evidence for lateglacial and holocene tree line fluctuations from pollen diagrams from the subalpine zone on mt hauhungatahi tongariro national park new zealand pollen diagrams from four sites along an altitudinal sequence on mt hauhungatahi support fossil wood data ogden et al 1997 in suggesting a fluctuating holocene tree line not exceeding the altit

revised calendar date for the taupo eruption derived by 14c wiggle matching using a new zealand kauri 14c calibration data set taupo volcano in central north island new zealand is the most frequently active and productive rhyolite volcano on earth its latest explosive activity about 1800 years ago generated the spectacu

theoretical investigation of the oceanic inverted barometer response dynamic tidal theory is generalized in order to predict the oceanic response to atmospheric pressure variations the oceans are found to exhibit distinct dynamic behavior when forced at periods less than 1 week depending on the harmonic type of forcing the amplitude of the response can differ by 20 or more from the static response even at roughly 2 months the traditional inverted barometer may not be sufficiently accurate for applications in which detection of long term sea level trends or vertical crustal motion is the goal for forcing at periods of order 1 year the oceanic response differs by at most a few percent from the static not the inverted barometer response thus calculations of meteorological excitation of the annual and chandler wobbles can employ the static approximation without reservation

landslide occurrence as a response to land use change a review of evidence from new zealand abstract vegetation cover is an important factor influencing the occurrence and movement of rainfall triggered landslides and changes to vegetation cover often result in modified landslide behaviour however it is difficult to relate the occurrence of landslides directly to variations in land use especially in some european countries in contrast new zealand provides a good opportunity to investigate geomorphic responses to anthropogenic land cover changes before european settlers first arrived in the 1840s hilly regions were only marginally influenced by human activity the maoris new zealand s first settlers lived largely on coastal plains or near lakes and rivers they influenced general vegetation cover only through localized burning practices in contrast european settlers moved into the back country and converted extensive hill areas from native forest and bush to pasture this reduced the strength of the regolith and rendered the slopes more susceptible to landslides pulses of natural sedimentation in the pre european period have been related to volcanic activity climatic variability including changes in frequency of cyclonic storms and wind erosion and fluvial erosion following forest fires initiated either by volcanic eruptions or lightning strikes since european deforestation began sediment production has largely been determined by landslide events on unstable slopes thousands of landslides were triggered by high magnitude low frequency climatic events during storms with estimated return periods in excess of 50 years in contrast low magnitude high frequency rainfall events have caused gully and channel erosion examples from different parts of new zealand indicate changes in sediment generating processes following land use modifications after deforestation landslides have contributed significantly to sediment sequences in depositional basins such as lakes swamps estuaries coastal wetlands and the nearshore and offshore zones of continental platforms

forest disturbance in the central north island new zealand following the 1850 bp taupo eruption the 1850 bp taupo eruption covered c 30 000 km2 of the central north island with airfall deposits and c 20 000 km2 with ignimbrite this paper reviews pollen and charcoal analyses of lake and peat sediment cores from sites at various distances and directions from the taupo vent to establish the effects of this eruption on the surrounding forests forests within range of the ignimbrite were destroyed and forests located up to 170 km east of the vent suffered variable degrees of damage from ashfall stands of pteridium esculentum and other seral taxa flourished immediately after the eruption fires occurred during the eruption and continued for several decades after the degree and nature of vegetation disturbance above the taupo tephra varied according to the thickness of ashfall local topographical features and probably the vigour of the forest revegetation was complete within 200 years of the eruption even at sites overwhelmed by the taupo ignimbrite post eruption forests were similar to those exi

local and regional scale impacts of the 74 ka toba supervolcanic eruption on hominin populations and habitats in india abstract the toba supervolcanic eruption of 74 000 years ago is argued to have devastated homo sapiens populations causing a human population bottleneck through a combination of rapid global climatic deterioration and ecological disruption following the widespread ash fall this dramatic eruption the largest in at least the last 2 million years is hypothesized to have shaped the genetic structure and diversity of human populations today past assessments of toba s human impacts however have been predominantly theoretical using archaeological and geological evidence from sites in india this study addresses toba s local scale impacts on hominin technology behavior demography and habitats in two valleys in india the jurreru and middle son valleys using paleoclimatological and volcanological data regional scale impacts throughout india are inferred a refugia hypothesis is presented that argues for variation in the scale of toba s impact throughout india driven by regional differences in monsoonal dynamics geography and topography areas of north west india the indo gangetic plain and parts of the deccan to the east of the western ghats are argued to have been the most affected whereas areas of southern and eastern india may have preserved the largest refugia for hominin populations

signals of watershed change preserved in organic carbon buried on the continental margin seaward of the waipaoa river new zealand abstract holocene sediments buried on the continental shelf seaward of the waipaoa river northeastern new zealand preserve a stratigraphic record of terrestrial environmental change the well characterized long term record of storms volcanism and human disturbance in this region provides an opportunity to examine how such changes are reflected in the character of organic carbon oc buried on the continental margin complimentary evidence obtained from analyses of the 14 c content and the elemental and stable carbon isotopic composition of different sedimentary fractions including charcoal wood and clay sized isolates indicates that these perturbations led to mobilization of oc components with variable storage histories in the watershed charcoal transported in the modern waipaoa river and buried in offshore depocenters includes a highly aged component that has apparently been slowly released from storage in soil or alluvial terraces the charcoal fraction ages become dramatically younger in sediments deposited after the taupo volcanic eruption 1717 cal yr bp and then polynesian settlement ca 700 cal yr bp both signaling biomass burning the mean age of woody plant fragments and clay bound oc deposited on the shelf also varies over time with older material having accumulated in the middle holocene and since human occupation deposition of older than average wood fragments and clay bound oc between about 5 and 3 6 kyr bp correlates with evidence for a period of increased storm frequency in the region and may reflect the enhanced delivery of aged soil and sedimentary rock mobilized from hill slopes via earthflows and or deep seated landslides similarly the deposition of older wood and clay bound oc commensurate with the first anthropogenic disturbance ca 700 years ago is consistent with accelerated mass wasting due to deforestation at the same time a change in the elemental and stable isotopic composition of bulk and clay bound oc buried on the shelf may reflect increased marine primary productivity and or mobilization of oc from deep levels in soil profiles deforestation of the waipaoa headwaters by european settlers beginning in the middle 19th century is evinced by a sharper rise in the age of clay associated oc buried offshore today deep gully incision into fractured sedimentary bedrock is a major source of sediment and kerogen to the river and this process has left its mark on the age of sedimentary oc delivered to the adjacent margin

evidence for continued disturbance of upland rain forest in sumatra for the last 7000 years of an 11 000 year record abstract a pollen diagram is presented from a swamp at 1100 m altitude in the sumatran rift valley indonesia the diagram covers the last 11 000 years and shows evidence of continuous cover by tropical rain forest there are indications of continuous disturbance probably by people during the last 7000 years this has caused little change in diversity which does not support the intermediate disturbance hypothesis of connell science 199 1978 1302

holocene vegetation and volcanic activity auckland isthmus new zealand a 12 000 to 4000 yr bp pollen and tephra bearing profile from auckland new zealand provides insights into the vegetation history and evidence for early holocene volcanic activity in this area centred on the mount wellington basaltic volcano possibly 500 yr separated initial scoriaceous ash deposition ca 9500 yr ago and subsequent major lava flows ca 9000 yr ago from mount wellington the local vegelation topography and drainage patterns were substantially modified during this time and damming by the lava flows resulted in the formation of lake waiatarua in a shallow valley head ca 9000 yr ago diatom evidence indicates that this lake was initially deep 5 m but was shallowing around 4000 yr ago in contrast to the mount wellington eruptions tephra deposition resulting from distant rhyolitic volcanic activity of the central north island and mayor island has had little effect on the auckland vegetation during this time interval 12 000 4000 yr ago between ca 12 000 and 10 000 yr ago conifer angiosperm forest was the predominant vegetation cover on auckland isthmus but during the early holocene forest dominated by metrosideros expanded probably on to fresh volcanic surfaces resulting from the mount wellington eruptions at this time swamp forest communities developed in waiatarua valley basin and included species indicative of moist mild relatively frost free climates some taxa show histories consistent with other records from the northern new zealand region including the rise of ascarina lucida ca 11 000 to 9000 yr ago and its subsequent decline and the expansion of agathis australis kauri forest communities from ca 6000 yr ago taken together the history of local and regional vegetation points to a mild moist and weakly seasonal early holocene climate which subsequently became drier with greater seasonal temperature extremes

north atlantic sea level and circulation summary monthly sea levels from an extensive array of north atlantic tide gauges 26 50 n are examined the spatial scale of the sea level variations and the reasons for them are discussed one application of such a study is clearly in the design of a tide gauge network for monitoring eustatic changes of sea level the spatial scale of the sea level changes is large there is a coherent sealevel signal which can be traced along the eastern boundary of the north atlantic from newlyn 50 n to tenerife 28 n there are also two distinct groupings of tide gauges along the western boundary separated by cape hatteras the contribution of local air pressure and wind stress is quantified at each gauge through multiple regression techniques and the gains are then interpreted in terms of recent theoretical and numerical modelling studies for example the gains suggest that the wind forced boundary current along the nova scotian shelf is trapped to within about 16 km of the coast the influence of local meteorology cannot account for the large scale modes of variability the coherent signal along the eastern boundary is correlated with changes in the sverdrup transport of the north atlantic and hence the large scale wind field the two modes on the western boundary appear to be related to baroclinic boundary current variations the newlyn sea level record is finally corrected for some of the above effects to illustrate the utility of such a residual series in the identification of eustatic changes and vertical crustal movement

new aspects of the equilibrium pole tide summary we have developed a new spherical harmonic algorithm for the calculation of the loading and self gravitating equilibrium pole tide based on a suggestion of dahlen this approach minimizes the distortions in tide height caused by an incomplete representation of the ocean function with slight modification our approach easily could be used to compute self gravitating and loading luni solar tides as well using our algorithm we have compared the static pole tide with tide observations at a variety of locations around the world we find statistically significant evidence for pole tide enhancements in mid ocean as well as the shallow seas we have also re investigated the effect of the static tide on the chandler wobble period the difference between the wobble period of an oceanless elastic earth with a fluid core smith dahlen and the period of an earth minus static oceans yields a 7 4 day discrepancy we conclude from tide observations that much of the discrepancy can probably be accounted for by non equilibrium pole tide behaviour in the deep oceans

comparison of enigmatic diamonds from the tolbachik arc volcano kamchatka and tibetan ophiolites assessing the role of contamination by synthetic materials abstract the enigmatic appearance of cuboctahedral diamonds in ophiolitic and arc volcanic rocks with morphology and infrared characteristics similar to synthetic diamonds that were grown from metal solvent requires a critical reappraisal we have studied 15 diamond crystals and fragments from tolbachik volcano lava flows using fourier transform infrared spectrometry ftir transmission electron microscopy tem synchrotron x ray fluorescence srxrf and laser ablation inductively coupled plasma mass spectrometry la icp ms ftir spectra of tolbachik diamonds correspond to typical type ib patterns of synthetic diamonds in tem films prepared using focused ion beam technique we find mn ni and mn si inclusions in tolbachik diamonds srxrf spectra indicate the presence of fe ni and fe ni mn inclusions with cr ti cu and zn impurities la icp ms data show variable but significantly elevated concentrations of mn fe ni and cu reaching up to 70 ppm these transition metal concentration levels are comparable with those determined by la icp ms for similar diamonds from tibetan ophiolites mn ni fe solvent was widely used to produce industrial synthetic diamonds in the former ussr and russia with very similar proportions of these metals hence it appears highly probable that the cuboctahedral diamonds recovered from kamchatka arc volcanic rocks represent contamination and are likely derived from drilling tools or other hard instruments kinetic data on diamond dissolution in basaltic magma or in fluid phase demonstrate that diamond does not form under the pressures and temperature conditions prevalent within the magmatic system beneath the modern day klyuchevskoy group of arc volcanoes we also considered reference data for inclusions in ophiolitic diamonds and compared them with the composition of solvent used in industrial diamond synthesis in china the similar inclusion chemistry close to ni70mn25co5 for ophiolitic and synthetic chinese diamonds scrutinized here suggests that most diamonds recovered from tibetan and other ophiolites are not natural but instead have a synthetic origin in order to mitigate further dubious reports of diamonds from unconventional tectonic settings and source rocks we propose a set of discrimination criteria to better distinguish natural cuboctahedral diamonds from those produced synthetically in industrial environments and found as contaminants in mantle and crust derived rocks

using rat gnawed seeds to independently date the arrival of pacific rats and humans in new zealand the pacific rat rattus exulans was transported throughout the south pacific with voyaging humans thus the earliest dated evidence of pacific rat can be used to infer first human contact until recently it was considered that rats arrived in new zealand with humans in the thirteenth century ad however controversial radiocarbon dates on pacific rat bones now suggest that rats reached the remote islands of new zealand with people c ad 50 150 these dates are anomalous because they imply human contact with new zealand more than 1000 years before any archaeological evidence for human presence and precede settlement of tropical eastern polynesia the ancestral homeland of maori the first new zealanders the early rat bone dates are controversial for other technical reasons which have been debated in the literature here distinctive rat gnawed seed cases preserved in sediments are used as a proxy to independently date the arrival of the pacific rat and humans in new zealand this method effectively b

late holocene vegetation and climate change at moraine bog tiedemann glacier southern coast mountains british columbia moraine bog lies just outside the outermost lateral moraine of tiedemann glacier in the southern coast mountains of british columbia a sediment core taken from the wetland was analyzed for pollen magnetic susceptibility and loss on ignition to reconstruct changes in vegetation and climate during the late holocene vegetation changed little between about 3500 and 2400 14 c years bp a period of local disturbance marked by deposition of a silty clay bed and increases in alnus pollen likely reflecting cooler moister conditions coincides with an extensive holocene advance of tiedemann glacier about 2400 14 c years bp warm dry conditions between about 1900 and 1500 14 c years bp are sug gested by peak values of pseudotsuga pollen and increasing nuphar sclereids the latter suggests lowered water levels this period coincides with a time of drought and increased fire frequency in the southernmost coast mountains about 1300 14 c years bp the forest became more coastal in composition with abundant tsuga heterophylla and abies a n increase in tsuga mertensiana pollen suggests the onset of cool and wet conditions by ca 500 14 c years bp coincident with the little ice age the record of inferred climate change at moraine bog is broadly synchronous with other paleoclimate records from the coast mountains and at the centennial scale with records elsewhere in the world

spectroscopic analysis of global tide gauge sea level data summary yearly and monthly tide gauge sea level data from around the globe are fitted to numerically generated tidal data to search for the 18 6 yr lunar nodal tide and 14 month pole tide both tides are clearly evident in the results with amplitudes and phases that are consistent with a global equilibrium response global atmospheric pressure data are fitted to global monthly sea level data to study the response of the ocean to pressure fluctuations the global response of sea level to pressure is found to be inverted barometer at periods greater than 2 months a large coherence at 437 days between pressure and sea level data is found for the north sea baltic sea and the gulf of bothnia the results are not entirely conclusive but they tend to support o connor s 1986 suggestion that the apparent enhanced pole tide in these basins may be due to meteorological forcing rather than to a basin scale resonance finally global averages of tide gauge data after correcting for the effects of post glacial rebound on individual station records reveal an increase in sea level over the last 80 yr of between 1 1 and 1 9 mm yr as part of the process of removing the effects of post glacial rebound we fit those effects to the global tide gauge data and obtain very good agreement with results predicted from post glacial rebound models this tends to support the post glacial model results and it suggests that the global tide gauge data are indeed capable of resolving changes in sea level at the mm yr level

accuracy assessment of the large scale dynamic ocean topography from topex poseidon altimetry the quality of topex poseidon determinations of the global scale dynamic ocean topography have been assessed by determining mean topography solutions for successive 10 day repeat cycles and by examining the temporal changes in the sea surface topography to identify known features the assessment is based on the analysis of topex altimeter data for cycles 1 through 36 important errors in the tide model used to correct the altimeter data have been identified the errors were reduced significantly by use of a new tide model derived with the topex poseidon measurements maps of the global 1 year mean topography produced using four of the most accurate models of the marine geoid show that the largest error in the dynamic ocean topography is now the uncertainty in the geoid temporal variations in the spatially smoothed maps of the annual sea surface topography show expected features such as the known annual hemispherical sea surface rise and fall and the seasonal variability due to monsoon influence in the indian ocean changes in the sequence of 10 day topography maps show the development and propagation of an equatorial kelvin wave in the pacific beginning in december 1992 with a propagation velocity of approximately 3 m s the observations are consistent with observed changes in the equatorial trade winds and with tide gauge and other in situ observations of the strengthening of the 1992 el nino comparison of topex determined sea surface height at points near oceanic tide gauges shows agreement at the 4 cm rms level over the tropical pacific the results show that the topex altimeter data set can be used to map the ocean surface with a temporal resolution of 10 days and an accuracy which is consistent with traditional in situ methods for the determination of sea level variations

late glacial to holocene paleoenvironmental change on the northwestern pacific seaboard kamchatka peninsula russia we used a new sedimentary record from a small kettle wetland to reconstruct the late glacial and holocene vegetation and fire history of the krutoberegovo ust kamchatsk region in eastern kamchatka peninsula russia pollen and charcoal data suggest that the late glacial landscape was dominated by a relatively fire prone larix forest tundra during the greenland interstadial complex gi 1 and a subarctic steppe during the younger dryas gs1 the onset of the holocene is marked by the reappearance of trees mainly alnus incana within a fern and shrub dominated landscape the holocene thermal maximum htm features shifting vegetational communities dominated by alnus shrubs diverse forb species and locally abundant aquatic plants the htm is further defined by the first appearance of stone birch forests betula ermanii kamchatka s most abundant modern tree species the late holocene is marked by shifts in forest dynamics and forest graminoid ratio and the appearance of new non arboreal taxa such as bayberry myrica and meadow rue filipendula kamchatka is one of earth s most active volcanic regions during the late glacial and holocene kamchatka s volcanoes spread large quantities of tephra over the study region thirty four tephra falls have been identified at the site the events represented by most of these tephra falls have not left evidence of major impacts on the vegetation although some of the thicker tephras caused expansion of grasses poaceae and at least in one case forest die out and increased fire activity

global atmospheric loading and gravity abstract the purpose of this paper is to model atmospheric pressure effects on surface gravity pressure corrections are usually done with the help of an empirical trans fer function called barometric admittance between pressure and gravity both measured locally we show the validity of this local approach with the help of spectral coherency between air pressure and gravity residuals after subtraction from the superconducting gravimeter observations in strasbourg france of luni solar tides polar motion and instrumental drift contributions we compute the atmospheric surface loading effects using a green s function formalism and global surface pressure data provided by the european centre for medium range weather forecasts ecmwf we model a specific oceanic response to atmospheric loading which incorporates interactions between ocean atmosphere and solid earth and differs from the classical inverted or non inverted barometer hypotheses we investigate the contribution of this global pressure correction in a 3000 day 1987 1996 tidal analysis of the french superconducting gravimeter

reduction of surface gravity data from global atmospheric pressure loading summary besides solid earth and ocean tides atmospheric pressure variations are one of the major sources of surface gravity perturbations as shown by previous studies merriam 1992 mukai et al 1995 boy et al 1998 the usual pressure correction with the help of local pressure measurements and the barometric admittance a simple transfer function between pressure and gravity both measured locally does not allow an adequate estimation of global atmospheric loading we express the response of the earth to pressure forcing using a green s function formalism farrell 1972 the atmosphere acts on surface gravity through two effects first a direct gravitational attraction by air masses which is sensitive to regional about 1000 km around the gravimeter pressure variations second an elastic process induced by the earth s surface deformation and mass redistribution which is sensitive to large scale pressure variations wavelengths greater than 4000 km we estimate atmospheric loading using green s functions and global pressure charts provided by meteorological centres we introduce different hypotheses on the atmospheric thickness and atmospheric density variations with altitude for the modelling of the direct newtonian attraction all computations are compared to gravity data provided by superconducting gravimeters of the ggp global geodynamics project network we show the improvement by modelling global pressure versus the local estimates in terms of reduction of the variance of gravity residuals we can also validate the inverted barometer ib hypothesis as the oceanic response to pressure forcing for periods exceeding one week the non inverted barometer nib hypothesis is shown to be definitely an inadequate assumption for describing the oceanic response to atmospheric pressure at seasonal timescales

evolution of the sedimentary system beneath the deep pacific inflow off eastern new zealand results from ocean drilling program sites 1121 1124 show the eastern new zealand oceanic sedimentary system enzoss evolved in response to 1 the inception of the circum antarctic circulation 2 orbital and non orbital regulation of the global thermohaline flow and 3 development of the new zealand plate boundary enzoss began in the early oligocene following opening of the tasmanian gateway and inception of the ancestral antarctic circumpolar current acc and sw pacific deep western boundary current dwbc widespread erosion marked by the marshall paraconformity was followed by extensive drift formation in the late oligocene early miocene alternating nannofossil chalk and nannofossil rich mud deposited in response to 41 kyr orbital regulation of the abyssal circulation with the mudstones representing times of increased inflow of corrosive southern source waters drift deposition at the deepest sites was interrupted by bouts of erosion coincident with mi1 5 isotopic events signifying expansions of the east antarctic ice sheet and enhanced bottom water formation by late miocene times the basic enzoss was established south of bounty trough the energetic acc instigated an erosional low depositional regime to the north where the dwbc prevailed orbitally regulated drift deposition continued increased convergence at the new zealand plate boundary enhanced the terrigenous supply but little of this sediment reached the deep enzoss as the three main sediment conduits solander bounty and hikurangi channels had not fully developed the plio pleistocene heralded a change from a carbonate to terrigenous dominant supply caused by interception of the dwbc by the three channels 1 6 ma for bounty and hikurangi time of solander interception unknown the solander and bounty fans and hikurangi fan drift systems formed and drifts downstream of those systems received terrigenous detritus supply increased with accelerating uplift along the plate boundary but delivery to the dwbc was regulated by eustatic fluctuations of sea level times of maximum supply to all three channels was during glacial lowstands whereas the supply either ceased bounty solander or reduced hikurangi in highstands in glacial times sediment was entrained by a dwbc invigorated by an increased input of antarctic bottom water the acc also accelerated under strengthened glacial winds thus glacials were times of optimum sediment supply to enzoss depocentres where depositional rates were 2 3 times more than interglacial rates

displacements of the earth s surface due to atmospheric loading effects on gravity and baseline measurements atmospheric mass loads and deforms the earth s crust by performing a convolution sum between daily global barometric pressure data and mass loading green s functions we estimate the time dependent effects of atmospheric loading including those associated with short term synoptic storms on surface point positioning measurements and surface gravity observations we calculate the response for both an oceanless earth and an earth with an inverted barometer ocean load responses for near coastal stations are significantly affected by the inclusion of an inverted barometer ocean peak to peak vertical displacements are frequently 15 20 mm with accompanying gravity perturbations of 3 6 gal baseline changes can be as large as 20 mm or more the perturbations are largest at higher latitudes and during winter months these amplitudes are consistent with the results of rabbel and zschau 1985 who modeled synoptic pressure disturbances as gaussian functions of radius around a central point deformation can be adequately computed using real pressure data from points within about 1000 km of the station knowledge of local pressure alone is not sufficient rabbel and zschau s hypothesized corrections for these displacements which use local pressure and the regionally averaged pressure prove accurate at points well inland but are in general inadequate within a few hundred kilometers of the coast

on the temporal variability of the transport through drake passage a recently obtained series of bottom pressure measurements from various positions in the drake passage dp has been used to estimate the transport variability of the antarctic circumpolar current acc under the assumption that the variability is predominantly barotropic and thus proportional to the north minus south pressure difference the standard deviations in derived transport range from 5 3 sv in 1993 to 8 9 sv in 1990 10 day filter 1 sv 106 m3 s 1 all values are less than the 10 sv 10 day filter obtained during the international southern ocean studies isos program at dp between the mid 1970s and early 1980s whitworth and peterson 1985 although some of this discrepancy is due to differences in procedure in dealing with gaps in the data our data suggest that the acc transport can be persistently less variable over several years than was previously thought in particular the isos data set contains two large amplitude changes in pressure difference over timescales less than 2 weeks while no similar events were observed in the more recent data although the more recent pressure gauges were deployed at different positions to those used in isos their reliability as indicators of acc transport changes has been established by examination of simultaneous pressure measurements within dp

qingsongite natural cubic boron nitride the first boron mineral from the earth s mantle qingsongite ima 2013 30 is the natural analog of cubic boron nitride c bn which is widely used as an abrasive under the name borazon the mineral is named for qingsong fang 1939 2010 who found the first diamond in the luobusa chromitite qingsongite occurs in a rock fragment less than 1 mm across extracted from chromitite in deposit 31 luobusa ophiolite yarlung zangbu suture southern tibet at 29 13 86n and 92 11 41e five electron microprobe analyses gave b 48 54 0 65 wt range 47 90 49 2 wt n 51 46 0 65 wt range 52 10 50 8 wt corresponding to b 1 113 n 0 887 and b 1 087 n 0 913 for maximum and minimum b contents respectively based on 2 atoms per formula unit no other elements that could substitute for b or n were detected crystallographic data on qingsongite obtained using fast fourier transforms gave cubic symmetry a 3 61 0 045 a the density calculated for the mean composition b 1 100 n 0 900 is 3 46 g cm 3 i e qingsongite is nearly identical to synthetic c bn the synthetic analog has the sphalerite structure space group f 43 m mohs hardness of the synthetic analog is between 9 and 10 its cleavage is 011 qingsongite forms isolated anhedral single crystals up to 1 m in size in the marginal zone of the fragment this zone consists of 45 modal coesite 15 kyanite and 40 amorphous material qingsongite is enclosed in kyanite coesite or in osbornite other associated phases include native fe tio 2 ii a high pressure polymorph of rutile with the pbo 2 structure boron carbide of unknown stoichiometry and amorphous carbon coesite forms prisms several tens of micrometers long but is polycrystalline and thus interpreted to be pseudomorphic after stishovite associated minerals constrain the estimated pressure to 10 15 gpa assuming temperature was about 1300 c our proposed scenario for formation of qingsongite begins with a pelitic rock fragment that was subducted to mid mantle depths where crustal b originally present in mica or clay combined with mantle n 15 n 10 4 3 in osbornite and subsequently exhumed by entrainment in chromitite the presence of qingsongite has implications for understanding the recycling of crustal material back to the earth s mantle since boron an essential constituent of qingsongite is potentially an ideal tracer of material from earth s surface

the rotation of the earth earth rotation studies are reviewed for the 1987 1990 time period it is noted that the emphasis in these studies has shifted from improvements in the observational techniques to interpreting and gaining greater understanding of the variations of the earth rotations there have been progressive improvements in the accuracy and the temporal resolution of earth rotation measurements

rapid deforestation of south island new zealand by early polynesian fires in most parts of the world where people have colonized and modified their landscapes for several millennia or more it is often difficult to discriminate anthropogenic burning from natural fire regimes that are linked to climate regimes new zealand provides a unique setting for identifying human influence on fire occurrence because it was settled recently c ad 1280 at a time when climates are considered to be similar to today late holocene pollen and charcoal records from new zealand provide striking evidence for initial polynesian m ori arrival being strongly associated with widespread burning and loss of native forest the duration of initial forest clearance and the spatial pattern of burning that led to this transformation are still poorly understood we present high resolution charcoal and pollen analyses of sediment cores from five lakes located on the deforested eastern side of the southern alps these records document the local fire history of the last 1000 years and the response of vegeta

a complete spherical harmonic approach to luni solar tides summary in this work a spherical harmonic theory of ocean tides is presented the theory is based on laplace tide equations modified to include turbulence with constant eddy viscosity linearized bottom friction and oceanic loading and self gravitation variable bathymetry is also treated in harmonic terms and no flow boundary conditions are applied at continental coastlines the tide and boundary constraint equations are reduced to matrix form and solved by a weighted least squares procedure five zonal luni solar tides ranging in period from 14 days to 18 6 yr are investigated using the theory such tides have typically been difficult to compute using traditional numerical approaches the polar motion and changes in the length of day induced by these long period tides are calculated tidal solutions are compared extensively with results from other tidal theories and from recent satellite and sea level observations the greatest limitation to accurate prediction of zonal tides for any theory appears to be the marginal failure of all tide theories to conserve mass globally the use of additional mass constraints may be warranted

structure and composition of the subalpine forest on mount hauhungatahi north island new zealand during the holocene tree stumps of holocene age were identified and measured at three sites above the present tree line on mount hauhungatahi tongariro national park new zealand wood and peat were radiocarbon dated and annual rings in stump cross sections counted for growth rates comparative measurements were made in three plots in the modern subalpine forests stem densities and basal areas in the ancient forest were within the range of the modern subalpine forest samples the conifers halocarpus biformis phyllocladus asplenifolius var alpinus and libocedrus bidwillii were present in both sets of samples but in different proportions modern forest plots also contained podocarpus hallii and angiosperm trees tree line forest composed predominantly of halocarpus bidwillii reached 1340 m by c 10000 cal bp and c 1390 m by 8700 cal bp these early holocene h bidwillii trees were slower growing and longer lived than the same species in current subalpine forests from c 5400 to 3800 cal bp woody vegetation was ag

determination of oceanic dynamic barometer corrections to atmospheric excitation of earth rotation the excitation of earth s rotation by atmospheric pressure fluctuations on timescales from days to years is modified by the oceanic response to the pressure load that response has often been approximated as a static inverted barometer ib change in sea level but evidence from theory and both tide gauge and altimetric data suggests that the ib poorly models the sea level response at short periods static models also fail to account for the currents induced by the pressure loading the actual dynamic response of the oceans to barometric loads depends on frequency and on the spatial structure of the loading this work presents a green s function approach to determining the rotational effects of that oceanic response the green s functions characterize the rotational effects of the oceanic response to pressure loads described spatially by individual spherical harmonics for each harmonic of forcing they were computed at nine periods ranging from 4 days to 18 years and interpolated at intermediate periods computations were based on solutions to the author s dynamic spherical harmonic ocean tide model the effects on rotation of the dynamic barometer oceanic response are obtained by a convolution type combination of the green s functions with actual atmospheric pressure data results for data spanning the past decade will be illustrated using harmonically decomposed national center for environmental prediction ncep and european centre for medium range weather forecasts ecmwf pressure fields

climatic implications of macro and microfossil assemblages from late pleistocene deposits in northern new zealand twenty two plant species were identified from leaves fruits or flowers and 41 taxa from pollen present in a macrofossil leaf layer in a peat swamp formed on pleistocene dunes on the aupouri peninsula in northern new zealand eight genera of gymnosperms are represented with the exception of lagarostrobos colensoi all tree species abundant as macrofossils are also common as pollen macrofossils enabled the on site flora to be compared with the regional flora represented by the pollen rain studies on leaf decomposition rates indicate bias toward sclerophyllous species in the macrofossils identification to species level and treering data from preserved kauri logs allow quantitative comparisons with similar extant communities current climatic conditions at those analogue sites are cooler 2 to 3 c cloudier 11 and much wetter 85 than those currently prevailing on the aupouri peninsula dendrochronological results also suggest that the far north of new zealand had a cooler cloudier and wetter climate at the time the fossil leaf assemblage was formed radiocarbon dates from possibly contaminated samples suggest that a diverse mixed gymnosperm angiosperm forest dominated by kauri agathis australis was present about or sometime before 41 00034 000 yr b p when the leaf layer was formed similar temperature reductions have been postulated for this period in new zealand by other authors

environmental impact of the laacher see eruption at a large distance from the volcano integrated palaeoecological studies from vorpommern ne germany abstract in order to investigate the environmental impacts of the laacher see eruption 12 900 calendar years b p and the deposition of the laacher see tephra at a large distance from the volcano fine resolution micromorphological diatomological and palynological investigations were carried out on closely spaced areas in the reinberg basin vorpommern ne germany the lower part of the lst originates from atmospheric input whereas the upper part was washed in from the surrounding basin slopes diatom populations expanded as a consequence of the input of silica while simultaneously dissolution of dead diatoms decreased the tephra provided a favourable habitat for many epilithic and epipelic diatom taxa the diatoms show a slight acidification and an increase in specific conductivity of the water whereas no eutrophication is indicated these effects disappeared after lake sediments covered the tephra the pollen diagrams from the reinberg basin as well as many other pollen diagrams from ne germany indicate that the vegetation reacted to rising temperatures after the cooler gerzensee fluctuation to a short lived water level rise connected with higher precipitation after the volcanic eruption and to minor openings in the forest vegetation due to increased fire probably connected with severe thunderstorms

wind field differences between three meteorological reanalysis data sets detected by evaluating atmospheric excitation of earth rotation 1 we compared atmospheric excitations of the varying earth rotation calculated from three different meteorological reanalysis data sets ncep ncar ncep doe and era 40 over 23 years from 1979 to 2001 atmospheric excitations are evaluated by atmospheric angular momentum aam functions we found that differences in aam functions are primarily caused by differences in the wind data especially the northward wind data between the three reanalysis data sets differences between the ncep doe and era 40 aam functions are larger than those between the ncep ncar and ncep doe ones the northward wind differences that have a large effect on the equatorial aam functions originate from the upper troposphere at the tropics and midlatitudes in the southern hemisphere especially in three regions east pacific off latin america africa and the indian ocean the eastward wind differences are seen at midlatitudes in the southern hemisphere these differences are not confined to a single frequency the difference spectra show a reddish frequency dependence with some peaks in seasonal bands and tidal diurnal bands since the eastward and northward winds over the tropics can most efficiently change the earth s spin rate and polar motion respectively the wind accuracy over the tropics directly determines the accuracy in evaluations of the atmospheric excitations

earth rotation and global change variations in the rotation of the earth include changes in the rate of rotation altering the length of the day lod in orientation of the rotation axis relative to a terrestrial frame polar motion pm and in orientation relative to a celestial frame due to external torques nutation and precession variations occur over a wide range of time scales from hours to the age of the earth scientific interest in and understanding of earth rotation variations have proceeded rapidly over the last several decades due in large part to enormous improvements in observations by space geodetic means including satellite laser ranging slr very long baseline interferometry vlbi lunar laser ranging llr and satellite positioning methods especially the global positioning system gps the study of the earth s rotation is a mature interdisciplinary field and extensive reviews of many aspects of the field are contained in the agu monographs contributions of space geodesy to geodynamics smith and turcotte 1993 articles by eubanks 1993 dickey 1993 hide and dickey 1991 and monographs by lambeck 1988 1980 and munk and mac donald 1960 provide excellent background material on these problems as well the reader may also wish to review other iugg report articles in this series on related subjects specifically those on the global gravity field vlbi technology satellite orbit dynamics and gps

evidence for excitation of polar motion by fortnightly ocean tides the second degree zonal tide raising potential which is responsible for tidal changes in the earth s rotation rate and length of day is symmetric about the polar axis and hence can excite the earth s polar motion only through its action upon nonaxisymmetric features of the earth such as the oceans ocean tidal excitation of polar motion in the diurnal and semidiurnal tidal bands has been previously detected and examined here the detection of ocean tidal excitation of polar motion in the long period tidal band specifically at the mf 13 63 day and mf 13 66 day tidal frequencies is reported spectra of the space94 polar motion excitation series exhibit peaks at the prograde and retrograde fortnightly tidal periods after removing effects of atmospheric wind and pressure changes an empirical model for the effect of the fortnightly ocean tides upon polar motion excitation is obtained by least squares fitting periodic terms at the mf and mf tidal frequencies to the residual polar motion excitation series the resulting empirical model is then compared with the predictions of two hydrodynamic ocean tide models

the self consistent dynamic pole tide in non global oceans summary fluid dynamic theories of the pole tide are in conflict with pole tide observations the former predict that the oceanic response to the chandler wobble should be nearly static while the latter reveal the tide to possess significant non equilibrium characteristics resolution of the conflict would determine whether mantle anelasticity or non equilibrium oceans is responsible for a measurable contribution to the chandler period it is possible that resolution might be achieved through a more exact mathematical investigation of pole tide fluid dynamics than theories have carried out to date the theories have also neglected to consider a unique property of the pole tide its ability to lengthen the period of its own forcing function this property implies that the pole tide characteristics and effects on wobble cannot be correctly determined unless the tide and wobble equations are jointly solved this work constitutes a first attempt to determine accurately and self consistently the nature of the pole tide and its effects on the chandler wobble the laplace tidal equations modified by the addition of bottom friction but with no simplifying approximations are employed together with the liouville equations to elucidate pole tide characteristics this work is a first attempt because the earth model chosen is a crude one consisting of global oceans of uniform depth overlying a rigid mantle with a fluid core results for this model suggest that departures of the pole tide from equilibrium may indeed be minimal the relevance of these results to the actual pole tide however must await the application of our self consistent and more exact dynamical theory to the situation of realistic oceans

high spatial resolution of pollen and charcoal in relation to the c 600 year bp kaharoa tephra implications for polynesian settlement of great barrier island northern new zealand analysis of high spatial resolution of nine pollen profiles 150 m 6 5 km apart from great barrier island shows that between 7500 and 600 calibrated year bp the island had a low frequency of natural fires compared with elsewhere in the northern north island except for one site which has locally sourced pre kaharoa charcoal source of this charcoal in the awana kaitoke area is uncertain if local pre kaharoa burning did occur at other sites in this area it was patchy occurring at different times in different places and was small scale charcoal was first recorded c 1700 year bp then again after c 1200 year bp pre kaharoa charcoal on great barrier may be interpreted as either an increased frequency of natural fires in the region due to climatic change to drier conditions or small scale localized initial human impact or some combination of these factors major post kaharoa burning in the awana kaitoke area was also patchy commencing at different times in different places the presence of the kaharoa tephra on great barrier island allows the commencement of major sustained polynesian deforestation at awana kaitoke to be reliably dated to c 600 year bp at some sites and possibly up to 50 years later at other sites

departures from the local inverse barometer model at periods of 5 days in the central south atlantic tide gauge data from ascension and st helena in the central south atlantic supplemented by altimeter data from the topex poseidon mission suggest that the local inverse barometer lib model for the forcing of sea level variability by means of air pressure changes is not applicable within a narrow band of the variability spectrum with periods of approximately 5 days this is in contrast to other sections of the wider frequency band spanning approximately 0 05 to 0 5 cycles d wherein the data are either consistent with approximate lib response or at least suggest no departures from the lib model of similar magnitude these results have similarities to findings from pacific gauges obtained over a decade ago but so far no comparisons have been to data from other ocean areas they are also qualitatively similar to predictions for the region from a recent global barotropic numerical model the anomalous part of the spectrum coincides in frequency with the madden and julian 1972 1973 5 day pressure wave in the atmosphere if that global scale forcing is responsible for both the atlantic and pacific departures from the lib model around 5 days then similar features should be observable in tide gauge data from other tropical areas

glacial interglacial control of terrigenous and biogenic fluxes in the deep ocean off a high input collisional margin a 139 kyr record from new zealand abstract sediment input to the deep ocean off the new zealand collisional plate boundary is large and variable as revealed by a 139 kyr old record from the 34 92 m long core md97 2121 mass accumulation rates mars were derived for terrigenous and biogenic carbonate and silica sedimentary components with temporal control from a stable isotope age model verified by tephra and radiocarbon ages terrigenous mars changed in phase with glacio eustatic fluctuations of sea level highest rates 30 g cm 2 kyr coincided with the late regressive lowstand early transgressive phase of marine isotope stage mis 2 when rivers discharged at or near the shelf edge lesser but still high terrigenous rates 20 30 g cm 2 kyr characterized peak warm phases of early mis 5 and 1 when a strengthened subtropical inflow probably introduced sediment from fluvial and seabed sources to the north of md97 2121 however during prolonged highstands the flux declined as more sediment was retained on a tectonically subsiding shelf with a shore parallel current paradoxically the lowest mars 10 5 g cm 2 kyr occurred in mis 4 either sea level was too high to allow much sediment to escape off shelf or the fluvial input was modest or both these factors despite the terrigenous dominance biogenic mars are high and are 2 4 times larger than sw pacific ocean rates mars were lowest during mis 4 and 3 possibly due to reduced marine production under a lowered input of fluvial micronutrients in contrast mars increased irregularly though glacial maxima to peak at 5 6 g cm 2 kyr carbonate and 2 2 5 g cm 2 kyr silica in early mid mis 5 and 1 such rates reflected the interaction of macronutrient rich subantarctic waters sourced from the south with local micronutrient rich subtropical waters production also responded to warmer temperatures elevated nutrient runoff and a more stratified surface ocean later in mis 5 and 1 fluxes reduced as less productive subtropical waters prevailed that biogenic and aeolian mar profiles are out of phase suggests fe fertilization by aerosolic dust was not a major influence

particle size evidence for source areas of charcoal accumulation in late holocene sediments of eastern north american lakes abstract two methods of analyzing charcoal in sediment reveal changes in charcoal accumulation across temperate eastern north america during the last several hundred years in one method the analyst counts mostly small particles that reflect regional emissions in the other the analyst counts only larger particles derived mostly from such local sources as catchment fires we used these methods to compare charcoal accumulation at 14 lakes from the prairie forest border in minnesota to eastern maine the two methods gave concordant accumulation rates for sediments of pre 1850 age at each of 4 lakes analyzed by both methods this concordance is consistent with the interpretation that pre 1850 emissions were controlled by broad scale factors such as climatically controlled regional differences in fuels and moisture since 1900 large particles decreased greatly and small particles decreased slightly in minnesota and wisconsin by contrast in the northeast the large particle accumulation has remained at the low values measured in pre 1900 sediments at most sites while small particles increased everywhere east of central new york and pennsylvania the observed patterns suggest that 1 large particles primarily reflect local fires that were common in the midwest before fire suppression became effective 2 large particles were rare in the northeast especially before extensive land clearance 3 small particles reflect regional combustion that increased in the northeast after extensive use of fire for land clearance and wood burning for industrial purposes of the 19th century and 4 small particles remain abundant in the midwest long after effective fire suppression probably because these well dispersed small particles have a large source area that extends beyond the local wildfires that account for large particles before european settlement

spectral and geographical variability in the oceanic response to atmospheric pressure fluctuations as inferred from dynamic barometer green s functions 1 a decade ago a novel theoretical approach was developed dickman 1998 for determining the dynamic response of the oceans to atmospheric pressure variations a response nicknamed the dynamic barometer db and the effects of that response on earth s rotation this approach employed a generalized spherical harmonic ocean tide model to compute oceanic green s functions the oceans fluid dynamic response to unit amplitude pressure forcing on various spatial and temporal scales and then construct rotational green s functions representing the rotational effects of that response when combined with the observed atmospheric pressure field the rotational green s functions would yield the effects of the db on earth s rotation the green s functions reflect in some way the geographical and spectral sensitivity of the oceans to atmospheric pressure forcing we have formulated a measure of that sensitivity using a simple combination of rotational green s functions we find that the db response of the oceans to atmospheric pressure forcing depends significantly on geographic location and on frequency compared to the inverted barometer ib the traditional static model the db effects differ slightly at long periods but become very different at shorter periods among all the responses the prograde polar motion effects are the most dynamic with large portions of the north atlantic and some of the north pacific no larger than one third of ib but most of the southern hemisphere oceans at least 50 greater than ib

interpreting charcoal in new zealand s palaeoenvironment what do those charcoal fragments really tell us the role of charcoal as a palaeoenvironmental indicator has never been fully or adequately explained charcoal fragments are often interpreted as evidence for natural fires caused by lightning strike during drought or dry climatic conditions generally no evidence is presented to show this to be the case the frequency of lightning strike in new zealand is not high and the extent to which it is a causal factor in generating forest fire is questioned the assumption is often made that charcoal fragments found in sedimentary deposits are local or at least reasonably local in origin this assumption is being challenged fine charcoal fragments appear to be transported regionally within new zealand it is highly likely that fine charcoal fragments are being transported from australia both by thermal convection during fires and during dust storm events to be deposited into new zealand sediments the consequences of this in interpreting new zealand s palaeo history requires researchers to at the very least provide charcoal counts within size parameters this is particularly so for archaeologists who would definitely need to show the presence of large charcoal fragments before interpreting the possibility of people in the landscape

terrestrial palynology from marine cores as an indicator of environmental change for the waipaoa sedimentary system and north eastern new zealand diverse terrestrial palynomorph assemblages of pleistocene to recent age have been recovered from mainly marine sediment cores along the eastern new zealand margin these assemblages record a range of environmental changes including climate deforestation reforestation rates of erosion sediment provenance and age volcanic activity polynesian and european settlement strength and direction of ocean currents astronomical cyclicity and other major events many of which can be correlated with shorter onshore terrestrial sequences as such pollen yields valuable information on the dynamic new zealand landscape which is of particular relevance to a source to sink approach this paper provides an integrated summary of published and unpublished late pleistocene palynological studies off eastern north island new zealand that gives context for an analysis of cores within and marginal to the waipaoa sedimentary system pollen assemblages faithfully reflect the last glacial vegetation dominated by grass and shrub land species together with elevated tertiary pollen from enhanced erosion of the regolith the glacial termination and holocene were marked by establishment of podocarp forest a mid holocene disappearance of sediment trapping mangroves and introduction of distal pollen with establishment of coastal current systems under rising sea level these natural signals are overprinted by abrupt changes in pollen species caused by volcanic eruptions finally endemic forest and shrub pollen were markedly reduced with human colonisation associated land use changes and introduction of exotic species

comment on comparison of enigmatic diamonds from the tolbachik arc volcano kamchatka and tibetan ophiolites assessing the role of contamination by synthetic materials by

stratigraphy chronology styles and dynamics of late quaternary eruptions from taupo volcano new zealand taupo volcano is the southerly of two dormant caldera volcanoes in the rhyolite dominated central portion of the taupo volcanic zone in the north island of new zealand taupo has an average magma output rate of 0 2 m 3 s 1 over the past 65 000 years and is one of the most frequently active and productive rhyolite volcanoes known the structure of the modern inverse volcano was formed largely by caldera collapse associated with the voluminous 22 600 14 c years bp oruanui eruption and has been little modified since except for collapse following the 1850 14 c years bp eruption the products of 28 eruptions labelled psi omega a ldots z all of which post date the oruanui eruption are defined and described here twenty seven of these eruptions are represented by pyroclastic deposits of which three were accompanied by a mappable lava extrusion and one eruption z solely by evidence for a lava extrusion the deposits of seven eruptions b c e s v x and y largely correspond to previously defined tephra formations karapiti poronui opepe waimihia whakaipo mapara and taupo respectively the previously defined motutere and hinemaiaia tephras are reinterpreted to represent the products of 12 eruptions g to r while the remaining eight deposits and one eruption are newly recognized eruption psi occurred at ca 17 200 14 c or 20 500 calibrated years bp and eruption z about 1740 calibrated years bp eruption volumes vary by more than three orders of magnitude between 0 01 and more than 44 km 3 and repose periods by more than two orders of magnitude from ca 20 to 6000 years the eruption deposits reflect great variations in parameters such as volume the dispersal characteristics of the fall deposits the presence or absence of intraeruptive time breaks the formation of pyroclastic flows the degree of magma water interaction the vesiculation state of the magma on fragmentation and the relative proportions of juvenile obsidian versus foreign lithologies in the lithic fractions all but seven fall deposits are plinian in dispersal two y1 and probably w are sub plinian one y5 has been termed ultraplinian while psi and a are too poorly preserved for their dispersal to be assessed the lengths of repose periods in the post oruanui sequence range are not randomly distributed but show self similar properties fractal dimensionality repose intervals r in years of not more than 350 years follow n 53 5r 0 21 and those of not less than 350 years follow n 2096r 0 83 where n is the number of eruptions the shorter repose periods may reflect triggering processes such as regional extension affecting magma bodies during their viable lifetimes while longer repose intervals i e not less than 350 years may reflect an episodicity of major rifting events or the production of magma bodies below the volcano bulk volumes v in km 3 of the eruption products also show self similar properties fractal dimensionality with n 6 17v 0 46 however there are then apparently random relationships between eruption volumes and the preceding or succeeding repose period such that prediction of the time and size of the next eruption is impossible the post oruanui activity at taupo represents noise superimposed on the more uniform longer term activity in the central taupo volcanic zone where large greater than 100 km 3 eruptions such as the oruanui occur at more evenly spaced intervals of one per 40 60 000 years

holocene treeline shifts and monsoon variability in the hengduan mountains southeastern tibetan plateau implications from palynological investigations abstract the upper 8 45 m of a sediment core from lake naleng were analysed for its pollen and charcoal content to detect vegetation climate and human activity changes on the southeastern tibetan plateau tp since the pleistocene holocene transition 11 7 cal kyr bp the application of pollen indicator taxa pollen sums biomisation and multivariate analysis helped to reconstruct environmental conditions during the holocene furthermore 64 surface samples from the southeastern tp and its foreland were analysed to investigate the relationship between modern pollen assemblages and vegetation the modern vegetation was recorded in the surface pollen assemblages by pollen indicator types although sediments also contain pollen spectra extra regional pollen transported from lower vegetation belts which is seen as a consequence of steep elevation gradients at the southeastern margin of the tp the relation between different vegetation belts and temperature from the modern sample sites was used to infer quantitative temperature trends for the holocene record spreading of forests at the beginning of the holocene marks the transition to warmer conditions from 10 7 to 4 4 cal kyr bp open abies betula forests were found at lake naleng probably reflecting a stronger than present summer monsoon temperature range reconstructions suggest a temperature that was about 2 3 c warmer and a treeline position that was 400 600 m higher than today a severe climate deterioration with temperatures about 1 2 c colder than before is documented by a retreating forest between 8 1 and 7 2 cal kyr bp forests retreated while subalpine rhododendron shrubs spread around lake naleng indicating colder conditions with temperatures 1 2 c below early and mid holocene level after 4 4 cal kyr bp the forest decline at 4 4 cal kyr bp is considered to reflect climatic conditions as low concentrations of charcoal particles found in this period exclude human induced fires as reason for the forest retreat however grazing indicators imply human influence on the environment since 3 4 cal kyr bp around lake naleng we therefore consider the rapid treeline shift seen at 3 4 cal kyr bp as partly generated by human activity and partly by climatic conditions

the influence of sea level and tectonics on late pleistocene through holocene sediment storage along the high sediment supply waipaoa continental shelf abstract we present geophysical and core evidence showing how subsidence caused by forearc shortening has accommodated late pleistocene and holocene sediments supplied to the tectonically active waipaoa shelf nz limiting off shelf export during the early sea level highstand the last glacioeustatic fall and subsequent rise exposed and then flooded a shelf segmented into subbasins separated by zones of uplift leaving key stratigraphic markers of shoreline regression and transgression that vary strongly in character across the shelf highstand sediment isopachs tied to piston cores dated using tephra correlation and a radiocarbon age model provide a sediment budget at 2000 yr intervals from the mid holocene 5500 cal yr bp to present sediment load estimates from our shelf budget are in agreement with published model estimates for suspended sediment discharge from the waipaoa river for the past 3000 yr but importantly do not show the 6 fold increase in the waipaoa s sediment output that began with human settlement 700 yr ago and accelerated with deforestation over the last century bypassing of waipaoa sediment to the slope may therefore be a recent phenomenon caused by unnaturally high sediment loads a conclusion supported by data reported elsewhere in this volume our study also reveals evidence for 1 a relatively thick mid shelf transgressive section deposited during the last eustatic rise that may correlate to estuarine sequences reported from numerous sites on the modern coastline of the north island 2 a slight decrease in total basin filling rates during the highstand and 3 variability in the partitioning of highstand sediments between individual subbasins that may reflect differing degrees of tectonic accommodation

the taupo eruption new zealand i general aspects the ca a d 186 taupo eruption was the latest eruption at the taupo volcanic centre occurring from a vent at horomatangi reefs now submerged beneath lake taupo in the central north island of new zealand minor initial phreatomagmatic activity was followed by the dry vent 6 km 3 hatepe plinian outburst large amounts of water then entered the vent during the 2 5 km 3 hatepe phreatoplinian ash phase eventually stopping the eruption though large amounts of water continued to be ejected from the vent area causing gullying of the ash deposits after a break of several hours to weeks phreatoplinian activity resumed generating the 1 3 km 3 rotongaio ash notable for its fine grainsize and for containing significant quantities of non or poorly vesicular juvenile material the vent area then became dry again and eruption rates and power markedly increased into the 23 km 3 taupo ultraplinian phase which is the most powerful plinian outburst yet documented synchronous with this ultraplinian activity lesser volumes of non to partially welded ignimbrite were generated by diversion of ejecta from or partial collapse of the eruption column the rapid rate of magma withdraw al during this phase removed support from the vent area to trigger local vent collapse and initiate the catastrophic eruption of the ca 30 km 3 taupo ignimbrite finally after some years lava was extruded on to the floor of the reformed lake taupo and floating fragments derived from the lava carapace were driven ashore the known eruption volume is more than 65 km 3 while additional volumes are represented by primary material now beneath lake taupo and layer 3 to the ignim brite phases a total volume of more than 105 km 3 is likely equivalent to more than 35 km 3 of magma plus more than 3 km 3 of lithic debris airfall deposits more than 10 cm thick blanketed 30000 km 2 of land east of the vent while ignimbrite covers a near circular area of 20000 km 2 widespread and locally severe ground shaking occurred during but mostly after the eruption associated with subsidence in the lake taupo basin secondary deposits are abundant above and extending beyond the taupo ignimbrite consisting of the products of surface water interacting with the still hot ignimbrite and subsequent water reworking of the light pumiceous materials the complexity and size of this eruption preclude accurate forecasting of the size nature and return period of the inevitable next eruption from the taupo volcanic centre

biodiversity and terrestrial ecology of a mid cretaceous high latitude floodplain alexander island antarctica the biodiversity and terrestrial ecology of the late albian triton point formation fossil bluff group alexander island antarctica is analysed to improve our understanding of polar biomes during the mid cretaceous thermal optimum this formation was deposited on a high latitude 75 s floodplain and consists of two facies associations a lower braided alluvial plain unit and an upper coastal meander belt unit analysis of fossil plants in well exposed palaeosols reveals the existence of spatially complex plant communities braidplains supported patchy low density 91 trees ha stands of podocarp and taxodioid conifers on floodbasin substrates and conifer cycadophyte fern angiosperm thickets in riparian settings coastal meander belts supported medium density 568 trees ha podocarp araucarian conifer forests on mature floodbasin soils and fern angiosperm ginkgo thickets in riparian settings growth ring analysis indicates plants experienced stressful growing conditions on the braidplain characterized by high frequency flood events but more favourable growing conditions on the coastal plain additional vegetation disturbances were caused by arthropod fungal attack frost and wildfire in terms of structure composition ecology and productivity these predominantly evergreen broad leafed conifer forests bear similarities to the extant temperate rainforests of new zealand

holocene climate fire and vegetation dynamics at the tree line in the northwestern swiss alps treelines are expected to rise to higher elevations with climate warming the rate and extent however are still largely unknown here we present the first multi proxy palaeoecological study from the treeline in the northwestern swiss alps that covers the entire holocene we reconstructed climate fire and vegetation dynamics at iffigsee an alpine lake at 2 065 m a s l by using seismic sedimentary surveys loss on ignition visible spectrum reflectance spectroscopy pollen spore macrofossil and charcoal analyses afforestation with larix decidua and tree betula probably b pendula started at 9 800 cal b p more than 1 000 years later than at similar elevations in the central and southern alps indicating cooler temperatures and or a high seasonality highest biomass production and forest position of 2 100 2 300 m a s l are inferred during the holocene thermal maximum from 7 000 to 5 000 cal b p with the onset of pastoralism and transhumance at 6 800 6 500 cal b p human impact became an important factor in the vegetation dynamics at iffigsee this early evidence of pastoralism is documented by the presence of grazing indicators pollen spores as well as a wealth of archaeological finds at the nearby mountain pass of schnidejoch human and fire impact during the neolithic and bronze ages led to the establishment of pastures and facilitated the expansion of picea abies and alnus viridis we expect that in mountain areas with land abandonment the treeline will react quickly to future climate warming by shifting to higher elevations causing drastic changes in species distribution and composition as well as severe biodiversity losses