palaeoclimate aptian mystery solved the volcanic eruption that created the ontong java plateau released large quantities of carbon dioxide a reconstruction of co2 concentrations suggests that the eruption promoted climate change and the expansion of ocean anoxia

cyclostratigraphic and δ13c record of the lower cretaceous adriatic platform croatia assessment of milankovitch forcing abstract the 700 m thick hauterivian to albian section from the interior of the large adriatic platform is exposed on mljet and korcula islands croatia the cyclic platform consists of meter scale parasequences bundled into parasequence sets superbundles and then into breccia bounded depositional sequences spectral analysis of time series cycle number vs cycle thickness shows peaks in the short term eccentricity 95 to 130 kyr bands and 160 to 200 kyr bands isotope samples from micrite matrix of mudstone and wackestone have 13c values generally from 1 5 to 2 vpdb and 18o from 1 to 3 5 vpdb adriatic platform 13c values are shifted 2 vpdb more negative than marine pelagic values a 13c and 18o meteoric signal is limited to just beneath sequence boundaries suggesting that the isotopic shift is due mainly to marine phreatic and synorogenic burial diagenesis major excursions on the 5 point smoothed 13c profile of the adriatic platform tied biostratigraphically to 13c curves from pelagic sections include the oceanic anoxic events oae1a 1b and 1c time series constructed from 13c values unsmoothed data vs stratigraphic position show peaks in the milankovitch band especially short term eccentricity most positive peaks are near parasequence set boundaries 50 to 60 and regressive parts of parasequences 20 although diagenetically shifted the 13c record retains a highly clipped memory of astronomically driven global 13c fluctuations albeit modified by platform water restriction during cyclic deposition

eccentricity paced monsoon like system along the northwestern tethyan margin during the valanginian early cretaceous new insights from detrital and nutrient fluxes into the vocontian basin se france high resolution changes in terrigenous and nutrient fluxes into the vocontian basin northwestern tethyan margin were investigated for the late berriasian late valanginian time interval in order to assess the precipitation patterns in the source areas and to evaluate the effect of orbital forcing on the strength of the hydrological cycle in this study new high resolution mineralogical bulk rock and clay fraction and geochemical phosphorus and oxygen isotope data are used from the astronomically calibrated orpierre section for the first time kaolinite detrital and phosphorus accumulation rates kar dar and par are calculated and compared to a set of 547 geochemical and 260 mineralogical published data from other vocontian sections it appears that three regional increases in the kar document three successive humid episodes during the valanginian this is confirmed by contemporaneous increases in dar and partly also in par which highlight higher terrigenous and nutrient fluxes to the vocontian basin during these episodes concomitant decreases in the 18owhole rock signals may reflect higher sea surface temperatures during the early valanginian and the early late valanginian transition the occurrence of the three humid episodes is interpreted to relate to an orbital paced monsoonal circulation pattern through seasonally reversing movements of air mass heat and precipitation over the northwestern tethyan margin in particular based on the correlation between the 405 kyr eccentricity cycles and the kar signal obtained at orpierre an eccentricity influenced monsoonal circulation is proposed as the possible forcing factor behind these climatic patterns the average duration between the climaxes of the three regional wetter episodes is approximately 2 43 myr the wetter and likely also warmer episode at the early late valanginian transition is in step with the onset of the weissert episode in this regard the intensification of monsoonal driven precipitations appears as a possible external forcing factor leading or at least accelerating the important perturbation in the global carbon cycle associated with the weissert episode

cyclostratigraphy and orbital tuning of the terrestrial upper santonian lower danian in songliao basin northeastern china abstract the songke 1 north sk 1n borehole recovered a continuous 1541 66 m late santonian early danian terrestrial succession in songliao basin sb northeastern china it provides a unique record for improving our understanding of continental paleoclimate and ecological system in cretaceous greenhouse world here we use thorium th logging data as a paleoenvironmental and paleoclimatic proxy to conduct a detailed cyclostratigraphic study on the sk 1n core power spectra evolutionary fast fourier transformation and wavelet analysis all reveal significant decameter to meter scale sedimentary cycles in the nenjiang k 2 n sifangtai k 2 s and mingshui k 2 m formations the ratios of cycle wavelengths in these stratigraphic units are 20 5 2 1 and are interpreted as milankovitch cycles of 405 kyr and 100 kyr eccentricity 38 4 kyr obliquity and 20 kyr precession cycles respectively an astronomical time scale ats is established by tuning filtered 405 kyr eccentricity cycles to a target curve of the astronomical solution la2010d based on the magnetostratigraphic time framework of the sk 1n borehole this ats provides precise numerical ages for stratigraphic boundaries biozones geological and geophysical events and serves as a basis for correlation of strata and events between marine and terrestrial systems the cretaceous paleogene k pg campanian maastrichtian santonian campanian boundaries are estimated at core depths of 318 m 752 8 m and 1751 1 m respectively a 3 8 myr long hiatus between the nenjiang k 2 n and sifangtai k 2 s formations occurs from 76 1 to 79 9 million years ago the ages and durations of magnetochrons c33r to c30n are precisely estimated and provide new constraints on the late cretaceous geomagnetic polarity time scale gpts and south atlantic sea floor spreading rates

conjunctive use of spectral gamma ray logs and clay mineralogy in defining late jurassic early cretaceous palaeoclimate change dorset u k abstract detrital clay mineralogy is controlled by weathered source rock climate transport and deposition that in turn influence the spectral gamma ray sgr response of resultant sediments whilst a palaeoclimate signal in clay mineralogy has been established in some ancient successions the sgr response remains contentious largely because the data sets have yet to be collected at the same or appropriate vertical scales to allow comparison in addition the influence of organic matter on sgr is not always considered here we present clay mineralogical total organic carbon toc and sgr analyses from the late jurassic and early cretaceous of the wessex basin a period of previously documented palaeoclimate change the aim of this paper is to estimate the sensitivity of sgr as palaeoclimatic tool sgr and clay mineral data having been collected at the same sample points making this one of the most rigorous comparison of clay mineral and sgr to date overall the correlation between high thorium potassium or thorium uranium and kaolinite associated with a well established palaeoclimate change shows that elevated thorium may be used as a proxy for humid palaeoweathering as suggested by few previous studies

astronomical tuning of the aptian stage from italian reference sections a high resolution grayscale series of the pelagic fucoid marls piobbico core central italy shows strong pervasive lithological rhythms throughout the aptian interval a hierarchy of centimeter to meter scale cycles characterizes the rhythms when calibrating 1 m cycles to earth s 405 k y orbital eccentricity cycle these rhythms correspond to the periods of the eccentricity obliquity and precession index tuning to orbital eccentricity cycles provides a high resolution time scale for the aptian correlation to the cismon core northern italy extends the tuning to the aptian barremian boundary the tuning indicates a minimum duration of 13 42 m y for the aptian stage where previous estimates range from 6 4 to 13 8 m y the combined aptian albian astronomical tuning of the entire 77 m long piobbico core and part of the cismon core provides a 25 85 m y long astronomically calibrated time scale for earth history

stable isotopic evidence for climate and basin evolution of the late cretaceous songliao basin china abstract because of the need to understand the links and feedbacks of the carbon cycle during times of global greenhouse conditions numerous studies have focused on the cretaceous climate much of what we know about this warm period in earth s history comes from the study of ocean sediments recovered from both ocean drill cores and marine sediments exposed at the earth s surface in contrast there are few studies of cretaceous terrestrial sediments the songliao basin located in northeast china offers a unique opportunity to understand cretaceous paleoclimate of terrestrial settings because it contains a nearly complete record of lacustrine sediments deposited throughout the cretaceous and there is an active drilling program to recover core from this paleolake we present carbon oxygen and strontium isotopic data from ostracods collected from two drill cores sk 1 n and sk 1 s that cover a time interval that extends from the turonian through the maastrichtian these data record robust isotopic trends with numerous carbon and oxygen isotope shifts that are both rapid and long term we tentatively interpret this record to reflect changes in both global climate and regional basin evolution in the turonian and coniacian qingshankou formation we observe several carbon isotope shifts that appear to be correlative to marine isotopic records based upon timing and magnitude of the isotopic changes we suggest that the carbon isotope record in the songliao basin reflect the decrease in carbon isotope ratios following the strong positive excursion at the cenomanian turonian boundary a positive isotope excursion in the late turonian and the negative isotope shift that occurs at the turonian coniacian boundary upward in the section however the marine and songliao isotopic records diverge as sediment sources shift from the southwest east and north to more northerly strontium isotopes record the change in source region as they increase markedly between the coniacian santonian yaojia and santonian campanian nenjiang formations as this is the first isotopic record of the songliao basin we are cautious about many of our interpretations of these isotopic data yet it is clear that with tighter age constraints and focused sampling centered on many of the isotope excursions presented here will allow for a deeper understanding of the terrestrial response to changing climate and the hydrologic response to basin evolution

axial obliquity control on the greenhouse carbon budget through middle to high latitude reservoirs carbon sources and sinks are key components of the climate feedback system yet their response to external forcing remains poorly constrained particularly for past greenhouse climates carbon isotope data indicate systematic million year scale transfers of carbon between surface reservoirs during and immediately after the late cretaceous thermal maximum peaking in the cenomanian turonian circa 97 91 million years myr ago here we calibrate albian to campanian 108 72 myr ago high resolution carbon isotope records with a refined chronology and demonstrate how net transfers between reservoirs are plausibly controlled by 1 myr changes in the amplitude of axial obliquity the amplitude modulating terms are absent from the frequency domain representation of insolation series and require a nonlinear cumulative mechanism to become expressed in power spectra of isotope time series mass balance modeling suggests that the residence time of carbon in the ocean atmosphere system is by itself insufficient to explain the myr scale variability it is proposed that the astronomical control was imparted by a transient storage of organic matter or methane in quasi stable reservoirs wetlands soils marginal zones of marine euxinic strata and potentially permafrost that responded nonlinearly to obliquity driven changes in high latitude insolation and or meridional insolation gradients while these reservoirs are probably underrepresented in the geological record due to their quasi stable character they might have provided an important control on the dynamics and stability of the greenhouse climate

flume measurements of sediment erodibility in boston harbor to obtain iin situ n measurements of sediment erodibility in defined bottom shear stress environments a portable straight flume was built tested and deployed in the field for six experiments at three locations in quincy bay of boston harbor mass the flume had a 1 0 m long inlet section which included a boundary layer trip and a roughened plexiglass bottom this design prevented erosion of the sediment bed in the boundary layer development region downstream of the inlet section was a 1 2 m long sediment test section which had a laboratory verified uniform bottom stress in the absence of algal mats our flume experiments on sites exhibiting a range of bed properties indicated quite uniform erodibility with a critical shear stress i dc of 0 10 0 04 pa and an erosion rate constant im of 3 2 0 2 10 u kg m u s u pa u ir 0 92 in 17 where in is the total number of erosion rate measurements made in the absence of algal mats the measured rates were consistent with those of many other iin situ n studies we observed markedly reduced erodibility in early october 1995 when the sediment was covered by a benthic diatom mat and measured erosion rates were lessened by 50 80 the possibility of depth dependent sediment erodibility in near surface top 3 mm was investigated by calculating a set of depth dependent erosion parameters the parameters obtained suggested that both the critical shear stress and the erosion rate constant were depth sensitive both doubling by 1 mm into the sediment

astronomically forced variations in multiresolution resistivity logs of lower upper cretaceous cenomanian coniacian terrestrial formations from the songliao basin northeastern china abstract continuous and high resolution well logs from the sk 2 east sk 2e borehole in the songliao basin provide an opportunity to understand the relationship between astronomically forced climate and electrical responses in terrestrial cretaceous strata here we present well logs mud logs and core measurement data of lacustrine deposits in the upper cretaceous qingshankou fm and of fluvial deltaic deposits in the quantou fm the multiresolution resistivity logs used for the cyclostratigraphic analysis include deep laterolog resistivity logs resistivity image logs and array induction logs the results show that the resistivity of strata in quantou fm mainly reflects changes in clay content and that resistivity logs can be used as paleoenvironmental and paleoclimate proxies in cyclostratigraphic studies of the quantou fm for the qingshankou fm formation resistivity is mainly affected by clay minerals which contribute to the overall electrical conductivity as well as nonconductive organic carbon increasing clay and organic carbon contents usually correspond to wetter and warmer climatic conditions the phase relationship between resistivity logs and astronomical cyclicity depends on factors that control resistivity spectral analyses of lithological changes and resistivity logs indicate the presence of eccentricity obliquity and precession cycles throughout the quantou fm this provides strong evidence that climate was the dominant control on cyclic sedimentation in the quantou fm the floating astronomical timescale which was established by calibrating extracted 405 kyr cycles from resistivity logs reveals that the duration of quantou fm was approximately 5 5 myr comparative analysis of power spectra reveals that the sensitivity of resistivity logs with specific resolutions to milankovitch cycles with different frequencies is variable comprehensive analysis of multiresolution resistivity logs is a new method in cyclostratigraphy analysis that has the potential to be effective in detecting signals of milankovitch cycles in terrestrial deposits

the late archaean to early proterozoic lead isotopic evolution of the northern baltic shield of norway sweden and finland abstract the late archaean rocks of the northern baltic shield comprise high grade gneiss terrains and granite greenstone terrains the high grade gneiss terrains consist mainly of older upper crustal material which became metamorphosed during the lopian orogeny ca 2 9 2 6 ga in contrast the 2 7 ga old granite greenstone terrains comprise mainly mantle derived materials at the southern and western edge the archaean craton became partially remobilized during the svecofennian orogeny 2 0 1 75 ga this orogeny represents a major crust forming event in the baltic shield during which mantle material was added to the crust and older material was remobilized whole rock galena and sulfide trace lead are used to outline lead provinces on the northern baltic shield the archaean lead from the baltic shield defines three secondary lead isochrons at 2 65 ga with different initial lead compositions which reflect average pre 2 65 ga 1 ratios of 8 0 8 1 and 8 3 respectively the variation of the initial lead composition of the high grade gneisses and tonalites lofoten and koitelainen area probably indicates 1 variable crustal residence time and or 2 different degrees of crustal contamination assimilation before the 2 65 ga metamorphic event and the lead from the eastern finland greenstone belts indicates a heterogeneous mantle with respect to u pb before 2 65 ga lead in proterozoic rocks of the different lead provinces defines sets of subparallel mixing fields which can be modelled by a 2 65 ga lead component and a 1 8 ga lead component the parallel offset of these fields reflects the pre 2 65 ga 1 ratio of these terrains i e it reveals the pre 2 65 ga 1 of the involved archaean rocks proterozoic terrains with involvement of archaean lower crustal lead show a poor correlation in the 206 pb 204 pb 208 pb 204 pb diagram whereas the other proterozoic terrains show a good correlation in the 206 pb 204 pb 208 pb 204 pb diagram

astrochronology of the valanginian stage from reference sections vocontian basin france and palaeoenvironmental implications for the weissert event abstract high resolution gamma ray measurements performed on five biostratigraphically well dated reference sections from the vocontian basin south eastern france are used to develop a new astrochronology of the valanginian stage and its subdivisions i e ammonite and calcareous nannofossil zones and subzones spectral analyses show a pervasive dominance of 405 kyr eccentricity cycles with the expression of 100 kyr eccentricity obliquity and precession previous rough estimates of valanginian stage duration ranged from 3 9 to 6 5 myr but were generally based on less reliable or indirect methods this study provides a precise duration of 5 08 myr tuning the series to the 405 kyr eccentricity cycle thus further enhancing the accuracy of the geologic time scale new durations of magnetochrons are proposed based on intercalibration between ammonite and calcareous nannofossil biozones cyclostratigraphy and carbon isotope stratigraphy after integrating orbitally calibrated durations and available radio isotopic ages for the berriasian hauterivian interval a link between the weissert event and the emplacement of the parana etendeka traps now appears unlikely strontium carbon and oxygen isotope stratigraphy sedimentological and palaeontological features clay mineralogy and the orbital record during the upper valanginian all suggest that a transient cool arid climate occurred after the carbon isotope event possibly associated with limited polar ice

timing of the north south china collision from new middle to late mesozoic paleomagnetic data from the north china block we collected paleomagnetic samples from 43 sites of middle and upper jurassic and cretaceous rocks along a 250 km wide east west trending belt located north of the suture between the north and south china blocks in each case laboratory treatment isolates dual polarity antipodal magnetizations that are demonstrably pre folding the paleomagnetic poles show very good coherence with coeval poles from other localities from the north china block ncb suggesting the apparent polar wander path apwp from the ncb is not distorted by post middle jurassic local vertical axis block rotations a comparison of the ncb apwp with that from the south china block suggests that collision continued after the early jurassic and ended no later than the late jurassic a cusp in the ncb apwp coincides with a marked angular unconformity that separates middle jurassic from upper jurassic and younger sediments together these observations indicate that the scissor like collision and associated deformation ceased at the middle to late jurassic boundary 159 ma the time of rapid 1 ma relative angular velocity between the two plates 225 to 190 ma coincides with a peak in u pb and ar ar dates obtained from metamorphic rocks in the suture the combined late jurassic and cretaceous paleomagnetic data from both blocks suggest that the united china plate traveled 2000 km north relative to eurasia during the late jurassic before docking in the cretaceous this younger collision event is also marked by a cusp on the cretaceous part of the eurasian apwp

influence of palaeoclimate and hydrothermal activity on organic matter accumulation in lacustrine black shales from the lower cretaceous bayingebi formation of the yin e basin china abstract the lacustrine black shales of the lower cretaceous bayingebi formation are an important hydrocarbon source rock in the yin e basin it is important to understand the mechanism of organic matter accumulation in these shales to reconstruct the palaeoenvironment and palaeoclimate in the early cretaceous in northwestern china and search for potential oil and gas resources based on petrological elemental geochemical and organic geochemistry analyses of typical field profile samples the influence of palaeoclimate and hydrothermal activity on organic matter accumulation in different sedimentary units unit i ii and iii is revealed unit ii has the highest total organic matter abundance tocavg 5 95 mainly type i kerogen lamalginite which is in the immature to low mature stage organic carbon isotope data 13corg element ratios sr cu and c value and weathering indexes including cia ciw and pia together revealed that the region experienced a semihumid to semiarid palaeoclimate in the middle of the early cretaceous the increase in rainfall in unit ii enhanced the abundance of lake algae and surrounding terrestrial vascular vegetation and elevated the lake level which contributed to adequate sources and favourable preservation conditions for organic matter accumulation several lines of evidence including high sulfur contents the combination of vein pyrite and micritic dolomite positive eu anomalies and element geochemical correlations confirm the existence of intermittent low temperature white smoker type hydrothermal activity the decrease of oxygen content in lake bottom water may be related to the input of hydrothermal fluid which provided necessary nutrient elements for biological productivity according to palaeontological and radioisotope dating data it can be inferred that the black shales of the bayingebi formation are the product of the combined effect of global palaeotemperature rise in the early aptian stage of the early cretaceous and intermittent low temperature hydrothermal activity

heat flow and thermal structure of the lithosphere across the baltic shield and northern tornquist zone abstract terrestrial heat flow data from archean and proterozoic provinces of the baltic shield its southwestern margin and the tectonic transition to the younger tectonic units of central europe northern segment of the european geotraverse are compiled and examined for local and regional variations a 2 d numerical lithospheric temperature and heat flux model is presented covering 1800 km of the deep seismic fennolora profile across the baltic shield and 500 km of eugeno s northern eugemi seismic lines across the northern tornquist zone and the danish and north german basins thermal lithosphere defined as the outer layer with relatively low temperatures t c in which heat transfer is dominantly by conduction is found to vary markedly in thickness from 85 110 km beneath basins and tornquist zone to about 150 km in central shield areas and 200 250 km in areas of low heat flow along the northern shield profile these results are in very good agreement with seismological information from surface wave dispersion analysis and the refraction wide angle seismic interpretation of fennolora data the combined thermal and seismologic evidence indicates that the uppermost mantle region stratified in seismic velocity is restricted to the upper relatively cold thermal layer which is interpreted to constitute shield lithosphere local and to some extent regional variations in surface heat flow are found to be closely related to variations in near surface radiogenic heat production for the southern baltic shield a heat flow heat production relationship of q 0 32 8 7 6 h 0 is derived regional increase in heat flow from northern and central shield provinces to the shield margin and the tornquist zone is interpreted to be related partly to differences in upper crustal heat generation partly and in southernmost areas mainly to an increased heat flux from the upper mantle upper mantle heat flux is estimated at 20 25 mw m 2 along the northern and central shield transect increasing to 30 40 mw m 2 beneath the shield margin basins and tornquist zone lithospheric thickness variations in this region of northern europe are found to be closely associated with variations in heat flux from the uppermost mantle and perhaps to a large extent controlled by geodynamically determined lateral differences in upper mantle heat flux earthquake focal depth data and information on crustal strength show baltic shield seismicity to be limited generally to the upper 20 25 km brittle part of the crust at temperatures less than 300 400 c maximum source depth of magnetic anomalies at temperatures near 600 c is in the deepest part of the crust near the crust mantle boundary in the southern region about 25 km depth along the tornquist zone and about 35 40 km in southern shield areas and in the uppermost mantle 60 70 km depth in the northern shield areas some petrologic implications are discussed the present deep crust is supposed to be at lower temperature pressure conditions than at early stages of formation however also the present deepest parts of the shield crust 35 40 km are within the stability field of eclogites the general absence of significant gravity anomalies in areas of marked crustal thickness variations indicate high density eclogites to be present in significant amounts in the deep shield crust

temperature field modelling along the northern segment of the european geotraverse and the danish transition zone abstract a two dimensional numerical solution of the heat conduction equation was used to calculate the crustal temperature field along two profiles of the northern segment of the european geotraverse the fennolora profile baltic shield and profile 2 of the eugeno s project danish transition zone the solution of the 2 d steady state equation of heat conduction was solved with the integrated finite difference method the crustal structure was discretized by a rectangular grid seismic refraction results were used to calculate the corresponding distribution of heat generation we applied empirical equations linking seismic velocity with heat generation to convert the characteristic seismic velocity into heat production in the upper crust the temperature field shows no significant lateral variation the lower crust on the other hand is characterized by lateral and vertical variations of the temperature field mainly at tectonic transition zones i e precambrian to phanerozoic crustal domains in the baltic shield temperatures tend to decrease towards the north with increasing age of the shield as expected relatively low moho temperatures were obtained beneath the baltic shield 300 500 c whereas a maximum of 900 to 1000 c at the moho was found to correspond to high surface heat flow in southern sweden in the geologically complex danish transition zone the calculated moho temperatures reached values between 550 c in the shield region and 650 c under the danish basin the variation of mantle heat flow reflects the pattern of surface heat flow in the fennoscandian part of the shield the moho heat flow is 5 40 mw m2 in the danish part 25 30 mw m2 and below the danish basin up to 45 mw m2 with the present data set the model shows a remarkable coincidence between high q0 the temperature field and areas of major tectonic change sensitivity analysis shows that the surface heat flow and the heat generation in the upper crust are the most critical thermal parameters due to their relatively limited range of variation the heat production in the lower crust the thermal conductivity and corrections applied to the seismic velocities play only a secondary role on the two dimensional temperature field the differences between 1 d and 2 d temperature models are most pronounced in the lower crust where significant lateral temperature variations are seen

chronology of the terrestrial upper cretaceous in the songliao basin northeast asia the cretaceous was a period of great environmental biological and geodynamical change but a paucity of an accurate time frame for continental strata has prevented our understanding of the terrestrial processes and the integration of marine and terrestrial records here we present an integrated chronology for the terrestrial upper cretaceous in east asia based on new high resolution magnetostratigraphic results and previously published sims u pb zircon analyses of the cretaceous continental scientific drilling borehole sequence from the songliao basin in northeast china hereafter termed ccsd sk i which consists of a sedimentary sequence from the upper quantou formation k2q to the mingshui formation k2m correlation to the geomagnetic polarity timescale was achieved by combining magnetostratigraphic and sims u pb zircon geochronologic data and lithostratigraphy our correlation suggests that the ccsd sk i sedimentary sequence spans from the upper chron c34n to chron c29r the age of the sedimentary sequence from the upper quantou formation k2q to the mingshui formation k2m in the songliao basin can thus be constrained to an interval from the turonian to the maastrichtian ages in addition our correlation puts the cretaceous paleogene boundary in the upper part of member 2 of the mingshui formation k2m2 the constructed comprehensive chronology allows the precise correlation of the terrestrial upper cretaceous of the songliao basin to marine strata as well as other continental sequences

stratigraphy correlation depositional environments and cyclicity of the early cretaceous yixian and jurassic cretaceous tuchengzi formations in the sihetun area ne china based on three continuous cores abstract three continuous cores acquired in the sihetun area of liaoning province famous for feathered non avian dinosaurs of the jehol biota reveal the stratigraphic and facies relationships of the divisions of the early cretaceous yixian and underlying jurassic early cretaceous tuchengzi formations based on these cores we propose a modified lithostratigraphic nomenclature in the sihetun sub basin in which the yixian formation is divided into three members the lujiatun member a fluvial and alluvial volcaniclastic sandstone and conglomerate unconformably overlying the tuchengzi formation with articulated tetrapods plausibly preserved in burrows the xiatulaigou member an extrusive basaltic flow and breccia comprising the only true lavas in the area and the jianshangou member a cyclical lacustrine mudstone containing a taphocoenosis of articulated compression fossils with soft tissue preservation including non avian dinosaurs birds pterosaurs mammals fish crustaceans insects mollusks and plants the latter is divided into 4 units the basal dajianshanzi bed a shallow water lacustrine unit with abundant mollusks and rooted zones the anjiagou bed the main tetrapod bearing unit consisting of microlaminated dark gray mudstones with many interbedded airfall ashes deposited in a meromictic lake the hengdaozi bed comprised of thin and rhythmically to medium bedded light gray to tan mudstones and sandstones with few discrete ashes famous for its diverse insects and plants including early angiosperms deposited in alternating dysoxic and oxygenated bottom water and the huangbanjigou bed the most obviously cyclical of the units with dark gray microlaminated intervals with articulated vertebrates alternating with more massive lighter colored mudstones and volcaniclastic sandstones deposited in lakes that oscillated in depth cyclicity in the jianshangou member is dominated by meter scale cycles that may be paced by orbital variations unambiguous relatively rapid lateral facies changes within the yixian formation are suggestive of local relief not the bottom of a giant flat bottomed basin

foraminiferal response to seasonality modulated by orbital cycles in the cretaceous mid latitudes the albian record from the lower saxony basin abstract the mid cretaceous serves as an excellent laboratory for testing the dynamics of the climate under greenhouse state of the earth this study is focused on the cyclicity record of foraminiferal assemblages in the lower saxony basin during the middle albian the short eccentricity obliquity and precession cycles are consistently recorded in absolute and relative abundance of most opportunistic benthic and planktic foraminifers the question is why foraminifers reacted to orbital cycles and what they actually record in the equable global climate it is suggested that seasonality changes modulated by orbital cycles are responsible for the milankovitch cyclicity records it is well known that the axial obliquity directly influences seasonal contrasts in mid and high latitudes the precession modulated by the eccentricity of the earth orbit further affects the contrast of seasons therefore seasonal dynamics of precipitation runoff and storm tracks patterns and to a lesser extent temperature contrasts are most likely factors controlling milankovitch scale cyclic fluctuations of foraminiferal assemblages and other proxies sensitive to productivity changes it can be deduced that periods of the highest seasonal contrasts were dominated by opportunistic abundant taxa such as benthic valvulineria gyroidinoides group and planktic hedbergellids which record the strongest obliquity signals the lower saxony and adjacent boreal basins were possibly controlled by humid climate with relatively dry summers and wet winter seasons this study confronted with the presented conceptual model and former climate models supports the conclusion that the temperate zone surrounding tethys was sensitive to seasonal changes modulated by orbital cyclicity the mid latitudinal climate of the greenhouse earth seems to be more dynamic and more seasonal than expected

cretaceous paleogeography and paleoclimate and the setting of ski borehole sites in songliao basin northeast china article i nfo as a paradigm of greenhouse climate in earth s history the cretaceous provides significant rock records of global climate changes under conditions of greenhouse climate the songliao basin among the longest dura tion 85 90 m y of continental sedimentary basins provides an excellent opportunity to recover a nearly complete cretaceous terrestrial sedimentary record extensive lake deposits ten kilometers deep and cover ing an area of 260 000 km 2 of the songliao basin provide unique detailed records that can be tied to the glob al stratigraphic time scale thereby improving our understanding of the continental paleoclimate and ecological system the two coreholes at skis and skin sites were drilled into this basin and completed with a total length of 2485 89 m of recovered core that spanned the complete middle to upper cretaceous strata in the basin the unique geological setting of long term continuous subsidence within the largest cretaceous landmass in the world makes the cretaceous songliao basin of northeastern china an ideal place to study cretaceous climate change on the continent this paper reviews the literature on the paleogeography and paleoclimate of the northern east asia and the songliao basin during the cretaceous based on the climatolog ically sensitive deposits oxygen isotope studies and paleontology the climate during the cretaceous in the songliao basin was temperate and humid with relatively abundant rainfall during the period significant changes four cooling three warming and three semiarid events are generally consistent with the oxygen isotope data from east asia and the four cooling events in berriasian valanginian aptian albian early santonian and campanian maastrichtian may be related to potential glaciations in cretaceous

cyclostratigraphy and astrochronology case studies from china abstract a high precision geologic time scale is the essential key for understanding the earth s evolutionary history and geologic processes astronomical tuning of orbitally forced stratigraphic records to construct high resolution astronomical time scales ats has led to a progressive refinement of the geologic time scale over the past two decades in turn these studies provide new insights regarding the durations and rates of major earth events evolutionary processes and climate changes all of which provide a scientific basis for contextualizing and predicting future global change trends south china hosts some of the best exposed and well dated neoproterozoic through mesozoic stratigraphic sections in the world many of which are suitable for cyclostratigraphy and calibrating the geologic time scale in north china several cenozoic oil bearing basins have deep boreholes with continuous sampling and or well logging that enable derivation of astronomically tuned time scales for an improved understanding of basin evolution and hydrocarbon generation this special issue focuses on case studies of astrochronology and applied cyclostratigraphy research using reference sections within china in this introductory overview we 1 summarize all existing astrochronology studies of the neoproterozoic through cenozoic sections within china that have been used to enhance the international geologic time scale 2 examine briefly the astronomically forced paleoclimate information recorded in various depositional systems and the modern techniques employed to analyze the periodicity of these signals encoded within the sedimentary record and 3 summarize the 20 contributions to this special issue of palaeogeography palaeoclimatology palaeoecology on cyclostratigraphy and astrochronology case studies from china

cohesive sediment transport model a mathematical model has been developed which simulates the transport of cohesive sediment the model solves the complete three dimensional version of the diffusion advection equation using a splitting method in conjunction with a characteristics technique and a mixed explicit implicit finite difference approach the effects of the flocculation deposition consolidation erosion and slump of the sediment are incorporated in the model which can also handle irregular layouts application of the model to a harbor siltation problem indicated that the large input data requirements can be satisfied economically and that the scheme yields realistic results the application also provided an insight into possible ways of operating the model for different field situations

early eocene carbon isotope excursions and landscape destabilization at eccentricity minima green river formation of wyoming repeated global reorganizations of carbon cycling and biotic oceanic and terrestrial processes occurred during the early eocene and appear to have been paced by cyclic variations in the eccentricity of the earth s orbit the phase relationship s between insolation variation terrestrial paleoclimate and atmospheric pco2 during these events remains enigmatic however due to their poorly constrained timing relative to specific orbital configurations here we use tiered interpolation between radioisotopic ages and paleomagnetic polarity chrons to compare high resolution 13c and lithofacies records from the wilkins peak member of the green river formation of western north america to a fe intensity xrf record from the western atlantic ocean and to numerical solutions for earth s orbital configuration wilkins peak member lithofacies stacking patterns record cyclic geomorphic responses to insolation and climate fluctuations spanning an interval of 1 8 ma previous macrostratigraphic analyses using 40ar 39ar and u pb ash bed ages indicate that these cycles reflect long and short eccentricity modulation of precession hydrologic variance appears to have occurred inversely with intervals of maximum sediment advection with carbonate and evaporite dominated lacustrine modes during eccentricity maxima and siliciclastic dominated alluvial modes during eccentricity minima stable carbon isotope analyses of 126 meters of wilkins peak member strata reveal a regular 5 per mil oscillation between high 13c lacustrine modes and low 13c alluvial modes tiered interpolation between paleomagnetically characterized terrestrial ash beds facilitates the integration of 11 radioisotopic ages with the geomagnetic polarity timescale resulting in significant expansion of chron c23 and shortening of chron c22 relative to timescales based on seafloor magnetic anomaly profiles the new proposed timescale permits direct comparison of terrestrial and marine climate proxy records from the early eocene climatic optimum at ca 250 kyr 250 kyr resolution and reveals prominent 100 kyr and 405 kyr scale oscillations within both records wilkins peak member 13c minima which occurred during low eccentricity alluvial modes likely coincided with global 13c minima scenario 1 but may alternatively reflect productivity driven local effects within lake gosiute scenario 2 if scenario 1 proves accurate early eocene negative 13c hyperthermal excursions occurred during eccentricity minima rather than maxima as formerly believed

high precision u pb geochronologic constraints on the late cretaceous terrestrial cyclostratigraphy and geomagnetic polarity from the songliao basin northeast china abstract the cretaceous continental sedimentary records are essential to our understanding of how the terrestrial geologic and ecologic systems responded to past climate fluctuations under greenhouse conditions and our ability to forecast climate change in the future the songliao basin of northeast china preserves a near complete predominantly lacustrine cretaceous succession with sedimentary cyclicity that has been tied to milankocitch forcing of the climate over 900 meters of drill core recovered from the upper cretaceous turonian to campanian of the songliao basin has provided a unique opportunity for detailed analyses of its depositional and paleoenvironmental records through integrated and high resolution cyclostratigraphic magnetostratigraphic and geochronologic investigations here we report high precision u pb zircon dates ca id tims method from four interbedded bentonites from the drill core that offer substantial improvements in accuracy and a ten fold enhancement in precision compared to the previous u pb sims geochronology and allow a critical evaluation of the songliao astrochronological time scale the results indicate appreciable deviations of the astrochronologic model from the absolute radioisotope geochronology which more likely reflect cyclostratigraphic tuning inaccuracies and omitted cycles due to depositional hiatuses rather than suspected limitations of astronomical models applied to distant geologic time age interpolation based on our new high resolution geochronologic framework and the calibrated cyclostratigraphy places the end of the cretaceous normal superchon c34n c33r chron boundary in the songliao basin at 83 07 0 15 ma this date also serves as a new and improved estimate for the global santonian campanian stage boundary

the floating astronomical time scale for the terrestrial late cretaceous qingshankou formation from the songliao basin of northeast china and its stratigraphic and paleoclimate implications abstract the upper cretaceous qingshankou formation k 2 qn in the songliao basin slb of northeast china consists of up to 550 m thick lacustrine mudstone and shale that constitute one of the most important source rocks of the daqing oil field a high resolution cyclostratigraphic analysis of the natural gamma ray logging from 10 wells of the qingshankou formation k 2 qn reveals orbital cycles of precession 20 ka obliquity 40 ka and eccentricity 100 ka and 405 ka providing strong evidence for astronomically driven climate changes in the late cretaceous terrestrial environments floating astronomical time scales ats are established for all sections which demonstrate variable durations of k 2 qn across the basin 1 09 ma 5 20 ma and strong diachroneity of the lacustrine strata four periods of high depositional rates can be identified in the central parts of the basin possibly recording deposition during times of sustained wet climate and high chemical weathering an ats established from well m206 in the central depression zone of the basin where the most complete and stable milankovitch cycles are present suggests that the maximum duration of the k 2 qn is 5 20 ma from 94 27 ma to 89 07 ma late cenomanian to early coniacian the lacustrine anoxic event 1 lae1 at the cenomanian turonian boundary lasted 210 310 ka during which the most prolific petroleum source rocks in slb were deposited the onset 94 21 94 18 ma and duration 210 310 ka of lae1 in slb are comparable to those of the oceanic anoxic event 2 oae2 onset at 94 21 ma and duration of 320 900 ka suggesting that the same trigger mechanism such as increased atmospheric co 2 from large scale igneous activity may have initiated high primary productivity and organic carbon burial in both marine and terrestrial systems

predictive model of three dimensional development and deformation of a river mouth delta by applying contour line change model a predictive model of the three dimensional development and deformation of a river mouth delta is developed this model enables the prediction of not only the shoreline change but also the three dimensional long term topographic changes around a river mouth and offshore sand transport can be taken into account when the sea bottom slope exceeds a critical value given by the angle of repose of sand numerical simulation of three cases of initial beach slopes is carried out and compared the calculated and actual beach changes measured around the fuji and tenryu river mouths are compared it is concluded that calculated results can reproduce real phenomena measured around river mouths qualitatively

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

evidence for early proterozoic plate tectonics from seismic reflection profiles in the baltic shield plate tectonics provides the linking framework for all tectonic and magmatic activity seen today but it is not known when plate tectonics first developed on earth new deep seismic reflection and

astrochronology of the late turonian implications for the behavior of the carbon cycle at the demise of peak greenhouse abstract a series of prominent carbon cycle perturbations indicated by carbon isotope excursions of up to 2 marked climatic and oceanographic changes that followed the peak mid cretaceous greenhouse the nature and forcing mechanisms of these changes remain poorly understood partly due to the lack of a detailed temporal control in this interval here we present an orbitally calibrated time scale which is based on hemipelagic rhythmites in the bohemian cretaceous basin and which can be linked to the established chronostratigraphic framework using inoceramid biostratigraphy and carbon isotope signature in the new age model the late turonian defined by the first occurrence of i perplexus below and the first occurrence of c deformis erectus above spans 1 56 0 07 myr when anchored to the newly refined age of the turonian coniacian boundary sageman et al in press the onset of the late turonian is 91 31 0 45 ma inoceramid zones i perplexus and m scupini span 0 76 0 05 myr and 0 80 0 05 myr respectively a time domain record of carbon isotope variations was obtained by pinning published 13ccarb data to the orbital time scale using 9 biostratigraphic and carbon isotope markers the timing of major carbon isotope excursions suggests a link to 405 kyr eccentricity changes and in the early late turonian to 100 kyr eccentricity variations however over 80 of the variance in the late turonian 13 c occurs at longer million year scales the key features of the 13ccarb signature including the amplified long term variance can be reproduced with simple models of orbitally driven isotopic mass balance at a constant carbon isotope fractionation the best fit to the 13ccarb signature is obtained with enhanced organic burial at high eccentricity in accordance with monsoonal forcing of organic accumulation in the low latitude atlantic and or buildup of low latitude terrestrial carbon reservoirs alternative solutions should consider changing carbon isotope fractionation due to pco2 and or nutrient flux changes

the geoelectric model of the polar profile northern finland abstract electromagnetic soundings have been made in order to construct a geoelectrical conductivity model of the crust along the european geotraverse egt polar profile forty magnetotelluric mt soundings eighteen audiomagnetotelluric amt soundings and ten magnetohydrodynamic mhd soundings were made on the main polar profile polar i and ten more mt soundings on a parallel profile polar ii 40 km to the southeast of the main profile analysis of simultaneous recordings by the eiscat magnetometer chain and thin sheet modelling of the effect of the barents sea indicate that neither the source field effects nor the presence of the ocean are significant at periods below 200 s in the measurement area the magnetotelluric data have been modelled with two dimensional models representing the regional structure along the profiles in addition to the regional structure a thin inhomogeneous surface layer is included in the models in order to explain some local features of the measured response functions although details of the surface electrical structures are poorly resolved the gross features of the geoelectrical cross section are considered to be reliable the results divide the polar profile into three different blocks the better conducting karasjok kittila greenstone belt in the south has an average resistivity of less than 10 m the more resistant lapland granulite belt with a resistivity between 100 and 200 m is underlain by conductive the geoelectric cross section agrees in gross detail with the corresponding gravity refraction seismic and reflection seismic cross sections of the polar profile all methods indicated a similar shape for the southwestern part of the lapland granulite belt i e granulites have a gently ne dipping boundary against the underlying karelian province in the northeastern part of the granulite belt the geoelectric model and the gravimetric model show a rather steep s dipping boundary against the inari terrain northeast of the granulite belt

astrochronology for the early cretaceous jehol biota in northeastern china article i nfo the early cretaceous jehol biota in northeastern china provides an evolutionary window for feathered dinosaurs primitive birds insects and early flowering plants it also provides critical information for the bio diversity changes of the early cretaceous terrestrial ecosystem here we report a time series analysis for the 11 2 m thick fossil bearing lacustrine deposits at the sihetun section in western liaoning northeastern china on the basis of high resolution magnetic susceptibility ms and anhysteretic remanent magnetization arm measurements a hierarchy of sedimentary cycle bands of 120 260 cm 50 67 cm and 18 42 cm was recorded in the ms and arm series with available radioisotope age constraints from the same section sedimentary cycles of 120 260 cm 50 67 cm and 18 42 cm were interpreted as milankovitch cycles of short eccentricity 130 and 95 kyr obliquity 36 6 and 46 kyr and precession 22 1 20 9 and 18 kyr respectively the 100 kyr tuned floating astronomical time scale indicates that the duration of the 11 2 m thick section is 0 67 myr and the average depositional rate is 1 70 cm kyr the duration of the 1 8 m thick main fossil bearing interval that contains 8 beds of feathered dinosaur primitive bird fossils can be estimated as short as 150 kyr the results suggest that climate fluctuations manifested in paleobotanical sedimentological and geo chemical records of the yixian formation may have been controlled by orbital forcing during early cretaceous 2013 elsevier b v all rights reserved

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

deccan volcanism caused coupled pco2 and terrestrial temperature rises and pre impact extinctions in northern china evaluating the terrestrial climate record provides a critical test of the roles of chicxulub impact and deccan traps volcanism during the cretaceous paleogene k pg mass extinction most evidence came from marine records but our new clumped isotopes data from paleosol carbonates in the songliao basin provide a terrestrial climate history from northern china this reveals there was a pre impact warming caused by the onset of deccan traps volcanism whereas the following short term cooling then another warming episode were likely caused by chicxulub impact and post boundary volcanism our study suggests that the pco levels were probably the main control on the latest cretaceous cooling and the climatic fluctuations across the k pg boundary interval in northern china in the songliao basin the pre impact deccan traps volcanism links to losses of half of the lacustrine algae species charophytes and almost all of the lacustrine ostracodes this suggests that the deccan traps volcanism had already destabilized the ecosystem and caused extinctions prior to the chicxulub impact

40ar 39ar and k ar dating on the volcanic rocks in the songliao basin ne china constraints on stratigraphy and basin dynamics precise 40ar 39ar and k ar ages were determined on sanidine and whole rock separates of volcanic rocks in the songliao basin sb the volcanism is characterized by a series of continual and episodic eruptions in the late jurassic 147 157 ma and early cretaceous 113 136 ma a fairly accurate chronostratigraphic column was first established based on those data the volcanic activities happened synchronously with closure of the mongolia okhotsk ocean north to the sb structures of the volcanogenic successions are s dipping or se dipping fault blocks coupled with n dipping or nw dipping major detachment systems distribution of the volcanics revealed by high resolution seismic reflections is neither restricted within nor in agreement with the framework of the overlying sedimentary sequence striking nne this new evidence fits the overlap model proposed in the present paper that formation of the volcanic successions in the sb is related to the subduction of the mongolia okhotsk plate under the mongolia north china block during the jurassic and early cretaceous whereas the overlying sedimentary sequence unconformably on the volcanics is tectonically controlled by the oblique subduction of the pacific plate under the eurasian plate since late aptian in addition the coal bearing epiclastic sediments intercalating the volcanics were deposited at the subduction quiescence episodes when extensional collapse occurred

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

an 11 million year long record of astronomically forced fluvial alluvial deposition and paleoclimate change in the early cretaceous songliao synrift basin china abstract in the cretaceous songliao basin northeastern china boreholes have recovered detailed geologic data from sub basins that developed during the early rifting of the basin among these the lower cretaceous shahezi formation k1s in the songshen 4 ss4 well is represented by an 836 m thick succession of fluvial alluvial deposits with coals distributed throughout the upper part of the formation gamma ray gr logging data are quantitatively related to grain size defined litho facies that recur throughout the succession with high gr values in mudstones and low gr values in sandstones cyclostratigraphic analysis of the gr log reveals depositional cycling at frequencies that are consistent with those of the earth s astronomical parameters the results also indicate that occurrence of coal beds occur every 100 kyr when development of vegetation at the depositional site was promoted by humid climate we propose a model of astronomically forced hydroclimate change to explain the cycling of depositional environments between fluvial and alluvial conditions the model describes a principally fluvial environment that episodically experienced at one extreme advancing alluvial conditions involving a drop in base level lake recession and increased aridity conglomerates and coarse sands and at the other extreme an advancing lakeshore with a rise in base level and increased humidity fine sands silts muds and coal a floating astronomical time scale was established by calibrating long orbital eccentricity 405 kyr cycles interpreted along the gr series the results indicate that the duration of the k1s is 11 14 myr 27 5405 kyr long orbital eccentricity cycles corresponding to an average sedimentation rate of 6 55 cm kyr the recognition of astronomical forcing in this early cretaceous fluvial alluvial dominated depositional setting offers a new framework for interpreting the sedimentary cyclicity and dynamics of early rift basins and for developing time scales

mid latitude terrestrial climate of east asia linked to global climate in the late cretaceous reply the late cretaceous late campanian to maastrichtian was characterized by a variable greenhouse climate with evidence for cooling and or glaciation and warming events most of these climatic signals are derived from marine records and knowledge of the terrestrial climate especially in the mid latitudes is limited due to fragmentary geological records on continents here we report mid latitude terrestrial stable oxygen and carbon isotope data from pedogenic carbonates in the nearly continuous late cretaceous age sk 1 core drilled in the songliao basin northeastern china our data indicate a punctuated mid latitude terrestrial climate in the late cretaceous we interpret the negative excursion of pedogenic carbonate 18o in the early maastrichtian to be the result of decreasing temperature and or strengthened westerlies during global cooling and possible glaciation providing valuable mid latitude terrestrial evidence for this event the negative 13c isotopic excursion ca 66 ma is modeled as higher primary productivity caused by increasing temperature and precipitation in response to a warming climate in the latest cretaceous our continuous stable isotopic records in the songliao basin are in accordance with previously published global late cretaceous records of climate variability from marine and terrestrial regions and demonstrate the sensitivity of mid latitude terrestrial climate in a greenhouse world

continental scientific drilling project of cretaceous songliao basin scientific objectives and drilling technology abstract the continental scientific drilling project at the cretaceous age songliao basin is a drilling initiative under the framework of the international continental scientific drilling program to recover a nearly complete cretaceous terrestrial sedimentary record in the songliao basin northeastern china the recovered cores will provide unique opportunities for the geosciences community to advance the understanding of climate change in the cretaceous greenhouse world and provide a documentation of geological events relevant to the carbon cycle during this time period this drilling project will address significant geological questions such as the identification of important stratigraphic boundaries and the marine terrestrial correlations of stratigraphy the reasons for the biotic response to the terrestrial environmental changes the terrestrial response to the cretaceous oceanic anoxic events the formation of terrestrial petroleum source rocks and the mechanisms for the cretaceous magnetic normal superchron cns in the first stage of this drilling project the ski drilling rock cores of 2485 89 m in total length were recovered and the recovery ratio reached 96 46 a series of drilling and coring technologies including regular confined directional and sealed coring were utilized to ensure a higher recovery ratio for the core and will be described at the end of this paper well loggings were conducted right after coring core handling and storage were arranged in such a way that the scientific research was conducted on half of each core whereas the other half of each core was preserved for long term storage the upcoming second stage the skii drilling will combine with data from the existing ski to provide complete high resolution climate records of the terrestrial environment for the whole cretaceous time period

development of a river delta a case study of cimanuk river mouth indonesia this paper describes delta development processes with particular reference to cimanuk delta in indonesia cimanuk river delta the most rapidly growing river delta in indonesia is located on the northern coast of java island the delta is subject to ocean waves of less than 1 m height due to its position in the semi enclosed java sea in the indonesian archipelago the study has been carried out using a hydrodynamic model that accounts for sediment movement through the rivers and estuaries as an advanced approach to management of river deltas a numerical model namely mike 21 is used as a tool in the management of cimanuk river delta from calibration and verification of hydrodynamic model it was found that the best value of bed roughness was 0 1 m for the sediment transport model the calibration parameters were adjusted to obtain the most satisfactory results of suspended sediment concentration and volume of deposition by comparing the computed and observed data in the calibration the best values of critical bed shear stress for deposition critical bed shear stress for erosion and erosion coefficient were 0 05 n m 2 0 15 n m 2 and 0 00001 kg m 2 s 1 respectively the calibrated model was then used to analyse sensitivity of model parameters and to simulate delta development during the periods 1945 1963 and 1981 1997 it was found that the sensitive model parameters were bed shear stresses for deposition and erosion while the important model inputs were river suspended sediment concentration sediment characteristics and hydrodynamic the model result showed reasonable agreement with the observed data as evidenced by field data the mathematical model proves that the cimanuk river delta is a river dominated delta because of its protrusion pattern and very high sediment loads from the cimanuk river it was concluded that 86 of sediment load from the cimanuk river was deposited in the cimanuk delta copyright 2008 john wiley sons ltd

late cretaceous stratigraphy songliao basin ne china sk1 cores abstract the songliao basin is the largest cretaceous oil and gas producing lacustrine basin in china with its greatest aerial extent in the middle cretaceous a coring program sk1 has to date yielded 2485 89 m of continuous core 96 46 recovery and provides significant material for cretaceous research the sequence of the core consists mainly of lacustrine sandstone dark grey mudstone shale and oil shale the upper cretaceous stratigraphic section has been subdivided into the quantou qingshankou yaojia nenjiang sifangtai and mingshui formations in ascending order late cretaceous microfossils are diverse and abundant a detailed biostratigraphic study has subdivided the sequence into high precision biozones 21 ostracode assemblages 10 phytoplankton assemblages 7 palynological zones and 4 charophyta assemblages respectively in addition marine foraminifera were first discovered from the basin three 206pb 238u ages and one 40ar 39ar age were analysed ten local magnetozones have been recognised in the sk1 north and two magnetozones have been indicated in the sk1 south based on biostratigraphy high resolution magnetostratigraphy and sims u pb zircon analyses the sk1 stratigraphy is correlated with upper cretaceous stages in the international geologic time scale the upper part of the quantou formation is the lower turonian the qingshankou formation is the upper turonian lower coniacian the yaojia formation is from the upper coniacian to middle santonian the nenjiang formation is the upper santonian to middle campanian the sifangtai formation is limited to the upper campanian and the mingshui formation is the uppermost campanian to maastrichtian it is likely that the upper part of the mingshui formation belongs to the paleocene and the k pg boundary is within the member 2 of the mingshui formation around the depth of 328 m by new micropalaeontologic and magnetostratigraphic data

erosion of soft cohesive sediment deposits erosion behavior of soft cohesive sediment deposits has been investigated in laboratory experiments such deposits are representative of the top active layer of estuarial beds an experimental procedure involving layer by layer erosion under a range of bed shear stresses b of successively increasing magnitude was utilized interpretation of the resulting concentrationtime data together with bed density profiles yielded a description of the variation of the bed shear strength s with depth as well as an expression for the rate of surface erosion in general s increased with depth and was also influenced by the type of sediment bed consolidation period and salinity the rate of erosion was found to vary exponentially with b s 1 2 in modeling estuarial bed erosion it is essential to take these characteristics of s and the rate of erosion into account

wave beach sediment interaction with shoreline changes along a headland bounded pocket beach west coast of india grain size analysis was carried out to understand the behavior of sediment distribution in a pocket beach and to examine the relationship between the sediment distribution on surficial beach sediments with the wave energy and shoreline changes three seasons surficial beach sediment were sampled and statistical characteristics were analyzed for september 2014 february 2015 and july 2015 the mike 21 spectral wave model was utilized to estimate the wave energy distribution and shoreline changes were also mapped using resourcesat 2 liss iv satellite images and net shoreline movement method was adopted for shoreline change analysis because shoreline changes directly indicate the erosion and accretion pattern of coastal zones the analyzed sediment statistical parameters were correlated with the wave energy and shoreline changes based on the correlation it was found that wave determines the sediment distribution pattern on vengurla sandy beach the result suggests that the beach sediment was mostly medium sand with moderately well sorted fine skewed to coarse skewed with platykurtic mesokurtic and leptokurtic characteristics the study area was under influenced medium wave to high wave action the backshore samples have an average skewness of 0 030 which suggests depositional settings whereas the bermline and foreshore have an average skewness of 0 392 and 0 075 respectively illustrating the erosional conditions the sediment categorization results indicated that the backshore is stable while the bermline is partly eroded as well as accreting in nature the results show that the wave energy is playing a vital role in sediment distribution and transportation

crustal structure of the fennoscandian shield a traveltime interpretation of the long range fennolora seismic refraction profile abstract the 1979 fennoscandian long range project fennolora was aimed at the determination of the detailed structure in the earth s mantle down to a depth of about 400 km observation distances reached almost 2000 km within scandinavia between shotpoints off the north cape and the southern coast of sweden to achieve an unbiased regarding the upper mantle structure a careful crustal survey was carried out along the entire profile at the same time beneath the fennoscandian shield i e the central section of the profile the crust is characterized by quite a smooth increase in p wave velocity down to the moho which lies at a depth of about 50 km in the southern half of the shield and at about 45 km further north the mean crustal velocity is 6 6 6 7 km s at the base of the crust the velocity increases gradually from about 7 km s to 8 0 8 4 km s in a 5 10 km thick crust mantle transition zone both in the south and in the north the relatively homogeneous crust of the baltic shield borders on areas with a more differentiated velocity structure first order discontinuities at shallower depth characterize the crust mantle boundary near the southeastern tip of sweden 38 km and under the caledonides in the north 43 km

crustal evolution of fennoscandia palaeomagnetic constraints abstract palaeomagnetic poles from fennoscandia ranging in age from archaean to tertiary are compiled and graded using a modified briden duff classification scale an new filtering technique is applied to select only the most reliable poles for analysis the filtering takes into account the following information 1 1 source block of rock unit 2 2 age of rock 3 3 age of magnetization component 4 4 scatter of palaeomagnetic directions 5 5 information from multicomponent analysis of natural remanent magnetization nrm 6 6 whether the pole considered belongs to a cluster or subcluster of poles 7 7 magnetic polarity and 8 8 the author s original assignment of results data are still insufficient for the drawing of separate apparent polar wander paths apwp for different blocks or cratons of fennoscandia treating fennoscandia as a single plate a new apwp from archaean to permian is constructed from the five previously drawn apwp loops or hairpins only one the jatulian loop 2200 2000 ma disappears in filtering the loops during 1925 1700 ma and during 1100 800 ma ago are linked to svecofennian and sveconorwegian orogenies respectively palaeomagnetic data support the concept that these orogenies took place episodically three distinct orogenic pulses early middle and late can be distinguished in the cluster plots of palaeopoles the drift history of fennoscandia from archaean to permian is presented during most of geological history fennoscandia has occupied low to moderate latitudes and undergone considerable latitudinal shifts and rotations the svecofennian and sveconorwegian orogenies have different kinematic characteristics during the svecofennian orogeny fennoscandia drifted slowly while rotating a large amount in an anticlockwise sense during the sveconorwegian orogeny it drifted rapidly and rotated first clockwise and then anticlockwise the most striking feature in the drift velocity curves is however the pronounced maxima in the latitudinal drift and rotation rates 9 cm yr and 0 8 ma respectively during the late subjotnian jotnian anorogenic magmatism and rifting phase 1450 1250 ma ago possibly reflecting the passage of fennoscandia across a thermal upwelling hotspot at equatorial latitudes the use of palaeomagnetism in delineating and dating movements between blocks is demonstrated with three examples from the polar profile area the northernmost section of the european geotraverse

crustal heterogeneities and the thermal structure of the continental crust the observed linear relationship between surface heat flow q0 and the radiogenic heat production of near surface rocks a0 discovered almost two decades ago has been a primary tool used to infer the distribution of heat production in the continental crust recent evidence on the nature of compositional heterogeneities in the continental crust has led us to reexamine the q0 a0 relationship and the likely implications for the thermal structure of the lower continental crust numerical simulations of crustal thermal models indicate that some interpretations derived from this relation may be flawed in particular the length scale determined from the q0 a0 function normally thought to describe the depth distribution of crustal heat sources is significantly affected by the horizontal scale of crustal heterogeneity as a consequence most estimates of lower crustal heat flow and lower crustal temperatures obtained using heat flow data with the q0 a0 relationship are overestimates this overestimation is proportionally largest in areas of low mantle heat flux such as cratons where basal heat flux may be overestimated by more than a factor of two

tempo of the end permian event high resolution cyclostratigraphy at the permian triassic boundary the permian triassic p t boundary is marked by the most severe mass extinction in the geologic record high resolution cyclostratigraphy on a 10 4 yr scale across the p t boundary in a core from the carnic alps austria revealed significant cycles in the ratio 40 10 4 7 2 3 m identified with milankovitch cycles of 412 100 40 20 k y eccentricity 1 and 2 obliquity and precession wavelet analysis indicates continuity of deposition across the boundary with an average accumulation rate of 10 cm k y the dramatic faunal changes at the p t boundary can be constrained within an interval of 60 k y possibly 8 k y with the accompanying sharp negative global carbonisotope shift within 30 k y suggesting a catastrophic cause

regional aeromagnetic and gravity studies in scandinavia abstract attention is drawn to some large scale structures in the baltic shield interpreted from the regional magnetic and gravity measurements one set of structures is of crustal scale and it is thought to be related to plate tectonic processes while the others are smaller expressing deformation in linear or circular patterns the mid proterozoic transscandinavian granite porphyry belt 1 6 1 7 ga is also a prominent magnetic feature related to high magnetic granitoids and associated volcanics and the most important reference structure for tectonic interpretations this belt traverses scandinavia in a north south direction and is partially covered by caledonian thrust sheets a 35 50 km area of low altitude aeromagnetic measurements in southern scandinavia illustrates the magnetic and structural characteristics of this belt these are high susceptibility intrusive rocks of great vertical extent and with rounded local structures which give an overall high magnetic anomaly the transscandinavian granite porphyry belt is limited to the west by a shear zone up to 20 km wide the protogine zone which is characterized by distinct magnetic lows this zone is examined in a 50 km wide traverse of low altitude aeromagnetic measurements to the west a distinctly different magnetic pattern is observed with dominating magnetic banding low angle thrust faults and highly magnetic sills contrasting to these large scale linear structures attention is drawn to two very large nearcircular structures characterized by regional gravity highs and aligned surrounding structures the age of these structures is as yet unclear but they are younger than archaean in the north or svecokarelian in the south it is speculated that these structures formed as a consequence of large meteorite impacts

quantifying k u and th contents of marine sediments using shipboard natural gamma radiation spectra measured on dv joides resolution during international ocean discovery program iodp expeditions shipboard generated data provide the first insights into the cored sequences the natural gamma radiation ngr of the recovered material for example is routinely measured on the ocean drilling research vessel dv joides resolution at present only total ngr counts are readily available as shipboard data although full ngr spectra counts as a function of gamma ray energy level are produced and archived these spectra contain unexploited information as one can estimate the sedimentary contents of potassium k thorium th and uranium u from the characteristic gamma ray energies of isotopes in the 40 k 232 th and 238 u radioactive decay series dunlea et al 2013 quantified k th and u contents in sediment from the south pacific gyre by integrating counts over specific energy levels of the ngr spectrum however the algorithm used in their study is unavailable to the wider scientific community due to commercial proprietary reasons here we present a new matlab algorithm for the quantification of ngr spectra that is transparent and accessible to future ngr users we demonstrate the algorithm s performance by comparing its results to shore based inductively coupled plasma mass spectrometry icp ms inductively coupled plasma emission spectrometry icp es and quantitative wavelength dispersive x ray fluorescence xrf analyses samples for these comparisons come from eleven sites u1341 u1343 u1366 u1369 u1414 u1428 u1430 u1463 cored in two oceans during five expeditions in short our algorithm rapidly produces detailed high quality information on sediment properties during iodp expeditions at no extra cost

patterns of nearshore sediment transport along the nile delta egypt abstract the nearshore sediment transport system along the nile delta has been determined from the response of beaches to the construction of engineering structures from the forms of geomorphological shoreline features from large scale changes in shoreline orientations due to erosion and accretion and from longshore variations in beach sand mineralogy and grain sizes the analyses reveal local patterns of erosion and accretion that have resulted from the interruption of the longshore sediment transport by jetties and groins as well as the major erosion of the promontories adjacent to the mouths of the rosetta and damietta branches of the nile river brought about by the cutoff of the supply of river sand by construction of the high aswan dam major zones of shoreline accretion are positioned to the east of the eroding promontories demonstrating that there are strong longshore gradients in the quantities of the eastward sand transport the variation east of the rosetta branch has been quantitatively evaluated from the patterns of erosion and accretion based on sediment continuity considerations a similar delta wide comparison is made between the patterns of longshore sediment movements found in this study and those calculated by others from wave refraction diagrams based on the various lines of evidence for beach erosion longshore sediment transport and shoreline accretion four nearly self contained cells have been identified in the littoral zone of the nile delta abu quir bay the eastern flanks of the rosetta and damietta promontories and the burullus central delta region

cyclostratigraphic analysis of magnetic records for orbital chronology of the lower cretaceous xiagou formation in linze northwestern china abstract in this study we report a tuned astronomical time scale for a sedimentary formation in early cretaceous the lower linze section located in the zhangye basin of the central hexi corridor northwestern china based on detailed field investigations we identified this sediment as the xiagou formation which is widely distributed in the region a thick prominent limestone layer crops out in the middle portion of the linze section and can be correlated to a similar limestone layer in the liupanshan group which has been dated via high resolution magnetostratigraphy this correlation places an age constraint of around 114 ma for the top of the underlying strata a total of 1245 samples were collected from the 474 m thick lower linze section for magnetic susceptibility measurements and cyclostratigraphic analysis spectral and continuous wavelet analyses were applied to the low frequency magnetic susceptibility series and the percentage frequency dependent magnetic susceptibility series as well as to specific subsections exhibiting visible rhythmic bedding a hierarchy of sedimentary cycles was identified with wavelengths of 21 5 37 0 m 7 5 9 5 m 2 1 4 4 m and 1 4 1 7 m the ratios between these lengths correspond well to the ratios between the durations of earth s orbital long eccentricity short eccentricity obliquity and precession cycles we interpret these sedimentary cycles to reflect the effects of orbital forcing on sedimentary processes using band pass filtering to specifically extract eccentricity cycles we established a tuned astronomical time scale for the xiagou formation in the lower linze section with a total duration of about 6 1 myr 114 1 ma to 120 2 ma based on this timescale the sedimentation rate of the xiagou formation is estimated to be in the range of 62 105 m myr with most intervals yielding rates in the 70 80 m myr range