oolitic sandbody depositional models and geometries mississippian of southwest britain implications for petroleum exploration in carbonate ramp settings abstract a 1000 m thick early mississippian carbonate supersequence the carboniferous limestone of southwest britain consists of three third order depositional sequences these comprise parasequences in various configurations and the whole forms a carbonate ramp stack within this framework five major oolitic carbonate sandbodies developed a castell coch limestone b stowe oolite c brofiscin oolite d gully oolite and e high tor limestone the depositional regime was storm and wave dominated throughout and the major sandbodies represent a range of progradational carbonate beaches barriers and detached subtidal shoals analysis of the three dimensional shapes and distribution of these five examples shows that they evolved to produce three major carbonate sandbody geometries a strings b sheets and c wedges these geometries are characterised using the five field examples and offered as a template which may assist in the exploration and reservoir modelling of petroleum rich high energy ramp systems progradation for up to 40 km of barrier islands stowe oolite and beach ridge plains gully oolite formation generated strings and thick sheets individually up to 10 20 m thick thin shoreface retreat carbonate packstone grainstone sheets up to 5 m thick high tor limestone developed during transgressions as veneers across flooding surfaces these are comparable with sheet sands developed in siliciclastic shelf depositional systems progradation for up to 30 km and vertical aggradation of shoreline detached oolite shoals castell coch limestone brofiscin oolite generated basinwards expanding or thinning wedges up to 30 m thick tectonically controlled stacking of strandplain sheets produced a composite carbonate sandbody up to 80 m thick gully oolite the intrinsic sedimentary and extrinsic eustacy tectonism climate factors which controlled these sandbody geometries are addressed establishing the positions of the sandbodies accurately within depositional sequences allows them to be located within inferred seismic sequence geometries and provides one possible solution to the difficult problem of predicting carbonate facies distribution in subtle stratigraphic plays in this ramp system the most homogeneous sandbodies up to 30 m grainstones with greatest reservoir facies potential are represented by shoal belt wedges potential grainstone reservoir facies in the prograding shorelines are limited to the upper parts of individual shoreface sequences max 10 m grainstones for shoreline carbonate sandbodies the greatest reservoir and stratigraphic trapping potential exists in the earliest ramp parasequences where enveloping offshore sediments are siliciclastic mudstones in later stages potential seals are likely to be less reliable low porosity outer ramp carbonates

organic geochemical proxies of paleoceanographic paleolimnologic and paleoclimatic processes abstract organic matter constitutes a minor fraction of marine and freshwater sediments yet its important contribution to the sedimentary record can be used to reconstruct marine and continental paleoenvironments the organic matter content of sediments is the residue of past biota the amounts and types of organic matter present in sediments consequently reflect environmental conditions that impacted ecosystems at different past times general sources of the organic matter are inferred from bulk properties such as elemental compositions carbon and nitrogen stable isotope ratios rock eval pyrolysis data and organic petrography details of organic matter origins are refined by analyses of biomarker molecular compositions source changes are proxies for fluctuations in sea level oceanic surface currents and continental climates algal paleoproductivity rates are indicated by organic carbon mass accumulation rates and carbon and nitrogen stable isotopic compositions these parameters record past availability of nutrients and therefore are proxies of surface mixing in the oceans and amount of land runoff to lakes sea surface paleotemperatures are recorded by the number of carbon carbon double bonds in lipid biomarkers produced by marine algae larger proportions of the double bonds are proxies for the cooler surface waters that accompanied periods of global glaciation and intervals of enhanced upwelling the 13c and d values of plant organic matter record past concentrations of carbon dioxide in the atmosphere and changes in delivery of atmospheric moisture respectively diagenesis which causes the concentration and composition of organic matter in sedimentary settings to differ from those of the original biologically synthesized materials can bias organic geochemical paleoenvironmental records the magnitude of this potential source of misinformation must always be considered and evaluated comparison of multiple organic geochemical proxies of past conditions helps to compensate for the effects of diagenetic alterations and thereby to improve interpretations of paleoenvironmental change

estimation of slip distribution using an inverse method based on spectral decomposition of green s function utilizing global positioning system gps data 1 an inverse method based on the spectral decomposition of the green s function was employed for estimating a slip distribution we conducted numerical simulations along the philippine sea plate ph boundary in southwest japan using this method to examine how to determine the essential parameters which are the number of deformation function modes and their coefficients japanese gps earth observation network geonet global positioning system gps data were used for three years covering 1997 1999 to estimate interseismic back slip distribution in this region the estimated maximum back slip rate is about 7 cm yr which is consistent with the philippine sea plate convergence rate areas of strong coupling are confined between depths of 10 and 30 km and three areas of strong coupling were delineated these results are consistent with other studies that have estimated locations of coupling distribution

an exhumed palaeozoic underwater scenery the visean mud mounds of the eastern anti atlas morocco about one hundred carbonate mud mounds covering an area of 440 km 2 in the eastern anti atlas of morocco constitute one of the largest mound agglomerations known so far from lower carboniferous settings they occur within a 4000 m thick succession of shales with intercalated bedded limestones sandstones and siltstones according to conodont and goniatite biostratigraphy mound formation started in the early gnathodus texanus zone and terminated during the g bilineatus zone of the visean stage individual mounds are a few metres to 30 m high have base diameters of up to 300 m and are concentrated in several parallel wnw ese running belts from their lithology and facies relationships four types of mounds can be distinguished 1 massive crinoidal wacke or packstones without stromatactis 2 massive crinoidal wacke or packstones with rare stromatactis 3 similar to 2 but allochthonous and 4 biodetrital skeletal grainstone mounds while carbonate deposition in types 1 to 3 was probably triggered by microbial precipitation type 4 is the result of a predominantly mechanical accumulation of skeletal debris biota in the four types comprise a great variety of invertebrates among which crinoids sponges and bryozoans are most common diagenesis of the mound carbonates was dominated by recrystallization of micritic matrix and organic remains and late burial cementation oxygen and carbon isotope data of brachiopod and crinoid ossicles matrix and early marine cements plot in a large field and do not allow definite conclusions about the composition of the ambient seawater microbial activity and the absence or scarcity of green algae colonial corals and coralline sponges suggest deposition of the mounds in moderate water depth close to the lower limit of the photic zone d 2001 elsevier science b v all rights reserved

carbonate slopes and gravity deposits in this special volume a series of papers are presented that concentrate on sedimentation patterns observed on the slopes and within the basins surrounding shallow water carbonate depositional systems four papers discuss depositional patterns on the slope to basin transect of the cainozoic sedimentary system of the bahamas four other papers examine gravity deposits of jurassic and cretaceous carbonate depositional systems

surface deformation associated with the november 23 1977 caucete argentina earthquake sequence leveling data are combined with seismic observations from the november 23 1977 ms 7 4 caucete earthquake in western argentina in order to constrain models of crustal deformation in the sierras pampeanas tectonic province the spatial pattern and amount of uplift 1 m that accompanied this earthquake suggest 4 m of slip on a north south trending west dipping fault with a dip of 35 a downdip width of 24 km and a length of 80 km the top of the fault is 17 km below the surface these fault parameters are generally consistent with the seismic focal mechanism and moment of the main shock which occurred near the top of the fault the fault length is derived from the distribution of local and relocated teleseismic aftershocks and from analysis of the main shock a double event in which the two shocks occurred 21s apart and were separated by 65 km along the proposed fault plane strike the fault width is determined from the locations of the larger hypocenters along the preferred fault plane this fault is buried beneath the north south striking sierra pie de palo a laramide style crystalline basement uplift in the western part of the sierras pampeanas province the buried fault model is consistent with the lack of observed coseismic surface faulting and the broad east west symmetric character of the overlying sierra pie de palo by combining the 1977 earthquake observations with topographic relief and with estimates of the age of deformation for the sierras pampeanas basement uplifts we calculate a shortening rate of the order of 10 mm yr for the past 5 m y for this andean back arc province and estimate an average recurrence time of the order of 1000 years for earthquakes of this magnitude beneath the sierra pie de palo

depositional facies and stratal geometry of an upper carboniferous prograding and aggrading high relief carbonate platform cantabrian mountains n spain seismic scale continuous exposures of an upper carboniferous bashkirian moscovian carbonate platform n spain provide detailed information about the lithofacies and stratal geometries quantified with differential global positioning system measurements of microbial boundstone dominated steep prograding and aggrading platform margins progradational and aggradational platform to slope transects are characterized by distinct lithological features and stratal patterns that can be applied to the understanding of geometrically comparable high relief depositional systems the bashkirian is characterized by rapid progradation at rates of 415 970 m my 1 characteristic outerplatform facies are high energy grainstones with coated intraclasts ooids and pisoids moderate energy algal skeletal grainstones to packstones and lower energy algal packstone and boundstone units the moscovian aggradational phase is characterized by aggradation rates of 108 m my 1 coated grain shoals are less common whereas crinoidal bars nucleated in well circulated settings below wave base boundstones form a belt 30 300 m wide at the platform break and interfinger inwards with massive algal skeletal wackestones mud rich banks the progradational phase has divergent outer platform strata with basinward dips of 12 to 2 steep clinoforms with dips of 20 28 are 650 750 m in relief and possibly sigmoidal to concave in the lower part the basinward dipping outer platform strata might be depositional for less than 6 consistent with lithofacies deepening seaward the basinward dip is attributed to the downward shift of upperslope boundstone forced by late highstand and relative sea level fall and to compaction induced differential subsidence during progradation the aggradational phase is characterized by horizontally layered platform strata clinoforms steepen to 30 45 reaching heights of 850 m and are planar to concave the evolution from progradation to aggradation at the bashkirian moscovian boundary is attributed to increased foreland basin subsidence and decreased boundstone accumulation rates progradation was primarily controlled by boundstone growth rather than by highstand shedding from the platform top within the major phases aggradational progradational increments are produced by third to fourth order relative sea level

paleoenvironmental reconstruction of microbial mud mound derived boulders from gravity flow polymictic megabreccias visean sw spain abstract the upper visean outcrops from the guadiato valley cordoba sw spain provide a well preserved record of the mud mound factory which was developed in a mainly siliciclastic synorogenic foreland basin during the oblique sinistral collision of two terranes ossa morena and central iberian blocks the first onset of mud mound development has been recorded as microbial mud mound derived boulders in polymictic megabreccias as result of strong tectonic activity the upper visean record from the mississippian central band at guadiato valley starts with lower heterolithic units up to 180 m thick and shows two major tectonically controlled cycles a fining upwards interval fu followed by a coarsening upwards interval cu these cycles are linked to two active margins with gravelly fan delta development and different source areas mud mound derived boulders occur in the cu interval and are formed by peloidal primary and secondary reworked automicrites and allomicrites showing a diverse faunal and floral assemblage although never as the main skeletal framebuilders however the observed coeval richness in sponges lyssacinose hexactinellids and non lithistid demosponges and the diverse calcareous algae assemblage in mud mound derived boulders are not common in other visean buildups the growth cavities display changes in the geopetal relationships between fillings and the secondary cavities containing sand to gravel fillings reflecting a complex pre boulder and mud mound derived boulder history detailed mapping sampling stratigraphic and microfacial analyses have allowed the reconstruction of the mud mounds sedimentary environment prior to the collapse transport and emplacement as boulders with polymictic gravels

sequence development of a latest devonian tournaisian distally steepened mixed carbonate siliciclastic ramp canning basin australia abstract the sequence development and evolution of latest devonian earliest carboniferous fairfield group in the canning basin have been established through integration of detailed sedimentological analysis of core petrophysical data existing biostratigraphic data and new seismic interpretations the fairfield group on the lennard shelf was deposited on a mixed carbonate siliciclastic distally steepened ramp with a broad inner ramp narrow mid ramp and steepened outer ramp the majority of facies associations fa1 fa8 were formed in intertidal shallow subtidal conditions in proximal to distal inner ramp including siliciclastic tidal flats fa1 carbonate intertidal flats fa2 tidal flats and channels fa3 lagoons fa4 fa5 and shallow subtidal fa6 backshoal fa7 and fore shoal areas fa8 bioclastic muddy sandstone fa9 and bioclastic mudstone fa10 are the dominant mid ramp facies recognition of turbiditic facies of middle to lower slope of the outer ramp fa11 fa13 led to the identification of a distally steepened ramp antecedent topography exerted a significant control on platform morphology and the development of the widespread inner ramp facies on the lennard shelf a sequence stratigraphic analysis reveals that the fairfield group ramp deposits consists of four third order sequences s1 s4 that were largely deposited during sea level highstands hst characterized by progradational trends and dominant shallow subtidal inner ramp facies associations transgressive systems tracts tst are well developed in s1 and s3 and have a retrogradational facies pattern with dominant deep subtidal mid outer ramp facies associations lowstand systems tracts characterized by lowstand wedges and turbiditic facies are identified in the lower parts of s2 and s3 coarse and fine grained siliciclastic facies are mixed with carbonate facies as a result of coeval deposition on the inner and mid ramp and reciprocal deposition on the outer ramp a temporal variation in the types of carbonate grains and the amount of siliciclastic facies from the mixed peloidal skeletal carbonate siliciclastic ramp in s1 and s2 to the mixed skeletal carbonate siliciclastic ramp in s3 and a siliciclastic dominated ramp in s4 is interpreted as the change from a greenhouse to an icehouse state

full interseismic locking of the nankai and japan west kurile subduction zones an analysis of uniform elastic strain accumulation in japan constrained by permanent gps we analyze permanent global positioning system gps data obtained over japan between 1995 and 1997 to estimate the instantaneous interseismic coupling ratio of the seismogenic zones due to the subduction of the pacific and philippine sea plates below the japanese islands we first derive the gps strain rate fields that characterize the crustal deformation of southern and northern japan and invert them to determine the effective subduction velocity along the central nankai trough on one side and the japan west kurile trench on the other these reference free velocities are close to those predicted by plate motion models with respect to eurasia we conclude that the eurasian reference frame gives a good approximation to the subduction motion and that to first order both subduction zones were fully locked during the period of measurements we then test whether the coupling ratio shows local variations within the seismogenic zones to do this we divide the subduction interface into 35 km 30 km elements that we model by point source groups and we invert the gps velocity field referenced to eurasia to derive the coupling ratio between 0 and 1 on each fault element the results are coherent over the 3 years and confirm that both the central nankai and the japan west kurile seismogenic zones are homogeneously fully locked most of the coupling ratios are close to 1 and a few are close to 0 intermediate values are rare the zones of decoupling correspond either to strong postseismic afterslip associated with the 1994 sanriku oki interplate earthquake japan trench or to a small overestimation of the actual lower limit of the locked zone we conclude that within the resolution of the gps data and the model 1 partial coupling did not exist during these 3 years along the nankai and japan west kurile trenches 2 the small seismic coupling ratio previously derived from earthquakes analysis for the japan and kurile trenches may indicate that a significant part of the elastic energy is dissipated silently through slow earthquakes and postseismic afterslip and 3 the heterogeneous coseismic slip pattern observed for the large and great earthquakes that rupture both subduction zones is in great contrast to the homogeneous loading finally we discuss the nonelastic residual deformation within the frame of the long term deformation of the japanese islands

intensified oceanic circulation during early carboniferous cooling events evidence from carbon and nitrogen isotopes abstract the early carboniferous was a climatic transition interval from a mid paleozoic greenhouse world into the late paleozoic ice age it was marked by a long term cooling trend that was punctuated by short glaciations in the tournaisian and visean early to mid early carboniferous here we generated organic carbon and nitrogen isotope profiles for two widely separated lower carboniferous sections arrow canyon range nevada and namur dinant basin belgium in order to assess the global nature and timing of changes in the carbon nitrogen cycles linked to oceanic productivity and redox conditions during this climatic transition interval the carbon and nitrogen isotope profiles of both study sections record major perturbations during the mid tournaisian and visean a mid tournaisian event tice is marked by increases in 13ccarb 13corg and 15nbulk at arrow canyon from 0 6 to 7 0 25 2 to 23 7 and 0 6 to 8 9 respectively and namur dinant from 0 3 to 4 7 27 9 to 22 2 and 5 7 to 5 2 respectively an early visean event vice named herein is marked by increases in 13ccarb 13corg and 15nbulk at arrow canyon from 0 6 to 3 1 28 4 to 23 6 and 1 4 to 9 4 respectively and namur dinant from 2 1 to 4 3 26 7 to 25 0 and 1 4 to 3 3 respectively the positive excursions in all three isotopic records during these events are consistent with increased fractional burial of organic carbon and enhanced denitrification implying intensification of marine productivity and expansion of hypoxia in the global ocean given that each event coincided with lowering of sea surface temperatures and increased glaciation as documented from published conodont 18o and sea level records we hypothesize that global cooling led to intensified oceanic circulation and upwelling on continental margins triggering increased marine productivity and attendant redox changes within the affected upwelling zones our results provide new insights into changes in early carboniferous oceanic conditions in response to the initial stages of cooling leading into the late paleozoic ice age

devonian carboniferous boundary glacioeustatic fluctuations in a platform to basin direction a geochemical approach of sequence stratigraphy in pelagic settings abstract we investigated high resolution stratigraphic distribution of selected major and trace elements and gamma ray spectra of fourteen devonian carboniferous d c boundary sections of europe located in the late palaeozoic laurussia and gondwana the aim was to trace the geochemical signature of a marked forced and normal regressive interval which was associated with rapid progradation of siliciclastics into the marine carbonate systems rhenish massif and a prominent hiatus in shallow water ramp settings namur dinant basin this interval represents the late devonian hangenberg event hbe sensu lato middle praesulcata conodont zone as defined by previous authors this regressive interval fsst to lst correlates with thin shale layers hbe shale sandwiched between monotonous nodular calcilutite calcisiltite successions at five pelagic sections of moravia carnic alps montagne noire and pyrenees in all sections with continuous d c sedimentation i e except those of the namur dinant basin the hbe s l interval is accompanied by elevated percentages of detrital proxies al k rb zr and changes in their ratios zr rb k al rb k which are normally interpreted as indicators of increased siliciclastic input provenance and grain size zr rb and other proxies are traceable even without apparent lithological evidence and can therefore facilitate stratigraphic correlation paleoredox and productivity proxies u th and ni rb enrichment factors only rarely show elevated values in the hangenberg black shale interval indicating that the associated water dysoxia anoxia was a local rather than global phenomenon global correlations based on the hbe black shales should therefore be dropped in favor of the hbe s l interval moreover analysis of sedimentation rates in the upper expansa to kockeli zone interval using the published radiometric ages suggests that the hbe s l was a time of significant increase in the rate of siliciclastic supply into the ocean even in the most distal pelagic sections consequently the previous interpretation of the hbe black shale as a condensed succession deposited during rapid sea level rise seems unlikely we interpret the hbe s l i e including the hbe black shale as a marine record of glacioeustatic sea level drop and increased aeolian transport in connection with late devonian climatic cooling and glaciation the set of geochemical markers related to the late devonian sea level fluctuation can be used for super regional to global correlations from platform to basin settings moreover they can facilitate current efforts to determine a new d c boundary definition

a fault model of the 1946 nankaido earthquake derived from tsunami data abstract a fault model of the 1946 nankaido earthquake m 8 2 is determined by the use of tsunami records of uwajima shimotsu and hososhima which were located within or near the area of major coseismic crustal deformation synthetic tsunamis computed for various fault models are matched with the observed tsunamis to determine the fault parameters a low angle thrust model slightly revised from a previous model by ando is consistent with the observed tsunamis the duration of faulting is constrained as less than 10 min based upon the tsunami the fault is divided into an eastern and a western segment corresponding to areas associated with and without aftershocks respectively the fault area and dislocation for the western segment are 150 70 km2 and 6 m and those for the eastern segment are 150 70 km2 and 3 m respectively the total seismic moment is 4 7 1028 dyn cm significantly smaller than that obtained from a geodetic model by fitch and scholz but still larger than that of the seismic model by kanamori the discrepancy in seismic moment between the seismic and the present models ran2 could be interpreted in terms of a slow dislocation on the fault but this interpretation does not match the seismic intensity distribution and damage pattern and the slow slip model for the nankaido earthquake is rejected the discrepancy between the two seismic moments is considered insignificant within error involved in data and modeling assumptions if the revised geodetic model ran2 is modified the seismic moment required to explain the observed tsunamis would be reduced further by 30 if we consider the uncertainties involved in the fault model of kanamori and the fault finiteness effect affecting the amplitude of seismic waves the seismic moment required to interpret the seismic wave data could be increased possibly being more than twice that of kanamori thus the two seismic moments from the different data sets could be close to each other within allowable tolerance this implies that the rise time of the nankaido earthquake was short enough to generate short period seismic waves from both the western and the eastern fault segments

the earthquake deformation cycle at the nankai trough southwest japan geodetic measurements made landward of the nankai trough site of great subduction zone thrust earthquakes in 1854 and 1946 provide a uniquely detailed picture of the strain buildup process supply constraints on the mechanism of strain accumulation and allow for improved estimates of earthquake recurrence provided the two most recent movement cycles are similar the observations dating from about 1890 may be used to reconstruct a single complete deformation cycle coseismic strain release postseismic transients interseismic strain accumulation very complete leveling and tidal gage data indicate that postseismic deformation extends more than 300 km inland from the plate boundary persists for at least 30 years and shows a clear tendency to become longer wavelength with increasing time the transient movements have two timescales the first of about a year or less corresponds to deformation largely uplift concentrated close to the coseismic fault and is most easily explained by aseismic slip or very localized deformation downdip of the earthquake rupture plane the second longer timescale is associated with a diffusion like spread of the deformation further landward an effect qualitatively similar to that first predicted by elsasser to be an expected consequence of faulting in an elastic plate overlying a viscoelastic asthenosphere cumulative uplift since 1890 correlates well with the distribution of uplifted marine terraces although average post 1890 tilt rates exceed late quaternary and holocene averages by at least a factor of three because of the nonlinearity of strain buildup and the significant permanent deformation simple recurrence calculations typically overestimate the true interval between great earthquakes by a factor of 2 to a factor of 3 strict application of the time predictable model assumed correct overcomes these difficulties provided the cumulative transient deformation and the proportion of permanent deformation per cycle can be estimated

disobedient sediments can feedback on their transportation deposition and geomorphology abstract most sediments are obedient to the winds waves and currents which direct their transportation and deposition it has long been recognized however that the grain size and or grain kind of sediments can feedback on the processes of their own transportation deposition and geomorphology as well as that of succeeding deposits this note is to review three examples of marine sediments in which a single grain size or grain kind produces multiple feedbacks tidal bars of holocene ooid sands on great bahama bank are an example of multiple feedbacks of one grain kind on tidal currents wave action and accumulations these feedbacks are responsible for the distinctive pattern of elongated bars and channels which in turn amplify tidal currents the near constant movement of grains on the shallow bars and in the channels is where pellet nuclei are coated to form ooids thus the development and growth of bars feeds back to produce more ooids regional encrinites which consist predominantly of the disarticulated highly porous skeletons of crinoids are common from ordovician to jurassic during blooms of these filter feeders the resulting grains which are equivalent to quartz grains a tenth of their size can be entrained by currents as low as a knot ca 0 5 m s the resulting mobile substrate deters other invertebrates taphonomic feedback and results in the prevalence of layering produced by traction transport of low velocity the belt of mud extending for some 1600 km between the amazon and orinocco rivers is a special example of the feedback of mud on depositional processes sedimentary structures and geomorphology of the accumulations the clay rich mud from the amazon produces fluid mud which dampens and transforms wave action from the open sea to promote its own accumulation in giant bars in the inner shelf and shoreline with a variety of familiar laminations the result is a wedge of mud rich deposits some 24 m thick and 30 km wide capped with cheniers of sand which has prograded seaward in some 6000 years

the amurian plate motion and current plate kinematics in eastern asia we use global positioning system gps velocity data to model eastern asian plate kinematics out of 15 stations in korea russia china and japan studied here three sites considered to be on the stable interior of the hypothetical amurian plate showed eastward velocities as fast as 9 10 mm yr with respect to the eurasian plate they were stationary relative to each other to within 1 mm yr and these velocity vectors together with those of a few additional sites were used to accurately determine the instantaneous angular velocity euler vector of the amurian plate the predicted movement between the amurian and the north american plates is consistent with slip vectors along the eastern margin of the japan sea and sakhalin which reduces the necessity to postulate the existence of the okhotsk plate the euler vector of the amurian plate predicts left lateral movement along its boundary with the south china block consistent with neotectonic estimates of the displacement at the qinling fault possibly the southern boundary of the amurian plate the amurian plate offers a platform for models of interseismic strain buildup in southwest japan by the philippine sea plate subduction at the nankai trough slip vectors along the baikal rift the boundary between the amurian and the eurasian plates are largely inconsistent with the gps based euler vector suggesting an intrinsic difficulty in using earthquake slip vectors in continental rift zones for such studies

transient and permanent deformation of central japan estimated by gps 1 interseismic loading and subduction kinematics abstract we analyze continuous global positioning system gps data to estimate the kinematics of the philippine sea plate subduction below southern central japan using a back slip dislocation model we invert the strain rate tensors derived from the gps velocity field to obtain the velocity of the downgoing slab with respect to the tokai and kanto forearcs along the eastern nankai suruga and sagami troughs respectively in both cases these velocities are smaller and slightly rotated with respect to the philippine sea plate subduction velocity in central nankai this result implies strain partitioning between the subduction thrusts and on land and or offshore deformation zones in both the eastern nankai suruga and the sagami area in southern kanto we predict 20 mm yr 1 of dextral shear in agreement with motion observed along the boso strike slip fault in the tokai region the slip deficit accumulated since the last earthquake 1854 ranges between 6 and 3 m considering the extent of the locked zone it would correspond to a magnitude m w 8 15 earthquake if the slip deficit were to be released now during a single event

palaeoenvironmental changes at col des tribes montagne noire france a reference section for the famennian of north gondwana related areas we present detailed biostratigraphy based on conodonts and palaeoenvironmental trends deduced from microfacies and conodont abundance through the famennian late devonian at col des tribes montagne noire france the succession is characterized by micritic limestones deposited in settings oscillating between mid to outer ramp facies contain poor fauna widely dominated by nektonic organisms this section is complete and one of the most conodont rich for the famennian of the north gondwana related area the upper kellwasser event frasnian famennian boundary and the hangenberg devonian carboniferous boundary have been lithologically identified they are characterized by decimetre thick black dysoxic to anoxic argillaceous sediments the condroz and annulata events although not materialized by lithological changes have been positioned due to the precise stratigraphy the first event occurred during the deposition of condensed ferruginous facies griotte limestones and the second event during the deposition of micrites barren of benthic fauna the combination of information from both facies and conodont biofacies changes allows a general sea level curve through the entire famennian for north gondwana to be proposed for the first time at col des tribes the general trend is a slight deepening upwards from triangularis to trachytera zones then a pronounced shallowing upwards trend from upper trachytera to praesulcata zones this curve correlates with the well known reference curve from euramerica concerning the late famennian trachytera to praesulcata zones there are some discrepancies in minor cycles which can be explained by tectonical phenomena at the onset of the edification of the variscan belt in europe

bacterial mediation red matrices diagenesis devonian montagne noire southern france abstract two devonian red carbonate rock sections are studied in the montagne noire at coumiac frasnian famennian and at the pic de vissou eifelian givetian the sediments are grey red mudstones and wackestones rich in pelagic fossils they are characteristic of an outer ramp the coumiac sequence is condensed with numerous hardgrounds and hiatuses the pic de vissou succession is more complete and of shallower origin in both cases the origin of the red coloration of the micritic matrix is probably linked to bacterial activity which produced submicronic hematite both iron and manganese concentrations are low average 0 2 bacteria form ferruginous microstromatolites blisters microtufts hedgehogs filling sponge perforations and thin continuous mineralized films probably biofilms hardgrounds are underlined by ferruginous microstromatolites the origin of the matrix color is probably related to the destruction of these bacterial constructions the submicronic hematite ultimately coating the crystal faces of the calcite mosaic during early lithification microfissures appeared and were invaded by microbial colonies scanning electron microscopy sem shows that these colonies are composed of spheroidal beads this suggests continuity of the bacterial activity during early diagenesis later on these early fissures were cut by burrows subsequently a secondary fissure network transected all the previously mentioned sedimentary structures this late fissure network is characterized by diagenetically remobilized hematite and or calcite the latest alterations are stylolites and ultimate tectonic fractures

thermal constraints on the seismogenic portion of the southwestern japan subduction thrust for coastal cities an important factor in earthquake hazard from subduction zone earthquakes is the landward extent of the seismogenic portion of the subduction thrust fault in this study we test the hypothesis that the maximum downdip extent is defined by a critical temperature we have developed a transient thermal model for the nankai subduction zone of southwest japan to allow comparison of the thermally estimated downdip extent of the seismogenic zone with that from 1 seismicity and tsunami data for two great subduction earthquakes 2 the coseismic faulting extent of these events estimated from geodetic deformation data and 3 the interseismic locked zone determined from interseismic geodetic data the nankai margin has extensive heat flow and heat production data to control thermal models and thus crustal temperatures it has earthquake tsunami and geodetic data that constrain the coseismic rupture portion of the subduction thrust fault for past great earthquakes and the portion of the thrust fault that is locked and storing interseismic elastic strain on the nankaido margin off shikoku island the thermal model indicates that a temperature of 350 c taken to be the limit for seismic initiation from laboratory and field data is reached on the subduction thrust fault 150 km from the trench a transition zone into which rupture may extend with decreasing offset taken to be 450 c extends an additional 45 km downdip the thermal model results are in excellent agreement with the maximum downdip extent of coseismic displacement for the 1946 nankaido ms 8 2 earthquake off shikoku island and with the downdip extent of the present locked zone in the region of the 1944 tonankai ms 8 2 earthquake to the northeast the subduction angle is much steeper and the thermal models indicate a narrower downdip seismogenic extent the seismogenic locked zone from earthquake and geodetic data is also narrower thus our analysis of the southwest japan margin indicates that all three constraints on the downdip extent of the seismogenic zone thermal coseismic and interseismic geodetic data are in general agreement the study also supports the hypothesis that the seismogenic portion of subduction thrust faults is limited primarily by temperature the thermal control implies that subduction thrust faults with shallow dip have wider seismogenic zones compared to those with steep dip the subducting plate age and thus heat flow and the thickness of the insulating sediments on the incoming plate are also very important to the thermal regime and thus to the seismogenic width the relation of the maximum seismic rupture area to the interseismic locked zone is particularly important for earthquake hazard estimation on subduction margins such as cascadia where there have been no great historical events

an application of numerical simulation techniques to improve the resolution of offshore fault kinematics using seafloor geodetic methods abstract geodetic measurements reveal a number of tectonic phenomena such as coseismic and postseismic displacements of earthquakes and interplate coupling on plate interfaces however since geodetic measurements are limited to land slip distribution is poorly resolved offshore though well constrained in the landward areas due to the poverty of offshore data tectonic motion near trench axes has not been measured seafloor geodetic observations provide important information on offshore tectonics improved offshore resolution would allow determination of strain accumulation and release processes near trench axes in this study using numerical simulation we discuss the potential for improvement of slip resolution in an offshore area using seafloor geodetic measurements the plate interface along the nankai trough is modeled by 36 planar fault segments whose length and width respectively are set to 60 km and 50 km three hundred and seventy five gps observation sites on land and 10 seafloor sites aligned 60 km off the coast are used for the simulation we carry out a checkerboard test and compare the estimated slip pattern with the given checkerboard pattern models that do not include seafloor sites generate large discrepancies in offshore deformation between the initial and estimated slip patterns although there are similarities in coastal regions this indicates poor resolution in offshore areas when we apply our model to include seafloor sites the difference between the initial and estimated slip patterns decreases for most of the modeled fault segments comparison between these two cases suggests the potential for use of seafloor geodetic techniques to improve offshore resolution

carbonate ramp depositional systems abstract the classification tectonic settings stratigraphy and early diagenesis of carbonate ramp systems are reviewed carbonate ramps are common in all geological periods but were dominant at times when reef constructing organisms were absent or inhibited ramps can be subdivided into inner mid and outer ramp environments the mid ramp zone extends from fair weather wave base to normal storm wave base although the water depths which these boundaries represent vary an additional outer slope environment occurs on distally steepened ramps as with siliciclastic shelves a range of wave storm and tide dominated ramps can be recognised and this forms the most convenient basis for ramp classification the carbonate productivity profile of ramps differs from that of rimmed shelves with the inner ramp showing lower production rates than comparable shallow water facies on rimmed shelves the zone of greatest organic carbonate sediment production appears to have shifted from the mid ramp to the inner ramp since the late jurassic carbonate ramps occur in most types of sedimentary basin but are best developed where subsidence is flexural and gradients are slight over large areas as in foreland and cratonic interior basins and along passive margins the featureless depositional profiles of many ramps means that sequence geometries are best observed on regional seismic lines some show low angle sigmoidal or shingled clinoforms suggesting that ramps may seldom be homoclinal but possess subtle slope geometries which reflect depositional environments because of their low angle slopes ramps respond differently to rimmed shelves during relative sea level changes although results seem to be strongly dependent on the rate of relative sea level change during a minor fall shallow ramp facies belts will simply shift basinwards in a forced regression in contrast the whole surface of a steep sloped flat topped rimmed shelf may be exposed so that sediment production ceases or is drastically reduced during a major fall shallow ramp bounded basins may empty completely conversely ramps also flood gradually whereas rimmed shelves do so more rapidly homoclinal ramps develop no resedimented lowstand deposits rimmed shelves and distally steepened ramps in contrast may develop lowstand talus or turbiditic wedges distally steepened ramps may behave more like homoclinal ramps during minor base level falls and like rimmed shelves during major base level falls many ramps consist of layered successions of several ramp sequences stacked one upon the other ramp stacks of this sort may show gross vertical accretion but individual ramp sequences seldom appear to develop in a keep up style apart from minor organic buildups as with many rimmed shelves steepening of the outer ramp margin due to tectonism slope inheritance or differential sedimentation may promote the development of a distally steepened ramp or rimmed shelf a wide variety of organisms have constructed buildups in mid and outer ramp environments isolated buildups may seed early in ramp development accrete to wave base or sea level and continue growth by stacking through successive ramp sequences so that depositional and diagenetic features within them are in concert with those of the shallow ramp the location of isolated buildups on ramps is governed by tectonism halokinesis antecedent topography or by the subtle slope geometry of the previous ramp sequence diagenesis on ramps shows some major variations compared with diagenesis on steep sloped flat topped carbonate platforms ramp bounded basins may form prolific petroleum sourcing and reservoiring systems and offer a range of subtle stratigraphic play types and lateral facies variations which determine reservoir quality and distribution isolated buildups in the mid and outer ramp environments represent one of the commonest petroleum reservoirs in ramp systems and tend to have their foundations in transgressive systems tracts grainstone and packstone reservoirs are widespread and range from shoreline carbonate sandbodies to major detached shoal complexes or shoals over offshore highs grainstone sandbodies occur in both highstand systems tracts and in prograding lowstand wedges

a model with rigid rotations and slip deficits for the gps derived velocity field in southwest japan abstract we interpret the gps derived velocity field in southwest japan by a superposition of the elastic deformation caused by fault interactions slips or slip deficits on the rigid motion of tectonic blocks or plates based on the strain rate field and crustal seismicity we apply a model with three blocks inner arc outer arc and the northern ryukyu block and slip deficits along the block boundaries several characteristics of the synthesized contributions are found 1 westward motion of the outer arc relative to the amurian plate and the inner arc 2 southeastward motion of the northern ryukyu block relative to the amurian plate 3 2 4 mm yr deficits of left lateral slip rates along the boundary at 32 n in southern kyushu 4 0 8 mm yr deficits of right lateral slip rates along the median tectonic line and the beppu shimabara graben 5 slip deficit rates on the plate interface smaller than those in the case without any consideration for rigid block motions 6 clockwise deflection of slip deficit rate vector on the plate interface from that estimated when not taking rigid block motions into consideration

lithofacies character and architecture across a pennsylvanian inner platform transect sierra de cuera asturias spain abstract seismic scale outcrops of lower pennsylvanian steep margined carbonate platforms in northern spain sierra de cuera cantabrian mountains provide the opportunity to link depositional facies to platform interior architecture lithofacies character vertical stacking patterns and spatial distribution of depositional facies and shallowing upward cycles were investigated to provide a semiquantitative depositional model for inner platform strata a 70 m thick succession of eight shallowing upward cycles 2 5 15 m thick was studied across a 2 km wide transect cycles consist of algal bioherms and skeletal packstone lithofacies association b deposited in an open marine and sub wave base environment which are locally lateral to crinoid dominated packstone lithofacies association d lithofacies association b developed on a transgressive one meter thick high energy coated grain grainstone lithofacies association a and is overlain by open marine to restricted lagoonal deposits lithofacies association c indicative of decreased paleo water depth cycle boundaries are marine flooding surfaces occurring at the base of lithofacies a and the top of lithofacies c petrographic and outcrop evidence of subaerial exposure is conspicuously lacking cycle and lithofacies thickness varies laterally and all the lithofacies can be either continuous for the 2 km width of investigation or discontinuous terminating within tens to hundreds of meters in most of the cycles the lithofacies succession changes laterally because of lateral facies transitions between lithofacies b and d and pinching out of lithofacies a and c meter scale variations in depositional topography are related to the stacked lens shaped bioherms assigned to lithofacies b and appear to control the thickness and lateral continuity of the overlying facies sierra de cuera strata do not resemble other pennsylvanian cycles driven by high frequency high amplitude glacio eustasy which are commonly characterized by subaerial exposure surfaces developed on subtidal deposits except for the absence of peritidal facies and the presence of low relief algal bioherms on the platform top the necessary accommodation to enhance the growth of bioherms on the platform top was probably due to high frequency 100 240 ky moderate amplitude nearly 40 m sea level fluctuations combined with subsidence rates of 70 140 m my tectonic subsidence might have been responsible for the lack of evidence of subaerial exposure surfaces in the examined moscovian strata the studied inner platform lithofacies character and architecture were controlled by the interplay of high frequency changes in accommodation and the presence of meter scale depositional topography attributed to lateral variations of carbonate accumulation

interseismic seafloor crustal deformation immediately above the source region of anticipated megathrust earthquake along the nankai trough japan 1 we monitored seafloor crustal deformation using the gps acoustic seafloor geodetic observation technique at three sites on the kumano basin off southwestern japan which is located immediately above the source region of the anticipated tonankai megathrust earthquake we directly measured landward crustal movements of 40 mm y in the n80 w direction with respect to the amurian plate on the seafloor the directions were found to be the same as those measured at the on land gps stations the magnitudes of the velocity vectors indicated significant crustal shortenings of approximately 10 20 mm y between the kumano basin and the southeastern coast of the kii peninsula of the japanese islands the present observational results show strong and direct evidence for interplate locking during the interseismic period coupling ratios were roughly estimated at 0 6 0 8 on the plate interface up to at least 10 km in depth

a transient subduction zone slip episode in southwest japan observed by the nationwide gps array 1 we investigate the spatiotemporal variation of fault slip on the subduction interface in southwest japan following the two 1996 hyuganada earthquakes m 6 7 using continuous gps observations a silent thrust slip event has been reported by hirose et al 1999 following these earthquakes approximately 100 km to the north beneath the bungo channel we employ the network inversion filter to rigorously invert for the fault slip distribution in space and time the gps time series is modeled as a sum of 1 secular deformation 2 coseismic station displacements 3 transient fault slip 4 random benchmark motion 5 reference frame shifts and 6 observational errors nonnegativity constraints effectively prohibit normal faulting on the subduction interface spatial and temporal smoothing parameters are estimated by the extended kalman filter the estimated fault slip rate images postseismic slip following the two hyuganada earthquakes slip associated with the silent thrust event began roughly 1 month after the second earthquake but initiated 100 km to the northeast of the hyuganada earthquakes the slow event propagated southwest and downdip beneath the bungo channel lasting approximately 1 year with maximum slip rates of 0 6 m yr the equivalent seismic moment was mw 7 2 we can rule out the possibility that slip propagated from the source region of the hyuganada earthquakes to the location of the silent earthquake however the timing of the events suggests a causal connection perhaps due to static stress transfer this kind of transient event or silent earthquake may reflect different fault zone characteristics and may be responsible for accommodating strain that would otherwise be released in large earthquakes

development of a late visean mississippian mixed carbonate siliciclastic platform in the guadalmellato valley southwestern spain abstract the penas rubias syncline southwestern spain exposes a well preserved shallow water platform succession containing a spectrum of facies corresponding to inner platform intertidal to supratidal environments across to deeper water middle to outer platform environments nineteen microfacies are recognized which are grouped into seven facies association corresponding to siliciclastic deltaic bars mixed carbonate siliciclastic shoals carbonate mud mound boundstones background platform carbonates background platform siliciclastics mixed tempestites and deep water siliciclastic shales and sandstones the age of the succession was determined mainly by foraminiferans and calcareous algae which permit the succession to be assigned to the late brigantian latest visean this upper brigantian platform is the only record of sedimentation of this age in the region and thus is key for interpreting the sedimentary and tectonic evolution of the carboniferous rocks in sierra morena biotic and sedimentological features were analyzed in order to assess the controls on the sedimentation several factors have influenced sedimentological changes turbidity subsidence siliciclastic discharges storms and bioturbation the siliciclastic discharges exerted a considerable control on the basal deposits mostly in their percentage of quartz sand grains and as microconglomerates however they did not develop as large deltaic deposits and their influence can be considered as virtually negligible in regards to the remaining part of the succession turbidity as a result of higher percentage of silt and mud in suspension seems to be the main factor controlling the change between the older intertidal deposits in the inner platform to the younger subtidal deposits of the middle and outer platform as a result of the increase of the mud and silt in suspension facies changed first to marlstones and nodular argillaceous limestones and second to predominantly calcimicrobial boundstones and shales in the uppermost part of the carbonate succession as well as showing a marked change from photic controlled benthic faunal and microfloral assemblages to assemblages more tolerant or better adapted to muddier dysphotic substrates bioturbation is also interpreted as one of the main controls influencing the different type of boundstones in the middle platform permitting the vertical growth of dome shaped mud mounds or as sheet like deposits storm influences seem to have exerted some control on the positive relief of the dome shaped boundstones which are usually capped by tempestites the differential subsidence observed in the northwestern sector of the platform allowed the accumulation of many stacked dome shaped mounds a feature not recognized in southeastern parts the general stratigraphical sequence seems to be controlled by eustasy and synsedimentary tectonics the overall succession exhibits a pronounced deepening upwards transgressive sequence from siliciclastic delta bars mixed shoals carbonates and shales of the middle platform with the growth of calcimicrobial boundstones and dark green shales passing up into black shales at the top of the sequence in the outer platform and possibly submarine slope settings although this transgressive sequence is in harmony with the 3rd order glacioeustatic cycle defined for the late brigantian in the western palaeotethys all these brigantian rocks accumulated in a synsedimentary extensional regime which is related to the initiation of a sinistral strike slip regime previously recognized as affecting only serpukhovian and younger rocks in sierra morena these synsedimentary faults allow us to recognize significant lateral variations in thickness over short distances

earthquakes quaternary faults and seismic hazard in california data describing the locations slip rates and lengths of quaternary faults are the primary basis in this work for constructing maps that characterize seismic hazard in california the expected seismic moment m0e and the strength of ground shaking resulting from the entire rupture of each mapped fault or fault segment are estimated using empirical relations between seismic moment m0 rupture length source to site distance and strong ground motions assuming a fault model whereby the repeat time t of earthquakes on each fault equals m0e m0g where the moment rate m0g is proportional to fault slip rate it is observed that the moment frequency distribution of earthquakes predicted from the geologic data agrees well with the distribution determined from a 150 year historical record the agreement is consistent with the argument that the geologic record of quaternary fault offsets contains information sufficient to predict the average spatial and size distribution of earthquakes through time in california the estimates of t for each fault are the foundation for constructing maps that depict the average return period of 0 1g peak horizontal ground accelerations and the horizontal components of peak acceleration peak velocity and the pseudovelocity response at 1 period and 5 damping expected to occur at the level of 0 1 probability during a 50 year period of time a map is also formulated to show the probability that 0 1g horizontal ground accelerations will occur during the next 50 years the maps serve to illustrate the potential value of quaternary fault studies for assessing seismic hazard interpretation of available slip rates indicates that the largest and most frequent occurrence of potentially destructive strong ground motions are associated principally with the san andreas san jacinto calaveras hayward and ventura basin fault zones other regions of similarly high hazard may yet remain unrecognized this inadequacy results primarily from an incomplete data set numerous faults for example are mapped along the coastal region of northern california and within the modoc plateau but relatively few studies relating to fault slip rate are reported a similar problem exists for other stretches of coastal california where marine reflection studies provide evidence of active faulting offshore yet yield little or no information of fault slip rate geological and geophysical field studies can work to remove these deficiencies a concerted effort to locate and define rates of activity on all faults in california is the most promising means to further quantify present levels of seismic hazard in california

sedimentary patterns and geometries of the bahamian outer carbonate ramp miocene lower pliocene great bahama bank core logging and high resolution seismic data from odp leg 166 were used to analyse deposits of the neogene miocene lower pliocene bahamian outer carbonate ramp ramp sediments are cyclic alternations of light and dark grey wackestones packstones with interbedded calciturbidite packages and minor slumps cyclicity was driven by high frequency sea level changes light grey layers containing shallow water bioclasts were formed when the ramp exported material whereas the dark grey layers are dominantly pelagic calciturbidites are arranged into mounded lobes with feeder channels internal bedding of the lobes shows a north directed shingling as a result of the asymmetrical growth of these bodies calciturbidite packages occur below and above sequence boundaries indicating that turbidite shedding occurred during third order sea level highstands and lowstands highstand turbidites contain shallow water components such as green algal debris and epiphytic foraminifera whereas lowstand turbidites are dominated by abraded bioclastic detritus gravity flow depocentres shifted from an outer ramp position during the early miocene to a basin floor setting during the late miocene to early pliocene this change was triggered by an intensification of the strength of bottom currents during the tortonian which was also responsible for shaping the convex morphology of the outer ramp the miocene and lower pliocene of the leeward flank of great bahama bank provides an example of the poorly known depositional setting of the outer part of distally steepened carbonate ramps the contrast between its sedimentary patterns and the well known upper pliocene quaternary slope facies associations of the flat topped great bahama bank shows the strong control that the morphology of a carbonate platform exerts on the depositional architecture of the adjacent slope and base of slope successions

timing and nature of alluvial fan and strath terrace formation in the eastern precordillera of argentina abstract sixty eight 10 be terrestrial cosmogenic nuclide tcn surface exposure ages are presented to define the timing of alluvial fan and strath terrace formation in the hyper arid san juan region of the argentine precordillera this region is tectonically active and numerous fault scarps traverse quaternary landforms the three study sites marquesado strath complex loma negra alluvial fan and carpinteria strath complex reveal a history of alluvial fan and strath terrace development over the past 225 ka the marquesado complex q3 m surface dates to 17 3 ka whereas the loma negra q1 ln q2 ln q3 ln q4 ln and q5 ln surfaces date to 24 3 ka 48 2 ka 65 13 ka 105 21 ka and 181 29 ka respectively the carpinteria complex comprises eight surfaces that have been dated and include the q1 c 23 3 ka q2 c 5 5 ka q3a c 25 12 ka q3b c 29 15 ka q4 c 61 12 ka q5 c 98 18 ka q6 c 93 18 ka and q7 c 212 37 ka 10 be tcn depth profile data for the loma negra alluvial fan complex and carpinteria strath terrace complex as well as osl ages on some carpinteria deposits aid in refining surface ages for comparison with local and global climate proxies and additionally offer insights into inheritance and erosion rate values for tcns 10 10 4 10 be atoms g of sio 2 and 5 m ma 1 respectively comparison with other alluvial fan studies in the region show that less dynamic and older preserved surfaces occur in the carpinteria and loma negra areas with only younger alluvial fan surfaces preserved both to the north and south these data in combination with that of other studies illustrate broad regional agreement between alluvial fan and strath terrace ages which suggests that climate is the dominant forcing agent in the timing of terrace formation in this region

spatio temporal evolution of a tertiary carbonate platform margin and adjacent basinal deposits abstract the variability in low to moderate energy carbonate platform margins is poorly known from the geological record here the spatial and temporal evolution of platform margin and adjacent basinal deposits is evaluated from the little known tertiary kedango limestone that developed in a semi enclosed marine embayment in se asia the hypothesis here is that platform margin development will reflect regional and perhaps global influences such as tectonics eustasy or biotic change rather than windward leeward effects and storms that typically impact strongly upon open oceanic platforms the development of the carbonate platform was determined through logging petrography facies evaluation provenance and high resolution dating studies eleven carbonate facies were identified from the 30 km long western margin of the 600 m thick platform and its adjacent slope and basinal deposits larger benthic foraminifera and coralline algal packstones and wackestones dominated in shallow waters during the oligo miocene coral patch reef related floatstones rudstones and less commonly boundstones were also present on the platform top perhaps surprisingly for a low energy platform there was considerable variation along the platform margin and much reworking of material into slope and basinal deposits during the oligo miocene reworked material includes shallow water bioclasts clasts from older siliciclastics fresh feldspars lithified slope and platform top carbonate clasts some of the latter showing evidence for karstification the western platform margin varied laterally over a few kilometres from a gently sloping unrimmed platform to a probable bank top with in places coral fringed bypass and erosional faulted escarpment margins eustasy may have influenced shallowing and deepening trends on the platform top but apparently had little impact on mass wasting instead platform margin development was strongly impacted by tectonics including active faulting terrestrial runoff together with changes in carbonate producers and local variability on the platform top

high resolution seismic refraction method using surface and borehole data for site characterization of rocks abstract the authors have developed a new method for the analysis of seismic refraction data which can handle both surface and borehole data simultaneously the main features of the method we developed are as follows 1 the algorithm of analysis is based on the tomographic reconstruction technique and refraction data can be analyzed almost automatically after traveltime picking 2 the method is applicable to both layered velocity structures and those showing a velocity gradient with depth 3 in order to apply the seismic refraction technique to a site that has a more complex structure the method can use the data obtained from sources and receivers on the surface as well as those within boreholes simultaneously numerical and actual field examples have shown that the method can greatly improve the accuracy and the reliability of the seismic velocity models obtained by the seismic refraction method as compared to the conventional analysis methods it can also shorten the data processing time drastically and reduce the survey cost

carbonate platform facies models various types of carbonate platforms are characterized by distinctive profiles facies and evolutionary sequences ramps may be homoclinal or distally steepened and may have fringing or barrier shoal water complexes of ooid pellet sands or skeletal banks homoclinal ramps pass seaward into deeper water without major break in slope and lack deep water breccias distally steepened ramps may be low energy and characterized by widespread shallow subwave base mud blankets or high energy with coastal beach dune complexes and widespread skeletal sand blankets slope facies may contain abundant breccias of slope derived clasts rimmed shelves have relatively flat tops and marked break in slopes at the high energy shallow shelf edge where they pass into deep water such shelves may be aggraded with peritidal facies extending over much of the shelf or incipiently drowned depending on magnitude of sea level fluctuations they may be accretionary or bypass types that include gullied slope escarpment and high relief erosional forms intrashelf basins occur on some shelves controlling distribution of reservoir and source beds isolated platforms are surrounded by deeper water and may be located on rifted continental margins or on submarine volcanoes most have high relief rimmed margins platforms that have been subjected to rapid sea level rise may be incipiently drowned and characterized by raised rims elevated patch or pinnacle reefs and widespread subwave base carbonate or fine clastic blankets completely drowned shelves develop where the shelf is submerged to subphotic depths terminating shallow water deposition and commonly resulting in blanketing of the shelf by deeper water facies some margins show extensive down to basin faulting that is contemporaneous with carbonate deposition or associated with thick prograding clastic sequences the various types of platforms change in response to variations in sedimentation subsidence or sea level rise and may form distinctive evolutionary sequences the relatively few models presented appear to accommodate most geological examples some of which contain major reservoir facies

observation of coseismic seafloor crustal deformation due to m7 class offshore earthquakes 1 we have developed an observation system for seafloor crustal deformation measurement combining the two following techniques the precise acoustic ranging and kinematic gps global positioning system positioning on july 14 2003 we installed the units for this observation system at the seafloor of the kumano basin japan 33 58 n 136 60 e we performed repeated observation six times on 1 july 15 16 and 21 2004 2 november 9 10 2004 3 may 18 and 20 2005 4 july 19 20 2005 5 august 18 19 2005 and 6 august 29 30 2005 the present observation system can stably determine the seafloor position with an rms repeatability of 3 cm in both horizontal components two m7 class offshore intraplate earthquakes occurred only 60 km from the kumano basin site on september 5 2004 we observed the coseismic horizontal displacement of 18 cm at the kumano basin site using the presently developed seafloor observation system our observation system can provide seafloor crustal deformation associated with crustal activities in offshore areas

lithofacies and depositional processes on a high steep margined carboniferous bashkirian moscovian carbonate platform slope sierra del cuera nw spain the depositional slope of the sierra del cuera a carboniferous bashkirian moscovian high steep margined carbonate platform provides excellent cross sections of lithofacies zonations and associated stratal geometries the steep 30 40 and nearly planar upper slope is dominated by massive sheet like layers of microbial cement rich boundstone which alternate with intercalations of red stained bryozoan cementstone with crinoids and brachiopods the slightly gentler 20 26 and concave upward lower slope is characterized by clast supported resedimented deposits the upper slope extended from platform break to ca 300 m water depth whereas lower slope sediments were deposited in water depths up to 600 700 m at which level the slope beds flatten to a few degrees toe of slope and interfinger with spiculitic and argillaceous basinal sediments between 250 and 450 m water depth boundstones and breccias alternated in a transitional zone the lower slope sediments include clast supported breccias with radiaxial fibrous cement in interparticle space mud to clast supported breccias with red stained carbonate mud matrix and packstone to grainstone and rudstone beds most of the clasts comprise boundstone reworked from an upper slope setting and smaller grains are platform and slope derived a pervasive submarine cementation occurs along the upper two thirds of the flank and this stabilized the slope slope deposition is interpreted as follows during active boundstone accretion microbial boundstone layers slid off and formed breccia tongues extending from the lower upper slope down to the toe of slope rock falls and avalanches were generated whenever the shear strength of the substrate of loose or partly lithified sediment was exceeded upper slope boundstone accretion and shedding independent of the depth of light penetration controlled most of the depositional processes on the slope cement dominated intervals are considered to be related to early highstand and or flooding phases relative sea level fluctuations and or associated changes in the water conditions are believed to be responsible for intervals of low boundstone production or cement precipitation whether the in situ boundstone and breccia are preferentially related to lowstand or highstand periods is as yet unclear

an andean model of interplate coupling and strain partitioning applied to the flat subduction zone of sw japan nankai trough abstract transcurrent motion is commonly observed in cases of oblique subduction yet the causes remain controversial a model of increased interplate coupling linked to flat subduction is proposed as a mechanism for producing strain partitioning at a great distance several hundred km from the trench the model originally developed for the north andean margin is applied to the geodynamics of sw japan here along the nankai trough and below adjacent sw honshu flat subduction occurs due to the relatively young age m 7 and nine additional m 6 earthquakes in the past 300 years dextral strike slip focal mechanisms for 15 modern and historical events indicate a significant degree of subduction related strain partitioning manifested by right lateral strike slip faulting along the adakitic volcanic arc some 400 km from the nankai trough

secular crustal deformation and interplate coupling of the japanese islands as deduced from continuous gps array 1996 2001 abstract data from the nation wide gps continuous tracking network that has been operated by the geographical survey institute of japan since april 1996 were used to study crustal deformation in the japanese islands we first extracted site coordinate from daily sinex files for the period from april 1 1996 to february 24 2001 since raw time series of station coordinates include coseismic and postseismic displacements as well as seasonal variation we model each time series as a combination of linear and trigonometric functions and jumps for episodic events estimated velocities were converted into a kinematic reference frame heki k 1996 horizontal and vertical crustal movements from three dimensional very long baseline interferometry kinematic reference frame implication for reversal timescale revision j geophys res 101 3187 3198 to discuss the crustal deformation relative to the stable interior of the eurasian plate a least squares prediction technique has been used to segregate the signal and noise in horizontal as well as vertical velocities estimated horizontal signals horizontal displacement rates were then differentiated in space to calculate principal components of strain dilatations maximum shear strains and principal axes of strain clearly portray tectonic environments of the japanese islands on the other hand the interseismic vertical deformation field of the japanese islands is derived for the same gps data interval the gps vertical velocities are combined with 31 year tide gage records to estimate absolute vertical velocity the results of vertical deformation show that 1 the existence of clear uplift of about 6 mm yr in shikoku and kii peninsula whereas pattern of subsidence is observed in the coast of kyushu district this might reflect strong coupling between the philippine sea plate and overriding plate at the nankai trough and weak coupling off kyushu 2 no clear vertical deformation pattern exists along the pacific coast of northeastern japan this might be due to the long distance between the plate boundary japan trench and overriding plate where gps sites are located 3 significant uplift is observed in the southwestern part of hokkaido and in northeastern tohoku along the japan sea coast this is possibly due to the viscoelastic rebound of the 1983 japan sea mw 7 7 and the 1993 hokkaido nansei oki mw 7 8 earthquakes and or associated with distributed compression of incipient subduction there we then estimate the elastic deformation of the japanese islands caused by interseismic loading of the pacific and philippine sea subduction plates the elastic models account for most of the observed horizontal velocity field if the subduction movement of the philippine sea plate is 100 locked and if that of the pacific plate is 70 locked however the best fit for vertical velocity ranges from 80 to 100 coupling factor in southwestern japan and only 50 in northeastern japan since horizontal data does not permit the separation of rigid plate motion and interplate coupling because horizontal velocities include both contributions we used the vertical velocities to discriminate between them so we can say there is strong interplate coupling 80 100 over the nankaido subduction zone whereas it is about 50 only over the kurile japan trench

analysis of neotectonic structures in the eastern precordillera of argentina in relation to seismic hazard by the application of integrated geophysical methods abstract the city of san juan in the central western region of argentina has been the target of very destructive superficial earthquakes some of which have not been associated to a clear structural source up to this date the city is constantly growing outside the valley where it is located towards the area of eastern precordillera which is currently having an increased socio cultural activity thus this study is focused on increasing the geological knowledge of the latter by studying the eastern flank of sierra chica de zonda eastern precordillera whose proved neotectonic activity represents a geohazard on the basis of the general geological setting the neotectonic structures in the study area are related to a major active synclinal folding located just under the western sector of the san juan city geophysical potential methods gravimetric and magnetometric surveys were used to recognize contacts by contrast of density and magnetic susceptibility in order to reduce the ambiguity of these methods the gravi magnetometric results were constrained by using seismic and electrical tomographies these contacts where geophysical properties abruptly change were interpreted as faults despite many of them not having a superficial expression the latter being of great importance to asses the seismic hazard of the study area

hypocenter depths of large interplate earthquakes and their relation to seismic coupling we examine locations of hypocenters of large interplate earthquakes mv 7 5 at subduction zones relative to their rupture areas to obtain a relation between the hypocentral depth and the seismic coupling coefficient which is the ratio of the long term slip rate estimated from cumulative seismic moment of large earthquakes to the relative plate motion we find 1 that the hypocentral depth is close to the bottom of the depth extent of the rupture area when the seismic coupling coefficient is nearly equal to 1 0 and 2 that the hypocentral depth relative to the depth extent of the rupture area shows a large scatter from shallow to deep when the seismic coupling coefficient is smaller than about 0 5 to interpret these observations we conduct a numerical simulation of seismic cycles of interplate earthquakes where the frictional stress on the plate boundary is assumed to obey a laboratory derived rate and statedependent friction law the observed result 1 is reproduced in the simulation when the critical fault length which is the size of the fault where the slip nucleation process takes place is much shorter than the seismogenic zone of the plate boundary in this case the plate boundary is strongly locked during an interseismic period and accordingly the calculated seismic coupling coefficient is close to 1 0 seismic slip starts near the bottom of the seismogenic zone because the maximum shear stress concentration is generated near the bottom of the seismogenic zone due to deeper steady plate motion on the other hand when the critical fault length is large appreciable aseismic sliding occurs in the seismogenic zone and therefore the calculated seismic coupling coefficient becomes significantly smaller than 1 0 the hypocentral depths of simulated large earthquakes tend to be shallow for large critical fault lengths heterogeneous frictional properties on the plate boundary may produce non uniform aseismic sliding during an interseismic period in this case the seismic coupling is small and seismic slip starts in various portions of the seismogenic zone this can explain the observed result 2 2 2003 elsevier science b v all rights reserved

aftershocks of the western argentina caucete earthquake of 23 november 1977 some tectonic implications an aftershock survey using a network of eight portable and two permanent seismographs was conducted for the western argentina caucete earthquake ms 7 3 of november 23 1977 monitoring began december 6 almost 2 weeks after the main shock and continued for 11 days the data set includes 185 aftershock hypocenters that range in the depth from near surface to more than 30 km the spatial distribution of those events occupied a volume of about 100 km long 50 km wide 30 km thick the volumnar nature of the aftershock distribution is interpreted to be a result of a bimodal distribution of foci that define east and west dipping planar zones efforts to select which of those zones was associated with the causal faulting include special attention to the determination of the mainshock focal depth and dislocation theory modeling of the coseismic surface deformation in the epicentral region our focal depth 25 35 km and modeling studies lead us to prefer an east dipping plane as causal a previous interpretation by other investigators used a shallower focal depth 17 km and similar modeling calculations in choosing a west dipping plane our selection of the east dipping plane is physically more appealing because it places fault initiation at the base of the crustal seismogenic layer rather than in the middle of that layer which requires fault propagation to be updip rather than downdip

nonlinear refraction traveltime tomography a few important issues for performing nonlinear refraction traveltime tomography have been identified they include the accuracy of the traveltime and raypath calculations for refraction the physical information in the refraction traveltime curves and the characteristics of the refraction traveltime errors consequently we develop a shortest path ray tracing method with an optimized node distribution that can calculate refraction traveltimes and raypaths accurately in any velocity model we find that structure ambiguity caused by short and long rays in the seismic refraction method may influence the inversion solution significantly therefore we pose a nonlinear inverse problem that explicitly minimizes the misfits of the average slownesses ratios of traveltimes to the corresponding ray lengths and the apparent slownesses derivatives of traveltimes with respect to distance as a result we enhance the resolution as well as the convergence speed to regularize our inverse problem we use the tikhon

estimation of interplate coupling in the nankai trough japan using gps data from 1996 to 2006 we used three component surface velocities in southwest japan to estimate plate coupling on the subducting plate interface at the nankai trough we analyzed continuous gps data from the japanese geonet network from 1996 to 2006 using a consistent analysis strategy that generates bias fixed solutions for the entire network we applied systematic time series analysis methods to estimate common mode error which improved position solutions for the entire network to allow for differences in regional deformation sources we modelled the plate coupling on the plate interface beneath shikoku island to kii peninsula and the tokai suruga trough separately the results show strong coupling at a depth of 10 30 km off shikoku and kii peninsula the spatial variation in plate coupling coincides well with the coseismic rupture zones of the past large earthquakes maximum slip deficit rates of 2 3 cm yr 1 at the depth of 5 25 km are found beneath the tokai area consistent with results from other studies the downdip limits of the highly coupled areas and transition zones beneath shikoku and the kii peninsula correspond approximately to estimates of the 450 c isotherms good correlation is observed between the lateral variations of the slip deficit distribution low frequency earthquakes and coseismic slip this correlation suggests that temperature and possibly fluid variations contribute to such correlation in space the interplate slip deficit derived from the gps velocities over the 10 yr of observations is generally compatible with the results over shorter time spans suggesting that plate coupling in sw japan does not change significantly over the period of these gps measurements

a systematic review of geological evidence for holocene earthquakes and tsunamis along the nankai suruga trough japan the nankai suruga trough the subduction zone that lies immediately south of japan s densely populated southern coastline generates devastating great earthquakes magnitude 8 characterised by intense shaking crustal deformation and tsunami generation forecasting the hazards associated with future earthquakes along this 700 km long fault requires a comprehensive understanding of past fault behaviour while the region benefits from a long and detailed historical record palaeoseismology has the potential to provide a longer term perspective and additional crucial insights in this paper we summarise the current state of knowledge regarding geological evidence for past earthquakes and tsunamis along the nankai suruga trough incorporating literature originally published in both japanese and english and enhancing available results with new age modelling approaches we summarise and critically evaluate evidence from a wide variety of sources palaeoseismic evidence includes uplifted marine terraces and biota marine and lacustrine turbidites liquefaction features subsided marshes and tsunami deposits in coastal lakes and lowlands while 75 publications describe proposed evidence from 70 sites only a limited number provide compelling well dated evidence the best available records enable us to map the most likely rupture zones of twelve earthquakes that occurred during the historical period this spatiotemporal compilation suggests that the 1707 ce earthquake ruptured almost the full length of the subduction zone and that earthquakes in 1361 ce and 684 ce may have been predecessors of similar magnitude intervening earthquakes were of lesser magnitude highlighting the variability in rupture mode that characterises the nankai suruga trough intervals between ruptures of the same seismic segment range from 450 years during the historical period over longer timescales palaeoseismic evidence suggests intervals between earthquakes ranging from 100 to 700 years however these figures reflect a range of thresholds controlling the creation and preservation of evidence at any given site as well as the genuine intervals between earthquakes at present there is no geological data that suggest the occurrence of a larger magnitude earthquake than that experienced in 1707 ce however few studies have sought to establish the relative magnitudes of different earthquake and tsunami events along the nankai suruga trough alongside the lack of research designed to quantify the maximum magnitude of past earthquakes we emphasise issues over alternative hypotheses for proposed palaeoseismic evidence the paucity of robust chronological frameworks and insufficient appreciation of changing thresholds of evidence creation and preservation over time as key issues that must be addressed by future research

a dislocation model of strain accumulation and release at a subduction zone strain accumulation and release at a subduction zone are attributed to stick slip on the main thrust zone and steady aseismic slip on the remainder of the plate interface this process can be described as a superposition of steady state subduction and a repetitive cycle of slip on the main thrust zone consisting of steady normal slip at the plate convergence rate plus occasional thrust events that recover the accumulated normal slip because steady state subduction does not contribute to the deformation at the free surface deformation observed there is completely equivalent to that produced by the slip cycle alone the response to that slip is simply the response of a particular earth model to embedded dislocations for a purely elastic earth model the deformation cycle consists of a coseismic offset followed by a linear in time recovery to the initial value during the interval between earthquakes for an elastic viscoelastic earth model elastic lithosphere over a viscoelastic asthenosphere the postearthquake recovery is not linear in time records of local uplift as a function of time indicate that the long term postseimic recovery is approximately linear suggesting that elastic earth models are adequate to describe the deformation cycle however the deformation predicted for amore simple elastic half space earth does not reproduce the deformation observed along the subduction zones in japna at all well if stick slip is restricted to the main thrust zone as recognized earlier by shimazaki seno and kato the uplift profiles could be explained if stick slips were postulated to extend along the plate interface beyond the main thrust zone to a depth of perhaps 100 km but independent evidence suggests that stick slip at such depths if unlikely less

variation of downdip limit of the seismogenic zone near the japanese islands implications for the serpentinization mechanism of the forearc mantle wedge abstract it has been proposed that the downdip limit of interplate thrust type earthquakes in subduction zones dlt is determined either by the brittle ductile transition around 350 450 c of the crustal material at the plate interface or the moho of the forearc of the upper plate the latter is due to possible serpentinization of the forearc mantle wedge above the subducting plate which makes the thrust zone slide in a stable manner i examine this criterion in subduction zones near japan where the pacific and philippine sea plates are subducting i show that in most of n honshu where the old pacific plate is subducting and in kanto and s kyushu where the izu bonin and kyushu palau ridges of the philippine sea plate are subducting the dlt is located at a depth of 60 70 km which is deeper than the moho of the upper plate this shows that the criterion does not hold and the mantle wedge is not likely to be serpentinized in these regions in contrast in the region off iwate in n honshu and in bonin where the old pacific plate is subducting the dlt is located at a depth of 20 30 km around the moho of the upper plate suggesting that the mantle wedge is serpentinized in these regions in sw japan where the young shikoku basin is subducting the dlt is around 30 km in depth which coincides with the moho but also with the 350 c temperature at the plate interface although seismic tomography indicates that the mantle wedge is serpentinized the dlt here does not help to examine the criterion assuming that hydration of the mantle wedge is conducted through hydro fracturing by water released from the dehydrating subducted crust i propose that the stress state of the wedge would determine the extent of serpentinization of the mantle wedge in the reverse fault type stress regime of n honshu kanto and s kyushu hydro fracturing is not favored and fractures in the thrust zone associated with repeated interplate earthquakes provide conduits for water to flow in the updip direction resulting in no serpentinization of the mantle wedge no serpentinization of the mantle wedge in turn causes interplate earthquakes in contrast in the normal fault type stress regime of the region off iwate and bonin and the strike slip fault type stress regime of sw japan hydro fracturing is favored resulting in serpentinization of the mantle wedge the frictional property at the thrust zone is governed by stable sliding resulting in no interplate earthquakes deeper than the moho thus the stress regime of the mantle wedge would determine bifurcation whether it is serpentinized or not and then the depth of dlt

microbially induced fe and mn oxides in condensed pelagic sediments middle upper jurassic western sicily abstract this article presents a petrographic comparison of the rosso ammonitico facies of western sicily and the original rosso ammonitico veronese of northern italy based on a total of 27 sections the rosso ammonitico has been the subject of numerous controversies that range from bathyal to shallow water platform sedimentation therefore it seemed interesting to verify if the term rosso ammonitico has the same geologic connotation from region to region the middle upper jurassic rosso ammonitico of western sicily is a condensed succession formed during a period of extensional synsedimentary tectonics related to the spreading of the ionian ocean slope to basin or pelagic carbonate deposits characterize the sedimentation which consists of reddish mudstones and wackestones the abundant fauna is composed of radiolarians protoglobigerinids saccocoma bositra associated with ammonites a few ferruginous hardgrounds fe mn oxide crusts and mn coated condensation horizons are also present the red matrices contain abundant fe mn encrusted microbored and bioeroded bioclasts sporadic fe mn oncolites composed of amorphous mn minerals and goethite are also conspicuous the matrix as well as the shells and the fillings of the complex associated veinlets are frequently altered into calcite microsparite submicronic iron bacterial and fungal filaments associated with mineralized extracellular polymeric substances eps are observed in the matrix they record dysaerobic microenvironments at or near the sediment water interfaces early mineralized discontinuities enhanced by subsequent pressure dissolution are reported in the succession mn ni bacterial filaments are exceptionally observed in the cortex of the fe mn oncolites as a consequence of an early lithification the mn filaments are poorly preserved the pigmentation of the rock is due to the dispersion of submicronic oxyhydroxides now goethite and amorphous iron formed by bacterial mediation during early diagenesis in microaerophilitic environments as in the case of the original rosso ammonitico veronese fe and mn bacteria fungi were able to produce bioconstructions which have no bathymetric significance the limiting factor must have been the oxygen content which was low in these very quiet and relatively deep environments thus the rosso ammonitico of northern and southern italy have a number of points in common but some obvious dissimilarities are observed that explain some of the various sedimentological interpretations among them the chemical composition is of particular importance more fe is present in veneto northern italy while mn is associated with the sicilian rosso ammonitico the sicilian localities were more proximal to oceanic magmatic sources which were related to the activity of the oceanic crust

time sequence and the recurrence models for large earthquakes along the nankai trough revisited it is suggested that time sequence of earthquakes can be explained by the time predictable recurrence model rather than the slip predictable recurrence model however the reliability of the model depends primarily on data accuracy missing large events seriously affect the evaluation of the models although the time predictable model can explain the recent three large events along the nankai trough back to a d 1707 there was serious discrepancy when the model was applied to older events recent archeological studies have discovered new events along the trough missed in historical documents i found that with the addition of the archeologically discovered new events the recurrence models can be applied to older events and that the time sequence including these new events suggests a time predictable recurrence pattern over a 1000 year interval

comparison of frictional strength and velocity dependence between fault zones in the nankai accretionary complex accretionary complexes host a variety of fault zones that accommodate plate convergence and internal prism deformation including the decollement imbricate thrusts and out of sequence thrusts or splays these faults especially the decollement and major splay faults are considered to be candidates for hosting slow slip events and large magnitude earthquakes but it is not clear what modes of slip should be expected at shallow levels or how they are related to fault rock frictional properties we conducted laboratory experiments to measure the frictional properties of fault and wall rock from three distinct fault zone systems sampled during integrated ocean drilling program expedition 316 and ocean drilling program leg 190 to the nankai trough offshore japan these are 1 a major out of sequence thrust fault termed the megasplay site c0004 2 the frontal thrust zone a region of diffuse thrust faulting near the trench site c0007 and 3 the decollement zone sampled 2 km from the trench site 1174 at 25 mpa effective normal stress at slip rates of 0 03 100 m s and in the presence of brine as a pore fluid we observe low friction 0 46 for all of the materials we tested however the weakest samples 0 30 are from the decollement zone material from the megasplay fault is significantly weaker than the surrounding wall rocks a pattern not observed in the frontal thrust and decollement all samples exhibit primarily velocity strengthening frictional behavior suggesting that earthquakes should not nucleate at these depths a consistent minimum in the friction rate parameter a b at sliding velocities of 1 3 m s 0 1 0 3 m d is observed at all three sites suggesting that these shallow fault zones may be likely to host slow slip events

calciturbidite composition related to exposure and flooding of a carbonate platform triassic eastern alps the compositional variation of calciturbidites pedata potschen formation deposited adjacent to the dachstein formation carbonate platform in the triassic hallstatt basin was analysed using detailed field measurements and point counting of thin sections the 35 m long section is located in the northern calcareous alps of austria six point count groups were distinguished separating basinal from platform derived input summary statistics cluster and correspondence analysis of the point count data reveals a close relationship between the biota present on the dachstein carbonate platform and the calciturbidite composition the variations in turbidite composition are attributed to fluctuations in sea level and resulting flooding and exposure of the platform which alternately created and destroyed shallow water habitats on the platform top

anatomy and global context of the andes main geologic features and the andean orogenic cycle the andes make up the largest orogenic system developed by subduction of oceanic crust along a continental margin subduction began soon after the breakup of rodinia in late proterozoic times and since that time it has been intermittently active up to the present the evolution of the pacifi c margin of south america during the paleozoic occurred in the following stages 1 initial proterozoic rifting followed by subduction and fi nal re amalgamation of the margin in early cambrian times as depicted by the puncoviscana and tucavaca basins and related granitoids in southern bolivia and northern argentina 2 a later phase of rifting in the middle cambrian and subsequent collisions in middle ordovician times of parautochthonous terranes derived from gondwana such as paracas arequipa and antofalla and exotic terranes originating in laurentia such as cuyania chilenia and chibcha 3 fi nal permian collision between south america and north america to form pangea during the alleghanides orogeny leaving behind rifted pieces of laurentia as the tahami and tahuin terranes in the northern andes and other poorly known orthogneisses in the cordillera real of ecuador in the late permian early triassic and 4 amalgamation of the mejillonia and patagonia terranes in early permian times representing the last convergence episodes recorded in the margin during the gondwanides orogeny these rifting episodes and subsequent collisions along the continental margin were the result of changes of the absolute motion of gondwana related to global plate reorganizations during proterozoic to paleozoic times generalized rifting during pangea breakup in the triassic concentrated extension in the hanging wall of the sutures that amalgamated the paleozoic terranes the opening of the indian ocean in early jurassic times was associated with a new phase of subduction along the continental margin the northeastward absolute motion of western gondwana produced a negative trench roll back velocity that controlled subduction under an extensional regime until late early cretaceous times the northern andes of venezuela colombia and ecuador record a series of collisions of island arcs and oceanic plateaus from the early cretaceous to the middle miocene as a result of interaction with the caribbean plate the remaining central and southern andes record periods of orogenesis and mountain building alternating with periods of quiescence and absence of deformation as recorded in parts of the oligocene based on the generalized occurrence of fl at slab subduction episodes through time as recorded in most ramos v a 2009 anatomy and global context of the andes main geologic features and the andean orogenic cycle in kay s m ramos v a and dickinson w r eds backbone of the americas shallow subduction plateau uplift and ridge and terrane collision geological society of america memoir 204 p 31 65 doi 10 1130 2009 1204 02 for permission to copy contact editing geosociety org 2009 the geological society of america all rights reserved

waulsortian type bioherm development and response to sea level fluctuations upper visean of bechar basin western algeria abstract an exceptionally well developed and well preserved upper visean succession rich in sponge bryozoan crinoid mounds in the foreland carboniferous bechar basin northwestern algerian sahara is described and discussed the succession is composed of recurrent facies mosaics forming individual superposed members an ideal member is made up of two distinct fades assemblages the lower assemblage forms the actual mounds and is composed of sponge bafflestone wackestone at the base overlain by massive sponge fenestellid bafflestone wackestone and capped by massive crinoid wackestone with bedded flanks of lithoclastic wackestone in contrast to massiveness of the mounds the upper facies assemblage is composed of well bedded crinoid packstone grainstone and ooid grainstone with local rugose coral and algal foraminiferal banks on the basis of benthic assemblages and nature of substrate seven bathymetric zones are defined and indicate that each member of the bioherm rich formations is a shallowing upward parasequence controlled by an asymmetrical transgressive regressive cycle the local curve of relative sea level for the late visean shows 13 cycles interpreted as fourth order eustatic sea level changes each cycle averaging half a million years in duration third order cycles could not be identified the platform model proposed is a distally steepened ramp 15 20 km wide that developed in a rapidly subsiding foreland basin lateral distribution of facies on the ramp depended strongly on local tectonic setting whereas vertical development was controlled by sea level fluctuation the deep water mud rich sponge bryozoan crinoid mounds developed in 100 150 m water depths during phases of sea level highstand whereas deposition of shallow water facies occurred on top of the mounds in less than 70 80 m water depths during regressive phases the bechar mounds share similarities with the classical lower carboniferous waulsortian mounds but they differ in two aspects the abundance of large sponges which is unique and their vertical zonation wherein basal facies consist of sponge dominated assemblages the proposed model can serve as a tool in developing exploration strategies in the search for hydrocarbon reservoirs in the bechar basin because the peculiar architecture of the platform may provide suitable plumbing systems for fluid migration and the depositional signature of the mounds and associated facies is possibly recognizable on seismic profiles

facies patterns and depositional environments of palaeozoic cephalopod limestones abstract in the eastern anti atlas morocco a platform and basin topography was established during the late devonian probably as a result of early variscan tensional tectonics cephalopod limestones were deposited on shallow pelagic platforms platform slopes and shallow slowly subsiding basins on the platform a transition from land areas into nearshore quartzose brachiopod coquinas crinoidal limestones condensed cephalopod limestones and finally into nodular limestones is observed the latter often become disintegrated into incipient debris flows which pass into nodular limestone marl alternations of a shallow basin deeper basins with shale sedimentation lack cephalopod limestones similar facies types also occur in the late devonian of the montagne noire france rheinisches schiefergebirge west germany moravian karst czechoslovakia holy cross mountains poland and in the early carboniferous of the cantabrian mountains spain due to strong late variscan compressional tectonics and limited outcrops detailed facies patterns could not be mapped in these regions but the same facies types as in the eastern anti atlas suggest similar coast platform slope and shallow basin topographies during cephalopod limestone deposition water depth on the platforms was in the order of several tens to about one hundred metres as is inferred from repeated subaerial exposures and distinctive depositional and faunal floral features water depth in the adjacent shallow basins might have reached several hundreds of metres cephalopod limestones represent a typical stage in the evolution of geosynclines characterized by extremely low sedimentation rates 1 5 m m y 1 this stage is preceded by deposition of thick neritic clastics and or carbonates and is succeeded by deposition of deep water clastics or flysch

are beds in shelf carbonates millennial scale cycles an example from the mid carboniferous of northern england abstract the mid carboniferous strata of northern england are characterised by mixed clastic carbonate cycles yoredale cyclothems attributed here to the short eccentricity milankovitch rhythm in a typical cycle transgressive normal marine shelf carbonates are succeeded by marine shales then highstand prodelta mudstones and delta front delta top sandstones with local coals a detailed study of one cycle the great limestone cyclothem of the northern pennines alston block reveals that within the transgressive carbonates the beds averaging 75 cm in thickness and defined by mm shale partings or cm mudrock layers form two thinning upward to thickening upward bed sets individual beds and the bed sets can be correlated across the region oxygen isotope and strontium trace element data also reveal patterns of increasing and decreasing values through the limestone which broadly correspond to the bed thickness cycles the beds are interpreted as millennial scale cycles the result of high frequency arid humid climatic fluctuations the bed sets are interpreted as the response to a longer term arid humid climate and sea level cycle driven by the precession rhythm it is postulated that millennial scale climatic changes which are a well known feature of the quaternary and are here inferred for the carboniferous were responsible for the deposition of the beds that are a characteristic feature of many marine sedimentary successions in the geological record the most likely over riding control is fluctuations in solar output

geodynamics of the baikal rift zone and plate tectonics of asia the baikal rift zone stretches from the southern termination of lake baikal as far as 118 e and includes the baikal basin and the barguzin upper angara and muysk grabens that form its easterly continuation coincident with the rift zone is a narrow seismic belt which extends further east along the stanovoy range to the okhotsk sea this belt can be considered as the boundary between the eurasian and amurian lithospheric plates earthquake focal mechanism solutions that show a consistent orientation of extensional axes across the strike of the rift zone indicate the behaviour of the eurasian and amurian plates as rigid bodies from 83 focal mechanism solutions the pole of rotation of the eurasian and amurian plates was computed to lie at the point 56 95n 117 45e the angular rate estimated from the amount of baikal opening is about 1 10 7 deg year the position of the pole at the eastern termination of the rift zone accounts for the dying out of the rift zone and for the appearance east of the pole of compressive structures in the stanovoy range to the southwest the baikal rift zone is replaced by the mosaic of microplates in central asia that occupy the space between the eurasian and indian lithospheric plates prominent are the mongolian dzungarian alashan tarim tibetan and pamir microplates earthquakes in central asia are dispersed although higher concentrations of earthquakes associated with microplate boundaries are prominent the tectonics of central asia are considered to be due to the interaction of rigid microplates assuming that plastic deformations occur within the relatively wide zones along the microplate boundaries by considering the strike slip faults to define the trajectories of microplate motions the parameters of relative movements of the microplates have been computed the microplate mosaic of central asia is moving northeasterly as a result of the collision and continued convergence of india and eurasia the mosaic acts as a wedge splitting off the amurian plate from eurasia causing it to rotate counterclockwise so opening the baikal rift

crustal velocity field of southwest japan subduction and arc arc collision we investigate crustal deformation in southwest japan over a 3 year period revealed by a permanent dense global positioning system gps array southwest japan is a part of the amurian plate a microplate moving about 10 mm yr toward the east with respect to the eurasian plate it overrides the philippine sea plate at the nankai trough and collides with the northeast japan arc in the central part of japan in this paper we first derive gps site velocities relative to the stable part of the amurian plate in order to isolate signals of crustal deformation caused by the subduction and or the collision the velocity field has a conspicuous feature indicating the interseismic elastic loading by the philippine sea plate slab at the nankai trough characterized by the northwestward movements of points throughout the studied area their amplitudes are the largest at the pacific coast and decay toward the japan sea coast with a subtle systematic shift of azimuths a model assuming an elastic half space the convergence rate at the nankai trough based on a refined euler vector and the strength of the coupling inferred from a thermal model could explain the velocity field in the western part of the studied area to a large extent those in the eastern part systematically deviate from them and the residual components there show east west shortening and north south extension this may represent crustal thickening and trenchward extrusion of crustal blocks caused by the collision between southwest and northeast japan this suggests that the collision between southwest and northeast japan gives rise to not only crustal thickening but also trenchward extrusion of crustal block a velocity contrast was found across the median tectonic line the largest inland active fault in japan but the current permanent gps network is not dense enough for us to discuss its coupling depth

mississippian coral assemblages from the khenifra area central morocco biostratigraphy biofacies palaeoecology and palaeobiogeography abstract analysis of mississippian coral assemblages from the khenifra region of central morocco together with data from foraminiferal algal microfossils has established new age dating of 5 localities within the azrou khenifra basin souk el had and sidi lamine where corals occur mainly in biostromes protected by oolitic shoals tabainout where corals have been recorded in different environments related to microbial mounds alhajra almatkouba where corals occur in biostromal reworked beds and tiouinine where corals occur in a well structured fringing reef this study demonstrates the presence of richer more diverse coral assemblages than previously recorded in a variety of environmental settings these coral assemblages strengthen correlations with the adarouch area in the ne part of the azrou khenifra basin it is emphasised that in the upper visean there are close similarities with rugose coral assemblages in other parts of the western palaeotethys including north africa sw spain and nw europe and that all belong to the same biogeographic province

internal structure and depositional environment of late carboniferous mounds from the san emiliano formation carmenes syncline cantabrian mountains northern spain well exposed mounds are common in limestone of the late carboniferous san emiliano formation cantabrian mountains northern spain they occur as obvious primary topographic features careful study of the mound intervals and surrounding strata revealed the internal structures of mounds and the factors controlling their growth the substrate 2 3 m of the mounds consists of greyish to reddish bedded oolitic and oncolithic packstone and grainstone crinoids fragments of the alga epimastopora and rarely bryozoans are present ooids and oncoids indicate a wave dominated high energy environment presence of quartz indicates the influence of terrigenous siliciclastic input mound intervals 6 12 m thick are characterized by skeletal microbial boundstone donezellid algae agglutinated worm tubes and calcisponges are the dominant fossils smaller foraminifers gastropods and brachiopods are also present a peloidal clotted matrix is characteristic and accounts for more than 30 of the mound volume intraframe pores are mainly filled by peloidal sediment and early marine cement intermound strata are approximately one third as thick as time equivalent mounds mound fossils algae agglutinated worm tubes and sponges are uncommon however intermound strata are generally more diverse than the mounds containing fusulinids smaller foraminifers bryozoans gastropods crinoids and bioclasts some of these fossils have micritic envelopes bedded packstone and grainstone 3 6 m thick with siliciclastic debris rugose corals and chaetetid sponges characterize the capping facies coated grains and small ooids are uncommon this facies indicates shallowing to a higher energy environment and or a higher input of siliciclastics inhibiting mound growth mounds are interpreted to have accreted in a quiet environment below wave base this position is comparable to the depositional environment inferred for many late paleozoic mounds described elsewhere e g from texas and new mexico canadian archipelago and carnic alps in austria mound relief is explained by 1 accumulation of peloidal clotted sediments limited to boundstone and probably related to microbial activities 2 widespread marine cementation within this area and 3 low export of mound fossils to intermound areas the position of the mounds within the sequence and their initiation size and termination seem to be mainly controlled by sea level fluctuations and siliciclastic input d 2001 elsevier science b v all rights reserved

the portland hills fault uncovering a hidden fault in portland oregon using high resolution geophysical methods abstract the portland metropolitan area historically is the most seismically active region in oregon at least three potentially active faults are located in the immediate vicinity of downtown portland with the portland hills fault phf extending directly beneath downtown portland the faults are poorly understood and the surface geologic record does not provide the information required to assess the seismic hazards associated with them the limited geologic information stems from a surface topography that has not maintained a cumulative geologic record of faulting in part due to rapid erosion and deposition from late pleistocene catastrophic flood events and a possible strike slip component of the faults we integrated multiple high resolution geophysical techniques including seismic reflection ground penetrating radar gpr and magnetic methods with regional geological and geophysical surveys to determine that the portland hills fault is presently active with a zone of deformation that extends at least 400 m the style of deformation is consistent with at least two major earthquakes in the last 12 15 ka as confirmed by a sidehill excavation trench high resolution geophysical methods provide detailed images of the upper 100 m across the active fault zone the geophysical images are critical to characterizing the structural style within the zone of deformation and when integrated with a paleoseismic trench can accurately record the seismic history of a region with little surface geologic exposure

the palaeoecological distribution of the endothyroids foraminifera in the guadiato area sw spain mississippian abstract this paper focusses on the distribution and methodological problems that are observed in the palaeoecological analyses of the endothyroids from the guadiato area in the southwestern part of the iberian peninsula in spite of a long history of taxonomical and biostratigraphical studies on endothyroids there have been few investigations of their palaeoecology and taphonomy the guadiato area contains a sequence of upper visean to pendleian marine carbonates the upper visean units were deposited in a storm dominated ramp the pendleian strata were deposited in a tectonically controlled shelf with narrow platform facies supra inter and subtidal and a wide area of slope deposits some of the foraminiferal assemblages of this succession typify intertidal facies and incipient shoals and are regarded as para autochthonous other assemblages such as the endothyroids in the higher part of the pendleian slope are of doubtful allochthony it is likely that endothyroids did not live in slope facies it was too deep but the extent of their transportation cannot be determined since their tests do not show signs of abrasion several factors controlled the endothyroid distribution such as salinity and depth deposits formed in high energy environments such as shoals and tidal flats were not favourable for the endothyroids particular palaeoecological factors also determine the distribution of certain families subfamilies or genera one of these factors is relative environmental stability for example some endothyroids that lack secondary deposits the archaediscinae and endothyra priscella were more abundant in stable environments in contrast other genera with secondary deposits the asteroarchaediscinae omphalotis and the evolved endothyra were more abundant in unstable or fluctuating microfacies this factor however did not control the distribution of every genus because this difference is not observed in some species of genera with or without secondary deposits e g globoendothyra

interplate coupling along the nankai trough off southwest japan derived from gps measurements we investigate interplate coupling between the philippine sea and the eurasian plates at the nankai trough off southwest japan during the interseismic period plate coupling is modeled by imaginary backward normal slip superposed on the steady state subduction we divide the plate interface into several segments and estimate coupling on each segment from gps horizontal velocity data estimated coupling is in general agreement with the rate of steady state subduction predicted from a plate motion model this implies that current coupling at the nankai trough is so strong that much of the relative plate motion is taken up by shortening of the leading edge of the overriding plate it seems that stronger interseismic coupling is realized on the segment where larger coseismic dislocation occurred and vice versa time fluctuation of plate coupling from 1995 to 1996 is found on a small segment

hemipelagic and turbiditic mudstone facies associations in the upper cretaceous gosau group of the northern calcareous alps austria abstract turbiditic and hemipelagic mudstones from the upper cretaceous to lower paleocene nierental formation of the northern calcareous alps austria can be differentiated by employing relatively simole laboratory and higher hemipelagic mudstones turn out to be characterized by finer grain sizes of the non carbonate fraction and higher carbonate contents sediment colour bioturbation distribution of microfossils weathering characteristics and bed sequence analysis were used as additional criteria to recognize the genetically different mudstone types for acquiring the non carbonate grain size data the samples were leached in hydrochloric acid and the remaining siliciclastic material was used for analysis with a sedigraph the median values of the grain size distributions of the turbidite mudstones reach up to 9 7 whereas the hemipelagic median values lie between 9 5 and 10 8 carbonate contents of the turbidite mudstones range between 22 and 68 those of the hemipelagic mudstones between 58 and 82 single bed profiles show distinct vertical trends of both grain size and carbonate content values for the turbidite mudstone division no such trends exist in the hemipelagic mudstone beds five basic types of turbiditic and or hemipelagic mudstones can be recognized 1 turbidite hemipelagite couplets 2 pure hemipelagic mudstone sequences 3 hemipelagic mudstone sequences with very thin turbiditic interacalations 4 a thorouthly mixed turbiditic hemipelagic mudstone type which is characterized by intense bioturbations and 5 mud turbidites without any hemipelagic intervals most of these types occur simultaneously at different localities of the nierental formation

upper devonian and mississippian foraminiferal and rugose coral zonations of belgium and northern france a tool for eurasian correlations the radiation of early carboniferous foraminifers and rugose corals following the devonian carboniferous crisis offers the best tool for high resolution correlations in the mississippian together with the conodonts in the tournaisian notably in the namur dinant basin however some of the guides are facies controlled and an integrated approach combining biostratigraphy sedimentology and sequence stratigraphy is critical to identify delayed entries potential stratigraphic gaps and to avoid diachronous correlations the main difficulty is in correlating shallow and deeper water facies at any given time in existing zonations the visean part of the scheme is always more detailed reflecting the widespread development of shallow water platforms in the early visean which created conditions more suitable for foraminifers and rugose corals over large areas in contrast the tournaisian zones less well documented reflect unfavourable environmental conditions in the lower ramp dinant sedimentation area and pervasive dolomitization of the inner ramp condroz and namur sedimentation areas recent progress in understanding the belgian early carboniferous sequence stratigraphy and lithostratigraphy and revision of the biostratigraphy of the key sections strongly modify former biostratigraphic interpretations improvements mainly concern the latest devonian the late tournaisian and the early visean the late devonian and the tournaisian are equated with foraminifer zones dfz1 to dfz8 and mfz1 to mfz8 respectively the visean correlates with zones mfz9 to mfz14 zone mfz15 straddles the visean namurian boundary and zone mfz16 is the youngest mississippian zone the rugose corals allow the recognition of ten zones rc0 to rc9 covering the strunian late famennian to serpukhovian interval discrepancies with former zonations are discussed the moliniacian stage is emended to restore the coincidence between its base and that of the visean

a mid tournaisian late visean carbonate ramp reconstructed from nappes and olistolites in the southern montagne noire france abstract the mainly calcareous succession from the mid tournaisian to the lower part of the upper visean in the southern montagne noire mont peyroux nappes and cabrieres slices is sedimentologically revised from the late visean the variscan orogeny affected the area and the studied mississippian part of the succession was considered as part together with the devonian of a period of tectonic quiescence later included as nappes and olistolites in a wildflysch this study presents the facies from pelagic limestones calciturbidites bioclastic limestones and microbial limestones and the relationship between platform and calciturbidites in the pre orogenic context of the montagne noire basin during the mississippian the differences in the lithostratigraphy is analyzed by means of four tectonostratigraphical units mont peyroux nappe roquessels band cabrieres area and la serre band previously defined by other authors that together with the deep water vieussan caragnas unit not studied here due to the poverty in chronostratigraphical data allow reconstructing the original carbonate platform the latter seems to correspond to a ramp for the latest tournaisian to early visean and a distally steppened ramp from the middle visean to the early late visean including basin plain to slope as the deepest water environments and middle ramp as the shallowest except for the uppermost part of the succession where the inner ramp is recognized during this period the shallowing tendency in the tectonostratigraphic units is well marked mont peyroux nappe roquessels band cabrieres area la serre band from deeper to shallower which differs from the shallowing trend defined by previous authors during the devonian strong similarities are observed with the preserved mississippian carbonates in the mouthoumet massif to the south which might represent the shallowest water deposits of the ramp not preversed in the cabrieres la serre areas

geodetic data inversion using a bayesian information criterion for spatial distribution of fault slip summary we developed a new inversion method to reconstruct static images of seismic sources from geodetic data using akaike s bayesian information criterion abic coseismic surface displacements are generally related with a slip distribution on a fault surface by linear integral equations parametric expansion of the fault slip distribution by a finite number of known basis functions yields a set of observation equations expressed in a simple vector form incorporating prior constraints on the smoothness of slip distribution with the observation equations we construct a bayesian model with unknown hyperparameters the optimal values of the hyperparameters which control the structure of the bayesian model are objectively determined from observed data by using abic once the values of hyperparameters are determined we can use the maximum likelihood method to find the optimal distribution of fault slip we examined the validity of this method through a numerical experiment using theoretical data with random noise we analysed geodetic data associated with the 1946 nankaido earthquake ms 8 2 by using this method the result shows that the fault slip distribution of this earthquake has two main peaks of 4 and 6 m located off kii peninsula and muroto promontory these two high slip areas are clearly separated by a low slip zone extending along kii strait such a slip distribution corresponds with the fact that the rupture process of this earthquake in the western part is notably different from that in the eastern part

crustal deformation at the nankai subduction zone southwest japan derived from gps measurements the interseismic strain accumulation process at the nankai subduction zone the plate boundary region between the philippine sea and the eurasian plates off southwest japan has been revealed by gps measurements spanning five years large strains characterized by a contraction of 2 2 3 4 10 7 yr have accumulated in a narrow region extending parallel to the strike of the plate boundary the contraction axes lie in a northwest southeast direction nearly parallel to the direction of relative motion of the philippine sea plate with respect to the eurasian plate gps derived deformation data including both rate and direction are consistent with the expected earthquake deformation cycle at the nankai subduction zone current interplate coupling in this zone is strong much of the relative plate motion has been taken up by deformation of the marginal parts of the eurasian plate

active tectonics of the andes nearly 90 mm a 1 of relative plate convergence is absorbed in the andean plate boundary zone the pattern of active tectonics shows remarkable variations in the way in which the plate slip vector is partitioned into displacement and strain and the ways in which compatibility between different segments is solved along any traverse across the plate boundary zone the sum of relative velocities between points must equal the relative plate motion we have developed a kinematic synthesis of displacement and strain partitioning in the andes from 47 s to 5 n relevant for the last 5 ma based upon 1 relative plate motion deduced from oceanic circuits giving a roughly constant azimuth between 075 and 080 2 moment tensor solutions for over 120 crustal earthquakes since 1960 3 structural studies of deformed plio pleistocene rocks 4 topographic geomorphic studies 5 palaeomagnetic data and 6 geodetic data we recognize four neotectonic zones with subzones and boundary transfer zones that are partitioned in different ways these zones are not coincident with the classic zones defined by the presence or absence of a volcanic chain or differences in finite displacements and strains and tectonic form the long term segmentation and finite evolution of the andes may not occur in constantly defined segments in space and time in segment 1 47 39 s the slip vector is partitioned into roughly orthogonal benioff zone slip with large magnitude large slip surface earthquakes and both distributed dextral shear giving clockwise rotations of up to 50 and dextral slip in the curved liquine ofqui fault system giving 5 10 of anticlockwise fore arc rotation in segment 2 39 20 s the slip vector is partitioned into benioff zone slip roughly parallel with the slip vector andean crustal shortening and a very small component of dextral slip including that on the atacama fault system between 39 and 34 s a cross strike dextral transfer which deflects the chile trench and the volcanic arc absorbs the shortening contrast between segments 1 and 2 in segment 3 20 6 s the slip vector is partitioned into roughly orthogonal benioff zone slip crustal shortening sinistral trench parallel faulting and northeast southwest extension compatibility between segments 2 and 3 is maintained by the sinistral east southeast trending cochabamba shear zone and north trending dextral faults in segment 4 6 s to 5 n the slip vector is partitioned into roughly orthogonal benioff zone slip and dextral strike slip faulting in the fore arc and volcanic chain

insight into the development of a carbonate platform through a multi disciplinary approach a case study from the upper devonian slope deposits of mount freikofel carnic alps austria italy the development and behavior of million year scaled depositional sequences recorded within palaeozoic carbonate platform has remained poorly examined therefore the understanding of palaeoenvironmental changes that occur in geological past is still limited we herein undertake a multi disciplinary approach sedimentology conodont biostratigraphy magnetic susceptibility ms and geochemistry of a long term succession in the carnic alps which offers new insights into the peculiar evolution of one of the best example of palaeozoic carbonate platform in europe the freikofel section located in the central part of the carnic alps represents an outstanding succession in a fore reef setting extending from the latest givetian indet falsiovalis conodont zones to the early famennian lower crepida conodont zone sedimentological analysis allowed to propose a sedimentary model dominated by distal slope and fore reef slope deposits the most distal setting is characterized by an autochthonous pelagic sedimentation showing local occurrence of thin bedded turbiditic deposits in the fore reef slope in a more proximal setting there is an accumulation of various autochthonous and allochthonous fine to coarse grained sediments originated from the interplay of gravity flow currents derived from the shallow water and deepwater area the temporal evolution of microfacies in the freikofel section evolves in two main steps corresponding to the freikofel unit 1 and the pal unit 2 limestones distal slope to fore reef lithologies and associate changes are from base to top of the section u1 thick bedded litho and bioclastic breccia beds with local fining upward sequence and fine grained mudstone intercalations corresponding in the fore reef setting to the dismantlement of the eifelian frasnian carbonate platform during the early to late frasnian time falsiovalis to rhenana superzones with one of the causes being the late givetian major rift pulse u2 occurrence of thin bedded red nodular and cephalopod bearing limestones with local lithoclastic grainstone intercalations corresponding to a significant deepening of the area and the progressive withdrawal of sedimentary influxes toward the basin in relation with late frasnian sea level rise ms and geochemical analyses were also performed along the freikofel section and demonstrate the inherent parallel link existing between variation in ms values and proxy for terrestrial input interpretation of ms in terms of palaeoenvironmental processes reflects that even though distality remains the major parameter influencing ms values carbonate production and water agitation also play an important role