small scale deformations associated with the 1992 landers california earthquake mapped by synthetic aperture radar interferometry phase gradients the landers earthquake mw 7 3 occurred on june 28 1992 and ruptured nearly 100 km of previously mapped and unmapped faults in the mojave desert we use synthetic aperture radar interferometry insar to examine the cumulative surface deformation between april 24 and august 7 1992 in a 100 100 km region surrounding the northern portion of the earthquake rupture also we introduce a technique for manipulating sar interferograms to extract short wavelength displacement information this technique involves computation and subsequent combination of interferometric phase gradient maps the insar results show significant deformation signatures associated with faults fractures dry lake beds and mountainous regions within 75 100 km of the main rupture using the phase gradient method we are able to extract small scale deformation patterns near the main rupture many of the preexisting mapped faults within 50 km of the main rupture experienced triggered slip these include the old woman lenwood johnson valley west calico and calico faults the insar results also indicate right lateral offsets along secondary fractures trending n ne within the left lateral zone of shear between the main rupture and the johnson valley fault additionally there are interesting interferogram fringe signatures surrounding troy dry lake and coyote dry lake that are related to deformation of dry lake beds

planktonic foraminiferal biostratigraphy and mechanisms in the extinction of morozovella in the late middle eocene the muricate planktonic foraminiferal genera morozovella and acarinina were abundant and diverse during the upper palaeocene to middle eocene and dominated the tropical and subtropical assemblages a significant biotic turnover in planktonic foraminifera occurred in the latest middle eocene with a notable reduction in the acarininid lineage and the extinction of the morozovellids these genera are extensively employed as palaeoclimatic and biostratigraphic markers and therefore this turnover episode is an important event in the record of the cenozoic planktonic foraminifera sediments from the western north atlantic ocean drilling program site 1052 were examined in order to investigate these extinction events in terms of both timing and mechanisms biostratigraphic events of the middle and late eocene have been examined with a sampling resolution of approximately 3 kyr these have been calibrated to the magneto and astrochronology to accurately define the timing of key biostratigraphic events particularly the extinction of morozovella spinulosa which is a distinct biomarker for late middle eocene sediments high resolution biostratigraphy reveals that the extinctions in the muricate group occurred in a stepwise form the large acarininids acarinina praetopilensis terminate 10 kyr prior to the extinction of m spinulosa and small acarininids acarinina medizzai and acarinina echinata continue into the upper eocene high resolution stable isotope analyses have been conducted on planktonic and benthic foraminifera from the western north atlantic to reconstruct sea surface temperatures ssts and deep water temperatures and the structure of the water column around this major biotic turnover whilst the extinctions of m spinulosa and a praetopilensis occur during a long term cooling trend the biotic turnover in the muricate group does not appear to be related to significant climatic change sea surface temperatures decrease slowly prior to the extinction events and there is no evidence for a large temperature shift associated with the faunal changes the turnover event was therefore probably related to the increased surface water productivity and the deterioration of photosymbiotic partnerships with algae d 2003 elsevier b v all rights reserved

changes in calcareous nannofossil assemblages during the middle eocene climatic optimum clues from the central western tethys alano section ne italy we present a study focused on changes in calcareous nannofossil assemblages of the alano section during the middle eocene climatic optimum meco this warming event is characterized by a prominent perturbation both in oxygen and carbon stable isotopes around the chron c18r c18n transition ca 40 ma and lasting ca 500 600 kyr semi quantitative analyses on calcareous nannofossil assemblages have been carried out our results show that the meco interval coincides with a significant shift in the relative abundance of calcareous nannofossil taxa suggesting a relationship between biotic changes and stable isotope shifts paleoecological studies at species level and or based on morphometric criteria i e small placoliths sometimes show the opposite behaviour between changes observed at the genus level and those observed at lower taxonomic levels for instance a taxon thought to be better adapted to oligotrophic warm waters e g sphenolithus shows a prominent decrease if analyzed at genus level but an increase was instead recorded for s spiniger moreover taxa preferentially thriving in eutrophic cold waters as for instance small reticulofenestrids increase remarkably in abundance during this warming phase while medium large placoliths do not show any significant trend an increase in reworked mainly cretaceous specimens is also observed during the meco these lines of evidence are consistent with a transient enrichment in dissolved nutrients in warmer sea surface waters suggesting that an enhanced nutrient availability could have driven the make up of the calcareous nannofossil assemblages the increase in reworking may indicate an increase in terrigenous input due to increased chemical weathering likely produced by an enhanced hydrological cycle

gulf stream reconstruction of cenozoic flow patterns over the blake plateau rugged and channeled topography excavated on the top of paleocene strata and buried by lower eocene deposits indicates that gulf stream interaction with the blake plateau occurred as early as late paleocene early eocene time initially the gulf stream flowed across the western edge of the blake plateau in an area now covered by the florida hatteras slope by early eocene the current had shifted 200 km to the south cutting channels 500 m bathymetrically lower across the central blake plateau and exiting just north of the blake spur the gulf stream flowed northeastward across the central plateau throughout the eocene and returned to near its paleocene position across the western edge of the plateau in the middle oligocene shortly thereafter it resumed its former track across the central plateau since the early miocene the current axis has alternated between a northeasterly flow path across the central blake plateau and a more northerly course along the inner blake plateau shifts in the position of the gulf stream are the result of eastward and southward deflection of the current by a prominent bathymetric high the charleston bump during periods of sea level lowering

microstructural and geochemical perspectives on planktic foraminiferal preservation glassy versus frosty in recent years it has become apparent that the cool tropic paradox of paleogene and cretaceous greenhouse climates arises because of the diagenetic alteration of tropical planktic foraminiferal calcite near the seafloor yielding artificially high 18o values because the mg ca compositions of foraminiferal and inorganic calcite are thought to be quite different mg ca measurements should be a sensitive way of monitoring diagenetic alteration here we examine the extent of diagenetic alteration of eocene planktic foraminiferal calcite using scanning electron microscope imaging of foraminiferal test microstructures and geochemical 18o and mg ca analyses we compare microstructural and geochemical characteristics between given species exhibiting two contrasting states of preservation those that appear frosty under reflected light and those that appear glassy microstructural evidence reveals extensive diagenetic alteration of frosty foraminiferal tests at the micron scale while 18o analyses document consistently higher 18o and therefore lower paleotemperatures in this material yet we find that 18o offsets between species in these frosty foraminiferal assemblages appear to be generally preserved suggesting that frosty foraminifera remain valuable for generating relatively short approximately 1 myr paleoceanographic time series that do not demand absolute estimates of paleotemperature we also find that the observed increase in mg ca for planktic foraminifera exhibiting diagenetic alteration compared to glassy taphonomies is far smaller than would be expected from the addition of inorganic calcite based on laboratory derived mg2 partition coefficients our findings imply that a much lower mg2 partition coefficient controls inorganic calcite formation in deep sea sedimentary sections in accordance with the findings of baker et al 1982

fracture surface energy of the punchbowl fault san andreas system the energetics of earthquake rupture slip weakening and rupture surface formation are poorly understood by measuring the energy associated with fracture damage along the punchbowl fault in the devil s punchbowl los angeles county park part of the san andreas system chester et al show that the fracture surface energy for rupture along a mature fault of this type accounts for only a small fraction of the energy released during large earthquakes as determined by seismologists this suggests that mechanisms such as melt lubrication and thermal pressurization are responsible for slip weakening fracture energy is a form of latent heat required to create an earthquake rupture surface and is related to parameters governing rupture propagation and processes of slip weakening1 2 3 fracture energy has been estimated from seismological and experimental rock deformation data4 5 6 7 8 yet its magnitude mechanisms of rupture surface formation and processes leading to slip weakening are not well defined8 9 10 here we quantify structural observations of the punchbowl fault a large displacement exhumed fault11 12 in the san andreas fault system and show that the energy required to create the fracture surface area in the fault is about 300 times greater than seismological estimates would predict for a single large earthquake if fracture energy is attributed entirely to the production of fracture surfaces then all of the fracture surface area in the punchbowl fault could have been produced by earthquake displacements totalling 1 km but this would only account for a small fraction of the total energy budget and therefore additional processes probably contributed to slip weakening during earthquake rupture

constraints on glaciation in the middle eocene 46 37 ma from ocean drilling program odp site 1209 in the tropical pacific ocean the presence of glacial ice in the late middle eocene has been vigorously debated recently published sedimentary data from the high latitudes is suggestive of episodic cooling events and near freezing sea surface temperatures during parts of the late middle eocene constraints on ice volumes and the significance of excursions in open ocean foraminifera and seawater 18o reconstructions are less clear and there are few high resolution 18o records we present a new detailed record of benthic foraminiferal 18o from site 1209 that exhibits variations 18o benthic of 0 6 1 3 different approaches have previously been used to interpret 18o benthic including 1 an a priori assumption of a 50 contribution of temperature similar to what is reconstructed for the last glacial maximum recent change 2 applying oligocene calibrations between apparent sea level asl and 18o benthic or 3 assuming temperature and seawater 18o contributions can be partitioned through comparison with benthic mg ca using assumption 1 the record from site 1209 indicates changes in seawater 18o of 0 3 0 7 equivalent to 33 72 m m of asl assuming mean ice 18o of 45 using assumption 2 and two different end member calibrations the 18o benthic record implies changes in asl of 23 50 m or 50 108 m the third approach yields changes in seawater 18o of up to 0 6 to 1 4 we explore the compatibility of the results of each of these approaches with other studies that discuss evidence for ephemeral glaciations during the middle eocene with variable ice storage at one or both poles

complex response of dinoflagellate cyst distribution patterns to cooler early oligocene oceans previous studies have made extensive use of dinoflagellate cysts to reconstruct past sea surface temperature sst analysis of associations of dinoflagellate cysts using two new ocean datasets for the mid eocene bartonian and early oligocene rupelian reveals clear latitudinally constrained distributions for the bartonian but unexpected changes in their rupelian distribution a significant number of species with low and mid latitude northern hemisphere occurrences in the bartonian extend their northward ranges in the rupelian including some forms characterised as warm water by previous studies this suggests either that dinoflagellates are faithfully tracking a complex oceanographic response to rupelian cooling or that dinoflagellate sensitivity adaptability to a range of ecological variables means that at a global scale their distributions are not primarily controlled by sea surface temperature variability previous use of dinoflagellate cysts for palaeoclimate work has relied on rather subjective and inconsistent identification of warm and cold water forms rather than comprehensive analysis of community associations at the global scale it is clear from this study that a better understanding of the palaeo ecology of dinoflagellates and their cysts is required rupelian dinoflagellate cyst distribution may reflect changes in a range of environmental variables linked to early oligocene climate cooling for example changes in nutrient fluxes triggered by glacially induced base level fall complex reorganisation of ocean current systems between the bartonian and rupelian or muted changes to rupelian summer ssts in the northern hemisphere that have previously been reported many extant dinoflagellate species also exhibit relatively broad temperature tolerance moreover they have potentially extensive cryptic diversity and are able to produce dormant cysts during short lived environmental deterioration all of which may act to limit the value of undifferentiated dinoflagellate cyst assemblages for identifying climate signals

middle eocene regional climate instability evidence from the western north atlantic high resolution 3 k y d 18 o records from middle eocene mixed layer dwelling planktonic foraminifera from the western north atlantic show pronounced 1 variability the magnitude of change is greater than that seen in open ocean pleistocene records but could not have been caused by ice volume and or sea level fluctuations instead the oxygen isotope shifts resulted primarily from large oscillations in sea surface temperatures and indicate that the regional paleoceanography of the middle eocene western north atlantic was not consistently warm or stable the large shifts in sea surface temperatures could reflect variations in the position of the gulf stream relative to blake nose or variations in upwelling intensity

the late lutetian thermal maximum middle eocene first record of deep sea benthic foraminiferal response abstract understanding the role of deep sea biota across global warming events in the past is key to unravel climate system dynamics during periods of increased pco2 levels here we present the first record of the benthic foraminiferal response to a middle eocene transient warming event named the late lutetian thermal maximum lltm 41 52 ma at odp site 702 in the south atlantic ocean changes in benthic foraminiferal assemblages such as a decrease in absolute abundance of certain taxa e g bulimina elongata are correlated with the negative carbon isotope excursion corresponding to the lltm event paleoecological interpretations of the assemblage turnover suggest changes in the type of organic matter arriving to the seafloor during the lltm benthic foraminifera and coarse fraction accumulation rates bfars and cfars decreased across the warming period of the lltm coeval with the negative 18o excursion associated with 2 c deep sea warming we suggest that increased temperatures led to enhanced metabolic rates in heterotroph organisms such as foraminifera triggering a population decline in food limiting environments such as the meso oligotrophic setting of site 702 a similar ecological response and a decrease in export productivity as inferred from decreased cfars and bfars have also been reported across the middle eocene climatic optimum at this site and support the hypothesis that metabolic rates accelerated during warming events in spite of their different magnitude and duration

oxygen isotope exchange in a two layer model of oceanic crust abstract a numerical model is presented for the transport and exchange of oxygen isotopes in an idealized two layer oceanic crust basalt carbonate that is saturated with a non advecting pore fluid open to the overlying ocean the model allows for time varying sedimentation rate porosity chemical diffusivity and temperature dependent 18o fractionation factors reaction is modeled as solution precipitation of calcite in the carbonate sediment and as modified solution precipitation basalt dissolves smectite precipitates in the basalt layer generic models using input parameters that are typical of those measured in dsdp odp cores and constant sedimentation rates illustrate the behavior of the system sufficiently well to allow first order effects to be discerned that have important implications for paleotemperature and ocean floor weathering studies the solution precipitation reactions allow oxygen to be exchanged between the low 18o basalt layer and the high 18o carbonate sediment through the medium of the pore fluids this results in 18o increasing upwards in the basalt and decreasing downwards in the sediment pore fluid 18o values decrease with depth from zero to values of 1 to 3 at the basalt sediment interface and to values of 7 to 15 within the basalt because reaction rates are slow relative to diffusion in the pore fluid high frequency 18o variations in the solid are preserved indefinitely but the amplitude of the variations decreases as e rt where r is the reaction rate fraction reacted per unit time the results suggest that the diagenetic shifts of the 18o values of benthic and high latitude planktonic foraminifera samples younger than oligocene age are typically negligible for samples older than 50 ma diagenetic effects are typically significant and generally cause estimates of bottom and high latitude surface ocean temperatures in the cretaceous and early tertiary to be too high on the other hand the model suggests that diagenesis will shift the 18o values of low latitude planktonic foraminifera to higher values and that paleotemperature estimates of low latitude surface waters particularly in the eocene and oligocene may be too low using a synthetic 18o record for dsdp site 167 we demonstrate how numerical models can be used to correct specific measured records for diagenesis this approach could provide a means of extracting paleotemperature information from heavily altered late cretaceous and older samples and for quantifying the subtle effects of diagenesis on the 18o record at all sites

in situ oxygen isotope micro analysis of faunal material and human teeth using a shrimp ii a new tool for palaeo ecology and archaeology a sensitive high resolution ion microprobe shrimp ii has been used to make high spatial resolution in situ micro analyses of oxygen isotopes in fish otoliths and teeth from fossil herbivores and a neanderthal large intra tooth variations in the oxygen isotopic composition up to 9 were observed in the enamel of herbivores from the neanderthal fossil site of payre consistent with preservation of seasonal cyclicity the range of isotopic compositions observed in neanderthal tooth enamel was much smaller w3 possibly the result of a longer enamel maturation time averaging out variability an archaeological otolith from a preceramic site in northern peru exhibited marked changes in d 18 o over life due either to the fish occasionally migrating from the sea to a lower salinity habitat or to short lived rises in sea water temperature a fish otolith from australia s willandra lakes world heritage area showed clear seasonal variations but also a general trend towards isotopically heavier and more saline water as indicated by higher d 18 o and sr ca values resulting from increased evaporation the results of these case studies are compared to results of oxygen isotope analysis using more conventional methods and demonstrate the ability of the shrimp ii to provide precise high spatial resolution in situ oxygen isotope analyses of a variety of biogenic materials this approach has major advantages over conventional methods it can provide rapid micro scale isotopic analyses of sub permil precision without the need for chemical preparation of the sample

cooler winters as a possible cause of mass extinctions at the eocene oligocene boundary the eocene oligocene boundary at about 33 7 myr ago marks one of the largest extinctions of marine invertebrates in the cenozoic period1 for example turnover of mollusc species in the us gulf coastal plain was over 90 at this time2 3 a temperature change across this boundary from warm eocene climates to cooler conditions in the oligocene has been suggested as a cause of this extinction event4 but climate reconstructions have not provided support for this hypothesis here we report stable oxygen isotope measurements of aragonite in fish otoliths ear stones collected across the eocene oligocene boundary palaeotemperatures reconstructed from mean otolith oxygen isotope values show little change through this interval in agreement with previous studies5 6 from incremental microsampling of otoliths however we can resolve the seasonal variation in temperature recorded as the otoliths continue to accrete new material over the life of the fish these seasonal data suggest that winters became about 4 c colder across the eocene oligocene boundary we suggest that temperature variability rather than change in mean annual temperature helped to cause faunal turnover during this transition

rapid fluctuations in mid latitude siliceous plankton production during the middle eocene climatic optimum odp site 1051 western north atlantic abstract the middle eocene climatic optimum meco 40 million years ago ma is one of the most prominent transient global warming events in the paleogene although the event is well documented in geochemical and isotopic proxy records at many locations the marine biotic response to the meco remains poorly constrained we present new high resolution quantitative records of siliceous microplankton assemblages from the meco interval of ocean drilling program odp site 1051 in the subtropical western north atlantic ocean which are interpreted in the context of published foraminiferal and bulk carbonate stable isotope 18o and 13c records high diatom radiolarian and silicoflagellate accumulation rates between 40 5 and 40 0 ma are interpreted to reflect an 500 thousand year kyr interval of increased nutrient supply and resultant surface water eutrophication that was associated with elevated sea surface temperatures during the prolonged onset of the meco relatively low pelagic siliceous phytoplankton sedimentation accompanied the peak meco warming interval and the termination of the meco during an 70 kyr interval centered at 40 0 ma following the termination of the meco an 200 kyr episode of increased siliceous plankton abundance indicates enhanced nutrient levels between 39 9 and 39 7 ma throughout the site 1051 record abundance and accumulation rate fluctuations in neritic diatom taxa are similar to the trends observed in pelagic taxa implying either similar controls on diatom production in the neritic and pelagic zones of the western north atlantic or fluctuations in sea level and or shelf accommodation on the north american continental margin to the west of site 1051 these results combined with published records based on multiple proxies indicate a geographically diverse pattern of surface ocean primary production changes across the meco notably however increased biosiliceous accumulation is recorded at both odp sites 1051 and 748 southern ocean in response to meco warming this may suggest that increased biosiliceous sediment accumulation if indeed a widespread phenomenon resulted from higher continental silicate weathering rates and an increase in silicic acid supply to the oceans over several 100 kyr during the meco

hydroquakes central apennines italy towards a hydrogeochemical monitoring network for seismic precursors and the hydro seismo sensitivity of boron abstract hydrogeochemical changes before mw 5 0 earthquakes are hoped to be applicable as seismic precursors it is now necessary to pass from single experiences to structured networks systematically monitoring large seismic areas for long periods our aim is to provide a pilot methodological experience for how such networks could be realized and the types of results they could deliver we present the method and some initial results to document the method s applicability in 2017 we started the hydroquakes project in seismically active central italy with the sulmona and matese areas selected as the two monitoring nodes each node includes 5 6 monitored springs and for each spring we performed laboratory analyses of major and trace elements and some isotopes we installed in situ probes for continuous monitoring between december 2017 and january 2020 the most energetic earthquakes were three events with mw of 3 9 4 1 and 4 4 they were not preceded by significant hydrogeochemical anomalies except for the mw 4 1 event despite its low mw this earthquake occurred over a large normal fault at a great depth in the crust 17 km and was preceded by weak but detectable hydrogeochemical anomalies of boron and 11b that were similar but milder than the hydrogeochemical anomalies before the 2016 mw 6 0 earthquake in the central apennines this and previous evidence show the b and 11b hydro seismo sensitivity and indicates that pre seismic hydrogeochemical anomalies could arise mostly before mw 5 0 earthquakes with weak exceptions occurring in specific conditions such as long and deep faults

numerical models of diagenesis sediment properties and pore fluid chemistry on a paleoceanographic transect blake nose ocean drilling program leg 171b a critical issue in many paleoceanographic studies is the potential of diagenetic processes to compromise the fidelity of geochemical proxies e g 18o in deep sea carbonate sediments and microfossils a recently established strategy for dealing with this issue is to drill depth transects in anomalously shallowly buried and therefore presumably well preserved target sediments here we report the results of an experiment designed to test the validity of this approach we apply a simple one dimensional numerical model to complex pore water chemical profiles for ca mg sr 87sr 86sr and 18o observed in a shallowly buried paleoceanographic transect of paleogene and cretaceous age drilled on blake nose during ocean drilling program leg 171b we show that it is possible to reproduce these complex pore water profiles simply by invoking 1 a deep seated zone of chemical reaction well below the recovered sections and 2 minimal chemical alteration within the overlying recovered sediments but significant restriction of advective flow by embedded low porosity layers these results suggest that the sediments recovered during ocean drilling program leg 171b can be considered to be virtually chemically inert at their present burial depth their carbonate recrystallization histories having been largely limited to events during early 10 ma timescale burial these findings support the strategy of selecting unusually shallowly buried sections for paleoceanographic transect drilling ironically however the very attraction of targeting such sections the lack of overlying sediments dictates that it is not possible to use pore water chemistry to constrain the early diagenetic histories of such sections because of the diffusion of the pore water signal through the sediment water interface diffusional loss may also account for the absence of pore water chemical anomalies associated with the ooze chalk transition at blake nose however our work suggests that traditional interpretations of this boundary as the inferred locus of maximum rates of carbonate recrystallization require reevaluation

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

middle eocene climate cyclicity in the southern pacific implications for global ice volume we use a multiproxy approach to determine surface and bottom water temperatures off the coast of new zealand during the middle eocene and to constrain the 18o of seawater we use these data to place constraints on the size and variability of global ice sheets at that time the hampden section in south island is characterized by exceptionally well preserved micro fossils and clear sedimentary cyclicity providing a remarkable window into conditions at paleo latitude 55 s in the pacific ocean the cyclicity was studied in detail over a 4 m section corresponding to an interval of 70 k y ca 41 7 ma the sedimentary cycles are defined by fluctuations in the sand 63 m component occurring on a wavelength of 1 m corresponding to milankovitch scale frequency analyses of foraminifer oxygen isotopic 18 o and mg ca composition combined with tex86 analyses from organic carbon are used to generate records of seawater temperature and oxygen isotopic composition 18osw these indicate bottom water temperatures of 11 13 c and sea surface temperatures of 23 25 c with good agreement between the proxies temperature cyclicity with a magnitude of 1 5 c occurs in both surface and bottom waters approximately in phase with the sedimentary cycles estimates of 18osw have a mean value of 1 2 throughout the study section taken together the data suggest a largely ice free world with orbital scale cycles expressed as temperature and hydrological variation with little or no ice volume change

astronomical forcing in late eocene marine sediments we use an x ray fluorescence xrf core scanner to obtain records of elemental concentrations in sediment cores from ocean drilling program odp leg 171b site 1052 blake nose atlantic margin of northern florida this record spans the middle to late eocene as indicated by bio and magnetostratigraphy and displays cyclicity that can be attributed to the orbital forcing of a combination of climate ocean circulation or productivity we use the xrf counts of iron and calcium as a proxy of the relative contribution from calcium carbonate and terrestrial material to construct a new composite depth record this new composite depth record provides the basis to extend the astronomically calibrated geological time scale into the middle eocene and results in revised estimates for the age and duration of magnetochrons c16 through c18 in addition we find an apparent change in the dominance of orbitally driven changes in obliquity and climatic precession at around 36 7 ma on our new time scale long term amplitude modulation patterns of eccentricity and obliquity in the data do not seem to match the current astronomical model any more suggesting the possibility of new constraints on astronomical calculations

stable isotopes in late middle eocene to oligocene foraminifera oxygen and carbon isotope ratios in eocene and oligocene planktonic and benthic foraminifera have been investigated from atlantic indian and pacific ocean locations the major changes in eocene oligocene benthic foraminiferal oxygen isotopes were enrichment of up to l in 18o associated with the middle late eocene boundary and the eocene oligocene boundary at locations which range from 1 to 4 km paleodepth although the synchronous eocene oligocene 18o enrichment began in the latest eocene most of the change occurred in the earliest oligocene the earliest oligocene enrichment in 18o is always larger in benthic foraminifera than in surface dwelling planktonic foraminifera a condition that indicates a combination of deep water cooling and increased ice volume planktonic foraminiferal 18o does not increase across the middle late eocene boundary at our one site with the most complete record deep sea drilling project site 363 walvis ridge this pattern suggests that benthic foraminiferal 18o increased 40 m y ago because of increased density of deep waters probably as a result of cooling although glaciation cannot be ruled out without more data stable isotope data are averaged for late eocene and earliest oligocene time intervals to evaluate paleoceanographic change average 18o of benthic foraminifera increased by 0 64 from the late eocene to the early oligocene 18o maximum whereas the average increase for planktonic foraminifera was 0 52 this similarity suggests that the eocene oligocene boundary 18o increase was caused primarily by increased continental glaciation coupled with deep sea cooling by as much as 2 c at some sites average 18o of surface dwelling planktonic foraminifera from 14 upper eocene and 17 lower oligocene locations when plotted versus paleo latitude reveals no change in the latitudinal 18o gradient the oligocene data are offset by 0 45 also believed to reflect increased continental glaciation at present there are too few deep sea sequences from high latitude locations to resolve an increase in the oceanic temperature gradient from eocene to oligocene time using oxygen isotopes

gas geochemistry and seismotectonics a review abstract publications on soil and spring gases have been examined regarding their relationships with both tectonic and seismic activities the main sources behaviours and uses of species detected in soils and springs are displayed and their mode of sampling and analysing briefly described the main patterns of degassing in soils are described and we outline the wide range of geochemical signatures as the result of both permeability and mineralogical contrasts because thermomineral waters have been in contact with great volumes of crustal rocks at various depths spring gases might be more representative of the local environment than soil gases moreover gas signature comparisons show that spring gases are much more enriched with deep gases and slightly contaminated by atmospheric gases therefore they can be considered as better samples for identifying precursors of earthquakes environmental perturbations are examined and it is shown from divergent cases that pressure temperature soil moisture or earth tides may generate very high perturbations of the degassing process such effects demonstrate that no systematic correction law can be proposed and that removing external contributions from gas concentrations must be performed case by case this demonstrates therefore the need for the simultaneous measurement of external parameters during gas monitoring a qualitative examination of about 150 claimed precursors proposed in the literature has been reviewed as noted by previous authors anomalies appear at distances sometimes much greater than typical source dimensions and occur in the field of strain higher than 10 9 most of them being in the field of strain higher than 10 8 taking into account the very high heterogeneity of such a set of data we can suggest that amplitudes of gas anomalies are independent of both magnitudes and epicentral distances of related earthquakes suggesting local conditions to control amplitudes on the contrary precursory time and duration of anomalies seem to increase both with magnitudes and epicentral distances abundant evidence demonstrates the major role of crustal fluids in the earthquake cycle many works have outlined the fact that crustal instabilities can appear as the result of low stress strain perturbations during loading it has been suggested that motion of fluids may occur at various scales from microcrack fluid transfer up to changes of hydraulic levels of water tables the study of subsequent anomalies is expected to supply a tool for earthquake prediction following previous authors we outline the need for further methodological improvements including the setting up of multiparameter station networks and the simultaneous recording of the main external parameters atmospheric pressure water and air temperature soil moisture for signal processing

atlantic eocene planktonic foraminiferal paleohydrographic indicators and stable isotope paleoceanography reconstruction of atlantic ocean vertical and meridional water characteristics is based on combined synoptic fossil census data stable isotope records and measurements of individual planktonic foraminiferal species correlations between planktonic foraminiferal indices and specific water types and or chemical conditions are used to trace seven stages in the history of atlantic circulation during eocene climatic changes 1 warm equable probably saline productive ocean of the early eocene characterized by lowest meridional and vertical thermal gradients and the maximal extent of tropical surface water 2 early middle eocene expansion of subtropical waters and faunas accompanying the first climatic cooling and eutrophication of equatorial surface waters 3 maximal partitioning of water types faunas and bioprovinces in middle eocene zone p11 accompanying maximum planktonic foraminiferal diversity accelerated near surface and deepwater cooling and intensified upwelling 4 latest middle eocene zone p14 maximal planktonic foraminiferal evolutionary overturn during accelerated cooling deep and surface water ventilation and transformation of tropical surface water habitat with the expansion of temperate water types and faunas this accompanied the reduction of meridional heat transport in boundary currents 5 late eocene bottom water and middle latitude cooling broadening of meridional temperature gradients and expanded oxygen minimum but faunal homogenization following the decreased import of mediterranean water ourflow 6 weakening and or shoaling of the nutricline an oxygen minimum and the thermocline preceding a diminution of primary productivity at the eocene oligocene boundary and 7 earliest oligocene low productivty ocean marked by diminished vertical thermal contrasts and homogeneous foraminiferal faunas dominated by small sized individuals the increased areal extent of upwelling with the outcropping of cooler waters over large geographic regions provides an important climatic forcing mechanism in the latest middle and late eocene

radon content of groundwater as an earthquake precursor evaluation of worldwide data and physical basis the properties of a worldwide data set of 91 radon 222 rn anomalies the frequency of occurrence the precursor time interval and the distribution of peak amplitudes are correlated with earthquake data such as the respective magnitude and epicentral distance these anomalies were reported as precursors to earthquakes in the united states ussr china japan and iceland although the data set is incomplete and limited by experimental deficiencies several consistent patterns emerge radon anomalies from different tectonic regions show similar patterns the radon anomalies occur at greater epicentral distances for earthquakes of the larger magnitude anomalies preceding large earthquakes m 6 are frequently observed at a distance of 100 to 500 km these distances are larger than several times the rupture dimensions of the future earthquakes the time from the onset of an anomaly to the time of the earthquake the precursor time increases with magnitude but decreases with distance between epicenter and radon station in addition radon anomalies are observed more frequently prior to large earthquakes than prior to small ones indicating that the preparation zone increases in size as magnitude increases the peak amplitude does not scale with magnitude but forms a consistent pattern with epicentral distance in that the larger the earthquake magnitude the farther away the largest amplitudes tend to occur the preparation zone of the earthquake where the anomalies occur forms an almost continuous annulus that expands with time away from the future rupture zone the outer radius of this annulus scales with the earthquake magnitude model calculations indicate that strain fields of at most 10 6 to 10 8 strain caused the radon anomalies if these strains are divided by the appropriate precursor time minimum strain rates from 10 7 day 1 to 10 10 day 1 are obtained such small strains and strain rates suggest that in most cases neither mechanical crack growth induced by dilatancy nor mechanical coupling between pore pressure and the rock matrix caused the anomalies large changes in the orientation of the local strain field however could occur and affect the local stress intensity factor since changes in the stress intensity factor can result in stress corrosion the occurrence of radon anomalies is attributed to slow crack growth controlled by stress corrosion in a rock matrix saturated by groundwater

the salinity contrast between the atlantic and pacific oceans during glacial time in today s ocean the salinity of low latitude surface waters in the pacific is on the average 1 per mil lower than in the atlantic oxygen isotope records for planktonic foraminifera suggest that an even larger salinity deficit may have existed for pacific surface water during glacial time if so the transport of water vapor from the atlantic to the pacific must have been as strong as or even stronger to balance the tendency toward salt buildup the atlantic would have had to export during glacial time waters saltier than it received from the other oceans

climate forcing of fine grained deep marine systems in an active tectonic setting middle eocene ainsa basin spanish pyrenees abstract a multi proxy approach to understand environmental change in deep time was undertaken on about 150 m of core from a 230 m long middle eocene core from the ainsa basin spanish pyrenees representing deep marine siliciclastic sediments using detailed sedimentary logging high resolution multi element xrf geochemistry total organic carbon and stable carbon isotopes the well a6 was drilled as part of an industry university consortium through siltstones fine very fine grained sandstone turbidites and hemipelagic structureless mudstones that were deposited as overbank and off axis deposits from a sandy submarine fan and interfan deposits for comparative mineralogy between the sandstone turbidites and siltstones scanning electron microscopy sem and x ray diffraction xrd were undertaken on selected samples the sandstone turbidites show enrichment of detrital elements such as si zr and ti that can be linked to greater quartz and heavy mineral content compared with adjacent siltstones structureless hemipelagic mudstones comprise mainly clay minerals and carbonate we interpret the sandstone turbidites as from hyperpycnal flows during high river sediment discharge whilst hemipelagic mudstones resulted from the suspension fall out of hypopycnal flows cyclostratigraphic analysis of the core reveals milankovitch cyclicity at frequencies of 0 03 cycles m short eccentricity 0 09 cycles m obliquity 0 15 cycles m precession couplet and 0 19 cycles m precession couplet orbital parameters appear to have controlled the cyclic delivery of coarser grained sediment by turbidity currents two equally plausible depositional models both as milankovitch driven can explain the cyclical changes in the deep marine sediments 1 climatic cycles with humid periods of enhanced chemical weathering increased storminess and greater riverine run off leading to high sediment flux to the deep basin as sandstone turbidites 2 climatic cycles with cooler conditions linked to high frequency small scale eustatic sea level fluctuations with lowstand shelf edge delta progradation resulting in greater volumes of coarse detrital sediment to the seafloor by hyperpycnal flows this study provides an insight into the likely depositional effects of orbitally induced climate change on the nature and delivery of terrigenous sediment into deep marine environments

eocene silicoflagellate and ebridian paleoceanography in the central arctic ocean the silicoflagellate and ebridian assemblages in early middle eocene arctic cores obtained by iodp expedition 302 acex were studied in order to decipher the paleoceanography of the upper water column the assemblages in lithologic unit 2 49 7 45 1 ma one of the biosiliceous intervals were usually endemic as compared to the assemblages that occurred outside of the arctic ocean the presence of these endemic assemblages is probably due to a unique environmental setting controlled by the degree of mixing between the low salinity arctic waters and relatively high salinity waters supplied from outside the arctic ocean such as the atlantic and possibly the western siberian sea using the basin to basin fractionation model the early middle eocene arctic ocean corresponds to an estuarine circulation type which includes the modern day black sea the abundant down core occurrence of ebridians strongly suggests the past presence of low salinity waters and may indicate that low oxygen concentrations prevailed in the euphotic layer on the basis of the ecology of the modern ebridian hermesinum adriaticum

equatorial pacific productivity changes near the eocene oligocene boundary there is general agreement that productivity in high latitudes increased in the late eocene and remained high in the early oligocene evidence for both increased and decreased productivity across the eocene oligocene transition eot in the tropics has been presented usually based on only one paleoproductivity proxy and often in sites with incomplete recovery of the eot itself a complete record of the eocene oligocene transition was obtained at three drill sites in the eastern equatorial pacific ocean odp site 1218 and iodp sites u1333 and u1334 four paleoproductivity proxies that have been examined at these sites together with carbon and oxygen isotope measurements on early oligocene planktonic foraminifera give evidence of ecologic and oceanographic change across this climatically important boundary export productivity dropped sharply in the basal oligocene 33 7 ma and only recovered several hundred thousand years later however overall paleoproductivity in the early oligocene never reached the average levels found in the late eocene and in more modern times changes in the isotopic gradients between deep and shallow living planktonic foraminifera suggest a gradual shoaling of the thermocline through the early oligocene that on average affected accumulation rates of barite benthic foraminifera and opal as well as diatom abundance near 33 5 ma an interval with abundant large diatoms beginning at 33 3 ma suggests an intermediate thermocline depth which was followed by further shoaling a dominance of smaller diatoms and an increase in average primary productivity as estimated from accumulation rates of benthic foraminifera

radiolarian magnetobiochronology and faunal turnover across the middle late eocene boundary at ocean drilling program site 1052 in the western north atlantic ocean quantitative radiolarian assemblage analysis has been conducted on middle and upper eocene sediments zones rp16 to rp18 from ocean drilling program site 1052 in order to establish the radiolarian magnetobiochronology and determine the nature of the faunal turnover across the middle late eocene boundary in the western north atlantic ocean we recognize and calibrate forty five radiolarian bioevents to the magneto and cyclo stratigraphy from site 1052 to enhance the biochronologic resolution for the middle and late eocene our data is compared to sites in the equatorial pacific leg 199 to access the diachrony of biostratigraphic events eleven bioevents are good biostratigraphic markers for tropical subtropical locations south of 30 n the primary markers lowest occurrences of cryptocarpium azyx and calocyclas bandyca which are tropical zonal boundary markers for zones rp17 and rp18 provide robust biohorizons for correlation and age determination from the low to middle latitudes and between the atlantic and pacific oceans some other radiolarian bioevents are highly diachronous 1 million years between oceanic basins a significant faunal turnover of radiolarians is recognized within chron c17n 3n 37 7 ma where 13 radiolarian species disappear rapidly in less than 100 kyr and 4 new species originate the radiolarian faunal turnover coincides with a major extinction in planktonic foraminifera we name the turnover phase the middle late eocene turnover mlet assemblage analysis reveals the mlet to be associated with a decrease in low mid latitude taxa and increase in cosmopolitan taxa and radiolarian accumulation rates the mlet might be related to increased biological productivity rather than to surface water cooling

ground water radon anomaly before the kobe earthquake in japan radon concentration in ground water increased for several months before the 1995 southern hyogo prefecture kobe earthquake on 17 january 1995 from late october 1994 the beginning of the observation to the end of december 1994 radon concentration increased about fourfold on 8 january 9 days before the earthquake the radon concentration reached a peak of more than 10 times that at the beginning of the observation before starting to decrease these radon changes are likely to be precursory phenomena of the disastrous earthquake

development of asian monsoon revealed by marked ecological shift during the latest miocene in northern pakistan carbon isotopes from soil carbonate1 4 and soil organic matter5 6 yield palaeoecological information because the carbon in the soil carbonate forms in isotopic equilibrium with local soil co2 refs 1 7 the isotopic composition of which is in turn determined by local plant cover siwalik group sediments in northern pakistan contain a well exposed palaeosol record spanning the past 18 myr here we report on stable carbon isotope results from associated pedogenic carbonate which indicate a dramatic ecological shift from to dominated floodplain biomass beginning 7 4 7 0 myr ago the earlier c3 floodplain biomasses were probably mainly composed of trees and shrubs whereas c4 grasslands dominated in the plio pleistocene oxygen isotopes also exhibit a shift in the latest miocene probably corresponding to a major climate change which may have induced the forest to grassland transition this dramatic ecological shift in the latest miocene may mark the inception or a marked strengthening of the asian monsoon system

reconstructing past sea surface temperatures correcting for diagenesis of bulk marine carbonate abstract a numerical model which describes oxygen isotope exchange during burial and recrystallization of deep sea carbonate is used to obtain information on how sea surface temperatures have varied in the past by correcting measured 18o values of bulk carbonate for diagenetic overprinting comparison of bulk carbonate and planktonic foraminiferal 18o records from odp site 677a indicates that the oxygen isotopic composition of bulk carbonate does reflect changes in sea surface temperature and 18o at odp site 690 we calculate that diagenetic effects are small and that both bulk carbonate and planktonic foraminiferal 18o records accurately reflect paleogene warming of high latitude surface oceans biased from diagenesis by no more than 1 c the same is likely to be true for other high latitude sites where sedimentation rates are low at dsdp sites 516 and 525 the effects of diagenesis are more significant measured 18o values of eocene bulk carbonates are more than 2 lower at deeply buried site 516 than at site 525 consistent with the model prediction that the effects of diagenesis should be proportional to sedimentation rate model corrections reconcile the differences in the data between the two sites the resulting paleotemperature reconstruction indicates a 4 c cooling of mid latitude surface oceans since the eocene at low latitudes the contrast in temperature between the ocean surface and bottom makes the carbonate 180 values particularly sensitive to diagenetic effects most of the observed variations in measured 18o values are accounted for by diagenetic effects rather than by sea surface temperature variations we show that the data are consistent with constant equatorial sea surface temperatures through most of the cenozoic with the possible exception of the early eocene when slightly higher temperatures are indicated we suggest that the lower equatorial sea surface temperatures for the eocene and oligocene reported in other oxygen isotope studies are artifacts of diagenetic recrystallization and that it is impossible to reconstruct accurately equatorial sea surface temperatures without explicitly accounting for diagenetic overprinting

changes in groundwater radon concentrations caused by the 2016 kumamoto earthquake abstract this study examined radon concentrations in springs in kumamoto and aso regions following the 2016 kumamoto earthquake in addition to monitoring springs near the futagawa hinagu fault zone for more than two years following the earthquake to investigate the relationship between crustal deformation and the radon concentration variation we compared these radon concentrations with those obtained prior to the earthquake the springs that showed elevated radon concentrations were located within the compressive strain quadrant of the earthquake the post seismic concentration variations of the monitored springs can be explained by rock porosity changes these results suggest that the radon concentration in spring water is affected by porosity changes caused by stress changes derived from earthquake deformation and subsequent post seismic relaxation our results are consistent with the previously inferred permeability enhancement model mass conservation calculations for radon release yielded porosity changes ranging from 30 to 70 for some aquifer systems this study explores the possibility of radon monitoring as a tool to investigate not only seismic precursors but also post seismic crustal deformation and aquifer property changes due to large earthquakes on a regional scale

orbitally forced climate change in late mid eocene time at blake nose leg 171b evidence from stable isotopes in foraminifera previous stable oxygen isotopic data from surface dwelling foraminifera indicate that eocene tropical sea surface temperatures ssts were significantly lower than at present here we show that stable isotopic analyses 180 13c of the late mid eocene mixed layer dweller morozovella spinulosa are consistent with in mid eocene mid latitudes ssts close to or slightly lower than modern temperatures at blake nose western north atlantic in contrast isotopic analyses of the benthic foraminiter nuttalides truempyi reveal a gradual fall in mean bottom water temperatures from 8 to 7 c over c 500 ka years these deep intermediate water temperatures are significantly higher than modern ones and are similar to intermediate and bottom water temperatures recorded from earlier in palaeogene and late cretaceous time large shifts arc seen in the 18o and 13c values of the planktonic foraminifers of up to 1 and 2 6 respectively that probably reflect temperature and nutrient fluctuations controlled by regional changes in upwelling intensity and runoff the surface to benthos 18o gradient decreases from 3 pdb to a minimum of c 0 5 pdb over 400 ka which could relate to the intensity of upwelling spectral analysis reveals precessional forcing in the foraminiferal 18o records which shows the direct influence of low latitude insolation on surface water stratification monsoonal wind systems may have forced the upwelling cycles and or freshwater input the benthic foraminifer 18o record also contains the obliquity cycle in addition to the precessional cycles indicating the inheritance of mid and high latitude forcing to subtropical deep waters

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

coupled greenhouse warming and deep sea acidification in the middle eocene 1 the middle eocene climatic optimum meco is an enigmatic warming event that represents an abrupt reversal in long term cooling through the eocene in order to further assess the timing and nature of this event we have assembled stable isotope and calcium carbonate concentration records from multiple deep sea drilling project and ocean drilling program sites for the time interval between 43 and 38 ma revised stratigraphy at several sites and compilation of 18o records place peak warming during the meco event at 40 0 ma chron c18n 2n the identification of the 18o excursion at sites in different geographic regions indicates that the climatic effects of this event were globally extensive the total duration of the meco event is estimated at 500 ka with peak warming lasting 100 ka assuming minimal glaciation in the late middle eocene 4 6 c total warming of both surface and deep waters is estimated during the meco at the study sites the interval of peak warming at 40 0 ma also coincided with a worldwide decline in carbonate accumulation at sites below 3000 m depth reflecting a temporary shoaling of the calcite compensation depth the synchroneity of deep water acidification and globally extensive warming makes a persuasive argument that the meco event was linked to a transient increase in atmospheric pco2 the results of this study confirm previous reports of significant climatic instability during the middle eocene furthermore the direct link between warming and changes in the carbonate chemistry of the deep ocean provides strong evidence that changes in greenhouse gas concentrations exerted a primary control on short term climate variability during this critical period of eocene climate evolution

evidence for general instability of past climate from a 250 kyr ice core record recent results1 2 from two ice cores drilled in central greenland have revealed large abrupt climate changes of at least regional extent during the late stages of the last glaciation suggesting that climate in the north atlantic region is able to reorganize itself rapidly perhaps even within a few decades here we present a detailed stable isotope record for the full length of the greenland ice core project summit ice core extending over the past 250 kyr according to a calculated timescale we find that climate instability was not confined to the last glaciation but appears also to have been marked during the last interglacial as explored more fully in a companion paper3 and during the previous saale holstein glacial cycle this is in contrast with the extreme stability of the holocene suggesting that recent climate stability may be the exception rather than the rule the last interglacial seems to have lasted longer than is implied by the deep sea specmap record4 in agreement with other land based observations5 6 we suggest that climate instability in the early part of the last interglacial may have delayed the melting of the saalean ice sheets in america and eurasia perhaps accounting for this discrepancy

paleoceanographic and paleoclimatic constraints on the global eocene diatom and silicoflagellate record abstract eocene diatom and silicoflagellate biostratigraphy are summarized and correlated with the most recent geologic time scale as well as with the global oxygen isotope and eustatic sea level curves the global distribution of eocene diatom silicoflagellate bearing sediments varies considerably reflecting changing oceanic gateways and paleoceanography with changing patterns that are punctuated by four major depositional events event 1 49 million years ago ma at the end of the early eocene climatic optimum eeco saw the cessation of diatom silicoflagellate deposition in epicontinental regions of the north sea region and in the northern russia and the onset of biosilica deposition in the arctic event 2 46 ma which coincided with intensification of the middle eocene cooling trend marked the widespread expansion of diatom silicoflagellate deposition in both the north and south atlantic a shift of diatom silicoflagellate deposition from the atlantic to the pacific began at event 3 at the end of the middle eocene climatic optimum meco 40 ma that was likely tied to the initial opening of the drake passage between antarctica and south america event 4 39 ma coincided with a major sea level fall and a widespread deep sea hiatus in the latest middle eocene late eocene diatom silicoflagellate deposition became more concentrated in middle to high latitude regions and coastal upwelling regions particularly in the pacific ocean tabulation of the first and last occurrences of 132 biostratigraphically important diatoms suggests increased species turnover during the latest paleocene to earliest eocene that may be in part due to a monographic effect an increasing rate of evolution of new diatom species between 46 and 43 ma and after 40 ma coincides respectively with the widespread expansion of diatom deposition in the atlantic and with an increased pole to equator thermal gradient that witnessed the expansion of diatoms in high latitude oceans and coastal upwelling settings

the middle eocene climatic optimum meco a multiproxy record of paleoceanographic changes in the southeast atlantic odp site 1263 walvis ridge the middle eocene climatic optimum meco 40 ma was a transient period of global warming that interrupted the secular cenozoic cooling trend we investigated the paleoceanographic paleoenvironmental and paleoecological repercussions of the meco in the southeast atlantic subtropical gyre ocean drilling program site 1263 tex86 and 18o records support an 4 c increase in surface and deepwater temperatures during the meco there is no long term negative carbon isotope excursion cie associated with the early warming consistent with other sites and there is no short term negative cie 50 kyr during the peak of the meco in contrast to what has been observed at some sites this lack of a cie during the peak of the meco at site 1263 could be due to poor sediment recovery or geographic heterogeneity of the 13c signal benthic and planktic foraminiferal mass accumulation rates markedly declined during meco indicating a reduction of planktic foraminiferal production and export productivity vertical 13c gradients do not indicate major changes in water column stratification and there is no biomarker or micropaleontological evidence that hypoxia developed we suggest that temperature dependency of metabolic rates could explain the observed decrease in foraminiferal productivity during warming the kinetics of biochemical reactions increase with temperature more so for heterotrophs than for autotrophs steady warming during meco may have enhanced heterotroph i e foraminiferal metabolic rates so that they required more nutrients these additional nutrients were not available because of the oligotrophic conditions in the region and the lesser response of primary producers to warming the combination of warming and heterotroph starvation altered pelagic food webs increased water column recycling of organic carbon and decreased the amount of organic carbon available to the benthos

environmental change in the subtropics during the late middle eocene greenhouse and global implications 1 oxygen isotope records from odp site 1052 blake nose subtropical north atlantic ocean indicate significant short term high amplitude variability up to 1 4 in about 2500 to 4000 years during the late middle eocene 37 9 37 5 ma these variations reflect a combination of changes in sea surface temperature and the oxygen isotope composition of the regional seawater in order to independently evaluate the magnitude of sst changes at blake nose and better understand the nature of environmental change during the late middle eocene we present planktonic foraminiferal mg ca data combined with 18o data from the same samples the calculated mg ca paleotemperatures indicate a decrease in ssts over the study interval from 33 to 28 c at the same time that previously published foraminiferal 18ocalcite values from the same samples also decrease thus the 18ocalcite values must reflect a significant component of seawater 18o change in order to reconcile the opposite paleotemperature trends reflected by both proxies calculated 18oseawater values decreased from 3 at 37 83 ma to 2 at 37 6 ma the combined trends of the sst and 18oseawater cannot be explained by an increase of continental ice over this time interval instead the data favor an overall weakening of the hydrological cycle as global climate transitioned from the greenhouse to icehouse

millennial scale climate instability during the early pleistocene epoch climate proxy records of the past 100 000 years show that the earth s climate has varied significantly and continuously on timescales as short as a few thousand years 1 7 similar variability has also recently been observed for the interval 340 500 thousand years ago8 these dramatic climate shifts expressed most strongly in the north atlantic region may be linked to and possibly amplified by alterations in the mode of ocean thermohaline circulation4 5 6 7 8 9 here we use sediment records of past iceberg discharge and deep water chemistry to show that such millennial scale oscillations in climate occurred over one million years ago this was a time of significantly different climate boundary conditions not only was the early pleistocene epoch generally warmer but global climate variations were governed largely by changes in earth s orbital obliguity our results suggest that such millennial scale climate instability may be a pervasive and long term characteristic of earth s climate rather than just a feature of the strong glacial interglacial cycles of the past 800 000 years

defining uncertainty and error in planktic foraminiferal oxygen isotope measurements foraminifera are the backbone of paleoceanography planktic foraminifera are one of the leading tools for reconstructing water column structure however there are unconstrained variables when dealing with uncertainty in the reproducibility of oxygen isotope measurements this study presents the first results from a simple model of foraminiferal calcification foraminiferal isotope reproducibility model firm designed to estimate uncertainty in oxygen isotope measurements firm uses parameters including location depth habitat season number of individuals included in measurement diagenesis misidentification size variation and vital effects to produce synthetic isotope data in a manner reflecting natural processes reproducibility is then tested using monte carlo simulations importantly this is not an attempt to fully model the entire complicated process of foraminiferal calcification instead we are trying to include only enough parameters to estimate the uncertainty in foraminiferal 18o records two well constrained empirical datasets are simulated successfully demonstrating the validity of our model the results from a series of experiments with the model show that reproducibility is largely controlled by the number of individuals in each measurement but also strongly a function of local oceanography if the number of individuals is held constant parameters like diagenesis or misidentification have an impact on both the precision and the accuracy of the data firm is a tool to estimate isotopic uncertainty values and to explore the impact of myriad factors on the fidelity of paleoceanographic records particularly for the holocene

post seismic hydrochemical changes in regional groundwater flow systems in response to the 2016 mw 7 0 kumamoto earthquake abstract an understanding of the detailed mechanisms and processes of hydrochemical changes in regional groundwater flow systems in response to large earthquakes has been hindered because of a lack of spatiotemporal datasets to describe these changes to clarify these issues we documented hydrochemical changes observed during the 2016 mw 7 0 kumamoto crustal earthquake using a large amount of analytical records for an area of ca 945 km2 from 139 wells for 82 measured parameters spatiotemporal distribution patterns of these changes were characterized based on a factor notation calculated using a 10 year data trend our results suggest that alteration of hydrogeological properties i e seismic rupturing coseismic mountain water release and release of soil pore waters caused changes in hydrochemical signatures at the regional scale most prominently reflected in elevated dissolved si diluted cl and increased co2 and organic compounds contents other hydrochemical anomalies detected at the local scale were induced by deep fluid upwelling and liquefaction this study identified the combined mechanisms and processes that generate the overall water chemistry changes in active groundwater flow systems in kumamoto our results provide new insights into coseismic hydrochemical changes that could be applied to other aquifer systems and importantly the use of groundwater resources during and after disasters

cenozoic deep sea temperatures and global ice volumes from mg ca in benthic foraminiferal calcite a deep sea temperature record for the past 50 million years has been produced from the magnesium calcium ratio mg ca in benthic foraminiferal calcite the record is strikingly similar in form to the corresponding benthic oxygen isotope 18o record and defines an overall cooling of about 12 c in the deep oceans with four main cooling periods used in conjunction with the benthic 18o record the magnesium temperature record indicates that the first major accumulation of antarctic ice occurred rapidly in the earliest oligocene 34 million years ago and was not accompanied by a decrease in deep sea temperatures