history and influence of the danube delta lobes on the evolution of the ancient harbour of orgame dobrogea romania on the coast of northern dobrogea south of the danube delta the greek settlement of orgame was founded in the mid 7th c bc probably by milesian colonists the ancient city was located on the cape dolojman which today overlooks a large lagoon complex we undertook a chronostratigraphic study to i understand coastal changes around cape dolojman since ca 5000 years bp in connection with the construction of the danube delta lobes and ii identify potential sediment impacts related to human occupation of the site three cores were extracted from the lagoon area sedimentological and biological analyses were undertaken to reconstruct the evolution of the coastal palaeoenvironments the results show a closure of the marine bay around 3500 cal bp and its transformation into a lagoon environment the first major environmental change was due to the construction of the lobe st george i and the formation of the barrier lupilor around 2000 cal bp the formation of an intra lagoonal lobe the dunavatz led to the gradual transformation of the lagoon into a fluvial dominated system paradoxically lagoon waters today still wash the ancient greek harbour environment which has not been totally infilled by alluvial sediments to understand this paradox in a context of coastal progradation we compared and contrasted the geomorphological data with the nearby city of istros histria which was already landlocked at this time the location of these two greek colonies relative to the coastal sediment cell and barriers partly explains their contrasting palaeoenvironmental evolution until 2650 cal bp the increase in charcoal and organic matter in sedimentary archives is interpreted as an anthropogenic signal for a more extensive use of the vegetation cover following the foundation of the city of orgame e g for domestic use and funeral rites

static bay beach concept for scientists and engineers a review abstract headland bay beach hbb is one of the most prominent physiographic features on the oceanic margin of many countries in the world under the influence of a predominant swell its curved periphery in natural environment may reach static equilibrium and remains stable without sediment supply from updrift and or a riverain source within its own embayment coastal scientists and engineers have attempted to develop mathematical expressions to quantify this ideal bay shape since the 1940s as the scenario with depleting sediment supply has become a common reality on many parts of the world coastline in more recent time some coastal engineers have advocated a rational approach to mimicking the static bay shape found in nature in order to mitigate beach erosion as well as for coastal management nowadays many useful applications have emerged since the publication of the parabolic bay shape equation pbse developed for static equilibrium planform sep in late 1980s the advance in modern computer technologies and international collaboration has further facilitated the exchange of knowledge and applications of this static bay beach concept sbbc this paper reviews the progress on the research in hbb made by geographers and geologists since the 1940s together with the involvement of coastal engineers working on shore protection and management from the 1960s aided by software mepbay developed in 2003 for the pbse several practical examples are demonstrated in this paper for the stability verification of natural and man made bay beaches shore protection mitigating downdrift erosion of a harbour design of recreational bay beach as well as for environmental impact assessment limitations on and clarifications for engineering applications based on the sbbc are also discussed in this paper

the onset of islandscapes in the balearic islands a study case of addaia northern minorca spain abstract paleoenvironmental and archaeological data show that mediterranean landscapes result from long term socio environmental interactions mediterranean islands constitute a place of passage where the creation of cultural landscapes can be traced through colonization and anthropization histories palynological studies carried out in the balearic islands highlight a deep vegetation change from the mid to late holocene but the climate environmental human interactions are not fully understood yet in this study we aim to disentangle the causalities of landscape changes during the last six millennia using a multi proxy approach on an off site core for the first time in minorca island we find that during the mid holocene the climate was wetter than today with less rainfall seasonality than in the current mediterranean this climate favoured the expansion of box formations and the predominance of forested formations with minimal anthropized conditions first agropastoral activities appeared in the sequence between ca 3500 2650 cal bce in north eastern minorca coinciding with other sporadic archaeological evidence cova dels morts rock shelter which support the possibility of a pre chalcolithic discovery and frequentation of the island we record deep environmental change during the third millennium cal bce reflected in the substitution of the former mesophytic vegetation by mediterranean maquis formations dominated by wild olive trees heathers mastic and cistaceae we propose that maquis garrigues and open land vegetation were favoured by human action in a context of increasing climatic dryness and seasonality promoting vegetation flammability and substitution of former mesic communities to more adapted termophilous vegetation the comparison of our new record from addaia with other pollen studies from the balearic islands highlights the resilience of mesic vegetation to climate change this is shown by the survival of box formations to the increased aridification initiated at ca sixth fifth millennium cal bce ca 7 6 cal kyr bp in the western mediterranean which culminated at ca fourth third millennium cal bce ca 5 4 cal kyr bp additionally whilst sporadic human presence versus stable occupation are difficult to detect in archaeological records the coupling with paleoenvironmental studies may offer new scenarios and information for human arrival in the balearic islands

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

saharan aeolian input and effective humidity variations over western europe during the holocene from a high altitude record saharan dust inputs affect present day ecosystems and biogeochemical cycles at a global scale previous saharan dust input reconstructions have been mainly based on marine records from the african margin nevertheless dust reaching western central europe is mainly transported by high altitude atmospheric currents and requires high altitude records for its reconstruction the organic and inorganic geochemical study of sediments from a southern iberia alpine lacustrine record has provided an exceptional reconstruction of saharan dust impact and regional climatic variations during the holocene after the last deglaciation results indicate that saharan dust reached western europe in a stepwise fashion from 7 0 to 6 0 cal kyr bp and increased since then until present promoting major geochemical changes in the lacustrine system effective humidity reconstruction indicates wetter conditions during the early holocene and progressive aridification during middle late holocene time boosting abrupt changes in the lacustrine system cyclostratigraphic analyses and transport mechanisms both point to solar irradiance and aridity as major triggering factors for dust supply over western europe during the holocene

holocene hydrological changes in south western mediterranean as recorded by lake level fluctuations at lago preola a coastal lake in southern sicily italy abstract this paper presents a high resolution lake level record for the holocene at lago preola sicily southern italy based on a specific sedimentological approach with a chronology derived from ams radiocarbon dates it gives evidence of three major successive palaeohydrological periods with 1 a pronounced dryness during the early holocene until ca 10300 cal bp 2 a highstand from ca 10300 to 4500 cal bp and 3 a marked lowstand from 4500 cal bp to present large amplitude lake level fluctuations characterise two transition phases at ca 10300 9000 and 6400 4500 cal bp period 2 was interrupted between 8300 and 7000 cal bp by a dry phase that was punctuated to ca 7300 cal bp by the deposition of a tephra from neighbouring pantelleria island comparisons of the preola record with other palaeohydrological records along north south and west east transects in the mediterranean show contrasting patterns of hydrological changes north south of around 40 n latitude the records highlight a mid holocene period characterised by lake level minima maxima humid mid holocene conditions over the mediterranean south of 40 n were probably linked to a strong weakening of the hadley cell circulation and of monsoon winds we suggest that the maximum of humidity in the mediterranean during the mid holocene was characterised by humid winters to the north of 40 n and humid summers to the south on a multi centennial scale the high resolution palaeohydrological reconstructions in the central mediterranean area reveal a strong climate reversal around 4500 4000 cal bp with contrasting changes in the hydrological cycle in addition to seasonal and inter hemispherical changes related to orbital forcing this major oscillation might be related to non linear responses of the climatic system to the gradual decrease in summer insolation at northern latitudes another major climate oscillation around 7500 7000 cal bp may have resulted from the combined effects of 1 a strong rate of change in insolation and 2 variations in solar activity finally comparisons of the preola lake level record with sicilian pollen records suggest a strong influence of moisture availability on vegetation development in sicily very dry early holocene conditions probably prevented the expansion of coastal evergreen forests while decreasing moisture availability since the onset of the late holocene may have exacerbated effects of intensive land use

variations of hydraulic properties of granular sandstones during water inrush effect of small particle migration the evaluation of the hydraulic properties evolution of granular sandstones in relation with groundwater inrush within faults is an important issue for mining engineering applications this paper presents the results of an experimental investigation of small particle migration from granular sandstone samples under different original porosities particle size compositions and water flow pressures a new rock testing system has been setup to carry out the tests based on the results it is observed that the overall permeability evolution during the tests can be divided into four different phases including i re arrangement of large rock fragments ii water inrush with substantial particle migration iii continued moderate particles seepage and iv steady state water flow the crushing of edges and corners of large rock fragments and the evolution of the fracture network has mainly been observed in the first two phases of the tests the results indicate that the migration of small particles has an essential effect on permeability and porosity increase during water inrush through fractured sandstone the samples with higher original porosity higher percentage of fine particles in their formation and under higher water flow pressures achieve higher permeability and porosity values when the test is complete furthermore using the measured data the performances of a number of empirical models for permeability evolution in fractured porous media have been studied the prediction results indicate that not all of the fractures in a sample domain contribute in small particle migration there are parts of the fracture network that are not effective in particle flow a sample with less original porosity more fine particles and under lower water pressure shows less ineffective fractures therefore using the concept of the effective porosity fracture is sufficient enough for the flow calculation

frictional viscous flow of phyllosilicate bearing fault rock microphysical model and implications for crustal strength profiles it is widely believed that around the brittle ductile transition crustal faults can be significantly weaker than predicted by conventional two mechanism brittle ductile strength envelopes factors contributing to this weakness include the polyphase nature of natural rocks foliation development and the action of fluid assisted processes such as pressure solution recently ring shear experiments using halite kaolinite mixtures as an analogue for phyllosilicaterich rocks for the first time showed frictional viscous behavior i e both normal stress and strain rate sensitive behavior involving the combined effects of pressure solution and phyllosilicates this behavior was accompanied by the development of a mylonitic microstructure a quantitative assessment of the implications of this for the strength of natural faults has hitherto been hampered by the absence of a microphysical model in this paper a microphysical model for shear deformation of foliated phyllosilicate bearing fault rock by pressure solution accommodated sliding along phyllosilicate foliae is developed the model predicts purely frictional behavior at low and high shear strain rates and frictional viscous behavior at intermediate shear strain rates the mechanical data on wet halite kaolinite gouge compare favorably with the model when applied to crustal materials the model predicts major weakening with respect to conventional brittle ductile strength envelopes in particular around the brittle ductile transition the predicted strength profiles suggest that in numerical models of crustal deformation the strength of high strain regions could be approximated by an apparent friction coefficient of 0 25 0 35 down to depths of 15 20 km

sporormiella fungal spores a palynological means of detecting herbivore density during the historic period spores of the dung fungus sporormiella are abundant in lake and cave sediment where livestock are plentiful in the western united states sporormiella spores occasionally exceed 50 of the upland pollen sum in samples from corral ponds and bed grounds and routinely reach 4 in lake and marsh samples in pastoral areas sporormiella spores are comparatively rare in mid holocene sedimentary records but they reach values of 2 4 in pleistocene samples from lake sediments sporormiella spores are directly linked to extinct megaherbivores by their presence in mammoth dung from bechan cave utah in several sites in the western united states a precipitous decline of sporormiella percentages after ca 10 800 radiocarbon yr b p 12 900 years ago marks a decline of herbivore density probably associated with the north american megaherbivore extinction

mechanisms of weak phase interconnection and the effects of phase strength contrast on fabric development abstract to determine how deformation mechanisms and fabrics evolve during the strain weakening and localization that accompany the transition from a load bearing framework to an interconnected weak phase shear experiments were conducted on a fine grained gneiss 58 quartz interconnected 28 plagioclase dispersed 13 biotite aligned but dispersed at 745 and 800 c 1500 mpa and two strain rates 2 10 5 and 2 10 6 s 1 in experiments with a high phase strength contrast hpsc 25 and 45 between dispersed biotite and framework quartz grains biotite grains become interconnected due to stress concentration at their tips that allow local semi brittle flow of intervening quartz and cataclasis of intervening plagioclase in the higher temperature hpsc samples the biotite partially dehydrated in high strain zones a single narrow shear zone formed because the psc between the quartz and biotite reaction product layers remained high in the lower temperature hpsc samples there was no reaction and a penetrative s c fabric formed the fabric is defined by the many multiply interconnected biotite strands that formed because the psc between the quartz and biotite decreased as the biotites kinked in slower strain rate experiments with a much lower psc 10 biotite interconnection occurs by shearing into quartz quartz boundaries where new weak strain free recrystallized grains form at low strain a weak s c fabric forms but it evolves to an s c fabric as the psc decreases with strain thus the magnitude of the strength contrast between a weak phase and its matrix influences the mechanism of weak phase interconnection the degree of strain localization and the fabric

use of extension testing to investigate the influence of finite strain on the theological behaviour of marble most mechanical testing of rocks at high temperatures is carried out under axisymmetric triaxial shortening to small 20 strains however the most significant geological deformations involve much higher strains especially in plastic shear zones where there has been strain localization highly strained rocks commonly are microstructurally modified by dynamic recrystallization so that the sheared rock is microstructurally quite different from its protolith high strain deformation in experiments can be induced by direct shear or through torsion or by taking advantage of the tendency for extensional deformations to result in necking it is important to be able to separate out the geometrical factors favouring localization from those arising from strain dependent microstructural changes here we present the results of high strain 1000 axisymmetric extension tests on carrara marble at 700 c and 800 c in the form of strain time plots for the evolution of material sections through the sample at different distances from the neck at 800 c it is clear that total dynamic recrystallization by grain boundary migration is accompanied by substantial mechanical weakening but sufficient strain could not be applied to reach the steady state condition for the recrystallized material the recrystallization is interpreted to produce weakening because the migration of grain boundaries sweeps grains clear of accumulating dislocation density faster than recovery by dislocation climb in nature such mechanical weakening would be expected to favour the stable development of a localized zone of deformation

environmental change in crete a 9000 year record of holocene vegetation history and the effect of the santorini eruption palynological investigations were carried out in the coastal lowland of northwestern crete in the area of lake kournas results comprise the longest continuous vegetation record 9000 radiocarbon years for crete from about 8500 to 7500 bp open deciduous oak forest occurred and appears to reflect the driest conditions of the holocene after 7500 bp tree pollen numbers increase some of these tree species are thought to be autochthonous but for at least six species this is doubted and the presence of their pollen is ascribed to long distance transport up to 6000 bp the local vegetation included deciduous and evergreen oaks pistacia phillyrea and a variety of herbs only after 7000 bp some species e g mercurialis annua cynocrambe and spores of pteridium might indicate the effects of neolithic habitation towards 6000 bp plane tree and styrax storax appear from about 6000 bp olive is present and human activity becomes more evident slowly pollen types indicative of the exploitation of present day mediterranean vegetation e g poterium and ericaceae appear and the presence of the alga gloeotrichia indicates a rise in phosphate a striking aspect of the sediment core nearest to the sea is a pumice layer originating from the theran santorini eruption from the manner of its deposition it is concluded that no tsunami met the cretan beach influence of the eruption from thera on the vegetation is hardly visible decrease of economically important cultivated plants e g olive already took place decades up to about a century before the volcanic eruption around the time of the eruption the values of some pollen types hardly changed others increased and another group decreased this pollen behaviour appears to be explained rather by socio economic changes such as withdrawing of the inhabitants to the interior for reasons other than volcanic effects it is concluded from the pollen cores that no major climatic changes affected northwestern crete during the holocene but the first two millennia of the holocene tended to be drier than the following period when there was an increase in moisture demanding trees it is difficult to assign changes in the cretan vegetation to climatic effects in a period when human impact was gathering strength

further evidence of abrupt holocene drowning of the black sea shelf a 1999 survey of the black sea continental shelf off the north central turkish seaport of sinop using a side scan sonar small remotely operated vehicles and a series of dredge lowerings located inspected and sampled an exposed high energy paleoshoreline at a depth of 155 m radiocarbon dating of mollusk shells collected from this ancient beach revealed that the marine flooding of the black sea took place between 7460 and 6820 yr b p all ages are reported in radiocarbon years not calendar years without correction for reservoir age or dendro calibration changing it from a lacustrine to marine environment this relic surface remained in contact with the bottom waters of the black sea for a long period of time before being draped by a thin layer of sapropel mud wood samples recovered from this same location were very well preserved and yielded dates as old as 3580 yr b p q 2000 elsevier science b v all rights reserved

palynological evidence for climatic change and human activity during the holocene on minorca balearic islands four pollen diagrams from minorca balearic islands have been correlated with other previously studied sequences from majorca and minorca to define a holocene landscape sequence for the region from 8000 yr b p to the present the lower part of the pollen diagrams reflects a climatic phase with more rain and less marked seasonality than today significant quantities ofcorylus buxus and mesophilous taxa are found in the middle part between 5000 and 4000 yr b p a strong change is recorded in composition and structure of the vegetational landscape with vegetation appearing that was adapted to mediterranean conditions this episode coincided with the first human colonization of the island and also with a widespread climatic change in the western mediterranean region the change in taxa was complex and some sclerophyllous taxa sucholeaplayed an important role in the transformation of the landscape physiognomy from the mid holocene until the present although human activities have removed much of the mediterranean vegetation on the balearic islands it seems clear that the changes have been brought about in part by increasing dryness

growth and deformation mechanisms of talc along a natural fault a micro nanostructural investigation this paper documents the occurrence of large amounts of talc within a continental normal fault the talc in reaction is deformation enhanced and occurs by the interaction between dolostones and silica rich hydrothermal fluids in the high strain foliated fault core talc forms an interconnected network of oriented 001 lamellae 200 300 nm thick locally associated with minor tremolite fibres up to 300 nm in diameter the talc structure is affected by several strain induced defects among which 001 interlayer delamination that produces talc sublamellae down to 10 30 nm thick micro nanostructural observations definitely point to a predominant deformation mechanism of 001 frictional sliding further enhanced by pervasive delamination that gives rise to an almost infinite number of possible sliding surfaces these effects have fundamental implications in fault mechanics resulting in significant fault weakening

linking the vicissitude of neolithic cities with mid holocene environment and climate changes in the middle yangtze river china abstract this study investigated fifteen neolithic cities distributed in a crescent shaped belt along the middle yangtze river from the period between 4750 and 3050 bc 6 7 5 0 cal ka bp the belt consists of a low lying medial alluvial plain surrounded by hills more than 50 m a s l above sea level the neolithic cities within this belt occupied three distinct topographies the highlands of alluvial plains the lower foothills and the surrounding hills all the cities were situated adjacent to the lowest level tributaries or smallest lakes and had complex trench defense systems with rivers and lakes interlinking the trenches and most of the cities had defensive moats construction peaks of defensive fortifications occurred during the daxi 4550 3050 bc and qujialing cultures 3050 2650 bc while most neolithic cities were abandoned in the late shijiahe period 2250 bc based on assessments on the locality age construction and the detailed information on the geographical characteristics of the neolithic cities the sites of neolithic cities were tightly associated with the development history of east civilization and the rise of the cities is well correlated with the warm and humid climate in mid holocene 5 2 cal ka bp or 3250 bc while the decline of the ancient cities is related with the dry and cold climate in mid late holocene 4 2 cal ka bp or 2250 bc the development and decline of these cities were also well linked with water accessibility topography and the occurrence of droughts floods and other extreme events during the mid holocene such environment conditions and climate changes played significant roles for the ancient people to determine the location structure and morphology of the cities although the military considerations were also important we cannot simply consider the prehistoric city construction in the middle yangtze river was a passive defense against foreign invasion

nanocoatings of clay and creep of the san andreas fault at parkfield california mudrock samples were investigated from two fault zones at 3066 m and 3296 m measured depth md located outside and within the main damage zone of the san andreas fault observatory at depth safod drillhole at parkfield california all studied fault rocks show features typical of those reported across creep zones with variably spaced and interconnected networks of polished displacement surfaces coated by abundant polished films and occasional striations electron microscopy and x ray diffraction study of the surfaces reveal the occurrence of neocrystallized thin film clay coatings containing illite smectite i s and chlorite smectite c s minerals 40 ar 39 ar dating of the illitic mix layered coatings demonstrated miocene to pliocene crystallization and revealed an older fault strand 8 1 3 ma at 3066 m md and a probably younger fault strand 4 4 9 ma at 3296 m md today the younger strand is the site of active creep behavior reflecting a possible re activation of these clay weakened zones we propose that the majority of slow fault creep is controlled by the high density of thin

frictional behavior of materials in the 3d safod volume 1 we report on frictional properties of rocks within the 3 d crustal volume surrounding the san andreas fault observatory at depth safod samples include lithologies adjacent to the san andreas fault saf in the subsurface safod borehole rocks and synthetic fault gouge composed of talc serpentinite and quartz granodiorite arkosic sandstone and siltstone samples from the safod borehole are frictionally strong 0 56 0 66 sand and clay rich lithologies from outcrop exhibit friction in the range 0 56 0 68 natural serpentinite thought to abut the saf at depth exhibits low friction 0 18 0 26 our results indicate that 1 serpentinite exhibits low strength but is not weak enough to completely satisfy weak fault models 2 all other samples are consistent with a strong fault and crust and 3 if the saf is weak 0 2 due to the presence of serpentinite or talc these minerals would likely need to constitute over 50 by weight of the shear zone

vegetation and landscape dynamics under natural and anthropogenic forcing on the azores islands a 700 year pollen record from the sao miguel island abstract the azores archipelago has provided significant clues to the ecological biogeographic and evolutionary knowledge of oceanic islands palaeoecological records are comparatively scarce but they can provide relevant information on these subjects we report the palynological reconstruction of the vegetation and landscape dynamics of the sao miguel island before and after human settlement using the sediments of lake azul the landscape was dominated by dense laurisilvas of juniperus brevifolia and morella faya from ca 1280 ce to the official european establishment 1449 ce after this date the original forests were replaced by a complex of erica azorica myrsine africana forests shrublands and grassy meadows which remained until ca 1800 ce extractive forestry cereal cultivation rye maize wheat and animal husbandry progressed until another extensive deforestation ca 1774 ce followed by the large scale introduction 1845 ce of the exotic forest species cryptomeria japonica and pinus pinaster which shaped the present day landscape fire was a significant driver in these vegetation changes the lake levels experienced a progressive rise during the time interval studied reaching a maximum by ca 1778 1852 ce followed by a hydrological decline likely due to a combination of climatic and anthropogenic drivers our pollen record suggests that sao miguel were already settled by humans by ca 1287 ce approximately one century and a half prior to the official historically documented occupation of the archipelago the results of this study are compared with the few palynological records available from other azores islands pico and flores

an abrupt drowning of the black sea shelf abstract during latest quaternary glaciation the black sea became a giant freshwater lake the surface of this lake drew down to levels more than 100 m below its outlet when the mediterranean rose to the bosporus sill at 7 150 yr bp 1 saltwater poured through this spillway to refill the lake and submerge catastrophically more than 100 000 km2 of its exposed continental shelf the permanent drowning of a vast terrestrial landscape may possibly have accelerated the dispersal of early neolithic foragers and farmers into the interior of europe at that time

frictional strengths of talc serpentine and talc quartz mixtures 1 talc is a constituent of faults in a variety of settings and it may be an effective weakening agent depending on its abundance and distribution within a fault we conducted frictional strength experiments under hydrothermal conditions to determine the effect of talc on the strengths of synthetic gouges of lizardite and antigorite serpentinites and of quartz small amounts of talc weaken serpentinite gouges substantially more than predicted by simple weight averaging in comparison mixtures of quartz and talc show a linear trend of strength reduction at talc concentrations 15 wt and enhanced weakening at higher concentrations all of the strength data are fit by a modified version of the reuss mixing law that allows for the dominance of one mineral over the other the difference in the behavior of serpentinite talc and quartz talc mixtures at low talc concentrations is a reflection of their different textures lizardite antigorite and talc all have platy habits and displacement within gouges composed of these minerals is localized to narrow shears along which the platy grains have rotated into alignment with the shear surfaces the shears in the mixed phyllosilicate gouges maximize the proportion of the weaker mineral within them when mixed with a strong rounded mineral such as quartz some minimum concentration of talc is needed to form connected pathways that enhance strength reductions the typical development of talc by the reaction of si rich fluids with serpentinite or dolomite would tend to localize its occurrence in a natural fault and result in enhanced weakening

effect of clay content and mineralogy on frictional sliding behavior of simulated gouges binary and ternary mixtures of quartz illite and montmorillonite 1 we investigated the frictional sliding behavior of simulated quartz clay gouges under stress conditions relevant to seismogenic depths conventional triaxial compression tests were conducted at 40 mpa effective normal stress on saturated saw cut samples containing binary and ternary mixtures of quartz montmorillonite and illite in all cases frictional strengths of mixtures fall between the end members of pure quartz strongest and clay weakest the overall trend was a decrease in strength with increasing clay content in the illite quartz mixture the trend was nearly linear while in the montmorillonite mixtures a sigmoidal trend with three strength regimes was noted microstructural observations were performed on the deformed samples to characterize the geometric attributes of shear localization within the gouge layers two micromechanical models were used to analyze the critical clay fractions for the two regime transitions on the basis of clay porosity and packing of the quartz grains the transition from regime 1 high strength to 2 intermediate strength is associated with the shift from a stress supporting framework of quartz grains to a clay matrix embedded with disperse quartz grains manifested by the development of p foliation and reduction in riedel shear angle the transition from regime 2 intermediate strength to 3 low strength is attributed to the development of shear localization in the clay matrix occurring only when the neighboring layers of quartz grains are separated by a critical clay thickness our mixture data relating strength degradation to clay content agree well with strengths of natural shear zone materials obtained from scientific deep drilling projects

development of interconnected talc networks and weakening of continental low angle normal faults fault zones that slip when oriented at large angles to the maximum compressive stress i e weak faults represent a significant mechanical problem here we document fault weakening induced by dissolution of dolomite and subsequent precipitation of calcite abundant talc along a low angle normal fault within the fault core talc forms an interconnected foliated network that deforms by frictional sliding along 50 200 nm thick talc lamellae the low frictional strength of talc combined with dissolution precipitation creep can explain slip on low angle normal faults in addition the stable sliding behavior of talc is consistent with the absence of strong earthquakes along such structures the development of phyllosilicates such as talc by fluid assisted processes within fault zones cutting mg rich carbonate sequences may be widespread leading to profound and long term fault weakness

holocene evolution of the danube delta an integral reconstruction and a revised chronology abstract the danube delta is one of the few large deltas in the world the evolution of which has involved numerous and varied episodes within a complex framework of interactivity between river sediment supply allochthonous sediments supplied by longshore currents marine dispersing forces vertical movements neotectonics sediment compaction and sea level the resulting complex morphology comprises diversified landscapes varying from labyrinthic net of channels and lakes fluvial delta to massive tracts of monotonous reed marshes large lagoons divided by barriers or beach ridge plains accommodating large transgressive dunefields maritime delta whilst previous studies have focused on various sectors of the danube delta the current paper proposes for the first time an integral reconstruction of delta evolution based on existing and new sedimentological and morphological analyses and absolute ages ams 14 c and osl enabling a comprehensive synthesis in terms of both evolutionary phases and growth patterns a chronological framework was established for all the deltaic lobes and beach ridge plains highlighting the relationship between formation timespan growth rates and the resultant morphology this work unveils the early stage of delta formation including the reconstruction of delta front advancement into danube bay old danube lobe prior to 7 5 5 5 ka and initial spit barrier development 6 7 6 5 5 8 ka inception of the bayhead delta started 1000 yr before the relative stabilization of sea level and of the initial spit formation the original fluvial delta plain topography is now buried at a depth of 4 6 m depth below the present topography representing the current stage of fluvial aggradation as a result of subsidence and sea level rise regarding the maritime delta six large open coast lobes developed in the last six millennia of which four were formed by the sf gheorghe branch attesting the long uninterrupted activity of this branch whereas the other two were created respectively by the sulina and the chilia branches the evolution of each lobe is derived from successive chronological shoreline positions and discussed in relation with changes in danube discharge special attention has been paid to their growth stages and progradation rates for the southern delta we bring in new arguments for an active southern distributary the dunav derived from the sf gheorghe branch that formed successive open coast lobes between 2 6 and 1 3 ka additionally we discuss the effects of modern anthropogenically driven fluvial sediment reduction on the morphology and morphodynamics of the active lobes of the danube

the late holocene evolution of the black sea a critical view on the so called phanagorian regression abstract throughout its geologic history the black sea experienced major sea level changes accompanied by severe environmental modifications including geomorphologic reshaping the most spectacular changes were driven by the quaternary glaciations and deglaciations that reflect responses to milankovitch cycles of 100 and 20 ky periodicity major sea level changes were also considered for a shorter and more recent cyclicity the concept of the phanagorian re and transgression cycle supposedly with a minimum sea level stand of 5 6 m below its present position in the middle of the 1st millennium bc was established in 1963 by fedorov for the black sea region it was based on archaeological and palaeogeographical research conducted around the ancient greek colonies of the cimmerian bosporus in particular at the name giving site of phanagoria where underwater prospection had revealed the presence of a large number of submerged relics of the classical greek era analyses of sediment cores as well as 14c dated fossil coastal bars in the western and southern parts of taman peninsula show that contemporary coastal bars are related to different sea levels the dissymmetry can reach up to 6 m around 500 bc this and more evidence from drill cores confirms that on taman peninsula many of the apparent sea level changes are tectonically induced the subsidence may have been initiated by the release of gas from mud volcanoes inherited along anticline axes other observations around the black sea confirm that submerged archaeological sites correspond to areas where subsidence has taken places while the so called holocene highstand said to have been located above the present day sea level is associated with uplift areas triggered by the ongoing caucasus orogeny recent oceanographic research carried out in the black sea area shows that since the black sea was reconnected with the mediterranean sea i e 7500 14c bp at the latest both marine water bodies have been in equilibrium this fact and arguments from archaeology history hydrodynamics etc lead us to question the existence of the phanagorian regression it is important to note that none of the sea level curves established for the eastern mediterranean shows a comparable regression transgression cycle of several metres during the 1st millennium bc

young danube delta documents stable black sea level since the middle holocene morphodynamic paleogeographic and archaeological implications new radiocarbon and optical dates show that the holocene danube delta started to build out of a black sea embayment 5200 yr ago delta lobe development phases differ by as much as 5 k y from previously proposed ages the new chronology allows for a better understanding of the danube delta paleogeography includ ing the demise of istria the main ancient greek roman city in the region prior reconstructions of sea level in the black sea inferred fluctuations to 15 m in range however stratigraphy of beach ridg es in the delta shows that the relative black sea level for the past 5 k y was stable in the danube delta region within 2 m and 1 5 of the current level hydroisostatic effects related to a proposed catastrophic reconnection of the black sea to the world ocean in the early holocene may have been responsible for the sea level reaching the highstand earlier than estimated by models the new sea level data suggest that submergence at several ancient settle ments around the black sea may be better explained by local fac tors such as subsidence rather than by basin wide sea level fluctuations

climate change versus land management in the po plain northern italy during the bronze age new insights from the vp vg sequence of the terramara santa rosa di poviglio abstract the sedimentary infilling of the moat surrounding the villaggio piccolo of the terramara santa rosa di poviglio was analysed in order to obtain palaeoenvironmental inferences from sediments and pollen assemblage the high resolution stratigraphic sequence preserves evidence of the environmental changes that occurred in the po plain in northern italy during the late holocene our interdisciplinary approach permitted to study climatic and anthropic contributions to the environmental changes in this region the relationships between these changes and land use changes were investigated focussing on adaptive strategies of the terramare people during the middle and recent bronze ages 1550 1170 yr bc the terramare are archaeological remains of banked and moated villages located in the central alluvial plain of the po river the terramara of santa rosa consists of two adjoining settlements villaggio grande and villaggio piccolo the moat that separates the two parts of the site is c 23 m large and reaches a maximum depth of 4 m from the extant ground level the stratigraphic sequence vp vg exposed by archaeological excavation inside the moat was sampled for pedosedimentary thin section and pollen analyses chronology is based on archaeological evidence stratigraphic correlations and radiocarbon dating pedosedimentary features and biological records pollen of aquatics and algal remains demonstrate that shallow water probably subjected to seasonal water level oscillations has always been present in the moat in the lower units of the sequence the laminations indicate standing water while occurrence of reworked pollen testified the supply of sediments to the plain from catchment zones located in the apennine open vegetation was widespread economy was based on wood management fruit collection on the wild or from cultivated woody plants crop fields with a fairly diversified set of cereals especially increasing in variety during dryness or phases of water crisis probably grapevines were cultivated near the moat where the wet habitat was favourable to the growing of wild plants the extraordinary high resolution of this sequence makes visible the management of woods including coppicing at the middle bronze and early recent bronze ages the economy of santa rosa di poviglio should have been probably less based on animal breeding than it was in the other terramare villages already studied for pollen this research also confirms the chronological correspondence between an environment stressed by dry conditions and the collapse of the terramare civilization

talc friction in the temperature range 25 400 c relevance for fault zone weakening abstract talc is one of the weakest minerals that is associated with fault zones triaxial friction experiments conducted on water saturated talc gouge at room temperature yield values of the coefficient of friction shear stress effective normal stress n in the range 0 16 0 23 and increases with increasing n talc gouge heated to temperatures of 100 400 c is consistently weaker than at room temperature and talc has a temperature pressure range of stability that extends from surficial to eclogite facies conditions making it of potential significance in a variety of faulting environments talc has been identified in exhumed subduction zone thrusts in fault gouge collected from oceanic transform and detachment faults associated with rift systems and recently in serpentinite from the central creeping section of the san andreas fault typically talc crystallized in the active fault zones as a result of the reaction of ultramafic rocks with silica saturated hydrothermal fluids this mode of formation of talc is a prime example of a fault zone weakening process because of its velocity strengthening behavior talc may play a role in stabilizing slip at depth in subduction zones and in the creeping faults of central and northern california that are associated with ophiolitic rocks

talc bearing serpentinite and the creeping section of the san andreas fault the section of the san andreas fault located between cholame valley and san juan bautista in central california creeps at a rate as high as 28 mm yr 1 ref 1 and it is also the segment that yields the best evidence for being a weak fault embedded in a strong crust serpentinized ultramafic rocks have been associated with creeping faults in central and northern california and serpentinite is commonly invoked as the cause of the creep and the low strength of this section of the san andreas fault however the frictional strengths of serpentine minerals are too high to satisfy the limitations on fault strength and these minerals also have the potential for unstable slip under some conditions here we report the discovery of talc in cuttings of serpentinite collected from the probable active trace of the san andreas fault that was intersected during drilling of the san andreas fault observatory at depth safod main hole in 2005 we infer that the talc is forming as a result of the reaction of serpentine minerals with silica saturated hydrothermal fluids that migrate up the fault zone and the talc commonly occurs in sheared serpentinite this discovery is significant as the frictional strength of talc at elevated temperatures is sufficiently low to meet the constraints on the shear strength of the fault and its inherently stable sliding behaviour is consistent with fault creep talc may therefore provide the connection between serpentinite and creep in the san andreas fault if shear at depth can become localized along a talc rich principal slip surface within serpentinite entrained in the fault zone

the nature and importance of phyllonite development in crustal scale fault cores an example from the median tectonic line japan abstract like many large crustal scale faults the median tectonic line mtl in sw japan has a long history of movement having been active predominantly as a strike slip fault since the mid cretaceous fault rock exposures in the core of the mtl preserve a history of deformation at a range of mid to shallow crustal depths ryoke mylonites 1 4 km north of the main contact record deeper level cretaceous top to the south sinistral movements the remainder of the fault zone core is surprisingly narrow exhibiting a wide variety of fault rocks that illustrate both the interaction and effects of syn tectonic fluid influx over a range of deformation conditions exposures within 50 m of the central slip zone display a progressive sequence in fault rock evolution from ultramylonite cataclasite foliated cataclasite phyllonite breccia gouge this sequence occurs because cataclasis in the vicinity of the fault core creates permeable pathways for the ingress of chemically active fluids into the fault zone this leads to the replacement of load bearing phases such as feldspar by fine grained foliated aggregates of intrinsically weaker phyllosilicates such as white mica and chlorite the grain size reduction associated with both cataclasis and mineral alteration creates conditions ideal for the operation of fluid assisted stress induced diffusive mass transfer mechanisms comparison with the findings of recent experimental studies suggest that the fault zone processes observed in the core of the mtl will lead to long term weakening provided the network of phyllosilicate rich fault rocks are able to form an interconnected thin layer of weak material on kilometre to tens of kilometre length scales

circum mediterranean fire activity and climate changes during the mid holocene environmental transition 8500 2500 cal bp a mid to late holocene synthesis of fire activity from the mediterranean basin explores the linkages among fire climate variability and seasonality through several climatic and ecological transitions regional fire histories were created from 36 radiocarbon dated sedimentary charcoal records available from the global charcoal database during the mid holocene thermal maximum around 7500 4500 cal bp charcoal records from the northern mediterranean suggest an increase in fire while records from the southern mediterranean indicate a decrease associated with wetter than present summers a north south partition between 40 and 43 n latitude is apparent in the central and western mediterranean relatively abrupt changes in fire activity are observed c 5500 5000 cal bp records of holocene fire activity appear sensitive to both orbitally forced climate changes and shorter lived excursions which may be related to north atlantic cold events possibly modulated by an nao like climate mechanism in cases wh

a beach ridge progradation complex reflecting periodical sea level and climate variability during the holocene gulf of almeria western mediterranean detailed mapping based on aerial photographs at various scales analysis of morpho sedimentary units and radiocarbon dating of the prograding beach ridge complex of campo de dalias almeria allow the differentiation of six prograding units these are called h1 7400 6000 cal bp h2 5400 4200 cal bp h3 4200 3000 cal bp h4 2700 1900 cal bp h5 1900 1100 cal bp and h6 500 cal bp present h units are deposited during periods of high relative sea level and increased sediment input to the coast they are bounded by large swales or erosional surfaces associated with lower sea levels and reduced input of sediment to the coast these correspond to short periods of increased aridity inside the general arid trend recorded in the western mediterranean since 5 4 ka changes in the flux of atlantic superficial waters into the mediterranean sea and relative strength of the w sw winds account for the recorded oscillations of relative sea level we deduce a decadal periodicity for the deposition of a beach ridge and the adjacent swale and suggest that it is related to fluctuations of the north atlantic oscillation nao index and to variations of solar activity the duration of h units shows a quasi millennial periodicity punctuated by short hundred years episodes of reduced progradation or erosion representing events of increased aridity likely to be related to bond s holocene cold events

the holocene sea level story since 7500 bp lessons from the eastern mediterranean the black and the azov seas abstract this paper addresses the obvious controversy between the so far published sea level curves of the black sea and the mediterranean it starts with a discussion of the methods of reconstructing sea level curves the evaluation of sea level indicators and the application of the radiocarbon dating method at least since 7500 bp when the black sea and the mediterranean were connected both water bodies must have reacted synchronously on glacio eustatic changes it is documented that none of the mediterranean sea level curves shows the major wiggles postulated for the black sea which are supposed to reflect trans and regression cycles the very shallow bathymetric condition of the azov sea and the northern black sea should have led to considerable and traceable shoreline displacements there is neither archaeological nor historical evidence of mid and late holocene regressions of several meters the tectonic setting of the black and azov seas implicates that the tectonic signal often overrides the eustatic one therefore only local sea level curves can be established in this paper based on vibracores a locally valid sea level curve for the taman peninsula is demonstrated layers of paralic peat were used as sea level indicators and for 14 c dating the shape of this curve follows the one known from the mediterranean this study also revealed that the present peninsula of taman evolved out of a former archipelago

reduction of friction on geological faults by weak phase smearing most common crustal rock types display friction coefficients of 0 6 or higher but some faults must be frictionally weak as they slip when the stress state is unfavourably oriented i e the resolved shear stress is low for a given normal stress across the fault surface a role for low friction minerals and high pore fluid pressures either separately or in combination is frequently invoked to explain such slip but volume fractions of dispersed weak phases often seem to be present in fault gouge in amounts too small to produce significant mechanical weakening by means of mechanical tests on synthetic fault gouge and microstructural study of run products we show that the effective area of an embedded weak phase graphite on a slip plane can be substantially increased by mechanical smearing and that the enlarged area of the weak phase on the slip plane follows a linear mixing law this allows a relatively small volume fraction of the initially dispersed weak phase to have a disproportionately large effect provided the smearing is concentrated into a narrow planar slip zone or into an interconnected network of them

frictional viscous flow in mylonite with varied bimineralic composition and its effect on lithospheric strength abstract a theoretical composite flow law is presented for mylonite containing interconnected layers of a weak mineral undergoing power law creep and porphyroclasts of a stronger mineral undergoing fracture and frictional sliding such mylonite termed clastomylonite is said to undergo frictional viscous fv mylonitic flow its bulk strength is expressed as a function of bimineralic composition temperature effective pressure and shear strain rate as well as the material parameters for the constituent minerals the fv flow law predicts that the rheology of clastomylonite is predominantly non linear viscous and only slightly pressure sensitive for most bimineralic compositions fv mylonitic flow is shown to occupy a depth interval between cataclastic flow involving adhesive wear in the upper crust and fully viscous mylonitic flow at greater depths the transition from adhesive wear to fv mylonitic flow is related to the onset of dislocation creep glide plus climb in the weakest phase and is inferred to coincide with a crustal strength maximum a peak strength of about 80 mpa is calculated with a combination of byerlee s constants for frictional sliding of granite and the fv flow law for granitic clastomylonite 30 vol quartz at elevated fluid pressures this value falls within the range of flow stresses independently obtained from quartz palaeopiezometry in many greenschist facies granitic mylonite zones

wave climate coastal sediment budget and shoreline changes for the danube delta abstract since its formation approximately 12 000 years ago the coastal zone of the danube delta experienced alternating periods of accretion and erosion related to the natural process of lobe abandonment caused by river avulsion over the last 150 years the effects of human interventions modified these natural trends regulation of the danube river e g the iron gates barrages facilitating navigation and controlling river discharge construction and extension of the sulina entrance jetties and dredging of the sulina mouth bar for navigational purposes are examples of human interventions that influenced and still influence the actual state of the danube delta coastal zone most importantly these interventions diminished the quantity of sediments reaching the coast and consequently led to a severe retreat of the shoreline especially in the sulina sf gheorghe coastal sector to investigate and quantify the recent sediment budget and associated shoreline changes along the danube delta coastal zone we constructed a hindcast of the wave climate the alongshore transport capacity and the resulting sediment budget using a numerical coastline model on a local scale it was found that overwash plays an important role i e the observed evolution of sahalin spit island shows a cross shore landward migration that is much larger than could be explained by the calculated alongshore sediment transport gradients on a delta scale however the resulting alongshore sediment transport gradients and associated sediment budgets comply very well with the observations confirming the dominant role of wave induced alongshore transport and giving confidence in our predictions regarding the shoreline position for the next 25 and 50 years the results of this study indicate the potential for broader applicability of the model to other deltas especially those in wave dominated settings

deltas south of the bosphorus strait record persistent black sea outflow to the marmara sea since 10 ka at the southern exit of the bosphorus strait in the northeastern marmara sea high resolution seismic profiles reveal two lobate progradational delta lobes in modern water depths of v40 65 m the younger delta was active from v10 to 9 ka based on radiocarbon dates of equivalent prodelta deposits and the elevation of its topset to foreset transition the topset to foreset transition climbs in the seaward direction because the delta prograded into a rising sea low abundances of marine fauna and flora in the 10 9 ka interval support a deltaic interpretation there are no rivers in the area that could have fed the delta instead all evidence points to the strait itself as the source of sediment and water when this outflow was strongest v10 6 6 0 ka sapropels accumulated in basinal areas of both the aegean and marmara seas benthic foraminiferal and dinoflagellate cyst data from contemporary deposits elsewhere in the marmara sea point to the continual presence through the holocene of a surface layer of brackish water that we ascribe to this same outflow from the black sea through the bosphorus strait by v9 1 8 5 ka two layer flow developed in the bosphorus strait as global sea level continued to rise and the sediment supply to the younger delta was cut off because the outflowing black sea water ceased to be in contact with the floor of the strait the older delta lobe lies below a prominent lowstand unconformity and is tentatively interpreted to have formed from v29 5 to 23 5 ka oxygen isotopic stage 3 when the marmara sea stood at v355 m and a second sapropel accumulated in deep basinal areas crown copyright 2002 elsevier science b v all rights reserved

radiocarbon dating of danube delta deposits abstract the holocene history of the danube delta has been studied using 14c analyses of faunal material the principal phases of development include 1 initial letea caroarman spit 11 700 9800 yr b p in its central part 8800 5500 yr b p in its southern part 2 sf gheorghe i delta 8900 7200 yr b p 3 sulina delta 7200 2000 yr b p and 4 sf gheorghe ii delta chilia delta 2000 yr b p present other smaller scale features have also been dated including secondary deltas cosna and sinoe deltas and littoral bars age determinations carried out on whole samples were erratic and it was found that individual species had to be separated and dated in all cases the older dates were of transported material whereas the younger dates gave the true age of the formation

formation of danube delta beach ridge plains and signatures in morphology abstract danube delta as most of the large deltas favours complex interactions between river sediment supply and marine dispersing forces which create complex configurations with concurrent morphologies i e river versus wave influenced or processes accretion versus erosion and even distinct landscapes for the same accretionary features strandplains with low monotonous beach ridges or covered by transgressive dunefields beach ridge plains brps are a common feature of the wave influenced deltaic lobes that are created by juxtaposition of succesive berms on the prograding sandy coasts with different shapes and sizes depending on the accretionary mechanisms and the accomodation space this study reports the formation and dynamics of danube delta brps based on numerical age determination osl and ams of the paleoshorelines topographic and geophysical gpr surveys and stratigraphic records by cores a chronological framework is established for all deltaic brps which points to the importance of formation timespan and growth rate as a consequence of sediment supply on the resultant morphology varying inter site from small brp formation time

holocene climate variability in the western mediterranean region from a deepwater sediment record 1 the detailed analysis of the international marine past global changes study core md99 2343 recovered from a sediment drift at 2391 m water depth north of the island of minorca illustrates the effects of climate variability on thermohaline circulation in the western mediterranean during the last 12 kyr geochemical ratios associated with terrigenous input resulted in the identification of four phases representing different climatic and deepwater overturning conditions in the western mediterranean basin during the holocene superimposed on the general trend eight centennial to millennial scale abrupt events appear consistently in both grain size and geochemical records which supports the occurrence of episodes of deepwater overturning reinforcement in the western mediterranean basin the observed periodicity for these abrupt events is in agreement with the previously defined holocene cooling events of the north atlantic region thus supporting a strong atlanticmediterranean climatic link at high frequency time intervals during the last 12 kyr the rapid response of the mediterranean thermohaline circulation to climate change in the north atlantic stresses the importance of atmospheric teleconnections in transferring climate variability from high latitudes to midlatitudes

geodynamic and hydro geological constraints regarding the extension of the prospective archaeo cultural area within the northern romanian coastal zone abstract an obvious discrepancy is noticed between the very few archaeological sites discovered until now on the danube delta plain area and the large number of such sites whose ages range from the middle paleolithic to the middle ages and more recently identified on its higher topography surroundings the combined effects of the regional subsidence of the coast and delta area with amplitudes of 2 to 4 mm y and of the secular mean sea level rise 0 5 1 0 mm y continuously change the land mean sea level relative relationship placing the prospective archaeo cultural layer corresponding to the late prehistory antiquity period at a burial depth which now exceeds 4 5 m this situation partly explains the limited success of the archaeological research carried out until now within the danube delta plain area and recommends a systematic use of the geophysical investigation methods in future the integrated interpretation of the coastal zone bathymetry and sedimentology mappings and of the shoreline geomorphological evolution in time highlights the sedimentary processes that presently shape the littoral study zone allowing to divide it in sectors where either sediments accumulation or erosion processes prevail the study draws attention to the impu ita c sla v danei and cosna vadu littoral sectors where the intense marine erosion of the shoreline and the adjacent seabed also imminently endangers their prospective archaeo cultural load

seven ambiguities in the mediterranean palaeoenvironmental narrative abstract a review of seven outstanding issues on mediterranean palaeoenvironments is presented these are related to the dominant orbital pacing of climate variability the length of the interglacial vegetation succession the influence of the african summer monsoon the seasonality of precipitation during boreal insolation maxima the moisture balance during glacial maxima and the appearance of the mediterranean type climate rhythm and evolution of mediterranean sclerophyllous plants what emerges is that 1 marine 18oplanktonic and sst records show that precession has been a fundamental tempo of mediterranean climate change representing both a low latitude signal runoff from north africa and the direct influence of insolation at mediterranean latitudes but high latitude glacial effects 41 kyr and 100 kyr cycles became superimposed after 2 8 ma sapropel and dust deposition patterns in marine cores reveal that obliquity also has an effect on mediterranean climate through dry wet oscillations which are independent of glacial interglacial variability 2 the temperate part of interglacial vegetation succession has a duration of approximately half a precession cycle this persisted during the interval of obliquity dominated glacial cycles 2 8 1 ma with distinct forest successions following the precessional cycles however these are not always separated by an open vegetation phase because of minimal ice growth producing an impression of a prolonged interglacial forest interval 3 the effect of an enhanced african monsoon during summer insolation maxima has been mainly indirect in terms of nile discharge and runoff along the north african coast leading to increased freshwater input into the mediterranean sea reduced deep water ventilation and sapropel deposition 4 the notion of an accentuated summer rain regime in the northern mediterranean borderlands also contributing to a freshening of the mediterranean sea during boreal insolation maxima is not supported by the available evidence which suggests increased summer aridity 5 recent improvements in chronological precision and data resolution point to an increase in aridity and decreased temperatures during the last glacial maximum 21 2 ka but suggest an increase in effective moisture during the immediately preceding interval of 24 27 ka 6 the mediterranean type climate is not exclusively a post 3 6 ma phenomenon but may have appeared intermittently during the course of the tertiary or before 7 if that is the case then the paradigm that the sclerophyllous evergreen habit represents a pre adaptation to summer drought may need re evaluation

towards an improved understanding of the mechanical properties and rheology of the lithosphere an introductory article to rock deformation from field experiments and theory a volume in honour of ernie rutter ernie rutter s influential contribution to our understanding of rock deformation spans the whole continental crust from deformation just under the grass e g rutter green 2011 to melt migration in the lower crust e g rutter neumann 1995 ernie has also worked on many aspects of the deformation of oceanic crust rutter brodie 1988 however here we reflect on the wide range of deformation conditions ernie has studied by presenting key aspects of the strength and rheology of the continental lithosphere as we understand it today with the aim of providing the context for the contributions included within this volume the continental crust forms just over a third of the earth s surface and it is different from the crust of any other planet in our solar system it is rich in those elements that partition in a silicate melt and its formation and evolution determined the composition of the mantle and that of the atmosphere hawkesworth 2006 thanks to its physical and chemical fingerprint the earth s crust has sustained life uninterrupted for 3 8 ga and it is the source of major natural resources such as hydrocarbons and mineral deposits and others such as geothermal energy the continental crust is less dense than its oceanic counterpart and is therefore more buoyant it forms a substantial part of the cold thermal layer of the earth and its rheology from greek r1v rhe flow and logia logia study the study of the flow of matter is a key factor controlling plate tectonic processes at the earth s surface and in its interior davies 2011 beneath the continental crust lies the lithospheric mantle and together they form the continental lithosphere considerable variations in structure thickness and composition of the continental lithosphere mean that despite its importance we currently have limited understanding of the rheology of this complex system thatcher pollitz 2008 significant advances in our knowledge of continental rheology have been possible through

the impact of the late holocene coastal changes on the rise and decay of the ancient city of histria southern danube delta histria istros is one of the earliest milesian colonies founded on the black sea coast during the archaic period 7th c bc its remains are located within what is today the razelm sinoe lagoon system which forms the southern part of the danube delta during its 13 centuries of existence histria experienced an environment favourable for a prosperous economy e g fishery farming grazing pottery marine trades as indicated by numerous archeological finds from both in situ and elsewhere in the black sea and mediterranean sea basins moreover it benefited from a strategic position on an open coast which was easy to defend important environmental changes occurred both during and after the existence of the ancient city and the most significant are related to major shoreline displacement this study reports late holocene coastal landscape changes from the open coast stage to the present day lagoon system based on numerical age determination of the paleoshorelines stratigraphic records by cores in lagoons and beach ridges and topographic surveys a new chronological framework is established which reports younger ages than previously suggested for the coastal morphosedimentary units of the histria region further the findings shed new light upon the evolution of the southern part of the danube delta the results point to the development of an ancient deltaic lobe dunav lobe 2000 1300 bp associated with the southernmost danube distributary which was situated 10 20 km north of the settlement the lobe was subsequently reworked by waves providing sediments which were accumulated downdrift southward as a continuous beach ridge plain saele chituc in front of the city leading to its isolation from the sea the abandonment of histria 7th c ad coincides with the decoupling of the city from the open coast as a consequence of the shoreline progradation the new beach ridge plain saele chituc is affected by intense neotectonic movements which led to the recent drowning of its central part and the formation of sinoe lagoon the same processes affected the downdrift part of the dunav lobe and histria and nuntasi lakes the new sea level curve obtained for the histria region shows relative stability within the last four millennia with oscillations within 0 to 2 m of the current level this contradicts the concept of a marine regression phanagorian which is suggested to have occurred during the 1st millennium bc however a few areas containing archeological remains are currently below sea level owing to local neotectonics

wetlands and lakes formation and evolution on the lower danube floodplain during middle and late holocene abstract river floodplains are amongst the most dynamic features which are continuously changing their shape and structure in relation to climate vegetation human pressure and base level variability in this study we focus on the lower reach of danube upstream of its delta and investigate the formation and transformations of wetlands and lakes during the last 8000 years using a multi proxy methodology we identified two main stages of floodplain landscape changes which are divided by a major shift in the regime of the most important controlling factor of this region which is the sea level the transgressive stage covers the 8000 5500 bp period with sustained sea level rise 6 3 mm yr when floodplain dynamics acted to adapt to the ever changing base level consequently successive transitions between wet and dry conditions have been recorded as intertwined thick coarse grained and thinner fine grained sedimentary units the latter stage 5500 bp present begins once with abrupt sea level rise deceleration which fostered the expansion of persistent wetlands and lakes within meta stable floodplain the depositional evidence of this stage is composed of fine grained sediments and peat the transition between the two floodplain stages corresponds to the blooming phase of lakes marshes and secondary channels which altogether persisted until the 20th century when during the communist period large floodplain areas were subject to drainage and desiccation works and their transformation into arable lands

seismic stratigraphy of late quaternary deposits from the southwestern black sea shelf evidence for non catastrophic variations in sea level during the last 10 000 yr abstract detailed interpretation of single channel seismic reflection and huntec deep tow boomer and sparker profiles demonstrates that the southwestern black sea shelf formed by a protracted shelf edge progradation since the miocene pliocene five seismic stratigraphic units are recognized unit 1 represents the last phase of the progradational history and was deposited during the last glacial lowstand and holocene it is divided into four subunits subunit 1a is interpreted as a lowstand systems tract 1b and 1c are interpreted as a transgressive systems tract and subunit 1d is interpreted as a highstand systems tract the lowstand systems tract deposits consist of overlapping and seaward prograding shelf edge wedges deposited during the lowstand and the subsequent initial rise of sea level these shelf edge wedges are best developed along the westernmost and easternmost segments of the study area off the mouths of rivers the transgressive systems tract deposits consist of a set of shingled shore parallel back stepping parasequences deposited during a phase of relatively rapid sea level rise and include a number of prograded sediment bodies including barrier islands beach deposits and thin veneers of seismically transparent muds showing onlap onto the flanks of older sedimentary features a number of radiocarbon dates from gravity cores show that the sedimentary architecture of unit 1 contain a detailed sedimentary record for the post glacial sea level rise along the southwestern black sea shelf these data do not support the catastrophic refilling of the black sea by waters from the mediterranean sea at 7 1 ka postulated by ryan pitman major shimkus maskalenko jones dimitrov gorur sakinc yuce mar geol 138 1997 119 126 ryan pitman touchstone book 1999 319 pp and ballard coleman rosenberg mar geol 170 2000 253 261

holocene vegetation dynamics fire and grazing in the sierra de gador southern spain this paper examines the mid to late holocene c 6850 1160 cal yr bp environmental history of sierra de gador in southern spain the local vegetation dynamics are reconstructed through the palaeoecological record obtained from a lacustrine deposit situated at 1530 m various hypotheses are considered to explain the vegetation dynamics apparent in the palaeoecological evidence including climatic change fire occurrence and human activity although the vegetation in this region is sensitive to climatic change threshold events driven by ecological factors are also apparent climatic events include a thermo mesophytic optimum with abundance of deciduous trees and maximum lake water level found from c 6850 to 5500 cal yr bp in contrast changes in the frequency of major fire episodes appear to have shaped interspecific relationships and vegetation change especially from c 4200 cal yr bp onwards biotic properties of the ecosystem such as the inertia of established tree populations interconnected wit

southward migration of the intertropical convergence zone through the holocene titanium and iron concentration data from the anoxic cariaco basin off the venezuelan coast can be used to infer variations in the hydrological cycle over northern south america during the past 14 000 years with subdecadal resolution following a dry younger dryas a period of increased precipitation and riverine discharge occurred during the holocene thermal maximum since approximately 5400 years ago a trend toward drier conditions is evident from the data with high amplitude fluctuations and precipitation minima during the time interval 3800 to 2800 years ago and during the little ice age these regional changes in precipitation are best explained by shifts in the mean latitude of the atlantic intertropical convergence zone itcz potentially driven by pacific based climate variability the cariaco basin record exhibits strong correlations with climate records from distant regions including the high latitude northern hemisphere providing evidence for global teleconnections among regional climates

catastrophic flooding of the black sea abstract decades of seabed mapping reflection profiling and seabed sampling reveal that throughout the past two million years the black sea was predominantly a freshwater lake interrupted only briefly by saltwater invasions coincident with global sea level highstand when the exterior ocean lay below the relatively shallow sill of the bosporus outlet the black sea operated in two modes as in the neighboring caspian sea a cold climate mode corresponded with an expanded lake and a warm climate mode with a shrunken lake thus during much of the cold glacial quaternary the expanded black sea s lake spilled into to the marmara sea and from there to the mediterranean however in the warm climate mode after receiving a vast volume of ice sheet meltwater the shoreline of the shrinking lake contracted to the outer shelf and on a few occasions even beyond the shelf edge if the confluence of a falling interior lake and a rising global ocean persisted to the moment when the rising ocean penetrated across

internal architecture of a raised beach ridge system anholt denmark resolved by ground penetrating radar investigations abstract the internal architecture of raised beach ridge and associated swale deposits on anholt records an ancient sea level the holocene beach ridges form part of a progradational beach ridge plain which has been interpreted to have formed during an isostatic uplift and a relative fall in the sea level over the past 7700 years the ridges are covered by pebbles and cobbles and commonly show evidence of deflation material presumably removed from the beach ridges and adjacent swales form the present dune forms on anholt ground penetrating radar gpr reflection lines have been collected with 250 mhz shielded antennae across the fossil ridge and swale structures the signals penetrate the subsurface to a maximum depth of 10 m below the fossil features the gpr data resolve the internal architecture of the beach ridges and swales with a vertical resolution of about 0 1 m gpr mapping indicates that the holocene beach ridges are composed of seaward dipping beachface deposits as well as minor amounts of inland dipping deposits of wash over origin the beachface deposits downlap on underlying shoreface deposits and we use these surfaces as markers of a relative palaeo sea level the new data indicate that the highest relative sea level at about 8 5 m was reached 6500 years ago 700 years later the relative sea level had dropped 0 7 m indicating a change in the relative sea level around 1 mm year this fall in the relative sea level most likely records the influence of an isostatic rebound causing younger beach ridge deposits to indicate lower sea levels

optical dating of dune sand for the study of sea level change a new widely applicable method to obtain well constrained relative sea level records presented here relies on optical dating of inorganic coastal landforms and sediments eighteen optical ages of basal dune sand from a barrier in massachusetts united states indicate that local relative sea level rose 8 m during the past 5 5 k y a sea level curve drawn from these optical ages shows good agreement with independent evidence from salt marsh peat sampled behind the barrier demonstrating the reliability of the method optical dating will be particularly useful in analyzing coastal records that contain too few organic indicators to allow high resolution 14 c based analyses

the evolution of an asymmetric deltaic lobe sf gheorghe danube in association with cyclic development of the river mouth bar long term pattern and present adaptations to human induced sediment depletion abstract the asymmetric sf gheorghe lobe is the only active lobe in the danube delta associated with a river mouth bar and related barrier islands and spits that has continuously displayed cyclic development during the last 1500 years during the early cycles the sf gheorghe distributary experienced a significant increase in sediment load by an order of magnitude as a result of the successive avulsions occurred 1 5 1 2 ka which redistributed more water and sediment captured from the neighboring branches of impu ita southern distributary of the sulina arm and dunav morphological and sedimentological analyses together with a newly obtained chronology throw light on the multiple ridgeset 10 structure of sf gheorghe lobe each of them excepting the first one following a common evolutionary pattern reflected by the cyclic succession of the recurring stages i subaqueous mouth bar building ii barrier island emergence and iii transformation into a barrier spit with several secondary spits the spits become encased into the muddy deltaic plain as narrow sandy ridges building out on the downdrift side of the lobe as a barrier marsh plain whereas the updrift side constantly accreted fed by longshore currents forming a classic beach ridge plain the size of each ridgeset increased exponentially with every new cycle due to the constant lengthening of the coastline as the downdrift side of the lobe advanced seaward through a series of progressively larger similar quadrilaterals yielding a corresponding geometric progression of the delta front size even though each newly formed ridgeset cycle had a longer lifespan the latest cycles lasting 4 5 times longer than the first ones 200 440 years versus 50 80 years the evolutionary model remained unchanged as long as the balance between wave and river borne sediments defined by the sedimentary index si remained constantly low si 0 1 whereas the mean advance rates of the river mouth remained constant at c 10 m year abrupt changes occurred within the last cycle since the beginning of the 20th century as a consequence of human induced depletion of sediment supplied by the danube flow and is mainly expressed by the complete cessation of the updrift coastal progradation and the prevalence of erosion in front of the river mouth these changes which engendered a threefold increase of the si 0 37 at present are reflected by the recent 1930s present river mouth dynamics characterized by cessation of its long term seaward expansion in favor of downdrift migration this is indicative of the transition of the sf gheorghe mouth from an asymmetric to a deflected wave influenced delta morphology whose current developments mark a significant change in the multicentennial cyclic evolutionary pattern the asymmetric to deflected transition reflects the net increase in the influence of wave driven sediment circulation on river mouth morphology corresponding to a critical si threshold of ca 0 2 0 2 asymmetric 0 2 deflected