late paleozoic glacial episodes in gondwanaland reflected in transgressive regressive depositional sequences in euramerica the late paleozoic glaciation of gondwanaland comprised two short episodes in the famennian i and visean ii confined to brazil and adjacent northwest africa and a long episode that started in the namurian iiia of eastern australia and bolivia argentina expanded to cover much of gondwanaland in the stephanian asselian iiib and collapsed in the early sakmarian iiic dropstones in eastern australia indicate that small ice centers lingered to the kazanian across the belt of low latitudes north of gondwanaland short ranging fossils in widespread shallow marine and paralic deposits indicate synchronous deposition of transgressive regressive sequences in different parts of euramerica these sequences correlate with glacial events in gondwanaland at three levels a four major regressions in euramerica in the famennian 1 visean 2 namurian 3 stephanian 4 and the tastubian transgression that preceded the sterlitamakian regression 5 also recorded in gondwanaland correlate with glacial episodes i ii and iiia iiib and iiic b the time interval of cyclothemic deposition in euramerica brigantian or latest visean to sterlitamakian correlates with that of glacial episode iii and c the dominant period of the euramerican cyclothems as estimated from the middle and late pennsylvanian deposits of the mid continent of north america and of the thickest known gondwanaland glacigenic sediment the earliest permian lyons group of western australia is 0 4 ma equivalent in turn to the long orbital eccentricity period of the quaternary ice age and the dominant period of fluctuation of the late miocene antarctic ice cap the three levels of correlations confirm wanless and shepard9s 1936 hypothesis that the late paleozoic cyclothems are controlled largely by sea level fluctuations related to the gondwanaland glaciation

palaeobiogeography and palaeogeographical implications of permian marine bivalve faunas in northeast asia kolyma omolon and verkhoyansk okhotsk regions northeastern russia abstract the paper considers the biogeography and palaeogeographic implications of the permian marine bivalve faunas of northeast asia with a focus on the dynamic relationships between biotic similarities and palaeogeographic distance through an interval of ca 50 million years a stage by stage time series analysis of the biotic similarities between two previously recognized biochores in northeast asia the kolyma omolon and verkhoyan okhotsk provinces has been carried out using both the jaccard and dice similarity indices based on the spatio temporal distributions of 355 permian marine bivalve species in northeast asia the outcome of this analysis combined with other empirical data and previously published tectonic sedimentological and palaeontological information suggests that 1 the bivalve faunas from these two provinces were distinctive from one another as two separate biochores throughout all but the earliest asselian permian stages and 2 the biotic similarities between the verkhoyan okhotsk and kolyma omolon provinces remained consistently low since sakmarian all falling well below the minimum threshold of the jaccard index of 0 42 required for distinguishing marine biotic provinces we interpret these below threshold jaccard biotic similarities as an indication of significant palaeogeographic separation between the verkhoyan okhotsk and kolyma omolon provinces which is in turn considered to indicate rifting and sea floor spreading of the omolon microcontinent and associated terranes and island arcs away from the north asian craton at least from the sakmarian to the beginning of the late permian palaeo distance separation appears to be the primary and most significant biogeographic determinant in accounting for the differences in the spatial distribution of most permian bivalve species in northeast asia several other variables also appear to have played a significant role including regional climate conditions ocean currents and merged island chains as geographic barriers in particular the relatively high biotic similarity between the verkhoyan okhotsk and kolyma omolon provinces during the late wuchiapingian and changhsingian may have been related to the shallowing of the deep water basins oimyakon ayan yuryakh balygychan and sugoi basins that had previously separated the two provinces and the flooding submergence of the okhotsk taigonos volcanic arc system thus allowing the invasion of lower latitude warm water palaeotethyan and even gondwanan species into northeast asia

climate simulation of the latest permian implications for mass extinction life at the permian triassic boundary ca 251 ma underwent the largest disruption in earth s history paleoclimatic data indicate that earth was significantly warmer than present and that much of the ocean was anoxic or euxinic for an extended period of time we present results from the first fully coupled comprehensive climate model using paleo geography for this time period the coupled climate system model simulates warm high latitude surface air temperatures related to elevated carbon dioxide levels and a stagnate global ocean circulation in concert with paleodata indicating low oxygen levels at ocean depth this is the first climate simulation that captures these observed features of this time period

response of late carboniferous and early permian plant communities to climate change abstract late carboniferous and early permian strata record the transition from a cold interval in earth history characterized by the repeated periods of glaciation and deglaciation of the south

dilemma of late palaeozoic mixed floras in gondwana abstract during carboniferous and permian periods the plant fossil assemblages of northern and southern hemispheres were distributed in four floral provinces and each flora had its own characteristics pteridosperms were dominant in the euramerian floras of europe and america cordaitales and equisetales along with angaridium angaropteris represent the angara flora of russia russian federation and far east provinces gigantopteris flora characterizes the cathaysian province of china japan and south east asian countries and glossopteris flora are present in southern hemispheric land masses of gondwana which includes india australia africa south america and antarctica well defined floral provinces quite often show the intermixing of different floristic elements exemplifying the presence of mixed floras the occurrence of mixed floras suggests that they have two modes of distribution one distribution pattern shows mixed floras along the marginal basins of the tethyan region during the middle and late permian another pattern is evident in the gondwana floras where glossopteris floras contain a number of extra gondwanic elements likewise some euramerian cathaysian and angaran floras show the possible presence of glossopterid related elements having comparative morphological features as part of the flora mixed floral elements of northern and southern floras have been examined in detail and it is suggested that in all probability the so called elements of the mixed floras had their ancestry or affiliation with carboniferous floras and during the early permian they duped due to severity of climatic conditions but developed again during late permian when climate became more hospitable for their development the cathaysian and euramerian forms discovered with gondwanan forms in the mixed floras of tethyan region i e hazro saudi arabia new guinea oman jordan kashmir central tibet and southern tibet belong to middle and upper permian sequences and during this time the warm humid and temperate climate helped to revive the northern hemispheric forms which had their endurance in a relatively similar climate of the late carboniferous the morphological conservatism flexibility radiation relationship and analogous features of mixed floral elements have been examined and attempts are made to sort out their disputed presence in different floral provinces

polar glaciers and life at the equator the history of dinantian and namurian carboinferous climate biotic migration patterns provide a history of relative climate change that can be used to study dinantian and namurian carboniferous climates high latitude warming between the middle and late visean may have been caused by the collision of laurussia and gondwana high latitude cooling and equatorial warming between the namurian a and b may have been caused by the onset of glaciation in the southern hemisphere patterns of faunal migration and extinction and floral radiation were similar during namurian and miocene glacial onsets and provide criteria for assessing other extinction events tied to changes in paleoclimate

mississippian early permian brachiopods from western argentina tools for middle to high latitude correlation paleobiogeographic and paleoclimatic reconstruction abstract brachiopod faunas from western argentina are reviewed to improve the current understanding of their biostratigraphic and paleobiogeographic value for intercontinental correlation and paleoclimatic reconstruction especially for middle to high paleolatitudes the oldest faunal assemblage the late tournaisian early visean malimanian fauna indicates an incipient biogeographic segregation of southwestern south america from contemporaneous peri gondwana and northern hemisphere regions likely due to the enhanced thermal gradient that predated the pronounced latest visean global cooling and the major latitudinal biotic differentiation on a global scale paleogeographical distribution of key brachiopod taxa provides evidence of faunal interchange along western gondwana during late early carboniferous the paleoclimate of the region by this time has been interpreted as temperate preglacial conditions in a higher paleolatitudinal setting global cooling and strong differentiation between marine biota of circum polar and paleoequatorial regions occurred after late visean the barrealian fauna rugosochonetes bulahdelia and levipustula assemblages represents the oldest faunal record in western argentina of this major latitude related biotic segregation linked with the onset of the mid carboniferous glaciation the barrealian fauna appeared during a major late visean serpukhovian glacial episode with short lived glacial and interglacial stages climatic fluctuations were probably related to local faunal changes and marine biotic exchange between higher and middle paleolatitudes of southwestern and eastern gondwana widespread postglacial deposits bearing bashkirian faunas demonstrate the beginning of a progressive climatic amelioration trend until early permian times barely affected by short lived colder paleoclimatic fluctuations the incoming of the late bashkirian early moscovian marginovatia maemia fauna was linked to a climatic change in the region following the disappearance of glacial conditions in westernmost argentina ocean currents from the north that reached the region bringing boreal brachiopods were warm enough since bashkirian times to build a thermal barrier for the biotic interchange with peri gondwana regions under subpolar settings and a faunal disconnection was established in addition asymmetrical climatic record between western argentina and regions still under strong glacial influence such as patagonia and eastern australia reflect the clockwise rotation of gondwana and consequent migration of western argentina to lower latitudes after a preceding mainly regressive depositional interval the marine incursion bearing the tivertonia streptorhynchus fauna accompanied the most extensive transgression that covered western argentina it was probably linked with the beginning of a thalassocratic regime by the global major sea level rise of late asselian sakmarian times the tivertonia streptorhynchus assemblage represents a middle paleolatitude temperate and mixed fauna which migrated toward southern gondwana regions indicating a marine faunal connection during a climatic amelioration trend the last marine incursion in western argentina brought the costatumulus fauna linked to a brief interruption of the mostly temperate paleoclimatic conditions established since the pennsylvanian a short lived minor glacial pulse associated with the costatumulus fauna reflected local mitigated climatic fluctuations by the paleolatitudinal gradient to circumpolar areas where a major glacial pulse occurred during sakmarian artinskian times

bimodal character of the late paleozoic glaciations in argentina and bipolarity of climatic changes abstract the upper paleozoic sedimentary rock sequences of argentina show an outstanding record of climatic fluctuations during this interval and the complexity and rapidity of the climatic changes there were two distinct events of cooling or glacial periods the older in the middle carboniferous late visean bashkirian and the younger in the early permian asselian tastubian and these were separated by a long lasting interval of warming during the late pennsylvanian it is postulated that climatic fluctuations in the northern paleotemperate realm may have had the same causes as in argentina and that these periods of cooling and warming probably occurred at the same time in both hemispheres in western argentina and central patagonia the occurrence of the early permian glacial phase and the absence of the younger phases like those present in eastern argentina and south africa suggest that during the final deglaciation in gondwana thawing gradually progressed to the east then located closer to the paleopolar region

the marine permian of east and northeast asia an overview of biostratigraphy palaeobiogeography and palaeogeographical implications abstract the permian marine biostratigraphy faunal successions and mutual correlations where possible throughout east and northeast asia are synthesized region by region based on both published literature and the author s field observations in certain parts of the region the correlation of the permian marine successions of ne asia with the permian international timescale and in particular with gondwanan permian marine sequences remains a major challenge due to profound marine provincialism during the permian however by employing biogeographically mixed faunas from east asia se mongolia ne china south primorye of far east russia and the south kitakami terrane of japan as biostratigraphic gateways coupled with some bipolarly and bi temperately shared permian marine taxa and faunas it has been possible to correlate with reasonable confidence some of the high palaeolatitude permian marine rock units and faunas of ne asia with those of the tethyan region and gondwana palaeobiogeographically the permian marine faunas of east and ne asia are assigned to four major provinces verkolyman sino mongolian japanese cathaysian and panthalassan provinces on the basis of their palaeogeographical distribution patterns and characteristics of faunal assemblages of these the sino mongolian japanese province has considerable significance for regional palaeogeographical plate tectonic and palaeoceanographical reconstructions during the middle permian because of its conspicuously mixed cool and warm water marine biota the origin of this biogeographically mixed marine biota is interpreted to have resulted from a combination of some key factors including the increased tectonic convergence between the bureya jiamusi terrane and the sino korean platform during the permian and the intermingling of both warm and cold water ocean currents off the eastern coastal areas of the bureya jiamusi terrane and the sino korean platform during the middle permian

the permian biostratigraphy of the kolyma omolon region northeast asia the main features of the tectonics permian paleogeography biota structural facies zonation of the kolyma omolon region are analysed the characteristics of the permian regional stratigraphic scale of the kolyma omolon region are described the permian deposits of the kolyma omolon region are divided into four regional stratigraphic subdivisions ranked as superhorizons which in turn are subdivided into nine horizons these horizons are further subdivided into 18 provincial zones lones in accordance with russian stratigraphical nomenclature most of the lones distinguished have dual index species representing the dominant brachiopod and bivalve species the chosen nominal species of these lones are as a rule related to each other phylogenetically and as such they represent key stages in the evolution of their respective taxonomic groups through the permian the resultant biostratigraphic scale is adopted as a regional one for the kolyma omolon chukotka and southeastern part of the verkhoyan okhotsk regions almost all the lones distinguished can also be recognized in the verkhoyansk region and many of the lones are also traceable outside northeast asia q 2006 elsevier ltd all rights reserved

siberian glaciation as a constraint on permian carboniferous co2 levels reconstructions of phanerozoic co2 levels have generally relied on geochemical modeling or proxy data because the uncertainty inherent in such reconstructions is large enough to be climatically significant inverse climate modeling may help to constrain paleo co2 estimates in particular we test the plausibility of this technique by focusing on the climate from 360 to 260 ma a time in which the siberian landmass was in middle to high latitudes yet had little or no permanent land ice our climate model simulations predict a lower limit for co2 the value beneath which siberia acquires excess ice simulations provide little new information for the period in which siberia was at a relatively low paleoaltitude 360 340 ma but model results imply that paleo co2 levels had to be greater than 2 4 modern values to be consistent with an apparently ice free siberia in the late permian these results for the later period in general agree with soil co2 proxies and the timing of gondwanan deglaciation thus providing support for a significant co2 increase before the end permian boundary event our technique may be applicable to other time intervals of unipolar glaciation

high frequency holocene glacier fluctuations in new zealand differ from the northern signature understanding the timings of interhemispheric climate changes during the holocene along with their causes remains a major problem of climate science here we present a high resolution 10be chronology of glacier fluctuations in new zealand s southern alps over the past 7000 years including at least five events during the last millennium the extents of glacier advances decreased from the middle to the late holocene in contrast with the northern hemisphere pattern several glacier advances occurred in new zealand during classic northern warm periods these findings point to the importance of regional driving and or amplifying mechanisms we suggest that atmospheric circulation changes in the southwest pacific were one important factor in forcing high frequency holocene glacier fluctuations in new zealand

distribution and characteristics of mixed transitional mid permian late artinskian ufimian marine faunas in asia and their palaeogeographical implications abstract the permian marine biogeography of the asian region is characterised by the development of three broad realms boreal tethyan and gondwanan in the early early permian asselian to early artinskian there seems to have existed sharp biogeographical boundaries with no transitional zones between the realms presumably due to the effect of gondwanan glaciation and sharp climatic zonation the mid permian late artinskian to ufimian of the asian region is distinguished by the rise of two broad transitional zones in which mixed marine faunas flourished the northern transitional zone north and northeast china sikhote alin central and northeast japan is characterised by an admixture of both warm water cathaysian and cold temperate boreal genera the southern transitional zone arabian peninsula iran afghanistan the karakorum southeast and central pamir salt range central and northwest tibet shan thai terrane timor and western irian jaya on the other hand is distinguished by incorporating faunal elements of both gondwanan and cathaysian origin the mixed faunas of both transitional zones share several antitropically distributed genera e g monodiexodina lytvolasma and spiriferella and are succeeded by palaeotropical tethyan faunas of late permian age it has been postulated that the mixed mid permian fauna of the northern transitional zone was probably formed in an epicontinental sea which was connected to both the asian tethys and the arctic which facilitated the migration of cathaysian and boreal forms into the epicontinental sea and subsequent faunal mixing the formation of the mixed faunas of the southern transitional zone on the other hand is probably related to the breaking off of the cimmerian blocks from northern gondwana and subsequent drifting into a lower latitudinal zone with geographical proximity to both gondwana and cathaysia during the mid permian

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

orbital and co2 forcing of late paleozoic continental ice sheets 1 contrasting views of the size duration and history of the gondwanan continental ice sheets have been proposed from late paleozoic glaciological and sedimentological evidence to evaluate these differing views a coupled ice sheet climate model is used to simulate continental ice sheets under a wide range of late paleozoic orbital and pco2 conditions the model experiments indicate that orbital variations at pco2 concentrations below 2x pre industrial atmospheric levels pal 280 ppm produce large changes in late paleozoic ice volume 1 3 108 km3 and sea level 20 to 245 m between 2 and 8x pal gondwana continental ice is simulated only under the most extreme southern hemisphere cold summer orbit but still produces significant ice volumes 8 12 107 km3 our results highlight the important role of atmospheric co2 in determining the distribution volume and stability of late paleozoic ice sheets factors that ultimately impacted sea level cyclothem deposition and global climate and reconcile disparate views of the late paleozoic ice age

stratigraphic signature of the late palaeozoic ice age in the parmeener supergroup of tasmania se australia and inter regional comparisons abstract recent research in eastern australia has established that rather than being a single long lived epoch the late palaeozoic ice age comprised a series of glacial intervals each 1 8 million years in duration separated by non glacial intervals of comparable duration in order to test whether the glacial events recognized in new south wales and queensland have broader extent we conducted a reappraisal of the parmeener supergroup of tasmania southeast australia a facies analysis of the pennsylvanian to permian section was carried out allowing rationalization of the succession into four recurrent facies associations a glacigenic facies association restricted to the basal pennsylvanian earliest permian wynyard formation and correlatives b glacially cold climate influenced to open marine shelf facies association which accounts for large parts of the permian succession c deltaic facies association which specifically describes the lower permian lower freshwater sequence interval and d fluvial to estuarine facies association which specifically addresses the upper permian cygnet coal measures and correlatives indicators of sediment accumulation under glacial influence and cold climate are restricted to four discrete stratigraphic intervals all of which indicate that glaciation was temperate in nature the lowermost of these incorporating the basal wynyard formation and its correlatives and overlying woody island formation shows evidence of proximal glacial influence subglacial grounding line fan and fjordal facies and is likely a composite of one or more pennsylvanian glacial event s and an earliest permian asselian glacial the second of late sakmarian to early artinskian age comprises an initial more proximal ice influenced section and an overlying more distal ice influenced interval the third kungurian to roadian and fourth capitanian intervals are both distal glacimarine records the four intervals are of comparable age to glacials p1 p4 respectively recognized in new south wales and queensland notwithstanding apparent discrepancies of

co2 forced climate and vegetation instability during late paleozoic deglaciation the late paleozoic deglaciation is the vegetated earth9s only recorded icehouse to greenhouse transition yet the climate dynamics remain enigmatic by using the stable isotopic compositions of soil formed minerals fossil plant matter and shallow water brachiopods we estimated atmospheric partial pressure of carbon dioxide pco2 and tropical marine surface temperatures during this climate transition comparison to southern gondwanan glacial records documents covariance between inferred shifts in pco2 temperature and ice volume consistent with greenhouse gas forcing of climate major restructuring of paleotropical flora in western euramerica occurred in step with climate and pco2 shifts illustrating the biotic impact associated with past co2 forced turnover to a permanent ice free world

permian higher latitude bryozoan biogeography abstract bryozoans from gondwana and northern eurasia are within the higher latitude gondwana and boreal realms respectively and display a clear antitropical faunal distribution with lower diversity than tropical realms within these realms however faunas at highest latitudes are the least diverse and dominated by cosmopolitan genera further separate geological and oceanographic developmental histories of the boreal and gondwanan regions have resulted in the boreal realm showing much higher diversity than its southern counterpart gondwana was in a high latitude position during the permian experiencing the polar climatic conditions of the late palaeozoic ice age and the distribution of bryozoans show a distinct diversity decrease towards cold water high latitudes where the eurytopic fenestrates and trepostomes were the dominant groups the eastern australian margin with the least diverse faunas of the gondwanan realm is oriented north south as a narrow shelf hindering the migration of taxa into the southern coldest environments in contrast northern hemisphere mid to high latitude basins experienced cooling through the permian as pangaea moved northward and tectonics altered oceanographic circulation however glaciomarine deposits were not widespread even at highest latitudes the marine shelf of the northern eurasian margin was broad and oriented west east allowing establishment of widespread stable faunas in waters that became increasingly nutrient fed through the permian from cool water upwelling from the panthalassa ocean in the west this cool water mid latitude setting west east shelf and nutrient enrichment resulted in a boreal realm bryozoan fauna of over 100 genera more diverse than the gondwanan realm with only 61 genera antitropical taxa restricted to boreal and gondwanan realms only include diploporaria lyropora and metelipora however a number of other genera are more abundant outside the tropics even if they occur in all realms these genera include alternifenestella rectifenestella polypora polyporella shulgapora dyscritella stenopora streblascopora pinegopora maychella maychellina ramipora tabulipora and hexagonella the wide nutrient fed mid latitude shelf of the boreal realm also allowed development of a number of endemic taxa or taxa that are rare elsewhere including permoheloclema timanodictya permofenestella lyrocladia wjatkella parafenestralia triznella and gilmouropora in southern gondwana endemic taxa are limited to crockfordia and paramaychella however there is an abundance of evactinostella etherella and liguloclema that are distinctive of western australia

simulated warm polar currents during the middle permian 1 during permian stage 6 wordian kazanian the pangaean supercontinent was surrounded by a superocean panthalassa an ocean general circulation model has been coupled to an atmospheric energy balance model to simulate the sensitivity of the wordian climate 265 million years ago to changes in greenhouse gas concentrations high latitude geography and earth orbital configurations the model simulates significantly different circulation features with different levels of greenhouse gas forcing ranging from a strong meridional overturning circulation in the southern hemisphere at low co2 concentration present level to more symmetric overturning circulation cells with deep water formation in polar latitudes of both hemispheres at high co2 concentration 8 times present level the simulated climate with 4 times present level co2 concentration agrees generally well with climate sensitive sediments and phytogeographic patterns the model simulates strong subtropical gyres with similarities to the modern south pacific circulation and moderate surface temperatures on the southern continent gondwana resulting from a strong poleward heat transport in the ocean an even more moderate climate is generated if high latitude land is removed from the southern continent so that ocean currents can penetrate into the polar regions of gondwana

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

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

self subduction of the pangaean global plate one of the most striking and rare occurrences in the earth s history is the amalgamation of most of the continental lithosphere into one supercontinent the most recent supercontinent pangaea lasted from 320 to 200 million years ago here we show that after the continental collisions that led to the formation of pangaea plate convergence continued in a large wedge shaped oceanic tract we suggest that plate strain at the periphery of the supercontinent eventually resulted in self subduction of the pangaean global plate when the ocean margin of the continent subducted beneath the continental edge at the other end of the same plate our scenario results in a stress regime within pangaea that explains the development of a large fold structure near the apex of the palaeotethys ocean extensive lower crustal heating and continental magmatism at the core of the continent as well as the development of radially arranged continental rifts in more peripheral regions of the plate

a new model for atmospheric oxygen over phanerozoic time a mathematical model has been constructed that enables calculation of the level of atmospheric o2 over the past 570 my from rates of burial and weathering of organic carbon c and pyrite sulfur s burial rates as a function of time are calculated from an assumed constant worldwide clastic sedimentation rate and the relative abundance and c and s contents of the three rock types marine sandstones and shales coal basin sediments and other non marine clastics red beds arkoses by our model values of o2 versus time using a constant total sedimentation rate agree with those for variable sedimentation derived from present day rock abundances and estimates of erosional losses since deposition this agreement is the result of our reliance on the idea that any increase in total worldwide sediment burial with consequently faster burial of c and s and greater o2 production must be accompanied by a corresponding increase in erosion and increased exposure of c and s on the continents to o2 consumption via weathering it is the redistribution of sediment between the three different rock types and not total sedimentation rate that is important in o2 control to add stability to the system negative feedback against excessive o2 fluctuation was provided in the modeling by the geologically reasonable assignment of higher weathering rates to younger rocks resulting in rapid recycling of c and s we did not use direct o2 negative feedback on either weathering of c and s or burial of c because weathering rates are assumed to be limited by uplift and erosion and the burial rate of c limited by the rate of sediment deposition the latter assumption is the result of modern sediment studies which show that marine organic matter burial occurs mainly in oxygenated shallow water and is limited by the rate of supply of nutrients to the oceans by rivers results of the modeling indicate that atmospheric o2 probably has varied appreciably over phanerozoic time during the late carboniferous and permian periods o2 was higher than previously because of the rise of vascular land plants and the widespread burial of organic matter in vast coal swamps a large decrease in o2 during the late permian was due probably to the drying up of the coal swamps and deposition of a large proportion of total sediment in c and s free continental red beds sensitivity study shows that major parameters affecting results are the mean c concentration in coal basins and the relative sizes of the reservoirs of young rapidly recycled versus old rocks less sensitivity was found for changes over time in total land area undergoing weathering and the use of direct o2 negative feedback on marine carbon burial good agreement for rates of c burial calculated via our model and via independent models which are based on the use of stable carbon isotopes indicates that the dominant factor that has brought about changes in atmospheric o2 level and the isotopic composition of dissolved inorganic carbon in seawater over phanerozoic time is sedimentation and not weathering or higher temperature phenomena such as basalt seawater reaction

surficial properties in melas chasma mars from mars odyssey themis data we examine the nature of the surface layer in a small area of the melas chasma region as determined from high resolution thermal and visible mars odyssey thermal emission imaging system themis data as well as how our conclusions compare to past analyses at themis resolution the thermal structure is dominated by local control and all significant thermal variations can be linked to morphology thus themis provides us with detailed images that contain thermophysical information as well allowing us to create a surficial geologic map intended to reflect the surface structure of the region eight units have been defined i blanketed plateaus with thermally distinct craters and fractures ii blanketed canyon walls with rocky edges iii indurated and or rocky canyon wall slide material partially covered by aeolian material iv an anomalous wall region with fluvial like depressions partially filled with particulate material v indurated and or rocky ridged and non ridged canyon floor landslide material mingled with aeolian material vi sand sheets vii indurated and or rocky rounded blocks intermingled with small areas of aeolian material and viii transverse dunes the themis thermal data support conclusions from previous studies but also reveal much more structure than was seen in the past we have found that all significant thermal variations in this region can be linked to morphology but all morphological variations cannot be linked to significant thermal variations themis visible images provide an intermediate resolution that bridges the gap between moc and viking and allow for a more meaningful interpretation of the geologic context of a region surfaces indicate that landslides were an important geologic process long ago shaping the canyon walls and floor while aeolian processes have subsequently altered the surface layer in many locations and may still be active

the marine upper palaeozoic in patagonia tepuel genoa basin chubut province argentina 85 years of work and future prospects abstract argentina is a special place to study late palaeozoic life and environmental change because of the excellent exposures of late palaeozoic sedimentary sequences in particular patagonia has an almost continuous late palaeozoic succession containing well preserved faunal assemblages characterized by both strong endemism and distinctive palaeobiogeographic links to australia and northeast asia in this contribution an overview of the current knowledge of the invertebrate faunas of patagonia and their biostratigraphic and palaeobiogeographic significance are presented along with comments on the future prospects of research in the light of new findings the late palaeozoic outcrops in central western patagonia belong to the tepuel genoa basin chubut province argentina then located in southwestern gondwana during the late palaezoic in this basin the succession is 6000 m thick and constitutes a continuous and complete succession from the lower carboniferous to lower permian as such it has the potential to serve as an important reference section for regional and intercontinental correlations the marine late palaeozoic of patagonia has yielded abundant and well preserved representatives of most invertebrate groups brachiopods bivalves gastropods cephalopods hyolithids pelmatozoans ostracods and cnidarians recently studies of the patagonian faunas have resulted in different opinions on the ages of the faunas biostratigraphic correlation is complex due to strong faunal provincialism for this reason there are several hypotheses concerning the biostratigraphic zonation in the basin since 1920 when studies of late palaeozoic strata in patagonia were first carried out numerous papers on stratigraphic palaeogeographic and taxonomic subjects have been published but our knowledge of carboniferous permian fossils from the tepuel genoa basin is still incomplete at present we are attempting to integrate and calibrate the different faunal associations with a view to achieving a unified biostratigraphic biozonation scheme and hence a much improved understanding of the palaeobiogeographic relationship of patagonian faunas with those from western argentina and other continents currently detailed stratigraphic and palaeontological research is being done in the type section of the tepuel genoa basin the aim of our studies is to integrate all partial sequences exposed throughout the basin and to propose a biostratigraphic chart based on key invertebrate taxa once this goal is achieved a global correlation can be conducted especially with other sections in gondwana and the arctic

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

oxygen isotope values from high latitudes clues for permian sea surface temperature gradients and late palaeozoic deglaciation abstract the permian was a period of waning large scale continental glaciations in the southern hemisphere the waning of these ice sheets during the early permian led to discharge of 18o depleted ice melt water into the oceans this coupled with rising seawater temperatures resulted in a concomitant decline of about 2 5 in the 18o of seawater as recorded by brachiopod shells from low latitude

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

mid carboniferous deglaciation of the protoprecordillera argentina recorded in the agua de jaguel palaeovalley abstract the agua de jaguel formation near uspallata mendoza province argentina was deposited within a palaeovalley along the southeastern margin of the calingasta uspallata basin adjacent to the protoprecordillera the basal glacigenic sequence of the formation was deposited in the serpukhovian early bashkirian near the beginning of the late palaeozoic ice age the sequence is composed of diamictite conglomerate sandstone and mudrock and records four depositional stages within a palaeofjord 1 morainal bank deposition by a wet based tidewater glacier 2 glacial retreat succession where ice retreated up the fjord out of the immediate area allowing iceberg deposition of dropstones and dump deposits 3 continued glacial retreat with ice receding onto land allowing a shoreface to develop within the palaeovalley and 4 transgression across the shoreface and resumption of iceberg deposition the thickness and facies of this succession are similar to deposits within modern alaskan fjords housing temperate tidewater glaciers comparison of the agua de jaguel formation with alaskan fjords indicates that sequence stratigraphy used for low latitude deposits must be applied with caution as glacimarine ice retreat within a fjord produces strata surfaces that are easily misidentified as flooding surfaces resulting from changes in water depth likewise the transgression during stage 4 is significant as it indicates a rise in sea level that occurred during glaciation of the protoprecordillera thus suggesting that the transgression between stages 3 and 4 was not driven by input of glacial meltwater additionally the sediment geochemistry suggests that the bottom waters of the palaeovalley were anoxic which may help explain the absence of bioturbation in the sequence as well as in other ancient glacimarine palaeovalleys the deglaciation succession and transgression are also recorded in the nearby hoyada verde and tramojo formations so it is proposed that all three formations record one glacial event in the protoprecordillera overlying fluvial and shallow marine strata in the agua de jaguel hoyada verde and tramojo formations show no indication of continued glaciation in the protoprecordillera following stage 4 and equivalent strata the deglaciation succession of the agua de jaguel formation affirms the emerging concept that the late palaeozoic ice age was characterized by alpine glaciers ice caps and small ice sheets that were not massive enough to have driven eustatic fluctuations of 100 m as previously understood and that ice never covered westernmost gondwana during later lpia events

late palaeozoic global changes affecting high latitude environments and biotas an introduction abstract the late palaeozoic ice age lpia spanning approximately from 320 ma serpukhovian late mississippian to 290 ma mid sakmarian early permian represents the vegetated earth s largest and most long lasting regime of severe and multiple glaciations involving processes and patterns probably comparable to those of the last ice age accompanying the lpia occurred a number of broadly synchronous global environmental and biotic changes these global changes as briefly reviewed and summarized in this introductory paper comprised but are not limited to the following massive continental reorganization in the lead up to the final assembly of pangea resulting in profound changes in global palaeogeography palaeoceanography and palaeobiogeogarphy substantially lowered global atmospheric carbon dioxide concentrations p co 2 coupled with an unprecedented increase in atmospheric oxygen concentrations reaching earth s all time high in its last 600 million year history sharp global temperature and sea level drops albeit with considerable spatial and temporal variability throughout the ice age and apparently a prolonged period of global sluggish macro evolution with both low extinction and origination rates compared to other times in the aftermath of the lpia the world s climate entered into a transitional climate phase through the late early to middle permian before its transformation into a greenhouse state towards the end permian in recent years considerable amount of data and interpretations have been published concerning the physical evidence in support of the lpia its broad timeframe and eustatic and ecosystem responses from the lower latitudes but relatively less attention has been drawn to the impact of the ice age on late palaeozoic high latitude environments and biotas it is with this mission in mind that we have organized this special issue with the central focus on late palaeozoic high latitude regions of both hemispheres that is gondwana and northern eurasia our aim is to gather a set of papers that not only document the physical environmental changes that had occurred in the polar regions of gondwana and northern eurasia during the lpia but also review on the biotic responses at different taxonomic ecological and spatial scales to these physical changes in a refined chronological timeframe this introductory paper is designed to provide a global context for the special issue with a brief review of key late palaeozoic global environmental changes including changes in global land sea configurations atmospheric chemistry global climate regimes global ocean circulation patterns and sea levels and large scale biotic biogeographic and evolutionary responses followed by a summary of what we see as unresolved scientific issues and various working hypotheses concerning late palaeozoic global changes and in particular the lpia as a possible reference to future research

earliest permian brachiopod faunas of west central argentina defining the pennsylvanian permian boundary in gondwana abstract late palaeozoic marine successions in the west central argentinian basins have one of the most complete stratigraphic records of the earliest permian in gondwana two brachiopod faunal assemblages characterize this interval the tivertonia jachalensis streptorhynchus inaequiornatus fauna widely documented in the rio blanco and western paganzo basins and the costatumulus amosi fauna identified in the earliest permian successions of the southern calingasta uspallata basin this study reviews the composition and biostratigraphy of these two brachiopod faunas with special reference to their global significance for defining the carboniferous permian boundary in gondwana and deciphering the early permian climate change in western gondwana

volcanism mass extinction and carbon isotope fluctuations in the middle permian of china the 260 million year old emeishan volcanic province of southwest china overlies and is interbedded with middle permian carbonates that contain a record of the guadalupian mass extinction sections in the region thus provide an opportunity to directly monitor the relative timing of extinction and volcanism within the same locations these show that the onset of volcanism was marked by both large phreatomagmatic eruptions and extinctions amongst fusulinacean foraminifers and calcareous algae the temporal coincidence of these two phenomena supports the idea of a cause and effect relationship the crisis predates the onset of a major negative carbon isotope excursion that points to subsequent severe disturbance of the ocean atmosphere carbon cycle

tropical atlantic thermal structures along the europe brazil ship line beginning in 1981 expendable bathythermograph xbt temperature sections down to 460 meters have been made two to three times per month between 20 n and 20 s along the ship of opportunity line from europe to brazil three thermal zones are described the guinea dome at 10 n 15 n the equatorial region and the brazilian warm waters between 2 s and 18 s the guinea dome is characterized by a shallow thermocline with little seasonal cycle and a doming or surfacing of the isotherms in the equatorial region the thermocline is almost flat but moves up and down with the season and the changes in the trade winds in the brazilian warm waters the mixed layer is always thick with some seasonal cycle and the thermocline spreads from 100 meters down to the maximum depth of the measurements the presence of absence of the major currents is infered from the slopes of the thermocline the most striking event of the period is the development of a warm anomaly in conjunction with light trade winds during the southern hemisphere warm seasons of 1982 1983 and 1984 reaching 1 5 c over a large area in april 1984

late paleozoic tropical climate response to gondwanan deglaciation coupled climate biome model simulations of the late paleozoic were developed to determine the response of pangean tropical climate to gondwanan deglaciation the model simulations predict substantial changes over equatorial pangea including continental drying a reversal of equatorial winds warming heavier 18 o values of meteoric precipitation and the expansion of deserts and the contraction of forests the magnitude of these tropical responses is sensi tive to the extent of gondwana continental ice and the deglacial rise in atmospheric pco 2 boundary conditions that are not well known for the late paleozoic nonetheless the model predictions are consistent with climatic and environmental trends determined from terrestrial proxy data implying that the deglaciation of gondwana was a transformational climate event in tropical pangea

stratigraphic imprint of the late palaeozoic ice age in eastern australia a record of alternating glacial and nonglacial climate regime stratigraphic and sedimentological data from new south wales and queensland eastern australia indicate that the late palaeozoic ice age comprised at least eight discrete glacial intervals each 1 8 ma in duration here termed glaciations separated by nonglacial intervals of comparable duration these events spanned an interval from mid carboniferous c 327 ma to the early late permian c 260 ma and illustrate a pattern of increasing climatic austerity and increasingly widespread glacial ice from initial onset until an acme in the late early permian followed by an opposite trend towards the final demise of glaciation in the late permian the alternating glacial nonglacial motif suggests that the late palaeozoic ice age was considerably more dynamic than previously thought these patterns are remarkably consistent with recent interpretations of palaeofloral change eustatic sea level fluctuations and co 2 climate glaciation relationships for this interval of time the detailed record of alternating glacial and nonglacial climate mode disclosed herein may facilitate more closely resolved evaluations of stratigraphic records elsewhere notably in far field ice distal northern hemisphere successions

the magnitude of late paleozoic glacioeustatic fluctuations a synthesis a comprehensive literature review shows that the magnitude of eustatic fluctuations varied throughout the carboniferous and permian and that at least eight distinct phases can be recognized facies juxtapositions in carbonate successions and erosional relief in clastic successions indicate that glacioeustatic fluctuations of 20 25 m and occasionally as much as 60 m took place throughout the early mississippian tournaisian a widely recognized glacial period middle mississippian mid chadian through holkerian shallow marine carbonate and clastic successions indicate that eustatic fluctuations were 10 25 m a decrease that matches well with the paucity of coeval glacial deposits late visean asbian through mid brigantian glacioeustatic fluctuations of 10 50 m record the initial phases of ice accumulation in advance of the widespread mid carboniferous glacial event the latest mississippian earliest pennsylvanian mid brigantian through langsettian was a time of widespread glaciation and strata of this age commonly exhibit evidence of glacioeustatic fluctuations of as much as 40 100 m although middle pennsylvanian duckmantian through asturian glacial deposits are present in eastern australia paleovalley depths suggest that coeval glacioeustatic fluctuations were less than 40 m glacioeustatic fluctuations of as much as 100 120 m have been widely reported from late pennsylvanian earliest permian stephanian through mid sakmarian successions in north america an increase that corresponds to the growth of large ice sheets across much of gondwana and the accumulation of ice in the northern hemisphere incision and facies juxtaposition in early middle permian mid sakmarian through kungurian successions in eastern australia indicate that glacioeustatic fluctuations of 30 70 m occurred during the waning stages of major glaciation erosional relief in paleoequatorial carbonates and the presence of coeval glacial deposits in australia suggests that eustatic fluctuations of 10 60 m occurred during the final stages of glaciation in the middle to late permian roadian through capitanian but the modest size of most of these fluctuations makes it difficult to isolate the glacioeustatic signature this review demonstrates that far field cyclic successions record changing glacial conditions in gondwana that the magnitude of glacioeustatic fluctuations was directly related to the volume of glacial ice that carboniferous permian glacioeustasy was more variable than previously recognized and that generalizations from short temporal intervals are probably not representative of the late paleozoic ice age as a whole although any attempt to quantify the magnitude of ancient eustatic changes is based on caveats and assumptions this review incorporates the results of over 100 published papers on the topic in an attempt to minimize the errors inherent in any one study

evolution in a cold climate abstract a brief appraisal of marine fossils from high latitudes and episodically cold climate especially in east australia and new zealand during late palaeozoic and early mesozoic times shows patterns of evolution and survival that differ from those adduced for the palaeotropics and northern hemisphere examples taken from amongst phyla scyphozoa bryozoa brachiopoda and classes bivalvia and class cephalopoda suggest these attributes 1 evolution and demise of species and genera proceeded at a rate close to that known for palaeotropical and northern hemisphere macro invertebrates but involved fewer families and orders 2 possibly intraspecific variation was greater amongst southern palaeohemisphere permian species than in those of the permian palaeotropics 3 there was no proven diminution of life at the end of the guadalupian middle permian at southern high latitudes where however the fossil record is meagre for this interval younger wuchiapingian and changhsingian faunas were moderately diverse 4 there is no evidence for a high latitude southern hemisphere anoxic event in the early triassic despite claims of a world wide anoxic interval nor has any substantial volcanic eruption or bolide impact left any marked traces in the sedimentary record 5 as a consequence some major groups such as bryozoa and conulariida staurozoa survived the end permian extinction shock in the southern hemisphere 6 other major groups appear to have survived better in the south than in the north notably mollusc bivalvia and cephalopoda it therefore appears likely that triassic seas were restocked substantially from the southern hemisphere and that the permian extinction shock was asymmetric with respect to latitudes in its distribution and affect