holocene reef growth in torres strait the platform and fringing reefs of torres strait are morphologically similar to reefs of the northern great barrier reef to the south except that several are elongated in the direction of the strong tidal currents between the coral sea and the gulf of carpentaria surface and subsurface investigations and radiocarbon dating on yam warraber and hammond islands reveal that the initiation and mode of holocene reef growth reflect antecedent topography and sea level history on the granitic yam island fringing reefs have established in some places over a pleistocene limestone at about 6 m depth around 7000 years bp emergent holocene microatolls of porites sp indicate that the reefs have prograded seawards while sea level has fallen gradually from at least 0 8 m above present about 5800 years bp on the warraber island reef platform drilling near the centre indicated a pleistocene limestone foundation at a depth of about 6 m over which reefs established around 6700 years bp reef growth lagged behind that on yam island microatolls on the mature reef flat indicate that the reef reached sea level around 5300 years bp when the sea was around 0 8 1 0 m above present on the reef flat on the western side of hammond island bedrock was encountered at 7 8 m depth overlain by terrigenous mud a progradational reef sequence of only 1 2 m thickness has built seaward over these muds as sea level has fallen over the past 5800 years reef flat progradation on these reefs is interpreted to have occurred by a series of stepwise buildouts marked by lines of microatolls parallel to the reef crest marking individual coalescing coral heads detrital infill has occurred between these this pattern of reef progradation is consistent with the radiocarbon dating results from these reefs and with seismic investigations on the torres reefs

vegetation distribution across the early eocene depositional landscape from palynological analysis abstract the usefulness of palynomorphs in reconstruction of vegetation in the pre quaternary has been hampered by uncertainty in distinguishing local from transported palynomorphs analysis of palynomorph transport in modern settings suggests that the importance of transported palynomorphs in a nonmarine depositional environment depends on its geomorphologic characteristics aerial transport will be a significant source of palynomorphs only if the environment is open waterborne transport depends on the access of water to the depositional environment the importance of transported palynomorphs relative to the local palynomorphs varies among depositional environments and can be assessed in each case in the early eocene of the bighorn basin wyoming five depositional environments pond levee crevasse splay swamp margin swamp reduced floodplain contain distinct palynomorph assemblages as measured by canonical variates analysis the relative importance of transported palynomorphs is greatest in the pond and progressively decreases in the levee reduced floodplain swamp margin and swamp in the pond reworked marine dinoflagellates and bisaccate conifer pollen are high in abundance reflecting transport taxodiaceae and alnus are rare and did not inhabit the vegetation surrounding the pond corylus ulmaceous and fagaceous taxa lived surrounding the pond the levee like the pond contains marine dinoflagellates and bisaccate pollen but in lower numbers than the pond pollen of fagaceae alnus locally and pteridophyte spores reflect the levee vegetation the abundance of pteridophyte spores results from their ability to respond quickly to substrate disturbance reduced floodplains contain pteridophytes taxodiaceae platycarya and plicatopollis swamp margin and swamp palynofloras are similar and are dominated by local plants taxodiaceae alnus platycarya sparganiaceaepollenites and locally pistillipollenites the palynofloral data is consistent with the megafloral record in the same environments this supports the vegetation reconstruction from palynology

characteristics features and compaction of plant tissues traced from permineralized peat to coal in pennsylvanian coals desmoinesian from the illinois basin abstract plant tissues were traced from coal balls to coal to identify and distinguish their characteristic structures in coal and to determine compaction ratios for specific tissues comparison of average cell sizes of lycopod aerial periderm in coal ball peat and coal gave compaction ratios ranging from 7 1 to 19 1 some of this compaction took place by three dimensional contraction of the periderm so that the shapes of the cells in cross section were not greatly changed compaction ratios of other tissues ranged from 3 1 to 60 1 tissues traced into vitrinite include lycopod stem periderm stigmaria periderm diaphorodendron cortex myeloxylon pennsylvanioxylon wood and bark marattialean fern leaves psaronius outer roots and stigmaria rootlets tissues traced into fusinite or semifusinite include lycopod stem periderm myeloxylon and psaronius inner roots cordaitean leaves cordaianthus and marattialean fructifications were identified in coal and coal balls from the same layer the coal balls were from the herrin springfield and houchin creek coal members of the carbondale formation desmoinesian series pennsylvanian system and an unnamed coal in indiana equivalent to the murphysboro coal member in illinois staunton formation desmoinesian series pennsylvanian system thin sections and etched polished blocks were characterized by light and sem microscopy

outwelling from tropical tidal salt flats abstract the norman river flows into the gulf of carpentaria north east australia the estuary is surrounded by 250 km2 of vegetation free saline supratidal mud flats which are only inundated by the tides at spring high tide in summer when the seasonal sea level is 0 5 1 m higher than in winter the first summer tidal inundation of the salt flats in november 1985 resulted in a readily measurable export from the salt flats of salt and nutrients outwelling values of 90 g salt m 2 per tidal cycle 1 0 mmol silicate m 2 and 3 10 2 mmol orthophosphate m 2 were measured about a quarter of the 4000 km2 of salt flats along the southern shore of the gulf of carpentaria outwell into the gulf the rest outwell into the estuaries where salt outwelling increases the strength of the salinity maximum zone of the estuaries further isolating the rivers from the gulf during the dry season

geologic framework of nonmarine cretaceous tertiary boundary sites raton basin new mexico and colorado iridium concentrations are anomalously high at the palynological cretaceous tertiary boundary in fluvial sedimentary rocks of the lower part of the raton formation at several localities in the raton basin of new mexico and colorado the iridium anomaly is associated with a thin bed of kaolinitic claystone in a discontinuous carbonaceous shale and coal sequence

late quaternary environments of the carpentaria basin australia abstract quaternary variations in the level of the sea have exposed the shallow 29 000 km2 but shallow maximum depth s 4 0 kyr the pollen assemblages closely resemble the black soil plains presently found along the southern gulf thus the biogeographic and climatic barrier across the australia papua new guinea land bridge has remained largely intact in spite of the range of environmental conditions that have occured during the last

discussion on the concepts in paleoenvironmental reconstruction from coal macerals and petrographic indices abstract organic facies analyses quantify the coal constituents and plot various associations to discriminate the paleoenvironment for coal bearing successions this allows the relation of coal composition to mire ecosystems or environments coal petrographic models are used extensively to reconstruct the nature of ancient peat forming environments many authors proposed relations between specific maceral assemblages and or micro lithotypes and peat forming environments the key controlling factors which affect peat environment include hydrogeology redox ph vegetation type clastic influx sedimentation and peat accumulation rate etc recent advancements in coal maceral study and organic petrology reveal the pros and cons of the available indices and models the main reasons for the failure of the petrographic models are oversimplification of the effects of humification on tissue preservation vs destruction the use of post diagenetic processes e g geochemical gelification in determining depositional environments changes in petrographic composition related to floral evolution geological age rank increase and compaction lack of distinction between different inertinite maceral in some models here the widely used petrographic indices and models are reviewed based on the observations of several workers and the applicability and concepts of paleo environmental reconstruction are discussed a multi disciplinary approach including petrography palynology chemistry etc has been recommended which is more logical and scientific than the exclusive use of petrographic composition for paleoenvironmental interpretation

holocene sea level changes and barrier reef formation on an oceanic island palau islands western pacific abstract internal facies and development of an oceanic island s barrier reef were revealed by the stratigraphical study of six drill cores in palau islands western pacific the holocene reef development is primarily constrained at its foundation by the antecedent topography of pleistocene substratum holocene barrier reef is an increment on the pleistocene barrier reef which had been subaerially exposed during glacial stages about 8300 cal year bp calibrated calendar years b p branching acropora facies initially formed a bank on the seaward side of a pleistocene limestone surface with a vertical accumulation rate as high as 30 m ka ka 1000 years after 7200 cal year bp when the sea level rise rate decreased reef crest facies caught up with the sea surface with an accumulation rate of less than 2 2 m ka corals found in the reef crest facies are similar to the present day reef crest corals dominated by acropora digitifera and a humilis after the reef crest was formed bioclastic sand and gravel facies prograded lagoonward of the reef crest and consisted mostly of reef derived materials the construction of patch reefs post dated the barrier reef formation the mature barrier reef provided calm conditions inside the lagoon which then led to the construction of patch reefs and fringing reefs sea level changes deduced from the accumulation curves show rapid rise before 7200 cal year bp followed by a slight rise of 4 m at its maximum this change in sea level rise rate inspired the change in reef facies from branching acropora to reef crest

trace element patterns at a non marine cretaceous tertiary boundary at the fossil pollen defined cretaceous tertiary boundary in the raton basin of new mexico and colorado an iridium abundance anomaly and excess scandium titanium and chromium are associated with a thin ash or dust fallout bed now kaolinitic clay that was preserved in freshwater coal swamps

a new coral reef province in the gulf of carpentaria australia colonisation growth and submergence during the early holocene abstract multibeam sonar mapping drill cores and underwater video data have confirmed the existence of a previously unknown coral reef province in the gulf of carpentaria australia seven reefs comprised of coral limestone that support living corals have been mapped so far and as many as 50 other reefs may exist in the region u th ages show that reef growth commenced shortly after limestone pedestals were submerged by rising sea level around 10 5 kyr bp making them the oldest holocene reefs known in australia reef growth persisted for 2 0 kyr but it had ceased at most locations by 7 0 kyr bp measurements of reef growth rates 0 95 to 4 m kyr 1 indicate that the reefs were unable to keep pace with contemporaneous rapid sea level rise 10 m kyr 1 which is consistent with a give up reef growth history core samples from reef platforms demonstrate that pleistocene limestone is exposed at depths of 27 and 30 m below present mean sea level these depths represent regionally significant phases of reef growth during a prolonged sea level still stand we conclude that the reefs are therefore mostly relict features whose major phase of growth and development relates to an earlier pre holocene sea level still stand

cretaceous black mud from the central arctic ocean perhaps the oldest sediment yet recovered from the central arctic ocean is a black organic carbon rich mud of late campanian or maastrichtian age the sediment is known in a single piston core f1 533 taken from the eastern alpha ridge the black mud has an average organic carbon content of 14 wt and contains abundant woody plant fragments and pollen in addition to amorphous organic matter in a marine dinoflagellate rich matrix moderate hydrogen and high oxygen indices determined by rock eval pyrolysis suggest a substantial contribution of terrestrial plant debris to the marine sediment the black mud is younger than organic rich strata deposited during the oceanic anoxic events proposed for aptian albian and late cenomanian to early turonian times in the atlantic and pacific oceans the high content of organic carbon and the abundance of terrestrial organic matter in the arctic black mud suggest a marine setting influenced by an abundant supply of organic detritus rather than by a low level of oxygenation in the water column sediment in this core demonstrates that the central arctic ocean may have been in existence by the late campanian to maastrichtian and that the area of core f1 533 probably was adjacent to an eroding vegetated land mass

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

extinction and survival of plant life following the cretaceous tertiary boundary event western interior north america the palynological cretaceous tertiary boundary is recognized in the northern part of the western interior by the abrupt disappearance of a few characteristic cretaceous pollen genera principally proteacidites and aquilapollenites in the southern part the boundary is recognized by the disappearance of a somewhat different group of pollen proteacidites tilia wodehousei and trisectoris the abrupt change in both regions takes place precisely at the stratigraphic horizon at which boundary clay layers containing anomalously high concentrations of iridium interpreted to be the result of an asteroid impact are found although some characteristic cretaceous taxa apparently became extinct others were minimally affected by this boundary event and reappear in strata above however all the principal cretaceous pollen genera though not species that disappear regionally have been reported from tertiary rocks in other parts of north america differential apparent extinction and or survival reflects a pronounced temporary disruption of plant life immediately after the event some cretaceous plants must have persisted in refugia to have provided the propagules for the rapid recovery of the flora no massive total extinction of plant genera at the end of the cretaceous can be seen from the palynologic record

fire across the k t boundary initial results from the sugarite coal new mexico usa abstract it has been hypothesized that major global fires occurred following a bolide impact at the cretaceous tertiary boundary evidence for this has been mainly from soot or black carbon at a number of marine boundary sites as well as the occurrence of inertinites fusinite in coals above the boundary in addition the occurrence of fossil charcoal inertinites in potential tsunami deposits has been used to strengthen this idea however fire is known to have been widespread throughout the cretaceous based on the distribution of fossil charcoal and it is necessary to evaluate the claims for a global fire at the k t boundary within the context of this more extensive record of ancient fires the occurrence of the k t boundary within the sugarite coal sequence in the raton basin new mexico offers the opportunity to assess the incidence of fire in local peat forming vegetation in the latest cretaceous across the cretaceous tertiary boundary interval and in the earliest tertiary the distribution of fire products i e fossil charcoal is assessed using a combination of inertinite group macerals in polished blocks of coal and plant particles released by chemical maceration of coal inertinite group macerals fusinite semifusinite inertodetrinite which represent fossil charcoal and particles of charcoal in maceration residues are abundant throughout the sugarite coal sequence both before during and after the k t boundary event samples from below the boundary yield inertinites that constitute more than 20 of the coal three horizons are inertinite rich 50 fire was obviously an important element of the terrestrial environment during the latest cretaceous high inertinite values and abundant charcoal particles characterize the latest cretaceous part of the coal the carbonaceous shale just below the boundary the boundary interval itself and tertiary coals and carbonaceous shales above the boundary charcoal in mineral rich units of the latest cretaceous immediately below the boundary in the boundary interval and in the tertiary is dominated by small inertodetrinite particles these might have been wind blown from regional fires or they may reflect reworking during erosion which led to sediment input into the mire in either case the charcoal signature in these units is the same irrespective of their position in the sequence our data combined with that from two other sites in terrestrial sequences in north america show that fires were an integral part of mire ecosystems through the latest cretaceous and into the early tertiary therefore evidence for distinctive global wildfires at the cretaceous tertiary boundary would have to be sought from careful consideration of other aspects of charcoal deposition including flux rates for charcoal and soot

quantitative estimates of the effect of climate change on dust storm activity in australia during the last glacial maximum quantitative estimates are made of the effect of climate change upon dust activity during the last glacial maximum lgm which peaked 18 000 years ago using present day measurements of the occurrence of dust storms recalculated in the light of information on lgm climatic change dust activity was increased by 57 in northeast australia and by 52 in the southeast in relation to present day dust storm seasons were lengthened and dust paths were modified estimates based upon climate alone without considering the increased supplies of sediment to dust source areas during the lgm however probably underestimate lgm dust activity

late quaternary evolution of coral reefs on a cool water carbonate margin the abrolhos carbonate platforms southwest australia late quaternary coral reefs have developed on the southwestern australian margin which has otherwise been characterised by cool water carbonates since the eocene the houtman abrolhos coral reefs are at the limits of existence extending with the assistance of the leeuwin current a poleward flowing warm water stream into a region dominated by more temperate communities coring in the easter group reefs supported by high precision dating by both view the mathml source tims and 14 c methods has shown vigorous coral growth with reefs over 26 m thick in the holocene and over 15 m thick in the last interglacial each of the three abrolhos platforms consists of a central platform composed of last interglacial reefs about which windward and leeward holocene reefs developed asymmetrically reef peritidal and eolian facies comprise the emergent last interglacial limestones which are extensively calcretized with reef facies up to 5 m above msl the last interglacial high stand lasted for at least 10 ka from 130 to 120 ka and possibly 15 ka from 132 to 117 ka holocene reef facies are also emergent by 0 5 m and are overlain by peritidal and storm ridge facies in an upward shallowing sequence windward 10 m thick and leeward 26 m thick holocene reefs in the easter group show contrasting lithofacies the wave exposed windward reefs consist of a slow growing association of coralline algal bindstones and coral framestones whereas fast growing coral framestones dominate the more protected leeward reefs the leeward reefs commenced growth 10 000 years ago and grew to the present sea level by 6500 years ago generating holocene constructional topography consisting of blue hole terrain in the leeward parts of the platforms

the structure of the easter platform houtman abrolhos reefs pleistocene foundations and holocene reef growth abstract seismic reflection profiles have been used to expand an evolutionary model developed from a drilling and dating program of the easter platform one of three shelf edge coral reef platforms on the western margin of australia the houtman abrolhos reefs are surrounded by an open shelf which is mantled by cool water carbonate sediments and exist in a temperate tropical transition zone in conditions which are close to the limits for coral reef development the easter platform has distinct windward and leeward reefs and a lagoon divided by a central platform consisting of several small islands reef limestones of the central platform are calcretised and are last interglacial in age whilst the windward and leeward reefs and associated blue hole and reticulate reef terrains are holocene features seismic investigations indicate that holocene reef growth was strongly asymmetrical about the antecedent last interglacial reef platform the windward reef front is dominated by relict reef morphology and relatively thin ca 9 m or less holocene reefs have recolonised the windward margin of the antecedent platform at the site of the present day windward reef most holocene reef growth took place on the lee side of the antecedent platform and colonised an essentially flat surface at sl 40 m which has been seismically identified as the last interglacial surface up to 40 m of interpreted holocene reef overlies this monotonous surface throughout the leeward reef and associated blue hole and reticulate reef terrains demonstrating that the antecendent surface has had little influence on the processes and morphology of holocene reef construction in addition to the last interglacial reflector three deeper subparallel reflectors at sl 46 m 52 m and 60 m interpreted to represent calcrete horizons are present beneath the leeward lagoon and leeward reef terrains and are traceable to beneath the adjacent shelf surface the unconformity bound sequences so defined are thin 6 8 m and blanket like and are likely to be shelfal equivalents of pre holocene reef buildup phases found within the central platform

late cretaceous terrestrial vegetation a near polar temperature curve quantitative estimates of terrestrial paleotemperatures near the north pole were derived from the physiognomy of the vegetation including leaf margin analysis from rocks of latest albian and late cretaceous age of the north slope of alaska during the latest albian and cenomanian mean annual temperature was approximately 10 3 c during the coniacian mean annual temperature may have been 2 3 c warmer than during the albian cenomanian but no higher than 13 c during the campanian and maastrichtian mean annual temperature would have been about 2 8 c although the ranges for the individual estimates overlap differences among the floras indicate that the relative changes in mean annual temperature did occur

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

palaeobotanical evidence for a marked temperature increase following the cretaceous tertiary boundary correspondence analysis of dicot leaf physiognomy of modern vegetational samples from a wide range of environments indicates that 70 of physiognomic variation corresponds to water or temperature factors or both despite wide variation in single physiognomic characters overall trends can be used to distinguish between samples from different climates some climate parameters are well correlated with changes in physiognomy so that climate characteristics can be inferred from physiognomic analyses here i apply this climate leaf analysis multivariate program clamp to leaf assemblages from the cretaceous tertiary boundary the results indicate a fourfold increase in precipitation at the boundary and an increase in mean annual temperature of 10 c these levels persisted for 0 5 1 0 myr after which prea cipitation decreased to about three times the values for the latest cretaceous and the mean annual temperature decreased to 5 6 c above latest cretaceous values

palaeoenvironmental reconstruction and evidence of marine influence in permian coal bearing sequence from lalmatia coal mine rajmahal basin jharkhand india a multi proxy approach abstract lalmatia coal bearing sequences belong to the barakar formation permian of lower gondwana the well developed coal bearing sequences approx 52 m exposed along the mine section have been studied to understand the depositional environment along with this a cuticle study was performed to understand the palaeoclimate with the help of the stomatal index the distribution of n alkanes n c15 to n c31 suggests major higher plant and algal dominant source input although variations are seen in the relative input steranes identified include c29 regular sterane and 4 methylsteranes the pr ph ratio varied from 0 43 to 4 26 warm temperate to subtropical palaeoclimate with fresh to brackish water bodies and reducing oxygen poor environment were inferred from the rb sr sr cu th u sr ba v v ni mean 13c value measured is 23 0 0 60 for coal and 22 6 for shale these values are well correlated with typical 13c values of the permian coal and shale the stomatal index of glossopteris leaves 280 million years was taken into account and it showed a value of 10 7 that assumes a higher level of atmospheric co2 during the barakar formation artinskian age the result also shows that permian taxon glossopteris can be used for co2 proxy during permian age the geochemical evidence suggests that towards the middle part middle coal seam of the studied section the depositional milieu was under a marine influenced marginal condition the geochemical studies and carbon isotopic ratios unequivocally suggest that fluctuating climatic conditions existed during the deposition of the lalmatia coal bearing sequence

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

vegetation climatic and floral changes at the cretaceous tertiary boundary the western interior of north america has the only known non marine sections that contain the iridium rich clay interpreted as the cretaceous tertiary k t boundary1 7 because vegetation and climate can be directly inferred from physiognomy of leaves8 15 and because leaf species typically represent low taxonomic categories studies of leaf floras in these sections provide data on the effects of a terminal cretaceous event on the land flora vegetation and climate a previous study based on detailed sampling of leaves and their dispersed cuticle16 in the raton basin provides a framework for interpretation of other leaf sequences over 20 degrees of latitude we conclude that at the boundary there were 1 high levels of extinction in the south and low levels in the north 2 major ecological disruption followed by long term vegetational changes that mimicked normal ecological succession 3 a major increase in precipitation and 4 a brief low temperature excursion which supports models of an impact winter

evidence for the recovery of terrestrial ecosystems ahead of marine primary production following a biotic crisis at the cretaceous tertiary boundary the fossil record demonstrates that mass extinction across the cretaceous tertiary k t boundary is more severe in the marine than the terrestrial realm we hypothesize that terrestrial ecosystems were able to recover faster than their marine counterparts to test this hypothesis we measured sedimentary 13 c as a tracer for global carbon cycle changes and compared it with palaeovegetational changes reconstructed from palynomorphs and cuticles across the k t boundary at sugarite new mexico usa different patterns of perturbation and timescales of recovery of isotopic and palaeobotanical records indicate that the 13 c excursion reflects the longer recovery time of marine versus terrestrial ecosystems

carbonate concretions an ideal sedimentary host for microfossils microfossils extracted from carbonate concretions tend to be better preserved more abundant and diverse and more likely to retain delicate and fragile structures than those extracted from the surrounding rocks enhanced preservation correlates with early diagenetic concretion formation at or near the sediment water interface and with higher carbonate organic material and metallic cation content than in surrounding rocks early diagenetic growth is inferred by diverging sedimentary laminations and small scale sedimentary structures in fossiliferous carbonate concretions high initial concentrations of microorganisms or fecal pellets may commonly be responsible for incipient carbonate concretion growth excellent preservation is demonstrated by radiolarians and palynomorphs extracted from a carbonate concretion from the middle jurassic shelikof formation southern alaska

interpreting environmental and biological signals from the stable carbon isotope composition of fossilized organic and inorganic carbon stable carbon isotope studies on marine and terrestrial organic and inorganic carbon provide a means for detecting global climate change and for reconstructing past concentrations of atmospheric co 2 comparison between the co 2 estimates reconstructed from carbon isotope studies for the past 150ma show good agreement with the predictions of a long term carbon cycle model based on mass balance studies further the co 2 estimates from these sources over the entire phanerozoic show agreement with the fossil record of leaf stomatal density change a feature inversely related to the concentration of atmospheric co 2 isotopic studies on temporal sequences of fossilized terrestrial organic matter have contributed to palaeoecological studies on shifts in the dominance of plants with the c 4 photosynthetic pathway in ecosystems and historical changes in the metabolic processes of leaves of individual species the long term perspective offered by these studies provides critical information for assessing the responses of biological systems to future global environmental change

extremely elevated co2 concentrations at the triassic jurassic boundary abstract although progress has been made in recent years in reconstructing the environmental conditions at the triassic jurassic boundary tjb published records of atmospheric co 2 concentrations have been of low resolution and or based on multi taxon estimates this is addressed here by reconstructing co 2 concentrations across the tjb using stomatal frequencies of four phylogenetically and ecologically distinct plant groups from two depositionally geographically and taphonomically separate boundary sections in east greenland and northern ireland with stomatal proxy methods and regression analysis the resulting co 2 records then are compared with an additional existing tjb record from a geological section in sweden the final results indicate that pre tjb rhaetian the co 2 concentration was approximately 1000 ppm that it started to rise steeply pre boundary and had doubled to around 2000 2500 ppm at the tjb the co 2 concentration then remained elevated for some time post boundary before returning to pre tjb levels in the hettangian these results are in very good accordance with published c isotope fire and leaf dissection records and clearly indicate steeply rising and lingering co 2 concentration at the tjb

general bathymetry of the gulf of carpentaria and the quaternary physiography of lake carpentaria abstract a generalized bathymetric map of the gulf of carpentaria has been prepared from royal australian navy sounding data the results confirm earlier work of nix and kalma and indicate that a closed basin lake carpentaria below 53 m present water depth could have existed during quaternary low sea level stands an evaluation of previous and present work shallow seismic records of the canadian superior mining co australia and oil company fathometer profiles indicate the preservation of lake sediments at 65 m and 53 m water depth preserved shoreline feature at 19 m 29 m and 65 m as well as extensive underlying erosion and incision these findings are consistent with erosion and incision of gulf sediments during sea level lowering aeolian infilling and dune formation on the present arafura sill during the dry phase of maximum glaciation and subsequent lake carpentaria formation and lacustrine sediment deposition most probably during the sea level rise phase lake carpentaria clearly dominates the physiography and climatology of this land bridge during quaternary time

anisotropic growth in the olivine spinel transformation of mg2geo4 under nonhydrostatic stress abstract the olivine spinel phase transformation in mg 2 geo 4 does not occur by a martensitic mechanism the evidence from samples transformed in a griggs type solid medium deformation apparatus are 1 1 lack of microstructural features in the olivine phase which can be specifically associated with a martensitic mechanism 2 2 the orientation relationship between the two phases that is predicted by the martensitic mechanism does not occur nor is there any apparent consistency of relative orientations 3 3 application of a differential stress to the transforming sample resulted in an anisotropic growth rate for the spinel phase indicating that growth was externally controlled rather than crystallographically controlled anisotropic growth of the spinel phase results in elongation of the residual olivine phase grains in the plane normal to the direction of maximum principal compressive stress a velocity ratio of 1 7 0 7 5 4 has been determined for the growth rate of the spinel from measurements on residual olivine grains the interphase grain boundary in samples transformed under stress has cusp shaped fingers of spinel with a blunt end separated by thin spikes of olivine samples transformed isostatically do not exhibit this feature providing further confirmation of anisotropic growth of the spinel the preferred growth of the spinel is consistent with a theory of phase transformation under nonhydrostatic stress the predicted spinel finger shape based on this theory is generally consistent with observed shapes except for the blunt end the discrepancy may be due to surface energy which has not been considered here or to local deviations of the applied macroscopic stress

holocene lagoonal sedimentation at the latitudinal limits of reef growth lord howe island tasman sea abstract the southernmost limit to coral reef growth occurs on lord howe island 33 30 s 159 05 e where a discontinuous fringing reef flanks the western side of the island coring and radiocarbon dating indicate that carbonate sediments were first deposited within the lagoon around 6500 radiocarbon years bp coincident with sea level reaching close to its modern level high energy conditions dominated the reef with robust branching corals dominating the developing reef growth of the reef crest between 6000 and 5000 yr bp is inferred to have caused a reduction in the energy conditions within the lagoon resulting in mud deposition during this period sedimentation occurred at average rates of around 5 mm yr though locally up to 10 mm yr which infilled almost all the available accommodation space in the lagoon by 4000 yr bp most of the lagoon had accreted to a level very close to the modern lagoon floor having accumulated over 11 m of sediment in the northern part of the lagoon and possibly up to 30 m in the south sediments younger than 3000 yr bp form a thin veneer over these older units with the main deposition being confined to embayments the coastal plain and the infilling of blue hole depressions the reef and lagoon fringing lord howe island appear to have developed their present form primarily during a phase of luxuriant growth in the mid holocene

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

holocene development of three isolated carbonate platforms belize central america abstract locally operating factors such as topography of the reef basement and exposure to waves and currents rather than regionally effective factors such as the post glacial sea level rise in the western atlantic explain the different holocene developments of the three isolated carbonate platforms glovers reef lighthouse reef and turneffe islands offshore belize a series of nne striking tilted fault blocks at the passive continental margin forms the deep basement of the belize reefs glovers and lighthouse reefs are located on the same fault block while turneffe islands is situated west of lighthouse reef on an adjacent fault block the three platforms are surrounded by deep water and have surfacebreaking reef rims significant differences exist between platform interiors glovers reef has only 0 2 of land and an 18 m deep well circulated lagoon with over 800 patch reefs lighthouse reef has 3 of land and a well circulated lagoon area patch reefs are aligned along a nne striking trend that separates a shallow western 3 m and a deeper eastern 8 m lagoon turneffe islands has 22 of land that is mainly red mangrove interior lagoons are up to 8 m deep and most have restricted circulation and no patch reefs surface sediments are rich in organic matter in contrast the northernmost part of turneffe islands has no extensive mangrove development and the well circulated lagoon area has abundant patch reefs holocene reef development was investigated by means of 9 rotary core holes that all reached pleistocene reef limestones and by radiometric dating of corals maximal holocene reef thickness reaches 11 7 m on glovers reef 7 9 m on lighthouse reef and 3 8 m on turneffe islands factors that controlled holocene reef development include the following 1 holocene sea level the margin of glovers reef was flooded by the rising holocene sea ca 7500 ybp that of lighthouse reef ca 6500 ybp and that of turneffe islands between 5400 and 4750 ybp all investigated holocene reefs belong to the keep up type even though the three platforms were flooded successively and hence the reefs had to keep pace with different rates of sea level rise 2 pre holocene topography pleistocene elevation and relief are different on the three platforms this is the consequence of both tectonics and karst different elevations caused successive reef initiation and they also resulted in differences in lagoon depths variations in pleistocene topography also explain the different facies distribution patterns on the windward platforms that are located on the same fault block on lighthouse reef tectonic structures are clearly visible such as the linear patch reef trend that is aligned along a pleistocene fault on glovers reef only short linear trends of patch reefs can be detected because the pleistocene tectonic structures are presumably masked by the higher holocene thickness the lower pleistocene elevation on glovers reef is probably a consequence of both a southward tectonic tilt and stronger karstification towards the south related to higher rainfall 3 exposure to waves and currents glovers reef lighthouse reef and the northernmost part of turneffe islands receive the maximum wave force as they are open to the caribbean sea adjacent lagoons are well circulated and have luxuriant patch reef growth and no extensive mangrove development by contrast most of turneffe islands is protected from the open caribbean sea by lighthouse reef to the east and is only exposed to reduced wave forces allowing extensive mangrove growth in these protected areas

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

carbonate sedimentation on subtropical shelves around lord howe island and balls pyramid southwest pacific abstract lord howe island and balls pyramid are mid oceanic basaltic islands 20 km apart in the tasman sea subaerial carbonates dating back at least 350 ka and a holocene fringing reef occur on lord howe island no reefs or subaerial carbonate deposits occur on balls pyramid both islands sit near the centre of wide shelves that are on average 40 50 m deep with a distinct break of slope between 70 and 100 m depth the lord howe shelf is characterised by a discontinuous drowned ridge which rises to 30 m depth and is located between the mid shelf and shelf edge it is composed of limestone and is interpreted as a fossil reef being veneered by holocene coralline algae early to middle holocene branching coral gravel is found in the lee of the fossil reef indicating limited give up reef growth during the postglacial transgression the surface sediments across the shelf are calcareous except in close proximity to the island where volcanic content is significant coralline algae represent the dominant grain type with minor amounts of coral bryozoans halimeda and foraminifera are common however they are not volumetrically important rhodoliths and molluscs occur near the shelf edge and appear to have accumulated at times of lower sea level these subtropical shelves are mid oceanic examples of the transition between tropical and temperate carbonate sedimentation they indicate the potential for carbonate production on broad planated shelves outside reef forming seas