calcareous nannofossil zonation of the jurassic cretaceous boundary interval and correlation with the geomagnetic polarity timescale abstract calcareous nannofossil stratigraphy has been investigated in six european land sections and at two deep sea drilling project sites 391c and 534a ranging from the upper kimmeridgian to the lower valanginian most of the sections contain a continuous record of the jurassic cretaceous boundary interval a time of rapid increase in nannofossil abundance and diversity and allow development of a revised nannofossil zonation scheme for this period numerous nannofossil lineages have been studied in detail and the results help to increase potential stratigraphic resolution in this interval the proposed scheme consists of six zones which are units recognizable in all sections regardless of nannofossil preservation and eleven subzones determinable in all but the most poorly preserved material thirty eight additional biohorizons are proposed based on the stratigraphy of the two dsdp sites these can be accurately established only in moderately well preserved material but spotty occurrences of these taxa in other sections may be stratigraphically useful most of the sections studied have been investigated magnetostratigraphically and the results of this study allow correlation between nannofossil zonation and the geomagnetic polarity time scale magnetostratigraphy indicates that many nannofossil events can be quite precisely determined and are not significantly time transgressive finally the magnetostratigraphic definitions of two stage boundaries are refined the kimmeridgian tithonian and berriasian valanginian boundaries are placed within chrons cm22n and cm15n respectively two new genera faviconus and umbria and seven new species are described umbria granulosa rhagodiscus nebulosus cretarhabdus octofenestratus faviconus multicolumnatus nannoconus infans nannoconus compressus and nannoconus wintereri eight subspecies and three taxonomic emendations are also described

thermal stresses differential subsidence and flexure at oceanic fracture zones geosat geoid undulations over four pacific fracture zones have been analyzed after correcting for the isostatic thermal edge effect the amplitudes of the residuals are shown to be proportional to the age offset the shape of the residuals seems to broaden with increasing age both geoid anomalies and available ship bathymetry data suggest that slip must sometimes occur on the main fracture zone or secondary faults existing models for flexure at fracture zones cannot explain the observed anomalies a combination model accounting for slip and including flexure from thermal stresses and differential subsidence is presented our model accounts for lateral variations in flexural rigidity from brittle and ductile yielding due to both thermal and flexural stresses and explains both the amplitudes and the shape of the anomalies along each fracture zone the best fitting models have mechanical plate thicknesses that are described by the depth to the 600 700 c isotherms

geomorphic response to seasonal variations in rainfall in the southwest united states the interaction of the north american monsoon with watershed hydrology and landscape response is evaluated by observing geomorphic characteristics of hillslopes hydrology and stream channels in two mountain ranges with contrasting intensity of precipitation the study compares watersheds in the hualapai and santa catalina mountains in arizona which are similar in lithology elevation tectonic setting vegetation and annual precipitation but differ in the proportion of precipitation received in summer thunderstorms the hualapai mountains receive most of their precipitation in winter whereas rainfall in the santa catalina mountains occurs mostly in summer drainages in the santa catalinas are more variable in local relief and exhibit much more exposed bedrock and higher drainage density the trunk channel of a major drainage in the santa catalina mountains has measured discharges several orders of magnitude greater than a channel draining a comparable area in the hualapai mountains the alluvial segment of the channel in the santa catalina piedmont additionally displays greater concavity smaller width to depth ratios and a larger caliber of bed material in contrast to conventional interpretation summer monsoonal precipitation is not primarily responsible for generating most of the discharges that modify channels in large scale drainages in the monsoonal climate regime of the santa catalinas small basins flood most often in summer whereas larger drainages exhibit peak discharges in response to low intensity winter precipitation we attribute the paradoxical discharge response of larger drainages to the small spatial scale of summer thunderstorms which fail to deliver enough precipitation to generate floods in these larger basins but do prime hillslopes by stripping colluvium and lowering hillslope infiltration rates making the large drainages more responsive to areally extensive winter storms

oceanic propagation of a potential tsunami from the la palma island 1 the likelihood of a large scale tsunami from the la palma island is considered small by most nevertheless the potential catastrophic consequences call for attention here we report on numerical simulations of a tsunami that might result from the extreme case of a flank collapse of the cumbre vieja volcano at the la palma island done by combining a multimaterial model for the wave generation with boussinesq models for the far field propagation our simulations show that the slide speed is close to critical effectively generating an initial wave of several hundred meters height our main focus is the wave propagation which is genuinely dispersive in the far field propagation becomes increasingly complex due to the combined effects of dispersion refraction and interference in the direction of propagation constructive interference of the trailing waves are found to decrease the decay of the maximum amplitude with distance compared to classical asymptotic theory at transatlantic distances thus the commonly used hydrostatic models fail to describe the propagation consequences of the la palma scenario would be largest at the canary islands but our findings also suggests that the whole central atlantic would face grave consequences however the largest surface elevations are smaller than the most pessimistic reports found in literature we also find undular bores towards the shorelines of america

the storegga slide tsunami comparing field observations with numerical simulations abstract deposits from the storegga tsunami have been found in coastal areas around the norwegian sea and north sea from the northeast coast of england to beyond the arctic circle in northern norway the tsunami deposits reach onshore elevations of 10 12 m above sea level of their time in western norway 3 6 m in northeast scotland and above 20 m on the shetland islands these elevations are compared with surface wave elevations derived from a numerical simulation of the storegga slide a good agreement is obtained for a retrogressive slide that descends at 25 30 m s and that has short time lags of 15 20 s between each individual slide block

paleomagnetism of the istria peninsula yugoslavia 280 core samples were collected from upper jurassic cretaceous and eocene sediments outcropping in the istria peninsula yugoslavia due to the very low intensities of the initial natural remanent magnetizations more than 50 of the collection consisting mainly of rock samples of jurassic and eocene sediments was not suitable for paleomagnetic studies the cretaceous samples yield a mean paleomagnetic pole lat 53 long 275 and 95 4 8 which is significantly different from the african and european paleomagnetic poles of the same age the position of the istria peninsula on the autochthonous adriatic platform allows the result to be interpreted as applicable to all the autochthonous periadriatic region this new paleomagnetic result indicates that the autochthonous adriatic platform rotated counterclockwise over an angle of about 30 with respect to africa in post mesozoic times

palaeomagnetically inferred tectonic rotations of the abruzzi and northwestern umbria abstract palaeomagnetic results are presented from the abruzzi and northwestern umbria monte nerone area for the cretaceous and the combined jurassic and cretaceous timespans the results for the cretaceous when combined with previously published work indicate that both the abruzzi and northwestern umbria underwent a post cretaceous tectonic rotation relative to apulia the rotation of the abruzzi is 40 clockwise while that of northwestern umbria is 22 23 counterclockwise apulia itself has been rotated only 11 relative to africa according to a recently proposed apparent polar wander path for africa

numerical simulation of waves generated by landslides using a multiple fluid navier stokes model abstract this work reports on the application and experimental validation for idealized geometries of a multiple fluid navier stokes model of waves generated by rigid and deforming slides with the purpose of improving predictive simulations of landslide tsunamis in such simulations the computational domain is divided into water air and slide regions all treated as newtonian fluids for rigid slides a penalty method allows for parts of the fluid domain to behave as a solid with the latter method the coupling between a rigid slide and water is implicitly computed rather than specifying a known slide kinematics two different volume of fluid algorithms are tested for tracking interfaces between actual fluid regions the simulated kinematics of a semi elliptical block moving down a water covered plane slope is first compared to an earlier analytical solution results for the vertical fall of a rectangular block in water are then compared to earlier experimental results finally more realistic simulations of two and three dimensional wedges sliding down an incline are compared to earlier experiments overall in all cases solid block velocities and free surface deformations are accurately reproduced in the model provided that a sufficiently resolved discretization is used the potential of the model is then illustrated on more complex scenarios involving waves caused by multi block or deformable slides

the last phase of the storegga slide simulation of retrogressive slide dynamics and comparison with slide scar morphology the prehistoric storegga slide one of the world largest known submarine slides took place about 8200 years ago most likely the slide was triggered by an earthquake in a steeper slope area in the distal part of the slide the present day s morphology of the slide area indicates that major parts of the slide took place as a sequential failure process spreading successively from the far end to the present shelf edge numerical simulations illustrating this retrogressive back stepping behaviour are presented for the last phase of the storegga slide as it reached today s upper headwall the applied rheological model is based on a bingham fluid with a history dependent yield strength and consistency

paleomagnetic data from umbria italy implications for the rotation of adria and mesozoic apparent polar wander paths abstract sixteen new jurassic and cretaceous paleomagnetic sampling sites are located in northern umbria along three river valleys bosso burano sentino the late jurassic and early cretaceous data are consistent in declination but not inclination with previously published data from these valleys early jurassic data from eight sites give site mean declinations which are significantly different from the two site mean declinations of this age which were previously available comparison of the data with cretaceous and jurassic mean directions from the southern alps indicate 20 anticlockwise rotation relative to the southern alps of this part of northern umbria during neogene deformation of the umbrian fold and thrust belt if the umbrian mean directions are rotated to compensate for the tectonic rotation the early jurassic and cretaceous umbrian and southern alpine pole positions coincide closely with a recently derived african apparent polar path apwp implying that adria moved with africa since at least early jurassic times the late jurassic umbrian and southern alpine poles however are not consistent with current apwps and imply rapid apparent polar wander in both african and north american coordinates from high latitude to lower latitude between bathonian and oxfordian times

jurassic magnetostratigraphy 2 middle late oxfordian of aguilon iberian cordillera northern spain abstract a reproducible magnetic polarity pattern has been obtained from four overlapping stratigraphic sequences of ammonite rich gray pelagic limestones spanning part of the middle and late oxfordian g transversarium toe bimammatum ammonite zones progressive thermal demagnetization removed a present field overprint fold tests both between and within outcrops are positive the mean direction of magnetization is 322 45 95 6 which implies a paleolatitude of 26 n frequent changes of polarity were observed the magnetostratigraphic sequence contains the ammonite zones subzones and horizons of the tethyan faunal realm using the reference horizons provided by this detailed ammonite zonation the polarity zones can be readily correlated among all sections the composite polarity pattern is predominantly of reversed polarity punctuated by a number of relatively shorter duration normal polarity intervals in order to compare this sequence to that of the marine magnetic anomalies we have revised the age estimates for the pre m25 marine magnetic normaly pattern according to the most recent time scale based on those ages the sedimentary record at aguilon suggests a much greater frequency of polarity changes than does either model derived from the two sets of marine magnetic anomalies of this time this sedimentary record probably is a truer approximation of the actual geomagnetic polarity history because of the continuity of sedimentation in these sections and the inherent ambiguities involved in determining a polarity pattern from the very low amplitudes that everywhere characterize this part of the marine record

stochastic analysis of tsunami runup due to heterogeneous coseismic slip and dispersion 1 most tsunami models apply dislocation models that assume uniform slip over the entire fault plane followed by standard analytical models based on volterra s theory of elastic dislocations for the seabed deformation in contrast we quantify tsunami runup variability for an earthquake with fixed magnitude but with heterogeneous rupture distribution assuming plane wave propagation i e an infinitely long rupture a simple stochastic analysis of 500 slip realizations illustrates the expected variability in coseismic slip along a fault plane and the subsequent runup that occurs along a coastline in the near field because of the need for systematically analyzing different fault geometries grid resolutions and hydrodynamic models several hundred thousand model runs are required thus simple but efficient linear models for the tsunami generation propagation and runup estimation are used the mean value and variability of the maximum runup is identified for a given coastal slope configuration and is analyzed for different dip angles on the basis of the ensemble runs nonhydrostatic effects are discussed with respect to their impact on generation nearshore propagation and runup we conclude that for the geometry and magnitude investigated nonhydrostatic effects reduce the variability of the runup that is hydrostatic models will produce an artificially high variability

anoxic events productivity rhythms and the orbital signature in a mid cretaceous deep sea sequence from central italy albian pelagic sediments from the umbrian apennines exhibit rhythmic bedding in outcrop high temporal resolution 4 kyr spacing sampling of carbonate si and al along a 1 6 m y interval of core demonstrates that changes in accumulation rate of calcareous and siliceous microorganisms were controlled by insolation cycles optical densitometry logging correlates variations of geochemical parameters to episodes of deep sea anoxia indicated by numerous black laminated zones black shales harmonic analysis of data shows oscillations at three frequencies which correspond closely in estimated duration and ratio to the modern eccentricity and precessional orbital cycles as in pleistocene marine sequences the eccentricity approximately 100 kyr term dominates the sedimentary variance in the umbrian cycles anoxic episodes occur in phase with a limestone marl repetition and reflect minima of the precessional 21 kyr cycle the covariance of carbonate and silica with estimates of foraminiferal abundances suggest that carbonate cycles are the result of changes in surface productivity of calcareous organisms rather than an effect of dissolution or diagenesis recognition of orbital cyclicity provides a tool for making quantitative estimates of these changes productivity during anoxic events was uniformly low 0 4 0 5 g cm2 kyr carbonate 0 05 g cm2 kyr silica but it rose to high levels during oxygenated periods 1 2 5 g cm2 kyr carbonate 0 1 0 3 g cm2 kyr silica vertical overturning and organic carbon flux decreased during anoxic episodes but decreased oxygenation of the deep water led to enhanced preservation of the organic matter delivered the degree of paleoceanographic variability indicated by this study requires that accepted notions of climate stability and oceanic quiescence during nonglacial times be reassessed

numerical modeling of tsunami waves generated by the flank collapse of the cumbre vieja volcano la palma canary islands tsunami source and near field effects 1 in this work we study waves generated by the potential collapse of the west flank of the cumbre vieja volcano cvv la palma canary island spain through numerical simulations performed in two stages i the initial slide motion and resulting free surface elevation are first calculated using a 3d navier stokes model ii generated waves are then input into a 2d horizontal boussinesq model to further simulate propagation to the nearby islands unlike in earlier work on cvv besides a similar extreme slide volume scenario of 450 km3 in our simulations i we consider several slide scenarios featuring different volumes i e 20 40 80 km3 which partly result from a geotechnical slope stability analysis ii we use a more accurate bathymetry and iii an incompressible version of a multiple fluid material navier stokes model we find wave trains for each scenario share common features in terms of wave directivity frequency and time evolution but maximum elevations near cvv significantly differ ranging from 600 to 1200 m for increasing slide volume additionally our computations show that significant energy transfer from slide to waves only lasts for a short duration order 200 s which justifies concentrating our best modeling efforts on the early slide motion phase the anticipated consequences of such wave trains on la palma and other canary islands are assessed in detail in the paper

tsunami excitation by submarine slides in shallow water approximation landslide induced tsunamis are receiving increased attention since there is evidence that recent large devastating events have been caused by underwater mass failures normally numerical models are used to simulate tsunami excitation most of which are based on shallow water known also as long wave approximation to the full equations of hydrodynamics analytical studies may handle only simplified problems but help understand the basic features of physical processes this paper is an analytical investigation of long water waves excited by rigid bodies sliding on the sea bottom based on the shallow water approximation which is here derived by properly scaling euler equations for an inviscid incompressible and irrotational ocean in one dimensional 1 d cases where motion depends only on one horizontal coordinate under the further assumptions of small height slide which permits the recourse to linear theory and of flat ocean floor a solution for arbitrary body shape and velocity is deduced by applying the duhamel theorem it is also shown that this theorem can be advantageously used to obtain a general solution in case of a non flat ocean floor when the sea bottom follows a special power law that can be adapted to study reasonable bottom profiles the characteristics of the excited tsunamis are then evaluated by computing solutions in numerous examples with special focus on wave pattern and wave evolution the energy of the wave system is shown to depend on time it grows expectedly in the initial phase of tsunami generation when the moving body transfers energy to the water but it may also diminish later implying that a certain amount of energy may pass back from water waves to the slide

luminescence chronology of late pleistocene loess paleosol and tephra sequences near fairbanks alaska abstract thermoluminescence tl and infrared stimulated luminescence irsl sediment dating methods have been applied to paleosol and tephra bearing loess sequences younger than marine oxygen isotope stage mis 7 at three important sites tl ages indicate the development of significant paleosols 75 000 and 30 000 yr ago in the loess sequence at the gold hill site relatively minor soil development occurred 70 000 and 48 000 yr ago like the 75 000 yr old soil the 30 000 yr old soil is apparently of global extent and consistent in timing with inferred warm intervals elsewhere e g greenland europe western and central china at birch hill replicate tl dating of primary loess combined with two earlier tl results from the same site and with an earlier mean fission track glass shard age of 140 000 10 000 yr for the associated old crow tephra yield a more precise numeric age of 142 300 6600 yr for this alaska yukon chronostratigraphic marker ash bed three of the tl ages at the halfway house site are difficult to interpret but combined with other evidence they indicate 1 the upper 5 6 m of loess from halfway house is not part of the gold hill loess equivalent to pre mis 5 age as long thought by t l pewe but rather is much younger 2 the regionally significant variegated tephra found in the fairbanks and klondike areas and previously thought to be older than mis 5 has an age of 77 800 4100 yr late mis 5

structural applications and discussion of a paleomagnetic post paleozoic data base for the central mediterranean abstract a post paleozoic paleomagnetic data base has been compiled for the central mediterranean with the intention of listing directions at the highest possible level of data combination the value of the entries depends on the number and quality of data available the most reliable data are those based on regionally distributed localities and sites where the age is known to a stage and where tectonic correction has been made these represent a whole tectonic unit in a given period of time the lowest quality directions are those based on few samples and isolated in space and time in the tectonic interpretation of the listed data this variation in quality of data has been taken into consideration indications for cenozoic movements having a fundamental influence on the now observable distribution of the clockwise and counter clockwise rotated paleomagnetic directions were treated first and those for older movements afterwards microplate block and nappe movements were considered as possible mechanisms for the rotation of these the last two mechanisms explained satisfactorily the occasional local deviations from a general pattern other differences however such as those which exist between the northern calcareous alps or the tisza unit and the counter clockwise rotated superunit of the central mediterranean which are large and persisted through a longer period of time are best explained by independent movement of the whole unit

micromorphological study of irrigation canal sediments landscape evolution and hydraulic management in the middle gila river valley phoenix basin arizona during the hohokam occupation the hohokam were a long lived 300 1450 ad agrarian society in the deserts of southern arizona with an efficient irrigation system and a complex socio political organization dependent on environmental conditions they coped with hydrological and geomorphic changes which potentially had an impact on their cultural evolution irrigation canals were regularly maintained and or abandoned and their fills record secondary signatures of fluvial dynamics landscape change and land use micromorphological studies allow for the creation of a typology of canal fills based on semi quantitative measurements a synchronous and diachronic analysis of canal systems can then be undertaken by means of pedosedimentary correlation as part of cultural resource management projects on the gila river indian reservation south of phoenix studies have been conducted on the prehistoric santan irrigation system in use from the 10th to the 15th century ad phases of low flow were identified followed by alluvial fan flooding and seasonal deposition between the 10th 14th century ad sedentary early classic period during the 14th 15th century ad late classic period evidence of active erosion is initially recorded in the sediments followed by seasonal water supply and ultimately canal abandonment despite probable efficient irrigation

tracking recorded fires using charcoal morphology from the sedimentary sequence of prosser lake british columbia canada abstract quantitative analyses of variations in morphological features of charcoal were undertaken in a 210pb dated sediment core from prosser lake british columbia canada seven morphological types of charcoal were defined by particle shape major minor axis ratio apparent porosity and progradation to unburned material the distribution of morphotypes and total charcoal abundances were assessed as a proxy for fire events recorded between 1919 and 2000 and to subsequent mechanisms of transportation sedimentation to lake sediments charcoal morphotypes showed distinct relationships to recorded area burned by fires fragile charcoal fragments with highly irregular porosity termed type m displayed the strongest correlation to burned area r2 0 51 p 0 0001 and did not produce any false positive signal for fires recorded within a radius of 20 km around the lake we infer that high porosity and low density type m fragments are aerially transported and directly deposited on the lake and that the fragility of type m charcoal prevents significant quantities from being secondarily transported and incorporated into the sedimentary record we propose that charcoal morphology is an important but underutilized technique that can yield important insights into fire type proximity and transportation sedimentation processes

tsunami wave height dependence on landslide volume tsunami generation from submarine landslides depends mainly on the volume of the slide material and also on other factors which include angle of the slide water depth density of the slide material the speed with which the material moves duration of the slide etc based on an incomplete data set of volume v of slide versus maximum amplitude h of the resulting tsunami waves gleaned through available literature a simple linear regression relationship was developed another partial data set was developed also from published literature on v versus h values based on numerical models it was found that the agreement between the results of the numerical simulations and the observations is rather poor it is not clear why this is so and which data set is of questionable relevance this is not to cast doubt on numerical models that do not use volume of the slide in an explicit manner

a revised correlation of mesozoic polarity chrons and calpionellid zones investigation of four sections of tithonian to valanginian pelagic limestone have led to refinement of the correlation of calpionellid zones to the magnetic polarity time scale the correlations are self consistent but differ slightly from those previously published the discrepancy with the published correlation from the bosso section 1 has been resolved by re evaluation of the biostratigraphy of this sequence the revised correlation places the base of thechitinoidella zone in the lower part of polarity chron cm21n the base of zone a near the top of cm20n the a b boundary at the base of cm18 theb c boundary in the upper part of cm17 thec d boundary at the top of cm16 and thed e boundary at the top of cm14

magnetostratigraphy in pursuit of missing links since the last quadrennial report magneto stratigraphy has continued to flourish the primary issues have been 1 refinements to the geomagnetic reversal time scale grts including recalibrations correlation of biostratigraphic data to the crts and revision of the terminology 2 use of magnetostratigraphic data for estimating rates of such processes as sediment accumulation evolution and faunal migration and 3 magnetic mineralogy and the origin of remanence for convenience we have divided the publications into studies of continental and marine sediments and highlight the most exciting issues within each of these sub headings in the first section of this review we will concentrate on the development of the geomagnetic reversal time scale grts with particular emphasis on refinements from the last few years we then turn our attention to applications of magnetostratigraphy in marine and continental sequences

paleomagnetism of the lower cretaceous redbeds from northern spain evidence for a multistage acquisition of magnetization abstract an extensive study of the wealden series from the cantabric chain and the sierra de los cameros northern spain reveals that the n r m contains four types of components tentatively classified in decreasing ages the older components group 1 are considered as the primary magnetization they yield a paleomagnetic pole located at lat 41 n long 237 e n 6 k 186 95 5 this pole position implies the existence of a large upper jurassic lower cretaceous swing in the iberian polar wander path the comparison with other polar paths north america africa supports the hypothesis of an initial lower cretaceous rotation of iberia prior to the main mid cretaceous shift the remainder of the components represent remagnetizations the major phase groups 2 and 3 extended from the upper cretaceous to the eocene at least a period closely correlated with the period of convergence between the european and iberian plates the directions of group 3 are characterized by low inclination this is a common behaviour for eocene directions in the mediterranean area previous data obtained from the wealden redbeds largely agrees with the directions of one or other of the groups 2 and 3 as there is strong evidence of an acquisition subsequent to the main mid cretaceous movement of iberia the geodynamical inferences of the paleomagnetic data have to be re examined the last type of components group 4 was built up during recent remagnetization and is of little interest

the pedosedimentary evolution and chronology of tortugas a late quaternary type site of the northern pampa argentina new micromorphological magnetic susceptibility geochemical and geochronological data have been collected from tortugas a key late quaternary type site of the northern pampa argentina thus enabling the detailed reconstruction of the pedogenic and sedimentary history of this loess paleosol sequence paleosols developed in the ceres formation and the overlying lower member of the tezanos pinto formation retain evidence for leaching bioturbation and particularly clay translocation processes being dominant both paleosols are truncated evidence for water sorting and sediment reworking as well as continued bioturbation and redistribution of carbonates suggests that intervening depositional phases were complex the previously recorded hypsithermal soil developed in the upper member of the tezanos pinto formation has similar characteristics to the buried paleosols yet does not appear to have been truncated at this site and is only covered by a thin layer of sediment san guillermo formation this latter unit has been pedogenically welded onto the hypsithermal soil thus creating the present day surface soil complex a series of optically stimulated luminescence dates from throughout the sequence provide a stratigraphically consistent chronological framework ca 1 150 ka for the pedosedimentary reconstruction yet conflict with the previously reported thermoluminescence based chronology for the site and region ca 1 90 ka

new cretaceous paleomagnetic results from the foreland of the southern alps and the refined apparent polar wander path for stable adria abstract the central western and the eastern southern alps are separated by the triangular shaped adige embayment which belongs to stable adria and was the site of pelagic sedimentation from the tithonian through maastrichtian the first part of this study presents paleomagnetic results from the tithonian cenomanian biancone and turonian maastrichtian scaglia rossa formations sampled at 33 geographically distributed and biostratigraphically dated localities the new and high quality paleomagnetic results from the adige embayment are then combined with coeval paleomagnetic directions from autochthonous istria marton et al 2008 which also belongs to stable adria the combined data set which for the late albian maastrichtian time period is constructed similarly to the synthetic african curve by besse and courtillot 2002 2003 reveals an important tectonic event late aptian early albian characterized by 20 ccw rotation and sedimentary hiatus comparison between paleomagnetic declinations inclinations expected in an african framework i e with the assumption that adria is still an african promontory leads to the following conclusions the time distributed tithonian and berriasian 150 135 ma paleomagnetic directions exhibit the african hairpin with an inclination minimum and a sudden change from cw to ccw rotation at 145 ma concerning the younger ages the declinations for adria continue to follow the african trend of ccw rotation till the end of cretaceous however the tithonian maastrichtian declination curve for stable adria is displaced by 10 from the african curve as a result of two rotations the first an about 20 cw rotation of adria with respect to africa took place between the maastrichtian and the mid eocene during this time the orientation of adria remained the same while africa continued its ccw rotation the younger rotation 30 ccw changed the orientation of adria relative to africa as well as to the present north

february 2003 marine atmospheric conditions and the bora over the northern adriatic 1 a winter oceanographic field experiment provided an opportunity to examine the atmospheric marine conditions over the northern adriatic mean february winds are from a northeasterly direction over most of the adriatic and a more northerly direction along the western coast wind speeds are fastest in jets over the ne coast during bora events and weakest in the mid northwestern adriatic diurnal air temperature cycles are smallest on the ne coast and largest in the midwestern adriatic the maximum sea air difference is 10 c on the eastern coast and near zero on the midwestern adriatic boras are northeasterly from wind events that sweep off croatia and slovenia bringing slightly colder and drier air over the northern adriatic the main bora season is december to march winter 2002 2003 was normal for bora events synoptic scale temporal variations are correlated over the northern adriatic fastest bora winds and highest wind stress over the northern adriatic is concentrated in four topographically controlled jets the strongest is the senj jet while the trieste jet extends across the entire northern adriatic between each two jets is a weak wind zone the greatest mean net heat loss is in bora jets in the ne adriatic where it was 438 w m 2 and is weakest in the midwestern northern adriatic where it was near zero wind stress is concentrated over the ne half of adriatic in four bora jets while wind stress is weak in the nw adriatic there is significant variation in wind stress mean and standard deviation structure over the northern adriatic with each bora event

reappraisal of paleomagnetic data from gargano south italy vandenberg j 1983 reappraisal of paleomagnetic data from gargano south italy in e mcclelland brown and j vandenberg editors palaeomagnetism of orogenic belts tectonophysics 98 29 41 the platform limestones of apulia italy outcropping in the gargano peninsula have been restudied paleomagnetic research has been carried out on upper cretaceous lower cretaceous and jurassic rocks despite the low intensities of the nrm 10 100 pa m all samples 268 could be cleaned by stepwise a f and or thermal demagnetization treatments nrm directions could be determined accurately and reproducibly for 85 of the samples using a sct cryogenic magnetometer and double precision measuring procedures nrm of the jurassic limestone is carried by secondary haematite and the results are therefore rejected from further consideration the upper and lower cretaceous limestones have an nrm carried by magnetite minor bedding tilt corrections improve the grouping of the site mean results the upper cretaceous scaglia limestone turonian senonian reveals a characteristic mean direction of decl 327 7 incl 38 2o a ss 4 3 21 sites while the lower cretaceous maiolica limestone neocomian aptian albian reveals a characteristic mean direction of decl 303 1 o incl 35 1 as s 8 7o 8 sites the cretaceous results show a post aptian albian counterclockwise rotation of about 25 which is expressed by the smeared distribution of the late cretaceous site mean results and a post senonian i e tertiary counterclockwise rotation of the same amount with respect to the pole these results are in excellent agreement with contemporaneous paleomagnetic results from other peri adriatic regions a tertiary counterclockwise rotation of all the stable adriatic block is strongly supported by the new results

late jurassic early cretaceous magnetic stratigraphy from the sumeg section hungary abstract the pelagic limestones exposed at sumeg appear to represent continuous deposition from kimmeridgian through berriasian detrital magnetite and haematite pigment are the carriers of remanence in the red and non red limestones in the lower part while magnetite becomes predominant in the upper half of the section thermal demagnetization has succesfully removed overprint magnetizations and a well defined magnetic stratigraphy has been obtained the late jurassic early cretaceous mixed polarity interval is correlated with the sequence of geomagnetic reversals derived from oceanic magnetic anomalies

milankovitch climatic origin of mid cretaceous black shale rhythms in central italy the earth s orbital variations reflected in pleistocene ice volume were also recorded in non glacial times carbonate production in pelagic mid cretaceous sediments quantified by calcium carbonate and optical densitometry time series reflects the orbital eccentricity and precessional cycles minimal eccentricity brought deep sea anoxia most of the sedimentary variability of this 100 myr old sequence lies within the milankovitch orbital frequency band

controlling factors for post failure evolution of subaqueous landslides subaqueous slope failures can evolve in various patterns whereas some slides run out and further evolve into highly mobile turbidity currents others maintain a continuum like structure and remain

multiple miocene block rotation in the bakony mountains transdanubian central range hungary abstract the bakony mountains of the transdanubian central range hungary are located in the western part of the pannonian basin their neogene structure is dominated by right lateral strike slip faults with offsets of up to 5 km these faults are organized in two sets the older one trending wnw is offset by the younger nw trending set neither set of faults i e the ne trending left lateral raba and balaton major strike slip faults extends across the boundary faults it is proposed here that the late miocene structural evolution of the bakony mountains can be best explained in terms of multiple block rotation on the basis of this simple geometric model a 15 counterclockwise rotation is suggested as a working hypothesis for the entire tectonic unit previous paleomagnetic measurements conform well to the block rotation predicted by the model the proposed detachment for the rotated rigid upper crustal blocks is a regional decoupling surface at an average depth of 10 km this surface probably emanated from a nappe system of cretaceous age

a refined apparent polar wander curve for the transdanubian central mountains and its bearing on the mediterranean tectonic history abstract recently obtained palaeomagnetic data have given a fairly detailed apparent polar wander a p w curve for the mesozoic of the transdanubian central mountains which has been compared with other a p w curves from the mediterranean area the similarity of the a p w curves enabled a unified a p w curve to be constructed for the central mediterranean region it has been shown that the new mediterranean a p w curve is in full agreement even in details with the updated a p w curve for africa this confirms the existence during the entire mesozoic of a single central mediterranean megatectonic unit rigidly attached to africa its positions with respect to the pole can now be traced back in more detail than before

catastrophic failure of submerged slopes in normally consolidated sediments the application of fracture mechanics methods to shear band growth in granular materials requires careful consideration of the elasto plastic nature of the material behaviour in this paper the palmer and rice fracture mechanics approach is applied to the problem of catastrophic shear band propagation in a submerged slope built of normally consolidated sediments this allows for catastrophic unstable and progressive stable types of soil failure to be properly distinguished many submerged landslides are triggered by earthquakes via the shear strength degradation due to the excess pore water pressure accumulation the conventional analysis assumes that the excess water pressure zone develops simultaneously along the entire landslide length often reaching several kilometres when a mechanism of the catastrophic shear band propagation is considered a much shorter excess water pressure zone e g several hundred metres can still cause a full scale landslide often generating a tsunami wave of consid

an integrated socio environmental approach to the study of ancient water systems the case of prehistoric hohokam irrigation systems in semi arid central arizona usa water systems lie at the interface between nature and culture and in that perspective are a rich but under explored research object their temporalities construction maintenance abandonment represent an image of a social cultural economic and political context as well as changing environmental conditions this socio environmental signature recorded in the spatial organization sedimentary fill and profile of hydraulic structures can be reconstructed by means of a systemic cross disciplinary approach geoarchaeology chronology and paleoenvironment the principle and limits of the methods applied to this research object are presented and discussed in this paper while they can be applied to different environmental contexts they will be presented through the example of hohokam irrigation systems in the semi arid phoenix basin arizona where this approach has been applied as a whole as water systems are structural elements of the spatial and socio political organization of societies this approach will provide elements to discuss the relative impact of human and or environmental factors on landscape change and cultural shifts and measure the long term vulnerability and resilience of agricultural communities to regional environmental changes

mesozoic palaeomagnetism of the transdanubian central mountains and its tectonic implications abstract the mesozoic apparent polar wandering apw of the transdanubian central mountains determined from thermally isolated natural remanences at 13 localities shows a remarkable similarity to the mesozoic apw of africa in that they both exhibit the same loop like movement moreover the difference between the two apw s can practically be eliminated by a 35 clockwise rotation of the palaeodeclinations it is concluded therefore that the region of the transdanubian central mountains was part of the african adriatic plate up to some time in the cenozoic when it moved to its present position resulting in a 35 anticlockwise rotation relative to africa

palaeomagnetic evidence of tectonic rotations in the southern margin of the inner west carpathians abstract palaeomagnetic samples were collected at 33 triassic localities from three nappes and a pseudo autochthonous unit in the aggtelek rudabanya mountains in order to establish the rotation pattern of the area as a whole with respect to the enclosing principal continents and to check whether relative movements in the past between the various units that make up the region are resolvable by the palaeomagnetic data after detailed thermal demagnetization and careful data selection it has emerged that the entire study area was rotated anticlockwise with respect to both europe and africa i e in a similar manner and to a similar degree as other units in the central mediterranean region e g the transdanubian central mountains on the other hand small scale relative movements such as those between the aggtelek and rudabanya areas are not apparent in the present data

environmental setting of the early irrigation in oasisamerica paleopedological evidences from the alluvial palaeosols in la playa sonoran desert abstract environmental conditions and human landscape interaction during the onset of the irrigated agriculture in oasisamerica are not clear yet in la playa site sonora nw mexico the evidences of sedentary population land cultivation and water management developed after the end of altithermal period around 4500 yr bp include more than 550 archaeological features including hundreds of human cremations and a net of buried artificial channels these findings were closely associated with several palaeosol levels alternating with sediments within a large alluvial fan we studied micromorphological features physical characteristics color texture rock magnetic properties and composition of organic matter from three profiles maravillas zanja and cuatro suelos to reconstruct pedogenesis and sedimentary environment of the palaeosol sequences additional paleoenvironmental information was extracted from pollen assemblages extracted from the cuatro suelos profile the results pointed to a long period of geomorphic and climatic stability in the early middle holocene marked by a well developed red cambisol this period was followed by an unstable interval around 4 5 kyr bp marked by severe erosion of earlier soil profiles and sedimentation of different kind channel floodplain and fluvio eolian later synsedimentary fluvisols were formed showing signs of predominantly arid pedogenesis interrupted by occasional flooding indicators of human impact were also encountered we conclude that the shift to irrigated agriculture as the main subsistence activity occurred during the period of major climatic and geomorphic fluctuation and then irrigation developed further under dry environment with limited water resources during the late holocene

model simulations of tsunamis generated by the storegga slides abstract a mathematical model based on the hydrodynamic shallow water equations is developed for numerical simulation of water waves generated by the submarine storegga slides on the norwegian continental slope the equations are solved numerically by a finite difference technique computations of wave amplification effects reveal run up heights for the second storegga slide between 3 and 5 m in exposed areas along the eastern coast of greenland iceland and scotland and the western coast of norway the calculated run up heights agree remarkably well with possible tsunami wave heights deduced from geological evidences along the eastern coast of scotland the generated wave heights are strongly dependent on the acceleration of the slide the effects of shear stress at the interface between the water and the slide body has turned out to be important

effectiveness of natural zeroing of the thermoluminescence in sediments the last exposure to sunlight of detrital feldspars and quartz grains in quaternary sediments can be dated directly by thermoluminescence tl methods but the effectiveness of zeroing of the light sensitive tl signal by daylight varies widely depending upon details of the sedimentation processes to document this variability and to help develop objective criteria useful for future sample selection and laboratory procedures i have collected and analyzed several eolian fluvial marine deltaic and lacustrine samples from less than 100 year old deposits as well as suspensions from sediment plumes also underwater spectral irradiance was measured during recovery of suspensions tl properties of polyrnineralic feldspar dominated 2 4 m and 4 11 m size fractions were measured in the laboratory unexpectedly some light sensitive tl was found to remain in all samples however the light sensitive tl was more effectively zeroed in some samples a proximal loess a sandy braided channel deposit tidal flat and upper delta front muds and thin clayey lacustrine laminae than in others a silty braided channel deposit submarine fan muds and silt bearing lacustrine laminae for the first group the minimum relict paleodose obtained with the partial bleach technique is about 0 4 0 3 gy corresponding to a relict tl age estimate of about 200 years for these sediments thus similar sediments excluding fluvial deposits as young as about 2 ka can be accurately and routinely dated without significant correction for a zero point error if one uses the partial bleach technique coupled with integrated optical bleaching energy fluences of less than 1 j cm 2 and wavelengths only above about 550 nm also some simple optical bleaching tests are reported that have a potential use in sample selection and in provenance studies of some surficial detrital sediments finally a simple mathematical model is presented that helps account for the gross features of the observed bleaching response curves

biostratigraphic correlation of mesozoic polarity chrons cm1 to cm23 at capriolo and xausa southern alps italy abstract two pelagic limestone sections in the southern alps spanning the kimmeridgian late jurassic to barremian early cretaceous interval yield magnetostratigraphies which can be correlated to oceanic magnetic anomalies m1 m3 and m8 m23 this includes the interval m11 m13 which has not previously been correlated to a sedimentary section detailed investigations of nanofossils and calpionellids in these sequences allow precise correlation of polarity chrons to biostratigraphic events and these results compare favorably to those of previous studies the close correspondence in polarity pattern between that interpreted from the m8 to m15 interval in the hawaiian lineations and that recorded at the capriolo section suggests that sedimentation rates in this sequence and spreading rates in the hawaiian lineations were rather constant during this interval in contrast the sedimentation rate at the xausa section appears to increase up section with the facies transition from the rosso ammonitico to the maiolica formation

valanginian to aptian calcareous nannofossil stratigraphy and correlation with the upper m sequence magnetic anomalies abstract calcareous nannofossil stratigraphy has been investigated in lower cretaceous italian sections at gorgo a cerbara presale and frontale all in the umbrian apennines and at cismon southern alps a modified sample preparation technique has allowed a thorough stratigraphic study of the well lithified maiolica limestone and although nannofossil preservation is generally quite poor the major valanginian to aptian marker species can be detected nine nannofossil events can be determined and correlated to magnetic stratigraphies previously established in these sections nannofossil stratigraphy confirms most magnetostratigraphic correlations made between sections and allows a more precise correlation of magnetic chrons m 0 to m 11 with the valanginian hauterivian barremian and aptian stages the results obtained differ considerably from previous timescales nannofossil events recorded in the various sections may be time transgressive by as much as one magnetic chron probably due to differential preservation

radiocarbon dating and the old wood problem the case of the hohokam chronology abstract many archaeological chronologies including that of the hohokam in southern arizona are based on a series of radiocarbon dates on wood this paper argues that because of variability in rates of wood decay processes in the environment and in systemic context such archaeological chronologies are potentially biased towards excessive antiquity by an old wood problem and must be reassessed following the theoretical insights of dean 1978 this paper sets forth principles and procedures for relating radiocarbon dates to cultural events emphasis is placed on identifying and taking into account the formation processes of 1 the dated specimens and 2 the deposits that yielded them this methodological framework is applied to hohokam radiocarbon dates and a chronology much shorter than the original gladwin haury formulation is supported

did a submarine landslide contribute to the 2011 tohoku tsunami many studies have modeled the tohoku tsunami of march 11 2011 as being due entirely to slip on an earthquake fault but the following discrepancies suggest that further research is warranted 1 published models of tsunami propagation and coastal impact underpredict the observed runup heights of up to 40 m measured along the coast of the sanriku district in the northeast part of honshu island 2 published models cannot reproduce the timing and high frequency content of tsunami waves recorded at three nearshore buoys off sanriku nor the timing and dispersion properties of the waveforms at offshore dart buoy 21418 3 the rupture centroids obtained by tsunami inversions are biased about 60 km nne of that obtained by the global cmt project based on an analysis of seismic and geodetic data together with recorded tsunami waveforms we propose that while the primary source of the tsunami was the vertical displacement of the seafloor due to the earthquake an additional tsunami source is also required we infer the location of the proposed additional source based on an analysis of the travel times of higher frequency tsunami waves observed at nearshore buoys we further propose that the most likely additional tsunami source was a submarine mass failure smf i e a submarine landslide a comparison of pre and post tsunami bathymetric surveys reveals tens of meters of vertical seafloor movement at the proposed smf location and a slope stability analysis confirms that the horizontal acceleration from the earthquake was sufficient to trigger an smf forward modeling of the tsunami generated by a combination of the earthquake and the smf reproduces the recorded on near and offshore tsunami observations well particularly the high frequency component of the tsunami waves off sanriku which were not well simulated by previous models the conclusion that a significant part of the 2011 tohoku tsunami was generated by an smf source has important implications for estimates of tsunami hazard in the tohoku region as well as in other tectonically similar regions

lower cretaceous magnetic stratigraphy in umbrian pelagic limestone sections abstract the magnetic stratigraphy of the lower cretaceous pelagic maiolica limestone has been investigated in three partially correlative sections at gorgo a cerbara presale and frontale in the northern umbrian apennines of central italy the white well bedded limestone has a magnetic mineralogy dominated by magnetite stable magnetic directions isolated by thermal demagnetization define alternating polarity zones in each section the magnetozone patterns are distinctive and can be correlated with the geomagnetic reversal history derived from the m sequence marine magnetic anomalies the three new sections confirm the polarity sequence for anomalies m0 to m10n although the maiolica is inadequately dated the correlated anomalies together with the results of other investigations allow tentative associations of anomalies m0 m19 with individual stages in the lower cretaceous and upper tithonian the investigations also demonstrate the usefulness of magnetic stratigraphy in basin analysis they yield mean sedimentation rates confirm that there is a hiatus between the base of the presale section and the underlying jurassic formations and show that a large part of the frontale section has been cut out by faulting

implications of a combined biostratigraphic and palaeomagnetic study of the umbrian maiolica formation abstract the study of a 275 5 m thick section of white pelagic limestones occupying the valley of the fonte del giordano river on the southern slope of mt montagnola has yielded a biostratigraphically controlled clear magnetic reversal pattern after thermal cleaning the magnetic stratigraphy of the lower 131 m of the section calpionellid zones is correlatable with the m sequence of oceanic magnetic anomalies between m 19 and m 14 the reversal stratigraphy of the upper 81 5 m of the section radiolaria zone has also been tied to the oceanic polarity time scale by making linear interpolation for a missing 63 m thickness underneath it besides the fonte del giordano section two berriasian outcrops each with a different bedding attitude were studied at gubbio and near cagli for tectonic tilt test giving positive results the mean palaeomagnetic pole position for the late jurassic early cretaceous after bedding correction is 19 1 288 2 k 148 7 95 10 2 n 3 confirming the presence of a large swing in the polar path a common behaviour of apparent polar wandering for the peri adriatic region during this time

magnetic properties of marine limestones numerous paleomagnetic investigations have been carried out on limestones but their rock magnetic properties have often been neglected in this review geological and rock magnetic factors which determine whether marine limestones are suitable for paleomagnetic study are summarized and laboratory techniques for the identification of the magnetic mineralogy are evaluated the conditions under which pelagic limestones form are especially favorable for the acquisition of a stable primary natural remanence nrm probably by a postdepositional alignment process the effectiveness and timing of acquisition of this remanence are influenced by the thoroughness of bioturbation other remanence components can be acquired during diagenesis in the soft sediment right after deposition or much later even in the indurated limestone the magnetic mineralogy of a limestone is difficult to describe optically because of the small grain size and low concentration magnetic techniques are more convenient direct analysis of extracted magnetic minerals is handicapped by the difficulty of obtaining a representative extract a particularly useful technique involves combined observations of isothermal remanent magnetization irm acquisition in strong fields up to at least 4 t and the subsequent destruction of this irm during stepwise or continuous thermal demagnetization the magnetic minerals most commonly identified by these techniques are magnetite goethite hematite and maghemite these magnetic minerals occur in different combinations in the marine limestones of central europe and the mediterranean realm pyrite is common in certain limestones where it can be the precursor of an unwelcome late goethite pyrrhotite may be responsible for unstable magnetization in the swiss helvetic limestones but otherwise is rare thermal demagnetization of some limestones causes changes of susceptibility and coercivity at quite low temperatures 300 400 c due to the breakdown of a metastable mineral such as maghemite goethite or pyrrhotite at high temperatures above 500 c pronounced changes of magnetic mineralogy occur in all limestones because of the growth of new magnetite this necessitates great care in interpretation of thermal demagnetization of high blocking temperature components and often results in observational difficulties due to viscous remanent vrm behavior of the newly formed magnetite vrm is a widespread component of nrm in many limestones but it can usually be removed effectively by standard magnetic cleaning techniques the susceptibility serves as a simple control of mineralogical change during heating and can serve as an indicator of lithologic variation of magnetic mineral concentration and type in magnetostratigraphic profiles the susceptibility is anisotropic and shows a classical depositional pattern of the distribution of principal axes however the probable postdepositional mechanism of nrm acquisition especially in bioturbated sediments implies that the anisotropy pattern results from postdepositional compaction of the sediment

the 125 150 ma high resolution apparent polar wander path for adria from magnetostratigraphic sections in umbria marche northern apennines italy timing and duration of the global jurassic cretaceous hairpin turn a new high resolution apparent polar wander path apwp segment has been obtained from the magnetostratigraphy of four kimmeridgian to lower aptian sections in the northern apennines italy the use of paleomagnetic data for determination of the adria apwp was hampered by the large local rotations linked to apennine tectonics characterized by folds and thrusts developed during the neogene to overcome this problem we have computed relative rotations between time overlapping sections and realigned them in a common declination reference frame namely the bosso section we synthesized a new high resolution 150 to 125 ma apwp for adria which has a similar shape to the time equivalent segment of the synthetic apwp of africa of besse and courtillot j besse v courtillot apparent and true polar wander and the geometry of the geomagnetic field over the last 200 myr j geophys res 107 b11 2002 doi 10 1029 200jb000050 a 26 clockwise rotation of our combined adria apwp places it in almost perfect overlap with african data of same age confirming that the adria promontory moved coherently with africa during this time span whereas the counterclockwise rotation of adria with respect to africa was introduced later most probably during apennines orogenesis finally we discuss in relation with worldwide plate evolution the peculiar shape of our apwp which displays a hairpin turn during berriasian time and dates the main late jurassic early cretaceous change in plate motion at around anomaly m16

apparent polar wander path for adria extended by new jurassic paleomagnetic results from its stable core tectonic implications abstract as a continuation of a systematic paleomagnetic research in the northern part of stable adria which provided a well defined apparent polar wander apw path for the cretaceous eocene we present new paleomagnetic results for the jurassic these new data were obtained from 15 geographically distributed localities from the trento platform eastern southern alps using standard paleomagnetic approach the lower jurassic shallow water carbonates are not considered for tectonic interpretation due to inconsistent inclinations the middle and upper jurassic rosso ammonitico provided excellent kinematic constraints with the new jurassic results an apw is now defined for adria for the 167 40 ma interval it is well constrained for timing of important changes like the speed and the sense of rotations this apw suggests that the cw rotation and southward shift changed to the opposite at 155 1 5 3 ma signifying a dramatic change in the life of the neo tethys from opening to closing the latter is manifested in fast ccw rotation and northward movement of adria up to 102 9 2 4 ma and moderate displacements in the same manner in post 103 ma times combined data sets from stable istria and the foreland of the southern alps point to an approximately 15 cw rotation with respect to africa at the end of the cretaceous and an about 25 in the ccw sense after the eocene

the coupling of a submarine slide and the surface waves which it generates underwater landslides are a common source of small scale tsunamis in coastal areas they have been the object of only a few theoretical and experimental studies a numerical model is developed to study the coupling of a submarine landslide and the surface waves which it generates a formulation of the dynamics of the problem is presented where the landslide is treated as the laminar flow of an incompressible viscous fluid and the water motion is assumed irrotational long wave approximation is adopted for both water waves and the mudslide the resulting differential equations are solved by a finite difference method we present the numerical results which contrast the behavior of the mud flow under a fixed surface in the presence of one way coupling bottom deformations affect the free surface and with full coupling surface pressure gradients react on the mud flow it is found that three main waves are generated by a landslide starting from rest on a gentle uniform slope the first wave is a crest which propagates away from the mudslide site into deeper water this crest is followed by a trough in the form of a forced wave which propagates with the speed of the mudslide front the third wave is a relatively small trough which propagates shoreward two major parameters dominate the interaction between the slide and the waves it produces the density of sliding material and the depth of water at the mudslide site the two way interactions are significant for the cases of a smaller mud density and shallower waters for the cases of larger mud density and shallower waters the two way interactions are small but the waves generated are very large for larger initiation depth of the mudslide the interactions are weak and the waves generated are small we also examined the possibility of a resonance between the slide and the waves our numerical results indicate that a resonance is not expected in many practical cases

washover fan and brackish bay sedimentation in the berriasian valanginian of bornholm denmark abstract the robbedale and jydegard formations berriasian valanginian of the danish island of bornholm represent a 100 m thick vertical sequence from shoreface foreshore and beach sands of a high energy coast through backbarrier flat bay margin pond and distal washover fan sand and clay brackish bay clay to fluvial sands the longevity of the backbarrier bay system c 10 myr thickness 100 m of the bay deposits and apparently stacked nature of the facies belts suggest a relatively stationary position of the individual subenvironments with only minor progradation this reflects strong tectonic control of the depositional system during an important phase of synsedimentary block faulting and wrenching along the tornquist zone the importance of washover fan sands in the backbarrier deposits and the lack of tidal indications in the whole sequence suggest a microtidal regime a system of migrating mud banks formed in shallow water on the landward side of the barrier the bay waters varied from almost fresh to brackish and anoxic conditions commonly occurred at the bottom adverse living conditions for most organisms in the bay caused seasonal possibly toxic dinoflagellate blooms resulting in mass mortality of infaunal bivalves bay margin ponds underwent periodic desiccation leading to mass mortality of freshwater gastropods as a general scenario it is envisaged that longshore currents redistributed bedload from a major delta and formed an extensive nw se barrier spit which partly enclosed a major bay to the ne the barrier was breached during heavy storms and the sand transported along the resulting washover channels was deposited on the backbarrier flat made up of the subaerial parts of coalescent washover fans enormous amounts of suspension load from the delta travelled further along the barrier to be deposited in the lee side bay

tethyan ferromanganese oxide deposits from jurassic rocks in hungary fossil manganese nodules and encrustations from seamount and basin localities in the transdanubian central mountains of hungary are lithologically mineralogically and chemically similar to some modern marine ferromanganese oxide deposits and show no evidence of postdepositional changes other than cementation five groups of deposits were encountered fe mn nodules encrusted shells pavements stains and fe oxide encrusted intraclasts the first three of which are specific to the 9seamount9 environment and the last to the basins optical and electron microprobe investigation of the samples shows them to exhibit many similarities with modern ferromanganese oxide deposits and that many of the nodules are surrounded by a halo of dispersed ferromanganese oxides strongly suggesting that they continued to accrete metals through the pore waters of unlithified sediments for a period after burial by contrast pavements which appear to have grown on hardgrounds at the sea floor show little or no evidence of derivation of metals from underlying sediments geochemical investigations on the deposits show the seamount varieties to be closer in composition to most modern nodules and crusts than the basin varieties and that the latter are essentially manganese and trace element poor ferruginous deposits nevertheless all can be more or less compositionally equated with modern ferromanganese oxide deposits forming in marginal atlantic environments which would be in accord with the proposed depositional environment of the transdanubian central mountains based on other evidence

a magnetic polarity time scale for the early cretaceous and late jurassic abstract the ages of polarity chrons in previous m sequence magnetic polarity time scales were interpolated using basal sediment ages in suitably drilled dsdp holes this method is subject to several sources of error including often large paleontological age ranges magnetostratigraphic results have now tied the early cretaceous and late jurassic paleontological stage boundaries to the m sequence of magnetic polarity the numeric ages of most of these boundaries are inadequately known and some have been determined largely by intuition an examination of relevant data suggests that 114 ma 136 ma and 146 ma are optimum estimates for the ages of the aptian barremian cretaceous jurassic and kimmeridgian oxfordian stage boundaries respectively each of these boundaries has a good correlation to the m sequence of magnetic reversals the magnetostratigraphic tie level ages are linearly related to the spreading distance and have been used to calculate a new magnetic polarity time scale for the early cretaceous and late jurassic all stage boundaries in this time interval were correlated by magnetic stratigraphy to the proposed new time scale which was then used to estimate their numeric ages these are with the approximate relative errors of placement within the m sequence aptian barremian 114 ma 0 5ma barremian hauterivian 121 ma 2 0 1 5ma hauterivian valanginian 126 ma 0 5 3 0ma valanginian berriasian 131 ma 0 5 2 5ma berriasian tithonian 136 ma 1 0ma tithonian kimmeridgian 143 ma 0 5ma kimmeridgian oxfordian 146 ma 0 2ma the absolute errors of these interpolated stage boundary ages depend on the accuracy of the tie level ages

on the characteristics of landslide tsunamis this review presents modelling techniques and processes that govern landslide tsunami generation with emphasis on tsunamis induced by fully submerged landslides the analysis focuses on a set of representative examples in simplified geometries demonstrating the main kinematic landslide parameters influencing initial tsunami amplitudes and wavelengths scaling relations from laboratory experiments for subaerial landslide tsunamis are also briefly reviewed it is found that the landslide acceleration determines the initial tsunami elevation for translational landslides while the landslide velocity is more important for impulsive events such as rapid slumps and subaerial landslides retrogressive effects stretch the tsunami and in certain cases produce enlarged amplitudes due to positive interference in an example involving a deformable landslide it is found that the landslide deformation has only a weak influence on tsunamigenesis however more research is needed to determine how landslide flow processes that involve strong deformation and long run out determine tsunami generation

tectonic rotations south of the bohemian massif from palaeomagnetic directions of permian red beds in hungary abstract palaeomagnetic studies were carried out in permian red beds of the balaton highlands the mecsek mountains and the bukk mountains of hungary statistically well defined directions were obtained from six localities in the balaton highlands and two localities in the mecsek mountains no meaningful results were obtained from the bukk mountains three magnetic components were identified from red beds of the balaton highlands 1 in haematite with a very high unblocking temperature 700 c interpreted as a permian magnetization d c 79 i c 11 k 24 95 13 6 in six samples from three beds in a single locality 2 a secondary but ancient component residing mainly inmaghemite d 314 i 49 k 48 95 10 0 in 84 samples from six localities with a within locality scatter increasing on unfolding and 3 a direction parallel to the present field d 7 i 62 k 46 95 7 7 in nine samples from a single locality for the balaton highlands the component 1 direction agrees with directions obtained from permian red beds and volcanics in the eastern part of the southern and eastern alps and the inner west carpathians all show large apparent rotations relative to stable europe since the permian component 2 is of post folding post aptian age its direction agrees with known late cretaceous directions from the transdanubian central mountains which also show significant counterclockwise rotation relative to stable europe the characteristic magnetization for the mecsek mountains resides in haematite and may be primary the directions indicate only a slight net counterclockwise rotation of the mecsek mountains with respect to stable europe since the permian

magnetostratigraphy of the jurassic cretaceous boundary there is no internationally recognized standard for the jurassic cretaceous boundary a precise biostratigraphical correlation between different paleobiogeographic provinces is impossible due to barriers blocking faunal exchange this problem may be overcome by using magnetic polarity events which are globally isochronous the magnetic polarity time scale of the latest jurassic and earliest cretaceous enables determination of the relative timing and age span of several possible definitions of this system boundary among different biostratigraphies within the tethys atlantic faunal realm therefore the polarity scale can be used as a regional standard for this interval of time the base of reversed polarity chron m18 falls in the middle of the interval covered by various recent definitions of the tethyan jurassic cretaceous boundary if polarity chron m18 also proves to be recognizable in the boreal realm then its basal magnetic reversal could serve as a precise globally correlatable event for defining the jurassic cretaceous boundary

paleomagnetic implications on the evolution of the tethys belt from the atlantic ocean to the pamirs since the triassic abstract we first re examined the apparent polar wander curves for stable eurasia and africa since the triassic these curves were then combined together with curves of north and south america according to the kinematics of the atlantic ocean and a synthetic polar wander curve was given then most of the paleomagnetic results from the tethys mobile belt from the atlantic to the pamirs were analysed several groups of plates microplates and blocks can be seen first relatively stable regions like maghreb and sicily which have not moved much then we have a group formed by iberia sardinia italy and to a lesser extent corsica and the western and central alps for these blocks movements are anticlockwise rotations chiefly driven by the anticlockwise rotation of africa but they are sometimes stronger to the east a major change takes place the north of the aegean sea and the ionian zone are clockwise rotated and these rotations are recent oligocene miocene for the first part pliocene to the present for the second part a major problem arises in turkey caucasus and iran paleomagnetic results indicate a position far to the south of eurasia and at the same time geological evidence is in favour of a position close to eurasia we discuss these discrepancies

late quaternary geology of the middle gila river gila river indian reservation arizona abstract stratigraphy and dating provide an 18 000 yr record of erosion and deposition by the middle gila river prior to 18 000 cal yr b p the gila river cut into its floodplain and created a deep wide channel sand and gravel accumulated within this channel until 4250 4400 cal yr b p by this time the channel of the gila river was narrow and deep around 5000 cal yr b p fine grained sediments began to accumulate on the floodplain at 800 950 cal yr b p there was a major period of channel widening after this erosional episode the channel again narrowed as it filled with sand and gravel until around 200 cal yr b p on the floodplain deposition continued from about 5000 cal yr b p to 500 cal yr b p a period of stability and soil formation occurred on the floodplain between 500 and 200 cal yr b p after which overbank deposition resumed and buried the soil channel widening again occurred in the late 19th century the changes observed in the sedimentologic history of the gila river show that during the late pleistocene the gila river was a competent stream capable of carrying and depositing coarse sediment loads later deposition of sand and gravel during the first half of the holocene implies an increase in sediment yield from upstream watersheds changes during the last 4000 years reflect the response of the river to climatic perturbations the timing of large floods internal landscape thresholds and human impacts

carbonatation in palaeosols formed on terraces of the tormes river basin salamanca spain abstract a macro and micromorphological study was made of the carbonate accumulations in a total of 21 relict unburied palaeosols haploxeralfs and palexeralfs of ages corresponding to the late middle and early pleistocene formed on fluvial terraces in the tormes river basin salamanca spain under a present day subhumid continental mediterranean climate the fluvial deposits were predominantly gravels and sands derived from the erosion of granite slate sandstone and quartzite with a notable absence of calcareous materials secondary carbonates commonly filled cracks forming laminae in preferentially horizontal disposition though also tipped and vertical giving rise to distinctive patterns that have long attracted scientific attention in the youngest soils of the lower terraces late pleistocene 300 000 years especially in the upper levels within the calcic horizon in rare cases the pseudomycelia and the coatings were comprised of fine needle fibre calcite the carbonates in these soils are recrystallized even in the some of the youngest soils of these terraces 40 000 years the older soils of the middle terraces and particularly in the upper terraces 300 000 years reflected an intense process of replacement of silicates by carbonates in addition the clays in the micromass and illuvial coatings as well as the detrital grains such as feldspars and quartz were progressively replaced by carbonates the carbonate accumulations as well as the subsequent recrystallization and replacement tended to increase with the age of the soils in addition the secondary carbonatation and dissolution of carbonate observed indicate the genetic complexity of these soils the form of the carbonates present at the micro as well as macroscopic level their distribution within the soil profiles and throughout the region as well as the relationship with other processes subsequent to clay illuviation and associated with hydromorphy imply that vadose water at certain geological stages must have been responsible for the carbonate accumulation in these soils the carbonates were deposited during the coldest periods of the isotope substages 6 2 7 4 10 2 12 2 13 2 and 16 2 the presence of dissolution in the soils corresponding to the isotope substages 7 4 and 13 2 appears to indicate the development of two wetter periods towards 200 000 and 500 000 years b p the absence of carbonates in the soils of the youngest surfaces plains flood and the lowest terraces holocene and late pleistocene

geomagnetic reversal history the history of geomagnetic polarity reversals in the cenozoic and late mesozoic is well known since the late jurassic oxfordian a continuous record of polarity has been derived for this time interval from the interpretation of oceanic magnetic anomalies most of the polarity chrons in this oceanic record have been verified and dated in coordinated magnetostratigraphic and biostratigraphic studies this has led to the generation of progressively refined and improved geomagnetic reversal time scales that provide a framework for absolute dating of palaeontological zonations by serving as a basis for statistical analysis of reversal frequency they provide information relevant to processes in the earth s core the rate of reversals since the late cretaceous shows a steady increase on which a cyclical variation appears to be superposed a stochastic model for reversals predicts a poisson distribution of polarity interval lengths the polarity time scales contain many fewer short 50 kyr polarity chrons than a poisson distribution and it has been suggested that a gamma renewal process with index greater than unity is a more appropriate statistical model the statistical arguments give no convincing reason for abandoning the model and other physical reasons must be sought to explain the incompleteness of the reversal record the discovery and verification of short chrons in the oceanic record may best be investigated by deep tow magnetometer surveys the reversal history before the late jurassic is not well known magnetostratigraphy in coeval early jurassic sections has not given correlatable records and it has not been possible to compile a definitive polarity sequence evaluation of geomagnetic polarity history for the early mesozoic and the palaeozoic will require unambiguous magnetostratigraphy in well dated sections where verification of the polarity pattern is possible at the fossil zone or stage level

escape models of the alpine carpathian pannonian region in the light of palaeomagnetic observations recent tectonic models of the alpine carpatho pannonian region alcapa assume a large eastward shift of the transdanubian range domain in the cenozoic since palaeomagnetism is one of the most powerful tools in solving geodynamic processes the authors present an approach to the escape problem by using all available and relevant palaeomagnetic data this data set demonstrates consistency with models put forward by geologists for jurassic and older ages from the mid jurassic on the northern calcareous alps nca did not share the rotations of the transdanubian range domain and of the southern alps after individual movements from neocomian to miocene the transdanubian range domain must have drifted northward in the mid miocene up to the southern margin of the northern calcareous alps before starting the escape in the geologists definition

large deformation finite element modelling of earthquake induced landslides considering strain softening behaviour of sensitive clay large scale landslides in sensitive clays cannot be explained properly using the traditional limit equilibrium or lagrangian based finite element fe methods in the present study dynamic fe anal

effects of shear band propagation on early waves generated by initial breakoff of tsunamigenic landslides the landslide mechanism based on the phenomenon of the dynamic shear band propagation suggests that landslide run out begins with a non zero initial velocity the initial uplift of the passive failure block during the landslide breakoff is similar to the reverse fault and therefore can generate an early tsunami wave that will be one of the first waves to start propagating and could be potentially detected by the deep ocean warning systems this paper attempts to quantify this phenomenon using the coupled eulerian lagrangian cel approach within abaqus and modeling both soil and water as eulerian materials this approach allows for capturing the entire process of failure initiation propagation and breakoff taking into account large landslide deformations soil plasticity and interaction of the sliding layer with the seawater the study shows that the highest breakoff velocities are achieved for the shortest lengths of the initial weak zones initiating the shear band propagation it also shows that both interaction of the sliding layer with water and appearance of the large plastic failure zones during the shear band propagation cause slower uplift velocities and accelerations for the computed example of a typical mid size landslide in normally consolidated clays with the initial weak zone length of several hundred meters and the final landslide length of about 1 km the breakoff velocities can reach up to 4 m s within 15 s leading to an early wave of 0 5 1 5 m height caused purely by this breakoff such waves can be easily detected by existing deep ocean assessment and reporting of tsunamis dart systems potentially allowing for some early tsunami warning

time and space distribution of coseismic slip of the 2011 tohoku earthquake as inferred from tsunami waveform data a multiple time window inversion of 53 high sampling tsunami waveforms on ocean bottom pressure global positioning system coastal wave and tide gauges shows a temporal and spatial slip distribution during the 2011 tohoku earthquake the fault rupture started near the hypocenter and propagated into both deep and shallow parts of the plate interface a very large slip approximately 25 m in the deep part off miyagi at a location similar to the previous 869 jogan earthquake model was responsible for the initial rise of tsunami waveforms and the recorded tsunami inundation in the sendai and ishinomaki plains a huge slip up to 69 m occurred in the shallow part near the trench axis 3 min after the rupture initiation this delayed shallow rupture extended for 400 km with more than a 10 m slip at a location similar to the 1896 sanriku tsunami earthquake and was responsible for the peak amplitudes of the tsunami waveforms and the maximum tsunami heights measured on the northern sanriku coast 100 km north of the largest slip the average slip on the entire fault was 9 5 m and the total seismic moment was 4 2 1022 n m m w 9 0 the large horizontal displacement of seafloor slope was responsible for 20 40 of tsunami amplitudes the 2011 deep slip alone could reproduce the distribution of the 869 tsunami deposits indicating that the 869 jogan earthquake source could be similar to the 2011 earthquake at least in the deep plate interface the large tsunami at the fukushima nuclear power station is due to either the combination of a deep and shallow slip or a triggering of a shallow slip by a deep slip which was not accounted for in the previous tsunami hazard assessments online material table of estimated slip for all subfaults at 0 5 min invervals

complex earthquake rupture and local tsunamis 1 in contrast to far field tsunami amplitudes that are fairly well predicted by the seismic moment of subduction zone earthquakes there exists significant variation in the scaling of local tsunami amplitude with respect to seismic moment from a global catalog of tsunami runup observations this variability is greatest for the most frequently occurring tsunamigenic subduction zone earthquakes in the magnitude range of 7 mw 8 5 variability in local tsunami runup scaling can be ascribed to tsunami source parameters that are independent of seismic moment variations in the water depth in the source region the combination of higher slip and lower shear modulus at shallow depth and rupture complexity in the form of heterogeneous slip distribution patterns the focus of this study is on the effect that rupture complexity has on the local tsunami wave field a wide range of slip distribution patterns are generated using a stochastic self affine source model that is consistent with the falloff of far field seismic displacement spectra at high frequencies the synthetic slip distributions generated by the stochastic source model are discretized and the vertical displacement fields from point source elastic dislocation expressions are superimposed to compute the coseismic vertical displacement field for shallow subduction zone earthquakes it is demonstrated that self affine irregularities of the slip distribution result in significant variations in local tsunami amplitude the effects of rupture complexity are less pronounced for earthquakes at greater depth or along faults with steep dip angles for a test region along the pacific coast of central mexico peak nearshore tsunami amplitude is calculated for a large number n 100 of synthetic slip distribution patterns all with identical seismic moment mw 8 1 analysis of the results indicates that for earthquakes of a fixed location geometry and seismic moment peak nearshore tsunami amplitude can vary by a factor of 3 or more these results indicate that there is substantially more variation in the local tsunami wave field derived from the inherent complexity subduction zone earthquakes than predicted by a simple elastic dislocation model probabilistic methods that take into account variability in earthquake rupture processes are likely to yield more accurate assessments of tsunami hazards

simple criteria for ploughing and runout in post failure evolution of submarine landslides this paper extends shear band propagation analysis of slope failures to the investigation of ploughing and runout phenomena in submarine landslides the ability to predict the two different modes of post failure landslide evolution is critical for determining the tsunami hazard and type of landslide impact on offshore structures the proposed analysis is based on the analogy between ploughing and spreading failures it uses the energy balance approach to develop the criterion for progressive shear band propagation driven by accumulation of sliding material on top of the stable slope this criterion is then combined with the kinematic passive block mechanism to produce analytical ploughing failure criteria formulated in terms of the critical rise in the seabed level if the minimum rise of the seabed level at which ploughing can take place is larger than the maximum possible free standing step in the seabed surface the first passive failure block will start crumbling over top the stable zone causing the l

paleomagnetism and integrated stratigraphy of the upper berriasian hemipelagic succession in the barlya section western balkan bulgaria implications for lithogenic input and paleoredox variations abstract a continuous late berriasian sedimentary and stratigraphic record is here presented from a hemipelagic succession from the western balkan barlya section bulgaria the section 39 m thick was stratigraphically calibrated using a variety of methods biostratigraphy calpionellids calcareous nannofossils and calcareous dinocysts magnetostratigraphy and carbon isotope stratigraphy additionally chemostratigraphy and rock magnetic stratigraphy were applied in order to identify major paleoenvironmental changes lithogenic input and paleoredox variations polarity zones from m17r to m14r were identified from the uppermost lower berriasian up to the berriasian valanginian boundary elliptica to darderi calpionellid subzones and nk 1 to nk 3 nannofossil zones late berriasian calcareous dinocyst zones of stomiosphaerina proxima stomiosphaera wanneri and colomisphaera conferta were correlated with magnetostratigraphy for the first time a carbon isotope profile correlates very well with the 13 c records from se france and the western atlantic documenting some well resolved minima and maxima in a generally decreasing trend magnetic susceptibility ms reveals a very good positive correlation with lithogenic elements e g al ti zr th and others and is regarded as a reliable proxy of detrital input influx of fine grained terrigenous material increases in the upper berriasian up to the berriasian valanginian boundary a prominent ms increase takes place in the lowermost part of polarity zone m16n close to the simplex oblonga subzonal boundary the ms event can be traced in the central carpathian apennine and se france sections exactly in the same stratigraphic position it is coeval with an important climatic turnover in western tethys however it might have been strengthened by a general regression and regional tectonic events in the carpatho balkan area two oxygen deficient intervals were documented the first in the lower berriasian m17r to m16r the second one in the uppermost upper berriasian up to the boundary with valanginian m15r to m14r both intervals correlate with an elevated sea level in the western tethys

development of the pannonian basin basement through the cretaceous cenozoic collision a new synthesis abstract a geodynamic analysis was carried out going back in time from the present the collision took place during the cretaceous and cenozoic based on the subduction origin of the neogene calc alkalic volcanites three microplates are delineated the southern and the northern ones are approximately the same as in previous plate tectonic syntheses but the third one is outlined here for the first time as the basement of a miocene island arc restoring the former position of microplates a basin of oceanic crust is outlined on the site of the present pannonian basin of continental crust at the beginning of the neogene the present northern microplate was located somewhere west of this basin and the present southern one was located on its southern shelf the reconstructed cretaceous paleogene histories of these microplates were different during the whole barremian to oligocene time interval the southern microplate was located on the passive margin of an oceanic basin which was coming into being through continental rifting of the european plate margin in the valanginian to hauterivian the northern microplate located on the african plate margin was undergoing collision with an island arc in the early cretaceous the oceanic basin of marginal see type behind this island arc was closed along a southerly directed subduction zone in the eocene this resulted in the appearance of a calc alkalic volcano chain along this microplate and in a new basin opening behind this marginal sea basin divided the present northern microplate from the african plate and joined the oceanic basin north of the present southern microplate the present pannonian basin was assembled as a lithospheric mosaic through convergent and transcurrent movements of the defined microplates during the neogene sediments of the former oceanic basin now strike along the contacts of continental microplates as flysch belts

palaeomagnetism of permo triassic rocks from northern slovenia yugoslavia and the eastern margin of the adriatic plate abstract in northern slovenia yugoslavia 15 e 46 n 41 sites of permo triassic red sandstones and volcanic rocks have been sampled for a palaeomagnetic study the rock units are situated either in the southern alps or in the transition zone between the southern alps and the dinarides more than half of the sampled sites revealed that the primary remanence was seriously affected by partial or entire magnetic overprint in connection with the alpine orogeny this was manifested by either too steep inclinations or too weak or inconsistent and unstable remanence only fourteen sites revealed the typical flat inclinations of permo triassic rocks a group of six sites in northwestern slovenia west of ljubljana gave a remanence direction n 6 r 5 431 d 151 4 i 11 4 k 8 8 95 19 3 which is in agreement with the mean permian remanence direction of the bolzano rhyolites in the italian part of the southern alps d 148 i 20 after zijderveld and van der voo 1973 indicating that this zone is still part of the adriatic plate however a group of eight sites in northeastern slovenia east of ljubljana has a remanence direction n 8 r 6 991 d 225 9 i 15 0 k 6 9 95 18 8 which is more in agreement with the central european permo triassic direction of remanence d 204 i 14 it is therefore concluded that the eastern margin of the adriatic plate crosses the region of ljubljana in an approximately north south direction

magnetic stratigraphy of kimmeridgian aptian sections from umbria marche italy new details on the m polarity sequence 1 the magnetic stratigraphy of the maiolica and calcari ad aptici pelagic limestones is documented from four umbro marchean land sections italy the overall biostratigraphic age of the sampled strata encompasses the whole kimmeridgian lower aptian the data were gathered from two new sections arcevia contessa and by resampling more densely than in the past two additional classical sections bosso gorgo a cerbara a detailed record of the polarity chrons m21n m14 and m9 m0 was derived and no difference was observed with respect to the sequence of m polarity chrons inferred from oceanic magnetic anomalies barely measurable remanent magnetization from chron m14 to m10n at contessa concurred with previous evidence from bosso indicating that the maiolica from umbria marche is characterized by a recording gap during chrons m14n to m11 possibly due to diagenetic magnetite dissolution related to the late valanginian carbon isotope event at arcevia and bosso the boundary between maiolica and calcari ad aptici occurs at the top of chron m19n and in the upper part of chron m20n respectively showing that the onset of maiolica sedimentation may be diachronous by 1 5 2 myr along the umbria marche domain arcevia is the most expanded mid upper tithonian land section documented so far here the subchrons m20n 1 and m19n 1 are found to represent 3 2 and 10 1 in time of chrons m20n and m19n respectively evidence is also provided for a reversal excursion occurring within the m20n 1 subchron at bosso an excursion and a reversal excursion were found within chrons m16n and m16 respectively

geomagnetic polarity in the early cretaceous and jurassic knowledge of the polarity history of the earth s magnetic field during the mesozoic stems primarily from oceanic m sequence magnetic anomalies certain of these anomalies have been biostratigraphically dated from sediments immediately overlying basaltic basement at deep sea drilling project d s d p sites within the m sequence the biostratigraphic control is such that these age estimates are generally imprecise and moreover the sediment ages represent only minimum ages for the basaltic basement itself magnetostratigraphy in sedimentary land sections provides improved age estimates for magnetozones which can then be correlated with m sequence anomalies magnetostratigraphy provides not only enhanced dating of the ocean floor and resolution of the behaviour of the geomagnetic field during the cretaceous and jurassic oceanic quiet zones but also a world wide correlation tool for sedimentary stratigraphy the middle cretaceous is characterized by a long period of normal polarity extending from the early aptian to the early campanian reversed magnetozones corresponding to oceanic anomalies m 0 m 1 and m 3 have been palaeontologically dated as early aptian middle barremian and early barremian respectively magnetozones corresponding to oceanic anomalies m 5 to m 15 are hauterivian to valanginian in age but have not been individually associated with stage boundaries mainly due to poor biostratigraphic control in italian pelagic limestone sections of this age however magnetozones corresponding to oceanic anomalies m 16 to m 22 have been individually correlated to lower berriasian and tithonian palaeontological zones and extrapolation of this correlation gives an age for anomaly m 25 close to the oxfordian kimmeridgian boundary the jurassic 9quiet zone in the oceans is recognized in land sections as an extended period of predominantly normal polarity and although poor biostratigraphic control in this interval limits our knowledge of its duration we consider that it extended through the oxfordian and callovian stages the bathonian and older jurassic stages are characterized by mixed polarity a precise correspondence of magnetozones to ammonite zonations and stage boundaries is only available for the aalenian to pliensbachian interval where the frequency of reversal was apparently very high