topographic expressions of mantle dynamics in the mediterranean abstract the surface of the earth is the ever changing expression of the dynamic processes occurring at depth and at or above its surface however our ability to read landscapes in terms of their underlying tectonic or climatic forcing remains rudimentary during the last decade particular attention has been drawn to the deep dynamic contributions to topography related to the stresses that are produced at the base of the lithosphere by mantle convection and their relevance compared to the iso static component of topography here we use examples from the mediterranean and estimate residual and dynamic topography we then compare those with surface uplift from geology for specific regions to disentangle the dynamic from the static components considering the different topographic signatures of tectonic processes e g actual residual and dynamic topography as well as uplift rates jointly provides a powerful way to distinguish between the contributions of mantle crustal and surface processes such an approach might bring us closer to reading topographic expressions in terms of their geological cause

contemporaneous extension and compression in the northern apennines from earthquake fault plane solutions summary the northern apenninic arc belongs to the deformation zones surrounding the adriatic plate which behaves as a rigid block it is a ne verging fold and thrust belt which developed since the miocene with the migration of an extensional compressional pair previous seismological data are roughly in agreement with this deformation picture although the outer compressional front was not clearly defined by the few available solutions in this work we confirm the existence of two adjacent zones of contemporaneous extension and compression in the northern apennines defining the extent of these two zones and their interim1 deformation better than was previously done this is accomplished through the analysis of 125 new focal mechanisms of earthquakes 2 6 md 4 8 recorded by the national network of the lstituto nazionale di geofisica in the period 1988 1995 the two deformation zones are clearly separated and lie very close to each other with a partial overlapping in the emilian tuscan apennines strikeslip events are scattered in most of the study area thrust faulting earthquakes are located in the internal part of the most recently active thrust front middle upper pleistocene there is a general trend of the compressional p axes of thrust fault and strike slip solutions to be perpendicular to the apenninic direction in the external zone while the tensional axes of the normal fault and strike slip solutions in the belt do not show a uniform orientation however clearly evident is the ene direction of extension in the peri tyrrhenian region consistent with the direction of shmln in the quaternary volcanoes of this region inferred from borehole breakouts and microearthquake fault plane solutions we determined the orientation of the stress tensor in the two main deformation zones by inversion of the 125 fault plane solutions determined in this study we found that the external belt is characterized by ne sw compression ol horizontal oriented n45 e while a normal faulting regime with o3 e w oriented is characteristic of the umbria tuscany back arc region

quaternary rock avalanches in the apennines new data and interpretation of the huge clastic deposit of the l aquila basin central italy abstract in this paper we inferred the origin of a huge clastic deposit i e l aquila breccia which widely crops out within the l aquila intermontane basin a tectonic depression in central apennines that is bounded by seismogenic active faults as demonstrated by the earthquake occurred on april 6 2009 mw 6 1 the genesis of this deposit is still debated in the literature for this reason a number of methods have been applied mainly aimed at evidencing its geomorphological and sedimentological features as well as at defining its geometry and volume through cross sections constrained by borehole data and field observations on the basis of the obtained results we identified such deposit as resulting from a quaternary rock avalanche event in particular the rock avalanche would have detached during the cold climate phases of late middle pleistocene from the southern slope of the gran sasso range a sector characterized by the presence of numerous dgsd related landforms we performed morphometric analyses of the gran sasso slope in order to define the potential source area of the inferred rock avalanche and according to the results the volume estimated from this area about 108 m3 is coherent with the volume calculated for the preserved rock avalanche deposit furthermore we analyzed the main features of the deposit i e age and morphometric parameters also in the light of similar rock avalanche events occurred in the same region during the quaternary with the aim of discussing potential analogues and better understanding the role of gravity induced processes in the quaternary morpho evolution of the apennine chain

last interglacial reef growth beneath belize barrier and isolated platform reefs we report the first radiometric dates thermal ionization mass spectrometry from late pleistocene reef deposits from offshore belize the location of the largest modern reef complex in the atlantic ocean the results presented here can be used to explain significant differences in bathymetry sedimentary facies and reef development of this major reef area and the results are significant because they contribute to the knowledge of the regional geology of the eastern yucatan the previously held concept of a neotectonically stable eastern yucatan is challenged the dates indicate that pleistocene reefs and shallow water limestones which form the basement of modern reefs in the area accumulated ca 125 130 ka significant differences in elevation of the samples relative to present sea level 10 m have several possible causes differential subsidence along a series of continental margin fault blocks in combination with variation in karstification are probably the prime causes differential subsidence is presumably related to initial extension and later left lateral movements along the adjacent active boundary between the north american and caribbean plates increasing dissolution toward the south during pleistocene sea level lowstands is probably a consequence of higher precipitation rates in mountainous southern belize

extension controls quaternary tectonics geomorphology and sedimentation of the n appennies foothills and adjacent po plain italy abstract in the middle pleistocene thrusting in the n apennine fold and thrust belt came to an end and foredeep sedimentation in the adjacent po plain basin ceased a new tectono sedimentary regime was installed extensional faults were activated in the foothills and are limited to the northeast by a major sw dipping normal fault the bologna fault for which a vertical displacement of 1000 m is estimated the region northeast of the fault i e its footwall was progressively tilted towards the po plain the sw sectors of the tilting region were progressively uplifted above sea level subjected to erosion thereby feeding a deltaic system which prograded towards the northeast in the subsiding regions compressional structures without major deformation are recorded in the zone of maximum curvature all these features are explained by the onset of extensional deformation along the bologna fault and consequent flexural unloading of its footwall the evidence therefore shows that the transition region between the n apennine foothills and po plain has been under a tensional stress regime since the middle pleistocene

new model of reef island evolution maldives indian ocean a new model of reef island evolution based on detailed morphostratigraphic analysis and radiometric dating of three islands in south maalhosmadulu atoll maldives is presented islands initially formed on a foundation of lagoonal sediments between 5500 and 4500 yr b p when the reef surface was as much as 2 5 m below modern sea level islands accumulated rapidly during the following 1500 yr effectively reaching their current dimensions by 4000 yr b p since then the high circum island peripheral ridge has been subject to seasonal and longer term shoreline changes while the outer reef has grown upward reducing the energy window and confining the islands this new model has far reaching implications for island stability during a period of global warming and raised sea level which will partially reactivate the energy window although it is not expected to inhibit upward reef growth or compromise island stability

plio quaternary uplift rates in the outer zone of the central apennines fold and thrust belt italy abstract geological seismic and borehole data permitted the reconstruction of the plio quaternary uplift subsidence and erosion sedimentation history for the outer sector of the central apennines during the latest contractional stages middle late pliocene the frontal sector of the belt experienced a net subsidence locally compensated by the growth of the fold and thrust system this tectonic uplift was localized at the axial culmination of the anticlines and particularly for the major structures was responsible for exhumation and erosion of the neogene succession and for near flat planation surfaces development on meso cenozoic carbonate rocks at the crest of the anticlines since the early middle pleistocene a regional doming involved the outer part of the belt peri adriatic domain this process interacted with quaternary eustatic sea level fluctuations and caused the basinward migration of shallow marine deposits forming an overall prograding system quaternary shoreline retreat base level drop and climatic changes were mainly associated with valley deepening and fluvial terrace formation the present study outlines that fold thrust growth and regional doming driving processes characterized by different amplitude wavelength and uplift rate amounts are both responsible for the morphological setting of the central apennines external zones

the importance of large benthic foraminifera to reef island sediment budget and dynamics at raine island northern great barrier reef low lying reef islands are among the most vulnerable environments on earth to anthropogenic induced climate change and sea level rise over the next century because they are low composed of unconsolidated sediment that is able to be mobilised by waves and currents and depend on sediments supplied by reef organisms that are particularly sensitive to environmental changes e g ocean temperatures and chemistry therefore the spatial and temporal links between active carbonate production and island formation and dynamics are fundamental to predicting future island resilience yet remain poorly quantified in this paper we present results of a detailed geomorphological and sedimentological study of a reef and sand cay on the northern great barrier reef we provide an empirical investigation of the temporal linkages between sediment production and reef island development using a large collection of single grain ams 14c dates large benthic foraminifera lbf are the single most important contributor to contemporary island sand mass 47 ranging from 36 to 63 at raine island reflecting rapid rates of sediment production and delivery standing stock data reveal extremely high production rates on the reef 1 8 kg m 2 yr 1 while ams 14c dates of single lbf tests indicate rapid rates of sediment transferral across the reef we also demonstrate that age is statistically related to preservation and taphonomic grade severely abraded tests moderately abraded tests pristine tests we construct a contemporary reef and island sediment budget model for raine island that shows that lbf baculogypsina marginopora and amphistegina contribute 55 of the sediment produced on the reef annually of which a large proportion 54 contribute to the net annual accretion of the island the tight temporal coupling between lbf growth and island sediment supply combined with the sensitivity of lbf to bleaching and ocean acidification suggests that islands dominated by lbf are likely to be very sensitive to short and long term climate change projections potential outcomes of this work relate to improving the understanding of the future change dynamics of reef islands in response to climate change

the pliocene pleistocene stratigraphic and tectonic evolution of the central sector of the western periadriatic basin of italy abstract the central portion of the western periadriatic basin is a foreland basins systems associated to the central apennine outer orogenic wedge that stretches along the marche and abruzzi regions of italy an area that has been studied since long time and where a plenty of surface and subsurface data are available the present study is aimed to review and synthetize these data add new surface and subsurface data in order to define a firm stratigraphic and tectonic framework that is base for the reconstruction of the pliocene pleistocene tectonic stratigraphic evolution of the central portion of the western periadriatic basin the study integrates field mapping published geological maps seismic lines well logs and an updated chronostratigraphic scheme six major nne ssw thrust stacks and eight unconformity bounded stratigraphic units have been defined then a ne sw oriented zone separates a northern from a southern sector which have differences in structural styles amount of shortening basins widths and thicknesses of stratigraphic units despite these differences the deformation timing the depositional history and the migration of basins system are common in both sectors and eight tectonic stratigraphic evolutionary stages have been reconstructed with sequential restoration of two representative cross sections the results highlight that the pliocene pleistocene stratigraphic and tectonic evolution of the central western periadriatic basin preserves the records of supra regional and global controls which drive thrust propagation orogen growth basins migration and basins sedimentary infill in particular the stratigraphy preserves global third order eustatic climatic changes that have a strict feed back and concomitance with tectonic pulses the latter are regulated 1 by cyclic growth of an orogenic wedge undergoing coeval erosion and sedimentation and 2 by eastward retreat of a westward subducting and flexing continental lithosphere

age and sedimentary characteristics of beach sediments from yongle atoll south china sea implications for sediments supply in a coral reef system abstract low lying reef islands constructed from unconsolidated sediments are of growing interest due to concerns over the future stability of island landforms in response to climatic change and sea level rise sediment characteristics combined with the constituents and physical processes are fundamental to understand the links between sediment production and their supply to an island s beach reservoir the grain size constituents and 230th age of beach sediments from five islands at yongle atoll in the south china sea were analyzed data reveal that coral grains are the dominant constituents of the beach sediments followed by mollusks coralline algae foraminifera halimeda and bryozoans the mean grain sizes of the beach sediment were within a range of 226 4215 m and the coarsest sands were located near the passages in the atoll rim transportation by tropical cyclone generated waves and winnowing by tides are potentially the main factors that influenced the grain size characteristics calibrated 230th age dates for bulk sand samples date the beach sediment between 424 yr bp and 5953 yr bp dating of coral sand samples from the beach sediment provides ages of 686 5780 yr bp the coral sands from a vertical section 1 2 m depth located on the beach at jinqing island were dated at 1154 3824 yr bp the age reversal on the vertical section with similar ages of beach sediment on any single island and different age ranges on different islands in an atoll indicates that the coral sediment supply processes occurred within a relatively close time period and that different islands had different sediment supply rates the temporal link between the coral dominated sediment production and the beach reservoir provides an important insight into understanding the sediments supply mechanism of atoll islands in the northwestern pacific ocean

coupling basin infill history and mammal biochronology in a pleistocene intramontane basin the case of western l aquila basin central apennines italy the western l aquila basin recorded in quaternary times two well distinguished phases of intramontane basin fill concomitant with uplift of central apennines and characterized by diverse large mammal assemblages the first phase was dominated by alluvial fan and lacustrine palustrine sedimentation respectively gelasian and calabrian in age that took place within an internally drained fault controlled hydrographic system a late villafranchian earliest galerian large mammal assemblage approximately 1 3e1 1 ma pertains to this phase and includes mammuthus meridionalis stephanorhinus etruscus and the large cervid arvernoceros aff a giulii the second phase of filling middle pleistocene to holocene in age is dominated by fluvial sedimentation which is related to a through going fluvial system developed after the emptying of the former lake a middle galerian large mammal assemblage approximately 600 ka comes from the oldest deposits of this phase biochronological data help date steps of geological and morphological evolution in an intramontane setting and permit to temporally constrain the major change in local hydrography and sedimentation at the early middle pleistocene transition this change was likely forced by an increment of uplift rates which is well recorded along the axial range and peripheral belts of the apennines 2011 elsevier ltd and inqua

small catchments evolution on clayey hilly landscapes in central apennines and northern sicily italy since the late pleistocene abstract the study aims to define a possible evolutionary geomorphological model of small catchments i e

isostasy dynamic topography and the elevation of the apennines of italy abstract the elevation of an orogenic belt is commonly related to crustal lithosphere thickening here we discuss the apennines as an example to show that topography at a plate margin may be controlled not only by isostatic adjustment but also by dynamic mantle driven processes using recent structural constraints for the crust and mantle we find that the expected crustal isostatic component explains only a fraction of the topography of the belt indicating positive residual topography in the central apennines and negative residual topography in the northern apennines and calabria the trend of the residual topography matches the mantle flow induced dynamic topography estimated from regional tomography models we infer that a large fraction of the apennines topography is related to mantle dynamics producing relative upwellings in the central apennines and downwellings in the northern apennines and calabria where subduction is still ongoing comparison between geodetic and geological data on vertical motions indicates that this dynamic process started in the early pleistocene and the resulting uplift appears related to the formation and enlargement of a slab window below the central apennines the case of the apennines shows that at convergent margins the elevation of a mountain belt may be significantly different from that predicted solely by crustal isostasy and that a large fraction of the elevation and its rate of change are dynamically controlled by mantle convection

sequence response to syndepositional regional uplift insights from high resolution sequence stratigraphy of late early pleistocene strata periadriatic basin central italy abstract this paper deals with the depositional sequences that occur within the uppermost part of the plio pleistocene periadriatic basin fill in the southern marche region central italy the succession is an early pleistocene easterly dipping clastic wedge showing an overall shallowing trend from slope clays to shallow marine and non marine deposits comprising two major sequences namely qmb and qmc analysis has provided new insights into i the nature of sedimentary facies and facies associations occurring within the upper part of qmb and qmc ii the gradual contact within qmb between regressive littoral deposits rld and underlying deep marine blue clays iii the composite origin of the emilian surface which is a widespread erosional unconformity separating qmb from qmc iv the cyclothemic pattern of qmc composed of downstepping small scale depositional sequences v the role played by synsedimentary uplift on the stacking pattern of small scale sequences and their internal architecture up to three small scale depositional sequences have been recognised within qmc qmc1 qmc2 and qmc3 they are up to 50 m thick and defined by previously unrecorded lower rank regionally extensive surfaces facies organization indicates that as a rule in ascending stratigraphic order each small scale sequence may includes a distinctive basal unconformity surface that can be traced from incised valleys to associated interfluves an incised valley fill a transgressive surface of marine erosion a transgressive systems tract a highstand systems tract a regressive surface of marine erosion and an attached falling stage systems tract in proximal positions the small scale sequences are dominated by transgressive and highstand systems tracts with incised valley fills and falling stage systems tracts absent or volumetrically much less significant in relatively basinward locations where the regressive surfaces of marine erosion converge with the lower sequence boundary the falling stage systems tract may represent the entire depositional sequence high frequency sequences display a distinctive stacking pattern and form a tectonically induced forced regressive sequence set underlain by a composite tectonically enhanced regressive surface of marine erosion formed by the lateral connection of lower rank sequence boundaries

chemical weathering of palaeosols from the lower palaeolithic site of valle giumentina central italy abstract the major archaeological site of valle giumentina abruzzo contains a well dated lower palaeolithic pedosedimentary sequence that provides an excellent opportunity to study the relationships among soil weathering volcanism and climate change at the glacial interglacial and submillennial timescales in central italy and the mediterranean area during the middle pleistocene as well as the human environment interactions of some of the earliest settlements in central southern europe high resolution analyses of geochemistry and magnetic susceptibility revealed the presence of eleven palaeosols ten of which s2 s11 were formed between 560 and 450 ka based on 40ar 39ar dating of sanidine in tephras i e spanning marine isotope stages mis 14 12 the evolution of the major and trace element composition suggests that the palaeosols were mainly formed by in situ weathering of the parent material the major phases of soil weathering occurred during the mis 13 interglacial period s8 and s6 as well as during episodes of rapid environmental change associated with millennial climatic oscillations during the mis 14 and 12 glaciations s11 and s2 respectively although global forcing such as orbital variations solar radiation and greenhouse gas concentrations may have influenced the pedogenic processes the volcanism in central italy climate change in the central mediterranean and tectono sedimentary evolution of the valle giumentina basin also impacted and triggered the formation of most palaeosols which provided subsistence resources for the lower palaeolithic human communities this study highlights the importance of having high resolution palaeoenvironmental records with accurate chronology as close as possible to archaeological sites to study human environment interactions

a mis 15 mis 12 record of environmental changes and lower palaeolithic occupation from valle giumentina central italy abstract an integrated geological study including sedimentology stable isotope analysis 18o 13c geochemistry micromorphology biomarker analysis 40ar 39ar geochronology and tephrochronology was undertaken on the quaternary infill of the valle giumentina basin in central italy which also includes an outstanding archaeological succession composed of nine human occupation levels ascribed to the lower and middle palaeolithic 40ar 39ar dating and other palaeoenvironmental and tephrochronological data constrain the sedimentary history of the whole succession to the mis 15 mis 12 interval between 618 13 ka and 456 2 ka palaeoenvironmental proxies suggest that over this time interval of about 150 ka sedimentary and pedogenic processes were mainly influenced by climatic changes in particular by the pulsing of local mountain glaciers of the majella massif specifically the valle giumentina succession records glacio fluvial and lacustrine sedimentation during the colder glacial periods and pedogenesis and or alluvial sedimentation during the warmer interglacial and or interstadial periods during this interval tectonics played a negligible role as a driving factor of local morphogenesis and sedimentation whereas the general regional uplift experienced in the middle pleistocene led to capture of the basin and its definitive extinction after mis 12 these data substantially improve previous knowledge of the chronology and sedimentary evolution of the succession providing for the first time a well constrained chronological and palaeoenvironmental framework for the archaeological and human palaeoecological record of valle giumentina

how and why the present tectonic setting in the apennine belt has developed the building of the apennine belt slowed down or ceased around the early pleistocene since then the belt has undergone strong uplift and considerable distortion this change from belt normal to belt parallel shortening has been determined by the fact that the continental adriatic domain adria was almost completely surrounded by buoyant orogenic structures in that context the mobility of adria underwent a considerable reduction whereas uplift and deformation of its southern part was strongly emphasized as an effect of the convergence of the confining plates around the middle pleistocene the deformation pattern in the peri adriatic zones changed again in response to acceleration of adria the outer adriatic sector of the apennine belt underwent belt parallel shortening accommodated by uplift and outward escape of upper crustal wedges the separation between the extruding wedges and the almost stable inner belt has generated a series of extensional or transtensional fault systems along the axial part of the apennines which now correspond to the main seismogenic sources the spatio temporal distribution of major tectonic events in the study area can plausibly be explained as an effect of the least action principle thematic collection this article is part of the apennines and tyrrhenian system collection available at https www lyellcollection org cc the apennines tyrrhenian system

fold uplift versus regional subsidence and sedimentation rate abstract fold uplifts compete during their development with regional subsidence in the frontal parts of thrust belts and accretionary wedges two cases exist in frontal thrust belts in the first more common case the uplift rate of the external folds is higher than the subsidence rate of the foredeep in the second case the fold uplift is less than the regional subsidence the total fold uplift may be considered as the fold uplift rate minus the regional subsidence rate this value can be either positive or negative positive total fold uplift occurs when folds rise faster than regional subsidence and the envelope of the fold crest rises towards the hinterland of the accretionary wedge in the opposite case negative total fold uplift the envelope dips towards the hinterland because folds rise more slowly than regional subsidence in the first positive case the folds are deeply eroded and the onlap of the growing strata moves away from the fold crest if the sedimentation rate is lower than the fold uplift rate in marine or alluvial environments in the second negative case where folds rise at lower rates than the regional subsidence the onlap moves towards the fold crest if the sedimentation rate is higher than the fold uplift rate this is also the more favorable case for hydrocarbon traps where growth strata can seal the fold moreover the fast subsidence rates in the foredeep provide a higher thermal maturation this second tectonic setting is commonly associated with accretionary wedges forming along westdirected subduction zones which are characterized by high subsidence rates in the foredeep or trench due to the fast eastward roll back of the subduction hinge e g apennines carpathians banda arc

transient landscape and stratigraphic responses to drainage integration in the actively extending central italian apennines abstract drainage networks in continental rifts are generally reported as dynamic features that produce transitions between endorheic and exorheic conditions while this is of major importance for landscape development sediment dispersal and basin stratigraphy the controls of drainage network evolution across an array of normal fault bounded basins are still not well understood in this study we use the central italian apennines an area that has been affected by active normal faulting and regional uplift over the last 3 myrs to determine the controls on drainage network evolution and its impact on transient landscape evolution and basin stratigraphy we compile previously published stratigraphic and fault related data with new geomorphological constraints for the aterno river system 1300 km2 for which a wealth of data has been collected following the destructive l aquila earthquake in 2009 we use this compilation to demonstrate how the different basins along the river system were initially isolated during the early pleistocene but became fluvially integrated with one another and the adriatic coast between ca 1 2 and 0 65 ma we conclude that the spatial and temporal pattern of drainage integration is mostly explained by a long term increase in sediment and water supply relative to basin subsidence due to the early to middle pleistocene climatic transition the progressive increase in fault related topography and the transport of sediment and water down system as drainage integration occurred overall we conclude that rates of sedimentation and basin subsidence in the central apennines are well matched allowing tipping points between over and under filled conditions to be easily reached we also show that consecutive drainage integration events produce discrete waves of river incision and terrace formation and conclude that drainage integration is of major importance at least equivalent to tectonics and climate in controlling transient landscape evolution and rift basin stratigraphy

nature and stability of atoll island shorelines gilbert island chain kiribati equatorial pacific islands rimming pacific atolls typically form narrow low lying lands that are commonly perceived to be particularly vulnerable to global changes such as sea level rise as these low islands form the only habitable land for many island nations understanding the character of shorelines and the rates and controls that operate to bring about changes is an issue of central importance the purpose of this study is to unravel the characteristics of coastal change on atoll islands of the gilbert island chain of the equatorial pacific nation of kiribati especially as they relate to autogenic shoreline processes and el nino southern oscillation variability integration of field observations differential global positioning system data historical aerial photographs and ultra high resolution remote sensing images demonstrates the nature spatial patterns and rates of change from 17 islands on maiana and aranuka atolls the results illustrate that between 2005 and 2009 ca 50 of the shorelines on these islands displayed a discernable shift in position some shorelines were accretionary at net rates up to ca 8 m year 1 and others were erosional up to ca 18 m year 1 long term net rates of change on maiana between 1969 and 2009 were lower than short term net rates measured between 2005 and 2009 both short term and long term observations illustrate some of the greatest change occur near terminations of the largest north south oriented islands associated with longshore movement of coarse sand and gravel direct hits by tropical depressions and marked seasonality factors interpreted as being essential in island growth and shoreline dynamics elsewhere do not directly impact these equatorial atolls and can be eliminated as fundamental controls on shoreline dynamics similarly observations over four years suggested that shoreline variability probably is not influenced directly by marked sea level change although a recent increase in the rates of shoreline change could reflect instability related to the cumulative effect of a long term increase in the rate of sea level rise within this framework of global change local anthropogenic effects autogenic shoreline processes and el nino southern oscillation influenced wind and wave variability control many aspects of these dynamic shorelines these results provide quantitative insights into the character and variability of rates of shoreline change information essential for evaluating and mitigating the vulnerability of island nations such as kiribati

a review on the driving mechanism of the tyrrhenian apennines system implications for the present seismotectonic setting in the central northern apennines abstract the formation of the tyrrhenian apennines system has been characterized by a complex distribution of major tectonic events such as opening of basins migration and distortion of orogenic belts retreat of trench zones stopping of consuming processes and starting of new subductions the various aspects of each event such as timing location dimension and deformation style impose important constraints on the genetic mechanism in this work we argue that the numerous constraints implied by all events together may be plausibly and coherently explained as effects of the convergence of the confining africa arabia and eurasia plates crucial evidence for discriminating among the various geodynamic hypotheses so far advanced is provided by the structural tectonic information recently provided by crop seismic sections in the study area the proposed evolutionary history is illustrated by several paleogeographic maps which provide a more detailed reconstruction than previous attempts particular attention is paid to describing the tectonic setting developed since the middle pleistocene in the apennines belt and its connection with seismic activity

stable isotope evidence for rapid uplift of the central apennines since the late pliocene abstract the central apennines an accretionary wedge overlying an area of slab detachment are characterized by prominent topography active normal faulting and high uplift rates however previous studies have failed to resolve the surface uplift history complicating efforts to link the topographic evolution with underlying geodynamic processes we aim to better quantify orographic changes by using stable oxygen isotope paleoaltimetry modern surface water 18 o are 5 lower at high elevation than at sea level reflecting orographic rainout over the apennines we present 262 new lacustrine and paleosol carbonate 18 o measurements collected from ten extensional intermontane basins spanning both high and low elevations and combine these with 1 166 published 18 o data permitting us to constrain changes in 18 o both spatially and temporally since the pliocene 18 o in present day high elevation basins has continuously decreased even as 18 o in lowland basins has remained constant over time we attribute this continuous 5 shift to increased orographic rainout as the central apennines were uplifted we estimate an increase in mean elevation of approximately 1 2 km since the late pliocene and these estimates match the suggested timing and expected amplitude of slab break off related uplift this supports the hypothesis that the opening of the adriatic slab window and associated mantle flow contributed significantly to building topography in the central apennines

quaternary catastrophic rock avalanches in the central apennines italy relationships with inherited tectonic features gravity driven deformations and the geodynamic frame abstract five cases of quaternary rock avalanches detached from carbonate mountain ridges in the central apennines are presented due to the large amount of rock masses involved the width of accumulation and detachment areas and the damming in the host environment the analysed rock avalanches can be considered as catastrophic rock slope failures sporadic events in a mountain region characterized by low elevation but where mountain ridges can have a relative elevation of up to 1 km above the lowermost valley floors the geological setting of tectonic structures that originated during the apennine orogenesis influenced rock avalanche characteristics determining the location and shape of detachment areas the kind of rock mass involved and the failure mechanisms two main types have been identified i forelimb rock slide avalanches frsa such as the lettopalena and mt arezzo rock avalanche which involved cenozoic heterogeneous sequences of carbonate ramp deposits detached from box shaped source areas according to a rock sliding mechanism and ii backlimb slide wedge rock avalanches bswra such as the campo di giove scanno and celano rock avalanches that detached from sub circular source areas carved on fault bounded ridges and involving meso cenozoic carbonate rocks with a combined sliding and rock wedge failure mechanism the campo di giove lettopalena and scanno rock avalanches originated from mountain ridges bounded by inactive fault zones and undergoing deep seated gravitational slope deformations dsgsds at the mountain scale these three rock slope failures are considered as isolated events of long lasting deformative processes featuring creep deformation gravity driven deformations firstly generated as a response to stacking processes and synchronous normal faulting during the neogene early pleistocene apennine tectonics in particular the caramanico fault system cfs and the genzana fault gf bordering the carbonate ridges from which the campo di giove and scanno rock avalanches originated respectively are here considered as backlimb collapse structures accommodating the passive uplift and deformation of positive tectonic structures gravity driven deformations persisted during the post early pleistocene dome like uplift of the whole apennine region the regional uplift created the first order 200 km topographic wave length of the belt i e a periodic loading which has been balanced by the deflection of the apennine crust and lithosphere on the contrary shorter topographic wave lengths inherited from former thrusting and synchronous normal faulting determined local isostatic imbalances bearing a large potential for the mature development of dsgsds on mountain ridges favoured also by lateral unloading due to linear erosion and increase of topographic stress thus a cause effect relationship is hypothesized between the geodynamic evolution of the belt and mountain sized gravity driven deformations including large rock slope failures

influence of wave energy on holocene coral reef development an example from ishigaki island ryukyu islands japan abstract wave energy induced by ocean swell and local winds is an important factor controlling the coral reef development here we compare and contrast facies ages and accretion rates of reefs that developed independently along windward and leeward margins of the same island as both reefs face the open ocean swells provide a background of low to medium energy condition with additional energy along windward margins due to prevailing winds this similarity of the wave energy regimes medium to high energy produced a similar framework facies that was constructed by robust branching acropora however much greater lateral accretion rates were observed in the high energy reef than in the medium energy reef also coral cobble facies were only found in the medium energy reef indicating that the reef framework was more susceptible to storm breakage than that in the high energy reef these differences are attributable to the differing biological and ecological responses of corals to wave energy and water motion

the role of slab detachment processes in the opening of the western central mediterranean basins some geological and geophysical evidence abstract a review of the geological and geophysical data from the central and western mediterranean region and the present day upper mantle structure derived from tomographic studies are utilized in order to define the oligocene recent geodynamic evolution for the area in line with previous work we suggest that the miocene quaternary opening of the western and central mediterranean basins is the result of back arc extension due to the roll back toward the southeast of a northwestward subducting african slab in a geodynamic setting pinned between the alpine and betic collisional zones we find however that this general pattern is complicated by four different detachment events which occurred beneath the alps early oligocene the betic chain aquitanian northern africa langhian and the apennines late miocene pliocene we show that each of these events determines a major tectonic reorganization within the european plate

effects of chemical weathering and sorting on the petrogenesis of siliciclastic sediments with implications for provenance studies the bulk chemical compositions mineralogy and mineral proportions of sands and muds of the mallacoota basin in southeastern australia reflect the composition of weathering profiles mantling source rocks rather than bedrock muds contain abundant clay minerals that are virtually absent from the source rocks but abundant in the weathering profiles sands are strongly enriched in quartz relative to source rocks even in the headwaters of the fluvial system demonstrating that feldspar destruction occurs by in situ chemical weathering within profiles and before detritus enters the fluvial system k feldspar is proportionally more abundant in fluvial sands than in source rocks because plagioclase is more rapidly destroyed than either quartz or k feldspar in weathering profiles subsequent erosion and sorting produce sands enriched in quartz with high k feldspar plagioclase ratios relative to source rocks the composition of plagioclase incorporated into the fluvial sands is also controlled by chemical weat

incremental accretion of a sandy reef island over the past 3000 years indicated by component specific radiocarbon dating 1 low lying reef islands appear particularly threatened by anticipated sea level rise and determining how they formed and whether they are continuing to accumulate sediment is essential for their sustainable management depositional chronology of warraber island a small sand cay in torres strait australia is re examined based on ams radiocarbon dating of specific skeletal components whereas radiometric dating of bulk sand samples indicated one or more discrete phases of mid late holocene deposition component specific ams radiocarbon dating of sand grains indicates sustained incremental growth over the past 3000 years ages on gastropods that lived on the reef flat around the island indicate continuing sediment production and island progradation in contrast to bulk ages and other components produced at greater distances growth of sand cays depends on the rate and pattern of sediment supply which are functions of the local ecology of the surrounding reef and reef flat and hydrodynamic constraints

marine and nonmarine deposition in a long term low accommodation setting an example from the middle pleistocene qm2 unit eastern central italy abstract facies anatomy and large scale stratigraphic organization of mid pleistocene strata qm2 unit exposed near the town of ortona eastern central italy have been defined through an integrated outcrop and subsurface dataset and record sedimentation within a long term low accommodation setting the studied interval can be subdivided into nine facies associations reflecting a range of continental marginal marine nearshore and innermost shelf environments and contains a well preserved record of high frequency relative sea level changes in the form of a stack of three unconformity bounded sequences each of the three sequences designated qm23 qm22 and qm21 from oldest to youngest consists of a specific subset of the nine identified facies associations as a function of preserved depositional systems and systems tracts typically the following architectural elements occur in ascending stratigraphic order i a basal unconformity molded by fluvial incision and subaerial exposure during sea level fall and shoreface erosion during subsequent rise ii a maximum regressive surface which is coincident with the sequence boundary iii a transgressive systems tract including braided river conglomerates and floodplain fines within the confines of an incised valley palustrine carbonates and back barrier lagoon mudstones and a deepening and fining upward shoreface to offshore transition facies succession bounded at the base by a wave ravinement surface iv a sharp regressive surface of marine erosion produced by shoreface incision during relative sea level fall and v a prograding downstepping and offlapping sharp based lithofacies assemblage of either beach conglomerates or sandstones ascribed to the falling stage systems tract overlain by a rooted paleosol marking subaerial exposure sequences were deposited on the uplifting palaeo adriatic shelf in response to repeated high frequency and high amplitude eustatic changes in sea level that would promote the creation of accommodation space by subtracting space to deposition the contemporaneous regional uplift of the basin margin may be accounted for the shingled downstepping configuration of individual sequences to form a falling stage sequence set of a larger composite sequence in dip view the erosional contact at the base of the qm2 falling stage sequence set is a composite regressive surface resulting from the downdip convergence and amalgamation of multiple erosional surfaces produced by the progressive basinward translation of successive sequences results from this study have direct implications for the oil and gas field development and exploration when making predictions of reservoir and seal geometries within shallow marine marginal marine and nonmarine sediments emplaced in similar long term limited accommodation settings

extensional basins in the tectonically bimodal central apennines fold thrust belt italy response to corner flow above a subducting slab in retrograde motion the apennines fold thrust belt has developed over the past 20 m y in response to southeastward retrograde migration of the adriatic trench in a region of ongoing subduction but little plate convergence the orogenic belt is characterized by a gently sloping southwestern flank in a state of regional extensional collapse and a steeply sloping northeastern flank in regional contraction in any given area in the central apennines the chronologies of thrusting and subsequent extension provide an estimate of the time required for attainment of high elevation 2 5 3 0 km the time between initial extension and eruption of local ultramafic lavas provides an estimate of the time required to collapse by regional crustal thinning these estimates suggest that the northeastern contractional flank of the range is rising at least twice as fast as the southwestern flank is collapsing we propose that the bimodal state of stress in the apennines is maintained by corner flow in the mantle wedge beneath the crest of the range

prediction of some weathering trends of plutonic and volcanic rocks based on thermodynamic and kinetic considerations abstract the exposed crust consists mainly of plagioclase 35 quartz 20 k feldspar 11 volcanic glass 12 biotite 8 and muscovite 5 quartz is a resistate thus feldspars and glass represent approximately 75 percent of the labile minerals the weathering characteristics of these constituents are summarized in the context of thermodynamic mass balance and kinetic considerations experimentally determined release rate constants were used to predict the proportions of ca na and k released by feldspars of plutonic rocks granites to gabbros to weathering solutions the chemical weathering trends of the weathered residues calculated from the kinetic data conform closely to the initial trends observed in some recent weathering profiles demonstrating the accuracy of the predictions since the weathering of feldspars is controlled by processes that should not change through geological time the relative release rates of ca na and k from the feldspars of granitic rocks can be calculated for future and past episodes of continental weathering experimentally determined release rate constants are not available for a wide range of volcanic glass compositions but the limited data indicate that compositional trends are predictable in weathering profiles developed on volcanic rocks the kinetic data available for rhyolitic glasses accurately predict the initial weathering trends observed in a recent rhyolite weathering profile

morphotectonic evolution of the adriatic piedmont of the apennines an advancement in the knowledge of the marche abruzzo border area abstract this study focuses on the morphotectonic evolution of the apennines central adriatic piedmont and in particular on the region along the marche abruzzo border stratigraphically the rocks of this area are typical of a marine environment which characterised the central periadriatic basin up to the early pleistocene a differential regional uplift produced a north eastward tilting of the area this led to the development of a parallel drainage network across the emerged coastal plain during the middle pleistocene these tectonic events along with a series of climatic changes during the quaternary caused alternating phases of fluvial incision and deposition which eventually produced four levels of fluvial terraces as outcropping lithologies seldom display a full record of significant tectonic deformation we carried out morphometric analysis along with a geomorphological survey in order to enhance our morphotectonic understanding of the area and to better define the role of neotectonics in the morphological evolution of the area we also analysed the morphological evidence of tectonics including field surveys focusing on fluvial and alluvial fan terraces as they are valuable indicators of neotectonic evolution finally we employed geostatistical analysis to facilitate the detection of fluvial terraces even when affected by neotectonics our results indicate an active control on drainage evolution by nw se to wnw ese tectonic lineaments intersected by sw ne and wsw ene ones these tectonic lines continued to be active up to the formation of the third level of terraces late pleistocene river captures and diversions followed during the late pleistocene and the holocene in some cases favoured by passive tectonic control

storm cycles in the last millennium recorded in yongshu reef southern south china sea large storm relocated porites coral blocks are widespread on the reef flats of nansha area southern south china sea detailed investigations of coral reef ecology geomorphology and sedimentation on yongshu reef indicate that such storm relocated blocks originated from large porites lutea corals growing on the spurs within the reef front living coral zone because the coral reef has experienced sustained subsidence and reef development during the holocene dead corals were continuously covered by newly growing coral colonies for this reason the coral blocks must have been relocated by storms from the living sites and therefore the ages of these storm relocated corals should approximate the times when the storms occurred rapid emplacement of these blocks is also evidenced by the lack of coral overgrowth encrustation or subtidal alteration u series dating of the storm relocated blocks as well as of in situ reef flat corals suggests that during the last 1000 years at least six strong storms occurred in 1064 30 1210 5 1201 4 1336 9 1443 9 1685 8 1680 6 1872 15 ad respectively with an average 160 year cycle 110 240 years the last storm which occurred in 1872 15 ad also led to mortality of the reef flat corals dated at similar to 130 years ago thus the storm had significant impacts on coral reef ecology and morphology c 2004 elsevier b v all rights reserved

distribution of large benthic foraminifers around a populated reef island fongafale island funafuti atoll tuvalu abstract low lying small reef islands on pacific atolls are vulnerable to coastal erosion and flooding mainly due to rises in sea level as well as local stresses associated with overpopulation because reef island sediments on pacific atolls are composed mostly of shells of large benthic foraminifers lbfs their future stability depends on understanding foraminiferal shell sources and their production rates around the islands here we report on the distribution and population density of lbfs around fongafale island the main populated island of tuvalu in the south pacific where coastal erosion and inundation have occurred we discuss their controlling factors in particular anthropogenic influences on foraminiferal distribution the results based on multivariate analyses canonical correlation analysis and multiple regression analysis demonstrated that baculogypsina sphaerulata and amphistegina lobifera were more common on the high energy intertidal ocean reef flats 10 6 and 10 4 individuals m 2 respectively and b sphaerulata was less common around the populated area of the island on the relatively low energy subtidal lagoon reef flats amphistegina lessonii was the most common species particularly in the dry leeward season with an increasing density in deeper offshore zones 10 4 individuals m 2 sorites orbiculus was less common than the other species but was found on both sides of the reef flats 10 3 individuals m 2 macroalgal 15 n values indicated that upwelling nutrient rich deep water could be the source of nitrogen for oceanic waters whereas nutrients in lagoon seawater could be partly derived from groundwater mixing with domestic wastewater especially near the populated area these results suggest that the distribution and population density of lbfs in the study area are influenced by spatial differences in water energy and water quality and that b sphaerulata is less tolerant of nutrient loading than other species comparison of distributions between living individuals and empty shells indicated that ocean reef flats are the primary source of foraminiferal shells for reef islands and lagoon beaches

sulfuric acid speleogenesis in the majella massif abruzzo central apennines italy abstract many active and inactive hypogene sulfuric acid cave systems are known along the apennines italy the cavallone bove cave system is located in the external part of the central apennine chain in the majella massif and opens at 1470 m asl along the taranta gorge south of chieti the presence in these caves of peculiar geomorphological features such as feeders rising channels megacusps cupolas and replacement pockets offers evidence of rising acidic fluids the secondary mineral deposits including meter size white gypsum deposits alunite jarosite black layers of iron manganese oxides and hydroxides along with a rare association of authigenic rutile ilmenite minerals indicate a sulfuric acid origin stable isotope analyses of sulfates further confirm a sulfuric acid speleogenetic sas origin of these minerals and in general of the whole cave system with h2s coming from the bacterial sulfate reduction of deep seated triassic evaporites interacting with hydrocarbons alunite dating demonstrates this water table sas cave to have been active at least until 1 52 0 28 ma all the evidence suggests that cavallone bove is an ancient sulfuric acid karst system that was uplifted

a proposal for the kinematic modelling of w dipping subductions possible applications to the tyrrhenian apennines system in w dipping subduction zones there is a general eastward progression of the back arc basin accretionary wedge foredeep complex with the forward progression early stages of the complex are revealed by slices of upper crust and sedimentary cover abandoned to the west left floating above a new section of mantle a major shear zone should form at the new moho separating upper crust slices of earlier accretionary stages and the eastward flowing mantle the mantle wedging at the top of the subduction plane could be responsible for the uplift of the central parts of the belt the retreating of the subduction hinge is interpreted as due to the push generated by the eastward mantle flow detected in the hot spot reference frame the foredeep depth is mainly a function of the radius of curvature of the subduction hinge the frontal wedge is constructed from the stacking of the upper layers of the subducting plate and the syntectonic clastics that fill the foredeep which are progressively involved in thrusting and later by extension in order to preserve volume balance the lithosphere of the eastern plate before subduction has to be the same size as that which has been subducted due to the longer length of the arc with respect to the original length of the linear margin between the two converging plates laterally stretched subducted lithosphere is predicted at depth w dipping subductions usually have a short life probably due to their inherent capability to produce new lateral heterogeneities of the lithosphere the thin back arc which are a key factor in controlling and generating new subductions both e and w dipping this model is applied to the apennines tyrrhenian sea system

sedimentology faunal content and pollen record of middle pleistocene palustrine and lagoonal sediments from the peri adriatic basin abruzzi eastern central italy abstract a 25 m thick outcrop section exposed at torre mucchia on the sea cliff north of ortona eastern central italy comprises a rare middle pleistocene succession of shallow water and paralic sediments along the western adriatic sea an integrated study of the section including facies and microfacies analyses and characterization of paleobiological associations mollusks fishes ostracods foraminifers and pollen enable a detailed reconstruction of the paleoenvironmental and paleoclimatic conditions during deposition the shallow water deposits include a transgressive deepening and fining upward shoreface to offshore transition facies succession overlain by a regressive shoreface foreshore sandstone body with an erosive base and a rooted and pedogenically altered horizon at the top that imply deposition during sea level fall this forced regressive unit is overlain by paralic strata forming a transgressive succession comprising palustrine carbonates and back barrier lagoonal mudstones the palustrine carbonates exhibit some of the typical features encountered in palustrine limestones deposited within seasonal freshwater wetlands marl prairies following the sea level rising trend the freshwater marshes were abruptly replaced by a barrier lagoon system that allowed deposition of the overlying mud rich unit within these deposits the faunal assemblages are consistent with a low energy brackish environment characterized by a relatively high degree of confinement the pollen record documents the development of open forest vegetation dominated by pinus and accompanied by a number of mesophilous and thermophilous tree taxa whose composition supports a tentative correlation with marine oxygen isotope stage 17 the new pollen record from torre mucchia improves our understanding of the vegetation development in the italian peninsula during the middle pleistocene and sheds new light on the role played by the most marked glacial periods in determining the history of tree taxa

the uplift of the adriatic flank of the apennines since the middle pleistocene new insights from the tronto river basin and the acquasanta terme travertine central italy abstract the apennines chain is an active neogene fold and thrust belt resulting from the westward subduction of the adriatic microplate starting from the end of the early pleistocene the chain was affected by an increase in regional uplift recent gps data resolved uplift rates of 1 2 mm yr for the whole apennines whereas in the adriatic flank several studies estimated rates between 0 3 and 0 5 mm yr over the last 1 myr a number of works investigated the evolution of the drainage systems along the periadriatic margin of the apennines providing long term incision rates studies from the northern part of this sector reported uplift rates varying from 0 2 to 1 1 mm yr whereas only few studies concentrated on the central sector of the adriatic flank of the apennines focusing mainly on the evolution of the lower reach of major rivers this work aims to quantify the long term rock uplift and incision rates of the eastern portion of the central apennines through the analysis of the tronto river basin because of its geologic and geomorphological configurations this basin is an ideal test site to investigate the influence of tectonics and climate on the recent topographic evolution of the central apennines the basin extends with a roughly wsw ene direction from the inner sector of the chain to the adriatic coast crossing several tectonic structures such as the amatrice extensional basin and the acquasanta and montagna dei fiori anticlines in particular in the acquasanta terme area the right flank of the tronto river valley is characterized by fluvial and travertine deposits organized and exposed in several levels in this work we investigated the hydrography river longitudinal profiles and topography swath profile slope and local relief of the tronto river basin coupling these data with field observations and geochronological analysis on the continental sediments fluvial deposits and travertines outcropping in the acquasanta terme area to better characterize the nature of travertines we performed geochemical characterization of three travertine forming thermal springs obtaining their physico chemical parameters the percentage of dissolved gases and the isotopes content finally we applied a knickpoint celerity model to chronologically constrain the geomorphological evolution of the whole drainage system the results show the occurrence of a continuous tectonic uplift 0 5 mm yr across the study area since middle pleistocene the uplift together with climate fluctuations drove the incision 0 6 mm yr of the landscape and the delineation of the present drainage network these data are consistent with previous estimates of uplift and incision rates in adjacent areas and provide new constraints on the quaternary evolution of the central apennines this study highlights how the coupling of field surveys with morphometric and topographic analyses of a drainage system is crucial to understand and quantify the influence of tectonic and climate changes in shaping the landscape

contemporary sedimentation in the cocos keeling islands indian ocean interpretation using settling velocity analysis abstract textural parameters of grain size distributions derived from sieve analysis and component analysis have been used to the exclusion of other methods to examine sedimentary processes in modern reef environments however because these methods do not reflect the hydraulic behaviour of bioclastic sediment this study uses settling velocity analysis accounting for grain size density and shape variability and component analysis of separated settling velocity fractions to describe and differentiate bioclastic deposits and infer transport pathways in the cocos keeling islands an indian ocean atoll principal component and cluster analysis of settling 251 samples and component 90 samples characteristics discriminated eight settling velocity and five component classes a derived settling velocity classification reflecting the hydraulic properties of the sediments describes a lagoonward gradient from those with fast settling characteristics on the outer reef flat to those with moderate settling character on sand aprons the active sediment transport system is constrained between these zones component analysis of bulk samples identifies two broad sediment types 1 those with reef derived components found throughout the active transport zone reef flat to sand aprons and 2 those characterised by greater proportions of gastropod and halimeda fragments which are produced and deposited in situ in the lagoon component analysis of settling fractions further resolves details of sediment movement in the active transport zone sediment is transported from the productive reef flat to passage entrances which form initial depositional environments slower settling material is selectively transported from the entrances through the passage conduits to passage exit environments these form the main depositional areas under mean energy conditions during moderate to high energy events sediment is flushed from the passage to sand apron zones with slower settling grains deposited in the deep lagoon sinks results show that settling velocity analysis and component analysis of settling fractions can resolve the nature of sediment transport patterns in reef environments at a much finer scale than studies in which analysis is based on grain size distributions

recent sedimentary facies of isolated carbonate platforms belize yucatan system central america abstract distribution of recent sedimentary facies is significantly different in four closely spaced isolated carbonate platforms off the coasts of belize and yucatan se mexico these differences are largely controlled by variations in submarine topography which are likely the result of differential subsidence and karstification from platform to platform a variety of depositional styles and patterns is found in platform interiors that developed during the same holocene sea level rise composition and texture of surface sediment samples were used to define four major sediment types and to distinguish nine depositional environments within the platforms facies maps are based on analysis of 454 sediment samples and high resolution satellite imagery glovers reef is characterized by a circular facies distribution the nearly continuous reef margin is composed of a coral red coralline algae halimeda grainstone mixed nonskeletal peloidal skeletal wackestones and packstones are present in shallow lagoon parts 5 m water depth behind the margin the deep interior from 5 to 18 m water depth is characterized by mollusk foram halimeda wackestones with over 860 patch reefs of coral red algae halimeda mollusk packstones lighthouse reef also has a coral grainstone and coral red algae halimeda grainstone rim but the facies distribution in the interior is strongly asymmetrical the 8 m deep eastern lagoon is floored by mollusk foram halimeda wackestones and packstones the 3 m deep western lagoon has the mixed peloidal skeletal wackestone to grainstone facies a linear trend of coalescing patch reefs and skeletal grainstone facies separates the two lagoons banco chinchorro is similar to lighthouse reef inasmuch as facies distribution patterns of the interior are strongly asymmetrical mollusk foram halimeda wackestones grainstones are present in eastern lagoon areas whereas shallow 5 m western parts of the lagoon are composed of mixed peloidal skeletal grainstones packstones and wackestones most of turneffe islands is protected on the east by lighthouse reef accordingly turneffe has a narrower reef and skeletal grainstone rim than the other two platforms restricted interior lagoons are up to 8 m deep and are enclosed by wide mangrove rims and surface sediments dominated by halimeda rich wackestone rich in organic matter coral patch reefs are absent in contrast the unprotected northernmost part of turneffe has a wide reef and grainstone rim and the open lagoon area consists of mollusk foram halimeda wackestones packstones with abundant patch reefs

evaluation of complex site effects through experimental methods and numerical modelling the case history of arquata del tronto central italy abstract this work deals with the experimental and numerical evaluation of the local seismic response of arquata del tronto area marche region central italy severely struck by the mw 6 0 august 24th 2016 earthquake arquata main village rises on elongated wnw ese trending ridge of the central apennines thrust belt central italy at elevations about 170 m higher than the underlying alluvial valleys where borgo and san francesco hamlets are built on despite their proximity less than 500 m arquata del tronto borgo and san francesco reported a different damage distribution after the august 2016 mainshock suggesting that the seismic response of the area may be controlled by site effects in order to explore this hypothesis we evaluated the 2d numerical local seismic response along four representative geological cross sections passing through arquata del tronto san francesco and borgo additional 1d analyses were carried out at strategic points along the cross sections in order to explore the 2d physical phenomena governing the local response the satisfactory agreement between numerical amplification functions in linear range and experimental amplification functions obtained by the generalized inversion technique git applied to a large number of aftershocks confirms the substantial reliability of the subsoil models numerical analyses representative of the 2016 mainshock were carried out and processed in terms of peak and key ground motion parameters a comparison with the damage induced by the 2016 mainshock was finally undertaken substantially justifying the observed pattern this study provides general implications about site response and seismic microzonation in sites characterized by similar complex geological and morphological settings

pre existing cross structures and active fault segmentation in the northern central apennines italy abstract the multideformed axial zone of the apennines provides a great opportunity to explore the influence of pre existing cross structures inherited from pre quaternary tectonic phases on the segmentation of quaternary active seismogenic extensional faults detailed geological and structural data and their comparison with seismological data show that although the attitudes strike and dip of oblique pre existing faults are certainly an important factor in determining a segment boundary the size of the inherited oblique structures seems to be more crucial pre existing cross structures with lengths ranging from several kilometers to a few tens of kilometers show a twofold behavior they can act as segment barriers during the rupture of a single fault segment or they can be reactivated as transfer zones inducing the activation of two adjacent segments that belong to the same fault system regional basement crustal oblique pre existing cross structures with lengths ranging from several tens of kilometers to hundreds of kilometers commonly nne striking may act as persistent structural barriers that halt both fault segment and fault system propagation thus determining their terminations and maximum sizes in the northern central apennines the nne striking ancona anzio valnerina and ortona roccamonfina tectonic lineaments although having been repeatedly reactivated since the mesozoic represent the most important examples of these structures moreover probably due to their misorientation with respect to the present extensional stress field regional nne striking pre existing structures appear to be less likely to produce strong magnitude events no surface evidence for quaternary faulting has been found thus far and historical and instrumental seismicity shows only m m 7 event on the other hand is more likely to occur along the n nw s se trending normal fault systems lastly we propose a model that can explain the different sizes of fault segments and fault systems on the basis of their location with respect to the persistent structural barriers and their spacing in this view our results may contribute to a more reasonable assessment of the nature and size of future surface ruptures in the northern central apennines which are of critical importance to estimating seismic hazard

high resolution sedimentological and geotechnical characterization of the late quaternary deposits in the italian central adriatic coast tronto river mouth abstract in order to investigate the effective role of sedimentological analysis in the interpretation of geotechnical data with special reference to coastal transitional paleoenvironments a study on the quaternary alluvial and coastal plain successions forming the upper 30 m of the tronto river valley subsoil facing the italian central adriatic sea has been carried out according to the analysis of a continuously cored borehole and a few adjacent piezocone tests four depositional facies have been recognized from last deglaciation to present reflecting the changes in sedimentation due to sea level changes and local erosion subsidence phenomena furthermore three 14c dates have provided the basis to establish the chronological framework of the succession the interpretation of piezocone data has allowed an accurate geotechnical characterization of the different soil units also accounting for their sedimentological environment specific issues concerning the mechanical response and the determination of soil parameters of facies with special reference to the heterogeneous sedimentary formation known as flaser bedding have been discussed and appropriate piezocone based interpretation procedures have been identified the final aim of this combined geo sedimentological and geotechnical study is to propose a possible methodological approach in which both analyses can contribute to a better understanding of local subsoil for territorial planning and related engineering applications

numerical modelling of plio quaternary slope evolution based on geological constraints a case study from the caramanico valley central apennines italy evidence of deep seated gravitational slope deformations dsgsd and of large prehistoric landslides is fairly widespread within the central apennines italy these gravity induced processes accompanied the intense plio quaternary uplift phases that affected the mountain chain in this study a multidisciplinary approach has been adopted in order to better constrain the relationship between the tectonic evolution and the gravitational morphogenesis of a typical apennine morphostructure such as the caramanico valley for this purpose a conceptual model of the morphostructural evolution of the area has been reconstructed on the basis of geo logical constraints derived by the integration of detailed geological structural and geomorpholo gical surveys with available literature data based on this evolutionary model a multistage numerical modelling using the finite difference method code flac 6 0 has been performed in order to i evaluate the effect of the uplift related morphological changes of the valley slope system and ii assess the role of the horizontal vertical stress ratio variations due to geodynamic regime shifts the results of the numerical model show a good fit with the actual geomorphical evidence and also confirm the presence during some evolutionary stages of stress strain conditions compatible with those necessary to produce the massive rock slope failures testified by the presence of large palaeo landslide deposits

hydrodynamics and sediment flux of hoa in an indian ocean atoll detailed hydrodynamic and sediment ux measurements are reported from 11 hoa shallow cross reef channels in the cocos keeling islands indian ocean all hoa exhibit unidirectional oceanside reef to lagoon uxes these currents are driven by tides wave set up and incident waves and the presence of islands that generate alongshore gradients so that currents ow toward the topographic low points of hoa entrances in the reef rim two functional groups of hoa are identi ed that extend chevalier s typology of hoa and possess different process signatures sediment limited hoa slh are ef cient conduits of sediment transport they are located close to the reef rim where incident wave energy propagates across the reef crest into the hoa and is able to entrain sediment transport limited hoa tlh are characterized by low rates of sediment transport because incident wave energy is negligible as they are located much further from the reef edge than slh in the absence of an entrainment mechanism the oceanside reef at is laden with sediment storm energy increases transport ef ciency through hoa however the net sedimentation response differs between the two hoa types proximity to the reef edge means that frequent storms ush sediment from slh increasing hoa depth and enhancing the potential for erosion of the conglomerate boundary in contrast the greater reef width fronting tlh means that sediment transport from reef ats to the lagoon is only activated during infrequent storms the contrasting process signatures account for morphological differences between sediment limited hoa lagoonward decrease in depth and increase in width and transport limited hoa lagoonward increase in depth the number and type of functional hoa are found to have signi cant implications for the rate of lagoon sedimentation in enclosed atolls in general an increase in frequency of functional hoa and increased proportion of slh will promote more rapid rates of lagoon in ll copyright 2004 john wiley sons ltd

recent massive coral mortality events in the south china sea was global warming and enso variability responsible the key to predicting the possible response s of coral reefs to hypothesized future global warming is the knowledge of their response s to previous extreme climatic events we obtained 80 high precision u th ages for 78 dead massive porites colonies from the nansha islands south china sea with an aim to understand the longterm history frequency timing and causes of local coral mortality our results reveal a number of significant episodes of coral mortality since 1860 ad with an apparent increase in frequency and severity since 1930 ad and more recently since 1970 especially when only synchronized mortality events found to have occurred on both reefs were compared the synchronized mortality events centered around 1865 1875 1895 1900 1910 1920 1930 1945 1970 1985 and 1990 2005 ad which imply regional common causes were found to correlate well with the warm phases of the el ni n over tildeo southern oscillation enso i e el ni n over tildeo years e g some recent ones during 1972 1973 1982 1983 1991 1994 1997 1998 ad on inter annual time scale as well as with positive phases of the pacific decadal oscillation pdo or its sharp phase transitions on inter decadal time scale synchronized coral mortality was absent during prolonged negative pdo phases e g during 1950 1970 ad overall the data shows that immediately before and at the time of modem local ecological monitoring the region s coral communities had already experienced several recent episodes of stress the increased frequency distribution of mortality ages since 1930 ad and more recently since 1970 ad appears to coincide with progressively warmer sea surface temperatures both regionally and globally our data highlight the vulnerability of local coral communities in the face of present and predicted future warming c 2012 elsevier b v all rights reserved

crustal section based on crop seismic data across the north tyrrhenian northern apennines adriatic sea abstract using deep seismic reflection data from the italian lithospheric exploration project crop in the central mediterranean region a 400 km long section composed of three different profiles crossing the northern tyrrhenian sea crop m 12a profile the northern apennines crop 03 and the adriatic sea crop m 16 is reconstructed and discussed new data allow us to outline a seismically consistent tectono stratigraphic setting for the crust and upper mantle of the northern apennines thrust belt system and its adriatic foreland time space analysis of the deformation of the investigated chain and identification of existing macrostratigraphic crustal intervals and tectonic units allow a reasonably controlled interpretation of the geodynamic evolution and of the main orogenic stages careful seismic reprocessing and application of advanced techniques to key zones of the explored area such as the tuscan archipelago were determinants in obtaining fundamental information for understanding of the complex lithospheric structures and their evolution profile interpretation supports that the northern apennine chain is dominated by a compressive thrust system crustal extension assumed by some authors as the dominating tectonic process for the whole tuscan apennine area represents a subordinate geodynamic event of the last stage tyrrhenian in the early cretaceous late jurassic the paleogeographic framework consisted of the europe and adria plates separated by the alpine tethys ocean during the late cretaceous early eocene adria europe convergence eo alpine stage and subduction beneath the adria plate closed the alpine tethys sea with the tethyan slab being clearly seismically imaged the first apenninic geodynamic stage occurred in the late oligocene early miocene with the opening of the balearic basin which generated a first lithospheric root of the apenninic chain in the tuscan archipelago area this root is represented by adria verging thrust faults that progressively flatten eastward upper parts of the west verging eo alpine thrust blocks were truncated by the east verging thrust faults of the balearic stage a deeper seismic reflector attributed to the top of the asthenosphere forms a mantle high below the elba island from the late miocene to present the corsica basin and western hinterland area were affected by extensional tectonics related to the tyrrhenian opening whereas compressional tectonics continued in the eastern hinterland and mostly on the eastward migrating foreland with development of a second lithospheric root constituted by high angle thrust faults these faults give rise to a huge basement culmination below the main apennines watershed impressive e directed gravity sliding of sedimentary blocks over their sloping basement occur generating the umbria marche shallow seismicity crustal shortening of the apennines system amounts to 170 km 14 km of which are due to the eo alpine stage 71 km to the balearic and 85 km to the tyrrhenian one in the frame of africa europe convergence the tyrrhenian apennines tectonodynamics were mainly conditioned by the mesozoic paleogeography

high precision tims u series and ams c 14 dating of a coral reef lagoon sediment core from southern south china sea accurate dating of lagoon sediments has been a difficult problem although lagoon profiles usually with high deposition rates have a great potential for high resolution climate reconstruction we report 26 high precision tims u series dates on 25 coral branches and five ams c 14 dates on foraminifera for a 15 4 m long lagoon core from yongshu reef nansha area southern south china sea all the dates are in the correct stratigraphical sequence providing the best chronology so far reported for lagoon deposits the results reveal a similar to 4000 a continuous depositional history with sedimentation rates varying from 0 8 to 24 6 mm a 1 with an average of 3 85 mm a 1 which corresponds to an average net carbonate accumulation rate of similar to 2700 g caco3 m 2 a 1 significantly higher than the mean value 800 400 g caco3 m 2 a 1 used for lagoons in general in previous studies of global carbonate budget episodes of accelerated depositions within the last 1000 years correlate well with strong storm events identified by u series dates of storm transported coral blocks in the area however in the longer term the sedimentation rates during the past 1000 years were much higher than earlier on probably due to more vigorous wave reef interaction as a result of relative sea level fall since 500 ad and expansion of reef flat area supplying more sediments the coral tims u series ages and foraminifera ams 14c dates reveal intriguing apparent radiocarbon reservoir ages r from 572 to 1052 years which are much higher than global mean values of similar to 400 years c 2006 elsevier ltd all rights reserved

major element geochemistry and paleoclimatology of the permo carboniferous glacigene dwyka formation and postglacial mudrocks in southern africa abstract a chemical index of alteration cia is used to quantify the degree of weathering of fine grained materials in the glacigenic permo carboniferous dwyka formation and succeeding stratigraphic units of southern africa diamictites in the dwyka formation have low cia values compatible with their glacigenic origin interbedded mudrocks show a wide scatter of values suggesting that at least some of them were deposited during periods when ice had retreated from the source areas samples from the prince albert shale which immediately overlies the dwyka formation show high cia values suggesting a rapid transition to a much more intensive weathering regime warmer climatic conditions samples from the succeeding whitehill shale have a low average value so that weathering was once more inhibited perhaps by a temporary return to a colder climate the highest stratigraphic units sampled the upper shales have an average cia value comparable to that of average shales and suggesting normal weathering conditions major element geochemical data can supplement sedimentological and paleontological information and provide a valuable contribution to the detailed paleoclimatic interpretation of such glacigenic successions

a detrital sediment budget of a maldivian reef platform abstract sediment dynamics are an important control on the morphology and development of reef systems by actively removing and redistributing excess detrital sediment this study presents quantitative data from direct point measurements of sediment transport on the platform surface and fore reef slope of vabbinfaru reef north male atoll maldives a suite of sediment traps were used to construct actual rates of platform sediment fluxes and off reef export over different spatial and temporal seasonal scales to establish key sediment transport pathways findings showed that high sediment fluxes occur on vabbinfaru platform in the absence of major storm activity up to 1905 g m 1 d 1 with 95 of annual transport occurring during the southwest monsoon as a result of increased wave energy climate driven changes in the platform process regime caused a reversal of net sediment transport pathways between each monsoon season off reef export rates were high reaching a maximum of 12 58 kg m 1 y 1 for gravel and 407 g m 1 d 1 for sand sized sediment an estimated 127 120 kg is exported from the platform annually equating to a significant loss from the reef sediment budget and contributing to the long term geomorphic development of the fore reef slope and atoll basin detrital sediment reservoirs on vabbinfaru are not purely depositional carbonate sinks but rather temporary stores that are important in the transfer of sediment between reef zones

residual topography lithospheric structure and sunken slabs in the central mediterranean abstract the central mediterranean comprises subduction collision and backarc extension all in a relatively small area in this paper we analyze the topography of this region examining the influence of subducting slabs on overriding plates we take the observed surface elevation remove the contribution of the crust to it and use the residual topography to identify regions that are unusually low unusually high or normal then we calculate lithospheric thickness where local isostasy applies the results provide information about the structure of the lithosphere in this complex region and about the vertical tectonics in particular we found a difference between the south tyrrhenian subduction zone and the apennines consistent with the processes of slab rollback and slab break off respectively in the south tyrrhenian the edge of the oceanic plate is strongly pulled down whereas the edge of the overriding plate the calabrian peninsula is uplifted this opposite trend indicates weak plate coupling that is the subducting slab which is rapidly rolling back hangs almost entirely on the oceanic plate and the overriding plate is free in contrast in the apennines high residual topography and uplifting are detected on both sides of the mountain belt consistent with complete break off of the subducted lithosphere

the durability of bioclastic sediments and implications for coral reef deposit formation the generation and composition of carbonate sediment within tropical carbonate settings is controlled by the skeletal production of caco3 in conjunction with physical biological and chemical processes which act to break down and disperse skeletal remains using the results of detailed tumbling barrel experiments this paper discusses the role the physical durability of common constituents of reef sediment plays in the composition of coral reef deposits the durability of the skeletal remains of six reef sediment constituents was determined experimentally using tumbling barrels results indicate that constituent durability varies considerably amongst common reef sediment constituents calcareous algae halimeda was the least durable constituent tested followed by larger benthic foraminifera baculogypsina sphaerulata and marginopora vertebralis and the pelecypod fragum fragum two species of branching coral acropora sarmentosa and acropora nasuta were found to be the most resistant to physical destruction these findings provide increased power to interpret reef and island deposits and the potential role skeletal durability plays in the retention of constituent skeletons within coral reef associated sedimentary systems

normal faulting vs regional subsidence and sedimentation rate abstract normal faults occur in a variety of geodynamic environments both in areas of subsidence and uplift normal faults may have slip rates faster or slower than regional subsidence or uplift rates the total subsidence may be defined as the sum of the hangingwall subsidence generated by the normal fault and the regional subsidence or uplift rate positive total subsidence obviously increases the accommodation space e g passive margins and back arc basins in contrast with negative total subsidence e g orogens where the hangingwall subsidence rate is faster than the sedimentation rate in cases of both positive and negative total subsidence the facies and thickness of the syntectonic stratigraphic package may vary from the hangingwall to the footwall a hangingwall subsidence rate slower than sedimentation rate only results in a larger thickness of the strata growing in the hangingwall with no facies changes and no morphological step at the surface the isostatic footwall uplift is also proportional to the amount and density of the sediments filling the half graben and therefore it should be more significant when the hangingwall subsidence rate is higher than sedimentation rate

new radiometric dating of volcanic ash layers in periadriatic foredeep basin system italy abstract new geochronological data are reported for two key ash beds interbedded in upper miocene messinian early pleistocene rocks at maccarone bellante and mosciano s angelo on the adriatic side of the italian peninsula major element chemistry of glass shards was determined with electron microprobe analysis on the younger key bed the older messinian age ash bed sampled at maccarone yields a corrected glass fission track age of 5 38 0 42 ma the younger ash bed sampled at mosciano s angelo and at two localities at bellante yields corrected glass ages of 2 1 ma similar to ages previously determined on pliocene pleistocene ash collected along the ionic coast and on the tyrrhenian side of italy apatite fission track dating of one of the bellante samples confirms the glass age whereas apatite from the mosciano s angelo sample yields an excessively old age due to the presence in the sample of a significant component of detrital grains an unusual bimodal spontaneous track diameter distribution is found in the maccarone glass similar to the distributions previously obtained on other messinian age tephra samples from the same region this anomalous track diameter distribution is interpreted as a thermal disturbance coeval with the volcanic activity that produced the pliocene pleistocene key volcanic ash bed sampled at bellante and mosciano s angelo the contemporaneity of this ash with the event detected by the maccarone glass suggests that it was related to the tectonic phase which marked with numerous erosive levels distributed along the whole apennine region the end of the pliocene sedimentary cycle and the onset of the pleistocene cycle

impact on the coral reefs at yongle atoll xisha islands south china sea from a strong typhoon direct sweep wutip september 2013 abstract relatively little is known about the extent and distribution of damage to coral reefs by typhoons in the south china sea especially in remote reefs where typhoons occur frequently a strong typhoon wutip jtwc category 3 directly struck the yongle atoll on 29 september 2013 causing 62 deaths and sinking dozens of ships in the yongle atoll maritime area xisha islands south china sea surveys on coral reefs at yongle atoll were conducted using scuba diving before july 2013 and after 8 days the typhoon sweep the results show that the effects of wutip on coral reefs were patchy as a result of varying coral reef geomorphology and depth the typhoon caused significant damage to reef associated depths on the passage of the atoll where currents generated by the typhoon produced the strongest energy coral destruction was most spectacular at the 2 m depth 46 living scleractinian corals were damaged at 6 m and 15 m depths damage to the coral reefs were minimal the shallow fore reef area on the steep slopes the upper region of the outer slopes with depths between 2 and 6 m were the principal zones of the typhoon effect however the vertical part of the steep slopes were mainly damaged indirectly waves rolling boulders or corals which were less severely affected than the shallow fore reef steep slope area on the low angle slopes the correlation between the typhoon damage to coral reefs and depth was low because the wave and current energy induced by the typhoon were homogenously attenuated along gentle slopes under the stress of global warming destructive damage to coral reefs on the xisha islands is expected to increase and will require frequent monitoring to determine trends in the near future

distribution of joints in the hinge line culmination of foreland verging overturned anticlines an example from the montagna dei fiori structure in the central apennines of italym francioni et al distribution of joints in overturned anticlines the distribution of joints veins and shear fractures in the montagna dei fiori overturned anticline is here reported two joint sets longitudinal and transverse to the nnw sse anticline axial trend and a conjugate system of shear fractures are recognized the transverse and longitudinal joint sets have a pre folding development likely related to the foreland foredeep flexure the transverse joints were reopened during layer parallel shortening along with the development of the shear fractures then during syn folding outer arc extension and hinge line culmination fold axial parallel extension both the longitudinal and transverse joints were enhanced and reactivated respectively

deformation of the 125 ka marine terrace in italy tectonic implications in peninsular italy marine terraces and shorelines created during oxygenisotope substage 5e known historically as the tyrrhenian highstand provide a reliable and homogeneous datum of vertical motions during the past 125 000 years published accounts of 121 locations on the tyrrhenian inner edge were reinterpreted and used to calculate both local and regional uplift rates the data show arching of southern italy between the tyrrhenian and the adriatic coasts and of the calabrian arc between the sangineto and the longi taormina tectonic lineaments at rates of up to 1 2 mm yr for the past 125 ka they also suggest that the present configuration of the southern apennines is the product of post early pleistocene regional uplift superimposed on tortonian to early pleistocene thrusting uplift patterns are characterised by different wavelength in different geodynamic settings suggesting a close link with the depth of the causative tectonic sources

controls on platform scale patterns of surface sediments shallow holocene platforms bahamas isolated carbonate platforms occur throughout geological history and commonly exhibit considerable spatial variability to evaluate the controls on the nature of sediment accumulation across the expansive shallow platform tops this study systematically compares and contrasts patterns in surface sediments from several shallow 10 m holocene bahamian examples remote sensing data field observations petrographic characterization and quantitative grain size analyses reveal the spatial patterns of sediment accumulation on crooked acklins platform and the berry islands bank integration of these data with synoptic observations of waves tides and currents along with regional geochemical data provides a means to explore the factors that influence platform scale sedimentary patterns these data illustrate that the platform interiors of both crooked acklins platform and berry islands bank are blanketed with medium to coarse sand size sediment peloids are most common in the interior of crooked acklins platform whereas the berry islands bank includes more abundant composite grains in both areas very little mud is present with surface sediments averaging 2 mud comparison of these results with published data from little bahama bank great bahama bank and caicos platform suggest that contrary to previous interpretations the presence of open margins and or brisk winds are not necessary for the occurrence of a platform top with little mud although the muddy sediment fraction of the interior can be suspended by elevated wave energy wind generated current speeds in protected platform interiors are relatively low instead in parts of the platform interiors transport and winnowing of fines is enhanced greatly by tidal currents which carry suspended sediments off the shallow platforms even if shielded by islands beyond physical influences however regional geochemical compilations suggest that the bahamian tides supply highly supersaturated waters rich in dissolved oxygen to these platform interiors this exchange is interpreted to facilitate favourable conditions for calcium carbonate precipitation in the form of ooids marine cements and hardened peloids across vast expanses of the platform interiors such fundamental controls on holocene platform scale sediment dynamics are likely to have influenced carbonate systems through the geological record

a half century of coastline change in diego garcia the largest atoll island in the chagos abstract being low and flat atoll islands are often used as case studies against which to gauge the likely impacts of future sea level rise on coastline stability furnished with lengthy temporal datasets pacific atolls form the majority of studies with scant information published for sites in the indian ocean to address this imbalance this study considers diego garcia an atoll island situated in the remote equatorial indian ocean which has undergone pronounced natural and anthropogenic change in the last fifty years to explore the former time separated remote sensing images spanning the years 1963 2013 are assembled to provide insight into the natural dynamics of the shoreline of this island and ocean climate data are compiled to investigate possible controls disregarding the precinct of the atoll on which a military complex has been constructed overall land area of diego garcia decreased by a net value of only 0 92 between 1963 and 2013 while net island area is relatively unchanged 12 of the shoreline that is not in the military precinct displayed discernible accretion and 15 has receded with the lagoon facing coastline having undergone the most pronounced changes and at rates higher than recorded for the island s exterior broad trends in the morphological adjustment of the island exist the north eastern limb of the atoll has generally receded while the south eastern limb has extended the south of the island has also extended the south western region has eroded and the north western part has generally also eroded with the exception of notable shoreline extension at simpson point the most common mechanism by which the lagoon ward coastline has aggraded is through the in filling of cuspate embayments with sediment which is later stabilized by the expansion of terrestrial vegetation this evolution is most active in the complex network of embayments in the south of the atoll lagoon the ocean facing coastline by contrast typically aggrades and erodes through the linear shift of the vegetated coast along the strike of the beach line while the areal extent of diego garcia has been almost static for the last half century the annualized rate of flux of the coastline is considerable at 0 30 m yr 1 a rate comparable to other atoll islands the literature consistently reports two factors as relevant to increasing the rate of shoreline migration human modification of it and sea level rise both are foreseeably set to increase for diego garcia the former due to its strategic importance not least its use as a military base and the latter due to global environmental change the findings of this work serve to remind that the coastline of diego garcia as for all atoll islands is naturally dynamic and will likely become more so in the future

the plio quaternary uplift of the apennine chain new data from the analysis of topography and river valleys in central italy abstract this study aims at the reconstruction of magnitude and timing of surface uplift affecting a wide sector of the central apennines italy by means of morphometric and morphostructural analyses in the chain interiors where stratigraphic and geomorphological markers of past sea level positions are lacking the study is based on analysis of erosional landforms and river valleys a large scale topographic analysis by processing 90 m and 230 m dems is performed the spatial distribution of several morphometric parameters together with characteristic wavelengths of relief allowed the differentiation of three main regions affected by different cumulative surface uplift and tectonic erosional fragmentation a peri tyrrhenian belt an axial belt and a peri adriatic belt particular attention is devoted to fluvial landforms with analysis of longitudinal profiles and geometric pattern of the main drainage lines and their relations with the major structures major differences occur between the tyrrhenian and adriatic valley systems the tyrrhenian drainage mainly consists of longitudinal valleys displaying overall concave up longitudinal profiles the adriatic drainage is mainly constituted by transverse streams and shows less regular longitudinal profiles topographic features and the river valley architecture seem related to different styles and amounts of uplift in the three belts within the study area a coast to coast transect gaeta vasto transect gvt has been investigated in detail focusing the analysis on its axial sector around the apennines main divide main divide area mda a possible scheme of quaternary surface uplift along the gvt is proposed in the mda the main stages of landscape evolution and drainage organization can be reconstructed by means of the analysis of paleosurfaces coupled with study of the relict and present day drainage networks this allowed the recognition of a major phase of surface uplift exceeding 1500 m in the meta mainarde massif that occurred in response to thrusting during the pliocene for quaternary surface uplift a minimum value of 400 m can be estimated this study suggests that during the quaternary the peri tyrrhenian belt suffered a subdued uplift acting over small wavelengths 10 15 km while the axial and peri adriatic belts were subject to a larger and long wavelength 90 km surface uplift with maximum values about 700 m shifted to the ne of the axial belt and tapering to zero towards the adriatic coast the reconstructed pattern of uplift is coherent with the topographic properties of the three belts and with the observed drainage features

interfering paths of deformation and development of arcs in the fold and thrust belt of the central apennines italy in the foreland fold and thrust belt of the central apennines the major thrust sheets design systems of arcs interfering with noncoaxial trends localization of shortening by thrusting and shearing appears to be controlled by the squeezing of low competence basinal units marche gran sasso monte picca and monte genzana in between the rigid blocks of the lazio abruzzi and adriatic carbonate platforms the geometrical interlocking has been resolved by differential rotations of the superposed thrust sheets as also substantiated by paleomagnetic data the structural analysis and the age of the syntectonic siliciclastic deposits suggest an irregular sequencing of superposed contractional and extensional events during late miocene middle pliocene times interfering kinematic paths characterize the arcuate belts where slip partitioning has adjusted the coeval deformation of the noncoaxially arranged tectonic units in the arcuate gran sasso monte picca thrust belt out of sequence thrusting displacement transfer on high angle strike slip faults and growth of high angle normal faults behind the most rotated blocks have resulted in the back and forth superposition of contractional and extensional structures in adjacent domains our kinematic reconstruction of the central apennines indicates that it is impossible to perform the retrodeformation of tectonic events by assuming a regular outward progression of deformation pulses in such a strongly arcuate belt the irregular trajectories of the displacement field and the complex overprinting relations between different sets of structures reflect the kinematic accommodation of blocks with contrasting rigidity and are not fitted easily within a regionally smoothed stress field

carbonate sediment production transport and supply to a coral cay at raine reef northern great barrier reef australia a facies approach abstract coral cays are low lying typically 2 mm grain size and the relative abundances of foraminifera and coral grains gravelly coral dominated sediment is concentrated at the reef margins whereas facies on and around the leeward cay are dominated by the sand size tests of benthic foraminifera mud is absent in reef sediments and reflects the prevailing high energy wave dominated setting as well as a paucity of mud producers benthic foraminifera tests are the major sediment component constituting an average proportion of 39 range 2 77 sediment derived from the skeletal remains of corals 24 1 65 mollusks 15 3 30 halimeda 14 4 36 and coralline algae 6 0 20 are present in lesser volumes foraminifera content is highest 40 on tidally emergent algal pavement where they live in greatest abundance and on the cay shorelines where their tests are deposited and comprise the bulk of beach sand 36 63 a comparison of the raine island data with other exposed modern reefs and platforms of the central and western pacific shows that occurrence and distribution of facies types is broadly consistent beyond these sedimentological data the taphonomy of foraminifera at raine island indicates that tests are vulnerable to destruction due to abrasion when transport and reworking is prolonged therefore the foraminifera rich facies adjacent to and on the cay disjunct from the source zones as well as taphonomic evidence imply that transport from the outer reef flat to the cay must be relatively quick these short temporal links between ecological source zones and depositional landforms are likely to have important ramifications for the contemporary management of reef associated landforms e g cays in the future

decoding temporal and spatial patterns of fault uplift using transient river long profiles we present detailed observations of rivers crossing active normal faults in the central apennines italy where excellent constraints exist on the temporal and spatial history of fault movement we demonstrate that rivers with drainage areas 10 km2 and crossing faults that have undergone an increase in throw rate within the last 1 my have significant long profile convexities in contrast channels that cross faults that have had a constant slip rate for 3 my have concave up profiles and have similar concavities and steepness indices to rivers that do not cross any active fault structures this trend is consistent across the central apennines and cannot be explained by appeal to lithology or regional base level change the data challenge the belief that active faulting must always be reflected in river profiles instead the long profile convexities are best explained as a transient response of the river system to a change in tectonic uplift rate moreover for these rivers we demonstrate that the height of the profile convexity as measured from the fault scales with the magnitude of the uplift rate increase on the fault and we establish that this relationship holds for throw rate variation along strike for the same fault segment as well as between faults these findings are shown to be consistent with predictions of channel response to changing uplift rate rates using a detachment limited fluvial erosion model and they illustrate that analysis of the magnitude of profile convexities has considerable predictive potential for extracting tectonic information we also demonstrate that the migration rate of the profile convexities varies from 1 5 10 mm y and is a function of the slip rate increase as well as the drainage area this is consistent with n 1 for the slope exponent in a classical detachment limited stream power erosion law but could potentially be explained by incorporating an erosion threshold or an explicit role for sediment in enhancing erosion rates finally we show that for rivers in extensional settings where the response times to tectonic perturbation are long in this case 1 my attempts to extract tectonic uplift rates from normalised steepness indices are likely to be flawed because topographic steady state has not yet been achieved

contribution of numeric dynamic modelling to the understanding of the seismotectonic regime of the northern apennines abstract in this paper we investigate the forces possibly active in the area of the northern apennines by means of two dimensional finite element modelling assuming a viscoelastic rheology the forces included in the models are related to continental convergence between africa and eurasia to negative buoyancy of the subducted adriatic lithosphere and to positive buoyancy of anomalously hot mantle material underneath tuscany model predicted stress distribution is compared with seismotectonic data available for the area of the northern apennines and with earthquakes distribution our results indicate that continental convergence cannot be the only mechanism acting in the study area since it causes insignificant subcrustal stresses in disagreement with intermediate seismicity observed under the apennines asthenospheric upwelling under tuscany back arc region is shown to play a crucial role in the present day dynamics of the tyrrhenian apennines positive buoyancy causes an upwards and eastwards flow that generates extensional bending stresses in tuscany and at the top of the slab under the apennines horizontal pushing of the slab is proposed as an alternative mechanism to slab pull to generate subcrustal stresses activation of slab pull does not result in a significant change in orientation of the principal stress axes at shallow depths with respect to the model in which only asthenospheric diapirism is active therefore the existence of a continuous gravitationally sinking slab cannot be ruled out on the basis of comparison with seismotectonic observations both models successfully reproduce extension in tuscany and compression in the outer margin of the apenninic belt but fail to reproduce extension along the inner portion of the chain our modelling highlights the importance of better constraining the lateral extent of the asthenospheric diapir in order to find out whether the extension and tectonic uplift in the apennines is caused by asthenospheric upwelling as in the area of tuscany

petrology geochemistry provenance and alteration of pennsylvanian permian arkose colorado and utah late paleozoic and modern feldspathic clastic sediments of the colorado rockies were derived from dominantly igneous and meta igneous precambrian basement rocks average composition expressed as gazzi dickinson qfl quartz feldspar lithicfragments is 36 64 0 in modern stream sands for the cutler formation is 54 46 0 for the minturn formation is 57 43 0 and for the fountain formation is 51 49 0 no major mafic components are present in the provenance as indicated by low co cr and ni abundances although higher fe and mg abundances in cutler formation rocks indicate derivation from somewhat more mafic provenance than the fountain and minturn formation rocks fountain formation rocks are more altered by predepositional weathering diagenesis and holocene weathering than their equivalents in the minturn and cutler formations thus plagioclase is albitized and clay altered or absent in the fountain formation whereas it is abundant and much less altered in the minturn and cutler rocks fountain formation sandstone in the steamboat mountain section lacks remaining detrital plagioclase but contains authigenic albite as overgrowths on and replacement of detrital k feldspar and as pore filling crystals in the eldorado springs section there is extensive epithermal potassic alteration in the fountain formation from the detrital assemblage quartz plagioclase k feldspar biotite muscovite to the assemblage quartz k feldspar authigenic adularia illite muscovite kaolinite k and rb have been metasomatically added to these rocks with concomitant removal of ca na co cr cu ni ga th u zn ba ce la and y during passage of hydrothermal fluids apparently in the tertiary these fluids were probably heated by deep seated magma adjacent to the colorado lineament and or range front faults that served as geothermal water conduits toward the surface

some remarks on the origin of foredeeps abstract geological observations show that there are two main types of foredeep basins on the base of their subsidence rate and their relationship with the associated orogen or accretionary wedge high rates of subsidence up to 1600 m myr and a ratio lower than 1 between the area of the elevated belt and the area of the basin characterize the foredeeps associated with w dipping subduction low rates of subsidence up to 300 m myr and a ratio higher than 1 between the area of the orogen and the area of the basin characterize the foredeeps associated with e or ne dipping subductions this observation enables us to interpret the slow filling of foredeeps of the first type and the much faster filling of foredeeps of the second type moreover w dipping subductions have a steeper and faster monocline bounding the base of the deep foredeep in contrast to e or ne dipping subductions which have a shallower monocline this differentiation supports the notion of the eastward mantle flow with respect to the lithosphere detected in the hot spot reference frame in this view the foredeep depth in w dipping subductions is mainly controlled by the roll back of the subduction hinge pushed by the relative eastward mantle flow while foredeep depth in e or ne dipping subductions is instead mainly generated by the load of the thrust sheets and by the roll back of the subduction hinge due to the advancing upper plate contrasting the upward push of the mantle the shape of the foredeeps is regularly arcuate in case of w dipping subduction while is linear or following the shape of the inherited continental margin in case of e or ne dipping subduction fold development in the two opposite foredeeps is significantly different in w dipping subduction the folds are transported down in subduction while they are forming and consequently they are poorly eroded syntectonic sediments drape a preserved fold in the e ne dipping subduction folds and thrust sheets are instead uplifted and deeply eroded this is also predicted by the envelope of the crests in the two distinct accretionary wedges in the w dipping case the envelope may dip toward the subduction while it is rising toward the hinterland in the other cases this approach may explain the differences in terms of geometries amount and rates of subsidence between the foredeeps around the adriatic plate for instance the foredeep of the southern alps back thrust belt foredeep is deformed in the western part by the later apenninic foredeep development associated with the sinistral oblique ramp of the w dipping adriatic plate subduction the relationship in the frontal parts of a thrust belt between accretion and eustacy has to be analyzed in terms of when where and how fast thrusts propagation took place with respect to the randomly distributed sea level third order fluctuations and by the type of subduction which is connected to the foredeep and thrust belt or accretionary wedge therefore the stratigraphic patterns in foredeep basins are peculiar and casual successions that record the combination of regional tectonic evolution with independent wider scale sea level changes

upper pleistocene amazon deep sea fan muds reflect intense chemical weathering of their mountainous source lands abstract upper pleistocene muds of the amazon deep sea fan contain an abundance of residual weathering products as indicated by their bulk chemical and mineralogical compositions the muds are chemically more mature than average shale average pelagic mud or the surrounding demerara abyssal sediments they are however very similar to the bulk chemical compositions of contemporary suspended sediments of both the amazon estuary and those carried by the major andean tributaries the modern sediment compositions reflect the rapid weathering now occurring in the andean source regions of the basin the major element geochemical signature of the upper pleistocene deep sea fan sediments suggests that intense chemical weathering in the mountainous source lands has controlled the chemistry of amazon river suspended sediments since at least the upper pleistocene minor and trace element signatures appear uniform throughout the fan and element concentrations are in general higher than in the intensely weathered amazon lowland soils but lower than in deep sea sediments

neogene to quaternary sedimentary basins in the south adriatic central mediterranean foredeeps and lithospheric buckling up to several kilometers deep sedimentary basins of neogene to quaternary age are found in the south adriatic between the apennines and the dinarides albanides they are the apennines foredeep the central adriatic basin and the south adriatic basin two regional seismic lines 260 and 170 km long across the entire system provide hitherto unavailable constraints on the kinematics and dynamics of basin development the apennine foredeep imaged along the lines formed in middle to late pliocene times through a rapid westward tilting of the basin floor a paleobathymetry of few kilometers was created in which allochthonous bodies were emplaced and sediments deposited unaffected by deformation and farther rotations the central and south adriatic basins formed in neogene to quaternary times and are both characterized by strong subsidence in their central parts gradually diminishing toward the edges in the sw and ne depocenters did not shift laterally through time subsidence rates increase through time and subsidence continued also following the end of main shortening episodes in the dinarides albanides the central and south adriatic basins form two crustal scale synclines with subsidence concentrated in their central parts basins geometries and subsidence patterns indicate that the adriatic crust has undergone episodes of buckling since miocene times wavelengths and amplitudes of such folds change along strike corresponding to mechanical changes of the folded medium

reconstruction of storm tsunami records over the last 4000 years using transported coral blocks and lagoon sediments in the southern south china sea large transported coral blocks on reef flats and elevated sedimentation rates in atoll lagoons were demonstrated to be excellent proxies for past strong storms tsunamis in the southern south china sea here we introduce another important proxy coarse fraction contents of lagoon sediments this proxy is based on the principle that coarse fractions of enclosed lagoon sediments are usually controlled by strong sedimentary dynamics on the surrounding reef flat and thus increases in the weight percentages of coarse grained fractions of the lagoon sediments should also reflect strong storm tsunami events or increases in storminess with the size of the content peak as the proxy for the degree of storminess bearing this in mind we measured the contents of the 1 mm grain size fractions referred to as coarse fraction content in an undisturbed lagoon core precisely dated to cover the last 4000 years the decadal resolution data show a systematic variation with some peaks strongly correlated with in timing with strong storm tsunami events dated at ad 1872 15 1685 8 similar to 1680 6 1443 9 1336 9 1210 5 similar to 1201 4 and 1064 30 using wave transported coral blocks using the mean coarsefraction content 9 2 for the entire core as a reference line a total of 77 peaks were identified for the past 4000 years twenty of these peaks are higher than 23 the mean value for peaks that are correlated in age with the six strong storm events identified using independently dated coral blocks among these 23 peaks 13 occurred within the last 1000 years the concentration of contentpeaks in the last millennium could be partially due to higher deposition rates and sampling resolution over the last similar to 4000 years there appears to be a weakly increasing trend in coarse fraction contents towards present time but this trend is not obvious within the last millennium this long term variation may be related to changes in both storminess and reef lagoon morphology however the data do suggest three extremely stormy periods centring around ad similar to 1200 similar to 400 bc and similar to 1200 bc respectively overall this study demonstrates that combined use of transported coral blocks and coarse fraction contents of lagoon sediments provides an excellent means for comprehensive reconstruction of past storm tsunami activity c 2008 elsevier ltd and inqua all rights reserved

eco geomorphic processes that maintain a small coral reef island ballast island in the ryukyu islands japan abstract landform changes in ballast island a small coral reef island in the ryukyu islands were investigated by remote sensing analysis and a field survey the area of the island almost doubled after a mass coral bleaching event in 1998 coral branches generated by the mass mortality and broken by waves were delivered and stocked on a reef flat and accumulated to expand the area of the island in 2012 high waves generated by typhoons also changed the island s topography overall the island moved in the downdrift direction of the higher waves waves impacting both sides of the island piled up a large volume of coral gravels above the high tide level eco geomorphic processes including a supply of calcareous materials from the corals on the same reef especially during stormy wave conditions were key factors in maintaining the dynamic topographic features of this small coral reef island