shock induced microdeformations in quartz and other mineralogical indications of an impact event at the cretaceous tertiary boundary abstract the event terminating the cretaceous period and the mesozoic era caused massive extinctions of flora and fauna worldwide theories of the nature of this event can be classed as endogenic volcanic climatic etc or exogenic extraterrestrial causes mineralogical evidence from the boundary clays and claystones strongly favor the impact of an extraterrestrial body as the cause of this event nonmarine k t boundary claystones are comprised of two separate layers an upper layer composed of high angle ejecta material shocked quartz altered glass and spinel and a basal kaolinitic layer containing spherules clasts and altered glass together with some shocked grains recognition of this dual layered nature of the boundary clay is important for the determination of the timing and processes involved in the impact event and in the assignment and interpretation of geochemical signatures multiple sets of shock induced microdeformations planar features in quartz grains separated from k t boundary clays provide compelling evidence of an impact event this mineralogical manifestation of shock metamorphism is associated worldwide with a large positive anomaly of iridium in these boundary clays which has also been considered indicative of the impact of a large extraterrestrial body global distributions of maximum sizes of shocked quartz grains from the boundary clays and the mineralogy of the ejecta components favor an impact on or near the north american continent spinel crystals magnesioferrite occur in the boundary clays as micrometer sized octahedra or skeletal forms their composition differs from that of spinels found in terrestrial oceanic basalts magnesioferrite crystals are restricted to the high angle ejecta layer of the boundary clays and their small size and skeletal morphology suggest that they are condensation products of a vaporized bolide hollow spherules ranging up to 1 mm in size are ubiquitously associated with the boundary clays in nonmarine sections where a high angle ejecta layer and an underlying kaolinitic layer can be distinguished the spherules are found only in the kaolinitic layer the morphologies and surface features of these spherules suggest that they are original forms and not secondary growths or algal bodies these impact spherules closely resemble microtektites in size and shape all of these features of the boundary clay are uniquely associated with impact and cannot have been formed by volcanic or other terrestrial processes

post processing removal of correlated errors in grace data 1 gravity fields produced by the gravity recovery and climate experiment grace satellite mission require smoothing to reduce the effects of errors present in short wavelength components as the smoothing radius decreases these errors manifest themselves in maps of surface mass variability as long linear features generally oriented north to south i e stripes the presence of stripes implies correlations in the gravity field coefficients here we examine the spectral signature of these correlated errors and present a method to remove them finally we apply the filter to a model of surface mass variability to show that the filter has relatively little degradation of the underlying geophysical signals we seek to recover

ru ir ratios at the cretaceous tertiary boundary implications for pge source and fractionation within the ejecta cloud abstract ruthenium and ir are the least mobile platinum group elements pges within the cretaceous tertiary k t boundary clay the ru ir ratio is therefore the most useful pge interelement parameter for distinguishing terrestrial and extraterrestrial contributions to the boundary clay the ru ir ratio of european marine k t sections 1 67 0 38 is statistically different from that of the north american continental sections 0 76 0 26 it is unlikely that this difference is due to secondary pge remobilization pge input to the boundary clay during multiple impacts or volcanic emissions the global difference in ru ir ratios in the boundary clay may therefore be primary the positive correlation between distance from the chicxulub impact structure yucatan mexico and ru ir ratio and the more than 1000 c difference in the condensation temperatures of these elements lead us to propose that fractionation of ru from ir during condensation from the ejecta cloud may have occurred resulting in the global difference in ru ir ratios

detectability of groundwater storage change within the great lakes water basin using grace groundwater is a primary hydrological reservoir of the great lakes water basin glb which is an important region to both canada and us in terms of culture society and economy due to insufficient observations there is a knowledge gap about groundwater storage variation and its interaction with the great lakes the objective of this study is to examine the detectability of the groundwater storage change within the glb using the monthly models from the gravity recovery and climate experiment grace satellite mission auxiliary soil moisture snow and lake smsl data and predictions from glacial isostatic adjustment gia models a two step filtering method is developed to optimize the extraction of grace signal a two dimensional basin window weight function is also introduced to reduce ringing artifacts caused by the band limited grace models in estimating the water storage change within the glb the groundwater storage gws as deviation from a reference mean storage is estimated for the period of 2002 to 2009 the average gws of the glb clearly show an annual cycle with an amplitude range from 27 to 91 mm in water thickness equivalent wte and a phase range of about two months the estimated phases of gws variations have a half year shift with respect to the phase of smsl water storage variations which show peaks in march and april the least squares estimation gives a gws loss trend of from 2 3 to 9 3 km3 yr within the glb for the period of study this wide range of the grace gws results is caused largely by the differences of soil moisture and snow storage from different land surface models lsms and to a lesser extent by the grace commission and omission errors and the gia model error

use of flow modeling to assess sustainability of groundwater resources in the north china plain 1 the north china plain ncp is one of the global hotspots of groundwater depletion currently our understanding is limited on spatiotemporal variability in depletion and approaches toward more sustainable groundwater development in this region this study was intended to simulate spatiotemporal variability in groundwater depletion across the entire ncp and explore approaches to reduce future depletion simulated predevelopment groundwater recharge 13 km3 yr primarily discharged as base flow to rivers and evapotranspiration initial groundwater storage was estimated to be 1500 km3 of drainable storage in shallow aquifers and 40 km3 of compressive storage in deep aquifers simulated groundwater depletion from 1960s to 2008 averaged 4 km3 yr cumulative depletion was 50 km3 20 of pumpage in the piedmont district 103 km3 20 in the central plain and 5 km3 12 in the coastal plain however depletion varied with time 2 5 km3 yr in the 1970s 4 0 in the 1980s 2 0 in 1990 1996 7 0 in 1997 2001 and 4 0 in 2002 2008 recharge also varied spatially averaging 120 mm yr and concentrated in the piedmont district 200 350 mm yr while lower in the central and coastal plains 50 100 mm yr simulation of several alternatives including managed aquifer recharge increased water use efficiency brackish water use and interbasin water transfer indicated that the combination of these strategies could be used to recover groundwater storage by 50 km3 over a 15 year period this study provides valuable insights for developing more sustainable groundwater management options for the ncp the methods are useful for managing other depleted aquifers

grace measurements of mass variability in the earth system monthly gravity field estimates made by the twin gravity recovery and climate experiment grace satellites have a geoid height accuracy of 2 to 3 millimeters at a spatial resolution as small as 400 kilometers the annual cycle in the geoid variations up to 10 millimeters in some regions peaked predominantly in the spring and fall seasons geoid variations observed over south america that can be largely attributed to surface water and groundwater changes show a clear separation between the large amazon watershed and the smaller watersheds to the north such observations will help hydrologists to connect processes at traditional length scales tens of kilometers or less to those at regional and global scales

time calibration of triassic jurassic microfloral turnover eastern north america abstract palynological data from the newark basin of the newark supergroup reveal a spike in the spore pollen ratio at the triassic jurassic boundary this spore spike is coincident with a 60 regional extinction of the palynoflora and approximately synchronous with terrestrial vertebrate extinctions orbitally controlled sedimentary cycles allow stratigraphic sections to be calibrated in time constraining the duration of the microfloral turnover to an interval of 21 ky the geologically brief palynofloral break is similar to cretaceous tertiary boundary fern spikes these data support a triassic jurassic boundary impact extinction scenario

detection of aquifer system compaction and land subsidence using interferometric synthetic aperture radar antelope valley mojave desert california interferometric synthetic aperture radar insar has great potential to detect and quantify land subsidence caused by aquifer system compaction insar maps with high spatial detail and resolution of range displacement 10 mm in change of land surface elevation were developed for a groundwater basin 103 km2 in antelope valley california using radar data collected from the ers 1 satellite these data allow comprehensive comparison between recent 1993 1995 subsidence patterns and those detected historically 1926 1992 by more traditional methods the changed subsidence patterns are generally compatible with recent shifts in land and water use the insar detected patterns are generally consistent with predictions based on a coupled model of groundwater flow and aquifer system compaction the minor inconsistencies may reflect our imperfect knowledge of the distribution and properties of compressible sediments when used in conjunction with coincident measurements of groundwater levels and other geologic information insar data may be useful for constraining parameter estimates in simulations of aquifer system compaction

a method to estimate groundwater depletion from confining layers 1 although depletion of storage in low permeability confining layers is the source of much of the groundwater produced from many confined aquifer systems it is all too frequently overlooked or ignored this makes effective management of groundwater resources difficult by masking how much water has been derived from storage and in some cases the total amount of water that has been extracted from an aquifer system analyzing confining layer storage is viewed as troublesome because of the additional computational burden and because the hydraulic properties of confining layers are poorly known in this paper we propose a simplified method for computing estimates of confining layer depletion as well as procedures for approximating confining layer hydraulic conductivity k and specific storage ss using geologic information the latter makes the technique useful in developing countries and other settings where minimal data are available or when scoping calculations are needed as such our approach may be helpful for estimating the global transfer of groundwater to surface water a test of the method on a synthetic system suggests that the computational errors will generally be small larger errors will probably result from inaccuracy in confining layer property estimates but these may be no greater than errors in more sophisticated analyses the technique is demonstrated by application to two aquifer systems the dakota artesian aquifer system in south dakota and the coastal plain aquifer system in virginia in both cases depletion from confining layers was substantially larger than depletion from the aquifers

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

the k pg boundary at brazos river texas usa an approach by marine palynology two cores and one outcrop section from the cretaceous palaeogen k pg boundary interval at the brazos river area texas usa have been high resolution sampled and analysed fully quantitatively by marine palynology the results have been compared and integrated with data from micropalaeontology sedimentology and isotope geochemistry from the same sections within all three sections the k pg boundary defined as the base of the p0 foraminifera zone and the onset of a negative carbon isotope anomaly closely corresponds to the appearance of lowermost danian organic walled dinocysts based on various palynological proxies as well as on sedimentologic features a sequence stratigraphic subdivision of the sections is proposed from a synopsis of all three sections a long term punctuated drop of relative sea level is indicated starting at about the top of the upper cretaceous cf2 foraminifera zone and reaching a minimum within the upper p1a zone of the lower palaeogene this is followed by a prominent transgression starting within the p1a p1b boundary interval the event deposit ed a siliciclastic unit located well below the base of the p0 foraminifera zone in the present sections most probably represents a combination of both episodic relative sea level fall and lag deposit due to initial transgression it is preceded by significant fluctuations of climatic boundary conditions with cool climates correlating to heavier 13c values and increased p g ratio of dinocysts suggestive of higher marine primary productivity across the k pg boundary a prominent increase and spike of the warm temperate waters dinocysts fraction is documented represented mainly by trithyrodinium evittii which is accompanied by climatic warming and an episodic relative sea level rise thus prominent paleo environmental changes and sea level fluctuations precede and coincide with the k pg boundary proper these data are inconsistent with a single catastrophic impact as the cause for the k pg boundary event but suggest relative longer term environmental stress as finally leading to end cretaceous crisis of the biosphere between the ed and the k pg boundary proper the gradual increase to peak abundance in trilete spores demonstrates a significant time lag between these two horizons according to the distinct distribution of this peak abundance it cannot be excluded that an impact tsunami event is related to the lower portion of the ed in contrast no significant changes within most palynologic proxies are documented across the yellow clay layer below the ed documented within one of the sections and recently suggested as the original chicxulub impact ejecta horizon this questions the impact origin of this horizon or at least suggests only little consequences of this event on the ecosystem

measurements of wave attenuation due to a soft bottom the swamp experiment the sea wave attenuation measurement program swamp was designed to provide measurements of the attenuation of waves as they travel from deep water to relatively shallow water off the mississippi delta the soft bottom was suspected of causing strong attenuation in the area this effect has now been measured a wave staff and electromagnetic current meter were used to estimate directional wave spectra at the cognac platform in 312 m 1025 feet of water and at platform vv in south pass block 27 in 19 m 63 feet of water in addition measurements of vertical bottom motion were made at platform vv seven storm periods from sepember 1979 to february 1981 were studied the directional spectral comparisons showed that the theoretically calculated refraction and shoaling can explain the changes in the spectra when the wave height is low however as the wave height increases a nonlinear attenuation mechanism becomes increasingly strong the attenuation is a strong function of deep water wave height and a weak function of wave frequency the bottom motion measurements showed that the bottom moved downward with small amplitude under wave crests

groundwater derived land subsidence in the north china plain land subsidence usually bears strong relationship to abstraction of underground fluid land subsidence occurs commonly in the north china plain ncp and has become a major environmental factor hindering regional sustainable development this paper focuses on issues associated with mechanism of land subsidence in the ncp the analysis shows that multi layer aquifer systems with deep confined aquifers and the thick normally consolidated or unconsolidated compressible clay layers are the key of geological and hydrogeological conditions favorable for the development of land subsidence in the ncp groundwater withdrawal results in an increase in the distribution of effective stress within the strata and the compression of the aquifers and the confining layers and then triggers land subsidence in the middle east plain of the ncp the land subsidence volume approximately represents the amount of water released from compression of deep aquifers and aquitards in that land subsidence is primarily caused by excessive groundwater withdrawal in deep aquifer system the percentage of water released from compression of aquifers and aquitards in deep groundwater abstraction is significant but distinct in cangzhou city and in the whole middle east plain this is due to the difference in local lithological structure and recharge and discharge conditions of deep groundwater system the hysteresis of land subsidence is also discussed in typical areas and the results reveal that the time for completing the primary consolidation ranges from less than one year to tens of years and that the rate of secondary compression tends to increase with the moisture content

terminal cretaceous environmental events the geologic record of terminal cretaceous environmental events indicates that iridium and other associated elements were not deposited instantaneously but during a time interval spanning some 10 000 to 100 000 years the available geologic evidence favors a mantle rather than meteoritic origin for these elements these results are in accord with the scenario of a series of intense eruptive volcanic events occurring during a relatively short geologic time interval and not with the scenario of a single large asteroid impact event

depositional environments of the hart coal zone paleocene willow bunch coalfield southern saskatchewan canada from petrographic palynological paleobotanical mineral and trace element studies abstract coal petrology palynology paleobotany and mineralogy of the hart coal indicate deposition under wet warm temperate to subtropical climatic conditions in low lying backswamps with fluvial channels and locally ponded areas the coal is dominated by mixed xylitic attrital lithotypes and by huminite macerals with secondary inertinite macerals and minor liptinite macerals good correlation exists between lithotypes and maceral composition local and vertical variations in proportions of huminites and inertinites reflect frequent fluctuations in water levels periodic flooding desiccation and burning of the peat swamps were dominated by glyptostrobus taxodium forest with betula myrica alnus communities and locally laevigatosporites which are the dominant contributors to the xylite rich lithotypes attrital lithotypes with abundant pandanus typha and azolla are consistent with wetter areas of a fluvial environment including ponds and channels trace elements cr cu mo ni si ti u se v w k and th typically associated with synergetic minerals kaolinite calcite and quartz may have a volcanic source high concentrations of na ba and ca found in organic complexes are of secondary origin and probably originate in deep source brines rather than marine surface waters

time to reach near steady state in large aquifers 1 a new analytical solution of the flow equation has been developed to estimate the time to reach a near equilibrium state in mixed aquifers i e having unconfined and confined portions following a large hydraulic perturbation near equilibrium is defined as the time for an initial aquifer perturbation to dissipate by an average 95 across the aquifer the new solution has been obtained by solving the flow system of a simplified conceptual model of a mixed aquifer using laplace transforms the conceptual model is based on two assumptions 1 the groundwater flow can be reduced to a horizontal 1 d problem and 2 the transmissivity a function of the saturated thickness is assumed constant on the unconfined portion this new solution depends on the storativity of the unconfined portion the lengths of the unconfined and confined portions and the transmissivity assumed to be constant and equal in both portions of the mixed aquifer this solution was then tested and validated against a numerical flow model where the variations of the saturated thickness and therefore variations of the transmissivity were either ignored or properly modeled the agreement between the results from the new solution and those from the numerical model is good validating the use of this new solution to estimate the time to reach near equilibrium in mixed aquifers this solution for mixed aquifers as well as the solutions for a fully confined or fully unconfined aquifer has been used to estimate the time to reach near equilibrium in 13 large aquifers in the world for those different aquifers the time to reach near equilibrium ranges between 0 7 kyr to 2 4 107 kyr these results suggest that the present hydraulic heads in these aquifers are typically a mixture of responses induced from current and past hydrologic conditions and thus climate conditions for some aquifers the modern hydraulic heads may in fact depend upon hydrologic conditions resulting from several past climate cycles

permanent scatterer insar reveals seasonal and long term aquifer system response to groundwater pumping and artificial recharge received 4 may 2007 revised 30 july 2007 accepted 10 october 2007 published 5 february 2008 1 permanent scatterer insar psinsark p rovides an ew high resolution methodology for detecting and precisely measuring long term and seasonal aquifer system response to pumping and recharge in contrast to conventional insar the permanent scatterer methodology utilizes coherent radar phase data from thousands of individual radar reflectors on the ground to develop displacement time series and to produce velocity field maps that depict aquifer system response with a high degree of spatial detail in this study we present the first results of a prototype study in las vegas valley nevada that demonstrate how this methodology can be utilized in heavily pumped groundwater basins to analyze aquifer system response to long term and seasonal pumping we have developed a series of velocity field maps of the valley for the 1992 1996 1996 2000 and 2003 2005 time periods that show that despite rising water levels associated with an artificial recharge program long term residual inelastic aquifer system compaction subsidence is continuing in several parts of the valley in other areas however long term subsidence has been arrested and locally reversed the seasonal elastic responses to alternating pumping and recharge cycles were segregated from the long term trends and analyzed for spatial and temporal patterns the results show oscillations in which the maximum seasonal responses are associated with the late stages of the annual artificial recharge cycles and that similar seasonal subsidence signals are related to summer pumping cycles the differentiation of the seasonal response through the use of time series data further allows the estimation of elastic and inelastic skeletal storage coefficients providing a basis for future work that could characterize the storage properties of an aquifer system with a high degree of spatial resolution

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

high resolution leaf fossil record spanning the cretaceous tertiary boundary theories that explain the extinctions characterizing the cretaceous tertiary k t boundary1 3 need to be tested by analyses of thoroughly sampled biotas palynological studies are the primary means for stratigraphic placement of the terrestrial boundary and for estimates of plant extinction4 12 but have not been combined with quantitative analyses of fossil leaves megaflora megafloral studies complement palynology by representing local floras with assemblages capable of high taxonomic resolution13 but have previously lacked the sample size and stratigraphic spacing needed to resolve latest cretaceous floral history5 14 18 we have now combined megafloral data from a 100 m thick composite k t boundary section in north dakota with detailed palynological analysis here the boundary is marked by a 30 palynofloral extinction coincident with iridium and shocked mineral anomalies and lies 2 m above the highest dinosaur remains the megaflora undergoes a 79 turnover across the boundary and smaller changes 17 and 25 m below it this pattern is consistent with latest cretaceous climatic warming preceding a bolide impact

stratigraphy sedimentology and palaeoecology of the dinosaur bearing kundur section zeya bureya basin amur region far eastern russia since 1990 the kundur locality amur region far eastern russia has yielded a rich dinosaur fauna the main fossil site occurs along a road section with a nearly continuous exposure of continental sediments of the kundur formation and the tsagayan group udurchukan and bureya formations the sedimentary environment of the kundur formation evolves from lacustrine to wetland settings the succession of megafloras discovered in this formation confirms the sedimentological data the tsagayan group beds were deposited in an alluvial environment of the gravel meandering type the dinosaur fossils are restricted to the udurchukan formation scarce and eroded bones can be found within channel deposits whereas abundant and well preserved specimens including sub complete skeletons have been discovered in diamicts these massive unsorted strata represent the deposits of ancient sediment gravity flows that originated from the uplifted areas at the borders of the zeya bureya basin these gravity flows assured the concentration of dinosaur bones and carcasses as well as their quick burial such taphonomic conditions allowed the preservation of sub complete hadrosaurid skeletons unearthed at the kundur site palaeobotanical data indicate a subtropical climate during the deposition of the kundur and udurchukan formations several elements in the composition of the kundur vertebrate fauna suggest a strong influence of the north american late cretaceous vertebrate communities the abundance of corythosaur like lambeosaurines the probable presence of a nodosaurid dinosaur and of a eucosmodontid or microcosmodontid multituberculate a late maastrichtian age is tentatively proposed for the dinosaur bearing sediments in amur region by comparison with the information collected in the western interior basin of north america as it is also observed in the latter area important floristic changes diminution of angiosperm pollens and predominance of modern families and the disappearance of dinosaurs mark the end of the maastrichtian age in the amur region late maastrichtian dinosaur localities from amur region are dominated by lambeosaurines whereas these dinosaurs apparently disappeared from western north america long before the iridium horizon that defines the k p boundary this local disappearance is therefore probably due to ecological factors rather than indicating a gradual extinction of the dinosaurs long before the k p boundary

climatic oscillations stall vegetation recovery from k pg event devastation sedimentary rocks filling the boltysh meteorite crater preserve an expanded record of post cretaceous palaeogene k pg event vegetation destruction and subsequent floral recolonization a post destruction barren zone is succeeded by a fern spore spike recording the initial recovery vegetation the boltysh fern spore spike is divisible into two phases phase 1 is characterized by low abundances of fern spores whereas the overlying phase 2 has high fern spore abundances and contains common palm pollen comparison of the boltysh phase 2 fern spore spike with other palynological records shows strong similarities to the immediately post k pg boundary record of the western interior north america variation in the composition of the boltysh palynofloras has been used to define four moisture availability cycles between the k pg boundary and the dan c2 negative carbon isotope excursion a period of some 300 kyr early post k pg event vegetation community recovery followed a common seral successional pathway at rates seen in large igneous provinces although enhanced by high moisture availability continued succession to the first true swamp community was at a considerably slower tempo the post k pg event vegetation recovery was therefore retarded by lack of moisture availability extending the apparent period of recovery

reevaluation of siderophile element abundances and ratios across the cretaceous paleogene k pg boundary implications for the nature of the projectile abstract the discovery over 30 years ago at gubbio italy and caravaca spain of an enrichment in the concentrations of iridium ir and the other platinum group elements pge by up to four orders of magnitude irmax 0 10 87 ng g compared to average continental crustal background levels remains one of the most important discoveries in the earth sciences since then similar anomalies have been detected in more than 120 cretaceous paleogene k pg boundary sites worldwide highly elevated ir and other siderophile element abundances in roughly chondritic ratios are considered strong indicators for the presence of a meteoritic contribution in impact related lithologies melt rocks impact ejecta material etc delivered when an extraterrestrial object strikes earth the presented work adds 113 unpublished pge analyses of 38 k pg sections worldwide to the existing literature the analytical protocol relied on for this purpose consisted of a combination of a nickel sulfide fire assay pre concentration technique and subsequent trace metal determination via inductively coupled plasma mass spectrometry icp ms through repeated determination of key siderophile elements i e cr co ni and pge the importance of sampling nugget effects and analytical methodologies applied becomes more apparent even more critically these analytical effects are superimposed by the local syn and post depositional conditions that have affected the pristine meteoritic signature of the k pg impactor including potential fractionation during vaporization and condensation dissimilar pge carrier phases terrestrial pge input sedimentation rate reworking diagenesis bioturbation and chemical diffusion while chondrite normalized pge patterns of individual sites appear relatively flat i e chondritic strong variations in siderophile element content and inter element ratios exist between k pg locations inter laboratory measurements and replicate analyses hampering a precise projectile identification using highly siderophile elements only when considering improved databases of siderophile element concentrations in meteorites in combination with linear regression analysis to calculate inter element ratios from a large suite of ejecta deposit sites the nature of the k pg projectile can be resolved application of this methodology to an extensive data set of continental and marine sites very proximal to distal to the chicxulub impact structure supports a carbonaceous chondritic impactor type cm or co

early palaeocene palaeoclimatic inferences from fossil floras of the western interior usa abstract twenty one early palaeocene floral assemblages were collected from a variety of alluvial depositional environments from sites in the williston powder river and raton basins of the western interior of the usa leaf fossils were assigned to morphotypes and their physiognomy was quantified for palaeoclimatic analysis two methods were used climate leaf analysis multi variate program clamp and leaf margin analysis lma temperature estimates and trends derived from clamp and lma indicate that early palaeocene palaeotemperatures decreased from the latest cretaceous particularly in northern areas of north america climatic zones shifted southwards from their latest cretaceous positions resulting in a steepened north south temperature gradient and decreased equability in the early palaeocene sub tropical conditions prevailed as far north as the raton basin with the 20 c mean annual temperature isotherm megathermal mesothermal boundary located at approximately 45 n palaeolatitude the 13 c mean annual temperature isotherm mesothermal microthermal boundary was located at approximately 55 n palaeolatitude to the south of the williston basin clamp estimates indicate that precipitation increased significantly in all areas sampled directly after the k t boundary event especially in the southern rockies precipitation levels decreased somewhat after this initial peak but remained high throughout the early palaeocene evidence from this and other studies suggests that seasonality increased from the latest cretaceous into the palaeocene and was most pronounced in central and northerly areas of the north american continent

phytogeography and paleoclimatic interpretation of the maestrichtian abstract insight into the true nature of cretaceous climate can best be grained through a worldwide study of the preserved climatic indicators this study focuses on reconstructing the climate of the maestrichtian latest cretaceous based on the abundant published information from the geologic record specifically the approach taken was to reconstruct the general patterns of the terrestrial ecological biomes based on the fossil megaflora and pollen record once the biomes were delineated the climatic constraints on the present counterparts of these biomes were used to determine the prevailing climate of each region biome boundaries were recognized by discontinuities in the phytogeographic distributions of a variety of fossil plant groups detailed comparisons of fossil plant assemblages with present day climatic preferences of nearest living relatives allowed each region to be assigned to a modern biome further comparisons with fossil leaf physiognomic studies and tree ring studies integrated with an extensive database of climatically important sediments helped to refine the biomal and climatic assignments altogether 12 climatic zones corresponding to 7 major biome types have been recognized for the late cretaceous period

low degree gravitational changes from grace validation and interpretation 1 we examine low degree gravitational variations c21 s21 and c20 observed by the gravity recovery and climate experiment grace satellites during the first 2 years of this gravity mission the grace observations are compared with independent estimates from accurately measured earth rotational changes and predictions from atmospheric oceanic and hydrological models the 18 grace monthly gravity solutions covering the period april 2002 to march 2004 show strong seasonal variability in the c21 s21 and c20 time series and generally agree with earth rotation derived changes and geophysical model estimates in particular for s21 and c20 the reason for the poorer agreement between the grace results and the earth rotation derived estimates for c21 is unclear we demonstrate that the omission of the ocean pole tide in the grace data processing does have significant effects on the estimated c21 and s21

sequential palynological changes across the composite cretaceous tertiary k t boundary claystone and contiguous strata western canada and montana u s a the boundary claystone in the western canada basin is composed of three intimately associated layers with a regional distribution a basal brownish grey hackly claystone a middle brownish black sa

interbed storage changes and compaction in models of regional groundwater flow water released from permanent compaction of compressible fine grained interbeds within confined aquifers may be a significant source of pumped water permanent or inelastic compaction of the interbeds occurs when head declines from pumping cause the effective stress or grain to grain load to exceed the elastic limits of the interbeds as a result the grains in the interbeds rearrange and excess water is expelled the amount of inelastic compaction generally is proportional to the increase in effective stress and the decrease in head a common approach for the simulation of elastic and inelastic compaction in groundwater flow models is to assume that head changes in the aquifer result in instantaneous storage changes in the compressible interbeds a term is added to the groundwater flow equation to account for the storage changes changes in specific storage may be computed explicitly from the results at the previous time step in the finite difference formulation of the groundwater flow equation a better approach is to implicitly apportion storage changes between elastic and inelastic components within a time step if storage changes cannot be considered to occur instantaneously with change in head in the aquifer another approach is taken equations for horizontal flow in the aquifer are coupled with equations for vertical flow in the compressible interbeds to simulate flow in half a representative doubly draining interbed storage changes and compaction are calculated for the representative half thickness and are extrapolated to the entire thickness of all interbeds within each cell this approach was applied to an existing model of groundwater flow in the central valley of california the simulation demonstrates that solving coupled systems of equations is feasible for a regional flow model

cretaceous tertiary palynofloral perturbations and extinctions within the aquilapollenites phytogeographic province a combination of detailed intermediate and large scale stratigraphic perspectives is necessary to understand the driving mechanisms for floral change across the cretaceous tertiary k t boundary because short term physical and biotic events occur within longer term trends most maastrichtian palynofloral extinctions have been identified within the northern circumpolar supra continental aquilapollenites province in mid continental north america the presence of a physically defined k t boundary provides opportunities to examine contemporaneous terrestrial palynofloras over a latitudinal also approximately paleolatitudinal distance of 3200 km seventy five percent of last appearances occur before the k t boundary at high latitudes and must have been caused by ongoing terrestrial processes palynofloral events directly associated with the k t boundary include both local last appearances and inferred extinctions and synchronous and diachronous changes in relative abundances two different styles of factors are reflected in these events the first possibly attributable to chemical or other profound atmospheric perturbations associated with the worldwide distribution of the fireball layer of the k t claystone resulted in extinctions of angiosperm with a zoophilous pollination strategy the second factor possibly reflecting energy released during the deposition of ballistically transported impact debris or hackly ejecta layer of the boundary claystone resulted in the selective northward attenuating removal of the canopy vegetation best documented for southwestern canada which was succeeded by a fern dominated vegetation in mid continental north america these consequences of the boundary event were mediated by independent preexisting circumstances climate regional and through time local depositional environment and ongoing background extinctions and origins

vertebrate extinctions and survival across the cretaceous tertiary boundary abstract a critical analysis of the fossil vertebrate record across the cretaceous tertiary boundary shows that the available evidence is far less accurate than that concerning invertebrates and microfossils far reaching conclusions have been drawn from generalisations about vertebrate extinctions in the continental realm based on the local record from western north america but little is known about patterns of terminal cretaceous vertebrate extinctions in other parts of the world and even the western north american record is ambiguous despite this unsatisfactory record it clearly appears that terminal cretaceous vertebrate extinctions were highly selective with some groups e g dinosaurs becoming completely extinct whereas others seem to be virtually unaffected this argues against devastating catastrophes of the kind postulated by some recent impact scenarios however the survival of groups known to be sensitive to climatic deterioration such as crocodilians and other non dinosaurian reptiles indicates that alternative hypotheses involving gradual but fairly important climatic changes on a world wide scale are not convincing either the pattern of extinction and survival among vertebrates across the cretaceous tertiary boundary may be explained as a consequence of the disruption of some food chains following a crisis in the plant kingdom which itself may have been the result of the atmospheric consequences of unusual extraterrestrial or internal events

anthropogenic impacts on mass change in north china the gravity fields from the gravity recovery and climate experiment grace satellite have been used to estimate groundwater depletion in many parts of the world groundwater depletion assessment in north china however is affected by large anthropogenic disturbance on mass variation using the water survey data and coal flow statistics we show that the mass variations in north china during 2003 2011 were largely affected by reservoir regulation water diversion and coal transport according to our estimates the mass loss rate of groundwater depletion 14 to 8 4 mm yr 1 was largely offset by the mass gains caused by reservoir regulation 1 3 mm yr 1 water diversion 4 4 mm yr 1 and coal transport 1 9 mm yr 1 in the north china plain we note that anthropogenic impacts on mass change must be taken into account when using the grace data to estimate groundwater change in the area intensively altered by human activities 2013 american geophysical union all rights reserved

mass extinctions the view of a sceptic the concept of periodic mass extinctions by extraterrestrial impacts has contributed very strongly to the current revival of interest in the problem of mass extinctions in this context several radical claims have been made asserting that the newly emerging picture of mass extinctions as a separate class of biological phenomena caused by a separate class of processes demands a far reaching revision of the the neodarwinian paradigm of evolution and implies a vindication of the cuvierian perspective on earth9s history the validity of these claims however is questionable at all levels from the interpretation of particular events to the concept of mass extinctions as a special class of phenomena to their proposed causation by impacts and to their alleged historical pedigree and implications for current evolutionary theory mass extinctions may actually be clusters of more or less accidentally aggregated in time but causally distinct extinction episodes

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

terminal cretaceous extinctions in the hell creek area montana compatible with catastrophic extinction inaccurate stratigraphic correlations in the hell creek area montana have led to the assumption that transitional vertebrate faunas bug creek anthills exist in the latest cretaceous refuting a catastrophic turnover at the cretaceous tertiary boundary establishment of the transitional faunas in paleocene channels that cut down through the cretaceous tertiary boundary renders the terrestrial faunal record compatible with the marine record and with catastrophic extinction

late cretaceous and paroxysmal cretaceous tertiary extinctions the various geological signatures at cretaceous tertiary time including iridium and other associated elements microspherules and shock deformation features are compatible with the suggestion that the transition is marked by a period of intense volcanism the volatile emissions from this volcanism would lead to acid rain reduction in the alkalinity and ph of the surface ocean global atmospheric temperature changes and ozone layer depletion these environmental effects coupled with those related to the major sea level regression of the late cretaceous provide the framework for an explanation of the selective nature of the observed extinction record

palynofacies coal petrographic facies and depositional environments amphitheatre formation eocene to oligocene and ravenscrag formation maastrichtian to paleocene canada abstract low rank coals from two disparate geological settings have been subjected to petrographic and palynological analysis the stratigraphic units studied and their locations are the amphitheatre formation st elias mountains yukon territory of eocene to oligocene age and the base of the ravenscrag formation south central saskatchewan of latest cretaceous to earliest paleocene age the depositional setting of the amphitheatre formation ranges from distal sand dominated braided stream and lacustrine environments to proximal gravel dominated fluvial environments the coals are low in inertinite 85 in localities with a dominance of angiosperm pollen the relative abundance of eu ulminite b and densinite is greatest whereas in the ones with a dominantly coniferous pollen assemblage eu ulminite a is the most prominent maceral these observations suggest as an immediate cause effect relationship an at least partial dependance of present maceral content on floral precursors this in turn probably reflects a certain combination of depositional environment conditions ph eh temperature etc that likely controlled the plant community and the preservation of vegetal matter the depositional environment of coals from the basal part of the ravenscrag formation contrasts sharply with that of the amphitheatre the ravenscrag coals formed within a low energy stable floodplain environment palynological and coal maceral profiles for the basal ravenscrag formation coal which spans the cretaceous tertiary boundary indicates that the environment of deposition progressed from an open canopied swamp forest with areas of open water through a phase of low lying to open water swamps with herbaceous pterophytic vegetation to at least locally raised bogs the change in coal petrography across the cretaceous tertiary boundary is shown to be relatively minor in comparison to subsequent changes in coal petrography in the earliest paleocene and to changes that occur in the palynological assemblages across the boundary interval

subregional scale groundwater depletion detected by grace for both shallow and deep aquifers in north china plain this study explores the capability of gravity recovery and climate experiment grace to detect heterogeneous groundwater storage gws variations in two subregions of the north china plain the piedmont plain pp 54 000 km2 mainly exploiting shallow groundwater and east central plain ecp 86 000 km2 mainly exploiting deep groundwater results show that the gws anomalies estimated from grace data 2003 2013 agree well with those estimated from in situ observations 2005 2010 for both pp r2 0 91 and ecp r2 0 75 the shallow gws 2003 2013 in pp declines faster 46 5 6 8 mm yr than the deep gws in ecp 16 9 1 9 mm yr however the shallow gws in pp recovered more quickly especially during the 2008 2011 drought period despite its lower magnitude the grace derived gws depletion in ecp reveals the overexploitation of deep gws this study demonstrated that the heterogeneous gws variations can potentially be detected by grace at the subregional scale smaller than the typical grace footprint 200 000 km2

terrestrial palynomorph biostratigraphy of the cypress hills wood mountain and turtle mountain areas upper cretaceous paleocene of western canada three cored test holes were drilled to study the stratigraphic interval spanning the cretaceous tertiary boundary one in the western cypress hills near elkwater alberta a second in the eastern portion of the wood mountain area near killdeer saskatchewan and a third on the western edge of turtle mountain near goodlands manitoba the terrestrial elements of the palynological assemblages are discussed the maastrichtian assemblages encompassed the scollardia trapaformis zone and two new subzones myrtipites scabratus aquilapollenites delicatus var collaris and porosipollis porosus aquilapollenites notabile within the wodehouseia spinata zone the paleocene zones encountered include the aquilapollenites reticulatus subzone of the w spinata zone the previously described wodehouseia fimbriata and momipites wyomingensis zones and the newly defined tricolporopollenites kruschii zone these provide a biostratigraphy for the cored intervals which can be related to polarity chrons the observations mad

phase difference between groundwater storage changes and groundwater level fluctuations due to compaction of an aquifer aquitard system abstract drainage and deformation of intercalated confining layers due to internal stress change discharge recharge cycle in an aquifer aquitard system not only can have great effects on the groundwater storage gws but also can cause unsynchronized water level wl fluctuations the phase relationship between gws and wl is crucial for the accuracy and attribution of gws changes we identify the dominating episodic components of gws and wl through the singular spectrum analysis ssa analysis and harmonic analysis first we analyzed a generic aquifer aquitard system using numerical simulations which showed that the dissipation of overpressure from the aquitard and flow from it is the inherent cause of a phase shift between the gws and wl observations water released from confining layers with compaction time constant of zero no delay to century time scale results in detected phase shift between total gws and wl in the aquifer then we analyzed the complex and varied phase relationship between gws derived using the gravity recovery and climate experiment grace data and measured wl time series in the subsiding north china plain ncp aquifer the spatially varied phase relationship between gws and measured wl is reasonably related to varied land subsidence development features and may be related with the compaction time constant and thickness of the confining layers results of the generic numerical model and the ncp observations suggest that elastic inelastic response need to be considered in the interpretation and correction of gws changes for a compacted aquifer aquitard system

a paleoclimatic and paleoatmospheric record from peatlands accumulating during the cretaceous paleogene boundary event western interior basin canada petrological and 13 c analyses were undertaken on contiguous specimens of coal and intercalated minor organic rich clastic sediments collected from coal seams spanning the cretaceous paleogene boundary in the alberta and saskatchewan portions of the western interior basin the generally high smectite content of the coal suggests that the original mires were largely small disconnected and rheotrophic readily receiving abundant waterborne detrital clastic material of largely volcanic origin nevertheless using the distinctive claystone that marks the cretaceous paleogene boundary as a regional datum it is possible to correlate cycles in the vitrinite and inertinite composition of the coals over 500 km estimates of peat accumulation rates suggest that the cycles in vitrinite and inertinite composition represent regional cyclic fluctuations in wildfire and oxidation of the peatlands and overlying canopy at a frequency of hundreds to thousands of years the likely causes of these fluctuations were cyclic regional scale changes in temperature the cretaceous paleogene boundary event occurred early during a phase of gradually increasing temperature and or decreasing rainfall but peak wildfire and desiccation of peat occurred up to 14 000 yr later than the cretaceous paleogene boundary and the mires did not experience significant water stress in the immediate aftermath of the extinction event a persistent 1 5 3 0 negative 13 c excursion occurs across the cretaceous paleogene boundary but it cannot be readily separated from four further negative excursions later in the earliest danian the negative carbon isotope excursion linked to the cretaceous paleogene boundary began a few hundred years before the event itself and recovery occurred within 21 k y and possibly in as little as just a few thousand years consistent with recently calibrated shallow marine 13 c records hence the atmospheric and surface ocean carbon pools were coupled at this time the absence of evidence for catastrophic change in the climatic regime at the time of the cretaceous paleogene extinction in these mires supports the notion that the negative shift in atmospheric 13 c was brought about by changes in the 13 c composition of the surface ocean this is consistent with the greater magnitude of extinction experienced by marine fauna relative to the terrestrial realm

upper cretaceous lower tertiary lithostratigraphic relationships of three cores from alberta saskatchewan and manitoba canada cores from three stratigraphic test holes provide a relatively complete section from the lower maastrichtian into the paleocene the hole drilled in the cypress hills of alberta recovered core from

a search for shocked quartz grains and impact ejecta in early silurian sediments on gotland sweden all bentonite and bentonite resembling layers thicker than a few millimetres from a 120m thick early silurian sequence on gotland sweden were searched for shocked quartz grains of comet or asteroid impact origin although more than 200000 quartz grains from 86 bentonite samples were studied not one single grain with multiple planar shock features was found the studied sequence represents sedimentation during a period of about 2 million years impact frequencies estimated from the cratering record and astronomical observations indicate that during a 2 myr period on average 20 comet or asteroid bodies larger than 0 5 km in diameter strike the earth the number of smaller impacting bodies is many times higher in the light of this high frequency of impacts the absence of any shocked quartz bearing fallout layer in our sequence indicates that lateral spreading of such ejecta is relatively restricted during small and medium scale impact events the results also show that shocked quartz in general is absent or extremely rare in volcanic ash this strengthens the case for an impact related origin of shocked quartz grains in the cretaceous tertiary boundary days

palaeobotanical evidence for a june impact winter at the cretaceous tertiary boundary a large bolide impact such as that thought to have occurred at the cretaceous tertiary k t boundary should produce large amounts of light attenuating debris thereby causing an impact winter 1 3 because of thermal buffering in the oceans evidence for a brief 1 2 months2 4 impact winter would be found only in terrestrial environments aquatic leaves in the k t boundary section near teapot dome wyoming preserve structural deformation that can be duplicated experimentally in extant aquatic leaves by freezing reproductive stages reached by the fossil aquatic plants at the time of death suggest that freezing took place in approximately early june both the existence of the structurally deformed plants and the high abundance of fern spores occur in a horizon containing sparse impact debris but below the horizon containing abundant impact debris i therefore suggest that the lower horizon represents debris and effects from a large distant bolide impact and the upper horizon represents a small nearby bolide impact

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

palynology of maastrichtian and paleocene rocks lower colville river region north slope of alaska outcrops of maastrichtian rocks are rare on the north slope of alaska and it is even more unusual to find outcrops of maastrichtian and paleocene age in the same vicinity in general late cretaceous and paleogene rocks have not been well dated in published papers pertaining to northern alaska in this article we describe palynomorph assemblages from 20 outcrop samples taken from nine localities along the lower colville river and nearby areas the latest cretaceous palynomorph assemblages that are from marine rocks contain late campanian or maastrichtian dinoflagellate cysts however these cysts and other marine fossils are absent from the tertiary samples indicating that the tertiary strata are nonmarine our latest cretaceous and early tertiary samples contain abundant spores and pollen grains and can be readily dated by reference to well known pollen assemblages from the northern great plains and northwestern canada by dating each sampled outcrop we can approximate the position of the cretaceous