estimation of model parameters and properties for numerical simulation on geomechanical stability of gas hydrate production in the ulleung basin east sea korea abstract the process of hydrate dissociation and production induced by depressurization incorporates intricate hydraulic thermal and mechanical phenomena thus coupled thermal hydraulic mechanical t h m simulation is critically necessary to evaluate the geomechanical stability of hydrate production in hydrate bearing sediments hbs however methods of estimating the input model parameters and properties of the target reservoir in particular in unconsolidated marine sediments have received limited attention compared to studies on production simulators the t h m properties of the marine sediments change considerably with depth geological strata and soil type of each layer therefore it is important that representative layers and their corresponding t h m properties should be properly estimated to analyze the stability and productivity of methane gas recovery in the field this study provides a comprehensive estimation for the model parameters and properties of unconsolidated marine sediments based on vast data from field seismic surveys and laboratory experimental results with core samples investigates empirical correlations between model parameters and methane hydrate saturation and finally summarizes the estimated model parameters and properties which can possibly be applied to on going numerical research into stability assessment of the pilot gas hydrate gh production test which is soon to be performed in the ulleung basin

cyclostratigraphy and astronomical tuning during the oligocene in the jizhong depression bohai bay basin northeastern china abstract the dongying formation ed and the first member of the shahejie formation es1 in the central raoyang sag cover about 1705 m long sedimentary series of terrestrial lacustrine infill we employed the gamma ray gr log data as a paleoclimatic and paleoenvironmental proxy to conduct the high resolution cyclostratigraphy research in well w33 and w62 prominent sedimentary cycles in decameters and meters were revealed by multi taper mtm power spectra evolutionary fast flourier transformation fft and correlation coefficient analyses in the es1 and ed intervals the 405 kyr long eccentricity 125 kyr and 100 kyr short eccentricity 40 kyr obliquity and 23 kyr precession can be recognized with a wavelength ratio of approximately 20 5 2 1 respectively by tuning the 405 kyr filter output in well w33 to the orbital target curve of la2010d astronomical solution we established an astronomical time scale ats that provided absolute age controls during the oligocene and shed light on the event correlation among isolated depressions in the bohai bay basin sediment accumulation rates sars were derived from the extracted 405 kyr long eccentricity and were tested with an average of 17 cm kyr age boundaries of ng ed1 ed1 ed2 ed2 ed3 ed3 es1 and es1 es2 are 23 03 ma 24 34 ma 25 53 ma 29 05 ma and 33 10 ma respectively based on the ats and sars we discussed the depositional evolution within age boundaries cause of high sars and origin of formation overpressure after the largest lake transgression shallow water deltas and fluvial plains transitionally dominate the central raoyang sag with shallowing water depth thin interlayers of mudstones and sandstones originate from shallow water deltaic systems with low sand to mud ratios under high sars enhanced by mountain uplift and low sand to mud ratios formation overpressure results mainly from high porosities in under compacted mudstone intervals

elasticity of marine sediments rock physics modeling we offer an effective medium model for the elastic moduli of high porosity ocean bottom sediments the elastic constants of the dry sediment frame depend on porosity elastic moduli of the solid phase and effective pressure the model connects two end points in the elastic modulus porosity plane the hertz mindlin modulus of a dense elastic sphere pack at critical porosity and zero at 100 porosity the elastic moduli of saturated sediment are calculated from those of the dry frame using gassmann s equation unlike the suspension model our model assigns non zero elastic constants to the dry sediment frame and can predict the shear wave velocity unlike various modifications of the travel time average equation it is first principle based and contains only physical parameters we justify this model by matching sonic data in shallow marine sediments and in an odp well

probabilistic sequence alignment of stratigraphic records the assessment of age uncertainty in stratigraphically aligned records is a pressing need in paleoceanographic research the alignment of ocean sediment cores is used to develop mutually consistent age models for climate proxies and is often based on the 18o of calcite from benthic foraminifera which records a global ice volume and deep water temperature signal to date 18o alignment has been performed by manual qualitative comparison or by deterministic algorithms here we present a hidden markov model hmm probabilistic algorithm to find 95 confidence bands for 18o alignment this model considers the probability of every possible alignment based on its fit to the 18o data and transition probabilities for sedimentation rate changes obtained from radiocarbon based estimates for 37 cores uncertainty is assessed using a stochastic back trace recursion to sample alignments in exact proportion to their probability we applied the algorithm to align 35 late pleistocene records to a global benthic 18o stack and found that the mean width of 95 confidence intervals varies between 3 and 23 kyr depending on the resolution and noisiness of the record s 18o signal confidence bands within individual cores also vary greatly ranging from 0 to 40 kyr these alignment uncertainty estimates will allow researchers to examine the robustness of their conclusions including the statistical evaluation of lead lag relationships between events observed in different cores

mechanical properties of sand silt and clay containing tetrahydrofuran hydrate 1 the mechanical behavior of hydrate bearing sediments subjected to large strains has relevance for the stability of the seafloor and submarine slopes drilling and coring operations and the analysis of certain small strain properties of these sediments for example seismic velocities this study reports on the results of comprehensive axial compression triaxial tests conducted at up to 1 mpa confining pressure on sand crushed silt precipitated silt and clay specimens with closely controlled concentrations of synthetic hydrate the results show that the stress strain behavior of hydrate bearing sediments is a complex function of particle size confining pressure and hydrate concentration the mechanical properties of hydrate bearing sediments at low hydrate concentration probably 50 of pore space the behaviorbecomesmoreindependentofstressbecausethehydratescontrolbothstiffnessand strength and possibly the dilative tendency of sediments by effectively increasing interparticle coordination cementing particles together and filling the pore space the cementation contribution to the shear strength of hydrate bearing sediments decreases with increasing specific surface of soil minerals the lower the effective confining stress the greater the impact of hydrate formation on normalized strength

estimation of the gas hydrate resource volume in a small area of the ulleung basin east sea using seismic inversion and multi attribute transform techniques we estimated the volume of gas hydrate and in place gas in a small 37 km 58 km area of the ulleung basin east sea from a dense grid of 2 d seismic and logging while drilling lwd data using seismic inversion and multi attribute transform techniques multi attribute transform finds the relationship between any measured or calculated logs and the combination of the seismic attributes and the acoustic impedance computed from inversion we assumed that the bottom simulating reflector marks the base of the gas hydrate stability zone ghsz first the pore space gas hydrate saturation at the wells was estimated from the simplified three phase biot type equation then the porosity and the pore space gas hydrate saturation along the seismic lines were predicted from multi attribute transform the ghsz was divided into ten layers of the equal time thickness the time thickness of each layer was converted into depth using the time depth relationship constructed from seismic to well tie at the wells and gridded at 500 m cell size the average porosity and pore space gas hydrate saturation were computed for each layer and multiplied to obtain the average total gas hydrate saturation which was gridded with the same cell size as the thickness grid thus each 2 d cell is represented by a rock volume and an average total gas hydrate saturation the gas hydrate volume for each cell was computed by the multiplication of the cell rock volume and the average total gas hydrate saturation finally the total gas hydrate volume was computed by summing the gas hydrate volumes of all cells the estimated gas hydrate and in place gas volumes in the study area are about 3 43 109 m3 1 21 1011 ft3 and about 4 50 1011 m3 1 59 1013 ft3 respectively the more conservative estimates excluding the top three layers that comprise about 50 m of the near seafloor sediments where the lwd data are often unreliable are 3 03 109 m3 1 07 1011 ft3 for gas hydrate and about 3 97 1011 m3 1 40 1013 ft3 for gas

quantification of deep time orbital forcing by average spectral misfit quantification of milankovitch orbital cyclicity within ancient strata has become a principal tool for refinement of the geologic time scale however accurate characterization of the orbital signal in deep time paleoclimate records is commonly challenged by inadequate radiometric time constraints for calibration of the spatial rhythms to temporal periods this problem can potentially introduce large errors into derivative orbital timescales in this study we develop a new method for the identification and calibration of orbital cyclicity in cyclostratigraphic records the method average spectral misfit or asm yields an objective estimate of the optimal sedimentation rate for a stratigraphic interval that preserves a record of orbital forcing the technique also provides a formal statistical test for rejecting the null hypothesis no orbital signal application of the method to assess orbital cyclicity in the upper bridge creek limestone member turonian of the western interior basin highlights the utility of this new cyclostratigraphic tool and provides a means to independently evaluate conflicting interpretations of the lithologic cycles importantly asm offers a new consistent standard by which orbital timescales may be compared hence the quality of an orbital timescale can be formally qualified by reporting its average spectral misfit and null hypothesis significance level this technique will permit improvement of mesozoic cenozoic orbital timescales and extension of orbital time scale development into the paleozoic as the method is not dependent upon well constrained radiometric age data

testing astronomically tuned age models astrochronology is fundamental to many paleoclimate studies but a standard statistical test has yet to be established for validating stand alone astronomically tuned time scales those lacking detailed independent time control against their astronomical insolation tuning curves shackleton et al 1995 proposed that the modulation of precession s amplitude by eccentricity can be used as an independent test for the successful tuning of paleoclimate data subsequent studies have demonstrated that eccentricity like amplitude modulation can be artificially generated in random data following astronomical tuning here we introduce a new statistical approach that circumvents the problem of introducing amplitude modulations during tuning and data processing thereby allowing the use of amplitude modulations for astronomical time scale evaluation the method is based upon the use of the hilbert transform to calculate instantaneous amplitude following application of a wide band precession filter and subsequent low pass filtering of the instantaneous amplitude to extract potential eccentricity modulations statistical significance of the results is evaluated using phase randomized surrogates that preserve the power spectrum structure of the data but have randomized amplitude modulations application of the new testing algorithm to two astronomically tuned data sets demonstrates the efficacy of the technique and confirms the presence of astronomical signals additionally it is demonstrated that a minimal tuning approach using at maximum one precession cycle per 100 kyr eccentricity cycle does not introduce systematic frequency modulations even when a narrow band pass filter is applied allowing direct comparison of data amplitudes and orbital eccentricity

application of dynamic programming to the correlation of paleoclimate records 1 signal matching is a powerful tool frequently used in paleoclimate research but it is enormously time consuming when performed by hand previously proposed automatic correlation techniques require very good initial fits to find the correct alignment of two records a new technique presented in this paper utilizes dynamic programming to find the globally optimal alignment of two records geological realism is instilled in the solution through the definition of penalty functions for undesirable behavior such as unlikely changes in accumulation rate examples with synthetic and real data demonstrate that the dynamic programming technique produces accurate high resolution results with much less effort than hand tuning or preexisting automated correlation techniques

insights into a million year scale rhenohercynian carbonate platform evolution through a multi disciplinary approach example of a givetian carbonate record from belgium in this paper we formulate answers to three important questions related to givetian carbonate records and their use for reconstructing million year scale past palaeoenvironmental changes first we provide detailed illustrations of the fascinating diversity that shaped a significant shallow reefal platform during early to late givetian time in the rhenohercynian ocean secondly we improve the sedimentological model of the extensive givetian carbonate platform in the dinant basin and thirdly we evaluate the application of magnetic susceptibility as a tool for long term trend correlations and palaeoenvironmental reconstructions these goals are reached by making a sedimentological geophysical and geochemical study of the la thure section through the early late givetian interval we discerned 18 microfacies ranging from a homoclinal ramp to a discontinuously rimmed shelf and then a drowning shelf the comparison of these sedimentological results with those published for the south of the dinant syncline allowed us to provide an up to date model of the vertical and lateral environmental development of one of the largest givetian carbonate platforms in europe this comparison also increased the knowledge on the distribution of facies belts in the dinant basin and allowed us to highlight the taghanic event palaeoredox proxies reveal a substantial change in the oxygenation level from oxygen depleted to more oxic conditions between middle and late givetian time we demonstrated the relationship between variation in magnetic susceptibility values and proxies for siliciclastic input such as si al the la thure section is considered a key section for the understanding of internal shelf settings bordering laurussia9s southeastern margin

astronomical calibration of the paleocene time the first complete cyclic sedimentary successions for the early paleogene from drilling multiple holes have been retrieved during two odp expeditions leg 198 shatsky rise nw pacific ocean and leg 208 walvis ridge se atlantic ocean these new records allow us to construct a comprehensive astronomically calibrated stratigraphic framework with an unprecedented accuracy for both the atlantic and the pacific oceans covering the entire paleocene epoch based on the identification of the stable long eccentricity cycle 405 kyr high resolution x ray fluorescence xrf core scanner and non destructive core logging data from sites 1209 through 1211 leg 198 and sites 1262 1267 leg 208 are the basis for such a robust chronostratigraphy former investigated marine odp sites 1001 and 1051 and land based e g zumaia sections have been integrated as well the high fidelity chronology is the prerequisite for deciphering mechanisms in relation to prominent transient climatic events as well as completely new insights into greenhouse climate variability in the early paleogene we demonstrate that the paleocene epoch covers 24 long eccentricity cycles we also show that no definite absolute age datums for the k pg boundary or the paleocene eocene thermal maximum petm can be provided by now because of still existing uncertainties in orbital solutions and radiometric dating however we provide two options for tuning of the paleocene which are only offset by 405 kyr our orbitally calibrated integrated leg 208 magnetostratigraphy is used to revise the geomagnetic polarity time scale gpts for chron c29 to c25 we established a high resolution calcareous nannofossil biostratigraphy for the south atlantic which allows a much more detailed relative scaling of stages with biozones the re evaluation of the south atlantic spreading rate model features higher frequent oscillations in spreading rates for magnetochron c28r c27n and c26n

tracking variable sedimentation rates and astronomical forcing in phanerozoic paleoclimate proxy series with evolutionary correlation coefficients and hypothesis testing abstract this paper addresses two fundamental issues in cyclostratigraphy and paleoclimatology identification of astronomical forcing in sequences of stratigraphic cycles and accurate evaluation of variable sedimentation rates the technique presented here considers these issues part of an inverse problem and estimates the product moment correlation coefficient between the power spectra of astronomical solutions and paleoclimate proxy series across a range of test sedimentation rates the number of contributing astronomical parameters in the estimate is also considered our estimation procedure tests the hypothesis that astronomical forcing had a significant impact on proxy records the null hypothesis of no astronomical forcing is evaluated using a monte carlo simulation approach the test is applied using a sliding stratigraphic window to track variable sedimentation rates along the paleoclimate proxy series in a procedure termed ecoco evolutionary correlation coefficient analysis representative models with constant and variable sedimentation rates and pure noise and mixed signal and noise series are evaluated to demonstrate the robustness of the approach the method is then applied to cenozoic mesozoic and paleozoic paleoclimate series the cenozoic case study focuses on a high resolution paleocene eocene iron concentration series from odp site 1262 leg 208 covering the paleocene eocene thermal maximum and eocene thermal maximum 2 events the ecoco time calibrated iron series confirms previous findings of a role for long term astronomical forcing of these eocene events the mesozoic case study applies ecoco to the classic late triassic newark depth rank series of eastern north america the estimated high resolution sedimentation rate map in this case demonstrates a causal link between variations in depositional environment and sedimentation rate finally the paleozoic case study supports the cyclostratigraphic interpretation of a devonian magnetic susceptibility series at la thure belgium and provides new insights into changes of the depositional setting at this location taken together ecoco is a powerful tool for simultaneously evaluating sedimentation rates and astronomical forcing for paleoclimate series throughout the phanerozoic

towards a robust and consistent middle eocene astronomical timescale abstract until now the middle eocene has remained a poorly constrained interval of efforts to produce an astrochronological timescale for the entire cenozoic this has given rise to a so called eocene astronomical timescale gap vandenberghe et al 2012 a high resolution astrochronological calibration for this interval has proven to be difficult to realize mainly because carbonate rich deep marine sequences of this age are scarce in this paper we present records from middle eocene carbonate rich sequences from the north atlantic southeast newfoundland ridge iodp exp 342 sites u1408 and u1410 of which the cyclical sedimentary patterns allow for an orbital calibration of the geologic timescale between 38 and 48 ma these carbonate rich cyclic sediments at sites u1408 and u1410 were deposited as drift deposits and exhibit prominent lithological alternations couplets between greenish nannofossil rich clay and white nannofossil ooze the principal lithological couplet is driven by the obliquity of earth s axial tilt and the intensity of their expression is modulated by a cyclicity of about 173 kyr this cyclicity corresponds to the interference of secular frequencies s3 and s6 related to the precession of nodes of the earth and saturn respectively this 173 kyr obliquity amplitude modulation cycle is exceptionally well recorded in the xrf x ray fluorescence derived ca fe ratio in this work we first demonstrate the stability of the s3 s6 cycles using the latest astronomical solutions results show that this orbital component is stable back to at least 50 ma and can thus serve as a powerful geochronometer in the mid eocene portion of the cenozoic timescale we then exploit this potential by calibrating the geochronology of the recovered middle eocene timescale between magnetic polarity chrons c18n 1n and c21n comparison with previous timescales shows similarities but also notable differences in durations of certain magnetic polarity chrons we present a revision of previous astronomical timescales from the equatorial and south atlantic to overcome the differences between different mid eocene astrochronologies using our new records from the north atlantic combined with existing records from the south atlantic odp site 1263 and hole 702b and equatorial atlantic odp site 1260 we revise the durations of magnetic polarity chrons c18n 1n to c21n thereby arriving at a robust and self consistent closure of the middle eocene astronomical timescale gap

distribution and origin of seismic chimneys associated with gas hydrate using 2d multi channel seismic reflection and well log data in the ulleung basin east sea abstract analysis of multi channel seismic reflection and well log data from the ulleung basin east sea reveals that two distinct types of seismic chimneys have been identified in the basin based on their geometries seismic reflection patterns well log response and lithology type i is a mound like feature with a transparent or chaotic reflection pattern well log interpretation and lithology of this type indicate that type i consists of mobilized homogeneous mud including fracture filling gas hydrate this type is mainly located on the structural highs and is mostly restricted to the pliocene sedimentary succession in contrast type ii is a pipe like feature with vertically stacked distorted reflectors based on well log data and lithology type ii filled with fracture filling gas hydrate without breaking up primary sedimentary structure this type appears along the deep seated fault and mainly developed within the quaternary deposit our primary conclusion is that type i resulted from the subsurface sedimentary remobilization in response to regional uplift in the pliocene whereas type ii resulted from the focused vertical fluid flow through fractures triggered by reactivation of deep seated fault during the quaternary

astronomical forcing of terrestrial climate recorded in the pleistocene of the western tarim basin nw china abstract astronomically forced variations of climate are well documented in lacustrine and marine settings however few studies have examined astronomical forced cycles within quaternary fluvial fan successions to explore whether milankovitch cyclicity might also be present in fluvial fan successions we carried out high resolution gamma ray gr from downhole logging magnetic susceptibility ms rb sr and total organic carbon toc analysis of a core from an 800 m borehole kt11 from the kashgar region in the western tarim basin china spectral analyses of the gr ms and rb sr data reveal cycles with 70 m 30 m and 14 m wavelengths these pertain to relative variations in grain size electron spin resonance esr dating and magnetostratigraphy imply that the cored interval spans the past 1 1 myr this age span constraint coupled with the comparison of the ratios of these cycle wavelengths to expected ratios of milankovitch frequencies suggests that these cycles represent 100 kyr short eccentricity 40 kyr obliquity and 20 kyr precession frequencies respectively we constructed an astronomical time scale ats spanning the past 1 13 myr using the 100 kyr short eccentricity period the average accumulation rate is about 70 cm kyr for this 800 m core succession and the evolutive spectrum emphasizes that long term sedimentation rates were stable we also applied correlation coefficient coco analysis to identify the astronomical forcing thus we conclude that orbitally forced climate change was the main driver of stratigraphic alternations between sand and clay rich intervals in the kashgar region during maxima of the 100 kyr short eccentricity cycles which correspond to interglacial intervals more chemical weathering and increased seasonal runoff delivered a larger amount of relatively coarser grained sediments to the fluvial fan in the kashgar region and vice versa the mid pleistocene transition mpt at ca 0 9 to 0 65 ma is also well recorded in our gr and rb sr data and is characterized by a shift in dominant cycle period from 41 kyr obliquity to 100 kyr eccentricity after 0 65 ma the average toc content decreases whilst rb sr values increase which suggests that there was an increase in regional aridity of the kashgar region in the western tarim basin following the mpt this regional change is synchronous with the trend toward aridification observed throughout central asia

coupled deformation flow analysis for methane hydrate extraction methane hydrate is estimated to be present in substantial amounts below deep sea floors particular scientific and engineering interests that encourage studies of mechanical behaviour of methane hydrate soils include submarine geohazards such as the initiation of marine landslides through hydrate dissociation wellbore stability and estimation of future gas production from wells to study these problems a formulation of a multi physics model of methane hydrate flow coupled to soil deformation is developed by assuming deformable porous media soil matrix that accommodate non movable but dissociable hydrate a two phase flow formulation of water and methane gas is suggested according to darcy s law and capillary pressure law a single phase elastic perfectly plastic constitutive model for hydrate soil sediments based on the concept of effective stress is developed to account for the effect of hydrate saturation on mechanical strength and stiffness the formulation is incorporated into the explicit sch

the astronomical calibration of the givetian middle devonian timescale dinant synclinorium belgium recent advances in radiometric dating result in significant improvements in the geo logical timescale and provide better insight into the timing of various processes and evolutions within the earth s system however no radiometric ages are contained within the givetian con sequently the absolute ages of the givetian stage boundaries as well as the stage s duration remain poorly constrained as an alternative the analysis of sedimentary cycles allows for the esti mation of the duration of this stage we examined the high resolution magnetic susceptibility signals of four givetian outcrops in the givet area for a possible astronomical imprint to fully understand the rates of evolutionary and environmental change all four sections are firmly corre lated and wavelet analyses of the magnetic susceptibility signals reveal the imprint of astronomical eccentricity forcing the highly stable 405 kyr cycles constrain the duration of the givetian stage at 4 35 0 45 myr which is in good agreement with the international chronostratigraphic chart 5 0 myr the studied sections also exhibit an imprint of obliquity suggesting a climatic telecon nection between low and high latitudes the corresponding microfacies curves demonstrate similar astronomical imprint and thereby indicate that the observed 10 5 year scale cyclicity is the result of climatic and environmental change

geotechnical and geophysical properties of deep marine fine grained sediments recovered during the second ulleung basin gas hydrate expedition east sea korea this study investigates the geotechnical and geophysical properties of minimally disturbed fine grained marine sediments recovered during the second ulleung basin gas hydrate expedition ubgh2 east sea korea conventional laboratory geotechnical engineering test methods were used to characterize the sediments from a geotechnical engineering perspective the sediments were mostly uncompacted and classified as highly plastic silty soils according to the unified soil classification system uscs they exhibited high compressibility when subjected to an increase in effective stress or a decrease in pore water pressure low hydraulic conductivities and low coefficient of consolidation or pressure diffusion it is expected that the application of a depressurization method for gas hydrate production at the investigated sites would cause a significant amount of settlement and compaction around the production hole because the shear wave velocity of gas hydrate bearing sediments is much less sensitive to the stress state and is much higher than that of sediments without gas hydrates it is possible to estimate the degree of hydrate saturation from shear wave velocity data measured in gas hydrate bearing sediments in addition the prior presence of gas hydrates in the sediments was verified through a comparison of water content compressibility and electrical resistivity of the sediments

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

characterization of gas hydrate reservoirs by integration of core and log data in the ulleung basin east sea abstract examinations of core and well log data from the second ulleung basin gas hydrate drilling expedition ubgh2 drill sites suggest that sites ubgh2 2 2 and ubgh2 6 have relatively good gas hydrate reservoir quality in terms of individual and total cumulative thicknesses of gas hydrate bearing sand hybs beds in both of the sites core sediments are generally dominated by hemipelagic muds which are intercalated with turbidite sands the turbidite sands are usually thin to medium bedded and mainly consist of well sorted coarse silt to fine sand anomalies in infrared core temperatures and porewater chlorinity data and pressure core measurements indicate that gas hydrate occurrence zones ghoz are present about 68 155 mbsf at site ubgh2 2 2 and 110 155 mbsf at site ubgh2 6 in both the ghoz gas hydrates are preferentially associated with many of the turbidite sands as pore filling type hydrates the hybs identified in the cores from site ubgh2 6 are medium to thick bedded particularly in the lower part of the ghoz and well coincident with significant high excursions in all of the resistivity density and velocity logs gas hydrate saturations in the hybs range from 12 to 79 with an average of 52 based on pore water chlorinity in contrast the hybs from site ubgh2 2 2 are usually thin bedded and show poor correlations with both of the resistivity and velocity logs owing to volume averaging effects of the logging tools on the thin hybs beds gas hydrate saturations in the hybs range from 15 to 65 with an average of 37 based on pore water chlorinity in both of the sites large fluctuations in biogenic opal contents have significant effects on the sediment physical properties resulting in limited usage of gamma ray and density logs in discriminating sand reservoirs

gas hydrate saturations estimated from fractured reservoir at site nghp 01 10 krishna godavari basin india 1 during the indian national gas hydrate program expedition 01 nghp 01 one of the richest marine gas hydrate accumulations was discovered at site nghp 01 10 in the krishna godavari basin the occurrence of concentrated gas hydrate at this site is primarily controlled by the presence of fractures assuming the resistivity of gas hydrate bearing sediments is isotropic the conventional archie analysis using the logging while drilling resistivity log yields gas hydrate saturations greater than 50 as high as 80 of the pore space for the depth interval between 25 and 160 m below seafloor on the other hand gas hydrate saturations estimated from pressure cores from nearby wells were less than 26 of the pore space although intrasite variability may contribute to the difference the primary cause of the saturation difference is attributed to the anisotropic nature of the reservoir due to gas hydrate in high angle fractures archie s law can be used to estimate gas hydrate saturations in anisotropic reservoir with additional information such as elastic velocities to constrain archie cementation parameters m and the saturation exponent n theory indicates that m and n depend on the direction of the measurement relative to fracture orientation as well as depending on gas hydrate saturation by using higher values of m and n in the resistivity analysis for fractured reservoirs the difference between saturation estimates is significantly reduced although a sizable difference remains to better understand the nature of fractured reservoirs wireline p and s wave velocities were also incorporated into the analysis

pliocene pleistocene magneto cyclostratigraphy of iodp site u1499 and implications for climate driven sedimentation in the northern south china sea abstract a high resolution astronomical tuned magnetostratigraphy was obtained from a continuous 333 m succession recovered at international ocean discovery program iodp hole u1499a in the north margin of the south china sea scs during joint legs 367 368 a total of 12 magnetic reversals are identified through the pliocene and pleistocene the cycle analysis of natural gamma ray ngr data shows an average suite of ca 33 m and 8 m wavelengths with lesser 1 5 m cycles which are consistent with the ratios of milankovitch orbital climate oscillations caused by long eccentricity 405 kyr short eccentricity 100 kyr and precession 20 kyr the astronomical tuned magnetostratigraphy correlates with nearly all features of the pliocene pleistocene geomagnetic polarity time scale there was a significant shift to 100 kyr dominated cyclicity at ca 1 3 ma which marks the onset of the mid pleistocene transition during which the influx of the clay component decreased a general enrichment in silt sand influx during the past 0 4 myr was punctuated by surges in coarser grained components lowest ngr during or at the end of each major global glacial event comparison to a high resolution sediment record spanning the pliocene pleistocene on the southern margin of the scs odp site 1143 indicates common intervals of changing rates of sediment accumulation in both regions there are relatively lower rates of sediment accumulation during the late zanclean mid pliocene ca 4 1 to 3 6 ma early gelasian ca 2 5 to 2 0 ma early calabrian ca 1 6 to 1 4 ma and the earliest middle pleistocene ca 0 6 ma the merger of magnetostratigraphy cyclostratigraphy and the ngr record to produce a high resolution profile of bulk sediment accumulation rates and relative clay to sand silt components is a powerful tool and climate proxy to reconstruct the general history of sediment input into the scs and its relationships to east asia monsoon and tectonic evolution

confirmation of a late miocene subchron c4n 2n 1r from the eastern qaidam basin in the ne tibetan plateau

modeling of the influence of gas hydrate content on the electrical properties of porous sediments the geophysical investigation of gas hydrate accumulations within marine sediments and the sediments of permafrost regions suffer from a lack of information on the influence of the hydrate content on the physical sediment properties the estimation of the hydrate content using downhole electrical measurements based on archie s law requires the knowledge of the saturation exponent the saturation exponent is an empirical parameter that includes influences from the internal rock structure such as pore shape connectivity and constrictivity of the pore network and the distribution of the conducting phase based on different models that account for the different morphological forms of gas hydrates found during gas hydrate sampling in various research wells the influence of gas hydrate content on the electrical properties of the hydrate bearing sediment was investigated for all studied forms of hydrate occurrence disseminated in the pore space nodular and layered the saturation exponent depends on the sediment properties and on saturation itself the growth of gas hydrate nodules lenses and layers is a process that is assumed to result in the displacement and compaction of the surrounding sediment because of this change of sediment properties during hydrate generation the saturation exponent for these forms of hydrate occurrence depends strongly on the relationship between porosity and formation resistivity factor expressed in the form of archie s cementation exponent for the case that hydrate occurs disseminated in the pore space and the assumption that capillary effects are important for hydrate generation the saturation exponent depends on grain size and grain size sorting for the parameters chosen for these model calculations the saturation exponent varies between 0 5 and 4 the use of a constant mean value for the saturation exponent of approximately 2 can result in both underestimation and overestimation of the hydrate content

structure of flow over alluvial bedforms an experiment on linking field and laboratory methods this paper presents results of a field study designed to examine the structure of flow over mobile and fixed bedforms in a natural stream and to compare the results with findings of previous laboratory studies within the framework of double time space averaging approach measurements of turbulence were obtained in a small river in illinois usa over a fine spatial grid of sampling points above a mobile sandy bedform and its artificially moulded replica flow structure over the artificial bedform is similar to that observed in laboratory studies but is markedly different from the flow structure over natural bedforms these differences are most pronounced in the roughness sublayer whereas flow in the logarithmic layer over natural and artificial sand waves is fairly similar and exhibits spatial uniformity the double time space averaged distributions of turbulence statistics conform to the multilayer model of flow structure over bedforms mean velocity distributions indicate neither classical flow recirculation nor substantial reduction of velocities in the lee of bedform crests however vertical patterns of turbulence statistics over depth suggest that stacked wakes similar to those observed in laboratory studies exist above the bedforms thus despite the absence of flow separation wake development seems to be induced by the systematic influence of upstream bedforms on the vertical structure of turbulence copyright 2006 john wiley sons ltd

are light dark coupled laminae in lacustrine shale seasonally controlled a case study using astronomical tuning from 42 2 to 45 4 ma in the dongying depression bohai bay basin eastern china abstract as a typical sedimentary structure in fine grained rocks laminae are widely distributed in shales and mudstones in sedimentary basins the shahejie formation 42 2 45 4 ma formed during the eocene of the paleogene in the dongying depression of china is recognized as a typical area to study lacustrine shale according to the composition of different lamina four types of couplets are identified including carbonate clay couplets carbonate organic couplets clay organic couplets and carbonate clay organic triplets all couplets are composed of light and dark layers a combination of core images microscopic observations mineral compositions geochemical data carbon and oxygen isotopes and strontium isotopes verifies that the laminae are primarily developed in a saline and anoxic or even euxinic environment with a high organic matter om flux through astronomical cycle analysis of the natural gamma ray gr curve from sample site well ny1 the data suggest that the lacustrine shale laminae are formed annually with an average duration of 1 34 yr the formation of laminae is affected by the season which is closely related to the seasonal growth and death of algae during the period of algae growth a large number of light colored carbonate laminae are deposited whereas when the algae dies organic matter accumulates at the bottom of lakes and forms dark organic rich laminae the interbedded and lenticular laminae which are subdivided by layering characteristics are primarily affected by diagenesis in postdepositional processes study of the laminae is helpful in understanding the formation process of lacustrine shale and it provides invaluable sources of information for paleoclimate reconstruction

pore fluid chemistry from the second gas hydrate drilling expedition in the ulleung basin ubgh2 source mechanisms and consequences of fluid freshening in the central part of the ulleung basin east sea during the second gas hydrate drilling expedition in the ulleung basin ubgh2 pore fluids were collected from sites that sampled sediments from the continental slope to the basin center and included locations within and outside seismic identified chimney like features at five non chimney sites established during the ubgh2 discrete excursions to low cl concentrations within the gas hydrate occurrence zone ghoz are associated with water enriched in d and 18o as expected from gas hydrate dissociation during core recovery estimates of gas hydrate saturation values sh based on cl and d values are in good agreement and show that when gas hydrate occurs in discrete horizons or within strata bound fractures throughout the ghoz it occupies 5 65 of the pore space fluids recovered from three sites characterized by seismic inferred chimneys show massive hydrate accumulation near the seafloor accompanied by the formation of shallow cl rich brines with d and 18o values lower than seawater chemical and isotopic data from fluids sampled at all drilled sites reveal significant fluid freshening below the gas hydrate stability zone ghsz the distribution of cl k and d indicate that the observed freshening is predominantly caused by clay mineral dehydration illitization previously reported heat flow values in the center of the basin indicate that the sediments deeper than 800 mbsf meter below seafloor are warm enough to expect clay diagenesis with the onset of smectite to illite transformation source fluid temperatures 70 c are confirmed through the use of na li and mg2 li geothermometry based on these observations we propose the following scenario for the evolution of formation fluids in the ulleung basin where high formation temperatures and rapid sedimentation at the basin center led to sediment compaction and clay dehydration reactions that result in fluid overpressures and associated fracturing of the formation sediment fractures and fluid possible gas migration in the chimney features imaged in seismic records are consistent with our postulated upward transport of fluids from 800 m depth though the ghsz and to the seafloor

optimizing significance testing of astronomical forcing in cyclostratigraphy the recognition of astronomically forced milankovitch climate cycles in geological archives marked a major advance in earth science revealing a heartbeat within the climate system of general importance and key utility power spectral analysis is the primary tool used to facilitate identification of astronomical cycles in stratigraphic data but commonly employed methods for testing the statistical significance of relatively high narrow band variance of potential astronomical origin in spectra have been criticized for inadequately balancing the respective probabilities of type i false positive and type ii false negative errors this has led to suggestions that the importance of astronomical forcing in earth history is overstated it can be readily demonstrated however that the imperfect nature of the stratigraphic record and the quasiperiodicity of astronomical cycles sets an upper limit on the attainable significance of astronomical signals optimized significance testing is that which minimizes the combined probability of type i and type ii errors numerical simulations of stratigraphically preserved astronomical signals suggest that optimum significance levels at which to reject a null hypothesis of no astronomical forcing are between 0 01 and 0 001 i e 99 99 9 confidence level this is lower than commonly employed in the literature 90 99 confidence levels nevertheless in consonance with the emergent view from other scientific disciplines fixed value null hypothesis significance testing of power spectra is implicitly ill suited to demonstrating astronomical forcing and the use of spectral analysis remains a difficult and subjective endeavor in the absence of additional supporting evidence

an automatic orbital tuning method for paleoclimate records the recognized linkage of climatic events to the earth s orbital variations has provided the basis for establishing time scales of pleistocene climatic records most of the classic orbital tuning methods developed so far however need visual judgements to add new time control points into the climatic records thus being time consuming and hindering the construction of high resolution climatic time series in this study we propose to use the dynamic optimization method to overcome the shortcomings with this technique the additional time control points can be automatically added into the climatic records and a best age for each of the climatic data can be calculated results of a case study conducted on the baoji loess section show that the automatic orbital tuning method can lead to a much better agreement of climatic time series with theoretical changes in the orbital elements relative to the classic ones

stability of the astronomical frequencies over the earth s history for paleoclimate studies the expected changes over the past 500 million years in the principal astronomical frequencies influencing the earth s climate may be strong enough to be detectable in the geological records and such effects have been inferred in several cases calculations suggest that the shortening of the earth moon distance and of the length of the day back in time induced a shortening of the fundamental periods for the obliquity and climatic precession from 54 to 35 41 to 29 23 to 19 and 19 to 16 thousand years over the last half billion years at the same time the precessional constant increased from 50 to 61 arc seconds per year the changes in the frequencies of the planetary system due to its chaotic motion are much smaller their influence on the changes of the periods of climatic precession obliquity and eccentricity of the earth s orbit around the sun can be neglected eccentricity periods used for quaternary climate studies may therefore be considered to have been more or less constant for pre quaternary times

physical properties of sediments from the ulleung basin east sea results from second ulleung basin gas hydrate drilling expedition east sea korea abstract physical properties including basic index properties undrained shear strength and thermal conductivities were measured on conventional cores retrieved from the ulleung basin during the second ulleung basin gas hydrate expedition ubgh2 the ubgh2 logged 13 sites and cored 10 sites to locate potential sites for an offshore test production a total of 211 conventional cores were recovered undrained shear strength thermal conductivity and index properties including porosity and grain density were measured onboard mineral composition analyses and grain size analyses were completed onshore after the expedition the averaged porosity at each site ranges from 65 to 71 the averaged grain density at each site ranges from 2 57 to 2 66 g cm3 and the mean grain size mostly lies between 4 m and 25 m with sparsely scattered coarse grained intervals the relatively high porosity and low grain density are due to the large portion of diatomaceous sediments the thermal conductivities average around 0 8 w mk and the low porosity and the abundance of clay mineral and oapl a may have caused the relatively low thermal conductivity in the ulleung basin the geomechanical analyses revealed a few relevant findings important for sediment physical behaviors during gas hydrate production the particle migration in coarse grained layers during production necessitates proper measure for sand productions while fine grained layers are mostly self filtering the vertical deformation estimated from the compression index suggested that the subsidence induced by the pore pressure change from the depressurization is much higher than those induced by the lost of gas hydrate particles from dissociation massive vertical deformation in fine grained layers has been predicted to occur due to the pore pressure change from depressurization induced gas hydrate production the drilling mud weight induced pressure window is mostly determined by the water depth in deep sea drilling but caution should be taken in determination of fracture pressures in hydrate bearing sediments because gas hydrate saturations alter poisson s ratio

astronomical forcing and sedimentary noise modeling of lake level changes in the paleogene dongpu depression of north china abstract challenges in interpreting continental sequence stratigraphy and typically uncertain geochronology hinder the understanding of paleolake evolution and hydrocarbon exploration in terrestrial basins the dongpu depression in north china is a lacustrine basin with abundant hydrocarbon resources an accurate chronology for the paleogene stratigraphy in the dongpu depression is lacking and the mechanism of lake level variation remains unclear in this study we utilize high resolution gamma ray logs to conduct a cyclostratigraphic analysis of the shahejie formation which is a paleogene succession in the dongpu depression characterized by sandstones and dark mudstones interbedded with thin salt rocks time series analysis reveals evidence for 405 kyr eccentricity cycles in the gamma ray series which is supported by statistical modeling of optimal sedimentation rates tuning of the gamma ray data to this 405 kyr eccentricity cyclicity enables a 14 7 myr long astronomical time scale to be constructed this astrochronology is anchored to the astronomical age of the dongying formation shahejie formation boundary 28 86 ma in the bohai bay basin thus providing an absolute timescale for the studied interval that extends from 28 86 ma to 43 59 ma using this anchored astrochronology we show that a recently established sedimentary noise model for inferring sea level change in marginal marine settings can be used to similarly infer lake level fluctuations in terrestrial basins in particular sedimentary noise modeling of the tuned gamma ray series reveals high resolution changes in sedimentary noise that are indicative of lake level variations linked to million year scale i e 4 8 myr 2 4 myr and 1 2 myr astronomical forcing these inferred changes in lake level are supported by previously published sequence stratigraphic interpretations moreover an evolutionary correlation coefficient ecoco analysis of the gamma ray series also indicates recurrent distortions in sedimentation that may be linked to lake level changes this study provides new methods for the assessment of paleolake level variations as well as insights into the connection between astronomical forcing and lake evolution across long timescales in terrestrial basins

stress dependent and strength properties of gas hydrate bearing marine sediments from the ulleung basin east sea korea abstract this paper presents a comprehensive laboratory experimental characterization of the host sediment from natural hydrate bearing sediments recovered during the ulleung basin gas hydrate expedition 2 ubgh2 in 2010 the basic geotechnical properties are characterized and compared with previously reported data the mineralogy and microstructure analyses confirm that the sediments mainly consist of illite kaolinite chlorite calcite and montmorillonite with a high concentration of microfossils diatoms the presence of microfossils may affect many of the geotechnical properties including plasticity activity specific surface and grain size the tested specimens have a relatively high initial void ratio with a high compression index e g cc ranging from 0 6 to 1 0 and swelling index e g cs ranging from 0 1 to 0 25 the shear wave velocities measured during loading indicate a high sensitivity to the stress state which demonstrates the critical role of effective stress in controlling the stiffness of the sediments the peak friction angles are determined to be 17 6 24 6 for clay and silt sediments and 27 1 for high sand fraction specimens the stress dependent and strength parameters obtained in this study may be very useful for performing stability analyses during hydrate dissociation and production

obliquity forced climate during the early triassic hothouse in china the start of the mesozoic era is marked by roughly 5 m y of earth system upheavals including unstable biotic recovery repeated global warming ocean anoxia and perturbations in the global carbon cycle intervals between crises were comparably hospitable to life the causes of these upheavals are unknown but are thought to be linked to recurrent siberian volcanism here two marine sedimentary successions at chaohu and daxiakou south china are evaluated for paleoclimate change from astronomical forcing in these sections gamma ray variations indicative of terrestrial weathering reveal enhanced obliquity cycling over prolonged intervals characterized by a 32 8 k y periodicity with strong 1 2 m y modulations these suggest a 22 h length of day and 1 2 m y interaction between the orbital inclinations of earth and mars comparing the 1 2 m y obliquity modulation cycles in these sections with early triassic records of global sea level temperature redox and biotic evolution suggests that long term astronomical forcing was involved in the repeated climatic and biotic upheavals that took place throughout the early triassic

physical properties and micro and macro structures of gassy sediments in the inner shelf of se korea abstract in order to characterize physical properties and sediment structure micro and macro structures for gassy sediments from the southeastern inner shelf of korea physical property measurements and sediment structure analysis for two sediment cores were carried out one core sg12 pc4 was collected from gassy sediments and the other core sg12 pc10 was obtained from gas free sediments the micro and macro structures for the gassy core were investigated using x ray computed tomography ct scanning and soft x radiography in addition scanning electron microscope sem photomicrographs were used for understanding the clay fabric in the gassy sediments wet bulk density and porosity for both gassy sediments and gas free sediments are characterized by a general trend caused by compaction with burial depth on the other hand the velocity shows different patterns in both burial depth and the correlation between velocity and other physical properties thus the gas plays an important role in the control of velocity in the gassy sediments this is clearly seen in the relationship between characteristic ct images and low velocity in the depth intervals characterized by gas and or degassing cracks in addition shear strength measurements for gassy sediments have lower values than gas free sediments due to the weak bond between clay particles caused by gas and or degassing this suggests that original clay microstructure could be rearranged due to forces that gas exerts on clay particles from ct images of both cross section and top views we may estimate possible conduits of gas migration within the gas charged interval using sem photomicrographs the various traces e g displacement of clay particles oval shape depressions created by the escape of gas bubbles were identified on the images therefore the presence of gas in marine sediments may control not only the variation of physical properties e g velocity shear strength but also the arrangement of clay particles

the evaluation of eccentricity related amplitude modulation and bundling in paleoclimate data an inverse approach for astrochronologic testing and time scale optimization cyclostratigraphic analysis has produced fundamental advancements in our understanding of climate change paleoceanography celestial mechanics geochronology and chronostratigraphy of central importance to this success has been the development of astrochronologic testing methods for the evaluation of astronomical climate influence on sedimentation most pre pleistocene astrochronologic testing methods fall into one of two categories 1 those that test for expected amplitude or frequency modulation imposed by an astronomical signal or 2 those that test for bedding hierarchies frequency ratios or bundling that are predicted by the dominant astronomical periods in this study a statistical methodology for combining these complementary approaches is developed which identifies the time scale that simultaneously optimizes eccentricity amplitude modulation of the precession band and the concentration of power at precession carrier and eccentricity modulator frequencies the technique is demonstrated to have high statistical power it is capable of identifying astronomical cycles when present under a wide range of conditions and its application to synthetic models illuminates a range of potential pitfalls that are encountered when more conventional nonoptimization approaches are used the method is also independent from the interpretation of power spectrum peak significance resolving previous concerns regarding appropriate confidence level assessment and multiple testing as two case studies the algorithm is applied to miocene strata of ocean drilling program odp site 926b and the paleocene eocene thermal maximum eocene thermal maximum 2 interval at odp site 1262 the results verify published cyclostratigraphic interpretations and support the theoretical astronomical solutions this new astrochronologic testing approach can be used to evaluate cyclostratigraphic records spanning the phanerozoic and potentially beyond

critical state soil constitutive model for methane hydrate soil 1 this paper presents a new constitutive model that simulates the mechanical behavior of methane hydrate bearing soil based on the concept of critical state soil mechanics referred to as the methane hydrate critical state mhcs model methane hydrate bearing soil is under certain geological conditions known to exhibit greater stiffness strength and dilatancy which are often observed in dense soils and also in bonded soils such as cemented soil and unsaturated soil those soils tend to show greater resistance to compressive deformation but the tendency disappears when the soil is excessively compressed or the bonds are destroyed due to shearing the proposed model represents these features by introducing five extra model parameters to the conventional critical state model it is found that for an accurate prediction of ground settlement volumetric yielding plays an important role when hydrate soil undergoes a significant change in effective stresses and hydrate saturation which are expected during depressurization for methane gas recovery

cycle calibrated magnetostratigraphy of middle carnian from south china implications for late triassic time scale and termination of the yangtze platform abstract thick successions from the margins of the triassic yangtze platform of the south china block record a transition from carbonate rich facies zhuganpo formation and equivalents to clastic rich facies xiaowa formation and equivalents during the carnian early late triassic that mark the final phase of termination of this long lived platform cyclostratigraphy derived from spectral gamma ray sgr intensity curves was combined with magnetostratigraphy of two sections in guizhou province wayao transect and its upward extension into the geopark wayao in guanling county and the laishike section in zhenfeng county and one location in sichuan province hanwang section the cyclostratigraphy from all the guizhou sections indicates a persistent suite of ca 34 m 9 m and 1 8 m cycles which are consistent with the ratios of orbital climate oscillations caused by long eccentricity 405 kyr short eccentricity 100 kyr and precession 20 kyr the magnetostratigraphy of all sections is consistent with the cyclicity and characteristic sgr features thereby enabling a cycle tuned magnetic polarity scale spanning 2 4 myr the main feature is a 1 3 myr interval of reversed polarity containing brief normal polarity subchrons and this reversed polarity chron appears to correspond to the significant reversed polarity dominated interval spanning the upper half of the trachyceras aonoides through the lower half of the austrotrachyceras austriacum ammonoid zones of the upper julian the lower substage of carnian this magnetostratigraphic correlation implies that the termination of the yangtze platform is coeval with the beginning of the mid carnian episode of climatic disruption in europe which is locally called the carnian pluvial event or wet intermezzo and with the temporary cessation of the platform carbonates in the dolomites the cycle scaled magnetic polarity time scale supports the short tuvalian long norian age model of the late triassic in which the base of the cycle tuned polarity pattern from the newark group of eastern north america is younger than the end of the julian substage

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

thermal conductivity of methane hydrate bearing ulleung basin marine sediments laboratory testing and numerical evaluation the thermal conductivity of gas hydrate bearing sediments is a key parameter used to evaluate the heat transfer process relevant to phase transformation during gas hydrate production and to assess heat flux properties within the hydrate stability zone relatively few thermal conductivity values for in situ hydrate bearing sediments and laboratory hydrate bearing sediments have been reported for under saturated conditions with vertical effective stress in this study we used sandy sediments obtained during the ulleung basin gas hydrate expedition 2 ubgh2 expedition in korea to synthesize methane hydrate bearing sediments with saline pore fluid the transient plane source method was implemented to measure the thermal conductivity of specimens with variable gas hydrate saturations the measured thermal conductivity was 1 47 w m k and was independent of hydrate saturation results from additional tests of ice and water unsaturated sediments were also compared to our findings both geometric mean and 3d thermal network models corroborated the experimentally measured thermal conductivities assuming expected physical properties

seeing red in cyclic stratigraphy spectral noise estimation for astrochronology 1 fundamental to the development of astronomical time scales is the recognition of oscillatory variability within stratigraphic data and its evaluation relative to a null noise hypothesis in this study monte carlo simulations are used to investigate the suitability of two commonly used noise hypotheses the conventional and robust ar1 approaches and the results highlight important limitations in both for cyclostratigraphic application perhaps most problematic the robust ar1 method can result in inflated confidence level estimates and excessive clumping of false positives within the low frequency portion of the spectrum especially when the underlying noise process has a high lag 1 autocorrelation given typical cyclostratigraphic records this technique will often impose significant eccentricity band variability even in the case of pure ar1 noise an alternative spectral noise estimation method is proposed to overcome these problems which simultaneously allows for departures from the ar1 assumption and obtains high statistical power that is the ability to accurately identify astronomical signals when they are present in the data we apply the method to un tuned 18o data from miocene sediments of the ceara rise indicating statistically significant spectral power at frequencies that are consistent with the published orbital interpretation of weedon et al 1997 furthermore evaluation of the frequency arrangement of the significant spatial bedding periods using the average spectral misfit method for astrochronologic testing reveals that the null hypothesis of no orbital influence can be rejected with a high degree of confidence the 99 8 confidence level

astronomical tuning of the end permian extinction and the early triassic epoch of south china and germany abstract the timing of the end permian mass extinction and subsequent prolonged recovery during the early triassic epoch can be established from astronomically controlled climate cycles recorded in continuous marine sedimentary sections astronomical cycle tuning of spectral gamma ray logs from biostratigraphically constrained cyclic stratigraphy through marine sections at meishan chaohu daxiakou and guandao in south china yields an integrated time scale for the early triassic which is consistent with scaling of magnetostratigraphy from climatic cycles in continental deposits of the germanic basin the main marine mass extinction interval at meishan is constrained to less than 40 of a 100 kyr kilo year cycle i e c 13 is estimated to have lasted c 13 from 2 to 4 across the smithian spathian boundary at chaohu was completed in 50 kyr the earliest marine reptiles in the mesozoic at chaohu that are considered to represent a significant recovery of marine ecosystems did not appear until 4 7 myr million years after the end permian extinction the durations of the griesbachian dienerian smithian and spathian substages including the uncertainty in placement of widely used conodont biostratigraphic datums for their boundaries are 1 4 0 1 0 6 0 1 1 7 0 1 and 1 4 0 1 myr implying a total span for the early triassic of 5 1 0 1 myr therefore relative to an assigned 251 902 0 024 ma for the permian triassic boundary from the meishan gssp the ages for these substage boundaries are 250 5 0 1 ma for base dienerian 249 9 0 1 ma for base smithian base of olenekian stage 248 2 0 1 ma for base spathian and 246 8 0 1 ma for the base of the anisian stage this astronomical calibrated timescale provides rates for the recurrent carbon isotope excursions and for trends in sedimentation accumulation through the early triassic of studied sections in south china

astrochronology of the anisian stage middle triassic at the guandao reference section south china abstract a high precision global timescale for the early and middle triassic is the key to understanding the nature pattern and rates of biotic recovery following the end permian mass extinction the guandao section of guizhou province of south china is an important reference section for the magnetic polarity pattern conodont datums geochemical anomalies and interpreted temperature history through the anisian middle triassic we analyzed the high resolution gamma ray and magnetic susceptibility series from the complete anisian stage intensity variations are indicative of fluctuating terrestrial clay influxes showing strong signals that match predicted astronomical solutions for eccentricity and precession astronomical tuning of these series to interpreted 405 kyr long eccentricity cycles yields a 5 3 myr duration for the anisian at guandao when combined with the astrochronology of the early triassic then the projected age of the anisian ladinian boundary relative to the base triassic date of 251 9 ma is 241 5 0 1 ma this provides a 10 myr reference timescale for other key geological events including conodont zones geomagnetic polarity chrons rates of marine carbon and oxygen isotope excursions and global sea level changes that were associated with the repeated biotic crises and recovery episodes after the end permian mass extinction the middle anisian humid phase in ca 244 244 5 ma was probably a global event which may have been linked to the middle anisian warming event and sea level change sea level fluctuations at guandao generally correlate with those in western tethyan and boreal regions in time confirming sea level changes during the anisian were of eustatic origin

cyclic late katian through hirnantian glacioeustasy and its control of the development of the organic rich wufeng and longmaxi shales south china abstract deposition of the organic rich shales of the wufeng and lowermost longmaxi formations late katian through hirnantian occurred in a relatively stable tectonic setting and commenced at approximately 4 5 myr prior to the end ordovician glacial maximum these organic rich shales are important because they provide a continuous sedimentary record of high frequency eustatic changes associated with ice sheet expansion and shrinkage here we carried out a high resolution cyclostratigraphic study of fe3 series and associated geochemical analysis of the wufeng and lowermost longmaxi shales in order to better understand sea level cyclicity in the late katian through hirnantian ocean the organic rich shales deposited during this interval in the ehd1 drill core yichang china record four major myr scale eustatic cycles which were associated with third order sea level fluctuations within each of these major cycles 3 4 minor eustatic cycles corresponding to 405 kyr long eccentricity astronomical cycles were recognized and representing fourth order eustatic changes the cyclostratigraphic age of this study is generally in agreement with the radiometric dates in gts2012 although the duration of the hirnantian stage is 0 5 myr longer than previously thought this study also infers glacial controls on the depositional environment of the organic rich shales as enhanced cooling triggered ice sheet expansion and concurrent sea level fall leading to higher thermohaline circulation intensity and enhanced paleoproductivity through upwelling and terrestrial influx in contrast warming intervals led to ice sheet shrinkage and concurrent deepening characterized by water column stratification and reduced nutrient supply the results provide evidence in support of continuous continental glaciation in the late katian through hirnantian

astronomical time scale of the paleogene lacustrine paleoclimate record from the nanxiang basin central china abstract the chronostratigraphy of the paleogene succession of the nanxiang basin a petroliferous basin in central china with a predominantly lacustrine fill remains controversial due to the lack of an accurate geological time scale in this work high resolution gamma ray gr logs from the b270 and bs1 boreholes from depocenters in the biyang depression of the nanxiang basin were used to analyze the cyclostratigraphy paleocene floodplain facies of red clastics and purple mudstone is conformably overlain by eocene through oligocene lacustrine facies of gray mudstone oil shale and clayey dolomite interbedded with siltstone sandstone the multitaper method of spectral analysis and gaussian bandpass filtering were used to identify milankovitch cycles based on the recognition of 405 kyr long eccentricity cycles the series was tuned to establish a 46 myr floating astronomical time scale ats which was then anchored to the paleogene neogene boundary age of 23 03 ma the ats enables the assignment of the ages to non marine biozones depositional facies and rifting episodes within the nanxiang basin the subsidence and rates of sediment accumulation within the rift basin of the nanxiang basin has an inverse relationship to the convergence rates between pacific plates and the eastern margin of eurasia the middle eocene slowing of the convergence rate at 50 ma coupled with the onset of the collision of the indian and eurasian plate corresponds to the beginning of the climax stage of rifting the development of deep lakes and the deposition of oil shales in the nanxiang basin the organic rich 3rd member of the hetaoyuan formation eh3 during this middle eocene interval preserved a range of climatic cycles from annual varves to a 1 2 myr modulation of obliquity cycles indicating the importance of climatic oscillations on the development of those hydrocarbon source rocks

solar system chaos and the paleocene eocene boundary age constrained by geology and astronomy astronomical calculations reveal the solar system s dynamical evolution including its chaoticity and represent the backbone of cyclostratigraphy and astrochronology an absolute fully calibrated astronomical time scale has hitherto been hampered beyond 50 million years before the present ma because orbital calculations disagree before that age here we present geologic data and a new astronomical solution zb18a showing exceptional agreement from 58 to 53 ma we provide a new absolute astrochronology up to 58 ma and a new paleocene eocene boundary age 56 01 0 05 ma we show that the paleocene eocene thermal maximum petm onset occurred near a 405 thousand year kyr eccentricity maximum suggesting an orbital trigger we also provide an independent petm duration 170 30 kyr from onset to recovery inflection our astronomical solution requires a chaotic resonance transition at 50 ma in the solar system s fundamental frequencies

improving gas hydrate saturation estimates using p wave velocity log data by incorporating xrd data for detailed matrix mineralogy definition logging while drilling lwd and wire line wl velocity data from the second korean ulleung basin gas hydrate drilling expedition in 2010 ubgh2 were used to predict gas hydrate saturations using the effective medium theory emt at four representative sites we used sites ubgh2 10 and ubgh2 6 where gas hydrate occurs mostly within strata bound sandy turbidite layers sites ubgh2 2 1 and ubgh2 2 2 are used to investigate a typical cold vent setting and fracture dominated systems we first use a new technique to correct the lwd velocity data within the shallower portions of the borehole typically upper 60 100 m below seafloor mbsf where the nature of soft sediments often results in erroneous low velocity readings of the lwd tool around values between 1350 m s and 1400 m s using the vertical seismic profile vsp data a smooth background velocity trend is defined onto which the lwd data is projected after this correction the lwd velocity data of all four sites were used to estimate gas hydrate saturation values using the emt for a 2 phase mineral assemblage of 90 clay and 10 quartz only as well as a detailed mineralogy based on the core xrd data both these estimates are then compared to the estimates from the electrical resistivity data using an empirical archie analysis the results from emt and archie are on average the same when gas hydrate occurs as a pore filling medium within thick sediment layers of homogenous nature such as that encountered at site ubgh2 10 where saturations are about 60 of the pore space in an interval of 124 128 mbsf if gas hydrate occurs in thin sand layers where the thickness of the layer is at or smaller than the vertical resolution of the velocity logging tool archie based results are higher than the emt based results due to the higher resolution of the resistivity logging tool in cold vent settings with fracture dominated gas hydrate settings such as that investigated at sites ubgh2 2 1 and 2 2 2 archie based results are non reliable and strongly over estimated due to the anisotropic effect of near vertical hydrate filled fractures in such cold vent settings velocity based techniques using the emt are the preferred method to estimate the gas hydrate saturations at site ubgh2 2 1 hydrate saturations are on average 5 10 of the pore space and even lower at site ubgh2 2 2 less than 5 on average

paleoclimate proxies for cyclostratigraphy comparative analysis using a lower triassic marine section in south china abstract multiple proxies for paleoclimatic and paleoenvironmental change within sedimentary sequences have been developed but understanding their relationships and their relative strengths or weaknesses are required to access a wealth of untapped paleoclimate information we propose two main criteria for multiple proxy datasets to estimate their individual signal to noise levels and to decipher the relationship between multiple proxies first for proxies affected by similar processes then their time dependent changes should be similar second a paleoclimate proxy that is more sensitive to an external forcing such as astronomical forcing is more useful than those that do not have such a response we introduce two methods to evaluate these criteria 1 hierarchical cluster analysis hca probes the relationships among multiple proxies based on similarities of their oscillation patterns and 2 power decomposition analysis pda tests proxy sensitivity to external climate forcing we evaluate 16 high resolution paleoclimate proxies in detail for their applications in paleoclimatology from the marine lower triassic daye formation at the daxiakou section in the three gorges region of south china which has carbonate claystone cycles deposited on an outer ramp the proxies are spectral gamma ray gamma ray intensity potassium uranium thorium thorium uranium and thorium potassium rock color lightness l redness a and yellowness b magnetic susceptibility measured in both laboratory and outcrop anhysteretic remanent magnetization arm lithologic rank simplified lithologic rank and non carbonate fraction carbonate thickness and couplet thickness hierarchical cluster analysis hca gathers these proxies into groups likely affected by the same process the arm and thorium uranium proxies seem to reflect the hinterland weathering process during the early triassic gamma ray potassium uranium thorium magnetic susceptibility and non carbonate fraction proxies refer to terrestrial input the l a and lithologic rank proxies indicate the productivity the redox state and the relative sea level respectively at this section this case study contributes to the understanding of the sensitivity of these types of proxies within marine strata for deep time paleoclimate and astronomical tuned time scales

elastic wave velocity in marine sediments with gas hydrates effective medium modeling we offer a first principle based effective medium model for elastic wave velocity in unconsolidated high porosity ocean bottom sediments containing gas hydrate the dry sediment frame elastic constants depend on porosity elastic moduli of the solid phase and effective pressure elastic moduli of saturated sediment are calculated from those of the dry frame using gassmann s equation to model the effect of gas hydrate on sediment elastic moduli we use two separate assumptions a hydrate modifies the pore fluid elastic properties without affecting the frame b hydrate becomes a component of the solid phase modifying the elasticity of the frame the goal of the modeling is to predict the amount of hydrate in sediments from sonic or seismic velocity data we apply the model to sonic and vsp data from odp hole 995 and obtain hydrate concentration estimates from assumption b consistent with estimates obtained from resistivity chlorinity and evolved gas data

a depth derived pleistocene age model uncertainty estimates sedimentation variability and nonlinear climate change 1 a new chronology of glaciation spanning the last 780 000 years is estimated from 21 marine sediment cores using depth as a proxy for time to avoid biasing this depth derived age estimate the depth scale is first corrected for the effects of sediment compaction to provide age uncertainty estimates the spatial and temporal variability of marine sediment accumulation rates are estimated and modeled as an autocorrelated stochastic process depth derived ages are estimated to be accurate to within 9000 years and within this uncertainty are consistent with the orbitally tuned age estimates nonetheless the remaining differences between the depth and orbitally tuned chronologies produce important differences in the spectral domain from the 18o record using the depth derived ages we infer that there are weak nonlinearities involving the 100 kyr and obliquity frequency bands which generate interaction bands at sum and difference frequencies if an orbitally tuned age model is instead applied these interactions are suppressed with the system appearing more nearly linear

time scale controversy accurate orbital calibration of the early paleogene 1 timing is crucial to understanding the causes and consequences of events in earth history the calibration of geological time relies heavily on the accuracy of radioisotopic and astronomical dating uncertainties in the computations of earth s orbital parameters and in radioisotopic dating have hampered the construction of a reliable astronomically calibrated time scale beyond 40 ma attempts to construct a robust astronomically tuned time scale for the early paleogene by integrating radioisotopic and astronomical dating are only partially consistent here using the new la2010 and la2011 orbital solutions we present the first accurate astronomically calibrated time scale for the early paleogene 47 65 ma uniquely based on astronomical tuning and thus independent of the radioisotopic determination of the fish canyon standard comparison with geological data confirms the stability of the new la2011 solution back to 54 ma subsequent anchoring of floating chronologies to the la2011 solution using the very long eccentricity nodes provides an absolute age of 55 530 0 05 ma for the onset of the paleocene eocene thermal maximum petm 54 850 0 05 ma for the early eocene ash 17 and 65 250 0 06 ma for the k pg boundary the new astrochronology presented here indicates that the intercalibration and synchronization of u pb and 40ar 39ar radioisotopic geochronology is much more challenging than previously thought

physical properties of hydrate bearing sediments 1 methane gas hydrates crystalline inclusion compounds formed from methane and water are found in marine continental margin and permafrost sediments worldwide this article reviews the current understanding of phenomena involved in gas hydrate formation and the physical properties of hydrate bearing sediments formation phenomena include pore scale habit solubility spatial variability and host sediment aggregate properties physical properties include thermal properties permeability electrical conductivity and permittivity small strain elastic p and s wave velocities shear strength and volume changes resulting from hydrate dissociation the magnitudes and interdependencies of these properties are critically important for predicting and quantifying macroscale responses of hydrate bearing sediments to changes in mechanical thermal or chemical boundary conditions these predictions are vital for mitigating borehole local and regional slope stability hazards optimizing recovery techniques for extracting methane from hydrate bearing sediments or sequestering carbon dioxide in gas hydrate and evaluating the role of gas hydrate in the global carbon cycle

astronomical forcing of middle permian terrestrial climate recorded in a large paleolake in northwestern china abstract geological records of milankovitch cycles provide a temporal framework for reconstructing earth climate evolution and mapping out the history of the ancient solar system understanding the fundamental celestial mechanics driving astronomical rhythms during the permian period from stratigraphic record is challenging because of the inherent limitations of astronomical solutions the chaotic nature of solar system motion and the paucity of cyclostratigraphic studies of geological records the junggar and adjacent basins of northwestern china constituted a large tectonic lake in the middle permian which deposited one of the thickest and richest petroleum source rock intervals in the world constructing an accurate timescale for the permian junggar basin is critical to understand the processes that controlled organic carbon burial as well as paleoclimatic and paleoenvironmental background conditions in this study detailed spectral analyses of natural gamma ray ngr data were performed on the lacustrine muddy dominated lucaogou formation from five exploitation wells the results reveal significant meter scale sedimentary cycles of 37 8 m 10 7 10 m 3 85 3 2 m and 2 0 1 58 m reflecting oscillations in lithologies variations in changing clay content within the mudstone sandstone and dolomite these cycle wavelength ratios match well with those of the milankovitch cycles predicted for middle permian period the depositional duration of the lucaogou formation was estimated at 3 myr correlation of the 1 2 myr obliquity modulation cycles among the ngr logs sedimentation rates and lake levels of the junggar basin as well as with the middle permian global sea level suggests that long term astronomical grand cycles tightly forced climatic and sedimentary processes throughout the lucaogou formation according to two independent approaches we reconstruct middle permian astronomical parameters earth precession constant k and fundamental frequencies terms gi i 1 2 3 4 5 and calculate astronomical periods eccentricity obliquity and precession these results document astronomical forcing of paleozoic lake systems constrain earth moon orbital evolution and refine the fundamental astronomical frequencies of the solar system during the middle permian

orbital tuning as an inverse problem chronology of the early aptian oceanic anoxic event 1a selli level in the cismon apticore 1 orbital tuning the process of fitting sedimentary cycles to orbital periodicities can estimate with high resolution the timing and duration of key events in the geological record we formulate here orbital tuning as the inverse problem of finding the variation in sedimentation rate that matches sediment cycles with orbital periodicities instead of obtaining a single best estimate we apply a bayesian formulation and define a probability distribution of sedimentation rate variations that result in powerful orbital periodicities by sampling this distribution with a monte carlo method we quantify the uncertainty in the inferred sedimentation rates due to uncertainties in the tuning periods and to components of the sedimentary signal that are unrelated to orbital cycles the method is applied to the chronology of a 30 m interval in the cismon apticore borehole southern alps italy that includes the early aptian oceanic anoxic event 1a selli level estimated to last 1 11 0 11 ma 95 interval the 13c record shows a sudden negative shift of about 1 at the base of the selli level 22 47 ka followed by a recovery to preshift values in 240 ka consistent with a scenario where light carbon is quickly added and then flushed out of the ocean atmosphere system

new perspectives on orbitally forced stratigraphy this survey of the current status of research into earth s orbitally forced paleoclimatic record summarizes recent developments in the theory of earth s orbital parameters and reviews how various techniques of data collection and analysis have fared in the search and recovery of orbital signals in ancient stratigraphy the emerging significance of the quasi periodicity of earth s orbital variations as a prin cipal tool in the analysis of orbitally forced stratigraphy is discussed in detail five case studies are presented that illustrate new directions in research a time series analysis of discontinuous strata b measurement of ultra high resolution stratigraphic signals c new perspectives on the 100 kyr pleistocene glaciation problem d strati graphic evidence for solar system resonance modes and e evaluating phanerozoic length of day from orbitally forced stratigraphy the study of how earth s orbital parameters came to be recorded in ancient stra tigraphy has recently moved into a new phase of scientific inquiry and discovery notable advances in celestial mechanics and in the analysis of stratigraphic data have given rise to new ways of solving old problems and have uncovered new problems for the first time new tools have facilitated the recovery of extended high resolution orbital signals from stratigraphy advanced analytical techniques have now been fully incorporated into the field an updated theory of earth s orbital parameters provides an accurate ephemeris for the past 16 million years for precision correlation between earth s orbital parameters and orbitally forced stratigraphy some orbital eccentricity modes can be used for orbital stratal cal ibrations to several hundred million years ago these breakthroughs have transformed the study of orbitally forced stratigra phy into an applied field that addresses long standing problems in disciplines as far ranging as geochronology geodynamics and astrodynamics orbital signals provide the framework for a high resolution orbital chronostratigraphy as far back