new age constraints for the salamanca formation and lower rio chico group in the western san jorge basin patagonia argentina implications for cretaceous paleogene extinction recovery and land mammal age correlations the salamanca formation of the san jorge basin patagonia argentina preserves critical records of southern hemisphere paleocene biotas but its age remains poorly resolved with estimates ranging from late cretaceous to middle paleocene we report a multi disciplinary geochronologic study of the salamanca formation and overlying rio chico group in the western part of the basin new constraints include 1 an 40ar 39ar age determination of 67 31 0 55 ma from a basalt flow underlying the salamanca formation 2 micropaleontological results indicating an early danian age for the base of the salamanca formation 3 laser ablation hr mc icp ms high resolution multi collector inductively coupled plasma mass spectrometry u pb ages and a high resolution tims thermal ionization mass spectrometry age of 61 984 0 041 0 074 0 100 ma for zircons from volcanic ash beds in the penas coloradas formation rio chico group and 4 paleomagnetic results indicating that the salamanca formation in this area is entirely of normal polarity with reversals occurring in the rio chico group placing these new age constraints in the context of a sequence stratigraphic model for the basin we correlate the salamanca formation in the study area to chrons c29n and c28n with the banco negro inferior bni a mature widespread fossiliferous paleosol unit at the top of the salamanca formation corresponding to the top of chron c28n the diverse paleobotanical assemblages from this area are here assigned to c28n 64 67 63 49 ma 2 3 million years older than previously thought adding to growing evidence for rapid southern hemisphere floral recovery after the cretaceous paleogene extinction important peligran and carodnia zone vertebrate fossil assemblages from coastal bni and penas coloradas exposures are likely older than previously thought and correlate to the early torrejonian and early tiffanian north american land mammal ages respectively

stable carbon isotope patterns of marine biomarker lipids in the arctic ocean during eocene thermal maximum 2 the middle paleocene through early eocene long term gradual warming was superimposed by several transient warming events such as the paleocene eocene thermal maximum petm and eocene thermal maximum 2 etm2 both events show evidence for extreme global warming associated with a major injection of carbon into the ocean atmosphere system but the mechanisms of carbon injection and many aspects of the environmental response are still poorly understood in this study we analyzed the concentration and stable carbon isotopic delta c 13 composition of several sulfur bound biomarkers derived from marine photoautotrophs deposited in the arctic ocean at similar to 85 degrees n during etm2 the presence of sulfur bound biomarkers across this event points toward high primary productivity and anoxic bottom water conditions the previously reported presence of isorenieratene derivatives indicates euxinic conditions in the photic zone likely caused by a combination of enhanced primary productivity and salinity stratification the negative carbon isotope excursion measured at the onset of etm2 for several biomarkers ranges between 3 and 4 5 much larger than the similar to 1 4 recorded in marine carbonates elsewhere suggesting substantial enhanced isotopic fractionation by the primary producers likely due to a significant rise in pco 2 in the absence of biogenic carbonates in the etm2 section of our core we use coeval planktonic delta c 13 from elsewhere to estimate surface water delta c 13 in the arctic ocean and then apply the relation between isotopic fractionation and pco 2 originally calibrated for haptophyte alkenones to three selected organic biomarkers i e s bound phytane c 35 hopane and a c 25 highly branched isoprenoid this yields pco 2 values potentially in the range of four times preindustrial levels however these estimates are uncertain because of a lack of knowledge on the importance of pco 2 on photosynthetic isotopic fractionation

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

stable isotope time series and precipitation origin from firn core and snow samples altai glaciers siberia in the summers of 2001 and 2002 glacio climatological research was performed at 4110 4120ma s l on the belukha snow firn plateau siberian altai hundreds of samples from snow pits and a 21m snow firn core were collected to establish the annual seasonal monthly depth accumulation scale based on stable isotope records stratigraphic analyses and meteorological and synoptic data the fluctuations of water stable isotope records show well preserved seasonal variations the d 18 o and dd relationships in precipitation snow pits and the snow firn core have the same slope to the covariance as that of the global meteoric water line the origins of precipitation nourishing the belukha plateau were determined based on clustering analysis of d 18 o and d excess records and examination of synoptic atmospheric patterns calibration and validation of the developed clusters occurred at event and monthly timescales with about 15 uncertainty two distinct moisture sources were shown oceanic sources with d excess 12 two thirds of the annual accumulation was from oceanic precipitation of which more than half had isotopic ratios corresponding to moisture evaporated over the atlantic ocean precipitation from the arctic pacific ocean had the lowest deuterium excess contributing one tenth to annual accumulation

using borehole logging and electron backscatter diffraction to orient an ice core from upper fremont glacier wyoming usa while glacier fabric reflects the accumulated strain detailed azimuthal information is required to link the microstructure to the flow and this is not easily gathered at depth borehole logging provides a way to obtain a log of azimuthal orientation of tilted stratigraphic features that can be used to orient the core with respect to glacier flow we demonstrate this using acoustic borehole logs and the ice core from a 162 m borehole in upper fremont glacier wind river range wyoming usa we measured the dip of tilted dust and bubble layers in the actual ice core identified them on the borehole log then used their strike to orient the core sections containing them we examined the crystal orientation fabric of our samples using electron backscatter diffraction in a scanning electron microscope when we compared the orientation of the tilted layers in some samples with the fabric we found that the normal to the foliation and the c axes maxima both pointed in the direction of maximum shear stress this illustrates the usefulness of borehole logs for orienting ice cores after removal from the borehole and for developing a better understanding of fabric development

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

ice core evidence of rapid air temperature increases since 1960 in alpine areas of the wind river range wyoming united states 1 site specific transfer functions relating delta oxygen 18 18o values in snow to the average air temperature ta during storms on upper fremont glacier ufg were used in conjunction with 18o records from ufg ice cores to reconstruct long term trends in air temperature from alpine areas in the wind river range wyoming transfer functions were determined by using data collected from four seasonal snowpacks 1989 1990 1997 1998 1998 1999 and 1999 2000 the timing and amount of each storm was determined from an automated snowpack telemetry snotel site 22 km northeast of ufg and 1060 m in elevation below ufg statistically significant and positive correlations between 18o values in the snow and ta were consistently found in three of the four seasonal snowpacks the snowpack with the poor correlation was deposited in 1997 1998 during the 1997 1998 el nino southern oscillation enso an ultrasonic snow depth sensor installed on ufg provided valuable insights into site specific storms and postdepositional processes that occur on ufg the timing of storms recorded at the ufg and cold springs snotel sites were similar however selected storms did not correlate snow from storms occurring after mid october and followed by high winds was most susceptible to redeposition of snow this removal of lower temperature snowfall could potentially bias the 18o values preserved in ice core records to environmental conditions reflecting higher air temperatures and lower wind speeds transfer functions derived from seasonal snow cover on ufg were used to reconstruct ta values from 18o values determined from two ice cores collected from ufg reconstructed air temperatures from the ice core data indicate an increase in ta of 3 5 c from the mid 1960s to the early 1990s in the alpine areas of northwestern wyoming reconstructed ta from the ice core records between the end of the little ice age lia mid 1800s and the early 1990s indicate a ta increase of 5 c the historically reconstructed ta values from the ufg were significantly higher than the global average observed during the 20th century but were in agreement with ta increases observed at selected high altitude and high latitude sites in other parts of the world additional research is required to determine if part of the observed trend toward heavier 18o values in ice from the ufg since the lia and increased ta is due to an increased proportion of snowfall from southerly storm tracks and moisture sources as seems to have been the situation in 1997 1998

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

association between atmospheric circulation patterns and firn ice core records from the inilchek glacierized area central tien shan asia 1 glacioclimatological research in the central tien shan was performed in the summers of 1998 and 1999 on the south inilchek glacier at 5100 5460 m a 14 36 m firn ice core and snow samples were collected and used for stratigraphic isotopic and chemical analyses the firn ice core and snow records were related to snow pit measurements at an event scale and to meteorological data and synoptic indices of atmospheric circulation at annual and seasonal scales linear relationships between the seasonal air temperature and seasonal isotopic composition in accumulated precipitation were established changes in the 18o air temperature relationship in major ion concentration and in the ratios between chemical species were used to identify different sources of moisture and investigate changes in atmospheric circulation patterns precipitation over the central tien shan is characterized by the lowest ionic content among the tien shan glaciers and indicates its mainly marine origin in seasons of minimum precipitation autumn and winter water vapor was derived from the arid and semiarid regions in central eurasia and contributed annual maximal solute content to snow accumulation in tien shan the lowest content of major ions was observed in spring and summer layers which represent maximum seasonal accumulation when moisture originates over the atlantic ocean and mediterranean and black seas

chronological refinement of an ice core record at upper fremont glacier in south central north america the potential to use ice cores from alpine glaciers in the midlatitudes to reconstruct paleoclimatic records has not been widely recognized although excellent paleoclimatic records exist for the polar regions paleoclimatic ice core records are not common from midlatitude locations an ice core removed from the upper fremont glacier in wyoming provides evidence for abrupt climate change during the mid 1800s volcanic events krakatau and tambora identified from electrical conductivity measurements ecm and isotopic and chemical data from the upper fremont glacier were reexamined to confirm and refine previous chronological estimates of the ice core at a depth of 152 m the refined age depth profile shows good agreement 1736 10 a d with the sup 14 c age date 1729 95 a d the delta sup 18 o profile of the upper fremont glacier ufg ice core indicates a change in climate known as the little ice age lia however the sampling interval for delta sup 18 o is sufficiently large 20 cm such that it is difficult to pinpoint the lia termination on the basis of delta sup 18 o data alone other research has shown that changes in the delta sup 18 o variance are generally coincident with changes in ecm variance the ecm data set contains over 125 000 data points atmore a resolution of 1 data point per millimeter of ice core a 999 point running average of the ecm data set and results from f tests indicates that the variance of the ecm data decreases significantly at about 108 m at this depth the age depth profile predicts an age of 1845 a d results indicate the termination of the lia was abrupt with a major climatic shift to warmer temperatures around 1845 a d and continuing to present day prediction limits error bars calculated for the profile ages are 10 years 90 confidence level thus a conservative estimate for the time taken to complete the lia climatic shift to present day climate is about 10 years suggesting the lia termination in alpine regions of central north america may have occurred on a relatively short decadal timescale c 2000 american geophysical union less

factors affecting the internal loading of phosphorus from calcareous sediments of baiyangdian lake in north china phosphorus p is the limiting macronutrient for primary production in most lakes sediment characteristics are strongly correlated to the internal p loading in lakes this study investigated speciation of p fe al and ca in sediments of six sampling sites with varying trophic status in baiyangdian lake of north china during the period of july 2008 and march 2009 the results of sequential extraction experiments of the top sediments showed that total extractable p ranged approximately from 13 to 28 mol g 1 for all sampling sites and the rank order of p fractions was hcl p naoh85 p naoh25 p bd p nh4cl p bd p and bd fe had a consistent change with seasons their concentrations were both much higher in early spring and mid autumn bd fe al extracted with naoh at 25 c and 85 c affected corresponding p concentration in sediments while high concentration of extractable ca from sediments showed no direct effects according to the kopacek et al model of the molar ratios of al fe and naoh25 al nh4cl p bd p there was potential p release from sediments twice a year for some hypereutrophic sites in early spring and mid autumn especially in the former season

fossil wood in coal forming environments of the late paleocene early eocene chickaloon formation the early cenozoic chickaloon formation is the main coal bearing sequence in south central alaska coal and associated plant macrofossils are well exposed in the eska premier and jonesville coal groups in the wishbone hill district there is a striking variation in the degree and mode of preservation of fossil trees in a vertical sequence through these coal groups we examined the wood taxonomy mineralogy and geochemistry to elucidate potential cause s for these differences the wood anatomy indicates that the wood is all assignable to the cupressaceae taxodiaceae s str and assignable to the form genus taxodioxylon hartig emend gothan however we found no significant variation in the taxonomy of the wood between stratigraphic layers the wood generally becomes better preserved in the jonesville coal group wood from the stratigraphically lower premier coal group exhibits greater plastic deformation and contains less well preserved wood anatomical features the wood from the overlying jonesville coal group retains most of its original morphology but has suffered from brittle fracture the geochemistry and mineralogy of the wood follow a pattern that corresponds to the degree of preservation the less well preserved wood tends to have a higher concentration of iron carbonate minerals e g siderite and ankerite whereas the better preserved wood contains more calcium carbonate or silica all evidence points to rapid permineralization of the original wood although the least well preserved wood shows evidence of greater organic matter decomposition than the better preserved wood the wood taxonomy and mode of preservation of wood from the upper part of the chickaloon formation is similar to wood from coeval fossil forests that developed at higher polar paleolatitudes

rapid and sustained surface ocean acidification during the paleocene eocene thermal maximum the paleocene eocene thermal maximum petm has been associated with the release of several thousands of petagrams of carbon pg c as methane and or carbon dioxide into the ocean atmosphere system within 10 kyr on the basis of the co occurrence of a carbon isotope excursion cie widespread dissolution of deep sea carbonates and global warming in theory this rapid carbon release should have severely acidified the surface ocean though no geochemical evidence has yet been presented using boron based proxies for surface ocean carbonate chemistry we present the first observational evidence for a drop in the ph of surface and thermocline seawater during the petm planktic foraminifers from a drill site in the north pacific ocean drilling program site 1209 show a 0 8 decrease in boron isotopic composition 11b at the onset of the event along with a 30 40 reduction in shell b ca similar trends in 11b are present in two lower resolution records from the south atlantic and equatorial pacific these observations are consistent with significant global acidification of the surface ocean lasting at least 70 kyr and requiring sustained carbon release the anomalies in the b records are consistent with an initial surface ph drop of 0 3 units at the upper range of model based estimates of acidification

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

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

a model of oxygen isotope composition of precipitation implications for paleoclimate data the ratio of oxygen isotopes in glacial ice is often used as an indicator of climatic conditions during the period of time in which the ice was deposited we have developed a model which predicts the isotopic composition of snow given the composition of the source water and the meteorological path between the formation of an air water parcel in the boundary layer and the final deposition of precipitation onto the ice sheets after comparing the model results with isotope data from the present we draw inferences about the past isotopic composition of continental ice sheets our results depend strongly on the details of the meteorological path they are consistent with standard interpretations of isotope data but in some cases they allow alternate interpretations

ice volume estimation inferred from ice thickness and surface measurements for continental glacier wind river range wyoming usa the wind river range in wyoming usa contains the largest concentration of glacial mass in the rocky mountains of the contiguous usa despite this distinction only a few field or remotely sensed studies providing glacier volume changes have been published the current study focuses on continental glacier located on the northern end of the range and uses two field datasets high accuracy gps surface elevation points and ice penetrating radar transects of the glacier bed to create a three dimensional model of glacier volume current surface elevations are compared with historical elevation data to calculate surface elevation change over time an average thinning rate of 13 8 7 8 m 0 30 0 17 m a 1 between 1966 and 2012 was found surface elevation change rates varied across the glacier ranging from 0 30 to 0 98 m a 1 taking into account variable melt rates across the glacier along with a glacial volume of 72 1 106 10 8 106 m3 we estimate that continental glacier will be reduced in volume by 43 over the next 100 years and will disappear completely over the next 300 400 years if current climatic conditions persist

how wet was the arctic eocene rain forest estimates of precipitation from paleogene arctic macrofloras the eocene was the warmest part of the cenozoic when warm climates extended into the arctic and substantive paleobotanical evidence indicates broadleaf and coniferous polar forests paleontological temperature proxies provide a basis for understanding arctic early paleogene climates however there is a lack of corresponding proxy data on precipitation both leaf physiognomic analysis and quantitative analysis of nearest living relatives of an arctic macroflora indicate upper microthermal to lower mesothermal moist climates mean annual temperature 13 15 c cold month mean temperature 4 c mean annual precipitation 120 cm yr for axel heiberg island in the middle eocene leaf size analysis of paleocene and eocene arctic floras demonstrates high precipitation for the paleogene western and eastern arctic the predicted enormous volume of freshwater entering the arctic ocean as a result of northward drainage of a significant region of the northern hemisphere under a high precipitation regime would have strongly affected arctic ocean salinity potentially supporting arctic ocean azolla blooms high paleogene precipitation around the arctic basin is consistent with high atmospheric humidity which would have contributed significantly to polar and global eocene warming

foraminifera as indicators of methane rich environments a study of modern methane seeps in santa barbara channel california methane hydrates have been implicated as a possible forcing mechanism for rapid climate change during the late quaternary via the release of methane from marine reservoirs carbon isotopic excursions of foraminifera observed in high resolution sediment records from santa barbara basin odp site 893 have been interpreted as evidence of episodes of methane release during the late quaternary however the potential relationship between methane in the modern environment and its effect on the stable isotopic composition of benthic and planktonic foraminifera is not well understood short cores taken inside a 500 m diameter pockmark with active methane seeps in santa barbara channel ca usa yield information on the effect of high concentrations of environmental methane on foraminiferal assemblages and their stable isotopic composition these seeps reside at 120 m water depth in the eastern portion of the channel associated with faults and fractures in the miocene monterey formation planktonic foraminiferal assemblages and radiocarbon ages show that surface sediments are of late glacial age 25 300 calendar years this finding suggests an absence of holocene and deglacial sedimentation in the seep area likely due the formation of the pockmarks and subsequent winnowing or lack of sedimentation benthic foraminiferal assemblages are marked by high abundance of bolivina tumida a species previously observed during interstadial episodes and the early holocene in santa barbara basin interpreted to include episodes of high methane flux from the basin while oxygen isotopic values of both benthic and planktonic foraminifera appear normal for cool glacial conditions negative carbon isotopic values are seen in benthic foraminifera primarily in the near surface intervals in one interval 1 2 cm below surface both benthic and planktonic species record highly negative carbon isotopic values implying that isotopically light methane influenced the entire water column this spike is of similar or larger magnitude than several earlier observed spikes in the late quaternary record from odp site 893 single specimen isotopic analyses give an indication of the total range of carbon isotopic values recorded 0 01 to 25 23 for benthics 0 07 to 22 22 for planktonics in the spike interval since modern methane seeps are commonly associated with authigenic carbonate precipitation scanning electron microscopy was used to assess the possibility that post depositional alteration may have affected the isotopic composition of the test these experiments indicate that authigenic carbonate is absent and therefore unable to account for the highly negative carbon isotopic signatures these data improve our understanding of methane associated environments by showing that foraminiferal isotopic composition and assemblages may be used to discern the flux of methane from the oceanic reservoir in the geologic record

macro and micro fauna from cold seeps in the palmahim disturbance israeli off shore with description of waisiuconcha corsellii n sp bivalvia vesicomyidae abstract chemosymbiotic micro and macro fauna related to cold seep sites were recovered in the palmahim disturbance pd offshore israel during eu eurofleets2 semseep cruise by box coring and remotely operated vehicle rov dives no live macrofauna was identified in the collected sediments with the exception of the seep related crustacean calliax lobata de gaillande and lagardere 1966 numerous calliax claws testify the past colonization of these soft bottoms by several generations of this ghost shrimp after sediment sieving on 1 mm we identified gastropods belonging to the families trochidae eucyclidae unassigned seguenzioidea genus anekes rissoidae elachisinidae raphitomidae mangeliidae architectonicidae orbitestellidae and acteonidae the identified bivalves belong to the families nuculidae yoldiidae mytilidae lucinidae thyasiridae semelidae kelliellidae vesicomyidae xylophagidae and cuspidariidae a seep related group of chemosymbiotic molluscs was detected including taranis moerchii malm 1861 lurifax vitreus waren and bouchet 2001 idas ghisottii waren and carrozza 1990 lucinoma kazani salas and woodside 2002 thyasira biplicata philippi 1836 isorropodon perplexum sturany 1896 and the newly described vesicomyid species waisiuconcha corsellii n sp that represents also the first record of the genus waisiuconcha in recent mediterranean sediments the rov dives recorded local patches of several m2 of seafloor covered by dead shells of l kazani with a density of up to about 200 loose shells per square meter the potential occurrence of seep related foraminifera among low oxygen tolerant species was explored by comparison with previously sampled adjacent localities and lead to the identification of chilostomella oolina globobulimina affinis and g pseudospinescens as potential foraminiferal seep indicators in the southeastern mediterranean sea the absence of live seep related fauna in surface sediments in the pd where seepage has been confirmed suggests intermittent activity and a pause or decline of the investigated seeps

cycles in perilacustrine facies of late mesozoic rift basins southeastern mongolia detailed study of 365 meters of core recovered from southeastern mongolia reveals fluvial marginal lacustrine and profundal lacustrine depositional environments in an early cretaceous rift basin multiple examples of cyclic sedimentation are superposed on these large scale facies transitions in fluvial facies more than 20 upward fining successions 2 10 m thick are present these contain cross stratified sandstone units with erosional bases that fine upward to mudstone with root marks and burrows they are interpreted as channel fill successions in a fluvial depositional environment whereas finergrained less erosional intervals with abundant soft sediment deformation and climbing ripples may represent a transition to fluvial deltaic environments at the lake margin coarse fluvial deltaic facies form the most likely hydrocarbon reservoirs as indicated by frequency of oil staining in the core physical transport processes dominate well oxygenated fluvial and marginal lacustrine facies whereas cycles in more distal lacustrine facies mainly reflect biogeochemical processes profundal lacustrine strata include kerogen rich laminated micrite distal turbidite beds and dolomitic breccia reminiscent of lacustrine facies in the green river formation of the western united states evidence for anoxia at the lake floor includes framboidal biogenic pyrite high toc content mainly light amorphous organic constituents and paucity of trace fossils relative to the rest of the core approximately 25 dolomite layers are interbedded with laminated micrite and calcareous siltstone units in poorly defined meter scale cycles these beds typically have brecciated or clotted textures and suggest evaporative concentration of magnesium ions at the lake floor the profundal lacustrine sequence displays a distinctive high resistivity low spontaneous potential log character that is observed in well logs from several fields in the zuunbayan subbasin correlative units can be traced at least 60 km to the northeast and southwest of the zuunbayan field indicating that this is a widespread lacustrine depositional unit these lacustrine strata include the most likely petroleum source facies found to date and are likely contemporaneous with other large lake systems in china and mongolia

downstream dilution of a lahar transition from debris flow to hyperconcentrated streamflow nearly instantaneous melting of snow and ice by the march 19 1982 eruption of mount st helens released a 4 106 m3 flood of water from the crater that was converted to a lahar volcanic debris flow through erosion and incorporation of sediment by the time it reached the base of the volcano over the next 81 km that it traveled down the toutle river the flood wave was progressively diluted through several mechanisms a transformation from debris flow to hyperconcentrated streamflow began to occur about 27 km downstream from the crater when the total sediment concentration had decreased to about 78 by weight 57 by volume the hyperconcentrated lahar runout flood wave transporting immense quantities of sand in suspension continued to experience progressive downstream dilution although turbulence was significantly dampened by the extremely high suspended load very large standing waves and antidune waves were observed the hyperconcentrated lahar runout flow deposited an unusual faintly stratified coarse sand which locally contained small isolated gravel lenses very similar deposits in the quaternary stratigraphy of mount st helens and other cascades volcanoes suggest that lahars may be more frequent than previously recognized

phosphorus release characteristics of sediments in erhai lake and their impact on water quality in view of the problems of high p concentration in the sediments and low p concentration in the overlying waters of erhai lake eh an indoor static incubation experiment was performed to determine the p release characteristics of sediments at different depths the differences in the p forms of the sediments before and after the incubation experiment were compared and the impact of such forms on the characteristics of the p release of sediments at different depths and that of p release on the water quality of eh were also investigated results were as follows 1 dissolved organic p dop is the main form of p released at the sediment water interface of eh which is approximately six times that of soluble reactive p srp which indicates that the dop release of sediments may have a more important impact on p composition and the content of the overlying water of eh than srp the release flux of the dop of sediments at the surface layer is higher than that at the bottom layer the vertical distribution of the release flux of srp is characterized by an increase at the surface layer and a decline at the lower layer 2 different p release potentials exist for different forms of p in the sediments of eh among the different p forms the loosely absorbed inorganic p nh4cl rp is the main source of srp that is released from the sediments into the overlying waters 3 the release flux of total p tp at the sediment water interface of eh amounts to 114 2 t a which accounts for 87 2 of the total external p input in the lake although the amount of the p release of sediments under indoor static simulation conditions is higher than that under real conditions the trend of the p release of the sediments of eh is accurate according to this result the contribution of the sediment p release to the tp concentration of the overlying water is up to 31 reaching a concentration of 9 4 g l the annual p release of the sediments of eh influences the p concentration in the overlying water the contribution of the sediment p release to the tp concentration of overlying water in the northern part of eh is obviously higher than to that of the other parts the water quality of this kind of lake can be improved by controlling the p release of sediments particularly the release of op

persistent environmental change after the paleocene eocene thermal maximum in the eastern north atlantic the paleocene eocene thermal maximum petm 56 ma is associated with abrupt climate change carbon cycle perturbation ocean acidification as well as biogeographic shifts in marine and terrestrial biota that were largely reversed as the climatic transient waned we report a clear exception to the behavior of the petm as a reversing climatic transient in the eastern north atlantic deep sea drilling project site 401 bay of biscay where the petm initiates a greatly prolonged environmental change compared to other places on earth where records exist the observed environmental perturbation extended well past the 13 c recovery phase and up to 650 kyr after the petm onset according to our extraterrestrial 3he based age model we observe a strong decoupling of planktic foraminiferal 18 o and mg ca values during the petm 13 c recovery phase which in combination with results from helium isotopes and clay mineralogy suggests that the petm triggered a hydrologic change in western europe that increased freshwater flux and the delivery of weathering products to the eastern north atlantic this state change persisted long after the carbon cycle perturbation had stopped we hypothesize that either long lived continental drainage patterns were altered by enhanced hydrological cycling induced by the petm or alternatively that the climate system in the hinterland area of site 401 was forced into a new climate state that was not easily reversed in the aftermath of the petm

warm arctic continents during the palaeocene eocene thermal maximum the palaeocene eocene thermal maximum petm 55 5 ma is a geologically relatively brief episode of extreme warmth both deep and surface ocean temperatures increased by up to 5 c in equatorial waters and up to 8 c in mid and high latitude waters from the continents the annual mean air temperature response during the petm is still largely unknown mainly due to a lack of quantitative temperature proxies and sufficient suitable continuous high resolution records recently a new proxy for continental temperature reconstructions has been proposed based on the distribution of membrane lipids of bacteria in present day soils j w h weijers s schouten j c van den donker e c hopmans j s sinninghe damste 2007 environmental controls on bacterial tetraether membrane lipid distribution in soils geochimica et cosmochimica acta 71 703 713 and shown to reconstruct annual mean air temperature in this study we applied this new proxy in an attempt to reconstruct the air temperature in high latitude continental areas during the petm by analysis of a marine sedimentary sequence obtained from the lomonosov ridge in the central arctic ocean integrated ocean drilling program expedition 302 site 004 hole a the results indicate a warming of 8 c above background values of 17 c this warming is coincident with a similar rise in sea surface temperatures documented earlier our results thus further confirm the warm conditions in the arctic and point to a strongly reduced latitudinal temperature gradient during the petm 2007 elsevier b v all rights reserved

tectonic implications of paleomagnetic poles from lower tertiary volcanic rocks south central alaska we have determined the paleolatitude of lower tertiary volcanic rocks in southern alaska to measure possible poleward translation of the wrangellia and the peninsular terranes after 50 m y ago previous paleomagnetic studies have shown that in triassic and jurassic time these terranes were located near the equator and have moved at least 3000 km poleward relative to the north american craton our sample localities are in the northern talkeetna mountains in mildly deformed andesite and dacite flows 50 4 51 3 53 9 and 56 3 m y by k ar that overlap lower cretaceous flysch lower permian volcanic rocks of wrangellia and upper triassic pillow basalt of the susitna terrane results from 26 cooling units 23 of reversed polarity and 3 of normal polarity give a mean paleomagnetic pole at 69 5 n 179 6 e 95 12 2 stratigraphic sections from opposite limbs of a syncline yield directional paths that pass the fold test satisfying a necessary condition for primary origin of the magnetization the corresponding mean paleolatitude 76 n of the northern talkeetna mountains is 8 10 higher than the latitude predicted from the eocene reference pole for north america therefore northward drift of the talkeetna superterrane which is the amalgamation of the wrangellia and peninsular terranes during and after middle jurassic time was probably complete by 50 m y ago our results are consistent with paleomagnetic poles from uppermost cretaceous and paleocene volcanic sequences in denali national park the lake clark region northern bristol bay region and near mcgrath these poles generally lie south of the cratonic poles suggesting that the region between the kaltag bruin bay and castle mountain faults has rotated counterclockwise relative to north america since the early eocene

the ketavik formation a new stratigraphic unit and its implications for the paleogene paleogeography and paleoclimate of southwestern alaska abstract a new formation the ketavik formation is proposed for paleogene rocks of katmai national park near brooks camp the type section is in an area previously mapped as the jurassic talkeetna formation the proposed formation was deposited in a fluvial environment it is distinct from the coeval copper lake formation on the southeast side of the alaska peninsula volcanic arc and was deposited in a different river system the ketavik formation may include previously mapped undifferentiated tertiary rocks at least some of which are similar in age that are scattered along a belt parallel to and northwest of the present magmatic arc the ketavik formation contains dicot and coniferous leaf and wood fossils that indicate a warm temperate climate

climate since ad 1510 on dyer plateau antarctic peninsula evidence for recent climate change a 480 year record of the oxygen isotope ratios dust content chemical species and net accumulation from ice cores drilled in 1989 90 on dyer plateau in the antarctic peninsula is presented the continuous analyses of small sub annual samples reveal well preserved annual variations in both sulfate content and 18o thus allowing an excellent time scale to be established this history reveals a recent pronounced warming in which the last two decades have been among the warmest in the last five centuries furthermore unlike in east antarctica on dyer plateau conditions appear to have been fairly normal from ad 1500 to 1850 with cooler conditions from 1850 to 1930 and a warming trend dominating since 1930 reconstructed annual layer thicknesses suggest an increase in net accumulation beginning early in the 19th century and continuing to the present this intuitive conflict between increasing net accumulation and depleted 18o cooler climate in the 19th century appears widespread in the peninsula region and challenges our understanding of the physical relationships among moisture sources air temperatures and snow accumulation the complex meteorological regime in the antarctic peninsula region complicates meaningful interpretation of proxy indicators and results in a strong imprint of local high frequency processes upon the larger scale climate picture

an 80 year summer temperature history from the xiao dongkemadi ice core in the central tibetan plateau and its association with atmospheric circulation abstract the climate significance of oxygen isotopes from the central tibetan plateau ctp ice cores is a debated issue because of large scale atmospheric circulation a high resolution 18 o record was recovered from the xiao dongkemadi xd ice core which expanded the spatial coverage of 18 o data in this region annual average 18 o correlated significantly with nearby mjjas air temperatures suggesting the 18 o can be used as a proxy to reconstruct regional climate change the reconstructed temperature anomaly is related to the regional and global warming trends and the greater warming amplitude since 1970s is related to the elevation dependency of the warming signal the close relationship of the warming to variations in glacier mass balances and discharge reveal that recent warming has led to obvious glacier shrinkage and runoff increase correlation analysis suggests that monsoon and westerly moisture substantially influence the ctp ice core records along with an increase in their level of contribution to the xd core accumulation in recent decades and confirms a teleconnection of regional climate of the ctp ice cores with climate parameters in the indian and north atlantic oceans

paleomagnetism of eocene volcanic rocks talkeetna mountains alaska previous paleomagnetic studies of eocene rocks deposited in the talkeetna mountains on the northern edge of the combined peninsular wrangellia and alexander terranes the southern alaska superterrane sas yield a paleolatitude of 76 n while late cretaceous rocks on the southern edge of the sas record a 32 n paleolatitude at face value these drastically different paleolatitudes imply that wrangellia moved 44 to the north in only 20 m y requiring a northward component of velocity of about 24 cm yr alternatively the discrepancy might be explained by postulating an unrecognized tectonic boundary separating the two localities allowing different emplacement ages we have tested the unrecognized tectonic boundary hypothesis allowing post eocene emplacement of the sas by sampling eocene volcanic rocks deposited near the southern edge of the sas in the talkeetna mountains our data set comprises measurements from 97 oriented cores collected from 26 lava flows and two tuffs distributed over a distance of 50 km a primary remanence is indicated by positive fold tests and penecontemporaneous intrusion tests age control is provided by nine new k ar whole rock age determinations ranging from 38 8 to 53 6 ma the mean paleomagnetic pole calculated for this study is not significantly different from the pole derived from the eocene flows to the north and gives a paleolatitude of 78 thus ruling out the hypothesis of an unrecognized suture accommodating major post eocene displacement this result has prompted a reevaluation of the data which suggest rapid movement including the precision of the age control the adequacy of averaging of secular variation and the possibility of sedimentary inclination error the bulk of the evidence suggests northward displacement from lower latitudes however the error limits are such that the dramatic velocities previously postulated are not required

late paleocene early eocene paleosols and a new measure of the transport distance of alaska s yakutat terrane abstractan intensely weathered paleosol representing a nearly isochronous landscape exists at many places in continental late paleocene early eocene strata in north america most commonly a single siderite spherule bearing horizon is found from which 18o values were obtained to construct a paleolatitudinal gradient for late paleocene early eocene north america comparison of the paleosol siderite spherule 18o composition from the displaced yakutat terrane of alaska to the north american paleolatitudinal gradient indicates that during the late paleocene early eocene the terrane existed at 44 paleonorth thus supporting hypotheses for a far traveled terrane history

changing lake dynamics and sequence stratigraphy of synrift lacustrine strata in a half graben an example from the triassic ischigualasto villa union basin argentina well exposed triassic rift strata from the ischigualasto villa union basin nw argentina include a 80 to ca 515 m thick lacustrine dominated package that can be correlated across a half graben using key stratigraphic surfaces sequence boundaries lacustrine flooding surfaces and forced regressive surfaces the characteristics of the synrift lacustrine fill in different parts of the half graben have been examined and the mechanisms controlling sedimentation inferred a variety of sedimentary environments are recognized including volcaniclastic floodplain mildly saline lake and playa lake offshore lacustrine delta front to fluvial dominated and wave dominated deltas distributary and fluvial channel and interdistributary bay the succession can be divided into four stratigraphic sequences ss1 to ss4 the oldest of which ss1 contains volcaniclastic fluvial and saline lake deposits it is thickest close to the western border fault zone reflecting more rapid subsidence here accommodation exceeded sediment and water input during ss1 the second and third sequences ss2 and ss3 mark the onset of widespread lacustrine sedimentation reflecting a balance between accommodation creation and water and sediment fluxes sequences ss2 and ss3 are represented by offshore meromictic lacustrine and deltaic deposits the latter mostly sourced from the flexural and southern axial margins of the half graben the presence of stacked parasequences bound by lacustrine flooding surfaces is related to climatically induced lake level fluctuations superimposed on variable rates of subsidence on the controlling rift border fault zone the youngest sequence ss4 is represented by the deposits of littoral lacustrine and shallow shelf deltas distinguished by a change in lithofacies palaeocurrents and sandstone composition suggesting a switch in sediment supply to the footwall margin to the nw the change in the sediment source is related to reduced footwall uplift the possible presence of a relay ramp and or supply from a captured antecedent drainage network during ss4 the rate of creation of accommodation was exceeded by the sediment and water discharge the stratigraphic evolution of lacustrine strata in the half graben was mainly controlled by tectonic processes including subsidence rate and the growth and evolution of the border fault zone but changing climate inducing changes in water balance and lake level and autocyclic processes delta lobe switching were also important

high frequency floral changes at the paleocene eocene boundary revealed by comparative biomarker and palynological studies abstract the cap d ailly area upper normandy france shows several terrestrial lagoonal sections recording the negative carbon isotope excursion cie associated with the paleocene eocene thermal maximum petm 55 8 ma a study of the biomarkers and spore pollen content of the vasterival section gave complementary information on paleofloral changes that occurred around the paleocene eocene p e boundary aliphatic hydrocarbon fractions revealed a high abundance of vascular plant biomarkers including tricyclic diterpanes derived from conifers fernenes derived from ferns and des a triterpenes derived from angiosperms whereas the vegetation of the depositional environment surroundings seemed alternately dominated by ferns and angiosperms revealed from biomarkers the regional flora seemed dominated strictly by angiosperms such as juglandaceae revealed by pollen spore pollen assemblages revealed no major turnover in the paleovegetation but slight variation in vegetation composition however both biomarkers and spores pollen exhibited two intervals of rapid floral change the first occurred around the p e boundary and the second at the top of the strictly terrestrial unit that coincides with a marine transgression comparison of the data with published paleoclimatic results obtained from the same samples indicated that the first interval of floral change correlates with strong paleohydrological perturbations whereas the second is linked to an increasing marine influence

paleoenvironment and paleoecology of a late paleocene high latitude terrestrial succession arkose ridge formation at box canyon southern talkeetna mountains alaska abstract paleogene sedimentary rocks of the arkose ridge formation talkeetna mountains alaska preserve a record of a fluvial lacustrine depositional environment and its forested ecosystem in an active basin among the convergent margin tectonic processes that shaped southern alaska an 800 m measured succession at box canyon indicates braid plain deposition with predominantly gravelly deposits low in the exposure to sandy and muddy facies associations below an overlying lava flow sequence u pb geochronology on zircons from a tuff and a sandstone within the measured section as well as an ar ar date from the overlying lava constrain the age of the sedimentary succession to between 59 ma and 48 ma fossil plant remains occur throughout the arkose ridge formation as poorly preserved coalified woody debris and fragmentary leaf impressions at box canyon however a thin lacustrine depositional lens of rhythmically laminated mudrocks yielded fish fossils and a well preserved floral assemblage including foliage and reproductive organs representing conifers sphenopsids monocots and dicots leaf physiognomic methods to estimate paleoclimate were applied to the dicot leaf collection and indicate warm temperate paleotemperatures 11 15 4 c mat and elevated paleoprecipitation 120 cm yr map estimates as compared to modern conditions results that are parallel with previously published estimates from the partly coeval chickaloon formation deposited in more distal depositional environments in the same basin the low abundance of leaf herbivory in the box canyon dicot assemblage 9 of leaves damaged is also similar to the results from assemblages in the meander plain depositional systems of the chickaloon this new suite of data informs models of the tectonostratigraphic evolution of southern alaska and the developing understanding of terrestrial paleoecology and paleoclimate at high latitudes during the late paleocene early eocene greenhouse climate phase

north south precipitation patterns in western north america on interannual to decadal timescales the overall amount of precipitation deposited along the west coast and western cordillera of north america from 258 to 558n varies from year to year and superimposed on this domain average variability are varying north south contrasts on timescales from at least interannual to interdecadal in order to better understand the north south precipitation contrasts their interannual and decadal variations are studied in terms of how much they affect overall precipitation amounts and how they are related to large scale climatic patterns spatial empirical orthogonal functions eofs and spatial moments domain average central latitude and latitudinal spread of zonally averaged precipitation anomalies along the westernmost parts of north america are analyzed and each is correlated with global sea level pressure slp and sea surface temperature series on interannual defined here as 3 7 yr and decadal 7 yr timescales the interannual band considered here corresponds to timescales that are particularly strong in tropical climate variations and thus is expected to contain much p

the paleocene eocene thermal maximum record in the organic matter of the claret and tendruy continental sections south central pyrenees lleida spain abstract the carbon isotope excursion cie associated with the paleocene eocene thermal maximum petm has been detected for the first time in the total organic carbon toc contained within the continental sediments of the tremp formation south central pyrenees lleida spain the 13 c toc magnitude of the cie is 4 3 in the claret section and 3 0 in the tendruy section with minimum values of 27 6 and 26 7 respectively previous studies have detected the cie in the south central pyrenees in both marine carbonates and within continental soil carbonate nodules these studies have located the onset of the cie either above or within the claret conglomerate interpreted as a megafan produced by a profound change in the precipitation regimen at the beginning of the petm our higher resolution 13 c toc study in the claret and tendruy sections places the onset of the cie below the base of the claret conglomerate and therefore suggests a 4 to 9 kyr time lag between the onset of the cie and an increase in intense seasonal precipitation rates furthermore this study suggests that the cie took place 30 55 kyr after the deposition of important late cernaysian tremp mammalian sites claret 4 tendruy v tendruy and palau which contain the youngest known occurrence of endemic paleocene mammalian taxa in europe before the mammalian dispersal event mde migration of new mammal groups such as perissodactyls artiodactyls primates marsupials carnivores creodonts and rodents the first immigrant mammals in europe are recorded at dormaal belgium above a hiatus the base of which has been dated to around the start of the cie our data indicate that the mde might have in fact occurred in europe within a time interval of about 67 kyr around the cie onset

continental glacier meltwater contributions to late summer stream flow and water quality in the northern wind river range wyoming usa the wind river range in wyoming contains more than 60 glaciers that are part of the headwaters for the wind missouri green colorado and snake columbia river systems continental glacier lies on the crest of the northern wind river range and covers approximately 2 5 km2 with meltwater flowing into west torrey creek and the wind river discharge measurements of upper continental glacier meltwater were made in august 2012 and 2014 water samples were collected in 2014 for the analysis of stable isotopes field parameters and 23 trace elements this study demonstrated that continental glacier meltwater accounted for a mean of 32 91 8 4 of torrey creek flow and 4 11 18 38 of wind river flow as measured above red creek for august 2012 and 2014 scaling of these results to all perennial snow and ice in the upper torrey creek basin yielded an estimate of 82 70 contribution to torrey creek flow and 10 32 of wind river flow above red creek during august glacier meltwater contributions versus snow melt to torrey creek based on 18o ratios ranged from 81 05 to 82 70 of flow with a mean of 81 88 1 17 for august 2014 continental glacier meltwater accounted for 89 99 of nitrate nitrite and 34 83 of total phosphorus loading to torrey creek in august 2014 the ph of the snow and glacier meltwater was less than 6 0 likely the result of nitrate nitrite and other atmospheric deposition finally analysis of trace elements showed distinct differences between water sources

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

the planktonic foraminiferal response to the paleocene eocene thermal maximum on the atlantic coastal plain abstract planktonic foraminiferal assemblages in two cores from maryland and new jersey show evidence for significant changes in surface ocean habitats on the continental shelf during the paleocene eocene thermal maximum petm at both sites significant assemblage shifts occur immediately before the onset of the event these changes include the appearance of abundant triserial biserial species as well as rare excursion taxa which are limited to the interval of the carbon isotope excursion at deep sea sites the assemblage shifts signal the development of new habitats immediately prior to the onset of the petm likely involving warming surface ocean acidification increased stratification and oligotrophy a sharp increase in diversity at the onset of the event is interpreted as a further increase in stratification and warming as well as increased water depth and more eutrophic conditions finally we observe variant morphologies of several planktonic foraminifera which may also signal the response of the assemblage to environmental perturbation

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

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

eocene volcanism above a depleted mantle slab window in southern alaska the caribou creek volcanic fi eld lies along the continent side edge of forearc basin rocks in south central alaska and consists of over 1000 m of shallow dipping basalt and andesite lavas with minor mafi c pyroclastic deposits dacite and rhyolite lavas along with shallow intrusions form dome complexes with associated pyroclastic deposits that overlie and crosscut the basalt and intermediate lavas the basalts are tholeiitic and strongly depleted in the light rare earth elements la yb 0 18 1 5 with concentrations of high fi eld strength elements e g zr hf ti y similar to mid ocean ridge basalt and with variable enrichment in fl uid mobile elements e g cs ba and pb intermediate and felsic rocks show enrichment in the rare earth elements and fl uid mobile elements plus rb and k but retain low la yb ratios 0 48 3 6 a few andesite and dacite samples are strongly depleted in the heavy rare earth elements and are geochemically similar to adakites e g sr y up to 52 ten 40 ar 39 ar ages for the caribou creek volcanic rocks range from 49 4 2 2 to 35 6 0 2 ma an adakite like tuff beneath the other volcanic rocks yields an age of 59 0 0 4 ma caribou creek basalts were derived from mid ocean ridge like depleted mantle that was emplaced beneath the southern margin of alaska through a slab window following spreading ridge subduction caribou creek volcanism was coeval with oblique subduction oroclinal bending and right lateral strike slip faulting in south central alaska all of which could have induced crustal extension to allow adiabatic melting of the depleted mantle reservoir to form basaltic magmas the basalts then evolved by fractional crystallization with moderate to high degrees of assimilation of jurassic arc basement rocks to form the intermediate and felsic magmas enrichment of the basaltic parent magmas in fl uid mobile elements occurred by contamination from the jurassic arc rocks and or by contamination with metasomatic mantle remnant from preceding subduction high heat fl ow through the slab window induced partial melting of garnet bearing mafi c parts of the jurassic arc basement to form the adakite like rocks the caribou creek volcanic rocks demonstrate that slab windows can directly infl uence magmatism inboard of accretionary prism and forearc basin settings given a suitable deformation regime e g crustal extension and that the infl uence of a slab window on continental margin magmatism can be long lived 20 m y

recent ice core climate records from the cordillera blanca peru ice cores recently drilled to bedrock on the col of huascaran 9 06 s 77 36 w 6047 m a s l offer the potential for a long annually resolved climate record from tropical south america this paper presents the record from 1950 to 1993 preserved in microparticle and nitrate concentrations and oxygen isotopic ratios average monthly temperatures from a satellite linked automatic weather station installed on nearby hualcan in 1991 are presented annual temperatures from local high altitude meteorological stations along with the annual huascaran isotopic record show a warming trend over the last two decades the marked preservation of the climate record in oxygen isotopic ratios on huascaran is absent at lower elevation sites which have been affected by the recent warming this paper demonstrates the establishment of a time scale for the huascaran core the preservation of the climatic signal with depth and the linkage of the ice core proxy climate parameters with measured climatic variations

seasonal progression of uranium series isotopes in subglacial meltwater implications for subglacial storage time abstract the residence time of subglacial meltwater impacts aquifer recharge nutrient production and chemical signals that reflect underlying bedrock substrate but is inaccessible to direct observation here we report the seasonal evolution of subglacial meltwater chemistry from the 2011 melt season at the terminus of the athabasca glacier canada we measured major and trace analytes and u series isotopes for twenty nine bulk meltwater samples collected over the duration of the melt season this dataset which is the longest time series record of 234 u 238 u isotopes in a glacial meltwater system provides insight into the hydrologic evolution of the subglacial system during active melting meltwater samples measured from the outflow were analyzed for 238 u 222 rn and 234 u 238 u activity conductivity alkalinity ph and major cations subglacial meltwater varied in 238 u and 222 rn from 23 to 832 ppt and 9 to 171 pci l respectively activity ratios of 234 u 238 u ranged from 1 003 to 1 040 with the highest 238 u 222 rn and 234 u 238 u activity values occurring in early may when delayed flow basal meltwater composed a significant portion of the bulk melt from the chemical evolution of the meltwater we posit that the relative subglacial water residence times decrease over the course of the melt season this decrease in qualitative residence time during active melt is consistent with prior field studies and model predicted channel switching from a delayed distributed network to a fast channelized network flow as such our study provides support for linking u series isotopes to storage lengths of meltwater beneath glacial systems as subglacial hydrologic networks evolve with increased melting and channel network efficiency

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

late paleocene early eocene climate changes in southwestern wyoming paleobotanical analysis the warmest global temperatures of the cenozoic era occurred in early eocene time following a warming trend that started in late paleocene time the greater green river basin of southwestern wyoming is one of the best areas in the rocky mountains for paleobotanical investigation of the paleocene eocene climatic transition intensive sampling has resulted in the recovery of an estimated 189 species of plant macrofossils from the tiffanian clarkforkian wasatchian and bridgerian land mammal ages the leaf morphologies and taxonomic affinities of these fossils were used in combination with other indicators to evaluate paleocene eocene climates following cool humid conditions in the tiffanian the clarkforkian was humid and subtropical and several plant families with modern tropical affinities appeared however as in the tiffanian clarkforkian floras had low diversity and were dominated by a single species in the birch family mean annual temperature mat rose from an estimated 12 c in the tiffanian to 19 c in the clarkforkian while mean annual precipitation map for the tiffanian and clarkforkian is estimated to have been 130 150 cm little fossil plant material is preserved from the latest clarkforkian or the earliest wasatchian which is thought to have contained an interval of cooling and drying followed by renewed warming by the middle wasatchian the time of the cenozoic thermal maximum the inferred mat was about 21 c and the map was near 140 cm a second influx of plant families with tropical affinities appeared in the area and diversity increased significantly but most plant families known from the clarkforkian persisted species turnover from the clarkforkian to the wasatchian was greater than 80 a second turnover of more than 80 of species but not families from the wasatchian to the early bridgerian accompanied drying and increased seasonality of precipitation the early bridgerian mat is inferred to have been near 20 c and the map to have been about 80 cm except for the tiffanian and possibly portions of the early wasatchian paleoclimates during the study interval were predominantly frost free although the moderating influence of the green river lake system has been suggested as a possible explanation for mild eocene winters in wyoming this study shows that virtually frostfree climates existed in the area prior to and independent of significant lake development

snow cover snowmelt timing and stream power in the wind river range wyoming article i nfo article history earlier onset of springtime weather including earlier snowmelt has been documented in the western united states over at least the last 50 years because the majority n70 of the water supply in the western u s comes from snowmelt analysis of the declining spring snowpack and shrinking glaciers has important implications for the management of streamflow the amount of water in a snowpack influences stream discharge which can also influence erosion and sediment transport by changing stream power or the rate at which a stream can do work such as move sediment and erode the stream bed the focus of this work is the wind river range wrr in west central wyoming ten years of moderate resolution imaging spectro radiometer modis snow cover cloud gap filled cgf map products and 30 years of discharge and meteorological station data are studied streamflow data from streams in wrr drainage basins show lower annual discharge and earlier snowmelt in the decade of the 2000s than in the previous three decades though no trend of either lower streamflow or earlier snowmelt was observed within the decade of the 2000s results show a statistically significant trend at the 95 confidence level or higher of increasing weekly maximum air temperature for three out of the five meteorological stations studied in the decade of the 1970s and also for the 40 year study period as a whole the extent of snow cover percent of basin covered derived from the lowest elevation zone 2500 3000 m of the wrr using modis cgf snow cover maps is strongly correlated with maximum monthly discharge on 30 april where spearman s rank correlation rs 0 89 for the decade of the 2000s we also investigated stream power for bull lake creek above bull lake and found a trend significant at the 90 confidence level toward reduced stream power from 1970 to 2009 observed changes in streamflow and stream power may be related to increasing weekly maximum air temperature measured during the 40 year study period possibly contributing to a reduction in snow cover in addition the strong relationship between percent of basin that was snow covered and maximum monthly streamflow indicates that modis snow cover maps are useful for predicting streamflow and can be used to improve management of water resources in the drought prone western united states published by elsevier b v

ice core record of dust sources in the western united states over the last 300 years over the past 5000 years amplified dust generation and deposition in the american west has been linked to human activity in recent decades intensified rates of agriculture and livestock grazing have been correlated with greater dust production detected on seasonal to annual timescales the combination of land use intensification and climate change i e increased drought frequency in north america highlights the importance of characterizing the sources of dust both before and after the influence of anthropogenic activity we apply high precision geochemical and isotopic sr and nd isotopes techniques to an ice core from the upper fremont glacier wyoming usa to produce the first glacial dataset from the american west our sr nd isotopic composition data indicates the evolving dust provenance to the upper fremont glacier ufg from a long range transport of mineral dust to a local source this increasing input of dust from a local source is supported by a rise in average dust particle diameter combined with greater average dust concentration throughout the record the greater presence of dust particles smaller than 2 5 m in the most recent samples from ufg ice core record support existing satellite and sediment core data regarding the effects of anthropogenic activity upon dust sources and pathways in the american west although the sr nd isotope database in north america needs be expanded our results provide a survey of windborne dust through the past 270 years

stratigraphy of late palaeocene events in the middle east implications for low to middle latitude successions and correlations we have investigated the upper palaeocene stratigraphical record in four sections in egypt and one in israel the sections are arranged on a depth transect across the southern tethyan margin in all sections a 13 c excursion and benthic foraminiferal extinctions coincide at a level within planktic foraminiferal zone p5 in three sections a bed sapropelic in two of the deeper profiles contains extraordinarily transient benthic and planktic foraminifera assemblages these planktic assemblages are dominated by acarinina and contain rare to common morozovella allisonensis and globanomalina luxorensis but unusually few other morozovella the extremely restricted stratigraphical range of m allisonensis to the lower part of the 13 c excursion enables 1 a three fold subdivision of zone p5 2 accurate correlation to the best sections spanning the 13 c excursion in the atlantic and pacific and 3 assessment of stratigraphical completeness over the 13 c excursion in other sub tropical successions discontinuities and especially dissolution intervals in many low to middle latitude marine successions elsewhere as in two middle east sections preclude an accurate correlation within the lower part of the 13 c excursion m allisonensis zone p5b three studied sections can provide the best coverage of the sequence of events over the onset and early part of the 13 c excursion in the middle east but as in most known sections probably none constitutes a complete upper palaeocene lower eocene record

coarse grained nonmarine volcaniclastic sediment terminology and depositional process modern and ancient volcaniclastic sedimentary sequences contain depositional units whose features cannot be attributed to fully turbulent dilute stream flow or viscous debris flow the characteristics of these poorly sorted sediments suggest rapid deposition from high concentration dispersions but not en masse sedimentation thus appears related to high discharge flows intermediate in sediment water ratio between stream flow and debris flow the term hyperconcentrated flood flow is proposed for describing this intermediate condition hyperconcentrated flood flow deposits are distinguished from debris flow deposits by lack of matrix support or reverse grading and instead exhibit distribution normal grading and horizontal stratification these deposits are distinguished from normal dilute stream flow deposits by lack of cross stratification in sand facies and by very poor sorting poor imbrication and numerous clasts with long axes oriented parallel to flow direction in gravel facies the horizontal bedding that dominates sandy hyperconcentrated flood flow deposits consists of sediment too coarse grained and strata too thick to have been produced in the boundary layer of the upper flow regime and should not be confused with the more familiar thin graded laminae of fine to medium grained sand often associated with parting lineation hyperconcentrated flood flow deposits are not unique to volcanic settings they also occur in arid alluvial fan sequences debris flow and hyperconcentrated flood flow deposits however are much thicker and more extensive in volcanic regions than on alluvial fans because explosive volcanism leads to rapid mobilization of large volumes of sediment and water on a scale unparalleled in nonvolcanic settings in volcanic regions therefore these deposits have greater preservation potential show greater lateral variability and are more voluminous transformation of channelized debris flow to hyperconcentrated flood flow by dilution with stream water recently observed at mount st helens is recorded in ancient volcaniclastic sequences and may serve as the primary mechanism for generating hyperconcentrated flood flow

geochemical evidence for hydroclimatic variability over the last 2460 years from crevice lake in yellowstone national park usa abstract a 2460 year long hydroclimatic record for crevice lake yellowstone national park montana was constructed from the 18 o values of endogenic carbonates the 18 o record is compared to the palmer hydrologic drought index phdi and pacific decadal oscillation pdo indices as well as inferred discharge of the yellowstone river during the last century high 18 o values coincide with drought conditions and the warm phase of the pdo index low 18 o values coincide with wet years and a negative pdo index comparison of tree ring inferred discharge of the yellowstone river with the 18 o record over the last 300 years indicates that periods of high discharge i e wet winters with significant snow pack correspond with low 18 o values extrapolating this relationship we infer wet winters and high river discharge for the periods of 1090 1030 970 870 670 620 and 500 430 cal years bp the wet intervals at 670 and 500 cal bp are synchronous with similar events in banff canada and walker lake nevada the wet intervals at 970 and 670 cal bp overlap with wet intervals at walker lake and major drought events identified in the western great basin these results suggest that the northern border of yellowstone national park straddles the boundary between northern rocky mountains and great basin climate regimes

the impact of paleocene eocene boundary events on middle neritic benthic foraminiferal assemblages from egypt abstract a 25 m upper paleocene to lower eocene marly sequence exposed at gebel duwi quseir red sea coast of egypt provides a good opportunity for studying paleocene eocene p e boundary stratigraphy and events various bio eco and isotope stratigraphic correlations accurately delineate the position of the p e boundary i e the level of stable isotopic excursions and deep sea benthic extinctions in the middle part of this section within zones p5 and np9 in this paper the impact of p e boundary environmental perturbations on benthic foraminiferal communities of the shallow tethyan shelf is examined benthic foraminiferal assemblages from gebel duwi characterized by large frondicularia phosphatica and f nakkadyi in addition to a number of other neritic taxa but without any typical outer neritic bathyal taxa suggest middle neritic 75 100 m deposition throughout the studied interval and only minor relative sea level variations perhaps some 10 20 m across the boundary sea level appears to have been stable yet a distinct faunal turnover marks the p e boundary of this shallow site which in contrast to deep sea records is less abrupt being preceded by a gradual diversity decrease starting some four meters below the boundary moreover most exits are either local or just temporary and thus not true extinctions many lazarus taxa reappear at some point above the boundary while all but one of the disappearing taxa are known from other lower eocene neritic deposits in egypt in general benthic foraminiferal assemblages display low diversities and high dominance values notably anomalinoides aegyptiacus up to 74 suggesting high levels of environmental stress at the sea floor in combination with occasionally very high p b ratio s up to 98 p and generally laminated sediments the character of the benthic assemblage points to a strong influence of recurrent dysoxia and or anoxia we suggest that these resulted from surface eutrophication by intermittent coastal upwelling and reduced ventilation of the bottom environment although these conditions prevailed during most of the time interval studied they were most severe during the latest paleocene and early eocene when eutrophication intensified and the organic carbon flux to the sea floor increased enhanced atmospheric contrasts between the tethys seaway and the african continent resulting in intensified longshore tradewinds may have controlled these changes at the p e boundary the bottom environment became minimally ventilated perhaps due to reduced oxygen advection from deeper waters three meters above the boundary a succession of increasingly diverse assemblages indicate a gradual decrease of environmental stress and a return to more normal conditions although the organic carbon flux to the sea floor remained high

high resolution stratigraphy of an underfilled lake basin wilkins peak member eocene green river formation wyoming u s a abstract lakes tend to respond noticeably to minor changes in sediment and water balance driven by climatic tectonic or geomorphic processes this unique behavior of lacustrine basins can provide a high resolution record of geologic processes within the continental setting far from the globally averaged record of marine strata the wilkins peak member of the eocene green river formation in wyoming usa is dominated by aggradation of repetitive sedimentary facies successions recording distinct lacustrine expansions and contractions these lacustrine cycles consist of up to four successive facies associations littoral profundal sublittoral palustrine and salt pan because they comprise disparate facies that may never have been simultaneously deposited in the basin wilkins peak member cycles are non waltherian successions that do not readily equate to any established sequence stratigraphic unit the completeness of the stratigraphic record in the wilkins peak member varies continuously across the basin at least 126 cycles are present in the erda white mountain 1 core near the basin depocenter whereas only about one third as many are recognizable 53 km north nearer to the basin margin cycle boundaries terminate northward by gradual amalgamation into palustrine facies reflecting the interplay between varying lake levels and a south dipping deposition gradient evidence for complete desiccation and hiatuses is commonplace even near the basin center a truly complete record may not be present anywhere based on recent 40ar 39ar geochronology of tuffs the average cycle duration in the white mountain 1 core is approximately 10 000 years however the true average duration is shorter due to the presence of lacunae and the time required for deposition of the thinnest cycles may have been less than 1000 years no external driving mechanism is presently known for eocene cycles of such short duration raising the possibility that they are instead autogenic cycles related to geomorphic instability of the surrounding landscape evaporite deposition corresponded closely in time and space to maximum differential subsidence suggesting that tectonic influences on drainage patterns and basin accommodation exerted a primary control differential accommodation was most pronounced during deposition of the lower wilkins peak member and became progressively less so after that time based on structural and stratigraphic observations a period of increased tectonic uplift commenced concurrent with deposition of the lower wilkins peak member

contribution of glacier meltwater to streamflow in the wind river range wyoming inferred via a bayesian mixing model applied to isotopic measurements the wind river range wrr of wyoming has the largest concentration of alpine glaciers in the american rockies and contributes to several major river systems in the western united states declines in the areal extent and volume of these glaciers are well documented and eventual loss of alpine glaciers will reduce the amount of water available for agricultural and domestic use the contribution of glacial melt to streamflow remains largely unquantified in wyoming we used isotope measurements and bayesian modeling to estimate the fractional contribution of glacier meltwater to dinwoody creek dc in the wrr on bi weekly and seasonal spring summer and fall time scales over 2 years in 2007 and 2008 we made temporally intensive measurements of the stable isotope composition of water from the dc watershed samples of the primary sources of streamflow snowmelt glacier melt rain and baseflow were collected during field campaigns and automated collection of stream samples occurred over the melt season isotope data d and 18o were analyzed within a hierarchical bayesian framework that incorporated temporal and spatial correlations glacial melt contributed a significant proportion 53 59 to streamflow in a low flow year 2007 or when streamflow was low during a high flow year 2008 in 2008 a large and persistent snowpack contributed significantly 0 42 51 to streamflow in mid summer the large contribution of glacial melt to streamflow suggests that the loss of glaciers may impact riparian ecosystems and human water supplies in the late summer and in years with low snowpack copyright 2011 john wiley sons ltd

the kanaka creek fossil flora huntingdon formation british columbia canada paleoenvironment and evidence for paleocene age using palynology and macroflora paleogene sediments of the huntingdon formation a correlative to the chuckanut formation of neighbouring washington state usa are exposed in the greater vancouver area british columbia canada

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

phosphorus fractions and bioavailability in relation to particle size characteristics in sediments from lake hongfeng southwest china information on the chemical composition of phosphorus p fractions in sediments is fundamental to understanding p bioavailability and eutrophication in lake ecosystems phosphorus fractions and its bioavailability in sediments cores of lake hongfeng southwest china were investigated using a chemical sequential extraction scheme relationships between p fractions p bioavailability and particle sizes were discussed p fractions concentrations were ranked in the order residual p naoh rp naoh nrp hcl p bd p nh4cl p and all of them decreased with increasing sediment depth statistical analysis showed that concentrations of bioavailable p bap which includes the nh4cl p bd p naoh rp and naoh nrp fractions ranged from 404 68 to 1 591 99 mg kg and accounted for 26 8 71 8 of the concentrations of total phosphorus tp in the top 5 cm sediments whereas in the whole sediment cores their concentrations ranged from 239 70 to 1 591 99 mg kg and accounted for 26 8 76 0 of tp the results suggested that the sediments were a large potential source of p for algae blooms in lake hongfeng phosphorus fractions and their potential bioavailability were influenced by the sediment particle sizes especially the bioavailability of the nh4cl p fraction which was strongly affected by the presence of fine particle sizes in the sediments

mass wasting and hiatuses during the cretaceous tertiary transition in the north atlantic relationship to the chicxulub impact deep sea sections in the north atlantic are claimed to contain the most complete sedimentary records and ultimate proof that the chicxulub impact is cretaceous tertiary boundary ktb in age and caused the mass extinction a multi disciplinary study of north atlantic dsdp sites 384 386 and 398 based on high resolution planktonic foraminiferal biostratigraphy carbon and oxygen stable isotopes clay and whole rock mineralogy and granulometry reveals the age stratigraphic completeness and nature of sedimentary disturbances results show a major hiatus across the ktb at site 384 with zones cf1 p0 and p1a missing spanning at least 540 ky similar to other north atlantic and caribbean localities associated with tectonic activity and gulf stream erosion at sites 386 and 398 discrete intervals of disturbed sediments with mm to cm thick spherule layers have previously been interpreted as the result of impact generated earthquakes at the ktb destabilizing continental margins prior to settling of impact spherules however improved age control based on planktonic foraminifera indicates spherule deposition in the early danian zone p1a 2 upper parvularugoglobigerina eugubina zone more than 100 ky after the ktb at site 386 two intervals of white chalk contain very small 63 m early danian zone p1a 2 assemblages 65 and common reworked cretaceous 35 species in contrast the in situ red brown and green abyssal clays of this core are devoid of carbonate in addition high calcite mica and kaolinite and upward fining are observed in the chalks indicating downslope transport from shallow waters and sediment winnowing via distal turbidites at site 398 convoluted red to tan sediments with early danian and reworked cretaceous species represent slumping of shallow water sediments as suggested by dominance of mica and low smectite compared to in situ deposition we conclude that mass wasting was likely the result of earthquakes associated with increased tectonic activity in the caribbean and the iberian peninsula during the early danian well after the chicxulub impact

wood mediated geomorphic effects of a jokulhlaup in the wind river mountains wyoming a jokulhlaup burst from the head of grasshopper glacier in wyoming s wind river mountains during early september 2003 five reaches with distinct sedimentation patterns were delineated along the dinwoody creek drainage this paper focuses on a portion of the jokulhlaup route where erosion of the forested banks created 16 large logjams spaced at longitudinal intervals of tens to hundreds of meters aggradation within the main channel upstream from each logjam created local sediment wedges and the jams facilitated overbank deposition during the jokulhlaup field surveys during 2004 and 2006 documented logjam characteristics and associated erosional and depositional features as well as initial modification of the logjams and flood deposits within the normal seasonal high flow channel overbank deposits have not been altered by flows occurring since 2003 field measurements supported three hypotheses that i logjams present along the forested portions of the jokulhlaup route are larger and more closely spaced than those along adjacent otherwise comparable stream channels that have not recently experienced a jokulhlaup ii logjams are not randomly located along the jokulhlaup route but instead reflect specific conditions of channel and valley geometry and flood hydraulics and iii the presence of logjams facilitated significant erosional and depositional effects this paper documents a sequence of events in which outburst floodwaters enhance bank erosion and recruitment of wood into the channel and thus the formation of large logjams these logjams sufficiently deflect flow to create substantial overbank deposition in areas of the valley bottom not commonly accessed by normal snowmelt peak discharges and through this process promote valley bottom aggradation and sediment storage changes in the occurrence of glacier outburst floods thus have the potential to alter the rate and magnitude of valley bottom dynamics in these environments which is particularly relevant given predictions of worldwide global warming and glacial retreat processes observed at this field site likely occur in other forested catchments with headwater glaciers

ice core net snow accumulation and seasonal snow chemistry at a temperate glacier site mount waddington southwest british columbia canada a 141m ice core was recovered from combatant col 51 385 n 125 258 w 3000ma s l mount waddington coast mountains british columbia canada records of black carbon dust lead and water stable isotopes demonstrate that unambiguous seasonality is preserved throughout the core despite summer surface snowmelt and temperate ice high accumulation rates at the site 4 m ice eq a 1 limit modification of annual stratigraphy by percolation of surface meltwater the ice core record spans the period 1973 2010 an annually averaged time series of lead concentrations from the core correlates well with historical records of lead emission from north america and with ice core records of lead from the greenland ice sheet the depth age scale for the ice core provides sufficient constraint on the vertical strain to allow estimation of the age of the ice at bedrock total ice thickness at combatant col is 250 m an ice core to bedrock would likely contain ice in excess of 200 years in age accumulation at combatant col is significantly correlated with both regional precipitation and large scale geopotential height anomalies

using fossil leaves as paleoprecipitation indicators an eocene example estimates of past precipitation are of broad interest for many areas of inquiry including reconstructions of past environments and topography climate modeling and ocean circulation studies the shapes and sizes of living leaves are highly sensitive to moisture conditions and assemblages of fossil leaves of flowering plants have great potential as paleoprecipitation indicators most quantitative estimates of paleoprecipitation have been based on a multivariate data set of morphological leaf characters measured from samples of living vegetation tied to climate stations however when tested on extant forests this method has consistently overestimated precipitation we present a simpler approach that uses only the mean leaf area of a vegetation sample as a predictor variable but incorporates a broad range of annual precipitation and geographic coverage into the predictor set the significant relationship that results in addition to having value for paleoclimatic reconstruction refines understanding of the long observed positive relationship between leaf area and precipitation seven precipitation estimates for the eocene of the western united states are revised as lower than previously published but remain far wetter than the same areas today abundant moisture may have been an important factor in maintaining warm frost free conditions in the eocene because of the major role of water vapor in retaining and transporting atmospheric heat

paleomagnetism of eocene plutonic rocks matanuska valley alaska paleomagnetic analysis of 88 samples from 14 sites in four eocene sills in the matanuska valley south central alaska yields a paleomagnetic pole at lat 72 9 n long 281 1 e precision parameter k 15 4 the paleolatitude of this result suggests that this part of the alaskan crust was at or near its present position relative to north america in the middle tertiary this pole also indicates that the region has been rotated clockwise by approximately 50 these results can be explained by local block rotations of fault bounded blocks in response to regional right lateral shear along both the castle mountain and border ranges faults

meco and alpine orogenesis constraints for facies evolution of the bartonian nummulitic and solenomeris limestone in the argentina valley ligurian alps

comment on coccolith sr ca records of productivity during the paleocene eocene thermal maximum from the weddell sea by heather m stoll and santo bains

glacial ice composition a potential long term record of the chemistry of atmospheric deposition wind river range wyoming during a reconnaissance study ice samples were collected from knife point glacier to determine if glaciers in the wind river range could provide a long term record of the chemical composition of wet deposition eight annual ice layers comprising the years 1980 1987 were identified the concentration of calcium chloride and sulfate in the annual weighted wet deposition samples collected at the national atmospheric deposition program nadp station near pinedale wyoming showed a significant positive correlation to the concentration of the same major ions in composite samples from the annual ice layers results of the study imply that continuous ice cores reaching to the deeper parts of glaciers in the wind river range could provide long term records of the chemical composition of wet deposition

stream dominated alluvial fan and lacustrine depositional systems in cenozoic strike slip basins denali fault system yukon territory canada ancient stream dominated wet alluvial fan deposits have received far less attention in the literature than their arid semi arid counterparts the cenozoic basin fills along the denali fault system of the northwestern canadian cordillera provide excellent examples of stream dominated alluvial fan deposits because they developed during the eocene oligocene temperate climatic regime in an active strike slip orogen the amphitheatre formation filled several strike slip basins in yukon territory and consists of up to 1200 m of coarse siliciclastic rocks and coal detailed facies analysis conglomerate sandstone percentages c s maximum particle size mps distribution and palaeocurrent analysis of the amphitheatre formation in two of these strike slip basins document the transition from proximal to middle to distal and fringing environments within ancient stream dominated alluvial fan systems proximal fan deposits in the bates lake basin are characterized by disorganized clast supported boulder conglomerate and minor matrix mud supported conglomerate proximal facies are located along the faulted basin margins in areas where c s 80 to 100 and where the average mps ranges from 30 to 60 cm proximal fan deposits grade into middle fan channelized well organized cobble conglomerates that form upward fining sequences with an average thickness of 7 m middle fan deposits grade basinward into well sorted laterally continuous beds of normally graded sandstone interbedded with trough cross stratified sandstone these distal fan deposits are characteristic of areas where c s 20 to 40 and where the average mps ranges from 5 to 15 cm fan fringe deposits consist of lacustrine and axial fluvial facies palaeogeographic reconstruction of the bates lake basin indicates that alluvial fan sedimentation was concentrated in three parts of the basin the largest alluvial fan system abutted the strike slip duke river fault and prograded westward across the axis of the basin two smaller coarser grained fans prograded syntaxially northward from the normal faulted southern basin margin facies analysis of the burwash basin indicates a similar transition from proximal to distal stream dominated alluvial fan environments but with several key differences middle fan deposits in the burwash basin define upward coarsening sequences 50 to 60 m thick composed of fine grained lithofacies and coal in the lower part trough cross stratified sandstone in the middle and conglomerate in the upper part of the sequence upward coarsening sequences 90 140 m thick also are common in the fan fringe lacustrine deposits these sequences coarsen upward from mudstone through fine grained ripple laminated sandstone to coarse grained trough cross stratified sandstone the upward coarsening sequences are basinwide facies independent and probably represent progradation of stream dominated alluvial fan depositional systems coal distribution in the amphitheatre formation is closely coupled with predominant depositional processes on stream dominated alluvial fans the thickest coal seams occur in the most proximal part of the basin fill and in marginal lacustrine deposits coal development in the intervening middle and distal fan areas was suppressed by the high frequency of unconfined flow events and lateral channel mobility

distortion of carbon isotope excursion in bulk soil organic matter during the paleocene eocene thermal maximum the paleocene eocene thermal maximum was a period of abrupt transient global warming fueled by a large release of 13c depleted carbon and marked globally by a negative carbon isotope excursion while the carbon isotope excursion is often identified in the carbon isotope ratios of bulk soil organic matter 13corg these records can be biased by factors associated with production degradation and sources of sedimentary carbon input to better understand these factors we compared 13corg values from paleocene eocene thermal maximum rocks in the southeastern bighorn basin wyoming with those derived from leaf wax n alkanes 13c n alk while both 13c n alk and 13corg records indicate an abrupt negative shift in 13c values the carbon isotope excursions observed in bulk organic matter are smaller in magnitude and shorter in duration than those in n alkanes to explore these discrepancies we modeled predicted total plant tissue carbon isotope 13ctt curves from the 13c n alk record using enrichment factors determined in modern c3 plants measured 13corg values are enriched in 13c relative to predicted 13ctt with greater enrichment during the paleocene eocene thermal maximum than before or after the greater 13c enrichment could reflect increased degradation of autochthonous organic matter increased input of allochthonous fossil carbon enriched in 13c or both by comparing samples from organic rich and organic poor depositional environments we infer that microbial degradation rates doubled during the paleocene eocene thermal maximum and we calculate that fossil carbon input increased 28 63 this approach to untangling the controls on the isotopic composition of bulk soil carbon is an important development that will inform not only future studies of global carbon cycle dynamics during the paleocene eocene thermal maximum hyperthermal event but also any study that seeks to correlate or estimate duration and magnitude of past events using soil organic carbon

sedimentology facies architecture and chemostratigraphy of a continental high latitude paleocene eocene succession the chickaloon formation alaska abstract the paleocene eocene chickaloon formation of southern alaska represents rapid deposition in a floodbasin setting contains abundant and diverse fossil plant material and spans the paleocene eocene thermal maximum petm sedimentologic lithofacies and chemostratigraphic analyses of exposures of the chickaloon formation were conducted in order to provide a contextual framework for this late paleocene early eocene high latitude sedimentary succession and to test if hyperthermal conditions are recorded in the unit at the main study area in the evan jones coal mine strata represent an alluvial sequence dominated by floodplain channel sandstone crevasse lobe crevasse channel and mire deposition floodplain environments are represented by medium gray commonly nodular and or carbonate cemented shaly siltstone and centimeter scale thick sheet sandstone interbeds most channel sandstone deposits are interpreted to be crevasse channels and are generally small 2 5 m thick rarely coarser than medium grained sandstone and sand grains are commonly coated with fe oxides carbonaceous shale and coal are localized and indicate a high rate of organic carbon accumulation in the area 13c analyses of bulk organic carbon from the succession at the evan jones mine are internally consistent with this interpretation they yield uniformly negative values that are typical of continental organic matter 21 7 to 28 5 x 25 4 fossil plant material is also very common and includes leaves wood seeds and resins from broad leaf angiosperms conifers ferns and sphenopsids considered together lithologic and paleontologic data suggest that these strata represent a floodbasin environment the observed crevasse channels probably originate from a main channel located within several kilometers of the depocenter ash fall tuffs punctuate the studied sequence and contain abundant reworked or recycled zircons indicating that the depocenter was proximal to a volcanic source across all of these chickaloon depositional environments a significant negative isotopic shift 5 8 occurs which we hypothesize to represent a short lived perturbation associated with a global hyperthermal event