nature and composition of shore zone sediments between jeddah and yanbu eastern red sea abstract the shore zone sediments between jeddah and yanbu west coast of saudi arabia are composed mostly of skeletal carbonate sands the nearshore sediments containing benthic foraminifera algal fragments and molluscs are multimodal the mean grain size varying between 0 76 and 2 35 o the beach sediments except samples dominated by cerithid gastropods in some localities are relatively finer than the nearshore sediments although the beaches to a great extent comprise sand sized material fine lime muds and coarse clastic gravels occur in certain areas the dune sediments comprising mostly algal grains and ooids are very fine with 50 percent of the material in the 0 25 0 18 mm size grade except a general northward decrease in mean grain size regional trends in the textural parameters of the sediments between jeddah and yanbu are not quite apparent lateral variations in the textural characteristics suggest a landward migration of the sediments in the shore zone under the influence of northerly and northwesterly winds the carbon and oxygen 13 c 4 80 to 4 84 pdb 13 o 0 04 to 0 53 pdb isotopic ratios of the lime muds occurring in certain shallow margins in the shore zone which are much higher than those of the green algae indicate that the fine carbonates are at least in part inorganic in origin like the shallow water carbonates in tropical seas aragonite and high mg calcite are the dominant carbonate minerals in the shore zone sediments there is a landward increase in aragonite contents caused by the landward migration of fine material from the nearshore the dominant clay mineral in the nearshore sediments is kaolinite with subordinate swelling chlorite and little illite kaolinite is contributed by the coastal regions under the sub tropical humid climate swelling chlorite is considered to have been formed in the nearshore by mechanical mixture of chlorite and montmorillonite derived from the metamorphic and igneous terrains of the tertiary mountains bordering the coastal plain

geochemical evidence of the 8 2 ka event and other holocene environmental changes recorded in paleolagoon sediments southeastern brazil abstract the paleoclimatic record of jureia paleolagoon coastal southeastern brazil includes cyclic and gradual changes with different intensities and frequencies through geological time and it is controlled by astronomical geophysical and geological phenomena these variations are not due to one single cause but they result from the interaction of several factors which act at different temporal and spatial scales here we describe paleoenvironmental evidence regarding climatic and sea level changes from the last 9400 cal yr bp at the jureia paleolagoon one of the main groups of protected south atlantic ecosystems geochemical evidences were used to identify anomalies from multi proxy analyses of a paleolagoon sediment core the anomalies of centennial scale were correlated to climate and transgression regression cycles from the holocene period decadal scale anomalous oscillations in the quaternary paleolagoon sediments occur between 9400 and 7500 cal yr bp correlated with long and short term natural events which generated high sedimentation rates mainly between 8385 and 8375 cal yr bp 10 cm yr our results suggest that a modern day short duration north atlantic climatic event such as the 8 2 ka event could affect the environmental equilibrium in south america and intensify the south american summer monsoon

lateglacial and holocene environmental changes in portuguese coastal lagoons 1 the sedimentological and geochemical records of the santo andre coastal area the sedimentological and geochemical study of a core corresponding to sedimentation in the santo andre lowland since 14 000 bp allowed the reconstruction of environmental changes of this area and discussion of the relative importance of local versus global forcing factors responsible for its evolution the pre holocene section of the core represents terrestrial sedimentation in a fluviatile environment contemporaneous of a low sea level and a distal shoreline sediment inputs were terrestrial and resulting from intensive weathering and high erosion rate in the adjacent watershed during the early holocene c 10 020 to 5380 bp the sea invaded this lowland and defined an open marine shallow environment corresponding to a wide gulf which has been disturbed by multiple terrestrial inputs that might have been induced by massive episodes of fluvial discharge the first symptoms of confinement were noticed close to 5400 bp and c 5380 bp a major environmental threshold occurred possibly reflecting the marke

lateglacial and holocene environmental changes in portuguese coastal lagoons 2 microfossil multiproxy reconstruction of the santo andre coastal area benthic foraminiferal ostracod calcareous nannoplankton and diatom assemblages have been analysed from the 25 45 sedimentary succession of a borehole drilled in the santo andre lagoon southwestern portugal the zones and subzones recognized according to their microfossil content have been used to define six palaeoenvironmental stages extending from the lateglacial to the present stage a and the lower part of stage b 14 2 to 10 0 ka represent a postglacial terrestrial environment when sea level was below present following eustatic sea level rise a normal marine open bay environment established during the upper part of stage b 10 0 to 5 4 ka before 5 4 ka a coastal lagoon developed as a consequence of a sandy barrier formation since then natural variation in the permeability of the detrital barrier through time has been the primary control of the physical chemical and biological features of the lagoonal environment during stage c 5 4 to 3 6 ka as a freshwater dominated lagoon stage d 3

blue arabia palaeolithic and underwater survey in sw saudi arabia and the role of coasts in pleistocene dispersals the role of coastal regions and coastlines in the dispersal of human populations from africa and across the globe has been highlighted by the recent polarisation between coastal and interior models the debate has been clouded by the use of the single term coastal dispersal to embrace what is in fact a wide spectrum of possibilities ranging from seafaring populations who spend most of their time at sea living off marine resources to land based populations in coastal regions with little or no reliance on marine foods an additional complicating factor is the fact of pleistocene and early holocene sea level change which exposed an extensive coastal region that is now submerged and may have afforded very different conditions from the modern coastal environment we examine these factors in the arabian context and use the term blue to draw attention to the fertile coastal rim of the arabian peninsula and to the now submerged offshore landscape which is especially extensive in some regions we further emphasise that the attractions of the coastal rim are a product of two quite different factors ecological diversity and abundant water on land which have created persistently green conditions throughout the vagaries of pleistocene climate change in some coastal regions especially along parts of the western arabian escarpment and potentially productive marine environments around its coastline which include some of the most fertile in the world we examine the interplay of these factors in the southwest region of saudi arabia and the southern red sea and summarise some of the results of recent disperse field investigations including survey for palaeolithic sites on the mainland and underwater survey of the continental shelf in the vicinity of the farasan islands we conclude that coastlines are neither uniformly attractive nor uniformly marginal to human dispersal that they offer diverse opportunities that were spatially and temporally variable at scales from the local to the continental and that investigating blue arabia in relation to its episodically green interior is a key factor in the fuller understanding of long term human population dynamics within arabia and their global implications

holocene sea level changes and barrier reef formation on an oceanic island palau islands western pacific abstract internal facies and development of an oceanic island s barrier reef were revealed by the stratigraphical study of six drill cores in palau islands western pacific the holocene reef development is primarily constrained at its foundation by the antecedent topography of pleistocene substratum holocene barrier reef is an increment on the pleistocene barrier reef which had been subaerially exposed during glacial stages about 8300 cal year bp calibrated calendar years b p branching acropora facies initially formed a bank on the seaward side of a pleistocene limestone surface with a vertical accumulation rate as high as 30 m ka ka 1000 years after 7200 cal year bp when the sea level rise rate decreased reef crest facies caught up with the sea surface with an accumulation rate of less than 2 2 m ka corals found in the reef crest facies are similar to the present day reef crest corals dominated by acropora digitifera and a humilis after the reef crest was formed bioclastic sand and gravel facies prograded lagoonward of the reef crest and consisted mostly of reef derived materials the construction of patch reefs post dated the barrier reef formation the mature barrier reef provided calm conditions inside the lagoon which then led to the construction of patch reefs and fringing reefs sea level changes deduced from the accumulation curves show rapid rise before 7200 cal year bp followed by a slight rise of 4 m at its maximum this change in sea level rise rate inspired the change in reef facies from branching acropora to reef crest

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

relative sea levels and coastal sedimentation in southeast australia in the holocene abstract in recent years australian studies of relative sea level change have shown reasonable consistency on the termination date of the postglacial marine transgression at c 6 500 14c years bp the following stillstand period has been characterized in some regions by a slight falling trend from a high stand or in other areas by a level not easily distinguished from the present the latter situation occurs on the embayed coast of new south wales here studies of depositional environments and sequences within bed rock embayments have linked the holocene sea level history to patterns of sedimentation on the inner shelf in bay barriers and in estuaries deposition of quartz rich sand in shoreface flood tidal delta and backbarrier environments occurred during the marine transgre sion and the subsequent stillstand shell fragments from these deposits have been radiocarbon dated shoreline displacement continues to the present day partly in response to changes in availability of sand in the shoreface zone and partly in response to variations in regional storminess patterns a nd the great shroud of the sea rolled on as it rolled five thousand years ago herman melville moby dick

benthic foraminiferal evidence and paleoenvironmental evolution of holocene coastal plains in the aegean sea greece abstract benthic foraminiferal composition of sedimentary successions during the last 7500 years was investigated from boreholes drilled in three rather tectonically stable coastal areas of the aegean sea alykes kitros lafrouda thrace and vravron attica the quantitative analysis of foraminiferal fauna enabled separation into two different groups that are supported by the analysis of modern benthic foraminiferal communities in the studied sites group a consists of ammonia tepida and haynesina germanica closed lagoon assemblage whereas the most common species of group b open lagoon assemblage are aubignyna perlucida miliolids elphidium spp and ammonia spp the foraminiferal composition integrated with radiometric dating provides information on holocene paleoenvironmental changes in the studied coastal plains related to sea land interaction alykes kitros and lafrouda thrace boreholes show a similar trend with an open lagoonal fauna in the lower part transitional upwards to closed lagoonal conditions this environmental change has taken place after 6500 cal bp in alykes kitros and around 3000 cal bp at lafrouda thrace the benthic communities of vravron attica borehole sediments seem to represent continuously an open lagoon shallow marine environment from 4700 to 400 cal bp

marine transgressions in the west coast of saudi arabia red sea between mid pleistocene and present abstract marine abrasion terraces cut in coralline limestone formations are to be noticed at various elevations in the coastal plain of the west coast of saudi arabia in between jeddah and yanbu three prominent terraces occur at altitudes of 1 3 and 10 m above the present level coral limestone samples from the terraces were dated by the carbon 14 method the radiometric ages reveal four marine transgressions in the west coast of saudi arabia eastern red sea from the mid pleistocene to present sea level maxima were recorded at about 31 000 16 600 18 100 9980 yrs b p and mid holocene the absolute altitude of the sea levels during the transgressions could not be evaluated because of the tectonic instability of the region however it is evident that relative to the first marine transgression mid wurm interglacial upto 31 000 yrs b p the successive transgressions in the west coast of saudi arabia occurred at progressively lower levels

paleoenvironmental changes since 3000 bc in the coastal marsh of vravron attica se greece abstract the coastal area of the vravron bay in the vicinity of the homonym archaeological site is a marshy plain located on the eastern part of the attica peninsula eastern greece in order to provide evidence for palaeoenvironmental changes and landscape evolution of the area detailed micropaleontological palynological and sedimentological analyses have been conducted at the underlying late holocene coastal deposits the recovered sediments lithostratigraphic units a d represent a continuous record of the environmental history of the area since the early bronze age covering all subsequent historical periods the base of the recovered deposits is older than the 3rd millennium bc until late medieval times the studied sequence contains plenty evidence for the existence of the natural port reported from the mycenaean lithostratigraphic unit a that infilled after repeated flooding events during the classic period lithostratigraphic unit b and gradually developed into a shallower marine environment lithostratigraphic unit c in the uppermost part of the sequence lithostratigraphic unit d a transition towards brackish environment with intense fresh water input is featured around 1540 ad signs of human agricultural activities in vravron appear since 3000 bc early bronze age and are linked to the history of inhabitation in the area

climatic changes in the northern red sea during the last 22 000 years as recorded by calcareous nannofossils 1 we present a high resolution record of calcareous nannofossils from the northern red sea for the last 22 kyr extreme conditions with enhanced salinities during the last glacial maximum are characterized by high values of gephyrocapsa ericsonii the dominance of emiliania huxleyi in heinrich event 1 indicates a climatic cooling favoring the bloom of opportunistic species the calcareous nannofossils record a two step onset of the postglacial humid climate punctuated by the younger dryas both steps show an early oligotrophic phase dominated by florisphaera profunda and gladiolithus flabellatus and a subsequent fertile phase characterized by e huxleyi the younger dryas is described by high values of gephyrocapsa oceanica indicating an increased mixing of the water column in the late holocene repetitive increases in abundance of f profunda and g flabellatus reflect restricted oligotrophic conditions caused by the high aridity following the holocene humid period

holocene environmental changes in the coastal tavoliere plain apulia southern italy a multiproxy approach abstract pollen molluscs and foraminifera are used to reconstruct holocene environmental changes in the palude frattarolo lago salso area tavoliere plain apulia italy near the coppa nevigata archaeological site this settlement inhabited from the early neolithic to the iron age was situated on the edge of a broad lagoon that extended for some 40 km along the eastern margin of the tavoliere plain the paleoenvironmental history was investigated using an 8 6 m deep core drilled in the ancient lagoon the records show a shoaling upwards sequence characterised by a semi closed lagoonal environment that gradually became isolated from the sea and ultimately transformed into a terrestrial environment the semi closed lagoon was in existence between 6340 and 4880 cal yr bp and contained a brackish environment with a moderate input of sea water undergoing frequent changes in size and salinity the vegetational landscape at this time was dominated by mixed oak forests between 4880 and 3230 cal yr bp the semi closed lagoon turned into a closed waterbody the surrounding landscape opened around 4000 cal yr bp similar to many other sites in the central mediterranean region a hiatus in deposition occurred between 3230 and somewhat before 180 cal yr bp when a freshwater environment prevailed and the area was an open and dry grassland our multiproxy approach shows that during the last few thousand years large natural habitats of northern apulia were progressively reduced in size in spite of an ancient human occupation a mainly natural cause for the evolution of the lagoon appears most likely

origins and development of holocene coral reefs a revisited model based on reef boreholes in the seychelles indian ocean until recently concepts of coral reef growth and accumulation have been predominantly based on a darwinian model in this the upwards and outwards growth of a reef core a coral framework takes place over a foreslope consisting of reef talus with the simultaneous filling of the back reef lagoon by reef derived debris the principal adaptations of this pattern relate to the influence of relative changes in sea level and commonly ignore oceanographic factors such as storm frequency and severity boreholes through the outer edge of a fringing reef in the seychelles western indian ocean reveal a record of holocene sediment accumulation first established approximately 8 ka ago faunal and floral associations show that growth of this body began in relatively deep water but that this shallowed to 5 m within 1 ka subsequent accumulation was of keep up style but as the rate of sea level rise slowed shoaling became more frequent and aggradation was limited by reducing accommodation space constructional facies are characterised either by massive corals including leptastrea porites and faviids or by branching corals typically acropora of the danai robusta group coral surfaces may be encrusted by red algae foraminifera and vermetids and are commonly bored by filamentous algae clionids and molluscs however detrital facies are volumetrically dominant and the paucity of a constructional framework requires a re evaluation of models of reef accretion new models relate the geometry of accretion to the interplay between extreme storm events and fairweather hydrodynamic conditions these suggest that a contiguous framework forms in areas of moderate fairweather energy without extreme storm events severe storms destroy the continuity of reef structures and generate increasing volumes of coarse detritus low storm severity coupled with low fairweather hydrodynamic energy may promote the accumulation of fine grained reef derived sediments that inhibit framework growth while ecology reflects year by year sea conditions lithology and structure are controlled by exceptional storms with the effects of changing sea level superimposed

recent holocene paleo environmental evolution and coastline changes of kition larnaca cyprus mediterranean sea abstract sedimentological paleontological analysis and 14c dating of 17 cores obtained in the vicinity of the phoenician military harbor viii iv bc of kition bamboula cyprus provide new paleo environmental information for the reconstruction of shoreline changes for kition and larnaca bay over the last 4000 years we propose that a communication existed between the inner harbor of bamboula presently 400 m inland and the northern district of lichines which was a marine embayment our core data led us to revisit the previous hypothesis of a direct east west channel between the harbor and the open sea nicolaou k 1976 the historical topography of kition studies in mediterranean archaeology goteborg vol 153 pp 1 373 gifford j a 1978 paleogeography of archaelogical sites of the larnaca lowlands southeastern cyprus phd thesis university of minnesota pp 1 192 we propose instead that a spit of coarse material isolated the lagoon from the open sea from 2600 to 1600 years bp

formation of earth s early archaean continental crust abstract subduction of oceanic crust at an unusually low angle has been proposed as a model for the growth of continental crust older than about 2 5 ga at modern zones of low angle or flat subduction magmatic additions to new crust come from partial melting of both the subducting oceanic crust slab and the thin wedge of mantle above the slab evidence for both a slab and wedge source is preserved in most late archaean 3 0 2 5 ga terrains but we find little evidence that a mantle wedge contributed to crustal growth prior to 3 1 ga this lack of evidence in part reflects a dearth of exposed crust aged between 3 0 and 3 3 ga but also suggests that subduction enriched mantle source regions did not develop before 3 3 ga and possibly not before 3 1 ga in contrast to most modern terrains and some late archaean terrains early archaean 3 3 ga continental crust evolved through direct melting of thick mafic crust we invoke a process of subduction that does not include the development of a mantle wedge and call this process archaean flat subduction to distinguish it from modern low angle subduction

cultural and human dynamics in southern arabia at the end of the middle paleolithic abstract the arabian peninsula has long been considered as a region devoid of long term human settlement until the holocene period as a result of drastic climatic changes throughout the pleistocene it might be expected that the area was deserted during hyper arid and arid periods and populated by new migrant groups during humid events according to a push and pull phenomenon although this scenario may be perfectly valid for a large part of the peninsula a set of recent data points to the persistence of populations in several regions which may have served as refugia for human groups who developed their own technological traditions such a scenario is suggested by 1 the succession of dense human occupations under arid conditions between ca 60 and 50 ka in the wadi surdud basin a small sedimentary basin in the foothills of the yemeni western highlands this archaeological site complex encompasses several successive human settlements characterized by a middle paleolithic tradition which significantly differs from the middle paleolithic and middle stone age contemporaneous traditions from neighboring regions 2 the regional diversity of the middle paleolithic throughout the saharo arabian arid belt during mis 3 expressed by an array of local techno typological facies that likely relate to distant and disconnected source regions where populations contracted when climate worsened together with a set of high resolution archaeological contexts recently discovered in the arabian peninsula and dated to mis 5 these data suggest that the major human expansion waves which occurred in the region during the upper pleistocene are correlated with the wet phases of mis 5 while populations probably contracted into a few refugia areas at the beginning of mis 3

a genetic classification of carbonate platforms based on their basinal and tectonic settings in the cenozoic abstract this paper reassesses the usefulness of the morphological classification of carbonate platforms into rimmed shelves and ramps whilst the existing classifications have value in describing platform margin morphology at any one time the terms rimmed shelf and ramp are less successful at categorising the entire morphology and stratigraphy of carbonate platforms research on cenozoic carbonate platforms from a range of different tectono stratigraphic settings indicates that the basinal and tectonic setting of a platform can be used to erect a first order genetic classification of carbonate platforms the basinal and tectonic setting of carbonate platforms is shown to control their occurrence the overall 3 d platform morphology the large scale stratigraphic features and depositional sequences climate ocean chemistry and biological evolution control grain types facies and some elements of platform margins but not the larger scale features considered in this new classification from a review of well exposed outcropping and seismically imaged cenozoic platforms it is proposed that eight types of carbonate platform can currently be recognised and characterised based on their basinal and tectonic setting fault block salt diapir subsiding margin offshore bank volcanic pedestal thrust top delta top and foreland margin carbonate platforms these eight types are described using information from cenozoic platforms worldwide and the controls on their development are discussed many platform types e g subsiding margin offshore bank salt diapir thrust top and foreland margin are typical of particular classes of sedimentary basins others e g fault block volcanic pedestal and delta top are more widespread in their occurrence and occur in a range of basin types the value of this classification is that it is genetic rather than morphological the classification reflects the entire morphology and large scale stratigraphy of the platform and the controls on its development in addition the platform models can be used to understand the details of less well exposed or seismically imaged platforms so that they can be characterised and understood in terms of tectono sedimentary processes conversely the classification also provides valuable information on basin evolution as carbonate platforms house information on palaeoenvironments sea level change and are sensitive recorders of the tectonic environment

sea level history 45 000 to 30 000 yr b p inferred from benthic foraminifera gulf st vincent south australia surficial sediments of gulf st vincent south australia are predominantly bioclastic cool temperate carbonates benthic foraminifera are abundant and distribution of species is closely related to water depth for example massilina milletti is most common at depths ca 40 m while discorbis dimidiatus is characteristics of shallow subtidal environments elphidium crispum a shallow water species and e macelliforme favoring deeper water provide a useful numerical ratio their logarithmic relative abundance in the sediment size fraction 0 50 0 25 mm correlates strongly with water depth vibrocores sv 4 and sv 5 recovered undisturbed sections of quaternary strata from the deepest part ca 40 m of gulf st vincent amino acid racemization and radiocarbon age determinations show that late pleistocene sections of the cores were deposited over the time ca 45 000 to 30 000 yr b p species of fossil foraminifera recovered from these sections are mostly extant in modern gulf st vincent thus allowing paleoecological inferences of late pleistocene sea levels these inferred sea level maxima can be correlated with those determined from study of huon peninsula coral reef terraces initial estimates of tectonically corrected sea levels for transgressions in gulf st vincent at 40 000 and 31 000 yr b p are 22 5 m and 22 m respectively the intervening regression lowered sea level to 28 m

geomorphological changes in the coastal area of farasan al kabir island saudi arabia since mid holocene based on a multi proxy approach abstract the geomorphological evolution of the southeastern coastal area of farasan al kabir island saudi arabia is revealed by the mapping of modern landforms and a multi proxy and high spatial resolution study including grain size particulate organic carbon mineralogy element geochemistry benthic foraminifera analysis and radiocarbon dating of a 3 3 m long sediment core the modern geomorphological features comprise a variety of arid landforms such as plateau cliffs and pediments of pleistocene coral limestones playa depressions located on plateau surfaces alluvial fans butte and sandy beaches the mid holocene evolution of the borehole area is resulted from the detailed analysis of five sedimentary units detected along the core matar 1 and includes three distinct stages a from 5253 223 y cal bp to 3138 223 y cal bp carbonate coarse grained material consisting of coral fragments molluscs calcareous algae and benthic foraminifera are deposited on a shallow marine fringing reefal platform which becomes progressively a nearshore backreef around 3675 215 y cal bp and later around 3138 223 y cal bp a reef ramp b since 3040 220 y cal bp the borehole area obtains the characteristics of a high energy beach that receives increasing inputs of terrigenous material c subsequently a supratidal backshore setting is established influenced mostly by terrestrial processes and occasionally by marine processes as it is indicated by the decreasing and sometimes sporadic presence of benthic foraminifera and recently a sedimentary veneer consisting of terrigenous carbonate and evaporite material is formed by terrestrial mainly wadi and aeolian processes

sea level and shoreline reconstructions for the red sea isostatic and tectonic considerations and implications for hominin migration out of africa the history of sea level within the red sea basin impinges on several areas of research for archaeology and prehistory past sea levels of the southern sector define possible pathways of human dispersal out of africa for tectonics the interglacial sea levels provide estimates of rates for vertical tectonics for global sea level studies the red sea sediments contain a significant record of changing water chemistry with implications on the mass exchange between oceans and ice sheets during glacial cycles and because of its geometry and location the red sea provides a test laboratory for models of glacio hydro isostasy the red sea margins contain incomplete records of sea level for the late holocene for the last glacial maximum for the last interglacial and for earlier interglacials these are usually interpreted in terms of tectonics and ocean volume changes but it is shown here that the glacio hydro isostatic process is an additional important component with characteristic spatial variability through an iterative analysis of the holocene and interglacial evidence a separation of the tectonic isostatic and eustatic contributions is possible and we present a predictive model for palaeo shorelines and water depths for a time interval encompassing the period proposed for migrations of modern humans out of africa principal conclusions include the following i late holocene sea level signals evolve along the length of the red sea with characteristic mid holocene highstands not developing in the central part ii last interglacial sea level signals are also location dependent and in the absence of tectonics are not predicted to occur more than 1 2 m above present sea level iii for both periods red sea levels at expected far field elevations are not necessarily indicative of tectonic stability and the evidence points to a long wavelength tectonic uplift component along both the african and arabian northern and central sides of the red sea iv the observational evidence is consistent with tectonic and isostatic processes both operating over the past 300 000 years without requiring changes in the time averaged over a few thousand years tectonic rates v recent bathymetric data for the bab al mandab region have been compiled to confirm the location and depth of the sill controlling flow in and out of the red sea throughout the last 400 000 years the red sea has remained open to the gulf of aden with cross sectional areas at times of glacial maxima about 2 of that today vi the minimum channel widths connecting the red sea to the gulf of aden at times of lowstand occur south of the hanish sill the channels are less than 4 km wide and remain narrow for as long as local sea levels are below 50 m this occurs for a number of sustained periods during the last two glacial cycles and earlier vii periods suitable for crossing between africa and arabia without requiring seaworthy boats or seafaring skills occurred periodically throughout the pleistocene particularly at times of favourable environmental climatic conditions that occurred during times of sea level lowstand

expert driven semi automated geomorphological mapping for a mountainous area using a laser dtm in this paper a semi automated method is presented to recognize and spatially delineate geomorphological units in mountainous forested ecosystems using statistical information extracted from a 1 m resolution laser digital elevation dataset the method was applied to a mountainous area in austria first slope angle and elevation characteristics were determined for each key geomorphological unit occurring in the study area second a map of slope classes derived from the laser dtm was used in an expert driven multilevel object oriented approach the resulting classes represent units corresponding to landforms and processes commonly recognized in mountain areas fluvial terrace alluvial fan slope with mass movement talus slope rock cliff glacial landform shallow incised channel and deep incised channel the classification result was compared with a validation dataset of geomorphological units derived from an analogue geomorphological map for the above mentioned classes the percentages of correctly classified grid cells are 69 79 50 64 32 61 23 and 70 respectively the lower values of 32 and 23 are mainly related to inaccurate mapping of rock cliffs and shallow incised channels in the analogue geomorphological map the accuracy increased to 76 and 54 respectively if a buffer is applied to these specific units it is concluded that high resolution topographical data derived from laser dtms are useful for the extraction of geomorphological units in mountain areas

geochemistry and mineralogy of the nw aegean sea surface sediments implications for river runoff and anthropogenic impact abstract surface sediments of the nw aegean sea were analyzed for clay mineral composition 94 samples organic c and carbonate content and major and minor elements 112 samples illite is the most abundant clay mineral followed by smectite chlorite and kaolinite clay minerals are preferentially deposited within the continental shelf and slope environment due to the prevailing cyclonic circulation and the formation of flocs in the rivers pro delta areas the spatial distribution of major lithogenic elements si al ti fe is substantially biased by the presence of relict sands located in the central eastern part of the thermaikos gulf continental shelf biogenic elements ca sr are noticeably pronounced on the northern flank of the north sporades islands organic c content and minor elements cu zn as and pb are enriched markedly over the thessaloniki bay and gulf suggesting substantial human impact deriving largely from untreated or partly treated domestic and industrial effluents the terrigenous component of the elements is preferentially contributed from the axios river zn and pb the aliakmon river cr co ni cu and as and to a lesser extent from the pinios river v co ni and cu a considerable part of the metals originates in ultra mafic and volcanic formations which are abundant in the rivers catchment basins carbonate content exhibits great variability with the highest values observed in biogenic sediments of the sporades basin in the latter area mn and fe oxides and hydroxides were found as coatings on calcite the coatings were enriched in cr co ni zn as mo and pb due to adsorption or ion exchange during early diagenesis the combined influence of the river systems the thessaloniki metropolis and the diverse sedimentological background generates great patchiness in the distribution of major and minor elements

effect of fluid viscosity and saturation on the ultrasonic velocities in a fontainebleau sandstone simultaneous measurements of the p and s wave velocities at 1mhz frequency as a function of temperature from 80 c to 80 c have been made in a fontainebleau sandstone saturated with glycerol we investigated 8 saturation degrees from fully saturated to almost dry state generally the velocity decreases with increasing temperature it is large between 40 c and 40 c the velocity dispersion is attributed to viscous shear relaxation the model of o connell and budiansky modified by introducing the saturation parameter and a gaussian distribution of crack aspect ratios is used to interpret the data a trial and error method is used to estimate the model parameters the model satisfactorily accounts for the data at high saturation

holocene lagoonal sedimentation at the latitudinal limits of reef growth lord howe island tasman sea abstract the southernmost limit to coral reef growth occurs on lord howe island 33 30 s 159 05 e where a discontinuous fringing reef flanks the western side of the island coring and radiocarbon dating indicate that carbonate sediments were first deposited within the lagoon around 6500 radiocarbon years bp coincident with sea level reaching close to its modern level high energy conditions dominated the reef with robust branching corals dominating the developing reef growth of the reef crest between 6000 and 5000 yr bp is inferred to have caused a reduction in the energy conditions within the lagoon resulting in mud deposition during this period sedimentation occurred at average rates of around 5 mm yr though locally up to 10 mm yr which infilled almost all the available accommodation space in the lagoon by 4000 yr bp most of the lagoon had accreted to a level very close to the modern lagoon floor having accumulated over 11 m of sediment in the northern part of the lagoon and possibly up to 30 m in the south sediments younger than 3000 yr bp form a thin veneer over these older units with the main deposition being confined to embayments the coastal plain and the infilling of blue hole depressions the reef and lagoon fringing lord howe island appear to have developed their present form primarily during a phase of luxuriant growth in the mid holocene

holocene coastal carbonates and evaporites of the southern arabian gulf and their ancient analogues abstract the holocene sediments of the coast of the united arab emirates in the southeastern arabian gulf are frequently cited in the literature as type examples for analogous assemblages of carbonates evaporites and siliciclastics throughout the geologic record this paper is intended as a convenient single source for the description of sediments of this region providing information on how to reach the classic localities and some of the analogs the holocene sediments of the region accumulate over an area that is 500 km long and up to 60 km wide the sediments collecting offshore are predominantly pelecypod sands mixed with lime and argillaceous mud with these latter fine sediments increasing as the water deepens the pelecypod rich sediments also collect east of abu dhabi island both in the deeper tidal channels between the barrier island lagoons and in deeper portions of the protected lagoons west of abu dhabi island the shallow water margin is the site of coral reefs and coralgal sands whereas to the east oolites accumulate on the tidal deltas of channels located between barrier islands grapestones accumulate to the lee of the reefs and the oolite shoals where cementation becomes more common they are particularly common on the less protected shallow water margins of the lagoons west of abu dhabi island pelleted lime muds accumulate in the lagoons in the lee of the barrier islands of the eastern abu dhabi lining the inner shores of the protected lagoons of abu dhabi and on other islands to the west are cyano bacterial mats and mangrove swamps landward of these a prograding north facing shoreline is formed by supratidal salt flats sabkhas in which evaporite minerals are accumulating this paper describes the localities associated with 1 the mangrove swamps of the west side of the al dhabaiya peninsula 2 the indurated cemented carbonate crusts cyanobacterial flats and sabkha evaporites on the shore of the khor al bazam south of qanatir island 3 the reef and oolitic sand flats on the coast just east of jebel dhana and 4 the marine travertine and aragonite coats associated with the beach sediments in a small bay south of jebel dhana and 5 the sabkha mutti between jebel barakah and al sila similar sedimentological associations of carbonate and evaporites to those of the holocene of the united arab emirates are to be found in the tertiary and mesozoic sedimentary rocks of the immediate subsurface in the arabian gulf other analogs to this setting include the paleozoic carbonates of the western usa europe and asia mesozoic carbonates of the gulf of mexico europe and middle east and tertiary sedimentary rocks in the middle east

palaeoceanographic evolution of the central red sea during the late holocene three multicores were studied in the central red sea off port sudan at a w e transect in order to reconstruct palaeoceanographic conditions of the past 6000 years downcore fluctuations in the rel

a pronounced dry event recorded around 4 2 ka in brine sediments from the northern red sea partly laminated sediments were sampled from the brine filled anoxic shaban deep basin in the northern red sea at about 4200 cal yr bp more than two millennia of anoxic sedimentation is replaced by a sub oxic facies strongly suggesting the episodic absence of the brine at the same time stable oxygen isotopes from surface dwelling foraminifera show a sharp increase within less than 100 yr pointing to a strong positive salinity anomaly at the sea surface this major evaporation event significantly enhanced the renewal of deep water and the subsequent ventilation of the small shaban deep basin the timing and strength of the reconstructed environmental changes around 4200 cal yr bp suggest that this event is the regional expression of a major drought event which is widely observed in the neighboring regions and which strongly affected middle east agricultural civilizations

paleoenvironmental changes during the last 8400 years in the southern yellow sea benthic foraminiferal and stable isotopic evidence we used benthic foraminiferal stable isotopic and grain size data from an ams c 14 dated core from the southern yellow sea to decipher holocene paleoenvironmental changes large amplitude changes in 6180 613 c and benthic foraminiferal assemblage composition indicate that major environmental changes occurred during the last 8400 years in the southern yellow sea we recognize 3 stages of environmental development 1 a low salinity estuarine environment stage at 8 4 6 9 cal kyr bp 2 a low salinity shallow sea environment stage at 6 9 to about 6 5 cal kyr bp and 3 a modem marine shelf environment stage after about 6 5 cal kyr bp the delta o 18 and delta c 13 values of ammonia aomoriensis asano combined with benthic foraminiferal assemblage data indicate a low bottom water salinity 15 parts per thousand during stage 1 suggesting a large amount of river runoff abrupt increases in delta o 18 and delta c 13 around 6 9 cal kyr bp were accompanied by a decrease in mean grain size and in abundance of benthic foraminifera possibly caused by a north ward shift of the yellow river s outlet during subsequent stage 2 the southern yellow sea was still characterized by a low salinity 28 parts per thousand even though sea level was high possibly due to the continued strong influence of river input and or limited exchange between the southern yellow sea and the open ocean at about 6 5 cal kyr bp an a aomoriensis dominated benthic foraminiferal assemblage was replaced by an ammonia ketienziensis ishizaki dominated assemblage indicating an increase in bottom water salinity grain size and stable isotope data suggest that the modem circulation was probably established at that time we speculate that the combined impacts of reduced river runoff enhanced east asia winter monsoon and increased influence of southern warm ocean currents caused this transition c 2007 elsevier b v all rights reserved

mid holocene stable isotope record of corals from the northern red sea we present a study based on x ray chronologies and the stable isotopic composition of fossil porites spp corals from the northern gulf of aqaba red sea covering the mid holocene period from 5750 to 4450 14c years bp before present the stable oxygen and carbon isotopic compositions of five specimens reveal regular annual periodicities compared with modern porites spp from the same environment the average seasonal 18o amplitude of the fossil corals is higher by ca 0 35 0 60 whereas annual growth rates are lower by ca 3 5 to 2 mm year this suggests stronger seasonality of sea surface temperatures and increased variability of the oxygen isotopic composition of the sea water due to changes in the precipitation and evaporation regime during the mid holocene most likely summer monsoon rains reached the northern end of the red sea at that time average annual coral growth rates are diminished probably due to an increased input and resuspension of terrestrial debris to the shallow marine environment during more humid conditions our results corroborate published reports of paleodata and model simulations suggesting a northward migration of the african monsoon giving rise to increased seasonalities during the mid holocene over northeastern africa and arabia