palaeoclimatic implications of the occurrence of the arcoid bivalve anadara trapezia deshayes in the quaternary of australasia abstract the arcoid bivalve anadara trapezia deshayes 1840 is a eurythermal estuarine mollusc that flourishes at present in eastern australia between port phillip bay victoria and townsville in northern queensland a trapezia first appeared in the australian quaternary fossil record during oxygen isotope stage ois 7 in new zealand where it is now extinct the earliest known occurrences are in the rangitawa fossil beds and in uppermost castlecliffian strata west of wanganui north island ois 11 ca 400 ka the species had an extensive distribution during the last interglacial maximum ois 5e in both australia and new zealand and appears to have had a slightly wider than present geographic range in southeastern australia during the middle holocene as shown by records from tasmania and western victoria where it no longer lives apart from an isolated population inhabiting oyster harbour western australia a trapezia has not been confirmed living in coastal waters west of port phillip bay victoria it became extinct in new zealand sometime after ois 5e the extensive distribution and abundance of a trapezia and other fauna of subtropical affinity during the last interglacial maximum in areas where both are now extinct appears to be associated with an enhanced leeuwin current at that time coinciding with higher less seasonally concentrated levels of precipitation and river discharge the arrival of a trapezia in australasian coastal waters may have been a consequence of planktonic dispersal from southern south america a bravardi del rio from the middle miocene puerto madryn formation on the valdes peninsula argentina may be a possible ancestor for a trapezia

the global mio pliocene climatic equability and coastal ostracod faunas of southeast australia this study on the mio pliocene ostracod successions of southeast australia outlines several faunal events indicative of climate warming and or increased rainfall events ostracod faunas associated with a late late miocene sea level rise event suggest that the climate of this time in southeast australia was similar to or slightly warmer than that of present day southeast australia however it was probably wetter and significantly warmer than immediately preceding mid late miocene palaeoclimatic conditions within the region evidence for a change to wetter and warmer conditions during the late late miocene is seen in the appearance of various extant euryhaline and semi thermophilic ostracod species in coastal ostracod faunas the appearance of euryhaline species which are mostly absent from older shallow marine cenozoic strata of the bass strait hinterland suggests a major influx of fresh water into coastal marine settings which contributed to the initial phase of development of the southeast australian late neogene barrier coastline and associated marginal marine palaeoenvironments during the time interval latest miocene to earliest pliocene and during the early late pliocene two subsequent global sea level rise events are also preserved in the southeast australian coastal plain many of the species present in ostracod faunas associated with these two events are the same as in older local late late miocene faunas in earliest pliocene faunas there is minor evidence for the reappearance of semi thermophilic ostracods faunas of early late pliocene age often exhibit a conspicuous faunal dominance by or large abundance of euryhaline species indicating the particularly strong influence of fresh water influxes into coastal marine palaeoenvironments this may reflect the presence of especially wet local temperate palaeoclimatic conditions during a time of equable global climates succeeding estuarine lagoonal and coastal embayment ostracod faunas of late late pliocene age are associated with marginal marine sediments that are interbedded with coastal dune aeolianites this suggests an overall seaward retreat of marginal marine environments that was initiated by a major global sea level fall linked to the onset of cooler late pliocene and quaternary global climates

late miocene molluscs from the southwestern atlantic ocean argentina and uruguay a palaeobiogeographic analysis abstract the analysis of the structure and evolutionary history of the late miocene marine molluscs along the southwestern atlantic littoral indicates that these faunas did not give rise to the present assemblages of the argentinean province of the same region the latter being characterised by a typically transitional association in the sense of scarabino 1977 com soc malac urug 4 177 285 that developed after miocene times once the cold malvinas falkland current was completely operating the late miocene valdesian and paranaian provinces mainly composed of paratropical warm water faunas are defined in this paper the former includes assemblages recovered from the puerto madryn formation its southern limit is placed at 42 s while in the north its boundary with the paranaian province is situated approximately between 37 and 39 s the paranaian province includes assemblages belonging to the parana and camacho formations it extends northwards along the uruguayan and southern brazilian littoral but its northern boundary still remains unknown an incipient thermal gradient is recognised as the temperature values for the paranaian province are slightly higher than those for the valdesian province taking into account that in the valdesian province water temperature was in fact warm it is concluded that the cold malvinas falkland current still had a very low activity in the area during the late miocene the presence of upwelling phenomena is also suggested by the presence of widely distributed turritellid beds in the northern patagonian region

tectonic evolution of the west scotia sea joint inversion of isochron and flowline data from the flanks of the extinct west scotia ridge spreading center yields five reconstruction rotations for times between the inception of spreading prior to chron c8 26 5 ma and extinction around chron c3a 6 65 9 ma when they are placed in a regional plate circuit the rotations predict plate motions consistent with known tectonic events at the margins of the scotia sea oligocene extension in powell basin miocene convergence in tierra del fuego and at the north scotia ridge and miocene transpression at the shackleton fracture zone the inversion results are consistent with a spreading history involving only two plates at rates similar to those between the enclosing south america and antarctica plates after chron c5c 16 7 ma but that were faster beforehand the spreading rate drop accompanies inception of the east scotia ridge back arc spreading center which may therefore have assumed the role of the west scotia ridge in accommodating eastwards motion of the trench at the eastern boundary of the scotia sea this interpretation is most easily incorporated into a model in which the basins in the central parts of the scotia sea had already formed by chron c8 contrary to some widely accepted interpretations and which has significant implications for paleoceanography and paleobiogeography

an evaluation of mesodon and other larger terrestrial gastropod shells for dating late holocene and historic alluvium in the midwestern usa abstract understanding the history of stream erosion and changes in channel morphology is important for managing and restoring unstable streams one of the significant challenges in this type of research is establishing accurate dating of late holocene and historic alluvium here we evaluate the potential of using 14c dating and amino acid racemization aar to date large terrestrial gastropod shells that are often preserved within alluvial sediments many terrestrial gastropods incorporate old carbon from limestone or other carbonate rocks into their shells and therefore are unsuitable for radiocarbon dating recent studies however have shown that some taxa avoid this limestone problem and can yield reliable 14c ages in this study we measured the 14c activity of specimens for the genera mesodon ventridens and allogona collected live and from alluvial sequences dated independently by dendrochronology 14c dating of wood and or 137cs analyses mesodon zaletus contained old carbon in similar concentrations up to 30 found in previous studies of other large taxa and should be avoided for 14c dating when possible in contrast shells of ventridens ligera and allogona profunda showed minimal limestone effects and therefore may be suitable for dating late holocene alluvium these results highlight the importance of taxonomic identification of gastropod taxa prior to their use for 14c dating and demonstrate that shell fragments that are not identifiable should be avoided we also measured d l ratios n 17 of aspartic and glutamic acid from eight different taxa of terrestrial gastropods recovered from four late holocene and historic stratigraphic sequences average d l ratios of aspartic and glutamic acid from historic sediments

the tectonic history of drake passage and its possible impacts on global climate this study provides an integrated review of plate tectonic models of the evolution of the antarctica patagonia connection compared to geological records collected on land in patagonia and tierra del fuego and offshore along the northern edge of the scotia sea a temporal framework for the sedimentary and tectonic events of the north scotia ridge and tierra del fuego is constructed with additional data compiled from entire patagonia and the austral basin this review provides robust correlations of seaways and tectonic events along the scotia and south america plates and indicates that the opening of the drake passage was not steady state since ca 30 ma rather the regions forming the present day northern limit of this gateway experienced important paleogeographic changes from deep marine basins to shallow ridges and emerged regions during the late oligocene and early middle miocene time our compilation of geological data shows that emergence along the north scotia ridge and tierra del fuego was achieved at 23 22 ma and has been followed by elimination of the patagoniano sea in patagonia starting at 22 23 ma and achieved at 20 ma this transition towards more continental sedimentation in southern south america is correlated with more shallow marine conditions in the austral basin this succession of events had a strong influence on the general geometry of the drake passage corresponding to a constriction of its northern limit starting in the window 29 22 ma and achieved at 21 ma this period of active deformation in southern south america also corresponds to a period of the global climate having two anomalies well known from the isotopic records the late oligocene warming around 26 ma and the mid miocene climatic optimum which ended between 15 and 14 ma the possible effects of the post oligocene tectonic evolution of the drake passage region on general oceanic circulation are discussed causes for the synchronicity between tectonic events and these global warming events are examined

holocene turbidites record earthquake supercycles at a slow rate plate boundary ongoing evidence for earthquake clustering calls for records of numerous earthquake cycles to improve seismic hazard assessment especially where recurrence times overstep historical records we show that most turbidites emplaced at the africa eurasia plate boundary off west algeria over the past 8 k y correlate across sites fed by independent sedimentary sources requiring a regional trigger correlation with paleoseismic data inland and ground motion predictions support that m 7 earthquakes have triggered the turbidites the bimodal distribution of paleo events supports the concepts of earthquake supercycles and rupture synchronization between nearby faults 13 paleo earthquakes underpin clusters of 3 6 events with recurrence intervals of 300 600 yr separated by periods of quiescence of 1 6 k y without major events on other faults over the study area this implies broad phases of strain loading alternating with phases of strain release our results suggest that fault slip rates are time dependent and call for revising conventional seismic hazard models

amino acid racemization geochronology of reworked quaternary mollusks on u s atlantic coast beaches implications for chronostratigraphy taphonomy and coastal sediment transport approximately 200 shells primarily mercenaria from 21 beach sites between new jersey and florida have been analyzed for the extent of racemization epimerization of their fossilized amino acids the greatest concentration of sites is in north carolina in regions least affected by human modification of natural beach sediment transport processes these results can be used to estimate the frequency of age mixing of pleistocene shell material in holocene depositional environments selected shells have also been dated by 14c conventional and or ams to provide direct calibration of the amino acid epimerization ratios shell taphonomic characteristics particularly color can be qualitatively related to apparent ages data for shell fragmentation combined with amino acid age estimates provide insights into probable transport distances of reworked shells shells with apparent pleistocene ages have epimerization values equivalent to those seen in onshore exposures of pleistocene coastal units amino acid epimerization measurements are a comparatively rapid and inexpensive chronologic tool for use in taphonomic and sediment shell transport studies paired amino acid 14c analyses on single shells provide insights into geochemical alteration of shells and permit modelling of the residence time of shells on beaches greater numbers of analyses at each site are needed before statistically valid estimates of age mixing can be obtained but the apparent distribution of pleistocene shells on atlantic coast beaches appears to be related to the distribution of pleistocene units in the shoreface and inner shelf and the thickness of holocene sedimentary cover in specific areas these observations provide useful criteria for the evaluation of possible age mixing of shells collected at outcrops of pleistocene units in the coastal plain

chronostratigraphic studies of sediments in the negev desert using amino acid epimerization analysis of land snail shells abstract the chronostratigraphy of mostly holocene sediments in the northern negev desert of israel was studied through amino acid epimerization analysis alloisoleucine isoleucine ratio a i of individual land snail shells and 14c analysis of bulk samples of land snail shells contained within the sediments analysis of 31 deposits shows a very strong correlation between a i and 14c age a i analyses indicate that age mixtures occur within all colluvial and in some fluvial deposits consequently radiocarbon dates of bulk samples which give an average age overestimate the time of deposition sedimentation rates were generally rapid in both fluvial and colluvial deposits colluviation shows a maximum in the early holocene and decreases progressively thereafter in accordance with the change in average rainfall accumulation of fluvial sediments shows a distinct mid holocene maximum and apparently relates to the interaction between variation in rainfall extent of bedrock exposure and vegetation density late holocene fluvial deposition may relate to agricultural activity the understanding of the chronology of sedimentation is dependent on an integrated approach employing amino acid epimerization analysis to study age variation within a layer and 14c analyses for establishment of an absolute chronology

geometry kinematics and deformation rates along the active normal fault system in the southern apennines implications for fault growth throw rates throws and kinematic data have been collected from a localised system of active normal faults in the southern apennines italy to assess how its growth history differs from that for a distributed fault system in the central apennines both show evidence for fault interaction in that 1 faults located centrally along strike have higher throws and throw rates than distal faults and 2 cumulative throw and throw rate profiles summed across strike show central maxima with values decreasing to zero at fault system tips however although throw rates increased through time in the central apennines we are unable to resolve such changes if they exist for the southern apennines specifically throw rates derived from offsets of 18 ka geomorphic surfaces are consistent with total throws in the southern apennines when extrapolated back through time but overestimate total throws in the central apennines by a factor of 2 4 suggesting an increase in throw rate through time for the latter we discuss why some fault systems appear to have throw rates that are constant through time whilst others accelerate during growth interaction

late miocene turnover of molluscan faunas new zealand taxonomic and ecological reassessment of diversity changes at multiple spatial and temporal scales abstract previous estimates of molluscan biodiversity during the neogene in new zealand have revealed a pattern of significant diversity decline during the latest miocene this study uses an occurrence based dataset derived from published literature to examine this pattern in further detail with both traditional synoptic measures and subsequent sampling standardization synoptic analyses of regional scale data reveal diversity trajectories similar to those previously established and rarefaction techniques demonstrate that the inferred pattern of late miocene diversity decline and early pliocene rebound is only somewhat biased by variations in sampling intensity the pattern is also affected by temporal variations in the preservation of shelf paleoenvironments with representation of highly diverse shallow water facies varying considerably between biostratigraphic stages the sampling and corresponding synoptic genus richness of biogeographic areas within the new zealand region is also uneven within a single sedimentary basin sampled at high temporal resolution wanganui basin new data suggest that late miocene faunas were as diverse as those of the early pliocene contrasting with the pattern of diversity decrease and subsequent increase observed at the regional spatial scale in prior studies however an ecological analysis of the new data demonstrates that turnover and restructuring of benthic communities did take place at the end of the late miocene these findings suggest that spatial scale and temporal resolution are important considerations in determining the magnitude of diversity and ecological change observed in paleontologic studies contemporaneous biodiversity may not be similarly expressed at varying spatial or temporal scales in the fossil record rather regional patterns of diversity change are governed by a complex interplay of not only large scale environmental factors e g temperature control but also independent basin scale processes e g basin subsidence and local sampling intensity

aminochronology and time averaging of quaternary land snail assemblages from colluvial deposits in the madeira archipelago portugal understanding the properties of time averaging age mixing in a stratigraphic layer is essential for properly interpreting the paleofauna preserved in the geologic record this work assesses the age and quantifies the scale and structure of time averaging of land snail rich colluvial sediments from the madeira archipelago portugal by dating individual shells using amino acid racemization calibrated with graphite target and carbonate target accelerator mass spectrometry radiocarbon methods gastropod shells of actinella nitidiuscula were collected from seven sites on the volcanic islands of bugio and deserta grande desertas islands where snail shells are abundant and well preserved in quaternary colluvial deposits results show that the shells ranged in age from modern to 48 cal ka bp calibrated radiocarbon age covering the last glacial and present interglacial periods snail shells retrieved from two of the colluvial sites exhibit multimillennial age mixing 6 ka which significantly exceeds the analytical error from dating methods and calibration the observed multimillennial mixing of these assemblages should be taking into consideration in upcoming paleoenvironmental and paleoecological studies in the region the extent of age mixing may also inform about the time span of colluvial deposition which can be useful in future geomorphological studies in addition this study presents the first carbonate target radiocarbon results for land snail shells and suggests that this novel rapid and more affordable dating method offers reliable age estimates for small land snail shells younger than 20 cal ka bp

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

post glacial slip history of the sparta fault greece determined by 36cl cosmogenic dating evidence for non periodic earthquakes 1 using 36cl cosmic ray exposure dating we obtained continuous exposure histories for 7 12 m high limestone surfaces at two sites 10 km apart on the sparta normal fault scarp as each major earthquake adds new surface to the cumulative scarp exposing new material to cosmic ray bombardment these exposure histories allow the slip history to be constrained the results show that an earthquake occurred on this fault 2800 300 yr ago we infer that this is the seismic event that destroyed ancient sparta in 464 b c four earlier earthquakes ruptured the sparta fault in the last 13 ka with similar slip amplitudes of about 2 m and with time intervals ranging from 500 yr to 4500 yr the observations also confirm that the sparta scarp is post glacial supporting the hypothesis that similar scarps elsewhere in the mediterranean region have a comparable age the absence of any event since 464 b c could suggest a future event is imminent however the irregularity of earthquake time intervals could also be due to changes of loading with important consequences for the mechanics of continental deformation

the application of radiocarbon age estimates to the dating of glacial sequences an example from the miami sublobe ohio u s a abstract despite the importance of dating glacial sequences little evidence has been available to highlight the stratigraphic issues associated with the interpretation of age analysis a compilation of radiocarbon data from the miami sublobe of the laurentide ice sheet provides a large enough data set more than 133 dates to identify at least two sources of error sample and unit variability and transportation problems analysis of different samples from the same stratigraphic level commonly differ by more than the reported one sigma error and 2 000 year differences do occur glacial entrainment and transportation emplace older organic material over younger in situ materials and this effect may also give age errors in the data set of up to 2 000 years at a minimum multiple radiocarbon ages from a sequence of units are necessary to assign a reliable age to events within a glacial sequence however representing multiple ages poses its own problems a graphical representation that combines the probability of each sample appears to be one solution

considerations on the significance of some post glacial fault scarps in the abruzzo apennines central italy abstract in this paper the tectonic and palaeoseismological significance of the fault scarps present in the massifs of the velino and of mount greco and in the plains adjacent to these massifs forming part of the abruzzo apennines is discussed the basic features of post glacial fault scarps already mentioned in the literature are illustrated found in the fucino plain in the ovindoli piani di pezza area on the mount magnola in the valle majelama alluvial fan and in the piano di aremogna others not previously mentioned surveyed by the author in the mount ocre cefalone area in the piana di corvaro and on the mount greco toppe del tesoro are also discussed on the basis of the characteristics of these scarps and of the chronological framework of the last phases of activity of the faults which gave rise to the scarps described the reliability of the assumptions made for palaeoseismological studies in other places is discussed for the abruzzo area the studies performed in the area of the velino and greco massifs suggest that to establish the possible co seismical activity of the faults the use of morphological indices and also of the results obtained with the excavation of trenches has to be very cautiously applied it is considered that the following can be stated it is probable that the majority of the mentioned fault scarps are co seismic in view of the height of some fault scarps it cannot be excluded that they were formed during the course of earthquake sequences lasting not more that 2 3000 years it is possible that some of the above mentioned scarps were produced during seismic events of great magnitude it does not seem possible at present to calculate a precise slip rate the amount of the offset often changes along the same fault even over short distances moreover there are many horst and graben type structures produced by local effects which contribute towards making an assessment of the fault offsets complicated it is also clear that erosion can change the aspect of the scarps an evaluation of the displacements caused by the faults producing them must therefore be made extremely cautiously caution is needed in assessing the magnitude of past earthquakes and in assuming recurrence intervals the dating of the phases of fault activity is approximate and there is great difficulty in recognizing with any certainty the duration the sort of activity and the length of the fault segment concerned in the activity moreover the existence in the past of aseismic creep and of movements linked to post glacial isostatic rebound cannot be excluded with any certainty these considerations must be regarded for the two massifs examined since there have been the epicentres of rare earthquakes of low intensity the only large earthquake known in history which caused surface ruptures occurred in the fucino area in 1915 the fault scarps reported in this paper seem however interpretable in general as indications of post glacial tectonic activity the intensity of which was unsuspected until a few years ago

calibration of cosmogenic 36cl production rates from ca and k spallation in lava flows from mt etna 38 n italy and payun matru 36 s argentina abstract published cosmogenic 36cl production rates from ca and k spallation differ by almost a factor of 2 in this paper we determine production rates of 36cl from ca and k in samples of known age containing little cl ca rich plagioclases and k feldspars were separated from a total of 13 samples collected on the surfaces of four basaltic lava flows at mt etna 38 n italy and from a trachyte lava flow at payun matru volcano 36 s argentina eruption ages determined by independent methods range between 0 4 and 32 ka sample site elevations range between 500 and 2500 m corresponding scaling factors were calculated using five different published scaling models four of which consider paleo geomagnetic field variations integrated over the exposure durations the resulting five data sets were then analyzed using a bayesian statistical model that incorporates the major inherent uncertainties in a consistent way spallation production rates from ca and k considering all major uncertainties are 42 2 4 8 atoms 36cl g ca 1 a 1 and 124 9 8 1 atoms 36cl g k 1 a 1 normalized to sea level and high latitude using the scaling method of stone 2000 scaling models that account for paleo geomagnetic intensity changes yield very similar mean values at most 4 if the uncertainties in the independent ages are neglected in the bayesian model the calculated element specific production rates would be about 12 higher our results are in agreement with previous production rate estimations both for ca and k if only low cl i e 20 ppm samples are considered

book review biogeochemistry of amino acids edited by p e hare t c hoering and k king jr wiley 1980 538 pp 30 50

a review of amino acid racemization studies in quaternary mollusks stratigraphic and chronologic applications in coastal and interglacial sites pacific and atlantic coasts united states united kingdom baffin island and tropical islands abstract amino acid racemization aar studies of quaternary mollusks mostly marine mollusks from coastal deposits are reviewed data obtained in regional studies from the u s atlantic and pacific coasts baffin island the united kingdom and tropical islands are discussed as they relate to method evaluation kinetic model development and aminostratigraphic applications u s pacific coast studies have been employed for estimating tectonic deformation rates study of molluscan zonation patterns in the late pleistocene and in kinetic model evaluation u s atlantic coast studies have identified multiple aminostratigraphic zones in areas with complex morphostratigraphic relationships and have also revealed some important conflicts between aminostratigraphic temperature concepts and radiometric data studies in the united kingdom involving coastal sites and non marine interglacial sites identify some stratigraphic and kinetic conflicts but provide a preliminary chronostratigraphic model for the classical interglacial terminology of the u k middle to late pleistocene baffin island studies involving aar data and u th dating of shells have resulted in some significant revisions of previous chronologic models the arctic environment has also stimulated some novel approaches in the collection and interpretation of aar results tropical island studies though few in number aid in calibration of observed racemization and also aid in correlation of coastal deposits with late pleistocene isotopic ice volume records

large earthquake triggering clustering and the synchronization of faults large earthquakes are sometimes observed to trigger other large earthquakes on nearby faults the magnitudes of the calculated coulomb stress transfers presumed to cause the triggering are 10 2 10 3 of the earthquake stress drops the earthquake stress drops and the triggering delay times are similarly small with respect to the natural recurrence time of the earthquakes this requires that both faults be simultaneously very close to the ends of their seismic cycles paleoseismological data show that for the same regions prior earthquakes have occurred in clusters of ruptures of several faults separated by long quiescent periods both observations suggest that synchronization is occurring between faults theory and observations indicate that synchronization can occur between nearby faults with positive stress coupling and intrinsic slip velocities within an entrainment threshold in the south iceland seismic zone the central nevada seismic belt and the eastern california shear zone several synchronous clusters that apparently act independently can be recognized this behavior is the 3d equivalent of the phase locking that results in the seismic cycle of individual faults being dominated by large characteristic earthquakes and for synchronization of fault segments along a given fault rupture patterns of repeated individual earthquakes or earthquake clusters are not identical in either the 2d or 3d cases the state of this system which exhibits strong indications of synchrony without exact repetition may be called fuzzy synchrony

comparison of geodetic and geologic data from the wasatch region utah and implications for the spectral character of earth deformation at periods of 10 to 10 million years the wasatch fault and adjacent fault zones provide an opportunity to compare present day deformation rate estimates obtained from space geodesy with geologic displacement rates over at least four temporal windows ranging from the last millennium up to 10 myr the three easternmost gps sites of the basin and range geodetic network bargen at this latitude define a 130 km wide region spanning three major normal faults extending east west at a total rate of 2 7 0 4 mm yr with an average regional strain rate estimated to be 21 4 nstrain yr about twice the basin and range average on the wasatch fault the vertical component of the geologic displacement rate is 1 7 0 5 mm yr since 6 ka 0 6 mm yr since 130 ka and 0 5 0 7 mm yr since 10 ma however it appears likely that at the longest timescale rates slowed over time from 1 0 to 1 4 mm yr between 10 and 6 ma to 0 2 to 0 3 mm yr since 6 ma the cumulative vertical displacement record across all three faults also shows time variable strain release ranging from 2 to 4 mm yr since 10 ka to 1 mm yr averaged over the past 130 kyr conventional earthquake recurrence models reid type behavior would require an accordingly large variation in strain accumulation or loading rate on a 10 kyr timescale for which there appears to be no obvious geophysical explanation alternatively seismic strain release given a wide range of plausible constitutive behaviors for frictional sliding may be clustered on the 10 kyr timescale resulting in the high holocene rates with comparatively low uniform strain accumulation rates on the 100 kyr timescale wallace type behavior the latter alternative combined with observations at the million year timescale and the likelihood of a significant contribution of postseismic transients implies maxima of spectral amplitude in the velocity field at periods of 10 myr variations in tectonic loading 10 kyr clustered strain release and of 100 years postseismic transients if so measurements of strain accumulation and strain release may be strongly timescale dependent for any given fault system

earthquake synchrony and clustering on fucino faults central italy as revealed from in situ cl 36 exposure dating we recover the holocene earthquake history of seven seismogenic normal faults in the fucino system central italy we collected 800 samples from the well preserved limestone scarps of the faults and modeled their 36cl concentrations to derive their seismic exhumation history we found that 30 large earthquakes broke the faults in synchrony over the last 12 ka the seven faults released strain at the same periods of time 12 9 ka 5 3 ka and 1 5 1 ka on all faults the strain accumulation and release occurred in 3 6 ka supercycles each included a 3 5 ka phase of slow 0 5 2 mm yr strain accumulation in relative quiescence followed by a cluster of three to four large earthquakes or earthquake sequences that released most of the strain in 1 2 ka the large earthquakes repeated every 0 5 0 3 ka during the paroxysmal phases and every 4 3 0 9 ka between those phases earthquakes on the northern faults produced twice larger surface slips 2 m and had larger magnitudes mw 6 2 6 7 than those on the southern faults on most faults the relative strain level was found to control the amount of slip and the time of occurrence of the next large earthquake faults entered a phase of clustered activity once they had reached a specific relative strain threshold the tre monti fault is identified as the most prone to break over the next century our data document earthquake synchrony and clustering at a broader space and time scale than has been reported to date

warmer or cooler late holocene marine palaeoenvironments interpreting southeast australian and brazilian sea level changes using fixed biological indicators and their δ18o composition abstract relic inter tidal assemblages of sessile organisms which are referred to as fixed biological indicators fbis are shown to be useful proxies for late holocene climatic and environmental changes as well as direct indicators of short term fluctuations in sea level a detailed comparison of change in the inter tidal assemblages of two southern hemisphere sites at comparable latitudes port hacking new south wales south east australia and the laguna imbituba region of southern brazil indicates periods of marked similarities in the timing and nature of changes at 5200 3800 cal years bp and differences after 2400 cal years bp there is sufficient concurrence of cooling phases and falling sea levels to strongly suggest that in some cases global rather than regional forcing factors are at work the value of inter tidal organisms as indicators of changed environments is developed by identifying the past and present distributions of the common marker species tubeworms barnacles and mussels the 18 o content of these extant specimens at port hacking confirmed changes in ocean water temperature and associated sea level behaviour corresponding to invasion or extinction of temperature sensitive species a similar pattern is repeated although in a less marked fashion in the laguna imbituba region of southern brazil

a unique assemblage of epibenthic sessile suspension feeders with archaic features in the high antarctic we suggest that the epibenthic communities of passive suspension feeders that dominate some high antarctic seafloors present unique archaic features that are the result of long isolation together with the effects of environmental features including reduced terrestrial runoff and favourable feeding conditions these features probably originated during the late cretaceous when the high antarctic environment started to become different from the surrounding oceans modern antarctic communities are thus composed of a mixture of palaeozoic elements taxa that migrated from the deep ocean during interglacial periods and a component of fauna that evolved from common gondwana cretaceous ancestors we explore this hypothesis by revisiting the palaeoecological history of antarctic marine benthic communities and exploring the abiotic and biotic factors involved in their evolution including changes in oceanic circulation and production plankton communities the development of glaciation restricted sedimentation isolation life histories and the lack of large predators the conditions favouring the retention of apparently archaic features in the antarctic marine fauna remain to be fully elucidated but high antarctic communities are clearly unique and deserve special conservation

east west extension and holocene normal fault scarps in the hellenic arc examination of surface fault traces with spot images and in the field corroborates the inference that the active tectonics of southern peloponnesus and crete are dominated by approximately north south normal faulting and approximately east west extension the heights of holocene normal fault scarps yield first order regional estimates of fault slip rates between 0 1 and 2 3 mm yr most of the surface scarps probably ruptured during past earthquakes such as that which destroyed sparta in 464 b c on the sparta fault the holocene average slip rate and the recurrence time of large earthquakes may be 1 mm yr and 3000 yr respectively the regional pattern of quaternary faulting suggests that the east west extension near the hellenic subduction zone is fast about 5 10 m y the change from north south to east west extension in the late pliocene 2 4 ma implies that the aegean is starting to collide with the northern margin of africa

the 2009 l aquila central italy mw6 3 earthquake main shock and aftershocks 1 a m w 6 3 earthquake struck on april 6 2009 the abruzzi region central italy producing vast damage in the l aquila town and surroundings in this paper we present the location and geometry of the fault system as obtained by the analysis of main shock and aftershocks recorded by permanent and temporary networks the distribution of aftershocks 712 selected events with m l 2 3 and 20 with m l 4 0 defines a complex 40 km long nw trending extensional structure the main shock fault segment extends for 15 18 km and dips at 45 to the sw between 10 and 2 km depth the extent of aftershocks coincides with the surface trace of the paganica fault a poorly known normal fault that after the event has been quoted to accommodate the extension of the area we observe a migration of seismicity to the north on an echelon fault that can rupture in future large earthquakes

pleistocene and holocene interglacial molluscan assemblages from patagonian and bonaerensian littoral argentina sw atlantic palaeobiodiversity and palaeobiogeography abstract our analysis of palaeobiodiversity and palaeobiogeography of quaternary molluscan assemblages provide information on the last coastal scenarios in the sw atlantic we present patterns of species richness areas of endemism and between areas relationships based on records 721 taxa from argentina and northwards in south america surinam brazil uruguay including pleistocene holocene and modern sites 48 localities in argentina our data since the mid late pleistocene mis11 1 ca 400 ka b p to present suggest environmental changes linked to sea level and climatic fluctuations large enough to alter benthic associations compositional geographical variations including a few extinctions the southwards decreasing diversity trend for modern bivalves mostly infaunal taxa and gastropods mostly epifaunal taxa from surinam to tierra del fuego responds mainly to latitudinal sst salinity barriers hydrodynamic forces rivers and shallow currents minima peaks fit with local estuarine and marginal marine sites influenced by the rio de la plata plume highest peaks with fully marine warmer waters influenced by the brazilian current bonaerensian sector a similar trend applies for the holocene pleistocene maxima peaks in patagonia belong to mis11 and mis5 highstands warmer than today multivariate cluster analysis ca minimum spanning trees superimposed to principal coordinates analysis pco and cladistic parsimony analysis of endemicity pae methods showed congruent relationships between localities discriminating marginal from open marine environments but pco combined with pae was most advantageous for our area and dataset 382 gastropods 339 bivalves 29 pleistocene 28 holocene and 35 modern sites allowing objective quick comparisons shifts of areas of endemism during the holocene and pleistocene relate with sst and salinity changes a more homogeneous mid holocene ca 7 5 ka b p scenario of regionally increased salinity and higher ca 2 c sst defined the bonaerensian and northern patagonian sectors facilitating southwards shifts of bivalve and gastropod taxa for patagonia a colder pleistocene scenario south of sao is documented by tegula atra exclusive pleistocene cold water species extinct in the swa probably a signal of post lgm palaeoceanographical changes in the mar argentino

evolution of the west andean escarpment at 18 s n chile during the last 25 ma uplift erosion and collapse through time abstract the geological record of the western andean escarpment warp reveals episodes of uplift erosion volcanism and sedimentation the lithological sequence at 18 s comprises a thick pile of azapa conglomerates 25 19 ma an overlying series of widespread rhyodacitic oxaya ignimbrites up to 900 m thick ca 19 ma which are in turn covered by a series of mafic andesite shield volcanoes between 19 and 12 ma the surface of the oxaya ignimbrites evolved into a large monocline on the western slope of the andes a giant antithetically rotated block oxaya block 80 km 20 km formed on this slope at about 10 12 ma and resulted in an easterly dip and a reversed drainage on the block s surface morphology topography and stratigraphic observations argue for a gravitational cause of this rotation a secondary gravitational collapse 50 km3 extending 25 km to the west occurred on the steep western front of the oxaya block alluvial and fluvial sediments 11 2 7 ma accumulated in a half graben to the east of the tilted block and were later thrust over by the rocks of the escarpment wall indicating further shortening between 8 and 6 ma flatlying upper miocene sediments

quantitative palaeobiogeographical analysis of south american neogene chioninae bivalvia veneridae abstract chionine bivalves are one of the most important components of neogene and recent molluscan faunas in southern south america but it was not until recently that their phylogenetic relationships has been explored quantitatively based on this robust framework we analyzed the palaeobiogeographical history of the group the geographic areas used in this analysis were discretized using a multivariate k means cluster analysis based on the palaeocoordinates of chionine bearing localities statistical comparison of quantitative event based biogeography models using likelihood suggests that our data best fits models that include long distance jump dispersal j with a slight preference for a model that also gives increased weight to vicariance the chione clade including the genera chione anomalocardia and chionopsis is mainly a caribbean and central eastern pacific lineage with expansions to california and the southern western atlantic coast the protothaca clade including protothaca nioche austrovenus and chionista is mainly an eastern pacific lineage with a proposed southern south american origin with occasional dispersals to the western pacific oceania and east asia a new alternative dispersal route is proposed across the north pacific from california and the north eastern pacific to east asia and oceania as shown by austrovenus stutchburyi tuangia crassicosta and protocallithaca adamsii the ameghinomya clade including all ameghinomya species is a southern south american lineage south eastern pacific origin that subsequently dispersed into the southern western atlantic the protothaca and ameghinomya clades show opposite histories the former being mainly pacific and the latter mainly atlantic the distribution of both clades on both sides of south america may have been allowed by the opening of the drake passage gateway around the oligocene miocene boundary

the 1984 abruzzo earthquake italy an example of seismogenic process controlled by interaction between differently oriented synkinematic faults the evolution of the seismogenic process associated with the ms 5 8 sangro valley earthquake of may 1984 abruzzo central italy is closely controlled by the quaternary extensional tectonic pattern of the area this pattern is characterised by normal faults mainly nnw striking whose length is controlled by pre existing mio pliocene n100f10j left lateral strike slip fault zones these are partly re activated as right lateral normal oblique faults under the quaternary extensional regime and behave as transfer faults integration of re located aftershocks focal mechanisms and structural features are used to explain the divergence between the alignment of aftershocks wsw ene and the direction of seismogenic fault planes defined by the focal mechanisms nnw sse of the main shock and of the largest aftershock ms 5 3 the faults that appear to be involved in the seismogenic process are the nnw sse barrea fault and the e w m greco fault there is field evidence of finite quaternary deformation indicating that the normal barrea fault re activates the m greco fault as right lateral transfer fault no surface faulting was observed during the seismic sequence the apparently incongruent divergence between aftershocks and nodal planes may be explained by interpreting the m greco fault as a barrier to the propagation of earthquake rupturing the rupture would have nucleated on the barrea fault migrating along strike towards nnw the sharp variation in direction from the barrea to the m greco fault segments would have represented a structural complexity sufficient to halt the rupture and subsequent concentration of post seismic deformation as aftershocks around the line of intersection between the two fault planes fault complexities similar to those observed in the sangro valley are common features of the seismic zone of the apennines we suggest that the zones of interaction between nw se and nnw sse plio quaternary faults and nearly e w transfer faults extending for several kilometres in the same way as m greco does might act as barriers to the along strike propagation of rupture processes during normal faulting earthquakes this might have strong implications on seismic hazard especially for the extent of the maximum magnitude expected on active faults during single rupture episodes d 2002 elsevier science b v all rights reserved

fault slip accumulation in an active rift over thousands to millions of years and the importance of paleoearthquake sampling abstract the catastrophic earthquakes that recently september 4th 2010 and february 22nd 2011 hit christchurch new zealand show that active faults capable of generating large magnitude earthquakes can be hidden beneath the earth s surface in this article we combine near surface paleoseismic data with deep 1 ma timescales in the taranaki rift new zealand our analysis shows that the integration of different timescale datasets provides a basis for identifying active faults not observed at the ground surface estimating maximum fault rupture lengths inferring maximum short term displacement rates and improving earthquake hazard assessment we find that fault displacement rates become increasingly irregular both faster and slower on shorter timescales leading to incomplete sampling of the active fault population surface traces have been recognised for

rapid racemization of aspartic acid in mollusc shells and potential for dating over recent centuries dating of deposits and materials less than 350 years old is hindered by the very poor time resolution of the radiocarbon method over this period1 2 fluctuations in atmospheric 14c levels result in the existence of several possible calendric ages for any given radiocarbon age for terrestrial samples in the marine record these fluctuations are dampened however only a small change in marine radiocarbon ages occurs over this period from ad 1700 to 1950 radiocarbon ages become only 100 yr younger2 consequently age resolution is poor furthermore there is an uncertainty in the amount of the correction for the reservoir effect the apparent radiocarbon age of modern marine carbon typically 400yr which reflects the average residence time of carbon in the oceans amino acid racemization epimerization analysis has been used primarily for dating samples older than the limit of radiocarbon dating 40 000 50 000 yr bp 3 4 here i show that aspartic acid asp in mollusc shells has racemized particularly rapidly over the past few centuries analyses done on land snails from deposits in the negev desert eolianites in madeira cave deposits in jamaica and from museum collections indicate racemization rates of 2 5 per century asp racemization thus provides a means of dating recent faunal assemblages of molluscs and other biogenic carbonates as well as recent terrestrial fluvial and marine sedimentary sequences that contain molluscs

the italian cmt dataset from 1977 to the present abstract the ingv harvard european mediterranean regional centroid moment tensor rcmt catalog collects solutions routinely computed since 1997 for earthquakes with moderate magnitude 4 5 m 5 5 in the mediterranean region the database represents an extension to smaller magnitudes of the harvard global cmt catalog based on analysis of seismograms recorded at regional distance and modeling of intermediate period surface waves the catalog includes about 600 events 200 of which in the italian region this study extends the catalog back in time for the italian region as long as made possible by available digital data i e since 1977 with the same analysis and inversion method used for current seismicity as a result we present here 65 new moment tensors for years between 1977 and 1997 these solutions represent 45 of the total number of events analyzed the existing seismograms being often too scarce to allow a stable solution the new dataset includes events in many seismic zones where moderate seismicity had previously been scarcely documented e g the po plain the central to southern apennines and the adriatic sea the complete dataset including previously determined rcmts and cmts represents the seismic deformation in the italian area during the last 25 years

polar emergence and the influence of increased sea ice extent on the cenozoic biogeography of pectinid molluscs in antarctic coastal areas abstract from the paleocene to the pliocene chlamys like genera of scallops pectinid bivalve molluscs inhabited coastal areas around the antarctic continent today all of the chlamys like genera are extinct around antarctica and restricted to lower latitude habitats along the surrounding continents the only remaining scallop in the high antarctic zone is the large greater than 108 mm in height endemic thin shelled adamussium colbecki adamussium has a circumpolar distribution with its highest abundances greater than 50 m 2 and 2 kg m 2 in antarctic coastal areas in contrast to the offshore habitats where its ancestors had predominated since the oligocene shell morphology and substrate data indicate that the chlamys like faunas were largely exposed to high energy conditions associated with open water in the coastal zone while the adamussium faunas have been associated with low energy hydrodynamic conditions modern and mid holocene distributions in the antarctic coastal zone further indicate that adamussium is largely restricted to protected embayments and habitats with extensive sea ice coverage in addition a decadal mark and recapture experiment demonstrates that adamussium has extremely slow growth and a century scale lifespan which complement the life history traits that are considered to be characteristic of species inhabiting predictable and constant environments in the deep sea stabilization of the water column by increased sea ice extent together with stenothermal conditions prolonged darkness and limited primary production would have enhanced the habitat similarities between polar coastal environments and the deep sea after the plio pleistocene climate threshold subsequently the deep antarctic continental shelf would have facilitated faunal shifts between deep sea and coastal habitats as with the polar emergence of the adamussium fauna such biogeographic interchanges across high latitude continental shelves since the end of the cenozoic would have contributed significantly to the latitudinal diversity gradients that have been noted from both deep sea and shallow water marine faunas

amino acid geochronology of individual foraminifer pulleniatina obliquiloculata tests north queensland margin australia a new approach to correlating and dating quaternary tropical marine sediment cores 1 in this study we demonstrate the utility of amino acid geochronology based on single foraminiferal tests in quaternary sediment cores from the queensland margin australia the large planktonic foraminifer pulleniatina obliquiloculata is ubiquitous in shelf slope and basin sediments of north queensland as well as pantropical oceans fossil tests are resistant to dissolution and retain substantial concentrations of amino acids 2 4 nmol mg 1 of shell over hundreds of thousands of years amino acid d and l isomers of aspartic acid asp and glutamic acid glu were separated using reverse phase chromatography which is sensitive enough to analyze individual foraminifera tests in all 462 pulleniatina tests from 80 horizons in 11 cores exhibit a systematic increase in d l ratios down core d l ratios were determined in 32 samples whose ages are known from ams 14 c analyses in all cases the asp and glu d l ratios are concordant with 14 c age d l ratios of equal age samples are slightly lower for cores taken from deeper water sites reflecting the sensitivity of the rate of racemization to bottom water temperature beyond the range of 14 c dating previously identified marine oxygen isotope stage boundaries provide approximate ages of the sediments up to about 500 000 years for this longer time frame d l ratios also vary systematically with isotope correlated ages the rate of racemization for glu and asp was modeled using power functions these equations can be used to estimate ages of samples from the queensland margin extending back at least 500 000 years this analytical approach provides new opportunities for geochronological control necessary to understand fundamental sedimentary processes affecting a wide range of marine environments index terms 4267 oceanography general paleoceanography 4850 oceanography biological and chemical organic marine chemistry 3022 marine geology and geophysics marine sediments processes and transport keywords queensland margin marine sediment amino acid racemization geochronology foraminifera quaternary stratigraphy citation hearty p j m j o leary d s kaufman m c page and j bright 2004 amino acid geochronology of individual foraminifer pulleniatina obliquiloculata tests north queensland margin australia a new approach to correlating and dating quaternary tropical marine sediment cores paleoceanography 19 pa4022 doi 10 1029 2004pa001059

amino acid racemization dating of marine shells a mound of possibilities shell middens are one of the most important and widespread indicators for human exploitation of marine resources and occupation of coastal environments establishing an accurate and reliable chronology for these deposits has fundamental implications for understanding the patterns of human evolution and dispersal this paper explores the potential application of a new methodology of amino acid racemization aar dating of shell middens and describes a simple protocol to test the suitability of different molluscan species this protocol provides a preliminary test for the presence of an intracrystalline fraction of proteins by bleaching experiments and subsequent heating at high temperature checking the closed system behaviour of this fraction during diagenesis only species which pass both tests can be considered suitable for further studies to obtain reliable age information this amino acid geochronological technique is also applied to midden deposits at two latitudinal extremes northern scotland and the southern red sea results obtained in this study indicate that the application of this new method of aar dating of shells has the potential to aid the geochronological investigation of shell mounds in different areas of the world

coseismic ground deformation of the 6 april 2009 l aquila earthquake central italy mw6 3 1 we provide field data of coseismic ground deformation related to the 6 april mw 6 3 l aquila normal faulting earthquake three narrow fracture zones were mapped paganica colle enzano p e mt castellano mt stabiata c s and san gregorio sg these zones define 13 km of surface ruptures that strike at 130 140 we mapped four main types of ground deformation free faces on bedrock fault scarps faulting along synthetic splays and fissures with or without slip that are probably due to the near surface lithology of the fault walls and the amount of slip that approached the surface coseismically the p e and c s zones are characterized by downthrow to the sw up to 10 cm and opening up to 12 cm while the sg zone is characterized only by opening afterslip throw rates of 0 5 0 6 mm day were measured along the paganica fault where paleoseismic evidence reveals recurring paleo earthquakes and post 24 8 kyr slip rate 0 24 mm yr

fault based earthquake rupture forecast in central italy remarks after the l aquila mw 6 3 event abstract in 2006 we published an earthquake hazard model called lassci layered seismogenic source model in central italy in october 2008 we began to update the model for use in 5 and 10 year forecasts the lassci 2006 model is supported by good fault based definitions of seismogenic sources and simple physically motivated models of earthquake occurrence the lassci 2009 model has been improved by revision of the error propagation assumptions and increased accuracy of the earthquake probabilities the 6 april 2009 earthquake that struck l aquila occurred on the model fault having the highest probability of occurrence in the 2009 revised lassci forecast it is therefore consistent with our model assumptions furthermore peak ground accelerations were in reasonable agreement with the values having 90 probability of not being exceeded in 50 yr in the revised 2009 model the aggregate probability of having a maximum sized event in the next 5 yr on at least one of the neighboring sources less than 25 km distance away decreases in l aquila from 10 to 7 after the earthquake occurrence but still remains a maximum there along the central apennines the lassci models 2006 and 2009 featuring characteristic fault sources and time dependence seem to be suitable for guidance in reconstruction and seismic retrofit in the central appenines

rare earth elements record past earthquakes on exhumed limestone fault planes evaluating the timing and size of past earthquakes is a constant challenge in palaeoseismology here we show that rare earth element ree concentrations can be used to constrain the number and slips of major past earthquakes we focus on one of the rare faults worldwide the magnola normal fault italy whose holocene earthquake history is precisely known we analysed 42 samples from along the 10 m that form the surface of the well preserved seismically exhumed fault scarp and seven samples extracted from the fault plane section buried in the ground we show that the first metre of soil contaminates the scarp rocks producing a marked concentration peak in ree similar peaks are recognized on the exhumed scarp at positions that coincide with the transitions between the known past ruptures we conclude that the ree peaks locate palaeoground levels and are excellent markers for the large earthquakes that exhumed the scarp

the presence of tawera gayi hupe in gay 1854 veneridae bivalvia in southern south america did tawera achieve a late cenozoic circumpolar traverse cenozoic tawera marwick 1927 from the southern hemisphere exhibits a pattern of disjunt distribution around the southern oceans a single species tawera gayi hupe in gay c 1854 historia fisica y politica de chile zoologia 8 paris is confined to southern south america taking into account the occurrence of tawera in the fossil record taxonomy based on shell morphology and available information on extant species of tawera it is plausible that the genus appeared first in southern australia during the early miocene and then expanded and radiated to new zealand it also appears that tawera first crossed from australasia to south america during the early pleistocene this picture can be better explained if tawera was able to achieve circumglobal range by means of the antarctic circumpolar current thus different potential factors of dispersal i e larval dispersal drifting kelp rafting and pleistocene cooling are considered and discussed shell morphology and overall appearance of tawera gayi is very similar to tawera philomela smith 1885 from south africa and tawera mawsoni hedley 1916 from macquarie island suggesting these taxa have a close relationship one postulated explanation which should be confirmed by means of a phylogenetic study is a subsequent migration of tawera from south america arriving first to the southern african region via the west wind drift islands province and then probably coming back again to australasia it could have been mediated via the same current during the late pleistocene and much later during the holocene

factors controlling carbonate dissolution rates quantified in a field test in the austrian alps carbonate dissolution rates were investigated by measuring the mass difference of carbonate tablets exposed to natural dissolution for 1 year 70 tablets were distributed over 13 test sites on the north slope of the hochschwab massif in the austrian alps the influences of altitude subsoil vs sub aerial exposure vegetation karst morphology soil humidity sample lithology and sample surface morphology were investigated the observed dissolution rates varied between 13 and 40 m a for subcutaneous samples and about 11 m a for sub aerial exposure outstandingly high rates of 48 m a were observed in a doline and nearly zero rates were measured at a site influenced by seeping spring water a mass balance using high resolution hydrological data was calculated for the klaffer spring which has an average outflow of 4 8 m3 s it indicated a loss of 21 106 kg of carbonate rock per year which gives an average dissolution rate of 95 m a for the catchment area of 83 km2 the dissolution rates of 10 m a from the sub aerially exposed samples are comparable to values from limestone pedestals which were protected from dissolution by glacial erratics for the past 15 ka

earthquake scaling fault segmentation and structural maturity abstract slip and length measurements on earthquakes suggest large stress drop variability we analyze an extended set of slip length measurements for large earthquakes m 6 to seek for the possible origin s of this apparent variability we propose that such variability arises from earthquakes breaking a variable number of major fault segments that number depends on the strength of the inter segment zones which itself depends on the structural maturity of the faults we propose new d max l parameterizations based on that idea of multiple segment ruptures in such parameterizations each broken segment roughly scales as a crack while the total multi segment rupture does not stress drop on individual segments is roughly constant only varying between 3 5 to 9 mpa the slight variation that is still observed depends on fault structural maturity more mature faults have lower stress drops than immature ones the new d max l functions that we propose reduce uncertainties with respect to available relationships they thus provide a more solid basis to estimate seismic hazard by integrating fault properties revealed by geological studies

reworking and discontinuities in holocene sedimentation in the nile delta documentation from amino acid racemization and stable isotopes in mollusk shells abstract the late holocene sedimentary history of the northwestern edge of the nile delta is reconstructed from amino acid racemization radiocarbon and stable isotope analysis of a series of bivalve shells from a core taken at the edge of lake maryut near alexandria amino acid racemization confirmed by radiocarbon and stable isotope analysis indicates that in many parts of the core mixed age mollusk assemblages are present dating of the time of sediment accumulation at various levels in the core is therefore based on the age of the youngest shells which are identified by amino acid racemization analysis lowest d l values ams radiocarbon analysis is used to determine the ages of the shells except for the most recent sediments last 100 yr for which aspartic acid racemization provides more precise ages amino acid racemization analysis of 59 shells from 21 levels in the 4 8 m holocene sequence in the core enabled identification of a large hiatus holocene sedimentation started at ca 2400 bc apparently corresponding to a westward shift of the course of the canopic nile distributary which lies to the east deposition continued at a rate of 1 4 mm per year ceasing at ca 550 bc at which time the canopic nile shifted eastward again and subsequently became defunct a marine connection during this period is indicated by stable isotope values of shells sediment accumulation began again only at the end of the 19th century when a series of irrigation canals was connected to the lake maryut basin stable isotope values indicate a strong freshwater influence deposition has continued to the present at a very high rate 19 mm per year due to supply of sediments by agricultural activity the relative ease with which racemization analyses can be carried out permits detailed analysis of core chronostratigraphy leading to more accurate reconstruction of core chronology hiatuses can be pinpointed and documented and age mixtures can be identified with appropriate individual shells being selected for ams radiocarbon analysis aspartic acid racemization analysis permits dating of samples from the last several hundred years a period for which radiocarbon analyses provide poor precision

opening of drake passage gateway and late miocene to pleistocene cooling reflected in southern ocean molluscan dispersal evidence from new zealand and argentina thirty two benthic marine molluscan genus group taxa are newly recognised as common to new zealand and argentina previously suggested examples including panis athlopecten austrovenus large cirsotrema lucinoma aulacomya and zygochlamys are confirmed from new collections the total of 46 cenozoic dispersed taxa now recognised falls into four main groups a oligocene early miocene dispersals from south america to new zealand 8 taxa b oligocene early miocene dispersals from new zealand to south america 22 c latest miocene pliocene dispersals from south america to new zealand 9 and d pleistocene holocene dispersals from south america to new zealand at least 7 taxa dispersal seems to have occurred in bursts both to and from south america when the antarctic circumpolar current acc initiated i e when drake passage opened late in the oligocene while dispersal from south america to new zealand only seems to have occurred again at two later times 1 during the latest miocene pliocene enhancement of acc circulation caused by the initiation of west antarctic glaciation and 2 during pleistocene glaciations however the incompleteness of the argentinian record exaggerates the size of the initial burst and allows no assessment of post middle miocene dispersal to south america formation of the acc through the opening of a passage south of australia at ca 43 40 ma and of drake passage at ca 23 ma not only led to the glaciation of antarctica but also greatly altered southern ocean biogeography

evidence for late oligocene establishment of the antarctic circumpolar current removal of the last impediment to circum antarctic flow opening of the drake passage between antarctica and south america is essential to establishment of the acc and has been placed in both the earliest oligocene and earliest miocene on the basis of paleomagnetic reconstructions the tasman gateway between antarctica and tasmania notably deepened following 33 5 ma completion of the acc circuit has been seen as the key to major growth of the east antarctic ice sheet by thermal isolation of the continent an alternative argument attributes ice sheet growth to changes in atmospheric pco2 we present evidence on current strength and water mass properties suggesting a clear increase in flow speed and homogeneity of southern ocean water masses in the latest oligocene after about 23 95 ma marking establishment of the acc attributable to deep opening of drake passage the mi 1 glaciation may be a consequence establishment of a permanent low altitude ice sheet does not appear to take place prior to mid miocene cooling

displacement history of a limestone normal fault scarp northern israel from cosmogenic 36cl the abundance of cosmogenic 36 cl measured in 41 limestone samples from a 9 m high bedrock fault scarp allows us to construct the 14 kyr fault displacement history of the nahef east normal fault northern israel 300 m above sea level n33 latitude the nahef east fault is one of a series of fault scarps located along the 700 m high zurim escarpment a major geomorphic feature samples at the top of the scarp have the highest nuclide concentrations 79 x 10 4 atoms g rock 1 samples at the base have the lowest 11 x 10 4 atoms g rock 1 using chemical data from the samples nahef east fault scarp geometry and surface and subsurface production rates for the 36 cl producing reactions we have constructed a numerical model that calculates 36 cl accumulation on a scarp through time given a series of unique displacement scenarios the resulting model 36 cl concentrations are compared to those measured in the scarp samples faulting histories that result in a good match between measured and modeled 36 cl abundances show three distinct periods of fault activity during the past 14 kyr with over 6 vertical meters of motion occurring during a 3 kyr time period in the middle holocene smaller amounts of displacement occurred before and after the period of most rapid motion the episodic behavior of the nahef east fault indicates that the average displacement rate of this fault system has varied through time

microbial controls on phosphate and lanthanide distributions during granite weathering and soil formation abstract both microbial and geochemical factors control the form distribution and abundance of lanthanides during weathering and soil formation in a profile in the bemboka granodiorite from southern new south wales australia during the initial stages of weathering hydrous ce bearing lanthanide and lanthanide aluminum phosphates including rhabdophane and florencite crystallize on etched apatite surfaces throughout the profile however their fate depends greatly on their location within the profile in rocks weathered 5 6 m below the soil zone the lower profile secondary lanthanide phosphates persist long after all apatite has been dissolved however in rocks weathered within 2 m of the soil zone the upper profile secondary phosphates are dissolved and lanthanides other than ce are removed bacteria and fungal hyphae are localized on secondary phosphate surfaces suggesting that rhabdophane and florencite are solubilized in the upper profile due to organic complexation of dissolved lanthanides and or uptake of phosphate by cells in the soils defined by loss of granitic texture secondary phosphates are replaced by ce oxides lanthanides other than ce removed in solution from the upper profile precipitate as ce poor phosphates in the lower profile when the solubility product is exceeded due to high dissolved phosphate concentrations in proximity to apatite thus the upper profile is the source of lanthanides added to the lower profile in both the lower and upper weathered granite the degree to which weight based ce abundances increase with increasing weathering is consistent with ce immobility on the centimeter scale we attribute the very high weight based ce abundances up to 12 concentrations in fresh rock to extensive leaching and compaction during transformation of weathered rock to soil

aspartic acid racemization dating of holocene brachiopods and bivalves from the southern brazilian shelf south atlantic abstract the extent of racemization of aspartic acid asp has been used to estimate the ages of 9 shells of the epifaunal calcitic brachiopod bouchardia rosea and 9 shells of the infaunal aragonitic bivalve semele casali both taxa were collected concurrently from the same sites at depths of 10 m and 30 m off the coast of brazil asp d l values show an excellent correlation with radiocarbon age at both sites and for both taxa r2site 9 b rosea 0 97 r2site 1 b rosea 0 997 r2site 9 s casali 0 9998 r2site 1 s casali 0 93 the asp ratios plotted against reservoir corrected ams radiocarbon ages over the time span of multiple millennia can thus be used to develop reliable and precise geochronologies not only for aragonitic mollusks widely used for dating previously but also for calcitic brachiopods at each collection site bouchardia specimens display consistently higher d l values than specimens of semele thermal differences between sites are also notable and in agreement with theoretical expectations as extents of racemization for both taxa are greater at the warmer shallower site than at the cooler deeper one in late holocene marine settings concurrent time series of aragonitic and calcitic shells can be assembled using asp racemization dating and parallel multi centennial to multi millennial records can be developed simultaneously for multiple biomineral systems

the palaeobiogeography of late cretaceous and cenozoic brachiopods from western australia abstract recent research on the late cretaceous and cenozoic fossil brachiopods from the carnarvon perth bremer and eucla sedimentary basins in western australia has added much to our understanding of their systematics and biodiversity fifty eight species including one new family two new genera and 30 new species have been described from these sources four possibly five genera and one species from the late cretaceous of western australia are common to the late cretaceous deposits of the antarctic peninsula this evidence suggests that in the late cretaceous there was a continuous shelf environment extending from the antarctic peninsula to the carnarvon basin of western australia these southern shelf environments formed the high latitude southern circum indo atlantic faunal province in this area brachiopods evolved genera and species differing from those of the northern hemisphere many subsequently dispersed into northern areas of the indian atlantic and finally pacific oceans examination of cenozoic material from the carnarvon basin indicates that there is a strong correlation with cenozoic material from the antarctic peninsula at least six brachiopod genera are common to the two areas if the distribution of brachiopod genera in australia and new zealand is analysed they first appear in the northwest of western australia they then appear in chronological order in the south western south eastern basins of australia and finally new zealand the apparent migration of brachiopods south and then eastward was most likely due to the proto leeuwin and great australian bight currents fifteen species are common to south western australia and south eastern australia brachiopods may well have used various migration mechanisms from the earliest breaching of the gap between australia and antarctica to be transported into the tasman sea and hence to new zealand this included attachment to living specimens and dead objects as well as possible extended larval life in lower temperature waters factors such as light avoidance food availability and competition with bivalves may provide an explanation for the small number of species and specimens of brachiopods in some deposits

characterization of energy gradient in enclosed bays of ubatuba region south eastern brazil abstract this paper deals with the characterization of the energy gradient of the sedimentary dynamics of enclosed bays of south eastern brazil through the utilization of coarse fraction analysis in the ubatuba coastal region south eastern brazil the use of traditional sedimentological techniques such as grain size and compositional analysis of surface sediments revealed little information on the spatial variability of the bottom dynamics many advances in the comprehension of the sedimentary processes were obtained with the utilization of coarse fraction analysis which allowed the identification of the sectors of marine and continental influence the utilization of a multivariate technique the correspondence analysis on coarse fraction analysis data reveals through a plot of the two first factors produced by the multivariate technique the existence of an energy gradient acting over the area inside and between the bays leading to the deposition of different constituents

twenty years of paleoseismology in italy abstract italy has one of the most complete and historically extensive seismic catalogues in the world due to a unique and uninterrupted flow of written sources that have narrated its seismic history since about the end of the iron age seismic hazard studies have therefore always been mainly based upon this huge mass of data nevertheless the italian catalogue probably lacks many m 6 5 events the seismogenetic structures responsible for which are characterized by recurrence times that are longer than the time span covered by our historical sources for these reasons and as in other countries earthquake data that in italy have been derived from paleoseismological studies should finally become a necessary ingredient in seismic risk assessment indeed over the past 20 years some hundred trenches have been excavated supplying reliable and conclusive data on the recent activities of many faults through to many robust datings of surface fault events these studies have provided the ages of several unknown or poorly known m 6 5 earthquakes here we summarize the state of the art of paleoseismology in italy and present a first catalogue of 56 paleoearthquakes pci that occurred mainly in the past 6 kyr the pci integrates the historical instrumental seismic catalogue and extends it beyond the recurrence time of the seismogenetic faults 2000 1000 yr we feel confident that the use of the pci will enhance future probabilistic seismic hazard assessment and thus contribute to more reliable seismic risk mitigation programs

seismotectonic zoning in east central italy deduced from an analysis of the neogene to present deformations and related stress fields this paper concerns the space time evolution of the late miocene to present contractional and extensional deformations within east central italy with an analysis of the pattern and orientation of the related stress field an insight into the cover basement relations and a discussion of the seismotectonic implications the pattern and orientation of the deformation and stress fields have remained unchanged since late miocene time and have been always characterized by the coexistence and parallelism in contiguous areas in a given time of shortening to the east and elongation to the west with time during a multistage deformation history both the contraction and the extension fields have moved eastward basement involved tectonics with a west dipping multiple detachment system would have allowed the progressive eastward shift of crustal slices corresponding at the surface to well defined tectonic domains with consequent crustal thinning in the tuscan zone and crustal thickening beneath the apennine mountain chain by comparing macroseismic epicenters hypocenters and focal mechanisms with crustal structure and independently known active faults it appears evident that the pattern frequency and distribution of the crustal seismicity are tectonically controlled and that a contraction extension pair is active also at the present time in fact along the adriatic coastline contractional deformation prevails with involvement of pleistocene layers whereas beneath the apennine range extensional deformation prevails both t axes in the inner domain and p axes in the outer domain are oriented southwest northeast or west south west east northeast and this coaxiality reflects the situation depicted by the geologic stress field on this basis we have produced a seismotectonic zoning of east central italy with three distinct domains intramountain seismic zone isz foothills seismic zone fsz and coastal seismic zone csz a plausible explanation for the genesis of the active seismic deformations of east central italy is that the locally intense extensional upper crustal seismicity of the intramountain seismic zone is confined to the hanging wall of a major west dipping active extensional discontinuity whereas the less frequent contractional seismic activity of the coastal seismic zone is within the hanging wall of an outer major active west dipping contractional discontinuity an area of overlap between these two zones is represented by the foothills seismic zone where superposed epicentral patterns from different surfaces of weakness at different depths are the predictable result of the asymmetry of the deformation

quaternary origin of the inverse latitudinal diversity gradient among southern chilean mollusks mollusks along the pacific coast of south america provide one of the main exceptions from the latitudinal diversity gradient of decreasing species numbers toward the poles from 42 degrees s southward coincident with the onset of the mosaic coastline of the southern chilean fiord lands species numbers show a twofold to threefold increase compared to the central chilean coast here we use the neogene fossil record of central and southern chile to test hypotheses on the origin of this unusual pattern contrary to previous suggestions we did not find evidence for a buildup of biodiversity since the eocene or for the northward spread of antarctic taxa into southern mid latitudes rather our data suggest that the mosaic coastline south of 42 degrees s was colonized after the retreat of the glaciers from their marine termini since the later pleistocene by taxa that were already present along the chilean coast the majority of the most species rich genera in this area are shallow water hardground inhabitants suggesting a rapid adaptive radiation of these taxa the unusually low present day diversity to the north of 42 degrees s most likely results from the severe late neogene extinction and only moderate subsequent origination in this area

active tectonics of the adriatic region from gps and earthquake slip vectors 1 to investigate the kinematics of the adriatic region we integrate continuous and episodic gps measurements with mw 4 5 earthquake slip vectors selected from the regional centroid moment tensor catalogue coherent motion of gps sites in the po valley in apulia and in the hyblean plateau allows us to estimate geodetically constrained angular velocities for these regions the predictions of the gps inferred angular velocities are compared with the earthquake slip vectors showing that the seismically expressed deformation at the microplate boundaries is consistent with the observed geodetic motion the remarkable consistency between geodetic seismological and geological evidence of active tectonics suggests that active deformation in the central adriatic is controlled by the relative motion between the adria and apulia microplates the microplates angular rotation rates are then compared with the rotation rates calculated with a simple block model supporting the hypotheses 1 that apulia forms a single microplate with the ionian sea and possibly with the hyblean region and 2 that adria and apulia rotate in such a way as to accommodate the eurasia nubia relative motion we suggest that the present day microplate configuration follows a recent fragmentation of the adriatic promontory that during the neogene rigidly transferred the africa motion to the orogenic belts that now surround the adriatic region

in situ produced 10be measurements at great depths implications for production rates by fast muons in situ cosmogenic 10be values have been used to investigate a brazilian quartz vein from the surface to a depth of 15 m at depths greater than 1000 g cm2 deep enough for neutron induced reactions to be insignificant there is only a slight decrease in 10be concentration with increasing depth our results are consistent with deep production of 10be by a mechanism presumably induced by fast muons with an attenuation length of 5300 950 g cm2 and a contribution of 0 65 0 25 to the total surface production results are compared with values from the literature and implications of this re evaluation are discussed

motion on the kaparelli fault greece prior to the 1981 earthquake sequence determined from 36cl cosmogenic dating in february and march 1981 three successive destructive earthquakes occurred at the eastern end of the gulf of corinth the third shock march 4 ms 6 4 ruptured the kaparelli fault about 40 cm of a limestone fault scarp was exhumed by the earthquake each major prehistoric earthquake has added new surface to this cumulative scarp exposing fresh material to cosmic ray bombardment using 36cl cosmic ray exposure dating we have obtained the continuous exposure history for this 4 5 m high limestone surface at two sites about 50 m apart the results suggest that the kaparelli fault has ruptured three times prior to 1981 at 20 3 ka 14 5 0 5 ka and 10 5 0 5 ka with slip amplitudes between 0 6 m and 2 1 m the kaparelli fault appears to have been inactive for 10 thousand years prior to the 1981 event

connecting seismically active normal faults with quaternary geological structures in a complex extensional environment the colfiorito 1997 case history northern apennines italy 1 the northern apennines of italy are characterized by a complex tertiary tectonic history where superposed compressional and extensional deformation occurred in such regions characterized by low active extensional strain rate the coseismic surface ruptures are rare and often a matter of much debate resulting in a difficult connection between geological faults i e faults which can be mapped at the surface and seismological faults i e faults which actually generate earthquakes the availability of detailed geological mapping and high resolution seismological data for the colfiorito area struck in 1997 by a sequence of six 5 mw 6 normal faulting earthquakes allow us to compare and verify the existence of geometric and kinematic correspondence between the mapped geological quaternary faults and the activated structures in map view the earthquakes distribution reflects the fault pattern mapped at the surface the length of activated and mapped faults is quite similar 7 10 km the coseismic subsided region imaged by interferometric synthetic aperture radar data is located in the hanging wall of the mapped normal faults that bound the quaternary basins in section view there is a geometric connection between mapped normal faults and the aftershock alignments used to image fault geometry at depth comparison of striated fault planes and aftershock focal mechanism solutions show a strong kinematic consistency this study points out that the quaternary tectonosedimentary evolution and the present day geological and geomorphologic setting of the colfiorito area can be interpreted as the result of repeated extensional earthquakes similar to the 1997 events occurring on nw se trending normal faults our data also show that the main shocks of the colfiorito sequence nucleated close to the intersections between the normal faults and the preexisting compressional transpressional structures which in 1997 acted as lateral barriers to rupture propagation and consequently constrained the fault size

circum antarctic palaeobathymetry illustrated examples from cenozoic to recent times abstract we use a revised set of seafloor spreading isochrons and updated plate tectonic reconstructions to produce palaeo age and basement depth grids for the southern ocean the palaeo depth maps illustrate the evolution of the ocean basins widening and deepening and oceanic gateway development surrounding antarctica we provide examples of palaeo basement depth profiles at selected times between 45 ma and the present across the tasman gateway and drake passage the digital grids provide improved boundary conditions for palaeoceanographic circulation models as well as for backtracking sediments from odp drilling

palaeobiogeography of austral echinoid faunas a first quantitative approach few studies have been devoted to the palaeobiogeography of antarctic echinoids all of them analysing and discussing distribution patterns in a qualitative way the present work aims at exploring the evolution of palaeobiogeographic relationships of austral echinoid faunas through four time intervals from the maastrichtian to the present day using a quantitative approach the bootstrapped spanning network procedure analyses were successfully performed and improve our knowledge of biogeographic relationships between the different austral regions biogeographic maps were produced that can be easily and intuitively discussed our results mostly agree with palaeobiogeographic studies performed on other benthic invertebrates and are congruent with the palaeogeographic evolution of antarctica however two main points markedly contrast with other works there is no evidence of an austral provincialism at the end of the cretaceous and early cenozoic and echinoid data suggest isolation of southern argentina from other austral regions including antarctica in the early miocene

well traveled cockles shell transport during the holocene transgression of the southern north sea radiocarbon dates from 34 shells of the intertidal bivalve cerastoderma edule demonstrate that shells were transported in both landward and seaward directions during the holocene transgression of the southern north sea old shells on the beaches of the east frisian islands of germany document landward transport and young shells in the german bight and dogger bank document seaward transport the area9s sea level curve and the shell ages were used to predict the original depth of each specimen the difference between a specimen9s predicted age and its present depth is a measure of depth displacement depth displacements ranged from 35 to 37 m eight shells remained within 2 5 m of their original depth and roughly equal proportions of the rest moved landward and seaward specimens transported into deeper water are a very small fraction of the shells at that depth whereas specimens transported into shallow water occur alongside abundant indigenous individuals of the same species rare fossils should not be used to estimate paleodepths

the distribution of rare earth elements in groundwaters assessing the role of source rock composition redox changes and colloidal particles rare earth element ree dissolved organic carbon doc and trace element al mn fe sr ba u and th concentrations were measured in fourteen well water samples 0 22 m and one spring located along two transects set up in a catchment from western europe kervidy coet dan catchment france previous hydrological and hydrochemical no3 so42 investigations demonstrated that three chemically and spatially distinct groundwater types are present in this catchment which is fully confirmed by the ree and doc results these include i a shallow organic rich groundwater 4 4 doc 34 6 mg l from the wetland areas close to the river network this first groundwater type characterized by the development of temporary reducing conditions records high and variable ree contents 2 ree 16 ppb and displays slight or no negative ce anomaly ce ce 0 8 1 05 ii a shallow organic poor doc 3 mg l no3 rich groundwater type 86 8 no3 155 mg l located in the weathered schists below the hillslope domains this second type corresponds to recently recharged oxidized water and displays also high and variable ree concentrations 2 ppb ree 15 ppb but distinguish from the former by the occurrence of very strong negative ce anomalies ce ce 0 05 0 10 finally iii a deep organic poor doc 1 mg l nitrate poor no3 close to 0 2 mg l detection limit groundwater this third type corresponds to reduced water flowing into the deep fresh schists and yields low to very low ree contents ree 0 15 ppb as well as slight negative ce anomaly ce ce 0 8 to 0 9 temporal ree concentration variations were assessed using samples regularly collected over a six month period results show that the spatially distributed ce anomaly and ree pattern signatures are preserved throughout the studied period by contrast ree concentrations are quite variable through time especially in the wetland waters where the ree concentrations are seen to vary in phase with both redox changes and doc fe u and th content variations three ree rich water samples one doc rich and two doc poor were also filtered through membranes of decreasing pore size 100 000 d 30 000 d 5 000 d the results show that between about 40 to 65 of the ree present in the shallow doc poor groundwater samples are controlled by the colloidal fraction which is likely to consist in these inorganic waters of a mixture of mineral phases in the wetland groundwaters the fraction of ree controlled by microparticles is higher than 65 which confirms the predominant role of organic colloids as major ree carriers in wetland waters using the above data set in conjunction with analyses of soil samples we show that the deep ce anomalies found in the upper non organic part of the aquifer are probably not source rock inherited features most likely these anomalies arise from the oxidative precipitation of ce the very low ree content displayed by waters flooding the deep fresh schists is interpreted as due to the combined effects of i ph variation ii secondary sulfate mineral precipitation and iii the trapping of colloids borne ree by the aquifer rock pores data from wetland groundwaters show that the ree fe u and th budgets of these waters are mainly controlled by seasonal changes in redox conditions and organic matter content however unlike organic poor waters it appears difficult to relate the ce behaviour in these organic rich waters solely to redox conditions it is likely that the complexation of ce by organic colloids in the organic rich waters may mask redox changes by inhibiting the development of negative ce anomalies

late pleistocene and holocene palaeoenvironments in golfo san jorge patagonia molluscan evidence palaeoenvironments suggested by molluscan assemblages preserved in late pleistocene and holocene raised marine terraces along the golfo san jorge central patagonia coastline argentina are reviewed in this work a better precision of the stratigraphical and geographical ranges of the molluscs through their systematic review shows that all taxa have living representatives mostly within the argentine and or magellanean zoogeographical provinces in general no significant taxonomic appearances or disappearances are evident along this coastal area since the last pleistocene highstand reinforcing that the modern palaeoceanographical pattern dominated by the cool malvinas falkland current has not been substantially modified and that the magellanean malacological province has lasted at least since the pleistocene although with varying boundaries the so called marine terrace v recently assigned to the last interglacial highstand oxygen isotope substage 5e showed in this area a molluscan assemblage characterised by very low diversity dominantly large shells of mulinia edulis and by cold water taxa in disagreement with higher sea surface temperatures within oxygen isotope substage 5e last interglacial maximum and suggesting softer substrates than in the modern adjacent littoral zone

relative sea level changes in the last 5500 years in southern brazil laguna imbituba region santa catarina state based on vermetid ages abstract twenty six new radiocarbon dates from vermetid shells collected in the southernmost sector of the brazilian rocky coast presented dates ranging from 5410 80 to 190 65 years b p with associated paleosea levels varying from 2 10 m to 0 20 m above present sea level the overall suggested trend of the relative sea level rsl declining until at least 190 years b p is somewhat contradictory to a proposed rsl rise in the last 1000 years in southern brazil the data also seem to undermine a more widely accepted rsl trend that suggests that at least two negative rsl oscillations occurred between 4100 and 3800 years b p and between 3000 and 2700 years b p the maximum elevation of the rsl in the holocene in southern brazil was possibly lower than that observed in most of the brazilian eastern coast discrepancies between ancient sea levels of similar ages are attributed to coincidental methodological problems to imprecisions in determining past relative sea levels and to possible changes in the geomorphology and wave climate close to shore during the last 5000 years a general trend of increasing 18 o with a reduction in age in the studied samples may suggest a gradual reduction of water temperature in the region during the same period

onset and role of the antarctic circumpolar current for some time onset of the antarctic circumpolar current acc was considered to have caused or stabilised full antarctic glaciation recently however the importance of the acc in this role has been questioned in order to understand the relationship between the acc and antarctic glaciation and thence the importance of ocean circulation to palaeoclimate we need to determine the development history of both processes to this end we summarise all published estimates of acc onset the time of onset of shallow circulation or deep is uncertain whether based on tectonic studies or the interpretation of changes in the sediment record two potential final barriers to circumpolar flow have been identified south of tasmania and south of south america the former is well constrained by tectonics and marine geology to before 32 ma for a deep gap with a shallow gap in place by 35 5 ma at the latest these ages fit nicely with the onset of full antarctic glaciation at 33 34 ma although some workers question the causality estimates of the time of opening of the latter range widely whether based on tectonics or sedimentary geology from as recently as 6 ma to as early as 41 ma with the gap depth uncertain also resolution of the tectonics based uncertainties by additional survey being most probably both time consuming and inconclusive and the geological estimates being open to alternative interpretations we define an optimal strategy for additional sampling and measurement designed to resolve the time of onset more certainly possibly also resolving between deep and shallow opening and thereby constraining the acc role sample sites would have to be close to likely final barriers to avoid extraneous influence and within modern zones of acc influence ideally would form a depth transect and would have continuous mixed terrigenous and biogenic sections a wide range of carefully selected parameters would be measured at each r 2007 elsevier ltd all rights reserved

a continuous multi millennial record of surficial bivalve mollusk shells from the sao paulo bight brazilian shelf abstract to evaluate the potential of using surficial shell accumulations for paleoenvironmental studies an extensive time series of individually dated specimens of the marine infaunal bivalve mollusk semele casali was assembled using amino acid racemization aar ratios n 270 calibrated against radiocarbon ages n 32 the shells were collected from surface sediments at multiple sites across a sediment starved shelf in the shallow sub tropical sao paulo bight sao paulo state brazil the resulting 14 c calibrated aar time series one of the largest aar datasets compiled to date ranges from modern to 10 307 cal yr bp is right skewed and represents a remarkably complete time series the completeness of the holocene record is 66 at 250 yr binning resolution and 81 at 500 yr binning resolution extensive time averaging is observed for all sites across the sampled bathymetric range indicating long water depth invariant survival of carbonate shells at the sediment surface with low net sedimentation rates benthic organisms collected from active depositional surfaces can provide multi millennial time series of biomineral records and serve as a source of geochemical proxy data for reconstructing environmental and climatic trends throughout the holocene at centennial resolution surface sediments can contain time rich shell accumulations that record the entire holocene not just the present

seismic slip history of the pizzalto fault central apennines italy using in situ produced 36cl cosmic ray exposure dating and rare earth element concentrations morphological and geological observations reveal that most apenninic faults are highly segmented and that the majority of the fault segments are less than 10 km long although these faults have undergone numerous paleoseismological investigations quantitative data remain crucially lacking for a large number of fault segments because such data are essential to understanding how these faults have ruptured and interacted in the past and how they might behave in the future we investigated the holocene seismic history of the pizzalto normal fault a 13 km long fault segment belonging to the pizzalto rotella aremogna fault system in the apennines we collected 44 samples from the pizzalto fault plane exhumed during the holocene and analyzed the 36cl and rare earth element ree contents together the 36cl and ree concentrations show that at least six events have exhumed 4 4 m of the fault scarp between 3 and 1 ka with slip per event values ranging from 0 3 to 1 2 m no major events have been detected over the last 1 kyr the rotella aremogna pizzalto fault system has a clustered earthquake behavior with a mean recurrence time of 1 2 kyr and a low to moderate probability ranging from 4 to 26 of earthquake occurrence over the next 50 years

earthquake supercycles in central italy inferred from 36cl exposure dating we use 36cl surface exposure dating to determine the slip release pattern over the last 15 kyr for the velino magnola fault a major active normal fault in central italy we sampled the fault at five well separated sites along its length and modeled the 36cl concentrations measured in the 376 samples we find that the fault broke in at least 9 large earthquakes that occurred in two 5 6 ka long supercycles each cycle included a 4 5 ka long phase of relative quiescence followed by a cluster of at least 3 large earthquakes or earthquake sequences that released most of the accumulated strain in 1 ka all 9 identified events broke the entire fault and produced maximum surface slips of 2 3 m though the velino magnola fault seems presently in a stage of relative quiescence it may re enter a phase of paroxysmal seismic activity in a few hundred of years

stratigraphy and holocene evolution of a regressive barrier in south brazil abstract the paranagua coastal plain is a 600 km 2 barrier system located in south brazil 25 30 s and is largely made up of pleistocene and holocene beach ridges sea level history in the area is characterized by a gradual 3 5 m sea level fall in the last 5000 years several reverse circulation drill logs from the pleistocene and holocene sectors allowed for the definition of a general morphostratigraphic model of the coastal plain which proposes the staking of at least two generations of marine deposits upon continental and paleo estuarine sediments analysis of shallow vibro cores and exposures along back barrier creeks indicates the existence of four transgressive estuarine estuarine channel overwash and flood tidal delta and three regressive beachface nearshore and upper shoreface sedimentary facies in the holocene section of the coastal plain the morphostratigraphy suggests that barrier emplacement took place at the last stages of the post glacial marine transgression when the back barrier estuary was squeezed in between the pleistocene and holocene barriers holocene barrier progradation was significant in both the shore normal and longshore direction and was apparently very swift in the last thousand years corresponding to a period when sea level fell by 1 5 m and when about half of the present barrier volume was accumulated higher progradation rates are ascribed to the arrival of sediment yielded by an active littoral drift system which appears to have eroded large extents of several holocene barriers along 100 km of coastline

morphotectonic analysis of the long term surface expression of the 2009 l aquila earthquake fault central italy using airborne lidar data abstract in this paper we present a morphotectonic study of the paganica san demetrio fault system psdfs responsible for the mw6 1 april 6 2009 earthquake l aquila central italy the discrepancy observed between the length of the seismologic geodetic modeled fault the limited size of the primary coseismic surface ruptures and the significant morphological expression of the psdfs stimulated a debate about the maximum rupture length of the psdfs and its capability to generate larger magnitude events to image the psdfs long term morphological expression and define its surface geometrical arrangement length number of fault splays and boundaries we took advantage of a high resolution airborne lidar dataset lidar topography substantially increased our confidence in detecting even subtle tectonic controlled morphologies we define the psdfs as a 19 km long fault system that displays a complex structural setting characterized by two different sectors 1 the paganica sector to the nw with a narrow deformation zone and 2 the san demetrio sector to se where the strain is accommodated by several fault splays dissecting a wider quaternary basin we also defined a first order hierarchy among the numerous fault splays across the psdfs the long term geomorphic expression of the psdfs suggests that it ruptured also involving the whole 19 km long structure besides rupturing only small sections as it occurred in 2009 this suggests a variable slip behavior empirical relations applied to this hypothesis allow up to m 6 6 earthquakes along the psdfs these results have a critical impact on the seismic hazard assessment of the area when compared with a m 6 1 event as the 2009

size all it s shaped up to be evolution of shape through the lifespan of the cenozoic bivalve spissatella crassatellidae

enhanced age resolution of the marine quaternary record in the arctic using aspartic acid racemization dating of bivalve shells abstract aspartic acid asp racemization occurs at a significantly higher rate than isoleucine epimerization and consequently provides better temporal resolution of arctic marine deposits from alaska spitsbergen and baffin island heating experiments at 100 c on the bivalvesmyaandhiatellashow the asp racemization rate decreases with increasing d l values as is typical for biogenic carbonates based on these experimental racemization rates and rates determined from racemization of samples radiocarbon dated to ca 10 000 12 000 yr b p activation energies formyaandhiatellaare estimated to be 30 6 and 30 0 kcal mol respectively for asp racemization and 29 0 and 29 5 for isoleucine epimerization analysis of a time series of plio pleistocenehiatellafrom the north coast of alaska shows that last interglacial mollusks can be readily distinguished from modern samples by asp but not by isoleucine d l asp values indicate a younger age for the fishcreekian transgression than does isoleucine epimerization for spitsbergen d l asp shows a slight age difference ca 12 000 yr between two units of the episode b interstadial and suggests that the age of these units may be closer to 65 000 than to 80 000 yr b p two possible ages suggested by other evidence the age of the loks land interstadial on baffin island is likely to be greater than that indicated by radiocarbon ages within deposits from each region d l asp values are less variable among individual shells than isoleucine epimerization values this may indicate better reliability of asp for geochronology

before the ice biogeography of antarctic paleogene molluscan faunas abstract new identifications are listed of antarctic paleogene molluscan faunas lopez de bertodano and sobral formations seymour island paleocene la meseta formation seymour island eocene mcmurdo sound erratics eocene and king george island oligocene early miocene these show that both cosmopolitan and antarctic subantarctic genera increased regularly as percentages of faunas with time 15 of paleocene genera 30 of eocene genera and 59 of oligocene early miocene genera still live in the antarctic subantarctic region the present major antarctic families of larger molluscs have remained the most diverse ones since middle eocene time and the antarctic fauna was well established by then however mytilidae and veneridae have decreased markedly in diversity mactridae and oysters have disappeared from the antarctic and antarctic trochidae volutidae and conoidea are now distinct guilds of more offshore taxa this reflects the present antarctic ice cover shallow water taxa that are no longer able physically to live in antarctica provide an index of antarctic glaciation glaciation was not extensive on the antarctic peninsula by late eocene time and a few genera of shoreface molluscs still inhabited the king george island area during oligocene early miocene time subduction has left only sparse localities around the margins of the pacific and indian australian plates containing shallow water early paleogene macrofossils almost none are known from the central regions of these plates few data points are available so apparent indications of taxa originating in antarctica are not interpretable new names are provided for two junior homonyms gaimardia zinsmeisteri replacing gaimardia flemingi zinsmeister 1984 prosipho stilwelli replacing aeneator huttoni stilwell and zinsmeister 1992

marshall paraconformity a mid oligocene record of inception of the antarctic circumpolar current and coeval glacio eustatic lowstand abstract the sedimentary fill of the canterbury basin new zealand is the product of a long term 80 ma tectonically controlled relative sea level cycle with a megasequence geometry analogous to the sequence stratigraphic model of vail am assoc petrol geol stud geol no 27 1 1 10 1987 the condensed section of the megasequence resolvable in detail in outcrop and on seismic profiles comprises a basin wide pelagic to hemipelagic limestone interval a regional mid oligocene unconformity the marshall paraconformity lies within the limestone interval onshore and correlates with hiatuses in at least two and possibly three offshore exploration wells and with a temporary lithological change from limestone to quartz sand at a fourth strontium isotopic age estimates confirm that a 2 4 ma hiatus is associated with onshore outcrops of the marshall paraconformity between 32 and 29 ma which correlates with the opening of the pacific sector of the southern ocean and the postulated mid oligocene sea level fall of haq et al science235 1156 1167 1987 spec publ soc econ paleonotol mineral no 42 71 108 1988 lowering of base level coupled with cooling and enhancement of current activity may have caused the temporary cessation of limestone deposition and a regional hiatus this hypothesis reconciles the apparently contradictory palaeogeographical evidence for a regional highstand the marshall paraconformity may exemplify the signature by which similar glacio eustatic events can be recognized in offshore platform facies

spatial and temporal variations in growth rates along active normal fault systems an example from the lazio abruzzo apennines central italy abstract the geometry kinematics and rates of active extension in lazio abruzzo italian apennines have been measured in order to gain a better understanding of the spatial and temporal variations in fault growth rates and seismic hazards associated with active normal fault systems we present fault map traces throws throw rates and slip directions for 17 parallel en echelon or end on active normal faults whose 20 40 km lengths combine to form a soft linked fault array ca 155 km in length and ca 55 km across strike throw rates derived from observations of faulted late glacial features and holocene soils show that both maximum throw rates and throw rate gradients are greater on centrally located faults along the strike of the array total throws and throw gradients show similar spatial variations but with weaker relationships with distance along strike when summed across strike throw rates are increasingly high towards the centre of the array relative to summed throws we interpret the above to suggest that throw rates have changed in the recent past ca 0 7 ma from spatially random fault growth rates initiating at 2 5 3 3 ma to growth rates that are greater on centrally located faults we interpret this as evidence for fault interaction producing throw rate variations that drive throw profile readjustment on these crustal scale soft linked faults the results are used to discuss seismic hazards in the region which are quantified in a second paper in this issue

scale and structure of time averaging age mixing in terrestrial gastropod assemblages from quaternary eolian deposits of the eastern canary islands abstract quantitative estimates of time averaging age mixing in gastropod shell accumulations from quaternary the late pleistocene and holocene eolian deposits of canary islands were obtained by direct dating of individual gastropods obtained from exceptionally well preserved dune and paleosol shell assemblages a total of 203 shells of the gastropods theba geminata and t arinagae representing 44 samples stratigraphic horizons from 14 sections were dated using amino acid isoleucine epimerization ratios calibrated with 12 radiocarbon dates most samples reveal a substantial variation in shell age that exceeds the error that could be generated by dating imprecision with the mean within sample shell age range of 6670 years and the mean standard deviation of 2920 years even the most conservative approach monte carlo simulations with a non sequential bonferroni correction indicates that at least 25 of samples must have undergone substantial time averaging e g age variations within those samples cannot be explained by dating imprecision alone samples vary in shell age structure including both left skewed 17 out of 44 and right skewed distributions 26 out of 44 as well as age distributions with a highly variable kurtosis dispersion and shape of age distributions of samples do not show any notable correlation with the stratigraphic age of samples suggesting that the structure and scale of temporal mixing is time invariant the statistically significant multi millennial time averaging observed here is consistent with previous studies of shell accumulations from various depositional settings and reinforces the importance of dating numerous specimens per horizon in geochronological studies unlike in the case of marine samples typified by right skewed age distributions attributed to an exponential like shell loss from older age classes many of the samples analyzed here displayed left skewed distributions suggestive of different dynamics of age mixing in marine versus terrestrial shell accumulations