paleoproterozoic tectonic transition from collision to extension in the eastern cathaysia block south china evidence from geochemistry zircon u pb geochronology and nd hf isotopes of a granite charnockite suite in southwestern zhejiang abstract the badu complex and associated paleoproterozoic granitoids are among the oldest known rocks in the cathaysia block in south china the paleoproterozoic units of the badu complex are dominantly composed of metapelitic rocks and meta greywackes here we report la ss icp ms laser ablation split stream inductively coupled plasma mass spectrometry zircon u pb data from a newly discovered garnet bearing granite which show an emplacement age of 1929 15 ma and metamorphism at 1872 34 ma we also report u pb ages of 1886 16 ma 1858 7 ma 1848 11 ma from a gneissic granodiorite and two charnockites respectively the garnet bearing granite is peraluminous with a cnk range from 1 1 to 1 3 the rock shows relatively high sio2 k2o and rb contents and low total ree sr cao and ferromagnesian components typical of leucogranites the whole rock nd two stage model age tdm2 nd of this rock is ca 2 7 ga zircon hf crustal model ages tdmc hf peak at about 2 7 ga and abundant inherited zircons occur with u pb ages in the range of 2044 to 2803 ma evidences from zircon u pb age and hf isotope compositions whole rock nd isotopes and whole rock major and trace elements suggest a metasedimentary protolith and that the garnet bearing granite leucogranite was derived by partial melting in a thickened crust at about 1 93 ga the gneissic granodiorite and charnockites show indistinguishable major and trace element features as well as zircon hf and whole rock nd isotope compositions indicating that they were generated from the same source rocks the gneissic granodiorite and charnockites are ferroan calc alkalic and metaluminous with a cnk range from 0 80 to 0 98 they display relatively low sio2 contents and ga al ratios suggesting their a type affinity their zircon tdmc hf age peak is 2 9 ga and whole rock tdm2 nd ages range from 2 8 to 2 9 ga these high temperature rocks were generated possibly through the partial melting of ancient amphibolites 2 9 ga with heat input from asthenosphere upwelling and magmatic underplating in an extensional setting at about 1 85 1 88 ga combined with data from previous studies we suggest three episodes of major crustal growth in this region at 1 8 1 9 ga 2 7 ga and 2 9 ga during the 1 8 1 9 ga event extensive reworking also took place from the 1 93 ga syn collision leucogranite garnet bearing granite the 1 88 1 85 ga post collision a type granites and charnockites the granite charnockite suite and the1 85 1 77 ga intraplate basaltic rocks li 1997 and xiang et al 2008 in the region a paleoproterozoic orogenic cycle can be deciphered in the cathaysia block the rapid transition of tectonic regime from collision to post collisional extension can be correlated to the assembly of the supercontinent columbia

an exotic mesoarchean microcontinent the coorg block southern india abstract sandwiched between the dharwar craton in the north and the neoarchean proterozoic crustal blocks to the south the coorg block in southern india is composed dominantly of a suite of arc magmatic rocks including charnockites ttg tonalite trondhjemite granodiorite related granitoid suite and felsic volcanic tuffs together with minor accreted oceanic remnants along the periphery of the block coeval mafic and felsic magmatism with magma mixing and mingling in an arc setting is well represented in the block here we present the petrology geochemistry zircon u pb geochronology and lu hf isotopes of all the major lithologies from this block computation of metamorphic p t conditions from mineral chemical data shows consistent granulite facies p t conditions of 820 870 c and up to 6 kbar our geochemical data from major trace and ree on representative samples of the dominant rock types from the coorg block corroborate an arc related signature with magma generation in a convergent margin setting the zircon data yield weighted mean 207pb 206pb ages of 3153 4 9 to 3184 0 5 5 ma for syenogranites 3170 3 6 8 ma for biotite granite 3275 5 1 ma for trondhjemite 3133 12 to 3163 8 6 9 ma for charnockites 3156 10 to 3158 3 8 2 for mafic enclaves 3161 16 ma for diorite and 3173 16 ma for felsic volcanic tuff an upper intercept age of 3363 59 ma and a lower intercept age of 2896 130 ma on zircons from a charnockite as well as an evaluation of the th u values of the zircon domains against respective 207pb 206pb ages suggest that the mesoarchean magma emplacement which probably ranged from 3 3 to 3 1 ga was immediately followed by metamorphism at ca 3 0 to 2 9 ga the ages of magmatic zircons from the charnockites and their mafic granulite enclaves as well as those from the volcanic tuff and biotite granite are all remarkably consistent and concordant marking ca 3 1 ga as the peak of subduction related crust building in this block within the tectonic milieu of an active convergent margin the majority of zircons from the coorg rocks show hf isotope features typical of crystallization from magmas derived from juvenile sources their hf crustal model ages suggest that the crust building might have also involved partial recycling of basement rocks as old as ca 3 8 ga the crustal blocks in the southern granulite terrane in india preserve strong imprints of major tectonothermal events at 2 5 ga 2 0 ga 0 8 ga and 0 55 ga associated with various subduction accretion collision or rifting events however the coorg block is exceptional with our data suggesting that none of the above events affected this block importantly there is also no record in the coorg block for the 2 5 ga pervasive regional metamorphism that affected all the other blocks in this region the geochronological data raise the intriguing possibility that this block is an exotic entity within the dominantly neoarchean collage in the northern domain of the southern granulite terrane of india the mesoarchean arc related rocks in the coorg block suggest that the magma factories and their tectonic architecture in the early earth were not markedly different from those associated with the modern style plate tectonics

shrimp zircon and titanite u pb ages lu hf isotope signatures and geochemical constraints for 2 56 ga granitic magmatism in western dharwar craton southern india evidence for short lived neoarchean episodic crustal growth abstract shrimp u pb zircon and titanite age data for granites adjacent to the gadag greenstone belt ggb in the western dharwar craton wdc india establish the occurrence of voluminous 2 56 ga granitic magmatism and indicate the development and evolution of the ggb over a time span of 70 m y these new data show that the ggb has an evolutionary history distinct from the chitradurga greenstone belt cgb to the south which was previously considered to be linked to that of the ggb based on the continuity of lithological associations whole rock geochemical data indicate granites marginal to the ggb are potassic were derived from intracrustal melting of an arc crust without the involvement of mantle and demonstrates the prevalence of horizontal tectonics in the evolution of dharwar craton lu hf zircon studies indicate that these rocks were derived from a heterogeneous arc crust with distinct crustal histories on either side of the ggb the voluminous 2 56 ga granitic magmatism surrounding the ggb in the wdc in addition to the known 2 61 and 2 56 2 52 ga felsic magmatism supports a number of short lived episodic crustal growth events within the dharwar craton during the neoarchean over a period of 100 m y short lived episodic crustal growth during the archean typically within the time scale of few million years marks the distinction with long lived modern style subduction processes these variations are often attributed to hotter archean mantle and prevailing geodynamic regime

persistent solar influence on north atlantic climate during the holocene surface winds and surface ocean hydrography in the subpolar north atlantic appear to have been influenced by variations in solar output through the entire holocene the evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon 14 and beryllium 10 and centennial to millennial time scale changes in proxies of drift ice measured in deep sea sediment cores a solar forcing mechanism therefore may underlie at least the holocene segment of the north atlantic9s 1500 year cycle the surface hydrographic changes may have affected production of north atlantic deep water potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally

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

paleoenvironmental and paleoclimatic interpretation of the stratigraphic sequence of lezetxiki ii cave basque country iberian peninsula inferred from small vertebrate assemblages naroa garcia ibaibarriaga aitziber suarez bilbao salvador bailon alvaro arrizabalaga maria jose iriarte chiapusso lee arnold martina demuro and xabier murelaga

zircon u pb geochronology and hf isotope of felsic volcanics from attappadi southern india implications for neoarchean convergent margin tectonics abstract the attappadi area on the south western flanks of the archean dharwar craton in southern india is located along the e w trending bhavani shear zone which marks the trace of a neoarchean suture zone the dominant rock types in the area include meta ultramafics amphibolites ttg tonalite trondhjemite granodiorite gneisses metapelites and sulphidic banded iron formation bif here we report the occurrence of felsic volcanic rocks preserving primary textures from the anaikatti area in eastern attappadi the felsic volcanics are interbanded with the bif amphibolite metapelite metapyroxenite and hornblende gneisses the felsic volcanics are divided into two types based on their textures the type 1 rock is medium grained with gneissic texture and lack unequivocal primary volcanic textures type 2 felsic volcanics are thinly laminated fine grained and at places preserve relict soft sediment deformation structures they also contain relict volcanic clasts or lapilli and are interpreted as felsic tuff geochemically the attappadi felsic volcanics are rhyolitic in composition and have arc related trace element signatures they also possess a calc alkaline volcanic affinity we report la icpms u pb ages from zircons in four samples of the felsic tuffs which show weighted mean ages of 2567 18 ma and mswd 1 4 2499 19 ma mswd 0 57 2555 24 ma mswd 1 7 and 2576 64 ma mswd 5 8 the late neoarchean early paleoproterozoic ages obtained in our study correlate well with the zircon u pb ages reported in recent studies from ophiolites and other suprasubduction suites from attappadi and surrounding regions the zircon ehf values range from 11 1 to 7 6 suggesting heterogeneous source material involving both juvenile and older reworked components we build a tectonic model for the sw margin of the dharwar craton with an oceanic realm characterized by island arcs and widespread submarine tholeiitic as well as komatiitic ultramafic and mafic volcanism during the neoarchean this predominantly mafic volcanism on the ocean floor is represented by primitive komatiitic lavas oxide and sulphide facies bif the birth of volcanic arc at the convergent margin is marked by felsic volcanism and the deposition of felsic volcanics and volcano sedimentary successions in the final stage of ocean closure the ocean plate and continental arc assemblages were brought in juxtaposition including the accretion of the ophiolitic fragments our study confirms the recent models of arc arc and arc continental accretion to the southern margin of the dharwar craton and major continental growth at the end of the archean

paleoenvironmental reconstruction of the early neolithic to middle bronze age pena larga rock shelter alava spain from the small mammal record abstract the pena larga site a rock shelter on the southern slopes of the cantabrian cordillera north spain is an archeological deposit covering nearly 4000 years from the early neolithic to the middle bronze age atlantic subboreal chronozones it was used both as a household and as a stable with a hiatus in the chalcolithic when it was used as a collective sepulcher nearly twenty eight thousand small vertebrate elements were recovered from its seven stratigraphic units of which 2553 items were identified to the genus and or species levels the assemblage is composed of mammals birds reptiles and amphibians of these small mammals were used for paleoenvironmental reconstruction since they are very sensitive to climatic conditions the sample sizes are large and their preservation is good their distributions over time measured in terms of relative abundance serve as reliable proxies of habitat and climate change the reconstruction of pena larga s past environments based on small mammals roughly coincides with the pollen and the amphibian reptile records on the local scale and with that of an ice core from central greenland on the global scale this makes it a valuable tool for comparative purposes both in the regional and continental scales

a coastal reservoir of terrestrial resources for neanderthal populations in north eastern iberia palaeoenvironmental data inferred from the small vertebrate assemblage of cova del gegant sitges barcelona coastal areas as reservoirs of resources for hominid groups have been widely studied in recent years these areas combine marine with terrestrial and wetland resources and would have been optimum sites for hominids including neanderthals this is the case with the cova del gegant a cave that today opens directly onto the mediterranean sea and is located in the north eastern iberian peninsula the geomorphological evolution of the massis del garraf has provided evidence that during the late pleistocene there was a littoral platform between 8 and 13 km wide in front of the cova del gegant within this framework the data derived from analysis of the small vertebrates and large mammals recovered from cova del gegant including taxa currently absent from the massis del garraf suggest that the landscape surrounding the cave provided a richer terrestrial ecosystem for neanderthals than is available in this zone today analysis of the small vertebrate association from the cave reveals that the landscape surrounding the cave was dominated by woodland edge and open environments and that the climate was mediterranean the results have been compared with the only iberian site with similar characteristics to the cova del gegant gorham s cave southern iberia gibraltar revealing differences and similarities in the landscape and climate on the basis of the small mammal assemblages as well as the differences in the accessibility to terrestrial mammalian resources for the neanderthal groups the landscape and the climate were reasonably similar at the two sites but the differences in the accessibility of resources for the neanderthals are directly related to the location of the sites and the coastal position whereas the cova del gegant was on a route of mammal migration between the ebro valley and france suited for securing terrestrial resources gorham s cave is located on a small peninsula with a lower abundance of terrestrial mammal resources this is probably why the neanderthal groups at gorham s cave exploited marine resources whereas there is no evidence of marine resources having been exploited at cova del gegant even though the seashore was nearby copyright 2011 john wiley sons ltd

airborne electromagnetic footprints in 1d earths existing estimates of footprint size for airborne electromagnetic aem systems have been based largely on the inductive limit of the response we present calculations of frequency domain aem footprint sizes in infinitehorizontal thin sheet and half space models for the case of finite frequency and conductivity in a half space the original definition of the footprint is extended to be the side length of the cube with its top centered below the transmitter that contains the induced currents responsible for 90 of the secondary field measured at the receiver for a horizontal coplanar helicopter frequency domain system the in phase footprint for induction numbers less than 0 4 thin sheet or less than 0 6 half space increases from around 3 7 times the flight height at the inductive limit to more than 10 times the flight height for a vertical coaxial system the half space footprint exceeds nine times the flight height for induction numbers less than 0 09 for all models geometries and frequencies the quadrature footprint is approximately half to two thirds that of the in phase footprint these footprint estimates are supported by 3d model calculations that suggest resistive targets must be separated by the footprint dimension for their individual anomalies to be resolved completely analysis of frequency domain aem field data acquired for antarctic sea ice thickness measurements supports the existence of a smaller footprint for the quadrature component in comparison with the in phase but the effect is relatively weak in phase and quadrature footprints estimated by comparing aem to drillhole data are considerably smaller than footprints from 1d and 3d calculations however we consider the footprints estimated directly from field data unreliable since they are based on a drillhole data set that did not adequately define the true 3d sea ice thickness distribution around the aem flight line

geochronological constraints on tectonic models for australian palaeoproterozoic high k granites high k granites extensively intruded all the palaeoproterozoic terrains of northern australia and have been interpreted as the culmination of widespread intracratonic orogeny one of these terrains the lamboo complex developed between the kimberley and north australian cratons the complex is divided into three terranes referred to as the western central and eastern zones and was intruded by a variety of i type granites and gabbros high k granites of the 1865 1850 ma paperbark supersuite are restricted to the western zone tonalite sheets of the dougalls suite and unassigned leucogranite sheets intruded the central zone at c 1850 ma the 1835 1805 ma sally downs supersuite is composed of tonalite and high k granite that mainly intruded the central zone however high k granites of the sally downs supersuite intruded all three zones from c 1820 ma onwards and mark the amalgamation of the terranes the youngest granites in the complex are high k granites of the 1805 1790 ma san sou suite which intrude the eastern and central zones the temporal and spatial distribution of the granites is not easily reconciled with previous intracratonic models but is consistent with tectonic processes similar to those operating at present

comparison of oxygen isotope records from the gisp2 and grip greenland ice cores recent results1 2 from the greenland ice core project grip summit ice core suggest that the climate in greenland has been remarkably stable during the holocene but was extremely unstable for the time period represented by the rest of the core spanning the last two glaciations and the intervening eemian inter glacial here we present the complete oxygen isotope record for the greenland ice sheet project 2 gisp2 core drilled 28 km west of the grip core we observe large rapid climate fluctuations throughout the last glacial period which closely match those reported for the grip core however in the bottom 10 of the cores spanning the eemian interglacial and the previous glacia tion there are significant differences between the two records it is possible that ice flow may have altered the chronological sequences of the stratigraphy for the bottom part of one or both of the cores considerable further work will be necessary to evaluate the likelihood of this and the extent to which it will still be possible to extract meaningful climate information from the lowest sections of the cores

oldest rocks from peninsular india evidence for hadean to neoarchean crustal evolution abstract the evolution of continental crust during hadean and archean and related geodynamic processes provides important clues to understand the early earth history here we report evidence for hadean and eoarchean crust from the fringe of the coorg block one of the oldest crustal blocks in peninsular india we present geological petrological and geochemical data together with zircon u pb ages and lu hf isotopes from a suite of metaigneous granitoids diorite charnockite metavolcanics and metasedimentary quartz mica schist calcareous schist ferruginous quartzite and bif rocks petrological and geochemical studies indicate that the igneous suite formed from subduction related arc magmatism and that the sedimentary suite represents an imbricated accretionary package of continental shelf sequence and pelagic components mineral thermometry suggests metamorphism under temperatures of 710 730 c and pressures up to 8 kbar magmatic zircons in the metaigneous suite show oscillatory zoning and high th u contents up to 3 72 and record multiple pulses of magmatism at ca 3 5 3 2 2 7 and 2 5 2 4 ga the metasedimentary rocks accreted along the margins of the coorg block show multiple zircon population with mean 207pb 206pb ages at 3 4 3 2 3 1 2 9 2 7 2 6 2 5 2 2 2 0 and 1 3 ga and overprinted by younger thermal event at ca 0 8 0 7 ga zircons in the 3 5 ga dioritic gneiss show positive ehf t values ranging from 0 0 to 4 2 and hf crustal model ages tdmc of 3517 to 3658 ma suggesting that the parent magma was derived from eoarchean juvenile sources the zircons in the 3 2 ga charnockite display ehf t values in the range of 3 0 to 2 9 and hf crustal model ages tdmc of 3345 to 3699 ma the neoarchean metagranites diorites and felsic tuff show both positive and negative ehf t values and a range of tdmc values from 2904 to 3609 ma suggesting magma derivation from meso to eoarchean juvenile and reworked components the tdmc values of the dominant zircon population in the metasedimentary suite range from 3126 to 3786 ma with the oldest value 4031 ma recorded by zircon grain in a ferruginous quartzite the ehf t values of detrital zircons also show both positive and negative values with a dominant crustal source our zircon u pb and lu hf data suggest vestiges of neohadean primordial continental crust in peninsular india with episodic crustal growth during eoarchean mesoarchean and neoarchean building the continental nuclei the results contribute to the understanding of crustal evolution in the early history of the earth

the importance of early crustal architecture for subsequent basin forming magmatic and fluid flow events the granites tanami orogen example abstract the paleoproterozoic granites tanami orogen gto consists of tightly folded predominantly greenschist facies rocks the orogen a component of the north australian craton includes a ca 1864 ma succession of turbiditic and pelagic sedimentary rocks interbedded with volcanic rocks and abundant dolerite sills in a back arc basin setting which is intruded by collision related ca 1800 ma granitic rocks integrated 4d interpretation of deep seismic profiles gravity and magnetic field observations associated with available surface geology and igneous isotope geochemistry suggest that the gto forms an imbricated crust developed on a partially inverted s dipping rifted archean basement the rifting took place in the paleoproterozoic around 1864 ma and was followed by e w orientated compressional deformation ca 1850 ma with the development of northerly trending isoclinal folds and associated faults orthogonal collisional tectonics followed at ca 1800 ma which is associated with s verging kilometre scale folds faults and orogenic lode gold deposits in the region recognition of the preserved early rift architecture in the gto has major implications for the subsequent evolution of the orogen the early architecture has influenced all subsequent deposition deformation magmatic and fluid events including spatial control of the ca 1864 ma rock succession to the location of intrusive bodies and fluid transfer during formation of ca 1800 ma orogenic gold mineralization

tectono thermal evolution of the palaeoproterozoic granites tanami orogen north australian craton implications from hornblende and biotite 40ar 39ar geochronology abstract the palaeoproterozoic granites tanami orogen gto hosts a number of gold deposits located in the southern margin of the north australian craton the major stratigraphic succession is the palaeoproterozoic tanami group which is subdivided into the dead bullock formation and conformably overlying killi killi formation new geochemical data for the ca 1864 coora and groundrush dolerite sills in the dead bullock formation suggests that they have the same characteristics with the enriched back arc basin basaltic rocks from the former stubbins formation such as tholeiitic affinity high tio 2 contents 0 94 to 1 24 wt and low mg 41 45 slightly enriched lile rb th u and k weakly depleted hfse nb ta and relatively flat ree patterns their magma was generated by high degree decompressional melting 5 15 of the asthenosphere source with an input of 3 4 subduction related material the petrological and geochemical similarities of igneous rocks provide new evidence for the assignment of the ca 1864 ma former stubbins formation and the mount charles formations in the dead bullock formation of the tanami group these conclusions confirmed that the extensive palaeoproterozoic tanami group was deposited in a back arc basin environment hornblende and biotite 40 ar 39 ar geochronological study identified three major tectono thermal events in the gto since the deposition of the dead bullock formation the ca 1840 ma 40 ar 39 ar cooling age of metamorphic hornblende from the coora and groundrush dolerite sills in the dead bullock formation provided precise age constraint for the first palaeoproterozoic tectono thermal event during the evolution of the granites tanami back arc basin this age is highly consistent with the ca 1850 1840 ma subduction and peak metamorphism events in the north australian craton nac associated with the halls creek orogeny in the halls creek orogen and the tennant orogeny in the tennant creek inlier the 40 ar 39 ar age of 1753 8 ma for the early biotite bi b from the dead bullock formation is a cooling age record of the peak greenschist facies metamorphism during the ca 1795 ma tanami orogeny which is interpreted as the continental continental collisional event between the gto and the arunta orogen in the central australian craton to the south the approximately 40 million year slow cooling is a combined result of exhumation heat released from the upwelling asthenospheric mantle regional magmatism and long term crustal residence this tectono thermal event was associated with gold mineralisation in the gto and the proterozoic nac was finally cratonised during this period the late biotite bi g is a recrystallization product of hydrothermal alteration its 40 ar 39 ar age of 1718 8 ma revealed the last tectono thermal overprint to the gto and arunta orogen this age reflected the distal thermal influence by the ca 1723 ma strangways event in the arunta orogen

nature of magmatism and sedimentation at a columbia active margin insights from combined u pb and lu hf isotope data of detrital zircons from nw india abstract detrital zircons from a palaeoproterozoic quartzite deposited between 1 85 and 1 82 ga in the northern aravalli orogen of nw india show a distinctive age peak of ca 1 85 ga and variable but largely subchondritic ehf1 85 ga between 1 3 and 21 0 corresponding to hafnium model ages of 2 5 to 3 6 ga these data indicate an important period of reworking of ancient eo to neoarchaean strongly heterogeneous continental crust at this time prevalence of ca 1 85 ga subduction related granitoids almost identical u pb age spectra and ehft of detrital zircons in ca 1 85 ga metasedimentary rocks in the aravalli orogen and the inner lesser himalaya indicate similar sediment provenances and thus a geological connection between these two terranes during late palaeoproterozoic all together the data constrain a rapid succession of sedimentation metamorphism and subduction related magmatic activity and support the interpretation of an active geodynamic realm along the entire north indian margin at ca 1 85 ga comparison of detrital zircon data in conjunction with published paleomagnetic data from north india and other crustal blocks of the columbia supercontinent additionally suggest a close affinity of north india with madagascar the cathaysia block of south china and south korea during columbia times

re advance of the fennoscandian ice sheet during heinrich event 1 abstract five sediment cores bathymetric and 2d seismic reflection data from vestfjorden northern norway were studied in order to constrain the timing and extent of a major ice stream draining the northwestern fennoscandian ice sheet during the last deglaciation 15 10 14 c ka b p the bathymetric and seismic data indicate that vestfjorden traenadjupet was covered by grounded ice reaching the shelf break during the last glacial maximum lgm after the lgm break up and recession towards outer inner vestfjorden at 13 6 14 c ka b p the ice re advanced towards the outer part of vestfjorden prior to 13 1 14 c ka b p this is inferred from glaciomarine sediments overlain by diamicton at the base of the sediment cores interpreted as basal tills and associated contemporaneous build up of grounding zone wedges in the central vestfjorden this sequence of events is coherent with the late weichselian ice sheet dynamics both along the western norwegian continental shelf and in the barents sea possibly indicating a direct response to meltwater injection and accompanied cooling during disruption of the thermohaline circulation associated with heinrich event 1 enhanced supply of suspension load resulted in deposition of laminated sediments at 13 14 c ka b p reflecting the retreat of the ice stream towards the inner fjord in response to global climate amelioration and increased atlantic water inflow two additional ice re advances towards the norwegian coastline are inferred from distinct input of ice rafted debris ird with a typical mineralogical fingerprint derived from neoproterozoic early silurian calcite and dolomite marbles in the ice sheet catchment area thus the re advances may be concurrent with the older dryas 12 2 14 c ka b p skarpnes and younger dryas 10 7 14 c ka b p tromso lyngen cooling events

a new concept for the paleoceanographic evolution of heinrich event 1 in the north atlantic new records of planktonic foraminiferal 18o and lithic and foraminiferal counts from eirik drift are combined with published data from the nordic seas and the ice rafted debris ird belt to portray a sequence of events through heinrich event 1 h1 these events progressed from an onset of meltwater release at not vert similar19 ka bp through the conventional h1 ird deposition phase in the ird belt starting from not vert similar17 5 ka bp to a final phase between 16 5 and not vert similar15 ka bp that was characterised by a pooling of freshwater in the nordic seas which we suggest was hyperpycnally injected into that basin after not vert similar15 ka bp this freshwater was purged from the nordic seas into the north atlantic which preconditioned the nordic seas for convective deep water formation this allowed an abrupt re start of north atlantic deep water nadw formation in the nordic seas at the bolling warming 14 6 ka bp in contrast to previous estimates for the duration of h1 i e 1000 years to only a century or two the total combined composite h1 signal presented here had a duration of over 4000 yrs not vert similar19 14 6 ka bp which spanned the entire period of nadw collapse it appears that deep water formation and climate are not simply controlled by the magnitude or rate of meltwater addition instead the location of meltwater injections may be more important with nadw formation being particularly sensitive to surface freshening in the arctic nordic seas

environmental processes of the ice age land oceans glaciers epilog knowledge of the state of the earth at the last glacial maximum lgm an interval around 21 000 years ago is an important benchmark for understanding the sensitivity of global environmental systems to change much progress in understanding climates of the lgm has occurred in the 20 years since the end of the climap project of the 1970s climate long range investigation mapping and prediction here we review this progress based on presentations and discussion at a rst open science meeting of the epilog project environmental processes of the ice age land oceans glaciers held in delmenhorst germany may 1999 we outline key controversies and document protocols for epilog contributions so that a new synthesis of the lgm earth can emerge as an open project of the world s community of scientists 2001 elsevier science ltd all rights reserved

detecting stratigraphical issues using direct radiocarbon dating from small mammal remains frequently preserved in archaeological and palaeontological sites the tiny size of small mammal remains favours percolations into underlying layers along stratigraphic sequences this is one of the various postdepositional processes that may affect the integrity of the original deposits and therefore the subsequent scientific interpretations recent developments in sample preparation offer the possibility of detecting intrusive episodes through the absolute dating of minute amounts of bone down to 10 mg meaning that isolated elements such as mandibles in this case are sufficient to obtain reliable radiocarbon dates if collagen is moderately to well preserved the radiocarbon dates obtained here for small mammal bones recovered from pre bolling to recent deposits and their comparison with previous dates obtained from other sources large mammal bones charcoal botanical samples etc with different protocols and instruments illustrate the potential of small mammal dating to reveal and eventually contribute a solution to stratigraphical issues in different archaeological contexts

depositional age and provenance of the marboo formation from shrimp u pb zircon geochronology implications for the early palaeoproterozoic tectonic evolution of the kimberley region western australia abstract the marboo formation is the oldest rock unit in the hooper complex in the west kimberley region of western australia the complex forms an elongate belt 350 km long and at least 100 km wide of deformed and metamorphosed palaeoproterozoic low to high grade metasedimentary rocks and mafic and felsic igneous rocks the marboo formation consists of a sequence of turbiditic metasedimentary rocks derived from the northwest an area of crust now buried beneath the unconformably overlying speewah and kimberley basins shrimp u pb dating of detrital zircons from a low grade quartz wacke indicate that the provenance terrain contributed zircons dated at around 2500 to 2400 ma 2300 ma 2200 to 2050 ma 1970 ma and 1910 ma the mount joseph migmatite formed by in situ melting of the marboo formation and zircons interpreted as detrital in origin give ages of 2500 to 2000 ma a maximum depositional age is provided by a population of zircon cores dated at 1872 9 ma growth of rims on zircons is dated at 1861 5 ma and is interpreted as the age of high grade metamorphism a minimum age for deposition is provided by the richenda microgranodiorite which forms a high level intrusive stock into the marboo formation and is dated at 1858 5 ma comparison with recent shrimp ages from the halls creek group in the east kimberley indicates that the turbidites of the marboo formation were deposited deformed metamorphosed and intruded by granitoid before the majority of the turbiditic metasedimentary rocks in the olympio formation were deposited this is not consistent with deposition of the turbiditic rocks in the same basin the assumption of contemporaneous turbidite deposition throughout the kimberley region has been taken as evidence of intracratonic palaeoproterozoic orogeny however these results provide support for plate tectonic models and the recognition of tectonostratigraphic terranes within the kimberley region detrital zircons from the marboo formation suggest that unexposed crust beneath the speewah and kimberley basins is largely early palaeoproterozoic in age rather than archaean as previously assumed the spread in ages indicates that the time period between formation of late archaean basement in northern australia and the formation of palaeoproterozoic orogens was marked by ongoing crust formation and was not a period of quiessence

the long paleoenvironmental sequence of santimamine bizkaia spain 20 000 years of small mammal record from the latest late pleistocene to the middle holocene abstract the cave of santimamine kortezubi bizkaia spain on the southern slopes of the erenozar mountain urdaibai biosphere reserve is one of the most famous prehistoric localities of the cantabrian range between 2004 and 2006 a test trench revealed a 6 m deep stratigraphic sequence in the inner vestibule of the cave covering 20 000 years from the latest late pleistocene mis 2 to the middle holocene mis 1 it comprises six chrono cultural units lower middle and upper magdalenian azilian neolithic and chalcolithic bronze age plus seven lower purely palaeontological levels more than 47 000 microvertebrate elements including mammals birds reptiles amphibians and fishes were recovered of which 1587 were identified to the genus and or species levels of these small mammals were used for paleoenvironmental reconstruction since they are very sensitive to climatic conditions and their distributions over time measured in terms of relative abundance serve as reliable proxies of habitat and climatic change the reconstruction of santimamine past environments based on small mammals roughly coincides with other proxies such as the amphibian reptile large mammal bird palynological and cryoclastic records on the local scale other paleoenvironmental reconstructions from north iberia on the regional scale and the oxygen isotopic curve of an ice core from central greenland on the global scale all magdalenian levels from santimamine were deposited during the oldest dryas a mostly cold and humid period including the heinrich event 1 small mammalian palynological and cryoclastic evidence likely document the shift from the cold younger dryas to the beginning of the holocene climatic optimum during azilian times the uppermost level deposited during a moderate re opening of the landscape at the subboreal slightly postdates the holocene cooling event 3

tectonic evolution of proterozoic australia proterozoic australia has long been interpreted as a single intact continent in which all tectonic and magmatic activity was intracratonic this paper proposes an alternative hypothesis in which numerous fragments of continental crust were assembled by plate tectonic processes the assembly was completed between 1300 and 1100 ma when the crustal fragments were combined as an early component of the rodinian supercontinent rifting and fragmentation of archaean continents began in the late archaean and continued into the proterozoic passive margin deposits such as those of the hamersley basin accumulated on isolated fragments of archaean crust these numerous fragments were subsequently assembled into three cratons by 1830 ma a west australian craton was established by collision of the archaean pilbara and yilgarn cratons which were joined along the capricorn orogen similarly a south australian craton developed by amalgamation of the proto gawler and proto curnamona cratons along the kimban orogen a north australian craton appears to have formed by accretion of numerous crustal fragments including the kimberley pine creek lucas and altjawarra cratons with sutures marked by the king leopold halls creek tennant creek and proto isan orogens the southern margin of the north australian craton was the site of repeated terrane accretion and orogenic activity between 1880 ma and 1400 ma this included an orogenic event at 1880 1850 ma the strangways 1780 1730 ma argilke 1680 1650 ma and chewings 1620 1580 ma orogenies and the intracratonic anmatjira uplift 1500 1400 ma intracratonic rifting at 1750 to 1710 ma and 1640 to 1600 ma produced the mcarthur basin and related minor basins parts of which were deformed by the isan orogeny at 1600 and 1530 ma rifting along the line of the capricorn orogen led to deposition in the overlying intracratonic bangemall basin between 1630 and 1300 ma along the eastern margin of the south australian craton the 1670 to 1600 ma olarian orogeny marks interaction with now obscured continental crust to the east tectonic activity between 1300 and 1100 ma led to the assembly of proterozoic australia as an early component of the supercontinent of rodinia this first involved the amalgamation of the west australian and north australian cratons followed by collision with the south australian craton the centralian superbasin developed over the junction of the north south and west australian cratons between 830 and 750 ma rifting to the east formed the adelaide geosyncline at 830 ma this was followed by the breakup of rodinia with the rifting apart of laurentia and gondwanaland along the eastern margin of proterozoic australia at 750 ma and the subsequent formation of the palaeo pacific ocean after the breakup of rodinia a series of northeast southwest compressional events followed by periods of relaxation reflect the assembly of a new supercontinent old lines of weakness were reactivated culminating in the intracratonic king leopold paterson petermann ranges and pinjarra orogenies between 620 and 540 ma subsequent reactivation continued into the phanerozoic with the widespread eruption of continental flood basalts and the formation of intracratonic basins 540 530 ma

the proterozoic mount isa fault zone northeastern australia is it really a ca 1 9 ga terrane bounding suture abstract in marked contrast to palaeoproterozoic laurentia the location of sutures and boundaries of discrete crustal fragments amalgamated during palaeoproterozoic formation of the north australian craton remain highly speculative interpretations of suture locations have relied heavily on the analysis of regional geophysical datasets because of sparse exposure of rocks of the appropriate age the mount isa fault zone has been interpreted as one such palaeoproterozoic terrane bounding suture furthermore the coincidence of this fault zone with major shale hosted massive sulphide pb zn ag orebodies has led to speculations that trans lithospheric faults may be an important ingredient for the development of this deposit type this study has integrated geophysical and geochemical data to test the statute of the mount isa fault as a terrane bounding suture forward modelling of gravity data shows that basement rocks on either side of the mount isa fault have similar densities these interpretations are consistent with geochemical observations and sm nd data that suggest that basement lithologies on either side of the mount isa fault are geochemically and isotopically indistinguishable from each other and that the mount isa fault is unlikely to represent a suture zone that separates different palaeoproterozoic terranes our data indicate that the crustal blocks on both sides of the mount isa fault zone must have been in within close proximity of each other since the palaeoproterozoic and that the western fold belt was part of the ancestral north australian craton well before the 1 89 1 87 ga barramundi orogeny it appears that deep crustal variations in density may be related to the boundary between a shallowly west dipping high density mafic to ultramafic plate and low density basement rocks this interpretation in turn impacts on crustal scale models for the development of shale hosted massive sulphide pb zn mineralisation which do not require trans lithospheric faults to tap deep seated metal reservoirs and or mantle plumbing systems the approach applied herein demonstrates the value of multi disciplinary investigations to the critical assessment of long lived proterozoic fault systems which in the absence of methodical analysis are commonly assumed to represent terrane bounding sutures

hf isotopes in detrital and inherited zircons of the pilbara craton provide no evidence for hadean continents predictions of large volumes of stabilized continental crust by the early archaean stand in stark contrast to the actual amount of pre 3 5 ga rocks presently exposed on earth s surface the pilbara craton of western australia one of the best preserved paleoarchean crustal blocks on earth is believed to have developed on a cryptic possibly 3 8 ga continental basement if substantiated this could support the notion of a widespread and enduring hadean ca 4 5 4 0 ga felsic intermediate crust to test this and to elucidate the earliest evolution of the pilbara craton we report hf isotope data from previously dated detrital zircon grains and inherited zircon crystals hosted by granitic gneisses the crystallization ages 3 80 3 55 ga of which substantially exceed those of the oldest exposed igneous rocks of the craton 3 52 ga the hf isotope compositions of the ancient zircons analyzed in this study are consistent with most of the earliest components of the pilbara craton being extracted from near chondritic mantle between 3 7 and 3 6 ga with little or no input from significantly older crust these new data suggest either that the pilbara craton developed remote from the isotopic influence of the putative eoarchean to hadean continental masses or that the stabilized volumes of the earliest continents have been overestimated the latter scenario would be consistent with the extreme scarcity of 3 9 ga rocks and minerals and the dominantly chondritic hf isotope composition of the oldest continental rocks in earth s most ancient archaean cratons

palaeoenvironmental studies in nw iberia cantabrian range vegetation history and synthetic approach of the last deglaciation phases in the western mediterranean abstract at the north western limit of the mediterranean basin in the mediterranean oceanic transition zone the multidisciplinary study of two palaeolakes villaseca and la mata province of leon provides data on the last deglaciation the juxtaglacial lakes were formed during a deglaciation phase of the last cold stage weichselian wurm estimated from the regional and pyrenean chronological data between circa 48 ka and 32 ka ka 1000 years ago their drainage occurred circa 17 ka and 15 ka respectively during the definitive glacial retreat phases these results provide evidence for a glacial maximum extension preceding the global last glacial maximum lgm and an early deglaciation comparisons with the pyrenean data show that in the most important glacial basins of the pyrenean cantabrian range glaciers were still present at middle elevation circa 18 20 ka the final deglaciation did not happen until around 16 ka during the period 48 13 3 ka along the pyrenean cantabrian range three stages can be distinguished in the deglacial processes between circa 48 and 32 ka the deglacial retreats were contemporaneous with d o events 12 to 6 between circa 32 ka and 18 ka major sedimentary modifications were rare two of them are synchronous with d o 4 and 3 a glacial readvance also occurred during this period along the pyrenean cantabrian range between 18 and 17 ka major sedimentary changes and an increase in the 18o records of the ngrip ice core record are synchronous between 15 and 13 3 ka glacial retreats and sedimentary changes are synchronous with the climatic improvement observed from the end of the oldest dryas to the end of the bolling allerod period these correspondencies suggest relationships between the deglacial processes in the western mediterranean and the palaeoenvironmental events in the north atlantic region during the last glacial interglacial transition during the full glacial period the pollen data indicates dominant steppic environments the oldest dryas was not a constant cooling phase and from around 15 5 ka the pollen data indicates a slight warming during the holocene until circa 2040 cal bp mixed oak forests developed and pine was a prominent component of the cantabrian landscape then the forests were destroyed due to mining agriculture and fire and this favoured the extension of heathland

relationship between magdalenian subsistence and environmental change the mammalian evidence from el miron spain abstract during the magdalenian roughly 20 13 ka cal bp intensive human occupation of the el miron cave coincided with oldest dryas and the climate amelioration of bolling allerod pleniglacial gs 2a interstadials gi 1e 1d 1c 1b 1a the evolution of small mammal assemblages throughout the stratigraphic sequence displays a pattern similar to those of pollen geological and other studies elsewhere in the cantabrian region during the magdalenian there was a climatic recovery indicated by the first record in the stratigraphic sequence of small mammals living in forested habitats such as dormice at the end of the magdalenian there was an important diminishment of species of small mammal especially those living in meadow habitats at the beginning of the younger dryas cold period surprisingly the small mammals living in forest habitats maintained or even further increased in numbers tardiglacial use of el miron cave coincided with several climate oscillations whose impact on hunting decisions is still debated this environmental variability during the late glacial has been indicated by different proxy records palynological geological etc throughout the cantabrian region however the exact timing and intensity of these changes is unclear due to the lack of continuous rich archaeological sequences with many radiometric determinations el miron cave sequence fills this gap in the record and this paper presents a detailed reconstruction of the development of biotopes around the site based on its micromammal assemblages it shows an interesting trend of increasing forest related species notably dormice during the pleistocene holocene transition that was preceded by a significant peak of wooded biotopes towards the end of the pleniglacial during heinrich event 1 this pattern can be correlated with the strategy of subsistence that was developed as shown by the macromammalian faunas in the search for any relationship that can shed light on the type of economy adopted by magdalenian populations in terms of their reaction to resource availability

comparing 1800 1600 ma accretionary and basin processes in australia and laurentia possible geographic connections in columbia abstract we focus on potential pinning points on the southern and eastern margins of australia and the southern and western margins of laurentia and interpret a convergent plate boundary along the southern margin of the proto australian continent during the palaeo to mesoproterozoic 1800 1600 ma specific geological events within the southern australian margin can be correlated with events preserved along the medicine bow yavapai mazatzal belt in southwestern laurentia these belts were characterised by southward continental growth with varying degrees of crustal reworking and accretion of juvenile material in australia crustal reworking appears to have been the dominant process from 1800 to 1670 ma with more juvenile material accreted at 1620 ma in contrast the southern laurentian terranes were dominated by accretion of juvenile material from 1800 to 1620 ma although reworked continental crust was also accreted to the margin in the interior of both continents basins developed with comparable histories from 1800 to 1670 ma thereafter the evolution of the interior basins diverged with sag phase processes dominant in northern australia and a protracted depositional hiatus in laurentia the geologic evolution is consistent with palaeomagnetic data and provides further evidence for geographic links between eastern australia and western laurentia from 1800 to 1600 ma

palaeoenvironmental and palaeoclimatic proxies of the gorham s cave small mammal sequence gibraltar southern iberia abstract gorham s cave is located in the british territory of gibraltar in the southernmost end of the iberian peninsula the cave was discovered in 1907 and first excavated in the 1950s by john waechter of the institute of archaeology in london new excavations which started in 1997 have exposed 18 m of human occupation in the cave spanning the late pleistocene as well as including brief phoenician carthaginian and neolithic occupations the late pleistocene levels consist of two upper palaeolithic occupations attributed to the solutrean and magdalenian technocomplexes level iii and which are dated by ams radiocarbon to between 18 000 and 10 000 years ago the underlying mousterian layer level iv dated by ams radiocarbon to between 23 000 and 33 000 years ago is separated from level iii by an archaeologically sterile layer which spans some 4000 years this paper presents previously unpublished palaeoenvironmental and paleoclimatic reconstructions of gorham s cave during these pleistocene occupations using the small mammal assemblage the small mammal assemblage at gorham s cave comprises of at least 12 species 4 insectivores crocidura russula sorex gr coronatus araneus sorex minutus and talpa occidentalis 3 chiropters myotis myotis myotis nattereri and miniopterus schreibersii and 5 rodents microtus iberomys cabrerae microtus terricola duodecimcostatus arvicola sapidus apodemus sylvaticus and eliomys quercinus the presence of these small mammal species indicates that the landscape surrounding the rock of gibraltar was predominantly an open habitat with the presence of woodland and water stream meadows as well as the presence of larger bodies of water these results are then compared with pollen and charcoal analysis as well as other faunal proxies such as the herpetofauna bird and large mammal assemblages providing an accurate reconstruction of the climatic and environmental conditions that prevailed during the late pleistocene in the southernmost of the iberian peninsula

palaeoenvironmental and palaeoclimatic reconstruction of the latest pleistocene of el portalon site sierra de atapuerca northwestern spain the site of el portalon is the entrance to the cueva mayor karst system located in the sierra de atapuerca burgos spain this is an important holocene archaeological site which was excavated in the 1970s but from which little has been published new excavations starting in 2000 have highlighted a deep stratigraphical sequence with human occupations starting at the end of the late pleistocene in this paper we present for the first time on the basis of the small vertebrate assemblage palaeoenvironmental and palaeoclimatic reconstructions of the latest pleistocene of the sierra de atapuerca well known for its early to middle pleistocene human bearing localities the small vertebrates of el portalon comprise at least 25 species 4 amphibians alytes obstetricans bufo bufo bufo calamita and rana temporaria 3 squamates an indeterminate small size lacertid an indeterminate large colubrine and vipera sp 6 insectivores sorex gr coronatus araneus sorex minutus neomys fodiens neomys anomalus talpa europaea and galemys pyrenaicus 2 bats myotis myotis and myotis gr myotis blythi 10 rodents microtus arvalis microtus agrestis microtus oeconomus iberomys cabrerae chionomys nivalis terricola duodecimcostatus arvicola sapidus arvicola terrestris apodemus sylvaticus and eliomys quercinus these taxa many of which are ecothermal sensitive to temperature show variations in their taxonomic diversity throughout the sequence although with the exception of m oeconomus they do not differ from the extant fauna of the iberian peninsula they do so in the abundance of their taxonomic assemblage when the small vertebrates are grouped and studied in terms of vertical trends through the sequence it is possible to follow environmental and climatic changes results from the small vertebrate associations indicate that the landscape had open habitats in the vicinity of the atapuerca caves throughout the sequence with wet locales in the surrounding area woodland and water stream meadows were more developed during warm periods is5 is6 is7 and is3 is4 whereas during cold periods h3 and lgm the environment was slightly more humid in response to winter precipitation and the opening of the landscape these results are compared with pollen analysis and marine isotopic curves giving a scenario for the palaeoclimatic and palaeoenvironmental changes that occurred during the latest pleistocene in the sierra de atapuerca

configuration of the late paleoproterozoic supercontinent columbia insights from radiating mafic dyke swarms abstract remnants of 2 1 1 8 ga orogens can be recognized in nearly every craton assembled within reconstructions of the rodinia supercontinent although no particular pattern of laterally extensive orogenic belts emerges these cratons may be the fragments of an older supercontinent formed in response to the collision and accretion of even older cratons during the early earth history paleomagnetic constraints have played a limited role in many previous reconstructions of the early precambrian supercontinent mainly because of the poor age control and a large scatter of the paleomagnetic poles the geometry of giant radiating dyke swarms and orogenic belts provide important constraints for the reconstruction of the pre rodinian supercontinent some early unmetamorphosed and undeformed mafic dyke swarms in north china southern peninsular india and north america share coeval age of 1 85 ga if these continents are assembled the overall pattern exhibited by the mafic dyke swarms appears to constitute a giant radiating swarm with a piercing point between the cuddapah rift in south india and the xiong er aulacogen in north china this suggests that the north china craton indian craton and canadian shield may be fragmented from the same landmass the reconstruction of 1 85 ga giant radiating dyke swarm attempted in this paper suggests that the north china craton india craton and canadian shield were united together to form a landmass within the columbia supercontinent before its extension and break up the 1 90 1 85 ga andean style north orogenic belt suggests that a subduction zone existed on the northern margin of the north china craton wopmay orogenic belt developed in a 1 88 1 84 ga continental volcano plutonic arc which is interpreted as the product of eastward subduction of oceanic lithosphere the transantarctica orogenic belt in east antarctica may be another candidate to be linked with the subduction zone the north orogenic wopmay orogenic and transantarctica orogenic belts could be connected to form a continuous subduction zone the orogenic comparison strengthens the configuration of the columbia supercontinent proposed by the reconstruction of the giant radiating dyke swarm the laurentia west australia and east antarctica were relatively stable from 1 85 ga to 1 20 ga as inferred from the data on dyke swarms magmatism and the paleomagnetism these continents constituted the core of the columbia supercontinent in the late paleoproterozoic time the north china craton and indian craton were however separated from the columbia supercontinent during the mesoproterozoic time

the late archean record a puzzle in ca 35 pieces abstract the global archean record preserves ca 35 large cratonic fragments and a less well defined number of smaller slivers most archean cratons display rifted margins of proterozoic age and therefore are mere fragments of supercratons which are defined herein as large ancestral landmasses of archean age with a stabilized core that on break up spawned several independently drifting cratons the tectonic evolution of individual archean cratons such as the slave craton of north america or the kaapvaal craton of southern africa should therefore always be considered in the context of their ancestral supercratons this is particularly true for many of the smaller cratons which are too limited in size to preserve the complete tectonic systems that led to their formation these limitations not only apply to the crustal geology of archean cratons but also to their underlying lithospheric mantle keels if these keels are archean in age as their broad correlation with ancient surface rocks suggests they also are rifted and drifted remains of larger keels that initially formed below ancestral supercratons the study of archean cratons and their lithospheric keels should thus be global in scope in the search for late archean supercratons a craton like the slave with three to four rifted margins has a ca 10 maximum probability of correlating with any of the ca 35 remaining cratons around the globe assuming wholesale recycling of archean cratons has been limited since ca 2 0 ga alternatively if the original number of independently drifting cratons was significantly larger the probability of successful correlations is much less due to repeated cycles of break up and plate tectonic dispersal since ca 2 0 ga the probability of correlation is probably independent of present day proximity unless there is independent evidence that two neighbouring cratons were only separated by a narrow ocean nevertheless most previously proposed craton correlations rely erroneously on present day proximity implicitly extrapolating relatively recent paleogeography back to the archean considering the fundamental differences between some of the better known cratons such as the slave superior and kaapvaal it seems likely that these cratons originated from independent supercratons sclavia superia vaalbara with distinct amalgamation and break up histories this is contrary to widely held opinion based largely on an idealized view of the supercontinent cycle that all cratons shared a common history in a single late archean supercontinent in contrast to the superior and kaapvaal cratons which are radically different from the slave craton and each other the dharwar craton of peninsular india the zimbabwe craton of southern africa and the wyoming craton of north america all show significant similarities to the slave craton it thus seems likely that at least some of these were nearest neighbours to the slave craton in the ca 2 6 2 2 ga sclavia supercraton

the greenland ice core chronology 2005 15 42 ka part 1 constructing the time scale the greenland ice core chronology 2005 gicc05 is extended back to 42 ka b2k before 2000 ad i e to the end of greenland stadial 11 the chronology is based on independent multi parameter counting of annual layers using comprehensive high resolution measurements available from the north greenland ice core project ngrip these are measurements of visual stratigraphy conductivity of the solid ice electrolytical melt water conductivity and the concentration of na c a 2 s o 4 n o 3 n h 4 a n uncertainty estimate of the time scale is obtained from identification of uncertain annual layers which are counted as 0 570 5 years the sum of the uncertain annual layers the so called maximum counting error of the presented chronology ranges from 4 in the warm interstadial periods to 7 in the cold stadials the annual accumulation rates of the stadials and interstadials are on average one third and half of the present day values respectively and the onset of the greenland interstadials 2 3 and 8 based on 20 year averaged d 18 o

high t low p metamorphism in the palaeoproterozoic halls creek orogen northern australia the middle crustal response to a mantle related transient thermal pulse high t low p metamorphic rocks of the palaeoproterozoic central halls creek orogen in northern australia are characterised by low radiogenic heat production high upper crustal thermal gradients locally exceeding 40 c km 1 sustained for over 30 myr and a large number of layered mafic ultramafic intrusions with mantle related geochemical signatures in order to account for this combination of geological and thermal characteristics we model the middle crustal response to a transient mantle related heat pulse resulting from a temporary reduction in the thickness of the mantle lithosphere this mechanism has the potential to raise mid crustal temperatures by 150 400 c within 10 20 myr following initiation of the mantle temperature anomaly via conductive dissipation through the crust the magnitude and timing of maximum temperatures attained depend strongly on the proximity duration and lateral extent of the thermal anomaly in the mantle lithosphere and decrease sharply in response to anomalies that are seated deeper than 50 60 km maintained for 5 myr in duration and or have half widths 100 km maximum temperatures are also intimately linked to the thermal properties of the model crust primarily due to their influence on the steady state background thermal gradient the amplitudes of temperature increases in the crust are principally a function of depth and are broadly independent of crustal thermal parameters mid crustal felsic and mafic plutonism is a predictable consequence of perturbed thermal regimes in the mantle and the lowermost crust and the advection of voluminous magmas has the potential to raise temperatures in the middle crust very quickly although pluton related thermal signatures significantly dissipate within 10 myr even for very large high temperature intrusive bodies the interaction of pluton and mantle related thermal effects has the potential to maintain host rock temperatures in excess of 400 450 c for up to 30 myr in some parts of the mid crust the numerical models presented here support the notion that transient mantle related heat sources have the capacity to contribute significantly to the thermal budget of metamorphism in high t low p metamorphic belts especially in those characterised by low surface heat flow very high peak metamorphic geothermal gradients and abundant mafic intrusions

the tanami deep seismic reflection experiment an insight into gold mineralization and paleoproterozoic collision in the north australian craton abstract imaging of a major collision zone between the tanami region and aileron province of the arunta orogen in northern australia and recognition that several of the major gold deposits within the tanami region are within near surface antiformal stacks or uplifted and exhumed crustal sections associated with major crustal penetrating shear zones are fundamental results from the 2005 tanami seismic collaborative research project the suture which is interpreted to have resulted from collision separates the northwest dipping structural grain of the aileron province crust in the south from the southeast dipping structural grain of the tanami crust in the northwest the collision between the tanami region and the aileron province is interpreted to have occurred prior to ca 1840 ma the correlation between the surface extension of crustal penetrating shear zones that extend to the moho boundary and the locations of known gold rich mineral fields is significant and has implications for minerals explorers within the tanami region and elsewhere in the near surface where the crustal penetrating structures cut relatively shallow upper crustal tanami group rocks there is a significant increase in the degree of local deformation and results in through going thrust faults associated pop up structures ramp anticlines and antiformal stacking all known ore deposits appear to be located within these more complexly deformed zones and therefore have a direct association with larger scale structures

crustal root of the eastern dharwar craton zircon u pb age and lu hf isotopic evolution of the east salem block southeast india abstract the salem block represents the northern part of the southern granulite terrane in se india adjacent to the southern dharwar craton new zircon u pb and lu hf results on charnockites granitoids and migmatites from the eastern salem block indicate that it mainly consists of bimodal juvenile neoarchaean early palaeoproterozoic 2 75 2 65 ga and 2 55 2 48 ga crust that underwent peak metamorphism at 2 53 ga these u pb ages and lu hf isotopic signatures characterize the salem block as part of the lower crust of the eastern dharwar craton the oldest 2 75 2 65 ga granulites can be traced along important shear zones salem attur and gangavalli shear zones which may thus expose deeper levels of eastern dharwar lower crust in a way similar to that proposed for the nilgiri granulites an additional minor contribution of recycled western dharwar craton in the salem block is suggested by the presence of limited 3 65 3 35 ga recycled crust and 2 9 2 6 ga detritus younger intrusions within the salem block include the cryogenian 820 800 ma yelagiri alkaline complex and the ediacaran 559 1 3 5 ma sankari tiruchengode granitoid complex these were sourced from recycled neoarchaean protoliths of the salem block cryogenian tonian age magmatism is widespread within the southern granulite terrane and is possibly related to initial subduction of the mozambique ocean the ediacaran a type granitoids are thought to have formed during the malagasy orogeny that is related with the final consumption of the mozambique ocean and the collision of india with azania east africa

sedimentary geochemistry geochronology and sequence stratigraphy as tools to typecast stratigraphic units and constrain basin evolution in the gold mineralised palaeoproterozoic tanami region northern australia abstract rare earth elements rees high field strength elements and detrital zircon populations typecast and establish the provenance of siliciclastic sedimentary rocks of the palaeoproterozoic tanami group this group is the main host of gold in the tanami region an important proterozoic gold province in northern australia these data also define chronostratigraphic surfaces which provide a framework for constructing sequence stratigraphic models for the tanami basin this basin model provides insight into the likely spatial distribution of deep water facies which are the best trap rocks for epigenetic gold deposition the largest gold deposits are hosted in the well bedded carbonaceous siltstone of the dead bullock formation which is the basal unit of the tanami group at the callie deposit which is the largest deposit in the region the host dead bullock formation is characterised by 1 enrichments of mgo tio2 cr sc 2 light ree depletion relative to paas 3 a dominant population of detrital zircons with an age of 2500 ma in contrast turbidites of the overlying killi killi formation which is less strongly mineralised are characterised by 1 enrichments in zr la sc la sm 2 relatively flat ree pattern and 3 the presence of a major population of detrital zircons with ages of 1880 1840 ma these characteristics are independent of grain size and are interpreted to indicate that the dead bullock formation was derived from a provenance dominated by archean mafic and felsic rocks whereas the killi killi formation was derived from a provenance dominated by felsic rocks of palaeoproterozoic age these characteristics which are best shown using zr sc versus th sc diagrams can be used as an exploration tool to differentiate the more favourable dead bullock formation from the less prospective killi killi formation these data combined with regional geologic data provide a first order understanding of the make up of the tanami basin fill with implications for the distribution of siltstone dominated facies that are the best host rocks for gold

neoarchean suprasubduction zone arc magmatism in southern india geochemistry zircon u pb geochronology and hf isotopes of the sittampundi anorthosite complex abstract the sittampundi anorthosite complex sac in southern india is one of the well exposed archean layered anorthosite gabbro ultramafic rock associations here we present high precision geochemical data for the various units of sac coupled with zircon u pb geochronology and hf isotopic data for the anorthosite the zircon ages define two populations the older yield a concordia age of 2541 13 ma which is interpreted as the best estimate of the magmatic crystallization age for the sittampundi anorthosite a high grade metamorphic event at 2461 15 ma is suggested by the upper intercept age of the younger zircon population a neoproterozoic event at 715 180 ma resulted in pb loss from some of the metamorphic zircons the magmatic age of the anorthosite correlates well with the timing of crystallization of the arc related 2530 ma magmatic charnockites in the adjacent salem block while the metamorphic age is synchronous with the regional metamorphic event the geochemical data suggest that the rocks were derived from a depleted mantle source sub arc mantle metasomatism of slab derived fluids and subsequent partial melting produced hydrous aluminous basalt magma the magma fractionated at depth to produce a variety of high alumina basalt compositions from which the anorthositic complex with its chromite rich and amphibole rich layers formed as cumulates within the magma chamber of a supra subduction zone arc the coherent initial176hf 177hf ratios and positive ehf values 1 7 4 5 of the magmatic zircons in the anorthosite are consistent with derivation of a rather homogeneous juvenile parent magma from a depleted mantle source our study further confirms that the southern part of the dharwar craton was an active convergent margin during the neoarchean with the generation and emplacement of suprasubduction zone arc magmas which played a significant role in continental growth

heinrich events massive late pleistocene detritus layers of the north atlantic and their global climate imprint 1 millennial climate oscillations of the glacial interval are interrupted by extreme events the so called heinrich events of the north atlantic their near global footprint is a testament to coherent interactions among earth s atmosphere oceans and cryosphere on millennial timescales heinrich detritus appears to have been derived from the region around hudson strait it was deposited over approximately 500 250 years several mechanisms have been proposed for the origin of the layers binge purge cycle of the laurentide ice sheet jokulhlaup activity from a hudson bay lake and an ice shelf buildup collapse fed by hudson strait to determine the origin of the heinrich events i recommend 1 further studies of the timing and duration of the events 2 further sedimentology study near the hudson strait and 3 greater spatial and temporal resolution studies of the layers as well as their precursory intervals studies of previous glacial intervals may also provide important constraints

the last occurrence of megaceroides algericus lyddekker 1890 mammalia cervidae during the middle holocene in the cave of bizmoune morocco essaouira region during the course of archaeological test excavations carried out in 2007 in the cave of bizmoune essaouira region morocco seven archaeological layers yielding pleistocene and holocene artefacts and faunal remains were identified in the layers c4 c3 and c2 respectively from the oldest to the most recent terrestrial helicidae mollusk shells helix aspersa were dated by 14c these layers also contained many fragments of eggshell belonging to struthio cf camelus associated with mammal remains such as oryctolagus lepus gazella sp sus scrofa ammotragus lervia alcelaphus buselaphus equus sp phacochoerus aethiopicus and an undetermined caprini among these remains an incomplete mandible of megaceroides algericus lydekker 1890 with m1 and m2 was found in layer c3 the 6641 to 6009 cal bp time range attributed to this layer has provided the most recent date known so far for m algericus in this study we review and contextualize the findings of this particular species both in time and space and discuss its systematic position we describe the morphology of the typical pachyostosic mandibular bone with the teeth and compare the dimensions with existing data the assumption of the combined development on the one hand of the pachyostosic phenomenon and on the other hand of the body weight fluctuations and growth of antlers for cervids strongly affected by seasonality is not supported in order to understand the origin and the extinction of m algericus we examined the ams radiocarbon dates available in the literature and calibrated them with rendatemodel software comparisons are then made with sea surface temperatures e g gisp2 18o eustasy and related environmental changes throughout the time span of this species based on these data a possible migration route by the strait of gibraltar connected with with eustatic rises in sea level rises are discussed the speciation extinction processes for m algericus and their correlations with climatic shifts on a long time scale in north africa e g heinrich events 8200 cal bp event are also considered finally this new discovery in bizmoune cave clearly shows that m algericus lasted until the very end of the epipaleolithic around 6000 cal bp middle holocene whereas this species was formerly not believed to have survived until the early epipaleolithic around 8000 cal bp

zircon provenances provide paleogeographic constraints on models reconstructing the paleoproterozoic columbia supercontinent abstract paleoproterozoic orogens of the north australian craton are related to the assembly of the columbia supercontinent the roles of the distinct orogens in the paleoproterozoic craton amalgamation are poorly understood due to the lack of surface exposure the age and isotopic systematics of detrital zircon grains hosted in paleoproterozoic sedimentary sequences are used to unravel the geological history of the craton in terms of paleogeography and tectonic setting the oldest early paleoproterozoic metasedimentary units are characterised by detrital zircon ages peaking at ca 2500 ma the zircon ehf values show large variations in the different orogens and range from 18 to 6 the overlaying youngest turbiditic units show minor accumulation of archean detritus units from apparently different metasedimentary sequences have a major detrital zircon age population at ca 1865 ma and a relatively restricted range of zircon ehf values between 7 3 and 2 6 the isotopic distinctiveness of the oldest units is attributed to local variations in the depositional environment probably due to horst graben architecture of the early paleoproterozoic basin the youngest turbiditic units blanketed this early horst graben architecture and in part have a local provenance potential detritus sources include south australian craton dharwar craton and aravalli lesser himalayan terrains in india south china and madagascar africa this finding indicates that these regions might have been connected before the columbia supercontinent was formed the ubiquitous ca 2500 ma magmatic event records the assembly of these cratonic fragments in a previous supercontinent called kernorland in addition the data do not support a proximity of the north australian craton with the north china block western laurentia north america and kaapvaal craton africa during columbia amalgamation

the burning heart the proterozoic geology and geological evolution of the west musgrave region central australia the musgrave province is one of the most geodynamically significant of australia s proterozoic orogenic belts lying at the intersection of the continent s three cratonic elements the west north and south australian cratons while remoteness and cultural sensitivity have slowed geological research into this region recent collaborative programs in western australia the west musgrave province have done much to address this this focus review provides a synthesis of this and previous work investigating the mesoproterozoic to neoproterozoic geological evolution of the province the musgrave province is a mesoproterozoic to neoproterozoic belt dominated by granites formed and deformed during several major events a cryptic juvenile basement is exposed mainly in the east musgrave province as c 1600 1550 ma orthogneiss and in the west musgrave province as isolated outcrops of granulite facies metagranites of the c 1575 ma warlawurru supersuite zircon hf isotopic data suggest an earlier major juvenile crust forming event at c 1950 1900 ma there is however no evidence that the province evolved over archean crust the c 1600 1550 ma period probably involved evolution within a primitive arc setting perhaps developed on c 1950 1900 ma oceanic or oceanic arc crust voluminous calc alkaline plutonism was accompanied by clastic and volcaniclastic basin formation during the 1345 1293 ma mount west orogeny this stage traced the evolution of a continental arc reflecting the final amalgamation of the combined north and west australian craton with the south australian craton the intervening c 1400 ma primitive crust the madura province on which the proto musgrave province had evolved was consumed during amalgamation the thickened crust resulting from this accretion was drastically thinned at the beginning of the c 1220 1150 ma musgrave orogeny as this central part of the new combined craton entered an extraordinary period of high heat flow characterised by c 100 m y of ultrahigh temperature metamorphism and high temperature anhydrous alkali calcic magmatism sourced from mash chambers developed at the base of the thinned crust the ridged cratonic architecture and a massive accumulation of high radiogenic heat producing granites within the mid crust perpetuated a thin crustal regime voluminous magmatism was again triggered during the c 1090 1040 ma giles event with the evolution of the magmatism dominated ngaanyatjarra rift this event was likely initiated through renewed movement along translithospheric faults that intersected the thermally perturbed musgrave province pinned at a cratonic junction mantle derived bimodal magmatism extended more or less continuously for 50 m y producing one of the world s largest layered mafic intrusions and supervolcano sized additions of juvenile felsic crust in the form of alkali calcic to alkali a type rhyolite deposits together the albany fraser orogen which developed over the southern margin of the west australian craton and the musgrave province mark the preserved edge of the north and west australian craton these two belts show remarkable chronological links between c 1345 and 1150 ma but contrasting histories before and after that period their period of shared evolution reflects collision and accretion of the south australian craton but their tectonic setting and basement geology throughout that event were very different