversal acr conversely greenland records show two rapid warming phases at the onset of the dansgaard oeschger 1 do1 event bllingaller dinterstadial b a andthe

in search of the harbours new evidence of late roman and byzantine harbours of ephesus abstract ephesus greek name ephesos in western turkey was an important harbour city during antiquity the progradation of the kucuk menderes delta has continuously shifted the coastline westwards thus along with the delta progradation new harbour sites had to be established in a western direction historical sources refer to different harbours while much is known about the roman and older ones the exact location of the ports and the coastline in late roman and byzantine times is still an open question this article presents the results of geoarchaeological research in the area located along the southern flank of the kucuk menderes graben near ephesus sediments from cores were examined with geochemical sedimentological and microfaunal analyses these data were combined with the study of ancient maps and satellite images the chronological framework was rendered by ams 14 c ages and diagnostic ceramics the farthermost inland shoreline dates from 5000 bc since then delta progradation has continuously shifted the shoreline westwards canakgol today a little lake to the west of the city of ephesus is identified as the harbour site in late roman and byzantine times this harbour persisted at least until the 16th century ad further a landing site with a pier was discovered west of canakgol presumably dating to the late byzantine ottoman times

updrift river mouth migration on cuspate deltas two examples from the coast of tuscany italy the configuration of the arno and ombrone deltas italy is evaluated the terminal courses of the rivers forming these deltas face the dominant wave orthogonal this configuration came about during rapid delta progradation as a consequence of increased river sediment input due to widespread deforestation within the catchment area a prevailing phenomenon from the early middle ages to the xviii century the rivers attained and maintained their directions as the result of the increased accretion rate on the less exposed downdrift side of the delta on the more exposed updrift side delta growth caused the shoreline to gradually rotate so that it directly faced the waves approaching the coast here due to the lower refraction wave energy per shore unit increased whilst accretion rate decreased this rotation of the shoreline induced longshore inversion on the updrift side whereas today cusp erosion is restoring the original drift direction