biomarker and carbon isotope variation in coal and fossil wood of central europe through the cenozoic abstract carbon isotope analyses of terrigenous organic matter are often used to reconstruct changes in the isotopic composition of upper ocean and atmospheric carbon reservoirs carbon isotope values from tree rings fossil wood and coal matrices have been related to climatic change e g temperature humidity via water use efficiency of land plants in this study we report on carbon isotope analyses on low rank coal deposits of the alpine realm and middle german lignite district covering the early eocene to pliocene time interval fossil wood and extracted wood cellulose from gymnosperms and angiosperms respectively are used for paleoenvironmental reconstructions the trend in 13c is parallel to the carbon isotope record obtained from benthic foraminifera because both data sets sample a common reservoir in the atmosphere the evaluation of the magnitudes of 13c variations of coal caused by environmental change requires the correction of the 13c data due to the effects of different contents of lipids in the organic matter differences in biogeochemical carbon cycling varying contributions of gymnosperms versus angiosperms to peat formation and differences in 13c of atmospheric co2 the resulting carbon isotope record of coal generally co varies with the estimated variability in mean annual temperatures during the tertiary based on paleobotanical data changes in humidity and pco2 may be responsible for deviations between the isotopic trend and the paleotemperature curve during the miocene the obtained temperature coefficient for 13c of c3 plants of about 0 3 c is in agreement with the results of previous studies

earthquake supercycle in subduction zones controlled by the width of the seismogenic zone some subduction zones experience earthquake supercycles numerical simulations show that successive megathrust earthquakes may load neighbouring parts of the fault causing it to eventually fail in a giant earthquake that completes a supercycle

diffusive retention of carbon and nitrogen in a microcrystalline quartz dominated chert implications for reconstructing earth s ancient atmosphere abstract we investigate the retention of volatile species and we analyze the volatile species released on low temperature crushing of a microcrystalline quartz

distinct origins for rovno and baltic ambers evidence from carbon and hydrogen stable isotopes abstract ambers fossilized plant resins are a rich and unique source of paleoecological data due to their ability to preserve soft body fossils however interpretations concerning their environmental context are often hampered by uncertainties in the relationship between assemblages of inclusions and geological context particularly in the case of secondarily redeposited ambers such as those from the paleogene of central europe here we use stable carbon and hydrogen isotope analyses as well as ftir spectroscopy from the northwestern ukrainian rovno amber deposit to provide independent constraints on the geographic and temporal origins of rovno amber these analyses address the relationship between the rovno and baltic amber deposits as well as german bitterfeld amber a subject of considerable debate regarding their provenance rovno amber has a 13c signature of 23 3 0 9 similar to both baltic and bitterfeld ambers since there is a secular decreasing 13c trend among amber deposits since the early eocene a roughly contemporaneous origin of these deposits in the eocene can be deduced however rovno amber displays a 2h signature of 258 9 19 more positive than baltic amber and directly comparable to bitterfeld amber this difference relates to precipitation sources and mean annual temperatures of the amber source regions and suggests a much more southerly origin of rovno amber relative to baltic amber ftir spectra of each of these ambers are nearly identical and suggest that resin producing trees were from similar families despite contrasting source regions thus we provide the first clear geochemical evidence for the distinct origin of rovno and baltic amber deposits with implications for paleoecological studies involving inclusions from these deposits and for determining the provenance of archaeological amber finds

carbon isotope systematics of a mantle hotspot a comparison of loihi seamount and morb glasses the carbon isotope geochemistry of glasses from loihi seamount has been compared with that of morb glasses stepped heating shows two carbon components in both sample suites 1 isotopically light carbon avg 13c 26 3 released 600 c regarded as indigenous the high temperature component in morb samples varied from 52 to 169 ppm c average 13c 6 6 consistent with previous studies overall mord average 13c 6 4 0 9 and new results for indian ocean glasses are similar to atlantic and pacific ocean samples carbon release profiles produced by stepped heating may be typical of locality but there are no significant differences in 13c values between morb samples from different areas lower yields 17 110 ppm c correlated with depth in the loihi samples suggest that they are partially degassed this degassing has not affected 13c values significantly avg 5 8 loihi tholeiites have higher 13c avg 5 6 than the alkali basalts avg 7 1 carbon abundances correlate well with he concentration data comparison of the 13c values with trace element and he sr nd and pb isotope data from the literature suggests that the loihi samples with highest 13c have high3he 4he and possibly the least depleted143nd 144nd and87sr 86sr the carbon isotope data are consistent with previous models for loihi involving several mantle sources lithospheric contamination and mixing the slightly higher 13c of loihi tholeiites suggests that the undegassed plume component manifested by high3he 4he values might have 13c about 1 higher than the morb average

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

a new discovery of early cretaceous wealden amber from the isle of wight a new discovery of in situ amber is reported from the southwest coast of the isle of wight the productive site is located within the wealden marls wessex formation generally regarded to be of earliest barremian early cretaceous age also making this amber amongst some of the oldest known occurrences in the world amber globules can be found within two thin black lignite horizons which form a channel lag deposit exposed in the cliffssoutheast of chilton chine examination of plant material above and below this site by other workers combined with infrared spectra of the amber in this study implies a coniferous possibly taxodiaceous origin for this resin palaeoenviron mental interpretation of the chilton chine site suggests that the amber was exuded locally and in some cases the globules have beenpartly replaced by iron pyrite

the 13c suess effect in scleractinian corals mirror changes in the anthropogenic co2 inventory of the surface oceans 1 new 13 c data are presented from 10 coral skeletons collected from florida and elsewhere in the caribbean dominica dominican republic puerto rico and belize these corals range from 96 to 200 years in age and were collected between 1976 and 2002 the change in the 13 c of the skeletons from these corals between 1900 and 1990 has been compared with 27 other published coral records from the atlantic pacific and indian oceans the new data presented here make possible for the first time a global comparison of rates of change in the 13 c value of coral skeletons of these records 64 show a statistically significant p 0 05 decrease in 13 c towards the modem day 23 out of 37 this decrease is attributable to the addition of anthropogenically derived co 2 13 c suess effect to the atmosphere between 1900 and 1990 the average rate of change of the 13 c in all the coral skeletons living under open oceanic conditions is approximately 0 01 o yr 1 in the atlantic ocean the magnitude of the decrease since 1960 0 019 yr 1 0 015 is essentially the same as the decrease in the 13 c of atmospheric co 2 and the 13 c of the oceanic dissolved inorganic carbon 0 023 to 0 029 yr 1 while in the pacific and indian oceans the rate is more variable and significantly reduced 0 007 yr 1 0 013 these data strongly support the notion that i the 13 c of the atmosphere controls ambient 13 c of the dissolved inorganic carbon which in turn is reflected in the coral skeletons ii the rate of decline in the coral skeletons is higher in oceans with a greater anthropogenic co 2 inventory in the surface oceans iii the rate of 13 c decline is accelerating superimposed on these secular variations are controls on the 13 c in the skeleton governed by growth rate insolation and local water masses

marked decline in atmospheric carbon dioxide concentrations during the paleogene the relation between the partial pressure of atmospheric carbon dioxide pco2 and paleogene climate is poorly resolved we used stable carbon isotopic values of di unsaturated alkenones extracted from deep sea cores to reconstruct pco2 from the middle eocene to the late oligocene approximately 45 to 25 million years ago our results demonstrate that pco2 ranged between 1000 to 1500 parts per million by volume in the middle to late eocene then decreased in several steps during the oligocene and reached modern levels by the latest oligocene the fall in pco2 likely allowed for a critical expansion of ice sheets on antarctica and promoted conditions that forced the onset of terrestrial c4 photosynthesis

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

volcanism co2 and palaeoclimate a late jurassic early cretaceous carbon and oxygen isotope record a composite tethyan late jurassic early cretaceous carbon and oxygen isotope curve is presented c isotope data provide information on the evolution and perturbation of the global carbon cycle o isotope data are used as a palaeotemperature proxy in combination with palaeontological information the resulting trends in climate and in palaeoceanography are compared with biocalcification trends and oceanographic conditions favouring or inhibiting biocalcification positive c isotope anomalies in the valanginian and aptian correlate with episodes of increased volcanic activity regarded as a source of excess atmospheric carbon dioxide a major warming pulse accompanies the aptian but not the valanginian c isotope event the observed change in early aptian temperatures could have triggered the destabilization of sedimentary gas hydrates and the sudden release of methane to the biosphere as recorded as a distinct negative carbon isotope pulse preceding the positive excursion both c isotope anomalies are accompanied by biocalcification crises that may have been triggered by p co 2 induced changes in climate and in surface water chemistry elevated nutrient levels in river influenced coastal waters and in upwelling regions further weakened marine calcification these conditions contrast with normal trophic conditions prevailing in the latest jurassic and favouring biocalcification the c and o isotope curves record a stable mode of carbon cycling and stable temperatures we conclude that biocalcification is mostly triggered and inhibited by co 2 conditions in the atmosphere ocean system

episodic slow slip events accompanied by non volcanic tremors in southwest japan subduction zone 1 episodic slow slip events have been recognized by means of tilt changes in the western shikoku area southwest japan the crustal tilt deformation was observed repeatedly with a recurrence interval of approximately six months coincident with the occurrences of major non volcanic deep tremor activities in this area observed tilt changes can be explained by slow slip events occurring around the source area of tremors in each episode the source of the slow slip event and tremor migrate simultaneously the spatial and temporal coincidence of tremors and slow slip events indicates that they both may be coupling phenomena reflecting the stress accumulation process at the subducting plate

variety and spatial heterogeneity of tectonic tremor worldwide 1 deep tectonic tremor occurs at various sites worldwide and the source characteristics are heterogeneous even at small scales in this study tremor sources were determined using data sets of seismic waveforms from various locations some of which are not well recognized as being a site of tremor activity the regions of interest are subduction zones at nankai and kyushu japan cascadia in western north america mexico southern chile and new zealand tremor locations are consistent with the geometry of subducting plates and tremor depth tends to be shallower where younger plate is subducting tremor duration shows a negative correlation with tidal sensitivity as reported previously in western shikoku in the nankai subduction zone the duration is also related to the width of the tremor zone in the dip direction of the subducting plate linear structures resembling striations are observed in hypocenter distributions in western shikoku and in the probability of short term migration direction these spatial heterogeneities in tremor activity may be controlled by the heterogeneous frictional properties of the downgoing slab due to long term plate subduction thereby providing information on the maturity of the plate interface

carbon isotope evidence implying high o2 co2 ratios in the permo carboniferous atmosphere abstract theoretical models predict a marked increase in atmospheric o2 to 35 during the permo carboniferous 300 ma occurring against a low 0 03 co2 level an upper o2 value of 35 however remains disputed because ignition data indicate that excessive global forest fires would have ensued this uncertainty limits interpretation of the role played by atmospheric oxygen in late paleozoic biotic evolution here we describe new results from laboratory experiments with vascular land plants that establish that a rise in o2 to 35 increases isotopic fractionation 13c during growth relative to control plants grown at 21 o2 despite some effect of the background atmospheric co2 level on the magnitude of the increase we hypothesize that a substantial permo carboniferous rise in o2 could have imprinted a detectable geochemical signature in the plant fossil record over 50 carbon isotope measurements on intact carbon from four fossil plant clades with differing physiological ecologies and ranging in age from devonian to cretaceous reveal a substantial 13c anomaly 5 occurring between 300 and 250 ma the timing and direction of the 13c excursion is consistent with the effects of a high o2 atmosphere on plants as predicted from photosynthetic theory and observed in our experiments preliminary calibration of the fossil 13c record against experimental data yields a predicted o2 co2 mixing ratio of the ancient atmosphere consistent with that calculated from long term models of the global carbon and oxygen cycles we conclude that further work on the effects of o2 in the combustion of plant materials and the spread of wildfire is necessary before existing data can be used to reliably set the upper limit for paleo o2 levels

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

the evolution of respiratory systems in theropoda and paracrocodylomorpha the end triassic extinction and the role of late triassic atmospheric o2 and co2 abstract during the late triassic period 235 201 3 ma paracrocodylomorpha and theropoda switched predatory roles with the former filling the subsidiary predator niche and the latter filling the top predator niche at the end triassic extinction reasons for the transition in predator guilds remain unknown but atmospheric conditions during this time which involved high co2 and low o2 concentration levels may be associated with the event evidence of bird like pneumatic post crania present in both groups as foramina and fossae correlates with an avian like respiratory system this may have allowed organisms to cope with declining atmospheric o2 environments of the late triassic this study estimated po2 throughout the late triassic using organic carbon isotope measurements from newark hartford basin paleosols and examined the morphological change in skeletal remains of theropoda focusing on pneumatic bones compared with paracrocodylomorpha during the late triassic and across the triassic jurassic boundary with data compiled from the paleobiology database and published anatomical literature the change of pneumaticity in taxa is quantified by a pneumatic index pi in which the number of pneumatized units is divided by the total number of bones examined patterns of pneumaticity are individually scored for the presence or absence of pneumatic bones morphological data are compared to corresponding femur length estimated atmospheric o2 and co2 level reconstructions and an ancestral state reconstruction depicting how pi values change throughout various clades our results suggest that pi values in theropoda and paracrocodylomorpha correspond with the vacillating po2 and pco2 throughout the late triassic and into the jurassic high pi values are prevalent in advanced theropod taxa while paracrocodylomorpha pi values vary by clade with a generally negative trend throughout the triassic ancestral state reconstruction analysis highlights the increasing pi values within theropoda and clade dependent trends in paracrocodylomorpha this study is instrumental in reconstructing how theropoda became evolutionarily successful and perhaps how and why the avian like respiratory system originated

do stable carbon isotopes of brown coal woods record changes in lower miocene palaeoecology stable carbon isotope ratios of fossil wood from the miocene brown coal deposits in former east germany are compared with palaeobotanical and sedimentological data to test the use of stable isotopes in determining palaeoenvironment significant differences in the chemical composition of samples from different horizons were observed those specimens preserved under the most bio degrading conditions yielded stable carbon isotope values least representative of original wood specimens overall the chemical preservation of the wood was seen to affect the stable isotope signal but deconvolving the preservational bias using a molecular approach enabled estimations of 13cbiomass and 13cpalaeoatmosphere that were then used to interpret more fully the palaeoenvironment

a modeling case for high atmospheric oxygen concentrations during the mesozoic and cenozoic changes in atmospheric oxygen concentration over earth history are commonly related to the evolution of animals and plants but there is no direct geochemical proxy for o2 levels meaning that estimations rely heavily on modeling approaches the results of such studies differ greatly to the extent that today s atmospheric mixing ratio of 21 might be either the highest or lowest level during the past 200 m y long term oxygen sources such as the burial in sediments of reduced carbon and sulfur species are calculated in models by representation of nutrient cycling and estimation of productivity or by isotope mass balance imb a technique in which burial rates are inferred in order to match known isotope records studies utilizing these different techniques produce conflicting estimates for paleoatmospheric o2 with nutrient weathering models estimating concentrations close to or above that of the present day and imb models estimating low o2 especially during the mesozoic here we re assess the imb technique using the copse biogeochemical model imb modelling is confirmed to be highly sensitive to assumed carbonate 13c and when this input is defined following recent compilations predicted o2 is significantly higher and in reasonable agreement with that of non imb techniques we conclude that there is no model based support for low atmospheric oxygen concentrations during the past 200 m y high mesozoic o2 is consistent with wildfire records and the development of plant fire adaptions but links between o2 and mammal evolution appear more tenuous

sedimentary organic matter record of early cretaceous environmental changes in western liaoning province ne china abstract the abundance and composition of organic matter and the 13 c compositions of some specific individual compounds were analysed in sediments collected from an excavated profile of the early cretaceous yi xian formation in liaoning province ne china in order to provide organic geochemical information on palaeoclimate and environmental changes the distribution of n alkanes varies steadily through the profile with long chain n alkanes dominating in the lower and upper sections and medium chain length n alkanes dominating in the middle section of the profile the 13 c values of n alkanes hopanes and steranes show similar upward positive trends through the profile suggesting that these compounds originated from the same source material and also reflect consistent changes in the environment of the sedimentary basin the c 24 17 21 seco hopane was only detected in the lower and middle sections of the profile and has a more positive carbon isotopic composition by about 3 7 6 7 than that of associated n alkanes hopanes steranes and c 30 8 14 seco hopane this implies that the c 24 17 21 seco hopane had a different origin possibly connected with the volcanic ash deposits and massive vertebrate remains reconstruction of the 13 c composition of atmospheric co 2 based on plant derived c 29 and c 31 n alkanes shows a change from 10 to 3 from the bottom to the middle of the profile this upward positive excursion through the profile is consistent with the worldwide variation of atmospheric co 2 during the early cretaceous and indicates an upward warming trend likely related to globally intensified volcanic activity

comparison of stable carbon isotope ratios in the whole wood cellulose and lignin of oak tree rings abstract the stable carbon isotope ratios 13c of whole wood cellulose and acid insoluble lignin from annual latewood increments of quercus robur l from modern and sub fossil wood were measured and their potential use as palaeoenvironmental indicators examined the resulting time series demonstrate a very high degree of coherence with 13c of cellulose isotopically enriched by approximately 3 compared to 13c of lignin the 13c values of all three components are influenced by the climate of july and august modern whole wood retains the strongest climate signal perhaps because its composition is closest to that of leaf sugars in sub fossil wood there is no evidence that differential decay leads to fractionation of carbon within either cellulose or lignin but differential decay can alter the cellulose to lignin ratio

the response of phanerozoic surface temperature to variations in atmospheric oxygen concentration recently poulsen et al 2015 suggested that o2 has played a major role in climate forcing during the phanerozoic specifically they argued that decreased o2 levels during the cenomanian stage of the mid cretaceous 94 100 ma could help explain the extremely warm climate during that time the postulated warming mechanism involves decreased rayleigh scattering by a thinner atmosphere which reduces the planetary albedo and allows greater surface warming this warming effect is then amplified by cloud feedbacks within their 3 d climate model this increase in shortwave surface forcing in their calculations exceeds any decrease in the greenhouse effect caused by decreased o2 here we use a 1 d radiative convective climate model with no cloud feedback to check their results we also include a self consistent calculation of the change in atmospheric ozone and its effect on climate our results are opposite to those of poulsen et al we find that the climate warms by 1 4 k at 35 o2 concentrations as a result of increased pressure broadening of co2 and h2o absorption lines and cools by 0 8 k at 10 o2 as a result of decreased pressure broadening the surface temperature changes are only about 1 k either way though for reasonable variations in phanerozoic o2 concentrations 10 35 by volume hence it seems unlikely that changes in atmospheric o2 account for the warm climate of the cenomanian other factors such as a higher than expected sensitivity of climate to increased co2 concentrations may be required to obtain agreement with the paleoclimate data

collapse of the late triassic megamonsoon in western equatorial pangea present day american southwest during the late triassic western equatorial pangea in the present day american southwest was unusually humid as indicated by sedimentological evidence and inferred from general circulation models these studies show that once equatorial pangea was assembled cross equatorial summer air flow penetrated into western equatorial pangea bringing abundant megamonsoon rainfall and warm temperatures however many of these investigations indicate that gradual aridification began sometime during the late triassic to jurassic we show from field properties geochemical transfer functions and isotopic analysis of paleosols in the chinle formation of petrified forest national park arizona that the western equatorial pangea megamonsoon collapsed by 214 7 ma during the middle norian climate shift paleosols include entisols inceptisols vertisols aridisols and alfisols with transfer functions for mean annual precipitation chemical index of alteration minus potassium cia k and mean annual temperature nak salinization developed from analogous modern data sets the most notable shift is the appearance of carbonate enriched paleo inceptisols and paleo vertisols after 214 7 ma and paleo aridisols after 210 ma prior to the middle norian climate shift the region is classified as humid humidity province based on rainfall estimates initiation of the middle norian climate shift was characterized by an increase in paleosol carbonate content and rapidly declining rainfall as the region shifted to subhumid and eventually to semiarid and arid after 210 ma paleosol derived temperatures are indicative of warm temperate to subtropical ecozones whereas general circulation models show higher temperatures and tropical conditions perhaps because boundary conditions were set to atmospheric p co 2 4 5 present elevations of 1 5 2 km adjacent to the cordilleran magmatic arc complex located 400 km west of the study area may account for nontropical temperatures after 210 ma however temperatures began to increase possibly as a result of escalating atmospheric p co 2 from shale oxidation during marine regression and from coal and paleosol organic matter oxidation during prolonged aridification paleomagnetic studies have suggested northward continental drift of western equatorial pangea to outside of the intertropical convergence zone as the cause of monsoonal collapse during the late triassic to early jurassic the formation of a rain shadow as a result of the evolving cordilleran magmatic arc as the cause of aridification is supported by recent magnetostratigraphic work substantiating that the region remained in the tropics through the triassic according to our age model the middle norian climate shift is dated to near the same time as the manicouagan impact crater but there is no evidence of such an event in the study area either geochemically or sedimentologically at our scale of observation however a regionally defined faunal turnover may have been a response to rapidly changing climates in the region

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

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

stable carbon isotopes of c3 plant resins and ambers record changes in atmospheric oxygen since the triassic estimating the partial pressure of atmospheric oxygen po2 in the geological past has been challenging because of the lack of reliable proxies here we develop a technique to estimate paleo po2 using the stable carbon isotope composition d 13 c of plant resins including amber copal and resinite from a wide range of localities and ages triassic to modern plant resins are particularly suitable as proxies because their highly cross linked terpenoid structures allow the preservation of pristine d 13 cs ignatures over geological timescales the distribution of d 13 c values of modern resins n 126 indicates that a resin producing plant families generally have a similar fractionation behavior during resin biosynthesis and b the fractionation observed in resins is similar to that of bulk plant matter resins exhibit a natural variability in d 13 c of around 8 d 13 cr ange 31 to 23 m ean 27 which is caused by local environmental and ecological factors e g water availability water composition light exposure temperature nutrient availability to minimize the effects of local conditions and to determine long term changes in the d 13 co f resins we used mean d 13 c values d 13 c resin for each geological resin deposit fossil resins n 412 are generally enriched in 13 c compared to their modern counterparts with shifts in d 13 c resin of up to 6 these isotopic shifts follow distinctive trends through time which are unrelated to post depositional processes including polymerization and diagenesis the most enriched fossil resin samples with a d 13 c resin between 22 and 21 formed during the triassic the mid cretaceous and the early eocene experimental evidence and theoretical considerations suggest that neither change in pco2 nor in the d 13 c of atmospheric co2 can account for the observed shifts in d 13 c resin the fractionation of 13 c in resin producing plants d 13 c instead is primarily influenced by atmospheric po2 with more fractionation occurring at higher po2 the enriched d 13 c resin values suggest that atmospheric po2 during most of the mesozoic and cenozoic was considerably lower po2 10 20 than today po2 21 in addition a correlation between the d 13 c resin and the marine d 18 o record implies that po2 pco2 and global temperatures were inversely linked which suggests that intervals of low po2 were generally accompanied by high pco2 and elevated global temperatures intervals with the lowest inferred po2 including the mid cretaceous and the early eocene were preceded by large scale volcanism during the emplacement of large igneous provinces lips this suggests that the influx of mantle derived volcanic co2 triggered an initial phase of warming which led to an increase in oxidative weathering thereby further increasing greenhouse forcing this process resulted in the rapid decline of atmospheric po2 during the mid cretaceous and the early eocene greenhouse periods after the cessation in lip volcanism and the decrease in oxidative weathering rates atmospheric po2 levels continuously increased over tens of millions of years whereas co2 levels and temperatures continuously declined these findings suggest that atmospheric po2 had a considerable impact on the evolution of the climate on earth and that the d 13 c of fossil resins can be used as a novel tool to assess the changes of atmospheric compositions since the emergence of resin producing plants in the paleozoic

interactions and triggering in a 3 d rate and state asperity model we present a 3 d continuous quasi dynamic rate and state model of multiple seismic asperities forced by surrounding aseismic creep and motivated by observations of coplanar multiplets our model allows to study the physics of interactions among a set of asperities first we show that the amount of interactions and clustering characterized by the omori law and interevent time distribution depends on how far the system is from a critical density of asperities which is related to the friction properties of the barriers separating the sources this threshold controls the ability of a population of asperities to destabilize the creeping barriers between them and therefore determines whether dynamic sequences including several asperities in the same event might occur in agreement with what is expected from observed magnitude frequency distributions therefore the concept of critical density of asperity provides a mechanical interpretation of statistical properties of seismicity as an illustration we used our numerical results in the specific case of parkfield in the period preceding the mw 6 2004 earthquake in order to infer the steady state friction parameter a b characterizing the creep of this part of the san andreas fault we estimate a value of a b that locally exceeds 0 001 which is in the upper range of what has already been proposed for the postseimic period of the mw 6 2004 parkfield earthquake

carbon isotope behaviour in wood and cellulose during artificial aging abstract modern wood was subjected to an artificial decay process to investigate its behaviour with respect to the stable carbon isotope composition of wood and the corresponding cellulose four different woods were used namely oak quercus robur beech fagus sylvatica pine pinus sylvestris sequoia sequoiadendron giganteum and pure spruce cellulose the process of decay was simulated by heating samples in water at 180 c from minutes to months during the decay period the carbon content of wood increased to almost 70 while the cellulose content decreased gradually to zero the degradation proceeds according to a two stage process an initial very fast break down is followed by a rather slow degradation after a strong discrimination against 13 c during the initial phase the 13c 12c ratio increases again mostly up to its initial value the carbon isotope trend for cellulose shows a similar pattern though it is less pronounced maximum discrimination was 1 relative to the untreated wood 13c values of cellulose decreased by up to 0 3 the 13 c depletion is presumably a consequence of the preferential decomposition of cellulose as compared to lignin data on fossil trees are compared with the results obtained from this treatment of aging the 13 c decrease is in line with observations from these fossil woods but the ensuing 13 c enrichment is at most weakly to be seen

co2 forced climate thresholds during the phanerozoic abstract the correspondence between atmospheric co2 concentrations and globally averaged surface temperatures in the recent past suggests that this coupling may be of great antiquity here i compare 490 published proxy records of co2 spanning the ordovician to neogene with records of global cool events to evaluate the strength of co2 temperature coupling over the phanerozoic last 542 my for periods with sufficient co2 coverage all cool events are associated with co2 levels below 1000 ppm a co2 threshold of below 500 ppm is suggested for the initiation of widespread continental glaciations although this threshold was likely higher during the paleozoic due to a lower solar luminosity at that time also based on data from the jurassic and cretaceous a co2 threshold of below 1000 ppm is proposed for the initiation of cool non glacial conditions a pervasive tight correlation between co2 and temperature is found both at coarse 10 my timescales and fine resolutions up to the temporal limits of the data set million year timescales indicating that co2 operating in combination with many other factors such as solar luminosity and paleogeography has imparted strong control over global temperatures for much of the phanerozoic

phanerozoic concentrations of atmospheric oxygen reconstructed from sedimentary charcoal varying concentrations of atmospheric oxygen have affected the development of animals and the role of wildfire in ecosystems reconstructions of past oxygen concentrations from fossil charcoal constrain atmospheric oxygenation over the past 400 million years variations of the earth s atmospheric oxygen concentration po2 are thought to be closely tied to the evolution of life with strong feedbacks between uni and multicellular life and oxygen1 2 on the geologic timescale po2 is regulated by the burial of organic carbon and sulphur as well as by weathering3 reconstructions of atmospheric o2 for the past 400 million years have therefore been based on geochemical models of carbon and sulphur cycling4 5 6 however these reconstructions vary widely4 5 6 7 8 9 10 particularly for the mesozoic and early cenozoic eras here we show that the abundance of charcoal in mire settings is controlled by po2 and use this proxy to reconstruct the concentration of atmospheric oxygen for the past 400 million years we estimate that po2 was continuously above 26 during the carboniferous and permian periods and that it declined abruptly around the time of the permian triassic mass extinction during the triassic and jurassic periods po2 fluctuated cyclically with amplitudes up to 10 and a frequency of 20 30 million years atmospheric oxygen concentrations have declined steadily from the middle of the cretaceous period to present day values of about 21 we conclude however that variation in po2 was not the main driver of the loss of faunal diversity during the permo triassic and triassic jurassic mass extinction events

blue fluorescing amber from cenozoic lignite eastern sikhote alin far east russia preliminary results abstract blue and greenish yellow in addition to ordinary yellow orange amber has recently been found in a lignite seam in the zerkal nenskaya depression primorsky krai russia the amber is associated with abundant charcoal and fusain fragments in the host rocks its ftir spectra indicate the presence of significant quantities of volatile matter including free hydroxyl groups and carbon dioxide both co 2 and oh contents are greater in the greenish yellow and blue hard varieties suggesting rapid heating possibly from a wildfire followed by rapid cooling in water as a causative agent of amber hardening and extreme polymerization this process and the following amber deposition in the reduced environment might produce the fluorescent aromatics that have been previously suggested and confirmed by this study as the blue glow main cause

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

radiometric age of the chickaloon formation of south central alaska location of the paleocene eocene boundary k ar and fission track ages from two volcanic ash partings in upper chickaloon formation coals range from 53 3 1 5 m y to 55 8 1 7 m y these ages establish that the paleocene eocene boundary 55 m y occurs within the dated upper part of this formation

carbon isotope variability of triassic amber as compared with wood and leaves southern alps italy abstract the carbon isotope signatures of carnian late triassic amber drops from rifugio dibona southern alps italy were studied and compared with that of other middle early late triassic fossil plant remains namely wood and leaves amber wood and leaf carbon isotope data are highly variable within the same beds 13camber values vary by up to 5 4 and are enriched by 2 5 with respect to associated wood 13cwood and 13cleaf ranges are narrower than that of amber 2 3 and the isotopic offset within each bed is similar over time the high triassic amber carbon isotope variability is similar to that of recent resin despite the high variability 13cwood and 13cleaf illustrate a middle early late triassic secular positive trend that is similar to that of marine 13cinorg data and must record the carbon isotope evolution of the ocean atmosphere system

δ13c and δ18o values of triassic brachiopods and carbonate rocks as proxies for coeval seawater and palaeotemperature abstract a dataset of 160 isotope 13c and 18o values from anisian ladinian carnian and rhaetian articulate brachiopod shells complemented by 158 carbon and oxygen isotope values from whole rock carbonates define the first continuous stable isotope baseline trends for the triassic seawater the carbon isotope data suggest the existence of several short term high amplitude excursions in the early triassic followed by a predominance of values around 0 5 1 during the middle triassic a rise to 3 5 during the carnian plateau at this level during the late carnian to early norian and a 1 5 decline in the middle norian to values around 2 during the late norian rhaetian interval the causation scenarios for these rapid oscillations are at present equivocal but may in part reflect a biological instability of the carbon cycle following the recovery from the end permian extinction event and or an input of mantle derived co2 from enhanced volcanic activity the 18o values from well preserved brachiopods from the tethyan realm range from 3 9 to 0 6 v pdb these values require open marine triassic seawater 18o values close to 0 v smow for the calculated temperatures to be within the range of tolerance of the coexisting reef building corals a 2 18o increase within the uppermost cordevolian and early julian suggests either a distinct temperature decline in the southern alps during that time interval an increase in seawater salinity or their combination oxygen isotope values for the muschelkalk brachiopods range between 6 2 and 2 0 and likely reflect a strong influx of meteoric waters into the germanic basin that shifted the oxygen isotopes to more negative values

triggering of tremors and slow slip event in guerrero mexico by the 2010 mw 8 8 maule chile earthquake 1 we investigate the triggering of seismic tremor and slow slip event in guerrero mexico by the february 27 2010 maule earthquake mw 8 8 triggered tremors start with the arrival of s wave generated by the maule earthquake and keep occurring during the passing of scs ss love and rayleigh waves the rayleigh wave dispersion curve footprints the high frequency energy envelope of the triggered tremor indicating a strong modulation of the source of tremors by the passing surface wave this correlation and modulation by the passing waves is progressively lost with time over a few hours the tremor activity continues during the weeks months after the earthquake gps time series suggest that the second sub event of the 2009 2010 sse in guerrero is actually triggered by the maule earthquake the southward displacement of the gps stations starts coincidently with the earthquake and tremors the long duration of tremors indicate a continuing deformation process at depth which we propose to be the second sub event of the 2009 2010 sse we show a quasi systematic correlation between surface displacement rate measured by gps and tremor activity suggesting that the nvt are controlled by the variations in the slip history of the sse this study shows that two types of tremors emerge 1 those directly triggered by the passing waves and 2 those triggered by the stress variations associated with slow slip this indicates the prominent role of aseismic creep in the mexican subduction zone response to a large teleseismic earthquake possibly leading to large scale stress redistribution

eocene amber from the pacific coast of north america fossil plant resins are common in late cretaceous rocks of north america and in oligocene and younger sediments of equatorial and southern hemisphere locations the scarcity of amber in early tertiary rocks however poses puzzling geological questions detailed examination of mid eocene amber bearing sediments from coalmont british columbia and seattle washington indicates that resins were produced by taxodiaceous conifers with metasequoia occidentalis being the most likely source laboratory heating experiments and paleotemperature analysis of these sediments based on coal rank and vitrinite reflectance suggest that burial temperatures may significantly affect infrared spectra of amber a phenomenon not previously recognized by researchers who have long used spectral characteristics to speculate on the botanical origin of fossil resins the occurrence of amber in mid eocene rocks of the pacific northwest arkansas and southern california suggests that resin production ended as the climate of north america cooled during the mid tertiary and that late tertiary amber was produced by flowering tropical plants not present in the eocene forests this evolutionary record appears somewhat different from that of western europe where progressive southward migration of coniferous amber forests occurred during mid tertiary time

slip localization on the southern alpine fault new zealand 1 results of a detailed field study of the southern onshore portion of new zealand s alpine fault reveal that for 75 km along strike dextral normal slip on this long lived structure is highly localized in phyllosilicate rich fault core gouges and along their contact with more competent rocks at three localities martyr river mckenzie creek and hokuri creek we document complete cross sections through the fault new 40ar 39ar dates on mylonites combined with microstructural and mechanical data on phyllosilicate rich fault core gouges show that modern slip is localized onto a single steeply dipping 1 to 12 m thick fault core composed of impermeable k 10 20 to 10 22 m2 frictionally weak s 0 12 0 37 velocity strengthening illite chlorite and saponite chlorite lizardite fault gouges fault core materials are 1 comparable to those of other major weak cored faults e g san andreas fault and 2 most compatible with fault creep despite paleoseismic evidence of quasiperiodic large magnitude earthquakes mw 7 on this portion of the alpine fault we conclude that frictional properties of gouges at the surface do not characterize the overall seismogenic behavior of the southern alpine fault

vascular plant biomarker distributions and stable carbon isotopic signatures from the middle and upper jurassic callovian kimmeridgian strata of staffin bay isle of skye northwest scotland the molecular and stable carbon isotopic composition of higher plant biomarkers was investigated in middle to upper jurassic strata of the isle of skye northwest scotland aromatic hydrocarbons diagnostic of vascular plants were detected in each of nineteen sedimentary rock samples from the early callovian to early kimmeridgian interval a succession rich in fossil fauna including ammonites that define its constituent chronozones the higher plant parameter hpp and higher plant fingerprint hpf calculated from the relative abundance of retene cadalene and 6 isopropyl 1 isohexyl 2 methylnaphthalene ip ihmn exhibit several large fluctuations throughout the skye succession studied these molecular profiles contrast with both 1 the more uniform profiles previously observed in jurassic successions putatively of the same age from other palaeogeographical settings including the carnarvon basin western australia and 2 the steady rise in global sea level during this interval this suggests that the hpf profiles of jurassic marine successions may not be reliable indicators of global climate change our results indicate that other factors such as local tectonism resulting in changes to the relief and landscape of the hinterland likely influenced the palaeoflora and the mode of transport of its detritus into adjacent marine depocentres however the skye succession showed similar 13c profiles of total organic carbon toc comprising mainly fossil wood the vascular plant biomarker retene and a predominant phytoplanktonic biomarker phytane the apparent isotopic relationship between terrigenous and marine derived biomarkers supports a strong coupling of the atmosphere and ocean the maximum isotopic excursion occurs in the cardioceras cordatum ammonite biozone of the early to middle oxfordian which may be indicative of changes in atmospheric and oceanic levels of co2

carbon isotope ratio of cenozoic co2 a comparative evaluation of available geochemical proxies 1 the carbon isotope ratio 13c of plant material is commonly used to reconstruct the relative distribution of c3 and c4 plants in ancient ecosystems however such estimates depend on the 13c of atmospheric co2 13cco2 at the time which likely varied throughout earth history for this study we use benthic and planktonic 13c and 18o records to reconstruct a long term record of cenozoic 13cco2 confidence intervals for 13cco2 values are assigned after careful consideration of equilibrium and non equilibrium isotope effects and processes as well as resolution of the data we find that benthic foraminifera better constrain 13cco2 compared to planktonic foraminiferal records which are influenced by photosymbiotes depth of production seasonal variability and preservation furthermore sensitivity analyses designed to quantify the effects of temperature uncertainty and diagenesis on benthic foraminifera 13c and 18o values indicate that these factors act to offset one another our reconstruction suggests that cenozoic 13cco2 averaged 6 1 0 6 1 while only 11 2 million of the last 65 5 million years correspond to the pre industrial value of 6 5 with 90 confidence here 13cco2 also displays significant variations throughout the record at times departing from the pre industrial value by more than 2 thus the observed variability in 13cco2 should be considered in isotopic reconstructions of ancient terrestrial plant ecosystems especially during the late and middle miocene times of presumed c4 grassland expansion

correlation of grassy lake and cedar lake ambers using infrared spectroscopy stable isotopes and palaeoentomology the late cretaceous grassy lake and cedar lake amber deposits of western canada are among north america s most famous amber producing localities although it has been suggested for over a century t

age and paleogeographical origin of dominican amber the age and depositional history of dominican amber bearing deposits have not been well constrained resinites of different ages exist in hispaniola but all of the main amberiferous deposits in the dominican republic including those famous for yielding biological inclusions were formed in a single sedimentary basin during the late early miocene through early middle miocene 15 to 20 million years ago according to available biostratigraphic and paleogeographic data there is little evidence for extensive reworking or redeposition in either time or space the brevity of the depositional interval less than 5 million years provides a temporal benchmark that can be used to calibrate rates of molecular evolution in amber taxa

warm tropical ocean surface and global anoxia during the mid cretaceous period the middle of the cretaceous period about 120 to 80 myr ago was a time of unusually warm polar temperatures1 repeated reef drowning in the tropics2 and a series of oceanic anoxic events oaes that promoted both the widespread deposition of organic carbon rich marine sediments and high biological turnover3 4 5 6 7 8 the cause of the warm temperatures is unproven but widely attributed to high levels of atmospheric greenhouse gases such as carbon dioxide7 8 9 10 11 12 in contrast there is no consensus on the climatic causes and effects of the oaes with both high biological productivity and ocean stagnation being invoked as the cause of ocean anoxia3 4 5 6 7 8 here we show using stable isotope records from multiple species of well preserved foraminifera that the thermal structure of surface waters in the western tropical atlantic ocean underwent pronounced variability about 100 myr ago with maximum sea surface temperatures 3 5 c warmer than today this variability culminated in a collapse of upper ocean stratification during oae 1d the breistroffer event a globally significant period of organic carbon burial that we show to have fundamental stratigraphically valuable geochemical similarities to the main oaes of the mesozoic era our records are consistent with greenhouse forcing being responsible for the warm temperatures but are inconsistent both with explanations for oaes based on ocean stagnation and with the traditional view reviewed in ref 12 that past warm periods were more stable than today s climate

beyond methane towards a theory for the paleocene eocene thermal maximum abstract extreme global warmth and an abrupt negative carbon isotope excursion during the paleocene eocene thermal maximum petm have been attributed to a massive release of methane hydrate from sediments on the continental slope 1 however the magnitude of the warming 5 to 6 c 2 3 and rise in the depth of the ccd 2 km 4 indicate that the size of the carbon addition was larger than can be accounted for by the methane hydrate hypothesis additional carbon sources associated with methane hydrate release e g pore water venting and turbidite oxidation are also insufficient we find that the oxidation of at least 5000 gt c of organic carbon is the most likely explanation for the observed geochemical and climatic changes during the petm for which there are several potential mechanisms production of thermogenic ch4 and co2 during contact metamorphism associated with the intrusion of a large igneous province into organic rich sediments 5 is capable of supplying large amounts of carbon but is inconsistent with the lack of extensive carbon loss in metamorphosed sediments as well as the abrupt onset and termination of carbon release during the petm a global conflagration of paleocene peatlands 6 highlights a large terrestrial carbon source but massive carbon release by fire seems unlikely as it would require that all peatlands burn at once and then for only 10 to 30 ky in addition this hypothesis requires an order of magnitude increase in the amount of carbon stored in peat the isolation of a large epicontinental seaway by tectonic uplift associated with volcanism or continental collision followed by desiccation and bacterial respiration of the aerated organic matter is another potential mechanism for the rapid release of large amounts of co2 in addition to the oxidation of the underlying marine sediments the desiccation of a major epicontinental seaway would remove a large source of moisture for the continental interior resulting in the desiccation and bacterial oxidation of adjacent terrestrial wetlands

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

the 25 october 2010 sumatra tsunami earthquake slip in a slow patch 1 various models for the generation of tsunami earthquakes have been proposed including shallow earthquake slip through low strength materials because these physical fault conditions would likely affect other earthquakes in the same rupture zone source properties of other events may provide a guide to locations of tsunami earthquakes the 25 october 2010 mw 7 8 mentawai tsunami earthquake and surrounding events provide a test of this hypothesis we determine slip patterns for the mainshock and relocate aftershocks with the majority occurring in the near trench region the two largest magnitude aftershocks occurred within the downdip end of the mainshock rupture area and have long moment normalized rupture duration likely related to fault zone conditions several older relocated earthquakes at the northern edge of the 2010 rupture area also have long duration character suggesting both spatial and temporal consistency in the conditions needed to produce slow seismic processes along this margin

the 25 october 2010 mentawai tsunami earthquake mw 7 8 and the tsunami hazard presented by shallow megathrust ruptures the 25 october 2010 mentawai indonesia earthquake m w 7 8 ruptured the shallow portion of the subduction zone seaward of the mentawai islands off shore of sumatra generating 3 to 9 m tsunami run up along southwestern coasts of the pagai islands that took at least 431 lives analyses of teleseismic p sh and rayleigh waves for finite fault source rupture characteristics indicate 90 s rupture duration with a low rupture velocity of 1 5 km s on the 10 dipping megathrust with total slip of 2 4 m over an 100 km long source region the seismic moment scaled energy release is 1 4 10 6 lower than 2 4 10 6 found for the 17 july 2006 java tsunami earthquake m w 7 8 the mentawai event ruptured up dip of the slip region of the 12 september 2007 kepulauan earthquake m w 7 9 and together with the 4 january 1907 m 7 6 tsunami earthquake located seaward of simeulue island to the northwest along the arc demonstrates the significant tsunami generation potential for shallow megathrust ruptures in regions up dip of great underthrusting events in indonesia and elsewhere

an isotopic study of paleosol carbonates from olduvai gorge the isotopic composition of paleosol carbonates from olduvai gorge can be used to give estimates of the paleoclimatic history of east africa during the plio pleistocene oxygen isotopes are indicative of major changes in the isotopic composition of meteoric water while carbon isotopes are indicative of major changes in the fraction of biomass using the hatch slack c4 photosynthetic pathway three major periods of climatic change in this terrestrial setting occurred at about 1 67 1 3 and 0 6 myr these involved major changes in flora as well as major changes in the isotopic composition of meteoric water overall the climate has become warmer and more arid over the past 2 2 myr

slow slip slow earthquakes period two cycles full and partial ruptures and deterministic chaos in a single asperity fault abstract the assimilation of geological geophysical and laboratory data in physics based models of fault dynamics promises increasingly realistic simulations of the seismic cycle to assist this effort i explore the dynamics of a single velocity weakening asperity to delineate the relationship between a fault physical properties and the style of faulting during the seismic cycle based on a micro physical model of rate and state friction from a dimensional analysis four non dimensional parameters control the characteristics of slip events and the behavior during the interseismic period including the dieterich ruina rice number ru which is proportional to the ratio of asperity to critical nucleation size w h and rb b a b where a and b control the direct and local evolutionary effects respectively for sufficiently large rb the ru number controls the spectrum of fault slip from periodic slow slip events to aperiodic fast ruptures in finite faults but not in semi infinite faults the transition between these end members includes a bifurcation that involves period two period four period six cycles and deterministic chaos with increasing ru macroscopic fault slip is stabilized as rb vanishes even as ru 1 for finite faults but not for semi infinite faults the transition between slow and fast ruptures for increasing rb includes another type of bifurcation with period two and period four cycles of slow and fast ruptures for 0

latest on the absolute age of the paleocene eocene thermal maximum petm new insights from exact stratigraphic position of key ash layers 19 and 17 abstract we constructed a precise early eocene orbital cyclostratigraphy for dsdp site 550 leg 80 goban spur north atlantic utilizing precession related cycles as represented in a high resolution x ray fluorescence based barium core log based on counting of those cycles we constrain the exact timing of two volcanic ash layers in site 550 which correlate to ashes 19 and 17 of the fur formation in denmark the ashes relative to the onset of the paleocene eocene thermal maximum petm are offset by 862 kyr and 672 kyr respectively when combined with published absolute ages for ash 17 the absolute age for the onset of the petm is consistent with astronomically calibrated ages using the current absolute age of 28 02 ma for the fish canyon tuff fct standard for calibrating the absolute age of ash 17 is consistent with tuning option 2 in the astronomically calibrated paleocene time scale of westerhold et al 2008 westerhold t rohl u raffi i fornaciari e monechi s reale v bowles j and evans h f 2008 astronomical calibration of the paleocene time palaeogeography palaeoclimatology palaeoecology v 257 p 377 403 using the recently recalibrated absolute age of 28 201 ma for the fct standard is consistent with tuning option 3 in the astronomically calibrated paleocene time scale the new results do not support the existence of any additional 405 kyr cycle in the early paleocene astronomically tuned time scale

a new model for atmospheric oxygen over phanerozoic time a mathematical model has been constructed that enables calculation of the level of atmospheric o2 over the past 570 my from rates of burial and weathering of organic carbon c and pyrite sulfur s burial rates as a function of time are calculated from an assumed constant worldwide clastic sedimentation rate and the relative abundance and c and s contents of the three rock types marine sandstones and shales coal basin sediments and other non marine clastics red beds arkoses by our model values of o2 versus time using a constant total sedimentation rate agree with those for variable sedimentation derived from present day rock abundances and estimates of erosional losses since deposition this agreement is the result of our reliance on the idea that any increase in total worldwide sediment burial with consequently faster burial of c and s and greater o2 production must be accompanied by a corresponding increase in erosion and increased exposure of c and s on the continents to o2 consumption via weathering it is the redistribution of sediment between the three different rock types and not total sedimentation rate that is important in o2 control to add stability to the system negative feedback against excessive o2 fluctuation was provided in the modeling by the geologically reasonable assignment of higher weathering rates to younger rocks resulting in rapid recycling of c and s we did not use direct o2 negative feedback on either weathering of c and s or burial of c because weathering rates are assumed to be limited by uplift and erosion and the burial rate of c limited by the rate of sediment deposition the latter assumption is the result of modern sediment studies which show that marine organic matter burial occurs mainly in oxygenated shallow water and is limited by the rate of supply of nutrients to the oceans by rivers results of the modeling indicate that atmospheric o2 probably has varied appreciably over phanerozoic time during the late carboniferous and permian periods o2 was higher than previously because of the rise of vascular land plants and the widespread burial of organic matter in vast coal swamps a large decrease in o2 during the late permian was due probably to the drying up of the coal swamps and deposition of a large proportion of total sediment in c and s free continental red beds sensitivity study shows that major parameters affecting results are the mean c concentration in coal basins and the relative sizes of the reservoirs of young rapidly recycled versus old rocks less sensitivity was found for changes over time in total land area undergoing weathering and the use of direct o2 negative feedback on marine carbon burial good agreement for rates of c burial calculated via our model and via independent models which are based on the use of stable carbon isotopes indicates that the dominant factor that has brought about changes in atmospheric o2 level and the isotopic composition of dissolved inorganic carbon in seawater over phanerozoic time is sedimentation and not weathering or higher temperature phenomena such as basalt seawater reaction

upper cretaceous stable carbon isotope stratigraphy of terrestrial organic matter from sakhalin russian far east a proxy for the isotopic composition of paleoatmospheric co2 abstract time stratigraphic patterns of stable carbon isotopic ratios recorded in terrestrial organic matter from cenomanian maastrichtian successions for the russian far east can be correlated to those of carbonate carbon from well studied successions for other parts of the world age indicative biostratigraphy based on regional ammonoids and inoceramid bivalves are well established in japan and can be applied to the whole cretaceous succession except for the upper cenomanian lower turonian and the upper part of the maastrichtian zones lacking macrofossils globally correlative carbon isotopic events previously documented with carbonate carbon from europe and with carbonate carbon and marine organic matter from the u s western interior are recognized with similar magnitude through uppermost cenomanian lower campanian in ascending order these events are positive spike across the cenomanian turonian boundary step like leveled segment followed by negative shift lower middle turonian trough like negative excursion middle upper turonian positive rebound coupled with following broad peak coniacian and positive peak basal campanian followed by modest negative excursion the parallel fluctuation of the 13 c value between the terrestrial organic matter and carbonate suggests carbon isotopic equilibrium between surface seawater and atmospheric co 2 and demonstrates that the isotopic curve of terrestrial organic carbon can be used to monitor carbon isotopic fluctuations of co 2 in the ocean atmosphere system in the upper campanian and maastrichtian a negative 13 c excursion within chron 33r and a following rapid rebound can be correlated with the same distinctive carbon isotopic feature of carbonate observed in the deep sea cores from south and north atlantic the indian and the pacific oceans within this interval the 13 c value of terrestrial organic matter also reflects carbon isotopic fluctuation of the global co 2 reservoir with relatively minor regional local noise

precise tremor source locations and amplitude variations along the lower crustal central san andreas fault 1 we precisely locate 88 tremor families along the central san andreas fault using a 3d velocity model and numerous p and s wave arrival times estimated from seismogram stacks of up to 400 events per tremor family maximum tremor amplitudes vary along the fault by at least a factor of 7 with by far the strongest sources along a 25 km section of the fault southeast of parkfield we also identify many weaker tremor families which have largely escaped prior detection together these sources extend 150 km along the fault beneath creeping transitional and locked sections of the upper crustal fault depths are mostly between 18 and 28 km in the lower crust epicenters are concentrated within 3 km of the surface trace implying a nearly vertical fault a prominent gap in detectible activity is located directly beneath the region of maximum slip in the 2004 magnitude 6 0 parkfield earthquake

onset of the mid cretaceous greenhouse in the barremian aptian igneous events and the biological sedimentary and geochemical responses basalts and biostratigraphy dated at 125 120 ma from the ontong java and manihiki plateaus in the western pacific evidence the largest volcanic event in earth history in at least the past 160 m y the intervening nova canton trough rifted at about 121 118 ma and a number of guyots and seamounts formed concurrently or slightly later geological events that probably were responses to these volcanic tectonic events occurred in the following chronostratigraphic order biotic fluctuations began at about 122 5 ma at about 122 0 ma 87sr 86sr began to decline slowly metal concentrations of co mn pb yb and cu in sediments peaked at about 121 5 121 2 ma changes in planktonic communities and sedimentation culminated in a nannoconid crisis just prior to 120 5 ma and in the selli black shale oae la at about 120 5 119 5 ma a sharp drop in 13c occurred at the beginning of the selli event and rebounded into a longer positive excursion that reached a peak after the selli event at about 119 5 118 5 ma at 120 5 ma 87sr 86sr declined rapidly and reached a minimum at about 116 113 ma we speculate that the intensity of these latter responses suggests a corresponding peak in volcanic tectonic activity at about 121 119 ma

global increase in plant carbon isotope fractionation following the last glacial maximum caused by increase in atmospheric pco2 changes in the carbon isotope composition of terrestrial plant tissue 13c are widely cited for evidence of shifts in climate vegetation or atmospheric chemistry across a wide range of time scales a global compilation of 13c data from fossil leaves and bulk terrestrial organic matter tom spanning the past 30 k y however shows wide variability and no discernable trend here we analyze these data in terms of a relative change in net carbon isotope fractionation between the 13c value of plant tissue and that of atmospheric co2 13c 13cco2 13c 1 13c 1000 and identify a global 2 1 shift in leaf and tom 13c that is synchronous with a global rise in p co2 documented from ice core data we apply a relationship describing the effect of p co2 on 13c to the global record of 13c change documented here to reconstruct p co2 levels across the past 30 k y our reconstructed p co2 levels are in excellent agreement with the ice core data and underscore the potential of the global terrestrial 13c record to serve as an accurate p co2 proxy

the 25 october 2010 mentawai tsunami earthquake from real time discriminants finite fault rupture and tsunami excitation 1 the moment magnitude 7 8 earthquake that struck offshore the mentawai islands in western indonesia on 25 october 2010 created a locally large tsunami that caused more than 400 human causalities we identify this earthquake as a rare slow source tsunami earthquake based on 1 disproportionately large tsunami waves 2 excessive rupture duration near 125 s 3 predominantly shallow near trench slip determined through finite fault modeling and 4 deficiencies in energy to moment and energy to duration cubed ratios the latter in near real time we detail the real time solutions that identified the slow nature of this event and evaluate how regional reductions in crustal rigidity along the shallow trench as determined by reduced rupture velocity contributed to increased slip causing the 5 9 m local tsunami runup and observed transoceanic wave heights observed 1600 km to the southeast

the carnian pluvial episode and the first global appearance of amber amber fossil resin is not common throughout the fossil record and previously the only globally significant deposits were thought to occur during the cretaceous eocene oligocene and miocene periods recent finds of late triassic carnian ambers highlight a significantly older set of deposits here we review these ambers that appear coincident with the carnian pluvial episode a time interval of major climate change and biotic turnover much of the amber is found in a palaeolatitudinal belt between 5 and 30 n and covers italian austrian swiss hungarian spanish and arizona usa deposits with one exception from lesotho southern africa c 40 s most deposits are small and allochthonous with the major exception of the autochthonous parautochthonous amber deposit found as droplets in a palaeosol from the dolomites italy in some of these deposits there is even direct evidence of the source plants that produced the preserved resin the oldest confirmed organisms found preserved in amber are from carnian droplets from the dolomites in italy and include arthropods and microorganisms the occurrence of amber in different localities and within the same time interval suggests a widespread stressed flora and major biological turnover in the terrestrial ecosystems during the carnian pluvial episode

evidence of widespread wildfires in coal seams from the middle jurassic of northwest china and its impact on paleoclimate abstract today wildfire is an important disturbance in many continental ecosystems and it is assumed that with ongoing climate changes the frequencies and impacts of wildfires will increase in many regions one way to obtain information about the potential long term influences of wildfires on ecosystems and the climate system itself is to study palaeo wildfires a total of 140 jurassic samples including 122 coal samples and 18 rock samples from roof and floor of coal seams were collected from 4 coalfields in northwestern china the samples were analyzed by macropetrography microscopy scanning electron microscopy gas chromatography and gas chromatography mass spectrometry to study the evidences of wildfires and their impact on the paleoclimate high contents of pyrogenic inertinites charcoal natural char and natural coke particles observed in the samples which indicate that widespread wildfire events occurred in the early middle jurassic in all over northwestern china additionally high molecular weight polycyclic aromatic hydrocarbons were detected in the coal samples these aromatic compounds were formed under high temperature and provide further evidence of wildfires according to a carbon emission model for modern forest fires the total carbon and gas emissions from wildfires in peat swamps of the middle jurassic in northwest china were calculated by the data from 21 575 coal samples of number of 1567 drill core samples the total carbon released from peat swamp forest wildfires was at least 1207 gt corresponding to emissions of co2 co and ch4 of 1926 gt 163 gt and 8 8 gt respectively the huge amount of co2 released by forest fires in the peat swamp systems of the middle jurassic in northwestern china alone was equivalent to 64 20 of the total co2 in the atmosphere at present 3000gt the large amounts of greenhouse gases released by wildfires must have led to long term changes in the atmospheric composition and have caused global warming which could have the reason of affected the paleoclimate

carbon isotope composition of lower cretaceous fossil wood ocean atmosphere chemistry and relation to sea level change the carbon isotope composition of fossil wood fragments collected through a biostratigraphically well constructed aptian lower cretaceous shallow marine siliciclastic succession on the isle of wight southern britain shows distinct variations with time the results indicate that the stratigraphic signature of delta sup 13 c sub wood through the aptian was influenced primarily by fluctuations in the isotopic composition of co sub 2 in the global ocean atmosphere system as registered in marine carbonates elsewhere and was not governed by local paleoenvironmental and or paleoecological factors negative and positive excursions in delta sup 13 c sub wood through the lower aptian occur in phase with inferred transgressions and regressions respectively a pattern that contrasts with that observed in many previous studies for different time intervals the relationship between delta sup 13 c variations and relative sea level change is tentatively interpreted as a response to various climatic and eustatic factors relating to rapid sea floor spreading thermal uplift of ocean floor emplacement of plateaus volcanic co sub 2 emissions weathering and sedimentary rate

the land plant δ13c record and plant evolution in the late palaeozoic abstract based on the evaluation of 1323 carbon isotope values for silurian to permian terrestrial organic carbon measured on plant fossils cuticules humic coals and bulk terrestrial organic matter tom we conclude that the temporal trend in 13ctom records variations in the global carbon cycle notably an increase in the fractional burial of light terrestrial organic matter in late palaeozoic sediments 13ctom values suggest that the late palaeozoic po2 peak could have been restricted to a time frame of 40 ma carbon isotope data from four taxonomic groups reveal small differences that could be a consequence of habitat conditions no significant differences in organic carbon isotopic composition in relation to variable climatic conditions are discernible the carbon isotopic composition solely reflects c3 plant metabolism

using systematically characterized low frequency earthquakes as a fault probe in guerrero mexico studies of low frequency earthquakes lfes have focused on detecting events within previously identified tectonic tremor however the principal lfe detection tools of matched filter searches are intrinsically incapable of detecting events that have not already been characterized previously as a template event in this study we therefore focus on generating the largest number possible of lfe templates by uniformly applying a recently developed lfe template detection method to a 2 5 yearlong data set in guerrero mexico using each of the detected templates in a matched filter search we then form event families that each represents a single source we finally develop simple empirical statistics to select the event families that represent lfes our resulting catalog contains 1120 unique lfe sources and a total of 1 849 486 detected lfes over the 2 5 yearlong data set the locations of the lfe sources are then divided into subcatalogs based on their distance from the subduction trench considering each lfe as a small unit of slip along the subduction interface we observe discrete episodes of lfe activity in the region associated with large slow slip events this is in direct contrast to the near continuous activity observed 35 km farther downdip within the previously identified lfe tremor sweet spot

geocarbsulf a combined model for phanerozoic atmospheric o2 and co2 abstract a model for the combined long term cycles of carbon and sulfur has been constructed which combines all the factors modifying weathering and degassing of the geocarb iii model berner r a kothavala z 2001 geocarb iii a revised model of atmospheric co2 over phanerozoic time am j sci 301 182 204 for co2 with rapid recycling and oxygen dependent carbon and sulfur isotope fractionation of an isotope mass balance model for o2 berner r a 2001 modeling atmospheric o2 over phanerozoic time geochim cosmochim acta 65 685 694 new isotopic data for both carbon and sulfur are used and new feedbacks are created by combining the models sensitivity analysis is done by determining 1 the effect on weathering rates of using rapid recycling rapid recycling treats carbon and sulfur weathering in terms of young rapidly weathering rocks and older more slowly weathering rocks 2 the effect on o2 of using different initial starting conditions 3 the effect on o2 of using different data for carbon isotope fractionation during photosynthesis and alternative values of oceanic 13c for the past 200 million years 4 the effect on sulfur isotope fractionation and on o2 of varying the size of o2 feedback during sedimentary pyrite formation 5 the effect on o2 of varying the dependence of organic matter and pyrite weathering on tectonic uplift plus erosion and the degree of exposure of coastal lands by sea level change 6 the effect on co2 of adding the variability of volcanic rock weathering over time berner r a 2006 inclusion of the weathering of volcanic rocks in the geocarbsulf model am j sci 306 in press results show a similar trend of atmospheric co2 over the phanerozoic to the results of geocarb iii but with some differences during the early paleozoic and for variable volcanic rock weathering lower co2 values during the mesozoic atmospheric oxygen shows a major broad late paleozoic peak with a maximum value of about 30 o2 in the permian a secondary less broad peak centered near the silurian devonian boundary variation between 15 and 20 o2 during the cambrian and ordovician a very sharp drop from 30 to 15 o2 at the permo triassic boundary and a more or less continuous rise in o2 from the late triassic to the present

the bruneian record of borneo amber a regional review of fossil tree resins in the indo australian archipelago abstract in this study we intend to provide an overview on fossilized tree resins amber commonly found in southeast asia more particularly in the indo australian archipelago iaa these remains are often referred in literature as indonesian amber borneo amber or simply as dammar they are very common in the region and the brunei sultanate is no exception as most of its neogene sedimentary successions contain amber rich layers although amber is a common fossil in the country and in northern borneo to our knowledge it has not been studied in great detail so far here we present an account on the borneo ambers from brunei regarding their stratigraphic origin basic physical properties their interaction with the biosphere and their botanical origin using fourier transform infrared spectroscopy ftir additionally a number of ambers and modern tree resins were analysed for their carbon isotope composition and a few were tested with gas chromatography we discuss the results in a regional and global context in comparison with available data from the iaa the ambers come from four different lithostratigraphic units with an age range of 12 to 3 million years middle miocene to pliocene recently reworked ambers from the coast ambers from younger alluvial deposits and several modern tree resins from dipterocarpaceae and araucariaceae agathis borneensis were also included in the study the 60 ftir analyses of modern and fossil specimens suggest that all the brunei ambers were produced by trees of dipterocarpaceae there is no indication of agathis in the fossil record in agreement with their lower abundance in the forests of borneo modern and fossil dipterocarp resins were found to be different based on the following criteria 1 different reactions to solubility hot needle and uv tests with faster reaction time and less fluorescence for the modern ones 2 clear distinction based on certain ftir absorbance band ratios mostly by those that represent carboxylic acids and esters e g 1700 and 1243 cm 1 3 modern resin yielded on an average 3 lower 13c values 4 gas chromatography data reflect maturation differences among the samples although there is some overlap in the chemical results between the two groups generally all these differences reflect different maturation stages of the resinous material and point towards loss of low 13c components from the organic structure of the resin the minor timewise decreasing trend in average 13c from the late middle miocene to late miocene can be explained by 1 gradual changes in local environmental conditions and or 2 increased amount of less mature specimens among the younger samples in contrast the highest obtained 13c values were found in the youngest pliocene ambers instead of maturation bias this can be linked to environmental factors such as cooler drier climate with increased seasonality probably reflecting the onset of the northern hemisphere glaciation

environmental history of the german lower rhine embayment during the middle miocene as reflected by carbon isotopes in brown coal stable carbon isotope investigations have been carried out on miocene brown coal from the garzweiler seam of the german lower rhine embayment material studied included fossil wood from seven different taxa and brown coal matrix isotope results from macrofossil analysis show variations of more than 6 within individual samples and reveal a general isotopic difference between angiosperm and gymnosperm wood specimens according to mean carbon isotope values found for gymnosperms angiosperms and brown coal matrix 23 3 26 0 and 25 8 the peat forming vegetation of the garzweiler seam was dominated by angiosperm taxa results from brown coal matrix establish a continuous high resolution depth profile of carbon isotope variations during the late middle miocene they show a significant and characteristic isotope pattern with distinct medium and short term cycles high frequency variations in the two main units of garzweiler seam locally split into three units the medium term 13c variations are most likely caused by varying proportions of gymnosperms within the peat forming vegetation while high frequency oscillations seem to be a direct signal of environmental changes a long term decline of carbon isotope values observed within the complete garzweiler seam from base to top is presumably due to a cooling trend in the miocene

the paleozoic to mesozoic carbon cycle revisited the carbon isotopic composition of terrestrial organic matter 1 two thousand one hundred forty eight carbon isotope values for terrestrial organic matter plant fossils coal bulk terrestrial organic matter provide a proxy record for temporal changes in the global carbon cycle 13ctom 13ccarb and 13cco2 allow a full evaluation of carbon transfer in the atmosphere ocean system as well as between the marine and the terrestrial realm the temporal evolution of 13ctom parallels respective data sets from marine carbonate carbon thus reflecting the linkage between both reservoirs via atmospheric carbon dioxide on the basis of a comparison between measured and predicted isotope records for 13ctom changes in the carbon isotopic fractionation associated with plant metabolism are discernible this contradicts the notion of an invariable carbon isotopic fractionation associated with c3 plant metabolism in light of results from current plant growth experiments these changes are viewed as dependent on the atmospheric o2 co2 hence 13ctom might serve as a proxy signal for atmospheric composition

late pleistocene and holocene dune activity and wind regimes in the western sahara desert of mauritania comment and reply comment lancaster et al 2002 1 provide some useful information on quaternary eolian dune activity in western mauritania as outlined below however their publication could benefit from 1 a statement regarding the relevance of their research to the debate on the age of ogolien dunes in western

evaluating the use of amber in palaeoatmospheric reconstructions the carbon isotope variability of modern and cretaceous conifer resins abstract stable carbon isotope geochemistry of fossilized tree resin amber potentially could be a very useful tool to infer the composition of past atmospheres to test the reliability of amber as a proxy for the atmosphere we studied the variability of modern resin 13 c at both local and global scales an amber 13 c curve was then built for the cretaceous a period of abundant resin production and interpreted in light of data from modern resins our data show that hardening changes the pristine 13 c value by causing a 13 c depletion in solid resin when compared to fresh liquid viscous resin probably due to the loss of 13 c enriched volatiles modern resin 13 c values vary as a function of physiological and environmental parameters in ways that are similar to those described for leaves and wood resin 13 c varies between plant species and localities within the same tree and between different plant tissues by up to 6 and in general increases with increasing altitudes of the plant growing site we show that as is the case with modern resin cretaceous amber 13 c has a high variability generally higher than that of other fossil material despite the high natural variability amber shows a negative 2 5 3 13 c trend from the middle early cretaceous to the maastrichtian that parallels published terrestrial 13 c records this trend mirrors changes in the atmospheric 13 c calculated from the 13 c and 18 o of benthic foraminiferal tests although the magnitude of the shift is larger in plant material than in the atmosphere increasing mean annual precipitation and p o 2 could have enhanced plant carbon isotope fractionation during the late cretaceous whereas changing p co 2 levels seem to have had no effect on plant carbon isotope fractionation the results of this study suggest that amber is a powerful fossil plant material for palaeoenvironmental and palaeoclimatic reconstructions improvement of the resolution of the existing data coupled with more detailed information about botanical source and environmental growing conditions of the fossil plant material will probably allow a more faithful interpretation of amber 13 c records and a wider understanding of the composition of the past atmosphere

geology of an amber locality in the hukawng valley northern myanmar abstract amber burmite from the hukawng valley of myanmar has been known since at least the 1st century ad it is currently being produced from a hill known as noije bum which was first documented as a source of amber in 1836 several geologists visited the locality between 1892 and 1930 all of them believed that the host rocks to the amber are tertiary most said eocene in age and this conclusion has been widely quoted in the literature however recent work indicates a cretaceous age insect inclusions in amber are considered to be turonian cenomanian and a specimen of the ammonite mortoniceras of middle upper albian age was discovered during the authors visit palynomorphs in samples collected by the authors suggest that the amber bearing horizon is upper albian to lower cenomanian the preponderance of the evidence suggests that both rocks and amber are most probably upper albian this determination is significant for the study of insect evolution indicating that the oldest known definitive ants have been identified in this amber american museum novitates 3361 2002 72 this site occurs within the hukawng basin which is comprised of folded sedimentary volcanic rocks of cretaceous and cenozoic age the mine exposes a variety of clastic sedimentary rocks with thin limestone beds and abundant carbonaceous material the sediments were deposited in a nearshore marine environment such as a bay or estuary amber is found in a fine clastic facies principally as disk shaped clasts oriented parallel to bedding a minority occurs as runnels stalactite shaped with concentric layering caused by recurring flows of resin an upper albian age is similar to that of orbitolina limestones known from a number of locations in northern myanmar one of these at nam sakhaw 90 km sw of noije bum has also been a source of amber

temperature dependence of frictional healing of westerly granite experimental observations and numerical simulations 1 temperature is believed to have an important control on frictional properties of rocks yet the amount of experimental observations of time dependent rock friction at high temperatures is rather limited in this study we investigated frictional healing of westerly granite in a series of slide hold slide experiments using a direct shear apparatus at ambient temperatures between 20 c and 550 c we observed that at room temperature coefficient of friction increases in proportion to the logarithm of hold time at a rate consistent with findings of previous studies for a given hold time the coefficient of friction linearly increases with temperature but temperature has little effect on the rate of change in static friction with hold time we used a numerical model to investigate whether time dependent increases in real contact area between rough surfaces could account for the observed frictional healing the model incorporates fractal geometry and temperature dependent viscoelasoplastic rheology we explored several candidate rheologies that have been proposed for steady state creep of rocks at high stresses and temperatures none of the tested laws could provide an agreement between the observed and modeled healing behavior given material properties reported in the bulk creep experiments an acceptable fit to the experimental data could be achieved with modified parameters in particular for the power law rheology to provide a reasonable fit to the data the stress exponent needs to be greater than 40 alternative mechanisms include time dependent gouge compaction and increases in bond strength between contacting asperities

bonebed amber as a new source of paleontological data the case of the pipestone creek deposit upper cretaceous alberta canada abstract amber deposits and dinosaur bonebeds provide some of the most detailed sources of information on terrestrial ecosystems but these sources have rarely been studied in tandem the pipestone creek bonebed from the campanian wapiti formation of alberta canada provides an opportunity to explore both data sources in the same deposit for the first time the site has yielded an exceptional fauna dominated by abundant remains of the centrosaurine ceratopsian pachyrhinosaurus the initial campaigns of excavation in the 1980s led to the collateral discovery of amber and the site became the first published source of insect bearing amber in a dinosaur bonebed here we describe amber inclusions in detail and analyze the composition and geochemistry of the amber ftir spectroscopy and stable isotope studies in order to draw paleoecological and paleoenvironmental inferences we describe a feather fragment from an aquatic bird as well as new species of psocodea and hymenoptera mymarommatidae with ecological constraints indeterminate aphid and spider inclusions were also found but preservation was not sufficient for formal description ftir spectroscopy suggests a botanical source among the cupressaceae while stable isotope data indicate that the resin producing forest did not receive precipitation directly from the western interior seaway these initial results show that amber is a valuable source of additional information about the habitat surrounding the vertebrates found in bonebed deposits given the abundance and range of inclusions encountered so far pipestone creek amber also appears to be a promising new source for a relatively diverse campanian amber assemblage

release of methane from a volcanic basin as a mechanism for initial eocene global warming a 200 000 yr interval of extreme global warming marked the start of the eocene epoch about 55 million years ago negative carbon and oxygen isotope excursions in marine and terrestrial sediments show that this event was linked to a massive and rapid approximately 10 000 yr input of isotopically depleted carbon it has been suggested previously that extensive melting of gas hydrates buried in marine sediments may represent the carbon source and has caused the global climate change large scale hydrate melting however requires a hitherto unknown triggering mechanism here we present evidence for the presence of thousands of hydrothermal vent complexes identified on seismic reflection profiles from the voring and more basins in the norwegian sea we propose that intrusion of voluminous mantle derived melts in carbon rich sedimentary strata in the northeast atlantic may have caused an explosive release of methane transported to the ocean or atmosphere through the vent complexes close to the palaeocene eocene boundary similar volcanic and metamorphic processes may explain climate events associated with other large igneous provinces such as the siberian traps approximately 250 million years ago and the karoo igneous province approximately 183 million years ago

real contacts and evolution laws for rate and state friction the well known formalism of rate and state dependent friction represents the transition between static and dynamic friction the instantaneous coefficient of friction is proportional to the logarithm of the sliding velocity v and the logarithm of a state variable whose inverse is a measure of the current amount of damage within a shearing gouge layer or on a sliding surface evolution equations that represent the change of the state variable with time include damage from sliding and healing the dieterich 1979 evolution law contains separate terms for the two effects the ruina 1983 law groups the two effects into one term proportional to v ln v in addition the state variable depends exponentially on porosity as exp f c where is the porosity at reference conditions and c is a dimensionless constant i obtain these relationships as well as relationships between friction law parameters and physical parameters by representing asperity contacts as rectangular deformable regions between two rigid sheets the creep rate within an asperity depends exponentially on the second invariant of the deviatoric stress in terms of asperity scale quantities the invariant includes normal traction and shear traction the derivations assume that contact stresses scale with macroscopic stresses this yields simple expressions analogous to those in rate and state friction the ruina 1983 evolution law in general and the decrease in compaction rate during a hold in a slider experiment in particular arise because a sudden decrease in sliding velocity implies that the shear traction and hence the invariant decrease the porosity state relationship arises when real stresses at contacts or the inverse real contact area depend linearly on the separation of the sheets and by analogy the porosity conversely the ruina 1983 evolution law is inapplicable when asperity scale stresses within a deforming material do not scale with macroscopic stresses