a new method for evaluating loess collapsibility and its application abstract collapsibility affects loess engineering stability currently there are two methods used to determine the collapsibility of loess the traditional indoor collapsibility test indoor test method and the field immersion test field test method however for the same loess site the collapse values under overburden pressure obtained by the two methods are quite different for sites that cannot be tested in situ it is easy to misjudge the collapsibility of the loess foundation when depending only on indoor test results to improve the accuracy of the indoor collapsibility determination the characteristics of the compression curves obtained from confined compression tests at six different loess sites are analyzed in this paper the compression curves of loess under different states are normalized and described by the composite power exponential model the collapsibility of loess is closely related to its structure a new method for analyzing and evaluating the collapsibility of loess is proposed the method combines the relationship between the compression characteristics and initial structural properties of loess and the relationship between the initial structural properties and physical comprehensive indexes to verify the applicability and accuracy of the new method the collapse values under overburden pressure of two test sites along the xi an metro line 5 were calculated using the physical indexes of loess at different depths and compared with the values calculated from the indoor test and field measured values the results show that the calculated value of the new method is closer to the measured value of the field test than is the calculated value of the indoor test and the new method can correctly determine the collapsibility type and grade of the site the new method provides a simple and feasible means by which to correctly and quickly evaluate site collapsibility in loess engineering which is beneficial for conducting loess site collapsibility evaluations under full operation to develop and implement the measures of foundation treatment in loess areas the method can be used as a reference at loess sites where field tests cannot be performed

reevaluation of the oxygen isotopic composition of planktonic foraminifera experimental results and revised paleotemperature equations cultured planktonic foraminifera orbulina universa symbiotic and globigerina bulloides nonsymbiotic are used to reexamine temperature 18o relationships at 15 25 c relationships for both species can be described by linear equations equations for o universa grown under low light ll and high light hl share a slope of 4 80 0 21 c 1 with a hl ll offset of 0 33 due to symbiont photosynthetic activity the effect of co32 on o universa is 0 002 mol 1 kg 1 and is insensitive to temperature for g bulloides ontogenetic effects produce size related trends in temperature 18o whereby larger shells are enriched in 18o relative to smaller specimens the o universa temperature 18o relationships are more accurate than previously published equations for describing plankton tow data our equations do not explain planktonic core top data with the same precision but provide a good fit to benthic cibicidoides data below 10 c temperature 18o relationships for g bulloides provide good agreement with field data for this species from the northeast pacific

phanerozoic atmospheric co2 change evaluating geochemical and paleobiological approaches abstract the theory and use of geochemical modeling of the long term carbon cycle and four paleo pco 2 proxies are reviewed and discussed in order to discern the best applications for each method geochemical models provide pco 2 predictions for the entire phanerozoic but most existing models present 5 10 m y means and so often do not resolve short term excursions error estimates based on sensitivity analyses range from 75 200 ppmv for the tertiary to as much as 3000 ppmv during the early paleozoic the 13 c of pedogenic carbonates provide the best proxy based pco 2 estimates for the pre tertiary with error estimates ranging from 500 1000 ppmv pre devonian estimates should be treated cautiously error estimates for tertiary reconstructions via this proxy are higher than other proxies and models 400 500 ppmv and should not be solely relied upon we also show the importance of measuring the 13 c of coexisting organic matter instead of inferring its value from marine carbonates the 13 c of the organic remains of phytoplankton from sediment cores provide high temporal resolution up to 10 3 10 4 year high precision 25 100 ppmv for the tertiary to 150 200 ppmv for the cretaceous pco 2 estimates that can be near continuous for most of the tertiary its high temporal resolution and availability of continuous sequences is advantageous for studies aiming to discern short term excursions this method however must correct for changes in growth rate and oxygen level at elevated pco 2 750 1250 ppmv this proxy loses its sensitivity and is not useful the stomatal density and stomatal index of land plants also provide high temporal resolution 2 year high precision 10 40 ppmv for the tertiary and possibly cretaceous pco 2 estimates and so also is ideal for discerning short term excursions unfortunately this proxy also loses sensitivity at some level of pco 2 above 350 ppmv which currently is largely undetermined our analysis of the recently developed 11 b technique shows that it currently is not yet well constrained most importantly it requires the assumption that the boron isotopic composition of the ocean remains nearly constant through time in addition it assumes that there are no biological or temperature effects and that diagenetic alteration of the boron isotopic composition does not occur a fifth co 2 proxy based on the redox chemistry of marine cerium has several fundamental flaws and is not discussed in detail here

new oxygen isotope evidence for long term cretaceous climatic change in the southern hemisphere a new composite 18 o record generated from calcareous fine fraction and bulk sediments from the exmouth plateau details long term cretaceous climatic change at mid latitudes in the southern hemisphere assessment of new and previously published 18 o data indicates that a mid cretaceous global climatic optimum was achieved sometime between the time of the cenomanian turonian boundary and the middle turonian when surface ocean paleotemperatures were the highest of the past 115 m y periods of cooling and warming that reversed the general patterns were superimposed on long term aptian turonian warming and turonian maastrichtian cooling trends respectively extrapolation of southern hemisphere paleotemperature trends to maastrichtian paleotemperature data from a low latitude pacific guyot implies that maximum mid cretaceous low latitude paleotemperatures could have been in excess of 33 c

equable climates during earth history eocene and cretaceous climate model experiments demonstrate that regardless of conditions of warm polar oceans differences in pole to equator surface temperature gradient or topography above freezing surface temperatures in winter for continental interiors at middle to high latitudes cannot be maintained continental interiors will have cold winter temperatures even during globally warm periods unless currently unrecognized forcing factors influenced past climates if model simulations of eocene and cretaceous climates are accurate the term equable as it applies to paleoclimate should be reconsidered

high temperature environments of human evolution in east africa based on bond ordering in paleosol carbonates many important hominid bearing fossil localities in east africa are in regions that are extremely hot and dry although humans are well adapted to such conditions it has been inferred that east african environments were cooler or more wooded during the pliocene and pleistocene when this region was a central stage of human evolution here we show that the turkana basin kenya today one of the hottest places on earth has been continually hot during the past 4 million years the distribution of 13c 18o bonds in paleosol carbonates indicates that soil temperatures during periods of carbonate formation were typically above 30 c and often in excess of 35 c similar soil temperatures are observed today in the turkana basin and reflect high air temperatures combined with solar heating of the soil surface these results are specific to periods of soil carbonate formation and we suggest that such periods composed a large fraction of integrated time in the turkana basin if correct this interpretation has implications for human thermophysiology and implies a long standing human association with marginal environments

effect of diagenesis on the sr o and c isotope composition of late cretaceous mollusks from the western interior seaway of north america evaluating the effects of diagenesis on the isotopic compositions of sr o and c in marine carbonates is critical to their use as proxies in reconstructing information on the salinity temperature and dissolved inorganic carbon of ancient oceans we have analyzed a series of samples of mollusk shells from the baculites compressus zone late campanian of the pierre shale of south dakota samples included outer shell material and septa of cephalopods collected inside and outside concretions preservation was evaluated using light microscopy scanning electron microscopy sem trace element analysis and x ray diffraction all of the material consists of aragonite based on x ray diffraction an sem preservation index pi was established based on comparison of the microstructure of the fossil material with that of modern nautilus excellent preservation pi 5 was characterized by well defined nacreous plates with discrete angular boundaries in contrast samples showing fused nacreous plates with indistinct boundaries were rated poor pi 1 87sr 86sr ratios vary with preservation and average 0 707648 000021 n 10 for excellent preservation pi 5 0 707615 000028 n 5 for good preservation pi 3 0 707404 000074 n 7 for fair preservation pi 2 and 0 707261 000053 n 8 for poor preservation pi 1 these data suggest that as the quality of the preservation declines the mean 87sr 86sr ratio decreases and the standard error of the mean increases oxygen and carbon isotope analyses of the same specimens also show decreases with preservation and 18o 13c and 87sr 86sr are well correlated suggesting that these tracers are all altered as the pi decreases the sr ca ratio increases as preservation decreases indicating that sr is added to the shell material during diagenesis in contrast mg ca shows no trend with preservation if the increasing sr concentration and decreasing 87sr 86sr of the shell material with decreasing preservation represents the addition of sr to the shell during diagenesis we calculate that the added sr had 87sr 86sr ranging from 0 707582 to 0 707032 potential sources of the added sr include older marine carbonates and weathering of volcanic ash layers present in the shale the mechanisms of alteration likely include epitaxial growth of strontianite on the original shell aragonite and isotopic exchange of c and o between alteration fluids and shell carbonate we conclude that sem preservation criteria are effective in screening shell material that records original isotopic values and that variations in sr o and c isotope composition in well preserved material can be used to assess paleoenvironmental parameters such as salinity and temperature our results also indicate that assessing preservation is a critical prerequisite to the determination of numerical ages of shell material using strontium isotope stratigraphy

stratification and paleocirculation of the late cretaceous western interior seaway of north america paleotemperature and salinity profiles for the western interior seaway are reconstructed by use of oxygen and carbon isotopic signatures of shell material data have been gathered on different groups of molluscs distributed in three distinct habitat types infaunal benthonic epifaunal benthonic and nektonic isotopic variations and inferred environmental tolerances of the organisms were used to determine upper and lower temperature boundaries for each habitat group and therefore water depth zones water density for each temperature salinity combination within a habitat range was calculated and used to develop a physically stable stratification model the results clearly show that the water column consisted of denser more saline warm bottom layers that were overlain by and decoupled from cooler less saline intermediate layers it is proposed that this profile originated due to a surface current transporting runoff water from the western highlands toward the eastern shallow border of the seaway where evaporation and heating of surface water in a warm humid atmosphere caused increased density and sinking followed by westward return flow of the warm saline bottom water this model is compatible with known climatic and oceanographic information for the cretaceous

13c 18o isotope signatures and clumped isotope thermometry in foraminifera and coccoliths accurate constraints on past ocean temperatures and compositions are critical for documenting climate change and resolving its causes most proxies for temperature are not thermodynamically based appear to be subject to biological processes require regional calibrations and or are influenced by fluid composition as a result their interpretation becomes uncertain when they are applied in settings not necessarily resembling those in which they were empirically calibrated independent proxies for past temperature could provide an important means of testing and or expanding on existing reconstructions here we report measurements of abundances of stable isotopologues of calcitic and aragonitic benthic and planktic foraminifera and coccoliths relate those abundances to independently estimated growth temperatures and discuss the possible scope of equilibrium and kinetic isotope effects the proportions of 13c 18o bonds in these samples exhibits a temperature dependence that is generally similar to that previously been reported for inorganic calcite and other biologically precipitated carbonate containing minerals apatite from fish reptile and mammal teeth calcitic brachiopods and molluscs aragonitic coral and mollusks most species that exhibit non equilibrium 18o 16o 18o and 13c 12c 13c ratios are characterized by 13c 18o bond abundances that are similar to inorganic calcite and are generally indistinguishable from apparent equilibrium with possible exceptions among benthic foraminiferal samples from the arctic ocean where temperatures are near freezing observed isotope ratios in biogenic carbonates can be explained if carbonate minerals generally preserve a state of ordering that reflects the extent of isotopic equilibration of the dissolved inorganic carbon species

influence of physical properties on deformation characteristics of collapsible soils abstract the paper introduces structural pressure values as separation points between elastic and plastic states of any soil including collapsible soils subjected to loading collapsibility of soils is identified as a non elastic deformation the collapse of soils starts when the applied stress exceeds soil structural pressure values initial collapse pressures according to some official documents which depend on change of some soil physical property ies new analytical expressions describing dependence of mechanical characteristics of collapsible soils on soil void ratios and moisture contents are proposed the obtained equations were verified by published test results the algebraic structure of previously obtained empirical expressions between mechanical characteristics of collapsible soils and their physical properties is similar to the structure of theoretically derived equations

late cretaceous sea level from a paleoshoreline the contemporary elevation of an ancient strandline provides a measure of eustasy at a single time in the geologic past if the elevation of a paleoshoreline has not changed since deposition or if it has changed by a known amount then the measured or corrected elevation equals the sea level at that time the ideal location for measuring an ancient sea level is a paleoshoreline deposited high on the shoulder of a stable craton where postdepositional elevation changes through tectonic movement lithospheric compensation to loads and sediment compaction are minimized the contemporary elevation of a late cenomanian 93 ma shoreline was determined at five localities along the tectonically stable eastern margin of the cretaceous western interior seaway north america this shoreline represented by marine to nonmarine facies transitions in strata of the greenhorn sequence uza 2 cycle of haq et al 1987 was identified from outcrop and borehole data biostratigraphic zonations constrained the geologic age at each locality sequence stratigraphic correlations based on identifying discrete progradational units and the surfaces that separate them were used to refine age correlations to better than 100 kyr between localities a single cenomanian shoreline was correlated within a single progradational unit and its elevation was determined at five localities this paleostrandline occurs 265 286 m above present day sea level at an average elevation of 276 m isostatic and flexural corrections were applied to remove the effects of postdepositional vertical movement including sediment compaction by loading uplift due to erosion and glacial loading and rebound errors inherent in each measurement and each correction were estimated corrections and their cumulative error estimates yield a late cenomanian elevation of 269 87 m above present sea level the corrected elevation approximates sea level at 93 ma and provides a measure of late cenomanian eustasy prior to the early turonian highstand establishing the absolute value for eustasy at a single point in geologic time provides a frame of reference for calibrating relative sea level curves as well as constraining the magnitudes of tectonic subsidence sediment flux and othervariables that controlled water depth and relative sea level

a new regime of volcanic eruption due to the relative motion between liquid and gas abstract in explosive magma eruptions magma ascends through a conduit as a poiseuille flow at depth and gas exsolves gradually and expands as the pressure decreases bubbly flow regime when the volume fraction of gas becomes sufficiently large liquid or solid parts of magma fragment into droplets or ashes and the flow dynamics becomes governed by the gas phase gas ash flow regime we propose a new flow regime which we call fractured turbulent flow regime between the bubbly flow regime and the gas ash flow regime in the new regime both liquid magma and gas are continuous phases the high connectivity of the two phases allows the relative velocity between them to increase significantly we present one sample calculation which displays basically explosive characteristics but has three features distinct from previous models the explosive characteristics are manifested as the fragmentation of the magma and the high speed jet that issues from the vent the first distinct feature is a nearly lithostatic pressure distribution which results from the increase of the height of the fragmentation surface the second one is the atmospheric pressure at the vent the flow is not choked the third one is that the relative velocity between the gas and the ash is large at the vent despite the large interaction force between the two phases the large relative velocity is established in the fractured turbulent regime and is maintained in the subsequent gas ash flow regime

carbon oxygen and strontium isotopes in paleozoic carbonate components an evaluation of original seawater chemistry proxies abstract brachiopods trilobites cements and whole rock matrix material were evaluated for their reliability as proxies of original seawater carbon oxygen and strontium isotope chemistry in this process coeval material was evaluated from individual horizons of formations spanning the permian to cambrian unaltered shells of low mg calcite articulated brachiopods retain original seawater oxygen carbon and strontium isotope compositions as old as late ordovician assessments of older specimens are hampered by a lack of suitable material coeval brachiopod whole rock sets a definitive assessment of cement marine chemistry is difficult due to the paucity of material but despite this caveat cements hold some promise for retaining original carbon and possibly strontium isotope seawater values in contrast the potential of whole rock material as a proxy of original seawater chemistry is quite complex in some but not all instances the carbon isotopic composition of whole rock after detailed scrutiny and evaluation appears to represent an original seawater chemistry signal in a few instances their oxygen isotope compositions reflect original seawater values unlike the stable isotope compositions the strontium isotopes of all studied whole rock material permian to upper cambrian appear not to reflect original seawater chemistry values thus the potential for retaining original seawater isotope chemistry and serving as specific proxies in order of decreasing reliability are 1 unaltered low mg calcite brachiopods c o and sr isotopes 2 pristine marine cements c and sr isotopes and 3 whole rock material c isotopes carbon oxygen and strontium isotope compositions of ordovician trilobites mirror those of coeval unaltered brachiopods cambrian trilobites hold significant promise as an important proxy of original seawater isotope chemistry but further studies are needed to ascertain their full potential the survey of isotopes in some ordovician and cambrian intermediate low mg calcite trilobites demonstrates their potential as an important proxy of original seawater chemistry

numerical climate modeling a frontier in petroleum source rock prediction results based on cretaceous simulations organic productivity and preservation are primary controls of the distribution of petroleum source beds both organic productivity and preservation are in part a function of geographic setting and climate therefore the prediction of paleoclimates is a major frontier in petroleum source rock prediction a climate model based on the fundamental laws thought to govern atmospheric circulation is applied here to the prediction of upwelling regions associated with very high productivity and bottom conditions that may become anoxic despite a high oxygen supply the potential and limitations of climate modeling in the prediction of upwelling regions are examined by 1 demonstrating the ability of the model to predict present day winds and upwelling regions 2 demonstrating t at the model and the location of upwelling regions is sensitive to geography continental positions sea level and topography and 3 investigating whether the model sensitivity to past geographies is realistic i e if predicted upwelling regions for the cretaceous period correspond to source rock localities the model predictions of ocean and coastal upwelling compare very favorably with present day observations and with estimates of primary productivity the location of middle latitude and high latitude upwelling locations are sensitive to model specified geography the location of low latitude upwelling is less sensitive to changes in global geography if coastlines are oriented appropriately despite some limitations a comparison of source rock localities with model predictions is promising the results of these studies suggest that numerical climate modeling is a potential tool in petroleum source rock prediction

middle late cretaceous climate of the southern high latitudes stable isotopic evidence for minimal equator to pole thermal gradients a detailed 18 o and 13 c stratigraphy has been generated from analysis of well preserved albian early maastrichtian foraminifera from deep sea drilling project dsdp sites 511 and 327 falkland plateau 58 s 62 s paleolatitude in the southern south atlantic and cenomanian and coniacian santonian foraminifera from dsdp site 258 naturaliste plateau 58 s paleolatitude in the southern indian ocean these results when combined with previously published maastrichtian stable isotope data from ocean drilling program odp site 690 weddell sea 65 s paleolatitude provide new insight into the climatic and oceanographic history of the southern high latitudes during middle late cretaceous time the planktonic foraminifer 18 o curves reveal a gradual warming of surface waters from the albian through the cenomanian followed by extremely warm surface waters from the turonian through the early campanian long term cooling of surface waters began in the late early campanian and continued through the end of the maastrichtian the benthic foraminifer 18 o record generally parallels changes in the oxygen isotopic curves defined by shallow dwelling planktonic foraminifera the vertical oxygen and carbon isotopic gradients were relatively low during the albian cenomanian high from the turonian early campanian and then low during the late campanian and maastrichtian foraminiferal oxygen isotopic data from published sources and this study are averaged for each site corrected for latitudinal changes in salinity based on modern day surface water values and plotted versus paleolatitude for the late albian coniacian santonian and late maastrichtian differences between lowand high latitude surface water paleotemperatures are estimated at 14 c during the late albian and late maastrichtian but the coniacian santonian reconstruction reveals only a 0 4 c latitudinal temperature gradient uncertainty regarding cretaceous salinity gradients and possible diagenetic alteration of 18 o values introduce error into our estimates of paleolatitudinal thermal gradients however apparent low equator to pole temperature differences could indicate much higher poleward heat transport than at present

tectonic controls on the genesis and distribution of late cretaceous western interior basin hydrocarbon seep mounds tepee buttes of north america abstract within the western interior basin of north america hundreds of small carbonate mounds associated with late cretaceous hydrocarbon emissions or seeps form the most extensively distributed occurrence of fossil seep mounds that is known the tepee buttes analysis of the stratigraphic literature for the basin reveals that tepee butte formation occurred intermittently over a 10 m yr period within a narrowly restricted paleogeographic region the modern geographic distribution of the tepee buttes is constrained roughly to between 101 30 documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 normalfont selectfont declaretextfontcommand textcyr cyr pagestyle empt

carbon and oxygen isotopic disequilibria of recent deep sea benthic foraminifera abstract the carbon and oxygen isotopic compositions of 149 samples of benthic foraminifera from deep sea core tops indicate that none of the nine species studied secrete calcium carbonate in isotopic equilibrium with ambient bottom water uvigerina pyrgo murrhina and oridorsalis tener are the closest to 18o equilibrium with average deviations about 0 4 while planulina wuellerstorfi and p murrhina are the closest to 13c equilibrium with average deviations about 1 p wuellerstorfi shows the most systematic relationship between 13c and bottom water apparent oxygen utilization the intraspecific variabilities in 18o and 13c suggest that estimates of bottom water paleotemperatures can be made to a precision of 0 7 c while estimates of past apparent oxygen utilization aou can be made to 35 mol kg based on intraspecific comparisons of the recent samples with fossils no temporal changes in the degree of either 18o or 13c disequilibrium have been detected for planulina wuellerstorfi uvigerina oridorsalis tener and globocassidulina subglobosa

paleoceanography of the late cretaceous maastrichtian western interior seaway of north america evidence from sr and o isotopes abstract well preserved fossils of the late cretaceous western interior seaway wis of north america have been analyzed for sr concentration and sr and o isotopes in order to decipher paleosalinities and paleotemperatures the samples are from four biofacies within the seaway late maastrichtian offshore interior pierre shale nearshore interior fox hills formation brackish reduced salinity fox hills formation and freshwater hell creek formation samples were also obtained from the severn formation of maryland considered to be representative of the open ocean all biofacies except the freshwater are demonstrably within the jeletzkytes nebrascensis ammonite zone 87 sr 86 sr ratios show significant and systematic decreases from marine mean 1 s d 0 707839 0 000024 to brackish facies mean 1 s d 0 707677 0 000036 consistent with dilution by freshwater with a lower 87 sr 86 sr ratio than seawater such variation disallows using the 87 sr 86 sr ratios of fossil shell material to assign ages to fossils from the late cretaceous wis without knowledge of the salinity in which the organism grew the sr isotope ratios for scaphitid ammonites within a single biofacies are similar to each other and different from those for scaphites in other biofacies implying that these organisms are restricted in their distribution during life the 87 sr 86 sr values of freshwater unionid mussels range widely and are not compatible with the freshwater endmember 87 sr 86 sr ratio required by the trend in 87 sr 86 sr vs biofacies established from the other samples paleosalinities for the biofacies are estimated to range from 35 in the open marine to a minimum of 20 in the brackish based on the presence of cephalopods in all four facies and the known salinity tolerance of modern cephalopods producing reasonable 87 sr 86 sr values for the freshwater endmember of a 87 sr 86 sr vs 1 sr plot requires a sr concentration 0 2 0 5 that of seawater for the dominant freshwater input to the wis such high sr concentrations relative to seawater are not observed in modern rivers and we suggest that the brackish environment in the wis arose through the mixing of freshwater and seawater in a nearshore aquifer system reactions of the solution with aquifer solids in this subterranean estuary moore mar chem 65 1999 111 125 produced brackish water with the sr concentration and isotopic composition recorded in the brackish biofacies 18 o values of the fossils show decreases from the marine to brackish biofacies consistent with increasing temperatures from 13 to 23 c or if temperatures were relatively constant to a decrease in the 18 o of the water in which the shell formed the latter interpretation is consistent with less than fully marine salinities in the nearshore biofacies but both changes in temperature and the isotopic composition of the water may have occurred in this environment

variability in late cretaceous climate and deep waters evidence from stable isotopes abstract strong climatic and temperature fluctuations mark the late campanian and maastrichtian as indicated by stable isotope records from the equatorial pacific site 463 and middle and high latitude south atlantic sites 525 689 and 690 the first major global cooling decreased intermediate water temperatures iwt by 5 6 c between 73 70 ma at the same time sea surface temperature sst decreased by 4 5 c in middle and high latitudes intermediate waters iw temporarily warmed by 2 c in low and middle latitudes between 70 68 5 ma global cooling resumed between 68 5 65 5 ma when iwt decreased by 3 4 c and sst by 5 c in middle latitudes about 450 ka before the cretaceous tertiary boundary rapid global warming increased iwt and sst by 3 4 c though sst in the tropics changed little during the last 200 ka of the maastrichtian climate cooled rapidly with iwt and sst decreasing by 2 3 c during the global cooling at 71 70 ma and possibly at 67 65 5 ma the sources of cold intermediate waters in the equatorial pacific indo pacific and south atlantic were derived from the high latitude north pacific in contrast during the global climate warming between 65 2 65 4 ma the middle latitude south atlantic was closest to the source of iw production and implies that the low latitude tethys played a major role in global climate change climate changes sea level fluctuations and associated restricted seaways appear to be the most likely mechanisms for the alternating sources of iw production

a simulation of mid cretaceous climate a series of general circulation model experiments utilizing genesis have been completed for the mid cretaceous based on geography variable atmospheric carbon dioxide concentrations 2 to 6 times present day concentrations and variable poleward oceanic heat flux 6 to 1 2 1015 w increased from present day by combining all three major variables co2 geography and oceanic heat flux the distribution of mid cretaceous temperatures can be achieved in the simulations increased co2 is required to promote global warmth and increased oceanic heat flux is required to prevent the tropics from overheating with higher levels of co2 four times present day co2 with 1 2 1015 w provided the best match to the distribution of mid cretaceous data the best match to the cretaceous observations was achieved with a globally averaged surface temperature increase of 6 2 c at the lower end of past estimates of mid cretaceous warmth this value may be a better estimate of mid cretaceous global warming finally the model experiments can be used to provide a paleocalibration of the global warming expected for a doubling of atmospheric carbon dioxide the best estimates for the mid cretaceous appear to be a 2 5 to 4 0 c sensitivity in the mid to upper range of the sensitivity of current climate models used to assess future global change

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

the long lived mollusc arctica islandica a new paleoceanographic tool for the reconstruction of bottom temperatures for the continental shelves of the northern north atlantic ocean the carbonate shell of the bivalve arctica islandica has been recognized for more than a decade as a potentially important marine geochemical biorecorder owing to this species great longevity 200 years and wide geographic distribution throughout the northern north atlantic ocean a region vital to global climate and ocean circulation however until now this potential has not been realized owing to the difficulty of precisely sampling the shell of this slow growing species using newly available automated microsampling techniques combined with micromass stable isotope mass spectrometry a stable oxygen isotope record 1956 1957 and 1961 1970 has been obtained from a live captured 38 year old a islandica specimen collected near the former position of the nantucket shoals lightship 41 n 69 w the shell s 18o signal is compared with an expected signal derived from ambient bottom temperature and salinity data recorded at the lightship for the same period the results show that a islandica s 18o record 1 is in phase with its growth banding confirming the annual periodicity of this species growth bands 2 is in oxygen isotopic equilibrium with the ambient seawater 3 shows a consistent shell growth shutdown temperature of 6 c which translates into an 8 month may december shell growth period at this location and 4 records the ambient bottom temperature with a precision of 1 2 c these results add important information on the life history of this commercially important shellfish species and demonstrate that a islandica shells can be used to reconstruct inter and intra annual records of the continental shelf bottom temperature

physical and mechanical properties of loess discharged from the yellow river into the bohai sea china abstract chinese loess is unique in having great scientific value whilst also playing an important role in societal development large volumes of loess are continually carried by the yellow river from the chinese loess plateau to the bohai sea northeast china forming the yellow river delta the physical and mechanical properties of this loess vary during transportation and these characteristics have been investigated in detail using several samples of estuarine loess collected from tidal flats with different depositional ages the wet densities natural moisture contents specific gravities atterberg limits grain size distributions microstructures and mineral compositions of these samples have been determined our results show that the estuarine loess is classified as silty loess and that its specific gravity plasticity and grain size characteristics were very similar to land derived loess its unit weight and water content increasd during discharge into the sea and its plastic index decreased the estuarine loess also had fewer large pores that were more closely connected than those in land loess as a result of these changes in index properties and pore water chemistry estuarine loess is less susceptible to liquefaction than land derived loess in addition these physical and mechanical properties show strong correlations to the long term depositional history of the delta with older deposits typically having a lower dry density and higher void ratio than younger deposits the results of this study have implications for hazard mitigation and improving our understanding of the mechanisms responsible for loess related geological disasters

study of the 1920 haiyuan earthquake induced landslides in loess china many large scale landslides induced by earthquakes have been reported in loess soils they often cause catastrophes because they travel long distances at high velocity to clarify the mechanism of these landslides field survey was performed on the landslides triggered by the haiyuan earthquake china 1920 and a series of ring shear tests was conducted on the loess soils collected from a landslide the field surveys revealed that most of the loess landslides triggered by the haiyuan earthquake occurred on concave slopes gentler than 15 with long runout distance showing very small equivalent friction angle cyclic ring shear tests on saturated specimens in the undrained condition showed that when cyclic shear stress was applied to a loose loess specimen pore pressure was built up gradually before the failure and after that large pore pressure was quickly generated due to the failure of loess soil structure meanwhile to investigate the mechanism that produces the high mobility of loess landslides ring shear tests were conducted on loess specimens with large shear displacement of up to several meters under the undrained condition and it was found that the initial normal stress has no effects and overconsolidation ratio has little if any effects on the apparent friction angle in the steady state for loess soils results of tests on soils at different saturation degrees revealed that the reduction in shear strength results more likely from the generation of pore water pressure not of pore air pressure

clumped isotope geochemistry the study of naturally occurring multiply substituted isotopologues clumped isotope geochemistry is concerned with the state of ordering of rare isotopes in natural materials that is it examines the extent to which rare isotopes d 13 c 15 n 18 o etc bond with or near each other rather than with the sea of light isotopes in which they swim abundances of isotopic clumps in natural materials are influenced by a wide variety of factors in most cases their concentrations approach within ca 1 relative the amount expected for a random distribution of isotopes deviations from this stochastic distribution result from enhanced thermodynamic stability of heavy isotope clumps slower kinetics of reactions requiring the breakage of bonds between heavy isotopes the mass dependence of diffusive and thermo gravitational fractionations mixing between components that differ from one another in bulk isotopic composition biochemical and photochemical fractionations that may reflect combinations of these simpler physical mechanisms and in some cases other processes we do not yet understand although clumped isotope geochemistry is a young field several seemingly promising applications have already emerged most importantly it appears that proportions of 13 c 18 o bonds in carbonate minerals are sensitive to their growth temperatures independent of bulk isotopic composition thus clumped isotope analysis of ancient carbonates can be used as a quantitative paleothermometer that requires no assumptions about the 18 o of waters from which carbonates grew this approach has been used to reconstruct marine temperatures across the phanerozoic reaching back to the silurian terrestrial ground temperatures across the cenozoic thermal histories of aqueously altered meteorites among other applications clumped isotope geochemistry is also placing new constraints on the atmospheric budget and stratospheric photochemistry of co 2 and should be capable of placing analogous new constraints on the budgets of other atmospheric gases finally this field could be extended to encompass sulfates volatile hydrocarbons organic moieties and other materials

new quantitative palaeocolimate data for the late cretaceous arctic evidence for a warm polar ocean abstract physiognomic analysis of four taphofloras one from the coniacian of n alaska one from the coniacian of kamchatka one from the turonian of kamchatka and one from the turonian of novaya sibir island using the clamp technique of wolfe 1993 yielded quantitative data on the mean annual warm month mean and cold month mean temperatures the length of the growing season mean annual precipitation mean growing season precipitation mean monthly growing season precipitation and the precipitation during the three consecutive driest months these new results represent the first application of multivariate statistical analysis of foliar physiognomy to determine palaeoclimatic parameters clamp to arctic cretaceous floras and demonstrate its robustness even in the context of vegetation which has no living analogues these new estimates were comparable to those from previous quantitative or qualitative sedimentological or palaeobotanical data where they were available but offer greater measurable precision the results also suggest that an arctic ocean with a winter surface temperature of approximately 6 c maintained n alaska coastal temperatures above freezing locally reversing the equator to pole temperature gradient a phenomenon not seen in the northern proto pacific this anomalously warm arctic ocean could have been produced by marine poleward heat transport precipitation in alaska kamchatka and novaya sibir island was predicted to have been high e g 1760 mm yr in the coniacian of n alaska reflecting a very weak polar high pressure cell and substantially different precipitation patterns to present

oxygen isotope fluctuations in a modern north sea oyster crassostrea gigas compared with annual variations in seawater temperature implications for palaeoclimate studies abstract a total of 181 oxygen isotope values from sequential samples of the left shell of a modern pacific oyster crassostrea gigas that lived on a sub tidal oyster bank in the list basin north sea germany shows periodically varying values between 1 3 and 2 5 in order to test whether these 18 o fluctuations reflect seawater temperature changes the isotope values of the shell were compared to actual seawater temperature variations from the region c gigas serves as an excellent proxy for temperature of palaeoseawater and the results show that the examined oyster precipitated its shell in 18 o equilibrium with the ambient seawater a cessation of the oyster shell calcification starts at water temperatures below 6 c at lower temperatures than previously thought for crassostrea for palaeoclimate investigations the termination of shell production is important because the lowest temperatures might not be represented in the shell higher water temperatures are therefore potentially over represented in time spans when the shell grows faster and mean oxygen isotope values may potentially bias the mean seawater temperatures of annual variations towards higher temperatures

global budget of water isotopes inferred from polar ice sheets 1 water isotope ratios in ice cores and marine sediments are a key indicator of past temperature and global ice volume quantitative interpretation of these ratios requires understanding of the storage capacity and exchanges among the ocean atmosphere and cryosphere we combine numerical models of ice dynamics and tracer transport to predict bulk ice properties by simulating the fine layering of ice sheets locally validated at ice core sites the 18o 16o content of ice sheets is found to vary between the present and 20 kyr ago from 34 to 37 for greenland from 41 to 42 5 for west antarctica and always remained near 56 5 for east antarctica their combined effect on sea water 18o 16o is a 0 08 0 12 increase 20 kyr ago a 1 11 decrease if ice sheets were to vanish we confirm that ice volume changes in antarctica and greenland linearly affect ocean composition though at different rates

fossil crocodilians as indicators of late cretaceous and cenozoic climates implications for using palaeontological data in reconstructing palaeoclimate abstract that the earth s climate has cooled over the last 100 million years has been recognized since the early nineteenth century the transition from the hot house world of the cretaceous a time interval without significant polar icesheets to the ice house world in which we now live today the dynamics process responsible for this change are being examined using computer models especially general circulation models gcm s through such work our understanding of the dynamics of the earth system improves and our ability to predict future trends is enhanced but the success of modelling experiments can only be assessed by comparing results with observations the pattern which for palaeoclimate are drawn exclusively from the geological record palaeoclimate interpreted from geological data is invariably based on analogy with the recent the validity of which depends on corroboration from multiple lines of evidence this requires the compilation and investigation of large global datasets of well constrained geological climate proxies this study uses the palaeodistribution of fossil crocodilians to examine the spatial distribution of palaeoclimate during this transition fossil crocodilians have a relatively good fossil record and are climatically limited in the recent they also provide a manageable global dataset with which to investigate other issues that impinge on the use of geologic data for reconstructing palaeoclimate taphonomy sampling effects time averaging tectonics and for fossils palaeobiogeography and evolution as such this study provides a possible template for examining other climate proxies in order to validate and hone palaeoclimatic interpretations an analysis of modern crocodilians indicates that temperature is the principal influence on their global distribution with the coldest month mean temperature cmm of 5 5 c marking the minimum thermal limit for the group corresponding today to a minimum mean annual temperature mat of 14 2 c the duration of warmth during the year partly indicated by the mean annual range of temperature mart is also important as this affects early juvenile development and survival the presence of standing water provides an essential thermal buffer against temperature extremes by analogy the palaeodistribution of fossil crocodilians suggests the following during the late cretaceous and early palaeogene mat s in excess of 14 2 c cmm s 5 5 c permeated throughout mid latitudes and coastal regions in high latitudes during the oligocene the restriction of fossil crocodilians to low latitudes suggests high latitude cooling as indicated by numerous other lines of evidence coeval restriction of crocodilians to coastal regions in mid latitude north america and much of asia consistent with increased seasonality and aridification in continental interiors may reflect local orographic changes as well as global climate change during the miocene fossil crocodilians return to the great plains of north america but do not reoccupy the continental interior of asia by the pliocene crocodilians are again restricted to low latitudes and coastal regions in mid latitudes coincident with further high latitude cooling and aridification and cooling of mid latitude continental interiors minor distributional changes during the holocene may reflect human effects

paleoclimate reconstruction using carbonate clumped isotope thermometry carbonate clumped isotope thermometry is a relatively new paleotemperature proxy based on measurements of the degree of ordering of 13 c and 18 o into bonds with each other making the 13 c 18 o 16 o 2 2 ion group in lattices of carbonate minerals this technique has several unusual properties that complement existing methods of paleoclimate reconstruction most importantly it is based on a homogeneous isotope exchange equilibrium and thus constrains temperature independent of the isotopic composition of waters from which carbonates grew this method also appears to be generally insensitive to vital effects that compromise many other paleothermometers based on the chemical properties of biominerals or organic matter at least for those organisms that have been subjected to systematic study to date corals and foraminifera however discrepancies among some calibrations particularly at low temperatures may point toward the existence of vital effects in mollusks and other organisms this review discusses the principles and calibrations of the technique its uses in combination with conventional stable isotope measurements to constrain the 18 o of past waters preservation of paleotemperatures in ancient materials as well as current problems in our understanding of calibrations and interlaboratory data comparisons

deep sea paleotemperature record of extreme warmth during the cretaceous oxygen isotope analyses of well preserved foraminifera from blake nose 30 n paleolatitude north atlantic and globally distributed deep sea sites provide a long term paleotemperature record for the late albian maastrichtian interval that is difficult to reconcile with the existence of significant cretaceous ice sheets given reasonable assumptions about the isotopic composition of cretaceous seawater our results suggest that middle bathyal water temperatures at blake nose increased from 12 c in the late albian through middle cenomanian to a maximum of 20 c during the latest cenomanian and earliest turonian bottom waters were again 12 c during the middle campanian and cooled to a minimum of 9 c during the maastrichtian correlative middle bathyal foraminifera from other ocean basins yield paleotemperature estimates that are very similar to those from blake nose comparison of global bottom water temperatures and latitudinal thermal gradients suggests that global climate changed from a warm greenhouse state during the late albian through late cenomanian to a hot greenhouse phase during the latest cenomanian through early campanian then to cool greenhouse conditions during the mid campanian through maastrichtian

the general and congruent effects of structure in natural soils and weak rocks the engineering properties of naturally occurring sedimentary and residual deposits which are usually treated in geotechnical engineering as soils are reviewed and it is shown that usually they have characteristics due to bonded structure which are similar to those of porous weak rock while this structure can arise from many causes its effects follow a simple general pattern that involves stiff behaviour followed by yield this yield can be described in a similar way to that occurring due to overconsolidation although it is a separate phenomenon the effects of structure are as important in determining engineering behaviour as are the effects of initial porosity and stress history which are the basic concepts of soil mechanics as it can be described in a general way it is concluded that structure and its effects should be treated as a further basic concept of equal importance l article passe en revue les proprietes des depots sedimentaires et residuels naturels qui sont nor malement traites comm

quantifying kinetic fractionation in bunker cave speleothems using δ47 abstract isotopic signals in speleothems are used for investigating paleoclimate variability on land and are useful to constrain the dating of prominent climate events a quantitative use however is limited by an incomplete understanding of parameters contributing to the carbon and oxygen isotope signals these include external and environmental parameters such as 18 o of cave drip waters as well as internal parameters associated with speleothem formation such as the presence of non equilibrium effects and especially the magnitude of their isotopic shifts we explore the use of clumped isotopes as a new tool for investigating the kinetic isotope effect in speleothems holocene and modern speleothems from bunker cave germany as well as modern material from the adjacent dechen cave are all offset from the equilibrium relationship due to kinetic fractionation this kinetic offset in clumped isotopes is observed in a stalagmite despite mostly negative hendy tests providing a sensitive indicator for kinetic fractionation in cave carbonates the temperature dependence of the clumped isotope values 0 005 per c is low compared to the observed magnitude of kinetic offsets between 0 021 and 0 075 so that the mean offsets in apparent temperatures due to kinetic isotope effects are on the order of 10 c as a result clumped isotopes are useful in identifying temporal variations in the kinetic fractionation in a stalagmite when the temperatures during the speleothem growth period are either relatively constant variations the variations in the kinetic isotope fractionation in bunker cave are associated with changing drip water super saturation with periods of stronger prior calcite precipitation associated with lower kinetic offsets in the speleothem calcite in contrast stalagmite growth rates show no direct correlation with the degree of kinetic fractionation in the investigated range 13 1500 m a

sr c and o isotope geochemistry of ordovician brachiopods a major isotopic event around the middle late ordovician transition here we present sr c and o isotope curves for ordovician marine calcite based on analyses of 206 calcitic brachiopods from 10 localities worldwide these are the first ordovician wide isotope curves that can be placed within the newly emerging global biostratigraphic framework a total of 182 brachiopods were selected for c and o isotope analysis and 122 were selected for sr isotope analysis seawater 87sr 86sr decreased from 0 7090 to 0 7078 during the ordovician with a major quite rapid fall around the middle late ordovician transition most probably caused by a combination of low continental erosion rates and increased submarine hydrothermal exchange rates mean 18o values increase from 10 to 3 through the ordovician with an additional short lived increase of 2 to 3 during the latest ordovician due to glaciation although diagenetic alteration may have lowered 18o in some samples particularly those from the lower ordovician maximum 18o values which are less likely to be altered increase by more than 3 through the ordovician in both our data and literature data we consider that this long term rise in calcite 18o records the effect of decreasing tropical seawater temperatures across the middle late ordovician transition superimposed on seawater 18o that was steadily increasing from 3 standard mean ocean water smow by contrast 13c variation seems to have been relatively modest during most of the ordovician with the exception of the globally documented but short lived latest ordovician 13c excursion up to 7 nevertheless an underlying trend in mean 13c can be discerned changing from moderately negative values in the early ordovician to moderately positive values by the latest ordovician these new isotopic data confirm a major reorganization of ocean chemistry and the surface environment around 465 to 455 ma the juxtaposition of the greatest recorded swings in phanerozoic seawater 87sr 86sr and 18o at the same time as one of the largest marine transgressions in phanerozoic earth history suggests a causal link between tectonic and climatic change and emphasizes an endogenic control on the o isotope budget during the early paleozoic better isotopic and biostratigraphic constraints are still required if we are to understand the true significance of these changes we recommend that future work on ordovician isotope stratigraphy focus on this outstanding middle late ordovician event

evolution of early cenozoic marine temperatures the equator to high southern latitude sea surface and vertical temperature gradients are reconstructed from oxygen isotope values of planktonic and benthic foraminifers for the following five time intervals late paleocene early eocene early middle eocene late eocene and early oligocene paleotemperatures are calculated using standard oxygen isotope temperature equations with adjustments to account for 1 variations in sea water 18o related to changes in global ice volume over time and 2 latitudinal gradients in surface water 18o these reconstructions indicate that sea surface temperatures sst of the southern oceans in the early eocene were as high as 15 c whereas temperatures during the late paleocene and early middle eocene reached maximum levels of 10 12 c by the late eocene and early oligocene high latitude sst had declined to 6 and 4 c respectively for most of the early paleogene low latitude sub tropical temperatures remained constant and well within the range of holocene temperatures 24 ndash 25 c but by the late eocene and early oligocene declined to values in the range of 18 to 22 c the late paleogene apparent decline in tropical temperatures however might be artificial because of dissolution of near surface foraminifera tests which biased sediment assemblages toward deeper dwelling foraminifera moreover according to recent plate reconstructions it appears that the majority of sites upon which the late eocene and early oligocene tropical temperatures were previously established were located either in or near regions likely to have been influenced by upwelling global deepwater temperature on average paralleled southern ocean sst for most of the paleogene we speculate based on the overall timing and character of marine sea surface temperature variation during the paleogene that some combination of both higher levels of greenhouse gases and increased heat transport was responsible for the exceptional high latitude warmth of the early eocene

late cretaceous neogene trends in deep ocean temperature and continental ice volume reconciling records of benthic foraminiferal geochemistry δ18o and mg ca with sea level history 1 we reconstruct trends in ice volume and deep ocean temperature for the past 108 myr resolving variations on timescales of 2 myr and longer we use a sea level record as a proxy for ice volume a benthic foraminiferal mg cabf record as a proxy for temperature and a benthic foraminiferal 18obf record as a proxy for both this allows us to construct dual estimates of temperature and ice volume variations for the interval 10 60 ma extracting temperature from 18obf by using sea level as a proxy for ice volume to constrain the 18osw component and extracting seawater 18osw which reflects ice volume from 18obf by using mg cabf to constrain the temperature component each of these approaches requires numerous assumptions but the range of plausible solutions are concordant on timescales 2 myr and within an uncertainty of 2 c temperature and 0 4 18osw the agreement between the two approaches for the last 50 myr provides empirical justification for the use of 18obf mg cabf and sea level records as robust climate proxies our reconstructions indicate differences between deep ocean cooling and continental ice growth in the late cenozoic cooling occurred gradually in the middle late eocene and late miocene pliocene while ice growth occurred rapidly in the earliest oligocene middle miocene and plio pleistocene these differences are consistent with climate models that imply that temperatures set by the long term co2 equilibrium should change only gradually on timescales 2 myr but growth of continental ice sheets may be rapid in response to climate thresholds due to feedbacks that are not yet fully understood

stable isotope records from sepia officinalis a key to understanding the ecology of belemnites abstract the stable isotope ratios 1 8 o 1 3 c of the aragonite of cuttlebones of sepia officinalis were measured on a high resolution scale where every septum was measured our studies aim at understanding whether variations of the isotope signature are controlled by ontogenetic and or ecological factors five specimens were reared from eggs under known water temperatures a sixth specimen was caught in the german part of the north sea the data suggest that the oxygen isotope composition is in isotopic equilibrium with the surrounding seawater and reflects ambient temperature migration and seasonal temperature changes are visible in the acquired data set the carbon isotope signature shows signs of biofractionation and no direct correlation to the oxygen signature as far as ontogeny and ecology are concerned

early maastrichtian carbon cycle perturbation and cooling event implications from the south atlantic ocean published stable isotope records in marine carbonate are characterized by a positive 18o excursion associated with a negative 13c shift during the early maastrichtian however the cause and even the precise timing of these excursions remain uncertain we have generated high resolution foraminiferal stable isotope and grey scale records for the latest campanian to early maastrichtian 73 68 ma at two ocean drilling program sites 525 walvis ridge and 690 weddell sea we demonstrate that the negative 13c excursion is decoupled from the 18o increase with a lag of about 600 kyr our 13c records both planktic and benthic show an amplitude for the negative excursion of 0 7 that falls between about 72 1 and 70 7 ma our planktic 18o records indicate an overall increase of 1 2 from 73 to 68 ma at site 690 whereas at site 525 they record a slightly smaller increase 1 that peaks around 70 1 ma with decreasing values thereafter our benthic 18o data indicate an increase of 1 5 at site 525 and 0 7 at site 690 between about 71 4 and 69 9 ma benthic 18o values show different baseline values at the two sites before and after the excursion but the larger increase at site 525 means that the values attained at the peak of the excursion are similar at the two sites we interpret this observation in terms of water mass changes the excursion is interpreted to reflect a cooling of bottom waters in response to the strengthening contribution of intermediate to deep water production in the high southern latitudes rather than increased ice volume the associated carbon cycle perturbations that we observe are interpreted to reflect a weakening of surface water stratification and increased productivity as supported by our grey value data

a warm equable cretaceous the nature of the problem abstract the nature of the problem of warm equable paleoclimates is defined by investigating the mid cretaceous period the problem consists of three components 1 defining precisely the climatic state during any specified interval of geologic time 2 specifying the external climatic forcing factors which may have been important and 3 understanding the climatic response to any specific modifying influence these components are characterized by limitations of critical importance in understanding paleoclimates the nature of the problem of a warm cretaceous is defined both qualitatively and quantitatively within these limits

paleoenvironment of the western interior seaway inferred from δ18o and δ13c values of molluscs from the cretaceous bearpaw marine cyclothem abstract 18 o and 13 c values of ammonites and inoceramids provide information on the paleoenvironmental conditions in the western interior seaway wis during the campanian maastrichtian bearpaw marine cycle the last major transgression regression t r cycle to affect the seaway during the cretaceous period ammonites and inoceramids exhibit distinct stable isotope values inoceramids have higher 13 c values 0 6 to 5 0 and lower 18 o values 4 0 to 2 8 whereas coeval baculitid ammonites have lower 13 c values 4 8 to 0 3 and higher 18 o values 2 3 to 0 0 with other ammonites having stable isotope values ranging between the baculitids and inoceramids the isotopic composition of the inoceramids and ammonites are unlikely due to kinetic or vital effects because species from open ocean environments have values expected from marine water and there is no correlation between the 13 c and 18 o values of the inceramids as has been reported for modern foraminifers and calcareous algae suspected of exerting vital effects the heterogeneity in stable isotope values of coeval molluscs implies that the bearpaw sea was isotopically stratified isotopic exchange between the water and sediments and the formation of 18 o depleted deepwater mass by mixing of tethyan and boreal waters in the wis may have caused such isotopic stratification a clear relationship exists between the 18 o values of bearpaw zonal baculitids and their biostratigraphic sequence baculitids from zones during peak transgression have the lowest average 18 o values 2 3 to 0 7 whereas those from the underlying and overlying zones have higher 18 o values 0 8 to 0 2 this pattern of 18 o values can be explained by fluctuations in temperature rather than variations in freshwater influx this influx probably having been reduced by lower precipitation and run off under drier warmer climatic conditions the bearpaw sea was not brackish and other paleoenvironmental factors likely account for the character of the bearpaw fauna that is dominated by ammonites and inoceramids and lacks many of the taxa prevalent in the contemporaneous open oceans and seas

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

isotopic evaluation of ocean circulation in the late cretaceous north american seaway the role of the north american seaway in creating and maintaining late cretaceous global greenhouse conditions has been unclear an isotopic analysis of marine turtle and fish fossils from western kansas and the mississippi embayment reveals that the inflow of tethyan surface waters to the seaway was limited during the mid and late cretaceous period north america was split by the north south oriented western interior seaway its role in creating and maintaining late cretaceous global greenhouse conditions remains unclear different palaeoceanographic reconstructions portray diverse circulation patterns1 2 3 the southward extent of relatively cool low salinity low 18o surface waters critically distinguishes among these models but past studies of invertebrates could not independently assess water temperature and isotopic compositions here we present oxygen isotopes in biophosphate from coeval marine turtle and fish fossils from western kansas representing the east central seaway and from the mississippi embayment representing the marginal tethys ocean our analyses yield precise seawater isotopic values and geographic temperature differences during the main transition from the coniacian to the early campanian age 87 82 myr and indicate that the seaway oxygen isotope value and salinity were 2 and 3 lower respectively than in the marginal tethys ocean we infer that the influence of northern freshwater probably reached as far south as kansas our revised values imply relatively large temperature differences between the mississippi embayment and central seaway explain the documented regional latitudinal palaeobiogeographic zonation4 5 and support models with relatively little inflow of surface waters from the tethys ocean to the western interior seaway2 3

early cenozoic benthic foraminiferal isotopes species reliability and interspecies correction factors 1 oxygen and carbon isotope records are important tools used to reconstruct past ocean and climate conditions with those of benthic foraminifera providing information on the deep oceans reconstructions are complicatedby interspecies isotopic offsets that result from microhabitat preferences carbonate precipitation in isotopically distinct environments and vital effects species specific metabolic variation in isotopic fractionation we provide correction factors for early cenozoic benthic foraminifera commonly used for isotopic measurements cibicidoides spp nuttallides truempyi oridorsalis spp stensioina beccariiformis hanzawaia ammophila and bulimina spp showing that most yield reliable isotopic proxies of environmental change the statistical methods and larger data sets used in this study provide more robust correction factors than do previous studies interspecies isotopic offsets appear to have changed through the cenozoic either 1 as a result of evolutionary changes or 2 as an artifact of different statistical methods and data set sizes used to determine the offsets in different studies regardless of the reason the assumption that isotopic offsets have remained constant through the cenozoic has introduced an 1 2 c uncertainty into deep sea paleotemperature calculations in addition we compare multiple species isotopic data from a western north atlantic section that includes the paleocene eocene thermal maximum to determine the most reliable isotopic indicator for this event we propose that oridorsalis spp was the most reliable deepwater isotopic recorder at this location because it was best able to withstand the harsh water conditions that existed at this time it may be the best recorder at other locations and for other extreme events also

ocean overturning since the late cretaceous inferences from a new benthic foraminiferal isotope compilation 1 benthic foraminiferal oxygen isotopic d 18 o and carbon isotopic d 13 c trends constructed from compilations of data series from multiple ocean sites provide one of the primary means of reconstructing changes in the ocean interior these records are also widely used as a general climate indicator for comparison with local and more specific marine and terrestrial climate proxy records we present new benthic foraminiferal d 18 o and d 13 c compilations for individual ocean basins that provide a robust estimate of benthic foraminiferal stable isotopic variations to 80ma andtentatively to 110ma first order variations ininterbasinal isotopicgradients delineate transitions from interior ocean heterogeneity during the late cretaceous 65 ma to early paleogene 35 65 ma homogeneity and a return to heterogeneity in the late paleogene early neogene 35 0 ma we propose that these transitions reflect alterations in a first order characteristic of ocean circulation the ability of winds to make water in the deep ocean circulate we document the initiation of large interbasinal d 18 o gradients in the early oligocene and link the variations in interbasinal d 18 o gradients from the middle eocene to oligocene with the increasing influence of wind driven mixing due to the gradual tectonic opening of southern ocean passages and initiation and strengthening of the antarctic circumpolar current the role of wind driven upwelling possibly associated with a tethyan circumequatorial current in controlling late cretaceous interior ocean heterogeneity should be the subject of further research

analysis of factors influencing tunnel deformation in loess deposits by data mining a deformation prediction model abstract due to the special properties of loess the deformation of tunnels constructed in loess is generally large and easily induced to control deformation during construction the degree of influence of multiple factors on tunnel deformation is analyzed by data mining and a deformation prediction model is established based on tunnels along the menghua railway of china both objective environment and manual operation are considered the surrounding rock level groundwater condition burial depth excavation method and support close time are selected as the main factors influencing tunnel deformation the influence degree of each factor is calculated through mining statistical data collected from the project finally using influencing factors as evaluation indices a rough set extension model for predicting loess tunnel deformation is established and tested results obtained via the prediction model are in good agreement with field observations the study quantifies the influence degree of each selected factor on deformation of the loess tunnel which in turn can help in deformation control efforts moreover the rough set extension model realizes a multi criteria prediction of the loess tunnel s deformation and provides a practical guide for construction of similar projects

the climate of the late cretaceous new insights from the application of the carbonate clumped isotope thermometer to western interior seaway macrofossil abstract we apply the carbonate clumped isotope thermometer 47 to macrofossils from the baculites compressus 73 5 ma and the hoploscaphites nebrascensis 67 ma ammonite zones of the western interior seaway wis of north america and nearby coeval terrestrial and open marine environments the carbonate clumped isotope thermometer is based on a single phase isotope exchange equilibrium that promotes the clumping of two heavy isotopes together within a single carbonate molecule as temperature decreases due to the thermometer s isotopic independence from water coupled measurements of 47 and the bulk oxygen isotopic composition of a carbonate 18 o c enable the reconstruction of both paleotemperature and the isotopic composition of the water in which the organisms grew before applying the technique to the aragonite shells of fossil marine organisms mostly ammonites but also some gastropods bivalves and one belemnite we measure the clumped isotopic composition of modern nautilus and cuttlefish two of the nearest living relatives to the cretaceous ammonites modern cephalopods exhibit disequilibrium isotope effects with respect to 47 but not 18 o c therefore a simple correctional scheme is applied to the late cretaceous macrofossil data before reconstructing paleotemperatures diagenesis is also assessed by visual preservation and previously measured sr concentrations cochran et al 2003 temperatures reconstructed for the late cretaceous western interior seaway range from 16 4 3 5 c for an offshore interior seaway environment from the h nebrascensis zone to 24 2 0 4 c for the b compressus ammonite zone the seaway itself has an isotopic composition of approximately 1 relative to vsmow the expectation for an ice free global ocean average while a nearby freshwater environment has an isotopic composition approaching 20 we compare the attributes of the reconstructed climate to predictions based on late cretaceous climate models and previous reconstructions of the seaway and also assess the sensitivity of our results to the modern cephalopods correction by comparisons to suitable modern analogs finally our clumped isotope data are consistent with cooling between the late campanian and maastrichtian as also seen in benthic foraminfera 18 o