early diagenesis of terrigenous triterpenoids and its implications for petroleum geochemistry abstract the distribution of triterpanes in sediments and crude oils is commonly used for oil oil and oil source rock correlation in petroleum geochemistry while isomer ratios of such compounds are applied as maturity parameters the triterpane pattern in terrestrially influenced geological samples is however remarkably less diverse than the triterpenoid skeletons occurring in the extant higher plant biosphere natural observations laboratory experiments and molecular mechanics calculations have revealed that acid catalysed double bond isomerization and skeletal rearrangement reactions of terrigenous triterpenoids during early diagenesis are the key to understanding the triterpane patterns in more matured geological materials examples studied in detail are the double bond isomerization of oleanenes and the subsequent hydrogenation of the products into oleanane and 18 oleanane and the transformation of taraxer 14 ene and lup 20 29 ene into oleanenes although the reactions are likely to be kinetically controlled the main products formed and ultimately preserved are the thermodynamically most stable ones the experimental results and natural observations have significant implications for the use of terrigenous triterpenoid compounds in petroleum geochemistry

enhanced terrestrial weathering runoff and surface ocean carbonate production during the recovery stages of the paleocene eocene thermal maximum 1 the carbonate saturation profile of the oceans shoaled markedly during a transient global warming event known as the paleocene eocene thermal maximum petm circa 55 ma the rapid release of large quantities of carbon into the ocean atmosphere system is believed to have triggered this intense episode of dissolution along with a negative carbon isotope excursion cie the brevity 120 220 kyr of the petm reflects the rapid enhancement of negative feedback mechanisms within earth s exogenic carbon cycle that served the dual function of buffering ocean ph and reducing atmospheric greenhouse gas levels detailed study of the petm stratigraphy from ocean drilling program site 690 weddell sea reveals that the cie recovery period which postdates the cie onset by 80 kyr is represented by an expanded 2 5 m thick interval containing a unique planktic foraminiferal assemblage strongly diluted by coccolithophore carbonate collectively the micropaleontological and sedimentological changes preserved within the cie recovery interval reflect a transient state when ocean atmosphere chemistry fostered prolific coccolithophore blooms that suppressed the local lysocline to relatively deeper depths a prominent peak in the abundance of the clay mineral kaolinite is associated with the cie recovery interval indicating that continental weathering runoff intensified at this time as well robert and kennett 1994 such parallel stratigraphic changes are generally consonant with the hypothesis that enhanced continental weathering runoff and carbonate precipitation helped sequester carbon during the petm recovery period e g dickens et al 1997 zachos et al 2005

eocene bipolar glaciation associated with global carbon cycle changes the transition from the extreme global warmth of the early eocene greenhouse climate 55 million years ago to the present glaciated state is one of the most prominent changes in earth s climatic evolution it is widely accepted that large ice sheets first appeared on antarctica 34 million years ago coincident with decreasing atmospheric carbon dioxide concentrations and a deepening of the calcite compensation depth in the world s oceans and that glaciation in the northern hemisphere began much later between 10 and 6 million years ago here we present records of sediment and foraminiferal geochemistry covering the greenhouse icehouse climate transition we report evidence for synchronous deepening and subsequent oscillations in the calcite compensation depth in the tropical pacific and south atlantic oceans from 42 million years ago with a permanent deepening 34 million years ago the most prominent variations in the calcite compensation depth coincide with changes in seawater oxygen isotope ratios of up to 1 5 per mil suggesting a lowering of global sea level through significant storage of ice in both hemispheres by at least 100 to 125 metres variations in benthic carbon isotope ratios of up to 1 4 per mil occurred at the same time indicating large changes in carbon cycling we suggest that the greenhouse icehouse transition was closely coupled to the evolution of atmospheric carbon dioxide and that negative carbon cycle feedbacks may have prevented the permanent establishment of large ice sheets earlier than 34 million years ago between 55 and 34 million years ago earth switched from a warm greenhouse ocean climate system to the icehouse that we now enjoy frustratingly the few oceanographic datasets that exist for this key period are of low resolution tripati et al now present measurements of sediment and foraminiferal geochemistry that provide the first continuous high resolution records for this period the data suggest that northern hemisphere glaciation started 34 million years ago rather than between 10 and 8 million years ago as previously thought

reanalysis of s to p amplitude ratios for gross attenuation structure long valley caldera california because of the strong interest in the magmatism and volcanism at long valley caldera eastern california and because of recent significant improvements in our knowledge of the caldera velocity structure and earthquake locations i have reanalyzed the local earthquake s to p amplitude ratio data of sanders 1984 for the gross three dimensional attenuation structure of the upper 10 km of long valley caldera the primary goals of the analysis are to provide more accurate constraints on the depths of the attenuation anomalies using improved knowledge of the ray locations and an objective inversion procedure the new image of the high s wave attenuation anomaly in the west central caldera suggests that the top of the principal anomaly is at 7 km depth which is 2 km deeper than previously determined because of poor resolution in much of the region some of the data remain unsatisfied by the final attenuation model this unmodeled data may imply unresolved attenuation anomalies perhaps small anomalies in the kilometer or two just above the central caldera anomaly and perhaps a larger anomaly at about 7 km depth in the northwest caldera or somewhere beneath the mono craters the central caldera s wave attenuation anomaly has a location similar to mapped regions of low teleseismic p wave velocity crustal inflation reduced density and aseismicity strongly suggesting magmatic association

ecological and biogeochemical change in an early paleogene peat forming environment linking biomarkers and palynology abstract sphagnum moss is the dominant plant type in modern boreal and sub arctic ombrotrophic bogs and is of particular interest due to its sensitivity to climate and its important role in wetland biogeochemistry here we reconstruct the occurrence of sphagnum moss and associated biogeochemical change within a thermally immature early paleogene 55 ma lignite from schoningen nw germany using a high resolution multi proxy approach changes in the abundance of sphagnum type spores and the c23 c31 n alkane ratio indicate the expansion of sphagnum moss within the top of the lignite seam this sphagnum moss expansion is associated with the development of waterlogged conditions analogous to what has been observed within modern ombrotrophic bogs the similarity between biomarkers and palynology also indicates that the c23 c31 n alkane ratio may be a reliable chemotaxonomic indicator for sphagnum during the early paleogene the 13c value of bacterial hopanes and mid chain n alkanes indicates that a rise in water table is not associated with a substantial increase in aerobic methanotrophy the absence of very low 13c values within the top of the seam could reflect either less methanogenesis or less efficient methane oxidation under waterlogged sulphate rich conditions

use of multiple oxygen isotope proxies for elucidating arctic cretaceous palaeo hydrology stable oxygen isotope analysis of siderite and dinosaur tooth enamel phosphate from the campanian maastrichtian prince creek formation alaska usa are analysed to determine the palaeohydrology of the ancient colville basin north of the ancestral brooks range do of freshwater siderites relative to v pdb ranges between 214 86 and 216 21 dinosaur tooth enamel do from three different sites kikak tegoseak pediomys point liscomb range between 3 9 and 10 2 0 dometeoric water are calculated from dosiderite that formed at seasonal temperatures ranging from 22 to 14 5 8c with a mean annual temperature of 6 3 8c at 6 3 8c the dow calculated from siderite ranged between 222 23 and 220 89 v smow ingested water compositions are estimated from dinosaur teeth assuming body temperatures of 37 8c and local relative humidity of 77 5 resulting in values ranging from 228 7 to 220 4 v smow suggesting consumption of meteoric water and orographically depleted runoff from the brooks range the ranges in calculated dometeoric water are compatible between the two proxies and are mutually corroborating evidence of extremely o depleted precipitation at high latitudes during the late cretaceous relative to those generated using general circulation models this depletion is proposed to result from increased rainout effects from an intensified hydrological cycle which probably played a role in sustaining polar warmth supplementary material parameters used for generation of equations compared to kohn 1996 can be found at http www geolsoc org uk sup18642 stable isotopic proxies are invaluable tools for understanding past and current climates pedogenic carbonates siderite and calcite are commonly used to determine the isotopic composition of meteoric water lohmann 1988 hays grossman 1991 ludvigson et al 1998 ufnar et al 2004a suarez et al 2011 when analysed over a range of latitudes the resulting isotopic gradients can be used to determine global isotopic groundwater gradients this gradient is related to the isotopic composition of the precipitation which is itself related to temperature gradients humidity and in some instances orographic effects isotopic studies of the cretaceous are of particular importance because future climatic conditions kiehl 2011 are predicted to approach those pco2 temperature seen in the various greenhouse worlds of the cretaceous several studies on the cretaceous climate have revealed shallow equatorial topole air and ocean temperature gradients wolfe upchurch 1987 amiot et al 2004 jenkyns et al 2004 puceat et al 2007 while others have indicated equator to pole precipitation do gradients that are steeper than the modern climate system ludvigson et al 1998 ufnar et al 2002 suarez et al 2011 this steep gradient has been explained as resulting from increased rainout thereby increasing latent heat transport from the equator to the poles during greenhouse conditions ufnar et al 2004b these conclusions are based on empirical from bojar a v melinte dobrinescu m c smit j eds isotopic studies in cretaceous research geological society london special publications 382 http dx doi org 10 1144 sp382 3 the geological society of london 2013 publishing disclaimer www geolsoc org uk pub ethics by guest on june 17 2013 http sp lyellcollection org downloaded from

observed performance of three adjacent 48 m depth concrete diaphragm wall panels in silty soils the performance of three adjacent 48 m depth concrete diaphragm wall panels in silty soils is measured throughout the complete process of the wall installation including trench excavation trench c

pre aged plant waxes in tropical lake sediments and their influence on the chronology of molecular paleoclimate proxy records sedimentary records of plant wax hydrogen ddwax and carbon d 13 cwax stable isotopes are increasingly applied to infer past climate change compound specific radiocarbon analyses however indicate that long time lags can occur between the synthesis of plant waxes and their subsequent deposition in marginal marine sediments the influence of these time lags on interpretations of plant wax stable isotope records is presently unconstrained and it is unclear whether such time lags also affect lacustrine sediments we present compound specific radiocarbon 14 cwax data for n alkanoic acid plant waxes n c26 to n c32 from 1 a sediment core from lake chichancanab yucatan peninsula mexico 2 soils in the lake chichancanab catchment and 3 surface sediments from three other lakes in southeastern mexico and northern guatemala 14 cwax ages in the surface sediments are consistently older than modern and may be negatively correlated with mean annual precipitation and positively correlated with lake catchment area 14 cwax ages in soils surrounding lake chichancanab increase with soil depth consistent with deep subsoil horizons being the primary source of lacustrine aged plant waxes which are likely delivered to lake sediments through subsurface transport plant waxes in the lake chichancanab core are 350 1200 years older than corresponding ages of bulk sediment deposition determined by 14 c dates on terrestrial plant macrofossils in the core a ddwax time series is in closer agreement with other regional proxy hydroclimate records when a plant wax 14 c age model is applied as opposed to the macrofossil based core chronology inverse modeling of plant wax age distribution parameters suggests that plant waxes in the lake chichancanab sediment core derive predominantly from millennial age soil carbon pools that exhibit relatively little age variance 200 years our findings demonstrate that high temporal resolution climate records inferred from stable isotope measures on plant waxes in lacustrine sediments may suffer from possible chronologic distortions as a consequence of long residence times of plant waxes in soils they also underscore the importance of direct radiocarbon dating of these organic molecules

high latitude hydrological changes during the eocene thermal maximum 2 abstract the eocene hyperthermals including the paleocene eocene thermal maximum petm and eocene thermal maximum 2 etm2 represent extreme global warming events 56 and 54 million years ago associated with rapid increases in atmospheric greenhouse gas concentrations an initial study on petm characteristics in the arctic region argued for intensification of the hydrological cycle and a substantial increase in poleward moisture transport during global warming based on compound specific carbon and hydrogen isotopic 2h 1h records from sedimentary leaf wax lipids in this study we apply this isotopic and hydrological approach on sediments deposited during etm2 from the lomonosov ridge integrated ocean drilling program expedition 302 our results show similar 2h 1h changes during etm2 as during the petm with a period of 2h enrichment 20 relative to pre event values just prior to the negative carbon isotope shift cie that is often taken as the onset of the hyperthermal and more negative lipid 2h values 15 during peak warming notably lipid 2h enrichment at the base of the event is coeval with colder tex 86 h temperatures if 2h 1h values of leaf waxes primarily reflect the hydrogen isotopic composition of precipitation the observed local relationship between temperature and 2h 1h values for the body of etm2 is precisely the opposite of what would be predicted using a simple rayleigh isotope distillation model assuming a meridional vapor trajectory and a reduction in equator pole temperature gradients overall a negative correlation exists between the average chain length of n alkanes and 2h 1h suggesting that local changes in ecology could have impacted the hydrogen isotopic compositions of leaf waxes the negative correlation falls across three separate intervals the base of the event the initial cie and during the h2 hyperthermal of which the assignment is not fully certain three possible mechanisms potentially explain 2h enriched signals at the base of the event including 1 intense local drying and cooling leading to evaporative 2h enrichment 2 changes in frequency intensity of storm events and its impact on high latitude amount effects and 3 changes in low latitude temperatures evidence for hydrological shifts at the base of both hyperthermals suggests that hydrological change or the factors promoting hydrological change played a role in triggering the release of greenhouse gases generation of similar high resolution isotopic and temperature records at other latitudes is crucial for understanding the causal links between temperature and hydrological changes and may help constrain the source and mechanism of carbon release that triggered the early eocene hyperthermals

global cooling during the eocene oligocene climate transition about 34 million years ago earth s climate shifted from a relatively ice free world to one with glacial conditions on antarctica characterized by substantial ice sheets how earth s temperature changed during this climate transition remains poorly understood and evidence for northern hemisphere polar ice is controversial here we report proxy records of sea surface temperatures from multiple ocean localities and show that the high latitude temperature decrease was substantial and heterogeneous high latitude 45 degrees to 70 degrees in both hemispheres temperatures before the climate transition were 20 c and cooled an average of 5 c our results combined with ocean and ice sheet model simulations and benthic oxygen isotope records indicate that northern hemisphere glaciation was not required to accommodate the magnitude of continental ice growth during this time

a full scale stability experiment on a diaphragm wall trench this paper presents the results of a full scale field experiment on the stability of a slurry filled diaphragm wall trench the objective of this experiment was to observe the failure pattern of a

no extreme bipolar glaciation during the main eocene calcite compensation shift major ice sheets were permanently established on antarctica approximately 34 million years ago1 2 3 close to the eocene oligocene boundary at the same time as a permanent deepening of the calcite compensation depth in the world s oceans4 until recently it was thought that northern hemisphere glaciation began much later between 11 and 5 million years ago1 2 3 5 this view has been challenged however by records of ice rafting at high northern latitudes during the eocene epoch6 7 and by estimates of global ice volume that exceed the storage capacity of antarctica8 at the same time as a temporary deepening of the calcite compensation depth 41 6 million years ago9 here we test the hypothesis that large ice sheets were present in both hemispheres 41 6 million years ago using marine sediment records of oxygen and carbon isotope values and of calcium carbonate content from the equatorial atlantic ocean these records allow at most an ice budget that can easily be accommodated on antarctica indicating that large ice sheets were not present in the northern hemisphere the records also reveal a brief interval shortly before the temporary deepening of the calcite compensation depth during which the calcite compensation depth shoaled ocean temperatures increased and carbon isotope values decreased in the equatorial atlantic the nature of these changes around 41 6 million years ago implies common links in terms of carbon cycling with events at the eocene oligocene boundary4 and with the hyperthermals of the early eocene climate optimum3 10 11 our findings help to resolve the apparent discrepancy between the geological records of northern hemisphere glaciation6 7 8 and model results12 13 that indicate that the threshold for continental glaciation was crossed earlier in the southern hemisphere than in the northern hemisphere

an attenuating structure beneath the aso caldera determined from the propagation of seismic waves the attenuation of amplitude is seen in seismic waves which pass through the central region of the aso caldera in kyushu japan it is also recognized from spectral analysis of seismic waves that the higher frequencies of the p wave are reduced in the waves which pass through the central region of the caldera it is shown that the relative attenuation increases remarkably for the frequency range of 5 to 10 hz the specific attenuation factor q of the p wave train is about 100 from the surface projection of the ray paths with low q values through the aso caldera to each station the attenuating region is located beneath the center of the caldera extending to the north of the central cones in conjunction with the low q value of the p wave and the decreases of s wave amplitudes the relative p wave residual times have comparatively large values for seismic waves passing through the central region beneath the caldera in order to attempt to provide additional information on the depth configuration of the attenuating material the ray paths of p wave s first arrivals are located in three dimensional space it indicates that the low velocity material is located beneath the center of the caldera at depths of about 6 to 9 km however lowvelocity anomalies above the depth of 6 km and below the depth of 15 km were not able to be detected because most of the available seismic ray paths had crossed the caldera at depths of about 6 to 15 km furthermore the relative residual times have numerous errors resulting from incorrect hypocenter locations origin times inhomogeneities in the structure and uncertainty of the velocity structure at shallow depths in the aso caldera refraction or reflection studies are required for an accurate estimate of the structure and more detailed properties of the attenuating material

abrupt increase in seasonal extreme precipitation at the paleocene eocene boundary a prominent increase in atmospheric co at the paleocene eocene boundary ca 55 ma led to the warmest earth of the cenozoic for similar to 100 k y high resolution studies of continental flood plain sediment records across this boundary can provide crucial information on how the hydrological cycle responds to rapidly changing co2 here we show from continental records across the paleocene eocene boundary in the spanish pyrenees a subtropical paleosetting that during the early most intense phase of co2 rise normal semiarid coastal plains with few river channels of 10 200 m width were abruptly replaced by a vast conglomeratic braid plain covering at least 500 km 2 and most likely more than 2000 km 2 this braid plain is interpreted as the proximal parts of a megafan carbonate nodules in the megafan deposits attest to seasonally dry periods and together with megafan development imply a dramatic increase in seasonal rain and an increased intra annual humidity gradient the megafan formed over a few thousand years to similar to 10 k y directly after the paleocene eocene boundary only repeated severe floods and rainstorms could have contributed the water energy required to transport the enormous amounts of large boulders and gravel of the megafan during this short time span the findings represent evidence for considerable changes in regional hydrological cycles following greenhouse gas emissions less

a novel proxy for terrestrial organic matter in sediments based on branched and isoprenoid tetraether lipids we propose a novel tracer for terrestrial organic carbon in sediments based on the analysis of tetraether lipids using high performance liquid chromatography mass spectrometry hplc ms analysis of terrestrial soil and peats shows that branched tetraether lipids are predominant in terrestrial environments in contrast to crenarchaeol the characteristic membrane lipid of non thermophilic crenarchaeota which is especially abundant in the marine and lacustrine environment based on these findings an index was developed the so called branched and isoprenoid tetraether bit index based on the relative abundance of terrestrially derived tetraether lipids versus crenarchaeol this bit index was applied to surface sediments from the angola basin where it was shown to trace the outflow of the congo river furthermore analyses of particulate organic matter from the north sea showed relatively higher bit indices in water column particulate organic matter near large river inputs a survey of globally distributed marine and lacustrine surface sediments shows that the bit index in these environments correlates with the relative fluvial input of terrestrial organic material making this index generally applicable the new proxy allows the rapid assessment of the fluvial input of terrestrial organic material in immature sediments up to 100 ma old

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

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

pollen corrected leaf wax d h reconstructions of northeast african hydrological changes during the late miocene abstract plant leaf wax hydrogen isotope dwax reconstructions are increasingly being used to reconstruct hydrological change this approach is based upon the assumption that variations in hydroclimatic variables and in particular the isotopic composition of precipitation dp dominate dwax however modern calibration studies suggest that offsets between plant types may bias the dwax hydrological proxy at times of vegetation change in this study i pair leaf wax analyses with published pollen data to quantify this effect and construct the first vegetation corrected hydrogen isotopic evidence for precipitation dcorrp in marine sediments from deep sea drilling program site 231 in the gulf of aden spanning 11 4 3 8 ma late miocene and earliest pliocene i find 77 swings in dwax that correspond to pollen evidence for substantial vegetation change similarities between dp and dcorrp imply that the hydrological tracer is qualitatively robust to vegetation change however computed vegetation corrections can be as large as 31 indicating substantial quantitative uncertainty in the raw hydrological proxy the resulting dcorrp values quantify hydrological change and allow us to identify times considerably wetter than modern at 11 09 7 26 5 71 and 3 89 ma more generally this novel interpretative framework builds the foundations of improved quantitative paleohydrological reconstructions with the dwax proxy in contexts where vegetation change may bias the plant based proxy the vegetation corrected paleoprecipitation reconstruction dcorrp represents the best available estimate as proof of concept for an approach that i hope will be refined and more broadly applied

biomarker determination as a provenance tool for detrital carbonate events heinrich events fingerprinting quaternary glacial sources into baffin bay sedimentary deposits associated with heinrich events are anomalously rich in detrital carbonate off hudson strait the dominant carbonate is calcite whereas at distal sites in the north atlantic dolomite is dominant more diagnostic a significant source for dolomite is its outcrop at the northern end of baffin bay where major ice streams from the laurentide innuitian and greenland ice sheets converged the provenance of samples containing detrital carbonate mainly dolomite from a core in baffin bay has been confirmed using organic geochemistry to distinguish between alternative sources based upon the thermal maturity of organic matter in carbonates of the source region the core contained five distinct carbonate units dating between 14 and 51 cal ka bp and indicates significant ice stream instability associated with iceberg calving and significant volumes of meltwater the exact temporal relationship to heinrich events is not yet clear a long mid wisconsin interval 38 to 22 cal ka bp devoid of detrital carbonate suggests a major reduction in ice extent at high northern latitudes the core samples yield thermally sensitive biomarker ratios comparable to those from laurentian carbonates in the canadian arctic islands but unlike those from north greenland identifying the former region as their provenance however a late holocene sample from off newfoundland shows a stronger affinity with greenland 2007 elsevier b v all rights reserved

salinity of the eocene arctic ocean from oxygen isotope analysis of fish bone carbonate stable isotope analysis was performed on the structural carbonate of fish bone apatite from early and early middle eocene samples 55 to 45 ma recently recovered from the lomonosov ridge by integrated ocean drilling program expedition 302 the arctic coring expedition the 18o values of the eocene samples ranged from 6 84 to 2 96 vienna peedee belemnite with a mean value of 4 89 compared to 2 77 for a miocene sample in the overlying section an average salinity of 21 to 25 was calculated for the eocene arctic compared to 35 for the miocene with lower salinities during the paleocene eocene thermal maximum the azolla event at 48 7 ma and a third previously unidentified event at 47 6 ma at the azolla event where the organic carbon content of the sediment reaches a maximum a positive 13c excursion was observed indicating unusually high productivity in the surface waters

spherical and ellipsoidal volcanic sources at long valley caldera california using a genetic algorithm inversion technique abstract we model the second inflation period at long valley caldera california using a genetic algorithm technique and high quality geodetic measurements of elevation changes and baseline extensions we compare two source inversions for both spherical mogi point sources and the finite prolate ellipsoid of yang and davis a sensitivity analysis for the genetic algorithm is performed based upon synthetic data set inversions on similar sources in order to better constrain the areal location orientation and volume of the potential sources the spherical sources are well constrained the larger located at 9 9 km beneath the resurgent dome with a volume of 0 036 km 3 while the second at only 0 008 km 3 is located at a depth of 7 3 km beneath the south moat the depths to the ellipsoidal sources are switched with the larger source at a depth of 9 6 km and the smaller at 11 8 km with volumes of 0 037 and 0 002 km 3 respectively

n alkane parameters from a deep sea sediment transect off southwest africa reflect continental vegetation and climate conditions abstract an isobathic transect of marine surface sediments from 1 n to 28 s off southwest africa was used to further evaluate the potential of the chain length distribution and carbon stable isotope composition of higher plant n alkanes as proxies for continental vegetation and climate conditions we found a strong increase in the n c 29 33 weighted mean average 13 c values from 33 near the equator to around 26 further south additionally c 25 35 n alkanes reveal a southward trend of increasing average chain length from 30 0 to 30 5 the data reflect the changing contribution of plants employing different photosynthetic pathways c 3 and c 4 and or being differently influenced by the environmental conditions of their habitat the c 4 plant proportions calculated from the data ca 20 for rivers draining the rainforest to ca 70 at higher latitude correspond to the c 4 plant abundance in continental catchment areas postulated by considering prevailing wind systems and river outflows furthermore the c 4 plant contribution to the sediments correlates with the mean annual precipitation and aridity at selected continental locations in the postulated catchment areas suggesting that the c 4 plant fraction in marine sediments can be used to assess these environmental parameters

changes in the occurrence of extreme precipitation events at the paleocene eocene thermal maximum abstract future global warming is widely anticipated to increase the occurrence of extreme precipitation events but such hydrological changes have received limited attention within paleoclimate studies several proxy studies of the hydrological response to the paleocene eocene thermal maximum hyperthermal 56 ma have recently invoked changes in the occurrence of extreme precipitation events to explain observations but these changes have not been studied for the geologic past using climate models here we use a coupled atmosphere ocean general circulation model hadcm3l to study regional changes in metrics for extreme precipitation across the onset of the petm by comparing simulations performed with possible petm and pre petm greenhouse gas forcings our simulations show a shift in the frequency intensity relationship of precipitation with extreme events increasing in importance over tropical regions including equatorial africa and southern america the incidence of some extreme events increases by up to 70 across the petm in some regions while the most extreme precipitation rates tend to relate to increases in convective precipitation in some regions dynamic changes in atmospheric circulation are also of importance although shortcomings in the ability of general circulation models to represent the daily cycle of precipitation and the full range of extreme events precludes a direct comparison of absolute precipitation rates our simulations provide a useful spatial framework for interpreting hydrological proxies from this time period our results indicate that changes in extreme precipitation behaviour may be decoupled from those in mean annual precipitation including for example in east africa where the change in mean annual precipitation is small but a large increase in the size and frequency of extreme events occurs this has important implications for the interpretation of the hydrological proxy record and our understanding of climatic as well as biogeochemical responses to global warming events

changes in the hydrological cycle in tropical east africa during the paleocene eocene thermal maximum the paleocene eocene thermal maximum petm at ca 55 8 ma is one of the most studied instances of past greenhouse gas induced global warming as such it provides a rich opportunity to examine the impact of such global change on local climates the effects of increased continental and sea surface temperatures on local precipitation and humidity during the petm remain poorly constrained and studies reveal complex regional differences whilst some localities appear to experience a net increase in humidity others exhibit the opposite crucially there are few records of hydrological change from tropical regions recent onshore drilling expeditions in tanzania have yielded expanded sedimentary sections deposited in a marine environment that span much of the late cretaceous and paleogene and show exceptionally good preservation of both calcareous microfossils and organic matter the petm interval has previously been constrained by both biostratigraphy and carbon isotopic records and spans ca 7 m of section lipid distributions including various terrestrial marine and bacterial biomarkers and their hydrogen isotopic compositions as well as mineralogy were used to examine east african vegetation and hydrological responses to the global change occurring at the petm although total organic carbon contents decrease the concentrations of both higher plant n alkanes n alkanoic acids and soil bacterial glycerol dialkyl glycerol tetraethers biomarkers increase dramatically at the onset of the petm negative carbon isotope excursion cie suggesting an increased discharge of fluvial sedimentary organic matter similarly mineralogical indicators of terrestrial input including ti al and si al ratios quartz contents and notably the proportion of kaolinite also increase at the onset of the cie however higher plant leaf wax n alkanes c27 c29 and c31 become more deuterium enriched throughout the same interval suggesting a more arid and or hotter rather than a more humid environment this evidence collectively suggests an east african early petm climate characterised by overall hot and arid conditions punctuated by intense perhaps seasonal precipitation events these data match observations from other locations at mid latitudes suggesting that the humid climate often suggested for the petm was not globally widespread

synchronous tropical and polar temperature evolution in the eocene palaeoclimate reconstructions of periods with warm climates and high atmospheric co2 concentrations are crucial for developing better projections of future climate change deep ocean1 2 and high latitude3 palaeotemperature proxies demonstrate that the eocene epoch 56 to 34 million years ago encompasses the warmest interval of the past 66 million years followed by cooling towards the eventual establishment of ice caps on antarctica eocene polar warmth is well established so the main obstacle in quantifying the evolution of key climate parameters such as global average temperature change and its polar amplification is the lack of continuous high quality tropical temperature reconstructions here we present a continuous eocene equatorial sea surface temperature record based on biomarker palaeothermometry applied on atlantic ocean sediments we combine this record with the sparse existing data4 6 to construct a 26 million year multi proxy multi site stack of eocene tropical climate evolution we find that tropical and deep ocean temperatures changed in parallel under the influence of both long term climate trends and short lived events this is consistent with the hypothesis that greenhouse gas forcing7 8 rather than changes in ocean circulation9 10 was the main driver of eocene climate moreover we observe a strong linear relationship between tropical and deep ocean temperatures which implies a constant polar amplification factor throughout the generally ice free eocene quantitative comparison with fully coupled climate model simulations indicates that global average temperatures were about 29 26 23 and 19 degrees celsius in the early early middle late middle and late eocene respectively compared to the preindustrial temperature of 14 4 degrees celsius finally combining proxy and model based temperature estimates with available co2 reconstructions8 yields estimates of an eocene earth system sensitivity of 0 9 to 2 3 kelvin per watt per square metre at 68 per cent probability consistent with the high end of previous estimates11

the apectodinium acme and terrestrial discharge during the paleocene eocene thermal maximum new palynological geochemical and calcareous nannoplankton observations at tawanui new zealand manifestations of profound perturbations in biogeochemical systems during the paleocene eocene thermal maximum petm include a prominent global negative 13c and a pronounced increase in the relative abundance of dinoflagellate cysts dinocysts assigned to the genus apectodinium while motile representatives of apectodinium were most likely thermophilic and heterotrophic the underlying causes of this dinoflagellate response are not well understood here we provide new insight by examining the palynology chemistry and calcareous nannoplankton across the petm in a continental slope section at tawanui new zealand across the petm marked changes in the relative abundance of apectodinium vary antithetically with significant changes in the 13c of carbonate and organic matter in general the high relative abundance of apectodinium relates to enhanced concentrations of dinocysts signifying a bloom of apectodinium in surface waters during the petm changes in apectodinium and 13c records correspond to variations in many other parameters including a smaller negative shift in bulk carbonate 13c than expected increased terrestrial palynomorphs elevated toc and c n ratios lower carbonate contents higher sio2 and al2o3 contents and lower si al ratios all of these variations can be explained by an increase in delivery of terrigenous material to the continental margin a peak in the relative abundance of glaphyrocysta dinocysts at the onset of the petm may indicate greater down slope transport of neritic material changes in calcareous nannoplankton abundances suggest increased nutrient availability in surface waters during the petm the combined results show that apectodinium dominated assemblages global perturbations in carbon isotopes and enhanced terrigenous delivery closely correspond in time at tawanui a sudden and massive carbon injection to the ocean atmosphere system may have enhanced weathering and increased terrigenous inputs to continental margins during the petm we further suggest that these inputs caused the apectodinium acme by elevating primary productivity in marginal seas

a magma mass beneath casa diablo further evidence from reflected seismic waves a forty station seismographic network operating in long valley caldera in california during the summer of 1997 recorded a number of earthquakes with unusual secondary phases the phases can be seen on several stations throughout the network allowing the use of particle motions and differential travel times to examine their nature and points of origin based on amplitude frequency and travel time considerations it appears that some of the phases are mode converted s to p reflec tions from a zone below the casa diablo area near mammoth lakes ca the locus of reflection points was imaged using time domain signal migration and stacking under the assumptions of first order scattering theory the results indicate that the reflecting zone is a curved 1 5 km by 2 km surface 7 6 km below and 1 4 km west of the casa diablo geothermal plant previous studies show low p wave velocities and high s wave attenuations in the same location as the reflecting zone an amplitude analysis of the suspected reflec tions suggests they are produced by large contrasts in material properties with the possible range of transitions including solid to partially molten or dry to fluid satu rated rock given these observations plus the volcanic history of the caldera and its recent tectonic activity the most straightforward interpretation of the reflections is that they come from either the top of a sill or intrusion or the overlying hydrothermal system of such structures

cyclic terpenoids of contemporary resinous plant detritus and of fossil woods ambers and coals abstract cyclic terpenoids present in the solvent extractable material of fossil woods ambers and brown coals have been analyzed the sample series chosen consisted of wood remains preserved in holocene to jurassic sediments and a set of of ambers from the philippines copalite israel canada and dominican republic the brown coals selected were from the fortuna garsdorf mine and miocene formations on fiji the fossil wood extracts contained dominant diterpenoid or sesquiterpenoid skeletons and aromatized species were present at high concentrations with a major amount of two ring aromatic compounds tricyclic diterpenoids were the predominant compounds in the ambers aromatized derivatives were the major components consisting of one or two aromatic ring species with the abietane and occasionally pimarane skeletons the saturated structures were comprised primarily of the abietane and pimarane skeletons having from three to five carbon c1 c2 etc substituents kaurane and phyllocladane isomers were present in only minor amounts bicyclic sesquiterpenoids as saturated and partial or fully aromatized forms were also common in these samples but only traces of sesterterpenoids and triterpenoid derivatives were found the brown coal extracts were composed of major amounts of one and two ring aromatized terpenoids with a greater proportion of triterpenoid derivatives than in the case of the woods and ambers this was especially noticeable for the german coal where the triterpenoids were predominant open c ring aromatized structures were also present in this coal steroid compounds were not detectable but some hopanes were found as minor components in the german brown coal an overview of the skeletal structure classes identified in each sample as well as the general mass spectrometric characteristics of the unknown compounds are included in the present paper it can be concluded from these structural distributions that aromatization is the main process for the transformation of terrestrial cyclic terpenoids during diagenesis constituting a general pathway for all terpenoids

constraints on the application of the mbt cbt palaeothermometer at high latitude environments svalbard norway abstract branched glycerol dialkyl glycerol tetraethers gdgts are membrane lipids of unknown bacteria that are ubiquitous in soil and peat two indices based on the distribution of these lipids in soils the cyclization of branched tetraethers cbt and the methylation of branched tetraethers mbt indices have been shown to correlate with soil ph and mean annual air temperature mat and soil ph respectively and can be used to reconstruct mat in palaeoenvironments to verify the extent to which branched gdgts in marine sediments reflect the distribution pattern on land and whether these proxies are applicable for palaeoclimate reconstruction in high latitude environments with a mat of

magnetostratigraphic calibration of eocene oligocene dinoflagellate cyst biostratigraphy from the norwegian greenland sea the presence of abundant age diagnostic dinoflagellate cysts in ocean drilling program odp hole 913b leg 151 deep sea drilling project hole 338 leg 38 and odp hole 643a leg 104 has enabled the development of a new biostratigraphy for the eocene oligocene interval in the norwegian greenland sea this development is important because the calcareous microfossils usually used for biostratigraphy in this age interval are generally absent in high latitude sediments as a result of dissolution in parallel with this biostratigraphic analysis we developed a magnetic reversal stratigraphy for these norwegian greenland sea sequences this has allowed independent age determination and has enabled the dinocyst biostratigraphy to be firmly tied into the global geomagnetic polarity timescale gpts the relatively high resolution of this study has enabled identification of dinoflagellate cyst assemblages that have affinities with those from the north sea and the north atlantic which allows regional correlation correlation of each site with the gpts has also allowed comparison of the stratigraphic record preserved in each drill hole hole 913b is the most complete and is the best preserved record of the eocene and oligocene in the northern hemisphere high latitudes and can serve as a reference section for palaeoenvironmental reconstructions of this age interval

aliphatic and aromatic terpenoid biomarkers in cretaceous and paleogene angiosperm fossils from japan abstract the distributions of aliphatic and aromatic terpenoids in cretaceous and paleogene angiosperm fossils from japan were investigated aliphatic a ring degraded oleanane ursane and lupane were found in all samples in addition aliphatic gymnosperm derived diterpenoids were detected in significant quantities aromatic oleanane type triterpenoids were the major components with ursane and lupane type triterpenoids being minor compounds in all angiosperm fossils in a cretaceous gymnosperm fossil major components included aliphatic labdane isopimarane and abietane type diterpenoids aromatic abietane type diterpenoids and chrysene and picene type polyaromatic hydrocarbons pahs trace amounts of oleanane ursane and lupane type triterpenoids were also identified it is likely that the aromatic triterpenoids were introduced to the gymnosperm fossil from the angiosperm derived material in the sediments we defined an angiosperm gymnosperm index al agi as an alternative to the aliphatic triterpenoid diterpenoid ratio proposed in the literature the al agi index may underestimate the angiosperm contribution because the aliphatic angiosperm derived triterpenoids are more readily converted to aromatic counterparts than the diterpenoids during diagenesis an aromatic angiosperm gymnosperm index ar agi can be calculated using aromatic diterpenoids and triterpenoids we suggest that ar agi is best calculated using only the oleanane ursane and lupane type aromatic triterpenoids and that the chrysene and picene type pahs be excluded

the owens river as a tiltmeter for long valley caldera california in the lower 11 km of its course around the resurgent dome of long valley caldera the owens river displays two parallel meander belts comparable in meander wavelength and amplitude but unequal in age elevation and discharge it appears the two belts take turns carrying the river s flow depending on whether the dome is inflating or subsiding the inboard belt some 200 300 m closer to the dome and now 30 60 cm higher in elevation contains an underfit stream and is now being abandoned the outboard channel formed in a series of avulsions apparently induced by recent uplift of the dome in the upper 4 km of the two channel reach avulsion occurred between 1856 and 1878 as inferred from the original u s coast and geodetic survey mapping in the caldera avulsion had already occurred by 1856 in the lower 4 km of the river suggesting a possible migration of the center of uplift through time muted remains of older oxbows in the outboard meander belt indicate an earlier occupancy by the river and thus an

arctic late paleocene early eocene paleoenvironments with special emphasis on the paleocene eocene thermal maximum lomonosov ridge integrated ocean drilling program expedition 302 we reconstruct the latest paleocene and early eocene 57 50 ma environmental trends in the arctic ocean and focus on the paleocene eocene thermal maximum petm 55 ma using strata recovered from the lomonosov ridge by the integrated ocean drilling program expedition 302 the lomonosov ridge was still partially subaerial during the latest paleocene and earliest eocene and gradually subsided during the early eocene organic dinoflagellate cyst dinocyst assemblages point to brackish and productive surface waters throughout the latest paleocene and early eocene dinocyst assemblages are cosmopolitan during this time interval suggesting warm conditions which is corroborated by tex86 reconstructed temperatures of 15 18 c inorganic geochemistry generally reflects reducing conditions within the sediment and euxinic conditions during the upper lower eocene spectral analysis reveals that the cyclicity recorded in x ray fluorescence scanning fe data from close to eocene thermal maximum 2 53 ma presence confirmed by dinocyst stratigraphy is related to precession within the lower part of the petm proxy records indicate enhanced weathering runoff anoxia and productivity along with sea level rise on the basis of total organic carbon content and variations in sediment accumulation rates excess organic carbon burial in the arctic ocean appears to have contributed significantly to the sequestration of injected carbon during the petm

constraints on the sources of branched tetraether membrane lipids in distal marine sediments abstract branched glycerol dialkyl glycerol tetraethers brgdgts are membrane lipids produced by soil bacteria and occur in near coastal marine sediments as a result of soil organic matter input their abundance relative to marine derived crenarchaeol quantified in the bit index generally decreases offshore however in distal marine sediments low relative amounts of brgdgts can often still be observed sedimentary in situ production as well as dust input have been suggested as potential though as yet not well constrained sources in this study brgdgt distributions in dust were examined and compared with those in distal marine sediments dust was sampled along the equatorial west african coast and brgdgts were detected in most of the samples albeit in low abundance their degree of methylation and cyclisation expressed in the mbt methylation index of branched tetraethers and dc degree of cyclisation indices respectively were comparable with those for african soils their presumed source comparison of dc index values for brgdgts in global soils congo deep sea river fan sediments and dust with those of distal marine sediments clearly showed however that distal marine sediments had significantly higher values this distinctive distribution is suggestive of sedimentary in situ production as a source of brgdgts in marine sediments rather than dust input the presence of in situ produced brgdgts in marine sediments means that caution should be exercised when applying the mbt cbt palaeothermometer to sediments with low bit index values i e

a new zealand record of sea level rise and environmental change during the paleocene eocene thermal maximum abstract the global warming associated with the paleocene eocene thermal maximum petm ca 55 5 myr ago is the most dramatic identified short term temperature increase of the cenozoic one direct consequence of a warming world is a rise in sea level due primarily to the thermal expansion of water as oceans warmed the kumara 2 core south island new zealand spans the paleocene eocene transition and provides a rare southern hemisphere continental margin record of the petm lithology palynology and compound specific stable isotope compositions of higher plant leaf wax n alkanes reveal a 4 85 m petm and a carbon isotope excursion cie of ca 4 5 larger than the 2 5 to 3 5 cies generally recorded by deep sea foraminifera there is a shift from a terrestrial to a marine potentially anoxic sedimentary depositional environment at the base of the petm interpreted as being the result of a local sea level rise coincident with the onset of the cie is the appearance of pollen associated with thermophilic conditions and the development of nypa mangrove swamps moreover there is a reorganisation of the angiosperm pollen assemblage during the petm and an initial increase in fern spores and decrease in gymnosperms crucially all of these changes occur below the horizon characterised by the most negative 13c values suggesting that 1 the recorded negative excursion of 4 5 may indeed reflect the shift in atmospheric co2 isotopic composition and 2 that the large input of 13c depleted carbon into the ocean atmosphere system was not geologically instantaneous with at least some of the added carbon lagging warming sea level rise and vegetation change furthermore compound specific hydrogen isotope analyses show a large degree of variability both directly before and during the cie suggesting that the petm in new zealand was characterised by complex and transient changes in the hydrological regime similar to those reported in north america the arctic and eastern africa thus the new petm record from kumara 2 reveals local climatic and biotic responses driven by a combination of global warming and the consequential change in local depositional environment induced by sea level rise

locations and spectral properties of earthquakes accompanying an eruption of mount st helens a joint hypocenter determination routine has been developed to accurately determine the locations of earthquakes occurring under mount st helens the method has a special application to mount st helens where most of the earthquakes are suspected to occur at shallow depth in a rather limited volume under the volcano differences in elevation among stations are allowed for in this routine the location procedure determines a best half space velocity and one station correction for each station simultaneously with earthquake hypocenters arrival time data from an array of portable digital seismic event recorders are supplemented with data from stations of the permanent university of washington seismic network operating at the volcano earthquakes are found to occur along a line trending south east of the dome inside the crater the shallowest events occur near the dome with hypocentral depth increasing with increasing distance from the dome station corrections can be interpreted to imply the existence of a high velocity body beneath the crater which extends at least between depths of 5 and 2 1 km beneath the crater floor spectra are calculated from earthquake waveforms recorded at three stations the spectra show very little evidence for local site or path effects on frequency content of waveforms stress drops of earthquakes are calculated from measurements of corner frequency and low frequency spectral amplitude stress drops of earthquakes vary between 5 and 5 bars there is no evidence for a limiting corner frequency for small earthquakes as has been found for earthquakes occurring in mammoth lakes california data fit well a linear trend between log seismic moment and log source radius fit to data for earthquakes ranging in size from 1014 to 1027 dyn cm suggesting that there is no limiting source radius observed for earthquakes in this range of size

crustal refraction profile of the long valley caldera california from the january 1983 mammoth lakes earthquake swarm seismic refraction profiles recorded north of mammoth lakes california using earthquake sources from the january 1983 swarm complement earlier explosion refraction profiles and provide velocity information from deeper in the crust in the area of the long valley caldera eight earthquakes from a depth range of 4 9 to 8 0 km confirm the observation of basement rocks with seismic velocities ranging from 5 8 to 6 4 km sec extending at least to depths of 20 km the data provide further evidence for the existence of a partial melt zone beneath long valley caldera and constrain its geometry this evidence is in the form of pronounced secondary arrivals which we interpret as waves that have propagated through a volume with low q the magma chamber and reflected from the lower boundary of the southern edge of this volume at depths of 18 to 20 km

onset of long term cooling of greenland near the eocene oligocene boundary as revealed by branched tetraether lipids the eocene oligocene e o boundary interval is considered to be one of the major transitions in earth s climate witnessing the fi rst major expansion of the east antarctic ice sheet however the extent of the associated climatic cooling especially for high northern latitude continental landmasses is poorly constrained in this study we reconstruct the fi rst mean annual air temperature maat for the greenland landmass during the late eocene and early oligocene by applying a new proxy based on the distribution of branched tetraether lipids derived from soil bacteria preserved in a marine sediment core from the greenland basin the temperature estimates are compared with a composite continental temperature record based on bioclimatic analysis of pollen assemblages both proxies reveal comparable late eocene maats of 13 15 c and a gradual long term cooling of 3 5 c starting near the e o boundary these data are in agreement with other maat reconstructions from northern midlatitude continents and suggest a general cooling of the northern hemisphere during the e o transition

a 35 myr north american leaf wax compound specific carbon and hydrogen isotope record implications for c4 grasslands and hydrologic cycle dynamics article i nfo hydrology source region and timing of precipitation are important controls on the climate of the great plains of north america and the composition of terrestrial ecosystems moisture delivered to the great plains varies seasonally and predominately derives from the gulf of mexico atlantic ocean with minor contributions from the pacific ocean and arctic region for this work we evaluate long term relationships for the past 35 million years between north american hydrology climate and floral change using isotopic records and average carbon chain lengths of higher plant n alkanes from gulf of mexico sediments dsdp site 94 we find that carbon isotope values 13 c of n alkanes corrected for variations in the 13 c value of atmospheric co2 provide minor evidence for contributions of c4 plants prior to the middle miocene a sharp spike in c4 input is identified during the middle miocene climatic optimum and the influence of c4 plants steadily increased during the late miocene into the pleistocene consistent with other north american records chain length distributions of n alkanes indicative of the composition of higher plant communities remained remarkably constant from 33 to 4 ma however a trend toward longer chain lengths occurred during the past 4 million years concurrent with an increase in 13 c values indicating increased c4 plant influence and potentially aridity the hydrogen isotope values d of n alkanes are relatively invariant between 33 and 9 ma and then become substantially more negative 75 from 9 to 2 ma changes in the plant community and temperature of precipitation can solely account for the observed variations in d from 33 to 5 ma but cannot account for plio pleistocene d variations and imply substantial changes in the source region of precipitation and seasonality of moisture delivery we posit that hydrological changes were linked to tectonic and oceanographic processes including the shoaling and closure of the panamanian seaway amplification of north atlantic deep water production and an associated increase of meridional winds the southerly movement of the intertropical convergence zone near 4 ma allowed for the development of a near modern pressure storm track system driving increased aridity and changes in seasonality within the north american interior

three dimensional finite element analysis of diaphragm wall installation a series of finite element analyses has been carried out to investigate the impact of three dimensional effects and panel length on horizontal ground movements and changes in lateral stress during the sequential installation of a number of diaphragm wall panels the analyses show that the magnitude and extent of lateral stress reduction in the vicinity of a diaphragm wall during construction depend on the panel length and are overpredicted in analyses assuming conditions of plane strain furthermore an overall increase in lateral stress below the toe of the wall is calculated in a plane strain analysis but is not evident following completion of the wall when a three dimensional analysis modelling the sequential installation of a number of panels is carried out the analyses also show that three dimensional effects tend to reduce lateral soil movements during installation of a diaphragm wall in panels compared with the plane strain case but soil movements increase markedly with panel length at aspect ra

increased seasonality through the eocene to oligocene transition in northern high latitudes a profound global climate shift took place at the eocene oligocene transition approximately 33 5 million years ago when cretaceous early palaeogene greenhouse conditions gave way to icehouse conditions during this interval changes in the earth s orbit and a long term drop in atmospheric carbon dioxide concentrations resulted in both the growth of antarctic ice sheets to approximately their modern size and the appearance of northern hemisphere glacial ice however palaeoclimatic studies of this interval are contradictory although some analyses indicate no major climatic changes others imply cooler temperatures increased seasonality and or aridity climatic conditions in high northern latitudes over this interval are particularly poorly known here we present northern high latitude terrestrial climate estimates for the eocene to oligocene interval based on bioclimatic analysis of terrestrially derived spore and pollen assemblages preserved in marine sediments from the norwegian greenland sea our data indicate a cooling of approximately 5 degrees c in cold month winter mean temperatures to 0 2 degrees c and a concomitant increased seasonality before the oi 1 glaciation event these data indicate that a cooling component is indeed incorporated in the delta 18 o isotope shift across the eocene oligocene transition however the relatively warm summer temperatures at that time mean that continental ice on east greenland was probably restricted to alpine outlet glaciers

paleoenvironmental implications from biomarker and stable isotope investigations on the pliocene velenje lignite seam slovenia a pliocene lignite seam up to 160 m thick occurs in the velenje basin slovenia the seam originated in a topogenous mire and evolved within a non marine transgressive setting differences in soluble organic matter yield and hydrocarbon content of borehole samples from the lignite are related to differences in the composition of free lipids of microbial origin and or hydrocarbons derived from the biogeochemical degradation of plant tissue variations of the redox conditions within the mire are reflected by pristane phytane ratios the abundance of terpenoid biomarkers indicates the predominance of gymnosperms over angiosperms which is consistent with palynomorphic spectra dominated by pollen of the sequoia taxodium metasequoia plant community rather than by angiosperms evidence is also provided that the content of land plant derived biomarkers and the preservation of plant tissue is controlled by the input of resin rich decay resistant conifers sections of the seam characterized by a high degree of gelification of humotelinite gelification index show high contents of hop 17 21 ene but low hopane concentrations the results suggest that the gelification of plant tissue may be governed by the activity of anaerobic rather than aerobic bacteria despite the minor variation in the proportions of gymnosperms versus angiosperms in the peat forming vegetation a general influence of the floral assemblage on carbon isotopic composition of the coals 13c 25 3 to 27 0 is proposed carbon cycling during biogeochemical decomposition of plant tissue by bacteria is assumed to affect the 13c value of the lignite petrographic and geochemical data of gelified and ungelified fossil wood provide evidence that gelification may be governed by microorganisms e g anaerobic bacteria different from those responsible for decreasing cellulose contents during early diagenetic aerobic degradation of wood based on the molecular composition of terpenoid biomarkers the wood fragments are identified as derived from gymnosperms the relative proportions of saturated versus aromatic hydrocarbon fractions of fossil gymnosperms display a general tendency towards lower values in gelified wood remains this indicates that bacteria involved in gelification of plant tissue may also be involved in aromatisation of diterpenoid hydrocarbons the chemotaxonomical classification of the macrofossils as gymnosperms is corroborated by the mean carbon isotopic compositions of the macrofossils 13c 24 5 and the extracted cellulose 13c 22 0 the higher isotopic difference of about 2 5 between cellulose and fossil wood compared to that found in modern trees can most probably be explained by the smaller effect of 13c discrimination for cellulose when compared with wood during decomposition chem geol 158 1999 121 compared with the coals the 13c values of wood and extracted cellulose are affected to a minor extent by microbial activity

a transient rise in tropical sea surface temperature during the paleocene eocene thermal maximum the paleocene eocene thermal maximum petm has been attributed to a rapid rise in greenhouse gas levels if so warming should have occurred at all latitudes although amplified toward the poles existing records reveal an increase in high latitude sea surface temperatures ssts 8 to 10 c and in bottom water temperatures 4 to 5 c to date however the character of the tropical sst response during this event remains unconstrained here we address this deficiency by using paired oxygen isotope and minor element magnesium calcium ratios of planktonic foraminifera from a tropical pacific core to estimate changes in sst using mixed layer foraminifera we found that the combined proxies imply a 4 to 5 c rise in pacific sst during the petm these results would necessitate a rise in atmospheric pco 2 to levels three to four times as high as those estimated for the late paleocene

deformation of long valley caldera between august 1982 and august 1983 geodetic and seismic data collected between july 1982 and august 1983 document an important event in the recent evolution of long valley caldera in january 1983 a substantial change in the pattern of deformation was associated with the most intense seismic swarm since may 1980 the earthquake hypocenters of the january 1983 swarm formed a vertical roughly tabular zone beneath the south moat of the caldera analysis of extensive intracaldera horizontal control data indicates that the shear strain distributed throughout this zone could not all be attributed to slip along any single fault plane the surface deformation of the resurgent dome and caldera floor is temporally associated with the swarm and was caused by an expansion of the upper levels of the residual magma chamber analysis of the 1983 data indicates a pressure distribution 2 5 km shallower than could be fit by analysis of the 1979 1982 caldera deformation the volume of this shallow expansion is 10 15 of the whole chamber expansion that occurred between 1979 and 1982 most of the 1983 deformation occurred between december 14 1982 and january 20 1983 and thus was associated with the january 6 7 1983 swarm though right lateral shear strain continued to accumulate in the south moat through 1983 we conclude that a shallow pressure increase probably occurred within the upper levels of the residual magma chamber of long valley caldera during the 5 week period following december 14 1982 it is not clear however whether this pressure increase preceded or accompanied the january 1983 earthquake swarm

detection of magma bodies beneath krakatau volcano indonesia from anomalous shear waves abstract the seismograms of 14 local earthquakes recorded by a temporary network in the sunda strait were used to construct an image of shear wave attenuating bodies in the vicinity of the krakatau volcanic complex seismograms for all ray paths going beneath the krakatau complex show a diminution of the amplitude of s waves these diminutions cannot be attributed to source mechanisms or station effects combination of all ray paths although in limited number demonstrates that the attenuating body is located in two zones which are probably disconnected although the limited set of data available does not allow us to draw a definite conclusion the upper zone is about 9 km deep and the lower one is at least 22 km deep the upper zone contains probably numerous irregular pockets of magma the deep zone appears to be a very wide body related to the extensional nature of the sunda strait the existence of a large deep reservoir should be taken into account for the mitigation of future hazards

absence of evidence for a shallow magma chamber beneath long valley caldera california in downhole and surface seismograms a downhole seismometer at 900 m depth and a temporary network of surface stations were deployed to use rays from local microearthquakes to study the upper and middle crust beneath the long valley caldera the downhole seismograms show s waves with high apparent amplitudes from earthquakes located 2 20 km to the south of the downhole seismometer in contrast s waves from earthquakes located in the distance range 20 30 km to the south have low apparent amplitudes if p and s amplitudes are normalized relative to the respective coda amplitudes the s to coda amplitude ratios appear to remain constant but the p to coda amplitude ratios vary significantly with takeoff angle a comparison of the calculated radiation patterns for a double couple in a uniform halfspace and focal mechanisms of the recorded earthquakes suggest that the observed variations in p and s amplitudes are caused by radiation pattern effects reanalysis of possible travel time delays found by elbring and rundle 1986 who used a subset of the borehole data analyzed in this study shows that they underestimated the epicentral distances to three of the earthquakes and hence generated an artificial kink in the reduced travel time versus depth curve synthetic calculations of reduced travel time versus depth suggest that an apparent velocity of 5 7 km s gives less scatter than 6 0 km s used by elbring and rundle 1986 plots of ts tp versus depth show that contrary to the findings of elbring and rundle 1986 the vp vs ratio stays fairly constant with depth and a small 3 km diameter magma chamber cannot easily be resolved furthermore combined analysis of downhole and surface data shows that neither data set requires a low velocity zone or a zone of anomalously high vp vs at depth below the casa diablo area

northern hemisphere controls on tropical southeast african climate during the past 60 000 years the processes that control climate in the tropics are poorly understood we applied compound specific hydrogen isotopes d and the tex86 tetraether index of 86 carbon atoms temperature proxy to sediment cores from lake tanganyika to independently reconstruct precipitation and temperature variations during the past 60 000 years tanganyika temperatures follow northern hemisphere insolation and indicate that warming in tropical southeast africa during the last glacial termination began to increase 3000 years before atmospheric carbon dioxide concentrations d data show that this region experienced abrupt changes in hydrology coeval with orbital and millennial scale events recorded in northern hemisphere monsoonal climate records this implies that precipitation in tropical southeast africa is more strongly controlled by changes in indian ocean sea surface temperatures and the winter indian monsoon than by migration of the intertropical convergence zone

changing atmospheric co2 concentration was the primary driver of early cenozoic climate the early eocene climate optimum eeco which occurred about 51 to 53 million years ago was the warmest interval of the past 65 million years with mean annual surface air temperature over ten degrees celsius warmer than during the pre industrial period subsequent global cooling in the middle and late eocene epoch especially at high latitudes eventually led to continental ice sheet development in antarctica in the early oligocene epoch about 33 6 million years ago however existing estimates place atmospheric carbon dioxide co2 levels during the eocene at 500 3 000 parts per million and in the absence of tighter constraints carbon climate interactions over this interval remain uncertain here we use recent analytical and methodological developments to generate a new high fidelity record of co2 concentrations using the boron isotope 11 b composition of well preserved planktonic foraminifera from the tanzania drilling project revising previous estimates although species level uncertainties make absolute values difficult to constrain co2 concentrations during the eeco were around 1 400 parts per million the relative decline in co2 concentration through the eocene is more robustly constrained at about fifty per cent with a further decline into the oligocene provided the latitudinal dependency of sea surface temperature change for a given climate forcing in the eocene was similar to that of the late quaternary period this co2 decline was sufficient to drive the well documented high and low latitude cooling that occurred through the eocene once the change in global temperature between the pre industrial period and the eocene caused by the action of all known slow feedbacks apart from those associated with the carbon cycle is removed both the eeco and the late eocene exhibit an equilibrium climate sensitivity relative to the pre industrial period of 2 1 to 4 6 degrees celsius per co2 doubling 66 per cent confidence which is similar to the canonical range 1 5 to 4 5 degrees celsius indicating that a large fraction of the warmth of the early eocene greenhouse was driven by increased co2 concentrations and that climate sensitivity was relatively constant throughout this period

descent toward the icehouse eocene sea surface cooling inferred from gdgt distributions the tex86 proxy based on the distribution of marine isoprenoidal glycerol dialkyl glycerol tetraether lipids gdgts is increasingly used to reconstruct sea surface temperature sst during the eocene epoch 56 0 33 9 ma here we compile published tex86 records critically reevaluate them in light of new understandings in tex86 palaeothermometry and supplement them with new data in order to evaluate long term temperature trends in the eocene we investigate the effect of archaea other than marine thaumarchaeota upon tex86 values using the branched to isoprenoid tetraether index bit the abundance of gdgt 0 relative to crenarchaeol gdgt 0 and the methane index mi we also introduce a new ratio gdgtrs which may help identify red sea type gdgt distributions in the geological record using the offset between tex86h and tex86l h l and the ratio between gdgt 2 and gdgt 3 2 3 we evaluate different tex86 calibrations and present the first integrated sst compilation for the eocene 55 to 34 ma although the available data are still sparse some geographic trends can now be resolved in the high latitudes 55 there was substantial cooling during the eocene 6 c our compiled record also indicates tropical cooling of 2 5 c during the same interval using an ensemble of climate model simulations that span the eocene our results indicate that only a small percentage 10 of the reconstructed temperature change can be ascribed to ocean gateway reorganization or paleogeographic change collectively this indicates that atmospheric carbon dioxide pco2 was the likely driver of surface water cooling during the descent toward the icehouse

kerogen bound glycerol dialkyl tetraether lipids released by hydropyrolysis of marine sediments a bias against incorporation of sedimentary organisms over the past 10 years the membrane lipids of archaea particular glycerol dialkyl glycerol tetraethers gdgts have been recognised as significant components of marine sediments and as potentially powerful tools in palaeoclimate reconstruction however relatively little is known about their preservation and in particular their incorporation into macromolecular organic matter fractions here we examine abundances distributions and stable carbon isotope ratio 13c values of gdgts and the diether archaeol in sediments from the benguela upwelling region ocean drilling program odp site 1084 and a mediterranean sapropel s5 these are compared with distributions of biphytanes released from the kerogen solvent extracted residue fraction using hydropyrolysis hypy gdgts likely derived from pelagic crenarchaeota are amongst the most abundant extractable components in both benguela and s5 sediments but are an order of magnitude more abundant in the former moreover the benguela sediments have far greater concentrations of the acyclic gdgt than expected consistent with the presence of methane in core 1084 co occurring archaeol and variable gdgt 13c values the excess acyclic gdgt probably arises from a contribution from sedimentary methanogens hypy released biphytanes have similar abundances in benguela and sapropel sediments and represent a significant proportion of the total tetraether lipid pool at the latter site however the distributions of hypy released biphytanes especially in benguela sediments do not always match those of the free gdgts at both sites hypy released biphytane 13c values are relatively invariant consistent with a single source again likely to be pelagic crenarchaeota these observations suggest that gdgts can be incorporated into sedimentary geomacromolecules relatively rapidly with those derived from pelagic crenarchaeota more likely to be incorporated than those derived from sedimentary methanogens it is likely that this bias arises from a lack of reactive substrates i e oxygen radicals in deeper anoxic sediments consistent with an important role for oxidative cross linking in kerogen formation

modelling the oxygen isotope distribution of ancient seawater using a coupled ocean atmosphere gcm implications for reconstructing early eocene climate one of the motivations for studying warm climates of the past such as the early eocene is the enhanced understanding this brings of possible future greenhouse conditions traditionally climate information deduced from biological or chemical proxies have been used to test computer model simulations of past climatic conditions and hence establish some of the uncertainties associated with model based predictions however extracting climate information from proxies is itself an interpretative process and discrepancies between climate information inferred from different types of proxy undermines the assumption that model data conflicts automatically mean that the model is inherently flawed a new approach which both acknowledges and reduces the uncertainties associated with both model and data is required although the oxygen isotopic ratio 18o preserved in calcareous marine fossils has been used to reconstruct past seawater temperature for several decades significant uncertainties associated with this method persist these include assumptions about past seawater 18o for which no proxy exists and which is a key control on the temperature inferred from fossil carbonate here we present the results of an early eocene simulation made using a state of the art general circulation model gcm hadcm3 with co2 set at six times pre industrial values and which has oxygen isotopes incorporated into the full hydrological cycle and hence simulates the 18o of past seawater this allows us to explore the implications of the different seawater 18o correction factors commonly used for 18o based temperature reconstruction it also allows us to focus model data comparison on 18o rather than interpret ocean temperature an approach that reduces uncertainties in model data comparison since the effects of both the temperature and the isotopic composition of ocean water on 18o of carbonate are accounted for the good agreement between model and data for both modern and well preserved early eocene carbonate increases confidence in climate reconstructions of this time

deformation of long valley caldera mono county california from 1975 to 1982 teleseismic and gravity data acquired in 1973 support the existence of a large body of partial melt magma beneath the resurgent dome of long valley caldera in eastern california whereas intermittent reoccupation of vertical and horizontal control networks in and near long valley caldera revealed only very small probably tectonic movements between 1932 and 1979 a leveling survey in september 1980 showed a 250 mm uplift of highway 395 on the west side of the resurgent dome this uplift was apparently related to expansion of the subjacent magma body beginning sometime between july 1979 and september 1980 and may have been coseismic with the mammoth lakes magnitude 6 earthquake sequence of may 25 27 1980 these earthquakes ushered in a period of almost continuous low level seismicity punctuated by relatively severe swarms in the southern moat vertical and horizontal displacements within long valley caldera between 1979 and 1982 define a striking radially symmetric pattern of uplift and horizontal distension that is consistent with expansion of the body of partial melt inferred from teleseismic and gravity data specifically the observed deformation of the caldera floor approximates the theoretical deformation due to expansion of a spherical magma chamber at a depth of at least 7 km the calculated maximum uplift is 430 mm and is located south of the center of the resurgent dome significant deviations from this simple model appear to be associated with either movement of mapped faults within and adjacent to the caldera or folding of weak surface deposits

contrasted distributions of triterpene derivatives in the sediments of lake caco reflect paleoenvironmental changes during the last 20 000 yrs in ne brazil lipid fractions extracted from sediment layers deposited in a small brazilian lake during the last 20 000 yrs were investigated by gas chromatography mass spectrometry considerable differences in the distribution and the amount of triterpene derivatives in the aliphatic as well as in the aromatic fractions were observed all along the series although no precise identification of these compounds was undertaken our interpretation of mass spectral data allowed us to discriminate between des a triterpenes mono and triaromatic derivatives of pentacyclic triterpenes and a series of compounds tentatively identified as diaromatic derivatives of tetracyclic triterpenes the largest compound diversity was found in the lowest levels of the series dated back to the end of the last glacial maximum when good preservation of terrestrial plant debris was ensured by rapid burial in a semi arid climate then except for a period corresponding to the younger dryas only des a lupane was detected in significant amounts the high predominance of des a lupane is interpreted to result from the development of a belt of eleocharis sp spike rush that filtered most of organic inputs from the catchment and was the site of des a lupane production and exportation towards the lake centre during the younger dryas a strong influx of des a lupane is attributed to the destruction of the spike rush belt consecutive to the lowering of the lake level under drier conditions the temporary destruction of this barrier allowed other triterpene derivatives to reach the lake the distinct dynamics of des a and aromatic triterpene derivatives under variable medium conditions led us to hypothesis that these two families of compounds derive from distinct pools that contributed differently to the sediment depending on environmental and climatic conditions des a lupane was most probably produced in sub aquatic conditions within the belt of spike rush conversely aromatic derivatives of triterpenes could have resulted from the degradation of their biological precursors within reducing micro environments in the catchment

persistent near tropical warmth on the antarctic continent during the early eocene epoch the warmest global climates of the past 65 million years occurred during the early eocene epoch about 55 to 48 million years ago when the equator to pole temperature gradients were much smaller than today1 2 and atmospheric carbon dioxide levels were in excess of one thousand parts per million by volume3 4 recently the early eocene has received considerable interest because it may provide insight into the response of earth s climate and biosphere to the high atmospheric carbon dioxide levels that are expected in the near future5 as a consequence of unabated anthropogenic carbon emissions4 6 climatic conditions of the early eocene greenhouse world however are poorly constrained in critical regions particularly antarctica here we present a well dated record of early eocene climate on antarctica from an ocean sediment core recovered off the wilkes land coast of east antarctica the information from biotic climate proxies pollen and spores and independent organic geochemical climate proxies indices based on branched tetraether lipids yields quantitative seasonal temperature reconstructions for the early eocene greenhouse world on antarctica we show that the climate in lowland settings along the wilkes land coast at a palaeolatitude of about 70 south supported the growth of highly diverse near tropical forests characterized by mesothermal to megathermal floral elements including palms and bombacoideae notably winters were extremely mild warmer than 10 c and essentially frost free despite polar darkness which provides a critical new constraint for the validation of climate models and for understanding the response of high latitude terrestrial ecosystems to increased carbon dioxide forcing

seismic velocity structure and earthquake relocation for the magmatic system beneath long valley caldera eastern california abstract a new three dimensional 3 d seismic velocity model and high precision location catalog for earthquakes between 1984 and 2014 are presented for long valley caldera and its adjacent fault zones in eastern california the simul2000 tomography algorithm is applied to derive the 3 d vp and vp vs models using first arrivals of 1004 composite earthquakes obtained from the original seismic data at the northern california earthquake data center the resulting vp model reflects geological structures and agrees with previous local tomographic studies the simultaneously resolved vp vs model is a major contribution of this study providing an important complement to the vp model for the interpretation of structural heterogeneities and physical properties in the study area the caldera is dominated by low vp anomalies at shallow depths due to postcaldera fill high vp and low vp vs values are resolved from the surface to 3 4 km depth beneath the center of the caldera corresponding to the structural uplift of the resurgent dome an aseismic body with low vp and high vp vs anomalies at 4 2 6 2 km depth below the surface is consistent with the location of partial melt suggested by previous studies based on vp models only and the inflation source locations based on geodetic modeling the sierran crystalline rocks outside the caldera are generally characterized with high vp and low vp vs values the newly resolved velocity model improves absolute location accuracy for the seismicity in the study area and ultimately provides the basis for a high precision earthquake catalog based on similar event cluster analysis and waveform cross correlation data the fine scale velocity structure and precise earthquake relocations are useful for investigating magma sources seismicity and stress interaction and other seismological studies in long valley

flow discharge influences on input and transport of particulate and sedimentary organic carbon along a small temperate river abstract the relative importance of hydrological conditions and upstream processes on the input and transport of organic carbon from land to sea was investigated in the mullica river a small system located in the southeastern new jersey usa using molecular and 13c compositions sediment and particulate organic carbon poc samples were collected along the river from upstream draining predominantly pine oak forests in the pinelands to the great bay estuary bordered by salt marshes under normal and high flow conditions during base river flow terrestrial biomarkers e g diterpenoids conifer biomarkers were detected predominantly upstream and sharply decreased downstream from mid to down river sites a mixture of higher plants primarily from the salt marsh vegetation and microbial biomarkers e g mycose cholesterol predominated 13c abundances of individual fatty acids presented a consistent pattern with depleted values e g 13csed 30 9 on average upstream becoming heavier toward the great bay e g 13csed 23 1 13cpoc 22 8 during the high discharge event significant amounts of upland biomarkers e g pimaric acid ferruginol ursolic acid and depleted 13c values were observed from the pinelands 13csed 34 6 to mid river 13csed 32 0 13cpoc 30 8 clearly demonstrating the transport of terrestrial material farther down river however downstream of this point the occurrence of the terrestrial material strongly decreased demonstrating that terrestrial plant biomarkers were not transported in significant amounts to the estuarine region even at high river discharge since the mid river site is situated in the upper limit of salt water intrusions it is likely that flocculation and sedimentation provide a depositional sink for terrestrial oc in the mid mullica river thereby depleting the terrigenous signature in downstream oc

attenuation of p and s waves in a magma chamber in long valley caldera california shallow earthquakes around the southwest boundary of long valley caldera west of the hilton creek fault are characterized by lack of s waves at regional seismic network stations to the northwest north and northeast and p waves for these same station event combinations are deficient in frequencies higher than about 2 3 hz earthquakes east of the hilton creek fault and southeast of the caldera have normal p and s wave signatures at the same stations these effects are explained by propagation through a magma chamber in the south central part of long valley caldera at depth greater than 7 8 km

geometry of magma bodies beneath long valley california determined from anomalous earthquake signals one hundred and ninety two small earthquakes which occurred recently near the southern edge of long valley caldera at depths from 1 to 13 km are used to map the subsurface geometry of magma bodies in the caldera seismograms of these events recorded northwest north northeast and east of long valley with ray paths through the caldera are often anomalous in that s wave arrivals are absent and high frequency p wave energy is missing these anomalous ray paths intersect in an area of the south central caldera which we interpret to be a region of molten or partially molten rock this magma body lies between about 4 1 2 and at least 13 km depth and is 10 km long by 5 km wide beneath 7 km the magma appears to be relatively contiguous below 7 km and more dispersed above another magma body may be present in the northwest caldera coincident with an interpreted 7 8 km deep reflection from the top of a magma chamber

composition age and provenance of organic matter in nw african dust over the atlantic ocean 1 eolian dust deposited on a meteorology buoy over the boreal winter and spring of 1992 1993 in the northeast atlantic off northwest africa 18 n 22 w afforded sufficient material for detailed assessment of its biogeochemical characteristics and provenance the sample was subjected to microscopic examination and bulk elemental isotopic black carbon and molecular lignin lipid analyses the bulk elemental composition and organic carbon oc content 1 02 dry weight establishes the dust s origin as continental upper crust and is typical of dusts that emanate from west africa these data are in accord with the extensive satellite imagery documenting the transit of dust clouds from the sahara and sahel regions e g nasa toms aerosol index microscopic examination reveals that charcoal like particles from vegetation fires black carbon bc are the most abundant morphologically distinct organic components accelerator mass spectrometry ams 14c analysis yields conventional 14c ages for bulk oc of 1260 40 years and bc of 2070 35 years taken together with corresponding stable carbon isotopic compositions 13c 18 9 and 15 1 respectively these results suggest the presence of biomass and burning residues derived from predominantly c4 vegetation that accumulated in soils over the late holocene molecular level measurements are also consistent with this scenario for example lignin derived phenols in the dustfall sample indicate a significant contribution of angiosperm grass type tissue the altered nature of the lignin suggests storage as residues in soils solvent extractable lipid constituents include a marked leaf wax type component with a molecular and stable carbon isotopic composition similar to those observed in surface marine sediments in this region the hydrocarbon fraction contained some diesel type contamination but the n alkanes c23 c33 retained a prominent odd even distribution with 13c ranging from 26 7 to 28 5 the suite of even carbon numbered n alkanols c22 c32 is 14c dated at 647 150 years with 13c values ranging from 23 9 to 30 4 the long chain n alkanoic acids c22 c32 exhibited 13c values ranging from 22 6 to 27 4 these waxes are evidently a mixed signal derived from contemporary c3 and c4 vegetation and from ablated soils and desiccated lake sediments of middle to late holocene age this molecular approach shows promise as a tool for continental paleoenvironmental assessment particularly with respect to past vegetation cover regional aridity and wind systems

distributional variations in marine crenarchaeotal membrane lipids a new tool for reconstructing ancient sea water temperatures it has recently been shown that membrane lipids of marine crenarchaeota a ubiquitous and abundant component of plankton occur in relatively high concentrations in recent and ancient sediments in this study we investigated the environmental controls on the relative distribution of these lipids in surface sediments we especially focussed on temperature as it is known from the thermophilic genetic relatives of marine crenarchaetoa that the composition of their membrane strongly depends on growth temperature indeed a significant linear correlation r2 0 92 is found between the number of cyclopentane rings in sedimentary membrane lipids derived from marine crenarchaeota and the annual mean sea surface temperatures this suggests that the mechanism of physical adaptation of their membrane compositions to temperature is identical to that of their thermophilic relatives in turn archaeal lipid distributions in sediments may thus allow the reconstruction of sea water temperatures of ancient marine environments

onset of north atlantic deep water production coincident with inception of the cenozoic global cooling trend here we show that the onset of deep water overflow from the norwegian greenland sea into the north atlantic interpreted to represent the onset of a modern style north atlantic deep water mass commenced close to the early to middle eocene boundary this finding is based on the identification of a large elongate contourite sediment drift the judd falls drift in the faeroe shetland basin through detailed mapping of high resolution two dimensional and three dimensional seismic data this sediment drift covers an area of 9000 km2 in one of the critical present day deep water gateways into the north atlantic ocean interpretation of the body as a contourite drift is based on standard seismic stratigraphic diagnostic criteria including tridirectional onlap lensoid sediment geometry upslope progradational configurations of stacked onlap units and an erosional base cut in a deepwater setting the internal reflection configuration indicates that the drift was deposited under a southwest flowing current regime which we propose represents the onset of north atlantic deep water production with continual deep water flow until at least the latest eocene ca 35 million years ago ma onset of drift deposition is dated by several key boreholes as occurring at ca 50 49 ma across the early to middle eocene boundary and is coincident with independent geochemical evidence for major changes in the configuration of deep sea circulation patterns global biological production and the onset of cenozoic climatic cooling these temporal concurrences suggest a strong link between the initiation of north atlantic deep water production and cenozoic global climate evolution

tracing the source of ancient reworked organic matter delivered to the north atlantic ocean during heinrich events a major effort of the geochemical and paleoclimate community has been to identify the specific sources of the ice rafted debris ird in heinrich layers hls although the general consensus is that the majority of the ird originated from the hudson area of northern canada the specific sources are not well constrained here we compare the diagnostic organic geochemical signature of hls to that of a number of paleozoic outcrops across the former margin of the laurentide ice sheet we show that the biomarker signature of upper ordovician strata from southampton and baffin island is compatible with that found in hls in the labrador sea and north atlantic while the biomarker signature of other paleozoic formations from the former margin of the laurentide ice sheet is not in addition to the biomarker signature key inorganic characteristics 18o end and 87sr 86sr ratios of these formations from southampton and baffin island are consistent with those reported from hls the location of these formations in and around the hudson strait is compatible with palaeo ice flow regimes through the hudson strait allowing for easy entrainment and rapid transport to the ocean based on these results we propose that these specific upper ordovician formations form a main source of ird in hls and hence infer an active role of the hudson strait paleo ice flow in these events

could changing ocean circulation have destabilized methane hydrate at the paleocene eocene boundary 1 during the paleocene eocene thermal maximum petm 55 ma marine and terrestrial carbon isotope values exhibit a negative shift of at least 2 5 indicative of massive destabilization of marine methane hydrates releasing 2000 gigatons of methane carbon the cause of the hydrate destabilization is unknown but has been speculated to be warming due to a change from high latitude to low latitude deepwater formation here we present results from a numerical ocean model indicating that a sudden switch of deepwater formation from southern to northern high latitudes caused middepth and deep ocean warming of 3 5 c the switch is caused by a slow increase in the intensity of the atmospheric hydrologic cycle as expected under increasing temperatures and consistent with petm sedimentary evidence deepened subtropical subduction prior to the thermohaline circulation switch causes warming of 1 4 c in limited areas at thermocline through upper intermediate depths which could destabilize methane hydrates gradually and at progressively greater depths warming accompanying a south to north switch in deepwater formation would produce sufficient warming to destabilize seafloor gas hydrates over most of the world ocean to a water depth of at least 1900 m

the paleocene eocene thermal maximum petm in svalbard clay mineral and geochemical signals abstract for the first time the paleocene eocene thermal maximum petm interval has been identified in drillcores and field outcrops from the paleogene central basin in svalbard based on mineralogical and geochemical information grumantbyen and frysjaodden formations a more than 300 m thick paleogene interval representing deltaic delta influenced marine shelf and deep water slope environments the petm has been recognized in the deepest and most distal deposits in the lower parts of the frysjaodden formation here this global event is displayed in clay mineralogical distributions as significantly increased kaolinite abundances reflecting a period with intensified chemical weathering in the land areas surrounding this paleogene basin the period was characterized by dominantly reducing sea floor conditions as seen in the th u distribution and the well developed parallel lamination in the pyrite rich shales all to be expected during an interval with increased temperature and precipitation

extreme warming of mid latitude coastal ocean during the paleocene eocene thermal maximum inferences from tex86 and isotope data changes in sea surface temperature sst during the paleocene eocene thermal max imum petm have been estimated primarily from oxygen isotope and mg ca records generated from deep sea cores here we present a record of sea surface temperature change across the paleocene eocene boundary for a nearshore shallow marine section located on the eastern margin of north america the sst record as inferred from tex86 data indicates a minimum of 8 c of warming with peak temperatures in excess of 33 c similar ssts are estimated from planktonic foraminifer oxygen isotope records al though the excursion is slightly larger the slight offset in the oxygen isotope record may reflect on seasonally higher runoff and lower salinity

observed performance of a short diaphragm wall panel the construction in hong kong of a 40 m deep excavated large rectangular section barrette i e a short diaphragm wall panel 2 8 m long by 0 8 m wide in sedimentary and weathered soils under bentonite has been heavily instrumented and closely monitored during excavation the maximum measured horizontal ground movements were only a few millimetres with similar subsurface settlements around the panel on the basis of three dimensional numerical simulations of the excavation of the trench an average mobilized shear strain greater than 0 1 around the excavated trench can be deduced at the soil wall interface the initial lateral earth pressures decreased to hydrostatic bentonite pressures during excavation and increased above their initial k0 pressures after concreting the measured lateral pressures just after concreting support a theoretical bilinear pressure envelope la construction d une barrette a grande section rectangulaire excavee a 40 m de profondeur c est a dire d un court panneau de mur

a long term high latitude record of eocene hydrological change in the greenland region abstract a range of proxy approaches have been used to reconstruct short term changes to earth s hydrological cycle during the early eocene hyperthermals however little is known about the response of earth s hydrological and biogeochemical systems to long term cenozoic cooling which began following the early eocene climatic optimum 53 3 49 4 million years ago ma here we use the molecular distribution and isotopic composition of terrestrial biomarkers preserved in marine sediments of odp site 913 east greenland to develop a long term record of high latitude hydrological change between 50 and 34 ma there is a marked decline in the concentration of conifer derived diterpenoids and angiosperm derived triterpenoids during the eocene as the input of wind blown conifer pollen remains stable during this interval this implies that decreasing di and triterpenoid concentrations reflect declining influence of fluvial inputs and perhaps terrestrial runoff throughout the eocene branched gdgts and bacterial derived hopanes indicate an increased input of soil and kerogen derived organic matter respectively after 38 ma this coincides with evidence for ice rafted debris and suggests input of organic matter via glacial processes this also implies some continental glaciation occurred on east greenland in the middle to late eocene leaf wax hydrogen isotopes extending throughout this section the first such long term record from the paleogene indicate that precipitation 2h was persistently higher than that of modern coastal greenland consistent with warmer ocean source waters and enhanced poleward moisture transport non intuitively however this effect appears to have been smallest during the warmest part of the record and higher 2h values occur in the middle eocene although interpretation of these hydrogen isotope trends is unclear they clearly indicate alongside the changes in biomarker abundances a perturbed hydrological cycle through the eocene in coastal greenland more long term records are required to ascertain if this represents regional or global hydrological reorganisation

marine and terrestrial environmental changes in nw europe preceding carbon release at the paleocene eocene transition environmental changes associated with the paleocene eocene thermal maximum petm 56 ma have not yet been documented in detail from the north sea basin located within proximity to the north atlantic igneous province naip the kilda basin and the northern rain belt paleolatitude 54 1n during the petm this is a critical region for testing proposed triggers of atmospheric carbon release that may have caused the global negative carbon isotope excursion cie in marine and terrestrial environments the cie onset is identified from organic matter d 13 c in exceptional detail within a

location and configuration of magma bodies beneath long valley california determined from anomalous earthquake signals recordings of 281 small earthquakes which occurred recently near the southern edge of long valley caldera at depths from 1 to 15 km are used to map the subsurface geometry of shear wave attenuating bodies in the caldera signatures of these events recorded northwest north northeast and east of long valley with ray paths through the caldera are often anomalous in that s wave arrivals have very low amplitudes and high frequency p and s wave energy is missing for the same station event combinations the volcanic and geothermal history of the region suggests that ray paths for these anomalous signals have passed through magma which absorbed much of the s wave energy and also attenuated the higher frequencies with over 1200 normal and anomalous ray paths through the caldera we have located two apparently massive magma bodies in the central and northwest caldera as well as two more dispersed magma areas in the southern caldera and beneath crowley lake the central magma body extends from 4 5 to at least 13 km beneath the surface and the northwest body is as shallow as 5 5 km these two magma bodies are probably connected below about 8 km secondary arrivals seen on select seismograms are tentatively interpreted as reverberations inside the central magma chamber and are consistent with the interpreted lateral extent of the magma the northwest and central magma bodies lie beneath the northwest and southeast corners of the caldera s resurgent dome and probably connect beneath the dome s center also the shallower parts of these magma bodies and the southern anomalous area lie beneath the surface expression of the medial graben faults suggesting that structural features seen at the surface of the valley may be related to magma location at depth

winter and summer temperatures of the early middle eocene of france from turritella δ18o profiles the mean annual range of temperature is from a climatological point of view at least as important as the mean annual temperature in order to examine intra annual temperature variations in the warm early cenozoic we have analyzed stable oxygen and carbon isotopes along the transect of growth on excellently preserved specimens of the gastropod turritella imbricataria and the bivalve venericardia imbricata from sedimentary rocks of early middle eocene age ca 46 ma in the paris basin turritella shell growth is fast throughout the year and the isotopic records give the first detailed information about early middle eocene seasonal variations the oxygen isotope profiles indicate winter temperatures of about 14 c and summer temperatures of up to 28 c i e a seasonality indistinguishable from the present situation but an annual temperature some 10 c higher our results contradict the opinion that the climate during this period was more equable than that of today

continental ice in greenland during the eocene and oligocene the eocene and oligocene epochs approximately 55 to 23 million years ago comprise a critical phase in earth history an array of geological records supported by climate modelling indicates a profound shift in global climate during this interval from a state that was largely free of polar ice caps to one in which ice sheets on antarctica approached their modern size however the early glaciation history of the northern hemisphere is a subject of controversy here we report stratigraphically extensive ice rafted debris including macroscopic dropstones in late eocene to early oligocene sediments from the norwegian greenland sea that were deposited between about 38 and 30 million years ago our data indicate sediment rafting by glacial ice rather than sea ice and point to east greenland as the likely source records of this type from one site alone cannot be used to determine the extent of ice involved however our data suggest the existence of at least isolated glaciers on greenland about 20 million years earlier than previously documented at a time when temperatures and atmospheric carbon dioxide concentrations were substantially higher

a comparison of terpenoid and leaf fossil vegetation proxies in paleocene and eocene bighorn basin sediments abstract plant derived terpenoids long recognized as biomarkers can help reveal the major taxonomic groups of land plants present in ancient environments even if rocks and sediments do not preserve plant macro or microfossils previous studies have used simple di to triterpenoid ratios to reconstruct floral changes in the geologic past but few have compared terpenoid ratios with estimates of floral composition from fossils further reconstructions have not taken into account differences in biomarker production i e concentration relative to leaf biomass between different types of plants here we have examined terpenoids from early cenozoic fluvial rocks from the bighorn basin wyoming usa where fossil flora has been studied in detail we analyzed the distributions of diterpenoids triterpenoids and n alkanes from leaf wax in a total of 43 samples from 15 stratigraphic horizons of late paleocene 63 ma to early eocene 53 ma in age in nearly all samples triterpenoids derived from angiosperms were significantly lower in abundance than conifer specific diterpenoids a finding that contrasted with plant fossil evidence for the same rocks this suggests that di to triterpenoid ratios severely underestimate the abundance of angiosperms in paleovegetation angiosperms dominated n alkane production among modern plants and we propose a new paleovegetation proxy based on the ratio of diterpenoids conifers to n alkanes angiosperms corrected for lipid production estimated from extant vegetation using diterpenoids and alkanes we infer the composition of paleovegetation to be similar to that inferred from plant fossils although the approach works well for the bighorn basin we stress the new paleovegetation proxy will need to be evaluated for other time periods communities paleogeography and depositional environments with pollen or megafossil data available