a multi proxy record of holocene climatic change in southwestern spain the laguna de medina cadiz palaeolimnological data diatoms ostracods foraminifera molluscs aquatic pollen and lithology from a radiocarbon dated sediment core from a saline lake the laguna de medina provide the first complete record of holocene lake level change for southwest spain for the last c 9000 cal years the lake has always been relatively shallow but has exhibited marked fluctuations in salinity and water depth especially in the earlier record when oscillations culminate in maximum lake levels from c 6960 6680 cal bp c 6070 5830 bp indicating enhanced early to mid holocene humidity and a mid holocene humidity maximum prolonged shallowing thereafter reflects in part increased aridity in the later holocene lake desiccation followed by a c 800 yr phase zone 2 of major limnological change commencing at c 8000 cal bp c 7200 bp and a number of other abrupt desiccation events are also noteworthy the mid holocene maximum is consistent with widespread evidence for high lake levels around 6000 bp but t

geometric analysis of fold development in overthrust terranes abstract fault bend folding fault propagation folding and detachment or decollement folding are three distinct scenarios for fold thrust interaction in overthrust terranes simple kink hinge models are used to determine the geometric associations implicit in each scenario bedding maintains constant thickness in the models except in the forelimb of the fold the forelimb is allowed to thicken or thin without limit the models address individual folds and the calculated fold geometries are balanced structures each mode of fold thrust interaction has a distinct set of geometric relationships final fold geometry is adequate in itself to discern many fault bend folds this is not the case for fault propagation and detachment folds these two fold forms have very similar geometric relationships some knowledge of the nature of the underlying thrust or decollement zone is usually needed to distinguish between them the geometry of a fold is altered in a predictable fashion by transport through an upper ramp hinge and by fault parallel shearing of the structure the shearing results in a tighter fold whereas transport through the ramp hinge produces a broader fold the viability of the geometric analysis technique is demonstrated through its application to a pair of detachment folds from the canadian cordillera the geometric analysis is also used to evaluate cross sections through subsurface structures in an example from the turner valley oil field the analysis indicates how the interpretation should be altered so as to balance the cross section the analysis reveals hidden assumptions and specific inconsistencies in structural interpretations

investigating the molybdenum and uranium redox proxies in a modern shallow anoxic carbonate rich marine sediment setting of the malo jezero mljet lakes adriatic sea abstract the molybdenum mo and uranium u isotope compositions recorded in carbonate rich sediments are emerging as promising paleo redox proxies however the effects of early diagenetic effects within the sediments on these isotope systems are not well constrained we examined the mo and u isotopic systematics in anoxic carbonate rich sediments in a semi enclosed karstic marine lake malo jezero of the island of mljet adriatic sea measurements of water column redox behavior in the lake since the 1950s have shown a transition from anoxic sulfidic conditions in the deeper water column to more oxic conditions and anoxia refined to the sediment and pore waters a 50 cm long sediment core from the deepest part of the lake show a transition from moderate to high authigenic mo and u accumulation with depth consistent with the changing lake redox environment in the past in the deep euxinic part of the core the authigenic mo and u are isotopically lighter and heavier respectively than seawater following similar systematics as observed in other modern euxinic basins with high but non quantitative mo and u uptake into the sediments based on bahamas bank carbonate sediments it has been suggested that the 238u 235u ratio is 0 25 higher compared to seawater from the effects of early carbonate sediment diagenesis and this carbonate vs seawater off set is applicable to carbonate rich sediments across the geological past the shallower part of lake sediment core was deposited under similar redox conditions as the bahamas sediments and these sediments show an average 238u 235u ratio 0 31 0 01 2se higher than seawater although the average 238u 235u ratios for these two carbonate rich settings are similar caution is necessary when inferring seawater 238u 235u compositions from such sediments as they contain u from different sources e g diagenetic uptake and carbonate bound the mo isotope compositions within the same malo jezero sediments are variable but approaches the seawater composition at low pore water h2s concentrations this show the potential of using the mo isotope composition from carbonate rich sediments to infer the seawater composition however further work is required to establish the link between the mo isotope composition and the chemistry of the pore water environment

adriatic deep water formation during the holocene implication for the reoxygenation of the deep eastern mediterranean sea under modern conditions the reoxygenation of eastern mediterranean deep water is the result of the formation of dense bottom water in the southern adriatic sea oxygen isotopic records of planktonic foraminfera used as a paleosalinity tracer show that po river and or the alpine glaciers meltwater are not directly responsible of the inhibition of the deep water formation in the adriatic during sapropel s1 formation at 9 000 years b p sedimentological evidence indicates that fully oxygenated conditions in the deep adriatic occurred only by 1 650 100 years b p a long time after the total reoxygenation of the deep eastern mediterranean organic carbon content and isotopic ratio indicate that persistence of a reduced sediment phase until 1 650 years b p does not result from increased primary productivity or large input of terrestrial organic matter

geometry and kinematics of the north monagas thrust belt venezuela abstract the complex geometry and structural evolution of the north monagas thrust belt were investigated and new exploration trends in this part of eastern venezuela considered the pirital thrust and related structures of the maturin basin are used to discuss the sequence of thrusting and to illustrate the constant balance between erosion and thrust reactivation in a recent fold and thrust belt a careful analysis of the chronostratigraphy and the internal geometry of the foredeep and piggy back syntectonic deposits has been used to constrain balanced cross sections and to establish the kinematics of each individual structure basement involvement is postulated for the pirital thrust which remobilizes previously emplaced cover structures such as the el furrial or orocual structural units it thus probably relates to the pinch out of a shallow decollement level coal measures of the barranquin formation older late jurassic to lower cretaceous evaporites or other mesozoic plastic horizons and to the reactivation of a deeper basement fault the westward emergence of the pirital and el furrial thrusts in a complex transfer area the urica fault is also analysed according to transverse profiles the surficial urica fault does not connect directly to a basement fault but instead acts as a lateral ramp for the el furrial cover unit and as a tear fault for the pirital thrust reactivation of ancient thrust faults also occurs at the rear of the pirital thrust in the west in areas where the topographic profile of the eastern venezuelan ranges has recently been modified by the pirital thrust emplacement these out of sequence thrusts resulting from fault reactivation in the inner parts of the prism are discussed in terms of the preservation of the critical taper they effectively relate directly to erosional processes which significantly decrease the load applied on this portion of the wedge the influence of the sequence of thrusting on the potential plays is considered

thrust fault mechanics and origin of a frontal ramp several features of thrust sheets in nonmetamorphic and relatively low grade metamorphic terrains indicate that the modes of faulting included both gradual and stick slip types of motion a first order quantitative analysis is made of the mechanics of this type of faulting in the analysis part of a wedge shaped thrust belt slips forward over a fault area of length l and unit width w producing a strain concentration in subhorizontal strata at the front of the growing thrust where a frontal ramp develops by shear fracturing equations for net slip x and the conditions for ramping are evaluated with limit equilibrium principles and coupled oscillator theory the quantitative analysis takes into account anisotropy resulting from contrasts in competency and facies changes a special case solution for maximum net slip associated with stick slip is lw ki 1 cos ot o 12 1 cos 1t where is the stress drop ki are spring constants of the strata 0 and 1 are natural frequencies of the system and t evaluated from another equation is the time for net slip the spring constants and natural frequencies can be evaluated from seismic and stratigraphic data a preliminary solution for piggy back thrusting indicates that ramp spacing can be systematic and that it depends upon the thickness of the deforming package the elastic parameters of the deforming package the slope of the topographic surface and the stresses along the trailing edge of the package

cover deformation above a blind duplex an example from west virginia u s a abstract pretectonic cover above blind thrust systems responds to underlying thrusting by combinations of forethrusting backthrusting and coupling the role of these responses was examined in the hanging rock cacapon mountain anticlinorium of the central appalachians this cover fold consists of middle ordovician and younger sedimentary rocks above a blind horse of cambro ordovician carbonates the cover has abundant folding and subsidiary faulting cover cleavage in carbonate and fine grained clastic rocks formed before regional folding in response to layer parallel shortening lps this 15 lps also produced grain suturing and fluid inclusion trails in quartzarenites the lps formed during cover forethrusting accommodating older blind horses in the hinterland with the formation of the underlying horse cover coupling occurred with bending folding additional secondary buckling and cleavage rotation by flexural flow with perhaps minor flattening this cover coupling was insufficient to accommodate horse formation no evidence exists for backthrusting but forelandwards abundant subsurface evidence exists for cover forethrusting with imbricate thrusting this thrusting accommodates horse formation and differs in style from the lps of the older forethrusting event so for this blind system the cover responded with a combination of coupling and forethrusting

late pleistocene and holocene paleoenvironmental reconstruction of a drowned karst isolation basin losinj channel ne adriatic sea abstract the results of a comprehensive study of submerged paleoenvironments developed along the karstified eastern adriatic coast during the late quaternary are presented in this study the losinj channel is a drowned karst basin filled with sediments a multi proxy analysis of two sediment cores lk 12 and lk 15 recovered from water depths of 62 and 64 m was conducted we used magnetic susceptibility grain size mineralogy xrf core scanning organic and inorganic carbon total nitrogen and paleontological data supplemented with ams 14c dating results and high resolution seismic data to reconstruct the infill history of the losinj basin during the late pleistocene and holocene our findings include the first detailed description of the presumed marine isotope stage mis 5a marine sediment succession along the eastern adriatic coast deposition in the brackish to freshwater lacustrine body losinj paleolake occurred during mis 3 sea level lowstand that followed caused the formation of environmental conditions typical of a karst polje the post last glacial maximum lgm sea level rise led to the establishment of a brackish marine lake with seawater seepage through the karstified sill at 13 7 cal kyr b p the transition to the present day marine conditions commenced at 10 5 cal kyr b p paleoenvironmental changes in the investigated area can be linked to the presence of a sill at 50 m depth that separates the losinj basin from the kvarneric bay the sill depth determines the isolation or inundation of the investigated basin in response to the changes in sea level paleoenvironments reacted sensitively to these changes and therefore the study area represents an ideal setting to track regional sea level and climate variabilty

experimental and field study of the effects of lithological contrasts on thrust related deformation 1 the influence of mechanical contrasts related to stratigraphy on thrust related deformation are investigated by sandbox modeling using combinations of granular materials possessing different mechanical properties and by structural analysis of a natural example from the spanish pyrenees the models used in this study consist of loose sand and glass microbeads in varied stratigraphic thicknesses and sequences and the natural example consists of a weakening upward sequence of sandstones and carbonates in both cases layers of different composition had a mechanical significance and accommodated shortening differently model sand and natural sandstone exhibited most shortening by thrust imbrication irrespective of stratigraphic position whereas glass microbeads and carbonates exhibited wider deformation zones and enhanced folding accompanied by displacement reduction along thrust surfaces cutting them transitions of structural style were guided by the stratigraphy rather than by a simple unidirectional propagation from a step up layer parallel shortening was accommodated by diverse mechanisms but did not vary significantly in layers which had different properties the magnitude with which mechanical contrasts were expressed in the models was influenced by the strength at the decollement zone the effect of mechanical contrast was more profound in models shortened above a low friction decollement

recent developments in centrifuge modelling of tectonic processes equipment model construction techniques and rheology of model materials abstract the experimental tectonics laboratory at queen s university is equipped with a large capacity centrifuge that is capable of subjecting tectonic models measuring 127 76 mm in plan and up to 51 mm in depth to accelerations as high as 20 000 g this high capacity greatly extends the range of potential model materials and permits the use of relatively stiff and or brittle substances a number of new techniques of model construction have been devised that permit internal and surface strain patterns and kinematic evolution to be monitored in detail one particularly useful technique which will find application in non centrifuged experiments as well allows the preparation of highly uniform anisotropic multilayers composed of alternating layers of plasticine and silicone putty with individual layer thicknesses as low as 20 m and with controllable ratio between thicknesses of the relatively competent and incompetent units examples of models constructed using these new techniques are illustrated one particular type of the commonly used model material silicone putty has been subjected to a series of rheological test the results indicate that at strain rates in the range 10 6 10 3 s 1 applicable to the centrifuge experiments the silicone putty exhibits power law rheology with n 7 2 at higher strain rates the material appears to tend towards linear behaviour available rheological data and dimensional analysis using standard scaling laws and appropriate model ratios suggest that the microlaminated plasticine silicone putty multilayer is a suitable analogue in centrifuged experiments for interbedded sequences of indurate limestone and incompetent shale the excellent degree of dynamic similitude attained is demonstrated by the realistic form of fold and fault structures developed in models constructed of this material

fold generated imbricates examples from the caledonides of southern norway abstract the cambro silurian sequence of the oslo region contains fold trains and closely spaced imbricate thrust faults the imbricates could be interpreted as having ramped off the sole detachment and generated fault propagation folds several imbricate thrusts however appear to die out both downwards and upwards into folds this suggests that the thrusts were generated within the cambro silurian sequence and propagated down to the sole thrust rather than propagating upwards from the sole thrust the mechanical stratigraphy is apparently responsible for this style where during folding relatively brittle limestone members faulted in the highly strained fold forelimbs prior to through going faulting developing in the shales understanding the origin of such imbricates is important when choosing a method of section restoration

interrelations of mesoscopic structures and strain across a small regional fold virginia appalachians abstract small regional folds such as the clover hollow anticline of the narrows thrust sheet in southwest virginia u s a are considered to be large buckle folds expressing lateral shortening above a subsurface decollement cleavage mesoscopic and regional folds and contraction faults have developed in these rocks under anchimetamorphic conditions in a single protracted deformation during thrust sheet emplacement the contraction faults dominate the structure at all scales three fault associations isolated contraction faults contraction faults in series and complex fault zones with intense folding determine the pattern and intensity of local structures regional displacement transfer of strain along and across faults has produced local variations in structural style duplex like systems of second order faults terminate laterally into zones of intense folding and third order faulting fold tightness cleavage intensity strain magnitude and total longitudinal strain e t are maximum in these regions contraction faults in this thrust sheet have propagated along zones of high strain rate associated with mesoscopic folding and intense cleavage regional hinge migration and greater structural complexity along the southeast limb of the clover hollow anticline are considered to be due to emplacement of the adjacent thrust sheet

sand beaches on highly indented karstic coasts where the sands come from and what should be protected se adriatic croatia abstract this study deals with sand beaches of the se adriatic archipelago and peljesac peninsula the beaches themselves as well as their genetically related surroundings are taken into consideration as both are critical for understanding beach features and processes two approaches have been followed in these two areas the study of sediment composition including heavy mineral associations and the study of geology morphology and sediment distribution these features and their combination present the basis for interpretation of present day processes as well as for reconstructing how and where the beaches developed and why have they in some places disappeared sediment composition of the studied beaches clearly indicates pleistocene deposits as the principal sediment source however much of this supplied sediment has a short residence time on the beaches due to marine reworking and the bulk of the beach sediment arrives from the sea floor the positioning of the studied sand beaches at bayheads their lengths and shapes as well as their present status have been influenced by several main factors they include 1 pre pleistocene tectonic deformations 2 pre pleistocene weathering and erosion of carbonate sediments mainly cretaceous in age 3 initial distribution of soft pleistocene cover sediments as well as 4 the history of their reduction and related decline in sediment source capacity or at some locations their complete disappearance other main factors are 5 the post lgm sea level rise and 6 two climatic events an important pluvial period from 8 4 to 6 ka bp maximum from 7 to 6 ka bp and the transition to mediterranean climate between 6 and 5 5 ka bp beaches with relatively high pleistocene hinterland supply and correlative relatively large widths seem to be quasi stable or possibly even prograde beaches of small width and minor to negligible hinterland supply or those completely deprived of it suggest ongoing beach recession suggested priorities for the protection of the beaches are directly related to the preservation of hinterland supply in the case of beaches with negligible or no hinterland sediment supply replenishment projects can be considered

a compositional approach to the reconstruction of geochemical processes involved in the evolution of holocene marine flooded coastal karst basins mljet island croatia abstract geochemical patterns in the environment are always the result of certain processes therefore it is essential to decipher a process to properly evaluate the environmental role and potential of chemical elements compounds this allows the distinction between natural and anthropogenic influence on elemental concentrations however if the compositional nature of geochemical data is neglected erroneous or misleading conclusions regarding the processes involved are probable in this study the reconstruction of depositional environments and processes through the holocene in two sediment cores obtained from submerged sinkholes located on the island of mljet croatia was performed by taking into account the compositional nature of geochemical mineralogical and grainsize data problems involving compositional data are always multivariate for example the concentration of a single element does not carry any interpretative information as only the ratios between elements do this has led to the discovery of a large number of geochemical proxies based on elemental ratios which describe certain environmental conditions and processes involved nevertheless some proxies have been found to be restricted to only some specific environments thus preventing them from being used in general therefore some kind of relation between different proxies is necessary to obtain final conclusions however when using simple elemental ratios those correlations cannot be obtained due to the nature of compositional data with a sequential binary partition of a compositional vector orthonormal log ratio olr coordinates proxies can be constructed when based on expert knowledge those proxies fully acknowledge the geochemical properties of the chosen elements with one major difference that the correlation between newly obtained variables is mathematically well grounded as a result the final conclusion is more accurate in this research geochemical proxies obtained as a representation in olr coordinates of the elements that are enriched compared to the local soil were used to perform principal component analyses it helped to unravel the evolution of sedimentary environments mineralogical xrd and heavy mineral data and grain size analyses supported the conclusions obtained based solely on geochemical data furthermore data analysis suggests that the proxies for redox conditions described in the literature should be used with caution as their use is somewhat limited

centrifuge modelling of fold thrust structures in a tripartite stratigraphic succession abstract analog models measuring 127 76 mm in plan were deformed at 2500 4000 g in a centrifuge scaled stratigraphic sequences were constructed of anisotropic multilayers with individual layers of plasticine and silicone putty as thin as 40 m the plasticine silicone putty multilayers are analogs for interbedded competent carbonates and clastics and incompetent pelites given the model ratios of acceleration 2500 g length 5 10 6 specific gravity 0 6 time 10 10 modelling of fold thrust tectonics emphasizes the influence of stratigraphic succession on structural evolution the models are constructed with a tripartite stratigraphic succession comprising basal and upper well laminated and incompetent units and a middle somewhat more isotropic and competent unit the models deform by three mechanisms layer parallel shortening folding and thrust faulting they reproduce a number of fold thrust relationships that have been observed in nature folds are typically periclinal in en echelon arrays folds and thrusts are arcuate in plan reflecting differential shortening fold attitudes grade from upright at high levels to overturned at deeper levels within a structural panel reflecting drag against the basal decollement fold axial surfaces and thrust faults are listric while competent units may be offset by localized displacement on thrust faults the discrete faults may die out both upwards and downwards into regions of ductile strain in less competent units thrust faults appear to follow staircase trajectories through the strata transecting incompetent units at shallow angles to bedding and competent units at steeper angles however the apparent staircase pattern results from propagation of a fault along a relatively straight trajectory through previously folded strata foreland verging thrusts are more common than back thrusts the latter have steeper dips the models suggest a mechanism of thrust ramp nucleation following detachment folding long wavelength buckling of a competent unit can initiate localized strain folding and layer parallel shear in an underlying incompetent unit beneath the anticlines of the competent unit thrust faults propagate up section from these high strain zones through the foreland dipping limbs of buckle folds in the competent unit this mechanism may explain the commonly observed spatial periodicity of thrust ramps the model results bear similarities to natural fold thrust belts in which the stratigraphic succession consists of three mechanical units for example the asiak foreland and bear creek hills fold thrust belts of the slave province northwest territories canada

three dimensional geometry and kinematics of experimental piggyback thrusting the three dimensional geometry and kinematics of piggyback stacks of imbricate thrust sheets are illustrated and discussed using a single model shortened in a squeeze box strike parallel geometric elements simulated include lateral ramps eyed sheath folds splays and thrust thrust interference fine details of these structures were exposed by eroding a shortened wedge of sand using a newly developed vacuum eroding technique a kinematic analysis of the model shows a stepwise increase in imbricate thrust spacing and or a decrease in rate of nucleation of imbricate thrusts in the direction of thrust transport despite the steady forward advance of a rear wall the piggyback wedge accreted episodically recording different strain domains in longitudinal cross sections strain partitioning in single layers by bed length balancing showed an increase in layer shortening with volume loss and a corresponding decrease in imbricate thrusting and ramp folding with depth

modelling the geometry of coulomb thrust wedges internal geometry and detachment of coulomb thrust wedges is examined in a combined gravity and pressure force field under various boundary conditions and coulomb parameters frontally buttressed sand wedges accreted with narrow tapers above soles with negligible friction in these models serial imbricates stepped up in conjugate sets which operated synchronously or serially with increases in sole friction model coulomb wedges accreted in piggyback style with enhanced taper but narrower spacing of imbricates in this mode flat topped box fold anticlines nucleated at the frontal tip of a sole thrust prior to the fore limb failing as a ramp the initial ramp thrusts subsequently rotated and steepened to acquire concave upwards listric geometry when cohesion was a significant component of strength and the sand grains interlocked thoroughly ramp climb during piggyback thrusting occurred through the generation of a stack of backthrusts the taper of cohesionless sand wedges which lack any length scale was consistent with the critical cohesionless coulomb wedge taper in contrast the taper of experimental cohesive sand wedges which are scale dependent was consistent with the theoretical cohesive coulomb narrow taper only when the cohesive length scale was lr sr rar 10 6 this was constrained by comparing geometry of cohesive sand wedges shortened at different body force per unit mass

alternative model of thrust fault propagation a widely accepted explanation for the geometry of thrust faults is that initial failures occur on deeply buried planes of weak rock and that thrust faults propagate toward the surface along a staircase trajectory we propose an alternative model that applies gretener s beam failure mechanism to a multilayered sequence invoking compatibility conditions which demand that a thrust propagate both upsection and downsection we suggest that ramps form first at shallow levels and are subsequently connected by flat faults this hypothesis also explains the formation of many minor structures associated with thrusts such as backthrusts wedge structures pop ups and duplexes and provides a unified conceptual framework in which to evaluate field observations

inelastic response of compliant fault zones to nearby earthquakes in three dimensions abstract using dynamic modeling of earthquake rupture on a strike slip fault and seismic wave propagation in a three dimensional inhomogeneous elastoplastic medium we investigate the inelastic response of compliant fault zones to nearby earthquakes we primarily examine the plastic strain distribution within the fault zone and the displacement field that characterizes the effects of the presence of the fault zone we find that when the fault zone rocks are close to failure in the prestress field plastic strain occurs along the entire fault zone near the earth s surface and some portions of the fault zone in the extensional quadrant at depth while the remaining portion deforms elastically plastic strain enhances the surface displacement of the fault zone and the enhancement in the extensional quadrant is stronger than that in the compressive quadrant inelastic response may be distinguished from elastic response by sympathetic motion or reduced retrograde motion exhibited in the fault parallel horizontal surface displacement in conjunction with enhanced vertical surface displacement in a strike slip faulting environment these findings suggest that taking into account both elastic and inelastic deformation of fault zones to nearby earthquakes may improve our estimations of fault zone structure and properties from small scale surface deformation signals furthermore identifying the inelastic response of nearby fault zones to large earthquakes may allow us to place some constraints on the absolute stress level in the crust

pedologic analysis of the danilo bitinj site central dalmatia croatia abstract as part of the early farming in dalmatia project an interdisciplinary effort toward understanding the origins of european agriculture we are performing a site specific geoarchaeological study of the middle neolithic danilo bitinj site and the early and middle neolithic pokrovnik site here we present the soil description and analysis for danilo bitinj the site farmed for at least 7000 years is located at the center of danilo polje a valley in dalmatia s well developed karst terrain soils both on and off site are fine grained and carbonate rich other measured pedologic properties indicate a stable valley bottom environment throughout the life of the analyzed solum the longevity of agriculture corresponds with the high measured calcite content while electric conductivity and ph measurements indicate a sodic plant toxic chemical environment soil organic matter stable carbon isotope data indicate a local environment heavily dominated by c3 plants soil carbonate stable carbon and oxygen ratios were also measured but appear to be out of equilibrium with those for organic carbon and therefore invalid for paleoclimatic interpretation according to regional paleoclimatic studies the earliest agricultural occupation at danilo coincided with a significant drought this evidence for regional drought is at odds with the on site isotope data indicating relatively cool moist conditions these findings present an interesting scenario in terms of human behavioral ecology that despite the soil s sodicity danilo may have represented a moist and productive resource refuge

temperature and salinity records of the tyrrhenian sea during the last 18 000 years abstract we have used the modern analogue technique to derive sea surface temperature sst records of the last 18 000 years from two well dated deep sea cores recovered in the tyrrhenian sea results show two major cooling events synchronous with the european and north atlantic oldest and younger dryas events a later cooling of lower amplitude is observed between about 8000 and 4500 yr bp tyrrhenian ssts were similar to those of the upper holocene only during the bolling allerod event and at the beginning of the holocene we compared the sst and the planktonic foraminiferal oxygen isotope records to estimate the surface salinity variations our reconstruction shows that salinity decreased in the tyrrhenian sea during the three cold events whereas high ssts correlate with high salinities during most of the last 18 000 years tyrrhenian sea salinity variations were similar to those of the north atlantic ocean near the entrance of the mediterranean sea the salinity gradient between the two basins was thus constant indicating that the western mediterranean circulation pattern and the freshwater budget were not significantly different from the modern one the case was however different during the middle holocene when the strong salinity decrease associated with the sapropel deposit in the eastern mediterranean basin had no equivalent in the north atlantic ocean this peculiar event can only be explained by a local climatic change and an increase of precipitation

mechanics of triangle zones and passive roof duplexes implications of finite element models abstract finite element models of passive roof duplexes simulate the evolution and distribution of fault slip and deformation as functions of boundary conditions friction on the roof fault cover strength and amount of overburden a foreland buttress is essential for backthrust displacement in the models this foreland buttress is analogous to a pin line between the cover and footwall forelandward of the triangle zone in a balanced cross section and could be caused by a stratigraphic pinchout of the upper detachment or a strong cover in the foreland with boundary conditions that prevent the cover from slipping toward the hinterland relative to the wedge incipient forethrust and backthrust ramps zones of high equivalent plastic strain cut through the cover in the models there is more backthrust displacement with a lower friction coefficient on the upper detachment and with a stronger cover because of pressure dependence both fault strength and material strength increase with increasing overburden therefore the effect of overburden on backthrust displacement is determined by the nature of the pressure dependencies for fault friction and material strength in models with multiple imbricate faults the distribution of equivalent plastic strain adjacent to each fault is similar to that in single fault models with differences resulting from bending strains in the wedge and cover the strain distribution in the cover of the models is similar to that above natural passive roof duplexes characterized by layer parallel shortening above the tip of each horse in the duplex

late pleistocene and holocene sea level change in greece and south western turkey a separation of eustatic isostatic and tectonic contributions summary sea level change during late pleistocene and holocene times is a combination of eustatic isostatic and tectonic contributions in the central mediterranean sea region of greece and western turkey the isostatic components are important due to the changing gravitational potential of the earth the readjustment of the crust upon the removal of the large ice sheets and the addition of the meltwater into the oceans including the mediterranean changes in relative sea level due to these glacio hydro isostatic adjustments have reached amplitudes of 1 mm yr 1 during the last few thousand years a model for the isostatic contribution to sea level change including the movement of shorelines due to the combined eustatic isostatic changes is developed based on earth model and ice sheet parameters estimated from sea level observations from other areas comparisons of this model with observations of sea level change permit rates of vertical movement to be estimated for late holocene time allowance for the isostatic factors makes a significant difference to these rates the plains of argolis lakonia messinia and navarine in the southern peloponnese for example appear to be tectonically stable on time scales of a few thousand years and longer consistent with the position of the last interglacial shoreline close to the present day sea level the observations here of a rising sea level are largely the consequence of the glacio hydro isostasy and not of a long term tectonic process crete as a whole is subject to tectonic uplift but at variable rates and forms part of an arcuate zone of uplift extending from rhodes and karpathos in the east to kithera in the west at rates that locally exceed 4 mm yr 1 the southern shore of the gulf of corinthos is also subject to uplift at rates approaching 1 5 mm yr 1 these isostatically corrected estimates for the past few thousand years are in agreement with longer term estimates based on the position of the last interglacial shoreline only on the perachora peninsula do the tectonic rates over these two time intervals appear to be in disagreement with the late holocene rates being much higher than the long term rates

varves in marine sediments a review the global compilation of reported marine varved sedimentary records throughout the quaternary contains 52 sites marine varve deposition and preservation typically depend on environmental and sedimentological conditions such as a sufficiently high sedimentation rate severe depletion of dissolved oxygen in bottom water to exclude bioturbation by macrobenthos and a seasonally varying sedimentary input to yield a recognizable rhythmic varve pattern additional oceanographic factors include the strength and depth range of the oxygen minimum zone omz and regional anthropogenic eutrophication from point sources such as large polluted rivers quaternary marine varves are not only found in those parts of the open ocean that comply with these conditions but also in fjords embayments and estuaries with thermohaline density stratification and nearshore marine lakes with strong hydrologic connections to ocean water this review critically describes settings and sedimentological characteristics of marine sites where varves have been reported broader applications of marine varve records are discussed for example in terms of radiocarbon calibration on high resolution time scales constraining paleoceanographic variability and global change teleconnections diagnosing factors affecting modern fish population dynamics based on past performance detailing biogeochemical cycles and deciphering complex factors influencing marine productivity varves in saline water bodies without hydrologic connection to the global ocean are not included in this review and instead pertain to the companion review on lacustrine varves where also general and fundamental principles of varve deposition classification and dating are covered zolitschka et al 2015 the postulated occurrence of varves in pre quaternary rocks is critically discussed in this review with representative examples in the case of non evaporitic laminations in fine grained ancient marine rocks such as banded iron formations and black shales laminations may not be varves but instead may have multiple alternative origins such as event beds or formation via bottom currents that transport and sort silt sized particles clay floccules and organic mineral aggregates in the form of migrating bedload ripples

a multi proxy core study of the last 7000 years of climate and alpine land use impacts on an austrian mountain lake unterer landschitzsee niedere tauern abstract analyses of diatoms pollen magnetic compounds grain size and selected elements were applied to a 3 45 m long sediment core spanning the last 7000 years from a high mountain lake unterer landschitzsee 1788 m a s l in the central austrian alps the pollen record indicates a series of negative climate oscillations superimposed on a long term trend towards increased humidity that culminated during the beginning few centuries of the 1st millennium bc partially these fluctuations the main follow roughly a 1000 year periodicity can be related to known climate oscillations and glacier advances in the alps the ph was inferred using an alpine diatom calibration dataset alps based on weighted average regression ph levels fluctuated within one unit warm and dry periods between 7000 and 5000 cal bp caused ph levels to rise close to the present value cool and wet periods with extended snow cover are the main reason for ph lowering between 5000 and 1400 cal bp the core can be subdivided into a pre anthropogenic section from 7000 to 3500 cal bp and an anthropogenic section from 3500 cal bp to present the pollen records indicate that high altitude land use is closely related to climate alpine pasturing which was initiated during the bronze age at about 3500 cal bp intensified during the iron age and extended during medieval times with the formation of alpine pastures the c n ratio distinctly declined the long term trend of the iron manganese ratio indicates an inverse distribution probably due to erosional features short term fluctuations in median grain size and saturation isothermal remanence mainly have been caused by fluviatile transport and catchment erosion related to climate oscillations and deforestation processes related to anthropogenic deforestation and to enhanced nutrient fluxes from extended pastures are thought to be responsible for the modifications to the diatom assemblages which took place around 1000 cal bp

holocene environmental record from lake sediments in the bokanjacko blato karst polje dalmatia croatia abstract the bokanjacko blato karst polje field is a typical depression along the eastern adriatic coast that is filled with lake sediments this large scale structure is also an hydrologically important region as wells in southern part of the karst polje comprise the water supply for surrounding towns and villages the evolution of this polje however remains poorly understood a 7 8 m long sediment core from the south eastern part of the karst polje is utilized in this study to enable a multiproxy approach to the reconstruction of depositional processes that have occurred over the last 10 3 ka cal bp the sedimentological mineralogical and geochemical characteristics as well as palynological analyses of this core indicate that the whole sediment sequence consists of lake sediments alongside a variable amount of carbonates and silicates the lake existed for approximately 10 300 years before it was drained for agricultural purposes in the 1960s depositional changes are also evident throughout the core between 10 3 and 4 2 ka cal bp a higher values of magnetic susceptibility ms and concentrations of lithogenic elements indicate increased erosion and input of material from the catchment and therefore wetter climatic condition deposition of siliciclastic detrital material gradually decreased from 4 2 ka cal bp onwards replaced by carbonate sedimentation alongside minimal input of the former the carbonate based sandy silt sedimentation remains until hydromelioration of the depression the results of this study show that the lake level gradually increased between 4 2 and 2 9 ka cal bp evidenced by a higher carbonate content and a lower proportion of detrital material reaching a maximum between 2 9 and 1 6 ka cal bp data also show that at 1 6 ka cal bp the lake level was likely lowered due to higher nutrient content including sulfur s and phosphorus p as well as organic compound levels prior to human intervention and hydromelioration for agriculture high concentrations of the nutrient elements lead pb copper cu and zinc zn in the upper 40 cm of this sequence are indicative of the influence of agricultural activities across the karst polje as well as anthropogenic atmospheric pollution geochemical and sedimentological proxies illustrate centennial scale variability in carbonate deposition and erosional runoff processes comparable with the natural climatic and anthropogenic factors that are known to influence the evolution of holocene karst poljes across the central mediterranean

natural and anthropogenic sources of hg cd pb cu and zn in seawater and sediment of mljet national park croatia abstract distributions of hg cd pb cu and zn in seawater and sediment from mljet national park adriatic sea are presented for the first time natural and anthropogenic factors play an important role in determining resultant trace metals concentrations in the region we place particular emphasis on the saline lakes of malo jezero and veliko jezero which have restricted flows of seawater in malo jezero lake fresh karstic spring water generated by flooding and weathering of dolomites are the main sources of naturally elevated cd pb and zn concentrations 20 7 1 6 289 19 1260 0 08 ng l 1 respectively anthropogenic input is negligible in veliko jezero lake enhanced cu and zn contents originate from anthropogenic input tourism and agriculture distributions of the pb and zn in the water columns of both lakes are influenced by natural aragonite precipitation and sedimentation exceptionally high total hg concentrations of 24 2 and 33 7 ng l 1 in the water column of malo jezero sampled during periods of high rainfall associated with strong eastern winds suggest an airborne input total hg concentrations in waters of both lakes are elevated because of inefficient mixing two different metal distribution patterns exist in the sediment columns first hg pb cu and zn show elevated concentrations in recent sediments due to anthropogenic input second cd content increases with depth due to reprecipitation via a downward redox boundary shift described natural processes as well as anthropogenic influence enhance levels of trace metals careful study followed by suitable interpretation based on geochemical data were necessary to distinguish natural from anthropogenic sources

diatom responses to holocene environmental changes in a karstic lake vrana in dalmatia croatia abstract the 11 m sediment core of karstic lake vrana located at the dalmatian coast of eastern adriatic croatia was investigated through the analyses of diatoms the diatoms exhibited six marked changes in diatom zones dz with included water sediment interface as the record of environmental changes detected by marine and other terrestrial palaeoclimate records the diatoms recorded at the deepest sediments were interpreted to represent pleistocene holocene transition the dated holocene history is top 810 cm core section ca 8 1 cal kyr bp to the present the first zone record 1101 1050 cm was interpreted as alkaline oligo mesotrophic oxic lentic ecosystem of the karstic flooding plain based on the dominance of epithemia adnata enhanced bioproductivity of the shallow and unstable environment was noticed in the second diatom zone 1050 815 cm which was interpreted as the beginning of the holocene and it was divided into 4 subzones because of rapid environmental fluctuations a warmer period of temperate climate with a pluvial phase initiated development of the oligo mesosaprobic shallow lake in the early holocene the expansion of the macrophytes and higher cyanobacteria production that caused acidification and oxygen depletion at the lake bottom was determined in the mid holocene 810 713 cm 8 1 7 1 cal kyr bp mid holocene 8 1 4 7 cal kyr bp is marked by oligohalobic freshwater epithemia argus characteristic for alkaline water high cyanobacteria production was determined as a consequence of algal production that induced anoxic conditions in the lake bottom sediments from the warmer period till today the initial marine influx through the permeable karst underground was observed in the sediment record from ca 5 cal kyr bp the discovered marine influence on the lake indicating brackish water conditions related to the holocene sea level high stand the sea intrusion had different intensities through time and is still observed today in the seasonal fluctuation of lake water salinity the late holocene 2 7 cal kyr bp to the present sediment record is characterized with the strongest marine influxes and highest biodiversity of the mesosaprobic lake major changes in the water sediment interface of very shallow karstic lake were caused by anthropogenic agricultural activity in vrana diatom compositions of lake vrana indicate that they are sensitive to both paleoclimatic changes freshwater influx and sea level rise marine intrusion through permeable karst

holocene lake development of two dalmatian lagoons malo and veliko jezero isle of mljet in respect to changes in adriatic sea level and climate abstract within the austrian igbp pages project palaeolimnology of adriatic alpine lakes paal geochemical and diatom analyses were performed on sediment cores of malo and veliko jezero two karstic coastal lakes on the island mljet croatia combined with diatom calibration they provide evidence of remarkable environmental changes during the holocene the formation of the lakes in the early holocene was triggered by a rise in the adriatic sea level from approximately 50 to 30 m which resulted in the transmission of seawater through karst and by a temporary increase in precipitation the onset of this pluvial period was dated in malo jezero at 8 4 kyr b p and had its maximum approximately 7 6 kyr b p it was briefly interrupted by a dryer episode from about 7 2 until 7 1 kyr b p between 6 and 5 5 kyr b p a transition to the present mediterranean climate occurred the marine ingression into veliko jezero through the soline channel with a present depth of 2 5 m took place about 5 kyr b p from 5 to 4 kyr b p the oscillating sea level gradually approached the present value a tephra layer at 7 3 kyr b p in both lakes was related to sudden environmental changes that were probably caused by tectonic movements accompanying italian volcanism

kinematic evolution of thrusts wedge and erratic line length balancing insights from deformed sandbox models kinematic evolution of fold thrust structures has been investigated by analogue models that include syntectonic sedimentation different decollement dips and basement thicknesses produced different wedge geometries and propagating characteristics a model with one decollement level was characterized by a closely spaced thrust system during early stages of shortening as compared to the late stages the frequency of fault nucleation was rapid during the early stages of deformation conversely the frequency of fault nucleation was low and thrust spacing was significantly wider in a model with two decollement levels individual faults became locked at steep dips and deformation stepped forward as a new fault nucleated in sequence in front of the older locked structure once the thrust system was established up to 27 overall shortening an overlying bed was introduced to simulate syntectonic deformation model sand wedge did not grow self similarly but rather its length and height increased episodically with deformation restoration of deformed models show that layer parallel shortening accommodated for approximately half of the total model shortening across the multilayers calculated error in apparent layer shortening from the restored layers revealed a direct relation with depth of the layers in the models the experimental results are comparable to a natural example from the northern apennines fold and thrust belts

mechanisms of thrust propagation some examples and implications for the analysis of overthrust terranes abstract evidence is presented for the existence of three fundamental mechanisms by which thrust sheets move the mechanisms are 1 failure of a stiff layer to form ramp flat geometry imbricated thrust sheets 2 detachment of a layer by folding decollement thrust sheets 3 differential layer parallel shortening lps thrust sheets the mechanisms are independent but may operate interactively to form families of hybrid thrust sheets since lps thrust sheets have not been previously described or documented data from the new york plateau deformed almost exclusively by differential lps is presented to demonstrate the physical characteristics of this thrust mechanism information from the plateau indicates that finite strain behavior closely reflects the geometric boundary conditions and is independent of temperature and depth of burial finite strain data are used to construct a set of iso strain maps in both the deformed and undeformed states the iso strain maps are in turn used to determine the displacement field for the thrust sheet the displacement field allows visualization of the effects of both lagrangian and eulerian transformations on an initially orthogonal grid utilizing sections from a number of overthrust belts it is shown that the three mechanisms occur universally although in various proportions lps is regionally developed throughout the central and northern appalachians the presence of the lps thrust sheets probably accounts for the failure of structural cross sections to bed length balance in these blind thrust terranes finally a series of examples drawn from the field as well as the literature are used to illustrate both the characteristics of hybrid thrust sheet families as well as to indicate how knowledge of their behavior can be utilized in developing strategies for the construction and balancing of structural cross sections

holocene climatic conditions in the eastern adriatic recorded in stalagmites from strasna pec cave croatia abstract in the study we present results of stable isotope analysis 18o 13c of two stalagmites spd 1 and spd 2 from strasna pec cave situated on dugi otok island in the central adriatic region the growth interval of the speleothems based on u th dating covers the period from 4 4 ka to 1 5 ka both speleothems show frequent 18o and 13c fluctuations with similar average values 18o value of 4 for both speleothems and average value of 13c 8 5 and 8 8 respectively in order to reconstruct the holocene climatic conditions in the eastern adriatic the speleothem isotopic record is discussed and compared with other holocene records they reveal periods of drought which occurred at 4 3 4 ka and around 3 5 ka with relatively wet phases between from 3 ka there is a general trend towards dryness as evidentiated by the relatively high 18o values of 3 5 to 2 5 recorded in speleothem spd 1 there is distinct trend of drying during the roman warm period and further toward the dark age cold period dacp with shorter periods of wetter conditions these changes coincide well with the other records thus revealing regional events along the eastern adriatic