climate reconstruction for the holsteinian interglacial in eastern poland and its comparison with isotopic data from marine isotope stage 11 abstract sediments of palaeolakes located in eastern poland represent the holsteinian interglacial and the initial part of the succeeding saalian glaciation they consist of 55 m thick lake marl and calcareous gyttja deposits reconstruction of climate during this part of the pleistocene was carried out by the analyses of oxygen and carbon isotope ratios of carbonates palynological data al and ca content of sediments isotope ratios and palynological results give in some cases contradictory results 18o ratios from lake ossowka eastern poland indicate relatively cool conditions at the climatic optimum of the holsteinian interglacial low ratios may have been caused by increased precipitation that led to high stands of the lake level during the initial stages of the following glaciation the 18o and 13c ratios increased probably resulting from low water level and strong evaporation in cool and dry climate phases additionally high al contents indicate high allochthonous siliciclastic input high ca concentrations indicate autochthonous carbonate precipitation from the lake epilimnion the combined climate indicators for the holsteinian interglacial in eastern poland suggest that this temperate episode corresponds to marine isotope stage 11 mis 11 of the north atlantic comparison of the continental record from eastern poland with the marine record from the north atlantic separated by about 2500 km indicates that even small climatic changes can be identified in genetically different deposits documenting the global nature of pleistocene climate trends

thrusting evolution in the southern cordillera oriental northern argentine andes constraints from growth strata abstract growth strata and unconformities in the cenozoic synorogenic sediments in the southern cordillera oriental of the northern argentine andes provide new evidence for the eastward migration of the andean deformation from the puna to the santa barbara system the growth sequences and unconformities allow us to constrain the age of the structures with greater precision and to determine the distribution of this deformation in the thrust and fold wedge over time thrust evolution was mainly controlled by the reactivation of earlier extensional faults of the cretaceous salta rift basin the geometry of the inverted structures together with the general forward migration of the deformation gave rise to different thrust sequences the foreland dipping imbricate stack of the western cordillera oriental developed forwards during middle late miocene resulting in a break back thrusting sequence thrust propagation rate increased in late miocene early pliocene times when the eastern part of the cordillera oriental developed at that time a widespread deformation and synchronous thrusting occurred in the cordillera oriental subsequently deformation was mainly confined to the eastern part of the cordillera oriental finally during the pleistocene holocene deformation affected a wider zone including the cordillera oriental and the santa barbara system giving rise to the reactivation of previously developed thrusts

the origin of low δ18o granites and related rocks from the seychelles the 750 ma seychelles granites have whole rock 18o values that range from 1 2 to 7 5 differences in 18o values between quartz feldspar and whole rock for samples that have a range of 18o values suggest that these minerals are in magmatic equilibrium and that the whole rock 18o values were little affected by post crystallization interaction with fluids two suites of granites the mahe type and the praslin type have previously been recognized on the basis of chemical and radiogenic isotope composition the former have a mean whole rock 18o value of 5 25 0 65 1 whereas the latter are much more variable with a mean whole rock 18o value of 3 00 3 27 biotite and amphibole separates from both granite types range in d from 69 to 116 and show a positive correlation with whole rock 18o values dolerite dykes that intruded the granites during or shortly after their crystallization also have whole rock 18o values mean 2 24 1 93 lower than that expected for mantle derived basaltic rocks but these values appear to be the result of fluid rock interaction we suggest that the mahe type granites are derived mainly from juvenile mafic to intermediate crust with normal d and 18o values whereas the praslin type granites are mixtures of this source and older crust that acquired its low d and 18o values by extensive interaction with meteoric water at high temperature it is unlikely that meteoric water sufficiently depleted in d and 18o was available at 750 ma because of the relatively low latitude of the region at that time we suggest that alteration of the source took place significantly before production of the granite magmas depletion in 18o of the seychelles granites does not necessarily require a regional extensional tectonic setting at 750 ma as has been proposed

holsteinian interglacial marine isotope stage 11 abstract the problem of correllating the holsteinian interglacial with the marine isotope stage mis is still disputed generally a view persists that this interglacial should be linked with mis 11 although this approach has many adversaries palynologic and geochemical data from well preserved fossil lake deposits from the holsteinian interglacial in eastern poland have enabled their correlation with mis 11

comment on numerical 230 th u dating and a palynological review of the holsteinian hoxnian interglacial by geyh and muller

850 790 ma bimodal volcanic and intrusive rocks in northern zhejiang south china a major episode of continental rift magmatism during the breakup of rodinia abstract shrimp u pb zircon ages and geochemical and nd isotopic data are reported for mid neoproterozoic igneous rocks in northern zhejiang province south china the shenwu dolerite dykes the daolinshan granite diabase complex and the shangshu bimodal basalt rhyolite volcanic rocks were dated at 849 7 ma 794 9 ma and 792 5 ma respectively all the studied mafic rocks are tholeiitic in compositions and exhibit overall moderate enrichments in most incompatible trace elements resembling intraplate basaltic rocks in continental rifts the 850 ma shenwu dolerites are the earliest anorogenic basaltic rocks identified so far after the ca 1 1 0 9 ga sibao orogeny but seem to predate the neoproterozoic rifting our results are clearly at variance with the alternative tectonic model that an active continental margin existed along the southern margin of the yangtze block until ca 800 ma the intensive 790 ma bimodal volcanic and plutonic rocks part of a major phase of mid neoproterozoic rifting are concurrent with the widespread mid neoproterozoic intraplate magmatism throughout south china they are most likely related to the proposed mantle superplume that led to the breakup of the supercontinent rodinia

neoproterozoic low to negative δ18o volcanic and intrusive rocks in the qinling mountains and their geological significance abstract the yaolinghe group in the central part of the qinling mountains includes neoproterozoic bimodal volcanic and sedimentary sequences and two units with fault contact can be divided the lower unit consists of bimodal volcanic and sedimentary rocks intruded by a coeval plutonic complex granitic dikes and small granitic bodies and the upper unit is made up of greenschist with minor rhyolitic tuff zircon u pb dating yields ages of 719 790 ma for meta rhyolitic tuff in the lower unit 714 721 ma for the intrusive rocks and 635 ma for meta rhyolitic tuff in the upper unit the 18 o values are 4 to 15 for whole rock quartz and zircon from the volcanic rocks and quartz veins in the lower unit and the intrusive rocks and 3 4 12 for whole rock and quartz veins in the upper unit low to negative 18 o values 4 to 4 are widely present in the rocks and quartz veins of the lower unit and the intrusive rocks suggesting that the lower unit and the intrusive rocks suffered meteoric fluids in hydrothermal alteration the 18 o values of whole rock and quartz veins in the upper unit do not exhibit striking 18 o depletion indicating that meteoric fluids in hydrothermal alteration did not occur in this unit low 18 o zircon grains 1 4 are common in some of meta rhyolitic tuffaceous and intrusive rocks and only two analyses have negative 18 o values the low 18 o values of zircon were inherited from crystallization of low 18 o magma which was formed through the remelting of previous magmatic rocks altered by meteoric water in a system of magma chamber caldera and weakly affected by meteoric fluid in hydrothermal alteration thus the presence of low 18 o magmatic zircon is an indicator for meteoric fluid in hydrothermal alteration the low 18 o zircon grains found in different samples yields the ages from 720 to 790 ma implying that meteoric fluid in hydrothermal alterations began earlier than 790 ma whereas the striking 18 o depletion of the intrusive rocks suggest that hydrothermal alteration continued to at least 714 ma and the lack of 18 o depletion in the upper unit constrains that meteoric fluid in hydrothermal alterations stopped before 635 ma the long duration of meteoric fluid in hydrothermal alteration do not support that the glacial meltwater from the neoproterozoic glaciations in the yangtze craton is responsible for the 18 o depletion of the rocks

last interglacial and early glacial circulation in the northern north atlantic ocean abstract studies of marine records from the northwestern european shelf and the northern north atlantic suggest that last interglacial environments were less stable in this area than in the mid latitude atlantic the influx of atlantic water masses to the northern north atlantic was generally higher and the meridional temperature gradient was steeper during the last interglaciation than during the holocene strong north south sea surface temperature gradients during the early weichselian indicate a generally low influx of atlantic water to the northern north atlantic even during interstades

new evidence for complex climate change in mis 11 from hoxne suffolk uk the climatic signal of marine isotope stage mis 11 is well documented in marine and ice sheet isotopic records and is known to comprise at least two major warm episodes with an intervening cool phase terrestrial records of mis 11 though of high resolution are often fragmentary and their chronology is poorly constrained however some notable exceptions include sequences from the maar lakes in france and tenaghi philippon in greece in the uk the hoxnian interglacial has been considered to correlate with mis 11 new investigations at hoxne suffolk provide an opportunity to re evaluate the terrestrial record of mis 11 at hoxne the type hoxnian interglacial sediments are overlain by a post hoxnian cold temperate sequence the interglacial sediments and the later temperate phase are separated by the so called arctic bed from which cold climate macroscopic plant and beetle remains have been recovered the later temperate phase was deposited during an episode of boreal woodland and is associated with the artefacts a diverse vertebrate fauna and molluscs new amino acid geochronological data and biostratigraphical considerations suggest that the post hoxnian sequence correlates with late substages of mis 11 the paper further investigates the correlation of the sequence at hoxne with the palynological sequences found elsewhere in europe and adjacent offshore areas

critical issues in european quaternary biostratigraphy abstract the papers presented here form the special issue of quaternary science reviews on european quaternary biostratigraphy new and testable frameworks for the subdivision of pleistocene time are proposed based upon the evidence from three fossil groups that have a long history of biostratigraphical application in europe namely pollen molluscs and mammals in addition the potential biostratigraphical value of beetles chironomids ostracods and testate amoebae is explored the diverse lines of fossil evidence are consistent with a more complex chronology than previously envisaged for the pleistocene and underline the need for future multiproxy studies underpinned by a sound lithostratigraphy and consistent numerical dating

constraints from zircon u pb ages o and hf isotopic compositions on the origin of neoproterozoic peraluminous granitoids from the jiangnan fold belt south china zircon textures and micro chemical compositions precisely record the origin and petrogenesis of granitoids which are crucial for evaluating crustal growth and reworking thermal and geodynamic evolution zircons in peraluminous granitoids from the three largest 820 ma complexes guibei yueyang and jiuling in the jiangnan fold belt in south china are used to constrain their sources and petrogenetic processes zircons in the guibei granitoids have complex internal structures nearly all magmatic and inherited zircons have similar ehf 6 8 to 5 6 and 18o values 8 8 11 6 and dominantly lie between ehf evolution vectors for a crust created between 1 7 and 2 1 ga suggesting that the guibei granitoids were produced by partial melting of recycled heterogeneous supracrustal material however the yueyang granitoids contain zircons with high ehf 0 5 to 9 7 and relatively low 18o values 5 9 8 4 and two stage model ages of 1 1 1 8 ga and thus may have been formed by melting of mafic rocks from the lower crust the jiuling granitoids and their enclaves contain more complex zircons with more variable ehf 7 2 to 9 7 and 18o values 7 0 10 6 and lie along the mixing trend between the above proposed infracrustal and supracrustal granitoids therefore the neoproterozoic peraluminous granitoids in the jiangnan fold belt were produced by melting and mixing of continental crust compared with extremely low 4 and negative 18o values of neoproterozoic igneous zircons formed in its northern active continental margin the high 18o peraluminous granitoids in the southeastern yangtze block are considered to have been formed by melting of hydrothermally unaltered continental crust triggered by asthenosphere upwelling in the nanhua back arc basin

contrasting zircon hf and o isotopes in the two episodes of neoproterozoic granitoids in south china implications for growth and reworking of continental crust abstract the genetic links among rift magmatism crustal growth and water rock interaction are an important issue about mass and heat transfer between mantle and crust during supercontinent breakup a combined study of hf and o isotopes in zircons from neoproterozoic granitoids in south china provides evidence for growth and reworking of juvenile and ancient crusts with different styles of water rock interactions along rift tectonic zones two generations of the granitoids show contrasting features in both zircon hf and o isotope compositions indicating their distinct petrogenesis the 825 ma granitoids exhibit negative ehf t values of 3 4 0 8 to 1 6 0 8 with old model hf ages of 1 81 0 07 to 1 92 0 10 ga and high 18o values of 8 7 to 10 4 these indicate that the source material of granitoid magmas was derived from melting of paleoproterozoic basement that has the hf isotope signature similar to the enriched mantle but experienced chemical weathering process before anatexis reworking of ancient crust is demonstrated to occur at 825 ma in the orogenic collapse zone with overprinting of subsolidus hydrothermal alteration during magma emplacement in contrast the 760 750 ma bimodal intrusives are characterized by positive ehf t values of 3 5 0 8 to 9 9 0 8 with young model hf ages of 0 94 0 06 to 1 18 0 06 ga and both low and high 18o values of 4 2 to 6 2 relative to 5 3 0 3 for the normal mantle zircon prompt reworking of juvenile crust is suggested to occur at 750 ma in the rifted tectonic zone with occurrence of supersolidus hydrothermal alteration and local low 18o magmatism during supercontinent breakup contributions of the depleted mantle to their magma sources are contrasting in the two episodes of magmatism in association with breakup of the supercontinent rodinia while the change in melt source from the crust to the mantle keeps pace with the advance from continental rifting to supercontinent breakup significant transport of both heat and material from the depleted mantle to the continental crust only occurred along the active rifting zone in either case the growth and reworking of continental crust are episodically associated with rift magmatism

paleoproterozoic basement beneath the eastern cathaysia block revealed by zircon xenocrysts from late mesozoic volcanics abstract the eastern cathaysia block located to the western side of the pacific plate was mainly covered by late mesozoic intrusive and volcanic rocks and the age and composition of its basement remain enigmatic here we firstly report u pb and hf isotopes in zircon xenocrysts from late mesozoic mafic sub volcanic rocks in pingtan island the east coastal area of the eastern cathaysia block with surprising paleoproterozoic to archean u pb isotopic ages neither ca 1 8 ga nor 1 0 0 7 ga age peaks that are very typical in the outcropping rocks including the neoproterozoic sedimentary rocks in pingtan island in the south china block is identified the two main precambrian age peaks of 3 4 3 0 ga and 2 6 2 2 ga of these zircon xenocrysts are explained by contamination from the sediments in the unexposed basement the youngest two paleoproterozoic zircon xenocrysts may indicate the deposition of the basement close to ca 1 8 ga the identification provides clues to the existence of the paleoproterozoic basement in the eastern cathaysia block it may further suggest that the late mesozoic continental arc magmatism in the eastern cathaysia block was most likely developed on and contaminated by the paleoproterozoic basement

new evidence for vegetation development and timing of upper middle pleistocene interglacials in northern germany and tentative correlations abstract this paper discusses palynological investigations and new 230th u ages of two upper middle pleistocene sequences of the formerly glaciated northern german lowlands the reinsdorf sequence at the open mine of schoningen lower saxony and the north friesian site of leck new 230th u ages of late interglacial organic layers of the archaeological lake margin site of the reinsdorf sequence ranging from 280 to 343 ka give evidence for a correlation of those deposits with marine isotope stage mis 9 near and long distance correlation by means of palynological investigations of holsteinian and related interglacial continental deposits and their correlation with the mis is discussed isotopic investigations of uranium and thorium from organic rich mud deposits at core leck 8 point to an open system and age estimation by 230th u dating remains therefore unclear compared to other upper middle pleistocene warm periods in north germany correlations of the leck interglacial with the holsteinian and the reinsdorf interglacial can be excluded in comparison with sediment successions from the nachtigall section at hoxter and the section ottostrase at gottingen the leck interglacial is discussed as a correlative of a warm temperate phase of mis 7

quaternary mammals and the end villafranchian dispersal event a turning point in the history of eurasia the history of land mammals is characterized by dispersal events i e short periods of rapid intercontinental migrations and faunal replacements one of these the elephant equus event of lindsay et al may be dated somewhere between 3 and 2 5 ma a second event the wolf event may fall near 1 7 ma the end villafranchian event is discussed in detail it may be dated between 1 0 and 0 9 ma and is marked by a practically total rejuvenation of the fauna with the appearance of new types of adaptation unknown in the villafranchian this faunal revolution is easily recognized all over eurasia and is accompanied by wide ranging changes in climate and vegetation this whole sequence of phenomena may have been triggered by extensive tectonic movements in the mountain belts of central and southern asia

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

metamorphic growth and recrystallization of zircons in extremely 18o depleted rocks during eclogite facies metamorphism evidence from u pb ages trace elements and o hf isotopes abstract a combined in situ sims and la mc icpms study of u pb ages trace elements o and lu hf isotopes was conducted for zircon from eclogite facies metamorphic rocks in the sulu orogen the two microbeam techniques sampled various depths of zircon domains revealing different element and isotope relationships between residual magmatic cores and new metamorphic rims and thus the geochemical architecture of metamorphic zircons which otherwise cannot be recognized by the single microbeam technique this enables discrimination of metamorphic growth from different subtypes of metamorphic recrystallization magmatic cores with u pb ages of 769 9 ma have positive 18o values of 0 1 10 1 high th u and 176lu 177hf ratios high ree contents and steep mree hree patterns with negative eu anomalies they are interpreted as crystallizing from positive 18o magmas during protolith emplacement in contrast newly grown domains have concordant u pb ages of 204 4 to 252 7 ma and show negative 18o values of 10 0 to 2 2 low th u and 176lu 177hf ratios low ree contents and flat hree patterns with weak to no eu anomalies they are interpreted as growing from negative 18o fluids that were produced by metamorphic dehydration of high t glacial hydrothermally altered rocks during continental subduction zone metamorphism differences in 18o between different domains within single grains vary from 0 8 to 12 5 suggesting different degrees of o isotope exchange between the positive 18o magmatic core and the negative 18o metamorphic fluid during the metamorphism the magmatic zircons underwent three subtypes of metamorphic recrystallization depending on their accessibility to negative 18o fluids the zircons recrystallized in solid state maintained positive 18o values and ree and lu hf isotopes of protolith zircon but their u pb ages are lowered the zircons recrystallized through dissolution exhibit negative 18o values similar to the metamorphic growths almost completely reset u pb ages and partially reset ree systems the zircons recrystallized through replacement show variably negative 18o values and partially reset ree and u pb and lu hf isotopic systems therefore this study places robust constraints on the origin of metamorphic zircons in eclogite facies rocks and provides a methodological framework for linking the different types of metamorphic zircons to petrological processes during continental collision

tectonic inversion in the santa barbara system of the central andean foreland thrust belt northwestern argentina 1 the santa barbara system sbs of northern argentina is a 400 km long segment of the subandean foreland thrust belt it is characterized by predominantly west verging relatively high angle thrust faults many of these faults are reactivated normal faults from one branch of a complex cretaceous to paleogene rift system heteroaxial folding in parts of the sbs is probably due to a slight component of range parallel dextral strike slip motion acting on preexisting faults striking north and ne during inversion regional balanced cross sections along two transects across the northern sbs indicate that the major faults flatten into a detachment in the basement at about 10 km depth neogene e w contraction in the sbs is of the order of 21 26 km rift extension is not very well constrained but was probably less than 10 km the structural style of the sbs differs from the thin skinned subandean thrust belt to the north and from the large wavelength sierras pampeanas basement uplifts to the south the changes between the different styles are sharp and coincide with the northern and southern boundaries of the rift in the foreland suggesting that crustal or lithospheric heterogeneities exert an overriding control on foreland structural style

oxygen isotope ratios of zircon magma genesis of low δ18o granites from the british tertiary igneous province western scotland igneous zircons from granites of the british tertiary igneous province btip in western scotland preserve magmatic oxygen isotope ratios in spite of hydrothermal alteration and thus provide new evidence for the genesis of granites co2 laser and mass spectrometer based bulk 1 3 mg oxygen isotope analyses from individual plutons show remarkable homogeneity in zircon 18o regardless of zircon size and magnetism average reproducibility of 18o zrc in a single pluton is 0 2 in addition ion microprobe analysis shows that individual zircons all have the same 18o and thus bulk samples are homogeneous fourteen granite bodies from the isle of skye show extreme variability in zircon 18o values from pluton to pluton 18o zrc 0 6 5 3 vsmow all the granites record zircon 18o values less than would be in high temperature equilibrium with normal mantle 18o zrc 5 except for the beinn an dubhaich granite zircons from one intrusion in the mafic cuillins center also have low 18o 2 5 similar variability is observed in 18o amongst three intrusions on the isle of mull 18o zrc 3 4 5 9 both mull and skye are characterized by intense shallow paleohydrothermal systems and the low and variable 18o values of the magmas likely result from melting or interaction with hydrothermally altered country rock analysis of granites on the isle of arran where the percentage of low 18o country rocks is much less yields higher 18o zrc of 6 8 and 5 4 published trace element and radiogenic isotope data for btip mafic and felsic rocks have supported the hypothesis that the granites are formed primarily by differentiation from the mantle with magmas experiencing minimal crustal input dickin et al phil trans r soc london a 310 1984 755 780 however conservative estimates based on oxygen isotope compositions suggest that some of the btip granites can only be formed from normal magmas 18o wr 6 if they assimilated significant amounts of hydrothermally altered crustal material some granites require up to 40 bulk crustal input and are better explained as the result of wall rock melting by an adjacent mafic pluton whereas pb and sr suggest a general trend towards increasing input of shallow crust for the younger granites dickin et al phil trans r soc london a 310 1984 755 780 the correlation between age and 18o is less apparent suggesting that pb and sr isotopic compositions are decoupled from oxygen isotopes this would be expected of melted country rock that was hydrothermally altered in oxygen isotope ratios but not in pb and sr isotope ratios

the 2010 m w 7 2 el mayor cucapah earthquake sequence baja california mexico and southernmost california usa active seismotectonics along the mexican pacific margin the el mayor cucapah earthquake sequence started with a few foreshocks in march 2010 and a second sequence of 15 foreshocks of m 2 up to m4 4 that occurred during the 24 h preceding the mainshock the foreshocks occurred along a north south trend near the mainshock epicenter the mw 7 2 mainshock on april 4 exhibited complex faulting possibly starting with a m6 normal faulting event followed 15 s later by the main event which included simultaneous normal and right lateral strike slip faulting the aftershock zone extends for 120 km from the south end of the elsinore fault zone north of the us mexico border almost to the northern tip of the gulf of california the waveform relocated aftershocks form two abutting clusters each about 50 km long as well as a 10 km north south aftershock zone just north of the epicenter of the mainshock even though the baja california data are included the magnitude of completeness and the hypocentral errors increase gradually with distance south of the international border the spatial distribution of large aftershocks is asymmetric with five m5 aftershocks located to the south of the mainshock and only one m5 7 aftershock but numerous smaller aftershocks to the north further the northwest aftershock cluster exhibits complex faulting on both northwest and northeast planes thus the aftershocks also express a complex pattern of stress release along strike the overall rate of decay of the aftershocks is similar to the rate of decay of a generic california aftershock sequence in addition some triggered seismicity was recorded along the elsinore and san jacinto faults to the north but significant northward migration of aftershocks has not occurred the synthesis of the el mayor cucapah sequence reveals transtensional regional tectonics including the westward growth of the mexicali valley and the transfer of pacific north america plate motion from the gulf of california in the south into the southernmost san andreas fault system to the north we propose that the location of the 2010 el mayor cucapah as well as the 1992 landers and 1999 hector mine earthquakes may have been controlled by the bends in the plate boundary

recent tims dating results from british late pleistocene vertebrate faunal localities context and interpretation new tims dates from british sites underpin and extend the growing model of mammalian faunal history during the late pleistocene the sequence of british faunas during the three successive warm phases of mis 5 presents a challenging model in which the mammal faunas of the first two temperate phases 5e and 5c is dominated by species of a classically interglacial character while that of the final phase sub stage 5a is dominated by bison and reindeer this we see as the cold fauna appearing in britain during the cool isotope sub stage 5b and subsequently isolated by the rising sea level of isotope sub stage 5a all these three faunas are true island faunas copyright 2007 john wiley sons ltd

spatial and temporal distribution of deformation at the front of the andean orogenic wedge in southern bolivia new observations from an active orogenic wedge help link the seismotectonic behavior of individual faults to wedge deformation rates and patterns over multiple timescales we provide the first detailed constraints on the distribution and timing of deformation at the front of the andean orogenic wedge in southern bolivia where a recent study suggests that great mw 8 earthquakes could rupture the master fault underlying the wedge we use stratigraphic relationships across fault related folds and elastic dislocation modeling of seismic reflection horizons to obtain probabilistic estimates of wedge front fault ages and slip rates our analyses reveal that at least half of the previously determined gps based wedge loading and quaternary whole wedge shortening rates are absorbed across a 20 40 km wide wedge front zone consisting of 1 4 en echelon and partially to fully overlapping faults and folds associated with blind thrust faults the difference between our slip rates and the geodetic geologic observations combined with evidence for activity across internal wedge structures supports the notion that nonsteady state mass balance conditions coupled with elevated erosional efficiency result in distributed wedge deformation the orogenic wedge in southern bolivia behaves in a similar fashion to the taiwanese and himalayan ranges slip accumulates at downdip locations along the master fault and is released incrementally by earthquakes that rupture the wedge front fault zone the faults and folds comprising this zone pose a major source of seismic hazard accumulating slip is also released in the wedge interior and older internal wedge faults must be considered in any future assessment of regional earthquake risk

the rare holsteinian mazovian interglacial limnic deposits in the ksiąznica outcrop at krzczonow near świdnica sudetic foreland abstract the article presents the results of research on peats muds and sands filling a palaeocavity within alluvial fans of the bystrzyca river valley in the sudetic foreland of sw poland in the 534 cm deep research profile in the central part of a palaeolake 267 samples were collected at an interval of 2 cm and lithologically structural and textural studies palaeobotanically studies of diatoms pollen plant macrofossils and fossil wood palaeozoologically cladocera mollusca and ostracoda geochemically chemical elements and isotopes and palaeomagnetically analyzed the profile consists of three parts organic with mineral layers lower mineral middle and organic upper the palynological diagram was divided into three zones that represent local sets of pollen zones this diagram although incomplete is clearly indicative of the younger part of the holsteinian mazovian pollen iii and iv periods interglacial the upper part of the diagram consists of four local pollen zones that are correlated with stadial and interstadial periods analysis of several samples of fossil wood shows the widespread presence of pinus remains and numerous fragments of rhytidome bark of betula development of the peat layer 1 36 0 68 m depth started with paludification of the forest with the betula forest analysis of cladocera shows the presence of chitin armor components species chydorus sphaericus alona rectangula and ephippia of alona rectangula in three samples lithological cladocera and palaeo magnetic research supported by geochemical studies indicate the existence of at least three main phases the lake originated during the younger part of the holsteinian mazovian intergalcial as an oxbow within the valley where the deposition of variously thick up to 1 5 m depth peats organic and minerogenic silts the first stage in the second phase a closed fairly deep late holsteinian lake continued to exist under relatively warm conditions with mainly mineral deposition from the slope the lake became shallower and wider and then more open and better oxygenated with through flow in the final phase the lake was completely filled by organic sediments under interglacial conditions the absence of diatom molluscan and ostracod communities indicates an acid lacustrine environment at this time the fluvial and limnic deposits are sealed by overlaying saalian odranian till

nature and causes of quaternary climate variation of tropical south america abstract this selective review of the quaternary paleoclimate of the south american summer monsoon sasm domain presents viewpoints regarding a range of key issues in the field many of which are unresolved and some of which are controversial 1 el nino southern oscillation variability while the most important global scale mode of interannual climate variation is insufficient to explain most of the variation of tropical south american climate observed in both the instrumental and the paleoclimate records 2 significant climate variation in tropical south america occurs on seasonal to orbital i e multi millennial time scales as a result of sea surface temperature sst variation and ocean atmosphere interactions of the tropical atlantic 3 decadal scale climate variability linked with this tropical atlantic variability has been a persistent characteristic of climate in tropical south america for at least the past half millennium and likely far beyond 4 centennial to millennial climate events in tropical south america were of longer duration and perhaps larger amplitude than any observed in the instrumental period which is little more than a century long in tropical south america these were superimposed upon both precession paced insolation changes that caused significant variation in sasm precipitation and eccentricity paced global glacial boundary conditions that caused significant changes in the tropical south american moisture balance as a result river sediment and water discharge increased and decreased across tropical south america lake levels rose and fell paleolakes arose and disappeared on the altiplano glaciers waxed and waned in the tropical andes and the tropical rainforest underwent significant changes in composition and extent to further evaluate climate forcing over the last glacial cycle 125 ka we developed a climate forcing model that combines summer insolation forcing and a proxy for north atlantic sst forcing to reconstruct long term precipitation variation in the sasm domain the success of this model reinforces our confidence in assigning causation to observed reconstructions of precipitation in addition we propose a critical correction for speleothem stable oxygen isotopic ratios which are among the most significant of paleoclimate proxies in tropical south america for reconstruction of variation of paleo precipitation or sasm intensity however it is already well known that any particular 18o value observed in speleothem carbonate is affected by two processes that have nothing to do with changes in precipitation amount the influence of temperature on carbonate water isotopic fractionation in the cave and the influence of changing 18o of seawater quantitatively accounting for both artifacts can significantly alter the interpretations of speleothem records in tropical south america both adjustments act in the same direction and have the tendency to increase the true amplitude of the paleo hydrologic signal but by different amounts in glacial and inter glacial stages these corrections have even graver implications for the interpretation of tropical northern hemisphere speleothem records e g chinese speleothems where the combined adjustments tend to decrease or even eliminate the true signal amplitude

neogene to quaternary broken foreland formation and sedimentation dynamics in the andes of nw argentina 25 s 1 the northwest argentine andes constitute a premier natural laboratory to assess the complex interactions between isolated uplifts orographic precipitation gradients and related erosion and sedimentation patterns here we present new stratigraphic observations and age information from intermontane basin sediments to elucidate the neogene to quaternary shortening history and associated sediment dynamics of the broken salta foreland this part of the andean orogen which comprises an array of basement cored range uplifts is located at 25 s and lies to the east of the arid intraorogenic altiplano puna plateau in the salta foreland spatially and temporally disparate range uplift along steeply dipping inherited faults has resulted in foreland compartmentalization with steep basin to basin precipitation gradients sediment architecture and facies associations record a three phase 10 5 and 2 ma east directed yet unsystematic evolution of shortening foreland fragmentation and ensuing changes in precipitation and sediment transport the provenance signatures of these deposits reflect the trapping of sediments in the intermontane basins of the andean hinterland as well as the evolution of a severed fluvial network present day moisture supply to the hinterland is determined by range relief and basin elevation the conspiring effects of range uplift and low rainfall help the entrapment and long term storage of sediments ultimately raising basin elevation in the hinterland which may amplify aridification in the orogen interior

small scale hf isotopic variability in the peninsula pluton south africa the processes that control inheritance of source 176 hf 177 hf diversity in s type granites directly transfer to their magmatic overgrowths smallscale modeling of zircon dissolution and re precipitation in a static magma generates sub mm melt domains having variable zr content and hf isotope composition the composition of these domains is controlled by the size and isotope composition of the nearest dissolving zircon crystals and the cooling rate of the magma these results suggest that in magma systems with a substantial inherited zircon load zircon crystals within the same rock should record variable 176 hf 177 hf in the magmatic zircon fraction

geochronological and geochemical study of palaeoproterozoic gneissic granites and clinopyroxenite xenoliths from nw fujian se china implications for the crustal evolution of the cathaysia block abstract u pb zircon dating of gneissic granite samples in northwestern fujian province southeast china gave neoarchean to palaeoproterozoic ages 2 6 1 9 ga for the rounded zircon cores and palaeoproterozoic upper intercept ages 1851 21 ma 1857 29 ma respectively for zoned rims that have oscillatory growth zoning and yield e hf t values between 8 8 and 3 7 and t dm model ages between 2 1 and 2 6 ga these gneissic granites are peraluminous a cnk 0 94 1 28 characterized by high sio 2 68 72 wt al 2 o 3 14 15 wt and low cao mgo feo t tio 2 and p 2 o 5 contents they also possess relatively low ree contents and moderate lree hree fractionation and display pronounced negative anomalies in nb ta sr p and ti all these features indicate that the precursor magmas were likely formed by partial melting of sedimentary rocks clinopyroxenite xenoliths with gneissosity structures are found in these gneissic granites and they have high mgo ni and cr but low contents of tio 2 and are characterized by high cao al 2 o 3 4 1 5 3 low al 2 o 3 tio 2 ratios 8 7 9 5 and hree depletion these features are similar to the typical al depleted type komatiites their geochemical characteristics such as high gd yb n and low hree y zr and hf suggest partial melting of the upper mantle source with residual garnet the negative nb ta and ti anomalies indicate a strong arc related affinity our results and recently published data for granitic and mafic basement rocks in this region reveal that 1 85 ga was an important period for the evolution of the cathaysia block possibly related to the columbia supercontinent assembly large amount of granitic magma was emplaced probably as a result of partial melting of old neoarchean to palaeoproterozoic materials

magmatic evolution and crustal recycling for neoproterozoic strongly peraluminous granitoids from southern china hf and o isotopes in zircon zircons can retain a grain scale record of granitoid compositional evolution that is accessible through microanalysis in situ u pb hf and o isotope data yield new insights into the petrogenesis and evolution of the neoproterozoic strongly peraluminous granitoids of the jiangnan orogen jo southern china a negative correlation of th u versus d 18 o is found for most analyses some zircons from eastern jo granitoids show d 18 o variations of 3 6 from core to rim indicating a dramatic shift toward higher oxygen isotope values by voluminous partial melting of supracrustal rocks and signaling a transition from i type like to s type like magmas during the later stage of magmatic evolution this mechanism provides a reasonable explanation why some granitoids have intermediate geochemical features between s type and i type granites hf isotope trends indicate that a larger proportion of mature continental crust was incorporated into the magma sources of the western jo granitoids whereas more juvenile arc crust was incorporated into the eastern jo magmas no significant depleted mantle derived mafic magma was injected into the jo granitoid magmas instead radiogenic hf and nd signatures in jo granitoids reflect incorporated juvenile arc crust and document crustal growth in southern china during the early neoproterozoic ca 900 ma thus our zircon data suggest that strongly peraluminous granitoids which are widely regarded as the products of orogenesis that primarily recycle evolved crust can also record important information about early crustal growth

sedimentary history of za hajovnou cave moravia czech republic a unique middle pleistocene palaeontological site za hajovnou cave in the javoricko karst moravia czech republic has a rich record of middle pleistocene typical holsteinian flora and fauna dominated by bear ursus deningeri sedimentological geochemical mineralogical geophysical palynological and zoopalaeontological analyses of the sediments along with u th dating of flowstones place the deposits into a numerical timeframe the cave origin dates to a period before the mid miocene badenian transgression the oldest fluvial deposits are lower pleistocene spanning the brunhes matuyama boundary the later terrestrial deposits range from middle pleistocene to holocene the most important result of u th dating is that the main holsteinian senso lato fossil bed can be correlated with mis 9 the lower fossil bed is probably mis 11 and the upper fossil bed mis 5e this represents one of the still relatively few numerically dated holsteinian sites contradicts the global chronostratigraphical correlation table that places the holsteinian only in mis 11 and supports the concept that the holsteinian is not a single unit and likely not confined to a single interglacial c 2013 elsevier ltd and inqua all rights reserved

current understanding of pleistocene temperate stages in ireland abstract research on irish pleistocene temperate stages has been dominated by investigation of deposits with very similar floristic records collectively termed the gortian and traditionally correlated with the continental holsteinian recently detailed investigation of interglacial material from cork harbour suggested the gortian group may contain floristically similar deposits of different ages the pollen record had gortian holsteinian characteristics and dating by measurement of uranium thorium disequilibrium and amino acid racemization suggested that the deposits were younger than stage 11 correlated with the holsteinian by reille and de beaulieu reille de beaulieu quat res 44 1995 205 the suggestion that there may have been more than one holsteinian style temperate stage in europe might explain the floristic similarity of gortian and holsteinian deposits and the apparent younger age of the cork deposits the lack of a last interglacial stratotype is the most outstanding problem in irish quaternary studies the pollen content of sediments at fenit co kerry dated to ca 118 ka bp suggested they may represent a cool temperate phase at the end of the last interglacial recently investigated sub drumlin organic rich deposits at knocknacran co monaghan are also possibly last interglacial in age and these are discussed in detail here

aminostratigraphy of european marine interglacial deposits molluscan fossils collected from shallow water marine sediment across nw europe and nearby arctic regions have been analysed for the extent of isoleucine epimerization dl ratio in indigenous protein residues the dl ratios confirm that essentially all classical eemian sites from nw europe are of the same age and are correlative with the type locality near amersfoort in the netherlands shells from interglacial marine sediment beneath the type weichselian till in poland also correlate with the type eemian site dl ratios in holsteinian marine shells 0 29 are substantially higher than in their eemian counterparts 0 17 late cromerian shells yield even higher ratios 0 46 dl ratios in late glacial shells 0 06 and middle weichselian shells 0 09 permit differentiation from modern 0 01 and last interglacial material based on the position of the matuyama brunhes boundary and the differences in dl ratios the eemian must correlate with isotope substage 5e whereas the holsteinian is most likely substage 7c possibly stage 9 but certainly younger than stage 11 intra saalian warm periods may be terrestrial equivalents of the younger substages of stage 7 extensive pre eemian marine sediments along the sw coast of denmark previously correlated with the holsteinian are shown to be of late cromerian age the underlying till there is the first widespread evidence of a pre elsterian till in nw europe dl ratios in molluscs from last interglacial sites along the arctic coast of the ussr the arctic islands and eastern greenland are substantially lower than in their european counterparts due to their low thermal histories the combined mid and high latitude data are used to develop a predictive model for the expected dl ratio in any of several moderate epimerization rate taxa for last interglacial sites with mean temperatures between 20 and 15 c not all sites could be unambiguously assigned to an established interglacial the fjosanger norway and margareteberg sweden sites previously thought to be eemian yield dl ratios higher than in secure nearby eemian material it is yet unresolved whether these are aberrant sites or if they predate the last interglacial in situ shoreline deposits encountered in borings in sw belgium and in exposures on the belgium coastal plain contain molluscs that yield dl ratios intermediate between secure eemian and late weichselian ratios raising the possibility that a late stage 5 high sea level event attained near modern levels in the southern north sea basin resolution of these uncertainties is the focus of future work

the flaw in the crustal zircon archive mixed hf isotope signatures record progressive contamination of late stage liquid in mafic ultramafic layered intrusions

high temperature glacial meltwater rock reaction in the neoproterozoic evidence from zircon in situ oxygen isotopes in granitic gneiss from the sulu orogen abstract to seek the occurrence of negative 18o magmas in the neoproterozoic we conducted in situ zircon o isotope analysis and u pb dating for granitic gneiss from the northeastern sulu orogen east central china zircon u pb dating yields protolith ages of 753 15 ma to 780 13 ma and metamorphic ages of 209 3 to 244 7 ma the neoproterozoic cores with concordant u pb ages exhibit a wide 18o range from 11 0 to 5 8 which is nearly the same as those for cores with discordant u pb ages the triassic rims of some samples have homogeneous 18o values of around 10 whereas the rims of the other samples show a wider range from 9 8 to 5 0 the 18o values as negative as 11 0 for zircons with concordant neoproterozoic u pb ages are reported for the first time representing the primary record of negative 18o magma in the neoproterozoic the continental subduction zone metamorphism in the triassic did not erase the abnormal 18o record in the protolith zircon cores despite metamorphic dehydration and partial melting under high pressure to ultrahigh pressure conditions a conservative estimate suggests that the hydrothermal fluid reacted with the rocks should have 18o values lower than 9 2 corresponding to the meteoric water in cold paleoclimate or the meltwater of local continental glaciation the spatial variation in the o isotope compositions of neoproterozoic zircons is a manifestation of the o isotope heterogeneity in the extinct hydrothermal magmatic system the hydrothermal alteration during the neoproterozoic was incongruent which was lately recorded by the wide range of 18o values in the metamorphic zircons of triassic age the extensive o isotope exchange between the surface water and the deep rock requires high temperature and high water rock ratios in continental rifting zones this is ascribed to neoproterozoic splitting of the south china block from the rodinia supercontinent

numerical 230th u dating and a palynological review of the holsteinian hoxnian interglacial abstract earth scientists increasingly consider the holsteinian interglacial and mis 11 as synonyms despite the limited number of numerical dates and ambiguous stratigraphic and palynological correlation with the numerical marine isotope timescale hence we present new tims 230th u dates from two fen peat layers of the holsteinian reference site at bossel in northern germany and re evaluate published numerical data from two sites with hoxnian deposits in england a new method for the calculation of methodically controlled minimum 230th u ages mcma was developed the synopsis of the 230th u dates allows a correlation of both the holsteinian and hoxnian interglacials to mis 9 this correlation is supported by supplementary 230th u dates of fen peat from several pre eemian but non holsteinian sites in germany there is palynological evidence for a reliable correlation between precisely investigated and numerically dated holsteinian deposits in poland germany england sw ireland and france an apparently contradictory palynological correlation from the french central massif is discussed

the eastern foothills of the eastern cordillera of colombia an example of multiple factors controlling structural styles and active tectonics we decipher the geometry timing and kinematics of deformation of a region in the eastern foothills of the eastern cordillera of colombia we assess the influence of inherited structural fabrics changes in basin geometry erosional denudation and the characteristics of the tectonic stress field with respect to the evolution of the structural styles of the deformation front in the eastern cordillera detailed structural and geomorphic mapping of an area of 5000 km 2 analysis of seismic reflection profiles cross section balancing tectonic stress field indicators and new apatite fission track data are used to characterize the partitioning of late cenozoic deformation in the eastern foothills of the eastern cordillera of colombia during the late miocene pliocene in the eastern cordillera deformation migrated from inverted master normal faults to low elevation low amplitude structures in the foreland however this shift in the locus of deformation was not spatially uniform the deformation front is wider in a northern sector of the cordilleran foothills where sedimentary units are thicker and shortening is perpendicular to the structures this shortening direction is identical to the direction of the greatest horizontal stress s hmax as seen in borehole breakouts during the late miocene pliocene basement ranges are passively uplifted by younger more frontal thrusts the eastern foothills of the eastern cordillera thus reveal a complex combination of factors responsible for the structural styles and partitioning of active deformation in an inversion orogen over time the most important factor changes from the role of inherited structural fabrics to the geometries of basin fills

origin of the late paleoproterozoic low δ18o a type granites on the southern margin of the north china craton and their geodynamic mechanism abstract a type granites with 18o depletion signatures are rather enigmatic as regards not only their typology and petrogenesis but also their rock forming geodynamic mechanism here we report a suite of late paleoproterozoic low 18o a type granites from the longwangzhuang pluton on the southern margin of the north china craton sims zircon u pb dating showed that the longwangzhuang pluton was emplaced at 1613 4 ma combined with previous data it is clear that the mineral components of longwangzhuang granites are variable and consist of perthite quartz plagioclase biotite and amphibole calcic hastingsite ferroedenite and sodic ferrogedrite geochemically they are metaluminous to peraluminous and have high alkali contents k2o na2o 8 76 wt k2o na2o 1 feot feot mgo 0 95 ratios zr nb ce y 993 ppm contents and 10000 ga al 4 31 ratios resembling a type granites in situ oxygen isotope analysis displayed low zircon 18o values between 4 0 and 4 9 with a weighted average of 4 4 based on the archean two stage zircon hf and whole rock nd model ages coupled with the low la yb cn ratios negative anomalies of eu and sr and high zr saturation temperatures and the presence of low pressures 3 3 5 7 kbar amphiboles the longwangzhuang a type granites were generated by self cannibalizing pre existing low 18o old rocks i e the taihua complex and emplaced at shallow depth combined with regional geological observations i e coeval tuffites a passive rift setting was the most plausible explanation for the generation of the late paleoproterozoic low 18o a type granites on the southern margin of the north china craton such a rifting could likely have lasted at least till 1 6 ga

loess chronology of the last interglacial glacial cycle in bohemia and moravia czech republic abstract combined infrared and green light stimulated luminescence and thermoluminescence dating applied to the extensively studied bohemian and moravian loess palaeosol sequences from sedlec suchdol kutna hora dolni v stonice lechovice mod ice bulhary and cerven kopec provides a reliable chronological framework for the last interglacial glacial cycle based on this luminescence dating study a new chronology is proposed for the last interglacial glacial loess palaeosol sequences from the czech republic irsl and tl dating suggests that the bt horizon of a truncated brown forest soil lower pk iii formed during the last interglacial equivalent to oxygen isotope substage 5e the upper chernozem of pkii belongs to oxygen isotope stage 3 if the combined irsl and tl age estimates are taken into account although from geological estimates an age range within oi substage 5a is most likely the upper weichselian loess accumulated at a very high rate owing to the high accumulation rate there is no time difference in sedimentation ages between the tundra gley palaeosols above pk i which include the upper weichselian sediments in central europe

oxygen isotope study of the long valley magma system california isotope thermometry and convection in large silicic magma bodies products of voluminous pyroclastic eruptions with eruptive draw down of several kilometers provide a snap shot view of batholith scale magma chambers and quench pre eruptive isotopic fractionations i e temperatures between minerals we report analyses of oxygen isotope ratio in individual quartz phenocrysts and concentrates of magnetite pyroxene and zircon from individual pumice clasts of ignimbrite and fall units of caldera forming 0 76 ma bishop tuff bt pre caldera glass mountain 2 1 0 78 ma and post caldera rhyolites 0 65 0 04 ma to characterize the long lived batholith scale magma chamber beneath long valley caldera in california values of 18o show a subtle 1 decrease from the oldest glass mountain lavas to the youngest post caldera rhyolites older glass mountain lavas exhibit larger 1 variability of 18o quartz the youngest domes of glass mountain are similar to bt in 18o quartz values and reflect convective homogenization during formation of bt magma chamber surrounded by extremely heterogeneous country rocks ranging from 2 to 29 oxygen isotope thermometry of bt confirms a temperature gradient between late 815 c and early 715 c bt the 18o quartz values of early and late bt are 8 33 and 8 21 consistent with a constant 18o melt 7 8 0 1 and 100 c temperature difference zircon melt saturation equilibria gives a similar temperature range values of 18o quartz for different stratigraphic units of bt and in pumice clasts ranging in pre eruptive depths from 6 to 11 km based on melt inclusions and document vertical and lateral homogeneity of 18o melt worldwide five other large volume rhyolites lava creek lower bandelier fish canyon cerro galan and toba exhibit equal 18o melt values of earlier and later erupted portions in each of the these climactic caldera forming eruptions we interpret the large scale 18o homogeneity of bt and other large magma chambers as evidence of their longevity 105 years and convection however remaining isotopic zoning in some quartz phenocrysts trace element gradients in feldspars and quartz and zircon crystal size distributions are more consistent with far shorter timescales 102 104 years we propose a sidewall crystallization model that promotes convective homogenization roofward accumulation of more evolved and stagnant volatile rich liquid and develops compositional and temperature gradients in pre climactic magma chamber crystal melt gas bubbles mush near chamber walls of variable 18o gets periodically remobilized in response to chamber refill by new hotter magmas one such episode of chamber refill by high ti sr ba zr and volatile richer magma happened 103 104 years prior to the 0 76 ma caldera collapse that caused magma mixing at the base mush thawing near the roof and walls and downward settling of phenocrysts into this hybrid melt

episodic growth of the gondwana supercontinent from hafnium and oxygen isotopes in zircon it is thought that continental crust existed as early as 150 million years after planetary accretion but assessing the rates and processes of subsequent crustal growth requires linking the apparently contradictory information from the igneous and sedimentary rock records for example the striking global peaks in juvenile igneous activity 2 7 1 9 and 1 2 gyr ago imply rapid crustal generation in response to the emplacement of mantle super plumes rather than by the continuous process of subduction yet uncertainties persist over whether these age peaks are artefacts of selective preservation and over how to reconcile episodic crust formation with the smooth crustal evolution curves inferred from neodymium isotope variations of sedimentary rocks detrital zircons encapsulate a more representative record of igneous events than the exposed geology and their hafnium isotope ratios reflect the time since the source of the parental magmas separated from the mantle these model ages are only meaningful if the host magma lacked a mixed or sedimentary source component but the latter can be diagnosed by oxygen isotopes which are strongly fractionated by rock hydrosphere interactions here we report the first study that integrates hafnium and oxygen isotopes all measured in situ on the same precisely dated detrital zircon grains the data reveal that crust generation in part of gondwana was limited to major pulses at 1 9 and 3 3 gyr ago and that the zircons crystallized during repeated reworking of crust formed at these times the implication is that the mechanisms of crust formation differed from those of crustal differentiation in ancient orogenic belts

zircon oxygen isotopic constraint on the sources of late mesozoic a type granites in eastern china abstract a type granites are usually derived from partial melting of the lower crust and or the upper mantle within extensional settings but their exact sources for specific plutons are required to unravel a systematic laser fluorination analysis of oxygen isotopes was carried out for five well documented late mesozoic a type granites in eastern china zircon from 41 samples was separated and 109 aliquots of fresh zircon were analyzed along with whole rock powder and quartz from the same samples hydrothermally altered whole rock samples show scattered 18 o values of 2 3 to 7 4 with a total variation up to 9 7 in contrast zircon 18 o values vary only from 3 1 to 5 4 with a range of 2 3 most available zircon 18 o values of a type granites are lower than normal mantle zircon values of 5 3 0 6 2sd and high temperature equilibrium fractionations are well preserved between quartz and zircon in most cases the above lines of evidence suggest that the low 18 o zircons in a type granites were crystallized from low 18 o magmas because low 18 o magmas cannot be derived entirely from the mantle reworking and or recycling of crustal igneous rocks are involved for their petrogenesis the low 18 o zircons in this study thus offer evidence for a dominantly crustal origin of the late mesozoic a type granites in eastern china

climatic evolution during the middle pleistocene warm period of bilshausen germany compared to the holocene abstract middle pleistocene warm periods are particularly useful for comparison with our present warm period one of them marine isotope stage mis 11 has been considered a potential analogue for the holocene whereas older interglacials e g mis 13 are distinctly different however terrestrial middle pleistocene sites other than the holsteinian and quantitative climate reconstructions for this period are very rare in europe a unique terrestrial site in north central europe is known from bilshausen germany the sediments are varved and indicate that this interglacial lasted 25 000 years more than twice as long as the holocene so far the warm period probably correlates to mis 11 or possibly to mis 13 a new palynological investigation with large pollen counts is presented which forms the basis for quantitative temperature reconstructions based on the probabilistic indicator taxa approach the so called pdf method the range of tree species that formed the vegetation during the bilshausen warm period is reminiscent of the holocene but the vegetational as well as the reconstructed climatic development shows distinct differences no pronounced initial successional phase is recorded in the pollen stratigraphy from bilshausen in addition a mesocratic or optimum phase of forest development as in the holocene is unclear in the bilshausen sequence reconstructed temperature values are several c lower than holocene temperatures for most of the bilshausen interglacial only for several millennia in the late phase of the bilshausen interglacial were july temperatures higher than the holocene july temperatures seasonality was much stronger during the bilshausen interglacial and the temperature trends differ between the two interglacials likely reasons for the pronounced differences are on one hand global temperature insolation changes and atmospheric circulation on the other hand more regional factors such as the configuration of the north sea basin may also be responsible for the colder winter temperatures and stronger seasonality during the bilshausen interglacial compared to the holocene reliable absolute dating of the bilshausen interglacial is needed which would allow a more detailed evaluation of the forcing factors that determined the climate during the bilshausen interglacial

late quaternary tectonics controlled by fault reactivation insights from a local transpressional system in the intermontane lerma valley cordillera oriental nw argentina abstract we analyzed the lomas de carabajal area in the intermontane lerma valley of the cordillera oriental to assess the level of neotectonic activity in a densely populated region of northwestern argentina in this region plio pleistocene synorogenic conglomerates are deformed locally associated with high angle faults and nnw sse oriented en echelon folds characterized by wavelengths of

dating intramontane alluvial deposits from nw argentina using luminescence techniques problems and potential abstract intramontane basin sediments are an archive of the interaction between basin bounding faults and alluvial fan and fluvial systems the chronologies of intramontane basin sedimentation enable an understanding of the cycling of sediments within a basin through time can be interrogated to identify periods of alluvial storage and erosion provide rates of sediment accumulation and storage and date fault movement if suitable dating methods in terms of resolution and timescale are applied to develop the chronologies of alluvial archives it is then possible to discriminate between climate and tectonic forcing mechanisms on long term basin behaviour optically stimulated luminescence osl dating of quartz grains from alluvial sediments is an ideal technique for establishing a chronological framework of basin sedimentation as the method directly dates sedimentation events however our experience of osl dating of quartz minerals extracted from late quaternary alluvial sequences in the quebradas of the eastern cordillera of nw argentina has presented a number of challenges concerning selection of appropriate facies to analyse mineral contamination failure of fundamental protocol tests proximity to saturation and broad and multi modal age distributions through careful analysis of the alluvial sedimentology and choice of sampling environments we have been able to locate suitable samples in most vertical sequences studied a post infrared osl approach demonstrated that contaminant signals were resulting in protocol test failure and conversely circumvention of this problem has increased confidence and reliability in the dating results assessment of dose response characteristics suggests that the luminescence for the oldest samples is not likely to be saturated and in turn ages are not considered to be underestimated finally different statistical tests have enabled objective identification of single low dose populations in complex distributions and confirmed that broad distributions in some samples may be treated as single populations these statistical approaches have considerably lowered uncertainty on osl ages and confirmed concordance with other dating evidence

dagmar cave czech republic moravian karst a unique palaeontological site of the cromerian interglacial abstract dagmar cave czech republic is the first locality in the moravian karst where sediments of cromerian age have been discovered and it is the first locality with such a large number of species of molluscs of this age it was originally a swallow hole initiated in the neogene which has since accumulated sediments basal sediments are palaeontologically sterile stream boulders originating from weathered lower carboniferous rock after this fossiliferous loamy sediments were carried in from the entrance by streams and or gravity molluscan and vertebrate assemblages along with palynological remains are indicative of interglacial conditions faunal analysis determined that this could only consist of one interglacial either cromerian iii or iv this is the first record of middle pleistocene molluscan fauna in the moravian karst palynology demonstrated a humid and thermophilic vegetation typical of a cromerian interglacial with forest and probably water and an open grassy bushy area close to the cave the age is constrained by a mis 7 u th date 182 ka on the calcite flowstone that overlies the interglacial material and underlies the palaeontologically more sterile upper sediments

the role of inversion tectonics in the structure of the cordillera oriental nw argentinean andes the salta basin of cretaceous age in the andes of nw argentina was inverted during the development of the cordillera oriental between the neogene and recent the different orientations of the extensional faults of the salta rift system and the subsequent w e shortening resulted in a great variety of inversion structures extensional faults dipping ne to ese were preferentially reactivated as contractional faults the initial stepped geometry of these faults gave rise to a distinctive sigmoidal pattern of basement involved thrusts and related folds these contractional structures tended to run parallel to the extensional faults and acquired a n s trend across the previous accommodation zones resulting in folding interference patterns other interference patterns are attributed to the superposition of contractional folds on previous rollovers and to the constrictional deformation imposed by the reactivation of adjacent extensional faults with different orientations the nnw to wsw dipping extensional faults show no evidence of reactivation despite the fact that some of them are folded the inversion at crustal scale is limited owing to the presence of the cretaceous salta rift across the different andean structural units and foreland

late middle pleistocene horse fossils from northwestern europe as biostratigraphic indicators abstract biostratigraphy provides a crucial tool for establishing temporal correlations between late middle pleistocene sites the caballoid horse lineage is one of the few large mammal groups that underwent changes in size and morphology over this period here univariate bivariate and multivariate statistics are used to identify temporal affinities of late middle pleistocene horse remains from northwest europe size and shape variation is limited in dental elements but clear differences between sites can be observed in the limb bones pca and dfa on the same samples produce highly similar results indicating the robusticity of the classifications found in the dfa thus dfa on measurements of the limb bones of caballoid horses provides a reliable method to distinguish between sites dating from different marine oxygen isotope stages mis and can give important clues to the temporal affinities of newly analysed faunal assemblages the analyses have important consequences for the relative dates of the sites bilzingsleben ii and schoningen ii which can be shown to date from different interglacials the age of the sample from the lower travertine at weimar ehringsdorf is confirmed as mis 7 the steinheim sample is highly distinct implying variation at the oxygen isotope substage level that must be resolved in greater detail when more samples become available

components and episodic growth of precambrian crust in the cathaysia block south china evidence from u pb ages and hf isotopes of zircons in neoproterozoic sediments abstract detailed lam icpms u pb dating and lam mc icpms lu hf isotope analysis were carried out on zircons from nine samples of basement metamorphic rocks in the southern cathaysia block south china the chemical compositions of these metamorphic rocks and zircon morphology indicate that their protoliths were sedimentary zircon u pb dating results show they mainly formed during the late neoproterozoic the precambrian crust of the cathaysia block can be divided into two distinct tectonic domains the wuyishan terrane to the northeast and the nanling yunkai terrane to the southwest the nearly e w boundary between these two terranes is also supported by geophysical petrological and geochemical evidence and the basement rocks of the two terranes are comprised of different components the wuyishan terrane is characterized by dominant paleoproterozoic 1 86 ga and lesser neoarchean magmatism and the southern central part of the terrane suffered strong neoproterozoic and early paleozoic tectonothermal reworking the zircon data suggest that there were five important episodes of juvenile crust generation 3 6 ga 2 8 ga 2 6 2 4 ga 1 85 ga and 0 8 0 7 ga in the wuyishan terrane strong paleoproterozoic 1 85 ga magmatism in northern wuyishan and neoproterozoic 0 8 0 7 ga magmatism in central and southern wuyishan both principally involved the remelting of old crust with minor input of juvenile material in contrast the nanling yunkai terrane contains abundant neoarchean and grenvillian zircons some evidence of mesoproterozoic activity and rare paleo to meso archean and neoproterozoic zircons u pb ages and hf isotopic compositions of the detrital zircons from the late neoproterozoic to early paleozoic meta sedimentary rocks in the nanling yunkai area suggest that the growth of juvenile crust mainly occurred at 3 6 ga 3 3 ga 2 5 2 6 ga 1 6 ga 1 0 ga and 0 8 0 7 ga neoarchaean 2 6 2 5 ga grenvillian 1 0 ga and neoproterozoic 0 8 0 7 ga magmatism mainly involved the recycling of old crust minor remnants of 4 1 ga crust may remain in the terrane this crustal history is distinct from that of the wuyishan terrane and analogous to those recorded for the eastern india east antarctic domain of northern gondwanaland suggesting that they probably were once linked

supereruptions of the snake river plain two stage derivation of low δ18o rhyolites from normal δ18o crust as constrained by archean xenoliths supereruptive volumes of low 18 o rhyolites define the snake river plain yellowstone plateau volcanic province begging the question of the sources and the processes by which 18 o depleted magmas are generated new analyses show that archean crustal xenoliths from the central and eastern snake river plain have normal 18 o signatures of 6 9 precluding them as a low 18 o source in the genesis of 10 000 km 3 of low 18 o 18 o 18 o rhyolites have variable crust 30 50 and mantle 50 70 proportions that are specific for each eruption low 18 o rhyolites can be traced along a genetic array of mixing lines from normal 18 o rhyolite end members to a low 18 o 1 source the data support a two stage magma genesis process in which normal 18 o rhyolites are generated by partial melting and hybridization of the crust by mantle derived basalt and low 18 o rhyolites tap 20 80 of hydrothermally altered portions of normal 18 o rhyolitic rocks this two stage magma genesis process may be applicable to other caldera systems around the world for which the characteristic o isotope depletions are either less pronounced or undiscovered

ipswichian fauna of victoria cave and the marine palaeoclimatic record the lack of age dating methods which can be applied beyond the limit of radiocarbon dating makes the global correlation of continental climatic events and stratigraphic sequences with the continuous palaeoclimate record obtained by isotopic and faunal analysis of deep sea sediment cores1 3 a difficult task often only a relative time scale can be obtained using complex and perhaps tenuous litho and biostratigraphical data speleothems may assist in this correlation for embodied in their calcium carbonate structures are elemental and isotopic variations which indicate both their age and climatic conditions prevailing during their deposition speleothems may be reliably dated by the 230th 234u method to an age of 350 kyr bp providing they consist of non porous unrecrystallized calcite which is essentially free of clastic detrital sediments4 6 they may also provide palaeoclimatic information for previously glaciated areas 1 because their presence indicates that groundwater movement was not prevented by ice formation at the surface and co2 was produced in the soil zone by root respiration and plant decay limestone bedrock may then be dissolved and reprecipitated as speleothems in caves below the surface and 2 because of the variations in stable isotopic content and fluid inclusion waters contained therein4 7 8 additional climatic and chronological information may be obtained where speleothems are interstratified with deposits characteristic of a particular climatic regime and with deposits containing organic remains we describe here the results of dating speleothems encrusting the remains of mammals from victoria cave in northern england and discuss their significance in terms of the correlation between continental and oceanic palaeoclimatic records

a rapid and synchronous initiation of the wide spread cryogenian glaciations abstract the neoproterozoic glaciations represent a remarkable milestone in earth evolution due to their major influence on atmosphere biosphere and hydrosphere the early cryogenian sturtian glaciations evidence for which has been recorded worldwide may have lasted for about 50 million years but the precise timing and synchroneity of these glaciations have been disputed jiangkou glacigenic strata in south china can be attributed to the sturtian glacial episode as they share sedimentological stratigraphic and lithological similarities with sturtian strata in south australia as such dating the onset of the jiangkou glaciation would contribute to testing the synchroneity of the worldwide sturtian glaciation in this paper we demonstrate by means of sims u pb zircon dating that the jiangkou glaciation in south china was initiated at 715 9 2 8 ma the new age is within uncertainty synchronous with dates obtained from the lower parts of glacigenic successions in laurentia and oman thereby indicating thereby indicating a synchroneity and global extent to the sturtian glaciation the synchronous occurrence of the sturtian glaciation in mid to low latitude regions implies rapid ice sheet advancement in response to ice albedo feedback as supported by numerical climatic modeling

u pb geochronology and hf nd isotopic geochemistry of the badu complex southeastern china implications for the precambrian crustal evolution and paleogeography of the cathaysia block abstract the oldest rocks of the cathaysia block south china comprise the badu complex and paleoproterozoic granites in the wuyishan area southern zhejiang and northwestern fujian provinces new zircon u pb ages hf isotopes and trace elements for metamorphic rocks from the badu complex and bulk nd isotope compositions of these rocks and granites in the wuyishan area provide important constraints on the precambrian crustal evolution of the cathaysia block inherited cores of zircon grains from the metamorphic rocks are of magmatic origin predominantly formed at ca 2 5 ga while overgrowth rims reflect two episodes of granulite facies metamorphism related to collisional orogeny at 1 89 1 88 ga and 252 234 ma the unimodal age distribution 2 5 ga of detrital zircons and the positive hf t of most neoarchean zircons suggest that the detritus of these sedimentary protoliths of the badu complex came from a proximal volcanic arc and that they were deposited in an arc basin synchronously with 2 5 ga volcanism zircon u pb ages and hf isotopes with whole rock nd isotopes suggest that the juvenile crust of the eastern cathaysia block was generated mainly at 2 5 ga and 2 8 ga and minor at 3 5 3 3 ga with some evidence for the generation at 3 7 3 6 ga and 4 0 ga a strong 1 9 ga orogeny and the 3 3 3 0 ga thermal event only involved the reworking of older crust material paleoproterozoic 1 89 1 86 ga granitic magmatic activity and high grade metamorphism in the eastern cathaysia block were synchronous with the assembly of the columbia supercontinent using integrated geochronological hf nd isotopic and petrologic data as a barcode we compare the cathaysia block with other paleoproterozoic orogens worldwide and argue that its closest affinity is with the south korean peninsula and the lesser himalaya of nw india consequently the eastern cathaysia block and the south korean massif as the united cathay south korea terrane was close to the lesser himalaya terrane in the paleoproterozoic configuration of the columbia supercontinent the spatial linkage was maintained for ca 1 ga until the fragmentation of the rodinia supercontinent during neoproterozoic time

origin and evolution of silicic magmatism at yellowstone based on ion microprobe analysis of isotopically zoned zircons the origin of large volume yellowstone ignimbrites and smallervolume intra caldera lavas requires shallow remelting of enormous volumes of variably o depleted volcanic and sub volcanic rocks altered by hydrothermal activity zircons provide probes of these processes as they preserve older ages and inherited do values this study presents a high resolution oxygen isotope examination of volcanism at yellowstone using ion microprobe analysis with an average precision of 0 2o and a 10 mm spot size we report 357 analyses of cores and rims of zircons and isotope profiles of 142 single zircons in 11 units that represent majoryellowstone ignimbrites and post caldera lavas many zircons from these samples were previously dated in the same spots by sensitive high resolution ion microprobe shrimp and all zircons were analyzed for oxygen isotope ratios in bulk as a function of grain size by laser fluorination we additionally report oxygen isotope analyses of quartz crystals in three units the results of this work provide the following new observations 1 most zircons from post caldera low do lavas are zoned with higher do values and highly variable u pb ages in the cores that suggest inheritance from pre caldera rocks exposed on the surface 2 many of the higher do zircon cores in these lavas have u pb zircon crystallization ages that postdate caldera formation but pre date the eruption age by 10 20 kyr and represent inheritance of unexposed post caldera sub volcanic units that have do similar to the lava creek tuff 3 young and voluminous 0 25 0 1ma intra caldera lavas which represent the latest volcanic activity atyellowstone contain zircons with both high do and lowdo cores surrounded by an intermediate do rim this implies inheritance of a variety of rocks from high do pre caldera and low do post caldera units followed by residence in a common intermediate do melt prior to eruption 4 major ignimbrites of huckleberry ridge and to a lesser extent the lava creek and mesa falls tuffs contain zoned zircons with lower do zircon cores suggesting that melting and zircon inheritance from the lowdo hydrothermally altered carapace was an important process during formation of these large magma bodies prior to caldera collapse 5 the do zoning in the majority of zircon core rim interfaces is step like rather than smoothly inflected suggesting that processes of solution reprecipitation were more important than intracrystalline oxygen diffusion concave downward zircon crystal size distributions support dissolution of the smaller crystals and growth of rims on larger crystals this study suggests that silicic magmatism atyellowstone proceeded via rapid shallow level remelting of earlier erupted and hydrothermally alteredyellowstone source rocks and that pulses of basaltic magma provided the heat for melting each postcaldera yellowstone lava represents an independent homogenized magma batch that was generated rapidly by remelting of source rocks of various ages and do values the commonly held model of a single large volume super solidus mushy state magma chamber that is periodically reactivated and produces rhyolitic offspring is not supported by our data rather the source rocks for theyellowstone volcanism were cooled below the solidus hydrothermally altered by heated meteoric waters that caused low do values and then remelted in distinct pockets by intrusion of basic magmas each packet of new melt inherited zircons that retained older age and do values this interpretation may have significance for interpreting seismic data for crustal low velocity zones in which magma mush and solidified areas experiencing hydrothermal circulation occur side by side new basalt intrusions into this solidifying batholith are required to form the youngest volcanic rocks that erupted as independent rhyolitic magmas we also suggest that the lava creek tuff

patterns and timing of exhumation and deformation in the eastern cordillera of nw argentina revealed by u th he thermochronology 1 the eastern cordillera ec and related ranges of bolivia and argentina exhibit a wide variety of structural features both thick and thin skinned that make this region a prime area to study the evolution of these two contrasting styles using a combination of structural geochronological and thermochronological techniques this study investigates how and in what order the various structures of the argentinean ec from 25 to 26 s have developed during the cenozoic new mapping in the angastaco area preserves one of the thickest cenozoic stratigraphic sections and records a complex structural evolution during the neogene characterized by inversion of cretaceous salta rift structures detrital zircon u pb geochronology combined with stratigraphic and structural features typical of synsedimentary deformation constrains the age of orgenic growth in the area to 14 ma detrital apatite u th he thermochronology on samples collected across the width of the southernmost ec at this latitude document an eastward younging of ages interpreted as the result of sequential eastward propagation of exhumation and inferred deformation from 14 to 3 ma at a rate of 8 3 mm a our data when compared with existing data show that the puna plateau of nw argentina was exhuming and deforming at the same time as the ec and inter andean regions of bolivia suggesting that the deformation front connects along strike despite of the differences in structural style whereas the deformation front reached the sub andes of bolivia by 10 ma deformation localized in the ec of nw argentina until 4 ma rates of propagation through the whole region seem to be quasi uniform regardless of different structural styles

evidence for melting mud in earth s mantle from extreme oxygen isotope signatures in zircon evidence for melting mud in earth s mantle from extreme oxygen isotope signatures in zircon

oblique half graben inversion of the mesozoic neuquen rift in the malargue fold and thrust belt mendoza argentina new insights from analogue models abstract the malargue fold and thrust belt located in the andean mountains between 34 s and 36 30 s formed in response to contraction during cenozoic times its structural style and geometry was controlled by the mesozoic rift system that formed the neuquen basin in west central argentina the rift architecture in the southern sector of this belt was previously interpreted in terms of the present n s compressive structural trends assuming the inversion of pre existing normal faults with the same orientation here we propose that the nw se trending el manzano liu cullin lineament located in the northern termination of the sierra azul reflects the presence of a half graben master fault in the subsurface this hypothesis is supported by subsurface data a balanced cross section and it is tested using a series of scaled sandbox analogue models we suggest that the lineament responds to a reactivated nw trending half graben fault hidden by the mainly n s trending andean structures the proposed orientation is in agreement with the ne sw extension developed in the neuquen basin during the triassic early jurassic the modeling of the inverted oblique half graben reveals that the strikes of the main structures of inversion related belts may often be independent of the orientation of the previously developed extensional system providing a new perspective for their interpretation

a new age constraint on the onset of the neoproterozoic glaciations in the yangtze platform south china abstract a sample from the top of the banxi group early neoproterozoic in hunan province south china was dated by the shrimp zircon u pb method the resulting age of 725 10 ma probably solves the debate between the synglacial and the preglacial correlation of the liantuo formation and indicates that the liantuo formation most likely correlates with the preglacial banxi group since the banxi danzhou group is upwardly transitional to the glacial jiangkou group the age becomes a new maximum age constraint on the onset of the jiangkou glaciation which therefore most likely correlates with the sturtian glaciation

foraminiferal isoleucine epimerization determinations from the nar valley clay norfolk uk implications for quaternary correlations in the southern north sea basin fully temperate freshwater brackish and marine sediments overlying anglian till and glacilacustrine sediments in the nar valley area of northwest norfolk uk have been attributed to the middle pleistocene hoxnian temperate stage on palynological grounds and basal peats associated with this sequence have been recently correlated with oxygen isotope stage 9 on the basis of a series of 230 th 238 u dates mean 317 14 ka at tottenhill these sediments nar valley freshwater beds nar valley clay underlie a deltaic complex attributed to the wolstonian ice margin the lithostratigraphical relations between the major formations in the nar valley and the pollen stratigraphy of the fully temperate sequence are very similar to the pleistocene sequence in the inner silver pit area of the southern north sea and correlation has been proposed between the successions described from these two localities however the inner silver pit sequence has yielded aminostratigraphic data consistent with isotopic stage 11 benthic foraminiferal assemblages and foraminiferal amino acid determinations have been investigated from the nar valley clay in order to test further the palaeoenvironmental setting of the sequence and to help resolve the age of the sequence and correlation with the inner silver pit interglacial the foraminiferal assemblages support previous sedimentological and palaeontological evidence for a transgressive tendency within this sequence multiple isoleucine epimerization determinations on ammonia beccarii and aubignyna perlucida from five levels within the nar valley clay give mean aile ile ratios of 0 135 and 0 111 respectively the a beccarii ratios are much lower than mean aile ile ratios on equivalent species from the interglacial sequence in the inner silver pit upper sand hole formation which are close to 0 2 and the two datasets fail to overlap at the 1 level the new aminostratigraphic ratios indicate correlation of the nar valley clay with oxygen isotope stage 9 and therefore support the pre existing 230 th 238 u data these results suggest that two temperate stages of hoxnian palynological affinity are present in the quaternary record of east anglia and the southern north sea basin a conclusion consistent with independent new u series data from other hoxnian sites in east anglia an alternative model in which the amino acid ratios are explained as a function of different post depositional thermal histories related to length of cover by ice and water is discussed but considered unlikely the conclusions have important implications for the timing and number of glacial events in and around the southern north sea basin and help to resolve discrepancies in relative sea level histories and biogeography in temperate sequences hitherto accommodated within a single stage

u series dating of hoxnian interglacial deposits at marks tey essex england a u th dating study was carried out on the authigenic carbonate component of interglacial lake sediments at marks tey essex england isochron methods were necessary because of the presence of non carbonate detritus calculated dates around the limit of the u th method were obtained for two horizons error limits were determined by monte carlo sampling from the normal distributions of errors in the isotope ratios comparison of the resulting empirical distribution functions with the marine oxygen isotope time scale indicates with 87 confidence that the marks tey sediments correlate with ois 11 or some older stage as the marks tey deposits rest without stratigraphical break on anglian till and can be firmly correlated with the hoxnian interglacial type site at hoxne suffolk england this result implies that the anglian glaciation took place in ois 12 acid the hoxnian stage of the british chronostratigraphy commenced in ois 11 copyright c 1999 john wiley sons ltd

response of intracontinental deformation in the central andes to late cenozoic reorganization of south american plate motions new stratigraphic chronologic and fault kinematic data from the quebrada del toro in northwestern argentina provide a detailed view of late cenozoic kinematic reorganization in the southern central andes the quebrada del toro is a thrust bounded basin filled with 2 km of synorogenic clastic deposits ranging in age from early miocene to holocene as observed elsewhere in northwestern argentina faults in the quebrada del toro record an early phase of horizontal nw se contraction beginning between early and late miocene and ending after 0 98 ma and a later phase of horizontal ne sw contraction beginning between late miocene and 4 17 ma and still active these results require both kinematic regimes to have been active between 4 17 and 0 98 ma compatible with timing and kinematic data from the adjacent central andes and best explained by a temporal pattern of serial recurrence of the kinematic regimes a hypothesis that intraplate deformation in the central andes is driven by the absolute motion of the south american plate with respect to the hotspot reference frame is tested by comparing quebrada del toro kinematics to plate reconstructions and space based geodetic results nazca south america relative motion and absolute nazca plate motion show consistent azimuths throughout the past 20 5 myr in contrast absolute south american plate motion azimuths mimic the changing contraction directions determined from intraplate andean faults although the timing of the south american plate motion change is poorly resolved by current data it is compatible with the quebrada del toro data absolute upper plate motion might control intraplate kinematics along many of the earth s convergent margins

comparison of u th paleomagnetism and cosmogenic burial methods for dating caves implications for landscape evolution studies caves are useful in landscape evolution studies because they often mark the level of previous water tables and when dated yield incision rates dating caves is problematic however because their ages are only constrained by the oldest deposits contained within which may be far younger than the cave itself we dated cave deposits in the sierra nevada using u th dating of speleothems paleomagnetic dating of fine sediment and cosmogenic 26 al 10 be burial dating of coarse sediment the sampled caves formed sequentially as the water table lowered providing an important stratigraphic test for the dating methods large discrepancies between deposit ages from similar cave levels demonstrate that even when accurately determined deposit ages can seriously underestimate the timing of cave development drip type speleothems are most prone to this minimum age bias because they can accumulate long after caves form and because the u th method is limited to 400 ka paleomagnetic dating requires correlation with the global reversal chronology and is hindered by a lack of continuous stratigraphy the fine sediment analyzed for paleomagnetism is also highly susceptible to remobilization and deposition in cave passages well above base level cosmogenic 26 al 10 be dates bedload material deposited when caves were at or very near river level and can date material as old as 5 ma in the sierra nevada speleothem u th ages and sediment burial ages from the same cave levels differ by as much as an order of magnitude these results suggest speleothem ages alone may significantly underestimate cave ages

shrimp u pb zircon geochronology and geochemistry of metavolcanic and metasedimentary rocks in northwestern fujian cathaysia block china tectonic implications and the need to redefine lithostratigraphic units abstract northwestern fujian province is one of the most important pre palaeozoic areas in the cathaysia block of south china metavolcano sedimentary and metasedimentary rocks of different types ages and metamorphic grades granulite to upper greenschist facies are present and previously were divided into several formations and groups tectonic contacts occur between some units whereas deformed unconformities have been reported between others new shrimp u pb zircon ages presented here indicate that the original lithostratigraphy and the old group and formation terminology should be abandoned thus the tianjingping formation was not formed in the archaean or palaeoproterozoic as previously considered but must be younger than its youngest detrital zircons 1790 ma but older than regional metamorphism 460 ma besides magmatic zircon ages of 807 ma obtained from metavolcano sedimentary rocks of the nanshan formation and 751 728 ma for the mamianshan group many inherited and detrital zircons with ages ranging from 1 0 to 0 8 ga were also found in them these ages indicate that the geological evolution of the study area may be related to the assembly and subsequent break up of the rodinia supercontinent the new zircon results poorly constrain the age of the mayuan group as neoproterozoic to early palaeozoic 728 458 ma and not palaeoproterozoic as previously thought many older inherited and detrital zircons with ages of 3 6 2 8 2 7 2 6 2 5 2 0 1 8 and 1 6 ga were found in this study a 3 6 ga detrital grain is the oldest one so far identified in northwestern fujian province as well as throughout the cathaysia block nd isotope tdm values of eight volcano sedimentary and clastic sedimentary rock samples centre on 2 73 1 68 ga being much older than the formation ages of their protoliths and thus showing that the recycling of older crust played an important role in their formation these rocks underwent high grade metamorphism in the early palaeozoic 458 425 ma during an important tectono thermal event in the cathaysia block