global dinoflagellate event associated with the late paleocene thermal maximum the late paleocene thermal maximum or lptm ca 55 ma represents a geologically brief time interval 220 k y characterized by profound global warming and associated environmental change the lptm is marked by a prominent negative carbon isotope excursion cie interpreted to reflect a massive and abrupt input of 12 c enriched carbon to the ocean atmosphere reservoir possibly as a result of catastrophic gas hydrate release on time scales equivalent to present day rates of anthropogenic carbon input the lptm corresponds to important changes in the global distribution of biota including mass extinction of marine benthic organisms the dinoflagellate cyst record indicates that surface dwelling marine plankton in marginal seas also underwent significant perturbations during the lptm we report on the dramatic response of representatives of the genus apectodinium from two upper paleocene lower eocene sections in the southern new zealand and northern austria hemispheres where the dinoflagellate records are directly correlated with the cie benthic foraminifera extinction event and calcareous nannofossil zonation the results indicate that the inception of apectodinium dominated assemblages appears to be synchronous on a global scale and that the event is precisely coincident with the beginning of the lptm apectodinium markedly declined in abundance near the end of the lptm this apectodinium event may be associated with 1 exceptionally high global sea surface temperatures and or 2 a significant increase in marginal marine surface water productivity such a globally synchronous acme of dinoflagellate cysts is unprecedented within the dinoflagellate cyst fossil record

geochemistry and geochronology of late cenozoic basalts of southeast asia summary geological maps of southeast asia asia 1971 vietnam 1971 thailand 1969 show numerous occurrences of basalt which are considered to be late cenozoic in age occurrences in thailand and western kampuchea are generally small and scattered those in eastern kampuchea southern laos and vietnam are larger and more extensive fig 1 basalt bodies of similar age also occur in malaysia and southern china fig 1 these basalts form a late cenozoic continental volcanic province comparable to those in eastern australia irving and green 1976 and the western united states christiansen and lipman 1972 leeman and rogers 1970 basalts in southeast asia are especially intriguing as they are a major source of gem quality ruby sapphire and zircon fontaine and workman 1978 berrange and jobbins 1976 the purpose of this paper is to describe the distribution geochemistry and age of basalts in southeast asia available geochemical and age data are compiled and combined with new data from previously unstudied areas this is the first known regional synthesis that has been attempted for this large but relatively undocumented basaltic province

abyssal circulation and benthic foraminiferal changes near the paleocene eocene boundary a major change in cenozoic deep sea benthic foraminifera occurred in the atlantic indian and pacific oceans near the paleocene eocene boundary benthic foraminiferal abundance changes began at about 61 5 ma at pacific deep sea drilling project dsdp site 577 a major extinction event followed at 58 57 ma between zones p6a and p6b and a series of first appearances continued until circa 55 5 ma zone p6c these faunal changes occurred during a 6 c warming of pacific bottom water and may indicate that the primary cause was changing temperature other potential causes of the faunal turnover include global changes in surface ocean productivity and changing bottom water source regions comparison of benthic and planktonic 13c records requires no change in the ratio of oceanic phosphorous to carbon during the late paleocene to early eocene which weakens the case for but does not disprove a change in surface ocean productivity at this time interbasinal comparisons of benthic foraminiferal 13c records document that water with high 13c values filled the cape basin during the late paleocene and possibly the early eocene circa 61 57 ma but apparently did not extend into the western basins of the atlantic this pattern suggests a supply of antarctic source water for the cape basin and possible tectonic isolation of the western atlantic basins during at least part of the late paleocene carbon isotope comparisons show that bottom water supply to the cape basin was reduced in the early eocene eolian grain size data suggest that a decrease in zonal wind intensity occurred at the end of the paleocene these late paleocene climatic changes bottom water warming and decreased wind intensity correspond with evidence for an important global tectonic reorganization and extensive subaerial volcanism which may have contributed to climatic warming through increased supply of co2

dissociation of oceanic methane hydrate as a cause of the carbon isotope excursion at the end of the paleocene isotopic records across the latest paleocene thermal maximum lptm indicate that bottom water temperature increased by more than 4 c during a brief time interval 104 years of the latest paleocene 55 6 ma there also was a coeval 2 to 3 excursion in the 13c of the ocean atmosphere inorganic carbon reservoir given the large mass of this reservoir a rapid 13c shift of this magnitude is difficult to explain within the context of conventional hypotheses for changing the mean carbon isotope composition of the ocean and atmosphere however a direct consequence of warming bottom water temperature from 11 to 15 c over 104 years would be a significant change in sediment thermal gradients and dissociation of oceanic ch4 hydrate at locations with intermediate water depths in terms of the present day oceanic ch4 hydrate reservoir thermal dissociation of oceanic ch4 hydrate during the lptm could have released greater than 1 1 to 2 1 1018 g of carbon with a 13c of approximately 60 the release and subsequent oxidation of this amount of carbon is sufficient to explain a 2 to 3 excursion in 13c across the lptm fate of ch4 in oceanic hydrates must be considered in developing models of the climatic and paleoceanographic regimes that operated during the lptm

empirical model of 90 120 km horizontal winds from wind imaging interferometer green line measurements in 1992 1993 an empirical model of horizontal winds is developed based on wind imaging interferometer windii green line observations between 90 and 120 km in 1992 1993 the model includes mean winds solar diurnal and semidiurnal tides and some planetary wave components as well as annual and semiannual variations in these fields its formulation is similar to that of hwm 90 and hwm 93 of hedin et al 1991 1996 but greatly modified and extended to use the higher resolution global wind measurements now available from windii while the technique will only reach fruition when results can be combined from the wind measurements of several years by the different instruments on the uars satellite this interim but updated model provides improved representation of the temporal and geographic variations of the wind fields compared to the current reference models the model generated climatological mean wind diurnal tides and some samples of the entire wind motion fields are presented and compared with the windii measurements and analysis results obtained from the data sets by different methods to check the consistencies between the model representations and the observations this study also reveals a dual cell structure in the meridional component of the diurnal tides with two amplitude maxima centered around 95 and 102 km near 20 latitude and strongly symmetric about the equator at equinox large interannual variabilities are found to exist in both diurnal wind components with maximum amplitudes of 40 and 55 m s for the zonal and meridional respectively at the vernal equinox of 1992

paleoceanography a review for the gsa centennial the central problem of paleoceanography is the history of the circulation of the ocean although speculation about ancient oceanic circulation goes back to the past century the field of paleoceanography was founded in the 1950s as oxygen isotope studies suggested that oceanic deep waters were warmer in the past than they are today extensive coring of deep sea sediments by numerous expeditions after world war ii was followed by the ocean drilling programs providing a rich data base paleoceanographic interpretations have tried to explain the most obvious changes in sea floor sediments and their contained fossils changing paleotemperatures indicated by oxygen isotopes fluctuations in the calcium carbonate compensation depth accumulations of organic carbon rich sediments and the unexpected abundance of hiatuses in a setting which had been thought to be the ultimate sedimentary sink the result has been the intriguing discovery that although the positions and circulation of the major surface gyres is generally stable the deep circulation of the ocean may reverse on a variety of time scales it has been suggested that formation of north atlantic deep water which causes the uneven distribution of nutrients alkalinity and oxygen in the deep sea today may have been replaced by formation of north pacific deep water during the last deglaciation reversing the concentration gradients of nutrients alkalinity and oxygen on a longer time scale the present general circulation which is dominated by production of oxygen rich cold deep water in the subpolar regions today may have replaced a pre oligocene general circulation in which warm saline oxygen poor deep waters were formed in warm seas in the arid zones paleoceanography is still in its infancy many new clues to the history of the ocean are being discovered and many new ideas about conditions in the past are being developed the beginning of the next century should see continuing rapid growth and maturation in this exciting new field

cenozoic volcanic and petrochemical provinces of mainland asia abstract mainland asia has been subdivided into 14 distinct volcanic petrochemical provinces alkaline rocks form about 88 of the extrusive materials potassic basalts form 62 of the basaltic clan andesitic rocks are relatively uncommon except near the seaboard and in tibet peralkaline rocks are found in korea and neighboring parts of china the majority of the potassic basalt appear to be derived by variable degrees of partial melting of a mantle with lateral compositional heterogeneity the peak of volcanic activity was during the miocene and corresponded to the collision of the indian continent and the development of back arc basins

structure of the nonmigrating semidiurnal tide above antarctica observed from the timed doppler interferometer 1 spatial structure and temporal evolution of the nonmigrating semidiurnal tidal components over antarctica are determined by analyzing horizontal wind measurements in the mesosphere and lower thermosphere mlt collected using timed doppler interferometer tidi on the nasa thermosphere ionosphere mesosphere energetics and dynamics timed satellite from 2002 to 2007 the data were organized into six specific intervals of approximately 60 days corresponding to the timed yaw periods the results confirm the existence of a westward propagating zonal wave number 1 w1 semidiurnal tidal component in the antarctic mlt meridional wind field prior to the austral summer solstice this wave achieves a peak amplitude near 20 m s 1 at 90 km and is vertically stratified while extending latitudinally from the pole to 60 s a similar structure is observed in the zonal wind field however the amplitude maximizes around the austral summer solstice during the yaw period spanning 15 november to 15 january in addition to a strong latitudinal gradient in amplitude the w1 component also shows a vertical wavelength from 20 km near the pole to 40 km at 60 s the amplitude and phase agree well with ground based meteor radar observations from the south pole evidence for significant though weaker standing s0 and w3 components is also found these components diminish in the vicinity of the pole and appear during the winter months with latitudinally restricted structures the vertical wavelength of the s0 component during the summer is 25 km similar to the w1 component during the winter the wavelength of the s0 component becomes nearly evanescent

paleogene stable isotope events the oxygen isotope record in paleogene benthic foraminifera shows that at the base of the paleogene the ocean deep waters had a temperature of about 10 c rising to about 12 c at the base of the eocene and cooling between 51 ma and 49 ma to about 9 c the most dramatic event occurred just after the eocene oligocene boundary at about 35 8 ma when ocean deep waters cooled by several degrees within 104 105 yr probably in association with temporary glaciation in the antarctic region another more intense glacial event in antarctica may have occurred later in the oligocene at about 31 ma and a third near the top of the oligocene at 24 ma in the marine carbon isotope record a very rapid negative excursion occurred precisely at the cretaceous tertiary boundary a recovery to unusually positive values in the late paleocene was followed by a second negative excursion close to the paleocene eocene boundary that was even more extreme in magnitude although it was not as rapid these major carbon isotope events permit very accurate stratigraphic correlation there are many other smaller features in the carbon isotope record that will also prove useful for this purpose

paleogene geochronology an integrated approach geochronology is the conceptual division of continuous time as measured geochronometry by the progression in an ordinal series of events this is best achieved by an approach which integrates four independent data sets magnetostratigraphy seafloor spreading magnetic lineation patterns biostratigraphy and isotopic ages this integrated approach results in an ordinal framework which can measure time with greater resolution though perhaps less accuracy than a radiometric approach alone a comparative analysis of two recently proposed paleogene geochronologic time scales is presented

basaltic explosive volcanism but no comet impact at the paleocene eocene boundary high resolution chemical and isotopic records from egypt spain and denmark in the search for a triggering mechanism for the paleocene eocene p e boundary event 55 ma centimeter resolution chemical e g ir os pt and isotope e g os o 187 os 188 he 3 he 4 sr 87 sr 86 records across this boundary have been established for six uplifted marine sections in egypt spain and denmark the sections studied represent some of the stratigraphically most complete records across the onset of the carbon isotopic excursion cie and associated benthic foraminifera extinctions that mark the paleocene eocene boundary high sensitivity analyses failed to uncover evidence of extraterrestrial element or isotope enrichments in the six sections refuting the hypothesis of a major comet impact at the boundary preliminary searches for other impact indicative features such as spherules or shocked quartz also gave negative results in the danish section studied three basaltic ir rich ash layers occur at the paleocene eocene boundary but no similar ashes were found in egypt or spain the three ashes represent the earliest known manifestation of an unusual i to 2 million year long phase of explosive basaltic volcanism in the faero greenland region this volcanism is synchronous with major flood basalt effusions in east greenland and is associated with prominent paleogeographic changes in the high latitude north atlantic region discharge of mantle derived os to seawater during this volcanism may explain a small decrease in os o 187 os o 188 ratio at the paleocene eocene boundary in the zumaya section in spain the environmental perturbations at the paleocene eocene boundary appear to have been triggered by basaltic volcanism but any model for the detailed causal relation remains speculative c 2004 elsevier b v all rights reserved less

tectono magmatic evolution of the west philippine mariana region and the origin of boninites re examination of published data on the tectomagmatic evolution of the west philippine mariana region indicate that arc magmatism and back arc extensional pulses are not synchronous but are largely asynchronous arc volcanism ceases within a few million years of the development of a back arc basin and recommences oceanward on a new arc during the final stages in the development of the back arc basin following karig s model we believe that ascent beneath the arc axial chain of a line of diapirs of morb source mantle interferes with processes of arc magma generation and arc magmatism wanes partial melting of the diapirs produces voluminous morb type tholeiites which split the arc and form the crust of a widening back arc basin we show for both the west philippine mariana region and occurrences of boninite like lavas in ophiolites that boninites appear to be erupted after arc magmatism and immediately before eruption of morb type lavas passage of a diapir of hot morb source mantle through refractory sub arc peridotite which has been enriched in lile and h2o will result in limited partial melting of the hydrous peridotite and the restricted production of boninitic magmas these are more likely to erupt modified or only slightly modified by crystal fractionation through the thin forearc crust continued ascent of the morb source mantle diapir will result in it partially melting to yield morb tholeiites which erupt shortly after and in considerably more voluminous amounts than the boninites finally we suggest that forearcs regions are likely to be incorporated into foldbelts and that boninite or low ti lava bearing ophiolites may characterize such regions

nonmigrating diurnal tides observed in global thermospheric winds 1 nonmigrating diurnal tides between 90 and 270 km are inferred from upper atmosphere research satellite uars wind imaging interferometer windii winds this study represents the first known effort to directly analyze tidal wave number structure and propagation direction in winds observed over this altitude range prominent diurnal tides include an eastward propagating wave number 3 a zonally symmetric tide and a westward propagating wave number 2 uars high resolution doppler imager winds between 60 and 100 km were analyzed identically and show excellent consistency with windii tides observed tides were compared with tidal fits to hough mode extensions windii tides are generally damped more slowly above 120 km than fitted tides and the zonally symmetric tide indicates a thermospheric source not captured by hough mode extensions our study provides additional confirmation that tides act as direct coupling agents between the troposphere and the thermosphere and f region in addition to their role in the e region dynamo

abrupt deep sea warming palaeoceanographic changes and benthic extinctions at the end of the palaeocene a remarkable oxygen and carbon isotope excursion occurred in antarctic waters near the end of the palaeocene 57 33 myr ago indicating rapid global warming and oceanographic changes that caused one of the largest deep sea benthic extinctions of the past 90 million years in contrast the oceanic plankton were largely unaffected implying a decoupling of the deep and shallow ecosystems the data suggest that for a few thousand years ocean circulation underwent fundamental changes producing a transient state that although brief had long term effects on environmental and biotic evolution

earth s atmosphere in dynamic coupling envisaged through atmospheric tides and atmospheric gravity waves a view on the past present future research in 1982 1985 an international scientific endeavor was attempted as the middle atmosphere program contributing successfully to exploring the last unknown part of the atmosphere on the planet earth the middle atmosphere now it seems timely for us to consider the whole atmosphere which extends from the ground to the upper atmosphere and further into space as an entity each part of the atmosphere couples not only horizontally globally but also vertically while the horizontal coupling is mainly important for conventional meteorology the vertical one is significant say for space physics and probably future meteorology and will be the present topic atmospheric waves play an important role for the dynamic coupling of the atmosphere transporting energy momentum and material mainly from below and releasing on the way in their propagation upward already in the last century the existence of the tidal dynamo for the geomagnetic sq variation in the upper atmosphere was known as a manifestation of the dynamic coupling by atmospheric tides atmospheric internal gravity waves are now found to play an important role among many others in the general circulation of the middle atmosphere which is another manifestation of the dynamic coupling of the atmosphere reviewing remarkable progress in the last 40 years in the research of this subject the author has suggested that frontiers of the future research would be to develop a gcm general circulation model to include the upper atmosphere and to establish an equatorial atmosphere observation system

ridge subduction kinematics and implications for the nature of mantle upwelling ridge subduction follows the approach of an oceanic spreading centre towards a trench and subduction of the leading oceanic plate beneath the overriding plate there are four possible kinematic scenarios 1 welding of the trailing and overriding plates e g aluk antarctic ridge beneath antarctica 2 slower subduction of the trailing plate e g nazca antarctic ridge beneath chile and pacific izanagi ridge beneath japan 3 transform motion between the trailing and overriding plates e g san andreas transform or 4 divergence between the overriding and trailing plates e g pacific north america in case 4 the divergence may be accommodated in two ways the overriding plate may be stretched e g basin and range province extension which has brought the continental margin into collinearity and therefore transform motion with the pacific north america relative motion or divergence may occur at the continental margin and be manifest as a change in rate and direction of sea floor

warming the fuel for the fire evidence for the thermal dissociation of methane hydrate during the paleocene eocene thermal maximum dramatic warming and upheaval of the carbon system at the end of the paleocene epoch have been linked to massive dissociation of sedimentary methane hydrate however testing the paleocene eocene thermal maximum hydrate dissociation hypothesis has been hindered by the inability of available proxy records to resolve the initial sequence of events the cause of the paleocene eocene thermal maximum carbon isotope excursion remains speculative primarily due to uncertainties in the timing and duration of the paleocene eocene thermal maximum we present new high resolution stable isotope records based on analyses of single planktonic and benthic foraminiferal shells from ocean drilling program site 690 weddell sea southern ocean demonstrating that the initial carbon isotope excursion was geologically instantaneous and was preceded by a brief period of gradual surface water warming both of these findings support the thermal dissociation of methane hydrate as the cause of the paleocene eocene thermal maximum carbon isotope excursion furthermore the data reveal that the methane derived carbon was mixed from the surface ocean downward suggesting that a significant fraction of the initial dissociated hydrate methane reached the atmosphere prior to oxidation

chicxulub crater a possible cretaceous tertiary boundary impact crater on the yucatan peninsula mexico we suggest that a buried 180 km diameter circular structure on the yucatan peninsula mexico is an impact crater its size and shape are revealed by magnetic and gravity field anomalies as well as by oil wells drilled inside and near the structure the stratigraphy of the crater includes a sequence of andesitic igneous rocks and glass interbedded with and overlain by breccias that contain evidence of shock metamorphism the andesitic rocks have chemical and isotopic compositions similar to those of tektites found in cretaceous tertiary k t ejecta a 90 m thick k t boundary breccia also containing evidence of shock metamorphism is present 50 km outside the crater s edge this breccia probably represents the crater s ejecta blanket the age of the crater is not precisely known but a k t boundary age is indicated because the crater is in a thick carbonate sequence shock produced co2 from the impact may have caused a severe greenhouse warming

trace element partitioning between alkali feldspar and peralkalic quartz trachyte to rhyolite magma part i systematics of trace element partitioning new alkali feldspar felsic magma trace element partition coefficients d values for rb sr ba eu y zr nb ga zn trivalent ree be cs hf pb th and u for 30 samples of peralkalic quartz trachyte and rhyolite are presented d values of incompatible elements vary systematically with melt polymerization parameters increasing with whole rock silica but decreasing in rocks with higher agpaitic indices a i mol na k al d values for sr and ba evaluated to be accurate vary systematically with crystal chemistry probably substituting for na in the ca poor alkali feldspar phases apparent d values for sr and ba from pre quaternary systems are fraught with contamination and analytical errors respectively and should be used with caution d eu decreases exponentially with a i ranging from compatible in weakly peralkalic a i 1 2 rocks these regular variations strongly suggest that partition coefficients for these elements may be predicted accurately if whole rock and crystal chemical parameters are known

on modeling migrating solar tides recent updates and extensions to a steady state two dimensional linearized model of global scale atmospheric waves have facilitated improved calculations of the subset of those waves which are subharmonics of a solar day and propagate with the apparent motion of the sun the model improvements are briefly described and some updated predictions of the migrating solar diurnal component are highlighted the latter represent the first numerical modeling effort to examine the seasonal variability of the migrating diurnal harmonic as it propagates into the mesosphere and lower thermosphere

dynamics of the tengchong volcanic region in the southeastern tibetan plateau a numerical study abstract the constraints of surface heat flow and lithospheric structure were used to investigate the dynamics of the tengchong volcanic region based on thermal mechanical modeling three different boundary conditions representing three types of tectonic movements were modeled to discuss the thermal state and lithospheric deformation the compressive model shows that the subduction of the indian plate causes the upwelling of asthenosphere beneath the tengchong block in this process upwelling of the asthenosphere causes thinning of the lithosphere beneath the tengchong block however the surface heat flow of this model is not consistent with the observations the regional extension model shows that under the extension the asthenosphere upwells along the preexisting weak suture zone in the southeastern tibetan plateau the thickness of lithosphere is the thinnest along the suture zone and the surface heat flow is the highest however the extension time was found to generally need 10 15 myr to conform to the surface heat flow however this is not consistent with accepted geochronological data when a boundary condition from compression to extension is imposed both the surface heat flow and the lithospheric structure fit well with the observations the results show that the subduction of the indian plate leads to the upwelling of the asthenosphere which causes a thinned lithosphere beneath the tengchong block since the late miocene 8 5 ma the extension or extrusion has been predominant the thermal erosion of the lithosphere caused by upwelling of the asthenosphere renders the lithosphere even thinner along the bangong nujiang suture zone the upwelling of the asthenosphere provides an upward driving force and high temperature environment for the tengchong volcanic region these findings suggest that the origin of the tengchong volcanic region is caused by both the subduction of the indian plate and regional extension across the bangong nujiang suture zone

cenozoic variations in the flux of interplanetary dust recorded by 3he in a deep sea sediment helium 3 concentrations and 3he 4he ratios in modern pelagic sediments are known to be far in excess of terrestrial values as a result of micrometeorite fallout here i report that extraterrestrial helium is easily detected in a pelagic clay core dating back more than 70 myr the remarkable preservation of the extraterrestrial signature arises from high retention of 3he within interplanetary dust particles coupled with loss of radiogenic 4he from terrestrial mineral grains the core provides a continuous record of the fallout of extraterrestrial helium for the cenozoic era this record suggests that there have been significant variations in the influx of interplanetary dust through time probably related to asteroidal breakup events or the passage of comets through the inner solar system the results also show 3he to be a far more sensitive tracer of the interplanetary dust flux than is iridium

global mesospheric tidal winds observed by the high resolution doppler imager on board the upper atmosphere research satellite this paper presents preliminary results of a study of mesospheric and lower thermosphedc diurnal tidal winds obtained with the high resolution doppler imager hi on the upper atmosphere research satellite uars zonal averages of the meddional and zonal wind fields are performed at fixed local times these analyses reveal tidal structures in the mean meridional wind field during the months of february and march 1992 results are presented for a typical day in february 1992 the observed maximum amplitude of meridional wind is approximately 75 m s 1 the observed vertical wavelength is about 20 km with amplitudes increasing linearly with height in addition to the tides the zonal wind field reveals many features of the mesospheric

cenozoic volcanic rocks of eastern china secular and geographic trends in chemistry and strontium isotopic composition abstract the cenozoic volcanic rocks of eastern china are subalkalic to alkalic basalts erupted in an early tertiary back arc rift environment and from scattered late tertiary and quaternary volcanic centers in a continental area crossed by active faults driven by subduction of the pacific plate and the collision of india and eurasia immobile trace elements and major elements conform very well to each other in classification of the 59 rocks for which complete data are reported and they correctly identify the tectonic setting lil element enrichments of the basalts lie between those of p morb and ocean island alkalic basalts and show a secular increase 87sr 86sr ratios of basalts vary from 0 7029 to 0 7048 alkalic basalts are systematically less radiogenic than geographically coextensive and contemporaneous tholeiitic basalts increase of radiogenic sr with increasing crustal thickness and crustal age and with silica enrichment of the magmas suggests crustal contamination but this is inadequate to explain the lil element enrichment patterns and variable lil element enrichments the preferred hypothesis is that the alkalic magmas come from a deeper source with long term lil element depletion and low rb sr ratio but relatively recent lil element enrichment conversely the tholeiitic magmas are melts of subcontinental mantle lithosphere that is more lil element depleted than the alkalic source at the time of magma genesis but has had an elevated rb sr ratio for much of its post consolidation history

the meridional wind component of the thermospheric tide observed by windii on uars thermospheric meridional winds measured by the wind imaging interferometer windii on the upper atmosphere research satellite uars are analyzed for migrating solar tides for march april 1993 tidal signatures are extracted by zonally averaging and binning the data in equally spaced intervals of local time latitude and altitude an examination of the binned data reveals vertically propagating tides in the lower thermosphere with the diurnal tide dominating at low latitudes above 120 km evidence of vertical propagation ceases and the vertical gradients are significantly reduced in regions where both daytime and nighttime data are available fourier decomposition of the binned winds is used to extract the diurnal component of the tide this analysis reveals that the propagating diurnal tide attains a maximum amplitude of 65 m s at 20 n and 20 s at 95 km and exhibits a vertical wavelength of about 25 km

uncorking the bottle what triggered the paleocene eocene thermal maximum methane release the paleocene eocene thermal maximum petm was a time of rapid global warming in both marine and continental realms that has been attributed to a massive methane ch 4 release from marine gas hydrate reservoirs previously proposed mechanisms for this methane release rely on a change in deepwater source region s to increase water temperatures rapidly enough to trigger the massive thermal dissociation of gas hydrate reservoirs beneath the seafloor to establish constraints on thermal dissociation we model heat flow through the sediment column and show the effect of the temperature change on the gas hydrate stability zone through time in addition we provide seismic evidence tied to borehole data for methane release along portions of the u s continental slope the release sites are proximal to a buried mesozoic reef front our model results release site locations published isotopic records and ocean circulation models neither confirm nor refute thermal dissociation as the trigger for the petm methane release in the absence of definitive evidence to confirm thermal dissociation we investigate an alternative hypothesis in which continental slope failure resulted in a catastrophic methane release seismic and isotopic evidence indicates that antarctic source deepwater circulation and seafloor erosion caused slope retreat along the western margins of the north atlantic in the late paleocene continued erosion or seismic activity along the oversteepened continental margin may have allowed methane to escape from gas reservoirs trapped between the frozen hydrate bearing sediments and the underlying buried mesozoic reef front precipitating the paleocene eocene boundary methane release an important implication of this scenario is that the methane release caused rather than resulted from the transient temperature increase of the petm neither thermal dissociation nor mechanical disruption of sediments can be identified unequivocally as the triggering mechanism for methane release with existing data further documentation with high resolution benthic foraminiferal isotopic records and with seismic profiles tied to borehole data is needed to clarify whether erosion thermal dissociation or a combination of these two was the triggering mechanism for the petm methane release

cenozoic global sea level sequences and the new jersey transect results from coastal plain and continental slope drilling the new jersey sea level transect was designed to evaluate the relationships among global sea level eustatic change unconformity bounded sequences and variations in subsidence sediment supply and climate on a passive continental margin by sampling and dating cenozoic strata from coastal plain and continental slope locations we show that sequence boundaries correlate within 0 5 myr regionally onshore offshore and interregionally new jersey alabama bahamas implicating a global cause sequence boundaries correlate with 18o increases for at least the past 42 myr consistent with an ice volume glacioeustatic control although a causal relationship is not required because of uncertainties in ages and correlations evidence for a causal connection is provided by preliminary miocene data from slope site 904 that directly link 18o increases with sequence boundaries we conclude that variation in the size of ice sheets has been a primary control on the formation of sequence boundaries since 42 ma we speculate that prior to this the growth and decay of small ice sheets caused small amplitude sea level changes 20 m in this supposedly ice free world because eocene sequence boundaries also appear to correlate with minor 18o increases subsidence estimates backstripping indicate amplitudes of short term million year scale lowerings that are consistent with estimates derived from 18o studies 25 50 m in the oligocene middle miocene and 10 20 m in the eocene and a long term lowering of 150 200 m over the past 65 myr consistent with estimates derived from volume changes on mid ocean ridges although our results are consistent with the general number and timing of paleocene to middle miocene sequences published by workers at exxon production research company our estimates of sea level amplitudes are substantially lower than theirs lithofacies patterns within sequences follow repetitive predictable patterns 1 coastal plain sequences consist of basal transgressive sands overlain by regressive highstand silts and quartz sands and 2 although slope lithofacies variations are subdued reworked sediments constitute lowstand deposits causing the strongest most extensive seismic reflections despite a primary eustatic control on sequence boundaries new jersey sequences were also influenced by changes in tectonics sediment supply and climate during the early to middle eocene low siliciclastic and high pelagic input associated with warm climates resulted in widespread carbonate deposition and thin sequences late middle eocene and earliest oligocene cooling events curtailed carbonate deposition in the coastal plain and slope respectively resulting in a switch to siliciclastic sedimentation in onshore areas oligocene sequences are thin owing to low siliciclastic and pelagic input and their distribution is patchy reflecting migration or progradation of depocenters in contrast miocene onshore sequences are thicker reflecting increased sediment supply and they are more complete downdip owing to simple tectonics we conclude that the new jersey margin provides a natural laboratory for unraveling complex interactions of eustasy tectonics changes in sediment supply and climate change

a case for a comet impact trigger for the paleocene eocene thermal maximum and carbon isotope excursion abstract we hypothesize that the rapid onset of the carbon isotope excursion cie at the paleocene eocene boundary 55 ma may have resulted from the accretion of a significant amount of 12c enriched carbon from the impact of a 10 km comet an event that would also trigger greenhouse warming leading to the paleocene eocene thermal maximum and possibly thermal dissociation of seafloor methane hydrate indirect evidence of an impact is the unusual abundance of magnetic nanoparticles in kaolinite rich shelf sediments that closely coincide with the onset and nadir of the cie at three drill sites on the atlantic coastal plain after considering various alternative mechanisms that could have produced the magnetic nanoparticle assemblage and by analogy with the reported detection of iron rich nanophase material at the cretaceous tertiary boundary we suggest that the cie occurrence was derived from an impact plume condensate the sudden increase in kaolinite is thus thought to represent the redeposition on the marine shelf of a rapidly weathered impact ejecta dust blanket published reports of a small but significant iridium anomaly at or close to the paleocene eocene boundary provide supportive evidence for an impact

orbital climate forcing of δ13c excursions in the late paleocene early eocene chrons c24n c25n 1 high resolution stable carbon isotope records for upper paleocene lower eocene sections at ocean drilling program sites 1051 and 690 and deep sea drilling project sites 550 and 577 show numerous rapid 40 60 kyr duration negative excursions of up to 1 we demonstrate that these transient decreases are the expected result of nonlinear insolation forcing of the carbon cycle in the context of a long carbon residence time the transients occur at maxima in earth s orbital eccentricity which result in high amplitude variations in insolation due to forcing by climatic precession the construction of accurate orbital chronologies for geologic sections older than 35 ma relies on identifying a high fidelity recorder of variations in earth s orbital eccentricity we use the carbon isotope records as such a recorder establishing a robust orbitally tuned chronology for latest paleocene earliest eocene events moreover the transient decreases provide a means of precise correlation among the four sites that is independent of magnetostratigraphic and biostratigraphic data at the 105 year scale while the eccentricity controlled transient decreases bear some resemblance to the much larger amplitude carbon isotope excursion cie that marks the paleocene eocene boundary the latter event is found to occur near a minimum in the 400 kyr eccentricity cycle thus the cie occurred during a time of minimal variability in insolation the dominant mechanism for forcing climate change on 104 year scales we argue that this is inconsistent with mechanisms that rely on a threshold climate event to trigger the paleocene eocene thermal maximum since any threshold would more likely be crossed during a period of high amplitude climate variations

the potential volume of oceanic methane hydrates with variable external conditions gas hydrate abundance in marine sediment depends on gas concentration and the available pore space within certain stability limits potentially gas hydrates can occur between the seafloor and a locus of subbottom depths where geothermal gradients intersect gas gas hydrate pore water equilibrium curves perpendicular to a given continental margin the lens shaped area between these two bounding surfaces a sl varies according to seven basic parameters gas composition water activity a w bottom water temperature t b geothermal gradient g slope depth z slb slope gradient z and sea level relative to the shelf break z 0 assuming pure ch 4 gas 35 km 2 of sediment can host gas hydrate across an average continental margin at a pleistocene lowstand a w 0 981 t b 0 c g 0 c z slb 4000 m z 0 04 z 0 0 however this potential area would decrease with smaller a w higher t b greater g shallower z slb steeper z and lower z 0 and increase with opposite external conditions of the basic parameters temperature t b and g and bathymetry z slb and z can particularly influence the distribution of gas hydrate on continental slopes a hydrothermal gradient with e g surface temperatures t b will also decrease a sl although minimally especially if t b is warm the sum of parallel cross sectional areas along a margin combined with porosity o gives the potential volume of gas hydrate v assuming 200 000 km of continental margin with a o of 50 3 5 10 6 km 3 of pore space can contain gas hydrates at present day a volume that compares favorably with previous estimates 1 2 to 6 4 10 6 km 3 although underlying approaches differ fundamentally since the triassic v glob probably has increased significantly because t b has cooled while total margin length has grown this trend was likely punctuated by at least one major decrease nominally 1 5 to 0 7 10 6 km 3 when t b suddenly rose by 5 c during the latest paleocene thermal maximum lptm a prominent global negative 13 c excursion across the lptm may signify massive release of ch 4 associated with this theoretical drop in v glob

evidence of surface water oligotrophy during the paleocene eocene thermal maximum nannofossil assemblage data from ocean drilling program site 690 maud rise weddell sea 1 nannoplankton assemblages at ocean drilling program site 690 maud rise weddell sea experienced an abrupt and dramatic transformation at the onset of the paleocene eocene thermal maximum petm at 55 m y the major assemblage shift suggests a change from colder more productive surface waters to warmer more oligotrophic conditions significant restructuring of assemblages during the later part of the petm indicates that nannoplankton communities were not stable and that surface water conditions changed although they remained warm and oligotrophic combined with benthic foraminiferal assemblage data nannoplankton assemblage results suggest increased sequestration of nutrients in shelf environments and starvation of the open ocean although the petm was a short lived event it appears to have had long term effects on nannoplankton leading to the extinction of fasciculithus a dominant paleocene genus

an osmium isotope excursion associated with the late paleocene thermal maximum evidence of intensified chemical weathering in the latest paleocene an abrupt shift to more negative 13c values has been documented at numerous marine and terrestrial sites bralower et al 1997 cramer et al 1999 kaiho et al 1996 kennett and stott 1991 koch et al 1992 stott et al 1996 thomas and shackleton 1996 zachos et al 1993 this carbon isotope event cie is coincident with oxygen isotope data that indicate warming of surface waters at high latitudes of nearly 4 6 c kennett and stott 1991 and more moderate warming in the subtropics thomas et al 1999 here we report 187os 188os isotope records from the north atlantic and indian oceans which demonstrate a 10 increase in the 187os 188os ratio of seawater coincident with the late paleocene cie this excursion to higher 187os 188os ratios is consistent with a global increase in weathering rates the inference of increased chemical weathering during this interval of unusual warmth is significant because it provides empirical evidence supporting the operation of a feedback between chemical weathering rates and warm global climate which acts to stabilize earth s climate walker et al 1981 estimates of the duration of late paleocene cie bains et al 1999 bralower et al 1997 norris and rohl 1999 rohl et al 2000 in conjunction with the os isotope data imply that intensified chemical weathering in response to warm humid climates can occur on timescales of 104 105 years this interpretation requires that the late paleocene thermal maximum os isotope excursion be produced mainly by increased os flux to the ocean rather than a transient excursion to higher 187os 188os ratios in river runoff although we argue that the former is more likely than the latter we cannot rule out significant changes in the 187os 188os ratio of rivers

the 1719 1721 eruptions of potassium rich lavas at wudalianchi china abstract eruptions between 1719 and 1721 at wudalianchi produced two monogenetic strombolian cones laoheishan and huoshaoshan and the 65 km 2 shilong lava field the lavas are unusual in that they are leucite bearing and lack modal plagioclase together with the earlier cones the historic cones form an orthogonal network with a 4 km average separation differences in the morphology of the historic cones are attributed to differences in explosivity the shilong lava is predominantly pahoehoe 70 of compound form and similar to plains style lavas it is concluded that there is little possibility that an eruption will take place at wudalianchi in the near future

simulation of large scale dynamics in the mesosphere and lower thermosphere with the doppler spread parameterization of gravity waves 2 eddy mixing and the diurnal tide turbulence is thought to be produced by gravity waves that become unstable in the upper atmosphere owing to a relatively short vertical wavelength of the solar diurnal tide turbulent viscous type mixing is expected to be particularly important for tidal dissipation in the mesosphere and lower thermosphere mlt within the doppler spread parameterization dsp of gravity waves the vertical eddy exchange coefficients may be calculated from the gw energy deposition rate the dsp as implemented in the spectral mesosphere lower thermosphere model is shown to provide realistic simulations of both the diurnal tide and turbulent mixing in the mlt in particular the vertical structure and seasonal variations of eddy mixing agree well with in situ observations and independent estimates from global thermal balance the seasonal variations of turbulence are found to be primarily responsible for a strong semiannual variation of the diurnal tide in agreement with recent satellite observations

a new model for atmospheric oxygen over phanerozoic time a mathematical model has been constructed that enables calculation of the level of atmospheric o2 over the past 570 my from rates of burial and weathering of organic carbon c and pyrite sulfur s burial rates as a function of time are calculated from an assumed constant worldwide clastic sedimentation rate and the relative abundance and c and s contents of the three rock types marine sandstones and shales coal basin sediments and other non marine clastics red beds arkoses by our model values of o2 versus time using a constant total sedimentation rate agree with those for variable sedimentation derived from present day rock abundances and estimates of erosional losses since deposition this agreement is the result of our reliance on the idea that any increase in total worldwide sediment burial with consequently faster burial of c and s and greater o2 production must be accompanied by a corresponding increase in erosion and increased exposure of c and s on the continents to o2 consumption via weathering it is the redistribution of sediment between the three different rock types and not total sedimentation rate that is important in o2 control to add stability to the system negative feedback against excessive o2 fluctuation was provided in the modeling by the geologically reasonable assignment of higher weathering rates to younger rocks resulting in rapid recycling of c and s we did not use direct o2 negative feedback on either weathering of c and s or burial of c because weathering rates are assumed to be limited by uplift and erosion and the burial rate of c limited by the rate of sediment deposition the latter assumption is the result of modern sediment studies which show that marine organic matter burial occurs mainly in oxygenated shallow water and is limited by the rate of supply of nutrients to the oceans by rivers results of the modeling indicate that atmospheric o2 probably has varied appreciably over phanerozoic time during the late carboniferous and permian periods o2 was higher than previously because of the rise of vascular land plants and the widespread burial of organic matter in vast coal swamps a large decrease in o2 during the late permian was due probably to the drying up of the coal swamps and deposition of a large proportion of total sediment in c and s free continental red beds sensitivity study shows that major parameters affecting results are the mean c concentration in coal basins and the relative sizes of the reservoirs of young rapidly recycled versus old rocks less sensitivity was found for changes over time in total land area undergoing weathering and the use of direct o2 negative feedback on marine carbon burial good agreement for rates of c burial calculated via our model and via independent models which are based on the use of stable carbon isotopes indicates that the dominant factor that has brought about changes in atmospheric o2 level and the isotopic composition of dissolved inorganic carbon in seawater over phanerozoic time is sedimentation and not weathering or higher temperature phenomena such as basalt seawater reaction

global change at the paleocene eocene boundary climatic and evolutionary consequences of tectonic events rea d k zachos j c owen r m and gingerich p d 1990 global change at the paleocene eocene boundary climatic and evolutionary consequences of tectonic events palaeogeogr palaeoclimatol palaeoecol 79 117 128 events of the paleocene eocene boundary provide the clearest example to date of how a tectonic event may have global climatic consequences recent advances permit well constrained stratigraphic determination of several events that occurred at that boundary in chron c24r a many fold increase in sea floor hydrothermal activity a global warming a reduction in the intensity of atmospheric circulation a conversion to salinity driven deep ocean circulation a marked lightening of oceanic 313c values extinction and evolution of both benthic foraminifera and land mammals and important plate boundary reorganizations including the outpouring of the east greenland volcanics and the initiation of the oceanic rift between norway and greenland we hypothesize that enhanced sea floor hydrothermal activity occasioned by global tectonism resulted in a flooding of the atmosphere with coz causing a reduced pole to equator temperature gradient and increased evaporation at low latitudes increased formation of warm salty probably low nutrient waters coupled with the warm temperatures at high latitudes occasioned a salinity driven rather than temperature driven deep water circulation this newly evolved ocean circulation pattern changed the apportionment of global heat transport from the atmosphere to the ocean with concomitant changes in the circulation intensity of both reduced intensity of atmospheric circulation resulted in lower oceanic biological productivity and enhanced seasonality of climate on the continents a major extinction event among benthic foraminifera was probably a response to the new low nutrient and chemically changed bottom waters and endemism following rapid evolution and dispersal of mammalian orders may have been in response to the new continental climate regime

ocean nutrient distribution and oxygenation limits on the formation of warm saline bottom water over the past 91 m y it has been proposed that deep water formation in the oceans would be quite different during geologic intervals with reduced equator to pole temperature gradients salinity rather than temperature differences might drive the deep ocean circulation saline water would tend to form at subtropical latitudes where evaporation exceeds precipitation we point out a likely consequence of warm saline bottom water formation on ocean chemistry the tendency to drive the ocean toward anoxia this effect is not due to the previously noted lower oxygen solubility with increasing ocean temperature but rather to the increased efficiency with which plankton will extract nutrients from convecting waters at low latitudes the present ocean nutrient content is sufficient to induce deep water anoxia if circulation were to change yet anoxia is rare in the paleoceanographic record a simple ocean chemical model makes explicit the tradeoffs between mean ocean nutrient content and circulation parameters that will satisfy the geologic observations of an oxygenated ocean since the mid cretaceous barring decreases of ocean phosphate on the order of 30 50 deep water formation at high latitudes was a major source of ocean ventilation in the warmer past

atmospheric tide 2 the solar and lunar semidiurnal components solar and lunar semidiurnal wind and temperature oscillations from the surface to 400 km are simulated for average solar activity conditions utilizing the numerical tidal model described in part 1 hough mode decomposition of the solstitial solar semidiurnal tide excited by h2o and o3 insolation absorption below 80 km indicates that it is characterized by a predominance of 2 2 below 60 km about equal contributions of 2 2 2 3 and 2 4 between 70 and 90 km mostly 2 4 with some 2 5 and 2 2 between 90 and 120 km and a predominance of 2 2 above 140 km with secondary contributions from 2 3 and 2 5 the solstitial lunar semidiurnal tide is characterized by a predominance of 2 2 below 70 km 2 4 with secondary contributions from 2 2 2 3 and 2 5 between 80 and 110 km and by 2 2 with a fairly strong secondary contribution from 2 3 above 120 km similar descriptions for both the solar and lunar oscillations apply at equinox except that the asymmetric 2 3 and 2 5 modes are absent relative to the solar component lunar temperature and wind amplitudes are sufficiently large 20 in the lower and upper thermosphere to account for some of the observed variability previously attributed to the solar tide amplitudes of the 2 4 and 2 5 modes above 100 km are significantly affected by mesospheric eddy diffusion coefficients in excess of 2 106 cm s 1 the total solar semidiurnal exospheric temperature oscillation for average solar conditions ranges from 10 20 k poleward of 40 n to 40 60 k equatorward of 30 n and has its origin in three sources of excitation all of comparable importance 1 euv solar radiation absorption in the lower thermosphere 100 200 km 2 in situ momentum coupling due to the interaction of diurnal winds and diurnally varying ion drag and 3 tides propagating upwards from below 100 km in addition the calculations are compared with rocket meteor radar partial reflection thomson scatter and satellite data to evaluate the consistency of the model with observations

the case against a phanerozoic kolyma plate in the northeastern ussr the kolyma omolon region in the northeastern ussr has been interpreted by several western geologists as having formed the core of a discrete continental plate the kolyma plate and has been used as such in pre jurassic continental reconstructions the region has also been considered as part of the pre jurassic north american plate and by some soviet geologists as part of the siberian plate however the available geological evidence suggests either that most of the region was part of the siberian platform since at least the ordovician period or that it is a mosaic of accreted terranes

high resolution iridium δ13c δ18o foraminifera and nannofossil profiles across the latest paleocene benthic extinction event at zumaya spain in the expanded upper paleocene lower eocene section 30 m of zone p5 sediments at zumaya northern spain the highest occurrence of many late paleocene deep sea benthic foraminifera species 40 extinction coincides with a transition from marl to calcite free clay our high resolution studies chemical elements 613c 6180 calcareous nannofossils planktic and benthic foraminifera show that below the marl clay transition there is a 40 50 cm thick interval corresponding to 10 20 kyr containing a detailed record of a gradual succession of faunal and geochemical events culminating in the benthic extinctions planktic foraminiferal and nannofossil changes e g the onset of demise in fasciculithus genus occur a few meters below the marl clay transition in the limestone 50 cm below the base of the clay a prominent glauconite maximum indicates that sea floor oxygenation suddenly decreased glauconite continues to be common until the onset of clay deposition a whole rock negative 613c shift 1 6 0 most likely reflecting an original sea water trend is gradually developed over the 40 cm of greenish brown marls immediately below the clay at the base of these marls there is a small significant iridium anomaly of 133 ppt ir compared with an average background of 38 ppt in the marls the demise of the fasciculithus species accelerates gavelinella beccariiformis becomes extinct and the abundance of acarinina species begins to increase the superjacent 4 m of clay is devoid of original calcite in its lower part and has a low calcareous content higher up at calcareous levels in the clay an unusual planktic foraminifera fauna occurs dominated by acarinina species when marl deposition returns 613c gradually increases and then stabilizes at values about 0 5 o lower than before the isotopic excursion the 613c excursion spans in total 5 m probably corresponding to 200 400 kyr the fasciculiths disappear shortly after the stabilization of 613c here we also present a whole rock 6 3c profile through the entire paleocene section at zumaya the profile is very similar to previous profiles registered in well preserved deep sea material suggesting that whole rock 613c at zumaya can be used for correlation

observations of tidal temperature and wind perturbations in the mesopause region above urbana il 40 n 88 w na lidar and mf radar measurements of temperature and horizontal winds were conducted simultaneously during several continuous 24 h periods in march and april 1996 at the urbana atmospheric observatory the data are used to determine the amplitude and phase profiles of the 24 and 12 h tides in the mesopause region between about 82 and 100 km the measured amplitudes and phases of the tidal components of the horizontal winds are generally consistent with the predictions of the global scale wave model gswm the measured 24 h temperature amplitude is comparable to the gswm predictions between 85 and 96 km but is significantly larger than gswm above 96 km the measured phase progression is downward below 94 km with an inferred vertical wavelength of 14 1 km above 94 km the temperature phase progression is upward with a vertical wavelength of 12 1 km the measurements suggest the presence of a diurnal heat source in the lower thermosphere which is generating a strong downwardly propagating 24 h wave

coeval 40ar 39ar ages of 65 0 million years ago from chicxulub crater melt rock and cretaceous tertiary boundary tektites 40 ar 39 ar dating of drill core samples of a glassy melt rock recovered from beneath a massive impact breccia contained within the 180 kilometer subsurface chicxulub crater in yucatan mexico has yielded well behaved incremental heating spectra with a mean plateau age of 64 98 0 05 million years ago ma the glassy melt rock of andesitic composition was obtained from core 9 1390 to 1393 meters in the chicxulub 1 well the age of the melt rock is virtually indistinguishable from 40 ar 39 ar ages obtained on tektite glass from beloc haiti and arroyo el mimbral northeastern mexico of 65 01 0 08 ma mean plateau age for beloc and 65 07 0 10 ma mean total fusion age for both sites the 40 ar 39 ar ages in conjunction with geochemical and petrological similarities strengthen the recent suggestion that the chicxulub structure is the source for the haitian and mexican tektites and is a viable candidate for the cretaceous tertiary boundary impact site

phanerozoic plate boundaries in mainland se asia the himalayas and tibet recently available geological data on tibet yunnan and burma facilitate recognition of phanerozoic subduction systems and two continental fragments of gondwanaland which extend through mainland se asia a cambrian subduction system and 5 mesozoic early caenozoic collision belts are identified in the region indochina eastern thailand and central tibet accreted to china in the early triassic western se asia and s tibet separated from gondwanaland in the permian or early triassic and collided with asia in the late triassic and the western burma island arc system collided with asia in the jurassic upper triassic flysch and schist in the eastern indoburman ranges were accreted to western burma in the jurassic early cretaceous during eastward subduction and formation of a back arc thrust belt following collision of greater india with arc complexes to the n in the cretaceous and with tibet in the early eocene western burma moved northwards about 450 km along the sagaing namyin ridge thrust transform fault formation of the 3 major belts of tin granites and the porphyry copper deposits in the region took place in specific tectonic settings within the subduction systems and collision belts

tephra layers of large explosive eruptions of baitoushan changbaishan volcano in the japan sea sediments this paper is based on the results of a comprehensive investigations of sediments from seven cores sampled during the international russian chinese cruise 53 of the r v akademik lavrentyev 2010 in the frames of the russian chinese collaboration between the pacific oceanological institute of the far eastern branch of the russian academy of sciences poi feb ras vladivostok russia and the first institute of oceanography fio qingdao china baitoushan chanbaishan volcano had several powerful explosive eruptions during the middle pleistocene holocene which produced widespread tephra layers the paper reports chemical composition of volcanic glasses and minerals from six tephra layers labeled as b og b sado b j b un1 b v and b tm which belong to baitoushan volcano and were identified in sediments of the northwestern part of the sea of japan the tephras were dated using geochronological data for the host sediments the estimated ages for the middle pleistocene tephra is 488 ka the late pleistocene tephras are 71 1 71 9 cal k b sado 50 8 cal ka b j 38 3 cal ka b un1 and 29 0 29 4 cal ka b v the ash layers consist of alkali rich glass of trachydacitic to alkaline rhyolitic composition and specific assemblage of minerals including fe rich augite hedenbergite aegirine augite aegirine arfvedsonite and fayalite the mineral assemblage is typical for alkalic volcanic rocks from continental rift setting aenigmatite a rare mineral from the group of inosilicates was firstly identified in distal tephra of baitoushan volcano supplied into marine sediments the composition of glasses and minerals from all layers are similar it testifies about steady state conditions of the magma accumulation under baitoushan volcano and about the bimodal character of magmatic chambers during the late pleistocene and holocene since 100 ka

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

satellite observations of thermospheric tides results from the wind imaging interferometer on uars thermospheric winds measured by the wind imaging interferometer windii on the upper atmosphere research satellite are analyzed for migrating solar tides the data cover a 2 year period commencing february 1992 and are obtained from the atomic oxygen o 1s 557 7 nm emission which provides observations of the 90 to 200 km altitude range during daytime and the 90 to 110 km range at night the subtropical lower thermosphere is dominated by the diurnal propagating tide which exhibits a vertical wavelength of approximately 22 km grows in amplitude up to 95 km and decays rapidly above where molecular diffusion greatly reduces the vertical shears although the phase remains fairly uniform throughout the year a pronounced semiannual oscillation is observed in the diurnal tide amplitude at both 20 n and 20 s the meridional and zonal wind components attain their maximum values at equinox of approximately 70 and 40 m s respectively while the solstitial minima are nearly a factor of 2 smaller at 35 n the diurnal tide semiannual amplitude oscillation is still present in the lower thermosphere but above 100 km it is replaced by an annual cycle with a maximum in july and august this contrasts with 35 s where the july august peak is absent and the semiannual oscillation extends to 110 km at midlatitudes the zonal and meridional winds are of similar magnitude and no significant hemispheric asymmetries in amplitudes are observed in the lower thermosphere the semidiurnal tide amplitude exhibits an annual oscillation with maximum values of 30 to 40 m s occurring in june july near 100 km at 35 n 35 s and the equator a bimodal structure in the seasonal variation of the semidiurnal phase is observed this feature is characterized by rapid equinoctial transitions and is particularly well defined at the equator examination of the equatorial middle thermosphere indicates that the semidiurnal tide attains its maximum amplitude at 140 km and exhibits a vertical wavelength of approximately 60 km these findings indicate the predominance of the antisymmetric 2 3 hough mode in the tropics

diurnal tide in the equatorial middle atmosphere as seen in lims temperatures abstract the distribution of day night temperature differences in the middle atmosphere determined by the nimbus 7 lims experiment is described day night differences maximize at and are approximately symmetric about the equator successive centers of opposite sign increase in amplitude with altitude the pattern having a vertical wavelength of 25 km profiles of rocket meridional wind at kwajalein 8 7 n and ascension island 8 0 s taken near local noon and averaged over the lims data period exhibit maxima which support the tidal interpretation of the equatorial temperature pattern these characteristics are in general agreement with previous observational and theoretical results for the solar driven diurnal tide substantial time variations in amplitude and in location of the temperature maxima are observed the diurnal tide near the equatorial stratopause appears to be influenced by the phase of the semiannual oscillation

diurnal migrating tide as seen by the high resolution doppler imager uars 1 monthly mean global meridional winds the high resolution doppler imager hrdi instrument on board the upper atmosphere research satellite measures global winds in the mesosphere and lower thermosphere on a day to day basis the horizontal coverage of the hrdi data is excellent and provides a unique opportunity to study global scale dynamic phenomena however the local time resolution and coverage are limited because of the nature of the satellite sampling the lack of local time coverage makes conventional methods of data analysis e g fourier analysis both difficult and erroneous an original method of analysis based on a numerical model of atmospheric thermal tides is proposed and applied to the hrdi data the tidal model is solved for the tidal oscillations in the meridional wind component the simulated diurnal meridional tidal winds are used as a first guess in the analysis the results of the model are adjusted to give meridional migrating tidal winds that have maximum consistency with hrdi measurements this technique is used to derive monthly mean tidal oscillations of the meridional velocity the derived tidal amplitudes show profound seasonal changes that seem to be consistent with gravity wave breaking theory the results are compared with mf radar data it is found that in the upper mesosphere and lower thermosphere the tidal amplitudes obtained by hrdi can be bigger than those from mf radars by a factor of 2

enhanced magnetization of the marlboro clay as a product of soil pyrogenesis at the paleocene eocene boundary abstract the kaolinite rich marlboro clay was deposited on the inner shelf in the salisbury embayment of the u s atlantic margin at the onset of the carbon isotope excursion marking the 56 ma paleocene eocene boundary and is characterized by an anomalously high concentration of magnetic nanoparticles of enigmatic origin that give rise to notably intense bulk magnetization recent studies point to a magnetic assemblage that is dominated by single domain magnetite particles that tend to be isolated rather than arranged in chains the most distinguishing feature of magnetotactic bacteria fossils on the other hand it is very unlikely that the nanoparticles can be condensates of an impact plume given the meter scale thickness of the marlboro clay we obtained new data from a landward proximal site at wilson lake on the new jersey coastal plain and find that the abrupt increase in magnetite nanoparticles is virtually coincident stratigraphically with the recently reported impact spherule layer at the base of the marlboro clay in the same core yet the high field magnetic susceptibility a measure of total iron concentration and strontium isotope values on bulk sediment an indicator of sediment weathering provenance are not different in the marlboro clay from the immediately underlying vincentown formation we suggest that the distinctive magnetic properties of the marlboro clay originated from pyromagnetic soil enhancement by widespread wildfires on the adjoining drainage area the pyrogenetic products were soon washed from the denuded landscape and rapidly deposited as mud waves across the shelf becoming the marlboro clay a few percent of incinerated biomass ends up as calcite known as wood ash stone and can inherit its light carbon isotope composition disseminated wood ash stone entrained in the marlboro clay could contribute to the landward increase in amplitude of the carbon isotope excursion in bulk carbonate data a plausible trigger for the initial conflagration is a fireball from the impact of a sizable extraterrestrial object at moderate range

the source and fate of massive carbon input during the latest paleocene thermal maximum lithologic faunal seismic and isotopic evidence from the blake nose subtropical western north atlantic links a massive release of biogenic methane 55 5 million years ago to a warming of deep ocean and high latitude surface waters a large perturbation in the combined ocean atmosphere carbon cycle the largest of the past 90 million years a mass extinction event in benthic faunas and a radiation of mammalian orders the deposition of a mud clast interval and seismic evidence for slope disturbance are associated with intermediate water warming massive carbon input to the global exogenic carbon cycle pelagic carbonate dissolution a decrease in dissolved oxygen and a benthic foraminiferal extinction event these events provide evidence to confirm the gas hydrate dissociation hypothesis and identify the blake nose as a site of methane release

rapid diversification of planktonic foraminifera in the tropical pacific odp site 865 during the late paleocene thermal maximum the planktonic foraminiferal generamorozovellaandacarininarapidly in 10 k y diversified during the late paleocene thermal maximum lptm giving rise to such morphotypes asm allisonensis new species m africana anda sibaiyaensis single specimen isotopicanalysisconfirmsthatm allisonensisanda sibaiyaensisarerestrictedtothelptm carbon isotope excursion recorded at ocean drilling program site 865 equatorial pacific ocean the short lived 50 to several 100 k y excursion taxa attest to the ephemeral effectsofthelptmonthecalcareousplankton single specimenoxygenisotopedatashow that evolution of m allisonensis and a sibaiyaensis was accompanied by migration to deeper water depths ancestralm velascoensisanda soldadoensiswere extremely rare or absent during the early stages of the lptm but immigrated back into the study area to coexist with their descendants in later lptm horizons photosymbiosis may have facilitatedthemorozovellidandacarininiddiversificationsduringtheoligotrophicconditionsof the lptm

global structure and seasonal and interannual variability of the migrating diurnal tide seen in the saber timed temperatures between 20 and 120 km 1 the present paper is focused on the global spatial altitude and latitude structure and seasonal and interannual variability of the migrating diurnal tide derived from the sounding of the atmosphere using broadband emission radiometry thermosphere ionosphere mesosphere energetics and dynamics saber timed temperature measurements for 6 full years january 2002 to december 2007 the tidal results are obtained by a new analysis method where the tides migrating and nonmigrating and the planetary waves zonally traveling and stationary are simultaneously extracted from the satellite data it has been found that above 70 km height the saber migrating diurnal tide reflects mainly the distinctive features of the first symmetric propagating 1 1 mode while below this height it reflects the features of the first symmetric trapped 1 2 mode the trapped component amplifies near 50 km and its phase is close to 1600 lt the seasonal behavior of the diurnal tide over the equator is dominated by semiannual variation with a primary maximum in february march 18 k average amplitude for 6 years and a secondary maximum in august september 15 k the tidal amplitude grows rapidly in the mesosphere lower thermosphere however it undergoes some decay near 90 km defining ubiquitous double peaked vertical structure a very rapid reduction in amplitude is detected at heights near 115 km however above this level the diurnal tide amplifies again the vertical wavelength of the propagating diurnal tide is 20 km over the equator at middle latitudes it is not very different from that over the equator but its magnitude depends on the season in the winter it is longer than that in summer the interannual variability of the diurnal tide indicates a clear correlation with the stratospheric quasi biennial oscillation

reply to a comment on a case for a comet impact trigger for the paleocene eocene thermal maximum and carbon isotope excursion by g r dickens and j m francis contrary to dickens and francis s claim 1 that we challenge the idea of a massive ch4 release during the petm paleocene eocene thermal maximum our consideration of an extraterrestrial carbon contribution to the carbon isotope excursion cie is speci cally limited to the initial and most rapid decrease in n13c which accounts for less than half of the full magnitude of the cie 2 thermal dissociation in response to the warming at the petm is explicitly allowed in our hypothesis as reiterated in our conclusions that the impact may have triggered a more gradual thermal dissociation of sea oor methane hydrates 2 we directly challenge only that portion of the hydrate dissociation hypothesis that relies on gradual warming intrinsic to earth s climate system as the triggering mechanism 3 such a mechanism is not consistent with the documented essentially synchronous and instantaneous warming and decrease in n13c values at the onset of the event 3 4 and is also at odds with the occurrence of the cie during an interval of low amplitude orbital forcing of climate 5 instead we postulate a comet impact as an explanation for the rapid onset of the event dickens and francis state that the primary di culty with invoking a comet t is that there is no supporting evidence and then list four points from our paper that taken out of context are construed as damaging to our hypothesis 1 there is no crater if this were to be taken as a fatal problem with hypothesizing an impact then the idea of a k t cretaceous tertiary impact would never have gained any traction it took 10 years to identify the smoking gun at chicxulub crater 6 8 in addition it is hardly contrived to acknowledge that the p e paleocene eocene impact may have occurred on oceanic crust which constitutes more than half of earth s surface area and where impact craters of any age have been very di cult to nd 2 the remarkable fossil turnovers t strongly contrast to those across the cretaceous tertiary boundary t in fact although we noted that the two events are clearly diierent 2 and that an a priori assumption that big impacts should be

bolide summer the paleocene eocene thermal maximum as a response to an extraterrestrial trigger the standard paradigm that the paleocene eocene thermal maximum petm represents a threshold event intrinsic to earth s climate and connected in some way with long term warming has influenced interpretations of the geochemical climate and biological perturbations that occurred at this event as recent high resolution data have demonstrated that the onset of the event was geologically instantaneous attempts to account for the event solely through endogenous mechanisms have become increasingly strained the rapid onset of the event indicates that it was triggered by a catastrophic event which we suggest was most likely a bolide impact we discuss features of the petm that require explanation and argue that mechanisms that have previously been proposed either cannot explain all of these features or would require some sort of high energy trigger a bolide impact could provide such a trigger and in the event of a comet impact could contribute directly to the shape of the carbon isotope curve we introduce a carbon cycle model that would explain the petm by global warming following a bolide impact leading to the oxidation of terrestrial organic carbon stores built up during the late paleocene our intention is to encourage other researchers to seriously consider an impact trigger for the petm especially in the absence of plausible alternative mechanisms

global distribution and interannual variations of mesospheric and lower thermospheric neutral wind diurnal tide 1 migrating tide 1 using the timed doppler interferometer tidi mesospheric and lower thermospheric neutral wind multiyear data set 2002 2007 and ncar time general circulation models gcm 1 2 annual run results 2002 2005 at the tidi sampling points we study the migrating diurnal tide s global distribution interannual and seasonal variations in connection with the mean zonal wind interannual variations a strong quasi biennial oscillation qbo effect on the diurnal tide was observed in the tidi data and reproduced to a lesser degree in the time gcm run the migrating diurnal tide amplitude is larger during the eastward phase of the stratospheric qbo and weaker during the westward phase westward mesospheric equatorial mean zonal winds appeared during the eastward phase of the stratospheric qbo in 2002 2004 and 2006 the strongest qbo effect on both the migrating diurnal tide and mean zonal winds was observed during the march equinox the stronger tides may be related to the weaker gravity wave filtering in the stratosphere during the eastward phase stratospheric qbo the tidi data also exhibit large interhemispheric asymmetry the westward mean zonal winds in the mesosphere appeared to be associated with the enhanced diurnal tide the time gcm 1 2 diurnal tide amplitudes are in general smaller than those observed by the tidi instrument limited vertical spatial resolution for the time cgm 1 2 is suggested as the cause future improvements are expected with a higher spatial resolution in the model