mineralogical characterization of a unique material having heavy oxygen isotope anomaly in matrix of the primitive carbonaceous chondrite acfer 094 abstract we report the mineral compositions and micro texture of the isotopically anomalous 17 18osmow 180 fe s ni o material recently discovered in matrix of the primitive carbonaceous chondrite acfer 094 sakamoto n seto y itoh s kuramoto k fujino k nagashima k krot a n and yurimoto h 2007 oxygen isotope evidence for remnants of the early solar system primordial water science 317 231 233 synchrotron radiation x ray diffraction and transmission electron microscopy studies indicate that this material consists of the symplectitically intergrown magnetite fe3o4 and pentlandite fe5 7ni3 3s8 with magnetite pentlandite volume ratio of 2 3 magnetite forms column shaped grains 10 30 nm in diameter and 100 200 nm in length pentlandite occurs as worm shaped grains or aggregates of grains 100 300 nm in size between magnetite crystals although both the x ray diffraction and electron energy loss spectra support identification of iron oxide as magnetite the electron diffraction patterns show that magnetite has a weak 3 fold superstructure possibly due to ordering of vacancies we infer that the isotopically anomalous symplectite formed by sulfurization and oxidization of metal grains either in the solar nebula or on an icy planetesimal the intersite cation distribution of pentlandite suggests that timescale of oxidation was no longer than 1000 years

the origin of crystalline residues in stardust al foils surviving cometary dust or crystallized impact melts abstract samples returned by the stardust mission from comet 81p wild 2 provide an unequaled opportunity to investigate cometary formation and evolution crystalline silicates have been identified in impact craters in stardust al foil yet their origin is ambiguous they may be original cometary components or they may have grown from melt generated by impact we have now studied experimental impacts of the calcium silicate mineral wollastonite using scanning and transmission electron microscopy to document the relationship between impact feature shape and crystal lattice orientation in impact residue wollastonite can have a characteristic acicular habit forming crater shapes that indicate crystal orientation upon impact from extracted impact residue we determined the lattice orientation of crystalline material for comparison with the whole particle orientation we assume that crystallization from melt without surviving seed nuclei should result in randomly oriented crystallite growth with no preferred direction for individual crystals however we find that the majority of crystalline material in the residue retains b axis orientation parallel to the long axis of the crater form this together with impact parameter calculations and lack of al incorporation by the residue suggesting melting did not occur indicates that these crystals and by analogy the majority of al free crystalline silicates in stardust foil are surviving remnants of the impactor furthermore amorphous wollastonite residue probably did not form via melting and subsequent quenching but instead by high pressure amorphization or degradation of unquenchable phases finally one crystal studied appears to be a new high pressure temperature polymorph of casio3 indicating that such polymorphs may be observed in stardust residues in craters

segmentation and differential post rift uplift at the angola margin as recorded by the transform rifted benguela and oblique to orthogonal rifted kwanza basins abstract we analyse tectonic and sedimentary field and subsurface data for the angola onshore margin together with free air gravity anomaly data for the offshore margin this enables us to characterize the mode of syn rift tectonism inherited from the precambrian and its impact on the segmentation of the angola margin we illustrate that segmentation by the progressive transition from the benguela transform rifted margin segment to the oblique rifted south kwanza and orthogonal rifted north kwanza margin segments the spatial variation in the intensity of post rift uplift is demonstrated by the study of a set of geomorphic markers detected in the post rift succession of the coastal benguela and kwanza basins upper cretaceous to cenozoic uplifted palaeodeltas erosional unconformities palaeovalleys quaternary marine terraces and perched gilbert deltas the onshore benguela transform margin has a distinctive mainly progradational stratigraphic architecture with long term sedimentary gaps and high elevation marine terraces resulting from moderate upper cretaceous cenozoic to major quaternary uplifting i e 775 1775 mm ky or m ma by contrast repeated synchronous episodes of minor cenozoic to quaternary uplift occurred along the orthogonal rifted north kwanza segment with its cenozoic aggradational architecture short term sedimentary gaps and low elevation pleistocene terraces margin style likewise governs spatial variations in the volume of offshore sediment dispersed in the associated deep sea fans along the low lying north kwanza margin sedimentation of the broad cenozoic to pleistocene kwanza submarine fan was probably governed by the width of the kwanza interior palaeodrainage basin combined with the wet tropical neogene climate along the high rising benguela margin the small size of the benguela deep sea fan is related to the interplay between moderate continental sediment dispersal from long lived small catchments and a warm very arid neogene climate however the driving forces behind the epeirogenic post rift uplift of the angola coastal bulge remain a matter of speculation

chondrule fragments from comet wild2 evidence for high temperature processing in the outer solar system abstract terminal grains from c2063 1 154 1 0 track 154 and c2061 1 113 5 track 113 from the stardust collection of comet wild2 s coma have been studied by tem and nanosims terminal grain 2 of c2063 1 154 1 0 consists of an al rich diopside en 97 99 al 2 o 3 9 11 wt pigeonite en 85 wo 15 with tio 2 and al 2 o 3 contents of 0 5 and 5 2 wt and minor forsterite and enstatite the mineral assemblage and al rich ti poor composition of the grain are consistent with being a fragment of an al rich chondrule similar to those present in carbonaceous chondrites the oxygen isotopic composition of the c2063 1 154 1 0 grain was determined by nanosims analyses and found to be 17 o 10 6 5 7 18 o 7 5 2 5 and 17 o 1 4 4 3 18 o 6 5 1 6 1 errors for the two sections these figures are distinct from cais and consistent with an origin as al rich chondrule fragments terminal grain 5 of c2061 1 113 5 consists of low ca pyroxene en 86 87 fs 10 11 wo 3 4 and 2 wt al 2 o 3 and in one section 5 10 of a na rich silicate phase this assemblage may be a fragment of a low ca pyroxene bearing chondrule and mesostasis the original chondrule diameter for the c2063 1 154 1 0 and c2061 1 113 5 samples by analogy with carbonaceous chondrite chondrules might have been in the range 0 2 1 0 mm if they were of that size then the presence of large grains of high temperature material e g 1500 k for such refractory assemblages could be explained through commonly invoked models of radial drift from inner to outer solar system but only if the chondrules were first fragmented to dust within the inner solar system an alternative scenario is that some chondrule formation was associated with high temperature processing and planetesimals in the outer solar system

earth structure and instrumental seismicity of madagascar implications on the seismotectonics abstract the aim of this study is to improve the knowledge of the seismotectonics of madagascar we first investigate the structure of the earth beneath madagascar through the joint inversion of receiver functions and rayleigh wave group velocities then we use the obtained velocity models to relocate local earthquakes in order to analyse the distribution of seismicity finally we use structural models and earthquake coordinates to compute focal mechanisms our retrieved earth structure models confirm a thin lithosphere beneath madagascar when compared to the nearby east african rift the high plateau in the central region coincides with the thinnest lithosphere over the slowest asthenosphere our results are in good agreement with the gravity anomalies and likely confirm a localised asthenospheric upwelling beneath the central part of madagascar the surface expression of the asthenospheric upwelling consists in a horst graben structure the moderate seismicity is localised along pre existing structures reflecting an e w extension that is mostly accommodated in the lower crust

sulfur isotopic composition of fe ni sulfide grains in ci and cm carbonaceous chondrites in situ secondary ion mass spectrometry analyses of 32 s 33 s and 34 s in iron nickel sulfide grains in two ci1 chondrites and six cm chondrites were performed the results show a wider range of both enrichment and depletion in 34 s relative to troilite from the canyon diablo meteorite cdt than has been observed in previous studies all data points lie within error of a single mass dependent fractionation line sulfides from ci1 chondrites show 34 scdt from 0 7 to 6 8 while sulfide grains in the cm1 chondrite are generally depleted in heavy sulfur relative to cdt 34 s from 2 9 to 1 8 cm2 chondrites contain sulfide grains that show enrichment and depletion in 34 s 34 scdt from 7 0 to 6 8 sulfates forming from sulfide grains during aqueous alteration on the chondrite parent body are suggested to concentrate light sulfur leaving the remaining sulfide grains enriched in the heavy isotopes of sulfur the average degree of enrichment in 34 s in cm chondrite sulfides is broadly consistent with previously suggested alteration sequences

transient convective uplift of an ancient buried landscape sedimentary basins in the north atlantic ocean preserve a record of intermittent uplift during cenozoic times1 these variations in elevation are thought to result from temperature changes within the underlying icelandic mantle plume2 when parts of the european continental shelf were episodically lifted above sea level new landscapes were carved by erosion but these landscapes then subsided and were buried beneath marine sediments3 here we use three dimensional seismic data to reconstruct one of these ancient landscapes that formed off the northwest coast of europe during the palaeocene eocene thermal maximum we identify a drainage network within the landscape and by modelling the profiles of individual rivers within this network we reconstruct the history of surface uplift we show that the landscape was lifted above sea level in a series of three discrete steps of 200 400 m each after about 1 million years of subaerial exposure this landscape was reburied we use the magnitude and duration of uplift to constrain the temperature and velocity of a mantle plume anomaly that drove landscape formation we conclude that pulses of hot chemically depleted mantle material spread out radially beneath the lithospheric plate at velocities of 35 cm yr 1

a 20 m middle pleistocene sea level highstand bermuda and the bahamas due to partial collapse of antarctic ice marine deposits at 20 3 m on the tectonically stable coastlines of bermuda and the bahamas support the hypothesis of a partial collapse of the antarctic ice sheet during the middle pleistocene beach sediments fill a sea cave at 22 m in bermuda and horizontal fenestrae filled beds crop out on platforms at two sites as high as 21 m in eleuthera bahamas carbonate beach sands are bound by an early generation of isopachous fibrous cement that is characteristic of a phreatic marine environment amino acid racemization and tims thermal ionization mass spectrometry dates constrain the age of the deposits to between 390 and 550 ka while proxy evidence supports a correlation with oxygen isotope stage 11 this direct geologic evidence of a 20 decrease in polar ice during the middle pleistocene has important implications for the stability of ice sheets during warm interglaciations

melting ice sheets 400 000 yr ago raised sea level by 13 m past analogue for future trends abstract marine isotope stage mis 11 was possibly the longest 423 000 362 000 yr ago and warmest interglacial of the entire quaternary period this resulted from a special arrangement of earth s orbital parameters similar to the present interglacial mis 1 suggesting that mis 11 provides an analogue for future natural climate forcing and sea levels although precise documentation of mis 11 sea level history is therefore crucial especially considering additional impetus from anthropogenic warming the maximum mis 11 sea level remains highly contentious estimates from onshore indicators have ranged from below present sea level to about 20 m resulting from uncertainties in reliability of sea level indicators estimates of their subsequent displacement by vertical crustal motion and in dating we used a clear and unambiguous sea level indicator interface between subtidal and intertidal deposits in well exposed regressive raised shoreline deposits along south africa s southern coast the coast is stable in terms of tectonic setting and falls within a zone of low predicted glacio isostatic adjustment gia and low sensitivity for plausible model parameters the sea level indicators were directly dated using thermally transferred optically stimulated luminescence tt osl which gave a mean age of 390 ka corresponding with mis 11 we determined a precise maximum elevation of 14 m for the mis 11 sea level indicator which corrected for minor crustal uplift and gia yielded a eustatic sea level of 13 m 2 m the complete mis 11 transgressive regressive shoreline succession is preserved and the wave cut platform extends 950 m inland from the present shoreline indicating a prolonged highstand we have also documented sea level fluctuations during mis 11 including an earlier lower highstand close to present sea level which may explain the lower elevation range of some previous estimates at one locality mis 11 deposits form a sea cliff against which mis 5e sediments at an elevation of 6 2 m abut the 13 m mis 11 sea level tallies with total melting of the greenland and west antarctica ice sheets regarded as most susceptible to melting our data predict notably higher sea levels in the future regardless of anthropogenic influence on climate

laboratory flume studies on monochromatic wave fine sandy bed interactions part 2 sediment suspensions abstract as reported in preceding paper part 1 soil fluidization the observed phenomena of sediment suspensions above a fluidized sandy bed of sand ii d50 0 092 mm under monochromatic wave actions are quantitatively investigated the suspended sediment concentration ssc at a single point within 5 cm above the bed was synchronously measured with water waves and bed soil s pore pressures with an intrusive optical sediment concentration probe the measurements show that ssc initiates several wave cycles after initiation of bed soil s fluidized response and grows to a peak value mainly in the post fluidization phase under similar wave loadings in the same test series ssc is usually higher over a resonantly fluidized rf bed than over a non resonantly fluidized nrf bed on the contrary only relatively low scc can be identified above an unfluidized bed the analyses illustrate that to certain extent peak values of ssc are directly proportional to the thickness of fluidized soil layer df values of df usually decrease with repeated fluidized response longer consolidation periods and in deeper water depths once the fluidized responses initiate pore pressures are generally much significantly amplified in both shallow fluidized soil layers and near below the fluidized layer especially during the resonance event the resulting depth gradients of dynamic pore pressure amplitudes in shallow layers are likely to have caused higher initial rises of ssc in a rf bed than in the subsequent nrf bed those in deeper layer should have contributed to sustain the fluidization state for further ssc increments immediately after termination of wave loading re deposited suspended sediments always result in a typical flat bed form for a pre fluidized bed wave induced drastic sediment suspensions are still obtainable very near above the bed with even a rather thin fluidized surface soil layer

the last interglacial sea level high stand on the southern cape coastline of south africa abstract the continental margin of southern south africa exhibits an array of emergent marginal marine sediments permitting the reconstruction of long term eustatic sea level changes we report a suite of optical luminescence ages and supplementary amino acid racemization data which provide paleosea level index points for three sites on this coastline deposits in the swartvlei and groot brak estuaries display tidal inlet facies overlain by shoreface or eolian facies contemporary facies relations suggest a probable high stand 6 0 8 5 m above modern sea level amsl at cape agulhas evidence of a past sea level high stand comprises a gravel beach ca 3 8 m amsl and an overlying sandy shoreface facies up to 7 5 m amsl osl ages between 138 7 ka and 118 7 ka confirm a last interglacial age for all marginal marine facies the high stand was followed by a sea level regression that was associated with the accumulation of eolian dunes dating to between 122 7 ka and 113 6 ka these data provide the first rigorous numerical age constraints for last interglacial sea level fluctuations in this region revealing the timing and elevation of the last interglacial high stand to broadly mirror a number of other far field locations

sea level rise due to polar ice sheet mass loss during past warm periods background although thermal expansion of seawater and melting of mountain glaciers have dominated global mean sea level gmsl rise over the last century mass loss from the greenland and antarctic ice sheets is expected to exceed other contributions to gmsl rise under future warming to better constrain polarice sheetresponse to warmer temperatures we draw on evidence from in terglacial periods in the geologic record that ex perienced warmer polar temperatures and higher gmsls than present coastal records of sea level from these previous warm periods dem onstrate geographic variability because of the influence of several geophysical processes that operate across a range of magnitudes and time scales inferring gmsl and ice volume changes from these reconstructions is nontrivial and generally requires the use of geophysical models advances interdisciplinary studies of geo logic archives have ushered in a new era of deciphering magnitudes rates and sources of sea level rise advances in our understanding of polar ice sheet response to warmer climates have been made through an increase in the number and geographic distribution of sea level reconstructions better ice sheet constraints and the recognition that several geophysical processes cause spatially complex patterns in sea level in particular accounting for glacial isostatic processes helps to decipher spatial variability in coastal sea level records and has reconciled a number of site specific sea level reconstructions for warm periods that have oc curred within the past several hundred thou sand years this enables us to infer that during recent interglacial periods small increases in

estimating past continental ice volume from sea level data we predict sea level change since the last glacial maximum lgm at four far field sites barbados bonaparte gulf huon peninsula and tahiti using a revised theoretical formalism this formalism includes a time varying shoreline geometry an accurate treatment of sea level variations near regions of ice retreat and the influence of glacial cycle perturbations in earth rotation we elucidate the physics of far field sea level change by de constructing the predicted signal into spatially uniform versus spatially varying components as well as isolating contributions due to the ice load the ocean load and the rotational potential we demonstrate that the sum of these three contributions plus the spatially uniform sea level fall associated the with retreat of grounded marine ice sheets can produce a significant difference between predictions of sea level change at far field sites and the eustatic or meltwater curve associated with the adopted ice model this difference is site and time dependent for example the total sea level rise since the lgm predicted using our ice earth model can be either smaller e g barbados or larger e g tahiti than the eustatic sea level change finally we review procedures that have been applied to estimate continental ice volume from far field sea level observations and apply these procedures to data from barbados and bonaparte gulf applying an ice earth model that is tuned to fit the barbados data we estimate a change in grounded ice volume from the lgm to the present of 43 5 51 106 km3 based on barbados data and an lgm ice volume estimate of 51 106 km3 based on bonaparte gulf data our results for the bonaparte gulf data are consistent with the recent study by yokoyama et al nature 406 2000 713 these lgm ice volume estimates map into a eustatic or meltwater sea level rise of 115 135 m taking into account plausible variations in the adopted radial earth model introduces uncertainties in the range of 1 5 106 km3 for ice volume estimates based on the barbados data

rapid water table fluctuations within the beach face implications for swash zone sediment mobility abstract to incorporate groundwater infiltration exfiltration in the description of swash zone sediment transport it is required that the details of groundwater dynamics within the beach face be clarified field measurements of the vertical pore pressure structure within the bed identify capillarity effects as the primary mechanism driving rapid and relatively large magnitude water table fluctuations within the swash zone when the upper extent of the fully saturated capillary fringe coincides with the beach face surface wave runup produces near instantaneous increase in pore pressures across the capillary fringe corresponding to a rapid rise of the phreatic surface i e the surface where pore pressure atmospheric pressure to the sand surface therefore counter to previous conclusions in the literature the rapid rise and fall of the water table under the swash zone do not equate to regions of the beach face alternating between states that favor sediment deposition unsaturated and erosion saturated similar reports that rapid fluctuations of the water table within the beach face correspond to rapid rates of vertical flow and hence bed fluidization are also a misinterpretation field measurements and a careful consideration of saturation and pore pressure characteristics within the beach face demonstrate that rapid water table rise is associated with minute downwards swash infiltration rather than rapid upwards groundwater exfiltration the cause of the pressure fluctuations and phreatic surface oscillations is the alternating appearance and disappearance of meniscuses at the sand surface which generate pressure head fluctuations of decimeters due to the addition of millimeters of water

terminal particle from stardust track 130 probable al rich chondrule fragment from comet wild 2 abstract a 4 6 m terminal particle from stardust track 130 named bidi is composed of a refractory assemblage of fo 97 olivine al and ti bearing clinopyroxene and anorthite feldspar an 97 mineralogically bidi resembles a number of components found in primitive chondritic meteorites including al rich chondrules plagioclase bearing type i ferromagnesian chondrules and amoeboid olivine aggregates aoas measured widths of augite pigeonite lamellae in the clinopyroxene indicate fast cooling rates suggesting that bidi is more likely to be a chondrule fragment than an aoa bulk element concentrations including an al 2 o 3 content of 10 2 wt further suggests that bidi is more akin to al rich rather than ferromagnesian chondrules this is supported by high anorthite content of the plagioclase feldspar overall bulk composition and petrogenetic analysis using a cosmochemical al 2 o 3 ca 2 sio 4 mg 2 sio 4 phase diagram measured minor element abundances of individual minerals in bidi generally support an al rich chondrule origin but are not definitive between any of the object types oxygen isotope ratios obtained from olivine minor high ca pyroxene fall between the tf and ccam lines and overlap similar minerals from chondrules in primitive chondrites but are generally distinct from pristine aoa minerals oxygen isotope ratios are similar to some minerals from both al rich and type i ferromagnesian chondrules in unequilibrated carbonaceous enstatite and ordinary chondrites although no single piece of evidence uniquely identifies bidi as a particular object type the preponderance of data including mineral assemblage bulk composition mineral chemistry inferred cooling rates and oxygen isotope ratios suggest that bidi is more closely matched to al rich chondrules than aoas or plagioclase bearing type i ferromagnesian chondrules and likely originated in a chondrule forming region in the inner solar system

comparing wild 2 particles to chondrites and idps we compare the observed composition ranges of olivine pyroxene and fe ni sulfides in wild 2 grains with those from chondritic interplanetary dust particles idps and chondrite classes to explore whether these data suggest affinities to known hydrous materials in particular wild 2 olivine has an extremely wide composition range from fa096 with a pronounced frequency peak at fa1 the composition range displayed by the low calcium pyroxene is also very extensive from fs48 to fs0 with a significant frequency peak centered at fs5 these ranges are as broad or broader than those reported for any other extraterrestrial material wild 2 fe ni sulfides mainly have compositions close to that of fes with less than 2 atom ni to date only two pentlandite grains have been found among the wild grains suggesting that this mineral is not abundant the complete lack of compositions between fes and pentlandite with intermediate solid solution compositions suggests but does not require that fes and pentlandite condensed as crystalline species i e did not form as amorphous phases which later became annealed while we have not yet observed any direct evidence of water bearing minerals the presence of ni bearing sulfides and magnesium dominated olivine and low ca pyroxene does not rule out their presence at low abundance we do conclude that new investigations of major and minorelement compositions of chondrite matrix and idps are required

oxygen isotopes in crystalline silicates of comet wild 2 a comparison of oxygen isotope systematics between wild 2 particles and chondritic materials abstract oxygen three isotope ratios of nine crystalline silicate particles from comet wild 2 were measured to investigate oxygen isotope systematics of cometary materials we are able to analyze particles as small as 4 m using an ion microprobe with a 1 2 m beam by locating the analysis spots with an accuracy of 0 4 m three particles of mn rich forsterite known as low iron manganese enriched lime olivine showed extremely 16 o rich signatures 18 o 17 o 50 similar to refractory inclusions in chondrites the three mn rich forsterite particles may have formed by condensation from an 16 o rich solar nebula gas other particles consist of olivine and or pyroxene with a wide range of mg molar mgo feo mgo from 60 to 96 their oxygen isotope ratios plot nearly along the carbonaceous chondrite anhydrous mineral ccam and young and russell lines with 17 o 17 o 0 52 18 o values of 3 0 to 2 5 these data are similar to the range observed from previous analyses of wild 2 crystalline silicates and those of chondrules in carbonaceous chondrites six particles extracted from stardust track 77 show diverse chemical compositions and isotope ratios two mn rich forsterites feo poor pigeonite and three feo rich olivines with a wide range of 17 o values from 24 to 1 6 these results confirmed that the original projectile that formed track 77 was an aggregate 6 m of silicate particles that formed in various environments the 17 o values of ferromagnesian wild 2 particles including data from previous studies increase from 23 to 2 5 with decreasing mg 17 o values of mn rich forsterite particles mg 98 99 8 cluster at 23 those of feo poor particles mg 95 97 cluster at 2 and those of feo rich particles mg 90 scatter mainly from 1 5 to 2 5 compared to chondrules in primitive chondrites the systematic trend between mg and 17 o among the wild 2 particles is most similar to that reported for cr chondrite chondrules we argue that cr chondrites and some cometary materials share multiple common chemical and isotope characteristics we suggest that many of the crystalline silicate particles formed in the outer regions of the asteroid belt or regions that share the common properties and were transported to comet forming regions and accreted into comet wild 2

scales of transient convective support beneath africa beneath sub equatorial africa there is convincing evidence for a gigantic slow velocity anomaly within the lower mantle that is inferred to be a thermochemical superplume here we define the spatial and temporal pattern of uplift across the northern edge of this putative superplume by analyzing stratal geometries and stacking velocities of neogene sedimentary rocks these marine deposits are imaged on a dense grid of seismic reflection profiles that straddle the southwest african coastal shelf inverse modeling of stacking velocity profiles demonstrates that there have been at least two significant phases of uplift a post pliocene uplift event increases from 0 to 500 m elevation over a distance of 1000 km in close agreement with geophysical estimates of the present day variation of dynamic topography an earlier phase of uplift occurred in middle oligocene time ca 30 35 ma ago we propose a two stage development of epeirogeny in which a middle oligocene phase of uplift may be related to initiation and growth of the african superplume post pliocene denudation records rapid 100 250 m ma vertical motions generated by upper mantle convection which vary on length scales of 500 1000 km our results support the existence of a convective circulation system that has operated on different temporal and spatial scales beneath the african plate

evidence for aqueous activity on comet 81p wild 2 from sulfide mineral assemblages in stardust samples and ci chondrites abstract the discovery of nickel copper and zinc bearing iron sulfides from comet 81p wild 2 wild 2 represents the strongest evidence in the stardust collection of grains that formed in an aqueous environment we investigated three microtomed tem sections which contain crystalline sulfide assemblages from wild 2 and twelve thin sections of the hydrothermally altered ci chondrite orgueil detailed structural and compositional characterizations of the sulfide grains from both collections reveal striking similarities the stardust samples include a cubanite cufe 2 s 3 grain a pyrrhotite fe ni 1 x s pentlandite fe ni 9 s 8 assemblage and a pyrrhotite sphalerite fe zn s assemblage similarly the ci chondrite sulfides include individual cubanite and pyrrhotite grains cubanite pyrrhotite assemblages pyrrhotite pentlandite assemblages as well as possible sphalerite inclusions within pyrrhotite grains the cubanite is the low temperature orthorhombic form which constrains temperature to a maximum of 210 c the stardust and orgueil pyrrhotites are the 4c monoclinic polytype which is not stable above 250 c the combinations of cubanite and pyrrhotite as well as pyrrhotite and pentlandite signify even lower temperatures the crystal structures compositions and petrographic relationships of these sulfides constrain formation and alteration conditions taken together these constraints attest to low temperature hydrothermal processing our analyses of these minerals provide constraints on large scale issues such as heat sources in the comet forming region aqueous activity on cometary bodies and the extent and mechanisms of radial mixing of material in the early nebula the sulfides in the wild 2 collection are most likely the products of low temperature aqueous alteration they provide evidence of radial mixing of material e g cubanite troilite from the inner solar system to the comet forming region and possible secondary aqueous processing on the cometary body

an interplanetary dust particle with links to ci chondrites abstract w7013f5 is a chondritic hydrated interplanetary dust particle whose composition and mineralogy is nearly identical to that found in the ci chondrites transmission electron microscope observations show that the phyllosilicates in w7013f5 consist largely of a coherent intergrowth of mg fe serpentine and fe bearing saponite on the unitcell scale this distinctive intergrowth of phyllosilicates has only been observed previously in the ci chondrites other secondary minerals in w7013f5 include mg fe carbonates magnetite and pentlandite the mineral assemblage in w7013f5 is generally not as oxidized as that in the ci chondrites the presence of kamacite in w7013f5 indicates that the particle is extraterrestrial and a thin amorphous rim surrounding the particle provides evidence that it is not a piece of a meteorite that fragmented during transit through the atmosphere the apparent lack of hydrated idps with ci mineralogy and chemistry may indicate that ci type dust producing asteroids are uncommon in the asteroid belt

infiltration effects on sediment mobility under waves sediment mobility measurements with a horizontal sand bed under non breaking waves are reported conditions include no seepage and steady downward seepage corresponding to head gradients up to 2 5 the results indicate that infiltration tends to inhibit sediment mobility for a horizontal bcd of 0 2 mm quartz sand exposed to moderated wave induced bed shear stresses the effect is weak for the parameter range of the present study the two opposing effects of shear stress increase due to boundary layer thinning and the stabilizing downward drag are successfully accounted for through the modified shields parameter of nielsen nielsen p 1997 coastal groundwater dynamics proc coastal dynamics 97 plymouth asce dp 546 555 using coefficients derived from independent studies that is from the shear stress experiments of conley conley d c 1993 ventilated oscillatory boundary layers phd thesis university of california san diego 74 pp and the slope stability experiments of martin and aral martin c s and m m aral 1971 seepage force on interfacial bed particles j hydraulics div proc asce vol 97 no hy7 pp 1081 1100 c 2001 elsevier science b v all rights reserved

comprehensive examination of large mineral and rock fragments in stardust tracks mineralogy analogous extraterrestrial materials and source regions abstract transmission electron microscopy examination of 87 large fragments from 16 carrot shaped and bulbous stardust sd tracks was performed to study the range and diversity of materials present in comet wild 2 olivines and low ca pyroxenes represent the largest proportions of fragments observed however a wide range of minerals and rocks were found including probable ferromagnesian al rich and si rich chondrule fragments a refractory inclusion possible matrix mineral lithic clasts and probable condensate minerals these materials combined with fine grained components in the tracks are analogous to components in unequilibrated chondrite meteorites and cluster interplanetary dust particles idps two unusual lithologies in the bulbous tracks are only observed in chondritic porous idps and may have direct links to idps the absence of phyllosilicates indicates that comet wild 2 may be a dry comet that did not accrete or form significant amounts of hydrated phases some large mineral fragments in the sd tracks are analogous to large mineral idps the large variations of the coarse grained components within and between all 16 tracks show that comet wild 2 is mineralogically diverse and unequilibrated on nearly all scales and must have accreted materials from diverse source regions that were widely dispersed throughout the solar nebula

disentangling interglacial sea level and global dynamic topography analysis of madagascar abstract global inventories of stable sea level markers for the peak of the last interglacial period marine isotopic stage mis 5e play a pivotal role in determining sea level changes and in testing models of glacial isostatic adjustment here we present surveying and radiometric dating results for emergent terraces from northern madagascar which is generally regarded as a stable equatorial site fossil coral specimens were dated using conventional and open system corrected uranium series methods elevation of the upper undated terrace decreases from 33 8 m to 29 5 m over a distance of 35 km an intermediate terrace has an average radiometric age of 130 7 13 2 ka i e mis 5e its elevation decreases from 9 3 m to 2 8 m over a distance of 80 km the record of the lowest terrace is fragmentary and consists of beach rock containing rare corals with ages of 1 6 3 8 ka the spatial gradient of the mis 5e marker is inconsistent with glacio isostatic adjustment calculations instead we propose that variable elevations of this marker around madagascar and possibly throughout the indian ocean at least partly reflect spatial patterns of dynamic topography generated by sub plate mantle convection

age progressive volcanism in the comores archipelago western indian ocean and implications for somali plate tectonics abstract the comores islands together with the tertiary volcanic province of northern madagascar form a sublinear trend of alkali olivine basalt shield volcanoes across the northern entrance of the mozambique channel potassium argon dating of shield building lavas confirms an eastward increase in age of volcanism along the chain consistent with a hotspot origin for the lineament the velocity of the somali plate over the mantle magma source is 50 mm yr we use the distribution of ages along the comores madagascar chain in conjunction with existing age data for the reunion mascarene plateau hotspot track to model the absolute motion of the somali plate for the last 10 m y we calculate the relative motion across the east african rift by subtracting the somali plate absolute motion from african plate absolute motion during this period the model predicts 320 km of total separation across the east african rift during the past 10 m y which is greater than has been estimated from surface geological evidence the geometry of older portions of the comores and reunion trends indicates that there was no significant relative motion between the african and somali plates prior to about 10 m y ago

mineralogy and petrology of stardust particles encased in the bulb of track 80 tem investigation of the wild 2 fine grained material abstract we have characterized by transmission electron microscopy the mineralogy of samples extracted from the walls of the stardust track 80 more than 500 fragments were studied using conventional imaging electron diffraction and edx microanalysis two categories of particles are distinguishable in equal proportions wt the first one is comprised of relatively large crystalline grains 1 m on average dominated by silicates olivine and pyroxene they display a wide range of compositions and microstructures comparable to those found in terminal particles minor phases including magnetite and apatite are also present their occurrence suggests that the wild 2 material underwent aqueous alteration to some extent the second type of particle called gems like material is made of silica rich glassy clumps embedding iron sulfide beads and vesicles their microstructure is characteristic of thermally modified particles that have suffered strong interaction with the silica aerogel during the hypervelocity impact this melted material may form by shedding of melted and vaporized material but given the shape of the impact track and high diversity of surviving mineral compositions much of it originated from fine grained aggregates that disaggregated during the collection chemical mapping at the nano scale allowed the localization of individual components within the silica rich glass they are dominated by mg rich components with a size less than 300 nm the average composition of this thermally modified material is close to the solar abundance for the major elements fe mg and s the fine grained material has probably not been chemically fractionated in the protoplanetary disk before its incorporation in comet wild 2 unlike the sulfur depleted matrix of chondrites from these two categories of particles we deduce that wild 2 is likely made of an assemblage of relatively large evolved grains first category cemented by a fine grained material with primitive chemistry second category the pre impact configuration of the incident material deduced from this study seems comparable to the matrix of the most primitive chondrites 3 0 or to chondritic porous interplanetary dust particles

influence of infiltration on suspended sediment under waves the effect of percolation through a permeable bed on sediment suspension under regular waves was examined in a laboratory wave tank 28 in x i in x 1 in using acoustic backscatter sensors to make rapid 3 hz suspended sand profile measurements 0 005 m vertical resolution waves of 1 7 s period and heights ranging from 0 14 to 0 185 m were used over sand with a d 50 of 255 mum infiltration velocities of 0 5 0 x 10 4 m s 1 were used with percolation through an initially flat bed ripple development was suppressed particularly at lower wave heights ripples took longer to form and were more three dimensional suspension was also suppressed the total suspended load was correlated with shields number at the 1 significance level when the shields number was modified to take account of both the infiltration nielsen p 1997 coastal groundwater dynamics proceedings of coastal dynamics american society of civil engineers pp 546 555 and ripple steepness coastal eng 1986 23 the ripple steepness was found to be the most important factor relating to the reduction in the total suspended loads the influence of infiltration on time averaged concentration profiles over equilibrium ripples was investigated by switching the percolation on and off for 5 min periods the total suspended loads were reduced by up to 50 with percolation on these results suggest that fluctuation of the water table and drainage within a beach will affect sediment transport and ripple dynamics and that for sand of 0 25 mm percolation will tend to reduce suspension and transport c 2002 elsevier science b v all rights reserved

ice volume and sea level during the last interglacial during the last interglacial period 125 000 years ago sea level was at least several meters higher than at present with substantial variability observed for peak sea level at geographically diverse sites speculation that the west antarctic ice sheet collapsed during the last interglacial period has drawn particular interest to understanding climate and ice sheet dynamics during this time interval we provide an internally consistent database of coral u th ages to assess last interglacial sea level observations in the context of isostatic modeling and stratigraphic evidence these data indicate that global eustatic sea level peaked 5 5 to 9 meters above present sea level requiring smaller ice sheets in both greenland and antarctica relative to today and indicating strong sea level sensitivity to small changes in radiative forcing

calcium aluminum rich inclusions and amoeboid olivine aggregates from the cr carbonaceous chondrites calcium aluminum rich refractory inclusions cais in cr chondrites are rare 1 vol fairly small 500 m and irregularly shaped and most of them are fragmented based on the mineralogy and petrography they can be divided into grossite hibonite rich melilite rich and pyroxene anorthite rich cais other types of refractory objects include fine grained spinel melilite pyroxene aggregates and amoeboid olivine aggregates aoas some of the pyroxene anorthite rich cais have igneous textures and most melilite rich cais share similarities to both the fluffy and compact type a cais found in cv chondrites one major difference between these cais and those in cv cm and co chondrites is that secondary mineral phases are rare in situ ion microprobe analyses of oxygen isotopic compositions of 27 cais and aoas from seven cr chondrites demonstrate that most of the cais are 16o rich 17o of hibonite melilite spinel pyroxene and anorthite 22 and isotopically homogeneous within 3 4 likewise forsterite spinel anorthite and pyroxene in aoas have nearly identical 16o rich compositions 24 17o 20 deg in contrast objects which show petrographic evidence for extensive melting are not as 16o rich 17o less than 18 o secondary alteration minerals replacing 16o rich melilite in melilite rich cais plot along the terrestrial fractionation line most cr cais and aoas are mineralogically pristine objects that largely escaped thermal metamorphism and secondary alteration processes which is reflected in their relatively homogeneous 16o rich compositions it is likely that these objects or their precursors condensed in an 16o rich gaseous reservoir in the solar nebula in contrast several igneous cais are not very enriched in 16o probably as a result of their having melted in the presence of a relatively 16o poor nebular gas if the precursors of these cais were as 16o rich as other cr cais this implies either temporal excursions in the isotopic composition of the gas in the cai forming regions and or radial transport of some cai precursors into an 16o poor gas the absence of oxygen isotope heterogeneity in the primary minerals of melilite rich cais containing alteration products suggests that mineralogical alteration in cr chondrites did not affect oxygen isotopic compositions of their cais

suspended sediment concentrations under waves abstract a predictive formula is derived for calculation of the magnitude of time averaged suspended sediment concentrations under waves by taking into account the effect of flow contraction near ripple crests the formula applies equally well for rippled beds and sheet flow conditions the formula is in qualitative agreement with the bed load flux formula of madsen and grant 1976

compositional evolution of the protoplanetary disk oxygen isotopes of type ii chondrules from cr2 chondrites chondrules are the dominant component of chondritic meteorites and attest to high temperature transient heating events within the protoplanetary disk they provide valuable constraint on the disk environments in which they formed and potentially the evolution of primitive planetary materials in the disk the oxygen isotopic composition of cr2 chondrite type ii chondrules was investigated our data show significant variation in the isotopic compositions of the chondrules with no petrographic or geochemical means to identify what chondrule will plot where on a three isotope diagram although we cannot rule out that these chondrules may have come from another chondrite forming region we argue in context of type i chondrules from cr2 chondrites that cr2 type ii chondrules record changes in solid and gas composition during formation due to the vaporization of icy bodies in localized regions of the inner disk

isotopic diversity in interplanetary dust particles and preservation of extreme 16o depletion two interplanetary dust particles idps investigated by nanosims reveal diverse oxygen isotope compositions at the micrometre scale the oxygen isotope values recorded at different locations across the single idp fragments cover a wider range than the bulk values available from all idps and bulk meteorites measured to date measurement of h c and n isotopes by nanosims and the use of scanning and transmission electron microscopy sem and tem to determine elemental compositions and textural information allows for a better understanding of the lithologies and organic signatures associated with the oxygen isotope features idp balmoral a 15 m sized fragment with a chondritic porous cp idp like texture contains a region a few micrometres in size characterised by 16o depleted isotope signatures in the range 17o 18o 80 to 200 the remainder of the fragment has a more 16o rich composition 18o 0 20 similar to many other idps and bulk meteorites other than in discrete pre solar grains such extreme 16o depletions have only been observed previously in rare components within the matrix of the acfer 094 meteorite however tem imaging and feo mgo si ion ratios indicate that the 16o depleted regions in balmoral did not form by the same mechanism as that proposed for the 16o depleted phases in acfer 094 as the level of 16o depletion is consistent with that expected from isotope selective self shielding it is likely that the 16o depleted reservoir was located close to that where oxygen self shielding effects were most pronounced i e the outer solar nebula or even interstellar medium individual regions within idp lumley cover a range in 18o from 30 to 19 with the oxygen isotope values broadly co varying with d 13c 15n light element ratios and texture the relationships observed in lumley indicate that the parent body incorporated material at the micrometre scale from discrete diverse isotopic reservoirs some of which are represented by inner solar system material but others which must have formed in the outer solar system the idp fragments support a model whereby primary dust from the early solar nebula initially formed a variety of reservoirs in the outer solar nebula with those at lower au incorporating a higher proportion of inner solar system chondritic dust than those at larger au these reservoirs were subsequently disrupted into micrometre sized clasts that were re incorporated into idp parent bodies presumably at large au these results reveal that any models accounting for mixing processes in the early solar nebula must also account for the presence of an extremely 16o depleted reservoir in the comet forming region

ferromagnetic resonance characterization of greigite fe3s4 monoclinic pyrrhotite fe7s8 and non interacting titanomagnetite fe3 xtixo4 ferromagnetic resonance fmr spectroscopy has become an increasingly useful tool for studying the magnetic properties of natural samples magnetite fe3o4 is the only magnetic mineral that has been well characterized using fmr this limits the wider use of fmr in rock magnetism and paleomagnetism in this study we applied fmr analysis to a range of magnetic minerals including greigite fe3s4 monoclinic pyrrhotite fe7s8 magnetically non interacting titanomagnetite fe3 xtixo4 and synthetic magnetite chains to constrain interpretation of fmr analysis of natural samples and to explore applications of fmr spectroscopy we measured the fmr signatures of a wide range of well characterized samples at the x and q bands fmr spectra were also simulated numerically to compare with experimental results the effects of magnetic anisotropy mineralogy domain state and magnetostatic interactions on the fmr spectra are discussed for all studied minerals our experimental and theoretical analyses of magnetically non interacting tuff samples and magnetically interacting chains enable quantitative assessment of contributions of magnetostatic interactions and magnetic anisotropy to the fmr spectra our results also indicate that intact magnetosomes are a unique system with distinct fmr signatures while fmr analysis is useful for characterizing magnetic properties of natural samples care is needed when making interpretations because of overlaps in a range of fmr signatures of different magnetic minerals with different magnetic properties our analyses will help to constrain such interpretations in rock magnetic studies

high eustatic sea level during the middle pliocene evidence from the southeastern u s atlantic coastal plain the middle pliocene approximately 3 5 2 5 ma was a period of global warmth preceding the growth of major northern hemisphere ice sheets the authors report on eustatic sea level for the middle pliocene based on microspaleontologic study of marine deposits of the duplin formation of south carolina and north carolina the duplin was deposited during a middle pliocene marine transgression that formed the orangeburg scarp a prominent wave cut geomorphic paleoshoreline of the southeastern u s atlantic coastal plain they concluded that 1 the scarp in south carolina was formed mostly during the middle pliocene 3 5 3 0 ma 2 eustatic sea level was about 35 plus minus 18 m higher than modern sea level the scarp has been uplifted about 50 65 m since the middle pliocene and 3 ocean water temperatures along eastern north america were warmer when the scarp was formed that they are at present

iron and iron nickel sulfides in chondritic interplanetary dust particles abstract we report the results of a study of iron and iron nickel sulfides in chondritic anhydrous and hydrated interplanetary dust particles idps the idps were characterized using chemical and mineralogical techniques including energy dispersive x ray analyses and transmission electron microscopy it is widely believed that the first sulfur containing mineral to form in the early solar nebula should have been stoichiometric fes troilite and that pyrrhotite is of secondary origin all examined interplanetary dust particles both anhydrous and hydrous types contain more pyrrhotite than troilite suggesting that the former was a common possibly predominant nebular condensate phase pyrrhotite could form from sulfidation of troilite after the latter had exfoliated from substrate metal grains in contrast to anhydrous idps hydrated ones contain ni rich sulfides including pentlandite which are probably of secondary origin

a sustained 21 m sea level highstand during mis 11 400 ka direct fossil and sedimentary evidence from bermuda abstract a small protected karstic feature exposed in a limestone quarry in bermuda preserved abundant sedimentary and biogenic materials documenting a transgressive phase still stand and regressive phase of a sea level in excess of 21 3 m above present during marine isotope stage mis 11 400 ka as determined by u th dating and amino acid racemization cobbles and marine sediments deposited during the high energy transgressive phase exhibit rim cements indicating a subsequent phreatic environment this was succeeded stratigraphically by a still stand deposition of fine calcareous lagoonal sediments containing bioclasts of red algae and benthic and planktonic foraminifera that was intensely burrowed by marine invertebrates probably upogebiid shrimp that could not be produced under any condition other than sustained marine submergence overlying this were pure carbonate beach sands of a low energy regressive phase containing abundant remains of terrestrial and marine vertebrates and invertebrates the considerable diversity of this fauna along with taphonomic evidence from seabird remains indicates deposition by high run up waves over a minimum duration of months if not years the maximum duration has yet to be determined but probably did not exceed one or two thousand years the most abundant snails in this fauna are two species indicative of brackish water and high tide line showing that a ghyben herzberg lens must have existed at 20 m the nature of these sediments and fossil accumulation is incompatible with tsunami deposition and given the absence of evidence for tectonic uplift of the bermuda pedestal or platform provide proof that sea level during mis 11 exceeded 20 m a fact that has widespread ramifications for geologists biogeographers and human demographics along the world s coastlines

mineralogy and texture of fe ni sulfides in ci1 chondrites clues to the extent of aqueous alteration on the ci1 parent body to better understand the role of aqueous alteration on the ci1 parent body we have analyzed the texture composition and mineral associations of iron nickel sulfides in four of the five known ci1 chondrites the most commonly occurring sulfide present in the ci1 chondrites is the iron deficient fe ni sulfide pyrrhotite fe ni 1 xs that has a composition close to that of stoichiometric troilite fes three of the ci1s alais ivuna and tonk also contain pentlandite fe ni 9s8 although pentlandite is a rare phase in ivuna cubanite cufe2s3 was found in both alais and ivuna in this study although it has also been reported in orgueil macdougall and kerridge 1977 the pyrrhotite grains in all four chondrites form hexagonal rectangular or irregular shapes and show no evidence of ni or co zoning the pyrrhotite grains in orgueil and ivuna are in general smaller and show more corrosions or embayments than those in alais or tonk we suggest that the precursor sulfide present in the ci1 chondrites was troilite which during brecciation and oxidation on the parent body at a temperature of 100 c or less converted the troilite to magnetite and pyrrhotite with pentlandite inclusions subsequently continued alteration on the parent body removed pentlandite partially from alais tonk and ivuna completely from orgueil leaving behind pyrrhotite with spaces corrosions where the pentlandite had been ni derived from the pentlandite was incorporated into ferrihydrite onto the surface of which the ni na sulfate ni bloedite formed based on the size and abundant corrosions within pyrrhotite grains combined with observations from other authors we conclude that orgueil and ivuna have undergone a greater degree of alteration than alais and tonk further work is needed to assess the conditions under which pentlandite would be dissolved preferentially to pyrrhotite as the study of terrestrial literature indicates that the latter mineral is preferentially removed

oxygen isotope ratios of feo poor chondrules in cr3 chondrites influence of dust enrichment and h2o during chondrule formation abstract we present detailed electron microprobe analyses and oxygen three isotope measurements by high precision secondary ion mass spectrometry on 45 type i feo poor chondrules fragments and 3 type ii feo rich chondrule fragments from meteorite hills 00426 and queen alexandra range 99177 two of the most primitive cr3 chondrites type i chondrules fragments have mg s defined as the mg of constituent olivine and or low ca pyroxene ranging from 94 2 to 99 2 type ii chondrule fragments have mg s of 53 63 oxygen three isotope measurements plot on the slope 1 primitive chondrule mineral pcm line within chondrules 17 o 17 o 0 52 18 o values of coexisting olivine pyroxene and plagioclase are homogeneous with propagated uncertainties of 0 3 this indicates each phase crystallized from the final chondrule melt and that efficient oxygen isotope exchange occurred between ambient gas and chondrule melt among type i chondrules there is a well defined increase in 17 o from 5 9 to 1 as mg s decrease from 99 2 to 96 type ii chondrule fragments are comparatively 16 o poor 17 o 0 2 0 6 the relationship between mg and 17 o among type i chondrules confirms that addition of a 16 o poor oxidizing agent to the highest mg chondrule precursors resulted in forming lower mg cr chondrules using aspects of existing equilibrium condensation models and a mass balance we estimate that type i cr chondrules formed at dust enrichments of 100 200 from dusts with 0 0 8 times the atomic abundance of ice relative to ci dust the type ii chondrule fragments are predicted to have formed at ci dust enrichments near 2500

sulfur four isotope nanosims analysis of comet 81p wild 2 dust in impact craters on aluminum foil c2037n from nasa s stardust mission abstract we present nanosims four isotope s analyses of 24 comet wild 2 dust impact residues in craters on aluminum foil c2037n returned by nasa s stardust mission except for one sample all impact residues have normal s isotopic compositions within 2 uncertainties of at least two s isotope ratios this implies that most s rich wild 2 dust impactors formed in the solar system instrumental isotope fractionation due to sample topography is the main contribution to our analytical uncertainty one impact crater residue shows small anomalies of 33s 57 17 and 34s 41 17 1 uncertainties although this could be simply a statistical outlier or the fingerprint of a chemical isotope fractionation it is also possible that the observed anomaly results from the mixture of a cometary fes particle with a small 150 nm diam presolar fes supernova grain this would translate into a presolar sulfide abundance of approximately 200 ppm

spatial and temporal patterns of cenozoic dynamic topography around australia 1 despite its importance the spatial and temporal pattern of dynamic topography generated by mantle convective circulation is poorly known we present accurate estimates of dynamic topography from oceanic basins and continental margins surrounding australia our starting point is measurement of residual depth anomalies on the oldest oceanic floor adjacent to the continental shelf these anomalies were determined from a combined dataset of 200 seismic reflection and wide angle images of well sedimented oceanic crust they have amplitudes of between 1 km and 0 5 km and their spatial variation is broadly consistent with long wavelength free air gravity and shallow seismic tomographic anomalies along the northwest shelf a regional depth anomaly of 300 to 700 m intersects the adjacent continental shelf the temporal evolution of this anomaly was determined by analyzing the stratigraphic architecture of an extensive carbonate platform which fringes the shelf and records a dramatic switch from progradation to aggradation during neogene times three dimensional seismic mapping calibrated by boreholes was used to calculate water loaded subsidence histories at rollover points of clinoforms along the shelf at 9 3 ma the rate of subsidence increases from 5 to up 75 m myr 1 generating a subsidence anomaly of 300 to 700 m the amplitude of this anomaly varies along the shelf and cannot be generated by glacio eustatic sea level variation instead we propose that a regional subsidence episode which affects both the proximal shelf and the distal oceanic basin was generated by convective drawdown by combining our results with other published estimates of uplift and subsidence a map of australia which shows the spatial and temporal pattern of dynamic topography is presented most but not all of australia s epeirogeny can be attributed to rapid northward motion of the australian plate over a pre existing pattern of convective circulation

coordinated mineralogical and isotopic analyses of a cosmic symplectite discovered in a comet 81p wild 2 sample we have discovered in a stardust mission terminal particle a unique mineralogical assemblage of symplectically intergrown pentlandite fe ni 9s8 and nanocrystalline maghemite fe2o3 mineralogically similar cosmic symplectites cos have only been found in the primitive carbonaceous chondrite acfer 094 and are believed to have formed by aqueous alteration the o and s isotopic compositions of the wild 2 cos are indistinguishable from terrestrial values the metal and sulfide precursors were thus oxidized by an isotopically equilibrated aqueous reservoir either inside the snow line in the wild 2 comet or in a larger kuiper belt object close association of the stardust cos with a kool mineral assemblage kosmochloric ca rich pyroxene feo rich olivine and albite that likely originated in the solar nebula suggests the cos precursors also had a nebular origin and were transported from the inner solar system to the comet forming region after they were altered

synchronous centennial abrupt events in the ocean and atmosphere during the last deglaciation antarctic ice core data reveal that the atmosphere experienced abrupt centennial increases in co2 concentration during the last deglaciation 18 thousand to 11 thousand years ago establishing the role of ocean circulation in these changes requires high resolution accurately dated marine records here we report radiocarbon data from uranium thorium dated deep sea corals in the equatorial atlantic and drake passage over the past 25 000 years two major deglacial radiocarbon shifts occurred in phase with centennial atmospheric co2 rises at 14 8 thousand and 11 7 thousand years ago we interpret these radiocarbon enriched signals to represent two short lived less than 500 years overshoot events with atlantic meridional overturning stronger than that of the modern era these results provide compelling evidence for a close coupling of ocean circulation and centennial climate events during the last deglaciation