paleogeographic and sedimentary evolution of the south pyrenean foreland basin abstract during the paleogene and neogene the ne iberian plate underwent significant paleogeographic changes driven by the iberian and european plate collision and the resulting formation of the pyrenean orogen and its corresponding foreland basin shortening resulted in the advance of the orogenic wedge emplacement of allochthonous units and progressive basin partitioning sediment transfer systems reacted to the evolving paleogeographic scenario shifting from forebulge to foredeep and wedge top settings critical reorganizations included successive shifts from open to close drainage conditions which had an strong impact on accommodation and the stratigraphic architecture of the basin infill overfill and later erosion the aim of this work is to synthesize the paleogeographic and sedimentary evolution of the south pyrenean foreland with emphasis on the reconstruction of sediment routing the evaluation of sedimentation rate trends the timing of sedimentary shifts and the analysis of their causes stratigraphic data are compiled in a comprehensive magnetostratigraphy based chronostratigraphic framework besides sedimentary and structural data are put together to produce a series of palinspastically restored paleogeographic maps which reflect five key stages in the evolution of the region these stages include 1 the late cretaceous tectonic inversion of the extended iberian margin 2 the early eocene formation of the southern pyrenean foredeep 3 the middle eocene widening and overfilling 4 the late eocene shift into an internal drainage and 5 the late miocene drainage opening and erosion in the light of these results the variable role of tectonics climate and eustacy at different time scales are discussed

temporal buffering of climate driven sediment flux cycles by transient catchment response abstract the marine sedimentary record can exhibit a systematic cyclicity that is consistent with climate variability driven by milankovitch scale forcing milankovitch band cyclicity is widely interpreted in the hemipelagic and pelagic sediments of the marine realm and in terrestrial paleoenvironments has been observed in lacustrine sediments soils and river floodplain successions it remains unclear however if and how mountain catchments as a primary sediment source respond to these high frequency 6 yr climatic cycles and whether particulate sediment flux signals can be expected to be recorded in the clastic sedimentary record of adjacent basin fills recent field and theoretical studies suggest that mountain catchments respond transiently to high frequency forcing and so sediment discharge from the catchment is a non linear function of forcing variables using a catchment basin model we demonstrate that climate driven cyclicity in particulate sediment discharge is strongly damped when the period of climate variability is shorter than the response timescale of the eroding landscape given that the response timescale of landscapes is of the order of 10 6 yr and that milankovitch driven climate cyclicity is of the order of 10 4 10 5 yr it is likely that climate driven perturbation of upland catchments at these periods will be strongly damped by transient landscape behaviour our results therefore suggest that stratigraphy built by particulate fluxes from upland catchments and long term trends in the sediment delivery to the ocean may be relatively insensitive to short term climate variability

small scale mantle convection produces stratigraphic sequences in sedimentary basins cyclic sedimentary deposits link stratigraphic sequences that are now geographically distant but were once part of the same depositional environment some of these sequences occur at periods of 2 to 20 million years and eustatic sea level variations or regional tectonic events are likely causes of their formation using numerical modeling we demonstrate that small scale mantle convection can also cause the development of stratigraphic sequences through recurrent local and regional vertical surface movements small scale convection driven stratigraphic sequences occur at periods of 2 to 20 million years and correlate only at distances up to a few hundred kilometers these results suggest that previous sequence stratigraphic analyses may contain erroneous conclusions regarding eustatic sea level variations

lacustrine basin dynamics and organosulphur compound origin in a carbonate rich lacustrine system late oligocene mequinenza formation se ebro basin ne spain abstract the late oligocene mequinenza formation se ebro basin ne spain records the development of extensive shallow low gradient lacustrine zones which evolved under a subtropical warm climatic regime affected by humidity aridity cycles carbonate dominated inner lacustrine sequences which include thin coal seams are laterally related to muddy carbonate and siliciclastic marginal lacustrine assemblages where evaporites occur water solute concentration of the lacustrine zones changed during the alternative high and low stand episodes with lacustrine waters ranging mainly from fresh to oligosaline nonsulphurised nsc and sulphurised osc organic compounds occur in the inner lacustrine facies and record significant contributions from aquatic and terrestrial higher plants bacteria cyanobacteria photosynthetic anaerobic bacteria and algae these biomarkers show that the lacustrine system was eutrophic and the water column was poorly oxygenated and sometimes stratified as evidenced by occasional finely laminated facies and gammacerane organic matter s c ratio lower in carbonate than in coal and coal related facies suggests significant variations in the lacustrine autotrophic production and or the allochthonous organic matter contribution higher plant biomarkers were recorded mainly as normal nonsulphurised lipids by contrast bacterial and algal lipids hopanoids steroids and isoprenoids under intense sulphate reduction conditions incorporated sulphur in their hydrocarbon skeleton and gave rise to osc with distributions of thienyl and thiolanylhopanoids epithiosteranes and polyprenoids linear thiols are new biomarkers which probably were generated by the early incorporation of sulphur into funtionalised precursors e g alkanols intense methanogenesis was enhanced in some lacustrine zones owing to high organic matter input and as a consequence biomarkers of methanotrophic and methylotrophic bacteria related to methane emission are also found

palaeoenvironmental significance of palustrine carbonates and calcretes in the geological record interest in palustrine carbonates and calcretes has increased over the last 20 years since they contain significant environmental information much of the work performed in this area has focused on either of two types of terrestrial carbonate palustrine carbonates or calcretes pedogenic and groundwater yet their simultaneous study shows there may be a gradual transition from one form to the other revealing the interplay between pedogenic sedimentary and diagenetic processes three main factors control the formation of these carbonates the position of the water table the host rock and the period of sub aerial exposure in pedogenic calcretes precipitation of carbonate takes places mostly in the vadose zone above the water table and within a previous host rock or sediment in groundwater calcretes the precipitation of carbonate also occurs within a previous host rock and around the groundwater table in palustrine carbonates however the precipitation of lime mud occurs in a lacustrine water body palustrine carbonates necessarily form on previous lacustrine mud whereas both types of calcretes may form on any type of sediment or soil the sub aerial exposure time needed to form palustrine carbonates may by relatively short even a season whereas pedogenic calcretes need more time several years to millions of years groundwater calcretes do not form on the topographic surfaces so there is no need of sub aerial exposure however stable surfaces favour the development of thick groundwater calcretes small fluctuations in the water table cause gradual transitions of these three types of terrestrial carbonates and the subsequent mixture of their characteristic features causing difficulties in the interpretation of these carbonates the formation of these carbonates is controlled by palaeoenvironmental factors both commonly form in semi arid climates arid climates are also suitable for calcretes but sub humid conditions are more suitable for palustrine carbonates more indications of climatic conditions may be obtained through the analysis of the d18o content of both calcretes and palustrine carbonates and from the depth of the horizon containing carbonate nodules in pedogenic calcretes vegetation is also important in the formation of these types of carbonates data on the prevailing vegetation can be obtained from the analysis of the micro and macrofabric as well as from the d13c signal of the primary carbonates which in pedogenic carbonates has also been used to estimate atmospheric pco2 during the phanerozoic these terrestrial carbonates are widely distributed on floodplains and distal areas of alluvial basins their presence and characteristics can be used as indicators of aggradation subsidence or accommodation rates and therefore as indicators of different tectonic regimes even though the study of these carbonates has notably increased in recent years much less is known about them than about marine carbonates presently there is much emphasis on obtaining a general model for sequence stratigraphy in terrestrial basins with a need to include the carbonates analysed in this paper

insights into the crustal scale dynamics of a doubly vergent orogen from a quantitative analysis of its forelands a case study of the eastern pyrenees this study was funded by the anr france pyramid research project the french norwegian foundation 13 06 pyr fftp sedimentary basin and north pyrenean foreland fold and thrust belt formation supported study visits to the university of bergen norway collaboration with csic barcelona spain was funded by the project alpimed pie csic 201530e082

long period astronomically forced terrestrial carbon sinks abstract sequestration of organic matter by peat accumulation constitutes a primary sink for carbon in the global carbon cycle the processes that control the formation and storage of peat at geological time scales are poorly understood but are of a non solved issue of fundamental importance for understanding the global climate system we analyzed a 7 million years long terrestrial record of late oligocene age from the as pontes basin in northern spain which demonstrates that minima in the 405 kyr and 2 4 myr eccentricity cycles play a key role in peat formation such nodes exhibit reduced precession amplitudes thus avoiding extremes in seasons and seasonal contrast for a prolonged period of time in the as pontes basin this orbital configuration is associated with a decrease in siliciclastic sedimentation and enhanced peat formation feedbacks between equilibrium landscapes and ecosystem stability will lead to a deceleration of weathering and erosion rates in catchment areas and to minimum and stable sediment flux along the sediment routing system mid latitude peat burial could contribute to disturb the carbon cycle by removing atmospheric carbon at times of minimum eccentricity

prognostic modeling studies of the keweenaw current in lake superior part i formation and evolution abstract the formation and evolution of the keweenaw current in lake superior were examined using a nonorthogonal coordinate primitive equation numerical model the model was initialized by the monthly averaged temperaturefield observed in june and september 1973 and run prognostically under different forcing conditions with and without winds as a rossby adjustment problem the model predicted the formation of a well defined coastal current jet within an inertial period of 16 4 h after the current field adjusted to the initial temperature field the magnitude and direction of this current jet varied with the cross shelf temperature gradient and wind velocity it tended to intensify during northeastward downwelling favorable winds and to lessen or even reverse during southwestward to northwestward upwelling favorable or southeastward downwelling favorable winds in a case with strong stratification and without external atmospheric forcings a well defined clockwise warm core eddy formed near the

the heartbeat of the oligocene climate system a 13 million year continuous record of oligocene climate from the equatorial pacific reveals a pronounced heartbeat in the global carbon cycle and periodicity of glaciations this heartbeat consists of 405 000 127 000 and 96 000 year eccentricity cycles and 1 2 million year obliquity cycles in periodically recurring glacial and carbon cycle events that climate system response to intricate orbital variations suggests a fundamental interaction of the carbon cycle solar forcing and glacial events box modeling shows that the interaction of the carbon cycle and solar forcing modulates deep ocean acidity as well as the production and burial of global biomass the pronounced 405 000 year eccentricity cycle is amplified by the long residence time of carbon in the oceans

shear velocity variation within the d region beneath the central pacific 1 small scale variability of shear velocity vs structure in the d region beneath the central pacific is imaged using 442 broadband tangential component s waveforms recorded in western north america for 37 intermediate and deep focus tonga fiji earthquakes double array stacking of spatially binned subsets of data reveals lateral variations in the relative timing and amplitude of deep mantle discontinuity reflections on scale lengths of about 130 km across the 6 8 region of d sampled waveform modeling using localized one dimensional structures indicates variations of the vs increase at the d discontinuity ranging from 0 5 to 2 3 and discontinuity depths ranging from 2490 to 2735 km deepening and weakening from southwest to northeast across the study area two abrupt vs reductions are also detected within the d layer we thus present a laterally variable three layer model of the d region beneath the central pacific the complex structure may be associated with lateral thermal and chemical gradients that produce a lens of postperovskite material above an ultralow velocity zone on the margin of a large low shear velocity province

sonic and gamma ray astrochronology cycle to cycle calibration of atlantic climatic records to mediterranean sapropels and astronomical oscillations a high resolution analysis of cyclical patterns in gamma ray and sonic logs of the lower pliocene sediments from the gulf of cadiz southern spain was carried out results suggest that these cycles can be successfully used for a bed to bed correlation with the global reference section for the astronomical time scale in capo rossello sicily cycle patterns were used to tune the logs to the astronomical solutions of j laskar the gamma ray and sonic cyclicity was interpreted in terms of precession induced oscillations of annual rainfall in southern spain that were in part responsible for the increasing input of freshwater into the mediterranean at times of sapropel formation we demonstrate that gamma ray and sonic astrochronology can be successfully used for interregional correlation and astronomical dating with errors not higher than 20 k y

light detection and ranging lidar and multispectral studies of disturbed lake superior coastal environments due to its high spatial resolution and excellent water penetration coastal light detection and ranging lidar coupled with multispectral imaging mss has great promise for resolving shoreline features in the great lakes previous investigations in lake superior documented a metal rich halo around the keweenaw peninsula related to past copper mining practices grand traverse bay on the keweenaw peninsula provides an excellent great lakes example of global mine discharges into coastal environments for more than a century waste rock migrating from shoreline tailings piles has moved along extensive stretches of coast damming stream outlets intercepting wetlands and recreational beaches suppressing benthic invertebrate communities and threatening critical fish breeding grounds in the bay the magnitude of the discarded wastes literally reset the shoreline and provided an intriguing field experiment in coastal erosion and spreading environmental effects employing a combination of historic aerial photography and lidar we estimate the time course and mass of tailings eroded into the bay and the amount of copper that contributed to the metal rich halo we also quantify underwater tailings spread across benthic substrates by using mss imagery on spectral reflectance differences between tailings and natural sediment types plus a depth correction algorithm lyzenga method we show that the coastal detail from lidar and mss opens up numerous applications for ecological ecosystem and geological investigations

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

a complete terrestrial oligocene magnetobiostratigraphy from the ebro basin spain abstract the integrated litho bio and magnetostratigraphic cross correlation of 11 continuous and correlatable sections in the southeastern ebro basin ne spain produced a complete oligocene magnetic polarity stratigraphy ranging from latest eocene to earliest miocene the magnetic polarity zonation of the different alluvial and shallow lacustrine sections has been correlated to the gpts using fossil mammals and the distinct sequence and pattern of polarity reversals the composite magnetic polarity sequence defines a continuous sequence from chron c15n to chron 6cn 2n from 34 8 to 23 7 ma late eocene early miocene in addition a few short normal and reverse polarity events that correlate to cryptochrons in the gpts are found i e in c11n 1r and c8n 1r the resulting regional magneto biostratigraphic framework based on fossil mammals is proposed to refine the dating of the european oligocene biochronological mammal paleogene units and correlate them with the standard oligocene marine stages and the north american land mammal ages the magnetochronology now established enables more precise dating of the late eocene and oligocene paleofloristic and paleofaunistic changes in southwestern europe which were coeval to ongoing global paleoclimatic and paleoceanographic changes on earth caused by high latitude cooling and ice sheet development in eastern antarctica

cyclostratigraphy and eccentricity tuning of the early oligocene through early miocene 30 1 17 1 ma cibicides mundulus stable oxygen and carbon isotope records from walvis ridge site 1264 few astronomically calibrated high resolution 5 kyr climate records exist that span the oligocene miocene time interval notably available proxy records show responses varying in amplitude at frequencies related to astronomical forcing and the main pacemakers of global change on astronomical time scales remain debated here we present newly generated x ray fluorescence core scanning and benthic foraminiferal stable oxygen and carbon isotope records from ocean drilling program site 1264 walvis ridge southeastern atlantic ocean complemented by data from nearby site 1265 the site 1264 benthic stable isotope records span a continuous 13 myr interval of the oligo miocene 30 1 17 1 ma at high resolution 3 0 kyr spectral analyses in the stratigraphic depth domain indicate that the largest amplitude variability of all proxy records is associated with periods of 3 4 m 3 4 m and 0 9 m 0 9 m which correspond to 405 and 110 kyr eccentricity using a magnetobiostratigraphic age model maxima in caco3 content 18o and 13c are interpreted to coincide with 110 kyr eccentricity minima the strong expression of these cycles in combination with the weakness of the precession and obliquity related signals allow construction of an astronomical age model that is solely based on tuning the caco3 content to the nominal la2011 ecc3l eccentricity solution very long period eccentricity maxima 2 4 myr are marked by recurrent episodes of high amplitude 110 kyr 18o cycles at walvis ridge indicating greater sensitivity of the climate cryosphere system to short eccentricity modulation of climatic precession in contrast the responses of the global high latitude climate system cryosphere and carbon cycle to the 405 kyr cycle as expressed in benthic 18o and especially 13c signals are more pronounced during 2 4 myr minima the relationship between the recurrent episodes of high amplitude 110 kyr 18o cycles and the 1 2 myr amplitude modulation of obliquity is not consistent through the oligo miocene identification of these recurrent episodes at walvis ridge and their pacing by the 2 4 myr eccentricity cycle revises the current understanding of the main climate events of the oligo miocene

checklist for the use of potassium concentrations in siliciclastic sediments as paleoenvironmental archives weathering indices quantify the release of mobile elements from source units of soils and sediments they have been employed in geosciences for more than three decades but their performance in sedimentary archives can still be improved by deciphering other forcing factors than climatic from the most common alkali and alkaline earth metals included in the weathering indices k seems to be most suitable for deciphering paleoclimate records of temperate to subtropical non arid climates assuming the interpretation respects the complex of controlling factors on sediment geochemistry as a case study normalised k concentrations in siliciclastic sediments of the most basin miocene period central europe are revisited here and variations compared with modern fluvially transported solids existing knowledge on manifold controls of k concentrations in sediments is summarised and used to propose list of possible controlling factors in particular al si and zr rb as grain size proxies ti al as provenance proxy relevant for k concentration in parent rocks and k rb as a measure for possible effects of metasomatism the k al or k ti element ratios may be efficient in chemostratigraphic correlations in siliciclastic basins and efficient proxies for chemical weathering in the source area the proposals in this work should stimulate future studies to overcome the underrepresentation of continental sediments in paleoclimate reconstructions

orbital forcing in pliocene pleistocene mediterranean lacustrine deposits dominant expression of eccentricity versus precession abstract milankovitch forcing of climate is expressed in the sedimentary record as lithological cycles that can have one or more of four typical periods related to precession 21 kyr obliquity 41 kyr and eccentricity 100 and 400 kyr in several mediterranean continental successions striking differences in the expression of particularly precession and eccentricity appear we present the results of an additional lower pliocene lacustrine succession from lupoaia southern romania and compare the cyclic expression in this lignite siliciclastic basin in detail with the time equivalent lignite carbonate basin of ptolemais northern greece the middle pleistocene lignite siliciclastic basin of megalopolis southern greece and the miocene carbonate clay basin of orera north eastern spain it appears that carbonate basins dominantly express precession while siliciclastic basins dominantly express eccentricity in their lithological cycles this can be explained by a more linear response to insolation forcing in carbonate basins than in siliciclastic basins alternatively it can be explained by the low amplitude of 100 kyr eccentricity at the times the carbonate sections were deposited this reduced 100 kyr amplitude was caused by minima in the 2 35 myr eccentricity cycle that co occurred with the deposition in both carbonate basins finally the expression of 100 kyr eccentricity appears to be independent of glacial cyclicity

latest oligocene late miocene lacustrine systems of the north central part of the ebro basin spain sedimentary facies model and palaeogeographic synthesis abstract in the central part of the ebro basin spain north of the ebro river three allostratigraphic or tectosedimentary units differentiated within the latest oligocene late miocene upper agenian vallesian interval are sedimentologically characterized these deposits represent carbonate and sulphate lacustrine environments fed by pyrenean alluvial systems luna system and huesca system in each unit several facies associations or lithofacies were mapped these interfinger through time gypsum lithofacies occupy the southernmost part of the study area and are surrounded by carbonate and or detrital lithofacies to the north each lithofacies consists of different carbonate sulphate and or detrital facies arranged in simple sequences decimetres to metres thick the four types of sequences characterized reflect a complex shallowing evolution involving carbonate or sulphate contexts thus each lithofacies represents the sedimentation in a particular lacustrine or alluvial subenvironment a single lacustrine system is proposed for the central part of the basin its evolution followed cycles of water level variations which caused kilometre scale migrations of the lake shoreline in this model two distinct situations or lakes alternated through time a one represents high levels associated with a single body of dilute carbonate water where massive carbonate facies formed influenced by organism proliferation these lakes had wide palustrine vegetated margins in which bioturbated facies developed b the other represents low levels that correspond to a playa lake model laminated sulphate deposits formed in the lake waters while nodular gypsum originated in the surrounding saline mud flats and within the exposed previously deposited carbonate sediments transitions from one situation to the other including minor water level fluctuations within carbonate sedimentation conditions were marked by the development of laminated and stromatolitic facies lake level variations were caused by climatic cycles and gave rise to the simple sequences and to the lithofacies lateral relationships recognized in this study correlation among tectosedimentary units in the studied pyrenean domain and in the iberian domain of the ebro basin shows that for units n1 and n2 the facies that resulted from dilute carbonate waters are rare in the lacustrine areas of the iberian margin this indicates that a strong hydrological contrast existed between both regions on this basis a theoretical asymmetrical facies model is proposed for the single lacustrine basin that extended over these regions

variable style of transition between palaeogene fluvial fan and lacustrine systems southern pyrenean foreland ne spain two palaeogene fluvial fan systems linked to the south pyrenean margin are recognized in the eastern ebro basin the cardona su ria and solsona sanau ja fans these had radii of 40 and 35 km and were 800 and 600 km2 in area respectively during the priabonian to the middle rupelian the fluvial fans built into a hydrologically closed foreland basin and shallow lacustrine systems persisted in the basin centre in the studied area both fans are part of the same upward coarsening megasequence up to 800 m thick driven by hinterland drainage expansion and foreland propagation of pyrenean thrusts fourteen sedimentary facies have been grouped into seven facies associations corresponding to medial fluvial fan channelized terminal lobe nonchannelized terminal lobe mudflat deltaic evaporitic playa lake and carbonate rich shallow lacustrine environments lateral correlations define two styles of alluvial lacustrine transition during low lake level stages terminal lobes developed whereas during lake highstands fluvial dominated deltas and interdistributary bays were formed terminal lobe deposits are characterized by extensive 100 600 m wide sheet like fine sandstone beds formed by sub aqueous quasi steady hyperpycnal turbidity currents sedimentary structures and trace fossils indicate rapid desiccation and subaerial exposure of the lobe deposits these deposits are arranged in coarsening fining sequences metres to tens of metres in thickness controlled by a combination of tectonics climatic oscillations and autocyclic sedimentary processes the presence of anomalously deeply incised distributary channels associated with distal terminal lobe or mudflat deposits indicates rapid lake level falls deltaic deposits form progradational coarsening upward sequences several metres thick characterized by channel and friction dominated mouth bar facies overlying white grey offshore lacustrine facies deltaic bar deposits are less extensive 50 300 m wide than the terminal lobes and were also deposited by hyperpycnal currents although they lack evidence of emergence sandy deltaic deposits accumulated locally at the mouths of main feeder distal fan streams and were separated by muddy interdistributary bays whereas the terminal lobe sheets expand from a series of mid fan intersection points and coalesced to form a more continuous sandy fan fringe

the age of the grande coupure mammal turnover new constraints from the eocene oligocene record of the eastern ebro basin ne spain abstract the grande coupure represents a major terrestrial faunal turnover recorded in eurasia associated with the overall climate shift at the eocene oligocene transition during this event a large number of european eocene endemic mammals became extinct and new asian immigrants appeared the absolute age of the grande coupure however has remained controversial for decades the late eocene oligocene continental record of the eastern ebro basin ne spain constitutes a unique opportunity to build a robust magnetostratigraphy based chronostratigraphy which can contribute with independent age constraints for this important turnover this study presents new magnetostratigraphic data of a 495 m thick section moia santpedor that ranges from 36 1 ma to 33 3 ma the integration of the new results with previous litho bio and magnetostratigraphic records of the ebro basin yields accurate ages for the immediately pre and post grand coupure mammal fossil assemblages found in the study area bracketing the grande coupure to an age embracing the eocene oligocene transition with a maximum allowable lag of 0 5 myr with respect to this boundary the shift to drier conditions that accompanied the global cooling at the eocene oligocene transition probably determined the sedimentary trends in the eastern ebro basin the occurrence and expansion of an amalgamated channel sandstone unit is interpreted as the forced response of the fluvial fan system to the transient retraction of the central basin lake systems the new results from the ebro basin allow us to revisit correlations for the controversial eocene oligocene record of the hampshire basin isle of wight uk and their implications for the calibration of the mammal palaeogene reference levels mp18 to mp21

prognostic modeling studies of the keweenaw current in lake superior part ii simulation the keweenaw current observed along the coast of the keweenaw peninsula in lake superior during july 1973 was simulated using a 3d nonorthogonal coordinate transformation primitive equation coastal ocean model the model domain covered the entire lake with a high resolution of 250 600 m in the cross shelf direction and 4 6 km in the alongshelf direction along the peninsula the model was initialized using the monthly averaged temperature field observed in june 1973 and was run prognostically with synoptic wind forcing plus monthly averaged heat flux good agreement was found between model predicted and observed currents at buoy stations near eagle harbor comparison of the model results with and without inclusion of heat flux suggested that combined wind and heat fluxes played a key role in the intensification of the keweenaw current during summer months the model predicted relatively strong near inertial oscillations occurred episodically under conditions of a clockwise rotating wind these oscillations intensified at the surface were weak near the coast and increased significantly offshore

orbit related long term climate cycles revealed in a 12 myr continental record from lake baikal quaternary records of climate change from terrestrial sources such as lake sediments1 2 and aeolian sediments3 4 in general agree well with marine records5 6 but continuous records that cover more than the past one million years were essentially unavailable until recently when the high sedimentation rate site of lake baikal was exploited1 2 7 8 because of its location in the middle latitudes lake baikal is highly sensitive to insolation changes9 and the entire lake remained uncovered by ice sheets throughout the pleistocene epoch making it a valuable archive for past climate here we examine long sediment cores from lake baikal that cover the past 12 million years our record reveals a gradual cooling of the asian continental interior with some fluctuations spectral analyses reveal periods of about 400 kyr 600 kyr and 1 000 kyr which may correspond to milankovitch periods reflecting orbital cycles our results indicate that changes in insolation were closely related to long term environmental variations in the deep continental interior over the past 12 million years

time scale evaluation and the quantification of obliquity forcing abstract the geologic time scale serves as an essential instrument for reconstructing earth history astrochronology linking regular sedimentary alternations to theoretical quasi periodic astronomical rhythms often provides the highest resolution age models for strata that underlie the time scale although various methods for testing astronomically tuned time scales exist they often present challenges such as the problem of circularity here we introduce an approach to extract a reliable obliquity envelope from astronomically tuned data avoiding the effects of frequency modulations that can artificially introduce astronomical beats this approach includes 1 the application of a broad obliquity filter followed by 2 a hilbert transform and 3 a low pass filter of the amplitude envelope to 4 test the significance of correlation between amplitude envelope and astronomical solution these data amplitudes provide a robust means to evaluate the climate response to obliquity forcing and more specifically to test the significance of correlation with the theoretical astronomical solution in a manner similar to the phase randomized surrogate approach previously introduced for the evaluation of precession tuning synthetic astronomical ice sheet models and several quaternary climate proxy records where obliquity can be a dominant component of astronomically driven climate variability are used to demonstrate the feasibility of the proposed method and yield new insight into climate system evolution

cenozoic vertical motions of the catalan coastal ranges ne spain the role of tectonics isostasy and surface transport 1 we analyze the cenozoic topographic evolution of the catalan coastal ranges ne spain and the role of fault activity erosion sedimentation and isostasy in controlling uplift and subsidence a forward numerical model constrained by an extensive geological and geophysical data set is used to examine the temporal and spatial record of cenozoic vertical motions we show that the effect of isostasy erosion and sedimentation is as important as the contribution of fault deformation to the topography of the catalan coastal ranges the model predicts that paleogene topography generation by thrusting was compensated by erosion up to 1 3 km and isostatic subsidence up to 1 2 km resulting in a 1 2 1 9 km high mountain range by the end of compression 29 ma during the neogene strong tectonic subsidence related to normal faulting and the consequent flexural uplift of 0 7 1 2 km surface erosion as much as 1 6 2 3 km and sedimentation up to 4 5 km led to the present landscape configuration extension rates along the barcelona fault controlled flexural uplift and in combination with erosion and sedimentation processes led to the migration of the topographic maximum of the prelitoral range toward the easternmost ebro basin

orbital forcing and abrupt events in a continental weathering proxy from central europe most basin czech republic 17 7 15 9 ma recorded beginning of the miocene climatic optimum abstract we describe orbital forcing in siliciclastic lacustrine sediments deposited in central europe ca 50 5 n and 13 5 e the most basin the czech republic between 17 7 and 15 9 ma i e before the miocene climatic optimum mco and in its early stage chemical element analysis combined with magneto and cyclostratigraphy produced a consistent stratigraphy for the studied basin fill the palaeoenvironmental record is mainly based on variations of the chemical weathering intensity in the lake catchment normalised potassium concentration k al or k ti the most basin sedimentary profile is specific by relatively high deposition rates typically 20 cm kyr sampling density corresponded to temporal resolution of 1 2 kyr and sensitivity to a regional continental climate for age control we used the atnts2012 for younger sediments and an alternative age of the onset of c5dn chron and the end of c5dr 1r short chron in the earliest studied interval the chemical weathering intensity in the catchment was controlled by precession while between 17 5 and 17 15 ma short eccentricity was mainly driving chemical weathering intensity after 17 05 ma i e just before the onset of the mco and in the period of persistent high eccentricity between 16 95 and 16 7 ma chemical weathering intensity reached its precession controlled maxima in the subsequent period of the persistent low eccentricity at 16 65 ma the orbital signal nearly vanished in the most basin abrupt but temporary environmental change occurred in the interval between 16 5 and 16 35 ma polarity chron c5cn 2n within two cycles of high eccentricity its trigger is uncertain but it might have been local or regional the obtained composite record was compared with marine 13c and 18o data showing certain global control of the most basin deposits the most basin record thus shows climatic events of the pre mco and early mco period in terrestrial settings of central europe with changes at 17 05 16 65 and 16 5 ma possibly representing triggers of the mco

spectral analysis of the lower eocene wilkins peak member green river formation wyoming support for milankovitch cyclicity abstract this study is the first to employ spectral analysis to examine meter scale sedimentary cyclicity in the wilkins peak member of the lower eocene green river formation of wyoming generally regarded as the classic example for orbital forcing of lacustrine sediments at eccentricity and precession time scales this long standing interpretation was recently contested with a much shorter duration 10 ky inferred for the dominant cyclicity earlier work lacked adequate age control or spectral analysis or both our analysis is based upon an evaluation in the frequency domain of oil yield values from four boreholes accuracy estimation for suggested orbital interpretations and comparison to independent geochronology cored intervals 266 364 m thick represent a span of 1 2 1 7 m y with temporal resolution of 3 5 ky 1 m for oil yield values variations in spectral power with depth within the original records are interpreted to reflect changes in the rate of sediment accumulation these changes are corrected prior to testing the orbital forcing hypothesis by using two methods 1 a minimal adjustment three segments accounting for the dominant changes of spectral frequency with depth and 2 correlating the published definitions of precessional cycles in these records to a 21 ky cosine curve orbital age models resulting from the two tuning methods are compared to available chronology and the tuned records are tested for the expected spectral peaks from orbitally forced records we conclude that the dominant cyclicity of the wilkins peak member is orbitally forced orbital age models overlap 40 ar 39 ar ages and inferred periods include long and short eccentricity weak obliquity and precession eccentricity is resolved in the analyzed records but the expected 95 and 125 ky periods are not resolved controlling the range of possible tuning periods and the accuracy of orbital age models sub milankovitch variability exists and can be resolved to a minimum period of 3 5 ky by the analyzed records however it cannot be characterized fully with the available chronology or by the previously calculated mean cycle duration

coexisting shear and compressional wave seismic velocity discontinuities beneath the central pacific stacking of broadband shear waves s and short period compressional waves p provides compelling evidence for the existence of a localized discontinuous increase in both s and p wave velocity 230 km above the core mantle boundary cmb beneath the central pacific modelling indicates a 1 7 increase in s velocity v s and a 0 75 increase in p velocity vp similar features have been detected intermittently on a global basis but seldom with s and p structure being resolved in the same location previous evidence for anisotropy near the cmb beneath the central pacific suggests that the discontinuity may be related to anisotropic fabrics induced by flow in the thermal boundary layer above the core

dating the northern deposits of the ebro foreland basin implications for the kinematics of the sw pyrenean front abstract dating the sedimentary infill of the northern margin of the ebro foreland basin informs about the orogen basin evolution a magnetostratigraphic section of 5 km thick combines new magnetostratigraphic results from the syntectonic alluvial uncastillo fm upper oligocene lower miocene 1 km thick the fuencalderas section with previous 3 3 km thick and new 0 7 km thick magnetostratigraphic data from the underlying fluvial campodarbe fm luesia and san marzal sections eocene oligocene this composite section allows dating the entire basin infill in this sector therefore bracketing the timing of the deformation in the southern margin of the pyrenees after considering previous kinematic studies deformation recorded by the continental deposits spans from syn gavarnie nappe activity broto and fiscal basement thrust sheets from 31 3 to 24 55 ma rupelian chattian oligocene to the syn guarga thrust activity from 24 55 to 21 2 ma chattian aquitanian oligocene miocene the accumulation rates vary from ca 22 to ca 39 cm kyr between the genetic stratigraphic units in the uncastillo fm through the section these rates are close to those of the underlying deposits of the campodarbe fm average of ca 36 cm kyr deformation for the latest pyrenean front syn guarga thrust is younger than previously assigned in 5 4 1 5 and 1 1 myr of the beginning of the punta comun thrust sheet from 29 4 ma to 24 ma lower riglos thrust sheet system from 24 to 22 5 ma and the upper riglos thrust system 22 5 to 21 4 ma respectively other significant changes in accumulation rate and its derivative also indicate variations in the tectonic activity ca 33 and 28 ma

climatic instability before the miocene climatic optimum reflected in a central european lacustrine record from the most basin in the czech republic abstract the work investigates the extensive freshwater lacustrine deposits of the most formation which formed in the period between 17 7 ma and ca 15 9 ma in order to describe climate changes just before the miocene climatic optimum mco the most basin an incipient rift within the european cenozoic rift system exhibited a sedimentary environment that was sufficiently stable to preserve orbital signatures of environmental changes changes in the mineral composition of the sediments were characterised in terms of variations in their elemental composition particularly their al si and k ti element ratios and fe sr and zr elemental abundances which were efficiently obtained using x ray fluorescence spectroscopy with a density of 3 4 samples per metre of core approximately 15 20 samples per precession cycle the sediments are distinguished by the presence of distinct and correlated horizons 1 10 cm thick containing sr ba rich crandallite a mineral from the aluminium phosphate sulphate aps group chemo magneto and cyclostratigraphy were used to correlate eight cores with lengths up to 240 m and to date the sediment discrepancies at scales of up to two precession cycles each ca 20 kyr typically 4 m per cycle were observed the primary age model was based on magnetic polarity analysis 5 reversals and later refined at the metre scale using cyclostratigraphy we interpret the onset of the basin wide lacustrine phase in the most basin as being a consequence of the enhanced input of fluvial clastic sediment to the former peat swamps during the high eccentricity period at 17 7 17 55 ma i e immediately after the initial decay of the east antarctic ice sheet according to levy et al 2016 the most important environmental change recorded by the lacustrine interval in the most basin occurred at 16 44 ma during an eccentricity maximum and is nearly coeval with further shrinkage of the east antarctic ice sheet the second stage of monotonous lacustrine deposition which exhibited enhanced precession controlled compositional variability in 16 1 16 0 ma witnessed the onset of the mco sediments younger than 15 9 ma are missing due to erosional removal after subsequent basin inversion the sediments of the most formation represent an archive of environmental change in central europe during the early stages of the mco and have a temporal resolution ca 5 kyr

constraints on localized core mantle boundary structure from multichannel broadband sks coda analysis 1 in recent years a wide range of geophysical results have offered evidence that earth s lowermost mantle is characterized by strong lateral variations in material properties among the structures of particular interest are intermittent ultralow velocity zones ulvzs located directly above the core mantle boundary cmb which were originally inferred from the distortion of teleseismic spdks phases ulvzs have been modeled as layers with sharp boundaries and seismic velocity reductions 10 and interpreted as regions of partial melt in this study we further constrain local ulvz structure beneath north america by signal processing and waveform modeling of the sks coda recorded at broadband seismic arrays secondary phases in the sks coda are effectively isolated by eigenimage processing residual i e sks less data sections from various western pacific events display clear spdks arrivals followed by a secondary phase whose timing and slowness are consistent with cmb origins one dimensional modeling of these phases by reflectivity and generalized ray synthetics favors an asymmetric model with ulvz present at only one of the cmb intercepts the preferred ulvz is characterized by reductions in p and s velocities of 18 and 50 respectively and a diffuse upper boundary these characteristics are consistent with local production and gravitational sinking of dense e g iron rich partial melt above the cmb we postulate that a gradational ulvz beneath north america may mark a lateral transition domain between regions of mantle upwelling where more uniform ulvzs exist and regions of downwelling where ulvzs are either nonexistent or imperceptibly thin

taphonomy and palaeoecology of the uppermost eocene flora from sarral eastern ebro basin palaeoclimatic implications abstract the global trend towards a colder and more arid climate at the eocene oligocene boundary triggered significant changes in the european flora here we study the latest eocene priabonian flora from lacustrine deposits at sarral in the ebro basin catalonia spain to evaluate vegetation changes near this boundary three main taphofacies are recognised 1 assemblages composed of small size sorted leaves represented by zizyphus fabaceae leaflets and pinus needles inferred to be wind transported from open woodlands located distal from the lake 2 assemblages composed of whole unsorted leaves belonging to salicaceae myricaceae myrica arensi and comptonia schrankii lauraceae daphnogene and laurophyllum and helophytic plant stems interpreted as remains of a riparian community 3 assemblages comprising disarticulated organs of tetraclinis cupressaceae and a few torn leaves of myrica arensi and salicaceae interpreted as derived from riparian or open woodland vegetation upstream from the lake the priabonian sarral flora is similar to the nearby early oligocene flora of cervera making it difficult to distinguish the effects of the eocene oligocene climatic crisis upon the vegetation sedimentological analysis indicates that the sarral leaf bed represents deposition during a drier period of small order climate cycles whereas the cervera flora represents vegetation during a wetter period of a similar cycle but under the cooler and more arid environmental conditions of the early oligocene thereby disguising large scale eocene oligocene climatic change understanding such short term sedimentary and climatic cycles is crucial in order to correctly interpret the regional climatic signal based on leaf physiognomy

how plausible are high frequency sediment supply driven cycles in the stratigraphic record abstract this paper is an attempt to quantify the plausible time scales of clastic sediment supply variations at the entrance of sedimentary basins our approach is based on the sedimentary system concept which simplifies natural systems by dividing them into three zones of dominant processes the erosion the transfer and the sedimentation subsystems we examine recent results from geomorphology which show that frequent climate changes can induce high frequency sediment flux variations at the outlet of the source area we put forward the crucial role of the transfer subsystem which conveys sediment from the erosion zone to the basin by applying a diffusive model to a number of worldwide rivers we extend from large 1000 km to intermediate 300 km rivers the previous finding that the transfer subsystem acts as a buffer for short periods sediment pulses tens to hundreds of kiloyears this implies that high frequency stratigraphic cycles in clastic accumulations fed by large drainage systems are unlikely to reflect sediment supply cycles of tens to hundreds of thousands of years of periodicities

small scale lateral shear velocity and anisotropy heterogeneity near the core mantle boundary beneath the central pacific imaged using broadband scs waves core reflected scs waves from 49 large m 5 1 deep tonga fiji events recorded in western north america are used to study a localized region of the core mantle boundary cmb under the central pacific ocean a total of 248 observations from the berkeley digital seismic network bdsn caltech united states geological survey usgs terrascope and the incorporated research institutions for seismology iris broadband arrays span epicentral distances of 73 85 scs reflection points sample a cmb patch southeast of the hawaiian islands at latitude 4 to 16 n and longitude 156 to 144 w near the proposed source location of the hawaiian plume highly variable scs travel times amplitudes waveforms and shearwave splitting indicate that the lowermost mantle in this region is heterogeneous both laterally and radially scsh sh differential travel times are on average 4 s larger than predicted by the preliminary reference earth model prem this is due to delayed scs arrivals and is largely accounted for by a model with a strong velocity decrease in d the scsh sh residuals also show a spatial trend not accounted for by a radial model indicating a lateral decrease in lower mantle shear velocity to the northeast this lateral velocity gradient appears to cause focusing of scs energy scsh sh amplitude ratios are larger than predicted by prem or by a model with a strong negative gradient with depth in d which enhances scs scs splitting corrected for lithospheric anisotropy beneath the receivers indicates spatial variations in d anisotropy with a systematic change in the orientation of the fast polarization direction from transverse to the ray path fast scsh to parallel to the ray path fast scsv along a northeast traverse these spatial trends suggest lateral gradients in the boundary layer shear flow on scale lengths of a few hundred kilometers which may be related to dynamical flow near the near the root of the large hawaiian plume

tracking rainfall in the northern mediterranean borderlands during sapropel deposition the role of mid latitude precipitation in the hydrological forcing leading to the deposition of sapropels in the mediterranean sea remains unclear the new gdec 4 2 borehole east corsica margin northern tyrrhenian sea provides the first precisely dated evidence for enhanced rainfall in the western mediterranean during warm intervals of interglacial periods over the last 547 kyr comparison of gdec 4 2 proxy records with pollen sequences and speleothems from the central and eastern mediterranean reveals that these pluvial events were regional in character and occurred probably in response to the intensification of the mediterranean storm track along the northern mediterranean borderlands in autumn winter our dataset suggests that the timing of maxima of the mediterranean autumn winter storm track precipitation coincide with that of the north african summer monsoon and sapropel deposition besides highlighting a close coupling between mid and low latitude hydrological changes our findings suggest that during warm intervals of interglacial periods the reduced sea surface water salinities together with the high flux of nutrient and organic matter produced by the monsoonal nile and wadi systems floods were maintained throughout the winter by the mediterranean rainfall this provides an important additional constraint on the hydrological perturbation causing sapropel formation

long period eccentricity control on sedimentary sequences in the continental madrid basin middle miocene spain article i nfo the middle miocene valdearenas muduex section in the internally drained continental madrid basin central spain is dated bio magnetostratigraphically between 15 2 ma and 11 5 ma the section contains two formation scale sedimentary sequences that both consist of a siliciclastic lower part and a calcareous upper part siliciclastic sedimentation took place in distal floodplain and fluvial environments while limestones resulted from carbonate precipitation in calcic soil profiles and in ephemeral lacustrine water bodies spectral analysis of the l colour time series points to the influence of the 405 kyr and 0 97 myr eccentricity cycles while the bases of the two calcareous intervals correlate to successive minima of the 2 4 myr eccentricity cycle the 405 kyr cycle lags maximum eccentricity whereas the 0 97 and 2 4 myr cycleslag minimum eccentricity each by approximately a quarter of a cycle no obliquity forcing isdetected the observed orbital configuration of 2 4 myr minima at the base of limestone dominated intervals is similar to a previously documented late miocene shift in the teruel basin of northeast spain our results indicate that long period eccentricity clim ate forcing may well be as ignificant player on long tectonic time scales in continental basin fill

evolution of the early antarctic ice ages understanding the stability of the early antarctic ice cap in the geological past is of societal interest because present day atmospheric co2 concentrations have reached values comparable to those estimated for the oligocene and the early miocene epochs here we analyze a new high resolution deep sea oxygen isotope 18o record from the south atlantic ocean spanning an interval between 30 1 my and 17 1 my ago the record displays major oscillations in deep sea temperature and antarctic ice volume in response to the 110 ky eccentricity modulation of precession conservative minimum ice volume estimates show that waxing and waning of at least 85 to 110 of the volume of the present east antarctic ice sheet is required to explain many of the 110 ky cycles antarctic ice sheets were typically largest during repeated glacial cycles of the mid oligocene 28 0 my to 26 3 my ago and across the oligocene miocene transition 23 0 my ago however the high amplitude glacial interglacial cycles of the mid oligocene are highly symmetrical indicating a more direct response to eccentricity modulation of precession than their early miocene counterparts which are distinctly asymmetrical indicative of prolonged ice buildup and delayed but rapid glacial terminations we hypothesize that the long term transition to a warmer climate state with sawtooth shaped glacial cycles in the early miocene was brought about by subsidence and glacial erosion in west antarctica during the late oligocene and or a change in the variability of atmospheric co2 levels on astronomical time scales that is not yet captured in existing proxy reconstructions

the trouble with seeing double 1 the recently discovered phase transition for mg fe sio3 from perovskite to post perovskite structure for pressure temperature conditions in the lowermost mantle provides a plausible mechanism to explain a several percent shear velocity increase detected at the top of the d region in many regions the phase transition has a large positive clapeyron slope and given the likely presence of a strong temperature increase just above the core mantle boundary d conditions may reintersect the phase boundary resulting in a thin layer of perovskite below a lens of post perovskite separated by a few percent velocity decrease detection of such a velocity decrease is shown to be much harder than detection of the shallower velocity increase due to fundamental properties of seismic waves purported observations in support of a double discontinuity are re evaluated based on waveform modeling waveform stacking procedures are required for reliable detection of the lower half of any double crossing of the phase boundary

short period p wave constraints on d reflectivity we present evidence of a p wave reflector in d beneath the central and eastern equatorial pacific obtained from nearly 7000 short period seismic recordings of earthquakes in the tonga fiji and south america subduction complexes both regions overlap previous observations of an s wave triplication at similar depths double array waveform stacking places the reflector 190 20 km above the core mantle boundary and allows for a velocity transition zone no thicker than 50 km the data admit a wide range of compressional v p and shear wave velocities v s the 2 3 increase in v s suggested by earlier long period s wave studies however necessitates only a 0 5 0 6 increase in v p the data stacks represent spatial averages over large areas of the lower mantle such that reflector intermittence and topography decrease stack amplitude and lower the apparent v p jump our results constrain these processes to act over length scales of 10 100 km

reconstruction of the chaotic behavior of the solar system from geologic records abstract astronomical solutions for planetary orbits beyond several tens of million years myr ago have large uncertainties due to the chaotic nature of the solar system mainly myr scale cycles related with the earth mars secular resonance our only accessible archive for unraveling the earth s orbital variations in the geologic past are sedimentological records yet their reliability and uncertainties are still debated here we describe myr scale orbital signals of early mesozoic monsoon records from two different sedimentary settings lake level records of the equatorial pangea and biogenic silica burial flux of deep sea panthalassa along with a marine carbon isotope compilation although most of the dominant multi myr cycles are not exactly of the same frequency 1 8 myr cycles during 216 210 ma are detected from the two mutually independent sedimentary settings and differ from available astronomical solutions this finding provides not only convincing evidence for the chaotic nature of the solar system in the geological past but also additional constraints on astronomical models on the other hand besides the orbital cycles tectonic forcing and consequent climatic perturbations could also have affected the proxies on multi myr timescales during episodes of large igneous province emplacement such as siberian trap volcanism 252 245 ma wrangellia 233 225 ma central atlantic magmatic province 202 200 ma and karoo ferrar volcanism 184 180 ma if we can distinguish orbital signals from other effects such as tectonic and volcanic processes the multi myr cycles in geologic records have the potential to reconstruct the chaotic evolution of the solar system

long periodic variations in the earth s obliquity and their relation to third order eustatic cycles and late neogene glaciations abstract evolutive spectra of four high resolution climatic proxy records reveal that the spectral power in the obliquity frequency band increases during five well defined intervals in the last 5 3 million years these intervals correspond to periods of high amplitude variations in the tilt obliquity of the earth s axis connected with a 1 2 myr cycle and to sea level lowstands of third order eustatic cycles in the haq et al 1987 curve this implies that the development of major plio pleistocene glaciations proceeded episodically and that third order cycles are glacio eustatically controlled in at least two of these intervals sinistrally coiled neogloboquadrinids entered the mediterranean at times of glacial periods one interval starts around 2 8 ma and is characterized by the first occurrence of n atlantica s another interval begins at the plio pleistocene boundary around 1 8 ma and is characterized by the common occurrence of sinistrally coiled n pachyderma also during the late miocene third order cycles correlate well with the 1 2 myr cycle of obliquity a significant drop in the third order eustatic curve starting at the tortonian messinian boundary for instance coincides with a period of high amplitude variations in the obliquity time series connected with the 1 2 myr cycle

shallow lacustrine carbonate microfacies document orbitally paced lake level history in the miocene teruel basin north east spain results are presented of a detailed carbonate petrographic study of an upper miocene lacustrine mixed carbonate siliciclastic succession in the teruel basin spain with the aim of constraining lake level variability at different stratigraphic scales regular alternations of red to green mudstone and lacustrine limestone termed the basic cycle reflect lake level variations at the metre scale in an earlier study the basic cycle was shown to be controlled by the climatic precession cycle petrographic analysis made it possible to distinguish two main carbonate microfacies groups characteristic of very shallow transient and shallow permanent lake environments respectively in addition to the basic cyclicity the microfacies analysis reveals lake level variations on a larger scale as a consequence the astronomical forcing hypothesis of the cyclicity in the cascante section is explored further a climate modelling study of orbital extremes indicates that high lake levels could relate to enhanced net winter precipitation and runoff during precession minima consistent with mediterranean geological data using this phase relationship an astronomical tuning of the cycles is established starting from astronomical ages of magnetic reversal boundaries subsequently successive basic cycles are correlated to precession minima the tuning reveals an identical number of basic cycles in the cascante section as precession related sapropel cycles in the deep marine succession at monte dei corvi italy corroborating the precessional control of the basic cycles at cascante lake level highstands in the large scale cycle identified by the microfacies analysis relate to maxima in both the ca 100 and 405kyr eccentricity cycles again consistent with mediterranean geological data subtraction of the identified astronomically related lake level variations from the palaeoenvironmental record at cascante indicates a shift to deeper and more permanent lacustrine environments in the upper half of the section the cause of this shift remains unclear but it may be linked to tectonics non astronomical climate long period astronomical cycles or autogenic processes 2008 the authors journal compilation 2008 international association of sedimentologists

coal deposition in carbonate rich shallow lacustrine systems the calaf and mequinenza sequences oligocene eastern ebro basin ne spain two main coal bearing sequences developed during the oligocene in the tertiary ebro basin the calaf early oligocene and mequinenza late oligocene coal basins coal deposition took place in shallow marsh swamp lake complexes which sometimes became closed and evolved under warm climatic conditions with fluctuating humidity these shallow lacustrine systems are closely interrelated with the terminal parts of the distributive fluvial systems which spread from the tectonically active ebro basin margins laterally extensive lignite bearing sequences including rather thin lenticular autochthonous and or hypautochthonous coal seams with high ash and sulphur contents characterized coal deposition in the shallow lacustrine systems coal seam geometry which makes them nearly subeconomic resulted from the tectonic instability during basin margin evolution and the sometimes closed arid conditions under which the lacustrine systems evolved high ash and sulphur contents resulted from the inadequate isolation of peat forming environments from clastic influx and from the very low acidity and sometimes high sulphate contents of the lacustrine waters coal exploration in shallow lacustrine sequences similar to those described here must take into account that the spread of coal forming environments and maxima of coal deposition are usually coincident with lake expansions and retraction or shifting of the terminal fluvial zones interrelated with the lacustrine areas

astronomical tuning of the la vedova high cliff section ancona italy implications of the middle miocene climate transition for mediterranean sapropel formation article i nfo continuous marine successions covering the middle miocene climate transition mmct 15 13 7 ma are scarce and the lack of a high resolution magnetobiostratigraphic framework hampers the construction of astronomically tuned age models for this time interval the la vedova high cliff section exposed along the coast of the conero riviera near ancona italy is one of the few mediterranean sections covering the critical time interval of the mmct starting from an initial magnetobiostratigraphic age model a robust astronomical tuning was constructed for the interval between 14 2 and 13 5 ma using geochemical element data and time series analysis a shift in 18 o of bulk sediment towards heavier values occurs between 13 92 and 13 78 ma and could be related to the mi3b oxygen isotope event which reflects the rapid expansion of the east antarctic ice sheet in the middle miocene the onset of the cm6 carbon excursion is reflected in the bulk record by a rapid increase in 13 c at 13 86 ma our results confirm the proposition that these events coincide with a 405 kyr minimum in eccentricity and a node in obliquity related to the 1 2 myr cycle from 13 8 ma onwards distinct quadruplet cycles containing sapropelitic sediments were deposited this may suggest a causal connection between the main middle miocene cooling step and the onset of sapropel formation in the

frequency modulation reveals the phasing of orbital eccentricity during cretaceous oceanic anoxic event ii and the eocene hyperthermals abstract major advances in our understanding of paleoclimate change derive from a precise reconstruction of the periods amplitudes and phases of the milankovitch cycles of precession obliquity and eccentricity while numerous quantitative approaches exist for the identification of these astronomical cycles in stratigraphic data limitations in radioisotopic dating and instability of the theoretical astronomical solutions beyond 50 myr ago can challenge identification of the phase relationships needed to constrain climate response and anchor floating astrochronologies here we demonstrate that interference patterns accompanying frequency modulation fm of short eccentricity provide a robust basis for identifying the phase of long eccentricity forcing in stratigraphic data one and two dimensional models of sedimentary distortion of the astronomical signal are used to evaluate the veracity of the fm method and indicate that pristine eccentricity fm can be readily distinguished in paleo records apart from paleoclimatic implications the fm approach provides a quantitative technique for testing and calibrating theoretical astronomical solutions and for refining chronologies for the deep past we present two case studies that use the fm approach to evaluate major carbon cycle perturbations of the eocene and late cretaceous interference patterns in the short eccentricity band reveal that eocene hyperthermals etm2 elmo h2 i1 and etm3 x 52 54 myr ago were associated with maxima in the 405 kyr cycle of orbital eccentricity the same eccentricity configuration favored regional anoxic episodes in the mediterranean during the middle and late cenomanian 94 5 97 myr ago the initial phase of the global oceanic anoxic event ii oae ii 93 9 94 5 myr ago coincides with maximum and falling 405 kyr eccentricity and the recovery phase occurs during minimum and rising 405 kyr eccentricity on a myr scale the event overlaps with a node in eccentricity amplitudes both studies underscore the importance of seasonality in pacing major climatic perturbations during greenhouse times

oligocene magnetostratigraphy from equatorial pacific sediments odp sites 1218 and 1219 leg 199 abstract an oligocene magnetostratigraphy from odp sites 1218 and 1219 equatorial pacific has been obtained by measurements made on u channel samples augmented by about 221 discrete samples u channel samples were measured at 1 cm intervals and were stepwise demagnetized in alternating fields af up to a maximum peak field of 80 mt the magnetization directions were determined at 1 cm intervals by principal component analysis of demagnetization steps in the 20 to 60 mt peak field range a similar treatment was carried out on the discrete samples which confirmed the results obtained with u channel measurements sites 1218 and 1219 were precisely correlated based on multisensor track paleontological and shipboard magnetostratigraphic data this correlation is substantiated by u channel measurements although the magnetostratigraphy obtained from the u channels is similar to the interpretation deduced from shipboard measurements based on blanket demagnetization at peak af of 20 mt the u channel results are substantially more robust since many interpretative uncertainties are resolved by the stepwise demagnetization and higher stratigraphic resolution the temporal resolution of u channel based magnetic stratigraphy in the oligocene section of sites 1218 and 1219 is better than 5 kyr and it is therefore suitable for detection of brief polarity subchrons however in spite of the high resolution we did not find any reversals corresponding to the numerous cryptochrons identified in this time span by cande and kent s c cande d v kent revised calibration of the geomagnetic polarity time scale for the late cretaceous and cenozoic j geophys res 100 1995 6093 6095

depositional process and astronomical forcing model of lacustrine fine grained sedimentary rocks a case study of the early paleogene in the dongying sag bohai bay basin abstract the paleogene strata of the bohai bay basin include multiple sets of lacustrine fine grained sediments which provide a detailed record of the climate changes that occurred in the lake basin early paleogene fine grained sedimentary rocks are the main target layers of continental shale oil exploration in eastern china therefore studies of the geological responses to astronomical factors have important theoretical and practical significance for understanding the depositional process of lacustrine fine grained sedimentary rocks in this paper we focus on the lower es3 es3l upper es4 es4u units in four shale oil wells in the dongying sag of the bohai bay basin based on the previous establishment of a high resolution astronomical time scale in this area we have further studied the petrological characteristics and lithofacies of the fine grained sedimentary rocks then the geological responses to astronomical cycles on different scales are investigated and the models for the depositional process of fine grained sedimentary rocks under the control of astronomical factors are revealed the results indicate that the cyclic changes in mineral content and lithofacies in fine grained sedimentary rocks in the dongying sag are controlled by short eccentricity and precession cycles periods near the maximum short eccentricity range had large precession amplitudes humid climates and the development of organic rich laminated calcareous mudstone lithofacies in contrast periods near the minimum short eccentricity range had small precession amplitudes a dry climates and the development of organic containing layered muddy limestone lithofacies this study explores the depositional process of fine grained sedimentary rocks from the perspective of astronomical cycles which is conducive to the comprehensive prediction of favorable shale oil layers

testing late cretaceous astronomical solutions in a 15 million year astrochronologic record from north america abstract astronomically forced insolation cycles milankovitch cycles serve as a primary control on climate and when preserved in the stratigraphic record they provide a high resolution in situ chronometer these celestial rhythms derive from the fundamental frequencies of the solar system and earth s precession constant the fundamental frequencies of earth and mars presently define a secular resonance of 2 1 2 4 myr to 1 2 myr and are hypothesized to have undergone a transition between 50 100 ma due to the chaotic behavior of the solar system in this study a 15 myr long cyclostratigraphic record from the mid latitude western interior seaway wis spanning 82 97 ma is assembled to quantify eccentricity amplitude modulation am and obliquity am which could reveal the 2 1 resonance when present ten high precision radioisotopic dates from the study interval permit a rigorous anchoring of the floating astrochronologies for comparison with theoretical astronomical models the analysis is complimented by the construction of an astronomically tuned 13 c org composite for the early cenomanian early campanian which allows a new assessment of linkages between million year scale astronomical forcing and perturbations of the late cretaceous carbon cycle evaluation of the la2004 model reveals a switch of eccentricity modulation from 2 4 myr cycles to a 1 2 myr cycle from 90 to 86 5 ma followed by a return to a 2 4 myr cycle in younger strata compatible with observations from the wis composite these two resonance transitions are absent in the la2010d and la2011 models among 11 solutions calculated by zeebe 2017 some show resonance transitions during this period but none of them match the geological record with respect to the observed long eccentricity modulation the results of this study also suggest that positive carbon isotope excursions are closely related to obliquity power minima but this interpretation will require further analysis for full confirmation

astronomically forced climate cooling across the eocene oligocene transition in the pearl river mouth basin northern south china sea abstract during the late eocene early oligocene major changes in the global climate and environment occurred including decreases in global temperature and the appearance of antarctic glaciation these changes marked the transition from early cenozoic greenhouse conditions to icehouse conditions research on this cooling trend in the atlantic and high latitude regions has increased but few reports have studied low latitude regions e g the northern south china sea and it remains unclear whether sediment records in these areas preserve signals related to this global cooling event in this study we studied records from a lacustrine well in the wenchang sag pearl river mouth basin prmb northern south china sea we conducted palynological and cyclostratigraphic analyses to reconstruct the depositional environment and assess the influence of orbital forcing the cyclostratigraphic analysis showed that depositional cycles including fining upwards and coarsening upwards sequences were controlled mainly by long eccentricity forcing the expansion and contraction of the lake system at 1 2 myr time intervals in addition changes in the pollen spore assemblage before and after the eocene oligocene e o transition show a dramatic shift from a moderately deep lake to a shallow lake with delta facies as recorded by the wenchang to enping formations in the wenchang sag prmb these findings suggest that the climate deteriorated in response to global cooling the amplification of obliquity forcing and the coevolution between obliquity power and global pco2 during the e o transition suggest that the low latitude sedimentary records from china contain a high latitude signal furthermore the low amplitudes of the precession obliquity and eccentricity cycles are coupled with the initial decreases in the global sea level and pco2 and a positive bias in the carbon oxygen isotopic compositions at 34 3 ma these results suggest that orbital forcing played a role in elevating pco2 across a critical threshold during the e o transition 33 9 ma

orbitally paced climate evolution during the middle miocene monterey carbon isotope excursion one of the most enigmatic features of cenozoic long term climate evolution is the long lasting positive carbon isotope excursion or monterey excursion which started during a period of global warmth after 16 9 ma and ended at similar to 13 5 ma approximately 400 kyr after major expansion of the antarctic ice sheet we present high resolution 1 9 kyr astronomically tuned climate proxy records in two complete sedimentary successions from the northwestern and southeastern pacific odp sites 1146 and 1237 which shed new light on the middle miocene carbon isotope excursion and associated climatic transition over the interval 17 1 12 7 ma we recog nize three distinct climate phases with different imprints of orbital variations into the climatic signals 1146 and 123 7 delta 18 o delta 13 c 1237 xrt fe fraction 63 pm 1 climate optimum prior to 14 7 ma characterized by minimum ice volume and prominent 100 and 400 kyr variability 2 long term cooling from 14 7 to 13 9 ma principally driven by obliquity and culminating with rapid cryosphere expansion and global cooling at the onset of the last and most pronounced delta 13 c increase 3 icehouse mode after 13 9 ma with distinct 100 kyr variability and improved ventilation of the deep pacific the monterey carbon isotope excursion 16 9 13 5 ma consists overall of nine 400 kyr cycles which show high coherence with the long eccentricity period superposed on these low frequency oscillations are high frequency variations 100 kyr which closely track the amplitude modulation of the short eccentricity period in contrast to delta 13 c the delta 18 o signal additionally shows significant power in the 41 kyr band and the 1 2 myr amplitude modulation of the obliquity cycle is clearly imprinted in the 1146 delta 18 o signal our results suggest that eccentricity was a prime pacemaker of middle miocene climate evolution through the modulation of long term carbon budgets and that obliquity paced changes in high latitude seasonality favored the transition into the icehouse climate c 2007 elsevier b v all rights reserved

paleolimnological study of copper mining around lake superior artificial varves from portage lake provide a high resolution record on the keweenaw peninsula region of lake superior 0 5 gt of copper mine tailings were dumped along rivers lakes and connecting waterways between 1850 and 1968 an era of active copper and silver mining in the low energy environment of portage lake a part of the keweenaw waterway clay particles from stamp sand discharges created artificially varved lake sediments that preserved a remarkably detailed record measurements of these varves in conjunction with radiodating techniques allow precise detcrminations of deposition rates sediment and cu fluxes concentration and flux profiles produce fundamentally different patterns copper concentrations have remained high in sediments despite complete cessation of active tailings discharge however densitometer scans of x rayed cores and flux calculations at sites closest to sluicing locations reveal a good correspondence with the historic record of stamp sand production sedimentation rates and cu fluxes have declined steadily since cessation of native copper mining although elevated cu levels continue to circulate in the ecosystem comparisons of cu profiles from sediment cores across eastern lake superior suggest widespread signatures of mining and major contribution to sediments

interplay between tectonics climate and fluvial transport during the cenozoic evolution of the ebro basin ne iberia 1 three dimensional modeling that integrates fluvial sediment transport crustal scale tectonic deformation and lithospheric flexural subsidence is carried out to simulate the landscape and drainage evolution of the ebro sedimentary basin ne iberia the ebro basin underwent a long period of closed intramountain drainage as a result of tectonic topography generation at the pyrenees the iberian range and the catalan coastal range in the late oligocene the catalan coastal range underwent extension leading to the formation of the valencia trough nw mediterranean but the ebro basin remained closed for nearly 15 myr more before the ebro river cut through the remnants of the topographic barrier this drainage opening caused widespread basin incision that shaped spectacular outcrops of the syntectonic and posttectonic infill here we investigate the processes controlling these major drainage changes the modeling results constrained by a large data set on the tectonic and transport evolution of the area predict a closed phase characterized by a large lake in the central eastern ebro basin dry climatic conditions probably lowered the lake level and contributed together with rift flank uplift to prolong this endorheic basin stage the age and amount of reworked sediment after the opening are consistent with an onset of basin incision between 13 and 8 5 ma as a result of lake capture by escarpment erosion and lake level rise associated with sediment accumulation and wetter climatic conditions sea level changes in the mediterranean had no major impact in the large scale drainage evolution of the ebro basin index terms 1625 global change geomorphology and weathering 1824 1886 1815 hydrology erosion and sedimentation 3210 mathematical geophysics modeling 3344 meteorology and atmospheric dynamics paleoclimatology 8102 tectonophysics continental contractional orogenic belts keywords pyrenees drainage evolution lake sediment budget erosion flexure

20 myr of eccentricity paced lacustrine cycles in the cenozoic ebro basin abstract long period orbital forcing is a crucial component of the major global climate shifts during the cenozoic as revealed in marine pelagic records a complementary regional perspective of climate change can be assessed from internally drained lake basins which are directly affected by insolation and precipitation balance the ebro basin in northeastern iberia embraces a 20 myr long continuous sedimentary record where recurrent expansions and retractions of the central lacustrine system suggest periodic shifts of water balance due to orbital oscillations in order to test climatic orbital forcing a key piece of the basin the los monegros lacustrine system has been analyzed in detail the cyclostratigraphic analysis points to orbital eccentricity as pacemaker of short to long term lacustrine sequences and reveals a correlation of maxima of the 100 kyr 400 kyr and 2 4 myr eccentricity cycles with periods of lake expansion a magnetostratigraphy based chronostratigraphy of the complete continental record allows further assessing long period orbital forcing at basin scale a view that challenges alternate scenarios where the stratigraphic architecture in foreland systems is preferably associated to tectonic processes we conclude that while the location of lacustrine depocenters reacted to the long term tectonic driven accommodation changes shorter wavelenght oscillations of lake environments still million year scale claims for a dominance of orbital forcing we suggest a decoupling between tectonic supply driven clastic sequences fed from basin margins and climatic base level driven lacustrine sequences in active settings with medium to large sediment transfer systems

an astronomical polarity timescale for the late middle miocene based on cyclic continental sequences 1 we present an astronomically tuned polarity timescale for the late middle miocene based on a cyclic shallow lacustrine mudflat succession exposed in the orera composite section ocs calatayud basin ne spain spectral analysis and band pass filtering of high resolution carbonate and color reflectance records in the depth domain reveal cyclic changes with different cycle lengths which correspond to lithological alternations observed in the field an initial age model was constructed by calibrating the ocs magnetostratigraphy to the geomagnetic polarity timescale of cande and kent 1995 subsequent spectral analysis of the proxy records in the time domain reveals periodicities close to 23 41 and 400 kyr and to a lesser extent 100 kyr supporting an astronomical origin for the sedimentary cyclicity in the ocs we established a new age model based on the astronomical calibration of the ocs to the laskar et al 1993 la93 solution by tuning the cycles to the astronomical target curves cross spectral analysis results of the tuned time series followed by band pass filtering reveal a remarkably good and in phase relation with precession and with obliquity despite a presumed uncertainty of 20 40 kyr in the tuning in some short intervals our tuning provides astronomical ages for sedimentary cycles and subsequently for polarity reversals in the interval between 12 9 and 10 6 ma comparison with cande and kent shows that the ocs polarity reversal ages are older by 80 kyr this age discrepancy decreases with increasing age to 50 60 kyr index terms 1035 geochemistry geochronology 1520 geomagnetism and paleomagnetism magnetostratigraphy 8105 tectonophysics continental margins and sedimentary basins 9335 information related to geographic region europe 9604 information related to geologic time cenozoic keywords geochronology magnetostratigraphy cyclostratigraphy astronomical timescale orbital forcing miocene

a new probe of ulvz s wave velocity structure array stacking of scs waveforms 1 s wave velocity reductions in thin layers above the core mantle boundary cmb are resolved by modeling precursors to the tangential components of core reflected scs phases unlike most phases used to study ultra low velocity zone ulvz structure scs provides direct sensitivity to shear velocity structure vs recordings of deep earthquakes in the tonga fiji and south american subduction zones at broadband seismic networks in western north america are used to map small scale ulvz variability a two layer low vs structure exists under the central pacific an abrupt 0 8 2 0 decrease 60 86 km above the cmb is underlain by a 24 30 km thick ulvz layer having reductions of 3 3 7 4 with respect to prem no corresponding velocity reductions are found under the cocos plate the structure above the ulvz may be associated with reverse transformation of post perovskite to perovskite in a steep thermal gradient in a boundary layer above the cmb