antarctic climate at the eocene oligocene boundary climate model sensitivity to high latitude vegetation type and comparisons with the palaeobotanical record abstract simulated climate for the antarctic continent using the genesis version 2 1 global climate model with 34 ma boundary conditions is shown to be highly sensitive to polar vegetation type six experiments were run using different levels of atmospheric co2 orbital configurations ice sheet geometries and vegetation types to assess model sensitivity to antarctica being covered with either a needle leaf evergreen forest or tundra simulations using 2 pre industrial levels of co2 combined mean annual temperature mat 19 c are about 7 c cooler than minimum estimates from the antarctic cenozoic plant record mat 12 to 15 c however simulations using 3 co2 mat 7 c are in good agreement with our empirical estimates of mean annual temperature with ice sheets and orbits set up to represent early oligocene interglacial conditions the tundra climate is significantly cooler than the evergreen forest climate with local austral summer averages up to 6 c cooler in non glaciated areas and continental averages 2 5 c cooler in the model this is mainly due to higher albedo and decreases in net radiation and sensible and latent heat flux especially during spring and summer feedbacks between coastal and continental cooling marginal sea surface temperatures and sea ice also appear to be significant a review of the late palaeocene to earliest miocene plant fossil record in the antarctic peninsula and ross sea regions shows that the vegetation was in transition 34 ma from a relatively diverse mainly evergreen forest to a tundra vegetation the modelled sensitivity of continental temperatures to a change from forest to tundra suggests vegetation climate feedbacks during the eocene oligocene transition played a significant role in the initial rapid glaciation of the continent

fire ecology of the carboniferous tropical zone abstract fossil charcoal fusain indicating the occurrence of wildfire is common in the carboniferous rocks of north america and europe during the carboniferous these regions lay on the southern margins of the laurasian continent and within the tropical zone this study examines the facies distribution and botanical identity of charcoal in order to investigate the influence of fire on carboniferous tropical ecology new data from charcoal bearing units in eastern canada poland and the british isles are presented and synthesised with previously published data of charcoal occurrence tournaisian visean charcoal bearing strata were deposited in volcanic lacustrine alluvial plain and coastal marine environments in these deposits charred floras are dominated by pro gymnospermous plants whilst uncharred compressed or permineralised floras are dominated by lycopsids uncharred lycopsid remains were probably derived from wetland communities growing close to the depocentres whilst charred gymnospermous remains may have been sourced from well drained extrabasinal settings based on the vertical distribution of charcoal layers in annually laminated lacustrine deposits it is estimated that fires occurred with high frequency approximately every 3 35 years palaeoclimatic analysis indicates that southern laurasia at this time was subject to a seasonal monsoonal tropical climate such environments today are characterised by tropical savannas with high fire frequencies and early carboniferous fire prone gymnospermous plant communities may have represented a comparable vegetation biome namurian stephanian charcoal bearing strata were deposited in alluvial plain coastal plain and coastal marine environments channelised sandstone units interpreted as river channel deposits contain charcoal derived from cordaitaleans and conifers this assemblage records fires in extrabasinal coniferopsid forests mudstone units containing coals are interpreted as the deposits of floodbasins and peat mires hollow uncharred lepidodendrid stumps occur in this facies and contain lepidodendrid charcoal in the stump bases and lepidodendrid pteridosperm coniferopsid and sphenopsid charcoal outside the stumps this assemblage records fires in wetland lepidodendrid dominated forests lepidodendrid trunks comprising of a spongy parenchymatous core surrounded by dense periderm became hollowed out during fire events an estimate of fire frequency based on the vertical spacing of charcoal layers in coals implies that fires occurred every 105 1085 years in the peat mires palaeoclimatic analysis indicates that southern laurasia was subject to a humid tropical climate during the late carboniferous such environments today are characterised by tropical rainforests where fires occur rarely and late carboniferous communities may have represented a comparable biome

frost rings in trees as records of major volcanic eruptions new data about climatically effective volcanic eruptions during the past several thousand years may be contained in frost damage zones in the annual rings of trees there is good agreement in the timing of frost events and recent eruptions and the damage can be plausibly linked to climatic effects of stratospheric aerosol veils on hemispheric and global scales the cataclysmic proto historic eruption of santorini thera in the aegean is tentatively dated to 1628 26 bc from frost ring evidence

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

in situ fossil forest from the upper fremouw formation triassic of antarctica paleoenvironmental setting and paleoclimate analysis abstract a structural and ecological study of a standing triassic forest containing 99 silicified trunks from the fremouw formation of antarctica is detailed utilizing quantitative methods forest density total forest cover per hectare mean separation of trees and basal area per stump were obtained this information integrated with sedimentologic taxonomic fossil wood and biomechanical data has allowed the reconstruction of a plant community that grew at very high paleolatitudes 70 75 s the paleoforest grew along river banks levees and within proximal floodplain environments where a taphocoenosis of permineralized stumps and compression impression foliage of the dicroidium type has been preserved in particular the intimate association of this leaf type with dense conifer like wood provides additional confirmation that the dicroidium foliage morphotype was attached to several types of stems this riparian forest stand was apparently in a mature stage prior to the beginning of preservation tree ring analysis as well as additional indirect evidence indicates that this middle triassic ecosystem in antarctica experienced a season very suitable for plant growth resulting from an overall favorable climatic regime this conclusion contrasts with earlier paleoclimate models based on physical parameters in which temperature ranges would make plant or animal growth at these latitudes almost impossible finally antarctic climatic change from latest permian through late triassic is considered in the context of tectonic and paleogeographic reconstructions of the east antarctic craton

precipitation melt and runoff in the northern tien shan abstract precipitation and snow distribution melt of glaciers and snow and runoff formation in two basins in the northern tien shan are calculated and described major climatic features are a spring summer precipitation maximum occurring simultaneously with ice and snow melt precipitation increases with altitude except in winter when an air temperature inversion occurs air temperature is a good predictor of glacial melt typical hydrographs have two floods one is formed from melt of seasonal snow cover and the other is formed from melt of glacial ice the second flood is usually larger than the first in mountain basins of the northern tien shan direct runoff from rainfall averages about 7 12 of annual volume the glacial runoff is 18 28 of average annual runoff in basins with area of glaciation not less than 30 40 but during summer it can increase to 40 70 of average annual runoff surface runoff from seasonal snow melt during spring and summer is 18 of average annual runoff the groundwater component is 34 38 of average annual runoff

climatic implications of the variable obliquity explanation of cretaceous paleogene high latitude floras the record of high latitude cretaceous paleogene floras has been interpreted as indicative of warmth and climatic equability and has also been the basis for arguments of reduced obliquity climate model simulations suggest that a reduced obliquity will result in a substantial polar cooling that is incompatible with the interpretation for polar warmth paleobiologic adaptations to low light levels may be an alternative to a variable obliquity

fire prone plant communities and palaeoclimate of a late cretaceous fluvial to estuarine environment pecinov quarry czech republic the botanical identity and facies distribution of fossil charcoal is described from middle to late cenomanian 90 94 ma fluvial to estuarine units at pecinov quarry near prague czech republic braided alluvial facies associations contain charred conifer woods family pinaceae possibly derived from upland forest fires and abundant charred angiosperm woods flowers and inflorescences families lauraceae and platanaceae derived from riparian gallery forest fires unit 2 retrogradational coastal salt marsh facies associations contain abundant charred conifer wood families cheirolepidiaceae and cupressaceae taxodiaceae derived from fires in halophytic backswamp forest and rare pinaceous charred cones and lauraceous angiosperm wood washed downstream from fires further inland units 3 4 progradational coastal facies associations within an estuary mouth setting contain abundant charred conifer wood family cupressaceae taxodiaceae common taxodiaceous conifer and angiosperm leaves fern rachises and lycopsid stems derived from fires in mesic backswamp taxodiaceous forests and supra tidal fern lycopsid thickets unit 5 growth rings in angiosperm and conifer woods leaf physiognomy and computer models indicate that climate was equable warm and humid but that there was a short annual dry season most fires probably occurred during these annual drought periods the abundance of charcoal and the diversity of taxa preserved in this state indicate that nearly all plant communities were fire prone physiognomically the pecinov flora resembles present day seasonally dry subtropical forests where fires are a common occurrence

new oxygen isotope evidence for long term cretaceous climatic change in the southern hemisphere a new composite 18 o record generated from calcareous fine fraction and bulk sediments from the exmouth plateau details long term cretaceous climatic change at mid latitudes in the southern hemisphere assessment of new and previously published 18 o data indicates that a mid cretaceous global climatic optimum was achieved sometime between the time of the cenomanian turonian boundary and the middle turonian when surface ocean paleotemperatures were the highest of the past 115 m y periods of cooling and warming that reversed the general patterns were superimposed on long term aptian turonian warming and turonian maastrichtian cooling trends respectively extrapolation of southern hemisphere paleotemperature trends to maastrichtian paleotemperature data from a low latitude pacific guyot implies that maximum mid cretaceous low latitude paleotemperatures could have been in excess of 33 c

the age and stratigraphy of fore arc magmatism on alexander island antarctica fore arc magmatic sequences associated with high mg number andesite lavas unconformably overlie lemay group accretionary complex in alexander island high resolution 40ar 39ar u pb zircon fission track and k ar ages demonstrate that subduction related fore arc magmatism migrated northwards along the length of alexander island between c 80 ma and c 46 ma the magmatic rocks represent a third of the western margin of the antarctic peninsula magmatic arc and are critical to the understanding of the final phase of subduction along the southern antarctic peninsula margin the onset of late cretaceous magmatism is recorded by poorly exposed volcanic rocks on monteverdi peninsula 79 7 2 5 ma in central and northern alexander island the magmatic rocks can be distinguished by the proportion range and types of lithofacies present and by the periods of magmatism represented the volcanic rocks of the colbert mountains range in age from c 69 62 ma and are dominated by large volume dacitic and rhyolitic crystal rich ignimbrites interpreted as caldera fill deposits elgar uplands sequences range in age from c 55 50 ma and contain approximately equal proportions of pyroclastic deposits and less evolved basaltic andesite and andesite lavas including high mg number andesite lavas near the base of three sequences the volcanic rocks of finlandia foothills probably represent the youngest calc alkaline units on alexander island 48 2 ma the sequence is lithologically similar to the elgar uplands and also contains high mg number andesite lavas but it is dominated by polymict conglomerates with minor lavas which were deposited in a graben associated with regional extension plutonic rocks exposed in the rouen mountains adjacent to the elgar uplands yielded a u pb age of 56 3 ma which is in discordance with a previously published rb sr age 46 3 ma probably due to hydrothermal perturbation of the rb sr system northwards migration of magmatism was caused by the progressive collision and subduction of three ridge segments prior to the previously reported ridge crest trench collisions that occurred c 20 30 ma later and following which subduction ceased

late cretaceous to early tertiary subduction history of the antarctic peninsula quantitative estimates of the rates and azimuths of phoenix plate convergence with the antarctic peninsula have been derived from plate rotation calculations for two periods in the late cretaceous and early tertiary 83 0 67 7 and 61 1 53 4 ma published marine magnetic anomaly identifications and flow lines interpreted from gravity anomaly maps were used in simple spherical geometry calculations to derive phoenix pacific stage rotations these were combined with published pacific antarctic rotation data to determine contemporaneous phoenix antarctic stage rotations the results indicate a significant change in azimuths of relative motion between the late cretaceous and early tertiary late cretaceous and perhaps earlier oblique subduction probably caused migration of fore arc slivers along the margin resulting in variations in width of the accretionary prism comparison between synthetic magnetic profiles and a 900 km long magnetic profile across ocean floor produced at the antarctic phoenix ridge during the early tertiary establishes the time of a major decrease in spreading rate and hence also in convergence rate as chron c23r 52 3 ma the associated change in subduction dynamics may have caused the dextral transtensional deformation observed in the george vi sound region and initiated uplift of blueschist facies rocks now exposed on smith island the calculated convergence history does not provide a simple explanation for the occurrence of high mg andesite lavas on alexander island which were erupted more than 20 ma before the antarctic phoenix ridge arrived at the margin the existence of these lavas implies either earlier subduction of another ridge or slab break up beneath alexander island

paleobotanical evidence for cool north polar climates in middle cretaceous albian cenomanian time mid cretaceous albian cenomanian floras are abundant and diverse on the north slope of alaska the older floras consist of conifers cycadophytes ferns ginkgophytes and sphenophytes horsetails angiosperms appeared in latest albian time and rapidly diversified the preserved floras consist entirely of deciduous plants with the exception of a microphyllous conifer ferns and sphenophytes deciduousness is evidence for strong seasonality which for these floras might be variations in either light or temperature or both cool temperatures are suggested by the prevalence of toothed leaves among the angiosperms and the presence of large leaved conifers the paleobotanical evidence points to a mid cretaceous climate that was no warmer than cool temperate on the north slope of alaska

an interpretation of cretaceous and tertiary biota in polar regions abstract rich fossil floras and vertebrate faunas lived within the arctic and atarctic circles during the cretaceous and paleogene these occurrences seem explicable by the nature of the thermal environments in polar regions and by the physiological responses of plants and animals allied to those that lived there there seems no need to invoke a lower tilt to the earth s axis to provide greater warmth and light in polar regions to account for these fossil records

palaeobotanical evidence for a warm cretaceous arctic ocean the cretaceous period was a time of global warmth1 4 mid cretaceous equatorial temperatures were similar to today s5 but the equator to pole temperature gradient is the subject of some controversy5 7 although it is unlikely that the poles were ice free8 10 fossil evidence3 5 11 12 indicates that near polar temperatures were much higher than they are today little is known moreover about oceanic poleward heat transport and this makes it hard to model the cretaceous climate or to evaluate the extent to which it provides an analogue for a greenhouse world warmed by increased atmospheric co2 alone here we use relationships between leaf physiognomy such as shape and size and modern climate to determine cretaceous climate conditions in the arctic region from fossil leaves we find that the arctic ocean was relatively warm remaining above 0 c even during the winter months this implies that there was significant poleward heat transport during all seasons

the influence of vegetation cover on soil organic matter preservation in antarctica during the mesozoic a possible biological component of the explanation for the lack of substantial coal formation on antarctica between the late jurassic and late cretaceous is hypothesised forcing a process based terrestrial biogeochemistry model with climate model simulations for three successive intervals of the mesozoic late jurassic 150 ma mid cretaceous 100 ma and late cretaceous 65 ma predicts the establishment of productive terrestrial ecosystems with substantial soil carbon pools throughout the land surface of antarctica between 150 and 65 million years ago sensitivity analyses indicate the annual land surface hydrological budget of antarctica 150 65 ma was largely balanced due to the effects of canopy transpiration on soil moisture post depositional erosion and tectonic setting must have played an important role in determining coal preservation on the continent however the model results indicate that an active vegetated land surface precluded the preservation of the substantial soil organic carbon inputs by minimising the potential for anaerobic preservation i e water logging

cretaceous patterns of floristic change in the antarctic peninsula cretaceous radiation of angiosperms from low to high palaeolatitudes coupled with the break up of gondwana played a major role in establishing and maintaining biogeographic patterns across the southern hemisphere uncertainties in details of plate reconstructions provide conflicting hypotheses about area relationships of gondwana fragments this has led to a number of competing proposals concerning angiosperm migration across gondwana central to this debate is the role of the antarctic peninsula a region that is often envisaged as providing the main connection between east and west gondwana the initial radiation of angiosperms into the antarctic peninsula region however postdates appearances elsewhere in east gondwana e g australia strongly suggesting that the antarctic peninsula was not the main gateway at least in the early stages of gondwana radiation a steep climatic gradient in this part of the world probably acted as an effective barrier to angiosperm radiation the peak of floristic replacement coincides with the peak of cretaceous warmth turonian which in turn suggests that climatic warming acted as a forcing mechanism by pushing latitudinal belts of vegetation southwards once into the southern high latitudes angiosperms diversified and as climates cooled during the late cretaceous a number of important groups seem to have their origins here recent investigations of antarctic macro and microfloras indicate progressive floristic replacement through the cretaceous bryophytes hepatophytes bennettites and other seed plants all show a rapid decline in diversity in contrast ferns initially decline then recover while conifers remain relatively stable the ecological preferences of the replaced groups imply that angiosperms initially occupied areas of disturbance and were understorey colonizers only later replacing fern thickets and becoming important in the overstorey this pattern is consistent with those observed elsewhere through the cretaceous

hydrologic inferences from tree ring studies on the hawkesbury river sydney australia abstract introduced salix trees in australian alluvial environments can be used to make a number of hydrologic inferences dendrochronological studies along the hawkesbury river near windsor suggest that the salix growth form and annual growth ring variability are closely associated with the local hydrologic regime detailed analyses of 33 trees showed that tree growth is suppressed close to water and increases with height above mean low stage levels because of the decreasing influence of flooding alluvial levels contain discrete vegetation patterns and growth characteristics that are not explained by variations in soil and climate growth of salix in thickets on low in channel benches is flood limited with fitted exponential growth curves having positive or zero slopes the high in channel bench contains vegetation influenced by flooding but growing according to classical exponential decay functions trees on floodplain levees show full canopy development and the most rapid growth because of fertile soils the high availability of water and limited influence of floods overtopping levee tops elevation and tree growth relations are used to develop a relation between growth and flood frequency this is applicable to catchments of similar size soil type and climate analyses of tree form and root distribution indicated that dendrochronological techniques may be used to determine the minimum land surface age and rates of accretion around the tree bole in alluvial areas of southeastern australia

metamorphosed palaeosols associated with cretaceous fossil forests alexander island antarctica fossil soils are present within mid cretaceous fluvial sediments of the fossil bluff group alexander island antarctica the palaeosols contain in situ fossil trees and rooted plants these palaeosols are typically composed of two dominant horizons an upper organic rich horizon with identifiable plant remains and a lower horizon with well developed blocky ped structures clay cutans and mottling these features are typical of modern soils in seasonally dry climates although evidence of flooding is apparent from interbedded fluvial sandstones and mudstones the palaeosols indicate that this high latitude mid cretaceous environment was predominantly seasonally dry the presence of the zeolites laumontite prehnite and pumpellyite indicates a later metamorphic overprint on the palaeosols resulting from burial diagenesis of this region at depths of about 3 8 5 2 km and temperatures of 150 170 c

rainfall patterns and the distribution of coals and evaporites in the mesozoic and cenozoic abstract paleoclimatologists have adequately demonstrated over the last twenty years that the distribution of climatically sensitive sediments can be related to present day climatic zones that are roughly parallel to latitude for example coals were deposited at paleolatitudes that correspond to the present day rainy zones at the equator and at about 55 n and 55 s indicating that those zones were present in the past from this it can be concluded that atmospheric circulation has not been radically different from its present configuration despite some apparently great differences in some climatic parameters such as the equator to pole temperature gradient nevertheless the zonal model for predicting the distribution of climatically sensitive sediments is not wholly adequate although general atmospheric circulation may not have been radically altered from its present pattern it would have differed in some respects because the paleogeography was different from the present geography therefore we have constructed what we believe are more realistic maps of the distribution of rainfall through time these maps are based on maps of atmospheric circulation that have been successfully used to predict the distribution of some petroleum source beds and phosphorites we have compared the predicted distribution of rainfall to the distribution of coals and evaporites for each of seven geologic stages the circulation rainfall maps were more successful than the zonal model for predicting the distribution of evaporites and coals for times when the paleogeography would have maximized the development of a monsoonal circulation which most effectively disrupts the general zonal pattern for times when a monsoonal circulation would not have been important the zonal model adequately predicted the distribution of these rocks

stable c and o isotopic study of the campanian chalk from the mielnik section eastern poland signals from bulk rock belemnites benthic foraminifera nannofossils and microcrystalline cements abstract exceptionally well preserved chalk from the mielnik section in eastern poland has been analyzed for sr c and o isotope composition recorded in bulk rock samples belemnite rostra hand picked benthic foraminifera and separated fine fractions incl calcareous nannoplankton and calcite cements the stratigraphic 13 c and 18 o trends are consistent with the global seawater variations during the campanian and confirm strong climatic perturbation accompanying the global sea level fall during the uppermost campanian chalk samples contain disseminated early diagenetic microcrystalline calcite cement having 13 c and 18 o values only slightly different by 13 c and 18 o values between different constituents measured from the same levels are discernible they are related with thermal gradients in the water column and with the habitat and vital effects of biogenic components benthic foraminifera reflect strong vital effects in 13 c and 18 o with a tendency to lower values than the other sample types the minimum strength of the disequilibrium fractionation effect for 18 o during foraminiferal shell secretion is estimated up to 2 belemnites show offsets in 13 c values which are difficult to estimate but their 18 o values appear to have recorded composition of seawater the large difference in 18 o values between belemnites and nannoplankton or bulk material suggests that belemnites were nectobenthic organisms living close to the seafloor the 87 sr 86 sr values and biostratigraphic position of the belemnites correspond well to those in the lagerdorf mcarthur et al 1993 the reference section for the european upper cretaceous epicontinental marine deposits but are not in agreement with the campanian stratigraphy defined in the geological time scale 2012 gradstein et al 2012 where positions of some biostratigraphic divisions are not well calibrated against the absolute age

early miocene climate and biomes of turkey evidence from leaf fossils dispersed pollen and petrified wood abstract the early miocene was a period of major palaeogeographic reorganization in the eastern mediterranean region during which time the anatolian plateau became subaerial and several intracontinental basins intermittently became connected to the paratethys and mediterranean seas in this paper we analyse early miocene vegetation and climate using leaf records palynological assemblages and fossil wood at 36 localities from western and central turkey most of which have precise age control based on radiometric dating and mammal faunal ages using the leaf flora of guvem bes konak kesekoy climate leaf analysis multivariate program clamp analyses and koppen signatures were employed to infer a palaeoclimate typical of modern laurel forest regions based on the palynological records abundance of various pollen taxa was used as a measure of openness of vegetation and regional presence of major tree taxa most pollen floras are dominated by tree pollen ranging from 85 to 98 and indicated widespread afforestation in the pollen diagrams shifts in dominance from swamp forest elements taxodioideae to well drained forests pinaceae indicate changes in lake levels or phases of basin development such shifts may have been associated with the development of more xeric forest vegetation wood anatomical features such as false tree rings further may indicate seasonal climate pollen diagrams and macrofossils reflect zonal and azonal broadleaf and needleleaf forest and extrazonal open vegetation the latter occurred in areas with shallow soils on volcanic rocks or limestone e g cycads dracaena or coastal areas herb dominance taxonomic composition and biogeographic affinities suggest laurel forest as a major forest biome on well drained soils and ecotones between laurel forest and broadleaf deciduous forest biomes a comparison with younger floras shows that these are neither more diverse nor more warmth loving despite an increase in global temperature mid miocene climatic optimum suggesting bottlenecks during previous oligocene cooler times for warmth loving taxa

a guide to phanerozoic cold polar climates from high latitude ice rafting in the cretaceous the high latitude extent of warm climate indicators at certain times in earth history has been considered as evidence that the globe was ice free for long intervals despite theoretical considerations and results from numerical modelling experiments1 2 indicating that this was unlikely one of the warmest periods the cretaceous displays faunal and floral evidence for cool temperate to sub tropical conditions very near to the poles however our studies of lower cretaceous mudstones of central australia that contain outsized exotic blocks have led to the conclusion that the blocks were emplaced by ice rafting implying that high latitude ice was present at sea level strata of a similar origin of mid jurassic to mid cretaceous age occur on other continents that were positioned between 65 and 78 palaeolatitude indeed there is a record of high latitude ice rafting throughout the phanerozoic suggesting that ice was present on earth for much of its history and that ice free conditions could have been at most only episodic over the past 600 myr

fire ecology of a late carboniferous floodplain joggins nova scotia the facies distribution and palaeobotanical identity of fossil charcoal is described from the upper carboniferous westphalian a b joggins section nova scotia in order to examine the fire ecology of early westphalian floodplains three charcoal assemblages are noted assemblage 1 consists of channel sandstone bodies containing beds of calcrete breccia cordaite logs up to 3 m long and coniferopsid wood charcoal this assemblage records upland coniferopsid forest fires which altered basin hydrology and promoted flooding in downstream floodplain rivers assemblage 2 consists of thin 1 8 mm thick coals containing hollow sigillarian tree stumps and lepidodendrid and medullosan plant compressions fifteen of the 29 stumps observed have a 2 5 cm thick basal layer infilling the stumps composed entirely of sigillarian charcoal sigillarian and medullosan charcoal is also scattered around the outside of these stumps this assemblage represents fire in lowland peat forming communities dominated by sigillaria and medullosan pteridosperms these forest fire profiles were slowly buried in floodplain muds assemblage 3 consists of a heterolithic sheet sandstone body containing a 2 5 m high sigillarian tree trunk with an internal basal trunk deposit of sigillarian charcoal and a lightly charred bark rind this also records fire in lowland sigillarian forests but in contrast to 2 this forest fire profile was buried rapidly in a distributary lobe

yangquanoxylon miscellum gen nov et sp nov a gymnospermous wood from the upper pennsylvanian lower permian taiyuan formation of yangquan city shanxi province with reference to the palaeoclimate in north china a silicified gymnospermous wood yangquanoxylon miscellum gen nov et sp nov is described from the upper pennsylvanian lower permian taiyuan formation yangquan city shanxi province north china the pycnoxylic wood is composed of thick walled tracheids and thin walled rays it is characterized by mixed radial tracheid pits uniseriate and homogeneous rays occurrence of scalariform radial pitting and various types of cross field pitting there are four types of cross field pitting in y miscellum gen nov et sp nov including simple taxodioid phyllocladoid and araucarioid the absence of growth rings within fossil woods described here and reported previously from north china suggests a humid climate with minimal precipitation variations during the late pennsylvanian early permian

three growth in the mesozoic and early tertiary and the reconstruction of palaeoclimates abstract evidence from the distribution and characteristics of fossil wood in the mesozoic and early tertiary indicates that a much warmer global climate prevailed in those times there appears to have been a broad zone of largely non seasonal climate stretching from about 32 n to 32 s palaeolatitudes in addition to this low latitude zone forest growth extended into very high palaeolatitudes where trees cannot grow at the present day a number of theories have been proposed to account for the palaeoclimate responsible for this distribution of forests most notable have been those involving changes in the amount of carbon dioxide in the atmosphere in the positions of the continents or in the obliquity of the earth s axis of rotation evidence from fossil forests indicates that a combination of the effects of an increased quantity of carbon dioxide in the atmosphere and the palaeopositions of the continents in the mesozoic and early tertiary appears at the moment to be the simplest explanation for the climate of those geological times without the need to invoke axial movement

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

multitrophic interactions in a geothermal setting arthropod borings actinomycetes fungi and fungal like microorganisms in a decomposing conifer wood from the jurassic of patagonia abstract a permineralized araucarioid conifer stem preserved in state of partial decay is described from the middle to late jurassic chon aike formation bahia laura group at laguna flecha negra in the deseado massif santa cruz province argentina the tree stem which comprises periderm to the secondary xylem shows evidence of interactions with xylophagous borers fungi actinomycetes and other fungal like microorganisms in the secondary phloem it displays rows of traumatic resin ducts which host abundant mycelium comprising very thin hyphae differentiated into spore producing structures comparable to actinomycete bacteria and spherical fungal like resting structures in the cortical and phloem regions there are cell groups with structural changes which appear variably degraded by fungi the secondary xylem displays decay of cellulose and lignified components at various spatial scales comparable with fungal decay patterns in modern wood further septate fungal filaments sometimes bearing clamp connections are associated with decayed regions the degraded secondary xylem shows circular to oval borings filled with frass containing degraded tracheids comparable to those bored by different wood boring beetles development of traumatic resin ducts in the phloem could have been triggered by penetration of the living stem by these xylophagous arthropods the association of the different components present suggests pathogenic and saprotrophic interactions promoting decomposition of the stem and represents a rarely documented example of multitrophic biological interactions involving several different biological groups in jurassic terrestrial paleoecosystems

tree growth at polar latitudes based on fossil tree ring analysis permineralized trunks and mature wood samples with well preserved growth rings are described and analyzed from the upper permian and middle triassic of the central transantarctic mountains this fossil wood is unique in that the plants lived in an environment with no modern analogue and exhibited luxuriant tree growth above 75 s paleolatitude ring width averages 1 69 2 3 mm with maximum width of 6 83 9 9 mm an order of magnitude larger than ring widths produced at near polar latitudes today tree rings in both the permian and triassic woods show similar structure consisting almost entirely of earlywood spring wood with between 0 12 of each ring classified as latewood summer wood the small amount of latewood 0 6 cells indicates a very rapid transition to seasonal dormancy probably in response to decreasing light levels at these paleolatitudes in order to accurately delimit the earlywood latewood boundary a comparison was done of classical dendroclimatological techniques and alternative techniques utilized primarily by paleobotanists analyzing fossil woods we found that classical wood anatomy techniques provided a more accurate explanation of wood development and tree growth for these high latitude samples the suggested cool temperate late permian glossopteris flora from this area differs substantially from the warm temperate middle triassic corystosperm flora leaf type dicroidium and very different paleoclimates have been reconstructed for these two time periods ring structure and wood growth from both sites however are very similar indicating that these plants were responding to the environment in very similar ways the structure of the tree rings including a large number of earlywood tracheids and a very low number of latewood cells provides evidence that growth at these polar latitudes was limited by light levels rather than water and temperature as occurs in modern high latitude forests these fossil tree rings have important implications for understanding woody shoot growth and cambial function at high latitudes during periods of global warmth 2007 elsevier b v all rights reserved

the sequence of magmatic and mineralization events in the abitibi greenstone belt isotopic evidence from taylor township timmins area northern ontario canada samples from the porphyry deposit and the shoot zone prospect of st andrew goldfields ltd in taylor township near matheson ontario have been dated by several different techniques and utilized as a test of the use of pb isotope measurements in determining the time of mineralization in gold deposits of the abitibi greenstone belt clear and abraded zircons from an altered sulfidic porphyry unit yield a well defined age of 2697 3 1 3 ma indicating that the original intrusive rock unit containing these zircons was either latest synvolcanic or earliest syntectonic larger bulk samples of zircon from the same unit contain many altered and cracked grains and yield an age of 2682 4 ma close to the peak of syntectonic igneous activity pb pb isochrons determined from sulfide samples in mineralized material from the taylor porphyry zone yield a two stage model age of 2663 17 ma and suggest that mineralization postdates the syntectonic granitoids these pb isotope data are compared with isotope r