palaeoclimatic implications of the occurrence of the arcoid bivalve anadara trapezia deshayes in the quaternary of australasia abstract the arcoid bivalve anadara trapezia deshayes 1840 is a eurythermal estuarine mollusc that flourishes at present in eastern australia between port phillip bay victoria and townsville in northern queensland a trapezia first appeared in the australian quaternary fossil record during oxygen isotope stage ois 7 in new zealand where it is now extinct the earliest known occurrences are in the rangitawa fossil beds and in uppermost castlecliffian strata west of wanganui north island ois 11 ca 400 ka the species had an extensive distribution during the last interglacial maximum ois 5e in both australia and new zealand and appears to have had a slightly wider than present geographic range in southeastern australia during the middle holocene as shown by records from tasmania and western victoria where it no longer lives apart from an isolated population inhabiting oyster harbour western australia a trapezia has not been confirmed living in coastal waters west of port phillip bay victoria it became extinct in new zealand sometime after ois 5e the extensive distribution and abundance of a trapezia and other fauna of subtropical affinity during the last interglacial maximum in areas where both are now extinct appears to be associated with an enhanced leeuwin current at that time coinciding with higher less seasonally concentrated levels of precipitation and river discharge the arrival of a trapezia in australasian coastal waters may have been a consequence of planktonic dispersal from southern south america a bravardi del rio from the middle miocene puerto madryn formation on the valdes peninsula argentina may be a possible ancestor for a trapezia

multi method dating comparison for mid pleistocene rangitawa tephra new zealand abstract the rangitawa tephra a widespread mid pleistocene marker in the new zealand region is dated by fission track thermoluminescence tl infrared stimulated luminescence irsl k ar and single crystal laser fusion sclf 40 ar 39 ar methods as well as by matching to the astronomical timescale via oxygen isotope stratigraphy in deep sea cores fifty one independent numerical age estimates for rangitawa tephra range from 173 to 456 ka however only 15 of these results are considered to be reliable five zircon fission track results four isothermal plateau fission track itpft age estimates on glass shards four sclf 40 ar 39 ar results and two astronomically calibrated age estimates from deep sea cores the weighted mean of the nine reliable fission track age determinations is 345 12 ka in excellent agreement with the weighted mean of 340 7 ka for the two reliable astronomically calibrated age estimates the weighted mean of the four reliable 40 ar 39 ar results 302 8 ka is significantly younger and further ar ar dating is recommended to investigate this difference since the tl and irsl dating methods are experimental for sediments beyond 200 ka we have excluded these from the group of reliable age results tl and irsl results on dunesand appear to be systematically younger than tl results on loess and loess results depend upon analytical procedures

the effects of secular disequilibrium on u th he systematics and dating of quaternary volcanic zircon and apatite the u th he dating method applied to u rich phases such as zircon and apatite has sufficient sensitivity and precision to be of potential use for dating relatively recent geologic events such as volcanic eruptions however in phases with crystallization ages less than 1 ma chemical fractionation within the 238 u decay series may modify the he ingrowth rate causing he ages computed from the secular equilibrium age equation to be incorrect the resulting systematic error depends on the 230 th 238 u activity ratio of the dated phase when it is erupted and on the eruption age zircons which exclude th relative to u will likely have secular equilibrium he ages that underestimate the eruption age by up to a few tens of decreasing with increasing eruption age apatites tend to accommodate u and th with little fractionation so apatite secular equilibrium he ages will be nearly concordant with eruption age if minerals are erupted immediately after crystallization the disequilibrium effect can be reasonably accounted for based on th u systematics however crystals are likely to reside for unknown but potentially long periods in a magma chamber such that the degree of secular disequilibrium will be reduced prior to the onset of he accumulation u th he analyses of co genetic phases that fractionate the u th ratio differently like apatite and zircon can be used to better constrain eruption age as well as to provide insights into magma chamber residence time we illustrate this approach with u th he analyses of zircons and apatites of the pleistocene age rangitawa tephra new zealand

new zircon fission track ages from new zealand quaternary tephra an interlaboratory experiment and recommendations for the determination of young ages abstract fission track dating of zircons from five pleistocene tephra in the wanganui basin north island new zealand has been carried out independently in two different laboratories the results from each are statistically identical even though there were some differences in laboratory techniques the resulting ages confirm recent isothermal plateau fission track itpft ages on two of these tephra but with increased precision the weighted mean ages 1 are potaka tephra 0 97 0 04 ma 4 determinations rewa pumice 1 00 0 06 ma 3 determinations mangapipi ash 1 26 0 08 ma 2 determinations pakihikura pumice 1 66 0 07 ma 4 determinations and the vinegar hill tephra 1 73 0 08 ma 3 determinations these new results further constrain the time control in this important pleistocene section which contains many cyclothems reflecting climatic and tectonic influences this study illustrates well the pitfalls that can occur when dating such young material using single crystal techniques the difficulties of determining when etching is optimal the presence of detrital grains and their subsequent removal from the data set are described as well as a recommendation that a minimum of 15 crystals but optimally at least 20 be counted before calculating the final age it may also be necessary to plot running means of the single crystal ages to determine when the final age has been approached

isothermal plateau fission track ages of hydrated glass shards from silicic tephra beds abstract the age of silicic tephra beds that have experienced a simple thermal history can be accurately and precisely determined by application of the isothermal plateau fission track technique to hydrated glass shards age estimates obtained by this means compare very well with those based on co existing mineral phases using the k ar 40ar 39ar external detector fission track and thermoluminescence techniques this concordance contradicts the popular belief that hydrated glass shards give unreliable ages distal tephra beds many of which are difficult to date because of their fine grainsize low abundance of crystals and common presence of detrital grains are readily dated by the isothermal plateau glass fission track method this new advance should greatly facilitate the development of detailed chronologies of tephra bearing sedimentary sequences located far from volcanic centres

onshore offshore correlation of pleistocene rhyolitic eruptions from new zealand implications for tvz eruptive history and paleoenvironmental construction abstract taupo volcanic zone tvz in the north island new zealand is arguably the most active quaternary rhyolitic system in the world numerous and widespread rhyolitic tephra layers sourced from the tvz form valuable chronostratigraphic markers in onshore and offshore sedimentary sequences in deep sea cores from ocean drilling program odp leg 181 sites 1125 1124 1123 and 1122 located east of new zealand ca 100 tephra beds are recognised post dating the plio pleistocene boundary at 1 81 ma these tephras have been dated by a combination of magnetostratigraphy orbitally tuned stable isotope data and isothermal plateau fission track ages the widespread occurrence of ash offshore to the east of new zealand is favoured by the small size of new zealand the explosivity of the mainly plinian and ignimbritic eruptions and the prevailing westerly wind field although some tephras can be directly attributed to known tvz eruptions there are many more tephras represented within odp cores that have yet to be recognised in near source on land sequences this is due to proximal source area erosion and or deep burial as well as the adverse effect of vapour phase alteration and devitrification within near source welded ignimbrites despite these difficulties a number of key deep sea tephras can be reliably correlated to equivalent aged tephra exposed in uplifted marine back arc successions of wanganui basin where an excellent chronology has been developed based on magnetostratigraphy orbitally calibrated sedimentary cycles and isothermal plateau fission track ages on tephra significant pleistocene tephra markers include the kawakawa omataroa rangitawa onepuhi kaukatea kidnappers b potaka unit d ahuroa ongatiti rewa sub rewa pakihikura ototoka and table flat tephras six other tephra layers are correlated between odp core sites but have yet to be recognised within onshore records the identification of pleistocene tvz sourced tephras within the odp record and their correlation to wanganui basin and other onshore sites is a significant advance as it provides 1 an even more detailed history of the tvz than can be currently achieved from the near source record 2 a high resolution tephrochronologic framework for future onshore offshore paleoenvironmental reconstructions and 3 well dated tephra beds correlated from the offshore odp sites with astronomically tuned timescales provide an opportunity to critically evaluate the chronostratigraphic framework for onshore plio pleistocene sedimentary sequences e g wanganui basin cf naish et al 1998 quaternary science reviews 17 695 710

forward modelling of the sequence stratigraphic architecture of shelf cyclothems application to late pliocene sequences wanganui basin new zealand we demonstrate a procedure for forward modelling of the sequence stratigraphic architecture i e positions of systems tract boundaries of shelf cyclothems as observed at outcrop sites or in well logs the 1 d model is based on the fact that the deposition of facies within shelf sequences and those defining the key stratigraphic surfaces between systems tracts respond directly to changes in depth between the sea surface and seafloor this accommodation bathymetry model incorporates three reference surfaces sea surface seafloor and lower sequence boundary each of which varies independently as a result of changes in the rates of eustatic sea level sedimentation and subsidence the model input and boundary conditions are an eustatic sea level curve i e late cenozoic deep sea 18o record an independent chronology for the outcrop or well section and a subsidence curve the model outputs are changes in accommodation and palaeobathymetry throughout the sequence and the time missing at erosional sequence boundaries the main variable in the model i e sedimentation rate is established by comparison of a model output bathymetry with the model target palaeobathymetry established from the faunal and facies content of the sequence being modelled when the model output and target are compatible the model sedimentation rate curve is adopted and the theoretical positions of the systems tract boundaries can be read off the model in relation to the lower sequence boundary and compared with independent field based interpretations of their stratigraphic position the model is designed to predict the architecture of sequences as they appear at particular outcrop sites or in well sections its usefulness lies in establishing the timing of accumulation of systems tracts in relation to stages in a eustatic sea level cycle in particular distinguishing between units deposited during highstand versus regressive systems tracts the model is applied to 6th order 41 ka plio pleistocene cyclothems in wanganui basin new zealand where it distinguishes the boundary between highstand systems tracts hst and regressive systems tracts rst the modelling has implications for the definition of systems tracts especially in late cenozoic successions for which the record of eustatic sea level changes is known independently

volcanic hazards in auckland new zealand a preliminary assessment of the threat posed by central north island silicic volcanism based on the quaternary tephrostratigraphical record

multidisciplinary high resolution correlation of the permian triassic boundary abstract biostratigraphic correlation of the ten most important permian triassic boundary sections throughout tethys enables establishment of four conodont and ammonoid subdivisions within a stratigraphic interval one to a few metres thick representing less than 1 ma in ascending order they are conodonts clarkina changxingensis c deflecta zone hindeodus typicalis interval isarcicella parva zone and i isarcica zone and ammonoids pseudotirolites pleuronodoceras zone lower otoceras zone upper otoceras zone and ophiceras zone most of them can be traced to north america and the arctic region carbon isotope investigations of 24 sections along tethys and in greenland and spitzbergen confirm the consistency of 13c negative excursions at the permian triassic boundary together with an inconsistent ir anomaly eight sections show that in most cases there is a succession of ir anomaly denoting the end permian catastrophic environment 13c excursion biomass loss extinction p t boundary origination of newcomers potentially capable of intercontinental correlation within that short time interval there is an intercontinental sequence boundary at the top of the permian and a transgressive surface at the p t boundary followed shortly by a maximum flooding surface an intercontinental anoxia event accompanied the transgression three delineations of the mass extinction phases and three population explosions have been recognized and can be more or less correlated in south china and the southern alps radiometric dating of the volcanogenic boundary clays of meishan shangsi and the main stage siberian tunguss traps give an almost identical age of 250 ma thus implying a synchronous interregional volcanic event there are a few palaeomagnetic transforms within the ptb strata thus multidisciplinary research of the p t boundary strata allows subdivision of this short interval into more than ten intercontinentally correlatable parts each subdivision averages less than 100 ka in duration this may be the highest resolution obtained so far in pre cretaceous rocks high frequency milankovitch type cyclic deposits within the p t boundary beds enable correlation of even higher resolution in the lower yangtze area this high resolution is made possible because the p t transition is a time of saltation and catastrophy in geological history causality of the aggregation of events merits further investigation

sequence stratigraphy of sixth order 41 k y pliocene pleistocene cyclothems wanganui basin new zealand a case for the regressive systems tract this study is based on a late pliocene and early pleistocene approximately 2 6 1 7 ma succession about 1 km thick of 20 sixth order 41 k y duration cyclothems of shelf origin exposed in the rangitikei river valley in the eastern part of wanganui basin the cyclothems correlate with 18 o isotope stages 100 58 and each 41 k y glacialinterglacial stage couplet is represented by an individual depositional sequence comprising transgressive highstand and regressive systems tracts unlike most examples inferred from the stratigraphic record these systems tracts were deposited during phases of known sea level cycles indicated by the contemporary oxygen isotope ice volume curve because of the high rate of subsidence of wanganui basin glacioeustatic sea level falls during most cycles were not of sufficient magnitude to expose the outer shelf thus the rangitikei section provides an exceptional example of regressive strata deposited landward of the contemporary shelf break simple one dimensional modeling shows that moderate to high rates of basin subsidence 1 2 mm yr and low rates of sedimentation 0 2 mm yr during transgressions combined to produce an accommodation surplus at the relative highstand this surplus accommodation was infilled during the late highstand and ensuing fall partly by aggradational highstand systems tract shelf siltstone and chiefly by strongly progradational shoreface sediments of the regressive systems tract rangitikei regressive systems tracts are distinguished from forced regressive systems tracts sensu hunt and tucker 1992 by their different stratal geometry by definition forced regressive systems tracts display an erosional contact with the underlying highstand systems tracts and typically occur as a series of downstepped disjunct shoreline wedges stranded on the shelf and or slope in contrast regressive systems tracts exhibit a gradational lower contact above which parasequences are stacked in a strongly progradational pattern terminated by the superjacent sequence boundary cyclothems display two types of motif termed rangitikei dt depositional transgression and rangitikei nt nondepositional transgression which include the following architectural elements in ascending stratigraphic order 1 a basal sequence boundary that is coincident with either the transgressive surface of erosion which displays small scale up to 50 cm erosional relief and may be penetrated by the ichnofossil ophiomorpha or its deeper water correlative conformity 2 either a thick 5 30 m transgressive systems tract comprising a deepening upward nearshore to inner shelf mixed carbonate siliciclastic lithofacies succession depositional transgression or a thin 2 m transgressive systems tract comprising condensed fossiliferous facies deposited on the sediment starved offshore shelf nondepositional transgression 3 a sharp downlap surface separating condensed fossiliferous facies of the transgressive systems tract from terrigenous siltstone of the superjacent highstand systems tract 4 a highstand systems tract comprising a 10 20 m thick interval of aggradational shelf siltstone and 5 a thick up to 45 m progradational inner shelf to shoreface lithofacies assemblage ascribed to the regressive systems tract condensed shell beds are associated with intrasequence and sequence bounding discontinuities and together with the sedimentological and stratal characteristics of the sequences are important indicators of stratigraphic architecture four types of shell bed are associated with surfaces formed by four different types of stratal termination onlap backlap downlap and flooding surface shell beds cf kidwell 1991 are associated respectively with the transgressive surface of erosion apparent truncation at the top of the transgressive systems tract the downlap surface and local marine flooding surfaces a fifth shell bed type termed a compound shell bed forms in offshore environments where the downlap surface converges with the sequence boundary and elements of both the downlap and the backlap shell beds become mixed or superposed the shell beds mark zones of stratal attenuation and can be used as surrogates for seismic discontinuities when applying sequence stratigraphic concepts at outcrop scale

causes and consequences of extreme permo triassic warming to globally equable climate and relation to the permo triassic extinction and recovery permian waning of the low latitude alleghenian variscan hercynian orogenesis led to a long collisional orogeny gap that cut down the availability of chemically weatherable fresh silicate rock resulting in a high co2 atmosphere and global warming the correspondingly reduced delivery of nutrients to the biosphere caused further increases in co2 and warming melting of polar ice curtailed sinking of o2 and nutrient rich cold brines while pole to equator thermal gradients weakened wind shear and associated wind driven upwelling lessened further diminishing productivity and carbon burial as the earth warmed dry climates expanded to mid latitudes causing latitudinal expansion of the ferrel circulation cell at the expense of the polar cell increased coastal evaporation generated o2 and nutrient deficient warm saline bottom water wsbw and delivered it to a weakly circulating deep ocean warm deep currents delivered ever more heat to high latitudes until polar sinking of cold water was replaced by upwelling wsbw with the loss of polar sinking the ocean was rapidly filled with wsbw that became increasingly anoxic and finally euxinic by the end of the permian rapid incursion of wsbw could have produced 20 m of thermal expansion of the oceans generating the well documented marine transgression that flooded embayments in dry hot pangaean mid latitudes the flooding further increased wsbw production and anoxia and brought that anoxic water onto the shelves release of co2 from the siberian traps and methane from clathrates below the warming ocean bottom sharply enhanced the already strong greenhouse increasingly frequent and powerful cyclonic storms mined upwelling high latitude heat and released it to the atmosphere that heat trapped by overlying clouds of its own making suggests complete breakdown of the dry polar cell resulting rapid and intense polar warming caused or contributed to extinction of the remaining latest permian coal forests that could not migrate any farther poleward because of light limitations loss of water stored by the forests led to aquifer drainage adding another 5 m to the transgression non peat forming vegetation survived at the newly moist poles climate feedback from the coal forest extinction further intensified warmth contributing to delayed biotic recovery that generally did not begin until mid triassic but appears to have resumed first at high latitudes late in the early triassic current quantitative models fail to generate high latitude warmth and so do not produce the chain of events we outline in this paper future quantitative modeling addressing factors such as polar cloudiness increased poleward heat transport by deep water and its upwelling by cyclonic storms and sustainable mid latitude sinking of warm brines to promote anoxia warming and thermal expansion of deep water may more closely simulate conditions indicated by geological and paleontological data

the timing and pattern of biotic recovery following the end permian mass extinction the aftermath of the great end permian period mass extinction 252 myr ago shows how life can recover from the loss of 90 species globally the crisis was triggered by a number of physical environmental shocks global warming acid rain ocean acidification and ocean anoxia and some of these were repeated over the next 5 6 myr ammonoids and some other groups diversified rapidly within 1 3 myr but extinctions continued through the early triassic period triassic ecosystems were rebuilt stepwise from low to high trophic levels through the early to middle triassic and a stable complex ecosystem did not re emerge until the beginning of the middle triassic 8 9 myr after the crisis a positive aspect of the recovery was the emergence of entirely new groups such as marine reptiles and decapod crustaceans as well as new tetrapods on land including eventually dinosaurs the stepwise recovery of life in the triassic could have been delayed either by biotic drivers complex multispecies interactions or physical perturbations or a combination of both this is an example of the wider debate about the relative roles of intrinsic and extrinsic drivers of large scale evolution from a much more devastated planet and biota than the others with only some 10 of species surviving the epme was much harsher than the other mass extinctions during which global species diversity reduced to only about 50 of the pre extinction total 1 2 24 26 this means that the triassic recovery has two profound implications first it may show qualitative as well as quantitative differences from the other post extinction recoveries and second it can act as an exemplar of what to expect at its most extreme when global biodiversity is pushed to the brink there are obvious implications for current concerns about biodiversity loss and recovery resulting from human impacts 27 28 in the past ten years attention has focused on the sedimentary successions in south china these are enormously laterally extensive with some formations extending more than 2 000 km from the zhejiang to yunnan provinces the huge exposures length of the sections and improving dating open up the opportunity to explore physical environmental and biotic changes through the extinction and recovery times in varied marine habitats and compare these with patterns elsewhere in the world fig 1 a fine scale forensic analysis of this extraordinary time in earth s history now becomes possible the end permian mass extinction the epme killed 80 96 of marine animal species and 70 of terrestrial vertebrate species

middle late pleistocene tephrostratigraphy of the eastern bay of plenty new zealand abstract up to fifty tephras ranging in age from ca 500 to 50 ka are recorded in a terrestrial sequence of loess and paleosols in the eastern bay of plenty north island new zealand tephra correlations are based on the distinctive physical characteristics of the airfall beds and confirmed by microprobe analysis of glass shards the deposits are divided into six subgroups with their boundaries marked by either major tephras or significant changes in the paleo climate indicator deposits such as loess and paleosols age control on these tephras has been provided by fitting the paleoclimatic data seen in the field to the specmap oxygen isotope curve with correlations to a few well dated tephras and ignimbrites providing key time planes within this record

revision of the marine chronology in the wanganui basin new zealand based on the isothermal plateau fission track dating of tephra horizons abstract the occurrence of tephra horizons in basins adjacent to volcanic arcs provide an excellent opportunity for establishing a reliable chronostratigraphic framework for detailed sedimentological studies in this study three widespread and stratigraphically important rhyolitic tephra horizons interbedded in plio pleistocene strata of the wanganui basin new zealand are dated by application of the isothermal plateau fission track itpft technique to hydrated glass shards all glass samples were corrected for annealing and consequently yield reliable ages rangitawa tephra yielded statistically indistinguishable ages from three localities that are in excellent agreement with recently determined zircon fission track age estimates of ca 0 35 ma itpft ages of 1 05 0 05 and 1 63 0 15 ma for potaka pumice and pakihikura pumice respectively are considerably older than previous ft estimates but consistent with new magnetostratigraphic data that places the potaka within the jaramillo subchron and pakihikura within the matuyama chron between the cobb mountain and olduvai subchrons combining our fission track ages with the magnetostratigraphy the true age of sediments within the wanganui basin is found to be significantly underestimated sedimentation rates of between ca 680 630 m ma from 1 63 ma to 0 35 ma are calculated in the eastern part of the basin and are much lower than those calculated using the previous ft chronology this new itpft age data demonstrates that the existing plio pleistocene marine chronology in new zealand will require age revision and has important implications when considering the evolution of several other sedimentary basins in southern north island that contain the same itpft dated tephra horizons

palaeoenvironments of the permian triassic transition sections in kashmir india abstract detailed measurements of two permian triassic boundary sections at guryul ravine and pahlgam in kashmir indicate continuous sedimentation across the boundary though with a marked change from shallow storm influenced shelf to deeper shelf below wave base successive shell beds through the 2 5 m thick transitional latest permian section at guryul formed as in situ accumulations with little sign of either erosional breaks or condensation faunal change takes place gradually in the late permian transition beds as elsewhere in the tethyan sections there is no major event layer at the permian triassic boundary and little evidence for dysaerobic conditions both the kashmir and east greenland permian triassic sections have sedimentation rates that are orders of magnitude greater than at the condensed meishan reference section they show that the end permian extinction was associated with transgression but not with immediate onset of anoxic conditions macrofaunal extinction seems associated with reduction in primary production which would also explain the dwarfism of fossils found in all permian triassic sections studied so far

zircon fission track thermochronology and applications to fault studies zircon is one of the most useful minerals used to unravel the earth s history recorded in rocks after the success of etching fission tracks in zircon fleischer et al 1964 naeser 1969 krishnaswami et al 1974 early studies focused primarily on dating young volcanic horizons for stratigraphic purposes e g naeser et al 1973 hurford et al 1976 seward 1979 gleadow 1980 kowallis et al 1986 kohn et al 1992 subsequently fission track analysis of zircon has been extensively employed along with other radiometric dating methods such as u pb and u th he techniques e g davis et al 2003 reiners 2005 to understand the thermochronology of rocks in a variety of geological settings i e thermal history analysis of basement rocks for orogenic studies e g zeilter et al 1982 hurford 1986 kamp et al 1989 sorkhabi 1993 seward and mancktelow 1994 hasebe and tagami 2001 spikings et al 2001 thermochronology using detrital zircon grains in sedimentary rocks for provenance analysis and thermal history analysis in or near faults which will be highlighted below in this present chapter the thermal sensitivity of the zircon fission track thermochronometry is reviewed in the context of laboratory and field studies then laboratory procedures of the zircon fission track analysis using the external detector method are outlined as practiced in the fission track laboratory of kyoto university for basic fundamentals of these fission track analyses including data analysis and graphical displays see the chapter by tagami and o sullivan 2005 finally as an example of recent geological applications of the technique the results of zircon fission track analysis of the nojima fault zone japan are presented these rocks were the target of systematic drilling of an active fault system using five boreholes and a trench applications to other geological settings and the

fundamentals of fission track thermochronology fission track ft analysis has developed into one of the most useful techniques used throughout the geologic community to reconstruct the low temperature thermal history of rocks over geological time the ft method is based on the accumulation of narrow damage trails i e fission tracks in uranium rich mineral grains e g apatite zircon titanite and natural glasses which form as a result of spontaneous nuclear fission decay of 238u in nature price and walker 1963 fleischer et al 1975 the time elapsed since fission tracks began to accumulate is estimated by determining the density of accumulated tracks in a particular material in relation to the uranium content of that material chemical etching can be used to enlarge fission tracks that have formed within a mineral in order to make them readily observable under an ordinary optical microscope price and walker 1962 if a host rock is subjected to elevated temperatures fission tracks that have formed up to that point in time are shortened progressively and eventually erased by the thermal recovery i e annealing of the damage fleischer et al 1975 because thermal diffusion basically governs the annealing process the reduction in ft length is a function of heating time and temperature importantly fission tracks are partially annealed over different temperature intervals within different minerals this characteristic allows for the construction of time temperature paths of many different rock types by a plotting ft and other isotopic ages from different minerals versus their closure temperatures which is applicable in the case of a monotonous cooling history e g wagner et al 1977 zeilter et al 1982 and or by b the inverse modeling of observed ft age and confined track length data e g corrigan 1991 lutz and omar 1991 gallagher 1995 ketcham et al 2000 see also ketcham 2005

survival brachiopod faunas of the end permian mass extinction from the southern alps italy and south china eight brachiopod species in seven genera are described from the permian triassic boundary beds of south china and northern italy the brachiopods from northern italy are described for the first time and include two new species orbicoelia dolomitensis chen and spirigerella teseroi chen the permian affinity of these brachiopods and their stratigraphical position above the extinction horizon demonstrate that they are survivors from the end permian mass extinction the surviving brachiopods from south china which was located at the eastern margin of the palaeo tethys ocean are considerably abundant and diverse and are dominated by geographically widespread generalist elements adapted to a wide variety of environments they were mostly limited to the upper permian to lowest griesbachian in contrast the survivors in northern italy which was situated at the western margin of the palaeo tethys comprise elements ranging from the carboniferous to permian or widespread tethyan genera these survivors did not occur in the pre extinction western tethyan oceans but migrated into this region after the end permian extinction event disaster taxon lingula proliferated slightly earlier in western tethyan oceans than in eastern tethyan regions following the event survival brachiopods from both regions appear to have a generic affinity although they do not share any species both south chinese and italian survival faunas support the view that the survival interval is the duration when survivors are dominated by geographically widespread generalist organisms adapted to a wide variety of ecological conditions

quaternary deposits and landscape evolution in northeast southland new zealand abstract three kinds of quaternary sediments are present in northeast southland aeolian deposits terrace gravels and hill slope colluvium the aim of this paper is to review and describe the quaternary sediments and erosion pattern of northeast southland and reconstruct the likely climate under which sedimentation and erosion occurred aeolian deposition occurred intermittently from 250 000 yr b p but stratigraphic studies indicate widespread erosion of loess in the period 80 000 25 000 yr b p before a final period of loess accumulation in the late otiran 18o stage 2 terrace gravels are attributable to two sources a younger suite of three terraces is attributed to aggradation phases of the mataura river an older suite of three more weathered terraces is attributed to aggradation by a river flowing eastwards through the waimea plains from lumsden to gore the river is named the lumsden river at about 180 000 yr b p this river ceased flowing through the waimea plains colluvium on hill slopes is regionally stratified into two layers the lower deposits are identified as weathered sand and gravel sized colluvium derived from argillite and siltstone screes dated as being formed before 29 000 yr b p and attributed to 18o stage 4 the upper stonier deposits are attributed to 18o stage 2 the erosion and deposition pattern of aeolian deposits terrace gravels and slope colluvium cannot be explained by a temperature drop of c 5 c calculated for the last glacial period we conclude that on lowlands vegetation cover was periodically limited by extreme droughts and cold windy conditions causing erosion of previously deposited loess and encouraging scree formation on slopes during these periods the severe climate of northeast southland approximated to that of a cold desert

ultra distal tephra deposits from super eruptions examples from toba indonesia and taupo volcanic zone new zealand abstract voluminous rhyolitic eruptions from toba indonesia and taupo volcanic zone tvz new zealand have dispersed volcanic ash over vast areas in the late quaternary the 74 ka youngest toba tuff ytt eruption deposited ash over the bay of bengal and the indian subcontinent to the west the 340 ka whakamaru eruption tvz deposited the widespread rangitawa tephra dominantly to the southeast in addition to occurrences northwest of vent extending across the landmass of new zealand and the south pacific ocean and tasman sea with distal terrestrial exposures on the chatham islands these super eruptions involved 2500 km 3 and 1500 km 3 of magma dense rock equivalent dre respectively ultra distal terrestrial exposures of ytt at two localities in india middle son valley madhya pradesh and jurreru river valley andhra pradesh at distances of 2000 km from the source caldera show a basal primary ashfall unit 4 cm thick although deposits containing reworked ash are up to 3 m in total thickness exposures of rangitawa tephra on the chatham islands 900 km from the source caldera are 15 30 cm thick at more proximal localities 200 km from source rangitawa tephra is 55 70 cm thick and characterized by a crystal rich basal layer and normal grading both distal tephra deposits are characterized by very fine ash with high pm 10 fractions and are crystal poor glass chemistry stratigraphy and grain size data for these distal tephra deposits are presented with comparisons of their correlation dispersal and preservation using field observations ash transport and deposition were modeled for both eruptions using a semi analytical model hazmap with assumptions concerning average wind direction and strength during eruption column shape and vent size model outputs provide new insights into eruption dynamics and better estimates of eruption volumes associated with tephra fallout modeling based on observed ytt distal tephra thicknesses indicate a relatively low

trace fossils and the aftermath of the permo triassic mass extinction evidence from northern italy abstract the duration of early triassic anoxia in the carbonate ramp settings of the werfen formation dolomites northern italy has been constrained using ichnofabric and sedimentological data this includes fine lamination and abundant pyrite framboids commonly reworked into lags by storm events the anoxic event spanned the entire griesbachian stage and extended from deep waters into extraordinarily shallow water settings evidence for oxygen deficiency can be found in mid and inner ramp facies the extent and duration of this event may at least partially explain the magnitude of the permo triassic mass extinction normal benthic conditions returned rapidly in the dienerian stage and pervasively bioturbated distal ramp facies testify to the ventilation of the deeper water areas of the region in post griesbachian times a post mass extinction radiation is not particularly well displayed in either trace fossil or body fossil diversity compilations from the dolomites moderate low levels of trace fossil diversity are maintained throughout the post griesbachian werfen formation whilst the body fossil data shows a moderate increase from the mid smithian stage there is thus a curious lag period spanning the dienerian to mid smithian when environmental conditions were apparently normal but the marine fauna failed to show any recovery

age and timing of the permian mass extinctions u pb dating of closed system zircons the age and timing of the permian triassic mass extinction have been difficult to determine because zircon populations from the type sections are typically affected by pervasive lead loss and contamination by indistinguishable older xenocrysts zircons from nine ash beds within the shangsi and meishan sections china pretreated by annealing followed by partial attack with hydrofluoric acid result in suites of consistent and concordant uranium lead u pb ages eliminating the effects of lead loss the u pb age of the main pulse of the extinction is 252 6 0 2 million years synchronous with the siberian flood volcanism and it occurred within the quoted uncertainty

rapid and synchronous collapse of marine and terrestrial ecosystems during the end permian biotic crisis a newly studied permian triassic p tr boundary section in jameson land east greenland contains an abundant and well preserved marine fauna as well as terrestrial palynomorphs for the first time it is possible to compare the biotic crises of the marine and terrestrial realms using the same samples from the same section the sediments record a negative excursion in 13 c carb values of 8 9 and in 13 c org values of 10 11 the presence of the conodont hindeodus parvus combined with the 13 c carb record enables correlation with the proposed global stratotype section at meishan this shows that the greenland section is the most expanded p tr section known collapse of the marine and terrestrial ecosystems took between 10 and 60 k y it took a further few hundred thousand years for the final disappearance of permian floral elements collapse of the terrestrial and marine ecosystems began at the same stratigraphic level and preceded the sharp negative excursion in the 13 c record

evolution of the marine permian carbonate platform in the salt range pakistan abstract during the permian a large carbonate platform developed on gondwana continental crust adjacent to the indian shield the various carbonates and mixed carbonate siliciclastic rocks record major depositional sequences and are a sedimentary expression of variations in the depositional environment as a result of the facies analysis in the salt range and trans indus ranges several sequences bounded by sequence boundaries are distinguished within the zaluch group and the basal kathwai member mianwali formation the amb formation wordian represents a complete sequence bounded by sequence boundaries associated with hiatuses the maximum flooding occurred within marly fossiliferous carbonates of the jan sukh member the second sequence comprises the lower wargal formation capitanian a climatic change towards higher water temperatures took place accompanied by decreased terrigenous input from the hinterland a carbonate platform developed with scattered coral patches the third sequence wuchiapingian is represented by the upper part of the wargal formation again a carbonate platform with coral patch reefs and abundant bars composed of echinodermal debris within the chhidru formation each member represents its own sequence with basal terrigenous sandstones and overlying mixed carbonate sandstone associations the white sandstone unit is interpreted as a further lowstand system tract of changhsingian age the lowest part of the kathwai member of the mianwali formation is still changhsingian in age and indicates a final permian transgression transgression continued during the basal triassic

sedimentary cyclicity in the marine pliocene pleistocene of the wanganui basin new zealand sequence stratigraphic motifs characteristic of the past 2 5 m y earth s climatic history since 2 5 ma has been controlled by milankovitch variations in the planetary orbit comprising alternate periods of glaciation and interglaciation with a dominant frequency of 41 000 yr concomitantly eustatic sea level has fluctuated 70 to 130 m causing rapid transgressions and regressions of the shoreline across the world s continental shelves the resulting sedimentary record is cyclothemic each cyclothem corresponding to a single climate and sea level cycle the wanganui basin new zealand contains a 2 km thick almost complete composite record since isotope stage 100 ca 2 5 ma in the form of 47 superposed cyclothems of shelf origin each cyclothem corresponds to an unconformity bound stratigraphic sequence and typically contains a transgressive systems tract sometimes a mid cycle shell bed a highstand systems tract and sometimes a regressive systems tract no advantage accrues from using transgressive regressive units rather than cyclothems and or sequences in description of the succession six basic sequence motifs represent deposition in locations between the shoreline and offshore shelf i e the hawera birdgrove turakina seafield castlecliff and rangitikei motifs a seventh the nukumaru motif which includes dominant coquina limestone represents deposition in shallow water areas of reduced terrigenous sediment on the flank of the basin the sequence motifs represented in any section change systematically in sympathy with basin scale changes in subsidence and sediment supply in contrast with the 41000 year length of individual glacioeustatic sequences these basin wide tectonic cycles have a periodicity of many hundreds of thousands to a few million years i e that of third or fourth order sequences of the exxon type this coupled with the restriction of strongly cyclothemic sediments to geological periods of known glacio eustasy permiancarboniferous pliocene pleistocene suggests that tectonic subsidence cycles rather than glacio eustasy are the driving forces behind the development of the third and fourth order unconformity bound sequences that are reported to occur throughout the stratigraphic record

fission track age 400 000 yr of the rockland tephra based on inclusion of zirco grains lacking fossil fission tracks abstract a zircon fission track age of about 400 000 yr b p has been determined for the rockland tephra a widespread pyroclastic layer in northern california and western nevada new ages of zircon separates from both proximal and distal exposures of this layer range from 370 000 to 460 000 yr ages of the best material provide a narrower range from 370 000 yr for unwelded ash flow tuff to 420 000 yr for distal air fall ash that appears to be uncontaminated by clastic detritus or xenocrysts detrital or xenocrystic grains in the ash flow tuff may have been annealed during emplacement and cooling of the tuff detrital and xenocrystic zircons are identified on the basis of their physical characteristics and distinctly older ages independent stratigraphic and magnetostratigraphic data constrain the age of the rockland tephra between 300 000 and 600 000 yr a range that is compatible with the fission track age zircon grains containing no spontaneous fossil tracks are regarded as part of the normal population of comagmatic grains because maximum ages calculated for these grains form a population that mimics the distribution of ages of individual zircon grains that contain fossil tracks modal ages of both groups fall between 250 000 and 500 000 yr induced fission tracks from grains that lack fossil tracks are included in the age calculations resulting in significantly younger and more coherent dates than would result if these tracks had been omitted especially those of the finer grained distal samples

a new 14 c age for the oruanui wairakei eruption new zealand the oruanui eruption was the largest known outburst of taupo volcano new zealand and is among the larger quaternary eruptions documented the eruption deposits are variously known as the oruanui wairakei kawakawa tephra or aokautere ash formations and represent a bulk volume probably exceeding 500 km 3 four new 14 c age determinations on carbonized vegetation in the non welded oruanui ignimbrite are combined to give a conventional age of 22590 230 yr b p compared with the previously accepted figure of 20000 yr b p this new age resolves the anomaly of apparently older 14 c ages being obtained from a demonstrably younger new zealand deposit and strengthens correlation of this eruption with an antarctic ice core acid anomaly the trace of this eruption has great potential as a time plane marker in the antarctic just prior to the last glacial maximum the close similarity in ages between the oruanui and a comparable sized eruption ito aira tn in japan suggests that this period of activity may represent the best chance of resolving any linkages between large scale explosive silicic volcanism and climate changes

pattern of marine mass extinction near the permian triassic boundary in south china the meishan section across the permian triassic boundary in south china is the most thoroughly investigated in the world a statistical analysis of the occurrences of 162 genera and 333 species confirms a sudden extinction event at 251 4 million years ago coincident with a dramatic depletion of 13ccarbonate and an increase in microspherules

some aspects of the permian triassic boundary ptb and of the possible causes for the biotic crisis around this boundary abstract the first appearance datum fad of hindeodus parvus is an excellent datum very close to the base of the otoceras woodwardi zone priority base of the triassic for the first time it allows an exact correlation of the ptb in all marine facies and faunal realms the following features of the extinction and recovery patterns near the ptb are most important for the search for causes of the ptb biotic crisis 1 most strongly affected were the siliceous plankton radiolarians and the warm water benthos and nekton 2 most of the cold water faunas were not significantly affected 3 the recovery of the warm water benthos and siliceous plankton occurred only after an unusually long time during the late olenekian and middle triassic 4 the productivity of the terrestrial plants dropped strongly and the recovery was mainly in the upper olenekian and in the middle triassic 5 several terrestrial extinction events occurred at different levels within the upper permian considerable before the marine ptb at or close to the fad of lystrosaurus no extinction event in the terrestrial faunas can be observed 6 terrestrial faunal elements that survived the dzhulfian dorashamian extinctions were able to survive some months of extreme climatic conditions by hibernation like life stages vertebrates or by dry and freezing resistant eggs conchostracans 7 about 50 of the genera that disappeared at the ptb re appeared in the olenekian middle triassic interval lazarus taxa or in this time interval genera appeared that had undoubtedly evolved from genera that had disappeared at the ptb and 8 the ptb is preceded by mass occurrences of marine and continental fungi and the fungal spike ends abruptly a little before the ptb a scenario for the ptb biotic crisis is elaborated that takes into consideration the real not interpolated diversity patterns of different marine and continental fossil groups the exact correlation of bioevents in different faunal realms and facies the strong biotic crisis in the tethyan warm water faunas in contrast to the much weaker biotic event in cold water faunas the severe dzhulfian dorashamian climate in many parts of the world caused by the continent ocean configuration and by siberian trap volcanism the cooling of the boreal area by the northward drift of pangaea that interrupted the exchange of warm water benthos between the tethys and western north america during the guadalupian the extinction event at the guadalupian lopingian boundary that restricted most of the affected warm water faunas to the tethys the importance of lower scythian anoxia that reached an unusually shallow level and above all the effects of the contemporaneous huge volcanic events about 250 m y ago on the siberian platform and in the eastern tethys that caused a 3 6 months lasting volcanic winter with strong cooling in low latitudes followed by a strong global warming

amino acid geochronology of pleistocene marine sediments in the wanganui basin a new zealand framework for correlation and dating amino acid analysis of indigenous protein preserved in fossil marine bivalves from plio pleistocene sediments in the wanganui basin north island new zealand has provided an aminostratigraphy d alloisoleucine l isoleucine d aile l ile ratios were measured in the venerid marine bivalves tawera spissa and austrovenus stutchburyi that show progressively increasing d aile l ile ratios with increasing stratigraphical age when calibrated by magnetostratigraphy fission track dating radiocarbon dating and coccolith biostratigraphy these relative d aile l ile ages range up to c 1 ma the aminostratigraphy provides a framework of correlation and dating for other sites in the new zealand area where other methods of dating are unavailable as well as facilitating correlation with oxygen isotope stratigraphy this is the first calibrated aminostratigraphical sequence from a long sequence of sediments that cover a significant proportion of the pleistocene

multivariate data analysis in palaeoecology and palaeobiogeography a review abstract palaeoecologists and palaeobiogeographers are often confronted with large multivariate data sets from which fossil communities assemblages or associations or faunal provinces are to be recognized the complex multidimensional nature of these data sets the recognition of the enormous variation of communities and environments both in space and time and the difficulties of dealing with these problems by the human mind justify the use of multivariate statistical methods in palaeoecology and palaeobiogeography concepts and basic procedures of several commonly used multivariated statistical methods of palaeoecology and palaeobiogeography are reviewed in the wider context of quantitative community ecology and biogeography basic assumptions about data structure and theoretical and practical limitations are discussed the emphasis is on evaluation of binary similarity coefficients and two multivariate approaches cluster analysis and ordination thirty nine binary similarity coefficients are evaluated against nine criteria jaccard s coefficient of community is found most suitable as a similarity measure between samples under the conditions tested algorithmic procedures of cluster analysis especially the agglomerative hierarchical cluster analysis techniques and indirect ordinations particularly polar ordination principal component analysis principal coordinate analysis correspondence analysis detrended correspondence analysis and nonmetric multidimensional scaling are outlined and their applicability to palaeoecological and palaeobiogeographical data is discussed where the data are appropriate an integration of cluster analysis and ordination is suggested to be applied to the same data

brachiopods from the permian triassic boundary beds at the selong xishan section xizang tibet china the brachiopods from the waagenites bed and the upper part of the coral bed above and below the permian triassic sequence boundary at the selong xishan section of southern xizang suggest a rich brachiopod fauna existing in selong and a rapid invasion of tethyan brachiopods into the himalayas at the very end of the permian a transgression beginning from the waagenites bed and a rapid flooding at the beginning of the triassic is reflected by changes in composition of the permian brachiopod assemblages in selong however the dominant forms in the permian triassic sequence boundary beds including krotovia spiriferella and neospirifer extend from the underlying beds of the selong group without significant evolutionary change a brief discussion of each taxon and descriptions of two new species stenoscisma selongensis and martinia attenuatelloides are presented

isothermal plateau fission track age for a paleomagnetic excursion in the mamaku ignimbrite new zealand and implications for late quaternary stratigraphy mamaku ignimbrite the youngest of the large welded ignimbrite sheet forming eruptions from the taupo volcanic zone in new zealand is dated at 230 12 ka by the isothermal plateau fission track itpft method on glass this age is older and more precise than that indicated by previous studies requiring the revision of loess paleosol coverbed chronologies the eruption occurred during a paleomagnetic excursion allowing the ignimbrite to be easily distinguished from other eruptive events by paleomagnetic methods this excursion is one of the few such events recorded in igneous rocks in the southern hemisphere may be widely recorded in new zealand and is now temporally well constrained

quaternary tephra marker beds and their potential for palaeoenvironmental reconstruction on chatham island east of new zealand southwest pacific ocean tephras provide one of the most reliable methods of time control and synchronisation within quaternary sequences we report on the identification of two widespread rhyolitic tephras the kawakawa and rangitawa tephras preserved in extensive peat deposits on chatham island 900 km east of new zealand the tephras both products of supereruptions from the taupo volcanic zone occur as pale fine ash dominated layers typically 10 150 mm thick mineralogically they are dominated by rhyolitic glass together with subordinate amounts of quartz feldspar hypersthene hornblende fe ti oxides and zircon phlogopite biotite was identified additionally in rangitawa tephra ages for each tephra were obtained via mineralogical and major element glass composition based correlation with well dated equivalent deposits on mainland new zealand and we also obtained a new zircon fission track age for rangitawa tephra 350 50 ka on chatham island both tephras were erupted at critical times for palaeoenvironmental reconstructions in the new zealand region the kawakawa at ca 27 cal ka near the beginning of the extended lgm early in marine isotope stage mis 2 and the rangitawa at ca 350 ka near the end of mis 10 the time constraints provided by the tephras demonstrate that chatham island peats contain long distance pollen derived from mainland new zealand which provides a reliable proxy for identifying glacial interglacial climate conditions in this case during the mis 11 10 and mis 2 1 cycles the two tephras thus provide important chronostratigraphic tie points that facilitate correlation and synchronisation not only across the quaternary deposits of the chatham islands group but also with climatically significant terrestrial and marine records in the wider new zealand region copyright 2010 john wiley sons ltd

pedogenic weathering of upper quaternary tephras in new zealand abstract at ahuroa road 12 km east of te kuiti a sequence of weathered mantling tephra beds resting on a weathered pyroclastic flow represents progressive accretion of tephras for 250 000 yr using known dated tephras a time scale is constructed and rates of accumulation of andesitic tephras are calculated progressive accretion has meant that the length of time each tephra was exposed to soil forming processes at the surface was limited the lack of development of soil horizons is considered to be due to this short exposure time even so large cation losses have occurred when measured by the isovolumetric method namely base cations si fe ti and al field observations indicate that some beds are rhyolitic in origin others andesitic analysis shows that darker coloured chocolate beds of andesitic origin have higher fe and ti contents than lighter coloured ginger beds of rhyolitic origin pallid brown and yellow brown beds in the column are attributed either an andesitic or rhyolitic origin on the basis of their fe and ti contents generally lower cation losses occur in rhyolitic beds than in andesitic beds some beds show losses that depart from the general pattern and it is considered that such departures are due to a decrease in leaching intensity in two cases and to topography changes accompanying increasing tephra accumulation for the beds in the latter part of the time period

direct marine terrestrial correlations wanganui basin new zealand the last 1 million years abstract wanganui basin a back arc basin in north island new zealand contains a detailed sequence of interfingering terrestrial and shallow marine sediments spanning the entire quaternary rhyolite tephras erupted from the taupo volcanic zone together with magnetostratigraphy and biostratigraphy facilitate correlations between wanganui basin and the astronomically calibrated oxygen isotope chronology of deep sea cores particularly over the last 1 ma eustatic changes are interpreted from both marine shelf sediments and marine terraces within the basin non marine sediments including loess dunesand and alluvial deposits coupled with pollen analyses are used to interpret climatic changes they can also be directly related to the marine record through stratigraphic relations between marine and non marine deposits in the basin

palaeoenvironments and faunal recovery after the end permian mass extinction abstract strata of the lower triassic werfen formation dolomites northern italy record deposition in a wide range of palaeoenvironments from peritidal to outer ramp settings this enables accurate assessment of faunal recovery following the end permian mass extinction by eliminating facies related effects extinction of the shelly taxa appears to be rapid and occurs in the latest permian tesero oolite horizon disappearance of the various trace fossil taxa appears to be more gradual following the extinction the lower and middle griesbachian are characterised by laminated sediments containing low diversity bedding plane assemblages ichnological geochemical and sedimentological data show evidence of widespread low oxygen conditions normally oxygenated waters return in the late griesbachian and there is a moderate increase in tiering above and below the surface macrofaunal and ichnofossil diversity decrease markedly during the smithian with the appearance of more terrigenous strata possibly reflecting an increased run off and more brackish conditions complete recovery begins in the basal spathian with an increase in tiering above and below the substrate crinoids and ammonoids appear for the first time in the werfen formation and the ichnogenus rhizocorallium re appears global correlation is hindered by poor biostratigraphy in the dolomites region however on a broad scale it appears as though many of the palaeoenvironmental changes are repeated worldwide current available data suggest that the re appearance of some trace fossil taxa e g diplocraterion rhizocorallium may be globally synchronous

geographic differentiation of triassic brachiopods abstract the main palaeobiogeographic patterns and trends of triassic brachiopods are analysed during the triassic taxonomic diversity of brachiopods increased and this was accompanied by intensification of their geographic differentiation thus the maximum differention was attained during the late triassic for which at least five biochores of first rank boreal northern tethyan peri gondwanian notal or maorian and eastern pacific may be distinguished

patterns of brachiopod faunal and body size changes across the permian triassic boundary evidence from the daoduishan section in meishan area south china abstract new analysis of permian triassic brachiopod assemblages and body size changes in south china provides insights into the process of the environmental crisis in the lead up to the end permian mass extinction the recently discovered daoduishan section of south china can be considered as an important auxiliary section for the study of brachiopods at the meishan section d of south china the gssp of the permian triassic boundary ptb this paper studied changes of the brachiopod assemblages and body sizes through the upper part of the changxing formation and basal yinkeng formation of daoduishan the results show that significant changes of brachiopod assemblages took place between beds 24e and 26 brachiopods prelissorhynchia sp and paracruirithyris pygmaea are the dominators in beds 14 24e while tethyochonetes pigmaea and paryphella spp are the dominators in beds 26 29 body sizes of brachiopods significantly decreased between beds 24e and 26 and then maintained smaller means in beds 27 29 studies of brachiopod morphological features indicate both tethyochonetes and paryphella had advantageous adaptations enabling them to copy with living in an anoxic dysoxic and or low productivity environment during the permian triassic crisis

luminescence chronology of loess paleosol sequences from southern south island new zealand abstract the loess paleosol sequences in new zealand are among the thickest in the southern hemisphere and preserve an important terrestrial record of paleoclimatic changes unlike loess paleosol sequences in north island most of those in south island lack discrete chronostratigraphic marker ash beds excepting perhaps the widespread 24 ka kawakawa tephra therefore any specific correlation to marine isotope stage mis proxy records or to loess paleosol sequences in the northern hemisphere has been unknown hence we applied luminescence sediment dating to four key loess paleosol sequences from southern south island although these pioneering results suggest that further sampling and luminescence dating are needed they do provide 1 the first numeric age constraint 44 3 ka on overlying loess for the end of deposition of the geomorphically and paleoclimatically important edendale terrace gravels 2 the first numeric evidence that the youngest loess paleosol unit l1 at the near coastal romahapa and inland stewarts claim sites began to be preserved much earlier at 60 ka than at the inland kingston crossing site 35 ka 3 the first direct evidence that the 6 m romahapa sequence extends at least to 350 ka the oldest yet tl dated such sequence in south island furthermore the stratigraphically self consistent with one exception luminescence ages between 60 and 350 ka conflict with a previous indirect chronostratigraphy inferred from trace concentrations of glass shards this trace shard chronology implies a major hiatus in loess paleosol preservation missing at least mis 6 7 not recognized by luminescence dating

a sulfur isotope event at the end of the permian abstract a hypothesis of light sulfur injection to the ocean atmosphere system at the end of the permian was presented by kaiho et al kaiho k kajiwara y nakano t miura y kawahata h tazaki k ueshima m chen z q shi g r 2001 end permian catastrophe by a bolide impact evidence of a gigantic release of sulfur from the mantle geology 29 815 818 based on a negative shift of 34 s 32 s ratio of carbonate associated sulfate in south china this hypothesis was discussed in some papers with additional data in other areas however the cause and distribution of the negative shift has not been clarified here we show that a significant decrease in the 34 s 32 s ratio of carbonate associated sulfate occurred simultaneously in south china and hungary at the end of the permian coincident with the end permian mass extinction the cause of the abrupt negative shift of 34 s 32 s in these two distant sites is the injection of light sulfur to the surface ocean from the deep ocean rich in h 2 s or deposits rich in sulfide or the mantle this sulfur isotope event was likely caused by either an abrupt warming a bolide impact to the ocean mantle plume induced volcanism or a harmonizing of these possible direct causes are 1 massive release of h 2 s gas from the euxinic surface and intermediate waters due to abrupt warming by volcanic co 2 or impact shock wave in the ocean 2 a huge volcanism penetrated sediments or ore rich in sulfide 3 an extraterrestrial impact to sulfide rich sediments or ore deposit and 4 release of mantle origin sulfur by an impact of 70 km asteroid to the ocean these are four possible causes for a mass extinction there is also a possibility of a local oceanic event only in the tethys

timing of the permian triassic biotic crisis implications from new zircon u pb age data and their limitations abstract the most profound biotic crisis in the earth s history causing the near extinction of both terrestrial and marine life occurred at the end of the permian period about 253 myr ago and marks the paleozoic mesozoic era boundary the cause of this event is still a matter of vigorous debate with both brief and catastrophic as well as gradual mechanisms having been proposed similar to a recent landmark study this study uses the u pb method on zircons from the uppermost permian lowermost triassic ash fall deposits at meishan zhejiang province se china in order to examine time and rate constraints for these events the results of both this study and previous work show that for these ash layers the effects of pb loss are combined with varying amounts and sources of inheritance resulting in an age scatter which prohibits the extraction of a statistically robust age in many cases though the effects of pb loss on the zircons analyzed in this study were reduced by leaching the grains in hydrofluoric acid as opposed to commonly applied air abrasion prior to analysis the presence within a single ash layer of multiple generations of older xenocrysts in many cases only slightly older than the depositional age has made quantitative interpretation even more difficult when these combined phenomena bias individual zircon ages by less than a percent they are extremely difficult to deconvolute and if multi grain analyses are used can become impossible to recognize because of the resulting age averaging monte carlo simulations using actual measurements of individual zircon crystals show that age excursions due to pb loss and xenocrystic contamination for the meishan bentonites are easily homogenized to the point of undetectability when replicate analyses of multi grain zircon samples are compared thus this study uses only high precision analyses of single crystals whether from our work or that of previous studies three main conclusions have emerged first our data require a significant increase in the age of the permian triassic boundary by more than 2 myr compared to the previous study which shifts the age to a value older than 253 ma second neither our data nor those from previous work can confirm or negate the possibility of a very abrupt biotic crisis third even large suites of very high quality single zircon u pb analyses for these tuffs cannot in most cases yield objective reliable and robust dates with accuracies at the sub myr level though the temptation to perform arbitrary selection of subsets of the analyses for that purpose is almost irresistible the last conclusion is not an indictment of zircon u pb dating in general other rocks and other zircon populations can and do behave very differently and further technical advances will likely improve our ability to prepare grains or sub grains of adequately enhanced quality for analysis consequently the results of the present study strongly suggest that for problems requiring time scale accuracy inferences from zircon u pb dating must be based on sufficiently large suites of single crystal or crystal domain high precision analyses

thermochronological analysis of the dynamics of the southern alps new zealand the isotopic ages of material exposed close to the alpine fault in the southern alps new zealand vary in a consistent fashion along the orogen for the k ar system muscovite and biotite ages display two distinct spatial trends that meet in the area of fox glacier where a strong relationship is observed between k ar age and altitude excess argon is present in samples between mount kinnaird and haast pass in the southwest of the southern alps giving unrealistically old inconsistent k ar ages across this region incorporation of excess argon appears to be highly variable however and minimization of its influence on dynamical interpretations of thermochronology is possible through considering only the youngest age from a given area such treatment indicates that excess argon contamination does not play an important role in the systematic k ar age variation identified along the southern alps the observed age distribution is consistent with estimates of the modern rapid uplift and exhumation of the southern alps beginning ca 5 ma k ar mica ages older than this south of the copland valley indicate that substantial late cenozoic exhumation occurred along the southern alps prior to the development of the modern tectonic regime but at rates lower than at present total exhumation during the current phase of tectonism in the southern alps decreases from the whataroa river southward north of fox glacier the southern alps have attained a dynamical steady state such that the observed distribution of exhumation will not change significantly with further deformation and denudation under current conditions

carboniferous permian extensive magmatism in the west junggar xinjiang northwestern china its geochemistry geochronology and petrogenesis abstract located between the tarim kazakhstan and siberian plates the west junggar terrane is a key component of the paleozoic central asian orogenic belt caob with widespread late paleozoic igneous rocks in this paper we report petrological geochronological and geochemical data for selected granitoids from the west junggar based on geochronology the i type and a type granites were formed predominantly at 347 9 319 0 ma and at 321 4 290 ma respectively the early stage i type granites are characterized by low sio2 na2o and k2o contents with na2o k2o ratios 1 and are metaluminous to weakly peraluminous they are enriched in large ion lithophile elements lile and in sr but depleted in high field strength elements hfse with 87sr 86sr i ratios of 0 7028 0 7044 and end t values varying from 5 74 to 7 76 the late stage i type granites are characterized by low contents of si2o and k2o and relatively high contents of feo mgo and na2o with na2o k2o ratios 1 and are metaluminous to weakly peraluminous they are also enriched in lile and depleted in hfse with eu anomalies 87sr 86sr i ratios of 0 703 0 704 and end t values varying from 5 20 to 8 00 the a type granites have high sio2 contents high k calc alkaline shoshonitic affinities positive end t values 5 76 7 77 and low initial 87sr 86sr ratios 0 7017 0 7045 along with reported sr nd isotopic data and regional geologic evidence the early carboniferous i type granites are interpreted as products of partial melting of trapped oceanic crust triggered by underplated mantle wedge derived basaltic magma the late carboniferous early permian i type granites as derivatives of partially melted trapped oceanic crust and the a type granites as resulting from partial melting of trapped juvenile oceanic crust in an extensional regime the a type granitoids with high positive end t values and high zr saturation temperatures could be genetically related to a mantle plume or a regional scale mantle upwelling in the caob

zircon fission track age for middle pleistocene rangitawa tephra new zealand stratigraphic and paleoclimatic significance rangitawa tephra is an important stratigraphic marker in mid pleistocene marine and terrestrial sequences in new zealand and adjacent ocean basins zircon fission track ages zfta on rangitawa tephra from five sites in the southern north island yield mean site ages in the range 0 34 to 0 40 ma with a weighted mean of 0 35 0 04 ma 1 on the basis of glass shard major element chemistry ferromagnesian mineralogy zfta and similarity of paleomagnetic dates of proposed tephra correlatives in deep sea cores it is concluded that rangitawa tephra represents a major eruptive event in the taupo volcanic zone most probably associated with eruption of the whakamaru group ignimbrites 0 35 0 39 ma or less likely the paeroa range group ignimbrites 0 36 0 38 ma pollen analyses from two onshore sites together with regional loess stratigraphy show that rangitawa tephra was erupted during a glacial period the zfta and previously reported oxygen isotope data from dsdp site 594 indicate that rangitawa tephra was erupted near the end of oxygen isotope stage 10

a refined succession of changhsingian and griesbachian neogondolellid conodonts from the meishan section candidate of the global stratotype section and point of the permian triassic boundary abstract a detailed study of new conodont collections from the changxing formation at the meishan section has resulted in taxonomic refinement of several important neogondolellid species most of the previously erected species are much more strictly redefined mainly based on the denticulation of the holotypes and the stratigraphic ranges attributed to key conodont taxa are modified three new species and two new subspecies all of which are form species are tentatively erected and described mainly for the purpose of taxonomic explanation as a result of the taxonomic refinement six neogondolellid conodont zones are recognized for the changxing formation and the permian triassic boundary interval

a review of wanganui basin new zealand global reference section for shallow marine plio pleistocene 2 5 0 ma cyclostratigraphy abstract wanganui basin new zealand contains one of the most complete late neogene marine stratigraphic records in the world the ca 2 km thick basin fill for the last ca 2 5 ma comprises 47 superposed cyclothems which correspond to successive 5th 100 ka and 6th 41 ka order glacio eustatic sea level fluctuations on the palaeo new zealand shelf since oxygen isotope stage 100 stages 100 to 5 are represented by marine cyclothems whereas stages 17 to 3 are represented by a suite of coeval and younger uplifted marine terrace sequences additionally a predominantly glacial loess stratigraphy exists for isotope stages 12 2 the presence of interbedded tephras and an established paleomagnetic stratigraphy allows the development of an integrated cyclostratigraphy for wanganui basin which correlates closely with the global oxygen isotope scale in all except two cases cycles 12 and 36 individual unconformity bound cyclothems sequences represent a single glacial interglacial couplet of milankovitch frequency lithologic and faunal variation within the cyclothems corresponds closely to that predicted by the sequence stratigraphic model each cyclothem generally contains a transgressive systems tract a mid cycle condensed shellbed a highstand systems tract and often a regressive systems tract six common cyclothem motifs are inferred to represent deposition in shelf locations between the highstand and lowstand shorelines viz the hawera maxwell turakina seafield castlecliff and rangitikei motifs a seventh type the nukumaru motif includes coquina limestone and represents deposition in shoreface and very shallow water marine environments

quaternary marine terrace chronology north canterbury new zealand using amino acid racemization and infrared stimulated luminescence extensive marine terraces along the north canterbury coast of the south island of new zealand record uplift in this tectonically active area although the terraces have been studied previously applications of quaternary geochronological techniques to the region have been limited we use infrared stimulated luminescence irsl amino acid racemization aar and radiocarbon to determine ages of terraces at three locations glenafric motunau beach and haumuri bluff we develop an aar calibration curve for the mollusk species tawera spissa from sites of known age including the sedimentary sequence of the whanganui basin bayesian model averaging of the results is used to estimate ages of marine shells from the north canterbury terraces by using both irsl and aar we are able to confirm ages using two independent dating methods and to identify one irsl result that is likely in error we develop new age estimates for the marine terraces of north canterbury and propose correlations between sites this terrace chronology differs significantly from most previous studies highlighting the importance of numerical dating the most extensive terraces are from marine isotope stages miss 5a and 5c with partial reoccupation of one terrace during mis 3 whereas mis 5e terraces are notably lacking among those dated

dispersed rhyolitic tephra from new zealand in deep sea sediments of the southern ocean dispersed rhyolitic tephra in deep sea piston cores collected from the south pacific sector of the southern ocean have previously been considered to originate from the balleny islands antarctica chemical composition of the materials suggests that a source in new zealand is more likely a strong correlation exists between paleomagnetically determined ages for these deep sea tephra layers and fission track ages determined on volcanic glasses and zircons from tephra sequences in wanganui basin and cape kidnappers new zealand the correlation suggests that the tephra extend more than 5000 km east and south of new zealand

record of climatic fluctuations from ca 500 ka loess deposits and paleosols near wanganui new zealand abstract in the wanganui region of north island new zealand a record of climate change for the last ca 500 ka is preserved in a terrestrial cover bed sequence eleven loess layers from five major glacial cycles are separated by paleosols and punctuated by both rhyolitic and andesitic tephra layers the dated rhyolitic tephras thermoluminescence dates from the loess and dated marine terraces on which the sequence rests provide good chronological control a detailed stratigraphy and the use of four physical and chemical parameters enables a climatic interpretation and a correlation with the marine oxygen isotope record to be made variations in dry bulk density and potassium content have resulted from weathering of the upper part of each loess unit during a warmer climate than that responsible for generation of the loess fluctuations in quartz content and magnetic susceptibility are of sedimentary origin and represent alternating quartzo feldspathic and andesitic provenance fluctuations in potassium content and dry bulk density are caused by weathering of the accumulating sediment glacial periods were times of environmental destabilization loess accumulation and least weathering while warm periods saw soil formation and gentle accession of andesitic tephra the main periods of environmental destabilization were during marine oxygen isotope stages 2 3 upper part 6 8 10 and 12 while stages 1 3 lower part 5 7 9 11 and 13 provided most stable conditions and soil formation

evolutionary dynamics of the permian triassic foraminifer size evidence for lilliput effect in the end permian mass extinction and its aftermath abstract there is growing evidence of the lilliput effect in the end permian mass extinction and its aftermath however very little has been published on assessing the lilliput effect on protozoans in the early triassic based on quantitative analysis of a great quantity of samples from outcrop sections this study investigates foraminiferal test size variations through the changhsingian to the olenekian based on fossil records from three outcrop sections in south china the sharp reduction in foraminifer sizes coincides with the first or main episode of the end permian mass extinction foraminifers remained small in sizes in the early induan their body sizes increased slowly in the late induan to olenekian but never recovered to the pre extinction test size levels the lilliput effect on foraminifera in the aftermath of the end permian crisis is indicated by the extinction of large taxa decrease in size for surviving taxa and rise of small sized new forms physiological reactions of various foraminifer groups reveal that several defaunation events such as anoxia ocean acidification and global warming that prevailed through the permian triassic interval may be responsible for both the end permian crisis and the lilliput effect

discriminant function analysis of glass chemistry of new zealand and north american tephra deposits major trace and rare earth element analyses of volcanic glass are used separately or in combination for correlating quaternary tephras often by graphical or simple comparative methods we have taken a statistical approach using discriminant function analysis dfa to assess the relative discriminating power of the different elements in volcanic glasses from several tectonovolcanic provinces we found that major oxides are powerful discriminating variables for widespread tephras from the taupo volcanic zone in new zealand and here they can be more discriminating than trace elements a wide selection of tephras from the western united states can also be distinguished on major oxides alone particularly those from cascade range volcanoes for tephras from large intracontinental calderas such as long valley or yellowstone ree and trace elements are more effective at discriminating than major oxides however tephras erupted from the long valley area can be distinguished on major oxide composition by dfa despite their similar chemistry the selection and relative significance of different elements for discriminating tephras depends on the total data set being compared as well as the source volcano and the individual eruptive events caution must be exercised in the nonstatistical selection of compositional data for characterizing tephras dfa is a more powerful and objective tool for the comparison of tephra chemistry

survival strategies of brachiopod faunas from the end permian mass extinction abstract global reviews reveal that 102 brachiopod species including 40 indeterminate species belonging to 43 genera within 27 families survived the end permian mass extinction in south china the himalayan regions southern tibet nepal salt range and kashmir southern alps italy arctic canada western usa and western australia of these the surviving brachiopods are most abundant and widespread in south china where they occur in 32 of the 42 permian triassic p t boundary sections around the world brachiopod faunas are the most abundant and diverse post extinction survivors and their appearance above the end permian mass extinction horizon somewhat masks recognition of the end permian extinction these surviving brachiopods occur in three stratal intervals corresponding to the mixed fauna beds mfb hereafter 1 3 of the p t boundary beds a sharp drop in diversity of the brachiopod faunas coincides with the widely accepted end permian mass extinction horizon the post extinction brachiopods were also affected by a subsequent crisis corresponding to the boundary between mfb 2 and mfb 3 so that most survivors were extinct approximately 0 7 ma after the end permian mass extinction the surviving brachiopods were mainly productida followed by spiriferida in particular small chonetids chonetid like productellids and smooth thin shelled ambocollid spiriferids are most abundant lingula is extraordinarily abundant and widespread approximately 0 7 ma after the greatest extinction when many regions became devoid of articulate brachiopods widespread broadly adapted and small sized taxa preferentially survived frequent intrageneric speciation of widespread widely adapted generalist genera enabled survival brachiopods to occupy rapidly and efficiently vacant ecospace in the aftermath of the end permian extinction the ecological habitats of the post extinction brachiopods are subdivided into nearshore epeiric sea restricted carbonate platform open carbonate platform ramp and outer shelf environments of these the survival brachiopods are most diverse in the open platform environments the nearshore zone provided ideal habitats for the nonarticulated brachiopods to occupy whereas the survivors in the outer shelf are predominantly chonetids and chonetid like productellids the most successful survivors the productid brachiopods are widely distributed in six types of ecological habitats and thus have no apparent preference for specific environments the end permian extinction resulted in the movement of biogeographical provinces towards the palaeo equator the brachiopods survived mostly in the palaeo equatorial provinces and along the southern margins of the palaeo tethys ocean

aftermath of the permian triassic mass extinction event paleoecology of lower triassic carbonates in the western usa paleoecologic study of invertebrate faunas from three successive early triassic seaways reveals that biotic recovery from the end permian mass extinction event was slow and that full recovery did not occur until after the early triassic simple cosmopolitan opportunistic generalists and low diversity low complexity paleocommunities were characteristic of the entire early triassic in the western usa an increase in guild and taxonomic diversity was observed with the addition of several new higher taxa in the late early triassic spathian to the almost exclusively molluscan faunas of the earlier early triassic nammalian potential disaster forms the inarticulate brachiopod lingula and the paper pecten claraia dominated the earliest early triassic faunas griesbachian and even occurred in the late early triassic normal marine stromatolites comparison with data on faunas from the permian and triassic suggests that even the most diverse early triassic faunas in the spathian were rather low in guild diversity and species richness these characteristics of genera and paleocommunities in the early triassic may be typical of mass extinction aftermaths

end permian catastrophe by a bolide impact evidence of a gigantic release of sulfur from the mantle our studies in southern china have revealed a remarkable sulfur and strontium isotope excursion at the end of the permian along with a coincident concentration of impact metamorphosed grains and kaolinite and a significant decrease in manganese phosphorous calcium and microfossils foraminifera these data suggest that an asteroid or a comet hit the ocean at the end of permian time and caused a rapid and massive release of sulfur from the mantle to the ocean atmosphere system leading to significant oxygen consumption acid rain and the most severe biotic crisis in the history of life on earth

the carbon isotope shift at the permian triassic boundary in the southern alps is gradual carbon isotope ratios in marine carbonate rocks have been shown to shift at some of the time boundaries associated with extinction events for example cretaceous tertiary1 and ordovician silurian2 the permian triassic boundary the greatest extinction event of the phanerozoic3 is also marked by a large 13c depletion4 5 new carbon isotope results from sections in the southern alps show that this depletion did not actually represent a single event but was a complex change that spanned perhaps a million years during the late permian and early triassic these results suggest that the permian triassic p tr extinction may have been in part gradual and in part stepwise 6 7 but was not in any case a single catastrophic event

integrated tephrochronology and magnetostratigraphy for cyclothemic marine strata wanganui basin implications for the pliocene pleistocene boundary in new zealand abstract the middle pliocene to earliest pleistocene part of the rangitikei river section in wanganui basin contains at least six distal tephras five are rhyolitic kowhai eagle hill ohingaiti waipura and vinegar hill tephras and one is andesitic mangamako tephra all tephras occur as macroscopic layers and are enclosed within cyclothemic marine sediments that accumulated in shoreface to outer shelf water depths under conditions of oscillating sea level driven by glacio eustacy the glass and ferromagnesian compositions of the silicic tephras imply derivation from calc alkaline rhyolitic sources either or both of taupo volcanic zone and southern coromandel volcanic zone the waipuru and vinegar hill tephras have isothermal plateau fission track itpft ages of 1 87 0 15 ma and 1 75 0 13 ma respectively paleomagnetic results allow identification of i the gauss matuyama boundary located ca 70 m below the top of the mangaweka mudstone and ii the top of the olduvai subchron placed at the base of the waipuru shellbed the itpft ages of the tephras are consistent with the interpreted magnetostratigraphy and also with astronomically tuned timescales correlation of the rangitikei sequences to the odp site 846 18o record indicates that each sequence corresponds to a glacial interglacial isotope stage couplet and allows ages to be interpolated for tephras not dated directly integration of the new ages for the waipuru and vinegar hill tephras the magnetostratigraphy and the sequence correlations to the astronomically tuned oxygen isotope timescale lead us to place the pliocene pleistocene boundary as defined at the vrica stratotype at the base of the highstand systems tract siltstone of sequence 17 in the rangitikei section 60 m below the vinegar hill tephra

griesbachian earliest triassic palaeoenvironmental changes in the salt range pakistan and southeast china and their bearing on the permo triassic mass extinction abstract facies and faunal analysis from pakistan and china show that the permo triassic mass extinction of marine invertebrate faunas was associated with a spectacularly rapid griesbachian transgression which lead to the widespread establishment of deep water anoxic and dysoxic conditions the extinction event was thus caused by habitat loss due to the extensive development of inhospitable conditions the initial griesbachian transgression in pakistan produced extensive shallow normal marine conditions in which permian holdover taxa were able to survive until the development of dysaerobic facies in the late griesbachian the exceptionally complete sections of china show a three phased deepening and extinction event beginning in the latest permia by the late griesbachian a variety of dysaerobic and anaerobic facies were developed in all the regions studied several of these contain evidence for minimal sulphate reducing activity suggesting that marine productivity and thus organic matter flux to the sediments was very low in early triassic seas

early triassic recovery of the brachiopod faunas from the end permian mass extinction a global review abstract brachiopod faunas in lower triassic deposits from spitzbergen primorye of russia japan mangyslak of kazakhstan alpine europe the caucasus the middle east the himalaya south china new zealand and western usa are taxonomically and stratigraphically reviewed they comprise survivors of the end permian extinction and taxa originating in the early triassic origination of the mesozoic type taxa represents the recovery of early triassic brachiopods the initial recovery of brachiopod faunas began in the late griesbachian and the time interval between the end of extinction and the onset of the recovery of brachiopods is much shorter than previously suspected the early triassic recovery of brachiopod faunas is characterized by widespread brachiopod dispersal multiprovincialism and the presence of rare lazarus genera at that time taxonomic selectivity of the recovery brachiopod faunas favors the rhynchonellids the re population of post extinction brachiopods varies geographically there is a preference for regions either previously barren of latest permian taxa or regions where the pre extinction changhsingian and surviving brachiopods are very rare this unique biogeographic selectivity is probably partly responsible for the impoverished nature of brachiopod faunas in the triassic even mesozoic oceans five intervals of extinction survival survival recovery recovery dispersal and radiation are recognized based on variations in brachiopod faunas from the latest permian to the early triassic a dramatic reduction in brachiopod diversity at the end permian mass extinction is followed by several stepwise declines in diversity in the survival interval the time during which the surviving brachiopods are dominated by geographically widespread generalist faunas that adapted to a wide variety of environments the survival interval was followed by a slow re population of new lineages dominated by progenitor taxa

u pb zircon geochronology and tempo of the end permian mass extinction the mass extinction at the end of the permian was the most profound in the history of life fundamental to understanding its cause is determining the tempo and duration of the extinction uranium lead zircon data from late permian and early triassic rocks from south china place the permian triassic boundary at 251 4 0 3 million years ago biostratigraphic controls from strata intercalated with ash beds below the boundary indicate that the changhsingian pulse of the end permian extinction corresponding to the disappearance of about 85 percent of marine species lasted less than 1 million years at meishan a negative excursion in 13 c at the boundary had a duration of 165 000 years or less suggesting a catastrophic addition of light carbon

toward a comprehensive upper quaternary tephra and ignimbrite stratigraphy in new zealand using electron microprobe analysis of glass shards abstract new zealand quaternary marine and terrestrial sequences contain numerous tephras or volcanic ash horizons that are the distal correlatives of voluminous welded ignimbrite sheets erupted from central north island electron microprobe analyses of glass shards from the distal tephras demonstrate their homogeneity and are shown to identify each tephra examined by matching tephras from stratigraphically controlled sequences the first comprehensive tephra stratigraphy spanning from 50 000 to 700 000 yr ago and covering the new zealand region is advanced analyses on glass shards from the unwelded base of ignimbrite sheets are comparable to the distal tephra analyses and allow correlation between ignimbrites and to the distal tephras the better exposed tephra record constrains the number of separate eruptive events and the stratigraphy of the ignimbrites both of which were previously confused by lack of outcrop samples from pumiceous marine sediments were found to contain two or more chemically distinct populations of glass the pumice is in cross bedded sands or sand lenses within conglomerate attesting to a shallow high energy environment where reworking could occur however each glass population could be matched to older known tephras

test of thermoluminescence dating of loess from new zealand and alaska abstract the accuracy of thermoluminescence tl ages for loess and sediments in general greater than 100 ka is disputed we tested the accuracy of three common tl sediment dating techniques applied to 4 11 m sized polymineral grains from known age loess using 16 samples from north island and south island new zealand and 2 samples from central alaska estimated sample ages range from 20 26 to 800 ka we varied the optical bleaching spectrum the selected window of the emission spectra ultraviolet or uv blue and green wavelengths the pre readout heat treatment and the tl equivalent dose measurement technique most of the 20 26 ka samples gave tl age underestimates of 3 6 ka that may be attributed to post burial open system behavior for the older samples the partial bleach tl method gave expected ages up to 300 ka and the total bleach tl method produced expected ages above 100 ka the partial bleach regeneration tl method gave significant age underestimates for samples older than 100 ka with a maximum tl age of 250 ka for samples having expected ages up to 350 ka two 300 360 ka samples which gave total bleach age underestimates with use of uv tl and green tl gave expected ages with use of blue tl these results demonstrate that reliable tl ages for loess from new zealand and alaska up to 800 ka can be obtained if uv and green emissions and the various regeneration methods are avoided this age range is well above the former putative 80 100 ka upper age limit for tl dating of loess from other regions which was thought to be a global limit application of our successful procedures to such loess is encouraged

the permo triassic extinction the end permian mass extinction brought the palaeozoic great experiment in marine life to a close during an interval of intense climatic tectonic and geochemical change improved knowledge of latest permian faunas coupled with recent advances in isotopic studies and biostratigraphy have greatly enhanced our understanding of the events of 250 million years ago and have begun to provide answers to many questions about the causes of extinction

late pleistocene sea level oscillations mis 10 2 recorded in shallow marine and coastal plain sediments of the southern wanganui basin new zealand abstract the northern wanganui basin new zealand is one of the key global sites for understanding marine cyclic sedimentation during the quaternary this paper presents the first evidence of marine cyclic sedimentation from its central southern parts sedimentological micropalaeontological and palynological analyses on a 280 m deep borehole encountered units dating back to mis 10 the sequence includes four marine cycles spanning mis 9 5 which are overlain by terrestrial fluvial aggradation surfaces dating from mis 4 2 each marine unit represents a progressively shallowing depositional environment from the mid shelf to coastal plain this is overlain by a terrestrial sequence of lowstand fluvial terraces localized fault movements appear to have influenced the sedimentary character of the sequence during mis 7a and 5e producing basement highs which provided protection to the shoreline the cyclothems described in this paper now extend the already extensive previously described record from mis 17 10 to produce a combined eustatic record of quaternary sea level change within the basin to mis 5 they also provide an excellent example of the sedimentary response of a coastal basin to a progressive loss of sedimentation accommodation space

upper quaternary marine terrace chronology and deformation south taranaki new zealand an extensive flight of late quaternary marine terraces in the south taranaki region of the north island of new zealand is dated using fission track radiocarbon and amino acid racemization methods a simple model of terrace deformation based on a doming type uplift pattern allows terrace strandline ages to be estimated twelve strandlines are recognized and are estimated to have formed during high sea level stands at 60 000 80 000 100 000 120 000 135 000 210 000 310 000 340 000 400 000 450 000 520 000 600 000 and 680 000 yr b p

permian gondwana boreal antitropicality with special reference to brachiopod faunas in a reconstructed global permian marine biogeographic framework antitropicality is defined as a biogeographic phenomenon whereby a taxon occurs only in the boreal and gondwanan realms and is lacking completely or nearly so in the intervening palaeoequatorial realm we recognise three types of antitropical distributions bipolar high latitude generally 50 latitude in each hemisphere bitemperate approximately between 30 and 50 latitudes in each hemisphere and a combination of both evidence of permian antitropicality has been reported from almost all major marine invertebrate groups both pelagic or benthic forms and is best known at the generic level although an increasing number of antitropical species have also been recognised antitropicality appears to have occurred throughout most of the permian but its strength varied from stage to stage judging by the number of brachiopod genera shared between the two hemispheres the phenomenon manifests itself most strongly from the sakmarian to the kazanian wordian suggesting a prolonged interval of enhanced biotic interchanges between the gondwanan and boreal realms possible migration pathways and mechanisms are reviewed and discussed among a number of existing scenarios invoked to explain the origin of both modern and geological antitropicality we here present data particularly supporting 1 a south to north stepping stone migratory mechanism via island terranes scattered in the eastern palaeotethys 2 a vicariance model exemplified by the spatio temporal distribution of tomiopsis and 3 a shelf north to south migration along the western coast of the palaeotethys as suggested by sowerbina in addition we also consider dispersal along the western coast of pangea facilitated at times by upwelling systems as an additional migration pathway for intercontinental biotic exchanges during the permian although corroborating data are required at present

mass extinctions and sea level changes abstract review of sea level changes during the big five mass extinctions and several lesser extinction events reveals that the majority coincide with large eustatic inflexions the degree of certainty with which these eustatic oscillations are known varies considerably thus the late ordovician and end cretaceous extinctions are associated with unequivocal major regressions demonstrated from numerous widespread regions in contrast the multiple high frequency sea level changes reported for the frasnian famennian crisis based on the supposed depth preferences of conodont taxa have little support from sequence stratigraphic analyses which reveals the interval to be one of highstand the end permian mass extinction has long been related to a severe first order lowstand of sea level newell n d 1967 revolutions in the history of life geol soc am spec pap 89 63 91 based primarily on the widespread absence of latest permian ammonoid markers but field evidence reveals that the interval coincides with a major transgression newell s hypothesis that marine extinctions are related to shelf habitat loss during severe regression remains tenable for the end guadalupian and end triassic extinction events but not for other crises rapid high amplitude regressive transgressive couplets are the most frequently observed eustatic changes at times of mass extinction with the majority of extinctions occurring during the transgressive pulse when anoxic bottom waters often became extensive the ultimate cause of the sea level changes is generally unclear a glacioeustatic driving mechanism can only be convincingly demonstrated for the end ordovician and end devonian events at other times it is speculated that they may relate to the widespread regional doming and subsequent collapse caused by the impingement of superplumes and ultimate eruption on the base of the lithosphere

a spectral analysis procedure for dating quaternary deep sea cores and its application to a high resolution brunhes record from the southwest pacific abstract date 32 is a fast and easily used computer program developed to date quaternary deep sea cores by associating variations in the earth s orbit with recurring oscillations in core properties such as carbonate content or isotope composition starting with known top and bottom dates distortions in the periodicities of the core properties due to varying sedimentation rates are realigned by fast fourier analysis so as to maximise the spectral energy density at the orbital frequencies this allows age interpolation to all parts of the core to an accuracy of 10 kyrs or about 1 5 of the record duration for a typical brunhes sequence the influence of astronomical forcing is examined and the method is applied to provide preliminary dates in a high resolution brunhes record from dsdp site 594 off southeastern new zealand

geomechanical and geochemical changes during early stages of weathering of karamu basalt new zealand abstract variations in geochemical and geomechanical characteristics were measured through a basalt weathering sequence exposed at an abandoned quarry at karamu near hamilton new zealand geochemical measurements show that at the early stages of weathering fresh to slightly weathered reductions in the concentrations cao and mgo are rapid although they are not accompanied by major mineralogical change during later stages of weathering secondary clay minerals form following well described mineralogical changes fresh basalt is strong uniaxial compressive strength 262 mn m 2 point load index 5 59 with well developed closely spaced columnar jointing slightly weathered material is distinguished in the field only by slight discolouration along joint planes but laboratory tests show a dramatic loss of strength in slightly weathered rock point load index 0 41 cbr 43 a causal relationship between the loss of cations and loss of strength in the early stages of weathering is suggested this stage of weathering is diffusion controlled whereby cations are lost from the constituent primary minerals and replaced by h this process disrupts the lattice structure and causes a marked loss of strength implications are that slightly weathered rock which appears competent in the field is likely to have much lower strength and durability than assumed from field evidence

anoxia as a cause of the permian triassic mass extinction facies evidence from northern italy and the western united states facies faunal and geochemical evidence from the permian triassic boundary sediments of the dolomites and idaho indicates a major anoxic event in the earliest triassic in both regions the basal beds consist of finely laminated micrites with common syngenetic pyrite the only fauna consists of occasional bedding plane assemblages of lingula or clacaria a typical lower dysaerobic assemblage this is a level where previous studies have shown a major negative carbon isotope excursion and a cerium anomaly in the dolomites the pyritic micrite directly overlies strata containing a diverse and typically permian marine fauna of algae foraminifers including fusulinids and articulate brachiopods implying an abrupt extinction in contradiction to many previous views sequence stratigraphic analysis of the dolomite boundary sediments reveals a minor sequence boundary in the late permian followed by extremely rapid transgression leading to the development of the relatively deep water pyritic micrite a maximum flooding surface at the permo triassic boundary a further pulsed deepening in the lower griesbachian recorded in both the dolomites and idaho lead to the widespread establishment of dysaerobic facies it is clear that most of the extinctions occurred at the erathem boundary although the subsequent failure of the marine benthos to fill the empty ecospace in the ensuing griesbachian may have been due to the widespread development of dysaerobic conditions

use of amphibole chemistry for detecting tephras in deep sea sequences chikyu c9001c cores and developing a middle pleistocene tephrochronology for ne japan abstract using amphibole crystals we detected tephras in deep sea sequences chikyu c9001c cores and correlated marine and terrestrial tephras in ne japan then we reconsidered some previously reported tephra ages by using the age model of the cores we identified 50 spikes in amphibole grains numbered a1 a50 from top to bottom among these 12 spikes a38 49 corresponded to a thick non tephric sand layer we selected 20 spikes containing amphibole grains with glass coatings as likely primary tephras and analyzed their chemistry for tephra characterization on the basis of its amphibole chemistry we correlated spike a34 with the tn cii ciii layers of the tanabu c tephra tn c which erupted from osore volcano on shimokita peninsula we then showed that spike a34 represents primary tephra deposition not secondary deposition through bioturbation or bottom current reworking because amphibole grains with homogeneous chemistry were accumulated only in sediment near the spike within 10 cm we also showed that the chemical variation within each amphibole grain was not as great as the variation between grains which further supports the correlation between spike a34 and tn cii ciii these findings show that amphibole grains which are resistant to weathering can be used for characterization and correlation of weathered tephras from which glass shards have been removed by dissolution the glass shard chemistry of the 16h6a 60 80 tephra at 4 58 m below spike a34 which does not correspond to an amphibole spike suggests that this tephra likely correlates with the amphibole free tn ci layer in the terrestrial sequences non tephric sediments marine sand and lahar deposits occur between tn ci and tn cii ciii suggesting that some time elapsed after the deposition of tn ci before tn cii ciii were deposited by using the stratigraphic information of the 16h6a 60 80 tephra and spike a34 together with the 18o stratigraphy of the deep sea sequence we re assigned the eruptive age of tn c from the previously reported zircon fission track age of 180 40 ka to mis 8 257 263 ka

weathering trends in terrace deposits up to 350 000 years old in northeast southland new zealand abstract gravelly floodplain deposits and six terrace treads in the waimea plains northeast southland new zealand range in age from ca 1000 years old to 350 000 yr old deposits are progressively more weathered with increasing parent material age soils developed in them are classified as recent soils brown soils and ultic soils in the new zealand soil classification and udifluvents dystrochrepts haplohumults hapludults and paleudults in the usda soil classification soil taxonomy the youngest soils are slightly acid those developed in deposits 35 000 70 000 yr old are strongly acid in soils in deposits 160 000 yr old and older that have weathered in two or three interglacial periods including the present one ph and total exchangeable bases values are higher than in soils in younger deposits the higher ph of the soils in older deposits is attributed to release of cations by stone weathering soils developed in deposits up to 70 000 yr old have clays dominated by mica and chlorite stones in these soils are at most weakly weathered and the two phases of weathering are distinguished a phase of approximate duration 100 000 yr in which most weathering and leaching occurs in the matrix which becomes increasingly acidified and a phase from 100 000 to 350 000 yr which is dominated by cation release from stones reversal of the acidification trend and breakdown of stone fabric

resolution of the age structure of the detrital zircon populations of two lower cretaceous sandstones from the weald of england by fission track dating modes in the frequency of distribution of fission track ages obtained from detrital zircon grains may prove characteristic of individual sandstone bodies supporting the identification of the sources from which a particular flow of sedimentary detritus was derived and thus allowing new inferences to be made concerning palaeogeography a computer program has been written and used to identify modes in the zircon fission track age distribution within two lower cretaceous sandstone samples from the weald of southern england pronounced modes appear in one rock around 119 ma 160 ma 243 ma and 309 ma and in the other around 141 ma 175 ma 257 to 277 ma and 394 to 453 ma the geological implications of these quite dissimilar zircon age spectra are discussed it is concluded that they support the palaeogeographical models of allen 1981 and indicate that the provenance of the first sample from the top ashdown sandstone member at dallington in east sussex was almost entirely southerly while that of the second from the netherside sand member at northchapel in west sussex was more varied but predominantly westerly and northerly

recurring global sea level changes recorded in shelf deposits near the g m polarity transition wanganui basin new zealand implications for redefining the pliocene pleistocene boundary abstract a well exposed 1 km thick association of late pliocene and early pleistocene ca 2 6 1 7 ma strata in wanganui basin new zealand contains a progradational stack of twenty 5th order 41 ka duration depositional sequences that accumulated in shelf to shoreface paleoenvironments in response to global glacioeustatic sea level fluctuations the sequences are correlated with 18o isotope stages 100 58 and each 41 ka glacial interglacial stage couplet is represented by an individual sequence comprising transgressive tst highstand hst and regressive rst systems tracts that can be readily related to generic sequence stratigraphic models in general deposition of each of the sequences occurred during odd numbered interglacial isotope stages and the sequence boundaries developed during the maxima of even numbered glacial isotope stages the key palaeomagnetic tiepoints used for pinning the isotope record to the section are the gauss matuyama boundary 2 60 ma in stage 104 and the top of olduvai subchron 1 77 ma in stage 63 a deeply incised sequence boundary with up to 30 m of relief at the base of te rimu sand represents the first widespread subaerial exposure in wanganui basin during the matuyama chron it is correlated with the high amplitude positive glacial 18o shift in isotope stage 100 which is considered to mark the initiation of major northern hemisphere continental glaciations at ca 2 52 ma the overlying hautawa shellbed containing the subantarctic bivalve chlamys delicatula defines the base of the nukumaruan stage and represents the earliest faunal evidence of climatic cooling in new zealand pliocene pleistocene marine sequences the sequence boundary at the base of hautawa shellbed is correlated with isotope stage 98 ca 2 48 ma traditionally the pliocene pleistocene boundary in new zealand was located at the base of hautawa shellbed but beu and edwards 1984 showed that the boundary as defined in the vrica stratotype astronomically calibrated age ca 1 81 ma actually lies in the upper part of the nukumaruan stage the hautawa shellbed which lies closer to the gauss matuyama palaeomagnetic transition 2 60 ma is therefore much older than the currently defined pliocene pleistocene boundary from a new zealand perspective a more logical position for the pliocene pleistocene boundary would be close to or just above the gauss matuyama polarity transition such a position would take advantage of the boundaries proximity to a readily identifiable polarity reversal and lie close to the time of initiation and development of major northern hemisphere ice sheets

500 000 year paleomagnetic record from new zealand loess abstract a paleomagnetic record of secular variation has been obtained from a 17 4 m long core drilled from loess in north island new zealand three dated rhyolitic tephra occur in the loess core at depths of 1 5 3 4 and 13 0 m with ages of 22 500 42 000 and 370 000 years respectively the base of the core is estimated to be 500 000 years old which makes this the longest continuous loess sequence yet described from the southern hemisphere two periods of anomalously low inclination in the core are correlated with the mungo event ca 35 000 years ago and the emperor event ca 490 000 years ago the blake event ca 115 000 years ago is not recorded

a micromorphological study of pedogenic processes in an evolutionary soil sequence formed on late quaternary rhyolitic tephra deposits north island new zealand abstract the influence of time as a soil forming factor was studied on an evolutionary sequence of five soils 1850 radiocarbo years bp ca 120 000 bp developed in rhyolitic tephra deposits in new zealand new micromorphological observations were combined with existing macromorphological chemical textural and clay mineralogical analyses to assess the extent of polygenesis in the soils the younger soils 1850 bp to ca 22 600 bp are characterised by initial weathering and little secondary mineral formation this status is expressed by abundant pumice fragments and fresh easily weatherable minerals as well as a low clay content with an isotropic character comminution and neoformation are the main pedological processes the older soils ca 120 000 bp are characterised by a high degree of alteration of primary minerals little or no pumice fragments clay illuviation gleying and a high clay content 80 consisting of a range of crystalline clay minerals including halloysite gibbsite kaolinite and vermiculite plus crystalline iron oxides evidence of polygenesis can be observed in the micromorphology of the older soils 1 the range of secondary minerals is the result of the integration and succession of soil forming processes through time 2 the accumulatory character of the tephra deposits has resulted in stronger weathering of the lower horizons than upper horizons because of continuous pedogenesis such polygenesis in the older soils supports the view that the older the soil the more polygenetic it is likely to be

luminescence dating using feldspars a test case from southern north island new zealand abstract luminescence dating using coarse grain potassium rich feldspars is applied to a suite of 12 dune sands collected from southern north island new zealand the expected ages of the samples range from modern to 350 ka luminescence ages were calculated using thermoluminescence and infra red stimulated luminescence measurements to determine total bleach and regeneration equivalent doses for each sample no systematic difference was observed between any of these different methods withstanding the uncertainties in the independent ages of some samples comparison of the luminescence ages with those suggested by the independent age control suggests that reliable luminescence ages can be obtained for samples younger than 130 ka luminescence ages for older samples appear to underestimate the true age and it is suggested that this may be due to long term fading of the luminescence signal as suggested by mejdahl 1989