late neogene sequence stratigraphic evolution of the foz do amazonas basin brazil the margin of the foz do amazonas basin saw a shift from predominantly carbonate to siliciclastic sedimentation in the early late miocene by this time the amazon shelf had also been incised by a canyon that allowed direct influx of sediment to the basin floor thus confirming that the palaeo amazon fan had already initiated by that time 9 5 8 3 ma above this interval during a prolonged lowstand messinian third order sequences are preserved only in the incised valley fills of the canyon with no equivalent strata on the shelf third and fourth order sequences younger than messinian are preserved on the shelf after sea level rise above the shelf by the early pliocene sequences younger than 3 8 ma often show fourth order cyclicity with an average duration of 400 ka larger scale eccentricity cycles often preserved in high sedimentation rate areas of river deltas mass wasting and transportation of slope sediments to the basin began to play an important role in sediment dispersal at least as far back as the mid pliocene after rapid progradation had produced steeper slopes more prone to failure

mass transport processes on amazon cone western equatorial atlantic three large mass transport deposits occur on the upper to middle amazon cone these slump debris flow complexes have been mapped from 3 5 khz echograms and cover approximately 75 000 sq km or about 10 of the cone the debris flows traveled down slopes with gradients as low as 1 90 to 1 165 0 3 to 0 6 for distances up to 300 km these deposits average 10 to 50 m in thickness and the total amount of sediments displaced may exceed 3 800 cu km the upslope parts of these complexes generally consist of hummocky slump or slide deposits which are commonly bounded by scarps of varying relief downslope from this zone of removal the deposits consist of thin the occurrence of such widespread mass movements on the amazon cone indicates that mass transport is probably an important sedimentation process on deep sea fans however most studies and models of modern deep sea fans have minimized or ignored the potential importance of mass transport processes in fan development we suggest that in the future both ancient and modern deep sea fans be more closely examined for mass transport deposits so that the importance of this process to overall fan development can be more accurately assessed

long term sea level fluctuations driven by ocean basin dynamics earth9s long term sea level history is characterized by widespread continental flooding in the cretaceous period 145 to 65 million years ago followed by gradual regression of inland seas however published estimates of the late cretaceous sea level high differ by half an order of magnitude from 40 to 250 meters above the present level the low estimate is based on the stratigraphy of the new jersey margin by assimilating marine geophysical data into reconstructions of ancient ocean basins we model a late cretaceous sea level that is 170 85 to 270 meters higher than it is today we use a mantle convection model to suggest that new jersey subsided by 105 to 180 meters in the past 70 million years because of north america9s westward passage over the subducted farallon plate this mechanism reconciles new jersey margin based sea level estimates with ocean basin reconstructions

sea level control on facies architecture in the cenomanian coniacian apulian margin western tethys a record of glacio eustatic fluctuations during the cretaceous greenhouse abstract the integrated chemo bio and sequence stratigraphy from the cenomanian coniacian base of slope succession of monte turno abruzzo central italy provides a fine scale calibration of the local sea level curve inferred from the adjacent platform to records of global sea level change our results indicate that regional marine regressions were coincident with episodes of global cooling and sea level fall providing evidences for a causal link between climate changes and sea level changes the presence of small polar ice caps during the assumed ice free cretaceous is a likely explanation for the observed pattern

high resolution stable isotope records from the upper cretaceous rocks of italy and spain glacial episodes in a greenhouse planet high resolution 13c and 18o records from upper albian to lower santonian pelagic carbonates of the contessa quarry section in italy exhibit large positive oxygen isotopic excursions of 1 in the lower cenomanian and upper turonian coniacian strata within the uncertainties of biostratigraphic correlation these positive excursions appear to correspond to times of large sea level regressions in global sequence stratigraphic sea level curves several lines of evidence suggest that the major 18o excursions in contessa reflect episodes of global cooling and not differential diagenesis numerical models of oxygen isotope exchange during diagenesis show that a high contrast in the degree of alteration would be required to produce these signals as artifacts of diagenesis and lithological data provide no evidence for such large contrasts in the degree of alteration furthermore although precise correlation with a section in the south of spain is hampered by stratigraphic complexities the general sequence of major positive 18o excursions is reproduced it is unlikely that differential diagenesis would produce similar artifacts in multiple sites one explanation for the link between episodes of global cooling and sea level falls is that global cooling events led to polar ice sheet accumulation lowering sea level although ice free conditions have been inferred from evidence for a much warmer climate in late cretaceous time our results suggest that the relationship between continental high latitude ice sheets and overall climatic warmth warrants further examination

late cretaceous orbitally paced carbon isotope stratigraphy from the bottaccione gorge italy abstract a refined astronomical tuning of the upper albian lower campanian is proposed from the bottaccione reference section gubbio central italy long term eccentricity cycles filtered from a high resolution 13c record were tuned to the highly stable 405 kyr cycles of the new la2010 astronomical solution for the earth s orbital elements the achieved orbital tuning provides a new precise and accurate age model for dating biostratigraphic magnetostratigraphic and carbon isotope events through a 23 myr long record cycles of 8 0 4 7 3 4 and 2 4 myr modulate the entire 13c record thus extending their detection from the cenozoic to 100 ma and represent primary and stable long term oscillation modes of earth s climate ocean system although an ultimate driver of these long term periodicities is lacking we speculate that specifically the periodicity at 4 7 myr represents a homologue of the present eccentricity grand cycles evolved by the chaotic behaviour of solar system planets during the mesozoic the long term periodicities potentially reflect an unexplored expression of the low frequency response of the carbon cycle to global biogeochemical dynamics of major nutrients particularly phosphorus associated with modulation of inputs to the ocean in turn triggered by high order marine transgressions and formation of highly productive shelf seas this very long term eccentricity control modulated by periodic low energy cycles is suggested to play a crucial role in carbon cycling controlling a chain of climate sensitive global biogeochemical processes on the earth finally these grand cycles provide a potential tool for geological correlation and provide a robust constraint for accurate calculation of the orbital evolution of the solar system

glacial cycles drive variations in the production of oceanic crust glacial cycles redistribute water between oceans and continents causing pressure changes in the upper mantle with consequences for the melting of earth s interior using plio pleistocene sea level variations as a forcing function theoretical models of mid ocean ridge dynamics that include melt transport predict temporal variations in crustal thickness of hundreds of meters new bathymetry from the australian antarctic ridge shows statistically significant spectral energy near the milankovitch periods of 23 41 and 100 thousand years which is consistent with model predictions these results suggest that abyssal hills one of the most common bathymetric features on earth record the magmatic response to changes in sea level the models and data support a link between glacial cycles at the surface and mantle melting at depth recorded in the bathymetric fabric of the sea floor

on the origin of cenozoic and mesozoic third order eustatic sequences abstract the origin of third order eustatic sequences is reviewed by comparing recent sequence stratigraphic data to the latest best constrained astronomical model middle eocene to holocene icehouse sequences correspond to 1 2 myr obliquity cycles constraints from oxygen isotope records highlight the link between icehouse sea level lowerings sequence boundaries and 1 2 myr obliquity nodes mesozoic greenhouse sequences show some relation with the 2 4 myr eccentricity cycles suggesting that orbital forcing contribute to sea level change we suggest that during the icehouse large ice sheets associated with significant glacioeustatic changes 25 m up to 120 m changes were mainly governed by obliquity forcing during icehouse worlds obliquity forcing was the stongest control on global sea level and depositional sequences additionally during the middle eocene third order sequences were glacioeustatically driven in tune with 1 2 myr obliquity cycle suggesting that the presence of significant ice sheets is earlier than previously supposed i e early eocene in contrast during greenhouse worlds e g ephemeral small to medium sized or no ice sheets 0 25 m glacioeustatic changes the expression of obliquity in the sedimentary record is weak and intermittent instead the eccentricity signature which is the modulator of climatic precession is documented moreover we presume that greenhouse sequences on the myr scale are global and hence cannot be caused by regional tectonism e g intraplate stress or mantle hot blobs instead the eccentricity link implies a weaker glacioeustatic control because thermoeustasy is too small to explain the sea level changes stratigraphically well documented fourth order sequences may be linked to the astronomically stable strongest amplitude 405 kyr eccentricity cycle and possibly to 160 200 kyr obliquity modulation cycles fifth order sequences to the short 100 kyr eccentricity cycles and finally sixth order sequences to the fundamental obliquity 40 kyr and climatic precession 20 kyr cycles these astronomical cycles could be preserved in the sedimentary record and have been demonstrated to control sea level changes accordingly by placing depositional sequence orders into a high resolution temporal framework i e orbital periodicities standardization of eustatic sequence hierarchy may be possible

isotopic evidence for glaciation during the cretaceous supergreenhouse the turonian 93 5 to 89 3 million years ago was one of the warmest periods of the phanerozoic eon with tropical sea surface temperatures over 35 c high amplitude sea level changes and positive 18 o excursions in marine limestones suggest that glaciation events may have punctuated this episode of extreme warmth new 18 o data from the tropical atlantic show synchronous shifts 91 2 million years ago for both the surface and deep ocean that are consistent with an approximately 200 000 year period of glaciation with ice sheets of about half the size of the modern antarctic ice cap even the prevailing supergreenhouse climate was not a barrier to the formation of large ice sheets calling into question the common assumption that the poles were always ice free during past periods of intense global warming

link between cyclic eustatic sea level change and continental weathering evidence for aquifer eustasy in the cretaceous abstract cyclic fluctuations in global sea level during epochs of warm greenhouse climate have remained enigmatic because absence or subordinate presence of polar ice during these periods precludes an explanation by glacio eustatic forcing an alternative concept suggests that the water bearing potential of groundwater aquifers is equal to that of ice caps and that changes in the dynamic balance of aquifer charge versus discharge as a function of the temperature related intensity of the hydrological cycle may have driven eustasy during warm climates however this idea has long been neglected for two reasons 1 the large storage potential of subsurface aquifers was confused with the much smaller capacity of rivers and lakes and 2 empirical data were missing that document past variations in the hydrological cycle in relation to eustasy in the present study we present the first empirical evidence for changes in precipitation continental weathering intensity and evaporation that correlate with astronomically long obliquity forced sea level cycles during the warmest period of the cretaceous cenomanian turonian we compare sequence stratigraphic data with changes in the terrigenous mineral assemblage in a low latitude marine sedimentary sequence from the equatorial humid belt at the south tethyan margin levant carbonate platform jordan thereby avoiding uncertainties from land ocean correlations our data indicate covariance between cycles in weathering and sea level predominantly chemical weathering under wet climate conditions is reflected by dominance of weathering products clays in deposits that represent sea level fall aquifer charge discharge conversely preservation of weathering sensitive minerals feldspars epidote and pyroxenes in transgressive sediments reflects decreased continental weathering due to dryer climate aquifer discharge charge based on our results we suggest that aquifer eustasy represents a viable alternative to glacio eustasy as a driver of cyclic 3rd order sea level fluctuations during the middle cretaceous greenhouse climate and it may have been a pervasive process throughout earth history

astronomical calibration of the early oxfordian vocontian and paris basins france consequences of revising the late jurassic time scale abstract magnetic susceptibility ms variations record earth s orbital parameters in the clays and marls of the early oxfordian in the paris and vocontian basins of france climatically driven weathering of surrounding emergent areas and the resulting detrital input to the basins is a significant source of the ms signal ms proves to be an effective tool for deciphering the orbital forcing signal in these sediments and for assessing the chronology of these formations the 405 kyr orbital eccentricity cycle is clearly visible in the ms signal and consequently is a valuable geochronometer for this portion of the jurassic time scale astronomical calibration of the mariae ammonite zone basal oxfordian stage indicates a duration of 2 2 myrs whereas current time scales assign only 0 6 myrs to this biozone however the late jurassic time scale has large uncertainties in stage boundary ages 4 myrs hence of interval durations these results could lead to significant revisions in the m sequence magnetic anomaly block model and greatly improve the resolution of the jurassic time scale

translating milankovitch climate forcing into eustatic fluctuations via thermal deep water expansion a conceptual link sedimentological evidence indicates metre scale cyclic changes in global sea level during mesozoic greenhouse climates the cyclicity is thought to be due to milankovitch forcing the absence of continental ice caps requires other mechanisms than glacier build up to explain these variations we propose that thermal expansion of the entire oceanic water column may partly explain the observed sea level variations on milankovitch timescales using existing climate model results we show that an increase in deep water temperature of 2 c and a corresponding sea level rise of 1 7 m by thermal expansion can be induced by milankovitch forcing via increased formation of warm deep waters in low latitudes

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

global sea level trend in the past century data derived from tide gauge stations throughout the world indicate that the mean sea level rose by about 12 centimeters in the past century the sea level change has a high correlation with the trend of global surface air temperature a large part of the sea level rise can be accounted for in terms of the thermal expansion of the upper layers of the ocean the results also represent weak indirect evidence for a net melting of the continental ice sheets

geologic constraints on the chaotic diffusion of the solar system the correlation of earth s orbital parameters with climatic variations has been used to generate astronomically calibrated geologic time scales of high accuracy however because of the chaotic behavior of the solar system two initially close calculations of earth s orbit diverge exponentially and have a large uncertainty beyond several million years in the past this chaotic behavior is related to a combination of angles in the precession motion of the orbits of earth and mars which currently is in resonance how long stays in libration critically depends on the dynamical model and initial conditions for the solar system here we show that geologic data can differentiate between astronomical solutions that do and do not exhibit a transition in since 40 ma and that sediments can thus provide a history for the evolution of we find that the chaotic transition of from libration to circulation did not occur after ca 30 ma we can thus constrain the chaotic diffusion of the solar system in the past and our results provide new and challenging constraints for astronomical models

cyclostratigraphy and its revolutionizing applications in the earth and planetary sciences over the past 25 yr the science of stratigraphy has evolved to include time correlative data from vastly disparate components of the earth system not least of these is the global signal afforded by cyclostratigraphy which has recorded the evolution of earth s astronomical milankovitch forcing of insolation and the paleoclimate system fossil astronomical signals are collected from cyclic sedimentary sequences by detailed sampling and study of facies geochemistry mineralogy rock magnetism color etc in step with the documentation of astronomically forced paleoclimate from ever older older geologic times innovations in computational science have provided ever longer high accuracy astronomical model targets that can be used for time scale calibration the earth s orbit is affected by motions of other planets notably the orbital perihelia of venus and jupiter which impose a dominant 405 k y eccentricity cycle on earth s orbital evolution the large mass of jupiter stabilizes this cycle over hundreds of millions of years the cyclostratigraphic record of 405 k y cycles is therefore often used to correct chronologies affected by variable sedimentation earth s shape and rotation rate are influenced by tidal dissipation and climate friction these effects affect earth s precession rate through time thus a record of earth moon evolution is also embedded in cyclostratigraphy the geochronologic value of cyclostratigraphy has been affirmed through intercalibration with high precision radioisotope dating which today has the potential to define the ages of stratigraphic horizons with 2 uncertainties at the scale of a precession cycle precession index phasing relative to that of the obliquity elucidates the seasonal nature of astronomical forcing of the paleoclimate system cyclostratigraphy contributes to our knowledge of planetary dynamics for times prior to the current ca 50 ma limit of accurate astronomical solutions and it will guide our future understanding of solar system evolution and the evidence for chaotic diffusion astronomical modeling is undergoing its own revolution with development of new numerical integrators to extend accuracy further back in time finally space exploration has revealed prominent sedimentary bedding and ice stratigraphy on the surface of mars with patterns suggestive of astronomical forcing analogous to earth

astronomical pacing of late cretaceous third and second order sea level sequences in the foz do amazonas basin abstract because of their relatively reduced tectonic influence post rift sedimentary successions have a propensity to preserve climatically driven cyclicity over long durations here we present an integrated cyclostratigraphic and sequence stratigraphic study of the post rift limoeiro sedimentary formation fm of the foz do amazonas basin offshore brazil which spans the entire late cretaceous epoch almost 35 myr long the principal goal of the present study is to decipher very long multi myr sedimentary cyclicities and their potential origin s in order to delineate the main controlling factors of post rift sediment sequences and packages we used gamma ray gr well log data for cyclostratigarphy and seismic data for sequence stratigraphy time series analysis of gr data shows a rich series of milankovitch frequency bands in particular long period cyclicities 405 kyr 2 4 myr 4 7 myr and 9 5 myr are detected with high fidelity seismic and sequence stratigraphic interpretation shows a striking sea level sl depositional sequence order matching the 4 7 myr orbital cyclicity inferred from cyclostratigraphy longer sl sequences interpreted in previous studies from the limoeiro fm closely match the 9 5 myr gr related orbital cycles thus we infer that the post rift limoeiro fm was deposited continuously under astronomical forcing over the late cretaceous epoch resulting in an extraordinary record of direct base and sea level responses to milankovitch climatic forcing including longer multi myr periodicities the 4 7 myr orbital component is recorded for the first time in sl sedimentary proxies thus allowing here to update sl hierarchical orders we suggest that third order and second order and suborders sl sequences were most likely paced by long period astronomical cycles 2 4 myr eccentricity and 4 7 and 9 5 myr orbital cycles respectively

visions of ice sheets in a greenhouse world abstract backstripped eustatic estimates from new jersey and the russian platform show large 25 m and rapid 18 o record highlights the enigma this was the warmest interval of the past 200 my yet it was bracketed by two inferred eustatic falls of 25 m that were associated with two large 0 75 deep sea 18 o increases 92 93 ma mid turonian and 96 ma mid cenomanian we reconcile records of warm high latitudes with glacioeustasy by proposing that late cretaceous early eocene ice sheets generally reached maximum volumes of 8 12 10 6 km 3 20 30 m glacioeustatic equivalent but did not reach the antarctic coast hence coastal antarctica hence deep water remained relatively warm even though there were significant changes in sea level as the result of glaciation unlike the oligocene and younger icehouse world these ice sheets only existed during short intervals of peak milankovitch insolation leaving antarctica ice free during much of the greenhouse late cretaceous to middle eocene these results highlight the need to re evaluate the paradigm that polar ice sheets did not exist during times of warm high latitude climates

mud induced wave damping and wave induced liquefaction abstract this paper describes the results of a study on potential wave damping in the dutch wadden sea by viscous wave energy dissipation within soft and or liquefied mud layers the results are relevant for wave height boundary conditions for levee design along the mainland coast from a site inspection we observed that the mud fields along the wadden sea coast are quite dynamic and seem to migrate in alongshore direction during storm conditions a site along the wadden sea coast with extensive soft mud deposits known as zwarte haan was selected for more detailed laboratory and model analyses both field and laboratory measurements on sediment cores indicated strengths of a few kpa i e slightly above the liquid limit to assess the sensitivity of the mud deposits to liquefaction induced by incoming waves we carried out cyclical triaxial tests in the laboratory on a series of samples taken from the field the stresses prescribed were established from the wave heights and periods expected during storm conditions however even at stresses well beyond these values the triaxial tests did not indicate full liquefaction of the mud samples only some frictional losses were monitored these results are in contradiction with laboratory studies where liquefaction has been measured frequently however our observations corroborate with other recent observations in literature indicating that wave damping does not occur during a storm but afterwards it is hypothesized that fluid mud dissipating wave energy is formed by so called auto saturation and or from deposition of mud eroded during that storm and not from liquefaction during the storm wave damping then occurs through viscous dissipation in the fluid mud layers until these mud layers regain their initial strength through consolidation next we assessed the degree of wave damping to be expected at the beginning of a storm when the bed is still unaffected and during after storm conditions when fluid mud is formed we used the measured mud properties and those typical for fluid mud as found in the literature this assessment was done through simulations with a new version of swan referred to as swan mud these simulations suggest significant wave damping under fluid mud conditions but only 10 damping at the beginning of the storm moreover the degree of wave damping over a muddy bed may decrease during the storm as the soft mud deposits may be eroded by the waves our analyses suggest that wave cannot liquefy soft mud beds under natural conditions and that fluid mud layers damping incoming waves by viscous dissipation are formed from mud eroded by the shear flow induced by the waves orbital motion note that in situ pore water pressure measurements are required to corroborate this hypothesis

depositional sequences in shallow carbonate dominated sedimentary systems concepts for a high resolution analysis abstract oxfordian and berriasian sections representing shallow water carbonate dominated sedimentary systems have been studied in the swiss and french jura in spain and in normandy they all display a hierarchical stacking of depositional sequences facies evolution and stacking pattern allow to define elementary small scale medium scale and large scale sequences some depositional sequences display well marked sequence boundaries others are limited by transgressive or maximum flooding surfaces the hierarchical organisation of such sequence stratigraphic elements implies that sea level fluctuations were an important factor in their formation and that these fluctuations had different frequencies the superposition of high frequency sea level changes on a long term sea level trend leads to repetition of diagnostic surfaces defining sequence boundary and maximum flooding zones wherein the corresponding high frequency surfaces are well developed chronostratigraphic tie points permit us to estimate the duration of large scale sequences this time control and the observed hierarchical stacking suggest that the high frequency sea level changes were controlled by climatic cycles in the milankovitch frequency band the variability of stacking pattern and facies evolution between sections illustrates the complexity of the studied environments furthermore because of the minimal accommodation space available in these shallow water settings much of the geologic time is not recorded nevertheless detailed analysis of the depositional sequences allows the interpretation of the evolution of the sedimentary system with a high time resolution thus there is a potential to monitor sedimentological ecological and diagenetic processes on a time scale of 20 to 100 ka

climate induced fluctuations in sea level during non glacial times during periods of time when the earth supports ice caps sea level fluctuates periodically at intervals of 104 105 yr with amplitudes of tens to more than 100 metres these fluctuations result from expansions and contractions of continental ice sheets that occur in phase with the milankovitch periodicities of the earth s orbit1 2 smaller amplitude sea level fluctuations associated with milankovitch periodicities are also evident during warm periods such as the late triassic3 5 which lack strong evidence for continental glaciation6 we argue here that in times of limited ice volume periodic climate induced changes in lake and groundwater storage have the potential to produce small fluctuations in sea level this mechanism could contribute a small component of the sea level change observed in the quaternary period and may dominate the milankovitch eustatic sea level signal during earlier periods with limited ice volume6 we present evidence of contemporaneous milankovitch periodicities in late triassic lake sediments7 and sea level fluctuation3 5 which support the causal link between lake water storage and eustasy

astronomical calibration of the toarcian stage implications for sequence stratigraphy and duration of the early toarcian oae the toarcian oceanic anoxic event t oae of the early jurassic period involves one of the largest perturbations of the carbon cycle in the past 250 ma recorded by a pronounced negative carbon isotope excursion cie numerous studies have focused on potential causes of the t oae and cie but are hampered by an uncertain timescale here we present high resolution 2 kyr magnetic susceptibility ms measurements from the marine marls of the sancerre couy drill core southern paris basin spanning the entire toarcian stage the ms variations document a rich series of sub milankovitch to milankovitch frequencies precession obliquity and eccentricity with the periodic g2 g5 405 kyr and quasi periodic g g 2 4 myr cenozoic mean periodicity eccentricity terms being the most prominent the ms related g g variation reflects third order eustatic sequences and constrains the sequence stratigraphic framework of the toarcian stage in addition ms variations reveal a modulation of g g by g g eccentricity related cycles suggesting that sea level change was the main control on the deposition of the toarcian sancerre marls in tune with the astro climatic frequencies the stable 405 kyr cyclicity constrains a minimum duration of the toarcian stage to 8 3 myr and the well documented cie associated with the t oae to 300 to 500 kyr the 405 kyr ms timescale calibrates the periodicity of the prominent high frequency c cycles that occur in the decreasing part of the cie to 30 to 34 kyr consistent with the toarcian obliquity period predicted for an earth experiencing sustained tidal dissipation

deep sea paleotemperature record of extreme warmth during the cretaceous oxygen isotope analyses of well preserved foraminifera from blake nose 30 n paleolatitude north atlantic and globally distributed deep sea sites provide a long term paleotemperature record for the late albian maastrichtian interval that is difficult to reconcile with the existence of significant cretaceous ice sheets given reasonable assumptions about the isotopic composition of cretaceous seawater our results suggest that middle bathyal water temperatures at blake nose increased from 12 c in the late albian through middle cenomanian to a maximum of 20 c during the latest cenomanian and earliest turonian bottom waters were again 12 c during the middle campanian and cooled to a minimum of 9 c during the maastrichtian correlative middle bathyal foraminifera from other ocean basins yield paleotemperature estimates that are very similar to those from blake nose comparison of global bottom water temperatures and latitudinal thermal gradients suggests that global climate changed from a warm greenhouse state during the late albian through late cenomanian to a hot greenhouse phase during the latest cenomanian through early campanian then to cool greenhouse conditions during the mid campanian through maastrichtian

review short term sea level changes in a greenhouse world a view from the cretaceous abstract this review provides a synopsis of ongoing research and our understanding of the fundamentals of sea level change today and in the geologic record especially as illustrated by conditions and processes during the cretaceous greenhouse climate episode we give an overview of the state of the art of our understanding on eustatic global versus relative regional sea level as well as long term versus short term fluctuations and their drivers in the context of the focus of unesco iugs igcp project 609 on cretaceous eustatic short term sea level and climate changes we evaluate the possible evidence for glacio eustasy versus alternative or additional mechanisms for continental water storage and release for the cretaceous greenhouse and hothouse phases during which the presence of larger continental ice shields is considered unlikely increasing evidence in the literature suggests a correlation between long period orbital cycles and depositional cycles that reflect sea level fluctuations implying a globally synchronized forcing of eustatic sea level fourth order depositional sequences seem to be related to a 405 ka periodicity which most likely represents long period orbital eccentricity control on sea level and depositional cycles third order cyclicity expressed as time synchronous sea level falls of 20 to 110 m on 0 5 to 3 0 ma timescales in the cretaceous are increasingly recognized as connected to climate cycles triggered by long term astronomical cycles that have periodicity ranging from 1 0 to 2 4 ma future perspectives of research on greenhouse sea level changes comprise a high precision time scale for sequence stratigraphy and eustatic sea level changes and high resolution marine to non marine stratigraphic correlation

black shale deposition atmospheric co2 drawdown and cooling during the cenomanian turonian oceanic anoxic event 1 oceanic anoxic event 2 oae2 spanning the cenomanian turonian boundary ctb represents one of the largest perturbations in the global carbon cycle in the last 100 myr the 13ccarb 13corg and 18o chemostratigraphy of a black shale bearing ctb succession in the vocontian basin of france is described and correlated at high resolution to the european ctb reference section at eastbourne england and to successions in germany the equatorial and midlatitude proto north atlantic and the u s western interior seaway wis 13c offset between 13ccarb and 13corg is shown to be a good pco2 proxy that is consistent with pco2 records obtained using biomarker 13c data from atlantic black shales and leaf stomata data from wis sections boreal chalk 18o records show sea surface temperature sst changes that closely follow the 13c pco2 proxy and confirm tex86 results from deep ocean sites rising pco2 and sst during the late cenomanian is attributed to volcanic degassing pco2 and sst maxima occurred at the onset of black shale deposition followed by falling pco2 and cooling due to carbon sequestration by marine organic productivity and preservation and increased silicate weathering a marked pco2 minimum 25 fall occurred with a sst minimum plenus cold event showing 4 c of cooling in 40 kyr renewed increases in pco2 sst and 13c during latest cenomanian black shale deposition suggest that a continuing volcanogenic co2 flux overrode further drawdown effects maximum pco2 and sst followed the end of oae2 associated with a falling nutrient supply during the early turonian eustatic highstand

astrochronology of the early turonian early campanian terrestrial succession in the songliao basin northeastern china and its implication for long period behavior of the solar system abstract the first complete early turonian early campanian lacustrine succession has been recovered from the sk i south sk is borehole in the songliao basin slb northeastern china we conducted a detailed cyclostratigraphic study of natural gamma ray gr log thorium th log and magnetic susceptibility ms data from this core spectral analysis of the upper quantou formation k 2 q 3 4 qingshankou formation k 2 qn yaojia formation k 2 y and lower nenjiang formation k 2 n 1 2 reveals a hierarchy of meter to decameter scale cycling in the data the wavelength ratios of the cycles in these stratigraphic units are 20 5 2 1 corresponding with those of milankovitch cycle periods of 405 kyr long eccentricity 100 kyr short eccentricity 37 kyr obliquity 20 kyr precession indicating astronomical control on sedimentation an astronomical time scale ats was established by tuning interpreted 405 kyr cycles to a 405 kyr orbital eccentricity target curve and to four sims u pb zircon radioisotope ages this absolute ats provides precise numerical ages for stratigraphic boundaries biozones geological and geophysical events and serves as a basis for correlation of strata and events between marine and terrestrial systems the ages of the c33r c34n geomagnetic polarity boundary in k 2 n 2 and three short reversal events in k 2 y are estimated as 83 633 ma 84 819 84 862 ma 84 982 85 092 ma and 85 240 85 629 ma respectively long period amplitude modulations in the obliquity and eccentricity bands of the 405 kyr tuned gr th series provide strong evidence that long period orbital forcing influenced climate change and depositional processes in the slb the extracted amplitude modulations provide evidence that the orbits of earth and mars were not in secular resonance and were undergoing chaotic interactions during this time although the modulations do not match those of recent astronomical models

two scale gravitational collapse in the amazon fan a coupled system of gravity tectonics and mass transport processes abstract gravity tectonics affects the entire marine sedimentary sequence of the foz do amazonas basin including the topmost amazon fan during the various stages of the margin9s evolution the sedimentary loading and bathymetric slope induced the formation of a linked extensional compressional system in which gravitational fold and thrust belts form significant structural features on the continental slope seismic analysis carried out in this study shows that sea floor relief created along these thrust belts can trigger recurrent mass transport deposits in the upper middle amazon fan suggesting a long lasting linkage between gravity tectonics and mass transport processes throughout the sedimentary evolution of the amazon fan supplementary material uninterpreted seismic sections are available at http www geolsoc org uk sup18393

third order depositional sequences reflecting milankovitch cyclicity the origin of third order depositional sequences remains debatable and in many cases it is not clear whether they were controlled by tectonic activity and or by eustatic sea level changes in oxfordian and berriasian valanginian carbonate dominated sections of switzerland france germany and spain high resolution sequence stratigraphic and cyclostratigraphic analyses show that the sedimentary record reflects milankovitch cyclicity orbitally induced insolation changes translated into sea level fluctuations which in turn controlled accommodation changes beds and bedsets formed in rhythm with the precession and 100 kyr eccentricity cycles whereas the 400 kyr eccentricity cycle contributed to the creation of major depositional sequences biostratigraphical data allow the correlation of many of the 400 kyr sequence boundaries with third order sequence boundaries recognized in european basins this implies that climatically controlled sea level changes contributed to the formation of third order sequences furthermore this cyclostratigraphical approach improves the relative dating of stratigraphic intervals

mechanism of thin skinned detachment in the amazon fan assessing the importance of fluid overpressure and hydrocarbon generation abstract since about 10 ma a wedge of clastic sediment up to 10 km in thickness has accumulated near the mouth of the amazon river forming the amazon fan thin skinned extensional and contractional structures root into a common basal detachment hundreds of kilometers long extensional faults have formed landward of the prograding delta slope and contractional folds and faults have formed seaward of it by plan view restoration we show that extension and contraction balance we therefore infer that slope instability has provided the driving force for thin skinned deformation on seismic data the detachment appears as a sharp surface within late cretaceous strata however there is no evidence at that level for soft layers such as evaporites or muds abnormal fluid pressure provides a more reasonable mechanism for the detachment at depths of several thousand meters deep wells have encountered fluid overpressures amongst the possible causes of abnormal fluid pressures are compaction and hydrocarbon generation although compaction may have contributed to fluid overpressures encountered in wells we argue that hydrocarbon generation provides the best explanation for detachment in cretaceous rocks which were old and lithified when it occurred in particular the broadly triangular area of detachment coincides with an inferred pod of cenomanian turonian source rock which is interpreted to have been in the gas window during detached deformation we have developed new techniques of sandbox modelling to investigate the geometries of fault patterns produced by fluid flow through porous media for the amazon fan we have been able to reproduce the structural pattern on the assumption that fluid overpressures existed over a broadly triangular area beneath the detachment

record of albian to early cenomanian environmental perturbation in the eastern sub equatorial pacific the present paper documents and discusses a new albian early cenomanian carbon isotope 13ccarb and 13corg curve from the subequatorial eastern pacific in peru chemostratigraphic evidences for the expression of the oae1b set and for oae1c and oae1d are presented this dataset is relevant inasmuch as previous work is strongly biased towards study sites in north america western interior basin in europe tethys and the pacific realm a comparison of the carbon isotope stratigraphy obtained in peru with published sections from the central and western pacific the western atlantic and northern and western tethys reveals an overall good agreement supporting the global nature of the isotope patterns described here the 13c from peru record is constrained by biostratigraphic evidence and 87sr 86sr isotope stratigraphy using well preserved oyster shells furthermore we document the development of a heterozoan epeiric neritic mixed carbonate siliciclastic ramp in the western platform of peru and its corresponding sedimentary facies associations this dataset was used to elucidate the complex interplay of climatic changes nutrient supply and platform drowning leading to the following conclusions i an upper aptian lower albian major change from siliciclastic dominated to carbonate sedimentation coincided with the impact of the kilian level ii a lower albian incipient platform drowning linked to the impact of the paquier level iii a lower middle albian major demise of neritic carbonate production that coincides with the leenhardt level followed by middle albian condensed sedimentation that reports prominent negative values in 13ccarb prior to the onset of oae1c and iv finally renewed carbonate ramp production during the upper albian lower cenomanian the data shown here represent the foundation for future work documenting the mid cretaceous of peru and its implications for the palaeoceanography of the se subequatorial pacific

astronomical dating in the 19th century abstract today astronomical tuning is widely accepted as numerical dating method after having revolutionised the age calibration of the geological archive and time scale over the last decades however its origin is not well known and tracing its roots is important especially from a science historic perspective astronomical tuning developed in consequence of the astronomical theory of the ice ages and was repeatedly used in the second half of the 19th century before the invention of radio isotopic dating building upon earlier ideas of joseph adhemar james croll started to formulate his astronomical theory of the ice ages in 1864 according to which precession controlled ice ages occur alternatingly on both hemispheres at times of maximum eccentricity of the earth s orbit the publication of these ideas compelled charles lyell to revise his principles of geology and add croll s theory thus providing an alternative to his own geographical cause of the ice ages both croll and lyell initially tuned the last glacial epoch to the prominent eccentricity maximum 850 000 yr ago this age was used as starting point by lyell to calculate an age of 240 million years for the beginning of the cambrium but croll soon revised the tuning to a much younger less prominent eccentricity maximum between 240 000 and 80 000 yr ago in addition he tuned older glacial deposits of late miocene and eocene ages to eccentricity maxima around 800 000 and 2 800 000 yr ago archibald and james geikie were the first to recognize interglacials during the last glacial epoch as predicted by croll s theory and attempted to tune them to precession soon after frank taylor linked a series of 15 end moraines left behind by the retreating ice sheet to precession to arrive at a possible age of 300 000 yr for the maximum glaciation in a classic paper axel blytt 1876 explained the scattered distribution of plant groups in norway to precession induced alternating rainy and dry periods as recorded by the layering in holocene peat bogs he specifically linked the exceptionally wet atlantic period to the prolonged precession minimum at 33 300 yr ago and further related basic stratigraphic alternations to precession induced climate change in general such a linkage was also proposed by grove karl gilbert for cyclic alternations in the marine cretaceous of north america extrapolating sedimentation rates he arrived at an astronomical duration for part of the cretaceous that was roughly as long as the final estimate of william thomson for the age of the earth assuming that orbital parameters directly affect sea level karl mayer eymar and blytt correlated the well known succession of tertiary stages to precession and eccentricity respectively remarkably blytt like croll before him used very long period cycles in eccentricity to establish and validate his tuning understandably these studies in the second half of the 19th century were largely deductive in nature and proved partly incorrect later nevertheless this fascinating period marks a crucial phase in the development of the astronomical theory of the ice ages and climate and in astronomical dating it preceded the final inductive phase which started with the recovery of deep sea cores in 1947 and led to a spectacular revival of the astronomical theory by a century the first half of the 20th century can best be regarded as an intermediate phase despite the significant progress made in both theoretical aspects and tuning

late cretaceous anoxic events in the brazilian continental margin abstract a combined geochemical and micropalaeontological study of cenomanian to maastrichtian pelitic sediments from the brazilian continental margin has been undertaken the organic carbon contents rock eval pyrolysis results and biological marker distributions together with the taxonomic selection and distribution patterns of microfossil assemblages indicate that intermittent anoxic events occurred in the brazilian marginal basins during the cenomanian santonian with deposition taking place in progressively deeper waters from neritic to bathyal such events are characterised by the following 1 i a predominance among the benthonic foraminifera of low diversity small sized specimens mainly composed of gavelinellids buliminids and nodosariids indicating dysaerobic bottom conditions 2 ii levels with virtually no benthonic foraminifera and a well developed planktonic biota foraminifera radiolarians and diatoms indicating anaerobic bottom conditions with oxygenated surface waters 3 iii the occurrence of organic rich calcareous mudstone sediments 4 iv features in the biological marker distributions such as high concentrations of 28 30 bisnorhopane and 25 28 30 trisnorhopane up to 130 ppm a predominance of phytane over pristane and medium to high concentrations of nickel and vanadyl porphyrins up to ca 5700 ppm the widely recognized cenomanian turonian and santonian oceanic anoxic events schlanger and jenkyns 1976 ryan and cita 1977 and jenkyns 1980 are therefore manifest in the cassipore ceara sergipe alagoas and campos basins within the brazilian continental margin as is the presence of such events in the coniacian in contrast the campanian maastrichtian appears to be a time interval when deposition under oxygenated conditions produced sediments with low organic carbon contents and poor hydrocarbon source potential containing highly diversified and abundant calcareous and agglutinated benthonic foraminifera

evidence for glacial control of rapid sea level changes in the early cretaceous lower cretaceous bulk carbonate from deep sea sediments records sudden inputs of strontium resulting from the exposure of continental shelves strontium data from an interval spanning 7 million years in the berriasian valanginian imply that global sea level fluctuated about 50 meters over time scales of 200 000 to 500 000 years which is in agreement with the exxon sea level curve oxygen isotope measurements indicate that the growth of continental ice sheets caused these rapid sea level changes if glaciation caused all the rapid sea level changes in the cretaceous that are indicated by the exxon curve then an antarctic ice sheet may have existed despite overall climatic warmth

a 9 myr cycle in cenozoic δ13c record and long term orbital eccentricity modulation is there a link abstract the 65 myr long cenozoic carbon isotope record 13 c of zachos et al 2001 2008 documents a strong long term cycle with a mean pseudoperiodicity close to 9 myr this cyclicity modulates the 2 4 myr eccentricity cycle amplitude hinting at a possible link between long term astronomical and geological variations some phase shifts between 9 myr 13 c and astronomical cycles suggest that additional processes e g tectonics contribute to these long term carbon cycle variations the strong response of 13 c to long term eccentricity periods 9 myr 2 4 myr 400 kyr supports the hypothesis that the long time residence of carbon in the oceans amplifies lower frequency or dampens higher frequency orbital variations additionally the strong expression of low amplitude 9 myr eccentricity cycle in the 13 c record could be explained by energy transfer process from higher to lower frequency cycles and all eccentricity components modulate the carrier climatic precession cycles finally the paleocene eocene thermal maximum petm 55 9 ma event which corresponds to a pronounced 13 c negative excursion is situated within a strong decrease in the most prominent 9 myr 13 c cycle hinting at a link between accelerated rates in 13 c variations and the petm this specific 9 myr 13 c cycle seems to be amplified by non orbital mechanisms in atmosphere continent ocean system such as previously suggested methane release from gas hydrate and volcanism

sedimentary record of subduction to forearc transition in the rotated eocene basin of western oregon systematic changes in compositions of eocene sandstones in the southern part of the oregon coast range constrain proposed models of tectonic accretion and rotation of this crustal fragment three basic petrofacies of lithic arkosic and volcanolithic composition can be defined sequentially from the base to the top of the section the lithic petrofacies was deposited prior to rotation and was derived from the nearby klamath mountains during collision of the subjacent seamount terrane the transition to arkosic composition coincided with the end of collision and the initiation of forearc basin subsidence the arkosic sands contain muscovite and potassium feldspar derived from a continental plutonic source area their presence in the forearc sequence suggests that the coast range block lay farther to the east and closer to interior parts of the mesozoic batholith belt prior to tectonic rotation volcanolithic sandstones were deposited after rotation of the coast range had begun and they mark the beginning of volcanic activity in the adjacent cascade arc