transgressive sand bodies on the maresme continental shelf western mediterranean sea abstract three large scale elongate asymmetrical sand bodies lie beyond the shoreface of the straight sandy coast of maresme barcelona in the northwestern mediterranean sea they are found on the continental shelf at water depths of 15 30 m 35 80 m and 95 113 m they are typically 12 20 m thick 1000 2000 m wide and trend parallel or subparallel to the coast for a distance of up to 24 km slopes on the steep offshore side vary between 3 and 20 while the shoreward slopes are gentler the shallowest sand body is modern in dynamic equilibrium with present conditions the other two however are relict bodies built up during the last postglacial rise in sea level development of these sand bodies occurs in the shoreface environment and in a space time evolution they show a punctuated but nearly continuous nature in the way that their preservation during the holocene transgression occurs only in specific locations on the continental shelf they begin growing on pleistocene scarps with offshore slopes and their growth pattern is mostly controlled by the sediment supply flow distribution and rate of sea level rise the formation of these sandy bodies is related to winter storms and southwesterly flows which cause large volumes of sediment to be transported downshelf and offshore by downwelling bottom currents generated by coastal set up the result is sand movement onto and across the sand body surface down to water depths of 15 20 m the thick sandy lenses of the maresme shelf are interpreted as topographically induced lee side sand bodies and not primarily as sand ridges in the classic sense the occurrence of these bodies on a low energy shelf may be significant for the interpretation of the geological record

influence of the atlantic inflow and mediterranean outflow currents on late quaternary sedimentary facies of the gulf of cadiz continental margin abstract the late quaternary pattern of sedimentary facies on the spanish gulf of cadiz continental shelf results from an interaction between a number of controlling factors that are dominated by the atlantic inflow currents flowing southeastward across the cadiz shelf toward the strait of gibraltar an inner shelf shoreface sand facies formed by shoaling waves is modified by the inflow currents to form a belt of sand dunes at 10 20 m that extends deeper and obliquely down paleo valleys as a result of southward down valley flow a mid shelf holocene mud facies progrades offshore from river mouth sources but atlantic inflow currents cause extensive progradation along shelf toward the southeast increased inflow current speeds near the strait of gibraltar and the strong mediterranean outflow currents there result in lack of mud deposition and development of a reworked transgressive sand dune facies across the entire southernmost shelf at the outer shelf edge and underlying the mid shelf mud and inner shelf sand facies is a late pleistocene to holocene transgressive sand sheet formed by the eustatic shoreline advance the late quaternary pattern of contourite deposits on the spanish gulf of cadiz continental slope results from an interaction between linear diapiric ridges that are oblique to slope contours and the mediterranean outflow current flowing northwestward parallel to the slope contours and down valleys between the ridges coincident with the northwestward decrease in outflow current speeds from the strait there is the following northwestward gradation of contourite sediment facies 1 upper slope sand to silt bed facies 2 sand dune facies on the upstream mid slope terrace 3 large mud wave facies on the lower slope 4 sediment drift facies banked against the diapiric ridges and 5 valley facies between the ridges the southeastern sediment drift facies closest to gibraltar contains medium fine sand beds interbedded with mud the adjacent valley floor facies is composed of gravelly shelly coarse to medium sand lags and large sand dunes on the valley margins by comparison the northwestern drift contains coarse silt interbeds and the adjacent valley floors exhibit small to medium sand dunes of fine sand because of the complex pattern of contour parallel and valley perpendicular flow paths of the mediterranean outflow current the larger scale bedforms and coarser grained sediment of valley facies trend perpendicular to the smaller scale bedforms and finer grained contourite deposits of adjacent sediment drift facies radiocarbon ages verify that the inner shelf shoreface sand facies sedimentation rate 7 1 cm kyr mid shelf mud facies maximum rate 234 cm kyr and surface sandy contourite layer of 0 2 1 2 m thickness on the cadiz slope 1 12 cm kyr have deposited during holocene time when high sea level results in maximum water depth over the gibraltar sill and full development of the atlantic inflow and mediterranean outflow currents the transgressive sand sheet of the shelf and the mud layer underlying the surface contourite sand sheet of the slope correlate respectively with the late pleistocene sea level lowstand and apparent weak mediterranean outflow current

the ebro continental shelf quaternary seismic stratigraphy and growth patterns abstract single channel seismic reflection profiles on the ebro shelf and upper slope between cap salou and the columbretes islands have been interpreted to outline the quarternary shelf evolution in this deltaic area three types of unconformity surfaces can be differentiated in the seismic records type 1 and 2 unconformities and toplap surfaces these surfaces are the stratigraphic expression of the difference between rate of eustatic sea level fall and subsidence on the outer shelf a type 1 unconformity forms if the rate of eustatic sea level fall is the more rapid a type 2 unconformity forms if subsidence is faster and toplap forms if subsidence and eustatic sea level fall are equal thirteen stratigraphic units can be differentiated on the basis of unconformities based on their relative location on the shelf these units are subdivided into inner and outer units the inner units occur on the inner and middle shelf and are characterized by an underlying transgressive surface while the outer units extend onto the middle to outer shelf and upper slope and show unconformities at their bases the inner units are interpreted to be stacked transgressive and highstand systems tracts bounded by a maximum flooding surface the outer units correspond to shelf deltas and shelf margin deltas that prograded southward and seaward over an unconformity in relatively stable water depths when sea level fall was compensated for by subsidence the progradation of these units ends with an episode of generalized erosion of the shelf and canyon cutting across the new shelf edge the growth pattern of the northern ebro shelf is characterized by important hiatuses condensed stratigraphic sections and units which are older than those on the southern shelf the depositional processes were mainly controlled by eustatic sea level oscillations subsidence and changes in sediment supply the subsidence during the late pleistocene was sufficient to compensate for the sea level falls and allow the development of shelf deltas and shelf margin deltas on the middle and outer shelf during low sea level stands

sources of metals in the porgera gold deposit papua new guinea evidence from alteration isotope and noble metal geochemistry the porgera gold deposit is spatially and temporally associated with the late miocene mafic alkalic epizonal porgera intrusive complex pic located in the highlands of papua new guinea png the highlands region marks the site of a tertiary age continent island arc collision zone located on the northeastern edge of the australasian craton the pic was emplaced within continental crust near the lagaip fault zone which represents an oligocene suture between the craton and volcano sedimentary rocks of the sepik terrane magmatism at porgera probably occurred in response to the late miocene elimination of an oceanic microplate and subsequent early pliocene collision between the craton margin and an arc system located on the bismarck sea plate gold mineralization occurred within 1 ma of the time of magmatism metasomatism accompanying early disseminated au mineralization in igneous host rocks resulted in additions of k rb mn s and co2 and depletions of fe mg ca na ba and sr rare earth and high field strength elements remained largely immobile pervasive development of illite k feldspar quartz carbonate alteration assemblages suggests alteration by mildly acidic 200 to 350 c fluids at high water rock ratios strontium and lead isotopic compositions of minerals from early base metal sulphide veins associated with k metasomatism and later quartz roscoelite veins carrying abundant free gold and tellurides are remarkably uniform e g 87sr86sr 0 70745 0 00044 n 10 207pb204pb 15 603 0 004 n 15 these compositions fall between those of unaltered igneous and sedimentary host rocks and specifically sedimentary rocks from the jurassic om formation which underlies the deposit igneous rocks 87sr86sr 0 7035 207pb204pb 15 560 om formation 87sr86sr t 0 7153 207pb204pb 15 636 it is therefore suggested that the hydrothermal fluids acquired their sr and pb isotopic signatures by interaction with or direct derivation from a plutonic root of the pic and host sedimentary rocks of the om formation it is likely that au was also derived from one or both of these two sources concentrations of au in unaltered igneous and sedimentary rocks from porgera 10 ppb au do not indicate that either lithology represents a significantly enriched protore although au and platinum group element pge abundances in the igneous rocks suggest a mild primary magmatic enrichment of au relative to the pge average au pt pd mantlenormalized 14 0 6 5 n 8 evidence that the porgera magmas were rich in volatiles permits speculation that au may have been concentrated in a magmatic fluid phase but alternative possibilities such as derivation of au by hydrothermal leaching of solidified igneous materials or sedimentary rocks cannot be excluded at this time

geochronology of the porgera gold deposit papua new guinea resolving the effects of excess argon on k ar and age estimates for magmatism and mineralization abstract mesothermal epithermal gold mineralization at porgera in the highlands of papua new guinea png occurs in structurally controlled veins and disseminations which overprint and cross cut a suite of shallow level comagmatic mafic alkaline stocks and dykes the porgera intrusive complex pic and their sedimentary host rocks conventional k ar apparent ages of twelve hornblende separates from eight different intrusions scatter between 7 and 14 ma but four biotite separates are concordant at 6 02 0 29 ma 2 40 ar 39 ar step heating experiments on six of the hornblende separates reveal saddleshaped age spectra which indicate the presence of excess 40ar one of these samples yields a well defined plateau with an apparent age of 5 96 0 25 ma 2 this age is identical to that of the biotites and suggests an age of 6 0 0 3 ma 2 for emplacement of the pic older apparent ages obtained from conventional k ar and 40 ar 39 ar analyses are explained by excess 40ar contamination conventional k ar analyses of six separates of hydrothermal illite and roscoelite associated with gold mineralization yield apparent ages of between 5 1 and 6 1 ma and indicate that ore deposition occurred within 1 ma of magmatism at porgera evidence for the evolution of a magmatic volatile phase and the presence of excess 40ar both in the intrusives and in hydrothermal fluids associated with the orebody suggest that magmatic fluids may have had some involvement in metallogenesis but the exact nature of this involvement is not yet clear late miocene magmatism and mineralization at porgera are thought to have occurred shortly prior to or during the initiation of continent arc collision and to pre date associated pliocene uplift and foreland deformation in the highlands

qualitative and quantitative approaches in palaeohydrography a case study from core top parameters in the gulf of cadiz palaeoceanography relies on the assumption that parameters measureable in sediment cores correlate reliably to hydrographic parameters areas of dynamic watermass mixing which generally have steep hydrographic gradients therefore provide both a tempting target large spatial and temporal differences in temperature and salinity and a significant challenge high flow velocities and high noise for palaeoceanographers here we investigate the ability of parameters measured on core tops to be used as the basis for simulating regional hydrography within one globally important area of watermass mixing the gulf of cadiz using grainsize sediment composition benthic foraminiferal assemblage and benthic foraminiferal stable isotope analysis it is possible to build an effective framework for qualitative constraint of the position of the modern mediterranean outflow water mw plume we propose that the gulf of cadiz slope can be sub divided into 8 hydrographic zones reflecting these parameters proximal mw core mw1 steep slopes core mw1 gentle slopes distal mw1 distal mw2 lower limit of mw plume north atlantic deep water and ambient atlantic water we anticipate that compilation of time slice data will reveal hydrographic sub divisions of the slope for the past in a similar manner improving our understanding of past changes in the size and position of the mw plume but more work needs to be done before a secure protocol for quantitative reconstruction can be created stable isotope analysis alone is insufficient for the task with 13c behaving in a non conservative manner and 18ocalcite acting in an ambiguous way due to the competing influences of 18owater and temperature it is likely that if a single parameter that unambiguously determines the difference between mediterranean water and atlantic water can be identified combination with 18ocalcite will allow extension of our qualitative analysis into a quantitative means of palaeohydrographic reconstruction for this region similar complexity to that found in this study would be expected in any mixing region and in particular on the majority of sediment drifts we recommend that core top surveys similar to this study are performed on these sediment drift systems before any form of quantitative palaeohydrology is attempted

late quaternary seismic facies of the gulf of cadiz spanish margin depositional processes influenced by sea level change and tectonic controls abstract seismic facies and quaternary depositional systems of the gulf of cadiz have been characterized by means of high resolution seismic profiles airguns geopulse and ore 3 5 khz a total of 11 pleistocene and two holocene sequences separated by type 1 or type 2 discontinuities were identified the age of the depositional sequences was determined based on foraminifera ages from boreholes and by correlation with seismic profiles of the slope areas with uniform deposition and without significant discontinuities these seismic units have been mapped throughout the margin allowing to establish the correlation with eustatic sea level curves and global climatic trends the distribution and geometry of the units reveals that most of the sedimentary record was developed during episodes of forced regression ten regressive periods corresponding to 5th order cycles arranged into 4th order were distinguished absolute water depths for the development of coastal deposits in each unit were calculated using depth from present day sea level corrected for tectonic subsidence in the area the model for the evolution of the depositional system of the gulf of cadiz continental margin highlights the strong influence of tectonism in the development of depositional bodies controlling the distribution of deposits generally produced during episodes of sea level fall

the cadiz margin study off spain an introduction abstract the cadiz continental margin of the northeastern gulf of cadiz off spain was selected for a multidisciplinary project because of the interplay of complex tectonic history between the iberian and african plates sediment supply from multiple sources and unique mediterranean gateway inflow and outflow currents the nature of this complex margin particularly during the last 5 million years was investigated with emphasis on tectonic history stratigraphic sequences marine circulation contourite depositional facies geotechnical properties geologic hazards and human influences such as dispersal of river contaminants this study provides an integrated view of the tectonic sediment supply and oceanographic factors that control depositional processes and growth patterns of the cadiz and similar modern and ancient continental margins

foraminiferal coloration index as a guide to hydrothermal gradients around the porgera intrusive complex papua new guinea the porgera intrusive complex and gold deposit is hosted in friable black mudstones of cretaceous age in the deformed northern part of the papuan basin papua new guinea hydrothermal fluids associated with the pliocene intrusions created thermal gradients in the surrounding sedimentary rocks these gradients were partitioned by preexisting faults in the sedimentary rocks creating cells of fluid circulation assemblages of agglutinated foraminifera reported from north america have shown color gradients which are interpreted as being related to the thermal maturation of sedimentary rocks down drill holes this paper presents the first known application of color changes in foraminifera marine protistan microfossils to hydrothermal mineral exploration the foraminiferal assemblages of the bathyal mudstones from the porgera region contain abundant agglutinated foraminifera color changes recognized in the agglutinated foraminifera were used to map the thermal maturation of sedimentary rocks in the porgera area palynological fluorescence used in petroleum exploration to determine thermal maturation could not be used owing to the over maturation of the organicmaterials throughout the area surrounding the porgera intrusive complex the agglutinated foraminifera showed a gradation in color from white to dark gray in surface samples taken throughout the porgera area mapping of the foraminifera colors using a geographic information system gis illustrated the thermal maturation of the sedimentary rocks around the intrusive complex owing to conductive heating in addition the mapping showed patterns consistent with convective heating caused by hydrothermal fluid circulation the foraminiferal coloration showed pairing of hot and cold areas across major structures interpreted to be associated with the upflow hot and recharge cold of fluids from the surrounding host sedimentary rocks illite crystallinity and vitrinite reflectance analyses conducted on a transect of samples from across the porgera intrusive complex supported the proposed hydrothermal fluid circulation model interpreted from the foraminiferal colors paleotemperatures associated with the foraminiferal coloration index from the porgera region range from 205 to 415 c and are anomalously high in comparison to other parts of the papuan fold and thrust belt the foraminiferal coloration index fci is a guide to the thermal maturation of sedimentary rocks and provides a useful and low cost exploration tool for locating and evaluating the size of buried intrusive systems in late palaeozoic to cenozoic marine shales it is an invaluable tool for determining the size and partitioning of a hydrothermal cell associated with hydrothermal epithermal mineral deposits the fci method is also useful on a regional scale in areas where sandstones shales or limestones blanket aero magnetic and resistivity data the technique is used currently to identify drilling targets for the exploration of the porgera deposit

surface facies and sediment dispersal patterns southeastern gulf of cadiz spanish continental margin abstract grain size of 294 samples and mineralogical analysis of 364 surface samples from the spanish continental shelf and upper slope of the gulf of cadiz delineate four sediment facies that derive mainly from siliciclastic sources the northern area is formed by the mud rich prodelta of the guadalquivir river parallel to the coast and progradational towards the southeast it exhibits a typical bulk mineral association of illite smectite kaolinite chlorite in the north central area there is a smaller coarser grained prodelta in the bay of cadiz linked to the guadalete river which offshore becomes connected to the guadalquivir prodelta its mineral association is quartz illite kaolinite chlorite in the southern area where fluvial input is negligible the characteristic coarse grained facies generally corresponds to relict late pleistocene reworked deposits the typical mineral association is quartz calcite aragonite smectite mixed layer clay minerals the fourth area corresponds to the shelf break and upper slope offshore cadiz bay where a westward grain size coarsening differentiates the deposits of the last low sea level stand and no typical mineral association exists the mineralogy of the terrigenous deposits indicates a source area from paleozoic sequences of the sierra morena to the north and the subbetic units and gibraltar flysch to the east the neogene deposits of the guadalquivir depression are an additional source of shelf sediments the surface sediment distribution on the inner continental shelf is largely determined by the southeastern atlantic water flow the terrigenous input from rivers and the shelf physiography sediment dispersal on the outer continental shelf and upper slope in contrast largely reflects the location of low sea level stand the development of palimpset deposits and the location of the mediterranean undercurrent over the margin

reworked calcareous nannofossils as ocean dynamic tracers the guadiana shelf case study sw iberia for most micropalaeontological studies the presence of reworked specimens is usually considered as a disturbing factor where palaeoenvironmental or biostratigraphic interpretations are to be made however reworking of microfossils such as calcareous nannofossils can be used as an additional parameter in routine micropalaeontological work providing useful information on erosion transport processes acting on silty clay sized particles deriving from areas surrounding the sedimentary basin under study most of the reworked calcareous nannofossils found in the guadiana estuary water column september 2001 adjacent shelf surface sediments and a slope section of the gulf of cadiz were mainly of upper cretaceous age campanian to maastrichtian being dominated by biscutum spp cribrosphaerella ehrenbergii prediscosphaera cretacea and watznaueria barnesae since there are no upper cretaceous outcrops in the guadiana s hydrographic basin or southern portugal the source of this material must be located elsewhere matrix breccias from mud volcanoes discovered in deeper water southern portuguese and western moroccan margins of the gulf of cadiz during the ttr 10 cruise in july august 2000 as well as silty clay sediments from its slopes revealed similar calcareous nannofossil assemblages as those found on the algarve continental shelf and inside the guadiana s estuary this may indicate that most of the reworked nannofossils have their origin in deepwater areas of the gulf of cadiz the good preservation of most of the reworked cretaceous nannofossils suggest that shortly after resuspension swift transport occurred from the source area to the coastal region of the guadiana s river mouth implicating a northward change in the deep mediterranean water direction within the gulf of cadiz which reaches the upper southwest iberia slope the mediterranean outflow is therefore the major mechanism accountable for transporting upper cretaceous material to the southwest iberian margin and the atlantic inflow together with longitudinal coastal currents is the probable responsible for carrying and spreading eastward these reworked silty clay sized particles over the portuguese and spanish continental shelf this case study is a clear example of the potential importance of calcareous nannofossils as ocean dynamic tracers for particles within the silty clay fraction

occurrence of acoustic masking in sediments in two areas of the continental shelf of spain ria de muros nw and gulf of cadiz sw abstract zones of acoustic masking in sediments in the continental shelf of cadiz and in the ria de muros have been mapped utilizing 3 5 khz and uniboom seismic reflection records in cadiz the masking may be generated by shell beds source of the shells is a pliocene conglomerate that corresponds to the acoustic basement in the area acoustic masking in the sediments of ria de muros was generated by the presence of gas within the sediments the gas is due to the decay of organic matter within the sediments that area of acoustic masking in the ria de muros roughly coincides with the zone of mud with high 15 5 organic content and that gas bubbles were noted in the water column in the same region support this hypothesis

mediterranean undercurrent sandy contourites gulf of cadiz spain abstract the pliocene quaternary pattern of contourite deposits on the eastern gulf of cadiz continental slope results from an interaction between linear diapiric ridges that are perpendicular to slope contours and the mediterranean undercurrent that has flowed northwestward parallel to the slope contours and down valleys between the ridges since the late miocene opening of the strait of gibraltar coincident with the northwestward decrease in undercurrent speeds from the strait there is the following northwestward gradation of sediment facies associations 1 upper slope facies 2 sand dune facies on the upstream mid slope terrace 3 large mud wave facies on the lower slope 4 sediment drift facies banked against the diapiric ridges and 5 valley facies between the ridges the southeastern sediment drift facies closest to gibraltar contains medium fine sand beds interbedded with mud the adjacent valley floor facies is composed of gravelly shelly coarse to medium sand lags and large sand dunes on the valley margins compared to this the northwestern drift contains coarse silt interbeds and the adjacent valley floors exhibit small to medium sand dunes of fine sand further northwestward sediment drift grades to biogenous silt near the faro drift at the portuguese border because of the complex pattern of contour parallel and valley perpendicular flow paths of the mediterranean undercurrent the larger scale bedforms and coarser grained sediment of valley facies trend perpendicular to the smaller scale bedforms and finer grained contourite deposits of adjacent sediment drift facies the bottom current deposits of valleys and the contourites of the cadiz slope intervalley areas are distinct from turbidite systems the valley sequences are not aggradational like turbidite channel levee complexes but typically exhibit bedrock walls against ridges extensive scour and fill into adjacent contourites transverse bedform fields and bioclastic lag deposits both valley and contourite deposits exhibit reverse graded bedding and sharp upper bed contacts in coarse grained layers low deposition rates and a regional pattern of bedform zones textural variation and compositional gradation the surface sandy contourite layer of 0 2 1 2 m thickness that covers the gulf of cadiz slope has formed during the present holocene high sea level because high sea level results in maximum water depth over the gibraltar sill and full development of the mediterranean undercurrent the late pleistocene age of the mud underlying the surface sand sheet correlates with the age of the last sea level lowstand and apparent weak mediterranean undercurrent development thus the cyclic deposition of sand or mud layers and contourite or drape sequences appear to be related to late pliocene and quaternary sea level changes and mediterranean water circulation patterns since its pliocene origin the contourite sequence has had low deposition rates of

numerical modeling of gravity driven sediment transport and deposition on an energetic continental shelf eel river northern california 1 a two dimensional numerical model was applied to predict large scale deposition by wave supported sediment gravity flows on the eel river continental shelf for four consecutive flood seasons using measured bathymetry waves and river forcing the model assumes that sediment induced stratification maintains the near bed richardson number at its critical value which determines the sediment carrying capacity of the wave boundary layer deposition is predicted when the gravity driven flux of sediment exceeds the carrying capacity the model predicted 26 of fine sediment discharged by the eel river to be deposited on the midshelf with a magnitude and distribution largely consistent with field observations greatest deposition on the midshelf was predicted well north of the river mouth despite greater sediment input nearest the river mouth model results indicate that when the river delivers sufficient sediment to critically stratify the wave boundary layer wave intensity and the bathymetry of the eel shelf are the dominant factors controlling the observed pattern of deposition large wave energy caused the majority of fine sediment 65 to escape the shelf as gravity driven flows the greatest amount of sediment was predicted to leave the shelf from the region off shelf of the river mouth including 11 into the eel canyon where inshore sediment input was high and the concave downward bathymetry associated with the eel river subaqueous delta prevents significant midshelf gravity driven deposition

recent benthic foraminiferal assemblages in deep high energy environments from the gulf of cadiz spain the benthic environment in the gulf of cadiz north eastern atlantic is strongly affected by the mediterranean outflow water undercurrent mow which flows northwards along the western iberian margin at 500 1500 m water depth foraminiferal census counts of living and dead assemblages from 27 surface samples ranging from 103 to 1917 m water depth and the examination of hard substrates reveal a close correlation of the fauna with the local hydrography and sediment facies four different faunal groups are separated by factor analysis of the living fauna assemblage 1 contains typical lower slope species and dominates samples from the lower mow core layer and in the north atlantic deep water below shelf edge foraminifera are common in assemblage 2a which shows the highest proportions in samples from 103 to 272 m assemblage 2b is dominated by upper slope species and suspension feeders that are frequent in the upper mow core layer and in distal settings between 396 and 901 m species from assemblage 3 prefer epibenthic habitats and are recorded with high proportions exclusively in the immediate flow paths of the upper mow between 496 and 881 m colonisation structures and species composition of epibenthic assemblages from the proximal facies largely differ from those in distal settings in general epibenthic foraminifers only use elevated substrates under the influence of near bottom flow under high current velocities epibenthic foraminifers prefer large and heavy objects they colonise high attachment levels where a maximum yield of advected food particles can be achieved in distal settings at lower flow velocities the elevation height does not exceed 20 mm above the surrounding sediment surface this level is related to a hydrologic transition layer with high concentrations of suspended particles the comparison of microhabitat preferences and faunal structure under high and low current velocities reveal that substrate stability may be a confining environmental variable for endobenthic and shallow epibenthic foraminifers the observations also indicate that the preferential settling height of epibenthic foraminifera is related to the highest lateral flux rates of food particles within reach from the sea floor a dynamic selection of elevated microhabitats is only used by 7 8 of all species recognised in the gulf of cadiz area

multicycle sediments on the continental shelf of cadiz sw spain abstract the study of recent sedimentation in the gulf of cadiz continental shelf sw europe is of interest due to its proximity to the strait of gibraltar where the atlantic and mediterranean waters are interchanged and the western mediterranean alpidic orogen closes through the gibraltar arch the existence of relict materials hinders the distinction of the past and present hydrodynamic regimes in present day sediments an adequate combination of techniques has allowed the establishment of the multicyclic character of the sediments as well as the stages undergone by the terrigenous grains different stages were identified eolian and energetic fluvial provenance chemical alterations acquired in a pedological environment and a marine coastal origin to verify the source areas textural and mineralogical features of marine sediments were compared with those found in geological units from fluvial basins three zones were differentiated a a sandy littoral which receives local sediment supplies b a clayey zone between the guadalquivir river and cadiz controlled by contributions from this river provenant of the iberian massif and betic mountain range and c a sandy continental shelf between cadiz and the cape of trafalgar with a low rate of supplies coming from the guadalete and barbate rivers which include materials from the occidental betic mountain range and neogene units

patterns of bottom current flow deduced from dune asymmetries over the gulf of cadiz shelf southwest spain abstract the analysis of dune like morphologies on the gulf of cadiz continental shelf using high resolution seismic reflection profiles and sediment samples reveals a well defined distribution pattern controlled by the area s hydrodynamics these bedforms are considered to be modern features from the holocene and therefore they provide information about the bottom circulatory patterns established over the continental shelf most of the submarine dunes have been identified over a shallow physiographic feature named the barbate high the current flows that generate the bedform fields can be attributed to a complex interaction of several hydrodynamic agents in which the process of current direction reversal related to the tidal cycle in the straits of gibraltar seems to be involved eastward oriented submarine dunes located on the onshore zones of the inner shelf are generated by the atlantic inflow which over these shallow zones is mainly orientated towards the east during high tide conditions in the straits of gibraltar bedforms oriented westwards and west northwestwards in the offshore zones indicate that a previously undescribed flow occurs on the gulf of cadiz continental shelf this flow is attributed to the influence of ebb tidal currents which move preferentially towards the west over these zones as a result of this complex bottom flow pattern a clockwise sand transport pattern over the barbate high is established

the alkaline porphyry associated yao an gold deposit yunnan china rare earth element and stable isotope evidence for magmatic hydrothermal ore formation the yao an vein type gold deposit is located in the ailaoshan jinshajiang alkaline intrusive belt yunnan province china and is associated both in time and space with 33 5 1 0 ma old alkaline intrusions the gold mineralization is associated with potassic wall rock alteration the ree distribution patterns of secondary k feldspar are generally similar to those of the igneous perthite but with about seven times higher total ree abundances the alteration is ascribed to a high ree magmatic fluid derived from the yao an alkaline intrusive suite the hydrothermal yao an gold deposit formed during two gold bearing stages i e a sulfide pyrite stage and a sulfide oxide stage pyrite specularite the ree abundance of early stage i pyrite is relatively high with strong enrichment in lree la yb n of 40 290 generally positive eu anomalies eu eu 0 86 1 55 and ree patterns very similar to those of secondary feldspar in contrast the later stage ii pyrite has much lower ree concentrations and lower la yb n of 5 5 11 8 eu eu of 0 49 0 76 and flat chondrite normalized spidergram patterns the stage i pyrite has 34s in the range of 2 2 to 3 2 and overlaps with regionally distributed pyrite in least altered syenite porphyry in contrast stage ii pyrite has much higher 34s values between 7 8 and 16 5 carbon isotope data for four samples from stage ii revealed 13c pdb values between 6 and 8 these stable isotope and ree data suggest that magmatic fluids of the alkaline intrusions caused both potassic alteration and stage i sulfide mineralization the system evolved from stage i to stage ii mineralization by influx of meteoric fluids with relatively heavier sulfur although calcite carbon isotope data suggest that the co2 remained dominantly of magmatic origin

the messinian guadalhorce corridor the last northern atlantic mediterranean gateway miocene tectonics with the last survi ving gateway occurring during the early messinian north west of malaga in the region of the guadalhorce river valley the guadalhorce gateway pro vided a significant control on messin ian pre evaporitic oceanic circulation in the mediterranean sea it acted as a major outflow channel of mediterra nean water into the atlantic and its closure induced water mass restriction and stratification in the western medi terranean immediately prior to the messinian salinity crisis abstract messinian marine deposits of the guadalhorce river valley in southern spain record evidence of the last northern gateway that existed between the mediterranean and the atlantic they comprise sandstones and conglomerates with unidirectional cross bed sets up to nearly 1 km long in their down sedimen tary dip direction these cross bed sets relate to extremely fast 1 0 1 5 m s 1 bottom currents flowing from the mediterra nean into the atlantic the guadalhorce gateway which had a maximum width of 5 km and a maximum water depth of 120 m was an important element controlling the messinian pre evaporitic oceanic circulation in the mediterranean sea as it acted as a major outflow channel its closure limited the exchange of water between the atlantic and the mediterranean to the rifian corridors of morocco inducing water mass restriction and stratification in the western mediterranean immediately prior to the messinian salinity crisis

the north anatolian fault zone and the role of fluids in seismogenic deformation a study of the north anatolian fault zone turkey in dicates significant spatial variations of deformation mechanisms and fluid flow along and across a major active strike slip fault brittle deformation and later dissolution are mostly localized within the fault core whereas crystal plastic deformation and diffusive mass transfer are more widely distributed the fault underwent a three stage development i repeated episodes of frictional failure pressure solution fluid migration and subsequent healing cataclasites and veins were formed during this stage we propose that the episodic events are associated with open and closed fluid systems during seismogenic cycles the progressive brittle failure led to stage ii a more open system with increasing dilation connected with dissolution the dramatic increase of dissolution processes terminated the episodic character of deformation and marked the beginning of a stage iii mostly characterized by diagenetic processes the fluid regime is now an op

mediterranean outflow mixing and dynamics the mediterranean sea produces a salty dense outflow that is strongly modified by entrainment as it first begins to descend the continental slope in the eastern gulf of cadiz the current accelerates to 1 3 meters per second which raises the internal froude number above 1 and is intensely turbulent through its full thickness the outflow loses about half of its density anomaly and roughly doubles its volume transport as it entrains less saline north atlantic central water within 100 kilometers downstream the current is turned by the coriolis force until it flows nearly parallel to topography in a damped geostrophic balance the mixed mediterranean outflow continues westward slowly descending the continental slope until it becomes neutrally buoyant in the thermocline where it becomes an important water mass

linking high grade gold mineralization to earthquake induced fault valve processes in the porgera gold deposit papua new guinea processes responsible for high grade gold enrichment are of significant economic interest and have long been elusive structural and geophysical models postulate that earthquake induced fault valve processes are frequently responsible for gold mineralization in structurally controlled hydrothermal systems although a comprehensive geochemical record of these processes has been lacking the porgera gold deposit papua new guinea provides an opportunity to examine the complex processes surrounding high grade au mineralization in structurally controlled hydrothermal systems new high resolution trace element and sulfur isotope data obtained in situ by laser ablation inductively coupled plasma mass spectrometry and sensitive high resolution ion microprobe stable isotope analysis of pyrite across a well constrained paragenetic sequence reveal a temporal evolution in fluid chemistry the data uncover a stratigraphy of repeated high au negative 34 s and low au positive 34 s zones within individual pyrite crystals present in the highest grade gold event stage ii results provide the first clear geochemical documentation of rapid complete switching in ore forming processes preserved in individual pyrite crystals throughout an evolving hydrothermal system it is postulated that geochemical variations are attributable to rapid au deposition during pressure release due to fault failure followed by switching to more reduced rock buffered metal poor fluids from adjacent sediments as the rupture seals the cyclicity of this process is reflected in the pyrite zonation seen at the porgera deposit this study demonstrates the usefulness of applying contemporary analytical techniques to pyrite in hydrothermal systems to gain new insights into ore genesis and fluid pathways revealing that deposition of exceptionally high grade ore at the porgera deposit was the result of multiple events in a fluctuating ore forming environment

geomorphology of the iberian continental margin abstract the submarine features and processes around the iberian peninsula are the result of a complex and diverse geological and oceanographical setting this paper presents an overview of the seafloor geomorphology of the iberian continental margin and the adjacent abyssal plains the study covers an area of approximately 2 3 million km 2 including a 50 to 400 km wide band adjacent to the coastline the main morphological characteristics of the seafloor features on the iberian continental shelf continental slope continental rise and the surrounding abyssal plains are described individual seafloor features existing on the iberian margin have been classified into three main groups according to their origin tectonic and or volcanic depositional and erosional major depositional and erosional features around the iberian margin developed in late pleistocene holocene times and have been controlled by tectonic movements and eustatic fluctuations the distribution of the geomorphological features is discussed in relation to their genetic processes and the evolution of the margin the prevalence of one or several specific processes in certain areas reflects the dominant morphotectonic and oceanographic controlling factors sedimentary processes and the resulting depositional products are dominant on the valencia catalan margin and in the northern part of the balearic promontory strong tectonic control is observed in the geomorphology of the betic and the gulf of cadiz margins the role of bottom currents is especially evident throughout the iberian margin the galicia portuguese and cantabrian margins show a predominance of erosional features and tectonically controlled linear features related to faults

climatically driven changes in sediment supply on the sw iberian shelf since the last glacial maximum the assemblages of marine sediments on the sw iberian shelf have been controlled by contributions from distinct sources which have varied in response to environmental changes since the last glacial maximum lgm the rapid decadal scale mediterranean overturning circulation permits mixing of suspended particles from the entire mediterranean sea they are entrained into the suspended particulate matter spm carried by mediterranean outflow water mow which enters the eastern north atlantic through the strait of gibraltar and spreads at intermediate depths in the gulf of cadiz and along the portuguese continental margin other major sediment sources that have contributed to the characteristics and budget of spm along the flow path of mow on the sw iberian shelf are north african dust and river transported particles from the iberian peninsula to reconstruct climate and circulation driven changes in the supply of sediments over the past 23 000 cal yr b p radiogenic nd sr and pb isotope records of the clay size sediment fraction were obtained from one gravity core in the gulf of cadiz 577 m water depth and from two gravity cores on the portuguese shelf 1745 m 1974 m water depth these records are supplemented by time series analyses of clay mineral abundances from the same set of samples contrary to expectations the transition from the lgm to the holocene was not accompanied by strong changes in sediment provenance or transport whereas heinrich event 1 h1 and the african humid period ahp were marked by significantly different isotopic signatures reflecting changes in source contributions caused by supply of ice rafted material originating from the north american craton during h1 and diminished supply of saharan dust during the ahp the data also reveal that the timing of variations in the clay mineral abundances was decoupled from that of the radiogenic isotope signatures

large scale sediment bodies and superimposed bedforms on the continental shelf close to the strait of gibraltar interplay of complex oceanographic conditions and physiographic constraints a previously unknown field of large scale sedimentary bodies has been mapped and studied on the continental shelf off the cape trafalgar near the strait of gibraltar with particular emphasis on the relationship between large scale sediment bodies and the superimposed bedforms this study is based on a grid of 975 km of high resolution seismic profiles collected at water depths ranging between 15 and 60 m high variability of large scale sedimentary bodies is attributed to the complex interaction of hydrodynamic agents the most prominent sedimentary features are sand banks and ridges that indicate long term southwest and southward directed sediment transport patterns possibly due to the interplay of two dominant current systems flowing southward and westward these sediment bodies evolve laterally to distinct external geometries such as sand shoals in shallow water and sand sheets in the vicinity of larger sand banks that indicate moderate current velocities in addition pre existing physiography is considered to play a role in the generation of certain sediment bodies developed over inclined surfaces or confined laterally by elevations relationships between superimposed bedforms mostly very large dunes and underlying sediment bodies vary across the study area most superimposed bedforms occur over the complex mosaic of sediment banks and sheets suggesting the interaction of several high energy currents with different directions such as tidal and or wind driven currents copyright 2010 john wiley sons ltd

sedimentary and tectonic evolution of the southern qiangtang basin implications for the lhasa qiangtang collision timing the mesozoic stratigraphic record of the southern qiangtang basin in central tibet records the evolution and closure of the bangong nujiang ocean to the south the jurassic succession includes toarcian aalenian shallow marine limestones quse formation aalenian bajocian feldspatho litho quartzose to feldspatho quartzo lithic sandstones shallow marine sewa formation and deep sea gaaco formation and bathonian outer platform to shoal limestones buqu formation this succession is truncated by an angular unconformity overlain by upper bathonian to lower callovian fan delta conglomerates and litho quartzose to quartzo lithic sandstones biluoco formation and callovian shoal to outer platform limestones suowa formation sandstone petrography coupled with detrital zircon u pb and hf isotope analysis indicate that the sewa and gaaco formations contain intermediate to felsic volcanic detritus and youngest detrital zircons 183 170 ma with ehf t ranging widely from 13 to 25 pointing to continental arc provenance from igneous rocks with mixed mantle and continental crust contributions an arc trench system thus developed towards the end of the early jurassic with the southern qiangtang basin representing the forearc basin above the angular unconformity the biluoco formation documents a change to dominant sedimentary detritus including old detrital zircons mainly 500 ma ages in the lower part of the unit with age spectra similar to those from paleozoic strata in the central qiangtang area a major tectonic event with intense folding and thrusting thus took place in late bathonian time 166 1 ma when the qiangtang block collided with another microcontinental block possibly the lhasa block

the porgera gold deposit papua new guinea the gold deposit at porgera is located in the highlands of papua new guinea alluvial gold was first recognized in 1939 but systematic exploration did not begin until 1961 the middle miocene porgera intrusive system which was derived from melting of thickened crust was emplaced within late cretaceous sediments on the northern margin of the papuan platform about 25 km south of the central orogenic belt mineralization is associated with several medium to fine grained high level porphyritic intrusions of mafic diorite composition with alteration assemblages of calcite dolomite chlorite and sericite plus subordinate clays and quartz sediments on the margin of the intrusions are also altered sulfide mineralization consisting of pyrite sphalerite and galena is hosted by both igneous and sedimentary rocks and occurs as veins disseminations and breccia matrix the distribution of sulfides hydrothermal alteration and associated gold and silver mineralization are largely a function of the intensity and extent of fracturing which is best developed at intrusive contacts and in breccias most of the gold mineralization is hosted by sulfides in particular pyrite and arsenical pyrite about 60 percent of the gold is apparently submicroscopic and not readily recoverable on the basis of the au ag cu zn and pb contents of drill core samples five mineralization types have been defined they reflect several episodes of gold mineralization from older highly refractory to younger less refractory types although overprinting is evident discrete zones dominated by one mineralization type occur and commonly transgress rock types and alteration assemblages subdivision of the deposit on the basis of mineralization type and the use of geostatistical procedures has resulted in improved precision of reserve estimates

deciphering bottom current velocity and paleoclimate signals from contourite deposits in the gulf of cadiz during the last 140 kyr an inorganic geochemical approach contourites in the gulf of cadiz gc preserve a unique archive of mediterranean outflow water mow variability over the past 5 3 ma in our study we investigate the potential of geochemical data obtained by xrf scanning to decipher bottom current processes and paleoclimatic evolution at two different sites drilled during iodp expedition 339 through contourites in the northern gc site u1387 which is bathed by the upper mow core and site u1389 located more proximal to the strait of gibraltar the lack of major downslope transport during the pleistocene makes both locations ideally suited for our study the results indicate that the zr al ratio representing the relative enrichment of heavy minerals zircon over less dense alumnosilicates under fast bottom current flow is the most useful indicator for a semiquantitative assessment of current velocity although most elements are biased by current related processes the bromine br record representing organic content preserves the most pristine climate signal rather independent of grain size changes hence br can be used for chronostratigraphy and site to site correlation in addition to stable isotope stratigraphy based on these findings we reconstructed mow variability for marine isotope stages mis 1 5 using the zr al ratio from site u1387 the results reveal abrupt millennial scale variations of mow strength during greenland stadials gs and interstadials gi with strong mow during gs and glacial terminations and a complex behavior during heinrich stadials millennial scale variability persisting during periods of poorly expressed gs gi cyclicities implies a strong internal oscillation of the mediterranean north atlantic climate system

the betic orogen and the iberian african boundary in the gulf of cadiz geological evolution central north atlantic abstract the study of the gulf of cadiz on the basis of multichannel seismic profiles and wells illustrates the stratigraphy and tectonics the evolution of the southern iberian margins was more complex than in most north atlantic margins since it entailed several phases of rifting convergence and strike slip motions three main tectonic provinces surround the internal zones of the gibraltar arc orogenic belt these include in the iberian margin of the gulf of cadiz the flysch units of the campo de gibraltar complex the betic external zones and the neogene basins of the guadalquivir valley fault bounded blocks of flysch and subbetic units crops out over large areas of the southeastern iberian shelf the basement of the northwestern area in contrast is represented by the paleozoic rocks of the hercynian massif of iberia half graben structures determined the main structural trends of the margin during the mesozoic which were affected by inversion structures during the neogene compressional stages the mesozoic and lower cenozoic units are best observed in wells and seismic profiles from the northern area these units are either obscure below a thick olistostrome deposit or are absent in most of the rest of the gulf of cadiz seven lithoseismic units from triassic to upper oligocene and another seven neogene and quaternary units are identified based on the relationship to the depositional sequence and the emplacement of the olistostrome the first tectonic phase was characterized by a passive margin which was controlled by the development of half graben extensional structures and carbonate platforms this evolution comprises the mesozoic and early cenozoic ocean spreading in the north atlantic induced extensional tectonics which deformed the cretaceous syn tectonic post aptian deposits increased amounts of terrigenous materials were supplied to the margin from aptian to albian times controlling depositional patterns while terrigenous siliciclastic facies replaced the jurassic carbonate platforms from middle eocene to early miocene the margin was influenced by the relative motions of iberia and africa and the development of the alpine orogeny the iberian african boundary in the gulf of cadiz experienced transpression and the mesozoic basins probably underwent subduction the emplacement of an olistostrome took place in the gulf of cadiz towards the central atlantic basin plains during the tortonian the end of the olistostrome emplacement during the late miocene coincides with accelerated tectonic subsidence while thick progradational and aggradational depositional sequences were developed the occurrence of closely juxtaposed regions of compression and extension during the miocene may reflect the westwards progression of the gibraltar arc mountain front over a subducting thinned tethys crust when the motion between iberian and africa was n s to nnw sse oriented the migration of the arcuate mountain front into the eastern gulf of cadiz is attributed to a mechanism of collision induced delamination of the mantle lithosphere in contrast to the betic rif belts however there is no geophysical evidence to postulate that continental collision took place in the gulf of cadiz during the cenozoic

interaction of tectonic and depositional processes that control the evolution of the iberian gulf of cadiz margin abstract this study provides an integrated view of the growth patterns and factors that controlled the evolution of the gulf of cadiz continental margin based on studies of the tectonic sedimentologic and oceanographic history of the area seven sedimentary regimes are identified but there are more extensive descriptions of the late cenozoic regimes because of the larger data base the regimes of the mesozoic passive margin include carbonate platforms which become mixed calcareous terrigenous deposits during the late cretaceous early tertiary the oligocene and early miocene terrigenous regimes developed in contrast over the active and transcurrent margins near the african iberian plate boundary the top of the gulf of cadiz olistostrome emplaced in the late miocene is used as a key horizon to define the post orogenic depositional regimes the late miocene progradational margin regime is characterized by a large terrigenous sediment supply to the margin and coincides with the closing of the miocene atlantic mediterranean gateways the terrigenous drift depositional regime of the early pliocene resulted from the occurrence of high eustatic sea level and the characteristics of the mediterranean outflow currents that developed after the opening of the strait of gibraltar the late pliocene and quaternary regimes are dominated by sequences of deposits related to cycles of high and low sea levels deposition of shelf margin deltas and slope wedges correlate with regressive and low sea level regimes caused by eustasy and subsidence during the highstand regimes of the holocene inner shelf prograding deltas and deep water sediment drifts were developed under the influence of the atlantic inflow and mediterranean outflow currents respectively a modern human cultural regime began 2000 years ago with the roman occupation of iberia human cultural effects on sedimentary regimes may have equalled natural factors such as climate change interplay of tectonic and oceanographic controls dominated the evolution of the cadiz margin during the cenozoic depositional sequences formed where the tectonic setting provided the accommodation space and the shape of the deposits has been greatly influenced by the strong unidirectional atlantic inflow currents on the shelf and mediterranean outflow currents on the slope the entire cycle of the inflow and outflow deposition along the margin has been controlled first by the tectonic evolution of the betic and rif gateways which become closed during the late miocene and after the messinian by the opening of the strait of gibraltar strong current development during eustatic sea level highstands of the pliocene and quaternary has controlled deposition because of maximum sill depths at gibraltar for water circulation lowstand sea levels slowed circulation and resulted in mud drapes over the slope and regressive stratigraphic sequences over the shelf more recently the human industrial revolution has caused heavy metal contamination of sediment and water over the cadiz margin human activity also has affected sedimentation rates because of deforestation that caused increased depositional rates near undammed rivers and decreased rates where rivers have been dammed future research efforts will need to focus on 1 the effect of increased mediterranean outflow caused by river damming plus global warming and the increased outflow as a potential trigger for new ice ages 2 assessments of geologic hazards for planning man made shoreline structures developing offshore petroleum resources and maintaining undersea communications cables and 3 confirmation of the general geologic history of the cadiz margin

headland associated banner banks generated during the last deglaciation near the strait of gibraltar gulf of cadiz sw spain the inception and evolution of large scale bedforms on the barbate platform gulf of cadiz sw iberian peninsula are investigated based on a detailed study of multibeam bathymetric data high resolution seismic profiles and tidal current simulations elongated rocky outcrops and several large scale bedforms classified as sand banks were identified on the platform barbate zahara el palmar el varadero and canos de meca banks the barbate and zahara banks exhibit the most complex internal stratigraphic architecture which comprises five seismic units the basal unit u1 is interpreted as incised valley infill and is overlain by nearshore bars u2 two high energy growth phases u3 and u4 that combine progradation and accretion form the present day external bank shape superimposed bedforms covered these banks under the modern hydrodynamic regime u5 the multiphase accretion and progradation of u3 and u4 in the zahara and barbate banks were closely linked to the presence of a palaeo headland termed here as palaeo cape trafalgar and strong tidal current eddies that resulted from the progressive flooding of the barbate platform during the last deglaciation this configuration was relatively stable while the rocky outcrops were exposed to sub aerial conditions forming a palaeo coast with coastal bluffs we suggest that during this period of coastal stabilization u3 and u4 grew as banner banks on either side of the palaeo cape trafalgar the present study proposes that the configuration of palaeo headland associated with palaeo banner banks zahara and barbate banks along each side of the palaeo cape trafalgar represents a transgressive analogue model of headland associated tidal bank systems developed in funnel shaped coastal systems terminating in narrow straits

high resolution seafloor images in the gulf of cadiz iberian margin in the gulf of cadiz the hydrodynamic process acting on particle transport and deposition is a strong density driven bottom current caused by the outflow of the saline deep mediterranean water at the strait of gibraltar the mediterranean outflow water mow new high resolution acoustic data including em300 multibeam echo sounder deep towed acoustic system sar and very high resolution seismic completed by piston cores collected during the cadisar cruise allow to improve the understanding of the hydrodynamics of the mow in the eastern part of the gulf of cadiz interpretation of data corrects the previous model established in this area and allows for the first time the accurate characterization of various bedforms and erosive structures along the mow pathway and the precise identification of numerous gravity instabilities the interaction between the mow the seafloor morphology and the coriolis force is presently the driving force of the sedimentary distribution pattern observed on the gulf of cadiz continental slope

the sedimentary record of the post glacial transgression on the gulf of cadiz continental shelf southwest spain abstract four seismic units ta to td have been identified from the analysis and interpretation of high resolution seismic profiles in a sector of the gulf of cadiz shelf they constitute a composite seismic unit attributed to the transgressive systems tract tst of the last depositional sequence the earliest transgressive unit was deposited on the outer shelf and represents the distal facies of a coastal deposit a process of shelf partitioning seems to have occurred during the formation of the three later transgressive parasequences the shelf sector offshore from the guadiana river mouth was a high energy environment dominated by storm events by contrast the shelf sector offshore from the donana national park was a low gradient shelf where large barrier island and lagoon systems were formed the sparse occurrence of marine deposits within the tst is a consequence of the episodic nature of the sea level rise the generation and preservation of these transgressive deposits results from the interaction of the following controlling processes 1 relative sea level rise the formation of coastal transgressive deposits is related to intervals of reduced sea level rise or stillstands within a period of continuous sea level rise those sea level changes were probably driven by short term periods of colder climate during the late pleistocene holocene deglaciation the younger dryas interval is the most widely recognised climatic event of this type but probably other events of similar characteristics had the same effect on the glacio eustatic sea level rise 2 sediment supply changes short lived climatic events probably also involved changes in the sediment supply to the continental shelf due to changes in erosion rates and river regimes of the river basin hinterlands 3 effect of the paleophysiography paleogeography the sedimentary environments differentiation processes are associated to the formation of an exposed coastal promontory offshore from the guadiana river mouth and a semi protected embayment offshore from donana national park this coastal configuration was controlled by previous tectonic evolution and influenced the non uniform landward migration of the coastline