the tindouf basin a marine refuge during the serpukhovian carboniferous mass extinction in the northwestern gondwana platform abstract several macrofaunas and microfossils of the carboniferous saharan basins have longer stratigraphic ranges than those of other basins in the western palaeotethys realm particularly in the tindouf basin morocco algeria foraminifers are particularly abundant and diverse in the serpukhovian and basal bashkirian compared to coeval basins and some taxa have longer ranges than in the neighbouring reggan and bechar basins although this effect is more marked compared to the western palaeotethyan assemblages in europe several rugose coral species are recorded from the early bashkirian that previously were considered to have disappeared in the serpukhovian the tindouf basin as one of the most western saharan basins in north africa shows the greatest stratigraphic ranges of taxa which diminish eastwards evidence for a mass extinction event during the serpukhovian in the tindouf basin has not been clearly recognized although a possible influence of glaciation is observed in the faunal diversity eustatic sea level changes were experienced in tindouf with the cyclic pattern of sedimentation but warm water ocean currents from the palaeoequator were able to maintain tropical conditions on the platform tectonics in the area led to emerging land masses and barriers and created a partly isolated basin in this sector of the western part of the sahara platform in northern gondwana the combination of those factors controlled the environmental conditions in the area allowing the persistence of the fauna for longer stratigraphic ranges than its equivalent counterparts in the western palaeotethys

broadband waveform modeling of moderate earthquakes in the san francisco bay area and preliminary assessment of the usgs 3d seismic velocity model abstract recently the united states geologic survey earthquake hazards program developed a 3d seismic velocity model of northern california based on geology including a detailed model of the urbanized san francisco bay area in this study we report comparisons of observed three component broadband 0 03 0 25 hz waveforms with synthetic seismograms computed with the new 3d model using an elastic finite difference method we selected a set of 12 moderate earthquakes m w 4 0 5 1 that occurred within the greater san francisco bay area having well constrained source parameters and broadband recordings with high signal to noise ratios the objective of this study was to investigate how well the 3d velocity model predicts observed waveforms and to identify features of the model that may require revision to improve the waveform fits and predictions of ground motions for future events we show for the 3 september 2000 yountville earthquake that reported source parameters accurately predict waveforms at two close strong motion stations approximately 10 km from the epicenter by comparing synthetics for the average 1d model gil7 stidham et al 1999 and the 3d structures we show that the effects of seismic wave propagation in the 3d model become important for frequencies at and above 0 1 hz periods less than 10 sec comparison of observed and synthetic seismograms for the 3d model consistently shows that the model predicts energy arriving earlier than is observed particularly for the surface waves indicating that the shear velocities in the upper crust must be reduced we cross correlated the observed and synthetic waveforms and recorded the delay time and linear correlation for best alignment of the data and delayed synthetic the results indicate that generally the 3d model predicts the observed waveforms well mean linear correlations 0 41 and includes features that arise from the interaction of the wave field with 3d structure especially the major sedimentary basins in san pablo bay san francisco bay santa clara valley and livermore valley simple conversion of the observed delay times for optimal alignment suggests shear velocities should be reduced by 4 5 on average based on these findings we conclude that the model is an excellent first step suggesting that the overall structure of the model is accurate i e the basin and discontinuity geometry however the velocities must be reduced to improve the observed timing of surface wave arrivals

brachiopod faunas after the end ordovician mass extinction from south china testing ecological change through a major taxonomic crisis classification of extinction events and their severity is generally based on taxonomic counts the ecological impacts of such events have been categorized and prioritized but rarely tested with empirical data the ecology of the end ordovician extinction and subsequent biotic recovery is tracked through abundant and diverse brachiopod faunas in south china the spatial and temporal ranges of some 6500 identified specimens from 10 collections derived from six localities were investigated by network and cluster analyses nonmetric multidimensional scaling and a species abundance model depth zonations and structure of brachiopod assemblages along an onshore offshore gradient in the late katian were similar to those in the latest ordovician earliest silurian post extinction fauna within this ecological framework deeper water faunas are partly replaced by new taxa siliciclastic substrates continued to be dominated by the more ordovician orthides and strophomenides shallow water carbonate environments hosted atrypides athyridides and pentamerides with the more typical ordovician brachiopod fauna continuing to dominate until the late rhuddanian the end ordovician extinctions tested the resilience of the brachiopod fauna without damage to its overall ecological structure that commenced later at the end of the rhuddanian

correlation of the base of the serpukhovian stage mississippian in nw europe the task group charged with proposing the gssp for the base of the serpukhovian stage mississippian lower carboniferous is likely to use the global first appearance datum fad of the conodont lochriea ziegleri in the lineage lochriea nodosa l ziegleri for the definition and correlation of the base of the stage it is important to establish that the fad of l ziegleri in different basins is penecontemporaneous ammonoids provide high resolution biostratigraphy in the late mississippian but their use in international correlation is limited by provincialism however it is possible to assess the levels of diachronism of the first occurrence datum fod of l ziegleri in sections in nw europe using ammonoid zones published conodont distribution in the rhenish slate mountains of germany show the fod of l ziegleri in the emstites novalis biozone upper part of the p2c zone of the uk and ireland but l ziegleri has also been reported as occurring in the neoglyphioceras spirale biozone p1d zone in the yoredale group of northern england the fod of l ziegleri is in either the p1c or p1d zone in nw ireland the oldest records of both l nodosa and l ziegleri are from the lusitanoceras granosum biozone p2a although there is some discrepancy in the recorded levels of the fod of l ziegleri in nw europe this may be as a result of collection failure the base of the serpukhovian based on the fad of lochriea ziegleri will be in the middle of the brigantian regional substage

use of nonparametric ranking statistics to characterize magmatic and post magmatic processes in the eastern south mountain batholith nova scotia canada abstract the south mountain batholith is a large post tectonic peraluminous granitoid complex consisting of many coalesced plutons compositions range from biotite granodiorite through two mica monzogranite to muscovite leucogranite application of the non parametric spearman rank correlation coefficient srcc statistic to major and trace element chemical data from one large pluton the halifax pluton and to two different groups of much smaller leucogranitoid bodies shows strongly different correlation coefficients in the three groups the halifax pluton shows strong srccs between compatible elements ba sr zr sc v la and weak srccs for the incompatible elements rb ta nb li f sn the leucogranites generally show correlations opposite to the halifax pluton and also show some strong correlations between elements that were poorly correlated in it na k li p non geological controls such as closure dissimilar compositional ranges dissimilar groupings and differing analytical precisions cannot account for the observed differences between the magnitudes and signs of the correlation coefficients in the three groups on the other hand geological controls principally magmatic vs hydrothermal do explain most of the differences in the correlation coefficients and the transition between magmatic and hydrothermal control is apparent spearman rank correlation coefficients can be used with compositional data drawn from populations with non normal distributions to provide a comprehensive and rapid nongraphical assessment of inter element correlations to quantify these inter element relationships and to both identify processes and to gauge their relative contributions to the observed compositions

astronomical cycles in the serpukhovian moscovian carboniferous marine sequence south china and their implications for geochronology and icehouse dynamics abstract the late paleozoic ice age ca 335 260 ma lpia has long been considered as an analogy for the cenozoic ice age since the oligocene the impact of astronomical forcing on the lpia glaciation has been hampered due to the low resolution multi million year scale time framework in the present study high resolution cyclostratigraphy based on magnetic susceptibility ms covering the serpukhovian to late moscovian icehouse climate has been investigated in the luokun section of south china power spectral analysis of the ms series reveals 3 44 4 m 0 8 1 07 m 0 3 0 32 m and 0 17 0 19 m thick sedimentary cycles based on the available biostratigraphic constraints calibrating the 3 44 4 m cycles to the 405 kyr eccentricity cycles indicates short eccentricity 136 and 100 kyr short obliquity 34 kyr and precession 19 and 15 9 kyr orbital bands in addition to long eccentricity 405 kyr band we assigned the basal serpukhovian and moscovian stages in luokun with the numerical ages from geological time scale 2012 to construct two floating time scales ranging from 331 55 0 5 ma to 323 2 0 5 ma and from 315 34 0 35 ma to 310 17 0 35 ma respectively the modulation of main obliquity s4 s3 term has a main periodicity of 1200 kyr the modulation of 100 kyr eccentricity g4 g3 term shows a main periodicity of 2400 kyr with subordinate periodicities of 1620 and 1200 kyr for the serpukhovian and a main periodicity of 1600 kyr for the moscovian they may provide the geological evidence for a chaotic resonance associated with interactions between the orbits of mars and the earth in the carboniferous a duration of 7 68 0 15 myr was estimated for the serpukhovian stage eight higher accumulation rate events due to glacioeustatic drawdown were temporally constrained and show close correspondence to far field and near field reconstructions of the lpia glaciation glacioeustasy was paced with 405 kyr long eccentricity and 1 2 myr obliquity amplitude cycles during the serpukhovian and moscovian stages likely indicating the nature in the warmer icehouse world similar to that of the oligocene to pliocene

imaging p and s attenuation in the sacramento san joaquin delta region northern california we obtain 3d q p and q s models for the delta region of the sacramento and san joaquin rivers a large fluvial agricultural portion of the great valley located between the sierra nevada batholith and the san francisco bay coast ranges region of active faulting path attenuation t values have been obtained for p and s data from 124 distributed earthquakes with a longer variable window for s based on the energy integral we use frequency dependence with an exponent of 0 5 consistent with other studies and weakly favored by the t s data a regional initial model was obtained by solving for q as a function of seismic velocity in the final model the great valley basin has low q with very low q 50 for the shallowest portion of the delta there is an underlying strong q contrast to the ophiolite basement which is thickest with highest q under the sacramento basin and a change in structure is apparent across the suisun bay as a transition to thinner ophiolite moderately low q is found in the upper crust west of the delta region along the faults in the eastern north bay area whereas moderately high q is found south of the delta implying potentially stronger ground motion for earthquake sources to the south very low q values in the shallow crust along parts of the major fault zones may relate to sediment and abundant microfractures in the lower crust below the san andreas and calaveras hayward rodgers creek fault zones the observed low q is consistent with grain size reduction in ductile shear zones and is lowest under the san andreas which has large cumulative strain similarly moderately low q in the ductile lower crust of the bay area block between the major fault zones implies a broad distributed shear zone online material distribution of earthquake magnitude figures of t values 3d initial regional velocity and q models station terms and q p inversion with 1d initial q p model

greenhouse to icehouse a biostratigraphic review of latest devonian mississippian glaciations and their global effects the latest devonian mississippian interval records the long term transition from devonian greenhouse conditions into the late palaeozoic ice age lpia this transition was punctuated by three short glaciation events in the latest famennian mid tournaisian and visean stages respectively primary evidence for glaciation is based on diamictite deposits and striated pavements in south america appalachia and africa the aim of this review is to assess the primary biostratigraphic and sedimentological data constraining diamictite deposits through this transition these data are then compared to the wider record of eustasy mass extinction and isotope stratigraphy in the lower palaeolatitudes precise age determinations are vital to integrate high and low palaeolatitude datasets and to understand the glacial control on wider global changes palynological techniques currently provide the best biostratigraphic tool to date these glacial deposits and to correlate the effects of glaciation globally this review highlights a high degree of uncertainty in the known history of early lpia glaciation as much of the primary stratigraphic data are limited and or unpublished future high resolution stratigraphic studies are needed to constrain the history of glaciation both spatially and temporally through the latest devonian and mississippian

global events of the late paleozoic early devonian to middle permian a review abstract the late paleozoic early devonian to middle permian was an interval of profound changes in earth surface systems reflected in dynamic interplay among the biosphere hydrosphere atmosphere and geosphere major events transpired including the colonization of landmasses by vascular plants the assembly of the supercontinent pangea two first order mass extinctions the frasnian famennian and devonian carboniferous boundary events and the most severe icehouse climate mode of the phanerozoic the late paleozoic ice age lpia the goals of the present review are 1 to summarize major global developments in climate oceanography and paleobiology during the late paleozoic 2 to examine the roles of land plant evolution global tectonics and large igneous province magmatism in driving these developments and 3 to serve as an introduction to the 23 contributions to this special issue of palaeogeography palaeoclimatology palaeoecology indicating how they advance our knowledge of various scientific issues related to these developments

post extinction diversification patterns of brachiopods in the early middle llandovery silurian abstract network and frequency distribution analyses of global brachiopod occurrences in the earliest silurian rhuddanian aeronian revealed that brachiopod recovery from the end ordovician mass extinction during the early late rhuddanian was represented mainly by the reestablishment of late ordovician cosmopolitan holdover taxa brachiopods nearly doubled their generic diversity from rhuddanian to aeronian owing to the radiation of both endemic and cosmopolitan taxa associated with an overall post glacial amelioration of global environment and increased habitat heterogeneity as a result of marine transgressions and expansion of epeiric seas a drastic turnover from the ordovician type to silurian type brachiopod faunas took place in the aeronian several million years after the terminal ordovician mass extinction compared with the orders of orthides and strophomenides that radiated and predominated in the ordovician the atrypides and pentamerides displayed pulses of drastic diversification from the rhuddanian to aeronian mainly in tropically located paleoplates to become the most abundant and diverse brachiopod orders in the silurian atrypides recovered in the early rhuddanian whereas diversification of pentamerides was delayed until the aeronian and becoming widespread in south china kazakhstan terranes baltica avalonia and laurentia

a new ecological severity ranking of major phanerozoic biodiversity crises a new ecological severity ranking of the major phanerozoic biodiversity crises is proposed in which the capitanian crisis is ranked lesser than the frasnian late devonian but greater than the serpukhovian end mississippian and the famennian end devonian crisis is ranked as equal in ecological impact to the hirnantian end ordovician two new decouplings between taxonomic severity and ecological severity are revealed in these analyses the capitanian and famennian crises in which the ecological impact of the biodiversity loss was markedly different from the magnitude of the biodiversity loss these analyses also reveal that the great devonian interchange gdi invasive species event in the givetian biodiversity crisis may provide an important palaeoecological analog for the study of present day extinction and homogenization in ecosystems produced by modern invasive species

three dimensional p wave velocity model for the san francisco bay region california 1 a new three dimensional p wave velocity model for the greater san francisco bay region has been derived using the double difference seismic tomography method using data from about 5 500 chemical explosions or air gun blasts and approximately 6 000 earthquakes the model region covers 140 km ne sw by 240 km nw se extending from 20 km south of monterey to santa rosa and reaching from the pacific coast to the edge of the great valley our model provides the first regional view of a number of basement highs that are imaged in the uppermost few kilometers of the model and images a number of velocity anomaly lows associated with known mesozoic and cenozoic basins in the study area high velocity vp 6 5 km s features at 15 km depth beneath part of the edge of the great valley and along the san francisco peninsula are interpreted as ophiolite bodies the relocated earthquakes provide a clear picture of the geometry of the major faults in the region illuminating fault dips that are generally consistent with previous studies ninety five percent of the earthquakes have depths between 2 3 and 15 2 km and the corresponding seismic velocities at the hypocenters range from 4 8 km s presumably corresponding to franciscan basement or mesozoic sedimentary rocks of the great valley sequence to 6 8 km s the top of the seismogenic zone is thus largely controlled by basement depth but the base of the seismogenic zone is not restricted to seismic velocities of 6 3 km s in this region as had been previously proposed

global paleobiogeography of brachiopods during the mississippian response to the global tectonic reconfiguration ocean circulation and climate changes abstract changes in mississippian global paleogeography derived from the reconfiguration of the continents a reversal in ocean currents and global cooling although the tectonic and climatic changes are well documented their effects on the distribution of brachiopod fauna are poorly documented here we present systematic quantitative analyses on global paleobiogeography based on a global brachiopod database from the mississippian i e tournaisian visean and serpukhovian the dataset consists of 2123 species of 344 brachiopod genera from 1156 localities our results reveal that global provincialism was not evident during the tournaisian and visean stages two realms i e the gondwanan and paleoequatorial realms are recognized during the tournaisian the paleoequatorial realm dominates during the visean stage whereas the gondwanan realm is not documented due to the absence of data points in contrast to the early and middle mississippian stages faunal provincialism is greatly enhanced in the serpukhovian stage with paleotethyan and north american realms easily distinguished this indicates that the rheic ocean was closed before the serpukhovian due to the collision between gondwana and laurussia that disrupted faunal interchange between the paleotethys and north america in addition the paleolatitude related thermal gradient was enhanced and the boreal realm was distinguished from the paleotethyan realm during the onset of the late palaeozoic ice age lpia in the serpukhovian the paleolatitude diversity gradient pattern further shows a distinct shift of diversity center from the southern tropic zone in the tournaisian and visean to the northern tropic zone in the serpukhovian

the late ordovician mass extinction abstract near the end of the late ordovician in the first of five mass extinctions in the phanerozoic about 85 of marine species died the cause was a brief glacial interval that produced two pulses of extinction the first pulse was at the beginning of the glaciation when sea level decline drained epicontinental seaways produced a harsh climate in low and mid latitudes and initiated active deep oceanic currents that aerated the deep oceans and brought nutrients and possibly toxic material up from oceanic depths following that initial pulse of extinction surviving faunas adapted to the new ecologic setting the glaciation ended suddenly and as sea level rose the climate moderated and oceanic circulation stagnated another pulse of extinction occurred the second extinction marked the end of a long interval of ecologic stasis an ecologic evolutionary unit recovery from the event took several million years but the resulting fauna had ecologic patterns similar to the fauna that had become e

the terminal triassic catastrophic extinction event in perspective a review of carboniferous through early jurassic terrestrial vertebrate extinction patterns abstract a catastrophic terminal triassic extinction event among terrestrial vertebrates is not supported by available evidence the current model for such an extinction is based on at least eight weak or untenable assumptions 1 a terminal triassic extinction inducing asteroid impact occurred 2 a terminal triassic synchronous mass extinction of terrestrial vertebrates occurred 3 a concurrent terminal triassic marine extinction occurred 4 all terrestrial vertebrate families have similar diversities and ecologies 5 changes in familial diversity can be gauged accurately from the known fossil record 6 extinction of families can be compared through time without normalizing for changes in familial diversity through time 7 extinction rates can be compared without normalizing for differing lengths of geologic stages and 8 catastrophic mass extinctions do not select for small size these assumptions have resulted in unsupportable and or erroneous conclusions carboniferous through early jurassic terrestrial vertebrate families mostly have evolution and extinction patterns unlike the vertebrate evolution and extinction patterns during the terminal cretaceous event only the serpukhovian mid carboniferous extinction event shows strong analogy to the terminal cretaceous event available data suggest no terminal triassic extinction anomaly but rather a prolonged and nearly steady decline in the global terrestrial vertebrate extinction rate throughout the triassic and earliest jurassic

the plant fossil record reflects just two great extinction events five great taxonomic extinctions the so called big five mass extinctions are widely recognized in life history at the end of the ordovician frasnian late devonian permian triassic and cretaceous all of them were originally identified in the marine fossil record and have been interpreted as the result of abrupt global environmental changes previous evidence has suggested that terrestrial biota were also subjected to ecological disruption during these events but it is unknown whether they suffered the same level of large scale taxonomic disruption as marine organisms here we show that the plant fossil record in fact only provides evidence of two mass taxonomic extinction events one through the carboniferous permian transition the other during middle late permian times this differs significantly from the mass extinctions recognized in the marine realm and suggests that vascular plants have a special capacity for surviving abrupt environmental changes

ecological ranking of phanerozoic biodiversity crises the serpukhovian early carboniferous crisis had a greater ecological impact than the end ordovician we propose a new ecological ranking of the major phanerozoic biodiversity crises in which the serpukhovian biodiversity crisis is ranked fifth in ecological impact lesser than the late devonian but greater than the end ordovician and the end ordovician mass extinction is ranked sixth it is interesting that both the end ordovician mass extinction and the serpukhovian biodiversity crisis were triggered by glaciations other than that common trigger the two events were very different glaciation in the ordovician triggered an enormous jump in the extinction rate of marine organisms and was taxonomically very severe yet the ecological impact of those extinctions was minimal glaciation in the serpukhovian triggered a precipitous drop in the speciation rate but only moderate diversity losses yet the ecological impact of those diversity losses and ecosystem restructuring was an ecological level of magnitude larger than that seen in the end ordovician mass extinction

peculiarities of surface wave propagation across central eurasia abstract the recent installation of six broadband digital iris ida seismic stations in the ussr has provided new opportunities for studying surface wave propagation across eurasia group velocities of fundamental rayleigh and love modes between epicenters and these stations were determined for 35 events that occurred since april 1989 to the middle of july 1990 near eurasia differential phase velocities were found for the same arrivals along paths between several pairs of stations group and phase velocities were obtained in the period range from 15 to 300 sec frequency time polarization analysis was used for studying polarization properties of surface waves in some cases significant anomalies in the particle motion for periods up to 100 sec were observed they are attributed to surface wave refraction and scattering due to lateral inhomogeneities at the boundaries and inside the eurasia continent

carbonate collapse and the late paleozoic ice age marine biodiversity crisis el set de datos contiente datos de la paleobiology database paleobbd org cruzados con los datos de macrostrat macrostrat org datos crudos de macrostrat y los scripts necesarios para reproducir el trabajo

regional three dimensional seismic velocity model of the crust and uppermost mantle of northern california 1 we present a three dimensional 3d tomographic model of the p wave velocity vp structure of northern california we employed a regional scale double difference tomography algorithm that incorporates a finite difference travel time calculator and spatial smoothing constraints arrival times from earthquakes and travel times from controlled source explosions recorded at network and or temporary stations were inverted for vp on a 3d grid with horizontal node spacing of 10 to 20 km and vertical node spacing of 3 to 8 km our model provides an unprecedented comprehensive view of the regional scale structure of northern california putting many previously identified features into a broader regional context and improving the resolution of a number of them and revealing a number of new features especially in the middle and lower crust that have never before been reported examples of the former include the complex subducting gorda slab a steep deeply penetrating fault beneath the sacramento river delta crustal low velocity zones beneath geysers clear lake and long valley and the high velocity ophiolite body underlying the great valley examples of the latter include mid crustal low velocity zones beneath mount shasta and north of lake tahoe

depressed rates of origination and extinction during the late paleozoic ice age a new state for the global marine ecosystem rates of origination and extinction for marine animal genera dropped to low levels in latest mississippian time immediately after massive glaciers formed in the southern hemisphere and a second order mass extinction occurred evolutionary turnover and diversity remained low for 50 m y shifting markedly upward precisely when extensive glaciation ended in early permian time all diverse taxa with good fossil records experienced low rates of origination and extinction during this major ice age such sluggish rates would be predicted for faunas of shallow seas on or adjacent to a heavily glaciated supercontinent such as pangea where cool and highly seasonal thermal regimes should dictate that species have broad ecological niches widespread geographic distributions and large and relatively stable populations

global and regional controls on marine redox changes across the ordovician silurian boundary in south china abstract the ordovician silurian o s transition coincided with significant environmental and biological changes in south china the yangtze platform experienced both global and regional events at this time including sea level fluctuations tectonic movements volcanic eruptions mass extinction and widespread anoxia the o s transitional strata of the yangtze platform comprise organic rich black shales that are an important oil source rock to explore the evolution of watermass chemistry and its relationship to organic matter accumulation we conducted an integrated fe s c geochemical study i e fe speciation 13corg 34spy pyrite s and toc of the o s boundary sections at datianba chongqing municipality and shuanghe sichuan province these sections were located in the restricted inner yangtze sea in contrast to the previously studied wangjiawan section which was deposited in a more open setting of the outer yangtze sea in contrast to the well oxygenated conditions at wangjiawan the datianba and shuanghe sections record persistently anoxic and episodically euxinic conditions during the hirnantian which can be explained by the unique paleogeography and restricted hydrography of the inner yangtze sea we propose that the regional kwangsian orogeny which was driven by collision of the yangtze and cathaysia blocks played a key role in basin development watermass chemistry changes and accumulation of wufeng formation black shales within the yangtze sea the more widespread black shales of the lower silurian lungmachi formation were linked to the post hirnantian global marine transgression

elevated marine productivity triggered nitrogen limitation on the yangtze platform south china during the ordovician silurian transition abstract the ordovician silurian transition ost coincided with global environmental and biological changes including perturbations of the carbon and sulfur cycles oceanic redox changes and a mass extinction event but their effects on the contemporaneous marine nitrogen cycle remain poorly known in this study we measured bulk nitrogen isotopes in the datianba and shuanghe ost sections of south china which accumulated in the semi restricted inner yangtze sea the uniformly low 15nbulk mostly 1 to 1 of wufeng and longmaxi formation black shales representing the pre and post hirnantian intervals imply large losses of bioavailable nitrogen i e nitrate and ammonium via denitrification anammox as well as strong nitrogen fixation by diazotrophs persistence of low 15nbulk values within the guanyinqiao bed representing the hirnantian glacial interval indicates that denitrification anammox remained strong even during this major glacio eustatic fall and deep ocean ventilation event we hypothesize that elevated primary productivity caused by upwelling was a key factor producing a shallow redoxcline in the inner yangtze sea by comparing our nitrogen data with records from other cratons we suggest that oceanic anoxia was prevalent globally during the late katian to early rhuddanian and that ocean redox conditions were spatially heterogeneous during the hirnantian glaciation these considerations imply that bioavailable nitrogen was the limiting factor on marine primary productivity during the ost and that oceanic anoxia may have contributed to the late ordovician mass extinction especially on the yangtze platform

ecosystem evolution in deep time evidence from the rich paleozoic fossil records of china preface for the special issue ecosystem evolution in deep time evidence from the rich palaeozoic fossil records of china

climatic basis for sluggish macroevolution during the late paleozoic ice age rates of origination and extinction for marine invertebrates fell at the onset of the late paleozoic ice age in late mississippian time and remained low until glaciation ended in middle permian time through the use of a database of stratigraphic and geographic occurrences of brachiopod genera these macroevolutionary changes are traced to the loss of genera with narrow latitudinal ranges which had intrinsically high turnover rates at the onset of glaciation in late visean time when glaciation waned in late sakmarian time narrowly distributed genera rebounded abruptly and restored the global fauna to its pre ice age configuration because narrowly distributed brachiopod genera had dominated tropical diversity the major biotic effects of the late paleozoic ice age were felt at low latitudes the climatic regime of this ice age thus altered the marine ecosystem to one characterized by broadly adapted long lived genera

conodont biostratigraphy of the mid carboniferous boundary in western ireland two stratigraphic sections spanning the mid carboniferous boundary were examined in the clare shale formation of the shannon basin in western ireland calcareous nodules intermittently occur within these generally non calcareous organic rich shales and these have yielded serpukhovian and bashkirian conodont elements the biostratigraphic range of the irish material is illustrated here for the first time results show that the mid carboniferous and arnsbergian chokierian boundaries are coincident at ballybunion gnathodus girtyi is restricted to the lower part of the serpukhovian stage late mississippian while g bilineatus bollandensis persists into much younger strata close to the first occurrence of declinognathodus noduliferus s l one element belonging to g postbilineatus is also present these findings support the argument that d noduliferus s l developed from g b bollandensis rather than from g girtyi the biostratigraphical tool for the identification of the mid carboniferous boundary globally and the suitability of the section at arrow canyon usa as a gssp may therefore need to be reassessed

evolutionary models in the early triassic marine realm abstract the relative influences of extrinsic compared to intrinsic drivers of evolutionary change have long been theorized and debated in the fossil record ecological recoveries from mass extinction events present records in which to examine these contrasts competition in a low diversity world reproductive strategy reconstruction of trophic systems and ecological specialization represent possible intrinsic controls on diversification feedback between diversity and abundance shifts of marine organisms with biogeochemical cycling and environmental conditions act as extrinsic controls on recovery process and rate disentangling these evolutionary pressures is a major challenge for understanding evolutionary recovery from mass extinction the end permian mass extinction 251 88 ma represents the largest mass extinction in earth history and led to an extended recovery interval which lasted the duration of the early triassic 4 8 myr and beyond recent analyses suggest that the survivors of the mass extinction were biased toward organisms with higher metabolic rates that were more resilient against the volatile environmental changes that pervaded the early triassic including extreme temperature events low ph and low oxygen conditions we use the early triassic recovery of gastropods echinoids and ammonoids to examine the processes of taxonomic and ecological evolution in response to or in spite of extrinsic environmental perturbations the case studies of benthic gastropods and echinoids when compared to pelagic ammonoids reflect similarities and differences in recovery following the end permian mass extinction gastropods and echinoids exhibit evidence of strong extrinsic environmental limitations which implicate the availability of refugia as a control on recovery low initial taxonomic diversity of survivors may have also limited the evolutionary recovery of both clades abundant and diverse microgastropod assemblages are interpreted as an adaptation to extreme environmental conditions the morphological diversity of disarticulated echinoid spines and plates described in the southwestern united states and examination of phylogenetic ghost lineages hints at a significant hidden diversity of early triassic echinoids ammonoids experienced taxonomic resets but are shown to be resilient to repeated environmental perturbations in the boreal ocean over the duration of the early triassic ammonoids may have adapted to persistent latitudinal temperature gradients and oxygen minimum zones that developed in the early triassic ocean basins

seismic velocity structure and seismotectonics of the eastern san francisco bay region california the hayward fault system is considered the most likely fault system in the san francisco bay area california to produce a major earthquake in the next 30 years to better understand this fault system we use microseismicity to study its structure and kinematics we present a new 3d seismic velocity model for the eastern san francisco bay region using microseismicity and controlled sources which reveals a 10 velocity contrast across the hayward fault in the upper 10 km with higher velocity in the franciscan complex to the west relative to the great valley sequence to the east this contrast is imaged more sharply in our localized model than in previous regional scale models thick cenozoic sedimentary basins such as the livermore basin which may experience particularly strong shaking during an earthquake are imaged in the model the accurate earthquake locations and focal mechanisms obtained by using the 3d model allow us to study fault complexity and its implications for seismic hazard the relocated hypocenters along the hayward fault in general are consistent with a near vertical or steeply east dipping fault zone the southern hayward fault merges smoothly with the calaveras fault at depth suggesting that large earthquakes may rupture across both faults the use of the 3d velocity model reveals that most earthquakes along the hayward fault have near vertical strike slip focal mechanisms consistent with the large scale orientation and sense of slip of the fault with no evidence for zones of complex fracturing acting as barriers to earthquake rupture online material velocity model validation experiments and additional seismicity plots

a global review of the late mississippian carboniferous gigantoproductus brachiopoda faunas and their paleogeographical paleoecological and paleoclimatic implications abstract the gigantic gigantoproductus bearing brachiopod fauna is one of the most distinct marine benthic faunas in the late mississippian early carboniferous in terms of its huge size extremely thick shell and delicate costation a global review of 145 different occurrences throughout the world reveals a total of 57 gigantoproductus species recorded our investigation into their spatial and temporal distributions indicates that gigantoproductus was originated from the moscow basin in the middle visean and then in the late visean migrated southwestward to western europe and north africa and eastward to north china south china and japan the genus reaches its acme stage in species diversity and abundance in the late visean then gradually declined in the early serpukhovian and finally disappeared in the late serpukhovian gigantoproductus and its related genera were distributed mainly in the circum paleotethys region in the tropical and subtropical zones and favored a relatively shallow shelf environment with high energy and warm water condition with little thermal tolerance the absence of the gigantoproductus and its related genera in america suggests the east west rheic seaway was closed before the gigantoproductus fauna appeared in the middle visean the waxes and wanes of the gigantoproductus faunas temporally coincided with the paleoclimatic shift from greenhouse to icehouse stage in the late visean and early serpukhovian and the final extinction of these gigantic brachiopods in the late serpukhovian implies tropical cooling towards the late serpukhovian by the expansion of the lpia glaciers

high precision u pb calibration of carboniferous glaciation and climate history paganzo group nw argentina the duration and geographic extent of carboniferous glacial events in southern gondwana remain poorly constrained despite recent evidence for a more dynamic glacial history than previously considered we report 10 high precision 2 0 1 u pb ages for the permian carboniferous paganzo group nw argentina that redefi ne the chronostratigraphy of the late paleozoic paganzo and rio blanco basins and signifi cantly refi ne the timing of glacial events and climate shifts in the western region of southern gondwana radiometric calibration of the paganzo group indicates three pulses of carboniferous glaciation in the mid visean the late serpukhovian to earliest bashkirian and between the latest bashkirian to early moscovian an abrupt shift in depositional style from high sinuosity single storied fl uvial deposits and clay rich paleosols to low sinuosity multi storied feldspathic fluvial deposits inter calated with eolianites and calcic paleosols is constrained to the latest moscovian and earliest kasimovian these constraints indicate a relatively abrupt climate shift from humid subhumid to nonseasonal semiarid regional climate conditions that occurred signifi cantly earlier than previously inferred early permian this period of high latitude aridity was contemporaneous with a shift to dryland depositional environments and a major vegetation regime shift documented throughout the pangean paleotropics in the pennsylvanian

the mid carboniferous eustatic event stratigraphic and paleontologic evidence from mid carboniferous namurian basin and shelf successions in widely scattered parts of the world indicates that a major eustatic event occurred about 330 ma the event began with a regression that is recorded in most shelf sequences the regression was followed by a brief transgression about 328 ma and the event ended with a transgression that flooded large shelf areas about 325 ma the mississippian pennsylvanian unconformity in north america is a well known product of this event but equally prominent and contemporaneous unconformity surfaces are also present in europe north africa and elsewhere the event is believed to have caused numerous extinctions and it resulted in marked fluctuations in faunal diversity 94 references 2 figures

ice volume and paleoclimate history of the late paleozoic ice age from conodont apatite oxygen isotopes from naqing guizhou china abstract a high resolution and continuous conodont apatite oxygen isotope record spanning the late visean to middle permian is reported from south china which is interpreted with respect to the ice volume and or tropical seawater temperature history of the late paleozoic ice age lpia the presented 18o record shows significant fluctuations in 18o from the late visean to middle permian with highest values observed in the bashkirian early pennsylvanian the 18o maximum coincides with a major eustatic sea level fall recorded in low latitude successions and postdates the significant increases in 87sr 86sr and 13ccarb measured on well preserved brachiopod calcite which can be interpreted as reflecting intensified weathering as consequence of the closure of rheic ocean as well as enhanced carbon burial both processes may have contributed to lower greenhouse gas levels and cooled down the earth s surface triggering the maximum glaciation the high bashkirian 18o values are interpreted to represent the glacial maximum of the lpia a coeval change in faunal composition and a decreasing diversity in climate sensitive marine invertebrates can be ascribed to icehouse cooling and or loss of habitat despite inconsistencies with earlier interpretations that the early permian represented the glacial maximum of the lpia as inferred from gondwanan glacial sediments records the suggested bashkirian glacial maximum agrees well with ice extent estimates based on the regional tectonic history in gondwana which suggests that the bashkirian glaciation occurred during gondwana interior uplift promoting maximum ice cover of the entire lpia however maximum glaciation is only poorly represented in the depositional record because large parts of the glacial deposits were possibly removed by erosion as outlined by a major regional unconformity

high temperature and low oxygen perturbations drive contrasting benthic recovery dynamics following the end permian mass extinction the end permian mass extinction event was the greatest loss of biodiversity ever experienced on the planet the event is thought to have been triggered by the initiation of the volcanic eruptions of the siberian traps the five million year recovery interval that followed the extinction event was strongly influenced by the environmental effects of sustained volcanic eruptions including extreme temperature events and persistent global and regional oxygen minimum zones the effects of these environmental perturbations on the paleoecological recovery of the benthic marine fauna were studied in two depositional units from the southwestern united states representing two substages during the early triassic recovery the smithian sinbad limestone was influenced by high sea surface temperatures and contains a relatively high diversity fauna that exhibits extremely small body size gastropods that lived in this environment were size limited a possible result of metabolic stress due to extreme temperatures these microgastropods were able to become dominate components of the benthic fauna by occupying niche space vacated by other taxa that were excluded by high temperatures the spathian virgin limestone shows evidence for low oxygen conditions the resulting low diversity benthic fauna had a more ecologically complex community structure than the smithian sinbad limestone including the occupation of epifaunal tiering space by crinoids as the prevalence of aerobic facies increased through time diversity body size and the complexity of faunal interactions also increased suggesting that low oxygen conditions were the limiting factor for the benthic recovery in that region the differences in diversity and community structure between the two units highlight the importance of environmental and temporal differences in driving the recovery patterns of the benthic fauna following the extinction event high temperature events and low oxygen conditions restricted the benthic fauna in different ways but both contributed to the delay in recovery from the end permian mass extinction

end ordovician extinctions a coincidence of causes the end ordovician hirnantian extinction was the first of the five big phanerozoic extinction events and the first that involved metazoan based communities it comprised two discrete pulses both linked in different ways to an intense but short lived glaciation at the south pole the first occurring at or just below the normalograptus extraordinarius graptolite biozone mainly affected nektonic and planktonic species together with those living on the shallow shelf and in deeper water whereas the second within the n persculptus graptolite biozone was less focused eradicating faunas across a range of water depths in all about 85 of marine species were removed proposed kill mechanisms for the first phase have included glacially induced cooling falling sea level and chemical recycling in the oceans but a general consensus is lacking the second phase is more clearly linked to near global anoxia associated with a marked transgression during the late hirnantian most recently however new drivers for the extinctions have been proposed including widespread euxinia together with habitat destruction caused by plate tectonic movements suggesting that the end ordovician mass extinctions were a product of the coincidence of a number of contributing factors moreover when the deteriorating climate intensified causing widespread glaciation a tipping point was reached resulting in catastrophe