flux and provenance of ice rafted debris in the earliest pleistocene sub polar north atlantic ocean comparable to the last glacial maximum relatively little is known in detail about the locations of the early pleistocene ice sheets responsible for ice rafted debris ird inputs to the sub polar north atlantic ocean during intensification of northern hemisphere glaciation inhg to shed new light on this problem we present the first combined in depth analysis of ird flux and geochemical provenance of individual sand sized ird deposited in the sub polar north atlantic ocean during the earliest large amplitude pleistocene glacial marine isotope stage mis 100 2 52 ma arguably the key glacial during inhg ird provenance is assessed using laser ablation lead pb isotope analyses of single feldspar grains we find that the pb isotope composition 206pb 204pb 207pb 204pb and 208pb 204pb of individual ice rafted 150 m feldspars deposited at dsdp site 611a odp site 981 and iodp site u1308 during mis 100 records a shift from predominantly archaean aged circum north atlantic ocean continental sources during early glacial ice rafting events to dominantly palaeozoic and proterozoic aged sources during full glacial conditions the distribution of feldspars in pb pb space for full glacial mis 100 more closely resembles that documented for feldspars deposited at the centre of the last glacial ird belt at iodp dsdp site u1308 609 during ambient non heinrich event ice rafting episodes of mis 2 23 8 ka than that documented for mis 5d 106 ka comparison of our early pleistocene and last glacial cycle datasets suggests that mis 100 was characterised by abundant iceberg calving from large ice sheets on multiple continents in the high northern latitudes not just on greenland

faunal and stable isotopic analyses of benthic foraminifera from the southeast seep on kimki ridge offshore southern california usa abstract we investigated the benthic foraminiferal faunal and stable carbon and oxygen isotopic composition of a 15 cm push core na075 092b obtained on a telepresence enabled cruise to the southeast seep on kimki ridge offshore southern california the seep core was taken at a depth of 973 m in the vicinity of a beggiatoa bacterial mat and vesicomyid clams calyptogena and compared to previously published data of living assemblages from 714 m four reference cores obtained at 1030 m and another one at 739 m all of the reference sites are also from the inner continental borderland but with no evidence of methane seepage no endemic species were found at the seep site and most of the taxa recovered there have been reported previously from other seep or low oxygen environments q and r mode cluster analyses clearly illustrated differences in the faunal assemblages of the seep and non seep sites the living assemblage at southeast seep was characterized by abundant takayanagia delicata cassidulina translucens and spiroplectammina biformis whereas the non seep san pedro basin reference assemblage was comprised primarily of chilostomella oolina and globobulimina pacifica density and species richness were lower at the seep site compared to the non seep site reflecting the harsher living conditions there the dead assemblage at the seep site was dominated by gyroidina turgida compared to cassidulina translucens at the 1030 m non seep site and cassidulina translucens pseudoparrella pacifica and takayanagia delicata at the 739 m non seep site density was three times lower at southeast seep than at the non seep sites of comparable water depth but species richness was 30 higher stable carbon isotopic values were considerably depleted in the seep samples compared to the non seep samples with a progression from lightest to heaviest average 13c values evident at the seep site reflecting microhabitat preference and vital effect the deep infaunal species of globobulimina the shallow infaunal species uvigerina peregrina the epifaunal species cibicidoides wuellerstorfi and the shallow infaunal but aragonite shelled species hoeglundina elegans the 13c values downcore among each benthic species indicates ongoing fluid seepage through at least the last 3800 cal yr b p at southeast seep besides the continual local seepage evidence from 13c values of planktic foraminifera in the seep core suggest two pulses of methane at 3000 and 3700 cal yr b p were released that were large enough to influence much of the water column paired benthic and planktic foraminiferal stable oxygen isotope records provide evidence that there were no paleoenvironmental changes such as increased bottom water temperature or changes in oxygen isotopic composition of bottom and pore waters during this 3800 year record to induce the methane releases instead southeast seep appears to be the result of local faulting providing pathways for fluid to flow to the seafloor at a fault stepover or transpressional bend in the regional strike slip system

reversed pyroxene phase equilibria in cao mgo sio2 from 925 to 1 175 c at one atmosphere pressure experiments using v2o5 as a high temperature solvent have produced compositional reversals defining the miscibility gap between enstatite and diopside on the join mg2si2o6 camgsi2o6 between 925 and 1 175 c at atmospheric pressure these experiments locate an equilibrium near 1 000 c among diopside protoenstatite and orthoenstatite they verify the stable coexistence of diopside and protoenstatite above 1 000 c and disprove the hypothesis that orthoenstatite has a stability field which is continuous from temperatures below 1 000 c to the solidus the phase relations suggest that the orthorhombic low ca pyroxene on the solidus in this system formerly identified as orthoenstatite is a phase distinct from the orthoenstatite stable with diopside at low subsolidus temperatures data locating the orthoenstatite diopside miscibility gap validate the use at low pressures of symmetric orthopyroxene and asymmetric clinopyroxene solution models in this system

variations of okhotsk sea oxygen minimum zone comparison of foraminiferal and sedimentological records for latest mis 12 11c and latest mis 2 1 abstract benthic foraminiferal assemblage compositions foraminiferal and sedimentological proxies were analyzed in core md01 2415 from the northern slope of the okhotsk sea to compare variations of productivity and oxygen minimum zone omz intensity during the latest marine isotope stage mis 12 11c and latest mis 2 1 the benthic assemblages reveal close similarity between the two climatic cycles the absence of benthic assemblages during the latest mis 12 and the presence of the low productivity angulogerina angulosa assemblage during the latest mis 2 suggest the disappearance of the omz this regime was related to almost perennial ice cover with periods of active ice rafting during the latest mis 12 while it was attributed to prolonged seasonal ice cover low surface productivity and enhanced formation of well oxygenated water masses in the okhotsk sea during the latest mis 2 in deglacial times the omz gradually intensified as evidenced by the high productivity uvigerina akitaensis assemblage during the early termination t tv and early ti and the low oxygen tolerant bolivina spissa assemblage during the late tv and late ti the orbitally forced similar rises of the global sea level during tv and ti caused a large offshore supply of organic matter synchronously nutrients from the melting sea ice and shelf erosion promoted high surface mainly carbonate productivity as a result a high and sustained flux of particulate degraded and refractory organic matter enhanced oxygen consumption in bottom waters and sediments leading to the similar gradual omz intensifications the b spissa assemblage also points to expansion of oxygen depleted water mass from the north pacific into the okhotsk sea fostering the omz intensifications the phytodetritus related islandiella norcrossi assemblage indicates weakening of the omz during full interglacial times of mis 11c and mis 1 after stabilization of the global sea level nutrients were mainly delivered by regional upwelling and fluvial discharge favoring increased biogenic opal and carbonate production in the surface water similar to the present in this way moderate to high although less than deglacial and pulsed flux of predominantly particulate organic matter caused the weakening of the oxygen consumption and omz notably during mis 11c the benthic assemblage with the dominance of the taxa with dissolution resistant tests such as miliammina herzensteini karreriella baccata and martinottiella communis reflects carbonate dissolution events in sediments these events might have been resulted from an interruption of the local surface carbonate production and inflow of more carbonate corrosive water masses from the north pacific driven by a drawdown of the global ocean carbonate saturation

significance of fracture sets associated with stylolite zones geologic notes stylolite zones consist of an irregular seam and often a variety of associated fracture sets the geometry of this zone can be used to determine paleostress directions of the fracture sets commonly observed in close proximity to stylolites one is generally induced by the coring procedure unloading fractures and another is natural and possibly associated with stylolites of tectonic origin so called tension gashes within a unit possessing abundant stylolites the stylolites are most common in zones of relatively low porosity in addition because of the relatively compact poorly sorted fine grained nature of the seam itself stylolite zones commonly have much reduced permeability compared to the undeformed rock above and below laboratory measured permeability associated with stylolite zones can however be misleadingly large owing to the presence of unloading fractures and or tension gashes these fractures may dramatically increase laboratory permeability but commonly are either not present in the reservoir or are relevant only to the size of the laboratory measurement sample it is critical therefore to understand the origin and scale of associated fracture development in interpreting su h data

a conceptual model for glacial cycles and the middle pleistocene transition milankovitch s astronomical theory of glacial cycles attributing ice age climate oscillations to orbital changes in northern hemisphere insolation is challenged by the paleoclimatic record the climatic response to the variations in insolation is far from trivial in general the glacial cycles are highly asymmetric in time with slow cooling from the interglacials to the glacials inceptions and very rapid warming from the glacials to the interglacials terminations we shall refer to this fast slow dynamics as the saw tooth shape of the paleoclimatic record this is non linearly related to the time symmetric variations in the orbital forcing however the most pronounced challenge to the milankovitch theory is the middle pleistocene transition mpt occurring about one million years ago during that event the prevailing 41 kyr glacial cycles corresponding to the almost harmonic obliquity cycle were replaced by longer saw tooth shaped cycles with a time scale around 100 kyr the mpt must have been driven by internal changes in climate response since it does not correspond to any apparent changes in the orbital forcing in order to identify possible mechanisms causing the observed changes in glacial dynamics it is relevant to study simplified models with the capability of generating temporal behavior similar to the observed records we present a simple oscillator type model approach with two variables a temperature anomaly and a climatic memory term the generalization of the ice albedo feedback is included in terms of an effective multiplicative coupling between this latter climatic memory term representing the internal degrees of freedom and the external drive the simple model reproduces the temporal asymmetry of the late pleistocene glacial cycles and suggests that the mpt can be explained as a regime shift aided by climatic noise from a period 1 frequency locking to the obliquity cycle to a period 2 3 frequency locking to the same obliquity cycle the change in dynamics has been suggested to be a result of a slow gradual decrease in atmospheric greenhouse gas concentration the critical dependence on initial conditions in the non autonomous glacial dynamics raises fundamental questions about climate predictability

the system mg2sio4 ca2sio4 caal2o4 naalsio4 sio2 one atmosphere liquidus equilibria of analogs of alkaline mafic lavas one atmosphere liquidus relationships in the system mg2sio4 fo ca2sio4 la naalsio4 ne caal2o4 ca sio2 sil are presented as analogs for alkaline mafic lavas liquidus diagrams are constructed from electron microprobe analyses of quenched liquids and coexisting mineral phases produced in melting experiments and they are depicted in terms of sub projections within the pseudo quaternary system fo la ne ca sil the ne and ca components are combined to create a normative feldspathoid component defined as ne ne ne ca liquidus relations at ne 0 5 from this study are compared to relations at ne 0 0 and 1 0 from previous studies in general liquidus temperatures decrease and positions of liquidus boundaries involving feldspathic phases shift toward the ne ca component as ne increases the pseudoinvariant points fo di pl mel l and fo pl mel sp l exist at ne 0 5 these equilibria between forsterite plagioclase melilite liquid are not present in the system when ne 1 0 because a boundary curve fo di ne l separates the plagioclase and melilite liquidus fields the liquidus diagrams provide useful analogs for the crystallization sequences of natural primary alkali olivine basalts basanitoids basanites olivine nephelinites olivine melilite nephelinites and olivine melilitites

evidence against the stability of orthoenstatite above 1005 c at atmospheric pressure in cao mgo sio2 reversals locating the equilibrium orthoenstatite protoenstatite diopside in cao mgo sio2 demonstrate that orthoenstatite cannot exist stably above 1005 10 c at one atmosphere pressure this in turn suggests that the orthorhombic low ca phase found near 1400 c at atmospheric pressure in this system formerly identified as orthoenstatite is in fact a previously unrecognized pyroxene polymorph

diagenesis of devonian reefal carbonates in the oscar range canning basin western australia abstract the oscar range part of the extensive devonian reef complex of the northern canning basin is a large atoll 80 10 km in which frasnian and famennian late devonian reefs grew around an emergent island of precambrian metasedimentary rocks many sediments in the oscar range had high depositional porosities but this porosity was largely occluded by diagenetic alteration diagenesis included marine cementation dolomitization pressure solution burial cementation and karstification field mapping petrography cathodoluminescence and carbon and oxygen isotope analyses have been used to document six major diagenetic episodes that affected oscar range sediments earliest cementation occurred in the marine environment where reef margin and associated subfacies developed abundant non luminescing radiaxial fibrous and microcrystalline calcite cements based on convergent covariant isotopic trends marine cements had a characteristic late devonian oxygen signature of 4 5 0 5 pdb and a carbon signature of 2 0 0 5 pdb in well cemented parts of the reef complex synsedimentary neptunian fissures formed and were filled with cement and sediment cements in these fissures have isotopic ratios that are essentially identical to the values determined for marine cements thereby suggesting that the fissures acted as conduits f r seawater flow and cementation early in the history of the reef complexes marine diagenesis was followed by marine burial and possible meteoric phreatic cementation and dolomitization marine cements are overgrown by non luminescing scalenohedral cements that grade into banded bright and non luminescing blocky calcite cements that are common on the platform but are missing in many reef margin and marginal slope deposits banded luminescence may represent fluctuating reducing and oxidizing conditions in pore waters across the intermittently emergent platform the reef complexes however were generally drowned reefs with little chance for prolonged meteoric exposure this sedimentologic evidence suggests that banded luminescing cements may have formed in the marine burial environment the next cement generation consists of non luminescing non ferroan bloc y calcites that occur throughout the reef complex stratigraphic relationships combined with isotopic results 18o 6 0 to 9 0 13c 2 0 suggest that this spar is a burial cement resulting from late devonian through early carboniferous burial the reef complex was exhumed and eroded in the late carboniferous dedolomite dolo moldic porosity pisolitic calcrete crusts iron oxide stained blocky cements and deep 200 m sinkholes formed at the unconformity surface non ferroan irregularly banded moderate to bright luminescing blocky calcite precipitated throughout the reef complex unconformity related cements calcrete crusts and dedolomites have distinctive isotopic signatures that show little variation in oxygen 7 0 to 9 0 but have a broad range of carbon values 1 5 to 8 0 highly negative carbon values are probably related to the interaction of meteoric fluids with isotopically light soil gas at the er sion surface in post carboniferous time most of the remaining porosity was filled with non ferroan bright luminescing blocky calcite that formed by pressure solution reprecipitation during burial isotopic analyses 18o 8 0 to 12 0 13c 1 5 support a burial origin for this generation of cements these cements fill primary porosity tension gashes along stylolites and hairline fractures along which hematite is leached a final generation of ferroan homogeneous dull to non luminescing blocky calcite cement formed in a late burial event that according to isotopic evidence 18o 10 5 to 15 0 13c 2 0 to 9 0 was probably related to movement of basinal brines through the reef complexes

a thermodynamic model for silicate melt in cao mgo al2o3 sio2 to 50 kbar and 1800 c a fully thermodynamic model for mafic melt in cao mgo al2o3 sio2 cmas has been calibrated for calculation of melting equilibria in the pressure range 0 50 kbar it is intended as a preliminary step towards a large system melt model suitable for exploring melting melt loss and crystallization processes in a wide range of natural rock compositions calibration was performed with attention to the model s behaviour in its compositional subsystems as a rigorous test of model structure and parameterization the model is consistent with the latest holland powell thermodynamic data set and can therefore be used to calculate phase relations in conjunction with the many solid phase activity composition models written for the data set model calculations successfully reproduce experimental melting reactions in cmas spinel lherzolite and garnet lherzolite assemblages as well as sapphirine and kyanite bearing assemblages at moderate to high pressure thermodynamically sensitive features such as thermal divides are also recovered however some changes to the model structure will be required before the model can describe the full range of mafic and ultramafic melt compositions known from experiment at low pressures

disequilibrium dihedral angles in layered intrusions a microstructural record of fractionation the dihedral angle formed at junctions between two plagioclase grains and a grain of augite is only very rarely in textural equilibrium in gabbros from kilometre scale crustal layered intrusions the median of a population of these disequilibrium angles cpp varies systematically within a single layered intrusion remaining constant over large stretches of stratigraphy with significant increases and decreases associated with the addition or reduction respectively of the number of phases on the liquidus of the bulk magma the stepwise changes in cpp are present in the upper zone of the bushveld complex the megacyclic unit i of the sept iles intrusion and the layered series of the skaergaard intrusion the plagioclase bearing cumulates of rum have a bimodal distribution of cpp dependent on whether the cumulus assemblage includes clinopyroxene the presence of the stepwise changes is independent of the order of arrival of cumulus phases and of the composition of either the cumulus phases or the inferred composition of the interstitial liquid the only parameter that behaves in an exactly analogous manner to cpp is the rate of change in enthalpy with temperature h t during crystallization both h t and cpp increase with the addition of a liquidus phase and decrease with the removal of a liquidus phase the replacement of one phase by another has little effect on h t and no discernible effect on cpp an increase of h t results in an increase in the fraction of the total enthalpy budget that is the latent heat of crystallization the fractional latent heat it also increases the mass crystallized in each incremental temperature drop the crystal productivity these increases of both fractional latent heat and crystal productivity are likely to cause an increase in the time taken to form three grain junctions in the mush via thermal buffering of a thickened mushy layer we suggest these are the underlying causes of stepwise increases in cpp stepwise changes in the geometry of three grain junctions in fully solidified gabbros thus provide a clear microstructural marker for the progress of fractionation down the liquid line of descent in layered intrusions

late pliocene quaternary evolution of redox conditions in the western qaidam paleolake ne tibetan plateau deduced from mn geochemistry in the drilling core sg 1 abstract manganese mn in lake sediments reacts strongly to changes of redox conditions this study analyzed mn concentrations in oxides carbonates and bulk phases of the calcareous lacustrine sediments of a 938 5 m long core sg 1 taken from the western qaidam basin well dated from 2 77 ma to 0 1 ma comparisons of extractions from diluted hydrochloric acid acetic acid and citrate bicarbonate dithionite demonstrate that variations of mn concentrations from acetic acid leaching mnhoac are mostly responsible for mn ii fluctuations in the carbonate phase taking into account the relevant processes during weathering transportation deposition and post deposition of mn bearing rocks we conclude that mn input from catchment weathering and paleolake redox condition provide the primary controls on variations in the mn records of carbonate and oxide phases we propose mnhoac as a new sensitive indicator of paleolake redox evolution and catchment scale climate change the mnhoac variations show a long term upward decreasing trend indicating a long term decrease of mn input from catchment weathering associated with increasing oxygen content in the paleolake bottom water the great similarities of the mnhoac record with other regional and global records suggest that paleolake redox changes and climatic drying in the qaidam basin may be largely related to global cooling

multiple climatic cycles imprinted on regional uplift controlled fluvial terraces in the lower yalong river and anning river se tibetan plateau abstract the development of fluvial systems on the southeastern margin of the tibetan plateau is linked to significant and rapid late cenozoic uplift the relatively complete fluvial terrace sequence preserved along the yalong river valley and that of its tributary the anning river provides an excellent archive for studying the development of terraces in rapidly uplifting mountainous areas this study reveals that terrace development is predominantly controlled by multiscale climate cycles and long term uplift as shown by terrace dating sedimentary characteristics and incision rates at least six alluvial terrace units were identified in 20 transverse sections through the terraces along about a 600 km length of river and were dated using electron spin resonance esr and optically stimulated luminescence osl the climatostratigraphic positions of the terrace deposits and their respective age constraints suggest that fluvial aggradation was concentrated during marine isotope stages mis 32 22 18 4 2 and the younger dryas yd and that incision occurred during the succeeding cold to warm transitions the changes in fluvial style marked by terraces 6 5 and 4 predominantly occurred in synchrony with the 100 ka milankovitch climate cycles while terraces 3 and 2 were controlled by the obliquity driven 41 ka climate cycles finally the aggradation of terrace t1 occurred in response to the yd stadial during the intervening time between 0 72 and 0 063 ma terraces either did not form or were not preserved which may suggest that uplift rates varied through time and influenced terrace formation preservation the progressive valley incision recorded by these fluvial terraces cannot be entirely explained by climate cycling alone temporal and spatial variations in incision rates indicate that the continuing long term incision has been driven by uplift the temporal distribution of the incision rates reveals two rapidly uplifting stages in the southeastern tibetan plateau including an accelerated uplift that has been taking place since 0 06 ma the spatial distributions of differing incision rates reflect the geomorphological response to crustal shortening and differential uplift in this region

a 240 000 year stable carbon and nitrogen isotope record from a loess like palaeosol sequence in the tumara valley northeast siberia abstract a 15 m loess like palaeosol sequence located in the tumara valley southwest of the verkhoyansk mountains was investigated to reconstruct the late quaternary environmental history of northeast siberia total organic carbon toc and total nitrogen n show several distinct and abrupt shifts during the last 240 ka both proxies have generally low values

constraints on the pleistocene chronology of sediments from the lomonosov ridge 1 despite its importance in the global climate system age calibrated marine geologic records reflecting the evolution of glacial cycles through the pleistocene are largely absent from the central arctic ocean this is especially true for sediments older than 200 ka three sites cored during the integrated ocean drilling program s expedition 302 the arctic coring expedition acex provide a 27 m continuous sedimentary section from the lomonosov ridge in the central arctic ocean two key biostratigraphic datums and constraints from the magnetic inclination data are used to anchor the chronology of these sediments back to the base of the cobb mountain subchron 1215 ka beyond 1215 ka two best fitting geomagnetic models are used to investigate the nature of cyclostratigraphic change within this chronology we show that bulk and mineral magnetic properties of the sediments vary on predicted milankovitch frequencies these cyclic variations record glacial and interglacial modes of sediment deposition on the lomonosov ridge as evident in studies of ice rafted debris and stable isotopic and faunal assemblages for the last two glacial cycles and were used to tune the age model potential errors which largely arise from uncertainties in the nature of downhole paleomagnetic variability and the choice of a tuning target are handled by defining an error envelope that is based on the best fitting cyclostratigraphic and geomagnetic solutions

quaternary ostracode and foraminiferal biostratigraphy and paleoceanography in the western arctic ocean abstract the stratigraphic distributions of ostracodes and selected calcareous benthic and planktic foraminiferal species were studied in sediment cores from 700 to 2700 m water depth on the northwind mendeleev and lomonosov ridges in the western arctic ocean microfaunal records in most cores cover mid to late quaternary sediments deposited in the last 600 ka with one record covering the last 1 5 ma results show a progressive faunal turnover during the mid pleistocene transition mpt 1 2 to 0 7 ma and around the mid brunhes event mbe 0 4 ma reflecting major changes in arctic ocean temperature circulation and sea ice cover the observed mpt shift is characterized by the extinction of species that today inhabit the sea ice free subpolar north atlantic and or seasonally sea ice free nordic seas echinocythereis sp rockallia cf enigmatica krithe cf aquilonia pterygocythereis vannieuwenhuisei after a very warm interglacial during marine isotope stage mis 11 dominated by the temperate planktic foraminifer turborotalita egelida the mbe experienced a shift to polar assemblages characteristic of predominantly perennial arctic sea ice cover during the interglacial and interstadial periods of the last 300 ka these include the planktic foraminifera neogloboquadrina pachyderma the sea ice dwelling ostracode acetabulastoma arcticum and associated benthic taxa pseudocythere caudata pedicythere neofluitans and polycope spp several species can be used as biostratigraphic markers of specific intervals such as ostracodes rabilimis mirabilis mis 5 and p vannieuwenhuisei extinction after mis 11 and foraminiferal abundance zones bulimina aculeata late mis 5 and bolivina arctica mis 5 11

multistage collapse of eight western canary island landslides in the last 1 5 ma sedimentological and geochemical evidence from subunits in submarine flow deposits volcaniclastic turbidites in the madeira abyssal plain provide a record of major landslides from the western canary islands in the last 1 5 ma these volcaniclastic turbidites are composed of multiple fining upward turbidite sands known as subunits the subunits indicate that the landslides responsible for the sediment gravity flows occurred in multiple stages the subunits cannot result from flow reflection or splitting because the compositions of volcanic glasses from each individual subunit in an event bed are subtly different this indicates that each subunit represents a discrete failure as part of a multistage landslide this has significant implications for geohazard assessments as multistage failures reduce the magnitude of the associated tsunami the multistage failure mechanism reduces individual landslide volumes from up to 350 km3 to less than 100 km3 thus although multistage failure ultimately reduce the potential landslide and tsunami threat the landslide events may still generate significant tsunamis close to source

the role of north brazil current transport in the paleoclimate of the brazilian nordeste margin and paleoceanography of the western tropical atlantic during the late quaternary abstract reconstructions of surface paleoceanographic conditions of the western equatorial atlantic and past climates of the adjacent northeast brazilian the nordeste continental margin were undertaken by analyzing sediments from a piston core and associated gravity and box cores recovered from 3107 meter water depth at 0 20 n on the equatorial brazilian continental slope the record is dated by radiocarbon analysis and oxygen isotopic stratigraphy of planktonic foraminifers and spans from near modern to approximately 110 ka high resolution xrf analysis provides insight into the paleoclimate history of the nordeste during the last glacial interval several large amplitude and abrupt peaks are observed in the time series of ti ca and are usually accompanied by peaks of fe k together these record periods of increased precipitation and intense weathering on the adjacent continent and increased terrestrial sediment discharge from nordeste rivers into the atlantic within the limits of dating accuracy most ti ca peaks correlate with heinrich events in the north atlantic this record thus corroborates and extends back in time the previous record of arz et al 1998 determined on sediment cores from farther southeast along the nordeste margin stable oxygen isotopic analysis and mg ca paleothermometry on the near surface dwelling planktonic foraminiferal species globierinoides ruber find that mean sea surface temperature sst during glacial time 20 55 ka n 97 was 23 89 0 79 c and the mean sst during the late holocene 0 5 ka n 14 was 26 89 0 33 c ssts were 0 5 2 c higher and inferred sea surface salinities were lower during most of the periods of elevated ti ca thus as observed in previous studies the western equatorial atlantic was warm at least locally and the adjacent southern tropical continent was wet at the same time that the high latitude north atlantic was cold using the syntrace ccsm3 fully coupled climate model with transient forcing for the period 22 ka to present we find that decreased transport of the north brazil current co occurs with reduced atlantic meridional overturning circulation and colder than normal ssts in the north atlantic region these simulated conditions are invariably associated with significantly increased precipitation in the nordeste region

the influence of melt composition on the partitioning of trace elements between anorthite and silicate melt the effect of melt composition on the partitioning of trace elements between anorthite and silicate melts has been studied experimentally in five compositions in the system cao al2o3 sio2 cas at 1400 c and four compositions in the system cao mgo al2o3 sio2 cmas at 1332 c melt composition has a significant impact on the substitution of trace elements into anorthite particularly if the trace element substitution is aliovalent and requires a charge balance for substitution melt composition strongly influences the partitioning of the trivalent rare earth element ree cations into the large cation site m of anorthite due to charge balance requirements the activity of alumina in the melt is the most important compositional variable for the ree partitioning in anorthite scandium another trivalent cation is much more compatible than is predicted for trivalent cations partitioning on the m site therefore scandium is likely partitioning onto the tetrahedral site in place of aluminium which requires no charge balance and therefore is not affected strongly by melt composition similarly the partitioning of the small divalent cations be and mg show a stronger relationship with changing melt composition than the large divalent cations ca sr and ba and therefore are likely to partition on the tetrahedral site t of plagioclase rather than the large cation site m detailed thermodynamic modelling of the effects of melt composition is required for an adequate parameterization of trace element mineral melt partition coefficients in addition to models of the effects of mineral composition

pleistocene water cycle and eastern boundary current processes along the california continental margin 1 coastal marine sediments contain mixtures of terrestrial and marine paleoclimate proxies that record how the coastal water cycle has behaved over long time frames we explore a 600 kyr marine record from odp site 1018 located due west of santa cruz california to identify coastal wet and dry periods and to associate them with oceanographic processes wet periods in central california identified by increased tree pollen relative to pollen from grasslands and scrublands are found on every major deglaciation in the last 600 kyr sea surface temperature sst data were collected for the last two deglaciations wet periods are associated with a rapid rise in sst off central california sst gradients along the california margin and changes in biogenic deposition show that wet periods in central california are associated with a weakening of the california current and weakened coastal upwelling high carbonate production suggests that there was significant curl of wind stress upwelling offshore we propose that wet periods in central california are associated with a meteorological connection to the tropical pacific and weakened southward flow in the california current that shunted temperate pacific water northward into the alaska gyre we do not observe evidence for a south shifted westerly storm track at the last glacial maximum but find that wet periods are diachronous along the california margin the wettest period around the santa barbara basin peaked at 16 ka preceding the wet peak in central and northern california by 4 kyr

facies development and porosity relationships in the dundee limestone of gladwin county michigan the devonian of the michigan basin was a time of transgressive seas and extensive carbonate deposition including coral and stromatoporoid buildups deposited during the middle devonian the dundee limestone represents deposition in subtidal intertidal and restricted environments the buckeye oil field located in south central gladwin county is a combined stratigraphic and structural carbonate trap that produces from a series of intertonguing patch reefs fringing sand bodies and intertidal island fenestral zones the major reef building organisms include stromatoporoids corals calcareous algae brachiopods and crinoids with the stromatoporoids providing the major framework the patch reef facies is composed of massive stromatoporoid boundstones that contain primary intraparticle porosity the fringing grainstone sands are composed of coarse crinoid and brachiopod skeletal debris that have interparticle porosity the intertidal island zone found in the north buckeye field is represented by a pelletal packstone that has abundant fenestral porosity

controls of initial topography on temporal and spatial patterns of glacial erosion abstract here we investigate the influence of initial pre glacial topography on spatial and temporal patterns of glacial erosion using numerical surface process modelling including a higher order ice sheet model first we consider glacier dynamics when simulating glaciation in two real landscapes representing plateau type topography southeast australia and characteristic steady state fluvial topography southern taiwan we find that the different initial landscape configurations result in distinctly different ice configurations and patterns of basal sliding the sliding patterns are controlled by ice configuration and the resulting basal shear stresses and by the thermal properties at the base of the ice we then investigate how these characteristic patterns of basal sliding control glacial erosion and long term landscape evolution using synthetic representations of the two landscapes the two landscape configurations result in markedly different spatial and temporal patterns of glacial erosion however the resulting landscapes may have similar morphology irrespective of initial landscapes and glacial erosion patterns being significantly different the numerical experiments also suggest that in addition to basal temperature basal shear stress is important in restricting long term glacial erosion which is relevant for the preservation of landforms during glaciations specifically pre glacial landforms may be eroded although they are initially protected by cold based ice when the ice configuration promotes significant basal shear stress glacial erosion at the edge of a plateau like landscape in contrast pre glacial landforms may be preserved irrespective of the ice being warm based when low gradients in the ice surface act to limit basal shear stress

the univariant curve liquid forsterite anorthite diopside in the system cmas at 1 bar solid solutions and melt structure one atmosphere liquid present experiments were carried out in the cmas system using an ordinary quench furnace apparatus the runs including reversal and duplicate experiments describe the univariant curve l fo an di between the invariant points q l fo an di sp and f l fo an di oen located respectively at 1245 1 c and 1244 1 c the thermal divide on this curve m3 l fo an di is located at 1275 1 c and plots well within the silica saturated field in agreement with longhi s 1987 experiments along the univariant curve l fo an di liquid composition evolves away from the thermal divide either toward invariant points q or f and pierces the silica saturation plane i e the join di an en in the silica saturated field in this compositional range the al solubility in clinopyroxene changes drastically from one side of the thermal divide to the other with great increase of al solubility in the silica undersaturated field four endmembers must be used to describe the complex solid solution of anorthite caal2si2o8 camgsi3o8 mgal2si2o8 and si4o8 the last two of these are present only within the silica saturated field unlike clinopyroxene the mg content of anorthite is insensitive to the thermal barrier but is only sensitive to silica saturation plane olivine composition can be described by a binary solid solution of forsterite and monticellite with no ca in the m2 site as with anorthite olivine compositions exhibit a marked change with crossing of the silica saturation plane the above features imply that the solubility of minor elements in crystalline phases al in clinopyroxene ca in olivine and mg in anorthite selectively respond to only one or another of these particular plane results have many important consequences one is the likelihood of changes in melt speciation depending on position with respect to the thermal divide and the silica saturation plane

climate related variations in atmospheric sb and tl in the epica dome c ice east antarctica during the past 800 000 years 1 a record of antimony sb and thallium tl from the european project for ice coring in antarctica epica dome c antarctic ice core provides the characteristics of climate related natural changes in concentrations and fluxes of these toxic elements over the time period back to marine isotope stage 20 2 800 kyr b p a strong variability in concentrations and fluxes are observed for both elements with considerably higher values during glacial maxima and lower values during intermediate and warm periods rock and soil dust accounts for on average 58 of sb and 76 of tl in ice during glacial maxima this contribution remains significant during warm periods accounting for 21 for sb and 27 for tl the contribution from volcanoes appears to be very important particularly for tl when climatic conditions become warmer with an estimated volcanic contribution of 72 for tl during interglacials the sea salt contribution is significant for sb particularly during intermediate climatic periods with an average contribution of 17 this sea salt contribution is most likely caused by greater production of sea salt from highly saline frost flowers and relatively more efficient transport of sb enriched sea ice salt from source areas on the east antarctic plateau our ice core data along with snow data recently reported from the antarctic snow layers at dome fuji shows that the present day sb flux 6 6 ng m2 yr is approximately double the highest natural level 2 8 ng m2 yr during glacial maxima throughout the last successive eight glacial interglacial cycles this result indicates that human activity has induced the greatest perturbation of the atmospheric cycle of sb ever experienced over a period of 800 kyr in the most remote area on earth

simulating the sea level imprint on marine oxygen isotope records during the middle miocene using an ice sheet climate model 1 oxygen isotopic ratios are implemented in an ice sheet climate model in order to directly compare the modeled isotopic ratio of the seawater to the high resolution isotopic records from deep sea sediment cores in the middle miocene the isotopic depletion resulting from the modeled ice sheet expansion explains the mean oxygen isotope step found in deep sea sedimentary records of 0 5 approximately 85 of the modeled increase in the isotopic composition of seawater is caused by an increase in ice volume the remainder is due to a stronger depletion in oxygen isotopes in the large ice sheet furthermore we also investigated the relation between sea level or global ice volume and the isotopic composition of seawater our experiments confirm the validity of the relation of approximately 1 enrichment per 100 m sea level lowering we further show that this relationship is r estricted by the mean ocean depth and the assumed oxygen isotopic composition of the ice sheet small deviations 10 from this general relationship occur depending on the size and the mean isotopic content of the ice sheet large continental ice sheets are more depleted in heavy oxygen isotopes and therefore reach a slightly higher ratio in contrast small ice sheets have a less depleted isotopic composition and correspondingly have a smaller effect on the isotopic composition of the ocean

fractured hydrothermal dolomite reservoirs in the devonian dundee formation of the central michigan basin the middle devonian dundee formation is the most prolific oil producing unit in the michigan basin with more than 375 million bbl of oil produced to date reservoir types in the dundee formation can be fracture controlled or facies controlled and each type may have been diagenetically modified although fracture controlled reservoirs produce more oil than facies controlled reservoirs little is known about the process by which they were formed and diagenetically modified in parts of the dundee preexisting sedimentary fabrics have been strongly overprinted by medium to coarse grained dolomite dolomitized intervals contain planar and saddle dolomite with minor calcite anhydrite pyrite and uncommon fluorite fluid inclusion analyses of two phase aqueous inclusions in dolomite and calcite suggest that some water rock interaction in these rocks occurred at temperatures as high as 120 150c in the presence of dense na ca mg cl brines these data in conjunction with published organic maturity data and burial reconstructions are not easily explained by a long term burial model and have important implications for the thermal history of the michigan basin the data are best explained by a model involving short duration transport of fluids and heat from deeper parts of the basin along major fault and fracture zones connected to structures in the precambrian basement these data give new insight into the hydrothermal processes responsible for the formation of these reservoirs

the effects of feo on the system cmas at low pressure and implications for basalt crystallization processes the common occurrence of olivine clinopyroxene and plagioclase in natural basalts may suggest that crystallization of these phases exerts important controls on the evolution of natural basalts at low pressure in order to understand the effects of such an assemblage on the evolution of basalt an experimental study of the divariant assemblage 1 an cpx ol in the system cmas feo was undertaken at 1 bar and under very reducing conditions experiments have been performed along three isothernal sections detailed electron microprobe data have been collected on all the coexisting phases combining these data with available data in the system cmas the compositions of all the coexisting phases have been described as functions of temperature and cao content in the melt by applying a multiple linear regression method this allows a quantitative characterization of the divariant assemblage 1 an epx ol in the system cmas feo from 1275 c to 1160 c with liquid compositions ranging from mg 1 to mg 0 28 knowing the composition temperature relationships the basic t x configuration of the assemblage 1 an cpx ol has been analysed and mass balance calculations have been performed to examine the feo effect on different crystallization processes addition of feo to the system cmas transforms the thermal divide in the assemblage 1 an cpx ol to a thermal ridge and shifts the spine of the thermal ridge towards sio2 poor compositions with decreasing temperature this indicates that tholeiitic basalts can be relatively silica poor and evolve towards slightly more silica poor compositions with increasing feo content pigeonite replaces ortheonstatite as a crystallizing phase along the silica rich boundary of the assemblage 1 an cpx ol in some iron and silica rich composition olivine possibly terminates its crystallization or even starts resorption prior to pigeonite precipitation this suppresses silica enrichment in the melt crystallization paths of the assemblage 1 an cpx ol are determined by the detailed t x relations of the thermal ridge with the melt evolving away from the spine the liquid evolution trend depends strongly on the initial compositions a tholeiitic liquid can follow a moderate silica enrichment path at the same very reducing condition of there is a high modal proportion of olivine a fenner mechanism therefore is at work at the same place as a bowen mechanism

experimental constraints on the evolution of transitional and mildly alkalic basalts crystallization of spinel abstract melting experiments on a mildly alkalic basaltic rock show that the spinel field penetrates slightly into the transitional volume of the natural basalt phase diagram at one atmosphere pressure and the fayalite magnetite quartz oxygen buffer the examined sample contains 22 5 wt al2o3 and crystallized spinel as the liquidus phase at 1290 11 c followed by plagioclase at 1261 10 c olivine at 1175 5 c and magnetite at 1145 5 c the amount of crystallizing spinel is about 4 wt and relatively constant throughout the melting interval compositionally the spinel is dominatly pleonaste with minor components of magnetite and ulvospinel in the solid solution and shows a marked rise in ti fe2 and fe3 with falling temperature reflecting the coexisting liquid the distribution of fe2 and mg between olivine and liquid defines a kdfe mg ol liq of 0 30 0 02 similarly calculated distribution of fe2 and mg between spinel and liquid gives kdfe mg p liq of 0 52 0 03 in pseudoternary projections of the basalt system the liquids reach pseudounivariant spinel plagioclase and olivine crystallization near the thermal divide with about 64 liquid remaining and slightly hypersthene normative compositions the position of the spinel saturated cotectic confirms that low pressure spinel crystallization is unlikely in most oceanic basalts a survey of high pressure mantle assemblage equilibria shows that oceanic mildly alkalic and transitional basaltic glasses plot significantly away from the low variance multiply saturated cotectics representing likely mantle melting therefore these types of oceanic basalts must reflect extensive olivine and plagioclase fractionation subsequently to separation from their mantle sources and prior to augite saturation at relatively low pressures

prediction of plagioclase melt equilibria in anhydrous silicate melts at 1 atm many models for plagioclase melt equilibria have been proposed over the past 30 years but the focus is increasingly on the effects of water content and pressure however many geological and petrological applications concern low pressure and low water systems such as the differentiation of large terrestrial basaltic magma chambers and lunar and asteroidal magmatism there is therefore a justified need to quantify the influence of anhydrous liquid composition on the composition of equilibrium plagioclase at 1 atm with this in mind a database of over 500 experimentally determined plagioclase liquid pairs has been created the selected low pressure anhydrous experiments include both natural and synthetic liquids whose compositions range from basalt to rhyolite four equations are proposed derived from this data the first is based on a thermodynamically inspired formalism explicitly integrating the effect of temperature this equation uses free energies and activities of crystalline anorthite available from the literature for the activity of anorthite in the liquid phase it is found that current models of the activity of individual oxides are insufficient to account for the experimental results we have therefore derived an empirical expression for the variation of anorthite activity in the liquid as a function of melt composition based upon inversion of the experimental data using this expression allows the calculation of plagioclase composition with a relative error less than 10 however in light of the fact that temperature is not necessarily known for many petrological applications an alternative set of t independent equations is also proposed for this entirely empirical approach the database has been divided into three compositional groups treated independently for regression purposes mafic ultramafic alkali rich mafic ultramafic and intermediate felsic this separation into distinct subgroups was found to be necessary to maintain errors below acceptable limits but results across group boundaries were found to be comparable overall 50 of plagioclase compositions are predicted to within 2 of the experimentally derived value and 90 to within 5 representing a significant improvement over existing models

habitats abundance patterns and isotopic signals of morphotypes of the planktonic foraminifer globigerinoides ruber d orbigny in the eastern mediterranean sea since the marine isotopic stage 12 article i nfo the chemical composition of shells of the planktonic foraminifer globigerinoides ruber white is frequently used to determine past sea surface conditions recently it has been shown that arbitrarily defined morphotypes within this species exhibit different chemical and isotopic signatures here we investigate the occurrence through time and in space of morphological types of g ruber white in late quaternary and holocene sediments of the central and the eastern mediterranean sea in 115 samples representing two distinct time intervals mis 1 2 and mis 9 12 at odp site 964 and the piston core geotu sl96 we have defined three morphological types within this species and determined their relative abundances and stable isotopic composition a quantitative analysis of morphological variation within g ruber white in four samples revealed that the subjectively defined morphotypes occupy separate segments of a continuous and homogenous morphospace we further show that the abundance of the morphotypes changes significantly between glacials and interglacials and that the three morphotypes of g ruber show significant offsets in their stable isotopic composition these offsets are consistent within glacial and interglacial stages but their sign is systematically reversed between the two sites since the isotopic shifts among the three g ruber morphotypes are systematic and often exceed 1 their understanding is essential for the interpretation of all g ruber based proxy records for the paleoceanographic development of the mediterranean during the late

timing and significance of maximum and minimum equatorial insolation variations in summer insolation at high northern latitudes on a timescale of 100 ka are very small thus a common belief is that the pronounced 100 ka glacial cycles are not directly linked to the very weak 100 ka insolation periodicity here we show analytically and numerically that the annual maximum and minimum of daily equatorial insolation has pronounced eccentricity periodicities with timescales of 400 ka and 100 ka as well as a pronounced half precession periodicity with timescale of 11 ka the timing of the maximum and minimum annual equatorial insolation may change around the equinoxes solstices alternating between the vernal and autumnal equinoxes summer and winter solstices where the time of the maximum minimum equatorial insolation may occur up to more than 1 month from the equinoxes solstices we also show that when considering the mean insolation of periods larger than 1 d the 11 ka periodicity becomes less dominant and it vanishes when the averaging period is half a year for the later case the maximum minimum may occur for any day in the annual cycle the maximum equatorial insolation may alter the timing and amplitude of the maximum surface temperature of the summer hemisphere and in this way may drastically affect the hadley circulation changes in hadley circulation affect the heat and moisture transport from low to high latitudes affecting the buildup of the high latitude northern hemisphere ice sheets

an updated astronomical timescale for the plio pleistocene deposits from south china sea and new insights into asian monsoon evolution abstract here we present an improved astronomical timescale since 5 ma as recorded in the odp site 1143 in the southern south china sea using a recently published asian summer monsoon record hematite to goethite content ratio hm gt and a parallel benthic 18o record correlation of the benthic 18o record to the stack of 57 globally distributed benthic 18o records lr04 stack and the hm gt curve to the 65 n summer insolation curve is a particularly useful approach to obtain refined timescales hence it constitutes the basis for our effort our proposed modifications result in a more accurate and robust chronology than the existing astronomical timescale for the odp site 1143 this updated timescale further enables a detailed study of the orbital variability of low latitude asian summer monsoon throughout the plio pleistocene comparison of the hm gt record with the 18o record from the same core reveals that the oscillations of low latitude asian summer monsoon over orbital scales differed considerably from the glacial interglacial climate cycles the popular view that summer monsoon intensifies during interglacial stages and weakens during glacial stages appears to be too simplistic for low latitude asia in low latitude asia some strong summer monsoon intervals appear to have also occurred during glacial stages in addition to their increased occurrence during interglacial stages vice versa some notably weak summer monsoon intervals have also occurred during interglacial stages next to their anticipated occurrence during glacial stages the well known mid pleistocene transition mpt is only identified in the benthic 18o record but not in the hm gt record from the same core this suggests that the mpt may be a feature of high and middle latitude climates possibly determined by high latitude ice sheet dynamics for low latitude monsoonal climate its orbital scale variations respond more directly to insolation and are little influenced by high latitude processes thus the mpt is likely not recorded in addition the hm gt record suggests that low latitude asian summer monsoon intensity has a long term decreasing trend since 2 8 ma with increased oscillation amplitude this long term variability is presumably linked to the northern hemisphere glaciation since then

geology of the devonian dundee reservoir west branch field michigan 1 west branch field located near the center of the michigan basin is a low relief asymmetric northwest southeast trending anticline since 1934 the dundee reservoir middle devonian dundee and rogers city limestones has produced more than 12 million bbl 2 million m 3 of oil from this field dundee sediments were deposited on a carbonate ramp that dipped gently to the northwest core studies and log correlations show that the reservoir is dominated by normal marine somewhat lenticular beds of skeletal peloidal grainstones and packstones crinoids are very abundant comprising nearly 100 of the grains in some intervals the uppermost dundee consists of micritic carbonates with a restricted faunal assemblage the dundee rogers city contact is a disconformity that ppears to be a pyritized extensively bioeroded hardground the overlying rogers city limestone is a dark nodular wackestone with rare packstone interbeds trace amounts of dolomite are common throughout the field however pervasive dolomite is common only in the top 10 15 ft 3 4 5 m of the dundee this dolomite generally has high porosity 5 15 but very low permeability 0 1 0 md primary interparticle porosity in limestones accounts for most of the reservoir porosity although previous workers have concluded that fracture controlled dolomites are responsible for porosity and permeability in this field we conclude that such dolomites are not important we also conclude that at west branch field there is no evidence for reefal growth over a pre existing fold as has been reported in other dundee rogers city reservoirs

crystallization kinetics in the system camgsi 2 o 6 caal 2 si 2 o 8 the delay in nucleation of diopside and anorthite the nucleation of diopside and anorthite is always delayed under supercooled conditions the delay in nucleation decreases with increasing degree of supercooling or increasing cooling rate with further increase in the degree of supercooling or the cooling rate the delay in anorthite nucleation increases for a given degree of supercooling the region of random nucleation of diopside is wider than that of anorthite steady state nucleation occurs for diopside and transient nucleation for anorthite modified journal abstract

a paleobathymetric transition during the mid pliocene warm period ostracode evidence from japan abstract we reconstructed a paleoenvironment reflecting the mid pliocene warm period mpwp off the coast of southwest japan on the basis of high resolution statistical analysis of fossil ostracodes a total of 107 ostracode taxa were obtained from the upper part of the mid pliocene sadowara formation 3 25 3 12 ma shintomi town miyazaki prefecture southwest japan most taxa such as acanthocythereis munechikai argilloecia spp bradleya albatrossia cytheropteron mediotumidum and krithe spp are extant species distributed in the lower sublittoral to upper bathyal zones these species have been reported in the pacific coast of southwest japan the tsushima strait and off the coast of china we estimated the paleobathymetry of the sadowara formation using q mode factor analysis the results of the factor analysis showed that a regression occurred during deposition of the upper part of the sadowara formation the lower part of the studied sequence was deposited at water depths greater than 300 m the water depth decreased upward and reached around 250 m in the upper parts of the formation the timing of the regression corresponds with the peak of the marine isotope stage km2 the large regression estimated to have occurred during deposition of the upper part of the sadowara formation could have been related to global cooling events during the mpwp

an integrated field and numerical modelling study of controls on late quaternary fluvial landscape development tabernas southeast spain the variability of quaternary landforms preserved in the tabernas basin of southeast se spain raises numerous questions concerning the roles of external forcing mechanisms e g tectonics and or climate and internal landscape properties e g lithological controls in the evolution of the basin wide fluvial system over late quaternary timescales in this study we apply the fluver2 numerical model to investigate the significance of these landscape controls upon patterns of landscape evolution we highlight the complications of generating realistic input datasets for use in the modelling of long term landscape evolution e g discharge and runoff datasets model outputs are compared to extensive field mapping of fluvial terraces their sedimentary architecture and optically stimulated luminescence dating results of the terraces the results demonstrate the significance of non linear rates of flexural tectonic uplift towards the west of the tabernas basin which have controlled base levels throughout the quaternary and promoted the formation of a series of diverging fluvial terraces our numerical model results further highlight the importance of climate cycles upon river terrace formation basin wide aggradation events were modelled during the transition from marine isotope stage mis 6 to 5 and the last glacial maximum lgm as supported by field evidence this aggradational pattern supports the regional hypothesis of terrace formation during global glacial cycles and cold to warm stage transitions and supports the use of sea surface temperature climate proxy data in the modelling exercise the availability of sediments derived from the surrounding hillslopes and adjacent alluvial fans explains the generation of substantial terrace aggradations copyright 2015 john wiley sons ltd

quaternary paleoceanography of the central arctic based on integrated ocean drilling program arctic coring expedition 302 foraminiferal assemblages the integrated ocean drilling program iodp arctic coring expedition acex hole 4c from the lomonosov ridge in the central arctic ocean recovered a continuous 18 m record of quaternary foraminifera yielding evidence for seasonally ice free interglacials during the matuyama progressive development of large glacials during the mid pleistocene transition mpt 1 2 0 9 ma and the onset of high amplitude 100 ka orbital cycles 500 ka foraminiferal preservation in sediments from the arctic is influenced by primary sea ice organic input and other environmental conditions and secondary factors syndepositional long term pore water dissolution taking these into account the acex 4c record shows distinct maxima in agglutinated foraminiferal abundance corresponding to several interglacials and deglacials between marine isotope stages mis 13 37 and although less precise dating is available for older sediments these trends appear to continue through the matuyama the mpt is characterized by nearly barren intervals during major glacials mis 12 16 and 22 24 and faunal turnover mis 12 24 abundant calcareous planktonic mainly neogloboquadrina pachyderma sin and benthic foraminifers occur mainly in interglacial intervals during the brunhes and very rarely in the matuyama a distinct faunal transition from calcareous to agglutinated foraminifers 200 300 ka in acex 4c is comparable to that found in arctic sediments from the lomonosov alpha and northwind ridges and the morris jesup rise down core disappearance of calcareous taxa is probably related to either reduced sea ice cover prior to the last few 100 ka cycles pore water dissolution or both

petrography and environmental controls on the formation of phanerozoic marine carbonate hardgrounds early marine seafloor lithification of carbonate sediments leads to the formation of hardgrounds and is known from rocks as old as the proterozoic hardground surfaces however are more commonly recorded in the phanerozoic sedimentological archive while ecological studies of hardground biota abound the environmental and physico chemical parameters leading to the development of seafloor lithification remain in many cases poorly understood and documented this paper reviews published evidence on the petrography mineralogy and geochemistry of phanerozoic carbonate hardgrounds within a process oriented context of their environmental controls hardgrounds typically develop in warm and shallow agitated tropical waters that are saturated with respect to caco3 but are also reported from hemi pelagic to bathyal realms and from cool water temperate settings a range of early marine cement types are documented from present day hardgrounds whereas preserved cement fabrics and related mineralogies are less diverse in early phanerozoic hardgrounds carbonate hardgrounds are widespread during calcite sea periods e g ordovician and cretaceous as opposed to some preservation bias ancient aragonite seas e g permian and triassic obviously the relation between seawater chemistry and hardground abundance and attributes is not an easy one here the concept of aragonite versus calcite seas serves as a first order template for the sake of a structured discussion whereas modern aragonite mode oceans document a significant diversity in spatial and bathymetric seawater properties this spatio temporal complexity is perhaps reflected in the scarce record of calcite sea hardgrounds from the devonian or paleogene rock record contrasted by the abundance in aragonite holocene and recent seas holocene hardgrounds allow for the direct assessment of rates of and reasons for early subaquatic lithification and in most cases escaped subsequent non marine diagenetic overprint conversely studies of ancient hardgrounds are often biased by early biological and mechanical erosion the degree of diagenetic overprint and tectonic to orogenic processes the formation distribution and physical properties of hardgrounds depend on the global climatic context greenhouse icehouse modes on sea level changes on ocean stratification on the spatial extent of epicontinental seas and carbonate depositional environments and on the spatially different mineralogies and rates of carbonate production the fabrics and mineralogies of early hardgrounds cement seem to substantially hinge on variations in atmospheric co2 thus the application of lessons from modern to ancient hardground case examples is not straightforward a holistic model explaining the full variability of controls on submarine hardground formation and their cement petrography throughout the phanerozoic is as yet lacking a more critical view on secular changes in hardground formation patterns is clearly needed future work should rely on the combination of sedimentological stratigraphic palaeoecological petrographic and geochemical approaches specific emphasis should be given to time intervals triassic carboniferous cambrian etc where the bulk of reported case studies is at best scarce

plio pleistocene increase of erosion rates in mountain belts in response to climate change here we review an ensemble of observations that point towards a global increase of erosion rates in regions of elevated mountain belts or otherwise high relief since the onset of northern hemisphere glaciation about 2 3 ma during that period of earth s history atmospheric co2 concentrations may have dropped and global climate cooled and evolved towards high amplitude oscillating conditions that are associated with the waxing and waning of continental ice sheets in the northern hemisphere we argue for a correlation between climate change and increased erosion rates and relief production which we attribute to some combination of the observed cooling onset of glaciation and climatic oscillation at orbital timescales in our view glacial erosion played a major role and is driven by the global cooling furthermore analyses of the sedimentary fluxes of many mountain belts show peaks of erosion during the transitions between glacial and inter glacial periods suggesting that the variable climatic conditions have also played a role

millennial scale climate variability in the subpolar north atlantic ocean during the late pliocene 1 large amplitude millennial scale climate oscillations have been identified in late pleistocene climate archives from around the world these oscillations appear to be of larger amplitude during times of enlarged ice sheets this observation suggests the existence of a relationship between large amplitude millennial variations in climate and extreme glacial conditions and therefore that the emergence of millennial scale climate variability may be linked to the pliocene intensification of northern hemisphere glaciation inhg here we test this hypothesis using new late pliocene high resolution 400 year records of ice rafted debris deposition and stable isotopes in planktic foraminiferal calcite globigerinoides ruber generated from integrated ocean drilling program site u1313 in the subpolar north atlantic a reoccupation of the classic deep sea drilling project site 607 our records span marine oxygen isotope stages mis 103 95 2600 to 2400 ka the first interval during inhg 3 5 to 2 5 ma in which large amplitude glacial interglacial cycles and inferred sea level changes occur our records reveal small amplitude variability at periodicities of 1 8 to 6 2 kyr that prevails regardless of inter glacial state with no significant amplification during the glacials mis 100 98 and 96 these findings imply that the threshold for the amplification of such variability to the proportions seen in the marine archive of the last glacial was not crossed during the late pliocene and in view of all available data likely not until the mid pleistocene transition

mg in plagioclase experimental calibration of a new geothermometer and diffusion coefficients abstract the temperature sensitive exchange of mg between plagioclase pl and clinopyroxene cpx has been studied experimentally accounting for different anorthite contents in plagioclase x an and various silica activities a sio 2 in the system the partitioning of mg between plagioclase and clinopyroxene was determined over a temperature range of 1100 1200 c using plagioclase single crystals of different compositions x an 0 5 0 8 surrounded by different clinopyroxene bearing matrix powders to account for different silica activities from 0 55 to 1 0 the experimental design also allows the diffusivity d mg pl of mg in plagioclase under these conditions to be determined both k mg pl cpx defined as k mg pl cpx c mg pl c mg cpx and d mg pl decrease with temperature and increase with a sio 2 isothermal data for different x an in plagioclase show a linear increase of ln k mg pl cpx with increasing x an but d mg pl appears to be insensitive to x an the partitioning data allow a new geothermometer to be calibrated which may be widely applicable to terrestrial and extraterrestrial rocks where plagioclase and clinopyroxene coexist t k 9219 2034 x an ln k mg pl cpx 1 6 ln a sio 2 application of this geothermometer to experimental data from this study reproduces the experimental temperatures within 20 c diffusion of mg in plagioclase is described by d mg pl m 2 s 1 1 25 10 4 m 2 s 1 exp 320 924 j mol 1 rt a sio 2 2 6

devonian dundee formation crystal field michigan basin recovery of bypassed oil through horizontal drilling carbonate reservoirs of the devonian dundee formation represent the most productive interval in the michigan basin yet have suffered widespread abandonment due to improper early reservoir management and completion practices dundee carbonate reservoirs deposited in marginal marine and shallow marine environments have produced over 351 mmbbl oil from 137 fields most of which were discovered in the 1930s and 1940s initial potentials for many dundee wells ranged from 2000 to 9000 bbl day presumably due to high permeability fractures and solution enhanced porosity in some areas and excellent primary interparticle porosity in other areas crystal field discovered in 1935 at a depth of less than 3500 ft 1060 m was aggressively developed and produced at high rates causing widespread water coning such that 95 of the field was drilled and abandoned in less than 5 yr leaving considerable interwell reserves in the ground no cores or wireline logs existed for the field prior to 1995 when the field became the subject of a multiyear study aimed at determining the feasibility of employing horizontal drilling to recover bypassed reserves a vertical test portion of the tow 1 3 horizontal well located in a structurally elevated portion of the field cored and logged the entire reservoir interval yielding crucial new information on the basis of relevant data a horizontal leg was drilled resulting in an excellent producer with estimated recoverable reserves of 200 000 bbl two subsequent horizontal tests with poor results were drilled in downdip locations and oriented perpendicular to the tow well suggesting the importance of both structural position and azimuth selective use of horizontal drilling is considered an appropriate cost effective means for recovering bypassed reserves in dundee fields where sufficient geologic data exist to adequately characterize the reservoir and oil occurrence for some fields this may require new coring and logging operations

abrupt termination of marine isotope stage 16 termination vii at 631 5 ka in santa barbara basin california the marine isotope stage 16 15 boundary termination vii is the first deglacial warming step of the late quaternary following the mid pleistocene transition mpt when 41 kyr climatic cycles shifted to strong 100 kyr cycles the detailed structure of this important climatic event has remained unknown until now core mv0508 19jpc from santa barbara basin california contains a decadal scale climatic and geochemical sediment record of 4000 years duration that includes the early part of this deglacial episode this record reveals that the climatic shift during the early deglacial occurred rapidly 700 years in a progression of three abrupt warming steps the onset of marine isotope stage mis 15 was remarkably abrupt with 4 5 c sea surface warming in 50 years the deglacial sequence contains the well dated lava creek tephra 631 3 4 ka from yellowstone caldera used to date the onset of termination vii at 631 5 ka the late mis 16 and early mis 15 interval exhibits multiple decadal scale negative excursions in 13c of planktic foraminifera likely the result of repeated discharges of methane from methane hydrates associated with both ocean warming and low sea level a warm interstadial that interrupts late mis 16 is marked by elevated concentrations of redox sensitive elements indicating sulfidic oxygen deficient bottom and pore waters and elevated concentrations of total organic carbon and cd reflecting increased surface productivity unlike younger sediments on the california margin these indicators of increased productivity and low dissolved oxygen do not consistently correspond with each other or with preserved laminations possibly reflecting instability of a still evolving ocean atmosphere system following the mpt

experimental constraints on the low pressure evolution of transitional and mildly alkalic basalts multisaturated liquids and coexisting augites basaltic liquids saturated at one atmosphere in augite olivine and plagioclase show a strong linear trend in pseudo quaternary projections from nepheline to slightly quartz normative compositions coexisting augites show a corresponding variation from slightly nepheline to hypersthene normative compositions consequently alkalic and mildly alkalic liquids coexist with nepheline normative augites tholeiitic liquids coexist with hypersthene normative augites and transitional liquids coexist with augites compositionally intermediate between those crystallizing in alkalic and tholeciitic melts the variation in augite composition is due to a decrease in wollastonite and non quadrilateral components going from mildly alkalic to transitional and tholeiitic augites the observed liquid and augite trends lack correlations between normative composition and crstallization temperature this is an artifact of plotting unrelated liquid lines of descent individual liquid lines of descent in contrast display good correlation between normative composition and crystllization temperature which for both liquids and coexisting augites are highly oblique to nearly perpendicular to the general trend because the composition of the first augite to appear on the liquidus varies as a function of the bulk system the location of the thermal divide shows corresponding variations as a consequence unifying cotectics and pseudo quaternary normative projections should not without specific experimental knowledge be used to address liquid lines of descent and common magmatic parentages

threshold behavior of millennial scale variability in deep water hydrography inferred from a 1 1 ma long record of sediment provenance at the southern gardar drift 1 integrated ocean drilling program iodp site u1314 of the north atlantic is a critical sedimentary archive record of subpolar deep water from the southern gardar drift for which we derived an age model of orbital resolution for the last 1 8 ma this chronology combined with high resolution cm scale x ray fluorescence core scanning measurements of major elements allows tracking changes in terrigenous provenance during the last 1 1 ma low potassium to titanium k ti ratios reflect enhanced transport of basalt derived titanomagnetites during warm climate intervals while high k ti ratios indicate a dominance of acidic sediment sources typical for glacial and stadial events changes in k ti and magnetic concentration at site 1314 are coeval with fluctuations in smectite content and grain size data from nearby piston cores suggesting that the provenance changes are mainly controlled by variable flow of the iceland scotland overflow water an important branch of north atlantic deep water furthermore k ti variations on orbital time scales show a striking similarity to the deep sea 13c record from odp site 607 pervasive features of the k ti time series during and after the mid pleistocene transition are suborbital changes similar to dansgaard oeschger and bond oscillations that appear to be strongly amplified during ice growth phases when global benthic 18o was within the range of 4 1 4 6 per mil the strong increase in variability of sediment provenance and subsequently deep hydrography at benthic 18o values below 4 1 suggests that the extent of glaciations and therefore sea level corresponding to this value constitutes an important physical threshold that was persistent at least for the last 1 1 ma

first records of winter sea ice concentration in the southwest pacific sector of the southern ocean we use a generalized additive model gam to provide the first winter sea ice concentration record from two cores located within the southwest pacific sector of the southern ocean to compliment the application of gam a time series analysis on satellite records of sea ice concentration data was used to extend the standard 13 25 year time series used for paleoceanography after comparing gam sea ice estimates with previously published paleo sea ice data we then focus on a new paleo winter sea ice record for marine sediment core e27 23 59 37 1 s 155 14 3 e allowing us to provide a more comprehensive view of winter sea ice dynamics for the southwest pacific ocean the paleo winter sea ice concentration estimates provide the first suggestion that winter sea ice within the southwestern pacific might have expanded during the antarctic cold reversal throughout the holocene core e27 23 documents millennial scale variability in paleo winter sea ice coverage within the southwest pacific holocene winter sea ice expansion may have resulted from the laurentide ice sheet deglaciation increased intensity of the westerly winds as well as a northern migration of the subtropical and or sub antarctic fronts brief consideration is given to the development of a paleo summer sea ice proxy we conclude that there is no evidence that summer sea ice ever existed at core sites so136 111 and e27 23 over the last 220 and 52 000 years respectively

pleistocene equatorial pacific dynamics inferred from the zonal asymmetry in sedimentary nitrogen isotopes 1 there is little agreement among models in predicting the average state of the tropical pacific when subjected to enhanced greenhouse gas forcing this uncertainty emphasizes the importance of reconstructing past variability in tropical pacific climate through episodes of significant and estimable radiative forcing thus far efforts along these lines have concentrated primarily on inferences of sea surface temperature variability from deep sea sediments here we offer a different view of the equatorial pacific over the past 1 2 million years myr before and after the mid pleistocene shift in the structure of ice ages the zonal gradient in the nitrogen isotopic composition of sediment across the equatorial pacific reflects nutrient delivery to the surface and by extension ocean dynamical properties over the last 1 2 myr the variability of eastern equatorial pacific nutrient upwelling inferred from relative nitrate utilization was highly correlated with local seasonal insolation by contrast nitrate utilization was insensitive to the 100 000 year cycle that dominated many other aspects of the pleistocene ice ages including greenhouse gas concentrations a strong linear relationship between relative nitrate utilization and seasonal insolation over the past 1 million years suggests a predictable response of one primary determinant of tropical pacific climate change

correlation of the subsurface lower and middle devonian of the lake erie region the completion of 6 detailed cross sections using the gamma ray logs of 94 closely spaced wells has provided new correlations and confirmed some earlier correlations of the lower and middle devonian strata of the lake erie region these sections connect western new york northwestern pennsylvania northern central and northwestern ohio southwestern ontario and southeastern michigan the lower devonian bois blanc limestone of western new york is continuous with the type bois blanc of northern michigan via southwestern ontario it has been traced southwestward across northern ohio and southward into the lower part of the type columbus limestone in central ohio the edgecliff clarence nedrow and moorehouse members of the overlying middle devonian onondaga limestone of western new york correlate with the upper columbus limestone of ohio the seneca member of the onondaga is equivalent to the overlying delaware limestone the amherstburg and lucas formations of the detroit river group of michigan and ontario can be traced southward across lake erie into the lower and middle parts of the upper columbus of ohio the amherstburg correlates with the edgecliff clarence nedrow and lower moorehouse members of the new york onondaga the lucas correlates with the middle part of the moorehouse member the dundee limestone of northwestern ohio michigan and ontario is an equivalent of the upper moorehouse and seneca members of the new york onondaga limestone it is not coterminous with the delaware of ohio as the base of the dundee is significantly older than the base of the delaware these correlations have been strengthened by tracing the stratigraphic positions of four different ash beds through the upper part of the carbonate sequence three of these ash beds are parts of the type tioga ash bed in the subsurface of northern pennsylvania a major regional unconformity separates the lower and middle devonian carbonate sequence from the overlying middle devonian terrigenous one the delaware and dundee limestones cannot be correlated with any part of the marcellus formation of the new york hamilton group in western new york the cherry valley limestone member of the marcellus formation rests directly and unconformably upon the onondaga in northwestern pennsylvania and northeastern ohio the union springs shale reappears between the cherry valley and the onondaga beneath central lake erie the union springs cherry valley and oatka creek members of the marcellus merge into the bell shale rockport quarry limestone and arkona shale of ontario the arkona can be traced across lake erie into the plum brook and lower olentangy shales of ohio the lower part of the terrigenous sequence of the lake erie region consequently is marcellus in age not skaneateles the prout ohio and hungry hollow ontario limestones are homotaxial and correlate with the centerfield limestone of new york the rockport quarry arkona and hungry hollow can be traced into the silica shale of southeastern michigan and northwestern ohio the widder shale and ipperwash limestone of ontario merge into the tenmile creek dolomite of michigan and ohio

a hydroclimate regime shift around 270 ka in the western tropical pacific inferred from a late quaternary n alkane chain length record abstract the inert leaf wax deposited in deep sea sediment preserves clues of the past climate change in particular the n alkane distribution patterns characterized by the n alkane average chain length index acl provide useful information on the hydrological changes as longer chain alkanes are more frequently biosynthesized under relatively arid condition to prevent water loss our data from the western south china sea reveal the superimposition of a systematic regime shift in the regional mean precipitation at ca 420 270 ka on the glacial interglacial changes in the quaternary the dominance of shorter n alkane chain length between 420 ka and 270 ka is interpreted as overall wetter conditions during this period compared to the older or younger intervals a similar timing of hydrological regime shifts has also been observed in other paleoclimate records including major changes in productivity in the eastern pacific and pollen records from the western pacific we suggest that the changes in the regional mean hydroclimate states near 420 ka and 270 ka are most likely related to a regime change in the frequency and or intensity of the el nino southern oscillation with the overall wetter hydroclimate prior to 270 ka resulting in a more prevalent la nina like condition in the pacific

paired bedrock and boulder 10be concentrations resulting from early holocene ice retreat near jakobshavn isfjord western greenland we measured in situ cosmogenic 10 be in 16 bedrock and 14 boulder samples collected along a 40 km transect outside of and normal to the modern ice margin near sikuijuitsoq fjord in central west

plio pleistocene fossil record of large predators in iberia diversity home range and climatic change abstract we investigated the patterns of change in diversity and home range size structure of the latest miocene pleistocene iberian carnivores to recognize the tempo and mode of the major shifts and place them in the context of late cenozoic climatic changes the database consists of 36 selected and taxonomically revised faunal lists a general pattern of carnivore diversity from iberia shows three maxima in diversity that can be correlated with major global changes the first coincides with the glacial trend during pliocene starting at 2 7 2 6 ma with the onset of glacial cycles of 41 ka second maximum happened at the beginning of the middle pleistocene and can be correlated with the switch at 1 ma third maximum in diversity occurs at the end of middle pleistocene when the amplitude of interglacials shifted from cooler to warmer interglacials the most significant shifts in carnivora diversity and home range size patterns were linked to dispersal phases that were tracked by a renovation of the carnivore guild from the patterns in home range size structure it seems that some multifaceted and not always straight interactions exist between ecological and climatic change and shifts in home range size the onset of the holocene home range size structure in iberian carnivores traces back to a high diversity pulse at the end of the middle pleistocene

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

new insights on chinese cave δ18o records and their paleoclimatic significance abstract in the last two decades stalagmite oxygen isotope 18o records have been widely used to study the evolution of the paleomonsoon nevertheless interpreting cave 18o records in eastern monsoonal china as an indicator of east asian summer monsoon easm rainfall has been intensively debated this study provides new insights into chinese cave 18o records and their paleoclimatic significance based on recent research progress the following points are highlighted 1 chinese cave 18o records do not reflect changes in summer rainfall throughout the whole of eastern monsoonal china which is evident by comparing monitored summer rainfall amount in eastern china and an integrated chinese cave 18osyn proxy 2 chinese cave 18o records can document millennial scale easm events due to the sensitive response to large scale atmospheric circulation changes 3 during the early holocene before 7 ka a decoupled relationship between chinese cave 18o records and easm rainfall as represented by precipitation in north china is attributed to the reduction of rainfall in north china due to the influence of remnant melting ice sheets in the northern high latitude region 4 when the ice sheet boundary conditions were stable and ice sheets were small after 7 ka there is an indirect correlation between the chinese cave 18o and rainfall changes in north china 5 the first continuous speleothem 18o record spanning the entire holocene is synthesized for the core region of the indian summer monsoon ism domain comparison of this integrated ism proxy with chinese cave 18o records reveals that in china cave 18o is primarily a signal of changes in the tropical monsoon and related large scale circulation the coupled relationship between rainfall in north china and tropical monsoon ism rainfall is attributed to the response of downstream circulation to changes in circulation upstream while their decoupled relationship is due to the possible effects of northern high latitude ice sheets on reducing rainfall in north china 6 due to the imprecise definition of monsoon intensity we suggest that cave 18o can be used as an easm proxy if monsoon intensity is defined by changes in atmospheric circulation

ice sheet grounding and iceberg plow marks on the northern and central yermak plateau revealed by geophysical data abstract we present new evidence for a grounded ice sheet and subsequent erosion by large fields of coherent icebergs for the central and northern yermak plateau 80 6 n to 82 2 n sediment echosounder and swath bathymetry data were combined with seismic reflection profiles and reveal at least three different glacial events marked by erosional unconformities i an erosional unconformity was observed at 70 90 m below seafloor down to depths of more than 850 m present water depth extending to 82 n the erosional unconformity is overlain by an acoustically chaotic layer of 50 m thickness interpreted as a diamicton originating from a grounded ice sheet the erosional unconformity and the overlying diamicton can be correlated to the overconsolidated sediments found at odp site 910 at a sediment depth between 19 and 70 95 m the oldest sediments just above the overconsolidated sediments are of late early pleistocene age mis19 20 and provide a minimum age for the grounding event ii parallel to sub parallel mega scale lineations are observed on large parts of the plateau west and northeast of the sverdrup bank at water depths between 725 and 850 m these lineations are mainly oriented nne ssw and were quite likely formed by the keels of deep draft mega scale tabular icebergs entrapped in a coherent mass of icebergs and sea ice the lineations are of late middle pleistocene age iii smaller scale curvilinear plow marks were found in the southernmost part of our study area at water depths between 640 and 775 m these were possibly caused by single icebergs and are of late pleistocene age iceberg scours are also found on three basement heights on the yermak plateau these however cannot be assigned to specific events they might as well originate from additional glacial phases the western at 850 m water depth and eastern at 1000 1200 m water depth flanks of the yermak plateau are relatively featureless and indicate the maximum depth of a grounded ice sheet and of iceberg armadas probably entrapped in sea ice

the effect of cao on the partitioning behavior of ree y and sc between olivine and melt implications for basalt carbonate interaction processes abstract the partitioning of ree y and sc r3 between olivine and melt has been investigated experimentally during basalt carbonate interaction three synthetic basalts meltmg 72 meltmg 75 and meltmg 78 were doped with 0 10 and 20 wt caco3 and then equilibrated for 72 h at 1 atm 1 150 1 200 and 1 250 c and the qfm oxygen buffer the thermal decomposition of caco3 produced cao contents in the melt up to 22 wt regular relationships are found between the ionic radius and the partition coefficient dr3 showing typical near parabolic patterns dr3 is weakly dependent on temperature but decreases with increasing caco3 in the starting material e g dsc decreases from 0 20 to 0 13 from the point of view of the lattice strain theory dr3 is described in terms of the radius of the crystal site r0 the young modulus e due to the elastic response of that site to lattice strain caused by cation insertion and the strain free partition coefficient d 0 3 the value of r0 decreases as ca cations are accommodated into the more distorted m2 site of olivine via progressive ca fe substitutions this mechanism is accompanied by a higher proportion of mg cations entering into the smaller m1 site making the optimum ionic radius smaller and favoring the crystallization of more forsteritic olivines from decarbonated melts the enrichment of ca in the crystal lattice is also proportional to the number of si and ca cations available in the melt this causes e to be anticorrelated either with ca in olivine or the activity of cao in the melt r3 cations behave as network modifiers and during basalt carbonate interaction the increasing abundance of non bridging oxygens enhances the solubility of ree y and sc in the melt as a consequence d 0 3 is negatively correlated with the degree of melt depolymerization additionally the strain of the crystal lattice dominates the dr3 parabolic patterns and d 0 3 is strongly controlled by forsterite and aluminium concentrations in olivine the accommodation of ree y and sc in the crystal lattice requires maintenance of local charge balance by the generation of vacancies in accord with a paired substitution of r3 and a vacancy for mg in octahedral sites

middle and late pleistocene loess of the western ciscaucasia stratigraphy lithology and composition due to the high preservation of the loess series and the availability of coastal outcrop sections loess cover of western ciscaucasia has ample opportunities for spatial paleogeographical reconstructions for the middle and late pleistocene currently the level of knowledge on the structure and composition of the loess paleosol sequences of western ciscaucasia remains unequal the azov coast is studied in more detail in comparison with the inner part of the region the structure and composition of the loess paleosol sequences of different parts of western ciscaucasia the sea of azov coast and western macroslope of the stavropol upland for the middle and late pleistocene are compared comparison of the loess paleosol sequences key sections are based on investigations of litho and pedostratigraphy magnetic susceptibility grain size elemental and mineral composition and luminescence dating recent results of luminescence dating allowed correcting the structure of the mezin pedocomplex s1 it was found out that this pedocomplex includes three phases of soil formation s1ss1 s1ss2 s1ss3 which approximately correspond to the warm stages of marine isotope stage 5 mis 5 5a 5c 5e in all sections a clear trend towards an increase in the accumulation rates over the last three climatic macrocycles is observed the last interglacial glacial macrocycle miss 2 5 is characterized by the most significant increase in average accumulation rates which were 1 8 times higher compared to miss 6 7 and 2 3 times higher than during the miss 8 9 a likely reason for the regional increase in the average dust accumulation rate was the directional increase in climate aridity the patterns of the spatial distribution of the loess thickness and material composition indicate that the main source of aeolian dust is situated in the east we suppose that the main sources of dust are sand masses of the alluvial plains of lover volga terek kuma and kura rivers in the caspian lowland the lower don sandy province is reconstructed to be a secondary source dust is blown from the sandy terraces of the don and in the past from the don deltas during the period when the sea of azov dried up

orbital scale timing and mechanisms driving late pleistocene indo asian summer monsoons reinterpreting cave speleothem δ18o 1 southeast china cave 18o often interpreted as a pure east asian summer monsoon proxy lags maximum northern hemisphere summer insolation by 2 9 0 3 kyrs at the precession cycle the arabian sea summer monsoon stack lags by 8 1 kyr consistent with 13 other indian and east asian summer monsoon proxies from marine lake and terrestrial archives this 5 kyr phase difference cannot be attributed to age control inadequacies in the marine chronology it requires reconciliation in the context of proxy interpretation both of these lags are incompatible with a direct response to northern hemisphere summer insolation implicating additional forcing mechanisms analysis of heterodynes in the cave 18o spectrum demonstrates that variance contained in the arabian sea summer monsoon proxies also resides in the cave 18o record this variance is subtracted from the cave 18o record yielding a residual that is highly coherent and in phase with precession minima reflecting the impact of winter temperature change on cave 18o meteorological precipitation under cold conditions thus we argue that the timing of light cave 18o peaks cannot be interpreted as reflecting the timing of strong summer monsoons alone the 2 9 kyr precession band phase lag of cave 18o reflects the combined influence of summer monsoon forcing with a phase lag of 8 kyrs relative to precession minima and winter temperature forcing that is in phase with precession minima this interpretation is consistent with modern seasonality in the amount and isotopic composition of rainfall in southeast china

experimental investigation of the stability of clinopyroxene in mid ocean ridge basalts the role of cr and ca al abstract the change in the stability field of clinopyroxene in mid ocean ridge basalt morb as a function of pressure has been used widely as a geobarometer based on results from crystallization experiments using morb like compositions it has been suggested that morb differentiation occurs at relatively high pressures at ultraslow and slow spreading ridges however differentiation requires the loss of substantial heat and it is unclear how this is possible at elevated pressures to better understand the controls on the stability field of clinopyroxene in morb like compositions we report a series of experiments performed at 0 1 mpa in which the temperature of clinopyroxene saturation was determined in melts with variable cr ca al and f o 2 the results show that increased cr and ca al lead to an expansion of the clinopyroxene stability field incorporating these results into a new model of morb differentiation shows that realistic parental melt cr contents can increase the temperature at which clinopyroxene saturation occurs relative to assuming a cr free melt as is commonly the case likewise high ca al melts will saturate clinopyroxene earlier than low ca al melts and their crystallization may provide an explanation for high mg clinopyroxene in oceanic gabbros the newly calibrated geobarometer gives lower crystallization pressures for morb at the slow spreading swir than previous calibrations but still suggests relatively higher pressures of crystallization with decreasing spreading rate

the loess palaeosol sequence of datthausen sw germany characteristics chronology and implications for the use of the lohne soil as a marker soil abstract a new loess palaeosol sequence from the westernmost loess area along the upper danube river in sw germany is presented the profile datthausen comprises a sequence of middle pleniglacial mpg and upper pleniglacial upg palaeosols separated by a prominent erosional discontinuity the uppermost mpg palaeosol consists of two olive brown horizons showing morphological characteristics of the lohne soil that represents the uppermost mpg palaeosol in many loess palaeosol profiles in the humid loess regions of central europe sedimentological palaeopedological and micromorphological analyses combined with luminescence dating were carried out compared to the profiles nussloch and schwalbenberg ii in the rhine river region the profile datthausen shows more intense pedogenesis mainly due to its position in a depression and lower loess accumulation rates further the mpg upg transition at datthausen seems to date later in time likely matching greenland interstadial gis 4 and or gis 3 rather than gis 7 to gis 5 we conclude that the lohne soil is a reliable pedostratigraphic marker whereas its use as a chronometric marker sensu stricto which should have formed during one well defined phase of soil formation is impeded as it evolved during several interstadials its use as a chronometric marker sensu lato which may have formed over several phases of soil formation is impeded too as its chronological position in different loess palaeosol profiles may not be specific enough the differences in pedogenesis and chronology between the profiles nussloch and schwalbenberg ii on one side and the profile datthausen on the other side are attributed to site specific factors such as topography the influence of these factors on pedogenesis at the local scale may prevail over the general climatic regime controlling soil formation at the regional level therefore spatial diversity of palaeosols needs to be considered when matching loess palaeosol profiles with marine and ice core records for evaluating the impact of climate forcing on terrestrial palaeoenvironments

identifying and quantifying erosion beneath the deposits of long runout turbidity currents along their pathway variations between the geochemical compositions coccolith species compositions and the physical properties of turbidite muds and their underlying hemipelagites can be used to understand the erosive nature of sediment gravity flows large volume submarine landslides on the nw moroccan continental margin produce long runout turbidity currents capable of traversing hundreds to thousands of kilometres across the adjacent moroccan turbidite system mts these turbidity currents are responsible for turbidites that are among the largest volume most aerially extensive and longest runout deposits recorded these resulting turbidite beds can be correlated over distances of 1800 km across the full 250 000 km2 area of the mts due to the ability to trace these individual flow deposits throughout the mts large volume beds a5 a7 a11 a12 and a15 can be shown to be erosive upon debouching agadir canyon whilst smaller volume flows were not erosive these aforementioned large volume flows have been capable of eroding up to 15 km3 of material in the canyon mouth equating to as much as 50 of the later deposit volume evidence suggests individual flows erode up to 4 5 m of sediment within scours in the mouth of agadir canyon however these scours are 8 0 m deep indicating that several flows contribute to forming the scours in a series of cut and fill episodes several flows including beds a5 a7 a11 and a12 were also erosive in agadir basin up to 210 km from the canyon the present study indicates that large volume flows a5 a7 and a12 are also erosive within the channel lobe transition zone within the proximal madeira abyssal plain after exiting the madeira channels over 800 km from agadir canyon studying the deposits of these flows and their compositional changes along their entire pathway has provided invaluable information of whether the flows are erosive where this erosion takes place and to what extent they erode the seafloor there are also broader implications towards gaining information about flow processes at the bed interface calculating basin sediment budgets and better understanding discontinuous stratigraphy in distal turbidite systems