closure of a seaway stratigraphic record and facies guadix basin southern spain during the late tortonian upper miocene the guadix basin in s spain formed one of the betic corridors that connected the mediterranean sea with the atlantic ocean the closure of this connection occurred in a series of steps documented by three sedimentary units a lower unit consisting of basinal marls shallow water calcarenites and sands records the formation of a wide seaway during deposition of the following unit this narrowed to a strait no more than 2 km in wide triggering an intensification of currents that caused migration of submarine dunes preserved as giant cross beds in bioclastic sands and conglomerates current flowed from the mediterranean to the atlantic the third unit constitutes the youngest marine episode of the filling of the guadix basin at this stage the connection between the mediterranean sea and the atlantic ocean was broken and a system of coastal coral reefs was established in the northern part of the basin

three dimensional quantitative modeling of clinoform development abstract clinoform geometry pervades stratigraphic sequences across a variety of scales it is a composite surface which records the complex interplay between accommodation sediment supply physiography and hydrodynamics much of the sequence stratigraphic technique employs clinoform geometry to discriminate between the various systems tracts that constitute depositional sequences however many sequence stratigraphic models treat the generation of accommodation and the input of sediment supply as a two dimensional problem by assuming a line source of sediment entering a system impacted by relative sea level fluctuations one common attribute of clinoforms regardless of size and or shape is that their formation is inherently three dimensional therefore the clinoform geometry varies spatially and temporally throughout a region depending on the proximity to the sediment source and the character of the hydrodynamic regime we present a three dimensional stratigraphic model that combines both diffusion and advection to simulate across and along margin sediment transport and deposition this model allows us to examine how the morphology and internal clinoform geometry of deltas vary away from the sediment source in this application we simulate the development of a delta in a low energy environment to understand the importance of along shelf diffusion on clinoform geometry and the morphology of the delta we predict the three dimensional geometry and how it varies throughout a relative sea level cycle our model indicates that when the clinoform rollover is spatially coincident with the shoreline position the clinoform geometry changes dramatically along strike away from the sediment source region throughout a relative sea level cycle for example oblique clinoforms develop near the source region and evolve into an onlapping sequence along strike on the basis of stratal geometry and the technique of sequence stratigraphy this deposit would be interpreted as two different sequences with very different connotations for their formation we surmise that when the clinoform rollover and the shoreline position are separated e g a subaqueous delta the along strike variability of the clinoform geometry diminishes because of the hydrodynamic forces operative across the shelf consequently it is important to determine how clinoforms develop in three dimensions and to ensure that our window of observation is sufficient to discern between local and regional variability

holocene carbonate sedimentation on the west eucla shelf great australian bight a shaved shelf the southern continental margin of australia is a cool water carbonate sedimentary province located in a high energy swell dominated oceanographic setting a vibrocore transect of 14c dated sediments across the centre of the eucla shelf is the first record of holocene shelf deposition in the great australian bight much of the seafloor shallower than 70 m water depth the base of wave abrasion is bare cenozoic limestone in some places encrusted by late pleistocene coral rich limestone that is cemented by high magnesium calcite 12 mole mgco3 the areally extensive 100 km wide hard bored substrate supports an epibiota of coralline algae minor bryozoans and soft algae or is covered by patches of holocene sediment up to 1 5 m thick generally a basal bivalve lag 3 ka overlain by quartzose bioclastic palimpsest sand this pattern of active carbonate production but little accretion on the wave swept mid to inner shelf is similar to that on other parts of the southern australian continental margin the term shaved shelf is proposed for this style of carbonate platform formed by alternating periods of sediment accretion cementation and erosion the palimpsest sand is typically rich in bivalves coralline algae and locally detrital dolomite outer shelf holocene sediment below the base of wave abrasion but inboard of the shelf edge is a metre thick unit of fine microbioclastic muddy sand with minor delicate bryozoans overlying a 9 13 ka rhodolith gravel some of this outer shelf sediment appears to have been resedimented the shelf edge is a sandy and rocky seafloor with active bryozoan growth and sediment production the holocene sediments are enriched in coralline algal particles and conspicuous large foraminifers cf marginopora and depleted in bryozoans as compared to coeval deposits on the lacepede and otway shelves off southeastern australia these differences are interpreted to reflect warmer waters of the leeuwin current and prevalent downwelling in this area as opposed to the general upwelling and colder waters in the east

sedimentary evolution of the holocene subaqueous clinoform off the shandong peninsula in the yellow sea abstract a subaqueous clinoform wraps around the end of the shandong peninsula in the yellow sea the clinoform previously called the shandong mud wedge is up to 40 m thick nearshore and thins seaward its origin has been controversial since it was first noted in the 1980s for our recent investigation offshore of the northeastern shandong peninsula high resolution shallow seismic profiles covering about 1700 km were obtained and two drilling cores penetrating the clinoform were recovered we described the lithofacies characteristics identified benthic foraminifera and ostracoda measured grain size analyzed the mineral components of the cores and obtained ams 14 c dates on 28 samples to decipher the sedimentary evolution of the clinoform in response to postglacial sea level changes the shallow seismic profiles show that the clinoform comprises three units a lowermost seismic unit su 3 less than 2 3 m thick showing a retrogradational aggradational stacking pattern with subhorizontal internal reflectors a middle seismic unit su 2 up to 35 m thick showing a prograding reflection pattern with mostly seaward stepping reflectors separated by several erosive surfaces and an uppermost seismic unit su 1 maximum thickness 18 m exhibiting an aggradational reflection pattern with subparallel reflectors the three seismic units are bounded on the bottom by distinct erosion surfaces analyses of the two cores indicate that the clinoform comprises three depositional units du 1 du 2 and du 3 in descending order corresponding respectively to su 1 su 2 and su 3 the depositional units are distinguished by lithofacies characteristics and the downcore distributions of benthic foraminiferal and ostracod assemblages mineral components of the cores suggest that the clinoform s provenance is predominantly yellow river derived sediments ams 14 c dates suggest that du 3 was formed from about 11 6 to 9 6 cal kyr bp du 2 from 9 6 to 6 5 cal kyr bp and du 1 after ca 6 5 cal kyr bp some major meltwater pulse mwp events during the deglacial transgression were registered in the clinoform stratigraphy with the basal surfaces sediments of du 3 and du 2 corresponding respectively to mwp 1b ca 11 6 11 3 cal kyr bp and mwp 1c ca 9 6 9 2 cal kyr bp events and with du 2 being largely formed after the 8 4 8 2 cal kyr meltwater event rapid centennial to multidecadal scale flooding events were presumably responsible for the erosive surfaces separating the downlapping internal reflectors in su 2 the change of depositional pattern from progradational in su 2 to aggradational in su 1 is attributed to a change from strong dominantly to and fro tidal currents to the modern circulation in the bohai sea as well as to the weakening of the tidal current field during the highstand after about 6500 cal yr bp as a product of complex interactions among sediment supply sea level changes and hydrodynamic regimes the clinoform can be regarded as the distal part of the tidal depositional system in the eastern bohai sea which was largely derived from the yellow river

seasonal variability of water transport through the straits of gibraltar sicily and corsica derived from a high resolution model of the mediterranean circulation abstract the variability of the water transport through three major straits of the mediterranean sea gibraltar sicily and corsica was investigated using a high resolution model this model of the mediterranean circulation was developed in the context of the mercator project the region of interest is the western mediterranean between the strait of gibraltar and the strait of sicily the major water masses and the winter convection in the gulf of lions were simulated the model reproduced the meso scale and large scale patterns of the circulation in very good agreement with recent observations the western and the eastern gyres of the alboran sea were observed but high interannual variability was noticed the algerian current splits into several branches at the longitude of the strait of sicily level forming the tyrrhenian branch and the atlantic ionian stream and the atlantic tunisian current in the eastern mediterranean the north current retroflexed north of the balearic islands and a dome structure was observed in the gulf of lions the cyclonic barotropic algerian gyre which was recently observed during the mater and elisa experiment was evidenced in the simulation from time series of 10 day mean transport the three straits presented a high variability at short time scales the transport was generally maximum in april for the strait of gibraltar in november for the strait of sicily and in january for the strait of corsica the amplitudes of the transport through the straits of gibraltar 0 11 sv and sicily 0 30 sv presented a weaker seasonal variability than that of the strait of corsica 0 70 sv the study of the relation between transport and wind forcing showed that the transport through the strait of gibraltar is dependent on local zonal wind over short time scales 70 which was not the case for the other straits less than 30 the maximum minimum of the transport occurred for an eastward westward wind stress in the strait an interannual event was noticed in november december 2001 which corresponded to a very low transport 0 3 sv which was characterised by a cyclonic circulation in the western alboran sea that circulation was also reproduced by the model for other periods than winter during the interannual simulation the transport through the strait of sicily is not influenced by local wind the wind stress curl of the northwestern mediterranean influenced the transport through the strait of corsica

tectonic significance of the present relief of the betic cordillera abstract tortonian calcarenites of the betic cordillera were deposited in coastal or very shallow marine environments and represent an ideal marker for estimating vertical movements from the late miocene to the present a map showing the heights at which these tortonian marine rocks are situated has a clear correlation with the present relief indicating that today s relief has been formed since the tortonian there is also a good correlation between present relief and the bouguer anomaly distribution in the betic cordillera as well as with crustal thickness likewise the present relief is directly related to the geodynamic setting of a horizontal n s to nnw sse compression and an almost perpendicular extension along with isostatic readjustment existing in the betic cordillera from the tortonian as a result of these regional stresses faults and folds have produced notable vertical movements the highest rates of uplift of the betic cordillera coincide with large antiforms in particular those of the sierra nevada and the sierra filabres several subsiding sectors also exist for example the granada basin or the guadalquivir basin the foreland guadalquivir basin has a complex history because the uplift in its eastern sector and subsidence in the western sector coexisted during the late tortonian today the whole betic cordillera is characterized by differential regional uplift even in the aforementioned subsiding sectors

migration and sedimentology of longshore sandwaves long point lake erie canada this paper describes the formation migration and sedimentology of sandwaves along the distal end of long point a 40 km long spit in lake erie some seven to nine sandwaves occur in a zone over the last 14 km of the spit they are characteristically 50 100 m wide at the downdrift end range in length from 350 m to 1500 m and migrate alongshore at rates that are typically 100 300 m year 1 measurements over a 7 year period show two forms of alongshore sandwave migration 1 a migratory jump and 2 downdrift accretion the migratory jump is commonly 200 500 m year 1 and results from the onshore migration and welding of an inner nearshore bar to the downdrift end of the sandwave this in turn leads to emergence of the bar over a distance of several hundred metres downdrift of the sandwave and isolation of the trough landward of the bar infilling of the trough abstracts large volumes of sediment from the local sediment transport system and may affect movement of the sandwave in the following year or movement of the next sandwave downdrift downdrift accretion commonly results in migration of 50 150 m year 1 and results from the refraction of waves around the distal end of the sandwave and episodic accretion of small swash bars this mechanism occurs less frequently and appears to reflect a local condition of lower sediment abundance often triggered by a large migratory jump in the previous year the process of bar emergence and infilling produces a distinct suite of sedimentary structures associated with the infilling of the landward trough and building of the sandwave berm the initial shoreline perturbation that generates the sandwave results from onshore migration and welding of inner nearshore bars and the development and growth of the sandwaves is promoted by refraction of highly oblique waves

neogene coralline algal growth forms and their palaeoenvironments in the almanzora river valley almeria s e spain abstract the almanzora river valley is an elongate e w depression containing mainly neogene sediments during the late tortonian several horizons of crustose coralline algae developed in three distinct sedimentary contexts a on coastal platforms and talus slopes b on fan deltas and c associated with corals in patch reefs growing at the furthermost extremes of coastal fan deltas in the former two cases the predominant growths are as rhodoliths associated with mobile substrates in the coastal systems an increase in depth results in a change in both the morphology and the composition of the rhodoliths with depth there is a significant increase in the diversity of algal species and a concomitant increase in the size of the algal covering compared to the nucleus and thus the morphology of the rhodolith depends less and less on the shape of the nucleus itself the massive crusts and columns which mark the limit of development of the shallow water rhodoliths in the deeper examples are covered by branching and thin leafy laminar growths in the fan deltas the development of the rhodoliths is similar to that of the deeper coastal zones in the patch reefs the specific composition of the algal associations changes somewhat and the growths developed on a stable substrate under low energy conditions are mainly vertical branches arising from thin crusts

holocene development of the yellow river s subaqueous delta north yellow sea high resolution seismic profiles from the north yellow sea reveal a 20 40 m thick subaqueous clinoform delta that wraps around the eastern end of the shandong peninsula extending into the south yellow sea this complex sigmoidal oblique clinoform containing an estimated 400 km 3 of sediment overlies prominent relict transgressive surfaces the nearshore topset of the clinoform 50 m contain less than 1 m of holocene sediment with low sedimentation rates 1 mm year in contrast to other clinoforms the shandong clinoform appears to be a compound subaqueous deltaic system with what we interpret to be proximal and distal phases of clinoform development the underlying proximal sequence formed proximally between f11 and 9 2 ka in response to a temporary pause in the rapid postglacial sea level rise after the meltwater pulse 1b mwp 1b and increased discharge from the yellow river to the north yellow sea due to intensification of the summer monsoon a flooding surface appears to separate the proximal and distal phases corresponding to the next rapid sea level rise 9 5 9 2 ka bp mwp 1c since 9 2 ka bp an overlying distal sedimentary sequence has accumulated reflecting the backstepping and shifting river mouth westward to the gulf of bohai some inputs from coastal erosion and nearby small streams may be locally important along shore transport cross shelf advection and upwelling in the north yellow sea have reworked post lgm sediment and have helped maintain the morphology of the clinoform in the shandong mud wedge d 2004 elsevier b v all rights reserved

eocene clinoform growth in front of a storm wave dominated shelf central basin spitsbergen no significant sand delivery to deepwater areas abstract eocene shelf slope clinoforms on spitsbergen reflect asymmetric basin infill across the coastal plain shelf slope and deepwater segments of a foreland basin although four main types of clinoforms are recognized in the basin this study focuses on clinoforms generated by a storm wave regime on the shelf margin the key aspect of this type of clinoform type 3 is that only modest volumes of sand were delivered across the shelf edge onto the slope and little or no sand onto the basin floor despite the sand prone nature of the sediment delivery system right to the shelf edge the sedimentology and geometry of a series of such clinoforms are documented along a continuously exposed outcrop transect some 800 m high and 4 km long sandstone units of individual clinoforms are 2 12 m thick and are separated by thicker shale clinothems have subhorizontal topset and bottomset segments and steeper mid portions and are up to 150 m high nearly an order of magnitude higher than the deltas and shorefaces that constructed them this clinoformal configuration is thus interpreted to reflect shelf shelf edge slope and base of slope depositional environments and water depths at least as great as the decompacted clinoform amplitudes exposed shelf segments dip up to 0 4 degrees whereas slope segments some 2150 m wide dip up to 4 degrees the shelf and upper slope reaches of clinothems consist of hummocky and swaly cross stratified sandstone units without any significant interbedded shale on the middle slope and below these sandstone units become finer grained are ripple and plane parallel laminated and separated with interbedded shale individual topsets of clinothems are interpreted to have formed by strandplain or wave dominated delta progradation across the morphological shelf platform during short periods of sea level stillstand or slight fall the shale units immediately above sandy clinothems developed during longer intervals of relative sea level rise when the wave dominated shoreline retreated back across the shelf platform the long term trajectory of shelf margin growth shows a significant aggradational component during overall progradation compared to other clinoforms in this same basin where the sediment delivery system was fluvially driven and brought great volumes of sand onto the basin floor and slope respectively storm wave generated clinoforms brought only limited sand to the upper slope and little or no sand to the basin floor

a new hypothesis about the surface circulation in the eastern basin of the mediterranean sea abstract in time the circulation of the atlantic water aw in the eastern basin of the mediterranean sea has been described differently according to two major representations the historical one which began with the scheme from nielsen in 1912 and has been refined up to the 1980s favours a counterclockwise circulation in the whole basin with aw flowing in its southern part as a broad flow off libya and egypt from the ionian to the levantine subbasins then continuing along middle east and turkey before flowing back westwards the more recent one issued in the 1990s favours a clockwise circulation in the northern part of the ionian continuing offshore across the basin from the cretan to the central part of the levantine as the so called mid mediterranean jet this jet is depicted then as splitting both clockwise in the southeastern part of the basin and counterclockwise off turkey where this representation agrees with the former because the recent representation cannot be considered as a refinement of the historical ones we have been interested in understanding why a given data set available to everybody is interpreted in such different ways in the algerian subbasin the combined use of satellite infrared images and a significant amount of in situ data sets hydrology and both eulerian and lagrangian current measurements allowed us to solve a similar controversy therefore we examined the circulation features in the eastern basin undertaking the detailed analysis of 1000 daily and weekly composite images spanning the period 1996 2000 and of monthly composite images available since 1985 whenever in situ observations were available we have confronted them with the satellite thermal signatures and have shown that both are consistent this paper focuses on the overall basin scale results while the detailed ones are published in an other paper the new scheme we propose is basically a refined version of the historical ones the circulation of aw is counterclockwise in the whole eastern basin but it is more constrained alongslope than previously thought and the broadening historically schematised appears to be due to intense mesoscale eddies mainly generated by the instability of this circulation

cyclicity in pleistocene upper slope cool water carbonates unravelling sedimentary dynamics in deep water sediments great australian bight odp leg 182 site 1131a abstract ocean drilling program site 1131 located in the central great australian bight recovered an expanded series of pleistocene cool water carbonates three distinct facies are arranged in repeating sedimentary cycles omission intervals form the base of the cycles and are overlain by laminated deposits the upper part of the cycles consists of bioturbated sediments facies cyclicity parallels glacial interglacial sea level changes firmground hardground surfaces formed during latest stages of sea level falls laminated sediments were deposited during later sea level fall and or early phases of the sea level lowstand and the bioturbated intervals are related to interglacial sea level highstands bottom current activity is interpreted to play an important control on facies and cycle development during the late stages of sea level fall upwelling currents winnowed the slope sediments leading to hardground formation during latest sea level falls and early sea level lowstands a relative increase in the ramp sediment supply to the slope leading to the formation of the laminated facies was also a response to the continued action of the near bottom upwelling currents that reworked previously deposited sediments along the slope during the early sea level rises laminated upwelling influenced facies were progressively covered by the bioturbated facies the adopted approach to decipher sedimentary cyclicity involving the integrated use of wireline logs geochemical data fms images and sedimentological analysis of the lithofacies has allowed to recognise subtle facies changes in upper slope settings of a distally steepened carbonate ramp and their relationship with the sea level as well as to unravel the importance of the oceanic current regime in the deposition style on the ramp that otherwise would remain unsolved this integrated method could be applied to study more precisely apparently homogeneous fine grained calcareous sediment successions of distal ramp outcrops

non tropical carbonates related to rocky submarine cliffs miocene almeria southern spain abstract upper miocene deposits in the cabo de gata region se spain provide a unique opportunity to study cliff related temperate carbonates a poorly known type of fossil non tropical carbonates the studied submarine cliffs lie on the western flank of the monte ricardillo volcanic dome two main biocenoses colonised the cliff walls vertical and subvertical walls were either overgrown by vermetid gastropods forming a vermetid framestone or colonised by robust branching bryozoans which were reworked post mortem and accumulated as aprons at the foot of the submarine cliffs coralline algae in the vermetid build up indicate palaeodepths below 15 20 m depressions in front of the cliffs were occupied by nodular bryozoans and bivalves within these depressions barnacles settled on secondary hard substrates with progressive flooding of the depositional area substrate relief was filled in and a carbonate ramp with facies belts following the palaeobathymetric gradient evolved a delicate branching bryozoan facies occurs in the proximal part of the ramp and a nodular bryozoan bivalve facies in its middle part distally these deposits give way to a coralline algal facies these results provide a first insight into temperate water carbonates related to rocky submarine cliffs this work also reveals a major control of substrate relief on temperate carbonate facies and biofacies

anatomy of shelf deltas at the edge of a prograding eocene shelf margin spitsbergen although shelf edge deltas are well imaged seismic features of holocene and pleistocene shelf margins documented outcrop analogues of these important sand prone reservoirs are rare the facies and stratigraphic architecture of an outcropping shelf edge delta system in the eocene battfjellet formation spitsbergen is presented here as well as the implications of this delta system for the generation of sand prone shelf margin clinoforms the shelf edge deltas of the battfjellet formation on litledalsfjellet and hogsnyta produced a 3 5 15 km shelf edge attached slope apron 70 m of sandstones proximally tapering to zero on the lower slope the slope apron consists of distributary channel and mouth bar deposits in its shelf edge reaches passing downslope to slope channels chutes that fed turbiditic lobes and spillover sheets in the transgressive phase of the slope apron estuaries developed at the shelf edge and these also produced minor lobes on the slope the short headed mountainous rivers that drained the adjacent orogenic belt and fed the narrow shelf and the shelf edge position of the discharging deltas made an appropriate setting for the generation of hyperpycnal turbidity currents on the slope of the shelf margin the abundance of organic matter and of coal fragments in the slope turbidites is consistent with this notion evidence that many of the slope turbidites were generated by sustained turbidity currents that waxed then waned includes the presence of scour surfaces and thick intervals of plane parallel laminae within turbidite beds in the slope channels and thick spillover lobes with repetitive alternations of massive and flatlaminated intervals the examined shelf edge to slope system now preserved mainly below the shelf break and dominated by sediment gravity flow deposits has a threefold stratigraphic architecture a lower progradational part in which the clinoforms have a slight downward directed trajectory a thin aggradational zone and an upper part in which clinoforms backstep up onto the shelf edge a greatly increased density of erosional channels and chutes marks the regressive to transgressive turnaround within the slope apron and this zone becomes an angular unconformity up near the shelf edge this unconformity with both subaerial and subaqueous components is interpreted as a sequence boundary and developed by vigorous sand delivery and bypass across the shelf edge during the time interval of falling relative sea level the studied shelf margin clinoforms accreted mostly during falling stage sea level below the shelf edge but the outer shelf later became estuarine as sea level became re established above the shelf edge

modern shoreface and inner shelf storm deposits off the east texas coast gulf of mexico abstract the modern shoreface and inner shelf sediments off the east texas coast on the gulf of mexico were examined using sediment cores and high resolution seismic data low sediment input and low effective accommodation space resulted in the overall thinness of the modern marine sediment cover in the region erosion on the inner shelf during historic 100 yr times produced patches of sand in a predominantly mud dominated environment storm beds are scarce on the inner shelf the shoreface succession off galveston island is characterized by offshore directed crosscutting storm channels of varying sizes the existence of these channels and the relatively high frequency of storms and hurricanes that have affected the region during historical imes are inconsistent with the paucity of storm deposits on the inner shelf the offshore directed channelized flows may have been prevented from going beyond the shoreface by strong along shelf storm currents that impinged on the shoreface in contrast to the storm record on the east texas shelf the central texas shelf shows a greater frequency of and more laterally persistent storm sand beds due to greater effective accommodation space and higher sediment supply there

late miocene stratigraphy and palaeogeographic evolution of the intramontane guadix basin central betic cordillera spain implications for an atlantic mediterranean connection abstract the guadix basin is an intramontane basin located in the central sector of the betic cordillera its late miocene stratigraphic record is divided into three depositional sequences limited by unconformities representing tectonic and or eustatic events depositional sequence i late tortonian is composed by two systems tracts the lower marks the beginning of marine sedimentation in the basin and comprises three retrograding lithological complexes or depositional systems coastal shallow platform and pelagic basin and is interpreted as a transgressive systems tract the upper systems tract consists of a shallow shelf prograding into a pelagic basin this systems tract exhibits a typically regressive pattern and was deposited during high sea level and is therefore interpreted as a highstand systems tract depositional sequence ii late tortonian is composed of both continental alluvial cones and shallow marine gilbert type delta shallow shelf and reef depositional systems the deposits of this sequence record a significant fall in sea level and are interpreted as a lowstand systems tract depositional sequence iii late turolian ventian or late tortonian messinian was formed of solely retrograding continental depositional systems alluvial fan lacustrine fan delta mud flat and lacustrine with this sequence begins the continental sedimentation in guadix basin in an endorheic context the palaeogeographic evolution of the guadix basin during the late miocene can thus be divided into three stages the first corresponds to depositional sequence i and is characterised by the development of shallow marine environments on the basin margins and deep water deposits in its centre during this stage the basin was connected to the west with the atlantic ocean via the granada and guadalquivir basins and toward the east with the mediterranean sea through the almanzora and campo coy basins in the second stage represented by depositional sequence ii most of the basin was occupied by shallow marine environments during this stage the connection with the atlantic and mediterranean was only open through the guadalquivir and campo coy basins respectively finally the third and last stage corresponding to depositional sequence iii is characterised by the development of continental environments throughout the basin this stage records the definitive closing of the connections with the atlantic ocean and the mediterranean sea

patterns and average rates of late neogene recent uplift of the betic cordillera se spain abstract the facies distribution in the sedimentary units infilling a series of neogene basins has been used to reconstruct the relief generation and uplift across the internal zone of the betic cordillera in southern spain uplift amounts and average rates can be estimated using the current elevation of the outcrops of well dated deposits indicative of ancient sea level positions coral reefs and coastal conglomerates record the initial development of emergent betic relief during the langhian continental and marginal marine deposits indicate the existence of a large island centred on the present sierra nevada sierra de los filabres chain by the end of the middle miocene the precursor of the sierra nevada sierra de los filabres chain originally part of this large island remained emerged whilst the surrounding areas were re invaded by the sea during the early tortonian at the end of the tortonian the inland basins granada and guadix basins became continental while the sierras de la contraviesa sierra de gador and sierra alhamilla emerged separating the alboran basin from the alpujarra tabernas and sorbas basins which became narrow passages of the mediterranean sea in contrast the sierra cabrera emerged during the late messinian suggesting a progressive uplift from west to east of the sierras south of the sierra nevada sierra de los filabres chain during the pliocene only the low areas closest to the present day coast remained as marine basins and progressively emerged throughout this stage the highest average uplift rate recorded is 280 m ma for the sierra de gador although the average uplift rates of upper neogene coastal marine rocks since depositon have maximum values of approximately 200 m ma most of the uplift of the betic mountains took place before the early pliocene the recorded uplift of neogene rocks was highest at the margins of western sierra nevada where peaks higher than 3000 m occur the average rates of uplift were lower to the east of this major relief the main sierras and depressions in the present day landscape correspond respectively to the emergent land in which uplift was concentrated and to the marine basins that existed before the final emergence of the region the altitude of the sierras reflects the time at which they became emergent the highest mountains being the first to rise above sea level

downslope migrating sandwaves and platform margin clinoforms in a current dominated distally steepened temperate carbonate ramp guadix basin southern spain during the late tortonian platform margin prograding clinoforms developed at the south western margin of the guadix basin large scale wedge shaped deposits here comprise 26 rhythms of mixed carbonate siliciclastic bedset packages and marl beds these sediments were deposited on a shallow water temperate carbonate distally steepened ramp a downslope migrating sandwave field developed in this ramp with sandwaves moving progressively down the ramp to the ramp slope where they destabilized folded and occasionally collapsed downslope sandwave migration was induced by currents flowing basinwards during the late tortonian the guadix basin was open north to the atlantic ocean via the dehesas de guadix strait and connected east to the mediterranean sea through the almanzora corridor according to the proposed current circulation model for the guadix basin for this time surface marine currents from the atlantic entered the basin from the northern seaway these currents moved counter clockwise and shifted the sediment on the ramp forming sandwaves that migrated downslope the development of platform margin prograding clinoforms by the basinward sediment transport mechanisms inferred here is known relatively poorly in the ancient sedimentary record moreover these wedge shaped geometries are similar to those found in some shelves in the western mediterranean sea and could represent an outcrop analogue to sub recent platform margin clinoforms revealed by high resolution seismic studies

biocalcarenite and mixed cool water prograding bodies of the mediterranean pliocene and pleistocene architecture depositional setting and forcing factors

plio pleistocene cliff bound wedge shaped warm temperate carbonate deposits from rhodes greece sedimentology and facies abstract the pliocene to pleistocene temperate carbonates of rhodes were deposited in a tectonically active region strongly influenced by a complicated and rapidly changing topography provided by the highly tectonised late cretaceous lindos limestone as basement rock deposition on this basement took place in accommodation loci restricted to micrograbens and their downslope extension to the foot of steep submarine cliffs to basement neptunian dykes and depressions in the basement rock consequently the sediments comprise a high degree of facies variability and are typically thin and laterally discontinuous the integration of several outcrops is necessary for the reconstruction of the stratigraphy and the relative sea level changes the sediments were deposited during a large scale tectonically driven transgressive regressive cycle in water depths changing from zero to several hundreds of metres at the studied lindos pefkos road cutting the kolymbia limestone bound to the foot of lindos limestone cliffs marks the onset of the marine deposition in the late pliocene its fabric is a rudstone consisting of unsorted angular lindos limestone clasts up to boulder size with a matrix dominated by molluscs and coralline algae the overlying plio pleistocene st paul s bay limestone consists of deep water float and rudstones containing the white coral community dominated by the coral lophelia pertusa its matrix shows a complex fabric of up to five sediment zones separated by differing states of lithification in this maximum flooding phase mineralised hardgrounds indicate depositional hiati the subsequent shallowing phase is represented by the cape arkhangelos calcarenite a series of distinctive facies of very patchy distribution they are characterised by the bryozoan brachiopod facies overlain by a facies heavily dominated by the bivalve mytilaster sp mytilaster facies conspicuous for the mytilaster facies is the inverse concave up stacking pattern of shelly material this facies is followed by a serpulid framestone and associated serpulid rudstone neptunian dykes cut through the first two facies and are filled with an intraformational breccia grading into a breccia with abundant mytilaster facies clasts neptunian dyke facies the sedimentology and interpretation of each facies include a description of the ichnology in particular the bioerosion peculiar to each facies the separation of different gravity transport processes in steep submarine environments is rarely described and most of the literature concentrates on siliciclastic dominated coarse grained sandy or gravely sand delta environments for a classification of the transport processes of the examined deposits the following criteria were evaluated sediment body symmetry inclination of the palaeorelief sediment constituents fabric complexity sedimentary structures and availability of fine matrix sedimentary structures and grading can be camouflaged in carbonates due to density differences of bioclasts however bioclast orientations such as bivalve stacking patterns can give information about the sedimentary process we suggest the inverse concave up stacking pattern of bivalve shells to be a texture potentially indicative for debris falls because of the above mentioned criteria we classified the kolymbia limestone as rock fall deposits and the st paul s bay limestone as well as the mytilaster facies of the cape arkhangelos calcarenite as debris fall deposits the bryozoan brachiopod facies could not be classified with certainty because of the lack of sedimentary structures and bioclast orientation however a grain flow or most likely a debris fall transport process seems probable

prediction of ignitive turbidity currents in scripps submarine canyon swift highly erosive continuous turbidity currents are known to be triggered in scripps submarine canyon during storms a relatively modest agitation due to edge waves can generate currents at least as swift as 1 9 m s 1 pantin 1979 and parker 1982 have described a mechanism by which a turbidity current can self accelerate by entraining sediment from the bed parker termed the mechanism ignition herein two models of steady spatially developing turbidity currents are developed and applied to scripps submarine canyon fairly specific predictions are obtained for the onset of ignitive acceleration and for the downstream development of the turbidity currents the results are in general agreement with available measurements in the same canyon it is speculated that ignitive turbidity currents constitute a major mechanism by which sand submarine canyons are eroded and by which sand is delivered to the abyssal plain

spit platform temperate carbonates the origin of landward downlapping beds along a basin margin lower pliocene carboneras basin se spain lower pliocene temperate carbonates exhibit landward downlapping beds at the southern margin of the carboneras basin in south eastern spain this rarely documented stratal geometry resulted from the accumulation of bedded bioclastic carbonate sand and gravel by longshore currents along a spit platform located a few hundred metres from the palaeoshoreline the top of the spit platform was covered by shoals that extended over a gently dipping ramp inclined to the north on the landward slope of the spit sediments washed over from the shoal area were deposited in parallel laminated beds with a southward dip of 8 11 these beds aggraded and retrograded after an increase in accommodation space probably related to an early pliocene eustatic sea level rise as a result the beds downlap onto the underlying unconformity surface in a shoreward direction eventually the depression between the shoreline and the spit platform was filled and a gentle ramp became established these pliocene exposures in the carboneras basin and a similar upper miocene example in southern spain suggest that landward downlapping stratal geometries can be expected in nearshore temperate carbonates along basin margins and demonstrate a similarity in sedimentary dynamics to siliciclastic sands and gravels

development of a prograding carbonate wedge during sea level fall lower pleistocene of rhodes greece a lower pleistocene carbonate platform is described from north east rhodes greece it comprises a succession of warm temperate calcarenites the cape arkhangelos calcarenite facies group developed in a steep sided coastal basin the depositional setting for the sediments is a carbonate wedge developed within a larger scale forced regression deposition began with aggradation of storm dominated lower and upper shoreface deposits later the development of a prograding platform produced giant clinoform foresets a marked alternation of cross bedded and bioturbated clinoforms indicates seasonal transport of carbonate material off the platform periodically the platform edge has been deeply scoured by exceptional storms after which further deposition repaired the platform margin and progradation resumed more than 20 such major storm cycles are preserved applying sequence stratigraphy to this succession leads to two different possible interpretations one with a lowstand systems tract and one with a forced regressive systems tract depending on the scale of view the implications of this are discussed the present example shows clearly that the application of sequence stratigraphic models to real carbonate sequences requires careful consideration of scale and context before interpretations are made

source of ore forming fluids in jinshan gold deposit of dexing county constraints from microstructures and stable isotopes the jinshan gold deposit a superlarge deposit with 200 t au is hosted in the jinshan ductile shear zone and located in the northeast jiangxi deep crustal fault the zone is a magnificent neo proterozoic melange suture zone the mineralized fault filling quartz veins that were elongated and boudinaged along with mylonitic foliations serve as main ore bodies textural and structural data indicate that mineralization was syn tectonic and the opening of the foliation planes played a fundamental role in facilitating gold mineralization auriferous quartz veins were laminated due to repeated foliation opening and fluid filling and precipitation banded and laminated textures suggest a crack and seal mechanism for gold precipitation and the continuation of the shear deformation during the emplacement of the veins this means that progressive deformation is closely associated with gold mineralization fluid inclusions in pyrite associated with quartz have 3he 4he ratios of 0 13 0 24 ra whereas their 40ar 36ar ratios are from 575 to 1 090 18o values calculated from quartz are between 5 5 and 8 4 and d values of the fluids in the fluid inclusions of quartz are between 61 and 73 the 13c values of ankerite range from 5 0 to 4 2 whereas the 18o values range from 4 4 to 8 0 these ranges demonstrate a mixing of mantle derived fluids and crustal derived fluids the crustal end member is composed of metamorphic water and meteoric water the microstructures along with noble gas isotope he and ar data as well as stable isotope c o and d data strongly suggest that diverse sources were involved in the hydrothermal activity in the jinshan gold deposit ore forming fluids were dominantly derived from the crustal source with the participation of less than 5 mantle components the deposit was formed in a transpressive tectonic setting

structural evolution of the hemlo greenstone belt in the vicinity of the world class hemlo gold deposit a complex history of volcano sedimentary deposition polyphase strain multiple intrusive events and various stages of porphyroblastesis is indicated for the hemlo gold deposit area within the hemlo greenstone belt structural elements can be assigned to at least six stages of development d1 d6 d1 generated small scale folds and low angle faults thrusts with no planar fabric except within strain aureoles around the earliest intrusions d2 was a progressive event resulting from northeast directed compression which generated regional predominantly s shaped folds early d2 penetrative planar and linear fabrics overturned stratigraphy and formation of an inflection in the strike of the greenstone belt mid d2 and development of high strain zones with dominant sinistral and local dextral shear sense late d2 d3 was a distinctly separate progressive event resulting from northwest directed transpression which generated variably penetrative east to northeast striking foliation s3 ductile de

surficial sediments of the great australian bight facies dynamics and oceanography on a vast cool water carbonate shelf abstract the great australian bight gab the largest sector of the southern australia continental margin is a site of cool water carbonate sedimentation throughout ranging from locally warm temperate inboard to cool temperate outboard surficial sediments are a mixture of calcareous pleistocene skeletal and lithic intraclasts relict grains and holocene biofragments with minor amounts of quartz inboard the inner shelf is an area of abundant macrophytes and seagrasses active carbonate sediment production and accumulation and little relict sediment the huge middle portion is a shaved shelf with active sediment winnowing and mostly relict sediment the outer shelf and upper slope is a variably productive sediment factory characterized by prolific calcareous epibenthic growth on hard substrate subaqueous islands shedding particles into surrounding sands and muds patterns of holocene sedimentation are linked to modern oceanographic parameters in this high energy setting characterized by overall downwelling prolific rhodoliths occur on the nw inner shelf where shallow summer waters are the warmest in the gab these warm saline nutrient depleted waters then drift eastward across the shelf suppressing heterozoan carbonate production on the central and eastern mid shelf this arrested production in the eastern gab is countered locally by summer coastal upwelling along western eyre peninsula with bryozoan rich sediment extending well inboard onto the mid shelf the outer shelf and upper slope is an area of prolific bryozoan growth likely linked to upwelling except in the central gab a region of year round downwelling where the area is one of off shelf fine sediment transport and carbonate mud deposition these patterns in the central gab at least are present in the underlying holocene and pleistocene suggesting that the general modern oceanographic dynamics and resultant carbonate sedimentation have persisted throughout the quaternary

sedimentary model and high frequency cyclicity in a mediterranean shallow shelf temperate carbonate environment uppermost miocene agua amarga basin southern spain uppermost tortonian to lower messinian temperate carbonates crop out in the agua amarga basin se spain they consist of four units the lower three units can be tentatively assigned to the lowstand systems tract of a fourth order sequence constituting in turn the lowstand megatrough unit transgressive breccia unit and highstand bedded unit stages of a higher order cycle all these materials were deposited in a small pull apart basin related to the sinistral carboneras strike slip fault system the best represented is the bedded unit up to 25 m thick which consists of bioclastic bryozoan bivalve dominated calcarenites calcirudites with abundant fragments of echinoids barnacles benthic foraminifers coralline algae brachiopods and solitary corals facies trends within this unit are roughly arranged in an e w direction with the coastline to the north of the basin the depositional model is that of a gentle ramp with prograding beaches and shoals in its higher parts seaward of the shoals was the factory area where most organisms lived and maximum carbonate production took place from this area some of the skeletons were washed landwards by waves and or currents during storms and incorporated into the shoals and beaches and others moved downslope along the ramp as mass flows accumulating to form the fan bedded zone the factory area and fan bedded sediments intercalate five well defined thick beds of calcarenites fine grained calcirudites they show bar morphologies single or amalgamated or make up sand waves with very consistent tabular cross bedding pointing landwards these beds formed in a very shallow wave current influenced coastal environment the bars and sand waves in the fan bedded zone developed during lowstands while those located higher up in the ramp interbedded with the factory facies are related to transgressive stages prograding beaches shoals factory facies and fan bedded layers developed during the highstands net skeletal production occurred mainly during the highstands sediment accretion values of these sediments are similar to those of present and ancient shallow marine temperate carbonates considering that the whole bedded unit was deposited in a 100 000 year interval equivalent to the short eccentricity cycle the five cycles inside the bedded unit would therefore correspond to the c 20 000 year precession cycles of the milankovitch band

quaternary stratigraphic stacking patterns on the continental shelves of the southern iberian peninsula their relationship with global climate and palaeoceanographic changes abstract a quaternary stratigraphic stacking pattern on the continental shelves of the southern iberian peninsula has been determined by analysing and comparing a dense network of low medium high and very high resolution mono channel and multi channel reflection seismic lines and well log data four major low resolution depositional sequences related to a 3rd order cycle at 1 4 1 6 ma have been recognised in the pliocene quaternary sedimentary record m p1 p2 p3 q i and q ii they are separated by four discontinuities corresponding to the most drastic changes in climate and palaeoceanography affecting the atlantic and mediterranean linkage and especially to the most prominent sea level falls in the messinian m at 5 5 ma in the lower pliocene at 4 2 ma in the upper pliocene at 2 4 ma and in the mid pleistocene at 900 920 ka mpr these major sequences were built up by asymmetrical sea level cycles the regressive and lowstand system tracts are the best developed deposits controlling the main progradation of the shelf basinwards as well the quaternary shelf stratigraphy can be divided into asymmetric 3rd order sequences of 800 ka q i and q ii and into 4th order asymmetric sequences of approximately 400 ka q1 q4 200 ka a h and 100 ka on low medium and high resolution seismics the overall architectural stacking of the shelf shows a change after the mpr discontinuity characterised by well differentiated sequences of shelf break wedges with progradational sigmoid configurations assumed to be related to approximately 100 ka sea level cycles this change in the configuration of the shelf wedges during the quaternary is attributed to the onset of the 100 ka eccentricity orbital cycles which abruptly increased the amplitude of sea level variations 100 120 m during the last 900 920 ka

late miocene pleistocene tectono sedimentary evolution and subsidence history of the central betic cordillera spain a case study in the guadix intramontane basin the guadix basin became established as an intramontane basin in the central sector of the betic cordillera at the beginning of late miocene time its geodynamic evolution starts with a unit of tortonian marine sediments and is completed by a unit of late turolian pleistocene continental sedi ments in the two units six depositional sequences have been differentiated whose boundaries in most cases coincide with tectonic events geohistorical diagrams show the results of quantitative analyses of subsidence in the northern sector of the basin and permit correlation of the main events with signif icant changes in the history of subsidence and uplift a period of strong subsidence occurred at the beginning of tortonian time causing the formation of a marine basin 800 m deep the mid and end tortonian tectonic events involved periods of uplift leading to shallowing in the basin after continen talization at the end of the tortonian the basin was uplifted continuously from late turolian to late pleistocene times finally accumulating sediments at a height of 1000 m