stratigraphy and paleoenvironmental evolution of the dinosaur rich baruungoyot nemegt succession upper cretaceous nemegt basin southern mongolia abstract portions of the dinosaur rich upper cretaceous baruungoyot nemegt succession are exposed in four geographic areas of the nemegt basin mongolia nemegt altan uul bugiin tsav and hermiin tsav lithostratigraphic correlations of these areas employ marker beds and non random stratigraphic patterns of lithology grain size variation and inferred paleoenvironments correlations suggest a minimum thickness of 350 m for the succession exposures at nemegt altan uul and bugiin tsav form a 100 km east west transect along the northern margin of the basin exposing 265 m of section from east to west the transect exposes higher portions of the succession extending from the uppermost baruungoyot formation and encompassing an almost complete section of the nemegt formation which has a minimum thickness of 235 m and can be consistently divided into three informal members lower middle and upper the lower nemegt is well exposed at nemegt and altan uul and is dominated by fluvial deposits the middle and upper nemegt are well exposed at altan uul 2 and bugiin tsav and consist of alluvial plain paludal lacustrine and fluvial deposits as confirmed by earlier studies the baruungoyot and nemegt formations exhibit an interfingering transition at nemegt the hermiin tsav section is a geographic outlier tens of kilometers west southwest of the northern transect it exposes about 150 m of section that overlaps with but is mostly lower stratigraphically than the northern transect the uppermost hermiin tsav section correlates with the lowermost nemegt section and also exhibits an interfingering contact between the baruungoyot and nemegt formations the remaining section at hermiin tsav comprises sediments of the baruungoyot formation 135 m that were deposited in alluvial fan fluvial paludal lacustrine and eolian environments and can be divided into two informal members designated as lower and upper the distribution of facies through the composite section records changes in paleoenvironments during the late cretaceous that may provide insights into the origins of the dinosaurian biostratigraphy

soil aggregate stability within morphologically diverse areas abstract knowledge of spatial distribution of soil aggregate stability as an indicator of soil degradation vulnerability and its possible prediction are required for many scientific and practical environmental studies the goal of our study was to provide a model for predicting soil aggregate stability within morphologically diverse areas where soil properties have been affected by soil material redistribution due to erosion the study was performed on a study site 6 ha area in the loess region of southern moravia czech republic haplic chernozem which is an original dominant soil unit has been transformed into different soil units eroded phases of chernozem regosol colluvial chernozem and colluvial soil 36 sampling spots were selected in order to represent diverse soils the following soil properties were measured oxidable organic carbon content cox caco3 content phh2o phkcl soil particle density s bulk density d porosity p actual field soil water content field content of iron and manganese in ammonium oxalate extract feo and mno and dithionite citrate extract fed and mnd and mass specific magnetic susceptibility lf and hf the aggregate stability was assessed using various tests to study different disruption mechanisms terrain attributes were derived from a digital elevation model in general the lowest soil aggregate stability was observed on steep slopes which were highly impacted by soil erosion the highest aggregate stability was measured on soils sampled at relatively flat upper parts which were less influenced by erosion processes higher stability was also obtained on toe slopes where the sedimentation of previously eroded soil material occurred the simple correlations revealed that characteristics resulting from the tests studying aggregate slaking due to the compression of the entrapped air water stable aggregate index and coefficient of vulnerability from fast wetting test were positively impacted by the cox p feo mno fed mnd lf and hf values and negatively by the d value the soil aggregate stability was also negatively influenced by the plan and total terrain curvatures i e larger aggregate stability was measured at concave parts in comparison with that at convex parts almost no statistically significant relationships were found in the case of the tests evaluating either aggregate disintegration caused by the micro cracking due to the different swelling or by the physico chemical dispersion due to the osmotic stress or the mechanical aggregate breakdown the multiple linear regressions resulted in the model for estimating the wsa index using the cox content total terrain curvature and actual field soil water content field in this model the cox content positively and the total terrain curvature and field value negatively influenced the value of the wsa index since cox was positively related with iron content and thus also with the magnetic susceptibility the alternative model was proposed for less costly and time consuming wsa estimation the wsa index may be predicted by combining the mass specific magnetic susceptibility lf and hf total terrain curvature and actual field soil water content field

selective dissolution of magnetic iron oxides with the acid ammonium oxalate ferrous iron extraction technique ii natural loess and palaeosol samples summary chemical extraction techniques are being introduced into environmental magnetism studies to aid in the interpretation of magnetic climate proxies previous studies have shown that the acid ammonium oxalate ferrous iron aao fe 2 extraction technique can be used to selectively dissolve very fine grained magnetite and maghemite from synthetic samples here we present the results of a study of this extraction technique to serve as a tool for selective dissolution of pedogenic magnetic minerals from a loess palaeosol transect before and after extraction the samples were subjected to classic mineral magnetic methods measurement of low field susceptibility and hysteresis parameters as well as first order reversal curve analysis in addition acquisition curves of the isothermal remnant magnetization irm were fitted with logarithmic distributions these analyses showed the magnetic dominance of lowcoercivity magnetic minerals by subtracting the irm remaining after extraction from that before extraction the magnetic fraction that was dissolved could be characterized as well supplying extra information concerning the performance of the extraction technique the aao fe 2 method successfully dissolved the superparamagnetic and part of the singledomain material from the palaeosol samples in one extraction step repeating the extraction resulted in hardly any further changes to the magnetic content of the samples the magnetic characteristics of the loess samples remained stable throughout the extraction experiment the combination of the aao fe 2 extraction with mineral magnetic analysis has successfully identified the pedogenic contribution in our samples therefore variations in the lithogenic fraction potentially present in pedogenically enhanced intervals can be assessed improving the merit of mineral magnetic climate proxy parameters

relations between subduction slab heating slab dehydration and continental growth abstract the hydrated altered basalts of the oceanic crust if subducted could release large volumes of water during their phase transformations and partial melting reactions if heat from shear strain recrystallizations largely heats the altered basaltic layer only a 2 km thick layer could be heated significantly before the slab reaches 80 125 km depth most of the released waters should be driven into the deeper but cooler regions at the slab and andesitic tonalitic partial melts should form in the heated altered basalt layer large volumes of water initially at the surface could be added to the mantle and tonalitic partial melts could be lost from the oceanic crust and added to the continental plate and could account for continental growth

pan african volcanism petrology and geochemistry of the dokhan volcanic suite in the northern nubian shield the late proterozoic dokhan volcanic suite 620 ma of the northern nubian shield is the product of late pan african volcanism the suite covers the entire spectrum from basalt to high silica rhyolite and occurs as two units a dark coloured unit containing basalt andesite dacite and a light coloured unit encompassing dacite rhyodacite rhyolite the latter unit is made up largely of ash flow tuffs and ign imbrites that are locally interstratified with basalt and andesite lava flows the suite forms a continuum in composition with a wide range of si0 2 48 77 wt cao 0 1 8 9 wt sr 81 906 ppm zr 85 340 ppm as well as most other elements and is moderately enriched in incompatible elements including rare earth elements ree the suite exhibits fractionated subparallel ree patterns that are similar overall to andean andesites and ignimbrites well defined major and trace element trends and fractionated ree profiles are consistent with a fractionated basalt to rhyolite calc alkaline magma series it is a typical calc alka line orogenic complex and exhibits mineralogical geochemical traits of arc related volcanism the suite neither resembles products of extensional nor transitional tectonic regimes as previously thought but was produced in a subduction related tectonic environment the mafic nature of the least evolved rocks of the suite along with its relatively low initial 87 sr 86 sr ratio 0 7039 are considered to indicate a mantle source a mantle derived basaltic magma fractionated with amphibole and plagioclase dominating the fractionating assemblage to produce the more felsic varieties as suggested by major and trace element fractionation modelling

quantification of the contribution of pedogenic magnetic minerals to magnetic susceptibility of loess and paleosols on chinese loess plateau paleoclimatic implications 1 this study investigates the grain size dependent properties of magnetic minerals in chinese loess samples with an aim to better understand the contribution of pedogenesis to magnetic susceptibility enhancement of the paleosols samples of loess and paleosol were divided into two fractions magnetic extracts and residues by extraction in a weak magnetic field both the raw samples of loess and paleosol i e before magnetic extraction and the samples of residues after magnetic extraction were then separated into five grain size fractions by gravitational settling and centrifugation low field magnetic susceptibility ms and the frequency dependent ms of these samples were measured and samples treated with citrate bicarbonate dithionite cbd to remove the iron oxides were also analyzed for loess samples coarse grains 2 m contribute more than 50 of the magnetic signal the 0 3 m fraction considered to be of pedogenic origin contributes 22 before magnetic extraction or 36 after magnetic extraction of the magnetic signal in loess a different pattern is found in the paleosol samples for these samples the 0 3 m fraction contributes 60 before magnetic extraction or 71 after extraction to the bulk ms in addition 91 of the magnetic signal in paleosol s5 is cbd extractable the cbd technique is able to extract pedogenic superfine grained magnetic particles and coarse dust magnetic particles these results confirm that pedogenesis leads to enhanced ms and helps to quantify the multiple origins of the bulk magnetic material that defines loess and paleosol ms this approach provides a reliable estimate of the contribution of pedogenic magnetic materials to ms our study indicates that multiple methods should be employed in analyzing paleoclimatic changes recorded by ms in the chinese loess paleosol sequences

ichnological evidence for quadrupedal locomotion in pterodactyloid pterosaurs trackways from the late jurassic of crayssac southwestern france abstract more than 30 well preserved pterosaurian trackways have been excavated from the site of crayssac lower tithonian southwestern france along with hundreds of isolated imprints the general pattern of pterosaurian trackways is described and corresponds to the morphology of the ichnogenus pteraichnus stokes 1957 a crocodilian origin for pteraichnus is rejected the morphology of the pes and manus prints is described and discussed and exhibits a great dynamic variability the three manus digit prints are confirmed as the marks of digits i iii but the high angle of divarication may reflect strong digit abduction as well as a backward folding of the digit iii the manus gait width is as much as 3 the pes gait width the narrowest manus trackways corresponds to low velocity walking in a semi erect stance whereas the widest manus trackways corresponds to higher velocity walking perhaps even running with a subhorizontal body

first order reversal curve forc diagrams of magnetic mixtures micromagnetic models and measurements first order reversal curve forc diagrams were modelled and experimentally measured for different assemblages of single domain sd magnetite particles with bimodal distributions of coercivities and varying concentrations when fitting end member forc diagrams to the forc diagrams of mixtures linear additivity is obeyed for the non interacting mixtures with predicted mixing ratios within the errorbars of the actual mixing ratios interacting mixtures are not always linearly additive experimental bimodal mixtures of magnetite particles sd pseudo single domain psd have forc diagrams that are usually linearly additive regardless of the magnetite concentration of the sample 10 or 1 measured forc diagrams of mixtures of sd magnetite and sd hematite again show that linear additivity of the two end members holds however the very small ms of hematite compared to that of magnetite makes it difficult to detect a contribution on a forc diagram from hematite unless it comprises at least 88 of the mixture

characterization of the chinese loess paleosol stratigraphy by whiteness measurement abstract changing color is one of the most striking features of loess paleosol sequences in central china the loess is light yellow and the interstratified paleosols are reddish brown until a few years ago conventional color description of loess sediments was made using a qualitative visual method the munsell system to better understand the character of the color changes and to quantify results whiteness and magnetic susceptibility were compared from four loess paleosol sequences results show that the two parameters are highly correlated in the four sequences studied grain size analysis and chemical extraction experiments indicate that the concentration and species of fine grained iron oxides are major factors determining color changes in loess and paleosols whiteness and latitude values from the last glacial interglacial sequence exhibit a linear relationship suggesting that whiteness will be a useful tool for reconstructing past atmospheric circulation especially the east asian summer monsoon whiteness and magnetic susceptibility in the luochuan profile over the past 0 9 myr display a strong correlation indicating that whiteness can be also used to reveal a long climatic history from chinese loess paleosol sequences

mapping the geochemistry of the northern rub al khali using multispectral remote sensing techniques spatial variations in sand sea geochemistry relate to mixing of different sediment sources and to variations in weathering due to problems of accessibility adequate spatial coverage cannot be achieved using field surveys alone however maps of geochemical composition produced from remotely sensed data can be calibrated against limited field data and the results extrapolated over large inaccessible areas this technique is applied to part of the rub al khali in the northern united arab emirates trend surface analysis of the results suggests that the sand sea at this location can be modelled as an east west mixing zone of two spectral components terrestrial reddened quartz sands and marine carbonate sands optical dating of these sediments suggests that dune emplacement occurred rapidly around 10 ka bp when sea level was rising rapidly the spatial distribution of mineralogical components suggests that this phase of dune emplacement resulted from coastal dune sands being driven inland during marine transgression thereby becoming mixed with rubified terrestrial sands copyright 2001 john wiley sons ltd

the composition and diagenesis of interstitial solutions ii fluxes and diagenesis at the water sediment interface in the high latitude north and south atlantic studies of the major element composition of in situ sampled pore waters are reported for the north atlantic and southern ocean between africa and antarctica the pattern of diagenetic modification of pore water composition is similar throughout the entire atlantic enrichment of na ca2 and alkalinity and depletion of mg2 and k are nearly universal only siliceous oozes consistently provide very limited evidence of cation diagenesis the changes observed and the calculated fluxes across the seawater sediment interface are much the same as those reported previously for other areas of the atlantic and caribbean fluxes of the major cations across the interface continue to be indicated as a major factor in the geochemical cycling of these elements particularly na mg2 and k diagenetic modelling indicates that aerobic oxidation of organic matter and consequent dissolution of caco3 is a dominant reaction throughout the north atlantic the data indicate that o2 oxidation to at least 30 cm is prevalent at nearly all stations dissolution of caco3 in response to the introduction of metabolic co2 can lead to significant post depositional modification of the sediments the modelling also indicates a 1 1 stoichiometric relationship between na release and mg2 uptake by sedimentary components although dissolved silica concentrations in biogenic siliceous sediments are among the highest yet reported 700 m calculations demonstrate that solubility control cannot be through equilibria with the mineral sepiolite further the influence of cation silicate surface phases generally upon solubility is contraindicated by si oh 4 mg2 h relationships evaluation of the influence of fluid advection on pore water profiles indicates that at the stations studied in the north atlantic it is small a more general consideration of the potential contribution of fluid advection to shaping interstitial water profiles demonstrates that advection can be a dominant factor in such circumstances serious misinterpretation of the nature of diagenetic reactions may result from a lack of knowledge and consideration of fluid advection

technogenic soils technosols developed from fly ash and bottom ash from thermal power stations combusting bituminous coal and lignite part i properties classification and indicators of early pedogenesis abstract large amounts of fossil fuel combustion wastes e g fly and bottom ash are discharged on land surface all over the world the uppermost layer of disposal sites is subject to soil forming processes after the development of plant cover due to natural succession or reclamation works the present study presents the analysis of technogenic soils technosols developed from ashes after combustion of bituminous coal and lignite the study involved the determination of their properties their classification and discussion of the indicators of early pedogenesis technosols located on the surface of settling ponds and landfills of selected thermal power stations in poland combusting both bituminous coal and lignite were examined standard pedological methods for the determination of soil morphology and physical chemical properties were applied dithionite and oxalate extractions of fe al si and mn were used in order to determine transformations of soil substrate during pedogenesis moreover optical microscope observations permitted finding microscale effects of soil forming processes in the studied technosols the properties of the analysed technosols are primarily influenced by the properties of the parent material i e ash from thermal power stations which in turn are strongly dependent on 1 the type of ash fly ash vs bottom ash 2 the kind of fuel bituminous coal vs lignite as well as 3 the mode of ash deposition and type of disposal site settling pond vs dry landfill properties of the studied soils are also controlled by the following soil forming factors vegetation input of soil organic matter human acceleration of soil forming processes by reclamation and climatic weather conditions leaching of soluble compounds by water from precipitation the most important morphological and physical chemical indicators of pedogenesis of the studied technosols over several decades of soil formation are as follows 1 the development of soil structure in a horizon related to the accumulation of soil organic matter 2 the decrease in ph a change in reaction from strongly alkaline towards less alkaline or acidic 3 the formation of pedogenic carbonates and their subsequent leaching from the topsoil after several dozen of years of pedogenesis and 4 the release of oxalate extractable al and si during the pedogenesis the studied soils were classified according to wrb as spolic technosols or leptic spolic technosols with various supplementary qualifiers alcalic or eutric arenic and or loamic calcic or protocalcic fluvic hyperartefactic laxic relocatic tephric or vitric certain suggestions to improve the wrb soil system are discussed in the paper

a giant sauropod footprint from the nemegt formation upper cretaceous of mongolia abstract an expedition to the nemegt formation in 2007 discovered new footprint sites at the nemegt locality the sites contained natural cast tracks identifiable as those of hadrosaurs tyrannosaurs and sauropods among the sauropod tracks was the best preserved pes print yet described from the late cretaceous of mongolia the footprint is referred to brontopodus sp on the basis of footprint morphology age and potential trackmakers from the same formation size estimations based on the track indicate the trackmaker had an acetabular height of approximately 3 0 3 5 m as such the size of the trackmaker exceeds that of any mongolian dinosaur yet reported from skeletal material

unraveling the mineralogical complexity of sediment iron speciation using sequential extractions author s slotznick sp sperling ea tosca nj miller aj clayton ke van helmond nagm slomp cp swanson hysell nl abstract 2019 american geophysical union all rights reserved iron speciation is one of the most widely applied proxies used to reconstruct oxygen levels and redox conditions in past aqueous environments the iron speciation proxy estimates proportions of different reactive iron species in fine grained sedimentary rocks which are mapped to redox conditions based on empirical calibrations from modern sediments it is based on a standardized extraction technique of sequentially applying acetate hydroxlamine hcl dithionite and oxalate solutions to a powdered sample in order to dissolve iron phases and quantify the amount of iron carried by carbonates easily reducible oxyhydroxides ferric iron oxyhydr oxides and magnetite respectively although tested on pure minerals and mixtures assessments of whether this sequential extraction process accurately dissolves the targeted minerals in natural sediments and sedimentary rocks are lacking in our study residues from each sequential extraction step were analyzed using rock magnetic and x ray diffraction experiments to identify and quantify the iron bearing minerals that were dissolved the dithionite extraction robustly removes the targeted mineralogy as magnetic data show it to solubilize nearly all of the goethite however magnetic quantification of magnetite was orders of magnitude less than the iron measured in the oxalate extraction x ray diffraction data suggest that dissolution of iron bearing clays specifically berthierine chamosite could explain this disparity our data compilation shows higher values of iron from the oxalate extraction in precambrian sedimentary rock samples suggesting a significant temporal shift in iron cycling recognition of heterogeneity in chemical extraction efficiency and targeting is vital for holistic multiproxy interpretation of past oxygen levels and communication between disciplines

unusual locomotion behaviour preserved within a crocodyliform trackway from the upper cretaceous bayanshiree formation of mongolia and its palaeobiological implications abstract crocodyliform tracks are reported from the upper cretaceous cenomanian santonian bayanshiree formation in southeastern mongolia ten tracks are preserved as natural casts forming a trackway with a quadrupedal gait pattern with a tail trail all tracks are short and wide and dominated by toe traces without plantar impressions pes tracks are characterized by four deep claw impressions and push back marks behind them manus tracks have shallow claw marks and long sub parallel scratch marks behind the preferential association of the scratch marks with only the distal digit impressions and irregular pattern of footfalls suggests that this trackway was made by a bottom walking and punting crocodyliform under water this trackway represents the first crocodyliform swim tracks in the late cretaceous of asia and the first evidence for punting behaviour of a fossil crocodyliform the swim tracks can be divided into two categories such as bottom walking tracks with punting for moving somewhat more quickly and subaqueous walking tracks without punting to be associated with slower underwater speeds the tracks show that crocodylians had adopted a bottom walking behaviour similar to extant crocodylians by cretaceous times

submarine hydrothermal weathering global eustasy and carbonate polymorphism in phanerozoic marine oolites abstract the age and fabric of 347 phanerozoic marine oolites have been compiled in order to evaluate secular variations in the original mineralogy of these physicochemically precipitated sedimentary carbonates variation in the abundance of oolite correlates with positions of global sea level ooids were common during transgressions and regressions but were rare during lowstands and highstands the rarity of oolite during continental emergence early cambrian permo triassic late tertiary quaternary probably relates to a diminished areal extent of shallow carbonate environments causes for a similar paucity during continental submergence silurian devonian late cretaceous are more problematic higher atmospheric co2 and lower hydrospheric co3 concentration during highstands may have inhibited a biotic carbonate precipitation ooids coeval with highstands display a preponderance of fabrics evincing a primary calcite mineralogy ooids formed during lowstands are more diverse but record dominance of aragonite variations in cortical mineralogy relate more closely to flooded continental areas than to sea level elevations supporting the suggestion of mackenzie and pigott 1981 that variations in hydrospheric carbonate concentrations were more important in determining phanerozoic ooid mineralogy than were magnesium calcium concentrations these data on oolite abundance and mineralogy demonstrate that abiotic phanerozoic marine carbonates have been responsive to secular changes in atmospheric hydrospheric chemistry and global eustasy and suggest that these changes are directly related to past rates of submarine weathering and sea floor hydrothermal activity

a combined o sr nd and pb isotopic and trace element study of crustal contamination in central andean lavas i local geochemical variations systematic variations in o sr nd and pb isotopic ratios and in sr nd pb and rb trace element abundances in central andean andesitic lavas are analyzed in terms of combined crustal assimilation and fractional crystallization the results of integrated isotopic model calculations show that observed local isotopic and trace element variations within the arequipa and barroso volcanic groups of southern peru are best fit by a simple model involving shallow or intermediate depth crustal assimilation of charcani gneiss or an equivalent rock accompanied by dominantly plagioclase fractional crystallization a consequence of this result is that the rbsr pseudoisochrons reported for the arequipa and barroso volcanics are wholly artifacts of the combined processes of assimilation and plagioclase fractionation as are all of the pb isotopic variations measured in the same lavas already interpreted by tilton and barreiro 14 to be the result of crustal contamination isotopic and trace element compositions of the primary magmas for the arequipa and barroso volcanic series are obtained by correcting for assimilation and fractional crystallization the starting magmas are characterized over the entire range of permissible primary compositions by high87sr 86sr ratios low143nd 144nd ratios and high sr concentrations relative to normal island arc andesites these results appear to require prior contamination of the magmas but not involving plagioclase fractionation the uncertainty in pb and o isotope ratios computed for possible primary magmatic compositions is sufficiently large however that it is not possible to preclude a subcrustal origin for at least some regional variation in sr and nd isotopic ratios

normalised natural remanent magnetisation intensity during the last 240 000 years in piston cores from the central north atlantic ocean geomagnetic field intensity or environmental signal we have examined in detail the stratigraphic variations in magnetic parameters of four cores from the north atlantic ocean in areas where the depositional environment has varied with climatic changes our objective is to assess whether normalisation of the natural remanent magnetisation nrm intensity can cancel the effect of climatically induced variations in magnetic mineral content and grain size and whether a reliable record of relative changes in geomagnetic field intensity can be obtained after selecting the core sections which meet published criteria for paleointensity normalisation we have attempted to obtain a record of the geomagnetic field intensity variations over the past 240 kyear using both arm and irm as normalising factors for the nrm the two methods yield overall similar results except for the interval 20 30 kyear where irm normalisation yields a record more consistent with previous sedimentary and volcanic results than does the more frequently employed arm normalisation the final intensity record docmments a picture of the dipole field moment which presents large similarities with profiles obtained from sediments deposited in different environmental conditions in various regions around the world we observe a major low at about 42 kyear which could correspond to the laschamp event a broad low in the interval 90 130 kyear possibly connected to the blake event and another low at about 190 kyear which could reflect the biwa i event the processes of acquisition of depositional and postdepositional remanent magnetisation and the physics of the normalising methods are still insufficiently understood however these results obtained from a region characterised by complex environmental dynamics confirm the potential of sedimentary deep sea cores for relative paleointensity determinations

were non avian theropod dinosaurs able to swim supportive evidence from an early cretaceous trackway cameros basin la rioja spain a fundamental question remaining unanswered in dinosaur behavior is whether they had the ability to swim we report the discovery of an exceptional swimming dinosaur trackway with 12 consecutive footprints in lacustrine nearshore sediment from the early cretaceous cameros basin la rioja spain the singular morphology of these footprints strongly suggests a fl oating animal clawing the sediment as it swam diagnostic traits of theropod dinosaur footprints are identifi able in these peculiar elongated s shaped ichnites paleoenvironmental reconstruction indicates an upper shoreface setting with a maximum water depth of 3 m substantiating the swimming hypothesis ichnological analysis of the trackway shows that this theropod used a pelvic paddle motion similar to that of modern bipeds and swam with amplifi ed asymmetrical walking movements to maintain direction into a leftward water current after recent hints of swimming dinosaurs this new evidence persuasively demonstrates that some non avian theropod dinosaurs were swimmers

role of pedogenesis in distribution of magnetic susceptibility in two california chronosequences abstract pedons from two soil chronosequences from coastal terraces in northern california were examined and sampled and samples were analyzed to determine the contribution of normal pedogenic processes to the distribution of mass magnetic susceptibility in soils commonly distribution in soils and the formation of susceptibility enhancement in near surface soil layers are attributed in large part to the in situ conversion of nonferrimagnetic iron oxides and oxyhydroxides to microcrystalline ferrimagnetic minerals solubilization of fe 2 and subsequent precipitation also contribute to enhancement we show that enhancement occurred throughout the eluvial and in some illuvial horizons to depths as great as 100 cm in these soils eluvial horizon and enhancement increased with increasing soil age the enhancement of magnetic susceptibility resulted from the accumulation of pedogenic ferrimagnetics and the preferential accumulation of both inherited magnetite and pedogenic maghemite we use the differential solubility of inherited magnetite and maghemite in citrate bicarbonate dithionite and x ray diffraction to distinguish between the two minerals although magnetite is a relatively more durable soil mineral it did weather and the total amount of magnetite decreased as soil age increased sonicated sand grains free of clay or fe coatings contributed to susceptibility enhancement silt and clay sized grains provided the larger part of illuvial horizon illuviation to or formation of clay sized ferrimagnetic particles in illuvial horizons probably reduced the observed eluvial enhancement enhancement of eluvial horizons and distribution throughout the soil oprofiles can be explained by common soil forming processes

archaeo directional and intensity data from burnt structures at the thracian site of halka bunar bulgaria the effect of magnetic mineralogy temperature and atmosphere of heating in antiquity abstract archaeomagnetic results are presented from a series of burnt structures at the thracian site of halka bunar archaeointensity and archaeodirectional studies were undertaken on three kilns from a pottery production complex this has been dated to the late 4th and early 3rd century b c 325 280 b c based on coins found associated with the kilns tonkova m 2003 newly discovered thracian centre of the early hellenistic age at the spring halka bunar in the land of c gorno belevo annuary of the institute of archaeology with museum bulgarian academy sci 2 148 196 in bulgarian this data provides a new point for the bulgarian archaeomagnetic curve dec 348 70 5 79 inc 62 20 2 70 and fa 77 23 2 17 t the kilns are thought to have been used for producing different types of pottery in a range of heating atmospheres and at different temperatures therefore special attention was paid to the magnetic mineralogy of the samples and its effect on the palaeodata kiln 3 orange clay samples were dominated by fine to ultra fine grained single domain and superparamagnetic magnetite with a small proportion of haematite the samples were heated in a high temperature oxidising environment kiln 2 was probably used to make grey ware pottery the samples are light grey and were dominated by stable single domain magnetite formed by high temperature heating in a more reducing environment kiln 4 mottled samples consisted of a variable mineralogy showing characteristics of both kiln 2 and kiln 3 samples it was probably used to make traditional mottled thracian ware pottery and was heated to lower temperatures in a mixed environment of heating samples heated in an oxidising environment gave more reliable thellier results than samples heated in a reducing environment in antiquity as the latter altered heavily on re heating a fourth kiln and a destruction feature from different trenches than the kiln complex were also investigated to establish their age archaeodirectional data was not recoverable from these two structures due to post burning disturbance the mean archaeointensity from kiln 5 mean 78 0 1 7 t is consistent with that from the main kiln complex mean 77 23 2 17 t and is therefore considered to be contemporary it was probably not used to make pottery the destruction feature records much lower archaeointensity values mean 65 1 1 1 t when this value is compared to the existing reference points of the bulgarian database it suggests this feature is younger than the kilns 250 140 b c multiple age use of the site is therefore confirmed with a main period of occupation in the late 4th and early 3rd century b c and another phase of occupation in the mid 3rd to mid 2nd century b c

phase relationships at 30 kbar for quartz eclogite composition in cao mgo al_2o_3 sio_2 h_2o with implications for subduction zone magmas synthetic starting material corresponding to oceanic tholeiite analysis wt sio 2 52 5 al 2o 3 15 6 mgo 14 6 cao 17 3 was run in sealed capsules at 30 kbar with 3 5 to 32 5 h 2o for comparison with the phase diagram previously reported for a natural gabbro h 2o the subsolidus assemblage is zoisite coesite eclogite with the solidus at 810 c coesite quartz disappears just above the solidus zoisite between 900 and 950 c eclogite liquid persists through a wider temperature interval and clinopyroxene liquid exists below the liquidus the liquidus is at 1110 c with excess h 2o and 1360 c with 7 5 h 2o compositions of glass clinopyroxene garnet and zoisite were measured by electron microprobe for runs with 7 5 h 2o glass analyses could not be obtained for runs below 1050 c glass analyses for runs at 1100 c and 1200 c included values that could not represent original liquid compositions suggesting that the liquid composition changes during the quench for reasons not fully understood equilibrium compositions of liquids were calculated from estimated modes and mass balance the equilibrium liquid paths for both model and natural rock compositions diverge from the average chemical variation of the calc alkaline rock series with divergence greatest for about 20 25 liquid where sio 2 content corresponds to that of andesite partial melting of quartz eclogite in subducted oceanic crust at 100 km depth would produce liquids with ca mg fe higher than andesites therefore andesite is not a primary magma from subducted oceanic crust deeper than amphibole breakdown

characterisation of soils by mineral magnetic measurements processes of iron mineral authigenesis diagenesis and dissolution in interaction with primary inputs of iron minerals act to produce vertical differentiation of soil magnetic properties thus magnetic iron oxides in common with other iron forms may both respond to and reflect soil forming processes investigation of the degree of detectable and persistent magnetic differentiation within different soil materials can provide insights into the nature and direction of distinct sets of soil processes evidence of clear association between magnetic variation and discrete types of soil environment also has applied significance in several areas of environmental study for example the observed magnetic variation can be used to discriminate between individual soils and soil horizons for the purposes of soil surveying sediment tagging and tracing and empirical modelling of source sediment linkages this paper reports the use of mineral magnetic techniques to characterise the iron oxide assemblages within soils of varying type and provenance the effect of different pedogenic regimes have been investigated through measurement of a range of magnetic parameters including magnetic susceptibility frequency dependent susceptibility and anhysteretic and saturation remanences contrary to current pedological thought but in accord with other magnetically based studies e g mullins the presence of magnetite maghemite typically of superparamagnetic single domain grain size within soils has been found to be an extremely widespread phenomenon its contemporary neoformation within the soil environment is inferred however the input of artificially generated ferrimagnetic material is indicated for one of the magnetically enhanced soils examined here and the possibility of extraneous sources of magnetite in topsoils should be considered before pedogenic processes of magnetic enhancement are inferred from the data presented discrimination of industrially derived magnetic particles appears possible on the basis of their very low levels of frequency dependent susceptibility fd low anhysteretic remanence arm and dissociation from the finer clay sized not the formation but the active dissolution of ferrimagnetic minerals is indicated for soils affected by the processes of gleying and podsolisation eluvial horizons of podsolised profiles demonstrate almost total loss of detectable magnetic content variations in the form of the iron reprecipitated in the underlying illuvial layers may reflect differences in the pedological characteristics of these horizons within gleyed waterlogged soils processes of magnetite dissolution appear to be grain size specific preferential reduction of those grains of ultrafine superparamagnetic and fine single domain magnetic grain size is indicated where soil forms a major contributor to catchment sediment loads this has significance in the area of source sediment modelling soil derived from permanently wet or highly leached catchment areas is unlikely to contribute to peaks in the magnetic content of deposited sediments further only those erosional processes that operate at a faster rate than those of magnetic depletion will have the capacity to produce peaks in sediment ferrimagnetic concentrations such as have been observed within the historical magnetic record

effect of citrate bicarbonate dithionite treatment on fine grained magnetite and maghemite mineral magnetic properties of soils and parent materials have been interpreted in terms of paleoclimate and rates of soil formation but it is important to understand which minerals contribute to the mineral magnetic signal citrate bicarbonate dithionite cbd treatment has been used to determine the amounts of fine grained often pedogenic ferrimagnetic minerals relative to coarse grained often inherited magnetic minerals however questions have been raised about the effect of particle size on the efficacy of cbd in dissolving magnetite and maghemite grains in this paper we use magnetic susceptibility and its frequency dependence and the low temperature behavior of a saturation isothermal remanent magnetization to track the dissolution of carefully sized magnetite grains we found that the standard cbd procedure dissolves fine magnetite particles ca 1 etm essentially intact thin oxidized coatings presumably maghemite are also dissolved by the cbd procedure these results support previous interpretations that the cbd procedure can be used to distinguish between pedogenic and lithogenic magnetic grains assuming that most pedogenic magnetic grains are sufficiently small ca 1 im these results also show that the standard procedure is too harsh to differentiate between 1 grm grains of magnetite and maghemite a modified cbd extraction that uses half as much dithionite reduces the magnetic susceptibility of 1 jam magnetite grains by only 10 this method may be useful in distinguishing between magnetite and maghemite grains in this size range

agents of low temperature ocean crust alteration 18o and87sr 86sr isotopic data from smectites calcites and whole rocks together with published isotopic age determinations alkali element concentration data and petrographic observations suggest a sequential model of ocean floor alteration the early stage lasts about 3 m y and is characterized by palagonite and smectite formation and solutions with a large basaltic component increasing with temperature which varies from 15 to 80 c at dsdp site 418a most carbonates are depositedafter this stage from solutions with a negligible basaltic sr component and temperatures of 15 to 40 c water of seawater sr and o isotopic composition is shown to percolate to at least 500 m into the basaltic basement no evidence was found for continuing exchange of strontium or oxygen after 3 m y

early diagenesis in an organic rich turbidite and pelagic clay sequence from the cape verde abyssal plain ne atlantic magnetic and geochemical signals abstract processes of early diagenesis in sediments from the cape verde abyssal plain are investigated using the complimentary techniques of environmental magnetism and solid phase geochemistry the sequence captured by a 2 m long box core comprises an organic rich turbidite derived from the nw african continental margin emplaced ca 330 ka bp overlain by brown pelagic clay diagenesis in the pelagic clay mainly involves slow in situ oxidation of the iron oxide phases present which mossbauer effect data suggest are detrital haematite and magnetite possibly maghaemitised in the turbidite diagenesis has proceeded in two stages the first involving suboxic reductive processes following depletion of porewater o2 and the second involving oxidative processes associated with the slow descent of an oxidation front through the bed due to diffusion of o2 from the overlying seawater carbonate free magnetic parameters interparametric quotients and remanence acquisition demagnetisation and coercivity measurements of the core reveal that significant depletion of detrital ferrimagnetic iron fe2 fe3 oxide grains like titano magnetite has occurred within the turbidite during suboxic diagenesis and confirm previous suggestions that reductive dissolution of such components is a grain size selective process however the higher oxidation state fe3 canted antiferromagnetic iron oxide grains like haematite and goethite are much less susceptible to reductive diagenesis remobilisation of transition metal ions from below the oxidation front in the turbidite has led to authigenic precipitation of ferrimagnetic fe mn micronodules in a distinct layer immediately overlying the front and above this a further interval of mn enriched diagenetic laminae however within the suboxic organic rich zone of the turbidite well below the oxidation front there is clear evidence for the presence of a significant concentration of fine single domain ferrimagnetic iron oxide grains which are most probably associated with a population of live magnetotactic bacteria between this zone and the oxidation front there is a transitional interval in which the number of live magnetotactic bacteria declines rapidly and fossil magnetosomes in the sediment are being reductively dissolved progressively up sequence these results are broadly similar though differing in some respects to magnetic and geochemical studies of hemipelagic and high productivity pelagic sediments in which mn and fe redox boundaries have been recognised and further illustrate the value of environmental magnetic parameters for characterising early diagenetic processes in sediments of this kind

secondary ferrimagnetic minerals in welsh soils a comparison of mineral magnetic detection methods and implications for mineral formation summary a range of low temperature and isothermal magnetic measurements are used to identify the secondary ferrimagnetic mineral sfm grain sizes in 10 representative soil samples from wales a comparison of percentage frequency dependent susceptibility fd percentage and low temperature remanence measurements shows that they are sensitive to different ranges of superparamagnetic sp grains the relative distributions of sp grains and stable single domain ssd grains are similar in nine of the samples typical distributions for soils dominated by sfms are 20 30 per cent ssd and 70 80 per cent sp multidomain md grains were not detected in the samples studied there is evidence that some soils contain significant numbers of ultrafine sp grains 0 010 m that are not detected by low temperature remanence measurements at 20 k and which will have the effect of depressing values of low field susceptibility lf and fd percentage a mixing model suggests that fd percentage may be used semi quantitatively to estimate the proportion of sp grains in a sample the positively skewed grain size distributions strongly suggest a mechanism of sfm formation that is driven by processes at the 10 8 m scale thus supporting weathering and fermentation as controlling processes rather than the degradation of ssd bacterial magnetosomes and primary minerals

the influence of submarine weathering of basalts on their partial melting during subduction abstract compositional changes beyond that of simple hydration are present in most of the analyzed examples of submarine weathering of basalt recalculations of 278 analyses from the literature of altered basalts to simplified basalt amphibolite and eclogite mineral assemblages result in significant increases of the quartz contents of the rock relative to fresh basalt in most examples the increased quartz contents result in mineral assemblages that have enhanced potentials to generate andesitic partial melts from the basalt or amphibolite forms of most altered basalts and trondhjemitic partial melts from the eclogite form of most altered basalts

early sediment diagenesis on the blake bahama outer ridge north atlantic ocean and its effects on sediment magnetism sediment magnetic and geochemical studies of a suite of deep sea sediment cores from the blake bahama outer ridge bbor north atlantic ocean have identified two current redox boundaries in surficial holocene carbonate rich sediments over much of the bbor the upper mn 4 mn 2 redox boundary is associated with a spike in the concentration of solid phase mn as mno2 the lower fe 3 fe 2 redox boundary is associated with a spike in the concentration of solid phase fe as goethite feooh over much of the bbor high sediment magnetic intensities occur in surficial carbonate rich sediments associated with these redox boundaries and lower intensities occur in deeper late pleistocene carbonate poor sediments this relationship is opposite to that expected if sediment magnetism simply reflects the clastic noncarbonate sediment fraction the surficial high sediment magnetic intensities are due primarily to the following two factors 1 magnetic mineral authigenesis associated with early diagenesis and 2 the presence of abundant 0 1 m magnetite crystals interpreted to be bacterial magnetosomes magnetosomes are almost absent in the late pleistocene low carbonate sediments owing most likely to local pleistocene environmental conditions high clastic flux low organic flux which did not favor their growth the sediment natural remanent magnetization is strongly correlated with the sediment clastic fraction and is relatively unaffected by early diagenesis and the presence of abundant bacterial magnetite if this is typical bacterial magnetite may be more abundant in nature but less important to sediment paleomagnetic records than previously thought

grain size dependence of the rock magnetic properties for a natural maghemite the natural maghemite from the robe river mining district australia is shown to be thermally very stable the maghemite hematite inversion occurs at 650 c for sized fractions 250 m to 5 m enabling determination of t c for maghemite at 610 c the maghemite is intimately intergrown with hematite and j s of the maghemite corrected for the hematite content is 64 am 2 kg j rs h cr and h c range between 7 46 10 18 am 2 kg 16 90 23 30 mt and 6 38 9 00 mt respectively indicating psd maghemite with grain sizes between 1 and 20 m the grain size dependence of the rock magnetic parameters of the maghemite is less prominent than those of magnetite of nominally the same size it is suggested that the lt behavior of arm can be diagnostic of the presence of maghemite upon cooling to 196 c it shows no change upon rewarming a gradual decrease in intensity occurs starting at 120 c

experimental stress remagnetization of magnetite abstract pseudo single domain psd and multidomain md magnetite grains remagnetize in weak magnetic field 30 t during experimental triaxial deformation the magnetite is supported in a calcite cement matrix minor remagnetization occurs with hydrostatic stress of 100 mpa significant remagnetization requires hydrostatic pressure of 150 mpa with differential stress of 5 mpa superposed on the sample intergranular differential stresses must be much higher due to amplification at grain asperities stress remagnetization does not need chemical or thermal energy new components of magnetic remanence are added parallel to the remagnetizing field however this only happens in grains or parts of grains with coercivities of remanence 60 mt grains with coercivities of 20 55 mt remember the primary magnetization and are not stress magnetized these coercivity limits do not depend on the differential stress or strain rate of the experiment the spatial distribution of vector components of remanence was isolated by af demagnetization after deforming a magnetized sample the components of remanence spread along a partial great circle between the initial remanence and the direction of the remagnetizing field the directions of the original magnetization and the remagnetizing field are the only factors controlling the course of the remagnetization path triaxial deformation shortened these samples by if the experimental results are transferable to nature it is possible that a pulse of excess crustal stress 25 mpa could partially remagnetize low dislocation density magnetite the experiments show that the directions of the remagnetizing field and the primary magnetization are the only variables that affect the demagnetization vector path we do not need to know the strain history coaxial or noncoaxial finite strains or principal strain directions to detect the paleofield directions unlike paleomagnetic vectors affected by large strains permanent changes in magnetic structure occur as a result of experimental deformation regardless of the differential stress the proportion of grains with remanence coercivities

isothermal magnetization of samples with stable preisach function a survey of hysteresis remanence and rock magnetic parameters isothermal magnetization curves like hysteresis loops initial curves back field curves acquisition curves and demagnetizing curves of isothermal remanent magnetization are commonly used for rock magnetic purposes in this study we investigate the relations among these curves and other useful magnetization curves saturation initial curve and induced and remanent hysteretic magnetization curves in order to compare coercivity and domain state parameters which can be derived from them most natural samples especially sediments are weakly magnetic and possess relatively stable preisach functions their magnetization states can therefore be described by classical preisach theory this approach verifies well known rules and establishes some formerly unreported relations between isothermal magnetization curves and parameters it is possible to point out sets of mathematically independent isothermal magnetization curves and to state theoretical interrelations between dependent curves by simply inspecting preisach diagrams furthermore we define six elemental isothermal magnetization curves from a general partition scheme of the preisach diagram they can be easily obtained from common measurements and generate all above mentioned curves the experimental applicability of our results is demonstrated for three single domain pseudo single domain multidomain marine sediment samples a physical rationale of the elemental curves reveals favorable properties for the investigation of interaction and domain state as a spin off from the general results a new hysteresis based procedure for the measurement of hcr is presented we also propose an apparently more robust hysteresis derived domain state parameter and a generalized version of the well known r parameter all presented methods can be applied without actually measuring preisach functions

quantifying ultrafine pedogenic magnetic particles in chinese loess by monitoring viscous decay of superparamagnetism we propose a new approach for quantifying pedogenically produced ultrafine nanometer scale magnetic particles in chinese loess we have recorded the viscous decay t 100 s of imposed isothermal remanent magnetization irm assumed to be selectively carried by superparamagnetic particles jv application of viscosity measurements relaxometry to loess paleosol sequences from the se extremity of the chinese loess plateau reveals that jv aptly reflects contributions of viscous superparamagnetic sp particles to the total remanence carried by an assemblage of magnetic particles time decay of jv can be determined with a higher resolution than the conventionally used frequency dependent susceptibility fd for characterizing the relative abundance of sp particles the nearly logarithmic time decay of irm implies a rather broad grain size distribution of pedogenic particles in chinese loess that may range from a lower size limit of 10 nm to an upper limit of 40 nm with a prevalent grain size maximum of 21 25 nm numerical calculations of the time dependence of irm decay demonstrate that the actual contribution of fine grained pedogenic magnetite maghemite to the total remanence is at least twice as large as that estimated by both fd and our proposed jv parameter we therefore propose that determination of superparamagnetic contributions by the time dependence of irm viscosity is a useful technique for tracking pedogenic processes and hence paleoclimatic conditions of chinese loess

dissolution behaviour of fine grained magnetite and maghemite in the citrate bicarbonate dithionite extraction method mineral magnetic properties of soils and sediments are increasingly used as proxy parameters for environmental and palaeoclimate analysis to investigate which magnetic minerals contribute to the environmental signal in the samples chemical techniques such as the citrate bicarbonate dithionite cbd extraction method have been introduced in environmental magnetism studies this technique is assumed to distinguish lithogenic magnetite from pedogenic maghemite mineral content in soils and sediments unfortunately interpretation of the cbd extractions is not straightforward because the procedure is sometimes more suitable for distinction between grain size than for distinction between minerals the procedure of the cbd extraction technique was investigated to determine the influence of extraction temperature and iron oxide concentration on the dissolution behaviour of the samples synthetic samples were extracted at three different temperatures 60o 70o and 80oc at similar iron oxide concentration 5 wt and for three different concentrations 0 1 wt 1 wt and 5 wt at the same temperature 60oc our results show that a lower extraction temperature reduces the dissolution rate for all samples while decrease in iron oxide concentration increases the dissolution rate thus the parameters in the cbd procedure have a major influence on the dissolution behaviour of the samples in practice this means that when natural samples of differing iron oxide concentration are extracted with this technique the results of the extractions cannot be compared therefore the outcome of this type of extraction experiment can only be accurately interpreted when the effect of the procedure on the dissolution behaviour is taken into account 1999 elsevier science b v all rights reserved

constraints on water transport and alteration in the oceanic crust from the isotopic composition of pore water the oxygen isotopic compositions of pore fluids from sediments of older oceanic crust commonly decrease with depth increases in calcium ion concentrations always accompany the 18o 16o decreases these changes are attributed principally to the alteration of basalts or alteration of volcanic ash in the sediments oxygen isotope material balance calculations suggest that 5 20 of the upper kilometer of basalt is altered at the time of subduction of the oceanic crust this corresponds to a flux of 18o into the oceanic crust of 2 3 1015 moles per million years evaluation of the oxygen and hydrogen isotope data from the pore fluids also suggests that the principal process of mass transfer in the sediments of older oceanic crust is diffusion convection of water in the basalts of the oceanic crust appears to continue until subduction

nanosized authigenic magnetite and hematite particles in mature paleosol phyllosilicates new evidence for a magnetic enhancement mechanism in loess sequences of china

podzolization over ophiolitic materials in the western alps natural park of mont avic aosta valley italy abstract soil surveys carried out on ophiolitic rocks and till under subalpine forest in the natural park of mont avic aosta valley west italian alps revealed the unexpected occurrence of soils showing a horizon set typical of the podzols podzolization is uncommon on mafic and ultramafic substrata the translocation of organo metallic compounds in soils developed from such parent materials slows down considerably due to the high fe and mg contents the high base saturation and the close to neutral ph in order to determine the real origin and evolution of such soils 6 pedons selected among 83 profiles with a similar podzol morphology were sampled and analyzed chemical mineralogical and petrographic analyses of the sampled soils and parent materials were performed and correlation analysis of the obtained data was carried out results show that in favourable environmental conditions mainly climate and vegetation even mafic and ultramafic parent materials can undergo different degrees of podzolization due to the adopted diagnostic criteria the most common classification systems particularly the wrb do not allow satisfactory taxonomic arrangement of such soils

dinosaur tracks at the nemegt locality paleobiological and paleoenvironmental implications abstract the nemegt locality is one of the most famous dinosaur localities in mongolia ever since the site was discovered in 1946 it yields abundant dinosaur skeletons however little attention had been given to dinosaur footprints at the locality the only nemegt dinosaur footprint study focused on descriptions of the footprints gave only a few taxonomic implications and provided no comparison with other dinosaur tracksites this study reports newly recorded dinosaur footprints hadrosaurs sauropods and theropods at the nemegt locality during the nemegt educational expedition of 2016 a single footprint bearing horizon that extends several kilometres was examined within the nemegt formation to determine the ichno taxonomic assemblage of the nemegt dinosaurs a significant difference was identified between taxonomic compositions based on skeletal remains and ichno taxonomic compositions based on footprints although the vast majority of the skeletal elements collected in the area belong to theropods the footprints suggest that the nemegt locality was dominated by herbivorous dinosaurs this suggests that the previously inferred tarbosaurus dominant taxonomic composition at the nemegt locality is a result of a preservational bias the size distribution of the newly studied footprints suggest that the nemegt hadrosaurs had an adult dominant and multigenerational population structure comparisons with dinosaur tracksites at the cantwell alaska usa and tremp spain formations show that the population structure and body sizes of the nemegt hadrosaurs were similar to those of the high latitude cantwell hadrosaurs it suggests that the nemegt area was more open and had higher plant productivity than the tremp area

the posture of floating pterosaurs ecological implications for inhabiting marine and freshwater habitats abstract the highly pneumatic skeleton of the extinct flying pterosaurs suggests that they would float high up on open water but in a posture rather different to that of birds however the exact posture of the body and head remains unknown and would be critical for an ocean going pterosaur forced onto the waters surface or animals that alighted to feed using computational methods with recent models and body mass estimates for four pterosaur genera dimorphodon rhamphorhynchus pteranodon and dsungaripterus we show that the floating posture of pterodactyloid pterosaurs led to the head neck and body being horizontal with the ventral 1 4 to 1 3 being immersed and the external nares being almost at or potentially partially below the waterline that could have left them vulnerable to drowning the floatation methods were verified using a model of a canada goose branta canadensis that is able to successfully replicate the expected orientation and depth of immersion of the bird while there is convincing ev idence for a number of pterosaurs foraging in marine and freshwater environments these results suggest that many did not regularly rest on the surface of the water and if immersed would need to take off again rapidly the high numbers of fossils of juvenile pterosaurs compared to the terrestrial mesozoic dinosaurs suggest that this may be linked to their floating posture

rock magnetism of late neogene and pleistocene deep sea sediments relationship to sediment source diagenetic processes and sediment lithology we use bivariate scatter plots to illustrate variations in selected rock magnetic properties low field susceptibility anhysteretic and isothermal remanence of late neogene and pleistocene deep sea sediments from 16 sites in the arctic ocean north atlantic equatorial atlantic and north pacific ocean and the arabian sea our intention is to examine the ability of the rock magnetic properties to differentiate the sediments according to factors such as lithology geographical area and the dominant mode of terrigenous sedimentation which at these sites is via ice rafting via bottom currents or via eolian processes overall correlations between sediment magnetic properties and gross lithology is poor and factors such as the source and transport path of terrigenous sediment and detrital magnetic minerals together with the action of reductive diagenetic processes are the major controls on the magnetic properties on the bivariate scatter plots sites with major ice rafted contributions tend to have high sedimentary ferrimagnetic mineral concentrations relatively coarse ferrimagnetic grain sizes and scattered sample point distributions in contrast sites where we infer significant bottom current supply of terrigenous material have tightly grouped sample point distributions carbonate sediments in which the terrigenous component is supplied by eolian processes tend to have a broad range of magnetic mineral concentration caused by glacial interglacial fluctuations in carbonate accumulation and eolian activity sediments containing significant volcanogenic material have high concentrations of relatively coarse grained ferrimagnetic material reductive diagenesis is a significant determinant of sediment magnetic properties in high productivity areas and has the effect of preferentially removing the fine grained ferrimagnetic fraction causing a coarsening of the ferrimagnetic grain size distribution and a rise in the antiferromagnetic ferrimagnetic ratio

crocodylomorph turtle and mammal tracks in dinosaur dominated middle upper jurassic and mid cretaceous ichnoassemblages of morocco abstract we report tetrapod traces from two stratigraphic intervals in morocco and discuss their palaeoecological implications in the first interval crocodylomorph footprints assigned to crocodylopodus meijidei are described from middle upper jurassic continental fluvial red beds of the isli formation in the imilchil region central high atlas morocco these traces are associated with a diverse dinosaur dominated ichnofauna including the footprints of theropods ornithischians sauropods and pterosaurs together with numerous invertebrate traces in the second interval we report crocodylomorph swim traces assigned to hatcherichnus isp turtle trackways assigned to emydhipus isp and isolated mammal footprints in the mid cretaceous midelt formation in the high moulouya region morocco these traces are also associated with a diverse dinosaur dominated ichnofauna including theropods and ornithopods as well as pterosaurs and abundant invertebrate traces together with plant remains conchostracans and fishes findings indicate a diverse community populating a fluvial brackish environment

theropod trackways associated with a gallimimus foot skeleton from the nemegt formation mongolia abstract a theropod tracksite was discovered in the nemegt formation maastrichtian at bugiin tsav mongolia by the korea mongolia international dinosaur project in 2009 a total of 67 tracks 14 trackways one didactylous 13 tridactylous and 12 isolated tracks belonging to four ichnomorphotypes were mapped on a single horizon this indicates at least four different theropod trackmakers lived in the same area at the same time this tracksite consists of laminated gray mudstone yellowish brown siltstone couplets interbedded with eolian yellowish brown sandstone deposited on a distal floodplain abundant footprints with v shaped profiles cross section within in the vertical section indicate that dinosaurs repeatedly walked across in this area before the discovery of the tracks the site was illegally excavated by fossil poachers a widespread problem in the gobi desert during excavation of the track horizon a clenched inclined gallimimus foot skeleton was found in the mudstone extended down 20 cm below the track bearing sandstone layer the occurrence of tracks closely associated with body fossils is unusual and taphonomically intriguing it is possible that the foot skeleton represents an animal that died in its tracks however the depth of the foot in mud is probably too shallow for the animal to have been mired sedimentological and taphonomic evidence also suggests that the pes of gallimimus may have passed straight through the track bearing sandstone layer the inclined right pes indicates that the body lay on its left side on the substrate during decomposition in the mud all digits were flexed but the distal phalanges were stuck and anchored in the stiff lower mud consequently as more proximal phalanges were able to accommodate flexing they were pulled away and dislocated from the anchored distal phalanges subsequent trampling by dinosaurs in the track bearing sandstone would have further distorted the underlying foot

the role of maghemite in the enhancement of magnetic signal in the chinese loess paleosol sequence an extensive rock magnetic study combined with citrate bicarbonate dithionite treatment we have conducted a rock magnetic study of selected chinese loess samples before and after citrate bicarbonate dithionite cbd treatment our study is more extensive than previous ones and reveals new details of the magnetic carriers which are related to paleoclimate change three pairs of paleosol s1 the top paleosol layer in the lishi formation and loess l2 underlying s1 from three localities xining xifeng and jixian were investigated by using a variety of magnetic methods after the paleosols were treated with cbd which removes all maghemite grains and the finest grains of magnetite magnetic susceptibility decreased from 77 10 8 to 20 10 8 m3 kg in xining from 165 10 8 to 30 10 8 m3 kg in xifeng and from 180 10 8 to 25 10 8 m3 kg in jixian anhysteretic remanent magnetizations arm were reduced to less than one tenth of the original values in the three sites and saturation magnetization js decreased by about 60 in xining and 70 in xifeng and jixian these reduced values in the paleosols after cbd treatment are similar to those of the corresponding underlying loess samples which however did not show significant decrease after cbd treatment room temperature frequency dependence of susceptibility high temperature dependence of susceptibility and low temperature sirm demagnetization of the paleosol and loess samples before and after cbd treatment confirm that in addition to superparamagnetic sp particles magnetite and or maghemite the cbd removable magnetic carriers also include maghemite of grain sizes larger than sp

footprints of marine reptiles from the middle triassic anisian ladinian guanling formation of guizhou province southwestern china the earliest evidence of synchronous style of swimming abstract subaqueously registered trackways of marine tetrapods are only rarely preserved some of the best examples so far come from the shizishan member member ii of the guanling formation middle triassic anisian ladinian of yunnan province in southwestern china the unit is well known for the luoping biota including abundant skeletons of marine reptiles the described footprints consist of impressions of fin like autopodia comprising numerous broad trackways that have been named dikoposichnus luopingensis and interpreted as having been made by foraging nothosaurs morphologically identical tracks and trackways have now been discovered near the city of anshun in guizhou province in slightly older strata and on a large surface of argillaceous dolostone belonging to the songzikan member member i of the guanling formation additionally a second morphotype is abundant on the same surface with long trackways that show semi plantigrade to plantigrade foot imprints with four distinct digit impressions all tracks are similar in shape and positioned symmetrically in broad trackways on either side of the trackway midline based on several unique features this morphotype is assigned here to the new ichnotaxon anshunpes aquacursor ichnogen nov ichnosp nov it is interpreted as the trackway of a buoyant and punting tetrapod using its forefeet only the trackmaker is inferred to be similar to some diapsid placodonts and saurosphargids whose skeletons have been found in the guanling formation middle triassic anisian ladinian and in the overlying falang formation middle upper triassic ladinian carnian comparative measurements of trackways and skeletons support this additional associated ichnofossils are enigmatic traces such as isolated large oval impressions and cord like knobby structures the palaeoenvironment was a shallow near coast marine habitat possibly a lagoon the ichnofauna from anshun is important because it is the first record of subaqueous progression activity by marine diapsid placodonts and or saurosphargids and also indicates the early adoption of a synchronous style of swimming by marine reptiles

the weathering of basalt and relative mobilities of the major elements at belbex france abstract a basalt and its weathered profile have been analysed for major elements graphical examination shows al fe and ti to have been essentially immobile determining mobility sequences for this deposit is complicated by the long pedogenetic history of the area three different sequences are presented two for different stages of weathering integrated over time and one that reflects the weathering regime of the present day

iron mineralogical proxies and quaternary climate change in se european loess paleosol sequences abstract the loess paleosol sequences batajnica stari slankamen serbia and mircea voda romania represent key archives for the climate and landscape development of the middle and lower danube basin during the last 700 000 years for deciphering the quaternary climate evolution in these regions the batajnica stari slankamen and mircea voda sites are for the first time studied by a multi proxy approach based on iron mineralogical parameters changes in the iron mineralogical composition are identified and characterized by rock magnetic investigations diffuse reflectance spectroscopy drs and munsell color based proxies the results show that environmental conditions during mid and early middle pleistocene interglacials were more favorable for hematite formation suggesting a more oxidizing pedoclimate as in the more recent interglacials this is also reflected in a gradual increase of the anhysteretic remanent magnetization vs saturation isothermal remanent magnetization arm sirm ratio in the studied profiles changes in this ratio can be linked to a preferential hematitization of coarse grained ferrimagnetica and relates to warmer climate conditions and a more extended estival dry period at the same time rock magnetic parameters indicate a preferential destruction of fine grained magnetic particles in older paleosols resulting from seasonal excess moisture a progressive cooling and decrease of rainfall during the middle and late pleistocene is evidenced not only for interglacial pedocomplexes but also for glacial loess layers this finding is in line with previously published proxy records of silicate weathering and clay formation at these sites and similar trends reported from other sites in the european steppe belt relating iron mineralogical proxies to paleopedological characteristics and proxies of silicate weathering additionally a change in the seasonal pattern of the interglacial temperature and precipitation regime from a mediterranean type to a steppe type climate is revealed highlighting the potential of such a multi proxy approach possible triggers for this paleoenvironmental evolution are discussed as well finally highlighting a quaternary uplift hypothesis which best could explain the inferred trend of cooling aridification and increasing continentality accordingly changes in atmospheric circulation and rain shadow effects induced by small scale uplift of european mountain belts alps carpathians dinaric alps would provide a driving mechanism for the westward extension of the eurasian steppe belt into central and se europe during the quaternary

late cenozoic alkaline volcanism in the northwestern caribbean tectonic setting and sr isotopic characteristics a province of alkaline volcanism has developed over the last 10 m y in the northwestern part of the caribbean plate most of the volcanism is quaternary in age and follows an apparent halving of the spreading rate at the cayman rise spreading center 2 4 m y ago intraplate deformation in central america and the nicaraguan rise has produced a series of north south orientated grabens this extensional tectonism is associated temporally and spatially with some of the alkaline magmatism strontium isotopic ratios of rocks from sixteen of these centers of volcanism enable three separate areas with different isotopic characteristics to be identified the largest area corresponds to the nicaraguan rise and is characterized by low87sr 86sr ratios 0 7026 0 7031 a more concentrated area of alkaline magmatism in northeastern costa rica has intermediate87sr 86sr ratios 0 7036 0 7038 which are within the range shown by the adjacent calc alkaline volcanoes in central hispaniola high87sr 86sr ratios 0 7047 0 7063 are found in strongly alkalic rocks and in rocks that are transitional to calc alkaline in nature in both costa rica and hispaniola the increased radiogenic strontium may have come from volatile rich fluids escaping from adjacent subducting slabs of oceanic crust the isotopic differences between the two areas may be related to the relative longevity and high rate of subduction in costa rica compared to hispaniola the costa rican alkaline rocks overlie a segment of the cocos plate which is being subducted at a smaller angle 35 than at the rest of the central american arc

mechanism of palygorskite formation in the red clay formation on the chinese loess plateau northwest china abstract the morphological characteristics and microstructures of the authigenic palygorskite occurring with smectite and carbonate minerals in the late miocene red clay formation on the chinese loess plateau have been investigated with the powder x ray diffraction xrd scanning electron microscopy sem and high resolution transmission electron microscopy tem the xrd results indicate that the red clay sediments contain quartz feldspar calcite dolomite illite kaolinite chlorite palygorskite and smectite and sem analyses show that palygorskite is a common component delicate palygorskite fibers radiate from the margins of platy smectite suggesting a pedogenic origin during the weathering of pre existing smectite a process that involved intense dissolution of the smectite and an adjustment in its structure moreover palygorskite occurs as coatings pore fillings and pore bridging cements among dolomite rhombs suggesting that the fibrous palygorskite was formed by a direct dolomite precipitation from pore fluids mostly after dolomite crystallization there is evidence to show that these two mechanisms took place synchronously in the red clay formation and that the two processes are related under alkaline conditions with high ph 8 0 fluids rich in magnesium magnesium ions occupy the interlayer positions in the smectite and this results in a misfit between the mg octahedral sheet and the smectite layer thereby allowing interaction between the magnesium ions and smectite layers and a reorganization of the structure to form palygorskite then with this kind of palygorskite as a crystal nucleus more palygorskite grows through a direct chemical deposition process according to previous studies the red clay sediments experienced a steady dry warm climate with periods of high rainfall and evaporation the warm climate would have increased the rate of weathering of minerals and subsequently enhanced the ions content and ph in the soil solutions during dry periods this soil environment is favorable for smectite transformation and palygorskite deposition this study has improved our understanding of the environmental and paleoclimatic changes during the time that palygorskite formed in the arid soils of the chinese loess plateau

geochemistry of high grade eclogites and metarodingites from the central alps analyses for major minor and trace element contents of metamorphosed variably rodingitized mafic rocks demonstrate substantial removal of na and as much as three fold gains in ca as a consequence of rodingitization modest declines in si and fe can be explained in terms of dilution effects losses in k and ba do not correlate with ca and may have been caused by an alteration process not related to the rodingitization the ca metasomatism was not accompanied by a gain in sr the relative contents of ti zr hf y co sc and heavy ree show no readily detectable changes despite the rodingitization other alteration and subsequent metamorphisms namely eclogite facies t 800 c p 20kbar followed by amphibolite facies sillimanite zone protoliths were tholeiitic basalt or diabase and gabbro with trace element contents indicative of a spreading center origin trace element and ree patterns indicate low pressure fractionation of this magma with plagioclase stable this petrogenesis is consistent with prior conclusions on the shallow crustal origin of the protolith of the eclogite metarodingite garnet lherzolite suite in the cima lunga adula nappe central alps based on their bulk chemical composition the mafic rocks in this suite could be the equivalent of mesozoic ophiolitic rocks in the more external parts of the alps