three dimensional cfd modeling of self forming meandering channel a three dimensional cfd model was used to compute the formation of the meandering pattern in an initially straight alluvial channel the numerical model was based on the finite volume method using an unstructured grid with dominantly hexahedral cells the k e model was used to predict turbulence and the simple method was used to compute the pressure the sediment transport was computed as bed load in addition to solving the convection diffusion equation for suspended sediment transport the bed changes were calculated and the grid was altered during the computation as channel erosion and deposition caused wetting and drying the model was tested by comparing with results from physical model studies carried out at colorado state univ fort collins colo the results showed successfully the replication of many of the meander characteristics including secondary currents cross sectional profiles meander planform meander wavelength downstream meander migration and chute formation

the 8 2 ka event from greenland ice cores we present a collection of high resolution chemistry and stable isotope records from the plateau of the greenland ice cap during the cold event 8200 yr ago using a composite of four records the cold event is observed as a 160 5 yr period during which decadal mean isotopic values were below average within which there is a central event of 69 yr during which values were consistently more than one standard deviation below the average for the preceding period four cores in north south and central greenland show differences at decadal and shorter timescales it is not yet clear if this represents significant spatial differences in response the results show clear evidence for colder temperatures and a decrease in snow accumulation rate however the changes in chemical concentrations for the ions looked at here are small suggesting only minor changes in atmospheric circulation for this event apart from the decrease in methane concentration greenland ice cores give only weak evidence for effects outside the north atlantic region

the depositional characteristics of turbidity currents in submarine sinuous channels abstract submarine channels with meandering patterns and extensive levee complexes are commonly found on continental slopes and fans here a three dimensional numerical model is applied to conduct a systematic study of poorly sorted depositional turbidity currents in sinuous submarine channels with different side slope and sinuosity multiple runs with the same inflow conditions are made to study deposition patterns inside the channel and levees not only many known facts such as the spilling and stripping of turbidity currents at channel bends as well as the different pattern of deposition at the inner and outer banks of channel bends are produced but also some important new findings such as i small river like circulation near the bottom corner of outer bank co exists with predominant lateral convection as secondary flow ii the levee on the outer bank of a channel bend apex of steeper lateral slope shows larger variation in grain size distribution than the thinner more smooth levee on its opposite side iii the levees at bend inflections inherit the characteristics of the upstream levees at channel bend apexes iv the downstream cross section that cuts both sinuous channel beds and banks is characterized by thicker channel bed deposits intersected by arch shaped thinner on bank deposits v the levee deposit displays an asymmetric wave pattern in the downstream direction and the flow direction is from the short rising side to the long dropping side the flow and sedimentation patterns summarized in this study may promote the understanding of physical processes of submarine turbidity currents and their depositions and assist in interpreting seismic outcrop and or borehole data for reconstruction of original depositional environment

reply to the comments by mauz b and antonioli f on sea level and climate changes during ois 5e in the western mediterranean we really appreciate the comments by mauz and antonioli on our paper bardaji et al 2009geomorphologic maps are often lacking in studies related to the reconstruction of past sea level changes in most cases these maps would be the only way of reconstructing past sea level oscillations see for example but here we respond to the erroneous statements made in their critical reading of our work we agree with the authors historic review of the problems raised when effects of tectonics and sea level oscillations are observed in the record of relative sea level changes in western mediterranean we should not forget that the mediterranean itself constitutes a collision plate boundary with few stable areas within it therefore the study of the last interglacial shorelines cannot be simply analysed according to altitude as they say what we do not share with mauz and antonioli is that the only solution to this seemed to be determining the age of a coastal deposit using radiometric dosimetric and chemical dating techniques it is obvious that we need a chronological approach to be as accurate as possible first of all however an exhaustive field analysis is needed and this is overlooked by mauz and antonioli at least in the spanish mediterranean sector to begin with field analysis would yield a deeper wider geological knowledge not only of the precise sections but also on a regional scope second a geomorphologic understanding of the selected sections is necessary geomorphology is the best tool that enables us to understand how many different sea level highstands or intervals we are dealing with in terms of their relation to former and younger sea level indicators i e 3d stratigraphic architecture sampling for dating purposes can only be done when the sedimentary sequence is clear and after detailed geomorphologic mapping unfortunately radtke and schellmann 2004

middle palaeolithic mode 3 lithic technology in the rock shelter of benzu north africa and its immediate environmental relationships abstract the rock shelter of benzu is located near the city of ceuta in north africa at the rock shelter of benzu there is a sequence of 7 archaeological levels which are associated with a clearly defined mode 3 lithic technology the similarities with other assemblages found in the south of the iberian peninsula are clear we emphasise the exploitation of marine resources by these hunter gatherer societies from the beginning of the middle pleistocene sequence on the basis of this archaeological evidence and in the context of recent studies on north africa this work assesses the possible relationships and contacts between societies on both shores of the historical region of the straits of gibraltar

progradational gravel beach sequences in a moderate to high energy microtidal marine environment the anatomy of progradational gravel beaches was analysed in two different tectonic settings the strongly subsiding messinian foreland basin of the eastern southern alps and the rising pleistocene marine terraces of the outer margin of the apenninic chain progradation took place near the mouths of fan delta or braid delta distributaries debouching in microtidal landlocked basins palaeo adriatic and palaeo ionian seas a wind wave climate comparable to that of the present day was characterized by periodic intense storm activity most of the beachface progradation is thought to have taken place during the post storm recovery and fair weather stages whereas the impact of storms is mostly recorded by the cutting of erosional surfaces on the beachface and by emplacement of poorly sorted and coarse grained gravels on the shoreface by storm intensified seaward trending flows and behind the highest berms by washover processes analysis of the sequences led to the identification of a number of typical divisions which are differently developed in the two settings compared here the characteristics of the apenninic sequences suggest a strongly variable wind wave climate with periodic changes from a relatively dissipative barred morphology during storms accompanied by strong longshore currents and rip development to a more reflective state typical of recovery and fair weather stages the southern alpine sequences on the other hand are characterized by poor evidence of barred morphology and of longshore currents and widespread effects of shear and gravity sorting in the lower beachface gravels these features indicate a comparatively more reflective average state due to location of beaches along the deeply embayed head of the palaeo adriatic and the very narrow directional width of the incoming wave spectrum which was almost shore normal most of the time in addition to well developed shape zonation of gravels the common presence of wave generated gravel megaripples in the southern alpine sequences indicates the greater influence of long period waves due to the greater available fetch distances in both settings the cyclicity is thought to be genetically related to minor changes of sea level

chevron ridges and runup deposits in the bahamas from storms late in oxygen isotope substage 5e abstract landward pointing v shaped sand ridges several kilometers long are common along the windward margin of the bahama islands their axes share a northeast southwest trend internally the ridges contain low angle oolitic beds with few erosional truncations commonly interbedded are tabular fenestrae rich beds such as those formed by the sheet flow of water over dry sand defined here as chevron ridges these landforms appear to have originated in the rapid remobilization of bank margin ooid bodies by the action of long period waves from a northeasterly source deposits along adjacent coastlines also preserve evidence of the impact of large waves reworked eolian sand bodies preserve beach fenestrae and hydraulic scour traces up to 40 m on older ridges on cliffed coasts 1000 ton boulders have been thrown well inland recording the impact of large waves amino acid ratios confirm a correlation of the ridges across the archipelago while stratigraphy spacing and cross cutting relationships indicate emplacement as sea level fell rapidly from the substage 5e maximum at or above 6 m

record of mis 5 sea level highstands based on u th dated coral terraces of haiti abstract new geomorphologic investigations and new u th series dates from haiti northwestern peninsula confirm the age of coral reef terraces assigned to mis 5 5 130 ka mis 5 3 107 ka and mis 5 1 83 ka sea level peaks they also provide evidence for a second high sea level occurring some thousand years before 118 ka and indicate a second mis 5 1 sea level stand at about 76 ka these results are in agreement with the raised terraces of barbados although the staircase of haiti consists of four steps compared to eight the haitian sequence can be compared with the maximal number of distinct mis 5 sea level highstands recorded in the world from coral reef tracts and their relative height above or below present sea level three mis 5 5 sea level changes have been recognized with sea level oscillating above or near the present level until 122 ka only dropping then rising to 11 m below present sea level at 120 ka three high frequency sea level oscillations occurred during mis 5 3 and a fourth during mis 5 3 5 2 two or three events may have occurred during mis 5 l according to whether the 73 ka event is considered to belong to mis 5 1

tracking the sea level signature of the 8 2 ka cooling event new constraints from the mississippi delta 1 the ever increasing need for accurate predictions of global environmental change under greenhouse conditions has sparked immense interest in an abrupt century scale cooling around 8200 years ago with a focal point in the north atlantic and with hemispheric teleconnections despite considerable progress in the unraveling of this striking feature including a conceivable driving mechanism rapid drainage of proglacial lake agassiz ojibway and a resulting reduced strength of north atlantic thermohaline circulation several key questions remain unanswered one salient aspect concerns the total amount of freshwater released during this catastrophic event likely echoed by a near instantaneous eustatic sea level rise so far no attempts have been made to perform high resolution sea level studies that explicitly focus on this critical time interval here we present new data from the mississippi delta suggestive of abrupt sea level rise associated with the 8 2 ka event however the amount of sea level rise was likely less than 1 2 m corresponding to a meltwater volume of less than 4 3 1014 m3 values lower than estimates used by several recent studies

deciphering holocene sea level history on the u s gulf coast a high resolution record from the mississippi delta published holocene relative sea level rsl curves for the u s gulf coast are in mutual conflict with some characterized by a smooth rsl rise akin to widely accepted eustatic sea level curves versus others including several recent ones that are characterized by a conspicuous stair step pattern with prolonged millennium scale rsl stillstands alternating with rapid meter scale rises in addition recent work in texas and alabama has revitalized the notion of a middle holocene rsl highstand estimated at 2 m above present mean sea level an extensive sampling program in the mississippi delta louisiana focused on the collection of basal peats that accumulated during the initial transgression of the pre existing consolidated pleistocene basement we used stable carbon isotope ratios to demonstrate that many of these samples accumulated in environments affected by frequent saltwater intrusion in the 30 cm zone between mean spring high water and mean sea level and we selected plant macrofossils that were subjected to ams 14c dating nearly 30 sea level index points from a 20 km2 study area on the eastern margin of the delta suggest that rsl rise followed a relatively smooth trend for the time interval 8000 3000 cal yr b p thus questioning the occurrence of major rsl stillstands alternating with abrupt rises given the narrow error envelope defined by our data set any sea level fluctuations if present would have amplitudes of 1 m although a true middle holocene highstand never occurred in the mississippi delta the high level of detail of our time series enables a rigorous test of this hypothesis correction of our data set for a hypothetical tectonic subsidence rate of 1 1 mm yr 1 assuming a constant subsidence rate compared to the tectonically relatively stable adjacent coast of texas leads to sea levels near 2 m above present during the time interval 6000 4000 cal yr b p however this model also implies a rsl position near 2 m around 8000 cal yr b p which is inconsistent both with data of this age from texas as well as with widely accepted sea level data from elsewhere we therefore conclude that a middle holocene highstand for the u s gulf coast is highly unlikely and that the entire area is still responding glacio isostatically by means of forebulge collapse to the melting of the laurentide ice sheet

whole process modeling of reservoir turbidity currents by a double layer averaged model turbidity current is formed as subaerial open channel sediment laden flow plunges into a reservoir the whole process of reservoir turbidity current i e formation propagation and recession is generally controlled by the water and sediment inputs from upstream and also the reservoir operation scheme specifying the downstream boundary condition enhanced understanding of reservoir turbidity current is critical to effective sediment management in alluvial rivers however until now there has been a lack of physically based and practically feasible models for resolving the whole process of reservoir turbidity current this is because the computing cost of three dimensional modeling is excessively high also single layer averaged models cannot resolve the formation process characterized by the transition from open channel sediment laden flow to subaqueous turbidity current or the upper clear water flow as dictated by the operation scheme of the reservoir which has significant impacts on turbidity current here a new two dimensional double layer averaged model is proposed to facilitate for the first time whole process modeling of reservoir turbidity current the two hyperbolic systems of the governing equations for the two layers are solved separately and synchronously the model is well balanced because the interlayer interactions are negligible compared with inertia and gravitation featuring a reasonable balance between the flux gradients and the bed or interface slope source terms and thus applicable to irregular topographies the model is benchmarked against a spectrum of experimental cases including turbidity currents attributable to lock exchange and sustained inflow it is revealed that an appropriate clear water outflow is favorable for turbidity current propagation and conducive to improving sediment flushing efficiency this is significant for optimizing reservoir operation schemes as applied to turbidity current in the xiaolangdi reservoir in the yellow river china the model successfully resolves the whole process from formation to recession the present work facilitates a viable and promising framework for whole process modeling of turbidity currents in support of reservoir sediment management c 2014 american society of civil engineers

a numerical investigation of the dynamics and structure of hyperpycnal river plumes on sloping continental shelves 1 a 3 d hydrodynamic model regional ocean modeling system is used to investigate the dynamics and structure of hyperpycnal river plumes over sloping continental shelves the focus is on the plume s response to varying slopes and settling velocities ws the idealized model is configured to represent small mountainous river systems during a flood event a hyperpycnal sediment concentration of 60 g l is specified at the river mouth such that the sediment freshwater mixture is denser than the seawater causing the plumes to traverse the shelves as undercurrents a realistic range of shelf slope of 0 001 0 03 is chosen the settling velocity is varied based on river s carrying capacity the model derived velocity profiles and the entrainment rate compare favorably against prior laboratory experiments both cross shore and alongshore momentum balances are primarily between gravitational forcing and bottom friction but the coriolis deflection is significant at the plume core in the alongshore momentum budget i e ekman balance as the slope increases and settling velocity decreases hyperpycnal plumes transition from depositional to autosuspending regime an estimate of critical slope governed by a dimensionless parameter ws3 qb qb is buoyancy input reasonably captures the regime transition in the depositional regime the plume s runout cross shore penetration scales with advective distance increasing slopes and discharge enhance the gravitational forcing and plume velocity leading to an increase in runout in contrast increasing settling velocity shortens the vertical settling time thereby reducing the plume s horizontal footprint for the range of parameters considered the runout of depositional plumes is confined within 15 km from the mouth whereas the penetration of autosuspending plumes is essentially unlimited

a glacial isostatic adjustment origin for double mis 5 5 and holocene marine notches in the coastline of italy abstract modern tidal notches on rocky coastlines are well developed in the mediterranean sea because of its microtidal regime and occur around much of the coast of italy uplifted fossil notch couplets here called double notches are well developed in some sites the two notches within a couplet have an average vertical separation of 2 4 m and are systematically observed at an elevation of a few metres above present sea level on tectonically stable coastal sites of western italy the upper notch has a morphology similar to that of the notch developed at present day mean sea level in the modern tidal regime however the lower notch has a smoother morphology and larger vertical dimension than the upper one and is pervasively bored by lithophaga activity although the upper notch is attributed to the mis 5 5 stage last interglacial 125 ka the origin of the lower one has so far remained enigmatic based on a quantitative assessment of the glacial isostatic adjustment gia expected at each single site from updated models we argue that both notches within a couplet were formed during a single highstand of the mis 5 5 substage and the superposed morphology resulted from isostatic motion and tidal erosion the lower notch of the couplet is argued to be formed during the earlier part of the highstand and its smooth vertically extended morphology is attributed to glacio hydro isostatic vertical movements crustal subsidence that extended tidal erosion over a large vertical distance as the crust slowly subsided in contrast the upper notch of the couplet is considered to develop in the later part of the highstand due to tidal action at times when eustatic and isostatic movements almost ceased the ridge between the two notches in a couplet was the site of organic encrustation protecting the rock there but subsequently removed by subaerial erosion when the notch couplet was uplifted observations of double notches formed on the present coastline show that a similar process has been active also during the late holocene transgression

bay head deltas across the northern gulf of mexico back step in response to the 8 2 ka cooling event abstract estuaries along the northern gulf of mexico show rapid landward shifts in estuarine environments back stepping around 8200 cal yr bp paleogeographic maps of the estuaries based on seismic data and cores and constrained chronologically by radiocarbon dates depict bay head delta retreat in excess of 25 m yr during these events the sub aerial delta plain flooded to create sub tidal upper and middle bay environments abrupt sea level rise associated with the 8200 cal yr bp climate change event caused these estuaries and others around the world to reorganize abruptly in the northern gulf of mexico the sea level rise associated with the event was only 0 1 m over a sub decadal time period this rise was superimposed on a background decelerating rate of sea level rise of 1 0 0 5 m century the widespread bay head delta back stepping documented here may be an appropriate analog for possible abrupt future climate change in response to global warming it also shows that estuaries fringed by low gradient shorelines are highly sensitive to low amplitude and sudden sea level rise

numerical modeling of poorly sorted depositional turbidity currents 1 the characteristics of poorly sorted turbidity currents are investigated by numerical simulation a multiphase approach is utilized to express the mass and momentum conservation equations for the bulk fluid the exner equation for multiple size classes of sediment is solved for the evolution of the bottom boundary the model is applied to simulate experiments on poorly sorted gravity currents and reproduced the vertical structures of velocity sediment concentration of individual size class and the total deposition depth satisfactorily the numerical simulation further reveals that the normalized vertical profiles of concentration of all size classes coincide at the position where the maximum longitudinal velocity occurs below this position in the logarithmic velocity region all concentration profiles are upwardly convex and coarser particle size classes are of larger concentration above it in the exponentially decaying velocity region all concentration curves are upwardly concave and finer particle size classes are of higher concentration the model also predicts that the position of maximum longitudinal velocity corresponds to a region of low turbulent kinetic energy the model has also been applied to study three dimensional poorly sorted depositional turbidity currents debouching from a straight channel into a horizontal unconfined area model results reveal the levee and channel building process in which the channel bed slope aggrades at a faster rate than that in the overbank area the simulation also shows that the contour of mean size of deposited sediment is closely related to the contour of deposit thickness and elongated somewhat in the flow direction

grain size analysis of the neogene red clay formation in the pannonian basin the red clay is a significant deposit underlying the pleistocene loess paleosols sequence in the pannonian basin the sedimentary processes involved and the origin of the materials remain controversial in order to determine the depositional processes of the pliocene red clay formation we studied many red clay sections in hungary here we present results of grain size analyses of the red clay from representative sites in particular their grain size distribution is compared with that of typical pleistocene eolian loess paleosols as well as lacustrine and fluvial sediments it appears from the sedimentological data that the majority of the red clay is of a wind blown origin the red clay might be transported by weak westerly winds and has been modified by post depositional alteration

elevation of the last interglacial highstand in sicily italy a benchmark of coastal tectonics well preserved mis 5 5 terraces in sicily are identified primarily by the index fossil strombus bubonius and dated by amino acid racemization aar electron spin resonance esr uranium thorium u th and thermo luminescence tl methods this review of published data and new results for the island of sicily and neighbouring small islands of egadi ustica and lampedusa identifies areas of rapid uplift in the east up to 175 m elevation above sea level slower uplift in the north 29 m and relative stability in the northwest 2 18 m in contrast about 250 km of the southern coastline of sicily does not appear to contain mis 5 5 outcrops in eastern sicily correlation of mis 5 5 highstands is based on strombus bubonius discovered at 86 m and correlated with the inner margin terrace at 110 m in the taormina area a fossiliferous marine conglomerate on a terrace with an inner margin at 115 m occurs in an area with undated terrace morphology and elevation data based on esr methodology applied to fossils sampled at 105 m in taormina we attribute this terrace to mis 5 probably 5 5 this age allows us to constrain the date of one point along a very long coastline that is otherwise undated a newly discovered fossil beach between 7 and 9 m at cefalu north central sicily attributed to mis 5 1 5 3 using aar analysis permits correlation of mis 5 5 to a 29 m high tidal notch geomorphologically related to a terrace at the same elevation cefalu lies in an important position between the uplifted coastline of northeastern sicily and the more stable coastline of western sicily this compilation of mis 5 5 data for all of sicily reflects the active tectonics of eastern sicily in contrast to the rest of the island

late pleistocene paleoclimates and sea level change in the mediterranean as inferred from stable isotope and u series studies of overgrowths on speleothems mallorca spain abstract phreatic overgrowths on speleothems form at the surface of brackish pools which are present in many coastal caves of mallorca spain unlike common vadose speleothems formed in subaerial environments their occurrence directly identifies the height of the sea level at the time of the carbonate deposition because such pools are physically connected with the sea these deposits from the late pleistocene have recorded the same global variations in oxygen isotopes as planktonic and benthonic foraminifera corals and cave deposits a number of phreatic overgrowths on speleothems have been dated using the th u method in order to determine the position of the sea level during late quaternary the same samples as well as some subaerial speleothems have been analysed for 18 o 16 o and 13 c 12 c ratios the former samples allow the analysis of variations in sea water component in the brackish pools associated with glacio eustatic mediterranean fluctuations and the latter permit inferences concerning past continental climate changes some high sea stands have been recognized in correspondence with oxygen isotope stages ois 9 or older 7 5e 5c and 5a phreatic overgrowths on speleothems have also been formed during a colder phase ois 4 demonstrating that also in that period there were environmental conditions favourable for this kind of carbonate precipitation vadose crystallizations have recorded a cold period at 36 ka corresponding with the end of ois 3

sea level and climate changes during ois 5e in the western mediterranean palaeontological geomorphological and sedimentological data supported by isotopic dating on oxygen isotopic stage ois 5e deposits from the spanish mediterranean coast are interpreted with the aim of reconstructing climatic instability in the northern hemisphere data point to marked climatic instability during the last interglacial ois 5e with a change in meteorological conditions and consequently in the sedimentary environment the oolitic facies generated during the first part of ois 5e ca 135 kyr shift into reddish conglomeratic facies during the second part ca 117 kyr sea surface temperature sst and salinity are interpreted mainly on the basis of warm senegalese fauna which show chronological and spatial differential distribution throughout the western mediterranean present hydrological and meteorological conditions are used also as modern analogues to reconstruct climatic variability throughout the last interglacial and this variability is interpreted within the wider framework of the north atlantic record all the available data indicate an increase in storminess induced by an increase in the influence of northwesterlies a slight drop of sst in the northern western mediterranean and an important change in meteorological conditions at the end of ois 5e 117 kyr these changes correlate well with the decrease in summer insolation and with the climatic instability recorded in north atlantic high latitudes

turbidity currents and submarine channel formation in rupert inlet british columbia 1 surge observations acoustic backscatter images obtained at 107 and 200 khz of surge type turbidity currents resulting from mine tailing discharge are presented excess densities in the head of the order of 100 kg m 3 are estimated from differences in acoustic backscatter intensity and in the amplitude of the bottom reflected signal these excess densities are comparable to estimates based on surge height and speed the speed being determined by assuming a universal head shape unlike gravity current surges from an impulsively started steady source the surge type turbidity flows consist of a high concentration slug of short duration followed by a longer lived wake in which sediment concentrations are lower by 2 3 orders of magnitude the profile of the high concentration slug resembles those for density slugs on small bottom slopes obtained in laboratory experiments discrete scatterers probably fish are observed to avoid the surges

eustatic and tectonic controls on quaternary ras leona marine terraces strait of gibraltar northern morocco well preserved quaternary staircased marine terraces appear on ras leona limestone relief this is a peculiar sector of the betic rif cordillera lying in the four way junction between the atlantic and the mediterranean and europe and africa the age and altitude correlation of the ras leona terraces with travertine covered lateral equivalent terraces fashioned in the neighbouring beni younech area and comparison with those along the moroccan atlantic coasts would suggest that the ras leona terraces were mainly formed by eustatic factors the importance of the eustasy is supported by further comparisons with spanish and moroccan mediterranean terraces and with different marine terraces developed on passive margin coasts around the world a tectonic event occurred mainly during the period between the formation of the maarifian and the ouljian terraces i e between 370 and 150 ka the moderate quaternary tectonic uplift deduced from the marine terraces and its comparison with uplifted marine terraces developed in active subduction setting disagrees with the model of an active eastwards subduction below the gibraltar tectonic arc

sedimentation processes in the eastern mediterranean sea during the late glacial and holocene revealed by end member modelling of the terrigenous fraction in marine sediments we present grain size distributions of the terrigenous fraction of two sediment cores from the southeast levantine sea sl112 and the northern aegean sea sl148 spanning the time interval from the late glacial to the present end member modelling of the grain size distribution allows discriminating between aeolian and fluvial transport of the sediments and helps to infer palaeoenvironmental conditions in the source areas sedimentary and depositional processes during the late glacial and holocene were controlled by climatic variations of both the northern high latitudes and the african climate system the sedimentation at site sl112 off israel is dominated by the suspension load of the river nile and aeolian dust from the sahara variations in grain size reflect the early to mid holocene climate transition from the african humid period to recent arid conditions this climate change was gradual in contrast to the abrupt humidity change documented in western saharan records this implies a successive decrease in nile river sediment supply due to a step wise aridification of the headwaters the grain size data of sl112 show a humidity maximum at 5 kyr bp coincident with a regionally restricted wet phase in the levantine sea the sediments at the north aegean site sl148 consist of riverine particles and low amounts of aeolian dust probably derived from south european sources and with probably minor saharan influence the sedimentation processes are controlled by climate conditions being characterized by enhanced deposition of dust during the cold and dry glacial period and by decreased aeolian influx during the temperate and humid holocene

irregular fenestrae in bahamian eolianites a rainstorm induced origin abstract fenestrae are primary or penecontemporaneous pores in the sediment framework that are larger than grain supported interstices these features have long been used to characterize peritidal environments and as a sea level indicator in ancient successions we report the occurrence of irregular i e equidimensional fenestrae in pleistocene eolianites on san salvador and eleuthera bahamas as much as 35 m above the coeval sea level a rainstorm induced origin is proposed as the mechanism for production of such voids in eolian deposits we suggest that fenestrae should be used as a sea level indicator only when they are associated with other intertidal or peritidal characteristics

subsidence of the texas coast inferences from historical and late pleistocene sea levels abstract changes in sea level observed at tide gauges are caused by actual changes in water level and by changes in elevation at the observing station recent research has focused on the relationship between climatic change and sea level but vertical land movement can be just as important particularly in subsiding sedimentary basins the purpose of this study is to compare long term rates of subsidence estimated from upper pleistocene strata along the central texas coast with historical subsidence rates from the same area obtained from geodetic surveys and tide gauge data this comparison shows that historical subsidence rates are much greater than long term averages and are equal or greater than actual sea level change along the texas coast south of galveston bay long term 10 5 yr subsidence rates were estimated by establishing the extent of marine marine influenced and nonmarine strata within the upper pleistocene beaumont formation in the copano bay area of the central texas coast and comparing the maximum elevation of in place marine influenced deposits with published maximum sea level estimates of 5 8 m above mean sea level msl from correlative well dated coral terraces from stable and uplifted areas in place shell bearing horizons deposited at or below sea level occur no higher than 2 m msl in the copano bay area suggesting that there has been no more than 6 m of subsidence since the probable time of deposition during the sangamon interglacial at 120 ka the long term average subsidence rate for this part of the texas coast is thus 0 05 mm yr or less historical subsidence rates were obtained by 1 1 calculating relative elevation changes between national geodetic survey first order leveling surveys conducted in the early 1950s with those conducted in the late 1970s to early 1980s 2 2 normalizing the relative elevation differences between surveys to annual rates of change relative to an arbitrarily chosen benchmark 3 3 referencing these lines to sea level at three tide gauges and 4 4 comparing calculated rates of relative sea level rsl rise along the lines with estimates of eustatic sea level esl rise rates of rsl rise for the texas coast south of galveston bay were generally 4 8 mm yr locally rates were as high as 23 mm yr these rates are significantly higher than global averages of 1 mm yr much of the difference is probably caused by subsidence of the texas coastal zone at rates of 1 22 mm yr or 20 440 times the long term average of 0 05 mm yr the highest subsidence rates were found locally where there has been historical water level decline in shallow aquifers lower subsidence rates of 3 7 mm yr occur regionally where groundwater decline is minimal or nonexistent increased subsidence over the long term average in these areas may be caused by pressure decline in underlying oil and gas reseivoirs

late quaternary vegetation and climate changes in central texas based on the isotopic composition of organic carbon stable carbon isotope analysis of organic carbon in alluvial deposits and soils of three streams in central texas reveals significant shifts in the ratio of c3 to c4 plant biomass production during the past 15 000 yr these temporal changes in vegetation appear to be in response to changes in climate during the late pleistocene c4 plants comprised only about 45 to 50 of the vegetative biomass in this area suggesting that conditions were cooler and wetter than at any time during the past 15 000 yr the time between 11 000 and 8000 yr b p is interpreted as transitional between late pleistocene conditions and warmer and drier holocene conditions based on a slight increase in the abundance of c4 plant biomass during the middle holocene between approximately 6000 and 5000 yr b p mixed c3 c4 plant communities were replaced almost completely by c4 dominated communities indicating prairie expansion and warmer and drier climatic conditions by 4000 yr b p the abundance of c4 plant biomass decreased to levels similar to the early holocene transitional period suggesting a return to cooler and wetter climatic conditions no significant shift in the ratio of c3 to c4 productivity has occurred during the last 4000 yr except for a slight increase in the abundance of c4 plant biomass around 2000 yr b p the results of this investigation correlate well with other regional late quaternary climatic interpretations for central and north texas the southern plains region and with other portions of the great plains

the sea level fingerprint of the 8 2 ka climate event the 8 2 ka cooling event was an abrupt widespread climate instability there is general consensus that the episode was likely initiated by a catastrophic outflow of proglacial lakes agassiz and ojibway through the hudson strait with subsequent disruption of the atlantic meridional overturning circulation however the total discharge and flux during the 8 2 ka event remain uncertain we compute the sea level signature or fingerprint associated with the drainage of lakes agassiz and ojibway as well as the expected sea level signal over the same time period due to glacial isostatic adjustment gia in response to the late pleistocene deglaciation our analysis demonstrates that sites relatively close to the lakes including the west and gulf coasts of the united states have small signals due to the lake release and potentially large gia signals and thus they may not be optimal field sites for constraining the outflow volume other sites such as the east coast of south america and western africa have significantly larger signals associated with the lake release and are thus better choices in this regard

millennial submillennial scale sea level fluctuations in western mediterranean during the second highstand of mis 5e abstract thispaperinvestigatesaseriesofsmall scale short lived uctuationsofsealevelregisteredinaprogradingbarrierspit thatgrew during the mis 5e this interglacial includes threehighstands zazoet al 2003 andwe focus on the second highstand of assumed duration 10 2 ka given that ueth ages do not providemoreaccuratedata geometryand3darchitectureofbeachfacies andthin sectionpetrographywereusedto investigate eight exposed of apping subunits separated by seven conspicuous erosion surfaces allinterpreted as the result of repeated small scale uctuations of sea level each subunit records a relatively rapid rise of sea level that generated a gravelly shoreface with algalbioherms and a sandy uppermost shoreface and foreshore where most sand accumulated a secondrange of still smaller scaled oscillations of sea level has been deduced in this phase of sea level uctu ation from lateral and vertical shifts of the foreshore plunge step uppermost shoreface facies eventually progradation with gently falling sea level took place and foreshore deposits underwentsuccessive vadose cementation and subaerial dissolution owing to relatively prolonged exposure laterrecovery of sea level re established the highstand with sea level at approximately the same elevation and there began deposition of a new subunit the minimum sea level variation fall and subsequent rise required to generate the observed features is 4 m the time span available for the whole succession ofevents and comparison with the holocene prograding beach ridge complex in the nearby roquetas almeria were used to calculate the periodicity of events a millennial suborbital time scale is suggestedfor uctuations separating subunits and a decadal scale for the minor oscillations inside each subunit 2010 elsevier ltd all rights reserved

wavy lamination in a mixed sand and gravel foreshore facies of the pleistocene hosoya sandstone aichi central japan although sandy foreshore facies are generally characterized by parallel lamination wavy lamination is predominant in the mixed sand and gravel foreshore facies of the pleistocene hosoya sandstone which crops out along the pacific coast of the atsumi peninsula aichi central japan the foreshore facies consists of three sedimentary subfacies interbeds of gravel and parallel laminated sand of the lower foreshore facies parallel laminated fine to medium sand beds containing scattered pebbles and cobbles of the middle foreshore facies and wavy laminated fine to medium sand beds containing scattered pebbles and cobbles of the upper foreshore facies a lack of erosional surfaces in the middle foreshore facies indicates the continuous accumulation of sand in flat beds under upper plane bed flow the wavy laminated sands of the upper foreshore facies exhibit erosional surfaces indicative of repeated deposition and erosion the erosional surfaces are undulatory with depressions 10 cm wide and 3 cm deep that contain scattered pebbles and cobbles these depressions reflect backwash erosion of sand around and below the pebbles and cobbles sand draping over the undulating erosional surfaces forms the wavy lamination the wavy laminated sand with scattered pebbles and cobbles is a key facies of an upper foreshore or swash zone and is a good sea level marker

cyclone induced hyperpycnal turbidity currents in a submarine canyon 1 density currents such as turbidity currents are major transport agents in various terrestrial lacustrine and marine environments worldwide however a gap exists between those who study the deposits by turbidity currents turbidite on a field scale and those who study turbidity currents using small scale laboratory experiments and theoretical numerical models we report two typhoon triggered hyperpycnal turbidity current events observed in a submarine canyon our findings verify turbidite sequences with the characteristics of suspended sediment carried by passing turbidity currents that displayed distinct waxing and waning phases our study also confirms the direct link between typhoon triggered hyperpycnal flows in a small mountainous river and turbidity currents in a nearby submarine canyon that transport sediment to the deep sea efficiently

sea level change and vertical land movements since the last two millennia along the coasts of southwestern turkey and israel abstract this paper provides new relative sea level data inferred from coastal archaeological sites located along the turkish coasts of the gulf of fethye 8 sites and israel between akziv and caesarea 5 sites the structures selected are those that for effective functioning can be accurately related to sea level at the time of their construction thus their positions with respect to present sea level provide a measure of the relative sea level change since their time of construction useful information was obtained from the investigated sites spanning an age range of 2 3 1 6 ka bp the inferred changes in relative sea level for the two areas are distinctly different from a rise of 2 41 to 4 50 m in turkey and from 0 to 0 18 m in israel sea level change is the combination of several processes including vertical tectonics glacio hydro isostatic signals associated with the last glacial cycle and changes in ocean volume for the israel section the present elevations of the mis 5 5 tyrrhenian terraces occur at a few meters above present sea level and vertical tectonic displacements are small data from gps and tide gauge measurements also indicate that any recent vertical movements are small the mis 5 5 shorelines are absent from the investigated section of the turkish coast consistent with crustal subsidence associated with the hellenic arc the isostatic signals for the israel section of the coast are also small ranging from 0 11 mm yr to 0 14 mm yr depending on site and earth model and the observed eustatic average sea level change corrected for this contribution is a rise of 13 5 2 6 cm during the past 2 ka this is attributed to the time integrated contribution to sea level from a combination of thermal expansion and other increases in ocean volume the observed sea levels from the turkish sites in contrast indicate a much greater rise of up to 2 2 mm yr since 2 3 ka bp occurring in a wide area between knidos and kekova the isostatic signal here is also one of a rising sea level of up to 1 mm yr and site and earth model dependent and the corrected tectonic rate of land subsidence is 1 48 mm yr this is the primary cause of dramatic relative sea level rise for this part of the coast

biological evidence of sea level rise during the last 4500 years on the rocky coasts of continental southwestern france and corsica on the rocky coasts of the northwestern mediterranean basin biogenic littoral rims built by the coralline rhodophyte lithophyllum lichenoides develop whose remains may be preserved for millennia when submerged in a rising sea environment these remains can be used as biological indicators of recent sea level variations our survey of the continental coasts of var and bouches du rhone west of marseilles southern france and of northern corsica shows that relative sea level rose about 1 6 m in the study area during the last 4500 years without exceeding the present datum the rate of sea level rise was 0 4 mm per year between 4500 and 1500 yr b p and slowed down to 0 2 mm per year from 1500 yr b p to present time there are also morphological indications of an acceleration of the rate of sea level rise during the last century supporting the evidence of tide gauges regions at the periphery of the above zone alpes maritimes italian border zone and the french and spanish catalonia regions were also surveyed but a weaker development of lithophyllum rims and bad preservation of algal remains led to unconvincing dates which could also be linked to regional tectonic trends

pleistocene raised marine terraces of the spanish mediterranean and atlantic coasts records of coastal uplift sea level highstands and climate changes detailed geological mapping morphostratigraphic palaeontological and geochronological uranium series analyses were undertaken on the raised marine terraces and interbedded terrestrial deposits along the spanish peninsular and insular atlantic and mediterranean coasts several sets of pleistocene shallow marine to coastal deposits exposed in a staircase arrangement are interpreted as being emplaced during sea level highstands coeval with interglacials or interstadials correlating with marine oxygen isotopic stages ois 5a 5c 5e 7 9 11 and older up to three highstands have been identified in deposits formed during ois 5e close to the end of ois 5e there is a record of sudden changes in sea surface conditions and climate marked by the disappearance of a major proportion of the warm senegalese fauna switches from oolitic to non oolitic facies and accumulation of boulder beaches dating of the coral cladocora caespitosa found in a layer that also contains strombus bubonius confirms the occurrence of warm fauna in the mediterranean basin during ois 7 as previously suggested by hillaire marcel et al 1986 goy et al 1986a b zazo and goy 1989 also the occurrence of warm faunas in deposits corresponding to an older interglacial probably ois 9 or 11 in the balearic islands suggests similar oceanographic conditions sea surface temperature assuming constant salinity during the last interglacial and at least two interglacials of the middle pleistocene in the western mediterranean a 2002 elsevier science b v all rights reserved

an early holocene sea level jump and delta initiation 1 early holocene sea level change controlled the evolution of clastic coastal depositional systems radiocarbon dated borehole cores obtained from three incised valley fill systems in asia changjiang song hong and kiso river record very similar depositional histories especially between about 9000 and 8500 cal bp sedimentary facies changes from estuarine sand and mud to shelf or prodelta mud suggest that the marine influence in the incised valleys increased during this period in addition large decreases in sediment accumulation rates occurred a sea level jump causes an estuarine system and its depocenter to move rapidly landward it is possible that the final collapse of the laurentide ice sheet accompanied by catastrophic drainage of glacial lakes at approximately 8500 cal bp caused such a jump the jump was followed immediately by a period of decelerated sea level rise that promoted delta initiation

high rates of sea level rise during the last interglacial period sea level during the last interglacial stood at least 4 m higher than at present with evidence of short term fluctuations of up to 10 m a new continuous sea level record from the red sea and coral ages suggest that during these fluctuations sea level changes were on the order of 1 6 m per century

the classic marine isotope substage 5e since its identi cation nearly fty years ago marine iso tope stage 5 mis 5 has been placed onto absolute time scaleson the basis of three independent approaches cesare emiliani who set up the isotope stages emiliani 1955 depended onuranium series dating of the sediments a method that today isregarded as not generally capable of yielding useful precisionor accuracy broecker and van donk 1970 pioneered the ap proach of correlating to radiometrically dated marine coral ter races thishasbeenmuchaidedinrecentyearsbyimprovementsin the precision and accuracy of these age determinations thathave owed from the development of thermal ionization massspectrometry tims for uranium series dating edwards

coastal uplift west of algiers algeria pre and post messinian sequences of marine terraces and rasas and their associated drainage pattern the north africa passive margin is affected by the ongoing convergence between the african and eurasian plates this convergence is responsible for coastal uplift folding and reverse faulting on new and reactivated faults on the margin the active deformation is diffuse and thus rather difficult to locate precisely we aim to determine how a coastal landscape evolve in this geodynamic setting and gain insights into active tectonics more particularly we evidence and quantify coastal uplift pattern of the chenoua sahel and algiers reliefs algeria using sequences of marine terraces and rasas and computing several morphometric indices from the drainage pattern upper and middle pleistocene uplift rates are obtained by fossil shoreline mapping and preliminary u th dating of associated coastal deposits extrapolation of these rates combined to analyses of sea level referential data and spatial relationships between marine terraces rasas and other geological markers lead us to tentatively propose an age for the highest coastal indicators purported the oldest values of morphometric indices showing correlations with uplift rate allow us to analyze uplift variation on area devoid of coastal sequence geological and geomorphological data suggest that coastal uplift probably occurred since the middle miocene it resulted in the emergence of the algiers massif followed by the sahel ridge massif the sahel ridge has asymmetrically grown by folding from west to east and was affected by temporal variation of uplift compared to previous study the location of the sahel fold axis has been shifted offshore near the coast the chenoua fault vertical motion does not offset significantly the coastal sequence mean apparent uplift rates and corrected uplift rates since 120 ka are globally steady all along the coast with a mean value of 0 055 0 015 mm year apparent and of 0 005 0 045 mm year corrected for eustasy mean apparent coastal uplift rates between 120 and 400 ka increase eastward from 0 045 0 025 to 0 19 0 12 mm year without correction for eustasy or from 0 06 0 06 to 0 2 0 15 mm year with correction for eustasy in addition the combination of structural and geomorphic data suggests a low uplift rate for the southern part of the algiers massif

c4 plant productivity and climate co2 variations in south central texas during the late quaternary abstract a continuous record of organic carbon 13c from a buried soil sequence in south central texas demonstrates 1 strong coupling between marine and adjacent continental ecosystems in the late pleistocene as a result of glacial meltwater entering the gulf of mexico and 2 ecosystem decoupling in the holocene associated with a reduction of meltwater and a shift in global circulation patterns in the late pleistocene reduction in c4 plant productivity correlates with two well documented glacial meltwater pulses 15 000 and 12 000 14c yr b p indicating a cooler than present adjacent continental environment increased c4 production between 11 000 and 10 000 14c yr b p suggests that the younger dryas was a warm interval responding to the diversion of glacial meltwater away from the mississippi river with waning meltwater flow c4 productivity generally increased throughout the holocene culminating in peak warm intervals at 5000 and 2000 14c yr b p shifts in the abundances of c3 c4 plants through the late quaternary show no correlation to ecophysiological responses to atmospheric co2 concentration

timing and duration of last interglacial conditions in europe a chronicle of a changing chronology abstract estimates of the length of the last interglacial in europe conventionally defined by the presence of forest as inferred from pollen diagrams have varied considerably here an account of recent developments largely instigated by a paper by kukla et al 1997 is presented these include the emergence of new records with improved chronologies and a re evaluation of previous assumptions of synchroneity between marine and terrestrial stage boundaries and also between northern and southern european changes the current scheme proposes that the onset of the last interglacial in europe started well into mis 5e after deglaciation was complete and was coincident with a rise to peak sea surface temperatures however the timing of the end of the last interglacial between northern and southern europe appears to have diverged considerably in the north the elimination of forest occurred ca 115 ka near the time of the mis 5e 5d transition while in the south tree populations persisted into the interval of global ice growth until the onset of significant ice rafting ca 110 ka this significant n s diachroneity may be a reflection of the effects of different bioclimatic parameters limiting tree growth in the two areas these developments highlight the problems of correlating records of different proxies and from different geographical regions

archaeological remains as sea level change markers a review abstract the mediterranean sea constitutes a unique basin from an historical and archaeological point of view as it has been a privileged way of communication for thousands of years for the people that dwelled on its shores their passage has left many traces on the seabeds in the areas where the ancient commercial routes passed and remains of structures where moorings havens or dwellings existed some of these structures nowadays submerged offer interesting indications aiding the reconstruction of the ancient coastlines this contribution aims to examine recent work in coastal geo archaeology targeting both 1 gathering and discussion of the data particularly those pertaining to the italian coasts and 2 commentary on the methodological debate and verification of the possibility of a protocol that may contain unequivocal referring elements to investigate the archaeological evidence currently underwater because of the relative sea level variations harbour infrastructures fishponds villae maritimae caves nymphaei private or public buildings or town quarters pre and protohistorical villages quarries caves etc a clear and more coherent methodological assumption may be needed the archaeological interpretation must initially establish the maritime and or harbour nature and vocation of the site determine its typology and specific usage analyze the elements of its building techniques that reveal themselves as meaningful markers of height or depth at the time of building and its functional elements the measure of the emerged part with respect to the average sea level and point out the time of construction its chronological range of usage frequentation the dynamics of its abandonment destruction obliteration the evaluation of both the height and functional depth to the mean sea level depends on the typology of the archaeological evidence its use and the local tide amplitudes the surface of a pier surely has a functional elevation different from that of a haulage area or a platea or a pavement

sea level history of the past two interglacial periods new evidence from u series dating of reef corals from south florida abstract as a future warm climate analog much attention has been directed to studies of the last interglacial period or marine isotope substage mis 5 5 which occurred 120 000 years ago nevertheless there are still uncertainties with respect to its duration warmth and magnitude of sea level rise here we present new data from tectonically stable peninsular florida and the florida keys that provide estimates of the timing and magnitude of sea level rise during the last interglacial period the last interglacial high sea stand in south florida is recorded by the key largo limestone a fossil reef complex and the miami limestone an oolitic marine sediment thirty five new high precision uranium series ages of fossil corals from the key largo limestone indicate that sea level was significantly above present for at least 9000 years during the last interglacial period and possibly longer ooids from the miami limestone show open system histories with respect to u series dating but show a clear linear trend toward an age of 120 ka correlating this unit with the last interglacial corals of the key largo limestone older fossil reefs at three localities in the florida keys have ages of 200 ka and probably correlate to mis 7 these reefs imply sea level near or slightly above present during the penultimate interglacial period elevation measurements of both the key largo limestone and the miami limestone indicate that local relative sea level was at least 6 6 m and possibly as much as 8 3 m higher than present during the last interglacial period

analysis and direct numerical simulation of the flow at a gravity current head part 1 flow topology and front speed for slip and no slip boundaries direct numerical simulations are performed of gravity current fronts in the lock exchange configuration the case of small density differences is considered where the boussinesq approximations can be adopted the key objective of the investigation is a detailed analysis of the flow structure at the foremost part of the front where no previous high resolution data were available for the simulations high order numerical methods are used based on spectral and spectral element discretizations and compact finite differences a three dimensional simulation is conducted of a front spreading along a no slip boundary at a reynolds number of about 750 the simulation exhibits all features typically observed in experimental flows near the gravity current head including the lobe and cleft structure at the leading edge the results reveal that the flow topology at the head differs from what has been assumed previously in that the foremost point is not a stagnation point in a translating system rather the stagnation point is located below and slightly behind the foremost point in the vicinity of the wall the relevance of this finding for the mechanism behind the lobe and cleft instability is discussed in order to explore the high reynolds number regime and to assess potential reynolds number effects two dimensional simulations are conducted for reynolds numbers up to about 30 000 for both no slip and slip i e shear stress free boundaries it is shown that although quantitative reynolds number effects persist over the whole range examined no qualitative changes in the flow structure at the head can be observed a comparison of the two dimensional results with laboratory data and the three dimensional simulation provides evidence that a two dimensional model is able to capture essential features of the flow at the head the simulations also show that for the free slip case the shape of the head agrees closely with the classical inviscid theory of benjamin

the vertical structure of turbidity currents and a necessary condition for self maintenance a simple numerical model predicts that properties of a turbidity current can vary significantly in the vertical direction particularly when more than one sediment size is in suspension each sediment size decreases in concentration with increasing distance from the bottom boundary at a rate which depends on its settling velocity the current velocity the entrainment coefficient and the bottom slope however it is shown that the details of the vertical distribution of sediment load do not necessarily greatly influence either the vertical structure of the hydraulic properties of the flow velocity stress or the bulk properties such as the entrainment coefficient at least when only one sediment size is in suspension the ability of a turbidity current to sustain itself is strongly dependent on the sediment load and an autosuspension criterion is obtained by taking into account the vertical structure of the currents the model turbidity currents often cannot maintain their sediment in suspension even when the bottom stress is greater than the critical stress of deposition for low concentration flows when this happens the concentration near the bottom increases without limit as the turbidity current evolves with time in real turbidity currents grain grain interactions which become important at high concentrations may at times cause the current to quickly deposit its near bottom sediment load this is suggested as a possible mechanism for the formation of the poorly sorted sediments frequently found in turbidites

in situ measurements of velocity structure within turbidity currents 1 turbidity currents are thought to be the main mechanism to move 500 000 m3 of sediments annually from the head of the monterey submarine canyon to the deep sea fan indirect evidence has shown frequent occurrences of such turbidity currents in the canyon but the dynamic properties of the turbidity currents such as maximum speed duration and dimensions are still unknown here we present the first ever in situ measurements of velocity profiles of four turbidity currents whose maximum along canyon velocity reached 190 cm s two turbidity currents coincided with storms that produced the highest swells and the biggest stream flows during the year long deployment

marine notches in coastal cliffs indicators of relative sea level change perachora peninsula central greece abstract in several sites in the complex faulted western part of perachora peninsula central greece three principal marine notches in rocky coasts are present in each site no holocene notches occur above the upper of the three notches only subaerial weathering affected the rocks lateral variation in the heights of notches demonstrates differential uplift due to fault control and illustrates the complexity of application of marine notches in interpretation of tectonic history the lower undated notch is prominent in places coincides with modern sea level and is interpreted to be forming now it suggests that the western part of the peninsula has been stable for a considerable time the middle and upper notches vary in height between sites and may not be time equivalent but represent earlier sea level positions in the harbour adjacent to the heraion archaeological site the middle and upper notches are preserved in most places as notch roofs so that gradual uplift led to removal of notch floors by physical chemical and biotic processes in exposed locations however within a few hundred metres west of the harbour four uplifted plus a fifth forming now notches have been illustrated by pirazzoli et al tectonophysics 229 1994 201 that cannot be readily correlated to the harbour site and indicate differential uplift by fault displacement in a more complex situation at mylokopi 6 km ne of heraion three different notch profiles occur in three blocks separated by two faults however within the central block of the three two very different profiles are preserved only tens of metres apart beneath one continuous upper notch roof at the same height this complex arrangement interpreted as variability of exposure to marine processes on different parts of this irregular embayment such that one profile containing three notches was controlled largely by abrasion and formed notches that are vertically more extensive while the other profile containing five narrow notches formed by dissolution and or biological erosion at the same time in the protected east end of the block however if only one or the other profile was visible very different tectonic interpretations would result the bedrock of perachora peninsula also shows important variations in resistance to erosion affecting the resulting notch profiles and some sites are influenced by structurally controlled differential subaerial weathering forming ridges and grooves giving the false impression of extra minor notches the distinction between dissolution controlled and structure controlled minor notches may not be possible in some places the interpretations of notch profiles can be highly complex and influence views of tectonic history in a given region overall the occurrence of three principal notches beneath one uplifted notch roof in several sites indicates that a holocene uplift rates outpaced post glacial sea level rise b there were three principal periods of relative sea level stillstand affecting the perachora peninsula and c uplift of the entire western part of the perachora peninsula is an important component of its tectonic processes probably more important than fault movement within the peninsula

morphometry and elevation of the last interglacial tidal notches in tectonically stable coasts of the mediterranean sea abstract we report detailed morphometric observations on several mis 5 5 and a few older mis 11 21 25 fossil tidal notches shaped along carbonate coasts at 80 sites in the central mediterranean sea and at an additional six sites in the eastern and western mediterranean at each site we performed precise measurements of the fossil tidal notch ftn width and depth and of the elevation of its base relative to the base of the present tidal notch ptn the age of the fossil notches is obtained by correlation with biologic material associated with the notches at or very close to the site this material was previously dated either through radiometric analysis or by its fossiliferous content the width i e the difference in elevation between base and top of the notches ranges from 1 20 to 0 38 m with a mean of 0 74 m although the ftn is always a few centimetres wider than the ptn probably because of the lack of the biological reef coupled with a small erosional enlargement in the ftn the broadly comparable width suggests that tide amplitude has not changed since mis 5 5 times this result can be extended to the mis 11 features because of a comparable notch width but not to the mis 21 and 25 epochs although observational control of these older notches is limited we regard this result as suggesting that changes in tide amplitude broadly occurred at the early middle pleistocene transition the investigated mis 5 5 notches are located in tectonically stable coasts compared to other sectors of the central mediterranean sea where they are uplifted or subsided to 100 m and over in these stable areas the elevation of the base of the mis 5 5 notch ranges from 2 09 to 12 48 m with a mean of 5 7 m such variability although limited indicates that small land movements deriving from slow crustal processes may have occurred in stable areas we defined a number of sectors characterized by different geologic histories where a careful evaluation of local vertical land motion allowed the selection of the best representative elevation of the mis 5 5 peak highstand for each sector this elevation has been compared against glacial isostatic adjustment gia predictions drawn from a suite of ice sheet models ice g5 ice g6 and anice selen that are used in combination with the same solid earth model and mantle viscosity parameters results indicate that the gia signal is not the main cause of the observed highstand variability and that other mechanisms are needed the gia simulations show that even within the mediterranean basin the maximum highstand is reached at different times according to the geographical location our work shows that besides gia even in areas considered tectonically stable additional vertical tectonic movements may occur with a magnitude that is significantly larger than the gia

sea level change during the holocene in sardinia and in the northeastern adriatic central mediterranean sea from archaeological and geomorphological data abstract we provide new data on relative sea level change from the late holocene for two locations in the central mediterranean sardinia and ne adriatico they are based on precise measures of submerged archaeological and tide notch markers that are good indicators of past sea level elevation twelve submerged archaeological sites were studied six aged between 2 5 and 1 6 ka bp located along the sardinia coast and a further six dated 2 0 ka bp located along the ne adriatic coast italy slovenia and croatia for sardinia we also use beach rock and core data that can be related to holocene sea level the elevations of selected significant archaeological markers were measured with respect to the present sea level applying corrections for tide and atmospheric pressure values at the time of surveys the interpretation of the functional heights related to sea level at the time of their construction provides data on the relative changes between land and sea these data are compared with predictions derived from a new glacio hydro isostatic model associated with the last glacial cycle sardinia is tectonically relatively stable and we use the sea level data from this island to calibrate our models for eustatic and glacio hydro isostatic change the results are consistent with those from another tectonically stable site the versilia plain of italy the northeast adriatic italy slovenia and croatia is an area of subsidence and we use the calibrated model results to separate out the isostatic from the tectonic contributions this indicates that the adriatic coast from the gulf of trieste to the southern end of istria has tectonically subsided by 1 5 m since roman times

historical coseismic uplift on euboea island greece abstract in the aegean region it is usually accepted that uplift is confined to the southern areas near the outer island arc whereas subsidence prevails in the inner basin areas however we give evidence of elevated notches andlithophaga shells dated by ams14c showing that holocene coseismic uplift of the order of about a metre occurred in inner aegean areas too and affected parts of the coasts of north and central euboea island between 510 and 380 b c and also possibly between 1050 and 900 b c

coastal notches their morphology formation and function deep coastal notches develop through undercutting of steep coastal slopes consisting of rocks that are strong enough to support the weight of the overburden notches are found from the tropics to the poles and in a wide range of rock types virtually tideless to megatidal seas and high to low wave energy environments the emphasis in the literature has been on notches in calcareous rocks in warm microtidal seas and with the general assumption that they have been produced by bioerosion or chemical dissolution few scientifically rigorous attempts have been made to determine the processes responsible for notch formation in different environments and rock types however or to determine whether different processes produce distinct notch morphologies within the same tidal and wave environments the use of notches as palaeo sea level markers and to determine rates of tectonic uplift has been particularly important in the mediterranean notches are more difficult to employ for this purpose in the middle latitudes where higher waves and tides amplify the range of elevations over which the erosional mechanisms are effective as well as increasing the exposure and effect of rocks of variable resistance to erosion to maximize the utility of notches as sea level markers and to better understand and model their development in a wide range of environments we need to understand and be able to quantify the relationship between notch shape and size and the elevational efficacy of the various erosional processes

structure and development of detrital reef deposits in turbid nearshore environments inhaca island mozambique coral communities are intermittently developed along the seaward margins of wide up to 500 m intertidal flats that fringe the western margins of inhaca island southern mozambique the coral communities occur in an environment that can be considered as marginal for coral growth in the sense that they are subject to high turbidity levels which results in rapid light attenuation and to the effects of periodic smothering and burial associated with a mobile siliciclastic dominated sediment substrate these constraints limit coral community development both spatially and bathymetrically in addition historical evidence suggests that the main sites of coral growth shift over decadal timescales due to periodic sediment remobilisation such rapid rates of turnover restrict the development of rigid framework deposits and in contrast the main depositional product of coral growth is an abundance of branched mainly acropora sp coral rubble rubble production is aided both by intense internal bioerosion sponge bivalve and worm traces and by periodic storm damage much of this rubble accumulates along the channel margins and provides a substrate for subsequent coral recruitment the deposits can be distinguished from those associated with clear water reef environments by 1 the lack of a rigid reef framework either comprising of in situ coral or encrusted coral rubble 2 the distinct lack of rubble encrustation syn depositional cementation and 3 the predominance of a siliciclastic rich sediment matrix the deposits indicate however a long term history of coral community occurrence in sites dominated by siliciclastic sedimentation cores recovered from a transect across the tidal flats identify a coral rubble floatstone facies extensively developed along the western margins of the island it comprises mainly branched coral rubble often heavily bioeroded but sparsely encrusted along with spheroidal rhodoliths and molluscan fragments set within a poorly sorted mixed siliciclastic carbonate sediment matrix 14c dating indicates that most of the rubble deposits date from the period 6500 4700 years bp which corresponds to a period of regional sea level highstand a detailed growth chronology cannot be established due to the lack of in situ coral but rapid rubble deposition and reef flat progradation around 350 m can be inferred for this period equivalent to an average progradation rate of around 0 2 m year 1 over the subsequent 4700 years progradation of only around 25 m has occurred this may be attributed to reworking and erosion of the seaward margin of the deposits during periods of fluctuating sea level between 4700 and 900 years bp or to a lack of seaward accommodation space

evidence of mis 5 sea level highstands in gebel mousa coast strait of gibraltar north of africa abstract the last interglacial is considered the most suitable episode from which to infer patterns of rapid sea level change since its climatic conditions were similar to those of the present interglacial however specifying the true position of its sea level with high accuracy is very troublesome in the absence of sedimentological erosional or even palaeontological markers this study investigates the morphosedimentary evidence beach deposits cliff notch and shore platform of two highstands registered and dated during mis 5 stage by u series dating in the north of morocco strait of gibraltar bioerosive notches and mixed siliciclastic and carbonate deposits high energy beaches with algal bioherms were formed in coastal environments during mis 5a a sea level height of 10 m asl can be inferred for this substage the record of mis 5e substage is less defined in the geomorphological record consisting of backshore foreshore deposits located at 13 to 15 m asl a tectonic uplift rate of 0 1 mm yr has been estimated for the last 130 kyr these data are consistent with models of coastal uplifting calculated for the strait of gibraltar

neotectonics and shoreline history of the rock of gibraltar southern iberia abstract several sets of staircased quaternary marine deposits can be observed along the gibraltar coast ranging from 1 to 210 m above the present mean sea level geomorphological mapping establishes from the relationship between shore scree and dune sedimentary formations five main morphotectonic steps on the rock marine terraces between 1 and 25 m 30 60 m 80 130 m 180 210 m and above each terrace level and its slope aeolian linked sediments is backed by a steep relict sea cliff margin so forming a composite cliff the most recent coastal landforms and sediments are associated with the last 250 ka linked to oxygen isotope stages ois 1 3 5 and 7 these landforms determine a morphosedimentary highstand lowstand sequence with several staircased and offlapped episodes comprising a major morphotectonic step a well developed palaeocliff usually separates the highstand marine terraces of ois 9 from those of ois 7 the gibraltar mean tectonic uplift value of 0 05 0 01 mm yr is maintained from 200 ka to the present before this at least to 250 ka the mean uplift rate was higher 0 33 0 05 mm yr possibly compatible with major tectonic events in response to a nnw sse compressive stress field between africa and iberia

hydraulic jumps in sediment driven bottom currents laboratory experiments were conducted to observe the behavior of turbidity currents in the vicinity of a slope transition both sediment laden and saline hydraulic jumps were produced the vertical structure of the currents was found to depend on flow regime the saline and turbid hydraulic jumps showed similar characteristics the amount of water entrained by the flows through a jump was small the change in flow regime caused a marked reduction of the bed shear stress downstream of the jump in nature a turbidity current experiencing a hydraulic jump will drop most of its bedload immediately downstream from the jump while the suspended load will respond more gradually to the change in flow regime and will deposit sediment over a distance far exceeding 1 000 times the jump height

numerical model of turbidity currents with a deforming bottom boundary a numerical model of turbidity currents with a deforming bottom boundary has been developed the model predicts the vertical structure of the flow velocity and concentration as well as change in the bed level due to erosion and deposition of suspended sediment the reynolds averaged navier stokes equations for dilute suspension have been solved using a finite volume method the bottom boundary and the grid system are allowed to adjust in response to sediment deposition and entrainment during the computation the model has been applied to simulate the evolution of a conservative saline density current and turbidity currents along an 11 6 m long flume that includes a slope followed by a horizontal bed the model successfully simulates the evolution of the currents model results have been compared with the experimental data good similarity profiles of velocity and excess density or suspended sediment concen tration are obtained at both the upstream supercritical and the downstream subcritical flow regions a turbulent schmidt number larger than one has been found to be appropriate for providing a good match with the experimental data changes in bed level predicted by the model have also been found to be in agreement with the experiment data

sediment transport part i bed load transport a method is presented which enables the computation of the bed load transport as the product of the saltation height the particle velocity and the bed load concentration the equations of motions for a solitary particle are solved numerically to determine the saltation height and particle velocity experiments with gravel particles transported as bed load are selected to calibrate the mathematical model using the lift coefficient as a free parameter the model is used to compute the saltation heights and lengths for a range of flow conditions the computational results are used to determine simple relationships for the saltation characteristics measured transport rates of the bed load are used to compute the sediment concentration in the bed load layer a simple expression specifying the bed load concentration as a function of the flow and sediment conditions is proposed a verification analysis using about 600 alternative data shows that about 77 of the predicted bed load transport rates are within 0 5 and 2 times the observed values

new age estimates for the palaeolithic assemblages and pleistocene succession of casablanca morocco marine and aeolian quaternary sediments from casablanca morocco were dated using the optically stimulated luminescence osl signal of quartz grains these sediments form part of an extensive succession spanning the pleistocene and contain a rich faunal and archaeological record including an acheulian lithic assemblage from before the brunhes matayama boundary and a homo erectus jaw from younger cave deposits sediment samples from the sites of reddad ben ali oulad j mel sidi abderhamane and thomas quarries have been dated in order to assess the upper limits of osl the revision of previously measured mammalian tooth enamel electron spin resonance esr dates from the grotte des rhinoceros oulad hamida quarry 1 incorporating updated environmental dose rate measurements and attenuation calculations also provide chronological constraint for the archaeological material preserved at thomas quarries several osl age estimates extend back to around 500 000 years with a single sample providing an osl age close to 1 ma in magnetically reversed sediments these luminescence dates are some of the oldest determined and their reliability is assessed using both internal criteria based on stratigraphic consistency and external lithostratigraphic morphostratigraphic and independent chronological constraints for most samples good internal agreement is observed using single aliquot regenerative dose osl measurements while multiple aliquot additive dose measurements generally have poorer resolution and consistency novel slow component and component resolved osl approaches applied to four samples provide significantly enhanced dating precision and an examination of the degree of signal zeroing at deposition a comparison of the osl age estimates with the updated esr dates and one u series date demonstrate that this method has great potential for providing reliable age estimates for sediments of this antiquity we consider the cause of some slight age inversion observed at thomas quarries and provide recommendations for further luminescence dating within this succession

rapid sea level rise and ice sheet response to 8 200 year climate event 1 the largest abrupt climatic reversal of the holocene interglacial the cooling event 8 6 8 2 thousand years ago ka was probably caused by catastrophic release of glacial lake agassiz ojibway which slowed atlantic meridional overturning circulation amoc and cooled global climate geophysical surveys and sediment cores from chesapeake bay reveal the pattern of sea level rise during this event sea level rose 14 m between 9 5 to 7 5 ka a pattern consistent with coral records and the ice 5g glacio isostatic adjustment model there were two distinct periods at 8 9 8 8 and 8 2 7 6 ka when chesapeake marshes were drown as sea level rose rapidly at least 12 mm yr 1 the latter event occurred after the 8 6 8 2 ka cooling event coincided with extreme warming and vigorous amoc centered on 7 9 ka and may have been due to antarctic ice sheet decay

coastal uplift in continental collision plate boundaries data from the last interglacial marine terraces of the gibraltar strait area south spain abstract the spatial height analyses of deposits belonging to isotopic substages 5e and 5c indicate the occurrence of differential uplift in the gibraltar strait area maximum mean uplift rates do not reach values of 0 2 mm year displaying a gentle deceleration from 0 15 to 0 10 mm year for the last 128 ka maximum estimated rates are recorded in the central sector of the gibraltar strait the combined analysis of the accumulated vertical movements before and after iss 5c indicates that differential uplift is accommodated along ne sw sinistral and nw se dextral mostly inherited strike slip fault systems separating coastal segments of contrasting uplifting subsiding behaviour the occurrence of inversions in the relative vertical offsets along some of these faults arises when this combined analysis is performed a model of asymmetric pure shear defined by these two fault systems generated in response to the roughly n s convergence between the african and eurasian plates can explain the recorded uplift patterns in this transpressive setting generated by the africa eurasia continental collision the recent convergence 4 mm year is mostly released by shear processes and subsidiary e w horizontal extension whilst the recorded coastal uplift only represents a low percentage of the recent convergence rates

the importance of sea level and climate change including changing wind energy on the evolution of a coastal estuary copano bay texas abstract 123 km of high resolution 2 d seismic lines and 6 sediment cores up to 16 m in length were collected from copano bay texas these data were used to examine the role of climate and sea level changes in the evolution of the bay paleogeographic maps of the bay were constructed to show how the bay evolved through time the overall transgression was punctuated by five environmental changes within copano bay over the past 9 6 ky the largest environmental change occurred at 8 2 ka when the bay head delta back stepped approximately 7 5 km as a result of a 0 4 1 2 m rapid rise in sea level with a well constrained model of how the bay changed through time textural data from the most continuous record of middle bay deposits was used to produce a proxy for wind strength over the last 8 2 ky our wind strength proxy reveals that copano bay experienced relatively tranquil winds during the early holocene followed by its windiest conditions from 5 2 to 4 1 ka and a return to more tranquil winds during the late holocene the wind strength proxy was compared with other published paleo climatic records for the region and a reasonable correlation was found between periods of higher wind energy and drier climate this study illustrates that despite their complex depositional systems and many sediment and water sources a system wide approach to studying an estuary can still be used to extract paleoclimate archives from estuarine deposits

on the links between a river s hyperpycnal plume and marine benthic nepheloid layer in the wake of a typhoon abstract in 2010 two moorings each configured with a ctd and an adcp one with an additional non sequential sediment trap nsst were deployed in the head region of the gaoping submarine canyon 3 days after the typhoon induced peaks of the runoff and suspended sediment concentration ssc of the gaoping river in southern taiwan our data show a demarcation between tidal and hyperpycnal regimes in the temperature salinity and flow fields the latter existed in the first 5 days out of the 18 day deployment as defined by higher water density due to high ssc several lines of evidence indicate the presence of the tail end of a hyperpycnal turbidity current htc including the retention of warm water near the canyon floor high ssc down canyon directed residual flow and its vertical structure and high terrestrial fraction larger than 70 of the organic particles carried by the flow the decreasing mass flux during the deployment is also an indication of a waning htc our findings also show that the vertical flow structure and the direction of the gravity driven down canyon htc were retarded by the instantaneous up canyon directed tidal oscillations in the submarine canyon

early use of marine resources by middle upper pleistocene human societies the case of benzu rockshelter northern africa abstract this article examines the role played by marine resources for hunter gatherer groups of the middle upper pleistocene in the geohistorical region around the straits of gibraltar on the basis of new evidence collected at the rock shelter of benzu north africa the stratigraphic sequence at benzu has been dated to between 254 and 70 ka the excavations have revealed the exploitation of marine gastropods and bivalves alongside fish the most common taxon in the sequence is the genus patella the analysis of the molluscs and their spatial distribution shows that these animals were purposely collected by humans probably as a food source in order to contribute to the debate about the origins and scale of the exploitation of marine resources during the middle and upper pleistocene the evidence collected at benzu is interpreted within the broader context of north africa and southern europe the similarity of groups of homo sapiens sapiens in north africa and homo sapiens neanderthalensis in southern europe in terms of lifestyle and subsistence strategies is interpreted as reflecting equally similar social and economic practices in spite of the diversity of anthropological perspectives on the relationship between humans and the environment currently in vogue

modeling turbidity currents with nonuniform sediment and reverse buoyancy 1 this study focuses on a numerical model of turbidity currents with reversing buoyancy i e flows that are rendered heavier than the ambient water due to the presence of suspended sediment but that as sedimentation progresses become lighter than the ambient water due to a difference in temperature or salinity the flows considered here may be either pulsed events or continuous flows it is well known that these flows are subject to a buoyancy reversal flows issuing upstream with a sufficient load of suspended sediment are heavier than the ambient water and thus form a bottom underflow as sediment deposits in the downstream direction however the flow gradually loses its density excess and eventually reverses its buoyancy detaching upward from the bed the nature of the sediment deposit emplaced near and downstream of the point of lofting can thus differ significantly from that emplaced upstream a novel aspect of the work reported here is a mechanistic description of the tendency for the current to sort in the downstream direction a sediment mixture containing a wide range of grain sizes the numerical model which is based in the closure for turbulence is verified with a unique set of experimental data intended to model sediment sorting associated with turbidity currents created by explosive undersea eruptions both cases with nonreversing buoyancy and reversing buoyancy are considered as such the model not only provides a detailed description of flows with reversing buoyancy but also provides a tool to aid sedimentologists in back calculating the flow emplaced by turbidity currents from the downstream variation in the grain size distribution of the bed deposit

the manciano sandstone a shoreface deposit of miocene basins of the northern apennines italy abstract well exposed diamond line cut quarry exposures of the manciano sandstone allow a detailed analysis of sandy fossiliferous nearshore deposits of the shelf of the northern apennines the manciano sandstone is characterized by medium to very coarse washed fairly well sorted lithic sandstone with thin interlayers of sandy conglomerates it displays two principal rhythmically alternating sandy facies a slightly burrowed mostly macaronichnus ophiomorpha skolithos units trough cross bedded locally showing possible tidal bundles with few whole scutella echinoid shells reworked on foresets or occasional large scale approximately 2 m planar cross bedded bar accretion units and b slightly finer darker coloured reddish brown sandstone units heavily bioturbated cruziana skolithos ichnofauna representing slightly more sheltered settings large oysters are present in near living position in a few thin layers and more commonly as reworked comminuted fragments in sandy layers many calcareous pebbles and oyster fragments are bored other fossils consist of echinoids scutella some balanids and reworked foraminifera and bryozoa the manciano sands were deposited primarily in a wave dominated shoreface containing migrating bars ridges and affected by wave induced possibly tidal enhanced currents this tidal influence confirms the opening of the miocene apenninic sea to oceans both the developing atlantic ocean to the west and through a long narrow seaway the asian portion of the tethys sea to the east

a 190 ky record of lithogenic grain size on the namibian slope forging a tight link between past wind strength and coastal upwelling dynamics abstract we inferred wind strength variations at the namibian coast and its effect on upwelling intensity over the last 190 ky by comparing grain size data and alkenone based sea surface temperatures ssts from one sediment core located on the upper slope off luderitz 25 6 s 13 38 e the wind strength proxy was defined by partitioning terrigenous grain size distributions gsds into two sub populations owing to a simple statistical model the fine poorly sorted component is assumed to include both fine aeolian dust and hemipelagic mud carried by rivers or winnowed from the shelf those two fractions are assumed to have been identically sorted during settling in the water column and are not distinguished by our approach the mode of the coarse well sorted sub population displays rapid high amplitude variations through time we ascribe a strictly aeolian origin to this component and consider that low altitude winds are able to carry coarse grained particles to the ocean as shown by grain size measurements of present dust material from the adjacent continent stuut j b w prins m a schneider r r weltje g j jansen j h f postma g 2002 a 300 kyr record of aridity and wind strength in southwestern africa inferences from grain size distributions of sediments on walvis ridge se atlantic mar geol 180 221 233 variations in the coarse grained dust diameter are closely correlated with sst changes past ssts records from the namibian upper slope have been previously hypothesized as reflecting upwelling intensity combined with occasional injection of warm water from the angola dome we challenge this view in considering that past long term ssts variations are primarily induced by the wind strength and witness coastal upwelling intensity early mis 6 is the only period with evidences of warm poleward water intrusion at the core site the windiest conditions occurred during isotopic stages 3 and 4 the wind strength proxy defined in this study can be used confidently as an independent proxy for past upwelling intensity over the last two climatic cycles

the critical densimetric froude number of subaqueous gravity currents can be non unity or non existent abstract for decades the critical densimetric froude number of subaqueous gravity flows has been regarded to be unity or close to unity the same as the critical froude number for open channel flows based on the analysis of specific energy a concept borrowed from hydraulic engineering it is shown that two correction terms the discharge correction and the concentration correction appear in the formulation of the critical densimetric froude number for subaqueous gravity flows in a channel as a result the critical densimetric froude number of a subaqueous gravity flow in a channel can be non unity or non existent depending on the degree of entrainment of ambient fluid and the density variation in the currents furthermore it is shown that the lower the critical densimetric froude number is in a supercritical subaqueous gravity flow the bigger the internal jump is if the flow experiences a change in flow regime

three dimensional numerical simulation of turbidity currents in a submarine channel on the seafloor of the niger delta slope 1 in the present work we use a three dimensional numerical model to simulate turbidity currents in a large scale submarine environment the model solves the reynolds averaged navier stokes equations along with a two equation turbulence closure model the sediment conservation equations for multiple grain size classes and the exner equation of bed sediment conservation four different grain size classes 30 64 125 and 250 m are considered the model is applied to a modern seafloor environment in the continental slope of the niger delta where bathymetric data and seven piston cores were collected in and around a sinuous channel detailed analyses show the grain size distribution for different beds within each core since the flow events responsible for the formation of this modern depository are unknown we perform simulations with different inflow conditions in order to match the grain size data the model realistically predicts the flow field and its evolution over the complex topography and shows the spatial distribution of different grain size classes a strong lateral flow from the inner to the outer bank is observed at the bends of the low relief channel from the computed deposition rate we obtain the fraction of each grain size class at the core locations and compared50 and d90 predicted from the model with the core data the discrete values predicted from the model fall within the range of d50 and d90observed in different beds in the cores the results demonstrates that a 3 d numerical model can be a useful tool for understanding the distribution pattern thickness and grain size of the turbidity currents and their deposits at the field scale and can help constrain the variabilities of reservoir architecture

global sea level fluctuations during the last interglaciation mis 5e the geomorphology and morphostratigraphy of numerous worldwide sites reveal the relative movements of sea level during the peak of the last interglaciation marine isotope stage mis 5e assumed average duration between 13072 and 11972 ka because sea level was higher than present deposits are emergent exposed and widespread on many stable coastlines correlation with mis 5e is facilitated by similar morphostratigraphic relationships a low degree of diagenesis uranium thorium u th ages and a global set of amino acid racemization aar data this study integrates information from a large number of sites from tectonically stable areas including bermuda bahamas and western australia and some that have experienced minor uplift 2 5 m 100 ka including selected sites from the mediterranean and hawaii significant fluctuations during the highstand are evident at many mis 5e sites revealed from morphological stratigraphic and sedimentological evidence rounded and flat topped curves derived only from reef tracts are incomplete and not representative of the entire interglacial story despite predictions of much different sea level histories in bermuda the bahamas and western australia due to glacio and hydro isostatic effects the rocks from these sites reveal a nearly identical record during the last interglaciation the last interglacial highstand is characterized by several defined sea level intervals slis that include sli 1 post glacial mis 6 5e termination ii rise to above present before 130 ka sli 2 stability at 2 to 3 m for the initial several thousand years 130 to 125 ka during which fringing reefs were established and terrace morphology was imprinted along the coastlines sli 3 a brief fall to near or below present around 125 ka sli 4 a secondary rise to and through 3 4 m 124 to 122 ka followed by sli 5 a brief period of instability 120 ka characterized by a rapid rise to between 6 to 9 m during which multiple notches and benches were developed and sli 6 an apparently rapid descent of sea level into mis 5d after 119 ka u th ages are used to confirm the last interglacial age of the deposits but unfortunately in only two cases was it possible to corroborate the highstand subdivisions using radiometric ages sea levels above or at present were relatively stable during much of early mis 5e and the last 6 7 ka of mis 1 encouraging a comparison between them the geological evidence suggests that significant oceanographic and climatic changes occurred thereafter midway through and continuing through the end of mis 5e fluctuating sea levels and a catastrophic termination of mis 5e are linked to the instability of grounded and marine based ice sheets with the greenland gis and west antarctic wais ice sheets being the most likely contributors late mis 5e ice volume changes were accompanied by oceanographic reorganization and global ecological shifts and provide one ominous scenario for a greenhouse world r 2007 elsevier ltd all rights reserved

freshwater forcing of abrupt climate change during the last glaciation large millennial scale fluctuations of the southern margin of the north american laurentide ice sheet occurred during the last deglaciation when the margin was located between about 43 and 49 n fluctuations of the ice margin triggered episodic increases in the flux of freshwater to the north atlantic by rerouting continental runoff from the mississippi river drainage to the hudson or st lawrence rivers we found that periods of increased freshwater flow to the north atlantic occurred at the same time as reductions in the formation of north atlantic deep water thus providing a mechanism for observed climate variability that may be generally characteristic of times of intermediate global ice volume