integrated stratigraphy and palaeoenvironment of the berriasian peri reefal limestones at stramberk outer western carpathians czech republic abstract a high resolution multidisciplinary study of two profiles in the kotouc quarry at stramberk was carried out to define the age and palaeoenvironmental setting of the peri reefal stramberk limestone calpionellids of the alpina and ferasini subzones of the standard calpionella zone confirm an early berriasian age for both studied sequences the presence of the calcareous nannofossils nannoconus kamptneri minor and speetonia colligata supports this stratigraphic interpretation an ammonite assemblage with pseudosubplanites grandis was found corresponding to the upper part of the lower berriasian grandis subzone foraminiferan assemblages contain several taxa previously reported from the valanginian magnetostratigraphy verifies that the studied sections span the magnetozones m18r to m18n rock magnetic measurements indicate magnetite as the carrier of characteristic remanent magnetization a palaeolatitude suggested location at 36 n microfacies indicate palaeoenvironments of slope fz 4 platform margin reefs sand shoals fz 5 fz 6 and possibly patch reefs in the inner platform fz 7 the presence of calpionellids and the polychaete terebella lapilloides suggests deposition within the deeper parts of the outer ramp of a platform slope with redeposited clasts derived from nearby reef slopes and or talus this research contributes to the berriasian working group s efforts to define the tithonian berriasian boundary

climatic dependence of stable carbon and oxygen isotope signals recorded in speleothems from soil water to speleothem calcite abstract understanding the relationship between stable isotope signals recorded in speleothems 13 c and 18 o and the isotopic composition of the carbonate species in the soil water is of great importance for their interpretation in terms of past climate variability here the evolution of the carbon isotope composition of soil water on its way down to the cave during dissolution of limestone is studied for both closed and open closed conditions with respect to co 2 the water entering the cave flows as a thin film towards the drip site co 2 degasses from this film within approx 10 s by molecular diffusion subsequently chemical and isotopic equilibrium is established on a time scale of several 10 100 s the 13 c value of the drip water is mainly determined by the isotopic composition of soil co 2 the evolution of the 18 o value of the carbonate species is determined by the long exchange time t ex between oxygen in carbonate and water of several 10 000 s even if the oxygen of the co 2 in soil water is in isotopic equilibrium with that of the water dissolution of limestone delivers oxygen with a different isotopic composition changing the 18 o value of the carbonate species consequently the 18 o value of the rainwater will only be reflected in the drip water if it has stayed in the rock for a sufficiently long time after the water has entered the cave the carbon and oxygen isotope composition of the drip water may be altered by co 2 exchange with the cave air exchange times ex co 2 of about 3000 s are derived thus only drip water which drips in less than 3000 s onto the stalagmite surface is suitable to imprint climatic signals into speleothem calcite deposited from it precipitation of calcite proceeds with time constants p of several 100 s different rate constants and equilibrium concentrations for the heavy and light isotopes respectively result in isotope fractionation during calcite precipitation since t ex p exchange with the oxygen in the water can be neglected and the isotopic evolution of carbon and oxygen proceed analogously for drip intervals t d p the isotopic compositions of both carbon and oxygen in the solution evolve linearly in time the calcite precipitated at the apex of the stalagmite reflects the isotopic signal of the drip water for long drip intervals when calcite is deposited from a stagnant water film long drip intervals may have a significant effect on the isotopic composition of the dic in this case the isotopic composition of the calcite deposited at the apex must be determined by averaging over the drip interval such processes must be considered when speleothems are used as proxies of past climate variability

middle and late jurassic radiolarian palaeoecology versus carbon isotope stratigraphy abstract jurassic radiolarians are sensitive to palaeoclimatic palaeoceanographic changes recorded by the stable carbon isotope curve carbon isotopic variations have been linked to changes in ocean structure productivity and concentrations of greenhouse gases in the atmosphere in the middle upper jurassic terminilletto section of the umbria marche sabina apennines central italy well preserved radiolarians are present in a sequence of cherty limestones interbedded with platform derived carbonates the 13 c curve in the aalenian kimmeridgian interval indicates three main positive 13 c events in the lower bajocian late bathonian lower callovian and middle oxfordian the positive 13 c shifts are correlated to increases in visible chert in the outcrop and may represent periods of increased biological productivity of surface sea water spumellaria nassellaria ratios and the fluctuations of relative abundance of selected genera tend to correlate with 13 c and chert abundance values and seem to be related to episodes of high nutrient mobilisation from the base of the bajocian the radiolarian associations show a slight tendency towards diversification coincident with increasing 13 c values in the upper part of the middle bajocian last appearances prevail over first appearances associated with the peak of the 13 c event this may indicate maximum eutrophic conditions coincident with the late bathonian early callovian positive 13 c shift the radiolarian associations record a different trend with respect to the bajocian event when the 13 c values are increasing to a maximum radiolarian associations tend to be reduced in species diversity followed by a small diversification trend when the 13 c values are decreasing we speculate that during the callovian a more stressful palaeoenvironment due to high level of eutrophication is indicated by the combination of high productivity of biogenic silica and low carbonate input although varying preservational conditions may have influenced the observed trends in the radiolarian associations the good correlation between changes of sedimentation patterns radiolarian assemblages and 13 c positive anomalies open interesting avenues for further investigations concerning the palaeoecology of mesozoic radiolarians

an alternative model for positive shifts in shallow marine carbonate 13c and 18o positive shifts in global seawater d 13 cdic are related to changes in the ratio of organic relative to inorganic carbon burial in oceanic basins whereas factors such as climatic cooling and the accumulation of polar ice are known to cause positive shifts in d 18 o here an alternative model is proposed for the formation of local positive isotope shifts in shallow marine settings the model involves geochemically altered platform top water masses and the effects of early meteoric diagenesis on carbonate isotopic composition both mechanisms are active on modern sub tropical carbonate platforms and result in low carbonate d 13 ca ndd 18 o relative to typical oceanic values during high amplitude transgressive events the impact of isotopically light meteoric fluids on the carbonate geochemistry is much reduced and 13 c depleted platform top water mixes with open oceanic water masses having higher isotope values both factors are recorded as a transient increase in carbonate 13 c and 18 o relative to low background values these processes must be taken into consideration when interpreting the geochemical record of ancient epeiric seas

manganese in pelagic carbonates indication of major tectonic events during the geodynamic evolution of a passive continental margin the jurassic european margin of the tethys ligurian sea abstract mid oceanic hydrothermal activity is the main source of manganese in the pelagic realm consequently long term fluctuations of manganese in bulk carbonates could represent the variations in the hydrothermal flow intensity through time depending on global tectonic activity within this scope we analysed three jurassic sedimentary series in the southeastern basin france thus providing valuable information for further palaeogeographic and geodynamic reconstructions of the european tethyan passive margin the long term variations of the manganese curve can be correlated with second order sea level changes the main transgressive phases early toarcian late aalenian to bajocian and late bathonian to callovian are marked by a manganese content increase whereas the regressive phases late pliensbachian late toarcian to middle aalenian early bathonian to middle bathonian oxfordian are characterized by decreasing trends furthermore some manganese positive anomalies can be superimposed on the global geochemical record of sea level changes these coincide with periods of increasing subsidence rate early toarcian late bajocian middle and late oxfordian and also with phases of extension early aalenian of the european margin of the ligurian ocean the major event is the very sharp increase of manganese content localised in the athleta zone late callovian and corresponds to the first occurrence of oceanic crust moreover the manganese enrichments recorded in carbonates deposited before callovian times may have resulted from hydrothermal emanations during the first stages of rifting

statistical evaluation of elemental concentrations in shallow marine deposits cretaceous lusitanian basin abstract the elemental geochemistry of ancient shallow marine carbonates represents an often underexplored archive of paleoenvironmental change and diagenetic pathways complex multi parameter datasets from a lithologically heterogeneous sedimentary succession in the southern part of the lusitanian basin ericeira portugal are presented and interpreted the section comprises marly carbonate and sandstone rich coastal marine deposits of early albian to early cenomanian age principal component analysis of bulk elemental abundance ca mg sr fe and mn lead to define four geochemical clusters based on common elemental attributes siliciclastics and dolomitized limestones facies yield evidence for significant diagenetic alteration but still preserve information on paleoshoreline position mixed carbonate siliciclastics and limestone facies bear evidence for relative sea level position and relevant paleoclimatic information in their elemental record accordingly mid albian mixed carbonate siliciclastic deposits present variable degrees of continental influx specifically a sharp increase of fe and mn concentrations in relation to continental input is in agreement with periods of enhanced hydrological cycling and increased weathering on adjacent emerged lands the progressive transition towards more marine conditions is accompanied by higher ca and sr content and represented by limestone facies corresponding to a higher sea level position during late albian to early cenomanian times moreover this facies records a trend towards warmer and more arid conditions early diagenetic stabilization and or dissolution of aragonite into low mg calcite can account for major elemental variations including higher sr content strongly coupled with ca content along with lower mg fe and mn concentrations data shown here provide solid evidence that the statistical analysis of the elemental record of ancient marine deposits when combined with conventional sedimentology and thin section petrography allow for elaborate conclusions on their depositional environment and diagenetic pathways cored wells and facies specific reservoir properties can be addressed by these methodologies able to detect and quantify changes in patterns both industry and academy can therefore benefit from approaching such a complex interplay

hollows on mercury messenger evidence for geologically recent volatile related activity high resolution images of mercury s surface from orbit reveal that many bright deposits within impact craters exhibit fresh appearing irregular shallow rimless depressions the depressions or hollows range from tens of meters to a few kilometers across and many have high reflectance interiors and halos the host rocks which are associated with crater central peaks peak rings floors and walls are interpreted to have been excavated from depth by the crater forming process the most likely formation mechanisms for the hollows involve recent loss of volatiles through some combination of sublimation space weathering outgassing or pyroclastic volcanism these features support the inference that mercury s interior contains higher abundances of volatile materials than predicted by most scenarios for the formation of the solar system s innermost planet

size sorting in marine muds processes pitfalls and prospects for paleoflow speed proxies the basis for and use of fine grain size parameters for inference of paleoflow speeds is reviewed here the basis resides in data on deposited sediment taken in conjunction with flow speed measurements in the field experimental data on suspended sediment transport and deposition and theoretical treatments of the generation of size distributions of deposits from suspension controlled by particle settling velocity and flow speed in the deep sea sorting events occur under resuspension deposition events in benthic storms at flow speeds below 10 15 cm s 1 size in the noncohesive sortable silt 10 63 m range is controlled by selective deposition whereas above that range removal of finer material by winnowing also plays a role the best particle size instruments to measure a flow speed related grain size employ the settling velocity method while laser diffraction sizers can yield misleading results because of particle shape effects potential problems including source effects downslope supply on continental margins spatial variability of flow over bedforms and influence of ice rafted detritus are examined a number of studies using the sortable silt flow speed proxy are reviewed and inverse modeling of grain size distributions is examined outstanding problems are that corroboration is sparse because almost no studies have yet used the full range of proxies for flow rate and water mass identification and that the sortable silt mean size is not yet properly calibrated in terms of flow speed

physicochemical characteristics of drip waters influence on mineralogy and crystal morphology of recent cave carbonate precipitates speleothems are one of the most intensively explored continental archives for palaeoclimate variability the parameters however that control speleothem petrography and its changes with time and space specifically calcite crystal morphology and carbonate mineralogy are still poorly understood in order to shed light on processes and their products precipitation experiments of recent carbonate crystals on watch glasses and glass plates were performed in seven selected caves drip water sites were analysed for their fluid mg ca molar ratio ph degree of saturation for calcite and aragonite and drip rates corresponding precipitates were analysed with respect to their mineralogy calcite crystal morphology and mg ca molar ratio of calcite the following results are found high fluid mg ca ratios are found only for caves situated in dolostone thus the hostrock lithology indirectly controls the carbonate mineralogy and calcite crystal morphology of speleothems the precipitation of aragonite in place of calcite occurred only in dolostone caves and is bound to very specific conditions these are high fluid mg ca ratios 0 5 high fluid ph 8 2 and low fluid saturation indices for calcite 0 8 these specific conditions are induced by slow drip rates of 0 2 ml min as often under more arid conditions causing the precipitation of calcite aragonite prior to reaching the stalagmite top due to this fluid chemistry is altered which in turn leads to changes in carbonate mineralogy and geochemistry on the stalagmite top calcite growth is inhibited at high fluid mg ca ratios and hence aragonite precipitation is kinetically stabilised an increase of the drip water mg ca ratio leads to an increased incorporation of mg2 into the calcite crystal lattice and thus to a change in calcite crystal morphology four distinctive changes occur with increasing mg2 incorporation i development of new forms steeper rhombohedra and base pinacoid at the edges and corners of the crystal seed ii crystal habit tend to elongate along 0 0 1 due to slower growth of faces with high mg2 densities iii reconstitution of crystal faces with low mg2 densities and iv occurrence of calcite crystals with bended faces and edges due to very high mg2 mg ca ratios of 0 009 0 051 incorporation growth rates and possibly also organic compounds however may also affect the morphology of calcite crystals based on the data shown here the relation of mg2 incorporation and the resulting changes in calcite crystal morphologies as well as the conditions of aragonite precipitation are now clearly better understood further work should aim at linking the calcite crystal morphology of watch glass precipitates with calcite crystal fabrics in speleothems in order to exploit the petrographic archive of speleothem deposits

sortable silt and fine sediment size composition slicing parameters for palaeocurrent speed and palaeoceanography fine sediment size 63 ixm is best measured by a sedimentation technique which records the whole size distribution repeated size measurement with intermediate steps of removal of components by dissolution allows inference of the size distribution of the removed component as well as the residue in this way the size of the biogenic and lithogenic noncarbonate fractions can be determined observations of many size distributions suggest a minimum in grain size frequency curves at 8 to 10 ixm the dynamics of sediment erosion deposition and aggregate breakup suggest that fine sediment behavior is dominantly cohesive below 10 1xm grain size and noncohesive above that size thus silt coarser than 10 ixm displays size sorting in response to hydrodynamlc processes and its properties may be used to infer current speed silt that is f mer than 10 ixm behaves in the same way as clay 2 xm useful parameters of the distribution are the 10 63 ixm mean size and the percentage 10 63 ixm in the fine fraction we cannot use size distributions to distinguish the nature of the currents therefore to infer water mass advection speeds i e the mean kinetic energy of the flow ku regions of high eddy kinetic energy ke must be avoided at the present such abyssal regions lie under the high surface k e of major current systems gulf stream kuroshio agulhas antarctic circmpolar current and brazil falldand currents in the argenthe basin this is probably a satisfactory guide for the pleistocene with regard to the carbonate subfraction of the size spectrum size modes due to both cocco iths and foramlnlferal fragments can be recognized and analyzed with the boundary between them again at about 10 lm the flux of less than 10 lm carbonate at pelagic sites above the lysocline is another candidate for a productivity indicator

martian climatic events on timescales of centuries evidence from feature morphology in the residual south polar ice cap flat floored quasi circular depressions on the southern residual cap of mars have been observed to expand rapidly analysis of the size distribution combined with modeling of the growth process yields information about the ages of these features we report on properties of a population of these features within a selected study area we find a narrow size distribution that indicates a common formation time and a finite period during which new features were forming some change in environmental conditions occurred during this period which we date at several martian decades to centuries ago depending on modeled growth rates we report on themis data that reveals the nature of larger features outside our study area underlying water ice is exposed on the flat floors of these depressions near the outer walls these features may record more than one growth phase indicating that conditions conducive to growth may switch on and off with characteristic timescales of martian centuries

matrix micrite δ13c and δ18o reveals synsedimentary marine lithification in upper jurassic ammonitico rosso limestones betic cordillera se spain abstract matrix micrites are a commonly used carbonate archive for the reconstruction of past environmental parameters but one that is submitted to known limitations main reasons for the often ambiguous value of many micrite based isotope data sets are the unknown origin of the micrite components and their poorly resolved diagenetic history here we present carbon and oxygen isotope data retrieved from oxfordian to tithonian ammonitico rosso nodular micrites sampled from three sections in the betic cordillera southern spain all three sections were correlated and sampled using a rigorous biostratigraphic framework a noteworthy feature is that analyzed matrix micrites are more conservative in terms of their isotopic composition than other carbonate materials commonly considered to resist diagenetic alteration under favourable circumstances remarkably this refers not only to 13 c ratios which reflect the typical late jurassic global trend but also to 18 o ratios that range around 0 3 the 18 o enriched oxygen isotope ratios are considered to represent diagenetic stabilization of carbonate ooze under the influence of marine porewaters within the sediment water interphase i e the immature sedimentary section usually submitted to biogenic activity this interpretation agrees with the very early lithification of micrite nodules with cements precipitated from marine porewaters enriched by the dissolution of aragonite skeletals i e ammonite shells according to the model proposed low sedimentation rates as well as rapid early marine differential cementation under the influence of currents and seawater pumping affected the sediment water interphase of epioceanic swells where deposition resulted in early lithified ammonitico rosso facies the data obtained show that special care must be taken to prevent oversimplified interpretations of carbonate archives particularly in the context of epioceanic settings

spatial geochemistry of a carboniferous platform margin to basin transect balancing environmental and diagenetic factors abstract conventional one dimensional chemostratigraphy of marine carbonates assesses the chemical archive of individual stratigraphic sections and their correlation in space and time whereas this approach has shown to be of value when linking isobathymetric domains usually characterised by similar facies more caution is needed when correlations are extended across different physiographic settings and hence different facies belts here the spatial geochemical record of pennsylvanian platform margin to basin transects across a bathymetric range of about 800 m is documented and discussed in a process oriented context particularly the presence of layered palaeo water masses and their potential control on slope facies distribution and geochemical properties requires attention whereas carboniferous thermo and or chemo clines most likely affected depth related slope facies zonation it was facies change and hence variances in porosity permeability properties that controlled differential early burial diagenetic alteration specifically the lower slope related breccia facies is characterised by higher volumes of early burial carbonate cements this implies that these sediments entered the shallow burial domain with a considerable open pore space and gave way to an increased rock fluid ratio whereas the 13 c record is invariant with bathymetry the more diagenesis sensitive 18 o proxy records pronounced shifts observed across major facies boundaries from this it is concluded that although the primary controlling factor of slope facies distribution with depth is probably palaeoceanographic in nature it is differential rock fluid ratios that control the first order spatial shifts in 18 o composition these findings show that one dimensional chemostratigraphy will severely underestimate the complexity of three dimensional bathymetric data sets across platform margins this is of relevance for the interpretation of the geochemical archive of fossil carbonate platforms in general

spatial geochemistry of upper jurassic marine carbonates iberian subplate abstract chemostratigraphy applied to ancient marine carbonates is commonly based on one dimensional stratigraphic sections or core data as demonstrated from modern oceans this approach underestimates the spatial complexity of physico chemical seawater properties here a several hundred kilometer long transect consisting of seven upper jurassic sections from settings ranging from proximal neritic middle shelf to the epioceanic distal fringe across the southern and eastern palaeomargins of the iberian sub plate reveals variability in sedimentologic stratigraphic and geochemical records the comparison of isotopic and elemental data from different carbonate materials matrix micrite carbonate cements in veinlets belemnite rostra and ammonite shells reveals differential diagenetic pathways microfacies cathodoluminescence and geochemical data retrieved from biostratigraphically well constrained sections reveal that epioceanic matrix micrite geochemical data provide valuable proxies for palaeo seawater properties our data are reviewed in the context of published late jurassic records the outcome shows a higher level of complexity including the potential admixture of marine continental and diagenetic geochemical signals in the epicontinental record the stratigraphic trend in carbon isotopes of epioceanic sections agrees upon that of upper jurassic reference sections from the northern tethyan margins while oxygen isotope ratios are relatively 18o enriched palaeo seawater temperatures across the transect investigated were estimated using 18o as tentative proxy for interpreting distance from shore differences in water masses relative depth variations and potential local forcing factors palaeoenvironmental conditions evaluated through the combined record of isotope 18o elemental mn and skeletal content contrast with relative fluctuations in sea level site specific changes in palaeoceanographic parameters such as water depth seawater temperature salinity and upwelling are considered in comparison to examples from ancient and modern oceans

contrast comparison of differential diagenetic pathways of lower tithonian carbonate materials from the betic cordillera s spain evidence for physico chemical paleo seawater properties abstract the reconstruction of paleoenvironmental conditions is based on the study of ancient rock materials for this purpose skeletal materials are often assumed to have higher preservation potential sometimes favored over the use of matrix micrite however factors such as ecology depositional setting mineralogy and diagenetic processes may obscure original geochemical signals and care must be taken when reading such an intricate record this work provides a thorough comparison between geochemical signatures of different carbonate materials interpreted in the light of their paleoenvironmental significance burial and diagenetic processes are taken into account contextualized by ammonite and belemnite ecology two sections deposited in epioceanic tethyan areas and corresponding to the same lower tithonian ammonite biozone are under scope a condensed pelagic and cephalopod rich limestone the alamedilla sector intercalated in thick mafic rocks piles and a typical ammonitico rosso facies the cardador section in contrast to depositional and taphonomic histories typical for a tethyan top swell site i e rather calcareous ammonitico rosso events of carbonate mud deposition rapid burial and early lithification synsedimentary sliding and over imposition of firmground horizons characterize pelagic cephalopod rich limestones differential taphonomy of carbonate skeletals agrees with differential preservation favoring inner cast preservation in ammonitico rosso and shell preservation neomorphic calcite in pelagic cephalopod rich limestones stable carbon and oxygen isotope data together with trace element data sr mg fe mn are presented for a wide range of carbonate materials matrix micrite neomorphic ammonite shells belemnite rostra and carbonate cements optical inspection including cathodoluminescence imaging and geochemical data suggest a fair preservation of the above mentioned materials except for diagenetic marine burial carbonate cements carbon isotope values fall within the typical tethyan late jurassic range ca 2 except data from belemnite rostra which are depleted around 1 which is interpreted as resulting from metabolic fractionation oxygen isotope values are more variable but the clustering of different carbonate materials within a narrow range of values between 1 and 1 is consistent with conservative diagenesis warmer burial fluids explain lower values in later diagenetic carbonate cements no evidence of pervasive diagenetic imprint is revealed by elemental composition the increased abundance of mg fe and especially mn up to 1500 ppm is recognized as hydrothermal contamination proximity to hydrothermal sources the mid subbetic volcanic ridge accords with higher mn concentration at the alamedilla site interestingly the timing of the mineralogical stabilization of each carbonate material reveals a potential record of a post sedimentary geochemical event the obtained information demonstrates the complexity of ancient carbonate records and encourages future research focused on the preservation potential of geochemical proxies throughout time the studied case hopes to be a representative example to approach the interpretation of potential past and present rare analogs

hydrogeochemistry and fractionation pathways of mg isotopes in a continental weathering system lessons from field experiments abstract the potential of magnesium isotope records from cave carbonate archives speleothems has been documented but remains underexplored this is due to the limited knowledge regarding the complex suite of physico chemical and biological disequilibrium fractionation processes affecting meteoric fluids in the soil zone the carbonate hostrock and calcite precipitation in the cave this study presents 26 mg data from a monitored cave in germany bunker cave including rain water 26 mg 0 70 0 14 soil water 26 mg 0 51 0 10 and drip waters 26 mg 1 65 0 08 sampled between november 2009 and may 2011 field precipitation experiments i e calcite precipitated on watch glasses 26 mg 3 56 0 26 may 2006 to june 2010 were found to be of limited use this is because of experimental crystallographic and sampling artefacts conversely variations in soil and drip water 26 mg over time are predominantly related to seasonal variations in water availability and air temperature affecting the subtle weathering ratio between mg bearing clay minerals in the soil here mainly chlorite and montmorillonite and the low mg calcite hostrock bunker cave 26 mg drip water values display a significant dependency on the air temperature outside the cave this is because air temperature influences co 2 levels in the soil and hence rock water interaction for fast drip sites the direct correlation of 26 mg soil water and 26 mg drip water documents a relative short residence time of the fluid in the carbonate aquifer and thus limited isotope equilibration and mixing of different reservoirs this result is encouraging and adds new evidence to the poorly understood hydro geochemistry of carbonate aquifers slow seepage flow drip sites display an annual 26 mg drip water pattern that is geochemically unrelated to that of the soil water further research including laboratory experiments must focus on the complex fractionation between drip water and speleothem calcite mg isotope record

ice sublimation as a geomorphic process a planetary perspective abstract sublimation plays a role in the shaping of landforms of planetary surfaces where ice is present as frost as polar caps or in the subsurface this review is focused primarily on the geomorphologic consequences of sublimation a summary of the suite of landforms that have been observed on the surface of various planetary bodies and whose formation is attributed to sublimation is presented this includes the sublimation of a range of different ices that are found on planetary bodies water ice carbonic ice etc at least four groups of landforms are distinguishable independent of the planetary body i residual lags that are depleted in ice which form after sublimation loss such residual lags isolate deeper ice from sublimation and thus can have an important impact on planetary volatile cycles ii landforms due to differential sublimation resulting from enhanced sublimation in low albedo warmer areas of the planet and preservation of ice in the high albedo regions iii landforms due to differential sublimation initiated by fractures or ground heterogeneities for example sublimation enhanced polygonal cracks iv pitted terrains that occur in a relatively homogeneous ice bearing subsurface or as an effect of local ice enrichment or segregation in the ground

where has all the aragonite gone mineralogy of holocene neritic cool water carbonates southern australia abstract surficial carbonate sediments on the southern continental shelf of australia are cool water in aspect and composed of biogenic particles produced largely during the late quaternary current understanding is that such sediments are calcite dominated as were their older cenozoic counterparts the holocene fraction of these sediments in modern open shelf neritic environments between 30 and 350 meters water depth is however 50 to 80 aragonite scant evidence of significant former aragonite in many cool water carbonate sedimentary rocks implies that most aragonite is lost before such sediments exit the marine diagenetic environment although marine dissolution must be taking place in such settings the conundrum is exacerbated because seawater over the shelf in southern australia is saturated with respect to aragonite it is proposed that the aragonite from skeletons of gastropods infaunal bivalves and certain bryozoans is dissolved in the shallow subsurface probably as the byproduct of bacterial degradation of sedimentary organic matter as a consequence the geological and paleontological record of many cool water carbonates is strongly biased and the inferred original calcitic composition of such sediments is the product of early diagenetic taphonomic loss not selective biogenic productivity the net result is not only dissolution of aragonite but also neomorphism of mg calcite to calcite with a marine geochemical signature synsedimentary aragonite loss by removing caco3 that is usually available for calcite cementation during meteoric diagenesis leads to retarded lithification of these cool water carbonates until deeply buried such removal of a significant carbonate fraction during deposition likely contributes to the low rates of cool water sediment accumulation

circulation in the glacial north atlantic inferred from grain size measurements records of nutrient proxies in marine sediments indicate that the nutrient distribution and hence circulation of the glacial north atlantic ocean was markedly different from that of today1 2 but these tracers are influenced by several biogeochemical factors unrelated to ocean circulation3 6 and thus do not provide a direct measure of the vigour of circulation distributions of grain size in marine sediments can provide such information owing to the sorting effects of currents7 8 if the characteristics of the input sediment flux are known here we present a record inferred from grain size measurements of variations in the relative strength of deep and intermediate currents in the eastern north atlantic over the past 25 000 years we find that glacial intermediate water flowed rapidly at depths of between 1 100 and 2 000 m in contrast deep water circulation was sluggish during the last glaciation but increased in strength shortly after the glacial maximum this would have resulted in increased heat flux to high latitudes and may have triggered sudden deglaciation deep current strengths declined again at the start of termination stage ia and during the younger dryas perhaps as a result of iceberg discharges the so called heinrich events9 10 a remarkably similar record of grain size variations has been found in the western north atlantic11 indicating that these changes in circulation are ocean wide

mass wasting and ground collapse in terrains of volatile rich deposits as a solar system wide geological process the pre galileo view the polar terrains of mars are covered in many places with irregular pits and retreating scarps as are some of the surfaces of the outer planet satellites these features are interpreted by us as diagnostic of exogenic degradation due to the loss of a volatile rock forming matrix or cement in this study we propose that sublimation degradation is a plausible solar system wide geological process candidate examples have been identified on mars io and triton and possibly europa and ganymede we envision this process as having two end member expressions pits and scarps for which we hypothesize two end member mechanisms massive localized lenses and areally extensive basal layers in this study we focus on the role this process may play on the surfaces of the galilean satellites our principle modeling results are that for these satellites h2s co2 and nh3are the only viable candidate volatiles for sublimation degradation of landforms in light of galilean satellite cosmochemistry for io s polar regions only h2s and then only from slopes that face the sun and have thin lags is volatile enough to cause the observed sublimation induced erosion at those latitudes so2is not a viable candidate as an agent of erosion especially for these polar landforms in the case of europa only co2and h2s are viable candidates given surface age constraints both species could be efficient eroders in nonpolar regions h2s could generate erosion within the polar regions if the deposition and erosion conditions were essentially identical as those we invoked for io s polar regions for ganymede and callisto nh3might be an agent of erosion in equatorial terrains of great age the sublimation of co2and h2s is much more robust than nh3 the much slower rate of sublimation degradation from nh3might be detectable by galileo and used as a compositional indicator

active formation of chaos terrain over shallow subsurface water on europa the galileo spacecraft revealed a number of chaos regions on jupiter s moon europa where the surface terrain appears to have been disrupted from below in many places the surface contains sharp edged blocks or rafts of ice that have at some point been flipped or rotated some characteristics of these regions have been hard to explain such as the fact that the archetypal conamara chaos stands above its surroundings and contains matrix domes schmidt et al apply lessons learned from analogous processes within earth s subglacial volcanoes and ice shelves to an analysis of archival data that suggests chaos terrain forms above liquid water lenses that are perched only 3 kilometres deep within the ice shell the data suggest that ice water interactions and freeze out give rise to the varied morphology of chaos terrains implying that more water is involved than has been previously appreciated for instance the sunken topography of thera macula a large chaos area may indicate that europa is actively resurfacing over a lens comparable in volume to north america s great lakes europa the innermost icy satellite of jupiter has a tortured young surface1 2 3 4 and sustains a liquid water ocean1 2 3 4 5 6 below an ice shell of highly debated thickness1 2 3 4 5 7 8 9 10 quasi circular areas of ice disruption called chaos terrains are unique to europa and both their formation and the ice shell thickness depend on europa s thermal state1 2 3 4 5 7 8 9 10 11 12 13 14 15 16 17 no model so far has been able to explain why features such as conamara chaos stand above surrounding terrain and contain matrix domes10 18 melt through of a thin few kilometre shell3 7 8 is thermodynamically improbable and cannot raise the ice10 18 the buoyancy of material rising as either plumes of warm pure ice called diapirs1 9 10 11 12 13 14 15 or convective cells16 17 in a thick 10 kilometres shell is insufficient to produce the observed chaos heights and no single plume can create matrix domes10 18 here we report an analysis of archival data from europa guided by processes observed within earth s subglacial volcanoes and ice shelves the data suggest that chaos terrains form above liquid water lenses perched within the ice shell as shallow as 3 kilometres our results suggest that ice water interactions and freeze out give rise to the diverse morphologies and topography of chaos terrains the sunken topography of thera macula indicates that europa is actively resurfacing over a lens comparable in volume to the great lakes in north america

the stable isotopic records of fossils from the peterborough member oxford clay formation jurassic uk palaeoenvironmental implications carbon and oxygen isotopic compositions of calcareous nekton aragonite kosmoceras and calcite belemnites and benthos aragonite nuculacean bivalves and calcite gryphaea from the peterborough member of the oxford clay formation vary considerably at any one horizon but show no obvious trend with time this suggests that the temperature and isotopic composition of ambient seawater may have varied considerably over short time intervals but did not change systematically during deposition of the unit thus short term fluctuations were superimposed on longer term 9stability9 in this shallow shelf environment the overlap in carbon isotopic compositions between calcareous nekton and benthos suggest a well mixed water column oxygen isotopic palaeotemperatures suggest thermal stratification provided that kosmoceras 16 28 c inhabited near surface waters and belemnites 12 19 c indistinguishable from the range for benthic bivalves were nektobenthic oxygen isotopic compositions of phosphate from both shallow and possible deeper dwelling vertebrates reptiles bony fish and sharks yield the same range of palaeotemperatures 20 29 c suggesting that all vertebrate taxa may have lived predominantly in warm shallow waters

carbon cycle history through the jurassic cretaceous boundary a new global δ13c stack we present new carbon and oxygen isotope curves from sections in the bakony mts hungary constrained by biostratigraphy and magnetostratigraphy in order to evaluate whether carbon isotopes can provide a tool to help establish and correlate the last system boundary remaining undefined in the phanerozoic as well provide data to better understand the carbon cycle history and environmental drivers during the jurassic cretaceous interval we observe a gentle decrease in carbon isotope values through the late jurassic a pronounced shift to more positive carbon isotope values does not occur until the valanginian corresponding to the weissert event in order to place the newly obtained stable isotope data into a global context we compiled 31 published and stratigraphically constrained carbon isotope records from the pacific tethyan atlantic and boreal realms to produce a new global 13c stack for the late oxfordian through early hauterivian interval our new data from hungary is consistent with the global 13c stack the stack reveals a steady but slow decrease in carbon isotope values until the early valanginian in comparison the late jurassic early cretaceous 13c curve in gts 2012 shows no slope and little variation aside from the well defined valanginian positive excursion chemostratigraphic correlation durschning the jurassic cretaceous boundary interval is difficult due to relatively stable 13c values compounded by a slope which is too slight there is no clear isotopic marker event for the system boundary the long term gradual change towards more negative carbon isotope values through the jurassic cretaceous transition has previously been explained by increasingly oligotrophic condition and lessened primary production however this contradicts the reported increase in 87sr 86sr ratios suggesting intensification of weathering and a decreasing contribution of non radiogenic hydrothermal sr and presumably a concomitant rise in nutrient input into the oceans the concomitant rise of modern phytoplankton groups dinoflagellates and coccolithophores would have also led to increased primary productivity making the negative carbon isotope trend even more notable we suggest that gradual oceanographic changes more effective connections and mixing between the tethys atlantic and pacific oceans would have promoted a shift towards enhanced burial of isotopically heavy carbonate carbon and effective recycling of isotopically light organic matter these processes account for the observed long term trend interrupted only by the weissert event in the valanginian

manganese distribution in the carbonate fraction of shallow and deep marine lithofacies middle ordovician eastern tennessee abstract a marked increase in manganese content from shallow to deep marine lithofacies can be observed within the carbonate fraction of the middle ordovician sequence in eastern tennessee the distribution of manganese is controlled by 1 the original aragonite and calcite mineralogy of shallow and deep marine environments respectively 2 preferential substitution of manganese for calcium in the rhombohedral structure of calcite 3 anoxic depositional and diagenetic environments and 4 possibly volcanism

sensitivity of bunker cave to climatic forcings highlighted through multi annual monitoring of rain soil and dripwaters abstract the last two decades have seen a considerable increase in studies using speleothems as archives of past climate variability caves under study are now monitored for a wide range of environmental parameters and results placed in context with speleothem data the present study investigates trends from a seven year long monitoring of bunker cave northwestern germany in order to assess the hydraulic response and transfer time of meteoric water from the surface to the cave rain soil and dripwater were collected from august 2006 to august 2013 at a monthly to bimonthly resolution and their oxygen and hydrogen isotope composition was measured furthermore drip rates were quantified due to different drip characteristics annual mean values were calculated for the drip rates of each drip site correlations of the annual mean drip rate of each site with precipitation and infiltration demonstrate that the annual infiltration and thus the annual precipitation control the inter annual drip rate variability for all except one site the hydraulic response is not delayed on an annual basis all drip sites display identical long term trends which suggests a draining of a common karst reservoir over these seven years of monitoring correlations of soil and dripwater monthly 18o and d values with atmospheric temperature data reveal water transfer times of 3 months to reach a depth of 40 cm soilwater at site bw 2 and 4 months for 70 cm depth soilwater at site bw 1 finally the water reaches the cave chambers 15 to 30 m below land surface after ca 2 5 years consequently a temporal offset of 29 to 31 months ca 2 5 years between the hydraulic response time no time lag on annual basis and the water transfer time time lag of 29 to 31 months was found which is negligible with regard to bunker cave speleothems because of their slow growth rates here proxies recording precipitation infiltration and temperature are registered on a decadal scale variations in drip rate and thus precipitation and infiltration are recorded by 13c and mg ca ratios in speleothem calcite speleothem 18o values reflect both temperature and precipitation signals due to drip rate related fractionation processes we document that long term patterns in temperature and precipitation are recorded in dripwater patterns of bunker cave and that these are linked to the north atlantic oscillation nao

geological structure and evolution of majorca implications for the origin of the western mediterranean abstract the island of majorca forms part of the ne sw continental balearic promontory which is surrounded by continental and oceanic extensional basins majorca has a basin and range physiography mainly resulting from late neogene extension the basins and ranges strike ne sw the structure of the ranges consists of thrust faults and associated folds involving mesozoic series paleogene series are also involved in the compressional structures located in the southeast whereas a stratigraphic hiatus embracing late cretaceous and paleogene is present in the rest of the island the age of syncompressive rocks and sediments is chattian to aquitanian in the se llevant ranges aquitanian to burdigalian in the central ranges and burdigalian to langhian in the nw tramuntana range thus compressive deformation progressed from southeast to northwest the thrust fault hangingwall displacement is to the northwest and shortening is large 44 seismic reflection sections reveal the presence of compressive structures in the substratum of the basins moreover normal faults due to wnw ese extension occurred during the serravallian and tortonian producing additional subsidence in the basins minor compression could have occurred since the onset of the pleistocene majorca was shortened when the extensional basins surrounding the island originated available models for the origin and evolution of extensional basins of the western mediterranean do not consider the structure observed in majorca

expanded secondary craters in the arcadia planitia region mars evidence for tens of myr old shallow subsurface ice abstract a range of observations indicates widespread subsurface ice throughout the mid and high latitudes of mars in the form of both pore filling and excess ice it is generally thought that this ice was recently emplaced and is not older than a hundred thousand to a few millions of years old based on ice stability and orbital induced climate change we analyze the distribution of subsurface ice in arcadia planitia located in the northern mid latitudes by mapping thermokarstically expanded secondary craters providing additional evidence for extensive excess ice down to fairly low latitudes less than 40 n we further infer the minimum age of this subsurface ice based on the ages of the four primary craters that are thought to be the source of a large portion of these secondaries which yields estimates on the order of tens of millions of years old much more ancient than anticipated this estimated ancient age suggests that ice can be preserved in the shallow subsurface for long periods of time at least in some parts of arcadia planitia where expanded secondary craters are especially abundant we estimate the amount of ice lost to sublimation during crater expansion based on measurements of expanded secondary craters in hirise digital terrain models the loss is equivalent to a volume of ice between 140 and 360 km 3 which would correspond to a global layer of 1 2 5 mm thick we further argue that much more ice at least 6000 km 3 is likely preserved beneath the un cratered regions of arcadia planitia since significant loss of this excess ice would have caused extensive terrain dissection and the removal of the expanded secondary craters both the loss of ice due to secondary crater expansion and the presence of this ice today have implications for the martian climate

evidence for chlorine recycling hydrosphere biosphere atmosphere in a forested wet zone on the canadian shield abstract the ability to measure environmental levels of 36 cl by accelerator mass spectrometry and 3 h by 3 he ingrowth mass spectrometry has made it possible to use the pulses of these two isotopes released into the atmosphere during nuclear weapons testing as tracers of cl and water movement in soils and groundwater the authors have investigated the movement of these tracers below a forested wet zone and have found that both are retarded to a differing extent in the near surface because of vegetative uptake and recycling adsorption by clay particles followed by slow release to the groundwater may also be significant the data accumulated in this region of near vertical recharge have gone a considerable distance towards explaining the anomalously low concentrations of 36 cl measured in the 5 laurentian great lakes as well as indicating possible mechanisms for large scale cl recycling in the atmosphere and biosphere identification of the near term non conservative behaviour of the cl is significant since such a phenomenon could introduce errors in many watershed calculations e g water residence times evaporation rates and mixing calculations

high velocity collisions from the lunar cataclysm recorded in asteroidal meteorites lunar samples suggest that the inner solar system was bombarded by asteroids about 4 gyr ago radiometric ages of meteorites suggest an unusual number of high velocity asteroids at this time consistent with a dynamical origin of the bombardment in which the asteroids were pushed by outer planet migration onto highly eccentric orbits

quantitative aspects of mn activated cathodoluminescence of natural and synthetic aragonite the cathodoluminescence analyses of the trigonal carbonates calcite and dolomite have been applied intensively in sedimentary petrology for a long time and the properties of these minerals are well known but much less attention has been paid to aragonite in this study the cathodoluminescence behaviour and the trace element composition of natural and synthetic aragonite have been studied employing trace element analyses proton induced x ray emission and luminescence spectroscopy aragonite doped with mn2 has been synthesized in a nh4 mg2 ca2 cl solution in contact with a co2 h2o nh3 atmosphere the low effective distribution coefficients indicate a rapid growth of the crystals of millimetre size which occurred within hours or days the natural aragonite samples contain mn fe and sr in different concentrations the mn bearing aragonites exhibit a bright green luminescence which is caused by a strong emission band at 575 nm with a half width of about 84 nm the luminescence intensity shows a strong positive correlation with mn in aragonite when fe and mn do not exceed 2000 p p m the intensity is depressed if the concentration of these elements exceeds the critical values in the shell of a recent unio sp the luminescence intensity deviates from the linear correlation although the trace element contents are not too high this is probably an effect of quenching by organic material between the crystallites of the biogenic aragonite

the distribution of meteoric cl 36 in precipitation across europe in spring 2007 abstract the cosmogenic isotope 36 cl is a valuable tool for understanding many earth system processes but an improved knowledge of its spatial distribution at the earth s surface is critical for several applications meteoric 36 cl fallout reflects complex interactions between atmospheric production transport and deposition processes and predictive models require experimental validation this study investigates for the first time in a systematic way the spatial distribution of meteoric 36 cl on a continental scale within the european landmass using precipitation samples collected during spring 2007 36 cl cl ratios increase with distance inland and the new data exhibit a strong exponential relationship with 18 o values of precipitation r s 0 75 yielding a useful predictive framework for future studies precipitation events in central european regions are characterised by high 36 cl cl ratios with a maximum measured in lyon france of 746 134 10 15 the new data confirm models for the dependence of 36 cl fallout on latitude with the highest mean springtime fallout 53 6 atoms m 2 s 1 occurring in the 40 50 n latitudinal band with sharp decreases in fallout in high latitude regions and more gradual decreases towards the lower latitudes the 36 cl bomb pulse introduced by thermonuclear weapon testing predominantly in the 1950 s has persisted in the environment for c 50 years but the new data indicate that 36 cl fallout has now essentially returned to natural pre bomb values

monitoring bunker cave nw germany a prerequisite to interpret geochemical proxy data of speleothems from this site summary monitoring cave environments is important to understand processes in karst systems if stalagmites from a specific cave are used as archives of past climate variability a quantitative understanding of the soil karst speleothem system is crucial the monitoring program performed in bunker cave nw germany which includes monthly collection of climatological data as well as air and water samples from the cave and the overlying soil since 2006 is a prerequisite for the interpretation of speleothem data from the cave in terms of climate variability the results show that bunker cave is a homogeneously ventilated cave with rather low pco2 values of 580 1200 ppmv which lacks strong seasonal variations the 18o value of cave drip water reflects the mean annual composition of the rain water and the seasonal variability is strongly attenuated indicating a well mixed karst aquifer hence stalagmites from bunker cave should be well suited to record interannual decadal climate trends seven drip sites in two cave chambers show three different types of discharge behaviour including slow seasonal drip fast seasonal drip and seepage flow the drip rate patterns of most drip sites are consistent with the main infiltration events taking into account a delay of several months an instantaneous response to precipitation i e piston flow is not observed for any drip site indicating a specific water capacity threshold in the soil karst aquifer prior calcite precipitation pcp was also identified especially during times of low discharge though pcp is not as pronounced at bunker cave as in other caves it probably has an influence on the mg ca ratios of the stalagmites

carbon isotope stratigraphy and pelagic biofacies of the middle upper jurassic transition in the tethys central atlantic connection abstract a bulk carbon isotope stratigraphy based on high resolution sampling of five stratigraphic ammonite dated sections from pelagic swells of the subbetic basin external zones of the betic cordillera southern spain is presented the studied sections are characterized by callovian oxfordian stratigraphic successions located in the south iberian palaeomargin a key area connecting the central atlantic to the tethys oceans the rocks are mainly nodular limestones with common extreme condensation rosso ammonitico facies discontinuities with hiatuses of variable duration submarine hardgrounds fe mn ooids limonite crusts and neptunian dykes are observed around the callovian oxfordian boundary the stratigraphic record although very time averaged allows for a consistent and accurate ammonite chronostratigraphy the carbon isotopes of marine carbonates show a marked trend towards high 13c values from lower oxfordian to the middle oxfordian 4 3 near the plicatilis transversarium boundary the isotopic values stand between 2 7 and 3 0 at the upper oxfordian bifurcatus and hypselum zones and lowermost kimmeridgian bimammatum zone afterward 13c values decrease and reach a relative minimum 2 3 2 5 in the lower kimmeridgian bimammatum planula boundary finally isotopic values increase again 2 6 2 7 in the lower kimmeridgian mid part of the planula zone comparison of carbon isotope stratigraphy between subbetic and other tethyan areas shows similar trends the replacement of thin shelled bivalves by planktonic foraminifers and radiolarians that took place in the callovian oxfordian boundary can be associated to the widening of the trans pangaean seaway this in turn triggered the global warming which increased nutrients concentration in upper water column due to intensified nutrient input by river plumes these phenomena are concomitant with the major oxfordian 13c positive excursion and with a transgressive cycle

the topography of iapetus leading side abstract we have used cassini stereo images to study the topography of iapetus leading side a terrain model derived at resolutions of 4 8 km reveals that iapetus has substantial topography with heights in the range of 10 km to 13 km much more than observed on the other middle sized satellites of saturn so far most of the topography is older than 4 ga neukum g wagner r denk t porco c c 2005 lunar planet sci xxxvi abstract 2034 which implies that iapetus must have had a thick lithosphere early in its history to support this topography models of lithospheric deflection by topographic loads provide an estimate of the required elastic thickness in the range of 50 100 km iapetus prominent equatorial ridge porco c c and 34 colleagues 2005 science 307 1237 1242 reaches widths of 70 km and heights of up to 13 km from their base within the modeled area the morphology of the ridge suggests an endogenous origin rather than a formation by collisional accretion of a ring remnant ip w h 2006 geophys res lett 33 doi 10 1029 2005gl025386 l16203 the transition from simple to complex central peak craters on iapetus occurs at diameters of 11 3 km the central peaks have pronounced conical shapes with flanking slopes of typically 11 and heights that can rise above the surrounding plains crater depths seem to be systematically lower on iapetus than on similarly sized rhea which if true may be related to more pronounced crater wall slumping which widens the craters on iapetus than on rhea there are seven large impact basins with complex morphologies including central peak massifs and terraced walls the largest one reaches 800 km in diameter and has rim topography of up to 10 km generally no rings are observed with the basins consistent with a thick lithosphere but still thin enough to allow for viscous relaxation of the basin floors which is inferred from crater depth to diameter measurements in particular a 400 km basin shows up domed floor topography which is suggestive of viscous relaxation a model of complex crater formation with a viscoplastic bingham rheology melosh h j 1989 impact cratering oxford univ press new york of the impact shocked icy material provides an estimate of the effective cohesion viscosity at 0 04 0 01 mpa 0 6 0 2 gpa s the local distribution of bright and dark material on the surface of iapetus is largely controlled by topography and consistent with the dark material being a sublimation lag deposit originating from a bright icy substrate mixed with the dark components but frost deposits are possible as well

petrographic and geochemical evidence for original aragonite mineralogy of upper jurassic carbonates mozduran formation sarakhs area iran abstract diverse skeletal and non skeletal grains with abundant red and blue green calcareous algae evaporites and early diagenetic dolomites in the mozduran carbonates are similar to those of modern warm water shallow marine carbonates isopachous and fibrous intragranular sparry calcite cements resemble modern aragonite morphologies concentric and radial ooids are like modern aragonitic forms which are formed in turbulent and in low energy environments respectively deformed ooids shattered micritic envelopes and spalled ooids indicate aragonite dissolution during meteoric diagenesis meteoric cements are equant mosaic to drusy calcites burial cements only occur as vein fillings sr and na covariance with mn supports evidence of inversion of aragonite to calcite with subsequent open phreatic diagenesis fe concentrations are a magnitude higher than mn due to a reducing phreatic environment high sr na ratios suggest original aragonite mineralogy the 18 o and 13 c field of mozduran limestone lies at the edge of the modern shallow marine field indicating a range from marine to meteoric cements differences in 18 o values between marine calcites and meteoric derived calcites is similar to that in the modern tropics the surface marine diagenetic trend line that passes through shallow marine modern whole carbonates cuts the mozduran limestone isotope field due to their formation in warm shallow marine waters given that atmospheric co 2 levels were similar to those at present increasing mn and fe values decreasing na and uniform sr values with increasingly lighter values of both 18 o and 13 c are exlained by extensive meteoric diagenesis the least altered marine calcite 18 o value of 2 6 pdb corresponds to 29 or 24 c depending on whether 0 of present seawater and 1 2 of ancient seawater with no ice caps are taken as a base an original calcite mineralogy postulated for some jurassic limestones is related to a non tropical origin

testing the viability of topographic relaxation as a mechanism for the formation of lunar floor fractured craters historically two modes of origin for lunar floor fractured craters have been proposed subcrater laccolith emplacement and topographic relaxation to test the viability of the topographic relaxation model we employ an elastoviscoplastic finite element model and ductile rheology measurements of a devolatilized terrestrial diabase an analog to lunar crustal materials trials were run under two situations 1 under extreme conditions e g high heat flow to determine the maximum degree of relaxation that the model can accommodate and 2 under more nominal conditions in order to resolve how much relaxation can be expected to occur under more plausible lunar conditions we find that in the extreme case topographic relaxation is a viable means only for explaining the observed shallowing of the largest floor fractured craters 100 km in diameter results from the less extreme case demonstrate that lunar materials are simply too rigid to experience degrees of relaxation as large as those observed in the floor fractured crater population these results indicate that topographic relaxation is not the primary mechanism for the formation of floor fractured craters because the topographic relaxation model does not apply for the vast majority of floor fractured craters i e those with diameters less than 60 km we conclude that the laccolith intrusion model is a more viable alternative

widespread crater related pitted materials on mars further evidence for the role of target volatiles during the impact process abstract recently acquired high resolution images of martian impact craters provide further evidence for the interaction between subsurface volatiles and the impact cratering process a densely pitted crater related unit has been identified in images of 204 craters from the mars reconnaissance orbiter this sample of craters are nearly equally distributed between the two hemispheres spanning from 53 s to 62 n latitude they range in diameter from 1 to 150 km and are found at elevations between 5 5 to 5 2 km relative to the martian datum the pits are polygonal to quasi circular depressions that often occur in dense clusters and range in size from 10 m to as large as 3 km pit sizes scale with both the host crater s diameter and the host deposit size these pits have subtle raised rims and unlike primary and secondary impact craters they lack well defined ejecta deposits and overlapping stratigraphic relationships they also lack any sign of any preferential alignment expected of volcanic or tectonic collapse features morphologic and stratigraphic evidence in support of an impact origin includes the observation that pitted materials primarily occur as ponded and flow like deposits on crater floors behind terraces and infilling the lowest local topographic depressions atop the ejecta blanket similar to the distribution of impact melt bearing bodies on the moon based on the observations and comparisons to terrestrial and lunar analogs we conclude that the pit bearing materials are impactite deposits the presence of these deposits in older craters where preserved suggests that they have formed on mars throughout most of its geologic history thus understanding their origin may help to constrain the hydrological and climate history of mars

central pit and dome craters exposing the interiors of ganymede and callisto central pit craters on the large icy satellites ganymede and callisto are an unusual crater class perhaps related to the unusual properties of water ice the detailed morphology and dimensions of pit crater features differ from those of smaller normal complex craters on these two satellites pit crater depths appear to be constant regardless of diameter rim collapse is also restricted relative to that in lunar craters or smaller ganymede craters the floors of pits in craters larger than 60 km are occupied by smooth bright domes pit to crater and dome to crater diameter ratios increase linearly with crater diameter and are indistinguishable on ganymede and callisto and with terrain type or surface longitude the floors and central structures of young bright rayed pit craters such as osiris are covered by a thin uniformly bright impact melt or frost deposit thus domes and pits form rapidly on the time scale of the impact itself rather than by long term postimpact intrusion or extrusion the bright domes in pit craters are most simply explained as the uplift and exposure of relatively ice rich material from depths of 3 5 to 5 km during impact this process is almost directly analogous to the uplift and exposure of anamolous deep seated material observed in terrestrial and lunar craters the unusual pit morphology on icy satellites may be the result of impact into crust that is mechanically much weaker at shallow depth than on rocky bodies such as the moon because crater morphology is strongly dependent on ice rock composition the similarity of pit and dome dimensions on ganymede and callisto indicates that the structure and rheology of the crusts of these bodies down to depths of 10 km are very similar and have been for several b y pit crater morphology indicates that the crusts of both satellites are probably ice rich and differentiated

palaeotemperatures indicated by upper jurassic kimmeridgian tithonian fossils from mallorca determined by oxygen isotope composition abstract the oxygen and carbon composition of calcite has been determined for belemnites ammonite aptychi and the matrix surrounding these fossils from the kimmeridgian tithonian of mallorca petrography cathodoluminescence and trace element analyses indicate that both ammonite aptychi and matrix has been diagenetically altered whereas the belemnites have been undergone minimal or no modification the belemnites give the heaviest oxygen isotope values of 0 04 to 0 99 pdb and lighter values of 0 71 to 3 98 pdb come from the ammonite aptychi and matrix the carbon isotopic compositions obtained from all the fossils are positive and are similar to those derived from modern marine shallow water skeletons palaeotemperatures calculated on the basis of the oxygen isotopic composition of the belemnites give a range of values from 13 6 to 16 c these results agree with late jurassic palaeotemperatures from similar palaeolatitudes

new insight into lunar impact melt mobility from the lro camera 1 the lunar reconnaissance orbiter camera lroc is systematically imaging impact melt deposits in and around lunar craters at meter and sub meter scales these images reveal that lunar impact melts although morphologically similar to terrestrial lava flows of similar size exhibit distinctive features e g erosional channels although generated in a single rapid event the post impact mobility and morphology of lunar impact melts is surprisingly complex we present evidence for multi stage influx of impact melt into flow lobes and crater floor ponds our volume and cooling time estimates for the post emplacement melt movements noted in lroc images suggest that new flows can emerge from melt ponds an extended time period after the impact event

structure stratigraphy and origin of husband hill columbia hills gusev crater mars 1 the strike and dip of lithologic units imaged in stereo by the spirit rover in the columbia hills using three dimensional imaging software shows that measured dips 15 32 for bedding on the main edifice of the columbia hill are steeper than local topography 8 10 outcrops measured on west spur are conformable in strike with shallower dips 7 15 than observed on husband hill dips are consistent with observed strata draping the columbia hills initial uplift was likely related either to the formation of the gusev crater central peak or ring or through mutual interference of overlapping crater rims uplift was followed by subsequent draping by a series of impact and volcaniclastic materials that experienced temporally and spatially variable aqueous infiltration cementation and alteration episodically during or after deposition west spur likely represents a spatially isolated depositional event erosion by a variety of processes including mass wasting removed tens of meters of materials and formed the tennessee valley primarily after deposition this was followed by eruption of the adirondack class plains basalt lava flows which embayed the columbia hills minor erosion impact and aeolian processes have subsequently modified the columbia hills

the origin of domes on europa the role of thermally induced compositional diapirism 1 the surface of jupiter s moon europa is peppered by topographic domes interpreted as sites of intrusion and extrusion diapirism is consistent with dome morphology but thermal buoyancy alone cannot produce sufficient driving pressures to create the observed dome elevations instead diapirs may initiate by thermal convection that induces compositional segregation exclusion of impurities from warm upwellings allows sufficient buoyancy for icy plumes to create the observed surface topography provided the ice shell has a small effective elastic thickness 0 2 to 0 5 km and contains low eutectic point impurities at the few percent level this model suggests that the ice shell may be depleted in impurities over time

cosmogenic 36cl in karst waters quantifying contributions from atmospheric and bedrock sources improved reconstructions of cosmogenic isotope production through time are crucial to understand past solar variability as a preliminary step to derive atmospheric 36 cl cl solar proxy time series from speleothems we quantify 36 cl sources in cave dripwaters atmospheric 36 cl fallout rates are a potential proxy for solar output however extraneous 36 cl derived from in situ production in cave hostrocks could complicate the solar signal results from numerical modeling and preliminary geochemical data presented here show that the atmospheric 36 cl source dominates in many but not all cave dripwaters at favorable low elevation mid latitude sites 36 cl based speleothem solar irradiance reconstructions could extend back to 500 ka with a possible centennial scale temporal resolution this would represent a marginal improvement in resolution compared with existing polar ice core records with the added advantages of a wider geographic range independent u series constrained chronology and the potential for contemporaneous climate signals within the same speleothem material

soil abrasion and eolian dust production implications for iron partitioning and solubility 1 eolian dust is a source of iron for phytoplankton in many ocean areas and there are complex pathways of atmospheric processing from soil to ocean overlooked parts of the pathways are the impact of large 10 m grains including a role as proxies for the behavior of smaller grains and the effect of multiple cycles of uplift and abrasion in the dust source region partitioning readily released acid leachable and refractory and dissolution rates of iron were determined for an artificial dust produced by abrading an australian soil untreated soil abraded soil after production of the artificial dust and a natural australian eolian dust sample taken during a dust storm readily released iron is not created during abrasion and therefore the amount of readily released iron in a dust or dust derived soil depends on processing events since the dust or soil last experienced an abrasion event our study develops a method for the partitioning of iron within airborne dusts and appears to be the first to consider the effect of multiple uplift events on iron partitioning

speleothem trace element signatures a hydrologic geochemical study of modern cave dripwaters and farmed calcite trace element variations in ancient cave speleothems are often interpreted as indicators of changes in paleo rainfall and hydrologic conditions however these records are difficult to interpret without an understanding of the physicochemical controls on stalagmite chemistry plus site specific calibration of changes in net rainfall to variations in dripwater and speleothem chemistry in this study we examine geochemical relationships between net rainfall precipitation minus evapotranspiration p et drip rates drip water chemistry and contemporaneous calcite chemistry to test the hypothesis that speleothem mg ca and sr ca records are proxies for rainfall amount hrc is contained within four low magnesium limestone units capped sporadically by a remnant dolomitic limestone aqueous concentrations of magnesium post evapotranspiration decrease with increasing vertical travel distance between the soil zone and the point of in cave drip emergence drip path length dpl as dissolved high mg solutions sourced from the dolomitic caprock are diluted with dissolved low mg limestone waters sourced from the host limestone dripwater mg ca and sr ca ratios covary and provide diagnostic indicators of the two dominant mechanisms controlling dripwater chemistry 1 mixing of post evaporative solutions derived from two geochemical endmembers dissolution of dolomite and limestone and 2 evolution of hydrochemistry away from dissolved bedrock compositions due to prior calcite precipitation pcp above the drip sites by resolving the linear mixing relationships for drip water mg ca and sr ca sources and the distribution coefficients for trace element transfer in the pcp dripwater to calcite precipitation reactions and applying these principles to our time series we find that the extent of pcp production within the karst is directly controlled by the balance between precipitation p and evapotranspiration et higher net rainfall p et 1 wet conditions reduces pcp and lower net rainfall with increased evapotranspiration p et 1 increases pcp farmed calcite x ca ratios faithfully track hydrologically influenced seasonal variations in dripwater chemistry for x mg sr and na however the relationship between changes in net rainfall and changes in mg ca and sr ca ratios in modern calcite is unique at each site and differs significantly at closely spaced drip stalagmite locations this suggests that in situ modern hydrochemical calibrations should be performed atop individual speleothems prior to harvesting for paleoclimate investigations and that such calibrations may not reflect past conditions as drip paths change we apply this understanding to published dripwater data and speleothem time series from other caves a major implication is that in order to interpret stalagmite sr ca and mg ca ratios as wet vs dry proxies speleothem sr ca and mg ca variations must be coherent and in phase over all time periods i e sr mg ratios must be constant these criteria will help to distinguish rainfall amount versus rainfall source in speleothem 18o records

localized sources of water vapour on the dwarf planet 1 ceres the largest asteroid of the solar system 1 ceres has been thought to have an icy surface here it is observed to be emitting water vapour the presence of hydrated minerals on the surface of ceres the largest body in the solar system s main asteroid belt suggested that there may be water there too now infrared spectra obtained by esa s herschel space observatory provide unambiguous evidence that there is water ice at or near the surface of ceres water vapour is issuing at a rate of at least 1026 molecules per second from sources on ceres localized to mid latitude regions the water evaporation could be due to comet like sublimation or to cryo volcanism in which volcanoes erupt volatiles such as water instead of molten rocks this finding supports models that propose that the icy bodies such as comets may have migrated into the asteroid belt from beyond the notional snowline dividing the early solar system into a dry inner and icy outer regions the snowline conventionally divides solar system objects into dry bodies ranging out to the main asteroid belt and icy bodies beyond the belt models suggest that some of the icy bodies may have migrated into the asteroid belt1 recent observations indicate the presence of water ice on the surface of some asteroids2 3 4 with sublimation5 a potential reason for the dust activity observed on others hydrated minerals have been found6 7 8 on the surface of the largest object in the asteroid belt the dwarf planet 1 ceres which is thought to be differentiated into a silicate core with an icy mantle9 10 11 the presence of water vapour around ceres was suggested by a marginal detection of the photodissociation product of water hydroxyl ref 12 but could not be confirmed by later more sensitive observations13 here we report the detection of water vapour around ceres with at least 1026 molecules being produced per second originating from localized sources that seem to be linked to mid latitude regions on the surface14 15 the water evaporation could be due to comet like sublimation or to cryo volcanism in which volcanoes erupt volatiles such as water instead of molten rocks

cosmogenic 36cl in karst waters from bunker cave north western germany a tool to derive local evapotranspiration abstract monthly rain and drip waters were collected over a period of 10 months at bunker cave germany the concentration of 36 cl and the 36 cl cl ratios were determined by accelerator mass spectrometry ams while stable 35 37 cl concentrations were measured with both ion chromatography ic and ams the measured 36 cl fluxes of 0 97 0 57 10 4 atoms cm 2 month 1 0 97 atoms m 2 month 1 in precipitation were on average twice as high as the global mean atmospheric production rate this observation is consistent with the local fallout pattern which is characterized by a maximum at mid latitudes the stable chloride concentration in drip waters ranging from 13 2 to 20 9 mg l and the 36 cl concentrations ranging from 16 9 10 6 to 35 3 10 6 atoms l are a factor of 7 and 10 above the values expected from empirical evapotranspiration formulas and the rain water concentrations respectively most likely the additional stable cl is due to human impact from a nearby urban conglomeration the large 36 cl enrichment is attributed to the local evapotranspiration effect which appears to be higher than the calculated values and to additional bomb derived 36 cl from nuclear weapons tests in the 1950s and 60s stored in the soil above the cave in the densely vegetated soil above bunker cave 36 cl seems not to behave as a completely conservative tracer the bomb derived 36 cl might be retained in the soil due to uptake by minerals and organic material and is still being released now based on our data the residence time of 36 cl in the soil is estimated to be about 75 85 years

magnesium isotope fractionation during low mg calcite precipitation in a limestone cave field study and experiments abstract the chemical and isotopic composition of speleothem calcite and particularly that of stalagmites and flowstones is increasingly exploited as an archive of past environmental change in continental settings despite intensive research including modelling and novel approaches speleothem data remain difficult to interpret a possible way foreword is to apply a multi proxy approach including non conventional isotope systems for the first time we here present a complete analytical dataset of magnesium isotopes 26 mg from a monitored cave in nw germany bunker cave the data set includes 26 mg values of loess derived soil above the cave 1 0 0 5 soil water 1 2 0 5 the carbonate hostrock 3 8 0 5 dripwater in the cave 1 8 0 2 speleothem low mg calcite stalactites stalagmites 4 3 0 6 cave loam 0 6 0 1 and runoff water 1 8 0 1 in the cave respectively magnesium isotope fractionation processes during weathering and interaction between soil cover hostrock and solute bearing soil water are non trivial and depend on a number of variables including solution residence times dissolution rates adsorption effects and potential neo formation of solids in the regolith and the carbonate aquifer apparent mg isotope fractionation between dripwater and speleothem low mg calcite is about 1000ln mg cc mg aq 2 4 a similar mg isotope fractionation 1000ln mg cc mg aq 2 1 is obtained by abiogenic precipitation experiments carried out at aqueous mg ca ratios and temperatures close to cave conditions accordingly 26 mg discrimination during low mg calcite formation in caves is highly related to inorganic fractionation effects which may comprise dehydration of mg 2 prior to incorporation into calcite surface entrapment of light isotopes and reaction kinetics relevance of kinetics is supported by a significant negative correlation of mg isotope fractionation with the precipitation rate for inorganic precipitation experiments

modelling the δ18o value of cave drip water and speleothem calcite abstract stable isotope signals recorded in speleothems have provided important insights about past climate variability in recent years quantitative reconstruction of mean annual temperature and the amount of precipitation however remains difficult because the stable isotope signals are influenced by various processes here we present a drip water model which shows how these climate parameters affect the oxygen isotope signal of cave drip water in the model the dependence of the 18 o value of drip water on mean annual temperature is established by correlation to the amount of winter precipitation and winter temperature application of the model to two caves in western germany reveals a strong influence of winter rainfall on the oxygen isotope composition of cave drip water in this region assuming equilibrium isotope fractionation between drip water and calcite we provide a function relating the 18 o value of speleothem calcite to mean annual surface temperature this function shows a clear anticorrelation between temperature and the 18 o value of speleothem calcite which has been previously reported for several caves in central and northern europe by inverse application of this function we tentatively reconstruct average temperatures for the period between 6 and 1 5 ka from the 18 o signals of two stalagmites from atta and bunker cave western germany the resulting temperature curves are very sensitive to the value used for the correlation between the amount of winter precipitation and winter temperature since this correlation was probably not constant in the past the reconstructed temperature curves are associated with substantial uncertainty

central pit craters on ganymede central pit craters are common on mars ganymede and callisto and thus are generally believed to require target volatiles in their formation the purpose of this study is to identify the environmental conditions under which central pit craters form on ganymede we have conducted a study of 471 central pit craters with diameters between 5 and 150 km on ganymede and compared the results to 1604 central pit craters on mars diameter range 5 160 km both floor and summit pits occur on mars whereas floor pits dominate on ganymede central peak craters are found in similar locations and diameter ranges as central pit craters on mars and overlap in location and at diameters 60 km on ganymede central pit craters show no regional variations on either ganymede or mars and are not concentrated on specific geologic units central pit craters show a range of preservation states indicating that conditions favoring central pit formation have existed since crater retaining surfaces have existed on ganymede and mars central pit craters on ganymede are generally about three times larger than those on mars probably due to gravity scaling although target characteristics and resolution also may play a role central pits tend to be larger relative to their parent crater on ganymede than on mars probably because of ganymede s purer ice crust a transition to different characteristics occurs in ganymede s icy crust at depths of 4 7 km based on the larger pit to crater diameter relationship for craters in the 70 130 km diameter range and lack of central peaks in craters larger than 60 km diameter we use our results to constrain the proposed formation models for central pits on these two bodies our results are most consistent with the melt drainage model for central pit formation

a prelanding assessment of the ice table depth and ground ice characteristics in martian permafrost at the phoenix landing site 1 we review multiple estimates of the ice table depth at potential phoenix landing sites and consider the possible state and distribution of subsurface ice a two layer model of ice rich material overlain by ice free material is consistent with both the observational and theoretical lines of evidence results indicate ground ice to be shallow and ubiquitous 2 6 cm below the surface undulations in the ice table depth are expected because of the thermodynamic effects of rocks slopes and soil variations on the scale of the phoenix lander and within the digging area which can be advantageous for analysis of both dry surficial soils and buried ice rich materials the ground ice at the ice table to be sampled by the phoenix lander is expected to be geologically young because of recent climate oscillations however estimates of the ratio of soil to ice in the ice rich subsurface layer suggest that that the ice content exceeds the available pore space which is difficult to reconcile with existing ground ice stability and dynamics models these high concentrations of ice may be the result of either the burial of surface snow during times of higher obliquity initially high porosity soils or the migration of water along thin films measurement of the d h ratio within the ice at the ice table and of the soil to ice ratio as well as imaging ice soil textures will help determine if the ice is indeed young and if the models of the effects of climate change on the ground ice are reasonable

the nature of the δ13c of periplatform sediments implications for stratigraphy and the global carbon cycle the carbon isotopic composition y 13 c of bulk carbonates obtained from a transect of sites drilled through platform and periplatform sediments of holocene to early miocene age has been compared to ascertain whether changes in the y 13 c can be correlated between sediments of equivalent ages and whether such changes can be related to global changes in the y 13 c of the dissolved inorganic carbon in the oceans over this time period five of the sites were drilled during leg 166 of the ocean drilling project 1003 1007 in a transect ranging from five km to 25 km away from the platform margin and penetrating sediments of holocene to oligocene age that are contained in 17 depositional sequences a q two shallow water sites clino and unda were situated on a extension of the same transect on great bahama bank in a water depth of 10 15 m with the exception of unda and clino the y 13 c of the carbonates ranges from 5x in the younger sequences to 1x in the early miocene in each of the sites the y 13 c is strongly positively correlated with the percentage of aragonite as a consequence the y 13 c of sequences a through f is strongly correlated reflecting the decreasing amount of aragonite with increasing depth in the two platform sites the y 13 c is significantly lower in the younger portions of the cores as a result of the influences of meteoric diagenesis during repeated exposure during the pleistocene although the y 13 c of the individual sequences can be correlated in most instances between the odp holes the changes are not related to global changes in the y 13 c of the oceans which in contrast to the y 13 c of the platform sediments become isotopically lower towards the present day instead variations in the y 13 c appear to be related to varying mixtures of y 13 c rich banktop sediments and pelagic material

origin of small pits in martian impact craters we propose a numerical model for the formation of the closely spaced pits found in the thin ejecta related deposits superposed on the floors interior terrace blocks and near rim ejecta blankets of well preserved martian impact craters our model predicts the explosive degassing of water from this pitted material which is assumed to originally be water bearing impact melt rich breccia at the time of deposition this process is analogous to what occurred in the fall out suevite deposits at the ries impact structure in germany at ries impact heating of water bearing target material resulted in the rapid degassing of its water and other volatiles the martian environment plays an important role in enhancing the effects of this degassing by increasing the flow speed of the escaping gas the high flow rate of gas through particulate materials such as suevite tends to quickly form segregation channels or vent pipes similar to those found in the ries deposits these pipes act as conduits for the efficient high speed escape of the gas and small clasts that it entrains escaping gas and entrained clasts abraded and eroded the conduit walls flaring them to form pits above a network of pipes

carbonate minerals major and minor elements and oxygen and carbon isotopes and their variation with water depth in cool temperate carbonates western tasmania australia cool temperature bryomol carbonates predominate on shallow shelves around western tasmania many samples are bored and encrusted due to the occurrence of submarine hardgrounds and to slow rates of sedimentation intragranular caco3 cementation is common tasmanian whole carbonates are mainly mixtures of high mg calcite hmc and low mg calcite lmc with minor amounts of aragonite hmc and aragonite contents decrease while lmc content increases with increasing water due to a decrease in water temperature mg concentrations in calcite correspond to temperatures of 10 c sr and na concentrations in bryozoa decrease due to calcite cementation whereas their concentrations increase with aragonite content mn and fe concentrations are higher than in warm shallow marine counterparts and increase with increasing aragonite percentage sr and na concentrations in calcite slightly increase with increasing lmc percentage due to decreasing water temperatures mn and fe values in calcite are independent of water temperature hmc percentage and hmc lmc ratios decrease while lmc percentage increases with increasingly heavier 18o values due to decreasing temperatures lmc is a marine mineral and not a product of meteoric diagenesis unusually high concentrations of sr na mn and fe in aragonite are due either to the tendency of aragonite formed in cold seas to incorporate more of these elements or to aragonite formation by transformation of metastable cold water caco3 minerals such as vaterite or hydrous calcite sr contents decrease with increasing water depth due to a decrease in aragonite and increase in low mg calcite na values increase with increasing water depth due to increasing salinity mn and fe concentrations decrease with increasing water depth due to decreasing continental terrigenous input depth related variations in mg sr na mn and fe are due to marine diagenesis and are unrelated to meteoric diagenesis 18o and 13c values are positively correlated and this isotopic field is bisected by the diagenesis trend line for upwelling water that passes through the point 1 18o 0 13c the 18o values become heavier and mg values decrease with increasing water depth due to decreasing temperatures from about 17 to 6 c for normal seawater and from 13 to 2 c for upwelling water these temperatures are lower than measured summer values because of the strong seasonal effect of surface waters influx of subantarctic water in winter and mixing of cold upwelling waters in the bottom water as carbonates in upwelling regions are in equilibrium with upwelling water having 18o values of 1 in paleotemperature determinations seawater values that are lower by 1 than those postulated for different geological periods should be considered for those carbonates suspected of being non tropical in origin on the basis of geological and geochemical evidence originally calcitic limestonesare abundant in ancient sequences and their temperatures of formation and diagenesis can be better understood by using the data base provided by this study

an assessment of evidence for pingos on mars using hirise pingos are small hills with cores of ice formed by injection and freezing of pressurized water the possibility of pingos on mars is of particular interest because of the associated implications for liquid water we have systematically searched for candidate pingos using images from the high resolution imaging science experiment hirise camera since pingos are expected to develop surface fractures due to extension of the frozen ground over the ice core we have searched for fractured features and identified a variety of mounds these features are confined to the martian mid latitudes in the bands where gullies are also most common the observed fractured mounds have a variety of morphologies and are likely of multiple origins isolated fractured mounds found on the floors of gullied craters in the southern hemisphere match the general morphologic characteristics of terrestrial pingos and are the best candidates for martian pingos but there is currently no direct evidence for presence of ice cores and it is difficult to produce the necessary water volumes so these features should still be interpreted with caution other fractured mounds appear more likely to be erosional remnants of an unusual mantling layer or possibly thermokarst structures flat topped mounds in utopia have some characteristics fracture pattern and latitudinal distribution consistent with pingos but differ in other aspects such as shape and setting while we do not rule out a pingo origin we prefer an erosional model for these enigmatic features

brine volcanism and the interior structures of asteroids and icy satellites abstract cryovolcanism is among the foremost processes responsible for modifying the surfaces of icy satellites volcanic brine petrogenesis in ammonia deficient satellites should mainly involve eutectic melting in relevant salt water systems carbonaceous chondrites provide useful insights into the compositions of salts and aqueously altered rock in icy satellites and asteroids c1 chondrites contain about one fifth by mass of salts in various states of hydration many aspects of the petrogenesis and physical volcanology of icy satellite brines should be well described in the system h2o mgso4 na2so4 minor components include sulfates of k ni mn and ca chondrites also contain abundant carbonates but these are probably not very important in brine magmatism due to their low solubilities under expected conditions chlorides are also unimportant under most circumstances because of the low cosmic abundance ratio of cl s soluble salts may have profound effects on the geology and structure of icy satellites and asteroids in some models late episodes of water volcanism are facilitated by high buoyant forces due to the relatively high densities of sulfate rich mantle and crustal layers in other models early hypersaline brine volcanism quickly yields to plutonic magmatism due to low crustal densities europa probably has a layered crust composed of anhydrous mg na sulfates near the base and a frozen or partially molten eutectic mixture of ice and hydrated mg and na sulfates near the surface ganymede may have a crust about 300 km thick composed of a 10 1 ratio of ice mirabilite and a mantle 500 km thick composed of 50 ice phases plus 50 hydrated mg and na sulfates

dating cave drip water by tritium summary speleothems are increasingly used as an archive of past climate but some of the proxy signals encoded in these deposits reflect hydrological characteristics of the karst aquifer and not necessarily climate variability a central aspect in karst hydrology is the time required for the rainwater to reach the point of discharge in a cave e g the tip of the stalactite one promising approach in determining this residence time is drip water dating by tritium 3 h in contrast to traditional tritium dating we do not refer directly to tritium concentrations in precipitation as input function but to an infiltration weighted annual mean of the rainwater values using concentration differences between this infiltration weighted mean and the drip water an age is calculated from the radioactive decay law assuming piston flow the approach was tested in three adjacent caves in northwestern germany which were monitored for about two years all of the studied drip sites yielded drip water ages between 2 and 4 years with uncertainties on the order of 1 year these results were confirmed at several drip sites by oxygen isotope data which show rather constant values with insignificant intra annual variability attempts to apply the 3 h 3 he method resulted in comparable ages despite several complicating factors

does europa have a subsurface ocean evaluation of the geological evidence it has been proposed that jupiter s satellite europa currently possesses a global subsurface ocean of liquid water galileo gravity data verify that the satellite is differentiated into an outer h2o layer about 100 km thick but cannot determine the current physical state of this layer liquid or solid here we summarize the geological evidence regarding an extant subsurface ocean concentrating on galileo imaging data we describe and assess nine pertinent lines of geological evidence impact morphologies lenticulae cryovolcanic features pull apart bands chaos ridges surface frosts topography and global tectonics an internal ocean would be a simple and comprehensive explanation for a broad range of observations however we cannot rule out the possibility that all of the surface morphologies could be due to processes in warm soft ice with only localized or partial melting two different models of impact flux imply very different surface ages for europa the model favored here indicates an average age of 50 myr searches for evidence of current geological activity on europa such as plumes or surface changes have yielded negative results to date the current existence of a global subsurface ocean while attractive in explaining the observations remains inconclusive future geophysical measurements are essential to determine conclusively whether or not there is a liquid water ocean within europa today

late jurassic climate and its impact on carbon cycling abstract the climate of the late jurassic has been characterized by high atmospheric co2 levels and by a monsoonal rainfall pattern in this study we traced the evolution of the global carbon cycle through the late jurassic with the help of carbonate carbon isotope stratigraphy the oxfordian tithonian 13c curve is marked by one major positive carbon isotope excursion with an amplitude 13 c 1 0 middle to late oxfordian and a second minor positive excursion with an amplitude 13 c late kimmeridgian the early kimmeridgian and early tithonian 13c values fluctuate around 13 c 2 0 3 and contrast with the less positive 13c values of early oxfordian and late tithonian age 13 c 1 0 5 a comparison of the late jurassic carbonate carbon isotope curve with the occurrence of organic rich sediments suggests that not only fluctuations in organic carbon burial but also in carbonate carbon burial had an impact on the c isotope record the oxfordian c isotope excursion appears to correspond to a time of overall increased organic carbon burial triggered by increased nutrient transfer from continents to oceans during a time of rising global sea level however episodes of enhanced organic carbon burial during the kimmeridgian and early tithonian are not reflected by prominent spikes in the c isotope record favourable conditions for carbonate platform growth at a time of high global sealevel may have resulted in the stabilisation of the c org c carb burial ratio and hence maintained the 13c record at steady but relatively positive values the middle and late tithonian c isotope values drop below 13 c 1 5 a similar shift to less positive c isotope values was recognized in other c isotope records from the tethys and atlantic oceans and reflects a decrease in the c org c carb burial ratio possibly related to a reorganisation of the global climate system globally widespread marine black shale mature quartzose sandstone assemblages suggest that the relative efficiency of the late jurassic carbon pumps was controlled by weathering erosion and runoff causing widespread marine eutrophication eutrophication favoured the organic carbon pump but it diminished the carbonate platform growth potential the monsoonal rainfall distribution pattern may explain why late jurassic carbonate platforms experienced less severe growth crises than early cretaceous carbonate platforms

reconstruction of jurassic bathonian palaeosalinity using stable isotopes and faunal associations abstract the bathonian is an interval from which salinity controlled benthic faunas are particularly well known this study examines late bathonian faunas from dorset uk from the wattonensis beds fuller9s earth of known marine origin the overlying elongata beds and the boueti bed marking the base of the forest marble 18 o values of belemnites belemnopsis from the wattonensis beds range from 1 4 to 0 7 and carbon isotope values range from 2 3 to 0 5 vpdb isotope values of well preserved rhynchonella from the wattonensis beds range from 2 4 to 1 3 for oxygen and 1 1 to 0 6 vpdb for carbon the 18 o data suggest high palaeotemperatures possibly up to 28 c a similar spread of data is derived from brachiopods goniorhynchia boueti from the boueti bed given the marine origin of the wattonensis beds and overlap of data the reduced faunal diversity of the boueti bed is considered unlikely to be the result of reduced salinity brachiopods therefore should not be regarded more sceptically as evidence for fully marine conditions as has been suggested the oysters praeexogyra hebridica elongata and brachiopods rhynchonella from the elongata beds have isotope values that also imply fully marine conditions and are interpreted as being indicative of slightly cooler conditions

new and recent gully activity on mars as seen by hirise 1 fresh appearing gully deposits are found at tens of sites in the southern hemisphere of mars these deposits have latitudinal and azimuthal dependences similar to the overall preferences of southern hemisphere gullies suggesting that most gullies can undergo such events definite changes are seen at ten sites including two previously reported these include visible modification of gully channels and aprons those formation intervals constrained to better than one mars year tend to include winter and exclude summer suggesting seasonal activity this seasonal activity is consistent with proposed models for gully formation driven by co2 frost although at least some of the new deposits are probably due to dry granular flow with no volatile involvement as these deposits are capable of effecting distinct topographic changes to gully aprons and channels they represent a significant component of recent gully evolution

evidence for recent climate change on mars from the identification of youthful near surface ground ice ground ice in the crust and soil may be one of the largest reservoirs of water on mars1 2 3 near surface ground ice is predicted to be stable at latitudes higher than 40 ref 4 where a number of geomorphologic features indicative of viscous creep and hence ground ice have been observed5 mid latitude soils have also been implicated as a water ice reservoir6 the capacity of which is predicted to vary on a 100 000 year timescale owing to orbitally driven variations in climate7 it is uncertain however whether near surface ground ice currently exists at these latitudes and how it is changing with time here we report observational evidence for a mid latitude reservoir of near surface water ice occupying the pore space of soils the thickness of the ice occupied soil reservoir 1 10 m and its distribution in the 30 to 60 latitude bands indicate a reservoir of 1 5 6 0 104 km3 equivalent to a global layer of water 10 40 cm thick we infer that the reservoir was created during the last phase of high orbital obliquity less than 100 000 years ago and is now being diminished

climatic and environmental controls on speleothem oxygen isotope values variations in speleothem oxygen isotope values d 18 o result from a complicated interplay of environmental controls and processes in the ocean atmosphere soil zone epikarst and cave system as such the controls on speleothem d 18 o values are extremely complex an understanding of the processes that control equilibrium and kinetic fractionation of oxygen isotopes in water and carbonate species is essential for the proper interpretation of speleothem d 18 o as paleoclimate and paleoenvironmental proxies and is best complemented by study of site specific cave processes such as infiltration flow routing drip seasonality and saturation state and cave microclimate among others this review is a process based summary of the multiple controls on d 18 o in the atmosphere soil epikarst and speleothem calcite illustrated with case studies primary controls of d 18 o in the atmosphere include temperature and relative humidity through their role in the multiple isotope effects variability and modifications of water d 18 o values in the soil and epikarst zones are dominated by evaporation mixing and infiltration of source waters the isotopically effective recharge into a cave system consists of those waters that participate in precipitation of caco3 resulting in calcite deposition rates which may be biased to time periods with optimal dripwater saturation state recent modeling experimental and observational data yield insight into the significance of kinetic fractionation between dissolved carbonate phases and solid caco3 and have implications for the hendy test to assist interpretation of speleothem d 18 o time series quantitative and semi quantitative d 18 o climate calibrations are discussed with an emphasis on some of the difficulties inherent in using modern spatial and temporal isotope gradients to interpret speleothems as paleoclimate proxy records finally several case studies of globally significant speleothem paleoclimate records are discussed that show the utility of d 18 o to reconstruct past climate

geochemical evidence for sediment provenance in mudstones and fossil poor wackestones upper jurassic majorca island terra nova 24 437 445 2012 abstract the notion that diagenetic imprint on ancient carbonates significantly compromises palaeoenvironmental interpretations is revealed as an oversimplification the enigmatic case at the core of this research is an extended homogeneous macrofossil poor deposit showing distinctive dark brown colour and very fine grain size aumedra fm majorca island this markedly contrasts with standard ammonitico rosso ar facies known from jurassic epioceanic swells geochemical analysis of matrix micrite carbonate cements and belemnite rostra are used to interpret the aumedra carbonates stable carbon and oxygen isotopes and elemental abundance are compared with data from under and overlying deposits and coeval sections conspicuously higher than expected c and o isotope signature together with strontium enrichment and a typically low iron and manganese concentrations favour a distant shallower probably aragonitic sedimentary supply modern and ancient examples of carbonate deposition are integrated with possible hydrodynamic conditions justifying transport over the studied area a potential ne source is envisaged terra nova 00 1 9 2012

new insights into geochemical behaviour in ancient marine carbonates upper jurassic ammonitico rosso novel proxies for interpreting sea level dynamics and palaeoceanography elemental concentrations in phanerozoic sea water are known to fluctuate both in time and space with regard to carbonates precipitated from marine fluids elemental concentrations in the carbonate crystal lattice are affected by a complex array of equilibrium and non equilibrium as well as post depositional alteration processes to assess the potential of carbonate elemental chemostratigraphy seven upper jurassic sections were investigated along a proximal to distal transect across the south east iberian palaeomargin the aim was to explore stratigraphic and spatial variations in calcium strontium magnesium iron and manganese elemental abundances the epicontinental geochemical record is influenced by the combination of continental runoff and a significant diagenetic overprint in contrast the epioceanic geochemical record agrees with reconstructed open marine sea water values reflecting a moderate degree of syn depositional to early marine pore water diagenesis establishing a fair degree of preservation of matrix micrite a thorough statistical approach was applied and elemental associations tested for their environmental significance principal component and hierarchical cluster analyses revealed a persistent relation between carbonate magnesium iron and strontium abundances processes related to early diagenetic nodulation in ammonitico rosso facies most probably account for the incorporation of these elements in the calcium carbonate lattice the clear decoupling of carbonate manganese abundance with respect to the remaining elements is documented and related to high sea floor spreading rates and hydrothermal activity during the late jurassic the investigation of potential time fluctuation of geochemical patterns was approached through variogram computation the observed temporal behaviour is most likely to be forced by relative sea level dynamics reflecting late jurassic palaeoceanographic conditions and potential planetary interactions the data obtained in this study highlight the utility of elemental data from carbonate matrix micrites as geochemical proxies for studying the influence of remote trigger factors

platform carbonates of the upper jurassic mozduran formation in the kopet dagh basin ne iran facies palaeoenvironments and sequences abstract the mozduran formation a thick carbonate succession over 1200 m of the upper jurassic callovian kimmeridgian in northeast iran has been studied to determine its palaeoenvironments and sequences detailed petrographic investigations have led to the recognition of several microfacies and microfacies groups which constitute four palaeoenvironmental associations tidal flat beach lagoonal platform margin and open marine most of the mozduran formation sediments were deposited on a rimmed carbonate platform adjacent to a deeper marine environment the mozduran carbonate succession consists of five thick shallowing upward sequences 3rd order cycles no major hiatus has been recognized between these cycles therefore the contacts are considered subtidal conformities drowning unconformities these 3rd order cycles can be correlated with those recognized in upper jurassic strata in other parts of the world thus they are considered largely eustatic mainly tectono eustatic in origin numerous small scale shallowing upward cycles parasequences are contained within the major shallowing upward cycles both subtidal and peritidal parasequences showing an abrupt deepening of microfacies have been recognized a combination of episodic subsidence and autocyclic processes could have been responsible for the formation of these small scale cycles rapid carbonate accumulation reflected in rare first generation marine cements including meteoric cements resulted in grain to grain pressure solution and sutured contacts during burial with late cements filling the remaining pores many of the platform margin grainstones packstones have been replaced by coarsely crystalline dolomite possibly through seawater pumping and kohout convection during the transgressive and highstand phases of sea level

cosmogenic chlorine 36 from calcium spallation calcium is a major target element for cosmogenic 36cl production consequently 36cl rapidly reaches detectable levels in minerals such as calcite and calcium feldspar exposed at the earth s surface spallation of calcium isotopes typically accounts for 80 90 of 36cl production in these minerals with subsidiary contributions from negative muon capture by 40ca and thermal neutron capture by 35cl to provide a basis for surface exposure dating we have calibrated cosmogenic 36cl production in calcium feldspar from the 17 300 year old tabernacle hill basalt at an altitude of 1445 m and an effective geomagnetic latitude of 40 9 the calcium spallation rate is 152 11 atoms g ca 1 a 1 the corresponding rate at sea level and high latitude is estimated at 48 8 3 4 atoms g ca 1 a 1 the muon capture rate used to derive these values is 8 8 2 2 atoms g ca 1 a 1 at the tabernacle hill site scaled from a value of 4 8 1 2 atoms g ca 1 a 1 at sea level and high latitude the calcium spallation rate determined in this study is in excellent agreement with previous whole rock calibration measurements at tabernacle hill when these are recalculated with respect to the absolute timescale the calibration of 36c1 production from calcium underpins development of an exposure dating technique for calcite due to its high calcium content the 36cl production rate in calcite is higher than in any other common rock forming mineral measurement of 36cl in calcite with an accelerator mass spectrometric detection limit of 5 103 atoms per gram allows dating of limestone surfaces exposed for periods ranging from 102 106 years alternatively erosion rates from less than 1 to greater than 1000 m per year can be determined in the case of eroding karst surfaces though the 36cl production rate is lower in calcium feldspar than in calcite measurements on this mineral will provide a useful means of dating young basalt lavas