kinematics of the north american caribbean cocos plates in central america from new gps measurements across the polochic motagua fault system 1 the polochic motagua strike slip fault system in guatemala marks the on land plate boundary between the north american na and the caribbean ca plates gps observations in 1999 and 2003 show that the far field velocity across the system na ca relative velocity is 20 mm yr this is significantly higher than the nuvel 1a velocity but is consistent with the gps based ca na velocity proposed by demets et al 2000 the observations are modeled by a fault centered on the motagua fault locked at a depth of 20 km with a slip rate decreasing from eastern to central guatemala from 20 to 12 mm yr towards the na ca cocos triple junction this decrease is accommodated by 8 mm yr of e w extension in the westernmost part of ca south of the motagua fault about 10 mm yr of dextral slip is observed across the mid american volcanic arc the na ca cocos triple junction is thus a complex 400 km wide wedge shaped area

early diagenesis and recrystallization of bone abstract one of the most challenging problems in paleobiology is determining how bone transforms from a living tissue into a fossil the geologic record is replete with vertebrate fossils preserved from a range of depositional environments including wetland systems however thermodynamic models suggest that bone modeled as hydroxylapatite is generally unstable in a range of varying geochemical conditions and should readily dissolve if it does not alter to a more thermodynamically stable phase such as a fluorine enriched apatite here we assess diagenesis of alligator bone from fleshed articulated skeletons buried in wetland soils and from de fleshed bones in experimental mesocosms with and without microbial colonization when microbial colonization of bone was inhibited bioapatite recrystallization to a more stable apatite phase occurred after one month of burial ca fe phosphate phases in bone developed after several months to years due to ion substitutions from the protonation of the hydroxyl ion these rapid changes demonstrate a continuum of structural and bonding transformations to bone that have not been observed previously when bones were directly in contact with sediment and microbial cells rapid bioerosion and compositional alteration occurred after one week but slowed after one month because biofilms reduced exposed surfaces and subsequent bioapatite lattice substitutions microbial contributions are likely essential in forming stable apatite phases during early diagenesis and for enabling bone preservation and fossilization

active seismic deformation in the grabens of northern central america and its relationship to the relative motion of the north america caribbean plate boundary abstract the active seismic deformation along the grabens of northern central america is calculated using a method which relates relative plate velocity with the seismic strain rate tensor the latter is in turn obtained from seismic moment tensors we calculate the typical or average moment tensor from available centroid moment tensors and fault plane solutions this average tensor is then used to obtain the sum of moment tensors of historical and modern earthquakes reported in the literature both historical and modern earthquakes yield an average extension rate of 8 mm yr along the grabens of northern central america while the relative motion between the north america and caribbean plates expressed along the motagua polochic fault system is 20 mm yr this result suggests that part of the seismic deformation related to the plate boundary is taken up as extension along the grabens which play the role of fault termination structures for the motagua polochic system

active faulting and paleoseismology along the bree fault lower rhine graben belgium paleoseismic analysis of the 10 km long bree fault scarp in the lower rhine graben yields numerous lines of evidence of earthquake activity in the holocene and late pleistocene this active normal fault a part of the feldbiss fault system dips 70 ne and is expressed at the surface by a prominent nw se trending 7 to 20 m high scarp formed since the deposition of the maas river main terrace 700 kyr b p trenches and geophysical prospecting show that the fault which is known to have 100 m of vertical offset since the late pliocene breaks late pleistocene and holocene deposits ground penetrating radar seismic refraction and electric tomography suggest that at shallow depth the amount of displacement is larger than the youngest vertical offset visible in the trenches and corresponds to cumulative fault displacements the analysis of 36 leveling profiles across the scarp indicates that its height can be classified into three groups likely corresponding to different events a morphologic dating gives approximate ages of 2 1 5 kyr b p 14 5 kyr b p and 41 6 kyr b p for the past three surface faulting earthquakes analysis of faulted stratigraphy and earthquake induced deformation structures exposed in trenches suggests the occurrence of three large earthquakes during the past 45 l03 years and yields 0 07 mm yr of relative vertical deformation rate the most recent seismic event occurred between a d 610 and 890 the first identification of an active fault with surface ruptures in the lower rhine graben area emphasizes that large earthquake sources exist within intraplate europe and that at least some of these events are preserved in the geologic record

a multi proxy geochemical investigation of the early paleocene danian continental palaeoclimate at the fontllonga 3 site south central pyrenees spain chronologically well constrained non marine deposits across the cretaceous tertiary boundary ktb are exceptionally rare the fontllonga section tremp formation south central pyrenees lleida spain constitutes one of these rare global records stable isotope 18oco3 and 13c analyses have been performed on the carbonate fraction of 29 samples from diverse skeletal micro remains charophyte gyrogonites gastropod shells ostracod valves and isolated skeletal remains of lepisosteids and pycnodonts from the earliest danian site fontllonga 3 a mean ba ca water palaeotemperature of 28 0 6 7 c has been obtained from the ganoine of 25 lepisosteid scales this mean palaeotemperature is comparable with the temperature tolerance range for extant relatives of fossil osteoglossiform fish found at fontllonga 3 which require a temperature range of 24 35 c mean annual temperature 27 30 c to survive using the temperature range provided by the ba ca palaeothermometer 21 3 34 7 c it is possible to determine 18owater values from the isotopic content of charophyte gyrogonites gastropod shells ostracod valves and fish remains mean 18oco3 5 00 0 21 18owater values of between 4 01 and 0 95 vsmow are calculated which when combined with la yb n versus la sm n plots are in good agreement with the sedimentary interpretation of the site as an estuarine environment based upon a comparison with modern day meteorical conditions these isotopic values are relatively high for subtropical freshwaters suggesting a low precipitation rate amount effect high evaporation rate and or long residence time when combined with other isotopic palaeobotanical and mineralogical studies carried out in the pyrenean and tethys realms this first geochemical study of an early paleocene site is consistent with there being a subtropical seasonally dry climate in the south central pyrenees at this time

a new carnosaur dinosauria theropoda from the jurassic of xinjiang people s republic of china in 1987 a sino canadian expedition known as the dinosaur project china canada alberta ex terra discovered a large theropod skeleton in the upper jurassic shishugou formation of the junggar

tracking mammoths and mastodons reconstruction of migratory behavior using strontium isotope ratios variations in the strontium isotope ratio 87 sr 86 sr of tooth enamel are used to examine the migration patterns of late pleistocene mammoths and mastodons from florida an animal s 87 sr 86 sr ratio tracks the ratios of its environment which vary with differences in bedrock and soil consequently the environmentally controlled differences in 87 sr 86 sr ratio recorded in mineralized tissue such as tooth enamel may be used to reconstruct the movement patterns of an individual we map variations in local 87 sr 86 sr ratios across modern florida and georgia through analysis of rodent teeth plants and surface water then use this map to interpret the movement patterns of extinct mammals mastodons from northern and central florida have higher 87 sr 86 sr ratios than both modern environmental samples from florida and fossils from nonmigratory species suggesting that mastodons migrated north into georgia mammoths display ratios similar to those of environmental samples and resident species suggesting that they did not migrate outside florida

diet preferences and climate inferred from oxygen and carbon isotopes of tooth enamel of tarbosaurus bataar nemegt formation upper cretaceous mongolia abstract stable isotopes of oxygen and carbon of tooth enamel are increasingly being used as tracers to study palaeoecology and the diet preferences of fossil vertebrates we serially sampled tooth enamel carbonate along the growth axes of five early maastrichtian carnivorous dinosaur teeth tarbosaurus bataar tyrannosaurid from the nemegt formation mongolia in order to identify seasonal climatic variations and determine the diet of this apex predator additional bulk samples of dentine bone and surrounding sediment were analyzed in order to exclude diagenetic obfuscation of the isotopic record enamel samples of potential prey species for dietary studies were also analyzed in the case of the largest specimens the sampled teeth usually recorded annual cycles ranging between two thirds and a full year fluctuations in 18o values in tyrannosaurid teeth suggest seasonality high annual temperatures with distinct precipitation humidity maxima during summer months with mean annual temperatures mat ten degrees higher than those of present day mongolia the seasonal pattern of 18o shows similarities to that of the modern day shijiazhuang global network of isotopes in precipitation station northern china and suggests that the nemegt biota flourished when exposed to a cool temperate monsoon influenced climate herbivore and carnivore carbon isotopes 13c values from tooth enamel imply the presence of a woodland ecosystem dominated by coniferous trees such as araucariaceae and are consistent with the hypothesis that large sauropods and hadrosaurids were the preferred prey of tarbosaurus mean annual precipitation map based on the relationship between modern day c3 gymnosperms and local average map is estimated at 775 835 mm yr these results show that large theropod teeth can serve as valuable archives for palaeoenvironmental studies

chemistry microstructure petrology and diagenetic model of jurassic dinosaur bones dinosaur national monument utah abstract the fossil bone mineral in dinosaurs from the morrison formation is well crystallized stoichiometric francolite the closely packed subparallel francolite crystals have equidimensional cross sections mostly 10 40 nm wide in contrast crystallites in unaltered mammal bone tissue are poorly crystallized nonstoichiometric carbonate hydroxyapatite a few nanometers thick and plate rod or needle shaped the diagenetic francolite crystals are elongated in the c axis direction as are bone tissue crystallites along permeable cracks francolite crystals grew to 250 nm wide compared to unaltered crystallites in mammal bones the francolite has higher concentrations of ba ce cr f la mn ni pb rb sr th u v and y and perhaps zr na and mg are lower in concentration diagene ic francolite grew from groundwater enriched in ions from silicic ashes in the brushy basin member and from dissolution of bone tissue crystallites after burial francolite grew on crystallite seeds filling the space formerly occupied by collagen perhaps half the tissue volume and dissolved crystallites the micron scale structures such as haversian canals and laminae are preserved because the diagenetic francolite retains the orientations of the seeds the laminae 1 10 m thick commonly preserve an orthogonal plywood structure the diagenetic growth of francolite during this type of bone fossilization implies that oxygen isotopic ratios measured in dinosaur bones even those that appear fresh and unaltered may dominantly reflect groundwater temperature rather than dinosaur body temperature trace element concentrations in the francolite may reflect groundwater composition rather than dinosaur diet pore filling cements precipitated in the sands and bones at shallow burial depths as evidenced by the 35 52 minus cement porosities of the sandstones and numerous uncompacted oversize pores filled by cements gypsum and calcite were precipitated from shallow alkaline groundwater as the groundwater became increasingly dominated by ions from silicic ash argentite chalcopyrite native gold native silver tiemannite and uraninite replaced areas of bone a few microns to tens of microns in size along cracks a thin chlorite crust commonly mantled francolite crystals along bone cracks and lined openings in bones and sandstones pervasive precipitation of a chalcedony crust followed with pseudomorphs of chalcedony after gypsum in larger cancellous openings the remaining space was fi led by the various forms of silica the bones are brown due to goethite filled cracks that cut pore filling minerals

effects of diagenesis on strontium carbon nitrogen and oxygen concentration and isotopic composition of bone abstract paleodietary analysis based on variations in the trace element and stable isotopic composition of inorganic and organic phases in fossil bone depends on the assumption that measured values reflect in vivo values to test for postmortem alteration we measured 87 sr 86 sr 13 c 12 c 18 o 16 o and 15 n 14 n ratios and sr concentrations in modern and prehistoric 610 to 5470 yr old bones of animals with marine or terrestrial diets from greenland bones from modern terrestrial feeders have substantially lower sr concentrations and more radiogenic 87 sr 86 sr ratios than those from modern marine feeders this contrast was not preserved in the prehistoric samples which showed almost complete overlap for both sr concentration and isotopic composition in bones from the two types of animals leaching experiments x ray diffraction analysis and infrared spectroscopy indicate that alteration of the sr concentration and isotopic composition in prehistoric bone probably results from nearly complete exchange with groundwater oxygen isotope ratios in fossil apatite carbonate also failed to preserve the original discrimination between modern terrestrial and marine feeders the c isotope ratio of apatite carbonate did not discriminate between animals with marine or terrestrial diets in the modern samples even so the ranges of apatite 13 c values in prehistoric bone are more scattered than in modern samples for both groups suggesting alteration had occurred 13 c and 15 n values of collagen in modern bone are distinctly different for the two feeding types and this distinction is preserved in most of the prehistoric samples our results suggest that postmortem alteration of dietary tracers in the inorganic phases of bone may be a problem at all archaeological sites and must be evaluated in each case while collagen analyzed in this study was resistant to alteration evaluation of the possibility of diagenetic alteration of its isotopic composition in bones from other contexts is also warranted

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

paleoclimatic inference from stable isotope profiles of accretionary biogenic hardparts a quantitative approach to the evaluation of incomplete data abstract variation in 18o of invertebrate and vertebrate skeletons has been widely employed to estimate annual means and seasonal ranges of temperature from many geologic settings among incertitudes encountered in employing this approach is the influence of unconstrained noise in environmental signals cessation of hardpart accretion during reproduction and or seasonal temperature extremes biasing of calculated mean temperatures toward seasons of maximum growth rate and dependence on the most extreme 18o values observed for estimating annual temperature range to better constrain paleoclimatic interpretations we describe several applications of a computational approach that address many of these uncertainties it is predicated on the presumption that annual variation in isotope composition across an accretionary skeleton represents sinusoidal variation in temperature and or the composition of ambient fluids the analysis resolves a best fit sinusoid for any portion of the data output consists of determinations of mean annual 18o seasonal range in 18o and sine period which reflects hardpart growth rate the procedure can be employed over some window of values within any data series and can be reiterated to arrive at solutions for all possible windows the technique allows for quantitative interpretation of mean values and annual amplitudes of 18o variation for every window regardless of whether or not that window actually spans a seasonal isotope extreme moreover it affords equal interpretational weight for every analysis in the data set in that mean annual and seasonal variation values estimated for each window are derived from every analysis in the data set it is therefore not necessary to estimate mean annual 18o as simply the arithmetic mean of all analyses and estimates of seasonality can be derived from data within any window rather than depending only on those several analyses that fall at compositional extremes in order to demonstrate the utility this methodology to the interpretation of paleoclimatological data we have applied it to published temperature data from several modern climatological data sets and to published 18o data from a paleogene gulf coast fish otolith a modern arabian sea coral a miocene texan equine tooth and an eocene bivalve from england each yields robust estimates of mean annual temperatures or isotopic compositions and of seasonal ranges in these values in addition unique features of data from each of these examples illustrate the power of this method to shed light on climatological and or biological phenomena that are also unique to each system

the last domicile of the iceman from hauslabjoch a geochemical approach using sr c and o isotopes and trace element signatures abstract we present sr c and o isotope ratios and quantitative ratios of trace element ratios in the rib and the femur of the tyrolean iceman otzi the results from the rib and the femur are compared with those obtained from pre industrial historic human skull bone fragments collected in the late 19th century from charnel houses located on different geological backgrounds throughout north and south tyrol comparison of strontium isotope data from the bone fragments locates the iceman s domicile during the last 5 to 10 years of his life to the crystalline part of the central alps statistical analysis of the trace element ratios together with oxygen isotope results suggests that the iceman probably spent most of his last years in southern elevated part of the otztal however the results from iceman only represent those from a single individual and are not a representative average of a group it cannot therefore be established with absolute certainty that the original trace element signatures were conserved especially during the first stage of mummification our conclusions should therefore be regarded as tentative but nevertheless the best possible indication his domicile and a stimulus for further research

late mesozoic to paleogene stratigraphy of the salar de atacama basin antofagasta northern chile implications for the tectonic evolution of the central andes abstract the salar de atacama basin the largest pre andean basin in northern chile was formed in the early late cretaceous as a consequence of the tectonic closure and inversion of the jurassic early cretaceous tarapaca back arc basin inversion led to uplift of the cordillera de domeyko cd a thick skinned basement range bounded by a system of reverse faults and blind thrusts with alternating vergence along strike the almost 6000 m thick upper cretaceous to lower paleocene sequences purilactis group infilling the salar de atacama basin reflects rapid local subsidence to the east of the cd its oldest outcropping unit tonel formation comprises more than 1000 m of continental red sandstones and evaporites which began to accumulate as syntectonic growth strata during the initial stages of cd uplift tonel strata are capped by almost 3000 m of sandstones and conglomerates of western provenance representing the sedimentary response to renewed pulses of tectonic shortening which were deposited in alluvial fan fluvial and eolian settings together with minor lacustrine mudstone purilactis formation these are covered by 500 m of coarse proximal alluvial fan conglomerates barros arana formation the top of the purilactis group consists of maastrichtian danian alkaline lava and minor welded tuffs and red beds cerro totola formation 70 64 ma k ar deposited during an interval of tectonic quiescence when the el molino yacoraite late cretaceous sea covered large tracts of the nearby altiplano puna domain limestones interbedded with the totola volcanics indicate that this marine incursion advanced westwards to reach the eastern cd slope cd shortening in the late cretaceous was accompanied by volcanism and continental sedimentation in fault bounded basins associated to strike slip along the north chilean magmatic arc to the west of the cd domain indicating that oblique plate convergence prevailed during the late cretaceous oblique convergence seems to have been resolved into a highly partitioned strain system where margin parallel displacements along the thermally weakened arc coexisted with margin orthogonal shortening associated with syntectonic sedimentation in the salar de atacama basin a regionally important early paleocene compressional event is echoed in the salar de atacama basin by a distinctive angular unconformity which separates paleocene continental sediments from purilactis group strata the basin also records the eocene early oligocene incaic transpressional episode which produced renewed uplift in the cordillera de domeyko and triggered the accumulation of a thick blanket of syntectonic gravels loma amarilla formation

annual monsoon rains recorded by jurassic dunes pangaea the largest landmass in the earth s history was nearly bisected by the equator during the late palaeozoic and early mesozoic eras modelling experiments and stratigraphic studies have suggested that the supercontinent generated a monsoonal atmospheric circulation that led to extreme seasonality1 2 3 but direct evidence for annual rainfall periodicity has been lacking4 in the mesozoic era about 190 million years ago thick deposits of wind blown sand accumulated in dunes of a vast low latitude desert at pangaea s western margin5 6 7 these deposits are now situated in the southwestern usa here we analyse slump masses in the annual depositional cycles within these deposits which have been described for some outcrops of the navajo sandstone8 twenty four slumps which were generated by heavy rainfall appear within one interval representing 36 years of dune migration we interpret the positions of 20 of these masses to indicate slumping during summer monsoon rains with the other four having been the result of winter storms the slumped lee faces of these jurassic dunes therefore represent a prehistoric record of yearly rain events

fault kinematics in northern central america and coupling along the subduction interface of the cocos plate from gps data in chiapas mexico guatemala and el salvador new gps measurements in chiapas mexico guatemala and el salvador are used to constrain the fault kinematics in the north america na caribbean ca and cocos co plates triple junction area the regional gps velocity field is first analysed in terms of strain partitioning across the major volcano tectonic structures using elastic half space modelling then inverted through a block model we show the dominant role of the motagua fault with respect to the polochic fault in the accommodation of the present day deformation associated with the na and ca relative motion the na ca motion decreases from 18 22 mm yr 1 in eastern guatemala to 14 20 mm yr 1 in central guatemala assuming a uniform locking depth of 14 28 km down to a few millimetres per year in western guatemala as a consequence the western tip of the ca plate deforms internally with 9 mm yr 1 of east west extension 5 mm yr 1 across the guatemala city graben alone up to 15 mm yr 1 of dextral motion can be accommodated across the volcanic arc in el salvador and southeastern guatemala the arc seems to mark the northern boundary of an independent forearc sliver ar pinned to the na plate the inversion of the velocity field shows that a four block na ca co and ar model that combines relative block rotations with elastic deformation at the block boundaries can account for most of the gps observations and constrain the overall kinematics of the active structures this regional modelling also evidences lateral variations of coupling at the co subduction interface with a fairly high coupling 0 6 offshore chiapas and low coupling 0 25 offshore guatemala and el salvador

neogene north american caribbean plate boundary across northern central america offset along the polochic fault abstract the polochic fault was a segment of the north american caribbean plate boundary across central america in the neogene its 130 km of left slip was previously determined by matching structures and stratigraphie outcrop patterns of northwest and central guatemala across the fault additional support for the model and the youthfulness of the recorded offset comes from an essentially perfect match of major geomorphic features across the fault a reconstruction process which eliminates 123 km of left slip brings together rivers and drainage divides that existed before the polochic became active with the reconstruction carried across the isthmus on an east west fault the regional structural geology assumes the coherent pattern of a continuous orogenic belt whose geometry is compatible with the model of collisional tectonics centered on the motagua suture zone confined within this belt narrowed to some 60 km by the reconstruction lie the major laramide thrusts folds and tectonically emplaced serpentinites of guatemala crystalline rocks of guatemala re join the chiapas massif and paleozoic sedimentary rocks exposed in the core of an almost continuous anticlinorium extend from southern chiapas to lake izabal the polochic does not bend in eastern guatemala but continues eastward to the motagua fault where it dies westward drift of the northern block resulted in rifting which extended from eastern guatemala into the caribbean along the cayman trough the honduras depression may represent an element of a triple junction along with the polochic and izabal cayman rift the polochic continues westward into the pacific ocean and offsets the middle america trench the polochic has offset the miocene volcanic belt of northern central america confirming the previous estimate of a neogene time of movement about 300 km of relative east west neogene displacement has been recorded on the mid cayman rise only 130 km of which can be accounted for across the polochic it is suggested that cumulative extension on north south faults south of the motagua fault zone between the trench and the honduras depression might make up that difference

vadose zone flow model parameterisation using cross borehole radar and resistivity imaging cross borehole geoelectrical imaging in particular electrical resistivity tomography ert and transmission radar tomography can provide high resolution images of hydrogeological structures and in some cases detailed assessment of dynamic processes in the subsurface environment through appropriate petrophysical relationships these tools offer data suitable for parameterising and constraining models of groundwater flow this is demonstrated using cross borehole radar and resistivity measurements collected during a controlled vadose zone tracer test performed at a field site in the uk sherwood sandstone both methods show clearly the vertical migration of the tracer over a 200 h monitoring period by comparing first and second spatial moments of changes in moisture content predicted from a numerical simulation of vadose zone flow with equivalent statistics from two and three dimensional ert and cross borehole radar profiles the effective hydraulic conductivity is estimated to be approximately 0 4 m d such a value is comparable to field estimates from borehole hydraulic tests carried out in the saturated zone at the field site and provides valuable information that may be utilised to parameterise pollutant transport models of the site

the retention of primary oxygen isotope compositions of fossil elephant skeletal phosphate fossil elephant remains from sediments of plio pleistocene age in the vicinity of lake turkana kenya provide insights into the ability of the phosphate oxygen system to preserve original 18o values 18op in the depositional environment individual fossil specimens exhibit systematic variations in the 18op values of their various tooth and bone components differences in 18op values between these skeletal components can be as high as 3 6 despite the fact that equivalent phases for individual modern elephants have 18op values which vary by less than 0 6 xrd traces of the different skeletal phases of modern and fossil samples also infer differential preservation of primary apatite crystallinities among the various fossil phases fossil samples of dentine cementum and bone have x ray spectra with sharper and more intense peaks compared to their modern counterparts but little change in crystallinity is observed for fossil enamel samples a model based on the premise that the enamel phase preserves primary isotope signatures and that the accompanying skeletal phases are partially re equilibrated with the fluids associated with the microbial decomposition of the elephant s carcass is consistent with the features of the 18op dataset this isotopic evidence in conjunction with the physical and chemical attributes of enamel has led us to postulate that enamel could be preserving primary isotope signatures while other skeletal components are affected to varying degrees by alteration processes in the burial environment

high resolution imaging of the high agri valley basin southern italy with electrical resistivity tomography abstract the first high resolution images of the fault controlled high agri valley basin obtained with the electrical resistivity tomography are presented the agri valley is one of the more complex components of the quaternary fault network of the apennine chain the geometry of the pre quaternary bedrock the location and dip of the master fault and the tectonic evolution of the basin are still a subject of debate therefore deep electrical resistivity tomography integrated with stratigraphic analyses has been carried out to improve knowledge of the geological setting of the basin the high resolution electrical images allow us to reconstruct the complex geometry of the basin the electrical imaging highlights the irregular shape of the basin which is bordered by shallow faults and filled with pleistocene alluvial deposits in longitudinal cross section the basin appears as a mosaic of fault bounded blocks forming three different depocenters separated by intrabasinal highs in transverse cross section the basin is an irregular graben locally asymmetric to the northeast and with secondary grabens due to antithetic faults

what is the cementation exponent a new interpretation in 2003 182 billion barrels of oil reserves worth about us 4 5 trillion were discovered worldwide johnson et al 2004 moreover between 1950 and 2002 the total volume of reserves discovered has run to more than 1500 billion barrels for oil and 7 5 trillion cubic feet for gas bentley 2002 more than half of these resources have already been produced and have driven the global economy for the last 50 years

analysis of the geochemical variability in lepisosteid scales from the fontllonga 3 site early danian tremp formation south central pyrenees spain implications for palaeoenvironmental studies rare earth element ree ba ca sr ca and 18opo4 analyses have been performed on the ganoine and isopedine of different types of isolated scales anterior middle posterior flank scales and dorsal body margin scales from juvenile lepisosteids from the fontllonga 3 site early danian tremp formation south central pyrenees spain with the aim of detecting the most suitable kind of scale to be used in palaeoclimate studies the ree flat shape patterns obtained in lepisosteid scales from fontllonga 3 are indicative of the absence of late stage diagenesis and recrystallization and have confirmed the identification of the palaeoenvironment where the fontllonga 3 lepisosteids inhabited to be that of an estuary the ba ca palaeothermometer shows that posterior flank scales record on average 4 52 c ganoine and 3 49 c isopedine higher temperatures when compared to middle flank scales which may be related to the fact that posterior flank scales grow preferentially during the warm season whilst middle flank scales which have the greatest number of layers of ganoine per unit of time and grow all year round record a greater amplitude with respect to palaeoenvironmental and palaeoclimatic variations temperature values obtained from anterior flank scales follow a pattern similar to that showed by middle flank scales whilst temperature values provided by dorsal scales resemble the pattern furnished by posterior flank scales the same relationship between scale position and temperature but to a lesser degree 1 48 c is also evident in the calculated 18opo4 temperatures the ba ca palaeothermometer was applied by considering ba ca ratios of the water for different types of environments and it has been found out that a ratio similar to that of marine waters yielded the best approximation to 18opo4 temperatures 29 82 3 76 c the mean ba ca temperature value obtained from the analysis of all the ganoine samples 26 96 5 72 c is also consistent with the temperature of the water in which extant relatives of osteoglossiform fish whose remains have been found in fontllonga 3 along with lepisosteid remains inhabit nowadays 24 40 c with mean values of 27 to 32 c the mean ba ca temperature values furnished by the isopedine are lower than that obtained on the ganoine which may be due to minor diagenetic alteration on account of these results it is recommended that a distinction should be made between different types of scales as this could provide information concerning the summer growth temperature posterior flank scales as well as the annual temperature range middle flank scales furthermore it is recommended that ganoine be used in all studies as it appears to be the most resistant tissue in lepisosteid scales to diagenetic alteration

the use of geophysical prospecting for imaging active faults in the roer graben belgium as part of a paleoseismological investigation along the bree fault scarp western border of the roer graben various geophysical methods electrical profiling electromagnetic em profiling refraction seismic tests electrical tomography ground penetrating radar gpr and high resolution reflection seismic profiles were used to locate and image an active fault zone in a depth range between a few decimeters to a few tens of meters these geophysical investigations in parallel with geomorphological and geological analyses helped in the decision to locate trench excavations exposing the fault surfaces the results could then be checked with the observations in four trenches excavated across the scarp geophysical methods pointed out anomalies at all sites of the fault position the contrast of physical properties electrical resistivity and permittivity seismic velocity observed between the two fault blocks is a result of a differences in the lithology of the juxtaposed soil layers and of a change

fossil isotope records of seasonal climate and ecology straight from the horse s mouth isotope analysis of a bulk fossil tooth gives a snapshot impression of paleoclimatic conditions a single point in time however hypsodont teeth grow over a period of a year or more so that stable carbon and oxygen isotope variations along their length are a tape recorder of short term seasonal variations from the distant past we have used a new in situ micro laser sampling method to determine submillimeter carbon and oxygen isotope variations in the enamel of individual fossil horse teeth to assess ancient annual meteoric water variations and feeding patterns the 18o values from a 6 8 ma fossil horse tooth astrohippus ansae from texas vary cyclically along the 6 cm length of the tooth with a smoothed amplitude of 4 similar to the monthly averaged amplitude measured in modern meteoric waters from the region the seasonal 18o values are 3 to 4 higher than those calculated from modern meteoric water data suggesting either a higher local meteoric water value in the miocene of texas or that the animal received a high proportion of its dietary water from plants or highly evaporated water a holocene horse tooth from the shores of glacial lake agassiz north dakota equus sp also has isotopic variations with the same 35 mm periodicity but a smoothed amplitude of only 2 this horse most likely had a buffered drinking supply the calculated 18o of the water in equilibrium with this tooth is the same as the modern measured annual average the variations within a single tooth can be as large as those generally observed in entire stratigraphic sections of fossil teeth analyzed by bulk methods the new method provides an important technique for evaluating fossil diagenesis conventional bulk analyses of teeth fragments may not be representative of the whole tooth thus explaining analytical scatter that has been previously attributed to diagenesis

evaluating the consequences of diagenesis and fossilization on bioapatite lattice structure and composition abstract changes to hydroxylapatite mineral structure composition and lattice configuration must occur during the transformation of fresh bone to fossil bioapatite mineral phases a paucity of analytical methods to characterize atomic level lattice composition and bonding arrangements in modern and fossil bone has resulted in limited knowledge of how depositional environments and thus diagenetic conditions may influence fossilization processes synchrotron based analyses can provide insight into bone fossilization specifically x ray absorption near edge structure xanes spectroscopy at the p and ca k edges to aid in the interpretation of xanes spectral data from modern bones and from late neogene and late cretaceous fossil bones we applied other established techniques used to characterize bone mineralogy and composition including x ray diffraction fourier transform infrared spectroscopy electron microprobe analysis and thermal analysis specific bone depositional origins and ages likely influenced the varying elemental chemistry preservation of organic matter and mineral content fossilized bones ranging from an almost pure fluorapatite to carbonated fluorapatite mineral phases had less preserved organic material than modern bone the atomic level p and ca lattice structures of fossilized bones differed from modern bones specifically having shifted and shortened ca o bonds due to ca 2 substitution by ionic phases such as iron or rare earth elements and carbonate substitution for phosphate the modified lattice structure regardless of bulk mineral chemistry provides thermodynamic stability in geochemically dynamic depositional environments that may dictate bioapatite preservation over geologic time

the 20 march 1992 south aegean greece earthquake ms 5 3 possible anomalous effects the earthquake m s 5 3 of 20 march 1992 and its aftershocks which occurred near the volcanic island complex of milos south aegean greece are studied on the basis of filed observations and instrumental data the mainshock caused some building damage the maximum intensity of vi mm being assigned to triovasalos milos ground cracks liquefaction in soil landslides and rockfalls were observed in milos liquefaction took place at an apparently anomalously long epicentral distance d 12 km and is associated with unusually small earthquake magnitude abnormal animal behaviour was reported no longer than twelve hours before the mainshock the b value 1 02 of the g r relation for the aftershock sequence the exponentially decreasing number of aftershocks with time and the difference 0 5 in magnitude between the mainshock and its largest aftershock imply that the origin of these earthquakes is tectonic and not associated with the volcanic field of milos

site effect evaluation in the basin of santiago de chile using ambient noise measurements summary we performed extensive ambient vibration measurements in the basin of santiago de chile chile and we look for testing the reliability of the horizontal to vertical amplitude spectra ratio method h v as a tool to provide qualitative and quantitative information of site effects in complex geological media the interpretation of the h v data was carried out conformably to the sesame project consensus criteria and outlines three major patterns 1 clear peaked h v curves related to sharp underground velocity contrast 2 h v peak of low amplitude and flat curve related to weak contrast and 3 broad h v peak indicating the presence of strong lateral variations of underground structure h v measurements however reveal a discrepancy between the computed soil resonance frequencies and the expected building resonance therefore not leading to a straight interpretation of the intensity distribution derived from observed damage to one storey houses in santiago after the 1985 valparaiso earthquake indeed the h v technique mostly maps the first fundamental frequency however it fails to show higher resonance modes in the case of the city of santiago this method works well for assessing the seismic hazard for high rise buildings but is questionable for smaller structures as is the case of a great percentage of constructions in the city

fluvial sedimentology of an upper jurassic petrified forest assemblage shishu formation junggar basin xinjiang china abstract a remarkable petrified forest assemblage is preserved in the upper jurassic shishu formation of the northeastern junggar basin xinjiang uygur autonomous region china discovered in 1965 the silicified wood occurs as two horizons of fallen logs and a group of rooted stumps in growth position coincident with the upper log horizon the largest log is 25 3 m in length the largest stump is 2 5 m in diameter the enclosing strata are fluvial silts sands and gravels wood characteristics indicate that climate was mild with seasonal variation in precipitation temperature or light paleohydrology and stratigraphy of the shishu formation suggest a wide shallow low sinuosity mixed load meandering stream regime that drained southward into the junggar basin during the late jurassic

dinosaur bones fossils or pseudomorphs the pitfalls of physiology reconstruction from apatitic fossils abstract a prerequisite to any attempt to reconstruct thermophysiology of ancient animals through analysis of stable isotopes of oxygen is the assumption that apatitic fossils are isotopically unaltered parts of their original skeletons we suggest that sufficient evidence is available to seriously question this assumption because living bones contain about 1 3 by weight of organic matrix mass balance considerations show that at least half of an apatitic fossil must be new material added post mortem furthermore living apatitic skeletons contain almost no rare earth elements and uranium whereas apatitic fossils bear high concentrations of these elements additionally we found that while in living fish correlation between 18o of oxygen in the phosphate and that in the carbonate of apatite is poor these two values are linearly correlated in fossil fish this suggests diagenetic recrystallization has taken place perfect preservation of micro textures such as haversian canals does not prove the pristine condition of a fossil some of the most beautifully preserved fossils are highly silicified most apatitic fossils probably are pseudomorphs replacing original skeletal elements whereas distribution of stable isotopes of oxygen in fossils might provide information about their burial environment it could be misleading in attempts to interpret the organisms physiology this cautionary note is supported by the similarity of 18op in bones of coexisting fossil fish dinosaurs and various other reptiles at different latitudes the overlap of predicted 18op values in fish and mammals living in contact with the same environmental water also weakens the hope that ectotherms can be distinguished from endotherms by the isotopic composition of oxygen in their bones and teeth

biologic and climatic signals in the oxygen isotopic composition of eocene oligocene equid enamel phosphate abstract oxygen isotope results for tooth enamel phosphate p from late eocene early oligocene fossil horses are presented to determine if paleobiologic and paleoclimatologic information is recorded in fossil tooth enamel chemistry teeth from jaws of mesohippus and miohippus from the white river formation or group in the western great plains are well preserved and have excellent geochronologic control although there is clear evidence for post depositional alteration of the enamel a hydroxylapatite mineralogy is preserved and isotopic exchange of oxygen does not appear to be significant there are distinctive patterns of p variation among individual teeth from the same jaw these patterns reflect season of birth and timing of enamel mineralization most of the horses were born in the spring and mineralization of the enamel is complete after 1 1 5 years these results show that paleoclimate reconstruction from enamel p must account for tooth position and timing of mineralization the observation that there are different intrajaw patterns of p variation among mesohippus and miohippus may provide a basis to reconstruct changes in climate seasonality in ancient environments

oxygen isotope variations in phosphate of biogenic apatites iv mammal teeth and bones groups of rats grown from birth to death in identical conditions but with different 18o of drinking water w were studied for variations of 18o of their body water bw and bone phosphate p there is a high linear correlation r 0 99 between bw and between p and w the regression lines have similar slope coefficients 0 53 and 0 49 values of p of different teeth and bones are the same within the precision of the method 0 5 the isotopic fractionation coefficient between phosphate and body water is 1 0178 and close to the estimated value of 1 0173 derived from the phosphate paleotemperature equation deviations from constant fractionation between bone phosphate and environmental drinking water depend primarily on rates of drinking and metabolism environment conditions have relatively little effect on oxygen isotope fractionation between water sources and bone phosphate

a multi technique approach by xrd xrf ft ir to characterize the diagenesis of dinosaur bones from spain abstract a combined investigation by x ray fluorescence xrf fourier transform infrared spectroscopy ft ir raman spectroscopy and powder x ray diffraction xrd supplemented with the rietveld analysis was conducted on sixty spanish dinosaur bone specimens from upper jurassic lower cretaceous to upper cretaceous age to investigate taphonomy and diagenetic processes the diffraction approach assessed in all specimens the presence of fluorapatite at various levels of percentage as the mineral phase constituting the fossil bone in addition to fluorapatite calcite and quartz were also found as main secondary phases in many specimens the infrared spectra of fossil bones show significant changes in the phosphate and carbonate band intensity with respect to a non fossil bone conversely the x ray fluorescence spectra turned out to be mainly dominated by the presence of ca obviously accompanied by phosphorus simultaneously other elements accompanying ca such as fe and sr were found at significant concentration levels a considerable amount of fe and sr ions were incorporated in the structure of fluorapatite but when their concentration was found elevated in the fluorescence spectrum the diffraction data revealed the presence of goethite feooh and celestite srso4 phases while the x ray diffraction phase analysis also revealed the presence of kaolinite dolomite barite and gypsum in some fluorescence spectra further elements like y as pb ti mn cr cu zn were present in concentration at trace level the introduction substitution of new elements with the infiltration of new phases due to diagenesis is also affecting to various extent the raman and ft ir spectra with modification of some bands and or the appearance of new bands the average crystallite size of the apatitic constituent phase was found to vary from a minimum of ca 183 a to an upper level of 2107 a no systematic relation between apatite crystallite size and age of the dinosaur bones was found that suggests a high variability of diagenetic processes affecting the growth of bone crystallites even in the same site

quaternary silicic pyroclastic deposits of atitlan caldera guatemala abstract atitlan caldera has been the site of several silicic eruptions within the last 150 000 years following a period of basalt andesite volcanism the silicic volcanism began with 5 10 km3 of rhyodacites erupted as plinian fall and pyroclastic flows about 126 000 yr b p at 85 000 yr b p 270 280 km3 of compositionally distinct rhyolite was erupted in the los chocoyos event which produced widely dispersed plinian fall deposits and widespread mobile pyroclastic flows in the latter parts of this eruption rhyodacite and minor dacite were erupted which compositionally resembled the earliest silicic magmas of the atitlan center as a result of this major eruption the modern atitlan iii caldera formed following this event rhyodacites were again erupted in smaller 5 13 km3 volumes partly through the lake and mafic volcanism resumed forming three composite volcanoes within the caldera the bimodal mafic silicic atitlan volcanism is similar to that which has occurred elsewhere in the guatemalan highlands but is significantly more voluminous mafic lavas are thought to originate in the mantle but rise intrude and underplate the lower crust and partly escape to the surface eventually silicic melts form in the crust possibly partly derived from underplated basaltic material rise crystallize and erupt the renewed mafic volcanism could reflect either regional magmato tectonic adjustment after the large silicic eruption or the onset of a new cycle

the upper jurassic lower cretaceous alluvial fan deposits of the kalaza formation central asia tectonic pulse or increased aridity the topographical evolution of tectonic systems as well as the sedimentation pattern and depositional environments in the associated basins are controlled by both tectonics and climate in the region of the tien shan central asia the jurassic lower cretaceous period was marked by complex low intensity tectonic deformation and major climate changes from humid to arid conditions jurassic to semi arid conditions cretaceous using the sediment record in the junggar tarim and fergana basins to describe the tectonic evolution of the tien shan area during the mesozoic thus requires differentiation between the tectonic and climatic influences on sedimentation the conglomerates of the upper jurassic lower cretaceous kalaza formation were commonly associated with renewed tectonic activity resulting from the docking of the lhasa block along the southern margin of asia from sedimentology and sequence stratigraphy analyses of several sections in the junggar tarim and fergana basins we reassess the main factors controlling the deposition of this formation we show that while some tectonic activity persisted throughout the jurassic cretaceous transition the switch from the sandy deposits of the upper jurassic qigu formation to the coarse deposits of the kalaza formation is largely linked to the development of an arid climate

oxygen isotope analyses of co existing carbonate and phosphate in biogenic apatite a way to monitor diagenetic alteration of bone phosphate abstract the oxygen isotopic composition of phosphate 18 op and structural carbonate 18 oc of hydroxylapatite was determined in 31 bone and tooth samples of modern mammals from different countries these two variables are highly correlate r 2 0 98 and the calculated best fit of linear regression is very similar to the equation calculated from the phosphate and carbonate palaeotemperature equations 1 2 according to previous measurements 3 6 on fossils of different ages from different areas it seems quite improbable to find isotopically altered skeletal remains showing a good correlation between 18 op and 18 oc as is the case with modern samples it therefore seems possible at least in some cases to use these measurements for monitoring fossil bone and tooth diagenetic alteration when a set of points lie on the equilibrium line or close to it the 18 o values could be considered close to the original values in contrast when the points lie to the left or to the right of this line this probably means that the values are diagenetically modified due to interaction with meteoric water or 18 o enriched water respectively

oxygen isotope variation in the tusks of extinct proboscideans a measure of season of death and seasonality centimetre scale laminae in tusk and molar dentine of late pleistocene mastodonts and mammoths have been interpreted as annual growth bands produced in part by seasonal variation in growth rate to test this interpretation we measured the oxygen isotope composition 18 o of the co 3 fraction of dentinal hydroxyapatite from samples covering consecutive inferred years of growth in tusks in mammals changes in the 18 o value of dental tissues within individuals predominantly reflect variation in the 18 o value of body fluids which is controlled mainly by the isotopic composition of ingested water in northern hemisphere continental regions winter precipitation has substantially lower 18 o values than does precipitation in other seasons if ingested water tracks focal precipitation then seasonal variations in dentinal isotope composition should result the lowest 18 o values representing winter growth we demonstrate that there are substantial variations in the oxygen isotope composition of proboscidean dentinal apatite and that isotopic identifications of winter i e low 18 o values coincide with those based on growth rate i e slow growth zones finally the potential of oxygen isotope analyses of terrestrial mammals for assessing the seasonality of paleoclimates is considered

paleobiology and skeletochronology of jurassic dinosaurs implications from the histology and oxygen isotope compositions of bones fossil biogenic phosphate of fast growing primary bone tissue of dinosaurs can preserve a histologic and isotopic time series of annual seasonality in temperature variations similar to tooth enamel and other accretionary skeletal phases such as corals or wood on two bone fragments from sympatric dinosaurs with different histologic patterns of bone growth high resolution oxygen isotope profiles were analyzed along the radial direction of bone growth the investigated specimens are from the jurassic shishugou formation in the junggar basin nw china and have distinct patterns of compositional variation a fibrolamellar dinosaur bone with multiple lines of arrested growth lags and periodic growth cycles of decreasing bone laminae thickness displays a cyclic intra bone variation in 18o values of about 2 corresponding with the lags these growth cycles in fast growing fibrolamellar bone provide evidence for seasonal growth of dinosaurs in lower latitudes 45 n possibly influenced by a monsoon type paleoclimate seasonal changes in temperature and water supply are consistent with the oxygen isotope composition measured in dinosaur bone phosphate as well as with growth rings in contemporaneous fossil conifer wood from the same locality in contrast a plexiform sympatric sauropod bone displays continuous growth free of lags and has a lower intra bone variation of 0 8 differences in bone histology are also reflected in the oxygen isotopic composition and its intra bone variability indicating different physiological responses to external climatic stress between sympatric dinosaur species seasonal intra bone oxygen isotope variations combined with bone histology may thus yield new insights into species specific response to climatic stress and its influence on dinosaur growth formation of growth marks growth rates as well as dinosaur thermophysiology

isotopic reconstruction of past continental environments abstract vertebrate fossils and continental sediments provide a rich record of variations in the isotopic composition of surface environments to interpret these records a greater understanding of isotopic sources as well as fractionations associated with animal physiology soil geochemistry and diagenesis has been essential tooth enamel and fish otoliths yield subannual records of surface environments whereas soil minerals may integrate signals over many thousands of years carbon isotope variations in fossil vertebrates and soils record changes in the structure of vegetation and the isotope composition and concentration of atmospheric co2 oxygen isotope variations may be indirectly related to climate through reconstruction of the oxygen isotope composition of meteoric water or directly related to temperature through application of oxygen isotope paleothermometry to soil minerals or otoliths in africa nitrogen isotope variations show promise as a proxy for rainfall abundance though the gen

interplay between tectonic fluvial and erosional processes along the western border fault of the northern upper rhine graben germany abstract the northern upper rhine graben situated in the central part of the european cenozoic rift system is currently characterized by low intra plate seismicity historical earthquakes have not been large enough to produce surface rupturing moreover the records of quaternary surface processes and human modifications are presumably better preserved than the record of the relatively slow tectonic deformation in order to gain information on the neotectonic activity and paleoseismicity in this setting the geological and geomorphological records of fault movements along a segment of the western border fault wbf were studied using an integration of techniques in paleoseismology structural analysis and shallow geophysics the wbf segment investigated follows a 20 km long linear scarp of unclear origin a series of geophysical measurements were performed and the results suggested that near surface deformation structures are present at the segments southern end several trenches opened at this location revealed fault structures with consistent extensional style and a maximum vertical displacement of 0 5 m in one trench the deformation structures were dated between 19 and 8 ka assuming the deformation has been caused by an earthquake a m w 6 5 earthquake would be implied aseismic deformation would point to a fault creep rate 0 04 mm yr a reconstruction of the sequence of events at the trench site from middle pleistocene to present demonstrates that the morphology at the base of the scarp is the result of interplay between tectonic activity and fluvial and erosional processes at the regional scale a mixed origin for the wbf scarp is proposed combining the effects of fluvial dynamics erosion regional uplift and localized tectonic activity on the wbf

reconstructing diagenetic conditions of bone at the gray fossil site tennessee usa abstract the preservation of vertebrate fossils requires transformation of the original bioapatite mineral matrix predominantly hydroxylapatite during diagenesis into a thermodynamically more stable phase fossil bone geochemistry and structure provides a wealth of information on the conditions present during diagenesis including site redox and ph and about sedimentation rates during burial the gray fossil site preserves late neogene lacustrine deposits that serve as one of a few records of north american paleoclimate during a critical period of the cenozoic despite having 40 vertebrate species and diverse plant assemblages none of the prior studies used bone composition to understand what paleoenvironmental and diagenetic conditions must have been like to facilitate bone preservation and fossilization alligator sp phalanges were examined using multiple geochemical tools including fourier transform infrared spectroscopy x ray diffraction and electron microprobe analyses evidence of bioerosion within thin cortical and isolated trabecular regions of bone suggests biotic utilization of organics collagen and or the mineral s following deposition chemically zoned and laminated cortical alligator bone is interpreted as preserved lines of arrested growth that developed during life and supports previous interpretations of a regional seasonal climate lastly the alligator bones are mineralogically heterogeneous as fluorinated and iron containing apatite phases compared to modern bone iron concentrations were high at up to 3 wt the uptake of fe by the alligator bones examined in this study suggests that fluids present during diagenesis that led to bone preservation within the lacustrine sediment at the gray fossil site were likely acidic anoxic and reducing

rainfall patterns and the distribution of coals and evaporites in the mesozoic and cenozoic abstract paleoclimatologists have adequately demonstrated over the last twenty years that the distribution of climatically sensitive sediments can be related to present day climatic zones that are roughly parallel to latitude for example coals were deposited at paleolatitudes that correspond to the present day rainy zones at the equator and at about 55 n and 55 s indicating that those zones were present in the past from this it can be concluded that atmospheric circulation has not been radically different from its present configuration despite some apparently great differences in some climatic parameters such as the equator to pole temperature gradient nevertheless the zonal model for predicting the distribution of climatically sensitive sediments is not wholly adequate although general atmospheric circulation may not have been radically altered from its present pattern it would have differed in some respects because the paleogeography was different from the present geography therefore we have constructed what we believe are more realistic maps of the distribution of rainfall through time these maps are based on maps of atmospheric circulation that have been successfully used to predict the distribution of some petroleum source beds and phosphorites we have compared the predicted distribution of rainfall to the distribution of coals and evaporites for each of seven geologic stages the circulation rainfall maps were more successful than the zonal model for predicting the distribution of evaporites and coals for times when the paleogeography would have maximized the development of a monsoonal circulation which most effectively disrupts the general zonal pattern for times when a monsoonal circulation would not have been important the zonal model adequately predicted the distribution of these rocks

oxygen isotope variations in phosphate of biogenic apatites i fish bone apatite rechecking the rules of the game abstract the major advantage of the oxygen in phosphate isotope paleothermometry is that it is a system which records temperatures with great sensitivity while bone and teeth building organisms are alive and the record is nearly perfectly preserved after death fish from seven water bodies of different temperatures 3 23 c and different 18 o values 16 to 3 of the water were analysed the 18 o values of the analysed po 4 vary from 6 to 25 the system passed the following tests a the temperatures deduced from isotopic analyses of the sequence of fish from lake baikal are in good agreement with the temperatures measured in the thermally stratified lake b the isotopic composition of fish bone phosphate is not influenced by the isotopic composition of the phosphate which is fed to the fish but only by temperature and water composition isotopic analysis of fossil fish in combination with analysis of mammal bones should be a useful tool in deciphering continental paleoclimates

lamellar zonal bone with zones and annuli in the pelvis of a sauropod dinosaur de ricqles1 7 distinguishes two principal types of primary unremodelled compact bone compacta which he terms lamellar zonal and fibro lamellar in the former bone laid down by accretion at the periosteal external surface shows a general coarsely lamellated texture and vascular canals for blood vessels are often sparsely developed and sometimes lacking primary osteons formed by inward growth of bone inside vascular canals may be present or absent this type of compacta is seen in bones which grow slowly or only to small sizes and is the only type seen in most ectotherms in contrast fibro lamellar bone is always rich in primary osteons set in a matrix of woven bone which is typically laid down rapidly this type of bone is seen mainly in medium to large sized endotherms and reflects their ability to reach such sizes more quickly than comparable ectotherms in ectotherms lamellar zonal bone may show a cyclical alternation of thin layers of dense bone termed annuli with thicker vascular layers known as zones but it is claimed2 that such features are not developed cyclically in endotherms the presence of fibro lamellar compacta without annuli and zones in various dinosaurs7 is hence seen as evidence that dinosaurs were endotherms however i report here a case in which compact bone from the pelvis of a dinosaur is instead lamellar zonal and shows typical zones and annuli

rapid least squares inversion of apparent resistivity pseudosections by a quasi newton method1 a fast inversion technique for the interpretation of data from resistivity tomography surveys has been developed for operation on a microcomputer this technique is based on the smoothness constrained least squares method and it produces a two dimensional subsurface model from the apparent resistivity pseudosection in the first iteration a homogeneous earth model is used as the starting model for which the apparent resistivity partial derivative values can be calculated analytically for subsequent iterations a quasi newton method is used to estimate the partial derivatives which reduces the computer time and memory space required by about eight and twelve times respectively compared to the conventional least squares method tests with a variety of computer models and data from field surveys show that this technique is insensitive to random noise and converges rapidly this technique takes about one minute to invert a single data set on an 80486dx microcomputer

results of 3 d georadar surveying and trenching the san andreas fault near its northern landward limit abstract as part of a program to determine the location and geometry of the san andreas fault saf buried beneath shallow sediments near its northern landward limit three 20 m long parallel trenches were constructed at positions distributed over a distance of 55 m the majority of excavated material comprised unconsolidated fluvial sediments deposited in a number of paleochannels single zones of active faulting identified in each of the trenches were initially interpreted in terms of a solitary strand of the saf to map the saf between and beyond the trenches and to detect other active fault zones hidden by the young sedimentary cover we collected a dense ground penetrating radar georadar data set across a 23 2 72 m area the data were recorded using a semi automated acquisition system that included a conventional georadar unit coupled to a self tracking laser theodolite with automatic target recognition capabilities since these data were plagued by system ringing as a result of the moderate to high electrical conductivities of the surficial sediments an extensive data processing scheme was required to extract meaningful subsurface information the final processed georadar volume cuboid contained numerous subhorizontal and trough shaped reflections that originated from the fluvial paleochannels using the geological interpretation of the trench walls as a guide to pick semi automatically the times of the most important reflecting horizons we discovered that alignments of the nearly linear boundaries of these horizons defined two nw se trending strands of the saf within the survey area the georadar expression of the eastern saf strand could only be traced over a distance of 38 m it had been intersected in the northern trench in contrast the western saf strand extended over the entire length of the georadar volume and had been intersected in the central and southern trenches prominent reflections on georadar cross sections were found to be vertically displaced by 0 2 0 3 m across both saf strands a conspicuous linear trending feature observed on horizontal sections at 3 3 3 6 m depth was laterally offset by 4 5 5 5 m along the eastern saf strand the interpreted vertical and horizontal offsets could have been generated by the 1906 san francisco earthquake and or earlier events undetermined amounts of aseismic slip may also have occurred along the newly defined saf strands

from bone to fossil a review of the diagenesis of bioapatite the preservation of bone or bioapatite over geologic time has presented paleobiologists with longstanding and formidable questions namely to elucidate the mechanisms processes rates and depositional conditions responsible for the formation of a fossil from a once living tissue approaches integrating geochemistry mineralogy physics hydrology sedimentology and taphonomy have all furthered insights into fossilization but several fundamental gaps still remain notably our limited understanding of 1 the timing of processes during diagenesis e g early and or late 2 the rate of bioapatite transformation into thermodynamically more stable phases 3 the controls imparted by depositional environment and 4 the role of micro biology in determining the fate of bone bioapatite dissolution or preservation the versatility of fossil bioapatite to provide information on the biology of extinct vertebrates rests on our ability to identify and characterize the changes that occurred to bioapatite during diagenesis this review will evaluate our current understanding of bioapatite diagenesis and fossilization focusing on the biogeochemical transformations that occur during diagenesis to the mineral and organic components of bone excluding teeth and enamel the analytical approaches applied to evaluate fossilization processes and outline some suggestions for future promising directions

imaging and characterisation of subsurface solute transport using electrical resistivity tomography ert and equivalent transport models abstract we assess the usefulness of electrical resistivity tomography ert in imaging and characterising subsurface solute transport in heterogeneous unconfined aquifers a field tracer experiment was conducted at the krauthausen test site germany the spatial and temporal evolution of the injected nabr solute plume was monitored in a 2d ert image plane located downstream of the injection well for 90 days since ert maps changes in bulk electrical conductivity the reconstructed images at selected time intervals are first converted to solute concentration maps by postulating a linear relation the concentration maps are then analysed using an equivalent convection dispersion model cdm which conceptualises the aquifer as a homogeneous medium with a uniform mean flow velocity as demonstrated by associated synthetic model studies ert resolution in terms of recovered equivalent dispersivities is limited due to spatial smoothing inherent to the imaging algorithm since for heterogeneous media local concentrations within the plume deviate from those predicted by the equivalent cdm we also interpret the ert derived pixel breakthrough curves in terms of an equivalent stream tube model stm the stm represents transport in the aquifer by a set of 1d convection dispersion processes allowing the degree of mixing and the heterogeneity of transport within the plume to be quantified we believe that the observed tracer plume is satisfactorily described by the equivalent cdm probably because the tracer plume was small relative to the heterogeneity scale of the aquifer even though application of the stm revealed some deviation from the ideal homogeneous case the equivalent dispersivity in the stm matches the longitudinal dispersivity of the cdm closely consistent with predominantly homogeneous mixing however the stm analysis illustrates how ert results can be used to quantify the variability of parameters relevant to flow and transport in heterogeneous aquifers

resistivity and induced polarization surveys for slope instability studies in the swiss alps a geoelectrical investigation has been carried out in the swiss alps near the dent de nendaz within the southern part of the rhone valley in the swiss alps to delineate groundwater circulation within an unstable slope this unstable zone is characterized by a landslide area with clear scarps and hummocky ground at the bottom of the slope large scale apparent resistivity mapping provided information on the main pathways for water transport within the slope subsequently 2d resistivity and induced polarization imaging supplied details on the region of instability located at the bottom of the slope polarizable units identified in the region of instability could be linked to a clay rich unit or to local enrichment of graphite within the bedrock our results illustrate how low permeability clay graphite units and permeable water bearing units could be distinguished using a combined interpretation of resistivity and ip data in slope instability studies

differentiating anisotropy and lateral effects using azimuthal resistivity offset wenner soundings azimuthal resistivity surveys increasingly are being used by hydrogeologists in the identification and characterization of fractured rocks in these investigations electrical resistivity is measured as a function of azimuth about a fixed central point in most recent published examples any observed change in apparent resistivity with azimuth is interpreted as being indicative of fracture anisotropy however interpretation of rotational sounding data is actually more complicated as azimuthal variations in apparent resistivity are also produced by the presence of dipping stratigraphy and other lateral changes in formation resistivity such effects are generally overlooked because the field techniques normally employed are incapable of detecting them consequently it is quite probable that the results of many published surveys have been wrongly interpreted an alternative field procedure and interpretation methodology has been developed to differentiate anisotropy dipping layers and lateral effects this approach makes use of the offset wenner technique and examines the different responses of the individual wenner resistances above different geological structures analysis of data obtained using the azimuthal offset wenner technique from sites in britain and ireland have successfully identified subsurface structures and determined the anisotropy where it is present

origin and migration of the alpine iceman the alpine iceman provides a unique window into the neolithic copper age of europe we compared the radiogenic strontium and lead and stable oxygen and carbon isotope composition of the iceman s teeth and bones as well as 40ar 39ar mica ages from his intestine to local geology and hydrology and we inferred his habitat and range from childhood to adult life the iceman s origin can be restricted to a few valleys within 60 kilometers south east of the discovery site his migration during adulthood is indicated by contrasting isotopic compositions of enamel bones and intestinal content this demonstrates that the alpine valleys of central europe were permanently inhabited during the terminal neolithic

fault scaling and 1 f noise scaling of seismic velocity fluctuations in the upper crystalline crust sonic logs are detailed measurements of the in situ seismic velocity along borehole walls power spectra of sonic logs typically decay approximately as the reciprocal of spatial frequency f regardless of the chemical composition geologic age and tectonic history of the probed lithologies data sequences of this type are fractal or scale invariant the origins of this uniform 1 f scaling of seismic structure are not clear particularly in low porosity crystalline rocks but faults fractures and cracks are considered to be important fault structures also follow fractal scaling laws and have significant effects on seismic velocity this paper presents a quantitative model that evaluates the role played by faults in determining the scaling laws of seismic velocity fluctuations the model is based on current knowledge of the structure and scaling properties of brittle faults and of associated regions of microcracking by approximating the relationship between crack density and velocity variation as linear this model yields a brownian power spectrum 1 f 2 for velocity perturbations across a single fault zone in a medium of otherwise constant velocity the power spectrum of velocity fluctuations induced by a population of faults is then obtained by superposing the corresponding brownian power spectra weighted according to the observed frequency size scaling relationship of brittle faults the results of this study indicate that the uniform 1 f scaling of velocity fluctuations in crystalline rocks seems to be linked to the correspondingly uniform scaling properties of fault structures

localization and characterization of an active fault in an urbanized area in central guatemala by means of geoelectrical imaging article i nfo article history the polochic and motagua faults define the active plate boundary between the north american and caribbean plates in central guatemala a splay of the polochic fault traverses the rapidly growing city of san miguel uspantan that is periodically affected by destructive earthquakes this fault splay was located using a 2d electrical resistivity tomography ert survey that also characterized the fault damage zone and evaluated the thickness and nature of recent deposits upon which most of the city is built ert images show the fault as a 50 m wide near vertical low resistivity anomaly bounded within a few meters by high resistivity anomalies forward modeling reproduces the key aspects of the observed electrical resistivity data with remarkable fidelity thus defining the overall location geometry and internal structure of the fault zone as well as the affected lithologies our results indicate that the city is constructed on a 20 m thick surficial layer consisting of poorly consolidated highly porous water logged pumice this soft layer is likely to amplify seismic waves and to liquefy upon moderate to strong ground shaking the electrical conductivity as well as the major element chemistry of the groundwater provides evidence to suggest that the local aquifer might at least in part be fed by water rising along the fault therefore the potential threat posed by this fault splay may not be limited to its seismic activity per se but could be compounded its potential propensity to enhance seismic site effects by injecting water into the soft surficial sediments the results of this study provide the basis for a rigorous analysis of seismic hazard and sustainable development of san miguel uspantan and illustrate the potential of ert surveying for paleoseismic studies

the caribbean north america cocos triple junction and the dynamics of the polochic motagua fault systems pull up and zipper models the polochic motagua fault systems pmfs are part of the sinistral transform boundary between the north american and caribbean plates to the west these systems interact with the subduction zone of the cocos plate forming a subduction subduction transform triple junction the north american plate moves westward relative to the caribbean plate this movement does not affect the geometry of the subducted cocos plate which implies that deformation is accommodated entirely in the two overriding plates structural data fault kinematic analysis and geomorphic observations provide new elements that help to understand the late cenozoic evolution of this triple junction in the miocene extension and shortening occurred south and north of the motagua fault respectively this strain regime migrated northward to the polochic fault after the late miocene this shift is interpreted as a pull up of north american blocks into the caribbean realm to the west the pmfs interact with a trench parallel fault zone that links the tonala fault to the jalpatagua fault these faults bound a fore arc sliver that is shared by the two overriding plates we propose that the dextral jalpatagua fault merges with the sinistral pmfs leaving behind a suturing structure the tonala fault this tectonic zipper allows the migration of the triple junction as a result the fore arc sliver comes into contact with the north american plate and helps to maintain a linear subduction zone along the trailing edge of the caribbean plate all these processes currently make the triple junction increasingly diffuse as it propagates eastward and inland within both overriding plates

detailed imaging of tectonic structures by multiscale earth resistivity tomographies the colfiorito normal faults central italy 1 this study is aimed to show how cost effective geophysical surveying integrated with detailed knowledge of the local geology can give a significant contribution to image the subsurface structure of complex areas of active faulting the combined inversion of a data set consisting of a large scale tomography and a target dependent multiresolution dipole dipole measurements the multiscale approach is shown to yield detailed structural information and to infer some characteristics of the fault zone the operating procedure applied to the colfiorito fault system allowed to differentiate the electrical signatures of the crossed faults minor faults show sharp lateral variations generated by a contact between different geological formations while the major faults are also characterized by a decrease in resistivity values distributed on the fault damage zones a close interpretation was supported by detailed geological surface data besides quantitative correlations between in situ resistivity distribution and geological units were supported by electrical logs

geophysical survey to estimate the 3d sliding surface and the 4d evolution of the water pressure on part of a deep seated landslide geophysical surveys were conducted on the very unstable front part of the la clapiere landslide in the french alps alpes maritimes the electrical resistivity survey was carried out to obtain for the first time on this deep seated landslide 3d information on the slipping surface and the vertical drained faults moreover we planned to follow within time 6 months the evolution of the saturated zones presence of gravitational water and their percolation into the shearing zones our 4d results showed the importance of the complex water channelization within the slope and relation to geological discontinuities

surface seismic and electrical methods to detect fluids related to faulting in the absence of drilling surface based geophysical methods are necessary to observe fault zones and fault zone physical properties at seismogenic depths these in situ physical properties can then be used to infer the presence and distribution of fluids along faults although such observations are by nature indirect and become less exact with greater depth multiple observations of a range of such geophysical properties as compressional and shear seismic velocity vp and vs vp v5 ratio related to poisson s ratio resistivity and attenuation in and adjacent to fault zones offer the greatest hope of making inferences of the fault zone geometry fluids in the fault zone and fluid reservoirs in the surrounding crust for simple geometries fault zone guided waves can provide information on fault zone width and velocities for faults of the order of 200 m wide to address the question of whether a narrow fault zone can be imaged well enough at depths of seismic rupture to infer the presence of anomalously high fluid rock ratios we present synthetic seismic tomography and magnetotelluric examples for an ideal case of a narrow fault zone with a simple geometry large changes in material properties and numerous earthquakes within the fault zone a synthetic 0 5 km wide fault zone with 20 velocity reduction is well imaged using local earthquake tomography when sequential velocity inversions are done the true fault width is found even to 9 km depth although the calculated amplitude of the velocity reduction is lower than the actual amplitude vp vs is as well determined as vp magnetotelluric imaging of a synthetic fault zone shows that a conductive fault zone can be well imaged within the upper 10 km further a narrow 1 km very low resistivity 3 ohm m fault core can be imaged within a broad 5 km low resistivity 10 ohm m fault zone illustrating that regions of a fault containing large quantities of interconnected fluids within a broader conductive fault zone should be detectable thus variations in fluid content and fluid pressure can be inferred from electrical and seismic methods but there will always be uncertainty in these inferences due to the trade off with other factors such as intrinsic variations in porosity mineralogy and pore geometry the best approach is combined modeling of varied seismic and electrical data

pangaean climates megamonsoons of the megacontinent the climate for a highly idealized geographic representation of the megacontinent of pangaea corresponding to the period 250 200 m y ago is explored using a low resolution atmospheric general circulation model that is coupled to a static mixed layer ocean of constant depth with a provision for sea ice formation and decay soil moisture is included as a predicted variable on the continent because there are large uncertainties about key factors that might influence the pangaean climate sensitivity experiments are used to examine the climate for two different mean elevations 0 and 1000 m two different snowcover prescriptions and two different levels of implied greenhouse heating and solar luminosity modern co2 concentration and modern solar luminosity fivefold increase in modern co2 concentration and a 1 decrease in modern solar luminosity in all of the experiments the large bipolar land masses of laurasia and gondwanaland joined near the equator in the west and separated by the tethys sea in the east exhibit extreme continentality with hot summers cold winters and large scale summer and winter monsoon circulations year round or seasonal aridity is simulated for all but the eastern coastal regions the tropical western coast and the regions poleward of 40 latitude the simulated climate of the idealized pangaean continent has many features that correspond qualitatively with geologic evidence for tropical warmth and aridity in the late permian and triassic however the model results serve mainly to indicate the importance of various climate forming factors geography topography heating detailed comparisons will require new experiments with better models and more accurate geologic boundary conditions

shallow geometry and displacements on the san andreas fault near point arena based on trenching and 3 d georadar surveying 1 to characterize buried portions of the san andreas fault saf near its northern extremity in california three trenches were excavated perpendicular to it and a 3 d georadar data set was acquired similar sequences of unconsolidated fluvial sediments franciscan serpentinite and active fault zones were observed in the three trenches fault traces in the trenches were initially assumed to be part of a single saf strand however the georadar data demonstrated the existence of two saf strands one of which was exposed in the central and southern trenches and the other in the northern trench offset of a linear trending georadar feature possibly a fluvial paleochannel suggests that 4 5 5 5 m of horizontal displacement occurred across the eastern saf strand either during the 1906 san francisco earthquake or earlier georadar reflections from flat lying and trough shaped sedimentary boundaries are vertically offset by 0 2 0 3 m along both fault strands

2d electrical resistivity imaging of some complex landslides in lucanian apennine chain southern italy we use high resolution electrical resistivity imaging to delineate the geometry of complex landslides in the lucanian apennine chain of southern italy to identify the discontinuity between the landslide material and bedrock and to locate possible surfaces of reactivation the lucanian apennine chain is characterized by high hydrogeological hazard and shows a complete panorama of mass movements in this area all typologies of landslides markedly predisposed and tightly controlled by the geostructural characteristics are found rotational and translational slides rototranslational slides earth and mudflows as well as deep seated gravitational slope phenomena with a predominance of rototranslational slides evolving as earthflow slides three test sites characterized by complex geology and a high hydrogeologic hazard are studied the giarrossa and varco izzo earthflow slides are located to the west and east of the town of potenza whereas the latronico slide is located close to the town of latronico

the correlation between 18o 16o ratios of meteoric water and surface temperature its use in investigating terrestrial climate change over geologic time abstract correlations between mean annual temperature mat and the weighted average oxygen isotope composition of yearly precipitation 18opt are well known but the utility of modern relations to make reliable estimates of temperature change over geological time is uncertain this question has been addressed by using seasonal subsets of the global data base of temperature and isotopic measurements to represent two different climate modes a comparison of middle to high latitude 18opt temperature relations for each climate mode reveals 1 a significant offset between them and 2 a difference in the strength of their correlations the offset in relations is due to differences in temperature and water vapor budget in the tropics and can lead to serious underestimates of temperature change differences in the strength of correlations arise from the influence of climate mode specific non temperature factors on 18opt the overall result is that no single relation can be used in all cases to make unambiguous temperature estimates using a temporal record of 18opt values one way to overcome these problems is to reconstruct 18opt temperature relations for the time periods being investigated if an appropriate proxy for 18opt is available it may also be possible to estimate temperature without relying on 18opt temperature relations a promising alternative to these options is to use records of 18opt to test predictions of global climate models an approach that may allow a reliable and more complete reconstruction to be made of climate change over geologic time

rolling bones taphonomy of jurassic dinosaur bones inferred from diagenetic microcracks and mineral infillings abstract dinosaur bones from the upper jurassic shishugou formation near qitai in the junggar basin nw china show black manganese oxide and light quartz infillings in the bone pore space such as haversian canals and diagenetic cracks the manganese oxides are identified by x ray diffraction as pyrolusite some haversian canals are only partially filled with pyrolusite which forms miniature geologic spirit levels the orientations of these spirit levels have been measured and several generations of pyrolusite infillings determined indicating that the bones were turned around once or several times during their fossilization characteristic desiccation cracks in the dinosaur bones indicate deposition on the soil surface and early diagenesis under dry climate conditions in the upper jurassic in nw china during dry season evaporation and resulting capillary forces drove the groundwater with dissolved manganese ii ions towards the soil surface and further into the capillary system of the bones hence the capillary system of the bones was already in contact with that of the sediment when the bones were still lying on the surface and were not yet totally embedded in the sediment mn oh 2 precipitated under high ph conditions in the pore space of the bones such as haversian canals and cracks during late diagenesis the mn oh 2 was oxidized to mno2 and transformed into pyrolusite mineral infillings and desiccation cracks in fossil bones thus can yield valuable insights into the taphonomic history of skeletal remains such as environmental conditions during diagenesis and fossil reworking

case studies of electrical and electromagnetic methods applied to mapping active faults beneath the thick quaternary it is of considerable importance to explore the geological structure around active faults especially near surface unconsolidated layers to estimate the faults activity there are numerous case studies to investigate active faults using geophysical exploration methods however only a few cases have been verified in detail by comparison with other geological information we have applied electric and electromagnetic methods which can be effective for exploring to several hundred meters depth to reveal geological structures covered by thick quaternary formations at four active fault sites in japan in this paper we used the controlled source audio frequency magnetotelluric csamt method the direct current dc resistivity method and the resistivity tomography method the resistivity profiles were analyzed by two dimensional inversion techniques and the resulting models were verified by comparison with geological evidence obtained by drilling or trenching our results are as follows 1 csamt is an effective method for defining an outline of geological structures around a fault to several hundred meters deep it enables us to define a resistivity boundary between different kinds of bedrock with a fault contact 2 the dc resistivity method distinguishes each sedimentary unit as a different resistivity zone and detects the vertical displacement in the quaternary formations 3 the resistivity tomography method is useful to determine in more detail the flexure structure produced by faulting using these latter two methods we can select drilling positions and trenching locations in addition it is verified from the data measured along trench walls and electrical logging that the resistivity of soft sedimentary layers and clayey cataclastic bedrock conforms to the relationship established between the resistivity and the clay content these resistivity methods have the advantages of detecting clayey layers as very low resistivity zones the overall conclusion is that the combination of these resistivity methods provides us with more detailed and accurate information for estimating fault activity

does burial diagenesis reset pristine isotopic compositions in paleosol carbonates abstract sedimentological study of early oligocene continental carbonates from the fluvial dagshai formation of the himalayan foreland basin india resulted in the recognition of four different types namely soil palustrine pedogenically modified palustrine and groundwater carbonates stable oxygen and carbon isotopic 18 o and 13 c analyses of fabric selective carbonate microsamples show that although the pristine isotopic compositions are largely altered during deep burial diagenesis complete isotopic homogenization does not occur 18 o and 13 c analyses of 200 calcrete and palustrine carbonates from different stratigraphic horizons and comparison with 18 o of more robust bioapatite fossil vertebrate tooth phase show that dense micrites 70 carbonate invariably preserve the pristine 18 o value mean of 9 8 while altered carbonates show much lower 18 o value 13 8 such inhomogeneity causes large intra sample and intra soil profile variability as high as 5 suggesting that soils behave like a closed system where diagenetic overprinting occurs in local domains a simple fluid rock interaction model suggests active participation of clay minerals to enhance the effect of fluid rock ratio in local domains during diagenesis this places an upper limit of 70 micrite concentration above which the effect of diagenetic alteration is minimal careful sampling of dense micritic part of the soil carbonate nodules therefore does provide pristine isotopic composition and it is inappropriate as proposed recently to reject the paleoclimatic potential of all paleosol carbonates affected by burial diagenesis based on pristine 13 c value of 8 8 0 2 in soil carbonates an atmospheric co 2 concentration between 764 and 306 ppmv is estimated for the early oligocene 31 ma dagshai time these data show excellent agreement between two independent proxy records viz soil carbonate and marine alkenone and support early oligocene survival of the antarctic ice sheet

the palaeoecology of the non mammalian cynodonts diademodon and cynognathus from the karoo basin of south africa using stable light isotope analysis abstract the palaeoecology of the coeval middle triassic non mammalian cynodonts diademodon and cynognathus therapsida remains poorly understood although their gross morphology has been studied intensively significant differences in their growth patterns suggest inherent biological differences despite having inhabited similar environments in this study the palaeoecology of cynognathus and diademodon specimens were examined using intra tooth stable carbon and oxygen isotope analyses of enamel carbonate the resulting stable isotope patterns of cynognathus and diademodon were compared with that of crocodylus niloticus and published mammalian tooth enamel data predictably the non mammalian cynodont 13 c values fall within the expected range for c 3 plant diets both 18 o and 13 c values of diademodon are markedly more depleted than those of cynognathus suggesting that the former fed in shadier damper areas was nocturnal and or depended more directly on environmental water the seasonal amplitude reflected in the cynognathus teeth is relatively low however high amplitude directional 18 o intra tooth variations in the diademodon teeth are comparable to or higher than those observed for extant mammalian and c niloticus teeth from semi arid seasonal regions this suggests that marked seasonality prevailed in the karoo basin during the middle triassic and that diademodon was sensitive to these variations these isotopic differences between diademodon and cynognathus indicate differing responses to climatic fluctuations and reveal new insights into the palaeoecology of non mammalian cynodonts

oxygen isotopes of east asian dinosaurs reveal exceptionally cold early cretaceous climates early cretaceous vertebrate assemblages from east asia and particularly the jehol biota of northeastern china flourished during a period of highly debated climatic history while the unique characters of these continental faunas have been the subject of various speculations about their biogeographic history little attention has been paid to their possible climatic causes here we address this question using the oxygen isotope composition of apatite phosphate from various reptile remains recovered from china thailand and japan values indicate that cold terrestrial climates prevailed at least in this part of asia during the barremian early albian interval estimated mean air temperatures of about 10 4 c at midlatitudes 42 n correspond to present day cool temperate climatic conditions such low temperatures are in agreement with previous reports of cold marine temperatures during this part of the early cretaceous as well as with the widespread occurrence of the temperate fossil wood genus xenoxylon and the absence of thermophilic reptiles such as crocodilians in northeastern china the unique character of the jehol biota is thus not only the result of its evolutionary and biogeographical history but is also due to rather cold local climatic conditions linked to the paleolatitudinal position of northeastern china and global icehouse climates that prevailed during this part of the early cretaceous

comparison of gpr 2d resistivity and traditional techniques for the subsurface exploration of the oschingen landslide swabian alb germany abstract numerous rotational and translational slides of different sizes cause considerable economic damage in the swabian alb sw germany and are a challenge for risk assessment the oschingen landslide is a typical example for landslides occurring along the escarpment lithology consists of jurassic sedimentary rocks involving clays overlain by marls and limestones a combination of traditional methods drilling mapping inclinometers and geophysical techniques 2d resistivity ert ground penetrating radar gpr was applied to gain knowledge about the thickness and internal structure of the landslide the drillings and penetration tests provided point information on landslide extent structure and material involved in general all inclinometers showed very little movement if at all the gpr results were affected by strong signal attenuation and by overhead reflections from the nearby woods despite these general obstacles for the application of gpr on landslides near surface sediment structures were detected in the 2d resistivity sections higher resistive limestone blocks reaching 10 15 m in thickness could be clearly distinguished from the underlying bedrock the detailed two dimensional data of the electrical resistivity tomography ert along with the rather high survey speed turned out to be the best choice to gain detailed spatial information on thickness and extent of the slope movement the measured profiles coincide with the gpr data and correspond to borehole data surprisingly all results from the applied methods clearly detected the absence of large landslide blocks in the north west of the study area this finding could not be concluded from local geomorphology of this area regarding the current landslide displacement derived from the inclinometer measurements the large landslide blocks seem to be dormant during the measured period

pseudo 3d imaging of a low slip rate active normal fault using shallow geophysical methods the geleen fault in the belgian maas river valley in a detailed site survey for paleoseismic trenching we applied shallow geophysical prospecting techniques including ground penetrating radar gpr electric resistivity tomography ert and resistivity mapping to identify locate and visualize in 3d the geleen fault an active normal fault bordering the roer valley graben in northeast belgium because of a low slip rate the geomorphic expression of this fault is very faint in the relatively young deposits of the maas river valley ert profiles show the fault as a broad near vertical anomaly characterized by sharp lateral resistivity contrasts with an associated vertical offset of sediment layers we observed offsets of 15 m and 5 m for the base and top respectively of a middle late pleistocene fluvial gravel layer shallow ert and gpr profiles indicate that younger sediments are also affected by faulting but the amount and sense of offset appear to be conflicting ert profiles show a near surface high resistivity layer with an apparent rever

timescales and mechanisms of ree and hf uptake in fossil bones abstract rare earth element ree patterns of fossil bones and teeth are widely used as proxies for provenance taphonomy and palaeoenvironment in order to investigate if fossil bones behave as closed systems over geologic time ree profiles were analysed by la icpms along cross sections of 54 bones from various well characterised and well dated settings these include terrestrial and marine diagenetic environments covering early triassic to holocene ages in general all fossil bones exhibit the highest ree concentrations at the outer rim gradually decreasing by up to four orders of magnitude toward the inner bone cortex intra bone ree concentration gradients decrease significantly from quaternary via tertiary to mesozoic specimens suggesting long term ree uptake and open system behaviour of fossil bone this view is further corroborated by 176lu 176hf dating of selected samples all yielding significantly younger ages than the known chronostratigraphic ages hence there is clear evidence for long term open system behaviour of fossil bones with respect to ree which is in marked contrast to currently accepted models suggesting that ree uptake is only early diagenetic although unexpected statistically significant four to seven point isochrons are observed for four fossil dinosaur bone samples and one upper triassic mastodonsaurus tooth with mswds ranging from 0 083 to 4 5 notably mobility of lu alone cannot account for the observed age patterns assuming constant lu uptake rates over time the radiometric ages should only be as low as half of the chronostratigraphic age however a six point isochron defined by subsamples of a single upper triassic mastodonsaurus tooth yields an age of 65 2 1 1 ma mswd 0 68 much younger than half of the stratigraphic age ca 234 ma hence hf must also undergo late diagenetic exchange likely mechanisms to account for the presence of statistically meaningful isochrons as well as for the late diagenetic exchange of both ree and hf are diffusion adsorption and dissolution reprecipitation processes

ground penetrating radar investigation of active faults along the dead sea transform and implications for seismic hazards within the city of aqaba jordan abstract ground penetrating radar gpr was used in an effort to locate a major active fault that traverses aqaba city jordan measurements over an exposed trenched cross fault outside of the city identify a radar signature consisting of linear events and horizontal offset flexured reflectors both showing a geometric correlation with two known faults at a control site the asymmetric linear events are consistent with dipping planar reflectors matching the known direction of dip of the faults however other observations regarding this radar signature render the mechanism generating these events more complex and uncertain gpr measurements in aqaba city were limited to vacant lots seven gpr profiles were conducted approximately perpendicular to the assumed strike of the fault zone based on regional geological evidence a radar response very similar to that obtained over the cross fault was observed on five of the profiles in aqaba city although the response is weaker than that obtained at the control site the positions of the identified responses form a near straight line with a strike of 45 although subsurface verification of the fault by trenching within the city is needed the geophysical evidence for fault zone location is strong the location of the interpreted fault zone relative to emergency services military bases commercial properties and residential areas is defined to within a few meters this study has significant implications for seismic hazard analysis in this tectonically active and heavily populated region

a large mamenchisaurid from the junggar basin xinjiang people s republic of china an articulated neck of a large mature sauropod with enormously elongated cervical ribs was discovered in strata of late jurassic age in the eastern junggar basin xinjiang people s republic of china the animal is estimated to have originally measured 26 m in length but was lightly proportioned relative to brachiosaurus and apatosaurus rudimentary spines on the anteriormost cervical vertebrae diagnose a previously undescribed species of mamenchisaurus cranial parts associated with the neck do not support a close relationship with diplodocids mamenchisaurs apparently belong to an endemic jurassic radiation of asian sauropods

diagenesis and reservoir potential of permian triassic fluvial lacustrine sandstones in the southern junggar basin northwestern china the junggar basin is one of the largest oil producing areas in china and contains upper permian lacustrine oil shales with some of the greatest hydrocarbon potental in the world in this study we present the diagenetic characteristics of permian triassic sandstones from the southern junggar basin and evaluate their reservoir potential the uppermost permian and lower triassic cangfanggou group in the southern junggar basin is characterized by alternating fluvial and lacustrine deposits whereas the middle upper triassic xiaoquangou group was deposited predominantly in a lacustrine environment fluvial and deltaic sedimentation was subordinate the sandstones of the cangfanggou and xiaoquangou groups are volcanic litharenites their detrital modes and textures of volcanic fragments suggest a primarily andesitic basaltic volcanic arc provenance early diagenesis of the sandstones is characterized by nonferroan calcite cementation grain coating pore lining clay minerals and the initial dissolution of detrital grains authigenic quartz pore filling phyllosilicates pore filling grain replacive zeolites albitized detrital plagioclase authigenic k feldspar copyright 1997 the american association of petroleum geologists all rights reserved 1manuscript received april 15 1996 revised manuscript received november 4 1996 final acceptance may 2 1997 2department of earth sciences university of western ontario london ontario n6a 5b7 canada 3school of geosciences queen s university of belfast belfast bt7 1nn united kingdom this work was done at the queen s university of belfast with funding from exxon bhp mobil and itotal which we gratefully acknowledge the karamay institute of petroleum exploration and development generously provided borehole samples geng ansong at the institute of geochemistry guangzhou academia sinica and zhou yisheng at the xinjiang institute of petroleum are thanked for assistance with field work and for valuable discussions special thanks go to the staff of the electron microscopy unit at the queen s university of belfast we also thank a h ruffell and s r lawrence for their constructive comments on an earlier version of the manuscript stable isotope analysis and ongoing research concerning the junggar basin at the university of western ontario have been supported by the natural science and engineering research council of canada the manuscript benefited substantially from critical commentary by kevin t biddle suzanne kairo w r kaiser and an anonymous reviewer