early diageneitc isotopic signal at the cretaceous tertiary boundary israel abstract carbon and oxygen isotope records from carbonate fractions in marls overlying the k t boundary in southern israel are used to interpret paleoenvironmental changes and the history of early diagenetic events in the earliest tertiary the 13c record of the whole rock does not significantly depart from the original values and reflects the global productivity drop shortly after the k t boundary and the subsequent recovery fine fraction oxygen isotope values reflect the addition of carbonate cement highly depleted in 18o throughout the profile the 18o record demonstrates two main episodes in which contact with fresh water affected the sediments one is below a short hiatus at planktic foraminiferal subzone transition po p1a guembelitria cretacea parvularugoglobigerina eugubina and the other at an pyrite rich clay layer near the top to planktic foraminiferal subzone p1b globigerina taurica the latter event suggests introduction of sapropelic bottom conditions in the oceanic paleoenvironment

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

late cretaceous sea level changes in tunisia a multi disciplinary approach a multi disciplinary study of sea level and climate proxies including bulk rock and clay mineral compositions carbon isotopes total organic carbon toc sr ca ratios and macro and microfaunal associations reveals seven major sea level regressions in the southwestern tethys during the last 10 million years of the cretaceous late campanian c 74 2 ma 73 4 72 5 ma and 72 2 71 7 ma early maastrichtian 70 7 70 3 ma 69 6 69 3 ma and 68 9 68 3 ma and late maastrichtian 65 45 65 3 ma low sea levels are generally associated with increased terrigenous influx low kaolinite chlorite mica ratios high toc and high sr ca ratios whereas high sea levels are generally associated with the reverse conditions these sea level changes may be interpreted as eustatic as suggested by the global recognition of at least four of the seven major regressions identified 74 2 ma 70 7 70 3 ma 68 9 68 3 ma and 65 45 65 3 ma climatic changes inferred from clay mineral contents correlate with sea level changes warm or humid climates accompany high sea levels and cooler or arid climates generally accompany low sea levels

stability and change in tethyan planktic foraminifera across the paleocene eocene transition abstract examination of planktic foraminifera in the tethys basin during the paleocene eocene transition reveals two stasis intervals that are separated by a major saltation event coincident with the p e short term perturbation in global climate and oceanography changes occurred at many spatial and temporal scales as well as many taxonomic and ecologic hierarchical levels though with various rates and magnitudes the stasis intervals are marked by slow changes at the species level and account for 50 of the observed first and last appearances during a 2 5 myr interval the saltation event is marked by rapid changes at the species and morpho guild levels and accounts for the remaining 50 of first and last appearances during an interval of about 100 200 kyr despite these changes many taxonomic and ecologic units such as the depth assemblages and genera and faunal parameters such as species richness and turnover rates are stable with respect to the p e perturbation this coexistence of change and stability marks the crisis of tethyan planktic foraminifera across the p e transition and reveals the possible dynamics of ecological evolution

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

nmo velocity surfaces and dix type formulas in anisotropic heterogeneous media reflection moveout of pure modes recorded on conventional length spreads is described by a normal moveout nmo velocity that depends on the orientation of the common midpoint cmp line here we introduce the concept of nmo velocity surfaces which are obtained by plotting the nmo velocity as the radius vector along all possible directions in 3 d space and use it to develop dix type averaging and differentiation algorithms in anisotropic heterogeneous media the intersection of the nmo velocity surface with the horizontal plane represents the nmo ellipse that can be estimated from wide azimuth reflection data we demonstrate that the nmo ellipse and conventional spread moveout as a whole can be modeled by dix type averaging of specifically oriented cross sections of the nmo velocity surfaces along the zero offset reflection raypath this formalism is particularly simple to implement for a stack of homogeneous anisotropic layers separated by plane dipping boundaries since our method involves computing j

geochemical evolution and paleoenvironments of the eocene continental deposits in the paris basin abstract the continental and lacustrine deposits of eocene age in the paris basin form a geochemical sequence extending from clastic sediments characterized by aluminous clay minerals to chemical sediments with dolomite gypsum and magnesian clay minerals during the early eocene flood plains and lakes with large deltas extended across the southern margin of the paris basin the clays were derived from the weathered mesozoic rocks calcretes and smectitic vertisols developed within the flood plain deposits indicating that the climate was warm with an alternation of wet and dry seasons during the middle eocene lacustrine limestones and palygorskite clays developed in small lakes subject to periodic desiccation and pedogenesis landwards pedogenetic silcretes developed on the early eocenc pediments palygorskite is indicative of environments with high concentrations of silica and magnesium and the presence of opal in silcretes confirms a high silica concentration in the soils solutions the paleoclimate was warm with distinct dry seasons or periods during the late eocene gypsum was deposited in the basin center surrounded by a marly deposit in which dolomite and sepiolite are the characteristic minerals lacustrine limestone with alumino magnesian smectite and palygorskite formed on the margin of the basin the development of the evaporitic sequence was favored by the flatness of the palaeolandscape and its silcrete capping which restricted erosion and detrital input to the basin the climate was warm with a tendency to aridity thus the continental deposits of eocene age in the paris basin reflect a progressively more aric climate moreover each depositional pedogenetic and encrusting phase modified the palaeolandscape and thus influenced the next sedimentary episode

atlantic eocene planktonic foraminiferal historical biogeography and paleohydrographic indices abstract analysis of a quantitative and synoptic data base of eocene atlantic planktonic foraminifera has illuminated many facets of foraminiferal faunal structure and composition reflective of bioprovince and useful for empirical establishment of ecologic and paleohydrographic indices tropical indigenes such as the morozovellids turborotaliids subquadrate acarininids and some globigerinathekids dissolve most rapidly along with juveniles of most species tropical faunas are high in diversity and dominance include oxygen minimum indices such as the biserial heterohelicids only in high productivity times such as the middle eocene are dominated by genera with high numbers of species and species consistently typical of warm water regions until the late eocene when faunas include a higher number of middle than lower latitude types truly tropical genera are replaced by subtropical eutrophic indicators such as the globigerinathekids and contract to the florida current region prior to their extinctions at the end of the middle eocene atlantic late paleogene tropical forms first appear in the gulf of mexico at the end of the middle eocene middle latitude faunas include high numbers of chiloguembelinids pseudohastigerinids small and biconvex morozovellids round and globigerinid form acarininids low spired subbotinids in the late middle eocene high spired subbotinids large and typical globigerinids in the late eocene these forms have intermediate dissolution susceptibilities middle latitude faunas are often high in diversity in midddle latitude frontal regions dominance is low even in warm intervals when tropical indigenes increase in number in middle latitude faunas especially in boundary currents low latitude species penetrate temperate areas also during cool eutrophic periods of vigorous circulation such as the late middle eocene typical of temperate slope faunas are high abundances of high spired subbotinids and small sized catapsydracids high latitude faunas are usually low in diversity except in the middle to late eocene when frontal regions were located in the southern labrador sea and over rockall bank typical forms are the low spired subbotinids until the late middle eocene globorotaloids catapsydracids tenuitellids and in the late eocene the biserial heterohelicids indigenous species are the most solution resistant and many are mesopelagic during warmings rare low latitude indices penetrate high latitudes subpolar faunas have greatest affinities with middle latitude faunas at these times

oceanographic and climatic implications of the palaeocene carbon isotope maximum we have compared detailed planktonic and benthonic foraminiferal carbon and oxygen isotope records from the palaeocene and early eocene successions at dsdp site 577 shatsky rise north pacific a composite section derived from dsdp leg 74 sites walvis ridge south atlantic and a composite section from odp leg 113 sites maud rise weddell sea the 13c records of palaeocene and early eocene foraminifera at site 577 and the leg 74 sites show that an increase in 13c values in surface waters at 64 ma end of zone p1 resulted in increased vertical carbon isotope gradients 13c between surface and deeper dwelling planktonic foraminifera and between surface dwelling planktonics and benthonic foraminifera which became progressively steeper until the iniddle late palaeocene zone p4 this steepening also occurs in the latest palaeocene of the composite leg 113 section and can be explained by an increase in surface ocean productivity this increase in productivity probably resulted in an expansion of the oxygen minimum zone omz benthonic 13c values increased during the late palaeocene in site 577 and the composite leg 74 section suggesting that the palaeocene carbon isotope maximum was composed of both within ocean reservoir increased surface water productivity and between reservoir organic carbon burial ftactionation effects the benthonic 13c increase lags the surface ocean 13c increase in the early palaeocene 63 64 ma suggesting that surface water productivity increase probably led an increase in the burial rate of organic carbon relative to carbonate sedimentation moreover inter site 13c comparisons suggest that the locus of deep to intermediate water formation for the majority of the palaeocene and the earliest eocene was more likely to have been in the high southern latitudes than in the lower latitudes oxygen isotope data show a decline in deeper water temperatures in the early and early late palaeocene followed by a temperature increase in the late palaeocene and across the palaeoceneeocene boundary we speculate that these changes in deeper water temperatures were related to the flux of co2 between the oceans and the atmosphere through a mechanism operating at the high southern latitudes

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 blast of gas in the latest paleocene simulating first order effects of massive dissociation of oceanic methane hydrate carbonate and organic matter deposited during the latest paleocene thermal maximum is characterized by a remarkable 2 5 excursion in delta 13c that occurred over approximately 10 4 yr and returned to near initial values in an exponential pattern over approximately 2 x 10 5 yr it has been hypothesized that this excursion signifies transfer of 1 4 to 2 8 x 10 18 g of ch4 from oceanic hydrates to the combined ocean atmosphere inorganic carbon reservoir a scenario with 1 12 x 10 18 g of ch4 is numerically simulated here within the framework of the present day global carbon cycle to test the plausibility of the hypothesis we find that 1 the delta 13c of the deep ocean shallow ocean and atmosphere decreases by 2 3 over 10 4 yr and returns to initial values in an exponential pattern over approximately 2 x 10 5 yr 2 the depth of the lysocline shoals by up to 400 m over 10 4 yr and this rise is most pronounced in one ocean region and 3 global surface temperature increases by approximately 2 degrees c over 10 4 yr and returns to initial values over approximately 2 x 10 6 yr the first effect is quantitatively consistent with the geologic record the latter two effects are qualitatively consistent with observations thus significant ch4 release from oceanic hydrates is a plausible explanation for observed carbon cycle perturbations during the thermal maximum this conclusion is of broad interest because the flux of ch4 invoked during the maximum is of similar magnitude to that released to the atmosphere from present day anthropogenic ch4 sources

estimation of fracture parameters from reflection seismic data part iii fractured models with monoclinic symmetry existing geophysical and geological data indicate that orthorhombic media with a horizontal symmetry plane should be rather common for naturally fractured reservoirs here we consider two orthorhombic models one that contains parallel vertical fractures embedded in a transversely isotropic background with a vertical symmetry axis vti medium and the other formed by two orthogonal sets of rotationally invariant vertical fractures in a purely isotropic host rock using the linear slip theory we obtain simple analytic expressions for the anisotropic coefficients of effective orthorhombic media under the assumptions of weak anisotropy of the background medium for the first model and small compliances of the fractures all effective anisotropic parameters reduce to the sum of the background values and the parameters associated with each fracture set for the model with a single fracture system this result allows us to eliminate the influence of the vti background by evaluating the differences between t

3 d moveout inversion in azimuthally anisotropic media with lateral velocity variation theory and a case study reflection moveout recorded over an azimuthally anisotropic medium e g caused by vertical or dipping fractures varies with the azimuth of the source receiver line normal moveout nmo velocity responsible for the reflection traveltimes on conventional length spreads forms an elliptical curve in the horizontal plane while this result remains valid in the presence of arbitrary anisotropy and heterogeneity the inversion of the nmo ellipse for the medium parameters has been discussed so far only for horizontally homogeneous models above a horizontal or dipping reflector here we develop an analytic moveout correction for weak lateral velocity variation in horizontally layered azimuthally anisotropic media the correction term is proportional to the curvature of the zero offset traveltime surface at the common midpoint and therefore can be estimated from surface seismic data after the influence of lateral velocity variation on the effective nmo ellipses has been stripped the generalized dix equat

antarctic subtropical humid episode at the paleocene eocene boundary clay mineral evidence clay mineral assemblages from east antarctica have been analyzed at high stratigraphic resolution 20 to 1 ka throughout the interval from 55 6 to 55 0 ma which includes the terminal paleocene isotopic excursion in ocean drilling program site 690b on maud rise lat 65 s in the weddell sea region changes in the clay associations reflect a major increase in chemical weathering caused by increased temperature and or rainfall in at least this sector of east antarctica for a brief 270 ka interval in the latest paleocene this represents the most intense warming known for the cenozoic this high latitude climatic episode is recorded synchronously by stable isotopes and clay minerals a progression is evident in the clay assemblages during the latest paleocene that apparently reflects changing relations between temperature and precipitation this sequence began with the interval of rapid temperature increase that marks the beginning of the oxygen isotopic excursion a brief increase in kaolinite at the inception of the excursion suggests a temporary increase in year round precipitation in antarctica in response to an increased continent to ocean temperature gradient this kaolinite spike was followed by almost total dominance by smectite for the remainder of the isotopic excursion 120 ka suggesting that warmer southern ocean surface temperatures of 18 to 22 c were associated with seasonal precipitation alternating wet and dry seasons claymineral variations on antarctica during the isotopic excursion reflect a tight coupling between oceanic and continental climate change immediately following the excursion at 55 22 ma kaolinite percentages increased to values similar to modern subtropical tropical areas for 150 ka a remarkable event for the antarctic abundant kaolinite suggests perennial rainfall and minimum soil temperatures of 15 c during at least part of the year the kaolinite increased during a time of lower southern ocean surface water temperatures suggesting increased atmospheric heat transport toward the poles a temporary change in atmospheric circulation is suggested from dominantly zonal to meridional

barium sio2 excess and p2o5 as proxies of biological productivity in the middle east during the palaeocene and the latest palaeocene benthic extinction event the distribution of barium and other elements related to biological productivity has been studied in two palaeocene sections from the middle east in the bathyal ben gurion section israel ba ba al2o3 15 concentrations are low in the range 0 04 to 0 3 in the lower palaeocene and very high 1 to 2 throughout most of the upper palaeocene in the neritic gebel aweina section in egypt ba values are low 0 1 throughout the entire palaeocene the ba enrichments at ben gurion and their correlations with increases in p2o5 and opaline silica and local and global 13c maxima indicate that upwelling and high productivity were important in this region during the late palaeocene the absence of ba enrichments in the shallower gebel aweina section probably reflects the strong depth dependence of biobarium deposition in the uppermost palaeocene at the level where the global benthic extinction event is registered ba concentrations in the ben gurion section increase to anomalous 6 which suggests that upwelling and possibly wind strengths intensified during this event the results speak against deep water formation in this region since downwelling and not upwelling is required

latest paleocene lithologic and biotic events in neritic deposits of southwestern new jersey in the southwestern new jersey coastal plain four drill holes contain continuous neritic sedimentation across the paleocene eocene boundary calcareous nannofossil zone np 9 np 10 boundary significant lithologic and biotic changes occur in these strata near the top of the paleocene global warming increased precipitation and other oceanographic and climatic events that have been recognized in high latitude deep oceanic deposits of the latest paleocene also influenced mid latitude shallow marine and terrestrial environments of the western north atlantic the diverse well preserved calcareous nannofossil flora that is present throughout the entire new jersey boundary section accurately places these events within the uppermost part of the upper paleocene zone np 9 several rapid but gradational changes occur within a 1 1 m interval near the top of zone np 9 the changes include 1 a change in lithology from glauconitic quartz sand to clay 2 a change in clay mineral suites from illite smectite dominated to kaolinite dominated 3 a change in benthic foraminiferal assemblages to a lower diversity fauna suggestive of low oxygen environments 4 a significant increase in planktonic foraminiferal abundance and 5 an increased species turnover rate in marine calcareous nannofossils pollen was sparse in the new jersey drill holes but terrestrial sporomorph species in virginia exhibit increased turnover rates at a correlative level foraminiferal assemblages and lithology indicate that relative sea level rose in new jersey at the same time as these late paleocene events occurred in late biochron np 9 the higher sea levels influenced sediment type and absolute abundance of planktonic foraminifers in the deposits above the initial increase of kaolinite in the upper part of zone np 9 the kaolinite percentage continues to increase and the maximum kaolinite value occurs in the uppermost part of zone np 9 there are few changes in either the sediments or the biota precisely at the zone np 9 np 10 boundary in new jersey the clay rich deposits with a high kaolinite clay mineral suite the lowered diversity benthic foraminiferal assemblages the abundant planktonic foraminiferal specimens and the calcareous nannofossil assemblages continued essentially unchanged into the earliest eocene zone np 10 within the lower part of zone np 10 the kaolinite percentage decreased to very low values

paleocene to eocene benthic foraminiferal isotopes and assemblages implications for deepwater circulation early paleogene warm climates may have been linked to different modes and sources of deepwater formation warm polar temperatures of the paleocene and eocene may have resulted from either increased atmospheric trace gases or increased heat transport through deep and intermediate waters the possibility of increasing ocean heat transport through the production of warm saline deep waters wsdw in the tethyan region has generated considerable interest in addition general circulation model results indicate that deepwater source regions may be highly sensitive to changing basin configurations to decipher deepwater changes we examined detailed benthic foraminiferal faunal and isotopic records of the late paleocene through the early eocene 60 to 50 ma from two critical regions the north atlantic bay of biscay site 401 and the pacific shatsky rise site 577 these records are compared with published data from the southern ocean maud rise site 690 islas orcadas rise site 702 during the late paleocene similar benthic foraminiferal 18o values were recorded at all four sites this indicates uniform deepwater temperatures consistent with a single source of deep water the highest 13c values were recorded in the southern ocean and were 0 5 more positive than those of the pacific we infer that the southern ocean was proximal to a source of nutrient depleted deep water during the late paleocene upper paleocene reflector ab was cut on the western bermuda rise by cyclonically circulating bottom water also suggesting a vigorous source of bottom water in the southern ocean a dramatic negative excursion in both carbon and oxygen isotopes occurred in the latest paleocene in the southern ocean this is a short term 100 kyr globally synchronous event which also is apparent in both the atlantic and pacific records as a carbon isotopic excursion of approximately 1 faunal analyses from the north atlantic and pacific sites indicate that the largest benthic foraminiferal faunal turnover of the cenozoic was synchronous with the isotopic excursion lending support to the hypothesis that the extinctions were caused by a change in deepwater circulation we speculate that the southern ocean deepwater source was reduced or eliminated at the time of the excursion during the early eocene southern ocean 13c values remained enriched relative to the north atlantic and pacific however the southern ocean was also enriched in 18o relative to these basins we interpret that these patterns indicate that although the southern ocean was proximal to a source of cool nutrient depleted water the intermediate to upper deep water sites of the north atlantic and pacific were ventilated by a different source that probably originated in low latitudes i e wsdw

the paleocene eocene transition in the antarctic indian ocean inference from planktic foraminifera isotopic depth stratification and relative abundance studies of planktic foraminifera at odp site 738 reveal three major faunal turnovers during the latest paleocene and early eocene reflecting the climatic and structural changes in the antarctic surface ocean faunal event 1 occurred near the paleocene eocene boundary and is characterized by a faunal turnover in deep dwellers decreased relative abundance in intermediate dwellers and increased relative abundance in surface dwellers this event marks a temporary elimination of the vertical structure in the surface ocean over a period of more than 63 000 years that is apparently associated with the sudden shutdown of the antarctic intermediate water production the appearance of morozovellids before this event suggests that polar warming is the cause for the shutdown in the production of this water mass at this time warm saline deep water may have formed at low latitudes faunal event 2 occurred near the ap5a ap5b subzonal boundary and is characterized by a faunal turnover in deep dwellers with no apparent change in surface and intermediate dwellers increased individual size wall thickness and relative abundance in deep dwelling chiloguembelinids suggests the formation of a deep oxygen minima in the antarctic oceans during the maximum polar warming possibly as a result of upwelling of nutrient rich deep water faunal event 3 occurred in subzone ap6 and is characterized by a faunal turnover in surface dwellers and a delayed diversification in deep dwellers this event marks the onset of antarctic cooling a drastic decrease in the 13c 18o values of the deep assemblage in zone ap7 suggests an intensified thermocline and reduced upwelling following the polar cooling

late paleocene to eocene paleoceanography of the equatorial pacific ocean stable isotopes recorded at ocean drilling program site 865 allison guyot an expanded and largely complete upper paleocene to upper eocene section was recovered from the pelagic cap overlying allison guyot mid pacific mountains at ocean drilling program odp site 865 18o26 n 179o33 w paleodepth 1300 1500 m reconstructions show that the site was within a few degrees of the equator during the paleogene because no other paleogene sections have been recovered in the pacific ocean at such a low latitude site 865 provides a unique record of equatorial pacific paleoceanography detailed stable isotopic investigations were conducted on three planktonic foraminiferal taxa species of acarinina morozovella and subbotina we studied benthic foraminiferal isotopes at much lower resolution on species of cibicidoides and lenticulina nuttallides truernpyi and gavelinella beccariiformis because of their exceptional rarity the 5180 and 513c stratigraphies from site 865 are generally similar to those derived from other paleocene and eocene sections the planktonic foraminiferal records at site 865 however include significantly less short term single sample variability than those from higher latitude sites indicating that this tropical oligotrophic location had a comparatively stable water column structure with a deep mixed layer and less seasonal variability low amplitude 0 1 0 8 o oscillations on timescales of 250 000 to 300 000 years correlate between the 513c records of all planktonic taxa and may represent fluctuations in the mixing intensity of surface waters peak sea surface temperatures of 24o 25oc occurred in the earliest eocene followed by a rapid cooling of 3 6oc in the late early eocene temperatures remained cool and stable through the middle eocene in the late eocene surface water temperatures decreased further vertical temperature gradients decreased dramatically in the late paleocene and were relatively constant through much of the eocene but increased markedly in the late eocene intermediate waters warmed through the late paleocene reaching a maximum temperature of 10oc in the early eocene cooling in the middle and late eocene paralleled that of surface waters with latest eocene temperatures below 5oc extinction patterns of benthic foraminifera in the latest paleocene were similar to those observed at other pacific sites and were coeval with a short term very rapid negative excursion in 513c values in planktonic and benthic taxa as at other sites during this excursion benthic foraminiferal 5180 values decreased markedly indicating warming of 4 to 6oc for tropical intermediate waters while planktonic taxa show slight warming 1 oc followed by 2oc of cooling convergence of 5180 values of planktonic and benthic foraminifera suggests that thermal gradients in the water column in this tropical location collapsed during the excursion these data are consistent with the hypothesis that equatorial pacific surface waters were a potential source of warm higher salinity waters which filled portions of the deep ocean in the latest paleocene oxygen isotopic data indicate that equator to high southern latitude sea surface thermal gradients decreased to as little as 4oc at the peak of the excursion suggesting some fundamental change in global heat transport

correlation between isotope records in marine and continental carbon reservoirs near the palaeocene eocene boundary changes in the isotope content of the large marine carbon reservoir can force shifts in that of the smaller carbon pools in the atmosphere and on land the carbon isotope compositions of marine carbonate sediments from the late palaeocene vary considerably exhibiting a sudden decrease close to the palaeocene eocene boundary which coincides with deep sea benthic extinctions1 and with changes in ocean circulation here we report that these fluctuations in the marine carbon isotope record are closely tracked by the terrestrial records provided by palaeosol carbonates and mammalian tooth enamel in using palaeosol carbonates to reconstruct the co2 content of the ancient atmosphere2 isotope shifts of this sort will have to be taken into account the sharp decrease in 13c 12c ratios in the late palaeocene provides a datum for precise correlation of marine and continental records and suggests that abrupt climate warming at this time may have played an important role in the evolution of land mammals

an interpretation of cretaceous and tertiary biota in polar regions abstract rich fossil floras and vertebrate faunas lived within the arctic and atarctic circles during the cretaceous and paleogene these occurrences seem explicable by the nature of the thermal environments in polar regions and by the physiological responses of plants and animals allied to those that lived there there seems no need to invoke a lower tilt to the earth s axis to provide greater warmth and light in polar regions to account for these fossil records

cretaceous climate a comparison of atmospheric simulations with the geologic record abstract atmospheric simulations using realistic cretaceous geography 100 million years ago suggest that paleography is an important factor governing the nature of the circulation the simulated cretaceous atmospheric circulations are markedly different both from the present day atmospheric circulation and from the classical hypotheses of a weaker circulation and poleward displacement of circulation features e g the subtropical high therefore they pose specific questions which can be tested against the geologic record aspects of the cretaceous simulations are verified in comparisons with the geologic record the simulations serve to guide areas of future paleoclimatic research and to formulate better the nature of the problem of warm equable climates

climatic evolution on the southeastern margin of the tethys negev israel from the palaeocene to the early eocene focus on the late palaeocene thermal maximum during the early palaeocene zones p1 to p2 the southeastern tethyan margin experienced a warm and humid climate with high rainfall as indicated by the abundance of kaolinite within marine sedimentary rocks subsequently in zone p2 arid climatic conditions evolved in the coastal basins of the southern tethys margin as indicated by the gradual disappearance of kaolinite and the increased abundance of palygorskite and sepiolite arid climatic conditions persisted during the selandian and thanetian late palaeocene and reached a maximum in the ypresian early eocene during the late palaeocene thermal maximum warm climatic conditions were associated with increased aridity and led to sea surface warming though not bottom water warming as suggested by the planktic 18 o excursion observed at the zomet telalim basin negev israel strongly reduced surface productivity accompanied by unusually light 13 c are associated with the late palaeocene thermal maximum in the negev as well as globally

latest paleocene benthic extinction event on the southern tethyan shelf egypt foraminiferal stable isotopic δ13c δ18o records the dramatic global extinction of 35 50 of benthic foraminifera species in the deep sea in the latest paleocene and associated negative excursions in 13 c and 18 o may be related to spreading of warm saline bottom water from subtropical tethyan shallow regions over the sea floor worldwide our study of neritic sections in egypt shows that in the southern shallow tethys a prominent long term change in bottom water chemistry sedimentation and benthic foraminifera fauna was initiated at the time when the deep sea benthic extinction event bee took place bottom water 13 c values on the tethyan shelf show a sudden 3 0 negative shift at this event however contrary to the deep sea in which the 13 c excursion was of short duration tethyan 13 c values did not fully return to preboundary values but remained depressed by 1 5 for at least 1 m y the 13 c values at the egyptian shelf during the bee are much lower than would be expected if this was a source region for global deep water the 18 o values indicate no significant change in bottom water salinity or temperature at the bee the long lasting environmental changes that began on the egyptian shelf at the bee may be related to for example gateway reorganization along the tethyan seaway paleogeographic changes possibly also triggered a change in the loci of global deep water formation however these loci must be sought in another part of the tethys

abrupt climate change and transient climates during the paleogene a marine perspective detailed investigations of high latitude sequences recently collected by the ocean drilling program odp indicate that periods of rapid climate change often culminated in brief transient climates with more extreme conditions than subsequent long term climates two examples of such events have been identified in the paleogene the first in latest paleocene time in the middle of a warming trend that began several million years earlier the second in earliest oligocene time near the end of a middle eocene to late oligocene global cooling trend superimposed on the earlier event was a sudden and extreme warming of both high latitude sea surface and deep ocean waters imbedded in the latter transition was an abrupt decline in high latitude temperatures and the brief appearance of a full size continental ice sheet on antarctica in both cases the climate extremes were not stable lasting for less than a few hundred thousand years indicating a temporary or transient climate state geochemical and sedimentolog

paleocene to early eocene paleoceanography of the middle east the δ13c and δ18o isotopes from foraminiferal calcite paleocene to early eocene benthic foraminiferal 13c and 18o records from southern tethyan sections at ben gurion israel paleodepth 500 700 m and gebel aweina egypt paleodepth 150 200 m show generally similar trends but 1 3 more negative values than coeval deep sea isotopic records in both tethyan sections a negative 13c excursion of 2 5 3 marks the benthic extinction event in the latest paleocene for at least 1 m y after this event 13c values were 1 5 2 more negative on the shelf than at upper bathyal depths reflecting a deepening of the oxygen minimum zone possibly related to an increase or spatial shift in upwelling benthic 18o records indicate a 2 4 c temperature gradient between the shelf and upper bathyal depths temperature salinity reconstructions suggest that upwelling was a dominant mechanism for surface water formation in this part of the southern tethys during the late paleocene

fracture detection using azimuthal variation of p wave moveout from orthogonal seismic survey lines an algorithm is proposed for determining the fracture orientation based on the azimuthal variations in the p wave reflection moveout for a target interval the differential moveout between orthogonal survey lines from the bottom of a given target shows cos 2 variations with the line azimuth measured from the fracture strike for a fixed offset a configuration of four intersecting survey lines may be used to quantify the fracture strike the four lines form two orthogonal pairs and the fracture strike can be obtained by analyzing the crossplot of the two corresponding pairs of the differential moveouts an offset depth ratio x z of 1 0 or greater up to 1 5 is often required to quantify the moveout difference reliably the sensitivity of the method is further enhanced by low high impedance contrast at the top target interface but is greatly reduced by high low impedance contrast the method may be particularly useful in marine exploration with repeated surveys of various vintages where continuous az

velocity analysis in the presence of amplitude variation conventional semblance velocity analysis is equivalent to modeling prestack seismic data with events that have hyperbolic moveout but no amplitude variation with offset avo as a result of its assumption that amplitude is independent of offset this method might be expected to perform poorly for events with strong avo especially for events with polarity reversals at large offset such as reflections from tops of some class 1 and class 2 sands we find that substantial amplitude variation and even phase change with offset do not compromise the conventional semblance measure greatly polarity reversal however causes conventional semblance to fail the semblance method can be extended to take into account data with events that have amplitude variation expressed by avo intercept and gradient i e the shuey approximation however because of the extra degrees of freedom introduced in avo sensitive semblance resolution of the estimated velocities is decreased this is because the data can be modeled acc

first observations of the interaction of ocean swell with sea ice using satellite radar altimeter data the action of ocean waves and swell on sea ice in the marginal ice zone miz controls the size distribution of ice floes and thus affects ice dynamics and the thermodynamics of ice growth and decay an understanding of ice processes is important because of the influence of the sea ice cover on high latitude weather and global climate1 also long term changes in average sea ice extent could provide a sensitive indication of climatic change if the degree of shorter term variability were better understood2 previous observations of the propagation of swell within the ice pack have been limited in spatial and temporal extent3 6 here we present new results from the us seasat satellite which suggest that radar altimetry can provide a powerful means of global synoptic monitoring of the interaction between ocean and ice

stable δ13c δ18o and strontium isotopes through the paleocene at gebel aweina eastern tethyan region abstract stable 13 c 18 o and strontium 87 sr 86 sr isotopic records have been established through the paleocene section at gebel aweina in the eastern desert egypt the section has been formed in a shelf upper bathyal environment and spans the interval from planktonic foraminiferal zones p1d to p6a or p6b integrated evaluation of isotopic results and scanning electron microscope observations suggest that strontium and whole rock 13 c records reflect primarily original isotopic trends whereas 18 o and foraminiferal 13 c values have been severely affected by diagenesis the whole rock 13 c record exhibits a continuous increase of 4 from the early paleocene to middle late paleocene the increase is followed by a stepwise 13 c decrease of the same magnitude through the late late paleocene and onwards the gross trends of this 13 c record have earlier been registered in many coeval deep sea sections but there are also some significant disparities at aweina for example the paleocene carbon isotopic changes have a higher amplitude in the deep sea the mid to late paleocene 13 c increase has been interpreted to reflect high biological productivity and or changes in the global carbon mass balance the 13 c decrease in the upper part of the aweina section can be identified as the paleocene eocene transitional long term 10 3 kyr negative 13 c shift which may reflect a major reorganisation in global oceanic circulation patterns the well known latest paleocene deep sea benthic foraminiferal extinction event has been found in the upper part of the aweina section and coincides with a distinct and rapid 13 c decrease of 1 5 the benthic extinction event and the associated 13 c anomaly thus represent important stratigraphic markers also in more shallow environments the gebel aweina 13 c record shows considerably lower values compared to the global 13 c record during early and early late paleocene and in the latest paleocene in the early late paleocene foraminiferal zones p3a to the base of p4 the aweina 13 c values increase rapidly by 1 5 and converge with the global record thereafter the two records covary up to the benthic extinction event after which they diverge the convergence between the records may reflect sea level rise and more open water mass exchange between the eastern tethys and the world ocean the similarity of pilot 13 c records from greece and tunisia with the aweina record support this interpretation diagenetic processes however cannot be ruled out and further studies are required to determine the significance of the 13 c depletions in the eastern tethyan sediments the 87 sr 86 sr ratios through the paleocene at gebel aweina are remarkably invariable close to a value of 0 7077 this is the same trend that has been reported in some earlier detailed studies conducted on well preserved calcitic material from the paleocene indicating original sr isotopic signatures at gebel aweina the homogeneity of sr isotopic ratios throughout the paleocene contrasts with the prominent changes observed in the carbon isotope record indicating a decoupling of the mechanisms regulating the mass fluxes of these elements the invariable sr isotopic ratios suggest stable conditions as regards to relative changes in mass fluxes of riverine and or hydrothermal sr during the paleocene

seismic traveltime analysis for azimuthally anisotropic media theory and experiment natural fractures in reservoirs and in the caprock overlying the reservoir play an important role in determining fluid flow during production the density and orientation of sets of fractures is therefore of great interest rocks possessing an anisotropic fabric and a preferred orientation of fractures display both polar and azimuthal anisotropy sedimentary rocks containing several sets of vertical fractures may be approximated as having monoclinic symmetry with symmetry plane parallel to the layers if in the absence of fractures the rock is transversely isotropic with symmetry axis perpendicular to the bedding plane a nonhyperbolic traveltime equation which can be used in the presence of azimuthally anisotropic layered media can be obtained from an expansion of the inverse squared ray velocity in spherical harmonics for a single set of aligned fractures application of this equation to traveltime data acquired at a sufficient number of azimuths allows the strike of the fractures to be estimated analysis of the traveltimes measured in a physical model simulation of a reverse vertical seismic profile in an azimuthally anisotropic medium shows the medium to be orthorhombic with principal axes in agreement with those given by an independent shear wave experiment in contrast to previous work no knowledge of the orientation of the symmetry planes is required the method is therefore applicable to p wave data collected at multiple azimuths using multiple offset vertical seismic profiling vsp techniques

paleocene and eocene kaolinite distribution in the south atlantic and southern ocean antarctic climatic and paleoceanographic implications abstract clay mineral associations of paleocene and eocene age have been examined in six drilled sequences from the southern south atlantic and southern ocean these sites are located to provide three depth transects across intermediate water masses widespread abundance of pedogenic smectite at all locations suggests globally warm climates and alternating wet and dry seasons on the adjacent continental margins including antarctica as was the case during the late cretaceous remarkably kaolinite is observed only in paleocene eocene sediments at the highest latitudes of these sites and must have originated from antarctica the restriction of kaolinite to the antarctic region is inferred to have resulted from especially higher rainfall there during the paleocene eocene relative to the lower latitude areas examined this inferred high rainfall is considered to have resulted from globally warm temperatures that increased poleward latent heat transport compensating for a strong heat deficit in the antarctic region relative to the tropics kaolinite was not observed in the latest cretaceous maastrichtian sediments of maud rise antarctica kaolinite first appears in the clay mineralogical assemblages in the earliest paleocene 64 to 64 5 ma at a time of relatively cool intermediate waters and before a warming trend of surface waters currents at intermediate water depths transported fine terrigenous sediments from the antarctica during the latest paleocene and early eocene 59 to 52 ma at a time when the oxygen isotopic strongly in east antarctica during the latest paleocene and early eocene 59 to 59 ma at a time when the oxygen isotopic data indicate maximum warmth of surface and intermediate waters of the southern ocean these are interpreted to reflect a paleocene maximum of antarctic rainfall this development peaked at 57 3 m close to the paleocene eocene boundary a time of maximum warmth based on oxygen isotopic data increased illite content and associated chlorite and random mixed layer clays at the end of the middle eocene 41 ma suggest local development of poorly weathered soils on antarctica favored by a cooling of the southern ocean coeval extension of kaolinite into shallower water depths and similar clay mineral associations in shallower and deeper sites indicate the development of cooler conditions led to an increasing influence of antarctic environments upon intermediate water masses at high latitudes

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

dense 3d residual moveout analysis as a tool for hti parameter estimation three dimensional residual moveout analysis is the basic step in velocity model refinement the analysis is generally carried out using horizontal and or vertical semblances defined on a sparse set of in lines or cross lines with densely sampled source receiver offsets an alternative approach which we call dense residual moveout analysis drma is to use all the bins of a three dimensional survey but sparsely sampled offsets the proposed technique is very fast and provides unbiased and statistically efficient estimates of the residual moveout indeed for the sparsest possible offset distribution when only near and far angle stacks are used the variance of the residual moveout estimate is only 1 4 times larger than the variance of the least squares estimate obtained using all offsets the high performance of drma makes it a useful tool for many applications of which azimuthal velocity analysis is considered here for a horizontal transverse isotropy hti model a deterministic procedure is proposed to define at every point of residual moveout estimation the azimuthal angle of the hti axis of symmetry the thomsen anisotropy coefficients and the interval or root mean square velocities in both the hti isotropy and symmetry planes the procedure is not restricted by drma assumptions for example it is also applicable to semblance based residual moveout estimates the high resolution of the technique is illustrated by azimuthal velocity analysis over an oilfield in west siberia