can biomass burning produce a globally significant carbon isotope excursion in the sedimentary record negative carbon isotope excursions have been comprehensively studied in the stratigraphic record but the discussion of causal mechanisms has largely overlooked the potential role of biomass burning the carbon isotopic ratios 13 c of vegetation soil organic matter and peat are significantly lower than atmospheric carbon dioxide co2 and thereby provide a source of low 13 c co2 when combusted in this study the potential role of biomass burning to generate negative carbon isotope excursions associated with greenhouse climates is modeled results indicate that major peat combustion sustained for 1000 yr increases atmospheric co2 from 2 5 present atmospheric levels pal to 4 6 pal and yields a pronounced negative 13 c excursion in the atmosphere 2 4 vegetation 2 4 and the surface ocean 1 2 but not for the deep ocean 0 9 release of co2 initiates a short term warming of the atmosphere up to 14 4 c with a duration of 1628 yr which is consistent with the magnitude and length of an observed toarcian excursion event these results indicate that peat combustion is a plausible mechanism for driving negative 13 c excursions in the rock record even during times of elevated pco2

cretaceous nubia formation and correlative deposits eastern egypt major regressive transgressive complex early to mid late cretaceous nubia formation in and around the natash basin in southeastern egypt incorporates a lower regressive nonmarine sandy facies 1 as much as 100 m thick a middle transgressive paralic to marine facies 2 several tens of metres thick and an upper prograding nonmarine to paralic sandy facies 3 about 120 m thick these deposits extend northwestward across the kharga arch into the large dakhla basin in central and southwestern egypt where facies 1 is several hundred metres thick and has an aptian marine tongue the nubia formation also has correlative lithofacies along the gulf of suez lowland in northeastern egypt there facies 1 is of varying thickness and is an important petroleum reservoir early cretaceous to early cenomanian facies 1 was deposited by high energy low sinuosity braided streams during a low stand of sea level that persisted with only minor interruption for about 50 m y sandy fining upward fluvial sequences record intermittent aggradation and repeated development of paleosols deposits in the dakhla basin were dispersed northward from the deeply weathered nubian shield those in southeastern egypt and in the gulf of suez lowland were dispersed southwestward and westward from uplands on the eastern desert and arabian platforms southward thinning late cenomanian turonian marine facies 2 marks the climax of the first major late cretaceous tethyan transgression waning of northward dispersed detritus fostered development of three extensive beds of oolitic ironstone in the vicinity of aswan as well as a few thin lenses of ironstone in central northern and northeastern egypt distinctive tabular planar cross bedded facies 3 reflects renewed uplift of the nubian shield in late turonian coniacian time and essentially continuous influx of quartzose sand for only a few million years facies 3 was spread across a prograding alluvial plain in migrating sand waves and channel bars in closely spaced non sinuous distributary systems the older regressive facies 1 was succeeded rather abruptly by marine facies 2 as a result of waning detrital influx followed by low energy transgression that developed only minor strand line sand bodies prograding nonmarine facies 3 is separated from overlying transgressive late cretaceous marine deposits by a gradational ripple bedded facies probably produced by gradual waning of detrital supply during continuing high stand of sea level the nubia formation and its correlatives in eastern egypt reflect uplands and irregular topography along the red sea suez tract that had been a broad zone of deformation in late precambrian time the pattern of distribution of early cretaceous facies 1 in the gulf of suez lowland suggests that there may have been very little spreading along the suez graben during cenozoic opening of the red sea

a paleogene flora from the upper bonnet plume formation of northeast yukon territory canada palaeontological exploration of the bonnet plume basin in northwestern yukon territory canada has revealed a late paleocene to early eocene macrofloral assemblage from a channel fill deposit the flora is typified by cosmopolitan taxa and dominated by deciduous angiosperms with the notable presence of zizyphoides ettingshausenia and corylites floras with a similar composition are known from late cretaceous through early eocene deposits in alaska and the canadian arctic archipelago where they have been interpreted as evidence for warm equable temperatures this collection represents the most diverse known paleogene plant macrofossil assemblage from the yukon territory and helps to expand our knowledge of ancient high latitude floras

climate and bioproductivity control on carbonate turbidite sedimentation paleocene to earliest eocene gulf of biscay zumaia spain abstract the paleocene to lowermost eocene zumaia series situated along the basque coast northern spain consists of pelagic limestones and marlstones with interbedded mixed calcarenite turbidites we have compared the composition and frequency of turbidite beds in time as well as the clay mineral and bulk rock carbon isotope composition of the pelagic beds to discern the factors controlling turbidite deposition the pelagic beds are coccolithic mudstones with mainly planktic foraminifera the sources of detrital material to turbidites were the carbonate producing shelves bearing foramol associations around the evolving bay of biscay and to a minor extent the incipient pyrenean chain for siliciclastic components we have found close relationships between variations of turbidite facies and depositional rates with clay mineral assemblages and carbon isotopes in the pelagic beds the latter are in line with global trends it appears that in the early bay of biscay climate and nutrient availability controlled turbidite sedimentation the bulk rock late paleocene np 5 np 9 positive carbon isotope excursion coincides with a period of relatively cool and dry climate characterized by the highest frequency of turbidity flow we propose that during this period globally enhanced latitudinal temperature gradients and strong thermohaline ocean circulation increased bioproductivity in surface waters by upwelling and or by wind driven ekman pumping in contrast warm perennially wet periods such as the early paleocene np 1 np 4 and the paleocene eocene transition upper np 9 np 10 are characterized by low frequency of turbidity flow in the basin this may have been caused by sluggish thermohaline circulation and low carbonate productivity during this time period

vertebrate fossils dinosauria from the bonnet plume formation yukon territory canada dinosaurs and other terrestrial vertebrates are poorly documented in the mesozoic of the canadian polar region here we provide a complete review of the upper cretaceous maastrichtian vertebrate fauna of the bonnet plume formation in the northeastern yukon territory canada which includes the description of the first newly collected dinosaur bones from this unit in almost half a century previously reported fragmentary dinosaur remains collected in the early 1960 s pertain to an indeterminate hadrosaurid new material includes a poorly preserved forelimb bone and a pedal phalanx these new remains pertain to at least one species of non hadrosaurid ornithischian dinosaur and the humerus is tentatively referred to a small bodied basal ornithopod the new vertebrate fossils from the bonnet plume formation provide further evidence of vertebrates from this unit however directed field surveys in 2008 and 2009 suggest that vertebrate fossils are not abundant a review of the known localities of terrestrial mesozoic vertebrates from the canadian arctic indicate that it had a relatively diverse community of terrestrial vertebrates including dinosaurs during the late cretaceous but emphasizes our limited knowledge of the mesozoic arctic and considerable potential for future exploration and discovery

latitudinal temperature gradient during the cretaceous upper campanian middle maastrichtian y18o record of continental vertebrates latitudinal variations in model biogenic apatite d18o values were calculated using fractionation equations of vertebrates and weighted rainfall y18o values along with mean annual air temperatures provided by iaea wmo meteorological stations the reference equation obtained was used to compute a continental temperature gradient for the late campanian middle maastrichtian interval by using published and new d18o values of phosphate from vertebrates samples are mainly tooth enamel from crocodilians and dinosaurs that lived at paleolatitudes ranging from 83 4 n alaska to 32 3 s madagascar the temperature gradient was less steep 0 4 0 1 c latitude than the present day one 0 6 c latitude with temperatures that decreased from about 30 c near the equator to about 5 c at the poles above 30 of paleolatitude air temperatures were higher than at present the validity of these results is discussed by comparison with climatic criteria inferred from paleontological paleobotanical and sedimentological data the latitudinal distribution of oxygen isotope compositions of continental vertebrates is potentially a powerful tool for quantifying mesozoic terrestrial climates

a stable isotopic record of the maastrichtian ocean climate system south atlantic dsdp site 528 abstract the upper maastrichtian interval of mid latitude south atlantic deep sea drilling project site 528 spans approximately the last 4 million years of the cretaceous the isotopic record of this sequence indicates that relatively large 0 5 1 0 late maastrichtian oxygen and carbon isotopic shifts occurred on geologically short time scales less than 100 500 kyr comparison with previous oxygen isotopic data suggests that in high and mid latitude southern oceans the multimillion year maastrichtian cooling trend largely resulted from geologically rapid climatic steps coincidence of the largest carbon and oxygen isotopic excursions suggests that relatively large and geologically rapid changes in marine and atmospheric carbon content may have directly contributed to the long term cooling of the late cretaceous greenhouse

direction finding of precursory radio emissions associated with earthquakes a proposal abstract the direction finding of precursory radio emissions associated with earthquakes is proposed based on the simultaneous measurement of the waveforms of multiple electric and magnetic field components at elf 1 525 khz 5 hz and ulf 0 10 hz at a few stations this measurement enables us to determine the wave mode of the observed signal for example its direction of arrival by measuring such parameters as the wave impedance wave polarization and wave coherence from these observations we hope to be able to obtain the first convincing evidence on the precursory emissions of earthquakes

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

paleoceanography of the cretaceous tertiary boundary event inferences from stable isotopic and other data we report the results of new stable oxygen and carbon isotope analyses on carbonate fine fraction whole rock and benthic foraminifers caco3 and coarse fraction percentage determinations and trace element sr analyses on carbonate constituents across the cretaceous tertiary k t boundary in deep sea drilling project dsdp sites 47 2 356 384 and 577 and compare them with published results from k t boundary sections in other dsdp sites we used the trace element data and scanning electron microscope examination to evaluate possible diagenetic alteration and relative preservation of the samples analyzed in this study the 18o data when interpreted as isotopic paleotemperatures indicate relative stable surface water and deepwater temperatures in the late maestrichtian followed by somewhat fluctuating temperatures in the early paleocene however there is no indication of either a significant warming or cooling at or following the k t boundary several sites do exhibit somewhat heavier 18o values by about 0 5 across the boundary which might suggest a 2 3 c cooling at most however we interpret these somewhat heavier 18o values as reflecting slightly better preservation of 18o of carbonate constitutents in relatively clay rich intervals e g lower diagentic potential characteristic of the k t boundary the 13c values of carbonate fine fraction and planktonic foraminifers indicate a major negative excursion in surface water total dissolved carbon across the boundary the surface water and deepwater 13c values from benthic foraminifers combined with calculated decreases in carbonate accumulation rates at all sites in the earliest paleocene are consistent with a major decrease in productivity across the k t boundary the decrease in caco3 accumulation rates is due not to increased rates of dissolution but to decreased production in surface waters the low productivity episode lasted at least 1 m y beyond the k t boundary crisis suggesting that hypothesized catastrophic events alone such as impact of an apollo object are not the only explanation for the observed long term decrease in productivity there is also an indication in the 13c curves from several sites that the surface water 13c decrease began in the latest maestrichtian suggesting that the decrease in productivity may have been independent of a hypothesized impact event

18o 16o and d h ratios of pedogenic kaolinite in a north american cenomanian laterite paleoclimatic implications abstract kaolinite gibbsite and quartz are the dominant minerals in samples collected from two outcrops of a cenomanian 95 ma laterite in southwestern minnesota a combination of measured yields and isotope ratios permitted mass balance calculations of the d and 18 o values of the kaolinite in these samples these calculations yielded kaolinite d values of about 73 and 18 o values of about 18 7 the d and 18 o values appear to preserve information on the ancient weathering system if formed in hydrogen and oxygen isotope equilibrium with water characterized by the global meteoric water line gmwl the kaolinite d and 18 o values indicate a crystallization temperature of 22 5 c a nominal paleotemperature of 22 c implies a 18 o value for the corresponding water of 6 3 the combination of temperature and meteoric water 18 o values is consistent with relatively intense rainfall at that mid paleolatitude location 40 n on the eastern shore of the north american western interior seaway the inferred cenomanian paleosol temperature of 22 c is in general accord with published mid cretaceous continental mean annual temperatures mat estimated from leaf margin analyses of fossil plants when compared with results from a published gcm based cenomanian climate simulation which specifies a latitudinal sea surface temperature sst gradient that was either near modern or smaller than modern the kaolinite paleotemperature of 22 c is closer to the gcm predicted mat for a smaller equator to pole temperature difference in the mid cretaceous moreover the warm kaolinite derived mid paleolatitude temperature of 22 c is associated with proxy estimates of high concentrations of atmospheric co 2 in the cenomanian the overall similarity of proxy and model results suggests that the general features of cenomanian continental climate in that north american locale are probably being revealed

past co2 changes and tropical sea surface temperatures the relationship between past co2 variations and tropical climate change on time scales of millions of years is reviewed explanations for cretaceous and early cenozoic climate change often involve higher atmospheric co2 levels climate models predict that such increases should have been associated with warmer tropical sea surface temperatures ssts however sparse mid cretaceous 18o based sst estimates from low latitude calcareous plankton are 1 0 1 5 heavier than predicted initial evaluations indicate that changes in salinity may not alleviate model data discrepancies for calcareous 18o and that interpretation of altered latitudinal 18o gradients in terms of increased poleward heat transport due to warm saline bottom water wsbw formation would require very large levels of wsbw production at least 60 sv calcareous 18o records may not always record true sst patterns as 18o analyses from phosphatic groups which are less sensitive to diagenesis indicate ssts 5 c higher this latter conclusion is supported by a number of other fossil groups which indicate temperatures warmer than those estimated from calcareous 18o in order to more rigorously test the paleo co2 hypothesis and indeed the models used to forecast future climates it is desirable to intensify investigations of past climate change in low latitudes in order to determine whether these preliminary conclusions stand the test of further scrutiny

dinoflagellate cysts from the upper campanian upper cretaceous of hornby island british columbia canada with implications for nanaimo group biostratigraphy and paleoenvironmental reconstructions abstract thirty mudstone samples from coastal exposures of the northumberland formation on hornby island british columbia canada yielded diverse dinoflagellate cyst and terrestrial sporomorph assemblages a late campanian age for the formation has been well defined through magnetostratigraphy macrofossil biostratigraphy and geochemical studies of the hornby island section dinoflagellate cyst taxa corresponding to 61 genera are exceptionally well preserved and include specimens referable to at least 68 formally established species the earliest occurrences of canninginopsis maastrichtiensis druggidium cf discretum phanerodinium belgicum renidinium cf vitilaire senegalinium simplex spiniferella cornuta and xenicodinium delicatum sensu slimani et al are reported along with the most recent occurrence of senoniasphaera protrusa extending their stratigraphic ranges into the upper campanian the palynomorph assemblages support a late campanian age two dinoflagellate cyst ecozones are recognized ecozone 1 and ecozone 2 assemblages suggest sediment deposition in an inner shelf environment with moderate to high nutrient input and primary productivity

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

petrologic evolution and paleogeography of the late cretaceous nanaimo basin washington and british columbia implications for cretaceous tectonics systematic variations in sandstone petrofacies of the upper cretaceous nanaimo group are related to basin evolution and uplift of surrounding tectonic provinces a subaerially exposed horst partially separated southern and northeastern portions of the nanaimo basin volcaniclastic and arkosic sediment was derived from this horst the horst subsided below wave base during very early evolution of the nanaimo basin but it controlled sediment dispersal throughout basin development lower units of the nanaimo group in the southern nanaimo basin are chert rich and were derived largely from terranes of the san juan islands and north cascades basaltic and plutonic debris from the insular belt was deposited into the northwestern nanaimo basin during early basin development minor deposition of arkosic debris from the coastal plutonic belt also occurred upper units of the nanaimo group contain abundant plagioclase rich sediment derived from the coastal plutonic belt rocks along the southeastern margin of the basin however reflect continued sedimentation from terranes of the san juan islands and north cascades arkosic and dacitic debris from insular belt sources is recognized in the northwestern nanaimo basin the nanaimo basin may have developed as a pull apart basin within a broad zone of normal and transcurrent faulting in response to oblique convergence or transform faulting between the kula plate and the pacific margin of washington and british columbia

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

spaced direction finding of nighttime whistlers at low and equatorial latitudes and their propagation mechanism the propagation mechanism of low latitude and equatorial latitude whistlers is investigated on the basis of spaced direction finding measurements in south china observations were made continuously in the local time lt interval from 0000h to 0400h during the period of january 5 11 1988 at the three stations zhanjiang geomagnetic latitude 10 1 guilin 14 1 and wuchang 19 4 and two horizontal magnetic components and one vertical electric field component were simultaneously recorded over a wide frequency range to enable comprehensive direction finding two major occurrence peaks on january 5 and january 6 and two minor ones on january 9 and january 11 have been analyzed and the following experimental results have emerged 1 the whistler occurrence at very low latitudes is generally very small compared with that at low latitude geomagnetic latitude 20 but once it occurs the occurrence rate becomes comparable to that at low latitudes 2 the whistler dispersion is single valued at any particular local time 3 the ionospheric exit region of whistlers is very much restricted to the geomagnetic latitude range of 10 14 and there are no observed whistlers whose path latitude is between 14 and 20 4 the extent of their ionospheric exit region is very stable on different days and the radius of the distribution is less than 40 50 km 5 surprisingly high occurrence of echo train whistlers is observed 6 the propagation of whistlers in the earth ionosphere waveguide after ionospheric transmission is more likely toward higher latitudes than toward the equator and the subionospheric propagation seems to exhibit a horizontal beaming around the magnetic meridian plane we attempt to interpret these characteristics of the observations in terms of either nonducted or field aligned propagation but discussion indicates that especially findings 4 and 5 are strongly indicative of field aligned propagation for very low latitude whistlers localized in geomagnetic latitudes of 10 14

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

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

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

mid cretaceous floras and climate of the russian high arctic novosibirsk islands northern yakutiya abstract two mid cretaceous floras collected in terrigenous and volcaniclastic deposits of the novosibirsk islands in the russian high arctic were studied these floras are the most poleward mid cretaceous floras known and existed at palaeolatitudes up to 82 85 n these represent our best insight into polar conditions at one of the warmest intervals in earth history an albian flora from the balyktakh formation of the kotel nyi island comprises 40 species of ferns bennettites cycadophytes ginkgoaleans czekanowskialeans conifers and gymnosperms incertae sedis this flora is most similar to the albian buor kemuss flora widespread in the arctic siberia and alaska and to a lesser extent to the aptian silyap flora of siberia a turonian flora from the derevyannye gory formation on the novaya sibir island includes approximately 50 taxa of ferns ginkgoaleans conifers and angiosperms this flora exhibits plants common for the early cretaceous as well as taxa typical for cenomanian senonian which implies that the age of the plant bearing deposits is likely to be turonian the cretaceous climate has often been described as warm with a higher degree of equability than today with the near polar regions in particular being much warmer than today our estimates using clamp and a new global gridded climate calibration demonstrate that for the turonian novaya sibir flora plant physiognomy reflects a humid climate with warm summers and mild frost free winters the mean annual temperature is estimated to have been 9 2 2 2 c the warm month mean temperature 17 2 2 8 c the cold month mean temperature 1 1 3 8 c and the mean growing season precipitation 537 392 mm these temperature parameters indicate that within 900 km of the turonian north pole the climate was similar to that of modern temperate or even warm temperate zones but must have differed considerably in having pronounced high latitude sunlight seasonality the ecology of the late cretaceous arctic plants reflects their adaptation to this climate synchronous shedding of foliage deciduousness was by far the most common strategy and retention of leaves year round evergreenness was also viable for a small number of taxa large deciduous leaves typical for the cretaceous arctic dicots probably reflect the combination of a warm and humid climate with high latitude light regime long days in summer and predominance of relatively weak and mostly diffuse sunlight the large range of leaf size in a given plant species of arctic angiosperms was most probably linked to the seasonal character of annual shoot development

strain and retrogression partitioning explain long term stability of crustal roots in stable continents away from tectonically active regions the continental crust has an average thickness of 40 1 km yet it shows a remarkable variability from 25 to 65 km comparable to that of the most tectonically active regions here we consider the problem of the formation and preservation of anomalous deep crustal roots in stable intracontinental regions using two dimensional thermomechanical experiments we show that the interplay between partial melting the formation of garnet pyroxene bearing rocks and their strain rate dependent retrogression result in the preservation of thick and strong crustal roots we argue that it is the partitioning into narrow regions of strain retrogression and weakening coupled into a positive feedback loop that explains why strong high grade crustal roots remain largely immune to gravitational stresses and are able to persist over hundreds of millions of years

paleoenvironmental significance of clay mineral associations at the cretaceous tertiary passage abstract the clay mineral stratigraphy at the cretaceous tertiary transition is considered by the study of new sections walvis ridge maud rise central italy northern tunisia which are compared with results of previous investigations increased contents of smectite and or kaolinite or substrate derived species e g illite group depending on the areas investigated are observed near the boundary these diversified modifications indicate increased erosion and predominance of local detrital supply including that of volcanic rocks over general related causes most probably these modifications of clay mineral associations express a major geodynamic disruption characterized by tectonic instability and sea level drop those events began prior to the cretaceous tertiary boundary i e prior to the major iridium anomaly recorded in sediments this could explain why a catastrophic event at the cretaceous tertiary boundary is hardly evidenced in the clay sedimentological record which is extremely sensitive to the global changes in the earth s terrestrial environment

oxygen isotope and paleobotanical estimates of temperature and δ18o latitude gradients over north america during the early eocene empirical estimates of climate parameters such as mean annual temperature mat are essential to describe both ancient climate and to ground truth climate model simulations of past climates in terrestrial settings no single proxy record is able to provide detailed temporal yet geographically widespread information and it thus becomes essential that paleoclimatic information obtained from different proxies be comparable as an example of how to compare estimates and to illustrate what can be learned by doing so we measured oxygen isotope ratios of phosphate in the tooth enamel of fossil mammals and the body scales of freshwater fish in order to estimate the mean annual temperature mat in which they lived the samples were collected from paleogene rocks of the bighorn green river and powder river basins of wyoming earliest eocene samples provide mat estimates that are similar to mat estimates for the same times and areas obtained from leaf margin analysis furthermore isotopic data from the paleocene eocene thermal maximum petm which has not yet yielded fossil floras indicate a significantly higher mat of 26 c we also used temperature estimates obtained by both methods to investigate paleoelevation and to reconstruct geographic patterns of mat over north america for the early eocene larger laramide basins have higher temperatures and lower inferred elevations compared to associated volcanic highlands where cooler temperatures are consistent with substantial elevations in turn latitudinal gradients in temperature indicate that warming centered on polar regions played an important role during the eocene hothouse lastly we show that the reconstructed eocene relation between oxygen isotope ratios of precipitation and mat is significantly different from the modern relation between these two variables because the relation has changed over time the modern correlation should not be used to estimate paleo mat from measurements of oxygen isotope ratios in fossil material

an early late cretaceous cenomanian sturgeon acipenseriformes from the dunvegan formation northwestern alberta canada a recent survey of the middle cenomanian dunvegan formation along the peace river alberta has yielded a partial skull of a large acipenseriform fish the fossil was from an animal approximately 5 m in length based on comparisons with living relatives though incomplete this represents an important record of mid cretaceous fish from northern north america as formations of this age are virtually unexplored in northern regions this fossil is the oldest acipenserid from north america and one of the most northerly known

palynological and iridium anomalies at cretaceous tertiary boundary south central saskatchewan the cretaceous tertiary boundary in south central saskatchewan is marked by coincident anomalies in abundance of iridium and fern spores at the extinction level of a suite of cretaceous pollen taxa evidence of disruption of the terrestrial flora includes the fern spore abundance anomaly and local extinction of as much as 30 percent of angiosperm species the reorganized earliest tertiary flora is made up largely of surviving species that assumed new roles of dominance persistence of climatically sensitive taxa across the boundary indicates that if paleoclimate was altered by the terminal cretaceous event it returned quickly to the pre event condition

goniometric direction finding for low latitude whistlers and their propagation mechanism in order to study the propagation mechanism of low latitude whistlers their ionospheric exit points have been determined by a triangulation of the goniometer polarimeter systems at the two stations of kagoshima geomagnetic coordinates 20 24 n 197 53 e l 1 22 and ohgata 22 06 n 199 51 e l 1 25 supplemented by the routine observation at sakushima 24 08 n 203 19 e l 1 28 detailed analyses were made for january 23 1978 when the whistler activity was most enhanced during one month s measurement the difference in temporal variations of the occurrence rate at the three stations and the temporal variation of the single valued dispersion enabled us to subdivide the daytime whistlers into three characteristic time intervals and the nighttime ones into two intervals the characteristics during the whole intervals were found to be satisfactorily accounted for in terms of ducted propagation the azimuth measurements have indicated that there is present a discontinuity in the characteristics between each two intervals indicative of the different duct group for different time intervals in other words indicative of the identity and persistency of ducts for each period then we obtained the apparent lifetime of ducts of 1 2 hours during the last interval for the daytime whistlers a few ducts were found to be aligned on a certain latitude which showed a temporal movement or first increased and then decreased the simultaneous presence of a few ducts at the same latitude is also seen at night

warm saline bottom water in the ancient ocean considerable isotopic evidence indicates that oceanic bottom water was much warmer in the geological past a simple convection model driven by multiple turbulent buoyant plumes and observations of present deep water formation have led to the development of a theory for the formation of warm saline bottom water it is suggested that changes in the size and configuration of marginal seas in net evaporation zones due to lithospheric plate motions and eustatic sea level change caused these seas to become sources of warm saline bottom water evidence from the palaeotemperature record and palaeogeography during the late cretaceous is used to reinforce the hypothesis climatic and chemical consequences of the formation of warm saline bottom water are discussed

characteristics of mid latitude whistler ducts as deduced from ground based measurements propagation characteristics of mid latitude whistlers especially whistler duct characteristics have been investigated based on measurements in august 1994 at dunedin new zealand l 2 78 and in august 1989 at ceduna australia l 1 93 both during local midnight polarization analyses have enabled us to locate whistlers which exited the ionosphere just above the observing station ldf is defined in this way the nose extension method was also applied to these whistlers their ln is estimated by this method the following findings have emerged from the analyses ldf ln at dunedin and ldf ln 0 43 at ceduna our analysis suggests that mid latitude ducts are likely to extend down to the ionosphere at l 2 8 ray tracing studies for realistic density profiles indicates that a whistler duct terminates at an altitude of about 3 500 5 500 km at an l value of 1 9 with its enhancement factor being a few percent at least these results may imply a strong variability of the latitudinal or temporal variations of mid latitude whistler ducts

on the structure of ducts for mid latitude whistlers and their ionospheric transmission as deduced from the ground based direction finding the ground based direction finding carried out at ceduna australia l 1 93 has yielded the structure for mid latitude whistlers and their duct ionospheric transmission mechanism it is found that the ducts tend to take place or be formed at the same latitudes and that such sheet shaped duct includes some inhomogeneities within it which act as field aligned ducts

formation history and physical properties of sediments from the mount elbert gas hydrate stratigraphic test well alaska north slope abstract the synthesis of available geological information and surface temperature evolution in the alaska north slope region suggests that biogenic and deeper thermogenic gases migrated through fault networks and preferentially invaded coarse grained layers that have relatively high hydraulic conductivity and low gas entry pressures hydrate started forming before the beginning of the permafrost eventually the permafrost deepened and any remaining free water froze so that ice and hydrate may coexist at some elevations the single tested specimen depth 620 47 620 62 m from the d unit consists of uncemented quartzitic fine sand with a high fraction of fines 56 by mass finer than sieve 200 the as received specimen shows no evidence of gas present the surface texture of sediment grains is compatible with a fluvial deltaic sedimentation environment and shows no signs of glacial entrainment tests conducted on sediments with and without thf hydrates show that effective stress porosity and hydrate saturation are the major controls on the mechanical and geophysical properties previously derived relationships between these variables and mechanical geophysical parameters properly fit the measurements gathered with mount elbert specimens at different hydrate saturations and effective stress levels we show that these measurements can be combined with index properties and empirical geomechanical relationships to estimate engineering design parameters volumetric strains measured during hydrate dissociation vanish at 2 4 mpa therefore minimal volumetric strains are anticipated during gas production at the mount elbert well however volume changes could increase if extensive grain crushing takes place during depressurization driven production strategies if the sediment has unexpectedly high in situ porosity associated to the formation history or if fines migration and clogging cause a situation of sustained sand production

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

north atlantic warming during global cooling at the end of the cretaceous differences in regional responses to climate fluctuations are well documented on short time scales e g el nino southern oscillation but with the exception of latitudinal temperature gradients regional patterns are seldom considered in discussions of ancient greenhouse climates contrary to the expectation of global warming or global cooling implicit in most treatments of climate evolution over millions of years this paper shows that the north atlantic warmed by as much as 6 c 1 5 decrease in 18o values of planktic foraminifera during the maastrichtian global cooling interval we suggest that warming was the result of the importation of heat from the south atlantic decreasing north atlantic 18o values are also associated with increasing gradients in planktic 13c values suggesting increasing surface water stratification and a correlated strengthening of the north atlantic polar front if correct this conclusion predicts arctic cooling during the late maastrichtian beyond implications for the maastrichtian these data demonstrate that climate does not behave as if there is a simple global thermostat even on geologic time scales

limits to northward drift of the paleocene cantwell formation central alaska volcanic rocks of the paleocene cantwell formation in central alaska apparently originated at a paleolatitude of 83 n 95 9 7 as indicated by paleomagnetic results when compared with the paleocene pole for the north american craton the 95 confidence limits of the results suggest that terranes north of the denali fault have moved no more than 550 km northward relative to the north american craton since paleocene time

upper cretaceous campanian phosphorites in jordan implications for the formation of a south tethyan phosphorite giant a record of sedimentary authigenic and biological processes are preserved within the upper cretaceous campanian alhisa phosphorite formation ap in central and northern jordan the ap formed near the eastern extremity of the south tethyan phosphorite province stpp a carbonate dominated upper cretaceous to eocene phosphorite giant that extends from colombia north africa to the middle east multidisciplinary research of the ap and associated cherts chalks and oyster buildups indicate that phosphatic strata formed on a highly productive storm dominated east west trending epeiric platform along the south tethyan margin the onset of phosphogenesis and the accumulation of economic phosphorite coincided with a rise in relative sea level that onlapped peritidal carbonates of the ajlun group pristine phosphates are associated with well developed micrite concretionary horizons and contain abundant non keeled spiral planktic foraminifera and a low diversity benthic assemblage of buliminacean foraminifera suggesting that pristine phosphates are a condensed facies and phosphogenesis was stimulated by the effects of a highly productive surface ocean and the suboxic diagenesis of sedimentary organic matter the bulk sediment composition and absence of fe bearing authigenic phases such as glauconite pyrite including pyrite molds siderite and goethite within pristine phosphates suggests that deposition and authigenesis occurred under conditions of detrital starvation and that iron pumping played a minimal role in phosphogenesis authigenic precipitation of phosphate occurred in a broad array of sedimentary environments herein termed a phosphorite nursery that spanned the entire platform this is a non uniformitarian phenomenon reflecting precipitation of sedimentary apatite across a wide depositional spectrum in a variety of depositional settings wherever the conditions were suitable for phosphogenesis sedimentologic data indicate that pristine phosphates were concentrated into phosphatic grainstones through storm wave winnowing and storm generated shelf parallel geostrophic currents economic phosphorites formed through the amalgamation of storm induced event beds stratigraphic packaging of phosphatic strata indicates that temporal variations in storm frequency were a prerequisite for the formation of economic phosphorite syndepositional phosphogenesis reworking and amalgamation to form phosphorites contrasts sharply with the principles of baturin cycling a transgressive systems tract coupled with high surface productivity created detritally starved settings favourable for phosphogenesis storm reworking of pristine

quantitative reconstruction of palaeoclimate from the middle miocene shanwang flora eastern china abstract the fossil leaf flora from the shanwang formation linqu county shandong province eastern china is diverse abundant well preserved and discretely spaced all of which make it suitable for the recognition and application of leaf physiognomic characters this article is the first study of chinese tertiary floras using the clamp climate leaf analysis multivariate program approach numerous bedding planes yield leaf assemblages through over 20 m thickness of diatomaceous shales within the middle miocene shanwang formation the diatomaceous shales containing abundant fossils have been divided into 19 units a working platform 3 3 m in the diatomite quarry of shanwang was studied for about 3 months in 1998 and as many fossils as possible were recorded layer by layer this collecting method used for the first time in the history of shanwang research enabled us to record the presence or absence of megafossils in distinct units so that we could investigate leaf physiognomic characteristics and palaeoclimate for each time interval leaf fossils from six units 5 6 7 13 15 and 16 have been used to estimate palaeoclimate parameters of the shanwang area using the clamp 3b dataset the predicted climate is that of a lakeside setting at over 1000 m above sea level and within the 17 15 ma time interval meteorological factors have been estimated using the clamp approach including mean annual temperature mat 9 5 11 2 c warmest month mean temperature 20 2 22 5 c growing season length 5 9 6 8 months mean growing season precipitation 83 165 cm and relative humidity 73 79 mat estimates from leaf margin analysis lma range from 12 5 to 15 2 c which are a maximum of 4 higher than those from our clamp analyses and from previous results of lma studies of the shanwang flora 10 13 c nearest living relatives nlr of other biota pollen fish insects diatoms microthyriaceous fungi etc indicate warm and moist temperate to subtropical conditions in the shanwang area during the miocene clamp predictions are similar to the climate predicted from nlrs although the mat prediction is a few degrees cooler the fact that the shanwang leaf flora is from a lacustrine sequence may have biased the clamp analysis towards cooler and possibly wetter climates the modern yangtze river valley is a reasonable environmental analogue for the shanwang middle miocene though shanwang may have had cooler summers cooler mat and less seasonality in rainfall the climate was essentially constant during deposition of the sequence studied with possible minor variations in precipitation

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

precipitation rates and atmospheric heat transport during the cenomanian greenhouse warming in north america estimates from a stable isotope mass balance model stable isotope mass balance modeling results of meteoric 18o values from the cenomanian stage of the cretaceous western interior basin kwib suggest that precipitation and evaporation fluxes were greater than that of the present and significantly different from simulations of albian kwib paleohydrology sphaerosiderite meteoric 18o values have been compiled from the lower tuscaloosa formation of southwestern mississippi 25 n paleolatitude the dakota formation rose creek pit fairbury nebraska 35 n and the dunvegan formation of eastern british columbia 55 n paleolatitude these paleosol siderite 18o values define a paleolatitudinal gradient ranging from 4 2 vpdb at 25 n to 12 5 vpdb at 55 n this trend is significantly steeper and more depleted than a modern theoretical siderite gradient 25 n 1 7 65 n 5 6 vpdb and a holocene meteoric calcite trend 27 n 3 6 67 n 7 4 vpdb the cenomanian gradient is also comparatively steeper than the albian trend determined for the kwib in the mid to high latitudes the steep latitudinal trend in meteoric 18o values may be the result of increased precipitation and evaporation fluxes amount effects under a more vigorous greenhouse world hydrologic cycle a stable isotope mass balance model has been used to generate estimates of precipitation and evaporation fluxes and precipitation rates estimates of cenomanian precipitation rates based upon the mass balance modeling of the kwib range from 1400 mm yr at 25 n paleolatitude to 3600 mm yr at 45 n paleolatitude the precipitation evaporation p e flux values were used to delineate zones of moisture surplus and moisture deficit comparisons between cenomanian p e and modern theoretical siderite and holocene calcite latitudinal trends shows an amplification of low latitude moisture deficits between 5 25 n paleolatitude and moisture surpluses between 40 60 n paleolatitude the low latitude moisture deficits correlate with a mean annual average heat loss of 48 w m2 at 10 n paleolatitude present 8 w m2 at 15 n the increased precipitation flux and moisture surplus in the mid latitudes corresponds to a mean average annual heat gain of 180 w m2 at 50 n paleolatitude present 17 w m2 at 50 n the cenomanian low latitude moisture deficit is similar to that of the albian however the mid latitude 40 60 n precipitation flux values and precipitation rates are significantly higher albian 2200 mm yr at 45 n cenomanian 3600 mm yr at 45 n furthermore the heat transferred to the atmosphere via latent heat of condensation was approximately 10 6 that of the present at 50 n the intensified hydrologic cycle of the mid cretaceous greenhouse warming may have played a significant role in the poleward transfer of heat and more equable global conditions paleoclimatological reconstructions from multiple time periods during the mid cretaceous will aid in a better understanding of the dynamics of the hydrologic cycle and latent heat flux during greenhouse world conditions