one hundred million years of geomagnetic polarity history since 1968 absolute ages have been assigned to the late cretaceous cenozoic geomagnetic reversal time scale by fixing the ages of two or more calibration points in a composite marine magnetic anomaly profile and interpolating between or extrapolating beyond these points assuming constant spreading rates in each interval previously no more than 4 calibration points were used but it is now possible to specify 11 calibration points in addition to the 0 m y datum this improvement is based on magnetostratigraphic studies in italian pelagic limestones these studies closely tie the geomagnetic reversal sequence to the foraminiferal and coccolith zonations absolute ages of calibration points are provided by the best available dates on stage boundaries which are located from the biostratigraphic zonation the greatest changes from previous scales come in the late paleocene early eocene where the new ages are as much as 3 m y younger than in the 1977 scale of labrecque and others and as much as 1 8 m y younger than in the 1980 scale of ness and others

deep mesoscale eddies in the canada basin arctic ocean 1 numerous eddies have been identified in a seven year time series of mooring observations in the canada basin arctic ocean we focus on a series of deep eddies centered at 1200 m depth and occupying up to 1500 m of the water column the deep eddies are found to be spatially localized only ever being observed at one of four mooring sites of the beaufort gyre observing system in the canada basin however despite only a few previously reported observations of deep eddies in the arctic ocean we find that they are the most prevalent eddy type at this location based on this observation together with an analysis of the temperature salinity structure and the exclusively anticyclonic rotation of the deep eddies we hypothesize that they are formed by a density driven outflow from the chukchi borderland region we also describe a simple analytical model to explain the observed vertical scales of the eddies

solutions in chronostratigraphy the paleocene eocene boundary debate and aubry vs hedberg on chronostratigraphic principles abstract in several recent papers m p aubry et al have argued that hedbergian principles of chronostratigraphy are being violated by the international commission on stratigraphy ics when selecting global stratotype sections and points gssps for the formal divisions of the geological time scale the current debate over the definition of the paleocene eocene p e boundary has been a major focus of their arguments unfortunately aubry et al have obscured matters by misusing the term unit stratotype and by equivocally using the term stage for the very different concepts of synthem and global chronostratigraphic stage the p e boundary option most repugnant to aubry et al carbon isotope excursion cie p e thanetian ypresian boundary is perfectly compatible with h d hedberg s views in contrast another option preferred by aubry et al recognition of new 1 m y duration age stage between thanetian and ypresian is inconsistent with hedberg s views additional problems with the p e boundary arguments of aubry et al include the fact that a ypresian unit stratotype does not exist the fact that the base of the ypresian synthem is not immutable and the fact that the nannofossil tribrachiatus digitalis is of dubious relevance to the boundary debate as for chronostratigraphy in general aubry et al have misrepresented hedberg s views by 1 falsely claiming that the content of a stage is what determines its boundaries 2 misunderstanding the general concept of the boundary stratotype 3 distorting the base defines boundary principle 4 falsely claiming that traditional pre gssp chronostratigraphic boundaries cannot be changed 5 falsely implying that traditional stage unit stratotype boundaries can be adjusted by no more than 300 000 years when defining formal age stage boundaries with gssps 6 falsely claiming that the definition of a geochronologic chronostratigraphic boundary should precede its correlation 7 claiming that traditional unconformable stage boundaries may be suitable horizons for gssps 8 distorting the meaning of arbitrariness in regard to the definition of geochronologic chronostratigraphic boundaries and 9 claiming that gssps are inherently unstable in that they are subject to redefinition whenever a more powerful element of correlation is discovered if taken seriously the unit stratotype sanctifying chronostratigraphic philosophy of aubry et al would require the creation of perhaps dozens of new phanerozoic ages stages of relatively very short duration wherever there was a significant gap between two successive historical stage unit stratotypes for all of these reasons the arguments of aubry et al have no merit

new evidence for subtropical warming during the late paleocene thermal maximum stable isotopes from deep sea drilling project site 527 walvis ridge the late paleocene thermal maximum lptm was a dramatic short term global warming event that occurred 55 ma warming of high latitude surface waters and global deep waters during the lptm has been well documented however current data suggest that subtropical and tropical sea surface temperatures ssts did not change during the event conventional paradigms of global climate change such as co2 induced greenhouse warming predict greater warming in the high latitudes than in the tropics or subtropics but nonetheless cannot account for the stable tropical subtropical ssts we measured the stable isotope values of well preserved late paleocene to early eocene planktonic foraminifera from south atlantic deep sea drilling project dsdp site 527 to evaluate the subtropical response to the climatic and environmental changes of the lptm planktonic foraminiferal 18o values at site 527 decrease by 0 94 from pre lptm to excursion values providing the first evidence for subtropical warming during the lptm we estimate that subtropical south atlantic ssts warmed by at least 1 4 c on the basis of possible changes in evaporation and precipitation the new evidence for subtropical sst warming supports a greenhouse mechanism for global warming involving elevated atmospheric co2 levels

oligocene calibration of the magnetic polarity time scale magnetostratigraphic studies of the oligocene white river group in wyoming colorado nebraska and the dakotas yield a radiometrically dated polarity stratigraphy that provides mid tertiary calibration points for the magnetic polarity time scale anomaly 12 13 reversal is bracketed by dates of 32 4 and 34 6 m y in best agreement with the time scale of labrecque and colleagues the magnetostratigraphy also helps calibrate the oligocene north american land mammal ages and allows correlation with the european marine microfossil zonation this correlation suggests that the age of the eocene oligocene boundary is 37 0 m y contrary to younger dates obtained from glauconites and microtektites

correlation and geochronology of middle eocene strata from the western united states abstract in this study i integrate marine and continental biostratigraphy magnetic polarity stratigraphy and radioisotopic chronology in a synthetic correlation of middle eocene strata from the western united states more than 2000 m of section were sampled from volcaniclastic deposits aycross and tepee trail formations northwestern wyoming lacustrine and fluviatile deposits washakie formation southwestern wyoming and intertonguing marine and continental strata la jolla and poway groups san diego area california detailed demagnetization studies on numerous pilot samples from all three field areas revealed moderately complex magnetizations most sample nrm s are dominated by a strong normal polarity magnetic component alternating field demagnetization does not consistently isolate the primary magnetization high blocking temperature hematite is frequently a significant carrier of remanence therefore most samples were subjected to detailed stepwise alternating field and thermal demagnetization to 600 650 c the east fork basin area northwestern wyoming magnetic polarity sequence consists of five major polarity intervals a to e the thick washakie formation sequence contains four a to d and the san diego area sequence has four polarity intervals a to d a new biochronologic interval the shoshonian land mammal subage earliest uintan is defined and characterized in all three field areas shoshonian earliest uintan faunas and the bridgerian uintan boundary occur within a single long reversed polarity interval correlation of marine biostratigraphy between the san diego area section and deep sea sections allows precise identification of san diego polarity interval b as chron c21n therefore the bridgerian uintan boundary and earliest uintan faunas occur within the reversed interval of chron c20r high temperature k ar dates bracketing this horizon in northwestern wyoming provide an age estimate of approximately 49 5 ma for the top of chron c21n and 49 ma for the bridgerian uintan boundary berggren et al 1985 use the age estimate of 49 5 ma for the top of anomaly 21 younger boundary of chron c21n as one calibration point for the generation of a paleogene geochronology the methodology and conclusions of this geochronology are compared to those of other recent geochronologies data from independent studies integrating high temperature radioisotopic dates biochronology and magnetochronology are used to test the validity of the berggren et al 1985 geochronology

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

spatial and temporal variability of seabed disturbance in the york river subestuary abstract seabed and water column observations from the microtidal york river subestuary were used to examine temporal changes in this fine grained environment and compare the impact of infrequent disturbance events annual to interannual time scales with more frequent events fortnightly to seasonal time scales an experimental across channel transect is described by time series observations of seabed radiochemical profiles x radiographs sidescan sonar and current meter data for 1999 four morphological subenvironments were distinguished based on the average maximum 137cs penetration depth and the character of excess 210pb profiles southern shoal flank secondary channel and main channel various combinations of long and short term events e g spring neap tidal cycle spring freshet storms influence subenvironment sediment structure and physical mixing depths shoal sediments were eroded deposited on the spring neap tidal cycle during the early spring months whereas the other three subenvironments were not noticeably influenced by tides on a fortnightly basis shortly after the peak currents of the annual spring freshet sediments were temporarily deposited on the shoal and flank major events such as hurricane floyd did not affect this section of the river except as a result of subsequent longitudinal sediment transport along the estuary main channel that resulted in rapid sediment erosion and deposition of 100 cm in 1 month the formation and infilling of longitudinal furrows have previously been implicated as contributing to shallow 25 cm seabed mixing in the secondary channel however interannual variations in river discharge and estuarine circulation likely control sediment supply to this section of the river and may augment the location and frequency of furrow formation within the secondary channel and the main channel overall the data indicate that the seabed at the upper york transect is frequently physically disturbed such that bioturbation structures are not preserved in surface sediments 0 30 cm however the presence of bioturbation structures below 30 cm in some of these subenvironments suggests either that this section of the river has experienced long term changes in the dominant mixing mechanism or that the sedimentary stratigraphy is event driven

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

qualitative and quantitative approaches in palaeohydrography a case study from core top parameters in the gulf of cadiz palaeoceanography relies on the assumption that parameters measureable in sediment cores correlate reliably to hydrographic parameters areas of dynamic watermass mixing which generally have steep hydrographic gradients therefore provide both a tempting target large spatial and temporal differences in temperature and salinity and a significant challenge high flow velocities and high noise for palaeoceanographers here we investigate the ability of parameters measured on core tops to be used as the basis for simulating regional hydrography within one globally important area of watermass mixing the gulf of cadiz using grainsize sediment composition benthic foraminiferal assemblage and benthic foraminiferal stable isotope analysis it is possible to build an effective framework for qualitative constraint of the position of the modern mediterranean outflow water mw plume we propose that the gulf of cadiz slope can be sub divided into 8 hydrographic zones reflecting these parameters proximal mw core mw1 steep slopes core mw1 gentle slopes distal mw1 distal mw2 lower limit of mw plume north atlantic deep water and ambient atlantic water we anticipate that compilation of time slice data will reveal hydrographic sub divisions of the slope for the past in a similar manner improving our understanding of past changes in the size and position of the mw plume but more work needs to be done before a secure protocol for quantitative reconstruction can be created stable isotope analysis alone is insufficient for the task with 13c behaving in a non conservative manner and 18ocalcite acting in an ambiguous way due to the competing influences of 18owater and temperature it is likely that if a single parameter that unambiguously determines the difference between mediterranean water and atlantic water can be identified combination with 18ocalcite will allow extension of our qualitative analysis into a quantitative means of palaeohydrographic reconstruction for this region similar complexity to that found in this study would be expected in any mixing region and in particular on the majority of sediment drifts we recommend that core top surveys similar to this study are performed on these sediment drift systems before any form of quantitative palaeohydrology is attempted

faunal turnover of intermediate water benthic foraminifera during the paleogene in new zealand abstract analysis of benthic foraminifera in upper cretaceous through oligocene bathyal sediments from east coast north island new zealand demonstrates that the catastrophic extinction event of intermediate water 100 1000 m taxa occurred approximately 58 57 ma during the latest paleocene early eocene global warming the following middle eocene cooling produced stepwise origination events signifying the greatest turnover of the fauna most of the extinct species are aerobic forms whereas the surviving taxa are dysaerobic forms this interpretation suggests that a change of environment to low oxygen conditions was the main cause of the extinction following the extinction event a dysaerobic fauna occupied the intermediate water for about one million years the stepwise appearance of new aerobic species in the middle eocene indicates a gradual increase of dissolved oxygen in the intermediate water

a mesoscale eddy pair southwest of taiwan and its influence on deep circulation 1 a pair of mesoscale eddies namely an anticyclonic eddy ae and a cyclonic eddy ce generated southwest of taiwan was investigated using long term moored observations augmented with satellite and reanalysis data ae ce increased the upper ocean current to 100 cm s 50 cm s and generated temperature anomaly t up to 7 5 c 3 0 c the vertical structure of ae presented a phase difference between t and velocity with the core of t located south of the zero velocity line this phase difference induced a 28 5 12 0 tw 1 tw 1012 w westward eddy heat transport southwest of taiwan ae also presented strong nonlinearity in the upper ocean and yielded an annual mean volume transport of 0 86 0 15 sv energy analysis showed that both baroclinic and barotropic instabilities were important for the generation and growth of the eddy pair and contribution from wind work was relative small in the deep sea ae ce intensified the deep currents and generated large positive negative t the deep and surface currents flowed in opposite directions during the eddy events which is consistent with the interpretation that the eddy pair is dominated by the first baroclinic mode the observed deep penetrating eddy pair could greatly influence the deep circulation of the northeastern south china sea

mammalian generic diversity and turnover in the late paleocene and early eocene of the bighorn and crazy mountains basins wyoming and montana usa abstract patterns of mammalian generic turnover richness and faunal composition were investigated for faunas from 17 biostratigraphic zones in middle paleocene through early eocene deposits of the bighorn and clarks fork basins of northern wyoming and the crazy mountains basin of south central montana significance of turnover was evaluated 1 by comparison of observed turnover to expected turnover calculated from the multiple regression of turnover on zone duration and generic richness and 2 by comparison of observed turnover to a bootstrapped turnover distribution patterns of turnover and richness also were assessed in light of relative sampling quality of each faunal zone the analysis identified four intervals of significant faunal change the torrejonian tiffanian transition the late tiffanian the earliest wasatchian and the middle to late wasatchian the first interval was characterized by a high number of last occurrences in the latest torrejonian resulting in a decrease in standing generic richness in the earliest tiffanian but no major changes in ordinal composition during the next interval of significant turnover the late tiffanian higher than expected first occurrences resulted in an increase in standing richness and a change in faunal composition most probably reflecting the immigration of taxa from outside north america the third and most dramatic interval of significant generic turnover took place in the earliest wasatchian and was distinguished by a high number of first occurrences but relatively few last occurrences this led to a marked increase in generic richness a pattern similar to that for the early wasatchian of north america as a whole the major change in faunal composition as in the late tiffanian was largely composed of immigrants from other continents the pattern of faunal change during the early wasatchian of the bighorn basin along with evidence for global warming at the paleocene eocene boundary supports previous interpretations associating this episode in mammalian evolution with the opening of high latitude intercontinental dispersal routes during the fourth interval of interest the middle to late wasatchian the bighorn basin fossil record shows a drop in generic richness this differs from the overall north american pattern and may be in part an artifact of still inadequate sampling for the latest part of the stratigraphic sequence in the bighorn basin

seismic and geologic evidence for early paleogene deepwater circulation in the western north atlantic previous studies of paleogeography global climate and foraminiferal stable isotopes have suggested that paleogene deepwater circulation was significantly different from that of today extracting details of deepwater history from the western north atlantic has been hampered by oligocene erosion and the lack of ideally located drill holes we report the discovery of a seismic disconformity on the sw bermuda rise that we have tied to a late paleocene erosional event in deep sea drilling project dsdp boreholes from this region distribution of this new seismic marker reflector ab indicates that it was formed by cyclonically circulating bottom water entering the western north atlantic from the south we attribute this vigorous deep circulation to a southern ocean source analogous to the effects of modern antarctic bottom water this interpretation is supported by isotopic comparisons that show the paleocene southern ocean was enriched in 13c relative to the pacific we distinguish reflector ab from the overlying reflector au on the basis of superposition and ages obtained at dsdp sites and piston cores using one of the cores we have estimated that the youngest age for reflector au is earliest oligocene 36 6 34 0 ma while its oldest age has been previously established as late eocene laminated sediments beneath reflector ab are enriched in organic carbon indicating that the early paleocene deep western north atlantic was occasionally anoxic these low oxygen levels may have been the result of sluggish deep circulation and or low latitude production of warm saline deep water wsdw sediments immediately above reflector ab show that deposition resumed on the western bermuda rise site 387 by the latest paleocene to earliest eocene biochron np10 57 2 0 6 ma while deposition resumed on the central bermuda rise site 386 during the late paleocene erosion nondeposition continued across much of the bermuda rise widespread resumption of pelagic deposition in the early eocene is consistent with 13c evidence for reduced southern ocean influence at this time however lower eocene sediments record well oxygenated conditions and 13c and 18o comparisons indicate that there were two early eocene deepwater sources the southern ocean and wsdw pak and miller this issue

higher temperatures and lower oceanic pco2 a climate enigma at the end of the paleocene epoch one of the largest and most abrupt climatic warming events documented in the geologic record occurred at the end of the paleocene epoch oceanic deep waters warmed to 10 c and high latitude surface waters warmed from 10 c to 20 c within several thousand years this coincided with weakened atmospheric circulation and the extinction of 50 of deep sea benthic foraminiferal species it has been suggested that this warm excursion was forced by higher atmospheric pco2 and greenhouse effects caused by a pulse of hydrothermal activity and or volcanism stable isotopic evidence is presented from two widely separated locations that suggest this warming was associated with a drop in oceanic pco2 rather than an increase oceanic pco2 change across this event was estimated using a model of 13c fractionation in photosynthate organic carbon versus co2aq with solubility constants for co2 and stable isotopic paleotemperature estimates to derive a well preserved record for surface ocean 13c change the organic carbon bound within the calcite lattice of well preserved planktonic foraminifera was extracted for isotopic analysis with allowance for uncertainty in the isotopic differences between phytoplankton and foraminiferal organic matter the initial results indicate a drop in surface ocean pco2 at high and low latitudes from 600 700 parts per million ppm to 200 ppm lower pco2 persisted for at least 10 000 years the duration of the pco2 excursion was long enough for the ocean and atmosphere to have reached a new steady state condition there is no evidence of increased organic carbon burial in the deep sea during this period two alternative explanations are presented to account for such a rapid drop in oceanic pco2 one involves reduced upwelling induced by diminished wind stress as atmospheric circulation weakened in response to climate warming this would have reduced the rate of metabolic co2 recycling into the surface ocean it will be necessary to obtain data from regions outside potential upwelling zones in order to evaluate this the second involves a readjustment of carbonate equilibria in the ocean to higher co3 in the surface ocean particularly at high latitudes where surface waters warmed to approximately 20 c such a shift in carbonate equilibria would have lowered the ocean s capacity to take in co2 if the initial results presented here do accurately reflect a change in the global ocean co2aq the paleocene eocene boundary event may provide clues about the ocean s physical and biological response to rapid large scale perturbations in atmospheric pco2 and to global warming

deep south china sea circulation 1 the analysis of an updated monthly climatology of observed temperature and salinity from the u s navy generalized digital environment model reveals a basin scale cyclonic circulation over the deep south china sea scs the cyclonic circulation lies from about 2400 m to the bottom the boundary current transport of the cyclonic circulation is around 3 0 sv our results suggest that the cyclonic circulation is mainly forced by the luzon overflow with bottom topography playing an important role the structures of potential temperature salinity and potential density in the deep scs are consistent with the existence of the cyclonic circulation specifically low salinity water is found in the interior region west of luzon island and surrounded by saline pacific water in boundary current regions to the north west and southwest our results show the potential density distribution and the corresponding cyclonic circulation in deep scs are primarily controlled by salinity variations in the deep basin

magnetostratigraphic correlation of the lincoln creek formation washington implications for the age of the eocene oligocene boundary paleomagnetic studies of the upper eocene to oligocene lincoln creek formation southern olympic peninsula washington produce a polarity pattern spanning chrons c15r to c6c this allows direct correlation of the provincial foraminiferal and molluscan biostratigraphy with the global marine chronology a high temperature basalt date of 38 5 1 6 ma correlates with a position just below chron c15 placing chron c15r at about 38 ma this suggests that the age of the eocene oligocene boundary within chron c13r is younger than 38 ma probably about 37 36 ma

the palaeogene time scale radiometric dating versus magnetostratigraphic approach numerical geological time scales rest firmly on the analysis of radiometric data since the discovery of oceanic magnetic stripes and their signification alternative time scales have been constructed whose numerical predictions are based on the hypothesis of a constant rate of sea floor spreading the most recent such scale uses only five tie points plus present day to subdivide a span of over 80 million years the present paper demonstrates that the rate of ocean floor spreading has varied markedly and without obvious pattern both in time and in space thus magnetostratigraphic scales based on large interpolations are fundamentally flawed an alternative scale based on a consideration of all radiometric data and using magnetostratigraphic data only for small interpolations is commended

subinertial variability in the deep ocean near the east pacific rise between 9 and 10 n 1 the subinertial variability of deep ocean currents near the crest of the east pacific rise in the tropical east pacific is examined using observations from a collection of moored instruments augmented with sea surface height data the moored velocity observations reveal low frequency currents with characteristic time scales of 1 3 months and maximum speeds up to 10 cm s directly over the ridge axis the subinertial motions are dominated by the along axial meridional velocities which are coherent in phase and amplitude along the entire length of the ridge segment between 9 and 10 n with increasing distance from the ridge crest the low frequency currents become weaker and less dominated by the along axial flow component lag correlations between the velocity records indicate westward signal propagation with a speed on the same order as the speed of westward propagating sea surface height anomalies which are also associated with characteristic time scales of 1 3 months as furthermore the subinertial velocities at depth are significantly correlated with geostrophic near surface currents estimated from sea surface height data we conclude that the subinertial velocity field near the epr crest is mainly a superposition of velocities associated with eddies propagating westward across the ridge and topographic flows such as trapped waves and boundary currents

a census of eddy activities in the south china sea during 1993 2007 1 numerous mesoscale eddies occur each year in the south china sea scs but their statistical characteristics are still not well documented a pacific basin wide three dimensional physical biogeochemical model has been developed and the result in the scs subdomain is used to quantify the eddy activities during the period of 1993 2007 the modeled results are compared with a merged and gridded satellite product of sea level anomaly by using the same eddy identification and tracking method on average there are about 32 9 2 4 eddies predicted by the model and 32 8 3 4 eddies observed by satellite each year and about 52 of them are cyclonic eddies the radius of these eddies ranges from about 46 5 to 223 5 km with a mean value of 87 4 km more than 70 of the eddies have a radius smaller than 100 km the mean area covered by these eddies each year is around 160 170 km2 equivalent to 9 8 of the scs area with water depths greater than 1000 m linear relationships are found between eddy lifetime and eddy magnitude and between eddy vertical extent and eddy magnitude showing that strong eddies usually last longer and penetrate deeper than weak ones interannual variations in eddy numbers and the total eddy occupied area indicate that eddy activities in the scs do not directly correspond to the el nino southern oscillation events the wind stress curls are thought to be an important but not the only mechanism of eddy genesis in the scs

land mammal ages faunal heterochrony and temporal resolution in cenozoic terrestrial sequences traditionally land mammal biochronology has subdivided the cenozoic into discernible time intervals with an average duration of about 3 5 times 10 6 years recent applications of chronological tools particularly magnetic polarity stratigraphy have increased the power of resolution by an order of magnitude so that time intervals of about 3 times 10 5 years can be discerned in terrestrial sequences this increased power of resolution has significant paleontological ramifications examples are cited of heterochronous time transgres sive datum planes however recently proposed examples of heterochrony of entire early cenozoic land mammal faunas result from incorrect correlations to the time scale given the recently increased power of temporal resolution it is possible to assess critically the quality of chronological data that have been used to propose or support drastic paleontological hypotheses such as faunal heterochrony heterochrony of entire land mammal faunas has not yet been documented

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

recalibration of the geomagnetic polarity timescale the quest for improved time control to estimate rates of geologic and paleoenvironmental processes is central to the earth sciences until the middle of this century geochronology was based solely on macrofossil evolution providing the largely unmodified definition of geologic stages in the last few decades with impetus from the deep sea drilling project dsdp and the ocean drilling program odp microfossil biostratigraphy has become increasingly important although new radiometric techniques have resulted in improved absolute age precision the direct correlation of absolute ages to biozonations and hence to geologic stage boundaries remains poor this is due to the difficulty of finding materials suitable for radiometric dating which can be directly correlated to biozonations the bridge between biozonations and absolute ages and the interpolation between absolute ages are best accomplished particularly for cenozoic and late mesozoic time through the geomagnetic polarity timescale gpts the template for late jurassic to quaternary geomagnetic polarity is derived from oceanic magnetic anomalies as demonstrated by heirtzler et al 1968 the gpts can be constructed using oceanic magnetic anomaly record s assuming constant seafloor spreading rate s and interpolating between available radiometric ages in the last quadrennium there have been outstanding developments in radiometric dating and astrochronology which have greatly improved the absolute age control of the gpts

a new geomagnetic polarity time scale for the late cretaceous and cenozoic we have constructed a magnetic polarity time scale for the late cretaceous and cenozoic based on an analysis of marine magnetic profiles from the world s ocean basins this is the first time since heirtzler et al 1968 published their time scale that the relative widths of the magnetic polarity intervals for the entire late cretaceous and cenozoic have been systematically determined from magnetic profiles a composite geomagnetic polarity sequence was derived based primarily on data from the south atlantic anomaly spacings in the south atlantic were constrained by a combination of finite rotation poles and averages of stacked profiles fine scale information was derived from magnetic profiles on faster spreading ridges in the pacific and indian oceans and inserted into the south ariantic sequence based on the assumption that spreading rates in the south atlantic were smoothly varying but not necessarily constant a time scale was generated by using a spline function to fit a set of nine age calibration points

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

stable isotope stratigraphy and paleoclimatology of the paleogene bighorn basin wyoming usa abstract climatic warming from the late paleocene into the early eocene had profound effects on atmospheric and marine circulation marine thermal gradients and benthic biota in addition marine carbon isotope values decreased substantially in both surface and deep waters because carbon is rapidly exchanged between reservoirs at the earth s surface such as marine surface water the atmosphere land plants and materials that obtain carbon from plants e g soil minerals and herbivores carbon isotope fluctuations provide time lines linking the marine and continental records we analyzed the carbon isotope composition of paleosol carbonates and mammalian tooth enamel from stratigraphic sections in northwestern wyoming carbon isotope correlation demonstrates that a short interval of extreme high latitude warming coincided precisely with the first appearance of several important modern mammalian orders in addition oxygen isotope analyses of fossils and paleosol carbonates provide information about climatic conditions on land in the paleogene we reconstructed the oxygen isotope composition of local meteoric water using biogenic minerals paleocene eocene meteoric water was significantly 18 o depleted indicating substantial loss of water vapor during its transport to the region soil temperature was calculated as a proxy for mean annual temperature assuming oxygen isotope equilibrium between soil carbonate and meteoric water calculated temperatures were plausible 10 25 c but highly variable prohibiting high resolution analysis of local temperature variations in response to global climatic warming

sequence stratigraphy eustasy or tectonic imprint sequence stratigraphy is viewed by many geologists as the expression in the stratigraphic record of the history of sea level changes sequence boundaries are its most distinctive elements and are used for global correlations until now correlations between unconformities and postulated lowerings of sea level have been seen primarily in terms of cause and effect relationships the postulated fall providing an explanation for the presence of an unconformity they have not been truly perceived in terms of stratigraphic correlations which would imply the establishment of synchrony between the cause and the effect to decipher the presence of a global sea level signal in the stratigraphic record the synchrony of sea level related unconformities in widely separated basins must be established which can be achieved by comparing the degree of overlap between hiatuses in different stratigraphic sections outcrop sections wells and the deep sea record reveal an apparently worldwide unconformity ies across the lower middle eocene boundary characterized by intensive reworking and or relatively rapid shallowing in some areas e g cyrenaica ne libya california egypt the lower middle eocene intervals in sections on the north atlantic margins have been correlated through magnetobiostratigraphy and the durations of the hiatuses have been precisely determined this record is compared with that in sections in other basins where shallowing and intensive reworking occur this study shows that there are two groups of unconformities and associated hiatuses around the lower middle eocene boundary the older hiatuses in the latest early eocene are generally short even on the shelf 1 m y the younger hiatuses in the early middle eocene are somewhat longer 2 m y the stratigraphic record around the lower middle eocene boundary suggests that there may be two mechanisms acting simultaneously to produce unconformities unconformities of a given age on the shelf may result from a global fall in sea level while their stratigraphically correlative unconformities on the slope and rise may result from tectonic instability unconformities related to the third order cycles in sea level changes in vail s model primarily may reflect tectonoeustasy

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

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

in situ observation of contour currents in the northern south china sea applications for deepwater sediment transport deepwater currents and related suspended sediment concentration were obtained by an acoustic doppler current profiler adcp mooring system in the northern south china sea from september 2011 to may 2013 to characterize the occurrence of contour currents and to evaluate their sediment transport capacity magnitude of the current velocity generally varied in the range of 0 2 cm s with a dominant flow direction of 250 southwestward the observed contour current defined as the along slope component of the deepwater currents has a tunnel like vertical structure with the largest velocity occurring in the middle of the tunnel and decreasing outwards both the magnitude and the depth range of the maximum velocity display evident inter seasonal variations with the strongest velocity in summer and the weakest in spring while the thickness of the contour currents was the highest in winter and the lowest in spring we also found that passing through of the deep reaching mesoscale eddies significantly affected the magnitude and direction of the contour currents the suspended sediment concentration ssc estimated from echo intensities of the adcp is the highest at the near bottom 400 g l and decreases upwards to 10 g l at water depth shallower than 1750 m high ssc is mostly observed during periods of low magnitude of the contour currents suggesting resuspension of sediment from the seafloor is not the major controlling factor of these high ssc events our observation also suggests that the major role that contour currents play is to transport sediment from the sources through keeping sediment suspended above the lower continental slope of the south china sea

the depositional characteristics and oil potential of paleo pearl river delta systems in the pearl river mouth basin south china sea abstract delta systems in the zhuhai zhujiang and hanjiang formations are interpreted as having formed during periods of sea level rise from the late oligocene to mid miocene 30 10 5 my b p deltas in the zhuhai formation were developed in a shallow water environment on a sandy wave or fluvial dominated coasts thick and blanket like sandstones are common but mudstones are infrequent oil bearing zones have been found only in the upper part of the systems overlain by mudstone of the zhujiang formation deltas in the zhujiang formation are interpreted as having formed in a deeper water environment on sandy wave or fluvial dominated coasts carbonate platforms started growing on the dongsha massif as the sea level slowly rose the moderate sandstone mudstone ratio in the delta systems and a zone of secondary porosity in the carbonate rocks provide an excellent reservoir rock and seal rock for the basin deltas in the lower hanjiang formation are similar to those of the zhujiang formation but the upper part of the formation is interpreted as having formed in a shelf environment the thick shelf mudstone interbedded with offshore bar sandstones would be one of the better regional seal rocks in the study area no carbonate rock developed on the dongsha massif due to the rapid rise in sea level all delta systems from the zhuhai to the zhujiang formation are stacked in an onlap pattern indicating a more and more expanding marine transgression which was caused by eustatic sea level rise this marine transgression is almost unique and contrasts to the progradational offlap pattern of cenozoic delta systems in the gulf of mexico it resulted in thick sandstone deposits immature or poorly mature source rock and no ductile mudstones with no growth faults or rollover structures hydrocarbons generated from eocene oligocene lacustrine source rocks are trapped by drape structures related to local basement highs or by carbonate rock with secondary porosity most of the remaining undiscovered reserves in the basin will be found in non structural subtle traps especially stratigraphic traps

stratigraphic and climatic implications of clay mineral changes around the paleocene eocene boundary of the northeastern us margin abstract kaolinite usually is present in relatively small amounts in most upper paleocene and lower eocene neritic deposits of the northern us atlantic coastal plain however there is a short period less than 200 000 k y in the latest paleocene upper part of calcareous nannoplankton zone np 9 when kaolinite dominated clay mineral suites replaced the usual illite smectite dominated suites during this time of global biotic and lithologic changes kaolinite increased from less than 5 of the clay mineral suite to peak proportions of 50 60 of the suite and then returned to less than 5 in uppermost paleocene lowermost eocene strata this kaolinite pulse is present at numerous localities from southern virginia to new jersey these sites represent both inner and middle neritic depositional environments and reflect input from several river drainage systems thus it is inferred that kaolinite rich source areas were widespread in the northeastern us during the latest paleocene erosion of these source areas contributed the kaolinite that was transported and widely dispersed into shelf environments of the salisbury embayment the kaolinite increase which occurred during a time of relatively high sea level probably is the result of intensified weathering due to increased temperature and precipitation the southern extent of the kaolinite pulse is uncertain in that uppermost paleocene beds have not been identified in the southern atlantic coastal plain the late paleocene kaolinite pulse that consists of an increase to peak kaolinite levels followed by a decrease can be used for detailed correlation between more upbasin and more downbasin sections in the salisbury embayment correlations show that more upbasin paleocene eocene boundary sections are erosionally truncated they have varying portions of the kaolinite increase and if present at all discontinuous portions of the subsequent kaolinite decrease as these truncated sections are disconformably overlain by lower eocene strata rapid erosional removal of large parts of the most kaolinite rich p e boundary clay deposits occurred by early eocene time erosion of the kaolinite rich p e boundary beds was enhanced during times of sea level fall when kaolinite rich sediments were redeposited to produce kaolinite spikes in basal beds of lower and middle eocene sequences that have little or no kaolinite elsewhere in the sequence in contrast more downbasin sites document only the upper decreasing part of the kaolinite pulse the absence of strata documenting the earlier kaolinite increase is attributed to slow sedimentation condensed interval as a result of a significant sea level rise that ponded most sediments in shallower waters combined with the probable subsequent erosional removal of these thin downbasin deposits by oceanic currents

sedimentological evidence for the formation of an east antarctic ice sheet in eocene oligocene time middle eocene to late oligocene sediments recovered at ocean drilling program sites 689 and 690 on maud rise in the southernmost atlantic ocean and at sites 738 and 744 on kerguellen plateau in the southernmost indian ocean were analysed in order to study the depositional environment and the palaeoclimate special emphasis was placed on the reconstruction of the formation of a cryosphere on the antarctic continent the investigations include quantifications of carbonate and opal contents grain size analyses and studies of clay mineral assemblages the sedimentary sequence at all sites under investigation is highly pelagic with nannofossil oozes and chalks dominant the first indication of probable glacierization at sea level is in the form of isolated gravel and terrigenous sand grains which indicate ice rafting from middle eocene time at c 45 5 ma this is supported by enhanced concentrations of detrital chlorite and reworked kaolinite probably some glaciers reached the sea while most of the continent remained under the influence of a humid and warm to temperate climate the growth of the inland ice resulted in enhanced physical weathering and in increased contents of detrital chlorite and kaolinite from about 40 ma a strengthening of the glacial conditions and the onset of continental east antarctic glaciation is recorded in early oligocene sediments with an age of 36 ma all major sediment parameters document this event the clay mineralogy changed between c 36 3 ma and c 35 5 ma from smectite dominated assemblages to illite and chlorite dominated assemblages the latter being indicative of physical weathering under cooler climates large quantities of ice rafted gravel and sand accumulated on the kerguelen plateau between 36 0 ma and 35 8 ma at the same time an increase in opal content occurred as well as a decrease in carbonate the sediment parameters imply that the east antarctic continent was more or less totally buried beneath the ice during oligocene time the ice sheet however probably did not have a polar but a temperate character as indicated by the occurrence of nothofagus and relatively warm surface water temperatures prohibiting the long distance transport of debris by icebergs

sediment dynamics driven by contour currents and mesoscale eddies along continental slope a case study of the northern south china sea abstract based upon 3 d seismic reflection data published drill core studies oceanographic observations and numerical modelling this study identifies a small scale contourite depositional system that is locally confined by canyons slope failures erosional terraces and erosional slopes on the jianfeng slope northern south china sea 1500 to 2300 m water depth possible oceanic driving mechanisms for the spatial heterogeneity in sedimentation and erosion within the quaternary deposits in this complex slope system are investigated numerical simulations show that the quasi steady south china sea deep water circulation which affects the study area is characterised by low velocities maximum 4 cm s with a slight modulation by tides 1 cm s this quasi steady deep water thermohaline circulation is able to keep sediment particles in suspension rather than to erode seafloor sediment the bottom hydrodynamic regime becomes energetic when mesoscale eddies horizontal scale of 10 to 100 km approach our modelling study indicates that both surface and bottom mesoscale eddies are essential to account for the spatial heterogeneity in sedimentation pattern along the northern south china sea continental slope according to simulation the eddy front contains the highest flow velocity over a mesoscale eddy cycle 45 days exceeding the threshold for resuspension of unconsolidated sediment 15 cm s as a consequence massive resuspension is produced at various sites and redistributed by sub mesoscale horizontal scale of 1 to 10 km circulations originated from an eddy topography interaction in contrast to the surrounding areas which are subject to erosional forcing for a relatively long part 7 of an eddy cycle both the locally confined drift and a further upstream large elongated mounded drift experience little erosion

radiometric time scale for the upper eocene and oligocene based on k ar and rb sr dating of volcanic biotites from the pelagic sequence of gubbio italy several samples of unaltered volcanic biotite were recovered from five biostratigraphically and magnetostratigaphically controlled bentonite horizons in the continuous upper eocene oligocene pelagic carbonate sequence of gubbio northern italy k ar and rb sr dates on these samples offer a unique opportunity to calibrate with closely spaced points the late paleogene biostratigraphic and magnetostratigraphic time scales until now time scales have been constructed by interpolating between less certain and more widely spaced data points our combined k ar and rb sr dates are here used to calibrate the following five stratigraphic levels from top to bottom level 5 upper part of globorotalia opima opima planktonic foraminiferal zone upper part of indistinct np23 np24 nannoplankton zone and cp18 nannoplankton zone bottom of magnetic anomaly 9n 28 0 0 3 ma level 4 globigerina ampliapertura and cassigerinella chipolensis zone lower part of np23 zone and bottom of cp18 zone upper part of anomaly 12r 32 0 0 8 ma level 3 pseudohastigerina micra zone upper part of np21 and cp16b zones top of anomaly 13n 35 4 0 4 ma level 2 upper part of globigerinatheka semiinvoluta zone upper part of np18 and cp15a zones top of magnetic anomaly 16n 36 0 0 4 ma level 1 lower part of g semiinvoluta zone between zones np18 and np19 middle part of zone cp15a upper part of anomaly 17n 36 4 0 3 ma from these data the interpolated age for the much debated eocene oligocene boundary is 35 7 ma with a 2 standard deviation uncertainty of 0 4 ma

middle eocene through early oligocene climate history and paleoceanography in the southern ocean stable oxygen and carbon isotopes from odp sites on maud rise and kerguelen plateau mackensen a and ehrman w u 1992 middle eocene through early oligocene climate history and paleoceanography in the southern ocean stable oxygen and carbon isotopes from odp sites on maud rise and kerguelen plateau mar geol 108 l 27 paleogene stable oxygen and carbon isotopes were measured in foraminifera from odp sites 689 and 690 at maud rise in the atlantic ocean sector of the southern ocean and from sites 738 744 748 and 749 at the southern kerguelen plateau in the indian ocean sector these data were compared with sedimentological data from the same sample set both benthic and planktic 6180 values document a cooling trend beginning around 49 5 ma at all sites during the late middle eocene planktic lso values indicate a steepening latitudinal temperature gradient from 14 c at the northern sites towards 10 c at the southernmost sites terrigeneous sand grains of probably ice rafted origin and clay mineral assemblages point to the existence of a limited east antarctic ice cap with some glaciers reaching sea level as early as middle eocene time around 45 5 ma between 45 and 40 ma average paleotemperatures were between 5 and 7 c in deep and intermediate water masses while near surface water masses ranged between 6 and io c during the late eocene between 40 and 36 ma average temperatures further decreased to 4 5 c in the deep and intermediate water masses and to 5 8 c near the sea surface abruptly increasing 61so values at approximately 35 9 ma exactly correlate with a sharp pulse in the deposition of icerafted material on the kerguelen plateau a dramatic change in clay mineral composition and an altered southern ocean circulation indicated by a differentiation of benthic 61 c values between sites increasing opal concentrations and decreasing carbonate contents for planktic and benthic foraminifera this 80 increase ranges between 1 0 and 1 3 o and between 0 9 and 1 4 o respectively we favour a hypothesis that explains most of the 61so shift at 35 9 ma with a buildup of a continental east antarctic ice sheet consequently relatively warm oligocene antarctic surface water temperatures probably are explained by a temperate wet based nature of the ice sheet this would also aid in the fast build up of an ice sheet by enhancing the moisture transport on to the continent

magnetostratigraphic correlation of palaeogene sediments in the hampshire and london basins southern uk magnetostratigraphic studies of the late palaeocene and early to middle eocene formations in the hampshire and london basins indicate that the geomagnetic field maintained a predominantly reverse polarity throughout the period of deposition of these sediments eight discrete normal polarity magnetozones have been identified within this dominantly reverse polarity interval three of these lie within the bracklesham group three within the london clay formation one in the oldhaven 9formation9 and one within the lowermost part of the thanet formation assuming that the magnetozone boundaries represent absolute time planes except where they correspond with stratigraphic hiatuses they may be used to provide a time framework for chrono stratigraphic correlation between sections and for investigating the dynamics of early palaeogene sedimentation patterns in this region the results indicate that the majority of the marine transgressive and regressive events which form the basis of king9s 1981 subdivisions of the london clay occurred very rapidly and may be regarded as being effectively 9instantaneous9 in marked contrast the boundaries between the sedimentary cycles of the bracklesham group represented by the wittering earnley selsey and huntingbridge divisions are significantly diachronous in relation to the absolute time planes provided by the magnetozone boundaries it is clear that the bracklesham group transgressive events occurred systematically earlier in the east than in the west as might be expected for westward directed transgressions certain biostratigraphic zonal boundaries within the bracklesham group appear also to have been influenced by the changing environmental conditions which accompanied these transgressive regressive cycles

environmental impact of volcanic margin formation late rift stage uplift and subsequent massive transient volcanism during breakup of rifted volcanic continental margins constrain paleoenvironments by modifying basin geometry and the composition of the atmosphere hydrosphere and thus biosphere on regional and global scales the early tertiary north atlantic breakup history shows that lava emplacement was accompanied by regional ashfalls and that extrusive complexes influenced paleogene oceanic and continental margin circulation and sedimentation temporal correspondence with the terminal paleocene deep sea extinction event and the earliest eocene greenhouse suggests a global impact possibly by enhanced atmospheric co 2 levels leading to polar warming and thereby changing patterns of deep water formation in this context transient subaerial volcanism at continental margins should be considered with the much discussed continental flood basalt provinces and oceanic plateaus

subthermocline eddies in the western equatorial pacific as shown by an eddy resolving ogcm abstractsporadic in situ observations have shown evidence that subthermocline eddies exist off the mindanao coast these subthermocline eddies are believed to play an important role in the heat freshwater and other ocean property transports of the region but their characteristics and in particular their pathway and source of energy are poorly explored because of the lack of long term observations analysis of results from an eddy resolving general ocean circulation model has revealed that most subthermocline eddies off the mindanao coast originate from the equatorial south pacific ocean to the west of the ninigo group these eddies propagate northward along the new guinea coast cross the equator in the far western pacific and reach the mindanao coast at a typical propagation speed of 0 12 m s 1 the dominant time scales of these eddies range between 50 and 60 days

late cretaceous eocene nannofossil and magnetostratigraphic correlations near gubbio italy abstract using a modified sample preparation technique we have been able to establish a detailed lower campanian to upper eocene nannofossil stratigraphy in the bottaccione and contessa highway sections near gubbio appearance and extinction levels of virtually all the commonly used calcareous nannofossil zonal markers have been recognized and can now be closely correlated with the planktonic foraminifera zonation and the magnetic reversal stratigraphy previously established in these sections comparisons with the nannofossil calibrations of the oceanic magnetic anomaly sequence in deep sea drilling project dsdp sites suggest that magmetic subchrons c17n and c25n are missing in the bottaccione section the observed variability of the relative stratigraphic position of most plankton events is confirmed to less than one magnetic subchron absolute abundance paleobiogeographic restriction and differential preservation render some of the traditionally used biostratigraphic events less reliable than others

nannoplankton zonation and the palaeocene eocene boundary beds of nw europe an indirect correlation by means of volcanic ash layers correlation of early palaeogene ash layers in dsdp hole 550 leg 80 goban spur with those of the north sea basin indicates that the base of nannoplankton zone np10 approximates the base of the sele formation of the north sea area the bases of the danish ash series the german ash bearing untereozan 1 and the paris basin sparnacian and the top of the woolwich reading bottom bed of the london basin if as is now common practice the palaeocene eocene boundary is placed at the np9 np10 boundary then the units listed above would constitute the basal units of the eocene in their respective countries the cessation of large scale pyroclastic activity took place at about the middle of the zone np10 interval

the formation and fate of internal waves in the south china sea internal oceanic waves are subsurface gravity waves that can be enormous and travel thousands of kilometres before breaking but they are difficult to study here observations of such waves in the south china sea reveal their formation mechanism extreme turbulence relationship to the kuroshio current and energy budget internal waves are the underwater version of more familiar surface waves they can be enormous and travel thousands of kilometres before breaking the south china sea is known to be home to the largest internal waves in the world s oceans but their size generation mechanisms and role in the regional energy budget are unknown matthew alford and colleagues now present the results from the iwise observational campaign and reveal that internal waves more than 200 metres high break in the south china sea and create turbulence that is orders of magnitude larger than in the open ocean and that wave formation is influenced by the kuroshio current these results now allow for a complete energy budget of the south china sea and for a more accurate incorporation of internal waves into climate models internal gravity waves the subsurface analogue of the familiar surface gravity waves that break on beaches are ubiquitous in the ocean because of their strong vertical and horizontal currents and the turbulent mixing caused by their breaking they affect a panoply of ocean processes such as the supply of nutrients for photosynthesis1 sediment and pollutant transport2 and acoustic transmission3 they also pose hazards for man made structures in the ocean4 generated primarily by the wind and the tides internal waves can travel thousands of kilometres from their sources before breaking5 making it challenging to observe them and to include them in numerical climate models which are sensitive to their effects6 7 for over a decade studies8 9 10 11 have targeted the south china sea where the oceans most powerful known internal waves are generated in the luzon strait and steepen dramatically as they propagate west confusion has persisted regarding their mechanism of generation variability and energy budget however owing to the lack of in situ data from the luzon strait where extreme flow conditions make measurements difficult here we use new observations and numerical models to 1 show that the waves begin as sinusoidal disturbances rather than arising from sharp hydraulic phenomena 2 reveal the existence of 200 metre high breaking internal waves in the region of generation that give rise to turbulence levels 10 000 times that in the open ocean 3 determine that the kuroshio western boundary current noticeably refracts the internal wave field emanating from the luzon strait and 4 demonstrate a factor of two agreement between modelled and observed energy fluxes which allows us to produce an observationally supported energy budget of the region together these findings give a cradle to grave picture of internal waves on a basin scale which will support further improvements of their representation in numerical climate predictions

ocean science eddy effects on biogeochemistry ocean eddies tens of kilometres in radius can delineate local ecosystems and contribute to biogeochemical budgets the characterization of three such eddies in a coastal upwelling region provides insight into these wonders of nature

book reviewxvit 263 p 25 us 49 50 hardbound 11 95 us 19 95 paperback a geologic time scale w b harland et al cambridge university press washington dc usa 1990 isbn 0 521 38361 7

planktonic and benthic foraminiferal extinction events during the last 100 m y abstract five major planktonic and benthic foraminiferal extinction events occurred during the past 100 m y at the cenomanian turonian c t boundary at the cretaceous tertiary k t boundary in the latest paleocene in the late eocene and in the early middle miocene to clarify the character of the five events i estimated 1 paleo waterdepths and paleoenvironments where foraminifera were affected 2 the duration of each extinction event and 3 evaluated possible causes for each extinction event on the basis of recent literature these extinction events can be classified into three fundamentally different types 1 the mass extinction event at the k t boundary was abrupt and concentrated among surface dwelling species 2 extinctions at the c t boundary and during the latest paleocene were abrupt and mainly affected intermediate and deep water taxa over short periods 3 the late eocene and early middle miocene events affected surface and deep water species and involved stepwise or gradual extinctions over a long period 4 m y i attributed the extinction events to 1 a bolide impact for the k t event 2 a decrease in dissolved oxygen in intermediate and deep waters due to climatic warming for the c t and latest paleocene events and 3 long term global cooling for the late eocene and early middle miocene events the following relationships exist between the causes and types of extinction events 1 large extraterrestrial impacts strongly affected surface dwelling organisms in short term extinction events 2 intermediate and deep water low oxygen conditions induced by climatic warming have severely affected intermediate and deep water organisms over medium and short terms

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

an analysis of the current deflection around dongsha islands in the northern south china sea based on the in situ data and adcp observation in fall it is found that a northeastward current at inter middle level flows on the northern south china sea nscs continental shelf this current flows almost along the isobaths and it deflects from the isobaths veering toward deep water when flowing over the dongsha islands geographic currents derived from the climatologic hydrography data woa01 and absolute dynamic topography adt data confirm the deflection of the northeastward current on nscs continent a fine resolution regional ocean model which can well reproduce the large scale circulation in the nscs is used to analyze the dynamic about the deflection the vorticity term balances shows that jebar joint effect of baroclinicity and relief drives the water column to depart from the isobaths to the east of the dongsha islands the isopycnal is almost orthogonal to the isobaths the joint effect of the topographic and the baroclinic effect supplies negative vorticity and drives the water column to deflect from the isobaths and veer to deeper water momentum analysis along the stream line shows that when the sea water flows around the dongsha islands the pressure gradient along the isobath pushes the sea water to accelerate and then the coriolis force orthogonal to the isobath increases and overcomes the corresponding pressure gradient which drives the water deflected from the isobath toward the deep sea citation wang d q wang w zhou s cai l li and b hong 2013 an analysis of the current deflection around dongsha islands in the northern south china sea j geophys res oceans 118 490 501 doi 10 1029 2012jc008429

oceanic crust production and climate during the last 100 myr in order to evaluate the possible influence of oceanic crust production on climatic changes during the past 100myr variations in total oceanic crust for this period including production at mid ocean ridges oceanic plateaus and back arc basins were calculated using the most recent and accurate time scales the rates presented here differ from those of larson 1991a b on cenozoic fluctuations and show that 1 maximum production values occurred during the cenomanian palaeocene and late oligocene early miocene and 2 minimum values occurred in campanian maastrichtian late eocene and middle miocene significantly variations of oceanic crust production correspond with variations in the 18o of deep water benthic foraminifera maximum values of oceanic crust production correspond with minimum values of 18o and minimum production values with maximum values of 18o this latter synchronism suggests that changes in land sea relationships and atmospheric co2 related to major fluctuations in oceanic crust production were the main cause of mid cretaceous warming and late cretaceous cooling and of climatic quasi cycles having a periodicity of 33 38 million years over the last 100 myr this is the first report showing variations of ocean crust production synchronized with the cenozoic climate changes

paleogene calcareous nannoplankton biostratigraphy mississippi alabama and tennessee abstract distribution and abundance of calcareous nannoplankton in the paleogene formations of mississippi ms alabama al and tennessee end page 1471 tn are reported in this study these data have been used to assign each of the following nannoplankton bearing formations and members to martini s 1971 internationally recognized calcareous nannoplankton zones table end of article last page 1472

paleogene calcareous nannoplankton biostratigraphy of northwestern europe abstract the classic paleogene stages thanetian cuisian lutetian bartonian ludian and stampian defined in the epicontinental deposits of the anglo paris basin s are placed within a standard biostratigraphic framework based on an analysis of their calcareous nannoplankton floras relatively precise biostratigraphic correlations can be made with some chronostratigraphic units e g lutetian while biostratigraphic resolution of others e g ludian is limited important hiatuses are recognized between certain chronostratigraphic units only the base of the lutetian late np14 and bartonian mid np16 stages can be precisely determined in terms of calcareous nannoplankton zones with the recent study of the magnetic polarity history of the paleogene of southern england and recent advances in magnetobiostratigraphic correlations in deep sea cores it is possible to interpret the paleogene history of the anglo paris basin s in a synoptic global framework in which paleomagnetic stratigraphy provides the chronologic and eustatic variations the graphic units of northwestern europe within rather than at the boundaries of i e at dynamic element redefinition of the boundaries of the standard paleogene chronostratigraphic unconformities eustatically controlled depositional cycles would result in more precise correlations in terms of standard calcareous nannoplankton biostratigraphy

magnetostratigraphy of the white river group and its implications for oligocene geochronology abstract magnetostratigraphic studies of the oligocene white river group in wyoming colorodo nebraska and the dakotas have yielded a radiometrically dated polarity stratigraphy they provided a mid tertiary calibration point for the marine magnetic polarity timescale an unusually long interval of reversed polarity in the flagstaff rim section natrona co wyoming is bracketed by k ar dates biotite of 32 4 ma slightly above its top and 34 6 ma at its base corrected for new decay constants it probably corresponds to the long reversed interval between marine magnetic anomalies 12 and 13 also the magnetostratigraphies of 17 other fossiliferous sections of chadronian whitneyan oligocene rocks have been correlated with anomalies 9 12 on this basis the boundaries of the oligocene north american land mammal ages are chadronian orellan mid anomaly 11 12 reversal about 32 4 ma orellan whitneyan mid anomaly 10 111 reversal about 30 7 ma whitneyan arikareenan base anomaly 9 about 29 0 ma these dates are in good agreement with recent estimates based on mammalian biochronology and with a corrected radiometric date of 28 7 0 7 ma at the base of the arikareean

deepwater overflow through luzon strait 1 this study examines water property distributions in the deep south china sea and adjoining pacific ocean using all available hydrographic data our analysis reveals that below about 1500 m there is a persistent baroclinic pressure gradient driving flow from the pacific into the south china sea through luzon strait applying hydraulic theory with assumptions of zero potential vorticity and flat bottom to the luzon strait yields a transport estimate of 2 5 sv 1 sv 106 m3 s 1 some implications of this result include 1 a residence time of less than 30 years in the deep south china sea 2 a mean diapycnal diffusivity as large as 10 3 m2 s 1 and 3 an abyssal upwelling rate of about 3 10 6 m s 1 these quantities are consistent with residence times based on oxygen consumption rates the fact that all of the inflowing water must warm up before leaving the basin implies that this marginal sea contributes to the water mass transformations that drive the meridional overturning circulation in the north pacific density distributions within the south china sea basin suggest a cyclonic deep boundary current system as might be expected for an overflow driven abyssal circulation

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

eocene magnetic stratigraphy at gubbio italy and its implications for paleogene geochronology the sequence of polarity zones established by alvarez and others for the cretaceous and paleocene in the scaglia formation in the bottaccione gorge at gubbio has now been extended through the uppermost paleocene into the upper eocene globigerinatheka semiinvoluta zone anomaly 18 the relationships between the standard paleogene foraminiferal zones and the sea floor anomalies are defined with the exception of the mid eocene zones of morozovella lehneri orbulinoides beckmanni and the base of the truncorota loides rohri zone which are obscured by inadequate preservation and a fault gap the base of the eocene lies above anomaly 25 the lower to middle eocene contact base lutetian lies in the upper part of anomaly 22 the base of the bartonian lies below the base of anomaly 18 and the base of the priabonian upper eocene lies within anomaly 18 radiometric ages appear to diverge systematically from a geochronology based on steady sea floor spreading rates suggesting that spreading may have been as much as a factor of 3 slower in the paleocene and the late eocene than in the early and middle eocene

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

simulation of the interactions between gravity processes and contour currents on the algarve margin south portugal using the stratigraphic forward model sedsim abstract the margin of the gulf of cadiz is swept by an intermediate current the mediterranean outflow water mow flowing from the mediterranean to the atlantic on the northern margin of the gulf algarve margin south portugal the mow intensity is low and fine grained contourite drifts are built up with an alongslope alignment recent sedimentological studies emphasize the presence of complex process interactions resulting in the formation of a unique depositional architecture alongslope processes related to contour currents generate contourite drift while downslope processes form canyons and channels aligned on deep faults this paper uses a combined oceanographic and geological dataset to simulate the different types of interactions between gravity processes and contour currents which were evidenced on this margin an extrapolation of the contour current intensity has been used based on the present day velocity field and sea level fluctuations over the simulated geological time scale according to our model results the construction of the contourite drift is closely linked to contour current velocities and directions the types of sediments transported and the existing topography using modern sedimentological understanding of the area we have correlated gravity flow s strongest activity to sea level lowstand periods mainly due to a closer connection between canyon s mouth and river or deltaic systems the simulated gravity flows are initialized at different locations and times on the margin depending on the preserved lobes retrieved from seismic analysis their resulting morphological features are identified as perched lobes with volumes and forms close to the ones observed on portimao and lagos drifts this study provides a process based understanding of the construction of contourite system and a physical evaluation of the interactions between gravity flows perpendicular to the slope and alongslope processes in addition it shows the influence of autocyclic factors in the construction of contourite sedimentation which is important to consider in future sedimentary paleo reconstruction interpretations

correlating the eocene oligocene mammalian biochronological scale from sw europe with the marine magnetic anomaly sequence magnetostratigraphic studies have been undertaken on sedimentary continental formations from western france and spain which have yielded palaeogene mammals the results obtained provide new constraints on the chronological distribution of the mammalian reference levels a magnetozone sequence associated with the reference levels is defined the correlation of this sequence with the geomagnetic polarity time scale is proposed this correlation links the late mid eocene to oligocene mammalian biochronological scale from western europe to other stratigraphic scales a numerical calibration of the palaeogene polarity sequence is made taking into account recent radiometric dating the equations to convert the ages proposed by several authors are given

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

chadronian early oligocene magnetostratigraphy of eastern wyoming implications for the age of the eocene oligocene boundary new magnetostratigraphic studies have been conducted on early oligocene sections at flagstaff rim and ledge creek natrona county wyoming and the dilts ranch converse county wyoming thermal demagnetization has considerably improved the polarity interpretation of flagstaff rim since af demagnetization had failed to remove a diagenetic normal overprint the polarity pattern in these sections appears to span the interval from chron c10r to chron c15 of the magnetic polarity timescale 31 to 37 5 m y based on k ar dates from flagstaff rim this additional more complete magnetostratigraphic evidence shows clearly that the eocene oligocene boundary must lie between 36 and 37 m y in age

paleogene magnetic stratigraphy in umbrian pelagic carbonate rocks the contessa sections gubbio the umbrian sequence of pelagic carbonate rocks provides an opportunity for precise correlation between paleogene biostratigraphy and geomagnetic polarity history the red to pink paleocene to middle eocene scaglia rossa limestone the varicolored upper eocene scaglia variegata limestone and the gray green oligocene scaglia cinerea marlstone form a 250 m thick continuous exposure in the contessa valley near gubbio italy magnetostratigraphic lithostratigraphic and biostratigraphic investigations in three sections covering the entire paleogene have confirmed and dated the geomagnetic reversal sequence for most of this period the ferromagnetic mineral in the scaglia cinerea is magnetite and af demagnetization to peak fields of 20 mt is sufficient to define the characteristic remanent magnetization the scaglia variegata and pink scaglia rossa samples contain an additional hematite component which is very pronounced in dark red paleocene scaglia rossa samples changes of magnetic mineralogy take place in these limestones during heating especially above 500 c however thermal demagnetization is effective in isolating the characteristic remanence vectors which form almost antipodal clusters of directions representing normal and reversed polarities the directions are rotated counterclockwise partly due to post oligocene tectonism paleontological zonations of planktic foraminifera and calcareous nannofossils were hampered by poor preservation but the major epoch and stage 29 as in the gubbio bottaccione section paleocene eocene just above anomaly 25 eocene oligocene between anomalies 13 and 15 oligocene miocene just below anomaly 6c these correlations require slight modifications to previous conclusions on paleogene sea floor spreading rates

magnetic and calcareous nannofossil stratigraphy of the lower palaeogene formations of the hampshire and london basins a magnetostratigraphic study of the lower palaeogene formations exposed in the hampshire and london basins southern uk has led to the identification of eight stratigraphically distinct normal polarity magnetozones within an otherwise reverse polarity sedimentary sequence which spans the late palaeocene to middle eocene a complementary study of the calcareous nannofossil biostratigraphy of these sections and related sections elsewhere in nw europe allows a correlation of this succession of normal polarity magnetozones with the biostratigraphically calibrated geomagnetic polarity timescale based on marine magnetic anomalies it is concluded that the normal polarity chrons corresponding to anomalies 20 21 and 23 are recorded within the huntingbridge earnley and wittering divisions of the bracklesham group respectively that anomalies 24a and 24b are represented within divisions d to b2 of the london clay and anomaly 26 is represented in the lower part of the thanet beds an additional normal polarity magnetozone within the oldhaven beds is believed to represent a short normal polarity event between anomalies 24b and 25 anomalies 22 and 25 appear not to be represented in the uk lower palaeogene succession because of major unconformities at the early middle eocene boundary within the wittering division of the bracklesham group and within the late palaeocene respectively the former appears to correlate with a widespread erosional event in the oceans identified from seismic records vail et al 1979 and interpreted as reflecting a major eustatic sea level fall

northwestern european paleogene magnetostratigraphy biostratigraphy and paleogeography calcareous nannofossil evidence global calcareous nannofossil biostratigraphy is used to correlate the paleogene chronostratigraphic units of northwestern europe and standard nannofossil biozones such biostratigraphic correlations show that the lithostratigraphic sequence is discontinuous and allows interpretation of the paleogeography of northwestern europe during the paleogene and evaluation of the influence of global sea level eustatic changes on northwestern european stratigraphy a well documented unconformity occurs near the lower middle eocene boundary in the paris basin this unconformity which also can be traced in the london hampshire basin and in belgium correlates with a coastal offlap event presumed sea level of vail et al on the basis of magnetostratigraphic biostratigraphic correlations the duration of the hiatus associated with this unconformity can be estimated to be 0 6 to 1 5 m y in the hampshire basin and 2 to 4 m y in the paris basin

ecological stasis and saltation species richness change in planktic foraminifera during the late paleocene to early eocene dsdp site 577 abstract a high resolution study of late paleocene to early eocene planktic foraminifera at dsdp site 577 indicates the presence of three rapid faunal turnovers or saltation events with durations varying between 200 400 kyr and species turnover rates between 4 12 species 100 kyr these saltation events are separated by slow faunal turnovers or stasis intervals with durations varying between 2 56 5 21 myr and species turnover rates between 0 6 1 8 species 100 kyr each saltation event has different characteristics with disappearances equal to appearances in event t1 appearances dominate in event t2 that nearly double species richness and primarily disappearances in event t3 that nearly halve species richness only event t2 near the p e boundary is associated with major and sudden environmental changes as marked by a rapid warming in the deep ocean and high latitude surface ocean and a negative excursion in carbonate 13c values that suggest a cause effect relationship the other two events occur during intervals of gradual environmental changes we suggest that all three faunal events are triggered by the attainment of threshold conditions during the oceanic environmental changes threshold conditions may be attained through rapid environmental changes as in the case of event t2 near the p e boundary or by gradual though cumulative environmental changes as appears to be the case in events t1 and t3 it is unclear however which environmental factors e g temperature salinity nutrients water mass stratification force rapid faunal turnovers or what role intrinsic biotic factors play

magnetostratigraphy and rock magnetism of the ilerdian stratotype at tremp spain abstract the first magnetic polarity stratigraphy of the ilerdian stratotype locality the tremp section spain has been established in total 315 samples from 66 levels have been demagnetized both thermally and by alternating field various types of rock magnetic behaviors and low and high temperature magnetization components have been distinguished and have been correlated with the three sampled rock types clays marls and fine grained sandstones and coarse grained sandstones the paleomagnetic directions have been classified according to their reliability in representing a primary magnetization the magnetostratigraphy of the tremp section is characterized by a long reversed polarity zone interrupted by a normal zone we conclude that the normal polarity interval found in the ilerdian stratotype may represent chron 24 2 the lower and upper reversed intervals of the section are then respectively chrons 24 1r and 24r