the early permian floras of prince edward island canada differentiating global from local effects of climate change new permian plant specimens are described from prince edward island canada they include attached specimens of leaf and stem genera walchia and tylodendron enabling reconstruction of this early permian conifer al though poorly preserved the study of these floras extends our knowledge of diversity and climate conditions in the re gion by placing these findings in a broader stratigraphic and geographic framework we can document the phytogeographic and climate trends through the carboniferous and permian in the maritimes basin combined data on temporal trends in climate sensitive sediments as well as macrofloral and microfloral diversities generally match the independently derived paleolatitudinal estimates these show the region migrating from the southern subtropics across the equator and into the northern subtropics between the early carboniferous and early permian evaporites and pedogenic carbonates together with low diversity floras match its subtropical position in the early carboniferous in contrast coals are present in the late carboniferous accompanied by high diversity macro and microfloral remains when the region was on or near the equator however the subsequent transition to pedogenic carbonates eolian sands and lower diversity floras is not matched by significant poleward latitudinal motion we ascribe these changes to a de crease in moisture availability as transgressions of epeiric seas became less frequent and finally stopped altogether causing an increase of continentality in euramerica resume cet article decrit de nouveaux specimens de plantes datant du permien provenant de l ile du prince edouard canada ils comprennent des specimens de feuilles et de tiges rattachees de genre walchia et tylodendron permettant la reconstruction de ce conifere du permien precoce bien que ces flores soient mal preservees leur etude etend nos connaissances de la diversite et des conditions climatiques de la region en placant ces decouvertes dans un cadre stratigraphique et geographique plus large nous pouvons documenter les tendances phytogeographiques et clima tiques du carbonifere et du permien dans le bassin des maritimes des donnees combinees sur les tendances temporel les dans des sediments sensibles au climat et des diversites relatives a la macro et a la microflore concordent generalement avec les estimations de paleoaltitude derivees de facon independante ces donnees montrent qu entre le carbonifere precoce et le permien precoce il y eut une migration des regions subtropicales meridionales par dela l equateur vers les regions subtropicales septentrionales des evaporites et des carbonates pedogenetiques avec des flo res faiblement diversifiees correspondent a sa position subtropicale au carbonifere precoce par contre on retrouve des charbons au carbonifere tardif accompagnes de restes de macro et de microflores grandement diversifiees lorsque la region etait a ou pres de l equateur toutefois la transition subsequente a des carbonates pedogenetiques a des sables eoliens et a une diversite florale moindre n est pas correlee par un mouvement meridien significatif vers le pole nous attribuons ces changements a une reduction de l humidite disponible alors que les transgressions des mers epicontinen tales devenaient de moins en moins frequentes et qu elles ont finalement cesse tout a fait causant une augmentation de la continentalite en euramerique

postapocalyptic greenhouse paleoclimate revealed by earliest triassic paleosols in the sydney basin australia the permian triassic boundary in the sydney basin of australia is coincident with a pronounced decrease in 13 c isotopic values of organic carbon the last coals anywhere in the world for all of the early triassic ca 6 m y time and extirpation of the glossopteris flora at the top of the illawarra and newcastle coal measures coal bearing paleosols of the latest permian represent extensive swamplands of the seasonally deciduous glossopteris flora in a humid cold temperate lowland southwest of an andean style volcanic arc stone rolls large ribs of floor rock up into the coal within some of the uppermost coals of the permian coal measures can be interpreted as string bogs of a kind now found in cold climates at latitudes of 68 70 which is compatible with a paleomagnetically estimated paleolatitude of 65 85 s for the sydney basin paleolatitude was not much different for earliest triassic time but paleosols of that age include inceptisols and entisols showing substantial chemical and textural weathering more like soils now forming at latitudes of 40 58 than those within polar circles this anomalous high latitude warmth set in at the permian triassic boundary sedimentation rates increased at the boundary marked by geochemically unusual acidification of clay and a dramatic carbon isotopic excursion these changes in environments and ecosystems can be explained by soil erosion following deforestation implied by the plant extinctions and abundant fungal remains at the permian triassic boundary evidence from paleosols can now be added to that from paleontological and isotopic studies showing that disruption of the carbon cycle at the permian triassic boundary resulted in a co 2 or ch 4 post apocalyptic greenhouse paleoclimate

raw material quality and oldowan hominin toolstone preferences evidence from kanjera south kenya the role of raw material quality in oldowan technology has not been fully explored there are numerous studies suggesting oldowan hominins preferred certain types of stone for artifact manufacture previous studies of the artifact assemblage from the early pliocene oldowan locality of kanjera south south rachuonyo district kenya show that raw material selection and transport was an important aspect of late pliocene hominin adaptations yet the exact properties of stones that hominins were selecting remain enigmatic two potentially important features of artifact raw material are durability and fracture predictability we investigate fracture predictability through mechanical tests of stone and investigations of the affect of stone properties on fracture patterns in archaeological collections we investigate stone durability with actualistic studies of edge attrition combined with further mechanical tests of various lithologies oldowan hominins at kanjera appear to have selected raw materials based on their durability the ability for a stone to fracture consistently does not appear to be as important in hominin toolstone preference as previously assumed hominins that produced the assemblages at kanjera south appear to have incorporated an extensive understanding of various attributes of raw material in the transport and production of stone artifacts when combined with previous research on the transport patterns at kanjera the results of this study provide evidence for a more complex raw material acquisition strategy than has previously been suggested for late pliocene oldowan hominins

peltasperms in the permian of india and their bearing on gondwanaland reconstruction and climatic interpretation abstract we report on the first find of peltasperms in the permian of gondwana well preserved leaf compressions and reproductive structures of these plants came from the lower permian barakar formation of satpura basin central india where they co occur with diverse glossopterids the indian peltasperm record is evidence of floristic exchanges between laurasia and gondwana in the early permian involving a dominant group of north american european arboreal vegetation of the time the phytogeographic differentiation leaf micromorphology and stratigraphic occurrence of permian peltasperms suggest a thermophilic group appearing in central india during the transition from humid peat forming to seasonally dry redbed environments therefore peltasperms are unlikely invaders to high latitude cool temperate zone postulated for early permian australindia instead their satpura occurrence assigns the indian subcontinent in the equatorial zone of mixed laurasian gondwanan floristic assemblages

first report of cisuralian early permian charcoal layers within a coal bed from baode north china with reference to global wildfire distribution abstract fossil charcoal is reported for the first time from a cisuralian coal bed of the shanxi formation in the qiaotou section baode shanxi north china based on anatomical characteristics these charcoal fragments consist of coniferous or cordaitalean xylem unidentified primary xylem and cordaitalean and possible fern leaves these charcoal fragments represent the evidence of palaeowildfire taking place in tropical peat swamps during the cisuralian in cathaysia the palaeowildfire is most likely to be a surface fire and burning litter and shrubby vegetation fire frequency for this early permian peat swamp might have been on the order of 176 294 588 1429 years close to modern values compared with modern analogues the north china block during the cisuralian was probably wet in general but could be occasionally seasonally dry for short time intervals previous charcoal and inertinite records moreover indicate that palaeowildfires were globally common during the cisuralian overall more wildfire evidence was found in the artinskian kungurian than the asselian sakmarian except in the euramerican realm probably due to more suitable regional climate vegetation to fuel fires and taphonomic circumstances

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

silica burp in the eocene ocean the eocene was a time of greatly increased silica accumulation in the ocean and the peak was in the early middle eocene at about 50 ma the responsible geohistorical configuration included the following elements extensive volcanism about 4 m y earlier as part of the chron 24 plate reorganization early eocene warming with deep weathering to high latitudes and accumulation of the released silica in a sluggish ocean and sharp cooling in the earliest middle eocene stimulating oceanic upwelling and biosilicification it is possible on the evidence of carbon and oxygen isotopic patterns that the trigger for the exhalation of silica was a reverse greenhouse effect

role of increased marine silica input on paleo pco2 levels changing the supply of silica to the ocean may alter pco2 levels the increase in dust delivered to the ocean during glacial times increased the availability of silica for biological uptake the increased silica levels shifted species composition diatom populations increased and coccolith populations decreased decreasing the population of coccoliths decreased the flux of calcite to the sediments which in turn lowered pco2 levels enough to explain the glacial interglacial pco2 transition furthermore the contemporary increase in dust delivered to the ocean s mixed layer may be removing significant amounts of carbon dioxide from the atmosphere at present to set the stage this silica hypothesis is compared with the iron fertilization and nitrogen fixation hypotheses

faunal turnover and changing oceanography late palaeozoic warm to cool water carbonates sverdrup basin canadian arctic archipelago abstract carbonate sedimentary rocks in the fosheim hamilton sub basin at the eastern end of the sverdrup basin contain a particularly sensitive record of changing palaeoceanography and faunal turnover during the northward movement of pangaea through the late palaeozoic carboniferous and earliest permian inner ramp carbonates are a photozoan association of colonial corals fusulinids algae and ooids with sparse heterozoan elements crinoids brachiopods and bryozoans based on modern analogues these biotic components reflect warm water oligotrophic marine environments contemporaneous mid ramp and basin biotas are dominated by a heterozoan fauna solitary corals crinoids bryozoans and brachiopods that grew in cooler deeper waters that may have been beneath a thermocline initial cooling began in the latest sakmarian with an influx of cool deep water and climatic deterioration allowing cool and warm waters to mix disrupting the thermocline and producing a sub tropical marine biota whose remains were reworked by storms and re deposited as tempestites faunas are heterozoan crinoids bryozoans brachiopods and sponges with photozoan elements colonial corals and symbiont bearing fusulinids prominent only in inner ramp facies by late artinskian these photozoan components are only present in shallowest basin margin environments artinskian subtropical waters contained somewhat elevated trophic resources that together with mixing of photozoan and heterozoan elements in the subtropical inner ramp produced the greatest faunal diversity seen in the sverdrup basin the biota was completely boreal in nature and warm shallow waters with a warm refuge biota were now supplemented by cool waters derived from the panthalassa ocean profound change took place in the kungurian coincident with localised uplift during the melville disturbance and increased siliciclastic input neritic storm dominated sediments are wholly heterozoan brachiopods bryozoans crinoids and sponges with no remaining photozoan elements nutrient levels are elevated but not eutrophic as indicated by phosphate and glauconite extensive bioerosion numerous infaunal foraminifers and an impressive and diverse shelly biota that during times of high siliciclastic input was replaced by a profuse zoophycos infauna brachiopod and bryozoan faunas are distinctly boreal continued cooling relatively high nutrients as indicated by abundant glauconite and phosphate and decreased siliciclastic input eventually resulted in an abundant heterozoan biota brachiopods bryozoans crinoids and sponges with local gigantism but reduced brachiopod and bryozoan diversity these middle permian rocks may be the coolest water deposits in the sverdrup basin the faunas are still part of a boreal arctic province with strong ties to cool water faunas of uralian basin the succession ends with late permian biosiliceous spiculitic cherts containing accessory heterozoan components brachiopods bryozoans and few crinoids these sediments in part coeval with evaporites and terrestrial red beds on the eastern european platform are interpreted to reflect a combination of cool waters elevated nutrients and mid latitude storminess

permian climates evaluating model predictions using global paleobotanical data the most recent global icehouse hothouse climate transition in earth history occurred in the permian warmer polar conditions relative to today existed from the middle permian through the mesozoic and into the cenozoic we focus here on one particularly well correlated middle permian stage that postdated the deglaciation the wordian 267 264 ma integrating floral and lithological data to determine wordian climates globally paleobotanical data provide the best means of interpreting terrestrial paleoclimates often revealing important information in the continuum between dry and wet end member lithological indicators such as evaporites and coals new statistical analyses of wordian floras worldwide have enabled a greater understanding of original vegetation patterns and prevailing climate conditions the derived climate interpretations are compared with new wordian atmospheric general circulation model simulations the model matches the data well in the tropics and northern high latitudes but predicts colder conditions in southern high latitudes we discuss possible reasons for this discrepancy

silica secreting biota and mass extinctions survival patterns and processes abstract high survival and at least regional blooms of siliceous marine groups with coeval retreat of calcareous organisms is known from the frasnian famennian radiolarians silicisponges and end cretaceous diatoms radiolarians mass extinctions a strictly actualistic approach to the palaeoecology of silica secreting biota is of limited significance especially for silica enriched and oligotrophic palaeozoic epeiric seas and in particular during biotic turnovers adaptation among silica secreting marine plankton has led toward more efficient utilization of shrinking dissolved silica resources within surface waters of cenozoic oceans as shown by both radiolarians and diatoms this biosiliceous signal during the major biotic crises is mostly explained by a large scale increase in volcano hydrothermal activity during major plate boundary re arrangements triggering global ecosystem perturbations the cumulative stimulus favoured siliceous versus calcareous biota growth deposition and preservation because of 1 a higher rate of input of silica and other nutrients promoting eutrophication pulses 2 a punctuated or reversed greenhouse climatic effect episodically coupled with 3 vigorous oceanic circulation due to a variety of volcanogenic upwellings and turnovers siliceous communities adapted to more eutrophic conditions have thrived in the stressed niches on the other hand expanding anoxia and nutrification may lead to a stepwise loss of deep water niches and consequent selective decline of more specialized oligotrophic radiolarians and other pelagic biota by contrast siliceous faunas experienced severe non selective losses during the end permian mass extinction recorded as a chert gap thus the greatest environmental disaster of the phanerozoic was driven by a unique set of killing factors extremely effective for radiolarian productivity e g due to the combination of a drastic volcanic winter with expanding superanoxia

methanogenesis in eocene arctic soils inferred from δ13c of tree fossil carbonates we report on the carbon and oxygen stable isotope composition of fossil tree material collected at the white mountain locality of the buchanan lake formation on axel heiberg island in the high arctic of canada the fossils are middle eocene in age and have been permineralized with carbonate microscopic examination of fossils revealed them to be the remains of metasequoia stems composed of secondary carbonate calcite and original wood intermingled at the cellular level because the specimens show little compression crushing or tissue degradation we believe that carbonate permineralization occurred soon after burial and therefore provides insight into eocene carbon cycling at the locality the carbon isotope signature of the carbonate suggests that methanogenesis resulted in a 13 c enriched co2 pool that equilibrated with soil water and gave rise to unusually 13 c enriched caco3 tree fossil carbonate exhibited strikingly high d 13 c values 4 0 to 7 4x compared to published phanerozoic pedogenic carbonate d 13 c values these d 13 c values in conjunction with fractionation factors a previously determined for carbonate precipitation and methanogenic pathways indicate an eocene soil co2 pool containing 80 95 co2 produced as a by product of acetate fermentation methanogenesis because methane in the atmosphere is a powerful greenhouse gas we suggest that methane emissions from axel heiberg soils contributed to the relatively warm arctic climate during the middle eocene d 2004 elsevier b v all rights reserved

diagenetic cycling of nutrients in seafloor sediments and the carbonate silica balance in a paleozoic cool water carbonate system sverdrup basin canadian arctic archipelago abstract seafloor processes are often destructive of biogenic remains while at the same time promoting growth of authigenic minerals such as hematite fluorapatite glauconite and chalcedony middle to late permian sedimentary rocks in the sverdrup basin are cool water marine sandstones shales limestones and cherts rich in carbonate and siliceous biotic components the authigenic minerals hematite fluorapatite glauconite and chalcedony are abundant from the interactions of nutrient elements silica phosphorus and iron with carbonate and siliceous biotas in ramp environments of variable energy and sediment accumulation rate these authigenic phases represent in part faunas that are no longer preserved and should not be viewed simply as diagenetic products early middle permian siliciclastic rocks the assistance formation contain carbonate heterozoan biotas with widespread siderite and hematite and local void filling phosphate deposited under moderate sediment accumulation rates sponge spicules were dissolved unless encased in hematite or siderite and incorporated in silica cement in contrast more slowly deposited younger middle permian inboard cherty limestones the lower trold fiord formation underwent frequent physical and biological reworking resulting in dissolution of biogenic silica and precipitation of glauconite and carbonate fluorapatite sediment reworking also excavated and produced rounded glauconite and phosphate clasts much of the glauconite was then oxidized to hematite on the seafloor again unless encased in phosphate sponge spicules were dissolved and the silica precipitated as glauconite or chalcedony coeval deeper water phosphatic cherty limestones the degerbols formation do however contain sponge spiculites reduced sediment reworking led to retention of silica in pore fluids and slowed dissolution of sponge spicules resulting in local preservation of sponge spiculite facies late permian organic rich cherts the lindstrom formation with prolific siliceous sponges and a less plentiful carbonate biota accumulated relatively slowly sponge spicules were preserved and carbonate biota partially dissolved in these organic rich deposits implying that the biota had to be overwhelmingly dominated by siliceous components to overcome ambient silica undersaturation in pore fluids each succession has a distinct composition depending upon the rate of sediment accumulation the original benthic biota and the nature and abundance of silica phosphate and iron in seawater at any given time these characteristics controlled the formation of authigenic minerals and the preservation or dissolution of carbonate and silica biotas

violent volcanism stagnant oceans and some inferences regarding petroleum strata bound ores and mass extinctions past changes from a well mixed aerated ocean to a stratified stagnant ocean are indicated by decreasing 13c of limestone opposite to prior conclusions as well as by increasing 34s of marine sulfates the proposed stagnant ocean model includes a warm co2 enriched atmosphere and a bathyal to abyssal marine system dominated by bacterial components in the food web and by consequent light carbon in organic material and biogenic carbonates culminations of prolonged stagnant episodes correspond with marine faunal extinctions of late permian and late cretaceous time and the protracted changes and correlations provide evidence against any hypothesis of mass extinction by sudden worldwide catastrophe including the asteroid impact hypothesis the cretaceous stagnant ocean taken as the prime example is attributed to climatic warming triggered by volcanic co2 greenhouse effect and several feedbacks including decreased earth albedo and increased sinking of warm evaporite brines instead of aerated polar waters marine extinctions are attributed to upward expansion of the oxygen minimum zone and to catastrophic mixing of surface waters with poisonous sulfidic waters of the deeps the stagnant ocean provided a counterbalance between deep reduction and shallow oxidation conditions that favored maximal formation of black sulfidic shales protopetroleum and sedimentary sulfide ores and shallow to mid depth barite phosphorite iron ore cherty iron formation and sulfate bearing red beds trace elements concentrated in stagnant ocean sediments include chalcophile and pt group metals negating claims that ir provides a unique fingerprint of meteorite impact and cosmic accretion

diffusion in magmas at depth in the earth the effects of pressure and dissolved h2o abstract experimental data on cation diffusion in silicate melts and glasses at atmospheric pressure cannot be quantitatively applied to diffusion in magmas at depth because pressure and dissolved h2o have significant effects diffusivities of ca and cs in soda lime aluminosilicate melt are reduced by roughly an order of magnitude as pressure increases from 1 to 30 kbar at 1100 c in the case of calcium the pressure effect is smaller at higher temperatures the influence of dissolved h2o is opposite to and for some ions far more important than that of pressure at 700 c cs diffusion in granitic obsidian is enhanced by four orders of magnitude by the addition of 6 wt h2o and ca diffusivity increases by 2 5 orders of magnitude sodium diffusion on the other hand is relatively immune to changes in h2o content the retarding effect of pressure on diffusion in deep seated magmas is largely compensated by higher magmatic temperatures such that overall depth effects on diffusion are of secondary importance diffusion rates in mantle melts are probably well approximated by 1 atm near liquidus values diffusion rates in crustal magmas however are extremely sensitive to h2o content so that models of rate controlled processes in hydrous magmas may be grossly in error if 1 atm diffusivity values are used

rock type variability and impact fracture formation working towards a more robust macrofracture method investigations into the development of weapon systems are increasingly important in archaeological debates about human evolution and behavioural variability diagnostic impact fractures are key but controversial lines of evidence commonly used in such investigations in 2009 a series of experiments was initiated to investigate the processes associated with macrofracture formation specifically focussing on the taphonomic factors affecting the formation of diagnostic impact fractures difs this paper adds to that experimental data set with macrofracture results from recent knapping experiments investigating rock type variability and dif formation these results show that rock type variation plays less of a role in dif formation than variables related to use and lithic taphonomy the collective results of this experimental series show that the location co occurrence type and proximity to retouch on a tool are all important means of distinguishing between weapon and non weapon related difs collectively these macrofracture patterns are more important in diagnosing weapon components than any one diagnostic impact fracture is alone overall these experimental studies are showing that background noise in the form of non hunting related impact fractures exists in many macrofracture results and that much work remains in securing the analytical robusticity of the method the paper concludes that the macrofracture method is not a stand alone method but when used with caution and in conjunction with other lines of evidence it is a useful time efficient tool for generating assemblage level use trace data

evidence for a western extension of the angaran phytogeographic province in the early permian abstract a newly described early permian fossil plant assemblage in the mt dall conglomerate in the farewell terrane alaska range usa is analyzed from a paleobiogeographic perspective these data constitute the youngest paleontological dataset yet discovered in this terrane represent the terrane s only predominantly terrestrial fossil assemblage and are the only plant macrofossil remains of early permian age within a 1500 km radius today a suite of multivariate statistical analyses comparing the mt dall paleoflora to similar age asselian artinskian collections from the angaran euramerican and cathaysian permian phytogeographic provinces reveals that the mt dall paleoflora has a paleobiogeographic affinity with sub angaran plant fossil assemblages collected from mongolia and the primorye region of southeastern russia the paleoflora has dual importance in the construction and testing of hypotheses for which there are geographically and temporally few controls first these data may be used in association with other faunal and floral remains to test models of the assembly of alaska which seek in part an understanding of the paleogeographic and lithological origins of accreted terranes that the mt dall paleoflora indicates mixed eurasia north america paleobiogeographic affinity among individual taxa and plots in multivariate space with mid latitude assemblages on northern pangea may suggest deposition in that latitudinal belt second contrary to the well sampled fossil plant bearing permo carboniferous of the paleotropics and the northeastern temperate pangean regions angaraland terrestrial biome structure and vegetation type of northwestern pangea are poorly known this lack of understanding is due to the paucity of paleofloral collections from this region in this time period and the paleogeographic uncertainty of their position along the ancient active margin of laurentia the mt dall paleoflora s phytogeographic affinity to paleobotanical collections from the northeastern pangea therefore suggests that the angaran province extended meridionally westward in the early permian into what is now northern north america

development of a largely anoxic stratified ocean and its temporary massive mixing at the permian triassic boundary supported by the sulfur isotopic record systematic sulfur isotope data for whole rock sulfides have been obtained from the chert dominated continuous pelagic sedimentary sequences spanning the permian triassic p tr boundary at tenjinmaru in the chichibu terrane and at sasayama in the tanba terrane in japan the p tr boundary is characterized by the occurrence of siliceous shales in association with a carbonaceous black mudstone which is similar in appearance to the worldwide distributed cretaceous tertiary k t boundary claystone the observed data clearly demonstrate a significant bimodalism the 34s 32s ratios with respect to cdt are generally low throughout the middle permian ca 39 to 25 0 and show a remarkable increase beginning in the lower upper permian and persisting into the lower triassic ca 20 to 2 0 with a temporary and drastic negative shift down to roughly the same isotopic level as in the middle permian just at the suspected p tr boundary ca 41 to 23 0 interestingly the mode of isotopic excursion across the p tr boundary is in striking contrast to that across the k t boundary which was recently described at kawaruppu in hokkado japan the apparent extent of fractionation with respect to contemporaneous seawater sulfate in the high 34s 32s group lies within the range of 25 10 0 which is quantitatively equivalent to the currently confirmed range of kinetic isotope effect during bacterial dissimilatory sulfate reduction and that in the low 34s 32s group mostly exceeds this range giving the values typically in the range of 45 10 0 which is similar to what is generally observed in the present day oceanic sediments the present data would provide strong evidence for the development of a largely stagnant anoxic stratified ocean which presumably began to form in the lower upper permian and persisted into the lower triassic and for a brief episode of its temporary massive mixing just at the suspected p tr boundary such an oceanic oxic anoxic history may account to some extent for the relatively high enrichments of chalcophile elements in basal triassic sediments in the world and add a significant constraint to the current arguments on the cause and consequence of the terminal permian mass extinction

eocene spiculites and spongolites in southwestern australia not deep not polar but shallow and warm siliceous spongolite and spiculite are generally interpreted as deep and or cold water deposits largely because modern analogs are found mostly in cold and or deep water environments however extensive shallow water biosiliceous accumulations are present in late eocene age deposits of southern western australia the attributes and paleoenvironmental setting of these accumulations frame the specific climatic and or oceanographic constraints that allow such shallow neritic sediments to form the generally fine grained siliciclastic biosiliceous sediments accumulated in a nearshore shallow water setting around numerous islands and offshore from a warm temperate rainforest covered upland sponges compose a lithistid hexactinellid assemblage of mesozoic tethyan affinity confined to deep water in the modern ocean that migrated into neritic paleoenvironments during late eocene time lithistids dominated shoreface environments and were reworked into sponge conglomerate beaches while hexactinellids flourished offshore in muddy subshoreface environments these deposits also contain common soft demosponge spicules and a rare but otherwise normal marine calcareous biota the biosiliceous sediments grade offshore into bryozoan rich marls and limestones sponges outcompeted the calcareous benthos in these inner shelf environments because of elevated amounts of land derived nutrients that included high dissolved silica and a calm hydrodynamic setting these deposits suggest that neither temperature nor water depth are critical factors for prolific sponge colonization the rarity of such deposits in the rock record likely reflects the necessity for the coincidence of all of these factors or they are misinterpreted

a brachiopod calcite record of the oceanic carbon and oxygen isotope shifts at the permian triassic transition the permian triassic p t mass extinction was the most dramatic of all such events but its cause has thus far remained elusive1 3 carbon and oxygen isotope analyses may offer clues to this puzzle because their results identify major changes in the earth s exosystem4 5 several studies have already dealt with carbon and oxygen isotope records at the p t transition2 6 11 but we present here empirical data derived from the brachiopod shell calcite whose isotope composition generally corresponds to that of the sea water in which the animals lived originally12 15 these data allow us to assess quantitatively the magnitude of changes in the earth s exosystem during that critical time interval

the earliest acheulean technology at atapuerca burgos spain oldest levels of the galeria site gii unit abstract this work presents a study of the oldest acheulean lithic assemblages from the galeria site specifically the giia subunit which has been dated to c 503 95 ka and compares them with the subsequent subunit in the sequence giib dated to around 237 269 ka the main goals of this study are to offer a detailed technological characterization of the earliest acheulean presence in atapuerca and to assess the elements determining the technological variability in a given site by studying the sequence evaluating the concept of variability and defining the aspects which determine it the galeria site does not display the features of a living space it is a cave which was accessed by both humans and carnivores in order to obtain the animal biomass of the herbivores that had fallen down into the cave through a natural shaft the archaeological record is therefore incomplete and fragmented since it is the product of highly changeable occupational dynamics in the lower galeria levels we identified the development from an almost exclusive use of cobbles as blanks for knapping activities in the earliest periods to an increasing use of flakes in terms of raw materials the initially predominant use of neogene chert and quartzite evolved towards a more balanced use of six raw materials furthermore there was an increase in the size of the large tools after comparing these two acheulean assemblages it is important to put them into context by taking into account a the significance of cobbles and flakes as blanks b the significance of cleavers and c the use of raw materials such as quartzite sandstone or chert these aspects have traditionally been used to facilitate comparisons of the technologies used within the iberian peninsula and comparisons between the acheulean technology of the iberian peninsula and north africa and the european i e trans pyrenean acheulean technology

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

the early permian thysanophyllum coral belt another clue to permian plate tectonic reconstructions early permian species of the related massive coral genera thysanophyllum stylastraea and protowentzelella are restricted geographically to a narrow belt stretching discontinuously from the southern ural mountains to texas by way of vestspitsbergen canadian arctic islands and the western cordillera british columbia and the basin and range of idaho utah nevada arizona and california in addition limited data suggest that this belt may have extended as far south as peru this coral belt developed at low and intermediate latitudes during early permian time along the northwestern and western margins of the pangaean supercontinent land a very wide paleopacific ocean and temperature barriers prevented these tropical to subtropical shallow water corals from invading similar warm water environments in the tethys ocean on the opposite coast of pangaea where faunas including different types of massive corals developed today the thysanophyllum association is represented in several geosynclinal belts which in the past have been difficult to relate to one another this coral belt therefore may constitute an important key for understanding the relationships between several of these great belts of sediment accumulation and in locating the position of permian continental margins and interpreting some subsequent plate margin tectonic events

the late permian climate what can be inferred from climate modelling concerning pangea scenarios and hercynian range altitude abstract a major unsolved geodynamic problem is the permian pangea plate configuration at the end of paleozoic era around 255 ma while consensual geology indicates a plate arrangement close to that of the jurassic prior to the atlantic opening pangea a paleomagnetic data indicates a nearly 3000 km more eastward position of gondwana with respect to laurussia leading to major plate and relieves reorganisation during permo triassic times pangea b using an atmospheric general circulation model agcm we simulate the climatic response to both configurations we also test the fundamental role of paleo elevations through sensitivity experiments each simulated climate is then compared with the aim of constraining the best fit to a particular paleogeographic scenario main trends of simulated late permian climate in agreement with paleoclimatic indicators are 1 a warm temperate climate accompanied by a monsoon circulation over the eastern side of gondwana 2 a cold temperate climate marked by strong annual thermal amplitude at high latitudes in gondwana and in siberia 3 an arid belt in the subtropics over the western side of gondwana and laurussia and 4 strong climatic differences over both hemispheres respectively main variance is found over laurussia with a simulated tropical climate while an arid climate is suggested by paleodata simulating different paleo elevations of the appalachian and the variscan fold belts can solve this discrepancy the best model data fit is reached for a mean altitude of 4500 m in the appalachians and appears to be dependent of pangea configuration with a southern europe variscan range of some 3000 m in a pangea a configuration or only 2000 m in for pangea b taking into account the geodynamic context we argue that pangea b appears to be the more probable configuration

siliceous sponge communities biological zonation and recent sea level change on the arctic margin ice island results discussion bathymetric profiles bottom camera photographs surface sediment samples and biological samples were obtained through a 44 m long hydrohole in the canadian ice island as it drifted over the canadian polar margin from western ellesmere island to meighen island continuous bathymetric profiles show a 300 km wide shelf with a narrow dissected shallow 200 m inner shelf and a deep 300 800 m sloping outer shelf extensive areas of siliceous sponge communities are present on the seafloor beneath the polar pack ice on the central shelf a clear biological zonation is evident above 130 m large living sponges support a diverse benthic community and form reef mounds up to 10 m high from 130 to 150 m there are few living sponges but extensive mats of sponge spicules are present from 150 to 300 m there are few small living sponges and radiocarbon dating of mud covered spicule mats indicates that formerly extensive sponge communities have died during the past 500 2000 years this zonation may reflec

chemical diffusion of major components in granitic liquids implications for the rates of homogenization of crustal melts abstract crustal anatexis coupled with melt extraction and ascent is the main mechanism by which the continental crust differentiates during diffusion controlled melting and in the absence of melt flow and mechanical mixing diffusion is the main process by which the melt phase ultimately homogenizes and mineral residuum and melt equilibrate knowing the diffusive properties of the elements within a granitoid melts is therefore essential for understanding the kinetics and mechanisms of melting as well as the compositions and nature of chemical heterogeneities in granites in this contribution we review a series of experimental studies aimed at an improved understanding of the nature and rates of chemical diffusion of major components of h 2 o saturated granite melts at anatectic conditions in the continental crust the hydrous granite system under investigation makes up 95 99 of natural restite free granitic magmas these experimental results have applications for predicting the composition of granitic liquids during processes such as anatexis magma mixing assimilation or crystallization regarding the diffusive properties the major elements of the liquid can be classified into two categories those whose diffusion is uncoupled with other elements e g si and others whose diffusion is highly coupled with the movement and gradients of other ions e g na and k with h na k ca and h with al one implication of coupled diffusion is that chemical gradients in fast diffusing ions such as na and k may persist for long times in the melt due to their chemical coupling with slow diffusing components such as al the diffusion of components through granitic melts entails two mechanisms local diffusion corresponds to the classical view of chemical diffusion and refers to the relative and random motion of an ion e g si al under apparently local gradients in chemical potential field diffusion corresponds to the long range and coordinated migration of an ionic species e g na driven by a long range chemical potential gradient created by other melt components with which it associates due to coupled diffusion this mechanism serves to erase compositional gradients at rates that are orders of magnitude greater than those by local diffusion this is because the coordinated movement requires individual ions to move only a small fraction of the entire distance over which the chemical potential gradient is established in order to achieve diffusion over distances that may span the entire liquid system the significance and implications of major element diffusivities and the occurrence of coupled diffusion and field diffusion in granitic liquids are highlighted by calculations of the rates of melt homogenization during anatexis of crustal protoliths

climate of the supercontinent pangea numerous climate models predict that the geography of the supercontinent pangea was conducive to the establishment of a megamonsoonal circulation in general geologic evidence supports the hypothesis of a megamonsoon that reached maximum strength in the triassic pangea in the late carboniferous had widespread peat formation in what is now central and eastern north america and europe and relatively dry conditions on the colorado plateau the equatorial region of the continent became drier through the end of the carboniferous by the permian the equatorial region of pangea was dry and indicators of aridity and rainfall seasonality became more widespread wind directions from colorado plateau eolian sandstones are consistent with an increasing influence of monsoonal circulation at this time in the triassic climate in the colorado plateau region became relatively wet though still seasonal and the few eolian sandstones indicate a major shift in wind direction at that time in addition sedimentation

new early triassic bryozoa trepostomata from spitsbergen with some remarks on the stratigraphy of the investigated horizons new trepostomatous bryozoan species paralioclema winsnesi sp nov paralioclema mariaholmensis sp nov and paralioclema sp cf mariaholmensis are described from the lower triassic succession of spitsbergen the investigated bryozoan faunas are associated with coarse sandstones calcareous siltstones and shelly limestones the bryozoan colonies are mostly well preserved in situ and show limited evidence of transportation some zoarial fragments show bioerosion the conodont species neogondolella elongata ellisonia triassica neospathodus dieneri and neospathodus svalbardensis extracted from the investigated horizons are dienerian smithian in age

late palaeozoic evolution of the north atlantic margin of pangea abstract eleven palaeogeographic maps spanning the earliest carboniferous tournaisian to late permian kazanian have been constructed for the northern north atlantic based on available onshore and offshore data each palaeogeographic map corresponds to an epoch i e 4 17 ma there are no reconstructions of the serpukhovian and tatarian and the kungurian ufimian are treated as one the palaeogeographic reconstructions outline a change in the overall depositional environment of the barents sea north greenland area from huge humid flood plains in the early carboniferous over shallow warm seas in the mid carboniferous to mid permian to cooler and possibly deeper marine environments in the late permian in east greenland non marine conditions occurred during the entire carboniferous and following a prolonged early permian hiatus warm water carbonates were deposited during the late permian the changes reflect large scale shifts in palaeoclimatic and subsidence patterns related to the northward drift of the area and ongoing rifting in the region

permo carboniferous climate early pennsylvanian to late permian climate development of central europe in a regional and global context a well justified stratigraphical correlation of continental successions and new palaeogeographic reconstruction of pangaea reveal new insights into the northern pangaean climate development influenced by palaeogeography palaeotopography glacio eustatic sealevel changes and ocean currents the overall permo carboniferous aridization trend was interrupted by five wet phases these are linked to the gondwana icecap the aridization and weakening of wet phases over time were not only caused by the drift of northern pangaea to the arid climatic belt but also by the successive closure of the rheic ocean which caused the expansion of arid semi arid environments in the lower middle permian the end of the gondwana glaciation rearranged ocean circulation leading to a cold coast parallel ocean current west of northern pangaea blocking moisture coming with westerly winds the maximum of aridity was reached during the roadian wordian the trans pangaean mountain belt was non existent its single diachronous parts never exceeded an average elevation of 2000 m the maximum elevation shifted during time from east to west the hercynian orogen never acted as an orographic east west barrier and the inter tropical convergence zone was widely displaced causing four seasons dry summer winter wet spring autumn at the equator and a strong monsoon system the climate history of the european realm during the late carboniferous pennsylvanian and permian is stored in many solitary basins fig 1 within the hercynian orogen and the foreland basin the story of westphalian climate is well known because of the numerous investigations of the coal bearing variscan foredeep the younger westphalian is characterized by a slight aridization abbink van kronijnenburgvan cittert 2003 oplustil 2004 which was accompanied by an increase of seasonality nevertheless the environment was strongly influenced by the ocean and epi continental seas with multiple transgression events the last extensive marine ingression was the aegir mansfield band westphalian b c the post westphalian climate development is more differentiated and

chemical diffusion in melts on the camgsi2o6 caal2si2o8 join under high pressures abstract this study was designed to obtain data on the rates of chemical diffusion between melt couples of diopside to di 40 an 60 composition and to determine changes in diffusion rates with temperature and pressure chemical diffusion in melts along the join diopside anorthite can be described as binary i e compositions remain on the join in the diffusion zone up to a difference of 20 wt between melt couple compositions for larger concentration differences multicomponent diffusion matrices should be calculated the diagonal elements of these matrices are similar to the effective binary diffusion coefficients determined from the binary diffusion equation but the off diagonal terms are of the same order of magnitude and cannot be neglected pressures up to 20 kbars do not change the diffusion coefficients significantly although a diffusivity maximum may exist near 10 kbars activation energies for mgo and al 2 o 3 diffusion are consistent with a mechanism of individual ionic species diffusing through the melt

evolution of permian conodont provincialism and its significance in global correlation and paleoclimate implication the main components of asselian through artinskian conodont faunas found around the world are basically the same and the provincialism is indicated only by less common endemic elements such as gondolelloides and new genus a henderson in north pangea sweetognathus bucaramangus around the equator and vjalovognathus in eastern gondwana provincialism is marked by differences at the species level of mesogondolella neostreptognathodus and sweetognathus during the kungurian and becomes very distinct with differences at the genus level during the guadalupian and lopingian three provinces of permian conodonts referred to as the north cool water province ncwp the equatorial warm water province ewwp and the peri gondwana cool water province gcwp are recognized the ncwp is marked by gondolelloides in the early cisuralian dominance of neostreptognathodus and no or rare sweetognathus in the late cisuralian dominance of merrillina and mesogondolella and absence of sweetognathus in the guadalupian and dominance of merrillina and mesogondolella and absence of iranognathus in the lopingian the ewwp is characterized by the absence of gondolelloides and vjalovognathus in the cisuralian abundance of sweetognathus and pseudosweetognathus in the kungurian late cisuralian jinogondolella and sweetognathus in the guadalupian and clarkina and iranognathus in the lopingian the gcwp is marked by vjalovognathus merrillina in the cisuralian vjalovognathus merrillina and mesogondolella in the guadalupian and vjalovognathus and merrillina in the lopingian mixed faunas are recognized in regions bordering between the ewwp and gcwp including western timor during the artinskian pamirs during the kungurian and the salt range during the guadalupian and lopingian three different conodont zonations are proposed one for each of the three conodont provinces four potential horizons for inter provincial correlation of permian conodonts are recognized they are in ascending order 1 the first appearance of sweetognathus whitei which is closely related to the last occurrence of carboniferous type conodonts such as streptognathodus and adetognathus 2 the first appearance of neostreptognathodus pequopensis 3 the base of the jinogondolella nankingensis zone and 4 the base of the clarkina postbitteri iranognathus erwini zone the spatial and temporal distribution pattern of permian conodonts suggests that temperature is the primary controlling factor evolution of permian conodont provincialism reveals a glaciation during the asselian and sakmarian a global warming during the artinskian a climate cooling in north pangea during the kungurian a continuation of kungurian climate trends in the guadalupian a relatively minor warming during the wuchiapingian a returned cooling in the changhsingian and lower and middle griesbachian and a global warming in the late griesbachian which ended the permian conodont lineage

kinetics of anorthite dissolution in basaltic melt abstract we report convection free anorthite dissolution experiments in a basaltic melt at 1280 1500 c and 0 5 gpa on two different crystallographic surfaces 1 2 1 and 3 0 2 to investigate dissolution kinetics the anisotropy of the anorthite dissolution rate along these two surfaces is negligible time series experiments at 1280 c show that anorthite dissolution is mainly controlled by diffusion in the melt within experimental uncertainty analytical solutions were used to model the dissolution and diffusion processes and to obtain the diffusivities and the saturation concentrations of the equilibrium determining component al2o3 for anorthite dissolution into the basaltic melt for the first time we are able to show the physical and chemical characteristics of quench growth effect on the near interface melt using high spatial resolution 0 3 m eds analyses for anorthite an 90 saturation in a melt with 39 53 wt sio2 and 0 4 wt h2o the concentration of al2o3 in wt depends on temperature as follows ln c s al 2 o 3 8 032 0 192 7882 287 t where t is temperature in k and errors are given at 1 level al2o3 diffusivity in basaltic melt during plagioclase dissolution can be expressed as ln d al 2 o 3 ebd plag diss 13 69 1 57 19 313 2485 t where d is in m2 s and the activation energy is 161 21 kj mol these results are applied to model the convective dissolution of anorthite in basaltic melts the model indicates that though anorthite crystals can survive for a longer time compared to olivine crystals of the same size in the same melt the former would rise for a much smaller distance compared to the olivine sinking distance due to the smaller density contrast between anorthite and melt

problems of a late palaeozoic glaciation in australia and subsequent climate in the permian the most recent information suggests two periods of glaciation separated by a considerable time interval the first is found in the namurian early carboniferous and may extend into the beginning of the late carboniferous evidence for the carboniferous glaciation is largely or entirely redeposited striated clasts known only from the new england area of northeastern new south wales these are considered to represent montane type glaciation associated with a developing alpine chain after a long interval glacial deposits are then found in many parts of australia in the asselian the lowest stage of the permian and the glaciation may extend into the beginning of the sakmarian the following stage in western australia a number of major fluctuations are recorded in the asselian the end of the glaciation seems to be associated with a worldwide eustatic rise in sea level in the tastubian the lower stage of the sakmarian after the tastubian no direct verifiable evidence indicates glaciation in the permian in australia or any other part of the world in australia there is no clear evidence on the climate in the interval between the two glacial periods but in south america and other parts of the world a warm interval is reported at this time most of the glacial debris is now found in sedimentary basins which were developing contemporaneously with the glaciation and is of a wet based type glaciers were active on steep hinterland carrying debris in adjacent water covered basins but how far the ice may have spread over lower lying land areas in not clear there is no real evidence of a thick dry based ice sheet like that of present antarctica after the tastubian there are a number of major fluctuations in climate during the rest of the permian at times seasonal ice and or perhaps icebergs may have been active but fluctuations which were cool or warm temperate or in some places in australia even subtropical or tropical are found in the sterlitamakian upper sakmarian beginning and end of the baighenzhinian upper artinskian kungurian kazanian and dzhulfian all separated probably by colder and in some cases considerably colder periods comparison of the marine faunas of the carboniferous and permian suggests that the levipustula fauna may not represent as cold sea water as the eurydesma fauna

biogenic facies in the antarctic glacimarine environment basis for a polar glacimarine summary abstract the association of glacial deposits diamicts or tillites with biogenic and or chemically derived sedimentary rocks in the ancient record is one which continues to challenge interpretation an analogous association can be found on portions of the east antarctic continental shelf where relict glacial and glacimarine diamictons are overlain by a varied and complex suite of modern biogenic deposits carbonate bioclastic material can be found in two distinct zones and its deposition may have been contemporaneous with partial glacial expansion onto the shelf a nearshore carbonate facies consists of in situ and partially reworked barnacles bryozoans ostracods pelycepods gastropods planktonic and benthonic foraminifera a siliceous biogenic component is intermixed within the shallow water 500 m siliceous facies of pelagic hemipelagic and sediment gravity flow origin is found within inner shelf depressions and consists predominantly of diatom frustules and radiolaria these accumulations of siliceous ooze and mud clearly post date glacial recession from the shelf and contain laminated cross laminated and massive interbeds which are accumulating at rates of 0 3 cm yr the extreme polar climate inhibits meltwater production and terrigenous influx into marine basins this allows for the accumulation of biogenic rich material which is also favored by the high seasonal productivity inherent in the south polar oceans ancient analogs to these modern deposits exist and their association with glacimarine strata could be used to infer polar climatic settings and glacial retreat that is related to eustatic sea level rather than regional warming

microwear features on vein quartz rock crystal and quartzite a study combining optical light and scanning electron microscopy abstract in general quartz and most of non flint rocks have not been extensively studied from a functional point of view very frequently the definitions of micro features connected with flint surfaces have been used to describe those encountered on non flint tools this circumstance has repeatedly posed serious methodological problems for evaluating the accuracy of functional results when analysing use wear on quartz and quartzite implements this is due to the intrinsic divergences in morphology and distribution of use wear with regard to the different lithic raw materials even though important efforts to systematise use wear features on quartz have been done almost since the beginning of the discipline there continues to be confusion and lack of standardisation regarding terminology in this aspect in this paper we try to contribute to new insights in this research by means of selecting examples from an extensive experimental programme involving different raw materials from rock crystal the purest form of quartz found in nature to vein quartz and quartzite with the latter two materials extensively used for knapping throughout prehistory and still poorly understood in terms of microwear for data recording we preferentially used sequential experiments and resorted to both optical light and scanning electron microscopy we focused our interest on describing the main groups of wear features the results obtained allowed us to assess the different mechanical behaviours under the stressors induced by tool use from a group of raw materials with the same chemical composition but very different in structure furthermore we propose the revision of some terms commonly employed when documenting micro wear on quartz and similar rocks as well as recurring concepts coming from materials and geological sciences e g tribology quartz exoscopy

climate of the late devonian to triassic abstract remarkable changes are apparent in climate during late devonian triassic times mostly the climate was rather different from the present the faunas and floras offer much evidence for understanding the climate but in turn understanding the palaeogeography of the faunas and floras is dependent on understanding the climate and the changes in climate the late devonian apparently had a warm climate the climate of the early carboniferous was warm and equable no cold climate can be identified and apparently no ice was present at the poles even a cold temperate climate is difficult to identify on the other hand the tropical zone does not appear to have been particularly hot apparently this reflects an ocean current system and a weather system different from the present ones during the late carboniferous the world became colder and the faunas and floras more provincial ice probably mountain ice appeared in boreal and austral regions widespread glaciation occurred in the earliest permian but it had a very assymetrical character whether continental ice sheets like those of the pleistocene were present is not proven during the early permian the world became warmer probably with some fluctuation in climate and with evidence for seasonal ice but not for glaciers during the late permian the warming continued and a new kind of provincialism developed within the broad tropical and subtropical zone by the end of the permian the earth was very warm in the early triassic no equatorial humid zone can be identified and whereas the tropical zone was hotter than at present the polar zones were also warm the early triassic appears to have been almost universally dry the climate remained warm during the middle and late triassic but humid zones can be recognized the climate also showed some apparent assymetry the pecularities of the climate and the change of climate in this interval of time are not readily explainable either on the basis of the present climate or the present or a similar distribution of land and sea nor are they readily explainable on reconstructions commonly accepted such as pangaea formed in the carboniferous as is often claimed probably more basic data are required before any satisfactory explanations are possible and as well as terrestrial effects including a change in the angle of the earth s rotation extra terrestrial planetary and galactic effects require study

viscosity of partial melts in the upper mantle the viscosity and density of melts of composition close to primary olivine tholeiite and alkali olivine basalt have been measured at pressures between 0 7 and 1 5 gpa and at temperatures between 1300 and 1475 c using the falling floating sphere method the viscosity of the olivine tholeiite melts decreases only slightly from 1 atm to 1 0 gpa whereas that of the alkali olivine basalt melts decreases by a factor of about 2 in the same pressure range and they become very close to one another about 2 0 pa s at 1 0 1 25 gpa at 1400 c the activation energy for viscous flow of the olivine tholeiite melt is about 250 kj mol at 1 0 gpa the viscosity of partial melts melts formed by partial melting in the upper mantle can be estimated based on the viscosities of the melts and the activation energy for viscous flow obtained by the present experiments the viscosity of the partial melts along the anhydrous solidus of peridotite decreases from about 2 5 pa s at 0 8 gpa 1220 c to only about 0 2 pa s at 3 5 gpa 1580 c thus the partial melts must be extremely fluid at depths greater than 100 km even under anhydrous conditions such partial melts might not ascend because of their high density and play an important role in the movement of the lithosphere the viscosities of the partial melts in the upper mantle may decrease with increasing depth until completion of the transformation of si to six fold coordination the viscosities of magmas and the diffusivity of oxygen in them have an inverse relation which is approximated by the eyring s equation the diffusivity of oxygen in the partial melts estimated from this relation and the viscosity increases from 10 7 cm2 s at 0 8 gpa to 10 5 cm2 s at 3 5 gpa along the anhydrous solidus of peridotite homogenization of partial melts or magmas would be greatly enhanced with increasing depth down to the viscosity minimum

carbonate buildup flank deposits an example from the permian barents sea northern norway challenges classical facies models mounds seen on seismic in the barents sea offshore northern norway occur in the upper palaeozoic of the finnmark platform a 160 m long cored section from such a mound dated as unspecified asselian artinskian lower permian documents a carbonate buildup of microbial origin and rich in stromatactis fabric the cored section of a buildup where depositional dip angles vary from a few degrees to about 45 approximately 2 3 of the flank consists of in situ microbial boundstone with abundant stromatactis and in the upper part bryozoan cement framestone the remainder is gravity flow sediment deposited on the flank and at the toe of the buildup consisting of argillaceous sediment alternating with crinoid grainstones modal thin section analysis indicates that biogenic particles make up 38 of the buildup flank diagenetic products such as early fibrous cement microcrystalline cement and late blocky calcite 46 and lime mud including that interpreted as microbially induced 16 the studied core interval shows that steeply inclined buildup flanks can be largely in situ deposits rather than allochthonous as predicted in classical facies models

late early permian plant fossils from the canadian high arctic a rare paleoenvironmental climatic window in northwest pangea abstract recently discovered megafossil plant remains in late early permian kungurian marine sediments on northern axel heiberg island canadian arctic archipelago provide a much needed datum point for paleobiogeographic considerations in this part of north america the fossil plants represent at least ten families belonging to several major groups sphenopsids ferns pteridosperms ginkgos cordaitaleans and conifers the conifers rufloria and walchia are the most commonly represented taxa while other gymnosperms constitute much of the remaining collection lycopsids are absent and sphenopsids as well as ferns are present but rare the plant material probably originated from crockerland and has a complex taphonomic history there appears to be a strong phytogeographic connection with the angaran floral realm in addition some floral elements occurring here are known mostly from the early mesozoic elsewhere these findings support the idea that plant evolution was most intensive in extrabasinal settings with migration into the depositional lowlands often occurring at times when climatic conditions became favorable for range expansion out of the uplands the axel heiberg island flora is another datum point for rare but significant late early permian age floras on the north american continent

intra raw material variability and use wear formation an experimental examination of a fossiliferous chert sjf and a silicified wood ysw from nw new mexico using the clemex vision processing frame this study is part of an ongoing research initiative designed to further standardize the collection and evaluation of use wear data through the use of a combination of digital image gis and nanoindentation analyses the focus of the present paper is on using digital imaging analysis to evaluate the role of intra raw material variability in use wear formation by experimentally making and using five flake scrapers made from san juan fossiliferous chert sjf and five made from yellow silicified wood ysw both raw materials were commonly used in prehistoric northwestern new mexico the results of clemex digital image analysis show that there is variation in use wear accrual rates between the five sjf flake scrapers and between the five ysw flake scrapers they also show that the degree of this variation differs between sjf and ysw it is argued that understanding this variability is a key element in clarifying the nature of use wear formation and therefore in improving the reliability of its archaeological interpretation

a geomagnetic polarity timescale for the permian calibrated to stage boundaries the reverse polarity kiaman superchron has strong evidence for at least three or prob ably four normal magnetochrons during the early permian normal magnetochrons are during the early asselian base ci1r 1n at 297 94 0 33 ma late artinskian ci2n at 281 24 2 3 ma mid kungurian ci3n at 275 86 2 0 ma and roadian ci3r an at 269 54 1 6 ma the mixed polarity illawarra superchron begins in the early wordian at 266 66 0 76 ma the wordian capitanian interval is biased to normal polarity but the basal wuchiapingian begins the beginning of a significant reverse polarity magnetochron lp0r with an overlying mixed polarity interval through the later lopingian no significant magnetostratigraphic data gaps exist in the permian geomagnetic polarity record the early cisuralian magnetochrons are calibrated to a succession of fusulinid zones the later cisuralian and guadalupian to a conodont and fusulinid biostratigraphy and lopingian magnetochrons to conodont zonations age calibration of the magnetochrons is obtained through a bayesian approach using 35 radiometric dates and 95 confidence intervals on the ages and chron durations are obtained the dating control points are most numerous in the gzhelian asselian wordian and changhsingian intervals this significant advance should provide a framework for better correlation and dating of the marine and non marine permian

a model for atmospheric co 2 over phanerozoic time a new model has been constructed for calculating the level of atmospheric co sub 2 over phanerozoic time which is much simpler mathematically than the blag model but more complex geologically and biologically results suggest that there has been a notable pattern of varying atmospheric co sub 2 level over the past 570 my with high levels during the mesozoic and early paleozoic and low levels during the permo carboniferous and late cenozoic sensitivity analysis shows that within reasonable limits of the principal governing parameters this qualitative trend of varying co sub 2 is relatively insensitive to the actual values chosen for these parameters causes of the co sub 2 variation are multiple and no single geological or biological process can be called upon to explain all co sub 2 variation for all time the calculated trend of co sub 2 over time agrees well with independent estimations of paleoclimates thus the greenhouse theory of paleoclimate on a long geological time scale is supported by the results of the present study

early permian asselian vegetation from a seasonally dry coast in western equatorial pangea paleoecology and evolutionary significance abstract the pennsylvanian permian transition has been inferred to be a time of significant glaciation in the southern hemisphere the effects of which were manifested throughout the world in the equatorial regions of pangea the response of terrestrial ecosystems was highly variable geographically reflecting the interactions of polar ice and geographic patterns on atmospheric circulation in general however there was a drying trend throughout most of the western and central equatorial belt in western pangea the climate proved to be considerably more seasonally dry and with much lower mean annual rainfall than in areas in the more central and easterly portions of the supercontinent here we describe lower permian upper asselian fossil plant assemblages from the community pit formation in prehistoric trackways national monument near las cruces south central new mexico u s a the fossils occur in sediments within a 140 m wide channel that was incised into indurated marine carbonates the channel filling can be divided into three phases a basal channel limestone conglomerate facies contains allochthonous trunks of walchian conifers a middle channel fill is composed of micritic limestone beds containing a brackish to marine fauna with carbon oxygen and strontium isotopic composition that provide independent support for salinity inferences the middle limestone also contains a par autochthonous adpressed megaflora co dominated by voltzian conifers and the callipterid lodevia oxydata the upper portions of the channel are filled with muddy gypsiferous limestone that lacks plant fossils this is the geologically oldest occurrence of voltzian conifers it also is the westernmost occurrence of l oxydata a rare callipterid known only from the pennsylvanian permian transition in poland the appalachian basin and new mexico the presence of in situ fine roots within these channel fill limestone beds and the taphonomic constraints on the incorporation of aerial plant remains into a lime mudstone indicate that the channel sediments were periodically colonized by plants which suggests that these species were tolerant of salinity making these plants one of if not the earliest unambiguous mangroves

growth and demise of permian biogenic chert along northwest pangea evidence for end permian collapse of thermohaline circulation abstract the permian chert event pce was a 30 ma long episode of unusual chert accumulation along the northwest margin of pangea and possibly worldwide the onset of the pce occurred at about the sakmarian artinskian boundary in the sverdrup basin canadian arctic where it coincides with a maximum flooding event the ending of high frequency high amplitude shelf cyclicity the onset of massive biogenic chert deposition in deep water distal areas and a long term shift from warm to cool water carbonate sedimentation in shallow water proximal areas a similar and coeval shift is observed from the barents sea to the northwestern usa a landward and southward expansion of silica factories occurred during the middle and late permian at which time warm water carbonate producers disappeared completely from the northwest margin of pangea biotically impoverished and increasingly narrow cold water carbonate factories characterised by non cemented bioclasts of sponges bryozoans echinoderms and brachiopods were then progressively replaced by silica factories by late permian time little carbonate sediments accumulated in the barents sea and in the sverdrup basin where the deep to shallow water sedimentary spectrum was occupied by siliceous sponge spicules by that time biogenic silica sedimentation was common throughout the world silica factories collapsed in the late permian abruptly bringing the pce to an end in northwest pangea the end permian collapse of the pce was associated with a major transgression and with a return to much warmer oceanic and continental climatic conditions chert deposition resumed in the distal oceanic areas during the early middle triassic anisian after a 8 10 ma interruption early triassic chert gap the conditions necessary for the onset expansion and zenith of the pce were provided by the thermohaline circulation of nutrient rich cold waters along the northwestern and western margin of pangea and possibly throughout the world oceans these conditions provided an efficient transportation mechanism that constantly replenished the supply of silica in the area created a nutrient and oxygen rich environment favouring siliceous biogenic productivity established cold sea floor conditions hindering silica dissolution while increasing calcium carbonate solubility and provided conditions adverse to organic and inorganic carbonate production the northwest margin of pangea was for nearly 30 ma bathed by cold waters presumably derived from the seasonal melting of northern sea ice the assumed engine for thermohaline circulation this process started near the sakmarian artinskian boundary intensified throughout middle and late permian time and ceased suddenly in latest permian time it led to oceanic conditions much colder than normally expected from the palaeolatitudes and the influence of cold northerly derived water was felt as far south southern nevada the demise of silica factories was caused by the rapid breakdown of these conditions and the establishment of a much warmer marine environment accompanied by sluggish circulation and perhaps a reduced input of dissolved silica to the ocean complete thawing of northern sea ice would have ended thermohaline circulation and led to warm and sluggish oceanic conditions inimical to the production accumulation and preservation of biogenic silica

permian triassic mass extinction event recorded in bedded chert sequence in southwest japan rock types in southwest japan change across the permian triassic boundary late permian bedded chert grades upward into latest permian siliceous claystone carbonaceous mudstone of unknown age early triassic siliceous claystone with carbonaceous mudstone and chert interbeds and then into middle triassic to jurassic bedded chert these stratigraphic lithologic variation also accompany the decline and recovery of radiolarians in the changxingian stage and smithian stage respectively the permian triassic boundary is not precisely defined because of poor stratigraphic control but it is thought to occur at the boundary between the carbonaceous mudstone and the changxingian siliceous claystone or somewhere in the carbonaceous mudstone during the griesbachian stage there was deposition of carbonaceous mudstone in deep pelagic seas bioturbation structures and the massive nature of carbonaceous mudstone indicate dysaerobic but not anoxic condition in a strict sense the dramatic decrease in productivity of radiolarians preceded the sedimentation of carbonaceous mudstone which suggests that oxygen deficient conditions were not the primary cause of mass extinction red tide type conditions inferred from the increased primary productivity in the pelagic seas and the oxygen deficiency in the epicontinental seas are the last hit against the biosphere in the chain of events that started from late permian and caused the greatest mass extinction of the phanerozoic correlation between lithologic variations of bedded cherts and 13c excursions of carbonate rocks clarifies the processes of simultaneous massive decline and recovery of biomass as represented in both group of rocks

use wear analysis of the late middle pleistocene quartzite assemblage from the gran dolina site td10 1 subunit sierra de atapuerca spain abstract quartzite has been poorly studied from a functional point of view since the foundation of use wear analysis as the method was largely built upon the observation of wear on fine grained raw materials e g chert in the case of the middle pleistocene gran dolina td10 1 site in spain ca 300 kya the sole raw material that can provide functional information for the artifacts used by the human occupants of the site is quartzite a sample of 51 quartzite artifacts was mainly analyzed with scanning electron microscopy and functional interpretation was possible for 36 of them the activities identified were mostly connected to the butchering of animals but bone and hide scraping as well as woodworking were also present the performance of activities other than butchering supports the idea that the site was used as a residential camp during the deposition of the basal part of the td10 1 subunit lower td10 1 this study demonstrates the possibility of obtaining functional data from relatively ancient artifacts made of a coarse grained lithology considering that metamorphic quartzose materials often dominate early and middle pleistocene lithic assemblages all over the world the standardization of the functional reading of quartzite will allow acquiring countless functional data with which to reconstruct ancient human behavior

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

characterization of the use wear and residues resulting from limestone working experimental approach to the parietal art of la vina rock shelter la manzaneda asturias spain abstract the palaeolithic rock engravings that are located along the nalon river basin in northern spain central area of asturias have been studied from various perspectives morphology depth style manual range but no use wear studies on the stone tools used to produce such engravings have ever been undertaken this paper aims to explore a new approach to this type of incisions based on use wear analysis of experimental lithic tools used to engrave limestone blocks and slabs our results show that the use wear traces generated by engraving limestone are well developed and can be defined with specific criteria the principal objective of this study was to provide the first experimental reference collection of use wear resulting from engraving limestone using flint and quartzite experimental tools to compare with the traces that appear on tools in the archaeological record in contexts with parietal and portable art and more specifically to add a new approach to the multidisciplinary study of the la vina rock shelter

structural study of two quartzite varieties from the utrillas facies formation olmos de atapuerca burgos spain from a petrographic characterisation to a functional analysis design abstract this overall research initiative was undertaken to evaluate the role of lithic raw material variability in use wear formation processes focusing specifically on two lithological varieties of quartzite present in the lower and middle pleistocene lithic assemblages of the gran dolina galeria and sima del elefante sites sierra de atapuerca burgos two arenas de utrillas facies varieties from a sand quarry located in olmos de atapuerca were studied using petrographic and sem analyses they were both identified as metaquartzites revealing differences in their granular structure and metamorphic grade sequential experiments employing the same quartzite varieties were then conducted involving different activities and several worked materials which made it possible to determine use wear formation on these two quartzite varieties the results helped to clarify the role of intra raw material variability in the process of use wear formation on quartzite and contributed to ongoing studies of the lithic materials from these archaeological sites

one million years of cultural evolution in a stable environment at atapuerca burgos spain abstract the present paper analyses the evidence provided by three sites sima del elefante gran dolina and galeria located in the trinchera del ferrocarril of the sierra de atapuerca these three sites are cave infillings that contain sediments deposited from approximately 1 2 ma to 200 kyr pollen herpetofauna and small and large mammal remains are used as proxies to obtain a general picture of the environmental changes that occurred at the sierra de atapuerca throughout the one million year period represented at these sites similarly cultural changes are tracked analyzing the evidence of human behavior obtained from the study of several bone and lithic assemblages from these three sites at least three periods with different cultural features involving technology subsistence and behavior are determined from the available evidence the first two periods correspond to the mode 1 technology and homo antecessor the first is dated around 1 2 to 1 0 ma and reflects opportunistic behavior both in technology and subsistence the second period is around 800 kyr bp mode 1 technology is still maintained but subsistence strategies include systematic hunting and the use of base camps the third period is dated between 500 ka and 200 ka and corresponds to the mode 2 technology and the acquisition of directional hunting and other organizational strategies by homo heidelbergensis a transition from mode 2 to mode 3 seems to appear at the end of this time range and may reflect the early phases of a fourth cultural change with regard to the environment our main conclusion is that there was an absence of extremely harsh conditions at atapuerca throughout this time period the presence of mediterranean taxa was constant and the dominant landscape was a savannah like open environment probably with small forest patches an alternation of mediterranean and mesic species as the dominant component of the tree storey was induced by the climatic cycles and steppes spread across the landscape during the drier periods in any case it is not possible to establish clear cut off points separating entirely different environmental episodes our results show no evidence of any relationship between environmental change and cultural change at the sierra de atapuerca

permian climate development in the northern peri tethys area the lodeve basin french massif central compared in a european and global context abstract the lodeve basin which contains an exceptional long and nearly uninterrupted profile of early to late permian continental red beds is well correlated to the other european permocarboniferous basins together they cover the time span from the late pennsylvanian to the permian triassic boundary although these basins were placed within the equatorial belt for the whole permian several climatic changes are recorded in the sediments terrestrial sedimentation is governed by the interaction of climate and tectonics as well as by volcanism to a variable degree therefore small scale climatic variations of the milankovitch band are hardly discernable and if so they could not be correlated between different basins indeed larger scale climatic shifts could be identified it is shown that the shift from the carboniferous icehouse to the mesozoic warmhouse was a multi stage process this global warming resulted in a general aridisation of northern pangea indicated by outspreading playa and sabkha red beds aeolianites and evaporites several short phases of increased humidity interrupted this trend indicated by wet red beds lake sediments and coal deposits in central and southern europe these wet periods are traceable within the late stephanian lower rotliegend gzhelian asselian topmost lower rotliegend asselian sakmarian upper rotliegend i late artinskian early kungurian and upper rotliegend ii zechstein wuchiapingian the aridisation of the northern pangea which accelerated near the sakmarian artinskian transition is attributed to a reorganisation of the major ocean currents cold water currents along the western flank of the pangea indicated by the permian chert event blocks moisture transport from west onto the continent during roadian and wordian the onset of an additional cold water current along the cimmerian continents blocks moisture transport from the east both phenomena together are responsible for the maximum of aridity at the early to middle permian transition additionally the equatorial climate has been affected by an increasing seasonality within the late pennsylvanian and permian caused by the wide shifting of the zone of inter tropical convergence itc over the equator based on a new reconstruction of the pangean assembly in this paper climatic changes in the permian are interpreted and causes of the arid humid arid shifts are examined phases of higher humidity are often related to events of global impact like the waxing and waning of the gondwanan glaciation obtained in the south african karoo basin dwyka group but also regional events had strong climatic influence the zechstein transgression in the northern and southern permian basin as well as the bellerophon transgression of the southern alps caused the wet phase in the wuchiapingian

the nature of technological changes the middle pleistocene stone tool assemblages from galeria and gran dolina subunit td10 1 atapuerca spain this article focuses on the origins for technological variation during the middle pleistocene through the analysis of the lithic assemblages from galeria and gran dolina subunit td10 1 atapuerca spain the technological study was organized into three main levels of analysis the first stage consisted of the technological characterization of the whole assemblage e g the general composition of each sample the exploitation and shaping methods used and the characteristics of each item the second stage involved the morphometric analysis of the large tools mainly handaxes and cleavers given the significance of these instruments in middle pleistocene assemblages in this case we combined traditional technical and metrical analyses with current morphometric methods lastly taking into account the general characteristics of these sites the third stage consisted of assessing how the different occupational strategies affected the lithic representation these analyses allowed us to define three technological groups the first includes unit galeria giia which corresponds to the appearance of the acheulean in the atapuerca caves the second is represented by the rest of the sequence of the galeria site mainly the upper part of the sequence unit giii and the third technological corresponds to gran dolina subunit td10 1 thus the galeria sequence shows the technological evolution of the acheulean over a period of 250 ka furthermore subunit td10 1 represents a new occupational strategy combining traditional acheulean tools with more evolved technical strategies

post glacial permian stratigraphy and geography of southern and central africa boundary conditions for climatic modelling abstract the post glacial stratigraphy of southern and central africa comprises mudrocks with subordinate sandstones and coal measures belonging to the ecca group overlain by fossiliferous mudstones and sandstones of the beaufort group madumabisa mudstone of south central africa preserved in the karoo congo and extreme western margin of the paranabasins the kalahari zambezi and east africa malagasy basin complexes and the nyasa basin and range complex the palaeogeography of the region was controlled by the stable elevated kalahari and congo cratons a ne trending weak zone between the cratons site of the kalahari zambezi malagasy basin complexes a nnw trending weak zone between the cratons and the mozambique mobile belt site of the nyasa basin and range complex and an e w mobile belt along the southern margin of the continent site of the foreland karoo basin the post glacial artinskian landscape which was inherited from the permo carboniferous glaciation consisted of a rugged interior plateau and shallow seas and seaways in the south and west the early late permian landscape was still dominated by an uneven coastline in the south and freshwater lakes in the congo basin and along the kalahari zambezi malagasy drainage systems a marine incursion occurred in the malagasy basin relief on the interior plateau was steadily denuded by kazanian times large lakes covered the karoo and paranabasins whereas along the coastal region all shallow seas were destroyed by an orogen freshwater lakes in the interior had reached their maximum extent the permo triassic landscape shows an increase in the interior relief due to renewed graben formation with lakes becoming smaller and more desiccated the surface area of southwestern gondwana covered by water reached a maximum of 34 during the early late permian and decreased to about 6 at the permo triassic boundary climatic zones shifted southeastwards as southwestern gondwana drifted into lower latitudes during the permian the ice margin started to retreat in central africa during the sakmarian but the marine ice sheet in the karoo basin collapsed only in the artinskian deglaciation was followed by a cool wet climate suitable for the formation of peatlands in central and south central africa this climate was followed by temperate to warm seasonal conditions which became progressively wetter with less seasonal fluctuation towards the east malagasy basin and drier towards the west these conditions lasted until the end of the kazanian in the karoo basin the cool wet climate of the artinskian became more temperate and also lasted until the end of the kazanian when warm semi arid conditions expanded over the entire southern and central africa the geographic controlling factors for permian climatic change were the interplay of latitudinal setting and continental evolution formation of orographic barriers and loss of coastal seas

carbon isotope and iridium event markers near the permian triassic boundary in the meishan section zhejiang province china abstract systematic investigations for carbon isotopes and iridium of the meishan section were carried out using very narrow sampling intervals the high resolution results demonstrate the following characteristics 1 a large drop in 13c 7 cm above the base of the triassic with a magnitude of about 6 2 a sharp ir peak of 2 02 ppb 10 cm above the base of the triassic whereas the ir mean of six samples equals 0 4 ppb the large negative carbon isotope shift the ir anomaly within a thin sublayer and microspherules all occur within a 20 cm thick section above the base of the triassic which has been defined to coincide with an abrupt facies change from carbonate to clay the geochemical results and the microspherules suggest that the permian triassic boundary event was catastrophic and probably caused by an extraterrestrial impact

non marine permian biostratigraphy and biochronology an introduction the permian time scale based on marine rocks and fossils is well defined and of global utility but non marine permian biostratigraphy and chronology is in an early phase of development non marine permian strata are best known from western europe and the western united states but significant records are also known from russia south africa china and brazil global time terms based on non marine permian strata such as rotliegend zechstein autunian saxonian and thuringian are either inadequately defined or poorly characterized and should only be used as lithostratigraphic terms macro and microfloras have long been important in non marine permian correlations but are subject to limitations based on palaeoprovinciality and facies climatic controls charophytes conchostracans ostracodes and freshwater bivalves have a potential use in non marine permian biostrati graphy but are limited by their over split taxonomy and lack of well established stratigraphic distributions of low level taxa tetrapod footprints provide poor biostratigraphic resolution during the permian but tetrapod body fossils and insects provide more detailed biostrati graphic zonations especially in the lower permian numerous radioisotopic ages are available from non marine permian sections and need to be more precisely correlated to the global time scale the middle permian illawarra reversal and subsequent magnetic polarity shifts are also of value to correlation there needs to be a concerted effort to develop non marine permian biostratigraphy to correlate it to radio isotopic and magnetostratigraphic data and to cross correlate it to the marine time scale

variation in 87 sr 86 sr of permian seawater an overview the strontium isotope ratio 87sr s6sr of seawater has changed significantly through time in response to variations in the input of sr to the oceans from various crust and upper mantle sources with differing 87sr 86sr values an important aspect of this temporal variation is the empirical finding that while the 87sr 86sr of seawater may vary through time at any given time the sr isotope ratio of the oceans is everywhere the same isotopic uniformity is achieved because the marine residence time of sr 4 x 106 yr is long e g veizer 1989 compared to the oceanic circulation time 103 yr the oceans therefore are well mixed with respect to both sr and sr isotope ratio and all coeval marine derived carbonates sulfates and phosphates will possess the same initial 87sr s6sr value consequently the temporal changes in the 87sr s6sr of seawater can be used to correlate and date marine strata and can provide insight into the global processes that have shaped our world

search for evidence of impact at the permian triassic boundary in antarctica and australia life on earth was almost destroyed some 250 m y ago in the most profound of all known mass extinction events we investigated the possible role of impact by an extraterrestrial bolide through chemical and mineralogical characterization of boundary breccias search for shocked quartz and analysis for iridium in permian triassic boundary sections at graphite peak and mount crean antarctica and wybung head australia thin claystone breccias at the isotopically and paleobotanically defined boundary at all three locations are interpreted as redeposited soil rather than impact ejecta the breccias at all three locations also yielded shocked quartz but it is an order of magnitude less abundant 0 2 vol and smaller only as much as 176 micrometers m diameter than shocked quartz at some cretaceous tertiary boundary sites faint iridium anomalies were detected up to 134 pg g 1 these values are an order of magnitude less than iridium anomalies at some cretaceous tertiary boundary sites furthermore peak iridium values are as much as 1 m below the isotopically and paleobotanically defined boundary the idea that impact caused the extinctions thus remains to be demonstrated convincingly

the mechanical properties of macrolithic artifacts a methodological background for functional analysis natural technical and social factors led to the use of a wide range of rocks for the production of macrolithic artifacts during the later prehistory in the case of some artifact types such as the grinding stones rocks with very different petrographic qualities appear analysis of the material behavior as developed by material sciences provides a tool which allows the translation of these petrographic characteristics into mechanical properties experiments with a group of rocks subjected to different forms of abrasion in industrial machines allow an evaluation of the adjustment between the mechanical properties of the rock and the functions for which they were chosen by prehistoric societies finally the understanding of the mechanical properties of the raw materials together with their forms of exploitation distribution and use allows the designation of social and economic meaning to the production systems linked to the macrolithic tools