the paleocene eocene transition at mead stream new zealand a southern pacific record of early cenozoic global change mead stream in marlborough new zealand exposes a spectacular 650 m thick stratigraphic section of well bedded micritic limestone chert and marl that was deposited on a south pacific upper continental slope from late cretaceous to middle eocene the 200 m upper paleocene lower eocene succession was examined for its lithology bulk carbonate carbon isotopes and assemblages of radiolarians calcareous nannoplankton and foraminifera so that it could be placed into a global context the interval displays several prominent carbon isotope anomalies and is correlated with south pacific radiolarian zones rp5 to rp9 and calcareous nannofossil zones np6 8 to np12 additionally planktic foraminiferal zones p4 to p6b are identified in uppermost paleocene and lower eocene strata mead stream has a near continuous paleocene lower eocene sediment record and three globally significant climate events the late paleocene carbon isotope maximum pcim the initial eocene thermal maximum ietm and the early eocene climatic optimum eeco have obvious expressions the pcim is a 50 m thick interval of biosiliceous micritic limestone in which 13c is 3 the lower part contains two organic rich biosiliceous mudstone units that may represent expansion of an oxygen minimum zone omz during a global increase in marine biological productivity the ietm is a 4 m thick interval in which 13c drops below 1 5 in a pattern seen at other locations the basal 2 4 m is a distinctive recessed marl rich unit that is defined herein as the dee marl the ietm is marked by a rapid decline in the nannoplankton genus fasciculithus short lived occurrences of discoaster cf araneus and morozovella aequa aequa and significant radiolarian faunal turnover owing to impoverished benthic faunas the benthic foraminiferal extinction event bfee is poorly defined the onset of the eeco is marked by a 1 negative 13c excursion a transition from limestone rich to marl rich facies and a marked decrease in radiolarian abundance compacted sedimentation rates vary between 1 4 2 7 cm kyr for upper paleocene lower eocene strata at mead stream although individual beds with average thickness of 10 cm were deposited too fast to directly represent cycles in orbital parameters time series analysis of bed thicknesses suggests that groups of beds may record milankovitch scale periodicity perhaps with a significant obliquity component thus the relative frequency and thickness of marl and limestone beds in this section is shown to be strongly influenced by climatic changes at a wide range of temporal scales from suborbital and orbital cycles to aberrant short term events and long term trends predominance of marl in ietm and eeco intervals indicates that episodes of extreme global warming resulted in reduced oceanic productivity and increased terrestrial discharge in the high latitude southwestern pacific

review of holocene glacial chronologies based on radiocarbon dating in tibet and its surrounding mountains a compilation of 53 14c ages on moraines constrains the holocene glacial history of tibet and the surrounding mountains several holocene glacial stages are identified the little ice age had three substages at 1 0 0 13 cal ka bp however the glacial advances may have occurred 200 600 a earlier in southern and eastern bordering mountains than in the northern bordering mountains the earlier glacial advance might have been driven by humid conditions in bordering areas of tibet most glacial advances in the neoglaciation occurred at 3 5 1 4 cal ka bp they can be identified in almost every mountain range an early holocene glacial advance occurred 9 4 8 8 cal ka bp in both central tibet and bordering mountains the timings of holocene glacial advances are synchronous with the cooling periods in the 18o record from ice cores and with the results of optically stimulated luminescence dating and cosmogenic exposure dating in tibet copyright 2008 john wiley sons ltd

evidence for a rapid release of carbon at the paleocene eocene thermal maximum the paleocene eocene thermal maximum petm and associated carbon isotope excursion cie are often touted as the best geologic analog for the current anthropogenic rise in pco2 however a causal mechanism for the petm cie remains unidentified because of large uncertainties in the duration of the cie s onset here we report on a sequence of rhythmic sedimentary couplets comprising the paleocene eocene marlboro clay salisbury embayment these couplets have corresponding 18o cycles that imply a climatic origin seasonal insolation is the only regular climate cycle that can plausibly account for 18o amplitudes and layer counts high resolution stable isotope records show 3 5 13c decrease over 13 couplets defining the cie onset which requires a large instantaneous release of 13c depleted carbon during the cie a clear 13c gradient developed on the shelf with the largest excursions in shallowest waters indicating atmospheric 13c decreased by 20 our observations and revised release rate are consistent with an atmospheric perturbation of 3 000 gigatons of carbon gtc

faunal turnovers in central pacific benthic foraminifera during the paleocene eocene thermal maximum abstract although it is well known that the paleocene eocene thermal maximum petm coincided with a major benthic foraminiferal extinction event the detailed pattern of the faunal turnover has not yet been clarified our high resolution benthic foraminiferal and carbon isotope analyses at the low latitude pacific ocean shatsky rise have revealed the following record of major faunal transitions 1 an initial turnover which involved the benthic foraminiferal extinction event bfe the bfe marked by a sharp transition from pre extinction fauna to disaster fauna represented by small sized bolivina gracilis expresses the onset of the petm and the abrupt extinction of about 30 of taxa this faunal transition lasted about 45 74 kyr after the initiation of the petm and was followed by 2 the appearance of opportunistic fauna represented by quadrimorphina profunda which existed for about 74 91 kyr after the initiation of the petm these two faunas which appeared after the extinction event are characterized by low diversity and dwarfism possibly due to lowered oxygen condition and decreased surface productivity the second pronounced turnover involved the gradual recovery from opportunistic fauna to the establishment of recovery fauna which coincided with the recovery about 83 91 kyr after its initiation

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

magnetofossil spike during the paleocene eocene thermal maximum ferromagnetic resonance rock magnetic and electron microscopy evidence from ancora new jersey united states previous workers identified a magnetically anomalous clay layer deposited on the northern united states atlantic coastal plain during the paleocene eocene thermal maximum petm the finding inspired the highly controversial hypothesis that a cometary impact triggered the petm here we present ferromagnetic resonance fmr isothermal and anhysteretic remanent magnetization first order reversal curve and transmission electron microscopy analyses of late paleocene and early eocene sediments in drillcore from ancora new jersey a novel paleogeographic analysis applying a recent paleomagnetic pole from the faeroe islands indicates that new jersey during the initial eocene had a 6 9 degrees lower paleolatitude 27 3 degrees for ancora and a more zonal shoreline trace than in conventional reconstructions our investigations of the petm clay from ancora reveal abundant magnetite nanoparticles bearing signature traits of crystals produced by magnetotactic bacteria this result the first identification of ancient biogenic magnetite using fmr argues that the anomalous magnetic properties of the petm sediments are not produced by an impact they instead reflect environmental changes along the eastern margin of north america during the petm that led to enhanced production and or preservation of magnetofossils

eocene carbonate accumulation in the north central pacific ocean new insights from ocean drilling program site 1209 shatsky rise abstract major climate transitions and perturbations in global carbon cycle are known to have occurred during the eocene between 56 and 34 million years ago ma a series of carbon isotope excursions cies mark variations in the global carbon cycle and changes in climate through early eocene paleocene eocene thermal maximum petm ca 56 ma is the most pronounced and well documented of these events expressed as a clay rich layer in many deep sea sections resulting from widespread carbonate dissolution on the seafloor which is in turn related to shoaling of the carbonate compensation depth ccd and lysocline other cies of early eocene had similar response however response of these geologically instantaneous hyperthermals differ from long term warmth multi million year time scale of the early eocene climate optimum eeco in terms of sea floor carbonate accumulation following the termination of eeco earth s climate transitioned into long term cooling pronounced fluctuations in ccd of equatorial pacific are known to have occurred during middle late eocene as well whose global extent and origin are still unresolved most proxy records either span the interval of early eocene or document particular climatic events in eocene which significantly limits visualizing the long term eocene climate change and response of open marine carbonate preservation the present study documents change in carbonate dissolution and carbonate mass accumulation rate through the entire eocene 56 34 ma at odp site 1209 on shatsky rise north central pacific and ties it to a stable carbon and oxygen isotope record our study determines the correlation between deep sea carbonate dissolution and carbon cycling process during the dynamic climate regime of eocene a strong correlation between magnitude of cies and intensity of dissolution for early eocene hyperthermal events appears to significantly weaken for multiple dissolution events in middle late eocene thereby indicating fundamental difference in their causal mechanism

high resolution records of the late paleocene thermal maximum and circum caribbean volcanism is there a causal link two recently drilled caribbean sites contain expanded sedimentary records of the late paleocene thermal maximum a dramatic global warming event that occurred at ca 55 ma the records document significant environmental changes including deep water oxygen deficiency and a mass extinction of deep sea fauna intertwined with evidence for a major episode of explosive volcanism we postulate that this volcanism initiated a reordering of ocean circulation that resulted in rapid global warming and dramatic changes in the earth s environment

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

response of larger benthic foraminifera to the paleocene eocene thermal maximum and the position of the paleocene eocene boundary in the tethyan shallow benthic zones evidence from south tibet

abrupt deep sea warming palaeoceanographic changes and benthic extinctions at the end of the palaeocene a remarkable oxygen and carbon isotope excursion occurred in antarctic waters near the end of the palaeocene 57 33 myr ago indicating rapid global warming and oceanographic changes that caused one of the largest deep sea benthic extinctions of the past 90 million years in contrast the oceanic plankton were largely unaffected implying a decoupling of the deep and shallow ecosystems the data suggest that for a few thousand years ocean circulation underwent fundamental changes producing a transient state that although brief had long term effects on environmental and biotic evolution

structure and magnitude of the carbon isotope excursion during the paleocene eocene thermal maximum abstract the paleocene eocene thermal maximum petm was a geologically rapid and transient warming event that occurred ca 56 million years ago ma it was associated with a pronounced negative carbon isotope excursion cie and with profound changes in the atmosphere hydrosphere and biosphere this event reflects injections of large amounts of carbon into the atmosphere ocean system but whether single or multiple episodes of carbon release caused this event is uncertain here we present carbon isotope data of bulk carbonate from two parallel limestone sections at tingri south tibet where the limestone was deposited on a tropical carbonate ramp during the petm carbon isotope data of bulk carbonate from both sections are almost identical displaying an expanded stepped cie profile with large magnitude the stepped cie profile consists of three discrete intervals of decreasing carbon isotope values which can be correlated on an inter regional scale between sections from different depositional environments lake carbonate ramp continental slope and open ocean the consistency of these correlations implies occurrence of at least three carbon releases within the cie and indicates complex processes of carbon injection during the petm moreover the cie magnitude of 7 recorded at tingri is tentatively interpreted to reflect carbon isotope changes in the atmosphere and the surface ocean which is larger than the generally accepted value of 4 but is still within the range of some previous records

towards an understanding of the ca isotopic signal related to ocean acidification and alkalinity overshoots in the rock record abstract in this contribution we explore the idea that the ca isotope proxy has utility as an indicator of carbonate authigenesis i e post depositional precipitation of caco3 within the sedimentary package given the strong contrast in isotopic fractionation factor between the formational and diagenetic environments ca isotopes have the potential to fingerprint carbonate authigenesis when it occurs close to the seawater sediment interface we demonstrate that ca isotopes are particularly applicable to exploring ocean acidification events and potentially ocean anoxic events and focus our attention on ocean acidification related to the paleocene eocene thermal maximum petm we present three scenarios that vary in the magnitude and duration of the carbon fluxes that are simulated using an earth system model of intermediate complexity cgenie and we use the cgenie output to constrain the upper boundary conditions of 1 d reactive transport models of authigenesis and recrystallization in the sedimentary section along with simple mixing calculations the models inform our exploration of the hypothesis that authigenic carbonate induced by a saturation state overshoot during the petm explains recently published ca isotope records and perhaps bulk carbonate records over ocean anoxic event oae 2 our simulations suggest that fractionation factor variability does not explain the petm 44ca records and we propose a 44ca caco3 space framework to assist with the elucidation of authigenic additions over time scales that are short relative to the residence time of ca in the ocean 1 ma ultimately we find that the authigenic zone generated in the sedimentary column may be influenced by alkalinity overshoots or redox state the caco3 produced in this zone can overprint temporal signals with depth dependent signals that reflect lithology and sedimentation rate and need not be spatially uniform even when driven by a global event ultimately we demonstrate the utility of ca isotopes for exploring short time scale climatic events and a quantitative framework to guide interpretations

constraints on hyperthermals the abrupt warming event 56 million years ago known as the palaeocene eocene thermal maximum petm was associated with the large scale release of 13c depleted carbon into the ocean atmosphere system in sedimentary records the event is reflected by a negative carbon isotope excursion1 cui et al used a carbon cycle model to estimate the rate of carbon release during the petm the model assumed that the onset of the carbon isotope excursion occurred over approximately 20 000 years an estimate based on a cyclostratigraphic model here we highlight several issues that weaken the conclusions of cui et al

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

south pacific intermediate water oxygen depletion at the onset of the paleocene eocene thermal maximum as depicted in new zealand margin sections 1 extreme global warming and massive input of 13c depleted carbon into the exogenic carbon cycle characterize the paleocene eocene thermal maximum petm circa 55 5 ma previous work indicates that dissolved o2 concentrations dropped in some regions of the ocean during this event but spatial temporal and causal relationships between warming carbon input and o2 deficiency remain elusive we present lithologic carbon isotopic and trace fossil results from outcrops in new zealand that clarify this issue sections exposed at mead and dee streams in eastern marlborough south island contain expanded sedimentary intervals that were deposited before during and after the petm on an upper continental slope the petm in these intervals is characterized by enhanced siliciclastic deposition a hallmark negative carbon isotope excursion and a loss of bioturbation importantly however the latter only occurs during the prominent drop in 13c and not during its recovery our results suggest that south pacific intermediate waters became hypoxic coincident to carbon injection at the start of the petm while higher sea surface temperatures throughout the petm would have decreased the dissolved oxygen content of sinking surface waters we argue here that oxygen depletion was driven by some combination of elevated temperature water column stratification and intermediate water methane oxidation

an extraterrestrial 3he based timescale for the paleocene eocene thermal maximum petm from walvis ridge iodp site 1266 in the deep sea the paleocene eocene thermal maximum petm is often marked by clay rich condensed intervals caused by dissolution of carbonate sediments capped by a carbonate rich interval constraining the duration of both the dissolution and subsequent cap carbonate intervals is essential to computing marine carbon fluxes and thus testing hypotheses for the origin of this event to this end we provide new high resolution helium isotope records spanning the paleocene eocene boundary at odp site 1266 in the south atlantic the extraterrestrial 3he 3he et concentrations replicate trends observed at odp site 690 by farley and eltgroth 2003 by assuming a constant flux of 3he et we constrain relative changes in accumulation rates of sediment across the petm and construct a new age model for the event in this new chronology the zero carbonate layer represents 35 kyr some of which reflects clay produced by dissolution of paleocene pre petm sediments above this layer carbonate concentrations increase for 165 kyr and remain higher than in the latest paleocene until 234 48 34 kyr above the base of the clay the new chronology indicates that minimum 13 c values persisted for a maximum of 134 27 19 kyr and the inflection point previously chosen to designate the end of the cie recovery occurs at 217 44 31 kyr this allocation of time differs from that of the cycle based age model of rohl et al 2007 in that it assigns more time to the clay layer followed by a more gradual recovery of carbonate rich sedimentation the new model also suggests a longer sustained 13 c excursion followed by a more rapid recovery to pre petm 13 c values these differences have important implications for constraining the source s of carbon and mechanisms for its subsequent sequestration favoring models that include a sustained release of carbon after an initial pulse

climate and sea level perturbations during the incipient eocene thermal maximum evidence from siliciclastic units in the basque basin ermua zumaia and trabakua pass northern spain abstract based on carbon isotope stratigraphy and lithology a revised high resolution correlation is proposed between sections spanning the incipient eocene thermal maximum ietm in the basque region northern spain in three studied sections the ietm event is represented by a prominent non to low calcareous siliciclastic unit su 4 20 5 m thick during formation of the su sedimentation rates for siliciclastic material increased by a factor of two to five whereas detrital grain size decreased significantly kaolinite and chlorite became more abundant in the clay fraction and calcite dissolution in the water column intensified the su reflects a significant change in climate and hydrological regime towards a warmer and seasonally drier climate the drying caused perennial vegetation cover to collapse and led to increased continental erosion but also to reduced hydrodynamic energy of freshwater debouching into the oceans a coeval relative sea level fall probably related to tectonic uplift or doming affecting major parts of western europe increased the land sea slope and further enhanced erosion rates palynological studies support periodic vegetation during seasonal rain instead of permanent conifer forests prominent caliche soils in coeval continental deposits in northern spain also support warm semiarid conditions during the ietm event net evaporation increased under the subtropical high pressure cells including the basque region whereas more northerly latitudes became more wet the su has a similar origin as detrital units previously assigned to the early palaeogene so called siderolithic discharge in other parts of western europe

black shale formation during the latest danian event and the paleocene eocene thermal maximum in central egypt two of a kind abstract the paleocene eocene thermal maximum petm 55 8 ma is considered as the most severe of a series of transient warming events hyperthermals that occurred during the early paleogene however the extent and magnitude of environmental changes during the short lived warming events pre and post dating the petm are still poorly constrained in this study we focus on the latest danian event lde 61 7 ma and compare it to the petm we present high resolution micropaleontological geochemical and mineralogical data of the petm and the lde in two adjacent sections from the gebel qreiya area in egypt there both events are characterized by a distinct set of event beds overlying an unconformity they are associated with intense carbonate dissolution and substantial changes in the benthic foraminifera fauna moreover both show an abrupt drop of siliciclastic input sediment starvation correlative to the onset of black shale formation and a strong enrichment in redox sensitive trace elements the evidence for enhanced detrital input during the onset of the petm and a longer recovery phase with enhanced phosphorus sedimentation during the petm attests a stronger environmental impact of this event compared to the lde according to rock eval and elemental analysis the petm as well as the lde event beds have up to 4 wt organic carbon small amounts of volatile hydrocarbons but high amounts of highly weathered and inert organic matter black carbon during pyrolysis the extremely high temperatures for the maximum release of hydrocarbons of the petm and lde samples correspond to thermal heating of 170 c which is incompatible with the sediment burial history therefore we suggest that the organic matter in both event deposits does not reflect well preserved marine biomass but predominantly represents a mixture of heavily weathered autochthonous marine material and allochthonous combustion residues differences in preservation and or type of organic matter are also likely to account for the divergent stable isotope anomalies of organic carbon the well known negative carbon isotope anomaly at the petm and a positive anomaly at the lde although warming water column stratification and enhanced nutrient input may have promoted anoxic conditions on the shelf during the lde as well as during petm our results support rapid sea level rise and clastic starvation as one important mechanism for black shale formation and carbon sequestration for both events this result underlines the similarity of both hyperthermal events in terms of environmental changes recorded on the southern tethyan margin with the petm showing an additional early phase of strong detrital input not revealed at the lde

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

warming the fuel for the fire evidence for the thermal dissociation of methane hydrate during the paleocene eocene thermal maximum dramatic warming and upheaval of the carbon system at the end of the paleocene epoch have been linked to massive dissociation of sedimentary methane hydrate however testing the paleocene eocene thermal maximum hydrate dissociation hypothesis has been hindered by the inability of available proxy records to resolve the initial sequence of events the cause of the paleocene eocene thermal maximum carbon isotope excursion remains speculative primarily due to uncertainties in the timing and duration of the paleocene eocene thermal maximum we present new high resolution stable isotope records based on analyses of single planktonic and benthic foraminiferal shells from ocean drilling program site 690 weddell sea southern ocean demonstrating that the initial carbon isotope excursion was geologically instantaneous and was preceded by a brief period of gradual surface water warming both of these findings support the thermal dissociation of methane hydrate as the cause of the paleocene eocene thermal maximum carbon isotope excursion furthermore the data reveal that the methane derived carbon was mixed from the surface ocean downward suggesting that a significant fraction of the initial dissociated hydrate methane reached the atmosphere prior to oxidation

on the duration of magnetochrons c24r and c25n and the timing of early eocene global warming events implications from the ocean drilling program leg 208 walvis ridge depth transect 1 five sections drilled in multiple holes over a depth transect of more than 2200 m at the walvis ridge se atlantic during ocean drilling program odp leg 208 resulted in the first complete early paleogene deep sea record here we present high resolution stratigraphic records spanning a 4 3 million yearlong interval of the late paleocene to early eocene this interval includes the paleocene eocene thermal maximum petm as well as the eocene thermal maximum etm 2 event a detailed chronology was developed with nondestructive x ray fluorescence xrf core scanning records and shipboard color data these records were used to refine the shipboard derived spliced composite depth for each site and with a record from odp site 1051 were then used to establish a continuous time series over this interval extensive spectral analysis reveals that the early paleogene sedimentary cyclicity is dominated by precession modulated by the short 100 kyr and long 405 kyr eccentricity cycles counting of precession related cycles at multiple sites results in revised estimates for the duration of magnetochrons c24r and c25n direct comparison between the amplitude modulation of the precession component derived from xrf data and recent models of earth s orbital eccentricity suggests that the onset of the petm and etm2 are related to a 100 kyr eccentricity maximum both events are approximately a quarter of a period offset from a maximum in the 405 kyr eccentricity cycle with the major difference that the petm is lagging and etm2 is leading a 405 kyr eccentricity maximum absolute age estimates for the petm etm2 and the magnetochron boundaries that are consistent with recalibrated radiometric ages and recent models of earth s orbital eccentricity cannot be precisely determined at present because of too large uncertainties in these methods nevertheless we provide two possible tuning options which demonstrate the potential for the development of a cyclostratigraphic framework based on the stable 405 kyr eccentricity cycle for the entire paleogene

an alternative model for caco3 over shooting during the petm biological carbonate compensation decreased caco3 content of deep sea sediments argues for rapid and massive acidification of the oceans during the paleocene eocene thermal maximum petm 56 ma bp in the course of the subsequent recovery from this acidification sediment caco3 content came to exceed pre petm levels known as over shooting past studies have largely attributed the latter to increased alkalinity input to the oceans via enhanced weathering but this ignores potentially important biological factors we successfully reproduce the caco3 records from walvis ridge in the atlantic ocean including over shooting using a biogeochemical box model replication of the caco3 records required 1 introduction of a maximum of 6500 gtc of co2 directly into deep ocean waters or 8000 gtc into the atmosphere 2 limited deep water exchange between the indo atlantic and pacific oceans 3 the disappearance of sediment bioturbation during a portion of the petm and 4 most central to this study a 50 reduction in net caco3 production during acidification in our simulations over shooting is an emergent property generated at constant alkalinity input no weathering feedback as a consequence of attenuated caco3 productivity this occurs because lower net caco3 production from surface waters allows alkalinity to build up in the deep oceans alkalinization thus promoting deep water super saturation restoration of caco3 productivity later in the petm particularly in the indo atlantic ocean leads to greater accumulation of caco3 ergo over shooting which returns the ocean to pre petm conditions over a time scale greater than 200 ka

new chronology for the late paleocene thermal maximum and its environmental implications the late paleocene thermal maximum lptm is associated with a brief but intense interval of global warming and a massive perturbation of the global carbon cycle we have developed a new orbital chronology for ocean drilling program odp site 690 weddell sea southern ocean by using spectral analysis of high resolution geochemical records the lptm interval spans 11 precessional cycles yielding a duration of 210 to 220 k y the 13 c anomaly associated with the lptm has a magnitude of about 2 5 to 3 we show that about 2 of the excursion occurs within two steps that each were less than 1000 yr in duration the remainder developed through a series of steps over 52 k y the timing of these steps is consistent with a series of nearly catastrophic releases of methane from gas hydrates punctuated by intervals of relative equilibria between hydrate dissociation and carbon burial further we are able to correlate the records between odp sites 690 and 1051 western north atlantic on the scale of 21 k y cycles which demonstrates that the details of the 13 c excursion are recognizable between distant sites comparison of cycle records at sites 690 and 1051 suggests that sediment representing the interval 30 k y just prior to and at the onset of the lptm are missing in the latter location this unconformity probably resulted from slope failure accompanying methane hydrate dissociation within 10 k y of the start of the lptm

north american continental margin records of the paleocene eocene thermal maximum implications for global carbon and hydrological cycling the impacts of the paleocene eocene thermal maximum petm 55 ma one of the most rapid and extreme warming events in earth history are well characterized in open marine and terrestrial environments but are less so on continental margins a major carbon sink here we present stable isotope carbonate content organic matter content and c n ratio records through the petm from new outcrop sections in california and from cores previously drilled on the new jersey margin foraminifer 18o data suggest that midlatitude shelves warmed by a similar magnitude as the open ocean 5 c 8 c while the carbon isotope excursion cie recorded both in carbonate and organic matter 13c records is slightly larger 3 3 4 5 than documented in open ocean records sediment accumulation rates increase dramatically during the cie in marked contrast to the open ocean sites in parallel mass accumulation rates of both organic and inorganic carbon also increased by an order of magnitude the estimated total mass of accumulated carbon in excess of pre cie rates suggests that continental margins at least along north america became carbon sinks during the cie mainly because of weathering feedbacks and rising sea level this result is significant because it implies that the negative feedback role of carbon burial on continental margins was greater than previously recognized

carbon isotopic distribution of methane in deep sea hydrothermal plume myojin knoll caldera izu bonin arc implications for microbial methane oxidation in the oceans and applications to heat flux estimation the concentration and stable carbon isotopic composition 13c of methane have been measured for both seafloor hydrothermal venting fluids and effluent plume waters supplied from the vents at the myojin knoll caldera izu bonin arc in the western north pacific the hydrothermal end member concentrations and 13c of methane show near homogeneity among vents 41 2 mol kg and 16 3 0 8 pdb respectively while those in the effluent plume are stratified in the caldera and vertically exhibit a large variation 2 1 11 nmol kg and 29 0 to 11 3 pdb respectively comparison of concentration and 13c data between vent fluids and plume waters suggest that the methane is not conserved but microbially oxidized along with the plume gradual decrease of diffusive methane flux in proportion to distance from the vent fields supports the occurrence of significant microbial oxidation within the plume assuming steady state emission of methane from the vents 1 kinetic isotope effect due to the microbial oxidation k12 k13 2 methane flux from the vents fvents 3 heat flux from the vents q and 4 average turnover time of hydrothermal methane tall are estimated to be k12 k13 1 005 0 001 fvents 90 340 mol d q 30 110 mw and tall 60 240 d respectively the estimated turnover times however are not uniform within the water column around the vents a turnover time of less than 50 d for methane is one of the shortest values in the pelagic ocean while those at the distant points correspond to values more typical for deep ocean water

structure and regional significance of the late permian sierra nevada death valley thrust system east central california abstract an imbricate system of north trending east directed thrust faults of late early permian to middle early triassic most likely late permian age forms a belt in east central california extending from the mount morrison roof pendant in the eastern sierra nevada to death valley six major thrust faults typically with a spacing of 15 20 km original dips probably of 25 35 and stratigraphic throws of 2 5 km compose this structural belt which we call the sierra nevada death valley thrust system these thrusts presumably merge into a decollement at depth perhaps at the contact with crystalline basement the position of which is unknown we interpret the deformation that produced these thrusts to have been related to the initiation of convergent plate motion along a southeast trending continental margin segment probably formed by pennsylvanian transform truncation this deformation apparently represents a period of tectonic transition to full scale convergence and arc magmatism along the continental margin beginning in the late triassic in central california

quantification of bioturbation in hemipelagic sediments via thin section image analysis traditional ichnofabric descriptive semiquantitative l schemes rely upon subjective estimates of the degree to which original sedimentary fabrics have been disrupted this paper presents an objective method of quantifying bioturbation in hemipelagic sediments based on a thin section image analysis technique in order to perform these analyses optical or backscattered electron micrographs are processed in order to obtain black and white images in these images black pixels are silt size larger grains and the clay size sedimentary matrix are white pixels once the initial processing has been accomplished an index h is defined to quantify the horizontal orientation of the larger grain size fraction of the sediment h is low for bioturbated fabric and high for laminated sediments in hemipelagic suspension deposits h can he used to quantify bioturbation assuming that no other sedimentary processes have disrupted the original depositional fabric the quantitive bioturbation scheme described here is consistent with existing semiquantitative bioturbation schemes in addition it is objective and provides higher resolution descriptions of biological processes that disrupted the sediment after deposition applying this quantitative scheme should refine future paleoecological reconstruction derived from lacustrine and marine successions

reversed deep sea carbonate ion basin gradient during paleocene eocene thermal maximum 1 the paleocene eocene thermal maximum petm 55 ma ago was marked by widespread caco3 dissolution in deep sea sediments a process that has been attributed to massive release of carbon into the ocean atmosphere system the pattern of carbonate dissolution is key to reconstructing changes in deep sea carbonate chemistry and ultimately the rate magnitude and location of carbon input here we show that during the petm the deep sea undersaturation was not homogeneous among the different ocean basins application of a sediment model to a suite of data records from different sites and ocean basins shows that a globally uniform decrease in deep sea carbonate ion concentration co32 is inconsistent with the data rather we demonstrate that deep sea co32 increased from the atlantic through the southern ocean into the pacific our results show that the petm deep sea co32 basin gradient during dissolution was reversed relative to the modern

an alternative age model for the paleocene eocene thermal maximum using extraterrestrial 3he a continuous age model for the brief climate excursion at the paleocene eocene boundary has been constructed by assuming a constant flux of extraterrestrial 3he 3he et to the seafloor 3he et measurements from odp site 690 provide quantitative evidence for the rapid onset few kyr and short duration 120 kyr of global warming and of the associated disturbance to the earth s surficial carbon budget at this time these observations support astronomically calibrated age models indicating extremely rapid release of isotopically light carbon possibly from seafloor methane hydrate as the proximal cause of the event however the 3he et technique indicates a previously unrecognized and extreme increase in sedimentation rate coincident with the return of climate proxies to pre event values the 3he et based age model thus suggests a far more rapid recovery from the climatic perturbation than previously proposed or predicted on the basis of the modern carbon cycle and so may indicate additional or accelerated mechanisms of carbon removal from the ocean atmosphere system during this period 3he et was also measured at odp site 1051 to test the validity of the site 690 chronology comparison of these data sets seems to require removal of several tens of kyr of sediment within the climatic excursion at site 1051 an observation consistent with sediment structures and previous age modeling efforts the site 1051 age model shows a 30 kyr period in which climate proxies return toward pre event values after which they remain invariant for 80 kyr if this rise represents the recovery interval identified at site 690 then the 3he et based age models of the two sites are in good agreement however alternative interpretations are possible and work on less disrupted sites is required to evaluate the reliability of the proposed new chronology of the climate excursion regardless of these details this work shows that the 3he et technique can provide useful independent evidence for the development and testing of astronomically calibrated age models

impact of dissolution on the sedimentary record of the paleocene eocene thermal maximum the input of massive amounts of carbon to the atmosphere and ocean at the paleocene eocene thermal maximum petm 55 53 ma resulted in pervasive carbonate dissolution at the seafloor at many sites this dissolution also penetrated into the underlying sediment column the magnitude of dissolution at and below the seafloor a process known as chemical erosion and its effect on the stratigraphy of the petm are notoriously difficult to constrain here we illuminate the impact of dissolution by analyzing the complete spectrum of sedimentological grain sizes across the petm at three deep sea sites characterized by a range of bottom water dissolution intensity we show that the grain size spectrum provides a measure of the sediment fraction lost during dissolution we compare these data with dissolution and other proxy records electron micrograph observations of samples and lithology the complete data set indicates that the two sites with slower carbonate accumulation and less active bioturbation are characterized by significant chemical erosion at the third site higher carbonate accumulation rates more active bioturbation and possibly winnowing have limited the impacts of dissolution however grain size data suggest that bioturbation and winnowing were not sufficiently intense to diminish the fidelity of isotopic and microfossil assemblage records

deep sea redox across the paleocene eocene thermal maximum large amounts of 13c depleted carbon were released to the oceans and atmosphere during a period of abrupt global warming at the paleocene eocene thermal maximum petm 55 ma investigations of qualitative sedimentologic and paleontologic redox proxies such as bioturbation and benthic assemblages from pelagic and hemipelagic sections suggest transient reductions in bottom water oxygen during this interval possibly on a global scale here we present bulk sediment manganese mn and uranium u enrichment factors ef in atlantic and pacific deep sea cores to constrain relative paleoredox changes across the petm mn ef range from 1 to 9 in atlantic sites 1 to 35 in southern ocean sites and are at crustal averages ef 1 in pacific sites u ef range from 1 to 5 in atlantic sites 1 to 90 in southern ocean sites and are at crustal averages in pacific sites our results indicate suboxic conditions prior to during and in the recovery from the petm at intermediate depth sites in the atlantic and southern ocean while the pacific sites remained relatively oxygenated the difference in oxygenation between the atlantic and pacific sites leads us to suggest the source for isotopically light carbon release during the petm was in the atlantic

multiple early eocene hyperthermals their sedimentary expression on the new zealand continental margin and in the deep sea the paleocene eocene thermal maximum petm ca 55 5 ma was a geologically brief interval characterized by massive influx of isotopically light carbon extreme changes in global climate and profound variations in earth system processes an outstanding issue is whether it was an isolated event or the most prominent example of a recurring phenomenon recent studies of condensed deep sea sections support the latter but this finding remains uncertain here we present and discuss lithologic and carbon isotope records across two lower eocene outcrops on south island new zealand the petm manifests as a marl rich horizon with a significant negative carbon isotope excursion cie above in sediment deposited between 54 and 53 ma are four horizons with similar though less pronounced expressions marl beds of all five horizons represent increased terrigenous sedimentation presumably linked to an accelerated hydrological cycle five corresponding clay rich horizons and cies are found in deep sea records although the lithologic variations represent carbonate dissolution rather than siliciclastic dilution the presence of five intervals with similar systemic responses in different environments suggests a mechanism that repeatedly injected large masses of 13 c depleted carbon during the early eocene

carbon addition and removal during the late palaeocene thermal maximum basic theory with a preliminary treatment of the isotope record at odp site 1051 blake nose the late palaeocene thermal maximum lptm was a brief interval at c 55 ma characterized by a 2 5 to 3 per thousand shift in the 13c of global carbon reservoirs the geochemical perturbation probably represents a massive input of 12c rich carbon to the exogenic carbon cycle largely unresolved issues concerning this carbon injection during the lptm are the rates of carbon input and removal simple expressions are developed here to describe a 13c excursion in the exogenic carbon cycle after carbon input a change in global 13c d ex dt can be explained to a first approximation by a set of parameters the initial mass and isotopic composition of the global carbon cycle mex o ex o and the fluxes and isotopic compositions of external carbon inputs outputs and injected carbon fin in fout out fadd add in general for a given exogenic carbon cycle a large fadd or low add results in a larger 13c excursion likewise for a given negative 13c excursion a large mex or low ex requires a greater input of 12c differences in fin in fout and out cause changes in the response of ex over time for a negative 13c excursion of given magnitude a greater fin requires a greater input of 12c and lessens the time for ex to return to initial conditions a decrease in out caused by an increase in the relative output of organic matter and carbonate has a similar effect variable dmadd dt produces transients in ex that are related to the source function but modified by carbon removal in theory a well dated and representative global 13c excursion could be used to derive the carbon inputs and ouputs ocean drilling program odp site 1051 has an expanded early palaeogene section and recent work at this location has provided a well dated 13c record across the lptm this 13c record contains transient variations of apparently global nature these observed transients are best explained by a pulsed injection of ch4 into an exogenic carbon cycle with a greater carbon throughput or enhanced burial of organic matter after carbon addition

anomalous shifts in tropical pacific planktonic and benthic foraminiferal test size during the paleocene eocene thermal maximum paleocene eocene warming and changes in oceanic hydrography should have significantly impacted the ecology of marine microorganisms both at the surface and on the seafloor we analyzed several key characteristics of foraminifera from two shatsky rise odp leg 198 cores spanning the p e boundary including the maximum test diameters of the largest calcareous trochospiral benthic foraminifera and largest shallow dwelling planktonic foraminifera and the stable carbon and oxygen isotope ratios of benthic foraminifera and bulk samples we also qualitatively constrained changes in bottom water dissolved oxygen concentrations by quantifying changes in benthic species abundances we find warming synchronous with an unusual increase in the size of surface water planktonic in contrast to deep water benthic foraminifera which decrease in size we suggest that a decline in bottom water dissolved oxygen is the primary mechanism responsible for the size reduction of pacific deep sea benthic foraminifera whereas the contemporaneous size increase of surface water planktonic foraminifera is attributed to an increase in thermal stratification and decrease in local nutrient supply

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

a biogenic origin for anomalous fine grained magnetic material at the paleocene eocene boundary at wilson lake new jersey 1 the paleocene eocene thermal maximum which occurred 55 5 ma was caused by a massive release of carbon as indicated by an 3 negative carbon isotope excursion recorded in the marine atmospheric and terrestrial reservoirs one suggested source for the carbon a cometary impactor is based on the sudden appearance and high concentration of single domain sd magnetite in paleocene eocene p e boundary cores from the north atlantic continental margin we evaluate the potential sources of sd magnetite at the p e boundary by presenting new magnetic hysteresis low temperature magnetic remanence and transmission electron microscopy data from the north atlantic coastal ocean our results show a similar increase in sd material but demonstrate that the magnetic material has a biogenic origin these findings indicate that the high concentrations of sd magnetite immediately above the p e boundary are the result of unusual accumulations and or preservation of magnetotactic bacteria such bacteria typically occupy the oxic anoxic transition zone near the sediment water interface or in the water column the high abundances of sd magnetite in sediments from across the shelf may be an artifact of nonsteady state redox conditions and exceptional preservation of sd magnetite it may also indicate that the oxic anoxic redox boundary shifted into the water column the latter explanation implies transient eutrophy of the coastal ocean in this region most likely due to seasonally enhanced runoff and increased stratification and nutrient loading

patterns and magnitude of deep sea carbonate dissolution during eocene thermal maximum 2 and h2 walvis ridge southeastern atlantic ocean 1 eocene thermal maximum 2 etm2 or h1 53 7 ma represents a short lived warming episode associated with the injection of a large mass of 13c depleted carbon into the ocean atmosphere system the mass of injected carbon the extent of deep sea dissolution and the amount of warming during etm2 appear to be approximately half of those documented for the paleocene eocene thermal maximum petm 55 5 ma but the pattern of lysocline migration during etm2 has not yet been documented sufficiently to decipher potential differences in carbon sources and sequestration mechanisms we present high resolution carbonate dissolution and bulk stable isotope records across etm2 and the successive h2 event 53 6 ma on a common age model for four sites along the walvis ridge depth transect 1500 to 3600 m paleowater depth to assess lysocline evolution the onset of etm2 is characterized by multiple depth dependent transitions of carbonate dissolution up to 96 of the total flux associated with rapid depletions in bulk carbonate carbon up to 1 1 5 and oxygen up to 0 7 1 5 isotope values h2 shows a 0 7 negative carbon isotope excursion with a coeval decrease in 18o of 0 5 and 80 of carbonate dissolution during etm2 the lysocline recovered within 30 ka we attribute this rapid recovery to terrestrial caco3 neutralization through enhanced chemical weathering of carbonates in soils and rocks according to theory carbonate dissolution was lower after recovery than prior to etm2 indicating carbonate ion oversaturation and a deeper position of the lysocline spectral analysis indicates that the changes in carbonate dissolution and 13c values were precession paced implying that weathering feedbacks and short term perturbations in the carbon cycle were important in determining early eocene background and hyperthermal ocean co32 conditions

trace fossil model for reconstruction of paleo oxygenation in bottom waters recognition of fluctuations in the degree of paleo oxygenation of bottom waters recorded in fine grained pelagic strata is important for interpretation of paleoceanographic and paleoclimatologic conditions general sedimentary fabric composition of trace fossil assemblages and burrow size and crosscutting relationships have been incorporated into a trace fossil tiering model that permits detailed reconstruction of changes in paleo oxygenation of bottom waters applications of this model to the miocene monterey formation california and the cretaceous niobrara formation colorado indicate that the ichnologic approach is more sensitive to both magnitude and rates of change in oxygenation levels compared to macrobenthic body fossil information

quantification of bioturbation in hemipelagic sediments via thin section image analysis research methods papers abstract traditional ichnofabric descriptive semiquantitative schemes rely upon subjective estimates of the degree to which original sedimentary fabrics have been disrupted this paper presents an objective method of quantifying bioturbation in hemipelagic sediments based on a thin section image analysis technique in order to perform these analyses optical or backscattered electron micrographs are processed in order to obtain black and white images in these images black pixels are silt size larger grains and the clay size sedimentary matrix are white pixels once the initial processing has been accomplished an index h is defined to quantify the horizontal orientation of the larger grain size fraction of the sediment h is low for bioturbated fabric and high for laminated sediments in hemipelagic suspension deposits h can be used to quantify bioturbation assuming that no other sedimentary processes have disrupted the original depositional fabric the quantitative bioturbation scheme described here is consistent with existing semiquantitative bioturbation schemes in addition it is objective and provides higher resolution descriptions of biological processes that disrupted the sediment after deposition applying this quantitative scheme should refine future paleoecological reconstruction derived from lacustrine and marine successions

mode and tempo of the paleocene eocene thermal maximum in an expanded section from the venetian pre alps mode and tempo of an expanded paleocene eocene thermal maximum section in the venetian pre alps

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

a molybdenum isotope record of eocene thermal maximum 2 implications for global ocean redox during the early eocene during the early eocene a series of short term global warming events hyperthermals occurred in response to the rapid release of carbon into the oceans and atmosphere in order to investigate the response of ocean redox to global warming we have determined the molybdenum isotope compositions 98 95 mo of samples spanning one such hyperthermal eocene thermal maximum 2 etm 2 54 1ma from integrated ocean drilling program expedition 302 site m0004a in the arctic ocean the highest 98 95 mo in our sample set 2 00 0 11 corresponds to the development of local euxinia at site m0004a during the peak of etm 2 which we interpret as recording the global seawater 98 95 mo at that time the etm 2 seawater 98 95 mo is indistinguishable from a recent estimate of seawater 98 95 mo from an earlier hyperthermal paleocene eocene thermal maximum petm 55 9ma 98 95 mo 2 08 0 11 it is argued that the similarity in seawater 98 95 mo during etm 2 and the petm was caused by the development of transient euxinia in the arctic ocean during each hyperthermal that allowed sediments accumulating in this basin to capture the long term 98 95 mo of early eocene seawater our new data therefore place a minimum constraint on the magnitude of transient global seafloor deoxygenation during early eocene hyperthermals

introducing fiji and icy image processing techniques in ichnological research as a tool for sedimentary basin analysis abstract in recent years image treatment has been appraised as a very powerful tool to facilitate ichnological analysis especially in marine cores of modern sediments supporting the determination of certain ichnological features however it is still a new approach and detailed research is necessary to encounter a faster and more efficient method the present study focuses on two image processing techniques fiji and icy and their comparison with a refined version of the well established high resolution image treatment strengths and weaknesses of the methodologies for the determination of three main features were explored i visibility of trace fossils ii quantification of the percentage of bioturbated surface and iii penetration depth estimation refined high resolution image treatment gives the best results for enhanced visibility of trace fossils whereas fiji is found to be a sound and rapid option one disadvantage shared by fiji and icy is the binary character of the produced images which may impede later ichnotaxonomical differentiation both fiji and icy fiji are rapid alternatives for quantifying the bulk amount of bioturbated surface the magic wand method refineedge based on high resolution image treatment provides good results regardless of the contrast of the images and it additionally allows for a more detailed quantification the semi automatic character of icy favors quick estimation of penetration depth and facilitates differentiation between distinct tracemaker communities based on a rapid quantification of pixel values thus fiji and icy methods offer good results and are much less time consuming than high resolution image treatment they are proposed as faster alternatives for the estimation of ichnological features especially useful at the beginning stages of research when a large number of samples must be analyzed

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