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

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

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

recognition genesis and evolution of manganese ore deposits in southeastern china abstract manganese ore deposits are common in the falang formation of ladinian age middle triassic southeastern yunan china the deposits containing manganese oxide and manganese carbonate ores are not metamorphic in origin and they commonly contain bioclasts concentric ring structures are clearly observed in oolitic and pisolitic manganese ores an integrated approach using sedimentology and paleoenvironment analysis provides new insight into the genesis of these ores systematic research has been conducted on typical deposits dounan yanzijiao laowu tujichong using cathodoluminescence and scanning electron microscope techniques which allow elucidation of changes in laminated microtextures at the mm m scale preliminary results show that manganese enrichment in triassic deposits of this region may be related to microbial activity and mineralization was a consequence of bacterially mediated diagenetic reactions in addition findings of biodetritus in the manganese ore indicate that manganese ore is close to the redox level the concentration of manganese in solution and in precipitates in triassic is controlled by bacterial oxidation and redox conditions corresponding to sea level changes during the ladinian

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

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

an extremely large magnitude eruption close to the plio pleistocene boundary reconstruction of eruptive style and history of the ebisutoge fukuda tephra central japan abstract an extremely large magnitude eruption of the ebisutoge fukuda tephra close to the plio pleistocene boundary central japan spread volcanic materials widely more than 290 000 km2 reaching more than 300 km from the probable source characteristics of the distal air fall ash 150 km away from the vent and proximal pyroclastic deposits are clarified to constrain the eruptive style history and magnitude of the ebisutoge fukuda eruption eruptive history had five phases phase 1 is phreatoplinian eruption producing 105 km3 of volcanic materials phases 2 and 3 are plinian eruption and transition to pyroclastic flow plinian activity also occurred in phase 4 which ejected conspicuous obsidian fragments to the distal locations in phase 5 collapse of eruption column triggered by phase 4 generated large pyroclastic flow in all directions and resulted in more than 250 350 km3 of deposits thus the total volume of this tephra amounts over 380 490 km3 this indicates that the volcanic explosivity index vei of the ebisutoge fukuda tephra is greater than 7 the huge thickness of reworked volcaniclastic deposits overlying the fall units also attests to the tremendous volume of eruptive materials of this tephra numerous ancient tephra layers with large volume have been reported worldwide but sources and eruptive history are often unknown and difficult to determine comparison of distal air fall ashes with proximal pyroclastic deposits revealed eruption style history and magnitude of the ebisutoge fukuda tephra hence recognition of the ebisutoge fukuda tephra is useful for understanding the volcanic activity during the pliocene to pleistocene is important as a boundary marker bed and can be used to interpret the global environmental and climatic impact of large magnitude eruptions in the past

impacts of explosive volcanism on distal alluvial sedimentation examples from the pliocene holocene volcaniclastic successions of japan abstract volcanic activities can create cataclysmic hazards to surrounding environments and human life not only during the eruption but also by hydrologic remobilisation lahar processes after the cessation of eruptive activity although there are many studies dealing with the assessment and mitigation of volcanic hazards these are mostly concentrated on primary eruptive processes in areas proximal to active volcanoes however the influence of volcaniclastic resedimentation may surpass the impacts of primary eruptive activity in terms of both extent and persistence and can ultimately result in severe hazards in downstream areas examination of the volcaniclastic successions of non marine pliocene holocene sedimentary basins in japan has revealed hydrological volcaniclastic sedimentation in fluvial and lacustrine environments hundreds of kilometres from the inferred source volcano impacts on these distal and often spatially separated basins included drastic changes in depositional systems caused by sudden massive influxes of remobilised pyroclastic material typical volcaniclastic beds comprise centimetre to decimetre thick primary pyroclastic fall deposits overlain by metre to 10s of metres thick resedimented volcaniclastic deposits intercalated in sedimentary successions of non volcanic provenance the relatively low component of primary pyroclastic fall deposits in the volcaniclastic beds suggests that 1 potential volcanic hazards would be underestimated on the basis of primary pyroclastic fall events alone and 2 the majority of resedimented material was likely derived from erosion of non welded pyroclastic flow deposits in catchment areas rather than remobilisation of local fallout deposits from surrounding hillslopes the nature distribution and sequence of facies developed by distal volcaniclastic sediments reflect the influence of 1 proximity to ignimbrite but not directly with the distance to the eruptive centre 2 ignimbrite nature non welded or welded and volume 3 temporal changes in sediment flux from the source area 4 the physiography and drainage patterns of the source area and the receiving basin and any intervening areas and 5 the formation of ephemeral dam lakes and intra caldera lakes whose potential catastrophic failure can impact distal areas models of the styles and timing of distal volcaniclastic resedimentation are thus more complicated than those developed for proximal settings of stratovolcanoes and their volcaniclastic aprons and hence present different challenges for hazard assessment and mitigation

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

depositional processes of primary to reworked volcaniclastics on an alluvial plain an example from the lower pliocene ohta tephra bed of the tokai group central japan abstract a change from primary to reworked volcaniclastic deposits in the lower pliocene ohta tephra bed has been identified using facies analysis the ohta tephra bed is a widespread marker tephra distributed over a distance of more than 130 km the source volcano of this tephra is inferred to lie 50 to 100 km north of the most proximal ohta tephra bed the ohta tephra bed shows a change in volcaniclastic facies in distal areas eight sedimentary facies are recognized these are interpreted as pyroclastic fall pyroclastic flow and reworked mudflow flood flow channel fill swamp or backswamp lacustrine and ephemeral pond deposits in underlying and overlying non volcaniclastic beds four sedimentary facies are recognized indicating a fluvio lacustrine depositional system on an alluvial plain from the successions of volcaniclastic sedimentary facies deposition of the ohta tephra bed can be divided into stages i to vi each depositional stage is intimately related to volcanic activity stage i is the first eruption during which only the northern part of the study area was covered with fallout ash the second eruption stage of stage ii involved fallout ash distributed over all the study area these two fallout ash beds are derived from precursor eruptions stage iii reflects a period of volcanic quiescence and development of widespread lacustrine conditions the fallout ash may have destroyed vegetation and prompted greater discharge to form the large lacustrine deposits of stage iii a pyroclastic flow stage in stage iv is associated with an explosive eruption and resulted in pyroclastic flow deposits reaching the northern part of the study area stage v is characterized by mudflow deposits widespread mudflow deposits also originated from high water and clastics discharge on the unvegetated surface mudflows extend more than 180 km from the source volcano abundant supply of volcaniclastic material and high water and clastic discharge enhanced a rapid progradation of alluvial plains final reworking occurred during stage vi when volcaniclastic sediments were deposited from a fluvio lacustrine system the reworking system comprises initial mudflows followed by a normal fluvial system normal stream flow the mudflow deposits of stage v are traceable with roughly constant thickness but the volcaniclastic content of the deposits decreases in distal areas the fluvial system deposits of stage vi are thicker and have less abundant volcaniclastics in distal areas fluvial systems were braided streams promoted by volcanic eruption while they were meandering streams during the pre eruption period some eruption induced braided streams remained for a while following the cessation of volcanic activity

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

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

geochemical studies on permian manganese deposits in guichi eastern china implications for their origin and formative environments abstract permian manganese ore deposits are widely distributed in southwestern and eastern china guichi permian manganese district in southern anhui province central eastern china is currently the most important manganese metal producers in eastern china manganese ores mno 18 2 45 4 wt in guichi region occur in calcareous argillaceous and siliceous mn bearing sequence of the permian gufeng formation in contrast to mn bearing rocks the ores have higher mn fe p sr more than 1500 ppm and ni contents 480 ppm higher mn fe 5 and lan cen 2 values and lower co ni

downstream dilution of a lahar transition from debris flow to hyperconcentrated streamflow nearly instantaneous melting of snow and ice by the march 19 1982 eruption of mount st helens released a 4 106 m3 flood of water from the crater that was converted to a lahar volcanic debris flow through erosion and incorporation of sediment by the time it reached the base of the volcano over the next 81 km that it traveled down the toutle river the flood wave was progressively diluted through several mechanisms a transformation from debris flow to hyperconcentrated streamflow began to occur about 27 km downstream from the crater when the total sediment concentration had decreased to about 78 by weight 57 by volume the hyperconcentrated lahar runout flood wave transporting immense quantities of sand in suspension continued to experience progressive downstream dilution although turbulence was significantly dampened by the extremely high suspended load very large standing waves and antidune waves were observed the hyperconcentrated lahar runout flow deposited an unusual faintly stratified coarse sand which locally contained small isolated gravel lenses very similar deposits in the quaternary stratigraphy of mount st helens and other cascades volcanoes suggest that lahars may be more frequent than previously recognized

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

extensive ash falls in and around the sea of japan from large late quaternary eruptions abstract five widespread ashes of late quaternary age have been recognized on land and also in deep sea sediments in and around the sea of japan all are favorable for determining the magnitude and type of the great eruptions and for establishing a quaternary chronology around japan accurate determination of refractive indices of volcanic glass shards and phenocrysts together with chemical data have enabled successful characterization of the tephra layers and correlation between land and sea of the five tephras two are alkalic and are the products of major eruptions of two korean volcanoes the baegdusan tomakomai ash b tm and the ulreung oki ash u oki the b tm ash is recognized at the top of most cores in the northern part of the sea of japan and also on hokkaido and the northern part of honshu where a reliable archeological age is given around the 11th century the u oki ash occurs between the kikai akahoya and aira tn ashes in cores from adjacent to the ulreung do to central honshu where three radiocarbon ages of around 9300 yr b p were obtained the other three tephras are subalkalic and are correlated with large scale eruptions producing voluminous pyroclastic flows and calderas in kyushu the kikai akahoya k ah aira tn at and aso 4 ashes the former two have been well described already but their fallout areas are partly revised in this manuscript the at ash is the most prominent marker recognized not only on land of japan but also in cores from the whole area of the sea of japan and part of the pacific ocean the airfall aso 4 ash simultaneous with the aso 4 pyroclastic flow eruption is also described it mantles very extensive areas and serves as an important time marker about 70 000 years ago

the plinian eruptions of 1912 at novarupta katmai national park alaska the three day eruption at novarupta in 1912 consisted of three discrete episodes episode i began with plinian dispersal of rhyolitic fallout layer a and contemporaneous emplacement of rhyolitic ignimbrites and associated proximal veneers the plinian column was sustained throughout most of the interval of ash flow generation in spite of progressive increases in the proportions of dacitic and andesitic ejecta at the expense of rhyolite accordingly plinian layer b which fell in unbroken continuity with purely rhyolitic layer a is zoned from 99 to 15 rhyolite and accumulated synchronously with emplacement of the correspondingly zoned ash flow sequence in mageik creek and the valley of ten thousand smokes vtts only the andesiterichest flow units that cap the flow sequence lack a widespread fallout equivalent indicating that ignimbrite emplacement barely outlasted the plinian phase on near vent ridges the passing ash flows left proximal ignimbrite veneers that share the compositional zonation of their valley filling equivalents but exhibit evidence for turbulent deposition and recurrent scour episode ii began after a break of a few hours and was dominated by plinian dispersal of dacitic layers c and d punctuated by minor proximal intraplinian flows and surges after another break dacitic layers f and g resulted from a third plinian episode iii intercalated with these proximally are thin intraplinian ignimbrites and several andesite rich fall flow layers both cd and fg were ejected from an inner vent 400 m wide nested within that of episode i into which the rhyolitic lava dome novarupta was still later extruded two finer grained ash layers settled from composite regional dust clouds layer e which accumulated during the d f hiatus includes a contribution from small contemporaneous ash flows and layer h settled after the main eruption was over both are distinct layers in and near the vtts but distally they merge with cd and fg respectively they are largely dacitic but include rhyolitic shards that erupted during episode i and were kept aloft by atmospheric turbulence published models yield column heights of 23 26 km for a 22 25 km for cd and 17 23 km for fg and peak mass eruption rates of 0 7 1x108 0 6 2x108 and 0 2 0 4x108 kg s 1 respectively fallout volumes adjusted to reflect calculated redistribution of rhyolitic glass shards are 8 8 km3 4 8 km3 and 3 4 km3 for episodes i ii and iii microprobe analyses of glass show that as much as 0 4 km3 of rhyolitic glass shards from eruptive episode i fell with cde and 1 1 km3 with fgh most of the rhyolitic ash in the dacitic fallout layers fell far downwind se of the vent near the rhyolite dominated ignimbrite however nearly all of layers e and h are dacitic showing that the downwind rhyolitic ash is of co plinian rather than co ignimbrite origin

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

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

sedimentology of triassic dounan type manganese deposits western margin yangtze platform china abstract manganese mn deposits formed during the ladinian middle triassic are widely distributed along the western margin of the yangtze platform all the mn deposits occur in condensed sections cs and are formed in similar depositional and structural settings related to late stage incipient spreading of the tethys seaway differences in the degree of development and sedimentary facies in different areas determined the size ore body strike and dip and ore composition four sedimentary facies occur 1 dolomite rich mn rocks 2 glauconite bearing oolitic mn rocks 3 phosphatic fe rich mn rocks and 4 silica rich mn rocks type 1 formed along the margin of a passive stable margin type 2 formed on basin slopes with relatively low topography and deep water and types 3 and 4 formed mainly in the ma erkang basin a deep depression on the shelf ore constituents partly derived from a western source area formed medium to low grade ores in offshore areas during the ladinian maximum sea level rise ocean currents and lower cycle sea level changes produced composite ore beds seafloor hydrothermal systems typical of tethyan rifting may have provided mn bearing fluids that ascended along faults and mixed with bottom currents those fluids and or diagenetic oxidation reformed and concentrated the previously formed medium to low grade ore bodies

sedimentary and geomorphic responses to ignimbrite emplacement readjustment of the waikato river after the a d 181 taupo eruption new zealand abstract the posteruption readjustment of landscapes to major explosive volcanic eruptions is one of the most dramatic processes in physical sedimentology and geomorphology large ignimbrite emplacing eruptions from rhyolitic caldera volcanoes can form new landscapes over 104 km2 create new depocenters in calderas and bury existing topography and drainage systems beneath hundreds of meters of pyroclastic material subsequent remobilization of this debris constitutes a widespread and enduring hazard in the central north island of new zealand the a d 181 taupo eruption destroyed hydrologic systems over 20 000 km2 when emplacement of the climactic ignimbrite filled valleys and depressions with up to 70 m of pyroclastic material and blocked the waikato river outlet to the intracaldera lake basin posteruption remobilization of this material in the waikato catchment was associated with axial stream reestablishment vertical lateral and proximal distal changes in volcaniclastic lithofacies preserved al

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

distal record of multi sourced tephra in onepoto basin auckland new zealand implications for volcanic chronology frequency and hazards we have documented 80 tephra beds dating from ca 9 5 to 50 ka contained within continuously deposited palaeolake sediments from onepoto basin a volcanic explosion crater in auckland new zealand the known sources for distal 190 km from vent tephra include the rhyolitic taupo volcanic centre 4 and okataina volcanic centre 14 and the andesitic taranaki volcano 40 and tongariro volcanic centre 3 the record provides evidence for four new events between ca 50 and 28 ka mangaone subgroup suggesting okataina was more active than previously known the tephra record also greatly extends the known northern dispersal of other mangaone subgroup tephra ten rhyolitic tephra pre date the rotoehu eruption ca 50 ka and some are chemically dissimilar to post 50 ka rhyolites some of these older tephra were produced by large magnitude events however their source remains uncertain eight tephra from the local basaltic auckland volcanic field avf are also identified interpolation of sedimentation rates allow us to estimate the timing of 12 major explosive eruptions from taranaki volcano in the 27 5 9 5 ka period in addition 28 older events are recognised the tephra are trachytic to rhyolitic in composition all have high k2o contents 3 wt and there are no temporal trends this contrasts with the proximal lava record that shows a trend of increasing k2o with time by combining the onepoto tephra record with that of the previously documented pukaki crater 15 avf basaltic fall events are constrained at 34 6 30 9 29 6 29 6 25 7 25 2 24 2 23 8 19 4 19 4 15 8 and 14 5 ka and three pre 50 ka events this provides some of the best age constraints for the avf and the only reliable data for hazard recurrence calculations the minimum event frequency of both distal and local fall events can be estimated and demonstrates the auckland city region is frequently impacted by ash fall from many volcanoes

ignimbrite morphology and the effects of erosion a new zealand case study ignimbrite morphology previously generalised using aspect ratios is here quantified as the relationships between the various thicknesses of material forming an ignimbrite and the areas and volumes represented by those thicknesses the morphology can be measured for the deposit in its present day eroded condition or reconstructed for the original deposit the reconstructed morphology of the 22 500 year bp ca 11 500 km2 ca 300 km3 oruanui ignimbrite in new zealand is documented to illustrate the latter approach the oruanui ignimbrite is an intermediate aspect ratio deposit and shows broadly linear relationships between 1 in thickness and the cumulative area occupied by that thickness or less of material and 2 thickness and the volume represented by that thickness or less of material two theoretical morphologies one where thicknesses exponentially decay with distance from a maximum and the other of uniform thickness slab are compared with the oruanui data limited comparative data suggest that low aspect ratio violently emplaced ignimbrites will show upward concave curves at one extreme following the exponential decay model and high aspect ratio gently emplaced ignimbrites downward concave curves with the slab model as an extreme when plotted on diagrams where the oruanui data show linear trends the effects of erosion on oruanui and model ignimbrite morphologies are modelled using two theoretical erosion scenarios 1 material is evenly removed from the land surface and 2 thinner non welded material is preferentially removed for the oruanui ignimbrite data area is lost much more rapidly in the first instance than volume for example 5 m of erosion is sufficient to remove 50 area whereas 40 m scenario 1 or 120 m scenario 2 of erosion is required to remove 50 volume in old ignimbrites volume estimates may be reasonably accurate even after strong erosion provided the original thicknesses of ponded landscape forming material can be inferred but estimates of original area and aspect ratio will be inaccurate an envelope enclosing all known outcrops of an ignimbrite will give a better estimate of original area and aspect ratio than simply summing the areas of known outcrops

environmental impact of the 1 8 ka taupo eruption new zealand landscape responses to a large scale explosive rhyolite eruption abstract large scale ignimbrite eruptions from rhyolitic caldera volcanoes can trigger geologically instantaneous changes in sedimentary systems over huge areas by either burying existing environments or overloading them with vast quantities of unconsolidated particulate material the post eruption readjustment of the landscape to such perturbations is one of the most dramatic processes in physical sedimentology exemplified here by the 1 8 ka taupo eruption in the central north island of new zealand this eruption generated voluminous fall deposits then climaxed with emplacement of a c 30 km 3 non welded ignimbrite over a near circular area of c 20 000 km 2 approximately 90 of the area but the headwaters of many of the north island s largest rivers were impacted by both the primary pyroclastic fall and flow material large scale post eruption remobilisation of this material coupled with the re establishment of fluvial systems occurred in a distinct sequence as recorded by the evolution of sedimentary facies in different sub environments following an initial period dominated by mass flows re establishment of fluvial systems began with the headward erosion of box canyons through the ponded ignimbrite deposits a process often associated with the break out of temporary lakes aggradational streams developed in these channels rapidly evolved from shallow ephemeral sediment laden outbursts associated with flash flood events to deeper permanent braided rivers before declining sediment yields led to retrenchment of single thread rivers and a return to pre eruption gradients and bedloads years to decades later typically the modern profile of many streams and rivers follow closely their pre eruption profiles and incision and erosion is overwhelmingly confined to the deposits of the eruption itself although the general remobilisation pattern is similar for all impacted river systems detailed studies of the waikato rangitaiki mohaka ngaruroro and whanganui catchments show that the relative timing and scale of each eruption response phase differs between each catchment these reflect differences in catchment physiography and hydrology and the volume and type of pyroclastic material deposited in each ultimately the landscape response reflects the relative spatial distributions of and the volumetric ratios between the volumes of pyroclastic debris water and accommodation space in the basin cf kataoka and manville this volume

volcaniclastic resedimentation in distal fluvial basins induced by large volume explosive volcanism the ebisutoge fukuda tephra plio pleistocene boundary central japan the ebisutoge fukuda tephra plio pleistocene boundary central japan has a well recorded eruptive style history magnitude and resedimentation styles despite the absence of a correlative volcanic edifice this tephra was ejected by an extremely large magnitude and complex volcanic eruption producing more than 400 km 3 total volume of volcanic materials volcanic explosivity index 7 which extended more than 300 km away from the probable eruption centre remobilization of these ejecta occurred progressively after the completion of a series of eruptions resulting in thick resedimented volcaniclastic deposits in spatially separated fluvial basins more than 100 km from the source facies analysis of resedimented volcaniclastic deposits was carried out in distal fluvial basins the distal tephra 100 300 km from the source comprises two different lithofacies primary pyroclastic fall deposits and reworked volcaniclastic deposits the resedimented volcaniclastic succession shows five distinct sedimentary facies interpreted as debris flow deposits facies a hyperconcentrated flow deposits facies b channel fill deposits facies c floodplain deposits with abundant flood flow deposits facies d and floodplain deposits with rare flood deposits facies e resedimented volcaniclastic materials at distal locations originated from unconsolidated deposits of a climactic large ignimbrite forming eruption factors controlling inter and intrabasinal facies changes are 1 temporal change of introduced volcaniclastic materials into the basin 2 proximaldistal relationship and 3 distribution pattern of pyroclastic flow deposits relative to drainage basins thus studies of the ebisutoge fukuda tephra have led to a depositional model of volcaniclastic resedimentation in distal areas after extremely large magnitude eruptions an aspect of volcaniclastic deposits that has often been ignored or poorly understood

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

youngest exposed granitoid pluton on earth cooling and rapid uplift of the pliocene quaternary takidani granodiorite in the japan alps central japan the takidani granodiorite is a pluton 13 x 4 km situated along a major axis of the japan alps that was intruded into late pliocene age 2 4 ma volcanic rocks rb sr k ar and fission track dates on coexisting minerals from the pluton are 1 9 0 8 ma geology and mineral dates for the takidani granodiorite indicate that emplacement and cooling of the pluton occurred from late pliocene to quaternary time making the takidani granodiorite the youngest granitoid pluton exposed on earth9s surface mineral ages give a nearly straight path on a temperature time t t diagram according to the closure temperature of the minerals the linearity of the t t path indicates high thermal input from deeper levels in the early stage and cooling through rapid uplift in the late stage the rapid exposure of the takidani granodiorite resulted from more than 2000 m of quaternary uplift along the major axis of the japan alps

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

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

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

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

the influence of explosive volcanism on fluvial sedimentation the deschutes formation neogene in central oregon abstract the upper miocene to lower pliocene deschutes formation of central oregon is a sequence of interstratified volcanic and sedimentary rocks as much as 700 m thick largely derived from the adjacent cascade range the formation is correlative with the early high cascade eruptive episode that included voluminous pyroclastic eruptions and culminated in the development of an intra arc graben in the central oregon high cascades facies associations and paleocurrent data define three depositional settings 1 the eastward sloping arc adjacent alluvial plain was the depositional site by sheetfloods debris flows and hyperconcentrated flood flows their deposits from 10 to 70 m thick sequences separated by erosion surfaces with up to 60 m of relief widespread superimposed paleosols overlie these facies and constitute the upper 10 to 50 m of the section sedimentation was episodic with pulses of rapid aggradation corresponding to periods of explosive volcanism and abundant sediment supply separated by periods of nondeposition when streams incised to reestablish grade as sediment loads diminished 2 a gravel bedload river flowed northward through the basin at the foot of the alluvial plain and is represented by channel fill conglomerates and overbank sandstones and siltstones 3 a thin sequence derived from older tertiary highlands was deposited on the east side of the basin and was little affected by cascade volcanism extensive development of thick superimposed paleosols reflects the inactive nature of the eastern basin margin as a sediment source deschutes formation deposition records the response of a fluvial system to large volcanism induced sediment loads popular facies models do not adequately allow for the influence of volcanism on fluvial systems because sediment is mobilized episodically and on a scale unparalleled in nonvolcanic settings

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

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

sedimentology of proximal to distal volcaniclastics dispersed across an active foldbelt ellensburg formation late miocene central washington late miocene volcaniclastics of the ellensburg formation washington northwestern usa are exposed in basins within an integrated palaeodrainage over the depositional reach from 15 to 120 km eastward from a cascade range source area two facies associations are recognized the first is composed of laterally restricted well sorted polymictic conglomerates representing a gravel bedload regime during inter eruption periods the second comprises laterally extensive sheets bounded by deeply developed paleosols composed of monomictic pebbly pumiceous dacitic sandstones with intercalated debris flow and hyperconcentrated flood flow deposits these sheets aggraded in response to eruptive events that are sometimes recorded by air fall tephras at the bases of sequences debris flow and hyperconcentrated flood flow deposits occur as far as 120 km from source but are uncommon beyond 50 km hyperconcentrated flood flow deposits initially increase in abundance away from source as debris flow deposits diminish suggesting formation of hyperconcentrated flood flows by dilution of debris flows sandy facies form broad sheets dominated by scour fill bedding in proximal and medial settings and grade to narrower trough cross bedded sheets in distal settings suggesting moderation of flood discharges with distance base level changes associated with episodic sediment influx caused incision aggradation cycles in mainstream settings and episodic impoundment of tributaries to form lakes or rapidly aggrading poorly drained floodplains although volcanism was the primary control on depositional style concurrent development of the yakima fold belt produced a structure consequent drainage pattern that determined sediment dispersal and basin subsidence permitted preservation of both syn eruption and inter eruption facies detritus from rising anticlines was generally diluted by the volumetrically superior extrabasinal volcaniclastics but dominates deposits of small tributary streams flowing toward rather than from the cascades

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

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

identification of a pair of co ignimbrite ash and underlying distal plinian ash in the early pleistocene widespread tephra in japan abstract the early pleistocene azuki and the ku6c tephras in japan have been correlated with a compositionally zoned ignimbrite the imaichi pyroclastic flow deposit using ratios of accurately determined refractive indices of volcanic glass shards and phenocrysts and paleomagnetic directions thin fine grained white ash layers at the base of the azuki and the ku6c tephras have been correlated with the imaichi plinian fall deposit which underlies the imaichi pyroclastic flow deposit near the source shishimuta caldera on central kyushu this indicates that the azuki and the ku6c tephras comprise a pair of compositionally zoned co ignimbrite ash and underlying distal plinian ash thus the initial sequence of physical and chemical changes at the source of the pyroclastic eruption has been retained in the distal widespread tephras even though the ashes were blown downwind by westerlies as much as 900 km identification of a distal plinian ash at the base of a co ignimbrite ash ensures the stratigraphic correlation of the distal tephra with the source ignimbrite

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

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

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

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 models for fluvial sediments in an intra arc basin an example from the upper cenozoic tokai group in japan abstract the upper cenozoic tokai group is an example of fluvial sedimentation in the japanese intra arc region the sedimentary basin in which the group was deposited consiss of several small basement blocks the depositional models and their controlling factors of the tokai group around the east coast of ise bay are clarified on the basis of facies analysis five sedimentary facies associations are recognized in the group they represent deposits from gravelly low sinuosity trunk streams gravelly to sandy low sinuosity streams sandy low to middle sinuosity streams sandy high sinuosity streams with a muddy flood plain and sandy tributary high sinuosity streams with an extensive flood plain spatial and termporal facies distributions within the stratigraphic framework of the group show depositioal processes with a resolution of 0 5 to 1 m y synthesizing tectonic movements and volcanism depositional models were mainly controlled by syndepositional movement of small basement blocks involving collapse subsidence and tilting in particular the change in tilt direction of a block resulted in high sinuosity streams instead of low to middle sinuosity streams fluvial sedimentation controlled by volcanism is also recognized in the group thus fluvial depositional models in this intra arc basin are controlled by the interaction of tectonism and volcanism

peak flow responses to landscape disturbances caused by the cataclysmic 1980 eruption of mount st helens washington years of discharge measurements that precede and follow the cataclysmic 1980 eruption of mount st helens washington provide an exceptional opportunity to examine the responses of peak fl ows to abrupt widespread devastating landscape disturbance multiple basins surrounding mount st helens 300 1300 km 2 drainage areas were variously disturbed by 1 a debris avalanche that buried 60 km 2 of valley 2 a lateral volcanic blast and associated pyroclastic fl ow that destroyed 550 km 2 of mature forest and blanketed the landscape with silt capped lithic tephra 3 debris fl ows that reamed riparian corridors and deposited tens to hundreds of centimeters of gravelly sand on valley fl oors and 4 a plinian tephra fall that blanketed areas proximal to the volcano with up to tens of centimeters of pumiceous silt sand and gravel the spatially complex disturbances produced a variety of potentially compensating effects that interacted with and infl uenced hydrological responses changes to water transfer on hillslopes and to fl storage and routing along channels both enhanced and retarded runoff rapid posteruption modifi cations of hillslope surface textures adjustments of channel networks and vegetation recovery in conjunction with the complex nature of the eruptive impacts and strong seasonal variability in regional climate hindered a consistent or persistent shift in peak discharges overall we detected a short lived 5 10 yr increase in the magnitudes of autumn and winter peak fl ows in general peak fl ows were larger and moderate to large fl ows q 2 yr were more substantively affected than predicted by early modeling efforts proportional increases in the magnitudes of both small and large fl ows in basins subject to severe channel disturbances but not in basins subject solely to hillslope disturbances suggest that eruptioninduced modifi cations to fleffi ciency along alluvial channels that have very mobile beds differentially affected fl ows of various magnitudes and likely played a prominent and additional role affecting the nature of the hydrological response

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

manganese in monoclinic members of the epidote group piemontite and related minerals according to mayo 1932 who provided a brief historical review of the names used for piemontite the first researcher who described this mineral has been cronstedt in 1758 who named it rod magnesia in 1790 chevalier napione analyzed the sample described by cronstedt and termed it manganese rouge on the basis of his chemical data hauy designated the substance as manganese oxide violet silicifere in 1801 later in his traite de mineralogie hauy 1822 adopted the name proposed by cordier 1803 who first recognized the mineral as an epidote manganesifere the name piedmontite was proposed in 1853 by kenngott the basis of the type locality and more recently transformed into piemontite according to the standard guidelines for mineral nomenclature the name piemontite should be reserved to members of the ternary solid solution ca2al2 mn fe al si2o7 sio4 o oh that basically contains mn3 dominant at one site nonetheless the use of this name for any monoclinic manganiferous epidote group members showing the characteristic strong red yellow violet pleochroism is very common and probably convenient with special regard to petrographic purposes indeed the color of manganian i e mn3 bearing epidote or clinozoisite ranges to red to pinkish while manganoan i e mn2 bearing members do not exhibit the characteristic reddish hue the discredited name withamite was used to describe poorly manganiferous piemontite hutton 1938 yoshimura and momoi 1964 but corresponds on the basis of the current nomenclature to a manganian clinozoisite the name thulite sometimes erroneously used for pinkish clinozoisite should be reserved to mn3 bearing orthorhombic members in this chapter we focus on piemontite sensu stricto with the ideal formula ca2al2mn3 si2o7 sio4 o oh but also include for the reasons explained above those members of the clinozoisite epidote piemontite

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

bacterially mediated diagenetic origin for chert hosted manganese deposits in the franciscan complex california coast ranges numerous manganese deposits in the franciscan complex california occur as conformable lenses within bedded radiolarian chert argillite sequences that are in turn intercalated within thicker sections of sandstone and shale the field relations composition and petro graphic and isotopic characteristics indicate that the manganese was concentrated by diagenetic reconstitution of siliceous and hemipelagic sediment during burial the ore lenses are mn rich and fe poor assemblages consisting largely of rhodochrosite manganese silicates opal ct disordered cristobalite tridymite and quartz highly negative 13 c values for the carbonate carbon in rhodochrosite indicate that co 2 likely originated from oxidation of methane less negative values result from mixing of methanogenic carbon and co 2 derived from bacterial degradation of organic matter the 18 o values for the carbonate of rhodochrosite indicate temperatures of formation between 12 and 100 c the oxidation of methane prior to carbonate precipitation may have used the minor 0 4 0 5 mn and fe oxyhydroxides and oxides deposited with the sediment the mobilization of manganese from biogenic and terrigenous sources in the sediment column into discrete horizons and the fractioriation of manganese from iron reflect the presence of oxidation reduction boundaries and gradients in the sediment column fluids derived from compaction and silica dehydration reactions in the transformation of opal a x ray amorphous biogenic silica to quartz were involved in transportation of principal components sedimentary and geochemical attributes suggest that the deposits formed in a deep water environment in a zone of oceanic upwelling near a continental margin

plio pleistocene pumice floods in the ancestral rio grande southern rio grande rift usa abstract at least four times during the late pliocene and early pleistocene pyroclastic eruptions in the jemez volcanic field northern rio grande rift flooded the ancestral rio grande with gravel sized pumice following as much as 400 km of fluvial transport the pumice was deposited in beds 0 2 to 2 0 m thick in the camp rice formation of the southern rio grande rift a combination of reversal magnetostratigraphy and single crystal sanidine 40 ar 39 ar dating constrains the ages of pumice clast conglomerates at 3 1 2 0 1 6 and 1 3 ma the coarsest pumice beds cobbles boulders were deposited as antidune like bedforms in a fluvial channel and as a crevasse splay sheet granule and pebble sized pumice was deposited as dune bedforms in fluvial channels and as ripple bedforms on the floodplain the abundance of pumice clasts in the gravel fraction 60 100 suggests very rapid transport downriver probably in a few days or weeks the two older pumice clast conglomerates correlate with the puye formation in the jemez volcanic field whereas the younger two are coeval to the lower bandelier tuff and cerro toledo rhyolite