global hydrocarbon seep carbonate precipitation correlates with deep water temperatures and eustatic sea level fluctuations since the late jurassic the anaerobic oxidation of methane aom in marine sediments most obviously at cold seeps is a major sink for this important greenhouse gas and is associated with the precipitation of carbonates the geological record of seep carbonates provides insights into the long term dynamics of this process since the late jurassic rates of seep carbonate precipitation have been high during times of low sea levels and cold deep water temperatures and vice versa one possibility is that sea level fall decreases the thickness of the methane hydrate stability zone in the sediment so that gas hydrates decompose in deeper sediments thereby increasing seepage and carbonate precipitation alternatively low deep water temperature facilitates gas hydrate formation on continental slopes and may thereby increase methane availability for aom performing consortia and associated carbonate precipitation these correlations and their potential causes may be of interest for the modelling of global carbon budgets and of past and future climates

recurrent hierarchical patterns and the fractal distribution of fossil localities understanding the spatial structure of fossil localities is critical for interpreting earth system processes based on their geographic distribution coordinates of marine and terrestrial sites in the conterminous united states for 17 time bins were analyzed using point pattern statistics lacunarity analysis shows that the spatial distributions of sites are fractal for almost every studied interval indicating that clumping of localities occurs at multiple scales random hierarchical multiplicative processes provide a theoretical null model for the distribution of collecting sites consistent with their occurrence being a complex product of numerous biological geological and anthropogenic processes acting at many spatial and temporal scales mechanistic models for the formation preservation and exposure of fossil localities and other geologic entities can be tested using point pattern and related spatial statistics

testing the fossil record sampling proxies and scaling in the british triassic jurassic the quality of the fossil record varies immensely across taxa geographic regions environments and time intervals because much of this variation can be confounded when examining global patterns we present a detailed investigation of the british triassic and jurassic one of the most intensively studied pairs of systems in the world marine jurassic palaeodiversity is at least partly controlled by rock availability and accessibility the terrestrial record is patchier and effects of rock availability are overprinted by a stronger signal of sporadic preservation these results also fit a sea level driven common cause explanation as one would expect to see close correlation between rock availability and palaeodiversity in the marine realm but less so in the terrestrial formation counts and palaeodiversity do not correlate a surprising result given the number of earlier studies that have found close correlations however this study differs from most others in that formation counts and palaeodiversity metrics are derived from independent data sources and so within study redundancy is avoided the study confirms the complexity of rock fossil time series and the likelihood that the fossil record documents a complex mix of potential biological signal common cause signal and rock record and sampling bias it may be impossible to identify a useful simple sampling proxy for the fossil record that captures every bias and sampling error ironically when preservation is good sampling proxies representing rock availability such as outcrop area can be used to predict palaeodiversity but are ineffectual when the fossil record is patchy

morphological disparity of ammonoids and the mark of permian mass extinctions the taxonomic diversity of ammonoids in terms of the number of taxa preserved provides an incomplete picture of the extinction pattern during the permian because of a strongly biased fossil record the analysis of morphological disparity the variety of shell shapes is a powerful complementary tool for testing hypotheses about the selectivity of extinction and permits the recognition of three distinct patterns first a trend of decreasing disparity ranging for about 30 million years led to a minimum disparity immediately before the permian triassic boundary second the strongly selective capitanian crisis fits a model of background extinction driven by standard environmental changes third the end permian mass extinction operated as a random nonselective sorting of morphologies which is consistent with a catastrophic cause

origination and extinction through the phanerozoic a new approach abstract temporal patterns of origination and extinction are essential components of many paleontological studies but it has been difficult to obtain accurate rate estimates because the observed record of first and last appearances is distorted by the incompleteness of the fossil record here i analyze observed first and last appearances of marine animal and microfossil genera in a way that explicitly takes incompleteness and its variation into consideration this approach allows estimates of true rates of origination and extinction throughout the phanerozoic substantial support is provided for the proposition that most rate peaks in the raw data are real in the sense that they do not arise as a consequence of temporal variability in the overall quality of the fossil record even though the existence of rate anomalies is supported their timing is nevertheless open to question in many cases if one assumes that rates of origination and extinction are constant through a given stratigraphic interval then

age and impacts of the caldera forming aniakchak ii eruption in western alaska the mid holocene eruption of aniakchak volcano aniakchak ii in southwest alaska was among the largest eruptions globally in the last 10 000 years vei 6 despite evidence for possible impacts on global climate the precise age of the eruption is not well constrained and little is known about regional environmental impacts a closely spaced sequence of radiocarbon dates at a peatland site over 1000 km from the volcano show that peat accumulation was greatly reduced with a hiatus of approximately 90 120 yr following tephra deposition during this inferred hiatus no paleoenvironmental data are available but once vegetation returned the flora changed from a cyperaceae dominated assemblage to a poaceae dominated vegetation cover suggesting a drier and or more nutrient rich ecosystem oribatid mites are extremely abundant in the peat at the depth of the ash and show a longer term increasingly wet peat surface across the tephra layer the radiocarbon sample immediately below the tephra gave a date of 1636 1446 cal yr bc suggesting that the eruption might be younger than previously thought our findings suggest that the eruption may have led to a widespread reduction in peatland carbon sequestration and that the impacts on ecosystem functioning were profound and long lasting

exceptional fossil preservation during co2 greenhouse crises abstract exceptional fossil preservation may require not only exceptional places but exceptional times as demonstrated here by two distinct types of analysis first irregular stratigraphic spacing of horizons yielding articulated triassic fishes and cambrian trilobites is highly correlated in sequences in different parts of the world as if there were short temporal intervals of exceptional preservation globally second compilations of ages of well dated fossil localities show spikes of abundance which coincide with stage boundaries mass extinctions oceanic anoxic events carbon isotope anomalies spikes of high atmospheric carbon dioxide and transient warm wet paleoclimates exceptional fossil preservation may have been promoted during unusual times comparable with the present co 2 greenhouse crises of expanding marine dead zones oceanic acidification coral bleaching wetland eutrophication sea level rise ice cap melting and biotic invasions

assessing sampling of the fossil record in a geographically and stratigraphically constrained dataset the chalk group of hampshire southern uk taphonomic geological and sampling processes have been cited as biasing richness measurements in the fossil record and sampling proxies have been widely used to assess this however the link between sampling and taxonomic richness is poorly understood and there has been much debate on the equivalence and relevance of proxies we approach this question by combining both historical and novel data a historical fossil occurrence dataset with uniquely high spatial resolution from the upper cretaceous chalk group of hampshire uk and a newly compiled 3d geological model that maps subsurface extent the geological model provides rock volumes and these are compared with exposure and outcrop area sampling proxies that have often been conflated in previous studies the extent to which exposure area true rock availability has changed over research time is also tested we find a trend of low cenomanian to high turonian to campanian raw richness which correlates with and is possibly driven by the number of specimens found after sampling standardization an unexpected mid turonian peak diversity is recovered and sampling standardized genus richness is best predicted by rock volume suggesting a species area or genus area effect additionally total exposure area has changed over time but relative exposure remains the same supplementary materials a locality list abundance matrix and all correlation and modelling results are available at https doi org 10 6084 m9 figshare c 3592208

application of new technology liquid scintillation spectrometry to radiocarbon dating of tephra deposits new zealand abstract two major technological advances in the radiocarbon dating method have recently enhanced its potential application to tephra studies the advent of accelerator mass spectrometry and the development of new technology liquid scintillation ls spectrometry the new technology ls spectrometer represents a significant refinement of the conventional dating method based on liquid scintillation counting of benzene it improves upon conventional ls counting by allowing spectral analysis and by providing a high degree of counting stability and efficiency in an ultra low level background radiation environment these attributes enable radiocarbon dating with greater accuracy and statistical precision and also allow the determination of both smaller and older samples than previously possible by conventional radiometric methods the new wallac oy quantulus ls spectrometer has been in operation at the university of waikato radiocarbon dating laboratory since 1988 the instrument achieves ultra low background levels by both passive and active forms of shielding the shielding comprises a massive asymmetric passive lead shield surrounding an aticoincident liquid scintillation guard in addition the quantulus contains dual multichannel analyzers which allow spectral analysis and windowless data acquisition the quantulus ls spectrometers at the waikato laboratory have been used to date a variety of carbonaceous materials associated with tephra deposits in new zealand ranging in age from ca 0 1 55 ka in particular we have tested the capability of the quantulus for determining ages of samples that are typically more difficult or impossible to date by conventional methods 1 very young samples e g tarawera tephra erupted ca 100 years ago 2 older samples e g mangaone tephra erupted ca 30 ka and 3 samples containing only sparse carbon e g lake sediments associated with tephra layers aged ca 20 ka or less the quantulus ls spectrometer is both more accurate and precise statistical counting errors are reduced than conventional instruments is capable of extending the limits of detection at both ends of the age scale and has a smaller sample handling ability analyses can be obtained at comparatively low cost such advances are potentially beneficial to tephrochronology and volcanology and a wide range of applications in quaternary research

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

current and historical perspectives on the completeness of the fossil record of pelycosaurian grade synapsids abstract understanding of the early evolution of tetrapods may have been influenced by the effects of geological and anthropogenic sampling biases as suggested by previous studies here we make a thorough assessment of how these and other biases affect the record of pelycosaurian grade synapsids a group of tetrapods that dominated the terrestrial realm during the late carboniferous and early permian modified versions of the character and skeletal completeness metrics are used to assess the completeness of the known specimens while a recently published supertree of basal synapsids is tested for congruence between the stratigraphic and phylogenetic hypotheses a historical analysis is also applied to the record in order to show how the biases in the study of this group over the past centuries may have influenced the current record the results show that the completeness of basal synapsid specimens shows very little variation throughout the early permian a peak in skeletal and character completeness metric values in the middle permian wordian is attributed to exceptional preservation of the mezen fauna a significant negative correlation is found between the skeletal completeness metric and a taxic diversity curve of pelycosaurs implying a tendency to name many species based on poor material the lack of correlation between the character completeness metric and diversity is attributed to the history of discovery in the group the majority of pelycosaur species were named between the 1930s and 1960s when character based assignments were secondary to size location and stratigraphy a strong correspondence between the phylogeny and stratigraphy implies a reliable phylogenetic hypothesis but the low relative completeness index score suggests that a great deal of the fossil record is missing while the relative completeness index has improved over the past century the rate of improvement has slowed in the last two decades and the slowing rate of discovery of new species suggests that the limit of what the fossil record of pelycosaurs has to offer is being approached a consistent shape of diversity curves over the past century implies that the same biases which affected the record in the past are still affecting it now this study highlights the need for sampling correction methods to be employed in studies of early synapsids

environmental change and tephra deposition the strath of kildonan northern scotland pollen analysis tephra counts and geochemical data are presented from the upper 200 cm of a core from a basin mire in the strath of kildonan northern scotland three main tephra concentrations are located and tentatively dated to c 7650bp k1 c 4250 bp k2 and 3250 bp k3 by cross correlation with the regional pollen chronology the identity of the tephra layers is unknown but the peak at 4250 bp may be from the hekla 4 eruption the associated changes in catchment soils and vegetation are highly variable k1 is associated with a major vegetation disturbance but no significant change occurs at k3 k2 is correlated with a large regional rise in pine pollen these results conflict with previous studies on distal impacts of volcanic activity during the holocene and demonstrate the diversity of environmental changes associated with holocene volcanic activity

the impact and significance of tephra deposition on a holocene forest environment in the north cascades washington usa high resolution palaeoecological analyses stratigraphy tephra geochemistry radiocarbon dating pollen and ordination were used to reconstruct a holocene vegetation history of a watershed in the pacific northwest of america to evaluate the effects and duration of tephra deposition on a forest environment and the significance of these effects compared to long term trends three tephra deposits were detected and evaluated mlf t158 and mlc t324 from the climactic eruption of mount mazama mlc t480 from a late pleistocene eruption of mount mazama and mlc t485 from a glacier peak eruption records were examined from both the centre and fringe of the basin to elucidate regional and local effects the significance of tephra impacts independent of underlying long term trends was confirmed using partial redundancy analysis tephra deposition from the climactic eruption of mount mazama approximately 7600 cal years bp caused a significant local impact reflected in the fringe location by changes to open habitat vegetation cyperaceae and poaceae and changes in aquatic macrophytes myriophyllum spicatum potamogeton equisetum and the alga pediastrum there was no significant impact of the climactic mazama tephra or other tephras detected on the pollen record of the central core changes in this core are potentially climate driven overall significant tephra fall was demonstrated through high resolution analyses indicating a local effect on the terrestrial and aquatic environment but there was no significant impact on the regional forest dependent of underlying environmental changes

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

passive bottom reflection loss estimation using ship noise and a vertical line array an existing technique for passive bottom loss estimation from natural marine surface noise generated by waves and wind is adapted to use noise generated by ships the original approach based on beamforming of the noise field recorded by a vertical line array of hydrophones is retained however additional processing is needed in order for the field generated by a passing ship to show features that are similar to those of the natural surface noise field a necessary requisite is that the ship position relative to the array varies over as wide a range of steering angles as possible ideally passing directly over the array to ensure coverage of the steepest angles the methodology is illustrated through simulation and applied to data from a field experiment conducted offshore of san diego ca in 2009

millennium scale volcanic impact on a superhumid and pristine ecosystem ecosystems damaged by distal volcanic ash and sulfur deposition usually recover within decades however sediment stalagmite and pollen records from the southernmost andes indicate a 2000 yr impact on forest and aquatic ecosystems after deposition of a thin tephra layer so 2 released from altering pumice produced intense soil and lake acidification in a 150 000 km 2 area acidification led to nutrient leaching and affected soil microorganisms causing plant decay and increased soil erosion in an area larger than 8000 km 2 we conclude that weakly buffered soils in humid environments are extremely vulnerable to volcanic and anthropogenic acidification causing long lasting ecosystem damage and perturbations of paleoclimate proxy records

distal volcanic impacts on peatlands palaeoecological evidence from alaska abstract despite the fact that volcanic ash tephra layers are found preserved in peat deposits around the world comparatively little research has investigated the impacts of distal volcanic emissions on peatlands this study investigates the impacts of several late holocene volcanic eruptions on five peatlands in southern alaska using a palaeoecological approach testate amoebae analysis peat humification analysis and a basic analysis of plant macrofossil components were applied across 11 tephra layers changes in macrofossil and testate amoebae assemblages occur across several of the tephra layers the humification results were considered unreliable because of a methodological problem a finding which may have implications for other studies using this technique redundancy analyses on testate amoebae data show statistically significant changes associated with two tephras the most likely causes of the impacts are volcanic gases acidic precipitation or tephra derived leachates the finding that some tephras are associated with impacts whereas others are not may relate to the season of the eruption or meteorological conditions at the time of ash fall these results suggest the sensitivity of peatlands and peatland microbial communities to distal volcanic products and imply that changes in key palaeoclimatic proxies may be caused by a mechanism independent of climate change implications of the results for peat based palaeoclimatic studies are discussed as are possible directions for future research

holocene vegetation climate and history of a raised bog complex northern new zealand based on palynology plant macrofossils and tephrochronology a holocene history of vegetation climate and ombrogenous mire development is presented from pollen and plant macrofossil analyses of sediments at kopouatai bog a large raised restiad bog in northern new zealand tephra layers of established ages supplemented by numerous radiocarbon dates provide a secure chronology the earliest peats overlying last glacial sediments and dated at c 11700 radiocarbon years bp with extensive accumulation after c 10360 bp are dominated by pollen of warm temperate podocarp angiosperm forest indicating a moist mild early holocene climate the bog began as a series of small soligenous mires within lowland podocarp dominated swamp forest but was mostly oligotrophic by c 8500 bp peat accumulation rates have varied spatially and temporally averaging 0 9 mm yr 1 in central and southern areas the deposition of deltaic muds in the northern part of the bog accompanied a marine transgression c 6500 5000 bp while elsewhere an associated groundwater table rise result

vertebrate diversity across the end permian mass extinction separating biological and geological signals abstract this study examines regional diversity patterns of permian triassic terrestrial vertebrates of the south african karoo basin and the russian fore ural region previous studies clearly established that the diversity patterns of synapsids the dominant terrestrial tetrapods of their time are significantly biased by heterogeneity in the permian triassic terrestrial rock record this conclusion was based on a positive correlation between taxonomic diversity estimates tdes and varying sampling proxies 1 number of formations and 2 outcrop area recently these proxies have been criticized to be non independent variables or problematic for other reasons and 3 number of localities or 4 number of specimens have been suggest as more reliable proxies in the present study i test the relevance of the latter proxies 2 4 with respect to vertebrate diversity in south africa and russia on these regional scales log transformed and generalized differenced tdes of vertebrates at varying taxonomic levels are with few exceptions not significantly correlated with the various sampling proxies 2 4 for the complete time series after eliminating the impact of the end permian extinction event by excluding the earliest triassic time intervals selected vertebrate tdes in south africa and russia show statistically significant strong positive correlations with outcrop area number of localities and number of specimens diversity residuals resulting from modeled diversity estimates exhibit clade specific patterns with little support for a mid permian end guadalupian event but strong support for a severe end permian extinction the results imply that although vertebrate diversity patterns in south africa and russia are at least partially biased by the permian triassic terrestrial rock record they still preserve genuine biological signals finally it is important to note that outcrop area represents a valid and useful sampling proxy at the regional scale of the south african karoo basin and that it should be used in concert with other sampling proxies such as the number of localities and specimens that accurately capture various aspects of sampling in a given study area as it has been performed in the present study

frequency based noise coherence function extension and application to passive bottom loss estimation accurate modeling of acoustic propagation in the ocean waveguide is important to sonar performance prediction particularly in shallow waters a crucial contribution to the total transmission loss is the bottom refection loss which can be estimated passively by beamforming the natural surface noise acoustic field recorded by a vertical line array of hydrophones however the performance in this task of arrays below 2 m of length is problematic for frequencies below 10 khz it is shown in this paper that when the data are free of interference from sources other than wind and wave surface noise data from a shorter array can be used to approximate the coherence function of a longer array this improves the angular resolution of the estimated bottom loss often making use of data at frequencies above the array design frequency application to simulated and experimental data shows that the technique rigorously justified for a halfspace bottom is effective also on more complex bottom types dispensing with

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

the great ordovician biodiversification event gobe the palaeoecological dimension abstract the great ordovician biodiversification event gobe saw a spectacular increase in marine biodiversity at all taxonomic levels largely within the phyla established much earlier during the so called cambrian explosion the diversification was probably the result of a combination of several geological and biological processes and the positive feedbacks resulting from them the present paper reviews the palaeoecological dimension of the gobe it involved major increases in s and biodiversity largely associated with the rise of the paleozoic evolutionary fauna dominated by suspension feeders and involving a greater occupation of ecospace and more complex ecological structures in the ecological evolutionary units p1 and p2 in the benthos these include more complex food webs than those of the cambrian greater tiering especially above the sediment water interface and the development of guild structures indicating increased competition between taxa for particular resources the ordovician is characterized by a profound change in reef composition with a switch from microbial dominated reefs in the early and middle ordovician to metazoan dominated reefs in the late ordovician increases in complexity of deep water trace fossil assemblages began in the early ordovician and mark the increasing exploitation in that environment and the development of hardgrounds permitted bioerosion and encrusting strategies together with the appearance of cryptic communities within the water column the gobe involved a significant increase in the diversity of the phytoplankton and the development of a diverse zooplankton including planktotrophic larvae from a range of invertebrate clades this revolution in the plankton enabled the establishment of a diverse fauna of pelagic vertebrates molluscs and arthropods and promoted the rise of suspension feeders in the benthos an escalation amongst predators and thus community evolution may also have been a major driver of biodiversification

mesozoic echinoid diversity in portugal investigating fossil record quality and environmental constraints on a regional scale several analyses of diversity through geological time use global synoptic databases and this practice often makes it difficult to distinguish true signals in changing diversity from regional scale sampling and or geological artefacts here we investigate how echinoid diversity changed through the mesozoic of the lusitanian basin in portugal based on a comprehensive revised database and seek to distinguish biological signal from geological or environmental constraints the observed diversity pattern is far from having a defined trend showing many fluctuations that appear to be linked with gaps in the geological record this study revealed that independently of the method used whether correlation tests or model fitting the diversity signal is not completely explained by the studied sampling proxies among the different proxies marine facies variation in combination with outcrop area best explains the palaeodiversity curve

determinants of extinction in the fossil record the causes of mass extinctions and the nature of biological selectivity at extinction events are central questions in palaeobiology it has long been recognized however that the amount of sedimentary rock available for sampling may bias perceptions of biodiversity1 2 3 4 5 6 7 and estimates of taxonomic rates of evolution5 6 7 8 this problem has been particularly noted with respect to the principal mass extinctions5 6 7 8 9 10 11 12 here we use a new compilation of the amount of exposed marine sedimentary rock to predict how the observed fossil record of extinction would appear if the time series of true extinction rates were in fact smooth many features of the highly variable record of apparent extinction rates within marine animals can be predicted on the basis of temporal variation in the amount of exposed rock although this result is consistent with the possibility that a common geological cause determines both true extinction rates and the amount of exposed rock it also supports the hypothesis that much of the observed short term volatility in extinction rates is an artefact of variability in the stratigraphic record

effects of volcanic activity on mire development case studies from hokkaido northern japan field stratigraphy and macrofossil composition of four mires in hokkaido northern japan were investigated to test whether tephra deposition induces long term vegetation shifts macroscopic tephras of known origin ranging from 0 5 to 25 cm in thickness were found in two or more of the study sites allowing correlation of the stratigraphic development of the mires major peat types and position of macroscopic mineral layers were determined in the field and selected cores were analysed by quantitative macrofossil analysis some macrofossil groups and the content of unidentifiable organic matter showed changes in the vicinity of tephra layers but they did not indicate a clear response pattern of the vegetation or the decomposition dynamics of plant material mosses were expected to be most strongly affected by tephra deposition but even in cases where tephra fell on sphagnum dominated vegetation no fundamental shifts to new plant communities were found this suggests that disturbance by widespread tep

tephrostratigraphic studies at tongariro volcanic centre new zealand an overview abstract detailed tephra studies at tongariro volcanic centre tgvc north island new zealand have followed several decades of tephrostratigraphic research principally at the more northern rhyolitic taupo and okataina volcanic centres the development of reliable fingerprinting techniques for correlating rhyolitic tephras sourced from these northern centres has permitted a volcanic stratigraphic framework to be established at tgvc where distal rhyolitic tephras are found interbedded with local andesitic tephras and volcanic sediments field studies at tgvc in recent years have established a detailed late quaternary stratigraphy dating back to 22 600 bp for both andesitic and rhyolitic tephra cover beds and laharic deposits of the ruapehu and tongariro ring plains the eruptive history of tgvc in late quaternary time is recorded in nine andesitic tephra formations in order of increasing age these are tufa trig formation ngauruhoe formation dated ca 1850 bp to present mangatawai tephra 2500 200 bp papakai formation between ca 9700 and 2500 bp mangamate tephra between ca 9950 and 9700 bp pahoka tephra ca 10 000 bp okupata tephra comprising units erupted between ca 13 000 and 10 000 bp rotoaira lapilli ca 13 800 bp and bullot formation between ca 22 600 and 10 000 bp several of these formations mangamate tephra pahoka tephra okupata tephra are sufficiently distinct and widespread to be defined as regional marker beds useful for the correlation and dating of local tephras and ring plain forming debris flow deposits of the tongariro and ruapehu ring plains with which they are interbedded similarly they are potentially important marker beds at sites distal to source where they are found interbedded with distal silicic tephra layers in non volcanic quaternary sediments the potential value of tgvc tephras as chronostratigraphic marker beds and thus a tool in quaternary geomorphological studies in distal environments is perhaps not fully appreciated given the traditional focus on using rhyolitic tephras in correlation studies and the wealth of information now available on these

extinction trajectories of benthic organisms across the triassic jurassic boundary abstract we analysed diversity and abundance patterns of benthic organisms across the triassic jurassic t j boundary based on the paleobiology database pbdb which compiles palaeontological collection data on a global scale while sepkoski s sepkoski j j jr 2002 a compendium of fossil marine animal genera bulletins of american paleontology 363 1 563 compendium on the stratigraphic ranges of marine animal genera suggests that the dominant macrobenthic groups of the late triassic experienced significant extinctions prior to the t j boundary a significant end triassic extinction peak is evident from pbdb s data this rhaetian extinction peak is found in both an analysis of the raw data of stratigraphic ranges and a sample standardized analysis of occurrence data 41 of all mesobenthic and macrobenthic genera crossing the norian rhaetian boundary became extinct within the rhaetian although this rate suffices to characterize the end triassic extinction as a true mass extinction against a middle triassic to middle jurassic background significantly reduced rhaetian origination rates add to the strong diversity depletion in the earliest jurassic as for other mass extinctions evidence for selective extinction is meagre when the analysis is limited to the boundary interval alone and when focused on taxonomic and ecological characteristics of individual genera when taxa are separated by environmental preferences however several determinants of extinction risk become evident suggesting that reef dwellers had a significantly higher extinction risk than level bottom dwellers taxa with an inshore preference were more strongly affected than offshore taxa taxa preferring carbonate substrates were more strongly hit than taxa preferring siliciclastic substrates and taxa preferentially inhabiting low latitudes had higher extinction rates than taxa more common at intermediate and high latitudes much of this selectivity is not independent and also seen in the intervals of background extinctions suggesting that the end triassic mass extinction represents an intensification of background extinctions but not a qualitatively different macroevolutionary regime one possible exception is related to preferences for depositional environments suggesting a selective rhaetian extinction in reefs and inshore settings

environmental determinants and ecologic selectivity of benthic faunas from nearshore to bathyal zones in the end permian mass extinction brachiopod evidence from south china abstract in south china the changhsingian brachiopods are extraordinarily abundant and diverse comprising 447 species in 143 genera they were widespread in nearshore shallow sea reef carbonate platform shelf basin and bathyal zones brachiopod attachment modes were also highly diversified and include burrowing body cementation pedicle attaching on substratum body spines anchoring on substratum pedicle attaching on objects and clasping spines anchoring on other objects they suffered the species and genus extinction rates of 91 5 and 86 respectively in the first episode of the end permian mass extinction and further species and genus extinction rates of 84 2 and 80 0 respectively in the second crisis for the permian triassic p tr brachiopods there were 1 selective extinction of the normal shallow marine dwellers relative to these inhabiting deep sea or marginal seas and 2 among the normal shallow marine habitats selective extinction of reef dwellers relative to non reef forms ecologically the body cementation forms suffered much higher extinction rates than other lifestyle elements in contrast both the burrowing and clasping spine anchoring forms had much lower extinction rates than other lifestyle elements although the reef and bathyal dwellers partly survived the first extinction event they migrated to other habitats to survive the crisis the estimation of extinction rates based on the single episode mass extinction pattern cannot reveal precisely the extinction severity of brachiopod faunas over the p tr transition brachiopod diversity changes support the two stage mass extinction pattern near the p tr boundary

the fossil record and spatial structuring of environments and biodiversity in the cenozoic of new zealand there is increasing evidence to suggest that drivers of bias in the fossil record have also affected actual biodiversity history so that controls of artefact and true pattern are confounded here we examine the role of spatial structuring of the environment as one component of this common cause hypothesis our results are based on sampling standardized analyses of the postmiddle eocene record of shelf molluscs from new zealand we find that spatial structuring of the environment directly influenced the quality of the fossil record contrary to our expectations however we find no evidence to suggest that spatial structuring of the environment was a strong or direct driver of taxic rates net diversity or spatial structuring in mollusc faunas at the scale of analysis stage to stage variation in sampling standardized diversity over the past 40 ma exhibits two superficially independent dynamics a changes in net diversity were associated primarily with changes in origination rate and b an unknown common cause related extinction rate to the quality of the fossil record and indirectly to spatial structuring of the environment we suggest that tectonic drivers manifest as second order sequence stratigraphic cycles are likely to have been a key element of this common cause our perceptions of biodiversity history are influenced strongly by secular biases in the quality of the fossil record e g raup 1976 peters foote 2001 many authors have argued against a literal reading of the record and various techniques to minimize the impacts of sampling biases have been developed e g connolly miller 2001 foote 2003 alroy 2010 in addition however a number of studies have proposed that the relationship between sampling biases and diversity dynamics may be complex these studies have suggested that there are latent common cause factors such as plate tectonics and sea level change which have affected simultaneously the quality of the fossil record and true macroevolutionary history e g newell 1952 sepkoski 1976 smith 2001 peters foote 2002 foote 2003 peters 2005 2006a wall et al 2009 demonstrating potential common causes separating their effects from simple preservation and sampling biases and interpreting them mechanistically are challenging problems that must be solved if palaeobiologists are to resolve true patterns and processes of macroevolutionary change through geological time the aim of the present paper is to examine the role of spatial structuring of the environment and of biodiversity in driving both macroevolutionary dynamics and biases in the fossil record fig 1 specifically we are interested in the extent to which partitioning of marine environments may have influenced biodiversity and the preservation of that diversity in part the study is founded on the expectation that the geographical range and evolution extinction dynamics of organisms occupying a particular habitat will be related to the area and fragmentation of that habitat e g rosenzweig 1995 maurer nott 1998 at the same time we anticipate that the quality of the marine fossil record will be influenced by for example the areal extent and distribution of depositional v non depositional or erosional environments factors that are also likely to affect habitat fragmentation and diversity to test the role of spatial structuring in the common cause hypothesis we use the exemplary well studied and relatively complete fossil record of post middle eocene level bottom shelf molluscs from new zealand e g crampton et al 2003 2006a this record is approximately from mcgowan a j smith a b eds comparing the geological and fossil records implications for biodiversity studies geological society london special publications 358 105 122 doi 10 1144 sp358 8 0305 8719 11 15 00 the geological society of london 2011 40 complete at the species level for the neogene as estimated using two very different approaches cooper et al 2006 crampton et al 2006a in this paper therefore we derive an index for spatial heterogeneity of the environment and adapt established indices of spatial differentiation in the new zealand cenozoic mollusc fauna we then compare time series of these measures to time series of sampling probability a proxy for the quality of the fossil record and sampling standardized estimates of overall species richness origination rate and extinction rate all analyses and computations reported here were undertaken using r r development core team 2010 materials and methods

estimating the rock volume bias in paleobiodiversity studies to interpret changes in biodiversity through geological time it is necessary first to correct for biases in sampling effort related to variations in the exposure of rocks and recovery of fossils with age data from new zealand indicate that outcrop area is likely to be a reliable proxy of rock volume in both stable cratonic regions where the paleobiodiversity record is strongly correlated with relative sea level and on tectonically active margins in contrast another potential proxy the number of rock formations is a poor predictor of outcrop area or sampling effort in the new zealand case

the ties linking rock and fossil records and why they are important for palaeobiodiversity studies a correlation exists between the quality of the rock record and the diversity of fossils recorded from that rock record but what drives that correlation and how consistent that correlation is across different environments remain to be determined palaeontologists wishing to investigate past diversity patterns need to first address issues of geological bias in their data the fossil record provides the only empirical evidence of how life has diversified over geological time but it needs to be interpreted with caution for many years the history of diversity was estimated simply by summing up the numbers of taxa species genera families palaeontologists have recorded from successive geological time intervals or extrapolated from their first and last occurrences in the geological record this time series approach led to what is now a classic view of how diversity has changed over time sepkoski et al 1981 benton 1995 sepkoski 1997 such counts take the fossil record at face value or assume that biases or errors are randomly distributed in such a way that the overall effect is negligible we now realize that this is only a first crude approximation that may be subject to a number of strong biases that arise because of the nature of the sedimentary rock record time series analysis requires that sampling be carefully controlled for best results ideally data should be collected so that sampling from each time interval is uniform or at least sampled fairly using the shareholder quorum subsampling method alroy 2010 otherwise apparent changes in diversity may arise for spurious reasons for example because a a time intervals being sampled are of variable duration longer time intervals 1 4 more recorded diversity or b a time interval has been more intensively sampled more localities specimens habitats formations sampled 1 4 more recorded diversity while for a biological survey it is easy to plan a sampling strategy that will give approximately equal effort and coverage for observations palaeontologists are faced with a much more difficult task firstly the time bins they work with are irregular and highly variable in their duration for example the durations of one of the most widely used time scales has intervals spanning two orders of magnitude gradstein et al 2004 secondly and much more critically palaeontologists are collecting from an already incomplete and highly biased set of rocks which in turn skew the range of taxa and habitats that can be sampled zuschin et al 2011 bluntly put we cannot sample what is not preserved in the rock record although phylogenetic and molecular approaches can attempt to compensate pol norrell 2006 bininda emonds et al 2007 wills 2007 o connor et al 2011 so while it may be possible to standardize for sampling effort from the rock record that remains those rocks might provide a far from uniform sample of the sediments and palaeoenvironments that were originally present palaeontologists cannot therefore assume uniform sampling of the fossil record and must try to assess how the rock record they have to work with has affected their ability to sample evenly and then develop methods that compensate appropriately for this variation in recent years therefore palaeobiodiversity studies have become more probabilistic in their approach concerned with establishing confidence limits around estimates that try to correct for uneven sampling alroy et al 2001 2008 and testing empirical patterns against model predictions foote 2001 smith mcgowan 2007 mcgowan smith 2008 if we are to improve our estimates of biodiversity over time then sampling parameters need to be better quantified and we need to better understand the complex interrelationship between rock and fossil records this is no simple task and requires a more systematic approach to recording culture as well as better documentation of the variables benton et al 2011 figure 1 summarizes the problem as we see it palaeontologists estimate past diversity from remains preserved in the rock record as with any from mcgowan a j smith a b eds comparing the geological and fossil records implications for biodiversity studies geological society london special publications 358 1 7 doi 10 1144 sp358 1 0305 8719 11 15 00 the geological society of london 2011 biological survey variation of sampling effort of the surviving rock record needs to be factored out but this rock record has already passed through a geological filter that has altered and distorted not only the rock area that survives to sample but also the proportions of facies and the preservational quality of its fossil record were this geological filter to remain approximately constant over time there would be little problem of interpreting the biological signal however it is far from uniform with amounts of rock to sample proportions of facies represented by those rocks and preservation potential all varying from one time interval to the next to interpret observed changes in sampled biodiversity estimates correctly we must therefore first understand the role of the geological filter variability of the rock and fossil records

vertical coherence of ambient noise in shallow water overlying a fluid seabed broadband 200 hz 20 khz measurements of the vertical coherence of ambient noise in two well surveyed shallow water channels with fluid sedimentary seabeds are reported the noise at one of the sites the strataform natural laboratory off eureka northern california was occasionally found to be exclusively wind generated with negligible contributions from surface traffic and biological sources under these conditions the theoretical coherence computed using the known properties of the sediment at eureka closely follows the coherence data up to a frequency of 20 khz subtle effects due to the finite depth of the sources that is the bubbles produced by wave breaking are evident in both the theory and the data at the second site in jellicoe channel new zealand some 64 km north of auckland wind noise again was a major factor but much of the time local shipping also contributed to the overall noise field two sets of coherence data from the new zealand site are examined the first taken in nea

the first half of tetrapod evolution sampling proxies and fossil record quality abstract the first half of tetrapod evolution witnessed substantial diversification of the clade and several major turnovers and mass extinctions in the time since their origin more than 380 myr ago to the beginning of the middle jurassic 175 myr ago tetrapods apparently diversified fitfully reaching their highest level in the middle permian and showing major diversity declines in the late moscovian early permian wordian lower wuchiapingian end permian lower anisian lower ladinian late triassic lower norian to upper rhaetian end triassic and early jurassic upper sinemurian lower pliensbachian of these diversity drops only the end permian and end triassic correspond to recognised mass extinctions and the late moscovian and early norian drops to other previously identified environmental crises the remainder could be real extinction or turnover events or partially artefacts of biased sampling there are strong correlations between formation counts and tetrapod palaeodiversity suggesting a sampling component in the raw data but the covariation is not uniform through the whole time span being poor from devonian to middle permian and better from late permian to early jurassic there is limited evidence for covariation between the tetrapod palaeodiversity time series and other putative sampling metrics such as specimen completeness numbers of publications map areas gap bounded sedimentary units rock volumes formations and fossil collections modelling by multiple correlations shows that formation count is generally the best explanatory model either on its own or combined with other sampling time series however it is not clear that formation count is independent of the palaeodiversity time series because rises and falls in both signals could reflect variations in original diversity or in preservation or in sampling

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

the immediate environmental effects of tephra emission the earth s history is punctuated by large explosive eruptions that eject large quantities of magma and silicate rock fragments into the atmosphere these tephra particles can sometimes be dispersed across millions of square kilometres or even entire continents the interaction of tephra with or in receiving environments may induce an array of physical chemical and biological effects the consequences for affected systems and any dependent communities may be chronic and localised in the event of frequent small eruptions while larger and rarer events may have acute regional scale impacts it is therefore necessary to document the range of possible impacts that tephra may induce in receiving environments and any resulting effects in interconnected systems we collate results from many studies to offer a detailed multidisciplinary and interdisciplinary review of the immediate post eruptive effects of tephra emission into the atmosphere onto vegetation soil or ice snow surfaces and in aquatic systems we further consider the repercussions that may be induced in the weeks to years afterwards in the atmosphere tephra can influence cloud properties and air chemistry by acting as ice nuclei in or by offering sites for heterogeneous reactions respectively tephra on vegetation causes physical damage and sustained coverage may elicit longer term physiological responses tephra deposits on soils may alter their capacity to exchange gas water and heat with the atmosphere or may have a specific chemical effect such as nutrient input or acidification on sensitive soils tephra deposition onto snow or ice may affect ablation rates rivers and lakes may experience turbidity increases and changes in their morphology as a result of fallout and prolonged months or years erosion from the tephra covered catchment in the first weeks after deposition tephra leaching may affect river chemistry the abundance and speciation of phytoplankton populations in lakes may be altered by tephra induced changes in water chemistry or sediment water nutrient cycling in the oceans tephra deposition may fertilise fe limited waters with potential impacts on the global carbon cycle embracing the full complexity of environmental effects caused by tephra fall demands a renewed investigative effort drawing on interdisciplinary field and laboratory studies combined with consideration of the interconnectivity of induced impacts within and between different receiving environments

marine diversity through the phanerozoic problems and prospects the fossil record provides direct evidence of how diversity has changed over time but cannot be taken at face value diversity curves constructed from counting taxa in the rock record are seriously biased by unevenness of geographical and stratigraphical sampling effort inequality in the rock record available for sampling and inconsistent taxonomic practice sample standardization removes some bias but does not overcome more general incompleteness problems modelling that accounts for potential biases is a newer approach but needs accurate estimates of rock record and consistent taxonomic data uncertainty remains over whether the steep rise in diversity over the last 100 ma is real or reflects sampling bias the repeated rise and fall of marine diversity over time correlates closely with the areal extent of sedimentary deposits and independent estimates of the quality of the fossil record implying a common driving factor namely tectonically mediated sea level change however whether changes in diversity are primarily biological in origin or reflect sampling artefact remains contentious there is a distinct possibility that many of the apparent rises and falls in diversity over the phanerozoic including most of the mass extinctions arise either partially or entirely from rock record bias

cascading trend of early paleozoic marine radiations paused by late ordovician extinctions the greatest relative changes in marine biodiversity accumulation occurred during the early paleozoic the precision of temporal constraints on these changes is crude hampering our understanding of their timing duration and links to causal mechanisms we match fossil occurrence data to their lithostratigraphical ranges in the paleobiology database and correlate this inferred taxon range to a constructed set of biostratigraphically defined high resolution time slices in addition we apply capture recapture modeling approaches to calculate a biodiversity curve that also considers taphonomy and sampling biases with four times better resolution of previous estimates our method reveals a stepwise biodiversity increase with distinct cambrian and ordovician radiation events that are clearly separated by a 50 million year long period of slow biodiversity accumulation the ordovician radiation is confined to a 15 million year phase after which the late ordovician extinctions lowered generic richness and further delayed a biodiversity rebound by at least 35 million years based on a first differences approach on potential abiotic drivers controlling richness we find an overall correlation with oxygen levels with temperature also exhibiting a coordinated trend once equatorial sea surface temperatures fell to present day levels during the middle ordovician darriwilian age contrary to the traditional view of the late ordovician extinctions our study suggests a protracted crisis interval linked to intense volcanism during the middle late ordovician katian age as richness levels did not return to prior levels during the silurian a time of continental amalgamation we further argue that plate tectonics exerted an overarching control on biodiversity accumulation

using remote sensing and a geographic information system to quantify rock exposure area in england and wales implications for paleodiversity studies rock outcrop area and number of sedimentary formations have been widely used as sampling proxies in paleodiversity studies and have often been found to correlate with apparent paleodiversity however rock exposure area is a better proxy for the amount of sedimentary rock available for study than the widely used measures of outcrop area i e map area or number of formations with the use of remote sensing and a geographic information system gis it is possible to quantify rock exposure area accurately on a regional scale rock exposure area does not correlate well with either outcrop area or number of sedimentary formations and the proportion of rock exposed in different areas can vary considerably with proximity to the coast bedrock age lithology land use and elevation therefore this suggests that the correlation of paleodiversity and rock volume estimates is best explained by a common cause hypothesis rather than a geologic sampling bias hypothesis gis methods offer an efficient and accurate method of quantifying regional sedimentary rock exposure and may provide a helpful approach to assessing rock record bias on patterns in the fossil record

covariation in macrostratigraphic and macroevolutionary patterns in the marine record of north america students of earth history have long recog nized the correlation between the quantity of preserved sedimentary rock and the diversity of life recorded as fossils but paleontologists have yet to determine whether this pattern refl ects a causal relationship or a unidirec tional sampling bias in fossil data imposed by preserved rock quantity distinguishing between these two alternatives has been com plicated by the fact that many of the basic patterns of paleontologic and lithologic co variation have yet to be quantifi ed rigorously here we present the fi rst analyses of the co variation between the macrostratigraphic and macroevolutionary histories of north america based on geographically and tem porally explicit co occurrences of rocks and fossils the analyses use independent quan titative summaries of the stratigraphic and fossil records by integrating the paleobiology database paleodb and macrostrat a mac rostratigraphy database for north america which allows a more direct comparison of the stratigraphic and biological histories of the continent than has heretofore been possible within the macrostrat database the rock re cord is divided into discrete packages of sedi ment that are bound by hiatuses resolvable at the stage level using per interval per pack age rates of sediment package initiation and truncation and genus fi rst and last appear ances herein regional origination and extinc tion we fia substantially stronger positive correlation between sediments and biology for extinction like parameters than we do for origination like parameters four of the largest coincident pulses of regional extinc tion and sediment truncation occur during the widely recognized end ordovician late permian end triassic and end cretaceous mass extinction intervals a further compari son of the global ranges of north american genera to north american macrostratigra phy indicates that the regional and global extinction of genera are more likely to oc cur in the same stage than are global and regional originations together these results suggest that our general understanding of biodiversity dynamics from the fossil record may not be strongly biased by the preserva tion of sediments and leaves open the pos sibility that certain large perturbations to the earth system are responsible for major changes of state in both the sedimentary and biological systems

foraminiferal zonation of late paleozoic depositional sequences from the later part of the devonian through the permian calcareous foraminifers became abundant and evolved rapidly this rapid evolution of taxa forms the basis of a detailed zonation through the carboniferous and permian comparison of this evolutionary history of foraminifers their biostratigraphic zonation and the depositional sequences in which they occur suggests that sea level events in late paleozoic depositional history contributed significantly in subdividing a fairly continuous evolutionary record into a succession of about 75 identifiable foraminiferal zones during a 100 125 myr time span although variable in terms of duration and vertical occurrences the more completely recorded high stand intervals give brief histories of the foraminiferal evolutionary record and are sandwiched between the poorly recorded or unrecorded low stand intervals many of the individual foraminiferal zones are confined to a single depositional sequence the late paleozoic carbonate foraminiferal fossil record as with the rest of the fossil record is strongly affected by sediment deposition nondeposition as a result of major changes in sea level this incomplete fossil record is the result of repeated depositional breaks because of the way that depositional sequences form it is not possible to ascribe macromutations punctuated evolution or punctuated gradualism as the cause of this evolutionary pattern of the shelf carbonate fossil record this pattern is distinctive and we refer to it as sequence evolution and sequence extinction in the later part of the middle permian and in the late permian the fossil record clearly illustrates that a series of faunal losses through sequence extinctions progressively exceeded faunal replacements and new species through sequence evolution but not a mass extinction as is commonly ascribed to the end of the permian period most permian faunas became extinct in the interval of 8 to 4 million years before the end of the late permian

simulating the impacts of distal volcanic products upon peatlands in northern britain an experimental study on the moss of achnacree scotland the potential impact of prehistoric volcanism on distal areas has been the subject of some discussion in both ecology and archaeology an experimental approach is used here to examine the potential effects of distant volcanism on a peatland environment simulations of different tephra and acidity loading designed to approximately replicate the prehistoric hekla 4 ashfall were monitored over 2 years impacts on the peatland ecosystem were assessed by qualitative observations of plant health and abundance semi quantitative observations of flowering measurements of peat ph humification and testate amoebae community composition plots with higher acid loading showed immediate and lasting impacts on plants although other treated plots were less affected changes in testate amoebae and peat humification were inconsistent both within and between plots the experiment demonstrates the potentially severe effects of high acid loading on peatland plants although some responses remain unclear

a new shallow ocean technique for determining the critical angle of the seabed from the vertical directionality of the ambient noise in the water column in the absence of interference from local shipping the vertical directionality of ambient noise in the shallow ocean overlying a fast fluid sediment is a stable feature of the noise field it is controlled primarily by the bottom reflectivity which is a time invariant property of the channel the noise field shows a peak symmetrically placed around the horizontal whose angular width is 2 c where c is the critical grazing angle of the bottom by measuring the noise power distribution in the vertical c can be determined and hence the compressional sound speed in the bottom sediment deduced measurements of the vertical directionality of ambient noise in shallow water have been made at six sites around the coast of the united kingdom using specially designed vertical line array sonobuoys estimates for the critical grazing angle and the sound speed in the bottom have been derived from the noise data for all six areas similar data from independent seismic surveys are available for only one of these s

hiatus distributions and mass extinctions at the cretaceous tertiary boundary much disagreement over the interpretation of data bearing on various cretaceous tertiary k t extinction scenarios results from a failure to view these data within their appropriate stratigraphic context combined biostratigraphic and chronostratigraphic analyses of k t boundary sequences have revealed systematic differences in patterns of sediment accumulation within continental shelf and deep sea depositional settings although virtually all deep sea boundary sequences are marked by intervals of nondeposition or hiatus formation during the latest cretaceous and earliest tertiary many continental shelf slope sequences appear to be temporally complete over this same interval this differential pattern of sediment accumulation can be related to the latest maastrichtian earliest danian sea level rise during which deep sea sediment accumulation rates would be expected to drop as the locus of sediment deposition migrated across the continental shelf our data suggest that the abrupt shifts in carbon isotope abundances single peak ir anomalies and apparently instantaneous mass extinctions of marine plankton which are routinely reported from deep sea k t boundary sequences and used to support a causal relation between late cretaceous bolide impacts and k t mass extinctions may be artifacts of a temporally incomplete or extremely condensed deep sea stratigraphic record

geoacoustic inversion in shallow tropical waters for a silty and sandy seabed seabed parameters are inverted from ambient noise measurements at two shallow tropical environments with dissimilar seabed characteristics a silty and a sandy seabed using an approach that matches the measured and modeled complex vertical coherence coherence is modeled using the green s function output from the model oases along with theoretical formulation for a range independent environment genetic algorithm is used to search the model parameter space consisting of sound speed density and attenuation in the sediment layers and half space reasonable estimates have been obtained for the silty site whereas the sandy site gave relatively poor parameter estimates due to reflective seabed and shipping interference

permian triassic boundary interval as a model for forcing marine ecosystem collapse by long term atmospheric oxygen drop ecological traits of reefs across the permian triassic boundary interval coincide with a modeled decline of atmospheric oxygen throughout the permian period selective extinction and recovery patterns within the reef system are observed both at the end of the middle permian end guadalupian and at the permian triassic boundary the end guadalupian event selectively affected corals and broke down the cool water carbonate factory sponges however were largely unaffected and bloomed in reefs toward the end of the permian the end permian total destruction of the metazoan reef system only left behind poorly diverse microbial communities the temporal reef patterns are thus similar to spatial patterns of modern benthic communities approaching oxygen minimum zones this observation suggests that a decline in oxygen concentrations was at least partly involved in the destruction of reefs even where there is no direct evidence of oceanic anoxia

drawing a line in the sand identifying and characterizing boundaries in the geological record the identification and characterization of boundaries is a fundamental activity in geoscience spatial and temporal boundaries are rarely sharp but are more usually zones of transition which may have variable characteristics the examination of palynological and micropalaeontological data is often crucial for the delineation of geological boundaries especially for the definition of global boundary stratotype sections and points gssps the sixteen papers in this volume highlight many productive methodological approaches to boundary identification this essay reviews the theoretical background to boundary identification in geology and provides the contextual perspective for the subsequent papers much of geoscience has to do with classification of organisms of rocks or of processes inevitably classification devolves into an exercise in drawing boundaries putting a limit on what is included and what is not in the geological record this exercise takes place in three dimensions with space and time interacting to produce a plethora of boundaries and boundary definitions although conventionally on stratigraphic charts for example temporal boundaries are often shown as sharp lines in reality they are rarely so similarly spatial boundaries on maps are seldom as abrupt as they are drawn process boundaries are yet more subtle and usually less clear indeed even to speak of a boundary is contentious since boundaries come in many forms and types boundaries are more often intervals or spaces of transition leaving plenty of room for argument over their placement perhaps for this reason some of the more truculent and long lasting debates in geology have been over the positioning and identification of boundaries drawing a line in the sand may seem a simple exercise but turns out to be fraught with complexities boundary definitions in geoscience the criteria for identifying chronostratigraphic biostratigraphic and lithostratigraphic units are outlined in rules set up by international agreement such as the international stratigraphic guide salvador 1994 or guidelines such as the north american stratigraphic code north american commission on stratigraphic nomenclature 1983 or the stratigraphic procedure rawson et al 2002 the demarcation of boundaries is generally a consequence of the identification of units rather than the other way round historically the identification of boundaries has often arisen from the practical exigencies of geological mapping the need to produce visual representations of geology primarily based on sections or surface exposures boundaries therefore were often synonymous with the limits of mappable units that were generally field identified on the basis of lithology this approach gave rise to the designation of body stratotypes a methodology that proved limiting for the subdivision of geological time because of gaps in the rock record harland et al 1990 modern geochronology emphasizes boundaries especially lower stage boundaries rather than units as fundamental for subdivision and correlation remane 2003 under the auspices of the international commission on stratigraphy ics various subcommissions have been established to examine the placement of particularly critical temporal boundaries in the geological record see list in gradstein ogg 2003 considerable effort has been devoted to the establishment of global boundary stratotype sections and points gssps with more than 40 defined so far gradstein et al undated for each boundary a type section and a specific 3b2 version number 7 51a w may 2 2001 jobsin m11251 00c geo introduction 3d date 27 10 04 time 11 48am page 1 of 10 m11251 the geological society tradespools frome somerset from beaudoin a b head m j eds 2004 the palynology and micropalaeontology of boundaries geological society london special publications 230 1 10 0305 8719 04 15 the geological society of

the kaharoa tephra as a critical datum for earliest human impact in northern new zealand the debate over the timing of arrival and earliest environmental impacts of the first new zealanders has intensified in recent years in part fuelled by new evidence or reinterpretation of old evidence from other points along prehistoric polynesian migratory routes an examination of two radiocarbon dated pollen records from northern new zealand shows how divergent interpretations could be drawn from the same evidence to support both early and late colonization models radiocarbon dated pollen records for deforestation at sites where the risk of contamination by older carbon may be high cannot be used to establish chronologies of settlement ombrogenous mires where peat accumulation proceeds independently of groundwater or surface runoff are likely to yield the most reliable records another solution applicable in northern new zealand is to base chronologies on tephra layers with reliable age estimates from multiple determinations analysis of 11 pollen records currently known to contain the 665 15 bp c 600 cal bp rhyolitic kaharoa tephra demonstrates the critical stratigraphic position that this isochronous surface occupies in new zealand prehistory the earliest inferred human impacts occurred at around the time of deposition of the tephra in eight of these sites 73 and well after it at the remainder these results are in agreement with a later colonization model and suggest that proximity to accessible food resources was more important than climate or latitude in determining early colonization sites these findings will be tested fully when the known range of kaharoa tephra is extended beyond its present limited range through the application of micro tephra analysis in line with anderson s 1995 128 premise that the later colonization model is eminently falsifiable we suggest that tephropalynological studies involving the kaharoa tephra may hold the key to resolving debates over the timing and spatial patterns of earliest human impact in northern new zealand in particular these records permit the investigator to avoid the ambiguities that emerge frequently when pollen profiles indicating deforestation are dated by radiocarbon alone

icelandic volcanic ash and the mid holocene scots pine pinus sylvestris pollen decline in northern scotland a volcanic ash layer in peat from northern scotland has been identified and coincides exactly with an abrupt decline in pinus sylvestris l scots pine pollen frequencies this provides an isochrone time equivalent marker horizon with which to investigate the timing of the holocene pine decline furthermore two possible causes of the southward shift of the range of pinus in scotland c 4000 bp are suggested a direct effect of acid pollution by chemicals produced by the eruption of hekla h 4 or a volcanically induced climatic perturbation these possibilities have wider implications for the influence of volcanism on postglacial environmental change

radiocarbon age of the kaharoa tephra a key marker for late holocene stratigraphy and archaeology in new zealand the kaharoa eruption the most recent rhyolitic volcanic event in new zealand resulted in the deposition of the compositionally distinctive kaharoa tephra over at least 30 000 km2 of northern and eastern north island the tephra forms an isochronous marker bed for various late holocene stratigraphic and palaeoen vironmental studies but is particularly important for evaluating the chronology of new zealand s notably short prehistory because it was erupted within the last millennium close to the time of first polynesian colonization we derive a definitive radiocarbon age previously ambiguous for the kaharoa tephra of 665615 bp using cluster analysis of 22 radiocarbon ages relevant to the kaharoa eruptive episode the error weighted mean age obtained on unscreened ages minus outliers is supported by statistically identical ages obtained from three sets of screened ages selected to minimize the effects of inbuilt age or contamination based on the intercepts method and 1 sigma range of northern hemisph

non biotic controls of observed diversity in the paleontologic record an example from the permo triassic karoo basin of south africa paleodiversity trends through geologic time can be affected by a number of geologic taphonomic and anthropogenic biases that obscure or prejudice paleoecological patterns in the fossil record although much work has concentrated on the relationship between geologic exposure sample size and taxonomic richness i e number of taxa few studies have investigated the potential effects of dataset quality and changing taxonomy we use four different specimen level datasets of permo triassic tetrapods from the karoo basin of south africa to investigate how sample size geologic outcrop dataset quality and taxonomic revision all affect observed estimates of generic richness evenness and relative abundance our results indicate that large scale patterns of richness evenness and abundance such as the effects of the end permian mass extinction are generally robust to these potential biases across the four different datasets in contrast absolute values vary significantly as do finer scale patterns in agreement with past studies taxonomic errors revised taxonomy and new taxa have little effect on patterns of richness and evenness instead the addition of large numbers of new specimens to the dataset has the largest effect on these paleodiversity metrics despite application of sample standardization we conclude that although large specimen datasets hundreds to thousands of specimens are robust to various potential biases and can recover large scale paleobiologic trends they are still affected by many non biotic controls and workers should strive to improve dataset quality and understand the underlying reasons for observed paleodiversity patterns

completeness of the fossil record and the validity of sampling proxies a case study from the triassic of england and wales many studies have highlighted correlations between palaeodiversity and sampling proxies these correlations have been interpreted as evidence for bias common cause or redundancy between signals here we compare a number of sampling proxies representing sedimentary rock volume rock accessibility and worker effort with palaeodiversity through the predominantly terrestrial triassic system in england and wales we find that proxies for sedimentary rock volume and accessibility do not correlate with palaeodiversity until the removal of facies related preservational and palaeoecological factors this indicates that a weak sampling signal may be present but the effects of changing palaeoenvironments are far more important at the regional scale significant correlations between worker effort and palaeodiversity are detected although this is likely to be a result of the preferential sampling of formations already known to be rich in fossils the fact that there is little evidence for sedimentary rock bias in the fossil record of the triassic of england and wales suggests that either 1 sampling bias is not a major source of error at the regional scale or 2 sampling proxies are inadequate representations of geological and human sampling bias supplementary material correlation test results and raw time series data from the study are available at www geolsoc org uk sup18567