petrified wood of southwestern oregon implications for cenozoic climate change abstract over 1900 petrified wood specimens were collected from six localities spanning the eocene to miocene along a northeast transect parallel to the dip of the payne cliffs formation and western cascades group in southwestern oregon this study also presents new 40ar 39ar plateau age data for cenozoic deposits in southern oregon lower to middle eocene deposits yielded 305 specimens of petrified wood from sandstones and conglomerates of the basal part of the payne cliffs formation with only 6 of dicotyledons exhibiting distinct growth rings and none having ring porous or semi ring porous wood middle eocene exposures just stratigraphically above the first locality produced 278 specimens from the lower to the middle part of the payne cliffs formation with 66 of the dicotyledons exhibiting distinct growth rings two specimens of palmoxylon were also collected from sediments at this locality an upper eocene exposure produced 792 petrified wood specimens from volcaniclastic sediments with 88 of the dicotyledons exhibiting distinct growth rings sediments at this locality also produced one specimen of cibotium oregonensis oregon tree fern and several specimens of palmoxylon middle oligocene deposits yielded 218 petrified wood specimens from volcaniclastic sediments of the middle part of the western cascades group with 97 of the dicotyledons exhibiting distinct growth rings an upper oligocene exposure yielded 254 specimens from volcaniclastic sediments of the upper part of the western cascades group with all dicotyledons exhibiting distinct growth rings and 59 having ring porous or semi ring porous wood further this study establishes a 40ar 39ar plateau age date of 24 09 0 24 ma from plagioclase crystals in a tuffaceous sandy to pebbly siltstone at this locality finally lower miocene rocks yielded 101 specimens including 20 dicotyledons of which 70 were ring porous or semi ring porous with most specimens consisting of gymnosperms the increase over time in the percentages of dicotyledon specimens with distinct growth rings and with ring porous and semi ring porous wood from this study suggests an overall climatic shift from tropical early eocene to cool temperate early miocene in southwestern oregon these results are consistent with a similar climatic shift evidenced by paleoecological reconstructions for the eocene to miocene of the john day fossil beds in central oregon

an extensive deposit of fossil conifer wood from the mesozoic of mali southern sahara abstract examination of an extensive deposit of silicified fossil wood in continental intercalaire rocks of northeastern mali suggests that the logs found at this locality were deposited under high energy conditions sometime between the late jurassic and the early cretaceous the woods have been identified as metapodocarpoxylon libanoticum edwards duperon laudoueneix and pons an extinct member of the podocarpaceae which has a restricted geographic and stratigraphic distribution northern gondwana and tethys from late jurassic to early cretaceous time anatomical analysis indicates that the tree rings are indistinct which supports previous suggestions that west africa was under an equable climate during this part of the mesozoic

highly productive polar forests from the permian of antarctica abstract two stratigraphically closely spaced bedding planes exposed at lamping peak in the upper buckley formation beardmore glacier area antarctica contain abundant in situ stumps n 53 n 21 and other plant fossils that allow reconstruction of forest structure and biomass of glossopteris forests that thrived at 75 s paleolatitude in the permian mean trunk diameter is 14 and 25 cm corresponding to estimated mean maximum heights of 12 and 19 m basal areas are 65 and 80 m 2 ha 1 the above ground biomass was calculated using allometric equations for ginkgo biloba yielding biomasses of 147 and 178 mg ha 1 biomass estimates based on comparison with biomass of modern forests with equivalent basal areas are higher 225 400 mg ha 1 the amount of above ground biomass added each year annual net primary productivity based on biomass estimates and growth rings in silicified plant material from the buckley formation nearby is poorly constrained ranging from 100 2000 g m 2 yr 1 compared to modern forests at all latitudes the permian forests have high basal areas and high biomass exceeded in both only by forests of the u s pacific northwest and sequoia forests the estimated range of productivity anpp is within that of many very productive modern forests the lamping peak forests basal areas and calculated biomass are also larger than younger high paleolatitude fossil forests except for arctic cenozoic forests the presence of these highly productive fossil forests at high paleolatitude is consistent with hothouse conditions during the late permian prior to the eruption of the siberian flood basalts

antarctic marine temperatures late campanian through early paleocene an oxygen isotope paleotemperature study of benthic foraminifera from the upper campanian through lower paleocene section at seymour island near the coast of antarctica was done in conjunction with careful scanning electron microscope observations to monitor the state of foraminiferal preservation the isotopic compositions of those samples which were deemed to be well preserved were the basis of the conclusion that campanian through paleocene high latitude shelf waters near antarctica had temperatures between approximately 4 5 and 10 5 c temperatures during early and middle maastrichtian time were slightly higher than those of either the late campanian or late maastrichtian the inference of temperate climatic conditions in antarctica is in agreement with paleoclimatic conclusions drawn on the species composition of the planktonic foraminiferal assemblages and the character of the planktonic foraminifera as well as with published conclusions based upon paleobotanical evidence the maastrichtian and campanian water temperatures at seymour island are similar to those inferred from published isotope ratios of pacific late cretaceous benthic foraminifera from low latitudes indicating that campanian through early paleocene deep ocean waters at least in the pacific and perhaps elsewhere as well could have formed by sinking of surface waters in polar regions

middle and late albian geography oceanography and climate and the setting of the kirchrode i and ii borehole sites abstract the paper reviews the literature on the geography oceanography and climate belts during the middle and late albian emphasis is placed on the northern hemisphere and the lower saxony basin the middle and late albian represents a time with a greenhouse climate the n s temperature gradient and the temperature gradient between the shallow and deep waters of the oceans were lower than at present meaning higher temperatures especially at middle and high latitudes a more sluggish ocean circulation than today and the absence of polar ice caps warming from the early to late albian is documented in the marine sediments by oxygen isotope studies and the poleward expansion of rudist dominated carbonate platforms in the terrigenous sediments of the northern hemisphere it is documented by northward migration of low latitude relatively arid flora the opening north atlantic was still narrow at the beginning of the albian it widened and deepened through the albian a shallow seaway between the south atlantic and the western tethys developed during the late albian wide shelf seas existed on the continental plates with rising sea level the basins of the western epicontinental seas of eurasia became increasingly connected and sedimentation gradually became more calcareous nevertheless these basins received a large clastic input from the land documenting the weathering conditions on the surrounding land masses they received also a considerable biogenic particle flux from the surface waters documenting productivity of the marine plankton because of these different origins of the sediment components as well as the connections with neighbouring seas the sediments in these shelf basins were expected to document changes in climate as well as palaeo oceanographic changes earlier interpretations based on ammonite studies that indicate changing connections between the arctic ocean and the tethys during the albian can thus be tested the lower saxony basin was a shelf sea in the southern part of the warm humid climate belt at mid latitudes in the northern hemisphere in which thick deposits of hemipelagic sediments accumulated mapping previous to our study indicated that a complete undisturbed albian basinal sequence ca 400 m thick is present below a thin quaternary cover in a sub basin between the nne ssw trending benthe and lehrte salt structures in the central part of the lower saxony basin the boreholes at the kirchrode i and ii sites 52 22 35 n 9 49 87 e and 52 22 16 n 9 49 12 e respectively in hannover were drilled into this sub basin the high sedimentation rates known for the albian of the lower saxony basin are ideal for studying climatic changes with a cyclicity of a few ten thousand to a few hundred thousand years milankovitch cyclicity

reconstruction of a fossil forest reveals details of the palaeoecology palaeoenvironments and climatic conditions in the late oligocene of south america abstract this research focuses on the three dimensional reconstruction of an in situ forest based on fossil wood assemblages recovered in the rancahue formation upper oligocene neuquen argentina atherospermataceae lauraceae nothofagaceae eucryphiaceae cunoniaceae and myrtaceae specimens are described the mapping of a forest floor section and in situ tree diameters enabled the estimation of the following palaeoecological quantitative data tree density dominance basal area biomass diametric classes canopy height and age classes palaeoclimatical data was determined on the basis of physiognomic anatomical features using multivariate anatomical analyses these results were compared with other proxies including carlquist s index coexistence approach ca nearest living relatives nlrs and growth rings analyses the structural data from the alumine forest inferred from these analyses includes tree density of 463 701 trees ha mean height of 15 22 m dominance of the genus nothofagoxylon 89 66 m2 ha total basal area of 158 20 m2 ha biomass between 43 and 712 tn ha and mean age of 223 years specimens between 31 and 700 years old these results are comparable to those of mature low to middle altitude extant forests dominated by nothofagus and developed under humid temperate conditions based on the nlrs method the alumine forest has a floristic composition similar to the present day valdivian forest the persistence of nothofagus as the dominant element in temperate rainforests correlates with regimes where large scale disturbances such as volcanism and earthquakes are prevalent the fossil taxa are closely related to the extant laurelia persea eucryphia nothofagus weinmannia myrceugenia and luma the forest shows intermixed deciduous and evergreen elements and taxa with shade intolerance and intermediate shade tolerance also the majority of these taxa need soils with available water the integrated analysis of multiple sets of proxy data suggests that the late oligocene forest grew under temperate and humid climate while the eco anatomical features and sedimentary data provide information about the environmental stress conditions of its development and the violent causes of burial

early tertiary palaeogeography landform evolution and palaeoclimates of the southern monaro n s w australia the age of the southern highlands of australia has long been controversial recent field investigations around bombala in southern new south wales have shed some light on this as well as on the early tertiary palaeoclimates in southern australia late palaeocene basalts were extruded on a landscape with a relief of at least 400 m and possibly as much as 800 m showing that the region had a substantial relief by the beginning of the tertiary fluvial and lacustrine sediments deposited on the earlier or prebasaltic landscape have been preserved by the basalt and contain palynofloras and fossil wood as do sediments deposited between basalt flows in the lower parts of the basalt pile the palynomorphs are representative of the lygistepollenites balmei zone in the upper late paleocene ca 58 60 ma the pollen and fossil wood indicate the region was covered by cool temperate rainforest podocarps and araucarian conifers were significant components of these forests in addition to nothofagus ferns were prominent in some localities the fossil wood is dominated by gymnosperms comparison of the palynofloras with bioclimatic data of a number of descendant extant species has shown that most belong to the mesotherm response category with mean annual temperatures in the range 14 20 c there is little evidence that frosts were significant data from tree rings support this and show that climates were markedly seasonal the annual rings are very thin suggesting cool climates their uniformity shows that conditions varied little from year to year

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

palaeoclimatic interpretation of the wood structures of the trees in the chinle formation upper triassic petrified forest national park arizona usa abstract typically the fossil woods in the upper triassic chinle formation in petrified forest national park arizona usa do not show annual growth rings but contain irregular growth interruptions similar to those found in trees now growing in the humid tropics these interruptions could be due to endogenous hormonal effects or to occasional local variations in water supply therefore it is conclucded that the late triassic fossil forests in the park lived in conditions that permitted continuous tree growth limited data from areas outside of the park suggests that similar conditions prevailed in adjacent areas in the southwestern united states during the late triassic although this region is reported to have been under the influence of a monsoonal circulation pattern during the late triassic the growth of the trees does not appear to have been greatly affected

plane strain lateral consolidation with non darcian flow new plane strain lateral consolidation equations are formulated that neglect the well resistance of vertical drains but are applicable for both darcian and non darcian flow the results of consolidation analyses using conventional darcian linear flow and the new solution based on non darcian exponential flow are compared a good match has been obtained between equivalent plane strain and axisymmetric solutions the advantage of the equivalent plane strain procedure is that it not only matches the average degree of radial axisymmetric consolidation but also yields a more realistic excess pore pressure distribution in the lateral direction than the darcian flow condition the relevant parameters are illustrated graphically for convenience good agreement was obtained between the prediction of the new equivalent plane strain solution and field data from a test area in ska edeby sweden key words plane strain consolidation soft clay vertical drains

correlation between changes in groundwater levels and surface deformation from gps measurements in the san gabriel valley california 1 changes in groundwater levels cause water bearing basins to deform here we provide a detailed history of horizontal surface displacements in the san gabriel valley california which we show are highly correlated with the water level changes measured at a nearby well correlation coefficient of 0 96 0 01 we use the surface response from a one year period during which water level change in the nearby well was over 16 m to monitor the deformations over a 14 year period from 1998 to 2011 the water level changes lead surface deformation by 21 days but the significance of the offset is only weakly supported p value 0 129 the projection method can be used as a real time monitoring or detection system for deformation caused by a variety of mechanisms such as fluid injection and removal groundwater development oil production carbon sequestration and by seismic and volcanic activity

late cretaceous early tertiary palaeoclimates of northern high latitudes a quantitative view analyses of plant community structure vegetational and leaf physiognomy and growth rings and vascular systems in wood provide qualitative and quantitative data that can be combined to define non marine palaeoclimatic parameters with better resolution than is available from other principally sedimentological methods application of these techniques to cenomanian through paleocene floras from high palaeolatitudes 75 85 n indicates a polar light regime similar to that of the present plant data suggests cenomanian sea level mean annual air temperatures mats of 10 c and mats of 13 c 5 c and 6 7 c in the coniacian maastrichtian and paleocene respectively evapotranspirational stresses at sea level were low and precipitation was in most part uniform throughout the growing season in the cenomanian with possible seasonal drying occurring by the maastrichtian maastrichtian winter freezing was likely but periglacial conditions did not exist at sea level permanent ice was likely above 1700 m at 75 n in the cenomanian and above 1000 m at 85 n in the maastrichtian these near polar data provide critical constraints on global models of late cretaceous to early tertiary climates

antarctica cretaceous cradle of austral temperate rainforests although it is well known that certain gondwanic elements of present day austral temperate rainforests occurred on antarctica during latest cretaceous to early tertiary times there has been insufficient factual evidence for pinpointing the cradle of these forests fossil evidence from antarctica and closely associated regions in the creataceous southern gondwanan assembly confirms that antarctica was a cretaceous origination and dispersal region of certain elements of today s southern hemispheric humid and perhumid forests antarctic origins are indicated for the fern lophosoria the podocarp gymnosperms lagarostrobus and dacrydium nothofagus ilex and several lineages of the proteaceae migration to their present regions of distribution was probably step wise antarctica also served as a cretaceous dispersal corridor for other angiosperms represented today in mid to low latitude austral regions these include ascarina or its stock myrtaceae gunneraceae and winteraceae all of which had earlier histories in northern gondwana or southern laurasia origination and dispersal appears to be related to changing environmental circumstances associated with fragmentation of gondwana and opening and enlargement of the southern oceans

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

characterization of a smear zone around vertical drains by large scale laboratory tests installation of prefabricated vertical drains using a mandrel causes disturbance of clay surrounding the drain resulting in a smear zone of reduced permeability in this paper an attempt is made to characterize the smear zone using large scale laboratory model tests two tests simulating the cases of no smear and with smear were conducted excess pore water pressures were monitored at seven different locations along the radial direction in addition undisturbed samples were collected at various locations in the clay layer for conducting oedometer tests the distribution of excess pore pressure due to drain installation gave a clear indication of the extent of the smear zone the effect of reconsolidation on the properties of clay was found to be much greater than that of the remoulding of the clay the extent of the smear zone was also confirmed from the change in permeability of the clay layer in the smear zone obtained from oedometer tests the radius of the smear zone is about four times tha

resolving volcanic activity of 20ma ago with relative accuracy of 1 yr from tree rings of petrified woods tree rings of petrified woods were analyzed to resolve a volcanic activity of 20 ma ago with a relative accuracy of 1 yr samples are those in the volcanic breccia of the early miocene formation of volcaniclastic rocks and tuffaceous lake sediments in central japan field observations indicate that these petrified woods are the fossils of the trees that were carried away from their growth sites with volcanic breccia ejected upon explosive eruption and included in it using a dendrochronological procedure we measured the relative years of the last rings of the petrified woods the relative years of the last rings are concentrated in 17 yrs where the ring width patterns show an anomalous behavior similar to one observed in firs growing in the area devastated by mt st helens we suggest that the last formed tree ring of a petrified wood is a record of volcanic eruption and that the activity of volcano continued over a period of 17 yrs in which eruption occurred at least five times high resolution regarding the activity period demonstrates uniqueness of tree ring study to investigate volcanism in the geologic past

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

endemism and heterochroneity in the late cretaceous campanian to paleocene palynofloras of seymour island antarctica implications for origins dispersal and palaeoclimates of southern floras

north american nonmarine climates and vegetation during the late cretaceous abstract analyses of physiognomy of late cretaceous leaf assemblages and of structural adaptations of late cretaceous dicotyledonous woods indicate that megathermal vegetation was an open canopy broad leaved evergreen woodland that existed under low to moderate amounts of rainfall evenly distributed through the year with a moderate increase at about 40 45 n many dicotyledons were probably large massive trees but the tallest trees were evergreen conifers megathermal climate extended up to paleolatitude 45 50 n mesothermal vegetation was at least partially an open broad leaved evergreen woodland perhaps a mosaic of woodland and forest but the evapotranspirational stress was less than in megathermal climate some dicotyledons were large trees but most were shrubs or small trees evergreen conifers were the major tree element some mild seasonality is evidenced in mesothermal woods precipitational levels probably varied markedly from year to year northward of approximately paleolatitude 65 n evergreen vegetation was replaced by predominantly deciduous vegetation this replacement is presumably related primarily to seasonality of light the southern part of the deciduous vegetation probably existed under mesothermal climate comparisons to leaf and wood assemblages from other continents are generally consistent with the vegetational climatic patterns suggested from north american data limited data from equatorial regions suggest low rainfall late cretaceous climates except probably those of the cenomanian had only moderate change through time temperatures generally appear to have warmed into the santonian cooled slightly into the campanian and more markedly into the maastrichtian and then returned to santonian values by the late maastrichtian the early eocene was probably warmer than any period of the late cretaceous latitudinal temperature gradients were lower than at present for the campanian and maastrichtian a gradient of about 0 3 c 1 latitude is inferred equability was high a mean annual range of temperature of about 8 c is inferred for paleolatitude 51 56 n during the campanian most late cretaceous plants evolved in a climate characterized by absence of freezing and low to moderate amounts of precipitation a brief low temperature excursion and a major long lasting increase in precipitation occurred at the cretaceous tertiary boundary in megathermal climates these events selected for plants that could exist in rainforest environments in mesothermal climates deciduousness and contamitant structural adaptations were selected the events at the cretaceous tertiary boundary had a major and long lasting impact on the evolution of land plants and their ecosystems low precipitation at low to middle late cretaceous latitudes is suggested to be the result of high levels of atmospheric co2 which in turn are probably related to inability of warm saline oceans to store large amounts of carbon conditions appear to have rapidly changed at the cretaceous tertiary boundary when oceanic circulation and stratification may have been fundamentally altered after the boundary the oceans were apparently able to store much greater amounts of carbon and the oceans withdrew large amounts of co2 from the atmosphere in turn more precipitation fell at low to middle latitudes the resulting high biomass vegetation formed a second major carbon reservoir to keep atmospheric co2 low relative to the late cretaceous changes in oceanic and atmospheric circulation probably resulted from some factor external to the ocean atmosphere system

a terrestrial scenario for the cretaceous tertiary boundary collapse of the marine pelagic ecosystem in this paper we present an expansion of the model for marine ecosystem collapse at the cretaceous tertiary boundary presented by brinkhuis and zachariasse 1988 a long term sea level drop at the end of the cretaceous culminated in a short term regressive pulse at k t time deep water production was curtailed minimizing the vertical advection of nutrients and oxygen in the oceans consequently a productivity crisis developed which could only be survived by cosmopolitan shallow dwellers and the oxygen minimum zone omz expanded no sustained oceanic anoxic event followed the k t boundary event since productivity had dropped to extremely low values at k t time however the short term expansion of the omz invoked by the combination of minimized oxygen advection and abrupt mass mortality caused dysoxic conditions even to reach up to the shelves as can be deduced from sedimentological chemical and faunistic observations

cretaceous climate a comparison of atmospheric simulations with the geologic record abstract atmospheric simulations using realistic cretaceous geography 100 million years ago suggest that paleography is an important factor governing the nature of the circulation the simulated cretaceous atmospheric circulations are markedly different both from the present day atmospheric circulation and from the classical hypotheses of a weaker circulation and poleward displacement of circulation features e g the subtropical high therefore they pose specific questions which can be tested against the geologic record aspects of the cretaceous simulations are verified in comparisons with the geologic record the simulations serve to guide areas of future paleoclimatic research and to formulate better the nature of the problem of warm equable climates

aspects of vertical drain design darcian or non darcian flow the classical consolidation equations developed by barron in 1944 and 1948 are well known among engineers working on soil improvement by preloading in combination with installation of vertical drains these equations have been gradually refined and are generally utilized in conventional design the design may seem simple in theory but is connected with a great number of uncertainties from a practical point of view the problems connected with the choice of consolidation parameters will be commented on and practical advice for the design will be given in this paper a number of case records will be presented and compared with on one hand the conventional method of design and on the other hand the so called method developed by the author in 1960 to take into account the effect of smear the method is based on an exponential correlation between hydraulic gradient and flow velocity we find that the correlation between the conventional theory and practice based on back analysis of field data is les

xenoxylon junggarensis sp nov a new gymnospermous fossil wood from the norian triassic huangshanjie formation in northwestern china and its palaeoclimatic implications abstract a permineralized gymnospermous wood xenoxylon junggarensis sp nov is described from the norian upper triassic huangshanjie formation in dalongkou section jimsar county xinjiang uygur autonomous region northwestern china the pycnoxylic wood consists of thick walled tracheids and thin walled rays it is characterized by commonly rounded to very compressed contiguous or sometimes separated uniseriate occasionally rounded and alternate biseriate radial pits and one or two simple large pits in each cross field the fossil wood genus xenoxylon gothan is known to be an indicator of cooler and or wetter climates in the boreal hemisphere during the mesozoic its occurrence in the huangshanjie formation from junggar basin together with the palaeobotanical and palynological data indicates that a wet and temperate climate prevailed in the northern xinjiang during the norian interval the mean sensitivity of analysis of 22 growth rings is 0 36 suggesting a seasonal response to climate growth rings in the fossil woods are large 2 3 mm average with a maximum of 5 44 mm representing either a longer growing season or more favorable conditions for growth including readily available water and higher temperature based on a considerable amount of earlywood and a small percentage of latewood and some indirect evidence it is hypothesized that growth of x junggarensis in the high latitude junggar basin in the late triassic was limited by light levels

wood decay of xenoxylon yunnanensis feng sp nov from the middle jurassic of yunnan province china abstract a permineralised gymnosperm wood xenoxylon yunnanensis feng sp nov is described from the middle jurassic shaximiao formation in huize county yunnan province southwest china the pycnoxylic wood consists of thick walled tracheids and thin walled rays it is characterised by uniseriate contiguous compressed bordered pits on the radial walls of tracheids and one large simple pit in each cross field growth rings exhibit narrow latewood the mean sensitivity of analysis of 25 growth rings is 0 2 suggesting that a climate with abundant rainfall and weak seasonality could have prevailed in yunnan at least locally during the middle jurassic the outer portion of the wood is largely decayed and shows poorly preserved cells lacking details decayed tracheids displaying various features including removal of middle lamellae separations of secondary walls presence of thickened corners and appositions are recognised as cell reactions to fungal activity irregularly distributed micro cavities are formed by complete decomposition of tracheids and rays in the wood abundant fungal remains occurring in the wood generally consist of multiple branched hyphae these fungal hyphae are either confined to individual cell lumens or extend through adjacent cells although the probable reproductive structure and typical clamp connection are very rarely observed with few septate hyphae the affinities of these fungal hyphae are somewhat obscure nevertheless our study sheds light on the palaeoecology of middle jurassic terrestrial ecosystems of southwest china

back calculation of consolidation parameters from field measurements at a reclamation site a pilot test was carried out at a land reclamation project site to study the effect of vertical drains on the rate of consolidation of a marine clay deposit in singapore theoretical and numerical analyses were conducted to interpret the field measurements of pore pressure and settlement and consolidation parameters were back calculated the back calculated preconsolidation pressure is similar to that obtained from the laboratory consolidation test on undisturbed samples but the field deduced compression index is generally larger than that measured in the laboratory the coefficient of consolidation back calculated from the settlement measurement is larger than that from the pore pressure measurement the coefficient of consolidation for horizontal flow obtained from the rowe cell test which is comparable to that back calculated from the field settlement measurement is recommended for the preliminary design of vertical drains without the need of considering the smear effect key words clays consolida

biogenic structures in modern slope to deep sea sediments in the sulu sea basin philippines abstract slowly accumulated slope and rise sediments 5 20 cm 1000 yr are totally bioturbated as compared to only 10 30 in rapidly deposited abyssal plain sediments 100 200 cm 1000 yr in contrast to a decrease in degree of bioturbation biogenic trace diversity increases with water depth all ichnocoenoses are clearly influenced by the low oxygen content of the bottom water caused by minimal circulation and restricted water exchange oxygen deficiency and relatively high sedimentation rates have created nutrient rich sediments thus there is no need for optimal fractionation into individual ecological niches and behavioral programs are not highly developed 1 in slope and rise sediments animal traces are associated with biodeformational structures 2 in slope to abyssal plain sediments trace assemblages are dominated by burrows with open tubes for circulation of respiration water 3 in abyssal plain sediments small diameter biogenic traces common in turbidite sequences graphoglyptids e g paleodictyon are absent this may be due to rapid sedimentation leading to inefficiency of graphoglyptid behavior where graphoglyptids are lacking ichnocoenoses are dominated by forms like phycosiphon in slope and rise sediments graphoglyptids may have been destroyed by deeper burrowing organisms

radial consolidation of clay using compressibility indices and varying horizontal permeability a system of vertical drains with surcharge load to accelerate consolidation by shortening the drainage path is one of the most popular methods of soft ground improvement the conventional radial consolidation theory including smear and well resistance has been commonly used to predict the behaviour of vertical drains in soft clay its mathematical formulation is based on the small strain theory and for a given stress range a constant volume compressibility mv and a constant coefficient of horizontal permeability kh are assumed however the value of mv varies along the consolidation curve over a wide range of applied pressure p in the same manner kh also changes with the void ratio e in this paper the writers have replaced mv with the compressibility indices cc and cr which define the slopes of the e log relationship moreover the variation of the horizontal permeability coefficient kh with the void ratio e during consolidation is represented by the e log kh relationship

tree ring analysis elucidating palaeo environmental effects captured in an in situ fossil forest the last 80 years within an early permian ecosystem abstract the early permian chemnitz fossil lagerstatte leukersdorf formation chemnitz basin se germany represents a diverse t 0 assemblage of a fossil forest ecosystem around the sakmarian artinskian transition 290 6 1 8 ma which was preserved by pyroclastic deposits of a multi phased volcanic eruption the multi aged plant community consists of predominantly hygrophilous elements which grew on an alluvial plain mineral substrate under sub humid conditions representing a wet spot environment strong seasonality triggered the formation of annual tree rings in arborescent woody plants such as pycnoxylic gymnosperms medullosan seed ferns and calamitaleans from several hundred fossil trees the 53 best preserved specimens were selected and investigated in detail by measuring 2 081 tree rings in individual sequences of up to 77 rings ring sequences were analysed by standard dendrochronological methods to determine both annual growth rates and mean sensitivity morphological and statistical analyses on single tree rings reveal different tree ring types according to the different plant groups pycnoxylic gymnosperms have distinct and regular tree rings whereas medullosan seed ferns and calamitaleans show indistinct and regular tree rings as well as so called event rings results reveal differences between plant groups regarding their physiological reactions or adaptations to seasonal fluctuations in comparison to pycnoxylic gymnosperms both medullosan seed ferns and calamitaleans exhibit reduced growth rates and more sensitive reaction to environmental perturbances as water deficiency pointing to comparably lower adaptation to seasonally dry palaeoclimate in this context event rings are in many cases traced back to plant physiological stress during particularly severe drought periods altogether these fossil trees serve as sensitive environmental archives which shed light on growth conditions several decades back in time from the entombing eruption

fossil charcoal as an indicator of palaeoatmospheric oxygen level charcoal results from incomplete combustion of plant material it is produced naturally by wildfire and being relatively tough and unbiodegradable it may be transported and incorporated into a variety of sedimentary environments wildfire requires adequate atmospheric oxygen for the combustion of plant fuel wood leaf litter fossil charcoal from the devonian onwards suggests that the oxygen level in the atmosphere has not fallen below 13 in this interval further the extreme flammability of even wet plant fuel at oxygen levels above 35 makes this the highest figure compatible with the occurrence of terrestrial vegetation

cretaceous forest composition and productivity inferred from a global fossil wood database abstractglobal patterns of cretaceous forest composition and produc tivity are analyzed using a comprehensive fossil wood database n 2238 to ascertain forest composition records were classi ed by botanical af nity plotted on georeferenced paleomaps and ana lyzed with arcgis tools results con rm previous conjecture that araucarioid and podocarpoid conifers were globally codominant in early cretaceous time especially in humid tropical and paratropi cal biomes but drastically reduced in numbers and range during the late cretaceous cupressoid conifers which were most common in seasonally dry mid latitudes and pinoid conifers which were asso ciated with temperate conditions at higher northern latitudes also declined at the same time though less markedly spatial analysis suggests that the loss of conifer forests especially araucarioids was linked to the rise of co occurring angiosperms our data also show that while angiosperms explosively diversi ed in mid cretaceous time they did not become forest dominants until the latest cretaceous 25 m y later by which time the modern relictual pattern of conifer distribution had been established to ascertain forest productivity mean tree ring width data were obtained from direct measurements and literature reviews n 284 and plotted by paleolatitude com parison with modern data shows that cretaceous forest productivity was signi cantly elevated 2 in mid and high paleolatitudes imply ing a poleward displacement of the temperate zone by 15 our data provide quantitative veri cation of cretaceous climate vegetation models and improve the understanding of the long term effects of future global warming introduction

cross bedded woody debris from a pliocene forested river system in the high arctic beaufort formation meighen island canada abstract cross bedding the inclined internal stratification that records the migration of certain transverse sedimentary bedforms is nearly ubiquitous in current transported bedload sediments although examples of the structure are known from inorganic clastic sediments and sedimentary rocks from practically all depositional environments and intervals of geologic history here we report cross bedded lenses that are composed wholly or significantly of woody debris in pliocene alluvium of the beaufort formation in the canadian high arctic the uniqueness of cross bedded woody debris has hitherto been overlooked but we demonstrate that in the entire phanerozoic record it is apparently restricted to alluvium deposited during a warm climatic interval that permitted the growth of boreal type forests within 10 latitude of the north pole the marked spatiotemporal restriction of cross bedded woody debris implies that there may be environmental factors unique to polar forests which promote the subaqueous transport of large amounts of fine woody debris as fluvial bedload we propose a non uniformitarian conceptual model for the formation of cross bedded woody debris in forested polar rivers whereby an exceptional abundance of woody debris could accumulate and become saturated and denser than water due to reduced decomposition on forest floors that were subject to prolonged periods of darkness and subzero temperatures

the plate tectonic impact on climatic change with particular relevance to mesoamerica the oceanic circulation and associated climatic zonations some 120 ma can be taken as more geologically normal than the last few million years it was dominated by a strong circum equatorial current accompanied by warm water circulation well into polar areas this resulted in a marked increase in salinity between 10 and 25 n s with consequential strong ocean stratificacion and circulacion mostly in the upper one kilometre this pattern was likely to be associated with a simple two hadley cell atmospheric circulacion orbitally forced periodical variacions in solar insolacion gave eustatic sea level changes of less than 10 m amplitude during the last 50 ma the relative posicions of the mesoamerican continental plates have not changed greatly and hence plate mocions have had little or no effect on the atlantic deep ocean haline circulacion secondary plate tectonic processes topographic change volcanism and seismic activity were more important and had marked local effects on the climate which could be mistaken for global changes the chihuahua area of mexico provides the optimum site for identifying recent global climatic changes

septomedullopitys szei sp nov a new gymnospermous wood from lower wuchiapingian upper permian continental deposits of nw china and its implication for a weakly seasonal humid climate in mid latitude ne pangaea abstract septomedullopitys szei sp nov is described from the wuchiapingian wutonggou formation of tarlong valley southern bogda mountains xinjiang in northwestern china the stem has a heterogeneous pith ca 15 20 mm in diameter and containing numerous linear secretory ducts and parenchymatous bands primary xylem is endarch and the tracheids contain scalariform thickenings secondary xylem is of the protophyllocladoxylon type comparisons with contemporaneous gymnospermous woods containing either heterogeneous pith with ducts or protophyllocladoxylon type secondary xylem from the angara palaeocontinent indicate that the tarlong stem represents a new permian morphotaxon for the region the presence of coprolites borings and spindle shaped cavities within the stem suggests well developed animal plant fungi interactions the occurrence of numerous growth interruptions and absence of true growth rings within the stem suggest weak seasonality of annual precipitation the interruptions suggest a humid climate with short term nonperiodic droughts

sensitivity of tree growth to a high co2 environment consequences for interpreting the characteristics of fossil woods from ancient greenhouse worlds abstract long term carbon cycle models and independent proxies indicate that the atmospheric co 2 concentration was substantially higher in the mesozoic and early tertiary than now the responses of tree growth to a high co 2 environment must therefore be understood if present day relationships between climate and tree growth are to be used with confidence for palaeoclimate reconstructions from mesozoic and tertiary fossil woods a brief review of experimental data shows that stimulation of leaf photosynthesis suppression of plant respiration and lower transpiration rates under elevated co 2 500 700 ppm can reduce the ratio of wood basal area to tree height but increase total basal area growth in wood by 20 25 to assess the consequences of these plant co 2 responses for tree growth during ancient greenhouse episodes we developed a mathematical model explicitly incorporating the physiological mechanisms underpinning the observed co 2 effects application of this model to predict the height of coniferous forests in the late jurassic 150 ma and mid cretaceous 100 ma indicated maximum heights in the mid latitudes of over 60 m and 40 60 m respectively corresponding wood growths of these forests expressed as basal area growth rates were 1 5 2 5 cm 2 and 0 75 1 75 cm 2 sapwood m 2 ground area yr 1 values exceeding those of modern conifers in warm temperate sites these results were highly sensitive to the concentration of atmospheric co 2 and this co 2 sensitivity depended strongly on climate consequently direct application of present day growth climate relationships to fossil woods may be inappropriate for the mesozoic and tertiary however models that explicitly consider the mechanisms of plant co 2 responses may provide a useful method for accounting for this co 2 sensitivity allowing more secure palaeoclimate reconstructions from material of this age

nonlinear drainage model of viscoelastic aquitards considering non darcian flow abstract numerous aquitard drainage models for dewatering induced land subsidence have been proposed in the past most of them are based on one or more of the following assumptions including the validity of darcy s law neglect of rheological nature and constant soil properties however these assumptions may fail to reflect actual characteristics of viscoelastic aquitards for this reason the present study improves terzaghi s one dimensional 1 d consolidation model by incorporating the exponential non darcian law the merchant viscoelastic model and the nonlinear correlations between soil compressibility hydraulic conductivity and void ratio the numerical solutions for the pore pressure change are obtained using a finite volume method the expression for compaction and consolidation of aquitard is derived a parametric study and comparison between the proposed model and the terzaghi model indicate that the nonlinear permeability and the rheological nature reduce the pore pressure change and the degree of consolidation in the aquitard the effects are more apparent for an aquitard with a higher compressibility and more obvious non darcian flow nature meanwhile the reduction in pore pressure change decreases the effective stress acting on the soil skeleton resulting in smaller compaction for an aquitard with more obvious nonlinear permeability rheological property and non darcian flow nature besides although the higher nonlinear compressibility also reduces the pore pressure change yet it can induce more significant compaction in the aquitard

disrupted vegetation as a response to jurassic volcanism in southern sweden central skane scania in southern sweden hosts evidence of extensive jurassic volcanism in the form of mafic volcanic plugs and associated volcaniclastic deposits that entomb wellpreserved macro plant and spore pollen assemblages palynological assemblages recovered from the hoor sandstone are of hettangian pliensbachian age and those from the overlying lahar deposits are dated as pliensbachian early toarcian palynomorph assemblages from these units reveal significantly different ecosystems particularly with respect to the gymnospermous components that represented the main canopy plants both palynofloras are dominated by osmundacean marattiacean and cyatheacean fern spore taxa but whereas the hoo r sandstone hosts abundant chasmatosporites spp pollen produced by plants related to cycadophytes the volcanogenic deposits are dominated by cypress family pollen perinopollenites with an understorey component rich in putative erdtmanithecales or possibly gnetales and collectively representing vegetation of disturbed habitats permineralized conifer wood attributed to protophyllocladoxylon sp belonging to plants that probably produced the abundant perinopollenites grains is abundant in the volcanigenic strata and shows sporadic intraseasonal and multi year episodes of growth disruption together with the relatively narrow but marked annual growth rings and the annual and mean sensitivity values that span the complacent sensitive domains these features suggest growth within mediterranean type biomes subject to episodic disturbance less

southern polar forests the early cretaceous floras of victoria and their palaeoclimatic significance abstract a diverse fossil flora including cryptogams pteridosperms cycadales bennettitales ginkgoales coniferales and angiosperms occurs in early cretaceous fluvial and lacustrine strata in the otway and gippsland basins in southern victoria both evergreens e g araucarians cycads ferns and deciduous or semi deciduous forms e g certain pteridosperms and ginkgoales seem to have been represented certain ferns ginkgos and conifers grew to a large size overall the assemblages are typical of early cretaceous floras the associated fauna includes dinosaurs hypsilophodontids allosaurs lepidosaurs chelonians birds fish including the lungfish ceratodus and insects the evidence of the biota as a whole suggests a warm to cool temperate relatively equable climate of moderate seasonality with no widespread winter freezing the complex mesozoic apparent polar wander path apw indicated for australia places victoria in high to polar palaeolatitudes ca 70 85 s during the early cretaceous this apw path is supported by paths for other gondwana continents the existence of the victorian early cretaceous forest and biotic communities through polar nights of about two to five months duration is difficult to accept evergreen species would have required relative equability of light whatever the temperature the dinosaurs foliage throughout the year and the lungfish warm to temperate conditions without freezing in view of the consistency of mesozoic palaeomagnetic results for gondwanaland and the enigmatic presence of mesozoic and early cenozoic fossil floras and faunas in very high northern palaeolatitudes the possibility of a reduced obliquity of the ecliptic in mesozoic early cenozoic time should be considered

do fossil plants give a climatic signal the agreement in the pattern of major biomes with that of climatic zonation of the earth gives a strong indication that climate is the overriding influence controlling the distribution of plant communities three aspects of plants which may be preserved in the fossil state give a signal of the climatic conditions under which they grew 1 the present climatic association of their 9nearest living relative9 2 leaf physiognomy of arborescent plants 3 the character of their secondary xylem 9wood9 of ordinary usage reflecting by the presence or absence of growth rings the seasonality or lack of it in their environment and the potential for tree growth that it offered the significance and limitations of these 9palaeoclimatic signals9 as they may be read from the fossil plant record are reviewed and evaluated the recent demonstration that stomatal frequency of leaves is responsive to changes in ambient carbon dioxide partial pressure offers promise for direct palaeobotanical evidence for past changes in the level of this climatically significant atmospheric constituent

cretaceous and early tertiary climates of antarctica evidence from fossil wood abstract fossil wood is abundant in cretaceous and early tertiary sediments of the northern antarctic peninsula region the wood represents the remains of vegetation that once grew in high palaeolatitudes when the polar regions were warmer during former greenhouse climates fossil wood is a unique data store of palaeoclimate information analyses of growth rings and anatomical characters in fossil wood provide important information about temperature rainfall seasonality and climate trends for this time period in antarctica climate signals from fossil wood supported by sedimentary and geochemical evidence indicate a trend of cool climates during the early cretaceous followed by peak warmth during the coniacian to early campanian narrower growth rings suggest that the climate cooled during the maastrichtian and palaeocene cool wet and possibly seasonal climates prevailed at this time with tentatively estimated mean annual temperatures mats falling from 7 c to 4 8 c respectively determined from dicotyledonous dicot wood anatomy the late palaeocene early eocene was once again warm with estimated mats of 7 15 c from dicot wood analysis but conditions subsequently deteriorated through the latter part of the eocene when cold seasonal climates developed ultimately leading to the onset of cenozoic ice sheets and the elimination of vegetation from most of antarctica

large strain vacuum assisted consolidation with non darcian radial flow incorporating varying permeability and compressibility abstracta numerical solution has been developed for large strain consolidation incorporating non darcian nonlinear radial flow with varying compressibility and permeability coefficients the solution can accommodate both conventional fill surcharge as well as vacuum preloading the smear effect caused by mandrel driven vertical drains is also captured in the analysis the proposed model is verified by comparing it with fem simulation existing laboratory data other existing theoretical solutions and its advantage of capturing the multiple factors influencing radial drainage and consolidation is demonstrated the effects of non darcian flow are found to be significant for obtaining an accurate solution unlike numerous past solutions that are based on linear darcy flow the salient finding of this study is that the conventional small strain theory can overestimate the rate of consolidation with radial drainage especially for highly compressible soils such as estuarine clays under substantial preloadin

significance of ring porosity in analysis of a sangamon flora abstract trees with ring porous wood are limited to the higher latitudes and form an important component of the vegetation of north america analysis of the occurrence of trees with this wood type in north america east of the rockies shows that they make up an increasing percentage of the upland tree flora as precipitation decreases the northern limit of ring porous trees is probably related to winter temperature extremes and a mechanism of avoiding frost damage based on supercooling of cellular water percent of ring porous species has the potential for use in the reconstruction of paleoclimates as an example the calculated value for the toronto don beds flora which dates from the last sangamon interglacial period is only slightly greater than that of the present day flora and thus suggests that the interglacial climate in this region was much the same or only somewhat different from today s the differences were probably related to lower winter temperatures or lower frequency of winter temperature extremes the climatic requirements of zonal vegetation and individual species indicate that summer temperatures were not higher than at present the extralocal species must be evaluated carefully since nonclimatic considerations may be important in explaining their presence

a warm equable cretaceous the nature of the problem abstract the nature of the problem of warm equable paleoclimates is defined by investigating the mid cretaceous period the problem consists of three components 1 defining precisely the climatic state during any specified interval of geologic time 2 specifying the external climatic forcing factors which may have been important and 3 understanding the climatic response to any specific modifying influence these components are characterized by limitations of critical importance in understanding paleoclimates the nature of the problem of a warm cretaceous is defined both qualitatively and quantitatively within these limits

a review of tertiary climate changes in southern south america and the antarctic peninsula part 2 continental conditions abstract climate changes in southern south america and the antarctic peninsula during the tertiary show a strong correlation with ocean warming and cooling events which are in turn related to tectonic processes during periods of accelerated sea floor spreading and mid ocean ridge activity sea levels rose so that parts of the continents were flooded and forests were destroyed however this was balanced by the large scale release of co2 during volcanic outgassing and carbonate precipitation on the continental shelves which caused rising air temperatures and the poleward expansion of sub tropical and temperate forests cooling episodes generally caused an increase in the north south thermal gradient because of an equatorward shift in climate belts so that the westerly winds intensified and brought higher rainfall to the lower latitudes an increase in wind blown dust caused temperatures to drop further by reflecting sunlight back into space the rising andes range had a marked influence on climate patterns up to the middle miocene it was still low enough to allow summer rainfall to reach central and north central chile but after about 14 ma it rose rapidly and effectively blocked the spill over of moisture from the atlantic ocean and amazon basin at this time the cold humboldt current was also established which together with the andes helped to create the arid diagonal of southern south america stretching from the atacama desert to the dry steppes of patagonia this caused the withdrawal of subtropical forests to south central chile and the expansion of sclerophytic vegetation to central chile however at the same time it intercepted more rain from the northeast causing the effect of the south american monsoon to intensify in northwestern argentina and southern bolivia where forest communities presently occur in patagonia glaciation started as early as 10 5 ma but by 7 ma had become a prominent feature of the landscape and continued apparently uninterruptedly into the pleistocene the antarctic peninsula saw its first mountain glaciation between 45 and 41 ma with major ice sheet expansion commencing at about 34 ma isolated stands of nothofagus forests were still present in low lying areas suggesting that the glaciers were initially wet based but dry based glaciers were established at around 8 ma although temperatures rose briefly during the messinian pliocene transition causing sub antarctic flora to retreat to higher elevations of the transantarctic mountains the present cold polar conditions were finally established by about 3 ma

some limitations in using leaf physiognomic data as a precise method for determining paleoclimates with an example from the late cretaceous pautut flora of west greenland abstract plant parts of the late cretaceous west greenland pautut flora are derived from vegetation growing in lower delta plain delta upland and levee habitats a large river system drained the uplands and deposited leaves from species there and levee areas into a shallow bay setting the large drainage area of the rivers caused a great diversity of species to be preserved in the bay when these upland and levee species are combined with those that grew and were deposited in the lower delta plain areas 12 fern six cycad cycadeoid 1 ginkgoalean 35 conifer and over 85 angiosperm species represent the pautut flora when the paleotemperature derived from the angiosperm leaf margin ratio of the complete pautut flora 8 c is compared to other paleobotanical data and oxygen isotope values warm temperate to subtropical there is a serious discrepancy that puts the leaf physiognomic approach for precisely determining paleoclimate in the cretaceous in serious doubt also paleoclimatic interpretations based on the angiosperm leaf margin data of leaves from the lower delta plain species would indicate slightly cooler conditions than that suggested by the upper delta plain species leaf size would indicate wetter conditions in the lower delta plain even though other leaf features e g drip tips suggest moist conditions did occur in the upper delta plain these preservation enough that regional paleoclimate scenarios drawn from only one depositional setting or loclity can be erroneous a sampling size of less than 30 angiosperm species for a fossil flora also is suspect for reliably indicating climatic conditions unless the flora was originally impoverished of angiosperm species taphonomic factors play a significant role in fossil leaf preservation so collected fossil assemblages must closely represent the original vegetation before paleoclimatic interpretations based on leaf physiognomy can have a degree of credibility a limit to plausibility is especially significant in cretaceous floras because they have a limited diversity due to evolutionary constraints and appear to have consisted of more successional species than younger floras thus displaying intermediate climatic conditions moisture and arctic light levels further restrict determination of paleoclimatic conditions derived from leaf margin ratios and leaf size

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

growth ring analysis of early tertiary conifer woods from the canadian high arctic and its paleoclimatic interpretation abstract fossil forests where petrified stumps were preserved in growth position have been found within early tertiary sediments near strathcona fiord ellesmere island canadian arctic archipelago these fossil forests are obvious evidence for early tertiary climate much warmer than that of today we analyzed the growth rings of petrified woods from two fossil forest sites one in middle paleocene and the other in late early eocene to extract information on climate change the woods consist most abundantly of metasequoia and cf glyptostrobus suggesting that these forests grew in similar environments of warm to cool temperate climates mean ring width mean sensitivity and power spectrum were calculated for ring width sequences although significant difference in the mean ring width between the two forests was found a comparison with living trees suggests that the difference can be attributed to the specific difference between the forests so that a significant climate change may not necessarily be invoked we found little significant difference in the mean sensitivity and power spectrum between the forests neither did we find any strong indication of periodicities consideration of all features suggests that there was no significant difference in climate of middle paleocene and late early eocene time in the high arctic however the mean ring widths of these forests were significantly smaller than that reported for mid cretaceous high arctic fossil forest

dendrochronology and middle miocene petrified oak modern counterparts and interpretation abstract this study reports the first successful statistical crossdating among many ring width time series from petrified wood thus providing a replicable continuous annual resolution window into tree growth and environmental influences during the middle miocene the petrified samples of the genus quercus originated at the stinking water sw locality in oregon a miocene aged exposure associated with the columbia river basalts 40ar 39ar dating on pillow basalt from the locality yielded a weighted plateau age of 13 79 0 09 ma placing the death of the trees at the end of the langhian stage of the middle miocene 15 97 0 05 to 13 65 0 05 ma during the middle miocene climate transition mmct ring width time series from 26 radii 17 different trees show significant intercorrelation a modified coexistence approach was applied to determine the likely climate range when the sw trees were growing the modified approach included regression of site mean ring width time series statistic values on estimated soil moisture for the site locations using site mean data from 126 modern quercus sites from across the united states identification of highly significant linearities indicated strong relationships between ring width intercorrelation and soil moisture and ring width variability and soil moisture comparison of individual modern site mean statistical values with values calculated for the sw locality suggests a mesic growing environment for the sw quercus with moderate temperatures geographic placement of modern quercus sites with site mean statistics similar to the sw values indicates a modern analogue in the eastern united states modern distributions of mesic species in the genera present at the sw locality suggest similarities with the central and southern appalachian mountains and the ozark ouachita mountains indicating a mean annual temperature range of 10 c to 15 c and a mean annual precipitation range of 750 mm to 1200 mm when the sw quercus were growing

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

dispersed angiosperm cuticles their history preparation and application to the rise of angiosperms in cretaceous and paleocene coals southern western interior of north america abstract cuticle the decay resistant outer layer of leaves and young stems provides a reliable means of identifying fossil plant remains and reflects the vegetative adaptations of plants to climate and other environmental parameters the study of dispersed angiosperm cuticles originated prior to world war ii and has focused on the origin and paleoecology of coal activity in dispersed cuticles reached a high point during the 1950s and 1960s with the study of tertiary lignites in central europe then subsided in central europe as workers from other regions expanded the technique to other time periods and geographic regions data from dispersed cuticles augment data from palynomorphs because dispersed cuticles originate from a different generation of the vascular plant life cycle and have different taphonomic histories because the analysis of dispersed angiosperm cuticles is unfamiliar to many geologists methods for the analysis and preparation of dispersed angiosperm cuticles are detailed in an appendix dispersed cuticle assemblages from coals in the upper albian longford member of the kiowa formation and the maastrichtian paleocene raton formation of the southern western interior provide new constraints on the times that angiosperms entered coal swamps and rose to dominance the kiowa assemblages indicate that angiosperms first entered coal swamp environments by the late albian while the raton assemblages indicate that angiosperms dominated primary productivity in some subtropical coal swamps by the late maastrichtian angiosperms in kiowa coals probably comprised pioneer species in conifer dominated vegetation the most common family of angiosperms was chloranthaceae angiosperms in upper maastrichtian raton coals comprised the dominant seed plants to the exclusion of conifers magnoliid dicots and monocots were the dominant taxa and comprised diverse genera and families evidence from palynology and types of preserved cuticle indicates that ferns were subordinate to seed plants in biomass in raton coals in contrast to some described assemblages from the northern western interior paleocene coals from the raton basin show the loss of many cretaceous angiosperm taxa as well as the appearance of new taxa including conifers belonging to taxodiaceae however these taxodiaceae were evergreen and subordinate in abundance to angiosperms vegetational patterns shown by cretaceous paleocene coals of the southern western interior contrast with those of more northerly regions and indicate a poleward gradient in the timing of angiosperm dominance in coal swamps

a high latitude gondwanan lagerstatte the permian permineralised peat biota of the prince charles mountains antarctica abstract the toploje member chert is a roadian to wordian autochthonous parautochthonous silicified peat preserved within the lambert graben east antarctica it preserves a remarkable sample of terrestrial life from high latitude central gondwana prior to the capitanian mass extinction event from both mega and microfossil evidence that includes cryptic components rarely seen in other fossil assemblages the peat layer is dominated by glossopterid and cordaitalean gymnosperms and contains moderately common herbaceous lycophytes together with a broad array of dispersed organs of ferns and other gymnosperms rare arthropod plant and fungal plant interactions are preserved in detail together with a plethora of fungal morphotypes peronosporomycetes arthropod remains and a diverse coprolite assemblage comparisons to other palaeozoic ecosystems show that the macroflora is of low diversity the fungal and invertebrate plant associations demonstrate that a multitude of ecological interactions were well developed by the middle permian in high latitude forest mires that contributed to the dominant coal deposits of the southern hemisphere quantitative analysis of the constituents of the silicified peat and of macerals within adjacent coal seams reveals that whilst silicified peats provide an unparalleled sample of the organisms forming permian coals they do not necessarily reflect the volumetric proportions of constituents within the derived coal the toploje member chert lagerstatte provides a snapshot of a rapidly entombed mire climax ecosystem in the closing stages of the palaeozoic but prior to the onset of the protracted crisis that engulfed and overthrew these ecosystems at the close of the permian