late messinian to early pliocene paleoenvironmental changes in the melilla basin ne morocco and their relation to mediterranean evolution abstract three major paleoenvironmental changes have been recognized during the late miocene to early pliocene in the melilla basin northeastern morocco and compared with the regional events that affected the mediterranean hydrology during this crucial period the first change was the definitive conversion of the restricted marine conditions that prevailed since the end of the reef carbonate complex into lacustrine environments this occurred around 5 8 ma which is earlier than in the rest of the mediterranean where the lower evaporites were still forming these lacustrine settings display great similarities with the lago mare environments that started in the mediterranean during the deposition of the upper evaporites and climaxed during the latest messinian the second change corresponds to a long period of subaerial exposure that caused a widespread erosional surface this resulted in a deep paleovalley which truncates the messinian sedimentary succession of the deeper southwestern part of the basin this event postdates a lava flow dated at 5 77 ma and confirms the importance of the latest messinian erosional event the third change was the infilling of this topography by marine sediments when the basin was rapidly reflooded in early pliocene the lack of evaporites indicates that the melilla basin did not experience the messinian salinity crisis this could be explained either by the drainage of the brines towards the deeper south alboran basin or rather by an early dilution of the basin due to local excess of continental water inputs while most of the other mediterranean basins evolved at the same time into evaporitic settings these data confirm that the rifian gateway was completely closed thus preventing atlantic water inputs in the mediterranean during the whole evaporitic deposition and the lago mare episode such an evolution fits well with the history of depositional environments in the alboran domain where evaporites are poorly developed and the messinian is mainly represented by an erosional surface

40ar 39ar dating of the pre evaporitic messinian marine sequences of the melilla basin morocco a proposal for some biosedimentary events as isochrons around the alboran sea in the mediterranean region the melilla basin ne morocco represents a key area that recorded biosedimentary events and environmental changes relative to the pre evaporitic messinian times 40ar 39ar dating of volcanic tuffs interbedded all along the melilla messinian shelf carbonates and coeval basin deposits has been performed in order to date accurately three main pre evaporitic biosedimentary events the prograding bioclastic deposition and the oligospecific prograding porites coral reef buildings with coeval halimeda blooms both within the platform and the diatomite deposition basinward the new age data allow a precise chronological framework to be established for the pre evaporitic sequence of melilla basin demonstrating that diatomitic deposits are coeval with both prograding bioclastic and reefal units the prograding bioclastic carbonate unit related to boreal influences in coeval basinal diatomites began at least at 6 73 0 02 ma and ended at 6 46 0 03 ma the oligospecific prograding porites coral reefs and halimeda beds and coeval warm water diatomites began at least at 6 46 0 03 ma previous 40ar 39ar ages indicate that they ended prior to 6 0 0 1 ma both biosedimentological similarities and chronological accordance within several platforms and adjacent basins all around the alboran sea show that these main bioevents dated in melilla are synchronous over the alboran realm this accurate time scale for these pre evaporitic biosedimentary events 6 9 6 0 ma is in accordance with the most recent work on the latter period corresponding to the messinian salinity crisis

controls on facies and sequence stratigraphy of an upper miocene carbonate ramp and platform melilla basin ne morocco abstract upwelling of cool seawater paleoceanographic circulation paleoclimate local tectonics and relative sea level change controlled the lithofacies and sequence stratigraphy of a carbonate ramp and overlying platform that are part of a temporally well constrained carbonate complex in the melilla basin northeastern morocco at melilla from oldest to youngest a third order depositional sequence within the carbonate complex contains 1 a retrogradational transgressive warm temperate type rhodalgal ramp 2 an early highstand progradational bioclastic platform composed mainly of a temperate type bivalve rich molechfor facies and 3 late highstand progradational to downstepping subtropical tropical type chlorozoan fringing porites reefs the change from rhodalgal ramp to molechfor platform occurred at 7 0 0 14 ma near the tortonian messinian boundary during a late stage in the development of the bioclastic platform a transition from temperate type molechfor facies to subtropical tropical type chlorozoan facies occurred and is bracketed by chron 3an 2n 6 3 6 6 ma comparison to a well dated carbonate complex in southeastern spain at cabo de gata suggests that upwelling of cool seawater influenced production of temperate type limestone within the ramp and platform at melilla during postulated late tortonian early messinian subtropical tropical paleoclimatic conditions in the western paleo mediterranean region the upwelling of cool seawater across the bioclastic platform at melilla could be related to the beginning of siphoning of deep cold atlantic waters into the paleo mediterranean sea at 7 17 ma the facies change within the bioclastic platform from molechfor to chlorozoan facies may be coincident with a reduction of the siphoning of atlantic waters and the end of upwelling at melilla during chron 3an 2n the ramp contains one retrogradational parasequence and the bioclastic platform three progradational parasequences minor erosional surfaces that bound the upper surface of the ramp and upper surface of the oldest platform parasequence are related to relative falls in sea level induced by local volcanism and associated tectonic uplift these local relative falls had little influence on a broader scale rise to stillstand in relative sea level that controlled development of the transgressive and early highstand systems tracts represented in the ramp and platform respectively

eustatic implications of late miocene depositional sequences in the melilla basin northeastern morocco abstract the age 5 78 ma or lower chron c3r of the major drawdown of the paleo mediterranean sea during the messinian salinity crisis has been established by combining results from stratigraphy paleontology magnetostratigraphy and argon dating for a late miocene sedimentary succession in the melilla basin ne morocco this event is inferred from a marine to continental series of carbonate and siliciclastic rocks that record the end of messinian marine deposition in the melilla basin and presumably marks the final isolation of the paleo mediterranean sea the evidence from the melilla basin is approximately coeval with an increase in benthic foraminiferal 18 o values from a deep marine section in the bou regreg valley nw morocco hodell et al 1994 this increase suggests that a glacio eustatic lowering of sea level at least contributed to the final closure of the mediterranean during the messinian salinity crisis the marine to continental succession onlaps a carbonate complex that contains evidence for multiple relative sea level changes leading up to the main drawdown from bottom to top the carbonate complex is composed of 1 an onlapping ramp 2 a prograding bioclastic platform 3 a prograding and locally downstepping porites reef complex and 4 a topography draping sequence composed of grainstones porites reefs and stromatolites terminal carbonate complex of esteban 1979 the transgressive ramp correlates to relatively low values of benthic foraminiferal 18 o values from a tortonian to lower messinian section at bou regreg hodell et al 1994 this correlation indicates at least in part a link between rising sea level and a reduction in global ice volume during deposition of the ramp a major fall in relative sea level 60 m occurred near the demise of the reef complex during chron c3n 1n at 5 95 0 10 ma this signals the initiation of drawdown and changing environmental conditions in the melilla basin a marginal basin and perhaps the entire paleo mediterranean sea a megabreccia interpreted as forming by solution collapse of evaporites on the basin margin of the reef complex occurs at the base of the terminal carbonate complex updip a major subaerial unconformity separates the reef complex and terminal carbonate complex evaporite deposition likely occurred during this exposure event and has been dated at 5 82 0 02 ma near the base of chron c3r we contend that these evaporites restricted to the shallow melilla basin are related to the continuation of the initial stage of the major drawdown of the paleo mediterranean sea

the late messinian erosional surface and the subsequent reflooding in the mediterranean new insights from the melilla nador basin morocco new field investigations in the cape des trois fourches peninsula northern morocco allow us to bring new insights on the late messinian erosional surface and the overlying marine deposits our results show that the late messinian erosional surface characterized by an erosional plateau is interrupted by an up to 70 m deep paleovalley thought to result from a landslide the minimum relative sea level drop is 70 m probably much more with regard to the indication that a large scale landsliding has occurred the post erosional deposits cycle 3 comprise one major depositional sequence composed of two high order sedimentary subcycles deposits of the first subcycle 3a filled in the erosional basin and the paleovalleys deposits of the second subcycle 3b overflowed the paleovalleys and the erosional plateau we found evidence of the transgressive systems tract of the deposits corresponding to the post messinian crisis reflooding for which a latest messinian onset can neither be proved nor entirely ruled out because the rare biostratigraphic data are not sufficiently conclusive the uppermost part of the reflooding deposits subcycle 3a is shown to be definitely pliocene in age based on the occurrence of globorotalia puncticulata and the composition of the assemblage of pectinids

onshore to offshore reconstruction of the messinian erosion surface in western sardinia italy implications for the messinian salinity crisis new outcrops in the sinis peninsula sardinia italy allow a detailed description of the messinian erosion surface the correlation between outcrops industrial seismic data and data collected offshore oristano from a recent cruise permits reconstruction of the geometry of this surface from presently emerged interfluves to the deep canyons offshore with onshore an eroded karstic plateau presently cropping out over a 20 km 5 km area well preserved karst structures occur locally and can form several metres high reliefs the southernmost edge of the plateau is limited by a cliff the karstic plateau and the cliff are sealed by transgressive deposits of pliocene age offshore an interfluve zone with a mostly flat and low angle dipping plateau westward dissected by paleovalleys which were identified down to a depth of 2000 m in the oristano gulf messinian paleovalleys were also identified the capo san marco paleocliff was probably located on the edge of a canyon onshore only one major erosion surface was identified located at the top the messinian sequence offshore this surface extends down to the abyssal plain the surface was emplaced above deposits related to the terminal carbonate complex this indicates that the marginal evaporites are older than the major drawdown of the mediterranean sea level the major drawdown is related to the deposition of the deep evaporites

thrust top lacustrine lagoonal basin development in accretionary wedges late messinian lago mare episode in the central apennines italy abstract we analysed in detail the geometry sedimentology and palaeontology both mollusc and ostracod assemblages of a small lacustrine lagoonal basin located at about 1100 m a s l in the marsica region of the apennines at le vicenne locality l aquila abruzzo central italy the structure of the basin infill deposits outlines an open syncline with an e w axis polygenic conglomerates interbedded with clay levels and sandy marls which constitute roughly coarsening upward progradational sequences are the dominant lithologies these sequences are interpreted as lacustrine to coastal lagoon deposits with episodic fan delta supplies this sedimentological interpretation is also supported by mollusc and ostracod assemblages which suggest that the sedimentary environment was characterized by a mesohaline closed water body with salinity probably ranging from 10 to 13 both mollusc and ostracod assemblages show a clear paratethyan influence in the ostracod assemblage ten species out of the fourteen collected forms belong to the loxoconcha djaffarovi zone as defined by carbonnel 1978 thus it is possible to refer the siltitic clayey intercalations of le vicenne to the top of the messinian post salinity crisis the presence of a strong angular unconformity at the base of the basin together with the structural setting of its deposits suggesting a light compressive deformation are common features in all the thrust top basins recognized in the central apennines taking into account the regional data the age of the youngest deposit involved in the substratum siliciclastic turbidites which recorded the messinian salinity crisis and the palaeobiological indications given by the mollusc and ostracod assemblages it is possible to constrain the origin of the le vicenne basin to the messinian lago mare early pliocene tectono sedimentary event of the apennines the recognition in the marsica range of this thrust top basin allows us to attempt a palinspastic reconstruction locating the marsica region in the latest miocene early pliocene active thrust zone of the apennine accretionary wedge

ground penetrating radar for assessing winter roads abstractsince its inception ground penetrating radar gpr has been a very effective method for examining ice structure the vast majority of early gpr use was focused on answering questions related to glaciology and ice sheets more recently as more and more activity occurs in arctic areas managing ice structures for a variety of applications has created new uses for gpr for the past 30 40 years gpr use for assessing transportation routes over lakes rivers and sea ice has been reported but only in the last decade has routine application occurred we have focused on the application of gpr for winter road safety explained the operational requirements discussed the current state of practice and illustrated modern gpr instrumentation based on widespread field observations we have provided information on the ice layer thickness variation and the variability on gpr ice bottom reflection combining extensive gpr and ice auger data provided insight into the variability of electromagnetic wave veloc

a critical re evaluation of the miocene pliocene boundary as defined in the mediterranean abstract a critical re evaluation of the miocene pliocene m p boundary as defined informally in the mediterranean is presented we show that ages reported earlier for this boundary ranging from 4 81 to 4 93 ma do not imply any diachroneity of the basal zanclean lithohorizon which reflects the pliocene flooding of the mediterranean and defines the m p boundary these ages most likely represent an artefact resulting from intraformational variations in sedimentation rate and inconsistent interpretation of coluor variations in terms of sedimentary cycles the best estimate for the age of this boundary arrives at 4 86 ma if the conventional geomagnetic polarity time scale gpts of berggren et al 1 is used and at 5 16 ma if the new gpts of cande and kent 2 is used an age of 5 32 ma is obtained if the astronomically calibrated time scale of hilgen 3 is adhered to because of its presumably global paleoclimatological significance the m p boundary as currently defined in the mediterranean is preferred to a redefinition of this boundary at the gilbert chron 5 boundary in a continous open marine sequence outside the mediterranean in addition this redefinition would lead to unnecessary confusion in global chronostratigraphy

a late messinian brackish water ostracod fauna of paratethyan aspect from le vicenne basin abruzzi central apennines italy abstract in the lower portion of the sedimentary succession of the le vicenne basin abruzzi central italy 8 m of siltitic clays crop out which bear a rich ostracod association in which the following fourteen taxa have been collected candona camptocypria cf c c venusta zalanyi candona camptocypria sp leptocythere idonea mandelstam markova rozyeva and stepanajtys leptocythere multituberculata livental leptocythere palimpsesta livental leptocythere propinqua livental euxinocythere maeotocythere praebaquana livental tyrrhenocythere pontica livental tyrrhenocythere ruggierii devoto cyprideis agrigentina decima cyprideis aff c tuberculata mehes loxoconcha eichwaldi livental loxoconcha sp and loxoconcha cf l ludica olteanu the composition of the ostracod fauna shows a remarkable paratethyan influence ten species out of twelve are characteristic of the paratethys domain and among those leptocythere multituberculata leptocythere idonea and loxoconcha cf l ludica are recorded for the first time in italy on the basis of comparison with similar ostracod assemblages found in the mediterranean basin spain corsica france greece the le vicenne association has been referred to the loxoconcha djaffarovi zone carbonnel 1978 correlated with the uppermost messinian during this time interval the mediterranean basin was characterized by several isolated shallow water brackish basins which reproduced the environmental conditions existing in the paratethyan domain during the neogene the existence of these widespread brackish water bodies favoured the westward migration of the paratethyan ostracod faunas and their colonization of the western tethys domain

upper miocene molluscs of monti livornesi tuscany italy biotic changes across environmental gradients abstract the upper miocene mollusc assemblages of monti livornesi used as a means to study the nature of mediterranean benthic communities at the edge of the messinian salinity crisis are framed in a high resolution stratigraphic scheme and quantitatively approached by the study of historical museum collections and modern samples instead of a single assemblage from either tortonian or messinian age as previously thought this fauna comes from three consecutive shallowing upward depositional sequences bounded by regional unconformities the luppiano upper tortonian lowermost messinian rosignano and raquese units early messinian facies analysis taphonomy and quantitative paleoecology show that the luppiano assemblage is characterised by aragonitic species from a eutrophic brackish water shallow marine muddy bottom the rosignano assemblage by calcitic species from an oligotrophic coarse grained seafloor close to a coral reef and the raquese assemblage from an open marine muddy bottom published comparisons between miocene and pliocene faunal lists should be considered only crude estimates of faunal change until more is known about the distribution of species along paleoenvironmental gradients the analysis of miocene and pliocene abundance data allows us to frame the monti livornesi molluscs along carbonate siliciclastic and water depth gradients and to reach a better understanding of the effects of salinity crisis on the mediterranean biota

reconstruction of the paleoenvironmental changes around the miocene pliocene boundary along a west east transect across the mediterranean abstract in order to reconstruct the environmental changes at the end of the messinian salinity crisis a multidisciplinary study has been carried out with a high sampling resolution of the late messinian early zanclean zone mpl 1 sediments along a west east mediterranean transect the studied examples comprise sections from southern spain vera almanzora balearic basin odp site 975 tyrrhenian basin odp site 974 sicily eraclea minoa zakynthos kalamaki corfu aghios stefanos crete aghios vlasis previously analyzed sections from the levantine basin cyprus and odp sites 968 and 969 are used for comparison the sections have been correlated using planktonic foraminiferal assemblages sedimentological and stable isotope variations and compared to the astronomical cyclicity defined in the miocene pliocene boundary stratotype of eraclea minoa sicily variations of caco3 content stable isotopes of carbonates 18o 13c and foraminiferal assemblages indicate similar environmental transition at the miocene pliocene boundary in all of the investigated sections the latest messinian deposits are barren of fossils or characterized by only reworked planktonic foraminifers except for the sporadic presence of ammonia tepida brackish or lacustrine ostracods and brackish mollusks typical of the lago mare facies the oxygen and carbon isotopic compositions of carbonates usually exhibit large variations with dominantly low values indicating freshwater dilution the earliest pliocene mpl 1 cycle 1 shows a rapid and progressive increase of the 18o values which indicates the restoration of marine conditions after the lago mare event normal marine environments were definitely established and stabilized at the top of cycle 1 these data confirm that the inflow of marine waters occurred contemporaneously within the whole mediterranean at the base of pliocene although stable marine conditions occurred only about 20 kyrs later

astrochronology for the messinian sorbas basin se spain and orbital precessional forcing for evaporite cyclicity the sorbas basin of se spain contains one of the most complete sedimentary successions of the mediterranean reflecting the increasing salinity during the messinian salinity crisis a detailed cyclostratigraphic study of these successions allows a correlation of the sedimentary cycle patterns to astronomical target curves here we present an astrochronological framework for the messinian of the central part of the sorbas basin this framework will form a solid basis for high resolution correlations to the marginal carbonate facies and to the central mediterranean area the early messinian abad member contains 55 precession induced sedimentary cycles marked by homogeneous marl opalrich bed alternations in the lower abad and by homogeneous marl sapropel alternations in the upper abad astronomical tuning results in an age of 5 96 ma for the transition to the yesares evaporites and thus for the onset of the messinian salinity crisis the marl sapropel cycles of the upper abad are replaced by gypsum sapropel cycles 14 in the yesares member indicating that the evaporite cyclicity is related to precession controlled oscillations in circum mediterranean climate as well as a consequence gypsum beds correspond to precession maxima insolation minima and relatively dry climate sapropelitic marls to precession minima insolation maxima and relatively wet climate an alternative glacio eustatic obliquity control for evaporite cyclicity can be excluded because the number of sedimentary cycles with a reversed polarity is too high sedimentation during the abad yesares and the overlying coastal sequences of the sorbas member took place in a continuously marine environment indicating that marine conditions in the sorbas basin prevailed at least until 5 60 5 54 ma according to our scenario deposition of the yesares and sorbas member took place synchronously with deposition of the lower evaporites in the central mediterranean finally the continental zorreras member consists of 8 sedimentary cycles of alternating reddish silts dry climate and yellowish sands wet climate which correlates very well with the upper evaporites and lago mare facies of the mediterranean q 2001 elsevier science b v all rights reserved

messinian events new constraints from sedimentological investigations and new 40ar 39ar ages in the melilla nador basin morocco abstract new 40ar 39ar ages obtained both from within a platform and from the adjacent basin allow through the extension of a previous argon dataset the establishment of a chronological framework for the messinian carbonate complex of melilla morocco in the platform prograding bioclastic deposits began around 6 87 0 02 ma whereas the youngest preserved deposits are 5 77 0 04 ma old the southern part of the basin was uplifted and emergent prior to 6 23 0 03 ma the tortonian messinian and the messinian pliocene boundaries have not yet been identified in the melilla region durations of the prograding bioclastic deposits ca 410 ka the prograding porites reefs ca 360 ka and the preserved part of the terminal carbonate complex tcc ca 330 ka can be estimated sedimentological and geochronological investigations do not indicate any major subaerial unconformity nor any major time gap if a major sea level fall did exist during messinian times it developed after 5 77 0 04 ma chronological correlations show that the onset of the sorbas gypsum deposition southern spain considered as the marker of the messinian salinity crisis onset is contemporaneous with aggrading porites reef building of the terminal carbonate complex of melilla a major paleoceanographic change in the marginal areas of the mediterranean with the cessation of upwelling systems could be partly coeval with the onset of the messinian salinity crisis

late miocene events in the mediterranean as recorded by carbonate evaporice relations the messinian stage in the mediterranean region is known mainly because of a major evaporitic event whose causes and global implications are still under discussion correlations between basinal evaporite bearing series and marginal carbonate platforms allow for improvement of the classical depostional models especially concerning the eustatic control of the environmental changes in the mediterranean these changes were controlled by the interplay of aperiodic and periodic factors 1 tectonics related to the relative motions of the african and eurasian plates and resultant linear increase in the basin restriction 2 sea level fluctuations that alternately aggravated the restriction or allowed marine replenishment and 3 climatic fluctuations that controlled the level of the mediterranean during stages of isolation the messinian sedimentary succession reflects a typical sequence of progressive isolation marine marls yields laminites yields transitional deposits yields evaporites yields lacustrine deposits the first stage of the so called salinity crisis was characterized by a mediterranean lowstand that resulted in erosion of former platforms and deposition of the lower evaporites during the next stage sea level rose tb3 3 cycle high enough to temporarily replenish the basin cyclic upper evaporites with development of stromatolite rich deposits finally the uppermost messinian freshwater to brackish lacustrine deposits reflect both themore cessation of sea water input maximum tectonic isolation low sea level and freshwater input related to increasing runoff less

sedimentary and diagenetic markers of the restriction in a marine basin the lorca basin se spain during the messinian abstract the lorca basin southeastern spain is part of a chain of small marginal neogene basins located in the structurally active betic area the upper miocene messinian sequence is composed of a thick diatomite bearing series tripoli unit overlain by the main evaporites analogous to the classical succession that records the main events during the salinity crisis in the mediterranean region the shallow restricted conditions of this region amplified the sedimentary responses to local and global forcings an integrated approach using sedimentology micropalaeontology stable isotope geochemistry and organic geochemistry has been applied to the tortonian messinian succession of the lorca basin in order to obtain a continuous record of the environmental changes the sediments record two major events which affected the whole mediterranean 1 high levels of productivity that led to the formation of the diatomite bearing deposits in the early messinian tripoli and 2 the messinian salinity crisis with its two major stages represented by the halite and gypsum units both mainly precipitated from marine derived brines the rapid reflooding of the mediterranean by normal marine waters at the base of the pliocene did not reach the lorca basin nor other basins of this part of the betic area instead continental sediments were deposited as a consequence of the regional uplift of se iberia which started close to the messinian pliocene boundary the most prominent feature of this basin concerns the record of its restriction by the time of the deposition of the tripoli unit which led to intercalations of precursor evaporitic layers consisting of ca sulphate deposited in sub aqueous and sabkha conditions interbedded with diatomites this alternation of evaporites and diatomites proves that the lorca basin was periodically restricted and reflooded by marine waters a possible cause for this being relative sea level fluctuations in the mediterranean this strengthens evidence of diachronism that suggests that the onset of the first messinian evaporitic deposition was not synchronous but was dependent on bathymetry and local tectonics high productivity during the early messinian in this basin is demonstrated by the thick deposits of diatomites however stagnation episodes may have occurred during this interval as suggested by the preservation of high amounts of organic matter organic rich shales and the extent of bacterial sulphate reduction which apparently occurred during early diagenesis the formation of organo sulphur compounds replacement of sulphates by carbonates and the high levels of elemental sulphur are by products of diagenetic processes occurring in a restricted hypersaline environment

high frequency cyclicity in the latest messinian adriatic foreland basin insight into palaeoclimate and palaeoenvironments of the mediterranean lago mare episode abstract late messinian lago mare deposits show high frequency cyclicity in the whole mediterranean basin both millimeter and centimeter scale cyclicities have been observed in several odp sites as well as in stratigraphic sections from the mediterranean borderland we have analyzed a well exposed late messinian lago mare section from the adriatic side of the central apennines italy at the fonte dei pulcini section se majella mts millimeter and centimeter scale white and dark couplets have been observed in the field a 50 cm regular spaced sampling has been performed in the uppermost 53 m of the late messinian lago mare clays on the 107 collected samples geochemical caco 3 content mineralogical xrd analyses and micropalaeontological investigations have been performed in addition sem and microprobe investigations as well as mineralogical and micropalaeontological analyses have been carried out on single lamina from a 34 cm thick interval of millimeter scale laminites besides the 10 3 cycles m and 10 2 cycles m frequencies observed in the field spectral analyses performed on the caco 3 data set indicated other high frequency cyclicities 0 47 cycles m 0 35 cycles m and 0 17 cycles m taking into account the estimated sedimentation rate these frequencies correspond respectively to periodicities of 1 year 10 years 2 1 kyr 2 8 kyr and 5 6 kyr these sub milankovitch cyclicities have been related to annual and sunspot solar activity the millimeter scale couplets are interpreted as varves sedimented in an ephemeral water environment marginal to a perennial brackish water lagoonal basin these varved sediments reflect a marked seasonality characterized by the alternation of arid and more humid climatic phases the presence of high values of smectite 60 80 in the clay minerals of the analyzed samples could be a consequence of these climatic oscillations from drier to moister conditions the climatic scenario suggested in this paper for the late messinian lago mare episode is in agreement with the monsoon system that according to some authors starting from 5 8 ma developed in the mediterranean area

the record of the messinian salinity crisis in mobile belts insights from the molise allochthonous units southern apennines italy abstract mediterranean marginal basins recorded the messinian salinity crisis msc in various structural settings including syn rift thrust top foredeep and foreland basins during the msc the apennines were one of the mobile belts of the peri mediterranean chain starting from more hinterland areas allochthonous units of both the northern and southern apennines migrated toward the adriatic foreland developing allochthonous top sedimentary basins one of these basins on top of the molise allochthonous units southern apennines recorded almost all of the main steps of the msc in a gypsum quarry district the occurrence of conduits yielding flow mobilized sediments which cross cut the lower evaporites testifies to a fluid migration event responsible for the formation of a brecciated mudgrade limestone buildup this event can be connected with the mediterranean drawdown responsible for the messinian erosional surface mes the post evaporitic marly succession that unconformably overlies the lower evaporites and the brecciated limestones is characterized by the presence of paratethyan molluscs and ostracods loxoconcha muelleri and loxocorniculina djafarovi zones and small mammals among which is recorded the occurrence of stephanomys debruijni a disconformity within the post evaporitic succession divides it into lower p ev1 and upper p ev2 lago mare deposits a further erosional surface separates the messinian lago mare sediments from fully marine lower zanclean mpl2 zone deposits whilst the unconformity separating the lower evaporites and the lago mare deposits although enhanced by a tectonic event could be related to a late messinian base level drop mes1 as well as the disconformity between p ev1 and p ev2 mes2 the younger angular unconformities affecting both the lago mare deposits p ev2 and the fully marine pliocene sediments might be related to two different phases of orogenic transport those events affected the molise allochthonous units during their late miocene early pliocene forelandward migration

palaeoenvironments of the mediterranean basin at the messinian hypersaline hyposaline transition evidence from natural radioactivity and microfacies of post evaporitic successions of the adriatic sub basin at the end of the messinian salinity crisis changes in the palaeoceanography and palaeoclimate induced a transition from hypersaline to hyposaline conditions in the mediterranean water body detailed investigation of natural radioactivity and microfacies analyses of two early post evaporitic messinian sections show that the transition occurred in poorly oxygenated and well stratified water masses these transitional deposits which mainly consist of marls and caco3 rich horizons are generally well laminated and totally barren in benthic and planktonic fauna the presence of barite small 5 8 lm authigenic framboidal pyrite and high values of u indicate persistent anoxic conditions during the early postevaporitic messinian stage in the adriatic sub basin of the mediterranean sea the presence of post evaporitic welllaminated barren deposits from both mediterranean borderland sections and odp sites suggests that these anoxic conditions extended to other sub basins of the mediterranean region

magnetostratigraphic dating of an upper miocene shallow marine and continental sedimentary succession in northeastern morocco abstract a high resolution magnetostratigraphy has been developed for an upper miocene shallow marine carbonate complex equivalent basinal marls diatomites and lime mudstones and an overlying succession of marine to continental carbonate and siliciclastic sedimentary rocks in the melilla basin northeastern morocco units of the carbonate complex from bottom to top contain a bryozoan red algal ramp bioclastic platform fringing reef complex and a unit referred to as the terminal carbonate complex tcc 1 lithologies from these units contain at least three components of magnetic remanence 1 a low unblocking temperature component that is likely carried by a viscous remanent magnetization 2 a low coercivity intermediate unblocking temperature component that is probably carried by magnetite or magnetite and maghemite and 3 a high unblocking temperature component that is probably carried by hematite lithologies are typically dominated by the low coercivity component and single domain to pseudo single domain grain behavior rock magnetic studies suggest biogenic magnetite may contribute to the magnetic remanence of the low coercivity component the melilla basin magnetostratigraphy independently corroborated with new 40 ar 39 ar dating of volcanic ashes and foraminifer biostratigraphy has been correlated to the recently developed geomagnetic polarity time scale of shackleton et al 2 this correlation suggests deposition of the bioclastic platform began approximately at the tortonian messinian boundary which is defined as the base of chron 3ar 3 and continued into chron 3an 2n the fringing reefs span an interval that begins in chron 3an 2n until just above the base of chron 3r lower gilbert the overlying tcc and mixed carbonate and siliciclastic succession correlate to within chron 3r the new magnetostratigraphy is not without minor ambiguities possibly due to either remagnetization within the tcc or the presence of a short duration normal subchron in the lower portion of chron 3r results of this study have important implications for correlating between late miocene shallow marine carbonate sections and basinal sections within the mediterranean basin for improving the understanding of the history of the messinian salinity crisis and for deciphering the roles of eustacy tectonics and regional processes in the development of shallow marine carbonate sequences in the mediterranean region

quantitative controls on location and architecture of carbonate depositional sequences upper miocene cabo de gata region se spain abstract sequence stratigraphy pinning point relative sea level curves and magnetostratigraphy provide the quantitative data necessary to understand how rates of sea level change and different substrate paleoslopes are dominant controls on accumulation rate carbonate depositional sequence location and internal architecture five third order 1 10 my and fourth order 0 1 1 0 my upper miocene carbonate depositional sequences ds1a ds1b ds2 ds3 tcc formed with superimposed higher frequency sea level cycles in an archipelago setting in se spain overall our study indicates when areas of high substrate slope 15 are in shallow water independent of climate the location and internal architecture of carbonate deposits are not directly linked to sea level position but instead are controlled by location of gently sloping substrates and processes of bypass in contrast if carbonate sediments are generated where substrates of low slope 15 6 cm ky to 2 cm ky and overall relative sea level rose at rates of 17 21 4 cm ky higher frequency sea level rates were about 111 to more than 260 cm ky producing onlapping fining deepening upward cycles decreasing accumulation rates resulted from decreasing surface area for shallow water sediment production drowning of shallow water substrates and complex sediment dispersal related to the archipelago setting typical systems tract and parasequence development should not be expected in bypass ramp settings facies of onlapping strata do not track base level and are likely to be significantly different compared to onlapping strata associated with coastal onlap basal and upper ds2 reef megabreccias indicating the transition from cool to warmer climatic conditions were eroded from steep upslope positions and redeposited downslope onto areas of gentle substrate during rapid sea level falls 22 7 cm ky of short duration such rapid sea level falls and presence of steep slopes are not conducive to formation of forced regressive systems tracts composed of downstepping reef clinoforms the ds3 reefal platform formed where shallow water coincided with gently sloping substrates created by earlier deposition slow progradation 0 39 1 45 km my is best explained by the lack of an extensive bank top progressively falling sea level and low productivity resulting from siliciclastic debris and excess nutrients shed from nearby volcanic islands although ds3 strata were deposited during a third order relative sea level cycle a typical transgressive systems tract is not recognizable indicating that the initial relative rise in sea level was too rapid 19 cm ky downstepping reefs forming a forced regressive systems tract were deposited during the relative sea level fall at the end of ds3 indicating that relatively slow rates of fall 10 cm ky or less over favorable paleoslope conditions are conducive to generation of forced regressive systems tracts consisting of downstepping reef clinoforms the tcc sequence consists of four shallow water sedimentary cycles that were deposited during a 400 ky to 100 ky time span such shallow water cycles typical of many platforms form only where shallow water intersects gently sloping substrates the relative thicknesses of cycles 2 m to 15 m thick magnitudes of relative sea level fluctuations associated with each cycle 25 30 m high rates of relative sea level fluctuations minimum of 25 120 cm ky and the widespread distribution of similar tcc cycles in the mediterranean and elsewhere are supportive of a glacio eustatic influence with rates of sea level change so high typical systems tracts do not form

post collision neogene volcanism of the eastern rif morocco magmatic evolution through time abstract neogene volcanism in the eastern rif morocco comprises a series of calc alkaline potassic calc alkaline shoshonitic and alkaline volcanic rocks according to new stratigraphical along with new and previous chronological and geochemical data the orogenic volcanism was successively 1 calc alkaline basaltic andesites and andesites 13 1 to 12 5 ma rhyolites 9 8 ma 2 k calc alkaline basaltic andesitic to rhyolitic lavas and granodiorites 9 0 to 6 6 ma and 3 shoshonitic absarokites shoshonites latites trachytes 7 0 to 5 4 ma the later pliocene volcanism was basaltic and alkaline 5 6 to 1 5 ma the calc alkaline and k calc alkaline series exhibit lower k2o 0 7 5 3 wt nb 8 19 ppm contents and higher 87 sr 86 sr 0 70773 0 71016 than the shoshonitic series k2o 2 4 7 2 wt nb 21 38 ppm 87 sr 86 sr 0 70404 0 70778 pliocene alkaline basalts have a sodic tendency na2o k2o 1 7 3 5 high nb content up to 52 ppm and low 87 sr 86 sr ratio 0 70360 0 70413 the variations through time of k2o nb and sr isotopic ratio reflect different mantle sources i calc alkaline potassic calc alkaline and shoshonitic series are derived from a mantle source modified by older subduction ii alkaline basalts are derived mainly from an enriched mantle source through time incompatible elements such as nb increased while 87 sr 86 sr decreased suggesting a decreasing influence of metasomatized mantle inherited subduction such evolution is related to the post collision regimes operating in this area and could be linked to the succession of extensional compressional and strike slip fault tectonics

interpretation of vlf em in phase data using current density pseudosections1 the interpretation of vlf em surveys in terms of buried conductors can be assisted by the application of a linear filter to the observed in phase component of the vertical magnetic field one such scheme is examined critically by using the calculated response from a variety of synthetic models to compute theoretical current density pseudosections the results confirm that this filter technique provides a useful complementary tool for studying the third i e depth dimension for single steeply dipping plates 45 diagnostic information may be derived concerning the depth size lateral location and direction of dip since the current density maxima seems always to occur within the conductor or at least within one data interval however there are some limitations which do not appear to be widely recognized for single plates the angle of dip cannot be resolved by the current density transformation pattern distortions can occur where targets are in close proximity where the cross sectional form of the conductor is complex or where the dip is shallow 45 in these latter cases the current density maxima may not occur within the conductive structure and therefore cannot be used to infer depth of burial and or conductor shape with the same degree of confidence

paleoenvironmental changes at the messinian pliocene boundary in the eastern mediterranean southern cyprus basins significance of the messinian lago mare abstract the study of the late messinian early pliocene sediments in south cyprus pissouri and polemi basins and the comparison with the offshore coeval deposits drilled in the odp leg 160 boreholes provide new data illustrating the environmental changes which occurred in the eastern mediterranean at the end of the salinity crisis the messinian pliocene transition is marked by a very rapid environmental change indicated by sharp variations in lithology sedimentology microfaunal assemblages and stable isotope composition the latest messinian interval is dominated by the lago mare oligo mesohaline environments the most striking feature in the pissouri basin is the intercalation between the uppermost gypsum bed and the base of the zanclean deposits of four main horizons of paleosols interbedded with carbonates and conglomerates paleosols indicate periods of subaerial exposure long enough to permit pedogenesis to develop conglomerates indicate intense erosion of the troodos massif and its sedimentary cover as a result of the water level drop tectonic activity and more humid climatic conditions thus several subaerial exposure phases occurred in the marginal areas like the pissouri basin whereas shallow oligohaline conditions persisted in the deeper parts of the basin as indicated at odp site 968 both in the pissouri basin and on the flank of the erathostenes seamount the late messinian paleosols are directly overlain by the lowermost pliocene sediments deposited in well oxygenated deep marine conditions this drastic change of water depth shows that the water level of the late messinian saline to brackish lakes dropped far below that of the world ocean at least more than several hundred meters both these base level fluctuations and the oligohaline conditions caused intensive erosion karstification of the upper gypsum beds as also reported from many other mediterranean regions moreover the study of the polemi sections shows that oligohaline conditions had already started during the deposition of the upper gypsum sub unit typical brackish and fresh water assemblages are present in the last two gypsum layers and intergypsum beds this indicates that freshwater dilution i e the lago mare conditions resulted from a progressive change of the hydrological budget which started during deposition of the upper evaporites and climaxed after the deposition of the uppermost gypsum layer classical lago mare facies during this time periods of increased evaporation over precipitation led to deposition of the uppermost gypsum layers this evolution is interpreted as being due both to the severance from the open ocean and to the increasing contribution of the runoff precipitation versus marine inputs in the hydrological budget of the mediterranean

sediment supply from the betic rif orogen to basins through neogene abstract we present a quantification of total and partial divided by time slices sedimentary volumes in the neogene basins of the betic rif orogen these basins include the alboran sea the intramontane basins the guadalquivir and rharb foreland basins and the atlantic margin of the gibraltar arc the total volume of neogene sediments deposited in these basins is 209 000 km3 and is equally distributed between the internal alboran basin and intramontane basins and the external basins foreland basins and atlantic margin the largest volumes are recorded by the alboran basin 89 600 km3 and the atlantic margin 81 600 km3 the guadalquivir and rharb basins amount 14 000 km3 and 14 550 km3 respectively whereas the intramontane basins record 9235 km3 calculated mean sediment accumulation rates for the early middle miocene show an outstanding asymmetry between the alboran basin 0 24 mm yr and the foreland basins 0 06 0 07 mm yr and the atlantic margin 0 03 mm yr during the late miocene sedimentation rates range between 0 17 and 0 18 mm yr recorded in the alboran basin and 0 04 mm yr in the intramontane basins in the pliocene quaternary the highest sedimentation rates are recorded in the atlantic margin reaching 0 22 mm yr sedimentary contribution shows similar values for the inner and outer basins with a generalized increase from late miocene to present from 3500 to 6500 km3 my interestingly the alboran basin records the maximum sedimentary contribution during the late miocene 5500 km3 my whereas the atlantic margin does during the pliocene quaternary 6600 km3 my the spatial and time variability of the sediment supply from the betic rif orogen to basins is closely related to the morphotectonic evolution of the region the high sedimentation rates obtained in the alboran basin during the early middle miocene are related to active extensional tectonics which produced narrow and deep basins in its western domain the highest sedimentary contribution in this basin as well as in the foreland and intramontane basins is recorded during the late miocene due to the uplift of wide areas of the betics and rif chains the analysis of the sedimentary supply also evidences strong relationships with the post tortonian crustal thickening and coeval topographic amplification that occurred in the central betics and rif with the concomitant evolution of the drainage network showing the fluvial capture of some internal basins by rivers draining to the atlantic ocean the ancestral guadalquivir

the beginning development and termination of the middle miocene badenian salinity crisis in central paratethys abstract middle miocene badenian evaporites of the carpathian region are underlain and overlain by deep water deposits the onset of evaporite deposition was sudden but not synchronous in all facies zones and the deposition of evaporites was controlled by the evolution of carpathian orogen in the carpathian foredeep and most probably in other basins the badenian evaporites represent the lower part of the nn6 zone halite and associated deposits in the central part of the badenian evaporite basin show the same facies successions and marker beds can be traced across and between individual basins characteristic marker beds made it possible to correlate various facies zones of the marginal ca sulfate platform these marker beds seem to reflect events that may be related to sudden and widespread changes in water chemistry which in turn imply major changes in basin hydrology the onset of the evaporitic deposition in the carpathian foredeep was clearly diachronous and the evaporites deposited in the basin centre preceded the beginning of evaporite sedimentation in the marginal basin however depositional history in the marginal basin and the basin centre was the same a general transgressive sequence of evaporites found in the carpathian foredeep resulted from the migration of facies zones induced by the nappe movement isotopic studies of badenian foraminifers occurring below evaporites suggest that the interrupted communication of the paratethys with the ocean was a consequence of eustatic sea level fall possibly related to climatic cooling and it was coupled with a tectonic closure of connection with the tethys thus both tectonics and eustacy have contributed to the origin of salinity crisis sedimentological and geochemical data indicate recycling of evaporites throughout most of the evaporite deposition the recycling at the end of gypsum deposition in the marginal sulfate platform was accompanied by a change in the hydrology of the central paratethys that was tectonically driven and possibly related to the block tectonic phase manifested in the marginal part of the carpathian foredeep basin the change in hydrology implied the dilution of brines by inflowing marine water and this terminated the middle miocene badenian salinity crisis the onset of the badenian salinity crisis shows great similarities to the onset of the messinian salinity crisis and the terminations of both crises were different

the buried afiq canyon eastern mediterranean israel a case study of a tertiary submarine canyon exposed in late messinian times abstract the afiq submarine canyon was one of a series of canyons initially incised in a drowned shelf edge and slope of the eastern mediterranean margins in early oligocene times p19 zone during most of the early miocene submarine erosion or non deposition prevailed this was followed by deposition of pelagic marls and debris flows in early middle miocene n8 times large scale sliding in late middle miocene times n14 resulted in the collapse of the slope the removal of most of the middle miocene sequence and the formation of a box shaped scar back cutting incision ultimately resulted in the incision of the shelf in late miocene times a sea level fall ranging between 50 and 800 m below the canyon s rim resulted in the deposition of the messinian lower evaporites mavqiim formation within the canyon a subsequent rise of a similar extent led to the deposition of the upper evaporites be eri gypsum which are found on the canyon s southern shoulder the final messinian sea level drop below the canyon s floor resulted in a subaerial environment in the canyon the erosion of the upper evaporites and the subsequent deposition of fluvial and brackish sediments afiq formation the latter correspond to the lago mare sediments known throughout the mediterranean the rapidly rising sea level during the pliocene along with the high rate of nilotic clastic sedimentation resulted in the final burial of the afiq canyon and a pronounced seaward progradation 20 30 km of the shelf edge

the messinian of the nijar basin se spain sedimentation depositional environments and paleogeographic evolution abstract the reconstruction of the depositional events related to the messinian salinity crisis msc of the mediterranean is generally hampered by an incomplete stratal record in the circum mediterranean basins the sediments of the northern part of the nijar basin however provide an excellent and continuous record of late messinian sediments because features of severe erosion are lacking especially the successions of the deeper part of the basin had sufficient accommodation space to warrant ongoing deposition and may thus serve as a testing ground for existing hypotheses regarding the msc conformable contacts with the overlying pliocene and good correlation possibilities with the adjacent astronomically dated messinian of the sorbas basin provide the necessary age constraints the main body of evaporites in the nijar basin yesares formation has been affected by local dissolution and erosion prior to deposition of the latest messinian lago mare facies pelitic float breccias show textures indicating flowage and or mass transport and include slumped and slided stratal packets due to foundering of the mixed evaporitic clastic margin increased runoff of meteoric waters probably played an important role as these packet slides are perfectly sealed by the hyposaline lago mare strata field observations show that marginal sediments commonly classified as the terminal carbonate complex tcc are a lateral equivalent of the basinal yesares evaporites the latest messinian deposits feos formation are characterized by a sedimentary cyclicity related to fluctuating base levels consisting of chalky marly laminitic strata alternating with continental coarser clastic intervals despite considerable w e facies changes and indications for discrete tectonic events a persistent sequential pattern of eight lago mare cycles is present which are interpreted as precession controlled variations in regional climate instead of one major desiccation event in the latest messinian the repeatedly fluctuating water levels of the lago mare episode may have been the cause of the widespread vigorous erosion and canyon cutting in the lower evaporites abrupt non erosional contacts with the normal marine pliocene take place above the continental interval of the last lago mare cycle indicating that flooding took place during a period of lowered water levels the paleogeographic configuration of the nijar sorbas and vera basins has changed considerably during the messinian separation of the formerly interconnected basins is thought to have started in the late yesares times by tectonic uplift of the basement complexes in the latest messinian of the nijar basin two different coarse clastic supply areas can be distinguished which point to the partial emergence of the sierra cabrera and the cabo de gata block and activity of the sierra alhamilla and carboneras faults concerning the overall regional tectonic activity tectonics were probably also instrumental for the restoration of the atlantic gateway in the basal pliocene

sedimentology and paleoenvironmental evolution of messinian evaporites in the iskenderun hatay basin complex southern turkey abstract messinian evaporites which resulted from the salinity crisis during the final closure of the mediterranean sea are exposed in se turkey these evaporites formed in two isolated sub basins iskenderun arsuz ia and hatay samandag hs which belong to different depositional configurations and tectonic structures the neogene fill of these sub basins consists of a thick sedimentary succession that started with early miocene terrestrial clastics followed by reefs middle miocene and shallow water siliciclastics tortonian early to late miocene and finally messinian evaporates these sub basins accumulated in a diverse range of depositional environments from very shallow to deeper water evaporite facies in the ia sub basin consist of sabkhas saline lagoons and ponds they are mainly represented by chemical deposits such as scattered gypsum nodules and balls nodular bedded gypsum laminated gypsum type a and selenites type s1 evaporites in the hs sub basin mainly consist of detrital gypsum composed of gypsum laminae type b c gypsum arenite rudites and deeper water selenites 20 m and resedimented selenites type s2 which were deposited on a sulfate platform with a slope basin transitional zone secondary gypsum with alabastrine and porphyroblastic textures as well as satin spar veins is commonly associated with the sabkha type evaporites of the ia sub basin deeper water clastic evaporites of the hs sub basin have generally remained as primary gypsum or have only been slightly affected by diagenetic alterations the isotope values 87 86 sr 18 o smow and 34 s cdt from the different kinds of gypsum lithofacies of the sub basin are similar to those of the messinian evaporites in other peri mediterranean basins indicating an origin from marine water without external or basinal contributions the messinian evaporites examined in this paper are overlain by early pliocene zanclean deposits composed of shallow and deep water siliciclastics and carbonates with local intercalations of lago mare type strata throughout the messinian evaporitic stage the ia sub basin was mainly comprised of shallow water evaporites while the hs sub basin underwent deepening related to regional tectonics induced by the dead sea fault during the construction of the hatay graben

the enigmatic messinian pliocene section of cuevas del almanzora vera basin se spain revisited erosional features and strontium isotope ages abstract the cuevas del almanzora section was in the late seventies the focus of a discussion because of alleged continuous marine messinian to pliocene sedimentation however a discontinuity has been shown to exist in the shape of laminated strata including the late messinian brackish lacustrine lago mare biofacies more recently benson and rakic el bied 1991 concluded that the section is still one of the best biostratigraphic successions for the western mediterranean in which to document terminal miocene events but that it entirely has an early messinian age i e it antedates deposition of the main evaporites this paper presents strontium isotope ages indicating that the classic threefold division in an earlier marine messinian a lago mare and a pliocene interval sensu geerlings et al 1980 cita et al 1980 should be maintained moreover the sr isotopic composition of the euryhaline cyprideis ostracodes from the lago mare laminites is similar to those from central mediterranean basins this stresses the importance of late messinian water exchange between the vera basin and the then enclosed mediterranean it thus refutes the opinion of benson and rakic el bied 1991 that this interval is a local facies of no particular stratigraphic importance a time gap of up to 0 8 ma between the youngest marine strata of the messinian and the overlying pliocene provides a maximum timing for the duration of the messinian salinity crisis during which very little net sedimentation occurred compared to coeval deposits in for example the nearby nijar and sorbas basins in the cuevas section an inconspicuous and hitherto overlooked erosional gap has been observed this separates the lago mare marls from the pliocene marls more field observations have been made and are discussed in the light of existing interpretations in order to demonstrate the importance of more widespread erosion in the vera basin gypsum containing mass flow deposits filling up a late messinian palaeorelief in the garrucha area are shown to be derived from the basin these probably continue offshore as feeder channels related to a late messinian sea level fall a holistic approach of a key section thereby not overlooking the regional geology is a necessary step to be made before far reaching claims can be made about its interregional significance

the end of the messinian salinity crisis evidences from the chelif basin algeria how did the messinian salinity crisis end is a matter of intense debate between two opposite concepts i e the generalised dilution event the so called lago mare followed by the sudden restoration of the marine conditions at the base of the zanclean or the early partial or complete marine refill that would have happened earlier during the upper messinian the chelif basin of northwestern algeria one of the greatest messinian marginal basins of the mediterranean provides an exceptional opportunity to study in detail how this major paleoenvironmental change occurred through continuous sedimentary records of the miocene pliocene boundary five sections representative of both the central and marginal areas of the chelif basin were analysed in detail for sedimentology mineralogy foraminifera and ostracod assemblages and stable isotope composition of carbonates the late messinian deposits exhibit a great lithological variability with predominant clastic deposits sandstones siltstones conglomerates carbonates with in some marginal areas large slided masses of lower messinian tripoli unit that settled just before the base of the zanclean most sediments are either azoic or contain microfossils typical of hyposaline conditions sometimes mixed with benthic foraminifera known to be adapted to stressed environments and even to lacustrine conditions fewer types of sediment contain assemblages of planktonic foraminifera including typical messinian species which are thought to be reworked in contrast diversified communities of benthic and planktonic foraminifera returned suddenly at the base of the zanclean the messinian pliocene transition was marked by an abrupt change of the 18o values of carbonates from variable but predominantly negative values characteristic of low salinity conditions in the upper messinian to higher and more stable values in the zanclean typifying marine conditions the southern margin continued however to be submitted to large inputs of continental waters the beginning of the marine inundation was a transitional period with poorly diversified assemblages of planktonic foraminifera and benthic communities tolerant to oxygen deficient bottom conditions more stable marine conditions with better bottom water ventilation were set up after a lag time which would roughly correspond to a precession cycle except for the more marginal areas where conglomerates and erosional features are observed the restoration of marine conditions occurred without any significant erosion in the more central areas where the contact is well marked by strong burrowing activity by benthic organisms this indicates the rapid substitution in the basin of brackish waters by marine waters both mixing of these two kinds of waters and permanence of freshwater inputs in the initial stage of the pliocene transgression may explain why the community of marine planktonic foraminifera introduced by the inflowing atlantic waters hardly survived in such unfavourable ecological conditions in the mediterranean and reached a normal development later when more stable marine conditions settled this study and the comparison with other sections from both marginal and deep mediterranean basins confirm that the lago mare was a widespread dilution event that affected the whole mediterranean at the end of the messinian which was abruptly interrupted by the sudden marine inundation at the base of the zanclean

clay mineral assemblages siliciclastic input and paleoproductivity at odp site 1085 off southwest africa a late miocene early pliocene history of orange river discharges and benguela current activity and their relation to global sea level change abstract a late miocene to early pliocene sequence drilled on the continental slope of southwest africa off the orange river mouth odp site 1085 has been investigated clay mineral assemblages coarse siliciclastics and benthic foraminifer accumulation rates bfar unravel a step by step evolution of marine and continental environments closely related to sea level variations ocean circulation and global climate 1 smectite is a typical tracer of the orange river load whereas illite is mostly transported by the benguela current like chlorite and winds and kaolinite is derived from low latitudes by the poleward undercurrent and the north atlantic deep water nadw 2 increased erosion and influence of the orange river after 9 6 ma is linked to a sea level drop at a time of antarctic ice growth this has been followed by an increased seasonality of precipitation and high productivity but low oxygen content and associated dissolution of carbonates 3 increased productivity and dissolution of carbonates and coeval increase of continental aridity after 8 9 ma express a further development of the benguela current and upwelling 4 better preservation of carbonates and increased contribution of terrigenous material from northern sources at 6 9 ma are related to increased circulation of nadw after an early stage of northern hemisphere glaciation 5 increased erosion and contribution from the orange river and westward shift of the area of higher productivity from 5 9 5 8 ma to 5 3 5 2 ma are related to a significant fall of sea level and encompass the time of the entire mediterranean salinity crisis 6 short term variations of the smectite illite ratio s i and bfar suggest a major control of productivity by wind and current activities and related upwelling but may express brief variations of sea level in specific intervals before 8 9 ma and during the late messinian especially

mediterranean messinian salinity crisis constraints from a coeval marginal basin sorbas southeastern spain abstract the extent timing and effects of late miocene desiccation and evaporite deposition in the mediterranean sea remain controversial marginal basins containing messinian 5 3 7 1 ma sequences now exposed onland supplement information from the deep mediterranean but have evaporites of a variety of ages some of these messinian evaporites pre date and others post date deep desiccation none appears to be exactly coeval with those of the deep mediterranean in the betic cordillera of southern spain basins e g granada basin far from the present day mediterranean lost connection with the mediterranean due to uplift 1 ma before the salinity crisis and have marine evaporites of early not late messinian age in contrast basins such as the sorbas basin in southeastern spain adjacent to the present day mediterranean record events directly reflecting the course of the salinity crisis the sorbas basin retained marine connection with the western mediterranean up until evaporative drawdown in the mid messinian and was rapidly reflooded immediately afterwards the sorbas messinian sequence is up to 320 m thick it is complete and normal marine except for an incised basinwide erosion surface overlain by a 130 m thick gypsum deposit we propose that this surface marks the interval of deep desiccation of the adjacent mediterranean basin erosion occurred shortly after 5 9 ma and the irregular unconformity has relief of at least 240 m confirming mediterranean drawdown significantly below the atlantic level sorbas gypsum deposits overlie the unconformity and are intercalated with marls estimated at 5 5 ma containing normal marine messinian biotas these gypsum deposits therefore post date deep desiccation and formed in a silled basin immediately following marine reflooding they mark the end of the salinity crisis and are overlain by 70 m of normal marine sediments containing unreworked foraminifers of latest messinian age this succession demonstrates that the salinity crisis occurred faster and was completed sooner than previously believed it took place within 0 4 ma time scale of berggren et al 1995b is 0 2 ma on the time scale of baksi 1993 and was completed before the end of the messinian this corrects previous views that the salinity crisis continued until the early pliocene there is no evidence in the sorbas basin for brackish lago mare conditions and the normal marine biotas that directly precede and follow drawdown rebut earlier suggestions of prolonged salinity effects

sr isotope constraints on the mediterranean environment at the end of the messinian salinity crisis probably the most profound event that has affected the mediter ranean is the desiccation which occurred at the end of the miocene1 8 during this period there was a very rapid change from deep open marine conditions to environments of shallow water carbonate and massive evaporite deposition1 10 here we show that ostracod valves found in messinian lago mare lake sea sediments have a uniform but generally lower sr isotopic composition than contemporary sea water thus providing evidence that some of the major mediterranean basins for example balearic and levantine basins formed large lacustrine systems that were probably interconnected towards the end of the messinian salinity crisis1 3 after the major evaporites were deposited the most likely source of fresh water is from continental rivers flowing from the eastern european inland paratethys sea or perhaps the nile river in the lower part of the lago mare some ostracods have sr isotopic compositions identical to contemporary sea water indicating a transient influence of marine derived water sr compo sitions greater than that in contemporary sea water are only found in ostracods from onshore sediments in the sorbas basin4 5 of southeastern spain suggesting that this small basin adjacent to the straits of gibraltar became isolated after the deposition of the major evaporite sequences