diatom productivity peak and increased circulation during latest quaternary alboran basin western mediterranean abstract diatoms were studied quantitatively in six latest quaternary 70 kyr b p to recent piston cores from the westernmost mediterranean the alboran basin and the atlantic region immediately to the west of the straits of gibraltar the atlantic cores completely lack diatoms in the alboran basin diatoms are common from late stage 3 27 5 kyr b p to termination ib 9 kyr b p and in recent core tops but are absent in the other latest quaternary intervals maximum accumulation of diatoms and highest abundance of species normally in sediments associated with increased productivity occurred during the latest quaternary deglaciation in the first phase of termination i 14 8 kyr b p in the modern alboran basin a region of high biological productivity occurs immediately east of the gibraltar straits this high productivity results from upwelling associated with the interaction between the atlantic inflow and the bottom topography near the spanish coast the upwelled nutrient rich waters are then advected to the east and southeast by the surficial anticyclonic gyral circulation late quaternary variations in diatom abundance are considered to reflect changes in this upwelling intensity with highest diatom abundances inferred to result from increased upwelling associated with an intensification of the anticyclonic gyral circulation highest inferred upwelling rates occurred during the first phase of latest quaternary deglaciation it is possible that an intensification of circulation within the mediterranean basin as a whole occurred from late stage 3 to mid termination i because widespread hiatus formation has been reported at this time in the straits of sicily due to an increase in the formation of intermediate waters diatoms were not preserved in other latest quaternary intervals due to insufficient productivity to counterbalance their dissolution

diatom derived ssts td ratio indicate warm seas off japan during the middle holocene 8 2 3 3 kyr bp abstract regression analysis was performed between the ratio of warm and cold water diatoms td ratio in 123 surface sediment samples in the northwest pacific ocean and the mean annual sea surface temperatures ssts c at the core sites in order to calibrate this proxy for paleo temperatures equations to derive annual sst c from diatom analysis were somewhat different for the tohoku area y 6 5711 0 273 r 0 89946 than for the japan sea y 5 4069 0 26841 r 0 89088 the annual paleo ssts c in the tohoku area were in general higher than in the japan sea despite lower td values because the warm water species fragilariopsis doliolus is abundant only in the tsushima warm current in the japan sea the reliability of the equations is supported by our understanding of the ecology of recent diatoms td derived annual paleo ssts c agree with alkenone derived summer paleo sst c at a site off central japan in the northwestern pacific in a south to north transect of cores around honshu and hokkaido paleo ssts c decreased when the kuroshio and tsushima warm currents weakened the middle holocene 8 2 3 3 cal kyr bp was warmer by 1 2 c than earlier and later parts of the holocene and mean annual paleo ssts c show rhythmic fluctuations with durations of 1000 years and 400 500 years these new data show that annual ssts were warm in the northwestern pacific at times that the northeastern pacific was cold in addition oceanic warm and cold water species defined by kanaya and koizumi kanaya t koizumi i 1966 interpretation of diatom thanatocoenoses from the north pacific applied to a study of core v20 130 studies of a deep sea core v20 130 part iv sci rep tohoku univ 2nd series geol 37 89 130 and koizumi et al koizumi i irino t oba t 2004 paleoceanography during the last 150 kyr off central japan based on diatom floras mar micropaleontol 53 293 365 are illustrated

japan sea oxygen isotope stratigraphy and global sea level changes for the last 50 000 years recorded in sediment cores from the oki ridge abstract we obtained twenty ams accelerator mass spectrometry radiocarbon dates 2 tephra layer chronologies and a planktonic foraminiferal 18 o stratigraphy for the last 50 000 years from japan sea cores from the oki ridge in this paper we report ams 14 c results that allow us to reconstruct a high resolution chronology of the cores and discuss millennial scale climate changes recorded in japan sea sediments the sedimentation rate for the site increased dramatically from the glacial stage to the holocene as a result of significant hydrological changes associated with deglaciation and global sea level rise a lighter 18 o anomaly for the planktonic foraminifers was found during the lgm last glacial maximum this shift corresponds to a freshening of the japan sea surface waters and is mainly due to a global sea level drop rather than anomalously warm ssts sea surface temperatures as previously reported our record combined with the global sea level data suggests that the lgm started about 30 kyr ago and that the salinity of the japan sea became fresher than at present the ssts during mis marine oxygen isotope stage 3 were relatively stable and global sea level was not lower than ca 80 m the surface water of the japan sea attained normal saline levels following the younger dryas cold event and reached the present day 18 o values 7 kyr ago

late quaternary paleoceanographic changes in the southwestern okhotsk sea evidence from geochemical radiolarian and diatom records abstract high resolution analyses of geochemical parameters biogenic opal calcium carbonate organic carbon and nitrogen and microfossil assemblages diatoms and radiolarians on core md01 2412 clarified detailed paleoceanographic changes such as sea ice cover and biological production in the southwestern okhotsk sea during the last 115 kyr an age model of core md01 2412 was established based on 18o stratigraphy accelerator mass spectrometer ams 14c and tephrochronology sea ice history reconstructed by siliceous microplankton records indicated that the present sea ice condition was formed during the last 8 kyr only during marine isotope stage mis 2 was the duration of sea ice cover in this region much longer than that of today 4 5 months a year two diatom species thalassionema nitzschioides and fragilariopsis doliolus revealed that the soya warm current water swcw flowed into the okhotsk sea near the site of core md01 2412 during the last 12 14 kyr and during mis 5a and was associated with sea level rise biological productivity rapidly increased during mis 1 associated with sea ice retreat two major increases of organic carbon oc contents wt and corg n ratios were observed and the timings of these events were 15 8 16 7 ka event 1 and 13 1 13 6 ka event 2 corresponding to these events the abundance of cycladophora davisiana an intermediate water dwelling radiolarian species increased this high c davisiana abundance can be correlated to the input of terrestrial organic matter from the submerged shelf to the intermediate water apart from the radiolarians the production of diatoms in the surface waters was suppressed by the development of well stratified surface water along with sea ice melting during the early holocene diatom production increased gradually during the last 10 kyr with enhanced vertical mixing

interannual variability of the kuroshio transport in response to the wind stress field over the north pacific its relation to the path variation south of japan we have investigated the interannual variability in the kuroshio transport focusing on the baroclinic response of the upper ocean to the long term variation of the wind stress field over the north pacific from 1961 to 1987 first temporal change of the kuroshio transport at the western boundary from 17 to 31 n has been estimated on the assumptions that the kuroshio is a baroclinic flow confined in the upper layer and that the effect of interior wind stress curl on the volume transport at the western boundary is transferred by nondispersive baroclinic rossby wave peak values in the estimated transport appear in its beginning region 17 21 n when or just before the kuroshio settles into a meandering state south of japan in 1975 1981 and 1986 these peaks are due to negative wind stress curl anomalies which are induced by the intensified trade winds in the central and eastern tropical north pacific on and just after an el nino event and in the western tropical north pacific months to years before the next el nino event such peaks are not found in the barotropic sverdrup transport in downstream regions i e in the east china sea and south of japan north of 23 n on the contrary the estimated transports through baroclinic and barotropic responses do not have such good correlation to the path variation temporal change in thermocline depths estimated from bathythermograph data clearly shows the westward propagations of positive anomalies by nondispersive baroclinic rossby waves at latitudes of the beginning of the kuroshio south of 21 n which is in phase with peaks of the kuroshio baroclinic transport at the western boundary on the other hand there are only the local propagations of the anomalies in the downstream regions as previous studies reported however it is emphasized that temporal change of the geostrophic transport in the east china sea 28 n is coincident with that of the baroclinic transport at the beginning of the kuroshio not with that at the same latitude a numerical experiment with a nonlinear reduced gravity model confirms that temporal changes of the transport in the east china sea and south of japan are due to the advective nonlinear effect of the kuroshio itself while the linear baroclinic response to the wind stress field is dominant in its beginning region

structure of the riddleville basin from cocorp seismic data and implications for reactivation tectonics seismic reflection data collected during cocorp s traverse of the southern appalachians reveal that the triassic riddleville basin is a half graben defined by strong north dipping basal reflections truncated on the north by a major south dipping normal fault lithologies observed in similar basins suggest that these high amplitude continuous reflections may be from lacustrine sediments or basaltic layers the high angle border fault soles into the augusta fault a major south dipping low angle paleozoic thrust geometric relations suggest that formation of the riddleville basin reactivated this older appalachian fault

varieties of a single cosmopolitan diatom species associated with surface water masses in the north pacific abstract a time series of 65 sediment trap samples representing 48 month changes in diatom flora and 62 sediment core tops from the western north pacific ocean were analyzed varieties of a single diatom species were found to be characteristic of two surface water masses bounded by the kuroshio current thalassionema nitzschioides var incurvata var inflata and var parva dominate in warm saline waters in the subtropical gyre while t nitzschioides sensu stricto is abundant in less saline waters northwest of this current time series data on percent abundances for the three t nitzschioides varieties in the t nitzschioides complex are compared with path variations of the current south of japan inter annual fluctuations in percent abundance are linked to changes in surface water masses over the sediment traps in association with migration of the kuroshio paths this finding makes the percent abundance a useful tool for deciphering path migrations of the kuroshio current in the geologic past down core analyses of two sediment cores collected beneath the modern kuroshio current were performed a sharp increase in percent abundances from 12 to 9 kyr bp with an abrupt change around 11 kyr bp records the previously reported transition of the kuroshio current from a predominantly offshore path to its modern path path migrations of the kuroshio current may be inferred from percent abundances of these diatoms which comprise a new proxy for delineating the paleoclimate of the northwestern pacific in relation to changes in northward heat transport from the western equatorial pacific ocean by the western boundary current

intraplate extensional tectonics of the eastern basin range inferences on structural style from seismic reflection data regional tectonics and thermal mechanical models of brittle ductile deformation the general lack of a correlation between earthquakes and surface faulting in the interior of the western u s cordillera has motivated our efforts to evaluate the geometry structural style and mechanism of normal faulting characteristic of this region of intraplate extension to address the problem we have interpreted over 1500 km of seismic reflection data and constructed detailed cross sections of the upper crust rheological models of the continental crust were calculated to examine the possibility of shallow quasi plastic flow and its influence on faulting in the eastern basin range the western colorado plateau and the middle rocky mountains our data and interpretations have revealed the following styles of cenozoic deformation 1 steep to low angle dip normal faulting along the wasatch fault 2 low angle dip and listric normal faulting possibly associated with movement on preexisting thrusts 3 the occurrence of asymmetric mostly eastward tilted tertiary basins that are bounded by low to moderate dipping planar and listric faults and 4 at least three vertically stacked en echelon low angle reflections in the mid to upper crust that dip gently westward from 3 km beneath the wasatch plateau to over 15 km at the utah nevada border these reflections are interpreted as normal detachment faults the structural style of the pervasive low to moderate angle dipping faults cannot be easily reconciled with classic brittle failure theory but the interpreted termination of normal faults at or above the deeper low angle reflections suggests the presence of shallow zones of ductile deformation that may have accommodated slip an important observation based on interpretations of seismic reflection profiles is that normal fault zones dip more gently in the subsurface than their associated scarps in unconsolidated surficial deposits segment boundaries of the wasatch fault zone apparently coincide with the positions of east trending displacement transfer structures in thrust sheets and the position of the precambrian uinta aulacogen suggesting that preexisting crustal structure partly controls the geometry of extension to examine the influence of ductile deformation quasi plastic flow was modeled for appropriate geotherms of the basin range and colorado plateau crusts these models provide constraints on the depth to the frictional quasi plastic transition that occurs as shallow as 8 km in the eastern basin range this depth also corresponds to the approximate depth above which most accurately determined earthquake foci for small earthquakes m 5 5 appear to nucleate at 10 15 km in or near the brittle ductile transition the rheological modeling suggests that a thermally deforming continental lithosphere plays an important role in the evolution of this extending intraplate region large scale low angle reflections may represent decollements and normal faults at the top of upper crustal zones of reduced shearing strength and higher ductility

tectonics and topography for a lithosphere containing density heterogeneities the purpose of this paper is to clarify the dynamic role of lithospheric density heterogeneities in particular with respect to mountain building and other processes of intraplate deformation density anomalies within or just beneath the lithosphere constitute major sources for tectonic stress fields the product of their magnitude by their depth is shown to characterize their ability to induce deformation this rule of the density moment directly yields the lithospheric thickening or thinning rate when applied to structures of large lateral extent for anomalies of lateral extent that is small in comparison with their depth the deformation is vertically inhomogeneous and has been computed with the help of simple physical models of a stratified viscous newtonian lithosphere the analytical treatment is based on fourier transform continent continent collision thickens not only the crust but the entire lithosphere the cold root underlying a mountain chain induces strong regional compressive stresses able to sustain the mountain bulding process without further help from forces transmitted from far away thus the continental lithosphere is in a somewhat metastable mechanical state adiabatic i e rapid thickening or thinning tends to grow further once initiated tectonic phases of strong compression correspond to the climax of such instabilities the response of models with cold lithospheric roots of various intensities has been computed both in two and three dimensions they yield velocity distributions and stress fields instructive comparisons are made with earthquake focal mechanisms and in situ stress measurements in the alpine and appalachian regions in the presence of lateral variations of the mechanical properties of the lithosphere the tectonic style is not only function of the local topography and of the nature of its compensation deformations in neighbouring provinces are coupled as shown by 3 dimensional models for example thickening sustained by a cold lithospheric root may generate extension in peripheral zones of weakness these last results illustrate the point that the computation of regional tectonic stresses requires the knowledge of the density anomalies within the lithosphere on the one hand and of geometrical constraints related to lateral mechanical heterogeneities on the other

the influence of depth on reactivation in normal faulting abstract the study examines the influence of depth on the development of steep normal faults above a gently dipping fault which is reactivated in its deeper part and abandoned in its upper part the isotropic and anisotropic mohr coulomb anderson theory is used to determine the ability of any part of a fault to be reactivated by calculating the difference between the stress deviator necessary to induce reactivation and that required to induce fracturing when linear depth dependent properties are assumed it appears that a new normal fault can branch off a gentle pre existing fault only if the friction coefficient of the latter is much less than that used by byerlee and if the ratio cohesion of fault cohesion of intact rock is non negligible for a 30 dip fault the friction coefficient has to be less than 0 35 friction angle less than 20 neither pore fluid pressure nor constant excess fluid pressure affects the above conditions when the cohesion of the surrounding rocks increases with depth steep normal faults can branch off byerlee faults with dips as gentle as 30 a low shear strength of the lowest part of the preexisting fault also increases the chances of reactivation of the deeper part and abandonment of the upper part

the ancash peru earthquake of 1946 november 10 evidence for low angle normal faulting in the high andes of northern peru summary the ancash peru earthquake is the largest and best documented intracontinental normal fault earthquake to have occurred in historically recorded time along the andean margin of south america the fault geometry and the rupture processes of this earthquake provide information on how normal faulting develops in a predominantly compressional regime and on the hazards associated with normal faulting in other parts of the andes a re evaluation of first motion data intensity data and epicentre locations coupled with waveform modelling suggests that the earthquake occurred along a fault that dips 30 10 at a hypocentral depth of 15 17 km geological information also suggests that the earthquake reactivated an older thrust fault that was favourably orientated with respect to the present regional stress regime

pliocene pleistocene evolution of the north pacific ocean atmosphere system interpreted from fossil diatoms the relative abundance of diatom taxa in 216 core tops has been quantified and compared using cluster analysis with assemblages in six cores located beneath different water masses of the north pacific ocean all but one sequence span at least 1 5 m y early pleistocene to holocene and one extends to 2 6 ma the quantitative abundance of each taxon and the space time occurrence of each cluster are interpreted as tracers of oceanographic conditions in addition to high frequency glacial interglacial oscillations the records display rapid steplike changes at 2 4 ma 1 6 1 5 ma 1 0 ma 0 8 0 7 ma and 0 35 ma two secondary transitions recorded only in the northwestern cores occur at 2 0 ma and 1 1 ma we conclude that both the high frequency oscillations and the stepwise transitions reflect variations in extent of subarctic water masses under the influence of the siberian high pressure and aleutian low pressure atmospheric cells we further conclude that 1 the subarctic water mass has developed progressively and attained its modern structure only in the late pleistocene 2 some stages of this evolution may have occurred earlier in the eastern subarctic 3 the holocene is an atypical warm extreme so that the present is not a very good key to the past 4 there were several glaciations between 2 4 and 2 0 ma and 5 the subtropical gyre is more conservative than the subarctic gyre and major changes in the region have been due to forcing from the north we propose a conceptual model of oscillating metastable climatic modes maintained by internal feedback and suggest that steplike changes may occur when one set of boundary conditions is temporarily exceeded

structural discordance between neogene detachments and frontal sevier thrusts central mormon mountains southern nevada detailed geologic mapping in the mormon mountains of southern nevada provides significant insight into processes of extensional tectonics developed within older compressional orogens a newly discovered wsw directed low angle normal fault the mormon peak detachment juxtaposes the highest levels of the frontal most part of the east vergent mesozoic sevier thrust belt with autochthonous crystalline basement palinspastic analysis suggests that the detachment initially dipped 20 25 to the west and cut discordantly across thrust faults nearly complete lateral removal of the hanging wall from the area has exposed a 5 km thick longitudinal cross section through the thrust belt in the footwall while highly attenuated remnants of the hanging wall nowhere more than a few hundred meters thick structurally veneer the range the present arched configuration of the detachment resulted in part from progressive domino style rotation of a few degrees while it was active but is largely due to rotation on younger structurally lower basement penetrating normal faults that initiated at high angle the geometry and kinematics of normal faulting in the mormon mountains suggest that pre existing thrust planes are not required for the initiation of low angle normal faults and even where closely overlapped by extensional tectonism need not function as a primary control of detachment geometry caution must thus be exercised in interpreting low angle normal faults of uncertain tectonic heritage such as those seen in the cocorp west central utah and birp s moist deep reflection profiles although thrust fault reactivation has reasonably been shown to be the origin of a very few low angle normal faults our results indicate that it may not be as fundamental a component of orogenic architecture as it is now widely perceived to be we conclude that while in many instances thrust fault reactivation may be both a plausible and attractive hypothesis it may never be assumed

postglacial environmental change of the pacific ocean off the coasts of central japan abstract downcore changes in microfossil assemblages and oxygen isotope ratios in three piston cores recovered from the northwestern pacific off central japan show that the subtropical kuroshio front was located to the south of c 4 core site lat 33 n during the last glacial the front then advanced northward passing over the c 4 site and the c 6 site 34 6 n at about 13 ka and 10 ka respectively and reached the c 1 core site 36 n at about 7 ka after 5 5 ka it retreated to the area between the c 1 and c 6 sites a brief but significant cold event the readvance of the cold oyashio current is recognized between 11 and 10 ka in the two northern cores but the current did not reach the southern c 4 site a contemporaneous cold event is known in the north atlantic and the cooling was probably a global phenomenon likely to be associated with lowering of sea level contamination of isotopically light water is apparent between 14 and 11 ka in the marked change in isotopic composition of benthic foraminifers oxygen isotope ratios of planktonic foraminifers show that prior to the advance of the kuroshio front the surface water at these core sites was isotopically lighter than the kuroshio water at that time

living diatom assemblages from north pacific and bering sea surface waters during summer 1999 diatom assemblages collected during july august 1999 along an e w transect comprising sixty two north pacific and bering sea surface water samples were identified and enumerated absolute abundance profiles of centric and raphid pennate diatoms show that the former group dominates in shallow coastal waters and through island passes whilst the latter group though less numerous dominates the oceanic regions this pattern is interpreted as nutrient related with centric diatoms especially chaetoceros section hyalochaete minidiscus and thalassiosira spp preferring eutrophic and upwelling conditions and raphid pennate diatoms especially nitzschioid genera like fragilariopsis neodenticula and pseudo nitzschia preferring oligotrophic pelagic conditions the absolute abundances of the two sections of chaetoceros chaetoceros ex phaeoceros and hyalochaete and some species belonging to the thalassiosirales and bacillariaceae show distribution patterns that can be interpreted as preferences for shallow or oceanic waters subtropical or subarctic waters or ice related arctic conditions r 2005 elsevier ltd all rights reserved

unstable holocene climate in the northeastern east sea sea of japan evidence from a diatom record abstract a total of 45 and 42 sediment subsamples from gravity cores gh98 1223 and gh98 1227 respectively were obtained in the northeastern east sea sea of japan and analyzed for diatom abundance a 14 c date for sediment organic carbon gh98 1223 along with probable and plausible correlation to the well established timeframe constrains the age to the mid to late holocene abundances of most species including neodenticulopsis seminae simonsen and kanaya simonsen and fragilariopsis doliolus wallich grunow were less than 20 in average relative to the most dominant species thalassionema nitzschioides grunow hustedt which ranged from 29 to 59 for core gh98 1223 and between 23 and 46 for core gh98 1227 frequencies of cold water species were generally higher than those of warm water species because of the high latitude cold water occupying dominantly in the basin the vertical distribution of cold water species was largely opposite to that of warm water species for example the frequency of a cold water species n seminae was inversely related to that of a warm water species f doliolus we conclude that changes in abundance of f doliolus and diatom temperature index t d value represent quasi periodic fluctuations demonstrating that the tsushima warm current and its branch of the soya warm current play a significant role in the transportation of diatom cells and heat the pulse like oscillations of this indicator species which are observed in basin wide and regional scales reflect that the strength or intensity of the dominant current is governed by a globally induced unstable climatic system during the holocene period

variations of current path velocity and volume transport of the kuroshio in relation with the large meander abstract the variations of the kuroshio current path and their relations with current velocity volume transport and upstream position of the kuroshio are examined using sea level data after the long time non large meander nlm path during 1963 75 the kuroshio takes a large meander lm path during most of 1975 91 1975 80 1981 84 1986 88 and 1989 91 the study of these meanders confirms the description of the path of the kuroshio based on the three typical paths and the transitions between them with an exception being the 1981 84 lm path the formation and decay of the large meander are associated with velocity and position of the kuroshio in the tokara strait south of kyushu a small meander precursor of the large meander seems to be formed southeast of kyushu in relation with a temporary increase of kuroshio velocity and a northward shift of the kuroshio in the tokara strait an eastward propagation of the small meander leading to the lm formation is associated with remaining in the northe

variability of the path of the kuroshio ocean current over the past 25 000 years the kuroshio current is the strong northwestern component of the subtropical north pacific ocean gyre and advects a large amount of heat from the tropics to northern mid latitudes the kuroshio has bimodal stationary flow patterns with small and large meander paths east of central japan1 2 which switch on annual and decadal timescales3 4 these switches seem to be caused by changes in current velocity and volume transport of the north equatorial current that are associated with variations in the trade wind intensity in the eastern equatorial north pacific ocean5 6 here we present alkenone derived sea surface temperature records at multicentennial resolution from sediment cores from the nishishichitou ridge off central japan these 25 000 year records show that the kuroshio path has also fluctuated on millennial timescales this variability resembles that of the subtropical high pressure of the north pacific reconstructed from terrestrial pollen distributions water levels in north american lakes and marine micropalaeontological records7 together these data indicate that climate variability off central japan over the past 25 000 years may be part of a circum pacific phenomenon reflecting the rate of subtropical surface circulation in the north pacific ocean

palaeomagnetic and structural evidence of neogene tectonic rotation of the gran sasso range central apennines italy abstract interference between discordant tectonic trends in the central apennines italy was investigated in a palaeomagnetic study of the arc shaped e w to n s oriented overthrust units of the lazio abruzzi carbonate platform gran sasso and the underlying n s oriented imbricates of the marche pelagic domain mt dei fiori samples were taken from 26 sites in the cretaceous palaeogene scaglia formation and in the messinian lower pliocene laga flysch stepwise thermal demagnetization was used to remove secondary components and a stable direction of the characteristic remanent magnetization chrm was determined for 24 sites the palaeomagnetic results point to counter clockwise rotation of the marche domain similar to that of the southern umbria directions in both the scaglia and laga formations of the lazio abruzzi units show counter clockwise rotations up to 90 in the easternmost segment of the gran sasso belt this setting may be framed in a structural context wherein superposition of the e w oriented gran sasso belt onto the n s oriented marche imbricates derives from progressive rotation of the lazio abruzzi platform decoupled by right lateral shearing along the n s oriented rigopiano bussi rivisondoli shear zone

anatomy of late orogenic extension the northern apennines case abstract late orogenic extensional structures overprint the compressional structures of the northern apennines fold and thrust belt the tyrrhenian sea is the result of major continental extension and rifting which started in the thickened zone of the apulian corso sardinian collision it is believed to have commenced as early as in the late oligocene or early miocene in the corsica basin extension post dates the collision by approximately 20 ma the extensional stress field observed in the internal part of the northern apennines co exists with compression in the foreland part of the belt field borehole and refraction and reflection data were used to investigate the geometry of extension and how it affected the compressional abric in the northern apennines analysis of the collected data has revealed a complex geometry for the extension across the belt a geological cross section from the island of elba to the west of the italian peninsula to ancona in the east as well as a geodynamic model for the evolution of the northern apennines is presented and discussed from the early miocene stretching of the collision thickened crust created a n s rift which evolved into the present northern tyrrhenian sea typically two sets of extensional faults a low angle e dipping and a w dipping one are observed across the chain usually the w dipping faults have similar attitudes to those of the older reverse faults reactivating some of the thrusts as normal faults the e dipping normal faults however cut down section through the pre existing thrusts and in the internal part of the belt accommodate most of the displacement associated with extension a change in fault polarity occurs in the tuscan region and major faults dip towards the west a type subduction of the apulian crust under the corso sardinian block occurred after collision leading to the delamination of the apulian lithospheric mantle away from the crust collision induced delamination of the mantle lithosphere away from the zone of collision resulted in mechanical thinning of the lithosphere beneath the orogenic belt this process induced late orogenic crustal stretching in the internal zone of the northern apennines as the convergence between the apulian and corso sardinian blocks continued the extensional and compressional fronts accompanied by the delamination migrated from the hinterland towards the foreland of the orogen

normal faulting in the upper continental crust observations from regions of active extension abstract observations of present day normal faulting in regions of active continental extension may be helpful when interpreting the geological record in older extensional basins the most obvious manifestation of active extension is normal faulting in earthquakes earthquake foci are mostly confined to the upper seismogenic continental crust whose thickness imposes a scale on the observed deformation large earthquakes move faults with lengths similar or large compared with the thickness of the seismogenic layer large seismogenic normal faults on the continents appear to be restricted to a dip range of around 30 60 dips significantly gentler than 20 have not been observed in fault plane solutions of large earthquakes large seismographic normal faults are approximately planar in cross section and cut through the base of the upper seismogenic layer rotating about a horizontal axis as they move a reasonable estimate of the regional extension can often be made from the dip of the large normal faults and the tilt of the blocks they bound the domino model such faults are rarely continuous for more than 15 20 km but commonly change strike or step in an en echelon fashion this segmentation may occur on a scale controlled by the thickness of the seismogenic layer and is an important influence on sedimentation and drainage these observations are common to large seismogenic normal faults from a variety of tectonic settings and suggest that the kinematics of normal faulting may not be strongly influenced by the forces responsible for the extension which can vary widely in nature and magnitude small earthquakes which move faults that are small compared with the seismogenic layer thickness show no simple pattern and often can be interpreted as internal deformation of blocks bounded by large faults in some places the seismogenic basement faults do not reach the surface but are decoupled from the sedimentary cover by layers of weak lithology faults in the sedimentary cover may be strongly curved in cross section requiring their hangingwalls to deform internally estimating extension from such faults is not straightforward and requires a knowledge of the hangingwall deformation estimates made in this way are often very non unique and prone to large errors we postulate that the thickness of the seismogenic upper crust controls both the maximum length of large normal fault segments along strike and the maximum size of blocks that can rotate coherently about a horizontal axis

flexural uplift of rift flanks due to mechanical unloading of the lithosphere during extension we suggest that the uplift of rift flanks results from mechanical unloading of the lithosphere during extension and consequent isostatic rebound this mechanism is presented as an alternative to explanations for rift flank uplift involving thermal or dynamic processes and magmatic thickening of the crust our hypothesis is based on two critical concepts first the lithosphere retains finite mechanical strength or flexural rigidity during extension second isostatic rebound uplift of the lithosphere follows when the kinematics of extension produces a surface topographic depression that is deeper than the level to which the surface of the extended lithosphere would subside assuming local isostatic compensation we develop and analyze two kinematic models for instantaneous extension of the lithosphere to show that flexural rebound is a viable explanation for the uplift of rift flanks we first investigate the isostatic consequences of finite simple slip on an initially planar dipping normal fault cutting the entire lithosphere when the lithosphere retains flexural rigidity during extension the topography resulting from this model resembles a half graben and the footwall rift flank is flexurally uplifted this simple normal faulting model explains free air gravity anomalies and topography observed at rift flanks in oceanic lithosphere such as broken ridge in the eastern indian ocean the caroline ridges sorol trough in the western equatorial pacific and the coriolis trough behind the new hebrides island arc we then investigate a general kinematic model for lithospheric extension where simple slip on a surface of arbitrary shape is accompanied by pure shear extension in the upper and lower plates when the simple slip component is not zero or the distribution of pure shear in the upper and lower plates is not identical the surface of slip can be regarded as a detachment by simplification our general model accounts for pure shear extension of the lithosphere that is uniform with depth in this case detachments have no meaning in the geologic sense however the kinematics of depth independent pure shear may nevertheless be described in terms of a surface which we term a kinematic reference surface at some depth in the lithosphere we speculate that the depth of this surface may be rheologically controlled the magnitude of rift flank uplift by flexure depends critically on the depth of this reference surface in contrast if local isostasy is assumed when the lithosphere undergoes a given amount of depth independent pure shear the resulting topography will be the same regardless of how the kinematics of that extension are formulated the basin and rift flank topography and free air gravity anomaly over young continental rifts such as the rhine graben can be satisfied using our general extensional model with a small amount 5 km of extension along a listric shaped detachment soling into the crust mantle boundary because the flexural rebound mechanism explains the observed topography and gravity anomaly over both oceanic and continental extensional domains we suggest that rheological differences between the two lithospheric types may not be important in their overall response to extension

diatom distributions in northern north pacific surface sediments and their relationship to modern environmental variables abstract the quantitative analysis of diatom assemblages preserved in 52 samples from the bellingshausen and the amundsen seas provides the first comprehensive view on the distribution of diatoms in surface sediments of the eastern and central pacific sector of the southern ocean on a latitudinal transect along 120 w diatom valve accumulation rates ar reach maximum values 8 10 108 valves m 2 yr 1 in a zone extending over ca 900 km between the antarctic polar front and the maximum average winter sea ice extent and exceed those ars obtained from an eastern transect along 90 w by one order of magnitude lowest diatom concentrations 1 3 106 valves g 1 were encountered in sediments of the sea ice zone affected by winter and summer sea ice the accumulation rate pattern of the most abundant diatom fragilariopsis kerguelensis 50 abundance in 47 samples mirrors the pattern of the total diatom valve ar and the biogenic silica bsi ar making f kerguelensis the major contributor to the bsi preserved at the sea floor relative abundances of diatom species and species groups were statistically compared with a selection of environmental variables such as the mean summer sea surface temperature and salinity mean annual surface nutrient concentration nitrate phosphate silicon mean annual water column stratification mixed layer depth in summer and mean summer and winter sea ice concentrations polynomial canonical redundancy analysis rda revealed the biogeographic distribution of diatom species had the strongest relationship with summer sea surface temperature ssst out of the nine tested environmental variables this relationship accounted for 69 6 of the total variance of the diatom distribution with 29 7 explained by the first gradient significantly correlated to ssst with r2 0 941 and 15 6 explained by the second gradient correlated to both summer and winter sea ice and silicon concentration azpeitia tabularis hemidiscus cuneiformis and roperia tesselata were associated with warmer water conditions 4 c whereas fragilariopsis curta f separanda f rhombica and thalassiosira gracilis were correlated with cold ssst confirming these environmental relationships is crucial for the development of reference data sets used in quantitative estimations of palaeoclimatic and palaeoceanographic conditions with statistical methods this new data set represents the first modernised treatment of diatom remains from the se pacific ocean and generally supports the use of a circum polar database for the determination of summer sst sea ice and potentially biogenic silica distribution of the southern ocean back into the late quaternary

basinward migration of rift border faults implications for facies distributions and preservation potential basinward migration of half graben footwall margins occurs throughout the active aegean extensional province and has significant implications for facies distributions and preservation potential in synrift fills worldwide recognition of this phenomenon is particularly important for predicting the preservation and distribution of hydrocarbon reservoirs in rift basins using an example from the gediz graben of western turkey it is shown that basinward migration of footwall margins exhumes proximal facies of lateral sedimentary systems severely limiting their preservation potential and providing a ready source of easily erodible material this in turn leads to the generation of extensive footwall derived depositional systems which frequently displace axial drainage systems toward the hanging wall dip slope

spatial and temporal variability of surface water in the kuroshio source region pacific ocean over the past 21 000 years evidence from planktonic foraminifera abstract the kuroshio current is the major western boundary current of the north pacific ocean and has had a large impact on surface water character and climate change in the northwestern pacific region the kuroshio current becomes a distinctive surface flow in the ryukyu arc region after diverging from the north equatorial current and passing through the okinawa trough therefore the ryukyu arc area can be called the kuroshio source region we reconstructed post 21 ka time space changes in surface water masses in the ryukyu arc region using 15 piston cores which were dated by planktonic 18 o stratigraphy and ams 14 c ages our analysis utilized spatial and temporal changes in planktonic foraminiferal assemblages which were classified into the kuroshio subtropical coastal and cold water groups on the basis of modern faunal distributions in the study region these results indicate that the kuroshio current and adjacent surface water masses experienced major changes during 1 the last glacial maximum lgm and 2 the so called pulleniatina minimum event pme from 4 500 to 3 000 yr bp the kuroshio lgm event corresponds to severe global cooling and is marked by decreases in planktonic 18 o values and estimated sea surface temperature sst with the dominance of the cold water group of planktonic foraminifera cooling within the kuroshio source region was enhanced during the lgm event because the kuroshio current was forced eastward due to the formation of a land bridge between taiwan and the southern ryukyu arc which prohibited its flow into the okinawa trough except for the severe reduction and disappearance of the pulleniatina group no clear cooling signal was identified during the pme based on 18 o values estimated sst values and variations in the composition of planktonic foraminiferal faunas the pme assemblages are marked by high abundances of neogloboquadrina dutertrei a distinctive kuroshio type species along with other species assigned to the coastal and central water groups subtle ecological differences exist between pulleniatina obliquiloculata and n dutertrei i e p obliquiloculata exhibits lower rates of reproduction under conditions of lower primary productivity in the central equatorial pacific ocean el nino like conditions in the equatorial pacific ocean result in lower rates of surface transport in the kuroshio current in turn this response triggers lower rates of primary productivity in central equatorial surface waters as well as in the upstream kuroshio source region ultimately resulting in a lower abundance of p obliquiloculata thus we interpret the pme as a possible proxy signal of el nino like conditions and enhancement of the el nino southern oscillation climate system after the pme in the tropical and sub tropical pacific ocean

diatom response to changes in palaeoenvironments of the northern south china sea during the last 15 000 years changes in palaeoenvironments over the last 15000 years have been documented by a high resolution diatom record of core 17940 from the northern slope of the south china sea four diatom assemblage zones each characterized by different diatom components are distinguished by cluster analysis t nitzschioides var parval t nitzschioides t nitzschioides var parva tnp tnp tn and the brackish littoral species used as the proxies for temperature and salinity are compared with previously published sea surface temperature fp 12e sstw and sea surface salinity sss data from the same core and with the dongge cave delta 18 o record the bolling allerod warm phase the younger dryas cold event the holocene climate optimum and three holocene cooling events 7150 6250 4150 3450 and 1800 1350 cal yr bp are clearly distinguished by changes in the abundance of the brackish littoral species and or in tnp tnp tn data a marked increase in the abundance of the coastal species paralia sulcata during the interval 11150 8050 cal yr bp indicates a strong coastal water influence probably due to both enhanced freshwater discharge from the pearl river and the opening of the taiwan strait this palaeoceanographic change might be caused partly by climate induced sea level lowering during the late pleistocene and the early holocene the palaeoceanography during most of the holocene appears to be primarily controlled by fluctuations in the east asian summer monsoon intensity c 2009 elsevier b v all rights reserved

the upper miocene diatomaceous sediments of the northernmost mediterranean region a lamina scale investigation of an overlooked palaeoceanographic archive

half graben structures balanced models of extensional fault bend folds one common structural style in extensional regimes is a half graben bounded on one side by a master normal fault and on the other side by a domain of beds dipping toward the master fault this geometry is modeled as being caused by a bend in the master fault the hanging wall beds dipping toward the master fault are bounded by axial surfaces formed as the hanging wall moves past the bend resulting in an extensional fault bend fold the footwall beds remain undeformed and unrotated the major assumptions used in the derivation are that the geometry is area balanced and that the axial surfaces in the hanging wall have dips equal and opposite to the dip of the master fault above the bend important consequences of the model include a relationship between master fault dip above and below a bend and the amount of hanging wall dip the horizontal width of the dipping beds in the hanging wall is twice the heave on the master fault above the bend the asymmetry of the axial surfaces in the hanging wall requires that the rotated beds be strained hanging wall beds dipping toward the master fault are predicted for a fault bend wherein the dip decreases downward hanging wall beds dipping away from the master fault are predicted for a bend wherein the dip increases downward the model fits measurements taken from a published ramp and flat clay model by e cloos and is used to develop a balanced and restorable cross section of the schell creek fault a basin and range structure in nevada

surface water changes recorded in late quaternary marine sediments of the ulleung basin east sea japan sea abstract in order to reconstruct past sea surface temperature sst and salinity sss in the east sea japan sea this study investigated the oxygen isotopic composition of the planktonic foraminifer globigerina bulloides and the degree of unsaturation of alkenones in bulk sediments of core ty99pc18 recovered from the southeastern part of the ulleung basin east sea between 11 and 15 cal kyr bp the surface waters were 2 4 c cooler than today the surface salinity was 12 lower during 14 15 cal kyr bp than today then increased after 14 cal kyr bp but remained lower during 11 14 cal kyr bp than present values between 14 and 15 cal kyr bp the northern east china sea surface waters were likely to be greatly diluted by fresh water discharge from land and coastal waters would have flowed into the east sea through the korea strait during 11 14 cal kyr bp the southern input waters most likely changed from fresh water influenced coastal water to open ocean water the increased salinity probably enhanced active deep water convection at that time during 7 11 cal kyr bp the surface waters were warmer 1 c and more saline 1 3 than today indicating that the warm and saline kuroshio current became stronger and that one of its branches flowed into the east sea during this time interval the cold 2 c and less saline waters 1 at 3 6 cal kyr bp may indicate a suppression of the kuroshio current the sst and sss values are close to the present values at about 3 cal kyr bp suggesting that the physiological conditions of the east sea approached that of the present at this time

the effect of volcanic constructs on rift fault patterns volcanoes in rift situations often show distinctive hour glass fault patterns with increased fault throw as the volcano is approached we present analogue models that show that this is caused by an interaction of the regional stress field with that set up by the volcano mass for faults to be reorientated there must be a ductile layer below the volcano this can be hot crust at mid ocean ridges continental rifts or weak sedimentary strata increased volcano size or mass and lower brittle ductile ratios lead to increased fault curvature whereas an increased regional extension rate decreases the effect volcanoes on one side of a rift may capture it forming the axis of a new rift with curved or en echelon zones on either side by concentrating extension magma is more easily erupted so volcanoes may erupt more magma of less evolved composition a positive feedback between increased extension and magma eruption rate will lead to rift narrowing which can favor the formation of oceanic crust

quaternary evolution of the corinth rift and its implications for the late cenozoic evolution of the aegean summary we present geological and morphological observations at different scales to constrain rates of faulting and the distribution of deformation in the seismically active aegean region we focus first on the 130 km long corinth rift an asymmetric graben where a flight of terraces of marine origin are uplifted we show that the edges of the terraces lie in the footwall of the normal fault bounding the corinth rift and correspond to sea level highstands of laic pleistocene age using a detailed analysis of aerial and spot imagery supported by field observations we have mapped 10 terrace platforms and strandlines ranging in elevation from 10 to 400 m over distances of 2 to 20 km from the fault the elevation of the terraces inner edges was estimated at 172 sites with an error of 5m this data set contains a precise description of the uplift and flexure of 10 different palaeohorizontal lines with respect to the present sea level to date the deformation we correlate the corinth terraces with late pleistocene oxygen isotope stages of high sea level stands and with global sea level fluctuations using a thick elastic plate model consistent with our current understanding of the earthquake cycle and a boundary element technique we reproduce the geometry of the shorelines to constrain both mechanical parameters and the slip on the fault we show that the seismogenic layer behaves over the long term as if its elastic modulus were reduced by a factor of about 1000 all the terraces are fitted for fault slip increasing in proportion to terrace age and the component of regional uplift is found to be less than 0 3 mm yr 1 the best fits give a slip rate of 11 3 mm yr 1 on the main rift bounding fault over the last 350 kyr other geological and morphologic information allows us to estimate the total age of the main fault 1 ma and to examine the mechanical evolution of the corinth rift the minimum observed sediment thickness in the gulf places an extreme check on the results of the modelling and a lower bound on slip rate of 6 7 mm yr 1 40 per cent less than estimated with modelling even this slip rate is nearly 10 times higher than for comparable features in most of the aegean and elsewhere in the world at a larger scale the spacing and asymmetry of the rift systems in the aegean suggest strain localization in the upper mantle with slow extension starting 15 myr ago or earlier the more recent 1 myr rapid phase of rifting in corinth partly reactivated this earlier phase of extension the younger faulting in corinth appears to result from its present location in the inhomogeneous stress field process zone of the south westward propagating tip of the southern branch of the north anatolian fault we extend these relations to propose a mechanical model for the late cenozoic evolution of the aegean as the arabia europe collision progressed in eastern turkey it caused anatolia to move to the west and the north anatolian fault to propagate into the aegean where the early slow extension started to be modified about 5 ma ago the process of propagation dramatically increased the activity of some but not all of the earlier rifts the model we present is compatible with tectonic observations as well as with the seismicity the palaeomagnetic rotations and the displacement field now observed with gps and slr

millennial scale variability of holocene hydrography in the southwestern okhotsk sea diatom evidence diatom analysis of two submarine cores off eastern hokkaido island northern japan provides insights into the holocene palaeoenvironmental history of the southwestern okhotsk sea diatom flora was

palaeoseismicity in the gran sasso massif abruzzo central italy abstract the upper maone and venacquaro valleys on the northern side of the gran sasso massif apennines central italy have been studied in detail from the geological and geomorphological standpoints to date the activity of the faults that produced spectacular fault scarps in the late glacial and holocene sediments and morphological features the faults that produced the studied scarps have been active at least four times during the last 18 000 years and each time on the basis of the indications emerging from the study of the scarp heights displacements of similar size were probably produced the first faulting seems datable to a period slightly more recent than 18 000 years ago the second faulting occurred after the moraines of the second apennine stage these preceding a lacustrine deposit dated 11 760 160 bp could be put in the older portion of the period between 16 000 and 13 000 years ago the third faulting must be more recent than 6000 7000 years ago and slightly older than 5450 170 and 6110 180 bp a fourth phase is appreciably later than 3490 160 bp and older than the year 1000 a d for the venacquaro valley the size of the displacements more recent than 18 000 years ago indicated by the height of the fault scarps and by geophysical data is about 16 18 m for the val maone the size of the displacements more recent than the moraines of the second apennine stage is 10 11 m the respective slip rates are 0 88 1 mm year for the venacquaro valley and approximately 0 67 0 78 mm year for the maone valley it is very probable that the fault activity occurred during a seismic event or events that took place during a short time the intervals between the seismic events or seismic periods although these cannot be defined with precision appear longer than 2500 3000 years and shorter than 6000 7000 years it is possible that also in the gran sasso as in other parts of the abruzzo apennines seismic activity is characterized by events of great magnitude with long return periods

late quaternary course changes of the kuroshio current in the ryukyu arc region northwestern pacific ocean the existence of a land bridge connecting the central southern ryukyu arc to taiwan during the last glacial stage oxygen isotope stages 2 to 4 and its postglacial disappearance are demonstrated by variations in the planktic 18o values and the frequency of pulleniatina in 11 piston cores from the okinawa trough region the upward increase in the pulleniatina group in the cores signals the progressive inflow of the kuroshio current into the okinawa trough area because this group is characteristic of the kuroshio current as revealed here by planktic foraminiferal distribution using 56 surface sediment samples collected from the whole area of this region the ryukyu taiwan land bridge caused eastward deflection of the kuroshio current at the southern end of the ryukyu arc a pulleniatina minimum event in the period from 4500 to 3000 yr b p is recognized in 10 cores from the okinawa trough and one from the northern ryukyu trench slope in contrast to the lgm the decline of pulleniatina in this event was not ascribed to cyclic climate changes such as worldwide cooling but to the formation of a barrier between taiwan and the southern okinawa arc however this regional event influences largely on the holocene climate of japan and its adjacent seas

paleobiogeographical implications of inner bay ostracoda during the late pleistocene shimosueyoshi transgression central japan with significance of its migration and disappearance in eastern asia abstract a total of 79 ostracode species were recognized from the embayment sediments deposited during the late pleistocene shimosueyoshi transgression in central japan the most dominant species was neomonoceratina delicata now abundant in tropical inner bays of the ryukyu islands the south china sea and southeastern asia bicornucythere bisanensis widely dominant species in enclosed middle muddy bays of temperate climatic zones in japan and northern china was also abundant in the middle and upper sequences most of the other main species were assigned to the japonic elements and are presently common in tropical or subtropical and temperate shallow seas near the japanese islands four ostracode biofacies were identified using the q mode cluster analysis a change in water depth was clearly revealed in the study sequence based on the vertical changes in the biofacies and the relative abundances of fossil ostracode species the single most dominant species n delicata does not currently exist in the japanese islands north of the tokara strait watase s line one of zoological lines of demarcation in southern japan based on a compilation of fossil and recent distribution records it is believed that n delicata migrated from the south of the tokara strait by the marine oxygen isotope stage mis 11 430 ka dominated other species in enclosed muddy bays and then spread to the northernmost areas during the mis 5 however almost all populations of this species probably disappeared north of the tokara strait during the last glacial maximum due to a decrease in water temperature this species could not survive colder water temperature and could not migrate north through the tokara strait during the postglacial transgression because the strait has been deep and wide since the early pleistocene we conclude that this species lived commonly during the glacial stages of mis 10 8 and 6 north of the tokara strait because of the favorable water temperature for reproduction

the influence of pre existing thrust faults on normal fault geometry in nature and in experiments relations between normal faults and pre existing thrust faults are classically described in terms of three basic situations normal faults can cross cut thrust faults they can branch out from thrust faults at depth on a de collement level or they can entirely reactivate thrust planes the mechanical aspects of these types of interaction were studied by analogue modelling in which sand simulates the brittle rocks and silicone putty an interlayered de collement the models underwent compression producing thrust faults with variable dips followed by extension three possible ways of interaction are described here a no interaction occurs in the case of low dip thrust faults 32 1 and normal faults are developed independently displaying a listric geometry b branching at depth on the de collement level occurs when dip of the thrust faults reaches 32 1 in this case the dip of the normal faults whose geometry becomes planar decreases with increasing thrust dip we suggest that this change in dip of normal faults depends upon the rotation of stress tensor axes along the pre existing fault zone where a drop in the friction coefficient is likely to occur c reactivation occurs in brittle material when dip of the pre existing fault exceeds 41 1

tectonic analysis of fault slip data sets using data that include the direction and the sense of motion on individual fault surfaces determined by slickenside lineations it is possible to reconstruct reduced stress tensors that correspond to the orientation of stress axes and to the ratio 2 3 1 3 between principal stress values 1 2 3 compression being positive no assumption is made concerning the orientation of fault planes relative to stress axes so that reactived faults are taken into account as well as newly created ones qualitative and quantitative methods for analysis of fault slip data were developed during the last 10 years the practical limitation of the methods and the necessity for critical field observations are emphasized these methods can be applied to focal mechanisms of earthquakes a more complex analysis of heterogeneous data sets involving an iterative separation of different stress systems is also discussed this analysis enables one to distinguish successive faulting events careful qualitative study in the field is in all cases essential

distribution of diatoms and geochemical features of holocene sediments from the kuril basin sea of okhotsk abstract sediments from the kuril basin were collected during the russian german deep sea expedition sokhobio sea of okhotsk biodiversity studies concentrations of biogenic and trace elements quantitative content and species composition of diatom assemblages in surface sediments and core samples were analyzed distribution in the surface sediments depending on different environmental conditions as well as changes in the diatom frustule content the ratio of dominant diatom species and the ecological structure of diatom assemblages were studied the collected sediments were silt and clayey silt with sio2am and corg contents ranging from 15 85 to 36 61 and 0 84 1 92 respectively the spatial distribution patterns of the elements studied and the diatoms as well as vertical profiles of the sediment cores revealed that the contents of biogenic components and trace elements such as amorphous silica organic carbon barium and phosphorus changed in parallel with the change in the number of diatoms and depended mainly on the biological productivity of the sea the change in water mass parameters and in the hydrological regime also affected the chemical composition of the bottom sediments over time a predominance of oceanic species is observed in the sediments at the bottom of the basin and the mixed oceanic neritic composition of diatoms is characteristic of slope deposits moreover the assemblages reflect the influence of pacific ocean water masses at stations close to the kuril straits as well as in the warm waters of the sea of japan at the station in the soya current zone a nearly synchronous increase in the impact of okhotsk water masses and the entry of the sakhalin current waters into the kuril basin as one moved deeper into the core at stations with different climatic conditions was observed the productivity and species diversity of diatoms and the chemical composition of sediments are reflections of the regional features of climatic processes

thrust belt development in the central apennines italy northward polarity of thrusting and out of sequence deformations in the gran sasso chain the lazio abruzzi carbonate platform overrides the outermost sectors of the foreland fold and thrust belt of the central apennines of italy along an arcuate thrust front which swings from e w to nnw sse orientation the e w striking north verging thrust faults of the gran sasso cut in their footwall the n s oriented east verging imbricates of the marche thrust belt and the adjacent adriatic foredeep our field mapping of the gran sasso imbricate system shows an array of six major thrust faults crosscutting each other in such a way that oblique propagation of higher thrust faults across the preexisting thrust sheets causes rethrusting of earlier imbricated units decapitation of previous folds and superposition of younger on older beds deformation in the gran sasso thrust belt mainly occurred between messinian and middle pliocene times and is partly synchronous with the development of the marche thrust belt thus implying that shortening resulted from a complex combination of northward and eastward propagating thrust systems increasing west to east shortening along the gran sasso thrust front indicates large differential anticlockwise rotation by decoupling along a n s transpressive right lateral shear zone this mechanism could have been induced by the maiella foreland uplift acting as a buttress against which the lazio abruzzi carbonate platform was stacked and forced to rotate anticlockwise with consequent shortening by out of sequence thrust propagation

mid holocene sea level fluctuation inferred from diatom analysis from sediments on the west coast of korea diatoms from the ks2009 core sediment on the coast of the west sea kunsan si and the kr07 trench sediment collected from the neighboring sabsi island korea were analyzed for holocene sea level fluctuations in ks2009 core sediment results of ams 14c dating identified five stratigraphic horizons ranging from 2200 to 9100 bp the results obtained by measuring the radiocarbon dating from the kr07 were as follows 0 34 m a s l 6108 bp 0 74 m 6488 bp 1 46 m 6838 bp and 1 58 m 7208 bp diatom assemblages from ks2009 indicated facies a barren zone ks2009 23 5 to 20 3 m facies b high tidal flat ks2009 20 3 to 14 6 m holocene marine transgression facies c mid tidal flat ks2009 14 6 to 2 0 m falling sea level rising sea level facies d high tidal flat ks2009 2 to 2 m rising sea level thus after seawater influx started at 8300 bp seawater rose with fluctuations rising and falling the kr 07 trench deposit of sabsi island showed facies a barren zone kr07 1 58 to 1 18 m facies b bog kr07 1 18 to 0 76 m facies c tidal marsh kr07 0 76 to 0 52 m facies d tidal flat kr07 0 52 to 0 28 m facies e tidal marsh kr07 0 28 to 0 08 m facies f tidal flat kr07 0 08 to 0 06 m transgression occurred first about 8 300 bp at the west coast of korea around 6300 6000 bp there was a drop in the sea level and around 6000 4000 bp there was a rapid rise also repetition of falling and rising occurred since 4500 bp

seasonal export and sediment preservation of diatomaceous foraminiferal and organic matter mass fluxes in a trophic gradient across the se atlantic abstract seasonal deposition fluxes of sinking phytoplankton zooplankton and major mass compounds i e calcium carbonate biogenic opal and organic matter intercepted by deep moored sediment traps are contrasted with their sediment accumulation rates over the 2700 m deep central walvis ridge in the oligotrophic se atlantic these data provide the first seasonally resolved record of biogenic particle fluxes in the south atlantic central gyre and serve as the oligotrophic end member of a gradient across the benguela system to the highly productive coastal upwelling off namibia maximum fluxes at the central walvis ridge were deposited in early austral spring following winter deepening of the surface mixed layer and associated nutrient entrainment nearly 25 of the annual mass flux arrived in october when sea surface temperature rose deep vertical mixing halted and surface production collapsed the annual flux of diatoms was dominated by small specimens of nitzschia bicapitata 60 whereas globorotalia inflata dominated the foraminiferal fluxes 25 diatom diversity dropped significantly during the bloom periods when up to 80 was composed of small n bicapitata but foraminiferal diversity remained about constant the diatom flux maximum together with those of biogenic silica and organic matter preceded those of the foraminifera pteropods carbonate and total mass by 1 week fluxes of the left and right coiled shells of the deep dwelling foraminifer globorotalia truncatulinoides peaked in different seasons a distinctive ecological behaviour which merits their taxonomic recognition as separate species these findings testify to recent evidence for the existence of several genetic species within g truncatulinoides and now suggest that such species may also have different seasonal responses the benguela trophic gradient showed a shoreward increase in particle fluxes but differences were surprisingly small testifying to only moderately enhanced export productivity and deposition at the namibian margin relative to the oligotrophic central gyre from the open ocean toward coastal upwelling small and weakly silicified diatoms were substituted by other larger and more heavily silicified species possibly in response to decreased silica limitation foraminiferal deposition fluxes were increasingly dominated by g inflata accompanied by a change over from many warm to few cold water minor species the late winter maximum at the namibian margin and the early spring maximum at the central walvis ridge were generated by the same process of collapsing surface productivity in response to the shut down of nutrient entrainment at the winter to summer transition although delayed by up to 2 months in the central gyre at the sediment water interface intense degradation of organic matter and biogenic silica resulted in poor preservation accompanied by pronounced changes in the species composition of siliceous phytoplankton of all particle groups at the central walvis ridge only the export of foraminiferal shells appeared to be fully transferred into the sediment and through their species assemblage to provide a sedimentary record of past seasonal productivity conditions of the upper ocean

geophysical characterization of udaeta lake as a possible pull apart basin associated to quaternary tectonic activity along magallanes fagnano fault system abstract pull apart basins are depressions formed at releasing bends or steps in strike slip fault systems between two parallel vertical strike slip fault sections in the present study the geometry of udaeta lake located in the central section of the magellan fagnano fault system mffs and previously defined by some authors as a pull apart basin is analysed the application of multiple geophysical methods constrained by surface geological information enabled us to reveal the subsurface geometry of a section of the mffs udaeta lake area magnetic gravimetric and detailed topographic profiles together with vertical electrical soundings were surveyed the obtained results were compared with fieldwork data this combined methodology allowed the identification of a transtensional zone with two e w main sinistral strike slip faults with a normal component that control the north and south coasts of the lake this central depression occupied by the lake with a depth of 30 m is also affected by inferred ne subparallel faults the geophysical characterization of the mffs also supports the influence of this fault system on the formation of some water bodies located along the fault zone finally in spite of the lack of detailed geological and structural data udaeta lake we suggest a genesis consistent with a pull apart basin model this work constitutes an important contribution to understand earthquake rupture parameters and pattern of surface and in depth deformation and so improve knowledge of the seismological behaviour of the mffs

alkenone temperature estimates for the east sea during the last 190 000 years abstract the late quaternary records of alkenone based sea surface temperature sst from a core located in the western margin of the east sea japan sea showed that the estimated temperature fluctuated greatly the variability being consistent with orbital scale global climate records during the period of marine isotope stage mis 6 the alkenone temperatures were low 7 10 c whereas during mis 5 5 the temperature increased rapidly up to 21 c during the entire period of mis 5 the temperature decreased from 21 c to 13 c then the temperature fluctuated between 10 c and 15 c during miss 4 and 3 after that it continued to fluctuate between 15 c and 17 c variation in the east sea sst is considered to be closely related to changes in the east asian monsoon system and seawater transport by the tsushima warm current the glacial surface cooling could be associated with the strong winter monsoon and or weakened summer monsoon in east asia during the glacial period when the sea level was low the influx of warm water was restricted and this might have enhanced the lowering of the surface temperature these conditions most likely caused significant changes in surface water circulation a basin scale cyclonic gyre might have occurred in the east sea without the development of the subpolar front during the interglacial period the surface warming seems to be related to the intensified summer monsoon system the high stand of the sea level and climate change most likely caused the development of cyclonic and anti cyclonic gyres in the north and south respectively and the subpolar front in the central part of the sea

paleoceanographic implications of a 90 000 year long diatom record in piston core kh94 3 lm 8 off ne japan abstract q mode principal component analysis pca of a fossil diatom assemblage reveals the late quaternary paleoceanography of the nw pacific margin based on submarine core kh94 3 lm 8 recovered off the sanriku coast of ne japan 38 53 46 n 143 22 19 e overall diatoms were abundant during interglacials but low in abundance and poor in preservation during the last glacial with each oxygen isotope stage having its own characteristic assemblage the results of pca are principal component 1 pc1 is composed mainly of thalassionema nitzschioides which predominated during the coldest oxygen isotopic stages 4 75 58 ka and 2 25 11 ka and by allochthonous taxa the diatom tests are poorly preserved and the diatom mass accumulation rate dmar is the lowest in these stages pc2 is characterized by ice related diatoms that predominate in stage 3 the interstadial whereas pc3 which is characterized by neodenticula seminae and odontella aurita shows high values in stage 1 diatom assemblages exhibit drastic changes between oxygen isotopic stages 3 and 1 11 0 ka distinct increases of dmar occurred during both periods we infer an intensified advection of sea ice from the sea of okhotsk toward the area off sanriku during stage 3 this interpretation explains the high dmar in stage 3 owing to high productivity at the sea ice edge our study can contribute to marine environmental reconstruction since the last glaciation because fewer micropaleontological data exist in the nw pacific margin for these time intervals compared with other oceans

a note on fault reactivation reactivation of existing faults whose normal lies in the 1 3 plane of a stress field with effective principal compressive stresses 1 2 3 is considered for the simplest frictional failure criterion n n p where and n are respectively the shear and normal stresses to the existing fault p is the fluid pressure and is the static friction for a plane oriented at to 1 the stress ratio for reactivation is 1 3 1 cot 1 tan this ratio has a minimum positive value at the optimum angle for reactivation given by 12tan 1 1 but reaches infinity when 2 beyond which 3 0 is a necessary condition for reactivation an important consequence is that for typical rock friction coefficients it is unlikely that normal faults will be reactivated as high angle reverse faults or thrusts as low angle normal faults unless the effective least principal stress is tensile

the role of pre existing thrust faults and topography on the styles of extension in the gran sasso range central italy abstract structural analysis and field mapping together with simple geometrical and flexural elastic models document that two styles of quaternary extensional tectonics characterized the gran sasso range central apennines italy in the western part of the range extension took place on 10 15 km long range front normal faults with associated 600 1000 m high escarpments showing evidence of late glacial holocene activity this topography has been reproduced with a thin elastic plate subjected to the isostatic forces induced by the movement along high angle 55 65 planar normal faults in the eastern part of the belt extension occurred on shallow dipping normal faults 30 35 which reactivated progressively deeper pre existing thrusts in this area antithetic domino faults formed to accommodate the mechanical adjustment of the hanging wall over a variably dipping major fault surface the eastward increase in shortening due to the earlier compressional phase documented in the gran sasso belt by previous authors accounts for the more developed zones of weakness and high topographic relief in the eastern sector this setting could explain the different styles of extension and the more advanced northeastern limit of normal faulting in the eastern sector this work suggests that normal faults can originate either with low or high angle geometry in the upper crust according to the pre existing tectonic setting and that topography could be important in controlling the geometry and pattern of migrating normal faulting

paleoceanography during the last 150 kyr off central japan based on diatom floras abstract the paleoceanographic history of the area above the northern boundary of the warm kuroshio current during the last two glacial interglacial cycles was reconstructed based on high resolution records of the diatom flora in core md01 2421 ecological categories of the diatom flora were extracted using q mode factor analysis the four most prominent factors explained 91 4 of the total variance cross spectral analyses were performed on temperature estimates derived from diatom data td the relative abundance of littoral neritic diatom associations and the oxygen isotope record of benthic foraminifera diatom derived temperatures show a 50 23 and 17 kyr periodicity with only the 23 kyr band coherent with that of benthic foraminiferal oxygen isotope values littoral neritic associations show a periodicity at 62 and 17 kyr coherent with td species composition and relative abundance of the diatom flora changed at the marine isotope stage boundaries when cold water and warm water mixed over the core site due to hydrographic disturbances by changes in transport trajectory of the kuroshio current transport and global climatic changes

the evolution of the gulf of corinth greece an aftershock study of the 1981 earthquakes summary a preliminary study of the aftershocks of three earthquakes that occurred near to corinth greece in 1981 is combined with observations of the morphology and faulting to understand the evolution of the eastern gulf of corinth the well located aftershocks form a zone 60km long and 20km wide they do not lie on the main fault planes and are mostly located between the north dipping faulting on which the first two earthquakes occurred and the south dipping faulting associated with the third event a cluster of aftershocks also lies in the footwall of the eastern end of the south dipping fault of the third event morphologically it is observed that in the evolution of the eastern gulf of corinth antithetic faulting apparently predates the appearance of the main faulting at the surface this evolution can be explained by motion on a deep seated shallow angle aseismic normal fault a model based on such a fault also accounts for the aftershock distribution of the 1981 earthquakes